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126-469: Toxoplasma gondii ( / ˈ t ɒ k s ə ˌ p l æ z m ə ˈ ɡ ɒ n d i . aɪ , - iː / ) is a parasitic protozoan (specifically an apicomplexan ) that causes toxoplasmosis . Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals , but felids are the only known definitive hosts in which the parasite may undergo sexual reproduction. In rodents , T. gondii alters behavior in ways that increase

252-416: A cell wall , as found in plants and many algae . This classification remained widespread in the 19th and early 20th century, and even became elevated to a variety of higher ranks, including phylum , subkingdom , kingdom , and then sometimes included within the similarly paraphyletic Protoctista or Protista . By the 1970s, it became usual to require that all taxa be monophyletic (derived from

378-470: A bigger threat in transporting T. gondii to other mammalian species, rather than otters who have a more restrictive breadth. Protozoa When first introduced by Georg Goldfuss , in 1818, the taxon Protozoa was erected as a class within the Animalia, with the word 'protozoa' meaning "first animals", because they often possess animal -like behaviours, such as motility and predation , and lack

504-441: A combination of drugs such as pyrimethamine and sulfadiazine , plus folinic acid . Immune-compromised patients may need continuous treatment until/unless their immune system is restored. In many parts of the world, where there are high populations of feral cats, there is an increased risk to the native wildlife due to increased infection of Toxoplasma gondii . It has been found that the serum concentrations of T. gondii in

630-572: A common ancestor existed about 10,000 years ago. Authors of a subsequent and larger study on 196 isolates from diverse sources including T. gondii in the bald eagle, gray wolf, Arctic fox and sea otter, also found that T. gondii strains infecting North American wildlife have limited genetic diversity with the occurrence of only a few major clonal types. They found that 85% of strains in North America were of one of three widespread genotypes II, III and Type 12. Thus T. gondii has retained

756-632: A common ancestor that would also be regarded as protozoan), and holophyletic (containing all of the known descendants of that common ancestor). The taxon 'Protozoa' fails to meet these standards, so grouping protozoa with animals, and treating them as closely related, became no longer justifiable. The term continues to be used in a loose way to describe single-celled protists (that is, eukaryotes that are not animals, plants , or fungi ) that feed by heterotrophy . Traditional textbook examples of protozoa are Amoeba , Paramecium , Euglena and Trypanosoma . The word "protozoa" (singular protozoon )

882-411: A decreased aversion to cat urine (but with divergent trajectories by gender) and an increased risk of schizophrenia . Preliminary evidence has suggested that T. gondii infection may induce some of the same alterations in the human brain as those observed in rodents. Many of these associations have been strongly debated and newer studies have found them to be weak, concluding: On the whole, there

1008-479: A drop of this infected culture fluid and the parasite indefinitely maintained without the need of animals. Following the initial period of infection characterized by tachyzoite proliferation throughout the body, pressure from the host's immune system causes T. gondii tachyzoites to convert into bradyzoites, the semi dormant , slowly dividing cellular stage of the parasite. Inside host cells, clusters of these bradyzoites are known as tissue cysts. The cyst wall

1134-513: A given MHC molecule differs dramatically between individuals, which is why these molecules are involved in transplant rejection. Individuals carrying certain genetic sequences of MHC molecules are much more likely to be infected with Toxoplasma . One study of >1600 individuals found that Toxoplasma infection was especially common among people who expressed certain MHC alleles (HLA-B*08:01, HLA-C*04:01, HLA-DRB 03:01, HLA-DQA*05:01 and HLA-DQB*02:01). IL-12

1260-410: A high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish. Although the absorption in the human digestive system is mainly a function of

1386-478: A host's red blood cell. Protozoa may also live as mixotrophs , combining a heterotrophic diet with some form of autotrophy . Some protozoa form close associations with symbiotic photosynthetic algae (zoochlorellae), which live and grow within the membranes of the larger cell and provide nutrients to the host. The algae are not digested, but reproduce and are distributed between division products. The organism may benefit at times by deriving some of its nutrients from

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1512-404: A lorica made from silicous sectretions. Loricas are also common among some green euglenids, various ciliates (such as the folliculinids , various testate amoebae and foraminifera . The surfaces of a variety of protozoa are covered with a layer of scales and or spicules. Examples include the amoeba Cochliopodium , many centrohelid heliozoa , synurophytes . The layer is often assumed to have

1638-492: A moist habitat; however, some can survive for long periods of time in dry environments, by forming resting cysts that enable them to remain dormant until conditions improve. All protozoa are heterotrophic , deriving nutrients from other organisms, either by ingesting them whole by phagocytosis or taking up dissolved organic matter or micro-particles ( osmotrophy ). Phagocytosis may involve engulfing organic particles with pseudopodia (as amoebae do), taking in food through

1764-533: A new kingdom called Primigenum, consisting of both the protozoa and unicellular algae, which he combined under the name "Protoctista". In Hoggs's conception, the animal and plant kingdoms were likened to two great "pyramids" blending at their bases in the Kingdom Primigenum. In 1866, Ernst Haeckel proposed a third kingdom of life, which he named Protista. At first, Haeckel included a few multicellular organisms in this kingdom, but in later work, he restricted

1890-448: A number of cells, with the function of the glands changing depending on their position within the stomach. Within the body and fundus of the stomach lie the fundic glands . In general, these glands are lined by column-shaped cells that secrete a protective layer of mucus and bicarbonate . Additional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor , chief cells that secrete pepsinogen (this

2016-445: A perpetual lifespan of individual cysts or bradyzoites. At any given time in a chronically infected host, a very small percentage of cysts are rupturing, although the exact cause of this tissue cyst rupture is, as of 2010, not yet known. Theoretically, T. gondii can be passed between intermediate hosts indefinitely via a cycle of consumption of tissue cysts in meat. However, the parasite's life cycle begins and completes only when

2142-452: A phylum or sub-kingdom composed of "unicellular animals" was adopted by the zoologist Otto Bütschli —celebrated at his centenary as the "architect of protozoology". As a phylum under Animalia, the Protozoa were firmly rooted in a simplistic "two-kingdom" concept of life, according to which all living beings were classified as either animals or plants. As long as this scheme remained dominant,

2268-430: A process called gastric emptying , rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into

2394-552: A protective role. In some, such as the actinophryid heliozoa, the scales only form when the organism encysts. The bodies of some protozoa are supported internally by rigid, often inorganic, elements (as in Acantharea , Pylocystinea , Phaeodarea  – collectively the ' Radiolaria ', and Ebriida ). Protozoa mostly reproduce asexually by binary fission or multiple fission. Many protozoa also exchange genetic material by sexual means (typically, through conjugation ), but this

2520-591: A rest period of 3 min should be allowed before consumption. Oocysts in cat feces take at least a day to sporulate (to become infectious after they are shed), so disposing of cat litter daily greatly reduces the chance of infectious oocysts developing. As these can spread and survive in the environment for months, humans should wear gloves when gardening or working with soil, and should wash their hands promptly after disposing of cat litter. These precautions apply to outdoor sandboxes/play sand pits, which should be covered when not in use. Cat feces should never be flushed down

2646-484: A rigid external cell wall but are usually enveloped by elastic structures of membranes that permit movement of the cell. In some protozoa, such as the ciliates and euglenozoans , the outer membrane of the cell is supported by a cytoskeletal infrastructure, which may be referred to as a "pellicle". The pellicle gives shape to the cell, especially during locomotion. Pellicles of protozoan organisms vary from flexible and elastic to fairly rigid. In ciliates and Apicomplexa ,

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2772-452: A specialized mouth-like aperture called a cytostome , or using stiffened ingestion organelles Parasitic protozoa use a wide variety of feeding strategies, and some may change methods of feeding in different phases of their life cycle. For instance, the malaria parasite Plasmodium feeds by pinocytosis during its immature trophozoite stage of life (ring phase), but develops a dedicated feeding organelle (cytostome) as it matures within

2898-477: A toilet. Pregnant women are at higher risk of transmitting the parasite to their unborn child and immunocompromised people of acquiring a lingering infection. Because of this, they should not change or handle cat litter boxes. Ideally, cats should be kept indoors and fed only food that has low to no risk of carrying oocysts, such as commercial cat food or well-cooked table food. No approved human vaccine exists against Toxoplasma gondii . Research on human vaccines

3024-436: A vital organ in the digestive system . The stomach is involved in the gastric phase of digestion , following the cephalic phase in which the sight and smell of food and the act of chewing are stimuli. In the stomach a chemical breakdown of food takes place by means of secreted digestive enzymes and gastric acid . The stomach is located between the esophagus and the small intestine . The pyloric sphincter controls

3150-410: Is distensible , and can normally expand to hold about one litre of food. In a newborn human baby the stomach will only be able to hold about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres, although volumes of up to 15 litres have been observed in extreme circumstances. The human stomach can be divided into four sections, beginning at the cardia followed by the fundus,

3276-442: Is a narrow tubular region, the proventriculus , lined by fundic glands, and connecting the true stomach to the crop . Beyond lies the powerful muscular gizzard , lined by pyloric glands, and, in some species, containing stones that the animal swallows to help grind up food. In insects , there is also a crop. The insect stomach is called the midgut . Information about the stomach in echinoderms or molluscs can be found under

3402-404: Is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete serotonin . Glands differ where the stomach meets the esophagus and near the pylorus. Near the gastroesophageal junction lie cardiac glands , which primarily secrete mucus. They are fewer in number than the other gastric glands and are more shallowly positioned in

3528-519: Is a term that is also used to describe the removal of the heart . A gastrectomy may be carried out because of gastric cancer or severe perforation of the stomach wall. Fundoplication is stomach surgery in which the fundus is wrapped around the lower esophagus and stitched into place. It is used to treat gastroesophageal reflux disease (GERD) . The word stomach is derived from Greek stomachos ( στόμαχος ), ultimately from stoma ( στόμα ) 'mouth'. Gastro- and gastric (meaning 'related to

3654-503: Is also the primary means by which cats are infected. An exhibit at the San Diego Natural History Museum states urban runoff with cat feces transports Toxoplasma gondii into the ocean, which can kill sea otters. Tissue cysts can be maintained in host tissue for the lifetime of the animal. However, the perpetual presence of cysts appears to be due to a periodic process of cyst rupturing and re-encysting, rather than

3780-475: Is commonly transmitted through ingesting microscopic cysts in the tissues of infected animals, meat that is not prepared to destroy these presents a risk of infection. Freezing meat for several days at subzero temperatures (0 °F or −18 °C) before cooking may break down all cysts, as they rarely survive these temperatures. During cooking, whole cuts of red meat should be cooked to an internal temperature of at least 145 °F (63 °C). Medium rare meat

3906-427: Is considered to have three stages of infection; the tachyzoite stage of rapid division, the bradyzoite stage of slow division within tissue cysts, and the oocyst environmental stage. Tachyzoites are also known as "tachyzoic merozoites" and bradyzoites as "bradyzoic merozoites". When an oocyst or tissue cyst is ingested by a human or other warm-blooded animal, the resilient cyst wall is dissolved by proteolytic enzymes in

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4032-468: Is distinct from other parts of the gastrointestinal tract, which do not possess this layer. The stomach contains the thickest muscular layer consisting of three layers, thus maximum peristalsis occurs here. The outer longitudinal layer is responsible for moving the semi-digested food towards the pylorus of the stomach through muscular shortening. To the outside of the muscular layer lies a serosa , consisting of layers of connective tissue continuous with

4158-458: Is essential for T. gondii sexual reproduction. Infected epithelial cells eventually rupture and release oocysts into the intestinal lumen , whereupon they are shed in the cat's feces. Oocysts can then spread to soil, water, food, or anything potentially contaminated with the feces. Highly resilient, oocysts can survive and remain infective for many months in cold and dry climates. Ingestion of oocysts by humans or other warm-blooded animals

4284-405: Is formed by the parasitophorous vacuole membrane. Although bradyzoite-containing tissue cysts can form in virtually any organ, tissue cysts predominantly form and persist in the brain, the eyes , and striated muscle (including the heart). However, specific tissue tropisms can vary between intermediate host species; in pigs, the majority of tissue cysts are found in muscle tissue, whereas in mice,

4410-455: Is formed from the Greek words πρῶτος ( prôtos ), meaning "first", and ζῷα ( zôia ), plural of ζῷον ( zôion ), meaning "animal". In 1848, with better microscopes and Theodor Schwann and Matthias Schleiden 's cell theory , the zoologist C. T. von Siebold proposed that the bodies of protozoa such as ciliates and amoebae consisted of single cells, similar to those from which

4536-525: Is from the celiac trunk , and venous drainage is by the portal venous system . Lymph from these organs is drained to the prevertebral celiac nodes at the origin of the celiac artery from the aorta . In the human digestive system , a bolus (a small rounded mass of chewed up food) enters the stomach through the esophagus via the lower esophageal sphincter . The stomach releases proteases (protein-digesting enzymes such as pepsin ), and hydrochloric acid , which kills or inhibits bacteria and provides

4662-500: Is generally asymptomatic but may lead to a serious case of toxoplasmosis . T. gondii can initially cause mild, flu-like symptoms in the first few weeks following exposure, but otherwise, healthy human adults are asymptomatic. This asymptomatic state of infection is referred to as a latent infection , and it has been associated with numerous subtle behavioral, psychiatric, and personality alterations in humans. Behavioral changes observed between infected and non-infected humans include

4788-429: Is generally cooked between 130 and 140 °F (55 and 60 °C), so cooking meat to at least medium is recommended. After cooking, a rest period of 3 min should be allowed before consumption. However, ground meat should be cooked to an internal temperature of at least 160 °F (71 °C) with no rest period. All poultry should be cooked to an internal temperature of at least 165 °F (74 °C). After cooking,

4914-487: Is generally decoupled from reproduction. Meiotic sex is widespread among eukaryotes , and must have originated early in their evolution, as it has been found in many protozoan lineages that diverged early in eukaryotic evolution. In the well-studied protozoan species Paramecium tetraurelia , the asexual line undergoes clonal aging, loses vitality and expires after about 200 fissions if the cells fail to undergo autogamy or conjugation. The functional basis for clonal aging

5040-447: Is in response to food products in the liver and gall bladder, which have not yet been absorbed. The stomach needs to push food into the small intestine only when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food. Epidermal growth factor (EGF) results in cellular proliferation, differentiation, and survival. EGF is a low-molecular-weight polypeptide first purified from

5166-509: Is meant by the word 'Protozoa', the need for disambiguating statements such as "in the sense intended by Goldfuß", and the problems that arise when new meanings are given to familiar taxonomic terms. Some authors classify Protozoa as a subgroup of mostly motile Protists. Others class any unicellular eukaryotic microorganism as Protists, and make no reference to 'Protozoa'. In 2005, members of the Society of Protozoologists voted to change its name to

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5292-553: Is one of the common routes of infection. Humans can be exposed to oocysts by, for example, consuming unwashed vegetables or contaminated water, or by handling the feces (litter) of an infected cat. Although cats can also be infected by ingesting oocysts, they are much less sensitive to oocyst infection than are intermediate hosts. Intermediate hosts found include pigs, chickens, goats, sheep and Macropus rufus by Moré et al. 2010. Cattle and horses are resistant and thought to be incapable of significant infection. T. gondii

5418-418: Is ongoing. For sheep , an approved live vaccine sold as Toxovax (from MSD Animal Health ) provides lifetime protection. There is currently no commercially available vaccine to prevent T. gondii infection in cats. However, research into feline vaccines for toxoplasmosis is ongoing, with several candidates showing positive results in clinical trials. In humans, active toxoplasmosis can be treated with

5544-434: Is passed to the lateral hypothalamus and limbic system in the brain as a palatability signal through the vagus nerve . The stomach can also sense, independently of tongue and oral taste receptors, glucose , carbohydrates , proteins , and fats . This allows the brain to link nutritional value of foods to their tastes. This syndrome defines the association between thyroid disease and chronic gastritis, which

5670-452: Is produced during T. gondii infection to activate natural killer (NK) cells . Tryptophan is an essential amino acid for T. gondii, which it scavenges from host cells. IFN-γ induces the activation of indole-amine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO), two enzymes that are responsible for the degradation of tryptophan. Immune pressure eventually leads the parasite to form cysts that normally are deposited in

5796-762: Is rare among free-living protozoa and it usually occurs when food is scarce or the environment changes drastically. Both isogamy and anisogamy occur in Protozoa, anisogamy being the more common form of sexual reproduction. Protozoans, as traditionally defined, range in size from as little as 1 micrometre to several millimetres , or more. Among the largest are the deep-sea–dwelling xenophyophores , single-celled foraminifera whose shells can reach 20 cm in diameter. Free-living protozoa are common and often abundant in fresh, brackish and salt water, as well as other moist environments, such as soils and mosses. Some species thrive in extreme environments such as hot springs and hypersaline lakes and lagoons. All protozoa require

5922-418: Is required to begin the action of motility because it phosphorylates T. gondii ' s myosin   A ( TgMYOA ). TgCDPK3 is the functional orthologue of CDPK1 in this parasite. Motile , and quickly multiplying, tachyzoites are responsible for expanding the population of the parasite in the host. When a host consumes a tissue cyst (containing bradyzoites) or an oocyst (containing sporozoites),

6048-750: Is thought to be contaminated by T. gondii oocysts that originate from cat feces, survive or bypass sewage treatment, and travel to the coast through river systems. T. gondii has been identified in a California mussel by polymerase chain reaction and DNA sequencing. In light of the potential presence of T. gondii , pregnant women and immunosuppressed persons should be aware of this potential risk associated with eating raw oysters, mussels, and clams." In warm-blooded animals, such as brown rats , sheep, and dogs, T. gondii has also been shown to be sexually transmitted. Although T. gondii can infect, be transmitted by, and asexually reproduce within humans and virtually all other warm-blooded animals,

6174-408: Is unknown whether this is common. Inside host cells, the tachyzoites replicate inside specialized vacuoles (called the parasitophorous vacuoles ) created from host cell membrane during invasion into the cell. Tachyzoites multiply inside this vacuole until the host cell dies and ruptures, releasing and spreading the tachyzoites via the bloodstream to all organs and tissues of the body, including

6300-437: The brain . The parasite can be easily grown in monolayers of mammalian cells maintained in vitro in tissue culture . It readily invades and multiplies in a wide variety of fibroblast and monocyte cell lines . In infected cultures, the parasite rapidly multiplies and thousands of tachyzoites break out of infected cells and enter adjacent cells, destroying the monolayer in due course. New monolayers can then be infected using

6426-469: The left crus of diaphragm , and the left colic flexure . The term was introduced around 1896 by Philip Polson of the Catholic University School of Medicine, Dublin. However this was brought into disrepute by surgeon anatomist J Massey. The lesser curvature of the human stomach is supplied by the right gastric artery inferiorly and the left gastric artery superiorly, which also supplies

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6552-417: The multicellular tissues of plants and animals were constructed. Von Siebold redefined Protozoa to include only such unicellular forms, to the exclusion of all Metazoa (animals). At the same time, he raised the group to the level of a phylum containing two broad classes of microorganisms: Infusoria (mostly ciliates ) and flagellates (flagellated protists and amoebae ). The definition of Protozoa as

6678-414: The nervous system . Chyme from the stomach is slowly released into the duodenum through coordinated peristalsis and opening of the pyloric sphincter. The movement and the flow of chemicals into the stomach are controlled by both the autonomic nervous system and by the various digestive hormones of the digestive system: Other than gastrin, these hormones all act to turn off the stomach action. This

6804-428: The peritoneum . Smooth mucosa along the inside of the lesser curvature forms a passageway - the gastric canal that fast-tracks liquids entering the stomach, to the pylorus. The mucosa lining the stomach is lined with gastric pits , which receive gastric juice , secreted by between 2 and 7 gastric glands . Gastric juice is an acidic fluid containing hydrochloric acid and digestive enzymes. The glands contains

6930-558: The International Society of Protistologists . In the system of eukaryote classification published by the International Society of Protistologists in 2012, members of the old phylum Protozoa have been distributed among a variety of supergroups. Protists are distributed across all major groups of eukaryotes, including those that contain multicellular algae, green plants, animals, and fungi. If photosynthetic and fungal protists are distinguished from protozoa, they appear as shown in

7056-536: The Kingdoms Protista and Protoctista became established in biology texts and curricula. By 1954, Protozoa were classified as "unicellular animals", as distinct from the "Protophyta", single-celled photosynthetic algae, which were considered primitive plants. In the system of classification published in 1964 by B.M. Honigsberg and colleagues, the phylum Protozoa was divided according to the means of locomotion, such as by cilia or flagella. Despite awareness that

7182-465: The Protista to single-celled organisms, or simple colonies whose individual cells are not differentiated into different kinds of tissues . Despite these proposals, Protozoa emerged as the preferred taxonomic placement for heterotrophic microorganisms such as amoebae and ciliates, and remained so for more than a century. In the course of the 20th century, the old "two kingdom" system began to weaken, with

7308-409: The acidic pH of 2 for the proteases to work. Food is churned by the stomach through peristaltic muscular contractions of the wall – reducing the volume of the bolus, before looping around the fundus and the body of stomach as the boluses are converted into chyme (partially digested food). Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine , where

7434-423: The algae Euglena and Dinobryon have chloroplasts for photosynthesis , like plants, but can also feed on organic matter and are motile , like animals. In 1860, John Hogg argued against the use of "protozoa", on the grounds that "naturalists are divided in opinion—and probably some will ever continue so—whether many of these organisms or living beings, are animals or plants." As an alternative, he proposed

7560-525: The algal endosymbionts or by surviving anoxic conditions because of the oxygen produced by algal photosynthesis. Some protozoans practice kleptoplasty , stealing chloroplasts from prey organisms and maintaining them within their own cell bodies as they continue to produce nutrients through photosynthesis. The ciliate Mesodinium rubrum retains functioning plastids from the cryptophyte algae on which it feeds, using them to nourish themselves by autotrophy. The symbionts may be passed along to dinoflagellates of

7686-445: The basis for the adult gastrointestinal tract. The sac is surrounded by a network of vitelline arteries and veins . Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the celiac artery , superior mesenteric artery , and inferior mesenteric artery . The areas supplied by these arteries are used to define the foregut , midgut , and hindgut . The surrounded sac becomes

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7812-495: The body and the pylorus. The cardia is defined as the region following the "z-line" of the gastroesophageal junction , the point at which the epithelium changes from stratified squamous to columnar . Near the cardia is the lower esophageal sphincter. The stomach bed refers to the structures upon which the stomach rests in mammals. These include the tail of the pancreas , splenic artery , left kidney , left suprarenal gland , transverse colon and its mesocolon , and

7938-421: The bradyzoites or sporozoites stage-convert into tachyzoites upon infecting the intestinal epithelium of the host. During the initial acute period of infection, tachyzoites spread throughout the body via the blood stream. During the later, latent (chronic) stages of infection, tachyzoites stage-convert to bradyzoites to form tissue cysts. Like tachyzoites, merozoites divide quickly and are responsible for expanding

8064-639: The capability for sex in North America over many generations, producing largely clonal populations, and matings have generated little genetic diversity. During different periods of its life cycle, individual parasites convert into various cellular stages, with each stage characterized by a distinct cellular morphology , biochemistry , and behavior. These stages include the tachyzoites, merozoites, bradyzoites (found in tissue cysts), and sporozoites (found in oocysts). Some stages are motile and some calcium-dependent protein kinases ( TgCDPK s) are involved in this parasite's motility. Gaji et al. 2015 find TgCDPK3

8190-426: The cardiac region. The greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly. The fundus of the stomach, and also the upper portion of the greater curvature, is supplied by the short gastric arteries , which arise from the splenic artery. The two sets of gastric lymph nodes drain the stomach. Like the other parts of the gastrointestinal wall ,

8316-489: The deaths were due to a closely related protozoan parasite known as Sarcocystis neurona . Minks, being semiaquatic, are also susceptible to infection and being antibody-positive toward T. gondii . Minks can follow a similar diet as otters and feasts on crustaceans, fish, and invertebrates, thus the transmission route follows a similar pattern to otters. Because of the mink's ability to transverse land more frequently, and often seen as an invasive species itself, minks are

8442-411: The definitive host of T. gondii . All other hosts – in which only asexual reproduction can occur – are intermediate hosts . When a feline is infected with T. gondii (e.g. by consuming an infected mouse carrying the parasite's tissue cysts), the parasite survives passage through the stomach , eventually infecting epithelial cells of the cat's small intestine. Inside these intestinal cells,

8568-439: The digesting and readsorbing ability, and lastly, similar ability to form iodotyrosines by peroxidase activity, where iodide acts as an electron donor in the presence of H 2 O 2 . In the following years, many researchers published reviews about this syndrome. A series of radiographs can be used to examine the stomach for various disorders. This will often include the use of a barium swallow . Another method of examination of

8694-464: The dorsal mesentery thins and forms the greater omentum , which is attached to the greater curvature of the stomach. The ventral mesentery forms the lesser omentum, and is attached to the developing liver . In the adult, these connective structures of omentum and mesentery form the peritoneum , and act as an insulating and protective layer while also supplying organs with blood and lymph vessels as well as nerves. Arterial supply to all these structures

8820-411: The duodenum. Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it. The fundus stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in

8946-497: The esophagus opening directly into the intestine. These animals all consume diets that require little storage of food, no predigestion with gastric juices, or both. The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands and a posterior portion lined with pyloric glands. Cardiac glands are unique to mammals , and even then are absent in a number of species. The distributions of these glands vary between species, and do not always correspond with

9072-429: The extraction of nutrients begins. Gastric juice in the stomach also contains pepsinogen . Hydrochloric acid activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides . Within a few moments after food enters the stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of peristalsis that mixes and softens

9198-399: The field working towards unraveling the molecular intricacies of this process. Bradyzoites are the slowly dividing stage of the parasite that make up tissue cysts. When an uninfected host consumes a tissue cyst, bradyzoites released from the cyst infect intestinal epithelial cells before converting to the proliferative tachyzoite stage. Following the initial period of proliferation throughout

9324-418: The food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed by more intense waves, starting at the body of the stomach and increasing in force as they reach the pylorus. The pylorus, which holds around 30 mL of chyme, acts as a filter, permitting only liquids and small food particles to pass through the mostly, but not fully, closed pyloric sphincter . In

9450-501: The fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates lingual lipase . Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides. The breakdown of protein begins in

9576-567: The genus Dinophysis , which prey on Mesodinium rubrum but keep the enslaved plastids for themselves. Within Dinophysis , these plastids can continue to function for months. Organisms traditionally classified as protozoa are abundant in aqueous environments and soil , occupying a range of trophic levels . The group includes flagellates (which move with the help of undulating and beating flagella ). Ciliates (which move by using hair-like structures called cilia ) and amoebae (which move by

9702-482: The growing awareness that fungi did not belong among the plants, and that most of the unicellular protozoa were no more closely related to the animals than they were to the plants. By mid-century, some biologists, such as Herbert Copeland , Robert H. Whittaker and Lynn Margulis , advocated the revival of Haeckel's Protista or Hogg's Protoctista as a kingdom-level eukaryotic group, alongside Plants, Animals and Fungi. A variety of multi-kingdom systems were proposed, and

9828-416: The growth of sea kelp, other marine populations are protected as well as CO 2 emissions are reduced due to the kelp's ability to absorb atmospheric carbon. An examination on 105 beachcast otters revealed that 38.1% had parasitic infections, and 28% of said infections had resulted in protozoal meningoencephalitis deaths. Toxoplasma gondii was found to be the root cause in 16.2% of these deaths, while 6.7% of

9954-588: The highest IgG seroprevalence to be in Ethiopia , at 64.2%, as of 2018. T. gondii contains organelles called rhoptries and micronemes , as well as other organelles. The life cycle of T. gondii may be broadly summarized into two components: a sexual component that occurs only within cats (felids, wild or domestic), and an asexual component that can occur within virtually all warm-blooded animals, including humans, cats, and birds. Because T. gondii can sexually reproduce only within cats, cats are therefore

10080-464: The host body, tachyzoites then convert back to bradyzoites, which reproduce inside host cells to form tissue cysts in the new host. Sporozoites are the stage of the parasite residing within oocysts. When a human or other warm-blooded host consumes an oocyst, sporozoites are released from it, infecting epithelial cells before converting to the proliferative tachyzoite stage. Initially, a T. gondii infection stimulates production of IL-2 and IFN-γ by

10206-404: The human stomach wall from inner to outer, consists of a mucosa , submucosa , muscular layer , subserosa and serosa . The inner part of the stomach wall is the gastric mucosa a mucous membrane that forms the lining of the stomach. the membrane consists of an outer layer of columnar epithelium , a lamina propria , and a thin layer of smooth muscle called the muscularis mucosa . Beneath

10332-454: The innate immune system. Continuous IFN-γ production is necessary for control of both acute and chronic T. gondii infection. These two cytokines elicit a CD4+ and CD8+ T-cell mediated immune response. Thus, T-cells play a central role in immunity against Toxoplasma infection. T-cells recognize Toxoplasma antigens that are presented to them by the body's own Major Histocompatibility Complex (MHC) molecules. The specific genetic sequence of

10458-424: The intestines. In humans, many bariatric surgery procedures involve the stomach, in order to lose weight. A gastric band may be placed around the cardia area, which can adjust to limit intake. The anatomy of the stomach may be modified , or the stomach may be bypassed entirely . Surgical removal of the stomach is called a gastrectomy , and removal of the cardia area is a called a cardiectomy . "Cardiectomy"

10584-400: The junction of the stomach with the duodenum. The stomach is surrounded by parasympathetic (inhibitor) and sympathetic (stimulant) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior , superior and inferior , celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles. The stomach

10710-416: The levels of kynurenic acid (KYNA) in the brains of infected mice and in the brain of schizophrenic persons. Low levels of tryptophan and serotonin in the brain were already associated with depression. The following have been identified as being risk factors for T. gondii infection in humans and warm-blooded animals: A common argument in the debate about whether cat ownership is ethical involves

10836-473: The majority of cysts are found in the brain. Cysts usually range in size between five and 50   μm in diameter, (with 50 μm being about two-thirds the width of the average human hair). Consumption of tissue cysts in meat is one of the primary means of T. gondii infection, both for humans and for meat-eating, warm-blooded animals. Humans consume tissue cysts when eating raw or undercooked meat (particularly pork and lamb). Tissue cyst consumption

10962-738: The mouse submandibular gland, but since then found in many human tissues including the submandibular gland , and the parotid gland . Salivary EGF, which also seems to be regulated by dietary inorganic iodine , also plays an important physiological role in the maintenance of oro-esophageal and gastric tissue integrity. The biological effects of salivary EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, stimulation of DNA synthesis, and mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin and from physical, chemical, and bacterial agents. The human stomach has receptors responsive to sodium glutamate and this information

11088-413: The mucosa lies the submucosa , consisting of fibrous connective tissue . Meissner's plexus is in this layer interior to the oblique muscle layer. Outside of the submucosa lies the muscular layer. It consists of three layers of muscular fibres, with fibres lying at angles to each other. These are the inner oblique, middle circular, and outer longitudinal layers. The presence of the inner oblique layer

11214-414: The mucosa. There are two kinds - either simple tubular glands with short ducts or compound racemose resembling the duodenal Brunner's glands . Near the pylorus lie pyloric glands located in the antrum of the pylorus. They secrete mucus, as well as gastrin produced by their G cells . About 20,000 protein-coding genes are expressed in human cells and nearly 70% of these genes are expressed in

11340-416: The mucosa; pepsinogen and gastric lipase , expressed in gastric chief cells ; and a gastric ATPase and gastric intrinsic factor , expressed in parietal cells . In the early part of the development of the human embryo , the ventral part of the embryo abuts the yolk sac . During the third week of development, as the embryo grows, it begins to surround parts of the yolk sac. The enveloped portions form

11466-433: The muscles and in the brain of the hosts. The IFN-γ-mediated activation of IDO and TDO is an evolutionary mechanism that serves to starve the parasite, but it can result in depletion of tryptophan in the brain of the host. IDO and TDO degrade tryptophan to N-formylkynurenine . Administration of L-kynurenine is capable of inducing depressive-like behavior in mice. T. gondii infection has been demonstrated to increase

11592-411: The normal stomach. Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients. Highly stomach-specific proteins include gastrokine-1 expressed in

11718-416: The parasite can sexually reproduce only within the intestines of members of the cat family (felids) . Felids are therefore the definitive hosts of T. gondii ; all other hosts (such as human or other mammals) are intermediate hosts . The following precautions are recommended to prevent or greatly reduce the chances of becoming infected with T. gondii . This information has been adapted from

11844-427: The parasite in response to the infection of the cat. Multiple studies revealed distinct differences in the transcriptomes of the asexual and sexual stages of T. gondii . Additionally, metabolic disparities within the feline host have been identified as key factors influencing the transition to sexual stages. However, linking gene expression patterns to stage transitions and deciphering the genetic triggers driving

11970-416: The parasite is passed to a feline host, the only host within which the parasite can again undergo sexual development and reproduction. In 2006, researchers reviewed evidence that T. gondii has an unusual population structure dominated by three clonal lineages called Types I, II and III that occur in North America and Europe, despite the occurrence of a sexual phase in its life cycle. They estimated that

12096-514: The parasite's reproductive success since rodents that do not avoid cat habitations will more likely become cat prey. The primary mechanisms of T. gondii –induced behavioral changes in rodents occur through epigenetic remodeling in neurons that govern the relevant behaviors (e.g. hypomethylation of arginine vasopressin -related genes in the medial amygdala , which greatly decrease predator aversion). In humans, particularly infants and those with weakened immunity , T. gondii infection

12222-430: The parasites undergo sexual development and reproduction, producing millions of thick-walled, zygote -containing cysts known as oocysts. Felines are the only definitive host because they lack expression of the enzyme delta-6-desaturase (D6D) in their intestine. This enzyme converts linoleic acid ; the absence of expression allows systemic linoleic acid accumulation. Recent findings showed that this excess of linoleic acid

12348-429: The passage of partially digested food ( chyme ) from the stomach into the duodenum , the first and shortest part of the small intestine, where peristalsis takes over to move this through the rest of the intestines. In the human digestive system , the stomach lies between the esophagus and the duodenum (the first part of the small intestine ). It is in the left upper quadrant of the abdominal cavity . The top of

12474-590: The pellicle includes a layer of closely packed vesicles called alveoli. In euglenids , the pellicle is formed from protein strips arranged spirally along the length of the body. Familiar examples of protists with a pellicle are the euglenoids and the ciliate Paramecium . In some protozoa, the pellicle hosts epibiotic bacteria that adhere to the surface by their fimbriae (attachment pili). Some protozoa live within loricas – loose fitting but not fully intact enclosures. For example, many collar flagellates ( Choanoflagellates ) have an organic lorica or

12600-1338: The phylogenetic tree of eukaryotic groups. The Metamonada are hard to place, being sister possibly to Discoba , possibly to Malawimonada . Ancyromonadida FLAGELLATE PROTOZOA Malawimonada FLAGELLATE PROTOZOA CRuMs PROTOZOA, often FLAGELLATE Amoebozoa AMOEBOID PROTOZOA Breviatea PARASITIC PROTOZOA Apusomonadida FLAGELLATE PROTOZOA Holomycota ( inc. multicellular fungi ) FUNGAL PROTISTS Holozoa ( inc. multicellular animals ) AMOEBOID PROTOZOA ? Metamonada FLAGELLATE PROTOZOA Discoba EUGLENOID PROTISTS (some photosynthetic), FLAGELLATE/AMOEBOID PROTOZOA Cryptista PROTISTS (algae) Rhodophyta ( multicellular red algae ) PROTISTS (red algae) Picozoa PROTISTS (algae) Glaucophyta PROTISTS (algae) Viridiplantae ( inc. multicellular plants ) PROTISTS (green algae) Hemimastigophora FLAGELLATE PROTOZOA Provora FLAGELLATE PROTOZOA Haptista PROTOZOA Telonemia FLAGELLATE PROTOZOA Rhizaria PROTOZOA, often AMOEBOID Alveolata PROTOZOA Stramenopiles FLAGELLATE PROTISTS (photosynthetic) Reproduction in Protozoa can be sexual or asexual. Most Protozoa reproduce asexually through binary fission . Many parasitic Protozoa reproduce both asexually and sexually . However, sexual reproduction

12726-484: The population of the parasite inside the cat's intestine before sexual reproduction. When a feline definitive host consumes a tissue cyst (containing bradyzoites), bradyzoites convert into merozoites inside intestinal epithelial cells. Following a brief period of rapid population growth in the intestinal epithelium, merozoites convert into the noninfectious sexual stages of the parasite to undergo sexual reproduction, eventually resulting in zygote-containing oocysts. Studying

12852-433: The primitive gut. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, and the esophagus, and stomach form from the foregut. As the stomach rotates during early development, the dorsal and ventral mesentery rotate with it; this rotation produces a space anterior to the expanding stomach called the greater sac, and a space posterior to the stomach called the lesser sac. After this rotation

12978-470: The protozoa were understood to be animals and studied in departments of Zoology, while photosynthetic microorganisms and microscopic fungi—the so-called Protophyta—were assigned to the Plants, and studied in departments of Botany. Criticism of this system began in the latter half of the 19th century, with the realization that many organisms met the criteria for inclusion among both plants and animals. For example,

13104-419: The protozoa, such as the ciliates , dinoflagellates , foraminifera , and the parasitic apicomplexans , which were moved to other groups such as Alveolata and Stramenopiles , under the polyphyletic Chromista . The Protozoa in this scheme were paraphyletic , because it excluded some descendants of Protozoa. The continued use by some of the 'Protozoa' in its old sense highlights the uncertainty as to what

13230-569: The question of T. gondii transmission to humans. Even though "living in a household with a cat that used a litter box was strongly associated with infection," and that living with several kittens or any cat under one year of age has some significance, several other studies claim to have shown that living in a household with a cat is not a significant risk factor for T. gondii infection. Specific vectors for transmission may also differ based on geographic location. "The seawater in California

13356-528: The rodents' chances of being preyed upon by felids. Support for this "manipulation hypothesis" stems from studies showing that T. gondii -infected rats have a decreased aversion to cat urine while infection in mice lowers general anxiety , increases explorative behaviors and increases a loss of aversion to predators in general. Because cats are one of the only hosts within which T. gondii can sexually reproduce, such behavioral manipulations are thought to be evolutionary adaptations that increase

13482-409: The same regions as in humans. Furthermore, in many non-human mammals, a portion of the stomach anterior to the cardiac glands is lined with epithelium essentially identical to that of the esophagus. Ruminants , in particular, have a complex stomach, the first three chambers of which are all lined with esophageal mucosa. In birds and crocodilians , the stomach is divided into two regions. Anteriorly

13608-413: The sexual phases of the T. gondii life cycle remains challenging and determining the precise triggers and molecular mechanisms governing this developmental program remains an ongoing area of research. Major challenges associated with the ability to cultivate presexual and sexual stages of T. gondii in vitro have limited our understanding of this developmental program and how it is triggered by

13734-449: The small intestine, some absorption of certain small molecules nevertheless does occur in the stomach through its lining. This includes: The parietal cells of the human stomach are responsible for producing intrinsic factor , which is necessary for the absorption of vitamin B12 . B12 is used in cellular metabolism and is necessary for the production of red blood cells , and the functioning of

13860-462: The stomach and small intestine, freeing sporozoites from within the oocyst. The parasites first invade cells in and surrounding the intestinal epithelium, and inside these cells, the parasites differentiate into tachyzoites, the motile and quickly multiplying cellular stage of T. gondii . Tissue cysts in tissues such as brain and muscle tissue, form about 7–10 days after initial infection. Although severe infection of M. rufus has been observed it

13986-418: The stomach lies against the diaphragm . Lying behind the stomach is the pancreas . A large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower esophageal sphincter (found in the cardiac region), at the junction of the esophagus and stomach, and the pyloric sphincter at

14112-432: The stomach through the actions of hydrochloric acid, and the enzyme pepsin . The stomach can also produce gastric lipase , which can help digesting fat. The contents of the stomach are completely emptied into the duodenum within two to four hours after the meal is eaten. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by high-protein foods. Meals with

14238-484: The stomach') are both derived from Greek gaster ( γαστήρ ) 'belly'. Although the precise shape and size of the stomach varies widely among different vertebrates, the relative positions of the esophageal and duodenal openings remain relatively constant. As a result, the organ always curves somewhat to the left before curving back to meet the pyloric sphincter. However, lampreys , hagfishes , chimaeras , lungfishes , and some teleost fish have no stomach at all, with

14364-414: The stomach, is the use of an endoscope . A gastric emptying study is considered the gold standard to assess the gastric emptying rate. A large number of studies have indicated that most cases of peptic ulcers , and gastritis , in humans are caused by Helicobacter pylori infection, and an association has been seen with the development of stomach cancer . A stomach rumble is actually noise from

14490-614: The study of presexual stages and opening new avenues for using genetics to drive the full sexual cycle in vitro . Specifically, the depletion of AP2XI-2 and AP2XII-1 in T. gondii induces merozoite-specific gene expression, raising the possibility for cultivating T. gondii sexual development in laboratory settings. Crucial questions still persist regarding the genetic determinants that dictate whether parasites develop into macrogametes or microgametes. The development of new molecular and genomic approaches, such as single-cell transcriptomics and proteomics , should be useful to those in

14616-420: The switch from asexual to sexual development remain unresolved. Important recent advancements in the field have shed new light on the regulatory mechanisms governing sexual development in T. gondii . Farhat and colleagues showed that chromatin modifiers MORC and HDAC3 play critical roles in silencing sexual development-specific genes. In MORC-depleted parasites, a broad activation of sexual gene expression

14742-490: The thyroid cells, such as primitive gastroenteric cells, migrated and specialized in uptake of iodide and in storage and elaboration of iodine compounds during vertebrate evolution. In fact, the stomach and thyroid share iodine-concentrating ability and many morphological and functional similarities, such as cell polarity and apical microvilli, similar organ-specific antigens and associated autoimmune diseases, secretion of glycoproteins (thyroglobulin and mucin) and peptide hormones,

14868-749: The traditional Protozoa was not a clade , a natural group with a common ancestor, some authors have continued to use the name, while applying it to differing scopes of organisms. In a series of classifications by Thomas Cavalier-Smith and collaborators since 1981, the taxon Protozoa was applied to certain groups of eukaryotes, and ranked as a kingdom. A scheme presented by Ruggiero et al. in 2015, placed eight not closely related phyla within Kingdom Protozoa: Euglenozoa , Amoebozoa , Metamonada , Choanozoa sensu Cavalier-Smith, Loukozoa , Percolozoa , Microsporidia and Sulcozoa . This approach excludes several major groups traditionally placed among

14994-571: The use of temporary extensions of cytoplasm called pseudopodia ). Many protozoa, such as the agents of amoebic meningitis, use both pseudopodia and flagella. Some protozoa attach to the substrate or form cysts, so they do not move around ( sessile ). Most sessile protozoa are able to move around at some stage in the life cycle, such as after cell division. The term 'theront' has been used for actively motile phases, as opposed to 'trophont' or 'trophozoite' that refers to feeding stages. Unlike plants, fungi and most types of algae, most protozoa do not have

15120-506: The websites of United States Centers for Disease Control and Prevention and the Mayo Clinic . Basic food-handling safety practices can prevent or reduce the chances of becoming infected with T. gondii , such as washing unwashed fruits and vegetables, and avoiding raw or undercooked meat, poultry, and seafood. Other unsafe practices such as drinking unpasteurized milk or untreated water can increase odds of infection. As T. gondii

15246-502: The wildlife population were increased where there are high amounts of cat populations. This creates a dangerous environment for organisms that have not evolved in cohabitation with felines and their contributing parasites. Toxoplasmosis is one of the contributing factors toward mortality in southern sea otters , especially in areas where there is large urban run-off. In their natural habitats, sea otters control sea urchin populations and, thus indirectly, control sea kelp forests. By enabling

15372-406: Was clarified by transplantation experiments of Aufderheide in 1986. These experiments demonstrated that the macronucleus, and not the cytoplasm, is responsible for clonal aging. Stomach The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals, including several invertebrates . The stomach has a dilated structure and functions as

15498-647: Was coined in 1818 by zoologist Georg August Goldfuss (=Goldfuß), as the Greek equivalent of the German Urthiere , meaning "primitive, or original animals" ( ur- 'proto-' + Thier 'animal'). Goldfuss created Protozoa as a class containing what he believed to be the simplest animals. Originally, the group included not only single-celled microorganisms but also some "lower" multicellular animals, such as rotifers , corals , sponges , jellyfish , bryozoans and polychaete worms . The term Protozoa

15624-420: Was first described in the 1960s. This term was coined also to indicate the presence of thyroid autoantibodies or autoimmune thyroid disease in patients with pernicious anemia, a late clinical stage of atrophic gastritis. In 1993, a more complete investigation on the stomach and thyroid was published, reporting that the thyroid is, embryogenetically and phylogenetically, derived from a primitive stomach, and that

15750-585: Was little evidence that T.   gondii was related to increased risk of psychiatric disorder, poor impulse control, personality aberrations, or neurocognitive impairment. However, there is evidence that T. Gondii may cause suicidal ideation and suicide in humans. T. gondii is one of the most common parasites in developed countries; serological studies estimate that up to 50% of the global population has been exposed to, and may be chronically infected with, T. gondii ; although infection rates differ significantly from country to country. Estimates have shown

15876-550: Was observed. In a later study, it was suggested that MORC-depleted parasites have disrupted sub-telomeric gene silencing. The disorganization in telomeres may have led to the misregulation of sexual development. Moreover, the discovery of specific transcription factors essential for sexual commitment has provided invaluable insights into the intricate regulatory network orchestrating stage specificity in T. gondii . Multiple parasite transcription factors have been identified as critical suppressors of presexual development, permitting

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