Forestomach Mucosa Research Articles

A 90-day repeated oral dose toxicity study of 2-Butylbenzo[d]isothiazol-3(2H)-one in rats

2-Butylbenzo[d]isothiazol-3(2H)-one (BBIT, CAS No. 4299-07-4) is widely used as an industrial antiseptic and antifungal agent. To investigate its toxicological properties and determine the no-observed-adverse-effect level (NOAEL), a 90-day repeated oral toxicological study of BBIT was conducted in Crl:CD (SD) rats at doses of 0 (vehicle control, corn oil), 30, 90, or 270 mg/kg/day. There was no mortality or abnormal clinical signs related to treatment in any group. Slightly decreased body weight and food consumption were observed in the 270 mg/kg group in females. Increased urine volume and kidney weight, increased liver weight, and thickening of the forestomach mucosa in autopsy were observed in both sexes in the 270 mg/kg group. Histopathological examination revealed that hyperplasia of the squamous epithelium of the forestomach with parakeratosis and/or hyperkeratosis was observed in both sexes in all the BBIT-treated groups. Moreover, centrilobular hypertrophy of hepatocytes was observed in both sexes of the 270 mg/kg group. Similarly, increased depositions of eosinophilic bodies and/or hyaline droplets in the proximal tubules of the kidney were observed among the male in the 270 mg/kg group. Based on the forestomach changes, NOAEL was judged to be less than 30 mg/kg/day in both sexes under this study’s conditions.

Stereomicroscopic and scanning electron microscopic observations of the forestomach mucosa of Akkaraman sheep fed with straw-concentrate diet

Stereomicroscopic and scanning electron microscopic observations of the forestomach mucosa of Akkaraman sheep fed with straw-concentrate diet

Histomorphometric Characterization of Forestomach of Yak (Bos grunniens) in the Qinghai-Tibetan Plateau

Six forestomachs of yaks (Bos grunniens) were studied with gross dissection and histological methods. It was found that the forestomach of yak consisted of the following three parts, rumen, reticulum and omasum, which were composed of the mucosa, submucosa, muscularis and serosa. In addition, the mucosal epithelium was covered with stratified squamous epithelium, with part of keratinized the shallow cells. Rumen, the mucosa of which formed ligulate papillae varying in size and shape, was no muscularis mucosa. Reticulum, consisted of a surface epithelium that invaginated to various extent into the lamina propria, formed various folds in shape, namely, grid-like small rooms. Furthermore, there are many secondary folds densely covered with keratinized papillae. The most striking feature of the omasum was to be formed the laminae omasi varying in length, with short and rough papillae distributing on both sides. Taken together, there was no glands within the mucosa and lamina propria of forestomach of yak, where diffuse lymphoid tissues can be observed clearly. It is, therefore, believed that the yak forestomach may have evolved those specific structural characteristics in response to the unique living environment and dietary habits impose on the Qinghai-Tibetan Plateau.

The effects of chronic bile reflux on the gastric mucosa of rats

To establish a rat model mimicking human bile reflux for studying the pathological effects of chronic bile reflux. The duodenum of Sprague-Dawley rats was transected below the opening of the common bile duct, and a gastrojejunostomy was performed at the greater curvature of the forestomach. After the rats demonstrated bile reflux for 1 year, we studied the pathological features of the glandular stomach and forestomach mucosa. We also studied the effect of bile reflux on gastrin expression in the glandular stomach mucosa by using immunohistochemistry. Chronic bile reflux caused significant hyperplasia and expansion of gastric glands in the glandular stomach. Dysplasia and cancer formation also developed, but the incidence was significantly lower than that reported in the literature. Intestinal metaplasia and ulceration in the glandular stomach were also rare. In the forestomach, the squamous epithelium showed significant hyperplasia and keratinization along with keratin pearls and keratocysts. Intestinal metaplasia was rare and no tumorigenesis was observed. Chronic bile reflux significantly increased gastrin expression in the glandular stomach mucosa. When simulating the physiological bile reflux pathway, chronic bile reflux caused hyperplasia and expansion of gastric glands in the glandular stomach and squamous epithelial hyperplasia and keratinization in the forestomach.

Clinical Epidemiological Investigation of Moldy Grain and Fodder Poisoning in Goat in Kathmandu Valley

An outbreak of a syndrome of unknown etiology associated with the feeding of moldy maize grain and green fodder to goat in a herd of male 3853goats for sale for the Dashahara festival during the month of October2010 in Kathmandu valley. In a period of 10 days 500 goats suddenly became ill with symptoms of anorexia, apathy, diarrhea and ruminal stasis .On clinical examination these goats were provisionally diagnosed with sudden illness and moldy corn/fodder poisoning was suspected. They were treated with Biolive,tetrachlor, polyte, C-lyte,Stress care, Antidegnala liquor, but 250 goats died. Necrosis of the fore stomach mucosa was the most characteristic gross pathological change. Clinical pathological findings included mild focal erosions to severe, diffuse, coagulative necrosis of the mucosa in the rumen, reticulum and omasum and congestion and hemorrhages in the abomasum. Liver with shrunken appearance and pale to yellowish discoloration with bile filled distended bladder pin point hemorrhage in kidney, intestine with excessive mucus. On mycological and microbiological examination of tissue samples from post-mortem of dead goat on respective medium revealed the growth of fungal pathogens like Penicillium spp with Staphylococcus..These results provide circumstantial evidence that feeding on moldy maize grain and green fodder leaves infested with Penicillium may cause outbreaks of systemic Mycosis in goats.

Clinical Epidemiological Investigation of Moldy Grain and Fodder Poisoning in Goat in Kathmandu Valley

An outbreak of a syndrome of unknown etiology associated with the feeding of moldy maize grain and green fodder to goat in a herd of male 3853goats for sale for the Dashahara festival during the month of October2010 in Kathmandu valley. In a period of 10 days 500 goats suddenly became ill with symptoms of anorexia, apathy, diarrhea and ruminal stasis .On clinical examination these goats were provisionally diagnosed with sudden illness and moldy corn/fodder poisoning was suspected. They were treated with Biolive,tetrachlor, polyte, C-lyte,Stress care, Antidegnala liquor, but 250 goats died. Necrosis of the fore stomach mucosa was the most characteristic gross pathological change. Clinical pathological findings included mild focal erosions to severe, diffuse, coagulative necrosis of the mucosa in the rumen, reticulum and omasum and congestion and hemorrhages in the abomasum. Liver with shrunken appearance and pale to yellowish discoloration with bile filled distended bladder pin point hemorrhage in kidney, intestine with excessive mucus. On mycological and microbiological examination of tissue samples from post-mortem of dead goat on respective medium revealed the growth of fungal pathogens like Penicillium spp with Staphylococcus..These results provide circumstantial evidence that feeding on moldy maize grain and green fodder leaves infested with Penicillium may cause outbreaks of systemic Mycosis in goats.

Zinc deficiency activates S100A8 inflammation in the absence of COX‐2 and promotes murine oral‐esophageal tumor progression

Zinc (Zn)-deficiency (ZD) is implicated in the pathogenesis of human oral-esophageal cancers. Previously, we showed that in ZD mice genetic deletion of cyclooxygenase-2 (Cox-2) enhances N-nitrosomethylbenzylamine-induced forestomach carcinogenesis. By contrast, Cox-2 deletion offers protection in Zn-sufficient (ZS) mice. We hypothesize that ZD activates pathways insensitive to COX-2 inhibition, thereby promoting carcinogenesis. This hypothesis is tested in a Cox-2−/− mouse tongue cancer model that mimics pharmacologic blockade of COX-2 by firstly examining transcriptome profiles of forestomach mucosa from Cox-2−/− and wild-type mice on a ZD vs. ZS diet, and secondly investigating the roles of identified markers in mouse forestomach/tongue preneoplasia and carcinomas. In Cox-2−/− mice exposed to the tongue carcinogen 4-nitroquinoline 1-oxide, dietary ZD elicited tongue/esophagus/forestomach carcinomas that were prevented by ZS. The precancerous ZD:Cox-2−/−vs. ZS:Cox-2−/− forestomach had an inflammatory signature with upregulation of the proinflammation genes S100a8 and S100a9. Bioinformatics analysis revealed overrepresentation of inflammation processes comprising S100a8/a9 and an nuclear factor (NF)-κB network with connectivity to S100A8. Immunohistochemistry revealed co-overexpression of S100A8, its heterodimeric partner S100A9, the receptor for advanced glycation end-products (RAGE), NF-κB p65, and cyclin D1, in ZD:Cox-2−/− forestomach/tongue preneoplasia and carcinomas, evidence for the activation of a RAGE-S100A8/A9 inflammatory pathway. Accumulation of p53 in these carcinomas indicated activation of additional inflammatory pathways. Zn-replenishment in ZD:Cox-2−/−mice reversed the inflammation and inhibited carcinogenesis. Thus, ZD activates alternative inflammation-associated cancer pathways that fuel tumor progression and bypass the antitumor effect of Cox-2 ablation. These findings have important clinical implications, as combination cancer therapy that includes Zn may improve efficacy.

Structural, Histochemical and Immunocytochemical Study of the Forestomach Mucosa in Domestic Ruminants

The forestomach plays an important role in the digestion physiology of ruminants. The aim of this study is to clarify the morpho-functional role of the mucosa in each of the three compartments of the forestomach in three domestic ruminants species, viz cattle, buffalo and sheep, by means of structural, histochemical and immunocytochemical methods, including transmission electron microscopy, light microscopy and scanning electron microscopy. These methods were chosen to demonstrate the indirect evidence for the presence of nitric oxide (NO) employing NADPHd and nitric oxide synthase I (NOS I). The various cell layers of the forestomach epithelium are described and illustrated in detail. An intense NADPHd staining was observed in the granulosa, spinosa and basal layers of the epithelium, in particular in the cytoplasm over the nucleus. NOS I immunoreactivity was found in all specimens of the forestomach mucosa. The results of this study might reflect a possible role of NO in delaying the onset of cellular apoptosis in the forestomach mucosa of the domestic ruminants, by playing a role in the production of cell energy.

Transfer and distribution of amoxicillin in the rat gastric mucosa and gastric juice and the effects of rabeprazole

To investigate the distribution of amoxicillin in the gastric juice and gastric mucosa of rats and to investigate the effects of proton pump inhibitor rabeprazole on amoxicillin concentrations in various compartments. One hundred and sixty anesthetized rats were divided into five groups, and given intravenously different doses of amoxicillin or amoxicillin and rabeprazole. The pH value and volume of gastric juice was aspirated were measured and separated gastric mucosa was homogenized. The concentrations of amoxicillin in the plasma, gastric juice and gastric mucosa were measured by high performance liquid chromatography (HPLC). The maximum concentrations of amoxicillin in gastric juice and gastric mucosa were significantly lower than those in plasma (P<0.001). Concentrations in the glandular stomach mucosa were higher than those in the forestomach mucosa. Rabeprazole did not significantly change the pharmacokinetic parameters of amoxicillin in the plasma and did not alter gastric antibiotic clearance or the gastric transfer fraction of amoxicillin in gastric juice. However, rabeprazole did increase the amoxicillin concentration and pH value in gastric juice and reduced the volume of the gastric juice. Amoxicillin could penetrate the gastric mucosa and achieve therapeutic concentrations at the target site after transfer from the blood to the stomach. Rabeprazole increased the amoxicillin concentration in gastric juice by decreasing the gastric juice volume but did not affect its concentration in blood or gastric mucosa.

Effects of the Antifungal Agent Itraconazole on Proliferative Changes of the Forestomach Mucosa in Alloxan-induced Diabetic Rats

Alloxan-induced diabetic rats frequently exhibit proliferative lesions of squamous hyperplasia accompanied by chronic inflammation and Candida albicans infection in the forestomach, and some lesions progress to squamous cell carcinoma (SCC). Candida infection causes not only hyperplastic changes with inflammation but might also lead to SCC in human oral mucosa. Thus, the present study was conducted to examine the effects of the antifungal agent itraconazole (ITCZ) on proliferative and inflammatory changes of the forestomach in alloxan-induced diabetic WBN/Kob rats. Diabetes was induced by alloxan at fifteen weeks of age. Rats were allocated to three groups at forty-five weeks of age and were given ITCZ by gavage 0 (vehicle control), 5, and 10 mg/kg/day for four weeks, and they were sacrificed at the sixty-fifth week of age. Mucosal hyperplastic changes were consistently accompanied by inflammation and Candida infections in the 0 mg/kg group. These lesions were reduced by ITCZ (0 mg/kg; 100%, 5 mg/kg; 53.5%, 10 mg/kg; 61.5%). Squamous cell carcinoma was detected in three rats from the 0 mg/kg, but only one rat from the 10 mg/kg dose groups in this study. Itraconazole reduced the degree of mucosal hyperplasia, inflammatory changes, and Candida infection. Therefore, C. albicans infection was an important factor in pathogenesis of mucosal proliferation and inflammation.

Prevention of proliferative changes of forestomach mucosa by blood glucose control with insulin in alloxan‐induced diabetic rats

Diabetes mellitus is one of the risk factors for carcinogenesis. Recently we reported that alloxan induces squamous cell carcinoma (SCC) with coincidental inflammation, bacteria/fungal infections, and a severe diabetic condition. The present study was conducted to examine the effects of blood glucose control with insulin on the proliferative changes of the forestomach in alloxan-induced diabetic rats. Male 15-week-old WBN/Kob rats were divided into a control group of non-treated rats with naturally occurring diabetes after 40 weeks of age (non-treated group), alloxan-induced diabetic rats (AL group), and alloxan-induced diabetic rats given insulin implant treatment (AL + In group). The animals were sacrificed at 90 weeks of age for histopathologic examination. The blood glucose and urinary glucose level of the AL + In group fluctuated variously from high to normal levels compared with a constantly high level of AL (for 75 weeks) as well as in the non-treated group (for 50 weeks). The mucosal hyperplasia in the forestomach developed in 88.2% of the AL group and 37.5% of the non-treated group, but in only 10.0% of the AL + In group. SCC was only detected in 23.5% of the AL group. Hyperplastic changes were constantly accompanied by inflammation and fungal/bacterial infections in the AL and non-treated groups, whereas inflammation and fungal infection were completely suppressed in the AL + In group. These findings demonstrate that blood glucose control suppressed neoplastic changes in alloxan-induced diabetic rats. We postulate that inflammation together with bacterial/fungal infections under prolonged severe diabetic conditions play a pivotal role in carcinogenesis.

Paradoxical effects of a selective cyclooxygenase-2 inhibitor, etodolac, on proliferative changes of forestomach in alloxan-induced diabetic rats

A single intravenous injection of alloxan, a non-genotoxic diabetogenic chemical, induces proliferative changes in forestomach mucosa of rats, and some lesions progress to squamous cell carcinoma accompanied with inflammatory change. The present study was conducted to examine the effects of a selective cyclooxygenase-2 (COX-2) inhibitor, etodolac, on the proliferative changes of forestomach mucosa in alloxan-induced diabetic rats. Alloxan-induced diabetic rats were fed a diet containing 0.01% etodolac (AL+Et group) and standard diet (AL group). They were sacrificed after 25 and 50 weeks of feeding, respectively. Squamous cell hyperplasia of forestomach was completely suppressed by etodolac after 25 weeks. After 50 weeks of treatment, the proliferative changes in forestomach developed in all rats of the AL+Et group, but in only 55.6% of the rats in the AL group. The severity of proliferative lesions was much enhanced in the AL+Et group compared to the AL group, and was parallel to the inflammatory changes in individual cases. Ulceration and erosion were more severe in the AL+Et group. These findings demonstrate that etodolac suppresses proliferative and inflammatory changes with COX-2 expression of forestomach in the early stage, but enhances them after 50 weeks.

Evaluation of potential human carcinogenicity of the synthetic monomer ethyl acrylate

Ethyl acrylate (EA) is an acrylic monomer used in the manufacture of a variety of polymers and copolymers as components of many commercially important products. Human exposure to EA occurs primarily in the workplace via inhalation or dermal contact. In F344 rat and B6C3F 1 mouse studies of EA carcinogenicity conducted by the National Toxicology Program [National Toxicology Program, NTP, 1986. Carcinogenesis Studies of Ethyl Acrylate (CAS No. 140-88-5) in F344/N Rats and B6C3F 1 Mice (Gavage Studies) (Tech. Rep. Ser. No. 259; NIH Publication No. 87-2515), Research Triangle Park, NC, USA], the only increased tumor incidences was in squamous cell papillomas and carcinomas of the forestomach, when EA was administered by gavage in corn oil at 100 or 200 mg/kg/day (high dose; HD). The neoplasms were preceded by forestomach irritation, inflammation, hyperkeratosis and hyperplasia of the forestomach mucosa. In studies in which rats and mice were exposed at comparable doses to EA in drinking water, by inhalation, or by dermal application, no neoplasms in the forestomach or in any other tissue were reported. EA exhibited clastogenicity and related mutagenicity in vitro, but was non-genotoxic in vivo, including in the forestomach of treated rats . The in vitro clastogenicity response correlates well with cellular toxicity, mediated by non-protein sulfhydryl depletion and mitochondrial impairment. Thus, the carcinogenicity in the forestomach can be ascribed to a non-genotoxic mode of action (MOA). The forestomach mucosal hyperplastic and even dysplastic changes, observed chronically, were reversible, provided the HD exposure was not longer than 6 months. This again supports a non-genotoxic MOA. In addition, the route and rate of EA exposure in rodents for forestomach neoplasia are irrelevant to potential human exposure, since humans do not have forestomach and are not exposed to EA by oral bolus. Thus, the weight of evidence indicates that the tumors produced in the rodent carcinogenicity studies arise from conditions that are irrelevant for human risk assessment.

Nitrapyrin: A scientific advisory group review of the mode of action and carcinogenicity in B6C3F1 mice

Nitrapyrin has been registered as a nitrogen stabilizer in the United States for many years based on a robust set of regulatory data. These data demonstrated that nitrapyrin was not genotoxic and that there were no tumors elicited in rats or mice that were relevant for human risk assessment. A repeat carcinogenicity study in B6C3F1 mice, conducted at two substantially higher-dose levels (0, 125 or 250 mg/kg/day) than the original study (0, 5, 25 or 75 mg/kg/day) identified liver, stomach, epididymal and Harderian gland tumors. In order to assess the relevance of these findings for human risk assessment, a Scientific Advisory Group (SAG) examined relevant microscopic changes in these tissues and also evaluated genotoxicity and mechanistic data. The SAG determined that the maximum tolerated dose had been exceeded in mice given 125 or 250 mg/kg/day, based on 26–33% decreased body weight gains (males—250 mg/kg/day), hepatocellular necrosis and compensatory hepatocellular proliferation (males and females—125 and 250 mg/kg/day). The SAG believed that the increased incidences of hepatocellular foci of alteration and hepatocellular neoplasms represented an epigenetic response to hepatocellular necrosis and increased mitogenesis. Increased incidences of proliferative lesions in the forestomach mucosa were likely secondary to the irritant effects of nitrapyrin. Neither the liver nor forestomach effects were interpreted to be a direct carcinogenic effect. Higher incidences of Harderian gland adenomas (females) and undifferentiated sarcomas in the epididymis represented normal biological variations in incidence and were unrelated to nitrapyrin. Therefore, it was the SAG’s opinion that nitrapyrin exposure that does not produce target organ toxicity in exposed individuals would not be expected to increase the risk of cancer.

In this issue

In this issue

Formation and persistence of DNA adducts during and after a long-term administration of 2-nitrofluorene

2-Nitrofluorene (NF) is an environmental pollutant. Our previous studies have shown that NF is a carcinogen, primarily targeting the liver, kidney and forestomach in rats. NF-induced DNA adducts were also shown higher levels in the tumor-targeting tissues compared to non-tumor targeting organs. The present study was aimed to observe the kinetics of DNA adduct formation and persistence during the process of NF-induced tumor formation. NF was supplemented in diet at three dose levels and was fed to rats continuously for up to 11 months. DNA adduct formation in the liver, kidney, spleen and stomach of rats after different period (10 days and 11 months) of NF administration was analyzed with 32 P -HPLC techniques. DNA adduct persistence in the liver was also assessed after the withdrawal of NF administration. Four major NF-DNA adducts (adducts A, B, C and D) were found in the liver and kidney. DNA adduct D showed high level in the forestomach mucosa after 10 days of NF feeding while adducts A and C were undetectable. DNA adduct C and D co-migrated with C3-(deoxyguanosin- N 2-yl)-2-acetylaminofluorene (dG- N 2-AAF) and N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF), respectively, by 32 P -HPLC co-chromatography. DNA adducts A and B constituted the major part (>80%) of NF-DNA adducts after a long period (11 months) of NF feeding. The four NF-DNA adducts showed different recovery from different enrichment procedures, i.e., nuclease P1 or butanol treatment. Three out of the four NF-DNA adducts were still detectable in the rat liver after 11 months on the basal diet. In conclusion, four major DNA adducts are induced by NF oral administration. Among those, one is identified as dG- N 2-AAF and another one as dG-C8-AF. The four NF-DNA adducts showed different kinetics of formation and persistence, which may play different roles in NF-induced tumor formation.

28-day repeated oral toxicity study of a hypolipidemic agent, NK-104 in rats.

NK-104, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, was administered orally to Wistar rats at a dose of 2, 10, 50 or 100 mg/kg for 28 days consecutively, and the toxicity of NK-104 and its recovery with 2 weeks cessation of drug treatment were examined. As major clinical signs, loose stool, diarrhea, crouching and emaciation were observed in both sexes at 50 or 100 mg/kg, and all females at 100 mg/kg died or became moribund due to severe emaciation before the completion of treatment. The suppression of body weight gain or decrease in body weight was observed in the female dose group at 50 mg/kg and both sexes at 100 mg/kg. Decreased food intake was observed in both sexes at 100 mg/kg. Moreover, an increase in cholinesterase (Ch.E) in the male dose groups at 50 and 100 mg/kg and an increase in glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in the female dose group at 50 mg/kg were observed in blood chemistry testing. Macroscopic examination showed thickening of the forestomach mucosa in the groups of 10 mg/kg or more. Microscopic examination revealed hyperkeratosis and hypertrophy of the spinous layer associated with both cell infiltration of the mucosal propria and submucosal edema. In addition, skeletal muscle lesions including atrophy, vacuolation and focal necrosis were observed in the female dose groups at 50 and 100 mg/kg. The above-mentioned microscopic changes were not observed on cessation of drug treatment. The non-toxic dose level of NK-104 in the 28-day repeated oral toxicity study using rats was determined to be 2 mg/kg.

Six-month repeated oral toxicity study of NK-104 in rats.

NK-104 is a novel potent inhibitor of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and has been shown to be a highly effective agent in lowering blood cholesterol. In the present study, NK-104 was orally administered to Wistar rats at a dose of 0.3, 1, 3 or 010 mg/kg for 6 months for examination of toxicity. Additional recovery groups of 8 rats each of both sexes receiving 0 and 10 mg/kg were maintained without treatment for 1 month in order to assess recovery. As a result, no toxicological changes were observed in general signs, body weight, food intake, ophthalmological examination, urinalysis, hematological and blood chemical examinations for organ weights. An autopsy revealed thickening of the forestomach mucosa in both sexes at a dose of 1 mg/kg or more. This change was microscopically recognized as hyperkeratosis and hypertrophy of the spinous layer associated with both cell infiltration of the mucosal propria and edema of sub-mucosa in the forestomach in both sexes at doses of 3 and 10 mg/kg. Forestomach changes were not observed in any cases after 1 month cessation of drug treatment. The non-toxic dose of NK-104 in the 6-month repeated oral toxicity study in rats is estimated to be 1 mg/kg/day.

Increase in γϖ T cells in the ruminal mucosa of reindeer calves ( Rangifer tarandus tarandus L.) induced by baled grass silage

Leukocytes in the forestomach mucosa of reindeer ( Rangifer tarandus tarandus L.) were investigated by immunoperoxidase staining of cryostat sections, using monoclonal antibodies against antigens on sheep leukocytes. Mucosal samples from three free-ranging reindeer calves were compared with samples from three calves fed baled grass silage previously shown to induce increased frequency of lesions in the ruminal epithelium. In both groups, MHC-II + cells and γϖ T cells were observed, located within or just below the basal layer of the stratified epithelium. Computer-assisted morphometric analysis showed that the number of γϖ T cells in the ruminal mucosa was higher in the silage-fed than in the free-ranging animals. No marked difference in number of MHC-II + Langerhans cells was observed between the groups.

T cell subsets and Langerhans cells in the forestomach mucosa of adult sheep and sheep foetuses

As part of a study on leukocytes in the ruminant forestomach the occurrence and distribution of T cells and major histocompatibility complex Class II positive (MHC-II +) cells in the forestomach mucosa of sheep were investigated. Samples were taken from the reticulum, atrium ruminis, ventral rumen, dorsal rumen and omasum of five healthy adult ewes and seven nearly fullborne foetuses. Frozen sections were stained with an indirect immunoperoxidase method using monoclonal antibodies against sheep MHC-II, CD4 and CD8 molecules and the sheep γδ T cell receptor. Both MHC-II + cells and T cells were distributed along the basal lamina of the epithelium, with either mainly intraepithelial (CD8 + and γδ + cells) or mainly subepithelial (MHC-II + and CD4 + cells) location. The MHC-II + cells showed dendritic morphology and were interpreted as Langerhans cells. In adult ewes CD4 + T cells comprised the major T cell subset at all sample sites. The number of T cells declined from the atrium ruminis through the ventral rumen to the dorsal rumen, while the number of Langerhans cells showed no marked variation between different sample sites. In foetuses, Langerhans cells showed a relatively high prevalence, while T cells were sparse and showed a more random distribution in the rumen wall. No marked variation between sample sites were observed in the fetal forestomachs. It is concluded that Langerhans cells and T cells are normally present in the forestomach mucosa of sheep, and it is suggested that the Langerhans cells represent a constituent component, while the prevalence and distribution of T cells may be influenced by antigen leakage through the epithelium.