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Biomedical subjects

J M Ward

Publications and source records attributed to J M Ward.

At least 19 recordsLinked to original sources
PubMed1992

Persistent infection of rabbits with bovine immunodeficiency-like virus.

Chronic infection of rabbits was induced by a single intraperitoneal injection of bovine immunodeficiency-like virus (BIV)-infected cells. Ten BIV-infected animals were monitored serologically for up to 2 years. Results of serologic and virus rescue assays indicated that all animals became infected and demonstrated a rapid and sustained BIV-specific humoral response. BIV was rescued by cocultivation from spleen, lymph nodes, and peripheral blood leukocytes of infected animals. Viral DNA in immune tissues was confirmed by polymerase chain reaction amplification of BIV sequences. These data and specific immunohistochemical staining of mononuclear cells of the spleen for BIV antigen suggest that the infection is targeted to immune system cells.

Animals↗
PubMed1992

Immunohistochemical evidence of high concentrations of metallothionein in pancreatic hepatocytes induced by cadmium in rats.

A recent study from our laboratory has shown that cadmium, a toxic heavy metal, is one of the most effective agents known for inducing hepatocytic transdifferentiation of the rat pancreas. With repeated injections of cadmium, the incidence of rats with pancreatic hepatocytic foci can be as high as 93%. Cadmium is also well known as a very potent inducer of metallothionein, a metal-binding protein that appears to be important in the biologic response to several toxic heavy metals in most tissues, including the pancreas. Therefore, the present study sought to determine if metallothionein was associated with cadmium-induced transdifferentiation of pancreatic cells. Expression of metallothionein was studied immunohistochemically by the peroxidase-antiperoxidase method in tissue sections of the pancreas of rats with pancreatic hepatocytes. High levels of metallothionein were localized primarily within the pancreatic hepatocytes. Surrounding normal pancreatic islet and acinar cells were not immunoreactive. Thus, metallothionein is expressed actively in cells transdifferentiated to hepatocytes by cadmium within the pancreas.

Animals↗
PubMed1992

Induction of tumours of the haematopoietic system by cadmium in rats.

Several of our recent studies in rats indicate an association between exposure to cadmium and haematopoietic tumours. In the first study, male WF rats received dietary cadmium (0-200 micrograms/g cadmium as cadmium chloride) for up to 77 weeks. A dose-related increase in large granular lymphocyte (LGL) leukaemia was observed with a maximal incidence in rats fed 100 micrograms/g cadmium. In a second study, male F344 rats received a single high dose of cadmium chloride (30 mumol/kg, s.c.) and were observed for 90 weeks. The high natural incidence of leukaemia in these rats (24%) was markedly reduced (6%) by this dose of cadmium. The paradoxical effects of cadmium on haematopoietic tumours may be the result of a dose-related spectrum of lymphotoxicity ranging from cell-specific cytotoxicity and carcinogenicity to destruction of key progenitor cell populations.

Animals↗
PubMed1979

Neoplastic and nonneoplastic lesions in aging (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice.

Neoplastic and nonneoplastic lesions in untreated (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice used as controls in carcinogenesis tests were tabulated and evaluated. The most common neoplasms in 2,543 male mice were hepatocellular adenomas and carcinomas. In 2,522 female mice, common tumors were lymphomas, leukemias, pulmonary adenomas and carcinomas, hepatocellular adenomas and carcinomas, and pituitary adenomas. The risk of developing most neoplasms increased with the age of the mouse. Hepatocellular carcinomas metastasized in 12% of the animals with these tumors. Other than lymphomas and leukemias, few other tumors metastasized. Nonneoplastic lesions included cystic hyperplasia of the uterus, nephritis, ovarian and uterine cysts, inflammatory lesions of the lung, mineralization in the brain, and focal hyperplasias in several tissues. The focal hyperplasias in lung and pituitary, adrenal, and thyroid glands were suggestive of the early stages of neoplasia. Comparative aspects of lesions in aging mice and their interpretation in carcinogenesis tests are discussed.

Age Factors↗
PubMed1979

Neoplasms and pigmentation of thyroid glands in F344 rats exposed to 2,4-diaminoanisole sulfate, a hair dye component.

2,4-Diaminoanisole sulfate was fed at dietary levels of 0.12% (low dose) or 0.5% (high dose) to groups of 50 male and 50 female inbred F344 rats for 78 weeks. By 107 weeks after the initial exposure, 58% of the male rats and 42% of the female rats administered the high dose had thyroid neoplasms, whereas only 7--8% of the controls developed them. Follicular cell carcinomas were the primary type of neoplasm induced. None of the controls had these tumors. The carcinomas, which were papillary, cystic, or solid, were highly invasive but did not metastasize. A brown pigment was present as granules primarily in thyroid follicular cells in all exposed rats. The amount of pigment as determined by an image-analyzing computer revealed that the cross-sectional area occupied by the pigment granules and the optical density of the granules were dose related.

Adenocarcinoma↗
PubMed1979

Histopathology of neoplastic and nonneoplastic hepatic lesions in mice fed diets containing tetrachlorvinphos.

Tetrachlorvinphos was fed at 8,000 or 16,000 ppm in diets to male and female (C57BL/6N X C3H/HeN)F1 mice for 80 weeks. Surviving mice were killed at 92 weeks, and all mice were completely necropsied. A high incidence of unusual nonneoplastic hepatic lesions in treated mice was present and characterized by pericellular fibrosis, hepatocyte nuclear pleomorphism, and intrasinusoidal foci of macrophages with intracytoplasmic crystalline structures. From 84 to 94% of the treated male mice and from 21 to 23% of the treated females had hepatocellular neoplasms. Only 17% of the control males and 7% of the control females had liver tumors. The induced tumors were frequently multiple in the liver, whereas the tumors in the controls were usually singular. The morphology of 241 liver tumors in 110 treated mice was different from that of tumors in controls. Liver tumors in control mice were generally composed of small basophillic hepatocytes. In treated mice, tumors were hepatocellular carcinomas composed of solid sheets of large basophilic or eosinophilic hepatocytes. Foci of prominent trabecular formation were seen in 51 tumors. Fifteen tumors were composed of small basophilic hepatocytes with oval cells interposed among them. Foci of capillary formation were noted in 3 of these tumors. In addition, 7 more typical hemangiosarcomas forming sinusoids and with thrombosis were observed.

Animals↗
PubMed1979

Renal carcinogenic and nephrotoxic effects of the flame retardant tris(2,3-dibromopropyl) phosphate in F344 rats and (C57BL/6N X C3H/HeN)F1 mice.

Tris(2,3-dibromopropyl) phosphate (TBP) was administered in the feed at one of two concentrations to groups of 55 male and 55 female inbred F344 rats and to 50 male and 50 female (C57BL/6N X C3H/HeN)F1 mice. The high and low dietary concentrations of TBP administered orally were 100 and 50 ppm for the rats, respectively, and 1,000 and 500 ppm for the mice, respectively. For each rodent type, 55 animals of each sex were used as contols. In both rodent types, renal epithelial tumors developed at incidences that were significant for male and female rats and mice that received the doses. These tumors included renal tubular cell adenomas and carcinomas that developed from the proximal convoluted tubular epithelium. Among female mice and rats, hyperplasia and/or dysplasia of the proximal convoluted tubular epithelium with or without cystic dilatation of the tubules and increase in the size of cell nuclei were dose dependent and recognized as preneoplastic and/or toxic lesions. The comparative histogenesis of renal tubular neoplasms was discussed.

Adenocarcinoma↗
PubMed1979

Histopathology of liver carcinomas in (C57BL/6N X C3H/HeN)F1 mice ingesting chlordane.

(C57BL/6N X C3H/HeN)F1 male mice that ingested 30 or 56 ppm chlordane and female mice that ingested 30 or 64 ppm chlordane in the diet had highly significant incidences of carcinomas of the liver. The carcinomas varied from well differentiated to poorly differentiated and undifferentiated and were capable of invasion and metastasis. They were more poorly differentiated in mice receiving chlordane than in controls.

Animals↗
PubMed1979

Evaluation of procedures suggested for reducing the pathology workload in a carcinogenesis testing program.

A sampling procedure for reducing the pathology workload in evaluating a carcinogenicity bioassay was utilized for a rodent bioassay. The use of the procedure resulted in 50 percent fewer tissues being examined histologically, in the control groups and 12 percent fewer tissues in the treatment groups. The obvious saving in pathologist's time was negated by an increase in technician time, interference with quality control procedures and loss of nontumor pathology information.

Animals↗
PubMed1979

Correlation between gross observations of tumors and neoplasms diagnosed microscopically in carcinogenesis bioassays in rats.

Microscopic diagnoses of spontaneous and induced neoplasms in F344 rats in two carcinogenesis bioassays were correlated with the gross observations made at the time of necropsy. The results for a negative and a positive compound with reference to carcinogenicity, indicate that of the gross descriptions indicative of tumors, 37 percent and 24 percent respectively, were not diagnosed as neoplasms microscopically. However, some of the gross lesions were diagnosed histologically as nonneoplastic lesions. Of the neoplasms diagnosed microscopically only 70 percent and 76 percent, respectively, were observed grossly. Endocrine tissues, liver and lung had the lowest correlation rates. The implications of these findings are discussed.

Animals↗
PubMed1978

Clinical and pathologic conditions of female nude (athymic) mice in two conventional maintained colonies.

Two colonies of female outbred nude (athymic) mice were maintained by conventional standards of husbandry, but with special sanitary methods and segregation from other rodents. A total of 1,526 mice entered the colonies. Of these, 802 were untreated and most remained healthy. Necropsies were performed on 312 untreated mice that were sick and were killed or died naturally, and the tissues were examined microscopically. Clinical and pathologic conditions in the untreated mice included subcutaneous abscessation, dermatitis, subcutaneous edema due to glomerulonephritis (nephrotic syndrome), rectal prolapse, and lymphomas and other neoplasms.

Abscess↗