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Biomedical subjects

R A Squire

Publications and source records attributed to R A Squire.

At least 37 records · Page 2Linked to original sources
PubMed1981

Cerebral venous thrombosis in the rhesus monkey.

Cerebral venous thrombosis was identified in four rhesus monkeys. Two initially showed neurologic signs and three had diarrhea or dysentery. All four had severe intestinal disease, including three cases of ulcerative colitis complicated by extracerebral thromboembolic disease. Central nervous system lesions, confined to the centrum semiovale, were multiple thrombi of internal cerebral veins, perivenular demyelination, and gemistocytic astrocytosis. The lesions resembled those found in people with cerebral venous thrombosis, and support the hypothesis that perivenular demyelination may occur as a sequela to venous occlusion. The lesions were identical to those found in "leukoencephalosis and perivascular myelosis," an entity of unknown cause previously described in monkeys.

Animals↗
PubMed1981

Histiocytic sarcoma with a granuloma-like component occurring in a large colony of Sprague-Dawley rats.

Tumors from a large colony of over 2000 Sprague-Dawley rats were reviewed by a panel of pathologists under the auspices of Universities Associated for Research and Education in Pathology, In the course of this study, a distinct malignancy in 105 rats was segregated and given the name "histiocytic sarcoma." This report describes the histologic features and anatomic distribution of the tumor, along with its incidence by age and sex of the rat. The neoplasm is characterized by a spectrum of histologic patterns, one extreme resembling a sarcomatous process and the other a granulomatous process. The exact morphologic composition varied from animal to animal, as well as in tumors from the same animal. The sarcomatous pattern is composed of sheets of uniform cells, occasionally exhibiting phagocytosis. The granulomatous pattern contains epithelioid histiocytes, central areas of tumor necrosis surrounded by palisading cells, and multinucleate giant cells. The liver is the organ most commonly containing histiocytic sarcoma, both in animals with multiple tumors and in those with involvement of only one organ. Hepatic invasion is typified by expansion of the portal areas and infiltration of the sinusoids by tumor cells. The lung is the second most common site. The distribution of pulmonary tumors is bronchiolocentric and angiocentric. Other common sites included the lymph node and spleen, along with large soft tissue tumors of the mediastinum and retroperitoneum. Although occasional previous reports apparently have described a similar or identical neoplasm under varying names, no large group of tumors of this unique type in rats has been studied and characterized previously.

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

Rabbit cardiomyopathy associated with a virus antigenically related to human coronavirus strain 229E.

A new disease of rabbits is described. Following an acute febrile course, animals die or recover by the 11th day postinoculation. The characteristic pathologic finding is multifocal myocardial degeneration and necrosis. The disease can be transmitted by various routes with tissue filtrates or with infectious sera diluted to 10(-6) and passed through 0.1 micron filters. Virus particles with morphologic features characteristic of a coronavirus are present in infectious but not in normal rabbit serums. The antigen(s) in the infectious serums cross-reacts with the 229E and the OC43 strains of human coronavirus. Antigen cross-reacting with the 229E virus is detectable by immunofluorescent staining in frozen sections of heart tissue from sick but not from healthy animals. Animals surviving infection seroconvert to coronavirus specificity, as demonstrated by the presence in convalescent serums of antibody capable of reacting with the 339E virus. Susceptibility to infection has not been demonstrated in mice, hamsters, or guinea pigs, and the virus was not adapted for growth in tissue culture. It is uncertain whether the agent is a natural pathogen of rabbits or a coronavirus contaminant from another species, possibly human. The name rabbit infectious cardiomyopathy is suggested for this disease.

Animals↗
PubMed1978

Pathology of esophageal neoplasms and associated proliferative lesions induced in rats by N-methyl-N-benzylnitrosamine.

Multiple squamous cell neoplasms of the esophagus were induced in 24 inbred F344 rats by sc injection of N-methyl-N-benzylnitrosamine at a dose level of 2.5 mg/kg weekly for 20 weeks. All of these rats also developed papillomas, 67% developed pedunculated papillary carcinomas, and 63% developed carcinomas that invaded the wall. Of 191 total neoplasms, 66% were papillomas, 17% were papillary carcinomas, and 17% were carcinomas that invaded the wall. The neoplasms were well differentiated with various degrees of keratinization. Anaplastic areas were found in most lesions, but were more common in carcinomas. Neoplasms that invaded the wall were sessile, with prominent intraluminal growth, or infiltrating, with predominant intramural growth. Penetration through the wall was observed, but neither metastases nor invasion of adjacent tissues was found. In addition to neoplasms, atypical endophytic proliferation of basal and spinous cells was observed in some of these rats. Proliferative or neoplastic changes were not observed outside the upper gastrointestinal tract.

Animals↗
PubMed1978

Inhibitory effect of 13-cis-retinoic acid on urinary bladder carcinogenesis induced in C57BL/6 mice by N-butyl-N-(4-hydroxybutyl)-nitrosamine.

The effect of 13-cis-retinoic acid on the induction of urinary bladder carcinoma by N-butyl-N-(4-hydroxybutyl)nitrosamine (OH-BBN) was studied in male C57BL/6 mice. Animals received a total dose of either 90 or 140 mg of OH-BBN via gastric intubations of 7.5 or 10.0 mg of OH-BBN 2 times each week for 6 or 7 weeks, respectively. Seven days after the last OH-BBN intubation, animals were fed laboratory chow diet supplemented with either 200 mg of 13-cis-retinoic acid per kg or its placebo. Animals were killed at 6 months after the first carcinogen intubation. Highly invasive squamous and transitional cell carcinomas of the urothelium were found at autopsy. In the majority of these carcinomas, invasion of the bladder muscle wall by tumor cells had occurred. At the two dose levels of OH-BBN, feeding of 13-cis-retinoic acid reduced the incidence of both carcinomas and noninvasive papillomas, as well as the extent of neoplastic development in the urinary bladder. In mice receiving the lower dose of OH-BBN, the feeding of 13-cis-retinoic acid prevented the appearance of both squamous and transitional cell carcinomas with a reduction in incidence from 33 to 0% (p less than 0.01). The results of this study indicate that 13-cis-retinoic acid reduced not only the severity of highly invasive urinary bladder carcinomas but also the incidence of such cancers.

Animals↗
PubMed1977

13-cis-retinoic acid: inhibition of bladder carcinogenesis in the rat.

Transitional cell and squamous cell cancer of the bladder was induced in Wistar/Lewis female rats by direct instillation of N-methyl-N-nitrosourea into the bladder. Feeding of the synthetic retinoid, 13-cis-retinoid acid, inhibited the incidence and extent of bladder cancer in these rats, even when 13-cis-retinoic acid administration was begun after completion of the carcinogen treatment.

Animals↗
PubMed1977

A carcinogenicity assay of Mirex in Charles River CD rats.

The long-term administration of 50 and 100 ppm of Mirex in the diets of male and female Charles River CD rats was associated with a spectrum of liver lesions, from foci or areas of cellular alteration and neoplastic nodules to hepatocellular carcinoma. Statistically significant numbers of neoplastic nodules were observed in the livers of male rats receiving the high dose. Neoplastic nodules and hepatocellular carcinomas were not observed in control rats.

Animals↗
PubMed1977

Histopathological evaluation of the inhibition of rat bladder carcinogenesis by 13-cis-retinoic acid.

An objective system for histopathological and statistical evaluation of rat bladder lesions induced by the carcinogen, N-methyl-N-nitrosourea, is described. This system has been used to measure the inhibitory effects of 13-cis-retinoic acid on the development of bladder cancer in female Wistar/Lewis rats. 13-cis-Retinoic acid caused significant inhibition of development of both preneoplastic and neoplastic lesions in bladder epithelium.

Animals↗
PubMed1975

Induction of liver tumor in Sherman strain female rats by polychlorinated biphenyl aroclor 1260.

Sherman strain female rats (200) were fed 100 ppm of polychlorinated biphenyl (Aroclor 1260) for apporximately 21 months, and 200 female rats were kept as controls. The rats were killed when 23 months old. Twenty-six of 184 experimental animals and 1 of 173 controls had hepatocellular carcinomas. None of the controls but 146 of 184 experimental rats had neoplastic nodules in their livers, and areas of hepatocellular alteration were noted in 28 of 173 controls and 182 of 184 experimental animals. Thus the polychlorinated biphenyl Aroclor 1260, when fed in the diet, had a hepatocarcinogenic effect in these rats. The incidence of tumors in other organs did not differ appreciably between the experimental and control groups.

Animals↗