Biomedical subjects

T J Gray

Publications and source records attributed to T J Gray.

77 records · Page 5Linked to original sources

PubMedDate not supplied

Alkaline phosphatase histochemistry discriminates peritubular cells in primary rat testicular cell culture.

Histochemical demonstration of alkaline phosphatase activity appears to be useful in identifying rat peritubular cells in primary testicular cell culture. In both frozen sections of rat testis and Mirsky's fixed, methacrylate-embedded rat testis, the reaction product localized primarily in peritubular cells, vascular endothelium and occasionally in interstitial cells, with much smaller amounts of reaction product associated with elongating spermatids in the germinal epithelium. Occasional late-stage tubules (X-XIV) showed weak reactivity in the epithelium, associated with spermatocytes or Sertoli cells. Ultrastructurally, Gomori-method reaction product was localized to peritubular cells, lymphatics, and spermatogonia in stage VII; no staining was found consistently in Sertoli cells. In isolated cell preparations enriched for Sertoli and germ cells, 1 to 8% of the cells demonstrated alkaline phosphatase activity, while greater than 50% of the cells stained positive for alkaline phosphatase activity in peritubular-enriched fractions. The histochemical demonstration of alkaline phosphatase activity can be useful for identifying peritubular cells in primary cultures of testicular cells.

Alkaline Phosphatase↗

PubMedDate not supplied

Development of an in vitro reporter gene assay to assess xenobiotic induction of the human CYP3A4 gene.

The current work concerns the development and validation of an in vitro reporter gene assay system for the assessment of induction of human CYP3A4. A plasmid containing approximately 1 kb of the CYP3A4 regulatory region (which contains several recognised regulatory elements including glucocorticoid responsive elements) coupled to the reporter gene for human secreted placental alkaline phosphatase (SPAP) was transfected into the human hepatoblastoma cell line HepG2. Calcium phosphate precipitation was the method of choice for transfection. The transfected cells were dosed with known inducers of CYP3A4 and the levels of SPAP in the medium were subsequently measured using a chemiluminescent assay, as an indirect measure of CYP3A4 induction. The inducers used in this study included dexamethasone, phenytoin, triacetyloleandomycin (TAO), rifampicin, carbamazepine, phenylbutazone and sulfinpyrazone. These compounds activated CYP3A4 by between 1.5-4.5-fold thus representing a major advance in assessing the induction of human CYP genes in vitro.

Alkaline Phosphatase↗

PubMedDate not supplied

Testicular toxicity in vitro: Sertoli-germ cell co-cultures as a model system.

Testicular damage is a comparatively common finding in toxicity studies. Part of the susceptibility of the testis to chemical toxicity stems from the complexity of its normal structure, function and regulatory control. This complexity has stimulated the development and extensive use of testicular cell cultures in the study of normal testicular function. However, the potential of such systems for investigating chemically induced testicular toxicity has only recently been considered. Using primary co-cultures of Sertoli and germ cells many features of the well characterized testicular damage produced by phthalate esters and glycol ethers could be reproduced in vitro. These encouraging findings are discussed in relation to some of the likely limitations to the application of in vitro models for testicular toxicity.

Acetates↗

PubMedDate not supplied

The mutagenicity and interactions of 2- and 4-(acetylamino)fluorene with cytochrome P450 and the aromatic hydrocarbon receptor may explain the difference in their carcinogenic potency.

A study has been undertaken to identify the properties of 2-(acetylamino)fluorene which render it carcinogenic, in contrast to the 4-isomer, the carcinogenic potential of which is, at best, very weak. Compared to the 4-isomer, 2-(acetylamino)fluorene was a more potent inducer of cytochrome P450 1A (P450 1A) activity, as exemplified by the O-deethylation of ethoxyresorufin (P450 1A1), the metabolic activation of Glu-P-1 (P450 1A2), and immunoblot analysis. These findings were consistent with the relative affinity of these compounds for the cytosolic aromatic hydrocarbon receptor, determined by the displacement of tetrachlorodibenzo-p-dioxin. In the presence of Aroclor 1254-induced hepatic microsomal and cytosolic preparations 2-(acetylamino)-fluorene elicited a potent mutagenic response in the Ames test whereas the 4-isomer, in both cases, elicited a weak mutagenic response. Molecular orbital calculations of the relative energetics of the nitrenium ions revealed that the ion of the 2-isomer was more stable than the nitrenium ion of 4-(acetylamino)fluorene. Control hepatic microsomal and cytosolic fractions could activate 2-(acetylamino)fluorene to mutagens in the Ames test. Pretreatment of animals with 2-(acetylamino)fluorene enhanced both the microsome- and cytosol-mediated activation. In contrast, microsomal and cytosolic fractions from control animals could not activate 4-(acetylamino)fluorene, but following pretreatment with the compound itself, a weak mutagenic response in the presence of microsomes, but not of cytosol, was evident.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Acetylaminofluorene↗

PubMedDate not supplied

Spectrum of peritoneal mesothelioma in childhood: clinical and histopathologic features, including DNA cytometry.

Different types of peritoneal mesothelioma (PM) occur in children and adults. All these share certain histopathologic features but differ in other aspects, such as age of occurrence, site and sex predominance, etiology, and biologic behavior. The article describes four patients, two with cystic PM (one of whom had multiple recurrences) and two with malignant PM (one of whom had pleural metastases). These cases illustrate the variable behavior of this tumor in childhood and highlight the difficulties encountered in diagnosis and treatment. Three different groups of mesothelioma are recognized: a classic, asbestos-related, malignant mesothelioma of adults, typically occurring in the pleural cavity; a multicystic mesothelioma, predominantly affecting the pelvic peritoneum of young women and associated with a good prognosis; and mesotheliomas in children, which are not associated with asbestos exposure and have an unpredictable biologic behavior requiring individual treatment strategies. In the patients studied, DNA index measured by flow cytometry showed a difference between the cystic (aneuploid) and malignant (diploid) tumors. The proliferative rate (S phase) of the tumor was low in all four cases.

Adolescent↗