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Biomedical subjects

M Pollard

Publications and source records attributed to M Pollard.

At least 181 records · Page 10Linked to original sources
PubMed1965

Detection of viruslike particles in germ-free mice.

Kajima, Masahiro (University of Notre Dame, Notre Dame, Ind.), and Morris Pollard. Detection of viruslike particles in germ-free mice. J. Bacteriol. 90:1448-1454. 1965.-Viruslike particles similar in structure to the mouse leukemia agent were detected by electron microscopy in thymus tissues of germ-free AK mice which had developed spontaneous leukemia. In addition, unique viruslike particles (type B) were detected in tissues from spontaneous mammary adenocarcinoma of germ-free C3H mice. Leukemia virus-like particles were also observed in the thymuses of the control AK mice and of the C3H control mice as well as of those with mammary tumors. Germ-free mice are not virus-free. The routes of transmission of leukemia as well as of mammary tumor viruses may be "vertical," through the embryo or placenta.

Animals↗
PubMedDate not supplied

Androgen receptor expression in primary prostate cancers of Lobund-Wistar rats and in tumor-derived cell lines.

Prostate tumors were induced in Lobund-Wistar rats by treatment with N-methyl-N-nitrosourea (MNU) and testosterone propionate (TP). Androgen receptor (AR) expression was confirmed in 16 (100%) of the primary prostate cancers, with strong uniform staining in well-differentiated tumors and more variable AR immunoreactivity in poorly differentiated tumors. Epithelial cell lines were established from nine of the tumors. At early passages, four of the tumor cell lines tested were strongly immunoreactive for AR; however, only two of the cell lines, E2(A) and F2, have remained AR-positive. These cell lines specifically bind 5H-DHT at 40 and 19 fmol/mg protein, respectively, and express a 110 kDa AR immunoreactive protein. Proliferation in in vitro culture of both E2(A) and F2 cells was increased in the presence of 5alpha-dihydrotestosterone (DHT). The antiandrogen, hydroxyflutamide was able to prevent the DHT-induced growth of E2(A) but not F2 cells. Furthermore, hydroxyflutamide alone increased proliferation of F2 cells, suggesting that the androgen signalling pathway in this cell line may be abnormal. Tumorigenicity of the AR-expressing and nonexpressing cell lines was confirmed by xenograft formation following subcutaneous inoculation into intact male nude mice. In summary, carcinogen-induced prostate tumors of Lobund-Wistar rats express AR and two of nine cell lines derived from the tumors express AR. Further evaluation of AR structure in primary prostate tumors forming spontaneously or following MNU and TP induction will determine whether, as in human prostate cancers, disease progression in Lobund-Wistar rats is associated with mutations in the AR gene.

Androgen Antagonists↗
PubMedDate not supplied

Tissue nitrogen and potassium variation in trauma, starvation, and realimentation.

Total body or exchangeable potassium is used as an important indicator of body cell mass in the study of body composition. Body composition studies have been used extensively in the study of nutrition but recent work has questioned the validity of using changes in total body potassium as a measure of protein or nitrogen variation. To investigate the relationship between tissue nitrogen and potassium during nutritional manipulation 382 tissue samples from 100 surgical patients were analyzed by Kjeldahl analysis for nitrogen content and flame photometric analysis for potassium content. Nitrogen was related to potassium in parenchymous or cellular tissues by the relationship N (mg/g) = 14.7 + 0.17 K (microEq/g). The tissue content of the two elements was highly correlated (r = 0.80, p less than or equal to 0.001). For skeletal muscle a similar relationship existed N (mg/g) = 16.6 + 0.15 K (microEq/g) (r = 0.76, p less than or equal to 0.001). These relationships held for all nutritional states and degrees of trauma and nutritional manipulation. In sequential parenchymous tissue samples obtained from 15 subjects delta N/delta K = 0.17 +/- 0.03 mg/microEq. Nonparenchymous or acellular tissue nitrogen and potassium were poorly correlated. The potassium content was very low in these tissues. Exchangeable potassium was a valid indicator of parenchymous tissue nitrogen and as such a legitimate measure of nutritional status.

Adult↗
PubMedDate not supplied

Prevention of induced prostate-related cancer by soy protein isolate/isoflavone-supplemented diet in Lobund-Wistar rats.

Based on epidemiological surveys, the low incidence of clinical prostate cancer among aged men in Japan and China were attributed to high consumption of soybean-derived food in which phytoestrogens have numerous anticancer mechanisms. The prostate model in Lobund-Wistar (L-W) rats produce high levels of testosterone (T). They are inherently predisposed to develop induced and spontaneous metastasizing adenocarcinomas, which are (T)-dependent in early stages and T-independent in advanced stages. In the experiment reported here, 2 groups of L-W rats (age 2 months) were fed soy-containing diets: (a) commercial diet L-485 (TekLad) with soy meal; or (b) a soy-free diet (L-474) in which casein was replaced by soy protein isolate/isoflavones (SPII). At age 3 months, all rats were inoculated i.v. with MNU; and 14 months later, 17/58 (29.3%) of rats on diet L-485 developed cancer in avg 12 months, compared to 5/50 (10%) of rats on the SPII diet in avg 12.1 months (P = 0.001). In the latter rats, the serum levels of T, and weights of testes were significantly reduced; but in the former rats, serum levels of T remained elevated, suggesting that soy meal in L-4,85 blocked the estrogenic effects of phytoestrogens.

Adenocarcinoma↗
PubMedDate not supplied

In vivo model systems for assessing an anti-cancer drug: responses of autochthonous and transplanted prostate tumors to cyclophosphamide.

Therapeutic effects of cyclophosphamide (CPA) were compared in L-W rats with (a) transplanted prostate adenocarcinomas (PAs), and (b) with induced autochthonous PAs. All rats, except controls, were treated by IP-administered CPA in slow-release silastic membranes (a) at time 0 after inoculation of transplanted PA cells; or (b) after development of palpable transplanted PAs thereof; or (c) after detection of palpable autochthonous PAs. The treated rats did not manifest evidence of CPA-related toxicity. The transplanted PAs and lung metastases thereof were suppressed by CPA; but, the same treatment schedule with CPA failed to modify continued growth of the autochthonous PAs. This report serves to emphasize the need for test systems of autochthonous model tumors of the counterpart disease in humans.

Animals↗