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Biomedical subjects

M J Wilson

Publications and source records attributed to M J Wilson.

At least 199 records · Page 11Linked to original sources
PubMed1976

Presence and androgen control of an alkaline phosphatase in the nucleus of rat ventral prostate.

The presence of alkaline phosphatase (EC 3.1.3.1) activity has been demonstrated in nuclei of rat ventral prostate. This enzyme activity remained after washing of isolated nuclei with 0.5% Triton X-100; an acid phosphatase initially present with the nuclear fraction was removed by this treatment. The nuclear alkaline phosphatase, examined by utilizing p-nitrophenyl phosphate as substrate, had a pH optimum of 9.5-10.3, and a broad substrate specificity: p-nitrophenyl phosphate greater than phosphothreonine greater than beta-glycerophosphate greater than phosphoserine. The nuclear phosphatase was sensitive to denaturation by heat or urea treatments and was also inhibited by Pi, L-phenylalanine, homoarginine, dithiothreitol, and EDTA. The EDTA-inhibited enzyme was maximally reactivated by Zn2+, although Mg2+, or Ca2+ were also effective at somewhat higher concentrations. Orchiectomy of adult rats resulted in an increase in the nuclear alkaline phosphatase activity (2-3-fold at 24 or 48 h postorchiectomy). A decline in the protein: DNA ratio also occurred following orchiectomy, but the increase in phosphatase specific activity was evident whether expressed per unit of protein or per unit of DNA. Testosterone replacement following orchiectomy abolished the increase in nuclear phosphatase activity. The results suggest that the prostatic nuclear alkaline phosphatase may be involved in events related to inactivation of the prostate nucleus following androgen deprivation.

Alkaline Phosphatase↗
PubMed1976

Rat liver cells in culture: effect of storage, long-term culture, and transformation on some enzyme levels.

Aryl hydrocarbon hydroxylase (AHH) and tyrosine aminotransferase (TAT) activities were determined in rat liver cell lines after frozen storage, long-term culture, and transformation in vitro. Levels of AHH activity after 17 months in frozen storage were comparable to levels prior to freezing. During long-term culture the AHH levels of the cell lines tended to decrease. Transformed lines had variable levels of AHH activity. Cell lines retained measurable TAT activity following long-term culture and frozen storage. TAT activity of transformed cells was comparable to that of normal lines. Prolonged frozen storage did not induce transformation up to one year.

Animals↗
PubMed1976

The melanogenic response to testosterone in scrotal epidermis: effects on tyrosinase activity and protein synthesis.

Pigmentation of the scrotum of the black-pelted rat, as expressed through melanocyte melanogenic activity, is controlled by androgens. Castration decreased in vitro incorporation of [14C]tyrosine into melanin. Testosterone pre-treatment for 4 days increased malanin radioactivity over castrate cont rols; the increment in vitro was prevented by an inhibitor of protein systhesis (cycloheximide) added to the incubation. However, cycloheximide only partially blocked melanin synthesis when added to tissue from animals hromone treated for 6 days in vivo, and was ineffective in tissue from intacts. Bulk protein snthesis in vitro (incorporation of [14C]tyrosine or -leucine) was not affected by castration or testosterone treatment but was uniformly inhibited by cycloheximide. The data suggest that new synthesis of specific protein in vitro was necessary for initial hormone-stimulation of melanogenesis, but with longer exposure to hormone sufficient protein was pre-synthetized in vivo to permit melanogenesis during incubation with the inhibitor.

Animals↗
PubMed1976

The differential response of prostatic nucleolar and extra-nucleolar protein phosphokinase activities following androgen deprivation.

Protein phosphokinase activities of nucleolar and extra-nucleolar compartments of rat ventral prostate nuclei were measured using the model acidic phosphoprotein, dephosphophosvitin, as substrate. Following orchiectomy, the activity in both of these fractions declined; however, the kinase activity of the nucleolus decreased at a much greater rate than that in the extra-nucleolar portion of the nucleus. Testosterone maintenance of castrated animals prevented this decline in activity. The regulation of protein phosphokinases which phosphorylate prostatic nucleolar acidic proteins may be an important mechanism in the androgen mediated activation of the nucleolus in this target tissue.

Animals↗
PubMed1975

Preparation of prostatic plasma membranes Distribution of (Na-+, K-+)-ATPase and Mg-2+-ATPase in the rat ventral prostate.

1. A method is described for the isolation of a plasma membrane fraction from rat ventral prostate. This fraction is greatly enriched in (Na-", K-+)-ATPase but also contains a small amount of Mg-2+-ATPase and 5'-nucleotidase activities. 2. The activity ratio (Mg-2+ plus Na-+ plus K-+/Mg-2+ or Mg-+ plus Na-+) of the plasma membrane (Na-+, K-+)-ATPase was 1.7. The enzyme system specifically requires ATP as substrate and is inhibited by Ca-2+ or ouabain.

Adenosine Triphosphatases↗
PubMed1975

Chromatin-associated protein phosphokinases of rat ventral prostate. Characteristics and effects of androgenic status.

Protein phosphokinase activity endogenous to rat ventral prostate chromatin was assayed by using edphosphophosvitin as an exogenous substrate. For maximal activity of the kinase reaction, the presence of 200 mM NaCl, 5 mM MgCl2, and 1 mM dithiothreitol was essential. Two apparent pH optima were observed, a broad one between pH 7 and 7.4, and one at pH 7.89. At pH 7.4 the apparent Km for 31% dephosphophosvitin was 0.3 mg per ml. With respect to ATP, two apparent Km values (0.04 and 0.41 mM) were found. The kinase activity was minimal toward exogenous histones when used as substrates (3% for lysine-rich and 0.3% for arginine-rich (f3) histones, compared with dephosphophosvitin controls). The protein phosphokinases were not significantly stimulated by cyclic adenosine 3':5'-monophosphate (cyclic AMP) when histones used as substrate. With dephosphophosvitin as substrate, cyclic AMP produced a small inhibition (5 to 15%). Orchiectomy of adult rats resulted in a rapid decline in the chromatin-associated protein phosphokinase activity assayed using optimal experimental condition described above. At 9 hours postorchiectomy, a 30% decline in the activity was observed; this was further reduced to about 50% of the control by 18 hours. This decrease in the kinase activity (e.g. at 9 hours postorchiectomy) appears to precede measurable changes in the protein and RNA complements of chromatin. Testosterone replacement following orchiectomy abolished this decline in the chromatin-associated activity. The chromatin-associated protein phosphokinase activity toward lysine-rich and arginine-rich histones was also sensitive to androgenic status of the animals and declined rapidly postorchiectomy. The results suggest the presence of multiple and androgen-sensitive protien phosphokinases associated with rat ventral prostate chromatin, which may modulate the phosphorylation of nuclear nonhistone phosphoproteins with changing gene action mediated by testosterone in this target tissue.

Adenosine Triphosphate↗
PubMed1975

Phosvitin phosphate content. Implications for protein kinase assay.

The maximal rates of the protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) reaction studied with chicken egg yolk phosvitin as substrate are dependent on the level of dephosphorylation of phosvitin. 30 per cent dephospho-phosvitin gives the optimal initial rates. With varying levels of dephosphorylation, the apparent Km for the substrate also changes in a biphasic manner. If this factor is taken into account, and a suitable adjustment is made for the concentration of dephospho-phosvitin in the reaction it is possible to achieve maximal rates for the kinase reaction with phosvitin preparations of varying levels of dephosphorylation. Such a consideration is important for comparing the results of protein kinase studies using phosvitin as the substrate.

Adenosine Triphosphate↗
PubMed1972

Quantitative sputum culture as a means of excluding false positive reports in the routine microbiology laboratory.

A relatively simple technique for sputum homogenization and dilution is described. Results show that this technique is reliable for isolation and quantitative culture of organisms from cases of chest infection. The technique has resulted in significant reduction in false positive reports, particularly when a system of interpretative reporting is utilized based on 10(7) organisms per millilitre of sputum being accepted as evidence of significant infection.

Bacteria↗