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M J Wilson

Publications and source records attributed to M J Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1987

Increased synthetic capacity for metallothionein in cultured liver cells following dimethyl sulfoxide pretreatment.

Cultured TRL 1215 cells in log phase of growth were exposed to dimethyl sulfoxide (DMSO; 14-280 mM) followed 48 h later by cadmium (10 micron). Intracellular concentrations of metallothionein (MT) were measured 24 h after cadmium addition. Cadmium alone caused a 10-fold increase in the levels of MT, while DMSO alone had no effect on cellular MT levels. DMSO pretreatment followed by cadmium exposure, however, resulted in MT levels that were elevated by a factor of as much as 25-fold those observed in control cells. Concurrent treatment with the DNA synthesis inhibitor hydroxyurea (HU) eliminated the enhancing effect of DMSO pretreatment on cadmium induction of MT, indicating the requirement of DNA synthesis. An enhancement of the cellular accumulation of the metal ion did not account for the increased cadmium-induced MT synthesis in DMSO-pretreated cells as these cells did not show significantly increased uptake of cadmium during the initial period of exposure. DMSO pretreatment enhances cadmium induction of MT synthesis through a mechanism that appears to be dependent on the synthesis of DNA.

Animals↗
PubMed1987

Phosphorylation of sperm-binding proteins from seminal vesicle secretion by sperm surface protein kinase.

Rat seminal vesicle secretion does not demonstrate protein kinase activity, either towards endogenous or exogenous proteins. When epididymal sperm were incubated in vitro with seminal vesicle secretion, three prominent secretory proteins were bound to the sperm. Two of these proteins were highly phosphorylated. Thus, selected sperm-binding proteins from accessory gland secretions are phosphorylated by sperm surface protein kinases.

Animals↗
PubMed1987

Heat-stress proteins of rat lung endothelial and mammary adenocarcinoma cells.

A rat mammary adenocarcinoma cell clone, MTC, and a rat lung endothelial cell clone, RLE cl.4, both syngeneic to the Fisher 344 rat, were compared for proteins synthesized at 37 degrees C and after a 1-h, 42 degrees C heat dose. The heat stress-induced or -enhanced synthesis of a series of molecular mass groups and isoelectric point species (isomers) was observed in both equilibrium and nonequilibrium two-dimensional gel electrophoresis. Tumor and endothelial cell heat-stress proteins (hsp) were strikingly similar with most hsp in 11 or 13 molecular mass groups having from 1 to 12 major isomers. In comparing the two cell types, 6 of about 23 major hsp isomers appeared different in equilibrium pH gels, with tumor cells seemingly exhibiting less synthesis of these 6 isomers. Four additional endothelial cell hsp isomers were apparent in nonequilibrium pH gels. Since two of these later hsp can be found at higher heat doses in tumor cells, some of these apparent differences between tumor and endothelial cells may be attributable to different dose ranges for induction of hsp. Fluorograms and silver-stained gels showed that several hsp were being synthesized at appreciable levels in unheated cells. However, there were hsp whose synthesis appeared to be de novo rather than representing enhanced synthesis of existing proteins. These last two observations were made in both tumor and normal cells. The constitutive levels of hsp synthesis appeared to be generally similar in unheated tumor and normal cells in vitro with few exceptions. These results indicate the presence of few unique hsp in syngeneic tumor and normal cells in vitro. However, focusing subsequent studies on the few differences may lead to insights concerning hyperthermic biology of tumor and normal cells, phenotypic differences between these cells, and roles of some hsp.

Adenocarcinoma↗
PubMed1986

Enzymic properties of a Ca2+-dependent protease in rat ventral prostate: differences in distribution between lobes of the prostatic complex.

Soluble extracts of rat ventral prostate contain a calcium-dependent, neutral thiol protease which is separated from an endogenous inhibitor by DEAE-cellulose chromatography. The Ca2+-dependent protease had a high calcium requirement (half maximal activation at 0.19 mM CaCl2), a pH optimum in the neutral range (pH 7-8), and it was inhibited by increased ionic strength (30% inhibition at 0.2 M NaCl). Leupeptin and antipain were strong inhibitors of the enzyme. Ca2+-activated protease activities of the coagulating gland (anterior prostate) were about 40% of those of the ventral prostate and were not detectable in the dorsolateral prostatic lobe. There was no difference in specific activities of this enzyme in chromatographed extracts of prostatic lobes from young sexually mature adults and 12 month old retired breeders. In addition, Ca2+-dependent protease activity was not detectable in chromatograms of rat ventral prostate and coagulating gland secretions. Therefore, the Ca2+-activated protease does not appear to be a secretory protein and probably acts at some intracellular site(s).

Aging↗
PubMed1986

The effects of hepes, bicarbonate and calcium on the cGMP content of vertebrate rod photoreceptors and the isolated electrophysiological effects of cGMP and calcium.

To evaluate the role of cGMP in vertebrate rod photoreceptors, two extracellular effectors of cGMP were used (calcium and buffer), and both cGMP content and electrophysiological responses were measured. In the dark when the cGMP content was reduced by 80%, electrophysiological effects mimicking a weak background light were observed. Continuous illumination, sufficient to suppress all electrophysiological responses, had only minor effects on cGMP. The data seem inconsistent with suggestions that steady-state levels of cGMP alone control the light responses of rod photoreceptors. The electrophysiological effects of extracellular calcium (under conditions of unaltered cGMP) were distinguishable from those of cGMP.

Action Potentials↗
PubMed1986

Enhancement of cadmium-induced metallothionein synthesis in cultured TRL 1215 cells by butyric acid pretreatment.

Cultured TRL 1215 cells in log phase of growth were exposed first to butyric acid (BA; 0.1-2.0 mM) and then 48 h later, to cadmium (Cd; 10 microM). Metallothionein (MT) concentrations were measured 24 h after Cd addition. Cd alone caused approx. a 10-fold increase in cellular MT levels, while BA alone had no effect. BA pretreatment followed by Cd exposure, however, resulted in MT levels up to 25 times those in control cells. Concurrent exposure to hydroxyurea (HU) eliminated the enhancing effect of BA pretreatment on induction of MT by Cd, indicating that DNA synthesis is required. BA-pretreated cells did not show marked increases in cellular uptake of Cd. BA pretreatment enhances Cd induction of MT synthesis through a mechanism that is dependent on the synthesis of DNA.

Animals↗
PubMed1986

Analysis of fixation effects on immunohistochemical localization of prostatic specific antigen in human prostate.

We studied human prostatic specific antigen (PSA) localization in human prostate to investigate the possibility that the previously reported variations in the intensity of antigen staining were due to fixation and embedding methods. We have evaluated the effects of physical and several chemical fixatives on prostate samples obtained immediately after prostatectomies and radical cystectomies. Our analysis of fixation effects and immunohistochemical staining of polyclonal antibody to PSA indicates that the formalin fixation and paraffin embedding methods used previously did provide optimum localization of the antigen and the variations in the intensity of PSA staining could not be attributed to the methodology. Although PSA staining was relatively uniform in the lower grade neoplastic tumors, the higher grade, moderately to poorly differentiated tumors showed intense-through-weak PSA localization or no PSA staining suggesting that PSA staining intensity was not uniformly related to tumor differentiation.

Adenocarcinoma↗
PubMed1986

Hepatic DNA methylation and liver tumor formation in male C3H mice fed methionine- and choline-deficient diets.

The effects of the chronic administration of methyl-deficient, amino acid-defined diets on liver tumor formation were examined in male weanling C3H/HeN mice previously treated with a single ip injection of 0 or 150 mg diethylnitrosamine/kg body weight [(DENA) CAS: 55-18-5]. Five diets were used: diet 1, adequate; diet 2, devoid of both methionine and choline; diet 3, devoid of methionine only; diet 4, devoid of choline only; and diet 5, devoid of methionine, choline, folic acid, and vitamin B12. Equimolar homocystine replaced methionine in all methionine-devoid diets. All diets were administered for 1 year. No hepatocellular carcinomas and only 3 liver adenomas were seen among the 129 animals at risk in the 5 groups that had received no DENA. Among the DENA-treated groups fed diets 1-4, the incidence of hepatocellular carcinomas in the mice at risk averaged 40%, with no significant differences noted among groups. A relatively low incidence of liver carcinomas (10%) was seen among DENA-treated mice subsequently fed diet 5; it could be ascribed to the enhanced mortality seen in these animals due to the dietary deficiencies. Lung tumors were seen in 44% of the DENA-treated mice surviving more than 35 experimental weeks and in only 2.5% of the corresponding DENA-untreated animals. Feeding diet 2, deficient in methionine and choline, to male C3H mice for 5-20 weeks decreased the hepatic ratio of S-adenosylmethionine (CAS: 29908-3-0) to S-adenosylhomocysteine (979-92-0) relative to that observed in mice fed the adequate diet 1. The 5-methyldeoxycytidine [(5-MC) CAS: 838-07-3] contents of liver DNA in animals fed diet 2 for 5, 10, and 20 weeks, however, were not significantly different from the corresponding levels in diet 1-fed mice. The results indicate that a methionine- and choline-deficient dietary regimen that lowers the 5-MC levels in DNA and enhances liver tumor formation in male F344 rats does not do so in male C3H mice.

Animals↗
PubMed1985

Reduced cadmium-induced cytotoxicity in cultured liver cells following 5-azacytidine pretreatment.

Recent work indicated that administration of the pyrimidine analog 5-azacytidine (AZA), either to cells in culture or to rats, results in an enhancement of expression of the metallothionein (MT) gene. Since MT is thought to play a central role in the detoxification of cadmium, the present study was designed to assess the effect of AZA pretreatment on cadmium cytotoxicity. Cultured rat liver cells (TRL 1215) in log phase of growth were first exposed to AZA (8 microM). Forty-eight hours later, cadmium (10 microM) was added. MT concentrations were then measured 24 hr after the addition of cadmium. A modest increase in MT amounts over control (1.7-fold) was detected after AZA treatment alone. Cadmium alone resulted in a 10-fold increase in MT concentrations. The combination of AZA pretreatment followed by cadmium exposure caused a 23-fold increase in MT concentrations over control. Treatment with the DNA synthesis inhibitor hydroxyurea (HU) eliminated the enhancing effect of AZA pretreatment on cadmium induction of MT, indicating that cell division is required. AZA-pretreated cells were also harvested and incubated in suspension with cadmium (250 microM, 37 degrees C) for 0 to 90 min. After incubation intracellular and extracellular fluids were separated by centrifugation through an oil layer. AZA-pretreated cells showed marked reductions in cadmium-induced cytotoxicity as reflected by reduced intracellular potassium loss, glutamic-oxaloacetic transaminase loss, and lipid peroxidation (assessed by thiobarbituric acid reactants) following cadmium exposure. AZA pretreatment had no effect on the cellular uptake of cadmium. Results suggest that AZA pretreatment induces tolerance to cadmium cytotoxicity which appears to be due to an increased capacity to synthesize MT rather than high quantities of preexisting MT at the time of cadmium exposure.

Animals↗
PubMed1985

Binaural interaction in auditory brain-stem responses: effects of masking.

Binaural interaction (BI) in auditory brain-stem responses (ABRs) can be shown by comparing a binaurally elicited ABR to the algebraic sum of monaurally elicited ABRs. Subtracting the summed monaural ABR from binaural ABR yields a wave form assumed to contain response components attributable to BI. It has been suggested that acoustic crosstalk accounts for some of the 'BI' seen with this technique and that contralateral masking should be used during monaural stimulation to eliminate crosstalk. However, this practice might in itself confound the results, even if the masking noise were not intense enough to affect the opposite ear, by 'central masking' of brain-stem neural activity. We studied the effects of contralateral wide-band masking on BI/ABR in 10 normal adult subjects. Clicks were presented at levels from 55 to 115 dB peSPL, at 10 dB intervals. Masking was presented at 73 dB SPL (47 dB effective masking level); based on pilot studies of interaural attenuation, this was a level expected to be at, or just below, the threshold of audibility in the contralateral ear. BI/ABR wave forms were not noticeably affected by the addition of contralateral noise in the monaural trials. In addition, BI/ABR was seen (as previously reported) at levels well below any possibility of crossover artifact. Thus, BI/ABR is not simply attributable to crossover. Contralateral masking is not necessary in recording BI/ABR, within the limits of the stimuli and transducers used in this study.

Brain Stem↗
PubMed1985

Divergent expression of laminin and fibronectin in non-tumorigenic and transformed liver epithelial cells.

The immunocytochemical expression of laminin and fibronectin by non-transformed liver epithelial cells and by transformed cells derived from the same cell line, TRL1215, was examined in ethionine-transformed cells (ETC), untreated control cells at the same high passage level (HPC), and untreated, low passage cells (LPC). At confluence, a divergent expression of laminin and fibronectin was observed in the three sublines. In flat areas of polygonal cells, LPC showed abundant laminin staining and sparse fibronectin staining; HPC had intermediate expression of both; and ETC had sparse laminin staining and abundant fibronectin. Specifically, the laminin network was often found at intercellular junctions, outlining individual LPC, outlining groups of HPC, and having a focal expression in ETC. A fine reticulum of laminin was seen in large areas of LPC, in relatively small areas of HPC, and in multilayered areas of ETC. Fibronectin was visible as thick, matted fibrils, which were sparse in LPC, loosely arranged in HPC and dense in ETC. Prior studies had shown that the increased fibronectin expression in the transformed cells was associated with increased expression of actin stress fibres, increased cell spreading and increased numbers of focal contacts between cell and substrate. The divergent expression of laminin and fibronectin shown here indicates that these two matrix proteins need not be expressed in a parallel manner during transformation, and that increased fibronectin, but not laminin, is associated with maximal cell spreading and adhesion.

Animals↗
PubMed1985

Transformation-associated increase of adhesion, cellular fibronectin, and stress fiber development in a liver epithelial cell line.

Cytoskeletal and adhesion characteristics of DL-ethionine (CAS: 67-21-0)-transformed rat liver epithelial cells (ETC) were compared with those of nontumorigenic, untreated cells of the same cell line both at the same passage level as ETC and at an early low passage level. ETC and high-passage-level cells (HPC) showed increased cell spreading and prominent actin stress fibers compared to low-passage-level cells (LPC). The number of adhesion plaques per unit cell area was higher for ETC than for LPC. At confluence, fibronectin expression was high for ETC, moderate for HPC, and low for LPC. The observed increases in cell spreading and in actin and fibronectin expression appeared to be associated with transformation of this cell line rather than being specific responses to ethionine treatment. This conclusion is suggested by the fact that HPC, which display preneoplastic markers, are similar in many respects to ETC.

Actins↗
PubMed1984

Hypomethylation of hepatic nuclear DNA in rats fed with a carcinogenic methyl-deficient diet.

A progressive decrease was observed in the 5-methyldeoxycytidine content of hepatic DNA in male F344 rats fed with a hepatocarcinogenic methyl-deficient diet. The same dietary regimen resulted in altered hepatic contents of S-adenosylmethionine, the methyl-donating species, and S-adenosylhomocysteine, an inhibitor of DNA methylase. The data indicate that this carcinogenic dietary manipulation is sufficient to alter a possible regulatory process, DNA methylation.

Animals↗
PubMed1984

Characterization of rat liver cells transformed in culture by DL-ethionine.

A rat liver-derived epithelial cell line transformed with DL-ethionine and the corresponding control cell line were characterized according to morphological and cytochemical criteria to establish their origin from liver epithelium and to identify cellular changes due to transformation by DL-ethionine. The presence of intermediate junctions confirms the epithelial nature; glycogen accumulation and glucose-6-phosphatase activity confirm the hepatic origin of the cells. Persistent alterations resulting from ethionine transformation were variations in cell shape and size, focal multilayered growth, an increase in the nucleolar:nuclear ratio, and a reduction in the number of cells displaying a primary cilium. Hyperplasia of the inner nuclear membrane, elongation and branching of mitochondria, and a reduction in the length and frequency of cell junctions were also characteristic of the transformed cells.

Animals↗