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Biomedical subjects

J Martin

Publications and source records attributed to J Martin.

At least 703 records · Page 39Linked to original sources
PubMed1989

Renal vein leiomyosarcoma: a case report and literature review.

A case of leiomyosarcoma of the renal vein occurring in a 48-year-old woman is reported, and the literature is reviewed. Ultrasonography (US) revealed a rounded uniform echogenic mass in the renal hilus. Computed tomography (CT) showed a well-demarcated, uniform, soft tissue density mass. Both US and CT were useful to detect the renal mass in the present case, and may be useful for staging of renal vein leiomyosarcoma. However, these imaging procedures did not reveal diagnostic features of leiomyosarcoma.

Female↗
PubMed1989

Essential histidine residues in lysolecithin:lysolecithin acetyltransferase from rabbit lung.

Both activities of rabbit lung lysolecithin:lysolecithin acyltransferase (EC 3.1.1.5), hydrolysis and transacylation, are inactivated by diethylpyrocarbonate. The reaction follows pseudo-first-order kinetics, and second-order rate constants of 1.17 mM-1min-1 for hydrolysis and 0.56 mM-1 min-1 for transacylation were obtained at pH 6.5 and 37 degrees C. The rate of inactivation is dependent on pH, showing the involvement of a group with a pK of 6.5. The difference spectra showed an increase in absorbance at 242 nm, indicating the modification of histidine residues. The activity lost by diethylpyrocarbonate modification can be partially recovered by hydroxylamine treatment. The statistical analysis of residual fractional activity versus the number of modified histidine residues leads to the conclusion that two histidine residues are essential for the hydrolytic activity, whereas transacylation activity depends on only one essential histidine. The substrate and substrate analogs protected the enzyme against inactivation by diethylpyrocarbonate, suggesting that the essential residues are located at or near the active site of the enzyme.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1989

Increased fragility of neuronal membranes with aging.

Changes in membrane integrity have been implicated as a contributing factor in the aging process. We have examined the relative stability of synaptosomal membranes from young and aged mice, in response to chemically induced damage. The basal characteristics of the resting synaptosomes prepared from mice of either age were indistinguishable, as judged by intracellular levels of ionic calcium and by efflux of the fluorescent probe employed, fura-2. However, the response of isolated nerve endings to the presence of a neurotoxic agent, the insecticide chlordecone, was markedly different. Exposure to this chemical invariably elevated free calcium and increased the rate of leakage of fura-2 into the extracellular space. These effects were much more pronounced in preparations derived from aged animals. The implication of these findings is that neural membranes of aged animals are more susceptible to malfunction induced by xenobiotic agents and are less able to maintain homeostasis under such circumstances.

Aging↗
PubMed1989

Adhesion characteristics of visible light-cured denture base material bonded to resilient lining materials.

This investigation compared the adhesion of resilient lining materials to Triad visible light-cured denture base material. The liners used were Tru-Soft, Molloplast-B, and Esscheem. Cylindrical samples were made from Triad VLC material and were sectioned to produce a flat bonding surface, which was roughened and treated with Triad bonding agent. Resilient liners 3 mm thick were processed according to the manufacturer's recommendations and samples were stored at 37 degrees +/- 1 degree C in distilled water for 48 hours and 30 days. Tensile bond strength was determined by using an Instron Universal testing machine for the three resilient liners.

Acrylic Resins↗
PubMed1989

Chromosome 1 studies in Wilms' tumor.

Ten newly diagnosed patients with Wilms' tumor had blood and tumor samples taken for cytogenetic analysis. DNA was also extracted from these samples, along with blood obtained from both parents and an age- and sex-matched control. Molecular biological techniques were employed to study changes present in these samples with respect to chromosome 1. Two DNA probes, PIB 174 and PFBl, mapping to 1q12-qter and 1p12-pter, respectively, were examined for the presence of restriction fragment length polymorphisms (RFLPs) and to detect copy numbers of sequences homologous to the probes. These were normalized with respect to themselves and with regard to a control probe P30. No RFLPs were found with the restriction enzymes used. However, seven patients showed a marked alteration in hybridization signal in tumor and/or blood samples compared to control samples and the control probe. This was apparent using probe PFBl, but just failed to reach statistical significance using nonparametric testing. This would suggest that submicroscopic chromosome 1 changes are present more often in Wilms' tumor than previously recognized, and they may play a leading role in the genesis of this tumor.

Blotting, Southern↗
PubMed1989

Preliminary molecular analysis of the TK locus in L5178Y large- and small-colony mouse lymphoma cell mutants.

Mouse lymphoma cells of the L5178Y TK+/- -3.7.2C line were exposed to sidestream and mainstream cigarette smoke condensates (CSC). Cells which survived the trifluorothymidine (TFT) challenge fell in 2 classes: large- and small-colony formers. Southern blot analysis of NcoI-digested DNA from mutant colonies yielded 2 distinct restriction fragment banding patterns when probed with the thymidine kinase (TK) cDNA clone pMtk4. One such pattern was composed of 4 bands at 6.4, 5.5, 4.7 and 2.9 kilobase pairs (kb) and was identical to that of TK+/- controls. A second pattern differed from the first only in the absence of the 6.4-kb band. The majority (83/95) of both large and small colonies derived from cells exposed to CSC exhibited restriction fragment banding patterns lacking the 6.4-kb band. The data from the present study suggest that there is no association between mutant colony size and the presence of the 6.4-kb NcoI restriction fragment at the TK locus in the mouse lymphoma mutants analyzed.

Animals↗
PubMed1989

Low level lead neurotoxicity in a pregnant guinea pigs model: neuroglial enzyme activities and brain trace metal concentrations.

Specific activities of the astroglial marker glutamine synthetase (GS), and the oligodendroglial marker glycerol-3-phosphate dehydrogenase (GPDH) were measured in the spinal cord of fetal guinea pigs and their dams following chronic exposure to low levels of lead (Pb) during gestation. In addition, the effects of Pb on intracellular trace metals (Cu, Fe, Zn) were measured in the blood, cerebellum and forebrain. Aminolevulinic acid dehydratase (ALAD) and zinc protoporphyrin IX (ZPP) were measured in order to monitor established parameters of Pb-exposure. Pregnant guinea pigs were orally administered 0, 5.5 or 11 mg Pb/kg body weight for 30 or 40 days commencing on day 22 of gestation. Blood Pb levels produced in dams and fetuses were at or near the currently identified "no effect" levels for children (10-30 micrograms/dl). These Pb blood levels produced a significant (P less than 0.05) dose-dependent decrease in GS and GPDH activity in the dams and fetuses. Fe and Zn concentrations in blood, cerebellum and forebrain of both dams and fetuses were significantly (P less than 0.05) decreased in a dose-dependent manner. However, Cu concentrations in the blood, cerebellum and forebrain were decreased in the dams but increased in the fetuses in a dose-dependent fashion. The alteration of trace metal concentrations is a proposed mechanism of Pb neurotoxicity. Blood ALAD activity was significantly (P less than 0.05) decreased and ZPP levels were significantly (P less than 0.05) increased, as expected in Pb-exposed animals. This study presents the first biochemical evidence for the alteration of neuroglial function at low levels of Pb exposure and focuses attention on the fetus as an important Pb target.

Animals↗
PubMed1989

Dosimetric evaluation of a variable energy superficial X-ray machine with applications for endocavitary radiotherapy techniques.

This investigation presents the beam characteristics of a newly-marketed variable energy superficial X ray machine for radiotherapy. The X ray system hardware, including a high voltage generator, and console software allow for nine independent operator-selected X ray beams from 10-150 kVp. Filament current values are also independently variable; 1.0-13.0 mA for 90-150 kVp, and 1.0-30.0 mA for 10-90 kVp. The HVL's, effective energies, and radiation outputs for the nine combinations of kVp and mA are presented. In addition, percentage depth dose and beam uniformity results are presented as a function of cone size. Radiation output stability and reproducibility results are included. Discussion of adaptation of this X ray system to the Papillon technique for the treatment of rectal cancers is presented.

Brachytherapy↗
PubMed1989

Nuclear chromatin texture to differentiate follicular and papillary carcinoma of the thyroid.

This study presents the results of an automatic classification of six purely papillary, five purely follicular and five mixed papillary-follicular carcinomas of the thyroid. All cases were correctly classified with only two chromatin textural parameters obtained in the Olga's scan software package developed in our laboratory. Chromatin texture lines were generated by a unidirectional grey level gradient, obtained as a natural logarithmic function of the integrated optical density of each nucleus; this increased the difference between clear papillary and granular follicular nuclei. The accuracy of the method allowed a follicular carcinoma to be correctly classified as a mixed follicular-papillary. Finally a columnar-cell carcinoma of the thyroid was detected by means of its atypical DNA histogram.

Adenocarcinoma↗
PubMed1989

Laboratory diagnosis of Mycoplasma pneumoniae infection. 3. Detection of IgM antibodies to M. pneumoniae by a modified indirect haemagglutination test.

The indirect haemagglutination (IHA) test was compared with the complement-fixation (CF) test for the measurement of antibodies to Mycoplasma pneumoniae. A modification of the IHA was used to measure M. pneumoniae IgM antibodies. Sera were obtained from various groups of patients who were either culture or antigen positive for M. pneumoniae in nasopharyngeal aspirates or who had fourfold or greater increase in CF antibody or a titre greater than or equal to 320. The results of these comparisons showed that the modified IHA test was specific and more sensitive (89% as opposed to 64%) than the CF test. The modified IHA test for the detection of IgM antibody was highly effective in the recognition of recent or current infection with the mycoplasma. It was also of equal sensitivity to an indirect enzyme immunoassay for the detection of IgM antibodies to M. pneumoniae.

Antibodies, Bacterial↗
PubMed1989

Residential density and psychological health: the mediating effects of social support.

People report excessive, unwanted social interactions, insufficient privacy, and are observed to be more socially withdrawn under crowded living conditions. If people socially withdraw from one another as a way to cope with crowding, this could lead to an unintended side effect of breakdowns in socially supportive relationships. A breakdown in socially supportive relationships could, in turn, account for some of the pathological consequences of chronic, high density living conditions. An empirical study of 175 male heads of household among inner city residents in India suggests that the adverse effects of residential crowding on psychological health are mediated by a breakdown of social support systems. The study also points to the value of examining social support as an endogenous variable in the stress and health process.

Adaptation, Psychological↗
PubMed1989

Characterisation of a tamoxifen-resistant variant of the ZR-75-1 human breast cancer cell line (ZR-75-9a1) and ability of the resistant phenotype.

A 6-month exposure of ZR-75-1 human breast cancer cells to tamoxifen (1 microM rising to 2 microM). resulted in a fall in oestrogen receptor (ER) levels from 225 fmol mg protein-1 to 56 fmol mg protein-1 while progesterone receptor (PGR) concentration fell from 63 fmol mg protein-1 to undetectable levels. Sensitivity to the anti-proliferative effects of tamoxifen was unchanged. A further 6 months' exposure to 4 microM tamoxifen resulted in loss of detectable ER and PGR and development of resistance to tamoxifen. Resistant cells, designated ZR-75-9a1, displayed morphological changes consistent with the acquisition of a less well differentiated phenotype. Flow cytometric studies demonstrated that the cell cycle distribution pattern of the resistant variant growing in the presence of 8 microM tamoxifen was identical to that of the untreated parent line, which showed marked accumulation of cells in G0/G1 when exposed to 8 microM tamoxifen. The resistant phenotype was not stable if cells were transferred to complete drug-free medium, but remained stable for at least 3 months in the presence of medium lacking oestrogenic activity. ZR-75-9a1 cells differ from previously reported tamoxifen-resistant variants of the MCF-7 line which retain ER and may prove a valuable model for the study of the development and stability of tamoxifen resistance in human breast cancer.

Breast Neoplasms↗
PubMed1989

Human mesangial cells secrete a GBM-degrading neutral proteinase and a specific inhibitor.

The factors operative during normal and disease states which govern the degradation of the glomerular extracellular matrix (ECM, glomerular basement membrane and mesangial matrix) remain poorly understood. These structures consist primarily of types IV and V collagen, which are highly resistant to the action of classical interstitial collagenases. Here we report that an intrinsic glomerular cell type, the human mesangial cell, secretes: 1) a neutral proteinase with specific activity against type IV basement membrane collagen and, 2) an inhibitory protein with the characteristics of the tissue inhibitor of metalloproteinases (TIMP). The purified enzyme has a neutral pH optimum, consists of a basic (pI 8.4) protein doublet with molecular weight of 66 and 68 kilodaltons, and is inhibited by calcium and zinc chelators. The enzyme degrades both soluble and basement membrane type IV collagen, but does not specifically degrade types I or V collagen or casein. Immunohistochemistry of cultured cells demonstrated homogeneous staining for the neutral proteinase antigen, while the TIMP antigen was detected in fewer than one-third of cultured cells. These findings suggest that the synthesis of these proteins may be independently regulated. The secretion of these factors may play an important role in the turnover of the glomerular ECM under basal or pathologic conditions.

Basement Membrane↗
PubMed1989

Chromatographic detection of 7-methyladenine in urine of rats administered N-methylnitrosourea: a potential marker for monitoring exposure to methylating carcinogens.

Relatively simple and rapid analytical procedures involving two sequential HPLC separations were developed for the isolation of methylated purines in the urine of rats administered radiolabeled methylating carcinogens. Following a dose of [3H]N-methyl-N-nitrosourea (MNU), 7-methyl-adenine (m7Gua) was detected by chromatography as a urinary methylpurine in addition to the expected 7-methylguanine (m7Gua) and 3-methyladenine (m3Ade). When methyl-labeled methionine was given to rats concurrently with MNU, urinary m7Gua was labeled, but no radioactivity was recovered in either of the two methyladenine fractions. The profile of urinary methylated purines following a dose of dimethyl sulfate to the rat was similar. Small amounts of 1-methyladenine (m1Ade) and 3-methylguanine (m3Gua) were also detected in the urine. The excretion of m7Ade derived from the methyl group of the carcinogen rather than from the normal precursor for methylation, implies that this adduct, like m3Ade, may serve as an indicator in urine for exposure to methylating carcinogens.

Adenine↗
PubMed1989

Trainee surgery in teaching hospitals: is there a cost?

The morbidity rate for 2858 patients undergoing thyroidectomy over the 10 year period January 1977-December 1986 was examined and related to the involvement of a surgical trainee in the operative procedure. There was no overall difference in specific complication rates related to the surgical procedure, being 13.8% when the procedure was undertaken by a consultant, and 13.1% when a surgical trainee was involved in the procedure. There was a significant increase (P = 0.0025) in operative time increasing from 127 min for the consultant to 146 min when the trainee was involved (a 15% increase). There was no significant difference in bed stay for any of the groups. Surgical trainees can be safely taught operative skills under supervision without risk of increased complications. There is a cost, however, to the hospital system in terms of increased demands on time and operative facilities.

Costs and Cost Analysis↗