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Biomedical subjects

M G Thomas

Publications and source records attributed to M G Thomas.

At least 163 records · Page 9Linked to original sources
PubMed1985

Enoxacin treatment of urinary tract infections.

We treated 20 patients with urinary tract infections with enoxacin, a new nalidixic acid analogue, in an open uncontrolled trial. Twelve of 13 patients with covert bacteriuria or cystitis and four of seven patients with pyelonephritis were cured. Two treatment failures occurred in patients with complicated infections. Nine patients reported mild side-effects.

Adolescent↗
PubMed1985

Mexiletine: long-term follow-up of a patient with prolonged QT interval and quinidine-induced torsades de pointes.

The use of class 1A antidysrhythmic agents in patients with or without prolonged QT intervals carries a risk of induction of polymorphic ventricular tachycardia. The class 1B antidysrhythmics have many similarities to the former group, but have different modes of action and electrophysiologic properties. Therefore, lidocaine and lidocaine-like drugs such as mexiletine may be used with relative safety in this clinical situation, as in the case we have reported, in which lidocaine and mexiletine controlled VPB in the acute stage and during long-term follow-up respectively, while quinidine induced "torsades de pointes."

Electrocardiography↗
PubMed1985

Central alpha-adrenergic agonists in chronic heart failure and ischemic heart disease.

Central alpha-adrenoceptor agonists (methyldopa, clonidine, guanabenz) decrease sympathetic outflow and renin and vasopressin secretion as well as increase parasympathetic activity. These drugs are commonly employed as antihypertensives. Two other conditions, chronic heart failure and ischemic heart disease, may also benefit from central alpha-adrenergic stimulation. In both acute and chronic heart failure, central alpha-adrenoceptor agonists reduced cardiac work load by decreasing heart rate, systemic arterial pressure and reducing venous tone. Also, plasma catecholamines were decreased. Exercise at comparable work loads was achieved at a lower pressure-rate product and effort capacity was sometimes increased. Central alpha-adrenoceptor agonists increased effort capacity in patients with ischemic heart disease and angina pectoris. Again, the benefits are thought to be decreased heart rate, systemic arterial blood pressure and rate-pressure products during exercise; catecholamines are reduced in these patients as well. Central alpha-adrenoceptor agonists offer another avenue of approach to alter neurohumoral factors in congestive heart failure and ischemic heart disease and thereby produce beneficial hemodynamic response.

Adrenergic alpha-Agonists↗
PubMed1984

Use of the HLA B27 test in Auckland.

An assessment was made of the probability of HLA B27 associated disease in 74 patients who had recently been tested. Six patients had definite, 31 possible, and 37 very unlikely HLA B27 associated disease. Thirteen patients were HLA B27 positive. Fourteen tests were ordered by rheumatologists (43% HLA B27 + ve) and 60 by other doctors (12% HLA B27 + ve) p less than 0.01. Non-rheumatologists ordered an excessive number of tests in patients with a low probability of HLA B27 associated disease.

Adolescent↗
PubMed1984

The human lymphocyte in vitro cytogenetic assay: positive and negative control observations on approximately 30000 cells.

Data are presented from the cytogenetic analysis of the peripheral lymphocytes from 94 male and 15 female donors. However, a much smaller number of regular donors were selected for regular use. A total of 28674 cells were analysed and these acted as negative and positive controls in the in vitro human lymphocyte tests accumulated in this laboratory over a 6-year period. The significant observations were:. (1) in untreated and solvent control treated cultures (a) no chromosomal interchanges were observed in 21570 cells; (b) the incidence of dicentrics was less than 1 per 10000 cells; (c) other types of aberrations were seen with an increased frequency, chromosomal gaps being the most variable. (2) The reference clastogens mitomycin C and cyclophosphamide produced high and remarkably consistent yields of all types of aberrations. It is concluded that when screening compounds in vitro for new genotoxins, aberrations such as chromosomal interchanges and dicentrics (due to their rarity in negative control cultures) should be accorded greater significance than the several other types of aberrations routinely seen. These conclusions emphasize the value of maintaining and updating adequate historical control records.

Antibiotics, Antineoplastic↗
PubMed1982

Isolation and characterization of plasma membranes containing LH sensitive adenylate cyclase from a Leydig cell tumour.

An LH sensitive adenylate cyclase from a tumour Leydig cell has been investigated. The plasma membranes, prepared by a 2 phase (dextran-polyethylene glycol) centrifugation method were found to have the following properties: In the presence of LH plus p(NH)ppG (guanosine 5'-beta, gamma-imido triphosphate) or fluoride ions, maximum adenylate cyclase activity was obtained in the plasma membranes with 4 to 6 mM Mg2+ plus 0.33 to 2 mM ATP. LH alone stimulated adenylate cyclase activity 2-fold when compared with basal activity and the time course of cyclic AMP production was linear up to 45 min. With GTP (10(-5)M) and GTP plus LH, adenylate cyclase activity was increased 3 and 6-fold, respectively, for up to 20 min and thereafter declined. In contrast p(NH)ppG (10(-5)M) and p(NH)ppG plus LH increased adenylate cyclase activity 7 and 14-fold which was maintained for at least 45 min. Fluoride ions increased the enzyme activity linearly over 45 min approx 18-fold. When GTP or p(NH)ppG were added alone there was a lag time of activation of approximately 10 min which was abolished by the addition of LH. GTP but not p(NH)ppG at concentrations greater than 10(-4) inhibited basal and LH stimulated adenylate cyclase when compared with 10(-5)M GTP. The tumour Leydig cell adenylate cyclase is thus essentially similar to other hormone sensitive somatic cells. The present study makes it feasible to prepare plasma membranes by a simple method from large quantities of pure Leydig cells.

Adenosine Triphosphate↗
PubMed1982

Guanine nucleotide mediated desensitization of adenylate cyclase in cell free preparations from a Leydig cell tumour.

Cell free desensitization of a tumour Leydig cell plasma membrane adenylate cyclase has been demonstrated in the presence of guanine nucleotides. In experiments in which the membranes were pre-incubated with various nucleotides and LH, it was shown that this decreased adenylate cyclase activity was dependent on the presence of GTP and occurred both in the presence and absence of ATP. While pre-treatment with LH alone appeared to enhance subsequent adenylate cyclase activity, this hormone was able to potentiate the desensitizing effect of GTP. The desensitizing effect of GTP was not inhibited by sodium fluoride. In contrast, the GTP analogue p(NH)ppG (guanosine 5'beta, gamma-imido triphosphate) caused a persistent activation of the adenylate cyclase. GMP and guanosine also initially inhibited the adenylate cyclase activity, but this was entirely reversed by p(NH)ppG plus LH. GDP in addition to GTP caused desensitization but this was only partially reversed by p(NH)ppG plus LH. It is proposed that in similarity with the ovary (Bockaert et al. 1976; Ezra & Salomon 1982a) desensitization of Leydig tumour cell plasma membrane adenylate cyclase may involve a GTP-mediated phosphorylation step.

Adenylyl Cyclases↗
PubMed1976

Metal clusters in catalysis: Hydrocarbon reactions.

A set of metal carbonyl clusters, Ru(3)(CO)(12), Os(3)(CO)(12), and Ir(4)(CO)(12), has been evaluated as catalysts for a series of hydrocarbon reactions which comprise skeletal rearrangement, metathesis, dehydrogenation, hydrogenation, isomerization, and H-D exchange. None was especially effective as a hydrogenation catalyst even for olefins. Os(3)(CO)(12) was a catalyst for H-D exchange between C(6)H(6) and D(2) at 195 degrees but the ruthenium congener was inactive at temperatures below 175 degrees , a temperature where ruthenium metal formed at an appreciable rate. Deuterium incorporation in the benzene was a single-step process. Ir(4)(CO)(12) was an effective catalyst for the conversion of cyclohexadiene to cyclohexene and benzene. A similar reaction occurred with cyclohexene but the rate was extremely low at 160 degrees . The ruthenium and osmium clusters catalyzed the isomerization of linear hexenes, with the former the more active. Relative rates for the hexenes were 1 > 2 > 3. At high temperatures, the osmium and iridium clusters catalyzed skeletal reactions of 2-hexene, as evidenced by the formation of pentenes, heptenes, heptanes, and small amounts of propane.

Journal Article↗
PubMedDate not supplied

Acalculous cholecystitis complicating hepatic intraarterial lipiodol: case report.

Hepatic intraarterial injection of Lipiodol has been used by various authors to enhance the diagnostic accuracy of computed tomography in hepatic tumors. The technique appears safe and seems free from serious complications when used judiciously. We report a case in which injection of hepatic intraarterial Lipiodol precipitated acalculous cholecystitis requiring urgent laparotomy.

Angiography↗