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Biomedical subjects

G Martin

Publications and source records attributed to G Martin.

At least 235 records · Page 13Linked to original sources
PubMed1992

Release and fixation of CO2 by guinea-pig kidney tubules metabolizing aspartate.

1. The metabolism of L-[U-14C]aspartate, L-[1-14C]aspartate and L-[4-14C]aspartate was studied in isolated guinea-pig kidney tubules. 2. Oxidation of C-1 plus that of C-4 of aspartate accounted for 90-92% of the CO2 released from aspartate, whereas oxidation of the inner carbon atoms of aspartate (which occurs beyond the 2-oxoglutarate dehydrogenase step) represented only 8-10% of aspartate carbon oxidation. 3. The formation of [1-14C]glutamine and [1-14C]glutamate from [1-14C]aspartate and [4-14C]aspartate indicated that about one-third of the oxaloacetate synthesized from aspartate underwent randomization at the level of fumarate. 4. With [U-14C]aspartate as substrate, the percentage of the C-1 of glutamate and glutamine found radiolabelled after 60 min of incubation was 92.7% and 47.5% in the absence and the presence of bicarbonate respectively. 5. That CO2 fixation occurred at high rates in the presence of bicarbonate was demonstrated by incubating tubules with aspartate plus [14C]bicarbonate; under this condition, the label fixed was found in C-1 of glutamate, glutamine and aspartate, as well as in C-4 of aspartate, demonstrating not only randomization of aspartate carbon but also aspartate resynthesis secondary to oxaloacetate cycling via phosphoenolpyruvate carboxykinase, pyruvate kinase and pyruvate carboxylase. 6. The importance of CO2 fixation in glutamine synthesis from aspartate is discussed in relation to the possible role of the guinea-pig kidney in systemic acid-base regulation in vivo.

Acetazolamide↗
PubMed1992

High-performance liquid chromatographic method to resolve and determine lipopolysaccharide sub-groups of Escherichia coli endotoxin in isolated perfused rat liver perfusate.

A high-performance liquid chromatographic method was developed for resolving heterogeneous preparations of fluorescently labelled endotoxin derived from Escherichia coli (Serotype 0111:B4) into separate lipopolysaccharide sub-groups. The endotoxin was chromatographed on an analytical gel permeation column using a mobile phase of acetonitrile (20%, v/v) and 100 mM phosphate buffer (pH 7.75). Four fluorescent peaks were resolved, representing sub-groups of markedly different molecular sizes. Three of the four sub-groups contained the core polysaccharide 2-keto-3-deoxyoctonate, confirming that they contained lipopolysaccharide. Fluorescein isothiocyanate (FITC)-labelled endotoxins derived from Vibrio cholerae and Salmonella minnesota chromatographed using the same system eluted with distinctly different patterns of peaks from each other and from E. coli. Extraction of E. coli FITC-endotoxin from a buffer solution using a phenol-diethyl ether method and subsequent chromatography allowed the determination of three of the four fluorescent sub-groups over the concentration range 1-15 micrograms/ml.

Animals↗
PubMed1992

New mRNA probes for hippocampal responses to entorhinal cortex lesions in the adult male rat: a preliminary report.

Three new mRNA responses were found in the hippocampus of the adult male rat after entorhinal cortex lesions (ECL) that induce synaptic reorganization. Hippocampus cDNA libraries were screened by a subtractive hybridization strategy designed to detect ECL-induced mRNAs. Partial sequencing showed clones with similarities to mouse vimentin, ferritin, and polypeptide 7B-2. A sequence similar to mouse SNAP-25 sequence was also detected. Using a mouse SNAP-25 probe, rat SNAP-25 mRNA increased in the hippocampus after ECL.

Animals↗
PubMed1992

Population, labour force and unemployment in Andalusia: prospects for 1993.

"This paper is concerned with forecasting population, employment, labour force and unemployment in Andalusia [Spain] to 1993. For this purpose, a block-recursive demoeconomic model is presented. The demographic submodel is based on the component-cohort method of forecasting population by age and sex. The economic submodel uses econometric and time series analysis to forecast employment both in the medium and short-term. In the labour market part, the labour force is forecasted taking into account the encouraged-discouraged worker effects of changes in the demand for labour."

Age Factors↗
PubMed1992

Contrast media-induced effects on blood rheology and their importance in angiography.

Factors which alter blood viscosity may have important consequences during angiography. The differential effects of various concentrations of five different radiocontrast media on the viscosity characteristics of erythrocyte-plasma suspensions were made over a range of applied shear rates. The results showed that, at both high and low shear rates, the rate of change of viscosity with contrast concentration differs markedly between the various types of contrast media. The conventional ionic monomers caused most disturbance to blood viscosity. The monoionic dimer hexabrix was least disturbing to the viscometric characteristics of blood, and the newer non-ionic monomers were intermediate in their effects. Significant effects on blood viscosity may be caused by radiocontrast agents during a number of in vivo angiographic situations, in particular: early after contrast bolus injection into large vessels, in the microcirculation after selective injections, and during angioplasty procedures.

Adult↗
PubMed1992

Ageing has no effect on the volume density of hepatocytes, reticulo-endothelial cells or the extracellular space in livers of female Sprague-Dawley rats.

1. The hepatic reticulo-endothelial cell population is generally assumed to increase in size, along with the liver, during ageing in rats. However, this has not been rigorously established. 2. Using electron microscopy and stereological techniques, the present study has shown that the volume densities of hepatocytes and Kupffer cells (and probably also of endothelial cells, fat storing cells and the extracellular space) of the livers of female Sprague-Dawley rats are the same at 2 and 24-25 months of age. 3. This result indicates that the increase in size of the liver during ageing in the rat is associated with an equivalent increase in the volume of each cell population and the extracellular space.

Aging↗
PubMed1992

Managers and medical audit.

A study of the role of the manager in medical audit showed that few people had a clear idea of the manager's role; indeed there was little recognition that managers might have a significant role. The picture today, however, is changing. Deborah Harman and Geraldine Martin, who carried out the study, describe progress.

Administrative Personnel↗
PubMed1992

Beliefs about smoking and health and attitudes toward tobacco control measures.

The opinions of a representative sample of adult South Africans about the effects of smoking on health and their attitudes toward tobacco control measures were surveyed by means of an interviewer-administered questionnaire. Seventy-five per cent of the respondents were black and 55.3% were female. More than 50% of blacks and Asians (61.7% and 53.2%) were non-smokers, whereas 52.1% of 'coloureds' were current smokers and 23.8% of whites ex-smokers. The majority of smokers (68.5%) acknowledged the harmful effects of direct smoking and a larger percentage of non- and ex-smokers (79.7% and 77% respectively) shared this view. A similar trend was observed in beliefs about passive smoking. Seventy-five per cent of participants felt that tobacco sales to minors should be banned and 55.8% thought that taxes on tobacco products should be increased. There was substantial white opposition to measures that prohibit tobacco companies from sponsoring sporting events. Most respondents felt that tobacco advertising should be banned on television (59.7%), radio (60.1%), in newspapers (58.4%), on billboards (58.7%) and in cinemas (59.3%). The results indicate that in the main the public supports the introduction of the measures proposed in the draft Tobacco Products Control Act and even more extensive legislation to control tobacco consumption. This augurs well for future strategies aimed at tobacco control in South Africa.

Adolescent↗
PubMed1992

[Lowering peripheral vascular resistance by distal arteriovenous fistula surgery. Clinical and experimental studies].

Vascular run off has an important influence on patency rates of infrapopliteal bypasses especially when prosthetic grafts are used. Construction of a distal arteriovenous fistula can improve volume and velocity of graft flow. 39 patients, 14 of them diabetic, had femoro-crural PTFE-bypasses. A distal arteriovenous fistula in common ostium technique was established in 20 cases. The patency rate (early occlusions) was improved, especially diabetic patients seemed to profit by lowering the peripheral outflow resistance, which was measured intraoperatively. The influence of arteriovenous fistulas of different calibre on bypass flow and perfusion was analysed in a circulation model.

Arteriovenous Shunt, Surgical↗
PubMed1992

Involvement of ventromedial medulla "multimodal, multireceptive" neurons in opiate spinal descending control system: a single-unit study of the effect of morphine in the awake, freely moving rat.

In the present work, we have studied the effects of systemic morphine on the electrophysiological properties of ventromedial medulla (VMM) neurons in the awake, freely moving rat. By means of a chronically implanted single-unit recording device, a drug delivery catheter, and the use of controlled innocuous and noxious cutaneous stimuli, we were able to study precisely the spontaneous and evoked VMM neuronal activities. We have particularly focused our attention upon the VMM "multimodal, multireceptive" units, excited by non-noxious and noxious stimuli (VMM MULT ON), which we have already determined as the neuronal class potentially involved in nociceptive processes at VMM level. We found that morphine (3 mg/kg, i.v.) does not affect the spontaneous activity of these neurons whereas their responses to noxious heat are strongly attenuated (70%), over a prolonged period (about 2 hr) associated with an increase in the response latency. This action of morphine appears to be pharmacologically specific since it is dose dependent to some extent, and is reversed by 0.3 mg/kg of naloxone. In parallel with this pharmacological specificity, we have also demonstrated a preferential physiological effect since the response of the VMM MULT ON neurons to light touch application is not affected by morphine. This specificity is emphasized by the fact that morphine does not modify the activity of the other VMM neuronal groups such as the units unresponsive to any kind of peripheral stimuli, and does not reveal "new" neuronal classes such as those we have found in previous studies after barbiturate administration. The differential effect upon the noxious versus innocuous inputs of these units produced by the opiate reinforces their participation in nociceptive processing since similar effects have been reported in well-known nociceptive somatosensory structures such as the dorsal horn of the spinal cord. Furthermore, although the precise mechanisms of action have not yet been determined, the spinal projection of the VMM MULT ON neurons, previously demonstrated by our group, suggests their involvement in an opiate descending spinal control system of nociception. Although speculative, one can imagine either a direct facilitatory MULT ON spinal effect being attenuated by morphine (disfacilitation), or a morphine-induced disinhibition of inhibitory GABAergic neurons acting upon the MULT ON neurons.

Animals↗