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M Thompson

Publications and source records attributed to M Thompson.

At least 289 records · Page 16Linked to original sources
PubMed1987

Change in energy reserves in different segments of the nephron during brief ischemia.

Rat kidneys were made ischemic for 5 to 120 seconds. Segments of individual nephrons were dissected from freeze dried sections and analyzed for ATP, phosphocreatine, glycogen, glucose, glucose-6-phosphate, lactate and creatine kinase. ATP fell most rapidly in proximal convoluted and straight tubules (PCT, PST) and distal convoluted tubules (DCT), and most slowly in glomerulus and papilla. Phosphocreatine levels ranged fivefold and was highest in DCT, where it approached that of brain. Creatine kinase ranged 100-fold with lowest level in PCT, where the ischemic fall in phosphocreatine was so slow as to suggest a function other than that of an energy reserve. Glycogen varied tenfold from modest levels in distal segments to very low levels in PST, and was not used rapidly in any segment. Glucose consumption and lactate production were most rapid in distal portions. High-energy phosphate consumption for the first 7.5 seconds of ischemia, calculated from these data, indicates roughly-equal energy metabolism in proximal and distal segments, with lower levels in papilla, and especially in glomerulus. The absolute values suggest that the in vivo metabolic rate of the nephron continued almost unabated for 5 or 10 seconds of ischemia.

Adenosine Triphosphate↗
PubMed1987

Bacterially catalysed N-nitrosation reactions and their relative importance in the human stomach.

Human exposure to endogenously formed N-nitroso compounds has frequently been suggested as a causative factor in carcinogenesis where this is related to chronic bacterial infection such as is seen in gastric achlorhydria. At least two distinct mechanisms of endogenous formation have been identified. The first, a direct chemical reaction between secondary amino compounds and nitrite, is strongly pH dependent and does not proceed rapidly at neutral pH even in the presence of chemical catalysts. The second depends on the direct bacterial catalysis of N-nitrosation. The data presented demonstrate that the bacterially mediated reaction is catalysed by bacterial enzyme systems and proceeds much more rapidly at neutral pH than the chemical reaction. This suggests a particular relevance to the in vivo situation where neutral pH, bacteria and elevated nitrite concentrations are found. Drawing on the kinetic information presented regarding the bacterially mediated nitrosation reaction, the known kinetics of the chemical reaction and the published values for the relevant substrate concentrations in both the colonised and the normal acid stomach the bacterial and chemical reactions have been compared. Using these criteria, and assuming the presence of bacteria with the appropriate metabolic activity, it may be predicted that N-nitroso compounds may be formed in the colonized stomach at much higher concentrations than in the normal acid stomach. The difference in yield may be by two to four orders of magnitude. Different bacterial species and different isolates of the same species show considerable variation in their abilities to catalyse N-nitrosation reactions. The most rapid catalysis is associated with those bacteria capable of reducing nitrate and nitrite by the process of denitrification. The most significant clinical corollary of these studies is that although bacterial catalysis of N-nitrosation has been demonstrated unequivocally, bacterial colonization of the stomach may not itself necessarily result in elevated endogenous N-nitroso compound exposure despite the elevated nitrite concentrations normally associated with such colonization. An increase in exposure to endogenously formed N-nitroso compounds would only be predicted in those individuals where a significant proportion of the colonizing bacteria expressed significant N-nitrosation activity. As a consequence the carcinogenic risk may be restricted to only a small proportion of colonized individuals depending on the prevalence of sustained infection by bacteria with significant N-nitrosation activity, particularly denitrifiers.

Humans↗
PubMed1987

Synergistic induction of interleukin-1 by endotoxin and toxic shock syndrome toxin-1 using rat macrophages.

We studied interleukin-1 (IL-1) secretion by rat peritoneal exudate macrophages stimulated with purified toxic shock syndrome toxin-1 (TSST-1). TSST-1 was observed to be a more potent inducer of IL-1 than was endotoxin. The induction of IL-1 secretion by TSST-1 was not blocked by polymyxin B but could be blocked by monoclonal antibodies directed against TSST-1. Synergistic induction of IL-1 was observed when the cells were stimulated with TSST-1 and endotoxin. The sequence of addition was found to be important for the synergistic response. Enhanced IL-1 production was observed only when macrophages were exposed to endotoxin before or simultaneously with TSST-1. Prior exposure of macrophages to TSST-1 had no enhancing effect on endotoxin-induced IL-1 secretion. We conclude that stimulation of the macrophage by endotoxin enhances the responsiveness of the cells to TSST-1 and may thereby play a role in the pathogenesis of toxic shock syndrome.

Animals↗
PubMed1987

Combined anti-muscarinic and H2 receptor blockade in the healing of refractory duodenal ulcer. A double blind study.

The purpose of this study was to determine if pirenzepine and cimetidine given together was superior to cimetidine alone in inducing healing of refractory duodenal ulcers which remained unhealed after treatment with cimetidine or ranitidine for at least eight weeks. One hundred and thirty one patients from six centres were randomised to receive either cimetidine (C) 800 mg daily or cimetidine 800 mg plus pirenzepine (C + P) 100 mg daily under double blind conditions for six weeks. The healing rate was similar in both groups, irrespective of the method of calculation. On an intent-to-treat analysis, healing was: C 66%, C + P 57%, and amongst the patients who completed treatment, healing was 70% in both groups. Patients on C and on C + P experienced a similar decrease in daytime and in night time pain. Side effects of treatment, notably dry mouth and blurred vision, were reported more often by patients on combination therapy. Combined treatment with cimetidine plus pirenzepine in patients with refractory duodenal ulcer is unlikely to be beneficial.

Adult↗
PubMed1987

T84 cell receptor binding and guanyl cyclase activation by Escherichia coli heat-stable toxin.

Escherichia coli heat-stable enterotoxin (STa) induces intestinal secretion by binding to enterocyte receptors and activating the guanylate cyclase-guanosine 3',5'-cyclic monophosphate (cGMP) system. The intermediate steps between binding of STa and secretion are poorly understood, due in part to the lack of a convenient system to study the effects of STa at the cellular level. To establish such a model, we investigated the binding of 125I-STa, STa activation of guanylate cyclase, and STa-induced increase in cGMP production in a well-characterized human colonic cell line, T84. Binding was specific, linear with cell number, and time, temperature and pH dependent, and reversible. ST may also be internalized by these cells. Addition of unlabeled STa competitively inhibited binding of 125I-STa. These parameters closely resemble those described in intact rat enterocytes and cell-free membrane preparations. STa stimulated guanylate cyclase and cGMP production in a dose-related manner. The similar dose-response relationships for binding, guanylate cyclase stimulation by STa, and cGMP production suggest that the guanylate cyclase-cGMP system is coupled to ST occupancy of specific receptors. These data, together with the fact that STa induces chloride secretion from T84 cells suggest that T84 cells are a suitable and convenient system to study the cellular mechanism of action of STa.

Bacterial Toxins↗
PubMed1987

Stressful life events and psychiatric hospitalization of mentally retarded patients.

The authors compared the type and number of life events experienced by 19 mentally retarded patients and 19 nonretarded control subjects in the month before their admission to the same unit of a state mental hospital. The retarded patients had exhibited fewer changes in eating and other personal habits. On admission they presented fewer signs of intrapsychic disturbance but more of self-destruction or aggression. These results imply that clinicians need specific training to diagnose and treat psychiatric disorders in the mentally retarded patients who now use community mental health facilities, because their presentations may be atypical.

Adolescent↗
PubMed1987

The toxicity of inhaled methyl isocyanate in F344/N rats and B6C3F1 mice. II. Repeated exposure and recovery studies.

F344/N rats and B6C3F1 mice were exposed to 0, 1, 3, or 6 ppm methyl isocyanate by inhalation for 6 hr on 4 consecutive days. Deaths of rats were observed following 3 ppm exposures, and mice died after exposures to 6 ppm. Deaths appeared to be related to severe respiratory distress. Survivors in high dose groups lost weight initially, then gained weight at rates equal to controls throughout a 91-day recovery period. Lung weights increased significantly in male and female rats exposed to 3 ppm, but no persistent changes in brain, kidney, thymus, spleen, liver, or testis weights were seen in either mice or rats. Blood and serum from male and female rats were taken for clinical pathology and hematology assessments on day 7 of postexposure, the day prior to the first observed deaths of these animals. No changes or only slight changes were seen in measures of serum alanine aminotransferase, sorbitol dehydrogenase, alkaline phosphatase, or in blood and brain cholinesterase activities. However, serum creatine kinase increased with dose in both males and females. Blood urea nitrogen, creatinine, and methemoglobin were unchanged. No changes were seen in counts of red blood cells or platelets, or in red cell indices. Hemoglobin concentrations and hematocrits were slightly elevated. No changes were noted in absolute leukocyte counts, but counts of segmented neutrophils increased and lymphocytes decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Toxicity of inhaled methyl isocyanate in F344/N rats and B6C3F1 mice. I. Acute exposure and recovery studies.

Male and female F344/N rats and B6C3F1 mice were exposed to lethal and sublethal concentrations of methyl isocyanate by inhalation. Mortality, clinical signs, body and organ weights, and changes in clinical pathology and hematology were monitored immediately after 2-hr exposures and during the ensuing 3 months. Additional studies investigated the possible involvement of cyanide in the toxicity of methyl isocyanate. During exposures, signs of restlessness, lacrimation, and a reddish discharge from the nose and mouth were evident in rats and mice. Following exposures, rats and mice were dyspneic and weak. Deaths of rats and mice exposed to lethal concentrations (20 to 30 ppm) began within 15-18 hr, with males more prone to early death than females. A second wave of deaths occurred after 8 to 10 days, affecting primarily female rats and mice exposed to 20 to 30 ppm of methyl isocyanate, and male and female rats exposed to 10 ppm. Most deaths occurred during the first month following the exposures and were preceded by periods of severe respiratory distress. Body weights decreased in proportion to dose early, but then weight gain resumed in survivors at control rates. The only organ with a consistent, dose-related weight change was the lung, which was heavier throughout the studies in animals exposed to high concentrations of methyl isocyanate. No significant clinical pathology, or hematologic changes were observed in exposed rats. Blood and brain cholinesterase were not inhibited. Studies attempting to measure cyanide in the blood of methyl isocyanate-exposed rats, and attempting to affect lethality with a cyanide antidote (sodium nitrite and sodium thiosulfate) gave negative results.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

What the codes say on life safety. Room smoke detectors for nursing homes.

The American Health Care Association will continue to monitor proposed new requirements in the code-making process, and will particularly concentrate on establishing a uniformity among the standards and determining the necessity for new requirements based on documentation of need. In so doing, AHCA's primary goal is to ensure a facility environment that enables residents and staff to function effectively in life-threatening situations.

Accident Prevention↗
PubMed1987

Preservation of platelets and blood products by intravenously administered dipyridamole in patients who undergo coronary artery bypass grafting.

The combination of dipyridamole and acetylsalicylic acid has been proven effective in preventing coronary artery bypass graft occlusion, but the benefits of dipyridamole alone have not yet been evaluated. In order to assess the value of dipyridamole alone, the authors randomized 24 patients (age range from 47 to 76 years) who underwent coronary artery bypass grafting to treatment with either dipyridamole (120 mg/d) by constant intravenous infusion or isotonic dextrose solution. They recorded platelet counts and aggregates, hemoglobin levels, total blood loss, blood products and intravenous fluids given and dipyridamole plasma levels, starting 8 hours before operation and continuing for 3 days after. The two groups were similar with respect to pump time, cross-clamp time and baseline demographic factors. Platelet counts during cross-clamping and 1 hour postoperatively were similar, but those on days 1, 2 and 3 postoperatively were significantly (p = 0.01 to 0.02) higher in the dipyridamole group. Mean blood losses in this group were 22% to 30% lower, but the difference was not significant. However, administration of erythrocytes and plasma was 49% to 58% less in the dipyridamole group (p = 0.005 to 0.048) over the same period. Dipyridamole plasma concentrations varied from 0.37 micrograms/ml before and during bypass to 1.5 micrograms/ml in the 3 days after. The authors conclude that dipyridamole administered intravenously to patients who undergo coronary artery bypass grafting may preserve hemostatically effective platelets so that fewer blood products are required.

Aged↗
PubMed1987

Think zinc.

Explore the source record for details and available documents.

Female↗
PubMed1986

Spontaneous lipid bilayer transmembrane electrical oscillations induced by concanavalin A-polysaccharide interaction.

Potassium ion currents through bilayer lipid membranes were modified by the membrane-surface reaction of concanavalin A and the polysaccharides dextran and glycogen. Aggregative reaction with glycogen occasionally induced spontaneous periodic ion current fluctuations with cycle times of minutes and durations of over one hour. Different electrochemical characteristics were observed between large planar lipid membranes and filter paper supported membranes, providing an indication that the aqueous unstirred surface layer participates in the control of the surface aggregative event. Lipid chemical composition was implicated in the development of spontaneous oscillations.

Concanavalin A↗
PubMed1986

Radiation-induced accelerated coronary arteriosclerosis.

There is a paucity of information on radiation-induced coronary heart disease. A young patient with myocardial infarction following mediastinal irradiation is described. The role of radiotherapy and chemotherapy on the subsequent development of coronary heart disease is discussed.

Adult↗
PubMed1986

A validation study of a simulation model for common source epidemics.

We consider an environment and a population of individuals who are susceptible to a disease caused by a pathogen spread from a common source. We view the sequence of events resulting in the illness of some individuals as consisting of three components: the introduction of the pathogens and their dispersion through the environment, the movement of susceptible individuals through the environment, and the physiological effects of exposure of susceptible individuals to various pathogen levels. We identify four important parameters: two for each of the first and third components. A computer simulation of a model with these features is developed and implemented to study a 1977 outbreak of toxoplasmosis. Questions of parameter estimation and model validation are considered in detail.

Computer Simulation↗
PubMed1986

In vivo probes: problems and perspectives.

Devices constructed for potential use as invasive bioprobes incorporate a selective receiving site for molecular or ionic recognition, and a transducer which is capable of translating a perturbation of physical chemistry of the determinant-site reaction (interaction) into a usable signal. Four types are envisioned--implants for general hospital use, transient-use probes to replace classical blood tests, short-term implantable probes and the long-term variety. Performance criteria are selectivity, sensitivity, fast response, site-reversible, small, rugged, inexpensive, biocompatible, calibratible, facile use by non-expert personnel and ease of telemetry. These demands, not surprisingly, create enormous challenges to the sensor specialist. With respect to biocompatibility the sensor must not be involved in infection, clot formation or antigenic response, and, furthermore, protein adsorption, etc., which can affect the sensor response should be avoided. Calibration remains a problem of monumental proportions. Many devices drift from calibrated levels even in in vitro experiments, let alone in the implanted milieu. One solution has been to carry out on-line switching between patient blood and standard solutions. However, this type of approach leaves a lot to be desired with respect to portability. Another method which is attracting increasing attention is the chemometric or artificial intelligence system involving compensation by multi-sensor array configurations. Sensitivity and limit-of-detection have attracted little research due to the overwhelming nature of other difficulties. In the present paper we evaluate a number of these technical problems and discuss the architecture of devices that are currently available. Finally, some thoughts as to priorities for re-directing sensor research in the bioprobe area are presented.

Biocompatible Materials↗