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Biomedical subjects

G A Thompson

Publications and source records attributed to G A Thompson.

At least 163 records · Page 9Linked to original sources
PubMed1982

Gentamicin disposition in children with chronic renal failure.

Gentamicin (G) disposition in six children with stable chronic renal failure (CRF) and in nine children with normal renal function (NRF) was determined by pharmacokinetic analysis of serum G concentration versus time data obtained over an 8-hour period following the administration of an intravenous loading dose. ES-TRIP curve fitting indicated that G disposition was best described by a biexponential function; however, a one-compartment open model also suitably characterized G disposition for an 8-hour period. Peak serum G concentrations were similar between the CRF and NRF groups, but concentrations were significantly different (P less than 0.005) at 8 hours following the loading dose. Also, significant differences (P less than 0.001) were found between the two groups for beta, t1/2 beta, plasma clearance, and k10. The relationship of creatinine clearance (Clcr) versus beta, described by the equation beta = 0.033 + 0.003 X Clcr (P less than 0.005, r = 0.97) permitted the best prediction of the G elimination constant from a parameter of renal function. This relationship remained linear over a broad range of Clcr values in our patients and in other previously reported children with CRF and NRF.

Adolescent↗
PubMed1982

Chest injuries in a district general hospital.

Patients with chest injuries requiring admission to the Kent and Canterbury Hospital over a period of one year have been reviewed. Good survival figures are possible when these patients are managed by general surgeons and anaesthetists once the initial traumatic insult and immediate resuscitation period are survived. Among the 54 patients admitted there were 11 deaths, of which 10 occurred within a few hours of the patient's reaching hospital. It seems unlikely that even with specialist facilities the outcome would have been different in these 10 patients. Provided that a combination of experienced surgical and anaesthetic teams supported by intensive care facilities are mobilised quickly enough the absence of specialised cardiothoracic expertise is not important.

Adult↗
PubMed1981

High performance liquid chromatographic analysis of catecholamines in growing and non-growing Tetrahymena pyriformis.

Tetrahymena pyriformis, strains NT-1 and W, harvested in logarithmic (growing) and stationary (non-growing) phases, were found by high-performance liquid chromatography to contain considerable quantities of dopamine. In addition, small amounts of epinephrine and norepinephrine were detected. Logarithmic-phase strain NT-1 cells contained 249 +/- 44 pg dopamine/10(6) cells compared to 477 +/- 42 pg/10(6) cells for logarithmic-phase strain W cells for logarithmic-phase strain W cells. The dopamine content of stationary-phase cells was approximately half the value of the logarithmic-phase cells. There was a significant amount of dopamine in the growth medium from stationary-phase cultures and, to a lesser extent, logarithmic-phase cells.

Animals↗
PubMed1981

Rapid membrane response during low-temperature acclimation. Correlation of early changes in the physical properties and lipid composition of Tetrahymena microsomal membranes.

When Tetrahymena pyriformis cells grown at 39 degrees C were chilled to 15 degrees C, a rapid desaturation of microsomal phospholipid-bound fatty acids was observed. A concurrent but even more rapid change in the physical properties of the microsomal lipids was detected by steady-state fluorescence polarization measurements of the probe 1,6-diphenyl-1,3,5-hexatriene in lipid multilamellar vesicles. Whereas polarization vs. temperature plots of lipids from 39 degrees C-grown cells showed discrete break points (abrupt slope changes thought to indicate altered phase separation rates) at characteristic temperatures, plots made using lipids from equivalent cells chilled to 15 degrees C for 15 or 20 min lacked such clearly defined break points. The sharp break points reappeared in plots of microsomal lipids from cells maintained at 15 degrees C for 30 min or longer, but in these curves the temperature of each break point was several degrees lower than in 39 degrees C-cell lipids and nearly the same as in cells fully acclimated to low temperature (48 h or more at 15 degrees C). Fluorescence polarization studies on mixtures of natural lipids from 39 degrees C-cells and cells shifted to 15 degrees C or on mixtures of natural and synthetic lipids revealed that each of the two break points in a polarization vs. temperature plot can respond to changes in lipid composition independently of the other. It is concluded that the expeditious desaturation of certain key fatty acids, perhaps coupled with limited retailoring of phospholipid molecular species, leads to pronounced physical changes in Tetrahymena microsomal membranes as the first step of low temperature acclimation.

Acclimatization↗
PubMed1981

Bilateral arterial injury in the lower limbs associated with open pelvic fractures: a case report.

The complications of pelvic fracture include blood loss, urinary tract injury, nerve injury and orthopaedic disability. Bleeding is quoted as the cause of death in 65 per cent of patients dying with a fractured pelvis (Rothenberger et al., 1978a). In a fifth of these patients disruption of the iliac or femoral vessels is the major source of bleeding. However, the incidence of major vessel injury in pelvic fractures is only 1 per cent. Arterial injury in both lower limbs is reported here, in association with an open fracture of the pelvis.

Adult↗
PubMed1981

Acute phencyclidine intoxication: incidence of clinical findings in 1,000 cases.

In 1,000 cases of phencyclidine (PCP) intoxication evaluated at the time of first examination in an emergency department, the incidence of "typical" findings was found to be lower than has been reported previously. Nystagmus and hypertension occurred in only 57% of our cases; some patients had only one of these findings and many had neither. The incidence of violence was 35%; bizarre behavior, 29%; and agitation, 34%. Changes in sensorium consisted of coma, lethargy/stupor, and acute brain syndrome; however, 46% of patients were alert and oriented. Motor signs included grand mal seizures, generalized rigidity, localized dystonias, catalepsy, and athetosis. Profuse diaphoresis, hypersalivation, bronchospasm, and urinary retention occurred in less than 5%. A small percentage had severe disturbances in vital signs, including three cases (0.3%) of cardiac arrest and 28 cases (2.8%) of apnea. Hypoglycemia and elevated serum CPK, uric acid, and SGOT/SPGT were common. Urine PCP levels did not correlate with the severity of the clinical findings.

Acute Disease↗
PubMed1981

Acute phencyclidine intoxication: clinical patterns, complications, and treatment.

We describe four major and five minor clinical patterns of acute phencyclidine (PCP) intoxication and give the incidence of findings in each pattern. Major patterns were acute brain syndrome (248 cases; 24.8%), toxic psychosis (166 cases; 16.6%), catatonic syndrome (117 cases; 11.7%), and coma (106 cases; 10.6%). Minor patterns included lethargy or stupor (38 cases; 3.8%), and combinations of bizarre behavior, violence, agitation, and euphoria in patients who were alert and oriented (325 cases; 32.5%). Patients with major patterns of PCP toxicity usually required hospitalization and accounted for most complications. In general, patients with minor patterns had mild intoxication and did not require hospitalization except for the treatment of injuries or autonomic effects of PCP. Various types of injuries occurred in 16%, and aspiration pneumonia occurred in 1.0% of all cases. There were 22 cases of rhabdomyolysis (2.2%), with three patients requiring dialysis for renal failure. One patient who had been comatose from PCP died suddenly. A fresh pulmonary embolism was found at autopsy.

Catatonia↗
PubMed1980

Effects of growth at different temperatures on the physical state of lipids in native microsomal membranes from Tetrahymena.

Fluorescence measurements of the probe 1,6-diphenyl-1,3,5-hexatriene in native Tetrahymena pyriformis microsomal membranes revealed characteristic "break points" in curves of polarization vs. temperature. In the 5--35 degree C range, membranes from cells grown at 39 degrees C exhibited two break points, one at 11.6 +/- 0.6 degrees C and another at 23.1 +/- 1.6 degrees C. Membranes from 15 degrees C grown cells also showed two break points, one at 8.0 +/- 1.7 degrees C and another at 17.7 +/- 1.7 degrees C. Complementary measurements of turbidity (absorbance at 360 nm) vs. temperature revealed break points at approximately the same temperatures as observed with the fluorescent probe, thus strengthening the likelihood that the break points signify the onset or termination of lipid phase separations or some other significant structural alteration of lipids. In general, break points measured in the native membrane samples occurred at slightly lower temperatures than did break points in lipids extracted from comparable membranes. This suggests two possible types of protein--lipid interaction. First, there may be a selective withdrawal of relatively highly saturated phospholipid molecular species from the bulk lipid phase and into protein annulus regions. Alternatively, the configuration of the hydrophobic core of certain key membrane proteins may be such that nonspecific interactions with the lipids stabilize the liquid-crystalline phase.

Chemical Phenomena↗
PubMed1980

The effects of high concentrations of sodium or calcium ions on the lipid composition and properties of Tetrahymena membranes.

Tetrahymena pyriformis cells have been grown in media varying in NaCl concentration from 3.7 mM (normal medium) to 0.3 M and varying in CaCl2 from 0.2 mM (normal medium) to 0.1 M. Tetrahymena grown in 0.3 M NaCl showed relatively few alterations in phospholipid composition, with significant changes being found only in the cell surface membranes (pellicle), which incrased in phosphatidylethanolamine content from 39% (low Na+) to 48% (high Na+) of the total phospholipids. The small decrease in fatty acid unsaturation and increase in shorter chain fatty acids in pellicle phospholipids were not statistically significant. No significant changes in phospholipid head group composition or fatty acid distribution were observed in high Ca2+-grown cells. Complementary studies of membrane fluidity, as inferred from freeze-fracture electron microscopy analysis, indicated that membranes of high Na+-acclimated cells were similar to those of control cells, when each was measured in its respective medium. However, the outer alveolar membrane of the pellicle and the food vacuolar membrane were considerably less fluid in high-Ca2+ cells. The lower fluidity in vacuolar membranes may have been responsible for alterations in the cells' capacity to form food vacuoles.

Animals↗
PubMed1980

Discontinuous thermotropic response of Tetrahymena membrane lipids correlated with specific lipid compositional changes.

Steady-state fluorescence polarization measurements of 1,6-diphenyl-1,3,5-hexatriene in microsomal lipids from Tetrahymena pyriformis cells grown at 39 or 15 degrees C revealed discrete slope discontinuities in plots of polarization vs. temperature. Two well-defined 'break points' were present in the 0-40 degrees C temperature range examined and their precise location was dependent upon the growth temperature of the cells. By mixing phospholipids from cells grown at different temperatures, the break points at 17.5 and 32 degrees C in 39 degrees C-lipid multilayer preparations were shown to correlate with the breaks at 12 and 27 degrees C, respectively, in similar preparations from 15 degrees C-grown cells. The discrete break points were also present, but at slightly different characteristic temperatures, in a phosphatidylcholine fraction and a phosphatidylethanolamine plus 2-amino-ethylphosphonolipid fraction purified from the phospholipids and in total microsomal lipids (phospholipids plus the sterol-like triterpenoid, tetrahymanol). However, catalytic hydrogenation of the phospholipid fatty acids or mixing the non-hydrogenated phospholipids with increasing proportions or synthetic dipalmitoyl phosphatidylcholine eliminated the break points. We interpret this discontinuous thermotropic response in microsomal lipids as signalling a lipid phase separation of importance in regulating physiological events.

Animals↗
PubMed1980

Studies on the size, location and turnover of calcium pools accessible to growing Tetrahymena cells.

Tetrahymena pyriformis cells in the logarithmic phase of growth accumulate 2.5--3.75 times as much calcium per unit volume as is present in the growth medium. It appears that most of this calcium is stored in a non-ionic form, with approximately 30% existing in the cilia, near its site of action in effecting ciliary reversal. The exchange of extracellular 45Ca2+ with the major internal pools is extremely rapid, exhibiting a t1/2 of less than 0.5 h. Sites located on the cilia are responsible for 35--50% of Ca2+ influx, with the remainder entering through other positions on the cell surface.

Animals↗
PubMed1980

Studies of membrane formation in Tetrahymena. The identification of membrane proteins and turnover rates in nongrowing cells.

Membrane proteins within cell fractions of Tetrahymena have been separated by polyacrylamide gel electrophoresis and the turnover of these proteins has been studied in nongrowing cells using double labeling procedures. Lactoperoxidase iodination and two-dimensional gel separations have revealed over 20 surface-labeled proteins, two of which are responsible for the single peak found in ciliary and nonciliary surface membranes. Turnover measurements show that there is heterogeneity in the rates at which membrane proteins turn over. The data suggest that larger proteins may turn over at higher rates in the microsomal fraction, as previously shown in mammalian cells. This was not found in the surface membrane fractions of Tetrahymena. However, membrane-associated cytoskeletal proteins had lower turnover rates than integral membrane proteins, and significant heterogeneity was found among the integral proteins measured. The implications of these findings for possible modes of membrane biogenesis in Tetrahymena are discussed.

Animals↗
PubMed1980

Evidence for a pronounced secretion of cyclic AMP by Tetrahymena.

The unicellular eukaryote Tetrahymena pyriformis secretes significant amounts of cyclic AMP into its external medium. Cells transferred from growth medium into any of the following three different non-nutrient media: (a) 5 mM phosphate buffer containing 47 mM NaCl and 1 mM MgSO4, (b) 10 mM Tris, or (c) 1.3 mM Tris containing 1 mM citrate and 1 mM Ca(OH)2, released to the outside almost 60--80% of the total cyclic AMP produced during 2--5 h of incubation. Tris-citrate-Ca+2 medium was chosen for further experiments because of its minimal nonspecific interference in the cyclic AMP radioimmunoassay. The identity of the secreted material recognized as cyclic AMP by radioimmunoassay was confirmed by demonstrating its almost complete hydrolysis with commerical beef heart phosphodiesterase. Furthermore, the radioimmunoassay-active material in the concentrated medium co-chromatographed on paper with [3H]cyclic AMP, as judged by assay of the eluted material. After resuspending cells in Tris-citrate-Ca2+ medium, the extracellular concentration of cyclic AMP rose steadily over a 5-h period, reaching a level equvalent to approximately 35--50 pmol cyclic AMP/10(6) cells vs. an internal cyclic AMP quantity at 5 h of 8--10 pmol/10(6) cells. After 5 h, the level of extracellular cyclic AMP reached a plateau. There was no degradation or uptake of external cyclic AMP by the cells during this period.

Animals↗
PubMed1980

Lipid Composition and Metabolism of Volvox carteri.

The membrane structural lipids of somatic cells and gonidia isolated from Volvox carteri f. nagariensis spheroids have been characterized. The principal polar lipid components of both cell types are sulfoquinovosyl diglyceride, mono- and digalactosyl diglyceride, phosphatidylglycerol, phosphatidylethanolamine, and 1(3), 2-diacylglyceryl-(3)-O-4'-(N,N,N,-trimethyl)homoserine. Light-synchronized cultures of spheroids were shown to incorporate [(14)C]bicarbonate, [(35)S]sulfate, [(14)C]palmitic acid, and [(14)C]lauric acid into complex lipids. [(14)C]Palmitic acid was incorporated mainly into diacylglyceryltrimethylhomoserine and was not significantly modified by elongation or desaturation. In contrast, [(14)C]lauric acid was incorporated into a wider variety of complex lipids and was also converted into longer chain saturated and unsaturated fatty acids. Volvox is a promising system for studying the role of membranes in algal cellular differentiation.

Journal Article↗
PubMed1980

Biopharmaceutic evaluation of etofylline clofibrate and its drug formulation.

The biopharmaceutic criteria of Duolip and its active principle, 1-(theophyllin-7-yl)-ethyl-2-[2-(p-chlorophenoxy)-2-methylpropionate] (etofylline clofibrate, ML 1024), are described. ML 1024 was found to be practically insoluble in water at pH values ranging from 2 to 7.4 and in human serum. A very low dissolution rate of the drug from the capsule preparation was found in artificial gastric and intestinal fluid, along with little cleavage to the individual components clofibric acid and etofylline. The particle size was mainly less than 40 micrometers. For the classification of granules the granule size, the angle of repose (tan alpha), the flow time, the stamp volume and the packing factor were determined.

Biopharmaceutics↗