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Biomedical subjects

A Cooper

Publications and source records attributed to A Cooper.

At least 325 records · Page 18Linked to original sources
PubMed1980

Relation of anthropometric and dynamometric variables to serious postoperative complications.

Prediction of serious postoperative complications by using standard anthropometric and biochemical nutritional variables was attempted in 225 patients admitted for major abdominal surgery. In 102 of the patients hand-grip dynamometry was also measured, and this proved the most sensitive test, predicting complications in 48 of the 55 patients (87%) who developed them (p < 0.001). Arm muscle circumference and forearm muscle circumference below 85% of the standard value were also of predictive value (p < 0.02 and p < 0.01 respectively); weight for height and serum albumin concentrations were less satisfactory, while weight loss of more than 10% was not significantly related to complications. Dynamometry is a useful, rapid, and inexpensive screening test for detecting malnutrition that is likely to predispose to serious postoperative morbidity.

Abdomen↗
PubMed1979

Energy uptake in the first step of visual excitation.

Perception of light by the retina starts with the absorption of a photon by 11-cis retinal, which is covalently incorporated into the membrane-bound protein, rhodopsin. The initial result of photon capture is the very rapid formation of a red-shifted species, bathorhodopsin (also known as prelumirhodopsin), which is (meta-)stable at liquid nitrogen temperature but which decomposes at higher temperatures, in the dark, through a series of intermediate stages, resulting in the release of all-trans retinal from the apoprotein, opsin. Bathorhodopsin formation is the only photochemical step in the overall reaction and, therefore, merits investigation. Several models for the process have been proposed, and have been critically reviewed, although no consensus yet exists as to the nature or mechanism of formation of the batho intermediate. I report here on the first direct measurement of photon energy uptake during bathorhodopsin formation from bovine rhodopsin, and on its possible significance.

Animals↗
PubMed1979

Glucose intolerance during pregnancy. I. A reappraisal of alleged screening criteria.

This study was designed to examine various risk factors in regard to their correlation with carbohydrate intolerance and in relation to birthweight and well-being of the newborn. Of the various alleged prediabetic stigmata among a selected group of 390 women, only marked maternal overweight, diabetes in previous pregnancy, family history of diabetes at the sibling level, and accompanying maternal morbidity were associated with increased risk for both gestational carbohydrate intolerance and for morbidity in the newborn. In women over 30 years of age a definite increase in the incidence of carbohydrate intolerance was noted among this high-risk population. Multiplicity of screening criteria presented a significantly (P less than 0.001) greater risk for the development of carbohydrate intolerance and was seen to be positively (P less than 0.001) with increased perinatal morbidity.

Adult↗
PubMed1979

Glucose intolerance during pregnancy. II. A comparative study of diagnostic screening methods.

The present study was designed to compare the relative validity of the 2-hour postprandial glucose test (2hpp) and the rapid intravenous glucose tolerance test (IVGTT) as predictors of the outcome of pregnancy. Both tests were performed at the onset of the third trimester of pregnancy in each of 77 women who constituted a selected group of patients considered to be at high risk of developing gestational diabetes. Data concerning newborns were recorded in each case. The IVGTT was found to give a significantly larger yield of positive results (44.15%) as compared to the 2hpp test (35.06%). Furthermore, significantly heavier babies and higher rates of perinatal morbidity were noted in those cases with abnormal IVGTT results as compared to those with normal values. No such association was seen in those cases with abnormal values of 2hpp. These results suggest that the rapid IVGTT is a more dependable test than a single postprandial blood glucose estimation in screening pregnant women for gestational diabetes.

Adult↗
PubMed1976

Energetics of primary processes in visula escitation: photocalorimetry of rhodopsin in rod outer segment membranes.

A sensitive technique for the direct calorimetric determination of the energetics of photochemical reactions under low levels of illumination, and its application to the study of primary processes in visula excitation, are described. Enthlpies are reported for various steps in the bleaching of rhodopsin in intact rod outer segment membranes, together with the heats of appropriate model reactions. Protonation changes are also determined calorimetrically by use of buffers with differing heats of proton ionization. Bleaching of rhodopsin is accompanied by significant uptake of heat energy, vastly in excess of the energy required for simple isomerization of the retinal chromophore. Metarhodopsin I formation involves the uptake of about 17 kcal/mol and no net change in proton ionization of the system. Formation of metarhodopsin II requires an additional energy of about 10 kcal/mol and involves the uptake on one hydrogen ion from solution. The energetics of the overall photolysis reaction, rhodopsin leads to opsin + all-trans-retinal, are pH dependent and involve the exposure of an additional titrating group on opsin. This group has a heat of proton ionization of about 12 kcal/mal, characteristic of a primary amine, but a pKa in the region of neutrality. We suggest that this group is the Schiff base lysine of the chromophore binding site of rhodopsin which becomes exposed on photolysis. The low pKa for this active lysine would result in a more stable retinal-opsin linkage, and might be induced by a nearby positively charged group on the protein (either arginine or a second lysine residue). This leads to a model involving intramolecular protonation of the Schiff base nitrogen in the retinal-opsin linkage of rhodopsin, which is consistent with the thermodynamic and spectroscopic properties of the system. We further propose that the metarhodopsin I leads to metarhodopsin II step in the bleaching sequence involves reversible hydrolysis of the Schiff base linkage in the chromophore binding site, and that subsequent steps are the result of migration of the chromophore from this site.

Animals↗
PubMed1976

Characterization of an adenylate cyclase system sensitive to histamine H2-receptor excitation in cells from dog gastric mucosa.

A method of preparing viable cells from dog gastric mucosa is described. Cyclic AMP in these cells is elevated by histamine and 4-methyl histamine but 2-methyl histamine is only a weak agonist. The effects on cyclic AMP levels are inhibited competitively by metiamide and burimamide which give apparent KBvalues of 3.5x10-7 M and 2.3x10-6 M, respectively. These values are similar to those reported for other histamine H2-receptor systems. The H1-receptor antagonists, mepyramine and chlorpheniramine, have no inhibitory effect on the histamine induced elevation of cyclic AMP: promethazine inhibits the system but not by a competitive mechanism. It is concluded that the histamine stimulated adenylate cyclase system is probably located in the parietal cell component.

Adenylyl Cyclase Inhibitors↗
PubMed1976

Thermodynamic fluctuations in protein molecules.

Apparently conflicting views of the physical nature of globular proteins, and other macromolecules, may be reconciled by consideration of the inevitable thermodynamic fluctuations inherent in microscopic systems. Discrete protein molecules, considered singly, undergo sizeable fluctuations in thermodynamic properties which are manifest in their stochastic properties. This is not incompatible with time-averaged studies of ensembles of proteins from which a more compact, rigid, and static view of these molecules may be obtained.

Proteins↗
PubMed1976

Selective N-actylation of gentamicin antibiotics-synthesis of 1-N-acyl derivatives.

Treatment of acid addition salts of aminoglycoside-aminocyclitol antibiotics of the gentamicin-sisomicin class, with one equivalent of triethylamine and an acylating agent results in selective formation of 1-N-acyl derivatives. This is in contrast to acylation of the antibiotic free bases which results in preferential acylation of other basic centres in the molecule. Origins of the observed selectivity are discussed. In vitro antibacterial activities of several new 1-N-acy1 derivatives of gentamicin, sisomicin and verdamicin are reported.

Acylation↗
PubMed1975

The management of glottic carcinoma by primary irradiation with surgery in reserve.

Four hundred nineteen cases of carcinoma of the larynx (1962-1965, Christie Hospital) treated primarily by radiation with surgery in reserve for cases where radiation failed, are reviewed. Two hundred ninety-one of these cases were glottic carcinomas and cure rates, and contribution from subsequent surgery is indicated in detail. Finally the overall results are compared with a larger series of 605 cases (1955-1961). Five-year cure rate in early cases is consistent at 89 percent; likewise in the latest cases at 30 percent, the intermediate group appear to have improved by some 8 percent over the period outlined. The overall cure rate is 70 percent.

Carcinoma, Squamous Cell↗