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Biomedical subjects

G Cooper

Publications and source records attributed to G Cooper.

At least 217 records · Page 12Linked to original sources
PubMed1979

An atomizer of high stability.

An atomizer having excellent stability and requiring little maintenance was tested. The basic design incorporates modifications to a previously described atomizer of Liu and Lee. This modified atomizer yielded a constant particle size and concentration output that varied by less than +/- 2% of the mean value for 25 hours. Liquid is aspirated at the rate of 100 mL/hr., making the atomizer suitable for use with solvents of various volatilities. The orifices, critical to the performance of the atomizer, are easily cleaned or replaced.

Aerosols↗
PubMed1979

Myocardial energetics during isometric twitch contractions of cat papillary muscle.

During myocardial tetanus, when activation is maximum and constant, there is a linear relationship throughout contraction between oxygen consumption (MVo2) and the cumulative product of active tension and time (integral of AT). The goal of this study was to determine the relation of MVo2 to integral of AT during isometric myocardial twitch contractions. Ten right ventricular cat papillary muscles were studied in a flow respirometer. MVo2 was determined during contractions unloaded from Lmax to a slack length at successive 100-ms intervals after stimulation. In contrast to the linear relationship observed during tetanus, MVo2/integral of AT varied during twitch contractions: when the muscles were made slack 100 ms after stimulation MVo2/integral of AT was 389 +/- 51 (SE) (nl of O2/mg of dry muscle)/(N of active tension/mm2.s of active tension). This value was 94 +/- 7 at peak active tension and was constant thereafter. There was a continuous increase in cumulative MVo2 as integral of AT increased; before integral of AT began, MVo2 was 0.41 +/- 0.04 (nl of O2/mg)/contraction at Lmax and 0.22 +/- 0.04 at a slack length; at peak isometric tension MVo2 was 1.84 +/- 0.19; for a complete contraction MVo2 was 2.89 +/- 0.25. These data support two concepts 1) activation energy is small and dependent on initial length and tension; and 2) integral of AT is variably energy dependent throughout the entire isometric twitch contraction.

Animals↗
PubMed1979

The combined effect of smoking and coffee drinking on LDL and HDL cholesterol.

Conflicting reports on the effect of smoking and coffee drinking on lipoproteins prompted us to study the combined effect of these two associated, widely prevalent habits in 361 persons randomly sampled from the Evans County cohort. Low-density lipoprotein (LDL) cholesterol levels were significantly higher among persons who smoked cigarettes and consumed five or more cups of coffee per day than among nonsmokers who abstained from coffee. Conversely, high-density lipoprotein (HDL) cholesterol was higher in persons who did not smoke or drink coffee than in coffee-consuming smokers. However, this trend was not statistically significant. Triglycerides and very low-density lipoprotein (VLDL) cholesterol were highest among smokers who drank five or more cups of coffee per day, but these differences did not reach statistical significance. Lipoprotein cholesterol levels were adjusted for age, sex and body mass. Smoking and coffee drinking interact in affecting LDL and total cholesterol, but coffee drinking alone did not appear to affect blood lipids.

Age Factors↗
PubMed1978

Bihemispheric decreases of regional cerebral blood flow in dementia: correlation with age-matched normal controls.

Regional cerebral blood flow (rCBF) was measured by the xenon 133 inhalation method in 20 patients with senile and presenile dementia, and values were compared with flow data obtained in a series of 44 age-matched normal controls. The rCBF was reduced in patients with both presenile and senile dementia, and the degree of decrease exceeded the age-related rCBF decline in normal subjects. Similar rCBF reductions were observed in the left and right cerebral hemispheres and in general were homogeneously distributed in the various areas. The rCBF reductions in normal aging and in dementia may be associated with similar underlying cerebral morphological changes. Our findings suggest that the greater rCBF decreases in dementia compared with the values in age-matched controls may quantitatively reflect more severe pathological alterations in the brains of patients with intellectual deterioration.

Adult↗
PubMed1978

Regional cerebral blood flow in parkinsonism. Measurement before and after levodopa.

Data from recent studies in experimental animals suggest that central dopaminergic mechanisms may be involved in regulation of the regional cerebral blood flow (rCBF) in the mammalian brain. In order to evaluate possible effects of dopaminergic stimulation on human cerebral circulation, rCBF was measured by the 133Xenon inhalation technique in 26 patients with Parkinson's disease before and after the chronic oral administration of levodopa combined with a peripheral Dopa-decarboxylase inhibitor. Treatment with levodopa did not induce significant alterations in the mean brain, mean hemispheric or regional flow values in these patients. These findings suggest that the dopaminergic system does not play an important role in modulation of the rCBF in man.

Adult↗
PubMed1978

Correlation between regional cerebral blood flow and brain atrophy in dementia. Combined study with 133Xenon inhalation and computerised tomography.

Measurement of the regional cerebral blood flow (rCBF) by the 133Xenon inhalation method and computerised tomography were performed in 25 patients with presenile and senile dementia. Reduction of rCBF and various degrees of ventricular enlargement and cortical sulcal widening were demonstrated in the majority of demented subjects. However, there was no correlation between rCBF values and the severity of ventricular dilatation or cortical atrophy. These findings suggest that loss of brain substance is not an important factor in the reduction of rCBF in dementia.

Adult↗
PubMed1978

Analytical performance and comparability of the determination of triglycerides by 12 Lipid Research Clinic laboratories.

Twelve Lipid Research Clinic laboratories performed automated fluorometric triglyceride analyses on four control serum pools of known concentration by a modified Hantzsch reaction. The analyses were done during a two-year period, with use of common standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through rigorous standardization and control of the entire analytical procedure. Individual instrument biases varied from an average of 4.9% below to 1.0% above reference values. Between-run variability was often less than within-run variability and interlaboratory variation was substantially less than intralaboratory variation. The total standard deviation for all instruments ranged from 37 to 63 mg/liter. Only 5 to 14% of this variation was due to differences among instruments. The among-instruments standard deviation ranged from 12 to 17 mg/liter; the between-run, within-instrument standard deviation ranged from 29 to 46 mg/liter, and within-run standard deviation from 27 to 40 mg/liter. The significance of the results for long-term collaborative studies is discussed.

Analysis of Variance↗
PubMed1977

Delay in migration of symbiotic algae in Hydra viridis by inhibitors of microtubule protein polymerization.

An English strain of the fresh water symbiotic coelenterate Hydra viridis was experimentally "bleached" of its Chlorella algae and maintained indefinitely by feeding. The algal symbiosis could be re-established by injecting other symbiotic algae into aposymbionts. Although algal uptake and recognition were not affected by microtubule protein polymerization inhibitors, these compounds i.e., podophyllotoxin, beta-peltatin and vinblastine had delaying effects on the migration of the algae through the host digestive cells. Picropodophyllotoxin did not delay migration. The rates, the reversibility and the sensitivity of algal migration to low concentrations of drugs known to bind tubulin suggests the symbionts migrate somehow via labile polymerization of host hydra tubulin into microtubules.

Animals↗
PubMed1977

Analytical performance and comparability of the determination of cholesterol by 12 Lipid-Research Clinics.

Twelve Lipid-Research Clinic laboratories performed automated cholesterol analyses on four control-serum pools of known cholesterol concentration, using the Liebermann-Burchard reaction. The analyses were done during a two-year period, with the same standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through the rigorous standardization and control of the entire analytical procedure. The significance of these results for long-term collaborative studies is discussed. Individual laboratory biases averaged from 0.5 to 2.0% below Abell-Kendall reference values. Between-run variability was about equal to within-run variability and inter-laboratory variation was substantially less than intra-laboratory variation. The total standard deviation for all instruments was about 0.04 g/liter. Only 8-15% of this variation was due to differences between instruments. The between-instrument standard deviation ranged from 0.011 to 0.015 g/liter; the between-run, within-instrument standard deviation ranged from 0.023 to 0.030 g/liter; and within-run standard deviation ranged from 0.023 to 0.028 g/liter. The significance of the achieved results for long-term collaborative studies is discussed.

Cholesterol↗
PubMed1976

The myocardial energetic active state. I. Oxygen consumption during tetanus of cat papillary muscle.

The potential role of active state maintenance as a determinant of myocardial oxygen consumption (MVO2) has not been defined. Right ventricular papillary muscles from 15 cats were studied in a polarographic myograph at 23 degrees C in a Krebs-Ringer solution containing 7.5 mM Ca2+ and 10 mM caffeine. MVO2 was determined for isometric tetani at Lmax of 1-5 seconds' duration. Increases in tetanus duration related linearly to increments in both active tension time (delta active tension) and MVO2. In order to examine the oxygen cost of active state maintenance not attributable to associated tension generation, both the same isometric and 2.5- to 10.0-second lightly preloaded isotonic tetani were produced in nine muscles. For each tetanus duration the contribution throughout the contraction of developed force (preload) to MVO2 could be subtracted from overall isotonic MV02. In the absence of the MVO2 associated with force development, the active state duration was related linearly to MVO2, with a mean active state MVO2 of 2.42 +/- 0.29 nl O2/mg dry muscle/sec of isotonic tetanus; this MVO2 is 68% of the value of 3.58 +/- 0.42 nl O2/mg dry muscle/sec that was obtained for isometric tetanus at Lmax. This study identifies active state maintenance as the major determinant of MVO2 during myocardial tetanus and, furthermore, suggests the possibility that alterations in ative state intensity and duration may be the biochemical mechanism by which other determinants of MVO2 act in a more physiological setting.

Animals↗
PubMed1975

Role of mitochondrial calcium metabolism in the altered contractility of pressure-hypertrophied right ventricular myocardium.

Pressure-hypertrophied right ventricular myocardium (RVH) demonstrates paradoxically increased oxygen consumption (MVO2) related to increase- in vitro energy-linked mitochondrial calcium flux. The present experiments were designed to measure mitochondrial Ca retention in intact RVH and relate changes in mitochondrial Ca metabolism to altered RVH contractility and relaxation. Sixteen cats were pulmonary artery banded and their hearts plus paired controls were perfused with 45Ca-labeled Krebs-Henseleit (30 degrees C) at 120 beats/min for 10 min. Papillary muscles from both right ventricles were studied in a muscle bath. Mitochondria were isolated from the right ventricles and retained 45Ca measured. At the length at which active tension is developed (Lmax) papillary muscle abnormalities were, for reduced active tension, 6.9 gm/mm2 +/- 0.6 SE for control, 4.0 +/- 0.6 for RVH, p less than 0.001; for slower contraction rate, 40.8 gm/mm2/sec +/- 6.3 control, 16.9 +/- 2.8 RVH, p less than 0.001; for slower relaxation rate, 22.0 gm/mm2/sec "/0 1.5 control, 11.1+/- 1.6 RVH, p less than 0.001; for greater time to peak tension, 317 msec +/- 7 control, 408 +/- 13 RVH, p less than 0.001; for greater relaxation time, 590 msec +/- 29 control, 800 +/- 39 RVH, p less than 0.001. Retained 45Ca of mitochondria was increased from 16.75 +/- 0.96 nM/mg of protein for control, to 20.82 +/- 0.98 for RVH, p less than 0.005. This increase in mitochondrial 45Ca retention correlated (r = 0.93, p less than 0.001) with the decreased rate of papillary muscle relaxation. These data show an increased 45Ca retention of mitochondria in pressure-induced RVH and relate this biochemical abnormality to a decreased myocardial relaxation in this state.

Animals↗