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Biomedical subjects

J Davis

Publications and source records attributed to J Davis.

At least 523 records · Page 29Linked to original sources
PubMed1976

Diaphragm function and alveolar hypoventilation.

A syndrome of alveolar hypoventilation has been identified in a group of patients with bilateral diaphragm paralysis. Eight patients were studied in whom diaphragm weakness had been suggested by paradoxical (inward) movement of the abdominal wall on inspiration, of whom seven had evidence of a generalized neuromuscular disorder. Diaphragm function was assessed quantitatively by measurement of the change in transdiaphragmatic pressure during a maximum inspiration (deltaPDi). In five patients, deltaPDi was zero and in the others ranged from 2-6 cm H2O (normal greater than 25 cm H2O) indicating paralysis and severe weakness in the respective groups. Fluoroscopy of the diaphragm was found to give misleading results, and the resons for this are considered. Vital capacity ranged from 65-30 per cent of the predicted normal in the upright posture, typically falling by about a half in the supine posture. Alveolar hypoventilation was present in five patients when supine and in six when asleep, the deterioration in blood gases associated with sleep generally being much greater in these patients than in normal subjects. Respiratory rate was significantly greater than age-matched controls. The ventilatory response to CO2 was impaired. The PCO2 could be brought to normal levels by voluntary hyperventilation, and the unreliability of voluntary respiratory manoeuvres of this kind as indices of ventilatory reserve is emphasized. Alveolar hypoventilation was associated with disturbed sleep, morning headache and day-time fatigue. Symptomatic benefit was achieved by the use of a cuirass respirator at night.

Adult↗
PubMed1976

The biochemical basis of nitroblue tetrazolium reduction in normal human and chronic granulomatous disease polymorphonuclear leukocytes.

Normal human polymorphonuclear leukocytes (PMN) placed in anaerobic chambers reaching pO2's of less than 5 mm Hg fail to generate O2-, iodinate ingested particles, and stimulate glucose-1-14C oxidation through the hexose monophosphate shunt. The observation that anaerobic cells are incapable of generating O2- or reducing nitroblue tetrazolium (NBT) to formazan supports the idea that NBT reduction in phagocytizing PMN is due exclusively to oxygen-dependent O2- generating oxidase which is deficient in chronic granulomatous disease leukocytes, despite their hyperphagocytic capacity.

Granulomatous Disease, Chronic↗
PubMed1975

Evidence for fidelity of chromatin reconstitution.

Several lines of evidence are presented which support the contention that chromatin may be dissociated, fractionated, and reconstituted without altering the compositional, structural, or transcriptional integrity of the genome. The similar compositions of native and reconstituted chromatins are suggested by the absence of significant differences in their protein/DNA ratios and in the polyacrylamide gel electrophoretic profiles of their histones and nonhistone chromosomal proteins. Criteria for fidelity of genome structure in reconstituted chromatin include binding of reporter molecules with specificity for the minor groove of DNA, binding of histones, number of sites available for addition of nucleotides, and circular dichroism spectra. When the transcriptional activities of native and reconstituted chromatins were compared under conditions where reinitiation is prohibited, significant changes were not observed. Taken together, the present results strongly suggest, but do not conclusively establish, fidelity of chromatin reconstitution.

Animals↗
PubMed1975

Effect of gas density and ventilatory pattern of steady-state co uptake by the lung.

The steady-state uptake of carbon monoxide was measured in five normal subjects to study stratified inhomogeneity of gases in the pulmonary airways. An attempt was made to assess the effect of stratified inhomogeneity by varying the physical properties of the inspired gases and the depth and rate of ventilation by the subjects. Twelve different controlled patterns of breathing were followed by each subject on each of three gas mixtures (20% O2 with N2, He and SF6 plus 0.04% CO in each case). The experimental results show that CO uptake was significantly different when breathing the different density gases but that it was always greatest from the most dense gas SF6 and least from He. If the uptake of CO from the inspired gas across the alveolar membrane were controlled by simple molecular diffusion then as gas density decreases uptake would increase. As inspiratory flow rate was increased there was an almost linear increase in CO uptake for each gas mixture with a difference in uptake between the different-density gases which became most marked at the higher flow rates. Flow rate was increased in two ways: by maintaining tidal volume and altering breathing frequency or by maintaining frequency and altering tidal volume. The results for the two extremes, helium and SF6, indicated a difference between these methods of increasing flow rate. In the case of SF6, doubling the flow rate by increasing breathing frequency gave an uptake only marginally lower than doubling the depth of penetration. With helium, however, it was necessary to treble the frequency to obtain the increment of CO uptake achieved by doubling the depth of penetration. The experimental observations are explained by the use of a model based on Taylor dispersion in the conducting airways. The conclusion is that the results confirm the presence of significant stratified inhomogeneity in the airways of the lung.

Carbon Monoxide↗
PubMed1975

Rebound phenomena in manic patients following physostigmine. Preliminary observations.

The authors have administered physostigmine intravenously to three hospitalized manic patients on a double-blind basis. All three individuals showed clinical change both during and after the physostigmine period, which can be clearly delineated into three distinct phases. The behavioral modifications occurring during the physostigmine run did not qualitatively alter the underlying mania. The authors focus on 'rebound' phenomena, or post-physostigmine changes, as a possible clinical index with which chemically to characterize the initial state of amine imbalance responsible for a given affective illness. The data are considered consistent with an adrenergic-dopaminergic-cholinergic balance hypothesis of affective disorders, and may provide a relevant link in understanding the interface or crossover between manic and schizo-affective illness.

Bipolar Disorder↗
PubMed1975

An antigenically related tryptic polypeptide from several mammalian type C RNA virus p30s.

Limited tryptic digestion of p30 antigen (the major internal viral protein) of type C viruses isolated from hamster, rat, and gibbon ape yielded a polypeptide fragment with a molecular weight of approximately 10,000 daltons. Some antigenic determinants with interspecies specificity were retained on these polypeptides, which in serological tests cross-reacted with antibody produced previously against a similar fragment obtained from mouse p30. Exhaustive trypsinization resulted in further fragmentation with concomitant loss of serologic activity. The results suggest that all mammalian type C virus p30s have an antigenically related polypeptide core which is not readily digested by trypsin.

Animals↗
PubMed1975

Effects of selected sulfhydryl inhibitors on nonhistone chromosomal proteins of HeLa cells.

Effects of the SH inhibitor sodium iodoacetate, alone and with adjuncts menadiol diphosphate, sodium malonate, sodium fluoride and heparin, on incorporation of tryptophane-3 H into nonhistone chromosomal proteins of HeLa cells were examined. The drugs block incorporation of tryptophane-3 H into nonhistone chromosomal proteins far more than incorporation of leucine-3 H into total cellular proteins. Drug effects on thymidine phosphorylation and DNA synthesis in HeLa cells exceed corresponding effects on fibroblasts from normal healing wounds.

DNA Nucleotidyltransferases↗
PubMed1975

Pulmonary parenchymal tissue volume measurements in graded degrees of pulmonary edema in dogs.

We investigated the accuracy and the sensitivity of a modification of the acetylene inhalation technique for the determination of lung tissue volume (Vt) during various grades of hemodynamic pulmonary edema in 23 dogs. After base-line acetylene measurements were obtained, intravascular driving force (pulmonary wedge pressure minus intravascular colloid osmotic pressure) was varied between -8 and +71 mm Hg by the inflation of an intra-aortic ballon and the infusion of isotonic saline. After 30 minutes at this new driving force, four timed acetylene samples were again collected. Vt (when factored by alveolar volume, VA) increased from base line to 0.23 plus or minus 0.07 ml/ml between a driving force of 0 and + 17 mm Hg. This same change in Vt/VA was accompanied by an increase in the lung wet weight-dry weight ratio from 3.84 plus or minus 0.31 to 5.2 plus or minus 0.25. Vt was 271 plus or minus ml compared with an actual lung wet weight of 288 plus or minus 57 g; Vt tended to overestimate lung wet weight in severe pulmonary edema. Alloxan-induced pulmonary edema (6 dogs) tended to parallel these data. We conclude that the acetylene method may ve a relatively accurate noninvasive method for the determination of increasing lung water in pulmonary edema.

Acetylcholine↗
PubMed1975

The role of superoxide anion and hydrogen peroxide in phagocytosis-associated oxidative metabolic reactions.

The contribution of hydrogen peroxide (H2O2) and one of its unstable intermediates, superoxide anion (O2), to the oxidative reactions that occur in phagocytizing leukocytes was explored by depleting these cells of O2. This was accomplished by allowing them to phagocytize latex particles coated with superoxide dismutase (SOD), which catalyzes the generation of H2O2 from O2. Although the rate and extent of phagocytosis of latex coated with bovine serum albumin was similar to latex coated with SOD, the rate of oxygen consumption, [14C]formate oxidation, [1-14C]glucose oxidation, and iodination of zymosan particles was significantly enhanced by SOD. In contrast, the rate and extent of reduction of nitroblue tetrazolium (NBT) was diminished by 60%. These studies indicate that the majority of NBT reduction by leukocytes is due to O2, whereas stimulation of the hexose monophosphate shunt and iodination of ingested particles requires H2O2 generated from the increased reduction of oxygen by phagocytizing leukocytes.

Anions↗
PubMed1975

Predicting memory for pictures from rankings of interestingness, pleasingness, complexity, figure-ground and clarity.

Pictures used in the test phase of a picture-recognition task were ranked by 10 university students for interestingness, pleasingness, complexity, figure-ground, and clarity. The scale values obtained from these rankings were then correlated with the errors made by other subjects in the test phase of the picture-recognition task. Figure-ground and clarity were found, for the most part, to be reliable predictors of the errors made to both the "old" and "new" subsets of pictures in two experiments. Complexity, while not as consistent a predictor of either figure-ground or clarity, was a reasonably good predictor. Interestingness and pleasingness were not reliable predictors of errors.

Exploratory Behavior↗