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Biomedical subjects

J Boyd

Publications and source records attributed to J Boyd.

At least 235 records · Page 13Linked to original sources
PubMed1982

Prostacyclin and thromboxane A2 release in isolated rat lungs.

The influence of platelets and platelet membranes on the generation of prostacyclin (PGI2) and thromboxane A2 (TXA2) by isolated rat lung and porcine aortic endothelial cell, as measured by RIA of their stable end-products, 6-oxo-PGF1 alpha and TXB2 respectively, was studied. After introduction of either aspirin-treated platelets or membranes from aspirin-treated platelets to the perfusate, a 5-fold increase in the amount of 6-oxo-PGF1 alpha and TXB2 in the perfusate was observed. Treatment of the lung with aspirin produced a 50% reduction in the platelet-stimulated release of PGI2 and TXA2. Treatment of the lung with the phospholipase inhibitor, mepacrine, significantly reduced the platelet-stimulated release of PGI2 and TXA2. Incubation of endothelial cells with untreated platelet membranes did not alter the generation of PGI2. These results suggest that platelet-stimulated release of PGI2 and TXA2 occurs via mechanical stimulation of phospholipase A2, liberating arachidonic acid.

Animals↗
PubMed1982

Dynamics of erabutoxin b as studied by nuclear magnetic resonance. Relaxation studies of methyl proton resonances.

Longitudinal and transverse relaxation times were measured for well-resolved and assigned methyl proton resonances of erabutoxin b at 270 MHz, 300 MHz and 500 MHz. Both longitudinal and transverse magnetization decay curves are non-exponential due to cross-relaxation and cross-correlation effects. The longitudinal and transverse relaxation rates were obtained from the initial slope of both magnetization decay curves. The correlation times for the isotropic tumbling motion of the protein were determined to be 2.82 ns at 300 K and 1.62 ns at 330 K from the analysis of the relaxation data of some alpha protons. Using these values, the relaxation data of methyl protons were fitted to various theoretical models. Most of the methyl resonances could be fitted well to a model which allowed methyl rotation (in the range 0.01-0.05 ns) and an external contribution from protons assumed to be in positions derived from X-ray coordinates. The data for a few methyl groups, however, could not be fitted in this way. For these a smaller number of external protons than predicted by the X-ray coordinates was assumed. Additionally, a larger amplitude motion had to be introduced into the model for particular residues. This additional motion requires concerted protein motion close to these residues, since the X-ray structure suggests that steric hindrance would prevent local motion. These results are consistent with the idea of a flexible and dynamic structure for proteins.

Elapid Venoms↗
PubMed1982

Cerebrospinal fluid prognostic indices in experimental pneumococcal meningitis.

The prognostic value of initial and sequential determinations of quantitative bacterial concentrations, leukocytes, glucose, lactate, lactic acid dehydrogenase, and creatine phosphokinase in CSF was examined in rabbits with experimental pneumococcal meningitis while they were receiving equivalent, rapidly bactericidal antibiotic therapy. The following mean CSF variables correlated with death due to meningitis: (1) an early (day 1) high bacterial titer and lactate concentration with simultaneous low leukocyte count and glucose level and (2) late (day 3) elevated lactate and lactic acid dehydrogenase levels and leukocyte count. A high concentration of bacteria inoculated into the CSF and a high plasma glucose level also adversely influenced prognosis. Careful analysis of these variables may identify high-risk patients with pneumococcal meningitis and ultimately may be useful in gauging the therapeutic response.

Animals↗
PubMed1981

Evaluation of the neurophysiologic effects of 1,2-propylene glycol dinitrate by quantitative ataxia and oculomotor function tests.

1,2-Propylene glycol dinitrate (PGDN), a nitrated ester found in the torpedo propellant Otto Fuel II, has been suspected of causing neurologic and cardiovascular effects. This study evaluated the possible acute and chronic neurophysiologic toxicity of PGDN in U.S. Navy torpedo facilities. The test procedures included a medical and occupational history, neuro-ophthalmologic examination, and quantitative tests of both oculomotor function and ataxia. A study population of 87 workers chronically exposed (CE) to PGDN during torpedo maintenance procedures was compared to a group of 21 controls (CON). Although workers often complained of vascular effects (headaches, nasal congestion), no evidence of chronic neurotoxicity was found, even among a subgroup of workers (CEsub) with the longest total duration of exposure. To detect possible acute effects, 29 subjects from the study group were tested before and immediately after PGDN exposure during a torpedo maintenance procedure or turnaround (TA). These personnel had a statistically significant decline in saccade velocity and a prolongation of saccade delay time, even though most peak airborne concentrations of PGDN were well below 0.2 ppm.

Adult↗
PubMed1981

Leukocyte and bacterial interrelationships in experimental meningitis.

Eighty-one rabbits were inoculated with known concentrations of type III pneumococci by cisternal puncture and then started on antibiotic therapy the following day. Aliquots of cerebrospinal fluid were sampled at regular intervals both before and after therapy and then analyzed for bacterial titer and leukocyte count. These data were used to examine the interrelationships of inoculum size, leukocyte count, and bacterial titer to each other and their effects both univariately and multivariately on outcome. Inoculum size was the most important single variable affecting outcome, followed in order by the pretherapeutic bacterial titer and leukocyte count. Higher leukocyte counts early in the course of the disease prior to therapy were associated with a favorable outcome. Continued leukocyte elevation after therapy was associated with a poor prognosis. No correlations were found between inoculum size and subsequent bacterial titers; however, the bacterial titer immediately prior to therapy correlated negatively with the level of the early white cell response. The best prognostic information was obtained from the multivariate analysis of inoculum size and pretherapeutic white cell response.

Animals↗
PubMed1981

A rapid procedure for measurement of the free testosterone fraction in human plasma using the centria radioimmunoassay centrifugal analyzer.

Following the incubation of plasma with a tracer amount of tritiated testosterone, the reaction mixture is separated into a sex hormone-binding globulin bound and an unbound fraction of radioligand using DEAE-cellulose columns placed in the incubator-separator module of the Centria radioimmunoassay centrifugal analyzer. Neural Tris-buffer elutes unbound steroid from the matrix, while acidic Tris-buffer can remove the protein-bound fraction in a subsequent step. Complementary and thus qualitatively equal results are obtained when counting either eluate. Comparison of this technique with an ammonium sulfate precipitation method showed high correlation. Free testosterone indices as determined by the Centria modification in a number of prepuberal children, normal men and women, as well as pregnant and hirsute women similar to those previously reported.

Adrenal Hyperplasia, Congenital↗
PubMed1981

Respiratory movements alter the generation of prostacyclin and thromboxane A2 in isolated rat lungs: the influence of arachidonic acid-pathway inhibitors on the ratio between pulmonary prostacyclin and thromboxane A2.

The influence of hyperventilation on the spontaneous generation of prostacyclin and thromboxane A2 by isolated rat lungs was studied. Both prostacyclin and thromboxane A2, as measured by RIA of their stable end-products, 6-oxo-PGF1 alpha and TXB2 respectively, were continuously released into the perfusate. However, the concentration of prostacyclin in the perfusate was higher than thromboxane A2. Under normal ventilation at a rate 40-50 breaths/min, the ratio between these two compounds was 5:1. Increasing the rate of respiration to 100 breaths/min preferentially stimulated the release of prostacyclin. During hyperventilation-stimulated release of prostacyclin and thromboxane A2. Hydroperoxy-fatty acids and tranylcypromine inhibited only the release of prostacyclin but did not affect the generation of thromboxane A2. Our findings confirm that the lung generates prostacyclin predominantly, and provide direct evidence that respiratory movements are involved in generation of pulmonary prostacyclin and thromboxane A2.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

The Clq receptor site on immunoglobulin G.

We propose that, the binding site for the complement subcomponent Clq on immunoglobulin G involves the last two (C-terminal) beta-strands of the C gamma 2 domain. This region contains a large number of accessible and highly conserved charged residues and charge is postulated as an important component of the Clq-IgG interaction. The conclusions are reached on the basis of accessibility and sequence conservation analyses of C gamma 2 amino acid residues, the use of specific inhibitors and chemical modification studies.

Amino Acid Sequence↗
PubMed1979

Postextubation atelectasis: a retrospective review and a prospective controlled study.

To determine the role of chest physiotherapy in the prevention of postextubation atelectasis in neonates intubated for greater than 24 hours, a retrospective survey compared the incidence of this complication in a newborn intensive care unit prior to and following the institution of a routine of chest physiotherapy. Eight of 23 infants extubated developed atelectasis in the "pre-physio" period, whereas only one collapse occurred in 20 infants treated with a routine of physiotherapy at extubation (P less than 0.025). Subsequently a prospective controlled trial compared the use of a routine of physiotherapy at extubation with no physiotherapy. Eight of 21 infants not receiving physiotherapy developed postextubation atelectasis and none of 21 infants receiving physiotherapy developed atelectasis (P less than 0.01). Seventy-six percent of the collapses involved the right upper lobe. A vigorous program of chest physiotherapy, including postural drainage emphasizing the positions of the right upper lobe and chest vibrations, will significantly reduce the incidence of postextubation atelectasis.

Drainage↗
PubMed1979

Lithium effects on normal subjects. Relationships to plasma and RBC lithium levels.

15 normal subjects took lithium carbonate for 10 days in dosage sufficient to attain plasma lithium concentrations in the range of 0.7-1.4 mEg/l. Periodic blood specimens were analyzed for both plasma and RBC lithium. Subjects completed Profile of Mood States questionnaires every other day, and listed side effects. Just prior to beginning and ending the lithium trial, 10 subjects completed three tests of psychomotor function. Results indicate that such a course of lithium in normals induces dysphoric mood change and psychomotor slowing, without significant relationship to either plasma or RBC lithium concentrations.

Choice Behavior↗