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Biomedical subjects

D B Carr

Publications and source records attributed to D B Carr.

At least 145 records · Page 8Linked to original sources
PubMed1982

Caffeine stimulates beta-endorphin release in blood but not in cerebrospinal fluid.

Plasma beta-endorphin and prolactin profiles were obtained from groups of unstressed, adult male rats. The infusion of caffeine (20 mg/kg) via a chronic, indwelling intra-atrial cannula results in a prompt and sustained (2-2.5 h) rise In plasma beta-endorphin levels. The infusion of the opiate antagonist naloxone causes a modest (40%) decrease in plasma beta-endorphin and blunts the elevation in plasma beta-endorphin following caffeine administration. In contrast, plasma prolactin levels were unchanged following caffeine administration and were decreased by treatment with naloxone. Caffeine treatment did not effect CSF beta-endorphin levels or the release of beta-endorphin from hemipituitaries incubated in vitro.

Animals↗
PubMed1982

Endotoxin-stimulated opioid peptide secretion: two secretory pools and feedback control in vivo.

Small doses of endotoxin evoked a dramatic biphasic response of opioid peptide secretion into blood in sheep. The first phase began within minutes and coincided with a brief hypertensive response to endotoxin well before the appearance of fever or hypotension. The ratio of beta-endorphin to beta-lipotropin fell abruptly at the onset of the second phase of release, suggesting early depletion of a pool rich in beta-endorphin and subsequent emergence of a pool rich in unprocessed precursor. The concentration of cerebrospinal fluid opioids increased tenfold during the second phase. Naloxone administration augmented endotoxin-induced opioid secretion in both early and late phases, suggesting a short-loop feedback regulation of stress-induced endorphin secretion.

Animals↗
PubMed1982

D-lactic acidosis simulating a hypothalamic syndrome after bowel bypass.

A 36-year-old man had one year of periodic symptoms suggestive of episodic hypothalamic dysfunction: hypersomnia, thirst, ravenous hunger and gorging behavior, pallor, and irritability. However, neuroendocrine testing proved normal. A mild transient acidosis at the onset of his attacks and a history of bowel bypass five years earlier prompted metabolic screening. Markedly increased urinary D-lactic and phenolic acids were present, as were intermittent elevations of plasma D-lactic acid during two symptomatic episodes. Prompt and sustained clinical remission coincided with disappearance of abnormal organic acid excretion during oral antibiotic therapy. D-Lactic acidosis must be considered in the differential diagnosis of otherwise unexplained neurological syndromes, particularly in patients with altered bowel anatomy.

Acidosis↗
PubMed1982

Dissociation of plasma and cerebrospinal fluid beta-endorphin-like immunoactivity levels during pregnancy and parturition.

The association between central (cerebrospinal fluid [CSF]) and peripheral (plasma) levels of beta-endorphin-like immunoactivity (beta-ELI) in nonpregnant women (n = 8) and pregnant women (a) at 16 to 20 weeks of gestation (n = 6), (b) at term (n = 21), and (c) in labor (n = 15) was investigated. Umbilical arterial (n = 11) and venous (n = 11) samples were also obtained. In agreement with previous investigations, it was found that plasma levels of beta-ELI increased during labor (mean +/- SEM: nonpregnant women, 63.5 +/- 18.2; pregnant women at term, 64.0 +/- 12.2; women in labor, 110.8 +/- 30.3 pg/ml), and that levels of umbilical arterial plasma of beta-ELI exceeded those in umbilical venous plasma (132.5 +/- 34.0 versus 68.2 +/- 22.2). However, CSF levels of beta ELI did not change over the course of pregnancy or during labor (nonpregnant women, 36.5 +/- 15.8; pregnant women at 16 to 20 weeks of gestation, 60.1 +/- 10.3; pregnant women at term, 57.5 +/- 8.4; women in labor 48.5 +/- 8.3 pg/ml). This evidence that plasma and CSF levels of beta-ELI are dissociated during labor calls into question inferences regarding behavioral changes during parturition based on plasma beta-ELI measurements.

Endorphins↗
PubMed1982

Exercise effect upon plasma melatonin levels in women: possible physiological significance.

The pattern of changes in plasma concentrations of melatonin was followed in 7 initially untrained young women subjected to periodic acute exercise testing during the course of an 8 weeks' progressive aerobic exercise training program. Training comprised cycle ergometry 2 days/week and running 4 days/week for increasingly prolonged periods of intense exercise eliciting 85% of maximum heart rate. Acute exercise tests consisted of one-hour graded submaximal endurance rides on a bicycle ergometer. After a mock ride for familiarization purposes, three test rides were conducted during the early follicular phase of three consecutive menstrual cycles at the beginning, middle and end of the training program. Blood was sampled atraumatically before the rides, at their conclusion and 30 minutes into recovery. During the rides, the plasma concentrations of melatonin rose significantly above baseline control values. Exercise-enhanced melatonin levels may contribute to impaired reproductive function in women engaging in endurance sports.

Animals↗
PubMed1981

Chronic exposure to a 60-Hz electric field: effects on neuromuscular function in the rat.

Neuromuscular function in adult male rats was studied following 30 days of exposure to a 60-Hz electric field at 100 kV/m (unperturbed field strength). Isometric force transducers were attached to the tendons of the plantaris (predominantly fast twitch), and soleus (predominantly slow twitch) muscles in the urethan-anesthetized rat. Square-wave stimuli were delivered to the distal stump of the transected sciatic nerve. Several measurements were used to characterized neuromuscular function, including twitch characteristics, chronaxie, tetanic and posttetanic potentiation, and fatigue and recovery. The results from three independent series of experiments are reported. Only recovery from fatigue in slow-twitch muscles was consistently and significantly affected (enhanced) by electric-field exposure. This effect does not appear to be mediated by field-induced changes in either neuromuscular transmission, or in the contractile mechanism itself. It is suggested that the effect may be mediated secondary to an effect on mechanisms regulating muscle blood flow or metabolism.

Age Factors↗
PubMed1981

Plasma melatonin increases during exercise in women.

Melatonin was measured in plasma of seven women volunteers before and after serial acute submaximal exercise tests performed during the course of a two-month, progressive endurance training program. Plasma melatonin increased during all exercise sessions and declined towards baseline values when re-measured thirty minutes after completion of each exercise. This finding indicates that vigorous physical activity elicits transient increases in plasma melatonin in both sedentary and trained women.

Adolescent↗
PubMed1981

U-500 insulin in the treatment of antibody-mediated insulin resistance.

Three patients with antibody-mediated insulin resistance were treated with U-500 regular insulin subcutaneously. Insulin requirements decreased dramatically (55% to 75%) when therapy was changed from U-100 NPH pork to equivalent doses of U-500 regular pork insulin. There was no difference in antibody affinity for the insulin in these two preparations as shown by competition experiments. These observations demonstrate that U-500 insulin is a useful alternative in the treatment of antibody-mediated insulin resistance. The mechanism for this effect is yet to be determined.

Adult↗
PubMed1981

Automated in-line ratio-correcting filter fluorometer.

We have developed a novel optical arrangement for the Abbott VP bichromatic analyzer, converting it into a fluorometer upon insertion of a specially designed filter carriage. Fluorescence intensity is measured by using straight-through excitation geometry and is corrected for fluctuations in light-source intensity by using the attenuated transmitted beam through the solution as a reference. The modification allows switching from the absorbance to fluorescence mode without an auxiliary light source or a major hardware change. The detection limit for an experimental prototype was estimated as 192 pmol of fluorescein per liter. In an application to a fluorescence immunoassay for theophylline in patients' sera, the data (y) correlated well with results by an enzyme immunoassay procedure (EMIT), giving a correlation equation of y = 1.849 + 0.988x (r = 0.969). A fluorometric standard curve for glucose and some performance data are also presented.

Filtration↗
PubMed1980

Chronic exposure to a 60-Hz electric field: effects on synaptic transmission and peripheral nerve function in the rat.

Several reports have suggested that the nervous system can be affected by exposure to electric fields and that these effects may have detrimental health consequences for the exposed organism. The purpose of this study was to investigate the effects of chronic (30-day) exposure of rats to a 60Hz, 100-kV/m electric field on synaptic transmission and peripheral-nerve function. One hundred forty-four rats, housed in individual polycarbonate cages were exposed to uniform, vertical, 60-Hz electric fields in a system free of corona discharge and ozone formation and in which the animals did not receive spark discharges or other shocks during exposure. Following 30 days of exposure to the electric field, superior cervical sympathetic ganglia, vagus and sciatic nerves were removed from rats anesthetized with urethan, placed in a temperature-controlled chamber, and superfused with a modified mammalian Ringer's solution equilibrated with 95% O2 and 5% CO2. Several measures and tests were used to characterize synaptic transmission and peripheral-nerve function. These included amplitude, area, and configuration of the postsynaptic or whole-nerve compound-action potential; conduction velocity; accommodation; refractory period; strength-duration curves; conditioning-test (C-T) response, frequency response; post-tetanic response; and high-frequency-induced fatigue. The results of a series of neurophysiologic tests and measurements indicate that only synaptic transmission is significantly and consistently affected by chronic (30-day) exposure to a 60-Hz, 100-kV/m electric field. Specifically, and increase in synaptic excitability was detected in replicated measurements of the C-T response ratio. In addition, there are trends in other data that can be interpreted to suggest a generalized increase in neuronal excitability in exposed animals.

Action Potentials↗
PubMedDate not supplied

Two new templates for epidemiology applications: linked micromap plots and conditioned choropleth maps.

This paper describes two interactive templates for representing spatially indexed estimates. Both templates use a matrix layout of small panels. The first template, called linked micromap plots, can represent multivariate estimates associated with each spatially indexed study unit. The second template, called conditioned choropleth maps, shows the connection between a dependent variable, as represented in a classed choropleth map, and two explanatory variables. The paper describes the cognitive considerations that motivate the layouts and representation details. The discussion also addresses topics of data quality and access, hypothesis generation, and interactive features such as pan and zoom and dynamic conditioning via sliders. The examples show epidemiological (mortality rates) and environmental (toxic concentrations) applications.

Benzene↗
PubMedDate not supplied

Designing linked micromap plots for states with many counties.

This paper describes the design of linked micromap plots for showing county estimates on a state by state basis. The linked micromap template was specifically developed to represent spatially indexed statistical summaries. Each plot shows regional names, spatial patterns and statistical patterns while linking them all together. Thus the design is useful for communicating summaries from a host of health and environmental studies. The specific design challenge in this paper is to create one-page plots for the states with 60 to 120 counties. While the county names and micromaps take up substantial space, the three examples demonstrate that there is sufficient space to represent two variables. The basic design has the potential for showing more. Consequently the new designs are suitable for presenting sophisticated summaries.

Adolescent↗