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Biomedical subjects

D Robertson

Publications and source records attributed to D Robertson.

At least 487 records · Page 27Linked to original sources
PubMed1979

First year clinical experience with six levonorgestrel rods as subdermal contraception.

Previous clinical experience with six levonorgestrel subdermal capsules showed a very good contraceptive effectiveness and continuation rate, but with a high proportion of bleeding disturbances, particularly of increased bleeding. It was hypothesized that bleeding could be reduced by higher plasma levels of the steroid, using subdermal rods instead of capsules, as rods have been shown to have a release rate 3 or 4 times that of the capsules. Fifty volunteers were enrolled in a study of the clinical performance of 6 subdermal levonorgestrel rods. Results were compared with a previous experience with 100 volunteers who wore 6 levonorgestrel capsules for a year in the same clinic. Requirement for volunteers to enter the study were the same for capsules and rods. The proportion of women wearing 6 subdermal rods who had increased bleeding was about one half as for the women using 6 levonorgestrel capsules. On the other hand, women using rods had about twice the incidence of amenhorrea, and about four times more hypomenorrhea (4 days or less of bleeding in a 90-day period). There were no pregnancies among the rod users and the discontinuation rate for medical reasons was not higher than for capsule users in the same clinic.

Adolescent↗
PubMed1979

Screening for nutritional deficiencies in the elderly following gastric surgery.

Following gastric resection a slightly reduced haemoglobin is common. The use of erythrocyte morphology as a screening test for deficient absorption of haematinics is unsatisfactory; false positive (42.8%) and false negative (41.6%) results are encountered too frequently to recommend its use. The elderly postgastrectomy patient with mild anaemia may have biochemical evidence of iron, folic acid, or vitamin B12 deficiency with normal erythrocyte morphology.

Aged↗
PubMed1979

Exacerbation of angina pectoris by prazosin.

A case of angina pectoris worsened by prazosin is presented. Since a hypertensive population includes many patients with known or occult coronary artery disease, physicians should use prazosin cautiously in this subgroup, particularly when beta-adrenergic antagonists cannot be used concurrently.

Acute Disease↗
PubMed1979

Chronic recurrent angina.

The natural history of variant angina is described in a patient with multiple exacerbations and remissions over a period of several years. Constant in-hospital electrocardiographic monitoring for 26 days documented 569 episodes of ST elevation, 89% of which were asymptomatic. Episodes ranged in duration from 15 seconds to 11 1/2 minutes, with 4% of episodes associated with premature ventricular contractions. Over the course of hospitalization, the episodes of ST elevation decreased in frequency and length, as did episodes of pain. During this period, a number of therapeutic agents, including propranolol, indomethacin, and chlorpheniramine were evaluated using double-blind crossover trials. No agent had a significant beneficial effect on the course of the disease, and there was an increase in the length of episodes with high doses of propranolol. Because of the great variability in the course of this disease, only double-blind crossover trials should be allowed to dictate the efficacy of therapeutic agents.

Angina Pectoris↗
PubMed1979

Cochlear action potential threshold and single unit thresholds.

There is a close correlation between the sound pressure of tone burst required to affect a primary auditory neuron at its characteristic frequency and that which will produce a detectable N1 response at the same frequency. Units with thresholds from 80--0 db SPL (recorded from damaged and undamaged cochleas) were 0--20 dB , respectively, more sensitive than the action potential response.

Action Potentials↗
PubMed1979

Aberrant tonotopic organization in the inner ear damaged by kanamycin.

Spiral ganglion cell recordings were obtained from normal and kanamycin-damaged guinea pig cochleas. Results show that kanamycin poisoning, which causes loss of outer hair cells, leads to a loss of sharp, sensitive tuning and, in addition, a shift to lower frequencies in the tuning curves from a damaged region. The normal tonoptic pattern of organization is therefore greatly disrupted in the damaged cochleas.

Animals↗
PubMed1979

Comparative assessment of stimuli that release neuronal and adrenomedullary catecholamines in man.

We assessed the release of neuronal and adrenomedullary catecholamines in response to various stimuli of the sympathetic nervous system in normal subjects. Plasma catecholamines and their urinary metabolites, normetanephrine and metanephrine, were measured. Sodium restriction increased supine plasma norepinephrine by 37% and ambulatory plasma norepinephrine by 22%, with urinary normetanephrine excretion increased 29%. The sodium restriction did not elevate plasma epinephrine or urinary metanephrine. The most potent stimuli of norepinephrine were treadmill exercise, orthostasis, caffeine, the cold pressor test, sodium restriction and handgrip exercise, in descending order. Plasma epinephrine was increased by caffeine, treadmill exercise, the cold pressor test, handgrip exercise and the Valsalva maneuver, in that order. Syncope resulted in profound changes in plasma epinephrine but only modest changes in plasma norepinephrine. We conclude that in man, there is frequent dissociation between the effects of different stimuli on neuronal and adrenomedullary catecholamine release.

Adolescent↗
PubMed1979

Hemodialysis hypotension is not the result of uremic peripheral autonomic neuropathy.

Five chronic hemodialysis patients with persistent hypotension during dialysis (MAP: 74.2 +/- 3.1 mm Hg) were given a number of standard tests of autonomic nervous system function and compared with eight normotensive hemodialysis patients (MAP: 96.4 +/- 3.4 mm Hg). Tests of efferent sympathetic nerves were normal in both groups, as were plasma catecholamine levels and the cold pressor test. The response to Valsalva maneuver and the venoconstriction reflex were generally abnormal and did not differentiate between the two groups. When adjusted for age and MAP, the baroreceptor slope to a high-pressure stimulus was diminished only in the hypotensive subjects. This result reinforces the previously described finding that many uremic patients do not develop a normal cardioacceleration during hypotension. Although reduced baroreceptor sensitivity may be a factor in the chronic hypotension of some hemodialysis patients, autonomic dysfunction alone is not a sufficient explanation of this phenomenon.

Adult↗
PubMed1979

Studies on the tissue specificity of a circulating renotropic factor.

In 1970, it was found that sera removed from rats 24 hr after unilateral nephrectomy stimulate the incorporation of 3H-Thymidine into the DNA of incubating rat renal cortex. The same sera did not influence isotope incorporation into the DNA of incubating liver, spleen, and lung tissue. Later, a substance was described in renal tissue that enhanced the action of the renotropic factor in sera. It was proposed that this tissue factor activated the circulating renotropic substance and that lack of this activator in other tissues was responsible for the specificity of the circulating renotropic substance to renal tissue. The present study suggests that this is the case as the addition of the renal tissue factor and sera from uninephrectomized rats can stimulate 3H-Thymidine incorporation into the DNA of rat liver slices.

Animals↗
PubMed1978

Effects of caffeine on plasma renin activity, catecholamines and blood pressure.

Using a double-blind, randomized, cross-over protocol, we studied the effect of a single dose of oral caffeine on plasma renin activity, catecholamines and cardiovascular control in nine healthy, young, non-coffee drinkers maintained in sodium balance throughout the study period. Caffeine (250 mg) or placebo was administered in a methylxanthine-free beverage to overnight-fasted supine subjects who had had no coffee, tea or cola in the previous three weeks. Caffeine increased plasma renin activity by 57 per cent, plasma norepinephrine by 75 per cent and plasma epinephrine by 207 per cent. Urinary normetanephrine and metanephrine were increased 52 per cent and 100 per cent respectively. Mean blood pressure rose 14/10 mm Hg one hour after caffeine ingestion. There was a slight fall and then a rise in heart rate. Plasma caffeine levels were usually maximal one hour after ingestion but there was considerable individual variation. A 20 per cent increase in respiratory rate correlated well with plasma caffeine levels. Under the conditions of study caffeine was a potent stimulator of plasma renin activity and adrenomedullary secretion. Whether habitual ingestion has similar effects remains to be determined.

Administration, Oral↗
PubMed1978

A selective and sensitive assay for urinary metanephrine and normetanephrine using gas chromatography mass spectrometry with selected ion monitoring.

Vapor phase methodology for quantitative analysis of urine for metanephrine and normetanephrine as the pentafluoropropionyl derivative is described. The use of selected ion monitoring provided sufficient sensitivity and selectivity that milliliter aliquots of urine required only a simple scheme of sample processing; preliminary purification consisted of percolation through a column of XAD-2 followed by solvent extraction. The sample extracts were converted to the pentafluoropropionyl derivatives and analyzed by gas chromatography mass spectrometry with selected ion monitoring. Quantitative analysis was based on alpha[2H2]-beta-[2H1]metanephrine and alpha-[2H2]-beta-[2H1]normetanephrine which were added to the urine sample at the outset. The calibration plots for metanephrine and normetanephrine were linear from 10 ng ml-1 to 2000 ng ml-1 of urine permitting the detection of metanephrine and normetanephrine levels throughout the normal range and well into the subnormal range. Examples of application of the methodology to clinical investigation are described. The overall reproducibility of the sample processing methodology and instrumentation was assessed by replicate analyses of the same urine sample over a period of several weeks; the coefficient of variation was +/- 2.5% (n = 8).

Chromatography, Gas↗
PubMed1978

The use of detergents and immunoperoxidase reagents for the ultrastructural demonstration of internal immunoglobulin in lymph cells.

Lymph-borne immunoblasts were fixed in dilute glutaraldehyde and then treated with saponin. This treatment made most parts of the cells permeable to ferritin, so that anti-immunoglobulin (Ig) antibodies which had been conjugated to horse radish peroxidase (HRP) had no difficulty in gaining access to Ig which thus could be demonstrated at an ultrastructural level. Best results were obtained by fixing the cells in 0.1% glutaraldehyde for 7 min and then treating them with a 1% solution of saponin for 100 min at 55 degrees C before exposing them to the Ig-HRP conjugate. The method yielded reproducible results and although it causes a small amount of ultrastructural damage, it may be of value in detecting a variety of intracellular antigens.

Animals↗