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Biomedical subjects

R Gray

Publications and source records attributed to R Gray.

At least 343 records · Page 19Linked to original sources
PubMed1982

Right atrial tamponade complicating cardiac operation: clinical, hemodynamic, and scintigraphic correlates.

Persistent bleeding into the pericardial space in the early hours after cardiac operation not uncommonly results in cardiac tamponade. Single chamber tamponade also might be expected, since in this setting the pericardium frequently contains firm blood clots localized to the area of active bleeding. However, this complication has received very little attention in the surgical literature. We are therefore providing documentation that isolated right atrial tamponade can occur as a complication of cardiac operation and that there exists a potential for misdiagnosis and hence incorrect treatment of this condition. Right atrial tamponade may be recognized by a combination of low cardiac output, low blood pressure, prominent neck veins, right atrial pressure in excess of pulmonary capillary wedge pressure and right ventricular end-diastolic pressure, and a poor response to plasma volume expansion. Findings on chest roentgenogram and gated wall motion scintigraphy may be highly suggestive. This review should serve to increase awareness of this complication and to provide some helpful diagnostic clues.

Bioprosthesis↗
PubMed1982

[Myelolipoma of the adrenal gland in whole-body computed tomography. Report on 2 histologically confirmed cases with clinic-radiological correlations].

Myelolipomas are rare non-functioning benign lesions. They occur almost exclusively in the adrenals and are usually small and asymptomatic. We report two cases of unusually large symptomatic myelolipomas of the adrenal which were examined by urography, ultrasound, angiography and computed tomography (CT). A review of the literature of 25 similar cases is presented with a discussion of the pathogenesis. Diagnostic features of an adrenal myelolipoma are (1) a non-functioning, (2) radiolucent, (3) solid and (4) avascular mass arising from the adrenal. With CT the preoperative diagnosis becomes possible by assessing the fat contents, tumor alignment and lack of invasiveness.

Adrenal Gland Neoplasms↗
PubMed1981

Prenatal detection of neural tube defects by maternal serum alphafetoprotein assay.

Mass screening for fetal neural tube defects using maternal serum alpha-fetoprotein assay as the initial test is financially justified in South Africa, despite the relatively low incidence of these defects in this country, using enzyme-linked immunosorbent assay. This technique is efficient and inexpensive and lends itself to mass screening. We report a pilot study in which 3153 maternal serum samples were received during a 4-month period. Of these 3102 were assayed and the outcome of pregnancy was recorded in 2069 cases. On the first assay 147 (4.7%) of the women had serum alpha-fetoprotein levels which were high for the gestational dates given, but in retrospect about half of these had been misinterpreted because of incorrect dates. Among the remainder, 6 women proved to be carrying twins, 4 aborted spontaneously, 10 delivered prematurely or had infants with intra-uterine growth retardation, and 4 had a fetus with a neural tube defect. Two affected fetuses were missed by screening, in both cases because serum was taken after 20 weeks gestation. In this sample the incidence in Indians (1/1000)and Coloureds (1/600) was as expected, but in Whites it was much higher (1/130), which probably reflects a sampling error and indicates that the epidemiology of neural tube defects in South Africa requires investigation.

Adolescent↗
PubMed1981

Cultured muscle from myotonic muscular dystrophy patients: altered membrane electrical properties.

Myotonic muscular dystrophy (MyD) is an inherited human disease involving skeletal muscle as well as many other organ systems. We have approached the study of this disorder by growing normal and diseased human muscle in a primary tissue culture system and investigating some of the electrical properties of the resulting myotubes. The most distinctive abnormality noted in MyD myotubes was an increased tendency to fire repetitive action potentials. A decreased action potential afterhyperpolarization amplitude and the presence of depolarizing afterpotentials were also noted, as were a decreased resting membrane potential, decreased action potential amplitude and overshoot, and decreased outward-going rectification. Although the ionic basis of these abnormal properties in vitro is not clearly defined, changes in the slow outward-going potassium current offer the best explanation. Furthermore, MyD cell culture offers a valuable model for critical analysis of the molecular mechanisms underlying MyD deficits.

Action Potentials↗
PubMed1981

Use of thallium-201 redistribution scintigraphy in the preoperative differentiation of reversible and nonreversible myocardial asynergy.

Thallium-201 (201Tl) redistribution scintigraphy might differentiate reversibly from nonreversibly asynergic myocardial segments and thus predict the response of these segments to coronary artery bypass grafting (CABG). To test this hypothesis, 25 consecutive patients undergoing CABG, preoperative stress-redistribution 201Tl scintigraphy, and both pre- and postoperative resting equilibrium radionuclide ventriculography were evaluated. For both types of scintigraphic study, each patient was imaged in the same three views. Because of the effects of CABG on septal motion, this region was considered separately. Postoperative improvement was noted in 54% of 72 preoperative asynergic segments. Improvement was common not only in hypokinetic but also in akinetic and dyskinetic segments, and occurred in a similar proportion of studies performed early (less than 2 weeks) or late (3-6 months) after CABG. Thallium-201 redistribution scintigraphy was highly predictive of the pattern of postoperative asynergy: The redistribution pattern was normal in 90% of segments with reversible asynergy and abnormal in 76% of segments with nonreversible asynergy. The presence or absence of pathologic Q waves was less sensitive in this differentiation. Septal segments, however, frequently demonstrated abnormal wall motion postoperatively, despite normal 201Tl redistribution scintigraphy. Resting left ventricular ejection fraction (LVEF) was generally unchanged postoperatively, but in some patients with multiple areas of reversible asynergy it did improve. Thus, 201Tl redistribution scintigraphy appears to reliably distinguish viable from nonviable asynergic myocardial zones, and predicts the response of these segments to CABG.

Coronary Artery Bypass↗
PubMed1981

Low cardiac output states after open heart surgery. Comparative hemodynamic effects of dobutamine, dopamine, and norepinephrine plus phentolamine.

The hemodynamic effects of dobutamine, dopamine, and a combination of norepinephrine-phentolamine were compared in nine patients with low cardiac output state after open heart surgery. Using a Latin square design for drug sequence, each patient was given each drug at three levels by continuous intravenous infusion. For dobutamine and dopamine the doses were 2.5, 5.0 and 10.0 microgram/kg/min; for norepinephrine, 0.02, 0.05 and 0.10 microgram/kg/min with phentolamine in the ratio of 1 (norepinephrine) to 2.5 (phentolamine). Dobutamine and dopamine both produced an increase in heart rate, mean arterial pressure, cardiac index, and stroke volume index. Both drugs reduced total pulmonary and systemic vascular resistance in the dose range of 5.0 to 10.0 microgram/kg/min. When the maximum tolerated doses were compared, the drugs equally increased cardiac index and stroke volume index, but dopamine did so at a smaller dose than dobutamine. At equivalent doses, dobutamine tended to produce less tachycardia and vasoconstriction than dopamine. The norepinephrine-phentolamine combination resulted in increases in both systemic arterial pressure and vascular resistance with no significant increase in cardiac index. Its unique feature was its predictable vasopressor response with absence of chronotropic effects and ventricular irritability.

Cardiac Output, Low↗
PubMed1980

Serum alphafetoprotein determination by enzyme-linked immunosorbent assay.

Enzyme-linked immunosorbent assay (ELISA) in microtitre trays has been adapted to the determination of alpha-fetoprotein (AFP); the method is described here. This assay has a lower limit of sensitivity of AFP 1 microgram/l and results compare well with those obtained with a commercial radio-immunoassay (RIA) kit (r = 0,994; y = 949x-3,00). ELISA has several advantages over RIA; it is considerably less expensive, the reagents are stable for longer periods and no elaborate equipment is required.

Costs and Cost Analysis↗
PubMed1980

Mortality in relation to smoking: 22 years' observations on female British doctors.

A total of 6194 female doctors who in 1951 replied to a questionnaire about their smoking habits were followed up prospectively for 22 years. During that time 1094 died. Ischaemic heart disease, lung cancer, and chronic obstructive lung disease were all significantly (p < 0.001) related to smoking, though the absolute excess risks were lower than in male doctors smoking equivalent amounts. Female smokers born before the first world war were less likely to describe themselves as inhalers or as having started to smoke while young than were female smokers who were born later. In these respects this younger group resembled male smokers, and as they move into their 60s and 70s their absolute risk of lung disease and relative risk of ischaemic heart disease will probably come to resemble the risks for men smoking the same numbers of cigarettes. These findings show only that cigarette smoking causes lung cancer, chronic obstructive lung disease, and heart disease in women as in men. Whether the proportional increase in mortality from these diseases is as great in women as in men might be estimated directly from new case-control studies on men and women born since 1920.

Adult↗
PubMed1980

Investigation of burst generation by the electrically coupled cyberchron network in the snail Helisoma using a single-electrode voltage clamp.

This paper describes the results of investigating burst generation by the cyberchron network in the snail Helisoma. The cyberchron network is composed of aproximately 20 electrically coupled neurons and controls the feeding behavior of the snail. The electrical coupling between network members has made it particularly difficult to distinguish between the importance and involvement of single-cell and network properties in burst generation by this system. The present investigations utilized the new single-electrode voltage clamp to examine the membrane properties and network interactions of the cyberchron neurons: (1) A slow outward current is activated by moderately large depolarizing commands (-40 to 0 mV) and does not undergo inactivation decay (i.e., decline in magnitude) during a command potential step maintained for 10 sec or more. The lack of inactivation of the outward current in cyberchron neurons appears to be due to the dominating role of a Ca-dependent K current. (2) There are two functionally distinct classes of cyberchrons--current generator cyberchrons and follower cyberchrons. (3) Primary current generator cyberchrons have membrane properties similar to endogenous bursting neurons (e.g., persistent inward Ca current and negative resistance region in I-V plot) and appear to provide the main driving and timing current for the rest of the network. (4) The vast majority of cyberchrons are secondary current generator cyberchrons with membrane properties which exhibit inward-going rectification and appear to burst as a result of regenerative excitation with one another and the primary current generator cyberchrons. (5) The second class of cyberchrons are driven by the electrical synaptic input from the current generator cyberchrons, do not exhibit inward-going rectification, and are called follower cyberchrons. (6) Burst termination is due to activation of a slow outward tail current in most cyberchrons during the burst (probably Ca-activated K current) which causes a hyperpolarization in individual cyberchrons, terminating the burst. (7) Decay of the outward tail current causes the cyberchrons to depolarize, which activates the persistent inward Ca current in the primary current generator cyberchrons, starting the burst cycle anew.

Action Potentials↗