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Biomedical subjects

J Black

Publications and source records attributed to J Black.

At least 325 records · Page 18Linked to original sources
PubMed1983

Release of cobalt and nickel from a new total finger joint prosthesis made of vitallium.

An in vivo study of a new total finger joint prosthesis was performed to evaluate a biological ingrowth system of attachment of the device to bone. The prosthesis consisted of two conical ribbed ultrahigh molecular weight polyethylene plugs that were fixed by impaction into the medullary cavity after reaming. A cobalt--chromium alloy metal stemmed hinge slides inside the plugs with the joint articulation at the end of the stem. The focus of this study was to measure the concentration of cobalt and nickel in the serum, erythrocytes, and periarticular tissue (muscle from the sartorius and vastus medialis) resulting from the implantation of this device in the knee of the cat for periods of up to 1 year. The results indicate significant elevation in serum cobalt concentrations only after 5 months and increased concentrations in serum nickel which, were more pronounced after two months. Column chromatographic separations on cross-linked Dextran (G-200) shows a different distribution across the three principal protein peaks for each metal.

Animals↗
PubMed1983

Electrical osteogenesis by low direct current.

A constant direct current cathode was employed in the medullary canal of the rabbit tibia to investigate electrical osteogenesis at low current levels. Currents of 0.015 or 0.075 microA were delivered to the bone and the biological response was compared with contralateral controls receiving 20 microA. This investigation was performed to determine if electrical osteogenesis occurs at current levels below the previously studied range of 1-100 microA with stainless steel electrodes. New bone formed by 0.015 microA cathodes was statistically comparable with that found around inactive cathodes from an earlier pertinent study. The osteogenic response to 0.075 microA cathodes was significantly elevated above that to inactive ones, thus substantiating electrical osteogenesis for currents below 1 microA. However, it is evident that this does not demonstrate a further stimulatory range but that currents near 0.075 microA probably approach the lower significant limit for electrically induced bone growth with stainless steel electrodes.

Animals↗
PubMed1983

Serum concentrations of chromium, cobalt and nickel after total hip replacement: a six month study.

Serum specimens were obtained from 15 patients before undergoing conventional total hip replacement and for periods of up to six months postoperatively. The specimens were analysed for chromium, cobalt and nickel by electrothermal atomic absorption spectroscopy. Serum chromium levels were found to rise to a pronounced postoperative peak and then diminish, although not falling to normal mean levels by six months. Serum cobalt levels either remained the same or decreased while serum nickel levels began to rise two to six weeks after surgery. These results are significant in that serum metal concentration changes have been reported for patients receiving metal-on-metal implants but not for patients with metal-on-polymer total hip implants of more modern designs.

Animals↗
PubMed1983

Nocturnal enuresis.

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Behavior Therapy↗
PubMed1983

Headache.

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Adolescent↗
PubMed1982

The education of the biomaterialist: report of a survey, 1980-81.

Biomaterials as a class includes a wide variety of both artificial and natural materials. The discipline of Biomaterials must be recognized as the study of the materials aspects of both fabricated materials and natural tissues, as well as their interactions. Emerging disciplines give rise to academic establishments. A survey of 97 U.S. and Canadian universities reveals a wide range in institutional settings and course offerings in Biomaterials. Plans for faculty additions suggest that the field is still actively expanding.

Biocompatible Materials↗
PubMed1982

Relationship between porosity and mineralization in the Haversian osteon.

Cortical bone, at the osteonal level, consists of three phases: mineral, organic, and pore or void phases. In osteonal segments excised from mature human cortical bone, organic volume percent is a constant. Determination of the mineral and organic phase densities present in these segments has led to defining a simple relationship between percent mineralization and void volume. Studies of a group of osteonal segments from 5 human tibias suggest that porosity of up to 22.7% may exist. This is much more than is suggested by histological examination, leading to the conclusion that the majority of the void phase is present as a dispersed porosity.

Bone and Bones↗
PubMed1982

Renin-angiotensin system inhibition in acute myocardial infarction in dogs. Effects on systemic hemodynamics, myocardial blood flow, segmental myocardial function and infarct size.

Acute left anterior descending coronary artery occlusion was produced in 21 conscious, chronically instrumented dogs. Forty minutes after coronary occlusion, nine dogs were given i.v. teprotide, 25 micrograms/kg/min, followed by oral doses of captopril, 10 mg/kg every 8 hours for 24 hours. The remaining 12 dogs served as saline-infused controls. In all dogs, acute coronary occlusion increased plasma renin activity and peripheral vascular resistance and reduced cardiac output, but did not change mean aortic blood pressure significantly. Teprotide significantly (p less than 0.05) decreased peripheral vascular resistance (from 3804 +/- 1158 to 2876 +/- 816 dy-sec-cm-5) (+/- SD) and mean aortic pressure (from 117 +/- 12 to 107 +/- 15 mm Hg), and increased cardiac output (from 2.63 +/- 0.67 to 3.12 +/- 0.74 l/min). Teprotide also produced a relative increase in flow to the renal and splanchnic circulations compared with the saline-treated controls. There were, however, no differences in segmental systolic shortening, blood flow in the normal or ischemic myocardium, or infarct size. These results indicate that the renin-angiotensin system may play an important role in dogs with acute coronary occlusion and that blockade of this system lowers systemic blood pressure and improves cardiac output. However, direct effects of renin-angiotensin system blockade on the myocardium are lacking; there were no changes in myocardial blood flow, myocardial mechanics or infarct size.

Animals↗
PubMed1981

Diagnosis and management of 528 abdominal aortic aneurysms.

Between 1960 and 1979 528 patients with abdominal aortic aneurysms presented to the university department of surgery. Of these, 222 (42%) were elective cases, 72 acute (14%), 174 had ruptured (33%), and four had had a spontaneous aortoduodenal fistula (1%). In all these patients resections were undertaken, but in another 56 patients (11%) the aneurysm was not resected. A review of these cases showed that 91% had symptoms at their first presentation; abdominal pain and backache being most common. The diagnosis could be established in 91% by the presence of pulsatile abdominal mass on clinical examination. The operative mortality for elective resection was 8%, for acute 19%, for ruptured cases 42%, and for spontaneous aortoduodenal fistula 50%. After successful resection the overall five-year survival was 65% by the life table method, and there was no significant difference between elective, acute, and ruptured cases. This five-year survival after resection compares favourably with the expected 76% survival of a similar normal population, and was considerably better than that for conservatively treated patients. As most cases have symptoms, and diagnosis may be established easily by routine physical examination in 91%, the prognosis for this condition could be considerably improved by increased awareness of its existence and early referral for treatment as an elective surgical procedure.

Acute Disease↗
PubMed1981

Dobutamine infusion in conscious dogs with and without acute myocardial infarction. Effects on systemic hemodynamics, myocardial blood flow, and infarct size.

We infused dobutamine (20 microgram/kg per min) intravenously, once before and once after coronary artery occlusion, in 10 chronically instrumented dogs. Both infusions increased cardiac output and left ventricular dP/dt and dP/dt/P, but divergent effects on heart rate and aortic blood pressure were observed. Dobutamine decreased heart rate and increased mean aortic blood pressure before coronary artery occlusion, whereas after occlusion it increased heart rate while mean aortic blood pressure remained unchanged. A greater decrease in total peripheral vascular resistance occurred during dobutamine infusion after coronary artery occlusion than before. These differences may relate to withdrawal of enhanced sympathetic tone after coronary occlusion. Similar infusions of normal saline (n = 9) produced no systemic hemodynamic changes either before or after coronary artery occlusion. Myocardial blood flow increased to both non-ischemic and ischemic regions of the heart during dobutamine infusion, but the endocardial:epicardial blood flow ratio did not change significantly. In addition, infarct size, measured by nitroblue tetrazolium stain, was smaller in the dobutamine group (10 +/- 1 g) than in the normal saline group (15 +/- 2 g). Neither left ventricular weight nor risk zone differed between the two groups. These results indicate that dobutamine may be a useful inotropic agent during acute myocardial infarction.

Animals↗
PubMed1981

Blood pressure response to central and/or peripheral inhibition of phenylethanolamine N-methyltransferase in normotensive and hypertensive rats.

We studied the effects on blood pressure and heart rate of two different phenylethanolamine N-methyltransferase (PNMT) inhibitors in normotensive, in two-kidney renal hypertensive, and in deoxycorticosterone-salt (DOC-salt) hypertensive rats. One compound (SK&F 64139) blocks the conversion of norepinephrine to epinephrine in both the central and the peripheral nervous system, whereas the other (SK&F 29661) does not cross the blood-brain barrier and therefore is active mostly in the adrenal glands. In the rats given SK&F 29661, practically no acute blood pressure changes were in the adrenal glands. In the rats given SK&F 64139 induced only a minor blood pressure and heart rate response in normotensive and two-kidney renal hypertensive rats. However, in DOC-salt hypertensive rats, it reduced arterial pressure to approximately normal levels and concomitantly slowed pulse rate. There was a close correlation between the magnitude of the blood pressure response observed in all SK&F 64139-treated animals and the control plasma norepinephrine (4 = -0.795, P less than 0.001) and epinephrine (r = -0.789, P less than 0.001) levels. These results suggest an important role for central epinephrine in regulating the peripheral sympathoadrenomedullary and the baroreceptor reflex activity, particularly when the maintenance of the high blood pressure is not renin-dependent.

Animals↗
PubMed1981

Grand rounds.

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Aged↗