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Biomedical subjects

D A Henderson

Publications and source records attributed to D A Henderson.

At least 19 recordsLinked to original sources
PubMed1992

Cellular morphology in outer medullary collecting duct: effect of 75% nephrectomy and K+ depletion.

The present study was designed to determine, in rats, whether 75% nephrectomy and potassium depletion affect the principal and intercalated cells in the outer medullary collecting duct in the same manner as they affect the principal and intercalated cells in the cortical collecting duct. Ten days after a 75% reduction of renal mass, whole animal glomerular filtration rate decreased and the fractional excretion of potassium increased in rats. However, no morphological changes occurred in either the principal or intercalated cells of the outer medullary collecting duct after the reduction of renal mass. When 75% nephrectomized rats were placed on a diet deficient in potassium, the concentration of potassium in plasma and the absolute and fractional excretion of potassium decreased significantly. In addition, marked hypertrophy occurred in both the principal and intercalated cells in the outer medullary collecting duct. Previous findings from the same animals used in the present study show that 75% nephrectomy caused hypertrophic changes in principal cells of the cortical collecting duct, which could be inhibited by potassium depletion induced by the dietary restriction of potassium. The findings also show that the intercalated cells of the cortical collecting duct in 75% nephrectomized rats were unaffected by potassium depletion. On the basis of our findings, it appears there is an absence of hypertrophy in either the principal or intercalated cells in the outer medullary collecting duct of the rat after renal mass in the animal is reduced significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Defining global medical education needs.

The graduates of medical education institutions should be, both in their numbers and in their acquired skills, appropriate to improving the health of the particular society they are intended to serve. Medical education should be tailored to deal with the diseases the physician is most apt to see--or at least apt to see in an academic medical center. Such logic does not prevail, however, in terms of either the numbers of physicians trained or the content of the medical curriculum. The Western model of a medical school curriculum has been adopted--but little adapted--for use by much of the Third World. Relevant subjects such as epidemiology, social sciences, and management are often either ineptly taught or omitted. A shift in attention from patient to community is recommended, accompanied by deliberate programs of education and health care to measure and improve the health of the community. Significant improvements in health in much of the world can be made only through community-based programs such as improved nutrition, education, sanitation, prevention of infectious diseases, and family planning. Two types of U.S. participation in international medical education are recommended: (1) specialty training of physicians from countries whose access to instrumentation and medical care support structures are similar to those in the United States, and (2) strengthening of institutions in developing countries in the areas of education, research, and practice appropriate to the particular needs of each of these countries.

Curriculum↗
PubMed1987

Principles and lessons from the smallpox eradication programme.

The eradication of smallpox required a unique, fully collaborative international effort on the part of WHO and Member States. In the course of the programme, many lessons were learned in its organization, execution and evaluation which have implications for other international activities. Most important among these was the need to establish measurable objectives and to evaluate progress and performance in terms of these; to establish procedures for quality control both of vaccines and performance; to recruit the best possible personnel and support them; and to assure an on-going programme of problem-oriented research which can facilitate activities and resolve apparently paradoxical observations. The inherent capacities of national health services to execute their smallpox eradication programmes was gratifying. It encouraged the belief that other, more complex health measures could be undertaken. Although this would necessitate that adequate numbers of competent leaders be recruited and given delegated responsibility, such persons were usually found to be available although often inexperienced. WHO's roles in catalysing and orchestrating this great effort were critical. Its potential for promoting other efforts in disease prevention and health promotion was apparent although still only partially realized.

Communicable Disease Control↗
PubMed1986

Delayed plasma clearance and hepatic uptake of lymph chylomicron 14C-cholesterol in marginally zinc-deficient rats.

Previously, chylomicrons from marginally zinc-deficient rats were shown to be abnormally large, with markedly reduced levels of apoproteins C and E. In the present study, effects of such changes on the plasma clearance and hepatic uptake of chylomicron cholesterol were investigated in rats fed 3 ppm of zinc (ZD), as compared with those fed 30 ppm of zinc (CT). The rate of plasma clearance was determined by plasma 14C-radioactivity at different intervals after intravenous injection of lymph chylomicrons labeled in vivo with 14C-cholesterol. The 14C-clearance curves were nonlinear, consisting of an initial rapid phase followed by a slow phase of clearance. The initial 14C-clearance was significantly (p less than 0.05) delayed whether the labeled chylomicrons from ZD donors were injected into ZD or CT recipients. The hepatic 14C-recovery in extracted lipids was also significantly lower in ZD rats. The present data provide first evidence that a marginal level of zinc deficiency produces a significant delay in the plasma clearance and hepatic uptake of chylomicron cholesterol. This may be attributable in part to the molecular alterations of chylomicrons induced by zinc deficiency.

Administration, Oral↗
PubMed1985

Effect of marginal zinc deficiency on the morphological characteristics of intestinal nascent chylomicrons and distribution of soluble apoproteins of lymph chylomicrons.

Effects of marginal zinc depletion on the compositional and morphological characteristics of chylomicrons were investigated in adult male rats fed 3 ppm of dietary zinc, as compared with pair-fed and ad-libitum controls given 30 ppm of zinc for 6 to 8 wk. Lymph was collected by cannulating the intestinal lymphatic duct during infusion of a 1:1 mixture of Intralipid and 150 mM NaCl via a duodenal catheter. Lymph chylomicrons were isolated by ultracentrifugation and further purified by agarose column chromatography. A marginal level of zinc deficiency produced decreases in the relative concentrations of apolipoproteins C and E, with an increase in apoprotein A-I and no change in apoprotein A-IV and no significant alterations in the lipid components. Nascent chylomicrons in the intestinal absorptive cells were irregular and larger in shape and size, as determined by light and electron microscopy. The present results suggest that the changes in chylomicron apoproteins produced by zinc deficiency are due in part to postsynthetic modification of intestinal chylomicrons upon their release into the lymph.

Animals↗
PubMed1978

The pathology and pathogenesis of chronic lead nephropathy occurring in Queensland.

Many children who suffered acute lead poisoning in Queensland eventually died with contracted kidneys. In most cases the kidneys were granular and showed microscopically fibrosis, hypertensive vascular changes and "alterative glomerulitis". Clinically in these patients, hypertension and chronic renal insufficiency had always preceded death which was usually due to uraemia. In a minority of cases the kidneys showed the changes of benign hypertension but were unusually small; fibrosis and "alterative glomerulitis" were not present. Clinically these patients had had hypertension but minimal renal insufficiency and death was usually due to cerebral haemorrhage. The evidence indicates that lead caused severe damage to the kidney at the time of the lead intoxication by some mechanism other than hypertension. The sequence of events postulated comprises severe renal damage with destruction of glomeruli during childhood lead poisoning, disappearance of the destroyed tissue during childhood and adolescence, onset of hypertension in adolescence or early adult life, gradual onset and progress of chronic uraemia during which fibrosis and granularity developed. In milder cases the sequence is not complete because renal function has remained adequate.

Adult↗
PubMed1976

Surveillance of smallpox.

An intensified global smallpox eradication programme was started by the World Health Organization in 1967. This paper describes the basic techniques employed and the experiences involved in implementing the procedures. Surveillance schemes have varied considerably in detail from country to country according to different health structures, and the emphasis is therefore placed on the more generally used approaches. Finally, important principles in the implementation of the smallpox surveillance programme are considered in relation to the development of such programmes for other communicable diseases.

Communicable Disease Control↗
PubMed1976

Monkeypox and whitepox viruses in West and Central Africa.

Prospects for the eradication of smallpox are now highly encouraging. With the cessation of man-to-man transmission, the question of possible animal reservoirs of smallpox becomes increasingly important. During the period 1970-1975, 20 cases of a smallpox-like disease were detected in smallpox-free areas of tropical rain forest in West and Central Africa. Epidemiological and virological investigations revealed that the disease was caused by an animal poxvirus termed monkeypox virus, a member of the orthopox virus group. The disease spread with difficulty even among susceptible close contacts and does not appear to be sufficiently transmissible to permit continuing infection to become established in man. During the investigations, four orthopox viruses termed whitepox viruses were isolated from rodents and monkeys. The isolates were not distinguishable from variola virus with currently available laboratory techniques, but there is no evidence so far that viruses of this group have infected man. Although there is now substantial and accumulating evidence that there is no animal reservoir for smallpox, continued surveillance and studies in West and Central Africa are warranted.

Africa, Central↗