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Biomedical subjects

A B Holt

Publications and source records attributed to A B Holt.

At least 19 recordsLinked to original sources
PubMed1982

Ontogeny of the brain in a marsupial (Macropus eugenii) throughout pouch life. I. Brain growth.

Growth characteristics of the tammar wallaby brain have been determined from 143 animals at various stages of growth from birth to adulthood, with particular emphasis on the 250 days of pouch life. The macroscopic anatomy of the brain is also described for pouch young at days 3, 5, 88 and 190 days after birth, and for the adult. The transition from the rapid to mature growth phases of each brain structure occurs between days 120 and 180 after birth, and coincides with the appearance of previously described developmental characters or behaviour. The allometric relationships of brain and body growth described in this marsupial resemble those described for primates. Because of the accessibility of the pouch young during the critical period of brain differentiation, this marsupial may provide a useful laboratory model for the study of brain development.

Aging↗
PubMed1981

Evidence for zinc deficiency in aboriginal settlements in Northwestern Australia.

Four coastal Aboriginal settlements in the northwest area of Australia have been investigated for plasma trace metal status--Zinc (Zn), Copper (Cu), and Iron (Fe). The 350 Aboriginals were considered in two groups; five to 20 years of age and 20 to 70 years of age. Forty per cent to 50% had plasma Zn levels below two standard deviations from the normal and 60% to 70% had plasma Cu levels greater than two standard deviations above the normal (almost 100% at Kalumburu). Hypoferraemia was common. These results are more significant than those of a previous study of 350 individuals living at two inland settlements. The coastal missions have access to fresh meat and fish, and at Kalumburu food is prepared for the people. While the climate, soil, and the Aboriginal predilection for white flour may play a role, it is speculated that the Zn deficiency is related to parasitic infestation in the intestine, loss of blood, and failure of zinc absorption.

Adolescent↗
PubMed1981

Compensatory renal growth in the mouse. I. Allometric approach to the effect of age.

Allometry, defined as the relationship between the growth rates of organs to the weight of the whole body (38), was used to study the effect of age on the degree of compensatory renal growth (CRG) in the mouse. The normal growth of the kidneys relative to body weight (BW) was determined in animals between 5 to 50 days of age. In one group, nephrectomy and sham operations were performed at 5, 15, and 35 days of age. The remaining ("renoprival") kidney was removed 15 days postnephrectomy. In a second group, nephrectomy was performed on 5-day-old animals, the renoprival kidney being removed after 30 or 45 days. Regression equations were calculated by least-squares after logarithmic transformation and different groups were compared by analysis of covariance. The regression equation for the control kidney was kidney weight (KW) = 0.0093 BW0.86 (r = 0.96). The regression for renoprival kidneys in females was KW = 0.0142 BW0.83 (R = 0.96) after 15 days and, in comparison, was not significantly different from 30 to 45 days. The interval between control and renoprival regressions was equivalent to a difference of congruent to 43% KW. In male mice, the regression for renoprival kidneys after 15 days was KW = 0.0103 BM0.96 (r = 0.98) and was not significantly different from 30 to 45 days. This study suggests that in young mice the time required for complete CRG may be a maximum of 15 days and that the amount of CRG does not depend on the age at operation. After CRG, a new equilibrium is reached which is thereafter maintained up to a minimum of 50 days of age.

Adaptation, Physiological↗
PubMed1980

Serum and plasma zinc, copper and iron concentrations in Aboriginal communities of North Western Australia.

Two aboriginal communities situated in the tropical north-west of the Australian continent have been investigated in regard to trace metal status (zinc, copper, and iron) and other laboratory and epidemiological information. A total of 364 persons, ranging in age from 5 to 77 years were studied. The incidence of hypozincemia (serum or plasma zinc concentration less than 0.71 micrograms/ml) of the two communities when combined was 24.4%, while hypercupremia (defined as serum or plasma copper levels greater than 1.38 micrograms/ml) was 47.9%. Depressed serum iron levels were demonstrated in more than 50% of the Aborigines studied. Hypozincemia was most prevalent (incidence 31 to 67%) in children at the time of the important pre- and postadolescent growth period (10 to 15 years) and in women beyond 60 years of age (incidence 33 to 64%). Serum total protein and vitamin B12 levels tended to be increased. Mild anemia was seen in approximately one in five persons aged less than 20 years. Intestinal parasites and pathogenic enterobacteria were frequently isolated in fecal specimens. In one community, half of the persons examined had positive isolates of enteric pathogens. Intestinal parasites predominated and were more frequently isolated from persons aged less than 20 years. Ancylostoma duodenale accounted for 32% of the pathogens isolated. Evidence is presented that suggests that both communities are exposed to numerous bacterial, viral, and parasitic infections. The diet consumed in these communities is predominately white flour and refined sugar. Geophagia is practiced in this area of Australia. It is emphasied that all the etiological prerequisites and many of the laboratory findings ascribed to the zinc deficiency syndrome appear to be operating in the two Aboriginal communities studied.

Adolescent↗
PubMed1978

Assessment of protein reserves (cellular mass) in Aboriginal children.

The body protein reserves, assessed indirectly by the measurement of intracellular water, was determined in free-living Aboriginal children and adolescents located in Central and Northwestern Australia. Fifty one individuals were studied--31 males and 20 females. Significant reductions were observed in intracellular water or cell mass relative to the cube of body length for Aboriginal females when compared to a control female group. Only marginal or borderline differences for the same parameters were observed when Aboriginal males were compared with controls. Comparison of Aboriginal females with Aboriginal males demonstrated significant reductions in cell mass (intracellular water) relative to body length cubed in the female. This finding in the Aboriginal female is of concern because many become pregnant in the early teenage years. Evidence was found during the course of this study that plasma zinc concentrations were frequently low. This led to a concomitant study on serum and plasma trace metals in two Aboriginal settlements (364 individuals) to be published in a subsequent paper.

Adolescent↗
PubMed1976

Nutritional studies in the pregnant rhesus monkey--the effect of protein-calorie or protein deprivation on growth of the fetal brain.

Twenty four pregnant nulliparous rhesus monkeys were distributed in three groups. While pregnant, the mothers were fed a diet, adequate in mineral and vitamins, that afforded 4.2 g protein and 100 cal; 1.2 g protein and 100 cal; or 1.2 g protein and 50 cal per kg per day. The fetuses were taken by cesarian section at 156 days gestation (term = 165 days) and the cerebrum and cerebellum were subsequently analysed chemically to assess composition and growth. Analyses revealed no statistically significant changes in protein, DNA, RNA, cholesterol, phospholipid, water, or chloride space of either tissue. The zinc concentration per gram of cerebral tissue or protein was significantly elevated in the low protein low calorie group. These results indicate that the brain of the fetus of this primate is protected during frank protein-calorie restriction of the mother. Moreover it is during this time that the major part of brain development takes place. It is argued that the differences observed after maternal restriction of protein and/or calories in subprimate mammals are not necessarily applicable to the human situation.

Animals↗