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Biomedical subjects

J Allman

Publications and source records attributed to J Allman.

At least 19 recordsLinked to original sources
PubMed1998

Parenting and survival in anthropoid primates: caretakers live longer.

Most anthropoid primates are slow to develop, their offspring are mostly single births, and the interbirth intervals are long. To maintain a stable population, parents must live long enough to sustain the serial production of a sufficient number of young to replace themselves while allowing for the death of offspring before they can reproduce. However, in many species there is a large differential between the sexes in the care provided to offspring. Therefore, we hypothesize that in slowly developing species with single births, the sex that bears the greater burden in the care of offspring will tend to survive longer. Males are incapable of gestating infants and lactating, but in several species fathers carry their offspring for long periods. We predict that females tend to live longer than males in the species where the mother does most or all of the care of offspring, that there is no difference in survival between the sexes in species in which both parents participate about equally in infant care, and that in the species where the father does a greater amount of care than the mother, males tend to live longer. The hypothesis is supported by survival data for males and females in anthropoid primate species.

Animals↗
PubMed1998

Bearing the burden or baring the soul: physicians' self-disclosure and boundary management regarding medical mistakes.

Within a boundary management framework, this study explored how physicians manage self-disclosure regarding medical mistakes amidst boundary constraints imposed by risk management, legal mandate, and the medical culture. Descriptive statistics from questionnaires and exemplars from accompanying narratives showed that the 39 internists and family physicians in this study chose to control their own boundaries by revealing errors most often to other physicians to facilitate learning. Although risk management and the medical culture do not appear to deter physicians from disclosing errors at a superficial level, physicians maintain tight personal boundaries at the emotional level. Perhaps if physicians could disclose errors at the emotional level, their mental energies could be more positively channeled to patients' needs, resulting in improved patient care.

Journal Article↗
PubMed1996

Demographic trends in Vietnam.

"Asia's four ¿little dragons' (South Korea, Hong Kong, Singapore and Taiwan) have in common not only an economic boom, but also the same rapid demographic transition. How does Vietnam, whose economy is poised for a take-off, stand in this respect? In an attempt to answer this question, [the authors] study the growing corpus of information which a number of ad hoc surveys have added to the 1979 and 1989 population censuses."

Asia↗
PubMed1993

Brain weight and life-span in primate species.

In haplorhine primates (tarsiers, monkeys, apes, and humans), there is a significant correlation between brain weight and maximum life-span when the effect of body size is removed. There is also a significant correlation in haplorhine primates between brain weight and female age at first reproduction. For strepsirhine primates (lorises and lemurs), there are no significant correlations between brain weight and either life-span or female reproductive age when the effect of body size is removed. This lack of correlation in strepsirhine primates may be related to the fact that these primates are nocturnal and/or natives of the island of Madagascar, both of which conditions may reduce competition for resources and predation pressure. These findings suggest that in haplorhine primates the genetic systems controlling brain growth are linked to the systems governing the life cycle so that species with longer cycles have larger brains. When the effect of body weight is removed, leaf-eating haplorhines have significantly smaller brains and shorter lives than haplorhines with other diets. Harem-living haplorhines also have significantly smaller brains and shorter life-spans than troop-living haplorhines when the effect of body weight is removed. We also sought to test the rate-of-living hypothesis by determining whether primates with basal metabolic rates that are higher than would be expected for their body size have shorter maximum life-spans than would be expected for their body size. Metabolic rate is not correlated with life-span or female age at first reproduction when the effect of body size is removed.

Adrenal Glands↗
PubMed1991

31P saturation transfer and phosphocreatine imaging in the monkey brain.

31P magnetic resonance imaging with chemical-shift discrimination by selective excitation has been employed to determine the phosphocreatine (PCr) distribution in the brains of three juvenile macaque monkeys. PCr images were also obtained while saturating the resonance of the gamma-phosphate of ATP, which allowed the investigation of the chemical exchange between PCr and the gamma-phosphate of ATP catalyzed by creatine kinase. Superposition of the PCr images over the proton image of the same monkey brain revealed topological variations in the distribution of PCr and creatine kinase activity. PCr images were also obtained with and without visual stimulation. In two out of four experiments, an apparently localized decrease in PCr concentration was noted in visual cortex upon visual stimulation. This result is interpreted in terms of a possible role for the local ADP concentration in stimulating the accompanying metabolic response.

Adenosine Diphosphate↗
PubMed1989

Evaluation of a simplified method for estimation of early childhood mortality in small populations.

The provision of simple health technologies in less developed countries has far outpaced the capabilities to evaluate their impact on health in general, and early childhood survival in particular. In rural Haiti, attempts to monitor the impact of health care delivery programmes have been frustrated by some of the same problems encountered elsewhere; ie lack of practicable yet scientifically sound methodologies that interface well with ongoing service delivery programmes. The 'preceding birth' technique, originally advanced by Brass and Macrae, holds promise as just such a method. Its practical appeal derives largely from simple data requirements. In its simplest form, the method requires only responses to a single question put to mothers at delivery regarding the survival status of her previous child. They have shown that the proportion of immediately preceding births dying before the 'index' birth date provides a good approximation of the standard life table probability of death before the second birthday. Given that in rural Haiti, as in much of the less developed world, few women deliver in clinic or hospital where such data could be systematically obtained, exploitation of the preceding birth method would require identification of a convenient and unobtrusive point of contact between questioner and mothers who have recently delivered. In Haiti, two options arose: (1) interview women at home after childbirth, and (2) interview women when they bring the 'index' child seeking vaccination or some other child survival intervention. Both of these deviate from the original technique of Brass and Macrae with respect to the timing and method of data collection, and could therefore introduce serious complications to the interpretation of trends in child mortality. To study this, we examined the effects of adapting the preceding birth method to a rural less developed country setting in Mirebalais, where since 1983 primary health care activities have been administered by MARCH (Management and Resources for Community Health), a private voluntary health organization. The Mirebalais study used a pregnancy register, originally developed for targeting of services, to identify women who were expected to have given birth during the 12-month period before each of two survey rounds. Brief interviews with these women would provide direct life table estimates of child mortality level and trend with which to compare estimates produced from use of the preceding birth method in modified form. Direct estimates of the probability of dying before the second birthday were 138/1000 from first round data and 134/1000 from second round data, indicating a 3% decline.(ABSTRACT TRUNCATED AT 400 WORDS)

Data Collection↗
PubMed1988

Perceptions of depth elicited by occluded and shearing motions of random dots.

A computer-controlled display of random dots was used to study perceptions of depth. In this display, a field of stationary random dots surrounded a rectangular area in which random dots moved with uniform velocity in a single direction. The boundaries of this rectangle did not move. When dot motion was perpendicular to the longer boundary of the rectangle (occluded motion), the rectangle seemed to be behind the stationary background surround. Motion parallel to the longer boundary of the rectangle (shearing motion) made it appear in front of the surround. The relative lengths of the sides of the rectangle determined which effect predominated. Thus, for motion perpendicular to the long axis of the rectangle the occlusion predominated and naive subjects reported that the central area seemed farther away than the surround. For shearing motion parallel to the long axis, the subjects reported that the rectangle was closer than the surround and the strength of both effects also depended on the length-to-width ratio of the rectangle. If there was occluded motion along the long axis, as the length-to-width ratio increased so did the likelihood that subjects would report seeing the rectangle behind the surround. Conversely, with shearing motion along the long axis, increasing the length-to-width ratio increased the likelihood that the rectangle would appear unambiguously in front of the surround. Some subjects integrated the two cues with the resulting perception being a rotating cylinder. The occlusion effect was stronger than the shearing effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗
PubMed1987

Women's status and family planning in Haiti.

"The paper argues that women's status in Haiti is a factor favorable to the spread of modern contraception and a potential rapid demographic transition from high to low fertility. After briefly reviewing recent theories on the determining of fertility declines, the paper considers women's status in Haiti. It discusses family patterns, conjugal unions, and economic activities. Finally, it reviews current patterns of contraceptive use and considers how these are related to various aspects of women's status."

Americas↗
PubMed1985

Direction- and velocity-specific responses from beyond the classical receptive field in the middle temporal visual area (MT).

The true receptive field of more than 90% of neurons in the middle temporal visual area (MT) extends well beyond the classical receptive field (crf), as mapped with conventional bar or spot stimuli, and includes a surrounding region that is 50 to 100 times the area of the crf. These extensive surrounds are demonstrated by simultaneously stimulating the crf and the surround with moving stimuli. The surrounds commonly have directional and velocity-selective influences that are antagonistic to the response from the crf. The crfs of MT neurons are organized in a topographic representation of the visual field. Thus MT neurons are embedded in an orderly visuotopic array, but are capable of integrating local stimulus conditions within a global context. The extensive surrounds of MT neurons may be involved in figure-ground discrimination, preattentive vision, perceptual constancies, and depth perception through motion cues.

Animals↗
PubMed1982

The impact on breastfeeding and pregnancy status of household contraceptive distribution in rural Haiti.

This paper presents data from an experimental project which distributed oral contraceptives, foam, and condoms to households in three rural areas of Haiti between January 1978 and March 1980. The contraceptive distribution had little apparent impact on traditional, prolonged breastfeeding patterns, and the percentage of women pregnant after eight months of field operations declined over 35 per cent in the two areas where contraceptive acceptance and use were highest. (Am J Public Health 1982; 72:825-838.)

Adolescent↗