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Biomedical subjects

J D Skinner

Publications and source records attributed to J D Skinner.

At least 55 records · Page 3Linked to original sources
PubMed1991

Seasonal energy requirements and thermoregulation of growing pouched mice, Saccostomus campestris (Cricetidae).

Pouched mice (Saccostomus campestris) were born in captivity during January and March and subsequently maintained under long photoperiod (14 h light: 10 h dark) at 25 degrees C. During their first winter (July) and the following summer (January) the pouched mice were exposed to natural photoperiod in an unheated laboratory for 3 weeks prior to measurement. The pouched mice continued to grow during the study, and were significantly heavier after summer exposure than after winter exposure 6 months earlier. Although this increase in body mass would result in a decline in their surface area to volume ratio there was no significant decline in minimal thermal conductance (Cm) and winter-exposed pouched mice had a relatively lower Cm than expected. Meanwhile the smaller, winter-exposed animals displayed a significantly higher capacity for non-shivering thermogenesis, together with higher levels of basal metabolism than summer individuals. These differences were not solely attributable to the contrasting body mass of each group and it is therefore clear that S. campestris can increase thermoregulatory heat production, and modify heat loss following exposure to short photoperiod and cold during their first winter. Despite the significant increase in metabolism, the overall energy requirements of small, winter-exposed animals were significantly lower than those for heavier pouched mice following exposure to summer conditions. These results suggest that growing pouched mice can effectively adapt to lower temperature conditions during their first winter, yet accrue considerable overall savings in total energy requirements as a result of their smaller body mass.

Animals↗
PubMed1991

The interspersed DNA repeat conserved in water birds' genomes.

A putative old and ubiquitous interspersed DNA repeat family was identified from TaqI restriction, M13 cloning, and sequencing of the genomic DNA of a Mallard (Anas platyrhynchos), a Muscovy Duck (Cairina moschata), a Toulouse Goose (Anser anser), and a Black Swan (Cygnus atratus). A 425-bp consensus core sequence was obtained for the interspersed family. The 425-bp unit was about 2% of the avian genome and was found to be conserved in at least four genera of the order Anseriforme: Anas, Anser, Cairina, and Cygnus.

Animals↗
PubMed1991

Plasma androgens in spotted hyaenas (Crocuta crocuta): influence of social and reproductive development.

Differences in plasma testosterone and androstenedione concentrations in male spotted hyaenas belonging to various reproductive and social categories 4 clans resident in South Africa and Botswana suggest that central-immigrant males have the highest concentrations of androgens, reflecting their roles as mating males. Social inhibition of reproductive function may occur in other males. A reversal in the ratio of testosterone: androstenedione occurs at puberty in most individuals, testosterone becoming the dominant hormone, especially in males that have procured mating rites. Cubs of either sex had low testosterone concentrations, except for a 4-day-old male that displayed adult concentrations, which were accompanied by a temporary testicular descent. Plasma testosterone concentrations in females largely reflected ovarian activity and showed no correlation with androstenedione concentrations. Female cubs had androstenedione concentrations significantly higher than those in all other social categories except for the central-immigrant males. The androgen profiles presented here suggest that the key to the behavioural dominance of female spotted hyaenas over males may lie with the neonatal developmental stages, rather than with the androgen patterns of adult animals.

Androgens↗
PubMed1991

Avian tandem repeats: nuclear protein binding sites and the origins of short tandem repetitive DNAS.

A 14 bp repeat isolated from the genome of a Mallard duck (Anas platyrhynchos) and a 13 bp repeat isolated from the genome of a Muscovy duck (Cairina moschata) were both tandem and genus-specific. There were 2.1 x 10(6) copies of the 14 bp repeat in the Mallard duck genome and 1.3 x 10(6) copies of the 13 bp repeat in the Muscovy duck genome. These two repeats were not obviously homologous but each contains different transcription protein binding sites. Experimentally, the two repeats were also observed to bind nuclear proteins specifically. A sequence-selective mechanism for the expansion of short tandem repeats from single ancestral sequences containing nuclear protein binding sites is presented.

Animals↗
PubMed1991

Relationship of self-concept to nutrient intake and eating patterns in young women.

The relationships between attitudes toward oneself (self-concept) and nutrition-related behavior were examined for 153 single women aged 18 to 35 years. Nutrition-related behaviors were assessed with 3-day food records that were analyzed for nutrient composition and eating patterns (Basic Four Food Group scores, number of meals per day, and percent of energy from meals and snacks). Attitudes toward self, knowledge and attitudes about nutrition, and general health practices were assessed with a written questionnaire that incorporated several existing scales. Because of potential overlap among the three self-concept scales, as well as nutrition-attitude and health-practice items, responses were factor analyzed, yielding 14 factors. These factors were then compared with nutrient intake and eating patterns. Scores for the seemingly desirable factors of the "Super Person" or "Do Your Own Thing" were negatively correlated with intake of several nutrients; scores on the self-perception of a "Traditional" orientation to life were positively related to calcium intake and meal patterns. The "Nutrition Is Important" and "Nutrition Knowledge" factors were also positively related to desirable eating patterns and nutrient intakes. We conclude that several self-concept variables, as well as nutrition attitudes and knowledge, can potentially influence nutrient intakes and eating patterns in young women.

Adult↗
PubMed1991

Practitioners beware: regional differences in beliefs about nutrition during pregnancy.

We surveyed 1,771 members of The American Dietetic Association, who worked in general nutrition, pediatrics, and public health nutrition, about their clients' beliefs about nutrition during pregnancy. The practitioners were chosen because they likely served pregnant women and/or women with young children. Items for the belief inventory were generated by surveying the beliefs of pregnant and nonpregnant adolescents and their families, teachers, and peers as well as by collecting beliefs heard from clients of social workers, nurses, and dietitians residing in the state of Tennessee. Using a modified q-sort, 26 statements were developed to survey dietitians practicing nationwide. Results indicate that beliefs about physiological needs during pregnancy, practices related to a healthy baby, and beverage recommendations were not significantly different across the regions designated by US Public Health Services (Standard Federal Administrative Regions). However, beliefs about cravings and folklore showed strong regional differences, with the Southeast regions and adjacent states differing significantly from other regions. The majority of beliefs are not supported by scientific information, and results support the need for each region to identify beliefs that could influence dietary patterns (eg, eating for two, eating only a few selected foods, restricting salt, taking vitamins to overcome an inadequate diet, and deciding pregnancy is a good time to lose weight). We recommend that dietetic practitioners become aware of clients' beliefs, support beliefs that are accurate according to current recommendations for pregnancy, and counsel clients about beliefs that are potentially detrimental to good nutrition during pregnancy.

Adolescent↗
PubMed1991

Pregnant adolescents report infrequent use of sugar substitutes.

The participants were not using sugar substitutes and, given their reported weight gain, they did not need to restrict their caloric intake during pregnancy. Taste was a primary deterrent to avoiding artificially sweetened carbonated beverages; they preferred milk, regular carbonated beverages, and fruit juices. Except for iron intake, their nutrient intakes met or exceeded the RDA. Although mean energy intakes were slightly less than recommended, maternal weight gain and infant birth weights were satisfactory.

Adolescent↗
PubMed1991

The effects of xylazine and fentanyl on various hormones and metabolites in karakul sheep and a blesbok.

Xylazine and fentanyl are commonly used in combinations for immobilisation of wild antelope. In order to ascertain the effects of the combination of these drugs on certain metabolites and hormones in ruminants, blood was sampled from 8 karakul sheep (4 experimental and 4 control) and one tame blesbok (Damaliscus dorcas phillipsii) for 30 min before and after immobilisation. The samples were assayed for glucose, free fatty acids, insulin, thyroxine, triidothyronine, progesterone and oestrogen. Significant changes, after the administration of xylazine and fentanyl, were recorded in circulating concentrations of glucose, which increased, and free fatty acids and insulin, which decreased. The other hormones tested were not affected within the sampling period. It is suggested that the combination of xylazine and fentanyl may act directly on pancreatic Beta cells to inhibit the secretion of insulin, which will consequently affect circulating concentrations of glucose and free fatty acids.

Animals↗
PubMed1990

Noradrenaline thermogenesis in conscious and anaesthetised pouched mice (Saccostomus campestris).

1. The metabolic response to injections of noradrenaline (NA) and saline (control) was investigated in conscious and anaesthetised (sodium pentobarbitone) pouched mice, Saccostomus campestris. 2. NA injection produced a calorigenic response which was significantly greater than that elicited by saline injection in both conscious and anaesthetised animals. 3. This calorigenic response was enhanced by motor activity in conscious pouched mice, but the exclusion of measurements recorded during visible activity eliminated the influence of movement. 4. Anaesthetised pouched mice underwent mild Hypothermia and displayed a retarded metabolic response to NA injection which suggests that anaesthesia affects the expression of NA-induced thermogenesis. 5. The validity of proposed techniques for the measurement of NA thermogenesis is further discussed.

Anesthesia↗
PubMed1989

Circulating progesterone concentrations and ovarian functional anatomy in the African elephant (Loxodonta africana).

Mean plasma progesterone concentrations measured in pregnant and non-pregnant elephants did not differ significantly from each other because of considerable variation, particularly for stage of pregnancy. Maximum progesterone values were recorded during pregnancy (5-8 months) and declined towards term (22 months). The numbers of corpora lutea or total luteal tissue volume were not critical in maintaining progesterone secretion. An increase in plasma progesterone concentrations with the luteal phase of the ovarian cycle was evident. A possible role of the placenta in the second half of gestation is indicated by an increase in fetal progesterone concentrations towards term.

Animals↗
PubMed1989

Aspects of reproduction in female Ross seals (Ommatophoca rossii).

Ovaries were collected from 26 Ross seals shot in the King Haakon VII Sea south of the 60 degrees latitude during 3 periods, between 12 January and 2 February 1980-1982. The structure of the ovaries resembled that of other pinnipeds. A corpus luteum was found in 18 of 26 females, which therefore were regarded as reproductive. However, no females were lactating or visibly pregnant (presence of fetus in the uterus). Of the remaining 8 females (non-reproductive), 3 had neither a corpus luteum nor a corpus albicans. Ovulation did not alternate between ovaries in 4 of 10 females. Ovarian weight was greater in reproductive females than in non-reproductive females, and was also correlated with presence of a corpus luteum. Follicular development was more advanced in reproductive females than in non-reproductive females, and it was also more pronounced in the ovary containing a corpus luteum. The finding of a high percentage of females with a corpus luteum, but with no fetus in the uterus, together with histological characteristics of the ovarian structures in the present study, and earlier published data on mating, pupping and moulting, provide circumstantial evidence for delayed implantation in Ross seals.

Animals↗
PubMed1988

Thermoregulatory circadian rhythms in the pouched mouse (Saccostomus campestris).

1. Circadian rhythms of body temperature (Tb), oxygen consumption (VO2), and minimal thermal conductance (C) were studied in the pouched mouse, Saccostomus campestris under natural photoperiod during February at a constant ambient temperature of 28 degrees C. 2. Circadian rhythms of body temperature were also studied under natural photoperiod and laboratory temperatures (Max: 28.1 degrees C; Min: 23.2 degrees C) during February. 3. The results of the present study suggest that changes in ambient temperature are not the main "zeitgeber" for body temperature rhythm, and it seems that photoperiod plays a major role in this species. 4. The relationship between the rhythms of Tb, VO2, and C are further discussed.

Animals↗
PubMed1988

Reproduction in female Hartmann's zebra, Equus zebra hartmannae.

Ovaries, fetuses and plasma were collected from zebra mares shot in the Etosha National Park in Namibia between 15 and 25 August 1983. Ovarian weight was affected by reproductive status and most of the non-pregnant mares were anoestrous. The number of follicles varied between individuals and only pro-oestrous/oestrous mares had follicles larger than 20 mm in diameter. The largest follicle in pregnant mares was only 9 mm in diameter. Corpora lutea and corpora albicantia were found in non-pregnant as well as pregnant mares: 4 pregnant mares had only corpora albicantia. The presence of secondary corpora lutea could not be confirmed in any of the pregnant mares. Implantation was estimated to occur at around 73 days of gestation, and most mares (84%) had conceived between November and April. Peripheral concentrations of plasma progesterone during pregnancy varied from 0.5 to 2.4 ng/ml.

Anestrus↗
PubMed1988

Improved separation of multi-locus hypervariable DNA restriction fragments by field inversion gel electrophoresis and fragment detection using a biotinylated probe.

DNA probes to multiple hypervariable human genomic loci are potentially highly informative as regards individual genome identification and parentage studies. However the resultant Southern blot patterns are generally highly complex and their interpretation difficult, with one important limitation being the extent of fragment separation and resolution. The separation of large DNA restriction fragments in agarose gels may be improved, in comparison to separations obtained by conventional electrophoresis, by the use of field inversion techniques. This is demonstrated by the analysis of the complex human Satellite III related DNA polymorphism. Detection of the Satellite III related restriction fragments is achieved either by using a [35S]-labelled probe (228S) or by using the same probe in a convenient non-isotopic form constructed by the photobiotin process. In addition, the probe 228S is useful for sexing the human genome, by the identification of a Y-specific restriction fragment.

Biotin↗
PubMed1988

Individual dietary intake methodology: a 50-year review of progress.

This article provides an overview of five decades (1936 through 1987) of publications on individual dietary assessment methodology, such as dietary histories, estimated and weighed food records, food frequency questionnaires, and 24-hour recalls. Representative studies were selected to characterize data collection and analyses methods of each decade. During the 1930s and 1940s, dietary intake methodology was in its initial stages; popular methods were the dietary history technique and lengthy food records. The 1950s were characterized by extensive comparisons of methodologies, which now often included shorter-term food records and 24-hour recalls. The 1960s ushered in large scale epidemiological studies, the food frequency technique, and use of computer technology for computation; the 24-hour recall was still widely used in that decade and the next. Advances of the 1970s and 1980s include expansion of nutrient databases, sophisticated statistical techniques for analysis, and refinement of data collection methodologies for analysis, and refinement of data collection methodologies. The chronological approach used in this review not only highlights progress of each decade but also identifies the repetitive efforts of some studies. The need for creative approaches is emphasized as current research needs are identified.

Data Collection↗
PubMed1987

Chromatin structures: dissecting their mixed patterns in nuclease digests.

Four separate features could be distinguished in Fe-DNAase-1 digestions of human lymphoblast nuclei: a di-nucleosomal (2N) repeat, a mono-nucleosomal (1N) repeat, a component of "random" DNA, and triple splitting of major peaks. The random component is major, is unlikely to be completely artifactual, and is what would be expected from the face to face layering model of Subirana et. al., (1). The 2N pattern appeared to be associated with compact, metaphase-type chromatin, whereas the 1N pattern was associated with more exposed chromatin. These two modes are explained in terms of orderly back-to-back folding of zig-zag nucleofilaments, and face-to-face folding respectively. Hybridization studies indicated that the centromeric classes of repetitive DNA had the same digestion spectra as the major interspersed classes of repetitive DNA, and DNA enriched in transcriptionally active sequences. It is suggested that current coil models are all inadequate explanations of higher order chromatin packing.

Chromatin↗