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The evolution of non-maternal care in anthropoid primates: a test of the hypotheses.

The amount of non-maternal care (allocare) found in primates varies greatly from species to species. Our paper examines this variation and focuses on possible reasons why mothers in some anthropoid primate species are prepared to relinquish their infants to other carers whereas others are not. We use data collected from the literature to test a number of hypotheses that attempt to explain the observed variation in non-maternal care. Analyses were carried out using comparative methods that control for the influence of both body size and phylogeny on life-history and ecological variation. The results support previous studies of both primates and other mammals in finding a clear link between the amount of allocare provided and female reproductive rates. Species with high allocare levels grow rapidly post-natally and wean their infants at a younger age (but at the same relative size) than species of the same body size with lower allocare levels. This early weaning allows high allocare species to support higher birth rates than low allocare species but does not result in earlier maturation. Our results, therefore, suggest that mothers allow non-maternal care of their infants in order to increase their own reproductive output. It is not clear whether such a strategy also benefits the infant, as we could find no link between the presence of allocare and early maturation (which would increase the infant's reproductive output) or between allocare levels and infant survival (as measured by vulnerability to infanticide). This suggests that mothers and infants might come into conflict over transfer to other carers, as the benefits to the mother may not be accompanied by benefits to the infant. However, although mothers may benefit from allocare in some circumstances, they will not be expected to allow allocare if the costs are high (e.g. if there is a high risk to the infant).

Altruism↗

Truncated AUC evaluates effectively the bioequivalence of drugs with long half-lives.

Crossover trials were simulated in order to evaluate whether shortening the duration of bioequivalence trials for drugs with long half-lives would adversely affect the statistical properties of estimated AUC ratios. The trials were simulated under a wide range of assumed kinetic and experimental conditions. The duration of the simulated experiments was gradually shortened and ratios of truncated AUCs were evaluated. In addition, simulations by Martinez and Jackson [1991] were substantially extended. It was demonstrated that the variation of truncated AUCs did not rise, and their bias was negligible when investigations were limited to 2 (and under many conditions to 1) half-lives following drug administration. With large variability of clearance, high limit of quantitation, and/or 2-compartmental models, the observed variation actually often increased when the duration of a study was extended. It was concluded that the assessment of bioequivalence for long half-life drugs would not be adversely affected by limiting the duration of an investigation and, consequently, by using truncated AUCs.

Analysis of Variance↗

Variations in lengths of stay and rates of day case surgery: implications for the efficiency of surgical management.

Variability in lengths of acute hospital stay and rates of day case surgery is shown to be a continuing pattern which occurs both between and within countries. A model of the determinants of health service activity is presented and the contribution of different factors to the observed variations is assessed. Differences in methods of funding health services are identified as a major determinant of the between country variations, while the within country variations largely reflect the influence of local differences in facilities and services and the organisation of care at a hospital level, as well as the independent effects of differences in clinical practice style. The main rationale for advocating a reduction in length of stay and increased use of day surgery is to increase efficiency by reducing costs per case while maintaining the quality of care. These criteria of costs, clinical outcomes and patient acceptability are examined in relation to day case surgery for an intermediate surgical procedure (inguinal hernia repair) and short stay surgery for cholecystectomy. The precise cost savings are shown to depend on the methods of costing, assumptions made and facilities employed, while factors influencing the outcomes achieved include the criteria of patient selection, the surgical techniques employed, and the adequacy of preoperative communication. Barriers to the more widespread adoption of short stay and day case surgery include practical and organisational constraints on clinical practice at a hospital level, lack of awareness among clinicians as to how far their practices differ from current norms, and clinical barriers raised by surgeons who do not see short stay policies as advantageous. Mechanisms to promote changes in clinical practice styles include independent professional audit, peer review, and involvement of clinicians in budgeting and resource allocation. Assessing quality requires that attention is given to patient acceptability and satisfaction as well as to the monitoring of clinical outcomes.

Ambulatory Surgical Procedures↗

Dislodgeable residues of ethion in Florida citrus and relationships to weather variables.

Five different treatments of ethion on Valencia orange trees were compared for decay rates and for ethion monoxon and ethion dioxon production under different environmental conditions. The oxon metabolite levels observed were low and always below the residue level of ethion itself. There were no significant differences in the decay rates of ethion between treatments. A model of ethion decay utilizing environmental variables as a time base is presented. This model explains 94% of the variation observed in ethion decay during very wet and very dry periods in Florida. The application of these results and general experimental approach to worker safety reentry standards is discussed.

Chromatography, Gas↗

An interlaboratory comparison of immunohistochemistry and PCR methods for detection of Neospora caninum in bovine foetal tissues.

Seven European laboratories contributed to a multi-centre evaluation of detection techniques for Neospora caninum in bovine foetuses. Six laboratories participated in immunohistochemistry (IHC) testing. All seven laboratories participated in PCR testing, but the results from one laboratory were not included in the analysis, because of contamination problems in the preparation of the samples. A coded panel of tissue sections from 36 infected and non-infected foetuses was used to evaluate the IHC detection of parasites. A coded panel consisting of 44 homogenized foetal brain samples from natural bovine abortion cases and 32 spiked samples were used to evaluate the PCR methods. Inclusion of a duplicate dilution series of spiked samples was used to evaluate detection limits and repeatability. IHC methods had a relatively low sensitivity, but a high specificity. There was considerable variation in IHC results between participating laboratories, which may be partly explained by examination practices that depended on the experience of the operator. In addition, the use of different antibody reagents, different antibody dilutions, and different enzymatic treatments of tissues may have contributed to the observed variation. PCR methods generally had a higher sensitivity than IHC methods and also a high specificity. The agreement between the majority scores of IHC and PCR methods was low. False positive PCR results indicated contamination problems in some instances. Agreement between the PCR results of the various laboratories was better, compared with the IHC results. There appeared to be no clear relationship between the PCR format (i.e. single or nested) and diagnostic sensitivity. Consequently, an improvement of diagnostic performance of PCR might possibly be achieved by optimizing DNA extraction methods.

Abortion, Veterinary↗

The immune system: a target for functional foods?

The immune system acts to protect the host from infectious agents that exist in the environment (bacteria, viruses, fungi, parasites) and from other noxious insults. The immune system is constantly active, acting to discriminate 'non-self' from 'self'. The immune system has two functional divisions: the innate and the acquired. Both components involve various blood-borne factors (complement, antibodies, cytokines) and cells. A number of methodologies exist to assess aspects of immune function; many of these rely upon studying cells in culture ex vivo. There are large inter-individual variations in many immune functions even among the healthy. Genetics, age, gender, smoking habits, habitual levels of exercise, alcohol consumption, diet, stage in the female menstrual cycle, stress, history of infections and vaccinations, and early life experiences are likely to be important contributors to the observed variation. While it is clear that individuals with immune responses significantly below 'normal' are more susceptible to infectious agents and exhibit increased infectious morbidity and mortality, it is not clear how the variation in immune function among healthy individuals relates to variation in susceptibility to infection. Nutrient status is an important factor contributing to immune competence: undernutrition impairs the immune system, suppressing immune functions that are fundamental to host protection. Undernutrition leading to impairment of immune function can be due to insufficient intake of energy and macronutrients and/or due to deficiencies in specific micronutrients. Often these occur in combination. Nutrients that have been demonstrated (in either animal or human studies) to be required for the immune system to function efficiently include essential amino acids, the essential fatty acid linoleic acid, vitamin A, folic acid, vitamin B6, vitamin B12, vitamin C, vitamin E, Zn, Cu, Fe and Se. Practically all forms of immunity may be affected by deficiencies in one or more of these nutrients. Animal and human studies have demonstrated that adding the deficient nutrient back to the diet can restore immune function and resistance to infection. Among the nutrients studied most in this regard are vitamin E and Zn. Increasing intakes of some nutrients above habitual and recommended levels can enhance some aspects of immune function. However, excess amounts of some nutrients also impair immune function. There is increasing evidence that probiotic bacteria improve host immune function. The effect of enhancing immune function on host resistance to infection in healthy individuals is not clear.

Animals↗

Behaviour of human heterochromatic regions during the synapsis of homologous chromosomes.

BACKGROUND: Alterations of synapsis can disturb or arrest meiosis and result in infertility. Synaptic abnormalities are frequently observed in infertile patients but also in fertile men. METHODS: The subtelomere-specific multiplex fluorescence in-situ hybridization (stM-FISH) has been applied in combination with immunofluorescence to identify all synaptonemal complexes (SCs) and to analyse those presenting synaptic anomalies in fertile and infertile men. RESULTS: SCs with heterochromatin blocks other than centromere (noncentromeric heterochromatin) presented a higher frequency of gaps (SC discontinuities) and splits (unsynapsed SC regions) at pachytene, the incidences for 9qh, 1qh, 15p and 21p being the highest ones. Inter-individual variability in the incidence of synaptic anomalies in these regions has been observed. In addition, synaptic anomalies in other SC regions are more frequent in infertile cases than in controls. Clear association of the SC15 and SC21 to the XY pair has been seen. CONCLUSION: Noncentromeric heterochromatic regions are the last to synapse. The inter-individual variation observed in the incidence of gaps and splits in these regions may be explained by the heteromorphism of these regions in the general population. The presence of synaptic anomalies in other SC regions may indicate nuclei with a severely affected synapsis. Noncentromeric heterochromatic regions might play a role in the association of autosomal SC15 and SC21 with the XY pair.

Centromere↗

Isolation and properties of heat-labile enterotoxin(s) from enterotoxigenic Escherichia coli.

Various techniques have been applied to the detection of skin reactivity associated with heat-labile Escherichia coli enterotoxin in fermenter-grown cultures of enterotoxigenic strains in syncase medium and in trypticase soy broth. Isolated products that were homogeneous, as determined by disc electrophoresis and sodium dodecyl sulfate gel electrophoresis, differed immunologically and in physicochemical characteristics depending on the strain and medium used, even though the products had similar specific activities in skin tests and in Chinese hamster ovary cells. In support of observations on porcine E.coli enterotoxin, and in contrast to the enterotoxin of Vibrio cholerae, the products were single polypeptide chains with molecular weights ranging from approximately 35,000 ot over 100,000 daltons. Proteolytic cleavage during culture and purification might account for some of the variations observed. The isolated products were almost 10(6)-fold less active than purified choleragen in causing morphologic alterations of Chinese hamster ovary cells, approximately 1,000-fold less active in skin tests, and at least 100-fold less active in rabbit ileal loops. In addition, only 1/100 as much active protein was produced by the strains employed as by V. cholerae. It is possible that accessory or host-derived factors are required. The most effective large-scale procedure for isolation from trypticase soy broth culture supernatants was a sequence of concentration by ultrafiltration, judicious (NH4)2SO4 precipitation, gel filtration on Sephadex G-150, and gel filtration on Agarose A5m, from which the E. coli products (like choleragen) are retarded in their elution. Toxin was isolated from an enterotoxigenic strain that caused diarrhea (total volume, 60-liters) for four days in a patient who had visited Mexico.

Animals↗

Variation in tolerance to Bacillus thuringiensis among and within populations of the spruce budworm (Lepidoptera: Tortricidae) in Ontario.

Variation in tolerance to Bacillus thuringiensis Berliner subsp. kurstaki (strain HD-1-S-1980) among and within populations of the spruce budworm, Choristoneura fumiferana (Clemens), was assessed in the laboratory. Force-feeding assays using offspring of females collected as pupae from nine locations throughout Ontario and from a laboratory colony (DCF) demonstrated limited variation in tolerance among populations. Variation among populations was comparable with the variation observed among repeated assays with different batches of larvae from the DCF colony. Population LC50s were not significantly associated with age of the outbreak, host-plant species, incidence of the microsporidian Nosema fumiferanae (Thomson), or size of the female parent. Upper limits for genetic variation in tolerance were estimated by examining variation among full-sibling families within same populations. Mortality of individual families ranged from 6.5 to 70.9% within five field populations and from 2.7 to 93.3% within two laboratory colonies in response to a dose that caused a mean mortality of 40%. Familial factors accounted for 32.8% of the phenotypic variation in response across field populations, as compared with 3% for population factors. These data suggest that the phenotypic variation in tolerance to B. thuringiensis has a substantial genetic component and may provide a basis for evolution of resistance given sufficient selection pressure.

Animals↗

Detecting adaptive trait introgression between Iris fulva and I. brevicaulis in highly selective field conditions.

The idea that natural hybridization has served as an important force in evolutionary and adaptive diversification has gained considerable momentum in recent years. By combining genome analyses with a highly selective field experiment, we provide evidence for adaptive trait introgression between two naturally hybridizing Louisiana Iris species, flood-tolerant Iris fulva and dry-adapted I. brevicaulis. We planted reciprocal backcross (BC1) hybrids along with pure-species plants into natural settings that, due to a flooding event, favored I. fulva. As expected, I. fulva plants survived at much higher rates than I. brevicaulis plants. Backcross hybrids toward I. fulva (BCIF) also survived at significantly higher rates than the reciprocal backcross toward I. brevicaulis (BCIB). Survivorship of BCIB hybrids was strongly influenced by the presence of a number of introgressed I. fulva alleles located throughout the genome, while survivorship in the reciprocal BCIF hybrids was heavily influenced by two epistatically acting QTL of opposite effects. These results demonstrate the potential for adaptive trait introgression between these two species and may help to explain patterns of genetic variation observed in naturally occurring hybrid zones.

Chimera↗

Effect of short term fasting on plasma composition of lactating rats.

The effects of a 24-h fast upon plasma and blood components of the lactating rat on day 20 after parturition have been determined. Body weight decrease observed with fasting was more marked in nursing dams than in controls. The changes observed agree with a limited use of lipidic resources, exhaustion of liver glycogen and considerable utilization of amino acids as energetic - as well as gluconeogenetic - substrates. Blood and plasma glucose were maintained in fasted dams at a level comparable with that of controls. The actual variations observed in the plasma aminogram were limited, showing a remarkable maintenance of the dam's own amino-acid homeostasis.

Amino Acids↗

Examination for tenderness: learning to use 4 kg force.

OBJECTIVE: To minimize interobserver variation in tender point examination, a training program was developed that focused on learning to deliver 4 kg force. METHODS: A 3 step process was designed to provide both measurement and feedback, serving both didactic and research functions. There were 5 repetitions within each step. During the first and 3rd steps, the subjects pressed on the footplate of a dolorimeter with no immediate feedback about the force measured. In the 2nd "training" step, they were given immediate feedback about the force delivered, and were taught to watch the amount and pattern of blanching beneath and around the thumbnail. RESULTS: Twenty-nine observers participated in 30 studies. Initial values varied from 1.78 to 8.92 kg (means within observers), although the mean value was 4.05 kg (means of all observers). The training step reduced observer variation by 65%, with reduction of mean absolute error from 1.25 to 0.44 kg. This improvement was sustained in the 3rd step, in which no feedback was given. Naïve participants performed as well as experts, and there were no detectable sex differences. One observer was retested after an interval of 8 months, and performed no better during the the initial phase of the 2nd test than in the first. Each training session required 3 to 5 minutes. CONCLUSION: Specific training efficiently reduces interobserver variations in pressure used in tender point examinations. These skills should be periodically refreshed to prevent drift into error.

Analysis of Variance↗

Enamel hypoplasia in deciduous teeth of great apes: do differences in defect prevalence imply differential levels of physiological stress?

This paper presents new data on enamel hypoplasia in the deciduous canine teeth of great apes. The enamel defect under consideration is known as localized hypoplasia of primary canines (LHPC), and is characterized by an area of thin or missing enamel on the labial surface of deciduous canine teeth (Skinner [1986a] Am. J. Phys. Anthropol. 69:59-69). Goals of this study are: 1) to determine if significant differences in the frequency of LHPC occur among three genera of great apes, and 2) to evaluate variation in LHPC prevalence among great apes as evidence of differential physiological stress. Infant and juvenile apes with deciduous teeth were examined at the Cleveland Museum of Natural History (n = 100) and at the Smithsonian Institution, National Museum of Natural History (n = 36). Deciduous teeth were observed under oblique incandescent light, with the naked eye and with a 10x hand lens. Enamel hypoplasia was scored using Federation Dentaire International (FDI)-Defects of Dental Enamel (DDE) standards. Hypoplasias were recorded by drawing defect location and size on a dental chart, and by measuring defect size and location with Helios needlepoint dial calipers. The prevalence of LHPC is reported by genus and sex, using two approaches: 1) the frequency of affected individuals-those having one or more deciduous canine teeth scored positive for LHPC; and 2) the number of canine teeth scored positive for LHPC as a percentage of all canine teeth observed. Variation in defect size and location will be described elsewhere. Localized hypoplasia of primary canine teeth was found in 62.5% of 128 individual apes, and in 45.5% of 398 great ape deciduous canines. As in humans, LHPC is the most common form of enamel hypoplasia in deciduous teeth of great apes, while LEH is rare or absent. The distribution and pattern of expression of LHPC in great apes is similar to that described in humans: side differences are not significant, but mandibular canines exhibit the defect two to five times more often than maxillary canine teeth. Differences in LHPC prevalence by sex are small and not significant. Intergeneric differences are large and non-random: chimpanzees (Pan) exhibit a significantly lower frequency of LHPC (22%, n = 50) by individual count, than either the orangutan (Pongo, 88.0%, n = 25) or the gorilla (Gorilla, 88.7%, n = 53). Tooth count prevalences exhibit a similar pattern of variation and are also statistically significant. These findings suggest that large bodied great apes (gorilla and orangutan) may be under greater physiological stress during perinatal and early postnatal development than the chimpanzee. The size, position, and timing of LHPC lesions are currently under analysis and may yield more insight into the etiological origin of this enamel defect.

Animals↗

Human hepatocyte and kidney cell metabolism of 2-acetylaminofluorene and comparison to the respective rat cells.

The metabolism and mutagenic activation of 2-acetylaminofluorene by human and rat hepatocytes and kidney cells were measured. High performance liquid chromatography was used to separate the 2-acetylaminofluorene metabolites, and a cell-mediated Salmonella typhimurium mutagenesis assay was used to detect mutagenic intermediates. Rat and human differences were observed with cells from both organs and levels of metabolism and mutagenesis were higher in human cells. Within a species, liver and kidney cell differences were also evident, with levels of hepatocyte-mediated metabolism and mutagenesis being greater than kidney cells. Human inter-individual variation was apparent with cells from both organs, but the variation observed was significantly greater in hepatocytes than kidney cells. A knowledge of such differences, including an understanding that they may vary with the chemical being studied, should be useful in the extrapolation of rodent carcinogenesis data to humans.

2-Acetylaminofluorene↗

Modelling health-related performance indices.

PRIMARY OBJECTIVE: The purpose of the present review is to critically examine the various models used to describe health-related performance indices (e.g. grip-strength, lung function, arterial blood pressure, anaerobic and aerobic power, etc.). MAIN OUTCOMES AND RESULTS: The majority of health-related performance indices are known to increase proportionally with body size and decline with age, although some, for example arterial blood pressure and cholesterol, increase with both age and excessive body weight. Historically, the confounding effects of body size and age have been controlled using multiple linear or polynomial regression models assuming a constant additive error variance. Based on maximum likelihood goodness-of-fit criterion, an alternative class of allometric models with a multiplicative error term arc shown to describe such proportional relationships more adequately in both cross-sectional and longitudinal studies. CONCLUSIONS: When modelling health-related performance indices, multiplicative, allometric models incorporate the concept of a proportional association as an integral part of its model form. Such models guarantee realistic values of health-related response variables both within and beyond the range of observations, ensuring biologically sound estimates of the response variables for subjects of all ages. After a logarithmic transformation, the models can be fitted using ordinary linear regression that will naturally help to overcome the heteroscedasticity observed in such data. However, if the logarithmic transformation fails to provide a constant error variance, an alternative approach is to model the error variance itself using log-linear regression. For longitudinal data, the use of multilevel modelling provides an alternative method of modelling error variation observed in health-related performance indices.

Adolescent↗

The evolution of trade-offs: testing predictions on response to selection and environmental variation.

The concept of phenotypic trade-offs is a central element in evolutionary theory. In general, phenotypic models assume a fixed trade-off function, whereas quantitative genetic theory predicts that the trade-off function will change as a result of selection. For a linear trade-off function selection will readily change the intercept but will have to be relatively stronger to change the slope. We test these predictions by examining the trade-off between fecundity and flight capability, as measured by dorso-longitudinal muscle mass, in four different populations of the sand cricket, Gryllus firmus. Three populations were recently derived from the wild, and the fourth had been in the laboratory for 19 years. We hypothesized that the laboratory population had most likely undergone more and different selection from the three wild populations and therefore should differ from these in respect to both slope and intercept. Because of geographic variation in selection, we predicted a general difference in intercept among the four populations. We further tested the hypothesis that this intercept will be correlated with proportion macropterous and that this relationship will itself vary with environmental conditions experienced during both the nymphal and adult period. Observed variation in the phenotypic trade-off was consistent with the predictions of the quantitative genetic model. These results point to the importance of modeling trade-offs as dynamic rather than static relationships. We discuss how phenotypic models can incorporate such variation. The phenotypic trade-off between fecundity and dorso-longitudinal muscle mass is determined in part by variation in body size, illustrating the necessity of considering trade-offs to be multi factorial rather than simply bivariate relationships.

Animals↗

A novel melanocortin 4 receptor (MC4R) gene mutation associated with morbid obesity.

Mutations in the melanocortin 4 receptor gene (MC4R) are the most common cause of monogenic human obesity. As part of our ongoing project entitled 'Turkish Obesity Genome Study' we determined the nucleotide sequence of the entire coding region of the MC4R gene in 40 morbidly obese subjects from independent families. Here we report a novel heterozygous mutation (N274S) in an adult female obese individual (age: 52 yrs, BMI 41.7 kg/m(2), height 158 cm, weight: 104 Kg). The sister of the index case (age: 55 yrs, height: 160 cm, weight: 110 Kg, BMI: 43 kg/m(2)) also carries the same mutation. Although both sisters were morbidly obese and hypertensive the index case had normal plasma insulin and fasting blood glucose levels whereas her sister had type 2 diabetes mellitus. No abnormalities of the reproductive function were present. Despite marked hyperphagia in childhood both sisters had a history of relatively diminished intensity of appetite after the age of 20. Of notice, index case was diagnosed to have cyclothymia whereas her sister was being treated for bipolar affective disorder. Detailed clinical evaluation revealed normal bone mineral density and serum calcium parameters as well as intact thyroid axis and hypothalamus-pituitary-adrenal axis in both patients. The human MC4-R deficient phenotype resembles the murine deficient state with regard to preserved reproductive function although hyperphagia, increased linear growth and absence of diabetes in mice are not observed in humans. Affected individuals have hyperphagia in childhood, which looses intensity later in life, and they also present with normal height and diabetes mellitus. Accumulating evidence indicate that melanocortin endocrine system or defective melanocortin signaling has inherently different characteristics in mice and humans resembling the variation observed with regard to leptin deficiency in both species.

Blood Glucose↗

Experimental infection of Columbian black-tailed deer with the Lyme disease spirochete.

The course of Borrelia burgdorferi-infection in Columbian black-tailed deer. (Odocoileus hemionus columbianus), its effect on the health of these animals, and their reservoir competence for fleas were evaluated experimentally. Four yearling females inoculated intramuscularly with 10(8) organisms of the CA4 strain of B. burgdorferi, and two yearling males unexposed to spirochetes, were monitored daily for 3 mo. Spirochetes were reisolated from the blood of three does at 14 or 70 days postinjection, and from several tissues of the fourth doe at necropsy. Considerable antigenic heterogeneity was observed among the reisolates as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Only two of the four infected deer developed significant antibodies (> or = 1:128) to B. burgdorferi with titers persisting for < or = 2 mo. Hematological values were highly variable and the degree of variation observed was much greater than that reported previously for Columbian black-tailed deer or other subspecies of mule deer. Infected deer did not manifest signs of Lyme disease. On histologic examination of eight tissues per deer, we observed a minimal hepatic lesion in all animals exposed to B. burgdorferi. No spirochetes were detected in 367 fleas (Pulex irritans) that had naturally infested these deer; thus this flea probably is an inefficient host of B. burgdorferi.

Animals↗