Adaptive sex ratio variation in pre-industrial human (Homo sapiens) populations?

Sex allocation theory predicts that in a population with a biased operational sex ratio (OSR), parents will increase their fitness by adjusting the sex ratio of their progeny towards the rarer sex, until OSR has reached a level where the overproduction of either sex no longer increases a parent's probability of having grandchildren. Furthermore, in a monogamous mating system, a biased OSR is expected to lead to lowered mean fecundity among individuals of the more abundant sex. We studied the influence of OSR on the sex ratio of newborns and on the population birth rate using an extensive data set (n = 14,420 births) from pre-industrial (1775-1850) Finland. The overall effect of current OSR on sex ratio at birth was significant, and in the majority of the 21 parishes included in this study, more sons were produced when males were rarer than females. This suggests that humans adjusted the sex ratio of their offspring in response to the local OSR to maximize the reproductive success of their progeny. Birth rate and, presumably, also population growth rate increased when the sex ratio (males:females) among reproductive age classes approached equality. However, the strength of these patterns varied across the parishes, suggesting that factors other than OSR (e.g. socioeconomic or environmental factors may also have influenced the sex ratio at birth and the birth rate.     

Genetic variation among Trypanosoma cruzi populations

Four experiments examined the effect of naloxone pretreatment on the expression and extinction of ethanol-induced conditioned place preference (experiments 1, 2, 4) or conditioned place aversion (experiments 1, 3). DBA/2 J mice received four pairings of a distinctive tactile (floor) stimulus (CS) with injection of ethanol (2 g/kg) given either immediately before or after 5-min exposure to the CS. A different stimulus was paired with injection of saline. Pre-CS injection of ethanol produced conditioned place preference, whereas post-CS injection of ethanol produced conditioned place aversion. Both behaviors extinguished partially during repeated choice testing after vehicle injection. Naloxone (10 mg/kg) had little effect on the initial expression of conditioned place preference, but facilitated its extinction. Moreover, repeated naloxone testing resulted in the expression of a weak conditioned place aversion to the CS that initially elicited a place preference. In contrast, naloxone (1.5 or 10 mg/kg) enhanced expression of conditioned place aversion, thereby increasing its resistance to extinction. A control experiment (experiment 4) indicated that repeated testing with a different aversive drug, lithium chloride, did not affect rate of extinction or produce an aversion to the CS previously paired with ethanol. These findings do not support the suggestion that naloxone facilitates the general processes that underlie extinction of associative learning. Also, these data are not readily explained by the conditioning of place aversion at the time of testing. Rather, naloxone's effects appear to reflect a selective influence on maintenance of ethanol's conditioned rewarding effect, an effect that may be mediated by release of endogenous opioids. Overall, these findings encourage further consideration of the use of opiate antagonists in the treatment of alcoholism.     

Isozyme variation within and among populations of Microsporum species

Isozyme variation among 54 isolates of Microsporum canis, 18 Microsporum cookei isolates and two Diheterospora isolates were studied using starch gel electrophoresis. Of eight enzymes examined, four were polymorphic (EST, G6P, MDH and PEP), having from two to four electrophoretic forms. Within each species, consistent and reproducible isozyme patterns of the eight enzyme systems were obtained. Phenotypic diversity (H) in M. canis was higher than in M. cookei (H = 0.459 and H = 0.408 respectively), but phenotypic differentiation of M. canis isolates from different geographical regions (Auckland, Wellington and Palmerston North, New Zealand) was low, with a proportion of total diversity (Gst) of 0.151 found among the localities. The results suggest that the isolates of M. canis from different geographical regions are closely related, supporting the theory of a common lineage.     

Seasonal variation in human fecundability

Seasonality of effective fecundability was investigated in a cohort of 402 women born in or near Rotterdam, The Netherlands, between 1873 and 1887, and married before the age of 40 years. Applying a newly developed method allowing simultaneous control for inherent couple fecundability, numbers at risk of pregnancy, and multiple confounders, we found a trend towards higher fecundability during the first half of June and the first half of December (P = 0.06). Seasonality of effective fecundability appeared to be strongest for women who married at <20 years of age. Potentially important implications for the study of seasonality of adverse reproductive outcome are discussed.     

Different patterns of variation at the X- and Y-chromosome-linked microsatellite loci DXYS156X and DXYS156Y in human populations

We compared the global pattern of variation at two homologous microsatellites mapping to the long arm of the X chromosome (DXYS156X) and to the short arm of the Y chromosome (DXYS156Y) in humans. A single pair of oligonucleotide primers amplifies these two nonallelic loci, each of which contains polymorphism in the number of pentanucleotide units. We observed 11 alleles in a sample of 2290 X chromosomes and 2006 Y chromosomes from 50 populations representing 6 major geographic regions. The overlapping size range of the X- and Y-chromosome alleles indicated a more complex distribution of alleles at these two loci than previously reported. Contrasting patterns of X-chromosome-linked and Y-chromosome-linked variation were reflected in statistically significant differences in genetic diversity values among geographic regions and between X and Y chromosomes. Higher levels of diversity characterized the DXYS156X locus in Africa (0.799 +/- 0.004) and the DXYS156Y locus in East Asia (0.700 +/- 0.006) compared with populations from other regions. These different patterns of variation can be explained by a combination of processes at both the molecular and population levels, including variable mutation rates, different effective population sizes, and genetic drift.     

mtDNA variation in caste populations of Andhra Pradesh, India

The aim of the study was to determine the association between PRL responses to suckling and maintenance of postpartum amenorrhea among breastfeeding mothers. Three blood spot samples (5, 30, and 50 min following a timed nursing bout) were collected from 71 intensively breastfeeding Nepali women for PRL determination. Maternal age, BMI (weight/height2), menstrual status, caste, infant age, nursing bout length, and duration of supplementation were recorded at time of sample collection. Independent and paired t tests, linear regression analyses, and general linear models were used to evaluate differences between cycling (n = 36) and amenorrheic (n = 35) women and associations among variables. Logistic regression analyses were used to relate PRL measures to the odds of maintaining lactational amenorrhea. Amenorrheic breastfeeding mothers had higher (P < .001) PRL levels at all 3 collection times than cycling breastfeeding mothers, and PRL levels declined with time since birth (P < 0.05). The odds (OR) of having ceased lactational amenorrhea was significantly higher (OR = 5.0, 95% Cl = 1.3-19.9) among mothers with lower PRL levels (< or = 10 ng/mL) at 50 min post-sucking, and PRL at 50 min showed a significant dose response relationship with menstrual status. The association between 50 min PRL levels and lactational amenorrhea appears to be independent of time postpartum, maternal age, BMI, nursing bout length, and duration of supplementation. Among intensively nursing women, maintenance of elevated PRL levels across the interbout interval increases the odds of maintaining lactational amenorrhea.     

Genetic variation and phylogenetic relationships among six populations of corn borers in China

The genetic variation among and within six populations of the corn borer was determined by using random amplified polymorphic DNA (RAPD) markers. Extensive genetic variability was detected. Of the 802 RAPD markers obtained, 781 (97.4%) were polymorphic among populations. Genetic similarities and distances between each pair of individuals were calculated. UPGMA cluster analysis showed that the YN population (Ostrinia nubilalis Hübner) and the other five populations (Ostrinia furnacalis Guenée) made up branches of the corn borer lineage, instead of deviating; there was no significant genetic differentiation between YN and the other five corn borer populations.     

Associations between polymorphic variety and anthropometric and biochemical variation in two New Guinea populations

During International Biological Programme studies in Papua New Guinea, on Karkar Island and at Lufa in the Eastern Highlands, information on anthropometric, biochemical and genetic characteristics was collected from the same individuals. Use has been made of this special situation to investigate whether any associations exist between genetic markers and anthropometric and biochemical variation. Those found, and which satisfy criteria established to help in distinguishing real from chance associations, include: P with haemoglobin concentration and serum albumin and cholesterol levels; acid phosphatase with serum albumin level and haemoglobin concentration; anhaptoglobinaemia and serum globulin level; haemoglobin J-Tongariki with serum phosphorus level. The associations are discussed in terms of their arising from the direct result of environmental factors modifying gene expression, chance concordance of environmental and genetic variation, or pleiotropy.     

Polymorphic admixture typing in human ethnic populations

A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (delta). The distribution of frequency differences (delta values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high delta values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066-.098), and < 10% of the measured overall molecular genetic diversity in these human samples can be attributed to "racial" differentiation. The median delta values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies.     

Skeletal progenitor cells and ageing human populations

PURPOSE: To investigate (1) the radiosensitivity of B versus T lymphocytes with respect to micronucleus (MN) induction and (2) the possible application of the B cell MN assay for biological dosimetry of individuals after acute exposure to low doses of ionizing radiation. MATERIALS AND METHODS: MN analysis was performed in T and B lymphocytes of six healthy volunteers exposed in vitro to gamma-ray doses ranging from 0.05 Gy to 1 Gy. For the MN assay on B cells, peripheral blood mononuclear cells were cultured and stimulated with pokeweed mitogen (PWM). Afterwards the B lymphocytes (characterized by the CD20+ phenotype) were separated with the FACSort flow cytometer and the number of MN in the sorted binucleate cells was scored. For T lymphocytes the standard MN protocol was applied. RESULTS: The number of spontaneous and radiation induced MN were significantly higher in B lymphocytes compared to T lymphocytes in the low dose range up to 1 Gy. An analysis of the present data showed that when the spontaneous MN frequencies are not known, doses from 0.08 Gy could be detected with the B cell MN assay while the conventional MN assay only allowed detection of doses > 0.25 Gy. However, in contradiction to the linear-quadratic dose-response for T cells, for B cells the initial steep increase of the MN yield with the very low dose was followed by a flattening of the curve towards higher doses. CONCLUSION: This study shows that B lymphocytes express a high number of MN for doses up to 1 Gy gamma-rays reflecting the highly radiosensitive behaviour of B cells. The results also point to the possible application of the B-cell MN assay for individual dose assessment. When blood samples can be taken within 24 h after acute accidental overexposure, the B-cell MN assay can be performed but only as a supplementary test to the conventional MN assay.     

Nocturnal variation in human sympathetic baroreflex sensitivity

INTRODUCTION: The differential diagnosis of malignancy in small foci of microcalcifications or in extremely small nodes can be difficult. We carried out a retrospective analysis of integrated mammographic and US results, correlated with histologic data, to assess the limitations of each method and to optimize and benign/malignant ratio. MATERIALS AND METHODS: Our series consisted of 485 nonpalpable breast lesions submitted to histologic examination after vegetable charcoal marking. We gave each lesion an 0-5 score according to the degree of diagnostic doubt/suspicion after mammography and US, which results were correlated with histologic data to assess the carcinoma frequency in the various groups identified. RESULTS: The analysis of mammographic and US images showed that the most frequent mammographic alteration in the lesions submitted to biopsy was an isolated cluster of microcalcifications (40.99%): of these, 36.86% were neoplastic. The nodules submitted to biopsy, which were 29.81% of the total, showed a cancer rate (36.80%) very similar to that of the microcalcifications. The carcinoma rate rose to 37.93% when the microcalcifications were associated with nodes. The highest carcinoma rates, i.e., 52.94% and 66.66%, respectively, were found in parenchymal distortions, either isolated or associated with microcalcifications, which however were only 7.03% and 3.10%, respectively, of the total number of cases. DISCUSSION AND CONCLUSIONS: Our study showed that: 1) a highly suspicious US result must be seriously considered when a negative mammography has poor intrinsic contrast; 2) a highly suspicious US image with a little suspicious good contrast mammography requires further confirmation before surgery is planned; 3) when the mammographic finding is mid-to-highly suspicious, further investigations are needed even if US is negative. To conclude, even though the histologic examination of nonpalpable breast lesions involves performing a biopsy, we believe this is acceptable when performed on an outpatient basis, under local anesthesia and removing a limited amount of tissue only. The benign/malignant ratio ranges 2 to 1.5: if it is further reduced (below 1.5), there will be the risk of missing some early neoplastic lesions.     

Methionine activating enzyme in various human platelet populations

Human platelets have been separated into four populations by a discontinuous sucrose gradient. MAE activity has been determined in the various platelet populations and significant differences were obtained with respect to platelet size, the large-heavy platelets showing a higher enzymatic activity than the small-light ones. These data suggest that higher MAE activity in the younger and large-heavy platelets may be responsible for a much higher biochemical and functional efficiency.     

Mononuclear phagocyte populations in the transplanted human lung

BACKGROUND: Dendritic cells (DC) are essential for the development of alloreactivity, however, little has been published regarding the distribution and phenotype of these and related mononuclear cells in human lung transplantation. METHODS: Lung frozen sections were examined for the presence of CD1a+ DC and for mononuclear cells and alveolar macrophages expressing CD11b and CD68. The effects of transplantation and immunosuppression were assessed by comparison of normal transplant transbronchial biopsy specimens to specimens from unused donor lungs; the normal transbronchial biopsy specimens also were compared with those showing rejection or obliterative bronchiolitis. RESULTS: All biopsy specimens, including those with obliterative bronchiolitis, showed a marked depletion of CD1a+ DC in lung allografts. This has not been described previously. In addition, transplantation and immunosuppression reduced alveolar macrophage coexpression of CD68 and CD11b, and this was reversed in acute rejection. CONCLUSION: The roles of pulmonary DC and other mononuclear phagocyte subpopulations need to be further defined, and data from animal models of lung transplantation should be interpreted with caution.     

Genetic composition of Chilean aboriginal populations: HLA and other genetic marker variation

The sensitivity of spores B. subtilis and B. stearothermophilus to steam under pressure depended on the growth medium and duration of cultivation. B. subtilis and B. stearothermophilus produced the largest number of spores on medium with Mn and yeast extract. However the spores grown on the medium were not the most resistant. The resistant spores was growing up with the age of cultures. The highest level of resistance was obtained in the case of the medium with Ca, after 7-10 days of cultivation. The sporicidal effect of steam under pressure depended on the number of spores on the test.     

Physiological role of human placental growth hormone

Described herein are the fragmentation pathways of kanamycin A and its 6'-N- and 1-N-acyl derivatives, as well as the determination of their positional isomers by FABMS and ESIMS in combination with tandem mass spectrometry. The presence or absence of key ions and the difference in abundance of common ions are correlated with the position of the substitution.     

Sexual selection by male choice in monogamous and polygynous human populations

The theoretical possibility of coevolution of a viability-reducing female physical trait and a male mating preference for that trait by Fisherian sexual selection in monogamous and polygynous populations is demonstrated using two-locus haploid models. It is assumed that there is dichotomous variation in male resources, resource-rich males have a wider choice among females than resource-poor males, and a female has greater reproductive success when mated with a resource-rich male than a resource-poor one. Under these assumptions, we find that sexual selection operates effectively when female reproductive success is strongly dependent on male resource, the proportion of females that mate with resource-rich males is neither small nor large, the degree of polygyny is low, and resources are inherited from father to son. We suggest that some human female physical traits may have evolved by sexual selection through male choice. The evolution of skin color by sexual selection is discussed as an example.     

Seasonal variation in urocanic acid isomers in human skin

Dual-energy X-ray absorptiometry (DXA), using a narrow pencil-shaped X-ray beam coupled to a single detector, has been used extensively. More recently, DXA using a fan- shaped X-ray beam coupled to an array of detectors has been introduced. This new generation of scanners causes an inherent magnification of scanned structures as the distance from the X-ray source decreases. This magnification, which occurs in the medial-lateral direction but not in the craniocaudal direction, does not affect bone mineral density (BMD). There are, however, significant changes of bone mineral content (BMC), bone area, and parameters of hip geometry, with varying distance of the bone scanned from the X-ray source. Variability of soft tissue thickness in vivo, by altering the distance of the skeleton from the scanning table and X-ray source, may cause clinically significant errors of BMC, bone area, and proximal femur geometry when measured using fan-beam densitometers. We analyzed the geometry of Lunar and Hologic fan beam scanners to derive equations expressing the true width of scanned structures in terms of the apparent width and machine dimensions. We also showed mathematic ally that performing an additional scan, at a different distance from the X-ray source than the first scan, provides simultaneous equations that can be solved to derive the real width of a scanned bone. This hypothesis was tested on the Lunar Expert using aluminium phantoms scanned at different table heights. There was an excellent correlation, r = 0.99 (p < 0.001), between the predicted phantom width and the measured phantom width. In conclusion, this study shows that the magnification error of fan beam DXA can be corrected using a dual scanning technique. This has important implications in the clinical usefulness of BMC and geometrical measurements obtained from these scanners.     

Behavior genetic differences within and between defined human populations

The small populations of the Caucasus offer a unique opportunity to consider concepts, such as heritability, which are often considered properties of a trait but which are really properties of a population. A comprehensive strategy is outlined for studying intra- and interpopulation genetic structure across a wide range of traits and environments. A three-way association is demonstrated between 12 of 16 psychophysiological traits, attitude, and the t allele for PTC sensitivity. Differences between populations and traits are evaluated in theoretical terms for morphological, physiological, and psychological measures. While decreases in performance with inbreeding are often predicted, in these small, isolated populations the effects are minimal.     

Gene-enzyme alcohol dehydrogenase system and adaptability in Drosophila melanogaster

As follows from the experiments on the genotypic related populations of Drosophila melanogaster with different frequency of ADH allozymes selection for postponement of ageing and resistance to hypothermia lead to saturation of population with S-allozyme ADH, and genotypic adaptation to ethanol-to increasing of frequency of F-allozyme. It is supposed that genotypic adaptation is realized by selection of specimens with the most favourable alleles of genes. At the same time ontogenetic adaptation is accompanied by biochemical modification of existing allozymes.