Nutritional influence on childhood development and genetic control of adolescent growth of Quechuas and Mestizos from the Peruvian Lowlands

The growth in height of 1,202 Quechua and Mestizo children aged 6 to 19 years of the province of Lamas in the Peruvian Eastern Lowlands was studied. As shown by evaluations of ABO, Rh systems, and skin reflectance measurements, the Quechuas are genetically different from the Mestizos. The heights of Quechuas and Mestizos were matched for nutritional status based on measurements of subcutaneous fat and body muscle. The study indicates that: (1) during childhood, Quechuas and Mestizos matched for the same nutritional status attain similar heights; (2) during adolescence (or after the age of 11 years), the Mestizos are significantly taller than the Quechuas of the same nutritional status; 3) during childhood, the relative difference in height between Quechuas and Mestizos matched for the same nutritional status is less than the difference between Quechuas (or Mestizos) of the same genetic composition characterized by good and poor nutritional status. These findings suggest that the influence of environmental factors, such as nutrition, have a greater influence in producing differences in body size during childhood than during adolescence. Conversely, the present findings support the hypothesis that the influence of genetic factors on body size are greater during adolescence than during childhood. However, comparison of adolescent samples of similar genetic composition (whether they be Quechuas or Mestizos), characterized by good and poor nutritional status, reveal large differences in height, suggesting that under conditions of malnutrition, the genetic control of growth is diminished.     

Statistical properties of the variation at linked microsatellite loci: implications for the history of human Y chromosomes [published erratum appears in Mol Biol Evol 1997 Mar;14(3):354]

It has recently been suggested that observed levels of variation at microsatellite loci can be used to infer patterns of selection in genomes and to assess demographic history. In order to evaluate the feasibility of these suggestions it is necessary to know something about how levels of variation at microsatellite loci are expected to fluctuate due simply to stochasticity in the processes of mutation and inheritance (genetic sampling). Here we use recently derived properties of the stepwise mutation model to place confidence intervals around the variance in repeat score that is expected at mutation-drift equilibrium and outline a statistical test for whether an observed value differs significantly from expectation. We also develop confidence intervals for the time course of the buildup of variation following a complete elimination of variation, such as might be caused by a selective sweep or an extreme population bottleneck. We apply these methods to the variation observed at human Y-specific microsatellites. Although a number of authors have suggested the possibility of a very recent sweep, our analyses suggest that a sweep or extreme bottleneck is unlikely to have occurred anytime during the last approximately 74,000 years. To generate this result we use a recently estimated mutation rate for microsatellite loci of 5.6 x 10(-4) along with the variation observed at autosomal microsatellite loci to estimate the human effective population size. This estimate is 18,000, implying an effective number of 4,500 Y chromosomes. One important general conclusion to emerge from this study is that in order to reject mutation-drift equilibrium at a set of linked microsatellite loci it is necessary to have an unreasonably large number of loci unless the observed variance is far below that expected at mutation-drift equilibrium.      

Relationship of skinfolds and muscle size to growth of children. I. Costa Rica

The relationships between triceps skinfolds and stature and between upper arm muscle size and stature were studied on 874 pairs matched for age derived from a cross-sectional sample of 2,445 Costa Rican rural subjects, aged 0 to 20 years. The results indicate that fatter children for their age, on the average, are not taller than their leaner counterparts. On the other hand, more muscular children, on the average, are taller than their less muscular counterparts of the same age.     

A-B-O and Rh affinities between highland and lowland Quechua-speaking Peruvian populations

According to the accounts of the Spanish chronicles and various historical analyses the Quechua-speaking population inhabiting the Province of Lamas in the Eastern Tropical Lowlands of Peru are descendants of the Chanca Tribes that migrated from the highlands about 500 years ago. The results of the present study indicate that in terms of the A-B-O and Rh systems the lowland Quechua-speaking population from the Province of Lamas and the highland Quechua population from the Province of Junin are more similar to each other than to other tropical tribes. Therefore, it is quite possible that the present lowland Quechua-speaking population from the Province of Lamas may be descendants of Andean populations.     

Effects of carbon dioxide exposure on early brain development in rats

The developing brain is vulnerable to environmental factors. We investigated the effects of air that contained 0.05, 0.1 and 0.3% CO₂ on the hippocampus, prefrontal cortex (PFC) and amygdala. We focused on the circuitry involved in the neurobiology of anxiety, spatial learning, memory, and on insulin-like growth factor-1 (IGF-1), which is known to play a role in early brain development in rats. Spatial learning and memory were impaired by exposure to 0.3% CO₂ air, while exposure to 0.1 and 0.3% CO₂ air elevated blood corticosterone levels, intensified anxiety behavior, increased superoxide dismutase (SOD) enzyme activity and MDA levels in hippocampus and PFC; glutathione peroxidase (GPx) enzyme activity decreased in the PFC with no associated change in the hippocampus. IGF-1 levels were decreased in the blood, PFC and hippocampus by exposure to both 0.1 and 0.3% CO₂. In addition, apoptosis was increased, while cell numbers were decreased in the CA1 regions of hippocampus and PFC after 0.3% CO₂ air exposure in adolescent rats. A positive correlation was found between the blood IGF-1 level and apoptosis in the PFC. We found that chronic exposure to 0.3% CO₂ air decreased IGF-1 levels in the serum, hippocampus and PFC, and increased oxidative stress. These findings were associated with increased anxiety behavior, and impaired memory and learning.     

A new technique for staining mast cells using ferroin

We describe here a new method for specific staining of mast cells using ferroin. Different hamster tissues were fixed in 4% formalin and processed for paraffin embedding. Sections were stained with hematoxylin followed by ferroin acidified with 2.5 N sulfuric acid to pH 4.0. Mast cells stained an intense orange color that contrasted markedly with bluish violet nuclei. High contrast was also observed when ferroin colored sections were counterstained with light green instead of hematoxylin. To evaluate the specificity of the stain, hamster cheek pouch sections were stained with toluidine blue, alcian blue-safranin O, and ferroin. Quantitative evaluation of mast cells stained with the three techniques showed no statistical difference. The simplicity and selectivity of this method is sufficient for image analysis of mast cells.     

Fungal virulence studies come of age

Sophisticated molecular biological research has revealed many virulence attributes in at least four pathogenic fungi, but the future study of fungal virulence requires investigators to distinguish between molecules that directly interact with the host, molecules that regulate these, and molecules that are always required for fungal growth and survival, independent of the host.     

The effect of estrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women

This study assessed the influence of estrogen (E₂) on muscle damage biomarkers [skeletal muscle - creatine kinase (CK); cardiac muscle - CK-MB] responses to prolonged aerobic exercise. Eumenorrheic women (n=10) who were physically active completed two 60-minute treadmill running sessions at ∼60-65% maximal intensity during low E₂ (midfollicular menstrual phase) and high E₂ (midluteal menstrual phase) hormonal conditions. Blood samples were collected prior to exercise (following supine rest), immediately post-, 30 min post-, and 24 hours post-exercise to determine changes in muscle biomarkers. Resting blood samples confirmed appropriate E₂ hormonal levels Total CK concentrations increased following exercise and at 24 hours post-exercise were higher in the midfollicular low E₂ phase (p<0.001). However, CK-MB concentrations were unaffected by E₂ level or exercise (p=0.442) resulting in the ratio of CK-MB to total CK being consistently low in subject responses (i.e., indicative of skeletal muscle damage). Elevated E₂ levels reduce the CK responses of skeletal muscle, but had no effect on CK-MB responses following prolonged aerobic exercise. These findings support earlier work showing elevated E₂ is protective of skeletal muscle from exercise-induced damage associated with prolonged aerobic exercise.