Birth weight and survival in relation to natural selection

Birth weight and perinatal mortality of 11,241 single born infants in Visakhapatnam (Andhra Pradesh, South India) are studied by fitting multiple regression techniques, with the natural log of the ratio of survivors to non-survivors. The optimal birth weight values are almost 475 g above the corresponding means. Selection intensity and selective mortality are relatively high.     

Plasma BDNF levels vary in relation to body weight in females

Brain derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of depression as well as neuropsychiatric and neurodegenerative disorders. Recent studies show a role of BDNF in energy metabolism and body weight regulation. We examined BDNF levels in plasma and cerebrospinal fluid (CSF) samples from age matched elderly depressed and control subjects. Also, the association of BDNF levels with age, gender, body weight, body mass index (BMI), and cognitive performance was evaluated. We did not find any significant differences in plasma and CSF BDNF levels between depressed and control subjects. Plasma BDNF levels were negatively correlated with age (but not with BMI and body weight), when analyses were performed including both depressed and control subjects. A significant reduction in plasma BDNF levels was observed in females as compared to male subjects, and the change in BDNF levels were significantly and positively related to body weight in females. Furthermore, significant increases in Total Recall and Delayed Recall values were found in females as compared to males. In conclusion, the lower BDNF levels observed in females suggest that changes in peripheral BDNF levels are likely secondary to an altered energy balance. However, further studies using larger sample size are warranted.     

Sexual dimorphism from birth to age 60 in relation to the type of body shape

Sexual dimorphism depends on age. It can be analysed within a population by a comparison of sex-specific body measurements based on cross-sectional samples. We analysed four length measurements, three circumferences, and one skinfold diameter of a representative cross-sectional sample of healthy German subjects aged 0 to 65 years. We here report that sexual dimorphism of these body measurements already is present in newborns. The percentages of anthropometric differences between female and male subjects behave in a specific pattern during growth age from birth up to adolescence. Girls are born smaller on an average, but they have a more accelerated growth than boys. Girls reach the peak of their adolescent growth spurt earlier in their chronological age. This means that their biological age at this time is at least 2 years older than that of boys of the same chronological age. This sex-specifically differential onset of the adolescent growth spurt, and its peak, as well as the differential decrease of growth velocity cause a dramatic change in sexual dimorphism. This change is clearly shown in this cross-sectional study. Except for the subcutaneous fat layer, there is a clear male growth advantage in all of the measurements investigated after the peak of the adolescent growth spurt. The largest differences between the measurements of both sexes in favour of the male sex are reached at young adult age. In the further course of life, the anthropometrical differences between the sexes decrease again. Sexual dimorphism within a population at a defined chronological age is therefore not only the result of a developing sex-specific physique, but also the result of a sex-specific growth velocity during the successive stages of biological development. Interestingly, we found that the sex-specific velocity of physical development, and by this the development of sexual dimorphism, proceeds differently in the tall and slim leptomorphic individuals in comparison to the smaller and more corpulent pyknomorphic individuals.     

Vitamin D status and its relation to age and body mass index

BACKGROUND/AIMS: While numerous studies have examined 25(OH)-vitamin D(3) (25-D) concentrations and their relation to parathyroid hormone (PTH) levels there is only limited information on the interrelation between 25-D, 1,25(OH)(2)-vitamin D(3) (1,25-D) and PTH. It was the aim of this study to assess the vitamin D endocrine system and its relation to age and body mass index (BMI). METHODS: This cross-sectional study comprised a convenience sample of 483 adults which attended the endocrinology outpatient service of a university hospital in the years 2002-2004. RESULTS: The mean concentrations of 25-D, 1,25-D, calcium and PTH were 21.0 +/- 10.6 ng/ml, 47.9 +/- 21.7 pg/ml, 9.48 +/- 0.48 mg/dl and 51.0 +/- 27.2 pg/ml, respectively. 25-D was related (p < 0.01) to BMI, age, PTH and 1,25-D. After correction for 25-D, we found no relation between BMI and 1,25-D. PTH was related (p < 0.01) to serum calcium, BMI, age and 1,25-D (p = 0015). There was a seasonal variation in both, 25-D and 1,25-D serum concentrations: 25-D levels were lowest in January and increased until July while the nadir and zenith of 1,25-D were found in April and October, respectively. CONCLUSION: Since BMI was negatively related to 25-D the prevalence of 25-D deficiency (<8.8 ng/ml) increased from 8.8% in subjects with BMI <30 kg/m(2) to 15.0% in subjects with BMI >30 kg/m(2). BMI, age and season should be taken into account when assessing a patients vitamin D status and more aggressive vitamin D supplementation should be considered for obese subjects.     

Contributions of body fat and effort in the 5K run: age and body weight handicap

The 5K handicap (5KH), designed to eliminate the body weight (BW) and age biases inherent in the 5K run time (RT), yields an adjusted RT (RTadj) that can be compared between runners of different BW and age. As hypothesized in a validation study, however, not all BW bias may be removed, because of the influences of body fatness (BF) and effort (run speed; essentially the inverse as measured by rating of perceived exertion (RPE)). This study's purpose was to determine the effects of BF and RPE on BW bias in the 5KH. For 99 male runners in a regional 5K race (age = 43.9 +/- 12.1 years; BW = 83.4 +/- 12.9 kg), BF was determined via sum of three skinfolds just before the race. RPE, on the 20-point Borg scale, was used to assess overall race effort on race completion. Multiple regression analysis was used to develop a new adjusted RT (NRTadj, the RTadj corrected for BF and RPE), which was computed for each runner and then correlated with BW to determine bias. Indicative of slight bias, BW was correlated with RTadj (r = 0.220, p = 0.029). Both BF (p = 0.00002) and RPE (p = 0.0005) were significant, independent predictors of RTadj. NRTadj was not significantly correlated with BW (r = 0.051, p = 0.61), but BF explained 90%, and RPE explained only 6%, of the remaining BW bias evidenced in the 5KH. The previous finding that the 5KH does not remove all BW bias is apparently accounted for by BF and not RPE. Because no handicap should be awarded for higher BF, this finding suggests that the 5KH, for men, appropriately adjusts for the age and BW vs. RT biases previously noted.     

Relationship of scrotal circumference to age, body weight and onset of spermatogenesis in goats

Scrotal circumference (SC) and body weight (BW) measurements were obtained from 122 crossbred (Saanen x Loca; Jumnapari x Local) bucks, ranging in age from 3 to 28 months. Spermatogenesis and semeniferous tubule diameters were studied from testicular biopsies in 24 bucks. The results showed that SC increased curvilinearly and was significantly correlated with age (P < 0.05). Scrotal circumference correlated more significantly with BW (P < 0.001). Spermatogenesis was completed at 6-7 months with a sudden increase in tubular diameter at the same time. Since SC is an indirect measurement of testicular size, a marked increase in testicular size indicated the onset of active spermatogenesis and, hence, the possibility of using bucks for breeding at an earlier age than normally recommended. Further, SC norms obtained in this study may become useful in the evaluation of bucks for breeding soundness.     

The oxygen affinity of mammalian hemoglobins in the absence of 2,3-diphosphoglycerate in relation to body weight

We studied the oxygenation of mammalian hemoglobins: mouse (Mus musculus molossinus), rabbit (Oryctolagus cuniculus domesticus), Japanese monkey (Macaca fuscata), man (Homo sapiens), sheep (Ovis aries), llama (Lama glama), pig (Sus scrofa domesticus), cow (Bos taurus domesticus) and horse (Equus caballus), in the absence of 2,3-diphosphoglycerate (DPG) and compared their oxygen affinity in relation to the body weight. The negative correlation between body weight and the oxygen affinity of the whole blood, observed by Schmidt-Nielsen and Larimer (1958), was not observed in the absence of DPG. Our results indicated that an adaptive evolution proposed for hemoglobin in terms of its oxygen affinity vs body weight of the animal can only be appreciated with DPG.     

Prolactin-induced gain in body weight in relation to caloric intake and energy expenditure in spotted munia

Prolactin, which induced significant gain in body weight and in the weight of the cervical and abdominal fat deposits had no effect on daily total food intake in spotted munia. The hormone changed the feeding pattern from a modal type to almost continuous feeding, increased whole body oxygen consumption of the birds, and had no effect on total hopping index. Prolactin-induced fattening, therefore seems due to neither an increased caloric intake, nor a decreased metabolic expenditure, but probably reflects better utilization of food.