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We report the rational engineering of a remarkably stable yellow fluorescent protein (YFP), ‘hyperfolder YFP’ (hfYFP), that withstands chaotropic conditions that denature most biological structures within seconds, including superfolder green fluorescent protein (GFP). hfYFP contains no cysteines, is chloride insensitive and tolerates aldehyde and osmium tetroxide fixation better than common fluorescent proteins, enabling its use in expansion and electron microscopies. We solved crystal structures of hfYFP (to 1.7-Å resolution), a monomeric variant, monomeric hyperfolder YFP (1.6 Å) and an mGreenLantern mutant (1.2 Å), and then rationally engineered highly stable 405-nm-excitable GFPs, large Stokes shift (LSS) monomeric GFP (LSSmGFP) and LSSA12 from these structures. Lastly, we directly exploited the chemical stability of hfYFP and LSSmGFP by devising a fluorescence-assisted protein purification strategy enabling all steps of denaturing affinity chromatography to be visualized using ultraviolet or blue light. hfYFP and LSSmGFP represent a new generation of robustly stable fluorescent proteins developed for advanced biotechnological applications.

Mitochondria are a major target for aging and are instrumental in the age-dependent deterioration of the human brain, but studying mitochondria in aging human neurons has been challenging. Direct fibroblast-to-induced neuron (iN) conversion yields functional neurons that retain important signs of aging, in contrast to iPSC differentiation. Here, we analyzed mitochondrial features in iNs from individuals of different ages. iNs from old donors display decreased oxidative phosphorylation (OXPHOS)-related gene expression, impaired axonal mitochondrial morphologies, lower mitochondrial membrane potentials, reduced energy production, and increased oxidized proteins levels. In contrast, the fibroblasts from which iNs were generated show only mild age-dependent changes, consistent with a metabolic shift from glycolysis-dependent fibroblasts to OXPHOS-dependent iNs. Indeed, OXPHOS-induced old fibroblasts show increased mitochondrial aging features similar to iNs. Our data indicate that iNs are a valuable tool for studying mitochondrial aging and support a bioenergetic explanation for the high susceptibility of the brain to aging.

To determine the role of cortisol in modulating the effects of energetics on muscle mass in a subsistence society, measures of cortisol and body composition were obtained from a sample of Turkana men. Subjects were 63 settled and 69 nomadic men, ages 24 and older. Urinary cortisol was determined along with measures of muscle mass. Cortisol/creatinine ratio was higher among nomadic men (57.8 ± 56.8 vs. 34.5 ± 44.6; P< 0.001). Controlled for age, urinary cortisol was inversely related to arm muscle plus bone area (MPBA) among the nomadic (β = −0.28; P= 0.04), but not the settled (β = −0.04; P= 0.78) sample. Urinary cortisol was not related to any other measures of body composition. These results suggest that even in chronically undernourished populations, cortisol may be elevated primarily under conditions of acute nutritional stress. However, the catabolic effects of cortisol on muscle in our results may be confounded by other energetic factors, including energy availability. Am. J. Hum. Biol. 17:489–495, 2005.© 2005 Wiley‐Liss, Inc.

To examine age‐related changes in body composition and testosterone (T) among men in an urban sub‐Saharan African population, measures of body composition and salivary T were obtained from 109 males ages 20–78 in Harare, Zimbabwe. Measures included height, weight, suprailiac and triceps skinfold, and percent body fat by bioelectric impedance (BIA). Saliva samples were assayed for T using radioimmunoassay. Average BMI of the overall sample (23.16 (SD = 18.12) kg/m2was close to Western populations, while salivary T levels (AM = 196 ± 96 pmol/l; pm= 172 ± 98 pmol/l) were much lower. Both morning (beta = –0.535; P< 0.001) and afternoon salivary T declined with age (beta = −0.385; P< 0.001). Multiple regression models indicate that pmsalivary T (beta = 0.24; P= 0.025), was a predictor of fat‐free mass, but neither amnor pmsalivary T was related to fat mass or other measures of body composition. In addition, height was significantly related to pmsalivary T levels in men under the age of 60. Multivariate regression indicates that pmsalivary T is a predictor of fat‐free mass when controlled for height and adiposity. These findings suggest that T is related to both lean mass and overall body size among men from a non‐Western nonsubsistence population. As such they are consistent with the hypothesis that bioavailable T plays a role in energetic allocation among human males. Am. J. Hum. Biol. 16:704–712, 2004. © 2004 Wiley‐Liss, Inc.

To compare the timing of reproductive maturation among urban and rural Tonga girls in Zambia, anthropometric measures and Tanner stages of breast development were obtained. Subjects were 774 (282 rural, 492 urban) girls ages 6–18. Results indicate that rural girls are shorter and have smaller triceps and subscapular skinfolds than their urban counterparts. Median age at menarche for the entire sample, as estimated by probit analysis, was 14.8 years (95% CL = 14.34–15.40). Onset of breast development among urban girls was significantly younger than for the rural girls: 11.47 (95% CL 11.22–11.71) years vs. 13.15 (95% CL 12.40–14.15) years. In contrast, the two groups did not differ in timing of pubertal completion as assessed by median age for Tanner Breast Stage 5: 17.01 (95% CL 16.30–18.33) vs. 16.96 (95% CL 16.37–17.56) years. Predictors of pubertal onset, based on multivariate logistic regression, included dental maturation, height, and triceps skinfold. Triceps skinfold was the only significant predictor of pubertal completion. These results suggest that rural girls progress through puberty more rapidly than the urban girls despite their later start. This finding of maturational catch‐up contrasts with earlier urban/rural comparisons of girls as well as previous results among Gwembe boys, for which later pubertal onset is associated with longer duration of pubertal maturation. While the mechanism remains unclear, biocultural explanations suggest preferential feeding during adolescence as a source for rural girl's maturational catch‐up. Am. J. Hum. Biol. 16:658–669, 2004. © 2004 Wiley‐Liss, Inc.

This article examines the health complaints of settled and nomadic Ngisonyoka Turkana of northwest Kenya. Samples of 152 nomadic and 124 settled men, aged 14 and over, were surveyed about their health status. The general pattern of disease reported concurs with previous studies of health among Turkana; that is, the primary complaints are respiratory tract infections and eye infections. The settled Turkana reported more severe complaints and higher rates of infectious disease than the nomads, including a significantly higher frequency of cold with cough, eye infection, and chest infection. Although the settled males as a group had slightly higher body mass index and other measures of body fat than the nomadic group, none of these indicators of body composition were predictive of health complaints. Observed differences in health patterns are possibly related to differences in dietary composition, exposure to pathogens associated with population density and environmental pollution, physical activity patterns, and psychosocial stress, [sedentarization, epidemiologic transition, nutrition and health, Turkana, pastoralists]

A measurable decrease in intraocular pressure is noted after orbital floor fracture repair, likely due to intraoperative manipulation of the globe.

Age-related declines in free and bioavailable testosterone are frequently reported for Western populations, but interpopulation variation in this pattern has not previously been investigated.

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