Serum testosterone levels and excessive erythrocytosis during the process of adaptation to high altitudes

Populations living at high altitudes （HAs）, particularly in the Peruvian Andes, are characterized by a mixture of subjects with erythrocytosis （16 g dl-1〈haemoglobin （Hb）≤21 gdl-1） and others with excessive erythrocytosis （EE） （Hb〉21 g dl-1）. Elevated haemoglobin values （EE） are associated with chronic mountain sickness, a condition reflecting the lack of adaptation to HA. According to current data, native men from regions of HA are not adequately adapted to live at such altitudes if they have elevated serum testosterone levels. This seems to be due to an increased conversion of dehydroepiandrosterone sulphate （DH EAS） to testosterone. Men with erythrocytosis at HAs show higher serum androstenedione levels and a lower testosterone/androstenedione ratio than men with EE, suggesting reduced 17beta-hydroxysteroid dehydrogenase （17beta-HSD） activity. Lower 17beta-HSD activity via A4-steroid production in men with erythrocytosis at HA may protect against elevated serum testosterone levels, thus preventing EE. The higher conversion of DHEAS to testosterone in subjects with EE indicates increased 17beta-HSD activity via the A5-pathway. Currently, there are various situations in which people live （human biodiversity） with low or high haemoglobin levels at HA. Antiquity could be an important adaptation component for life at HA, and testosterone seems to participate in this process.

Effect of alcoholic extract of Lepidium meyenii (Maca) on testicular function in male rats

<abstract>Aim: To evaluate the effect of the alcoholic extract of Lepidium meyenii (Maca) on the spermatogenesis in male rats. Methods: In Holtzman rats, Maca alcoholic extract (5%) was given by oral route at doses of 48 mg/day or 96 mg/day for 7 days, 14 days and 21 days. Testicular function was assessed by measurements of lengths of different stages of seminiferous epithelia and by epididymal sperm count. Results: Ethanolic extract of Maca increased the length of stages IX-XI of seminiferous epithelium at treatment day 7, day 14 and day 21. Progression of spermatogenesis was evident only after day 21 when lengths of stages XII-XIV of seminiferous epithelium were increased; at day 7 and day 14, no important change in spermatogenesis was observed. Epididymal sperm count was increased with 48 mg/day at all times. With 96 mg/day an increase in sperm count was observed at day 7, but it was reduced at day 14 and day 21 of treatment. Serum testosterone levels were not affected. Conclusion: The alcoholic extract of Maca activates onset ant progression of spermatogenesis at 48 mg/day or 96 mg/day in rats.

Cycloheximide prevents production of arresting,a fraction of 30-50 kDa obtained from seminiferous tubule conditioned medium

Aim: To evaluate the effect of a protein synthesis inhibitor cycloheximide on arresting activity in spermato-genesis and sperm count in male rats. Methods: The study used seminiferous tubule (ST) segments from adult rats cultured in vitro with or without cycloheximide to condition culture media, which have been concentrated, size fractioned (30-50 kDa) and administered 7 days to adult rats by intraperitoneal injections. The effects on testicular and epididymal weights, spermatogenesis and epididymal sperm count were determined. Results: The fraction (30-50 kDa), named arresting, obtained from the culture without cycloheximide decreased testicular and epididymal weights (P<0.01) and reduced the epididymal sperm count significantly. Study of the spermatogenic cycle by transillumination showed spermatogenic arrest at stage VII in rats treated with arresting compared to that observed in controls. The length of stage VII in the group receiving the seminiferous tubules culture media with cycloheximide (30-50 KDa CHX-STCM fraction) was similar to control. Conclusion: The difference in the effect may be the result of the presence or absence of arresting, a protein secreted by the tubules.

秘鲁高海拔地区的新生儿体重

Objective:To determine whether birth weights are lower at high altitudes,and whether gestational age at birth and a population’s length of residence mitigate the effect of high altitude. Methods:The birth weights of 84,173 neonates recorded in the Peruvian Perinatal Information SystemDatabase were analyzed between 1995 and 2002 for the cities of Lima (150 m),Huancayo (3280 m),Cuzco (3400 m),and Juliaca (3800 m). Results:Birth weight was lower at high altitude,but there was no linear relation between altitude of residence and birth weight. Mean birth weight was higher in Juliaca than in Huancayo. There were no significant differences between the 4 cities regarding birth weights of infants born between 28 and 35 weeks of gestation. However,for infants born between 36 and 42 weeks,birth weight was lower at higher altitudes. This may be due to inadequate maternal oxygenation later in pregnancy at high altitude. In the multivariate analysis,after controlling for maternal age,marital status,parity,body mass index,pre-eclampsia or hemorrhage during pregnancy,and education,as well as sex of the newborn and gestational age at birth,birth weightwas lower in all cities located at a higher altitude than Lima. Yet,longer residence at high altitudes may play a protective role. Juliaca (3800 m),where the population has resided the longest,had the lowest reduction in birth weight compared with Lima (150 m); Cuzco had intermediate values; and Huancayo (3280 m),where the population has resided the shortest,had the highest reduction in birth weight. Conclusions:Birth weight reduction,which is independent of socioeconomic factors,occurs only in births at term and may be less severe in populations that have resided longer at high altitudes.