Elevated plasma S100B levels in high altitude hypobaric hypoxia do not correlate with acute mountain sickness.

OBJECTIVES: Ascent to high altitude may result in a hypobaric hypoxic brain injury. The development of acute mountain sickness (AMS) is considered a multifactorial process with hypoxia-induced blood-brain barrier (BBB) dysfunction and resultant vasogenic oedema cited as one potential mechanism. Peripheral S100B is considered a biomarker of BBB dysfunction. This study aims to investigate the S100B release profile secondary to hypoxic brain injury and comment on BBB disturbance and AMS. METHODS: A prospective field study of 12 subjects who ascended Mt Fuji (3700 m) was undertaken. RESULTS: The mean baseline plasma S100B level was 0·11 µg/l (95% CI 0·09-0·12), which increased to 0·22 µg/l (95% CI 0·17-0·27) at the average of three high altitude levels (2590, 3700, and 2590 m on descent) (P < 0·001). The mean level for the seven subjects who experienced AMS rose from 0·10 to 0·19 µg/l compared to 0·12 to 0·25 µg/l for the five subjects who did not develop AMS (P  =  0·33). CONCLUSION: Ascending to 3700 m resulted in elevated plasma S100B levels but this was not associated with AMS.

Differential requirement for pulsatile LH during the follicular phase and exposure to the preovulatory LH surge for oocyte fertilization and embryo development in cattle.

The requirement for pulsatile LH and the LH surge for the acquisition of oocyte fertilizing potential and embryo developmental competency was examined in Zebu heifers. Follicular growth was superstimulated using the GnRH agonist-LH protocol in which pulsatile LH and the preovulatory LH surge are blocked. In experiment 1, heifers were assigned on Day 7 of the estrous cycle to receive: group 1A (n = 5), 1.5 mg norgestomet (NOR) implant; group 1B (n = 5), GnRH agonist implant. Follicular growth was superstimulated with 2x daily injections of FSH from Day 10 (a.m.) to Day 13 (p.m.), with PGF2alpha injection on Day 12 (a.m.). Heifers were ovariectomized on Day 15 (a.m.) and oocytes were placed immediately into fertilization, without 24 h maturation. Respective cleavage and blastocyst development rates were: group 1A, 0/64 oocytes (0%) and 0/64 (0%); group 1B, 34/70 oocytes (48.6%) and 2/70 (2.9%). In experiment 2, heifers were assigned on Day 7 of the estrous cycle to receive: group 2A (n = 10), 1.5 mg NOR implant; group 2B (n = 10), GnRH agonist implant; group 2C (n = 10), GnRH agonist implant. Follicular growth was superstimulated as in experiment 1 above. Heifers in groups 2A and 2B received an injection of 25 mg LH on Day 14 (p.m.) and all heifers were ovariectomized on Day 15 (a.m.); oocytes were placed immediately into fertilization without 24 h maturation. Cleavage rates were similar for heifers in group 2A (84/175 oocytes, 48.0%), group 2B (61/112 oocytes, 54.5%) and group 2C (69/163, 42.3%). Blastocyst development rates were similar for heifers in group 2A (22/175 oocytes, 12.6%) and group 2B (25/112 oocytes, 22.3%) and lower (P < 0.05) for heifers in group 2C (9/163 oocytes, 5.5%). Oocytes obtained from heifers treated with GnRH agonist, without injection of exogenous LH, underwent cleavage indicating that neither pulsatile LH nor the preovulatory LH surge are obligatory for nuclear maturation in cattle oocytes. Exposure to a surge-like increase in plasma LH increased embryo developmental competency indicating that the preovulatory LH surge promotes cytoplasmic maturation. The findings have important implications for controlling the in vivo maturation of oocytes before in vitro procedures including nuclear transfer.