Systemic Concentrations of Endogenous and Exogenous FSH in Anoestrous Ewes Superstimulated with Folltropin®-V

The synchronization of follicular waves with medroxyprogesterone acetate (MAP) and oestradiol‐17β (E₂‐17β) prior to ovarian superstimilation in anoestrous ewes reduces the variability in superovulatory responses by an unknown mechanism. Follicle stimulating hormone (FSH) is a primary promoter of antral follicular development, but the relevance of circulating FSH concentrations to the superovulation performance in ewes has not been examined. Eighteen anoestrous Rideau Arcott ewes (May–June) were superovulated with Folltropin^®‐V (porcine FSH), with (n = 8; treated ewes) or without (n = 10; control ewes) a single i.m. dose of 350 μg of E₂‐17β, given on the sixth day of a 14‐day treatment with MAP‐releasing intravaginal sponges (60 mg). The superovulatory treatment, begun 6 days after E₂‐17β injection, consisted of six i.m. applications of Folltropin^®‐V given twice daily (at 08:00 and 16:00 h), followed by an i.m. injection of GnRH (50 μg). Blood samples collected every 8 h throughout the 3‐day treatment, were analysed by radioimmunoassays for concentrations of ovine and porcine FSH, using species‐specific standards and primary antibodies. Serum concentrations of oFSH were greater (p < 0.05) in the controls compared to treated ewes at 40, 64 and 72 h and the variability in mean oFSH concentrations was greater (p < 0.05) in control ewes at 40, 48, 64 and 72 h after the 1^st Folltropin^®‐V injection. There were no differences (p > 0.05) between the two groups in serum concentrations of pFSH. Significant correlations were recorded between the number of corpora lutea (CL) and oFSH concentrations at 8 h (r = 0.72, p < 0.05), 16 h (r=0.63, p < 0.05) and 64 h (r = 0.84, p < 0.01) after the 1^st Folltropin^®‐V injection. The total number of recovered embryos was positively correlated to oFSH concentrations at 56 h (r = 0.69, p < 0.05). We concluded that changes in endogenous FSH concentrations during ovarian superstimulation with pFSH might contribute to the variability in superovulatory responses in ewes.     

留茬高度对人工草地牧草产量及质量的影响

试验对黑麦草／白三叶混播草地在不同留茬高度下的生产特性进行了分析研究,研究结果表明,草地牧草的枯死率与留茬高度呈正比关系,在不同留茬高度下,草地牧草青绿物质的生长速度和产量呈抛物线形式变化;青绿牧草产量占牧草总产量的百分比随留茬高度的上升而下降,而死亡物质的数量占牧草产量的百分比随留茬高度的上升而增加。     

Plasma cortisol concentrations in normal dogs given hydrocortisone sodium succinate

OBJECTIVE: To evaluate the effects on plasma cortisol concentration of a continuous infusion of a readily available steroid with equipotent glucocorticoid and mineralocorticoid effects. PROCEDURE: Plasma cortisol concentrations were measured before and regularly after hydrocortisone sodium succinate was administered as a continuous intravenous infusion over 6 h at 0.32 and 0.65 mg kg-1 h-1 to 12 healthy dogs weighing 12 to 22 kg. RESULTS: The infusion at both does rates produced significant and stable increases in plasma cortisol concentrations. The plateau concentrations produced by the large and small doeses were respectively above and below plasma cortisol concentrations likely to provide adequate glucocorticoid and mineralocorticoid activity in stressed dogs with significantly decreased adrenal function. CONCLUSION: This paper presents information regarding the changes in plasma cortisol concentrations in 12 normal dogs given an hydrocortisone sodium succinate infusion at two dose rates. The marked and continuous increase in plasma cortisol concentrations suggests a continuous HSS infusion may be a possible alternative to desoxycorticosterone acetate and dexamethasone in the treatment of acute adrenal dysfunction.     

Carbon nanotube quantum resistors

The conductance of multiwalled carbon nanotubes (MWNTs) was found to be quantized. The experimental method involved measuring the conductance of nanotubes by replacing the tip of a scanning probe microscope with a nanotube fiber, which could be lowered into a liquid metal to establish a gentle electrical contact with a nanotube at the tip of the fiber. The conductance of arc-produced MWNTs is one unit of the conductance quantum G0 = 2e2/h = (12.9 kilohms)-1. The nanotubes conduct current ballistically and do not dissipate heat. The nanotubes, which are typically 15 nanometers wide and 4 micrometers long, are several orders of magnitude greater in size and stability than other typical room-temperature quantum conductors. Extremely high stable current densities, J > 10(7) amperes per square centimeter, have been attained.