Search Results

You are looking at 1 - 5 of 5 items for

  • Author: J. C. DAVIS x
Clear All Modify Search
Free access

L. J. HIPKIN, J. C. DAVIS, V. K. SUMMERS, S. BENDER and C. EASTMOND

Summary.

Growth hormone (HGH) responses to insulin-induced hypoglycaemia were examined in sixteen normal women and twenty-eight women with secondary amenorrhoea. A normal response (blood levels rising above 10 ng/ml) was found in fifteen of sixteen (94%) of the controls but in only nineteen of twenty-eight (68%) of the patients with amenorrhoea. Oestrogen administration induced a normal response in only two out of six patients with a previously abnormal result. The patients with subnormal HGH responses all had a low gonadotrophin excretion, but tests of thyroid and adrenocortical function were normal and pituitary fossa X-rays were normal. This tendency to a poor HGH response must be taken into account when screening amenorrhoeic patients for pituitary tumours.

Free access

C. G. Gravance, I. K. M. Liu, R. O. Davis, J. P. Hughes and P. J. Casey

The heads of stallion spermatozoa were analysed by computer automated sperm head morphometry and the morphometric values of the major subpopulations of sperm heads were assessed. The criteria for normal dimensions of stallion sperm heads are proposed based on the analysis of these measurements. Semen samples were collected from 10 fertile and 10 subfertile stallions, processed by a standard method, smeared onto microscope slides and stained using haematoxylin. At least 200 properly digitized sperm heads were analysed from each stallion. The measurements for length, width, area, perimeter and width/length were recorded for each stallion. All sperm head measurements were placed in a statistical database and multivariate cluster analysis performed. Mean measurements for all parameters of the major clusters of fertile and subfertile stallions were compared by analysis of variance. The ranges of the values of the major clusters of fertile stallions were applied to all stallions to determine the percentage of normal sperm heads for each stallion. The mean values for length, width, area and perimeter in the major cluster of sperm head dimensions of fertile stallions were significantly different from those of the subfertile stallions (P < 0.001). The range of values of the major cluster of fertile stallions was length = 4.9–5.7 μm, width = 2.5–3.0 μm, width/length = 0.45–0.59, area = 10.3–12.1 μm, and perimeter = 12.9–14.2 μm. On the basis of these values, a significantly (P < 0.001) higher percentage of normal sperm heads were found in the fertile group than in the subfertile group of stallions (52% versus 19%).

Free access

H. W. Burden, J. Zary, I. E. Lawrence, P. Jonnalagadda, M. Davis and C. A. Hodson

The effect of space flight in a National Aeronautics and Space Administration (NASA) shuttle was studied in pregnant rats. Rats were launched on day 9 of gestation and recovered on day 20 of gestation. On day 20 of gestation, rats were unilaterally hysterectomized and subsequently allowed to go to term and deliver vaginally. There was no effect of space flight on pituitary and ovary mass postpartum. In addition, space flight did not alter healthy and atretic ovarian antral follicle populations, fetal wastage in utero, plasma concentrations of progesterone and luteinizing hormone (LH) or pituitary content of follicle stimulating hormone (FSH). Space flight significantly increased plasma concentrations of FSH and decreased pituitary content of LH at the postpartum sampling time. Collectively, these data show that space flight, initiated during the postimplantation period of pregnancy, and concluded before parturition, is compatible with maintenance of pregnancy and has minimal effects on postpartum hypophyseal parameters; however, none of the ovarian parameters examined was altered by space flight.

Free access

R. M. Blair, C. M. Coughlin, J. E. Minton and D. L. Davis

The primary objective of this study was to determine whether embryo survival in gilts and primiparous sows is related to variations in the peri-oestrous profiles of oestradiol, progesterone and LH. A secondary objective of the present work was to compare embryo development and certain endocrine characteristics in gilts and primiparous sows. Sows (n = 6) and gilts (n = 6) were catheterized in the jugular vein on the day after weaning or on day 14 of the oestrous cycle, respectively. Additional females (one gilt and seven sows) were examined only for characteristics of embryonic development. Embryos were recovered on day 11.5–11.75 of gestation, and size and volume of individual embryos were recorded. Minimal differences were observed between sows and gilts for endocrine and embryo data. Embryo recovery was 71.38 ± 4.77% based on the number of corpora lutea. However, endocrine differences were noted for pigs with high embryo survival (> 71% recovery) compared with those with low survival. Peak oestradiol concentration occurred closer (P < 0.05) to the onset of oestrus in pigs with high embryo survival than in pigs with low embryo survival (3.3 ± 4.6 h after oestrus versus 13.0 ± 5.5 h before oestrus) and peak LH concentration occurred later (P < 0.05) after the onset of oestrus for pigs with high embryo survival. Peak oestradiol concentration tended (P = 0.07) to be higher in pigs with low embryo survival (35.21 ± 2.56 pg ml−1) compared with pigs with high embryo survival (28.17 ± 2.14 pg ml−1). Pigs with high embryo survival tended (P=0.10) to have less variation in embryonic development than did those with low embryo survival (40.76 ± 7.14% versus 59.39 ± 8.06%, respectively). These data suggest that increased embryo survival and decreased embryonic diversity might be associated with a closer synchrony between the onset of the LH surge and oestrus and the peak concentration of oestradiol.

Free access

P. G. Groothuis, R. M. Blair, R. C. M. Simmen, J. L. Vallet, D. M. Grieger and D. L. Davis

During early pregnancy, progesterone stimulates the secretion of proteins and other molecules that support the developing conceptus. Some gilts are able to support conceptus development as early as 110 days of age. The objective of this study was to evaluate the onset of responsiveness of the prepubertal uterus to progesterone. Thirty gilts were assigned to receive 2.2 mg progesterone kg−1 body mass per day or corn oil daily for 14 days starting at 6, 46, 76, 106, and 136 days of age. Hysterectomies were performed the day after the last treatment of progesterone, and the uterine horns were weighed and flushed with sterile saline (0.85% NaCl). Recovered flushings were analysed for total luminal protein, retinol binding protein, uteroferrin, prostaglandin E and prostaglandin F. An interaction between age and progesterone occurred for uterine wet mass (P < 0.001). Progesterone did not affect the uterine mass of gilts that underwent hysterectomy at 20 days of age, but did increase the uterine mass (P < 0.05) in other age groups. Progesterone increased (P < 0.01) the amount of total luminal protein in all but the youngest gilts. An increase in the amounts of retinol binding protein and uteroferrin (P < 0.001) by progesterone was first observed in 90-day-old gilts. Prostaglandins exhibited a different age-related pattern. The amount of prostaglandin E was increased (P < 0.001) by progesterone treatment in gilts aged 90–150 days, with a greater (P < 0.05) response at 120 days than at 90 days old. The response at 150 days old decreased (P < 0.05) to that observed at day 90. The response of prostaglandin F to progesterone followed a similar age-related pattern. Therefore, uterine responsiveness to progesterone develops between 20 and 90 days after birth, and uterine mass responds earlier than the secretory responses measured in our study.