Zinc tolerance in populations ofDeschampsia cespitosa (Gramineae) beneath electricity pylons

Patterns of zinc tolerance were examined in eightDeschampsia cespitosa (L.)Beauv. populations from normal and zinc-contaminated soils, using solution culture methods. Zinc-tolerant populations have evolved beneath pylons, and their tolerance patterns (degree, variance, heritability) vary. Tolerance is genetically based in all of them. In contrast to the cases of other species previously reported, some within-population differences are considerable, and may be due to both heterogeneity of the soils zinc contents, various gene combinations and gene recombinations between genotypes. One control population contains many tolerant plants, an original result which is discussed.     

Effect of FSH on ovarian inhibin secretion in anoestrous ewes

In Exp. 1, 7 Finn-Merino ewes which had one ovary autotransplanted to a site in the neck had jugular and timed ovarian venous blood samples collected at 10-min intervals for 2 h before and 3 h after injection of 5 micrograms NIAMDD-oFSH-S16. In Exp. 2, 8 Finn-Merino ewes with ovarian autotransplants had jugular and timed ovarian venous blood samples collected at 15-min intervals for 2 h before and 12 h after bolus injection of 40 micrograms NIAMDD-oFSH-S16 and infusion of oFSH-S16 at 6 micrograms/min for 4 h. In Exp. 2 the follicular population of the ovary was assessed by real-time ultrasound at the beginning and end of the experimental period. In both experiments the secretion rates of inhibin (1-3 ng/min) and oestradiol (0.5-8 ng/min) were similar to those observed during the luteal phase of the cycle in the breeding season, indicating significant follicular development in these animals. In Exp. 1 there was no change in the secretion of oestradiol or inhibin after the injection of FSH which resulted in a 25% increase (P less than 0.05) in the concentration of FSH in plasma. Inhibin secretion was pulsatile but there was no difference in inhibin pulse frequency before (1.6 +/- 0.2 pulses/h) or after (1.2 +/- 0.5 pulses/h) injection of FSH. In Exp. 2 injection of FSH resulted in an increase (P less than 0.001) in plasma concentrations of FSH in the sample taken 10 min after injection from a baseline of 1.2 +/- 0.2 ng/ml to a peak of 10.6 +/- 1.0 ng/ml (mean +/- s.e.m.).(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma prolactin, thyroxine, triiodothyronine, testosterone, and luteinizing hormone during a photoinduced reproductive cycle in mallard drakes

The temporal relationships between plasma concentrations of prolactin, thyroxine (T4) and triiodothyronine (T3) were determined in a group of six wild mallard drakes during the development and maintenance of long-day refractoriness after transfer from 6 h light: 18 h darkness (6L:18D) to 20L:4D for 24 weeks. As shown by changes in the plasma concentrations of luteinizing hormone (LH) and testosterone, the birds came into breeding condition and then became long-day refractory within 5 weeks of photostimulation. Long-day refractoriness was maintained for the remainder of the study. Plasma prolactin began to increase immediately after photostimulation, although not as fast as the increases in plasma LH and testosterone. The concentration of plasma T4 also increased after photostimulation but, as shown by decreased plasma LH and testosterone levels, only after the birds had become long-day refractory. The development of long-day refractoriness was thus directly correlated with an increased plasma prolactin and not with a change in plasma concentration of T4. Plasma T3 decreased after photostimulation but returned to prestimulation values as the birds became long-day refractory and remained stable for the remainder of the study. Concentrations of plasma T4 and prolactin returned to baseline values after about 15 weeks photostimulation showing that the long-term maintenance of long-day refractoriness is not directly related to continuously high plasma concentrations of either hormone.     

Endocrine differences in rams after genetic selection for testis size

Testis diameter and body weight were recorded from 6 to 76 weeks of age in ram lambs from two established lines selected for high (H) and low (L) testis size. While testis growth was greater in the H line up to 14 weeks of age (P less than 0.001), body weight was significantly lower, with the L line rams being 10 kg heavier by 76 weeks. There were no differences in plasma LH up to 20 weeks of age, but FSH concentrations were significantly lower at 14 and 20 weeks in the H line. Testosterone concentrations were not significantly higher in the H line from 6 to 20 weeks. In lambs castrated at birth, significantly higher FSH values were recorded from 6 to 20 weeks of age in the H line (P less than 0.001) whereas there was no difference in LH concentration at 6 and 10 weeks of age between the lines. At 14 and 20 weeks, however, the concentrations of LH were greater in the H than L line lambs (P less than 0.05). After hemicastration at 6 weeks of age, the rate of growth of the remaining testis in the L line lambs was significantly faster than in entire lambs of that line from 10 to 20 weeks (P less than 0.05 at 10 weeks to P less than 0.001 at 20 weeks). There was no difference in the rate of testis growth between the the entire and hemicastrated lambs from the H line from 6 to 12 weeks of age. It can be concluded that there is an underlying genetic difference in pituitary gland and/or hypothalamic activity in ram lambs from the two selected lines.     

Tolerance ofHolcus lanatus andAgrostis stolonifera to sodium chloride in soil solution and saline spray

Summary Inland and sea cliff populations of bothAgrostis stolonifera L. andHolcus lanatus L. were subjected to soil NaCl treatments, of 100 and 200 mol m⁻³ NaCl, and tolerance examined using plant dry weight data. A parallel experiment subjected them to salt spray treatments of 2.5%, 5% and 10% NaCl in distilled water, and tolerance assessed from leaf damage. Both populations of each species were equally sensitive to soil NaCl. When subjected to salt spray the sea cliff populations however showed marked resistance to leaf damage. Soil salinity resistance and salt spray resistance thus appear to be independent characteristics in these two species.     

Effect of enucleation of the corpus luteum at different stages of the luteal phase of the human menstrual cycle on subsequent follicular development

To investigate the mechanism of suppression of follicular development during the luteal phase of the human menstrual cycle, the corpus luteum was enucleated surgically from 10 women at various times after ovulation. In the 24 h after CL enucleation there was an immediate and rapid fall in the concentration of oestradiol and progesterone and a temporary decline in the concentration of FSH and LH. Within 3 days, however, all 10 women showed evidence of renewed follicular activity as indicated by a progressive rise in the concentration of oestradiol. This rise was preceded by a rise in the concentration of FSH and LH, and ovulation, as indicated by a mid-cycle surge in LH and rise in the concentration of plasma progesterone, occurred 16-19 days after enucleation. There was no significant difference in the time to ovulation following enucleation at different times of the luteal phase. The post-operative follicular phase, measured from the time of enucleation, was 3 days longer than that observed pre-operatively from the first day of menstrual bleeding. In the follicular phase of post-operative cycles the concentration of FSH was higher and that of oestradiol lower than the corresponding values before surgery. These results indicate that the absence of healthy antral follicles in the luteal phase of the cycle is due to the inhibitory effects of the corpus luteum. The fact that, after CL enucleation, emergence of the dominant follicle was always preceded by a rise in the concentration of FSH and LH suggests that suppression of gonadotrophins by ovarian steroids secreted by the corpus luteum is responsible for the inhibition of follicular development during the luteal phase of the cycle.     

Galactorrhoea: Successful Treatment with Reduction of Plasma Prolactin Levels by Brom-ergocryptine

In five patients with inappropriate lactation and amenorrhoea or impotence brom-ergocryptine was found to suppress the lactation and to diminish the raised plasma prolactin levels. The responses to treatment suggest that there may be an inverse relationship between prolactin secretion and gonadotrophin secretion in man.     

Seasonal cycles in the blood plasma concentration of FSH, inhibin and testosterone, and testicular size in rams of wild, feral and domesticated breeds of sheep

Seasonal cycles in testicular activity in rams were monitored in groups of wild (mouflon), feral (Soay) and domesticated breeds of sheep (Shetland, Blackface, Herdwick, Norfolk, Wiltshire, Portland and Merino) living outdoors near Edinburgh (56 degrees N). The changes in the blood plasma concentrations of FSH, inhibin and testosterone, and the diameter of the testis were measured every half calendar month from 1 to 3 years of age. There were significant differences between breeds in the magnitude and timing of the seasonal reproductive cycle. In the mouflon rams, the seasonal changes were very pronounced with a 6-15-fold increase in the plasma concentrations of FSH, inhibin and testosterone from summer to autumn, and a late peak in testicular diameter in October. In the Soay rams and most of the domesticated breeds, the seasonal increase in the reproductive hormones occurred 1-2 months earlier with the peak in testicular size in September or October. In the two southern breeds (Portland and Merino), the early onset of testicular activity was more extreme with the seasonal maximum in August. In cross-bred rams, produced by mating Soay ewes (highly seasonal breed) with Portland or Merino rams (less seasonal breeds), there was a seasonal reproductive cycle that was intermediate compared to that of the parents. A comparison between all 11 breeds showed a significant correlation between the timing of the seasonal cycle in plasma FSH concentration and testicular diameter (time of peak FSH vs testis, r = 0.95). The overall results in the rams are consistent with a primary role of FSH in dictating the seasonal cycle in testicular size and the secretion of inhibin. The earlier seasonal onset in the testicular cycle in the southern breeds of domesticated sheep, and the differences from the wild type, are taken to represent the effects of genetic selection for a longer mating season.     

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes.

Nineteen Scottish Blackface ewes were given LH-RH (3 X 30 micrograms i.v., 90-min intervals) during anoestrus when prolactin levels were elevated. Plasma levels of prolactin were suppressed with CB 154 (twice daily, i.m.) on Days -5 to 0 (N = 5), 0 to +5 (N = 5) or -5 to +5 (N = 5) around the day of LH-RH treatment (Day 0). Control animals (N = 4) received saline on Days -5 to +5. Nine animals ovulated forming corpora lutea as judged by laparoscopy on Day +7. No difference in FSH or LH levels was found between treatments and ovulations occurred equally in all treatment groups. Progesterone levels were less than ng/ml in all animals up to Day 14. It is concluded that short-term suppression of prolactin does not affect the incidence of ovulation or corpus luteum progesterone production in LH-RH-treated anoestrous ewes.