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Biomedical subjects

K Ball

Publications and source records attributed to K Ball.

At least 127 records · Page 7Linked to original sources
PubMed1984

Effects of long-term treatment with LH on induction of cyclic ovarian activity in seasonally anoestrous ewes.

The aim of the present study was to establish whether cyclic ovarian activity could be induced and then maintained in anoestrous Romney ewes by the long-term administration of regular intravenous pulses of LH (10 micrograms ovine LH i.v. once every 1 or 2 h for 29-91 days). The LH pulse regimen was designed to generate plasma profiles of LH that were comparable to those experienced during the luteal and follicular phases of the oestrous cycle. The results showed that the LH treatments were capable of inducing cyclic ovarian activity, as assessed from the concentrations of progesterone in plasma, but that the treatments were inadequate for sustaining cyclic activity beyond two consecutive progestational phases. After 35-56 days of treatment, the plasma concentrations of FSH declined significantly (P less than 0.05) relative to those in the untreated animals. These data suggest that FSH supplementation as well as LH might be required for the long-term maintenance of cyclic ovarian activity in seasonally anoestrous ewes.

Animals↗
PubMed1984

Increase in ovulation rate after active immunization of sheep with inhibin partially purified from bovine follicular fluid.

Four Romney ewes were actively immunized with a partially purified preparation of inhibin derived from bovine follicular fluid and their ovulation rates in four successive oestrous cycles were compared with those of four ewes receiving adjuvant alone. The ovulation rates of the ewes immunized with the inhibin preparation were significantly higher than those of the control ewes (2.06 +/- 0.16 (S.E.M.) vs 1.31 +/- 0.06 ovulations/ewe, n = 4). Plasma concentrations of FSH and LH, measured in blood samples taken three times a week for 11 weeks, during which time each ewe was immunized three times, were not significantly different between the two treatment groups. These results suggest that active immunization with inhibin-enriched follicular fluid may be a potential means of increasing fecundity in sheep.

Animals↗
PubMed1982

A specific and enduring improvement in visual motion discrimination.

Training improves the ability of human observers to discriminate between two similar directions of motion. This gradual improvement is specific to the direction on which an observer is trained, and it endures for several months. Improvement does not affect motion perception generally, nor does it depend on recognition of details of the movement.

Discrimination, Psychological↗
PubMed1982

Induction of cyclic ovarian activity in seasonally anoestrous ewes with exogenous GnRH.

Anoestrous ewes (N = 3) were treated with a 500 ng GnRH pulse administered via a jugular cannula every 2 h for 40 to 80 days. Plasma concentrations and therefore presumed ovarian activity changed cyclically with each progestational cycle (n = 10) lasting 14.0--18.5 days. It is concluded that, by increasing the frequency of GnRH secretory episodes from an apparent endogenous level of one episode per 3.6 h to at least one every 2.0 h, cyclic ovarian activity can be restored to seasonally anoestrous sheep.

Anestrus↗
PubMed1981

Adaptive processing of visual motion.

Three studies relating perception of motion to stimulus uncertainty are reported. Generally, detectability declines when the observer is uncertain about the direction in which a target will move, but the visibility loss associated with direction uncertainty can be attenuated if the observer has adequate practice. This attenuation seems to depend upon the observer's ability to switch among directionally selective visual mechanisms in an adaptive fashion. The implications of these findings for models of motion detection are discussed.

Adaptation, Ocular↗