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Biomedical subjects

K Ball

Publications and source records attributed to K Ball.

At least 109 records · Page 6Linked to original sources
PubMed1987

Direction-specific improvement in motion discrimination.

With training, an observer's ability to discriminate similar directions of motion gradually improves. A series of studies reveals that this improvement, (1) is restricted to the trained direction and other, similar directions, (2) persists for at least several months, (4) shows appreciable, but not complete, transfer between the two eyes, and (5) is largely restricted to the stimulated region of the field. Moreover, the improvement in direction discrimination does not produce a concomitant change in detection thresholds. In all likelihood, most of the improvement in direction discrimination represents a change in visual function, rather than changes in nonsensory processes.

Discrimination, Psychological↗
PubMed1987

Differences in gonadotrophin concentrations and pituitary responsiveness to GnRH between Booroola ewes which were homozygous (FF), heterozygous (F+) and non-carriers (++) of a major gene influencing their ovulation rate.

The mean plasma concentrations of FSH and LH were significantly higher in FF ewes than in ++ ewes with those F+ animals being consistently in between. These gene-specific differences were found during anoestrus, the luteal phase and during a cloprostenol-induced follicular phase, suggesting that the ovaries of ewes with the F-gene are more often exposed to elevated concentrations of FSH and LH than are the ovaries of ewes without the gene. The gene-specific differences in LH secretion arose because the mean LH amplitudes were 2-3 times greater in FF compared to ++ ewes with the LH amplitudes for F+ ewes being in between. The LH pulse frequencies were similar. In these studies the pulsatile nature of FSH secretion was not defined. The pituitary contents of LH during the luteal phase, were similar in all genotypes whereas for FSH they were significantly higher in the F-gene carriers compared to ++ ewes. The pituitary sensitivity to exogenous GnRH (0.1, 0.5 and 25 micrograms i.v.) was related to genotype. Overall the LH responses to GnRH were lower in FF ewes than in ++ ewes with the results for the F+ ewes being in between. The FSH responses to all GnRH doses in the FF genotype were minimal (i.e. less than 2-fold). In the other genotypes a greater than 2-fold response was noted only at the highest GnRH dose (i.e. 25 micrograms). Treatment of FF and F+ but not ++ ewes with GnRH eventually led to a reduced FSH output, suggesting that the pituitary responses to endogenous GnRH were being down-regulated in the F-gene carriers whereas this was not the case in the non-carriers. Collectively these data confirm that peripheral plasma and the pituitary together with the ovary are compartments in which F-gene differences can be observed. In conclusion, these findings raise the possibility that F-gene-specific differences may also extend to the hypothalamus and/or other regions of the brain.

Animals↗
PubMed1986

Improving visual perception in older observers.

Younger observers (M = 21 years) proved to be better than older observers (M = 68 years) at discriminating one direction of motion from another, highly similar one. Several days' practice steadily improved performance for both groups equally. Improvement was well restricted to the direction with which that observer practiced, and the full gains were retained for at least 1 month. Control measurements with various degrees of optical blur demonstrate that direction discrimination does not require a well-focussed retinal image. This rules out optical factors as the potential cause of the prepractice differences between groups.

Adult↗
PubMed1986

Visual localization: age and practice.

Older people seem to be highly susceptible to the distracting effects of irrelevant or interfering visual stimuli. We studied this susceptibility using visual displays in which observers had to localize the position of a face. When a face appeared in isolation, observers of all ages did equally well; when distracting stimuli surrounded the face, older observers alone performed poorly. Brief periods of practice produce substantial and long-lasting improvement in performance.

Adult↗
PubMed1986

Use of bovine follicular fluid to increase ovulation rate or prevent ovulation in sheep.

Romney ewes were injected intramuscularly once or twice daily for 3 days with 0, 0.1, 0.5, 1 or 5 ml of bovine follicular fluid (bFF) treated with dextran-coated charcoal, starting immediately after injection of cloprostenol to initiate luteolysis on Day 10 of the oestrous cycle. There was a dose-related suppression of plasma concentrations of FSH, but not LH, during the treatment period. On stopping the bFF treatment, plasma FSH concentrations 'rebounded' to levels up to 3-fold higher than pretreatment values. The mean time to the onset of oestrus was also increased in a dose-related manner by up to 11 days. The mean ovulation rates of ewes receiving 1.0 ml bFF twice daily (1.9 +/- 0.2 ovulations/ewe, mean +/- s.e.m. for N = 34) or 5.0 ml once daily (2.0 +/- 0.2 ovulations/ewe, N = 25) were significantly higher than that of control ewes (1.4 +/- 0.1 ovulations/ewe, N = 35). Comparison of the ovaries of ewes treated with bFF for 24 or 48 h with the ovaries of control ewes revealed no differences in the number or size distribution of antral follicles. However, the large follicles (greater than or equal to 5 mm diam.) of bFF-treated ewes had lower concentrations of oestradiol-17 beta in follicular fluid, contained fewer granulosa cells and the granulosa cells had a reduced capacity to aromatize testosterone to oestradiol-17 beta and produce cyclic AMP when challenged with FSH or LH. No significant effects of bFF treatment were observed in small (1-2.5 mm diam.) or medium (3-4.5 mm diam.) sized follicles. Ewes receiving 5 ml bFF once daily for 27 days, from the onset of luteolysis, were rendered infertile during this treatment period. Oestrus was not observed and ovulation did not occur. Median concentrations of plasma FSH fell to 20% of pretreatment values within 2 days. Thereafter they gradually rose over the next 8 days to reach 60% of pretreatment values where they remained for the rest of the 27-day treatment period. Median concentrations of plasma LH increased during the treatment period to levels up to 6-fold higher than pretreatment values. When bFF treatment was stopped, plasma concentrations of FSH and LH quickly returned to control levels, and oestrus was observed within 2 weeks. The ewes were mated at this first oestrus and each subsequently delivered a single lamb.

Animals↗
PubMed1986

Differences in ovarian activity between booroola X merino ewes which were homozygous, heterozygous and non-carriers of a major gene influencing their ovulation rate.

Differences in the function and composition of individual ovarian follicles were noted in Booroola Merino ewes which had previously been segregated on at least one ovulation rate record of greater than 5 (FF ewes, N = 15), 3-4 (F+ ewes, N = 18) or less than 3 (++ ewes, N = 18). Follicles in FF and F+ ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. In FF (N = 3), F+ (N = 3) and ++ (N = 3) ewes, the respective mean +/- s.e.m. diameters for the presumptive preovulatory follicles were 3.4 +/- 0.3, 4.1 +/- 0.2 and 6.8 +/- 0.3 mm and in each of these follicles the respective mean +/- s.e.m. numbers of granulosa cells (X 10(6)) were 1.8 +/- 0.3, 2.2 +/- 0.3 and 6.6 +/- 0.3. During a cloprostenol-induced follicular phase, the oestradiol secretion rates from FF ewes with 4.8 +/- 0.4 'oestrogenic' follicles, F+ ewes with 3.2 +/- 0.2 'oestrogenic' follicles and ++ ewes with 1.5 +/- 0.02 'oestrogenic' follicles were not significantly different from one another. Moreover, the mean total numbers of granulosa cells from the 'oestrogenic' follicles from each genotype were identical, namely 5.4 X 10(6) cells. Irrespective of genotype the mean weight of each corpus luteum was inversely correlated to the ovulation rate (R = 0.91, P less than 0.001). Collectively, these findings support the notion that the maturation of greater than or equal to 5 follicles in FF ewes and 3-4 follicles in F+ ewes may each be necessary to provide a follicular-cell mass capable of producing the same quantity of oestradiol as that from 1-2 preovulatory follicles in ++ ewes.

Animals↗
PubMed1985

Ovarian activity in Booroola X Romney ewes which have a major gene influencing their ovulation rate.

A marked difference in both the function and composition of individual ovarian follicles was noted in Booroola X Romney ewes (6-7 years of age) which had previously been segregated on at least one ovulation rate record of 3-4 (F + ewes, N = 21) or less than 3 (++ ewes, N = 21). Follicles in F + ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. In F+ ewes (N = 3), the presumptive preovulatory follicles were 4.4 +/- 0.5 (s.e.m.) mm in diameter and contained 2.1 +/- 0.3 X 10(6) (s.e.m.) granulosa cells, whereas in ++ ewes (N = 3), such follicles were 7.3 +/- 0.3 mm in diameter and contained 6.5 +/- 0.8 X 10(6) cells. During a prostaglandin (PG)-induced follicular phase, the secretion rate of oestradiol from ovaries containing 3 presumptive preovulatory follicles in F + ewes was similar to that from ovaries with only one such follicle in ++ ewes. We suggest that the putative 'gene effect' in F + ewes is manifested during early follicular development and that it may be mediated via an enhanced sensitivity of granulosa cells to pituitary hormones. As a consequence, the development of 3 preovulatory follicles in F + ewes may be necessary to provide a cell mass capable of producing the same quantity of oestradiol as that from one preovulatory follicle in ++ ewes.

Androstenedione↗
PubMed1985

FSH influences follicle viability, oestradiol biosynthesis and ovulation rate in Romney ewes.

Injection of steroid-free bovine follicular fluid (bFF; 2 X 5 ml s.c. 12 h apart) into anoestrous ewes lowered plasma FSH concentrations by 70% and after 24 h had significantly (P less than 0.01) reduced the number of non-atretic follicles (greater than or equal to 1 mm diam.) without influencing the total number of follicles (greater than 1 mm diam.) compared to untreated controls. Hourly injections of FSH (10 micrograms i.v. NIH-FSH-S12) for 24 h did not influence the number of non-atretic follicles but did negate the inhibitory effects of bFF on follicular viability. Hourly injections of FSH (50 micrograms i.v., NIH-FSH-S12) + bFF treatment for 24 h significantly increased the total number of non-atretic follicles, and particularly the number of medium to large non-atretic follicles (greater than 3 mm diam.) compared to the untreated controls (both P less than 0.01). The 10 micrograms FSH regimen (without bFF) significantly increased aromatase activity in granulosa cells from large (greater than or equal to 5 mm diam.; P less than 0.01) but not medium (3-4.5 mm diam.) or small (1-2.5 mm diam.) follicles compared to controls. The 10 micrograms FSH + bFF regimen had no effect on granulosa-cell aromatase activity compared to the controls. However, the 50 micrograms FSH plus bFF regimen increased the aromatase activity of granulosa cells from large, medium and small non-atretic follicles 2.6-, 8.3- and greater than or equal to 11-fold respectively compared to that in the control cells. Ewes (N = 11) that ovulated 2 follicles had significantly higher plasma FSH concentrations from 48 to 24 h and 24 to 0 h before the onset of a cloprostenol-induced follicular phase (both P less than 0.01) than in the ewes (N = 12) that subsequently ovulated one follicle. Hourly FSH treatment (1.6 micrograms i.v., NIAMDD-FSH-S15) for 24 h but not for any 6 h intervals between 48 and 24 h or 24 and 0 h before a cloprostenol-induced luteolysis also resulted in significant increases (P less than 0.05) in the number of ewes with 2 ovulations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Thems 'n us-es.

Explore the source record for details and available documents.

Australia↗
PubMed1984

Changes in gonadotrophin secretion and ovarian antral follicular activity in seasonally breeding sheep throughout the year.

Overall, significantly more antral follicles greater than or equal to 1 mm diameter were present in Romney ewes during anoestrus than in the breeding season (anoestrus, 35 +/- 3 (mean +/- s.e.m.) follicles per ewe, 23 sheep; Day 9-10 of oestrous cycle, 24 +/- 1 follicles per ewe, 22 sheep; P less than 0.01), although the mean numbers of preovulatory-sized follicles (greater than or equal to 5 mm diam.) were similar (anoestrus, 1.3 +/- 0.2 per ewe; oestrous cycle, 1.0 +/- 0.1 per ewe). The ability of ovarian follicles to synthesize oestradiol did not differ between anoestrus and the breeding season as assessed from the levels of extant aromatase enzyme activity in granulosa cells and steroid concentrations in follicular fluid. Although the mean plasma concentration of LH did not differ between anoestrus and the luteal phase of the breeding season, the pattern of LH secretion differed markedly; on Day 9-10 of the oestrous cycle there were significantly more (P less than 0.001) high-amplitude LH peaks (i.e. greater than or equal to 1 ng/ml) in plasma and significantly fewer (P less than 0.001) low amplitude peaks (less than 1 ng/ml) than in anoestrous ewes. Moreover, the mean concentrations of FSH and prolactin were significantly lower during the luteal phase of the cycle than during anoestrus (FSH, P less than 0.05, prolactin, P less than 0.001). It is concluded that, in Romney ewes, the levels of antral follicular activity change throughout the year in synchrony with the circannual patterns of prolactin and day-length. Also, these data support the notion that anovulation during seasonal anoestrus is due to a reduced frequency of high-amplitude LH discharges from the pituitary gland.

Anestrus↗