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Biomedical subjects

C J Scott

Publications and source records attributed to C J Scott.

47 records · Page 3Linked to original sources
PubMed1993

Inhibition of luteinizing hormone secretion in ovariectomized ewes during the breeding season by gamma-aminobutyric acid (GABA) is mediated by GABA-A receptors, but not GABA-B receptors.

We have investigated the effects of agonists and antagonists to gamma-aminobutyric acid-A (GABA-A) and GABA-B receptors microinjected (1 microliters) into the preoptic area (POA) on LH in ovariectomized (OVX) ewes with or without estrogen (E) treatment during the breeding season. Guide tubes were placed into the preoptic area of OVX ewes using lateral ventriculograms for localization of the target area. Doses of 10 micrograms of the GABA agonists muscimol (GABA-A) and baclofen (GABA-B) or the GABA antagonists bicuculline (GABA-A) and phaclofen (GABA-B) were injected into the POA of tame conscious animals. Jugular venous blood was collected at 10-min intervals for 3 h, the injection of GABA drug or vehicle was given, and samples were collected for a further 3 h. The plasma samples were assayed for LH. On completion of the experiments, the brains were sectioned to locate the site of injection. In the first year, 17 ewes were used, of which 16 had correct guide tube placement. In OVX sheep, both muscimol and bicuculline injections caused suppression of plasma LH concentrations, with a cessation of pulses in many instances. When OVX sheep were treated with 1.0-cm Silastic implants (sc) of E for at least 7 days, there was a decrease in LH interpulse interval. In these sheep, muscimol and bicuculline injections had effects on plasma LH concentrations similar to those in OVX sheep. In addition, bicuculline was injected into the POA of OVX ewes treated with 2.0-cm E implants. Despite E treatment resulting in reduced plasma LH levels, due to an increase in the interpulse interval, bicuculline injection further suppressed plasma LH levels. Neither baclofen nor phaclofen injection had any effect on plasma LH secretion in either OVX ewes or OVX ewes given 1.0-cm E implants. In the second year, eight sheep were used, all of which had correct guide tube placement. These sheep were treated with 2.0-cm E implants and injected with phaclofen. Phaclofen had no effect on LH secretion. These results suggest that GnRH secretion is regulated by GA-BAergic neurons at the level of the GnRH cell bodies in the POA and that during the breeding season, this is effected by GABA-A and not GABA-B receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Evidence that changes in the function of the subtypes of the receptors for gamma-amino butyric acid may be involved in the seasonal changes in the negative-feedback effects of estrogen on gonadotropin-releasing hormone secretion and plasma luteinizing hormone levels in the ewe.

We have investigated the effects of gamma-amino butyric acid (GABA) agonists and antagonists to GABAA and GABAB receptors microinjected (1 microliter) into the medial preoptic area (MPOA) on LH secretion in ovariectomized (OVX) ewes with or without estrogen (E) treatment, during the nonbreeding season. Guide tubes (19 gauge) were placed into the MPOA of OVX ewes and injections of 1 microgram or 10 micrograms of the GABAA agonist muscimol or the GABAA antagonist bicuculline, and 10 micrograms of the GABAB agonist baclofen or the GABAB antagonist phaclofen were made into conscious animals. Jugular venous blood was collected at 10-min intervals for 3 h, the injection of GABA drug or vehicle was given and samples collected for a further 3 h. The plasma samples were assayed for LH. On completion of the experiments the brains were sectioned to locate the sites of injection. Thirty-four ewes were used, of which 30 had correct guide tube placement. In OVX sheep, both muscimol and bicuculline injection caused suppression of plasma LH concentrations, with a cessation of pulsatile release in many instances. Injection with baclofen or phaclofen into these sheep had no effect on LH secretion. When OVX sheep were treated with 0.5-cm Silastic implants (sc) of E for at least 7 days, there was a variable response to muscimol and bicuculline injection, depending on the degree of suppression of LH secretion by E. When E had little effect on plasma LH levels, muscimol and bicuculline both suppressed LH secretion in a similar manner to that observed in OVX ewes. When E treatment fully suppressed plasma LH levels, muscimol and bicuculline both stimulated LH secretion. This stimulation often took the form of a sustained, nonpulsatile secretion of LH. Baclofen injection into OVX ewes treated with E increased mean plasma LH levels through an increase in pulse amplitude, although there was only an effect on the amplitude of the first pulse after injection. Conversely, phaclofen injection in OVX ewes treated with E resulted in a reduction in LH pulse amplitude. These results provide evidence for a seasonal shift in the regulation of GnRH secretion by GABAergic neurons in the MPOA of the ewe. In contrast to the breeding season, where there was no effect of GABAB ligands, these appear to function in non-breeding season, this may be part of the mechanism for the seasonal shift in the negative-feedback effect of E on LH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Analysis of a smoking policy in the workplace.

Following implementation of the smoking policy, an overall decrease in tobacco consumption was reported among 33% of the employees; of these, 32% quit completely. Smokers who reported smoking more than one pack of cigarettes a day were three times more likely to decrease consumption than those who reported smoking one pack or less a day. Among those who decreased their tobacco consumption, 43% associated this decrease with the policy implementation. A notable inverse relationship existed between smokers' tobacco consumption and attitudes about the policy: as cigarette consumption decreased, attitude about the policy increased positively.

Adult↗
PubMed1984

A low-cost chromatograph data-collection system.

A data collection system has been constructed, based on the low-cost BBC microcomputer, which provides for the digitization and storage of the data from one or more g.l.c. or h.p.l.c. instruments, or from other data sources with similar data rates. The data can be observed during collection on the graphics screen, and are then stored on disk for subsequent processing. This processing is designed to be interactive, so that the operator can influence decisions about base-line drifts, peak separations, etc. when integrating the peaks, and can decide which peaks are to be stored in a time/intensity record, on the basis of a visual display of the trace. A low cost multi-channel precision ADC, using isolated voltage-to-frequency transducers sited at the sources of data, and multiple counters at the computer, may be used to measure several signals simultaneously even when they originate at some distance from the computer, and extra memory can also be added to the BBC microcomputer to allow temporary storage of data. The software is written in machine code (for the data collection) and BASIC (for the analysis routines) so that modifications to the latter routines can be made easily. The user interface is suitable for routine users who have no computing experience.

Chromatography↗
PubMed1984

Hospitals for the disabled.

Current policy in the United Kingdom is that disabled people under the age of 65 who require hospital care because of their disability are cared for in hospitals and wards separate from geriatric patients. A number of Young Disabled Units have opened during the past 15 years but have been subject to criticism. This survey suggests that much of the criticism is justified--many units are badly designed, poorly staffed, and have ineffective operational policies. However, some units are attempting to provide a therapeutic and stimulating environment and by emulating them Young Disabled Units may find a useful and uncontroversial role in the spectrum of services for the disabled.

Adult↗
PubMed1978

An evaluation of undergraduate family care programs.

Evaluation of the many new family care programs (FCP), and others of similar intent, however defined, is as essential as determining the value of any other curriculum change. Replies to a questionnaire from 101 U.S. and 15 Canadian medical schools indicated that 80% of the former and 93% of the latter had FCPs; 35% and 29%, respectively, were not evaluating their program by any method. No single evaluative technique was used by more than 42% of the American medical schools. A review of the literature on FCPs frequently indicated that the conclusions that could be drawn about the programs were ambiguous. Students in the University of Cincinnati Medical Center FCPs elected family practice or pediatric internships significantly more often than did the FCP nonparticipants, but they indicated that the program had little effect on this choice, despite almost uniformly favorable testimonials. We discuss the possibility that FCPs may be educating the wrong students, that FCPs, if not reinforced in other clinical areas, may have few lasting effects on student attitudes or career choice, and that we may be asking the wrong questions, and with inadequate methods.

Adult↗