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Biomedical subjects

H McGregor

Publications and source records attributed to H McGregor.

12 recordsLinked to original sources
PubMed2000

Exposure to prenatal carbon monoxide and postnatal hyperthermia: short and long-term effects on neurochemicals and neuroglia in the developing brain.

The effects of prenatal exposure to carbon monoxide (CO), a major component of cigarette smoke, was studied alone or in combination with postnatal hyperthermia, on the structural and neurochemical development of the postnatal brain at 1 and 8 weeks. Pregnant guinea pigs (n = 11) were exposed to 200 p.p.m CO for 10 h/day from midgestation until term (68 days), whereas control mothers (n = 10) breathed room air. On postnatal day 4, neonates from the control and CO-exposed pregnancies were exposed to hyperthermia (35 degrees C) for 75 min or remained at ambient (23 degrees C) temperature. Using semiquantitative immunohistochemical techniques the following neurotransmitter alterations were found in the medulla at 1 week: a decrease in met-enkephalin-immunoreactivity (IR) following postnatal hyperthermia and an increase in 5-hydroxytryptamine-IR following a combination of CO and hyperthermia. No alterations were observed in substance P- or tyrosine-hydroxylase-IR in any paradigm. At 8 weeks of age the combination of prenatal CO exposure followed by a brief hyperthermic stress postnatally resulted in lesions throughout the brain and an increase in glial fibrillary acidic protein-IR in the medulla. Such effects on brain development could be of relevance in cardiorespiratory control in the neonate and could have implications for the etiology of Sudden Infant Death Syndrome, where smoking and hyperthermia are major risk factors.

Animals↗
PubMed2000

Chronic prenatal exposure to carbon monoxide results in a reduction in tyrosine hydroxylase-immunoreactivity and an increase in choline acetyltransferase-immunoreactivity in the fetal medulla: implications for Sudden Infant Death Syndrome.

Maternal cigarette smoking during pregnancy is associated with a significantly increased risk of Sudden Infant Death Syndrome (SIDS). This study investigated the effects of prenatal exposure to carbon monoxide (CO), a major component of cigarette smoke, on the neuroglial and neurochemical development of the medulla in the fetal guinea pig. Pregnant guinea pigs were exposed to 200 p.p.m CO for 10 h per day from day 23-25 of gestation (term = 68 days) until day 61-63, at which time fetuses were removed and brains collected for analysis. Using immunohistochemistry and quantitative image analysis, examination of the medulla of CO-exposed fetuses revealed a significant decrease in tyrosine hydroxylase-immunoreactivity (TH-IR) in the nucleus tractus solitarius, dorsal motor nucleus of the vagus (DMV), area postrema, intermediate reticular nucleus, and the ventrolateral medulla (VLM), and a significant increase in choline acetyltransferase-immunoreactivity (ChAT-IR) in the DMV and hypoglossal nucleus compared with controls. There was no difference between groups in immunoreactivity for the m2 muscarinic acetylcholine receptor, substance P- or met-enkephalin in any of the medullary nuclei examined, nor was there evidence of reactive astrogliosis. The results show that prenatal exposure to CO affects cholinergic and catecholaminergic pathways in the medulla of the guinea pig fetus, particularly in cardiorespiratory centers, regions thought to be compromised in SIDS.

Animals↗
PubMed1997

Terror management theory and self-esteem: evidence that increased self-esteem reduces mortality salience effects.

On the basis of the terror management theory proposition that self-esteem provides protection against concerns about mortality, it was hypothesized that self-esteem would reduce the worldview defense produced by mortality salience (MS). The results of Experiments 1 and 2 confirmed this hypothesis by showing that individuals with high self-esteem (manipulated in Experiment 1; dispositional in Experiment 2) did not respond to MS with increased worldview defense, whereas individuals with moderate self-esteem did. The results of Experiment 3 suggested that the effects of the first 2 experiments may have occurred because high self-esteem facilitates the suppression of death constructs following MS.

Analysis of Variance↗
PubMed1985

Variable schedules of ibuprofen for ankle sprains.

In a study of 144 patients, with Grade 1 and 2 inversion injuries to the ankle sustained in sport, treatment with a non-steroidal anti-inflammatory was considerably superior to placebo with respect to joint tenderness, level of training and injury severity. No difference in efficacy could be determined between ibuprofen 2400 mg given in two or four equally divided daily doses. Ten patients withdrew from the study because of side effects, five from ibuprofen twice daily, three from ibuprofen four times daily and two from the placebo group. This study confirms the efficacy, flexibility and tolerability of high dose ibuprofen.

Adult↗
PubMed1979

The effects of social reinforcement on dominant and dependent mildly intellectually handicapped school-leavers.

The aim of this study was to replicate Exline & Messick's (1967) study of eye-contact interview behaviour with college students on a group of mildly intellectually handicapped students. Twenty subjects (mean CA 14.02 years, SD 0.45 years, mean IQ 72.0, SD 7.6) attending a metropolitan school for the mildly mentally handicapped were classified as dominant or dependent by teacher ratings and sociogram analysis. They were given large or small amounts of reinforcement for eye-contact when interviewed by their teacher. Although the study failed to replicate some of Exline & Messick's findings, results indicated a feedback rather than reward model in explaining the effects of social reinforcement on eye-contact in interviews. Implications for communication training for such intellectually handicapped students is discussed.

Adolescent↗
PubMed1977

Postcoital contraceptive effects of agonist analogs of luteinizing hormone-releasing hormone.

Various analogs of synthetic hypothalamic luteinizing hormone-releasing hormone (LH-RH) were evaluated for agonistic (ovulation-inducing), postcoital contraceptive, and direct uterotrophic activities. All analogs showing agonistic activity also possessed the ability to terminate pregnancy, as did LH-RH; there appeared to be a direct relationship between agonistic and postcoital potency and activity. The highly potent and active LH-RH agonist, D-[Ala]6-des-[Gly]10-pro9-ethylamide-LH-RH, proved to be the most potent and active postcoital preimplantational and postimplantational antifertility agent. In contrast to LH-RH, none of the analogs tested in the hypophysectomized animal produced a uterotrophic effect, revealing a selective extrapituitary effect of the parent hormone. The collective data demonstrate that peptides derived from LH-RH and bearing agonistic properties can terminate pregnancy postcoitally, via disruption of the pituitary-ovarian reproductive complex. Possible mechanisms are discussed, and the use of members of this neurohormonal class as potential profertility agents should be weighed with caution.

Animals↗