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C MacGregor

Publications and source records attributed to C MacGregor.

At least 19 recordsLinked to original sources
PubMed1998

The situational risks of young drivers: the influence of passengers, time of day and day of week on accident rates.

This paper provides new insight into the situational risks of young drivers, especially in terms of the passenger effect. Two 1988 data bases from the Ontario Ministry of Transportation were used to estimate accident involvement rates by number of passengers, time of day and day of the week--first individually and then for all two-way combinations with the passenger variable. Accident data were derived from police reports for all accidents involving a fatality, personal injury or property damage exceeding $700. Estimates of exposure were based on the most up-to-date provincial travel survey available at the time of the study. Results indicate that the accident involvement rates of 16-19 year old drivers are higher than those of 20-24 and 25-59 year olds in all situations that were examined, but that they were disproportionately high on weekends, at nighttime and with passengers. The results of the passenger variable are particularly interesting because, unlike weekends and nighttime, the negative effect of passengers on overall accident rates was evident only for 16-19 year old drivers. This effect was quite pronounced for both sexes, with accident involvement rates being approximately twice as high with passengers as without. For 16-19 year olds, accident rates were also significantly higher for two or more passengers versus one passenger. The highest rates for this age group occurred with passengers at nighttime. Possible explanations for these patterns and policy implications are discussed.

Accidents, Traffic↗
PubMed1996

Major lower limb amputation for vascular disease in the Grampian area: the outcome of rehabilitation.

The outcome of lower limb amputation in the Grampian Region has been studied. In the years 1990-1991, 93 patients had 104 amputations for vascular disease. Rehabilitation was supervised by a multidisciplinary team. The amputation level was: unilateral and below-knee (BKA), 55 patients; unilateral and above-knee (AKA), 27 patients; and bilateral (BA) in 11 patients. At a median follow-up of 27 months, survivors who had had a limb fitted were sent a questionnaire to assess their physical mobility. The response rate was 95%. There were 33 (60%) survivors in the BKA group. Fourteen patients (25%) indicated good mobility and seven (13%) indicated fair mobility. There were five (19%) survivors in the AKA group, only one of whom described fair mobility with a prosthetic limb. There were 5 (46%) survivors of BA. Two described good and one fair mobility. Although vascular amputees have a high mortality rate, physical mobility tends to be good in those fitted with a prosthesis after BKA.

Activities of Daily Living↗
PubMed1989

Two distinct pathways for cAMP-mediated down-regulation of the beta 2-adrenergic receptor. Phosphorylation of the receptor and regulation of its mRNA level.

We have studied cyclic AMP-mediated regulation of the beta 2-adrenergic receptor (beta 2AR). The effects of cAMP were assessed in Chinese hamster fibroblast (CHW) cells expressing either the wild type human beta 2AR receptor (CH-beta 2) or mutated forms of the receptor lacking the consensus sequences for phosphorylation by the cAMP-dependent protein kinase. Treatment of the CH-beta 2 cells with the cAMP analogue dibutyryl cAMP (Bt2cAMP) induces a time-dependent "down-regulation" of the number of beta 2AR. This down-regulation of the receptors is accompanied by a decline in the steady state level of beta 2AR mRNA. Moreover, the treatment with Bt2cAMP induces an increase in the phosphorylation level of the membrane-associated beta 2AR. Both the reduction in beta 2AR mRNA and the enhanced phosphorylation of the receptor are rapid and precede the loss of receptor. The down-regulation of beta 2AR induced by Bt2cAMP is concentration-dependent and mimicked by the other biologically active cyclic nucleotide analogue, 8-Br-cAMP, by forskolin, and by the phosphodiesterase inhibitor, isobutylmethylxanthine. In the CHW cell lines expressing receptors lacking the putative protein kinase A phosphorylation sites, the Bt2cAMP-induced phosphorylation of beta 2AR is completely abolished. In these cells the down-regulation of beta 2AR receptor number produced by cAMP is significantly slowed, whereas the reduction in beta 2AR mRNA level is equivalent to that observed in CH-beta 2 cells. These data indicate that there are at least two pathways by which cAMP may decrease the number of beta 2ARs in cells: one involves phosphorylation of the receptor by the cAMP-dependent protein kinase and the other leads to a reduction in steady state beta 2AR mRNA levels.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Functional activity and regulation of human beta 2-adrenergic receptors expressed in Xenopus oocytes.

The recently cloned human beta-adrenergic cDNA and several mutated forms have been expressed in Xenopus laevis oocytes by injection of RNA made from the cDNA under the control of the bacteriophage SP6 promoter. The cDNA and gene of the beta 2-adrenergic receptor possess the unusual feature of having a second upstream ATG (-101 base pairs) and a 19-codon open reading frame 5' to the initiator methionine codon of the receptor (Kobilka, B. K., Dixon, R. A. F., Frielle, T., Dohlman, H. G., Bolanowski, M., Sigal, I. S., Yang-Feng, T. L., Francke, U., Caron, M. G., and Lefkowitz, R. J. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 46-50). RNA lacking this upstream AUG and open reading frame was translated approximately 10-fold more efficiently both in an in vitro rabbit reticulocyte system and in oocytes. Injected oocytes but not water injected controls expressed typical beta 2-adrenergic receptors as assessed by ligand binding (450 fmol/mg membrane protein) and catecholamine-stimulated adenylate cyclase (approximately 20 fold). Moreover, these receptors displayed typical agonist-induced homologous desensitization when oocytes were incubated with isoproterenol at room temperature for 3-24 h. Among a series of mutations, truncations of the membrane-anchored core of the receptor eliminated receptor binding and cyclase stimulating activity. In contrast, disruption of one of the cAMP-dependent protein kinase phosphorylation sites or removal of the serine/threonine-rich carboxyl terminus had little or no effect on these functions or on the extent of agonist-induced desensitization relative to that observed with native receptor. These studies validate the beta 2-adrenergic nature of the cloned human beta-adrenergic cDNA, document the utility of the Xenopus oocyte system for studying functional and regulatory properties of receptors coupled to adenylate cyclase, and suggest the possibility that elements in the 5' untranslated region of the beta 2-adrenergic receptor RNA may regulate its translation in vivo.

Adenylyl Cyclases↗
PubMed1986

Signal peptidases.

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Amino Acid Sequence↗
PubMed1983

[Program for instruction in comprehensive general medicine: conceptualization and strategies for its evaluation].

This article describes the concepts and strategies underlying the evaluation of the Comprehensive General Medicine Program of the School of Medicine of the Autonomous National University of Mexico. The exact purpose of that evaluation, done in 1982, was to strengthen and redirect the lines of this program's current development, which had been conceived since its inception in 1974 as an experimental study plan based on a system of modular and tutorial instruction. The article describes the identified conceptual, methodological, logistic, operational and attitudinal obstacles to this evaluation process. The methodology involves a sequence consisting in the evaluational experiences of basically innovative programs of undergraduate medical instruction, the selection of an evaluation model, identification of the aspects to be evaluated, the determination of priorities, and the definition of specific evaluation projects. From the aspects identified and given priority the following 12 evaluation projects emerged: curriculum review, follow-up of alumni, instruction materials, tutors, integration of knowledge, student performance, instructional activities, students in social service, student enrollments, dropping out, professional examination, and education administration.

Curriculum↗
PubMed1977

Prolactin responsiveness to TRH in amenorrheic women with and without galactorrhea.

Sixty women were given intravenous injection of 200 microgram TRH to assess its diagnostic potential as a stimulus to PRL release. Following the administration of TRH, there was a prompt increase in serum PRL to 614.6%, to 296%, to 282.1%, and 34% in normal women, amenorrheic patients, non tumoral galactorrheic cases, and patients with pituitary tumors respectively. The TRH response above baseline of PRL levels was statistically significant in all groups, but the women with pituitary tumors which showed a blunted response. The per cent of increment of PRL levels after TRH was similar in amenorrheic women regardless the presence or not of galactorrhea; this increase was significantly greater than in patients with pituitary tumors (p less than 0.01). The per cent of increment above baseline of PRL was significantly greater in menstruating women than in amenorrheic patients (p less than 0.001). In basis of present data: 1) there is a diminished PRL secretion after TRH in amenorrheic women regardless the presence of galactorrhea or hyperprolactinemia; 2) a blunted response to TRH in hyperprolactinemic women may be indicative of a pituitary tumor.

Amenorrhea↗
PubMed1976

Studies on maternal mortality in Mexico.

The sociocultural, psychological, and medical effects of maternal death are described and analyzed for the purpose of appraising the value of the given death as a measure of the quality of medical care. The work of the Maternal Mortality Committee of the Hospital de Gineco-Obstetetricia No. 1 of the Mexican Social Security Institute over its three years of operation and some results on responsiblity for death and its possible predictabilty are presented. The results show that it is necessary to broaden the Committee's functions in a social, professional, and institutional context so that the indicated factors may be objectively assessed and also that the Committee be transformed into a dynamic organism that will contribute to solving the problem. Recommendations for the operation of the Maternal Mortality Committees are given.

Adolescent↗
PubMed1976

The effect of oral administration of thyrotropin-releasing hormone on lactation.

Sixteen puerperal women between the ages of 17-30 years, were studied in a double blind trial during the four weeks postpartum. Eight women received orally 20 mg of synthetic TRH three times a day, 30 minutes before the corresponding breast feeding; the remaining group received a placebo in the same fashion. The women receiving TRH exhibited higher basal concentrations of serum PRL as well as a higher increment in response to suckling; however, the PRL concentrations before and after breast feeding in this group were similar to those of the control group by the fourth week postpartum. TRH treatment showed no effect on the yield or content of milk during the four-week period. In a conjoint study, PRL concentrations did not rise after TRH administration in women with defective lactation, suggesting that some impairment of the PRL release mechanism was present. TRH caused no clinical hyperthyroidism in the mothers nor in the children. Serial determinations of serum T3 and TBG revealed values within the normal limits. It was also observed that TRH administration had no effect on FSH and LH secretion, and gonadotropin secretion was not inhibited despite of the increments on PRL concentrations. In both groups, suckling had no effect on serum levels of pituitary gonadotropins determined before and after breast feeding. We have concluded that in full lactating mothers: a) the oral administration of TRH produced a marked increment in PRL concentration but no significant augmentation of milk production was observed; b) in some cases of hypogalactia, TRH did not improve the milk production; and c) the PRL-enhanced secretion showed no effect on gonadotropin secretion.

Administration, Oral↗
PubMed1976

Effect of prolactin suppression on gonadotrophic secretion in the puerperium.

Serum levels of prolactin (PRL), FSH, LH and oestradiol-17 beta were determined by radioimmunoassay in 57 lactating women and in 20 women in whom lactation was inhibited by ergocryptine (CS-154). Women who breast fed their infants exhibited high PRL levels which abruptly declined within 48 h post-partum, and remained low for the duration of the study. Serum FSH was undetectable during the first week post-partum in lactating as well as in CB-154 treated women. Thereafter, lactating women showed increasing FSH levels which reached a maximum by the third week post-partum. These FSH values were higher in lactating women than in the CBS-154 treated group. In contrast, LH levels were higher in those women receiving CB-154. Serum oestradiol-17 beta remained in low levels throughout the study, and no difference was observed between the two groups of subjects. From these results it seems that: 1) inhibition of PRL secretion leads to a faster recovery of gonadotrophin secretion toward the "menstrual type", and 2) PRL suppression produces no effect on the ovarian oestrogen production.

Adolescent↗
PubMed1975

[Puerperium].

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Female↗