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Biomedical subjects

John J Morrison

Publications and source records attributed to John J Morrison.

5 recordsLinked to original sources

Preterm delivery.

Preterm delivery and its short-term and long-term sequelae constitute a serious problem in terms of mortality, disability, and cost to society. The incidence of preterm delivery, which has increased in recent years, is associated with various epidemiological and clinical risk factors. Results of randomised controlled trials suggest that attempts to reduce these risk factors by use of drugs are limited by side-effects and poor efficacy. An improved understanding of the physiological pathways that regulate uterine contraction and relaxation in animals and people has, however, helped to define the complex processes that underlie parturition (term and preterm), and has led to new scientific approaches for myometrial modulation. The continuing elucidation of the mechanisms that regulate preterm labour, combined with rigorous clinical assessment, offer hope for future solutions.

Female↗

Polyamine effects on human myometrial contractility.

OBJECTIVE: This study was undertaken to investigate the effects of the polyamine spermine on human uterine contractility. STUDY DESIGN: Under physiologic conditions, an isometric tension recording was performed in isolated myometrial strips from biopsy specimens obtained at elective cesarean delivery (n = 24 specimens) and from premenopausal hysterectomy specimens (n = 6 specimens). The effects of spermine (1 micromol/L-10 mmol/L in cumulative doses) on spontaneous, agonist-induced myometrial contractions were measured, and dose response curves were constructed. The pD(2) (-log EC(50)) values and the maximal inhibition values achieved were compared for spontaneous and agonist-induced contractions. RESULTS: Spermine exerted a potent relaxant effect on all spontaneous and agonist-induced myometrial contractions, with mean maximal inhibition values between 62.8% +/- 4.3% and 91.4% +/- 1.8% and pD(2) values between 2.66 +/- 0.23 and 4.01 +/- 0.20. Its inhibitory effect varied significantly with different contraction types (pD(2), P <.05; mean maximal inhibition, P <.001), and it was least potent on BAY K 8644-elicited contractions (pD(2), P <.05; mean maximal inhibition, P <.01). CONCLUSION: The polyamine spermine exerts a potent relaxant effect on human uterine tissue. This effect appears to be mediated, at least partially, by calcium antagonism. Polyamines may play a role in the maintenance of uterine quiescence during pregnancy.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

Beta2- and beta3-adrenoreceptor agonists: human myometrial selectivity and effects on umbilical artery tone.

OBJECTIVE: The purpose of this study was to investigate the functional selectivity of the beta(3)-adrenoreceptor agonist BRL 37344 and the beta(2)-adrenoreceptor agonist ritodrine for their putative receptors in human pregnant myometrium in vitro and to examine the possibility that BRL 37344 may exert an effect on other beta-adrenoreceptor subtypes. This study also aimed comparatively to evaluate the in vitro effects of BRL 37344 and ritodrine on human vascular tissue tone. STUDY DESIGN: The effects of BRL 37344 (1 nmol/L-100 micromol/L) and ritodrine (1 nmol/L-100 micromol/L) on isometric tension recordings that were performed in isolated myometrial strips that were obtained at elective cesarean delivery and in human umbilical artery rings that were obtained at term were measured. Antagonism of the effects of BRL 37344 and ritodrine in human myometrial tissue was investigated with the antagonists butoxamine (1 micromol/L), propranolol (1 micromol/L), and bupranolol (1 micromol/L). The concentrations that produced a 50% maximal effect, the mean maximal inhibition that was achieved, and the percentage of contractility that was observed were compared. RESULTS: Bupranolol (n = 6), but not butoxamine (n = 6) or propranolol (n = 6), antagonized the relaxant effects of BRL 37344 in human pregnant myometrium; all three compounds (n = 6, respectively) antagonized the effects of ritodrine. At concentrations of >1 micromol/L, ritodrine exerted a significantly more potent vasodilatory effect than BRL 37344 on human umbilical artery tone (P <.01). CONCLUSION: The relaxant effects of BRL 37344 appear to be mediated solely through the beta(3)-adrenoreceptor agonist, although ritodrine may exert an effect on beta(1)-, beta(2)-, and beta(3)-adrenoreceptor agonists. This and the reduction in vascular tissue effects observed with BRL 37344 suggest that uterine beta(3)-adrenoreceptor modulation may provide a novel scientific approach to tocolysis with fewer vascular adverse effects.

Adrenergic beta-2 Receptor Agonists↗

Preterm birth.

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Adrenal Cortex Hormones↗

Preterm birth.

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Adrenal Cortex Hormones↗