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Biomedical subjects

M R Rubin

Publications and source records attributed to M R Rubin.

22 records · Page 2Linked to original sources
PubMed1981

Effect of bethanechol or vagal nerve stimulation on ileocecal sphincter pressure in the cat.

Ileocecal sphincter pressure was studied in the cat, using an open-tipped perfused catheter system. Ileocecal sphincter pressure was measured under basal conditions and in response to bethanechol or direct vagal nerve electrical stimulation. The pressure was 26.1 +/- 5.0 mmHg basally, and was unaltered by section of either or both cervical vagi (p less than 0.05). Peripheral cervical vagal stimulation gave a 9.1 +/- 1.1 mmHg increase in ileocecal sphincter pressure (p less than 0.05) but central stimulation had no effect on ileocecal sphincter pressure. The ileocecal sphincter response to peripheral vagal nerve stimulation was antagonized completely by propranolol or phentolamine. Bethanechol gave a dose-response increase in ileocecal sphincter pressure with a maximal response of 18.0 +/- 2.9 mmHg at 50.0 microgram/kg (p less than 0.01). The ileocecal sphincter relaxed with ileal distension and contracted with colonic distension. These studies indicate that (a) the ileocecal sphincter shows an excitatory response to vagal stimulation and cholinergic agonists; (b) basal ileocecal sphincter pressure is independent of the vagi; (c) ileocecal sphincter inhibition can be initiated by ileal distension but not by vagal stimulation.

Animals↗
PubMedDate not supplied

The effect of heavy resistance exercise on the circadian rhythm of salivary testosterone in men.

Circadian rhythms of serum testosterone concentrations in men have been shown, in general, to be highest in the morning and lowest in the evening. Thus, the purpose of this investigation was to determine the effects of acute resistance exercise upon the waking circadian rhythm of salivary testosterone over 2 days (with or without resistance exercise). The subjects included ten resistance-trained men (with at least 1 year of lifting experience) with the following characteristics [mean (SD)]: age 21.6 (1.1) years; height 177.8 (9.5) cm; body mass 80.5 (11.5) kg; percent body fat 7.9 (1.7)%. A matched, randomized, crossover study design was used such that each subject was tested under both the resistance exercise and control (no exercise) conditions. The resistance exercise protocol consisted of ten exercises performed for three sets of ten repetitions maximum with 2 min of rest between sets. Saliva sample 1 was collected at 0615 hours and resistance exercise began immediately afterwards at approximately 0620 hours, and sample 2 was collected at 0700 hours, which corresponded approximately to a mid-exercise (or control) time point. Saliva samples were then obtained every hour on the hour from 0800 hours until 2200 hours. No significant differences were observed between the exercise and resting conditions for salivary testosterone, with the exception of a significant decrease at 0700 hours during the resistance exercise protocol. The results of this investigation indicate that resistance exercise does not affect the circadian pattern of salivary testosterone secretion over a 16-h waking period in resistance-trained men.

Adult↗