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Biomedical subjects

M Hunter

Publications and source records attributed to M Hunter.

At least 163 records · Page 9Linked to original sources
PubMed1983

The dependence of fluid secretion by mandibular salivary gland and pancreas on extracellular calcium.

Acetylcholine-stimulated fluid secretion from the perfused rabbit mandibular salivary gland was inhibited in a biphasic manner when extracellular calcium concentration was reduced in the range 5 X 10(-4) - 10(-5)M. An initial rapid inhibition was followed by partial recovery to a plateau, the level of which depended upon the calcium concentration. Since no recovery was observed during substitution of calcium by strontium, recovery may depend upon an increased membrane permeability to calcium. It is concluded that acetylcholine evokes fluid secretion in this gland by enhancing calcium entry from the extracellular space, an action which can be mimicked by the calcium ionophore A23187. Changes in the electrolyte composition of saliva during calcium-depletion were such as to suggest that ductal reabsorption of sodium and chloride, and secretion of potassium are inhibited as extracellular calcium concentration is reduced. Secretin-stimulated fluid secretion from the cat pancreas was unaffected when perfusate calcium concentration was reduced to 2.5 X 10(-6)M and carbachol-stimulated amylase secretion was only slightly reduced. Since the latter is a calcium-dependent process, the source of calcium is presumably intracellular. In both glands, reducing calcium to 1 X 10(-6)M caused rapid and irreversible inhibition of fluid secretion.

Acetylcholine↗
PubMed1982

A laboratory technique for the assessment of pain behavior.

The understanding and assessment of headache has been handicapped by inadequate assessment of pain behavior. The current study aimed to develop a simple laboratory technique to evaluate a headache sufferer's apparent oversensitivity to, and avoidance of, stimuli such as noise and bright lights. The results revealed that subjects could reliably calibrate the stimuli on a scale from "comfortable" to "definitely unpleasant." Significant group differentiation (controls/headache prone) was possible on the basis of auditory stimulus sensitivity, irrespective of current pain state. On the other hand, endurance time at an intense level differentiated subjects in pain from those pain-free, irrespective of group (headache/nonheadache). The advantages and potential of such an objective assessment of pain are discussed.

Adult↗
PubMed1982

Headache in a psychiatric population.

The frequency and quality of headaches reported by 300 psychiatric patients were analyzed and compared to findings drawn from a general practice sample. Migraine and tension headaches were commonly reported and were found to be considerably more severe and frequent among psychiatric patients than among those patients attending a general practice. However, few of the psychiatric patients regarded their headaches as a major problem. Those who were headache sufferers had significantly higher scores on a psychometric assessment of neurotic tendency and were more frequently diagnosed as suffering from neurons than were those who reported few or no headaches. There was no association between headache and the diagnosis of depression, but psychometric scores on depression were significantly higher among the headache cases. The scale may have been reflecting general psychiatric distress rather than depression as such. The possibility that headaches contribute significantly to psychiatric distress, and are not merely a symptom of such distress, is considered.

Adolescent↗
PubMed1981

Secretion of saliva by the rabbit mandibular gland in vitro: the role of anions.

Salivary glands form their secretions by first elaborating an isotonic plasma-like primary fluid in the endpieces and then modifying the composition of this secretion during its passage along the gland duct system. We have studied the role of extracellular anions in both primary secretion and ductal modification with a recently developed technique for isolation and perfusion of the rabbit mandibular gland. Neither of the major extracellular anions (Cl- or HCO-3) is essential for primary fluid secretion. HCO-3 can be removed altogether and replaced with Cl- without diminution in secretory rate, provided that extracellular pH is maintained at 7.4, and its replacement with acetate actually enhances secretion. Complete replacement of Cl- with Br- also enhances secretion and replacement with I-, NO-3, CH3SO-4 or isethionate supports secretion but at progressively diminishing rates. Our data do not yet allow us to distinguish between an electroneutral Na+-Cl- cotransport model or a double countertransport (Na+-H+ plus Cl--HCO-3) model as the basis of primary salivary secretion, or to propose any more suitable alternative model. With respect to ductal modification of the primary saliva, HCO-3 omission inhibits ductal Na+ absorption (i.e. salivary Na+ concentration rises). This inhibition is probably related to an effect of pH on the postulated Na+-H+ exchanges mechanism in the luminal duct membrane since it can also be induced by lowering perfusate pH, and reversed by substitution of perfusate HCO-3 with acetate (which enters saliva) but not HEPES (which does not enter the saliva). Substitution of perfusate Cl- with other anions seems not to inhibit ductal Na+ and K+ transport markedly.

Acetylcholine↗
PubMed1981

Inadequate corpus luteum function after the induction of ovulation in anoestrous ewes by LH-RH or an LH-RH agonist.

Scottish Blackface ewes were given LH-RH (3 x 30 micrograms i.v., at 90 min intervals) or D-Ser-(But)6-des Gly10 LH-Rh ethylamide (LH-RH agonist) as a single injection (8 or 40 micrograms) during anoestrus. Ovulation as judged by laparoscopy occurred in 8 of the 27 animals. Despite the fact that the LH-RH agonist induced a greater release of LH and FSH the different treatments had no effect on the number of ewes ovulating and within each treatment group there was no apparent difference in the amounts of gonadotrophins released between the ewes that did or did not ovulate. All ovulations resulted in the formation of CL associated with plasma progesterone concentrations of less than 1 ng/ml (1--5 ng/ml in the normal luteal phase). In comparison with CL of the normal cycle the induced CL were of lower weight and had reduced progesterone content and ability to secrete progesterone in vitro. However, the binding of hCG was equivalent to that of normal CL. These results suggest that the inadequate CL formed in anoestrous ewes after a single LH-RH injection have not developed the ability to synthesize and secrete progesterone in spite of the presence of normal amounts of LH receptors.

Animals↗
PubMed1978

Structure-activity relationships of eighteen somatostatin analogues on gastric secretion.

1. The effect of somatostatin and eighteen somatostatin analogues on pentagastrin-stimulated gastric acid and pepsin secretion was investigated in the conscious vagotomized cat prepared with chronic gastric fistulae. The majority of the analogues are peptides where D-amino acids are incorporated into the molecule instead of the natural L-isomers. 2. The ID50 for cyclic-somatostatin inhibition of near-maximal gastric acid secretion stimulated by pentagastrin 8 microgram kg-1 hr-1 was found to be 1.29 +/- 0.13 n-mole kg-1 hr-1. Pentagastrin-stimulated pepsin secretion had a lower threshold to somatostatin inhibition than did acid secretion. 3. D-Phe6, D-Phe7, D-Thr10, D-Thr12 and D-Phe6-D-Trp8 analogues all show low biological activity against the secretion of gastric acid and pepsin, growth hormone, insulin and glucagon. None of these analogues are antagonists of the cyclic-somatostatin inhibition of gastric secretion, suggesting that they have low affinity for this somatostatin receptor. 4. The analogues under investigation show parallel changes in activity against gastric and growth hormone secretion, suggesting a similarity between the gastric and growth hormone receptors for somatostatin. 5. D-Cys14 analogues are equipotent with or have a greater potency than cyclic-simatostatin in inhibiting the secretion of gastric acid, growth hormone and glucagon but show low insulin inhibiting activity.

Animals↗