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Biomedical subjects

G M Vaughan

Publications and source records attributed to G M Vaughan.

At least 19 recordsLinked to original sources
PubMed1991

Dissociation of blood volume and flow in regulation of salt and water balance in burn patients.

The relationship between effective blood volume and related hormones in burn patients following resuscitation is not well understood. Previous reports have suggested that hormone secretion is altered by a resetting of neural control mechanisms. Serum and urine sodium, plasma renin activity, serum ADH, cardiac index, effective renal plasma flow, and total blood volume were measured in seven burn patients (mean age, total burn size, and postburn day: 32 years, 56%, and 9 days, respectively). The same values (with the exception of cardiac index and blood volume) were measured in 10 control patients (mean age, 24 years). The blood volume of patients was measured by 51chromium red blood cell (RBC) labeling and compared to normal predicted values based on body surface area and sex. Mean serum sodium and osmolality were 138 mmol/L (millimolar) and 286 mosm/kg, respectively, in both patients and control subjects. Mean +/- standard error of the mean total blood volume in the patients was low, 81% +/- 4% of predicted values. Cardiac index and renal plasma flow were significantly elevated. Plasma renin activity and antidiuretic hormone (ADH) levels were elevated and altered in the direction expected from blood volume measurements despite the findings of increased blood flow. Dissociation of organ flow and hormonal response suggests that simultaneous direct blood volume measurements are necessary to elucidate factors other than altered neural control settings to explain hormonal changes in the flow phase of injury. Depressed total blood volume appears to promote elevated ADH levels in burn patients following resuscitation. Whether there is an additional role of altered neural control settings remains to be established.

Adrenocorticotropic Hormone↗
PubMed1979

Low- and high-dose intravenous insulin therapy for diabetic ketoacidosis.

We compared low-dose, continuous insulin infusion with a conventional high-dose intravenous bolus method of insulin administration in 18 episodes of diabetic ketoacidosis. The average rate of reduction in serum glucose concentration was 9.5 +/- 3.8%/hr in the continuous infusion group and 10.7 +/- 4.7%/hr in the bolus group. Arterial blood pH was corrected to 7.35 by 9.9 +/- 2.6/hours in the continuous infusion group and by 10.4 +/- 3.2/hours in the bolus group. The above means are not significantly different between groups. By the time pH was corrected to 7.35, patients in the continuous infusion group had received 121 +/- 44 units of insulin, whereas those in the bolus group had received 326 +/- 152 units. The continuous low-dose insulin infusion method is as safe and efficacious as the conventional high-dose intravenous bolus method.

Blood Glucose↗
PubMed1979

Rapid melatonin transients.

Two normal male subjects exhibited rapid pulses of melatonin concentration in plasma, apparently unrelated to stages of sleep and undisturbed with spontaneous waking during the night. Pulse intervals of approximately 8 and 12 min., respectively, for subjects 1 and 2, were associated with excursions of 35% and 33% of the nadir or 28% and 26% of the mean value. The pulses were detected with a 2.5 min. sampling interval.

Adult↗
PubMed1978

Effects of melatonin and natural and synthetic analogues of arginine vasotocin on plasma prolactin levels in adult male rats.

A significant elevation in plasma prolactin was observed 10 min following the intravenous injection of 100 microgram of melatonin into either estrogen-progesterone (EP) primed or into nonsteroid-treated male rats. 60 min postinjection in the EP primed rat, the groups treated with 100 microgram or 10 mg of melatonin had signficantly elevated plasma prolactin levels while no effect was observed with these same doses in the nonsteroid-treated rats. Compared to diluent-treated controls, a significant elevation in plasma prolactin was observed at 10, 20 and 60 min following the intravenous injection of either 1 microgram arginine vasotocin (AVT) or 1 mg melatonin into EP primed male rats. A consistent rise in plasma prolactin was also evident after the injection of 1 microgram of either arginine vasopressin, lysine vasopressin or AVT. Oxytocin had no effect on plasma prolactin values. The intravenous administration of 1 microgram of (deamino-1,6 dicarba, 8-arginine)-vasotocin caused a significant elevation of plasma prolactin 10 and 20 min after injection. However, the injection of another analogue of AVT, (4-leucine, 8-arginine)-vasotocin, had no effect on prolactin release at the time points measured.

Animals↗
PubMed1978

Overnight plasma profiles of melatonin and certain adenohypophyseal hormones in men.

Melatonin levels exhibited a day-night rhythm with highest levels at night. Nocturnal plasma melatonin concentrations were unrelated to sleep stages, whereas secretion of GH was temporally related to slow wave sleep. Levels of corticotropin rose in the later sleep cycles. We found no relationship between endogenous nocturnal melatonin and adenohypophyseal hormone levels. The results indicate that in young men nocturnal levels of melatonin are controlled separately from those of LH, PRL, corticotropin, and GH.

Adrenocorticotropic Hormone↗
PubMed1977

Stimulation of rat prolactin secretion in vivo by arginine vasotocin: influence of age of solution, nighttime administration, and dose.

In male rats pretreated for 3 days with 50 microgram of estradiol benzoate (E) and 25 mg of progesterone (P), the i.v. administration of 1 microgram of arginine vasotocin (AVT) from solutions that were 0, 6, 24 or 48 h old caused a significant rise in plasma prolactin (Prl) 10 min after injection. In the 2nd experiment, the i.v. injection of 1 microgram AVT into EP-primed adult male rats at either 01:00 (during darkness) or 13:00 h (during light) resulted in a significant and similar elevation in plasma Prl levels. In the 3rd experiment, normal adult male rats under urethane anaesthesia were given an i.v. injection of diluent or of 100 ng, 1 microgram or 10 microgram AVT. A significant rise in plasma Prl was observed at 10 and 20 min following injection only in the group treated with 1 microgram AVT. In none of these experiments did AVT alter the content of pituitary Prl.

Animals↗
PubMed1976

Influence of melatonin, constant light, or blinding on reproductive system of gerbils (Meriones unguiculatus).

Male and female gerbils were implanted s.c. with a pellet containing 2 mg melatonin/23 mg beeswax every 2 weeks for a total of 3 implants. A significant depression of ovarian and uterine weight was noted in female gerbils receiving melatonin implants. In the melatonin-treated male gerbils, growth of the accessory organs was significantly inhibited although testis size was not depressed.

Animals↗
PubMed1976

Prolactin-releasing and release-inhibiting factor activities in the bovine, rat, and human pineal gland: in vitro and in vivo studies.

The effects of crude extracts of bovine, rat, and human pineal glands on prolactin (PRL) release were studied using an in vitro system. In addition, the effects of a known pineal constituent, arginine vasotocin (AVT), and crude bovine pineal extract (bPE) on PRL secretion were studied in vivo. Normal male rat hemipituitaries (HP), incubated with bPE (13 mg tissue/HP)released 200%, 150%, and 285% more PRL into the medium than did their corresponding untreated control halves incubated in either Medium 199 alone, hypothalamic extract, or cerebral cortical extract, respectively. HP incubated with either rat (6 mg of tissue/HP) or human (25 mg of tissue/HP) pineal extract released 110% and 75% more PRL, respectively, than did their corresponding untreated control halves. HP exposed to 10 mg tissue eq of either bovine pineal fraction A1 or bovine pineal fraction A3 released 88% and 63%, respectively, less PRL than did their corresponding untreated control halves incubated in Krebs-Ringer Bicarbonate (KRB) medium. Quantitites of melatonin, thyrotropin-releasing hormone (TRH), or estrogen, comparable to those found in the pineal, had no significant effect on PRL secretion in vitro. The iv injection of either bPE (90 mg tissue/rat) or AVT (10 mug/rat) into estrogen and progesterone-treated male rats resulted in a 40% and 138% increase, respectively, in plasma PRL titers, 10 min after injection, over pre-injection control levels. The per cent of increase in plasma PRL levels in these animals was significantly greater than that observed in control rats receiving either saline or cortical extract. The results suggest that crude extracts of pineal glands of three different species contain prolactin-releasing factor (PRF) activity which is probably not due to any endogenous melatonin, TRH, or estrogen that may be present. Conversely, two bovine pineal fractions, A1 and A3, appeared to exhibit prolactin-inhibiting factor (PIF) activity. We have concluded that the pineal gland may serve as an alternate or supplemental source of PRF and/or PIF.

Aged↗
PubMed1976

Dose-dependent prolactin releasing activity of arginine vasotocin in intact and pinealectomized estrogen-progesterone treated adult male rats.

Estrogen-progesterone (EP) treated adult male rats were injected intravenously (iv) with 0.1, 1 or 10 mug arginine vasotocin (AVT) or Ringers lactate solution. A significant dose-related rise in plasma prolactin was evident 10 min after injection with AVT. In a second experiment, sham-operated or pinealectomized EP-treated male rats were injected iv with 0.1 or 1 mug AVT or diluent. Plasma prolactin was significantly elevated in both sham-operated and pinealectomized groups at both 10 and 20 min post-injection of 1 mug AVT. These results indicate that AVT has prolactin-releasing activity and that this activity is not dependent upon the presence of an intact pineal gland.

Animals↗
PubMed1976

Nocturnal elevation of plasma melatonin and urinary 5-hydroxyindoleacetic acid in young men: attempts at modification by brief changes in environmental lighting and sleep and by autonomic drugs.

In order to determine whether the human pattern of circulating melatonin resembles that previously described in lower animals, men 19-32 years old were exposed to a light-dark cycle with 14 hours of light per day (L:D 14:10). In whites and blacks, nocturnal (dark phase, sleeping) melatonin levels were almost always elevated to 0.05-0.1 ng/ml plasma compared with lower or undetectable levels during the day, measured by the tadpole bioassay. Thin-layer migration of bioactive material was identical to that for melatonin standard. A rhythm with nocturnal elevation of urinary 5-hydroxyindoleacetic acid (5-HIAA) was observed. Nocturnal (sleep phase) rise in blood melatonin (but not urinary 5-HIAA) continued during 21/2 day-night cycle lengths after the onset of constant light. Though the dark phase plasma melatonin rise was less marked after reversal of the sleep-wake cycle (no change in the light cycle), dark phase rise in urinary 5-HIAA continued. Though marked cardiovascular and other effects were produced by intravenous isoproterenol or scopolamine, no definite effect on melatonin levels was observed after either drug during the light phase in waking subjects.

Adult↗
PubMed1976

Inhibition of human chorionic gonadotrophin-induced hypertrophy of the ovaries and uterus in immature mice by some pineal indoles, 6-hydroxymelatonin and arginine vasotocin.

Administration of the indoles 5-methoxytryptophol, 6-hydroxymelatonin, melatonin, N-acetylserotonin or 5-methoxyindole-3-acetic acid (six 100-mug injections given at intervals of 12 h) inhibited both the absolute and relative ovarian and uterine weights of immature female mice pre-treated with HCG. Administration of 5-hydroxytryptophol or 5-methoxytryptamine at the same dosage inhibited ovarian but not uterine hypertrophy in mice pre-treated with HCG.

Animals↗