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Biomedical subjects

J M Walker

Publications and source records attributed to J M Walker.

At least 253 records · Page 14Linked to original sources
PubMed1983

Cessation of thermoregulation during REM sleep in the pocket mouse.

Electrophysiological sleep patterns, respiration frequency, brain temperature (Tbr), and ear temperature (Tear) were recorded from five pocket mice (Perognathus longimembris) exposed to ambient temperatures (Ta) of 22.5, 27.5, 32.5, and 35.0 degrees C. Thermoregulation was curtailed during rapid-eye-movement (REM) sleep, since Tbr declined following REM onsets at Ta's below thermoneutrality and increased at Ta's above thermoneutrality. Tbr subsequently returned to pre-REM levels following the termination of each REM episode. Respiratory frequency was inversely related to Ta but not as strongly during REM sleep as during slow-wave sleep (SWS). These results confirm previous reports of loss of thermoregulatory ability during REM sleep. Mean duration and proportions of wakefulness, SWS, and REM sleep were unaffected by Ta, consistent with earlier findings on ground squirrels, but differing from reports of decreased REM sleep in nonhibernators. Hibernators may have lower peripheral thermosensitivities than nonhibernators, facilitating sleep at low ambient temperatures and during entrance into hibernation.

Animals↗
PubMed1982

Nonopiate effects of dynorphin and des-Tyr-dynorphin.

Intracerebroventricular administration of dynorphin produced potent and long-lasting effects on motor function and the electroencephalogram in rats. In addition, local iontophoretic or pressure ejection of dynorphin consistently inhibited hippocampal unit activity. None of these effects were significantly affected by naloxone even at high doses. Moreover, a fragment of dynorphin that failed to displace any of a number of tritiated narcotics from rat brain homogenates produced similar effects on these physiological measures in vivo. On the basis of a variety of criteria for "opiate action," the results suggest that a second biologically active site within the dynorphin sequence is capable of quite potent but nonopiate effects.

Action Potentials↗
PubMed1982

A prevention and early intervention mental health program for disadvantaged pre-school children.

In this study, 155 disadvantaged pre-school children, ages 3 to 6, were screened for developmental delays using the Cooperative Pre-school Inventory as the primary evaluation tool. Thirty-eight children participated in the experimental group and 20 children were designated the control group. Experimental group children received developmental therapy and their regular classroom experience. In addition, intervention was provided to parents and teachers in order to affect the child's total environment more positively. The control group received only classroom experience. Sixty-five percent of the control group passed the Cooperative Preschool Inventory per-test compared to 50 percent of the experimental group. On the Cooperative Preschool Inventory post-test, 100 percent of the experimental group passed, compared to only 85 percent of the control group. These results suggest that for disadvantaged children early intervention of developmental therapy and classroom experience help eliminate their developmental delays and provide them with age-appropriate developmental skills.

Child↗
PubMed1981

Hibernation at moderate temperatures: a continuation of slow wave sleep.

Golden-mantled ground squirrels (Citellus lateralis) displayed virtually continuous electrophysiological states of sleep when hibernating at moderate ambient temperatures (22 degrees C). Rapid-eye-movement sleep progressively diminished with the fall in body temperature so that at a body temperature of 23 degrees C it was completely absent. At this temperature hibernation was characterized by slow wave sleep isomorphic with slow wave sleep episodes at non-hibernating (euthermic) body temperatures.

Animals↗
PubMed1981

Induction of analgesia by central administration of ORG 2766, an analog of ACTH4--9.

Dose-dependent analgesia was produced by microinjection of ORG 2766 into the periaqueductal gray (PAG). This analgesia was found to be potent and long-lasting and occurred at doses which were equimolar to those necessary for morphine analgesia. The same doses failed to produce analgesia by the cerebroventricular route, suggesting that the PAG was the site of action of this effect. Naloxone failed to reduce the analgesia and morphine tolerant did not diminish the effect significantly. Additionally, ORG 2766 at concentrations up to 10 micrometer failed to inhibit binding of [3H]naloxone to brain opiate receptors in vitro. These results suggest a non-opiate mechanism of action and are discussed in terms of a proposed alpha-MSH or ACTH receptor.

Adrenocorticotropic Hormone↗
PubMed1981

The effects of high and low ambient temperatures on human sleep stages.

Six male subjects slept nude except for shorts on a bed made from nylon webbing at 5 different ambient temperatures (TaS): 21, 24, 29 (thermoneutrality), 34 and 37 degrees C. Standard electrophysiological recordings were obtained and analyzed for sleep stages. Temperature displayed a significant quadratic trends for nearly every sleep variable, such that TaS above or below thermoneutrality had similar effects on sleep patterns. Multiple comparisons showed that 21 degrees C was the most disruptive condition, and that cold TaS were generally more disruptive to sleep than warm TaS. There were marked individual differences in sensitivity of sleep to cold. Decreases in REM sleep in humans produced by heat or cold probably result from a general disruption of sleep processes rather than being specifically related to the status of the thermoregulatory system during REM sleep.

Adolescent↗
PubMed1981

Blockade of endogenous opiates reduces activity in the rat.

Naloxone (2 mg/kg, SC) was found to result in a substantial and significant reduction in general activity levels in the rat (90--120 days old). This effect was seen both under baseline conditions and after stress manipulations which would be expected to result in elevated levels of endogenous opiate peptides. Thus, under baseline conditions general activity was reduced to less than half of the saline control value thirty min after injection. Similarly, a reduction was seen after stress induced by a 30 min swim. While naloxone may have some non-opiate effects, these results support the view that endogenous opiate systems may play an important activational role in behavioral regulation, under baseline conditions and conditions of stress.

Animals↗
PubMed1981

Metabolism and thermoregulation during stages of sleep in humans exposed to heat and cold.

Electrophysiological stages of sleep, oxygen consumption (VO2), and skin (Tsk) and rectal (Tre) temperatures were recorded from six virtually naked male subjects exposed to ambient temperatures (Ta) of 21, 24, 29, 34, and 37 degrees C. VO2 increased during sleep as a whole as Ta departed from thermoneutrality (29 degrees C) and was significantly greater during rapid-eye-movement (REM) sleep than during adjacent nonrapid-eye-movement (NREM) periods at low and high Ta but not at 29 degrees C. Tsk showed small but significant increases during REM sleep at 29, 34, and 37 degrees C, but Tre did not change during REM sleep at any Ta. Shivering was present during wakefulness at 21 and 24 degrees C but occurred only occasionally during stages 1 and 2 sleep at 21 degrees C. The increases in VO2 and the absence of marked changes in vasomotor tone during REM sleep in the cold were unexpected and possibly indicate that REM sleep is not as thermally disruptive in humans as in other mammals.

Adolescent↗
PubMed1981

Guanfacine: a new centrally-acting antihypertensive agent.

The centrally-acting antihypertensive drug guanfacine was studied in a group of 11 moderate hypertensives. In doses of 2 mg daily, an average reduction in diastolic blood pressure of 10.8 mmHg was achieved. Side-effects were few when doses were maintained below 3 mg daily. The blood pressure reduction was associated with a fall in plasma renin activity and an average weight gain of 1.8 kg. When guanfacine was tried in 6 very severe hypertensives who had proved resistant to other antihypertensive drugs, a similar reduction in diastolic pressure of 7 mmHg was achieved using a dose of 3 mg daily. It is considered that guanfacine is a useful new antihypertensive drug, effective in mild hypertension, and side-effects are few if doses are maintained below 3 mg daily. Above this dose, side-effects became prominent, and these included sedation, dry mouth and constipation.

Adult↗
PubMed1980

Evidence for homologous actions of pro-opiocortin products.

alpha-Melanocyte-stimulating hormone (alpha-MSH), a modified fragment of adrenocorticotropic hormone, derives from the same biosynthetic route as beta-endorphin and is stored by the same arcuate neurons. Microinjection of alpha-melanocyte-stimulating hormone and several related peptides into the periaqueductal gray matter significantly reduced responsiveness to pain and had a behavioral profile similar to that produced by beta-endorphin.

Adrenocorticotropic Hormone↗