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Biomedical subjects

A J Lewy

Publications and source records attributed to A J Lewy.

89 records · Page 5Linked to original sources
PubMed1983

Effects of light on human melatonin production and the human circadian system.

Bright artificial light appears to have similar effects in humans as in other species. Bright light may therefore be used as a clinical research tool and as a therapeutic modality for treating certain biological rhythm disorders. Melatonin production appears to be a particularly useful "biological marker" for the human endogenous circadian pacemaker and the effects of light.

Animals↗
PubMed1983

Different types of melatonin circadian secretory rhythms in some blind subjects.

Six of 10 blind subjects had unusual melatonin circadian secretory patterns. One of these subjects, studied longitudinally, appeared to have a free-running melatonin secretory rhythm with a period of 24.7 h. Another subject, also studied longitudinally, appeared to secrete melatonin during the day (instead of during the night). Therefore, some blind subjects appear to have different types of circadian rhythm abnormalities. These findings along with previous work demonstrating suppression of human melatonin secretion by light suggest that the light-dark cycle may be important in the regulation of the human melatonin circadian secretory rhythm. These findings may stimulate more research on the endocrinological consequences of blindness as well as on the biological effects of light in humans.

Adult↗
PubMed1980

Light suppresses melatonin secretion in humans.

Bright artificial light suppressed nocturnal secretion of melatonin in six normal human subjects. Room light of less intensity, which is sufficient to suppress melatonin secretion in other mammals, failed to do so in humans. In contrast to the results of previous experiments in which ordinary room light was used, these findings establish that the human response to light is qualitatively similar to that of other mammals.

Circadian Rhythm↗
PubMed1980

Effects of melatonin and propranolol on sleep of the rat.

Melatonin and L-propranolol, which inhibits melatonin synthesis, were administered to rats at 07.45 h and 19.45 h. Melatonin given in the morning decreased non-REM sleep, but when given at night had no effect on sleep stages. L-propranolol given in the morning had no effect on non-REM sleep, but increased it at night. L-propranolol produced decreased in percentage REM sleep at both times.

Animals↗
PubMed1980

Pinealectomy abolishes plasma melatonin in the rat.

Using gas chromatography-negative ionization mass spectrometry, plasma melatonin levels in pinealectomized and sham-operated rats were assessed. The pinealectomized rats consistently demonstrated an absence of plasma melatonin while the intact animals showed detectable amounts. This suggests that although melatonin may be formed in tissues other than a pineal gland, the contribution to plasma is of pineal origin. Thus, plasma melatonin levels can be used as a marker of circadian melatonin secretion by the pineal gland and of its beta-adrenergic regulation.

Animals↗
PubMed1978

Analysis of melatonin in human plasma by gas chromatography negative chemical ionization mass spectrometry.

Three techniques have been used to measure human plasma melatonin: bioassay, radioimmunoassay, and gas chromatography--mass spectrometry (GC-MS). GC-MS is theoretically capable of the greatest specificity, but in general suffers from insufficient sensitivity. Negative chemical ionization, a new technique, provides a 150-fold increase in GC-MS sensitivity for electron-capturing compounds. Negative chemical ionization GC-MS permits routine measurement in human plasma of melatonin at a concentration as low as 1 picogram per milliliter.

Adult↗
PubMed1972

Operant behavior changes norepinephrine metabolism in rat brain.

Rats performing a lever-pressing response for water reward in an operant situation, when compared with control groups, showed an increase in brain norepinephrine metabolism. One control group included rats which were handled and deprived of water in the same way as the experimental group but were not trained to perform the operant task. We conclude that performance in an operant situation affects norepinephrine metabolism.

Animals↗
PubMedDate not supplied

Is winter depression a bipolar disorder?

Sixty-one winter depressive patients were evaluated for evidence of bipolar illness. Using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version and the General Behavior Inventory, only nine (15%) could be considered bipolar. On prospective evaluation of patients during the summer following winter depression, few showed signs of manic or hypomanic symptoms. Also, few patients had a family history of bipolar illness. When patients were asked to evaluate symptoms of winter depression, lack of energy was found to be the most prominent feature of the syndrome.

Adult↗
PubMedDate not supplied

The dim light melatonin onset, melatonin assays and biological rhythm research in humans.

The most useful marker for human circadian phase position is the dim light melatonin onset (DLMO). This is optimally obtained by sampling blood or saliva in the evening at intervals of 30 min or less. Ambient light intensity should not exceed 30-50 lx. For many years, the DLMO was determined mainly with the 'gold standard' GCMS technique for measuring melatonin in human plasma. However, new and improved RIAs now provide the requisite sensitivity and accuracy (specificity) for detecting the time that low daytime levels begin to increase in the evening: the lower the operational threshold for the DLMO, the more reliable it is as a phase marker.

Biomarkers↗