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The present study on overnight urinary melatonin was conducted on the most geographically dispersed population to date, over a 1 year period, also covering a broad age range (18-62 years). An inverse relationship between melatonin and age, as well as between melatonin and weight was observed for both genders. Females as a whole, had higher melatonin values than males. Furthermore, the excretion of melatonin exhibited a bimodal distribution, distinguishing two groups of individuals: low and high melatonin excretors, The cut-off point was set at 0.25 nmol/l for ages up to 40 years and at 0.20 nmol/l for subjects above this age, Since melatonin may be involved in several physiological and pathological processes, it could be of importance to detect the type of melatonin excretion that prevails in various conditions, using a simple noninvasive procedure such as the overnight urinary measurement. For that purpose, this large sample could serve as a worldwide reference databank across different ages and locations. (C) 1999 Elsevier Science Ltd. All rights reserved.

Using a newly characterized anti-melatonin serum it has been possible to establish human serum melatonin concentrations at short time intervals during 24h. A clear circadian rhythm with peak values during the dark phase was demonstrated in both men and women. Values (pg/ml;mean +/- SE) were as follows: females 02.00h: 130 +/- 7, 18.00h: 45 +/- 5 males 02.00h: 140 +/- 11, 18,00H: 70 +/- 5. The estimation (pg/ml; mean +/- SE) of melatonin in human serum (males: 63 +/- 22 and females: 100 +/- 45) and cerebrospinal fluid simultaneously taken has shown that melatonin is lower in cerebrospinal fluid (males: 59 +/- 33 and females: 57 +/- 28). Blanks are not subtracted.

Magnetic resonance imaging (MRI) at low magnetic field strengths is known to have a comparatively high contrast resolution. Current techniques increasing the signal to noise ratio 3 to 4 times allow for an improvement in the spatial resolution still maintaining the high contrast resolution. The contributing features to this advancement are improvements in software, development of new radiofrequency coils and image processing computors. The subsequent improvement in image evaluation and the access to added information make for a high accuracy in clinical diagnosis and research. The present potential of imaging at ultra-low (0.02 tesla) magnetic field strengths is illustrated with examples from clinical practice and research.

Melatonin secretion is dependent both on the environmental lighting and noradrenergic control and seems to be related to the ACTH-cortisol secretion. The aim of the present study was to further elucidate the relationship between ACTH-cortisol and melatonin. For this purpose we chose the Metyrapone test. The melatonin secretion was studied in 10 patients, and increased significantly in 8/10 during and in one after the Metyrapone administration. These results further support a relationship between melatonin and ACTH-cortisol secretion, possibly through a suprapituitary interaction.

The use of MRI in clinical psychiatry is evaluated on the basis of over four years' experience. Of 931 psychiatric patients examined, 156 were found to manifest pathological cerebral conditions, a frequency of 17 per cent, as compared with 2 per cent (2/101) among apparently healthy controls. The occurrence of intracerebral lesions, with exclusively psychiatric symptoms, is illustrated with case reports. The importance is stressed of early examination with neurodiagnostic imaging techniques in cases of psychiatric disorders where any of the following symptoms or preliminary diagnoses are present: atypical psychiatric features, first episode psychosis, late onset depression, dementia, HIV and other infections in conjunction with psychiatric symptoms, hysteria, and alcohol or drug abuse. The findings suggest MRI to be a useful supplementary diagnostic tool for improving the care of the psychiatric patient, while relieving the burden both on the patient's family and on mental health care resources.