A disturbed sleep-wake rhythm is common in Alzheimer disease (AD) patients and correlated with decreased melatonin levels and a disrupted circadian melatonin rhythm. Melatonin levels in the cerebrospinal fluid are decreased during the progression of AD neuropathology (as determined by the Braak stages), already in cognitively intact subjects with the earliest AD neuropathology (Braak stages I-II) (preclinical AD). To investigate the molecular mechanisms behind the decreased melatonin levels, we measured monoamines and mRNA levels of enzymes of the melatonin synthesis and its noradrenergic regulation in pineal glands from 18 controls, 33 preclinical AD subjects, and 25 definite AD patients. Pineal melatonin levels were highly correlated with cerebrospinal fluid melatonin levels. The circadian melatonin rhythm disappeared because of decreased nocturnal melatonin levels in both the preclinical AD and AD patients. Also the circadian rhythm of beta(1)-adrenergic receptor mRNA disappeared in both patient groups. The precursor of melatonin, serotonin was stepwise depleted during the course of AD, as indicated by the up-regulated monoamine oxidase A mRNA and activity (5-hydroxyindoleacetic acid:serotonin ratio). We conclude that a dysfunction of noradrenergic regulation and the depletion of serotonin by increased monoamine oxidase A result in the loss of melatonin rhythm already in preclinical AD.

A method using gas chromatography (GC)-mass spectrometry (MS) for the simultaneous determination of the smoke uptake parameters thiocyanate, nicotine and cotinine in human tissues is reported. Nicotine, cotinine and thiocyanate, in combination with a phase-transfer catalyst, were extracted from urine, saliva and hair into dichloromethane (DCM). Thiocyanate was alkylated in the DCM-layer to form a pentafluorobenzyl derivative. The biochemical markers in DCM were directly injected into the GC system and separated on a DB-1MS column using a 9.4 min temperature program. The method was validated in urine and saliva between the limits of quantitation (1.0-15 microg ml(-1) thiocyanate, 0.010-3.0 microg ml(-1) nicotine and cotinine in urine, 0.010-1.0 microg ml(-1) nicotine and cotinine in saliva). The calibration curves were found to be linear (r > 0.996), the within- and between-day accuracy's were 83-120%, the repeatability coefficients of variation were 3-20% and the limits of detection were 0.060 ng ml(-1) thiocyanate and 0.60 ng ml(-1) nicotine and cotinine. The results of the analysis of the biomarkers in the urine of 44 volunteers were used to develop a predictive model for smoking status, using discriminant analysis. The classification model correctly classified 93.2% of cross-validated grouped cases. Saliva samples were used to confirm the results of the classification method.

Riluzole exerts a dose-dependent effect on survival of patients with ALS and, although serum levels show a high interindividual variability, is usually prescribed in a fixed dose. In this study, riluzole serum levels and area under the curve per kilogram of body weight (AUC/kg) of 169 patients with ALS showed a high interindividual variability. Patients with high serum levels and AUC/kg more often had diarrhea but less often had fasciculations and muscle stiffness. It may therefore be advantageous to raise the riluzole dose in patients with low riluzole serum concentrations without the risk of serious side effects.