Mental health, suicidal ideation, and related factors among workers from medium-sized business establishments in northern Japan: comparative study of sex differences.

A questionnaire survey was conducted among 3,233 workers (2,442 males and 791 females) from 17 medium-sized business establishments in northern Japan with respect to GHQ-12 score, suicidal ideation, sociodemographic characteristics, work-associated factors, and attitude toward mental health resources. Sex differences were assessed for each questionnaire item, and logistic regression analyses were performed separately for males and females. Significant correlations between common mental disorder (CMD: GHQ-12 score≥3) and the following factors were found for both sexes: short sleep, irregular working schedule, working in specific businesses, and attitude toward mental health resources. Associations between CMD and excess workload were significant only in male workers. While correlations between suicidal ideation and demand for mental health resources were observed in both sexes, significant correlations were observed between suicidal ideation and use of mental health resources for female workers alone. These results suggest that screening of a high-risk population and provision of mental health resources contribute to suicide prevention as a part of mental health promotion measures in medium-sized business establishments. They also suggest the need for identification of business/job type-specific stressors while considering sex differences in lifestyle factors, working environment, and help-seeking behavior.

An atlas-based image registration method for dopamine receptor imaging with PET in rats.

For analysis of in vivo dopamine receptor binding in the rat brain by positron emission tomography (PET), a convenient method to obtain precise anatomical registration for striatum and cerebellum on the PET image was developed. On the PET measurements, a control, an anesthetized rat was positioned in a stereotaxic holder so that the horizontal plane of the PET image would be parallel to the horizontal plane of the brain atlas. After the positioning, [11C]raclopride was intravenously injected into the rats and scanned to obtain PET images of dopamine D2 receptor in the brain. The striatum was bilaterally identified in the obtained PET image. The atlas-based regions of interest (ROIs) of the whole brain were preliminarily created according to the atlas, and were superimposed on an early phase PET image. The early phase PET image was compatible to the whole brain ROI in the atlas, which enabled determination of striatal and cerebellar ROI difficult to determine by the PET image alone. Using the cerebellar radioactivity as a reference input function, rate constants between the free/nonspecific compartment and the receptor bound compartment (k3 and k4) were calculated by a two-parameter compartment model, and the binding potential (k3/k4) was estimated. The binding potential and its coefficients of variation were 1.56+/-0.30, 19.3% in Wistar rats, 1.05+/-0.14, 13.4% in Sprague-Dawley (SD) rats, and 1.29+/-0.07, 5.2% in Fischer F344 rats, in which binding potential in Wistar rats was significantly higher than that in SD rats. This method is objective and convenient in routine use for PET studies in rats, regardless of differences in the rat strains.

Increased binding potential of [(11)C]raclopride during unilateral continuous microinjection of nicotine in rat striatum observed by positron emission tomography.

Nicotine injections and nicotine skin patches significantly improve attention, memory, and learning in Alzheimer's disease. In animal studies, nicotine improves the performance of various memory-related tasks, an effect that is thought to be mediated by the neuronal dopaminergic system as systemic administration of nicotine decreased [(11)C]raclopride binding in the anesthetized state. Since high doses of systemically administered nicotine are harmful, we administrated it directly into the rat striatum via microdialysis. We then examined the acute effects of continuous central administration of high doses of nicotine on striatal dopamine concentrations by measuring [(11)C]raclopride binding by positron emission tomography. The concentration of dopamine in the dialysates was significantly increased from basal levels when microdialysis with 100 mM nicotine was initiated. However, contrary to expectations, the binding potential (BP) of [(11)C]raclopride in the nicotine-perfused striatum was significantly higher than that in control striatum. Preinjection of mecamylamine (3 mg/kg), a nicotinic antagonist, had no effect on either extracellular dopamine levels or on the BP of [(11)C]raclopride. These findings suggest that the high dose of local nicotine administration induced mecamylamine-insensitive local increases in extracellular dopamine, but might have decreased the total amount of extracellular dopamine in the striatum.

Three-dimensional electron microscopic studies of the transitional oligodendrocyte associated with the initial stage of myelination in developing rat hippocampal fimbria.

We identified the transitional oligodendrocyte and their processes of rat hippocampal fimbria associated with the initial stage of myelination in both the morphological and functional classifications by means of three-dimensional ultrastructural analysis. Transitional oligodendrocytes appeared around P7, and their cell bodies were morphologically an intermediate form between the light and medium oligodendrocytes described by Mori and Leblond [J. Comp. Neurol. 139 (1970) 1]. Three phenotypes of the transitional oligodendrocytic processes were recognized. Spiral wrapping processes were ensheathing processes, club-like processes were nonensheathing processes, and sheet-like processes were possibly the transmuting form between the nonensheathing and ensheathing processes. Club-like processes were the major part of the nonensheathing processes, and most likely function as sensors to perceive axon maturation and find target axons. Multivesicular bodies that appeared to be associated with the initial ensheathment were observed in the transitional oligodendrocytic processes, suggesting that their roles are crucial in myelinogenesis.

Comparison of perivascular astrocytic structure between white matter and gray matter of rats.

Regional differences in perivascular glial structures were investigated between the white matter (hippocampal fimbria, corpus callosum, cerebellar medulla) and the gray matter (cerebral cortex) of adult rats. Sparser vascular distribution, perivascular glial rows and cylinder-like segmented astrocytic endings were characteristic in the white matter. The perivascular astrocytic processes covered microvessels extensively in the white matter. Comparison of transverse microvessel sections by transmission electron microscopy (TEM) between the two sites revealed significantly larger perivascular astrocytic spaces in the white matter.