Toshifumi Yokoyama

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Maternal alcohol ingestion during pregnancy adversely affects the developing fetus, often leading to fetal alcohol syndrome (FAS). One of the most severe consequences of FAS is brain damage that is manifested as cognitive, learning, and behavioral deficits. The hippocampus plays a crucial role in such abilities; it is also known as one of the brain regions(More)
To clarify the relationship between M cells and intestinal microflora, histoplanimetrical investigation into the bacterial colonization and the differentiation to M cells was carried out in rat Peyer's patch under physiological conditions. The follicle-associated epithelium (FAE), except for the narrow area of apical region, was closely covered with both(More)
A major question is whether exposure to mixtures of low-dose endocrine disruptors (EDs) having different action mechanisms affects neurodevelopment differently than exposure to EDs individually. We therefore investigated the effects of fetal and neonatal exposure to three typical EDs - bisphenol A (BPA), di-(2-ethylhexyl)-phthalate (DEHP), and(More)
Effects of early postnatal ethanol exposure on brain-derived neurotrophic factor (BDNF) mRNA expression in the rat hippocampus were investigated. Wistar rats were assigned to either ethanol treatment (ET) separation control (SC) or mother-reared control (MRC) groups. Ethanol exposure was achieved by a vapor inhalation method for 3 hours a day between(More)
Recent animal experiments confirmed that paternal 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure decreases the sex ratio of offspring at birth without altering litter size. However, the timing of this decrease remained unclear. Male mice were administered TCDD at 7-12 weeks of age and mated with non-treated females. The Y-bearing/X-bearing sperm ratio(More)
Stereology is a group of mathematical and statistical methods that allows the extrapolation of three-dimensional structural information from two-dimensional sections (or slices). This allows researchers to derive important quantitative structural information, such as the volume, surface area or numbers of particular particles (e.g. cells) within defined(More)
The ultrastructure of epithelial responses against the membrane adhesion of indigenous bacteria was investigated in the follicle-associated epithelium (FAE) of rat small intestine. The most frequent adherence of the various morphological types of bacteria to the epithelial membranes was found at the apex of the FAE. The attachment sites were deeply(More)
Clothianidin (CTD) is a neonicotinoid developed in the 1990s as an insecticide having selective toxicity, but it was later found to cause reproductive abnormalities in rats through oxidative stress. There is an attempt to preserve endangered animals, including the Japanese crested ibis, in Japan. However, there is a concern that neonicotinoid affects the(More)
The purpose of the present study was to elucidate regional differences in the vulnerability of cerebellar foliations of rats exposed to X-irradiation. Effects of X-irradiation on foliations were examined with respect to histological changes in Purkinje cells and Bergmann glial fibers by calbindin-D28k (CB) and glial fibrillary acidic protein (GFAP)(More)
AIMS This study was carried out to examine the effects of early postnatal maternal separation stress on the development of the cerebral cortex with respect to time-dependent fluctuations of neurotrophic factor ligand and receptor expression. MAIN METHODS Wistar rats were separated from their mothers for 3h per day during postnatal days (PND) 10 to 15. The(More)