Effect of Particle Sizes of Starting Materials on Microstructure Development in Textured Bi0.5(Na0.5K0.5)0.5TiO3

Microstructure development in Bi_0.5(Na_0.5K_0.5)_0.5TiO₃ prepared by a reactive-templated grain growth process was dependent on the sizes of platelike Bi₄Ti₃O₁₂ (BiT) and equiaxed TiO₂ particles used as starting materials. Calcined compacts were composed of large, platelike template grains and small, equiaxed matrix grains, the sizes of which were determined by those of the BiT and TiO₂ particles, respectively. Texture was developed by the growth of template grains at the expense of matrix grains during sintering, and a new mechanism of grain growth was proposed on the basis of microstructure observation. The grain growth rate was determined by the template and matrix grain sizes, and a dense ceramic with extensive texture was obtained using small BiT and TiO₂ particles.     

Comparative study on formation of hydroxy and sulfur-containing metabolites from different chlorinated biphenyls with 2,5-substitution in rats

2,4',5-Trichlorobiphenyl (TriCB), 2,3',4',5-tetrachlorobiphenyl (TetraCB), 2,2',4',5,5'-pentachlorobiphenyl (PentaCB), and 2,2',3',4',5,5'-hexachlorobiphenyl (HexaCB) were studied with regard to the fecal excretion and tissue distribution of their metabolites after intraperitoneal injection to rats. Major fecal metabolites were 3- and 4-hydroxy and 3- and 4-methylthio derivatives, the substitution ratios depending largely on the degree of chlorination. As the degree of chlorination increased, hydroxy products were more efficiently excreted, whereas the formation of methylthio metabolites greatly decreased. As a result, the excretion ratios of methylthio and hydroxy products varied with 2.8 for TriCB, 1.3 for TetraCB, 0.04 for PentaCB, and 0.02 for HexaCB. The 3-/4-hydroxy substitution ratios were 0.6 for TriCB, 1.4 for TetraCB, 21 for PentaCB, and 35 for HexaCB, whereas the 3-/4-methythio substitution ratios were 1.2 for TriCB, 0.8 for TetraCB, 0.18 for PentaCB, and 0.12 for HexaCB. The formation rate of 3- and 4-methylthio metabolites from each congener was correlated to the accumulation and distribution of 3- and 4-methylsulfonyl derivatives in tissues. The tissue/blood concentration ratios of methylsulfonyl metabolites showed that the 3-methylsulfonyl derivatives from higher chlorinated biphenyls had a relatively high affinity for liver and adipose tissue, whereas the 4-methylsulfonyl derivatives were selectively retained in the lung in all cases.     

Apamin-sensitive SK(Ca) channels modulate adrenal catecholamine release in anesthetized dogs

Physical activity is defined as skeletal muscle contraction resulting in a quantifiable expenditure of energy, whereas exercise is a specific type of physical activity in which planned, structured, and repetitive bodily movement is done to improve or maintain one or more components of physical fitness. The focus of laboratory studies of the physical activity-breast cancer hypothesis has been on evaluating how various types of physical activity including exercise affect the process of mammary carcinogenesis. A key objective has been the evaluation of the characteristics of physical activity, i.e. intensity, duration, and frequency, required to confer protection against experimentally-induced breast cancer. The results of those studies indicate that exercise rather than physical activity can exert a greater inhibitory effect against experimentally-induced breast cancer, and that the duration of exercise may not be as important as its intensity. This finding differs from evidence that other health benefits attributed to physical activity are proportional to the total amount of activity rather than the manner in which it is obtained. In this review criteria are defined for categorizing laboratory studies into those that investigated the effects of physical activity versus exercise on experimentally-induced mammary carcinogenesis, and the literature is reinterpreted in this context.     

Frontopolar ictal epileptiform discharges on scalp electroencephalogram in temporal lobe epilepsy

OBJECTIVE: To determine the prevalence of the smoking habit among Mexican physicians as well as some of their attitudes and information on specific issues concerning smoking. MATERIAL AND METHODS: In 1993, a survey was carried out among 3,568 physicians of the three major official health care institutions in Mexico City. A questionnaire designed for The Mexican National Survey of Addictions (ENA 1993) was used. Prevalence of cigarette smoking, age of onset, number of cigarettes per day; also information and attitudes concerning smoking were assessed. RESULTS: The mean age was 37, 66% were males. Of the 3,488 (98%) surveyed, 26.9% were smokers (62% daily), 20.6% were ex-smokers and 52.5% non-smokers. There were differences related to age and sex (p < 0.05). Of daily smokers, 36% smoked between 1 and 5 cigarettes. There was a significant trend among ex-smokers that linked the time they had ceased smoking with the fear to start smoking again. Physicians were well informed of the relationship between cigarette smoking and lung cancer. Over 80% considered tobacco an addictive drug but only 65% were in favor of banning smoking from their workplaces and over 10% were not aware that it is forbidden to smoke inside health care facilities. CONCLUSIONS: These results differ from other studies that find the prevalence of smoking among physicians lower than in the general population. Our study revealed a greater prevalence of the smoking habit among female physicians and the number of cigarettes smoked per day was greater than in the general population regardless of sex.     

T cell response to Borrelia garinii, Borrelia afzelii, and Borrelia japonica in various congenic mouse strains

The infectivity and T cell response to Borrelia garinii SIKA2, Borrelia afzelii BFOX, and Borrelia japonica 0612, the organisms that cause Lyme disease in Japan, were examined in various inbred and congenic strains of mice. Infectivity differed among the species: B. garinii SIKA2 and B. afzelii BFOX were each able to infect 90% to 100% of C3H/He mice; B. japonica 0612 was able to infect only 20% of C3H/He mice. The pattern of infectivity to various inbred and congenic strains of mice may influence the pathogenicity of the organism and the clinical signs of Lyme disease. Cross-reactivity between Borrelia antigens was observed, but there was no cross-reactivity between Borrelia antigens and Leptospira antigens. We evaluated the genetic control of the delayed-type hypersensitivity (DTH) reaction in the form of footpad swelling produced by Borrelia antigens using viable or sonicated bacteria as sensitization. Differences in strains of mice infected by viable antigen were observed. However, all strains of mice showed a strong DTH reaction using sonicated antigens without genetic background. A DTH reaction in the form of footpad swelling did not appear to be associated with genetic background. The footpad reaction was mediated by CD4+8- and Ia- T cells, as revealed by in vitro monoclonal antibody treatment. However, CD8+ T cells did not suppress footpad swelling. These results indicate that many antigenic epitopes of the Borrelia spirochete can stimulate the DTH reaction.     

Effect of aging on the expression of iNOS and cell death in the mouse cochlear spiral ganglion

The age-related induction of inducible nitric synthase (iNOS) and apoptotic cell death in spiral ganglion cells (SGCs) of ddy strain mice were studied with immunohistochemical method and TdT-mediated dUTP-biotin nick end labeling (TUNEL), respectively. A large amount of iNOS was expressed in SGCs of 18- to 24-month-old mice, but not in those of the mice less than 12 months of age. Moreover, these mice were accompanied by a great rise in auditory brainstem response threshold as well as a great decrease in the number of SGCs that seemed to be due to preceding cell death of the cells. However, we were unable to find apoptotic TUNEL-positive cells in the spiral ganglions. This was assumed to be due to a very short clearance time of the dead cell bodies of less than one hour. As has been known, NO produced by iNOS can implicate in causes for either protection of cells from peroxidation and cell death. In the present study, therefore, the steep augmentation of iNOS in the SGCs of senescent mice implies that the iNOS initially induced to protect SGCs from the cytotoxicity of cellular peroxidation eventually contribute to the cell death of SGCs themselves.     

Muscle-specific calpain, p94, responsible for limb girdle muscular dystrophy type 2A, associates with connectin through IS2, a p94-specific sequence

p94, a muscle-specific member of calpain family, is unique in that it undergoes rapid and exhaustive autolysis with a half-life of less than 1 h resulting in its disappearance from muscle. Recently, p94 was shown to be responsible for limb girdle muscular dystrophy type 2A. To elucidate the muscular proteolytic system mediated by p94 and to solve the mystery of its unusually rapid autolysis, we searched for p94-binding proteins by the two-hybrid system. Although calpain small subunit plays a crucial role for regulation of ubiquitous calpains, it did not associate with p94. After a screening of skeletal muscle library, connectin (or titin), a gigantic filamentous protein spanning the M- to Z-lines of muscle sarcomere, was found to bind to p94 through a p94-specific region, IS2. The connectin-insoluble fraction of washed myofibrils contained full-length intact p94, suggesting that connectin regulates p94 activity.