Cloning and chromosomal mapping of the mouse DNA-dependent protein kinase gene

 Severe combined immune deficiency (scid) mice are assumed to have two types of abnormalities: one is high radiosensitivity and the other is abnormal recombination in immunoglobulin and T-cell receptor genes. The human chromosome 8 q1.1 region has an ability to complement the scid aberrations. Moreover, the localization of the subunit DNA-dependent protein kinase [DNA-PK_cs] participating in DNA double-strand break repair in the same locus was clarified. In scid mouse cells, the number of DNA-PK_cs products and extent of DNA-PK activity remarkably decrease. These observations gave rise to the assumption that DNA-PK_cs is the scid factor itself. In order to determine whether the DNA-PK _cs gene is the scid gene, we isolated the mouse DNA-PK _cs gene and investigated its chromosomal locus by fluorescence in situ hybridization (FISH). Consequently, it became clear that the mouse DNA-PK _cs gene existed in the centromeric region of mouse chromosome 16, determined by cross-genetic study, as a scid locus. This finding strongly suggests that mouse DNA-PK _cs is the scid gene. Received: 22 March 1996     

A comparison of sweating responses during exercise and recovery in terms of sweating rate and body temperature

Based on the hypothesis that the relation between sweating rate and body temperature should be different during exercise and rest after exercise, we compared the sweating response during exercise and recovery at a similar body temperature. Healthy male subjects performed submaximal exercise (Experiment 1) and maximal exercise (Experiment 2) in a room at 27° C and 35% relative humidity. During exercise and recovery of 20 min after exercise, esophageal temperature (Tes), mean skin temperature, mean body temperature ( ), chest sweating rate ( ), and the frequency of sweat expulsion (F _SW) were measured. In both experiments, andF _SW were clearly higher during exercise than recovery at a similar body temperature (Tes, ). was similar during exercise and recovery, or a little less during the former, at a similarF _SW. It is concluded that the sweating rate during exercise is greater than that during recovery at the same body temperature, due to greater central sudomotor activity during exercise. The difference between the two values is thought to be related to non-thermal factors and the rate of change in mean skin temperature.     

Developmental study onHypolepis punctata (Thunb.) Mett.

The third petiolar bud ofHypolepis punctata appears on the basiscopic lateral side of the petiole above the fairly developed first petiolar bud. This investigation clarified the fact that the third bud is formed neither by the activity of the meristem of the first bud nor by the meristem directly detached from the shoot apical meristem, but is initiated in the cells involved in the abaxial basal part of the elevated portion of the leaf primordium. Thus the third bud is of phyllogenous origin. This investigation further revealed that the cells to initiate the third bud are originally located in the abaxial side of the leaf apical cell complex like the cells to initiate the first bud, but are not incorporated into the meristem of the first. After the first, second and third petiolar buds have been initiated, they are carried up into fairly high regions on the petiolar base by the intercalary growth which occurs in the leaf base below the insertion level of the first and the second buds.     

Generality of the action of various maturation-promoting factors

It has been known in amphibians and starfishes that a cytoplasmic factor called maturation-promoting factor (MPF), produced in maturing oocytes under the influence of the maturation-inducing hormones, can induce germinal vesicle breakdown (GVBD) and the subsequent process of meiotic maturation. The present study revealed that injection of cytoplasm of maturing starfish oocytes (starfish MPF) into immature sea cucumber oocytes brought about maturation of the recipients. Amphibian MPF obtained from mature oocytes of Xenopus laevis or Bufo bufo was found to induce maturation of starfish oocytes following injection. Cytoplasm taken from cleaving starfish blastomeres induced maturation when injected into immature starfish oocytes. The maturation-inducing activity of cytoplasm of starfish blastomeres changed along with the mitotic cell cycle during 1- to 4-cell stages so far tested and reached a peak just before cleaving. Furthermore, an extract of mammalian cultured cells, CHO or V-79, synchronized in M phase, induced GVBD in starfish oocytes following injection, whereas S phase extract had little activity. These facts suggest that MPF generally brings about nuclear membrane breakdown in both meiosis and mitosis, and that the nature of MPF is very similar among vertebrates and invertebrates.     

Adrenocortical function in mice selectively bred for different sensitivity to ethanol

The adrenocortical response to ethanol, histamine and electric shock was studied in the Short-Sleep (SS) and Long-Sleep (LS) mice. The plasma corticosterone levels measured at 60 min following ethanol injection were consistently higher in LS mice (males and females) than in SS mice. The corticosterone levels determined 60 min after histamine injection (50 mg/kg) or electric foot shock were not statistically different in these two lines of mice. The initial rise of the corticosteroid after ethanol injection was identical in SS and LS mice, whereas the costicosteroid response to mild stress of saline injection was different: SS mice showed higher levels of corticosterone than LS mice at 20 and 30 min after the injection. Corticosterone increment attributable to alcohol stress clearly seemed greater in LS than in SS mice, even though the adrenals of the SS mice were 20–30% heavier than those of LS. The possible significance of these endocrine differences with respect to sensitivity to ethanol and behavioral arousal level was discussed.     

Immunological similarity between NADH-cytochrome b5 reductase of erythrocytes and liver microsomes

In a number of animal species soluble NADH-cytochrome b₅ reductase of erythrocytes was compared with membrane-bound NADH-cytochrome b₅ reductase of liver microsomes by using an antibody to purified NADH-cytochrome b₅ reductase from rat liver microsomes. The results obtained indicated clearly that they are immunologically very similar to each other. The data with erythrocyte ghosts suggested that cytochrome b₅ and NADH-cytochrome b₅ reductase are also present in the ghost.     

Cold-active acid beta-galactosidase activity of isolated psychrophilic-basidiomycetous yeast Guehomyces pullulans

In the present study, psychrophilic yeasts, which grow on lactose as a sole carbon source at low temperature and under acidic conditions, were isolated from soil from Hokkaido, Japan. The phenotypes and sequences of 28S rDNA of the isolated strains indicated a taxonomic affiliation to Guehomyces pullulans. The isolated strains were able to grow on lactose at below 5 degrees C, and showed cold-active acid beta-galactosidase activity even at 0 degrees C and pH 4.0 in the extracellular fractions. Moreover, K(m) of beta-galactosidase activity for lactose in the extracellular fraction from strain R1 was found to be 50.5 mM at 10 degrees C, and the activity could hydrolyze lactose in milk at 10 degrees C. The findings in this study indicate the possibility that the isolated strains produce novel acid beta-galactosidases that are able to hydrolyze lactose at low temperature.     

Effects of selenium status and supplementary seleno-chemical sources on mouse T-cell mitogenesis

Although selenium is thought to be essential for various immune responses, the excess supplementation may have an adverse effect on certain immunological functions. The present study was designed to determine the effective chemical forms of selenium and their optimal levels on T-cell mitogenesis with splenic cells from mice given a selenium-deficient diet for 8 weeks to avoid effects of cellular selenium sources. Although selenium in tissues, except for spleen and thymus, was almost depleted by feeding selenium-deficient diet, the lymphoid organs still contained low levels of selenium. Both activities of cellular glutathione peroxidase (cGPx) and thioredoxin reductase (TR) in liver and splenic cells showed a tendency to decrease by selenium deficiency. However, splenic cells were tolerant against decrease of the selenoenzyme activities, and TR was also more tolerant than cGPx. T-cell proliferation of the selenium-insufficient splenic cells induced by concanavalin A was increased by addition of Na₂SeO₃, Na₂SeO₄, Na₂Se, seleno-dl-cystine, seleno-l-methionine and selenocystamine. Their promoting action was observed at levels lower than 0.1 μmol/L and was completely suppressed at the highest concentration (1 μmol/L), except for selenocystamine. Na₂SeO₃ was one of the efficient selenocompounds for the mitogenesis, which was concomitant with the significant induction of cGPx and TR. However, recovery of cGPx activity in the selenium-insufficient cells by supplementary Na₂SeO₃ was only partial, while TR activity was readily recovered from selenium deficiency. These results therefore indicate that only low levels of selenium is essential for T-cell mitogenesis even in selenium-insufficient splenic cells, and TR, which is readily recovered by Na₂SeO₃, may be the critical enzyme.     

Persistent High Numbers of Clostridium perfringens in the Intestines of Japanese Aged Adults

TSN agar was applicable for enumeration of Clostridium perfringens in fecal samples of adults but not in those of infants. It was demonstrated using TSN agar that some healthy aged adults had persistently carried C. perfringens at levels ranging from 10⁷ to 10⁹, while some others ranged from 10³ to 10⁶ per ml volume of fecal sample although all of these adults had the same diets. In the test for agglutinability of isolates of C. perfringens collected from two elderly adults, a younger adult and a baby, it was demonstrated that most of the isolates obtained from an aged adult of high levels for 19 months belonged the same serotype, while rapid alteration of serotypes could be observed in three other persons with high or low levels. In spite of as many as 10⁹ C. perfringens per ml of feces, no trace of α-toxin could be detected in the fecal samples. In in vitro tests, fecal suspension suppressed the production of α-toxin although it allowed the organism to grow sufficiently.     

Ultrastructure of perivascular amyloid fibrils in Alzheimer’s disease

Perivascular amyloid fibrils in the brains of patients with Alzheimer's disease have been examined by electron microscopy. The amyloid fibrils showed a hollow rod structure and consisted of globular substances. Each turn appeared to be composed of five globular subunits. These findings coincide with the ultrastructure of amyloid fibrils obtained from replicas made by a rapid freezing method.