Tritium distribution in newborn mice after providing mother mice with drinking water containing tritiated thymidine

Throughout gestation pregnant mice received drinking water which contained [methyl-3H]thymidine (18.5 kBq/ml). The newborn mice were divided into two groups. One group was nursed by their own mothers, which were further supplied with tritiated thymidine until 4 weeks after delivery (Experiment I). The other group was nursed by "nonradioactive mothers" which were given no tritiated thymidine (Experiment II). Tritium incorporation into the small molecular components of the acid-soluble fraction, lipid, RNA, DNA, and protein was analyzed for the newborn mice at various ages. In Experiment II, total radioactivity per gram tissue decreased initially after birth with a half life of 2.5-2.9 days in spleen, liver, intestine, stomach, thymus, lung, kidney, heart, and brain. At about 2 weeks after birth, a slower component of tritium elimination due mainly to the DNA-bound tritium appeared. Specific activity of DNA at birth was organ specific, highest in heart and lowest in thymus. Cumulative absorbed dose in various organs was estimated for the first 4 weeks after birth based upon an assumption that total and DNA-bound tritium are uniformly distributed. The result showed that organ specificity of dose accumulation is obvious for DNA-bound tritium, highest in spleen (1.15 mGy) and lowest in brain (0.13 mGy). It was also shown that the tritium supply from mother's milk is of minor importance for dose accumulation of DNA-bound tritium in the cell nuclei of organs of suckling mice.     

Separation of the Effects of Photoperiod and Hormones on Sex Expression in Cucumber

The effects of photoperiod on the sex expression of cucumberflowers were examined in relation to the endogenous GA and ethyleneproduction with short day (SD)- and long day (LD)-sensitivecultivars under controlled environmental conditions. Growth of plants was greatly reduced under LD in both typesof cultivars. Reflecting this, GA activity was greater and ethyleneevolution less in plants grown under SD than in those underLD. However, the number of pistillate flowers increased underSD and LD in SD- and LD-sensitive cultivar, respectively, indicatingthat a change in sex expression did not coincide with hormonalchanges in the SD-sensitive cultivar. Thus, the effect of photoperiodon the sex expression was found to be separate, at least inpart, from the effect of GA or ethylene in cucumber. (Received September 16, 1982; Accepted December 7, 1982)     

Quantitative isolation of total glycosphingolipids from animal cells

The quantitative isolation of total glycosphingolipids from crude lipid extracts without contamination from other lipid classes is described. The method consists of (a) acetylation of total lipids with pyridine and acetic anhydride, (b) separation of acetylated glycolipids from nonglycolipids on a magnesia-silica gel (Florisil) column, and (c) deacetylation of glycolipid in chloroform-methanol-sodium methoxide. This method is useful for determination of microgram quantities of glycolipids derived from less than 1 ml of packed cells.     

Possible site of flavonoid synthesis in the photosynthetic apparatus (Short Communication)

Chloroplasts were prepared in aqueous suspension from buckwheat (Fagopyrum esculentum Moench.) seedlings, and the incorporation of [1-(14)C]acetic acid into quercetin (3,5,7,3',4'-pentahydroxyflavone) by the isolated chloroplast preparations was investigated.     

Comparison of the Pathogenicity for Mice of Mycobacterium fortuitum and Mycobacterium abscessus

The pathogenicity for mice of 12 strains of Mycobacterium abscessus was compared with that for 8 strains of M. fortuitum. Both species caused lesions in kidneys and produced "spinning disease" resulting from inner ear infections. No major differences in pathogenicity of these two species were demonstrated. Strain to strain variation was marked, especially with M. abscessus. For example, 1.6 x 10(6) organisms of strain 11188 of M. abscessus produced death in four of five animals within 42 days, whereas strain 380 of M. abscessus failed to produce any deaths within 42 days. In the case of M. fortuitum, the greatest mortality observed was one of five animals, yet the incidence of spinning disease and kidney disease occurred earlier postinfection than in mice infected with M. abscessus. Histologically, abscess formation by a strain of M. abscessus was greater than by a strain of M. fortuitum, but this difference cannot be interpreted as a species difference.