Characterization of postreplication repair in Saccharomyces cerevisiae and effects of rad6, rad18, rev3 and rad52 mutations

Summary Postreplication repair of nuclear DNA was examined in an excision defective haploid strain of yeast lacking mitochondrial DNA (ral ⁰). The size of the DNA synthesized in cells exposed to various fluences of ultraviolet light (UV) corresponds approximately to the average interdimer distance in the parental DNA. Upon further incubation of cells following exposure to 2.5 J/m², the DNA increases in size; by 4 h, it corresponds to DNA from uniformly labeled cells. The alkaline sucrose sedimentation pattern of DNA pulse labeled at various times after UV irradiation, for up to 4 h, does not change substantially, indicating that dimers continue to block DNA replication. A significant amount of postreplication repair requires de novo protein synthesis, as determined by its inhibition by cycloheximide. The rad6 mutant does not carry out postreplication repair, the rad18 and rad52 mutants show great inhibition while the rev3 mutation does not affect postreplication repair. Both recombinational and nonrecombinational repair mechanisms may function in postreplication repair and most of postreplication repair is error free.     

Effect of imipramine hydrochloride on the activity of gamma-aminobutyric acid transaminase in regions of the rat brain

The effect of intraperitoneal injection of imipramine hydrochloride on the activity of gamma-aminobutyric acid transaminase was determined in three regions of the rat brain.The cerebral hemispheres did not show a significant change in the activity of gamma-aminobutyric acid transaminase. Cerebellum and brain stem, both, however, showed a very significant decrease in the activity of the enzyme at 15 and 30 minutes after drug administration. At 90 minutes after drug administration, the activity of gamma-aminobutyric acid transaminase had returned to nearly control values.     

Light microscopic features of the rete testis,the vas efferens,the epididymis and the vas deferens in the adult rhesus monkey

The present study was carried out to determine the detailed histological and cytological features of the excurrent ducts of the male reproductive system in the rhesus monkey. The excurrent ducts show a regional difference in their histological features. The use of some of these features as histological markers and their possible functional significance are discussed. The epithelial cells in the different components of the excurrent duct system possess cytological features which suggest their involvement in absorption and the secretion of different products into the lumen.     

Predatory behaviour of lutzia on Culex fatigans

The carnivorous mosquito Lutzia (= Culex) raptor devours 20 to 50 larvae (third instar) of Culex fatigans in a day. The predatory capacity of L. raptor is not influenced by changes in volume of water, but significantly influenced by changes in prey density. With increasing prey density, the percentage of prey killed and left unconsumed increases. The duration required to subdue and consume a single larva is 15 min for L. raptor previously deprived of food for 3 to 24 hrs; the handling duration of prey increases to 20 min for the predator previously deprived food for 1 hr. The duration increases with increasing prey size; L. raptor requires 1, 6, 62 or 113 min to handle a single II, III, IV or mini pupa of Culex fatigans weighing 0.2,1.2,4.2 and 4.0 mg respectively.     

Acetophenone and stilbene derivatives from Gnetum ula

The isolation of bergenin, 2-hydroxy-4-benzyloxyacetophenone and the related dimer and stilbene from Gnetum ula is reported.     

The Role of Fluoride in Montmorillonite-Catalyzed RNA Synthesis

The montmorillonite-catalyzed reactions of the 5′-phosphorimidazolide of adenosine in the presence of fluoride were investigated to complete our study on the effect of salts on this type of reaction. Both anions and cations have been found to influence the oligomerization reactions of the activated nucleotides, being used here as a model system for pre-biotic RNA synthesis. However, in total contrast to the behavior of the activated nucleotides in the presence of montmorillonite and other salts, alkali metal fluorides did not yield any detectable oligomerization products except in very dilute (<0.005 M) solutions of fluoride. Instead, 5′-phosphorofluoridates were formed. Their identity was confirmed by a combination of HPLC, mass spectrometry, synthesis, and NMR.     

Evaluation of the probiotic characteristics of Bacillus species isolated from different food sources

Probiotics have established their efficacy as dietary adjuncts providing benefits to consumers. However, selection of probiotics before incorporation into diet requires close scrutiny in the form of in vitro as well as in vivo tests. Three bacteriocinogenic Bacillus sp., namely, B. licheniformis Me1, B. flexus Hk1, and B. subtilis Bn1 previously isolated from milk, cheese and fermented beans, respectively, were characterized for typical in vitro probiotic criteria. When compared to probiotic Bacillus coagulans, all three cultures were found to possess better acid and bile tolerance. Cultures Me1 and Bn1, except Hk1, showed bile salt hydrolase activity. A marked difference in adhesion to hydrocarbons and auto-aggregation properties from 10–80 and 60–99%, respectively, were observed for the tested cultures. Highest antioxidant activity was measured for culture Hk1 (66.6%), whereas least activity of 53% was observed for culture Bn1. Cultures Me1 and Bn1 were sensitive to all the antibiotics tested, whereas Hk1 and B. coagulans showed resistance to the penicillin group of β-lactum antibiotics. All the tested cultures showed a broad spectrum of activity against food-borne pathogens. In co-cultivation studies, B. licheniformis Me1 completely inhibited the growth of the indicator pathogen Listeria monocytogenes ScottA. Overall, the test cultures exhibiting potential probiotic characteristics, particularly B. licheniformis Me1, can serve as probiotics of commercial interest.     

Copy number variation-based polymorphism in a new pseudoautosomal region 3 (PAR3) of a human X-chromosome-transposed region (XTR) in the Y chromosome

A 3.5-Mb region of the X chromosome underwent duplication and transposition to the Y chromosome ~5–6 Mya. This X-transposed-region (XTR) originated at Xq21.3 and was inserted at Yp11.2. The two locations have 98.78 % homology and a high concentration of tandem repeats. In whole-genome scans of ten large families with dyslexic members, we identified transposed blocks comprising >102 kb of the Yp11.2 region in its homologous region at Xq21.3 in three females from three different families. Although recombination is known to be limited only to the pseudoautosomal regions (PARs) of the X and Y chromosomes, we report allelic unequal recombination between the XTR region Yp11.2 and Xq21.3, indicating the presence of a new PAR, which we named PAR3. This PAR3 region was also found in 2 % of the general population. An additional layer of justification could be provided from six other dyslexic cases which harbored duplications and deletions in the same Xq21.3 and Yp11.2 regions through allelic unequal recombination.