Influence of cellular differentiation on ultraviolet induced DNA damage and its repair mechanisms in B. cereus

Susceptibility to UV irradiation of B. cereus BIS-59 spores undergoing germination at various stages-dormant spores to vegetative cell stage and their ability to recover from radiation damage were studied. For a given dose of radiation, the number of spore photoproducts (SPP) formed in the DNA of dormant spores was about 5-times greater than that of thymine dimers (TT) formed in the DNA of vegetative cells. At intermediate stages of the germination cycle, there was a rapid decline in the UV radiation-induced SPP formed in DNA with a concomitant increase in the UV radiation-induced TT formed in DNA. Bacterial spores undergoing germination (up to 3 hr) in the low nutrient medium (0.3% yeast extract) displayed much higher resistance to UV radiation than those germinating in the rich nutrient medium, even though there was no discernible difference under the two incubation conditions in respect of the extent of germination and the time at which the outgrowth stage appeared (3 hr). This was due to the formation TT in the DNA of spores germinating in the low nutrient as compared to that of spores germinating in the rich-nutrient medium. In UV-irradiated dormant spores, SPP formed in the spore DNA did not disappear even after prolonged incubation in the non-germinating medium. However, when the UV-irradiated dormant spores were germinated in low or rich nutrient medium, a significant proportion of SPP in DNA was eliminated. The dormant spores incubated in either of the germinating media for 15 min and then UV-irradiated were capable of eliminating SPP (presumably by monomerization) even by incubation in a non-germinating medium and in the complete absence of protein synthesis (buffer holding recovery), thereby implying that spore-repair enzymes were activated in response to initial's germination. The acquisition of photo-reactivation ability appeared in spores subjected to germination only in the rich-nutrient medium at the outgrowth stage and required de novo synthesis of the required enzymes.     

Morphological and cytoskeletal changes caused by non-membrane damaging cytotoxin of Vibrio cholerae on Int 407 and HeLa cells

End-group mediated conjugation of bacterial polysaccharides (PSs) to carrier proteins containing T-helper cell epitopes renders such polysaccharides immunogenic also in young infants. Optimal construction of such conjugate vaccines requires fragmentation of the PS prior to the coupling reaction. In the present study a general simple and inexpensive method for the fragmentation of PSs is presented. It is based on the irradiation of isolated PSs in an electron beam accelerator. Exposure of isolated pneumococcal capsular polysaccharides (PnPSs) to ionizing radiation resulted in their partial depolymerization in a radiation dose-dependent manner. Radiation, unlike sonication, generated PnPS fragments of molecular size lower than 50 kDa and as small as 1.5 kDa when high radiation doses were used. These PnPS fragments have terminal reducing groups that can be easily used for chemical activation and subsequent coupling to any chosen carrier protein. The radiation-produced PnPS fragments retained their antigenic epitopes, when compared to native, full-size PnPSs as determined by enzyme-linked immunoassay.     

Studies of vertebrate kidney. VI. Histochemical localization of phospholipids in kidneys of fishes from different habitats.

Six fish species living in different habitats such as fresh water, estuarine, and marine were studied for the distribution of phospholipids in various regions of the kidney. Well known histochemical methods, including those for choline-containing phospholipids were employed. The distribution pattern of phospholipids in different parts of the kidney such as the brush border, basal border and cytoplasmic granules of the proximal tubule cells, the cytoplasmic granules of the distal tubule cells, glomeruli and interstitial cells is given. Choline-containing phospholipids are present in the brush border of the proximal tubules of all the species studied and in the basal border of some. In the discussion an attempt at correlation of this histochemical pattern with the excretory functions and osmoregulation in these fishes is given.     

Biochemical analysis as a measure of dynamic equilibrium in genomic setup during processing of tea

The genetic characteristic such as ‘fermentability’ of a tea cultivar could be utilised to obtain maximum colour/bloom during manufacture of black tea. Pigment profile analysis has been used as a tool to assess the characteristic of a black tea brew. Fine plucking and optimum processing conditions are two basic requirements in producing good quality black tea. The assamica variety is characterised by linalool content while geraniol is specific in chinary clones. The higher amounts of terpenoids improved the flavour characteristic of second flush tea of north east India in general and Darjeeling in particular. Further, the surplus fatty acid degradation products lower the quality of black tea during monsoon flush. Presented at the 3rd National Symphosium on Bioorganic Chemistry, 1987, Hyderabad.