Studies on exopolysaccharide production by probiotic Lactic acid bacteria

The thesis mainly discussed the isolation and identification of a probiotic Lactobacillus plantarum, fermentative production of exopolysaccharide by the strain, its purification, structural characterisation and possible applications in food industry and therapeutics. The studies on the probiotic characterization explored the tolerance of the isolated LAB cultures to acid, bile, phenol, salt and mucin binding. These are some of the key factors that could satisfy the criteria for probiotic strains . The important factors required for a high EPS production in submerged fermentation was investigated with a collection of statistical and mathematical approach. Chapter 5 of the thesis explains the structural elucidation of EPS employing spectroscopic and chromatographic techniques. The studies helped in the exploration of the hetero-polysaccharide sequence from L. plantarum MTCC 9510. The thesis also explored the bioactivities of EPS from L. plantarum. As majority of chemical compounds identified as anti-cancerous are toxic to normal cells, the discovery and identification of new safe drugs has become an important goal of research in the biomedical sciences. The thesis has explored the anti-oxidant, anti-tumour and immunomodulating properties of EPS purified from Lactobacillus plantarum. The presence of (1, 3) linkages and its molecular weight presented the EPS with anti-oxidant, anti-tumour and immunomodulating properties under in vitro conditions.

Adrenergic and serotonergic function in dna synthesis during rat liver regeneration and in hepatocyte cultures

The adult mammalian liver is predominantly in a quiescent state with respect to cell division. This quiescent state changes dramatically, however, if the liver is injured by toxic, infectious or mechanic agents (Ponder, 1996). Partial hepatectomy (PH) which consists of surgical removal of two-thirds of the liver, has been used to stimulate hepatocyte proliferation (Higgins & Anderson 1931). This experimental model of liver regeneration has been the target of many studies to probe the mechanisms responsible for liver cell growth control (Michalopoulos, 1990; Taub, 1996). After PH most of the remaining cells in the renmant liver respond with co-ordinated waves of DNA synthesis and divide in a process called compensatory hyperplasia. Hence, liver regeneration is a model of relatively synchronous cell cycle progression in vivo. In contrast to hepatomas, cell division is terminated under some intrinsic control when the original cellular mass has been regained. This has made liver regeneration a useful model to dissect the biochemical and molecular mechanisms of cell division regulation. The liver is thus, one of the few adult organs that demonstrates a physiological growth rewonse (Fausto & Mead, 1989; Fausto & Webber, 1994). The regulation of liver cell proliferation involves circulating or intrahepatic factors that are involved in either the priming of hepatocytes to enter the cell cycle (Go to G1) or progression through the cell cycle. In order to understand the basis of liver regeneration it is mandatory to define the mechanisms which (a) trigger division, (b) allow the liver to concurrently grow and maintain dilferentiated fimction and (c) terminate cell proliferation once the liver has reached the appropriate mass. Studies on these aspects of liver regeneration will provide basic insight of cell growth and dilferentiation, liver diseases like viral hepatitis, toxic damage and liver transplant where regeneration of the liver is essential. In the present study, Go/G1/S transition of hepatocytes re-entering the cell cycle after PH was studied with special emphasis on the involvement of neurotransmitters, their receptors and second messenger function in the control of cell division during liver regeneration