Cell Biological and Biophysical Aspects of Lipid-mediated Gene Delivery

Cationic lipids are conceptually and methodologically simple tools to deliver nucleic acids into the cells. Strategies based on cationic lipids are viable alternatives to viral vectors and are becoming increasingly popular owing to their minimal toxicity. The first-generation cationic lipids were built around the quaternary nitrogen primarily for binding and condensing DNA. A large number of lipids with variations in the hydrophobic and hydrophilic region were generated with excellent transfection efficiencies in vitro. These cationic lipids had reduced efficiencies when tested for gene delivery in vivo. Efforts in the last decade delineated the cell biological basis of the cationic lipid gene delivery to a significant detail. The application of techniques such as small angle X-ray spectroscopy (SAXS) and fluorescence microscopy, helped in linking the physical properties of lipid:DNA complex (lipoplex) with its intracellular fate. This biological knowledge has been incorporated in the design of the second-generation cationic lipids. Lipid-peptide conjugates (peptoids) are effective strategies to overcome the various cellular barriers along with the lipoplex formulations methodologies. In this context, cationic lipid-mediated gene delivery is considerably benefited by the methodologies of liposome-mediated drug delivery. Lipid mediated gene delivery has an intrinsic advantage of being a biomimetic platform on which considerable variations could be built to develop efficient in vivo gene delivery protocols.     

Pivotal Role of Mitochondrial Calcium Uptake in Neural Cell Apoptosis and Necrosis

Abstract : Perturbed cellular calcium homeostasis has been implicated in both apoptosis and necrosis, but the role of altered mitochondrial calcium handling in the cell death process is unclear. The temporal ordering of changes in cytoplasmic ([Ca²⁺]C) and intramitochondrial ([Ca²⁺]M) calcium levels in relation to mitochondrial reactive oxygen species (ROS) accumulation and membrane depolarization (MD) was examined in cultured neural cells exposed to either an apoptotic (staurosporine ; STS) or a necrotic (the toxic aldehyde 4-hydroxynonenal ; HNE) insult. STS and HNE each induced an early increase of [Ca²⁺]C followed by delayed increase of [Ca²⁺]M. Overexpression of Bcl-2 blocked the elevation of [Ca²⁺]M and the MD in cells exposed to STS but not in cells exposed to HNE. The cytoplasmic calcium chelator BAPTA-AM and the inhibitor of mitochondrial calcium uptake ruthenium red prevented both apoptosis and necrosis. STS and HNE each induced mitochondrial ROS accumulation and MD, which followed the increase of [Ca²⁺]M. Cyclosporin A prevented both apoptosis and necrosis, indicating critical roles for MD in both forms of cell death. Caspase activation occurred only in cells undergoing apoptosis and preceded increased [Ca²⁺]M. Collectively, these findings suggest that mitochondrial calcium overload is a critical event in both apoptotic and necrotic cell death.     

Neuropathological Aspects of Mitochondrial DNA Disease

Mitochondrial DNA disorders are an important cause of neurological disease, yet despite our awareness of the importance of these conditions, relatively little is known about the neuropathology of these disorders and even less about the mechanisms involved in neuronal dysfunction and death. In this review we detail important features from neuropathological studies available and highlight deficiencies that are currently limiting our understanding of mitochondrial DNA disease. We also discuss possible future approaches that might resolve some of these outstanding issues. Further study of these disorders is critical because mitochondria play a central role in neuronal survival and it is likely that an understanding of the mechanisms involved in neuronal dysfunction and cell death in mitochondrial DNA disease may have implications for other neurodegenerative diseases.     

Some Physiological Aspects of Copper and Zinc Tolerance in Agrostis tenuis Sibth.: Cell Elongation and Membrane Damage

Three clones of Agrostis tenuis Sibth. were studied with respectto the effects of Zn and Cu on the growth of root segments excisedfrom the zone of cell elongation. Elongation growth in segmentsfrom a Cu-tolerant and a Zn-tolerant clone was inhibited toa lesser extent by Cu and Zn respectively than was the growthof a clone which was not tolerant to these metals. Concentrationsof Cu²⁺ which inhibited root growth also caused leakage of K⁺from the cells but toxic concentrations of Zn²⁺ did not induceK⁺ leakage. Copper induced a higher rate of K⁺ leakage at 25than at 0 °C. The impllcations of these results for thesite of the toxic effects of Zn and Cu and the nature of theresistance mechanisms are discussed.     

Physiological and Biochemical Aspects of Halophyte Ecology

Physiological and biochemical features of euhalophytes, сrinohalophytes, and glycohalophytes growing in natural conditions in El’ton Lake area were studied. The water content in tissues, intensity of lipid peroxidation, and membrane permeability were found to determine the differentiation of plants by their salt accumulation strategy. The concentration of pigments and their ratio are related to the mesostructure of leaves and are dependent on the salt accumulation strategy and life form. The membrane complex is connected with the cell structure and photosynthetic apparatus. The specificity of ion transportation depends on the specific features of plants.     

Chemical and Biological Aspects of Garcinol and Isogarcinol: Recent Developments

The natural polyisoprenylated benzophenone derivatives garcinol and isogarcinol are secondary plant metabolites isolated from various Garcinia species including Garcinia indica. This review takes stock of the recent chemical and biological research into these interesting natural compounds over the last five years. New biological sources and chemical syntheses are discussed followed by new insights into the activity of garcinol and isogarcinol against cancer, pathogenic bacteria, parasite infections and various inflammatory diseases.     

Applicability of Yeast Extracellular Proteinases in Brewing: Physiological and Biochemical Aspects

A general screening survey for expression of extracellular acid proteinase production was performed on over 100 cultures belonging to the genus Saccharomyces. Although two strains of Saccharomyces cerevisiae showed positive extracellular proteinase phenotypes in plate tests, it was not possible to demonstrate proteolytic activities in cell-free culture supernatants in assays performed at beer pH values. Of several yeasts from other genera examined, Saccharomycopsis fibuligera and Torulopsis magnoliae produced extracellular proteinases with desirable properties. Proteolytic activities were detected in assays performed at beer pH values and at lower temperature. Brewer's wort served as a highly inducing medium for extracellular proteinase production, with T. magnoliae yielding enzyme of highest specific activity. In fact, commencement of enzyme production was detected shortly after the onset of exponential growth in brewer's wort. Inclusion of crude enzyme preparations in brewer's wort inoculated simultaneously with brewer's yeast reduced final ethanol yields slightly and was found to be effective in reducing chill haze formation in bottled beer.