The hyperbolic effect of density and strength of inter beta-cell coupling on islet bursting: a theoretical investigation

Background  

Insulin, the principal regulating hormone of blood glucose, is released through the bursting of the pancreatic islets. Increasing evidence indicates the importance of islet morphostructure in its function, and the need of a quantitative investigation. Recently we have studied this problem from the perspective of islet bursting of insulin, utilizing a new 3D hexagonal closest packing (HCP) model of islet structure that we have developed. Quantitative non-linear dependence of islet function on its structure was found. In this study, we further investigate two key structural measures: the number of neighboring cells that each β-cell is coupled to, n _c, and the coupling strength, g _c.     

Characterization of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Strain DOR4 Toxic to Castor Semilooper <Emphasis Type="Italic">Achaea janata</Emphasis>: Proteolytic Processing and Binding of Toxins to Receptors

We have isolated a strain of Bacillus thuringiensis (Bt) from Indian soil samples that was shown to be toxic to Achaea janata larvae. The isolate, named B. thuringiensis DOR4, serotypically identified with the standard subspecies kurstaki (H3a3b3c) and produced bipyramidal inclusions along with an amorphous type. Although the plasmid pattern of DOR4 was different from that of the reference strain, a crystal protein profile showed the presence of two major bands (130 and 65 kDa) similar to those of Bt subsp. kurstaki HD-1. To verify the cry gene content of DOR4, triplex PCR analysis was performed; it showed amplification of the cry1C gene in addition to cry1Aa, cry1Ac, cry2A, and cry2B genes, but not the cry1Ab gene. RT-PCR analysis showed the expression of cry1Aa and cry1Ac genes. In vitro proteolysis of DOR4 protoxin with midgut extract generated products of different sizes. Zymogram analysis of DOR4 protoxin as substrate pointed to a number of distinct proteases that were responsible for activation of protoxins. Furthermore, toxin overlay analysis revealed the presence of multiple toxin-binding proteins in midgut epithelium. Based on all these characterizations, we suggest that the Bt DOR4 strain can be exploited for an A. janata control program.     

Assembly and disassembly of the photosystem II manganese cluster reversibly alters the coupling of the reaction center with the light-harvesting phycobilisome

The light-driven oxidative assembly of Mn (2+) ions into the H 2O oxidation complex (WOC) of the photosystem II (PSII) reaction center is termed photoactivation. The fluorescence yield characteristics of Synechocystis sp. PCC6803 cells undergoing photoactivation showed that basal fluorescence, F 0, exhibited a characteristic decline when red, but not blue, measuring light was employed. This result was traced to a progressive increase in the coupling of the phycobilisome (PBS) to the PSII reaction center as determined by observing the changes in room temperature and 77 K fluorescence emission spectra that accompany photoactivation. The results support the hypothesis that strong energetic coupling of the PBS to the PSII reaction center depends upon the formation of an active WOC, which presumably diminishes the likelihood of photodamage to reaction centers that have either lost an intact Mn cluster or are in the process of assembling an active WOC.     

Some studies on characterization of three phase partitioned chitosan

Three phase partitioning (TPP) is generally carried out by adding ammonium sulfate and t-butanol to a solution of a macromolecule. Chitosan could be obtained as an interfacial precipitate with 88% yield by subjecting 0.2% (w/v) chitosan solution to TPP with 45% (w/v) ammonium sulfate, with an equal volume of t-butanol at 40 °C. TPP resulted in structural changes which could be seen in its UV spectra, FT-IR spectra and solubility characteristics. TPP-treated chitosan also showed decreased susceptibility towards hydrolysis by chitinase. Thus, TPP can be used as a useful way of altering the properties of chitosan.     

Lactobacillus plantarum USM8613 Aids in Wound Healing and Suppresses Staphylococcus aureus Infection at Wound Sites

Probiotics and Antimicrobial Proteins - This study aimed to elucidate the targets and mechanisms of anti-staphylococcal effects from bioactive metabolites produced by lactic acid bacteria. We aimed...