Comparative field cage tests of the population suppressing efficiency of three genetic control systems for Aedes Aegypti.

Cycling populations of Aedes aegypti were set up in cages and managed in such a way that the populations had a maximum of threefold recovery potential in response to control measures. Into three such populations daily releases were made of males which had been chemosterilised, or were double translocation heterozygotes (T1T3) or T1T3 with sex ration distortion (DT1T3). Eradication of the populations was achieved with all cases, but the rate of suppression was markedly slower with T1T3 than the other two systems, with which the rates were similar. T1T3 and DT1T3 releases introduced considerable inherited genetic loads into the target populations. The results were in general agreement with computer predictions.     

Efficacy of l-proline administration on the early responses during cutaneous wound healing in rats

Proline (Pro) plays a versatile role in cell metabolism and physiology. Pro and hydroxypro are major imino acids present in collagen, an important connective tissue protein, essential for wound healing, which is a primary response to tissue injury. This study explains the role of l-pro on cutaneous wound healing in rats when administered both topically and orally. Open excision wounds were made on the back of rats, and 200 μl (200 mg) of pro was administered topically and orally once daily to the experimental rats until the wounds healed completely. The control wounds were left untreated. Granulation tissues formed were removed after day 4 and 8 of post excision wounding, and biochemical parameters such as total protein, collagen, hexosamine, and uronic acid were estimated. Levels of enzymatic and non-enzymatic antioxidants such as catalase, superoxide dismutase, glutathione peroxidase, ascorbic acid, and reduced glutathione were evaluated along with lipid peroxides in the granulation tissues. Tensile strength and period of epithelialization were also measured. It was observed that the treated wounds healed very fast as evidenced by augmented rates of epithelialization and wound contraction, which was also confirmed by histological examinations. The results strappingly authenticate the beneficial effects of the topical administration of l-proline in the acceleration of wound healing than the oral administration and control.     

Structural basis for triclosan and NAD binding to enoyl-ACP reductase of Plasmodium falciparum

Recent discovery of type II fatty acid synthase in the malarial parasite Plasmodium falciparum responsible for the most debilitating form of the disease in humans makes it ideal as a target for the development of novel antimalarials. Also, the identification of the enoyl-acyl carrier protein reductase from P. falciparum and the demonstration of its inhibition by triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol], a potent antibacterial compound, provide strong support for the above. In the studies reported here, a model of the enzyme in complex with triclosan and the cofactor NAD has been built by homology modeling with a view to understand its binding properties and to explore the potential of triclosan as a lead compound in designing effective antimalarial drugs. The model indeed provided the structural rationale for its interaction with ligands and the cofactor and revealed unique characteristics of its binding site which could be exploited for improving the specificity of the inhibitors.     

The effect of nerve growth factor on the early responses during the process of wound healing

In this study, we investigated the role of nerve growth factor (NGF)-incorporated collagen on wound healing in rats. Full-thickness excision wounds were made on the back of female rats weighing about 150-160 g. Topical application of NGF-incorporated collagen, at a concentration of 1 microg/1.2 mg collagen/cm(2), once a day, for 10 days resulted in complete healing of wounds on the 15th day. The concentrations of collagen, hexosamine and uronic acid in the granulation tissue were determined. The NGF-incorporated collagen-treated rats required shorter duration for the healing with an increased rate of wound contraction. Histological and electron microscopical evaluations were also performed, which reveal the activation of fibroblasts and endoplasmic reticulum and therefore increased level of collagen synthesis due to NGF application. These results clearly indicate that the topical application of NGF-incorporated collagen enhanced the rate of healing of excision wounds.     

Conformational stability and thermodynamic characterization of homotetrameric Plasmodium falciparum beta-ketoacyl-ACP reductase

The conformational stability of the homotetrameric Plasmodium falciparum beta-ketoacyl-ACP reductase (FabG) was determined by guanidinium chloride-induced isothermal and thermal denaturation. The reversible unfolding transitions were monitored by intrinsic fluorescence, circular dichroism (CD) spectroscopy and by measuring the enzyme activity of FabG. The denaturation profiles were analyzed to obtain the thermodynamic parameters associated with unfolding of the protein. The data confirm the simple A(4) <--> 4A model of unfolding, based on the corroboration of CD data by fluorescence transition and similar Delta G estimation for denaturation curves obtained at four different concentration of the FabG. Denaturation is well described by the linear extrapolation model for denaturant-protein interactions. In addition, the conformational stability (Delta G(s)) as well as the Delta C(p) for the protein unfolding is quite high, 22.68 kcal/mole and 5.83 kcal/(mole K), respectively, which may be a reflection of the relatively large size of the tetrameric molecule (Mr 120, 000) and a large buried hydrophobic core in the folded protein. This study provides a prototype for determining conformational stability of other members of the short-chain alcohol dehydrogenase/reductase superfamily of proteins to which PfFabG belongs.     

Structural basis for the functional and inhibitory mechanisms of β-hydroxyacyl-acyl carrier protein dehydratase (FabZ) of Plasmodium falciparum

The β-hydroxyacyl-acyl carrier protein dehydratase of Plasmodium falciparum (PfFabZ) catalyzes the third and important reaction of the fatty acid elongation cycle. The crystal structure of PfFabZ is available in hexameric (active) and dimeric (inactive) forms. However, PfFabZ has not been crystallized with any bound inhibitors until now. We have designed a new condition to crystallize PfFabZ with its inhibitors bound in the active site, and determined the crystal structures of four of these complexes. This is the first report on any FabZ enzyme with active site inhibitors that interact directly with the catalytic residues. Inhibitor binding not only stabilized the substrate binding loop but also revealed that the substrate binding tunnel has an overall shape of “U”. In the crystal structures, residue Phe169 located in the middle of the tunnel was found to be in two different conformations, open and closed. Thus, Phe169, merely by changing its side chain conformation, appears to be controlling the length of the tunnel to make it suitable for accommodating longer substrates. The volume of the substrate binding tunnel is determined by the sequence as well as by the conformation of the substrate binding loop region and varies between organisms for accommodating fatty acids of different chain lengths. This report on the crystal structures of the complexes of PfFabZ provides the structural basis of the inhibitory mechanism of the enzyme that could be used to improve the potency of inhibitors against an important component of fatty acid synthesis common to many infectious organisms.     

Signature of quaternary structure in the sequences of legume lectins.

Legume lectins exhibit a wide variety of oligomerization and sugar specificity while retaining the characteristic jelly-roll tertiary fold. An attempt has been made here to find whether this diversity is reflected in their primary structures by constructing phylogenetic trees. Dendrograms based on sequence alignment showed clustering related to the oligomeric nature of legume lectins. Though the clustering primarily follows the oligomeric states, it also appears to correlate with different sugar specificities indicating an interdependence of these two properties. Analysis of the structure-based alignment and the alignment of the sequences of the carbohydrate-binding loops alone also revealed the same features. By a close examination of the interfaces of the various oligomers it was also possible, in some cases, to pinpoint a few key residues responsible for the stabilization of the interfaces.     

Phenotypic and genotypic characterization of B.t.LDC-391 strain that produce cytocidal proteins against human cancer cells

An indigenous Bacillus thuringiensis strain B.t.LDC-391 producing cytocidal proteins against human colon cancer cell line, HCT-116, was subjected to phenotypic and genotypic characterization to evaluate its relatedness to B.anthracis. The morphological features of this strain were meta-analyzed with data of other parasporin and insecticidal protein producing Bacillus thuringiensis strains. The conventional biochemical analysis and antibiotic sensitivity test proved it as an ampicillin resistant which is a salient feature, absent in B.anthracis Ames. PCR analysis showed the absence of cyt and parasporin related genes in the genome of B.t.LDC-391. But the strain was positive for cap gene. The sequencing and bio-informatic analysis of cap gene and 16S rDNA of B.t.LDC-391 placed it closer to B.thuringiensis and revealed significant divergence from that of any B.anthracis strain. However our strain lacked β- hemolysis on human erythrocytes which is a common feature of B.anthracis strains and parasporin producers.     

Influence of calcium chloride and benzyladenine on lipoxygenase of Vigna unguiculata leaf discs during senescence

Cowpea ( Vigna unguiculata L.) leaf discs incubated in the dark in CaCl₂ and benzyladenine maintained higher levels of chlorophyll and protein than controls. The CaCl₂ or benzyladenine treatments reduced lipoxygenase activity, and the effect of these compounds in combination was additive. HPLC analysis of the product profile of lipoxygenase activity with arachidonic acid as a substrate showed a single peak comigrating with standard 15-hydroperoxyeicosatetraenoic acid. There appears to be a strong temporal correlation between the CaCl₂+ benzyladenine delay of senescence and lipoxygenase activity.     

Purification and partial characterization of a type V like collagen from the muscle of marine prawn,Penaeus indicus

The muscle collagen of marine prawn,Penaeus indicus, was isolated by limited pepsin digestion. Based on selective salt precipitation, amino acid composition and gel electrophoretic pattern, the major collagen was found to be a homotrimer of á 1 chain, similar to type V collagen of vertebrates. Electron microscopy of reconstituted fibrils, made for the first time from a crustacean species, revealed a characteristic 64 nm periodicity. Biochemical studies indicate a less than normal amount of associated carbohydrates and an increased alanine content The major collagen had a denatu ration temperature of 37°C with an intrinsic viscosity of 11.3 dl/g. Spectral characteristics of the major collagen were studied. Results suggest the presence of genetically distinct collagen types and acid resistant cross links in crustacean muscle.