Ascorbic acid formulation for survivability and diazotrophic efficacy of Azotobacter chroococcum Avi2 (MCC 3432) under hydrogen peroxide stress and its role in plant-growth promotion in rice (Oryza sativa L.).

Oxidative stress generates reactive oxygen species which causes cell damage of living organisms and are normally detoxified by antioxidants. Indirect reports signify the damages caused by reactive oxygen species and neutralized by antioxidant, but the direct evidence to confirm this hypothesis is still unclear. To validate our hypothesis, an attempt was made in a diazotrophic bacterium (Azotobacter chroococcum Avi2) as a biological system, and hydrogen peroxide (H2O2) and ascorbic acid were used as oxidative stress and antioxidant supplement, respectively. Additionally, rice plant-growth attributes by Avi2 was also assessed under H2O2 and ascorbic acid. Results indicated that higher concentration of H2O2 (2.5 mM-4.5 mM) showed the complete mortality of Avi2, whereas one ppm ascorbic acid neutralized the effect of H2O2. Turbidity, colony forming unit, DNA quantity, nifH gene abundance, indole acetic acid and ammonia productions were significantly (p < 0.5) increased by 11.93%, 17.29%, 19.80%, 74.77%, 71.89%, and 42.53%, respectively in Avi2-treated with 1.5 mM H2O2 plus ascorbic acid compared to 1.5 mM H2O2 alone. Superoxide dismutase was significantly (p < 0.5) increased by 60.85%, whereas catalase and ascorbate peroxidase activities were significantly (p < 0.05) decreased by 64.28% and 68.88% in Avi2-treated with 1.5 mM H2O2 plus ascorbic acid compared to 1.5 mM H2O2 alone. Germination percentage of three rice cultivars (FR13a, Naveen and Sahbhagi dhan) were significantly (p < 0.5) increased by 20%, 13.33%, and 4%, respectively in Avi2-treated with 0.6 mM H2O2 plus ascorbic acid compared with uninoculated control. Overall, this study indicated that ascorbic acid formulation neutralizes the H2O2-oxidative stress and enhances the survivability and plant growth-promoting efficacy of A. chroococcum Avi2 and therefore, it may be used as an effective formulation of bio-inoculants in rice under oxidative stress.

Mosquito control by larvivorous fish.

There is growing of the effects of insecticide used controlling the vectors of human diseases. Manipulating or introducing an auto-reproducing predator into the ecosystem may provide sustained biological control of pest populations. The selection of a biological agent should be based on its self-replicating capacity, preference for the target pest population in the presence of alternate natural prey, adaptability to the introduced environment, and overall interaction with indigenous organisms. In order to achieve an acceptable range of control, a sound knowledge of various attributes of interactions between the pest population and the predator to be introduced is desirable. Biological larviciding for the control of mosquito borne diseases is feasible and effective only when breeding sites are relatively few or are easily identified and treated. Larval control appears to be promising in urban areas, given that the density of humans needing protection is higher than the limited number of breeding sites. Since 1937, fish have been employed for controlling mosquito larvae. Different types of fish have been used so far in this operational technique. However, use of fish of indigenous origin is found to be more appropriate in this operation. This review presents information on different larvivorous fish species and the present status of their use in mosquito control and provides a ready reference for workers involved and interested in mosquito research.

Lymphatic filariasis in the coastal areas of Digha, West Bengal, India.

The state of West Bengal, India, has a long coastline with the Bay of Bengal. No information exists regarding filarial epidemiology and its vector in these coastal areas. The present study was designed to assess the epidemiology of lymphatic filariasis and the role of available mosquitoes as its vector in eight coastal villages around Digha, West Bengal. Night blood samples of 4016 individuals were collected and each of them was examined clinically for any manifestations of the disease. Overall, microfilaria rate, mean microfilarial density and disease rate were 9.06%, 8.63% and 7.72%, respectively. The causative parasite was identified as Wuchereria bancrofti and Culex quinquefasciatus was incriminated as the vector responsible. Vector infection and infectivity rates were assessed to be 12.5% and 0.73%, respectively. The human blood index of human-house-frequenting vector population was 70%. Vector density, vector infection, infectivity rates and human blood index were higher in the rainy season in the study area. Overall, the filarial situation was bad and, as a measure, single-dose diethylcarbamazine citrate (6 mg/kg body weight) treatment was given to all the microfilariaemic patients. Night blood samples of the treated individuals were tested for microfilariae on days 10 and 365, which revealed interesting results.

Eco-friendly control of mosquito larvae by Brachytron pratense nymph.

The study reported here revealed the biocontrol efficacy of aquatic nymphs of the dragonfly Brachytron pratense against larvae of the mosquito Anopheles subpictus. It was found that during a 24-hour study period, a nymph of B. pratense would consume (mean value of three observations) 66 fourth-instar An. subpictus larvae released in a water bowl containing 3 liters of pond water. The consumption rate was significantly higher (p < .05) during the lights-on phase of the experiment than during the lights-off phase (t = 2.15). Under field conditions, a significant decrease (p < .05) in larval density in dipper samples was observed 15 days after the introduction of dragonfly nymphs (10 individuals) in concrete tanks. The biocontrol potential of the nymphs under field conditions was also indicated by a significant increase (p < .05) in the density of mosquito larvae 15 days after the removal of nymphs. In the control tanks (where no nymphs were introduced), mean larval-mosquito density did not differ significantly throughout the study period (p > .05).

Lipopolysaccharides of Vibrio cholerae: III. Biological functions.

This review presents the salient features of the biological functions including the (i) endotoxic activities, (ii) antigenic properties, (iii) immunological responses to and (iv) phage receptor activities of the Vibrio cholerae lipopolysaccharides (LPS). The biological functions of the capsular polysaccharide (CPS) of V. cholerae have also been discussed briefly as a relevant topic. The roles of LPS and other extracellular polysaccharides in the (i) intestinal adherence and virulence of the vibrios and (ii) the biofilm formation by the organisms have been analysed on the basis of the available data. Every effort has been made to bring out, wherever applicable, the lacunae in our knowledge. The need for the continuous serogroup surveillance and monitoring of the environmental waters and the role of LPS in the designing of newer cholera vaccines has been discussed briefly in conclusion.

Molecular analysis of divergence in tachinid Uzi (Exorista sorbillans) populations in India.

Exorista sorbillans is a tachinid endoparasitoid of silkworm, Bombyx mori, and is globally known as uzi. It causes economic injury to the cocoon crop in silkworm cultivating areas of India, except those above 400 m above mean sea level (AMSL) in the foothills of the Himalayas (Darjeeling). It is reported that the sericulture tract of south India became infected with this pest only since 1980 through an accidental transportation of cocoons from West Bengal. To ascertain whether the genome of this parasitoid is differentiating into discrete gene pools in contrasting geo-climatic conditions, molecular profiling of four populations (Es (Annatapur), Es(Ramanagaram), Es (Channapatna) and Es(Kodathi) from south India and Es(Murshidabad) from Murshidabad, West Bengal was undertaken with 13 ISSR, 3 RAPD and six non-random primers designed from various repeat sequences of B. mori . MANOVA indicated significance for the Roy's largest root estimate (55.4; F =18.47; p = 0.002) for the variability contributed by the replication. Further, hierarchical clustering done on the basis of Euclidean distance matrix and Nei's unbiased Phylip clustering put Es(Murshidabad) at the maximum distance from those of south India and 29 markers could also be identified which significantly differentiateEs(Murshidabad) from others. However, Nei's statistics for gene diversity in sub-populations reveal considerably high gene-flow (3.44 and 2.51) among the populations around Bangalore. The gene-flow between Es(Murshidabad) and other population is lowest but cannot be ignored. The comparison of endosymbiont specific 16SrRNA and fts Z gene (partial) sequences through clustalW (gcgMSF) revealed a closer relationship of Es(Murshidabad) with Es(Annatapur) and Es (Ramanagaram) and is not congruent with the relationships discussed above. The significance of this maiden study with a tachinid fly-pest is discussed in the context of understanding the diversification of Uzi fly-pest and also establishing this pest as a relevant biological material for studying microevolution in future.

Molecular genetic approach for identifying markers associated with yield traits in the silkworm, Bombyx mori using RFLP-STS primers.

Bombyx mori, the mulberry silkworm, exhibits wide variability in yield and developmental attributes. The genetics of yield expression, shown to be of polygenic nature, is poorly studied in silkworm. To identify markers associated with 10 selected yield traits, multiple regression analysis (MRA) and discriminant function analysis (DFA) were applied on 64 markers generated with eight RFLP-derived sequence-tagged-site (STS) primers on the genomic DNA of 20 silkworm stocks of different origin and diverse yield potential. The analyses led to the identification of ten markers showing significant association with the different yield traits. The markers could classify the stocks according to yield potential, irrespective of their origin and status of diapause. Trait means were significantly different for stocks with and with out the associated marker. The inheritance of a marker G2(1300bp), selected at the first step of MRA for five yield traits was shown to segregate in 1:1 ratio in the F2 progeny from a cross between two divergent stocks. The relevance of the STS primers is discussed in the context of applying multiple regression model for identifying markers associated with yield expression and suitability for molecular breeding work in B. mori for yield improvement.

Lipopolysaccharides of Vibrio cholerae II. Genetics of biosynthesis.

An account of our up to date knowledge of the genetics of biosynthesis of Vibrio cholerae lipopolysaccharide (LPS) is presented in this review. While not much information is available in the literature on the genetics of biosynthesis of lipid A of V. cholerae, the available information on the characteristics and proposed functions of the corepolysaccharide (core-PS) biosynthetic genes is discussed. The genetic organizations encoding the O-antigen polysaccharides (O-PS) of V. cholerae of serogroups O1 and O139, the disease causing ones, have been described along with the putative functions of the different constituent genes. The O-PS biosynthetic genes of some non-O1, non-O139 serogroups, particularly the serogroups O37 and O22, and their putative functions have also been discussed briefly. In view of the importance of the serogroup O139, the origination of the O139 strain and the possible donor of the corresponding O-PS gene cluster have been analyzed with a view to having knowledge of (i) the mode of evolution of different serogroups and (ii) the possible emergence of pathogenic strain(s) belonging to non-O1, non-O139 serogroups. The unsolved problems in this area of research and their probable impact on the production of an effective cholera vaccine have been outlined in conclusion.

Morphological and molecular variation of Morus laevigata in India.

Morus spp., commonly known as mulberry, is significantly associated with human civilization and spread of silk-culture from Asia to Europe, Africa and Latin America. One of its species, Morus laevigata, traditionally well known for its timber value, forage use and silkworm's feed, is widely distributed in India extending from Himalayan foothill to Andaman islands. The variability occurring for 12 morpho-biochemical parameters and RAPD profiles, generated with 13 selected RAPD primers, for M. laevigata accessions from six different zones were investigated. Analyses revealed high degree of genotypic similarity of collection from Himalayan foothill (West Bengal) with those from Andaman Islands. Specific accessions from central India and south India also revealed genotypic similarities with specific accessions from north-east India. These observations are discussed in the context of clonal propagation of mulberry and evolutionary perspective of dispersal of this species, through human activities

ISSR profiling of genetic variability in the ecotypes of Antheraea mylitta Drury, the tropical Tasar silkworm.

Antheraea mylitta, Drury, the semi-wild silk-producing lepidopteran insect commonly known as tasar silkworm is unique to India and is distributed over a wide tropical forest range covering the states of Andhra Pradesh, Bihar, Chhattisgarh, Madnya Pradesh, Maharashtra, Orissa and Uttaranchal. The populations found in different areas are know by their specific local names and are considered as different ecotypes, but it is difficult to separate the populations on the basis of morphological and life-cycle traits and thus molecular characterization was attempted. The present communication relates to the results obtained from the analysis of polymorphism unraveled by twelve ISSR primers for 11 populations of A. mylitta belonging to six ecotypes and 41 individuals of "Railey"--ecotype collected from five zones of Dandakarnya forest in Madnya Pradesh. This communication, further, presents molecular evidences on genetic differences between eleven ecotype populations and highlights the genotypic diversification of a single ecotype into further separate discrete gene pools. The canonical discriminant function analysis revealed grouping of the five populations of Railey ecotype into two "clumps", while accessions of other ecotypes stood separated from each other. Thr "Railey" populations on detailed study, further, revealed separation of two (Tokapal and Nangur) populations into discrete gene pools and the other three (Kondagaon, Darba and Tongpal) populations, in spite of larger geographic distance between them, overlapped one on the other. The analysis also identified nine markers, which can be utilized to characterize specific population and will be of help to follow the ongoing genetic changes triggered by various ecological factors and human influences on the "Railey" ecotype.

Molecular profiling of silkworm biodiversity in India.

Molecular tools opened a new vista to understand nature's bio-diversity and its relevance and the same approach was availed of to build-up the foundation work on the bio-diversity of silkworm spp in India. It is well established that the heritage of usage of silk for dress materials in India, Russia and China dates back to premedieval period and in spite of industrial development resulting to de-forestation, India still can claim as the owner of wide bio-diversity, espicially in northern India for silkworm spp. The molecular diversity was assessed among Antheraea mylitta, A. assama, A. pernyi, A. provlei, A. roylei and Philcosomia cynthia wiht 11 ISSR and 8 non-random primers on agarose gel. Nei's statistics as also Euclidean distance matrix was applied to find the genetic diversity between the six species, wherein the closest relationship between A. pernyi and A. proylei is established. With the help of POPGEN statistics, the average genetic heterozygosity appeared as 0.271 while Shanon's index is 0.4312 and alleles with segregation ratios of 3:1, 2:1, 1:1, 9:1 (generated with ISSR primers) were identified which can be utilized for future molecular breeding porgram. Further, and attempt was made to isolate a number of bands generated with 3 ISSR and six non-random primers, specific for different species and 22 such markers have been characterized through sequencing which will be made available through international public domain database.

Lipopolysaccharides of Vibrio cholerae. I. Physical and chemical characterization.

Vibrio cholerae is the causative organism of the disease cholera. The lipopolysaccharide (LPS) of V. cholerae plays an important role in eliciting the antibacterial immune response of the host and in classifying the vibrios into some 200 or more serogroups. This review presents an account of our up-to-date knowledge of the physical and chemical characteristics of the three constituents, lipid-A, core-polysaccharide (core-PS) and O-antigen polysaccharide (O-PS), of the LPS of V. cholerae of different serogroups including the disease-causing ones, O1 and O139. The structure and occurrence of the capsular polysaccharide (CPS) on V. cholerae O139 have been discussed as a relevant topic. Similarity and dissimilarity between the structures of LPS of different serogroups, and particularly between O22 and O139, have been analysed with a view to learning their role in the causation of the epidemic form of the disease by avoiding the host defence mechanism and in the evolution of the newer pathogenic strains in future. An idea of the emerging trends of research involving the use of immunogens prepared from synthetic oligosaccharides that mimic terminal epitopes of the O-PS of V. cholerae O1 in the development of a conjugate anti cholera vaccine is also discussed.

Identification of ISSR markers associated with productivity traits in silkworm, Bombyx moni L.

Bombyx mori L., commonly recognised around the world as the mulberry silkworm, is characterized by a wide variability in yield and developmental traits, which have been proven through conventional genetic analysis to be of polygenic nature. A large number of morpho-biochemical traits and RFLP and RAPD markers are mapped on different linkage groups, but to this point very little attention has been given to unravelling the genetics of yield traits. To address this issue, polymorphic profiles of 147 markers generated with 12 ISSR primers on the genomic DNA of 20 silkworm stocks of diverse yield status were subjected to multiple regression and discriminant function analyses (DFA). This led to the identification of eight markers generated by six primers, which demonstrated high beta-coefficient indices of -0.451 to -0.940. Furthermore, a significant difference between the yield traits for stocks with and without the specific marker could also be established. The inheritance pattern of one marker, L13800bp, identified at the first step of selection of markers through stepwise regression analyses for five yield parameters is discussed in the context of applying multiple regression analysis for establishing association, if not linkage, between a group of DNA markers and a particular yield trait of polygenic nature and using such markers in molecular marker-assisted breeding programs.

Treatment of microfilaraemics with DEC and its effect on vector infection and infectivity in tribal and non-tribal areas of Bankura district, West Bengal, India.

Single course DEC treatment (6 mg/kg body weight/day for 12 days) was administered to 66 tribal and 442 non-tribal microfilaria (mf) carriers detected through a Filariasis survey in Bankura district, West Bengal, India. All the mf carriers remained amicrofilaraemic on 22nd, 180th and 365th post-treatment day. As a result of DEC treatment to the mf carriers, vector (Culex quinquefasciatus) infection rate in tribal study areas reduced from 2.06% to 1.07%. Infectivity rate was "nil" both before and after treatment. In non-tribal study areas, vector infection rate reduced from 4.33% to 2.22% and infectivity rate from 0.51% to 0.29%.

Molecular markers (RAPD) associated with growth, yield and origin of the silkworm, Bombyx mori L. in India.

To identify the molecular markers associated with growth and yield parameters in silkworm, Bombyx mori, RAPD profiles generated with seven UBC primers for fourteen silkworm stocks, originated from China, Japan, India and Russia, were statistically analyzed. Stepwise Multiple Regression Analysis establishes significant association of 45 markers with larval span, growth indices and four cocoon yield parameters relevant for silk production and t-test attest significance of the association of 89.5(1500 bp) and 54.13(300 bp), respectively with longer larval duration and high cocoon weight. The validity of this selection of markers was further supported with Discriminant Function Analysis (DFA) done on the basis of Mahalanobis D2 statistics. The two indices of yield/growth were also tested with DFA, which helped in identifying a few markers and thereby opened scope of using such marker (e.g. 91.11(900 bp)) for incorporating molecular markers in the breeding program for crop improvement in silkworm.

Computerised tomographic study of tuberculous meningitis in children.

Twenty-one patients with clinical and laboratory diagnosis of tuberculous meningitis were studied at the paediatric department and neuroradiology unit of Bangur Institute of Neurology, both attached to IPGME & R, Kolkata, during the period from 1st February, 1996 to 31 st July, 1996. The age group of the patients were between 1 and 8 years. It clearly appears that CT is an extremely powerful investigative modality for the diagnosis, management and follow-up assessment of development of any complications like hydrocephalus, cerebral infarction, etc. CT examination also can predict the prognosis of the patients.

On the inhibitory activities of a new boron compound and ultrasound against the mouse ascites tumour.

The inhibitory effects of a new boron compound, dihydroxy (oxybiguanido) boron (III) hydrochloride monohydrate (HB), and ultrasound (US) of a frequency 25 kHz on the growth of ascites tumour in female Swiss mice were studied by monitoring the survival, weight of tumour-associated material, tumour cell count, serum alkaline phosphatase activity and the haematological parameters of the treated animals. 5-Fluorouracil (5-FU), a well-known anticancer agent, was used as positive control. While HB exhibited a very significant antitumour action, US alone produced a small but significant inhibitory effect. The combination of US with HB or 5-FU produced an extra antitumour action as compared to the actions of these chemicals used singly. The mechanisms of action of the new boron compound (HB) and US are discussed.

On the possible use of a new boron compound, hydroxysalicylhydroxamato boron(III), and ultrasound in the treatment of female mice bearing the Ehrlich ascites carcinoma cells.

The inhibitory effects of a new boron compound, hydroxy salicylhydroxamato boron (III) (SHB) and ultrasound of frequency 25 KHz (US) on the growth of ascites tumor in female Swiss mice were studied by monitoring the survival and the tumor growth in the treated tumor bearing mice and also the transplantability and the DNA synthesis in the treated tumor (Ehrlich ascites carcinoma) cells. While SHB alone produced a highly significant antitumor activity, US alone produced a small but significant effect. The combination of SHB and US produced significantly greater antitumor activity than SHB alone. The mechanisms of SHB and US actionary are discussed.

On the induction of protective responses in Salmonella typhimurium strain TA1535/pSK1002 by UVA (365 nm).

Exposure to UVA (365 nm) led to growth delay, loss of viability and inhibition of 3H-thymidine incorporation into the cells of Salmonella typhimurium strain TA1535 containing multiple copies of a plasmid pSK1002 carrying a umuC'-'lacZ fusion gene. Ultraviolet-A induced umu gene expression, as monitored by the estimation of beta-galactosidase, in a linear fluence-dependent manner. The induction of umu gene expression increased with the increase of postirradiation incubation period of the cells in the LB-ampicillin (LBA) medium at 37 degrees C and leveled off from 2 h onward. The induction of gene expression depended on concomitant protein synthesis and represented the induction of the SOS response in the particular S. typhimurium cells used. The exposure to low fluences (sublethal) of UVA also led to the induction of an adaptive response in the same bacterial cells, which made them resistant to subsequent challenge by a much higher fluence of the same radiation. The adaptive response, as monitored by the assays of viability and beta-galactosidase units, increased with the period of exposure to sublethal fluences of UVA, attained a maximum at the UVA exposure of 4.5 kJ/m2 (15 min) and thereafter gradually decreased with further increase of UVA exposure period. Modulation studies involving D2O, LBA growth medium, different scavengers of free radicals and quenchers of activated oxygen species indicated the involvement of both hydroxyl free radicals and singlet oxygen in the UVA-induced umu gene expression.