IGF1 stimulates differentiation of primary follicles and their growth in ovarian explants of zebrafish (<Emphasis Type="Italic">Danio rerio)</Emphasis> cultured <Emphasis Type="Italic">in vitro</Emphasis>

The present study is an attempt to elucidate the involvement of insulin-like growth factor (IGF1) in the differentiation and growth of primary follicles in ovarian explant cultures of zebrafish. Ovaries from adult females were cultured in triplicate sets/treatment group for 15 days at 22°C in the laboratory. Culture medium was supplemented with either insulin (1 ng/mL) or IGF1 (1 ng/mL) or insulin + IGF1 (Experiment 1) or 0.1 or 1.0 or 10 ng/mL of IGF1 (Experiment 2). Ovaries cultured in medium alone served as controls and those fixed at the beginning of the culture as initial controls. Experiments were repeated. On the 16th day ovarian explants were fixed in Bouin’s fluid and processed for paraffin embedding, sections (3 µm) were cut and stained with hematoxylin-eosin. Follicles were classified into 6 stages and atretic follicles (AF). Previtellogenic, vitellogenic and total follicle number was calculated. At the start of the culture, ovaries contained all stages of growing and degenerating follicles. In in vitro cultured control ovaries, vitellogenic follicles underwent atresia, while, primary follicles remained unaffected. Insulin or insulin + IGF1 treated ovaries did not differ significantly while IGF1 exposed ovarian explants had greater (P < 0.05) number of primary follicles compared to controls. IGF1 also caused an increase in the number and growth of primary follicles in a dose dependent manner although; cultures were not supplemented with gonadotrophic hormones. Results suggest that locally derived intra-ovarian IGF1 may have a role in the differentiation and growth of primary follicles in zebrafish ovary.     

Selection of flowering forbs for conserving natural enemies in rice fields

The diversity of natural enemies harboured by flowering forbs on rice field bunds was recorded. Ageratum conozoides with a maximum Shannon diversity index of 1.8 followed by Acmella uliginosa, Eclipta alba and Tridax procumbens are amenable for ecological engineering, providing nectar, pollen and alternate prey to natural enemies.     

Immunodiagnosis of tuberculous meningitis: rapid detection of mycobacterial antigens in cerebrospinal fluid by reverse passive hemagglutination assay and their characterization by Western blotting

Tuberculous meningitis (TBM) is one of the commonest chronic infections of the central nervous system (CNS). Diagnosis of TBM has been a problem as it causes various clinical manifestations which can be confused with those of other chronic infections of the CNS such as neurocysticercosis (NCC), neurobrucellosis and cryptococcal meningitis, that are prevalent in many underdeveloped and developing countries. Differential diagnosis of TBM can be made by detecting circulating mycobacterial antigens in CSF by immunoassays. In this study, a reverse passive hemagglutination (RPHA) has been developed using rabbit antimycobacterial IgG for detection of circulating mycobacterial antigens in CSFs from chronic infections of the CNS in order to develop a rapid, simple, sensitive and cost-effective method. Circulating mycobacterial antigens were characterized by immunoblot assay. The sensitivity limit of RPHA was 400 ng ml(-1). RPHA was specific as antimycobacterial IgG did not show any reaction with porcine Cysticercus cellulosae which was used as a control antigen. RPHA could detect mycobacterial antigens in CSF at a sensitivity level of 94.11% with a specificity of 99.0%. Immunoblot analysis of RPHA positive CSFs revealed predominantly 30-32 kDa and 71 kDa antigens whilst 6, 86, 120, 96 and 110 kDa showed varied degree of reactivity. Antigens of masses 30-32 and 71 kDa were absent in culture filtrate of Mycobacterium tuberculosis H37Rv grown in Proskeur-Beck liquid medium. RPHA is a rapid, simple and sensitive immunological method with a long shelf life of 6-8 weeks if stabilized coated erythrocytes are stored at +4 degrees C. RPHA could be used as an additional immunodiagnostic tool in both differential diagnosis and prognosis of TBM. Immunoblot results indicate that 30-32 kDa and 71 kDa antigens are cell wall derived.     

Mineral proximity influences mechanical response of proteins in biological mineral-protein hybrid systems

The organic phase of nacre, which is composed primarily of proteins, has an extremely high elastic modulus as compared to that of bulk proteins, and also undergoes large deformation before failure. One reason for this unusually high modulus could be the mineral-organic interactions. In this work, we elucidate the specific role of mineral proximity on the structural response of proteins in biological structural composites such as nacre through molecular modeling. The "glycine-serine" domain of a nacre protein Lustrin A has been used as a model system. It is found that the amount of work needed to unfold is significantly higher when the GS domain is pulled in the proximity of aragonite. These results indicate that the proximity of aragonite has a significant effect on the unfolding mechanisms of proteins when pulled. These results will provide very useful information in designing synthetic biocomposites, as well as further our understanding of mechanical response in structural composites in nature.     

Living in the city: resource availability, predation, and bird population dynamics in urban areas

This article explores factors that shape population structure in novel environments that have received scant theoretical attention: cities. Urban bird populations exhibit higher densities and lower diversity. Some work suggests this may result from lower predation pressure and more predictable and abundant resources. These factors may lead to populations with few winners and many losers regarding access to food, body condition, and reproductive success. We explore these hypotheses with an individual-energy-based competition model with two phenotypes of differing foraging ability. We show that low frequency resource fluctuations favor strong competitors and vice versa. We show that low predation skews equilibrium populations in favor of weak competitors and vice versa. Increasing the time between resource pulses can thus shift population structure from weak to strong competitor dominance. Given recent evidence for more constant resource input and lower predation in urban areas, the model helps understand observed urban bird population structure.     

Differential distribution of simple sequence repeats in eukaryotic genome sequences.

Complete chromosome/genome sequences available from humans, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, and Saccharomyces cerevisiae were analyzed for the occurrence of mono-, di-, tri-, and tetranucleotide repeats. In all of the genomes studied, dinucleotide repeat stretches tended to be longer than other repeats. Additionally, tetranucleotide repeats in humans and trinucleotide repeats in Drosophila also seemed to be longer. Although the trends for different repeats are similar between different chromosomes within a genome, the density of repeats may vary between different chromosomes of the same species. The abundance or rarity of various di- and trinucleotide repeats in different genomes cannot be explained by nucleotide composition of a sequence or potential of repeated motifs to form alternative DNA structures. This suggests that in addition to nucleotide composition of repeat motifs, characteristic DNA replication/repair/recombination machinery might play an important role in the genesis of repeats. Moreover, analysis of complete genome coding DNA sequences of Drosophila, C. elegans, and yeast indicated that expansions of codon repeats corresponding to small hydrophilic amino acids are tolerated more, while strong selection pressures probably eliminate codon repeats encoding hydrophobic and basic amino acids. The locations and sequences of all of the repeat loci detected in genome sequences and coding DNA sequences are available at http://www.ncl-india.org/ssr and could be useful for further studies.     

Nanofibers and their applications in tissue engineering

Developing scaffolds that mimic the architecture of tissue at the nanoscale is one of the major challenges in the field of tissue engineering. The development of nanofibers has greatly enhanced the scope for fabricating scaffolds that can potentially meet this challenge. Currently, there are three techniques available for the synthesis of nanofibers: electrospinning, self-assembly, and phase separation. Of these techniques, electrospinning is the most widely studied technique and has also demonstrated the most promising results in terms of tissue engineering applications. The availability of a wide range of natural and synthetic biomaterials has broadened the scope for development of nanofibrous scaffolds, especially using the electrospinning technique. The three dimensional synthetic biodegradable scaffolds designed using nanofibers serve as an excellent framework for cell adhesion, proliferation, and differentiation. Therefore, nanofibers, irrespective of their method of synthesis, have been used as scaffolds for musculoskeletal tissue engineering (including bone, cartilage, ligament, and skeletal muscle), skin tissue engineering, vascular tissue engineering, neural tissue engineering, and as carriers for the controlled delivery of drugs, proteins, and DNA. This review summarizes the currently available techniques for nanofiber synthesis and discusses the use of nanofibers in tissue engineering and drug delivery applications.