• Volume 17, Issue 4

      December 1992,   pages  353-515

    • The determination of spatial pattern inDictyostelium discoideum

      Vidyanand Nanjundiah Shweta Saran

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      Free-living amoebae of the cellular slime mouldDictyostelium discoideum aggregate when starved and give rise to a long and thin multicellular structure, the slug. The slug resembles a metazoan embryo, and as with other embryos it is possible to specify a fate map. In the case ofDictyostelium discoideum the map is especially simple: cells in the anterior fifth of the slug die and form a stalk while the majority of those in the posterior differentiate into spores. The genesis of this anterior-posterior distinction is the subject of our review. In particular, we ask: what are the relative roles of individual pre-aggregative predispositions and post-aggregative position in determining cell fate? We review the literature on the subject and conclude that both factors are important. Variations in nutritional status, or in cell cycle phase at starvation, can bias the probability that an amoeba differentiates into a stalk cell or a spore. On the other hand, isolates, or slug fragments, consisting of only prestalk cells or only prespore cells can regulate so as to result in a normal range of both cell types. We identify three levels of control, each being responsible for guiding patterning in normal development: (i) ‘coin tossing’, whereby a cell autonomously exhibits a preference for developing along either the stalk or the spore pathway with relative probabilities that can be influenced by the environment; (ii) ‘chemical kinetics’, whereby prestalk and prespore cells originate from undifferentiated amoebae on a probabilistic basis but, having originated, interact (e.g. via positive and negative feedbacks), and the interaction influences the possibility of conversion of one cell type into the other; and (iii) ‘positional information’, in which the spatial distribution of morphogens in the slug influences the pathway of differentiation. In the case of possibilities (i) and (ii), sorting out of like cell types leads to the final spatial pattern. In the case of possibility (iii), the pattern arisesin situ

    • Genome analysis: A new approach for visualization of sequence organization in genomes

      Pradeep Kumar Burma Alok Raj Jayant K Deb Samir K Brahmachari

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      In this article we describe and demonstrate the versatility of a computer program, GENOME MAPPING, that uses interactive graphics and runs on an IRIS workstation. The program helps to visualize as well as analyse global and local patterns of genomic DNA sequences. It was developed keeping in mind the requirements of the human genome sequencing programme, which requires rapid analysis of the data. Using GENOME MAPPING one can discern signature patterns of different kinds of sequences and analyse such patterns for repetitive as well as rare sequence strings. Further, one can visualize the extent of global homology between different genomic sequences. An application of our method to the published yeast mitochondrial genome data shows similar sequence organizations in the entire sequence and in smaller subsequences

    • Quantitation of spermatogenesis by DNA flow cytometry: Comparative study among six species of mammals

      R Suresh G R Aravindan N R Moudgal

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      Suspensions of testicular germ cells from six species of mammals were prepared and stained for the DNA content with a fluorochrome (ethidium bromide) adopting a common technique and subjected to DNA flow cytometry. While uniform staining of the germ cells of the mouse, hamster, rat and monkey could be obtained by treating with 0.5% pepsin for 60 min followed by staining with ethidium bromide for 30 min, that of the guinea pig and rabbit required for optimal staining pepsinization for 90 min and treatment with ethidium bromide for 60 min. The procedure adopted here provided a uniform recovery of over 80% of germ cells with each one of the species tested and the cell population distributed itself according to the DNA content (expressed as C values) into 5 major classes-spermatogonia (2C), cells in S-phase, primary spermatocytes (4C), round spermatids (1C), and elongating/elongated spermatids (HC). Comparison of the DNA distribution pattern of the germ cell populations between species revealed little variation in the relative quantities of cells with 2C (8–11%), S-phase (6–9%), and 4C (6–9%) amount of DNA. Though the spermatid cell populations exhibited variations (1C:31–46%, HCl:7–20% and and HC2:11–25%) they represented the bulk of germ cells (70–80%). The overall conversion of 2C to 1C (1C:2C ratio) and meiotic transformation of 4C cells to 1C (1C:4C ratio) kinetics were relatively constant between the species studied. The present study clearly demonstrates that DNA flow cytometry can be adopted with ease and assurance to quantify germ cell transformation and as such spermatogenesis by analysing a large number of samples with consistency both within and across the species barrier. Any variation from the norms in germ cell proportions observed following treatment, fore.g. hormonal stimulation or deprivation can then be ascribed due to a specific effect of the hormone/drug on single/multiple steps in germ cell transformation

    • Characterization of the genome ofOryctes baculovirus, a viral biocide of the insect pestOryctes rhinoceros

      K S Mohan K P Gopinathan

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      Oryctes baculovirus is a viral biocide exploited for the control of the insect pestOryctes rhinoceros. We have recently established a physical map of the genome of the Indian isolate ofOryctes baculovirus (OBV-KI). Here we examine the genomic relatedness between OBV-KI and OBV-PV505, the type isolate (originally from the Philippines), by DNA reassociation kinetics and by the use of restriction endonucleases. On the basis of differences in restriction-enzyme profiles between the two genomes, and previously reported differences in protein profiles and antigenic makeup, we propose the taxonomic status of a variant ofOryctes baculovirus for the Indian isolate

    • Molecular aggregation of nucleotides and carbohydrates—their implication to prebiotic polymerization

      N Sukumar Vasantha Pattabhi

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      Hydrogen bonding pattern of nucleotides and carbohydrates has been analysed using Cambridge database. An analysis on ribonucleotides shows the 3′ …5′ hydrogen bond mediated aggregation to be the most common alignment. The 2′ …5′ alignment, which occurs under special circumstances in nature, is found to be the second choice. An analysis on carbohydrates suggests that self assembly of these molecules is not conducive to the formation of polysaccharides of the type which are found in present day living organisms. Further, the role of water molecules in the polymerization of three important biomolecules, namely nucleotides, carbohydrates and amino acids, has been analysed. Implication of these results to prebiotic polymerization is discussed

    • Chemical modification studies onCocos nucifera pollen allergens

      P Roy Karmakar B P Chatterjee

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      Two highly active allergens Cn II (Mr 158,000) and CnVII (Mr 2900) isolated fromCocos nucifera pollen extract were treated with various protein modifying reagents in order to ascertain the amino acid residues responsible for their allergenicity, In Cn II modification of carboxy group and tryptophan residue led to 30 and ≽ 75% loss in allergenicity and those of lysine and tyrosine reduced 62 and 38% activity, Lysine, tyrosine, tryptophan and carboxy group of CnVII were also modified causing 81, 17, ≽ 70 and 26% loss of allergenicity respectively, Allergenicity of both was highly affected by pronase and moderately affected by heat, Periodate destroyed about 50% of their allergenicity and other chemical reagents except urea had no remarkable effect

    • Immune response to an allergenic fraction ofSetaria digitata in human filariasis

      M K Beuria Manoj K Das

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      A low molecular weight antigenic fraction has been isolated from saline-soluble extracts of cattle filarial parasiteSetaria digitata. This glycoprotein fraction (Fr III) which appears to have low phosphorylcholine content cross-reacted with infective larval (L3) antigens ofWuchereria bancrofti. Binding of human chronic filarial serum with L3 antigens could be inhibited partially by Fr III. The fraction elicited immediate cutaneous hypersensitivity reaction in people living inWuchereria bancrofti endemic regions. The proportion of skin test positive cases was found to be highest in endemic normals in contrast to infected cases. IgE levels were however not different in chronic filariasis and in endemic normals (or in asymptomatic microfilaraemic carriers). On the other hand, specific IgG level was considerably enhanced only in chronic filariasis

    • 33-kDa C-terminal heparin binding fragment of fibronectin promotes attachment and spreading of hepatocytes

      N Anil Kumar P R Sudhakaran

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      The possibility of interaction of hepatocytes with the heparin binding domain of Fibronectin was examined. Rat hepatocytes adhered to coverslips coated with the 33-kDa heparin binding fragment of the C-terminal region of plasma fibronectin. When different concentrations of the heparin binding fragment were used to coat coverslips and used as substratum, cell attachment showed saturation kinetics. Half the maximum attachment was observed at 30–40 min after seeding of cells. The cells became flat after 2–3 h indicating that they spread on the heparin binding domain as they do on intact fibronectin. Among the different glycosaminoglycans tested, maximum inhibition of attachment was observed for heparin. However it was not possible to completely inhibit attachment even at high concentrations. These results indicate that hepatocytes interact with fibronectin not only through the Arg-Gly-Asp-containing cell binding fragment, but also through the heparin binding domain of fibronectin and, further, that there exist heparin-dependent and heparin-independent mechanisms of interaction of cells with the 33-kDa heparin binding fragment of fibronectin

    • Effect of fatty acids on the synthesis and secretion of apolipoprotein B by rat hepatocytes

      N Suresh Kumar Rita Abraham G Suresh Kumar P R Sudhakaran P A Kurup

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      The modulation of apolipoprotein B synthesis and secretion by fatty acids in rat hepatocytes was studied. Maximum apolipoprotein B production was obtained in the case of oleic acid followed by linoleic, stearic and palmitic/linolenic acid when compared to control which was not supplemented with any fatty acids. Oleic acid was found to exert a concentration dependent increase in the secretion of [3H] apolipoprotein B into the medium while that associated with the cell layer was not affected. Pulse chase experiments in the presence of oleic acid showed that it caused an increase in the secretion of apolipoprotein B into the medium.14C-acetate incorporation into cholesterol and cholesteryl ester associated with the cell layer and secreted very low density lipoproteins also showed an increase in the presence of oleic acid indicating an increase in cholesterogenesis. The effect of oleic acid on [3H] apolipoprotein B and very low density lipoproteins secretion appeared to be mediated through cholesterol as (i) ketoconazole, an inhibitor of cholesterol synthesis caused significant reduction in the stimulatory effect of oleic acid on apolipoprotein secretion and (ii) mevinolin, another inhibitor of cholesterol synthesis also reversed the stimulatory effect of oleic acid on apolipoprotein B secretion. These results indicated that oleic acid may influence apolipoprotein B synthesis and secretion in hepatocytes probably by affecting cholesterol/cholesteryl ester formation which may be a critical component in the secretion of apolipoprotein B as lipoproteins

    • Influence of chemical profiles of host plants on the infestation diversity ofRetithrips syriacus

      T N Ananthakrishnan R Gopichandran G Gurusubramanian

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      The onset of biotic stress in the host plants as a result of increased insect population size leads to enhanced levels of secondary metabolites and associated phenolic enzyme activity. Of the three host plants examined, viz.Ricinus communis (castor),Eucalyptus globulus (eucalyptus) andManihot utilissima (tapioca), castor was the host most preferred byRetithrips syriacus. Despite the fact that tapioca had the highest levels of secondary compounds, thrips infestation persisted. However, fecundity and growth were reduced because of the relatively high levels of primary metabolites. Gallic acid was found to be the most toxic of the phenolic acids, followed by pyrogallol, resorcinol, phloroglucinol and vanillic acid. The less toxic phenolic acids and flavanoids were detected in leaves that harboured thrips, while the preponderance of gallic acid was found in uninfested hosts. Thus the interaction ofRetithrips syriacus with the hosts is governed essentially by the biochemical profiles of its hosts, which tend to be altered subsequent to infestation, thus manifesting induced resistance through enhanced production of phenolics

    • Distribution of natural radionuclide40K in biotic and abiotic components of the Cauvery river system, Tiruchirapalli, India

      R Asokan P Shahul Hameed

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      Abiotic components like water and sediment, and biotic components such as mussels, fish and grass collected from Cauvery river at Tiruchirapalli were analysed for40K activity. The highest level of40K activity was found in the sediment (342 mBq g-1 dry weight) and the lowest activity was found in water (2·209 mBq ml−1). In the freshwater musselParreysia favidens (Benson)40K activity was estimated in the total soft tissues and shells of mussels belonging to three different size groups. In all the size groups40K activity was two times higher in shells (68–39 mBq g-1 fresh weight) than in the total soft tissues (25–17 mBq g-1 fresh weight). The results indicate that the younger mussels accumulated more40K than the older ones. The ability of internal organs of mussels belonging to group III to accumulate40K was in the following order: gills > digestive gland > foot > mantle. The values ranged from 47 to 18 mBq g−1 fresh weight in the various organs. Concentration of40K in the mussel was distinctly higher than in the grassEchinochloa colonum (J Koenig) (95 mBq g−1 fresh weight), and the concentration of40K in the bone of the fishCirrhina cirrhosa (Bloch) (126 mBq g−1 fresh weight) was higher than to that of muscle (113 mBq g−1 fresh weight)

    • Prime mover: an obituary of Barbara McClintock

      N K Notani S B Allagikar

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    • Acknowledgements

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