Morpho-anatomical characterization of Rhizopogon himalayensis - Cedrus deodara mycorrhiza

Rhizopogon himalayensis (Castellano, S.L. Miller, Singh & Lakhanpal) A.B. Mujic & M.E. Sm., comb. nov. -an edible truffle-like fungus- normally exists in a symbiotic association with Cedrus deodara (Roxb.) Loud. Because of this important association and the ecological significance as per the available literature attached to this fungus, the present study was undertaken with a specific objective to test the mycorrhizal viability of this mycobiont with this important tree species of Himalaya -the theme tree of Himachal Pradesh. An attempt to investigate and record morphological and anatomical characteristics and variations in this mycorrhizal association was also made in nursery conditions using pure culture (wheat grain spawn) of R. himalayensis. The seedlings grown and inoculated in the nursery were harvested after six months for further examination, including the microscopic details. The study and subsequent analysis revealed that that mycobiont had invaded most of the feeder roots, imparting a typical swollen appearance to the mycorrhizal root tips. These root tips were light ochre with moderately thick plectenchymatic fungal mantle with occasional clamp connections on the inner layer of the fungal mantle. The root surface, as seen, was found smooth and frequently covered with a loose aggregation of inter-woven hyphae that uniformly pervaded the epidermis extending into the inter-cortical spaces of outer cortical cells and formed a characteristic Hartig net. Thus, results obtained in fact for the first time, presented an in-depth analysis of the morphological and anatomical characteristics of R. himalayensis and C. deodara association.

Nucleation-dependent aggregation kinetics of yeast Sup35 fragment GNNQQNY

An N-terminal hepta-peptide sequence of yeast prion protein Sup35 with the sequence GNNQQNY is widely used as a model system for amyloid fibril formation. In this study, we used a reproducible solubilisation protocol that allows the generation of a homogenous monomeric solution of GNNQQNY to uncover the molecular details of its self-assembly mechanism. The aggregation kinetics data show that the GNNQQNY sequence follows nucleation-dependent aggregation kinetics with a critical nucleus of size ~7 monomers and that the efficiency of nucleation were found to be inversely related to the reaction temperature. The nucleus reduces the thermodynamic energy barrier by acting as a template for further self-assembly and results in highly ordered amyloid fibrils. The fibers grown at different temperatures showed similar Thioflavin T fluorescence, Congo-red binding and β-sheet rich structures displaying a characteristic cross-β diffraction pattern. These aggregates also share morphological and structural identity with those reported earlier. The mature GNNQQNY fibers did not exert significant oxidative stress or cytotoxicity upon incubating with differentiated SHSY5Y cells. To our knowledge, this is the first study to experimentally validate previous nucleus size predictions based on theoretical and molecular dynamics simulations. These findings provide the basis for understanding the kinetics and thermodynamics of amyloid nucleation and elongation of amyloidogenic proteins/peptides associated with many systemic and neurodegenerative diseases

Slow amyloid nucleation via α-helix-rich oligomeric intermediates in short polyglutamine-containing huntingtin fragments

The 17-amino-acid N-terminal segment (httNT) that leads into the polyglutamine (polyQ) segment in the Huntington\u27s disease protein huntingtin (htt) dramatically increases aggregation rates and changes the aggregation mechanism, compared to a simple polyQ peptide of similar length. With polyQ segments near or above the pathological repeat length threshold of about 37, aggregation of htt N-terminal fragments is so rapid that it is difficult to tease out mechanistic details. We describe here the use of very short polyQ repeat lengths in htt N-terminal fragments to slow this disease-associated aggregation. Although all of these peptides, in addition to httNT itself, form α-helix-rich oligomeric intermediates, only peptides with QN of eight or longer mature into amyloid-like aggregates, doing so by a slow increase in β-structure. Concentration-dependent circular dichroism and analytical ultracentrifugation suggest that the httNT sequence, with or without added glutamine residues, exists in solution as an equilibrium between disordered monomer and α-helical tetramer. Higher order, α-helix rich oligomers appear to be built up via these tetramers. However, only httNTQN peptides with N=8 or more undergo conversion into polyQ β-sheet aggregates. These final amyloid-like aggregates not only feature the expected high β-sheet content but also retain an element of solvent-exposed α-helix. The α-helix-rich oligomeric intermediates appear to be both on- and off-pathway, with some oligomers serving as the pool from within which nuclei emerge, while those that fail to undergo amyloid nucleation serve as a reservoir for release of monomers to support fibril elongation. Based on a regular pattern of multimers observed in analytical ultracentrifugation, and a concentration dependence of α-helix formation in CD spectroscopy, it is likely that these oligomers assemble via a four-helix assembly unit. PolyQ expansion in these peptides appears to enhance the rates of both oligomer formation and nucleation from within the oligomer population, by structural mechanisms that remain unclear. © 2011 Elsevier Ltd

Polyglutamine Disruption of the Huntingtin Exon 1 N Terminus Triggers a Complex Aggregation Mechanism

Simple polyglutamine (polyQ) peptides aggregate in vitro via a nucleated growth pathway directly yielding amyloid-like aggregates. We show here that the 17-amino-acid flanking sequence (HTTNT) N-terminal to the polyQ in the toxic huntingtin exon 1 fragment imparts onto this peptide a complex alternative aggregation mechanism. In isolation, the HTTNT peptide is a compact coil that resists aggregation. When polyQ is fused to this sequence, it induces in HTTNT, in a repeat-length dependent fashion, a more extended conformation that greatly enhances its aggregation into globular oligomers with HTTNT cores and exposed polyQ. In a second step, a new, amyloid-like aggregate is formed with a core composed of both HTTNT and polyQ. The results indicate unprecedented complexity in how primary sequence controls aggregation within a substantially disordered peptide and have implications for the molecular mechanism of Huntington\u27s disease

Plasmodium vivax lineages: geographical distribution, tandem repeat polymorphism, and phylogenetic relationship

<p>Abstract</p> <p>Background</p> <p>Multi-drug resistance and severe/complicated cases are the emerging phenotypes of vivax malaria, which may deteriorate current anti-malarial control measures. The emergence of these phenotypes could be associated with either of the two <it>Plasmodium vivax </it>lineages. The two lineages had been categorized as Old World and New World, based on geographical sub-division and genetic and phenotypical markers. This study revisited the lineage hypothesis of <it>P. vivax </it>by typing the distribution of lineages among global isolates and evaluated their genetic relatedness using a panel of new mini-satellite markers.</p> <p>Methods</p> <p><it>18S SSU rRNA S-type </it>gene was amplified from 420 <it>Plasmodium vivax </it>field isolates collected from different geographical regions of India, Thailand and Colombia as well as four strains each of <it>P. vivax </it>originating from Nicaragua, Panama, Thailand (Pak Chang), and Vietnam (ONG). A mini-satellite marker panel was then developed to understand the population genetic parameters and tested on a sample subset of both lineages.</p> <p>Results</p> <p><it>18S SSU rRNA S-type </it>gene typing revealed the distribution of both lineages (Old World and New World) in all geographical regions. However, distribution of <it>Plasmodium vivax </it>lineages was highly variable in every geographical region. The lack of geographical sub-division between lineages suggests that both lineages are globally distributed. Ten mini-satellites were scanned from the <it>P. vivax </it>genome sequence; these tandem repeats were located in eight of the chromosomes. Mini-satellites revealed substantial allelic diversity (7-21, <it>AE </it>= 14.6 ± 2.0) and heterozygosity (<it>He </it>= 0.697-0.924, <it>AE </it>= 0.857 ± 0.033) per locus. Mini-satellite comparison between the two lineages revealed high but similar pattern of genetic diversity, allele frequency, and high degree of allele sharing. A Neighbour-Joining phylogenetic tree derived from genetic distance data obtained from ten mini-satellites also placed both lineages together in every cluster.</p> <p>Conclusions</p> <p>The global lineage distribution, lack of genetic distance, similar pattern of genetic diversity, and allele sharing strongly suggested that both lineages are a single species and thus new emerging phenotypes associated with vivax malaria could not be clearly classified as belonging to a particular lineage on basis of their geographical origin.</p

Addressing challenges in insulin storage: An ethical dilemma among physicians

Background and Aims: Insulin is a temperature-sensitive protein; hence, its potency is highly dependent on appropriate storage. Ideally, insulin should be stored in the refrigerator, but when in use it can be stored at room temperature for up to four weeks. However, room temperatures vary widely across regions and countries, and all rural areas of developing countries like India are not electrified. This study explored physicians' perception of alternative methods for appropriate storage of insulin, such as indigenous storage methods like clay pots. Methods: A Study was conducted among 188 Indian physicians attending a diabetes conference in December 2018 to evaluate the feasibility of indigenous storage methods. Results: It was observed that although the use of alternate indigenous methods like clay pots was recommended by them, the proportion was low. The awareness of literature on these methods for insulin storage validation was also less than 50%. Owing to the lack of validation studies on indigenous methods, nearly 80% of the physicians felt that they were not confident to recommend them. Besides, the study results highlighted the necessity of conducting an adequate number of validation studies on indigenous methods in the Indian setting, considering their scarcity. Conclusion: This is the first time we highlight ethical dilemmas through a study among physicians when they advise non-refrigerator methods for insulin storage, in the event of a lack of electricity supply. It is hoped that results from these studies would highlight ethical dilemmas among physicians and would motivate researchers in this field to conduct studies to validate alternative methods of insulin storage

Not Available

Not AvailableField experiments were conducted in Bhubaneswar, Orissa, India, during the dry season (January–May) in 2008 and 2009 to investigate whether practices of the System of Rice Intensification (SRI), including alternate wetting and drying (AWD) during the vegetative stage of plant growth, could improve rice plants’ morphology and physiology and what would be their impact on resulting crop performance, compared with currently recommended scientific management practices (SMP), including continuous flooding (CF) of paddies. With SRI practices, grain yield was increased by 48% in these trials at the same time, there was an average water saving of 22% compared with inundated SMP rice. Water productivity with AWD-SRI management practices was almost doubled (0.68 g/l) compared to CF-SMP (0.36 g/l). Significant improvements were observed in the morphology of SRI plants in terms of root growth, plant/culm height, tiller number per hill, tiller perimeter, leaf size and number, leaf area index (LAI), specific leaf weight (SLW), and open canopy structure. These phenotypic improvements of the AWD-SRI crop were accompanied by physiological changes: greater xylem exudation rate, crop growth rate, mean leaf elongation rate (LER), and higher light interception by the canopy compared to rice plants grown under CF-SMP. SRI plants showed delayed leaf senescence andgreater light utilization, and they maintained higher photosynthetic rates during reproductive and grain-filling stages. This was responsible for improvement in yield contributing characteristics and higher grain yield than from flooded rice with SMP. We conclude that SRI practices with AWD improve rice plants’ morphology, and this benefits physiological processes that result in higher grain yield and water productivity.Not Availabl

Oligoproline Effects on Polyglutamine Conformation and Aggregation

There are nine known expanded CAG repeat neurological diseases, including Huntington\u27s disease (HD), each involving the repeat expansion of polyglutamine (polyGln) in a different protein. Similar conditions can be induced in animal models by expression of the polyGln sequence alone or in other protein contexts. Besides the polyGln sequence, the cellular context of the disease protein, and the sequence context of the polyGln within the disease protein, are both likely to contribute to polyGln physical behavior and to pathology. In HD, the N-terminal, exon-1 segment of the protein huntingtin contains the polyGln sequence immediately followed by an oligoproline region. We show here that introduction of a P10 sequence C-terminal to polyGln in synthetic peptides decreases both the rate of formation and the apparent stability of the amyloid-like aggregates associated with this family of diseases. The sequence can be trimmed to P6 without altering the suppression, but a P3 sequence is ineffective. Spacers up to at least three amino acid residues in length can be inserted between polyGln and P10 without altering this effect. There is no suppression, however, when the P10 sequence is either placed on the N-terminal side of polyGln or attached to polyGln via a side-chain tether. The nucleation mechanism of a Q40 sequence is unchanged upon addition of a P10 C-terminal extension, yielding a critical nucleus of one. The effects of oligoPro length and structural context on polyGln aggregation are correlated strongly with alterations in the circular dichroism spectra of the monomeric peptides. For example, the P10 sequence eliminates the small amount of alpha helical content otherwise exhibited by the Q40 sequence. The P10 sequence may suppress aggregation by stabilizing an aggregation-incompetent conformation of the monomer. The effect is transportable: a P10 sequence fixed to the C terminus of the sequence Aβ similarly modulates amyloid fibril formation

Polyglutamine Disruption of the Huntingtin Exon 1 N Terminus Triggers a Complex Aggregation Mechanism

Simple polyglutamine (polyQ) peptides aggregate in vitro via a nucleated growth pathway directly yielding amyloid-like aggregates. We show here that the 17-amino-acid flanking sequence (HTTNT) N-terminal to the polyQ in the toxic huntingtin exon 1 fragment imparts onto this peptide a complex alternative aggregation mechanism. In isolation, the HTTNT peptide is a compact coil that resists aggregation. When polyQ is fused to this sequence, it induces in HTTNT, in a repeat-length dependent fashion, a more extended conformation that greatly enhances its aggregation into globular oligomers with HTTNT cores and exposed polyQ. In a second step, a new, amyloid-like aggregate is formed with a core composed of both HTTNT and polyQ. The results indicate unprecedented complexity in how primary sequence controls aggregation within a substantially disordered peptide and have implications for the molecular mechanism of Huntington\u27s disease

Kinetically Competing Huntingtin Aggregation Pathways Control Amyloid Polymorphism and Properties

In polyglutamine (polyQ) containing fragments of the Huntington’s disease protein huntingtin (htt), the N-terminal 17 amino acid htt^NT segment serves as the core of α-helical oligomers whose reversible assembly locally concentrates the polyQ segments, thereby facilitating polyQ amyloid nucleation. A variety of aggregation inhibitors have been described that achieve their effects by neutralizing this concentrating function of the htt^NT segment. In this paper we characterize the nature and limits of this inhibition for three means of suppressing htt^NT-mediated aggregation. We show that the previously described action of htt^NT peptide-based inhibitors is solely due to their ability to suppress the htt^NT-mediated aggregation pathway. That is, under htt^NT inhibition, nucleation of polyQ amyloid formation by a previously described alternative nucleation mechanism proceeds unabated and transiently dominates the aggregation process. Removal of the bulk of the htt^NT segment by proteolysis or mutagenesis also blocks the htt^NT-mediated pathway, allowing the alternative nucleation pathway to dominate. In contrast, the previously described immunoglobulin-based inhibitor, the antihtt^NT V_L 12.3 protein, effectively blocks both amyloid pathways, leading to stable accumulation of nonamyloid oligomers. These data show that the htt^NT-dependent and -independent pathways of amyloid nucleation in polyQ-containing htt fragments are in direct kinetic competition. The results illustrate how amyloid polymorphism depends on assembly mechanism and kinetics and have implications for how the intracellular environment can influence aggregation pathways