Singh RN et al. (1977) Worm Breeder's Gazette "Some Observations on Moulting"

Singh RN, Sulston JE

[Worm Breeder's Gazette, 1977]

Before each moult, the seam cells (i.e. the lateral hypodermal stem cells, together with an extra cell anteriorly) take on a characteristic granular appearance in Nomarski optics. Electron microscopy reveals large Golgi bodies in the seam cells at these times. Presumably this means that the lateral cuticle is specialized in some way (maybe mechanically). The seam is required for ala formation. When groups of seam cells are destroyed by the laser microbeam in the L3 or young L4, corresponding gaps appear in the adult alae. E1348 (lin-5 II) and E1466 (lin-6 I) both have defective seams; both have defective alae as dauers and usually none as adults. Regions without a seam fail to undergo the diametric shrinkage- normally characteristic of dauer maturation. Thus dauer larvae of E1348 and E1466 have a lumpy appearance. They are also less resistant to SDS than N2 dauers. Laser experiments indicate that the excretory system is not essential for moulting. The g1 pharyngeal glands are very active just before ecdysis; their secretions may well be necessary to weaken the head cuticle.

Singh, A. et al. (2019) International Worm Meeting "Role of neuronal-peptides in intestinal and organismal aging."

Singh, A., Hansen , M., Chalasani , S.

[International Worm Meeting, 2019]

Inter-tissue communications are vital for organism development and survival. This becomes particularly relevant in the context of aging, as various tissues have been shown to age at different rates. One particular challenge is to identify age-altered, cross-tissue signals that can modulate organ health and organismal survival. To identify such signals, we engineered C. elegans for tissue-specific RNAi to probe neuron-to-intestine peptide signals in modulating intestinal health. We focused on the readily quantifiable age-associated increase in intestinal leakiness, which is conserved from worms to mammals. Interestingly, we found that abrogating the secretion of neuronal peptides delayed age-related intestinal leakiness, and extended survival. These findings imply that neuronal peptides might play a role in timing intestinal aging. Next, we posited that neuronal peptides likely exert their effect on intestinal health by signaling through, either G-coupled protein receptor- (GPCR-) or non-GPCR class of peptide-receptors. Interestingly, the intestine-specific knockdown of both G-protein gamma subunit encoding genes, as well as the insulin/IGF-1-like receptor daf-2,cell-autonomously delayed age-associated intestinal leakiness. These results indicate that aged neurons may release peptide signals that are sensed by DAF-2/InR and/or possibly GPCR-like receptors on the intestine, modifying the integrity of intestinal cells in aged animals. To identify the specific neuronal peptide(s) that exert a pro-aging effect on intestine, we knocked-down individual insulin-like peptides specifically in the neurons. Our preliminary data indicate that knockdown of at least one insulin gene delayed the age-related intestinal leakiness, similar to the effect of blocking peptide secretion in neurons. These studies implicate a novel role for neuronal peptides in modifying intestinal health. In future experiments, we aim to establish the precise neuronal circuitry of intestine-modifying peptide signals, and the key intestine-specific genes and pathways that modulate intestinal aging downstream of neuronal peptides. As a long-term goal, this study seeks to establish the functional conservation of neuronal peptides in the etiology of intestinal and organismal aging.

Singh SK et al. (2012) Int J Nanomedicine "Novel microfilaricidal activity of nanosilver."

Sharma RD, Dash D, Goswami K, Singh SK, Reddy MV

[Int J Nanomedicine, 2012]

PURPOSE: The currently available drug repertoire against lymphatic filariasis, a major health hazard in the developing world, is inadequate and is fraught with serious limitations. Thus, the development of an effective antifilarial strategy has become a global research thrust mandated by the World Health Organization. Nanoparticles of silver endowed with antibacterial potency are known to induce apoptosis in eukaryotic cells. The present study was designed to investigate the possible microfilaricidal efficacy of silver nanoparticles and to establish the validity of apoptotic rationale in antifilarial drug designing. METHODS: This report analyzed the effect of nanoparticles of silver as well as gold (size range: 10-15 nm) on the microfilariae of Brugia malayi obtained from the lavage of peritoneal cavities of infected jirds (Meriones unguiculatus). The study included a microfilarial motility assay, a trypan blue exclusion test, a poly(adenosine diphosphate-ribose) polymerase activity study, ethidium bromide/acridine orange differential staining, and transmission, as well as scanning electron microscopic evaluation of ultrastructural changes in microfilariae. RESULTS: The study demonstrates that nanoparticles of silver, but not of gold, elicited significant loss in microfilarial motility. Differential staining of parasites with ethidium bromide and acridine orange, poly(adenosine diphosphate-ribose) polymerase activity in microfilarial lysate, and electron microscopic findings underscored apoptotic death of parasites attributable to nanosilver. In a trypan blue exclusion test, the 50% lethal dose of nanosilver was measured to be 101.2 M, which was higher than the recorded complete inhibitory concentration value (50.6 M), thus supporting nanosilver as a potential drug candidate against lymphatic filariasis. CONCLUSION: The present report provides the first ever conclusive proof in support of apoptosis as a novel stratagem in antifilarial drug designing and nanoscale silver as a valid lead in research on antifilarial therapeutics. The main embargo about the current drug diethylcarbamazine citrate is its empirical use without rationale. Effective microfilaricidal activity of nanosilver at relatively low concentrations as reported in this study, with evidence of the induction of apoptosis in microfilariae, projects nanosilver as a potential drug adjuvant against lymphatic filariasis. The much higher 50% lethal dose value of nanosilver compared to the complete inhibitory concentration value reported in this study argues in favor of a safe therapeutic window of this agent in its antifilarial efficacy.

Singh RN et al. (1978) Nematologica "Some observations on molting in C. elegans."

Sulston JE, Singh RN

[Nematologica, 1978]

Moulting of Caenorhabditis elegans has been observed by Nomarski interference contrast microscopy, and by electron microscopy of animals at selected stages. The wild type, cell division mutants and animals in which cells had been ablated by a laser microbeam were examined. The median lateral hypodermis, or "seam", is required for the formation of alae and for dauer larva maturation. During cuticle deposition, large Golgi bodies are seen in the seam cells. The excretory system is not essential for moulting.

Singh SS et al. (2016) Sci Rep "Scaling in topological properties of brain networks."

Lewis JD, Khundrakpam B, Ishrat R, Singh RK, Sharma BI, Evans AC, Reid AT, Singh SS

[Sci Rep, 2016]

The organization in brain networks shows highly modular features with weak inter-modular interaction. The topology of the networks involves emergence of modules and sub-modules at different levels of constitution governed by fractal laws that are signatures of self-organization in complex networks. The modular organization, in terms of modular mass, inter-modular, and intra-modular interaction, also obeys fractal nature. The parameters which characterize topological properties of brain networks follow one parameter scaling theory in all levels of network structure, which reveals the self-similar rules governing the network structure. Further, the calculated fractal dimensions of brain networks of different species are found to decrease when one goes from lower to higher level species which implicates the more ordered and self-organized topography at higher level species. The sparsely distributed hubs in brain networks may be most influencing nodes but their absence may not cause network breakdown, and centrality parameters characterizing them also follow one parameter scaling law indicating self-similar roles of these hubs at different levels of organization in brain networks. The local-community-paradigm decomposition plot and calculated local-community-paradigm-correlation co-efficient of brain networks also shows the evidence for self-organization in these networks.

Singh K et al. (2013) Sleep "Do C. elegans sleep? A closer look."

Hart AC, Huang H, Singh K

[Sleep, 2013]

Singh RN et al. (1977) International C. elegans Meeting "Some observations on moulting"

Sulston JE, Singh RN

[International C. elegans Meeting, 1977]

Singh D et al. (2014) Commun Integr Biol "A function for the midbody remnant in embryonic patterning."

Singh D, Pohl C

[Commun Integr Biol, 2014]

Asymmetric cell divisions combine cell division with fate specification and one general model of how this is achieved was proposed already decades ago(1,2): During interphase, the cell polarity axis is specified, followed by orientation of the spindle along the polarity axis and segregation of fate determinants along the polarity axis during mitosis. In most cells, the polarity axis and the spindle will usually align with the long axis that the cell had before division, also called Hertwig's rule(3-6). In the C. elegans embryo, the first polarity axis also forms along the long axis of the embryo by enrichment of myosin in the anterior(7) and formation of mutually exclusive anterior and posterior cortical polarity domains, mediated through directional cortical contractile flow(8-10). The directionality of this flow is determined by an extrinsic cue, the entry of the sperm, which inhibits Rho-dependent myosin activation at the future posterior pole by bringing with it the Rho GTPase activating protein CYK-4(11,12). Moreover, since there is no previous division 'history' before the first cleavage, mechanisms have to ensure that the nucleus-centrosome complex undergoes a 90 degree rotation so that the spindle can subsequently elongate along the long axis(13-15). Additional mechanisms ensure that the site of cleavage is perpendicular to the long axis(16,17). Hence, tight coupling of an extrinsic cue to intrinsic polarity formation and spindle elongation enables alignment of the division orientation with the long axis of the organism and successful segregation of fate determinants.

Singh J et al. (2019) MBio "Similar Neural Pathways Control Foraging in Mosquitoes and Worms."

Aballay A, Singh J

[MBio, 2019]

Female <i>Aedes aegypti</i> mosquitoes bite human hosts to obtain a blood meal and, in the process, act as vectors for many disease-causing viruses, including the dengue, chikungunya, yellow fever, and Zika viruses. After a complete meal, the female mosquitoes lose attraction to their hosts for several days. New research shows that pharmacological activation of neuropeptide Y-like receptor (NPYLR) signaling elicits host aversion in female mosquitoes. This behavior of mosquitoes shows remarkable similarities to a bacterial-aversion behavior of the nematode <i>Caenorhabditis elegans</i> Feeding on pathogenic bacteria causes bloating of the gut in <i>C. elegans</i> that leads to activation of NPYLR signaling and bacterial aversion. Several studies suggest that this newly discovered mechanism underlying foraging may be conserved across a large number of species. A better understanding of the regulation of NPYLR signaling pathways could provide molecular targets for the control of eating behaviors in different animals, including human-disease vectors.

Singh J et al. (2019) Elife "Intestinal infection regulates behavior and learning via neuroendocrine signaling."

Singh J, Aballay A

[Elife, 2019]

The recognition of pathogens and subsequent activation of defense responses are critical for the survival of organisms. The nematode <i>Caenorhabditis elegans</i> recognizes pathogenic bacteria and elicits defense responses by activating immune pathways and pathogen avoidance. Here we show that chemosensation of phenazines produced by pathogenic <i>Pseudomonas aeruginosa</i>, which leads to rapid activation of DAF-7/TGF- in ASJ neurons, is insufficient for the elicitation of pathogen avoidance behavior. Instead, intestinal infection and bloating of the lumen, which depend on the virulence of <i>P. aeruginosa</i>, regulates both pathogen avoidance and aversive learning by modulating not only the DAF-7/TGF- pathway but also the G-protein coupled receptor NPR-1 pathway, which also controls aerotaxis behavior. Modulation of these neuroendocrine pathways by intestinal infection serves as a systemic feedback that enables animals to avoid virulent bacteria. These results reveal how feedback from the intestine during infection can modulate the behavior, learning, and microbial perception of the host.