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Vipin Kumar

Publications and source records attributed to Vipin Kumar.

At least 19 recordsLinked to original sources
PubMed2025

Pyramidal neurons proportionately alter the identity and survival of specific cortical interneuron subtypes.

The mammalian cerebral cortex comprises a complex neuronal network that maintains a precise balance between excitatory pyramidal neurons and inhibitory interneurons. Accumulating evidence indicates that specific interneuron subtypes form stereotyped microcircuits with distinct pyramidal neuron classes. Here we show that pyramidal neurons play an active role in this process by promoting the survival and terminal differentiation of their associated interneuron subtypes. In wild-type cortex, interneuron subtype abundance mirrors the prevalence of their pyramidal neuron partners. In Fezf2 mutants, which lack layer 5b pyramidal neurons and are expanded in layer 6 intratelencephalic neurons, corresponding subtype-specific shifts occur through two distinct mechanisms: somatostatin interneurons adjust their programmed cell death, whereas parvalbumin interneurons switch their subtype identity. Silencing neuronal activity or blocking vesicular release in L5b pyramidal neurons revealed that their communication with interneurons does not require voltage-gated synaptic activity and engages both tetanus toxin-sensitive and -insensitive pathways. Moreover, a targeted bioinformatic screen for ligand-receptor pairs displaying subtype-specific expression and reduced expression of pyramidal neuron-derived ligand in Fezf2 mutants identified candidate secreted factors and adhesion molecules. These findings reveal distinct, pyramidal neuron-driven mechanisms for sculpting interneuron diversity and integrating them into local cortical circuits.

Journal Article↗
PubMed2006

Regulation of immunity by a novel population of Qa-1-restricted CD8alphaalpha+TCRalphabeta+ T cells.

Regulatory mechanisms involving CD8+ T cells (CD8 regulatory T cells (Tregs)) are important in the maintenance of immune homeostasis. However, the inability to generate functional CD8 Treg clones with defined Ag specificity has precluded a direct demonstration of CD8 Treg-mediated regulation. In the present study, we describe the isolation of functional lines and clones representing a novel population of TCRalphabeta+ Tregs that control activated Vbeta8.2+ CD4 T cells mediating experimental autoimmune encephalomyelitis. They express exclusively the CD8alphaalpha homodimer and recognize a peptide from a conserved region of the TCR Vbeta8.2 chain in the context of the Qa-1a (CD8alphaalpha Tregs). They secrete type 1 cytokines but not IL-2. CD8alphaalpha Tregs kill activated Vbeta8.2+ but not Vbeta8.2- or naive T cells. The CD8alphaalpha Tregs prevent autoimmunity upon adoptive transfer or following in vivo activation. These findings reveal an important negative feedback regulatory mechanism targeting activated T cells and have implications in the development of therapeutic strategies for autoimmune diseases and transplantation.

Animals↗
PubMed2006

Mini review: immune response to myelin-derived sulfatide and CNS-demyelination.

Here we briefly review our understanding of the immune response to myelin-derived glycolipids during an inflammatory autoimmune response in the central nervous system (CNS). We focus primarily on the recognition of the self-glycolipid sulfatide by a distinct population of non-invariant NK T cells. The results of studies we have obtained so far in investigating the presentation of sulfatide by CNS-resident cells including microglia and their interactions with T cells indicate that this pathway might be successfully targeted for the treatment of autoimmune demyelination in multiple sclerosis.

Animals↗
PubMed2006

Investigation in tea on fate of fenazaquin residue and its transfer in brew.

Fenazaquin is a non-systemic acaricide/insecticide used widely in controlling mites and other related pests in fruits, vegetables and tea. The objective of this research was to investigate the disappearance trend in tea of fenazaquin residue level and its transfer in brew. Fenazaquin was applied on a tea crop at two rates, 125 and 250 g AI/ha in wet and dry seasons under field conditions. Samples (green shoots, made tea and its brew) were analyzed for fenazaquin and quantification was by high performance liquid chromatography using a UV detector. The residue dissipated faster in the wet season than in the dry season. Seven days after the treatment (normal round of plucking) the residues observed in the green shoots at the two rates were 2.17, 3.07 mg/kg and 2.04, 2.84 mg/kg in the wet and dry seasons, respectively. However, the degradation rale in both seasons followed first-order kinetics. Half-lives in green shoots were in range 1.43-1.70 and 2.10-2.21 days and in made tea 1.59-1.73 and 1.87-1.94 days for wet and dry seasons, respectively. During processing of green shoots to made tea considerable loss (42-70%) of residue was observed. The transfer of residue from made tea brew was in the range 3-22%. In brew residue were below 0.02 mg/l after 5 days of application at both the rates in either of the seasons. The estimated intake with brew (normal consumption of 10 cup/day/adult) thus would be below the acceptable daily intake for fenazaquin (0.005 mg/kg-body weight). To avoid health hazards due to the toxic effect of residues in brew, a waiting period for plucking the tea shoots after fenazaquin application of more than 5 days for both the seasons at recommended rate (125 g AI/ha) may be suggested and considered quite safe.

Beverages↗
PubMed2005

Structural basis for CD1d presentation of a sulfatide derived from myelin and its implications for autoimmunity.

Sulfatide derived from the myelin stimulates a distinct population of CD1d-restricted natural killer T (NKT) cells. Cis-tetracosenoyl sulfatide is one of the immunodominant species in myelin as identified by proliferation, cytokine secretion, and CD1d tetramer staining. The crystal structure of mouse CD1d in complex with cis-tetracosenoyl sulfatide at 1.9 A resolution reveals that the longer cis-tetracosenoyl fatty acid chain fully occupies the A' pocket of the CD1d binding groove, whereas the sphingosine chain fills up the F' pocket. A precise hydrogen bond network in the center of the binding groove orients and positions the ceramide backbone for insertion of the lipid tails in their respective pockets. The 3'-sulfated galactose headgroup is highly exposed for presentation to the T cell receptor and projects up and away from the binding pocket due to its beta linkage, compared with the more intimate binding of the alpha-glactosyl ceramide headgroup to CD1d. These structure and binding data on sulfatide presentation by CD1d have important implications for the design of therapeutics that target T cells reactive for myelin glycolipids in autoimmune diseases of the central nervous system.

Animals↗
PubMed2005

Insulin-dependent diabetes loci Idd5 and Idd9 increase sensitivity to experimental autoimmune encephalomyelitis.

The spontaneous development of autoimmune diabetes in NOD mice suggests that they are unable to establish and maintain immunologic self-tolerance. Congenic NOD mice expressing B10-derived alleles are protected from pancreatic beta cell destruction and autoimmune diabetes. To determine if the B10 alleles in loci Idd5 and Idd9 could influence susceptibility to autoimmunity in other organs, we compared MOG35-55-induced EAE in NOD mice to that of diabetes-resistant NOD.B10.Idd5 and NOD.B10.Idd9 mice. Surprisingly, the severity and chronicity of EAE were enhanced in the diabetes-resistant congenic mice. Our findings indicate that some alleles may influence susceptibility to immune-mediated damage in an organ or tissue-specific fashion, and highlight the necessity of disease-specific investigations.

Animals↗
PubMed2005

A method for solvent-free fabrication of porous polymer using solid-state foaming and ultrasound for tissue engineering applications.

Most of the existing fabrication techniques for tissue engineering scaffolds require the use of organic solvents that may never be fully removed even after long leaching hours. The residues of these organic solvents reduce the ability of biological cells to form new tissue. This paper presents an approach toward solvent-free fabrication of tissue engineering scaffolds. Interconnected porous structures were created using solid-state foaming and ultrasound. The material used in this study was polylactic acid (PLA) and the blowing agent was CO(2). In order to determine suitable process conditions, saturation and foaming studies were first conducted. Selected foam samples were then processed using pulsed ultrasound. The microstructures before and after the ultrasound processing were compared. It was shown that the inter-pore connectivity of the solid-state foams was substantially enhanced. The combined solid-state foaming and ultrasound processing provide a way to fabricate porous polymer for potential tissue engineering applications.

Biocompatible Materials↗
PubMed2005

Targeted expression of IGF-1 in the central nervous system fails to protect mice from experimental autoimmune encephalomyelitis.

Insulin-like growth factor 1 (IGF-1) has been identified as a critical molecule in the induction of myelination in the central nervous system (CNS). Systemic injection of IGF-1 has been shown to have a varied and transiently protective effect on the clinical course of experimental autoimmune encephalomyelitis (EAE). Since systemic IGF-1 can also modulate peripheral immune lymphocytes, we examined whether a sustained and local delivery of IGF-1 into the spinal cord would have any influence on the chronic course of EAE in C57/BL6 mice. The capability of adeno-associated virus (AAV) to be retrogradely transported efficiently from muscle to motor neurons of the spinal cord was used to overcome the difficulty routinely encountered when attempting chronic delivery of molecules into the CNS. We demonstrate that AAV-mediated delivery of IGF-1 in CNS did not have any beneficial effect on the clinical course of EAE. Injection of AAV-IGF1 after induction of the disease worsened the clinical symptoms. Furthermore, CNS expression of IGF-1 did not affect the pathogenic anti-MOG T cell response, as examined by proliferation and cytokine secretion. Thus, enhanced expression of IGF-1 in the CNS during inflammation does not have a significant effect on myelination. These data have important implications for the potential use of IGF-1 in the treatment of multiple sclerosis.

Animals↗
PubMed2005

Dissipation behavior of propargite--an acaricide residues in soil, apple (Malus pumila) and tea (Camellia sinensis).

Propargite, recently introduced in India, is an effective acaricide on a large number of crops most of which are consumed by human beings directly or after processing. Therefore, it has become important to check the dissipation behavior of propargite in edible raw commodities, processed products and in the environment. In the present study, dissipation of residue of this acaricide in soil, apple fruit and tea (green tea leaves, manufactured tea, infusion and spent leaves) was studied. Analysis was carried out using high performance-liquid chromatography with UV detection system. The dissipation rate was found to vary with the nature of studied crop/sample. In soil, half-life ranged from 43 to 45 days, while in plant matrices (tea and apple) it ranged 1.66-2.61 days. The percent transfer of propargite residue from manufactured tea to infusion was 23.60-40.00; however, 35.71-53.20% of the residues remained stuck to the spent leaves.

Cyclohexanes↗
PubMed2005

Application of graph theory: prediction of glycogen synthase kinase-3 beta inhibitory activity of thiadiazolidinones as potential drugs for the treatment of Alzheimer's disease.

The relationship of Wiener's index, a distance-based topological descriptor; Zagreb group parameter, M(1), an adjacency-based topological descriptor and eccentric connectivity index,an adjacency-cum-distance based topological descriptor with the glycogen synthase kinase-3 beta inhibitory activity of thiadiazolidinones has been investigated. A training set comprising 28 analogues of substituted thiadiazolidinones was selected for the present investigations. The values of the Wiener's index, Zagreb group parameter, and eccentric connectivity index for each of 28 analogues comprising the data set were computed. Resulting data was analyzed and suitable models developed after identification of active ranges. Subsequently, biological activity was predicted for each analogue involved in the data set using these models, which was then compared with the reported glycogen synthase kinase-3 beta inhibitory activities. Accuracy of prediction was found to vary from a minimum of approximately 83% for model based on Zagreb group parameter to a maximum of approximately 87% for model based on Wiener's index.

Alzheimer Disease↗
PubMed2005

Identification of functional modules in protein complexes via hyperclique pattern discovery.

Proteins usually do not act isolated in a cell but function within complicated cellular pathways, interacting with other proteins either in pairs or as components of larger complexes. While many protein complexes have been identified by large-scale experimental studies, due to a large number of false-positive interactions existing in current protein complexes 10, it is still difficult to obtain an accurate understanding of functional modules, which encompass groups of proteins involved in common elementary biological function. In this paper, we present a hyperclique pattern discovery approach for extracting functional modules (hyperclique patterns) from protein complexes. A hyperclique pattern is a type of association pattern containing proteins that are highly affiliated with each other. The analysis of hyperclique patterns shows that proteins within the same pattern tend to present in the protein complex together. Also, statistically significant annotations of proteins in a pattern using the Gene Ontology suggest that proteins within the same hyperclique pattern more likely perform the same function and participate in the same biological process. More interestingly, the 3-D structural view of proteins within a hyperclique pattern reveals that these proteins physically interactwith each other. In addition, we show that several hyperclique patterns corresponding to different functions can participate in the same protein complex as independent modules. Finally, we demonstrate that a hyperclique pattern can be involved in different complexes performing different higher-order biological functions, although the pattern corresponds to a specific elementary biological function.

Algorithms↗
PubMed2005

Specific control of immunity by regulatory CD8 T cells.

T lymphocytes with dedicated suppressor function (Treg) play a crucial role in the homeostatic control of immunity in the periphery. Several Treg phenotypes have now been identified in the CD4 and CD8 T cell populations, suggesting their down-regulatory function in both human and animal models of autoimmunity, transplantation and tumor immunity. Here we will focus on the CD8 Treg population and their ability to specifically inhibit a pathogenic autoimmune response. This review will detail the current advances in the knowledge of CD8 Treg in the context of antigen specificity, phenotype, MHC restriction, mechanism of action, and priming.

Animals↗
PubMed2004

Predicting anti-HIV activity of 2,3-diaryl-1,3-thiazolidin-4-ones: computational approach using reformed eccentric connectivity index.

The eccentric connectivity index, which has recently been employed successfully for the development of numerous mathematical models for the prediction of biological activities of diverse nature, has been reformed to overcome its limitations caused by degeneracy and insensitivity towards heteroatoms. The reformed eccentric connectivity index, termed the eccentric connectivity topochemical index, overcomes the limitations of the eccentric connectivity index by exhibiting very low degeneracy and displaying sensitivity to both the presence and relative position of heteroatoms without compromizing the discriminating power of the eccentric connectivity index. The relationship of the eccentric connectivity topochemical index, eccentric connectivity index and Wiener's index with regard to the anti-HIV activity of 2, 3-diaryl-1, 3-thiazolidin-4-one derivatives was subsequently investigated. The values of the eccentric connectivity topochemical index, the eccentric connectivity index and Wiener's index of each of 31 analogues comprizing the data set were computed using in-house computer program. Resultant data was analyzed and suitable models developed after identification of active ranges. Subsequently, each derivative was assigned a biological activity using these models, which was then compared with the reported anti-HIV activity. The accuracy of prediction using these models was found to vary from 81 to 90%. The proposed index offers a vast potential for virtual screening of combinatorial libraries, structure property/activity studies and drug design. [figure]. Basic structure of 2,3-diaryl-1, 3-thiazoidin-4-ones.

Anti-HIV Agents↗
PubMed2004

Prevention of autoimmunity by targeting a distinct, noninvariant CD1d-reactive T cell population reactive to sulfatide.

Class I and class II MHC-restricted T cells specific for proteins present in myelin have been shown to be involved in autoimmunity in the central nervous system (CNS). It is not yet known whether CD1d-restricted T cells reactive to myelin-derived lipids are present in the CNS and might be targeted to influence the course of autoimmune demyelination. Using specific glycolipid-CD1d tetramers and cloned T cells we have characterized a T cell population reactive to a myelin-derived glycolipid, sulfatide, presented by CD1d. This population is distinct from the invariant Valpha14+ NK T cells, and a panel of Valpha3/Valpha8+ CD1d-restricted NK T cell hybridomas is unable to recognize sulfatide in the presence of CD1d+ antigen-presenting cells. Interestingly, during experimental autoimmune encephalomyelitis a model for human multiple sclerosis, sulfatide-reactive T cells but not invariant NK T cells are increased severalfold in CNS tissue. Moreover, treatment of mice with sulfatide prevents antigen-induced experimental autoimmune encephalomyelitis in wild-type but not in CD1d-deficient mice. Disease prevention correlates with the ability of sulfatide to suppress both interferon-gamma and interleukin-4 production by pathogenic myelin oligodendrocyte glycoprotein-reactive T cells. Since recognition of sulfatide by CD1d-restricted T cells has now been shown both in mice and humans, study of murine myelin lipid-reactive T cells may form a basis for the development of intervention strategies in human autoimmune demyelinating diseases.

Animals↗
PubMed2004

Vaccination with an immunodominant peptide of bovine type II collagen induces an anti-TCR response, and modulates the onset and severity of collagen-induced arthritis.

T cell responses directed toward TCR-derived peptides have been shown to be an important regulatory mechanism of protection against autoimmunity. Here, we show that a naturally induced TCR-directed immune response can delay the onset of collagen-induced arthritis (CIA), an animal model of autoimmune rheumatoid arthritis in humans. DBA/1 mice were pretreated with an immunodominant peptide, p245-270, from bovine type II collagen (bCII) and were subsequently immunized with whole bCII for the induction of arthritis. The results showed that preactivation of p245-270-reactive cells delayed the onset and reduced the severity of CIA, compared with animals in the control group. Interestingly, the serum antibody response to bCII and the bCII-specific cytokine were not affected under these conditions. This result indicates that the observed protection was neither directly due to a lower antibody response nor due to the immune deviation of the anti-bCII T cell response. Furthermore, immunization with p245-270, but not bCII, induced a strong response to the B5 peptide, an immunodominant region of the TCR V(beta)8.2 (amino acids 76-101) that binds very strongly to I-A(q). These data suggest that at a critical phase in the loss of self-tolerance, an effective anti-TCR response, induced naturally, can regulate the pathogenic autoimmune response and thus may provide protection against autoimmunity.

Animals↗
PubMed2004

Limited clonality in autoimmunity: drivers and regulators.

The available T cell repertoire directed against self is appreciable owing to the escape of many clones from negative selection, largely because many determinants on self proteins are cryptic and not presented adequately. In addition, the degeneracy of T cell receptor specificity permits each lymphocyte a broad recognitive potential. Within the available self-reactive repertoire are T cells with high affinity, and these can compete favorably with other T cells with the same specificity. We have studied a "driver clone" and its two specific regulators in the B10.PL model of experimental autoimmune encephalomyelitis and found that each of these repertoires is highly limited. There is a single major clonal family comprising the aggressive driver population, which is public and of high affinity, and just one other minor public clonotype. The receptors of this Vbeta8.2/Jbeta2.7 driver are presented to a CD4 regulator and a CD8 suppressor, each of limited clonality, the latter killing the driver clone by apoptosis, completing a feedback control loop. This tightly regulated group of three cell types furnishes an excellent example of the immune homunculus.

Animals↗