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Biomedical subjects

Sanjay Kumar

Publications and source records attributed to Sanjay Kumar.

At least 145 records · Page 8Linked to original sources
PubMed2002

Role of long-range repulsive forces in organizing axonal neurofilament distributions: evidence from mice deficient in myelin-associated glycoprotein.

When the axon of a motor neuron is sectioned and visualized by electron microscopy, a two-dimensional distribution of neurofilaments (NFs) with nonrandom spacing is revealed; this ordered arrangement implies the presence of physical interactions between the NFs. To gain insight into the molecular basis of this organization, we characterized NF distributions from mouse sciatic nerve cross sections using two statistical mechanical measures: radial distribution functions and occupancy probability distributions. Our analysis shows that NF organization may be described in terms of effective pairwise interactions. In addition, we show that these statistical mechanical measures can detect differences in NF architecture between wild-type and myelin-associated glycoprotein null mutant mice. These differences are age dependent, with marked contrast between the NF distributions by 9 months of age. Finally, using Monte Carlo simulations, we compare the experimental results with predictions for models in which adjacent NFs interact through rigid cross bridges, deformable cross bridges, and long-range repulsive forces. Among the models tested, a model in which the filaments interact through a long-range repulsive force is most consistent with the results of our analysis.

Aging↗
PubMed2002

Vaccination of donkeys against Babesia equi using killed merozoite immunogen.

Protective efficacy of a killed Babesia equi immunogen was assessed in donkeys. The immunogen was prepared from B. equi infected blood so as to contain lysate of 2 x 10(10) parasitised erythrocytes per dose. The immunogen was mixed with an adjuvant Quil A (3mg) and inoculated into four susceptible donkeys (group I). A booster inoculation was given after 21 days of first inoculation followed by challenge with fresh infected blood containing 1x10(11) parasitised erythrocytes 14 days later. Two groups of two donkey each were included as adjuvant only control (group II) and uninoculated control (group III), respectively. After challenge, donkeys were observed for a period of 4 weeks. The immunised donkeys (group I) showed significantly high (P<0.05%) enzyme linked immunosorbant assay (ELISA) antibody titres and significantly high (P<0.05%) stimulation indices (SI) in lymphocyte proliferation assay (LPA) than that of groups II and III donkeys from day 14 PI and day 7 PI onwards, respectively. All the immunised donkeys withstood lethal challenge, whereas, control donkeys died within 10 days post-challenge (PC). Parasitaemia rose to mean maximum 8.0+/-6.0% for 5-7 days in group I donkeys after challenge, whereas, it rose to 55.5% in control groups. The percent rise in rectal temperature, total leucocyte count (TLC), fall in haemoglobin (Hb) was less severe in immunised group as compared to the control groups. Two immunised-challenged donkeys were splenectomised recovery. No parasites appeared in the blood during the observation period following splenectomy 4-week. Three times increase in skin-fold thickness at 24h of intradermal inoculation prior to challenge in group I donkeys was observed, thus, indicating a good in vivo cell mediated immunity. It can be concluded that the B. equi immunogen along with adjuvant Quil A, used in the present study, was optimum to elicit a strong immune response against B. equi in experimental donkeys.

Adjuvants, Immunologic↗
PubMed2002

A single unbranched S-phase DNA damage and replication fork blockage checkpoint pathway.

The eukaryotic intra-S-phase checkpoint, which slows DNA synthesis in response to DNA damage, is poorly understood. Is DNA damage recognized directly, or indirectly through its effects on replication forks? Is the slowing of S phase in part because of competition between DNA synthesis and recombination/repair processes? The results of our genetic analyses of the intra-S-phase checkpoint in the fission yeast, Schizosaccharomyces pombe, suggest that the slowing of S phase depends weakly on the helicases Rqh1 and Srs2 but not on other recombination/repair pathways. The slowing of S phase depends strongly on the six checkpoint-Rad proteins, on Cds1, and on Rad4/Cut5 (similar to budding yeast Dpb11, which interacts with DNA polymerase epsilon) but not on Rhp9 (similar to budding yeast Rad9, necessary for direct damage recognition). These results suggest that, in fission yeast, the signal activating the intra-S-phase checkpoint is generated only when replication forks encounter DNA damage.

Cell Cycle Proteins↗
PubMed2002

Adsorption and collapse transitions in a linear polymer chain near an attractive wall.

We deduce the qualitative phase diagram of a long flexible neutral polymer chain immersed in a poor solvent near an attracting surface using phenomenological arguments. The actual positions of the phase boundaries are estimated numerically from series expansion up to 19 sites of a self-attracting self-avoiding walk in three dimensions. In two dimensions, we calculate phase boundaries analytically in some cases for a partially directed model. Both the numerical and analytical results corroborate the proposed qualitative phase diagram.

Journal Article↗
PubMed2002

Interleukin-1F7B (IL-1H4/IL-1F7) is processed by caspase-1 and mature IL-1F7B binds to the IL-18 receptor but does not induce IFN-gamma production.

We have recently reported the identification of four novel members of the interleukin-1 (IL-1) family which we designated as IL-1 homologue 1-4 (IL-1H1-4). These proteins exhibit significant sequence homology to other members of the IL-1 family. Of these homologues, only IL-1H4 (renamed IL-1F7b) was predicted to contain a propeptide domain and a caspase cleavage site. We now report that caspase-1 cleaves IL-1F7b at the predicted site to generate mature IL-1F7b. Caspase-4 was also able to process IL-1F7b, albeit inefficiently. Other caspases and Granzyme-B did not cleave IL-1F7b. Furthermore, adenovirus-mediated expression of IL-1F7b in HEK 293 cells led to in situ processing and secretion of mature IL-1F7b. In a screen to identify a potential receptor, both pro and mature IL-1F7b bound to the soluble IL-18 receptor alpha-Fc (IL-18Ralpha-Fc) but not to the soluble IL-1R-Fc or ST2R-Fc fusion proteins. Mature IL-1F7b bound to the IL-18Ralpha-Fc protein with higher affinity than the pro form, although the affinities for both proteins were significantly lower than that observed for IL-18. Consistent with this observation, only IL-18 and not IL-1F7b induced IFN-gamma production by KG1a cells. We also report that pro and mature IL-1F7b form homodimers with association constants of 4 microM and 5 nM, respectively, suggesting biological relevance to IL-1F7b processing. Finally, we have localized the expression of IL-1F7b protein in discrete cell populations including plasma cells and tumor cells. These data suggest that IL-1F7b may be involved in immune response, inflammatory diseases and/or cancer.

Amino Acid Sequence↗
PubMed2002

Relating interactions between neurofilaments to the structure of axonal neurofilament distributions through polymer brush models.

Neurofilaments (NFs) have been proposed to interact with one another through mutual steric exclusion of their unstructured C-terminal "sidearm" domains, producing order in axonal NF distributions and conferring mechanical strength to the axon. Here we apply theory developed for polymer brushes to examine the relationship between the brush properties of the sidearms and NF organization in axons. We first measure NF-NF radial distribution functions and occupancy probability distributions for adult mice. Interpreting the probability distributions using information theory, we show that the NF distributions may be represented by a single pair potential of mean force. Then, to explore the relationship between model parameters and NF architecture, we conduct two-dimensional Monte Carlo simulations of NF cross-sectional distributions. We impose purely repulsive interaction potentials in which the sidearms are represented as neutral and polyelectrolyte chains. By treating the NFs as telechelic polymer brushes, we also incorporate cross-bridging interactions. Both repulsive potentials are capable of reproducing NF cross-sectional densities and their pair correlations. We find that NF structure is sensitive to changes in brush thickness mediated by chain charge, consistent with the experimental observation that sidearm phosphorylation regulates interfilament spacing. The presence of attractive cross-bridging interactions contributes only modestly to structure for moderate degrees of cross-bridging and leads to NF aggregation for extensive cross-bridging.

Action Potentials↗
PubMed2002

Conjugate-based targeting of recombinant adeno-associated virus type 2 vectors by using avidin-linked ligands.

The development of targeted vectors, capable of tissue-specific transduction, remains one of the important aspects of vector modification for gene therapy applications. Recombinant adeno-associated virus type 2 (rAAV-2)-based vectors are nonpathogenic, have relatively low immunogenicity, and are capable of long-term transgene expression. AAV-2 vectors bind primarily to heparan sulfate proteoglycan (HSPG), a receptor that is present in many tissues and cell types. Because of the widespread expression of HSPG on many tissues, targeted transduction in vivo appears to be limited with AAV-2 vectors. Thus, development of strategies to achieve transductional targeting will have a profound benefit in the future application of these vectors. We report here a novel conjugate-based targeting method to enhance tissue-specific transduction of AAV-2-based vectors. The present report utilized a high-affinity biotin-avidin interaction as a molecular bridge to cross-link purified targeting ligands, produced genetically as fusion proteins to core-streptavidin, in a prokaryotic expression system. Conjugation of the bispecific targeting protein to the vector was achieved by biotinylating purified rAAV-2 without abolishing the capsid structure, internalization, and subsequent transgene expression. The tropism-modified vectors, targeted via epidermal growth factor receptor (EGFR) or fibroblast growth factor 1alpha receptor (FGFR1alpha), resulted in a significant increase in transduction efficiency of EGFR-positive SKOV3.ip1 cells and FGFR1alpha-positive M07e cells, respectively. Further optimization of this method of targeting should enhance the potential of AAV-2 vectors in ex vivo and in vivo gene therapy and may form the basis for developing targeting methods for other AAV serotype capsids.

Biotinylation↗
PubMed2002

AgNORs in squamous cell carcinoma of head and neck.

The number of AgNORs per nucleus correlates with cellular proliferation and independently with malignant change. AgNOR number was studied in 200 cases of squamous cell carcinoma of head and neck, the count increased with increasing grade and the size became smaller and irregular with increasing grade of carcinoma. This study seems to suggest that this method has utility in grading of squamous cell carcinoma of head and neck.

Adult↗
PubMed2002

Pain measurement: a formidable task.

Pain is defined as unpleasant sensory and emotional experience, associated with actual or impending tissue damage. It consists of multi-dimentional phenomenon having sensory discriminative, cognitive-evaluative and effective motivational components. Though the technology has advanced, still it is very difficult to objectively assess all the attributes of pain, including alteration in cognitive behaviour. However, subjective methods like Visual Analog Scale rating (VAS) and preliminary objective methods like pain evoked responses, behaviral monitoring and event related evoked potentials for cognition are currently in vogue. It will take some more time and effort to evolve yet other newer and sophisticated techniques to measure all aspects of pain in human beings.

Animals↗