PubMed Health⌕ Search

Biomedical subjects

Vikas Sharma

Publications and source records attributed to Vikas Sharma.

11 recordsLinked to original sources

Periocular dermatitis artefacta in a child.

Dermatitis artifacta is a factitious dermatological disorder with many forms of presentation in any part of the body. It is commonly documented in dermatological cases but rarely presented as an ophthalmic condition. The diagnosis of dermatitis artifacta is often concluded after rigorous and repeated investigation. Histological sampling of skin lesions is usually required in these cases to exclude masquerading skin lesions such as basal cell carcinoma, vasculitis, or herpetic skin lesions.

Child↗

Acrokeratosis paraneoplastica (Bazex syndrome): case report and review of literature.

Acrokeratosis paraneoplastica of Bazex is a rare syndrome. This condition is a distinct skin marker of supra-diaphragmatic neoplasia. This syndrome is important because the cutaneous findings preceed the onset of symptoms referable to the underlying neoplasm by several months in majority of the cases. We report here a case of a 63-year-old cachectic female who had classic psoriasiform lesions of acrokeratosis of Bazex with underlying bronchogenic carcinoma of the right lung.

Carcinoma, Bronchogenic↗

Granzyme B, a new player in activation-induced cell death, is down-regulated by vasoactive intestinal peptide in Th2 but not Th1 effectors.

Following antigenic stimulation and differentiation, Th1 and Th2 effector cells contribute differently to cellular and humoral immunity. Vasoactive intestinal peptide (VIP) induces Th2 responses by promoting Th2 differentiation and survival. In this study, we investigate the mechanisms for the protective effect of VIP against activation-induced cell death (AICD) of Th2 effectors. Surprisingly, microarray and protein data indicate that VIP prevents the up-regulation of granzyme B (GrB) in Th2 but not Th1 effectors. This is the first report of GrB expression in Th cells and of its involvement in activation-induced apoptosis. The enhanced responsiveness of Th2 cells to VIP is probably due to the higher expression of VIP receptors. The effect of VIP on Th2 survival and GrB expression is mediated through the VIP receptors 1 and 2 and cAMP signaling through exchange protein activated by cAMP and, to a lesser degree, protein kinase A. In addition to effects on GrB, VIP also down-regulates Fas ligand (FasL) and perforin (Pfr) expression. The extrinsic Fas/FasL pathway and the intrinsic GrB-dependent pathway act independently in inducing AICD. The mechanisms by which GrB induces cell death in Th1/Th2 effectors include both fratricide and suicide. Fratricide killing, prevalent in wild-type cells, is calcium and Pfr dependent, whereas the cell death of Pfr-deficient Th cells involves Fas and GrB but is calcium independent. This study identifies GrB as a new significant player in Th1/Th2 AICD and characterizes two mechanisms for the protective effect of VIP on Th2 survival, i.e., the down-regulation of GrB and FasL expression.

Animals↗

VIP protects Th2 cells by downregulating granzyme B expression.

Selective differentiation of Th1/Th2 effectors contributes to cell- or antibody-mediated immunity. Vasoactive intestinal peptide (VIP) induces Th2 responses by promoting Th2 differentiation and survival. Here we investigate the mechanisms of VIP-induced Th2 survival. Microarray and protein data indicate that VIP prevents the upregulation of granzyme B (GrB) in Th2, but not Th1 effectors. This is the first report of GrB expression and of its involvement in activation-induced apoptosis of T helper cells. The enhanced responsiveness of Th2 cells to VIP is probably due to the higher expression of VIP receptors and alternative signaling pathways. This study identifies GrB as a new significant player in Th1/Th2 activation-induced cell death, and characterizes the mechanisms for the protective effect of VIP on Th2 survival.

Apoptosis↗

Effect of head group polarity and spacer chain length on the aggregation properties of gemini surfactants in an aquatic environment.

The aggregation behavior of cationic gemini surfactants with respect to variation in head group polarity and spacer length is studied through conductance, surface tension, viscosity, and small-angle neutron-scattering (SANS) measurements. The critical micellar concentration (cmc), average degree of micelle ionization (beta(ave)), minimum area per molecule of surfactant at the air-water interface (A(min)), surface excess concentration (gamma(max)), and Gibb's free energy of micellization (delta G(mic)) of the surfactants were determined from conductance and surface tension data. The aggregation numbers (N), dimensions of micelles (b/a), effective fractional charge per monomer (alpha), and hydration of micelles (h(E)) were determined from SANS and viscosity data, respectively. The increasing head group polarity of gemini surfactant with spacer chain length of 4 methylene units promotes micellar growth, leading to a decrease in cmc, beta(ave), and delta G(mic) and an increase in N and b/a. This is well supported by the observed increase in hydration (h(E)) of micelles with increase in aggregation number (N) and dimension (b/a) of micelle.

Journal Article↗

Substrate specificity of glucose dehydrogenase (GDH) of Enterobacter asburiae PSI3 and rock phosphate solubilization with GDH substrates as C sources.

Enterobacter asburiae PSI3 is a rhizospheric isolate that solubilizes mineral phosphates by the action of a phosphate starvation-inducible GDH (EC 1.1.5.2). We report here that GDH activity of this isolate shows broad substrate range, being able to act on mono and disaccharides. Enterobacter asburiae PSI3 was proficient at bringing about a drop in pH and solubilization of RP with the use of 75 mmol/L of each of the GDH substrate sugars tested as the sole C source. It liberated amounts of P ranging from 450 micromol/L (on arabinose) to 890 micromol/L (on glucose). When grown on a mixture of 7 GDH substrates at concentrations of 15 mmol/L each, the bacterium solubilized RP equivalent to 46% of the value when 75 mmol glucose/L was the C source. HPLC analysis of the culture supernatant under these conditions showed that the acidification of the media is primarily due to the production of organic acids. The significance of these results on the efficacy of E. asburiae PSI3 at solubilizing phosphates under rhizospheric conditions is discussed.

Carbohydrates↗

Prostaglandin E2 promotes the survival of bone marrow-derived dendritic cells.

Since dendritic cells (DC) participate in both innate and adaptive immunity, their survival and expansion is tightly controlled. Little is known about the mechanisms of DC apoptosis. PGE(2), an arachidonic acid metabolite, plays an essential role in DC migration. We propose a novel function for PGE(2) as a DC survival factor. Our studies demonstrate that PGE(2) protects DC in vitro against apoptosis induced by withdrawal of growth factors or ceramide. DC matured in conditions that inhibit endogenous PGE(2) release are highly susceptible to apoptosis and exogenous PGE(2) re-establishes the more resistant phenotype. The antiapoptotic effect is mediated through EP-2/EP-4 receptors and involves the PI3K --> Akt pathway. PGE(2) leads to increased phosphorylation of Akt, protection against mitochondrial membrane compromise, and decreased caspase 3 activity. Macroarray data indicate that PGE(2) leads to the down-regulation of a number of proapoptotic molecules, i.e., BAD, several caspases, and granzyme B. In vivo, higher numbers of immature and Ag-loaded CFSE-labeled DC are present in the draining lymph nodes of mice inoculated with PGE(2) receptor agonists, compared with animals treated with ibuprofen or controls injected with PBS. This suggests that PGE(2) acts as an endogenous antiapoptotic factor for DC and raises the possibility of using PGE(2) agonists to increase the survival of Ag-loaded DC following in vivo administration.

Animals↗

Synthesis, characterization, and SANS studies of novel alkanediyl-alpha,omega-bis(hydroxyethylmethylhexadecylammonium bromide) cationic gemini surfactants.

A series of novel gemini cationic surfactants alkanediyl-alpha,omega-bis (hydroxyethylmethylhexadecylammonium bromide) with polymethylene spacer chain length of 4, 6, 8, and 10 carbon atoms was synthesized and characterized. Critical micellar concentrations of the gemini surfactants in aqueous solutions as determined by the surface tension and conductance measurements were observed to be in the range 1.39-3.63 microM. The critical micellar concentration was observed to increase initially with spacer length up to 6 methylene groups and to decrease thereafter with the increase in spacer length. The micellar microstructure in aqueous solutions examined through small angle neutron scattering (SANS) revealed that the extent of aggregation growth and variation in shapes of micelles strongly depend on head group polarity, spacer chain length, and temperature. The propensity to micellar growth with spacer chain length 4 was found to be much higher than with the longer spacer lengths. The fractional charge on the micelle increases with increased spacer chain length and temperature.

Cations↗

VIP/PACAP oppositely affects immature and mature dendritic cell expression of CD80/CD86 and the stimulatory activity for CD4(+) T cells.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) released within lymphoid organs from nerve terminals and/or immune cells play a significant, anti-inflammatory role by inhibiting macrophage-induced inflammatory reactions and promoting T helper cell type 2 (Th2) responses. However, dendritic cells (DC) and not macrophages often are the major antigen-presenting cells and link between innate and adaptive immunity. The role of VIP/PACAP in DC development and function is mostly unknown. Here, we report that bone marrow-derived DC express VIP/PACAP receptors and that VIP and PACAP exert a differential effect on immature DC (iDC) and lipopolysaccharide (LPS)-treated DC. In iDC, VIP/PACAP up-regulates CD86 expression and enables them to stimulate T cell proliferation and differentiation into Th2 effectors in vivo and in vitro. In contrast, VIP/PACAP down-regulates CD80/CD86 expression in LPS-stimulated DC and strongly reduces their capacity to stimulate T cell proliferation and secretion of Th1 and Th2 cytokines. The VIP/PACAP effects on iDC and LPS-stimulated DC are mediated primarily through the VIP receptor 1. These results indicate that neuropeptides such as VIP and PACAP can differentially affect the function of iDC and mature DC. In the absence of an ongoing immune response, VIP/PACAP contributes to the initiation of Th2-type immunity, whereas in the presence of a full-blown, inflammatory reaction, VIP/PACAP act as anti-inflammatory agents.

Animals↗

Calcipotriol versus coal tar: a prospective randomized study in stable plaque psoriasis.

BACKGROUND: Topical therapies are the first line of treatment for patients with stable plaque psoriasis (SPP) affecting a limited body surface area. Very few trials comparing newer agents, such as 0.005% topical calcipotriol, with conventional modes of therapy, such as coal tar ointment, have been reported. METHODS: A prospective, right-left randomized, investigator-blinded study with a 12-week treatment period and an 8-week follow-up period was performed. Thirty-six patients with nearly bilaterally symmetrical SPP lesions on the limbs were instructed to apply 5% coal tar ointment overnight on one side once daily and 0.005% calcipotriol ointment on the other side twice a day. All patients were advised to expose both sides to the sun for 2 h every day. Psoriatic lesions and progress during treatment were evaluated using the severity (0-3) scale of erythema, scaling and induration (ESI score). Evaluation was carried out every 2 weeks during the treatment period and monthly during follow-up. At the end of 12 weeks, patients with > 75% reduction in the ESI score were considered to be markedly improved, those with 51-75% reduction to be moderately improved, those with 26-50% reduction to be minimally improved and those with < 25% to be non-responders. Self-assessment by the patients regarding the efficacy and acceptability of the two modalities was on a five-point scale. Serum calcium, serum phosphate, total and differential serum proteins, 24-h urinary calcium and phosphate were monitored both at baseline and after completion of therapy. RESULTS: Thirty of the 36 recruited patients completed the study. The difference in clinical response between the two sides was statistically significant at 4, 6 and 8 weeks, with the percentage reduction in ESI score with calcipotriol being 65.7 +/- 12.2% compared with 45.8 +/- 16.6% with coal tar at 8 weeks (P < 0.01, t = 6.4). However, the difference in clinical response at 10 and 12 weeks between the two sides was not significant, with a mean reduction of 71.9 +/- 13.3% in ESI score on the calcipotriol-treated side compared with 69.4 +/- 15.4% with coal tar ointment (P > 0.05). In the follow-up period of 8 weeks, recurrence of lesions was noted in 10% of patients treated with calcipotriol compared with 16.7% in those treated with coal tar after an average period of 6 +/- 1.2 and 5 +/- 1.3 weeks, respectively (P > 0.05). CONCLUSIONS: It was found that 0.005% calcipotriol ointment produced a faster initial response and had better cosmetic acceptability in patients, although after a long period of treatment, i.e. 12 weeks, 5% coal tar ointment had comparable efficacy. There was no statistically significant difference in the relapse rates between the two modalities.

Administration, Topical↗