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Biomedical subjects

P K Sehajpal

Publications and source records attributed to P K Sehajpal.

At least 19 recordsLinked to original sources
PubMed2005

Association of G-308A TNF-alpha polymorphism with bronchial asthma in a North Indian population.

Bronchial asthma is an inflammatory disorder in which genetic and environmental factors play an important role. Several susceptible genes have been identified using whole genome scan and candidate gene approaches. Tumor necrosis factor alpha, a pro-inflammatory cytokine, is one such gene that figures prominently in such investigations. The secreted levels of this cytokine are under genetic control and attributed to the presence of single nucleotide polymorphism G-308 A in the promoter region of its gene. However, the association of this polymorphism varies from population to population. As there are no data available on North Indians, the present study aims to fill this void. For this, 366 subjects (155 asthmatic and 211 normal control subject) were genotyped using Amplification Refractory Mutation System Analysis (ARMS-PCR) and agarose gel electrophoresis. The distribution of G/A alleles between the two groups revealed statistically significant differences (p = 0.016). Furthermore, the asthma patients categorized on the basis of pattern (Seasonal versus Perennial) and age of onset of disease (Childhood versus Late Onset) revealed significant association with only seasonal (p = 0.021) and late onset asthmatic groups (p = 0.039). The data from the present study strongly suggest an association between TNF-alpha and asthma in the North Indian population.

Asthma↗
PubMed2005

Development of a competitor DNA template of the 38 kDa gene for molecular quantification of M. tuberculosis.

The molecular quantification of Mycobacterium tuberculosis (TB) from clinical samples can improve the management of TB. Competitive polymerase chain reaction (C-PCR) is an accepted technique often used for this purpose, and IS6110 is the most popular target in such studies. As the number of these elements varies from 0 to 16 in clinical isolates, it is prone to give inconsistent results. A simple PCR-based approach is described in this study to generate a novel competitor for a single copy 38 kDa gene for the development of C-PCR for the quantification of the M. tuberculosis genome.

Adolescent↗
PubMed2004

Quantitative detection of serum HBV DNA levels employing a new S gene based cPCR assay.

Hepatitis B virus (HBV) infection is a major public health problem and a leading cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma. Worldwide, there are about 350 million carriers of this pathogen and India bears the second highest carrier pool in the world. Early diagnosis and measurement of viral load in hepatitis B patients is very helpful for the better management of this disease. The existing methods for viral quantification are either cumbersome or expensive. Since viral replication correlate well with HBV DNA levels a new sensitive, reliable and cost effective competitive PCR assay has been developed for quantifying the viral load in the serum of hepatitis B patients. The S gene based cPCR assay was able to detect as low as 100 genome equivalent/ml of HBV DNA from human serum and was applied to determine viral load among inactive and chronic hepatitis B carriers demonstrating the usefulness of the developed test.

Adolescent↗
PubMed1999

Reversible S-nitrosation and inhibition of HIV-1 protease.

Nitric oxide (*NO) is a short-lived free radical with many functions including vasoregulation, synaptic plasticity, and immune modulation and has recently been associated with AIDS pathology. Various pathophysiological conditions, such as viral infection, trigger inducible nitric oxide synthase (iNOS) to synthesize NO in the cell. NO-derived species can react with thiols of proteins and form nitrosothiol adducts. HIV-1 protease (HIV-PR) contains two cysteine residues, Cys67 and Cys95, which are believed to serve a regulatory function. We have found that HIV-PR is inactivated by nitric oxide produced in vitro by NO donors and by iNOS. Sodium nitroprusside inhibited HIV-PR by 70%, and S-nitroso-N-acetylpenicillamine completely inhibited the enzyme. Furthermore, iNOS generated sufficient NO to inhibit HIV-PR activity by almost 90%. This inactivation was reversed by the addition of reducing agents. Treatment of HIV-PR with NO donors and ritonavir (a competitive peptide inhibitor) indicates that NO exerts its effect through a site independent of the active site of HIV-PR. Using electrospray ionization mass spectrometry, we found that NO forms S-nitrosothiols on Cys67 and Cys95 of HIV-PR which directly correlate with a loss of activity. These data indicate that NO may suppress HIV-1 replication by directly inhibiting HIV-PR.

Binding, Competitive↗
PubMed1999

Targeting cysteine residues of human immunodeficiency virus type 1 protease by reactive free radical species.

Nitric oxide (NO) is a naturally occurring free radical with many functions. The oxidized form of NO, the nitrosonium ion, reacts with the thiol group of cysteine residues resulting in their modification to S-nitrosothiols. The human immunodeficiency virus type 1 (HIV-1) protease (HIV-PR) has two cysteine residues that are conserved amongst different viral isolates found in patients with acquired immunodeficiency syndrome (AIDS). In an active dimer, these residues are located near the surface of the protease. We have found that treatment of HIV-PR with different NO congeners results in loss of its proteolytic activity and simultaneous formation of S-nitrosothiols. Sodium nitroprusside inhibited HIV-PR up to 70% and S-nitroso-N-acetylpenicillamine completely inhibited the protease within 5 min of treatment. The pattern of inhibition by NO donors is comparable to its inhibition by N-acetyl pepstatin. Using electrospray ionization-mass spectrometry, we identified the modification of HIV-PR by NO as that of S-nitrosation. Our findings point towards a possible role of NO in mediating resistance to HIV-1 infection.

Bacteria↗
PubMed1994

Which way for drug-mediated immunosuppression?

The basic immunosuppressive protocol involves the use of multiple drugs, each directed at a discrete site in the T-cell activation cascade. The prevailing paradigm regarding the mechanisms of action of immunosuppressants is that they function to prevent allograft rejection by preventing cell activation, proliferation and/or cytokine production. A new hypothesis is that some of the immunosuppressants might function by stimulating the expression of immunosuppressive molecules and/or cells.

Animals↗
PubMed1993

Nitric oxide signaling: a possible role for G proteins.

We have previously reported various inductive effects of nitric oxide on human PBMC. We describe a novel and potentially important mechanism of nitric oxide signaling-through direct activation of guanine nucleotide-binding proteins (G proteins). We have found that nitric oxide treatment of membranes isolated from fresh human PBMC enhances the ability of these membranes to hydrolyze [gamma-32P]GTP and bind [gamma-35S]GTP. In addition, treatment of whole cells with nitric oxide yielded membranes with enhanced GTPase activity. Furthermore, the GTPase activity of pure, recombinant Gs alpha, Gi alpha 1, and p21ras was greatly enhanced by nitric oxide. In support of the existence of this pathway in whole cells, we found that the G protein inhibitor, GDP-beta-S, blocked NF-kappa B translocation induced by nitric oxide or LPS in permeabilized cells. In addition, nitric oxide greatly reduced the pertussis toxin-mediated ADP-ribosylation of 45- and 41-kDa proteins in membranes of these cells. Because G proteins play a central role in many diverse signaling systems, activation by an endogenous and inducible oxidant may represent a novel signaling pathway.

Adenosine Diphosphate Ribose↗
PubMed1993

Synergism between the CD3 antigen- and CD2 antigen-derived signals. Exploration at the level of induction of DNA-binding proteins and characterization of the inhibitory activity of cyclosporine.

We have demonstrated earlier that the crosslinkage of the CD3/TCR complex with the CD2 antigen results in the proliferation of normal human T cells. The effect of this synergism was perceptible at the level of induction of the IL-2 gene, a process critical for T cell growth. To further understand the molecular and nuclear basis for this synergism, we have explored the induction of DNA-binding proteins in highly purified normal human T cells signaled via the CD3 and/or CD2 proteins. The effect of transmembrane signaling of T cells with ionomycin, and/or sn-1,2 dioctanoyl glycerol, was also determined. The emergence of nuclear binding proteins was investigated using interleukin-2 sequence specific oligonucleotide probes in the electrophoretic mobility shift assay. Our studies demonstrate for the first time that CD3 antigen-derived signals and CD2 antigen-derived signals are synergistic in inducing the emergence of transcription factors that bind to the NF-AT1, AP-1, and NF-kB sites located in the promoter/enhancer region of the IL-2 gene. Moreover, cyclosporine, at concentrations readily accomplished in clinical practice, was found to inhibit the emergence of these DNA-binding proteins in normal human T cells signaled via cell surface proteins implicated in antigen-dependent T cell activation and in T cells stimulated by mobilization of cellular calcium and activation of protein kinase C.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Inhibition of interleukin 2 receptor expression in normal human T cells by cyclosporine. Demonstration at the mRNA, protein, and functional levels.

In view of the importance of the IL-2 receptors in the expression of antiallograft immunity and the currently existing controversy regarding the effect of CsA on the induction of IL-2 receptors, we explored the effect of cyclosporine on the induction of interleukin-2 receptor alpha and beta in normal human T cells. The effect of CsA on the induction of IL-2 receptors was examined at the levels of mRNA expression (with the aid of the polymerase chain reaction), protein (by SDS-PAGE analysis of chemically crosslinked 125I-IL-2 membrane protein complexes and by FACS), and function (by Scatchard analysis of 125I-IL-2 binding to T cells). The T cells were signaled with sn-1,2-dioctanoylglycerol and ionomycin or with crosslinked anti-CD3 and anti-CD2 mAbs. Our experimental design revealed that (A) CsA inhibits the induction of IL-2 receptor alpha and beta in normal human T cells, (B) the inhibitory activity is realized by a direct effect on T cells, and (C) the inhibitory activity is detectable at the pretranslational level--CsA significantly reduced the induction of mRNA encoding IL-2 receptor alpha and IL-2 receptor beta. These observations together persuasively demonstrate the ability of CsA to interrupt the emergence of IL-2 receptors on the surface of normal human T cells.

Antibodies, Monoclonal↗
PubMed1991

Differential regulation of transforming growth factor beta and interleukin 2 genes in human T cells: demonstration by usage of novel competitor DNA constructs in the quantitative polymerase chain reaction.

The regulation of mRNA encoding transforming growth factor beta (TGF-beta) and interleukin 2 (IL-2) in normal human T cells was explored using novel competitor DNA constructs in the quantitative polymerase chain reaction and accessory cell-independent T cell activation models. Our experimental design revealed the following: (a) TGF-beta mRNA and IL-2 mRNA are regulated differentially in normal human T cells, quiescent or signaled with the synergistic combinations of: sn-1,2-dioctanoylglycerol and ionomycin or anti-CD3 monoclonal antibody (mAb) and anti-CD2 mAb; (b) the steady-state level of TGF-beta mRNA in the stimulated T cells, in contrast to that of IL-2 mRNA, is increased by the immunosuppressant cyclosporine (CsA); and (c) the paradoxical effect of CsA on TGF-beta mRNA levels is also appreciable at the level of production of functionally active TGF-beta protein. Our findings, in addition to demonstrating the utility of the competitor DNA constructs for the precise quantification of immunoregulatory cytokines, suggest a novel and unifying mechanistic basis for the immunosuppression and some of the complications (e.g., renal fibrosis) associated with CsA usage.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

The molecular basis for the synergism between the CD3/alpha beta T cell receptor and the CD2 antigen-derived signals in promoting T-cell proliferation.

Northern blot analysis and a highly sensitive methodology for mRNA phenotyping, polymerase chain reaction (PCR), were used to explore the basis for the synergism between CD3/alpha beta T cell receptor (TCR) and the CD2 antigen-derived signals in promoting proliferation of T cells. Northern blotting of RNA isolated from highly purified normal human T cells revealed that crosslinking of anti-TCR-1 (a mAb directed at a framework determinant of the TCR) and OKT11 (a mAb directed at the SRBC-binding epitope of the CD2 antigen) induced the expression of the interleukin-2 gene and the gene for IL-2 receptor alpha, mRNA phenotyping by PCR revealed that crosslinkage of TCR with the CD2 antigen, and not independent crosslinking of TCR or the CD2 antigen, results in the induction of IL-2, IL-2 receptors alpha and beta, and IL-4-specific transcripts. Highly purified CD4+ T cells, as well as CD8+ T cells proliferated by crosslinking TCR with CD2 antigen. Moreover, crosslinkage of TCR with the CD2 antigen and not of either antigen with the CD4 antigen (on the surface of CD4+ T cells) or the CD8 antigen (on the surface of CD8+ T cells) resulted in marked proliferation. Our demonstration that the CD2 antigen-derived signal(s) contribute to the expression of growth promoting genes elicited via the TCR, and that the CD2 antigen is more efficient compared with the CD4 or CD8 antigen in evoking T cell proliferation, suggests that autoimmunity as well as alloimmunity might be regulated by targeting the CD2 antigen.

Antigens, CD↗
PubMed1984

Serum protein polymorphisms in breast cancer.

Serum haptoglobin, transferrin and albumin were studied electrophoretically in 50 patients with carcinoma of breast and in 50 normal healthy women. Results on haptoglobin show a preponderance of products of gene Hp1 (0.26) in patients as compared to controls (0.14). No variation was observed at the transferrin locus in either sample. The most notable finding was the detection of four cases of alloalbuminaemia (8%) in breast cancer Patients. The high incidence of alloalbuminaemia prompted us to extend our observations further. For this purpose sera from 41 patients was collected. One more case of alloalbuminaemia of the fast type was detected. However, in contrast to our first series of patients, quite high incidence (12.2%) of transferrin variants was recorded in this sample. Family studies were conducted on all the patients with protein anomalies.

Blood Proteins↗
PubMed1984

C3 polymorphism in North India.

C3 polymorphism has been studied in 428 individuals from four populations of North India. The frequency of the C3F gene ranges between 0.086 to 0.139. The C3F gene frequency is comparatively higher in the studied samples as compared to other Indian populations, but lower than in most European and West Asian populations.

Complement C3↗
PubMed1982

Palmar dermatoglyphics of the Khatri males.

From an analysis of the bilateral palm prints of 230 khatri males from district Hoshiarpur area, the following points emerge: (1) Line D ends at higher position (11) more often in right palms than in the left, while endings at lower positions (7, 8, 90 and 10) are less frequent in the right palms as compared to the left. (2) The trend for the three modal types for line D is 11 greater than 9 greater than 7. (3) Line C is more often abortive in the left palms than in the right. (4) The value of axial triradii of "t" type has been found to be maximum in both the hands. (5) Most of the patterns in the hypothenar area are found to be less frequent in the right palms as compared to the left. The total frequency of the patterns is 28.693. Radial and ulnar loops are the most predominant types of patterns in this area. (6) The frequency of patterns in the thenar/Ist interdigital area is very much higher in the left palms than in the right. The total frequency (right + left palms) is 15.434. (7) The frequency of patterns in the IInd, IIIrd and IVth interdigital area has been found to be 11.806, 56.956 and 59.130, respectively. Patterns are found to be more frequent in the right palms as compared to the left in case of the IInd and IIIrd interdigital areas, while this is just the reverse in case of the IVth interdigital area.

Dermatoglyphics↗