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Biomedical subjects

A K Chauhan

Publications and source records attributed to A K Chauhan.

18 recordsLinked to original sources
PubMed2007

Abnormal kappa:lambda light chain ratio in circulating immune complexes as a marker for B cell activity in juvenile idiopathic arthritis.

Patients with juvenile idiopathic arthritis (JIA) have been shown to have elevated levels of circulating immune complexes (CICs) which correlated with disease activity. Our aim was to assess B cell activity by measuring the amount of and the kappa:lambda chain immunoglobulin light (L) chain ratio in CICs from JIA patients and to determine potential evidence for either an antigen-driven response or B-cell receptor editing. We used an enzyme-linked immunosorbent assay to measure kappa and lambda chains present in the CICs from the sera of patients with JIA. Statistical analysis was performed using Pearson's correlation, one-way ANOVA and Bonferroni post hoc analysis. Sera from 44 JIA patients were examined for the concentration of L chains in CICs. Healthy controls had a kappa:lambda chain ratio of 1.2:1, whereas this ratio was reversed among JIA subgroups with RF-positive polyarthritis (1:1.2), RF-negative polyarthritis (1:1.3), oligoarthritis (1:2.3) and systemic-onset arthritis (1:2.5). In addition, overall lambda chain selection was not significantly associated with a particular immunoglobulin heavy (H) chain and occurred with all immunoglobulin isotypes. We showed preferential selection of lambda chains contributing to the formation of potentially pathogenic CICs from JIA patients, of all onset types compared to healthy controls, in an H chain-independent manner. The reversal of kappa:lambda chain ratio within the JIA CICs and association with all immunoglobulin isotypes demonstrated the potential for L chain editing. Furthermore, we conclude that a reversal of the normal kappa:lambda chain ratio in JIA CICs may be used as a marker for increased B-cell activity.

Adolescent↗
PubMed2006

Formation of platelet strings and microthrombi in the presence of ADAMTS-13 inhibitor does not require P-selectin or beta3 integrin.

BACKGROUND: Ultra-large von Willebrand factor (ULVWF) and the receptor P-selectin are released from endothelial Weibel-Palade bodies during injury or inflammation. VWF mediates platelet adhesion and P-selectin promotes leukocyte rolling. ADAMTS-13 limits the duration of platelet adhesion by cleaving the ULVWF. In the absence of ADAMTS-13, long VWF filaments decorated with platelets form. Recent in vitro studies suggested that P-selectin might anchor these platelet strings to endothelium, but whether the same mechanism exists in vivo remains to be elucidated. METHODS: We address the role of P-selectin and beta(3) integrin in platelet string formation in vivo using intravital microscopy by infusing inhibitory ADAMTS-13 antibody in P-selectin-/- and beta(3)-deficient mice and activating the endothelium by injecting histamine. RESULTS: We show that inhibition of ADAMTS-13 combined with endothelial activation leads to similar extents of platelet string formation in wild-type, P-selectin- and integrin beta(3)-deficient mice. Further, in venules the platelet strings can coalesce into VWF-platelet aggregates. This process utilizes neither the platelet beta(3) integrin nor P-selectin. We also show in vitro that platelets can act as a bridge between the VWF fibers and that VWF can self-associate even in areas devoid of platelets. CONCLUSIONS: The formation or retention of the platelet strings does not require P-selectin or the endothelial VWF receptor alpha(v)beta(3). Furthermore, in the presence of low ADAMTS-13 activity, VWF-dependent and alpha(IIb)beta(3)-independent platelet clustering occurs in veins, as has been shown at high arterial shear rates. Our study further supports the importance of regulation of VWF multimer size upon secretion from Weibel-Palade bodies.

ADAMTS13 Protein↗
PubMed2006

Presence of plasma complement regulatory proteins clusterin (Apo J) and vitronectin (S40) on circulating immune complexes (CIC).

The complement regulatory (CR) proteins clusterin and vitronectin bind to the membrane attack complex (MAC) and thus prevent cytolysis. In this report, we demonstrate the presence of both of these CR proteins on MAC bound to circulating immune complexes (CIC). We measured the amount of clusterin and vitronectin on MAC in plasma, also referred to as soluble MAC (SMAC), as well as on MAC bound to CIC (MAC-CIC), using antibody directed to polymerized C9 in systemic lupus erythematosus (SLE) patients. We observed a strong correlation among the quantities of SMAC and MAC-CIC. The amount of both clusterin and vitronectin associated with MAC-CIC was two- to threefold higher in comparison to the SMAC. Patients with high levels of clusterin and vitronectin demonstrated renal involvement. We hypothesize that these complement regulatory proteins besides regulating the insertion of MAC play other critical roles, in disease pathogenesis.

Antigen-Antibody Complex↗
PubMed1994

Crystallization and initial X-ray crystallographic characterization of recombinant bovine inositol polyphosphate 1-phosphatase produced in Spodoptera frugiperda cells.

Bovine inositol polyphosphate 1-phosphatase, a monomeric protein with a molecular mass of 44,000 Da, hydrolyzes the 1-position phosphate from inositol 1,3,4-trisphosphate and inositol 1,4-bisphosphate. The low abundance of inositol polyphosphate 1-phosphatase in tissues has precluded structural studies requiring large quantities of enzyme. We used recombinant Baculovirus harboring the cDNA of bovine inositol polyphosphate 1-phosphatase to infect Spodoptera frugiperda (Sf9) insect cells. Recombinant protein (25 mg per 1 x 10(9) cells) was purified to homogeneity. The enzyme produced in Sf9 cells was similar to the native purified protein as determined by immunoblotting catalytic properties, and inhibition by lithium ions. Crystals of the purified recombinant enzyme were grown by vapor diffusion. Precession photography was used to determine the parameters of inositol polyphosphate 1-phosphatase crystals. The tetragonal crystals belong to the space group P4(1) or P4(3), have unit cell dimensions of a = b = 51.6 A, c = 143.3 A, alpha = beta = gamma = 90 degrees, and contain one molecule per asymmetric unit. We have collected a complete diffraction data set extending to 2.3 A and are currently attempting to solve the three-dimensional structure of bovine inositol polyphosphate 1-phosphatase using a multiple isomorphous replacement strategy.

Animals↗
PubMed1993

Pleiotrophin transforms NIH 3T3 cells and induces tumors in nude mice.

The pleiotrophin (PTN) gene (Ptn) encodes an 18-kDa protein that is highly conserved among mammalian species and that functions as a weak mitogen and promotes neurite-outgrowth activity in vitro. To further investigate the role PTN plays in regulating cell growth, we overexpressed the bovine PTN cDNA and now show that PTN phenotypically transforms NIH 3T3 cells, as evidenced by increased cell number at confluence, focus formation, anchorage-independent growth, and tumor formation in the nude mouse. The results demonstrate that the Ptn gene has the potential to regulate NIH 3T3 cell growth and suggest that PTN may influence abnormal cell growth in vivo.

3T3 Cells↗
PubMed1993

The significance of serum magnesium in diabetes mellitus.

The mean serum magnesium level in normal individual was found 1.967 +/- mgm/dl. No significant difference in serum magnesium level was found in various age groups. All diabetic patients, having normal renal function, exhibited hypomagnesemia. The hyperglycemia in these cases was inversely related to hypomagnesemia and its restoration towards normal by insulin therapy restored the normal serum magnesium concentration. These existed in inverse correlationship between serum magnesium and cholesterol (r = -0.56). The hypomagnesemia was the result and not the cause of alterations in the cholesterol metabolism. A positive correlation was observed between blood urea level and serum magnesium (r = +0.7) and it was significant. The magnesium correlated with major diabetic complications too, e.g. micro and macroangiopathies. Thus, serum magnesium can be used for prognostic assessment in diabetic individuals.

Adolescent↗
PubMed1991

Sequencing and expression of the rne gene of Escherichia coli.

RNase E is a major endonucleolytic RNA processing enzyme in Escherichia coli. We have sequenced a 3.2 kb EcoRI-BamHI fragment encoding the rne gene, and identified its reading frame. Upstream from the gene, there are appropriate consensus sequences for a putative promoter and a ribosome binding site. We have translated this gene using a T7 RNA polymerase/promoter system. We determined 25 amino acids from the N-terminal of the translated product and they are in full agreement with the DNA sequence. The translated product of the rne gene migrates in SDS containing polyacrylamide gels as a 110,000 Da polypeptide, but the open reading frame found in the sequenced DNA indicates a much smaller protein. The entity that migrates as a 110,000 Da contains RNA, which could account, at least partially, for the migration of the rne gene product in SDS containing polyacrylamide gels.

Amino Acid Sequence↗
PubMed1990

Cloning and expression of a developmentally regulated protein that induces mitogenic and neurite outgrowth activity.

A heparin binding mitogenic protein isolated from bovine uterus shares NH2-terminal amino acid sequence with a protein isolated from newborn rat brain. The cDNA's of the bovine, human, and rat genes have been isolated and encode extraordinarily conserved proteins unrelated to known growth or neurotrophic factors, although identity of nearly 50 percent has been found with the predicted sequence of a retinoic acid induced transcript in differentiating mouse embryonal carcinoma cells. Lysates of COS-7 cells transiently expressing this protein were mitogenic for NRK cells and initiated neurite outgrowth from mixed cultures of embryonic rat brain cells. RNA transcripts encoding this protein were widely distributed in tissues and were developmentally regulated. This protein, previously designated as heparin binding growth factor (HBGF)-8, is now renamed pleiotrophin (PTN) to reflect its diverse activities. PTN may be the first member of a family of developmentally regulated cytokines.

Amino Acid Sequence↗
PubMed1989

The gene for a small stable RNA (10Sa RNA) of Escherichia coli.

A gene that codes for a small stable RNA (362 nucleotides) has been sequenced. It is a monocistronic gene, with its own promoter and terminator. It produces a precursor that is about 100 nucleotides longer than the mature RNA with all the extra nucleotides at the 3' end. The gene contains an open reading frame that corresponds to a small protein 25 amino acids long.

Base Sequence↗
PubMed1988

A review of medicinal plants showing anticonvulsant activity.

The term epilepsy is collectively designated for a group of chronic central nervous system disorders characterized by spontaneous occurrence of seizures generally associated with the loss of consciousness and body movements (convulsions). The disease has its origin from an early age. Anticonvulsant drugs are used to control the convulsions by inhibiting the discharge and then producing hypnosis. Various synthetic drugs, viz. sodium diphenyl hydantoin (Dialtin) barbiturates, pyrimidon, succinamides, diazepines etc. are used for the treatment. In this paper various medicinal plants and plant components, which are being used as anticonvulsant and antiepileptic, are discussed.

Animals↗
PubMed1986

Muscle dysfunction in male hypogonadism.

Twenty-eight consecutive male patients with primary and secondary hypogonadism (14 each) were evaluated clinically and electrophysiologically for muscle dysfunction. Although generalised muscle weakness was initially reported by only 9 patients, on direct questioning, it was recorded in 19. Objective weakness was found in 13 patients and it involved both the proximal and distal limb muscles. Quantitative electromyography showed evidence of myopathy in the proximal muscle in 25 patients, i.e., reduced MUP duration and amplitude with increased polyphasia in the deltoid and the gluteus maximus. There were no denervation potentials. None of the patients showed clinical neuropathy or NCV abnormalities. Thus, the profile of muscle involvement in hypogonadism closely simulates limb-girdle muscular dystrophy and other endocrine myopathies. The incidence of muscle involvement was higher in secondary hypogonadism. Diminished androgens in primary hypogonadism and diminished growth hormone in the secondary hypogonadism are probably responsible for the myopathy.

Action Potentials↗
PubMed1983

Functional significance of beta-galactosidase and beta-glucuronidase in lipid metabolism in the medulla oblongata and pons of hedgehog (Paraechinus micropus).

The study presented deals with histochemical mapping of GAL-A, GLUC-A, phospholipids and neutral lipids in the medulla oblongata and pons of hedgehog. Interesting features observed are: 1. The distribution of the enzymes can best be observed in preparations incubated at a pH-level of 4.95. 2. The distributive patterns of both glycosidases are exactly identical. Both enzymes are observed in myelinated nerve fibres, whereas their activity in nerve cells is either subdued or completely missing. The neuropil shows an appreciable amount of enzymes. 3. The distribution of phospholipids and neutral lipids parallels to that of glycosidases. These enzymes form the mirror image of the myelin preparations. The functional significance of the enzymes in relation to lipid metabolism is discussed.

Animals↗
PubMed1982

Glycosidases vis-à-vis-lipid metabolism in the central nervous system of the hedgehog (Paraechinus micropus).

The distributions of beta-galactosidase and beta-glucuronidase in the forebrain of the hedgehog are quite similar to the distribution of phospholipids. Both enzymes and the phospholipids are mainly localized in the fibrous components. Their pattern of distribution is also identical to myelin staining. The functional significance of enzymes in lipid and myelin metabolism is discussed.

Animals↗