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S Gulati

Publications and source records attributed to S Gulati.

At least 91 records · Page 5Linked to original sources
PubMed1996

Cloning, mapping and RNA analysis of the human methionine synthase gene.

Elevated levels of plasma homocysteine is a risk factor in both birth defects and vascular disease. Methionine synthase (MS) is a cobalamin dependent enzyme which catalyzes methylation of homocysteine to methionine. Impaired MS activity is expected to lead to increased levels of plasma homocysteine. In addition, defects in this gene may underlie the methionine-dependence observed in a number of human tumor cell lines. We describe here the isolation and characterization of the human MS cDNA. It contains an open reading frame of 3798 nucleotides encoding a protein of 1265 amino acids with a predicted molecular mass of 140 kDa. The amino acid sequence of the human MS is 55% identical with that of the Escherichia coli enzyme (METH) and 64% identical with the predicted Caenorhabditis elegans enzyme. Seven peptide sequences derived from purified porcine MS have substantial similarity to the human protein. Northern analysis indicates that the MS RNA is present in a wide variety of tissues. We have mapped the human gene to chromosomal location 1q43, a region found monosomic in individuals with deletion 1q syndrome. The isolation of the MS cDNA will now allow the direct determination of whether mutations in this gene contribute to folate-related neural tube defects, cardiovascular diseases, and birth defects.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1996

Defects in human methionine synthase in cblG patients.

Inborn errors resulting in isolated functional methionine synthase deficiency fall into two complementation groups, cblG and cblE. Using biochemical approaches we demonstrate that one cblG patient has greatly reduced levels of methionine synthase while in another, the enzyme is specifically impaired in the reductive activation cycle. The biochemical data suggested that low levels of methionine synthase activity in the first patient may result from mutations in the catalytic domains of the enzyme, reduced transcription, or generation of unstable message or protein. Using Northern analysis, we demonstrate that the molecular basis for the biochemical phenotype in this patient is associated with greatly diminished steady-state levels of methionine synthase mRNA. The biochemical data on the second patient cell line implicated mutations specific to reductive activation, a function that is housed in the C-terminal AdoMet-binding domain and the intermediate B12-binding domain, in the highly homologous bacterial enzyme. We have detected two mutations in a compound heterozygous state, one that results in conversion of a conserved proline (1173) to a leucine residue and the other a deletion of an isoleucine residue (881). The crystal structure of the C-terminal domain of the Escherichia coli MS predicts that the Pro to Leu mutation could disrupt activation since it is embedded in a sequence that makes direct contacts with the bound AdoMet. Deletion of isoleucine in the B12-binding domain would result in shortening of a beta-sheet. Our data provide the first evidence for mutations in the methionine synthase gene being culpable for the cblG phenotype. In addition, they suggest directly that mutations in methionine synthase can lead to elevated homocysteine, implicated both in neural tube defects and in cardiovascular diseases.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1996

Immunogenicity of Neisseria gonorrhoeae lipooligosaccharide epitope 2C7, widely expressed in vivo with no immunochemical similarity to human glycosphingolipids.

Natural infection with Neisseria gonorrhoeae may elicit a substantial antibody response directed against gonococcal lipooligosaccharide. Monoclonal antibody (MAb) 2C7 recognized a gonococcal lipooligosaccharide epitope, identified the epitope directly in 94% of 68 consecutive culture-positive genital secretions, and recognized 95% of 101 randomly chosen fresh (second-passage) gonococcal isolates. The epitope was stably maintained after multiple in vitro passages and did not compete with any of the known cross-reactive human glycosphingolipid structures. MAb 2C7 mediated in vitro killing and phagocytosis by human polymorphonuclear leukocytes of 1 serum-sensitive (sialylated or not) and 1 stably serum-resistant gonococcal isolate that expressed the epitope. Gonococcal endometritis and disseminated infection elicited increases (6.5-fold IgM, 4.4-fold IgG; 18-fold IgM, 17-fold IgG, respectively) in anti-2C7 epitope antibody. Immunization with a gonococcal outer membrane vaccine elicited a mean 44.5-fold increase in IgG anti-2C7 epitope antibody in 20 of 28 subjects. The epitope identified by MAb 2C7 may represent an excellent target for a potentially protective gonococcal vaccine candidate.

Adult↗
PubMed1996

Experimental immunization with a monoclonal anti-idiotope antibody that mimics the Neisseria gonorrhoeae lipooligosaccharide epitope 2C7.

An anti-idiotope monoclonal antibody (MAb), called CA1 (Ab2), was produced in mice against MAb 2C7, which recognizes a widely in vivo-expressed gonococcal lipooligosaccharide (LOS) epitope. Mice immunized with MAb CA1 initially had a 2.5-fold increase in IgG (12-fold after a booster) but no increase in IgM anti-LOS (Ab1') antibody. Control mice immunized with LOS had a 4.5-fold rise in IgG and 4-fold rise in IgM anti-LOS antibody. In rabbits, MAb CA1 elicited a 9-fold rise in IgG and a 3.3-fold rise in IgM anti-LOS (Ab1') antibody. Ab1' antibody bactericidal activity was 1-2 logs greater than that produced by immunization with LOS. Ab1' mediated complete human polymorphonuclear leukocyte phagocytosis of 2C7 epitope-positive (but not 2C7 epitope-negative) gonococci. MAb CA1 acts as a molecular surrogate (Ab2beta) for the nominal LOS antigen and may form the basis for vaccine candidates for human immunization against Neisseria gonorrhoeae.

Animals↗
PubMed1996

Urinary tract infection in nephrotic syndrome.

BACKGROUND: The aim was to study the frequency, etiology and predisposing factors of urinary tract infection (UTI) in children with nephrotic syndrome. METHODS: A retrospective analysis of all children with nephrotic syndrome was made to determine the occurrence of infectious complications. RESULTS: UTI was found to be the most common infection (40.26%); 49 episodes of culture-positive UTI were observed in 37 children. All 49 episodes occurred in patients who were initially considered to be steroid nonresponders or in relapse. Fourteen of the 49 episodes (28.6%) were asymptomatic. One child had Grade IV reflux and another had a ureteric calculus. The majority of the children had no underlying urinary tract malformations. The children with UTI had significantly lower serum albumin (P < 0.05) and higher serum cholesterol (P < 0.001) concentrations than the group of 206 children without infections. Non-Escherichia coli organisms accounted for 39% of the culture isolates. CONCLUSIONS: We believe that UTI is an important but often underdiagnosed infection in children with nephrotic syndrome.

Adolescent↗
PubMed1996

Visceral leishmaniasis in a renal transplant recipient: diagnostic and therapeutic problems.

Visceral leishmaniasis is infrequently reported in renal transplant recipients. A 40-year-old renal transplant recipient developed hepatosplenomegaly and pyrexia of unknown origin 5 months after transplantation. Visceral leishmaniasis was confirmed on bone marrow examination. The usual dose of antiparasitic therapy with stibogluconate sodium failed to eradicate Leishmania donovani. High-dose conventional therapy with stibogluconate sodium for an extended period of time was successful in the treatment of a relapse of leishmaniasis.

Adult↗
PubMed1996

Malignant hypertension in children in India.

BACKGROUND: Malignant hypertension is now an uncommon entity in the western world but still remains a significant problem in India. Therefore we studied the aetiological spectrum, management, and outcome of these patients. METHODS: Forty consecutive children (<16 years) with malignant hypertension were admitted and investigated to exclude or confirm the secondary causes of hypertension. For acute control of blood pressure sublingual nifedipine was used in dosage of 0.3-0.6 mg/kg, failing which intravenous nitroglycerin was used. In patients with aortoarteritis with active disease, steroids were used. Angioplasty was carried out for renal artery stenosis whenever possible. RESULTS: Renoparenchymal disease was the commonest cause of malignant hypertension, and was seen in 25 cases, renovascular hypertension in 13 cases (11 aortoarteritis and two fibromuscular dysplasia) and two had essential hypertension. For acute control of severe hypertension, sublingual nifedipine was effective in 92.5% of patients. Of the patients with renoparenchymal disease five became normotensive with treatment of the underlying disease, four received renal allograft, seven died, and nine are stable on antihypertensive drugs. Renal angioplasty was carried out in seven patients with renovascular hypertension (4 cured, 3 improved) and six are controlled on drugs. CONCLUSIONS: We conclude that apart from renoparenchymal disease, aortoarteritis is a common cause of malignant hypertension in children. Sublingual nifedipine is effective for the rapid control of severe hypertension, and angioplasty is effective in aortoarteritis for short-term preservation of renal function and control of hypertension.

Adolescent↗
PubMed1995

Effect of ischemia-reperfusion injury on the morphology of peroxisomes.

We have previously demonstrated that ischemic injury changed the density of peroxisomes into two distinct peaks, one with a normal density (1.21 g/cm3; Peak I) and a second peak with a lighter density (1.14 g/cm3; Peak II). We studied the peroxisomes from both peaks under the Electron microscope. Examination of peak I following ischemia showed loss of matrix proteins and damaged limiting membranes with leakage of DAB positive material in direct proportion to the duration of ischemia. Upon reperfusion of the ischemic liver Peak I showed more severe damage to the organelle. These observations clearly demonstrated that ischemia reperfusion injury causes structural damage to peroxisomes. Interestingly ultrastructural examination of Peak II following ischemia showed evidence of perisomal proliferation with budding of existing peroxisomes and the presence of micro peroxisomes (changes similar to those noted under conditions leading to perisomal proliferation). However, peak II following reperfusion showed only damaged organelle. These observations underline the importance of peroxisomes in the response of the cell to ischemia-reperfusion injury.

Animals↗
PubMed1995

Spectrum of infections in Indian children with nephrotic syndrome.

We conducted a retrospective analysis of infections in 154 children (114 boys, 40 girls) with nephrotic syndrome who satisfied the International Study of Kidney Disease in Children criteria. Their mean age at onset of symptoms was 6.2 years (range 6 months to 16 years) and the mean duration of follow-up was 32 months (range 6-55 months). One or more infectious complications were observed in 59 of the 154 children (38%), with urinary tract infection being the commonest (13.7%), followed by pulmonary tuberculosis (10.4%), peritonitis (9.1%), skin infections (5.2%), upper respiratory infections (5.2%), lower respiratory tract infections (3.9%) and pyomeningitis (0.6%). There were 3 deaths, the mortality in 2 patients being attributable to infections. There was no significant difference between children who developed infection and those who didn't in terms of age of onset, sex, duration of disease, serum creatinine, blood urea nitrogen and 24-h proteinuria. However, the children who developed infectious complications had significantly higher serum cholesterol levels (P < 0.01) and lower serum albumin levels (P < 0.02). The frequency of infections was higher in children who were frequent relapsers, steroid dependent and subsequent non-responders (28/60) compared with infrequent relapsers and initial non-responders (29/94).

Adolescent↗
PubMed1995

Abnormal liver function in patients undergoing autologous bone marrow transplantation for hematological malignancies.

Autologous bone marrow transplantation (AuBMT) is an accepted treatment modality for patients with high-risk or relapsed hematological malignancies. Hepatotoxicity, in particular veno-occlusive disease (VOD), is a significant complication of this therapy. The purpose of this study was to determine the clinical relevance of abnormal liver function in the patients who received high-dose cytotoxic therapy and AuBMT for hematological malignancies at Memorial Sloan Kettering Cancer Center. Medical records of 180 consecutive patients between 1984 and 1991 treated with cytotoxic chemotherapy and AuBMT for acute myelogenous leukemia, non-Hodgkin's lymphoma, and Hodgkin's disease were reviewed. Forty-six patients (26%) developed jaundice with bilirubin > 4 mg/dl. These patients had a 43% toxic death rate compared to an 11% toxic death rate in patients with lower bilirubins (p < 0.001). The main etiology of hyperbilirubinemia was VOD of the liver noted in 22 of the 180 patients (12%). Other etiologies of jaundice included hepatitis, sepsis with multiorgan dysfunction, cholecystitis, and recurrent disease. Hyperbilirubinemia of various etiologies is a significant complication of AuBMT. Several new strategies are under investigation to decrease the toxicity of intensive therapy.

Adolescent↗
PubMed1994

Phytanic acid alpha-oxidation in rat liver mitochondria.

The alpha-oxidation of phytanic acid in rat liver is a mitochondrial function. The inhibition of phytanic acid oxidation activity by inhibitors of acyl-CoA ligases (Naproxen and Triacsin C) and that of carnitine acyltransferase I (2-(5-(4-chlorophenyl)pentyl)oxirane-2 carboxylic acid (POCA) and 2-bromopalmitate) and increase in phytanic acid oxidation activity by the addition of exogenous carnitine and CoA to purified mitochondria suggests that phytanoyl-CoA ligase and carnitine acyltransferase I are essential for the activation and transport of phytanic acid across the mitochondrial membrane. This was further supported by the fact that activation of phytanic acid to phytanoyl-CoA was required only in intact mitochondria but not in mitochondria permealized with digitonin. DesulfoCoA, Naproxen and POCA treatment resulted in a significant decrease in phytanic acid oxidation in intact mitochondria but not in digitonin permealized mitochondria. These results show that alpha-oxidation of phytanic acid to pristanic acid, in contrast to beta-oxidation of fatty acids, requires free fatty acid as substrate. The inhibition of alpha-oxidation (approximately 90%) of phytanic acid by different cytochrome P-450 enzyme inhibitors indicated that alpha-oxidation of phytanic acid is mediated through cytochrome P-450 containing enzyme system. Similar to the omega-hydroxylation system in endoplasmic reticulum, alpha-hydroxylation and the subsequent alpha-oxidation of phytanic acid in mitochondria is induced by ciprofibrate, a hypolipidemic drug.

Animals↗
PubMed1994

Purification and kinetic mechanism of a mammalian methionine synthase from pig liver.

Porcine hepatic methionine synthase has been purified to near homogeneity. The enzyme is isolated in two forms which were purified approximately 9,000- and approximately 7,000-fold and were obtained in 0.9 and 2.5% overall yield, respectively. The mammalian enzyme from pig liver is a large monomeric protein with a molecular mass of 151-155 kDa. It is characterized by the absence of any metals other than cobalt which is associated with the cofactor, cobalamin. This enzyme, like the methionine synthase from Escherichia coli is dependent on S-adenosylmethionine for activity. The steady state kinetic studies demonstrate that the reaction operates via an ordered sequential mechanism in which binding of CH3-H4-folate precedes homocysteine, and methionine is released prior to H4-folate.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1994

Serum resistance of Neisseria gonorrhoeae. Does it thwart the inflammatory response and facilitate the transmission of infection?

N. gonorrhoeae differentially subvert the effectiveness of complement (C) and alter the inflammatory responses elicited in human infection. Disseminated (DGI) isolates typically resist killing by normal serum (are serum-resistant), inactivate more C3b (to iC3b preferentially bound via amide linkages), generate less C5a, and result in less inflammation at local sites. Pelvic inflammatory disease isolates are serum-sensitive, inactivate less C3b (while maintaining active C3b via stable amide linkages), generate more C5a, and result in more inflammation at local sites. Sialylation of SS gonococci, presumed to occur in vivo, converts them to serum-resistant, but it does not change the patterns of C3b inactivation and therefore may not affect local inflammation. IgG antibody directed against gonococcal reduction modifiable protein (Rmp) blocks C-mediated killing of N. gonorrhoeae. Anti-Rmp blocking antibodies may harbor specificity for OmpA sequences shared with other neisserial species or Enterobacteriaceae or may be directed against unique Rmp upstream cysteine loop specific sequences, or both. Preexisting antibodies directed against Rmp facilitate transmission of gonococcal infection to exposed women; exclusion of highly immunogenic Rmp antigens from vaccine candidates may be important.

Antibodies, Bacterial↗
PubMed1994

Intravenous pulse cyclophosphamide--a new regime for steroid-resistant minimal change nephrotic syndrome.

The treatment of steroid-resistant minimal change nephrotic syndrome (MCNS) continues to pose a therapeutic challenge. We conducted a randomised prospective controlled trial to evaluate the efficacy of i.v. cyclophosphamide compared with oral cyclophosphamide in 13 children with biopsy-proven steroid-resistant MCNS. All 7 patients receiving i.v. cyclophosphamide achieved remission; this was sustained in 4 patients, while 3 relapsed. However, even these 3 patients subsequently became steroid sensitive. Of the 6 patients who received oral cyclophosphamide, 2 dropped out, 1 responded and 3 children continued to remain steroid resistant. The children who received IV cyclophosphamide had more sustained remissions, longer periods without proteinuria and fewer significant side effects; this was achieved at a lower cumulative dose.

Administration, Oral↗