Biomedical subjects
S Nair
Publications and source records attributed to S Nair.
Spectrum of inherited bleeding disorders from Western India.
OBJECTIVE: The study was undertaken to assess the magnitude and diversity of different bleeding disorders in Western India. MATERIALS AND METHODS: 768 cases referred to our Institute for evaluation of an underlying bleeding diathesis were investigated appropriately to detect the cause of the abnormal hemostatic function. RESULTS: 630 patients were diagnosed to have hereditary bleeding diathesis. Amongst these, 598 patients had a coagulation disorder while only 32 patients had a platelet function abnormality. Amongst the coagulation disorders, hemophilia A (70.5%) was the most common disorder followed by hemophilia B (14%) and VWD (10.8%). Glanzman's thrombasthenia (84.3%) was the most common platelet function disorder followed by Bernard-Soulier syndrome (12.5%). Some rare disorders have also been diagnosed. CONCLUSION: In spite of their apparent rarity, India has a substantial number of cases of inherited bleeding disorders. A large number of these patients is referred to many tertiary care institutions. It is therefore desirable that district hospitals must develop their laboratories to detect most of these disorders so that the patients need not travel long distances to get an appropriate diagnosis and proper management. All 1st degree female relatives of severe and moderate hemophilia must get factor assays done because some of them may be vulnerable to post-procedural or post-traumatic bleeding.
Directional genome walking using PCR.
We describe here a PCR-based "directional genome walking" protocol. The basic procedure for the amplification consists of two rounds of PCR. A primary PCR was performed, on the genomic DNA using a biotinylated primer specific to a known sequence in the genome along with four universal walker primers that were designed with partial degeneracy. The biotinylated primary PCR products were immobilized on streptavidin-linked paramagnetic beads. This step removed all nonspecific amplification products, and the purified template was used for the second PCR using a nested primer and the walker primer-2 to increase specificity. This technique is potentially useful for cloning promoter regions and has been successfully used to isolate 5'-flanking genomic regions of many cDNA clones previously isolated by us.
Infrasellar craniopharyngioma mimicking a clival chordoma: a case report.
An unusual case of entirely infrasellar craniopharyngioma mimicking a clival chordoma is described. Only 22 cases of craniopharyngioma with nasopharyngeal extension have been reported in the literature. Of the reported cases, most were primarily intracranial with secondary downward extension; only two were thought to originate from an infrasellar location. The present case is another example of an entirely infrasellar craniopharyngioma, with extensive clival destruction, mimicking a clival chordoma. Relevant literature on the subject is reviewed.
Mutation analysis of the BRCA1 gene in Malaysian breast cancer patients.
Thirty patients with early onset breast cancer or familial breast cancer from Malaysia were analysed for germline mutation in the early onset breast cancer I gene (BRCA1). Direct sequencing of the entire coding region of BRCA1 identified a frameshift mutation, c.5447-5448insC (insC5447) (codon 1776 of exon 21) in a patient aged 32 of the Malay ethnic origin, who had no family history of breast and/or ovarian cancer. Eight polymorphisms (2201C > T, 2430T > C, P871L, E1038G, K1183R, 4427T > C, S1613G and IVS8-57delT) were identified in the samples tested.
A study of heat-treatment induced framework contraction in strontium-ETS-4 by powder neutron diffraction and vibrational spectroscopy.
The effects of heat-treatment on the structure of the strontium ion-exchanged titanosilicate ETS-4 have been studied by Rietveld analysis of powder neutron diffraction data and by FT-Raman spectroscopy. Hydrous Sr-ETS-4 (space group Cmmm), upon heat-treatment under inert atmosphere at temperatures between 423 and 573 K, exhibits framework contraction as evinced by the decrease in the unit cell dimensions. The effects of heat-treatment on the dimensions of the transport-controlling eight-membered ring (8MR) are elucidated by Rietveld analysis. It is also found that during heat-treatment: (a) the double three membered rings (D3MRs) in ETS-4 are sites of structural instability, (b) the titania chains running along [010] exhibit a large degree of disorder in the bridging oxygen atoms, and (c) significant relocations of the strontium cations take place, which may affect the separation properties of the heat-treated materials. Raman spectra of heat-treated ETS-4 crystals exhibit strong cation-framework interaction effects. Vibrational modes involving the atoms in the titania chains show progressive frequency shifts and loss of intensity with increasing heat-treatment temperature, in a manner consistent with the crystallographic results. The study indicates the potential for continuously varying the effective pore dimension of ETS-4 by combining heat-treatment with appropriate ion-exchange procedures.
A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules.
Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2.
Structural mechanism for rifampicin inhibition of bacterial rna polymerase.
Rifampicin (Rif) is one of the most potent and broad spectrum antibiotics against bacterial pathogens and is a key component of anti-tuberculosis therapy, stemming from its inhibition of the bacterial RNA polymerase (RNAP). We determined the crystal structure of Thermus aquaticus core RNAP complexed with Rif. The inhibitor binds in a pocket of the RNAP beta subunit deep within the DNA/RNA channel, but more than 12 A away from the active site. The structure, combined with biochemical results, explains the effects of Rif on RNAP function and indicates that the inhibitor acts by directly blocking the path of the elongating RNA when the transcript becomes 2 to 3 nt in length.
Cloning and expression of a nuclear encoded plastid specific 33 kDa ribonucleoprotein gene (33RNP) from pea that is light stimulated.
We report the cloning and sequencing of both cDNA and genomic DNA of a 33 kDa chloroplast ribonucleoprotein (33RNP) from pea. The analysis of the predicted amino acid sequence of the cDNA clone revealed that the encoded protein contains two RNA binding domains, including the conserved consensus ribonucleoprotein sequences CS-RNP1 and CS-RNP2, on the C-terminus half and the presence of a putative transit peptide sequence in the N-terminus region. The phylogenetic and multiple sequence alignment analysis of pea chloroplast RNP along with RNPs reported from the other plant sources revealed that the pea 33RNP is very closely related to Nicotiana sylvestris 31RNP and 28RNP and also to 31RNP and 28RNP of Arabidopsis and spinach, respectively. The pea 33RNP was expressed in Escherichia coli and purified to homogeneity. The in vitro import of precursor protein into chloroplasts confirmed that the N-terminus putative transit peptide is a bona fide transit peptide and 33RNP is localized in the chloroplast. The nucleic acid-binding properties of the recombinant protein, as revealed by South-Western analysis, showed that 33RNP has higher binding affinity for poly (U) and oligo dT than for ssDNA and dsDNA. The steady state transcript level was higher in leaves than in roots and the expression of this gene is light stimulated. Sequence analysis of the genomic clone revealed that the gene contains four exons and three introns. We have also isolated and analyzed the 5' flanking region of the pea 33RNP gene.
Collagenous lectins in tunicates and the proteolytic activation of complement.
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Anti-idiotypic antibody (ab2) vaccines: coupling of Ab2 BR3E4 to KLH increases humoral and/or cellular immune responses in animals and colorectal cancer patients.
The colorectal carcinoma (CRC)-associated CO17-1A/GA733 antigen (Ag) has been the target of a phase II/III randomized trial of passive immunotherapy with monoclonal antibody CO17-1A (Ab1), and phase I active immunotherapy trials with polyclonal anti-idiotypic antibodies (Ab2) mimicking the CO17-1A or GA733 epitope of the Ag. However, monoclonal rat Ab2 BR3E4 directed against Ab1 CO17-1A was superior to polyclonal Ab2 in inducing antigen-specific humoral and cellular immune responses in mice and rabbits. Various forms of Ab2 BR3E4, i.e., BR3E4-F(ab')2 precipitated with aluminum-hydroxide (alum), BR3E4-F(ab')2 coupled to KLH and precipitated or non-precipitated with alum, and BR3E4-IgG in alum or incomplete Freund's adjuvant were compared for their capacity to induce in rabbits anti-anti-idiotypic antibodies (Ab3) that specifically bind to the CO17-1A Ag. BR3E4-F(ab')2 coupled to KLH and precipitated with alum was shown to induce the highest Ab3 titers, followed by Ab2 BR3E4-IgG in alum. Therefore Ab2 BR3E4 as intact IgG (IgG group) or as F(ab')2 coupled to KLH (KLH group), was administered in a phase I trial to 45 patients with CRC, stage Dukes'D (UICC stage IV), with the goal to modulate patients' immune responses to their tumors. Fifteen of 23 patients in the IgG group developed Ab3 binding specifically to Ab2, and in four of these patients the Ab3 also specifically bound to Ag-positive CRC cells. Lymphoproliferative responses to Ab2 and/or GA733-2E Ag stimulation were observed in three of these patients. Eighteen of the 22 KLH group patients tested developed Ab3 and the Ab3 bound specifically to CRC cells in eight patients. Five of the 15 KLH group patients tested developed lymphoproliferative responses to Ab2 and/or GA733-2E Ag. Thus, there was a trend for the KLH group demonstrating higher immune response rates than the IgG group. Clinical responses were rare in these patients with liver metastases.
Acoustic neurinomas during pregnancy: report of two cases and review of literature.
Though infrequent, acoustic neurinomas have been described during pregnancy and represent a therapeutic challenge for excision without producing any problem for the mother and the foetus. First Author experienced two cases of acoustic neurinomas presenting during pregnancy. One patient presented in the terminal stages of the third trimester of pregnancy and underwent caesarean section, followed by retromastoid craniectomy and excision of the tumour. Operative management of the pregnancy and tumour in the same sitting has not been reported in the literature. Second patient who presented during 2nd trimester of pregnancy, was operated on for the tumour and had a successful continuance of pregnancy. Details of the management are discussed and the relevant literature reviewed. In addition to causing aggravation of symptoms, the larger size and increased vascularity of these tumours during pregnancy, makes them more vulnerable to acute bleeding, which in turn may initiate new or exacerbate pre-existing symptoms, as noted in one of the cases presented in this report.
Development of inhibitors in patients with haemophilia from India.
Four hundred and seven patients (352 haemophilia A and 55 haemophilia B) were investigated for the presence of factor VIII and IX inhibitors. Twenty-four out of 292 severe and two out of 36 moderate haemophilia A patients showed the presence of inhibitors. The mean age at development of inhibitors was 17.7 years (range 6-52 years). In 12 patients the inhibitors were detected due to suboptimal response to factor replacement therapy (symptomatic) and in the remaining 14 patients the inhibitors were detected during the routine screening of the patients' samples for inhibitors. They had, however, responded well to the usual doses of factor concentrates and there was no suspicion in these patients that they had developed an inhibitor (asymptomatic). There were two families in which the inhibitors were detected in more than one family member. The level of inhibitors in symptomatic patients ranged from 2.2 Bethesda units (BU) mL(-1) to 460.6 BU mL(-1), and in asymptomatic patients it ranged from 0.8 BU mL(-1) to 3.2 BU mL(-1). The inhibitors persisted in all patients except one, who developed an inhibitor postoperatively for a brief period of 3 months. All these patients were followed up from first factor exposure and were tested for inhibitors at least twice a year. The mean number of exposure days before they developed inhibitors was 47.5 exposure days (range 17-98 exposure days). No inhibitors appeared after more than 100 exposure days in any of the patients. When 50 consecutive patients were investigated for intron 22 inversions of the factor VIII gene, 17 patients were found to be positive for inversions (10 proximal inversion; seven distal inversion) out of whom four patients developed inhibitors, three patients belonging to the same family. Out of 35 haemophilia B patients, only one patient developed an inhibitor. The overall prevalence of inhibitors was thus 8.2%, which is similar to the reports from western countries, prior to the introduction of highly purified factor concentrate therapy.
Wolbachia in the Asian rice gall midge, Orseolia oryzae (Wood-Mason): correlation between host mitotypes and infection status.
Using a PCR-based method, we detected Wolbachia in the Asian rice gall midge. Furthermore, results showed that all females across all biotypes are infected with Wolbachia. However, all male flies are not infected and show different infection frequency in different biotypes. We have also identified three mitotypes, in the rice gall midge, based on DraI restriction pattern of a portion of the 12S rRNA gene that was PCR amplified using primers specific to this gene. All the females and infected male flies had type 1 mtDNA while uninfected males showed only type 2 or 3 mtDNA. Inheritance patterns of mtDNA revealed the existence of a correlation between mtDNA type and Wolbachia infection in the Asian rice gall midge. Evidence for paternal inheritance of mtDNA in Wolbachia-free gall midge is also presented.
Diversity of pseudomonads isolated from three different plant rhizospheres.
AIMS: To study the diversity of the Pseudomonas populations isolated from three different plant rhizospheres, namely pearl millet, cotton and paddy, grown in saline soils along the coastline of Southern India. METHODS AND RESULTS: The Pseudomonas populations were analysed for their biochemical characters and genetic diversity using molecular tools including RAPD and PCR-RFLP. The biochemical characterization, antibiotic resistance assay and RAPD profiles revealed a largely homogeneous population. Even in PCR-RFLP restriction studies, only two groups of isolates were seen. One group was predominant in all three rhizospheres, while the other minor group consisted of salt-sensitive isolates restricted to the paddy rhizosphere alone. CONCLUSIONS: It was observed that increasing salinity caused a predominant selection of salt-tolerant species, in particular Ps. pseudoalcaligenes and Ps. alcaligenes, irrespective of the host rhizosphere. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has reinstated the importance of the soil over the host plant with regard to rhizosphere populations. It has also resulted in the isolation of several salt-tolerant Pseudomonas strains, which are being screened for their biological control activity against common plant pathogens of the coastal agri-ecosystem.
Serum alanine aminotransferase flares during interferon treatment of chronic hepatitis B: is sustained clearance of HBV DNA dependent on levels of pretreatment viremia?
During interferon treatment of chronic hepatitis B, an alanine aminotransferase (ALT) flare may herald a sustained loss of viral replication, but the relationship between virologic response, the extent of a flare, and pretreatment hepatitis B virus (HBV) DNA level has not been defined. We retrospectively examined the impact of an ALT flare on sustained virologic response in 121 interferon-treated patients and 42 untreated controls with either low-level (<100 pg/mL) or high-level (> or =100 pg/mL) viremia. The degree of ALT flare was classified as mild (increase in ALT of 86-171 IU/L above baseline), moderate (increase of 172 to 343 IU/L above baseline), and severe (increase of > or =344 IU/L above baseline). Undetectable serum HBV DNA and hepatitis B e antigen (HBeAg) loss were significantly more likely at the end of follow-up in patients having a flare (P =.0001 and.001, respectively). In the high viremia group, a proportionate increase in virologic response was observed as the degree of flare increased. By multivariate analysis, high baseline HBV DNA, high pretreatment ALT, and both moderate and severe ALT flare were independently predictive of a virologic response with severe flare being the most powerful predictor for a sustained loss of serum HBV DNA (odds ratio, 5.3; P =.004). Severe flare was predictive of a virologic response in the high but not low viremia group. We conclude that a virologic response in patients with high-level viremia is dependent on the degree of ALT flare. Induction of a robust flare may enhance virologic response when high-level viremia is detected.
Steroid-free liver transplantation using rabbit antithymocyte globulin induction: results of a prospective randomized trial.
Steroids have been 1 of the primary modes of immunosuppression since the inception of transplantation and have been credited with both the prevention and treatment of rejection. Steroids also have been held responsible for increased infections, posttransplantation diabetes, and recurrent hepatitis after orthotopic liver transplantation (OLT). The purpose of this ongoing prospective randomized trial is to eliminate steroid use in OLT through induction with rabbit antithymocyte globulin (RATG). This is the first report of a prospective randomized trial in OLT achieving complete absence of steroids. Seventy-one adult patients were prospectively randomized to administration of RATG or steroids. Thirty-six patients were randomized to the administration of RATG induction at a dose of 1.5 mg/kg intravenously (IV) beginning during the anhepatic phase. No steroids were administered. Patients were administered a second 1.5-mg/kg dose of RATG post-OLT day 1. Thirty-five patients were randomized to the administration of methylprednisolone, which had been our standard immunosuppressive protocol. These patients were administered methylprednisolone, 1,000 mg IV, initiated during the anhepatic phase and followed by steroid taper. Maintenance immunosuppression consisted of tacrolimus and mycophenolate, with or without prednisone. Three patients died in each group, for an overall survival rate of 91% in each group. One patient in each group required re-OLT, for a graft survival rate of 89% in each group. Seven patients administered RATG had biopsy-proven rejection (20.5%), all of whom were successfully treated by increasing tacrolimus doses. Eleven patients administered steroid had biopsy-proven rejection (32%), 7 (64%) of whom required additional steroids for treatment, whereas 4 patients (36%) were successfully treated by increasing tacrolimus doses. The incidence of rejection was not statistically significant; however, there was a significant difference in the incidence of steroid-requiring rejection (P =.01). The incidence of recurrent hepatitis C was 50% in RATG patients and 71% in steroid patients (P = not significant). The incidence and severity of infectious complications were slightly lower in RATG patients, accounted for by a greater incidence of cytomegalovirus (CMV) infection in the steroid patients. RATG induction enables complete avoidance of steroid use in OLT with a trend toward a lower rejection rate, decreased incidence of post-OLT diabetes and recurrent hepatitis C, and decreased CMV infection. This prospective randomized trial gives encouraging support that steroids can be safely eliminated in OLT.