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S Nair

Publications and source records attributed to S Nair.

At least 19 recordsLinked to original sources
PubMed2000

The anticodon-binding domain of tyrosyl-tRNA synthetase: state of folding and origin of the crystallographic disorder.

The C-terminal domain (residues 320-419) of tyrosyl-tRNA synthetase (TyrRS) from Bacillus stearothermophilus is disordered in the crystal structure. Its function consists of binding the anticodon of tRNA(Tyr). We undertook to characterize its conformational state. A hybrid between the C-terminal fragment and a His-tag sequence was constructed and purified in large amounts. Analyses by mass spectrometry and analytical ultracentrifugation showed that the C-terminal fragment, thus purified, was not degraded and that it neither dimerized nor aggregated. Its far- and near-UV circular dichroism spectra revealed a high content in secondary structures and an asymmetrical environment of its aromatic residues. Each spectrum could be reconstructed by the difference between the corresponding spectra for the full-length TyrRS and for its N-terminal fragment. The Stokes radius of the C-terminal fragment, measured by size exclusion chromatography, indicated a condensed globular state. The fluorescence of ANS (a small hydrophobic probe) showed that the surface of the C-terminal fragment was more hydrophilic than that of a molten globule. These results on the C-terminal fragment and our previous observations that it can undergo cooperative transitions, demonstrated the following points: it is not in a disordered or molten globular state, it has a defined and stable three-dimensional structure, its structures are similar in its isolated and integrated forms, and the apparent disorder in the crystals of the full-length synthetase must be due to the flexibility of the polypeptide segment that links the N- and C-terminal domains. Thus, TyrRS has not evolved strong noncovalent interactions between its catalytic and anticodon-binding domains, contrary to the other synthetases.

Anilino Naphthalenesulfonates↗
PubMed2000

A phase II study of paclitaxel plus carboplatin as first-line chemotherapy for women with metastatic breast carcinoma.

BACKGROUND: This Phase II multicenter study evaluated the efficacy and toxicity of paclitaxel (200 mg/m(2) by 3-hour infusion) with carboplatin (area under the curve 6 mg/mL per minute) administered every 3 weeks as first-line therapy for women with metastatic breast carcinoma. METHODS: Eligible patients had measurable metastatic disease and an Eastern Cooperative Oncology Group performance status of 0-2. Prior adjuvant chemotherapy, including anthracycline-based therapy, was allowed, as was prior hormonal therapy as part of either adjuvant treatment or treatment for metastasis. Prior therapy with taxanes or platinum was not allowed. RESULTS: A total of 53 patients were enrolled in this study, with 50 patients evaluable for response and toxicity. The overall response rate was 62% (95% confidence interval ¿CI, 48-75%); 16% of patients had complete responses and 46% had partial responses. The median time to progression was 7.3 months (95% CI, 5.9-12.9), and the 12-month survival estimate was 72% (95% CI, 61-86%). Therapy was generally well tolerated. Grade 3-4 neutropenia was the predominant toxicity, observed in 82% of patients, but there were no episodes of febrile neutropenia or sepsis. Hematopoietic growth factors were not routinely necessary. Grade 3 peripheral neuropathy occurred in 16% of patients. CONCLUSIONS: Paclitaxel (200 mg/m(2)) with carboplatin (area under the curve 6 mg/mL per minute) demonstrated substantial efficacy in patients with metastatic breast carcinoma, and the 12-month survival rate of 72% was encouraging. This therapy represents a viable option for patients with metastatic disease.

Adult↗
PubMed2000

An AFLP marker that differentiates biotypes of the Asian rice gall midge (Orseolia oryzae, Wood-Mason) is sex-linked and also linked to avirulence.

In an attempt to identify a specific marker for biotype 2 of the Asian rice gall midge (Orseolia oryzae, Wood-Mason), we used AFLP (amplified fragment length polymorphism) fingerprinting. We identified an AFLP marker that is specifically amplified in biotypes 1, 2 and 5 of the rice gall midge, but not in biotype 4. Biotypes 1, 2 and 5 are avirulent to hosts bearing the Gm2 resistance gene (found in rice variety Phalguna), whereas biotype 4 is virulent to Gm2. Based on the sequence of this AFLP marker, SCAR (sequence characterized amplified region) primers were designed and used in combination with previously developed SCAR primers to distinguish effectively all five biotypes in a multiplex PCR-based assay. The inheritance pattern of this marker in the progenies of inter-biotype crosses between biotypes 1, 2 and 4 shows that the marker can be amplified by PCR from all F1 females, irrespective of the biotype status of their parents. However, the marker is present only in those male progenies whose mother was of a Gm2 avirulent biotype. The specific amplification of this marker in the avirulent biotypes and its pattern of inheritance show that avirulence with respect to carriers of the Gm2 gene in rice gall midge is sex-linked.

Animals↗
PubMed2000

CtsR controls class III heat shock gene expression in the human pathogen Listeria monocytogenes.

Stress proteins play an important role in virulence, yet little is known about the regulation of stress response in pathogens. In the facultative intracellular pathogen Listeria monocytogenes, the Clp ATPases, including ClpC, ClpP and ClpE, are required for stress survival and intracellular growth. The first gene of the clpC operon of L. monocytogenes encodes a homologue of the Bacillus subtilis CtsR repressor of stress response genes. An L. monocytogenes ctsR-deleted mutant displayed enhanced survival under stress conditions (growth in the presence of 2% NaCl or at 42 degrees C), but its level of virulence in the mouse was not affected. The virulence of a wild-type strain constitutively expressing CtsR is significantly attenuated, presumably because of repression of the stress response. Regulation of the L. monocytogenes clpC, clpP and clpE genes was investigated using transcriptional fusions in B. subtilis as a host. The L. monocytogenes ctsR gene was placed under the control of an inducible promoter, and regulation by CtsR and heat shock was demonstrated in vivo in B. subtilis. The purified CtsR protein of L. monocytogenes binds specifically to the clpC, clpP and clpE regulatory regions, and the extent of the CtsR binding sites was defined by DNase I footprinting. Our results demonstrate that this human pathogen possesses a CtsR regulon controlling class III heat shock genes, strikingly similar to that of the saprophyte B. subtilis. This is the first description of a stress response regulatory gene in a pathogen.

Adenosine Triphosphatases↗
PubMed2000

The ClpP serine protease is essential for the intracellular parasitism and virulence of Listeria monocytogenes.

We identified the stress-induced ClpP of Listeria monocytogenes and demonstrated its crucial role in intracellular survival of this pathogen. ClpP is a 21.6 kDa protein belonging to a family of proteases highly conserved in prokaryotes and eukaryotes. A clpP-deleted mutant enabled us to demonstrate that ClpP is involved in proteolysis and is required for growth under stress conditions. Intramacrophage survival of this mutant was strongly restricted, thus resulting in loss of virulence for the mouse. The activity of listeriolysin O, a major virulence factor implicated in bacterial escape from phagosomes of macrophages, was much reduced in the clpP mutant under stress conditions. Direct evidence for the role of ClpP in the intracellular parasitism was obtained by showing that virulence and haemolytic activity were fully restored by complementation of the mutant. These results suggest that ClpP is involved in the rapid adaptive response of intracellular pathogens during the infectious process.

Adenosine Triphosphatases↗
PubMed2000

Unusual extra-axial central nervous system involvement of non-Hodgkin's lymphoma: magnetic resonance imaging.

The MR imaging findings in a patient with non-Hodgkin's lymphoma with unusual involvement of the sella, pituitary stalk and left parasellar region are reported here. On the basis of the MR imaging findings, the initial differential diagnosis included invasive pituitary adenoma, a granulomatous lesion and en plaque meningioma. Trans-sphenoidal biopsy of the sellar mass showed chronic inflammatory changes and the patient was initially treated for tuberculosis. Because follow-up imaging showed the lesion to be progressive, a biopsy was done of an enlarged right inguinal lymph node. This revealed non-Hodgkin's lymphoma.

Adult↗
PubMed2000

Hypoalbuminemia is a poor predictor of survival after percutaneous endoscopic gastrostomy in elderly patients with dementia.

OBJECTIVE: Percutaneous endoscopic gastrostomy (PEG) is widely used for long-term enteral nutrition in patients with dementia and inadequate oral intake, although its benefit in prolonging the survival of the patient is not clear. Patients are often referred for PEG placement after a significant weight loss or fall in serum albumin. It is not known whether this delay in referral adversely affects the survival. Our aim was to determine the survival after PEG placement in patients with inadequate oral intake secondary to cognitive impairment and to determine whether-the nutritional parameters at the time of placement of PEG predict survival. METHODS: After excluding patients with cancer, cerebrovascular accident (CVA), and anoxic encephalopathy, 56 consecutive patients with dementia and inadequate oral intake were included in the study. The following parameters were analyzed to predict survival benefit: demographics, reason for admission to the hospital, nutritional indices, Karnofsky performance status before and after PEG, comorbid medical illnesses, and complications after PEG. A control group was selected from patients admitted to the geriatric division who did not receive PEG. Patients with CVA, cancer, and anoxic encephalopathy were also excluded in the control group. Both groups were followed-up for 6 months. RESULTS: One patient was lost to follow-up and complete data were available for 55 patients. The control group of 33 patients was comparable to the patients in age, gender, and comorbid illnesses. During a 6-month follow-up period, the mortality was 44% among patients and 26% among controls (p = 0.03). The only factor that predicted poor survival in patients at 6 months was a serum albumin of <2.8 g/dl. The predictive value of low serum albumin was higher in patients with sepsis on hospital admission and in patients younger than 85 yr. The mean serum albumin of the patients was significantly lower than the control group (p = 0.0001). CONCLUSIONS: Only 50% of demented patients with inadequate oral intake are likely to survive beyond 6 months after PEG placement. No improvement in performance status is likely to occur in any patient. These limited benefits should be realized before initiating PEG feeding. Since the survival in the age-matched control group with a higher mean serum albumin was better than in the patients who had PEG, there may be some benefit in performing PEG before the onset of severe hypoalbuminemia.

Aged↗
PubMed2000

Sex differences in fluorouracil-induced stomatitis.

PURPOSE: A meta-analysis of six North Central Cancer Treatment Group (NCCTG) trials involving patients receiving their first ever fluorouracil (5-FU)-based chemotherapy was undertaken to explore the association of sex with reports of the incidence and severity of stomatitis. PATIENTS AND METHODS: Data were obtained on a total of 731 patients (402 men and 329 women). Comparisons of incidence and severity rates and average stomatitis across sex were performed using standard binomial testing and t tests, respectively. Logistic regression analysis and a weighted analysis using data summarized to study level served as evidence of cross-validation. RESULTS: Women reported stomatitis both more often and with greater severity than did men. The incidence of any stomatitis for women was 63% versus 52% for men (P =.002). The incidence of severe or very severe stomatitis for men and women was 22% and 12%, respectively (P =. 0006). On average, women reported stomatitis of roughly 0.4 points higher than men on a 0 to 4 ordinal scale (P <.00001). Comparison of results across treatment and placebo arms was carried out to validate the initial findings. Logistic regression modelling further confirmed the results conditional on the presence of a number of potentially confounding covariates. Women were also 11% more likely than men to experience leukopenia of common toxicity criteria grade >/= 1, (70% v 59%, respectively; P <.00001) and grade 3+ (18% v 11%, respectively; P =.004). CONCLUSION: More women than men reported 5-FU-induced stomatitis. The precise mechanism resulting in different degrees of stomatitis across sex is not evident.

Adult↗
PubMed2000

Medial trigonal arteriovenous malformations.

A retrospective analysis of 48 patients of medial paratrigonal arteriovenous malformations (AVMs) which constituted 18% of the total 258. AVMs surgically managed in our institute for 16 years was carried out to study their clinical presentation, radiological features, operative approaches and functional outcome. While hemorrhage was the initial presenting symptom in 35, it was longstanding headache in 10, focal seizures in two and progressive weakness in one. However, 41 of these presented with bleed at the time of admission to our hospital and in 15 there was history of multiple bleeds. Twelve and eleven patients had field cut and hemiparesis respectively. Arterial supply to the malformation was quite uniform with posterior (43 patients) and anterior cerebral (25 patients) being the most frequent source. Venous drainage was predominantly into the galenic system (70%). Preoperative embolization was carried out in six patients. While the AVM was excised through a parasagittal interhemispheric approach in 34 patients, the nidus was approached through a direct transcortical (superior parietal lobule) approach in fourteen patients. There was only one operative mortality. Twelve patients whose preoperative fields were normal developed field cut postoperatively. An improvement of the preoperative field deficit was noted only in one patient. While eight of the ten patients with preoperative weakness improved and remained independent the remaining two were moderately disabled. Only two of the 10 patients who developed postoperative weakness remained severely disabled. Our operative results suggest that these AVMs which are prone to recurrent bleeds can be resected with acceptable morbidity. Hemianopia resulting from bleed or surgery is unlikely to improve.

Adolescent↗
PubMed1999

Calreticulin displays in vivo peptide-binding activity and can elicit CTL responses against bound peptides.

Calreticulin is an endoplasmic reticulum (ER) chaperone that displays lectin activity and contributes to the folding pathways for nascent glycoproteins. Calreticulin also participates in the reactions yielding assembly of peptides onto nascent MHC class I molecules. By chemical and immunological criteria, we identify calreticulin as a peptide-binding protein and provide data indicating that calreticulin can elicit CTL responses to components of its bound peptide pool. In an adoptive immunotherapy protocol, dendritic cells pulsed with calreticulin isolated from B16/F10.9 murine melanoma, E.G7-OVA, or EL4 thymoma tumors elicited a CTL response to as yet unknown tumor-derived Ags or the known OVA Ag. To evaluate the relative efficacy of calreticulin in eliciting CTL responses, the ER chaperones GRP94/gp96, BiP, ERp72, and protein disulfide isomerase were purified in parallel from B16/F10.9, EL4, and E.G7-OVA tumors, and the capacity of the proteins to elicit CTL responses was compared. In both the B16/F10.9 and E.G7-OVA models, calreticulin was as effective as or more effective than GRP94/gp96 in eliciting CTL responses. Little to no activity was observed for BiP, ERp72, and protein disulfide isomerase. The observed antigenic activity of calreticulin was recapitulated in in vitro experiments, in which it was observed that pulsing of bone marrow dendritic cells with E.G7-OVA-derived calreticulin elicited sensitivity to lysis by OVA-specific CD8+ T cells. These data identify calreticulin as a peptide-binding protein and indicate that calreticulin-bound peptides can be re-presented on dendritic cell class I molecules for recognition by CD8+ T cells.

Animals↗
PubMed1999

Brain substrate utilisation during acute hypoglycaemia.

AIMS/HYPOTHESIS: Our study was undertaken to examine directly the utilisation of glucose and alternative substrates, in particular amino acids, during hypoglycaemia. METHODS: Catheters were positioned in the jugular venous bulb and an artery in six healthy subjects in the overnight fasted state. Arterio-venous differences for glucose, amino acids, lactate and pyruvate were measured in the basal state, during hyperinsulinaemic euglycaemia and during hyperinsulinaemic hypoglycaemia. The subjects were studied on two different occasions, once during intravenous infusion of amino acids and once during infusion of saline. RESULTS: In the basal state the fractional extraction of glucose across the brain was 10 +/- 2%, glucose uptake accounted for 106 +/- 5% of the brain's oxidative metabolism. There was a small release of lactate and pyruvate. During hyperinsulinaemia glucose uptake continued to account for the entire fuel requirement of the brain. Hyperaminoacidaemia did not result in net amino acid uptake by the brain. During hypoglycaemia (2.4 +/- 0.2 mmol/l) fractional extraction of glucose by the brain increased (p < 0.01) and glucose uptake accounted for 90 +/- 15% of the brain's oxidative metabolism. Uptake of amino acids, lactate or pyruvate could not be detected. CONCLUSION/INTERPRETATION: 1) Brain fractional extraction of glucose increases during hypoglycaemia, 2) hyperinsulinaemia does not change fractional extraction of glucose by the brain, 3) augmented availability of amino acids does not result in brain amino acid uptake during euglycaemia or hypoglycaemia and 4) under the present study conditions glucose remains the major substrate for cerebral metabolism during hypoglycaemia; lactate or pyruvate uptake by the brain can not be detected.

Acute Disease↗
PubMed1999

Changing characteristics of a colloid cyst of the third ventricle.

We describe extremely unusual radiological characteristics in a colloid cyst of the third ventricle, where the cyst became dense and its size decreased following a cerebrospinal fluid diversion procedure. Such a course of events has been reported in colloid cysts only twice in the literature.

Adolescent↗
PubMed1999

Convenient and versatile DNA extraction using agarose plugs for ribotyping of problematic bacterial species.

We describe a convenient, versatile and safe method for preparing bacterial DNA for ribotyping analysis. In this method, extraction of bacterial DNA from Salmnonella typhi and Burkholderia pseudomallei. and subsequent restriction endonuclease digestion, was performed in agarose blocks/plugs thus minimizing shearing and loss of DNA, problems commonly associated with liquid phase phenol extraction. Digested DNA in the plugs was then electrophoresed directly, transferred to nylon membranes and hybridized with labeled rDNA probes in the usual manner to provide reproducible restriction patterns. This method is particularly useful for bacterial species where standard DNA extraction in the liquid phase using phenol has been problematic (e.g. B. pseudomallei) but can be used for any bacterial species. The DNA extracted within the agarose plugs can be stored for long periods and can be used in other, widely-used typing methods such as pulsed-field gel electrophoresis (PFGE) and PCR-based techniques. Embedding live cells directly in agarose plugs also minimizes the risk of exposure to these virulent human pathogens among laboratory workers.

Bacterial Typing Techniques↗
PubMed1999

Cloning and characterization of a cDNA encoding topoisomerase II in pea and analysis of its expression in relation to cell proliferation.

We have isolated and sequenced four overlapping cDNA clones to identify the full-length cDNA for topoisomerase II (PsTopII) from pea. Using degenerate primers, based on the conserved amino acid sequences of other eukaryotic type II topoisomerases, a 680 bp fragment was PCR-amplified with pea cDNA as template. This fragment was used as a probe to screen an oligo-dT-primed pea cDNA library. A partial cDNA clone was isolated that was truncated at the 3' end. RACE-PCR was employed to isolate the remaining portion of the gene. The total size of PsTopII is 4639 bp with an open reading frame of 4392 bp. The deduced amino acid sequence shows a strong homology to other eukaryotic topoisomerase II (topo II) at the N-terminus end. The topo II transcript was abundant in proliferative tissues. We also show that the level of topo II transcripts could be stimulated by exogenous application of growth factors that induced proliferation in vitro cultures. Light irradiation to etiolated tissue strongly stimulated the expression of topo II. These results suggest that topo II gene expression is up-regulated in response to light and hormones and correlates with cell proliferation. Besides, we have also isolated and analysed the 5'-flanking region of the pea TopII gene. This is first report on the isolation of a putative promoter for topoisomerase II from plants.

3' Untranslated Regions↗
PubMed1999

Differentiation of Asian rice gall midge, Orseolia oryzae (Wood-Mason), biotypes by sequence characterized amplified regions (SCARs).

We developed a polymerase chain reaction (PCR)-based assay that distinguished five different biotypes of the Asian gall midge (Orseolia oryzae), a major insect pest of rice. A total of 400 random primers were screened using random amplified polymorphic DNAs (RAPDs). Five diagnostic PCR products were isolated, cloned, sequenced and converted to sequence characterized amplified regions (SCARs). Primers specific to these SCARs were able to amplify specific DNA fragments from genomic DNAs of five biotypes of gall midge in a multiplexed-PCR-based assay. The amplified DNA fragments were used as diagnostic markers to identify different biotypes of gall midge. The SCAR primers were also capable of differentiating the Asian from the African rice gall midge (Orseolia oryzivora) as well as detecting a variant of biotype 5 which caused an outbreak in Kerala, India. Unlike the use of plant host differentials and midge feeding behaviour for identifying biotypes, this assay is fast, reliable and unaffected by environmental factors.

Animals↗
PubMed1999

ClpE, a novel member of the HSP100 family, is involved in cell division and virulence of Listeria monocytogenes.

We identified, in the facultative intracellular pathogen Listeria monocytogenes, a previously unknown Clp ATPase, unique among the HSP100 proteins because of the presence of a short N-terminal region with a potential zinc finger motif. This protein of 726 amino acids is highly homologous to ClpE of Bacillus subtilis, and is a member of a new subfamily of HSP100/Clp ATPases. The clpE gene is transcribed as a monocistronic mRNA from a typical consensus sigma A promoter. clpE is not stimulated by various stresses, but is upregulated in a clpC mutant. This is the first example of cross-regulation between Clp ATPases. By constructing a clpE mutant of L. monocytogenes, we found that ClpE is required for prolonged survival at 42 degrees C and is involved in the virulence of this pathogen. A double mutant deficient in both ClpE and ClpC was avirulent in a mouse model and completely eliminated in the liver. Electron microscopy studies did not show any morphological alterations in clpE or clpC mutants. In the clpE-clpC double mutant, however, cell division was affected, indicating that ClpE acts synergistically with ClpC in cell septation. These results show that the Clp chaperones play a crucial role in both cell division and virulence of L. monocytogenes.

Adenosine Triphosphatases↗