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A Srivastava

Publications and source records attributed to A Srivastava.

At least 19 recordsLinked to original sources
PubMed2007

Pathology of non-infective gastritis.

The discovery of Helicobacter pylori and its intimate role in the development of the most common form of chronic gastritis has elicited a much-needed interest in non-neoplastic gastric pathology. This has been paralleled by an increase in upper endoscopic examinations, which allow recognition of novel patterns and distribution of mucosal injury. Numerous attempts at classification have been made, most based on the acuteness or chronicity of gastric mucosal injury. In this review, we will not offer a new classification but present a detailed description of the major clinicopathological entities, based either on the salient morphological features or the underlying aetiologies, i.e. iatrogenic, autoimmune, vascular or idiopathic.

Acute Disease↗
PubMed2006

Adeno-associated virus 2-mediated gene transfer: role of a cellular serine/threonine protein phosphatase in augmenting transduction efficiency.

We have documented that a cellular chaperone protein, FKBP52, when phosphorylated at tyrosine and/or serine/threonine (Ser/Thr) residues, interacts with the D-sequence in the inverted terminal repeats of the adeno-associated virus 2 (AAV) genome, inhibits the viral second-strand DNA synthesis, and leads to inefficient transgene expression from recombinant AAV vectors in certain cell types. We have also demonstrated that FKBP52 is dephosphorylated at tyrosine residues by T-cell protein tyrosine phosphatase (TC-PTP), and that deliberate overexpression of TC-PTP leads to more efficient viral second-strand DNA synthesis, and increased transgene expression. However, the identity of the putative Ser/Thr protein phosphatase that dephosphorylates FKBP52 at Ser/Thr residues has remained elusive. Using known inhibitors of Ser/Thr phosphatases, we have now identified protein phosphatase 5 (PP5) to be a candidate enzyme. Deliberate overexpression of PP5 in 293 cells, which does not influence cellular growth, leads to approximately 5-fold increase in the transduction efficiency of conventional single-stranded AAV vectors, but no significant enhancement in the transduction efficiency of self-complementary AAV vectors, suggesting that PP5 plays a role in AAV second-strand DNA synthesis. Electrophoretic mobility-shift assays show that in cells overexpressing PP5, the extent of the complex formation between FKBP52 and the AAV D-sequence is significantly reduced. These studies suggest that PP5-mediated dephosphorylation of FKBP52 at Ser/Thr residues augments viral second-strand DNA synthesis and enhances AAV transduction efficiency, which has implications in the optimal use of these vectors in human gene therapy.

Cell Line↗
PubMed2006

Adenosine diphosphate ribosylation of dinitrogenase reductase and adenylylation of glutamine synthetase control ammonia excretion in ethylenediamine-resistant mutants of Azospirillum brasilense Sp7.

Azospirillum brasilense is a nitrogen-fixing, root-colonizing bacterium that brings about plant-growth-promoting effects mainly because of its ability to produce phytohormones. Ethylenediamine (EDA)-resistant mutants of A. brasilense were isolated and screened for their higher ability to decrease acetylene and release ammonia in the medium. One of the mutants showed considerably higher levels of acetylene decrease and ammonia excretion. Nitrogenase activity of this mutant was relatively resistant to inhibition by NH(4)Cl. Adenosine triphosphate ribosylation of dinitrogenase reductase in the mutant did not increase even in presence of 10 mM NH(4)Cl. Although the mutant showed decreased glutamine synthetase (GS) activity, neither the levels of GS synthesized by the mutant nor the NH (4) (+) -binding site in the GS differed from those of the parent. The main reason for the release of ammonia by the mutant seems to be the fixation of higher levels of nitrogen than its GS can assimilate, as well as higher levels of adenylylation of GS, which may decrease ammonia assimilation.

Adenosine Diphosphate Ribose↗
PubMed2006

Update on the pathophysiology and classification of von Willebrand disease: a report of the Subcommittee on von Willebrand Factor.

von Willebrand disease (VWD) is a bleeding disorder caused by inherited defects in the concentration, structure, or function of von Willebrand factor (VWF). VWD is classified into three primary categories. Type 1 includes partial quantitative deficiency, type 2 includes qualitative defects, and type 3 includes virtually complete deficiency of VWF. VWD type 2 is divided into four secondary categories. Type 2A includes variants with decreased platelet adhesion caused by selective deficiency of high-molecular-weight VWF multimers. Type 2B includes variants with increased affinity for platelet glycoprotein Ib. Type 2M includes variants with markedly defective platelet adhesion despite a relatively normal size distribution of VWF multimers. Type 2N includes variants with markedly decreased affinity for factor VIII. These six categories of VWD correlate with important clinical features and therapeutic requirements. Some VWF gene mutations, alone or in combination, have complex effects and give rise to mixed VWD phenotypes. Certain VWD types, especially type 1 and type 2A, encompass several pathophysiologic mechanisms that sometimes can be distinguished by appropriate laboratory studies. The clinical significance of this heterogeneity is under investigation, which may support further subdivision of VWD type 1 or type 2A in the future.

ADAM Proteins↗
PubMed2006

Influence of pressure on the electric-field-induced phase transitions in liquid crystals.

Within the framework of Landau-de-Gennes formulation, we analyse the effect of pressure on electric-field-induced phase transitions in a liquid crystal which shows spontaneously an isotropic-smectic A transition. Inferring from the experimental pressure dependences on the layer spacing in smectic A phase, as well as the nematic-smectic A metastable temperature T*(AN), we incorporated the pressure dependence in the free energy through (the surface energy term) and the coupling between the quadrupolar nematic ordering Q(ij) and the smectic order parameter psi. From the S-T phase diagram, we found that the stability of field-induced nematic phase increases with pressure, whereas the discontinuity of the transition decreases. Also, the region where paranematic phase transits directly to smectic A phase increases with pressure.

Electricity↗
PubMed2006

Developing an algorithm of informative markers for evaluation of chimerism after allogeneic bone marrow transplantation.

Analysis of chimerism by polymerase chain reaction amplification of STR or VNTR has become a routine procedure for the evaluation of engraftment after allogeneic stem cell transplantation. Knowledge of the frequency of different STR or VNTR alleles in unrelated individuals in a population is useful for forensic work. In the context of HLA identical sibling bone marrow transplantation the informativeness of these markers needs to be evaluated. We evaluated five STRs (THO1, VWA, FES, ACTBP2, and F13A1) and 1 VNTR (APOB) for informativeness in stem cell transplants from HLA identical sibling donors. All four markers used individually allowed us to discriminate 20-56% of the patient donor pairs. Using a combination of all these markers along with a polymorphic marker in the beta-globin gene and the sex chromosome specific amelogenin marker, we were able to discriminate 99% of the patient donor pairs. We have established an algorithm for evaluating chimerism following HLA identical sibling donor transplants in the Indian population using molecular markers in 310 patients. Analysis of heterozygote frequencies in different populations is similar suggesting that this algorithm can be used universally for transplant centers to evaluate chimerism following allogeneic bone marrow transplantation.

Algorithms↗
PubMed2006

Quantitative determination of reserpine, ajmaline, and ajmalicine in Rauvolfia serpentina by reversed-phase high-performance liquid chromatography.

A sensitive and reproducible reversed-phase high-performance liquid chromatography (HPLC) method using photodiode array detection is established for the simultaneous quantitation of important root alkaloids of Rauvolfia serpentina, namely, reserpine, ajmaline, and ajmalicine. A Chromolith Performance RP-18e column (100 x 4.6-mm i.d.) and a binary gradient mobile phase composed of 0.01 M (pH 3.5) phosphate buffer (NaH(2)PO(4)) containing 0.5% glacial acetic acid and acetonitrile are used. Analysis is run at a flow rate of 1.0 mL/min with the detector operated at a wavelength of 254 nm. The calibration curves are linear over a concentration range of 1-20 microg/mL (r = 1.000) for all the alkaloids. The various other aspects of analysis (i.e., peak purity, similarity, recovery, and repeatability) are also validated. For the three components, the recoveries are found to be 98.27%, 97.03%, and 98.38%, respectively. The limits of detection are 6, 4, and 8 microg/mL for ajmaline, ajmalicine, and reserpine, respectively, and the limits of quantitation are 19, 12, and 23 microg/mL for ajmaline, ajmalicine, and reserpine, respectively. The developed method is simple, reproducible, and easy to operate. It is useful for the evaluation of R. serpentina.

Ajmaline↗
PubMed2006

Genetic diagnosis of haemophilia and other inherited bleeding disorders.

Inherited deficiencies of plasma proteins involved in blood coagulation generally lead to lifelong bleeding disorders, whose severity is inversely proportional to the degree of factor deficiency. Haemophilia A and B, inherited as X-linked recessive traits, are the most common hereditary hemorrhagic disorders caused by a deficiency or dysfunction of blood coagulation factor VIII (FVIII) and factor IX (FIX). Together with von Willebrand's disease, a defect of primary haemostasis, these X-linked disorders include 95% to 97% of all the inherited deficiencies of coagulation factors. The remaining defects, generally transmitted as autosomal recessive traits, are rare with prevalence of the presumably homozygous forms in the general population of 1:500,000 for FVII deficiency and 1 in 2 million for prothrombin (FII) and factor XIII (FXIII) deficiency. Molecular characterization, carrier detection and prenatal diagnosis remain the key steps for the prevention of the birth of children affected by coagulation disorders in developing countries, where patients with these deficiencies rarely live beyond childhood and where management is still largely inadequate. These characterizations are possible by direct or indirect genetic analysis of genes involved in these diseases, and the choice of the strategy depends on the effective available budget and facilities to achieve a large benefit. In countries with more advanced molecular facilities and higher budget resources, the most appropriate choice in general is a direct strategy for mutation detection. However, in countries with limited facilities and low budget resources, carrier detection and prenatal diagnosis are usually performed by linkage analysis with genetic markers. This article reviews the genetic diagnosis of haemophilia, genetics and inhibitor development, genetics of von Willebrand's disease and of rare bleeding disorders.

Blood Coagulation Disorders, Inherited↗
PubMed2006

Recent developments in clinimetric instruments.

Assessment of impairment and function is essential in order to monitor joint status and evaluate therapeutic interventions in patients with haemophilia. The improvements in the treatment of haemophilia have required the development of more sensitive tools to detect the more minor dysfunctions that may now be apparent. This paper outlines some of the recent developments in this field. The Haemophilia Joint Health Score (HJHS) provides a systematic and robust measure of joint impairment. The MRI Scoring System has been designed to provide a comprehensive scoring system combining both progressive and additive scales. The Functional Independence Score for Haemophilia (FISH) has been developed to assess performance of functional activities and can be used in conjunction with the Haemophilia Activities List (HAL) which provides a self report measure of function. It is recommended that both measures are evaluated as these tools measure different constructs. Further refinement and testing of the psychometric properties of all of these tools is in progress. More widespread use of these tools will enable the sharing of data across the world so promoting best practice and ultimately enhancing patient care.

Activities of Daily Living↗
PubMed2006

Achieving and maintaining quality in the laboratory.

In order to ensure the delivery of a service of the highest possible quality, it is an essential requirement that laboratories undertake strict internal quality control (QC) measures as well as participate in external quality assessment (EQA) schemes. For any given test, a critical part of the internal QC process involves the establishment of reference intervals using samples taken from normal individuals, and then calculating limits representing the 95% range. This forms the basis for assessment of abnormal test results, which will in turn impact on laboratory performance in proficiency testing exercises in EQA programmes. Whereas for plasma-based assay systems, variability in performance in EQA exercises is usually determined by measurement of a coefficient of variation (CV), results of genetic testing is usually measured in absolute terms. Despite this, results of genetic EQA programmes confirm that errors in testing do occur, as much because of inadvertent sample switching and transcription errors as to analytical mistakes. EQA programmes involving identification of mutations by DNA sequencing, such as haemophilia, is made difficult by the high information content of sequence data. Nevertheless, results show that errors are usually made in the naming of the mutations, indicating that this is an evolving and poorly standardized area. Developing countries face particular challenges in the encouragement of laboratories to participate in local EQA programmes, as well as in relation to the logistical issues of sample provision, distribution and result collation in an effective and affordable manner.

Blood Coagulation Disorders↗
PubMed2006

Laboratory issues in bleeding disorders.

The clinical history of the patient and of his/her relatives is the most important tool for making correct diagnosis of inherited or acquired bleeding disorders. Several attempts have been made by clinicians to evaluate the sensitivity and specificity of bleeding symptoms. Specific and detailed questionnaires have been designed to quantify the bleeding tendency of patients with von Willebrand's disease (VWD) and a bleeding score has been calculated. VWD is considered the most frequent inherited bleeding disorder according to population studies: however, due to the complexity of its diagnosis, the number of patients with correct diagnosis of VWD in many developing countries is relatively low and most cases remain still under- or misdiagnosed. Once bleeding history is carefully evaluated by means of a bleeding score, the laboratory workout should be organized to find out the specific defect of haemostasis responsible for bleeding. Since factors involved in haemostasis are many, the correct approach must include first level screening tests with the aim to identify the abnormal phase of haemostasis involved: then, second level tests should be focused on the specific factors within the abnormal step of haemostasis. Among many other acquired bleeding disorders related to clinical conditions or to the use of drugs, the acquired inhibitors of haemostasis are rare but should be immediately characterized by appropriate laboratory tests because they can be often life-threatening for the patients.

Blood Coagulation Disorders↗
PubMed2006

Diversity of Glanzmann thrombasthenia in southern India: 10 novel mutations identified among 15 unrelated patients.

BACKGROUND: Glanzmann thrombasthenia (GT) is a congenital bleeding disorder caused by either a lack or dysfunction of the platelet integrin alphaIIbbeta3. OBJECTIVES: To determine the molecular basis of GT in patients from southern India. PATIENTS: Fifteen unrelated patients whose diagnosis was consistent with GT were evaluated. RESULTS: Platelet surface expression of alphaIIbbeta3 was < 10%, 10%-50%, and > 50% of controls in five, nine, and one patient(s), respectively. Immunoblotting of the platelet lysates showed no alphaIIb in 14 patients, and no beta3 in 10 patients, although severely reduced in four patients. Platelet fibrinogen was undetectable in 13 patients, and severely reduced in one patient. One patient showed normal surface alphaIIbbeta3 expression, and normal alphaIIb, beta3 and fibrinogen levels in the lysate. Ten novel candidate disease-causing mutations were identified in 11 patients. The missense mutations included Gly128Ser, Ser287Leu, Gly357Ser, Arg520Trp, Leu799Arg in alphaIIb, and Cys575Gly in beta3. We have already shown that Gly128Ser, Ser287Leu, and Gly357Ser mutations variably affect alphaIIbbeta3 surface expression. The Cys575Gly mutation may disrupt the disulphide link with Cys586 to cause the GT phenotype. The molecular pathology of the other missense mutations is not clear. Two nonsense mutations, Trp-16Stop and Glu715Stop in alphaIIb, and a 7-bp deletion (330-336TCCCCAG) in beta3 are predicted to result in truncated proteins. An IVS15(-1)G --> A mutation in alphaIIb induced a cryptic splice site as confirmed by reverse transcription-polymerase chain reaction (RT-PCR) analysis. Thirteen polymorphisms were also identified (five in alphaIIb and eight in beta3), among which five were novel. CONCLUSIONS: While identifying a significant number of novel mutations causing GT, this study confirms the genetic heterogeneity of the disorder in southern India.

Adolescent↗
PubMed2006

Hemorrhagic symptoms and bleeding risk in obligatory carriers of type 3 von Willebrand disease: an international, multicenter study.

OBJECTIVES: We undertook an international, multicenter study to describe the clinical picture and to estimate the bleeding risk in a group of obligatory carriers of type 3 von Willebrand disease (VWD). PATIENTS AND METHODS: Obligatory carriers (OC) of type 3 VWD were identified by the presence of offspring with type 3 VWD or by being an offspring of a type 3 patient. Normal controls were age- and sex-matched with the obligatory carriers. A physician-administered standardized questionnaire was used to evaluate hemorrhagic symptoms at presentation. A score system ranging from 0 (no symptom) to 3 (hospitalization, replacement therapy, blood transfusion) was used to quantitate bleeding manifestations. Odds ratios were computed for each symptom. RESULTS: Ten centers participated to the study, enrolling a total of 35 type 3 VWD families, with 70 OC. A total of 215 normal controls and 42 OC for type 1 VWD were also included. About 40% of type 3 OC had at least one bleeding symptom compared to 23% of normal controls and 81.8% of type 1 OC (P < 0.0001 by chi-squared test), showing that type 3 OC clearly represent a distinct population from type 1 OC. The clinical situations associated with an increase of bleeding risk in type 3 OC were epistaxis [odds ratio 3.6; 90% confidence intervals (CI) 1.84-21.5], cutaneous bleeding (odds ratio 5.5; 90% CI 2.5-14.1) and postsurgical bleeding (odds ratio 16.3; 90% CI 4.5-59). The severity of bleeding score correlated with the degree of factor (F) VIII reduction in plasma. CONCLUSIONS: OC for type 3 VWD represent a distinctive population from type 1 OC. These patients, however, present with more frequent bleeding symptoms in comparison to normal controls, especially in case of significantly low FVIII. Desmopressin and/or tranexamic acid might be useful to prevent or treat bleeding in these cases.

Adolescent↗