PubMed Health⌕ Search

Biomedical subjects

V Shah

Publications and source records attributed to V Shah.

At least 19 recordsLinked to original sources
PubMed2003

Influence of caveolin on constitutively activated recombinant eNOS: insights into eNOS dysfunction in BDL rat liver.

Diminished endothelial nitric oxide (NO) synthase (eNOS)-derived NO production from the hepatic vascular endothelium contributes to hepatic vasoconstriction in portal hypertension. The aim of this study was to examine the mechanism of this process by testing the influence of a constitutively active form of eNOS (S1179DeNOS) in both primary and propagated liver cells in vitro and in the sham and bile duct ligated (BDL) rat liver in vivo, using an adenoviral vector encoding green fluorescent protein (AdGFP) and S1179DeNOS (AdS1179DeNOS). AdS1179DeNOS transduction augmented basal and agonist-stimulated NO generation in nonparenchymal liver cells. Sham rats transduced in vivo with AdS1179DeNOS evidenced a decreased pressor response to incremental doses of the vasoconstrictor methoxamine compared with sham rats transduced with AdGFP. However, BDL rats transduced with AdS1179DeNOS did not display improved vasodilatory responses as evidenced by similar flow-dependent pressure increases to that observed in BDL rats transduced with AdGFP, despite similar levels of viral transgene expression. We next examined the influence of the eNOS inhibitory protein caveolin on S1179DeNOS dysfunction in cirrhotic liver. Immunogold electron microscopic analysis of caveolin in BDL liver demonstrated prominent expression not only in liver endothelial cells, but also in hepatic stellate cells. In vitro studies in the LX2 hepatic stellate cell line demonstrate that caveolin precipitates recombinant S1179DeNOS in LX2 cells, that recombinant S1179DeNOS coprecipitates caveolin, and that binding is enhanced in the presence of overexpression of caveolin. Furthermore, caveolin overexpression inhibits recombinant S1179DeNOS activity. These studies indicate that recombinant S1179DeNOS protein functions appropriately in normal liver cells and tissue but evidences dysfunction in the cirrhotic rat liver and that caveolin expression and inhibition in BDL nonparenchymal cells, including hepatic stellate cells, may account for this dysfunction.

Animals↗
PubMed2003

Early p53 mutations in nondysplastic Barrett's tissue detected by the restriction site mutation (RSM) methodology.

Barrett's oesophagus is a premalignant condition whose incidence is rising dramatically. Molecular markers are urgently needed to identify Barrett's patients at the highest risk of cancer progression. To this end, we have used a rapid molecular technique, restriction site mutation (RSM), to detect low-frequency mutations in the p53 tumour suppressor gene in premalignant Barrett's tissues of cancer-free patients. In total, 38 endoscopically diagnosed Barrett's patients with a range of histological stages of Barrett's progression, plus four control patients without Barrett's oesophagus, were analysed for early p53 mutations. Tissue samples taken from these patients (93 samples in total) were analysed for the presence of low-frequency p53 mutations at hotspot codons: 175, 213, 248, 249, 282. In total, 13 of the 38 Barrett's patients were shown to possess a p53 mutation in at least one sample (no mutations in the four control patients). Although no statistically significant associations were found, p53 mutations reflected histological progression in Barrett's patients with p53 mutations found in 30% of metaplasia patients (P=0.4) and low-grade dysplasia patients (P=0.33) and 45% of high-grade dysplasia patients (P=0.15). Detected p53 mutations were mainly GC to AT transitions at CpG sites.

Barrett Esophagus↗
PubMed2003

Ultrastructure of the cyanobacterium Nostoc muscorum and exploitation of the culture for hydrogen production.

An effect of various physico-chemical parameters on nitrogenase-catalyzed oxygen-free hydrogen production by Nostoc muscorum was demonstrated. More hydrogen was produced in the light than in the dark. Optimum temperature was 40 degrees C Various sugars increased hydrogen production whereas on easily metabolized nitrogen sources it was inhibited. The production was sensitive to salinity and Fe3+, Cu2+, Zn2+ and Ni2+ ions. Ultrastructural study revealed many electron-dense layers outside the cell-wall area that have not been observed earlier.

Carbon↗
PubMed2003

T cell Vbeta repertoires in childhood vasculitides.

Superantigens (SAgs) are potent stimulators of T cells bearing specific Vbeta T cell receptors (TCR) and may play a role in the aetiopathogenesis of systemic vasculitis, although this remains contentious. To investigate the possible aetiological role of SAgs, this study examined peripheral blood T cell Vbeta repertoires in children with systemic vasculitis. FACS analysis of 17 different peripheral blood T cell Vbeta families was performed in 20 healthy control children, 27 disease control children with nonvasculitic inflammatory disease, 25 children with primary systemic vasculitis, six patients with Kawasaki disease (KD) and six patients with Henoch-Schönlein purpura (HSP). There was a significantly increased variance of CD4 Vbeta12 and Vbeta17, and CD8 Vbeta1 in the primary systemic vasculitis group compared to control and disease controls. Moreover, 80% of the primary systemic vasculitis children had one or more CD4 Vbeta expansions or deletions, compared with 30% of controls (P < 0.002), and 37% of the disease controls (P < 0.002). In the KD group, the mean percentage of CD4 Vbeta2 T cells was higher than in controls or disease controls. In the HSP group, there was no consistent skewing of the T cell Vbeta repertoire. We have observed changes in the T cell Vbeta repertoire in children with vasculitis over and above those observed in disease controls. While these data provide impetus for further research into this contentious field, they do not resolve unequivocally the question of the role of SAgs in childhood vasculitic syndromes.

Adolescent↗
PubMed2003

Chromosome 4 hyperploidy represents an early genetic aberration in premalignant Barrett's oesophagus.

BACKGROUND AND AIMS: Characterisation of the underlying molecular mechanisms that promote Barrett's progression may ultimately lead to identification of potential predictive genetic markers that classify patients' malignant risk. In an attempt to understand these causative pathways, fluorescence in situ hybridisation (FISH) was used in this study to determine when specific genetic alterations arise during Barrett's associated neoplastic progression. METHODS: Endoscopic cytology brushings were obtained from 28 patients with Barrett's metaplasia, 28 with dysplasia (20 low grade dysplasia (LGD) and eight with high grade dysplasia (HGD)), and seven with adenocarcinoma, together with paired control brushings from regions of normal proximal squamous cell epithelium. The exfoliated epithelial cells were washed and deposited onto slides. Probes specific for the centromeres of chromosomes 4, 8, 20, and Y, and locus specific probes for the tumour suppressor genes p16, p53, and Rb were subsequently hybridised. RESULTS: Aneuploidy was found early in progression, with metaplastic tissues displaying increased copy numbers of chromosomes 4 and 8. Chromosome 4 hyperploidy was found in 89%, 90%, 88%, and 100% of metaplasias, LGD, HGD, adenocarcinomas, respectively, while chromosome 8 hyperploidy occurred in 71%, 75%, 100%, and 100% of patients with the respective staging. Loss of the p16 tumour suppressor gene also presented in metaplastic epithelium (7%) but most other genetic aberrations were only seen in HGD. CONCLUSIONS: Genetic instability arises well before dysplasia in Barrett's oesophagus, with chromosome 4 and 8 hyperploidy representing the earliest and most common alterations identified. As these aberrations are widespread at all the premalignant stages, there may be genes on chromosomes 4 and 8 that are involved in both the initiation and progression of Barrett's oesophagus.

Adenocarcinoma↗
PubMed2001

Cytoskeletal organization in tropomyosin-mediated reversion of ras-transformation: Evidence for Rho kinase pathway.

Tropomyosin (TM) family of cytoskeletal proteins is implicated in stabilizing actin microfilaments. Many TM isoforms, including tropomyosin-1 (TM1), are down-regulated in transformed cells. Previously we demonstrated that TM1 is a suppressor of the malignant transformation, and that TM1 reorganizes microfilaments in the transformed cells. To investigate how TM1 induces microfilament organization in transformed cells, we utilized ras-transformed NIH3T3 (DT) cells, and those transduced to express TM1, and/or TM2. Enhanced expression of TM1 alone, but not TM2, results in re-emergence of microfilaments; TM1, together with TM2 remarkably improves microfilament architecture. TM1 induced cytoskeletal reorganization involves an enhanced expression of caldesmon, but not vinculin, alpha-actinin, or gelsolin. In addition, TM1-induced cytoskeletal reorganization and the revertant phenotype appears to involve re-activation of RhoA controlled pathways in DT cells. RhoA expression, which is suppressed in DT cells, is significantly increased in TM1-expressing cells, without detectable changes in the expression of Rac or Cdc42. Furthermore, expression of a dominant negative Rho kinase, or treatment with Y-27632 disassembled microfilaments in normal NIH3T3 and in TM1 expressing cells. These data suggest that reactivation of Rho kinase directed pathways are critical for TM1-mediated microfilament assemblies.

3T3 Cells↗
PubMed2001

Ultrastructure of the fresh water cyanobacterium Anabaena variabilis SPU 003 and its application for oxygen-free hydrogen production.

Photoproduction of hydrogen has been studied as one of the ways to produce a clean, renewable energy source. Ultrastructure of the selected strain Anabaena variabilis SPU 003, a heterocystous cyanobacterium, has been done to understand the cell structure. The organism was found to be essentially a dark hydrogen producer. While pH had no significant effect on hydrogen production, optimum temperature was found to be 30 degrees C. Various sugars increased the production of hydrogen while the presence of various nitrogen sources inhibits the production. The production of hydrogen is highly sensitive to salinity and micronutrients.

Anabaena↗
PubMed2001

Continuous heparin infusion to prevent thrombosis and catheter occlusion in neonates with peripherally placed percutaneous central venous catheters.

BACKGROUND: Peripherally placed percutaneous central venous catheters (PCVC) are used in neonates to provide long-term vascular access. Major complications associated with these catheters include mechanical complications (catheter thrombosis, occlusion or dislodgement) and infection. Strategies to prevent catheter thrombosis and occlusion include the use of heparin. Systematic review has revealed that heparin is effective in prolonging the umbilical arterial catheter stay in neonates. However, heparin is known to be associated with complications such as bleeding and thrombocytopenia which may result in serious long-term sequelae. OBJECTIVES: The primary objective is to assess the effectiveness of heparin for prevention of catheter related thrombosis. The secondary objectives are to assess the effectiveness of heparin on catheter occlusion, duration of catheter patency, catheter related sepsis and complications associated with the use of heparin. SEARCH STRATEGY: A literature search was performed using the following databases: MEDLINE (1966- February 2001), EMBASE (1980-February 2001), CINAHL (1982-February 2001) and the Cochrane Controlled Trials Register ((Issue 1, 2001 of Cochrane Library) and abstracts from the annual meetings of the Society for Pediatric Research/American Pediatric Society and Pediatric Academic Societies published in Pediatric Research (1991-2000). No language restrictions were applied. SELECTION CRITERIA: Selection criteria applied to the clinical trials were: the population had to be neonates, intervention had to be heparin infusion compared to placebo or no treatment for prevention of any of the complications related to peripherally placed PCVC, the trial had to be randomized or quasi-randomized and at least one of the primary or secondary outcomes reported. DATA COLLECTION AND ANALYSIS: The methodological quality of included trials was assessed using criteria for masking of randomization, masking of intervention, completeness of follow-up and masking of outcome measurement. Data on relevant outcomes were extracted and the effect size was estimated by calculating relative risk (95% CI) and risk difference (95% CI). MAIN RESULTS: One randomized trial on the use of heparin for peripherally placed PCVC was identified. The trial was excluded due to several methodological issues: 1. randomization was at the time of umbilical catheter placement rather than later PCVC placement 2. multiple PCVC were used in some infants, with reported results based on number of catheters rather than infants. Thus, the trial was not included in the review. REVIEWER'S CONCLUSIONS IMPLICATIONS FOR PRACTICE: Prophylactic use of heparin for prevention of complications related to peripherally placed PCVC has not been studied in well designed randomized controlled clinical trials. With the current state of knowledge routine use of heparin for this purpose cannot be recommended. Implication for research: Increasing survival of extremely low birth weight infants may be accompanied by prolonged intravenous access for nutrition. Well designed randomized controlled trials of sufficient power to determine the benefits and risks of continuous infusion of heparin in neonates with peripherally inserted PCVC are warranted.

Anticoagulants↗
PubMed2001

Cellular and molecular basis of portal hypertension.

The molecular basis of the vascular wall abnormalities that contribute to development of portal hypertension are an area of active investigation. Studies to date suggest that diminution in eNOS-derived NO production in liver contributes to this process by causing increased intrahepatic resistance. This process seems to be mediated through inhibitory posttranslational regulatory mechanisms of eNOS. Endothelin-1 signaling is also increased in the intrahepatic vasculature. The mechanisms responsible for increased ET-1 signaling include increased ET-1 production and increased ET-A receptor expression, particularly within hepatic stellate cells, although the stimulus responsible for activation of the ET-1 system remains uncertain. In the splanchnic circulation, increases in eNOS-derived NO contribute to increased portal venous inflow through transcriptional and posttranslational regulation of eNOS. Development of the porto-systemic collateral circulation characteristic of portal hypertension occurs through a combination of NO-dependent dilation of preexisting vessels and through growth factor-mediated angiogenesis and neovascularization (Fig. 3). Further studies in vascular wall biology are continuing to elucidate more clearly the molecular mechanisms of portal hypertension. The [figure: see text] mechanism by which eNOS-derived NO production is increased in the splanchnic arteriolar endothelial cell but decreased in the liver endothelial cell and the role of specific ET receptor subtypes in the mechanism of activation of the ET-1 system and its effect on contractile cells in liver cirrhosis are areas that require further investigation. Further studies are needed to determine the intrahepatic site of pressure and perfusion regulation, be it the hepatic sinusoid and its unique, specialized cell types or the endothelial and smooth muscle cells in the hepatic and portal venules. The role of more recently delineated vasoactive pathways such as urotensin-II/GPR 14 and anandamide/CB1 receptor in portal hypertension must be examined. Most importantly, future studies must focus on novel experimental therapies, using pharmacologic and genetic approaches to modulate these vascular biologic systems and thereby to ameliorate complications and symptoms relating to portal hypertension in patients with cirrhosis.

Animals↗
PubMed2001

Bioavailability and bioequivalence: an FDA regulatory overview.

Bioavailability and/or bioequivalence studies play a key role in the drug development period for both new drug products and their generic equivalents. For both, these studies are also important in the postapproval period in the presence of certain manufacturing changes. Like many regulatory studies, the assessment of bioavailability and bioequivalence can generally be achieved by considering the following three questions. What is the primary question of the study? What are the tests that can be used to address the question? What degree of confidence is needed for the test outcome? This article reviews the regulatory science of bioavailability and bioequivalence and provides FDA's recommendations for drug sponsors who intend to establish bioavailability and/or demonstrate bioequivalence for their pharmaceutical products during the developmental process or after approval.

Biological Availability↗
PubMed2001

Release of hydrocortisone from a cream matrix: dependency of release on suspension concentration and measurement of solubility and diffusivity.

The principal object of the present research was to investigate the sensitivity of drug release from a semisolid system to the manner of its preparation and to the concentration of drug placed within it. Established theory indicated that release should be concentration dependent, with the specific dependency determined by whether the drug in the system is fully in solution or is present substantially as suspended matter. To purposefully explore these relatively untested performance expectations, the total amount of drug in the formula was varied from a low concentration of 0.25% to a high concentration of 3%. Conditions were established such that drug release conformed to release from a semi-infinite medium into a receptor sink. At every concentration, release profiles were well reproduced in replicate samples and, where multiple lots of a kind were employed, from lot to identical lot. In all cases square root of time release kinetics were observed. Moreover and without exception, the square root of time release rate from run to run was directly proportional to the square root of the total concentration of hydrocortisone placed in the formulations. The amount released per square root of time per square root of total concentration was nearly identical from run to run irrespective of total concentration. The overall behavior fit theoretical expectations for suspensions having only a small fraction of the drug they contain in solution. That this condition prevailed even at the lowest 0.25% hydrocortisone strength was proven by independently measuring hydrocortisone's solubility (0.02%). Measurement of solubility permitted estimation of the effective diffusivity of the drug through the cream (2 x 10(-7) cm2/s).

Administration, Cutaneous↗
PubMed2001

Behçet's disease in UK children: clinical features and treatment including thalidomide.

OBJECTIVE: To study the clinical spectrum of Behçet's disease (BD) in childhood, and to report our experience of using thalidomide. METHOD: Ten children, diagnosed with BD, were studied retrospectively. RESULTS: The median (range) age at first presentation was 4 (1.2-12.0) yr, at diagnosis was 11 (3-15) yr and the follow-up period was 4.1 (0.6-6.3) yr. Oral ulcers were present in all patients (100%), genital ulcers were present in six (60%), peri-anal ulcers were present in three (30%), skin manifestations were present in nine (90%), intracranial hypertension was present in two (20%), mild gastrointestinal symptoms were present in five (50%), joint symptoms were present in six (60%), ocular lesions were present in five (50%), but only one child had anterior and posterior uveitis. Therapeutically, a range of drugs was used, including colchicine, that resulted in good responses in five children. Thalidomide (1 mg/kg/week to 1 mg/kg/day) was used in five children who were unresponsive to other immunosuppressive agents. It resulted in complete remission in three children and less frequent milder oral ulcers in two. Neuropathy developed in two children and in one it was irreversible. CONCLUSION: BD in children is similar to the disease in adults. Thalidomide provided a useful therapeutic option for severe oral and genital ulceration which was unresponsive to other therapies. Awareness of the danger of axonal neuropathy and teratogenesis at all times during thalidomide therapy is crucial. A low dose is probably as effective as higher doses.

Adolescent↗
PubMed2001

Regulation of hepatic eNOS by caveolin and calmodulin after bile duct ligation in rats.

In carbon tetrachloride-induced liver cirrhosis, diminution of hepatic endothelial nitric oxide synthase (eNOS) activity may contribute to impaired hepatic vasodilation and portal hypertension. The mechanisms responsible for these events remain unknown; however, a role for the NOS-associated proteins caveolin and calmodulin has been postulated. The purpose of this study is to characterize the expression and cellular localization of the NOS inhibitory protein caveolin-1 in normal rat liver and to then examine the role of caveolin in conjunction with calmodulin in regulation of NOS activity in cholestatic portal hypertension. In normal liver, caveolin protein is expressed preferentially in nonparenchymal cells compared with hepatocytes as assessed by Western blot analysis of isolated cell preparations. Additionally, within the nonparenchymal cell populations, caveolin expression is detected within both liver endothelial cells and hepatic stellate cells. Next, studies were performed 4 wk after bile duct ligation (BDL), a model of portal hypertension characterized by prominent cholestasis, as evidenced by a significant increase in serum cholesterol in BDL animals. After BDL, caveolin protein levels from detergent-soluble liver lysates are significantly increased as assessed by Western blot analysis. Immunoperoxidase staining demonstrates that this increase is most prominent within sinusoids and venules. Additionally, caveolin-1 upregulation is associated with a significant reduction in NOS catalytic activity in BDL liver lysates, an event that is corrected with provision of excess calmodulin, a protein that competitively binds eNOS from caveolin. We conclude that, in cholestatic portal hypertension, caveolin may negatively regulate NOS activity in a manner that is reversible by excess calmodulin.

Animals↗
PubMed2001

Correlation of the local distribution of topically applied substances inside the stratum corneum determined by tape-stripping to differences in bioavailability.

Tape-stripping and optical spectroscopy are used as a suitable combined method to determine the horny layer profile. Firstly, typical ultraviolet filter substances are used as active substances which are fixed inside the horny layer. Secondly, clobetasol propionate was applied topically in two formulations, Temovate Cream and Temovate and Emollient. The measured changes in the local distribution of the drug inside stratum corneum reflect the observed differences in the biological response visualized as blanching. The concentration of the drug in deeper parts of the horny layer proposes the existence of a small channel available for the percutaneous absorption. The observed low intensity blanching is correlated to the follicle orifices of the skin. After application of Temovate and Emollient, a lateral spreading of the drug must be taken into account.

Administration, Topical↗
PubMed2001

Selective screening for neonatal galactosemia: an alternative approach.

UNLABELLED: No universal consensus exists for population-based neonatal screening for galactosemia. In our institution, selective screening for classical galactosemia is carried out on infants under 2 wk of age and those with symptoms suggestive of this disorder. Eighteen cases were diagnosed from 25,099 tests done; 17 were symptomatic at the time of diagnosis. CONCLUSION: We suggest that improved clinical vigilance and selective screening would identify most infants with severe galactosemia as early as a population-based program.

Biomarkers↗