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Biomedical subjects

P Sharma

Publications and source records attributed to P Sharma.

At least 217 records · Page 12Linked to original sources
PubMed1998

Squamous islands in Barrett's esophagus: what lies underneath?

OBJECTIVE: Squamous islands are frequently visualized at the time of upper endoscopy in patients with Barrett's esophagus, especially those on proton pump inhibitor therapy (PPI). The significance of these islands is not clearly understood. The aim of this study was to systematically biopsy macroscopic squamous islands and to examine their histologic characteristics. METHODS: Patients with Barrett's esophagus undergoing surveillance had squamous islands documented and biopsied at the time of endoscopy. Barrett's esophagus was defined as the presence of a columnar lined esophagus on endoscopy with intestinal metaplasia on biopsy. All biopsies were obtained by a single senior endoscopist and were stained with alcian blue at pH 2.5. Biopsy samples with inadequate tissue quantity were not included in the study. RESULTS: A total of 39 biopsies were obtained from 22 patients. Twenty of the 22 patients were male, with a mean age of 65.4 yr (range 47-80 yr). The mean length of Barrett's mucosa was 5.6 cm (range 1-11 cm). Eleven of 22 patients were on omeprazole (mean dose 29.1 mg/day), whereas seven patients were on lansoprazole (60 mg/day). The mean duration of PPI therapy was 2.3 yr (range 9-71 months) at the time of biopsy of the squamous islands. Three patients were on H2-blocker therapy whereas the remaining patient had not been started on acid suppression therapy. On histology, 24 biopsy specimens (61.5%) revealed only squamous epithelium, whereas 15 (38.5%) showed the presence of intestinal metaplasia underlying the squamous epithelium. There was no significant difference between the patients with and without underlying intestinal metaplasia in regard to age, Barrett's length, dose, and duration of PPI therapy. CONCLUSION: In more than one-third of biopsies of macroscopic squamous islands within Barrett's esophagus, microscopic intestinal metaplasia is detected. The presence of squamous islands should not be equated with regression of Barrett's esophagus or with decreased cancer risk.

Aged↗
PubMed1998

Characterization of protective epitopes in a highly conserved Plasmodium falciparum antigenic protein containing repeats of acidic and basic residues.

The delineation of putatively protective and immunogenic epitopes in vaccine candidate proteins constitutes a major research effort towards the development of an effective malaria vaccine. By virtue of its role in the formation of the immune clusters of merozoites, its location on the surface of merozoites, and its highly conserved nature both at the nucleotide sequence level and the amino acid sequence level, the antigen which contains repeats of acidic and basic residues (ABRA) of the human malaria parasite Plasmodium falciparum represents such an antigen. Based upon the predicted amino acid sequence of ABRA, we synthesized eight peptides, with six of these (AB-1 to AB-6) ranging from 12 to 18 residues covering the most hydrophilic regions of the protein, and two more peptides (AB-7 and AB-8) representing its repetitive sequences. We found that all eight constructs bound an appreciable amount of antibody in sera from a large proportion of P. falciparum malaria patients; two of these peptides (AB-1 and AB-3) also elicited a strong proliferation response in peripheral blood mononuclear cells from all 11 human subjects recovering from malaria. When used as carrier-free immunogens, six peptides induced a strong, boostable, immunoglobulin G-type antibody response in rabbits, indicating the presence of both B-cell determinants and T-helper-cell epitopes in these six constructs. These antibodies specifically cross-reacted with the parasite protein(s) in an immunoblot and in an immunofluorescence assay. In another immunoblot, rabbit antipeptide sera also recognized recombinant fragments of ABRA expressed in bacteria. More significantly, rabbit antibodies against two constructs (AB-1 and AB-5) inhibited the merozoite reinvasion of human erythrocytes in vitro up to approximately 90%. These results favor further studies so as to determine possible inclusion of these two constructs in a multicomponent subunit vaccine against asexual blood stages of P. falciparum.

Amino Acid Sequence↗
PubMed1998

Induction of protective immune responses by immunization with linear multiepitope peptides based on conserved sequences from Plasmodium falciparum antigens.

A cysteine-containing peptide motif, EWSPCSVTCG, is found highly conserved in the circumsporozoite protein (CSP) and the thrombospondin-related anonymous protein (TRAP) of all the Plasmodium species analyzed so far and has been shown to be crucially involved in the sporozoite invasion of hepatocytes. We have recently shown that peptide sequences containing this motif, and also the antibodies raised against the motif, inhibit the merozoite invasion of erythrocytes. However, during natural infection, and upon immunization with recombinant CSP, this motif represents a cryptic epitope. Here we present the results of immunization studies with two linear multiepitopic constructs, a 60-residue (P60) and a 32-residue (P32) peptide, containing the conserved motif sequence. Both the peptides per se generated high levels of specific antibodies in BALB/c mice. P32 was found to be genetically restricted to H-2(d) and H-2(b) haplotypes of mice, whereas P60 was found to be immunogenic in five different strains of mice. The antibody response was predominantly targeted to the otherwise cryptic, conserved motif sequence in P60. Anti-P60 antibodies specifically stained the asexual blood stages of Plasmodium falciparum and Plasmodium yoelii in an immunofluorescence assay, recognized a 60- to 65-kDa parasite protein in an immunoblot assay, and blocked P. falciparum merozoite invasion of erythrocytes in a dose-dependent manner. Immunization with P60 also induced significant levels of the cytokines interleukin-2 (IL-2), IL-4, and gamma interferon in BALB/c mice. Moreover, >60% of mice immunized with P60 survived a heterologous challenge infection with a lethal strain of P. yoelii. These results indicate that appropriate medium-sized synthetic peptides might prove useful in generating specific immune responses to an otherwise cryptic but critical and putatively protective epitope in an antigen and could form part of a multicomponent malaria vaccine.

Amino Acid Sequence↗
PubMed1998

Circular intermediates of recombinant adeno-associated virus have defined structural characteristics responsible for long-term episomal persistence in muscle tissue.

Adeno-associated viral (AAV) vectors have demonstrated great utility for long-term gene expression in muscle tissue. However, the mechanisms by which recombinant AAV (rAAV) genomes persist in muscle tissue remain unclear. Using a recombinant shuttle vector, we have demonstrated that circularized rAAV intermediates impart episomal persistence to rAAV genomes in muscle tissue. The majority of circular intermediates had a consistent head-to-tail configuration consisting of monomer genomes which slowly converted to large multimers of >12 kbp by 80 days postinfection. Importantly, long-term transgene expression was associated with prolonged (80-day) episomal persistence of these circular intermediates. Structural features of these circular intermediates responsible for increased persistence included a DNA element encompassing two viral inverted terminal repeats (ITRs) in a head-to-tail orientation, which confers a 10-fold increase in the stability of DNA following incorporation into plasmid-based vectors and transfection into HeLa cells. These studies suggest that certain structural characteristics of AAV circular intermediates may explain long-term episomal persistence with this vector. Such information may also aid in the development of nonviral gene delivery systems with increased efficiency.

Animals↗
PubMed1998

Meta-analysis of the ACE gene in ischaemic stroke.

OBJECTIVES: The angiotensin-1 converting enzyme (ACE) gene is known to have two polymorphic alleles I/D. People with the DD genotype have been shown to be at greater risk of myocardial infarction, but only in some studies. Similar studies in stroke patients also show inconsistent results, but most of these studies have been underpowered to detect a small contribution to stroke risk from the ACE gene. A meta-analysis was undertaken using all known publications of the ACE polymorphism in ischaemic stroke. METHODS: Two computerised databases were searched for all publications relating to case-control studies using the ACE I/D variant in human ischaemic stroke. Seven association studies were identified and a meta-analysis was conducted using the Mantel-Haenszel estimate for odds ratio (OR) to determine whether the DD genotype predicted outcome in either a genetically dominant or recessive model. RESULTS: 1918 white subjects (1196 cases and 722 controls) were used in the meta-analysis. There was no difference in ACE genotype (chi2=2.92, p>0.05) or I/D allele frequency (chi2=3.28, p>0.05) in cases or controls. The overall OR for the D allele as an independent risk factor in ischaemic stroke was 1.31 (95% confidence interval (95% CI): 1.06-1.62, p=0.01) under a recessive model, and 1.14 (95% CI: 0.91-1.44, p=0.26) under a dominant model. CONCLUSIONS: This meta-analysis shows that the the D allele, acting recessively, is a modest but independent risk factor for ischaemic stroke onset. Meta-analysis may usefully be employed in allelic association studies for detecting small attributable risks of candidate genes in polygenic disorders.

Aged↗
PubMed1998

Consequences of aging on mitochondrial respiratory chain enzymes in cultured human fibroblasts treated with ascorbate.

The activities of mitochondrial respiratory chain enzymes with and without ascorbate pretreatment were assayed in 10- to 20-week-old cultures of human fibroblasts. Aging was associated with a significant loss of respiratory chain enzyme activities. The presence of ascorbate in the medium reduced the rate of loss of these enzymes. Free radical-mediated injuries may also contribute to aging since the changes seen in respiratory chain enzyme activities are similar to those seen in oxidatively stressed cells. This study demonstrates an age-related decline in mitochondrial respiratory chain activity as well as a protective role for ascorbate in aging.

Ascorbic Acid↗
PubMed1998

Positive association of tyrosine hydroxylase microsatellite marker to essential hypertension.

Despite advances in the understanding of monogenic hypertensive disorders, the genetic contribution to essential hypertension has yet to be elucidated. The position of tyrosine hydroxylase (TH) as the rate-limiting enzyme in catecholamine biosynthesis renders it a candidate gene for the etiology of hypertension. The TH gene contains an internal, informative microsatellite marker (TCAT)9. We undertook (1) an association study in a group of well-characterized hypertensive subjects (HT) and control subjects (NT) and (2) an affected sibling pair (ASP) study using sibships from our local family practices. Two hundred twenty-seven hypertensive patients (pretreatment systolic/diastolic blood pressure [BP] range, 139/94 to 237/133 mm Hg; age range [SD], 30 to 71 [8.5] years) were age- and gender-matched with 206 control subjects (BP range, 96/62 to 153/86 mm Hg; age range, 40 to 70 [7.6] years). One hundred thirty-six affected sibling pairs were recruited for our linkage study; 73 young borderline hypertensive subjects (YHT) (pretreatment BP range, 123/76 to 197/107 mm Hg; age range, 20 to 51 [9.4] years) were also recruited in whom recent pretreatment norepinephrine and epinephrine levels were available. All subjects were white. The TH short tandem repeat (STR) was amplified using specific polymerase chain reaction cycling conditions in all subjects, and products were run on an ABI 373A sequencer. TH alleles were assigned using Genescan and Genotyper software. Five TH alleles were present and designated A through E. Allele frequencies in the NT population (A, B, C, D, and E: 0.24, 0.17, 0.13, 0.20, and 0.26, respectively) were significantly different from the HT cohort (A, B, C, D, and E: 0.24, 0.19, 0.11, 0.11, and 0.35, respectively), P<0. 0005 (Pearson's test chi2=19.94; 4 df). The E allele appears overrepresented in the HT group, whereas the D allele appears to be overrepresented in the NT group. TH genotype frequencies were also significantly different between cases and controls (P<0.001; chi2=36. 57; 14 df). Both groups were in Hardy-Weinberg proportion. There was a trend (NS) for the D allele to be associated with a lower BP when BP was analyzed as a quantitative trait. ASP linkage data was analyzed using Splink, a nonparametric program. Expected values for sharing 0, 1, and 2 alleles (Z0, Z1, and Z2, respectively) may be expected to be 25%, 50%, and 25%, respectively, by chance (assuming identity by descent). These probabilities were calculated by Splink as 34, 68, and 34, respectively, and compared with observed values of 36.8, 67.9, and 31.3, respectively; thus, there was no excess sharing of TH alleles among affected sibling pairs (P=0.59; logarithm of odds ratio score, 0.0). TH allele frequencies in our YHT group (A, B, C, D, and E: 0.24, 0.20, 0.12, 0.15, and 0.29, respectively) were similar to those of our NT cohort (P>0.05). There was a trend for lower pretreatment plasma norepinephrine levels with the D allele in this YHT cohort. A common and potentially functional variant at codon 81(Val-->Met) within exon 2 of the TH gene (which we show to be in linkage disequilibrium with TH-STR) was also typed in our YHT but did not associate with catecholamine levels and is therefore unlikely to account for our findings with D and E TH-STR. In conclusion, the TH locus strongly associates with essential hypertension in a case-control model using well-characterized hypertensive and control groups. An ASP linkage model was negative, presumably because of lack of power. This study suggests that the TH gene, or a nearby gene, may be involved in the etiology of essential hypertension.

Adult↗
PubMed1998

MUC5B and MUC7 are differentially expressed in mucous and serous cells of submucosal glands in human bronchial airways.

Mucins are high molecular-weight glycoproteins involved in the protection and lubrication of respiratory, gastrointestinal, and reproductive tracts. Hypersecretory diseases such as cystic fibrosis (CF), chronic bronchitis, and asthma result in dysregulated levels of mucin production stemming from increased abundance of mucin-secreting cell types in the surface airway epithelium and submucosal glands. The isolation of at least nine mucin genes has prompted studies to characterize the cellular expression patterns of these mucins in normal and diseased tissues. In the present study, in situ hybridization and immunocytochemical methods were used to determine the cellular distribution of MUC5B and MUC7 expression in CF and non-CF human bronchus. Our findings indicate that MUC5B and MUC7 have expression patterns in human bronchial airways that are limited exclusively to submucosal glands. Specifically, MUC5B expression was confined to all mucous tubules, whereas MUC7 expression was seen in a subset of lysozyme expressing serous tubules of submucosal glands. Interestingly, heterogeneity of MUC7 expression between glands of the same bronchus ranged from 0 to 93% of serous tubules, suggesting that functional diversity may exist between glands within the same bronchial sample. No remarkable differences were observed in the expression patterns of MUC5B or MUC7 between CF (n = 7) and non-CF (n = 10) bronchial samples. In conclusion, MUC5B and MUC7 expressions define different cellular compartments within submucosal glands of human bronchus and lend insight into the heterogeneity of mucin production in the lung.

Bronchi↗
PubMed1998

Plants showing antiplasmodial activity--from crude extracts to isolated compounds.

The derivation of important antimalarial compounds started with the discovery of Cinchona bark powder with wine. Subsequently, post World War-I was a period of intensive work in maintaining such ethnobotanical records, in which the use of quinine has remained the drug of choice in malaria. After World War-II new chemical techniques were used to fractionate and isolate, and also for structure determinations, which led to an ever increasing number of potential antiplasmodial compounds. Recently experimental studies in animals and in clinical trials, showed the emergence of CQ-sensitive and CQ-resistant strains of Plasmodium. This paper is an attempt to update a historical list of antimalarial plants and their natural products as studied by pharmacognostic extraction methods of crude drug research of those times. Further an attempt has been undertaken to list the compounds as classified into three major groups, namely alkaloids, terpenes and quassinoids and aromatic and miscellaneous compounds. The most promising is a quassinoid, artemisinin derived from Artemisia annua which has caused a resurgence for the quest of newer antimalarial compounds.

Alkaloids↗
PubMed1998

Simulated glomerular hypertension promotes mesangial cell apoptosis and expression of cathepsin-B and SGP-2.

BACKGROUND: Focal glomerulosclerosis (FGS) is characterized by the accumulation of mesangial matrix and lack of mesangial cells (MC). We studied the role of glomerular hypertension (GH) in the development of MC hypoplasia. METHODS: We used an in vitro model of GH to study the effect of GH on MC apoptosis. Cultured rat endothelial cells were grown in the intracapillary space and MCs were grown in the extracapillary space. MC proliferation as well as apoptosis was evaluated under simulated normal glomerular pressure (SNGP) as well as simulated glomerular hypertension (SGH). Apoptosis was determined morphologically by DNA fragmentation using Hoechst staining as well as with the use of DNA gel electrophoresis. MCs grown under SNGP and SGH were also evaluated for the expression of genes associated with active cell death. In addition, we evaluated the effect of direct applied pressure on MC apoptosis. RESULTS: MCs grown under SGH were less elliptical and had a tendency to develop a dome in the center. Direct applied pressure promoted MC apoptosis in a dose and time dependent manner. DNA gel electrophoresis from MCs grown under SGH also showed integer multiples of 180 base pairs (ladder pattern); whereas cells grown under SNGP showed no DNA fragmentation. SGH increased mRNA expression of cathepsin-B (SNGP, 0.31 +/- 0.04 vs SGH, 0.57 +/- 0.03, P < 0.01, n = 3) and SGP-2 (SNGP, 0.55 +/- 0.05 vs SHG, 1.08 +/- 0.12, P < 0.01, n = 3) in MCs when compared to cells grown under SNGP. CONCLUSIONS: The present in vitro study suggests that GH has the potential to convert a hypercellular mesangium into a hypocellular one. This effect of GH is associated with expression of genes associated with active cell death.

Animals↗
PubMed1998

HIV-1 gp120 envelope protein and morphine-tubular cell interaction products modulate kidney fibroblast proliferation.

BACKGROUND: Renal interstitial scarring is an important feature of HIV-associated nephropathy. Intravenous drug abuse has been demonstrated to be a risk factor for the development of HIV-associated nephropathy in patients with HIV infection. We studied the effect of tubular cell-morphine and/or HIV-1 gp120 envelope protein interaction products on kidney fibroblast (KF) proliferation and apoptosis. METHODS: Tubular cell-morphine and/or gp120 interaction products were prepared by incubating confluent human proximal tubular cells with buffer (TCP), morphine (10(-3) mol/L) (TCM-IP), gp120 (0.01 microgram/mL)(TC-120IP), or morphine (10(-3) mol/L) + gpl20 (0.01 microgram/mL) (TCM-120IP). To evaluate the effect of tubular cell interaction products (TCIP) on KF proliferation, growth arrested kidney fibroblasts were treated with variable concentrations (5%, 10%, 20%, 30%, and 50%) of TCP, TCM-IP, TC-120IP, or TCM-120IP for 48 hours. To evaluate the role of cytokines in TCIP-induced KF proliferation, cells were incubated with TCIP with or without cytokine neutralizing antibodies to TGF-beta, TNF-alpha, FGF, or IL-6 for 48 hours. Subsequently, cells were counted in a hemocytometer (n = 3). To evaluate the effect of TCIP on KF apoptosis, cells were treated with 50% TCP, 50% TCM-IP, 50% TC-120IP, or 50% TCM-120IP for 24 hours and stained with H-33342 and propidium iodide. In parallel experiments KFs were harvested under identical conditions, DNA was isolated and run on gel electrophoresis. To evaluate the role of early growth genes in TCM-120-induced KF proliferation, TCM-120IP-treated cells were probed with cDNA for c-fos and c-jun. RESULTS: TC-120IP at a lower concentration (20%) enhanced (P < 0.001) proliferation of KF when compared with TCP. TCM-IP did not stimulate KF proliferation. On the contrary, TCM-120IP at a lower concentration (20%) promoted (P < 0.001) KF proliferation when compared with TCP, TCM-IP and TC-120IP. TCM-120IP at a lower concentration (20%) also enhanced KF mRNA expression of c-fos and c-jun. TCM-120IP enhanced KF proliferation in a dose-dependent manner. All tubular cell interaction products at a higher concentration (50%) promoted apoptosis of KF. CONCLUSIONS: Tubular cell-gp120 interaction products stimulated KF proliferation. Morphine amplified the effect of tubular cell-gp120 interaction on the proliferation of KF. TCM-120IP-induced KF proliferation may be mediated through the expression of early growth genes; whereas TCM-120IP-induced KF growth suppression may be mediated through the induction of apoptosis.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Enhanced proliferation, apoptosis, and matrix accumulation by mesangial cells derived from HIV-1 transgenic mice.

BACKGROUND: Mice, transgenic for HIV-1 genes, have been demonstrated to develop renal lesions mimicking HIV-associated nephropathy. Focal glomerulosclerosis (FGS) has been reported to be the predominant glomerular lesion in these animals. In the other models of FGS, the accumulation of mesangial matrix and mesangial cell proliferation have been shown to be the preceding abnormalities. We evaluated the proliferation, apoptosis, and matrix accumulation by mesangial cells derived from mice transgenic for HIV-1 genes as well as from nontransgenic mice. METHODS: Mesangial cells were cultured from mice transgenic for HIV-1 genes (HTrMC) and nontransgenic mice (NTrMC) of the same age and sex. The growth rate of HTrMC and NTrMC was determined under identical conditions. Morphologic evaluation of apoptosis was performed by staining cells with Hoechst (H)-33342 and propidium iodide. Accumulation of mesangial cell collagen type IV, laminin, and fibronectin was measured by the dot blot assay. Total RNA was extracted from HTrMC and NTrMC and Northern blots were generated. These blots were probed with specific probes for TGF-beta, proteoglycan (P16), and GAPDH. RESULTS: Mesangial cells (HTrMC) derived from transgenic mice had greater (P < 0.004) proliferation when compared to mesangial cells (NTrMCs) from nontransgenic mice (HTrMCs, 4.2 +/- 0.3 vs NTrMCs, 3.0 +/- 0.2 x 10(4) cells/well). HTrMCs also showed enhanced (P < 0.0001) apoptosis compared to NTrMCs (HTrMCs, 13.2 +/- 1.5% vs NTrMCs, 3.1 +/- 0.5% apoptotic cells/field). HTrMCs accumulated an increased (P < 0.02) amount of collagen type IV (HTrMCs, 5659.7 +/- 472.8 vs NTrMCs, 3882.2 +/- 339.7 ng/well); whereas NTrMCs accumulated a greater amount of laminin when compared to HTrMCs (HTrMCs, 12.8 vs NTrMCs, 29.6 +/- 2.9 ng/well). HTrMCs also showed an enhanced mRNA expression of TGF-beta and an attenuated expression of proteoglycan (P16). CONCLUSIONS: These results suggest that mesangial cells derived from mice transgenic for HIV-1 genes have enhanced proliferation and collagen accumulation. The enhanced expression of TGF-beta may have contributed to enhanced HTrMC proliferation and the accumulation of collagen. The present study provides the basis for a hypothesis that mesangial cells may be contributing to the development of focal glomerulosclerosis in mice transgenic for HIV-1 genes.

AIDS-Associated Nephropathy↗
PubMed1997

Chlorine-36 in fossil rat urine: an archive of cosmogenic nuclide deposition during the past 40,000 years.

Knowledge of the production history of cosmogenic nuclides, which is needed for geological and archaeological dating, has been uncertain. Measurements of chlorine-36/chlorine (36Cl/Cl) ratios in fossil packrat middens from Nevada that are radiocarbon-dated between about 38 thousand years ago (ka) and the present showed that 36Cl/Cl ratios were higher by a factor of about 2 before approximately 11 ka. This raises the possibility that cosmogenic production rates just before the close of the Pleistocene were up to 50% higher than is suggested by carbon-14 calibration data. The discrepancy could be explained by addition of low-carbon-14 carbon dioxide to the atmosphere during that period, which would have depressed atmospheric radiocarbon activity. Alternatively, climatic effects on 36Cl deposition may have enhanced the 36Cl/Cl ratios.

Animals↗
PubMed1997

An increased gamma delta T cell population in the intestine of thymus-leukemia antigen transgenic mice.

In an approach to study thymic leukemia antigen's (TL's) function, we have developed transgenic mice that express T18d on virtually all somatic cells; in such mice, we initially observed changes in T cells within the thymus and lymph nodes as well as the ability of TL to undergo recognition by splenic T cells. As phase II of our study, we now present the results on the composition of gut T cell populations which may be a better measure of TL's true function. We have demonstrated an increase in the number of gamma delta T cells as well as the increase in gamma delta T cells expressing the V gamma 2 chain. These cells appear to be both CD4 and CD8 negative. This suggests that TL may select for a subset of gamma delta T cells within the gut and bolsters earlier reports implicating an H-2T regional gene product as the major histocompatibility complex ligand for gamma delta T cells.

Animals↗