Biomedical subjects

S Sharma

Publications and source records attributed to S Sharma.

At least 793 records · Page 44Linked to original sources

PubMed1995

Suppression of RAS and MOS transformation by radicicol.

Activated versions of ras and mos oncogenes subvert the signal transduction pathway by mimicking transducers at the plasma membrane and cytosol respectively. Radicicol (UCS1006), an antifungal antibiotic, had the ability to suppress transformation by ras and mos oncogenes in a rapid, reversible and dose-dependent manner. UCS1006 inhibited MAP kinase activity (both ERK1 and ERK2) in untransformed as well as ras and mos transformed cells. However, ERK2 but not ERK1 activity was constitutively elevated in ras and mos transformed cells used in this study. In addition, a 62 kDa (kilodalton) phosphoprotein was identified whose tyrosine phosphorylation was inhibited by UCS1006, in both ras and mos transformed cells. This 62 kDa phosphoprotein, which was found to be heavily phosphorylated on tyrosine residues only in the ras and mos transformed cells but not in untransformed NIH3T3 cells, was identical to the previously described GAP-associated tyrosine phosphoprotein, p62, that is the major target for phosphorylation in cells transformed by tyrosine kinase oncogenes. These results suggest that agents such as radicicol can suppress transformation by diverse oncogenes such as src, ras and mos at least in part by inhibiting the function of key signal transduction intermediates such as MAP kinase and GAP-associated p62.

3T3 Cells↗

PubMed1995

Cloning, overexpression, purification, and characterization of the carboxyl-terminal nucleotide binding domain of P-glycoprotein.

Multidrug-resistant tumor cells overexpress P-glycoprotein (170 kDa), a member of the ABC (ATP Binding Cassette)-transporter superfamily. P-glycoprotein has been implicated in transport of a broad range of amphiphilic, hydrophobic drugs from tumor cells. The sequence and structural organization of P-glycoprotein, which consists of 12 transmembrane helices and two cytoplasmic nucleotide binding domains, is similar to other ABC-transporters. It is believed that the nucleotide binding domains of various ABC transporters, which have 30-50% sequence identity, play an important role in coupling ATP hydrolysis to the transport process. To allow structure-function studies of the nucleotide binding domains, the carboxyl-terminal nucleotide binding domain (NBD) of Chinese hamster P-glycoprotein has been cloned, overexpressed, and purified both by itself and as a fusion with maltose-binding protein. It has been demonstrated that the carboxyl-terminal NBD, when overexpressed in Escherichia coli in the absence of transmembrane helices, has very low ATPase activity. This suggests that the amino-terminal nucleotide binding domain and possibly interaction with the transmembrane domains may be required for full ATPase activity. It is also consistent with the idea that the ATPase activity of P-glycoprotein is stimulated in the presence of drugs. Circular dichroism spectral analysis and the ability of carboxyl-terminal NBD, both by itself and as a fusion with maltose-binding protein, to bind ATP-agarose beads and P-glycoprotein specific monoclonal antibodies suggests that the polypeptide folds into a functional domain. Gel filtration chromatography and cross-linking studies indicate that the carboxyl-terminal NBD has a tendency to self-associate to form oligomers. It is speculated that the carboxyl-terminal NBD may play a role in self-association of P-glycoprotein molecules in the plasma membrane.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Down-regulation of murine fibrosarcoma transforming growth factor-beta 1 expression by interleukin 7.

BACKGROUND: Cytokine genes encode proteins that modulate immune system responses. Modification of tumor cells by the introduction of cytokine genes has been used as a strategy to augment host immunity. Interleukin 7 (IL-7) gene transfer enhances the immune response to tumor cells and can result in tumor regression. Transforming growth factor-beta 1 (TGF-beta 1) is a potent immunosuppressive cytokine produced by many tumors. We have previously reported that recombinant IL-7 decreases the expression of TGF-beta 1 by murine macrophages. PURPOSE: This study investigates the inhibition of tumor-derived TGF-beta 1 production as a possible mechanism for the enhanced antitumor immunity that accompanies IL-7 gene transfer. METHODS: A fibrosarcoma cell line (FSA-JmIL-7) genetically modified to produce IL-7 was used to evaluate the effects of IL-7 on tumor production of TGF-beta 1. The control cell line (FSA-Jneo) originated from the same parental fibrosarcoma cell line (FSA) and was produced by transduction with the same retroviral vector without the IL-7 gene. FSA-Jneo and FSA-JmIL-7 tumor cells were evaluated for the expression of TGF-beta 1 messenger RNA (mRNA). To determine if the observed change in TGF-beta 1 mRNA was associated with an alteration in protein secretion, we compared supernatants from tumor cell cultures for TGF-beta 1 production. Specific anti-TGF-beta 1 monoclonal antibody (MAb) was used to confirm the role of TGF-beta 1 in these assays. RESULTS: Compared with FSA parental and FSA-Jneo cells, FSA-JmIL-7 cells expressed TGF-beta 1 mRNA at a lower level. Compared with supernatants from FSA-Jneo cells, FSA-JmIL-7 supernatants contained consistently lower levels of TGF-beta 1 activity (P < .05). In addition, FSA-Jneo supernatants suppressed lymphocyte proliferation to a significantly greater degree than supernatants from FSA-JmIL-7 cells (P < .05). Studies with anti-TGF-beta 1 MAb added to the supernatants confirmed the role of TGF-beta 1 in inhibition of lymphocyte proliferation. CONCLUSION: These findings suggest that IL-7 gene transfer inhibits the production of TGF-beta 1 by tumor cells and thus may enhance the efficacy of the host's antitumor immune response. IMPLICATION: The regulation of endogenous tumor-derived cytokines in response to cytokine gene transfer may contribute to altered immune responses in the tumor microenvironment and thus may be an important additional parameter to assess in gene therapy.

Animals↗

PubMed1995

Evaluation of chemopreventive agents in different mechanistic classes using a rat tracheal epithelial cell culture transformation assay.

The rat tracheal epithelial (RTE) cell focus inhibition assay was used to identify potential chemopreventive agents. Ninety-nine agents were evaluated for their ability to inhibit benzo[a]pyrene-induced transformation of RTE cells. Freshly isolated RTE cells were exposed to benzo[a]pyrene alone or in combination with a chemopreventive agent. After 30 days in culture, transformed foci were scored and inhibition was quantitated. In these studies, foci formation was inhibited mainly by agents which modulate the initiation of carcinogenesis by altering drug-metabolizing enzymes, inhibiting the binding of benzo[a]pyrene to DNA, enhancing detoxification of activated carcinogens, or by inducing epithelial cell differentiation. Such agents include antioxidants, free radical scavengers, glutathione S-transferase enhancers, vitamins, retinoids, and sulfhydryl compounds. Agents which inhibit ornithine decarboxylase and arachidonic acid metabolism were not as effective. The RTE assay provides important data for agent selection prior to whole animal-screening assays in the development of chemoprevention drugs.

Animals↗

PubMed1995

Sex-specific effects of prenatal stress on hypothalamic-pituitary-adrenal responses to stress and brain glucocorticoid receptor density in adult rats.

Previous research indicates that the offspring of dams exposed to stress during late gestation show altered hypothalamic-pituitary-adrenal (HPA) responses to stress. However, the results are inconsistent and a review of the literature suggests that the effects may differ depending upon the gender of the offspring. In the present study, we measured plasma adrenocorticotropin (ACTH) and corticosterone (B) levels prior to, and at 0, 20, 40 and 70 min following restraint stress in catheterized adult male and female offspring of dams stressed in the last week of gestation (i.e. days 15-19 of gestation). Prenatal stress significantly increased both plasma ACTH and B levels in response to restraint, but only in females; male offspring were largely unaffected. In addition, plasma corticosteroid-binding globulin (CBG) levels were significantly increased in prenatally-stressed females, but not in males. Despite these differences in plasma CBG, estimated free B levels following restraint were also significantly elevated in prenatally-stressed females. We then examined glucocorticoid receptor binding in a variety of forebrain structures. Prenatal stress had no effect on glucocorticoid receptor density in the hypothalamus or hippocampus in either males or females. Differences in glucocorticoid receptor density across groups were observed in the septum, frontal cortex, and amygdala. However, the pattern of observed differences across the groups was not consistent with the pattern of hormonal differences. In summary, the effect of prenatal stress on HPA function is substantially more marked in females than in males. Interestingly, a similar pattern of effects on HPA activity has been reported for prenatal alcohol exposure.

Adrenocorticotropic Hormone↗

PubMed1995

Fatal aortic rupture following balloon angioplasty of aortic restenosis in aortoarteritis.

We report a case of fatal aortic rupture following balloon dilation in a young female with aortoarteritis in whom restenosis of the aorta was observed 16 years after a patch aortoplasty operation. To the best of our knowledge, this complication has not been reported in aortoarteritis, although such instances have been reported in recoarctation. This unfortunate experience leads us believe that aortic segment in operated cases may be resistant to balloon dilation and vulnerable to rupture. In such cases, balloon angioplasty should either be avoided or performed with extreme caution. A sequential balloon dilation technique starting with a smaller balloon may be helpful in avoiding this complication.

Adult↗

PubMed1995

Balloon mitral valvotomy in patients with systemic and suprasystemic pulmonary artery pressures.

Mitral stenosis with severe pulmonary artery hypertension constitutes a high risk subset for surgical commissurotomy or valve replacement. Balloon mitral valvotomy has been proposed as a technique for treating high risk surgical patients with mitral stenosis. The efficacy of this technique in patients with severe pulmonary artery hypertension, however, has not been fully evaluated. Percutaneous transvenous mitral commissurotomy (PTMC) was performed in 450 consecutive patients. Of these, forty-five (10%) patients had systemic or suprasystemic systolic pulmonary artery pressures (110 +/- 20, range 96 to 170 mm Hg). The baseline characteristics and immediate hemodynamic results of these 45 patients with systemic/suprasystemic systolic pulmonary artery pressures (group I) were analysed and compared with those of 405 patients with subsystemic systolic pulmonary artery pressures (group II). Patients in group I were more symptomatic (New York Heart Association functional class > or = III, 96 vs. 55%, P < 0.001) and had severe subvalvular fibrosis (mitral subvalvular distance ratio [MSDR], 0.14 +/- 0.04 vs. 0.22 +/- 0.04, P < 0.01). Before PTMC, mean transmitral gradient was higher (34 +/- 8 vs. 25 +/- 4 mm Hg, P < 0.02) and mitral valve area smaller (0.5 +/- 0.3 vs. 0.9 +/- 0.4 cm2, P < 0.02) in group I patients, who also had higher pulmonary vascular resistance (16 +/- 5 vs. 9 +/- 5 U, P < 0.005). After PTMC final mean transmitral gradients (7 +/- 3 vs. 5 +/- 3 mm Hg) and mitral valve areas (1.9 +/- 0.4 vs. 2.0 +/- 0.4 cm2) were similar in both groups (P = NS). Group I patients had a greater decrease in pulmonary artery pressures (34 +/- 4 vs. 25 +/- 2%, P < 0.05) but final systolic pulmonary artery pressures (82 +/- 20 vs. 50 +/- 14 mm Hg) and pulmonary vascular resistance (12 +/- 4 vs. 6 +/- 4 U) remained significantly higher in this group (P < 0.005). Thus, in patients with severe pulmonary artery hypertension, PTMC is a safe and effective technique providing good immediate hemodynamic results.

Adult↗

PubMed1995

Effects of oltipraz and related chemoprevention compounds on gene expression in rat liver.

One promising approach to cancer chemoprevention involves the induction of phase II xenobiotic metabolism enzymes. Since this approach requires drugs specifically intended to alter tissue gene expression patterns over long periods, it will be important to determine experimentally which proteins are increased or decreased by treatment, and how such alterations may (or may not) be related to the postulated chemopreventive mechanism. We have employed two-dimensional electrophoresis to detect and quantitate gene expression effects of candidate chemoprevention compounds in the livers of treated rats. Oltipraz, an inducer of several phase II enzymes, affected a series of at least 26 proteins, most of which were slightly decreased by treatment. Several proteins were increased, the prime example being rat liver spot 693, which was induced more than 7-fold by oltipraz. This protein was excised from multiple 2-D gels and subjected to in situ tryptic digestion followed by microchemical sequence analysis. The resulting multiple peptide sequences match perfectly with the cDNA-derived sequence of rat aflatoxin B1 aldehyde reductase (AFAR). Using quantitative measurements of AFAR from 2-D gels, we compared a series of dose regimens. Oltipraz administration by gavage or in diet appeared equally effective, while recovery studies indicated a half-time of 5.5 days for disappearance of the AFAR protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Evaluation of chick embryo neural retinal cell culture as a screen for developmental toxicants.

This paper describes a study to evaluate the concordance with in vivo results of an in vitro screen for developmental toxicants. The screen is a primary culture of chick embryo neural retina cells (CERC) which undergo processes of cell-cell recognition and interaction, growth, and differentiation over a 7-day culture period. Each of these developmentally significant events is measured separately as formation of multicellular aggregates, protein content, and glutamine synthetase activity, respectively. A total of 45 chemicals, 24 of which have been shown to be teratogenic at some dosage to mammalian embryos in utero, 7 of which are embryotoxic (but not teratogenic) in utero at high dosage, and 14 of which have not produced developmental toxicity in vivo, were evaluated in this assay by investigators who were blinded to the identity of the chemicals. Chemicals were tested up to concentrations that were frankly cytolethal, or up to a maximum of 5 mg/ml. Chemicals were present only during the first 24 hr of culture. The chemicals were selected to be representative of a variety of chemical classes (e.g., solvents, metals, food additives, anticonvulsants, antineoplastics). In several cases, pairs of structurally similar compounds with different developmental toxic potencies (e.g., valproate and 2-en-valproate, formamide, and N,N-dimethylformamide) were tested. Of the 31 developmental toxicants, 25 affected at least one endpoint in the assay at concentrations which are achievable in vivo (i.e., below the systemic concentration at a lethal dose), yielding a false-negative rate of 19%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

A study on the nutritional status of adolescent girls.

One hundred and twenty school girls in the age group of 13-15 years from four Government schools of Ludhiana city were selected for the study. On the basis of their family income they were divided into three experimental groups i.e. income group I (IgI), income group II (IgII) and income group III (IgIII). The results showed that the intake was low for all the foods. However, the consumption of fruits, milk and milk-products, sugar and jaggery, fats and oils by the subjects of IgII and IgIII was significantly higher (p < 0.05) than IgI. The mean daily intake of energy, protein, iron, calcium, vitamin A & vitamin C was inadequate while the intake of fibre was adequate by the subjects as compared to ICMR recommendations. There was no significant difference in energy, protein and iron intakes among the subjects of three groups. However, the fibre intake by the subjects of IgI was significantly higher (p < 0.05) than the subjects of IgIII, whereas the intake of calcium, vitamin A and ascorbic acid by the subjects of IgII & IgIII was significantly higher (p < 0.05) than those of IgI. The average body weights and heights of the subjects were normal. The haemoglobin (Hb) level of the subjects ranged from 8.5-12.5 g/dl with a mean value of 10.73 + 0.07 and reported that only 23 percent of the subjects had acceptable level.

Adolescent↗

PubMed1995

Colorectal manifestations of endocrine disease.

PURPOSE: The aim of this review is to alert the colon and rectal surgeon to the colorectal manifestations of endocrine disease. METHODS: This report was obtained by a review of the medical literature. Endocrine disease may initially present as a symptom felt to be referable to colorectal disease. Furthermore symptoms of well-established endocrine disorders may have refractory colorectal symptoms. RESULTS: Constipation is the most common gastrointestinal symptom of diabetics; however, in patients with brittle diabetes, diarrhea may be chronic and intermittent. Unexplained diarrhea, despite an exhaustive work-up for an etiology, should alert the clinician to the possibility of a pancreatic endocrine tumor. Thyroid disorders, depending on activity of the gland, may have refractory constipation, diarrhea, or steatorrhea as the only presenting symptoms. Constipation is a common symptom of hypercalcemia, secondary to hyperparathyroidism. Primary hyperparathyroidism has been associated with increased incidence of malignancies, specifically of colonic origin. In patients with acromegaly a threefold to eightfold increased risk of colon carcinoma or adenomatous polyps is seen. Chronic adrenal insufficiency may present initially as diarrhea and malabsorption. The adrenal gland is a frequent site of metastases from colorectal cancer. Pheochromocytomas may be a cause of occult gastrointestinal bleeding or ischemic colitis. CONCLUSION: Unexplained symptoms referable to the colon and rectum should alert the clinician to the possibility of an underlying endocrine disorder.

Colonic Diseases↗

PubMed1995

Constituents of human urine alter siderophore production of Escherichia coli.

Four uroisolates and four faecal isolates of Escherichia coli were randomly selected for studying the siderophore production in an iron-deficient, chemically defined, medium. Glucose, lactose, urea and creatinine were added individually, as well as in combination, to estimate their influence on siderophore production. No difference in siderophore production was observed between stool and urinary isolates of E. coli. Alterations in phenolate production were observed to be constituent-dependent while a uniformly significant increase in hydroxamate production (p < 0.05) was recorded after addition of the constituents, either each individually or in combination.

Creatinine↗

PubMed1995

Differential effect of heat shock on RNA metabolism in human Burkitt's lymphoma B-cell lines.

Thermal stress induces expression of a family of heat shock proteins which may regulate the synthesis of various cellular genes. We investigated the effect of heat shock on polyadenylation in Epstein-Barr Virus (EBV) negative and EBV transformed human Burkitt's lymphoma (BL) B-cell lines. Incubation of the BL B-cell line P3HR-1, carrying the defective EBV genome [EBV nuclear antigen-2 gene deletion] at 46 degrees C for 15 min increased nuclear poly(A) polymerase (PAP) activity. Thereafter, enzymatic activity declined and at 60 min it was reduced to about 50% of that observed in cells incubated at 37 degrees C. In contrast, no significant increase in PAP activity was observed at 15 min or thereafter in an EBV- BL cell line, ST-486, in response to elevated temperature. Furthermore, no heat shock mediated change in nuclear poly(A)-specific endonuclease activity was observed in either P3HR-1 or ST-486 cells suggesting a specific effect on PAP activity. However, thermal stress dependent increase in c-myc expression was detected only in P3HR-I cells. These results suggest an association between EBV transformation and enhanced expression of c-myc and PAP activity. To further determine the role of EBV, and EBV- BL cell line, BL-30, and BL-30 cells infected in vitro with a wild type strain of EBV, BL-30/B95-8, were investigated. BL-30/B-95-8, unlike the parental BL-30 cells, exhibited c-myc and PAP gene upregulation at 15 min but were downregulated at 60 min following exposure of cells to elevated temperatures. These results suggest that infection of human B-cells with EBV is associated with their ability to respond to thermal stress by increased PAP activity which may stabilize mRNA through enhanced polyadenylation.

Burkitt Lymphoma↗

PubMed1995

Expression of the ROS1 oncogene for tyrosine receptor kinase in adult human meningiomas.

Oncogenes have been implicated in the promotion and progression of cancer in humans. Expression of the ROS1 oncogene, a member of the receptor tyrosine kinase superfamily, was examined in human meningiomas by coupled reverse transcription and polymerase chain reaction (RT-PCR) assays. Two sets of region-specific oligonucleotides, specific for different regions of the ROS1 messenger ribonucleic acid (mRNA), were used in RT-PCR assays to independently examine ROS1 transcripts from primary human meningiomas. ROS1 was expressed at high levels in approximately 55% (17 of 31) of the meningiomas examined, but not expressed in non-neoplastic brain samples. The commonplace expression of the ROS1 oncogene in meningiomas suggests a role for this oncogene in the etiology of these tumors.

Gene Expression↗

PubMed1995

Management of symptomatic malignant ascites with diuretics: two case reports and a review of the literature.

Malignant ascites is a common complication of advanced cancer. It is associated with distressing symptoms and poor prognosis. Treatment may be aimed at the underlying cancer but is rarely successful. Therapeutic success for the available symptomatic treatment options for ascites is often limited. Control of symptomatic malignant ascites is possible with the use of diuretics in selected patients, is well tolerated, and should be tried first.

Aged↗

PubMed1995

A comparison of transesophageal and transthoracic echocardiographic assessment of left ventricular function in pediatric patients with congenital heart disease.

OBJECTIVE: To determine the quantitative utility of transesophageal echocardiographic assessments of left ventricular function in pediatric patients with congenital heart disease by evaluating the variability between observers and between echocardiographic windows. DESIGN: Retrospective, blinded analysis. SETTING: University-associated pediatric hospital. PARTICIPANTS: Transthoracic and transesophageal echocardiographic images of 25 pediatric patients with congenital heart disease were reviewed. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: End-diastolic area, end-systolic area, and fractional area change were measured from short-axis images of the left ventricle at the midpapillary level by two separate investigators. These measurements were compared by the method of Bland and Altman and Sheiner and Beal. Significant differences in measurements of end-diastolic and end-systolic area by different observers were noted, but they were systematic. A similar situation was noted for the comparison of transthoracic and transesophageal measurements of end-diastolic and end-systolic area. In the comparison of fractional area change between observers or windows, bias and absolute prediction error were lower, with 95% confidence limits of bias or absolute prediction error of 10% or less. CONCLUSIONS: The potential error in the measurement of fractional area change in 10% under optimal conditions. This would suggest that the assessment of ventricular function in the operating room or intensive care unit, under less than optimal conditions, should be viewed as a qualitative, rather quantitative, measurement. There may be significant interobserver and interwindow variability.

Bias↗

PubMed1995

Calcium alginate swab versus Bard Parker blade in the diagnosis of microbial keratitis.

A prospective comparative evaluation of Bard Parker blade no. 15 and calcium alginate swab in the collection of corneal material was conducted. The study group included 30 consecutive cases of bacterial (n = 17), fungal (n = 11), and mixed (n = 2) cases of microbial keratitis. The samples collected by blade and swab were processed in an identical manner for viable colony counts. The yields from blade and swab were compared using the proportion test, taking into consideration the mean counts of each organism. The swab yielded significantly greater growth than blade (p = 0.003) in mycotic ulcers. However, the two patients (2/11) who showed no growth by blade but were positive by swab had smears positive and were diagnosed as mycotic ulcers. The difference between the two methods was not significant for bacterial and mixed ulcers. Replacement of blade with calcium alginate swab did not appear to be advantageous for the investigation of infectious keratitis.

Alginates↗

PubMed1995

An ascending non-obstructive model for chronic pyelonephritis in BALB/c mice.

Chronic pyelonephritis was successfully produced in female BALB/c mice with Escherichia coli after introduction of the bacterial inoculum by the ascending route. E. coli strain 31-B, a nalidixic acid-resistant derivative of strain TN675 expressing type-1 pili, and E. coli strain BH-5, a mutant of 31-B, not expressing type-1 pili, were used in the model. Both the strains were able to induce chronic renal inflammation in the experimental animals. Whereas the initial colonisation was greater with strain 31-B, its non-pilate mutant BH-5 caused a significantly greater inflammatory response and also caused renal scarring observable 5 months after the infection.

Animals↗