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Biomedical subjects

S Sharma

Publications and source records attributed to S Sharma.

At least 649 records · Page 36Linked to original sources
PubMed1997

Preclinical and clinical strategies for development of telomerase and telomere inhibitors.

BACKGROUND: Telomerase is an important enzyme whose activity has been convincingly demonstrated in humans recently. It is required for maintenance of ends of chromosomes (telomeres) during cell division. Since its presence has been selectively demonstrated in dividing cells including tumor cells, it has generated considerable excitement as a potential anti-cancer strategy. DESIGN: In this article, we review the current relevant biology of the enzyme, the challenges encountered in the preclinical phase of target development and the current efforts that focus on telomeres and telomerase as therapeutic targets. We also speculate on the potential toxicities and mechanisms of resistance that may be encountered during use of such therapies.

Animals↗
PubMed1997

Multicomponent gene therapy vaccines for lung cancer: effective eradication of established murine tumors in vivo with interleukin-7/herpes simplex thymidine kinase-transduced autologous tumor and ex vivo activated dendritic cells.

Multiple antitumor modalities may be necessary to overcome lung tumor-mediated immunosuppression and effectively treat non-small cell lung cancer (NSCLC). To evaluate a multimodality gene therapy approach for control of local tumor growth, a weakly immunogenic murine alveolar cell carcinoma, L1C2, was transduced with either the interleukin-7/hygromycin-herpes simplex thymidine kinase (IL-7/HyHSVtk) internal ribosome entry site (IRES) retroviral vector or a vector containing the HyHSVtk, but not the IL-7 gene. Of the many cytokines available for gene transfer, IL-7 was chosen for these studies because it both stimulates CTL responses and down-regulates tumor production of the immunosuppressive peptide TGF-beta. Following selection in hygromycin, IL-7 transduction was confirmed by ELISA. Clones produced 1.25 to 10 ng of IL-7/ml/10(6) cells per 24 h. In vitro, genetically modified tumor cells were significantly more sensitive to ganciclovir (GCV) than unmodified parental tumor cells. The in vivo growth of ex vivo modified L1C2 cells was evaluated. There was a dose-response relationship between the amount of IL-7 secreted in vitro and the growth of genetically modified murine tumor in vivo. Transduced tumor cells regressed in mice following GCV therapy. Although ex vivo gene modification of tumor cells led to complete resolution of the tumor following implantation in vivo, IL-7 and HSVtk gene modified tumor cells were not effective in treating established parental tumors. However when 5 x 10(5) bone marrow-derived, in vitro activated dendritic cells (DC) were administered in combination with transduced tumor and GCV, 5 day old established tumors were eradicated in 80% of mice. These studies suggest that multicomponent vaccines may facilitate improved host responses by replacing host immune deficits and thus could have a role in adjuvant therapy and local control of NSCLC.

Animals↗
PubMed1997

Dynamic variations in plasma corticosteroid-binding globulin and basal HPA activity following acute stress in adult rats.

We report on dynamic changes in plasma corticosteroid-binding globulin (CBG) binding and basal hypothalamic-pituitary-adrenal (HPA) activity following acute stress in adult rats. Plasma CBG binding was significantly reduced at 24 and 48 h following a single 60 min period of restraint. Basal levels of plasma ACTH and total corticosterone (B) during the light phase of the cycle were elevated at 24 h following restraint. These effects occurred only when animals were stressed in the light phase of the cycle; animals exposed to restraint stress during the dark phase of the cycle showed no change in plasma CBG binding or in basal HPA activity. Pituitary intracellular transcortin, which is derived from circulating CBG, was also decreased by restraint stress. The decrease in CBG binding was also associated with a significant increase in resting-state free B levels. Together, these effects produced a substantially (i.e. approximately 10-fold) increased 'basal' glucocorticoid signal 24 h following acute stress. These data suggest that the increase in the circulating glucocorticoid signal associated with acute stress endures well beyond the period of increased total B levels.

Adrenal Glands↗
PubMed1997

Interfetal heart rate and size variation in first-trimester multifetal pregnancies and heart rate of surviving fetuses after fetal reduction.

The objective of this study was to determine the variation in first-trimester fetal size and fetal heart rates in multifetal pregnancies, and to study the effect of fetal reduction on the surviving fetal heart rate. Fetal crown-rump length and fetal heart rates were measured in 44 patients with multifetal pregnancies who underwent fetal reduction. The heart rates of the surviving fetuses were also measured immediately after, and 1 h following the procedure. A total of 143 fetuses were evaluated prior to reduction and 75 fetuses following the procedure. There was no significant difference in crown-rump length between fetuses of the same gestation. The interfetal fetal heart rate variation between fetuses of the same gestation, expressed as a standard deviation, was 4.78 +/- 0.51 beats/min (mean standard deviation +/- standard error of the mean) before reduction; this was a significantly greater variation than could be attributed to error in the measurement of heart rate. In the surviving fetuses, the mean heart rate did not change. However, immediately after the reduction, interfetal heart rate variation was abolished, but was observed again 1 h after the reduction. We conclude that in first-trimester multifetal pregnancies (1) there is no significant difference in fetal crown-rump length; (2) there is interfetal variation in heart rates; and (3) fetal reduction has only a limited effect on the heart rates of surviving fetuses.

Embryonic and Fetal Development↗
PubMed1997

Fluorescent Gram stain in the microbiologic diagnosis of infectious keratitis and endophthalmitis.

PURPOSE: To verify the sensitivity of a recently described technique of fluorescent Gram stain (FGS) and evaluate its role in direct microscopic examination of clinical ocular samples. METHODS: In the first part of the study, culture suspensions of 10 bacterial isolates were stained, using FGS and conventional Gram stain (CGS), and were assessed for morphology, and Gram sign. In the second part, 39 corneal scrapings and 18 vitreous biopsy materials were stained and observed by both methods. RESULTS: Gram reaction and morphology of the bacteria, using CGS and FGS, were compared against culture. In both parts of the study, the sensitivity of CGS was significantly higher than FGS in the detection of Gram positive reaction (p = 0.01, 0.02). The specificities and predictive values of CGS and FGS were comparable in the evaluation of clinical samples. The bacterial morphology was demonstrated better (p = 0.01) with CGS. Significant quenching of fluorescence and change in Gram reaction with time were noted in FGS. CONCLUSIONS: The low sensitivity, quenching of fluorescence and change in Gram reaction presently preclude the usage of FGS as a diagnostic tool in ocular infections.

Endophthalmitis↗
PubMed1997

Response to interferon-gamma plus pentavalent antimony in Indian visceral leishmaniasis.

One hundred fifty-six previously untreated Indian patients with visceral leishmaniasis were treated with pentavalent antimony (Sb) alone for 30 days (group A), Sb plus interferon-gamma (IFN-gamma) for 30 days (group B), or Sb plus IFN-gamma for 15 days (group C). The purpose was to show that IFN-gamma would increase the response to 30 days of Sb treatment and that short-course (15 days) combination therapy was as effective as 30 days of Sb alone. Six months after treatment, 36% of group A, 49% of group B, and 42% of group C patients were designated as definitively cured. The success rates for long-term responses to Sb alone (36%) and Sb plus IFN-gamma (49%) were unexpectedly low, and responses in groups A, B, and C were not significantly different. These results suggest that the beneficial effects of adjunctive IFN-gamma in visceral leishmaniasis may be limited in regions where this disseminated intracellular infection shows high-level resistance to Sb.

Adolescent↗
PubMed1997

Prooxidant effects of maternal smoking and formula in newborn infants.

BACKGROUND: The purpose of this study was to use the breath ethane test to determine if either maternal cigarette smoking, formula, and/or deficiency of the antioxidant nutrients vitamins A and E was associated with oxidant stress in newborn infants. The rationale for this study was: (1) our observation that cigarette smoking was a source of oxidant stress in pregnant women, suggesting that it could be a source of oxidant stress for infants exposed in utero; (2) formula was predicted to be prooxidant compared to colostrum, which contains several compounds with antioxidant activity in vitro; and (3) deficiencies of vitamins A and E have been shown to promote oxidant stress in experimental animals. METHODS: Breath ethane, a volatile alkane produced by peroxide of n-3 fatty acids, was utilized as an index of oxidant stress status. Forty-five healthy full-term infants of the women mentioned above were studied at 18-24 h of age, after four to six feedings of breast milk (colostrum) or caseinbased infant formula. Relationships between infant breath ethane, maternal smoking, mode of infant nutrition, and serum concentrations of the antioxidant vitamins A and E of infants were examined. RESULTS: The breath ethane of the entire group of infants whose mothers smoked (n = 19) was increased compared to values of infants whose mothers did not smoke (n = 26): 97 +/- 16 versus 43 +/- 9 pmol/kg/min, p < 0.03. When infants of mothers who smoked were eliminated from the analysis in order to study effects of nutrition alone, formula appeared to be prooxidant compared to breast milk. Breath ethane of formula-fed infants (n = 16) was 62 +/- 13 versus 13 +/- 4 pmol/kg/min for breast-fed infants (n = 10), p < 0.04. For the group as a whole, there was no correlation between infant breath ethane and serum concentrations of vitamins A and E. CONCLUSIONS: Exposure to maternal smoking in utero is prooxidant in newborn infants. Formula also has a prooxidant effect compared to colostrum in newborn infants not exposed to maternal smoking in utero. Further investigations will be necessary to explore the clinical consequences of these observations.

Antioxidants↗
PubMed1997

Possible antioxidant effect of vitamin A supplementation in premature infants.

BACKGROUND: Increased lipid peroxidation caused by oxygen free radicals is thought to be one of the common pathogenetic mechanisms for the so-called oxygen radical diseases of prematurity. Since in vitro studies have shown that various forms of vitamin A can exert antioxidant effects that are more potent than those of vitamin E (treatment with which has been ineffective in these diseases), the purpose of this prospective, controlled study was to determine whether administration of supplemental vitamin A to premature infants deficient in this vitamin would have an antioxidant effect in vivo. METHODS: Fourteen infants (1181 +/- 35 g; gestational age 29 +/- 0.04 weeks) with a serum retinol concentration at 7 +/- 2 days of age in the deficient range, lower than 0.7 mumol/l (< 20 micrograms/dl), were enrolled in the study. Infants were randomized to receive the standard amount of vitamin A or standard plus supplemental (2.6 mumol/l [2500 IU] orally each day) vitamin A, beginning at 1 week of age. Antioxidant effects of supplementation were assessed by a decrease in lipid peroxidation, quantified by the ethane content of expired air. RESULTS: Three weeks after study enrollment, total daily vitamin A intake in the infants receiving supplements was 4.565 +/- 0.236 mumol (4354 +/- 225 IU) versus 1.879 +/- 0.317 mumol/l (1792 +/- 302 IU) in infants receiving standard amounts of the vitamin. In spite of the difference in intake of vitamin A, 3 weeks after study enrollment, serum retinol concentrations did not differ between the infants given supplements and those receiving standard amounts of vitamin A, 0.70 +/- 0.21 versus 0.66 +/- 0.07 mumol/l (20 +/- 6 micrograms/dl versus 19 +/- 2 micrograms/dl, respectively). In the infants receiving supplemental vitamin A, breath ethane values declined from baseline values. There was an inverse correlation between the number of weeks of supplementation and breath ethane values, whereas there was no significant correlation between the duration of the study and breath ethane values in the infants not given supplements. CONCLUSIONS: Our data suggest that supplementation with vitamin A in a small group of vitamin A-deficient preterm infants was associated with an antioxidant effect. Although no immediate clinical benefits were associated with supplementation, the data provide the rationale for future investigations of possible antioxidant effects of (larger amounts?) of vitamin A in higher risk premature infants born with subnormal serum retinol concentrations.

Administration, Oral↗
PubMed1997

Aesthetic outcome of breast implant removal in 85 consecutive patients.

As we began to see increasing numbers of women concerned about their gel-filled breast implants, we became aware that we could not advise them with any degree of confidence what they might expect in terms of aesthetic result after implant removal. We decided to review the records and outcomes over a 2-year period of a number of patients who underwent implant removal. Eighty-five consecutive patients were reviewed, 69 of whom had undergone cosmetic augmentation and 16 of whom had breast reconstruction with silicone gel implant(s). Thirty-nine of the 69 cosmetic augmentation patients had removal of implants alone, and 27 had removal accompanied by mastopexy. Three had reaugmentation with saline-filled implants; one had replacement with saline-filled implants. Fifteen of the 16 reconstruction patients underwent autogenous tissue transfer. Preoperative and postoperative photographs of all patients were mixed randomly and rated by two independent raters in four aesthetic categories on a five-point scoring system. Repeatability was measured several weeks later, when each rater scored randomly selected photographs from this patient pool. The patients also performed their own outcome evaluations by means of questionnaire. We discovered that cosmetic augmentation patients who undergo implant removal only often suffer adverse aesthetic results. The postremoval appearance of many cosmetic augmentation patients actually will be improved over their preoperative appearance when mastopexy is performed in conjunction with implant removal. The study demonstrated that patients with certain body types could expect a particular outcome; i.e., women with asthenic builds and older patients with lax, striated breast skin generally had unsatisfactory aesthetic outcomes with implant removal only. Patients selected for autogenous breast reconstruction had favorable results, with extended latissimus dorsi and TRAM flaps yielding equally good outcomes. The study allows us to offer patients an optimistic view of postoperative results following breast implant removal. We have begun to advise selected patients that implant removal accompanied by mastopexy provides a more pleasing aesthetic outcome than implant removal alone.

Adult↗
PubMed1997

TH1 pattern of cytokine secretion by splenic cells from pyelonephritic mice after in-vitro stimulation with hsp-65 of Escherichia coli.

Splenic lymphocytes and peritoneal macrophages from BALB/c mice with Escherichia coli pyelonephritis were obtained at various intervals after infection. These cells were stimulated in vitro with different antigens and cytokine release was assayed in the supernate of the cultured cells. It was observed that both specific antigens such as outer-membrane proteins (OMPs), porins and heat-shock protein-65 (hsp-65), as well as non-specific mitogens such as phytohaemagglutinin (PHA), were able to induce cytokine production by splenic cells from infected mice. Of all these antigens, hsp-65 was found to be the best inducer of cytokine release. In the acute stage of pyelonephritis, the release of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) was found to increase with time; both reached their peak values on the seventh day after infection. The TH1 pattern of cytokine secretion by splenic cells was observed, i.e., IL-2 and IFN-gamma, whereas there was complete absence of IL-4 secretion. In the chronic stage of pyelonephritis, i.e., 150 days after infection, a decrease in the level of IL-2 and IFN-gamma was observed. Peritoneal macrophages released IL-1 on stimulation with hsp-65, which increased with the progression of disease. The possible implications of this study for the disease process are discussed.

Acute Disease↗
PubMed1997

Microbial contamination of hydrogel contact lenses.

Bacterial contamination of contact lenses (CLs) may contribute to CL-related corneal infection and inflammation. This study reports CL biota over time during daily and extended wear. Microbial contamination of a 58% water, ionic hydrogel CL and a 38% water, non-ionic hydrogel CL was evaluated in an Australian and an Indian population. Fifty wearers were repeatedly sampled over 18 months. Overnight CL use did not alter the frequency of positive cultures, nor the spectrum of organisms compared with daily CL wear. There were no differences in type and frequency of CL contamination between the CL types. Positive cultures were more frequently recovered from the Indian population compared with the Australian population. Streptococcus spp. and Propionibacterium spp. were more frequently isolated from the Australian population. Fungi and Bacillus spp. were more frequently isolated from the Indian population. Normal CL biota alone cannot explain the increased rate of infection and inflammation in extended wear.

Bacillus↗
PubMed1997

Mutation of a single MalK subunit severely impairs maltose transport activity in Escherichia coli.

The maltose transport system of Escherichia coli, a member of the ABC transport superfamily of proteins, consists of a periplasmic maltose binding protein and a membrane-associated translocation complex that contains two copies of the ATP-binding protein MalK. To examine the need for two nucleotide-binding domains in this transport complex, one of the two MalK subunits was inactivated by site-directed mutagenesis. Complexes with mutations in a single subunit were obtained by attaching a polyhistidine tag to the mutagenized version of MalK and by coexpressing both wild-type MalK and mutant (His)6MalK in the same cell. Hybrid complexes containing one mutant (His)6MalK subunit and one wild-type MalK subunit were separated from those containing two mutant (His)6MalK proteins based on differential affinities for a metal chelate column. Purified transport complexes were reconstituted into proteoliposome vesicles and assayed for maltose transport and ATPase activities. When a conserved lysine residue at position 42 that is involved in ATP binding was replaced with asparagine in both MalK subunits, maltose transport and ATPase activities were reduced to 1% of those of the wild type. When the mutation was present in only one of the two subunits, the complex had 6% of the wild-type activities. Replacement of a conserved histidine residue at position 192 in MalK with arginine generated similar results. It is clear from these results that two functional MalK proteins are required for transport activity and that the two nucleotide-binding domains do not function independently to catalyze transport.

ATP-Binding Cassette Transporters↗
PubMed1997

Hormonal regulation of an islet-specific enhancer in the pancreatic homeobox gene STF-1.

The homeobox protein STF-1 appears to function as a master control switch for expression of the pancreatic program during development. Here we characterize a composite enhancer which directs STF-1 expression to pancreatic islet cells via two functional elements that recognize the nuclear factors HNF-3beta and BETA-2. In keeping with their inhibitory effects on islet cell maturation, glucocorticoids were found to repress STF-1 gene expression by interfering with HNF-3beta activity on the islet-specific enhancer. Overexpression of HNF-3beta suppressed glucocorticoid receptor-mediated inhibition of the STF-1 gene, and our results suggest that the expansion of pancreatic islet precursor cells during development may be restricted by hormonal cues which regulate STF-1 gene expression.

Animals↗
PubMed1997

Abrogation of interleukin-3 dependence of myeloid cells by the v-src oncogene requires SH2 and SH3 domains which specify activation of STATs.

The v-src oncogene encodes a nonreceptor tyrosine kinase. When this gene was expressed in the myeloblastic cell line 32Dcl3, it was found to abrogate interleukin-3 (IL-3) dependence of this cell line and to block its ability to terminally differentiate into granulocytes in response to granulocyte colony-stimulating factor (GCSF). In contrast, a highly related tyrosine kinase gene, v-fgr, fails to render this cell line IL-3 independent for growth or to block its ability to undergo terminal differentiation in the presence of GCSF. The active structural domains of v-src that are responsible for the abrogation of IL-3 dependence of myeloid cells and the mechanisms by which v-src transforms these cells are at present unclear. To identify the domains in v-src which are responsible for this activity, we constructed several chimeric recombinants between the v-src and the related Src family member v-fgr by replacing portions of v-src with corresponding domains of v-fgr. These chimeric DNAs were transfected into 32Dcl3 cells and examined for their abilities to render this cell line IL-3 independent. Our results show that only chimeras containing both the SH3 and the SH2 domains of v-src were capable of rendering the 32Dcl3 cell line IL-3 independent. To understand the possible mechanisms underlying the IL-3-independent growth of v-src-transformed 32Dcl3 cells, we examined the phosphorylation status of JAK-1, JAK-2, and JAK-3 kinases in the v-src- and v-fgr-transformed 32Dcl3 cells. Our results show that none of the JAK kinases are constitutively phosphorylated by v-src or v-fgr. We then examined the phosphorylation status of the STAT (signal transducers and activators of transcription) family of transcription factors. Our results show that STAT1, STAT3, and STAT5 exist in a constitutively phosphorylated state in v-src-transformed 32Dcl3 cells, while such constitutive phosphorylation is not seen in v-fgr-transformed cell lines. Our results also show that STAT3 coimmunoprecipitates with v-Src, suggesting that the activation of STAT3 occurs due to direct association with v-Src. However, STAT1 and STAT5, which also exist in a constitutively phosphorylated state in v-src-transformed 32Dcl3 cells, do not coimmunoprecipitate with v-Src, suggesting that these proteins either interact weakly with v-Src or are phosphorylated by a mechanism distinctive from that of STAT3.

Acute-Phase Proteins↗