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Biomedical subjects

M Levine

Publications and source records attributed to M Levine.

At least 145 records · Page 8Linked to original sources
PubMed1998

The snail repressor establishes a muscle/notochord boundary in the Ciona embryo.

Previous studies have identified a minimal 434 bp enhancer from the promoter region of the Ciona Brachyury gene (Ci-Bra), which is sufficient to direct a notochord-specific pattern of gene expression. Here we present evidence that a Ciona homolog of snail (Ci-sna) encodes a repressor of the Ci-Bra enhancer in the tail muscles. DNA-binding assays identified four Ci-Sna-binding sites in the Ci-Bra enhancer, and mutations in these sites cause otherwise normal Ci-Bra/lacZ transgenes to be misexpressed in ectopic tissues, particularly the tail muscles. Selective misexpression of Ci-sna using a heterologous promoter results in the repression of Ci-Bra/lacZ transgenes in the notochord. Moreover, the conversion of the Ci-Sna repressor into an activator results in the ectopic induction of Ci-Bra/lacZ transgenes in the muscles, and also causes an intermixing of notochord and muscle cells during tail morphogenesis. These results suggest that Ci-Sna functions as a boundary repressor, which subdivides the mesoderm into separate notochord and tail muscle lineages.

Animals↗
PubMed1998

In vivo cimetidine inhibits hepatic CYP2C6 and CYP2C11 but not CYP1A1 in adult male rats.

We previously reported that in vivo cimetidine inhibits hepatic microsomal enzyme activities mediated by cytochrome P450 (CYP)2C11 and at least one other CYP enzyme but does not inhibit CYP2A1-, CYP2B- or CYP3A-mediated activities in adult male rats. To investigate the effects of in vivo cimetidine on CYP1A1, cimetidine (150 mg/kg i.p.) or saline was administered to beta-naphthoflavone-induced (40 mg/kg i.p. once daily for 3 consecutive days) or uninduced adult male Wistar rats, and hepatic microsomes were prepared 90 min after the cimetidine injection. Cimetidine had no effect on either methoxyresorufin O-dealkylase (MROD) or ethoxyresorufin O-dealkylase (EROD) activity in microsomes from beta-naphthoflavone-induced rats. In these same microsomes, polyclonal anti-CYP1A1 IgG inhibited both MROD and EROD activities by >90%, whereas monoclonal anti-CYP1A1 IgG inhibited MROD and EROD activities by 60% and 80%, respectively. In contrast, cimetidine inhibited MROD and EROD activities in microsomes from uninduced rats by 50% and 65%, respectively (P < .05). Immunoinhibition studies with polyspecific and monospecific anti-CYP2C11 IgG indicated that MROD and EROD activities are mediated by a CYP2C enzyme or enzymes other than CYP2C11 in these microsomes. To investigate the possibility that the drug affected EROD activity in uninduced rats by inhibiting CYP2C6, cimetidine was administered as described to rats that had been pretreated with phenobarbital (80 mg/kg i.p once daily for 4 consecutive days). In hepatic microsomes from these rats, cimetidine inhibited progesterone 21-hydroxylase activity (mediated by CYP2C6) by 62% and progesterone 2alpha-hydroxylase activity (mediated by CYP2C11) by 39% but had no effect on progesterone 6beta-hydroxylase activity (mediated by CYP3A). Taken together, the results indicate that in vivo cimetidine has no effect on CYP1A1 but inhibits CYP2C6 in addition to CYP2C11. Preincubation of microsomes from uninduced rats with cimetidine and NADPH in vitro increased the potency of inhibition of EROD activity by 20-fold, suggesting that cimetidine inhibits CYP2C6, as it does CYP2C11: by forming a metabolite/intermediate complex.

Animals↗
PubMed1998

The occurrence of subsequent malignancy in patients presenting with deep vein thrombosis: results from a historical cohort study.

BACKGROUND: Several studies have reported that patients who present with idiopathic deep vein thrombosis (DVT) have an increased risk of subsequently developing cancer. A clinical trial had previously been conducted examining the optimal duration of oral anticoagulant therapy following initial heparin treatment in patients with proximal DVT. METHODS: A historical cohort study was performed on patients enrolled in the duration of anticoagulant trial. Patients known to have cancer at the time of entry into the trial were excluded. The qualifying DVTs were classified as idiopathic (no known associated risk factors) or secondary without knowledge of subsequent recurrent venous thrombosis or cancer. The patients were then followed for the development of cancer. RESULTS: Thirteen (8.6%) of the 152 patients in the idiopathic cohort subsequently developed cancer compared to eight (7.1%) of 112 patients in the secondary cohort, P = 0.86. Two (5.4%) of 37 patients with recurrent venous thromboembolism and 19 (8.4%) of 227 patients without recurrent thromboembolism developed cancer, P = 0.7. CONCLUSION: Our study did not detect an increased risk of subsequent cancer in patients presenting with idiopathic DVT compared to secondary DVT; nor did we detect an increased incidence of cancer in patients with recurrent venous thromboembolism. Further studies are required prior to pursuing a policy of aggressive screening for cancer in patients with idiopathic venous thromboembolism.

Administration, Oral↗
PubMed1998

Mycophenolate mofetil versus azathioprine immunosuppressive regimens after lung transplantation: preliminary experience.

BACKGROUND: Mycophenolate mofetil reduces episodes of biopsy-proven acute cellular rejection or treatment failure in the first year after kidney transplantation; however, limited data exist regarding the efficacy after lung transplantation. METHODS: In a 2-center, nonrandomized concurrent cohort study (level III evidence), we analyzed the incidence of biopsy-proven acute cellular rejection (International Society for Heart and Lung Transplantation grade > or=A2) and decrement in pulmonary function during the first 12 months after successful lung transplantation. All patients received induction immunosuppression with antithymocyte globulin (< or=5 days' duration), cyclosporine and prednisone, in addition to either mycophenolate mofetil (2.0 g/d) [n=11] or azathioprine (1 to 2 mg/kg per day) [n=11]. RESULTS: During the first 12 months after lung transplantation, the mycophenolate mofetil group experienced significantly fewer episodes of acute cellular rejection than the azathioprine group (0.26+/-0.34 vs 0.72+/-0.43 episodes/100 patient-days [mean+/-SD], p < 0.01; 95% CI for the difference=0.126 to 0.813). The change in forced expiratory volume -1 second [deltaFEV1] (liters) between the 3rd and 12th months after lung transplantation was analyzed for the two treatment groups. For this interval, deltaFEV1 for the mycophenolate mofetil group was +0.158+/-0.497 L vs -0.281+/-0.406 L for the azathioprine group (p < 0.05; 95% CI for difference=+0.0356 to 0.843). During the first year, there was 1 death in each group attributed to bronchiolitis obliterans syndrome with concurrent pneumonia. There were no differences in incidence of cytomegalovirus or bacterial infections between the treatment groups; however, a higher prevalence of aspergillus sp airway colonization in bronchoalveolar lavage fluid was observed for the mycophenolate mofetil group (p < .05). The prevalence of bronchiolitis obliterans syndrome at 12 months was 36% for the azathioprine group vs 18% for the mycophenolate mofetil group (p=NS). CONCLUSIONS: Our preliminary experience with mycophenolate mofetil after lung transplantation suggests a decreased incidence of biopsy-proven acute cellular rejection. Furthermore, less decline in FEV1 after 12 months may suggest a reduced incidence or delayed onset for development of bronchiolitis obliterans syndrome. Prospective randomized trials with low beta error (level I evidence) should be performed to assess the efficacy of mycophenolate mofetil vis-à-vis acute allograft rejection and bronchiolitis obliterans syndrome.

Azathioprine↗
PubMed1997

Ascorbate recycling in human neutrophils: induction by bacteria.

Ascorbate (vitamin C) recycling occurs when extracellular ascorbate is oxidized, transported as dehydroascorbic acid, and reduced intracellularly to ascorbate. We investigated microorganism induction of ascorbate recycling in human neutrophils and in microorganisms themselves. Ascorbate recycling was determined by measuring intracellular ascorbate accumulation. Ascorbate recycling in neutrophils was induced by both Gram-positive and Gram-negative pathogenic bacteria, and the fungal pathogen Candida albicans. Induction of recycling resulted in as high as a 30-fold increase in intracellular ascorbate compared with neutrophils not exposed to microorganisms. Recycling occurred at physiologic concentrations of extracellular ascorbate within 20 min, occurred over a 100-fold range of effector/target ratios, and depended on oxidation of extracellular ascorbate to dehydroascorbic acid. Ascorbate recycling did not occur in bacteria nor in C. albicans. Ascorbate did not enter microorganisms, and dehydroascorbic acid entry was less than could be accounted for by diffusion. Because microorganism lysates reduced dehydroascorbic acid to ascorbate, ascorbate recycling was absent because of negligible entry of the substrate dehydroascorbic acid. Because ascorbate recycling occurs in human neutrophils but not in microorganisms, it may represent a eukaryotic defense mechanism against oxidants with possible clinical implications.

Ascorbic Acid↗
PubMed1997

Investigation of a possible interaction between ciprofloxacin and cyclosporine in renal transplant patients.

BACKGROUND: Bacterial infection is a common complication during the first few months after renal transplantation. Ciprofloxacin, a fluoroquinolone broad-spectrum antibiotic, is used frequently in treating infections in the early posttransplant period. Evidence from in vitro studies has suggested that ciprofloxacin can antagonize the cyclosporine (CsA)-dependent inhibition of interleukin-2 production. Such an effect in renal transplant patients could antagonize the immunosuppressive activity of CsA and lead to rejection of the graft. METHODS: To investigate the possibility of a pharmacodynamic interaction between ciprofloxacin and CsA, we conducted a case-control study in 42 patients who had received a kidney transplant and who were prescribed ciprofloxacin in the first 1-6 months after transplantation and in their matched controls (two per case) who did not receive ciprofloxacin during the study period. RESULTS: There was a twofold greater incidence (P=0.008) of ciprofloxacin use at 1-3 months (65%) than was observed at 4-7 months (35%) after transplantation. The proportion of cases experiencing at least one episode of biopsy-proven rejection 1-3 months posttransplant (45%) was significantly greater (P=0.004) than that of controls (19%). Furthermore, there was a marked increase (P<0.001) in the incidence of rejection temporally associated with ciprofloxacin use among cases (29%) compared with that experienced by the controls (2%). CONCLUSIONS: The possibility that ciprofloxacin increases rejection rates in renal transplant patients may be of clinical importance and therefore warrants further investigation.

Anti-Infective Agents↗
PubMed1997

The human glutaredoxin gene: determination of its organization, transcription start point, and promoter analysis.

A genomic clone for the human glutaredoxin gene was isolated and sequenced. An intron was located within the coding region and began 211 nt downstream of the initiator codon. Except for this intron, the genomic sequence shares 100% identity to the published glutaredoxin cDNA sequence. A second intron was located in the 3' UTR 6 bp downstream of the terminator codon. The tsp of the glutaredoxin gene was determined by primer extension and confirmed by S1 mapping analysis. Analysis of the 5'-flanking region of the gene revealed that the promoter sequences TATA and CCAAT were 30 and 160 bp upstream, respectively, from the tsp. Other potential transcription factor binding sites included NF-E1, HNF-5, P2II and AP-1. Glutaredoxin promoter constructs inserted into a reporter plasmid for firefly luciferase were transfected into fibroblasts, and luciferase activity was 8-10-fold higher compared with controls lacking glutaredoxin promoter. These data indicate that the promoter region of the isolated glutaredoxin gene is functional.

Amino Acid Sequence↗
PubMed1997

Primary prevention of heart disease and stroke: a simplified approach to estimating risk of events and making drug treatment decisions.

Long-term population-based studies have identified and quantified risk factors for cardiovascular and cerebrovascular (CCV) events. In addition, a number of well-designed clinical trials have shown that various drug therapies that reduce these factors decrease the risk of some CCV events. In the practice of evidence-based medicine, data from clinical trials should inform treatment decisions. The clinician and patient, however, are faced with the difficult task of assessing the patient's particular risk and likelihood of benefit on the basis of the results of large, randomized trials. To assist clinicians and their patients in arriving at treatment decisions, the authors provide simple nomograms for estimating the risk of a CCV event for an individual patient and suggest an approach to estimating the potential benefit of drug therapy for primary prevention.

Cerebrovascular Disorders↗
PubMed1997

An anteroposterior Dorsal gradient in the Drosophila embryo.

Dorsoventral (DV) patterning of the Drosophila embryo is initiated by a broad Dorsal (Dl) nuclear gradient, which is regulated by a conserved signaling pathway that includes the Toll receptor and Pelle kinase. We investigate the consequences of expressing a constitutively activated form of the Toll receptor, Toll(10b), in anterior regions of the early embryo using the bicoid 3' UTR. Localized Toll(10b) products result in the formation of an ectopic, anteroposterior (AP) Dl nuclear gradient along the length of the embryo. The analysis of both authentic dorsal target genes and defined synthetic promoters suggests that the ectopic gradient is sufficient to generate the full repertory of DV patterning responses along the AP axis of the embryo. For example, mesoderm determinants are activated in the anterior third of the embryo, whereas neurogenic genes are expressed in central regions. These results raise the possibility that Toll signaling components diffuse in the plasma membrane or syncytial cytoplasm of the early embryo. This study also provides evidence that neurogenic repressors may be important for the establishment of the sharp mesoderm/neuroectoderm boundary in the early embryo.

Animals↗
PubMed1997

Glucose transporter isoforms GLUT1 and GLUT3 transport dehydroascorbic acid.

Dehydroascorbic acid (DHA) is rapidly taken up by cells and reduced to ascorbic acid (AA). Using the Xenopus laevis oocyte expression system we examined transport of DHA and AA via glucose transporter isoforms GLUT1-5 and SGLT1. The apparent Km of DHA transport via GLUT1 and GLUT3 was 1.1 +/- 0.2 and 1.7 +/- 0.3 mM, respectively. High performance liquid chromatography analysis confirmed 100% reduction of DHA to AA within oocytes. GLUT4 transport of DHA was only 2-4-fold above control and transport kinetics could not be calculated. GLUT2, GLUT5, and SGLT1 did not transport DHA and none of the isoforms transported AA. Radiolabeled sugar transport confirmed transporter function and identity of all cDNA clones was confirmed by restriction fragment mapping. GLUT1 and GLUT3 cDNA were further verified by polymerase chain reaction. DHA transport activity in both GLUT1 and GLUT3 was inhibited by 2-deoxyglucose, D-glucose, and 3-O-methylglucose among other hexoses while fructose and L-glucose showed no inhibition. Inhibition by the endofacial inhibitor, cytochalasin B, was non-competitive and inhibition by the exofacial inhibitor, 4,6-O-ethylidene-alpha-glucose, was competitive. Expressed mutant constructs of GLUT1 and GLUT3 did not transport DHA. DHA and 2-deoxyglucose uptake by Chinese hamster ovary cells overexpressing either GLUT1 or GLUT3 was increased 2-8-fold over control cells. These studies suggest GLUT1 and GLUT3 isoforms are the specific glucose transporter isoforms which mediate DHA transport and subsequent accumulation of AA.

Animals↗
PubMed1997

hairy mediates dominant repression in the Drosophila embryo.

hairy encodes a bHLH repressor that regulates several developmental processes in Drosophila, including embryonic segmentation and neurogenesis. Segmentation repressors such as Krüppel and knirps have been shown to function over short distances, less than 50-100 bp, to inhibit or quench closely linked upstream activators. This mode of repression permits multiple enhancers to work independently of one another within a modular promoter. Here, we employ a transgenic embryo assay to present evidence that hairy acts as a dominant repressor, which can function over long distances to block multiple enhancers. hairy is shown to repress a heterologous enhancer, the rhomboid NEE, when bound 1 kb from the nearest upstream activator. Moreover, the binding of hairy to a modified NEE leads to the repression of both the NEE and a distantly linked mesoderm-specific enhancer within a synthetic modular promoter. Additional evidence that hairy is distinct from previously characterized embryonic repressors stems from the analysis of the gypsy insulator DNA. This insulator selectively blocks the hairy repressor, but not the linked activators, within a modified NEE. We compare hairy with previously characterized repressors and discuss the consequences of short-range and long-range repression in development.

Animals↗
PubMed1997

The gypsy insulator can function as a promoter-specific silencer in the Drosophila embryo.

The Drosophila gypsy retrotransposon disrupts gene activity by blocking the interactions of distal enhancers with target promoters. This enhancer-blocking activity is mediated by a 340 bp insulator DNA within gypsy. The insulator contains a cluster of binding sites for a zinc finger protein, suppressor of Hairy wing [su(Hw)]. Recent studies have shown that a second protein, mod(mdg4), is also important for normal insulator function. Mutations in mod(mdg4) exert paradoxical effects on different gypsy-induced phenotypes. For example, it enhances yellow2 but suppresses cut6. Here, we employ a stripe expression assay in transgenic embryos to investigate the role of mod(mdg4) in gypsy insulator activity. The insulator was inserted between defined enhancers and placed among divergently transcribed reporter genes (white and lacZ) containing distinct core promoter sequences. These assays indicate that mod(mdg4) is essential for the enhancer-blocking activity of the insulator DNA. Moreover, reductions in mod(mdg4)+ activity cause the insulator to function as a promoter-specific silencer that selectively represses white, but not lacZ. The repression of white does not affect the expression of the closely linked lacZ gene, suggesting that the insulator does not propagate changes in chromatin structure. These results provide an explanation for why mod(mdg4) exerts differential effects on different gypsy-induced mutations.

Animals↗
PubMed1997

A randomized trial of paracentesis plus intraperitoneal tumor necrosis factor-alpha versus paracentesis alone in patients with symptomatic ascites from recurrent ovarian carcinoma.

PURPOSE: Previous phase I and II studies of intraperitoneal recombinant human tumor necrosis factor-alpha (rhTNF-alpha) suggested a high degree of efficacy in reducing or eliminating ascitic fluid. To more accurately determine the efficacy of this agent, the role of paracentesis versus paracentesis plus intraperitoneal rhTNF-alpha was studied in a randomized trial. PATIENTS AND METHODS: Thirty-nine patients with symptomatic ascites with a volume of > 1000 ml from recurrent epithelial ovarian carcinoma or primary peritoneal carcinoma, which was refractory to standard therapy, were randomized either to receive 0.06 mg/m2 rhTNF-alpha (Knoll, Canada) (the dose determined optimal from phase I and II studies) intraperitoneally after drainage of fluid or to receive drainage alone. A maximum of three treatments were given at weekly intervals. Eighteen patients were randomized to receive rhTNF-alpha. RESULTS: None of 18 evaluable rhTNF-alpha patients had either a complete response (CR) (no clinical evidence of ascites and < 400 ml of fluid on ultrasound) or a partial response (PR) (asymptomatic ascites and < or = 1000 ml of fluid ultrasound). There were no CRs or PRs in the 17 evaluable patients who received drainage alone. The intraperitoneal infusion of rhTNF-alpha was generally well tolerated. Moderate to severe toxicity consisted of pain/discomfort in 42.1%, fever/chills in 36.9%, nausea/vomiting in 10.5%, edema in 10.5%, and hypotension in 5.3% of patients receiving rhTNF-alpha. CONCLUSION: rhTNF-alpha, as given in this study, was not effective in preventing recurrence of ascites in this patient population.

Ascites↗
PubMed1997

Transcranial magnetic stimulation reveals a hemispheric asymmetry correlate of intermanual differences in motor performance.

Hemispheric asymmetries in the threshold for eliciting motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS) are associated with hand preference. We posited that hemispheric asymmetries in TMS thresholds may be strongly correlated with some hand-differences in motor performance. MEPs result from the activation of neuronal networks targeting large cortical motoneurons. Thus, MEP thresholds might reflect physiological features of the corticospinal motor system. Considering the role of corticospinal pathways in the control of independent finger movement, we hypothesized that MEP thresholds would better predict speed and dexterity than strength. In 30 right-handers and 30 left-handers, we correlated right and left hand-differences in the threshold for eliciting MEPs with hand-differences in the performance of three manual tasks: finger-tapping speed, pegboard dexterity, and grip strength. Correlations of hand-differences in TMS thresholds with hand-differences in performance indicated that a lower TMS threshold for one hand is strongly associated with greater ability with that hand. The correlations of hand-differences in TMS thresholds with hand-differences in finger-tapping and pegboard dexterity were significantly larger than the correlation of hand-differences in TMS thresholds with hand-differences in grip strength. Our results indicate that hemispheric asymmetries in MEP thresholds may have functional significance related to basic parameters of movement. These results are consistent with the critical role of the corticospinal motor system in the control of independent finger movement. Furthermore, they imply that asymmetry in the corticospinal motor system may be an important substrate for asymmetries in hand preference and performance.

Adult↗