Biomedical subjects

M Haber

Publications and source records attributed to M Haber.

At least 73 records · Page 4Linked to original sources

PubMed1997

Low specificity of PGP9.5 expression for detection of micrometastatic neuroblastoma.

To determine the specificity of neuroendocrine protein gene product (PGP9.5) gene transcripts for detecting micrometastatic neuroblastoma, we have used a highly sensitive polymerase chain reaction (PCR) technique to evaluate expression of this gene in normal blood and bone marrow. While expression of the tyrosine hydroxylase gene was not detected in any normal sample, low-level PGP9.5 expression was detected in eight out of ten blood and seven of 12 marrow samples. PGP9.5 gene transcripts in normal tissues have the potential to interfere with the detection of micrometastatic neuroblastoma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Sensitive non-radioactive PCR detection of clonal T-cell receptor-gamma gene rearrangements in childhood acute lymphoblastic leukaemia.

Rearrangement of the T-cell receptor gamma (TCRgamma) gene potentially provides a valuable target for monitoring minimal residual leukaemia by the Polymerase Chain Reaction (PCR). However, existing strategies directed at this locus frequently lack sensitivity or specificity. We describe a novel PCR strategy for improved detection of clonal TCRgamma gene rearrangements based on the design of two overlapping clone-specific reverse PCR primers spanning the TCRgamma junctional region, which are used sequentially in conjunction with forward V-region specific primers. Unlike other strategies, specificity is generated from the initial and subsequent round of PCR amplification. This non-radioactive technique is highly specific and sensitive, and should prove effective for monitoring minimal residual leukaemia.

Base Sequence↗

PubMed1996

Retinoic acid receptors beta and gamma distinguish retinoid signals for growth inhibition and neuritogenesis in human neuroblastoma cells.

Retinoids induce marked growth inhibition and neuritic differentiation in human neuroblastoma cells. Expression patterns of nuclear retinoic acid receptors (RAR) in embryonic and adult tissues suggests that RAR subtypes alpha, beta and gamma have tissue-specific functions. We have transfected a human neuroblastoma tumor cell line with a vector expressing either human RAR alpha, beta or gamma cDNAs. In the absence of exogenous retinoid, RAR beta transfectants demonstrated marked growth inhibition without morphologic evidence of differentiation, whereas transfectant clones overexpressing RARs alpha and gamma had no significant reduction in cell growth rates. Although RAR gamma transfectants were sensitive to the growth inhibitory effects of exogenous retinoids, these cells demonstrated resistance to the neuritogenic retinoid effects. Only RAR beta transfectants exhibited increased sensitivity to retinoids added in vitro. These results suggest that distinct neuritogenic and growth inhibitory signalling pathways exist in neuroblastoma cells and that RAR beta expression may be necessary for the retinoid growth inhibitory pathway.

Cell Differentiation↗

PubMed1996

Effective maintenance treatment of reflux esophagitis with low-dose lansoprazole. A randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To compare the efficacy of two doses of lansoprazole with that of placebo in preventing recurrence of erosive esophagitis in a 12-month period. DESIGN: Randomized, double-blind, parallel, placebo-controlled trial. SETTING: 25 U.S. medical centers. PATIENTS: 173 patients with documented healing of erosive esophagitis after 8 weeks of acid-suppressing therapy. INTERVENTION: Lansoprazole, 15 mg or 30 mg, or placebo once daily for as long as 12 months. MEASUREMENTS: Endoscopy and symptom evaluation after 1, 2, 3, 6, 9, and 12 months of treatment. Endoscopy was also done whenever symptoms suggested erosive changes. RESULTS: Lansoprazole was significantly superior to placebo in maintaining healing and preventing recurrence of symptoms. By month 1, 45% of placebo recipients remained healed compared with more than 90% of patients in either lansoprazole group. By month 12, only 24% of placebo recipients remained healed compared with 79% of patients receiving 15 mg of lansoprazole and 90% of patients receiving 30 mg of lansoprazole. During the same period, 35% of placebo recipients remained asymptomatic compared with 72% of recipients of 15 mg of lansoprazole and 67% of recipients of 30 mg of lansoprazole. The 15-mg and 30-mg lansoprazole doses did not differ significantly in maintaining healing and controlling symptoms. Follow-up after recurrence of erosion indicated that during the 12 months, 35% of placebo recipients and 2% of lansoprazole recipients had three or more recurrences. CONCLUSION: Lansoprazole effectively maintains healing of erosive esophagitis. The 15-mg and 30-mg lansoprazole doses did not differ significantly for use as maintenance treatment.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

Involvement of MDR1 P-glycoprotein in multifactorial resistance to methotrexate.

Cellular resistance to methotrexate (MTX) is believed to be unaffected by expression of MDR1 P-glycoprotein (Pgp), a pleiotropic efflux pump acting on different hydrophobic compounds that enter cells by passive diffusion. A series of human leukemic CCRF-CEM sublines, isolated by multi-step selection for very high resistance to MTX, exhibit multiple mechanisms of MTX resistance, including decreased carrier-mediated uptake of MTX and DHFR gene amplification. These sublines show cross-resistance to drugs of the multi-drug resistance (MDR) family, which is correlated with relative resistance to MTX. The MTX-selected sublines show increased expression and function of the MDR1 gene, based on the measurement of MDR1 mRNA, Pgp and rhodamine 123 accumulation. Sequence analysis of the MDR1 cDNA from MTX-selected CCRF-CEM cells revealed no mutations in the protein coding region. MTX resistance in these cell lines is partially reversible by a Pgp-specific monoclonal antibody (MAb) UIC2 and a monovalent FaB fragment of UIC2. Our results indicate that Pgp can contribute to multifactorial resistance to MTX.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Expression of the gene for multidrug-resistance-associated protein and outcome in patients with neuroblastoma.

BACKGROUND: Overexpression of the gene for the multidrug-resistance-associated protein (MRP) has been linked with resistance to chemotherapeutic agents (multidrug resistance) in vitro. The expression of MRP by neuroblastoma cells correlates with N-myc oncogene amplification, a well-established prognostic indicator in patients with neuroblastoma. METHODS: To relate MRP gene expression to established prognostic markers and the clinical outcome of neuroblastoma, we analyzed MRP expression in specimens of primary tumors from 60 patients with neuroblastoma. RESULTS: Levels of MRP gene expression were significantly higher in tumors with N-myc amplification than in tumors without such amplification (P < 0.001). High levels of MRP expression were strongly associated with reductions in both survival and event-free survival (P < 0.001) in the overall study population and in subgroups of patients without N-myc amplification and patients with localized disease. For the overall study population, the five-year cumulative survival rates in the groups with high and low levels of MRP expression were 57 percent (95 percent confidence interval, 37 to 78 percent) and 94 percent (95 percent confidence interval, 86 to 100 percent), respectively. In contrast, expression of the MDR1 multi-drug-resistance gene was not predictive of survival or event-free survival. After adjustment by multivariate analysis for the effects of N-myc amplification and other prognostic indicators, high levels of MRP expression retained significant prognostic value for poor survival (relative hazard, 14.9; P = 0.01) and poor event-free survival (relative hazard, 9.7; P = 0.004), whereas N-myc amplification had no prognostic value. CONCLUSIONS: High levels of MRP gene expression in patients with neuroblastoma correlate strongly with poor outcome. The findings suggest that expression of this multidrug-resistance gene accounts for the association between N-myc amplification and reduced survival.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Triple therapy with lansoprazole, clarithromycin, and amoxicillin for the cure of Helicobacter pylori infection: a short report.

BACKGROUND: Given the therapeutic potential of proton pump inhibitor-based triple therapy for successful cure of Helicobacter pylori infection, we evaluated the efficacy and safety of lansoprazole with clarithromycin and amoxicillin in an open-label, single-center study. MATERIALS AND METHODS: H. pylori-positive patients self-administered lansoprazole, 30 mg; clarithromycin, 500 mg; and amoxicillin, 1 gm bid for 14 days. Patients were assessed pretreatment, at which time the presence of H. pylori was documented by rapid urease test, culture, or histology, following study drug administration (week 2) for a brief evaluation only, and at least 4 weeks posttreatment (week 6), which included endoscopy with collection of biopsy specimens for culture and histology testing. RESULTS: Primary clarithromycin and metronidazole resistance were observed in 6% (2 of 30) and 43% (13 of 30) of study patients, respectively. One month after the end of therapy, H. pylori infection was cured in 23 of 25 patients (92%; 95% confidence interval, 74%-99%). The triple-therapy regimen was well-tolerated; 17% of patients (5 of 30) reported mild to moderate adverse effects during the treatment period. CONCLUSION: A 2-week, triple-drug combination of lansoprazole, clarithoromycin, and amoxicillin is highly effective for cure of H. pylori infection. Additionally, the triple-drug combination was well-tolerated by patients infected with H. pylori.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

Double-blind, multicenter evaluation of lansoprazole and amoxicillin dual therapy for the cure of Helicobacter pylori infection.

BACKGROUND: Treatment with amoxicillin plus omeprazole results in disappointing cure rates of Helicobacter pylori infection. The minimal inhibitory concentration of lansoprazole for H. pylori in vitro is lower than that for omeprazole, prompting interest in treatment with amoxicillin plus lansoprazole. MATERIALS AND METHODS: H. pylori-infected patients with endoscopically documented duodenal ulcer either currently or within the past year were randomized to 14 days of (1) lansoprazole, 30 mg bid, plus amoxicillin, 1 gm tid; (2) lansoprazole, 30 mg tid, plus amoxicillin, 1 gm tid; (3) lansoprazole, 30 mg tid alone; or (4) amoxicillin, 1 gm tid alone. Endoscopy was done at enrollment and at 4 to 6 weeks after completion of treatment or for recurrent symptoms. H. pylori status was assessed by culture and histology. Ulcer prevalence was evaluated at follow-up endoscopy. RESULTS: Two hundred sixty-two patients met enrollment criteria and were treated. By per-protocol analysis, H. pylori infection was cured in 57% of those treated with lansoprazole twice daily plus amoxicillin and in 67% of those treated with lansoprazole three times daily plus amoxicillin, compared with 0% treated with lansoprazole alone or amoxicillin alone (p < .001 for dual therapy versus either monotherapy). Amoxicillin resistance was not observed. At follow-up endoscopy, ulcer prevalence was 17% in patients treated with lansoprazole twice daily plus amoxicillin, 23% in those treated with lansoprazole three times daily plus amoxicillin, 33% in those treated with lansoprazole alone, and 35% in those treated with amoxicillin alone (p = .024; lansoprazole twice daily plus amoxicillin versus amoxicillin alone). CONCLUSIONS: Treatment with amoxicillin plus lansoprazole, 30 mg tid, led to cure of H. pylori infection in 67% of patients with active or recently healed duodenal ulcer.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

Seven-day triple therapy with lansoprazole, clarithromycin, and metronidazole for the cure of Helicobacter pylori infection: a short report.

BACKGROUND: To refine our understanding of anti-Helicobacter pylori treatment regimens further, we evaluated the efficacy and safety of lansoprazole given in combination with clarithromycin and metronidazole for 7 days in an open-label, multicenter study. MATERIALS AND METHODS: H. pylori-positive patients self-administered lansoprazole, 30 mg; clarithromycin, 500 mg; and metronidazole, 500 mg bid for 7 days. Patients were assessed at pretreatment, at which time the presence of H. pylori was documented by rapid urease test or histology and culture, following study drug administration (week 1) for a brief evaluation only, and at least 4 weeks posttreatment (week 5), including endoscopy with collection of biopsy specimens for culture and histology testing. RESULTS: Of the 60 patients enrolled in the study, 59 had confirmed H. pylori infection, and 51 were included in an intent-to-treat analysis of efficacy. Primary metronidazole and clarithromycin resistance were observed in 84% and 8% of study patients, respectively. One month after the end of therapy, H. pylori infection was cured in 40 of 51 patients (78%); 95% confidence interval, (65%-89%). The triple-therapy regimen was well-tolerated, with only 2 patients (4%) requiring premature withdrawal from the study due to treatment-related adverse events. Taste perversion (15.0%) and diarrhea (11.7%) were the most frequently reported adverse events possibly or probably related to study medication during the treatment period. CONCLUSION: Despite a high prevalence of metronidazole resistance, a 1-week, triple-drug combination of lansoprazole, clarithromycin, and metronidazole is effective treatment for and well-tolerated by patients with H. pylori infection.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

Lansoprazole prevents recurrence of erosive reflux esophagitis previously resistant to H2-RA therapy. The Lansoprazole Maintenance Study Group.

OBJECTIVE: This randomized, double-blind study was designed to determine whether the proton pump inhibitor lansoprazole could prevent relapse among patients with healed erosive reflux esophagitis that had been resistant to healing with at least 3 months of H2-receptor antagonist therapy. RESULTS: By the end of the year, 13% of placebo patients remained healed compared with 67% of lansoprazole 15 mg and 55% of lansoprazole 30 mg patients (p < 0.001 for time to first relapse). All placebo patients were symptomatic by the end of the study whereas only one-third of the lansoprazole patients was symptomatic at the end of the 12-month study period. The two lansoprazole doses were comparably effective in maintaining healing and in symptom control and were well tolerated. Fasting serum gastrin values increased significantly to about 1.5-2 times the baseline values over the first 2 months of lansoprazole treatment; no further increase was noted. CONCLUSION: Erosive relapse can be prevented in most patients for up to 1 yr with lansoprazole 15 mg or 30 mg once daily.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1995

Altered expression of M beta 2, the class II beta-tubulin isotype, in a murine J774.2 cell line with a high level of taxol resistance.

A series of taxol- and taxotere-resistant J774.2 cell lines has been characterized with respect to altered expression of beta-tubulin, the cellular target for these drugs. Vertebrates have six classes of beta-tubulin isotypes, each displaying a distinct pattern of expression. Although the functional significance of multiple beta-tubulins has not been fully defined, there is evidence that the individual isotypes contribute to differences in microtubule dynamics and drug binding. To determine if alterations in the expression of beta-tubulin isotypes play a role in taxol resistance, a PCR-based methodology was developed that permits highly specific amplification of each of the six known murine beta-tubulin isotypes. Two isotypes, M beta 5 and M beta 3, were expressed abundantly in the drug-sensitive parental J774.2 cells. Although expressed at an extremely low level in the parental cells, expression of the M beta 2 isotype was increased 21-fold (< 0.005) in the cell line most resistant to taxol. These findings suggest that a cell can alter its relative tubulin isotype composition in response to an external stress and specifically imply that altered expression of M beta 2, the class II beta-tubulin isotype, may contribute to the development of high resistance to taxol.

Animals↗

PubMed1995

An assay for the determination of reduced methotrexate accumulation in cells displaying limited viability in vitro.

Amongst the mechanisms known to mediate resistance to methotrexate (MTX), a major component in the treatment of childhood leukemia, reduced drug accumulation appears to have direct clinical relevance. However, due to the poor viability of patient-derived acute lymphoblastic leukemia cells in vitro, determination of this parameter in clinical samples is associated with a number of difficulties. We have therefore developed an assay for reduced MTX accumulation, which controls for the metabolic state of the cell population under study by utilizing accumulation of the nucleoside thymidine as an independent indicator of this parameter. To establish this assay, we have utilized pediatric leukemic cell populations maintained as xenografts in nude mice, which, despite displaying sensitivity to MTX, demonstrated reduced accumulation of MTX when assayed using standard methodology. When accumulation of MTX by such cell populations was expressed, however, relative to their accumulation of thymidine, MTX accumulation was shown to be equal to that of drug-sensitive CCRF-CEM cells maintained in long-term culture. In contrast, significantly less MTX was accumulated, in this assay, by xenografted cell populations with demonstrated resistance to MTX. Identical results were obtained using either fresh or cryopreserved cells. The data thus indicate that by controlling for variable metabolic status of leukemic cells, it is possible to accurately assess MTX accumulation in leukemic samples displaying limited viability in culture.

Animals↗

PubMed1995

Increased retinoic acid receptor gamma expression suppresses the malignant phenotype and alters the differentiation potential of human neuroblastoma cells.

Human neuroblastoma (NB) tumor cell lines treated in vitro with the retinoid, all-trans-retinoic acid (aRA), form neurites and undergo growth arrest. Retinoids exert their diverse morphologic effects through a signalling pathway which involves the nuclear retinoid receptors. Defective retinoic acid receptor (RAR) function contributes to the malignant phenotype of several human and experimental tumors. Considerable evidence from gene disruption studies now suggests that one of the RARs, RAR gamma, may directly mediate some retinoid effects on embryonic and malignant cells. We, firstly, examined primary NB tumor tissue for a correlation between endogenous RAR gamma expression and clinical stage of the tumor and secondly, the effects of exogenous over-expression of the RAR gamma gene on a human NB tumor cell line. RAR gamma mRNA expression in 32 primary NB tumor tissue samples were significantly higher in clinically localised tumors compared with advanced or disseminated tumors. The human NB tumor cell line, BE(2)-C, was stably transfected with a mammalian expression vector (pREP4) over-expressing the human RAR gamma cDNA. Two selected clones over-expressing RAR gamma (BE/G1 and 2) exhibited a reduced growth rate compared to control cells. Tumorigenicity was inhibited for BE/G1 cells and there was a delayed onset to tumor formation for BE/G2 cells. aRA caused growth inhibition but not neuritic differentiation of the BE/G clones, while 9-cis-retinoic acid caused both growth arrest and neuritic differentiation. Taken together these results suggest that reduced endogenous RAR gamma expression may contribute to the malignant phenotype of human NB. In NB cells the retinoid signalling pathway for neuritic differentiation may be distinct from that causing growth inhibition.

Adrenal Glands↗

PubMed1995

The effect of disease prior to an outbreak on estimates of vaccine efficacy following the outbreak.

A common source of bias in evaluating vaccine efficacy following a disease outbreak is the presence of persons who had the disease prior to the outbreak. This paper examines the effects of including and excluding pre-outbreak disease cases from the calculation of vaccine efficacy based on the cumulative incidence at the end of an outbreak. Using a five-stage model, the effects of the following factors on the bias of vaccine efficacy estimates are examined: the true protective efficacy of the vaccine, the prevaccination infection rate, differences in vaccine uptake among the previously diseased and nondiseased, differences in pre-outbreak exposure to infection between vaccinees and nonvaccinees, and differences in exposure during the outbreak between vaccinees and nonvaccinees. Numerical calculations of the bias are performed for a hypothetical outbreak of measles in a developing country. Exclusion of pre-outbreak disease cases requires accurate data on disease rates prior to the outbreak, and such data are often unreliable or nonexistent. Inclusion of pre-outbreak cases contributes to the bias of the estimated vaccine efficacy, especially when there is a high prevaccination infection rate and vaccine uptake among the previously diseased is considerably lower than that among the nondiseased. In most practical cases, however, this bias is not very large.

Disease Outbreaks↗

PubMed1995

Analysis of a novel cDNA encoding a C219-reactive peptide isolated from methotrexate-selected multidrug-resistant human leukemic cells.

We have isolated and sequenced a novel cDNA clone (D320), from methotrexate-selected multidrug-resistant (MDR) human leukemic CCRF-CEM cells, which encodes a peptide reactive with monoclonal antibody (mAb) C219. Despite having been cloned using this ostensibly P-glycoprotein-specific mAb, clone D320 has no significant homology with either the MDR-encoding gene or, at the amino acid (aa) level, with its product, P-glycoprotein. A putative C219-binding site has been identified in D320, which differs at two positions from the 6-aa C219 epitope previously described in P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Multiple focal nodular hyperplasia of the liver associated with hemihypertrophy and vascular malformations.

A case of multiple focal nodular hyperplasia of the liver occurring in a 22-year-old woman with musculoskeletal hemihypertrophy and anomalous vascular supply to the liver is described. The patient had Klippel-Trénaunay-Weber syndrome and abdominal pain and tender massive hepatomegaly. Visceral angiography showed marked dilatation of the celiac axis and both the main trunk and peripheral branches of the hepatic artery. Large abdominal veins drained from the dome of the liver into the hepatic veins. The vascular anomalies were evident on contrast-enhanced computed tomography and magnetic resonance imaging. Multiple focal nodular hyperplasia was confirmed by laparoscopic liver biopsy. The findings in this patient support the concept that multiple focal nodular hyperplasia characteristically occurs in a syndromic form and is induced by an irregular arterial supply in the liver, with localized hyperfusion that leads to nodular areas of hepatocyte hyperproliferation.

Adult↗

PubMed1995

On individual and population effectiveness of vaccination.

BACKGROUND: The protective effect of a vaccine following an outbreak is often measured by the vaccine efficacy statistic, namely one minus the ratio of attack rates in vaccinees and non-vaccinees. This quantity is not an adequate measure of the population-level benefits of the vaccine. METHODS: We discuss two measures of the effectiveness of a vaccination programme. The first is the commonly used vaccine efficacy statistic. This is called here the individual vaccination effectiveness. The second measure, called the population effectiveness, is defined as one minus the ratio of the overall (or average) attack rate in the population when the vaccination programme is implemented to the expected attack rate in the same population without vaccination. We outline a method for computing the population effectiveness following an outbreak of a directly transmitted acute infectious disease in a closed heterogeneous population. We then explore and compare the behaviour of the two measures of vaccination effectiveness under various conditions. RESULTS: The population vaccination effectiveness is more robust than individual effectiveness to factors that may interfere with the evaluation of the performance of vaccination. Such factors are non-uniform vaccination, changes in contact patterns by vaccinees, and the ability of the vaccine to reduce infectiousness. CONCLUSION: The population vaccination effectiveness is a more adequate measure of the population-level benefits of a vaccination programme. The main disadvantage of this measure is that it cannot be readily calculated from observed attack rates.

Immunization Programs↗

PubMed1995

Characterization of clonal immunoglobulin heavy chain and I cell receptor gamma gene rearrangements during progression of childhood acute lymphoblastic leukemia.

Instability of antigen receptor gene rearrangements during progression of acute lymphoblastic leukemia (ALL) has important implications for polymerase chain reaction (PCR)-based techniques using these genes for the detection of minimal residual disease (MRD). Antigen receptor gene instability may lead to false negative results in bone marrow samples taken during remission. Utilizing the PCR and consensus primers for rearranged immunoglobulin heavy chain (IgH) and T cell receptor gamma (TCR gamma) gene sequences, we analyzed the bone marrow samples at diagnosis and first relapse for 37 children with ALL. The incidence of clonal evolution at the IgH locus was 9/33 (27%) and at the TCR gamma locus 1/15 (7%). In four of the nine patients with clonal evolution at the IgH locus, the sequence at relapse retained the diversity and joining region (D-N-J) sequences from diagnosis. Patients with clonal evolution were characterized by a higher incidence of more than one IgH PCR band at diagnosis and by late relapse (> 18 months from diagnosis). These results suggest that, where possible, patients with more than one IgH PCR rearrangement at diagnosis should be monitored using another antigen receptor gene, such as TCR gamma, since evolution for this gene was found to be a rare event. By combining this approach with a strategy directed at the more stable D-N-J region of the IgH gene, MRD false negativity would have occurred in less than 10% of patients in the present study.

Adolescent↗