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Adams J, Hakim EW, Hakim DJ, Myers BA, Horowitz J. A Critical Analysis of Existing Evidence on the Management of a Wound with Malignant Desmoplastic Melanoma and Neurofibromatosis: A Case Report. REHABILITATION ONCOLOGY 2009. [DOI: 10.1097/01893697-200927010-00013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Horowitz J, Jarzynski C. Comment on "Failure of the work-Hamiltonian connection for free-energy calculations". PHYSICAL REVIEW LETTERS 2008; 101:098901-098902. [PMID: 18851665 DOI: 10.1103/physrevlett.101.098901] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Indexed: 05/26/2023]
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Shapiro W, Martinez C, Charytan C, Horowitz J, Tharpe D, Droge J, Ling X, Belozeroff V, Goodman W, Block G, Sprague S. 240: Treatment Patterns in Patients Progressing Through Later-Stage Chronic Kidney Disease (CKD): Baseline Data from a Prospective Observational Registry. Am J Kidney Dis 2008. [DOI: 10.1053/j.ajkd.2008.02.250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Thomas D, Dumont C, Pickup S, Misselwitz B, Zhou R, Horowitz J, Ferrari VA. T1-weighted cine FLASH is superior to IR imaging of post-infarction myocardial viability at 4.7T. J Cardiovasc Magn Reson 2006; 8:345-52. [PMID: 16669177 PMCID: PMC2581493 DOI: 10.1080/10976640500451986] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
PURPOSE Data are unavailable for rational selection of pulse sequences to assess postinfarction myocardial viability in rodents at high field strength. We implemented a widely used clinical inversion recovery (IR) sequence at 4.7T and compared the results to a heavily T1-weighted cine FLASH sequence (T1-CF) for assessment of infarction size. MATERIALS AND METHODS Eleven infarcted rats were examined within 24 h of infarction after injection of Gadophrin-3 contrast agent. Images were acquired using both pulse sequences and a standard cine (SC) sequence. Estimates of infarct size were compared to TTC. Global LV function was compared between the T1-CF and SC sequences. RESULTS SNR, relative SNR, and CNR for the infarcted and normal myocardium were significantly greater for the IR sequence. Infarction size was overestimated by both sequences, but correlated highly and showed very close agreement with TTC. Global function revealed no significant differences between T1-CF and SC. CONCLUSION Both IR and T1-CF produced reliable results for assessment of infarction size at 4.7T. While the IR sequence delivers better overall SNR and CNR, the T1-CF allows concomitant assessment of global cardiac function with a much shorter acquisition time.
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Gilbert MR, Gaupp P, Liu V, Conrad C, Colman H, Groves M, Puduvalli V, Levin V, Hsu S, Horowitz J, Yung W. A phase I study of temozolomide (TMZ) and the farnesyltransferase inhibitor (FTI), lonafarnib (Sarazar, SCH66336) in recurrent glioblastoma. J Clin Oncol 2006. [DOI: 10.1200/jco.2006.24.18_suppl.1556] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
1556 Background: Farnesylation is essential for the post-translational modification of several proteins that play a role in cell proliferation and growth. FTIs demonstrate antiproliferative effects in a variety of tumor cell lines and xenograft models and enhanced efficacy by combining lonafarnib with TMZ compared with TMZ alone. Clinical studies show that dose-intense TMZ may have better efficacy then conventional dosing (Wick, Neurology 2004). Objective: Determine the maximum tolerated dose of lonafarnib when combined with a dose-intensified schedule of TMZ. Eligibility criteria: Histologically proven GBM; evidence of relaspe or progression; up to 2 prior chemotherapy regimens, prior TMZ permitted; KPS ≥ 60. No enzyme-inducing anticonvulsants. Methods: TMZ was given at 150 mg/m2 days 1–7 and 15–21; lonafarnib escalated by cohort: 100 mg BID, 150 mg BID, 200 mg BID on days 8–14 and 22–28 of a 28-day cycle. Response: Toxicity measured after cycle 1 using NCI CTCAE v3. Patient (pt)accrual used a 3 + 3 design. Response was evaluated q2 cycles. Standard response criteria (MacDonald) were used. Results: 15 patients were accrued. Median age 47 yrs; median KPS 90. M:F ratio was 11:4. No DLTs in any dose cohort, a pt (cohort 1) died day 29 of unrelated cardiac disease. 4 pts demonstrated partial response, all with prior TMZ failure, 3 pts showed prolonged stable disease. 6-month PFS rate estimated at 33%, median PFS 14 weeks. Treatment was well tolerated: 1 episode each of grade 3 diarrhea, esophagitis, fatigue and hypokalemia; 3 episodes of grade 3/4 leukopenia, 2 episodes of grade 3/4 neutropenia, and 2 episodes of grade 4 thrombocytopenia. Seven pts had grade 3/4 lymphopenia, some with persistant lymphopenia from prior TMZ. 1 pt had grade 4 pneumonitis of uncertain etiology. Conclusions: The alternating week schedule of TMZ/lonafarnib was well tolerated. Preliminary results suggest anti-tumor activity even in pts who had failed prior TMZ. It is not certain whether this activity is due to the dose-intensified TMZ or the treatment combination. Studies are planned to evaluate potential predictors of response (i.e MGMT gene promoter methylation) and expand the trial to obtain pharmacokinetic and additional efficacy data. [Table: see text]
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Thomas D, Horowitz J, Bal H, Araujo L, Acton P, Dumont C, Misselwitz B, Ferrari VA. Nichtinvasive Quantifizierung des akuten Myokardinfarktes in einem Kleintiermodell: MRT vs. SPECT vs. PET. ROFO-FORTSCHR RONTG 2006. [DOI: 10.1055/s-2006-941008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Gerlic M, Horowitz J, Horowitz S. Mycoplasma fermentans inhibits tumor necrosis factor alpha-induced apoptosis in the human myelomonocytic U937 cell line. Cell Death Differ 2005; 11:1204-12. [PMID: 15286682 DOI: 10.1038/sj.cdd.4401482] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Mycoplasma fermentans (M. fermentans) was shown to be involved in the alteration of several eukaryotic cell functions (i.e. cytokine production, gene expression), and was suggested as a causative agent in arthritic diseases involving impaired apoptosis. We investigated whether M. fermentans has a pathogenic potential by affecting tumor necrosis factor (TNF)alpha-induced apoptosis in the human myelomonocytic U937 cell line. A significant reduction in the TNFalpha-induced apoptosis (approximately 60%) was demonstrated upon either infection with live M. fermentans or by stimulation with non-live M. fermentans. To investigate the mechanism of M. fermentans antiapoptotic effect, the reduction of mitochondrial transmembrane potential (DeltaPsim) and the protease activity of caspase-8 were measured. In the infected cells, the reduction of DeltaPsim was inhibited (approximately 75%), and an approximately 60% reduction of caspase-8 activity was measured. In conclusion, M. fermentans significantly inhibits TNFalpha-induced apoptosis in U937 cells, and its effect is upstream of the mitochondria and upstream of caspase-8.
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Engel R, Normand M, Horowitz J, Peleg M. A model of microbial contamination of a water reservoir. Bull Math Biol 2001; 63:1005-23. [PMID: 11732173 DOI: 10.1006/bulm.2001.0238] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A three year record of daily fecal coliform counts in a Massachusetts water reservoir has the appearance of an irregular time series punctuated by outbursts of varying duration. The pattern is described in terms of a probabilistic model where the fluctuations in the 'regular' and 'explosive' regimes are governed by two sets of probabilities. It has been assumed that the random oscillations has a lognormal distribution, and that once an explosion threshold has been exceeded the increments or decrements in the population size have fixed probability distributions. The threshold for triggering an outburst was estimated by examining the randomness of the autocorrelation function of the record after it is filtered to eliminate peaks of progressively increasing magnitude. Once the threshold has been identified, the mean and standard deviation of the underlying lognormal distribution could be estimated directly from remains found in the record after all the peaks were removed. The probabilities of an increment and decrement during the outbursts and their relative magnitudes could also be estimated using simple formulas. These estimated parameter values were then used to generate realistic records with known threshold levels, which were subsequently used to assess the procedure's feasibility and sensitivity.
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Tardif KD, Liu M, Vitseva O, Hou YM, Horowitz J. Misacylation and editing by Escherichia coli valyl-tRNA synthetase: evidence for two tRNA binding sites. Biochemistry 2001; 40:8118-25. [PMID: 11434781 DOI: 10.1021/bi0103213] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Valyl-tRNA synthetase (ValRS) has difficulty discriminating between its cognate amino acid, valine, and structurally similar amino acids. To minimize translational errors, the enzyme catalyzes a tRNA-dependent editing reaction that prevents accumulation of misacylated tRNA(Val). Editing occurs with threonine, alanine, serine, and cysteine, as well as with several nonprotein amino acids. The 3'-end of tRNA plays a vital role in promoting the tRNA-dependent editing reaction. Valine tRNA having the universally conserved 3'-terminal adenosine replaced by any other nucleoside does not stimulate the editing activity of ValRS. As a result 3'-end tRNA(Val) mutants, particularly those with 3'-terminal pyrimidines, are stably misacylated with threonine, alanine, serine, and cysteine. Valyl-tRNA synthetase is unable to hydrolytically deacylate misacylated tRNA(Val) terminating in 3'-pyrimidines but does deacylate mischarged tRNA(Val) terminating in adenosine or guanosine. Evidently, a purine at position 76 of tRNA(Val) is essential for translational editing by ValRS. We also observe misacylation of wild-type and 3'-end mutants of tRNA(Val) with isoleucine. Valyl-tRNA synthetase does not edit wild-type tRNA(Val)(A76) mischarged with isoleucine, presumably because isoleucine is only poorly accommodated at the editing site of the enzyme. Misacylated mutant tRNAs as well as 3'-end-truncated tRNA(Val) are mixed noncompetitive inhibitors of the aminoacylation reaction, suggesting that ValRS, a monomeric enzyme, may bind more than one tRNA(Val) molecule. Gel-mobility-shift experiments to characterize the interaction of tRNA(Val) with the enzyme provide evidence for two tRNA binding sites on ValRS.
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Corradini MG, Normand MD, Nussinovitch A, Horowitz J, Peleg M. Estimating the frequency of high microbial counts in commercial food products using various distribution functions. J Food Prot 2001; 64:674-81. [PMID: 11347999 DOI: 10.4315/0362-028x-64.5.674] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Industrial microbial count records usually form an irregular fluctuating time series. If the series is truly random or weakly autocorrelated, the fluctuations can be considered as the outcome of the interplay of numerous factors that promote or inhibit growth. These factors usually balance each other, although not perfectly, hence, the random fluctuations. If conditions are unchanged, then at least in principle the probability that they will produce a coherent effect, i.e., an unusually high (or low) count of a given magnitude, can be calculated from the count distribution. This theory was tested with miscellaneous industrial records (e.g., standard plate count, coliforms, yeasts) of various food products, including a dairy-based snack, frozen foods, and raw milk, using the normal, log normal, Laplace, log Laplace, Weibull, extreme value, beta, and log beta distribution functions. Comparing predicted frequencies of counts exceeding selected levels with those actually observed in fresh data assessed their efficacy. No single distribution was found to be inherently or consistently superior. It is, therefore, suggested that, when the probability of an excessive count is estimated, several distribution functions be used simultaneously and a conservative value be used as the measure of the risk.
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Horowitz J, Melamud A, Sela L, Hod Y, Geyer O. Internal carotid artery hypoplasia presenting as anterior ischemic optic neuropathy. Am J Ophthalmol 2001; 131:673-4. [PMID: 11336955 DOI: 10.1016/s0002-9394(00)00886-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To describe the occurrence of anterior ischemic optic neuropathy in a young woman with internal carotid artery hypoplasia. METHODS Case report with clinical and radiologic observations. RESULTS A 38-year-old woman suffered from a sudden, painless loss of vision in her right eye. The diagnosis of anterior ischemic optic neuropathy was based on the clinical course and appearance of the fundus. Doppler evaluation of the carotid arteries, computed tomography (CT) scan, magnetic resonance imaging (MRI), and CT angiogram all demonstrated internal carotid artery hypoplasia on the same side. CONCLUSION Although carotid artery disease (mainly atherosclerosis) is not a common predisposing factor for anterior ischemic optic neuropathy, our patient had an ipsilateral coexisting internal carotid artery hypoplasia and anterior ischemic optic neuropathy. We believe that the carotid artery anomaly might have contributed to the development of anterior ischemic optic neuropathy in this patient.
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Horowitz J. [When the elites and the workers agreed: resistance to the welfare program sponsored by the Argentinian government, 1923-24]. ANUARIO IEHS 2001; 16:109-128. [PMID: 19526642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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63
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Horowitz S, Evinson B, Borer A, Horowitz J. Mycoplasma fermentans in rheumatoid arthritis and other inflammatory arthritides. J Rheumatol 2000; 27:2747-53. [PMID: 11128659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
OBJECTIVE To evaluate the association between infection with Mycoplasma fermentans (Mf) and rheumatoid arthritis (RA) and other inflammatory arthritides. METHODS Screening of synovial fluid samples (SF) for Mf was done by culture and by polymerase chain reaction (PCR) in 38 and 34 RA patients, respectively, 8 undifferentiated arthritis (UDA), 9 reactive arthritis (ReA), and in 40 other arthritides. The prevalence of antibodies to Mf in these SF was determined by both ELISA and immunoblotting (IB). Antibodies were measured also in sera of 88 RA patients, 28 ReA, 14 UDA, 71 other arthritides, and in 102 healthy blood donors. RESULTS All SF were culture-negative for Mf, while 7 SF were positive by PCR (6/34 RA and 1/8 UDA). SF from patients with other arthritides and ReA were PCR-negative. The prevalence of anti-Mf antibodies in SF of RA patients was significantly higher than in SF of other arthritides (p = 0.01). In 47% (17/38) of all RA (including the 6 PCR-positive patients), the level of antibodies to Mf in their SF was higher than that in sera, compared to 7.5% (3/40) in other arthritides (p = 0.0002). There was no significant difference in the prevalence of serum antibodies to Mf between patients with RA, other arthritides, and healthy controls. By IB with Mf sonicate, binding to Mf peptides P107, P48, and P29 was detected in SF of 7/11 RA patients but not in 11 patients with traumatic arthritis. Specific binding to Mf membrane lipoproteins was also more prevalent in SF of RA patients than in other arthritides (p = 0.038). CONCLUSION The finding that both Mf DNA and specific antibodies to Mf were present in the SF of RA patients suggests that in some RA patients Mf may play a role in initiating or perpetuating synovitis.
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Peleg M, Nussinovitch A, Horowitz J. Intrepretation of and Extraction of Useful Information From Irregular Fluctuating Industrial Microbial Counts. J Food Sci 2000. [DOI: 10.1111/j.1365-2621.2000.tb13580.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Geffen DB, Horowitz J. Gemcitabine-induced severe extremity edema with muscle contractures and subsequent prevention with prednisone. THE ISRAEL MEDICAL ASSOCIATION JOURNAL : IMAJ 2000; 2:552-3. [PMID: 10979335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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Menashe G, Borer A, Gilad J, Horowitz J. Rhabdomyolysis after correction of severe hyponatremia. Am J Emerg Med 2000; 18:229-30. [PMID: 10750940 DOI: 10.1016/s0735-6757(00)90028-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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Peleg M, Horowitz J. On estimating the probability of aperiodic outbursts of microbial populations from their fluctuating counts. Bull Math Biol 2000; 62:17-35. [PMID: 10824419 DOI: 10.1006/bulm.1999.0112] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The irregular sequence of counts of a microbial population, in the absence of observable corresponding environmental changes (e.g., temperature), can be regarded as reflecting the interplay of several unknown or random factors that favor or inhibit growth. Since these factors tend to balance one another, the fluctuations usually remain within bounds, and only by a coincidence--when all or most act in unison--does an 'outburst' occur. This situation can be represented mathematically as a sequence of independent random variables governed by a probability distribution. The concept was applied to reported microbial counts of ground meat and wastewater. It is found that the lognormal distribution could serve as a model, and that simulations from this model are indistinguishable from actual records. The parameters of the lognormal (or other) distribution can then be used to estimate the probability of a population outburst, i.e., an increase above a given threshold. Direct estimation of the outburst probability based on frequency of occurrence is also possible, but in some situations requires an impractically large number of observations. We compare the efficiency of these two methods of estimation. Such methods enable translation of irregular records of microbial counts into actual probabilities of an outburst of a given magnitude. Thus, if the environment remains 'stable' or in dynamic equilibrium, the fluctuations should not be regarded merely as noise, but as a source of information and an indicator of potential population outbursts even where obvious signs do not exist.
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Horowitz J, Normand M, Peleg M. On modeling the irregular fluctuations in microbial counts. Crit Rev Food Sci Nutr 1999; 39:503-17. [PMID: 10595297 DOI: 10.1080/10408699991279268] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Daily or other periodic microbial counts in many foods, particularly ground meats, poultry, and raw milk, show an irregular fluctuating pattern. The cause of the fluctuations is the interplay of many random factors that tend to promote or inhibit microbial growth. Therefore, the actual size of a microbial population can vary randomly around a typical level or around a trend determined, for example, by seasonal variations or changing sanitary conditions. Fluctuations around a fixed level can often be modeled as a sequence of independent counts having a lognormal or other parametric distribution. The independence of the counts and the type of distribution can be established by standard statistical tests. Once selected, the distribution function can be used to estimate the probability of encountering a population in any given size range. The model can be modified to describe sequences that include zero counts, which are the result of the organisms' absence, or of the failure of the method to detect them. In the case of fluctuations around a trend, a modified version of the model can be used to estimate the probability of deviations from the trend. A more thorough modification is required in order to account for fluctuating patterns that include outbursts of appreciable duration, like those caused by massive contamination of a water reservoir.
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Szarewski A, Kitchener HC, Horowitz J, Kahlenborn C, Grant ECG, Steel CM, Price EH, Anthony HM, Downing D, Radcliffe MJ, Myhill S. Mortality associated with oral contraceptive use. West J Med 1999. [DOI: 10.1136/bmj.319.7206.386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Horowitz J. Mortality associated with oral contraceptive use. Relative risk of liver cancer remains high. BMJ (CLINICAL RESEARCH ED.) 1999; 319:386. [PMID: 10490326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
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Horowitz J. Adenovirus-mediated p53 gene therapy: overview of preclinical studies and potential clinical applications. CURRENT OPINION IN MOLECULAR THERAPEUTICS 1999; 1:500-9. [PMID: 11713766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Disruption of p53 function through mutation, or other means, occurs very frequently in human cancer and is associated with an unfavorable prognosis in various cancers. Evidence from in vitro and in vivo transduction experiments have demonstrated that adenoviral-mediated expression of wild-type p53 suppresses the transformed phenotype of many cell types and potentiates the cytotoxicity of both chemotherapeutic agents and radiation therapy. Recently several phase I studies have evaluated the safety, biological effect and different routes of administration of adenoviral-mediated p53 gene therapy in various tumor types. These studies indicate that adenovirus-mediated p53 gene therapy and introduction of wild-type p53 into tumor cells represents a potentially valuable tool for the therapy of many types of human cancers. This review presents an overview of the most recent advances in the preclinical and clinical evaluation of adenoviral p53 gene therapy as well as the challenges that lay ahead forfuture clinical studies.
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Horowitz J, Chu WC, Derrick WB, Liu JC, Liu M, Yue D. Synthetase recognition determinants of E. coli valine transfer RNA. Biochemistry 1999; 38:7737-46. [PMID: 10387013 DOI: 10.1021/bi990490b] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied the interactions between Escherichia coli tRNAVal and valyl-tRNA synthetase (ValRS) by enzymatic footprinting with nuclease S1 and ribonuclease V1, and by analysis of the aminoacylation kinetics of mutant tRNAVal transcripts. Valyl-tRNA synthetase specifically protects the anticodon loop, the 3' side of the stacked T-stem/acceptor-stem helix, and the 5' side of the anticodon stem of tRNAVal against cleavage by double- and single-strand-specific nucleases. Increased nuclease susceptibility at the ends of the anticodon- and T-stems in the tRNAVal.ValRS complex is indicative of enzyme-induced conformational changes in the tRNA. The most important synthetase recognition determinants are the middle and 3' anticodon nucleotides (A35 and C36, respectively); G20, in the variable pocket, and G45, in the tRNA central core, are minor recognition elements. The discriminator base, position 73, and the anticodon stem also are recognized by ValRS. Replacing wild-type A73 with G73 reduces the aminoacylation efficiency more than 40-fold. However, the C73 and U73 mutants remain good substrates for ValRS, suggesting that guanosine at position 73 acts as a negative determinant. The amino acid acceptor arm of tRNAVal contains no other synthetase recognition nucleotides, but regular A-type RNA helix geometry in the acceptor stem is essential [Liu, M., et al. (1997) Nucleic Acids Res. 25, 4883-4890]. In the anticodon stem, converting the U29:A41 base pair to C29:G41 reduces the aminoacylation efficiency 50-fold. This is apparently due to the rigidity of the anticodon stem caused by the presence of five consecutive C:G base pairs, since the A29:U41 mutant is readily aminoacylated. Identity switch experiments provide additional evidence for a role of the anticodon stem in synthetase recognition. The valine recognition determinants, A35, C36, A73, G20, G45, and a regular A-RNA acceptor helix are insufficient to transform E. coli tRNAPhe into an effective valine acceptor. Replacing the anticodon stem of tRNAPhe with that of tRNAVal, however, converts the tRNA into a good substrate for ValRS. These experiments confirm G45 as a minor ValRS recognition element.
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MESH Headings
- Anticodon/chemistry
- Anticodon/metabolism
- Base Sequence
- Binding Sites
- Endoribonucleases/chemistry
- Escherichia coli/enzymology
- Kinetics
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Nuclear Magnetic Resonance, Biomolecular
- RNA, Transfer, Phe/chemistry
- RNA, Transfer, Phe/genetics
- RNA, Transfer, Phe/metabolism
- RNA, Transfer, Val/chemistry
- RNA, Transfer, Val/metabolism
- Single-Strand Specific DNA and RNA Endonucleases/chemistry
- Valine-tRNA Ligase/chemistry
- Valine-tRNA Ligase/genetics
- Valine-tRNA Ligase/metabolism
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Bantz DL, Wieseke AW, Horowitz J. Perspectives of nursing executives regarding ethical-economic issues. NURSING ECONOMIC$ 1999; 17:85-90. [PMID: 10410026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
The authors grapple with the very real issue of how to allocate scarce health care resources while trying to hold down costs, especially in the face of changing federal and managed care reimbursement realities. Nurse executives (NEs) were surveyed in an attempt to discover their perspectives on a number of related ethical-economic issues. The NEs' responses to the entire "ethical-economic" survey were contrasted with answers offered to the same tool earlier by staff RNs. Among the questions raised was the impact of cost controls on staffing patterns. Not surprisingly, the staff nurses reported perceiving that budget cuts had a greater negative impact on staff positions and the quality of patient care than the nurse executives reported. Both groups were in favor of taxpayers covering a greater part of the cost of medically indigent care. When asked if they would be willing to pay higher taxes themselves, slightly less than half of the nurse executives answered in the affirmative while only 17% of the staff nurses indicated a similar willingness.
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Lincoff H, Kreissig I, Horowitz J, Silverman R. Intravitreal gas injection diminishes hyaluronic acid. Klin Monbl Augenheilkd 1999; 214:100-2. [PMID: 10218203 DOI: 10.1055/s-2008-1034757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVES To determine if compression of the vitreous by an intraocular gas bubble diminishes the concentration of hyaluronic acid (NaHA). MATERIALS AND METHODS Eighteen albino rabbits had air, xenon or perfluoroethane (C2F6) injected into the vitreous to displace 12.5% to 90% of the vitreous volume. After the gas was absorbed, the vitreous was analyzed for NaHA by the Carbazole method (1, 13). RESULTS A 90% displacement diminished the NaHA concentration by 18.6%. Lesser displacements caused a lesser loss, but the differences are not significant. CONCLUSION Intraocular gas injections, both large and small, reduce the concentration of NaHA and destabilize the vitreous structure.
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Borer A, Metz I, Gilad J, Riesenberg K, Weksler N, Weber G, Alkan M, Horowitz J. Massive pulmonary haemorrhage caused by leptospirosis successfully treated with nitric oxide inhalation and haemofiltration. J Infect 1999; 38:42-5. [PMID: 10090507 DOI: 10.1016/s0163-4453(99)90029-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A patient with leptospirosis who developed oliguric renal failure, massive pulmonary haemorrhage and respiratory failure is described. The patient's clinical condition and arterial oxygenation failed to improve despite vigorous supportive measures. Nitric oxide inhalation and haemofiltration resulted in a marked clinical improvement and subsequent full recovery. We suggest that the addition of haemofiltration and nitric oxide inhalation therapy should be considered in patients with pulmonary haemorrhage and renal failure caused by leptospirosis, in whom conventional therapy fails.
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