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M J Nowak

Publications and source records attributed to M J Nowak.

15 recordsLinked to original sources
PubMed2006

UV-induced generation of rare tautomers of allopurinol and 9-methylhypoxanthine -- a matrix isolation FTIR study.

Monomers of allopurinol and 9-methylhypoxanthine were studied using the matrix isolation technique combined with Fourier transform infrared spectroscopy. The oxo tautomeric forms of both compounds were found to dominate in freshly deposited low-temperature argon matrices. For 9-methylhypoxanthine, a small amount of the hydroxy tautomer was also detected in an Ar matrix before any irradiation. Upon exposure of the matrices to the UV (lambda>230 nm or lambda>270 nm) light, a proton transfer photoreaction converting the oxo forms of both compounds into the corresponding hydroxy tautomers occurred. Generation of conjugated ketenes as minor photoproducts was also observed. For 4(3H)-pyrimidinone (a model compound for both allopurinol and 9-methylhypoxanthine), photoreversibility of the UV-induced oxo --> hydroxy transformation was experimentally proven by direct observation of the back hydroxy --> oxo photoreaction. The substrates (oxo tautomers) and products (hydroxy tautomers) of the observed phototransformations were identified by comparison of their IR spectra with the spectra theoretically predicted at the DFT(B3LYP)/6-31++G(d,p) level. The IR bands in the experimental spectra were assigned to the calculated normal modes.

Allopurinol↗
PubMed2005

Preferred conformers and photochemical (lambda > 200 nm) reactivity of serine and 3,3-dideutero-serine in the neutral form.

A systematic investigation of the conformational potential energy surface of neutral serine [HOCH2CHNH2COOH] and 3,3-dideutero-serine [HOCD2CHNH2COOH] was undertaken, revealing the existence of 61 different minima. The structures and vibrational spectra of the most stable conformers, which were estimated to have relative energies within 7 kJ mol(-1) and account for ca. 93% of the total conformational population at room temperature, were calculated at both the MP2 and DFT/BLYP levels of theory with the 6-311++G(d,p) basis-set and used to interpret the spectroscopic data obtained for the compounds isolated in low-temperature inert matrixes. The assignment of the main spectral infrared features observed in the range 4000-400 cm(-1) to the most stable conformers of serine was undertaken. In addition, UV irradiation (lambda > 200 nm) of the matrix-isolated compounds was also performed, leading to decarboxylation, which was found to be strongly dependent on the conformation assumed by the reactant molecule.

Algorithms↗
PubMed2001

Tautomerism and infrared spectra of 2-thiopurine: an experimental matrix isolation and theoretical ab initio and density functional theory study.

Infrared spectra of 2-thiopurine (2-mercaptopurine, 2-purinethiol ) isolated in low-temperature Ar and N2 matrixes are reported. These spectra indicate that the compound adopts exclusively the thiol N9H tautomeric form. The theoretical calculations of relative energies of 2-thiopurine tautomers have been carried out at the MP4(SDTQ)//HF level using the 6-31G(d,p) basis set. The thiol N9H tautomer was predicted to be the most stable of all isomers of 2-thiopurine. The infrared spectra of the tautomers of 2-thiopurine have been calculated at the DFT(B3LYP)/6-31G(d,p) level. Good agreement between the experimental spectra and the spectra calculated for thiol N9H tautomer supported the identification of the dominant tautomer. It has also allowed for the reliable assignment of the bands observed in the experimental IR spectrum.

Mercaptopurine↗
PubMed2001

Photochemical syn-anti isomerization reaction in N4-hydroxycytosine. An experimental matrix isolation and theoretical study.

Infrared spectra of N4-hydroxycytosine isolated in argon and nitrogen low-temperature matrixes are reported. The compound was found to adopt the syn structure of the imino-oxo tautomeric form exclusively. A photoreaction (lambda > 250 nm) converting this form into the anti isomer was observed. The reaction is reversible and leads to a photostationary point. The initial infrared spectrum and the spectrum of the photoproduct were assigned to the syn and anti isomers, respectively. This assignment is based on a close agreement between the experimental spectra and the spectra theoretically simulated at the DFT(B3LYP)/6-31++G** level of theory.

Journal Article↗
PubMed2001

The Payment Error Prevention Program (PEPP): reducing Medicare payment errors in prospective payment system hospitals.

Peer Review Organizations (PROs) are charged by the Health Care Financing Administration (HCFA) to assist in protecting the integrity and solvency of the Medicare program. Recent audits of the Medicare program from the Office of Inspector General (OIG) revealed that more than $12 billion Medicare dollars in 1998 were spent in improper payments, with more than 25% attributed to prospective payment system (PPS) hospitals. The Payment Error Prevention Program (PEPP) is an initiative designed by HCFA in 1999 to assist PROs in meeting the goal of reducing payment errors in PPS hospitals. PEPP is implemented through the development of quality improvement (QI) methodologies. These projects are designed to achieve measurable improvements in processes and outcomes of payment errors. PEPP works to reduce payment errors at PPS hospitals through cooperative efforts with Ohio agencies and licensing boards, federal law enforcement organizations, HCFA contractors, hospital medical staffs, and medical and osteopathic associations.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1998

Spectroscopic identification of 2,4-pyrimidinedithiol; an experimental matrix isolation and ab initio Hartree-Fock and density functional theory study.

2,4-Pyrimidinedithiol (the dithiol form of 2,4-dithiouracil) was generated by UV (lambda > 335 nm) irradiation of the dithione form of 2,4-dithiouracil isolated in low-temperature argon or nitrogen matrices. The IR and UV spectra of the photoproduct are reported. The dithiol form of 2,4-dithiouracil was identified by comparison of the experimental spectrum with the spectrum theoretically predicted for this form at the HF/6-31 (d,p) and DFT(B-3LYP)/6-31 (d,p) levels. This comparison resulted also in assignment of the bands observed in the IR spectrum of 2,4-pyrimidinedithiol to the theoretically predicted normal modes.

Spectrophotometry, Ultraviolet↗
PubMed1993

Theoretical and matrix-isolation experimental studies on 2-thiocytosine and 5-fluoro-2-thiocytosine.

2-Thiocytosine (s2Cyt) and 5-fluoro-2-thiocytosine (f5s2Cyt) were studied by means of IR spectroscopy under different environmental conditions: isolated in low-temperature inert gas matrices, associated in thin amorphous and polycrystalline films. The compounds isolated in matrices were only very slightly influenced by the environment. From the analysis of the IR spectra of both compounds it appears that they exist in inert gas matrices only in the amino-thiol tautomeric form. Strong environmental effects were observed for s2Cyt and f5s2Cyt deposited in the form of thin polycrystalline films. Contrary to matrices, in polycrystalline films the amino-thione form dominates for both s2Cyt and f5s2Cyt. The experimental findings are in agreement with the ab initio quantum mechanical calculations of the relative total energies of the tautomeric forms. Those energies were calculated using the Self Consistent Field method corrected for electron correlation effects with the use of the second-order many-body perturbation theory (SCF+MBPT(2)). The theoretical calculations show that the amino-thiol tautomeric form is more stable than the amino-thione form by 38 kJ mol-1 and 48 kJ mol-1 for s2Cyt and f5s2Cyt, respectively. Both molecules, s2Cyt and f5s2Cyt, may also appear in the uracil-like imino-thione tautomeric form, which is predicted to be only 8 kJ mol-1 less stable than the amino-thione form. A new method of the preparation of f5s2Cyt is reported.

Crystallization↗
PubMed1987

Nonrandom chromosomal aberrations and clonal chromosomal evolution in acute leukemia associated with Down's syndrome.

Nine Down's syndrome (DS) children, four with acute leukemia, one with acute leukemia as well as rhabdomyosarcoma, and four with other hematologic disorders, were analyzed for constitutional and acquired chromosomal aberrations. Acquired clonal chromosomal aberrations were identified only in the acute leukemia cases, and four of the five acute leukemia demonstrated numerical and/or structural aberrations involving chromosomes #8, #19, and #21. Of the 11 aneuploid stem cell lines identified in the five acute leukemia cases, trisomy 21, trisomy 8, trisomy 19, and tetrasomy or pentasomy 21 was found in 11, seven, four, and two lines, respectively. The frequent appearance of multiple stem cell lines with common and/or overlapping chromosomal aberrations in acute leukemia cases demonstrates the existence of genomic instability and heterogeneity of the neoplastic cell population, which results from clonal chromosomal evolution. Furthermore, trisomy 19 was identified only with the concurrent presence of trisomy 8, suggesting that the nondisjunction of chromosome #19 probably occurred after that of #8. Trisomy 21 was observed in every aneuploid stem cell line and, in one case, trisomy 21 was maintained in the bone marrow leukemic cells but not in the orbital rhabdomyosarcoma cells, indicating that this constitutional chromosomal aberration is probably crucial for and predisposed to the development of acute leukemia in DS patients. The association of acquired clonal chromosomal aberrations, especially those involving chromosomes #8, #19, and #21, with DS acute leukemia strongly suggests the clinical implication of cytogenetic analysis in the diagnosis of acute leukemia development in DS patients.

Acute Disease↗
PubMed1981

Morphine dependence in rats assessed in a shock discrimination task.

The effects of chronic morphine sulfate (5 mg/kg/day for 14 days) on shock discrimination performance of rats was assessed in Experiment 1. Significant tolerance developed to the disruptive effects of morphine on performance. A significant increase in discrimination performance was found 48 h after the last injection in tests conducted without the injection environment cues present. Ten days after the chronic drug regimen, tests conducted 30 min after exposure to the injection-environment cues revealed no differences between animals previously administered morphine and control animals administered saline. In Experiment II, shock discrimination performance was assessed in a separate group of rats after exposure to a single injection of morphine sulfate (30 mg/kg), which eliminated associative processes, e.g., Pavlovian or instrumental conditioning, as factors in the subsequent behavioral tests for hyperalgesia. Significant changes in discrimination performance (primarily enhanced percent correct to the high shock stimulus) indicative of increased pain sensitivity were obtained in tests conducted 1, 2, and 3, but not 9 days after the injection. These experiments indicate that increased pain sensitivity, as opposed to hyperresponsivity operationally measured in traditional analgesia tests (e.g., hot plate, jump-flinch, and tail flick), is a component of morphine withdrawal of a nonassociative origin.

Animals↗
PubMed1980

Effects of morphine, d-amphetamine, and pentobarbital on shock and light discrimination performance in rats.

The effects of 2 and 4 mg/kg morphine sulfate, 0.5 and 1 mg/kg d-amphetamine sulfate, and 6 and 12 mg/kg pentobaribital sodium were tested in rats in two different discrete-trial two-choice discrimination tasks. The discriminative stimuli for one task were high and low intensity shocks. In the other, correct choices were signaled by the position of a brief light flash. Morphine (4 mg/kg) significantly disrupted performance of both tasks, with more reliable disturbance occurring in the shock discrimination animals. Pentobarbital (12 mg/kg), while exerting noticeable effects on gross motor behavior, had little effect on discrimination performance; d-amphetamine (1 mg/kg) was disruptive of discrimination performance in only some animals. The results indicate that much of the effect of relatively low doses of morphine on the shock discrimination performance of rats may be due not to its putative specific antinociceptive properties, but to alterations in conceptual-judgmental processes or decreases in motivation (e.g., hunger) unrelated to pain.

Animals↗