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Biomedical subjects

I Nowak

Publications and source records attributed to I Nowak.

17 recordsLinked to original sources
PubMed1998

Pharmacokinetics of mycophenolic acid in renal transplant patients with delayed graft function.

The pharmacokinetics of mycophenolic acid (MPA), the immunosuppressant form of the prodrug mycophenolate mofetil (MMF), and the primary glucuronide metabolite, MPAG, were characterized in renal transplant patients with delayed graft function using random effects piecewise linear models. Eight patients were evaluated after receiving their first and subsequent daily oral doses of 1.5 g mycophenolate mofetil twice daily on study days 1 (n = 8), 7 (n = 8), 14 (n = 5), 21 (n = 2), and 28 (n = 7). The area under the concentration-time curve from zero to 12 hours (AUC0-12) for MPA, MPAG, MPA free fraction, and free MPA were analyzed in serial plasma samples using validated high-performance liquid chromatography and ultrafiltration procedures. Random effects piecewise linear models, fit by maximum likelihood methods, were applied to AUC0-12 of MPA and MPAG, MPA free fraction, AUC0-12 of free MPA, and serum creatinine concentration, the index of renal function used in this study. Two hemodialysis sessions did not lower MPA plasma concentration, although some MPAG was removed. The AUC0-12 of MPA increased as a function of time, although it was not possible to fit a statistical model to the data due to considerable among-patient variation in the pattern of increase with time. The AUC0-12 of MPAG, MPA free fraction, and AUC0-12 of free MPA reached maximal values on day 7; each of these parameters had unique day 1 to 7 positive slope values and unique day 7 to 28 negative slope values. The average creatinine concentration was maximal at day 1 and a unique negative slope was obtained between days 7 and 28. Thus, this study provides statistical models for the alteration of AUC0-12 of MPAG, MPA free fraction, AUC0-12 of free MPA, and serum creatinine in renal transplant patients with delayed graft function. These results provide evidence that renal dysfunction is associated with altered pharmacokinetics of MPA, particularly increased AUC0-12 of MPAG, MPA free fraction, and AUC0-12 of free MPA. The perturbed pharmacokinetics normalized with improving renal function.

Adult↗
PubMed1998

Suppression of proliferation and phosphorylation of Jak3 and STAT5 in malignant T-cell lymphoma cells by derivatives of octylamino-undecyl-dimethylxanthine.

IL-2R signal transduction involves tyrosine phosphorylation of several proteins including Jak3 and STAT5. In the present study we examined the effect of two octylamino-undecyl-dimethylxanthine (OUDMX) derivatives, designated CT2576 and CT5589, on proliferation and protein tyrosine phosphorylation in human malignant T-cell lymphoma lines. These T-cell lines (PB-1, 2A, and 2B), obtained from a progressive T-cell lymphoma involving skin, are IL-2 independent but have constitutively activated IL-2R-associated signal transduction pathway common to IL-2 and several other cytokines: IL-4, IL-7, IL-9, and IL-15. CT2576, characterized previously on the functional level as an inhibitor of IL-2 signaling and, on the biochemical level, as an inhibitor of phosphatidic acid biosynthesis, suppressed completely growth of the malignant T cell lymphoma lines. CT5589 which is a novel analog of the CT2576, displayed a similar, although weaker, effect. Furthermore, both CT compounds inhibited constitutive tyrosine phosphorylation of two proteins: Jak3 and STAT5 which are key downstream elements in the signal transduction pathway activated by IL-2 and the other cytokines. The CT compounds inhibited also Jak3 phosphorylation induced by IL-2 in the IL-2 dependent SZ-4 cells. Inhibition of phosphorylation by CT2576 and CT5589 was only partially selective since phosphorylation of several other proteins was also affected. Phosphorylation of many others was, however, unaffected. These findings demonstrate that the OUDMX derivatives suppress proliferation of malignant T lymphocytes. Furthermore, they suggest that this suppression may be mediated by inhibition of the IL-2R-associated Jak/STAT signaling pathway. A potential role for OUDMX derivatives in therapy of human T-cell lymphoma should be further explored.

Antineoplastic Agents↗
PubMed1997

Effect of mycophenolic acid glucuronide on inosine monophosphate dehydrogenase activity.

Mycophenolic acid glucuronide (MPAG) inhibition kinetics were evaluated using purified recombinant human type II inosine monophosphate dehydrogenase (IMPDH). MPAG inhibitory concentrations (IC50) were found to be 532- to 1022-fold higher than those for MPA. As expected, according to tight-binding inhibitor kinetics, mycophenolic acid (MPA) IC50 values increased as IMPDH concentrations increased, whereas IC50 values for xanthosine monophosphate (competitive IMPDH inhibitor used as control), an inhibitor known not to be tight binding, remained independent of enzyme concentration. Although MPAG exhibited only weak inhibition of IMPDH activity, in comparison with MPA, IC50 values increased with increasing enzyme concentration. The presence of trace quantities of MPA (0.2% on a molar basis) in the MPAG preparation, detected by high-performance liquid chromatography analysis, could account for this observation. These data support the proposal that MPAG is a pharmacologically inactive metabolite of MPA.

Chromatography, High Pressure Liquid↗
PubMed1996

Activation of Jak/STAT proteins involved in signal transduction pathway mediated by receptor for interleukin 2 in malignant T lymphocytes derived from cutaneous anaplastic large T-cell lymphoma and Sezary syndrome.

Signaling through the interleukin 2 receptor (IL-2R) involves phosphorylation of several proteins including Jak3, STAT5, and, in preactivated cells, STAT3. In the present study, we examined the functional status of the IL-2R-associated Jak/STAT pathway in malignant T lymphocytes from advanced skin-based lymphomas: anaplastic large T-cell lymphoma (ALCL) and Sezary syndrome (SzS). Proliferation of three ALCL cell lines (PB-1, 2A, and 2B) was partially inhibited by rapamycin, a blocker of some of the signals mediated by IL-2R, but not by cyclosporin A, FK-506, and prednisone, which suppress signals mediated by the T-cell receptor. All the cell lines expressed on their surface the high-affinity IL-2R (alpha, beta, and gamma c chains). They showed basal, constitutive phosphorylation, and coassociation of Jak3, STAT5, and STAT3. Weak basal phosphorylation of IL-2R gamma c was also detected. In regard to SzS, peripheral blood mononuclear cells from 10 of 14 patients showed basal phosphorylation of Jak3, accompanied by phosphorylation of STAT5 in 9 patients, and STAT3 in 4 patients. However, in vitro overnight culture of SzS cells without exogenous cytokines resulted in markedly decreased Jak3 and STAT5 phosphorylation, which could be reversed by stimulation with IL-2. This indicates that the basal phosphorylation of Jak3 and STAT5 in freshly isolated SzS cells is induced rather than constitutive. The basal activation of the Jak/STAT pathway involved in IL-2R signal transduction in ALCL and SzS cells reported here suggests that this pathway may play a role in the pathogenesis of cutaneous T-cell lymphomas, although the mechanism (induced versus constitutive) may vary between different lymphoma types.

Cell Membrane↗
PubMed1995

Mycophenolic acid: measurement and relationship to pharmacologic effects.

Validated high-performance liquid chromatographic (HPLC) methods have been developed for the reliable measurement in plasma of mycophenolate mofetil (MMF), mycophenolic acid (MPA), its pharmacologically active metabolite, and mycophenolic acid glucuronide (MPAG), the inactive and primary metabolite of MPA. Using these validated HPLC methods, the pharmacokinetic behavior of MMF has been characterized in renal transplant patients as part of double-blind randomized multicenter clinical trials. The analytical performance characteristics of the HPLC methods are described. Based on investigations of the metabolism of MMF in animals, normal volunteers, and renal transplant patients, it has been established that MMF is rapidly converted to MPA. MPAG is the primary urinary excretion product derived from MPA. In vitro binding studies have revealed that MPA is extensively bound to plasma proteins and that human serum albumin is the primary binding protein. Pharmacokinetic studies have revealed the following: (1) MPA exhibits enterohepatic circulation in humans as a result of biliary excretion of MPAG followed by MPA production in the gastrointestinal tract and the appearance of secondary MPA peaks in plasma; (2) chronic renal impairment produces little change in the clearance of MPA but a marked decrease in plasma MPAG clearance, with a consequent substantial increase in the circulating MPAG concentration; and (3) pharmacokinetic/pharmacodynamic (PK/PD) studies have revealed a good correlation between drug exposure (AUC) and the probability of rejection. The implications of the PK/PD studies for the development of TDM practices are discussed.

Antibiotics, Antineoplastic↗
PubMed1995

Mycophenolic acid binding to human serum albumin: characterization and relation to pharmacodynamics.

Mycophenolate mofetil, the prodrug form of the immunosuppressive agent mycophenolic acid (MPA), is currently in clinical trials evaluating its effectiveness in transplant recipients. In this study, we validated an ultrafiltration system for the reliable measurement of free MPA. Using this technique, we evaluated factors that might be important in modulating the free fraction of this drug. Human serum albumin (HSA), high concentrations of the primary glucuronide metabolite of MPA, and sodium salicylate significantly affected MPA binding. For HSA the mean +/- SE binding capacity (Bmax) and the dissociation constant (Kd) were 1095 +/- 34 mumol/L and 12.98 +/- 0.93 mumol/L, respectively. The dose for 50% inhibition (IC50) of inosine monophosphate dehydrogenase isoform II by MPA increased 5.4-fold as the concentration of HSA added to the enzyme reaction mixture increased from 0 to 50 g/L (0-724 mumol/L). Furthermore, the IC50 MPA concentration for phytohemagglutinin A-stimulated human peripheral blood mononuclear cells increased 4.8-fold when incubations were performed in the presence of 10 g/L (145 mumol/L) HSA vs no added HSA. These data support the hypothesis that the pharmacological activity of MPA is a function of unbound drug concentration.

Dialysis↗
PubMed1987

Isolation of a cDNA and characterization of the 5' flanking region of the gene encoding the type I regulatory subunit of the cAMP-dependent protein kinase.

A bovine cDNA probe for the type I regulatory subunit of the cAMP-dependent protein kinase [Lee et al. (1983) Proc. Natl Acad. Sci. USA 80, 3608-3612] was used to screen two lambda gt11 libraries constructed from poly(A)-rich RNA from the porcine kidney cell line, LLC-PK1. A series of overlapping clones were isolated and characterized. The largest clone, lambda RI15, of 1426 bp was found to code for the entire RI protein but was apparently missing the 3' end of the mRNA. The porcine cDNA codes for a protein of 389 amino acids that shows 99% homology to bovine RI and hybridizes to two major mRNA transcripts of approximately 2.0 kb and 4.5 kb from LLC-PK1 cells. The porcine cDNA for RI was used to screen a genomic library of LLC-PK1 DNA constructed in the EMBL-3 vector and several clones were isolated and characterized. By using a probe from the 5' end of the RI cDNA we isolated the 5' end of the gene and 700 bp of the promoter region of the gene were sequenced. The promoter region lacks a characteristic TATA box but contains two inverted CAAT boxes and is rich in G + C residues. Several sequence motifs were identified in the 5' promoter region which could be responsible for the regulation of synthesis of this gene. Multiple transcription initiation sites were identified by S1 nuclease mapping.

Animals↗
PubMed1987

An isoelectric focusing study of acid phosphatase heterogeneity in rat liver.

The different forms of acid phosphatase (EC 3.1.3.2) in rat liver homogenates, lysosomal, mitochondrial, microsomal fractions and cytosol were studied with isoelectric focusing. Evidence is presented that isoelectric focusing of acid phosphatase in subcellular fractions shows individual changes and time related patterns. Mild autolysis shifted all enzyme activity peaks of isoelectric focusing patterns to the one at pH 7.04.

Acid Phosphatase↗
PubMed1984

Raman and infrared studies of homogeneous forms of acid phosphatase from rat liver.

Raman spectra of acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) forms from rat liver in water solution, and infrared spectra of the same forms as thin films, have been investigated. The spectra show strong bands belonging to phosphodiester or phosphomonoester residues. These groups are modified during the postsynthetic modification of acid phosphatase and are probably connected with the process of bonding and splitting of mannose 6-phosphate and N-acetylglucosamine, in agreement with previous biochemical models for the intracellular transport of newly synthesized lysosomal hydrolases to lysosomes. Some other bands in the infrared spectra are assigned to vibrations of N-H groups which may belong to N-acetylglucosamine.

Acid Phosphatase↗
PubMed1978

Influence of heating and keeping warm on the quality of meals.

Meals produced on a large scale for public feeding establishments (sterilized, quick frozen, cooled) have to be heated before they are served. Meals prepared in central kitchens are kept warm for several hours. The influence of heating and holding is explained with quick frozen meals being kept warm as examples. If quick frozen meals in multi-portion trays are heated (hot-air oven) under unfavourable conditions and up to high central temperatures, the content of the various vitamins is notably reduced. Vegetable meals also show an inferior sensorical quality. The meals should be kept warm in a way that, on the one hand, microbiological risks are avoided and that, on the other, quality changes are minimized. The higher the holding temperature, the more thermolabile ingredients are destructed. During a holding time up to 5 hours at temperatures ranging from 60 degrees C to 80 degrees C, losses to varying degrees of vitamins C, B1, B2, niacin, retinol and beta-carotin occurred in nearly all meals. A holding time of max. 3 hours seems possible if a certain detraction from the nutrition-physiological and sensorical quality is tolerated.

Cooking↗
PubMedDate not supplied

Serum cytoplasmic and mitochondrial aspartate aminotransferase in Duchenne's progressive muscular dystrophy.

The activities of cytoplasmic and mitochondrial aspartate aminotransferase isoforms in serum in 20 outpatients with Duchenne's progressive muscular dystrophy and seven carriers of the gene of that disease were determined. The control group consisted of 19 patients with other neuromuscular disorders. Twenty, age-matched healthy persons comprised the normal control group. The activity of the cytoplasmic isoform was increased in 85% of Duchenne's dystrophy cases. In these cases the reaction of the cytoplasmic isoenzyme in the presence of pyridoxal 5'-phosphate was abnormal. In the remaining Duchenne's dystrophy cases normal activity of this isoform and normal stimulation to pyridoxal 5'-phosphate was found. The mitochondrial isoform was significantly increased in 30% of Duchenne's dystrophy cases. In all Duchenne's dystrophy patients the reaction of the mitochondrial isoenzyme to supplementation with pyridoxal 5'-phosphate was normal. We conclude that the evaluation of aspartate aminotransferase isoforms in serum in Duchenne's dystrophy can be of clinical importance, especially in evaluating the degree of muscle cell damage.

Aspartate Aminotransferases↗