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Biomedical subjects

M Stoltz

Publications and source records attributed to M Stoltz.

At least 19 recordsLinked to original sources
PubMed2001

Phase II study of the cyclin-dependent kinase inhibitor flavopiridol administered to patients with advanced gastric carcinoma.

PURPOSE: Flavopiridol is the first cyclin-dependent kinase inhibitor to enter clinical trials. Activity in gastric cancer xenografts and in a patient with gastric cancer on the phase I trial led to this phase II study of flavopiridol in patients with metastatic gastric cancer. PATIENTS AND METHODS: Sixteen patients were entered onto the study, and 14 were assessable for response. Flavopiridol was administered initially at a dose of 50 mg/m(2)/d by continuous infusion for 72 hours every 2 weeks. Assessment of plasma pharmacokinetics was performed in all patients. Peripheral mononuclear cells were collected throughout the 72-hour infusion for determinants of apoptosis. RESULTS: There were no major objective responses (exact confidence interval 0% to 23%). One patient achieved a minor response in his liver metastases, though the primary progressed. Other patients exhibited histologic and radiographic evidence of tumor necrosis. Common toxicities included fatigue in 93% of patients (grade 3 or 4 in 27%) and diarrhea in 73% of patients (grade 3 or 4 in 20%). Five patients (33%) developed venous thromboses at the central catheter tip. The studies performed on peripheral mononuclear cells indicated no induction of apoptosis. CONCLUSION: Flavopiridol administered as a single agent for 72 hours every 14 days is inactive in the treatment of gastric cancer. The drug also induced an unexpected higher incidence of vascular thrombosis and fatigue than was anticipated from the phase I trials. Future development of flavopiridol will depend on other doses and schedules in combination with chemotherapy.

Adenocarcinoma↗
PubMed1998

Pharmacokinetics, pharmacodynamics, and tolerance of single- and multiple-dose fexofenadine hydrochloride in healthy male volunteers.

BACKGROUND: Fexofenadine is a selective, nonsedating H1-receptor antagonist that relieves symptoms of allergic conditions. METHODS: Two randomized, double-blind, parallel-group, placebo-controlled dose-escalation studies were performed in healthy men to determine the maximum tolerated oral dose, pharmacokinetics, pharmacodynamics, and safety of fexofenadine hydrochloride. In the first study, 87 subjects (6 in the active drug group and 2 in the placebo group) received single oral doses of fexofenadine hydrochloride ranging from 10 to 800 mg or placebo. In the second study, 32 subjects (3 in the active drug group and 1 in the placebo group) received multiple fexofenadine hydrochloride doses ranging from 20 to 690 mg or placebo twice daily for 28 1/2 days. Serial plasma and urine samples were collected. Fexofenadine concentrations were determined by HPLC and fluorescence. Wheal and flare response to intradermal histamine was used to evaluate antihistaminic activity. RESULTS: Fexofenadine hydrochloride was rapidly absorbed, reaching peak concentrations in 0.83 to 1.33 hours. Single-dose mean concentration ranged from 46 to 6383 ng/mL, and steady-state maximum plasma concentration ranged from 58 to 4677 ng/mL. Mean area under the plasma concentration-time curve was approximately proportional to dose. Oral clearance, renal clearance, and cumulative percent of drug excreted in urine were similar after single and multiple doses and were generally constant over the dose range studied. Inhibition of skin wheal and flare was shown for single doses of 40 mg and higher and for all multiple doses. No fexofenadine dose-related trends or apparent differences from placebo were found for any safety parameter. CONCLUSIONS: Fexofenadine hydrochloride was well tolerated at oral doses up to 11 times the recommended therapeutic dose. In addition, fexofenadine hydrochloride showed significant antihistaminic activity and dose-proportional pharmacokinetics over a wide dosing range.

Administration, Oral↗
PubMed1998

The conformational change induced by FAD in covalently flavinylated 6-hydroxy-D-nicotine oxidase does not require (8alpha)FAD-(N3)histidyl bond formation.

The contribution of (8alpha)-(N3)histidyl bond formation to the conformation of covalently flavinylated proteins was investigated by trypsin treatment of wild type and mutant versions of a model enzyme, 6-hydroxy-D-nicotine oxidase (6-HDNO) of Arthrobacter nicotinovorans. In the absence of FAD, apo-6-HDNO exhibited a conformation exposing a protease accessible site. Holoenzyme formation through FAD-attachment to His71 induced a conformational change in the protein that shielded the trypsin recognition site. This conformational change, however, did not require FAD-histidyl bond formation since trypsin resistance was also exhibited by a 6-HDNO.Cys71 mutant protein which was unable to bind FAD covalently. Replacement of Arg67, an amino acid residue supposed to be essential in flavinylation, by Ala rendered the protein protease sensitive as did replacement of Pro73 by Ala. These amino acids apparently play an essential role in stabilizing the native protein conformation. The inability to reach the native conformation also prevented FAD attachment, indicating that a specific conformation of the protein is a prerequisite for FAD-histidyl bond formation. Deletion of Phe448 and Arg449 from the 458 amino acid residues-containing enzyme resulted in complete protease sensitivity, demonstrating that flavinylation takes place posttranslationally.

Flavin-Adenine Dinucleotide↗
PubMed1996

Covalent attachment of FAD derivatives to a fusion protein consisting of 6-hydroxy-D-nicotine oxidase and a mitochondrial presequence. Folding, enzyme activity, and import of the modified protein into yeast mitochondria.

Autoflavinylation of 6-hydroxy-D-nicotine oxidase (6-HDNO) was successfully employed to modify the protein covalently with FAD derivatives. The model compounds N6-(2-aminoethyl)-FAD and N6-(6-carboxyhexyl)-FAD were spontaneously bound to a fusion protein consisting of the mitochondrial targeting sequence of Neurospora crassa F0-ATPase subunit 9 (Su9) attached to 6-HDNO. When translated in the rabbit reticulocyte lysate, Su9-6-HDNO was in the trypsin-sensitive apoenzyme form; when translated in the presence of flavins it adopted a trypsin-resistant conformation characteristic of the 6-HDNO holoenzyme. With flavin derivatives, Su9-6-HDNO exhibited approximately 50% of the 6-HDNO activity observed with FAD. The covalently modified Su9-6-HDNO was imported into Saccharomyces cerevisiae mitochondria with an efficiency equal to that of the apoenzyme. Apparently the increase in size and charge of the FAD moiety did not hamper translocation across the mitochondrial membranes. Yeast mutant ssc1-2 mitochondria deficient in mtHsp70 unfoldase activity imported the flavinylated Su9-6-HDNO protein. In mutant ssc1-3 mitochondria deficient in both mtHsp70 unfoldase and translocase activity Su9-6-HDNO was trapped as translocation intermediate; the Su9 presequence was passed to the matrix where it was proteolytically cleaved by the mitochondrial processing peptidase; (MPP); the translocation-arrested 6-HDNO moiety adopted a trypsin-sensitive conformation. Our results indicate that unfolding of the FAD-stabilized flavin-binding domain of 6-HDNO in passage through the mitochondrial general insertion pore does not require the activity of mtHsp70.

Animals↗
PubMed1996

The design of an alternative, covalently flavinylated 6-hydroxy-D-nicotine oxidase by replacing the FAD-binding histidine by cysteine and reconstitution of the holoenzyme with 8-(methylsulfonyl)FAD.

The cofactor of several flavoenzymes is autocatalytically bound to the polypeptide via a histidyl(N3)-(8alpha)-FAD linkage which makes the generation of apoenzyme difficult. We introduced an alternative covalent protein-FAD bond at the active site of 6-hydroxy-D-nicotine oxidase (6HDNO) by replacing the FAD-binding histidine with cysteine. The resulting mutant enzyme was expressed with noncovalently attached cofactor. Incubation with 8-(methylsulfonyl)FAD, and less efficiently with 8-chloro-FAD, resulted in the spontaneous replacement of the noncovalently bound FAD by the flavin derivative and the formation of an 8-(N-acetylcysteinyl)FAD linkage. The flavinylated 6HDNO.cys exhibited close to wild-type activity levels. This strategy may be generally applicable to the attachment of artificially designed flavin derivatives to the active site of covalently flavinylated enzymes.

Coenzymes↗
PubMed1996

Biogenesis of the covalently flavinylated mitochondrial enzyme dimethylglycine dehydrogenase.

Rat dimethylglycine dehydrogenase (Me2GlyDH) was used as model protein to study the biogenesis of a covalently flavinylated mitochondrial enzyme. Here we show that: 1) enzymatically active holoenzyme correlated with trypsin resistance of the protein; 2) folding of the reticulocyte lysate-translated protein into the trypsin-resistant, holoenzyme form was a slow process that was stimulated by the presence of the flavin cofactor and was more efficient at 15 degrees C than at 30 degrees C; 3) the mitochondrial presequence reduced the extent but did not prevent holoenzyme formation; 4) covalent attachment of FAD to the Me2GlyDH apoenzyme proceeded spontaneously and did not require a mitochondrial protein factor; 5) in vitro only the precursor, but not the mature form, of the protein was imported into isolated rat liver mitochondria; in vivo, in stably transfected HepG2 cells, both the precursor and the mature form were imported into the organelle; 6) holoenzyme formation in the cytoplasm did not prevent the translocation of the proteins into the mitochondria in vivo; and 7) lack of vitamin B2 in the tissue culture medium resulted in a reduced recovery of the precursor and the mature form of Me2GlyDH from cell mitochondria, suggesting a decreased efficiency of mitochondrial protein import.

Amino Acid Sequence↗
PubMed1995

Folding, flavinylation, and mitochondrial import of 6-hydroxy-D-nicotine oxidase fused to the presequence of rat dimethylglycine dehydrogenase.

We analyzed the folding, covalent flavinylation, and mitochondrial import of the rabbit reticulocyte lysate-translated bacterial 6-hydroxy-D-nicotine oxidase (6-HDNO) fused to the mitochondrial targeting sequence of rat liver dimethylglycine dehydrogenase. Translation of 6-HDNO in FAD-supplemented reticulocyte lysate resulted in a protein that contained covalently incorporated FAD, exhibited enzyme activity, and was trypsin-resistant, a characteristic of the tight conformation of the holoenzyme. The attached mitochondrial presequence did not prevent folding, binding of FAD, or enzyme activity of the 6-HDNO moiety of the fusion protein (pre-6-HDNO). Pre-6-HDNO was imported into rat liver mitochondria and processed by the mitochondrial processing peptidase. Incubation of the trypsin-resistant pre-holo-6-HDNO protein with deenergized rat liver mitochondria demonstrated that upon contact with mitochondria, the protein was unfolded and became trypsin sensitive. Mitochondrial import assays showed that the unfolded pre-holo-6-HDNO with covalently attached FAD was imported into rat liver mitochondria. Inside the mitochondrion the holo-6-HDNO was refolded into the trypsin-resistant conformation. However, when pre-apo-6-HDNO was imported only part of the protein became trypsin resistant (approximately 20%). Addition of FAD and the allosteric effector glycerol 3-phosphate to apo-6-HDNO containing mitochondrial matrix was required to transform the protein into the trypsin-resistant conformation characteristic of holo-6-HDNO.

Amino Acid Sequence↗
PubMed1995

Pharmacokinetics and pharmacodynamics of the monoamine oxidase B inhibitor mofegiline assessed during a phase I dose tolerance trial.

The safety, pharmacokinetics, and pharmacodynamics of single oral doses of up to 48 mg and daily (for 28 days) doses of up 24 mg mofegiline were investigated in healthy male volunteers. Plasma pharmacokinetics indicated rapid absorption and elimination: time to reach maximum concentration occurred at about 1 hour; half-life ranged from 1 to 3 hours. Maximal plasma concentration and area under the plasma concentration-time curve increased and oral clearance decreased disproportionately with dose. Mofegiline rapidly and markedly inhibited platelet monoamine oxidase B (MAOB) activity, which returned to baseline within 14 days. Urinary excretion of phenylethylamine increased proportionately with doses up to 24 mg. No changes in urinary elimination of catecholamines, blood pressure, heart rate, or ECG were observed. A classic maximum tolerated dose was not achieved in these studies. However, the 48 mg single dose and the 24 mg multiple daily dose far exceeded the dose (1 mg) that was associated with > 90% platelet MAOB inhibition.

Administration, Oral↗
PubMed1991

High-resolution solid-state carbon-13 nuclear magnetic resonance spectra of mofebutazone, phenylbutazone, and oxyphenbutazone in relation to X-ray crystallographic data.

The solid-state 13C NMR spectra of mofebutazone, phenylbutazone, and oxyphenbutazone monohydrate and anhydrate are presented. The crystal structures of these pyrazolidinedione derivatives, obtained by single-crystal X-ray analysis, were previously reported, revealing distinct differences in crystal structure. In this report, the chemical shift values observed for the solid-state 13C spectra are related to the chemical environment of the various carbon atoms and compared with the crystallographic data. Results indicate that solid-state NMR spectroscopy is potentially useful in the study of drugs in the solid state.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1989

Physical and structural comparison of oxyphenbutazone monohydrate and anhydrate.

Two crystal forms of oxyphenbutazone (a monohydrate and an anhydrate) were prepared by recrystallization. The forms were characterized by means of differential scanning calorimetry, thermogravimetry, infrared spectrophotometry, X-ray powder diffraction patterns, thermomicroscopy, scanning electron microscopy, as well as powder and intrinsic dissolution rates. The crystal structure of the anhydrate has been elucidated and compared with that of the monohydrate.

Calorimetry, Differential Scanning↗
PubMed1988

Physical characterization of two oxyphenbutazone pseudopolymorphs.

Two pseudopolymorphic forms of oxyphenbutazone, a benzene solvate (Solvate B) and a cyclohexane solvate (Solvate C), were prepared by recrystallization from benzene and cyclohexane, respectively. The forms were characterized by means of differential scanning calorimetry, thermogravimetry, infrared spectrophotometry, X-ray powder diffraction, and thermomicroscopy, as well as powder and intrinsic dissolution rates. The dissolution rates of the two pseudopolymorphs were shown to be superior to those of the anhydrate, hemihydrate, and monohydrate which were previously reported. A brief stability report is included.

Calorimetry, Differential Scanning↗
PubMed1981

Fractures of the radial head and neck in children.

In thirty-three children with fractures of the radial head or neck, and with a minimum follow-up of two years, fractures of the radial neck were most common. The proximal radial epiphysis was usually closed by the age of fifteen years. The older children in the series had the worst prognosis, as did children with other associated upper-extremity injuries, usually on the medial aspect of the elbow. The results were best if treatment was initiated early, and closed reduction usually gave the most satisfactory results. Roentgenograms of the involved elbow were often abnormal even with a good clinical result, but the long-term result in such situations is uncertain.

Adolescent↗
PubMed1978

Determination of uric acid on continuous-flow (AutoAnalyzer II and SMA) systems with a uricase/phenol/4-aminophenazone color test.

This report describes a new specific colorimetric procedure for uric acid assay with AutoAnalyzer II and SMA (Technicon) systems, made specific by the application of uricase. Hydrogen preroxide, formed in this reaction, effects the oxidative coupling of 4-aminophenazone and 2,4-dichlorophenol under the catalytic influence of peroxidase. The red dye formed is measured at 505 or 520 nm. A sample blank measurement is not necessary, and the reagents show very good stability. The test shows linearity up to 714 mumol of uric acid per liter. Results of thie method correlate very well with those by the uricase-ultraviolet and uricase--catalase methods. There is no interference by hemoglobin, bilirubin, lipemia, and various drugs, except a minor interference by alpha-methyldopa. Interference from ascorbate is eliminated by ascorbate oxidase. This method can be regarded as a considerably improved routine test for uric acid on continuous-flow systems in clinical laboratories as compared with the commonly used phosphotungstate method.

Aminopyrine↗