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Biomedical subjects

C M Metzler

Publications and source records attributed to C M Metzler.

At least 19 recordsLinked to original sources
PubMed1992

Pharmacokinetics and pharmacodynamics of oral diazepam: effect of dose, plasma concentration, and time.

Eleven healthy subjects received single oral doses of placebo, 2 mg diazepam, 5 mg diazepam, and 10 mg diazepam in a randomized four-way crossover study. Plasma diazepam levels, the Digit Symbol Substitution Test (DSST), and fraction of total electroencephalographic (EEG) amplitude falling in the sigma plus beta (13 to 31 Hz) frequency range were determined during the 12 hours after drug administration. Peak plasma diazepam concentration and area under the 12-hour curve were proportional to dose; time of peak was independent of dose. Baseline percentage of EEG amplitude falling in the 13 to 31 Hz range averaged 15.7% and did not differ among the four trials. The percentage of EEG amplitude falling in the 13 to 31 Hz range did not change over baseline with placebo or 2 mg diazepam but was increased 1/4 to 2 1/2 hours after 5 mg diazepam, (maximum, +7.3%) and 3/4 to 12 hours after 10 mg diazepam (maximum, +15.2%). The increase in the percentage of EEG amplitude falling in the 13 to 31 Hz range was highly correlated with plasma diazepam concentration. DSST scores for placebo and 2 mg diazepam were nearly identical. DSST decrements with 5 and 10 mg diazepam paralleled and were correlated with the changes in the percentage of EEG amplitude falling in the 13 to 31 Hz range and with plasma diazepam levels. Thus the EEG analysis provides objective quantitation of benzodiazepine central nervous system effects, in turn reflecting plasma levels and other clinical measures.

Administration, Oral↗
PubMed1991

NMR observation of exchangeable protons of pyridoxal phosphate and histidine residues in cytosolic aspartate aminotransferase.

Observation of the 93-kDa cytosolic aspartate aminotransferase by 500-MHz 1H NMR spectroscopy in H2O has revealed a series of resonances in the 10-18 ppm range arising from exchangeable protons. One of these (peak A) has been assigned to the proton bound to the ring nitrogen of the coenzyme pyridoxal 5'-phosphate. A second (peak B) is assigned to H143 which participates in a chain of hydrogen bonds that includes also the coenzyme-bound proton. There is a mutual nuclear Overhauser effect between these two resonances. Peaks A and B respond to changes in pH and to interaction of the enzyme with coenzyme derivatives and inhibitors. Peak A moves from 15.4 to 17.4 ppm as the pH is lowered, while peak B moves in the opposite direction from 14.7 to 13.7 ppm, both with an apparent pKa of 6.15. This pKa is associated with deprotonation of the imine nitrogen at the Schiff base linkage of the coenzyme with K258 of the enzyme. In spectra of enzyme containing pyridoxamine 5'-phosphate, peak A is observed at 16.5 ppm and peak B is at 13.9 ppm over a broad pH range. Peaks A and B are found at 17.8 and 14.0 ppm, respectively, for the enzyme complex with glutarate. When alpha-methylaspartate is added to the enzyme several new resonances appear in the spectrum, which are attributed to formation of the external aldimine. The position of peak A in spectra of various forms of the enzyme is interpreted to reflect the electronic distribution in the coenzyme ring. Several other peaks in this region of the spectrum also are sensitive to changes in pH or the addition of inhibitors. Some possible assignments of these resonances are discussed.

Aspartate Aminotransferases↗
PubMed1991

NMR spectra of exchangeable protons of pyridoxal phosphate-dependent enzymes.

We have recorded 1H NMR spectra in H2O for exchangeable protons of four pyridoxal phosphate-dependent enzymes: D-serine dehydratase, aspartate aminotransferase, tryptophan: indole-lyase and glutamate decarboxylase. The molecular masses range from 48-250 kDa. In every case there are downfield peaks which are lost when the apoenzyme is formed. In most cases some peaks shift in response to interactions with substrates and inhibitors and with changes in pH. We associate one downfield resonance with the proton on the ring nitrogen of the coenzyme and others with imidazole groups that interact with coenzyme or substrates. The chemical shift for the coenzyme-bound proton differs for free enzyme, substrate Schiff base or quinonoid forms.

Animals↗
PubMed1991

Equilibria and absorption spectra of tryptophanase.

Tryptophanase (tryptophan: indole-lyase) from Escherichia coli has been isolated in the holoenzyme form and its absorption spectra and acid-base chemistry have been reevaluated. Apoenzyme has been prepared by dialysis against sodium phosphate and L-alanine and molar absorptivities of the coenzyme bands have been estimated by readdition of pyridoxal 5'-phosphate. The spectrophotometric titration curve, whose midpoint is at pH 7.6 in 0.1 M potassium phosphate buffers, indicates some degree of cooperativity in dissociation of a pair of protons. Resolution of the computed spectra of individual ionic forms of the enzyme with lognormal distribution curves shows that band shapes are similar to those of model Schiff bases and of aspartate aminotransferase. Using molar areas from the latter we estimated amounts of individual tautomeric species. In addition to ketoenamine and enolimine or covalent adduct the high pH form also appears to contain approximately 18% of a species with a dipolar ionic ring (protonated on the ring nitrogen and with phenolate -O-). We suggest that this may be the catalytically active form of the coenzyme in tryptophanase. The equilibrium between tryptophanase and L-alanine has also been reevaluated.

Escherichia coli↗
PubMed1991

Sample sizes for bioequivalence studies.

In recent years a number of decision rules, based on sound statistical principles, have been proposed for deciding if a test formulation is bioequivalent to a reference formulation. The decision rule based on confidence intervals has been accepted by regulatory agencies, at least by the Food and Drug Administration of the United States. A useful property of this decision rule is that the regulatory agency need not require a certain sample size, since the level of protection against wrongly deciding bioequivalence is set by the choice of the alpha level used to compute the confidence intervals. The manufacturer claiming bioequivalence is concerned about sample size, for sample size determines the probability of falsely deciding non-bioequivalence when the test formulation does indeed have an acceptable relative bioavailability. Curves of probability of rejecting bioequivalence have been computed for error coefficient of variation of 10, 20 and 30 per cent, for relative bioavailability from 70 to 130 per cent, and for protection levels of 90 and 95 per cent. These curves can be used for choosing the sample size for a bioequivalence study.

Bayes Theorem↗
PubMed1990

Lack of effect of fluoride on reproductive performance and development in Shetland sheepdogs.

A 10-y history of high rates of perinatal deaths and congenital anomalies in dogs in a Shetland Sheepdog kennel prompted investigations into the cause(s). Skeletal fluorosis (mottled teeth in pups, bony exostoses in adults) followed use of a commercial dog food later found to contain 460 ppm fluoride (F) from rock phosphate added as a mineral source. The effects of the water source and fluoride in dog food on female reproduction and teratogenicity were investigated in a 2-y, 2-way factorial study in the kennel. Twenty adult shelties of proven fertility were brought into the kennel and randomized into 4 treatment groups, each consisting of 4 females and 1 male. Treatments were: Group A, high F (460 ppm) dog food, well water; Group B, high F dog food, distilled water; Group C, low F (55ppm) dog food, well water; Group D, low F dog food, distilled water. Only Group C produced as many pups as expected. Overall the missed pregnancy rate (44%) in study bitches and perinatal death rate (50%) in 48 study pups paralleled the problems in shelties resident in the kennel. Higher rates for both variables in the high F and the distilled water groups seemed likely due to chance. The only major anomaly was in Group D; minor anomalies appeared in all groups. Although 460 ppm F in dog food did produce bony exostoses, we did not find convincing evidence that it adversely affected reproduction in shelties. The cause of the reproductive problems was apparently not the dog food, water, foliage, genetic factors, or infectious disease and currently remains undetermined.

Abnormalities, Drug-Induced↗
PubMed1989

Reactions of phosphonate analogs of pyridoxal phosphate with apo-aspartate aminotransferase.

We have investigated reactions of the 5-phosphonoethyl and 5-phosphonoethenyl analogs of pyridoxal 5'-phosphate in the coenzyme site of cytosolic aspartate aminotransferase. Acid dissociation constants and equilibrium constants for hydration and for tautomerization have been evaluated for these compounds. In confirmation of previous results, both compounds are partially active. They bind to apoenzyme well and undergo conversion in the presence of glutamate to amine forms which show induced circular dichroism comparable to that of native enzyme. A normal "external" Schiff base is evidently formed with 2-methylaspartate, but the amounts of quinonoid intermediate formed with erythro-3-hydroxyaspartate are less than those formed with pyridoxal phosphate. The pKa of the imine group of the enzyme reconstituted with the phosphonoethyl analog is more than two units lower than that in the native enzyme. Binding of the dicarboxylates glutarate, 2-oxoglutarate, and succinate shifts the pKa upward. The absorption spectra of the resulting complexes indicate the existence of at least three low pH species. A shift of 2.3 to 2.9 ppm to a lower frequency was observed for the 31P NMR signal upon binding of these dicarboxylates or of 2-methylaspartate. Enzyme containing the analogs crystallizes. Polarized absorption spectra suggest that the coenzyme has an orientation similar to that of pyridoxal phosphate in the native enzyme.

Amines↗
PubMed1989

The effects of cefmetazole and latamoxef on platelet function in healthy human volunteers.

This study has compared the effects of normal saline (placebo), cefmetazole, and latamoxef (moxalactam) on platelet function in healthy human volunteers. Twenty-nine volunteers were randomized to receive placebo (n = 10), cefmetazole 2 g (n = 9) or latamoxef 2 g (n = 10) intravenously every 6 h for six days. Under double-blind conditions template bleeding time and ex-vivo adenosine diphosphate (ADP) induced platelet aggregation were measured before drug dosing, after the first, ninth, and last drug doses and one and three days after the last drug dose. Latamoxef caused progressive impairment of platelet function with statistically significant increases in the mean bleeding time to 7.4 +/- 3.7 min (P = 0.02) and the amount of ADP (0.2 mM) required to induce 50% platelet aggregation to 77.3 +/- 91.1 microliters (P = 0.03) on day 6 of treatment compared with values before drug administration (4.2 +/- 0.7 min; 3.7 +/- 22 microliters, respectively). These changes were reversible following discontinuation of drug dosing. Cefmetazole and placebo had no significant effects on either measure of platelet function at any time during the study.

Adenosine Diphosphate↗
PubMed1989

Clinical experience with cefmetazole sodium in the United States: an overview.

The clinical development programme for cefmetazole sodium included over 4000 patients treated by 78 investigators. Cefmetazole therapy was compared with that of cefoxitin sodium (cefoxitin) for the treatment of urinary tract, skin and soft tissue, lower respiratory, abdominal, and gynaecological infections (with cefoxitin-sensitive pathogens) and for the prevention of postoperative wound infection in patients undergoing surgical procedures. Both cefmetazole and cefoxitin were administered intravenously in all studies. Cefmetazole was as effective as cefoxitin in the treatment of the infections studied. In the surgical wound infection prophylaxis studies, multiple-dose cefmetazole therapy was more effective than multiple-dose cefoxitin therapy in patients undergoing lower gastrointestinal surgery; this difference approached statistical significance. Both multiple-dose and single-dose cefmetazole therapy were as effective as multiple-dose cefoxitin treatment in the other types of surgery studied. Clinical laboratory findings and adverse medical events reported among cefmetazole patients were similar to those observed in patients treated with cefoxitin.

Bacterial Infections↗
PubMed1988

Correlation of polarized absorption spectroscopic and X-ray diffraction studies of crystalline cytosolic aspartate aminotransferase of pig hearts.

Absorption spectra of large, well-formed crystals of cytosolic aspartate aminotransferase have been recorded using plane polarized light. Making use of measurements of crystal thickness we have calculated extinction coefficients with the electric vector of the light parallel to both the a and c axes of the crystals of the enzyme in space group P2(1)2(1)2(1). The spectra have been resolved into components with lognormal distribution curves and the resulting integrated intensities have been used to calculate the c/a polarization ratios for the absorption bands of the bound co-enzyme pyridoxal 5'-phosphate. From the polarization ratio and the co-ordinates of the co-enzyme ring atoms, provided by X-ray crystallography, we have assigned principal molecular directions of the transition dipole moment within the plane of the co-enzyme ring. Of two possible orientations, only one predicts the correct crystal extinction coefficients for the 436 nm band. In this orientation, when viewed from the B face of the ring (i.e. looking into the active site of the enzyme), the transition moment is related to the N-1-C-4 axis of the ring by counterclockwise rotation by 27 degrees. A tentative assignment of the principal molecular directions of the transition moment has also been made for the 368 nm band of the high pH form of the enzyme. In each case, the plane of the co-enzyme ring was located from the atomic co-ordinates of the ring atoms and of those atoms attached directly to the ring. The projection of the N-1 to C-4 axis on to this plane was used to evaluate the orientation of the transition moment, which was presumed to lie precisely within the plane of the ring. We have tilted this plane systematically to evaluate the error in transition moment direction resulting from uncertainties in the atomic co-ordinates. When 2-methylaspartate is diffused into the crystals if forms a Schiff base with the co-enzyme in which the ring has tilted about 32 degrees from its original position and the polarization ratio of the 436 nm band drops from 1.6 in the free enzyme to about 0.38. On the assumption that the orientation of the transition moment within the co-enzyme does not change during this rotation, this value of the polarization ratio is within experimental error of that predicted from X-ray structures on the two forms. The 2-methylaspartate binds only to subunit 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Spectroscopic studies of quinonoid species from pyridoxal 5'-phosphate.

To establish the state of protonation of quinonoid species formed nonenzymically from pyridoxal phosphate (PLP) and diethyl aminomalonate, we have studied absorption spectra of the rapidly established steady-state mixture of species. We have evaluated the formation constant and the spectrum of the mixture of Schiff base and quinonoid species. For N-methyl-PLP a singly protonated species with a peak at 464 nm is formed from the unprotonated aldehyde and the conjugate acid of diethyl aminomalonate with a formation constant Kf of 240 M-1. The very intense absorption band with characteristic vibrational structure (most evident as a shoulder at 435 nm) is accompanied by a weaker, structured band at about 380 nm and a weak, broad band at 330 nm. We suggest that the 380-nm band may represent a tautomeric form of the quinonoid compound. Protonation of the phosphate group appears to affect the spectrum only slightly. The corresponding mixture of Schiff base and quinonoid species formed from PLP has a very similar spectrum at pH 6-7. It has a formation constant Kf of 230 M-1 and a pKa of 7.8, which must be attributed to the ring nitrogen atom. The dissociated species, which may be largely carbanionic, has a strong structured absorption band at 430 nm and a weaker one, again possibly a tautomer, in the 330-nm region. The analysis establishes that in all species a proton remains on either the phenolic oxygen or the imine nitrogen. Proton NMR spectroscopy, under some conditions, reveals only two components: free PLP and what appears to be Schiff base. However, we suggest that the latter may, in fact, be a quinonoid form, either alone or in rapid equilibrium with the Schiff base. Absorption spectra of quinonoid species formed in enzymes are analyzed and compared with the spectra of the nonenzymic species.

Chemical Phenomena↗
PubMed1988

Effects of a fish oil concentrate in patients with hypercholesterolemia.

The effects of a fish oil supplement on lipid and lipoprotein levels, platelet function, and vital signs were investigated in 31 hypercholesterolemic patients. Thirteen patients took 5 g of encapsulated fish oil per day and 18 patients took 5 g of encapsulated safflower oil "placebo" per day for 28 days. Diet and exercise patterns were kept as constant as possible during the study. The fish oil group had significant increases in several lipid/lipoprotein values at the end of the treatment, including an increase of total cholesterol of 14% (P = 0.0001), LDL of 16% (P = 0.003), HDL of 13% (P = 0.015) and HDL2 of 36% (P = 0.009). The triglyceride level fell 24%, a nonsignificant change (P = 0.217). The ratios of total cholesterol/HDL and LDL/HDL were increased at the end of fish oil treatment, and returned to baseline 30 days after fish oil was stopped. The placebo group had no significant changes in any of the lipid/lipoprotein values. Neither the fish oil nor the placebo group had significant changes in vital signs or platelet function tests (bleeding time, thromboxane B2, platelet factor 4 and beta-thromboglobulin) during the study. These results suggest that fish oil supplements may have an adverse effect on lipid/lipoprotein values in hypercholesterolemic patients.

Adolescent↗
PubMed1988

Ciprostene in patients with peripheral vascular disease (PVD). An open-label, tolerance trial.

Epoprostenol (Prostacyclin) has been studied with various success in patients with peripheral vascular disease (PVD). We investigated the tolerance of a new, stable prostacyclin derivative ciprostene (9-beta-methyl carbacyclin) in 9 PVD patients. The drug was infused intravenously for 8 hours a day, once a week for 4 consecutive weeks, at a dose of 120 ng/kg/min. There were 6 men and 3 women with a mean age of 63 years (42-78). The PVD was verified by arteriography (9 patients) and by clinical findings. Patient #9 was lost to follow up after the first infusion and, consequently, was excluded from further evaluation. In patient #5 with a history of arrhythmias, the last ciprostene infusion had to be discontinued at 4.5 hours due to arrhythmias but his data were included into the evaluation. The cardiac disturbances were not judged to be ciprostene-related. Patients were followed monthly for 3 months after last infusion. Ciprostene was well tolerated although it produced adverse medical events (AMEs); most of them were rated as mild. The most frequent were those typical of prostacyclin: headache, facial flushing and warmth, body warmth, jaw pain and sleepiness. No consistent changes in blood pressure and heart rate were observed. One patient who initially had 9 ischemic ulcers underwent transmetatarsal amputation at month 4. The absolute and relative claudication time was measured by treadmill. As compared to baseline, the absolute claudication time increased significantly at week 2 and 4 of the infusion period and also at the end of month 3, but not at the end of month 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Nasal airway response to infused phenylephrine in normals and in patients with allergic and non-allergic rhinitis.

To find whether patients with chronic rhinitis might be congested because of hyporesponsiveness to adrenergic vasoconstrictive influences, we measured nasal airway resistance (NAR) in normals and allergic and non-allergic rhinitics during intravenous infusion of graded doses of phenylephrine. All responded with decreases in NAR and first evidences of NAR fall appeared no later in those with rhinitis than in normals. Nasal congestion and response were asymmetrical; absolute NAR in the low resistance side was similar in all groups and there was little response to phenylephrine. In the high resistance side, NAR reached its minimum by the time the total infused dose was 1400 mcg, indicating maximum response to drug was achieved within the dose range studied. Minimum NAR achieved on the high resistance side was higher in rhinitics suggesting residual vascular engorgement resistant to phenylephrine or non-vascular mucosal swelling. Resistance to adrenergic vasoconstriction does not appear to be the primary contributor to mucosal swelling in chronic rhinitis.

Airway Resistance↗
PubMed1987

Quantitative description of absorption spectra of a pyridoxal phosphate-dependent enzyme using lognormal distribution curves.

Ultraviolet-visible absorption spectra of cytosolic aspartate aminotransferase of pig hearts have been analyzed by resolution with lognormal distribution curves. These have been compared with spectra of reference Schiff bases of pyridoxal 5'-phosphate. Spectra of the free enzyme in two different states of protonation and of complexes with monoanions, dicarboxylates, the substrates L-glutamate, L-aspartate, and L-erythro-3-hydroxyaspartate, and the quasi-substrate 2-methylaspartate have been analyzed. Relative amounts of three tautomeric species have been estimated, as have amounts of various enzyme-substrate intermediates. Bandshape parameters which can be used as a guide to analysis of spectra of other pyridoxal phosphate-dependent enzymes are tabulated. Some formation constants and pKa values, which were evaluated at the same time as the spectra of the complexes, are also reported.

Animals↗
PubMed1987

The effect of itazigrel and aspirin on the mucosa of the esophagus, stomach, and duodenum of normal subjects.

The effects of aspirin, itazigrel (U-53,059; a new antiplatelet drug), and placebo on the mucosa of the esophagus, stomach, and duodenum were evaluated in this double-blind, randomized, placebo-controlled study. Six normal male subjects were included in each of five treatment groups: aspirin (325 mg each morning for five doses), aspirin (325 mg tid for 12 doses), itazigrel (25 mg each morning for five doses), itazigrel (50 mg tid for 12 doses), and placebo. Aspirin and itazigrel, at all doses investigated, significantly inhibited ex vivo, ionophore (A23187)-stimulated thromboxane B2 synthesis. Collagen-induced platelet aggregation was significantly inhibited on day 3 (P = .021) and day 5 (P = .002) in both aspirin and itazigrel groups as compared with placebo. Upper gastrointestinal endoscopy was performed before the first dose of drug (day 1) and two hours after the last dose (day 5) for each subject. A rating scale was used to score the amount of mucosal damage. The baseline (day 1) endoscopic scores revealed no significant differences between groups. On day 5, neither placebo nor itazigrel treatment groups showed any significant change compared with baseline. On day 5, both aspirin groups had significantly (P less than .001) more mucosal damage than the placebo group and either itazigrel group. It is concluded that in this relatively acute study, at doses that produce comparable inhibition of platelet aggregation and platelet cyclo-oxygenase, itazigrel was superior to aspirin in terms of toxicity to the upper gastrointestinal tract.

Adolescent↗