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Biomedical subjects

M A Gonzalez

Publications and source records attributed to M A Gonzalez.

At least 55 records · Page 3Linked to original sources
PubMed1989

Insertion of the SfMNPV polyhedrin gene into an AcMNPV polyhedrin deletion mutant during viral infection.

The Autographa californica nuclear polyhedrosis virus (AcMNPV) polyhedrin deletion mutant, d10A, was cotransfected with the recombinant plasmid SfMNPV.HindIII-L, which contains the Spodoptera frugiperda nuclear polyhedrosis virus (SfMNPV) polyhedrin gene. An occlusion-positive hybrid virus was obtained which contained a DNA insertion at approximately 13 map units on the AcMNPV.d10A genome. A fine structure restriction map of cloned viral DNA fragments from this region revealed that most of the 1.7-kb AcMNPV.PstI-O fragment (13.4-14.7 map units) had been replaced with a 3.7-kb fragment, containing the SfMNPV polyhedrin gene with flanking sequences and the entire pUC8 plasmid. Subclones of this region were sequenced and the exact site of insertion was determined. Flanking the insert were 43 and 60 bp of unknown origin at the 5' and 3' ends, respectively. Transcription was examined in the region of the insertion in both wild-type AcMNPV and the AcMNPV/SfMNPV (Ac/Sf) hybrid. In the AcMNPV, a nested set of seven overlapping transcripts ranging from 2.2 to 5.3 kb was found, each with coterminal 3' ends. Only the 2.2-kb transcript was found to be expressed early and throughout infection. The SfMNPV insertion interrupted this transcriptional unit and produced a more complex pattern of transcription. Alterations included a nested set of three overlapping transcripts with coterminal 5' ends, including the SfMNPV polyhedrin mRNA, transcripts originating in AcMNPV and terminating in either SfMNPV or pUC8 sequences, and other minor transcripts. The SfMNPV polyhedrin gene was sequenced and the locations of the 5' and 3' ends of polyhedrin mRNA were mapped. An analysis of SfMNPV polyhedrin protein expression showed that the SfMNPV polyhedrin gene in the hybrid virus was expressed at approximately one-fourth the level of the wild-type AcMNPV polyhedrin gene. Expression of a beta-galactosidase gene under the control of the SfMNPV polyhedrin promoter in the AcMNPV.d10A mutant was also investigated.

Amino Acid Sequence↗
PubMed1987

Comparison of two-dimensional and Doppler echocardiography and intracardiac hemodynamics for quantification of mitral stenosis.

Forty-three patients with mitral stenosis (MS) were studied to assess the relation of catheter-derived pressure gradient half-time (P 1/2), mitral valve areas (calculated by the Gorlin formula and 2-dimensional echocardiography [2-D echo]) to mitral valve areas derived from Doppler pressure half-time (T 1/2) in order to establish an accurate line-drawing method in nonlinear velocity tracings and to revalidate the use of the empiric constant of 220 ms as the T 1/2 that predicts a 1.0-cm2 mitral valve area. Mitral valve area could be quantified by 2-D echo in 39 of 43 patients and by Doppler in 31 of 34 patients, for a success rate of 91%. A reliable technique for measuring Doppler T 1/2 in nonlinear Doppler velocity tracings was a "mid-diastolic" line-drawing method, validated with the "anatomic" mitral valve area by 2-D echo (r = 0.89) and with the "hemodynamic" mitral valve area by the Gorlin formula (in pure MS without regurgitation) (r = 0.95). By both Doppler T 1/2 and hemodynamic P 1/2, the use of 220 ms to predict a mitral valve area of 1.0 cm2 was validated. Each T 1/2 and P 1/2 had an exponential inverse relation to the mitral valve area by the Gorlin formula in pure MS. Doppler and 2-D echocardiographic quantification of MS are complementary. Reliable measurement of T 1/2 in nonlinear velocity tracings is achieved by a mid-diastolic line-drawing method and use of the equation 220 ms/T 1/2 = mitral valve area accurately quantifies MS.

Adult↗
PubMed1987

A multiple-dose pharmacokinetic comparison of naproxen as a once-daily controlled-release tablet and a twice-daily conventional tablet.

The bioequivalence and absorption kinetics of naproxen in a new controlled-release tablet (750 mg or 1,000 mg naproxen) administered once daily were determined relative to an equivalent dose of the conventional naproxen tablet (375 mg or 500 mg naproxen) administered q12h. Naproxen was well absorbed from the controlled-release tablet (about 90%) compared with the conventional tablet. Absorption was dependent on drug release from the tablet matrix. The mean absorption time of naproxen averaged 8.4 hours for the 750-mg controlled-release tablet and 9.2 hours for the 1,000-mg controlled-release tablet. Once-daily administration of the controlled-release tablet resulted in equivalent trough concentrations of naproxen, and steady-state plasma concentrations were maintained within narrower limits than with twice-daily naproxen.

Adult↗
PubMed1987

High-performance liquid chromatographic (HPLC) assay using fluorescence detection for the simultaneous determination of gallopamil and norgallopamil in human plasma.

Gallopamil is a calcium-channel antagonist with reported activity in experimental animals three to five times higher than that of verapamil. An automated high-performance liquid chromatographic (HPLC) method with fluorescence detection is described for the simultaneous determination of gallopamil and its metabolite norgallopamil in plasma. Gallopamil was well resolved from norgallopamil and other metabolites, allowing simultaneous quantitation of both drugs. The detection limit for both gallopamil and norgallopamil was 0.9 ng/ml. This method has been successfully used for the determination of gallopamil and norgallopamil following the administration of 25-, 37.5-, and 50-mg oral doses of drug.

Chromatography, High Pressure Liquid↗
PubMed1987

Bioavailability and pharmacokinetics of a new sustained-release potassium chloride tablet.

The bioavailability of a new sustained-release potassium chloride (KCl) tablet, designed for once-a-day dosing, was compared to a KCl elixir using urinary excretion data. The study utilized 25 male volunteers dosed in a crossover design in a dietary/activity-controlled environment. The regimens consisted of a total of 80 mEq of potassium in three equally divided doses of elixir every 6 hr and a single 80-mEq dose using four 20-mEq sustained-release (SR) tablets. The mean time to maximum rate of potassium urinary excretion was 2.2 hr for the first elixir dose and 5.5 hr after the SR tablet (P less than 0.01), thereby supporting the prolonged-release properties of this formulation. After correction for baseline urinary potassium excretion, the mean total 24-hr urinary potassium excretion was 42.18 mEq for the elixir and 40.41 mEq for the SR tablet. The results indicate that the absorption pattern from the SR tablet is equal to three doses of KCl elixir dosed 6 hr apart.

Adult↗
PubMed1986

Glutamic acid-149 is important for enzymatic activity of yeast inorganic pyrophosphatase.

Modification of Saccharomyces cerevisiae inorganic pyrophosphatase (PPase) with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide is known to lead to a loss of enzymatic activity, the rate of which is decreased in the presence of ligands binding to the active site [Cooperman, B. S., & Chiu, N. Y. (1973) Biochemistry 12, 1676-1682; Heitman, P., & Uhlig, H. J. (1974) Acta Biol. Med. Ger. 32, 565-594]. In this work we show that, when such inactivation is carried out in the presence of [14C]glycine ethyl ester (GEE), GEE is covalently incorporated into PPase, incorporation into the most highly labeled tryptic peptide is site-specific, as evidenced by the reduction of such incorporation in the presence of the active site ligands Zn2+ and Pi, the extent of formation of this specifically labeled peptide correlates with the fractional loss of PPase activity, and the specifically labeled peptide corresponds to residues 145-153 and the position of incorporation within this peptide is Glu-149. The significance of our findings for the location of the active site and for the catalytic mechanism of PPase is briefly considered in the light of the 3-A X-ray crystallographic structure of Arutyunyun and his colleagues [Arutyunyun, E. G., et al. (1981) Dokl. Akad. Nauk SSSR 258, 1481-1485; Kuranova, I. P., et al. (1983) Bioorg. Khim. 9, 1611-1919; Terzyan, S. S., et al. (1984) Bioorg. Khim. 10, 1469-1482].

Amino Acids↗
PubMed1986

Relative bioavailability of a new transdermal nitroglycerin delivery system.

The purpose of this study was to measure the bioavailability of nitroglycerin from a new transdermal delivery system, Nitro-Dur II, relative to that of Nitro-Dur. Twenty-four healthy male volunteers completed a two-way crossover study. Each subject randomly received Nitro-Dur (I) and Nitro-Dur II (II) for a 24-h period. Both transdermal systems had an active surface area of 20 cm2. Blood samples were collected immediately before treatment, at 0.5, 1, 2, 3, 4, 6, 8, 12, 18, and 24 h after topical application of the units, and 30 min after the units were removed. Nitroglycerin was determined with an analytical sensitivity of 50 pg/mL using gas chromatography with electron capture detection (GC-EC). Mean steady-state concentrations of nitroglycerin were 182 and 224 pg/mL for I and II, respectively. There were no statistical differences between I and II in the pharmacokinetic parameters measured (Css, AUC, Cmax, % fluctuation). Residual nitroglycerin content was measured in each transdermal unit after application to each of the 24 volunteers. The amounts of nitroglycerin delivered by I and II were 9.78 +/- 4.11 and 10.67 +/- 4.78 mg, respectively, or approximately 10 mg in 24 h. Statistical analysis of these data using an analysis of variance indicated no significant difference between these treatments (p = 0.27). Since there were also no differences in the plasma concentrations and pharmacokinetic parameters calculated after treatment with I and II, the bioequivalence of the two delivery systems was established.

Administration, Cutaneous↗
PubMed1986

Physiologic considerations in drug absorption from the gastrointestinal tract.

The dynamic interaction between variables within the gastrointestinal tract and the physiochemical properties of a drug in a delivery system determine the rate and extent of absorption of that drug. Among the major physiologic variables are pH, gastric emptying time, and intestinal transit time. Some physicochemical properties of interest include solubility, particle size, and chemical form of the drug. Attributes of the formulation such as controlled-release mechanism, pH sensitivity, and size, shape, and density of the product can also affect absorption. Food has also been reported to influence the absorption from some but not all controlled-release products. As a more thorough understanding of the many factors involved in drug absorption is developed, the formulation of more sophisticated oral drug delivery systems will be possible.

Chemistry, Pharmaceutical↗
PubMed1986

Rhizobins, a group of peptides in the free-amino-Acid pool of the soybean-Rhizobium system.

Free-living Rhizobium (according to Bergey's Manual of Systematic Bacteriology, [1984, The Williams & Wilkins Co., Baltimore], Bradyrhizobium) japonicum was found to release a peptide into the nutrient media. Soybean nodules contained this peptide and exuded it into the soil. The name "rhizobin A" is suggested for this peptide. Nodules also contained another peptide, rhizobin B, as well as an unidentified, ninhydrin-positive compound, rhizobin C. The three peptides were confined to the free-amino-acid pool of the soluble fraction and eluted consecutively from a cation-exchange column. Rhizobin A was isolated in a highly purified form; its molecular mass was approximately 1,600 daltons as determined by Sephadex gel filtration and mass spectrometry. The amino-acid composition could be determined only approximately, because a long time was necessary for acid hydrolysis, possibly due to unusual linkages. The rhizobin concentration in soybean nodules continually increased during 50 days of growth, from 2 to approximately 400 mug/g (fresh weight). When combined nitrogen was added to nodulated soybean and subsequently removed, nitrogenase activity, nodulation, and nodule growth first decreased and then recovered. The relative amount of rhizobin A followed a similar pattern. Rhizobins were not detected in the roots, stems, and leaves of nodulated soybean plants. They were present in Lupinus nodules, but absent in alder nodules.

Journal Article↗
PubMed1986

Complete Sequence and Enhancer Function of the Homologous DNA Regions of Autographa californica Nuclear Polyhedrosis Virus.

The nucleotide sequence of the five regions of homologous DNA in the genome of Autographa californica nuclear polyhedrosis virus DNA was determined. The homology of repeated sequences within a region was 65 to 87%, and the consensus sequences for each region were 88% homologous to each other. Sequences proximal to the EcoRI sites were most conserved, while the distal sequences were least conserved. The EcoRI sites formed the core of a 28-base-pair imperfect inverted repeat. All homologous regions functioned as enhancers in a transient expression assay. A single EcoRI minifragment located between EcoRI-Q and -L enhanced the expression of 39CAT as efficiently as the regions containing numerous EcoRI repeats did.

Journal Article↗
PubMed1985

Multiple-dose ciprofloxacin dose ranging and kinetics.

We injected multiple doses of intravenous ciprofloxacin over 10 minutes every 12 hours for 1 week to nine healthy subjects, while three other subjects received placebo. Ciprofloxacin doses of 25, 50, and 75 mg were evaluated with a 1-week washout between each dose level. Mean (+/- SD) terminal excretion t1/2S were 3.56 +/- 0.66, 4.15 +/- 0.68, and 3.46 +/- 0.42 hours for the 25, 50, and 75 mg doses. Serum clearances were 35.4 +/- 6.8, 31.8 +/- 3.0, and 31.3 +/- 5.4 L/hr/1.73 m2 for these doses. Urine concentrations remained above the minimal inhibitory concentration of most urinary tract pathogens for the full 12-hour dosing interval at each dose. Renal clearance accounted for 65% to 70% of the serum clearance, but because biologically active renally excreted metabolites have been identified, our values exceed the true values. The doses of ciprofloxacin we intravenously injected were well tolerated and appeared adequate for treatment of urinary tract infections. For serious hospital-acquired sepsis, however, larger doses should be evaluated.

Adult↗
PubMed1985

Multiple-dose pharmacokinetics of ciprofloxacin administered intravenously to normal volunteers.

We administered multiple doses of ciprofloxacin intravenously over 30 min every 12 h for 1 week to nine healthy volunteers. Three volunteers received a placebo (vehicle) intravenously. Doses of 100, 150, and 200 mg were evaluated with a 1-week wash-out period intervening between each dose level. Terminal excretion half-lives averaged 3.67 +/- 0.65, 3.60 +/- 0.26, and 4.00 +/- 0.69 h for the 100-, 150-, and 200-mg doses, respectively. Serum clearances were 30.1 +/- 3.4, 29.8 +/- 4.0, and 26.9 +/- 4.1 liters/h per 1.73 m2 for these doses. Urine concentrations remained in excess of the MIC for 90% of the relevant urinary tract pathogens for the full 12-h dosing interval at each dose. Renal clearance accounted for 56 to 71% of the serum clearance. However, because a microbiologic assay was used and biologically active, renally excreted metabolites were identified, the renal clearance determinations are likely to be in excess of the true values. The doses of ciprofloxacin administered intravenously were well tolerated, and the drug concentrations appeared adequate for the treatment of the vast majority of cases of nosocomially acquired sepsis and urinary tract infections. For patients with serious Pseudomonas infections and perhaps staphylococcal infections, either an 8-h dosing schedule or larger doses on a 12-h schedule should be considered.

Adolescent↗
PubMed1984

Evidence that catalysis by yeast inorganic pyrophosphatase proceeds by direct phosphoryl transfer to water and not via a phosphoryl enzyme intermediate.

In this work, we show that adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S) is a substrate for yeast inorganic pyrophosphatase (PPase) (EC 3.6.1.1) and further, using chirally labeled [gamma-17O,18O]ATP gamma S, that enzyme-catalyzed hydrolysis to produce chiral inorganic thio[17O,18O]phosphate proceeds with inversion of configuration. Both the synthesis of chiral ATP gamma S and the determination of inorganic thiophosphate configuration were carried out as described by Webb [Webb, M. R. (1982) Methods Enzymol. 87, 301-316]. We also show in a single turnover experiment performed in H2(18)O that 1 mol each of 18O16O3P and 16O4P is produced per mol of inorganic pyrophosphate hydrolyzed, a strong indication that oxygen uptake to form inorganic phosphate on PPase catalysis of inorganic pyrophosphate hydrolysis comes directly from H2O. These two results provide strong evidence for the conclusion that PPase catalyzes inorganic pyrophosphate hydrolysis via a single-step direct phosphoryl transfer to water and does not involve formation of a phosphorylated enzyme intermediate.

Adenosine Triphosphate↗