Search PubMed⌕ Search

Biomedical subjects

E Miyamoto

Publications and source records attributed to E Miyamoto.

At least 217 records · Page 12Linked to original sources
PubMed1983

Physiologically based pharmacokinetic model for beta-lactam antibiotics I: Tissue distribution and elimination in rats.

The disposition characteristics of beta-lactam antibiotics in rats were investigated, and a physiologically based pharmacokinetic model capable of predicting the tissue distribution and elimination kinetics of these drugs was developed. Protein-binding parameters in rat serum were determined by equilibrium dialysis. Linear binding was found for penicillin G, methicillin, dicloxacillin, and ampicillin; however, nonlinear binding was observed for penicillin V and cefazolin. After intravenous bolus dosing, cefazolin was recovered almost completely in urine and bile, while for the penicillins, penicilloic acid was found to be the major metabolite. Biliary excretion of cefazolin followed Michaelis-Menten kinetics, and no significant inhibition of urinary secretion was observed after probenecid administration. The renal clearance of unbound drug was 0.82 ml/min with a reabsorption ratio (R) of 0.22. Tubular secretion was inhibited for the penicillins by probenecid plasma concentrations of 50 micrograms/ml, resulting in an R-value of 0.32. Erythrocyte uptake, serum protein binding, and tissue-to-plasma partition coefficient (Kp) were measured. Theoretical Kp values were calculated and found to be in good agreement with the Kp values for three of the antibiotics. Plasma and tissue concentrations (lung, heart, muscle, skin, gut, bone, liver, and kidney) were measured as a function of time at various doses for inulin and cefazolin in rats after an intravenous bolus dose, and were found to be in reasonable agreement with concentrations predicted by the model. These correlations demonstrate that the proposed model can accurately describe the plasma and tissue contributions of inulin and cefazolin in the rat and suggest that this model could have utility in predicting drug distribution in humans.

Animals↗
PubMed1983

Calmodulin and Ca2+- and calmodulin-dependent protein kinase in rat anterior pituitary gland.

Calmodulin and Ca2+- and calmodulin-dependent protein kinase were identified in the rat anterior pituitary gland. The concentration of calmodulin was 1.18 +/- 0.11 microgram/mg protein (n = 7) in the cytosol fraction. The calmodulin of the anterior pituitary gland co-migrated with brain calmodulin on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Ka value of the partially purified enzyme for Ca2+ was 3.3 microM in the presence of 0.30 microM calmodulin. Trifluoperazine and chlorpromazine, calmodulin-interacting agents, inhibited enzyme activity, with Ki values of 1.3 and 2.6 X 10(-5) M, respectively. The enzyme was resolved into two peaks of activity, with sedimentation coefficients of 5.5 S and 16.5 S, by sucrose density gradient centrifugation. At least nine proteins were phosphorylated by the enzyme in a Ca2+- and calmodulin-dependent manner. In light of these results, the possibility that calmodulin and the calmodulin-activatable protein kinase system are involved in the mediation of the Ca2+ effect on hormone release from the anterior pituitary gland must be given consideration.

Animals↗
PubMed1983

Ca2+- and calmodulin-dependent phosphorylation of microtubule-associated protein 2 and tau factor, and inhibition of microtubule assembly.

Microtubule-associated proteins (MAPs) were phosphorylated by a Ca2+- and calmodulin-dependent protein kinase from rat brain cytosol. The maximal amount of phosphate incorporated into MAPs was 25 nmol of phosphate/mg protein. A Ka value of the enzyme for calmodulin was 57.0 nM, with MAPs as substrates. Among MAPs, MAP2 and tau factor were phosphorylated in a Ca2+- and calmodulin-dependent manner. The phosphorylation of MAPs led to an inhibition of microtubule assembly in accordance with its degree. This reaction was dependent on addition of the enzyme, Ca2+, and calmodulin, and had a greater effect on the initial rate of microtubule assembly rather than on the final extent. The critical tubulin concentration for microtubule assembly was unchanged by the MAPs phosphorylation. Therefore assembly and disassembly of brain microtubule are regulated by the Ca2+- and calmodulin-dependent protein kinase that requires only a nanomolar concentration of calmodulin for activation.

Adenosine Triphosphate↗
PubMed1983

Regulation by estrogen and progesterone of protein kinases in rabbit myometrium.

We report on hormonal regulation of protein kinases in the rabbit myometrium. The injection of estrogen or progesterone produced 5.2 +/- 0.7- or 4.7 +/- 0.4-fold increases, respectively, of the total activity when histone was used as the substrate in the cytosol fraction of the tissue. The analysis of the activity by DEAE-cellulose column chromatography revealed that estrogen had no effect on increases in the levels in both types I and II cAMP-dependent protein kinases, on the basis of mg protein, while progesterone produced a 50% decrease in type I cAMP-dependent protein kinase and a 50% increase in type II cAMP-dependent protein kinase. Thus, the activity ratio of types II to type I did not change by treatment with estrogen and increased from 2.8 to 7.9 with progesterone administration. As the activity patterns by treatment with human chorionic gonadotropin closely resembled those seen with progesterone, our findings in case of the latter hormone are probably valid. The results indicate that the levels of protein kinases in the myometrium are altered in response to estrogen and progesterone and may possibly be involved in the physiological functions of the tissue.

Animals↗
PubMed1983

Hormone treatments and pregnancy alter myosin light chain kinase and calmodulin levels in rabbit myometrium.

Myosin light chain kinase activity and the amount of calmodulin were measured in rabbit myometrium after the rabbits had been treated with oestrogen, progesterone and human chorionic gonadotrophin, and also during pregnancy. Injections of oestrogen and progesterone produced significant increases of of 2.8- and 2.1-fold in the enzyme activity/mg protein and of 1.4- and 1.2-fold in the calmodulin content/mg protein respectively. The increases seen with oestrogen treatment were inhibited by cycloheximide administration, suggesting that protein synthesis is involved in the process. Calmodulin increased about twofold in the particulate fraction under conditions of oestrogen and progesterone treatments and the raised level of calmodulin detected in the cytosol fraction was not due to translocation from the particulate fraction. During pregnancy the specific enzyme activity significantly increased in comparison with the values seen in samples from the non-treated rabbits. These findings suggest that myosin light chain kinase and calmodulin in the myometrium are under hormonal regulation and may play a role in expulsion of the fetus at the latter phase of pregnancy.

Animals↗
PubMed1982

Multiple specificities of brain Ca2+- and calmodulin-dependent protein kinase for substrate.

The purified Ca2+- and calmodulin-dependent protein kinase from rat brain, which has a M.W. of 120,000 by gel filtration analysis, showed a broad substrate specificity. In addition to myosin light chain from chicken gizzard, the enzyme phosphorylated myelin basic protein, casein and two endogenous substrates in a Ca2+- and calmodulin-dependent manner. In contrast, chicken gizzard myosin light chain kinase exclusively phosphorylated myosin light chain.

Animals↗
PubMed1982

Carbenicillin prodrugs: kinetics of intestinal absorption competing degradation of the alpha-esters of carbenicillin and prediction of prodrug absorbability from quantitative structure-absorption rate relationship.

The intestinal absorption of alpha-esters of carbenicillin disodium, carbenicillin phenyl sodium, and carbenicillin indanyl sodium was investigated using the in situ rat intestinal recirculating method. In the in situ intestinal lumen at pH 7, two prodrugs were rapidly converted to poorly absorbable carbenicillin, possibly by the action of intestinal nonspecific esterase in competition with the slow absorption of prodrugs. At pH 5, the reduced action of esterase and the increased absorption rate after 3 hr resulted in 50 and 60% absorption of carbenicillin phenyl sodium and carbenicillin indanyl sodium, respectively. The absorption rate constants determined for both prodrugs were in good agreement with the prediction from the quantitative structure-absorption rate relationship derived from the two-compartment aqueous diffusion model.

Animals↗
PubMed1982

Effects of surfactants on the aqueous stability and solubility of beta-lactam antibiotics.

Studies were undertaken to elucidate the interaction between beta-lactam antibiotics and surfactant micelles and to examine the effects of surfactants on their aqueous stability and solubility. The apparent binding constant of the micelle-antibiotic complex was determined as a function of the solution pH at 37 degrees and mu = 0.15 by the dynamic dialysis method and hydrolysis study. In the interaction with nonionic and anionic micelles of polyoxyethylene-23-lauryl ether (I) and sodium lauryl sulfate (II), large differences were noted in the binding constants between the undissociated and ionized species of penicillins. However, the cationic surfactants, cetyltrimethylammonium bromide (III), showed no significant difference in the binding constants for both species. Acid degradation of penicillins was protected in micellar solutions of I and III but was facilitated in micelles of II. The surfactants exerted no influence on the neutral degradation of the antibiotics used. The solubilization of penicillin V acid by micelles of I was studied at pH 2.0 and 35 degrees. The solubility increased threefold in the presence of 10 mM I.

Anti-Bacterial Agents↗
PubMed1982

Purification and characterization of a Ca2+- and calmodulin-dependent protein kinase from rat brain.

A Ca2+- and calmodulin-dependent protein kinase was purified from rat brain cytosol fraction to apparent homogeneity at approximately 800-fold and with a 5% yield. The purified enzyme had a molecular weight of 640,000 as determined by gel filtration analysis on Sephacryl S-300 and a sedimentation coefficient of 15.3 S by sucrose density gradient centrifugation, and resulted in a single protein band of MW 49,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results suggest that the native enzyme has a large molecular weight and consists of 11 to 14 identical subunits. The purified enzyme exhibited Km values of 109 and 30 microM for ATP and chicken gizzard myosin light chain, respectively, and Ka values of 12 nM and 1.9 microM for brain calmodulin and Ca2+, respectively. In addition to myosin light chain, myelin basic protein, casein, arginine-rich histone, microtubule protein, and synaptosomal proteins were phosphorylated by the enzyme in a CA2+- and calmodulin-dependent manner. The purified enzyme was phosphorylated without the addition of the catalytic subunits of cyclic AMP-dependent protein kinase. Our findings indicate that there is a multifunctional Ca2+- and calmodulin-dependent protein kinase in the brain and that this enzyme may regulate the reactions of various endogenous proteins.

Animals↗
PubMed1982

Dissociation of alterations in levels of myosin light chain kinase and cyclic AMP-dependent protein kinase in rabbit myometrium during pregnancy.

The alteration in levels of myosin light chain kinase and cyclic AMP-dependent protein kinase was studied in rabbit myometrium during pregnancy. The specific activity of myosin light chain kinase was 160.9 +/- 2.7, 128.1 +/- 3.5, and 126.5 +/- 4.4% at the 10th, 20th and 28th days after pregnancy, respectively, in comparison with the value seen in samples from non-pregnant rabbits. On the other hand, the specific activity of cyclic AMP-dependent protein kinase gradually decreased to 75.9 +/- 1.7, 58.7 +/- 3.5 and 36.9 +/- 1.9% of that of the control at each time with the increase in the time of gestation. The protein kinase inhibitor was not involved in the decrease in cyclic AMP-dependent protein kinase. These results suggest that the dissociation of the dynamic states of the two enzymes may make it possible for the myometrium to efficiently respond to contraction in the last stage of pregnancy.

Animals↗
PubMed1981

Regulation by human chorionic gonadotropin of protein kinases in rabbit endometrium.

The effect of human chorionic gonadotropin (CG) on protein kinase levels has been studied in rabbit endometrium. A good correlation was observed between alterations of total protein kinase activity and DNA content in the tissue. The level of type I cyclic AMP-dependent protein kinase had slightly increased by 6 h after human CG treatment, and then decreased later. In contrast, the type II enzyme gradually increased after 3 days. The increase of the activity at 7 days was mainly due to that of type II enzyme, and the ratio of type II to type I enzyme increased. The activity pattern at the later stage closely resembled that of treatment with progesterone.

Animals↗