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Biomedical subjects

K Nakatsu

Publications and source records attributed to K Nakatsu.

At least 127 records · Page 7Linked to original sources
PubMed1978

Reliable fifteen-minute assay for theophylline.

We describe a reliable, rapid high pressure liquid chromatography assay for serum theophylline which can be performed on 0.5 ml or smaller samples. The procedure involves extraction, centrifugation and sampling all in the same disposable centrifuge tube. In the therapeutic range the coefficients of variation for within-day and day-to-day assays are 1.0% and 2.6%, respectively. The sensitivity of the method is better than 1 microgram/ml in serum. The minimum number of steps, rapid elution and use of only peak heights contribute to the reliability and rapidity of the assay.

Chromatography, High Pressure Liquid↗
PubMed1978

Spectrophotometry of theophylline-7-acetic acid and theophylline.

A spectrophotometric assay procedure is described for individually measuring theophylline-7-acetic acid and theophylline in 2.0 ml of serum. Absorbance is a linear function of concentration over a range of 0.5-40 mg/liter for theophylline-7-acetic acid and 0.5-40 mg/liter for theophylline. No endogenous or exogenous compounds were found that interfere with theophylline-7-acetic acid determinations. As with other spectrophotometric theophylline assays, theobromine and, to a slight extent, phenobarbital interfere with theophylline determinations.

Humans↗
PubMed1978

Muscle proteolysis induced by neural colchicine cuffs cast in situ.

The effects of neurotrophic factors on muscle protein degradation in rat leg muscle were studied. In order to inhibit axoplasmic transport and therefore transport of "trophic" factors, the colchicine cuff method of Albuquerque et. al. (1972) was modified so that the cuffs were cast in situ. Protein degradation was estimated by monitoring the release of tyrosine from the muscle. Our observations that colchicine cuffs increased tyrosine release are consistent with the concept of nerve-muscle trophism.

Animals↗
PubMed1976

Adenosine inhibition of isolated rabbit ileum and antagonism by theophylline.

The spontaneously contracting isolated rabbit ileum was used to study adenosine stimulated receptors. The inhibitory effects of adenosine were not reduced by pretreating the rabbits with either reserpine of 6-hydroxydopamine which were used to eliminate adrenergic function. Similarly the addition of tetrodotoxin to the muscle bath had no effect on the ability of adenosine to produce its inhibitory response. Of the compounds tested for agonistic activity, adenosine and ATP were the most potent (ED50 6 X 10(-7) M). The inhibition by adenosine was antagonized by both theophylline and caffeine in a surmountable manner. Theophylline analogs with charged substituents in position 7 were without antagonist activity. The results suggest that 1) receptors for adenosine or adenine nucleotides are located on the smooth muscle cells of rabbit ileum, 2) receptor stimulation requires and intact adenosine moiety and 3) methylxanthines exert their antagonistic effects by acting as competitive antagonists.

Adenosine↗
PubMed1975

Adenylate deaminase. A method for its localization in skeletal muscle.

A method for light microscopic localization of adenylate deaminase in sections of frozen rat quadriceps muscle is described. The method depends on the hydrolysis of 6-chloropurine ribonucleotide (the 6-chloroanalogue of adenylate) and the trapping of Cl minus by Ag plus. The resulting AgCl precipitate was made visible by exposing the sections to light. After this treatment black deposits about 1 mu in diameter were seen in muscle cells. These observations indicate that adenylate deaminase of rat quadriceps muscle is located at discrete sites within the muscle cells.

Adenosine Monophosphate↗
PubMedDate not supplied

Disposition of intravenous theophylline-7-acetic acid in rabbits.

Theophylline-7-acetic acid (T7AA) was administered intravenously to rabbits so that its distribution and rate of elimination could be ascertained. The analytical techniques used were liquid scintillation counting (14C) and high pressure liquid chromatography. T7AA was eliminated rapidly in the urine; the T 1/2 was 11.6 min. This drug appears to accumulate in the kidney because after 60 min, approximately 15 per cent of the intravenous dose was found in that organ.

Animals↗
PubMedDate not supplied

Determination of isosorbide dinitrate biotransformation in various tissues of the rabbit by capillary column gas-liquid chromatography.

A selective and sensitive capillary column gas-liquid chromatographic procedure has been developed for the simultaneous determination of isosorbide dinitrate (ISDN) and its mononitrate metabolites in rabbit blood and tissue homogenates. The method has a limit of detection of 0.1 ng ml-1 for ISDN, 1 ng ml-1 for isosorbide 5-mononitrate (5-ISMN), and 2 ng ml-1 for isosorbide 2-mononitrate (2-ISMN). The day-to-day coefficients of variation were 2.5, 6.8, and 11.3 per cent for ISDN, 5-ISMN, and 2-ISMN, respectively. The within-day coefficients of variation were 2.7, 4.9 and 6.5 per cent for ISDN, 5-ISMN, and 2-ISMN, respectively. The procedure was used to determine the biotransformation of ISDN (2 X 10(-7) M) to 5-ISMN and 2-ISMN by various rabbit tissue homogenates. The relative rate of biotransformation of ISDN was liver greater than lung approximately equal to intestine greater than kidney greater than blood approximately equal to skeletal muscle, with the lung and intestine homogenates being about two-thirds as active as liver homogenates. These results indicate that extrahepatic biotransformation of ISDN, especially by lung and intestine, may contribute to the systemic clearance of ISDN in the rabbit.

Animals↗
PubMedDate not supplied

Do adenine derivatives have a special role in biological regulation?

The hypothesis is raised "that adenine by way of its many derivatives plays an important role in regulating a wide variety of biological functions". Evidence is cited for such a role in cell-to-cell communication, intracellular regulation and interorganism communication. It is predicted that many more key biological functions will be found to be modulated by adenine derivatives and that adenine compounds which have not yet been studied in great depth will become recognized as biological regulators. The hypothesis also predicts that some disease states may be caused by perturbations of the adenine derivative-receptor system.

Adenine Nucleotides↗
PubMedDate not supplied

Heme oxygenase activity and acute and chronic ethanol exposure in the hippocampus, frontal cerebral cortex, and cerebellum of the near-term fetal guinea pig.

Heme oxygenase (HO) catalyzes the oxidation of heme to produce carbon monoxide, which is considered to be a novel neuronal messenger in the brain and may play a role in neuronal development. The objective of this study was to determine the effects of in vitro, acute in vivo, and chronic in vivo ethanol exposure on HO activity in the hippocampus, frontal cerebral cortex, and cerebellum of the near-term fetal guinea pig. HO activity was determined using a gas chromatographic method to quantitate CO formation in the microsomal fraction of the homogenate of each selected brain region, incubated with saturating concentrations of heme, NADPH, and O2. Fetal body, brain, hippocampal, and cerebellar weights were recorded. In vitro ethanol exposure (25-100 mM) did not affect hippocampal, cerebral cortical, or cerebellar HO activity of the fetal guinea pig at gestational day (GD) 62 (term, about GD 68). Acute maternal oral administration of 4 g ethanol/kg maternal body weight at GD 62 did not affect HO activity in these three fetal brain areas compared with control fetuses (maternal administration of isocaloric sucrose or water). For chronic daily maternal oral administration of 4 g ethanol/kg maternal body weight throughout gestation, fetal body, brain, hippocampal, and cerebellar weights were decreased at GD 62 compared with isocaloric-sucrose/pair-fed and water treatment control groups. Furthermore, isocaloric-sucrose/pair-feeding treatment decreased fetal body and brain weights compared with water treatment. Chronic in vivo ethanol exposure did not alter HO activity in the near-term fetal hippocampus, frontal cerebral cortex, or cerebellum. This is the first study of the effect of ethanol exposure on HO activity in the developing brain of any species. The data demonstrate, for ethanol CNS teratogenesis in the guinea pig manifesting as fetal brain growth restriction, there is no associated change in HO activity in the hippocampus, frontal cerebral cortex, or cerebellum.

Animals↗
PubMedDate not supplied

Carbon monoxide decreases perfusion pressure in isolated human placenta.

Carbon monoxide (CO) is one of the metabolites formed via heme oxidation catalysed by the enzyme heme oxygenase (HO). Endogenous formation of CO, mediated by HO, has been noted in both placental and umbilical vessels. In blood vessels from different mammalian sources, it has been proposed that the vasodilator effect of CO is mediated via stimulation of soluble guanylyl cyclase (sGC) and consequent increased cGMP formation. The purpose of the present study was to determine the effect of exogenous CO on placental cotyledon perfusion pressure and to determine the role of sGC in the CO-induced decrease of perfusion pressure using the in vitro human placental perfusion preparation. A thromboxane A2 mimetic (U46619) was added to the foetal perfusion medium to constrict the placental blood vessels. Carbon monoxide was added to the foetal perfusion medium in increasing concentrations to determine its effect on placental perfusion pressure. Carbon monoxide produced a concentration-dependent decrease in placental perfusion pressure. The addition of ODQ, a sGC inhibitor, attenuated the CO-induced decrease in placental perfusion pressure, while addition of YC-1, an activator of sGC, augmented the CO-induced decrease in placental perfusion pressure. The data indicate that CO causes vasorelaxation of placental resistance blood vessels, in large part, via activation of sGC.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗