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Biomedical subjects

T Uematsu

Publications and source records attributed to T Uematsu.

At least 19 recordsLinked to original sources

Characterization of the cytosolic epoxide hydrolase-catalyzed hydration products from 9,10:12,13-diepoxy stearic esters.

In a previous report we hypothesized that diepoxy fatty methylesters are metabolized to tetraols and/or tetrahydrofurandiols through an epoxydiol intermediate. In this study, p-nitrophenyldiepoxystearate was incubated with affinity-purified liver cytosolic epoxide hydrolase and product formation was monitored by reverse phase HPLC. The diepoxystearate was converted to the corresponding 9,10,12,13-tetraol using a concentrated enzyme (greater than or equal to 100 micrograms/ml). When lower concentration of the enzyme was used, simultaneous elevation of 9,10-epoxy-12,13-dihydroxy and 12,13-epoxy-9,10-dihydroxystearate along with disappearance of tetraol was observed. The epoxydiols were intermediates which could be isolated and cyclized quantitatively to form two chromatographically distinct tetrahydrofurandiols (A with a low Rf value and B with a high Rf value on TLC). Gas chromatographic analysis on a cyclodex-beta capillary column revealed that each compound was composed of two different isomers. The structure of these isomers was 9(12)-oxy-10,13-dihydroxystearate and 10(13)-oxy-9,12-dihydroxystearate using mass spectrometry. Stereochemistry of the aliphatic chain across the tetrahydrofuran moiety was determined by nuclear Overhauser effect spectroscopy. Chemically and enzymatically generated tetrahydrofurandiols had similar retention time on GC and HPLC, and identical mass spectra using the electron impact mode.

Animals

Possible effect of pigment on the pharmacokinetics of ofloxacin and its excretion in hair.

The mechanism of excretion of the antimicrobial ofloxacin in human scalp hair was investigated. When black and white hairs were taken from a patient with grizzled hair, who had been treated with ofloxacin, a much larger quantity of the drug was detected in the black hair. To study this difference and to elucidate the cause, ofloxacin (6, 20, and 60 mg/kg/day, b.i.d.) was administered ip for 5 weeks to albino and pigmented rats, whose backs had been depilated beforehand. In the last week of administration, the time-plasma concentration profile of ofloxacin was determined. One week after the last dosing, the newly grown hair on the depilated area was collected, and the drug concentration in hair was measured. The concentration in hair of the pigmented rats correlated significantly with the daily dose, area under the plasma concentration curve (AUC), and maximum plasma concentration (Cmax) at steady state, whereas that in the albino rats correlated with the dose and Cmax only, because AUC did not increase linearly with the dose in the albino rats. Moreover, the drug concentration in the hair of the pigmented rats was always much larger than that in the hair of the albino ones, although AUC and Cmax did not differ greatly between both rat groups. The findings suggest that ofloxacin is excreted in the hair in relation to the dose administered, and that the mechanism of the excretion is closely linked with the presence of melanin.

Animals

Steady-state pharmacokinetics of haloperidol and reduced haloperidol in schizophrenic patients: analysis of factors determining their concentrations in hair.

Profiles of the steady-state concentrations of haloperidol (HL) and its major metabolite, reduced haloperidol (RHL), in plasma versus time were determined in 10 Japanese patients whose schizophrenic symptoms were clinically controlled by fixed, oral maintenance doses (4-30 mg/day, three times a day) for greater than 4 months. These data were used to determine the pharmacokinetic factor(s) that correlate best with HL and RHL concentrations in hair. The concentrations of HL and RHL in plasma or hair were simultaneously measured by high-performance liquid chromatography with an electrochemical detector. The observed values of minimal and maximal concentrations in plasma (Cmin and Cmax, respectively) varied widely among patients: 3.0-22.9 and 6.2-32.7 ng/mL for HL and 2.8-21.4 and 5.7-33.3 ng/ml for RHL, respectively. The ratio of the area under the plasma concentration-time curve (AUC) of RHL for 1 day to that of HL also ranged widely from 0.39 to 1.99 (1.04 +/- 0.48, mean +/- standard deviation). When the concentration of HL or RHL in hair was compared with the daily dose of HL and respective AUC, Cmax, or trough concentration in the plasma in the morning, the parameter that best correlated with the concentration of HL in hair was AUC. The concentration of RHL in hair correlated with all three parameters, but the correlation with AUC was better than that with Cmax. Therefore, the concentrations of these substances in hair were considered to be representative of their mean amounts in the body.

Administration, Oral

Antiarrhythmic and electrophysiological effects of SD-3212, a novel Na+ and Ca++ channel blocker, in anaesthetized dogs with myocardial infarction in comparison with its stereoisomer (SD-3211) and bepridil.

Antiarrhythmic and electrophysiological effects of SD-3212, a novel antiarrhythmic agent, which has both Na+ channel and Ca++ channel blocking activities, were compared with those of its (+)-stereoisomer, SD-3211, which has only a Ca++ channel blocking activity, and bepridil, a known Ca++ channel blocker with additional Na+ channel blocking activity, using the two-stage coronary ligation induced arrhythmia (24 h after the ligation of the left anterior descending coronary artery) and 7 day-old myocardial infarcted hearts in anaesthetized dogs. SD-3212 showed a dose-dependent antiarrhythmic effect on the two-stage coronary ligation induced arrhythmia. SD-3212 at a dose of 3 mg/kg reduced the arrhythmic ratio, i.e. ectopic beats per min divided by the sum of ectopic beats and sinus beats per min, significantly from 1 up to 12 min after the administration. Neither bepridil (1-6 mg/kg) nor SD-3211 (1 mg/kg) had an antiarrhythmic effect. SD-3212 (0.3-3 mg/kg) prolonged both the conduction time in the normal myocardium and the delayed potential in the infarcted myocardium in the 7 day-old myocardial infarcted hearts in anaesthetized dogs in a dose-dependent manner. This effect of SD-3212 was shown at coupling intervals of 150-1000 ms increasing with decreasing interval. In this respect, SD-3212 is similar to drugs which show fast recovery of Vmax from use-dependent block such as lidocaine. Bepidril (1-6 mg/kg) also prolonged these parameters in a dose-dependent manner, however, the prolongation induced by bedripil was limited to shorter coupling intervals as compared with that induced by SD-3212. SD-3212 (0.1-1 mg/kg) did not show this prolonging effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Photochemically induced thrombosis of the rat coronary artery and functional evaluation of thrombus formation by occurrence of ventricular arrhythmias. Effects of acetylsalicylic acid and a thromboxane A2 synthetase inhibitor of thrombus formation.

During i.v. infusion of rose bengal (48 mg/kg/h), the proximal portion of the rat left coronary artery was illuminated from the outside of the myocardium by green light (540 nm) to produce a transluminal thrombus subsequent to endothelial damages. The primary endothelial damages within the illuminated vascular portion, which resulted from the photochemical reaction between the dye and green light, and the subsequent formation of transluminal platelet-rich thrombus, were easily revealed by both light and electron microscopy. The establishment of the thrombus was accompanied in all cases by the occurrence of ventricular arrhythmias due to myocardial ischaemia. The times required to initiate ventricular premature beats (VPBs) and ventricular tachycardia (VT) were 381 +/- 96 s and 444 +/- 114 s (mean +/- SEM, n = 10), respectively. Pretreatment of the rat with acetylsalicylic acid (3 and 10 mg/kg, i.v.) before the initiation of illumination had no effect on the times required to exhibit the first VPBs and VT, the incidences of both types of arrhythmias were not reduced, and the thrombus was finally formed. On the other hand, pretreatment with Y-20811, a novel thromboxane A2 synthetase inhibitor (0.3, 1 and 3 mg/kg, i.v.), delayed the onset of both VPB and VT in a dose-dependent manner. The incidences of VPBs and VT were significantly reduced at 1 and 3 mg/kg, and the thrombus formation was prevented. The formation of a transluminal thrombus in the left coronary artery by the present technique was highly reproducible and could be functionally evaluated by the occurrence of ventricular arrhythmias.

Animals

Pilot study of the uricosuric effect of DuP-753, a new angiotensin II receptor antagonist, in healthy subjects.

The uricosuric effect of DuP-753, a novel, specific angiotensin II receptor antagonist, has been explored in a healthy male Japanese volunteers, given single oral doses of 25, 50, 100 or 200 mg (n = 6), or 100 mg (n = 6) or placebo (n = 3) once daily for 7 consecutive days. In the single-dose study, serum uric acid measured at 4 h after dosing showed a dose dependent decrease; the reductions from the corresponding pre-dose values were: 0.32 (25 mg), 0.77 (50 mg), 1.25 (100 mg) and 1.33 mg.dl-1 (200 mg). The urinary excretion of uric acid within the first 4 h after treatment was also increased in a dose-dependent manner, whereas the urinary excretion of creatinine remained unchanged. In the multiple-dose study, DuP-753 significantly decreased the serum uric acid concentration measured 4 h both after the first (pre-dose value: 5.68 vs 4 h after: 4.48 mg.dl-1) and last administrations (4.42 mg.dl-1). Simultaneously, the ratio of urinary uric acid to creatinine excretion was significantly increased within the first 4 h both after the first (DuP-753: 1.190 vs placebo: 0.576) and last administrations (1.02 vs 0.576). The findings suggest that DuP-753 possesses a uricosuric effect both after single and multiple doses in healthy subjects. The effect should be further examined in hypertensive patients.

Adult

A new model of equilibrium dysfunction in the rat induced by photochemical damage to the inner ear's microcirculation.

A new photochemical method was employed to damage the inner ear microcirculation in the rat. Under pentobarbital anesthesia, the middle ear was exposed by a ventral approach and the tympanic membrane and the malleus and incus were removed. The vestibule was then illuminated by a filtered xenon light (wave length: 540 nm) while rose bengal was infused intravenously. Microscopic examination revealed disintegration of the hair cells in the vestibule. Changes could be prevented by pretreatment with intravenous acetylsalicylic acid (ASA) or heparin. Twenty-four hours after the completion of photo-illumination the rats exhibited nystagmus toward the intact ear and showed rolling during the swimming test, both signs of equilibrium dysfunction. These findings were inhibited by ASA or heparin pretreatment. Our present results indicate that our method causes a photochemically induced occlusion in the rat's inner ear microcirculation and may be useful for evaluating the various effects of drugs on the inner ear.

Animals

Pharmacokinetics of temocapril hydrochloride, a novel angiotensin converting enzyme inhibitor, in renal insufficiency.

The pharmacokinetics of temocapril hydrochloride, a novel prodrug-type angiotensin-I converting enzyme (ACE) inhibitor, has been studied in patients with mild (Group II) to severe (Group III) renal insufficiency in comparison with subjects with normal renal function (Group I). The pharmacokinetic parameters of the active diacid metabolite, including Cmax, AUC and half-life (t1/2), showed only slight changes between the three groups: AUC (0-inaffinity) was significantly larger in Group III than Group I, and t1/2 tended to be prolonged in Group III, but the change was not significant. The urinary recovery of the diacid was significantly decreased in Group III. (Group I, 28.1%, Group II, 21.6%, Group III, 12.8%). Compared with other ACE inhibitors, which are mainly excreted through the kidney, the plasma concentration of the active diacid metabolite was hardly influenced by renal function. It was speculated that lowering of the dose of temocapril might be recommended only in patients with severe renal insufficiency.

Angiotensin-Converting Enzyme Inhibitors

Analysis of ofloxacin in hair as a measure of hair growth and as a time marker for hair analysis.

The distribution of ofloxacin (OFLX) along a single hair shaft was analyzed in detail for use as an index of hair growth and as a time marker for drug analysis in hair. A single hair obtained from each of seven subjects, who had taken OFLX for 1-4 days (total of 200-1,200 mg) 2.7-5.3 months before hair sampling, was cut into 1-cm-long portions successively from its scalp end. OFLX in each hair portion was measured by high-performance liquid chromatography with a fluorescence detector, and the distance from the scalp end of the hair portion containing OFLX was determined. Then the other 2-cm long segment of hair, which had the above-determined distance at its middle, was cut successively into 2-mm-long pieces and OFLX was determined in each piece. This procedure was repeated in a total of three to four hair strands collected from one subject. OFLX was observed to distribute only in one to three consecutive 2-mm-long pieces of hair, showing no large diffusion of OFLX along the hair shaft with time. Therefore, OFLX distribution may serve as a time marker for analyzing other drugs in hair. Hair growth rate could be thus estimated and ranged from 0.99 to 1.27 cm/month (1.12 +/- 0.11 cm/month, mean +/- SD) among individuals. The intraindividual variability of hair growth rate was 4.8-18.1% (10.3 +/- 5.1%) as coefficient of variation.

Adult

Effects of vapiprost, a novel thromboxane receptor antagonist, on thrombus formation and vascular patency after thrombolysis by tissue-type plasminogen activator.

1. A thrombus was induced in the rat femoral artery by endothelial damage due to the photochemical reaction between systemically-injected Rose Bengal and transillumination with green light (wavelength: 540 nm). The artery of the control rat was completely occluded in 302.8 +/- 27.0 s after the initiation of the reaction. 2. Pretreatment with vapiprost (0.1, 0.3 and 1.0 mg kg-1, i.v., 5 min before the reaction) prolonged the time required to occlude the femoral artery in a dose-dependent manner. The efficacy of vapiprost on the time required for occlusion was over 10 times higher than that of aspirin which was administered 30 min before the reaction. 3. The thrombolytic effects of tissue-type plasminogen activator (tPA) on the established arterial thrombus in the presence and absence of vapiprost were also studied in the same model. When vapiprost (0.3 mg kg-1, i.v.) was administered just before tPA infusion (100 micrograms kg-1 min-1 for 30 min), the time required to reperfuse the occluded artery was reduced, the incidence of the reperfusion was increased and the arterial blood flow after reperfusion was improved. 4. When vapiprost (1.0 mg kg-1 daily p.o.) was administered for 1 week after the establishment of reperfusion by tPA combined with vapiprost, the patency of the reperfused artery was improved and the femoral arterial blood flow was better preserved than after treatment with only tPA. 5. These findings suggest that this thromboxane receptor antagonist may be a useful adjunct to anti-thrombotic therapy. The combination therapy with tPA may be more effective than treatment with tPA alone and provides greater protection against reocclusion after reperfusion.

Animals

Serum dipeptidyl peptidase (DPP) IV activity in hamster buccal pouch carcinogenesis with 9,10-dimethyl-1,2-benzanthracene.

Dynamic change of serum DPP IV activity in carcinogenesis of hamster buccal pouch epithelium with DMBA was investigated. The serum enzyme level in hamster (21.5 +/- 3.1 IU/l serum) was decreased gradually from the 8th to the 10th wk when papillomas were induced by DMBA application (18.9 +/- 2.7 IU/l serum). The enzyme level was further decreased in the formation of carcinoma in situ or early invasive carcinoma (13.2 +/- 0.5 IU/l serum), and reached to less than half of the normal level at the time when tumors were diagnosed as squamous cell carcinoma histologically (8.1 +/- 1.3 IU/l serum). This enzyme level was increased by tumor excision and decreased again by tumor recurrence toward death. These findings suggested that the decrease of serum DPP IV activity occurred from the early stage of hamster buccal pouch carcinogenesis as a tumor-burden marker.

9,10-Dimethyl-1,2-benzanthracene

Phase I clinical studies of S-1108: safety and pharmacokinetics in a multiple-administration study with special emphasis on the influence on carnitine body stores.

S-1108, the prodrug of S-1006, was given to healthy volunteers three times a day (TID) for 8 days in a dose of 200 mg in a crossover placebo-controlled study. The safety of S-1108 and the pharmacokinetics of S-1006 and pivalic acid liberated from pivaloyloxymethyl ester of S-1108 were investigated. There were no abnormal symptoms or signs, as observed by physical and laboratory tests. The half-life and area under the concentration-time curve of S-1006 was reduced from 1.11 +/- 0.17 h at the first dose to 0.87 +/- 0.18 h at the last dose and from 7.30 +/- 1.10 to 5.20 +/- 0.85 micrograms.h/ml, respectively. However, there was no significant difference in the peak concentration between the two doses. Pivalic acid was found to be completely detoxified by conjugation with carnitine. The total urinary recovery of pivalic acid as pivaloylcarnitine was 98.7 +/- 3.6%, resulting in an increase of daily carnitine urinary excretion two- to threefold the predose value. During the multiple administration of S-1108, the plasma carnitine concentration was reduced to and maintained at 50 to 70% of the control value, suggesting that there might be enough carnitine store in the body to detoxify the pivalic acid in a dose of 200 mg TID. Moreover, the reduced plasma carnitine was rapidly returned to the control value within a few days after the cessation of the administration of 200 mg TID.

Adult

[Establishment of a method to analyze drugs in the hair and its application for determining patient compliance].

The human scalp hair is a useful tissue that retains the past dosage history over a rather long period of time, acting like a "tape-recorder". It should be emphasized that the sampling of hair can be made noninvasively by cutting a few to several pieces of hair nearest to the scalp. Because the hair continues to grow at the rate of about 1 cm/month, each 1-cm hair length contains the drug corresponding to the amount ingested over a 1-month period when the hair is cut into 1-cm lengths successively from the scalp end. However, the hair growth rate is variable both within and between individuals, and the hair has its own growth cycle, i.e., 2 to 8 years or more of the growing stage and a few months of the resting stage. Therefore, the validity of the obtained results must always be considered cautiously, especially in relation to whether a resting phase hair might have been sampled. For obtaining information on the growth rate and stage of a hair, a drug that can be detected in the hair even after a short-term exposure to the drug has been found. These drugs are antimicrobial quinolones such as ofloxacin. By analyzing the axial distribution of ofloxacin along the hair shaft, we can expect to determine the so-called "tape-speed" and "uniformity of tape-running" of a single hair.

Animals

Pharmacokinetics of the new antiplatelet agent 2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine in human subjects.

The pharmacokinetics of KC-764 (2-methyl-3-(1,4,5,6-tetrahydronicotinoyl)pyrazolo[1,5-a]pyridine, CAS 94457-09-7) was studied in healthy male adult volunteers after single ascending oral dose and multiple dosing for 7 days. Serum KC-764 concentration attained the peak in 1 h and declined with a half-life of about 2 h at a single oral dose of 5, 10, 20 and 40 mg. No dose dependent pharmacokinetics of KC-764 was demonstrated. Three metabolites were detected in serum, but their concentrations were lower than that of KC-764. 48-h urinary recoveries after single doses were 41.6-46.6% of dose, not being dose-dependent. Urinary recovery of unchanged KC-764 was 1.1-1.6% of dose. Three metabolites were present in greater amount in urine than unchanged KC-764 and two metabolites were less than KC-764. There was little daily variation of serum concentrations and urinary excretion of KC-764 and its metabolites in the multiple dosing (20 mg twice a day) study. The daily and total urinary recovery were same as those after single doses. Food reduced Cmax and tended to delay tmax, but did not influence AUC0----infinity and urinary recovery. Serum protein binding of KC-764 was about 60%, being not dependent on total serum concentration.

Adult

Effects of DPI 201-106, a novel cardiotonic agent, on hemodynamics, cardiac electrophysiology and arrhythmias induced by programmed ventricular stimulation in dogs with subacute myocardial infarction: a comparative study with dobutamine.

DPI 201-106 (DPI), a novel and potent cardiotonic agent, exhibits its effects by prolonging the open state of Na+ channels, resulting in an increase in action potential duration, and thus, is supposed to share the class III antiarrhythmic activity. The effects of DPI on the hemodynamics, intraventricular conduction and refractoriness of heart, and the incidence of arrhythmias induced by programmed electrical ventricular stimulation (PES) were compared with (+/-)-dobutamine. Dogs which survived for 5 to 7 days after the induction of myocardial infarction were used as the model. The presence of subacute myocardial infarction caused by occluding the left anterior descending coronary artery elicited a mild left ventricular dysfunction represented by a significant decrease in peak LV dp/dt by about 20%. Both i.v. bolus injection of DPI (1, 3 and 5 mg/kg) and i.v. continuous infusion of dobutamine (3, 5 and 10 micrograms/kg/min), which were administered in a cumulative manner, dose-dependently improved the hemodynamic parameters. At the higher doses of both DPI (3 and 5 mg/kg) and dobutamine (5 and 10 micrograms/kg/min) the control values were reached or even exceeded. DPI dose-dependently increased the effective refractory period (ERP) of both non-infarcted and infarcted ventricular myocardia to a similar degree, but the conduction time showed a frequency-dependent increase in the infarcted myocardium to a greater degree than in the non-infarcted myocardium after DPI. In contrast, dobutamine decreased the ERP in both non-infarcted and infarcted myocardia, and slightly increased the difference of refractoriness between the non-infarcted and infarcted zones with no effect on the intraventricular conduction. In the PES study, DPI (3 and 5 mg/kg) produced a significant decrease in the incidence of ventricular tachycardia, whereas dobutamine (5 and 10 micrograms/kg/min) tended to worsen the arrhythmias. These findings suggest that cardiotonic agents with a class III antiarrhythmic property such as DPI may be potentially useful for the management of heart failure accompanied by ischemic heart disease.

Animals

Ofloxacin in human hair determined by high performance liquid chromatography.

A procedure is presented for quantitating ofloxacin (OFLX) in human scalp hair by high performance liquid chromatography (HPLC) with a fluorescence detector. An octadecylsilane (ODS) column was used and the mobile phase was a mixture of potassium phosphate buffer (pH 2.6) and acetonitrile. The recovery of OFLX was 90.9-93.8% and within- and between-run precisions were 0.35-1.41% and 1.41-5.49% as the coefficient of variation (CV), respectively, when 5-50 ng OFLX was added to 1 mg blank hair. The calibration curve was linear in the range of 0.5-50 ng/tube (0.5 ml). Interference with other quinolone derivatives could be avoided according to the difference in their retention times or fluorescence spectra. Several pieces of hair were obtained from each of twelve healthy male volunteers, who had taken OFLX (100, 300 or 900 mg total dose) over a 1-3 day period 2 weeks before the hair sampling. In all hair samples except one obtained from a volunteer, who had taken the lowest dose, the 2-cm long segments nearest the scalp contained OFLX (5-45 ng/mg hair), while the upper segments did not. A highly significant positive correlation was observed between the total dose and the concentration of OFLX in the 2-cm long hair segments. Such a positive correlation was also revealed in rat hair sampled after repeated i.p. administration of OFLX over a 5-week period. These results suggest that the measurement of OFLX in hair by the present method would be useful for testing patient compliance in clinical pharmacology as well as for application to forensic science.

Adult

[The anti-pyretic mechanism of alminoprofen].

The anti-pyretic activity of alminoprofen (AP), a non-steroidal anti-inflammatory agent, and its mode of action were investigated in conscious febrile rabbits. A fever was evoked by i.v. injection of lipopolysaccharide (LPS), intracisternal (i.c.) injection of leukocytic pyrogen (LP) or i.c. injection of arachidonic acid (AA). The amount of PGE2 or AP in the cerebrospinal fluid (CSF) after i.v. LPS was estimated using an RIA or HPLC method. AP (3-30 mg/kg, p.o.) dose-dependently inhibited the LPS (0.5 micrograms/kg, i.v.)-induced fever; AP, ibuprofen, indomethacin and pranoprofen had ED50 values of 9.64, 26.45, 4.41 and 11.91 mg/kg, p.o., respectively. PGE2 in the CSF was markedly increased during the elevation of body temperature after i.v. LPS (0.5 microgram/kg). AP (30 mg/kg, p.o.) markedly inhibited the increase in PGE2 that was observed in the CSF during fever developed in response to i.v. LPS (0.5 micrograms/kg). The AP concentration in the CSF 2 hr after AP (30 mg/kg, p.o.) was 2.86 x 10(-6) (1.15-4.57 x 10(-6) M, a concentration too low to inhibit PG synthesis. A dose-dependent fever was observed after i.c. LP (1-8 unit) or AA (10-100 micrograms). AP (30 mg/kg, p.o.) shifted the dose-response curves for the i.c. LP-induced fever to the right, but did not have any effect on the i.c. AA-induced fever. These results suggest that AP has a relatively potent anti-pyretic activity, and its mechanism of action involves competition with LP at a site in the CNS, but does not involve an inhibition of cyclooxygenase at a central site, which has been considered as an anti-pyretic mechanism of nonsteroidal anti-inflammatory drugs.

Animals