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Biomedical subjects

Y Akimoto

Publications and source records attributed to Y Akimoto.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effects of extraneuronal accumulation of isoprenaline on cAMP production in perfused rat heart.

The effects of extraneuronal accumulation of isoprenaline on the level of cAMP in perfused rat hearts were investigated. When catechol-O-methyl transferase (COMT) was intact, perfusion with isoprenaline (10(-6) M) for 5 min and 30 min (low accumulation of isoprenaline in the heart) enhanced the cAMP level. Propranolol (10(-6) M) significantly decreased the high level of cAMP produced by the perfusion with isoprenaline for 5 min and 30 min (low accumulation of isoprenaline). When COMT was inhibited by tropolone, perfusion with isoprenaline (10(-6) M) for 5 min (slight accumulation of isoprenaline in the heart) slightly increased the level of cAMP, while perfusion for 30 min (high accumulation of isoprenaline in the heart) did not increase the level of cAMP. Propranolol (10(-6) M) significantly decreased the cAMP level produced by 5 min perfusion with isoprenaline, but did not change the level by 30 min perfusion. The perfusion length (5 min and 30 min) and COMT inhibition by tropolone (10(-4) M) in the absence of isoprenaline did not affect cAMP levels. These results suggest that extraneuronally accumulated isoprenaline may inhibit the adenylate cyclase in perfused rat hearts.

Animals↗
PubMed1990

Effects of nitroglycerin on stable thromboxane A2 analogue-induced, nifedipine-resistant contraction in canine basilar artery.

The stable thromboxane A2 analogue, STA2, caused concentration-dependent contractions in the canine basilar artery. In Ca2(+)-free medium containing EGTA (0.1 mM) and nifedipine (10(-6) M), the addition of Ca2+ (2.5 mM) in the presence of STA2 (10(-8) M) caused a tonic contraction (nifedipine-resistant Ca2(+)-induced contraction). In the basilar artery, nitroglycerin did not significantly affect such nifedipine-resistant Ca2(+)-induced contractions, but nearly abolished the contraction in the coronary artery. The present experiments suggest that the regulatory mechanism of mobilized Ca2+ for the nifedipine-resistant Ca2(+)-induced contraction produced by STA2 in the basilar artery is different from that in the coronary artery.

Animals↗
PubMed1990

Concentrations of ampicillin in human serum and mixed saliva following a single oral administration of lenampicillin, and relationship between serum and mixed saliva concentrations.

The concentrations of ampicillin in serum and mixed saliva after a single oral administration of lenampicillin (500 mg) were determined by the paper disc method. The samples of serum and mixed saliva were obtained at 1, 2, 3 and 4 h after administration. The highest concentrations of ampicillin in serum and mixed saliva occurred 1 h after administration of lenampicillin, and were 11.55 and 0.060 micrograms/ml, respectively. A significant correlation coefficient between the concentrations of ampicillin in serum and mixed saliva, r = 0.71, P less than 0.001, was found.

Administration, Oral↗
PubMed1990

[Nocturnal hypoxia and treatment in the patients with Duchenne muscular dystrophy].

Overnight monitoring using pulse oximeter was performed on 10 patients with Duchenne muscular dystrophy (mean age, 22; mean %FVC, 26.6%; mean PaCO2, 54.1 Torr; mean PaO2 76.6 Torr). At the same time, spinal deformity and obesity were examined. In 4 patients, the measurement of the chest and abdominal wall movements were performed by using a respisomnograph. In 5 patients, nocturnal desaturation below 95% occurred despite normal daylight blood gas tension. In the other 5 patients with hypercapnea of over 50 Torr, nocturnal desaturation below 85% occurred, and 3 patients required oxygen supplementation treatment using a low concentration of oxygen. In 4 patients with hypercapnea over 50 Torr, cuirass-assisted respirators were used and they prevented mild nocturnal desaturation, but did not have much effect on severe nocturnal desaturation. Nocturnal desaturation was associated not only with hypopnea and hypoventilation, but with normal chest and abdominal wall movement using cuirass-assisted respirators. It seemed that desaturation with normal respiratory pattern can be attributed to ventilation-perfusion mismatching. The severity of the desaturation did not always correlate to the spinal deformity and the obesity.

Adolescent↗
PubMed1989

Effects of specific alpha-adrenoceptive agents on extraneuronal uptake (uptake2) of isoproterenol in perfused rat heart.

Effects of specific alpha-adrenoceptive agents (alpha 1-agonist, alpha 1-antagonist, alpha 2-agonist and alpha 2-antagonist) on the extraneuronal accumulation of 3H-isoproterenol in the perfused rat heart were examined. The extraneuronal accumulation of 3H-isoproterenol in the hearts perfused with 3H-isoproterenol (10(-6)M) under COMT inhibition by tropolone (10(-4)M) was about 6 times higher than that of intact COMT. The increase in the accumulation by COMT inhibition was regarded as 100% and the effects of specific alpha-adrenoceptive agents on the accumulation was evaluated. alpha 1-agonists, methoxamine and phenylephrine, did not affect the accumulation. alpha 1-antagonists, prazosin, bunazosin and YM-12617, significantly decreased the accumulation of 3H-isoproterenol and these IC50 values were 2 x 10(-6)M, 3.5 x 10(-6)M and 2.3 x 10(-5)M, respectively. alpha 2-agonists, clonidine and guanabenz, significantly reduced the accumulation and these IC50 values were 3.4 x 10(-5)M and 2.9 x 10(-7)M, respectively. The alpha 2-antagonist, yohimbine, did not affect the accumulation. The present experiments clearly demonstrated that the tested alpha 1-antagonists and alpha 2-agonists inhibited uptake2 in rat heart but the tested alpha 1-agonists and an alpha 2-antagonist did not inhibit it.

Adrenergic alpha-Agonists↗
PubMed1989

Josamycin concentrations in human dental granuloma after a single oral administration of josamycin.

1. Josamycin concentrations in human serum and dental granuloma after a single oral administration of josamycin (600 mg) were assayed by an agar diffusion (paper disc) method. 2. The mean peak josamycin concentrations in serum and dental granuloma occurred at an identical time, approximately 90 min, and were 0.88 micrograms/ml and 1.61 micrograms/g, respectively. 3. The mean concentration ratio of dental granuloma to serum at the peak time was 2.24. 4. Josamycin concentration in dental granuloma at the peak time exceeded MIC80 for clinically isolated strains of Streptococcus group A, Peptostreptococcus spp., and Bacteroides spp.

Administration, Oral↗
PubMed1989

A novel orally active dopamine prodrug TA-870. I. Renal and cardiovascular effects and plasma levels of free dopamine in dogs and rats.

Intraduodenal administration of N-(N-acetyl-L-methionyl)-O, O-bis(ethoxycarbonyl)dopamine (TA-870), a newly synthesized dopamine derivative, increased the renal blood flow (RBF) and mesenteric blood flow in anesthetized dogs, while blood pressure and heart rate were less affected. It also increased the glomerular filtration rate, urine volume, and urinary sodium excretion in saline-loaded anesthetized dogs. In conscious dogs, TA-870 and dopamine hydrochloride (DA-HCl) increased RBF in parallel with increases in plasma free dopamine (free-DA) concentration. At an equimolar dose of 71 mumols/kg, p.o., the effect of TA-870 continued for greater than 4 h, while that of DA-HCl lasted for only 2 h: the peak free-DA concentration and maximum increase in RBF were 155 +/- 57 ng/ml and 56 +/- 15%, respectively, for TA-870, and those for DA-HCl were 32 +/- 13 ng/ml and 36 +/- 10%. Similarly, TA-870 showed greater increases in both RBF and plasma free-DA concentration than DA-HCl in anesthetized rats. In contrast to enteral administration, intravenously administered TA-870 exhibited weaker effects than intravenous DA-HCl in anesthetized dogs. In conclusion, TA-870 is an orally effective dopamine prodrug capable of producing higher and more sustained plasma concentrations of dopamine than DA-HCl when administered by the enteral route.

Administration, Oral↗
PubMed1989

A novel orally active dopamine prodrug TA-870. II. Evidence that TA-870 is a dopamine prodrug.

The mechanism of action of a new orally active dopamine (DA) prodrug, TA-870 (N-(N-acetyl-L-methionyl)-O,O-bis(ethoxycarbonyl)(DA) was studied. When TA-870 (1 mg/kg) was injected in anesthetized dogs, renal vascular resistance was decreased and renal blood flow was increased. The renal vasodilatory effect of TA-870 correlated with the plasma level of DA but not with the level of de-ethoxycarbonyl metabolite of TA-870 (i.e., N-(N-acetyl-L-methionyl)DA; DEC-TA-870). The renal vasodilatory effect of TA-870 was inhibited strongly by haloperidol and slightly by propranolol. Pretreatment with phenoxybenzamine enhanced the renal vasodilatory effect of TA-870. In the isolated rabbit splenic artery, TA-870 and DEC-TA-870 showed no effects, whereas dopamine showed a contracting effect, which was inhibited by phentolamine. In the propranolol- and phentolamine-treated splenic artery, TA-870 and DEC-TA-870 caused weak relaxant effects on PGF2 alpha-induced contraction. These effects were not antagonized by metoclopramide. On the other hand, DA showed a strong relaxant effect, which was competitively inhibited by metoclopramide. In addition, TA-870 and DEC-TA-870 further relaxed the artery that had been maximally relaxed by DA. We concluded that TA-870 and DEC-TA-870 exert weak vasodilatory effects that are different from that of DA in vitro, and that TA-870 exerts its vasodilatory effect after its conversion to free DA in vivo.

Animals↗
PubMed1989

[Susceptibility and beta-lactamase-producing strains of methicillin-resistant Staphylococcus aureus].

Thirty-three strains of methicillin-resistant Staphylococcus aureus (MRSA, MIC for methicillin greater than or equal to 16.0 micrograms/ml) isolated from sputum were examined for their susceptibilities against 8 antimicrobial agents. Ampicillin (ABPC), methicillin (DMPPC), cefazolin (CEZ), minocycline (MINO), erythromycin (EM), tobramycin (TOB), refampicin (RFP), and ofloxacin (OFLX) were used as the antimicrobial agents. The production of beta-lactamase was also determined. The results are as follows: 1) The highest susceptibility was given by RFP, and followed by MINO, and OFLX. All strains were resistant against EM and TOB. 2) The percentage of beta-lactamase-positive strains was 75.8%, which was distributed nearly identical among each MIC to DMPPC (72.0-77.8%). 3) Since the beta-lactamase-positive strains were found among the sensitive strains to ABPC, it was suggested that the use of beta-lactam antimicrobial agents might bring into the higher MIC value to ABPC. 4) Since there were beta-lactamase-negative strains among the resistant strains to ABPC, it was indicated that penicillin binding protein-2' might be produced by giving beta-lactam antimicrobial agents.

Ampicillin Resistance↗
PubMed1988

Epidermal growth factor (EGF)-induced morphological changes in the basement membrane of chick embryonic skin. An electron-microscopic study.

The effect of epidermal growth factor (EGF) on the basement membrane structure of chick embryonic skin cultured in a chemically defined medium (BGJb) containing 20 mM hydrocortisone, and EGF at 10, 50, or 100 ng/ml supplemented with 5% delipidized fetal calf serum, was examined by electron microscopy. During development of the epidermis in vitro, EGF (100 ng/ml) caused striking changes to occur in the basement membrane structure and in the keratinization process. The basement membrane frequently became discontinuous with many gaps apparent in section, and occasionally became folded following detachment from the basal surface of the epidermis and protruded into the underlying dermis. In the basal and intermediate cells of EGF-treated epidermis, tonofilament bundles were decreased in number, while desmosomes and hemidesmosomes revealed no significant changes in morphology.

Animals↗
PubMed1988

Effects of NC-1300-B, a new benzimidazole derivative, on hog gastric H+, K+-ATPase, gastric acid secretion and HCl.ethanol-induced gastric lesions in rats.

This study was designed to determine the effect of a newly synthesized benzimidazole derivative NC-1300-B on H+, K+-ATPase (proton pump) in the hog gastric mucosa and on the basal gastric acid secretion and necrotizing agent-induced gastric lesions in rats. NC-1300-B inhibited the proton pump in a concentration-dependent manner and concentrations which inhibited the enzyme activity by 50% were 4.4 x 10(-6) M at pH 6.0 and 3.1 x 10(-5) M at pH 7.4. NC-1300-B administered orally or intraperitoneally 0.5 hr before ligating the pylorus inhibited the gastric acid secretion in a dose-dependent manner. The ED50 values (doses which inhibit acid output or lesion formation by 50%) for acid secretion were 11.5 and 11.0 mg/kg with oral and intraperitoneal administration, respectively. The antisecretory effect in a dose of 100 mg/kg persisted for up to 72 hr. NC-1300-B administered orally or intraperitoneally 0.5 hr before HCl.ethanol administration protected against damage of the gastric mucosa in a dose-dependent manner. The ED50 values for lesion formation were 13.3 and 23.0 mg/kg with oral and intraperitoneal administration, respectively. This protection with an oral dose of 100 mg/kg persisted for up to 72 hr. While pretreatment with 5 mg/kg of indomethacin given subcutaneously did not appreciably reverse the NC-1300-B protection, the pretreatment with 10 mg/kg of N-ethylmaleimide given subcutaneously potently reversed the NC-1300-B protection. NC-1300-B administered intragastrically at 30 mg/kg significantly inhibited the amplitude of gastric contraction for 50 min after intragastric administration. These effects of NC-1300-B on gastric secretion and lesion formation are much the same as those of the established proton pump inhibitor omeprazole, except for the short duration of the action of omeprazole (less than 24 hr).

Adenosine Triphosphatases↗
PubMed1988

Extraneuronal accumulation of isoproterenol in atria and ventricle of perfused rat heart.

Extraneuronal accumulation of isoproterenol in atria and ventricle of perfused rat heart was investigated. Rat hearts were perfused with various concentrations of 3H-isoproterenol for 30 min in the absence and the presence of catechol-O-methyltransferase (COMT) inhibitor (tropolone). When COMT was intact, the accumulation of 3H-isoproterenol in both atria and ventricle after perfusion with low concentration of 3H-isoproterenol (0.01 to 1 mumol/l) was less than that of perfusing concentration; the tissue/medium ratio (T/M) of isoproterenol for artia was lower than that for ventricle. The T/M of isoproterenol after perfusion with 10 and 20 mumol/l of 3H-isoproterenol were 0.94 and 1.76 for atria and 3.25 and 2.95 for ventricle, respectively. When COMT was inhibited by tropolone, the T/M increased 6.3-9.0 folds for atria and 5.1-6.7 folds for ventricle after perfusion with 3H-isoproterenol (0.01 to 1 mumol/l). From these results, it was concluded that both atria and ventricle of the rat heart have an extraneuronal O-methylating system as reported in rat whole heart, and was suggested that there might be different capacities of extraneuronal uptake and COMT between them.

Animals↗
PubMed1988

Ampicillin concentrations in human serum and periodontal membrane following a single oral administration of talampicillin.

1. Ampicillin concentrations in human serum and periodontal membrane after a single oral administration of talampicillin (500 mg) were assayed by the agar diffusion (paper disc) method. 2. The peak times of serum and periodontal membrane were identical, being 150 min after administration. 3. The peak concentrations of serum and periodontal membrane were 7.81 micrograms/ml and 4.11 micrograms/g, respectively. 4. The mean ratio of periodontal membrane to serum concentration at the peak time was 0.53.

Administration, Oral↗
PubMed1988

Telecommunication and international health research.

Telecommunication will revolutionize how international medical research is completed. It is faster, more accurate, less expensive, and potentially more accessible than all other existing modes of communication. It is time for medical scientists to come into the age of electronic communication.

International Cooperation↗
PubMed1988

Ampicillin concentrations in human dental granuloma after a single oral administration of talampicillin.

Ampicillin concentrations in human serum and dental granulomas of 31 patients were determined after a single oral dose of talampicillin (equivalent to 500 mg of ampicillin) was administered to each. The specimens were taken at 1.5, 2.0, 2.5, 3.0, and 3.5 h after the administration of talampicillin. The mean peak ampicillin concentrations in serum and dental granulomas occurred at identical times, 2.5 h, and were 8.29 micrograms/ml (range, 1.81 to 13.20 micrograms/ml) and 2.94 micrograms/g (range, 1.14 to 7.16 micrograms/g), respectively. The mean dental granuloma/serum ampicillin concentration ratio at the peak time (2.5 h) was 0.42 (range, 0.29 to 0.56). Ampicillin concentrations in dental granulomas exceeded most of the MICs for the bacteria commonly isolated from odontogenic infection.

Administration, Oral↗