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Biomedical subjects

H Yamaguchi

Publications and source records attributed to H Yamaguchi.

At least 793 records · Page 44Linked to original sources
PubMed1994

Continuous non-invasive finger blood pressure monitoring in children.

We evaluated the performance of continuous non-invasive finger arterial pressure measurement using the volume-clamp technique (Finapres). This study was designed to compare finger arterial pressure with brachial blood pressure estimated by the auscultatory method in 217 children (90 boys and 127 girls) aged 4-16 years and in 38 adults (aged 18-45 years). Finger and brachial artery pressure readings were obtained consecutively from the ipsilateral side in the supine position. Finger arterial pressure waveforms were recorded in all children except 4 with small and thin fingers. There was good agreement for systolic pressure with only a slight underestimation of 1.9 mmHg and 5.1 mmHg lower for diastolic pressure. This difference most probably reflects inaccuracy of the auscultatory cuff method rather than an error in the Finapres. There was large inter-individual variability in Finapres recordings which might be due to differences in vasomotor tone, as demonstrated by systolic amplification in 5 patients with anorexia. However, Finapres showed a small within-subject variability (3.8 mmHg for systolic and 4.1 mmHg for diastolic pressure) determined in 5 patients during phenylephrine infusion, and as good reproducibility as the auscultatory method. These results suggest that finger arterial pressure measurement in children older than 6 years of age has similar accuracy as that in adults, and that this method is useful for clinical applications in children, especially for the non-invasive evaluation of autonomic control and cardiovascular reflexes involving transient and rapid blood pressure changes.

Adolescent↗
PubMed1994

Circulatory responses in children with unexplained syncope evaluated by continuous non-invasive finger blood pressure monitoring.

Cardiovascular responses on active standing in children with unexplained syncope were investigated with continuous non-invasive finger artery pressure monitoring (Finapres). We examined 34 symptomatic patients (13 boys and 21 girls), aged 8-16 years, and 24 age-matched controls. Finger blood pressure and heart rate were monitored continuously for 5 min in the supine position and for 10 min while standing. Ten of 34 patients developed fainting symptoms with hypotension during upright posture (fainters). In the initial standing phase (0-30 s), two prominent abnormal blood pressure responses were found in patients: a marked decrease 45 +/- 18/23 +/- 8 mmHg and a prolonged recovery time (16.5 +/- 2.9 versus 27.7 +/- 13.6 s), which appeared to be based on impaired vasoconstriction. Either or both abnormalities were observed in 21 (62%) of the 34 patients and in 2 (8%) of the controls. In addition, fainters also had a more marked increase in heart rate during standing compared with non-fainters. Our findings suggested that more than half of children with syncope had abnormal cardiovascular reflexes in the initial phase which appeared to be associated with vasodepressor syncope. The active standing test with a continuous beat-to-beat blood pressure recording has a high sensitivity in detecting abnormalities of autonomic function in patients with unexplained syncope.

Adolescent↗
PubMed1994

Interaction of oxyimino beta-lactams with a class C beta-lactamase and a mutant with a spectrum extended to beta-lactams.

The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids, and substitution of the glutamic acid at position 219 in the enzyme by lysine was previously shown to broaden its substrate spectrum to oxyimino beta-lactams (K. Tsukamoto, R. Ohno, and T. Sawai, J. Bacteriol. 172:4348-4351, 1990). To clarify this spectrum extension from the kinetic point of view, the interactions of cefuroxime, ceftazidime, and aztreonam with the wild-type and mutant enzymes were analyzed. In addition to aztreonam, known as a progressive inhibitor of class C beta-lactamases, cefuroxime and ceftazidime were found to act as progressive inhibitors of the wild-type enzyme. On the other hand, only aztreonam showed weak progressive inhibition of the mutant enzyme. On the basis of kinetic parameters, a minimum scheme for interaction of the oxyimino beta-lactams with the wild-type enzyme was proposed, and the rate-limiting step of the hydrolysis of unfavorable substrates was indicated to be conversion of the stable acyl-enzyme intermediate to the unstable intermediate. In aztreonam hydrolysis by the mutant enzyme, the reaction rate at the rate-limiting step was 2,000 times that of the wild-type enzyme. These results indicate that the mutation at position 219 disturbs the stabilization of the stable intermediate.

Anti-Bacterial Agents↗
PubMed1994

Therapeutic efficacy of lanoconazole, a new imidazole antimycotic agent, for experimental cutaneous candidiasis in guinea pigs.

The therapeutic efficacy of 1% cream and 1% solution of lanoconazole, a new imidazole antimycotic agent, in the model of cutaneous candidiasis in prednisolone-treated guinea pigs was evaluated in comparison with that of comparable formulations of bifonazole. Each preparation was topically applied once a day for 3 consecutive days, starting on the fifth day postinfection, and quantitative culture study wsa conducted on the ninth day postinfection. Both formulations of lanoconazole were much more highly effective in terms of eradication of fungi than the bifonazole formulations.

Administration, Topical↗
PubMed1994

Localization of Alzheimer amyloid beta protein precursor and its relation to senile plaque amyloid.

The authors examined the ultrastructural localization of amyloid beta protein precursor (APP) in normal human brains immunohistochemically using 3 kinds of APP antisera. The patterns of immunoreaction differed between the antisera used. Antiserum 770, against APP1-770, predominantly labeled the cytoplasm of neurons, whereas antiserum Z31, against the pre-beta region of the APP, labeled astroglial processes intensely and neurons to a lesser extent. Antiserum 1736, against the N terminal of beta protein, labeled both neurons and astrocytes. Vascular smooth muscle cells and some of the endothelial cells in the cerebral arterioles and capillaries were labeled with Z31 and 1736. The APP exists in every cells, while various patterns of immunoreactivity may reflect the difference in the metabolic pathway of APP between cell types.

Aged↗
PubMed1994

"Myocardial stunning"-like phenomenon during a crisis of pheochromocytoma.

A woman with a pheochromocytoma crisis initiated by cardiogenic shock showed severely impaired left ventricular contraction at the time of admission. Heart failure was improved rapidly, and an endomyocardial biopsy performed on the 11th day of admission showed findings compatible with "catecholamine cardiomyopathy". Regarding the pathogenesis of short-duration left ventricular dysfunction, catecholamine-induced cardiotoxicity would probably be the initial consideration. However, in this case, after considering the electrocardiogram on admission and a series of left ventriculograms, "myocardial stunning" following diffuse coronary vasospasm induced by catecholamine crisis may have also contributed to the dysfunction.

Adrenal Gland Neoplasms↗
PubMed1994

Histamine H2-receptor antagonism of T-593: studies on positive chronotropic responses in guinea pig atria.

Histamine H2-antagonistic properties of the novel H2-antagonist T-593, (+-)-N-[2-hydroxy-2-(4-hydroxyphenyl)ethyl]-N'-[2- [[[5-(methylamino)methyl-2-furyl]methyl]thio]ethyl]-N"- (methylsulfonyl) guanidine were investigated on the histamine-induced positive chronotropic responses in isolated guinea pig right atria. T-593 at 3 x 10(-7)-3 x 10(-6) M suppressed the maximal responses of the histamine concentration-response curves in a concentration-dependent fashion, indicating that T-593 is an unsurmountable antagonist. The pD'2 values were 5.50 for T-593 and 5.61 for famotidine; and the IC50 values at 1 x 10(-5) M histamine were 1.05 x 10(-6) M for T-593, 1.59 x 10(-6) M for ranitidine and 1.67 x 10(-7) M for famotidine. T-593 is a racemic compound composed of two enantiomers, (-)-T-593 and (+)-T-593. The histamine H2-antagonistic activity of (-)-T-593 was 1.5-fold more potent than that of racemic T-593, but (+)-T-593 scarcely inhibited the histamine-induced positive chronotropic response. Histamine H2-antagonism by racemic T-593 was mainly attributed to (-)-T-593. Isoproterenol-induced positive chronotropic responses were not affected by T-593 even at 3 x 10(-5) M. Pretreatment of ranitidine for 10 min prior to application of T-593 protected H2-receptors from unsurmountable antagonism by T-593. Reversibility of H2-antagonism was determined every 1 hr after a 30-min treatment of H2-antagonists. T-593 inhibited the positive chronotropic responses for over 6 hr in contrast to fast recovery from inhibition by ranitidine or famotidine. This result showed that T-593 is a slowly dissociable, long-acting histamine H2-antagonist.

Animals↗
PubMed1994

Structure-depolarizing activity relationship for achatin-I, a tetrapeptide with a D-Phe residue, and its derivatives toward the crayfish giant axon.

Achatin-I (Gly-D-Phe-Ala-Asp) is a tetrapeptide isolated from the ganglia of an African giant snail (Achatina fulica Férussac). The compound and its derivatives were synthesized, and their effects on the action potential of the crayfish giant axon elicited by electrical stimulation were examined by an intracellular recording method. The membrane potential after the action potential had fallen was elevated by some compounds at an acidic but not neutral pH level. An analysis of the structure-activity relationship for the activity to elevate the afterpotential at an acidic pH level, suggests that the factors favorable for activity were the beta-turn conformation, a beta- or gamma-carboxyl group in the C-terminal residue, appropriate hydrophobicity and/or bulkiness in the protecting groups for the alpha-amino group at the N-terminus, and the number of negative charges in the entire molecule.

Action Potentials↗
PubMed1994

Reconstitution of Phaseolus vulgaris alpha-amylase inhibitor from isolated subunits.

The reconstitution of Phaseolus vulgaris alpha-amylase inhibitor from its two kinds of subunits was studied. The inhibitor was reconstituted by quick dilution from its subunits denatured in 6 M guanidine hydrochloride with a concomitant restoration of the inhibitory activity. Various environmental factors had a profound influence on the rate and extent of the reconstitution. Especially low protein concentration and high ionic strength were essential for a high yield of regained activity, and Zn2+ was also effective in promoting reconstitution. The maximum specific activity of reconstituted inhibitor was obtained at a 1:1 molar ratio of alpha-subunit: beta-subunit. Under the optimal conditions obtained, the activity regain was about 60% of the activity of the native inhibitor. Further, this report advances the possibility that the glycan chains of each subunit may be important in proper folding and assembly of the subunit polypeptides.

Asparagine↗
PubMed1994

Effect of orally administered heat-killed Enterococcus faecalis FK-23 preparation on leukopenia in mice treated with cyclophosphamide.

Cyclophosphamide (CY) treated mice were orally administered heat-killed Enterococcus faecalis FK-23 preparation (FK-23) to define the effect of FK-23 on leukopenia associated with chemotherapy. FK-23 had no inhibiting effect on CY induced leukopenia, whereas it augmented leukocyte reconstitution in CY-treated mice. The percentage of neutrophils increased in the mice orally given FK-23. Furthermore, an increase in a myeloid/erythroid ratio and neutrophilic lineages was found in bone marrow of FK-23 treated mice. These findings suggest that FK-23 may have a potent effect on the augmentation of leukocyte reconstituting capacity in patients receiving chemotherapy.

Animals↗
PubMed1994

Mesothelioma in the atrioventricular node. Case report.

A patient with complete atrioventricular block and an implanted permanent pacemaker died of colon cancer at the age of 64 years. At autopsy, a cardiac tumor in the region of the atrioventricular node (mesothelioma of the atrioventricular node) was found. The origin of this type of tumor is controversial. Histochemical findings suggested that the tumor in this case was of endodermal origin.

Atrioventricular Node↗
PubMed1994

A case of arrhythmogenic right ventricular dysplasia with atrial flutter.

A 57-year-old male who had arrhythmogenic right ventricular dysplasia (ARVD) with recurrent atrial flutter (AF) is reported. The patient had more frequent episodes of AF than of ventricular arrhythmias. Magnetic resonance imaging, echocardiography and right ventriculography revealed dilatation of the right ventricle and endomyocardial biopsy specimens from the right ventricle showed findings which were compatible with ARVD. The left ventricular specimen, however, also revealed a loss of myocytes and interstitial fibroelastic changes. The present case demonstrates an overlap of post-inflammatory or primary endomyocardial fibroelastic changes with ARVD.

Aged↗
PubMed1994

Adamantinoma of the rib metastasizing to the liver.

Adamantinoma is a rare bone tumor, most of which originates in the long bone. Here, we present a case of adamantinoma of the rib with liver metastasis. The patient, a 69-year-old man, complained of dull chest pain for over 6 months. Chest X-ray and CT film revealed osteolytic mass of the right 7th rib. Under the clinical diagnosis of hepatic tumor with rib metastasis, resection of the rib and partial hepatectomy were performed. Pathologically, the bone tumor was diagnosed as primary adamantinoma and the liver tumor was its metastasis. The patient has been well without adjuvant chemotherapy for 5 years after the operation.

Aged↗
PubMed1994

A low calcium condition; important roles of ionized calcium in biology.

Calcium is the most widely distributed and inevitably important bivalent ion which has an intimate relation both to functions and structures in living organisms. However, studies on the structural and functional alterations induced under a low calcium condition have been ignored. In the last two decades, to clarify the role of ionized calcium in biology, the morpho-functional alterations in various organs and tissues under a low calcium condition provoked by calcium chelating drugs have been examined. In this paper, the range of results obtained through our experiments will be reviewed and the almost miraculous roles of the calcium ion in biology will be discussed. Most of the presented results offer just the beginning of a new era of the research in this field, therefore further continuous studies can be expected.

Animals↗
PubMed1994

Development of a novel drug release system, time-controlled explosion system (TES). I. Concept and design.

A novel controlled drug release system. Time-Controlled Explosion System (TES) has been developed. TES has a four-layered spherical structure, which consists of core, drug, swelling agent and water insoluble polymer membrane. TES is characterized by a rapid drug release with a precisely programmed lag time; i.e. expansion of the swelling agent by water penetrating through the outer membrane, destruction of the membrane by stress due to swelling force and subsequent rapid drug release. For establishing the concept and development strategy, TES was designed using metoprolol and polystyrene balls (size: 3.2 mm in diameter) as a model drug and core particles. Among the polymers screened, low-substituted hydroxypropylcellulose (L-HPC) and ethylcellulose (EC) were selected for a swelling agent and an outer water insoluble membrane, respectively. The release profiles of metoprolol from the system were not affected by the pH of the dissolution media. Lag time was controlled by the thickness of the outer EC membrane; thus, a combination of TES particles possessing different lag times could offer any desired release profile of the model compound, metoprolol.

Chemistry, Pharmaceutical↗
PubMed1994

[Direct observation of the tympanic cavity by superfine fiberscopy through the eustachian tube].

It was impossible to observe directly the tympanic cavity with the ear drum intact. The superfine fiberscope, developed by the Department of Otolaryngology, Tokyo Medical College, makes it possible to observe the tympanic cavity through the eustachian tube without any surgical intervention such as myringotomy. This fiberscope is flexible and very fine, having an outer diameter of 0.6-0.8mm. Using this new fiberscope, the following structures can be observed: the handle of the malleus, the long process of the incus, the incudostapedial joint, the head of the stapes, the crus of the stapes, the tendon of the tensor tympani muscle and the promontory. Observation results are presented for 138 ears with various disorders: cholesteatoma, tympanosclerosis, congenital malformation, ossicular dislocation, otosclerosis, otitis media with effusion, chronic otitis media, etc. All patients could be tested with local anesthesia in the outpatient clinic except very young children. The findings were easily recorded on either photographs or video tapes. This superfine fiberscope was of great value in the diagnosis of pathologies affecting middle ear structures in outpatient clinics, since no surgical intervention was necessary in the procedure. In addition, it was very useful for making highly detailed studies and for discussion after the examination.

Adolescent↗
PubMed1994

The novel immunostimulant N-563, an analogue of deoxyspergualin, promotes resistance to Candida albicans infection in mice.

An analogue of deoxyspergualin, N-563 has an immunostimulating activity whereas the mother compound has been found to be a potent immunosuppressant. In this study, the protective effect of the analogue against C. albicans infection was investigated in normal and immunosuppressed mice. In normal mice, N-563 treatment at 10 mg/kg for 3 days prior to infection significantly prolonged the survival time. In immunosuppressed mice treated with a single dose of cyclophosphamide 4 days prior to infection, N-563 at 3 and 10 mg/kg for 3 days prior to infection also significantly prolonged the survival time of mice. In addition, it augmented the phagocytic activity of neutrophils and enhanced the delayed type hypersensitivity reaction against C. albicans. Coincidentally, N-563 appeared to protect against secondary infection with C. albicans in the delayed type hypersensitivity-positive mice.

Adjuvants, Immunologic↗