Search PubMed⌕ Search

Biomedical subjects

M Arita

Publications and source records attributed to M Arita.

At least 271 records · Page 15Linked to original sources
PubMed1988

Poliovirus type 1/type 3 antigenic hybrid virus constructed in vitro elicits type 1 and type 3 neutralizing antibodies in rabbits and monkeys.

Poliovirus exists as three stable serotypes (PV-1, PV-2, and PV-3). These viruses display three antigenic sites each, designated N-AgI, N-AgII, and N-AgIII. When mice are immunized with poliovirus, N-AgI is the major neutralization antigenic site for PV-3, whereas N-AgII and N-AgIII are immunodominant over N-AgI for PV-1. To study the relationship between structure and antigenicity, a hybrid virus was constructed in which N-AgI of PV-1 was replaced by N-AgI of PV-3. PV-3- and PV-1-specific antisera, including those elicited by PV-3 in primates, neutralized the hybrid virus. Injection of the hybrid virus into rabbits or into primates resulted in the production of antisera that neutralized both PV-1 and PV-3. The data show that sequence replacement at N-AgI of poliovirus is compatible with viral proliferation, an observation useful for the development of multivalent picornavirus vaccines.

Amino Acid Sequence↗
PubMed1988

Microbial Conversion of alpha-Ionone, alpha-Methylionone, and alpha-Isomethylionone.

alpha-Ionone, alpha-methylionone, and alpha-isomethylionone were converted by Aspergillus niger JTS 191. The individual bioconversion products from alpha-ionone were isolated and identified by spectrometry and organic synthesis. The major products were cis-3-hydroxy-alpha-ionone, trans-3-hydroxy-alpha-ionone, and 3-oxo-alpha-ionone. 2,3-Dehydro-alpha-ionone, 3,4-dehydro-beta-ionone, and 1-(6,6-dimethyl-2-methylene-3-cyclohexenyl)-buten-3-one were also identified. Analogous bioconversion products from alpha-methylionone and alpha-isomethylionone were also identified. From results of gas-liquid chromatographic analysis during the fermentation, we propose a metabolic pathway for alpha-ionones and elucidation of stereochemical features of the bioconversion.

Journal Article↗
PubMed1988

Evaluation of a nonisotopically labeled oligonucleotide probe to detect the heat-stable enterotoxin gene of Escherichia coli by the DNA colony hybridization test.

A commercially available, alkaline-phosphatase-conjugated oligonucleotide probe for detecting the heat-stable enterotoxin gene of Escherichia coli was compared with cloned gene probes by examining E. coli isolates from traveler's diarrhea by DNA colony hybridization tests. The oligonucleotide probe was useful in specifically identifying the so-called STh gene. No deproteinization of sample was necessary to prepare the colony blots.

Animals↗
PubMed1988

A recombinant virus between the Sabin 1 and Sabin 3 vaccine strains of poliovirus as a possible candidate for a new type 3 poliovirus live vaccine strain.

Biological tests including the monkey neurovirulence test performed on recombinants between the virulent Mahoney and attenuated Sabin 1 strains of type 1 poliovirus indicated that the genome region encoding mainly the viral capsid proteins had little correlation with the neurovirulence or attenuation phenotype of the virus. The results suggested that new vaccine strains of type 2 and type 3 polioviruses may be constructed in vitro by replacing the sequence encoding the antigenic determinants in viral capsid proteins of the Sabin 1 genome by the corresponding sequences of the type 2 and type 3 genome, respectively. Accordingly, we constructed recombinants between the Sabin 1 and Sabin 3 strains of poliovirus in which genome sequences of the Sabin 1 strain encoding most or all capsid proteins were replaced by the corresponding genome sequences of the Sabin 3 strain. One of the recombinant viruses thus constructed was fully viable and showed antigenicity and immunogenicity identical to those of type 3 poliovirus. The monkey neurovirulence tests and in vitro phenotypic marker tests (temperature sensitivity of growth, sodium bicarbonate concentration dependency of growth under agar overlay, and size of plaque) were performed on the recombinant virus. The stability of the virus in regard to the temperature sensitivity phenotype was also tested. The results suggested that the recombinant virus is a possible candidate for a new type 3 poliovirus vaccine strain.

Animals↗
PubMed1988

Production of pili on Vibrio parahaemolyticus.

Electron microscopic examination showed that all strains of Vibrio parahaemolyticus examined had pili on their surface when the organism was grown on marine agar at 28 degrees C for 6-12 h. The pili were morphologically stable on heat treatment at 60 degrees C for 10 min, but both the lateral and polar flagella possessed by this organism were labile. No immunological cross-reactivity between pili of enterotoxigenic Escherichia coli and Vibrio cholerae non-01 and those of V. parahaemolyticus was observed.

Agglutination Tests↗
PubMed1988

Day-to-day variation of the frequency of ventricular premature contractions depends on variation of heart rates.

To examine the manner in which spontaneous variation in the frequency of ventricular premature contractions (VPCs) relates to the variation of heart rate (HR), 68 patients with frequent VPCs were studied, by using 24-hour ECG recordings. All patients had more than 40 VPCs/hour on an initial 24-hour ECG recording and a second recording was made within 2 months (mean: 15 days). For each patient, the HR-dependency of VPCs was evaluated. Plots of VPC frequency per minute (VPCs/min) vs. HR were made at 1-beat/min steps for all HRs recorded for at least 5 min during 24 hours. Based on the patterns of correlation between VPCs/min and HR observed at the first recording, patients were divided into 2 groups: 1) 26 with a positive correlation or the P group (a linear increase in VPCs/min with increasing HRs) and 2) 42 with a non-positive correlation or the NP group. The NP group included: 1) an increased VPCs/min at low HRs and a decrease at high HRs (38 patients), 2) a linear decrease in VPCs/min with increased HRs (2 patients) and 3) constant VPCs/min at all HRs (2 patients). The patterns of correlation were reproducible at the second recording period in 65 of 68 patients (96%). Variability in the VPC frequency per 24 hours between two 24-hour recording periods was significantly greater in the P than in the NP group, while the variability in the mean daily HR was similar between the 2 groups. Thus, the 95% confidence limit for spontaneous reduction in the VPC frequency was greater for the P (67%) than for the NP group (50%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Characteristics of contractile response of isolated portal veins from chronic portal hypertensive rats under altered levels of external K+, Ca2+, and norepinephrine concentrations: a comparison with normal Wistar rats.

We studied contractile properties of portal veins isolated from chronic portal hypertensive rats (PHR) resulting from liver cirrhosis, a model obtained by repeated subcutaneous injections of CCl4 (2 mg/kg) twice weekly for over 45 weeks. Portal venous pressure in vivo was significantly higher in PHR (167.0 +/- 38.7 mmH2O) than in the control normal Wistar rats (NWR) (102.0 +/- 25.5 mmH2O). A pair of portal veins from PHR and NWR were mounted longitudinally in an organ bath and perfused with Tyrode's solution with different K+, Ca2+, and norepinephrine concentrations. The isometric tension was measured by a strain-gauge. Under control conditions, spontaneous phasic contractile force, corrected by cross-sectional area, was greater, and the frequency was lower in PHR than in NWR preparations. The averaged peak contractile force measured at different [K]o (5.4-86.4 mM) was also greater in PHR than in NWR. Force of the tonic contraction measured at different [Ca]o (0.45-5.4 mM), under conditions of 86.4 mM [K]o was significantly larger in PHR than in NWR preparations. However, the Ca2+ sensitivity of both preparations was the same. D-600 (greater than or equal to 0.1 microM) inhibited the tonic contraction in both preparations with an identical sensitivity to the drug. In the presence of norepinephrine (10 microM), the Ca2+ sensitivity of the tonic contraction increased both in PHR and NWR preparations. The increase was more pronounced in PHR and was completely reversed in the presence of the alpha 1-adrenoceptor blocker, prazosin (0.1 microM). The alpha 1-adrenoceptor sensitivity to norepinephrine was not altered in PHR preparations. The rate of Ca2+ release and uptake of intracellular Ca2+ seemed identical in both preparations. Thus, in the absence of norepinephrine, the phasic and tonic contractile forces of portal veins from PHR are larger than that of NWR, probably due to increased membrane Ca2+ permeability. The PHR preparations have a higher affinity for external Ca2+ in the presence of norepinephrine, an additional factor contributing to elevation of portal blood pressure in the presence of chronic liver cirrhosis.

Animals↗
PubMed1988

Effects of mechanical stretch on the membrane potential of guinea pig ventricular muscles.

We studied the effect of stretch on the membrane potentials and ultrastructure of isolated ventricular papillary muscles of guinea pigs. The muscles were stimulated at 0.5 Hz and stretched stepwise from slack length (90% of Lmax) to 100% (mild stretch), 110-120% (moderate stretch), and 130-140% of Lmax (severe stretch), under microscopic control. In control Tyrode solution (K+ = 5.4 mM, Ca2+ = 1.8 mM, Mg2+ = 0.5 mM), the mild to moderate stretch significantly depolarized the resting potential (RP) by about 6 mV as compared to that in slack length, whereas the severe stretch hyperpolarized the membrane by about 5 mV. The latter finding was new and was focused on in later experiments. Both the hyperpolarization and depolarization became more marked when [K+]o was decreased to 1.35-2.7 mM, and became less with elevated [K+]o to 10.8-21.6 mM, thereby suggesting the participation of altered K+ conductance (gK) with these changes in the RP. Perfusion with low [Ca2+]o (0.45 mM) enhanced the depolarization but eliminated the hyperpolarization; high [Ca2+]o (7.2 mM) inhibited the depolarization without effect on the hyperpolarization. D-600 (1 microM), caffeine (10 mM), and ryanodine (1 microM), all of which may produce decreases in [Ca2+]i, abolished the hyperpolarization with inconsistent effects on the depolarization. Moderate to severe stretches decreased the maximum rate of rise of action potential (Vmax), by shifting the Vmax-RP relationship toward hyperpolarizing direction. The shift could be reversed partially after increasing [Mg2+]o to 8.0 mM. Electron microscopic examination revealed that the sarcoplasmic reticulum (SR) remained intact with mild to moderate stretches with significant lengthening of sarcomere length, while with a severe stretch, the SR showed a structural disarrangement with a non-uniform lengthening of sarcomere length. Our observations suggest that stretch-induced hyperpolarization is probably mediated by the increase in gK, presumably secondary to the increase in [Ca2+]i. Ca2+ may be released from the SR upon mechanical stretch of the organelle.

Action Potentials↗
PubMed1988

Two differential mechanisms of automaticity in diseased human atrial fibers.

The ionic mechanisms of automaticity in spontaneously active preparations (n = 38) from "diseased" human atria were investigated. The cycle length (CL) of the automatic action potential (AAP) ranged from 0.6 to 4.5 s (mean +/- S.D.: 2.0 +/- 1.0 s). The AAP from preparations obtained from non-digitalized patients (group 1, n = 29) showed various CLs, in that 16 patients had a CL longer than 2.0 s (slow-type AAP) while in tissues from the other 13 patients, the CL was 2.0 s or less (fast-type AAP). On the other hand, all preparations obtained from the digitalized patients prior to cardiac surgery (group 2, n = 9) had the fast-type AAP (CL less than or equal to 2.0 s). The slow-type AAP was accelerated and changed to the fast one after application of ouabain (1 microM) or by perfusing with 50% [Na+]o Tyrode solution. Ryanodine (1 microM), a specific inhibitor of calcium release from the sarcoplasmic reticulum (SR), markedly lengthened the CL of fast-type AAP, without affecting the slow-type AAP. In contrast, caffeine (15 mM) shortened the CL of the slow-type AAP and remarkably lengthened the CL of the fast-type AAP, as is the case in ryanodine. The rate of slow-type AAP was enhanced with an increase in [Ca2+]o and depressed with a decrease in [Ca2+]o or with application of diltiazem, a Ca2+ channel blocker. The slow-type AAP was changed to the fast-type AAP by stretching the preparation by about 20%. In vitro preparations excised from patients with dilated atria revealed a shorter CL of AAPs. We conclude that in "diseased" human atrial preparations, the ionic mechanism responsible for generation of slow- and fast-type automaticity differs. Slow automaticity (CL greater than 2.0 s) perhaps relates to activation of the slow inward Ca2+ current, while the fast-type automaticity (CL less than or equal to 2.0 s) is linked to cyclic increases in [Ca2+]i.

Action Potentials↗
PubMed1988

Contributions of the sympathetic nervous system, vasopressin and baroreceptor function in brain angiotensin II excess-induced hypertension in the dog.

To determine the principal effects of brain angiotensin(Ang) II on the sympathetic nervous system, vasopressin (AVP), and the high and low pressure baroreceptor systems, we observed the hemodynamic and neurohumoral characteristics induced by the acute(1-hr) and chronic(1-wk) infusion of Ang II into the brain ventricle in conscious dogs, and then evaluated the hemodynamic responses to sole-innervated carotid artery occlusion(COR) after Ang II infusion and again after vagotomy in anesthetized dogs. Both acute(50ng/kg/min) and chronic(15ng/kg/min) infusion of Ang II caused a significant rise in arterial pressure without changes in heart rate. Neither acute nor chronic Ang II treatment produced significant changes in plasma renin activity and norepinephrine in plasma and cerebrospinal fluid(CSF), while the plasma and CSF level of AVP was increased in the acute Ang II treatment, but not in the chronic Ang II treatment. The COR was blunted in the acute Ang II treatment compared with those obtained in the chronic Ang II or sham treatment. The blunted pressor response to carotid occlusion in the acute Ang II treatment was restored by cutting the remaining vagus nerve. These results suggest that baroreceptor reflexes are impaired by the acute excess of Ang II in the brain, and it might be mediated through increased vagal afferent activity, changes in the central integration of low and high pressure baroreceptors, and a combination of both.

Angiotensin II↗
PubMed1988

[Tissue characteristics in left ventricular hypertrophy using magnetic resonance imaging].

For 15 normotensive patients with asymmetric septal hypertrophy (ASH), 10 hypertensive patients with concentric hypertrophy (CH), and five normal subjects (N), we examined changes in myocardial T1 and T2 values related to the cardiac cycle. The usefulness of those values in differentiating diseases with left ventricular hypertrophy was evaluated. Left ventricular (LV) short-axis spin echo images and inversion recovery images were obtained at endsystolic and diastolic cardiac phases, and T1 and T2 images were calculated. The regional wall thickness (WT) and T1 and T2 values were measured in the anterior septum, anterior wall, lateral wall, posterior wall and posterior septum. Myocardial T1 and T2 values were significantly decreased in systole (T1: 185.6 +/- 37.9 msec, T2: 24.4 +/- 6.3 msec, mean +/- SD) compared to those in diastole (T1: 249.2 +/- 56.7 msec, T2: 31.7 +/- 9.4 msec). In both the ASH and CH groups, significant correlations were observed between diastolic T1 values and WT (ASH: r = 0.80, p less than 0.01, CH: r = 0.45, p less than 0.01), and between diastolic T2 values and WT (ASH: r = 0.58, p less than 0.01, CH: r = 0.60, p less than 0.01). In the regions where diastolic WT were more than 17 mm, T1 values in the ASH group (343.4 +/- 40.5 msec) were significantly higher than those of the CH group (247.3 +/- 21.4 msec), although the mean wall thickness values were similar in both groups. The T1/WT and T2/WT were significantly lower in the CH group than those in the ASH and N groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Binding of [3H]saxitoxin to the voltage-dependent Na channels and inhibition of 22Na influx in bovine adrenal medullary cells.

The binding characteristics of [3H]saxitoxin and its binding site were examined in bovine adrenal medullary cells. These cells showed a specific binding of [3H]saxitoxin which was saturable and reversible. Scatchard analysis showed a single class of high-affinity binding sites with an equilibrium dissociation constant of 5.8 nM and a maximum binding capacity of 427.2 fmoles/10(7) cells (124.2 fmoles/mg of cell protein). A Hill plot revealed that there were no co-operative interactions among the binding sites. Unlabeled saxitoxin inhibited the specific binding of [3H]saxitoxin as well as veratridine-induced 22Na influx with a similar potency as did tetrodotoxin. However, veratridine, aconitine and scorpion venom, at concentrations that increased 22Na influx, did not inhibit [3H]saxitoxin binding. These results indicate that saxitoxin binds to a specific site on voltage-dependent Na channels and inhibits the influx of 22Na. [3H]Saxitoxin would be useful for the detailed analysis of voltage-dependent Na channels in adrenal medullary cells.

Adrenal Medulla↗
PubMed1987

Potassium channels in cultured bovine adrenal medullary cells: effects of high K, veratridine and carbachol on 86rubidium efflux.

To investigate the K permeability mechanism(s) in cultured bovine adrenal medullary cells, we measured the effects of high K, veratridine and carbachol on 86Rb efflux from the 86Rb preloaded cells. In non-stimulated cells, the basal efflux of 86Rb into Krebs-Ringer phosphate buffer containing 5.6 mM K proceeded gradually at the rate of 0.7% of cell 86Rb per min. High K caused a rapid 86Rb efflux; it was considerably reduced in Ca free medium. Mn, Co and Mg strongly inhibited high K-induced 45Ca influx and 86Rb efflux. Veratridine induced a sustained 86Rb efflux; it was inhibited by tetrodotoxin and abolished in Na free sucrose medium, but little affected in Ca free medium. Carbachol evoked a rapid and transient efflux of 86Rb; it amounted to 16.9% of cell 86Rb during 1 min. Carbachol-induced 86Rb efflux was inhibited by hexamethonium and d-tubocurarine. Nicotine caused 86Rb efflux, but muscarine had no effect. Carbachol-induced 86Rb efflux was substantially reduced in Na free sucrose medium, but little affected in Ca free medium. Mn, Co and Mg strongly reduced carbachol-induced 45Ca influx, but they did not appreciably alter carbachol-induced 22Na influx and 86Rb efflux. These results suggest that adrenal medullary cells have, at least, three distinct types of K permeability mechanisms: (1) basal K efflux, (2) Ca dependent K efflux, and (3) Na dependent K efflux. It seems that nicotine receptors mediate K efflux by increasing Na influx via nicotinic receptor-associated ionic channels rather than Ca influx via voltage dependent Ca channels.

Adrenal Medulla↗
PubMed1987

Electrophysiologic properties differ in the ventricular endocardium and epicardium of the Japanese monkey.

We measured action potential duration (APD) from the endocardium (Endo) and epicardium (Epi) of the left ventricular free wall in Japanese monkey hearts and found that the APD of Endo is significantly longer than that of Epi at a stimulus cycle length of 1500 msec in normal Tyrode solution (control condition). We then hypothesized that shorter APD of Epi results from greater outward pump current and that the difference in the current may be due to a difference in membrane Na,K-ATPase activity between Endo and Epi. If this were the case, interventions which alter the Na,K-pump activity should alter electrophysiologic characteristics in the endocardium and the epicardium to different degrees. An application of ouabain (10(-6) M), an inhibitor of Na,K-ATPase, produced greater shortening of APD and greater depolarization of the resting potential in Endo as compared with Epi. Shortening of stimulus cycle length shortened the APD more markedly in Endo than Epi, resulting in a significantly longer APD in Epi than Endo at a stimulus cycle length of 200 msec. The hyperpolarization and the APD shortening produced when the tissues were returned to 5.4 mM K+ Tyrode solution from K+-free medium were also more marked in Endo than in Epi. Such findings suggest that endocardial cells are more liable to accumulate Na ions intracellularly and K ions extracellularly when the Na, K-pump is suppressed by ouabain or K+-free perfusion, presumably due to lower activity of Na, K-ATPase in Endo compared to Epi.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1987

Differential effects of L-propionylcarnitine on the electrical and mechanical properties of guinea pig ventricular muscle in normal and acidic conditions.

We studied the effects of L-propionylcarnitine (PC) on transmembrane action potentials and isometric contractile tension in isolated guinea pig ventricular papillary muscles. The effects of 5 concentrations of PC (10(-5), 10(-4), 10(-3), 10(-2) and 3 X 10(-2)M) were examined in both normal (pH 7.4) and acidic (pH 6.9) conditions. The concentrations of 10(-5) to 10(-2)M had no significant effect on action potential amplitude, maximum upstroke velocity of phase 0 and resting potential, in either condition. At pH 7.4, action potential duration (ADP) was significantly (P less than 0.05) or insignificantly shortened by the drug depending upon the concentration used. At pH 6.9, however, the APD was prolonged by moderate PC concentrations (10(-3) and 10(-2)M), in which the effective refractory period (ERP) was also lengthened, associated with an increased ERP/APD ratio. In both pH conditions, the highest concentration (3 X 10(-2)M) significantly (P less than 0.05) decreased all these action potential parameters. PC had a biphasic effect on the developed tension. In both pH conditions, low PC concentrations (10(-5) to 10(-3)M) produced an initial augmentation of the contraction, followed by subsequent reduction. The initial augmentation disappeared by pretreatment with reserpine or propranolol, suggesting the involvement of beta-adrenoceptors. In the steady state, all PC concentrations produced a negative inotropic effect at pH 7.4, while at pH 6.9 only high concentrations (10(-2)M and 3 X 10(-2)M) had this effect. These results suggest that the effects of PC in an acidic condition differ considerably from those in a normal pH condition and that limited concentrations of PC (10(-3) to 10(-2)M) may prevent re-entrant arrhythmias from developing under acidic conditions via lengthening of the ERP, without deleterious effects on the contractile force.

Action Potentials↗
PubMed1987

Antigenic and biochemical characterization of poliovirus type 1 isolates.

By the introduction of Sabin oral poliovirus vaccine, the circulation of wild type polioviruses has virtually disappeared in Japan. However, an outbreak of poliomyelitis associated with sporadic transmission of type 1 wild strain occurred in Nagano in 1980. Furthermore, we found that some type 1 wild strains were introduced into Japan from abroad in 1981. In recent surveys, the two poliovirus type 1 isolates which have non-vaccine-like antigenic character were detected in Aichi. Then, an investigation to trace the origin of these strains was performed, by using intratypic serodifferentiation and biochemical techniques. Electrophoretic migration patterns of their structural polypeptides were quite different from the vaccine virus. In the oligonucleotide mapping, however, one of them gave patterns very similar to those of the vaccine virus. We could conclude that one originated most probably from wild strains, and the other was an antigenic variant derived from the vaccine virus. It showed that oligonucleotide mapping was a very useful method for identification of antigenic modified Sabin type 1 derivatives.

Antibodies, Monoclonal↗