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Biomedical subjects

M Arita

Publications and source records attributed to M Arita.

At least 253 records · Page 14Linked to original sources
PubMed1989

Purification and characterization of the CS2 pili of colonization factor antigen II produced by human enterotoxigenic Escherichia coli.

A subtype (CS2) of the colonization factor antigen II (CFA/II) of human enterotoxigenic Escherichia coli (ETEC) was studied. Analysis revealed that CS2-possessing ETEC was predominant among isolates from traveller's diarrhea at Osaka, Japan. TH61 pili produced by a clinical strain (TH61) were purified as a native form to homogeneity by zone electrophoresis and successive column chromatographies on Sepharose 4B and Phenyl-Sepharose CL-4B. It was demonstrated by immunogold staining technique and bacterial agglutination test that antisera against the purified pili of strain TH61 recognized pili of both strain TH61 and strain #C91f, a control strain possessing only CS2 pili. This suggests that TH61 pili purified in this study are CS2 pili. Subunit (pilin) of the purified pili has a molecular weight of about 16,000. Strains bearing CS2 could attach to human jejunal epithelial cells, and this attachment was inhibited by pretreating the enterocytes with purified pili. These indicate that CS2 pili are a factor responsible for attachment of ETEC bearing CS2 to human intestinal cells.

Agglutination Tests↗
PubMed1989

Production and characterization of monoclonal antibodies to a pilus colonization factor (colonization factor antigen III) of human enterotoxigenic Escherichia coli.

Three monoclonal antibodies (MAbs) to a pilus colonization factor (colonization factor antigen III [CFA/III]) of human enterotoxigenic Escherichia coli (ETEC) were developed and characterized. All of the MAbs isolated belonged to the immunoglobulin G2a subclass. The specificity of these MAbs for CFA/III pili was demonstrated by the immunogold-labeling technique. The presence of more than one epitope in CFA/III pili was suggested. One of the three MAbs appears to recognize a polymeric conformational epitope(s) of CFA/III. CFA/III antigenicity distinct from that of other pilus colonization factors of ETEC was demonstrated by both a bacterial agglutination test and a sandwich enzyme-linked immunosorbent assay using the MAbs. Of the 100 strains of ETEC isolated from persons with traveler's diarrhea, 8% were found to carry CFA/III pili. Two enzyme-linked immunosorbent assay systems which could detect as little as several or 50 ng of CFA/III per ml were developed.

Antibodies, Bacterial↗
PubMed1989

Detection with synthetic oligonucleotide probes of nucleotide sequence variations in the genes encoding enterotoxins of Escherichia coli.

We examined variations in the genes encoding heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT) in 88 strains of Escherichia coli isolated from individuals with traveler's diarrhea to find suitable sequences for use as oligonucleotide probes. Four oligonucleotide probes of the gene encoding ST of human origin (STIb or STh), one oligonucleotide probe of the gene encoding ST of porcine origin (STIa or STp), and three oligonucleotide probes of the gene encoding LT of human origin (LTIh) were used in DNA colony hybridization tests. In 15 of 22 strains possessing the STh gene and 28 of 42 strains producing LT, the sequences of all regions tested were identical to the published sequences. One region in the STh gene examined with a 18-mer probe was relatively well conserved and was shown to be closely associated with the enterotoxicity of the E. coli strains in suckling mice. This oligonucleotide, however, hybridized with strains of Vibrio cholerae O1, V. parahaemolyticus, and Yersinia enterocolitica that gave negative results in the suckling mouse assay.

Animals↗
PubMed1989

Construction of less neurovirulent polioviruses by introducing deletions into the 5' noncoding sequence of the genome.

Viral attenuation may be due to lowered efficiency of certain steps essential for viral multiplication. For the construction of less neurovirulent strains of poliovirus in vitro, we introduced deletions into the 5' noncoding sequence (742 nucleotides long) of the genomes of the Mahoney and Sabin 1 strains of poliovirus type 1 by using infectious cDNA clones of the virus strains. Plaque sizes shown by deletion mutants were used as a marker for rate of viral proliferation. Deletion mutants of both the strains thus constructed lacked a genome region of nucleotide positions 564 to 726. The sizes of plaques displayed by these deletion mutants were smaller than those by the respective parental viruses, although a phenotype referring to reproductive capacity at different temperatures (rct) of viruses was not affected by introduction of the deletion. Monkey neurovirulence tests were performed on the deletion mutants. The results clearly indicated that the deletion mutants had much less neurovirulence than with the corresponding parent viruses. Production of infectious particles and virus-specific protein synthesis in cells infected with the deletion mutants started later than in those infected with the parental viruses. The rate at which cytopathic effect progressed was also slower in cells infected with the mutants. Phenotypic stability of the deletion mutant for small-plaque phenotype and temperature sensitivity was investigated after passaging the mutant at an elevated temperature of 37.5 degrees C. Our data strongly suggested that the less neurovirulent phenotype introduced by the deletion is very stable during passaging of the virus.

Animals↗
PubMed1989

Determinants in the 5' noncoding region of poliovirus Sabin 1 RNA that influence the attenuation phenotype.

A number of recombinants between the virulent Mahoney and attenuated Sabin strains of type 1 poliovirus were constructed by using infectious cDNA clones of the two strains. To identify a strong neurovirulence determinant(s) residing in the genome region upstream of nucleotide position 1122, these recombinant viruses were subjected to biological tests, including monkey neurovirulence tests. The results of the monkey neurovirulence tests suggested the important contribution of an adenine residue (Mahoney type) at position 480 to the expression of the neurovirulence phenotype of type 1 poliovirus. This nucleotide, however, had only a minor effect, if any, on viral temperature sensitivity. Monkey neurovirulence tests on the recombinant virus whose genome had a guanine residue (Sabin type) at position 480 and variants generated from this recombinant virus in the central nervous system of monkeys strongly suggested that only one nucleotide change, from adenine to guanine, was not sufficient for full expression of the attenuation phenotype encoded by this genome region. These results suggest that the expression of the attenuation phenotype depends on the highly ordered structure formed in the 5' noncoding sequence and that the formation of such a structure is possibly influenced by the nucleotide at position 480. Furthermore, in vitro biological tests performed on viruses recovered from the central nervous system of monkeys injected with a temperature-sensitive recombinant virus showing the small-plaque and d phenotypes revealed that most of the recovered viruses had even higher temperature sensitivities and that all of the recovered viruses that had acquired the large-plaque phenotype had lost the d phenotype to some extent. These results indicate that there may be an unknown selection pressure(s) in the central nervous system and that common determinants might be involved in the expression of the small-plaque and d phenotypes.

Animals↗
PubMed1989

Isoproterenol, DBcAMP, and forskolin inhibit cardiac sodium current.

We studied the effects of isoproterenol (ISP), dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), and forskolin on the sodium current (INa) of guinea pig ventricular myocytes using the tight-seal, whole cell voltage-clamp method. The extracellular [Na+] [( Na+]o) was decreased to 60 mM by replacing NaCl with sucrose (temperature, 32-33 degrees C). Ionic currents other than Na+ were suppressed using appropriate channel blockers. Depolarizing clamp pulse (duration, 30 ms) was applied at a rate of 0.2 Hz from a holding potential of -80 mV. ISP (1 microM) decreased the peak INa by 34% from 6.1 +/- 1.9 (SD) nA (control) to 4.0 +/- 1.5 nA (n = 7). The inhibition was more prominent at less negative potentials and disappeared in the presence of a beta-blocker (10 microM atenolol). The effects of DBcAMP (1-5 mM) and forskolin (3 microM) mimicked those of ISP and depressed the peak INa reversibly. DBcAMP (5 mM) shifted the inactivation curve of INa [h infinity-membrane potential (Em) relationship] to a hyperpolarizing direction, by 3.4 +/- 0.8 mV (n = 5). These findings suggest that ISP inhibits the cardiac INa+, probably by altering the gating mechanism of the Na+ channel, and that the effect is secondary to the increased levels of intracellular cAMP, with possible acceleration of cAMP-dependent phosphorylation of the channel.

Animals↗
PubMed1989

Late sodium current and its contribution to action potential configuration in guinea pig ventricular myocytes.

We used the patch clamp technique to study the nature of the late sodium current in guinea pig ventricular myocytes. In a cell attached mode of single channel recording at room temperature (22-24 degrees C) two kinds of late (100 msec or more after beginning of the depolarizing pulse) sodium channel activities were recognized. One is isolated brief openings appearing once for about 120 depolarizations per channel (background type), while the other type is sustained openings with rapid interruptions (burst type) that occurred only once for 2,700 depolarizations per channel. The time constant obtained from the open time histogram of the burst type (1.05 msec) was about five times longer than that of background type (0.18 msec, measured at the potential 10 mV above the threshold). Magnitude of the late sodium current flowing through the entire surface of a myocyte was estimated with tetrodotoxin (60 microM), a specific inhibitor of sodium channels, in whole-cell clamp experiments. The steady tetrodotoxin-sensitive current of 12 to 50 pA was registered at -40 mV (26 +/- 14 pA, mean +/- SD, n = 5), in good agreement with the late sodium current calculated from the single channel recording. Tetrodotoxin produced small (congruent to 10%) but significant decreases in the action potential duration. These results suggest the presence of a small but significant late sodium current with slow inactivation kinetics and that this current probably plays a significant role in maintaining the action potential plateau and the duration in guinea pig ventricular myocytes.

Action Potentials↗
PubMed1989

Unaffected electrogenic Na-K pump activity in "diseased" human atrial fibers, as assessed by intracellular K+ activity.

To investigate the role of the electrogenic Na-K pump in the resting membrane of "diseased" or "depolarized" human atrial muscles, intracellular K+ activity (aiK) and resting membrane potential (Vm) were simultaneously measured using double-barreled K(+)-selective microelectrodes. Under perfusion with normal Tyrode's solution (37 degrees C) containing 5.4 mM [K]o, Vm averaged -43.9 +/- 1.4 mV, and aiK was 99.7 +/- 1.3 mM (mean +/- S.E., n = 33). The aiK was comparable to that of atrial muscles obtained from other intact mammalian species. In 5.4 mM [K]o, dihydro-ouabain (DHO) at concentrations of 10(-6) and 10(-5) M significantly decreased aiK and depolarized Vm. Similar decreases in aiK were observed when [K]o was decreased from 5.4 to 0.5 mM or when the temperature of the perfusing solution was decreased from 37 to 22 degrees C. Upon returning [K]o from 0.5 to 5.4 mM at 37 degrees C, aiK increased, Vm hyperpolarized markedly for about 3 min, and this was followed by less marked levels of hyperpolarization in the steady state. The high [K]o-induced increases in aiK were inhibited in the presence of DHO, and at low temperature (22 degrees C). Isoproterenol (10(-7) M) increased aiK and hyperpolarized Vm. Acetylcholine (10(-5) M) hyperpolarized Vm with no change in aiK. The rate of reduction of Na(+)-efflux during application of DHO (10(-5) M) was calculated based on the change in aiK and surface-to-volume ratio of the cell measured electronmicroscopically in the same tissue, and estimated to be 2.6 to 3.8 pmol/(cm2.s), close to the value reported for Purkinje fibers excised from intact animals. We conclude that the Na-K pump functions normally even in "diseased" human atrial muscles, thereby keeping aiK within a physiological range.

Adolescent↗
PubMed1989

Blood pressure and sympathetic activity following responses to aerobic exercise in patients with essential hypertension.

Fourteen untreated patients with essential hypertension (EH) were subjected to mild aerobic exercise with the intensity at 50% of the maximum oxygen uptake (VO2max) twice a week for 12 weeks, as compared with 14 normotensive subjects (NT). Blood pressure and norepinephrine (NE) in plasma, platelet and urine were measured as the indices of sympathetic activity. In EH, a significant fall in both systolic and diastolic blood pressure was observed. In addition, exercise training produced a significant decrease both urinary and platelet NE, but not in plasma NE. Neither significant changes in blood pressure nor NE in plasma, platelet and urine were observed in NT. These results suggest that an inhibition of the sympathetic nervous system might be related to the blood pressure fall in physical exercise training.

Adult↗
PubMed1989

Electrophysiologic effects of nicainoprol, a putative class I antiarrhythmic agent, on the guinea pig ventricular papillary muscle.

We examined the effects of nicainoprol (1-50 microM), a new antiarrhythmic agent, on the transmembrane action potentials in isolated papillary muscles of the guinea pig. Nicainoprol (greater than or equal to 5 microM) produced dose-dependent decreases in the maximal upstroke velocity (Vmax) of the action potential. Only the highest concentration (50 microM) decreased the amplitude and the overshoot of the action potential and shortened its duration at 50 or 90% repolarization levels (APD50, APD90). The potential at rest was not affected by any concentration tested (1-50 microM). In the presence of nicainoprol, trains of stimuli at the rate of 0.2, 0.5, 1.0, and 2.0 Hz, introduced after a sufficient period of rest, led to an exponential decay of the Vmax to the steady state levels (use-dependent block, UDB). The UDB was augmented with an increase in the stimulation frequency or with a decrease in the potentials at rest. The time constant for the recovery from the UDB was 51.6 +/- 9.4 s at 50 microM. The Vmax and the amplitude of the slow response elicited in the presence of 27 mM [K+]o and 0.2 mM Ba2+ was significantly decreased by application of nicainoprol (10-100 microM), with a significant shortening of APD50 (100 microM). These findings suggest that nicainoprol has electrophysiologic properties in common with those of other class I antiarrhythmic drugs with slow kinetics (Ic) and has a minor but significant inhibitory effect on slow inward current (class IV effect).

Action Potentials↗
PubMed1989

[Echocardiographic features of left ventricular hypertrophy and contractility in malignant hypertension].

To assess the hemodynamic characteristics in malignant hypertension, echocardiography was performed in 18 patients with malignant essential hypertension (MH-I, n = 9) and secondary hypertension (MH-II, n = 9). Patients with benign hypertension with or without left ventricular hypertrophy (n = 8 and 7, respectively), patients with hypertensive heart failure (n = 7) and normotensive volunteers (n = 10) were subjected to controls. Plasma noradrenaline (NA) and renin activity (PRA) were also measured prior to the antihypertensive therapy. There were no significant differences in the durations of hypertension before the malignant phase, and the mean arterial pressure between MH-I and MH-II. Although posterior wall thickness (PWTd) in MH-II was similar to that in MH-I, interventricular septal thickness (IVSTd) was less marked in MH-II. The plasma NA and PRA were markedly increased in both MH-I and MH-II. End-diastolic dimension (Dd) of the left ventricle was within normal range, but end-systolic dimension (Ds) was significantly increased in MH-I, MH-II and hypertensive heart failure. The moderate decreases in ejection fraction (EF) and mean velocity of circumferential fiber shortening (mVcf) were observed in both MH-I and MH-II. Marked decreases in EF and mVcf were also observed in patients with hypertensive heart failure. The relationship between systolic blood pressure and Dd/PWTd was shifted toward the right and upper portion of the normal relation in MH-I and MH-II. The present study demonstrated that the hemodynamic characteristics in malignant hypertension are an inappropriate left ventricular hypertrophy due to a marked increase in systolic stress; dilatation of the left ventricle in systole; and a moderate decrease in ventricular systolic function. It is suggested that a decrease in left ventricular systolic function in malignant hypertension might be due in part to a marked increase in the influence of neurohumoral factors on hemodynamics.

Adult↗
PubMed1989

Pilus colonization factors of enterotoxigenic Escherichia coli isolated from infantile diarrheal patients in Papua New Guinea.

We examined the possibility of pilus colonization factor (or adhesin) production by 9 enterotoxigenic Escherichia coli isolated from infantile diarrheal patients in Papua New Guinea. By hydrophobicity, hemagglutination and bacterial agglutination with antisera against various known adhesins, none of the 9 strains produced known pilus adhesins. Three strains which produce heat-labile and heat-stable enterotoxins may produce a new type of pili which is not hydrophobic and differs from common (type 1) pili.

Adhesins, Escherichia coli↗
PubMed1989

[Contribution of hypertension to left ventricular diastolic function in patients with asymmetrical apical hypertrophy].

This study was designed to ascertain the contribution of hypertension to the early diastolic time intervals in asymmetrical apical hypertrophy (AAH). Eighteen patients with untreated AAH were categorized as those with (n = 13) and without (n = 5) hypertension. Isovolumic relaxation time and early diastolic filling were determined in four groups: normotensive subjects (n = 20), patients with essential hypertension (n = 20), AAH with hypertension, and AAH without hypertension. Early diastolic function was measured by the interval from the aortic closure sound (IIA, phonocardiography) to the opening of the mitral valve (MVO, echocardiography) and the interval from MVO to the O point of the apexcardiogram. The IIA-O interval was also calculated. Peak velocities in the rapid filling phase (R) and atrial contraction phase (A) were measured using two-dimensional Doppler echocardiography in the center of the mitral orifice in diastole. The MVO-O/IIA-MVO and A/R ratios were also calculated. 1. In the AAH with and without hypertension groups, the IIA-O, IIA-MVO, and MVO-O intervals were significantly prolonged. The IIA-O and MVO-O intervals in the AAH without hypertension group were more prolonged than were those in the AAH with hypertension group. In patients with essential hypertension, the IIA-O and the IIA-MVO intervals were prolonged, but there was no prolongation of the MVO-O interval. 2. The MVO-O/IIA-MVO ratio was lower in essential hypertension and in the AAH with hypertension groups, and significantly higher in the AAH without hypertension group. 3. There was no significant change of the R, A, and A/R in each group. These results indicated that prolonged left ventricular relaxation was distinguished in essential hypertension. In AAH with hypertension, the same prolongation was observed, but the disturbance of early diastolic filling was mild. It is suggested that apical hypertrophy has a possible association with hypertension, though it may more properly belong to cardiomyopathy.

Adult↗
PubMed1988

Effects of L-propionylcarnitine on electrical and mechanical alterations induced by amphiphilic lipids in isolated guinea pig ventricular muscle.

We examined the effects of L-propionylcarnitine (Prop. C), a short-chain acylcarnitine, on amphiphile (L-lysophosphatidylcholine or L-palmitoylcarnitine)-induced electrophysiological and ultrastructural changes in isolated guinea pig ventricular papillary muscles, under acidic conditions (pH 6.9). Conventional microelectrode, tension-recording, and electron microscope techniques were used. Both amphiphiles, at a concentration of 10(-4) M, significantly decreased the resting membrane potential, action potential amplitude, and action potential duration, but increased the developed and resting tension. Such amphiphile-induced electrical changes were not observed in muscles pretreated with the beta-blocker, atenolol, although the mechanical changes remained unaffected. The application of Prop. C (10(-2) M), in the continued presence of the amphiphiles caused a return of the action potential duration and the developed tension to the control level. However, the resting potential and action potential amplitude remained unaffected; in fact, the maximum upstroke velocity (Vmax) of the action potential tended to decrease further. Pretreatment with Prop. C prevented all the amphiphile-induced electrophysiological and mechanical changes, except for Vmax. Electron microscopic studies revealed that amphiphile-induced ultrastructural changes were prevented, at least in part, in the presence of Prop. C. Thus, Prop. C antagonizes some of deleterious effects of amphiphiles, such as lysophosphatidylcholine and palmitoylcarnitine, upon the electrical and mechanical activities of the ventricular muscle, under acidic conditions.

Animals↗
PubMed1988

Binding of [3H]phencyclidine to adrenal medullary cells: inhibition of 22Na influx, 45Ca influx, 86Rb efflux and catecholamine secretion caused by carbachol and veratridine.

In bovine adrenal medullary cells, phencyclidine inhibited carbachol-induced influx of 22Na, 45Ca and secretion of catecholamines in a concentration-dependent manner with a similar potency (IC50 7.0 microM). Phencyclidine also suppressed veratridine-induced influx of 22Na, 45Ca and secretion of catecholamines (IC50 60.0 microM). High K-induced 45Ca influx and catecholamine secretion were not affected by phencyclidine. In the cells preloaded with 86Rb (an alternative tracer for 42K), phencyclidine inhibited the efflux of 86Rb caused by carbachol (IC50 10.0 microM) or by veratridine (IC50 56.0 microM), but had no effect on high K-induced 86Rb efflux. [3H]Phencyclidine bound specifically to adrenal medullary cells, and binding was saturable, reversible and with two different equilibrium dissociation constants (4.3 and 77.4 microM). In a competition experiment, the specific binding of [3H]phencyclidine was not inhibited by carbachol, muscarine, D-tubocurarine, hexamethonium, tetrodotoxin, veratridine and scorpion venom. The present findings suggest: (1) phencyclidine does not inhibit voltage-dependent Ca channels and Ca-dependent K channels; (2) phencyclidine binds to two populations of sites, each of which is functionally linked to nicotinic receptor-ion channel complex and to voltage-dependent Na channels, and inhibits Na influx caused by carbachol and veratridine. Inhibition of Na influx by phencyclidine leads to the reduction of Ca influx, K efflux and catecholamine secretion caused by carbachol and veratridine.

Adrenal Medulla↗
PubMed1988

Strategy for construction of live picornavirus vaccines.

A number of recombinant viruses between the virulent Mahoney and the attenuated Sabin 1 strains of type 1 poliovirus were constructed in vitro using their infectious cDNA clones. Monkey neurovirulence tests on these recombinant viruses revealed that the surface structure of the virion particle had a little correlation with the neurovirulent phenotype, and that the strong neurovirulence determinant(s) resided in the 5' noncoding sequence. These results in turn led to two possible strategies for constructing live attenuated picornavirus strains. One is to use the Sabin 1 strain as a vector carrying foreign antigenicities. The other is the construction of the attenuated picornaviruses by introducing mutations into the 5' noncoding sequences. The antigenicity of the Sabin 1 strain was successfully changed to those of other poliovirus serotypes without loss of vaccine quality. Furthermore, it was proved that introduction of deletion mutation into the 5' noncoding sequence of genomes of the Sabin 1 and Mahoney strains resulted in construction of viruses with a less neurovirulent phenotype.

Chromosome Deletion↗