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Biomedical subjects

H Misawa

Publications and source records attributed to H Misawa.

At least 109 records · Page 6Linked to original sources
PubMed1992

Incidence and natural course of trabecular ventricular septal defect: two-dimensional echocardiography and color Doppler flow imaging study.

This study was designed to determine the prevalence of trabecular ventricular septal defect (t-VSD) in neonates and to evaluate the effects of its location, morphologic features, and size on its natural course during infancy. One thousand twenty-eight term newborn infants were examined by color Doppler flow imaging with orthogonal ultrasonographic views. Ten girls and 11 boys (2.0%) were found to have t-VSD. The natural course of the defect was examined in 42 consecutive cases, consisting of this group of 21 neonates and another group of 21 neonates with t-VSD. The morphologic features of the defect within the trabecular septum were classified as one or two defects (36 cases) and as a mesh-like defect (six cases). Reduction in size began from the right ventricular side or from within the trabecular septum. Spontaneous closure occurred most commonly during the first 6 months of life and was observed in 32 cases (76%) by 12 months of age: the frequency of closure was not related to the morphologic features and the initial size of the defect, but apical defects tended to have higher persistent patency than did defects in other locations (p less than 0.05). We conclude that the frequency of t-VSD in neonates and the frequency of spontaneous closure during early infancy are higher than previously believed. This information is important for predicting the natural course of t-VSD and deciding on its proper management.

Blood Flow Velocity↗
PubMed1992

Cross sectional and Doppler echocardiographic evaluation of aortopulmonary shunts.

BACKGROUND: Shunt vessels were imaged and shunt flow was analysed by cross sectional and Doppler echocardiography in 12 patients who had had 14 shunt procedures (nine left Blalock-Taussig shunts, three right Blalock-Taussig shunts, one modified Waterston shunt, and one central shunt). METHODS: The shunt vessels were classified by echocardiography as uniformly patent, segmentally stenosed, and uniformly stenosed. These findings were compared with those of angiography. Also the peak flow velocities at the aortic and the pulmonary ends of the shunt vessels were measured by Doppler echocardiography and the ratio of these values was calculated for each shunt. RESULTS: Twelve (85.7%) of 14 shunt vessels were imaged along their entire length by cross sectional echocardiography. The two remaining shunt vessels were only partially imaged. In 10 patients who also had angiography the echocardiographic and angiographic images of the shunt vessels were identical. The ratio of the peak flow velocity measured at the aortic and the pulmonary ends of the shunt vessel was significantly larger in the segmentally stenosed shunt vessels than in the uniformly patent shunt vessels (p < 0.001). The ratio in the two shunt vessels only partially imaged by cross sectional echocardiography indicated that they were segmentally stenosed. CONCLUSION: The combination of cross sectional and Doppler echocardiography may be useful for determining either the patency or the morphology of an aortopulmonary shunt.

Anastomosis, Surgical↗
PubMed1992

[In vitro study on efficacy of combination use of aspoxicillin and beta-lactam preparations (ceftazidime, cefmetazole and aztreonam) against bacteria isolated from abdominal infections].

An in vitro study was done to evaluate combination use of aspoxicillin (ASPC) with each of 3 beta-lactam preparations, ceftazidime (CAZ), cefmetazole (CMZ) and aztreonam (AZT). The results obtained are summarized as follows: 1. ASPC has strong activity against Gram-positive bacteria and anaerobic bacteria, while CMZ and CAZ have strong activity against Gram-negative bacteria. 2. Rates of beta-lactamase producing strains among the isolated bacteria (a total of 383 isolates) were 4.4% among Gram-positive bacteria, 71.6% among Gram-negative bacteria and 89.3% among anaerobic bacteria. The overall rate of beta-lactamase secreting strains among all isolates was 46.5%. 3. Efficacies of combination uses were studied using the FIC index. Combination of ASPC and CAZ was effective against 95.0% of the isolates, ASPC and AZT against 85.7%, and ASPC and CMZ against 83.5%. Combination of ASPC and CMZ showed antagonism in 12.8% of the isolates. In conclusion, combination use of ASPC with any one of CMZ, AZT or CAZ proved to be highly effective. In particular, combination of ASPC and CAZ appeared to be the best in view of complementing antibacterial spectra.

Amoxicillin↗
PubMed1991

Changes in left ventricular output from fetal to early neonatal life.

Using pulsed Doppler and two-dimensionally directed M-mode echocardiographic techniques, we measured left ventricular (LV) output, stroke volume, heart rate, LV end-diastolic dimension (LVEDD), LV end-systolic dimension, and LV percent fractional shortening (%FS) in 34 normal term infants 12 to 24 hours before parturition and thereafter serially 1, 24, and 96 hours after birth. Stroke volume was calculated as the product of the aortic flow velocity integral and aortic valve area. There was a twofold increase in LV output 1 hour after birth (fetal 170 +/- 46 ml/min/kg vs 1 hour 327 +/- 66 ml/min/kg; p less than 0.01) which was associated with significant increases in stroke volume, %FS, and LVEDD (stroke volume 1.21 +/- 0.33 ml/kg vs 2.25 +/- 0.37 ml/kg; %FS 34.3% +/- 5.8% vs 37.7% +/- 5.4%; LVEDD 15.4 +/- 1.1 mm vs 17.7 +/- 1.4 mm). Heart rate did not change 1 hour after birth. During the subsequent hours after birth, LV output decreased significantly to a value of 245 +/- 56 ml/min/kg (p less than 0.01) at 24 hours, which did not change 96 hours after birth. There were significant declines in stroke volume, LVEDD, and heart rate 24 hours after birth (stroke volume 2.02 +/- 0.42 ml/kg; LVEDD 17.0 +/- 1.1 mm; heart rate 121 +/- 11 beats/min). The %FS remained unchanged within the first 96 hours of age. These results indicate that the major regulator of LV output immediately after birth is stroke volume and not heart rate. The increase in stroke volume is related to an increase in LV size and LV myocardial contractility. Our data provide a useful basis for the interpretation of abnormal LV function in the early neonatal period.

Cardiac Output↗
PubMed1991

Interatrial shunt flow profiles in newborn infants: a colour flow and pulsed Doppler echocardiographic study.

Interatrial shunt flow profiles in 36 normal term infants were examined serially by colour flow and pulsed Doppler echocardiographic techniques from within an hour of birth to four or five days after birth. Shunt flow across the foramen ovale was detected in 33 normal infants (92%) within an hour of birth (mean 40 minutes). The occurrence of interatrial shunting decreased with age, but a shunt signal was still detected in 17 infants (47%) on the fourth or fifth day of life, by then the ductus arteriosus had already closed in all the normal infants. The direction of interatrial shunt flow was predominantly left-to-right, but in 64% there was a coexistent small right-to-left shunt in diastole within an hour of birth; by four to five days it was found in 19%. In the six patients with persistent fetal circulation the direction of the interatrial shunt flow was predominantly right-to-left with biphasic peaks in diastole and systole at the early stage of the disease, and the period of right-to-left shunt flow during each cardiac cycle was significantly longer than that in normal infants examined within 1 hour of birth. In all patients the ductus closed before the foramen ovale. At the time of ductal closure in all patients with persistent fetal circulation right-to-left shunt flow was seen during diastole and its period was still prolonged. These findings suggest that interatrial shunting, predominantly left-to-right, is common in normal newborn infants. Evaluation of the characteristics of the interatrial shunt by Doppler echocardiography may be useful for predicting the progress of or improvement in neonates with persistent fetal circulation.

Blood Flow Velocity↗
PubMed1991

Altered Ca2+ dynamics in single cardiac myocytes from renovascular hypertensive rats.

Several functional and biochemical characteristics of hypertrophied hearts isolated from rats with renovascular hypertension provide indirect evidence that cellular Ca2+ dynamics during myocardial contraction-relaxation are altered. In this study, intracellular Ca2+ concentration ([Ca2+]i) dynamics were examined in paced left ventricular (LV) myocytes isolated from rats with hypertension (HYP) induced by partial occlusion of the left renal artery and from normotensive rats (Sham). Characteristic myocardial changes produced by renovascular hypertension included a 40% increase in LV weight and a 3.6-fold increase in the fractional expression of the beta-heavy chain of myosin in isolated LV myocytes. In periods of mechanical quiescence between contractions, basal [Ca2+]i values were similar in Sham and HYP LV myocytes. During a contraction-relaxation cycle in HYP myocytes, peak [Ca2+]i, +d[Ca2+]i/dt, and -d[Ca2+]i/dt were reduced, whereas the time required for [Ca2+]i to rise from a basal value to a peak value (time-to-peak [Ca2+]i) was unaffected. In both Sham and HYP myocytes, the fall in [Ca2+]i from peak to basal values could be approximated by a monoexponential rate constant, kf. Values for kf were significantly smaller in HYP than in Sham myocytes. After treatment with 4 microM isoproterenol, peak [Ca2+]i, +[Ca2+]i/dt, -d[Ca2+]i/dt, and kf increased in both Sham and HYP myocytes. In contrast, basal [Ca2+]i and time-to-peak [Ca2+]i did not change. Thus, despite recent reports of inefficiencies of beta-adrenergic receptor coupling, there was no evidence of blunted beta-adrenergic responsiveness in HYP myocytes with respect to [Ca2+]i dynamics during contraction-relaxation. Finally, no Sham vs. HYP differences in the number of specific [3H]-PN200-110 binding sites per cell in quiescent, rod-shaped myocytes were detected, but a significant reduction in [3H]-PN200-110 binding sites in an enriched sarcolemmal membrane fraction isolated from HYP animals was observed. These observations are suggestive of a reduction in slow, Ca2+ channel surface density in HYP myocytes. The results of this study clearly indicate that [Ca2+]i dynamics during contraction-relaxation in single left ventricular myocytes are affected by residence in a chronic setting of renovascular hypertension. In addition, the prolonged [Ca2+]i removal phase observed in HYP myocytes can be restored toward normal by beta-adrenergic agonists.

Analysis of Variance↗
PubMed1991

Are the initial frequency-modulated components of the mustached bat's biosonar pulses important for ranging?

1. FM-FM neurons in the auditory cortex of the mustached bat, Pteronotus parnellii, are specialized to process target range. They respond when the terminal frequency-modulated component (TFM) of a biosonar pulse is paired with the TFM of the echo at a particular echo delay. Recently, it has been suggested that the initial FM components (IFMs) of biosonar signals may also be important for target ranging. To examine the possible role of IFMs in target ranging, we characterized the properties of IFMs and TFMs in biosonar pulses emitted by bats swung on a pendulum. We then studied responses of FM-FM neurons to synthesized biosonar signals containing IFMs and TFMs. 2. The mustached bat's biosonar signal consists of four harmonics, of which the second (H2) is the most intense. Each harmonic has an IFM in addition to a constant-frequency component (CF) and a TFM. Therefore each pulse potentially consists of 12 components, IFM1-4, CF1-4, and TFM1-4. The IFM sweeps up while the TFM sweeps down. 3. The IFM2 and TFM2 depths (i.e., bandwidths) were measured in 217 pulses from four animals. The mean IFM2 depth was much smaller than the mean TFM2 depth, 2.87 +/- 1.52 (SD) kHz compared with 16.27 +/- 1.08 kHz, respectively. The amplitude of the IFM2 continuously increased throughout its duration and was always less than the CF2 amplitude, whereas the TFM2 was relatively constant in amplitude over approximately three-quarters of its duration and was often the most intense part of the pulse. The maximum amplitude of the IFM2 was, on average, 11 dB smaller than that of the TFM2. Because range resolution increases with depth and the maximum detectable range increases with signal amplitude, the IFMs are poorly suited for ranging compared with the TFMs. 4. FM-FM neurons (n = 77) did not respond or responded very poorly to IFMs with depths and intensities similar to those emitted on the pendulum. The mean IFM2 depth at which a just-noticeable response appeared was 4.48 +/- 1.98 kHz. Only 14% of the pulses emitted on the pendulum had IFM2 depths that exceeded the mean IFM2 depth threshold of FM-FM neurons. 5. Most FM-FM neurons responded to IFMs that had depths comparable with those of TFMs. However, when all parameters were adjusted to optimize the response to TFMs and then readjusted to maximize the response to IFMs, 52% of 27 neurons tested responded significantly better to the optimal TFMs than to the optimal IFMs (P less than 0.05, t test).(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1991

[Response of the cochlear nucleus neurons of the cat to tone-burst-trains].

Although both posteroventral cochlear nucleus (PVCN) and dorsal cochlear nucleus (DCN) are innervated by the descending branch of auditory nerve fibers, their intrinsic morphological organizations are so different that their physiological roles are expected to be different in signal processing. Temporal information coding of acoustic signals in the cochlear nucleus was examined by using stimuli of "tone-burst-trains (TBT)". Responses of cochlear nucleus neurons of anesthetized cats were recorded either intracellularly or extracellularly. Responses of the neurons to TBT stimuli were classified into "adaptive type" and "non-adaptive type". The "adaptive type" neurons were mainly recorded from PVCN. Responses of these neurons to TBT stimuli decayed exponentially, because of short-term adaptation, in the subsequent tone-bursts. These neurons faithfully preserve the adaptative behavior of auditory nerve fibers. On the contrary, the "non-adaptive type" neurons were mainly found in DCN. They showed variety of responses to TBT stimuli including facilitation, disinhibition and inhibition depending on duration and/or interval of tone-bursts. Our results suggest that some "non-adaptive type" neurons, showing facilitative and/or inhibitory responses to TBT stimuli, act as temporal filters that extract temporal information from acoustic signals.

Acoustic Stimulation↗
PubMed1990

Kappa-opioid agonist inhibits phospholipase C, possibly via an inhibition of G-protein activity.

In synaptic membranes of guinea pig cerebellum, in which preparations U-50, 488H, a kappa-opioid agonist inhibits G-protein activity, the same kappa-agonist at 100 nM inhibited the phospholipase C (PLC) activity stimulated by 100 microM GTP in the presence of 10 microM Ca2+. The present study provides a unique hypothetical mechanism that the receptor-mediated inhibition of PLC is mediated by inhibition of G-protein activity.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1990

Functional reconstruction of purified Gi and Go with mu-opioid receptors in guinea pig striatal membranes pretreated with micromolar concentrations of N-ethylmaleimide.

Functional coupling between mu-opioid receptors and GTP-binding regulatory proteins (G proteins) was investigated in reconstituted membranes of the guinea pig striatum. Selective mu-opioid agonists stimulated low-Km GTPase in striatal membranes, in a Na(+)-dependent manner. The same mu-opioid agonist [( D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAGO)] caused no stimulation when the membranes were exposed to islet-activating protein (IAP; pertussis toxin). There was also no DAGO stimulation in preparations pretreated with a lower concentration (5 microM) of N-ethylmaleimide (NEM), which abolished the ADP-ribosylation of purified Gi (the G protein that mediates inhibition of adenylate cyclase) and Go (a G protein of unknown function purified from bovine brain) by IAP. In addition, as the NEM treatment caused no change in the mu-agonist binding, NEM could probably substitute for IAP in inactivating native G proteins, without exhibiting effects on the receptor binding in membranes. The mu-agonist stimulation of low-Km GTPase activity in NEM-treated membranes was recovered by reconstitution with purified Gi or Go. The mu-agonist stimulation of low-Km GTPase was additive when Gi and Go were simultaneously reconstituted in NEM-treated membranes in amounts of 0.5 pmol/assay, which was required for maximal recovery, in either reconstitution experiment. The present findings provide the first evidence that the mu-opioid receptor may exist in at least two different forms, separately coupled to Gi or Go.

Adenylate Cyclase Toxin↗
PubMed1989

The kyotorphin (tyrosine-arginine) receptor and a selective reconstitution with purified Gi, measured with GTPase and phospholipase C assays.

We attempted to identify the kyotorphin receptor and the post receptor mechanisms mediated by GTP-binding proteins (G-proteins), using reconstitution techniques. The specific binding of [3H]kyotorphin in rat brain membranes was composed of high affinity (Kd = 0.34 nM) and low affinity (Kd = 9.07 nM) binding. As the high affinity binding disappeared in the presence of guanosine 5'-O-(3-thiotriphosphate) and MgCl2, we investigated the kyotorphin receptor-mediated changes in membrane G-protein activity by measuring low Km GTPase activity. Kyotorphin produced a stimulation of low Km GTPase, and this stimulation was antagonized by Leu-Arg, a synthetic dipeptide which showed a potent displacement of [3H]kyotorphin binding, yet in itself had no effect on the low Km GTPase. The kyotorphin stimulation of low Km GTPase was abolished by pretreating membranes with islet-activating protein, pertussis toxin, and was recovered by reconstitution with purified G-protein, Gi, but not with Go. Similar evidence of selective coupling of kyotorphin receptor to Gi was obtained with the phospholipase C assay. Kyotorphin-induced stimulation of phospholipase C was also abolished by islet-activating protein-treatment and recovered by reconstitution with Gi but not with Go. These findings indicate that specific high and low affinity kyotorphin receptors exist in the rat brain and that the kyotorphin receptor is functionally coupled to stimulation of phospholipase C, through Gi. This study provides the first evidence of a selective involvement of Gi in the receptor-mediated activation of phospholipase C.

Animals↗
PubMed1987

The specific opioid kappa-agonist U-50,488H inhibits low Km GTPase.

DAGO, a specific opioid mu-agonist stimulated the low Km GTPase activity of membranes of the guinea-pig striatum at 1-1000 nM and this effect was antagonized by naloxone 10-100 nM. On the other hand, U-50,488H, a specific opioid kappa-agonist inhibited the low Km GTPase activity of membranes of the guinea-pig cerebellum at 1-100 nM. As this effect was antagonized by MR2266 but not by naloxone, the findings suggest that opioid mu- and kappa-receptor stimulation is probably linked to the stimulation and inhibition of low Km GTPase, respectively.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1987

Purified opioid mu-receptor is of a different molecular size than delta- and kappa-receptors.

Opioid mu-receptors were solubilized from rat brains with 0.5% Triton X-100 in the presence of 0.32 M sucrose and then purified with 6-succinyl morphine-Affi-Gel 102 column. Purified materials showed a major band with mol.wt. 58,000 Da and a minor band with mol.wt. 41,000 Da. Affinity cross linking with [3H]DAGO, a selective mu-opioid agonist, to the neural membranes and purified materials revealed that opioid mu-binding protein has a mol.wt. of 58,000 Da, a value totally different from that of delta- (mol.wt. 18,500 Da) and kappa- (mol.wt. 36,000 Da) binding protein.

Animals↗
PubMed1987

Two-dimensional Doppler echocardiographic assessment of closure of the ductus arteriosus in normal newborn infants.

To elucidate the mechanism involved in closure of the ductus arteriosus (DA), 50 normal full-term infants were examined with two-dimensional and pulsed Doppler echocardiography. The examinations were performed initially within 1 hour after delivery and serially for 3 days. The two-dimensionally derived long-axis plane of the DA disclosed a characteristic localized protrusion into its lumen in 30% of the subjects within 1 hour, in 80% by 4 hours, in 96% by 8 hours, and in all by 24 hours after birth. In 10 infants in whom the intraluminal protrusion did not appear within 4 hours after birth, none had any recognizable changes in the inner diameter or length of the DA during this initial period. The development of the intraluminal protrusion resulted in localized narrowing of the ductal lumen. Doppler echocardiography revealed a high-velocity jet within and downstream from the narrowed portion of the DA. Thereafter, ductal narrowing progressed along the entire length. The intraluminal protrusion may be early evidence of ductal changes leading to eventual functional and anatomic closure.

Age Factors↗
PubMed1987

Noninvasive Doppler echocardiographic evaluation of shunt flow dynamics of the ductus arteriosus.

The pulsed Doppler technique was used to record the flow velocity patterns in the ductus arteriosus and the pulmonary artery in 26 patients with either isolated or complicated patent ductus arteriosus (PDA). In all patients, abnormal Doppler signals indicating left-to-right (L-R) or right-to-left shunt flow or both could be obtained at the site of the ductus arteriosus. These Doppler flow patterns determined within the ductus coincided with the direction of ductal flow seen on the contrast two-dimensional echocardiogram. No Doppler signals of shunt flow were demonstrated in any of 42 control subjects. The peak, mean, and diastolic velocities of the L-R shunt flow within the ductus were measured from the ductal flow velocity profiles. With the Doppler-derived measurements of the mean and diastolic velocities, patients with normal pulmonary arterial pressure and those with evidence of pulmonary hypertension could be correctly identified. In addition, the mean velocity of the diastolic antegrade flow portion obtained from the proximal left pulmonary artery, which was related to ductal L-R shunting, was measured in 16 patients with isolated PDA. This Doppler flow determinant showed a good linear correlation with the L-R shunt ratio determined by Fick's method (r = .88, p less than .01). Our technique permits the noninvasive evaluation of shunt flow dynamics in patients with PDA.

Blood Flow Velocity↗
PubMed1986

Isolation of an antigenically unique methanogen from human feces.

A methanogenic bacterium with the morphological and physiological properties of the genus Methanobrevibacter was isolated from the feces of a Japanese man who excreted methane in his breath. Indirect immunofluorescence staining revealed that the isolate had an antigenicity unrelated to that of any known members of the genus Methanobrevibacter.

Antigen-Antibody Complex↗
PubMed1985

Seroepidemiology of human T-lymphotropic retrovirus type I (HTLV-I) in residents of Niigata Prefecture, Japan. Comparative studies by indirect immunofluorescence microscopy and enzyme-linked immunosorbent assay.

A large sample of carriers of human T-lymphotropic retrovirus type I (HTLV-I) in Niigata Prefecture was examined for the detection of natural antibodies to HTLV-I-related antigens in sera using both indirect immunofluorescence microscopy (IFM) and enzyme-linked immunosorbent assay (ELISA). The present findings are based on multiple surveys, using each assay technique at least twice. Although Niigata Prefecture has been considered a non-endemic region for HTLV-I, Sado Island has been proven by this study to be a relatively endemic pocket within this non-endemic area. Seropositivity was highest in residents of Sado Island; 97/1, 117 (8.7%) by IFM and 33/1,061 (3.1%) by ELISA; followed by Niigata City, 18/650 (2.8%) by IFM and 16/638 (2.5%) by ELISA; and lowest in the remaining areas, 57/2,631 (2.2%) by IFM and 20/2,551 (0.8%) by ELISA. Seropositivity was demonstrated in 172/4,398 (3.9%) by IFM and 69/4,250 (1.6%) by ELISA in Niigata Prefecture taken as a whole. In general, the incidence of seropositive residents increased gradually with age. The sex difference was not significant. The serum samples tested were categorized into 4 groups; (1) IFM and ELISA both positive, (2) IFM positive but ELISA negative, (3) IFM negative but ELISA positive, and (4) IFM and ELISA both negative. By absorption tests, IFM and ELISA seemed to recognize different specific antibodies in sera; IFM recognized antibodies to HTLV-I-related cellular antigens in addition to HTLV-I viral antigens, but ELISA recognized antibodies to HTLV-I viral antigens alone. Thus, IFM detected a broader spectrum of antigens, resulting in recognition of more positive sera than those detected by ELISA.

Adolescent↗