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Biomedical subjects

K Tsuda

Publications and source records attributed to K Tsuda.

At least 91 records · Page 5Linked to original sources
PubMed1998

The effect of cold cardioplegic cardiac arrest and electrically induced ventricular fibrillation on human cardiac beta-adrenoceptors during open-heart surgery.

This study was designed to test the hypothesis that distinct alterations in cardiac beta-adrenoceptors (betaARs) may occur during cardiopulmonary bypass (CPB) alone, during CPB with cold cardioplegic cardiac arrest (CCCA), and during CPB with electrically induced ventricular fibrillation (EIVF). We assessed the density and affinity of right atrial betaARs in 27 patients undergoing open-heart surgery by (-)-[125I]iodocyanopindolol binding before CPB, defined as the "control," immediately after initiation, defined as "before," and immediately before the cessation of CCCA or EIVF, defined as "after." The density of betaARs was equivalent between the "control" and "before" groups; however, during CPB with EIVF, the density of betaARs decreased significantly (P < 0.001), whereas during CPB with CCCA, it increased significantly (P < 0.01). The rate of changes of the betaAR density was not correlated with the "before"-"after" interval, and the affinity of the betaARs did not change throughout these CPBs. These findings demonstrate that: CPB alone does not affect cardiac betaARs, at least until the onset of EIVF or CCCA; CPB with EIVF induces rapid desensitization of cardiac betaARs; and CPB with CCCA induces rapid sensitization of cardiac betaARs.

Adolescent↗
PubMed1998

Theta rhythms associated with sucking, crying, gazing and handling in infants.

In order to specify the locations and to clarify the electrophysiological significance of the transitory rhythmic theta activities detected on scalp electrodes in infants, we performed simultaneous EEG and video recording with power spectral map analysis in 29 normal infants of less than 1 year of age. The rhythmic theta activities appeared in posterior temporal regions with sucking or crying, in the parietal region with gazing, and in the frontal region with handling. Each specific location of the theta rhythm seemed to correspond to the functional localization in the infant's brain. We thus concluded that these rhythmic theta activities might originate from direct cortical activation, or from the cortical activation driven by the neuronal impulses from the limbic system through the connection between that system and the cortex.

Brain Mapping↗
PubMed1998

Beaded nerve terminals in feline laryngeal mucosa.

To investigate the mechanism of airway defense reflex, beaded nerve terminals were studied by immunohistochemical techniques. In the supraglottic region the density of PGP 9.5-immunoreactive nerve fibers was the highest at the base of the glottic surface in the epiglottis, and in the glottic region it was the highest in the arytenoid region. In the subglottic region the number of positive nerve fibers was less than the number at the base of the glottic surface in the epiglottis, and when the laryngeal mucosa was processed with NaOH to dissolve the epithelium, it was possible to observe beaded nerve terminals more clearly. These beaded nerve terminals were found just beneath, in the epithelial basement membrane. Electron microscopic examination of beaded nerve terminals revealed a large quantity of secretory granules and mitochondria, suggesting that their structure is similar to that of nerve terminals. Thus these beaded nerve terminals may function as mechanoreceptors.

Animals↗
PubMed1998

Effects of galanin on dopamine release in the central nervous system of normotensive and spontaneously hypertensive rats.

Galanin is a 29-amino acid peptide and widely distributed in the brain, although its significance in the control of neural activities is undefined. In the present study, we describe the effects of galanin on the electrically evoked release of dopamine in the rat central nervous system. In addition, to elucidate a possible role of galanin in the regulation of dopaminergic transmission in hypertension, we examined whether the effect of galanin on dopamine release might be altered in the central nervous system of spontaneously hypertensive rats (SHR). Galanin (1 x 10(-8) to 1 x 10(-7) mol/L) inhibited the stimulation (1 Hz)-evoked [3H]dopamine release by a comparable amount in striatal slices of Sprague-Dawley rats, although the basal release of dopamine was not affected by the peptide. In the striatum of SHR, the electrical stimulation (1 Hz)-evoked [3H]dopamine release was significantly smaller than in the striatum of Wistar-Kyoto (WKY) rats. However, the inhibitory effect of galanin on the stimulation-evoked [3H]dopamine release was significantly more pronounced in SHR than in WKY rats. These results show that galanin significantly reduced the release of dopamine in rat striatum. Furthermore, the greater inhibitory effect of galanin on dopamine release in SHR suggests that galanin might actively participate in the regulation of dopaminergic nerve activity in hypertension.

Animals↗
PubMed1998

Flow-through vascularized toe-joint transfer for reconstruction of segmental loss of an amputated finger.

A segmental finger defect was reconstructed in a 46-year-old woman with a free flow-through vascularized toe-joint, including the proximal interphalangeal joint, the plantar digital nerve, and tendons of the second toe. The advantages of this composite flap are: (1) The segmental loss of the finger can be easily reconstructed to achieve a normal anatomic structure. (2) Excellent cosmesis is achieved, compared with conventional flaps such as the groin flap. (3) The distal segment of the donor toe can be preserved. (4) The transected digital arteries of the amputated finger can be simultaneously reconstructed with a flow-through arterial interposition. (5) The digital nerve can be repaired with a vascularized plantar digital nerve graft.

Female↗
PubMed1998

Distribution and origin of the intraepithelial nerve fibres in the feline pharyngeal mucosa.

Sensory inputs from the pharynx play an important role in initiation of the swallowing reflex and in feedback control of motor activities. Using an immunohistochemical technique and denervation procedures, we examined the distribution and origin of the intraepithelial nerve fibres in the feline pharyngeal mucosa to clarify the role of the afferent nerve in swallowing. The posterior pillar was very densely innervated, and the posterior and lateral walls of the mesopharynx had a moderate nerve density. In contrast, the base of the tongue, the vallecula, the pharyngeal surface of the epiglottis, and the pyriform sinus had only a few nerve fibres. The epithelium of the rostral and caudal portions of the pharyngeal mucosa were innervated by the glossopharyngeal nerve and superior laryngeal nerve, respectively, with a borderline at the middle level of the epiglottis. A portion of the intraepithelial nerve fibres in the lateral and posterior walls of the mesopharynx originated from the pharyngeal branch of the vagus nerve. It is hypothesized that the intraepithelial nerve fibres that exist in densely innervated areas are related to the initiation of the swallowing reflex induced by stimulation of the pharyngeal mucosa.

Afferent Pathways↗
PubMed1998

Distribution of NADPH-diaphorase activity in the feline laryngeal mucosa.

We studied nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity in the feline laryngeal mucosa using a histochemical technique in an effort to clarify the role of nitric oxide (NO) in the larynx. Many NADPH-diaphorase-positive nerve fibres were distributed around the blood vessels and the laryngeal glands. The majority of neuronal cells in the intralaryngeal ganglia were NADPH-diaphorase-positive. It is likely that NADPH-diaphorase-positive nerve fibres around the blood vessels and glands in the laryngeal mucosa originate from the intralaryngeal ganglia, and that NO regulates circulation and secretion in the larynx.

Animals↗
PubMed1998

Ultrastructure of the myelinated nerve fibers in the feline laryngeal mucosa.

We studied the myelinated sensory nerve fibers in the feline laryngeal mucosa. Myelinated afferent nerve fibers (A-delta type) present in the lamina propria showed deterioration of the myelin sheath and Schwann cells under the basement membrane. Axons penetrated the basement membrane and entered the intercellular space of the epithelium. Nerve endings with many mitochondria and small clear vesicles existed in the intercellular space. No synapse-like structure was found between the endings and the surrounding epithelial cells. It is likely that these endings act as mechanosensitive receptors that respond to water or chemical stimuli and that participate in eliciting swallowing, coughing, and bronchoconstriction.

Animals↗
PubMed1998

Captopril inhibits both dopaminergic and cholinergic neurotransmission in the central nervous system.

1. The present study was performed to investigate the effects of captopril on both dopaminergic and cholinergic neurotransmission in the rat central nervous system. 2. Slices of rat striatum were prepared and prelabelled with [3H]-dopamine or [3H]-choline. Slices were continuously superfused with Krebs'-Ringer solution and electrical stimulation (1 Hz) was performed. 3. Captopril significantly inhibited stimulation-evoked [3H]-dopamine release from rat striatal slices in a concentration-dependent manner (S2/S1 ratios: control 0.835 +/- 0.018 (n = 6); 1 x 10(-5) mol/L captopril 0.597 +/- 0.035 (n = 6; P < 0.05); 5 x 10(-5) mol/L captopril 0.561 +/- 0.041 (n = 6; P < 0.05)). However, the basal release of [3H]-dopamine was not affected by captopril. 4. Captopril also reduced stimulation-evoked [3H]-acetylcholine release in the striatum (S2/S1 ratios: control 0.891 +/- 0.016 (n = 6); 1 x 10(-5) mol/L captopril 0.794 +/- 0.011 (n = 6; P < 0.05)). 5. These results show that captopril inhibits the release of both dopamine and acetylcholine in the rat striatum. Although the mechanisms underlying the neurosuppressive effects of captopril remain to be determined, the findings suggest that the inhibition of dopaminergic and cholinergic neurotransmission may be related to the central action of the angiotensin-converting enzyme inhibitor.

Acetylcholine↗
PubMed1998

Preoperative staging of endometrial carcinoma: diagnostic effect of T2-weighted fast spin-echo MR imaging.

PURPOSE: To evaluate the usefulness of T2-weighted fast spin-echo magnetic resonance (MR) imaging with a 512 x 256 matrix for assessment of the preoperative stage of endometrial carcinoma. MATERIALS AND METHODS: Twenty-eight women with histopathologically proved endometrial carcinoma underwent preoperative T2-weighted fast spin-echo, dynamic T1-weighted fast spin-echo, and postcontrast T1-weighted spin-echo MR imaging with a phased-array surface coil. The uterine long-axis planes in each sequence were reviewed at separate sessions by three radiologists blinded to the histopathologic data. RESULTS: For the diagnosis of myometrial invasion, no statistically significant differences were found among T2-weighted imaging, dynamic imaging, and postcontrast T1-weighted imaging. For the diagnosis of deep myometrial invasion, T2-weighted and dynamic images showed higher specificity than postcontrast T1-weighted images (T2-weighted, 89%; dynamic, 88%; and postcontrast T1-weighted, 80%). For cervical invasion, T2-weighted and dynamic images showed larger areas under receiver operating characteristic curves than did postcontrast T1-weighted images (T2-weighted, 0.78; dynamic, 0.71; and postcontrast T1-weighted, 0.67). CONCLUSION: T2-weighted imaging is useful for identifying the stage of endometrial carcinoma.

Carcinoma↗
PubMed1998

Metabolic inhibition impairs ATP-sensitive K+ channel block by sulfonylurea in pancreatic beta-cells.

The effect of metabolic inhibition on the blocking of beta-cell ATP-sensitive K+ channels (KATP channels) by glibenclamide was investigated using a patch-clamp technique. Inhibition of KATP channels by glibenclamide was attenuated in the cell-attached mode under metabolic inhibition induced by 2,4-dinitrophenol. Under a low concentration (0.1 microM) of ATP applied in the inside-out mode, KATP channel activity was not fully abolished, even when a high dose of glibenclamide was applied, in contrast to the dose-dependent and complete KATP channel inhibition under 10 microM ATP. On the other hand, cibenzoline, a class Ia antiarrhythmic agent, inhibits KATP channel activity in a dose-dependent manner and completely blocks it, even under metabolic inhibition. In sulfonylurea receptor (SUR1)- and inward rectifier K+ channel (Kir6.2)-expressed proteins, cibenzoline binds directly to Kir6.2, unlike glibenclamide. Thus, KATP channel inhibition by glibenclamide is impaired under the condition of decreased intracellular ATP in pancreatic beta-cells, probably because of a defect in signal transmission between SUR1 and Kir6.2 downstream of the site of sulfonylurea binding to SUR1.

2,4-Dinitrophenol↗
PubMed1998

Clinical manifestations due to a point mutation of the mitochondrial tRNAleu(UUR) gene in five families with diabetes mellitus.

It has been shown that an adenine (A) to guanine (G) transition at position 3243 of the mitochondrial transfer RNA(tRNA)leu(UUR) gene is associated with a subgroup of diabetes mellitus. Therefore, we screened for this transition in 86 patients with non-insulin-dependent diabetes mellitus (NIDDM) in which two or three generations were affected with diabetes, in 14 patients with insulin-dependent diabetes mellitus, and in 9 families with diabetes mellitus and/or associated disorders suggesting mitochondrial gene abnormalities. We failed to identify the mutation in 100 diabetic patients, 86 NIDDM and 14 insulin-dependent diabetes mellitus (IDDM). Out of the latter 9 families, we identified an A to G transition in 14 individuals in 5 families. Diabetes mellitus was shown to be maternally inherited in one family. In 9 of 14 patients with the mutation, insulin was required to treat diabetes mellitus, indicating impaired insulin secretion. A hyperglycemic clamp test performed in one subject revealed significant impairment of insulin secretion, whereas euglycemic clamp test showed normal insulin sensitivity in this patient. The heteroplasmy of the mutant mitochondrial DNA (mtDNA) in leukocytes does not appear to correlate with the severity of diabetes in terms of the insulin therapy required. Body mass index of the affected individuals was less than 23.3. In one family, in addition to diabetes mellitus and hearing loss, hypoparathyroidism was associated with the mutation, suggesting that hypoparathyroidism is caused by the impaired processing and/or secretion of proparathyroid hormone due to the mutation. In addition, the affected subjects presented with proteinuria at the time of diagnosis of diabetes mellitus which appeared not to be related with diabetic nephropathy.

Adolescent↗
PubMed1998

Effects of injection rates of contrast material on arterial phase hepatic CT.

OBJECTIVE: Our goal was to assess the effects of the i.v. injection rate of contrast material on arterial phase hepatic CT. SUBJECTS AND METHODS: One hundred patients were randomly divided into four groups of 25 with different injection rates of 90 ml of contrast material: 2, 3, 4, or 5 ml/sec. Single-level serial CT was performed at the level of the middle section of the main portal vein before injection and every 2 sec from 12 sec to 60 sec after injection of contrast material. The enhancement value was calculated as the difference in attenuation value between the unenhanced and contrast-enhanced images for the aorta and liver parenchyma. The duration of the arterial phase was defined as the interval beginning when the enhancement value for the aorta reached 100 H and ending when the value for the liver parenchyma reached 20 H. RESULTS: Faster injection rates increased the maximum enhancement of the aorta. Although faster injection rates decreased the time from injection to the beginning and the end of the arterial phase, faster injection rates did not decrease the duration of the arterial phase itself. CONCLUSION: A faster injection rate increases arterial enhancement of the liver, and the duration of the arterial phase remains the same as that occurring with a slower injection rate. We hypothesize that faster injection rates can provide better results using CT to reveal hypervascular liver tumors.

Adult↗
PubMed1998

[Three-dimensional gadolinium-enhanced dynamic MRI of whole liver using spectrally selected enhanced fast gradient recall sequence].

Three-dimensional gadolinium-enhanced dynamic MRI of whole liver using the spectrally selected enhanced fast gradient recall sequence (spec IR-efgre3d) was performed in five patients with HCC. Ten HCC nodules were confirmed by CTA, CTAP and Lipiodol CT, and all of them were detected with dynamic MRI. MIP images reconstructed from 3D gadolinium-enhanced dynamic MR studies clearly showed the main portal vein and its branches in all cases. Portal vein thrombosis was also demonstrated with the MIP images.

Carcinoma, Hepatocellular↗