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Biomedical subjects

Y Kihara

Publications and source records attributed to Y Kihara.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Pheochromocytoma of the left retroperitoneal paraganglion associated with torsade de pointes: a case report].

A 54-year-old woman developed torsade de pointes with secondary QT prolongation due to hypokalemia and hypomagnesemia. Her serum K and Mg levels were 2.5 mEq/l and 1.5 mg/dl, respectively. This electrolyte imbalance was due to intentional overdosing of metolazone. Attacks of torsade de pointes occurred three times in the intensive care unit and were corrected by intravenous lidocaine administration. Her serum K level was corrected using KCl infusion, restoring the normal QT interval. Routine computed tomography found a left retroperitoneal paraganglioma. Urinary and serum catecholamine examination revealed extremely high values of epinephrine and norepinephrine. The diagnosis was pheochromocytoma in the left retroperitoneal paraganglion. The tumor which was removed measured 70 x 65 x 60 mm in size. Microscopic examination revealed the characteristic patterns of pheochromocytoma.

Diuretics↗
PubMed1997

[CT-guided lung needle biopsy using a new supporting implement].

We contrived a new supporting implement to increase the hit rate of CT-guided needle biopsy (CTNB) for localized pulmonary lesions. Using this implement, twenty-two CTNB examinations for localized pulmonary lesions were performed. In 21 out of the 22 examinations (95%), the lesions were hit, and specimens appropriate for cytological or histological diagnosis were obtained. The course of needle insertion, which was difficult to define in the past, has become to be easier and more precise with this method. Using this new implement, CTNB is now applicable to smaller and deeper lesions.

Adult↗
PubMed1996

An impaired carotid sinus distensibility and baroreceptor sensitivity alter autonomic activity in patients with effort angina associated with significant coronary artery disease.

Baroreceptor sensitivity and carotid sinus distensibility were lower in patients with angina associated with significant coronary artery disease than in patients with vasospastic angina. Baroreceptor sensitivity was significantly correlated with carotid sinus distensibility in both groups of patients.

Angina Pectoris↗
PubMed1996

Efficacy of limb cooling on the salvage of peripheral nerve from ischemic fiber degeneration.

Since peripheral nerve has a large ischemic safety factor, hypothermia, by reducing metabolic demands, is potentially an efficacious technique to rescue nerve from ischemic fiber degeneration (IFD). We therefore evaluated the influence of temperature on the severity of IFD resulting from a standard ischemic stress. Ischemia to the left sciatic nerve in the rat was produced by embolization of 2 x 10(6) microspheres (14 microns) into its supplying arteries. The limb was embolized at three temperatures, 37 degrees C, 32 degrees C, and 28 degrees C and was maintained at each temperature for an additional 4 h. End points, evaluated 7 days after embolization, for the embolized limb were: (1) behavioral scores, 0-11 in increasing limb function; (2) compound nerve action potential of sciatic-tibial nerve; (3) sciatic nerve blood flow (NBF, in mL/100 g/min); and (4) histologic grade, expressed as percentage of fibers undergoing IFD (0 = < 5%; 1 = 5-25%; 2 = 26-50%; 3 = 51-75%; 4 = > 75%). NBF was reduced in all groups, varying with temperature, and all indices of nerve structure and function were significantly improved with hypothermia. We conclude that hypothermia, easily achievable in a limb nerve, is highly efficacious in the rescue of nerve from IFD. These findings are of clinical relevance.

Animals↗
PubMed1996

Distribution of activated complement, C3b, and its degraded fragments, iC3b/C3dg, in the colonic mucosa of ulcerative colitis (UC).

The third component of complement (C3) is central to both the classical and alternative pathways in complement activation. In this study, involvement of C3 activation in the mucosal injury of UC was investigated. We examined the distribution of activated (C3b) and degraded fragments (iC3b/C3dg) of C3, terminal complement complex (TCC), and complement regulatory proteins in normal and diseased colonic mucosa including UC and other types of colitis using immunohistochemical techniques at the level of light and electron microscopy. While C3b and iC3b/C3dg staining was negligible in the normal mucosa, iC3b/C3dg and, to a lesser extent, C3b were deposited in UC mucosa along the epithelial basement membrane. The deposition was enhanced in relation to the severity of mucosal inflammation (C3b, P less than 0.05; iC3b/C3dg, P less than 0.01). Epithelial deposition of TCC was not observed in most UC mucosa. Immunoelectron microscopy showed that C3b and iC3b/C3dg were distributed mainly along the epithelial basement membrane and the underlying connective tissue in a granular, studded manner, and weakly present along the basolateral surface of epithelial cells. These C3 fragments were also deposited in inflammatory control mucosa such as ischaemic and infectious colitis. Our findings suggest that deposition of the C3 fragments occurs in inflamed colonic mucosa of diverse etiologies, including UC, but to define a role of the deposition in the development of mucosal injury in UC awaits direct study.

Adult↗
PubMed1996

Mechanisms of negative inotropic effects of class Ic antiarrhythmic agents: comparative study of the effects of flecainide and pilsicainide on intracellular calcium handling in dog ventricular myocardium.

We studied the subcellular mechanisms responsible for the negative inotropic effects of the two Ic drugs flecainide and pilsicainide. Aequorin luminescence (Ca2+i) and isometric tension were recorded simultaneously in isolated trabeculae from the dog ventricle. In isolated myocytes from the same ventricle, the slow inward current (ICa) was recorded. Both flecainide and pilsicainide decreased peak Ca2+i, peak tension, and peak ICa concentration dependently. Each effect with flecainide was more marked than that with pilsicainide; however, Ca2+i and ICa paralleled each other in changes in tension, and the tension-Ca2+i-ICa relationship showed the same curve for each drug. We conclude that the difference in negative inotropic effects of these class Ic drugs are primarily related to their effects on L-type Ca2+ channels and the subsequent decreases in the amount of Ca2+ released from the sarcoplasmic reticulum (SR) during each cardiac cycle. Therefore, their negative inotropic effects may not be directly correlated with the essential mechanisms responsible for their antiarrhythmic action.

Animals↗
PubMed1996

Mechanism of the negative force-frequency relationship in physiologically intact rat ventricular myocardium--studies by intracellular Ca2+ monitor with indo-1 and by 31P-nuclear magnetic resonance spectroscopy.

We studied the subcellular mechanisms of the negative force-frequency relationship in rat myocardium by measuring 1) intracellular Ca2+ transients by indo-1 fluorometry and 2) intracellular pH (pHi) and phosphate compounds with 31P-nuclear magnetic resonance (NMR). The data were compared with those from guinea pig hearts, which show a positive force-frequency relationship. By increasing the pacing rate from 3 Hz to 5 Hz, the peak positive first derivative of left ventricular pressure (LVdP/dt) in rat heart decreased by 10 +/- 1% (n = 6). In contrast to this negative inotropic response, simultaneously measured peak Ca2+ transients increased by 6 +/- 1%. Guinea pig heart (n = 6) showed an increase in peak positive LVdP/dt (33 +/- 1%) which was associated with an increase in peak Ca2+ transients (8 +/- 1%). Under equivalent experimental conditions in an NMR spectrometer, this increase in the pacing rate did not affect intracellular levels of phosphate compounds in either rat (n = 6) or guinea pig heart (n = 6). In contrast, pHi showed a decrease of 0.031 +/- 0.006 pH units in rat heart, while no changes were observed in guinea pig heart. These results suggest that in physiological rat myocardium, pHi is susceptible to changes in the stimulus frequency and may affect the Ca(2+)-responsiveness of contractile proteins, which results in the negative force-frequency relationship.

Animals↗
PubMed1996

Left ventricular hypertrophy in mild essential hypertension. Its progression, prediction and treatment strategy.

Since the pathogenesis of left ventricular hypertrophy (LVH) in hypertension is thought to be multifactorial, the antihypertensive strategy also has to be multifaceted. Diagnosis of LVH is more reliable than ever with echocardiography either of the M-mode or 2D method. Diagnostic criteria have already been proposed by Ganau et al who classified LV morphology into 4 different sectors based on the standard values of left ventricular mass index (LVMI) and relative wall thickness in diastole (RWTd); normal, concentric remodeling, concentric hypertrophy and eccentric hypertrophy. The concentric hypertrophy pattern is the most risky with regard to prognosis. Therefore, its detection and prediction for further progression have to be conducted with relatively easy routine work-up procedures such as echocardiography and maximal exercise testing. The prediction of LVH progression has already been proposed based on several studies conducted in patients with borderline or mild hypertension. The following two predictors were defined as LVMI > 124 g/m2 and peak Ps at maximal exercise testing > 200 mmHg. Therefore, the patient who meets these criteria has to be treated with medications that are appropriately selected on an individualized basis. Both hyperinsulinemia and insulin resistance are thought to be involved in the initiation, promotion and potentiation of remodeling of the LV in hypertension. Physical fitness also seems to be decreased in a parallel manner. Selection of the most appropriate drug for a given patient has to be individually determined based on the risks that have to be corrected. Finally, arteriosclerosis, which is almost always initiated and progresses in concert with hypertension, must also be targeted with regard to such prognostic aspects as cardiovascular morbidity and mortality. Arteriosclerosis is pathogenetically independent from hypertension, but usually behaves in concert with it. Selection of medication must be focussed on an individualized basis not only for LVH, but also for improvement in arterial elasticity. Further clinical research is still needed to provide more reasonable approaches to patients with hypertension.

Angiotensin II↗
PubMed1996

[Natural history of cloudy zone of pulmonary adenocarcinoma on HRCT].

Seven pulmonary adenocarcinomas with cloudy zone (CZ), which was defined as a lower density zone in the pulmonary lesion than pulmonary vessels in the surrounding normal lung on high resolution computed tomography (HRCT), were followed up for at least 3 months. There were three tumors with homogeneous CZ, one of which showed no change when rescanned after three months, the others showed enlargement with or without replacement by high density areas on rescanned images obtained after more than one year. Two tumors containing some high density areas on the initial scans showed slight decreases in size on rescanned images obtained after 1 to 3 months. However, on rescanned images obtained after more than 1 year and 9 months, these tumors also showed enlargement of CZ. Pathologically, CZs corresponded to well-differentiated adenocarcinoma of the bronchioloalveolar type with no or mild interstitial change, whereas high density areas mainly corresponded to papillary adenocarcinoma with severe interstitial fibrosis. In conclusion, long-term careful follow-up of CZ is necessary to detect enlargement or the appearance of high density. Unchanged CZ in short-term follow-up should be considered a finding suggestive of malignancy.

Adenocarcinoma, Papillary↗
PubMed1996

[Primary right atrial hemangiosarcoma manifesting as cardiac tamponade: a case report with transesophageal echocardiography].

A 39-year-old woman presented with a right atrial hemangiosarcoma manifesting as cardiac tamponade with complaints of chest discomfort and dyspnea. Transthoracic echocardiography revealed remarkable pericardial effusion and a right atrial mass. Transesophageal echocardiography disclosed the tumor extending into the right atrial cavity. Surgery found the tumor was poorly demarcated, immobile and adhered to the adjacent right atrial wall and septum. The echocardiographic findings correlated well with the surgical and autopsy findings.

Adult↗
PubMed1995

Neurohumoral factors during transition from left ventricular hypertrophy to failure in Dahl salt-sensitive rats.

The relationship between the reduction in the positive inotropic effects (PIE) of beta-adrenergic stimulation and the level of systemic and tissue neurohumoral factors during the course from left ventricular (LV) hypertrophy to congestive heart failure (CHF) was studied in Dahl salt-sensitive rat (DS) CHF model. Control studies were performed in age-matched Dahl salt-resistant (DR) rats. In DS rats at CHF stage, plasma atrial natriuretic peptide (ANP) and norepinephrine (NE) levels were elevated markedly and myocardial NE level was decreased compared with those in the age-matched DR rats. On the other hand, at the hypertrophy stage, we observed no significant differences in plasma ANP or NE level between the two strains in spite of decrease in myocardial NE concentration. The PIE induced by isoproterenol was reduced at the stage of compensatory LV hypertrophy, which was followed by further reduction of PIE at CHF stage. The results distinctively indicate that beta-adrenergic desensitization in the myocardium which was accompanied with the abnormalities in local sympathoneuronal regulation begins during mechanically compensated LV hypertrophy and precedes systemic augmentation of sympathomimetic hormones.

Animals↗
PubMed1995

Experimental ischemic neuropathy: salvage with hyperbaric oxygenation.

Hyperbaric oxygenation is effective in augmenting the delivery of oxygen to tissue, but also causes oxidative stress. As part of our focus on improving peripheral nerve salvage from ischemic fiber degeneration, we evaluated whether hyperbaric oxygenation rescues peripheral nerve, rendered ischemic by microembolization, from ischemic fiber degeneration. The supplying arteries of rat sciatic nerve were embolized with microspheres of 14 microns diameter at moderate (2 x 10(6)) and high (5.6 x 10(6)) doses. Rats were randomized to receive hyperbaric oxygenation treatment (2.5 atm 100% oxygen for 2 hours/day for 7 days beginning within 30 minutes of ischemia), or room air. End points for the embolized limb were (1) behavioral scores (0-11 in increasing levels of limb function), (2) nerve action potential of sciatic-tibial nerve, (3) nerve blood flow, and (4) histological grade as percentage of fibers undergoing ischemic fiber degeneration (0 = < 5%; 1 = 5-25%; 2 = 26-50%; 3 = 51-75%; 4 = > 76%). Nerve blood flow and nerve action potential were uniformly absent and more than 90% of fibers had degenerated in both control and treatment groups receiving high doses. Control and treatment groups receiving moderate doses were well matched by level of ischemia (8.5 +/- 0.3 [N = 18] vs 7.7 +/- 0.4 ml/100 gm/min [N = 18], p > 0.05) but were significantly different by behavior score (5.6 +/- 0.7 vs 9.2 +/- 0.5 [N = 19], p < 0.001), nerve action potential (1.4 +/- 1.0 vs 3.9 +/- 0.5 [N = 6], p < 0.05), and histology (2.4 +/- 0.4 [N = 5] vs 0.8 +/- 0.5 [N = 4], p < 0.05). On single teased fiber evaluation, the predominant abnormality was E (axonal degeneration). We conclude that hyperbaric oxygenation will effectively rescue fibers from ischemic fiber degeneration, providing the ischemia is not extreme.

Action Potentials↗
PubMed1995

Contrast-enhanced MR imaging of intrahepatic cholangiocarcinoma.

The unenhanced spin-echo T1-weighted images, contrast-enhanced (dynamic and conventional) T1-weighted images and spin-echo T2-weighted images of 19 patients with histologically proven intrahepatic cholangiocarcinoma were reviewed. The results showed that typical intrahepatic cholangiocarcinoma presented as a large mass of low signal intensity on T1-weighted images. On T2-weighted images tumours generally presented as high signal intensity masses. In five patients the tumours exhibited varying degrees of central hypointensity on T2-weighted images. On contrast-enhanced images, large tumours (diameter larger than 4 cm, n = 14) typically showed peripheral enhancement with delayed or incomplete central filling. This pattern was seen most commonly. Smaller tumours (diam. 2-4 cm, n = 5) typically exhibited homogenous enhancement. On dynamic studies, enhancement of the tumours showed a centripetal pattern. Complete enhancement was observed in the small tumours. Among the larger lesions central sparing of the tumours was seen. It is concluded that contrast-enhanced MR imaging is useful in the diagnosis of intrahepatic cholangiocarcinoma. The characteristic enhancing pattern of intrahepatic cholangiocarcinoma was seen less commonly in smaller tumours. Definite differentiation from other liver masses in this case could be less certain.

Adult↗
PubMed1995

Different inhibitory effects of the newly developed CCK receptor antagonists FK480 and KSG-504 on pancreatic exocrine and endocrine secretion in the isolated perfused rat pancreas.

Cholecystokinin (CCK) receptor antagonists are shown to have therapeutic as well as preventive effects in some types of acute pancreatitis. However, there is a possibility that administration of CCK receptor antagonists with a high inhibitory potency on the endocrine pancreas to patients with acute pancreatitis exacerbates the associated glucose intolerance. In the present study we simultaneously examined the effects of the newly developed benzodiazepine derivative FK480 and proglumide-related antagonist KSG-504 on CCK octapeptide (CCK-8)-stimulated exocrine and endocrine function in the isolated perfused rat pancreas. FK480 and KSG-504 inhibited CCK-8-stimulated pancreatic juice flow, protein output, and insulin release in a dose-dependent manner. FK480 was approximately 10 times more potent than KSG-504 in inhibiting exocrine and endocrine secretion. Both antagonists inhibited CCK-8-stimulated insulin release more potently than exocrine secretion. FK480 caused a dose-dependent residual inhibition of exocrine secretion after its removal from the perfusate, whereas insulin release was only slightly impaired even at the highest dose. In contrast, termination of KSG-504 infusion resulted in an immediate increase in both exocrine and insulin responses without causing any residual inhibition. With regard to the residual inhibition, therefore, KSG-504 had no significant influences on exocrine and insulin release, whereas FK480 inhibited exocrine secretion more potently than insulin response. These results suggest that FK480 might become a useful therapeutic agent for pancreatitis with respect to its long-duration inhibitory effect on exocrine secretion and short-duration inhibitory effect on insulin release.

Animals↗
PubMed1995

L-methionine augments mammalian myocardial contraction by sensitizing the myofilament to Ca2+.

L-Methionine is an essential amino acid that has been reported to have a potent positive inotropic effect on the mammalian myocardium. We studied the mechanisms of the inotropic effect in ventricular myocardium from the rabbit. In the isolated coronary-perfused whole heart, L-methionine in a millimolar range exerted concentration-dependent positive inotropic effects on the isovolumic left ventricle, which were associated with negative lusitropic effects (prolonged time course of relaxation). The chronotropic state and the coronary perfusion pressure were not affected. These complex effects on the isolated whole heart were not blocked by pretreatment with (mumol/L) propranolol 1, prazosin 1, carbachol 3, staurosporine 1, or [Ser1,Ile8]angiotensin II 0.1. To further study the subcellular mechanisms, isolated ventricular papillary muscles from the same species were loaded with a bioluminescent indicator, aequorin, to monitor [Ca2+]i. In the presence of 3 mmol/L L-methionine, the isometric tension showed a similar combination of the positive inotropic and negative lusitropic effects as observed in the whole heart. In contrast, the simultaneously recorded intracellular Ca2+ signals did not increase in amplitude but instead decreased. The [Ca2+]i-tension relation shifted to the left compared with that obtained in response to [Ca2+]o. In saponin (250 micrograms/mL)-treated skinned preparations, 3 mmol/L L-methionine also shifted the force-pCa curve to the left by 0.16 pCa units. This is the first demonstration that an essential amino acid directly acts on the myofilaments and modulates their responsiveness to Ca2+, thereby producing a positive inotropic effect.

Actin Cytoskeleton↗