Pimobendan directly sensitizes reconstituted thin filament to slide on cardiac myosin.

To elucidate the mechanism of the Ca(2+)-sensitizing action of pimobendan, cardiac thin filaments were reconstituted from actin and tropomyosin-troponin complex and made to slide on a myosin layer. Although filaments showed Brownian movement with a low Ca2+ concentration, they slid at a constant velocity above a certain level of Ca2+ concentration, showing that the sliding was regulated by Ca2+ within a narrow pCa range. Acidosis, addition of inorganic phosphate, and phosphorylation of troponin I increased the threshold Ca2+ concentration.

MCI-154 increases Ca2+ sensitivity of reconstituted thin filament. A study using a novel in vitro motility assay technique.

MCI-154 (6-[4-(4'-pyridylamino)phenyl]-4,5-dihydro-3(2H)pyridazinone hydrochloride trihydrate) is a potent novel cardiotonic agent whose positive inotropism is shown to be mainly based on an increase in Ca2+ sensitivity of the contractile apparatus. To elucidate the exact mechanism through which this drug acts, we investigated the movement of the reconstituted thin filament on a myosin layer in vitro. Cardiac thin filaments were reconstituted from actin and tropomyosin-troponin complex purified from rat cardiac acetone powder separately.

Effects of exercise on plasma level of brain natriuretic peptide in congestive heart failure with and without left ventricular dysfunction.

This study was designed to determine whether plasma brain natriuretic peptide (BNP) increases in response to exercise in patients with congestive heart failure and to show what kind of hemodynamic abnormalities induce increased secretion of BNP during exercise. Plasma levels of atrial natriuretic peptide (ANP) and BNP and hemodynamic parameters were measured during upright bicycle exercise tests in seven patients with dilated cardiomyopathy and nine with mitral stenosis. At rest, there were no intergroup differences in cardiac output or pulmonary capillary wedge pressure; however, the group with dilated cardiomyopathy had higher left ventricular end-diastolic pressures and lower left ventricular ejection fractions than did the group with mitral stenosis.

A new in vitro motility assay technique to evaluate calcium sensitivity of the cardiac contractile proteins.

We attempted to introduce calcium regulation into in vitro motility assay. Cardiac thin filament was reconstituted from actin and tropomyosin-troponin complex purified from rat myocardium separately. Double staining of the filaments showed tropomyosin-troponin complex was integrated along actin filaments homogeneously.

Recognition of monosialoganglioside (GM3) reconstituted in sphingomyerin and glucosylceramide membranes against wheat germ agglutinin: quantitative analyses by a quartz crystal microbalance.

Specific binding of Wheat Germ Agglutinin (WGA) to GM3-containing mixed monolayer at the air-water interface was studied by using a quartz crystal microbalance to know the binding amount and initial binding rate of WGA to GM3. GM3 in the glucosylceramide matrix membrane showed the high recognizability compared to GM3 in sphingomyeline matrix membrane. It is demonstrated that matrix lipids surrounding GM3 regulated the recognition of GM3.

[A case report of giant epidermoid in the temporal lobe: considerations of the occurrence of intramedullary epidermoids].

A case of giant epidermoid which was mainly located in the right temporal lobe was presented. The intracranial epidermoid is commonly located in the CSF space, such as the cerebello-pontine (C-P) angle, parasellar region, middle cranial fossa and ventricles. The intramedullary epidermoid is extremely rare.

Nitric oxide-mediated effects of interleukin-6 on [Ca2+]i and cell contraction in cultured chick ventricular myocytes.

Cytokines have significant roles in some cardiovascular disorders, but direct myocardial effects of cytokines remain to be elucidated. In the present study, we examined both the early and delayed effects of interleukin-6 (IL-6) on cultured chick embryo ventricular myocytes. Exposure of these cells to human recombinant IL-6 significantly decreased peak systolic [Ca2+]i (71.

ADP inhibits the sliding velocity of fluorescent actin filaments on cardiac and skeletal myosins.

We studied the effect of MgADP on the mechanical interaction of actomyosin in cardiac and skeletal muscles using an in vitro motility assay. The sliding velocities of fluorescently labeled actin filaments on rat cardiac and skeletal myosins were measured at various MgATP and MgADP concentrations. The filament velocity depended on MgATP concentration according to classic Michaelis-Menten kinetics with apparent Michaelis constants (Km) of 43 and 137 mumol/L and maximum velocity of 5.

[Microsurgical anatomy of the anterior communicating artery and its perforating arteries important for interhemispheric trans-lamina terminalis approach: analysis based on cadaver brains].

Microsurgical anatomy of anterior communicating artery (ACoA) and its perforating arteries important for interhemispheric trans-lamina terminalis approach is examined in 25 cadaver brains under magnification using a surgical microscope. ACoA were found in all cases but 60% of those cases had variations such as plexiform ACoA, dimple ACoA, fenestrated ACoA, triple A2 and azygous ACA. In cases with variations such as plexiform ACoA, triple A2 and azygous ACA, it seems difficult to section and divide the ACoA to obtain a better operative field.

Effects of endothelin-1 on [Ca2+]i and pHi in trabecular meshwork cells.

We examined the effects of endothelin-1 (ET-1) on [Ca2+]i and intracellular pH in cultured bovine trabecular meshwork cells and compared the effects of ET-1 with those of angiotensin II (another phospholipase C activating peptide). [Ca2+]i was measured with the Ca2+ fluorescent dye indo-1. Intracellular pH was measured using the pH sensitive fluorescent dye BCECF.

New subtype of apical hypertrophic cardiomyopathy identified with nuclear magnetic resonance imaging as an underlying cause of markedly inverted T waves.

Objectives: The aim of this study was to elucidate the clinical importance of a new subtype of apical hypertrophic cardiomyopathy that could not be diagnosed with the classical diagnostic criteria.

Background: Apical hypertrophic cardiomyopathy is recognized by a characteristic spade-shaped intraventricular cavity on the end-diastolic left ventriculogram in the right anterior oblique projection, often associated with giant negative T waves [negativity > or = 1.0 mV (10 mm)].

Dynamic interaction between cardiac myosin isoforms modifies velocity of actomyosin sliding in vitro.

To study the functional significance of cardiac isomyosin heterogeneity, active sliding of actin-myosin was studied using two different types of in vitro motility assay systems: (1) a sliding actin filament assay, in which fluorescently labeled actin filaments were made to slide on a myosin layer attached to a glass coverslip, and (2) a myosin-coated bead assay, in which myosin-coated latex beads were made to slide on actin cables of an alga. Two different isomyosins were obtained from 3-week-old (V1) and hypothyroid (V3) rat hearts and were mixed to form solutions with various mixing ratios [V1/(V1 + V3)]. For these myosin mixtures, both ATPase activity and sliding velocity of actin-myosin were determined.

Variable effects of endothelin-1 on [Ca2+]i transients, pHi, and contraction in ventricular myocytes.

We examined the effects of endothelin-1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) transients, intracellular pH (pHi), and cell contraction in both embryonic and neonatal as well as in adult ventricular myocytes. Exposure of chick ventricular myocytes to ET-1 (10 nM) significantly decreased both peak systolic and end-diastolic [Ca2+]i (from 949 +/- 43 to 628 +/- 59 nM and from 230 +/- 13 to 162 +/- 8 nM, respectively; P < 0.05, n = 12).

Analysis of cardiac assistance by latissimus dorsi cardiomyoplasty with a time varying elastance model.

Objective: The clinical use of skeletal muscle cardiomyoplasty is limited because of its inadequate haemodynamic benefits. To facilitate experimental and clinical efforts to improve the efficacy of this technique, a mathematical model was proposed and its validity was tested in acute experiments.

Methods: The model was based on the assumption that the skeletal muscle wrapped around the heart behaves as a time varying elastance that is connected in series with another time varying elastance representing the native heart.

Increased tolerance of ventricular function and energy metabolism to hypoxia in cardiomyopathic hamsters.

To study the responses of myocardial function and metabolism to hypoxia in normal hamsters and cardiomyopathic hamsters (Bio 14.6), left ventricular pressure was measured in an isolated isovolumically beating heart preparation, and myocardial high energy phosphates (ATP and creatine phosphate), inorganic phosphate, and intracellular pH were also measured by 31P nuclear magnetic resonance spectroscopy. In 20-week-old cardiomyopathic hamsters, the heart weight was increased and the baseline left ventricular developed pressure, peak positive dP/dt, and peak negative dP/dt were decreased, indicating depression of left ventricular function.

[Cardiac contractile proteins].

Structure and function of cardiac contractile proteins were summarized in connection with the pathophysiology of the heart muscle. Myosin is a large molecule consisting of two heavy chains and four light chains. Functional domains including ATP binding and actin binding sites reside in heavy chain.

Effects of a nonpeptide angiotensin II receptor antagonist (CV-11974) on [Ca2+]i and cell motion in cultured ventricular myocytes.

We studied the effects of angiotensin II and CV-11974 (a newly synthesized angiotensin II receptor antagonist) on cell contraction and [Ca2+]i in cultured neonatal rat ventricular myocytes. Exposure of these cells to 10 nM angiotensin II significantly decreased peak systolic cell position (60.1 +/- 3.

[The recent studies of myocardial blood flow and metabolism by using positron emission computed tomography].

Since the application of positron emission computed tomography (PET) for myocardium, the evaluation of myocardial blood flow, glucose metabolism, fatty acid metabolism, oxygen consumption and etc. has been performed. Especially, it has been regarded very important clinically to evaluate myocardial viability from the mismatch of myocardial glucose metabolism and blood flow.

Depressed sliding velocity of isolated cardiac myosin from cardiomyopathic hamsters: evidence for an alteration in mechanical interaction of actomyosin.

We measured the relative sliding velocity of cardiomyopathic hamster cardiac myosin on actin cables by using an in vitro motility assay system. We also investigated the relationship between the velocity and both myosin isozyme content and ATPase activity. Cardiac myosin was obtained from cardiomyopathic hamsters (BIO 14.