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Biomedical subjects

M Nagano

Publications and source records attributed to M Nagano.

At least 271 records · Page 15Linked to original sources
PubMed1987

Comparison of electrical responses of terminals, axons, and somata of a peptidergic neurosecretory system.

Spontaneous and evoked electrical activity was recorded intracellularly from somata, axons, and terminal dilatations of an isolated peptidergic neurosecretory system, the X-organ-sinus gland, of the crabs Cardisoma carnifex and Podophthalmus vigil in order to compare their electrical characteristics. Spontaneous impulse activity was present in most penetrations and included irregular and pacemaker-like firing, as well as patterned activity (bursting). Extracellular recording showed that spontaneous impulses and bursting originate in a proximal region of the axon tract. Somata vary from being electrically nonresponsive to having overshooting impulses with a relatively slow rate of rise. Overshooting impulses were consistently recorded from axons and terminals. Regional differences include (1) a longer action potential duration in terminals, (2) ability of axons and terminals but not somata to sustain repetitive firing, (3) presence of depolarizing afterpotentials in axons but of hyperpolarizing afterpotentials in somata and terminals, and (4) occurrence of impulse broadening during repetitive firing in some terminals but not in axons or somata. Somata and terminals sustained reduced and slowed, but regenerative impulses in nominally Na-free saline and showed alterations of waveform in nominally Ca-free salines, while axons showed no regenerative responses in Na-free saline and no change of impulse form in Ca-free saline. Terminal responses in the presence of tetraethylammonium chloride (TEA) (50 mM) or Ba (50 mM) exhibited long depolarized plateaus, while impulses of somata were much less prolonged. Bursts often took the form of impulses superimposed on a depolarized plateau. Bursts could be evoked by single stimuli applied to the axon tract but not by current passed intracellularly. After addition of TTX, axon tract stimulation evoked plateaus without superimposed impulses. Terminals exhibit specialization of their electrical responses by comparison to axons and somata in having long-duration action potentials attributable to participation of Ca, capability of sustained firing, impulse broadening, and channels supporting sustained inward currents, all of which might enhance the admission of Ca for initiation of peptide secretion.

Action Potentials↗
PubMed1986

Significant increase in plasma immunoreactive atrial natriuretic polypeptide concentration during head-out water immersion.

To investigate the physiological regulatory mechanism of human atrial natriuretic polypeptide (hANP) secretion, plasma hANP was measured by a direct radioimmunoassay during head-out total body water immersion (WI) in normal men. Five healthy men were immersed in water for 1 hr. Urine volume and Na excretion were significantly increased during WI. Plasma hANP increased significantly during WI peaking at 30 min. and returned toward the baseline after WI. Plasma renin activity and norepinephrine were suppressed occasionally during WI. Plasma ADH did not change throughout the study period. Maximal increments in plasma hANP correllated with that in urine output or urinary Na excretion during WI. These data suggest that acute central hypervolemia caused by WI increases hANP secretion and that this increase may participate in the diuretic response to WI.

Adrenal Cortex Hormones↗
PubMed1986

Circulating factor with ouabain-like immunoreactivity in patients with primary aldosteronism.

Circulating factor with ouabain-like immunoreactivity was studied in patients with primary aldosteronism. Anti-ouabain antibody was prepared from specific pathogen-free rabbits. In the plasma of patients with primary aldosteronism, the level of a factor with ouabain-like immunoreactivity was 2.59 +/- 1.39 pmol ouabain equivalent/ml plasma. This value was significantly (p less than 0.05) higher than that of age-matched normotensive subjects, 1.06 +/- 0.86 pmol ouabain equivalent/ml plasma. The plasma level of ouabain-like immunoreactivity correlated significantly (p less than 0.05) with blood pressure. These results indicate that the factor with ouabain-like immunoreactivity may play a pathophysiological role in the maintenance of the high blood pressure observed in patients with primary aldosteronism.

Antibody Affinity↗
PubMed1986

Heterogeneity of neurons in the crustacean X-organ as revealed by intracellular recording and injection of horseradish peroxidase.

The intracellular injection technique of HRP with simultaneous recordings of intracellular potential was applied to the crab X-organ-sinus gland peptidergic neurosecretory neurons. At least two classes of neurons were discriminated from the usual type of neurosecretory neurons morphologically as well as electrophysiologically. Possible roles of those neurons were suggested as the modulation and coordination of activities of the neurosecretory system.

Action Potentials↗
PubMed1986

Functional and metabolic properties in hearts from aged spontaneously hypertensive rats.

The effect of long-term pressure overload on myocardial functional and metabolic alterations was investigated in hearts from spontaneously hypertensive rats of 16 weeks (young SHR) and 44 weeks (aged SHR) and age matched normotensive Wistar Kyoto strain rats (young WKY, aged WKY). The hearts were perfused by working heart mode and whole heart ischemia was induced by one-way valve. Following 20 min of ischemia, the hearts were reperfused for 30 min. The heart-body weight ratio in both SHR groups was significantly higher than in the respective age-matched WKY groups. Coronary flow relative to heart weight in both SHR groups was significantly lower than that of the respective age-matched WKY during both preischemic and reperfused periods. There was no significant difference in the recovery rate of cardiac output between young and aged WKY, whereas the young and aged SHR revealed significantly less recovery than their respective age-matched WKY. Tissue creatine phosphate and energy charge in both aged groups were significantly lower than in the young groups. These results indicate that long-term pressure overload increases susceptibility to ischemia and decreases the myocardial reserve presumably resulting from relative ischemia, whereas deterioration was minimal in the normotensive aged rat heart.

Aging↗
PubMed1986

Polymorphonuclear leukocytes and the induction of alpha 2-macroglobulin synthesis.

Peritoneal exudate-polymorphonuclear leukocytes (PMNLs) secreted a factor, PMN factor (PMN-F), which stimulated hepatocytes to synthesize alpha 2-macroglobulin (a2M), in vitro. The synthesis of a2M was enhanced by the factor in the presence of dexamethasone (Dex), and the effect was dose-dependent. After harvesting from the peritoneal exudate, PMNLs released the factor within 1 hr of the incubation. Physicochemical properties of the factor were as follows: nondialyzable, heat-labile, stable in wide pH change, inactivated by a protease inhibitor, aprotinin, and apparent molecular weight being 12,000-21,000, determined by gel filtration. Treatment of PMNLs with zymosan resulted in increases in the activity of lysosomal enzymes but not that of the factor. These results indicate that the factor is a protease other than lysosomal enzymes.

Animals↗
PubMed1985

Effects of vitamin B12 and B6 on 2,5-hexanedione-induced neuropathy.

The therapeutic effect of Vitamin B12 or Vitamin B6 on 2,5-hexanedione induced-neuropathy in animals was examined by using our electrodiagnostic technique in order to investigate the mechanism of the development of the neuropathy. Pyridoxal phosphate and two forms of Vitamin B12 were administered to rats intoxicated by the neurotoxin for a period of 18 weeks, and the sensory and motor fiber conduction velocity and the motor distal latency of the tail nerve were periodically determined. None of the groups treated with the therapeutic drugs exhibited a definite improvement in the nerve fiber conduction velocity and motor distal latency of the rat tail nerve, as compared with those of the 2,5-hexanedione-treated controls.

Animals↗
PubMed1985

Electron-microscopic cytochemistry of alkaline-phosphatase activity in endothelium, pericytes and oligodendrocytes in the rat brain.

The fine structural localization of alkaline-phosphatase (ALP) activity was investigated in the endothelial cells and pericytes of blood vessels and in the oligodendrocytes of rat cerebral cortex and corpus callosum by means of electron-microscopic (EM) cytochemistry using the lead-citrate method. ALP activity was associated with both the luminal and abluminal plasma membranes of some endothelial cells, but in other endothelial cells, this activity was found inside the cytoplasm. In some pericytes, ALP activity was associated with the plasma membrane but in others, strong activity was exhibited within both the cytoplasm and nucleus. Light, medium and dark oligodendrocytes showed ALP activity on their plasma membranes; on the other hand, immature oligodendrocytes exhibited activity within the cytoplasm and on the part of their plasma membrane. Within the cytoplasm of these reacted immature cells, the rough endoplasmic reticulum, nuclear membrane and outer membrane of the mitochondria were the main sites of ALP reaction. Endothelial cells, pericytes and oligodendrocytes demonstrated ALP activity along their plasma membrane or within their cytoplasm, and pericytes showed it within their nuclei. In particular, oligodendrocytes retained ALP activity throughout their cell life, and the intracellular distribution of this activity altered as they matured.

Alkaline Phosphatase↗
PubMed1985

Alpha 2-macroglobulin secretion enhanced in rat hepatocytes by partially characterized factor from Kupffer cells.

Isolated rat Kupffer cells produced a factor which stimulated the synthesis of alpha 2-macroglobulin (alpha 2M) in primary cultured rat hepatocytes. Although Kupffer cells placed in culture produced the factor without stimulation by lipopolysaccharide (LPS), the LPS-stimulated cells produced larger amounts of the factor. On the other hand, the production of the factor was inhibited by addition of actinomycin D. The induction of alpha 2M synthesis by cultured hepatocytes was enhanced in the presence of dexamethasone (Dex), in that hepatic synthesis of alpha 2M increased by addition of the factor alone and with Dex 1.5 and three- to four-fold, respectively. The factor was nondialyzable and stable at 60 degrees C for 30 min. When the factor was fractionated using the molecular sieve method, the activity recovered in the fraction had a molecular weight of over 30,000.

Animals↗
PubMed1985

Clinical application of NMR-CT for idiopathic cardiomyopathy.

The accuracy of a newly developed nuclear magnetic resonance-computed tomography (NMR-CT) technique in diagnosing idiopathic cardiomyopathy was assessed and compared with other procedures such as echocardiography, coronary angiography, left ventriculography, myocardial biopsy, and electrocardiography. In case 1, the NMR-CT clearly revealed thickening of the lateral ventricular free wall and ventricular septum, which strongly suggested hypertrophic cardiomyopathy. Catheterization showed a pressure gradient of 54 mm Hg and this patient was diagnosed as having hypertrophic obstructive cardiomyopathy. In case 2, the NMR-CT showed dilatation of the ventricular cavity indicative of dilated cardiomyopathy. This was confirmed by echocardiography, which revealed the enlarged cavity of the ventricle and poor movement. In case 3, the patient had marked hypertension; the cardiac silhouette was enlarged, but the NMR-CT revealed that the ventricular free wall and septum were of normal thickness. This study shows that NMR-CT is of value in the differential diagnosis of idiopathic cardiomyopathy.

Adult↗