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Biomedical subjects

M Yoshimura

Publications and source records attributed to M Yoshimura.

At least 667 records · Page 37Linked to original sources
PubMed1987

The central nervous system and effective antihypertensive effects of a calcium channel blocker.

Whether or not the central nervous system is involved in the genesis of hypertension in an individual patient, it becomes a major determinant of the responses to antihypertensive therapy once a treatment strategy is adopted. The major mechanisms through which the central nervous system influences blood pressure are sympathetic and parasympathetic nervous system activity and vasopressin release, either together or separately, but additional mechanisms may also contribute. When vasodilators are used, for example, the reactive increase in plasma catecholamines makes a substantial contribution to limiting the blood pressure fall. The sympathetic activation may lead to the reactive increase in plasma renin activity and sodium retention, which also plays an important role in limiting the antihypertensive action. Among newer agents, the effectiveness of calcium channel blockers could reflect a special action on the central nervous system that may contribute to reducing the reactive vasopressor responses. Treatment strategies that address the problem of the central nervous responses are more likely to be effective than approaches that avoid or ignore it.

Animals↗
PubMed1987

Impaired immunoglobulin G production in minimal change nephrotic syndrome in adults.

Serum IgG, T and B cell subsets, cytoplasmic IgG positive cells (cB gamma) and IgG in the medium (cIgG) of a 5 day culture of peripheral lymphocytes in both stimulated and non-stimulated (spontaneous) conditions with pokeweed mitogen (PWM) were studied in 30 adult patients with minimal change nephrotic syndrome (MCNS). In the nephrotic phase (11 patients), surface IgG positive B cells (sB gamma) and spontaneous cB gamma increased (P less than 0.05), whereas PWM-stimulated cIgG did not increase, and serum IgG decreased significantly (P less than 0.05). The cB gamma/sB gamma ratio calculated as an index of IgG synthesis in B cells increased spontaneously (P less than 0.05), but did not increase under PWM-stimulation. The cIgG/cB gamma ratio as an index of IgG secretion from each matured B cell, reduced in both spontaneous and stimulated conditions (P less than 0.05, P less than 0.01, respectively). In the phase of unstable remission maintained by steroid therapy (10 patients), these parameters tended to normalize and the OKT4/OKT8 ratio decreased (P less than 0.05), while the ratio remained unchanged in the nephrotic phase. However, after discontinuation of steroid (nine patients), spontaneous cB gamma and the spontaneous cB gamma/sB gamma ratio were again increased, and the cIgG/cB gamma ratio decreased (P less than 0.05) as observed in the nephrotic phase. These results suggest that B cells in patients with MCNS both in the nephrotic state and stable remission after discontinuation of steroid are activated spontaneously, but the secretory process of IgG from the matured cells is impaired, and that steroid improves these abnormalities.

Adolescent↗
PubMed1986

Inhibitory roles of the hypothalamic atrial natriuretic polypeptide on the vasopressin release in the sodium-loaded rats.

Implication of the brain atrial natriuretic polypeptide on the vasopressin release was investigated using rats fed with a high-sodium containing diet. Sodium loading increased not only the blood pressure but also the urinary output of vasopressin significantly. The plasma vasopressin concentration increased about 10 times after the intracerebroventricular injections of angiotensin II. Thereby, magnitude of the response was significantly smaller in the rat fed with a high sodium diet than in rats with the regular-diet. The hypothalamic content of both vasopressin and atrial natriuretic polypeptide was significantly larger in the high-salt group than the regular-salt. The intraventricular injections of atrial natriuretic polypeptide abolished the vasopressin release induced by the intraventricular injections of angiotensin II. These results indicate that the vasopressin production in the hypothalamus is increased, but the release is relatively suppressed in the sodium-loaded rats, and that increased hypothalamic atrial natriuretic polypeptide is involved in the suppression of the vasopressin release and in decreasing their sodium appetite to avoid the high sodium environment.

Angiotensin II↗
PubMed1986

Dopaminergic modulation of salt sensitivity in patients with essential hypertension.

The present study was designed to investigate the possible role of dopaminergic mechanisms in contributing to the pathogenesis of hypertension in salt sensitive patients. Eighteen patients with essential hypertension were studied while under a diet ranging from low salt to high salt, which enabled a classification in "salt-sensitive" (SS) and "nonsalt-sensitive" (NSS) groups based on a tentative criteria of a 10% increase of mean blood pressure with high salt diet. The SS patients showed reduced urinary excretion of sodium as compared with that from NSS patients. Urinary norepinephrine excretion in all patients with salt loading was suppressed, but urinary excretion of epinephrine showed a tendency to increase in SS patients after salt loading. Urinary excretion of dopamine increased in NSS patients with salt loading, but did not change in SS patients. To further evaluate the role of dopaminergic mechanisms in salt-sensitive hypertension, metoclopramide, a dopamine antagonist, was injected intravenously to all patients. With salt loading, plasma aldosterone levels increased after injection of metoclopramide in NSS patients, but did not change in SS patients. These results suggest that salt-sensitive hypertension is modulated by dopaminergic activity, which in turn is attenuated in SS patients. Decreased dopaminergic activity induced sodium retention both by a direct effect on the kidney as well as indirectly via relatively increased aldosterone secretion. Both mechanisms would help to increase intravascular volume and blood pressure in salt-sensitive hypertension.

Aged↗
PubMed1986

Noradrenaline modifies sympathetic preganglionic neuron spike and afterpotential.

Sympathetic preganglionic neurons were antidromically identified in the slice of the upper thoracic spinal cord of the adult cat, maintained in vitro. In normal Krebs solution, spikes evoked by intracellular stimulation had a marked 'hump' on the repolarization phase and were followed by an afterhyperpolarization of 2.8 s duration and 16.6 mV peak amplitude. Superfusion with Krebs solution containing noradrenaline 10-50 micron reversibly abolished the 'hump' of the spike and the late component of the afterhyperpolarization. In addition, it caused the appearance of a depolarizing afterpotential of 100-600 ms duration. This depolarization could result in repetitive firing of the neuron in response to a single intracellular current pulse.

Action Potentials↗
PubMed1986

Free peroneal flap coverage of the great toe defect resulting from a wrap-around flap transfer.

In thumb reconstruction, the wrap-around free flap from the great toe with distal terminal phalanx attached gives a better replica of a thumb esthetically and functionally and has many advantages. However, there are problems in the great toe, such as delayed wound healing, pain caused by long-time walking, ulceration, and skin erosion. We closed the skin defect of the great toe with a free peroneal flap in seven cases. In all cases of both the wrap-around flap and peroneal flap complete healing was obtained after the operation without trouble. The donor great toe causes no significant morbidity.

Adult↗
PubMed1986

Electrophysiological properties of sympathetic preganglionic neurons in the cat spinal cord in vitro.

Intracellular recordings were obtained from sympathetic preganglionic neurons of the intermedio-lateral nucleus of the adult cat in slices of upper thoracic spinal cord maintained in vitro. The neurons were identified by their antidromic responses to stimulation of various ipsilateral sites. Sites from which antidromic responses could be evoked were the white ramus, the ventral root, the ventral root exit zone, the white matter between the latter and the outer edge of the tip of the ventral horn, the lateral edge of the ventral horn. Resting membrane potential was --61.3 +/- 1.6 mV (mean +/- SEM), input resistance 67.5 +/- 3.7 M omega, time constant 11.5 +/- 1.2 ms. The amplitude of the action potential generated by antidromic or direct stimulation was 77.4 +/- 2.3 mV. Threshold for direct spikes was 18.2 +/- 1.8 mV. The action potential had an average duration of 3.03 +/- 0.16 ms. It showed a prominent "hump" on the falling phase. The action potential had a tetrodotoxin (TTX)-sensitive and a TTX-resistant component. The latter was abolished by cobalt. Tetraethylammonium, cesium and barium prolonged the action potential duration which acquired a plateau-shape. A prolonged after-hyperpolarization (AHP) followed the sympathetic preganglionic neuron spike. Following a single spike, AHP duration and peak amplitude were 2.8 +/- 0.3 s and 16.6 +/- 0.7 mV, respectively. The AHP was abolished by cesium or barium, but enhanced by tetraethylammonium. An AHP followed the TTX-resistant spike. EPSPs and IPSPs could be generated by focal stimulation. The EPSP triggered spikes when threshold (15.0 +/- 2.0 mV) was reached.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1986

Progressive supranuclear palsy with Lewy bodies.

An autopsy case is reported which revealed not only clinical and neuropathological features of progressive supranuclear palsy, but also the presence of large numbers of Lewy bodies in the brain stem nuclei and cerebral cortex. This case seems to be progressive supranuclear palsy with Lewy bodies distributed as in Parkinson's disease. Such case has not been previously reported.

Aged↗
PubMed1986

Paracrine regulation of mammary gland growth.

The growth and differentiation of the mammary gland is a complex process involving the interactions of various steroid and polypeptide hormones. The mammary growth occurs in a discontinued way during five distinct phases, i.e. fetal, prepubertal, postpubertal, pregnancy, and early lactation periods. The gland expresses its differentiated function by producing milk during the period of lactation. Although the mammary gland has been regarded as one of the well-known target tissues for various types of hormones, evidence has been accumulating in recent years indicating the involvement of other factors and substances in the process of mammary growth and differentiation. In this chapter the importance of the mesenchymal component in mammary epithelial cell growth has been documented. This component, including embryonic mesenchyme and adipocytes in adult tissue, play an essential role by not only serving as a structural entity of the gland but also by producing extracellular matrix substances and various factors that promote the growth, morphologic development and differentiation of mammary epithelium in a paracrine fashion. Other possible paracrine peptide factors for mammary cell growth have been isolated from several other sources including mammary tumors and milk. Thus, it is possible that paracrine growth factors play a role in mammary tumorigenesis. Since most of these factors are present in minute amounts, it is difficult to obtain pure forms of these factors in sufficient amounts for detailed physicochemical characterization. Moreover, further studies are needed to assess the physiological importance of these growth factors, their mode of action, and the mechanism of regulation relating to their production. It is conceivable that some mammary paracrine agents interact with each other or with endocrine agents in promoting the normal and neoplastic growth of mammary cells. Furthermore, the possibility exists that the production and release of paracrine factors are under the endocrine control. In view of the rapid progress and great interest in this area, these questions may be answered before long, along with the discovery of some other new growth regulating agents in this system. Clearly such information is important for understanding the complex process of normal and neoplastic growth of the mammary gland.

Animals↗