Biomedical subjects

Y Takata

Publications and source records attributed to Y Takata.

291 records · Page 17Linked to original sources

PubMedDate not supplied

Spontaneous fall in blood pressure and reactivity of sympathetic nervous system in hospitalized patients with essential hypertension.

We evaluated whether reduction in sympathetic reactivity plays a major role in the spontaneous falls in blood pressure (BP) experienced during hospitalization by patients with essential hypertension. In the present case BP fell on the 2nd day of hospitalization. The responses of plasma catecholamines (CA) and BP to both handgrip and tilting were not altered during either the first 24 hours or the entire 7 days of hospitalization. The effect of phentolamine on BP was similar on the 1st, 2nd and 7th days. However, the resting levels of plasma norepinephrine before handgrip, tilting and phentolamine were significantly diminished on the 7th day, but not on the 2nd day. In conclusion, the diminution of sympathetic activity may be partly responsible for the hospitalization-induced fall in BP in the late stages.

Adult↗

PubMedDate not supplied

Pressor responses to intracisternal administration of hypertonic NaCl in conscious normotensive and spontaneously hypertensive rats.

We evaluated the mechanisms of pressor responses to hypertonic NaCl solution administered intracisternally (i.c.) to conscious normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). In conscious rats of both strains, increases in mean arterial pressure (MAP) and heart rate (HR) induced by i.c. NaCl appeared immediately after the injection and MAP returned rapidly to the basal levels. In the urethane-anesthetized animals, the increases in MAP and HR occurred gradually and persisted. The early phase of the pressor actions of i.c. NaCl was considered to be mostly abolished by blockade of the sympathetic nervous system (SNS), and to be partly diminished by the vascular receptor blockade of vasopressin (AVP), in the conscious animals. The following phase of pressor responses to i.c. NaCl was not suppressed by the blockade of ganglionic transmission, alpha-adrenergic receptor, AVP or angiotensin II (AII). However, bilateral adrenalectomy practically abolished the pressor action of both early and late phases, thereby suggesting that catecholamines (CA), released from the adrenal gland, may play a major role in this pressor response to i.c. NaCl. The pressor responses to i.c. NaCl in conscious or anesthetized animals were slightly but significantly greater in SHR than in WKY. It is concluded that an early phase of increase in MAP, as induced by hypertonic NaCl administered i.c. to conscious SHR and WKY, may be attributed mainly to the increased activity of the SNS and partly to the increased release of AVP. The major part of the pressor effect of i.c. NaCl, including the late phase, may result from an enhanced secretion of CA from the adrenal gland. The present study also shows that the pressor action of i.c. NaCl in rats may be altered when the animals are anesthetized with urethane.

Anesthesia↗

PubMedDate not supplied

Insulin-like growth factor I signalling through heterodimers of insulin and insulin-like growth factor I receptors.

PURPOSE: To clarify the specific signalling pathway of IGF-I, we studied the functional role of heterodimers composed of IGF-I receptor and insulin receptor for the IGF-I signalling. METHODS: Either wild type or truncated insulin receptor lacking 365 amino acids from the carboxyl-terminus, were overexpressed in the Rat-1 fibroblasts. Heterodimers between rat IGF-I receptor and exogenous insulin receptors were identified by a human specific anti-insulin receptor monoclonal antibody after ligand affinity-labeling. IGF-I-stimulated auto-phosphorylation of the receptors, mitogenesis and AIB uptake were compared among the Rat-1 cells, Rat-1 cells overexpressing wild type insulin receptors and truncated insulin receptors. RESULTS: Thirty to sixty percent of IGF-I receptors were found to form heterodimer complex with either wild type insulin receptors or truncated insulin receptors. Although heterodimers with the truncated receptors were not autophosphorylated in response to IGF-I in vitro, in vivo autophosphorylation of IGF-I receptors occurred in these three cell lines. The dose response curves of IGF-I stimulated DNA synthesis were comparable among the three cell lines. The responsiveness to IGF-I stimulation was increased for mitogenesis in the cells with heterodimers, but was comparable in the AIB uptake study. CONCLUSIONS: These results indicated that the heterodimer receptors, even with the kinase-defective insulin receptors, retained functional activities for the IGF-I-stimulated mitogenic signaling.

Aminoisobutyric Acids↗