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Endothelin (ET), originally characterized as a vasoconstrictive peptide, has been found to have many different biological functions, including acting as a local hormonal regulator of pressure, fluid, ions and neurotransmitters in the inner ear. The objective of this study was to examine and quantify the mRNA expression of the endothelin type A and B receptors (ETAR and ETBR) in the strial vascularies (StV) and non-strial tissues (NSt) of the cochlear lateral wall using the real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique. The mouse tissue samples were harvested and RNA was extracted. RT was performed to obtain cDNA, and then the mRNA expression of each gene was measured via real-time PCR. We found that both receptor subtypes were expressed in the cochlear lateral wall, with a predominance of ETAR over ETBR. We showed that the mRNA expression of the two receptor subtypes was higher in the StV with a 1.8 times higher level of ETAR and an 8.1 times higher level of ETBR mRNAs than in the adjacent NSt of the lateral wall tissue. This study shows the existence and the quantity of ET receptor subtypes in the StV and NSt of the mouse cochlea. Our results suggest that an endothelin-mediated response via two different receptors, ETAR and ETBR, may play an important role in the physiological functions of the cochlear lateral wall by maintaining the homeostatic environment of the cochlea.
Severe acute pancreatitis (SAP) is a common disease with a poor prognosis. Heart failure is one cause of SAP patient death. Intermedin (IMD) is a potent endogenous cardio-protective substance. Administration of exogenous IMD showed beneficial effects in cardiovascular diseases. The aim of this study was to investigate the myocardial damage in SAP and to determine the therapeutic potential of IMD for SAP. Using an SAP rat model, we examined endogenous IMD expression following SAP induction, and determined the effect of IMD on myocardial function, histological morphology, apoptosis-related gene expression, and prognosis. Our results indicated that the cardiac function and histological structure were significantly disrupted in SAP rats. Infusion of exogenous IMD significantly preserved cardiac function and ameliorated myocardial damage. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) revealed that myocardial apoptosis was extensively present in SAP rats, and IMD infusion led to increased expression of the prosurvival factor Bcl-2, but decreased pro-apoptotic factors Bax and caspase-3. In addition, IMD infusion also reversed the change of IMD receptor systems in SAP rat heart tissue. Furthermore, we found that IMD infusion greatly decreased mortality of SAP rats. In conclusion, administration of SAP produced therapeutic effects in SAP through modulating apoptotic and pro-survival gene expression, inhibiting myocardial apoptosis, preserving cardiac function, and a useful therapeutic agent for SAP, and provides us an insight for a clinical trial of IMD for treating human severe acute pancreatitis.
High aldosterone (Ald) levels can induce hypertrophy of vascular smooth muscle cells (VSMCs), which carries high risks of heart failure. A previous study showed that Ald induces hypertrophy of VSMCs by up-regulating NOX1, a catalytic subunit of NADPH oxidase that produces superoxides. However, the precise mechanism remains unknown. Diphenylene iodonium (DPI) is known as an inhibitor of complex I in the mitochondrial respiratory chain, and it was also found to almost completely suppress the induction of NOX1 mRNA and the phosphorylation of activating transcription factor (ATF-1) by PGF2α or PDGF in a rat VSMC cell line. In this study, we found that the Ald-induced phosphorylation of ATF-1 and NOX1 expression was significantly suppressed by DPI. Silencing of ATF-1 gene expression attenuated the induction of NOX1 mRNA expression, and over-expression of ATF-1 restored Ald-induced NOX1 expression. On the basis of this data, we show that the mitochondria mediate aldosterone-induced NOX1 gene expression in an ATF-1-dependent manner.
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