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M Toth

Publications and source records attributed to M Toth.

90 records · Page 5Linked to original sources
PubMed1979

A comparison of the effects of PGI2, PGE2 and PGH2 on the cyclic nucleotide levels in rat anterior pituitary gland in vitro.

Rat anterior pituitary explants were incubated with PGI2, PGH2 and PGE2 in the presence of theophylline (1mM) and the production of cyclic AMP was measured. PGE2 was found to be about 20 times more potent than PGI2 while PGH2 was slightly more effective than PGI2. The results suggest that PGI2 does not play a AMP was measured. PGE was found to be about 20 times more potent than physiological role in cyclic AMP mediated events in the rat anterior pituitary.

Animals↗
PubMed1979

Detergent-induced oviposition is mediated by prostaglandins.

Local administration of small volumes of dilute detergents into the avian uterus (shell gland) induced premature oviposition within a few minutes with a success rate of over 90 percent. Indomethacin and cortisol blocked the action of detergents. Exogenous prostaglandins counteracted the inhibitory effect of indomethacin. It is suggested that detergents promote endogenous prostaglandin production which in turn induces oviposition. The possible significance of these observations in mammalian parturition is discussed.

Animals↗
PubMedDate not supplied

Adrenomedullin and diabetes mellitus.

Adrenomedullin (AM) is a novel 52 amino acid peptide hormone, originally isolated from human pheochromocytoma. AM acts as a local autocrine and/or paracrine vasoactive hormone and has vasodilator and blood pressure lowering properties. AM as a vasodilative molecule protects the vascular wall but its exact role is still uncertain. AM is considered to play an important endocrine role in various tissues in maintaining electrolyte and fluid homeostasis. Its plasma concentration in healthy conditions is low. In hypertension, chronic renal failure and congestive heart failure its plasma concentration increases in a parallel manner with the severity of the disease. It is assumed that this peptide plays an important role in physiological and pathological conditions compensating the effects of vasoconstrictive molecules. Investigations have proven that in diabetic angiopathies the levels and production of vasoconstrictive factors and AM are increased, while other relaxing substances such as nitric oxide (NO) are decreased. It is still uncertain whether the increased release of AM is a compensatory mechanism or a coincidental event. Although the precise role of AM in the pathogenesis of diabetic complications is still to be elucidated, the altered concentration of AM in diabetes could indicate a certain interaction between AM induction and vascular function. Hence, the induction of vascular AM can be a new target of therapeutic approach to diabetic complications.

Adrenomedullin↗
PubMedDate not supplied

The role of induced contrast in images obtained using the environmental scanning electron microscope.

Generation of contrast in images obtained using the environmental scanning electron microscope (ESEM) is explained by interpretation of images acquired using the gaseous secondary electron detector (GSED), ion current, and the Everhart-Thornley detector. We present a previously unreported contrast component in GSED and ion current images attributed to signal induction by changes in the concentration of positive ions in the ESEM chamber during image acquisition. Changes in positive ion concentration are caused by changes in electron emission from the sample during image acquisition and by a discrepancy between the drift velocities of negative and positive charge carriers in the imaging gas. The proposed signal generation mechanism is used to explain contrast reversal in images produced using the GSED and ion current signals and accounts for discrepancies in contrast observed, under some conditions, in these types of images. Combined with existing models of signal generation in the ESEM, the proposed model provides a basis for correct interpretation of ESEM images.

Aluminum Oxide↗
PubMedDate not supplied

Systemic and regional vascular effects of atrial natriuretic peptide in a rat model of chronic heart failure.

To characterize the systemic and regional vascular effects of atrial natriuretic peptide (ANP) in chronic heart failure, central hemodynamics, regional blood flow and plasma ANP levels were determined in a rat model of myocardial infarction and failure and in sham-operated animals. Measurements were made in the conscious state before and after intravenous rANP [99-126] (8 micrograms bolus followed by continuous infusion of 1.0 microgram/kg/min). With this protocol, ANP significantly decreased cardiac output, right atrial, left ventricular end-diastolic and arterial pressures and there were increases in heart rate, systemic and intestinal vascular resistances in sham animals. Renal blood flow per gram of tissue was unchanged with ANP, but when expressed as a percentage of cardiac output, increased significantly, indicating a preferential renal vasodilatory effect of ANP. In rats with infarction and failure, this dose did not alter cardiac output or arterial pressure, but decreased right atrial and left ventricular blood flow. Although significantly reduced as compared to the control group, renal blood flow was not improved with ANP in the heart failure group. ANP plasma levels of the heart failure group were elevated at baseline (p less than 0.01), and increased 5-10 times after infusion of rANP. Thus, in rats with chronic heart failure, the renal vascular effects of ANP are blunted, which may, in part, explain the failure of ANP to restore the altered volume homeostasis in heart failure despite elevated ANP plasma levels. However, the effects on venous return were preserved which, in turn, improved cardiac performance via a reduction of preload.

Animals↗
PubMedDate not supplied

Interpretation of secondary electron images obtained using a low vacuum SEM.

Charging of insulators in a variable pressure environment was investigated in the context of secondary electron (SE) image formation. Sample charging and ionized gas molecules present in a low vacuum specimen chamber can give rise to SE image contrast. "Charge-induced" SE contrast reflects lateral variations in the charge state of a sample caused by electron irradiation during and prior to image acquisition. This contrast corresponds to SE emission current alterations produced by sub-surface charge deposited by the electron beam. "Ion-induced" contrast results from spatial inhomogeneities in the extent of SE signal inhibition caused by ions in the gaseous environment of a low vacuum scanning electron microscope (SEM). The inhomogeneities are caused by ion focusing onto regions of a sample that correspond to local minima in the magnitude of the surface potential (generated by sub-surface trapped charge), or topographic asperities. The two types of contrast exhibit characteristic dependencies on microscope operating parameters such as scan speed, beam current, gas pressure, detector bias and working distance. These dependencies, explained in terms of the behavior of the gaseous environment and sample charging, can serve as a basis for a correct interpretation of SE images obtained using a low vacuum SEM.

Journal Article↗
PubMedDate not supplied

Molecular pathways of anxiety revealed by knockout mice.

Anxiety is a normal reaction to threatening situations, and serves a physiological protective function. Pathological anxiety is characterized by a bias to interpret ambiguous situations as threatening, by avoidance of situations that are perceived to be harmful, and/or by exaggerated reactions to threat. Although much evidence indicates the involvement of the gamma-aminobutyric acid, serotonin, norepinephrine, dopamine, and neuropeptide transmitter systems in the pathophysiology of anxiety, little is known about how anxiety develops and what genetic/environmental factors underlie susceptibility to anxiety. Recently, inactivation of several genes, associated with either chemical communication between neurons or signaling within neurons, has been shown to give rise to anxiety-related behavior in knockout mice. Apart from confirming the involvement of serotonin, gamma-aminobutyric acid, and corticotrophin-releasing hormone as major mediators of anxiety and stress related behaviors, two novel groups of anxiety-relevant molecules have been revealed. The first group consists of neurotrophic-type molecules, such as interferon gamma, neural cell adhesion molecule, and midkine, which play important roles in neuronal development and cell-to-cell communication. The second group comprises regulators of intracellular signaling and gene expression, which emphasizes the importance of gene regulation in anxiety-related behaviors. Defects in these molecules are likely to contribute to the abnormal development and/or function of neuronal networks, which leads to the manifestation of anxiety disorders.

Animals↗