Biomedical subjects

Gabor Szabo

Publications and source records attributed to Gabor Szabo.

22 records · Page 2Linked to original sources

PubMed2002

Brain death impairs coronary endothelial function.

BACKGROUND: To characterize the impact of brain death (BD) on endothelial dysfunction after cardiac transplantation we investigated coronary circulation and vasomotor function in a canine model. METHODS: Left ventricular pressure-volume data (conductance catheter) and coronary blood flow (CBF) were monitored continuously. Endothelium-dependent vasodilatation after acetylcholine and endothelium-independent vasodilation after sodium nitroprusside were assessed before and 3 hr after BD induction (inflation of a subdural balloon). RESULTS: BD led to an initial hyperdynamic reaction with significant (P<0.05) increase of CBF. After 3 hr, CBF decreased significantly (P<0.05). Although before BD, application of acetylcholine led to a monophasic vasodilatative response, after BD a short mild vasodilatation was followed by a longer vasoconstriction. Endothelium-independent vasodilatation remained unchanged. CONCLUSIONS: BD affects coronary circulation by two means: (1) impairment of CBF to decrease in parallel in afterload with consecutive hemodynamic deterioration and (2) severe endothelial dysfunction that may be a contributing factor to posttransplant outcome.

Acetylcholine↗

PubMed2002

NO donors potentiate the beta-adrenergic stimulation of I(Ca,L) and the muscarinic activation of I(K,ACh) in rat cardiac myocytes.

The effects of nitric oxide (NO) donors on the L-type Ca(2+) current (I(Ca,L)) and the muscarinic activated K(+) current (I(K,ACh)) were studied in isolated rat cardiac myocytes. The nitrosothiol S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1 pM-1 microM) strongly potentiated the stimulation of the I(Ca,L) elicited by subthreshold concentrations of isoprenaline (Iso, 0.1-0.5 nM) in ventricular myocytes. The effect of SNAP was mimicked by 2-(N,N-diethylamino)-diazenolate-2-oxide (DEANO, 1 pM-1 nM), a NONOate that spontaneously releases NO in a pH-controlled manner, and was blunted by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (100 microM), a NO trap. 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxaline-1-one (10 microM), a guanylyl cyclase inhibitor, did not alter the effect of SNAP. SNAP (1 pM-1 microM) did not modify the effect of L858051 (0.1-0.3 microM), a forskolin analogue that activates adenylyl cyclase, on I(Ca,L) and did not enhance the basal I(Ca,L) in the presence of rolipram (1 microM), a phosphodiesterase type 4 inhibitor. Superfusion with Rp-CPT-cAMPS (500 microM), or internal dialysis with cAMP-dependent protein kinase (cA-PK) inhibitory peptide (PKI; 20 microM), inhibitors of the cA-PK, blunted the effect of SNAP (1 nM and 1 microM) on the Iso-stimulated (1-100 pM) I(Ca,L). SNAP (1 nM and 1 microM) potentiated the threshold stimulation of I(Ca,L) elicited by internal GTP-gammaS (10 microM), a non-hydrolysable analogue of GTP. SNAP (1 pM-1 microM) and DEANO (1 microM) potentiated the stimulation of I(K,ACh) elicited by low concentrations of ACh (1-2 nM) in rat atrial myocytes. The threshold stimulation of I(K,ACh) elicited by internal 5'-guanylylimidodiphosphate (10 microM) was also potentiated by NO donors. SNAP (1 microM) did not modify I(K,ACh) reconstituted in human embryonic kidney 293 cells, in the absence or in the presence of ACh (1 or 10 nM). Taken together, these data suggest that NO is a cGMP-independent modulator of G-protein-coupled muscarinic and beta-adrenergic receptor actions on cardiac ion channels. Although this action of NO seemed to occur at the level of G proteins, it appeared to require a component distinct from receptors, G proteins or their effectors.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2002

Near-infrared diode laser based spectroscopic detection of ammonia: a comparative study of photoacoustic and direct optical absorption methods.

A photoacoustic spectroscopic (PAS) and a direct optical absorption spectroscopic (OAS) gas sensor, both using continuous-wave room-temperature diode lasers operating at 1531.8 nm, were compared on the basis of ammonia detection. Excellent linear correlation between the detector signals of the two systems was found. Although the physical properties and the mode of operation of both sensors were significantly different, their performances were found to be remarkably similar, with a sub-ppm level minimum detectable concentration of ammonia and a fast response time in the range of a few minutes.

Acoustics↗

PubMed2002

A variable valve area, lumped parameter model of left ventricular filling.

A variable valve lumped parameter model was developed and validated in porcine trials. The model was used to simulate ventricular and atrial pressures and flows during diastolic filling. The variable valve area model simulations provide reasonable results and take into account other considerations like venous inflow and initial valve aperture. Comparisons between model outputs and in-vivo porcine experiments suggest that the model may be used in the future to assess compliance and effective orifice area based on parameters derived from non-invasive Doppler waveforms.

Animals↗