Biomedical subjects

K László

Publications and source records attributed to K László.

At least 19 recordsLinked to original sources

PubMed2005

Chromatographic behavior of silica-polymer composite molecularly imprinted materials.

Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based HPLC packing materials. Detailed physical and chromatographic characterization of such a silica-MIP composite material is presented. The chromatographic peak shape obtained with the uniformly sized spherical silica-MIP composite is mainly determined by the nonlinear adsorption isotherm. Comparison of the composite with the conventional sieved and grinded bulk MIP is therefore based on the nonlinear isotherm and not on retention factors and plate numbers.

Chromatography, High Pressure Liquid↗

PubMed1999

Effects of synthetic pyrethroids and methidation on activities of some digestive enzymes in carp (Cyprinus carpio L.).

The effects of pyrethroid pesticides (deltamethrin, permethrin and cypermethrin) and an organophosphate ester (methidation) on the activities of carp trypsin, alpha-chymotrypsin, carboxypeptidase A and lipase were studied. The enzymes were isolated from the gastrointestinal tract and the effects of the pesticides were investigated during incubation for 5 min. The activity of trypsin was influenced only slightly by the presence of deltamethrin and methidation, whereas permethrin and cypermethrin caused significant inhibition. The pyrethroid pesticides at lower concentrations resulted in a slight activation of alpha-chymotrypsin. Methidation inhibited the alpha-chymotrypsin activity by about 20%. These pesticides modified the lipase activity to a lesser extent; the highest inhibition was measured with cypermethrin. The carboxypeptidase A activity was inhibited by both pyrethroid pesticides and methidation. The results suggest that these pesticides might interact with the active conformation of the studied hydrolytic enzymes, resulting in changes in their activities.

Animals↗

PubMed1996

[The first heart suturing was performed in 1896, not 1897].

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Animals↗

PubMed1985

Effect of imidazole and indomethacin on hemodynamics of the obstructed canine kidney.

In the anesthetized dog renal blood flow (RBF) and its intrarenal distribution were investigated by the radioactive microsphere technique 24 hr after bilateral (BUL) and unilateral (UUL) ureteral ligation. In the control series indomethacin (IM) led to a decrease in RBF with outward shifting of zonal perfusions; imidazole (IA) did not cause significant changes in renal hemodynamics. In the BUL series there was a sharp drop in RBF with a proportional decrease in outer (OC) and inner (IC) cortical perfusion; IM treatment resulted in a further decrease in overall and zonal perfusions. IA, a selective inhibitor of thromboxane synthetase, relieved IC vasoconstriction. In the ligated kidney of the UUL preparations decrease in RBF was due to OC vasoconstriction, while IC perfusion equalled controls. IM led to an overall vasoconstriction in all cortical layers; IA did not influence either total RBF or its distribution. It was concluded that BUL "unmasked" TXA2 production in the IC layers, while IM treatment, by inhibiting the production of PGE2, PGI2, and TXA2, resulted in an overall vasoconstriction both in controls and the BUL and UUL preparations.

Animals↗

PubMed1985

Renal haemodynamics in chronic unilateral ureteral obstruction in the dog.

Renal blood flow and its intrarenal distribution have been investigated after 7 and 14 days of unilateral ureteral ligation (UUL) in both the ligated and the undisturbed kidney by the radioactive microsphere technique without opening the abdomen and the obstructed ureter. It has been found that renal blood flow (RBF) decreased to about 26% after 7 days and to about 10% after 14 days of normal controls in the obstructed kidney. There was a pronounced inward shifting of the much reduced RBF. The slight increase in RBF of the undisturbed kidney was not significant and did not compensate the pronounced decrease of RBF in the obstructed one.

Animals↗

PubMed1981

Reliability of the measurement of intrarenal haemodynamics in the dog, as determined by the radioactive microsphere technique.

In the anaesthetized dog total renal blood flow (RBF) and its intrarenal distribution were investigated by the radioactive microsphere technique under control conditions and after various experimental interventions. (i) In five control series performed within the last four years, there was a small but significant scatter in total RBF, due entirely to changes in inner cortical (IC) perfusion, while outer cortical (OC) perfusion proved to be constant. (ii) Repeated measurements in the same dog, performed after 1 h interval revealed constancy of total RBF with some inward shifting in cortical perfusion. (iii) Surgical intervention or manipulation of the kidney did not alter total RBF but led to an increase in IC, compensated by a decrease in OC perfusion (iv) The possible role of local intrarenal hormones (angiotensin and prostaglandin) in the above changes is discussed.

Animals↗

PubMed1980

Prostaglandin-dependent changes in renal haemodynamics and excretory patterns before and after release of 24 hours bilateral ureteral ligation.

In the anesthetized dog during and 1 hr after release of 24 h bilateral ureteral ligation (BUL) renal blood flow (RBF) decreased to 44 and 51%, respectively, as compared with normal controls. After release there was a marked increase in sodium and water excretion, so-called postobstructive diuresis (POD), in spite of a considerably reduced glomerular filtration rate (GFR). Radioactive microspheres revealed a proportionate decrease of perfusion in all cortical layers before, and inward shifting after release of the ligature. Inhibition of intrarenal prostaglandin (PF) synthesis by indomethacin (IM) before release of BUL led to a further pronounced decrease in RBF both in the pre- and postrelease phases, characterized by a proportionate decrease of perfusion in all cortical layers. Fractional excretion of sodium and water remained moderately increased in spite of a very pronounced hypofiltration. It is assumed that, in contrast to PG-dependent changes in renal haemodynamics due to BUL, enhanced sodium and water excretion (POD) are due to a PG-independent mechanism, most probably to some natriuretic substance produced and/or accumulated during 24 h complete retention.

Animals↗

PubMed1979

Intrarenal haemodynamics in postobstructive diuresis in the dog.

Intrarenal haemodynamics were investigated in the dog prior to and after relief of 24 hr bilateral ureteral ligation (BUL), by the radioactive microsphere technique. Prior to release of 24 hr BUL there was an about 50% reduction in total blood flow (RBR), with a nearly proprotional decrease in the perfusion of the four cortical layers. Following release of the obstruction, total renal and outer cortical (zones 1 and 2) blood flow remained diminished, while perfusion of the inner (juxtamedullary) layers (zones 3 and 4) increased as compared to its prerelease values and equalled controls. Glomerular filtration rate (GFR) amounted to about 27% of controls in the postrelease phase. A marked increase in absolute and fractional sodium water excretion was observed after release of 24 hr BUL, as contrasted to normal controls and dogs after 24 hr unilateral ureteral ligation (UUL). This state, designated as postopstructive diuresis, might be explained by redistribution of intrarenal blood flow towards the juxtamedullary zones, and by a powerful natriuretic substance accumulated during complete obstruction.

Animals↗

PubMed1978

Functional changes in compensatory hypertrophy of the canine kidney after uninephrectomy.

Kidney weight and renal functional parameters were investigated in dogs 7 to 68 days after uninephrectomy. Average enlargement of the remaining kidney amounted to 35.1%. Renal blood flow (RBF) and glomerular filtration rate (GFR) calculated per 100 g actual kidney weight were identical in the non-hypertrophied controls and in the hypertrophied kidneys, i.e. structural and functional changes were strictly proportional. Calculation of mean nephron parameters (MNRBF and MNGFR) revealed an increase of about 43% in the hypertrophied kidneys, with an appropriate decrease in nephronal vascular resistance. The hypertrophied kidney showed an enhanced responsiveness to mannitol; increased MNRBF under stop flow conditions was due to a pronounced dilatation of the postglomerular vessels. There was no difference between control and hypertrophied kidneys in cortical zonal blood flow, as investigated by the labelled microsphere technique. Increase in parallel-connected cortical resistances towards the inner (juxtamedullary) zones was pronounced.

Adaptation, Physiological↗

PubMed1978

Renal haemodynamics prior to and after release of 24 hr unilateral ureteral ligation in the dog.

Renal functional parameters were investigated prior to and following release of 24 hr unilateral ureteral ligation (UUL). In the obstructd kidney renal blood flow (RBF) and glomerular filtration rate (GFR) decreased to about 50% and 14%, respectively, as compared to normal controls. Relief of the obstruction did not cause any change in renal haemodynamic parameters in the ligated kidney. Urine flow rate and urine osmolality in the previously obstructed kidney were decreased, the excreted fraction of filtered sodium increased as compared to the undisturbed kidney. The excretory lesion of the obstructed kidney is due to arteriolar, presumably preglomerular, vasoconstriction. Radioactive microspheres revealed that the decrease of RBF in the obstructed kidney was caused by diminished perfusion of the outer cortical zones, while blood flow to the inner cortical zones was unaltered. Fractional flow to the outer cortex was decreased, that to the inner cortex increased as compared with normal controls. In the undisturbed kidney there was a shifting of flow from the outer towards the inner cortex, while total blood flow remained unaltered.

Animals↗

PubMed1978

Pathomechanism of postischaemic renal failure in the dog induced by temporary occlusion of the renal artery.

Intrarenal haemodynamics were investigated in previously uninephrectomized dogs, immediately after release and on the third day following two hours clamping of the renal artery. Postischaemic renal failure (PIRF) was considered moderate or severe, if three days after clamping plasma NPN values were under or over 150 mg/dl, respectively. Renal blood flow (RBF) as determined by measuring the renal venous effluent and by radioactive microspheres did not differ significantly from controls either immediately after release, or three days following arterial occlusion. Glomerular filtration rate (GFR) was, however, severely depressed in all postischaemic kidneys. An increase in preglomerular and a decrease in postglomerular resistance was assumed, resulting in unaltered total vascular resistance and a sharp drop in glomerular capillary pressure. Radioactive microspheres revealed a shifting of intrarenal blood flow from the superficial cortex towards the deeper (juxtamedullary) cortical layers. Fractional flow to the outer cortex was decreased, that to the inner cortex increased, as compared with uninephrectomized controls.

Acute Kidney Injury↗

PubMed1977