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Biomedical subjects

L Takács

Publications and source records attributed to L Takács.

At least 55 records · Page 3Linked to original sources
PubMed1985

Heterogeneity of chicken photoreceptors as defined by hybridoma supernatants. An immunocytochemical study.

Immune cells producing antibodies to chicken photoreceptor membranes were fused with myeloma cells and supernatants of the resulting hybridoma cells were used to test various types of photoreceptor cells in the chicken retina by means of immunocytochemistry. A polyclonal antibody raised against the protein component of bovine rhodopsin was also used. Outer segments of various photoreceptor cells were labelled by the following antibodies: rods were positive with the anti-rhodopsin antibody, both members of the double cones were stained by supernatant A1, while one type of single cones (designated as type A) was specifically labelled by supernatants A5, B3 and D6. The other type of single cones (type B) reacted with anti-rhodopsin and supernatant A1. The results indicate that there are distinct differences in the molecular structure of various photoreceptor outer segments.

Animals↗
PubMed1985

Proximal tubular transport and urinary excretion of sodium after renal denervation in sodium depleted rats.

The effect of unilateral renal denervation on renal handling of water, sodium and potassium was studied with clearance and micropuncture techniques in sodium depleted anaesthetized rats in the nondiuretic state. In clearance experiments renal denervation resulted in a +140 and +320% increase in urine flow and potassium excretion, but sodium excretion of innervated (I) and denervated (D) kidneys was similar (I: 12.0 +/- 2.0, D: 14.0 +/- 3.6 nM . min-1 . g-1; NS). However, upon the loop diuretic furosemide (1 mg . kg-1), a marked denervation natriuresis was observed (I: 2.8 +/- 0.9, D: 5.9 +/- 1.0 microM . min-1; P less than 0.05) and denervation diuresis and kaliuresis persisted, too (+95 and +60%, respectively). Micropuncture results revealed that fractional reabsorption of filtrate to late proximal puncture site was depressed by renal denervation from 62 to 49% while no change in time control rats was seen (64 +/- 2 vs. 64 +/- 1%; NS). In micropuncture experiments besides augmented urine flow (+82%) from D kidneys also a small denervation natriuresis was present (I: 21.6 +/- 6.4, D: 29.2 +/- 7.0 nM . min-1; P less than 0.05). It is concluded that the lack or marked attenuation of denervation natriuresis in sodium depleted rats were the result of an almost complete compensatory distal reabsorption of the excess sodium (but not of water and potassium) leaving the proximal tubule after denervation. The distal adaptive response can be overcome by furosemide.

Animals↗
PubMed1985

Water and electrolyte transport in Henle's loop and distal tubule after renal sympathectomy in the rat.

The effect of acute renal denervation (AD) on transtubular movement of water and electrolytes in Henle's loop (LH) and distal tubule (DT) of superficial nephrons was studied by the technique of in vivo microperfusion in Inactin-anesthetized hydropenic male rats. In time-control experiments (n = 6) no changes in either whole kidney or single nephron function were detected. Predenervation results of denervation experiments (n = 10) were similar to those of the time-control series. AD resulted in increased urine, sodium, and potassium excretion in the absence of changes of either arterial blood pressure or GFR. Compared with predenervation data, AD led to significant decreases in net transtubular fluxes (J) of water and sodium in both perfused segments with delivery kept constant (delta JNa: LH = 144 +/- 26 peq X min-1, 9.1 +/- 0.3%; DT = 94 +/- 11 peq X min-1, 22.3 +/- 1.1%). Potassium absorption in the loop decreased but an increase in net addition (secretion) of K in the distal tubule on denervation occurred (delta JK = 8.7 +/- 1.9 peq X min-1, 68.7 +/- 3.2%). Use of the reperfusion technique gave similar results. These results indicate that efferent renal sympathetic nerve activity directly influences water, sodium, and potassium transport in the loop of Henle and distal tubule of the anesthetized rat.

Animals↗
PubMed1985

Fasting induces denervation natriuresis in the conscious rat.

The participation of renal nerves in the regulation of sodium excretion was studied in fed and overnight-fasted rats subjected to acute or chronic left kidney denervation or sham operation. Clearance experiments were performed on conscious restrained animals. Urine flow, glomerular filtration rate (GFR), and urinary sodium excretion were not different in left and right kidneys of sham-operated rats. In fed conscious rats, urine flow, GFR, and urinary sodium excretion of innervated (I) and denervated (D) kidneys were similar. In fasted conscious rats, significant denervation natriuresis was observed after both acute (I, 1.06 +/- 0.27; D, 1.56 +/- 0.40 mumol . min-1 . g-1, P less than 0.05) and chronic (I, 1.55 +/- 0.19; D, 2.20 +/- 0.18 mumol . min-1 . g-1, P less than 0.01) renal sympathectomy, whereas urine flow and GFR in I and D kidneys were not different. Additional experiments revealed that extracellular fluid and plasma volumes of fasted rats were decreased by approximately 10% compared with those of fed animals due to a significant overnight natriuresis and negative water balance. In fed conscious rats, the renal nerves do not seem to participate in the regulation of sodium excretion. The presence of denervation natriuresis in conscious fasted rats suggests that renal nerves are involved in sodium conservation during fasting to maintain extracellular fluid and plasma volume.

Animals↗
PubMed1985

Time course of denervation diuresis and natriuresis in the anaesthetized rat.

The effect of unilateral renal sympathectomy on renal excretion of water and sodium was studied in three groups of Inactin-anaesthetized rats: 1-3, 4-19, and 20-35 weeks after denervation. Increased sodium excretion from the denervated kidney in the absence of changes in GFR was observed up to 35 weeks following renal denervation. Thus, in a functional sense, renal reinnervation may have only been partial during the time interval studied.

Anesthesia↗
PubMed1985

Expression of MHC class II antigens on bile duct epithelium in experimental graft versus host disease.

Recently we observed the expression of MHC class II antigens on bile duct epithelium in human liver transplantation rejection. In this report we present evidence for the expression of MHC class II antigens on bile duct epithelium in experimental GVHD. These findings support the idea, that the target tissue elements in liver transplantation rejection and GVHD are the bile ducts, on the other hand this is a new experimental model for the analysis of MHC class II antigen expression on epithelial tissue.

Animals↗
PubMed1985

Effect of Yoshida ascites tumour on the circulation in rats.

The circulation in anaesthetized rats with Yoshida ascites tumour was studied. Cardiac output was determined according to the reference flow method, while the distribution of cardiac output by labelled microspheres 15 mu in diameter. Arterial blood pressure decreased by 39 mm Hg and TPR by 23% at unaltered cardiac output. Blood flow of the brain and the coronaries increased by 39-43% while that of the kidney and the intestines decreased by 43 and 28%, respectively. The cardiac output fractions of the brain, the coronaries and the hepatic artery increased considerably, while that of the kidney decreased. The haematocrit decreased from 43 to 23%. It is assumed that part of the circulatory alterations (redistribution of cardiac output) were due to the anaemia and its consequences, while the others (arterial hypotension, lack of increase in cardiac output) should be regarded as an effect of a factor reaching the circulation from the cells of the ascites tumour.

Anemia↗
PubMed1984

Detection of a nerve-specific membrane protein on differentiating PCC3/A/1 cells.

Attempts were made to prepare monoclonal antibodies specifically reactive with cell surface components of a murine neuroblastoma cell line, Neuro 2a. One of the antibodies (1c2) reacts with a varying proportion of in vitro cultivated Neuro 2a cells, but does not react with murine embryonal carcinoma cell lines (PCC3/A/1 and F9) or with a murine fibroblast line (LM). This antibody selectively stains a subpopulation of nerve cells in murine adult central nervous system, e.g. granular cells in cerebellar cortex. Immunoaffinity purification of adult brain and Neuro 2a plasma membrane fractions with the antibody resulted in an electrophoretically pure protein of approx. 28 kD molecular weight as estimated by SDS-PAGE. Although this antigen is absent from PCC3/A/1 embryonal carcinoma cells, it can be demonstrated after 9 days of growth and differentiation under low density conditions by indirect immunoperoxidase staining. This monoclonal antibody may prove useful in further analysis of neural tissue development.

Animals↗
PubMed1984

(D-Met2,Pro5) enkephalinamide causes a decrease in plasma prolactin levels of lactating rats continuously suckled and an increase in those deprived of their litter.

The effect of an enkephalin analogue, (D-Met2,Pro5)enkephalinamide (EKNH2) on prolactin (PRL) secretion of lactating rats continuously suckled or separated from their pups was investigated. In rats together with their pups 0.5 mg/kg EKNH2 caused a dramatic decrease, 0.25 mg/kg a mild and short-lasting reduction in plasma PRL levels. In contrast, in lactating rats separated for 4 h from their pups 0.5 mg/kg of the drug induced a slight and 1.0 mg/kg a considerable increase in plasma PRL levels. The data indicate that in lactating rats depending on the circumstances the enkephalin analogue causes opposite effects on PRL secretion.

Animals↗
PubMed1984

Rat thymocyte subpopulations: heterogeneity of the fetal calf serum dependent rosette forming cells.

We demonstrate heterogeneity within a rat thymic cortical population, the fetal calf serum dependent rosette forming cells. Approximately half of these cells are guinea pig serum sensitive. Guinea pig serum sensitive and insensitive rosette forming cells show different distribution patterns on a continuous gradient of Percoll. They contain different amounts of TdT enzyme and regenerate with different time kinetics following sublethal irradiation. These data demonstrate new aspects of heterogeneity within the rat thymic cortical population.

Animals↗
PubMed1984

Effect of erythrocyte transfusion on the circulation of Guérin carcinoma-bearing rats.

In Guérin carcinoma-bearing rats during tumour growth cardiac output and blood flow to several organs were increased whereas TPR, vascular resistance of some regions and haematocrit gradually decreased. In response to erythrocyte transfusion the anaemia of tumour-bearing rats was considerably improved or corrected, however, the parameters for systemic and regional circulation were only partially restored. We presume that the circulatory "hyperkinesis" of tumour-bearing rats is partly due to the anaemia but also an unknown factor must be considered. The blood perfusion of the Guérin carcinoma was not affected by the erythrocyte transfusion thus it is feasible that the tumour vasculature is maximally dilated even with a normal haematocrit of the host.

Anemia↗
PubMed1983

Intratubular and peritubular capillary hydrostatic and oncotic pressures after chronic renal sympathectomy in the anaesthetized rat.

The possible role of peritubular capillary physical forces in the diuretic-natriuretic effects of chronic renal denervation was investigated in Inactin-anaesthetized nondiuretic control (C) and unilaterally denervated (D) rats. Micropuncture techniques were combined with measurement of intratubular and peritubular capillary hydrostatic pressures and afferent and efferent arteriolar plasma oncotic pressures were determined, as well. Compared to data of C rats and of innervated kidneys, marked denervation diuresis and natriuresis were seen without changes in GFR. Both late proximal and early distal (F/P)In values were significantly lower in D kidneys with similar SNGFR. Afferent (pia) and efferent (pi e) arteriolar oncotic pressures were unchanged by denervation (C-pi a = 23.3 +/- 0.79, pi e = 29.9 +/- 0.87 mm Hg; D-pi a = 23.2 +/- 0.94, pi e = 29.8 +/- 1.04 mm Hg). Proximal intratubular hydrostatic pressure was moderately but significantly higher in D kidneys (C = 11.9 +/- 0.5, D = 13.7 +/- 0.3 mm Hg, P less than 0.01), while peritubular capillary pressures were: efferent arteriole (C = 13.9 +/- 0.5, D = 13.4 +/- 0.6 mm Hg, NS). It is concluded that the tubular effects of chronic renal sympathectomy are not dependent on changes in Starling forces of the peritubular environment.

Animals↗
PubMed1983

Rapid decrease of plasma prolactin levels in lactating rats separated from their pups.

The time course of the effect of separation of the pups on plasma prolactin (PRL) of the mother and the mechanism of this effect were investigated in conscious primiparous lactating rats. Within the first 15 min the separation of the mother from her litter caused a very rapid decrease in the concentration of plasma PRL. There was already a very marked depression by the end of the first 3 min period. During the first 3 min the disappearance rate of PRL from the blood was identical to that occurring after hypophysectomy and thus similar to the biological half-life of plasma PRL in lactating rats. The observed marked decrease in PRL could be completely blocked by alpha-methyl-p-tyrosine pretreatment (250 mg kg-1 i.p.) or by haloperidol (2 mg kg-1 i.p.) at 90 min prior to the start of separation. It was demonstrated that the marked depression in plasma PRL concentration develops within the first hour and particularly in the first few minutes. Thus, the separation of lactating rats apparently results in an immediate complete blockade of PRL release from the pituitary. Finally, the data suggest that a dopaminergic mechanism plays an important role in the inhibition of PRL release induced by separation of the mother.

Animals↗