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L Takács

Publications and source records attributed to L Takács.

At least 73 records · Page 4Linked to original sources
PubMed1982

Water and sodium excretion in unilaterally denervated normal and sodium depleted anesthetized rats before and after plasma volume repletion.

The possible role of a reduction in plasma volume (PV) by surgery as well as the importance of dietary Na supply in denervation natriuresis have been investigated on Inactin-anesthetized male rats subjected to acute unilateral renal sympathectomy. Four groups were studied: I. Normal Na diet (n = 14); II. Low Na diet (boiled rice for 2 weeks) -- isotonic glucose infusion (n = 10); III. Low Na diet -- isotonic saline infusion (n = 5); IV. Normal and low Na diet rats served as conscious control (n = 10). Surgery caused a 9-11% increase in hematocrit and a 15-18% decrease in PV in groups I-III. Plasma volume repletion (PVR) reverted these changes. In group I sodium excretion from both kidneys was only a fraction of that in conscious animals kept on the same diet (group IV) and marked denervation natriuresis was observed. After PVR sodium output of innervated (I) kidneys was not different from that of conscious rats but denervated (D) kidneys excreted twice that amount. In group II Na excretion was increased compared to conscious Na depleted controls, and PVR augmented further this difference. Surprisingly, the difference in urinary sodium excretion (UNaV) between I and D kidneys was absent after surgery and was minimal after PVR in this group. In group III physiological saline infusion reverted the effect of Na depletion and denervation natriuresis was present both before and after PVR. It is concluded that PV reduction does not play a major role in denervation phenomenon. In Na depleted anesthetized rats denervation natriuresis is absent or minimal.

Anesthesia↗
PubMed1982

Renal excretion of sodium after bilateral renal sympathectomy in the anaesthetized and conscious rat.

1. The effect of bilateral renal denervation on sodium excretion was studied in conscious rats on normal, low and high sodium diet, and in rats recovering from anaesthesia, as well as in anaesthetized rats fed a normal sodium diet. 2. Sodium excretion of bilaterally denervated conscious rats on normal sodium intake and during either 2 weeks of sodium depletion or 6 days of sodium loading was not different from that of controls, despite changes in sodium supply of more than two orders of magnitude. Cortical noradrenaline concentration of control kidneys was 138 +/- 12 ng/g, but was only 7 +/- 3 ng/g (P less than 0 . 001) 6 weeks after denervation. 3. In rats recovering from anaesthesia urine flow, sodium excretion and glomerular filtration rate (G.F.R.) were not affected by denervation. 4. In anaesthetized non-diuretic rats on normal sodium diet chronic bilateral renal denervation increased urine flow and sodium excretion four and five times, respectively, with no changes in G.F.R. 5. Mean arterial blood pressure in bilaterally denervated anaesthetized rats and in those recovering from anaesthesia was decreased by 2 . 7 kPa, P less than 0 . 001 and 1 . 2 kPa, P less than 0 . 05, respectively. 6. The participation of renal nerves in the regulation of sodium excretion in conscious rats seems improbable. The denervation natriuresis in anaesthetized rats can be related to higher pre-denervation renal sympathetic nervous activity due to narcosis and surgical stress.

Anesthesia, General↗
PubMed1981

Tubular transport and urinary excretion of phosphate after renal denervation in the anesthetized rat.

Tubular transport of phosphate (Pi) was studied using clearance and tracer microinjection techniques in Inactin-anesthetized male rats subjected to left kidney denervation. Experiments were conducted in the following groups: i) acute denervation (AD); ii) chronic denervation (CD); iii) acute denervation plus thyroparathyroidectomy (AD + TPTX); iv) microinjection with AD. Besides a marked diuresis and natriuresis with no difference in GFR between innervated (inn) and denervated (den) kidneys, unilateral renal denervation resulted in an increased urinary excretion and decreased tubular reabsorption of inorganic phosphate. Maximum tubular reabsorption of Pi (TmPi) calculated per unit GFR was (means +/- SE): AD, inn: 2.38 +/- 0.04, den: 1.98 +/- 0.06 mumol/ml; CD, inn: 2.66 +/- 0.10, den: 2.19 +/- 0.11 mumol/ml; AD + TPTX, inn: 4.78 +/- 0.06, den: 4.26 +/- 0.08 mumol/ml. Thus, differences in TmPi between the two sides were of the same magnitude in the three groups. Fractional recovery of 32Pi from microinjections in control (C) and postdenervation (D) periods was: early proximal, C: 53.0 +/- 0.81, D: 61.3 +/- 1.07%; late proximal, C: 77.0 +/- 0.81, D: 70.6 +/- 0.60%; early distal, C: 93.7 +/- 0.75, D: 03.5 +/- 0.72%. It is concluded that renal sympathectomy depresses tubular transport of inorganic phosphate in anesthetized rats by a primary action on the proximal convoluted tubule and with a partial compensation in the loop of Henle.

Animals↗
PubMed1981

Effect of carotid sinus reflex on the circulation of rats bearing Guérin carcinoma.

The effect of carotid occlusion was studied on cardiac output (Evans blue dilution) and its fractional distribution (Sapirstein's isotope fractionation technique) in rats with and without Guérin carcinoma. In response to the carotid sinus hypertensive reflex (CSHR), in normal rats blood pressure and TPR were augmented; vascular resistance of the kidneys, intestines, skin and carcass was increased. In tumour bearing rats CSHR resulted in comparable increments of vascular resistance in various organs. Tumour blood flow remained unchanged, whereas vascular resistance of the tumour was considerably increased.

Animals↗
PubMed1981

Renorenal vasomotor reflex.

The acetylcholine induced contralateral renorenal vasomotor reflex has been re-examined. In dogs under pentobarbital anaesthesia blood flow of the contralateral kidney as measured by electromagnetic flow probe did not change after an infusion or bolus injection of Ach. Basal sympathetic nervous activity of the contralateral kidney increased only slightly and these changes correlated with the decrease of arterial blood pressure. In conclusion, the renorenal vasomotor reflex could not be evoked under the present experimental conditions.

Acetylcholine↗
PubMed1981

Effect of renal denervation on free flow proximal tubular potential difference in the rat.

Proximal transtubular potential difference (PD) was measured using the semi-microelectrode technique in control (C, n = 10) and unilaterally denervated (D, n = 10) rats. Acute renal sympathectomy resulted in a twofold and fourfold increase in diuresis and sodium excretion, respectively, with no change in GFR. PD (mean +/- S.E.M.) in the earliest accessible proximal convolutions (EPT) of group C was +/- 0.27 +/- 0.08 mV (n = 16), while in group D it was -0.16 +/- 0.07 mV (n = 18) (p less than 0.01). PD in mid (MPT) and late (LPT) proximal segments was unchanged by denervation (MPT: C = 0.94 +/- 0.05, n = 21; D = 0.98 +/- 0.04, n = ns. LPT: C = 1.04 +/- 0.11, n = 17; D = 0.95 +/- 0.06, n = 18 NS.). The shift to the negative of PD in EPT caused by denervation lends support to our earlier suggestion that active transport of solutes and organic substances is depressed by sympathectomy in the proximal tubule. The unaltered PD in MPT and LPT seems to indicate that passive forces promoting reabsorption in this part of the nephron are probably preserved.

Animals↗
PubMed1981

Effect of cyclophosphamide on the rat thymus.

A single large dose (200 mg/kg) of cyclophosphamide (Cy) caused thymic involution. Thymic cortex was almost depleted of lymphocytes while medullary thymocytes were not affected. This resulted in thymic inversion on day 4. During the period of involution the cortex was invaded by positive acid phosphatase granules containing macrophages. Later the cytoplasms of these macrophages were loaded with lipid droplets and residual materials. Extensive vacuolization of the cytoplasms of epithelial and special cells were revealed. Regeneration began on day 4. Repopulating cells appeared primarily in subcapsular region. Regeneration was complete by day 11 as examined by morphological technics. While FCS dependent rosette formation capacity remained below the control level even on day 16.

Animals↗
PubMed1981

Effects of cyclophosphamide on the rat's mesenteric lymph node.

A single large dose (200 mg) of cyclophosphamide (Cy) given to adult rats caused a drastic depletion of lymphocytes occurring earlier in the B dependent compartment than in the T dependent one of the lymph node cortex. The drug had a somewhat facilitating effect on the early differentiation of plasma cells (between 12 and 24 h) which later were also depleted. By Cy administration two types of macrophage were distinguished morphologically and topographically in the lymph nodes. Cy effect the endothelial cells lining the blood vessels and lymph sinuses. From day 4 to 7 Cy caused a constant flooding of red blood cells into the lymph node sinuses like in the normal rat haemolymph gland. Regeneration of the mesenteric lymph nodes occurred by a repopulation of lymphoid cells and a proliferation of other cell types. Repopulation of the B dependent compartment lagged behind that of the T dependent compartment. Regeneration of endothelial cells seemed to be one of the factors facilitating the repopulation of lymphoid cells. The distribution of T and B dependent cells in different compartments of the rat lymph node and activation of mononuclear phagocytes in Cy treated rat lymph node are discussed.

Animals↗
PubMed1980

Postocclusion hyperemia in the isolated fibrillating blood-perfused dog heart.

Reactive hyperemia following occlusions of 15, 30, 60 and 120 sec duration was studied in the left coronary vascular bed of the isolated fibrillating dog heart perfused with arterial blood at constant pressure or constant volume. Except for repayment, linear correlations were found between occlusion time and the characteristics of reactive hyperemia. At a basal perfusion pressure of 50 mm Hg the postocclusion reaction was absent. The maximum hyperemic response was observed at 100 mm Hg, while on a further increase of perfusion pressure reactive hyperemia decreased. The postocclusion reaction was more marked but of briefer duration under constant pressure perfusion. The results can be explained by the joint effects of metabolic, myogenic, and physical factors on coronary vascular tone.

Animals↗
PubMed1980

Retransfusion acidosis and ventilation.

The blood pressure of dogs anaesthetized with 0.1 g/kg of chloralose was reduced to 40 mm Hg by arterial bleeding. Thirty percent of the drawn blood refluxed spontaneously, the rest was retransfused either suddenly arterially or slowly in 15 minutes by the venous route. In other groups a total quantity of 25 ml/kg was drawn from an artery at a rate of 50 ml/kg and after about one minute the entire quantity of blood was rapidly retransfused through the artery. The control group breathed spontaneously, the other groups were given artificial respiration, or the sinus nerves and the vagus were transected separately or simultaneously, or transection was combined with artificial ventilation.

Acidosis↗
PubMed1980

Effect of phenoxybenzamine, propranolol, phenylephrine and isoproterenol on the circulation of rats bearing Guérin carcinoma.

Effects of phenoxybenzamine (1 mg per 100 g i.v.), propranolol (0.2 mg per 100 g i.v.), phenylephrine (0.1--0.3--1.0--3.0 micrograms per 100 g per min) and isoproterenol (0.01--0.03--0.1--0.3 micrograms per 100 g per min) were studied on cardiac output (Evans-blue dilution), organ and tumour blood flows (Sapirstein's isotope indicator dilution technique) in rats bearing Guérin carcinoma. In agreement with our earlier results data for haematocrit, blood pressure, TPR and organ vascular resistance were lower whereas cardiac index and organ blood flow were higher in control untreated tumour-bearing animals than in untreated normal rats. Phenoxybenzamine, depending on tumour size, decreased blood pressure, TPR and vascular resistance of organs, while it was found ineffective in rats with tumours of very large size (60--80 g). Propranolol treatment produced slight and similar effects in both normal and tumour-bearing rats. Phenylephrine enhanced peripheral resistance as a function of log dose in both normal and tumour bearing animals, nevertheless in the latter group it elicited more marked responses in the vascular bed of the kidneys, intestines and skin. The vasodilatory log dose dependent effect of isoproterenol was not present in tumour-bearing rats. In addition to the anaemia, the continuous decrease of alpha adrenergic activity in the systemic circulation parallel with tumour growth appears to be the most reasonable explanation for the "hyperkinesis" observed in tumour-bearing rats. Resistance of tumour vascular bed was increased by both phenoxybenzamine and propranolol. During the course of phenylephrine infusion (1.0 or 3.0 micrograms per min) the resistance of tumour vessels was more increased than that of other organs. Isoproterenol infusion resulted in a vasoconstriction of the tumour vessel. It appears that with maximally dilated vessels, vasoconstriction remains the only possible vascular response in Guérin carcinoma. In the vascular bed of the tumour a preponderance of beta adrenergic receptors also seems to be feasible.

Animals↗
PubMed1980

Effect of tourniquet-shock on the circulation of rats bearing Guerin carcinoma.

Blood pressure, cardiac output (Evans blue dilution) and its fractions (Sapirstein's indicator dilution technique), nutritive organ and tumour blood flow and circulatory resistance were studied under anaesthesia 1.5 hour post-release of both hind limbs constricted for 2.5 hours in rats bearing Guérin carcinoma. In tourniquet-shock the redistribution of cardiac output was essentially similar in normal and tumour bearing rats: e.g. skin and kidney fractions of cardiac output were diminished in both instances. In tumour bearing animals the circulatory resistance of tumour vasculature was more markedly enhanced than that of organ vessels, thus tumour fraction of cardiac output was decreased accordingly. It appears that the tumour might also contribute considerably to the development of a circulatory redistribution in shock.

Animals↗
PubMed1979

Regional vascular reactivity in rats with Guérin carcinoma (GC).

Increased sensitivity to phenylephrin and a decreased one to isoproterenol has been found in regional vascular beds of GC implanted rats. Circulatory sympathetic reflex adaptation, alfa- and beta-adrenergic stimulation or blockade provoked a uniform response pattern: i.e. increase in vascular resistance of GC.

Animals↗