The effect of arachidonic acid on junctional conductance in isolated murine hepatocytes

Arachidonic acid (AA) is known to inhibit intercellular conductance in normal and tumour cells. We showed that junctional conductance (Gj) in isolated murine hepatocytes was relatively tolerant to the uncoupling effect of AA. Extracellular application of 100 microM AA decreased Gj in less than 50% of hepatocytes, and the effect was much slower in other cells (10-15 min vs. 2-5 min, respectively). The uncoupling effect of AA did not depend on the intracellular [Ca2+] within the pCa(i) range 7.7-9.0. Similar results were obtained using the pipette-filling solutions with low (1 mM) and high (10 mM) concentrations of a Ca-chelating agent (EGTA). To verify whether the resistance of the hepatocyte Gj to AA may result from the "wash-out" of the intracellular intermediates during the intracellular dialysis, Gj was measured 10-45 min after the preincubation of hepatocytes with AA. After such a treatment, in 62% of cell pairs the Gj values recorded did not differ from the control. Extracellular or intracellular acidification (pHo 6.0 or pHi 5.0-6.0) did not markedly affect the AA action. However, in some cases AA induced the recovery of Gj blocked after intracellular acidification, the phenomenon suggesting the activation of the H+ transport in the presence of AA. Possible mechanisms of the observed resistance of junctional conductance of mouse hepatocytes in primary culture are discussed.

Quantitative evaluation of the kinetics of lipid probe redistribution between fusing cells

Redistribution of a fluorescent lipid probe in a cell-fusion system was analyzed by solving numerically the time-dependent diffusion equations on two spheres connected by a cylindrical pore. The half-times of the process were calculated for different values of the diffusion coefficient Dp for a lipid probe in the pore. It was shown that the kinetics of the redistribution was relatively insensitive to the length and radius of the pore, whereas Dp significantly affected the redistribution rate constant. Based on the results of the numerical analysis, the minimal lag time between the start of the process and the appearance of experimentally measurable quantities of the probe in the acceptor cell was roughly estimated.

Redistribution of lipid probes at early stages of bilayer lipid membrane fusion

Redistribution of hydrophobic probes (R18 and dipicrylamine DPA-) through a water gap between two bilayer lipid membranes (BLM) was studied. Both probes are widely used for monitoring lipid redistribution in different cell systems. The donor membrane loaded with the probe was brought into a close contact with the acceptor membrane, and the redistribution of the probe, was recorded as changes in the permittance of the acceptor membrane. It was shown that DPA- easily penetrated the water gap, whereas R18 was not detected in the acceptor membrane 30 min after the close contact formation. After fusion, R18 rapidly spread into the acceptor membrane; hence, only R18 reflects the behaviour of membrane lipids in the fusion process.

[Dynamics of ultrastructural changes in guinea pig cardiomyocytes in experimental diphtheria intoxication]

Electron microscopy of the left and right ventricles from guinea pigs was made 24, 72, and 120 hours after they were administered diphtheria toxin, 0.3 DLM/kg. The important pathogenetic mechanism responsible for dysfunction of the "diphtheritic heart" was found to be left and right ventricular cardiomyocytic lesion discordance developing in the mid-process, by causing serious intracardiac hemodynamic disorders. The lysosomal system influencing the ultrastructure of the two ventricles may exist in the heart. In diphtheritic intoxication, cardiomyocytic lysosomes exert mainly a damaging effect on their ultrastructure.

[Myocardial capillary changes and formation of the "wear complex of the hypertrophic heart]

The myocardial capillary network was experimentally studied in aortic coarctation and decoarctation. Two factors were found to play an important role in the development of the wear complex of the hypertrophic heart. These included 1) failure of the myocardial capillary proliferation rate to keep up with increases in cardiac mass and 2) lag of mitochondrial hyperplasia and myofibrillar hypertrophy.

[Changes in myocardial ultrastructure in diphtheria intoxication]

A drastic discoordination in the left and right ventricular ultrastructures was observed 72 hours after diphtheria toxin given to rabbits with experimental diphtheria intoxication. This may cause cardiac death in diphtheria intoxication.

[The right heart ventricle during hemodynamic overload of the left ventricle]

Two types of hemodynamic overload were simulated in rabbits: renovascular arterial hypertension by the Goldblatt method and the half coarctation of the ascending aorta versus the baseline diameter. The functional indices and ultrastructure of the left and right ventricles were studied in different periods of these processes. If the left ventricle is hemodynamically overloaded, the right one immediately takes part in the process and then largely governs the performance dynamics of the whole heart.

[Defining the concept "cardiac insufficiency"]

The paper analyzes various definitions of the concept "heart failure" and shows disadvantages of these definitions. Based on the analysis of the time course of myocardial functional and structural changes during various pathological processes, heart failure is defined as a condition characterized by lower cardiac reserve potentialities. A process of cardiac desynchronization is analyzed as a predisposition to heart failure.

[Dynamics of the interrelationships of functional and morphologic parameters of the left and right ventricle in coarctation and decoarctation of the ascending aorta]

The contractile and ultrastructural parameters of the left and right ventricles were studied in rabbits 3 weeks after ascending aortic coarctation by a third of the baseline diameter. In other rabbits, the same parameters were studied 1, 2, 3, and 4 weeks after recovery of the normal aortic lumen following three weeks of its narrowing. It was found that a rapid recovery of the parameters under study did not occur after decoarctation despite the fact that left ventricular overload was abolished. A fortnight after decoarctation there was a profound increase in the contractility of the two ventricles and three weeks there was a significant enhancement of cardiomyocytic mitochondrial function.

[The interventricular functional-morphological correlations in chronic overloading of the primarily intact left heart in a model of experimental vasorenal hypertension]

This investigation shows the work of the heart as an integral functional system where each of the ventricles plays its own vital role, especially in the case where only one ventricle is pathologically affected. Moreover, the changes in the right heart have been carefully studied, thus showing its immediate involvement in cases of left heart hemodynamical overloading. The experiment was carried out on 178 mature rabbits with a model of vasorenal arterial hypertension based upon coarctation of the abdominal aorta just above the renal arteries. Arterial and intraventricular parameters of blood pressure were registered and morphological investigation involved transmission electron microscopy of the left and right ventricular myocardia, especially paying attention to mitochondrial changes in the cardiomyocytes. The right ventricle reacts at the same time as the left ventricle, although it shows a more intensive function and reaches decompensation earlier than the left heart.

[An assessment of the differences in the reaction of the left and right heart ventricles to a long-term rise in systemic arterial pressure in experimental renoprival arterial hypertension in rabbits]

Different parameters of the function of the left and right heart ventricles were investigated in rabbits with renoprival arterial hypertension during a period of 52 weeks from the moment of modelling the process. As a result, this process was divided into 3 stages: 1. The establishment of compensation (1-4 weeks); 2. Compensation (6-10 weeks); 3. Decompensation (22-52 weeks). In mathematical prognosis of the time-course changes in the parameters associated with different stages of the process, the prognostic data were shown to be close to the experimental ones during prognosis for the left ventricle in the second stage, and for the right ventricle in the first stage. While prognosing for the left ventricle in the first stage and for the right ventricle in the second stage, the data obtained were significantly different from the experimental ones. These results suggest a conclusion that the right ventricle adapts itself to cardiac overload quicker than the left ventricle, but it also gets "worn out" quicker than the latter due to the conditions of "rigid" functioning in the second stage of the process when the adaptive potentials of the heart are limited.

[Effect of verapamil on arterial pressure and various parameters of heart contractile function in rabbits with prerenal artery hypertension when administered at various times of day]

The dynamics of arterial blood pressure and some data of cardiac contractility in rabbits with vasorenal hypertension were investigated in 4 seasons of the year. Simultaneously, the effects of verapamil on the said data were studied in rabbits with vasorenal hypertension (verapamil was administered at 12 and 18 h during last 2 weeks of experiment). In different seasons the definite differences in therapeutic effect of verapamil depending on the time of its administration were revealed.

[Relationship between left and right ventricular function in experimental acute focal ischemia]

Experiments were conducted on rats to record the parameters characterizing the real and maximally accessible function of the left and right ventricles in acute focal ischemia of the myocardium of these parts 5, 20, 40, and 60 minutes after ligation of the corresponding coronary artery. It was established that disorders of synchronism in heart activity are greater in injury to the right than in those to the left ventricle.

[Seasonal changes in blood pressure and certain indicators of cardiac contractile function in intact rabbits]

Some data of intact rabbits' cardiovascular system (arterial blood pressure, data of real and maximum function of heart ventricles) were investigated in different seasons of the year. It was revealed, that in winter the cardiovascular system functions with definite degree of overstrain, and in summer these data are on the lower level of the norm. Correlative analysis showed that in summer the degree of synchronization of the function of cardiovascular system drops and this can open wide possibilities for it's adaptation to variable conditions.

[Effect of altitude hypoxia on ultrastructure of the left ventricle of rabbit heart and the response of the myocardium to acute verapamil administration at different altitudes]

It was shown in experiments on intact male rabbits that moderate-altitude hypoxia causes over-stress of the cardiomyocyte energy-producing apparatus in unadapted animals. Acute infusion of verapamil leads to a high mortality rate among these animals, whereas among aborigines of moderate and low altitudes as well as among animals living in the planes mortality in acute verapamil infusion does not exceed 30%.

[Activity of lysosomal enzymes in cardiomyocytes, hepatocytes and blood in experimental diphtheritic intoxication]

Non-sedimentable activity of N-acetyl-beta-D-galactosaminidase and beta-D-glucuronidase was studied in left and right ventricles of myocardium, in liver tissue and blood plasma of rabbits with experimental diphtheritic intoxication. Specific dynamics of the enzymatic activity was found during the diphtheritic intoxication, indicating that various mechanisms were involved in regulation of lysosomal membranes permeability under conditions of the disease.

[Spectrophotometric study of the physico-chemical properties of lysosomes isolated from rat liver]

Physico-chemical properties of intact lysosomes isolated from rat liver tissue were studied using spectrophotometric methods. The lysosomal suspension did not show specific maximal peaks in spectra of light passing through, scattering and absorbance. Stability of the suspension was most suitably evaluated at 520 nm. The rate of lysosomes lysis was distinctly increased at temperature above 37 degrees at pH below 3.0 and above 7.0 as well as in osmotic pressure (pi) exceeding 0.75 MPa. The temperature of phase conversion at 12.5 degrees and 38.5 degrees was calculated from Arrhenius plot. Activating energy of the lysosomes thermolysis was equal to 50, 2 and 18 kcal/mol for solid, mixed and liquid phases of lysosomal membranes, respectively. Additional incubation of the initial lysosomal suspension at 0-4 degrees within 24 hrs led to an increase in osmosis- and acid-stability within all the ranges of pi and pH values studies as well as to decrease of its sensitivity to hypothermia (10-30 degrees) but not to hyperthermia (above 37 degrees). Cadaverine at final concentration 1.0 and 0.1 mM protected lysosomes from thermolysis. Osmotic-resistance, acid-stability and thermotolerance may be used as available dynamic parameters of the particles structure state as well as in evaluation of deteriorating effects of various physicochemical factors in vivo and in vitro.

[The characteristics of thermal action on the stability of liver lysosomes in rats]

The direct effect of temperature on the structural integrity of lysosomes was studied. Destruction of these particles was minimum in hypothermia but increased sharply in hyperthermia. A studied concentrated lysosome fraction proved to be heterogeneous in thermoresistance. The lysosome membranes started melting at 12.5 degrees C and melted completely at 38.5 degrees C. The results of the study show that the surrounding temperature may produce a direct damaging effect on the lysosomes, and support the assumption that the lysosomes play an important role as one of the key factors of the molecular mechanisms of the formation of a pathological condition in generalized hypo- and hyperthermia.