Reconstruction of the Rat Sciatic Nerve by Using Biodegradable and Non-Biodegradable Conduits.

The aim of the study was to compare two types of conduits made of either non-resorbable Reperen or resorbable Tissucol for their effects on the regeneration of the rat sciatic nerve under conditions of stump diastasis. MATERIALS AND METHODS: The experiments were carried out using outbred white male rats of the reproductive age (n=14). The animals were divided into three groups: group 1, intact (n=5), used for studying the morphology of the sciatic nerve; group 2 (n=4) - nerve plastic surgery was performed using a conduit made of non-resorbable Reperen; group 3 (n=5) - surgery was performed using a conduit made of resorbable Tissucol. The animals were anesthetized with isoflurane. After a complete transection of the sciatic nerve in the middle third of the thigh, its stumps were inserted into a conduit of an internal diameter of 2 mm and a length of 10 mm, filled with saline. Diastasis of 5 mm in length was created by spreading the nerve ends and securing the epineurium to the tube edges with 8/0 polypropylene sutures. A total count of myelinated nerve fibers was performed in the area of repair (tubulation) and the distal part of the nerve; the formation of connective tissue sheaths was assessed 14 weeks after the operation. RESULTS: According to the morphological assessment, both types of conduits (resorbable and non-resorbable) caused the similar number of fibers to restore in the distal part of the repaired nerve; clinical characteristics of the animals in both groups were close to each other and to the norm. CONCLUSION: The results allow us to consider the conduit made of non-resorbable Reperen as a device promising for neuroplasty along with the resorbable conduit made of Tissucol.

Synthesis and Excretion of Atrial Natriuretic Peptide in Secretory Cardiomyocytes in Experimental Hypertension.

The intensity of accumulation and excretion of atrial natriuretic peptide in myocytes of the right atrium in rat models of renovascular hypertension and salt loading was studied by immunocytochemical analysis and transmission electron microscopy. The data suggest that high BP is not the decisive factor affecting secretion of atrial natriuretic peptide in atrial cardiomyocytes. The regulatory mechanisms of the accumulation and release of the peptide from myocyte granules can vary and depend on the pathogenesis of hypertension.

Ultrastructural Morphological Characterization of Right Atrial and Left Ventricular Rat Cardiomyocytes during Postreperfusion Period.

Immunocytochemistry and transmission electron microscopy were employed to examine the ultrastructural morphometric parameters of the left ventricular cardiomyocytes and right atrial secretory myocytes in rats during early and delayed postreperfusion periods. The revealed alterations in these cells are stereotypical, but differed by their severity, probably due to specific morphofunctional peculiarities of these heart structures.

[ATRIAL AND BRAIN NATRIURETIC PEPTIDES OF CARDIAC MUSCLE CELLS IN POSTREPERFUSION PERIOD IN RATS].

Accumulation and release of atrial and brain natriuretic peptides (ANP and BNP) in right atrial cardiac muscle cells has been investigated in rats after 60 minutes and 60 days after the reperfusion start. The total ischemia was simulated by the method of V. G. Korpachev. Immunocytochemical localization of peptides in cardiomyocytes was performed in ultrathin sections using polyclonal antibodies. The intensity of accumulation/excretion of ANP and BNP were analyzed by the method of counting the number of granules (A- and B-types) with immunoreactive labels in 38 x 38 mkm2 visual fields in transmission electron microscope Morgagni 268D (FEI). The results were assessed using Mann-Whitney U-test (p < 0.05). After 60 minutes and 60 days post-reperfusion period, we detected an increase in the synthesis and release of ANP and BNP. The reaction of BNP was more pronounced than ANP. This is due to the fact that ANP is the main hormone of the natriuretic peptide system involved in the regulation of blood pressure in normal conditions, while BNP is the principal regulator of pressure in cardiovascular pathology.

PHARMACOLOGICAL CORRECTION OF MICROCIRCULATION IN RATS SUFFERED A TRAUMATIC BRAIN INJURY.

We investigated the action of mexicor on functional indices of erythrocytes and the structure of myocardial microcirculation in rats suffered from traumatic brain injury (TBI). At 3, 7 and 12 day after TBI we measured the concentration of 2,3-diphosphoglycerate (2,3-DPG), the degree of erythrocyte aggregation and their electrophoretic mobility (EPME) in the blood of rats, and also analyzed sections of left ventricular myocardium. During the first day after the TBI we observed a decrease in EPME, an increase of erythrocyte aggregation and an increase of 2,3-DFG concentration in erythrocytes compared with intact animals. Intraperitoneal injection of mexicor led to an increase of EPME, 2,3-DPG level and reduce an aggregation of erythrocytes, which was the most pronounced during the 3­7 day of post-traumatic period. Improved functional parameters of erythrocytes were combined with the dynamics of regenerative processes in the heart. Intraperitoneal injection of mexicor restrained architectonic damage of microvasculature and cardiomyocytes ultrastructure of the myocardium of the left ventricle of the heart.

[QUANTITATIVE ANALYSIS OF BRAIN NATRIURETIC PEPTIDE OF CARDIAC MUSCLE CELLS IN EARLY POSTREPERFUSION PERIOD IN RATS].

The intensity of accumulation and release of brain natriuretic peptide (BNP) in right atrial cardiac muscle cells was investigated in rats after 5 and 60 min from the reperfusion start. Total ischemia was simulated by cardiovascular bundle compression according to V. G. Korpachev. Immunocytochemical identification of BNP in atrial myocyte granules was investigated in ultrathin cuts. We applied polyclonal antibodies to BNP. The calculation of granules (A- and B-types) with BNP was carried out in (38 x 38 µm) visual fields in transmission electronic microscope. The results were assessed using Mann-Whitney U-test (p < 0.05). After 5 min from the reperfusion start, the amount of the granules with BNP did not change compared to intact animals rate. On the 60th min of the post-reperfusion period was shown active accumulation and release of BNP; the amount of A-type granules increased by 134%, B-type granules increased by 210 % in comparison with intacy level. The results showed stimulating effect of ischemic and reperfusion factors on the processes of the brain natriuretic peptide synthesis and secretion in the early post-reperfusion period.

Method for Correction of Consequences of Radiation-Induced Heart Disease using Low-Intensity Electromagnetic Emission under Experimental Conditions.

Effects of successive exposure to ionizing irradiation and low-intensity broadband red light on electrical activity of the heart and myocardium microstructure were studied in rats. Lowintensity red light corrected some ECG parameters, in particular, it normalized QT and QTc intervals and voltage of R and T waves. Changes in ECG parameters were followed by alterations in microstructure of muscle fi laments in the myocardium of treatment group animals comparing to control group.

[Changes in the proportion of A- and B-types of granules containing atrial and brain natriuretic peptides in atrial myocytes in vasorenal hypertension in rats].

The system of cardiac natriuretic peptides (NP) is a very important factor opposing the effects of the rennin-angiotensin-aldosterone system (RAAS), sympathoadrenal system and vasopressin to reduce blood pressure. In the present study, we analyzed the release of atrial and brain natriuretic peptides in the myocytes of the right atrium in rats by the quantitative morphometric method using double immunocytochemical labeling of atrial granules comprising NP in vasorenal hypertension induced by the renal artery ligation. The decrease in the total amount of secretory granules in atrium myocytes by 18% was detected on the 30th day after the operation. The number of the A-type granules was reduced by 53%, and the number of B-type granules was increased by 64% in comparison with the intact animals. Our data indicate activation of NP secretion in vasorenal hypertension. The results suggest that high arterial pressure might be explained by reduced expression of NP receptors in this pathology.

[Atrial natriuratic peptide and experimental vasorenal hypertension in rats].

Vasorenal hypertension in rats resulted in increase of arterial pressure, the plasma concentration of creatinine and potassium. By EM immunocytochemistry we have demonstrated that atrial natriuretic peptide (ANP) was kept in the granules of secretory cardiomyocytes of the right atrium. It has shown that cardiomyocytes released ANP by means of diffusion. The increased secretion of atrial natriuretic peptide has been detected in blood. However the physiological effects this peptide probably was impaired due to the reducing of the density of natriuretic peptide receptors.

Contrasting properties of gold nanoparticles for optical coherence tomography: phantom, in vivo studies and Monte Carlo simulation.

The possibility of using silica-gold nanoshells with 150 nm silica core size and 25 nm thick gold shell as contrasting agents for optical coherence tomography (OCT) is analyzed. Experiments on agar biotissue phantoms showed that the penetration of nanoshells into the phantoms increases the intensity of the optical coherence tomography (OCT) signal and the brightness of the corresponding areas of the OCT image. In vivo experiments on rabbit skin demonstrated that the application of nanoshells onto the skin provides significant contrasting of the borders between the areas containing nanoshells and those without. This effect of nanoshells on skin in vivo is manifested by the increase in intensity of the OCT signal in superficial parts of the skin, boundary contrast between superficial and deep dermis and contrast of hair follicles and glands. The presence of nanoshells in the skin was confirmed by electron microscopy. Monte Carlo simulations of OCT images confirmed the possibility of contrasting skin-layer borders and structures by the application of gold nanoshells. The Monte Carlo simulations were performed for two skin models and exhibit effects of nanoparticles similar to those obtained in the experimental part of the study, thus proving that the effects originate exactly from the presence of nanoparticles.