Study of water exchange in skin tissues by microwave dielectrometry

The complex dielectric permitivity of human skin was measured at a frequency of 42 GHz, and a method for calculating water content in skin tissues in vivo was proposed. The water content reaction of skin to standard physical exercises and nontoxic doses of nicotine was investigated. The functionally related changes in skin dielectric properties were interpreted as structural rearrangements of water contained in blood and tissues fluids.     

UHF-dielectrometry in the assessment of the structural organization of salt solutions and interstitial fluids in normal and cicatricial tissues

The complex dielectric permittivity of salt solutions with positive and negative salvation as well as healthy and cicatricially changed human skin in situ at the frequencies of 42 and 56.6 GHz was measured. The relation between the dielectric characteristics of water and diluted salt solutions and changes in their structural organization conditioned by different temperatures of samples and the type of salvation of electrolytes was studied. The differences in the dielectric characteristics of healthy and cicatricially changed skin are interpreted in terms of the dependence of the structural organization of interstitial fluids on the morphological and functional state of biological tissues.     

The comparative effect of serotonin agonists on the presynaptic and somatodendritic autoreceptors of serotoninergic neurons

Experimenting on the slices of cortex and dorsal raphe nucleus of midbrain of rats which were incubated with 3H-hydroxytrypta-mine (3H-HT) studies showed the influence of series of serotonin agonists on the spontaneous and electrically stimulated release of 3H-HT from the slices. It was established that the serotonin in concentration of 10(-5) mol/l similarly inhibits the release of 3H-HT from the electrically stimulated slices of the brain cortex (78.6%) and on slices of the dorsal raphe nucleus of the midbrain (81.6%) had no effect on the spontaneous release of serotonin. The serotonin agonists in order of increasing ability to inhibit the electrically stimulated release of 3H-HT from the cortex slices is as follows: ipsapirone (0%), 8-OH-DPAT (23%), kampirone (26.5%), 1.2-PP (28.6%), kaplapirone (35.7%), buspirone (48%) and TFMPP (67%). On the ability to influence the release of 3H-HT from the electrically stimulated slices of the dorsal raphe nucleus of the midbrain of the rats serotonin agonists were in the following order: TEMPP (12.3%), kampirone (40%), 1.2-PP (42.9%), ipsapirone (52%), 8-OH-DPAT (54.1%), kampirone (57.2%) and buspirone (65.3%). It is suggested that the effect of both ipsapirone, kampirone and 8-OH-DPAT is greatly localized on the somato-dendritic synapses P1A-HT receptors, TEMPP is more on the terminal axons of HT-ergic neurones while kampirone, buspirone and active metabolite 1.2-PP act on the presynaptic and somatodendritic autoreceptors of serotonin.     

Postsynaptic mechanisms of induction of NMDA-dependent long-term post-tetanic potentiation of synaptic transmission

Experiments on hippocampus slices of rats showed that the pattern of induction of long-term post-tetanic potentiation of synaptic transmission is determined by the frequency of tetanic stimulation of Schaffer collaterals. With their high-frequency (>10/sec) stimulation, a phase of reversible increase in the amplitude of population EPSP (pEPSP) is observed within the initial 30-min-long interval; it is related to an increase in the intracellular Ca²⁺ concentration resulting from simultaneous activation of NMDA and metabotropic glutamate receptors and voltage-activated calcium channels. With the participation of calmodulin, Ca²⁺ activate Ca²⁺-calmodulin-dependent protein kinase II. The latter phosphorylates AMPA/kainate receptors (their kainate-responsive compartments), which promotes an increase in their chemosensitivity. Under conditions of low-frequency (<10/sec) tetanic stimulation of synaptic inputs, for the same reasons, an increase in the intradendritic Ca²⁺ concentration exerts no expressed influence on protein kinase II, but activates calcineurin. The latter, with the involvement of other phosphoprotein phosphatases, dephosphorylates AMPA/kainate receptors and turns some of them into the refractory state; this is expressed in a reversible depression of pEPSP. After 30 min of either high-frequency, or low-frequency stimulation, a non-decremental phase of long-term post-tetanic potentiation develops, which is related to the increase in the protein kinase C activity, phosphorylation of the AMPA-responsible compartments of AMPA/kainate receptors, their rising sensitivity, and a stable increase in the pEPSP amplitudeNeirofiziologiya/Neurophysiology, Vol. 28, No. 4/5, pp. 163–172, July–October, 1996.     

Myocardial contractility in chickens (Gallus gallus): analysis of systolic time intervals

The avian cardiovascular system is of special interest because avian hearts are relatively larger than mammalian hearts, and activation of ventricular myocardium in birds has a "flash" pattern. Systolic time intervals and indices of myocardial contractility were examined in anaesthetized open-chest chickens by polycardiography, including synchronous recordings of electrocardiogram, phonocardiogram, and apex cardiogram. The asynchronous contraction time, isometric contraction time, pre-ejection period and ejection time were 26 +/- 3 (Mean +/- SD), 21 +/- 9, 47 +/- 12, and 83 +/- 23 ms, respectively, for heart rates of 260 +/- 57 bpm. The myocardial tension index, isometric contraction index and the pre-ejection period/ejection time ratio were 0.39 +/- 0.11, 0.42 +/- 0.10, and 0.54 +/- 0.14, respectively. A "flash" pattern of ventricular myocardial depolarization causes more rapid excitation and as a consequence shorter asynchronous contraction time of relatively larger chicken hearts compared with rabbit hearts. Inverse relation (P < 0.05) of the asynchronous contraction time to the heart rate in chickens is probably associated with the specific activation pattern of avian ventricles. Establishment of the values of systolic time intervals will facilitate a better understanding of cardiac function in birds. The obtained results are discussed in comparison with the rabbit. The indices calculated from the systolic time intervals show disadvantageous contractile function of chicken heart compared to rabbit heart.     

Left ventricular myocardal activation under ventricular paced beats in chickens Gallus gallus domesticus

The aim of the study was to advance our knowledge regarding the activation process of the ventricular myocardium in birds in which Purkinje fibres penetrate into the ventricular wall to reach the epicardium. A depolarization pattern of the left ventricular free wall was studied in chickens (Gallus gallus) during ventricular paced beats. Duration of the activation process of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm. Its lowest increase occurs during subendocardial pacing of the middle part of the left ventricle, but its greatest increase is observed during subepicardial pacing of the left ventricular base. Multifocality and mosaicity of depolarization of the left ventricular free wall myocardium in chicken are expressed in a considerably less degree during ventricular paced beats in comparison with sinus rhythm. During ventricular paced beats, excitation of the left ventricular free wall is mostly due to the successive spreading of the depolarization wave from pacing sites.