[Contractility of the left ventricle of the human heart noninvasive measurement in each cardiac cycle].

History of development of the method of measurement of duration of the preejection (DPE) period - characteristic of left ventricular (LV) contractility is presented. On the basis of physiological prerequisites a novel computerized method of DPE measurement in each consecutive cardiocycle has been created. Distinct features of this method are: 1) principle of measurement - tetrapolar impedancemetry, with signal electrodes located along projection of the ascending aorta, one in the center of presternum, second - 5 cm caudally; 2) starting point for DPE counting - the point on ascending portion of R wave of electrocardiogram at which the first derivative of ECG signal reaches maximum, stopping point - the point of maximum of the second derivative of the primary impedance signal on the ascending front of its pulse wave. The method has been tested on healthy people for 10 functional tests. The results are presented characterizing dynamic peculiarities of changes of LV contractility during veloergometer exercise test with staderly increasing work load and reflecting development of positive inotropic action of sympathetic nervous system. Special characteristics of this action: small concealed period, preservation of achieved elevated level during lowering of work load (before its switching off) and subsequent slow (compared with chronotropic effect) diminution, as well as turning on at low loads.

[Pre-ejection period as a cardiac cotractility index: noninvasive beat-by-beat evaluation in the human study].

Beat-by-beat evaluation of left ventricular contractility provides and insight to the current dynamics of cardiac control. In non-invasive studies, pre-ejection period is conventionally used as an index of contractility. Pulse waves of electrical impedance (deltaZ) reflect the systolic dilations of the aorta segment confined between the properly placed signal electrodes. The relation of B-wave in the differentiated signal dZ/dt to the dalation of the aortic root prior to the start of ejection is discussed. The previous findings and our own experience indicate that the conventional method of identification of the end of the pre-ejection period by the B-point is not suitable for its reliable determination in each cardiac cycle. Instead of this, we defined the start of election by the maximum of the d(2)Z/dt2 signal associated with maximum acceleration of the ascending aorta dilation during the early ejection phase. It can be reliably found beat-by-beat. The proposed technique was successfully aplied for monitoring of fine dynamics of pre-ejection period changes during Valsalva maneuver, as well as in active and passive orthostatic tests.

Antidromic vasodilation in frog: identification of the nerve fiber types involved.

In anesthetized, immobilized frogs arteriolar vasodilation in the submaxillaris muscle in response to electrical stimulation of the submaxillar nerve (peripheral end) was observed directly and vasodilation in the hind leg in response to stimulation of the sciatic nerve (peripheral end) measured by plethysmography. With pulses of 0.1 ms duration at 20 Hz, the threshold for arteriolar vasodilation in the submaxillaris muscle was close to 3 T, where T was the activation threshold of the most excitable fraction of motor fibers of the submaxillar nerve. Atropine had no effect on the arteriolar vasodilation. When the sciatic nerve was stimulated with pulses of 0.1 ms duration, the threshold for vasodilation in the hind leg was 3.6 +/- 1.2 T (mean +/- SEM). The thresholds for excitation of the A alpha beta, A delta and C-afferent fibers in the sciatic nerve and the range of stimulus intensities for recruiting each of these fiber groups were evaluated by recording compound action potentials in the VIII-X dorsal roots. Excitation of A delta-afferent fibers was found to occur in the same intensity range as that which evoked vasodilation in the hind leg. It is concluded that, in the frog, these myelinated afferent fibers are capable of dilating the blood vessels by antidromic action in both submaxillaris muscle and hind leg. This finding is in accordance with recent reports of an antidromic vasodilator action of A delta-afferent fibers in rabbit and rat skin.

[An experimental verification of the histomechanical theory of the working hyperemia of the skeletal muscles: biomicroscopic research]. / Eksperimental'naia proverka gistomekhanicheskoi teorii rabochei giperemii skeletnykh myshts: biomikroskopicheskoe issledovanie.

The histomechanical hypothesis of working hyperemia in skeletal muscle was verified by comparison of the dynamics and values of frog submaxillary muscle arterioles dilation under: 1) 4-Hz twitch contraction and 2) imitation of mechanical component of the twitch contractions. Deformation of arterioles occurred during incomplete tetanus with the maximal effect at the peaks of twitches. The repetitive displacements of a small bunch of muscle fibers with the frequency of 4 Hz and the amplitude of 0.05 to 0.25 mm caused a dilation of the arterioles attached to the fibers. The outer diameter of the arterioles might increase up to 2.2-2.3-fold, i.e. in the same range as under twitch contractions. The data showed the similarity in latency values, in the dynamics of arteriole dilation, and the dependency of the latter on the phase of the spontaneous vasomotion preceding the compared stimuli. These findings suggest that arteriolar dilation is determined by mechanically induced inactivation of pace-makers of these vessels both during passive deformations and under twitch contractions.

The dilation of arterioles in frog submaxillaris muscle caused by visible light.

Transillumination of submaxillaris muscle with incandenscent lamp led to arteriolar dilation if the illuminance exceeded 1-2 x 10(3) lux or reached the time-mean value of 3 x 10(4) lux when a flash lamp was used (pulse duration 10 microseconds, repetition rate 50 s-1). The temperature increase within a light spot on the muscle did not exceed 0.1 degrees C, visible light being the only reason of the dilation of arterioles. At 6.3 x 10(4) lux (incandescent lamp, green filter) the latency of dilation in 64% of trials was less than 20 s while the average increase in diameter amounted to 69 +/- 5.0% within 2 to 4 min of radiation. In the muscle with intact innervation, dilation of arterioles slower. We supposed that due to the limitation of Bunsen-Roscoe law powerful, but short light pulses may fail to induce a photochemical reaction and the ensuring dilation. Indeed, repetitive flashes (10 microseconds, 30 s-1) producing the time-mean illuminance of 2 x 10(4) lux caused neither dilation of arterioles nor suppression of their vasomotion. The light-induced dilation allowed the conversion of closed and plasmatic arterioles into the vessels filled with moving blood. Photodilation of frog muscle arterioles may be employed to investigate a number of basic properties of their smooth muscles.

[Arteriole reactions of the submaxillary muscle to stationary and periodically repetitive displacements of its fibers and to their contraction]. / Reaktsii arteriol podcheliustnoi myshtsy na statsionarnye i periodicheski povtoriaiushchiesia smeshcheniia ee volokon i na ikh sokrashchenie.

Stationary local displacement of resting fibers in the frog decentralized submaxillary muscle affected by a piezoelectric device did not usually result in persistent changes of the diameter of nearby arteries. During oscillatory displacement (4 s-1) the same arterioles, exposed to microdeformation of a similar form and amplitude, dilated with a mean diameter increase averaging 36%. During contraction of submaxillary muscle (incomplete tetanus with 4 s-1) the diameter of these vessels increased by 32.69%. Comparison of the data obtained made it possible to suggest that arteriolar myocytes responded with selective relaxation only to the dynamic component of microdeformation.

[Arteriole reactions to rhythmic displacement of the fibers of the submaxillary muscle]. / Reaktsii arteriol na ritmicheskoe smeshchenie volokon podcheliustnoi myshtsy.

The fibers of acutely decentralized resting submaxillary muscle of anesthetized frogs were locally shifted by a piezoelectric device (frequency--about 4 Hz) in the direction of fiber shortening during muscular contractions. Arteriole configuration in the affected area changed and they became dilated. The maximum increase of the diameter was 16 to 126%. The latent period, the time during which peak reaction was reached, and the degree of arteriole dilatation during configuration changes were similar to those observed during 4 Hz muscle twitches. It is suggested that a mechanical factor, namely arteriole microdeformations, plays an essential role in the working hyperemia of skeletal muscles.

[Structure and functional properties of the arterial system of the frog submandibular muscle as an object for studying working hyperemia]. / Stroenie i nekotorye funktsional'nye svoistva arterial'noi sistemy podcheliustnoi myshtsy liagushki kak ob'ekta dlia issledovaniia rabochei giperemii.

Architectonics and ultrastructure of the arterial blood vessels of the frog submaxillary muscle are described. Intramuscular arterial vessels 100 divided by 8 micron in diameter have a single layer of smooth muscle cells (SMC), while SMC themselves look simplified and undifferentiated. The contacts between SMC in arterial vessels of all the sizes and myoendothelial contacts in the vessels 80-8 microns in diameter are noted. In the resting muscle, the arterial vessels of all the sizes show spontaneous changes in the diameter. During muscular contraction, the time course of the dilatation of different vessels is different, which is likely to be caused by vasomotion phase differences seen immediately before the contraction.

[Dilatation of arterioles in the frog submaxillary muscle under the influence of visible light]. / Rasshirenie arteriol podcheliustnoi myshtsy liagushki pod vliianiem vidimogo sveta

Frog denervated submaxillar muscle arterioles dilates under the influence of visible light. In darkness the vessel returns to tis initial condition. The degree of dilatation is in the main inversely proportional to the initial diameter of the vessel. Besides, the vessel reactivity also depends on the thickness of its wall. Thick-walled arterioles are the most reactive ones. Their diameter becomes 2 -3 times greater under the influence of visible light. This light-evoked vasodilatation should be taken into account during intravital microscopy, as such a considerable dilatation of arterioles caused by light changes their reactivity considerably.