Quantitative estimation of connection of the heart rate rhythm with motor activity in rat fetuses

In rat fetuses over E17-20 with preserved placental circulation with use of mathematical analysis there were revealed value and character of connections of slow wave oscillations of the heart rhythm with motor activity for 30 min of observation. In the software PowerGraph 3.3.8, normalization and filtration of the studied signals were performed in three frequency diapasons: D1-0.02–0.2 Hz (5–50 s), D2-0.0083-0.02 Hz (50 s-2 min), and D3-0.0017–0.0083 Hz (2–10 min). The EMG curves filtrated by diapasons or piezograms were compared with periodograms in the corresponding diapasons of the heart rhythm variations. In the software “Origin 8.0”, quantitative estimation of the degree of intersystemic interrelations for each frequency diapason was performed by Pearson correlation of coefficient, by the correlation connection value, and by the time shift of maximum of cross-correlation function. It has been established that in the frequency D1, regardless of age, the connection of heart rhythm oscillations with motor activity is expressed weakly. In the frequency diapason D2, the connection in most cases is located in the zone of weak and moderate correlations. In the multiminute diapason (D3), the connection is more pronounced. The number of animals that have a significant value of the correlation connection rises. The fetal motor activity fires in the decasecond diapason in all age groups are accompanied by short-time decelerations of the heart rhythms. In the minute diapason, there is observed a transition from positive connections in E17 and E18 to the negative ones in E19-20. Results of the study are considered in association with age-related changes of ratios of positive and negative oscillations of the heart rhythm change depending on the character of motor activity.     

Secondary rhythms of automatically functioning systems

In wakeful rats at the age from newborn to 3 weeks there were studied interrelations of rhythmical oscillations of heart rate, respiration rate, and periodic spontaneous motor activity. In all studied systems, these oscillations are coordinated and occur in several frequency diapasons. Frequencies in the near-minute diapason (the period from 30 to 90 s) are the most constant and do not change with age. Regular oscillations are the most stable in newborns. Bursts of motor activity usually are irregular, but episodically the distinct near-minute rhythm is traced. Studies of the character of interaction of the heart activity, respiration, and periodic somatomotor excitation allow stating that the main coordination pathway of spontaneous autorhythmic functions in early postnatal ontogenesis is formation of secondary rhythms. Possible ways of formation of the secondary rhythms are considered.     

Organization of endogenous rhythms of motor functions (To the 100-Anniversary of A.V. Voino-Yasenetskii)

Two categories of endogenous rhythmical activity of somatic and visceral muscle are considered: the basic rhythms determined by morphofunctional and age-related characteristics of an organ or system and the secondary rhythms characterized by wide spreading in different systems, age-related stability, and many-level organization. In early ontogenesis, both forms of rhythmical activity has the common goal—to provide homeostasis of the growing organism under conditions of limited external afferentation and imperfection of adaptive regulatory mechanisms. Formation of the secondary rhythms is considered as the way and the result of coordination of functions that have endogenous rhythmicity.     

Development of the Ontogenetic Method in Studying Evolution of Contractile Functions

Practically all organism's visceral organs and systems performing contractile function as well as the somatomotor apparatus of higher animals, regardless of the type of muscles and character of control of their activity, start their work at early stages of ontogenesis with autorhythmic contractions. This activity is endogenous, as it does not have any external rhythmic analogs. Two fundamentally different components can be distinguished in the endogenous rhythm: the basic ones, specific of each system, and the secondary ones, built over the basic rhythms that reflect oscillatory processes in the whole organism and serve the basis for integration of endogenous periodic processes. Formation and synchronization of the secondary rhythms is the earliest stage of coordination of the automatically working systems. The broadening of possibilities for regulation and age-dependent inhibition of the autorhythm provide a transition to reflex-determined forms of activity. In various contractile systems, stages of evolution of neuromuscular relationships, from the independent autorhythm to the voluntary control of contractions, find their reflection.     

Organization and development of pacemaker of the gastrointestinal tract

Rhythmical depolarization and automatic contractions of smooth musculature of the gastrointestinal tract are a consequence of pacemaker activity of c-Kit-immunoreactive cells of mesenchymal origin—interstitial Cajal cells (ICC) that have a peculiar mechanism of intercellular Ca²⁺ balance, which is controlled by mitochondria. Intermuscular layer cells (ICC-MY) generate pacemaker potentials. Their induced depolarization is enhanced by unitary potentials generated by intracellular population—ICC-IM. Summation of unitary potentials in the tact of the pacemaker ones leads to creation of the second potential of slow waves—plateau potentials. Due to the presence of synapse-like structures, ICC serve messenger of transmission of the enteral nervous system onto the muscle. Long processes and close intercellular contacts similar to tight junction provide conductance and coordination of excitation in the intestinal musculature. Electrical rhythmicity appears in the intestinal muscle at the prenatal development period in parallel with the structural and functional ICC maturation, but establishment of mature rhythm parameters occurs in early postnatal ontogenesis. Features of similarity and difference in organization of control by pacemakers of the heart and musculature of the gastrointestinal tract are discussed.     

Synchronization of Endogenous Somato- and Visceromotor Activities in Rats in Ontogenesis

It is shown in the experiments on rat pups at the age from neonatal to the end of the 3rd week that bursts of spontaneous somatosensory excitation characteristic of altricial animals at the early postnatal ontogenesis have a pronounced tendency for synchronization with oscillations of the electrical activity level in the antral part of the gastric wall and duodenum. These oscillations represent the so-called secondary rhythms that superpose basic rhythms and are responsible for intersystem interactions. Since the 2nd week after birth the synchronization level decreases essentially. Vagotomy performed at this period increases again the synchronization, which suggests the desynchronizing role of parasympathetic innervation in the process of development.     

The formation of activity-rest cycles in early ontogeny

The cyclic variations of the motor activity consist of many rhythmic components which appear nonsimultaneously in the ontogenesis. The earliest component is the autogenic periodic motility with the duration about one minute which can be observed in rats during first two-three weeks after the birth. From the second week a new type of cyclic activity appears. It can be qualified as a sleep-wakefulness cycle with the duration about several minutes. It is suggested that this cycle is a true novel rhythm which is able to modulate the earliest more frequent periodicity.     

Ecological cues, gestation length, and birth timing in African buffalo (Syncerus caffer)

We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year.     

The temporal organization of human fetal motor function]

Fetal motor bursts were recorded in pregnant women at 11-18, 20-24 and 30-32 weeks of pregnancy. It was stated that spontaneous motor activity in human fetus is similar to autogenic periodic motor excitation observed in other species of vertebrates, i.e. presence of the main rest-activity circles with a period near 1 minute, the existence of rhythmic components with 6-8-second intervals during active phases and decreasing of quantity of excitation bursts with age.