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Biomedical subjects

N P Alekseev

Publications and source records attributed to N P Alekseev.

At least 19 recordsLinked to original sources
PubMed2003

[Changes in temporal parameters of compression stimuli in milk ejection during feeding a baby].

The temporal changes of compression stimuli exerted by baby on the areola-nipple complex during the entire suckling period were investigated in 6 mother-baby pairs of the 4-6-day lactation. It was found that compression stimuli had a triangle form. The duration of the stimuli and inter-stimuli interval varied from 0.3 s to 0.8 s and from 0.1 s to 0.25 s, respectively. The compression stimuli were organized in bursts and a pause of variable duration between the bursts. The mean frequency of the compression stimuli in the bursts was within the range 0.9 imp/s-1.7 imp/s. The average frequency of the entire suckling period in babies was within the range 0.9 +/- 0.3 imp/s-1.1 +/- 0.1 imp/s. Implications of these findings in the suckling neonates are discussed.

Adult↗
PubMed2000

[Dynamics of milk ejection reflex during continuous rhythmic stimulation of areola-nipple complex of the mammary gland].

In continuous 10-minute simultaneous action of the vacuum and compression stimuli at a 1 cycle/second frequency, the rate of the milk ejection from the breast was periodically changing in lactating women. The milk flow first peaks latency was 0.5-3.0 minutes, the number of peaks being 2-7 per minute with the inter-peak interval 2-4 minutes during a 10-minute milk ejection. The women revealed an individual pattern of the milk flow peaks. The findings suggest that a central gate mechanism intervenes to set the periodicity of the milk ejection.

Adolescent↗
PubMed1998

Compression stimuli increase the efficacy of breast pump function.

OBJECTIVE: The dynamics of milk ejection and also prolactin concentration in the blood during milk expression by means of a breast pump were studied in 82 lactating women. STUDY DESIGN: The design of the breast pump used in this study is new. It is based on the correlation with the amplitude, duration and frequency of vacuum and compression stimuli formed by the baby's mouth apparatus during the suckling process. RESULTS: It was found that during continuous co-action of the vacuum and compression stimuli at a frequency of 1 cycle per second, the rate of milk ejection from the breast changed periodically. The highest rates of milk ejection coincided with the greatest rises in intramammary pressure. When the compression stimulus was turned off, leaving only the vacuum, the period of the first rise in pressure increased 1.5-2 fold, with a 1.5-2 fold reduction in the milk ejection rate as compared with the normal function of the breast pump. The basal prolactin level on day 3 and 5 post delivery in women who used a breast pump was not significantly different from that of puerperal women who only breast-fed their babies. Prolactin concentration in the blood of puerperal women did not change within the 5-6 min of expression and stimulation with the breast pump. The prolactin level began to increase by the 10th minute, whereas by the 25th minute it exceeded the initial concentration 1.3-1.5-fold. CONCLUSION: It is suggested that by introducing a tactile component to the mechanism of the breast pump, milk secretion is enhanced, as well as stimulating the breast milk flow. This directly improves the dynamics of breast milk expression.

Adolescent↗
PubMed1994

[The role of vacuum and tactile stimuli during milk ejection from the human breast].

Milk ejection in lactating women was performed by breast pump with vacuum and tactile (touch-compression) components. It was found that milk flow rate changed in a pulsatile manner at about 1-2 min interval and peaks milk flow coincided with peaks intramammary. Switch off the tactile component increased the latency of milk ejection 1.5-2 fold and decreased total flow rate 2 fold. It was concluded that touch-compressions stimuli necessary for generation milk ejection reflex and milk ejection from the women mammary gland.

Breast↗
PubMed1992

The influence of tactile stimulation of nipples on the milk ejection reflex in the rat.

Changes of positive pressure exerted by pups on nipples during sucking were investigated using anesthetized, lactating dams. It was found that, every 50-60 s, individual pups performed bouts of pressure oscillations (3/s) of high amplitude which lasted about 10-12 s and coincided with periods of increased motor activity. During the intervals, when pups were quiet, series of low-amplitude oscillations (3/s) were also observed. Using a strain measuring method to record the activity of sucking pups, synchronization of activity of two or more pups was found to occur periodically every 25-30 s and, most frequently, 10-30 s before the reflex increase of milk pressure. In further experiments, artificial tactile stimulation was applied to the dam's nipples using the joint action of suction and positive pressure. Following a short-term (10-20 s) increase in frequency and amplitude of artificial nipple stimulation, 60%-80% of all reflexive peaks of milk pressure were elicited with a latency of 19 +/- 5 s. This suggests that there are specific conditions under which the stimulation of nipples by pups may trigger the formation of the milk ejection reflex in the rat.

Animals↗
PubMed1992

Transepithelial potential difference in the goat mammary gland and its change during hand milking, and administration of oxytocin and catecholamines.

The reaction of secretory epithelium and myoepithelial cells in the alveoli to hand milking and i.v. injection of oxytocin and catecholamines was studied in lactating goats. The reaction of secretory cells was assessed by changes in the transepithelial (blood-milk) potential difference (PD), and the contractile reaction of myoepithelial cells by the growth of intramammary pressure (IP). The initial value of PD was 24.6 +/- 0.6 mV, that of IP 3.32 +/- 0.08 kPa (24.9 +/- 0.6 mmHg). Milking and oxytocin administration caused a rise in PD and an increase in IP. After noradrenaline and adrenaline injections two-phase PD changes and a short-term rise in IP were recorded. Isoproterenol, a beta-agonist, caused a rise in PD but did not affect IP. Phenylephrine, an alpha-agonist, caused two-phase and one-phase changes in PD. Simultaneously, a rise in IP was recorded. The results show that the reaction of the mammary gland to the substances administered is complex. Myoepithelial and secretory cells respond differently to short-term rises in the level of mediators and hormones in the blood.

Animals↗
PubMed1991

[The characteristics of the motor activity of rat pups during the milk ejection reflex].

The motor activity of newborn rats sucking on anesthetized mothers was studied during the milk ejection reflex. When sucking before obtaining milk every 22 +/- 12 sec, newborn rats displayed an increased motor activity which lasted for 5 +/- 3 sec and coincided with the period of high-amplitude fluctuations of the pressure exerted on the nipple. The periods (5-10 sec) of increased motor activity were observed simultaneously in two or more rats at intervals of 25-30 sec. Simultaneous activity of the newborn rats was most frequently observed 10-30 sec before reflex rise of milk pressure in the mammary gland. Factors regulating the milk ejection reflex in rats, are discussed.

Animals↗
PubMed1991

[The characteristics of the milk ejection reflex in the rat during mechanical stimulation of the mammary gland].

Milk ejection reflex (MER) was studied in the lactating rat measuring the intramammary pressure during mechanical stimulation of the nipples with vacuum and pressure. The incidence of MER was 60-80% (latency 19 +/- 5 sec) after short-lasting (10-20 sec) stimulation of the nipples. The periods of MER increased when the frequency of stimulation of the nipples was decreased. The role of the mechanical stimuli in the MER occurrence in discussed.

Animals↗
PubMed1988

[Inhibitory reactions of the neurosecretory cells of the supraoptic hypothalamic nucleus in lactating rats to subiculum stimulation].

The effects of the subiculum stimulation were studied in 80 antidromically identified hypothalamic supraoptic neurons of lactating rats. Inhibition of antidromic responses evoked by stimulation of the neurohypophysial stalk after conditioning stimulation of the subiculum was detected in 26% of cells studied. Sometimes the inhibition followed each separate subicular stimulus with 5-25 ms latency and was transitory, sometimes it developed gradually as the conditioning stimulation was applied. No excitatory responses to subiculum stimulation were found. Nature of the inhibition observed is discussed as related to the morphofunctional organization of subicular synaptic inhibitory inputs to neurosecretory cells.

Animals↗
PubMed1979

[Responses of individual receptor units of rat mammary gland parenchyma to tactile stimulation].

Two types of slowly adapting mechanosensitive units were revealed in the parenchyma of the rat mammary gland (SAI and SAII). At constant mechanical displacement of the parenchyma surface SAI exhibited irregular and SAII--regular firing. The diameter of the receptive fields of the SAI and SAII was 1.0--1.5 mm with the central point of this area being the most sensitive. Trapezoidal stimuli elicited both dynamic and static responses proportional to the velocity of the movement and its displacement amplitude; the threshold of the SAI and SAII increased as stimuli of increasing velocity were used.

Action Potentials↗
PubMed1979

[Effect of inhibitors of the active transport of ions on the spontaneous and evoked electrical activity of parenchymal mammary gland receptors].

In the potassium-free saline spontaneous activity of the mammary gland parenchyma receptor increased within first 30--40 min., then decreased and, finally, ceased. Sensitivity of the receptor to the mechanical stimuli decreased gradually. After washing in normal saline the evoked and spontaneous activities recovered. Ouabain (5 . 10(-5)--10(-4) g/ml) exerted an effect similar to that of the potassium--free solution except that the impulse activity could not be restored by the washing in physiological saline.

Action Potentials↗
PubMed1977

[Slowly-adapting mechanoreceptor units of the guinea pig mammary nipple].

Slowly--adapting mechanoreceptor units of areola and nipple (MAI and MAII) at rest exhibited spontaneous 1--2/sec firing in 6% only. At constant mechanical displacement of the skin surface. MAI had an irregular firing while MAII--regular one. Mean frequency of MAI and MAII APs linearly depended on the amplitude of mechanical stimulus. trepeated stimulation of MAI and MAII reduced number of APs for each successive stimulus. At sinusoidal mechanical stimulation, the smallest AP threshold for MAI and MAII was about 10--15 Hz.

Adaptation, Physiological↗
PubMed1977

[Properties of mechanoreceptor units of mammary gland parenchyma].

Two types of mechanosensitive units were found in the parenchyma of the rat mammary gland (SA and RA). Most of SA units had a spontaneous activity 1-3/sec. and responded to an abrupt displacement with a decline in the activity for 5-10 sec. RA had no such a response. The relation between average firing rate and displacement velocity at a constant displacement amplitude was linear for both SA and RA. RA however had the velocity threshold higher than SA. The number and frequency of SA afferent impulses decreased at a repeated stimulation. Electron microscopy revealed that free nerve endings correspond to SA and RA.

Action Potentials↗