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Biomedical subjects

V A Lysenko

Publications and source records attributed to V A Lysenko.

10 recordsLinked to original sources
PubMed2006

The mechanical reaction of the pars flaccida of the eardrum to rapid air pressure oscillations modeling different levels of atmospheric disturbances.

Atmospheric pressure fluctuations (APF) might induce mechanical effects in the pars flaccida (PF) of the eardrum. To clarify these effects, different kinds of pressure oscillations (PO), chosen within the range of naturally occurring APF, were applied to the middle ears (ME) of gerbils. The linear displacement of the PF during a PO in the ME was measured by laser interferometry. The compliance of the PF to PO was calculated as the ratio of the amplitude of a PF oscillation to the amplitude of a PO. The displacement of the PF traced the PO in the entire range of frequencies (from 10mHz to 200mHz) and amplitudes (from 10Pa to 110Pa) applied to the ME. Moreover, the PF is found to be displaced by pressure pulses of a few pascals only using a PO with a complex shape. The differences found in the compliance of the PF due to PO with low (less than 20Pa) and high (more than 90Pa) amplitude point out that the mechanism of pressure regulation in the ME through the mechanical reaction of the PF in gerbil ears is better adapted to ordinary levels of natural APF than to extraordinary levels. The implications of these findings for the physiology of the human ME with respect to adaptation to natural APF are discussed.

Animals↗
PubMed2006

The effects of slight pressure oscillations in the far infrasound frequency range on the pars flaccida in gerbil and rabbit ears.

This study was designed to clarify whether the pars flaccida (PF) as a flexible part of the tympanic membrane is capable of reacting to pressure oscillations (PO) with amplitudes and frequencies typical for natural atmospheric pressure fluctuations in the far infrasound frequency range (APF). If so, the PF mechanical reactions to APF might be involved in the overall physiologic regulation processes, which make organisms susceptible to APF. The displacements of the PF in response to PO were measured in vitro in ears of gerbils and rabbits by means of laser Doppler vibrometry. The index of the PF reactivity (R(a)) was determined as the ratio of the amplitude of the PF oscillations (PFO) to the amplitude of the PO. All kinds of PO applied caused PFO. The amplitude of the PFO increased when the amplitude of the PO was increased. In gerbils, a decrease in R(a) with the increase in amplitude of the PO was observed. In the range of PO lowest amplitudes (4-20 Pa) R(a) proved to be 1.4 times higher than in the range of highest amplitudes (90-105 Pa). Considering that the natural APF are usually within the range of +/-20 Pa, this fact points to an important contribution of the PF to the pressure dynamics in the middle ear (ME) of gerbils. In rabbit ears, R(a) was lower and recovery from plastic deformation was slower than in gerbils. Our findings are in line with the suggestion that the PF might play an important role in respect of adaptation to natural APF.

Acoustic Stimulation↗
PubMed2000

[Circadian rhythms of hypophysis-thyroid hormones secretion in patients with bronchial asthma].

AIM: To examine circadian rhythms of hypophysiothyroid system in patients with bronchial asthma and effects of exogenic glucocorticoids on thyroid function. MATERIALS AND METHODS: Free T3, T4 and TTH were measured in plasma using immunochemiluminescence in 16 patients with nonallergic bronchial asthma running a severe course. The plasma samples were taken each 6 hours for 48 hours. RESULTS: In patients with severe bronchial asthma (SBA) thyroid functional activity changed. Production of T3 increased while that of T4 dropped at night. TTH concentration rhythm for 24 hours was like that in healthy subjects. Glucocorticoids induced no significant changes in circadian rhythms of hypophysiothyroid system in SBA patients. CONCLUSION: In SBA functional activity of the hypophysiothyroid system changes with rearrangement of hormonal production at night.

Adult↗
PubMed2000

[Blood plasma level of insulin and sensitivity to it in tissues of patients with newly detected diabetes mellitus type II].

Type II diabetes mellitus is the most common type of the condition. But little is yet known about mechanisms responsible for its development in persons with different body masses. We studied blood plasma levels of insulin and assessed sensitivity to it in 32 patients with freshly detected type II diabetes mellitus with normal and above normal body weight. Of these, 20 subjects were obese, the other 12 being not fat; the control group comprised 30 persons obese and non-obese, with n = 15 and 15 respectively. Recordable in patients was a marked elevation of blood plasma level of insulin accompanied by decrement of the peripheral tissue sensitivity to it in obese diabetic patients while in those persons with normal body mass there was a substantial reduction in the production of insulin, which differences may indicate different pathogenesis of development of type II diabetes mellitus in persons with different body masses.

Body Mass Index↗