Effect of menthol on human temperature sensitivity

Application of 1% methol, which, along with cold, activates specific thermosensitive ionic channels, changes the number of functioning cold receptors on the skin of the forearm similarly to the cold exposure test; however, it does not affect the number of heat receptors and does not significantly change the threshold of cold sensation. Group variants of responses to menthol that indicate individual differences in the sensitivity of skin receptors to the effects of methol and cold have been found. The results obtained give grounds to suggest that, from the variant of response to menthol (a decrease, increase, or absence of changes in the number of functioning cold receptors 5 min after menthol application), it is possible to predict specific features of response to cold.     

Effects of cold adaptation and noradrenaline on thermosensitivity of rat hypothalamic neurons studiedin vitro

The experiments performed on rat brain slices have shown that cold adaptation of an animal influences the thermosensitivity of hypothalamic medial preoptical neurons. The adaptation is followed by an increase in the proportion of 38–41°C-thermoresponsive neurons and by a decrease in the proportion of 35–38°C-thermoresponsive units. In control animals, noradrenaline (NA) increased the responses of hypothalamic neurons to the action of 35–38°C temperature and decreased them to the action of 38–41°C temperature. Cold adaptation prevented the effects of NA on neuronal thermosensitivity, which suggests that their NA sensitivity is modified by cold adaptation.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 171–176, May–June, 1994.     

Effect of cold on the antigen binding function of splenic cells at different periods of immunogenesis in rats

The patterns of changes in the immune response when deep cooling with different rates acted at various periods during development of the immune response, were examined in Wistar rats. Cold exposure causes not only a suppression but also stimulation of the immune response to antigen. The suppressive effect of deep cooling when it preceded immune challenge (the antigen injected at a body temperature decreased by 3-4 degrees C) waned and became stimulating with increasing time interval between antigen challenge and cold exposure. The stimulating effect on the immune response was most pronounced when cold exposure occurred in 5 days after the antigen challenge. These changes differed quantitatively also when cooling was either rapid, or slow. Thus the modulating effect of the thermal afferent signal was differently manifested depending in the cooling rate, i.e. the presence or absence of the dynamic activity of the peripheral thermosensitive afferents, and the time elapsed between antigen challenge and cold exposure.     

Structural and functional characteristics of the heart of professional soccer players after retirement from long-term sports activity

The structural and functional characteristics of the heart of 51 retired soccer players who ceased training 3–15 years ago are presented. A number of structural and functional signs of “athlete’s heart” detected in the subjects indicate more efficient heart functioning at rest and during exercise. The myocardium requires less oxygen per unit power of muscle work, and each gram of the myocardium of retired athletes performs more mechanical work than the myocardium of untrained subjects of the same age. This indicates long-term adaptation of the heart of retired athletes to muscle work. The heart functioning at rest and during exercise in retired athletes becomes less efficient with age, this trend being more pronounced in older former athletes than in younger ones. This is expressed in an increased oxygen consumption by the myocardium, a higher occurrence of atypical electrocardiogram patterns, age-related changes in myocardial contractility, and a decreased capacity of each gram of the myocardium for generating mechanical work.     

Central and peripheral thermoreceptors. Comparative analysis of effects of the long-term adaptation to cold and noradrenaline

The data obtained in our experiments concerning the effect of long-tern adaptation to cold and noradrenaline on impulse activity of the central hypothalamic and peripheral skin thermoreceptors, are reviewed. The problems of sympathetic system participator in cold adaptive modifications and importance of thermoreceptors in formation of cold-defense responses, as well as the role of different types of thermoreceptors in thermal sensation, are discussed.     

Effect of long-term cold adaptation on the mRNA expression of serotonin 5-HT1A and 5-HT2A receptors

The mRNA expression of serotonin receptors 5-HT1A and 5-HT2A was investigated by the quantitative method RT-PCR in rats adapted to cold (5 weeks at +4 -(+6) degrees C) and in control (5 weeks at +20-22 degrees C). Four brain regions were examined: frontal cortex, hypothalamus, hippocampus, and midbrain. The influence of cold adaptation on the mRNA expression of 5-HT15 receptor was not found to be absent. The mRNA expression of 5-HT2A receptor changed under long-term cold exposure. These changes in different brain regions were various: in hypothalamus, there was an increase of the 5-HT2A receptor mRNA expression; in the cortex, a decrease; in the hippocampus and midbrain, significant changes of the mRNA expression were absent. The findings appear bo te adaptive and, according to their localization in the central nervous system, regulatory. They also suggest involvement of brain serotoninergic system in mechanism of adaptive reorganization of temperature regulation.     

The Relationship between the Traits of the Two-Row Spike,the High Number of Thillers,and the High Regeneration Capacity in in vitro Culture in Barley

In barley (Hordeum vulgare L.), the traits of the two-row spike, the high rate of plant tillering, and the high capacity for multiple plant regeneration (MPR) in a callus culture of immature embryos were shown to correlate. When a dihaploid line (DH) obtained from cv. Golden Promise (two-row spike, high number of thillers) was crossed to a DH line from cv. Bruce (six-row spike, low number of thillers), the two-row trait dominated the F₁ generation, whereas, in F₂, the segregation ratio was 3 : 1. From F₃ progeny, we isolated the families comprising two-row homo- and heterozygotes and six-row homozygotes. In an F₃ hybrid population, the two-row plants manifested higher tillering and MPR rates as compared to the six-row plants. The correlation between the traits of the two-row spike, the high tillering, and the high MPR capacity may depend on the pleiotropic V gene, which controls the general mechanisms of meristem functioning essential for the development of these three traits.