Regulation of the heat resistance of muscle fibers in Rana temporaria tadpoles by selecting the parental gametes using quaternary ammonium compounds and chelators

In experiments on the frog Rana temporaria, studies have been made on the effect of selection of the parental sperm by quaternary ammonium compounds--tetraethylammonium and tetramethylammonium, as well as by chelating agents--EDTA and EGTA--on the heat resistance of muscle tissue in the progeny of the first generation. It was found that selection of the sperm for its maximum stability to the injurious (immobilizing) effect of these drugs affects quantitative relationship in the family between tadpoles with a high and low heat resistance of muscle fibers. Insemination of the eggs by the sperm with maximum stability to elimination by TEA and TMA favours the development of tadpoles with relatively low heat resistance of muscle fibers. On the contrary, sperm selection by EDTA and EDTA increases the amount of tadpoles with a higher heat resistance of muscles.     

Physiological polymorphism of grass frog populations. IV. Effect of stress on the phenotypic expression of population polymorphism judged by the level of heat resistance of muscle tissue

A study was made on the polymorphism of the population of Rana temporaria by the heat resistance of muscle tissue. Stress resulted in the elimination of group differences in the heat resistance of muscles. Thus, the phenotypical response of individuals to stress is masking the genotypical heterogeneity of the population judged from the heat resistance of muscle tissue.     

Thyroid activity in common frogs and the heat resistance of their bodies and muscle tissue

Thyroid activity of single individuals of the grass frog has been studied during winter hybernation (2-5 degrees) and heat acclimation (15 degrees) in relation to the heat resistance of the organism and muscle tissue at 2-5 degrees. A positive correlation has been observed between thyroid activity and the organismal heat resistance. At 15 degrees thyroid activity increases. It is the highest in females with a low initial heat resistance of the organism. It is assumed that changes in the heat resistance of the organism and muscle tissue are controlled by the thyroid gland. However, no correlation has been found between the initial (winter) level of the heat resistance of muscle tissue and the activity of thyroid.     

Physiological model of the stabilizing form of natural selection at the cellular level

By means of directional elimination of the parental gametes in frogs, the effects of two basic forms (i.e. normalizing and canalizing ones) of natural selection on the heat resistance level of muscle fibers in the progeny have been reproduced. Experimental evidence is presented that both male and female gametes account for hereditary transformation of cellular heat resistance as a quantitative physiological parameter. Polymodal pattern of regulation of this parameter is suggested which includes indispensable participation of both thermal and non-thermal factors of selection. The environmental temperature, as a selective factor, accounts for the formation of cellular heat resistance directly, whereas non-thermal factors exert their control on this parameter indirectly, associatively. It is suggested that the polymodal pattern of regulation of physiological functions presents the main mode of realization of canalizing form of natural selection.     

Heat resistance level of muscles and muscle models of salamander larvae kept at different temperatures and their thermal selection

The larvae of salamanders isolated from 19 pregnant females were grown to the middle of pre-metamorphosis. The siblings obtained from each single female were divided into two parts; larvae of one group were kept at 21 degrees C (control group), and those of the other--at 27 degrees C (experimental group). In all, 38 groups of experimental animals were employed. In animals kept at 21 degrees C the heat resistance of the organism, muscles and contractile muscle models were determined, whereas in those kept at 27 degrees C only the thermoresistance of muscles and their models only was registered. The time of loss of excitability in response to the electrical stimulus during heating in the Ringer solution at 36 degrees C served a criterion of heat resistance of muscles. The time of loss of contractility with the addition of ATP at 36 degrees C was a criterion of heat resistance of muscle models. The time of the onset of thermal shock at 34 degrees C being a criterion of heat resistance of the organism. It has been found that siblings showing a lower resistance level of muscles and of their models at 21 degrees C, when kept at 27 degrees C, increased their resistance much more as did siblings with the initially higher resistance. During the thermal selection, individuals of such initially less resistant families displayed selective advantages.     

Relationship between the heat resistance of different muscles and frog viability during heat selection]

An attempt was made to elucidate the relation between the survival of mature frogs Rana temporaria during sudden (unforeseen) thermal selection and the heat resistance of several muscles: m. interfalangealis, m. ileofibularis, m. sartorius, m. gastrocnemius and m. rectus abdominis. It has been found that of greater selective value are the individuals with lower heat resistance not in all muscles, but in those having lesser heat resistance, such as m. ileofibularis and m. sartorius.     

The relation of changes in the individual levels of heat resistance of muscle tissue to their initial values during heat acclimation of Asellus aquaticus

1. 1.|In hog slater, Asellus aquaticus, five extremities were consecutively isolated in the course of heat acclimation to study the pattern of changes in the level of the heat resistance of muscle tissue of each single specimen.

2. 2.|The initial response of the population, during acclimation, is for the muscle resistance of different individuals to become less varied. Then a simultaneous increase in tissue resistance occurs in all ammals, which is complete by the 6th day of acclimation. Afterwards the heat resistance of muscles in the majority of animals shows little change and then, in spite of maintenance of acclimation, it starts to return to its initial level.

3. 3.|Thermal acclimation causes a temporary decrease in the variability of the heat resistance of the muscle tissue and also a temporary stabilization of this physiological characteristic to a new level. This phenomenon is a phenotypical masking of genotypic differences in a physiological characteristic in the population studied during changes in environmental temperature.

4. 4.|At all the stages of acclimation the relation of individual increases in cellular heat resistance to their initial levels follows a hyperbolic exponential equation. This implies that to a rise in environmental temperature a population responds as an integral functional system.

Acclimation and Selection for Increased Resistance to Thermal Stress in Drosophila Buzzatii

Direct selection for increased resistance to a heat shock (41.9° for 90 min) was carried out using two replicate lines of Drosophila buzzatii that were derived from a large base population. Selected individuals were first acclimated to high temperature before selection, while control individuals were acclimated but not selected, and selection was performed every second generation. Resistance to heat shock with acclimation increased in selected lines. Without acclimation, a correlated smaller increase in heat-shock resistance was suggested. Survival of males was higher than that of females in all lines when tested with acclimation, but with direct exposure to high temperatures, survival of females was greater than that of males both in selection and control lines but not in the base population. From analysis of reciprocal cross progeny between lines, one selection line was found to possess a dominant autosomal factor that significantly increased resistance of males much more than resistance of females. Also suggestive was recessive traits on the X chromosome in both selection lines that increased thermotolerance. No cytoplasmic effects were found. After accounting for other effects, survival of F(1) flies was intermediate, suggesting that additive variation is present for one or more of the autosomes.     

Mating success at high temperature in highland‐ and lowland‐derived populations as well as in heat knock‐down selected Drosophila buzzatii

Thermal‐stress selection can affect multiple fitness components including mating success. Reproductive success is one of the most inclusive measures of overall fitness, and mating success is a major component of reproduction. However, almost no attention has been spent to test how mating success can be affected by thermal‐stress selection. In this study, we examine the mating success in the cactophilic Drosophila buzzatii Patterson & Wheeler (Diptera: Drosophilidae) derived from two natural populations that nearly represent the ends of an altitudinal cline for heat knock‐down resistance. Furthermore, we extended the analysis using laboratory lines artificially selected for high and low heat knock‐down resistance. Mating success at high temperature was found to be higher in the lowland than the highland population after a heat pre‐treatment. Moreover, individuals selected for heat knock‐down resistance showed higher mating success at high temperature than did individuals selected for low knock‐down resistance. These results indicate that adaptation to thermal stress can confer an advantage on fitness‐related traits including mating success and highlight the benefits of earlier heat exposure as an adaptive plastic response affecting mating success under stress of higher temperature.     

Method of repeated determination of muscle heat resistance in individual frog specimens]

The heat resistance of m. interphalangialis of fingers of hind extremities of Rana temporaria L. has been determined. No significant differences were observed in the average values of the heat resistance in fingers 3 and 5 isolated simultaneously. In separate individuals there exists a high positive correlation between the heat resistance levels of these muscles. When the muscles are isolated successively rather than simultaneously, the correlation degree depends on the time lapse between their isolation from the organism. With 1-14 days lapse the correlation breaks down, to be restored after a longer interval. Taking this into account, a method of successive isolation of m. interphalangialis can be used when studying the dynamics of muscle resistance within the same organism.     

Mechanistic model of fuel selection in the muscle

Fuel selection in human muscle is key to explaining insulin resistance. In obesity and type 2 diabetes mellitus, there is an increased content of lipid within and around muscle fibers. Changes in muscle fuel partitioning of lipid, between oxidation and storage of fat, contribute to the accumulation of intramuscular triglycerides and to the pathogenesis of both obesity and type 2 diabetes mellitus. A mathematical model of the aggregated metabolism in skeletal muscle was developed and the effects of fuel selection for lean and obese individuals under fasting conditions, insulin-stimulated conditions, and oscillating insulin conditions were examined. Model results were complementary to prior observations that elevated lipid oxidation during insulin-stimulated conditions is correlated with insulin resistance. The model also adequately simulated metabolic inflexibility between fat and glucose oxidation in the obese individual. A novel sensitivity analysis indicated the strong interaction effects of parameters of glucose and lipid oxidation pathways on the variables of each pathway.     

Effect of thermal selection of the male gametes on the resistance to temperature and chlorophos of the body and muscles in tadpoles of the common frog

A study was made of the effect of thermal selection of parental spermatozoa on the heat resistance of the whole organism and of muscles in progeny of Rana temporaria, as well as of the organismal resistance to pesticides (0.0025 M chlorophos). The thermal selection of spermatozoa was performed by exposing their suspension to 36 degrees C for 30-40 minutes. With tadpoles, the resistance of muscles to 38 degrees C, was determined, in addition to the resistance of the organism to 34 degrees and to 0.0025 M chlorophos. The results of selection were stage--specific: at stages of growth (stages 39, 42, 50) the heat resistance of the organism was lower and that of muscles was higher than in controls. At the stage of metamorphosis proper (stage 52) the heat resistance of both the organism and muscles increased. The thermal selection of parental spermatozoa exerted no effect on the resistance of the progeny to 0.0025 M chlorophos.     

The environmental temperature and physiological polymorphism of populations. 4. The effect of heat acclimation on the intensity and the genetic effectiveness of selection caused by heating

Heat acclimation is shown to result in the decrease in the intensity of thermal selection which is more evident at the lower as compared with higher heat doses. Heat acclimation is accompanied by a sharp decrease in the genetic effectiveness of thermal selection. Therefore the directed selection of individuals turns into a poorly selective or even completely non-selective order of death. This effect is achieved in three ways: (1) a decrease in individual variability of organismal heat resistance. (2) a decrease in the heritability of this trait and (3) a change in the order of death of individuals during thermal selection (rearrangement of selectivity).

The change in the intensity (δi) and genetic effectiveness (δE) of thermal selection due to the effect of acclimation demonstrates a functional homeostasis of the population. This homeostatic mechanism maintains population numerical composition and genetic structure under conditions of variable temperature. This can be expressed as follows: H = 1 - δi·δE where H is the level of homeostasis, δi is the organismal and δE the populational components of the total homeostasis.     

Seasonal changes in the body and muscle heat resistance of the green toad

A study was made of the dynamics of seasonal changes in heat resistance of the organism and muscles of the green toad taken from micropopulation living in the North-Eastern suburbs of Tashkent. The heat resistance of the organism was determined by the time of onset of the irreversible heat shock caused by the immersion of animals into water at 39 +/- 0.1 degrees C. The heat resistance of muscles (m. gastrocnemius) was determined by the time of the loss of response to electrical stimulus during heating in the Ringer solution (41 +/- 0.1 degrees). It has been shown that the organism as a whole is much more dependent on seasonal variations of environmental temperature as compared with muscle tissue. Of much importance for the changes in the heat resistance of muscle tissue are cyclic hormonal changes in the organism associated with the process of reproduction and preparation to it.     

Physiological polymorphism of a population of the common frog. II. The polymorphism of the type of muscle tissue heat resistance in stress]

A study was made of the dynamics in the heat resistance of m. interphalangealis of individual grass frogs under stress. The response of muscle tissue to injury can be differentiated into three types according to the initial heat resistance level: increase, decrease and phase change of the resistance. The pattern of response of muscle tissue of individual frogs to stress is one of manifestationss of physiological polymorphism of the population.     

Reactive changes in the heat-resistant muscle tissue of lake frogs during heat acclimation

A study was made of the effect of heat acclimation of animals on the individual changes in the muscle heat resistance in populations of Rana ridibunda belonging to European or Asiatic groups of the species. The relationship between the levels of heat resistance of muscle cells and the value of its changes are the same in the populations of these groups. It is believed that this relationship forms on the level higher than populational one.     

福建省中部地区抗寒速生尾巨桉优株筛选

本文通过自然选择与优势木选择方法,选择了适生性状良好的尾巨桉品种的多个优良单株。根据不同选择标准,筛选出抗寒适生优良单株21株,抗寒速生优势木单株13株;对所选单株采用无性系繁殖方法,利用1000mg/L ABT生根粉处理所选择优良单株的穗条,用营养袋扦插培育无性系种苗,并建立无性系采穗圃和优良单株基因库。     

Parasitism increases and decreases the costs of insecticide resistance in mosquitoes

Adaptations conferring resistance to xenobiotics (antibiotics, insecticides, herbicides, etc.) are often costly to the organism's fitness in the absence of the selecting agent. In such conditions, and unless other mutations compensate for the costs of resistance, sensitive individuals are expected to out-reproduce resistant individuals and drive resistance alleles to a low frequency, with the rate and magnitude of this decline being proportional to the costs of resistance. However, this evolutionary dynamic is open to modification by other sources of selection acting on the relative fitness of susceptible and resistant individuals. Here we show parasitism not only as a source of selection capable of modifying the costs of organophosphate insecticide resistance in mosquitoes, but also that qualitatively different interactions (increasing or decreasing the relative fitness of resistant individuals) occurred depending on the particular form of resistance involved. As estimates of the parasite's fitness also varied according to its host's form of resistance, our data illustrate the potential for epidemiological feedbacks to influence the strength and direction of selection acting on resistance mutations in untreated environments.     

Physiological polymorphism in a population of the common frog. I. The polymorphism of a population of the common frog for the trait of muscle tissue heat resistance]

A study was made of heat resistance (36+/-0.2 degrees C) of m. interphalangealis of the third finger of a hind extremity in animals of one population of Rana temporaria L. living on the boundary between Leningrad region and Pskov region. Within this population, the existence of three groups of individuals differing in heat resistance levels of their m. interphalangealis is postulated. This conclusion is based on the distribution curve of heat resistance values and on the application of the probit-method. The distribution of the frequency of occurrence of individuals in these three groups follows Hardy-Weinberg's equation.