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Том 6, № 1 (2016)

Article

Localization and functions of mesenchymal stromal cells in vivo

Payushina O.

Аннотация

The study of mesenchymal stromal cells (MSCs) is a very topical problem. Numerous experiments in vitro advanced the understanding of MSC biology to a great extent. However, many aspects of their behavior in vivo still remain unclear. This review deals with MSC localization and functioning in an organism. MSCs are present in various tissues, changing their numbers and traits during ontogenesis. Pericytes, or adventitial cells, can be considered possible equivalents of MSCs in vivo. Self-maintenance, proliferation, and differentiation of MSCs are controlled by their tissue microenvironment, which includes the surrounding cells, soluble molecules, and extracellular matrix. At early stages of ontogenesis, MSCs probably migrate throughout an organism and populate various tissues. The migration occurs also through a mature organism when tissues happen to be damaged. MSCs move pointedly to the damaged parts and render a reparative effect that is due primarily to the paracrine production of bioactive molecules and immunomodulatory properties of MSCs rather than their differentiation. An important function of MSCs is the creation of hematopoietic microenvironment by the secretion of cytokines and chemoattractants, as well as by direct interaction with hemopoietic cells. It is possible that MSCs sustain the stable functioning of not only hematopoietic but also other tissues. Their unique features make them quite attractive for clinical use, although the successful introduction of MSC into medical practice requires further study of their interaction with the recipient organism and their effect on regeneration.

Biology Bulletin Reviews. 2016;6(1):1-10
pages 1-10 views

Assessing the relative strength of the effects of food resources and predators on a population: A review of methods

Kasparson A.

Аннотация

An understanding of the mechanisms that underlie species distribution and abundance is one of the key problems in population ecology. In order to tackle this problem, it is important to assess the relative strength of the effects of food and predators (consumers) on a focal population. In this study we analysed the advantages and disadvantages of the basic methods that are used to quantify the relative strength of the two types of effects. These methods can be divided into two groups. In the first group, we included the search for examples that are consistent with a proposed hypothesis, the assessment of correlations of abundance at adjacent trophic levels and biomanipulations. What is common for these methods is that they assume the existence of only one type of effect—either bottom-up or top-down. The methods of the second group assume the simultaneous presence of both types of effects and are aimed at quantifying their relative strength. This group includes factorial design experiments and the population-dynamics approach (analysis of population growth, death and birth rates). Here, we have shown that, due to the constraints of each of the methods of the second group, none of them can be considered universal. However, their combined application can be a promising approach to the assessment of the mechanisms that drive population abundance variability, both in experimental and field studies.

Biology Bulletin Reviews. 2016;6(1):11-23
pages 11-23 views

CO2-exchange in tundra ecosystems of Vaygach island in an unusually warm and dry vegetation season

Zamolodchikov D.

Аннотация

In the summer of 2013, field studies on the CO2 exchange in the tundra ecosystems of Vaygach Island were conducted by the chamber method. Models establishing the relationship between the values of CO2 fluxes and key ecological factors, such as temperature, photosynthetic active radiation, the leaf mass of vascular plants, and the depth of soil thawing, have been proposed. According to the model estimates, during the vegetation season of 2013, the tundra ecosystems of Vaygach Island were a source of CO2 emission into the atmosphere (31.9 ± 17.1 g C m–2 season–1) with a gross primary production of 136.6 ± 18.9 g C m–2 season–1 and an ecosystem respiration of 168.5 ± 18.4 g C m–2 season–1. The CO2 emission from the soil surface (soil respiration) was, on average, 67.3% of the ecosystem respiration. Unusually warm and dry weather conditions in the summer of 2013 were the cause of carbon losses by tundra ecosystems. The air temperature during summer months was twice as high as the values of the climatic norm for 1961–1990. A trend revealed in the works of recent decades of an increased carbon sink to the tundra ecosystems in the circumpolar Arctic may be interrupted by an increased frequency and scale of unusually warm weather events.

Biology Bulletin Reviews. 2016;6(1):24-38
pages 24-38 views

Succession caused by beaver (Castor fiber L.) life activity: II. a refined markov model

Logofet D., Evstigneev O., Aleinikov A., Morozova A.

Аннотация

The refined Markov model of cyclic zoogenic successions caused by beaver (Castor fiber L.) life activity represents a discrete chain of the following six states: inundated forest, swamp forest, pond, herbaceous swamp, shrub swamp, and moist forest, which correspond to certain stages of succession. Those stages are defined, and a conceptual scheme of the probable transitions between them for one time step is constructed from a knowledge of beaver behavior in small river floodplains of the Bryanskii Les Nature Reserve. We calibrated the corresponding matrix of transition probabilities according to the optimization principle: minimizing differences between the model outcome and reality; the model generates a distribution of relative areas corresponding to the stages of succession, which must be compared to those gained from case studies in the Bryanskii Les Reserve during 2002–2006. The time step of the model is two years, and the first-step data in the sum of differences are given various weights, w (between 0 and 1). The value of w = 0.2 is selected due to its optimality and for some additional reasons. Using the formulas of the finite homogeneous Markov chain theory, we obtained the main results of the calibrated model, namely, a steady-state distribution of stage areas, indexes of cyclicity, and mean durations (Mj) of succession stages. The calibration results provide an objective quantitative character to the expert knowledge of the course of succession and are properly interpreted. The data from 2010, which are not involved in the calibration procedure, made it possible to assess the quality of prediction by the homogeneous model in the short term (as of 2006): the error of the model area distribution relative to the distribution observed in 2010 falls into the range of 9–17%, with the best prognosis being for the least optimal matrices (rejected values of w). This fact indicates a formally heterogeneous nature of succession processes in time. Thus, the refined version of the homogeneous Markov chain has not eliminated all of the contradictions between the model results and expert knowledge, which suggests a further model development towards a “logically inhomogeneous” version and/or refusal to postulate the Markov property in the conceptual scheme of succession.

Biology Bulletin Reviews. 2016;6(1):39-56
pages 39-56 views

Gypsy moth Lymantria dispar L. in the southern Urals: Patterns in population dynamics and modeling

Soukhovolsky V., Ponomarev V., Sokolov G., Tarasova O., Krasnoperova P.

Аннотация

The population dynamics of gypsy moths from different habitats of the southern Urals was analyzed. Patterns of cyclic changes in the population density were examined. The conjugation of the time series of gypsy moth population dynamics from different habitats at the territory of the southern Urals was assessed. Relationships between the population density and weather conditions were studied. Based on the results, a statistical model of population dynamics in gypsy moth from the southern Urals was developed. The effects of regulatory and modifying factors on the population dynamics were assessed.

Biology Bulletin Reviews. 2016;6(1):57-69
pages 57-69 views

Selective feeding in fish: Effect of feeding and defensive motivations evoked by natural odors

Kasumyan A., Marusov E.

Аннотация

The effect of feeding and defensive motivations evoked by natural olfactory signals (food odor, alarm pheromone) on the choice and consumption of food items of different colors and tastes were examined in fish (koi Cyprinus carpio, roach Rutilus rutilus). Agar-agar pellets of red and green color containing one of the amino acids (glycine, L-proline, L-alanine; in the concentration of 0.1 M) were simultaneously given to single fish in pure water or in water extract of Chironomidae larvae or in water extract of fish skin. It was found that odors have different effects on the food-searching activity and food selectivity in fish. On the background of food odor, fish grasp pellets more often than in pure water. The equal choice of red and green pellets in pure water changes to a preference for red ones in the presence of food odor. Despite an increase in the absolute number of grasped pellets, their relative consumption is reduced and is replaced by a selective consumption of pellets with glycine regardless of their color. The increasing demand for food quality due to increased feeding motivation in response to food odor is an important adaptation enhancing the mechanisms of food selection and consumption. The defensive motivation caused by the alarm pheromone suppresses the feeding activity of fish. Fish grasp pellets several times less often than in pure water and reject most of them. There are no changes in color or taste preferences. The feeding behavior of both species is characterized by manipulation activity; it is higher in the cases of fish stimulation by food odor and when the pellet was finally rejected.

Biology Bulletin Reviews. 2016;6(1):70-83
pages 70-83 views

Correlations between gynoecium morphology and ovary position in angiosperm flowers: Roles of developmental and terminological constraints

Sokoloff D.

Аннотация

The angiosperm gynoecium consists of elementary units called carpels. These can be free (apocarpy) or united (coenocarpy, or syncarpy in a wide sense). One of the most complicated problems of evolutionary morphology of angiosperms is distinguishing monomerous and pseudomonomerous gynoecia. The former are assumed to be derived by the reduction of the carpel number in apocarpous gynoecia, and the latter are assumed to be derived by reduction of gynoecia with united carpels. Pseudomonomerous gynoecia have one fertile carpel and more or less prominent traces of sterile carpel(s). In extreme cases of reduction, pseudomonomerous gynoecia are very similar to monomerous, even though the two types have completely different evolutionary histories. G.B. Kedrov (1969) proposed a new approach to resolve the issue. Using the absence of polymerous free-carpellate gynoecia with inferior ovaries, he suggested that there is a constraint for epigyny in plants with free carpels. Therefore, in taxa with disputable morphological interpretations, the gynoecium should be treated as pseudomonomerous (and not monomerous) if the ovary is inferior. A critical review of the concept of G.B. Kedrov showed that his ideas would suggest reinterpretation of widely accepted views on gynoecium morphology in several key families of basal angiosperms. An alternative view is proposed: for the most important types of epigyny in angiosperms, the “constraint” for the combination of inferior ovary and apocarpy is due to the definition of the term “apocarpy” only. There is no biological sense in this “constraint.” The existence of two other morphogenetic constraints is proposed: (1) on the presence of a typical inferior ovary in monomerous gynoecia with conduplicate carpel and (2) on the radial (sectorial) fusion of individual carpels with stamens or perianth members without fusion of these groups into an entire structure. The possible biological nature of these constraints is discussed.

Biology Bulletin Reviews. 2016;6(1):84-95
pages 84-95 views

The effect of photosynthesis parameters on leaf lifespan

Vasfilov S.

Аннотация

Leaf longevity (LL) varies widely among higher plants. LL is a sum of the functional component LLf (the duration of active photosynthesis) and the nonfunctional component LLn (duration of the period during which photosynthesis does not occur). LLn corresponds to the period of winter dormancy in the case of evergreen boreal species. The photosynthetic potential of the leaf (PPL)—that is, the maximal possible amount of CO2 fixed during the leaf lifespan—is inferred from the dynamics of the maximal rate of photosynthesis (Pa) during LLf. Pa reaches a peak value (Pa max) during leaf “maturation.” The photosynthetic potential depends on the functional lifespan to a greater degree than on the maximal rate of photosynthesis. The PPL/LLf ratio determines the rate of realization of the photosynthetic potential during the lifetime of the leaf. LLf is strongly and positively correlated to LL, and LL can therefore be considered a parameter determining the rate of PPL realization, along with LLf (for a first approximation). The prolonged LLf characteristic of evergreen species gives them an advantage—a higher photosynthetic potential than that of deciduous species. Consequently, PPL is realized more slowly in evergreen species than in deciduous species. An increase of LLf and LL is accompanied by an increase of leaf construction cost (LCCa) and a decrease of the photosynthesis rate, with the decrease per unit dry weight (Pm) being much more pronounced than that per unit leaf area (Pa). This points to a much higher contribution of cell wall weight to the total dry weight of longlived leaves of evergreen species than to that of short-lived leaves of deciduous species. Unidirectional changes of PPL and LCCa stabilize leaf payback (LP). Species with a short (long) LLf and high (low) rate of PPL realization are characteristic of early (late) succession and habitats with favorable (unfavorable) environmental conditions for photosynthesis and growth, since these species are more competitive under said conditions. Species with a high rate of PPL realization have an advantage in competition under conditions favorable for photosynthesis and growth, since they use environmental resources for rapid growth and expansion. The rate of photosynthetic potential realization characterizes the aging rate of the leaf.

Biology Bulletin Reviews. 2016;6(1):96-112
pages 96-112 views

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