The problem of the skin derivatives' origin in the amniote evolution. The skin appendages--scale, feather, and hair

Overview of modern data on morphology of the skin derivatives in the higher vertebrates is given. Analysis of convergent similarities between the hair and feathers themselves as well as between their follicles makes it possible to forward a "generative" concept of the evolutionary origin of various ecto-mesodermal derivatives, such as keratinized dermal appendages (scales, feathers, hair). This concept appeared as a result of the author's studies on the skin derivatives, as well as of the data on molecular biology and the tissue engineering showing similar mechanisms of morphogenesis of the dermal appendages. Recurrently published ideas on various heterochronies in generations of the skin derivatives both in the onto- and the phylogeneses are also taken into acount. Various dermal appendages have appeared in the evolution of the higher vertebrates as independent generations of the ecto- and mesodermal tissues. Their parallel origin was caused by similar changes in the metabolism and molecular regulation of morphogenesis.     

The cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Urals Radioactive Trace zone

In bone marrow cells of rodents (Apodemus (Sylvaemus) uralensis Pall., 1811, Apodemus agrarius Pall., 1771) inhabiting the Eastern Urals Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of Urals, the chromosome instability and 90Sr accumulation in bones were investigated. Intensive mutagenic process in both species from impact plots (the soil pollution by 90Sr 2322-16690 kBq/m2) was found. Significant positive correlation of aberrant cells frequencies and 90Sr was shown. Possible causes of the lack of resistance to long-term mutagenic factor (over 100 generations since 50 years from the accident) such as migration of animals and specific configuration of the EURT zone (narrow extended territory with sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.     

Differentiation of rat lens epithelial cells in tissue culture. (I) Effects of cell density, medium and embryonic age of initial culture.

The growth and differentiation of rat lens epithelial cells in tissue culture were studied. Cells could be maintained for a number of generations in an undifferentiated state in suspension culture. When cultured as monolayers, they grew and differentiated in a series of six defined stages described here. These stages include morphological changes (elongation, followed by cell "spreading" or formation of cell aggregates), and biochemical changes (appearance of nu-crystallin protein as detected by immunofluorescence). The process of differentiation appeared to be accelerated in the vicinity of elongated cells, occurred more rapidly at high cell density, and required frequent changes of medium. This suggests that cell-cell communication, and not medium factors, may be essential for promoting differentiation. The final morphology of the differentiated cells differed, depending on the embryonic age of the rats used as a source of lens epithelial cells. This implies that the programme for differentiation changes as a function of the embryonic age of the lens.     

Stability of the carrier state in bacteriophage M13-infected cells.

Bacteriophage M13-infected carrier cells were shown to be unstable to prolonged growth under all conditions. Carrier Hfr cells were transferred in dilute culture (10(3) to 10(4)/ml), where reinfection was impossible and the physiology of the cell was minimally altered. After an initial period of about 10 generations, during which all cells in the culture remained infected, there was exponential decay in the proportion of infected cells in the culture. Uninfected cells that appeared were M13 sensitive. Hfr and F' males were also transferred serially at high cell densities (10(7) to 10(9)/ml), where high levels of phage should permit reinfection. The proportion of phage-producing cells in the cultures remained constant for 7 to 15 generations and then dropped exponentially on further growth. Non-phage-producing cells appearing in the culture were refractory to infection by M13; in some cases cells scored as non-phage producers for 20 generations were observed to produce phage on further growth in liquid culture. F'trp+ males infected with M13 lost trp+ function almost immediately; this was not regained in these experiments. Infected cells grown in dilute culture or on plates remained infected longer, produced more PFU per cell for a longer period, and retained trp+ function in F'trp+ males for over 90 generations. Non-phage-producing cells that appeared were sometimes phage resistant, sometimes phage sensitive. The existence of a phage-related material accumulating at high cell densities and affecting expression of free episomes, episomal expression in Hfr males, and phage synthesis itself is suggested.     

Kinetic aspects of follicle development in the rat

The eighth and ninth generations of follicle growth in rats represent a turning point in development. This stage is characterized by establishing a complete regulatory control based on feedback in follicle development. The feedback between follicles and gonadotropin secretion regulates a number of follicles maturing for ovulation. Gonadotropins seem to play a permissive, and not a directive part in regulation of follicle development in the eighth and ninth generations. By this stage of development, possibilities for theca and granule cells become sharply limited. Whereas expression of many maturation features may be hastened or hindered by changes in hormonal status, the result of development cannot be changed. Although only last generations of theca and granule cells exhibit mature functional features, their precursors seem to become committed to a single direction of development at early stages of follicle development. Neither the stage when precursor cells become irreversibly committed to differentiation into granule or theca cells, neither regulatory factors which determine this process have been identified yet. We suppose that precursor cells become committed to thecal tissue compartment when the follicle is at a primordial stage of development. Precursors of all the follicle components may already be assembled into one unit by the beginning of follicle growth. Accumulation of sufficient number of precursor cells around the primordial follicle may serve as a signal for follicle growth initiation. We think that the understanding of follicle postnatal growth and development should be based on understanding of origins, destiny, and possibilities of cells which form ovary and its compartments. First generations of follicle growth seem to be most promising for future research.     

Analysis of mutations induced by alkylating compounds in Drosophila sperm. I. Character of visible changes induced by N-nitrosoethylurea and ethylmethanesulfonate in a succession of Drosophila generations]

Newly appearing hereditary traits were observed in several generations of Drosophila melanogaster: changes in eye and body colour, wing shape, number and shape of chaetae. The results obtained may be interpreted as the evidence for the realization of potential changes induced by NEU and EMS into visible mutations during 1-4th generations. X-irradiation (at a dose of 1000 r) of males from the first generation did not affect the realization of long-living potential changes induced by NEU.     

The use of the immobilization of whole living cells to increase stability of recombinant plasmids in escherichia coli

Immobilization of whole living cells was used as an experimental approach to enhance plasmid stability in cultured recombinant micro-organisms. pTG201 plasmid which is very unstable in continuous cultures with free cells, was found to be extremely stable in continuous cultures with immobilized cells.To elucidate the mechanism by which immobilization increases the plasmid stability, we analyzed the growth of pTG201-containing E. coli W3101 cells within the gel beads. We found that in immobilized continuous culture, plasmid-free segregants were not detected even after 240 generations. This appears to be due to the mechanical properties of the gel-bead system that allow only a limited number of cell divisions (10–16) to occur in each clone of cells before the clone escapes from the gel bead. This number of generations is not sufficient for the plasmid-free cells to appear within the cavities compared to what was observed in a free-system (plasmid-free segregants were detected after a lag period of approximately 25–30 generations). Even when they appear, they cannot overcome the culture. From the data described in this paper we conclude that cells released from the gel beads at any time during continuous culture are cells which are issued from cells grown in the cavities for only 10–16 generations.     

The influence of climatic changes on range expansion and phenology of the Colorado potato beetle (Leptinotarsa decemlineata,Coleoptera, Chrysomelidae) in the territory of Russia

Analysis of expansion of the potential range of the Colorado potato beetle Leptinotarsa decemlineata Say and shifts of the zones with different number of generations per season was carried out using cartographic modeling. The shifts were caused by the climate changes in Russia observed in recent decades. The annual sum of effective mean daily air temperatures was selected as the main criterion which determines both the suitability of the area for the Colorado potato beetle and the number of generations that can be produced in one season. The main range expansion was observed in the east direction, and the greatest changes took place during expanding of the zones with the possible development of one or two generations. The boundaries of the zone where development of three generations is possible changed to a lesser degree.     

Cyclic localization change of Golgi apparatus in Sertoli cells induced by mature spermatids in rats

Previously we reported that the intracellular localization of the Golgi apparatus of rat Sertoli cells changes during the seminiferous epithelial cycle, and that the cyclic changes seem to be correlated to specific generations of germ cells. To ascertain which generations of germ cells are responsible for the cyclic changes, we determined the relative volume of the Golgi apparatus within the basal, mid, and apical cytoplasm of Sertoli cells in testes with and without mature spermatids. In normal adult rats, the Golgi apparatus was usually localized exclusively in the basal cytoplasm, whereas at stages VII-IX it increased remarkably in mid and apical cytoplasm, with a concomitant decrease in the basal cytoplasm. In young adult testes without spermatids at steps 15-19 of spermiogenesis (2nd layer spermatids), the Golgi apparatus was localized in the basal cytoplasm throughout the seminiferous epithelial cycle. Orchiopexy maintained for 35 days following 60 days of cryptorchidism allowed germ cells to regenerate to spermatids at steps 1-14 of sperminogenesis (1st layer spermatids), but failed to change the intracellular localization of the Golgi apparatus in Sertoli cells. At 50 days after orchiopexy, when all generations of germ cells appeared in the tubules, the cyclic changes in localization of the Golgi apparatus were restored similar to those in normal adult testes. These findings indicate that the cyclic change in localization of the Golgi apparatus in Sertoli cells is evoked by the presence of 2nd layer spermatids.     

Structure and Function of Transfer Cells in the Sporophyte Haustorium of Funaria hygrometrica Hedw: I. THE DEVELOPMENT AND ULTRASTRUCTURE OF THE AUSTORIUM

The development of the sporophyte-gametophyte interface in themoss, Funaria hygrometrica Hedw., is described with the aidof light- and electron-microscopy. The outer walls of the cellsthat abut the haustorial cavity in both generations developlabyrinths typical of transfer cells. This feature is more apparentin the epidermal cells of the sporophyte foot (haustorium),where development can be split into three main stages. The primarygrowth stage, which is complete at about the time the calyptradetaches from the ripened archegonium, involves the formationof transfer cells. The secondary stage is characterized by thedeposition of amorphous inclusions in the wall labyrinth ofthe transfer cells. The tertiary stage, which commences as thesporophyte capsule ripens, entails de-differentiation of thetransfer cell wall labyrinth to form a thick, heavily encrusted,outer cell wall. The pattern of development of these cells iscorrelated with changes in gametophyte- sporophyte translocationcapabilities.     

Transgenerational consequences of acute antenatal stress in pregnant rats

The aim of the present study was to investigate the effects of acute hypobaric hypoxia in early organogenesis on three following generations including pregnant females (FO) and two generations of their posterity (F1 and F2). Animals of all generations mentioned above demonstrated marked changes in motor and exploratory activity as well as in anxiety level while the litter of F1 and F2 generations showed also changes in learning ability. Besides, acute hypobaric hypoxia interfered in maternal behavior of females of the FO and F1 generations. The revealed changes kept till pubertal period. Possible mechanisms of gestational stress influence are discussed.     

Variation in the Competence of Tobacco Pith Cells for Cytokinin-Habituation in Culture

Pith parenchyma tissues of tobacco sometimes lose their exogenous requirement for a cell division factor such as the cytokinin, kinetin. This process, known as cytokinin habituation, appears to involve epigenetic changes since it is a heritable change in cell phenotype which is directed, regularly reversible, and leaves the cell totipotent. In this report, we show that pith cells in culture consist of at least two types of cytokinin-requiring cells. The first type habituates rapidly under inductive conditions. The second type continues to express the cytokinin-requiring phenotype for many cell generations in culture but retains the capacity for habituation. These findings suggest that pith cells differ in their competence to habituate and that different states of competence are inherited by individual cells.     

Asynchrony in the growth and motility responses to environmental changes by individual bacterial cells

Knowing how individual cells respond to environmental changes helps one understand phenotypic diversity in a bacterial cell population, so we simultaneously monitored the growth and motility of isolated motile Escherichia coli cells over several generations by using a method called on-chip single-cell cultivation. Starved cells quickly stopped growing but remained motile for several hours before gradually becoming immotile. When nutrients were restored the cells soon resumed their growth and proliferation but remained immotile for up to six generations. A flagella visualization assay suggested that deflagellation underlies the observed loss of motility. This set of results demonstrates that single-cell transgenerational study under well-characterized environmental conditions can provide information that will help us understand distinct functions within individual cells.     

The biological effects in animals in relation to the accident at the Chernobyl Atomic Electric Power Station. 8. The status of cellular immunity in different generations of rats]

In studying immunity in laboratory rats of different generations (P, F1 and F2) brought up in Chernobyl in 1989-1990 the authors have revealed the development of leuko- and lymphopenia; decrease in the absolute content of immunocompetent cells bearing Fc receptors to IgG; stable and long-lasting suppression of blood NK cell activity; reduction of antibody-dependent cytotoxicity; and changed ability of blood lymphocytes to interact contactly with allogenic mast cells. The most considerable disorders have been found in 6- and 9-month-old F1 rats and in 3- and 6-month-old F2 rats.     

PRIMITIVE ERYTHROPOIESIS IN EARLY CHICK EMBRYOGENESIS : I. Cell Cycle Kinetics and the Control of Cell Division

The primitive line of embryonic chick blood cells develop as a relatively homogeneous cohort of cells. Using an analysis based on the continuous uptake of thymidine-³H, we have established the generation time, G1, S, and G2 for progressively more mature generations of these immature erythroblasts. The data indicate that after the initiation of hemoglobin synthesis, the average cell will yield six generations of hemoglobin producing erythroblasts. The older generations of erythroblasts exhibit a longer generation time, G1, S, and G2 than the earlier generations of erythroblasts. Other methods of analysis corroborated these findings. One of these methods, an estimate of total erythrocyte productivity from the primitive stem cells (hematocytoblasts), led to the conclusion that the erythroblast cell lineage might be initiated as early as the sixth or seventh division following fertilization. In addition, primitive erythroblasts characterized by one set of cell cycle parameters, when grown in serum associated with erythroblasts of different parameters, showed no alteration in mitotic behavior. These results suggest the presence of programmed cell division not immediately cued by extracellular influence.     

Evidence for cell generation controlled proliferation in the small intestinal crypt

In this paper we discuss the hypothesis that cell proliferation is controlled by the number of generations after leaving an 'eternal' stem cell. The theory is based on a simulation of the kinetic behaviour of cells in the intestinal crypts. There is evidence of three, four and five generations of cells which are allowed to enter mitosis in the lower and upper part of the normal intestinal tract, and in some disease states, respectively. We suggest an internal proliferation control: some kind of knowledge that cells carry from generation to generation. It is an open question what sets and changes the generation counter: internal genetic information or external influences such as growth factors or chalones. The geometric shape of the epithelial tissue in the intestinal tract can be understood as the steady state of a highly dynamic process. Age and death are determined from the beginning; cell-cell interaction or communication is not necessary and can be neglected. Our theory will be illustrated using the intestinal crypts as they are easily accessible, of a simple structure and completely described in the literature.     

On Temporal Dynamics of Morphological Variations in the Black Sea Mussel Mytilus galloprovincialis Lam.

Temporal variations in morphological characters of the shells were studied in 12 samples of mussels M. galloprovincialis Lam. from the Black Sea commercial collectors that belong to different generations. The samples were shown to be diverse in every studied character and the degree of characters' variability in the samples was different. The morphological diversity of samples diminished with age. Different generations from the same habitat had specific features of age-related variability expressed as different rates of age-related changes and direction and degree of variability. This effect is considered as an index of the influence of ecological conditions on the shell growth and formation.     

The effective number of a population that varies cyclically in size. I. Discrete generations

We consider a dioecious population having numbers of males and females that vary over time in cycles of length k. It is shown that if k is small in comparison with the numbers of males and females in any generation of the cycle, the effective population number (or size), N(e), is approximately equal to the harmonic mean of the effective population sizes during any given cycle. This result holds whether the locus under consideration is autosomal or sex-linked and whether inbreeding effective population numbers or variance effective population numbers are involved in the calculation of N(e). If, however, only two successive generations in the cycle are considered and the population changes in size between these generations, the inbreeding effective population number, N(eI), differs from the variance effective population number, N(eV). The mutation effective population number turns out to be the same as the number derived using calculations involving probabilities of identity by descent. It is also shown that, at least in one special case, the eigenvalue effective population number is the same as N(eV).