Control Of Ontogeny Research Articles

Genes and Ontogenes in Drosophila: The Role of RNA Forms

The independent hereditary factors, such as Mendelian genes, are not sufficient for the existence and operation of genetic systems. The hereditary factors of different type were searched for. A new class of mutations, referred to as conditional mutations, was discovered in Drosophila melanogaster. Such a mutation dies in a restrictive genotype but survives and reproduces in a permissive genotype. Besides their conditional nature, mutations in a permissive genotype display a set of specific features that drastically distinguish them from conventional mutations, namely, they (1) are dominant; (2) are as a rule, lethal; (3) have drastically decreased fertility; (4) interact with chromosomal rearrangements; (5) switch the genome from a stable to an unstable state; (6) increase the basal metabolism; (7) induce modifications and morphoses; and (8) their manifestation is inherited in a parental manner. Four properties of these mutations-conditional manifestation together with (1), (4), and (8) suggest that the mutant genes (1) are segments of DNA; (2) their products are RNA duplexes (3) active in germ cells and (4) repeated in the genome. Emergence of morphoses in mutants suggests that the genes are involved in the control of ontogeny. Correspondingly, these genes were named ontogenes. Thus, the genetic system comprises the genes working according to a DNARNA- protein script and the ontogenes following a DNA-RNA script. The first entity is engaged in production of the building material for the organism, proteins, while the second entity controls this process during preparation of the individual developmental program. These different functions of genes depend on the type of transcript formed from DNA as well as the time and place of its origin on DNA.

Thyroid responsiveness of the large African barb Labeobarbus intermedius (Teleostei; Cyprinidae): Individual variability and morphological consequences

Thyroid hormones (THs), produced by the thyroidgland, play an important role in the regulation of ontog-eny in bony fishes. They influence the rate of individualdevelopment of the body as a whole, as well as the ratesof growth and differentiation of its particular structures[1]. Definitive morphology of fishes is a result of inter-action between the developing body and a hormone,and depending on the TH level and an ability of thebody to respond to TH, i.e., TH-responsiveness.The TH level depends on the functional activity ofthe thyroid gland. A low activity and, as a result, lowTH levels lead to slowing down the ontogeny. On thecontrary, high TH levels accelerate the ontogeny [1, 2].Differences in the activity of the thyroid gland canresult in variability of the expression of morphologicalfeatures [2]. Recently, indirect data on individual vari-ability of TH-responsiveness in the large African barbLabeobarbus intermedius were reported. They demon-strated that juveniles of this fish differently respondedto similar doses of exogenous THs under experimentalconditions [3, 4]. Taking into account an important roleof TH-responsiveness in the ontogeny control, we stud-ied individual variability of TH-responsiveness and itsinvolvement in intraspecific morphological diversifica-tion in fishes.We compared morphological changes inL. intermedius siblings grown at a high level of exoge-nous TH. We focused our attention on the serial struc-tures that usually decrease in number when theL. intermedius siblings are growing under a high THlevel [3, 4].The eggs were obtained from the crossing ofL. intermedius spawners taken from a Lake Tana tribu-tary, the Gumara River (Ethiopia) and divided into twogroups. The first experimental group was put into amedium with a high TH content, namely, 2 × 10

The reproductive strategy and immune status of rodents in an environment altered by industrial activity

27 The nature and mechanisms of animal population adaptation to chronic irradiation is one of the most important problems of modern radioecology. The results of long-term monitoring of mouselike rodent populations in the head portion of the Eastern Ural radioactive trail (EURT) show numerous quantitative and qualitative disturbances in the hemopoietic and immune systems of the animals [1, 2], as well as substantial cytogenetic [3] and morphogenetic [4] alterations. At the same time, the numbers of dominant rodent species in the EURT zone have remained the same as in the background areas for many years, and their fertility is sometimes even higher than the control values [1, 5]. Functions of the immune system are diverse, it is involved in maintenance of the cytogenetic homeostasis, control of offspring quality [6], adaptation [7], and control of ontogeny [8]; immune reactivity is also related to demographic processes. Therefore, it may be presumed that disturbances caused in animals by radioactive contamination of the environment are also related to alteration in the immune system. The results presented below demonstrate that disturbances in the controlling (eliminating) and regulatory functions of the immune system are leading factors of the increase in the reproduction rate of mouselike rodent populations of areas altered by industrial activities and may be regarded as mechanisms of adaptation to radioactive contamination. Experiments were performed to analyze the reproductive characteristics of laboratory mice under the conditions of immunosuppression, and the results of the model experiment were compared with the reproductive parameters of rodents from the EURT and neighboring areas. The immunosuppressant Cyclophosphanum was intraperitoneally injected to females from the experimental group (strain CBA) during seven days before mating; control animals were injected with physiological saline (a total of 84 mice were used). The immunomodulator effect was verified by morphological, physiological, and immunohematological parameters. The fertility parameters and embryo loss were calculated, the total number of the offspring was recorded, and the changes in body weight during early ontogeny were monitored. The Excel software package was used for treatment of the data. The morphological and physiological verification of the immunosuppressant effect showed that the groups significantly differed in almost all indices of internal organs (Table 1). Regarding the hemopoietic system, the experimental group was characterized by a considerable decreased in the cellular density of the bone marrow and spleen, a considerable leukopenia accounted for by a decrease in the main populations of leukocytes

Ontogeny affects response of northern red oak seedlings to elevated CO2 and water stress: II. Recent photosynthate distribution and growth.

Northern red oak in the western Lake States area of the USA exists on the most xeric edge of its distribution range. Future climate-change scenarios for this area predict decreased water availability along with increased atmospheric CO2 . We examined recent photosynthate distribution and growth in seedlings as a function of CO2 mole fraction (400, 530 and 700 μmol mol-1 CO2 ), water regime (well watered and water-stressed), and ontogenic stage. Water stress effects on growth were largely offset by elevated CO2 . Water stress increased root mass ratio without concurrently increasing allocation of recent photosynthate to the roots. However, apparent sink strength of water-stressed seedlings at the completion of the third growth stage tended to be greater than that of well watered seedlings, as shown by continued high export, which may contribute carbon reserves to support preferential root growth under water-stressed conditions. Elevated CO2 decreased apparent shoot sink strength associated with the rapid expansion of the third flush. Carbon resources for the observed enhanced growth under elevated CO2 could be provided by enhanced photosynthetic rate over an increased leaf area (Anderson & Tomlinson, 1998, this volume). Increased sink strength of LG seedlings under water-stressed conditions, together with decreased apparent shoot sink strength associated with growth in elevated CO2 provide mechanisms for offsetting water stress effects by growth in elevated CO2 . Careful control of ontogeny was necessary to discern these changes and provides further evidence of the need for such careful control in mechanistic studies.