ABSTRACT
We studied the effects of extremely low-frequency electromagnetic field on the ovaries in rats. The female rats were exposed to a 30 Hz sinusoidal magnetic field of 4 kA/m for 2 h per day for a period of 10 weeks, including the period of embryonic development. After the exposure, the duration of the estrous cycle and serum levels of luteinizing hormone, follicle stimulating hormone, progesterone, and estradiol E2 were measured in different phases of the estrous cycle and morphological changes in the ovaries were evaluated. Lower levels of follicle stimulating hormone in the proestrus and progesterone in the estrus phase were found; in the ovaries, the content of primordial follicles was lower than in the control. The exposure to electromagnetic field in the selected mode caused no significant defects in the structure and function of rat ovaries.
Subject(s)
Electromagnetic Fields , Ovary/metabolism , Animals , Estradiol/metabolism , Estrous Cycle/metabolism , Female , Follicle Stimulating Hormone/metabolism , Gonadotropins/metabolism , Luteinizing Hormone/metabolism , Ovarian Follicle/metabolism , Ovary/radiation effects , Progesterone/metabolism , Rats , Rats, WistarABSTRACT
An attempt was undertaken to develop a model system based on artificial cell cycle synchronization by means of reversible mitosis blocking in zebrafish embryos for studying the role of cell cycle synchrony in embryogenesis. Dechorionized and intact embryos at the stages of 512-cell blastula and 75% epiboly were treated with nocodazole and then washed within several times of exposure. When working on dechorionized embryos, we succeeded to obtain complete block mitosis in the presence of low nocodazole concentrations: 0.5-1.0 microg/ml. Block of mitosis was relieved in all experimental series within a certain time after the beginning of washing. This inertia depended on both nocodazole concentration and duration of treatment. The nocodazole elimination was significantly accelerated only after five (or more) changes of washing medium containing DMSO. As a result, the conditions were established for obtaining a parasynchronous cell population in the zebrafish gastrulas with a peak of mitosis up to 17.2%.
Subject(s)
Embryo, Nonmammalian/cytology , Zebrafish/embryology , Animals , Blastula/cytology , Cell Cycle , Female , Male , Mitosis/drug effects , Nocodazole/pharmacology , Tubulin Modulators/pharmacologyABSTRACT
The most adequate method for carrying out radioautographic investigation on proliferation in the chorioallantoic tissues and in the chick embryo proper is dropping 3H-thymidine on the membrane under the shell in the area where the chorioallantois grows under. Using the application method, the radioautographic analysis of proliferation could be performed by the saturation method.
Subject(s)
Allantois/metabolism , Chorion/metabolism , DNA/biosynthesis , Extraembryonic Membranes/metabolism , Thymidine/metabolism , Allantois/cytology , Animals , Autoradiography , Chick Embryo , Chorion/cytology , MitosisABSTRACT
The intensity of entry of cells of different rudiments of the chick embryo in mitosis and S-phase at the stages of gastrulation and early organogenesis was studied by means of statmokinetic method and thymidine autoradiography. Regular changes in the percentage of cells entering mitosis and S-phase during development were found. The fluctuations of one index do not coincide often with those of another. The values of these indices within the limits of one rudiment may be interrelated in different ways. These interrelations change in their turn from one stage to another. A suggestion is put forward to the effect that the regular changes found represent a form of expression of parasynchronous proliferation pattern, related to the regular changes of the composition of cell polations due to unequal pasage of cells through the mitotic cycle.
Subject(s)
Blastoderm/ultrastructure , Gastrula/cytology , Mitosis , Animals , Cell Division , Chick Embryo , DNA/biosynthesis , Interphase , Kinetics , Morphogenesis , Time FactorsABSTRACT
Manifestation of mitotic activity of colchicin in 4- and 5-day-old chick embryos was studied under different modes of colchicin injection into the eggs. Three methods were tested: colchicin solution was injected into the serous-amniotic cavity (1) and into the yolk sac (2) and also by dripping on the serous membrane over the enbryo (3). Perfect metastatic effect was observed only when colchicin was used in concentration of 1 X 10(-4) g/ml and injected by the third mehtod. Increase in the solution volume over 0.1 ml resulted in a greater percentage of embryo death. Lack of a definite inhibitory action after colchicin injection into the serous-amniotic cavity might be explained by decrease of the substance concentration as a result of its dilution by the cavity fluid. A complete lack of blocked mitoses in the embryo tissues after colchicin injection into the yolk sac can be explained, according to the authors, by the presence, in the yolk, of a great number of ovoflavins capable to inhibit mitotic activity of colchicin.
Subject(s)
Chick Embryo , Colchicine/pharmacology , Mitosis/drug effects , AnimalsABSTRACT
The effect of colchicine and 3H-thymidine on the proliferation and mitotic cycle of cells of different rudiments of the chick embryo has been studied during gastrulation. Colchicine (1-10-6 g/ml) was shown not to influence both the portion of cells synthesizing DNA and entering mitosis and the intensity of DNA synthesis. No changes in the intensity of cell entrance in mitosis and the frequency of mitotic figures were found following the injection of 3H-thymidine (4.1 Cu/mM) at a dose of 2.5 muCu per egg. Taking into account the great possibilities of the complex utilization of stathmokinetic and autoradiographic methods for studying the kinetics of developing cell populations, a conclusion is drawn that the chick embryo at the early developmental stages is a convenient model for such an analysis.
