The incorporation of labeled amino acids into the total proteins of muscle tissue and cell organelles during the regeneration of limbs of axolotls and after the suppression of the regenerative capacity by x-irradiation and its experimental restoration were investigated. In the case of suppression of the regenerative capacity of the limbs by x-irradiation, the protein synthesis in the muscle tissue is impaired. The intensity of the incorporation of labeled amino acids into the proteins of a homogenate of muscle tissue, nuclei, mitochondria, and the mitochondria-free fraction is reduced in comparison with normal regeneration. Under the influence of biopreparations (a salt extract from a homogenate of the rat gastrocnemius muscle), a restoration of protein synthesis, processes of differentiation, and the formation of regenerates was observed. C-14-lysine was incorporated most intensively into the proteins of the mitochondria-free fraction and nuclei at the spatula stage (exceeding this index in the series with irradiation of the limbs without treatment with the biopreparation by 5 and 7-fold, respectively).
The synthesis of the protein component of thyroglobulin was studies by the method of immunofluorescence in the thyroid glands of rat, guinea pig, chicken, and calf embryos. Diffuse specific fluorescence of the cytoplasm was observed in the prefollicular stage of thyroid gland differentiation. It was assumed that the specific fluorescence is due to low molecular weight precursors of thyroglobulin. During the formation of the follicles specific fluorescence is found at the apical poles of the cells and later it is concentrated at the cell-colloid boundary and in the follicular cavity. In calf fetuses in the second half of embryonic development specific fluorescence is observed in addition in the cytoplasm of the follicular cells.
The distribution of total RNA and its individual fractions in two regions of Acetabularia mediterranea stem during regeneration was investigated. During regeneration of both the nuclear and enucleated cells, RNA concentration increases in the cytoplasm of growth zone whereas it changes insignificantly in the central stem region. A study of the qualitative RNA composition in the same stem regions has shown that during regeneration high molecular weight RNA fractions (main peaks - 0,56-10(6) and 1.04-10(6) Dalton) are found in the growth zone and are practically absent from the central cell region. Low molecular weight RNA (supposedly, tRNA and products of RNA destruction) are present in both the cell regions under study.
The effect of water-soluble retinal factors on lens differentiation in 11-day chick embryos was studies in vivo. Retinal extract accelerated cell transfer from zone to zone, promoted lens-fiber formation, and reduced total protein in the lens. Acrylamide-gel electrophoresis detected four basic protein fractions in the lens. Retinal factors caused a fraction identified as gamma-crystallin to disappear and lowered the peak of delta-crystallin. The data obtained are evidence that retinal factors participate in the regulation of cell differentiation and protein turnover in the lens.
It is shown that the constant k in the equation QO2 equals apk and the constant b in the equation qo2 equals aP-b change during the oogenesis of the loach. Hence, the growth of oocytes differs considerably from the growth of animals, where the constants k and b do not change with increase in weight. It is suggested that the relationship between the respiration rate and weight of the oocytes is due to the change in the amount of mitochondria in the oocytes.
A growth equation is presented, differing from Robertson's equation only in its constnats. It is shown that this equation satisfactorily describes the growth of birds and mammals.
Monophasic diurnal rhythms of mitosis and DNA synthesis are characteristic of the thyroid gland epithelium of young rats (unlike adults). It is postulated that the diurnal rhythm of mitotic activity is under the influence of a mechanism synchronizing the cell population before mitosis. With an increase in thyrocyte differentiation the number of mitoses and of DNA-synthesizing cells falls. Diurnal changes in the duration of mitosis affect the dynamics of the diurnal rhythm of mitotic activity. Changes in the height of the follicular cells during the 24-hour period are evidence of a diurnal rhythm of thyroid function in young rats.
An extract from 13-day embryos of mice homozygous with respect to the bp-H gene contains a growth-inhibiting factor (GIF), which inhibits the growth of normal bones in vitro. The activity of the GIF depends on the concentration of the extract in the culture medium. The sensitivity of the GIF to heating and proteolytic enzymes is an indication of its protein nature. The precipitation of the GIF from the embryonic extract with ammonium sulfate, followed by fractionation on columns with Sephadex G-200 and DEAE-Sephadex gave a 400-fold degree of purification. The active growth-inhibiting preparation obtained is represented by three proteins, which migrate slowly in electrophoresis in polyacrylamide gel. The molecular weight of the basic component is 76,000.
The amount of DNA and the dry weight of the nuclei of cells of the external geniculate body, as well as the photoreceptor, bipolar, and ganglionic cells of the retina of the eye, were studied at the early stages of postnatal development of guinea pigs by the methods of cytospectrophotometry and interferometry on prints of the tissue. In the photoreceptor and bipolar cells of the retina, a stable, diploid amount of DNA is detected. In the ganglionic cells and nerve cells of the external geniculate body, in addition to the diploid cells a small group of tetraploid cells was detected. The dry weight of the nuclei of the external geniculate body and retina increased appreciably on the third day of postnatal development.
The number of cells in diapausing silkworm embryos of different ploidies was determined. Thermal activation was shown to lead to a decrease in the number of cells in parthenogenetic embryos in comparison with normal, zygotic development. The number of cells in the embryo is a direct function of egg volume and a reciprocal function of embryo ploidy and is affected by the maternal genotype.
Antimycin A blocks cleavage divisions in concentrations 1-10-15-1-10-14 g/ml (experiments on Arbacia lixula) or 1-10-11-1-10-9 g/ml (experiments on sea urchins of the genus Strongylocentrotus). Subthreshold and threshold concentrations of this antibiotic do not affect the sensitivity of fertilized Strongylocentrotus intermedius to 1-benzyl-2, 5-dimethylserotonin, but increase their sensitivity to 5-butyltryptamine by a factor of 3-5. These data provide the basis for a discussion of the possible nature of the reception of serotonin and other low-molecular-weight regulators of early embryogenesis.
The accumulation of myoglobin in the muscles was studied in the ontogenesis of rabbits and chickens. A connection was found between the myoglobin content and the degree of the functional load of the muscles in different age periods. Myoglobin appears first in the myocardium. In the femoral muscles of chick embryos myoglobin is first found on the 16th day of incubation. Myoglobin is not detected quantitatively in the masseter and femoral muscles of the rabbit during prenatal development. The myoglobin content is highest in the gizzard of a mature hen.
