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The repeated sequences situated in 5'- and 3'-flanking regions of the bovine growth hormone gene were cloned and characterized. It was shown that they are related to a described before PstI-family of bovine repeats with a frequency of repetition about 10(5). PstI-repeats are found only in genomes of sheep and goats subfamily (Carpinae) and not found in DNA of other analysed vertebrate species. Repeats of this family are situated in the genome as a number of dispersed clusters, they have conservative structure and are alike by the frequency of repetition in the DNA of all organisms that contain them. The presence of sequences homologous to PstI-repeats are shown in bovine pituitary poly(A)+ cytoplasmic RNA by means of North-hybridization.

From pigeon DNA two families of repeats have been isolated: one (frequency of repetitions 30--40 times per haploid genome) actively transcribing and the second (frequency of repetitions 2000--2800 times) weakly transcribing in erythroid cells. The reassociation kinetics, GC-content and size of isolated repeats were investigated. Actively transcribing repeats (average length of 350 nucleotides) contain about 55% GC-nucleotides and alternate in the genome with AT-rich sequences of the unique type. Comparison of isolated families of repeats revealed differences in the structure and posttranscriptional fate of RNA transcribed from them.

The 17-mer oligonucleotide probe homologous to the fragment of the gene for human erythrocyte differentiation factor erythropoietin was used to screen the human genomic library for this gene. Restriction analysis and partial sequencing of one of the identified clones have confirmed that the clone does contain the human erythropoietin gene. We are planning to use the cloned human erythropoietin gene for developing a stably transfected mammalian cell line that should secrete erythropoietin.

The erythropoiesis during anemia is characterized by the reduction of the bone marrow period of cell development. Two immature forms, absent in the normal state, were shown to be present under anemia: basophilic erythroblasts and reticulocytes with basophilic cytoplasm. These forms are interposed between the bone marrow basophilic erythroblasts and erythrocytes. Some basophilic erythroblasts turn out in the peripheral blood and transform into basophilic reticulocytes there. The level of transcription in anemic animals during the transformation of basophilic erythroblasts into basophilic reticulocytes does not decrease and is higher than that in polychromatophilic erythroblasts. The total chromatin condensation does not reflect the decrease of the transcription level.

Two discreet in size molecular classes of metabolically stable messenger-like RNA molecules with sedimentation coefficientes about 28S and 18S have been revealed in the nuclei of pigeon bone marrow cells. The structural pecularities of 28S RNA class were investigated more carefully. It was shown to constitute the largest fraction of nuclear messenger-like RNA and is characterized by a GC/AU ratio 1.13. As pulse-labeled nuclear RNA, 28S stable nuclear RNA hybridizes with the unique and rare repeated DNA, it does not contain poly(A)-sequences and is found in a form of RNP particles with density of 1.41 g/sm3, tightly bound to chromatin.

Proliferation and differentiation processes of chick embryo primary erythroid cells (PEC) were studied. A novel differentiation pathway was discovered by which cells of proerythroblastic and erythroblastic stages are blocked in G1 or G2 phases, to develop then directly into reticulocytes, i.e. terminally differentiated non-dividing cells with high hemoglobin contents differing in shape from erythrocytes. These cells appear in blood two days earlier than erythrocytes, then they co-exist with the latter and are eliminated in parallel with them. This pathway leads to a rapid enrichment of PEC with hemoglobin. A fraction of PEC forms accessory nuclei, which, as it is shown here, contain an extra quantity of DNA. Compared to the diploid ones, such cells reveal increased hemoglobin contents which enabled us to assume that they may have amplified the globin genes. The above-mentioned pecularities of cytodifferentiation may be presumably an adaptation to oxygen supply of growing embryos which are known to stay in hypoxia. A comparison of these results with results of our earlier study on experimental anemia makes it possible to suppose that pecularities of these two types of cytodifferentiation may be based on similar or, perhaps, analogous mechanisms of regulation.

Heterogenic population of the follicular oocytes of bovine ovaries has been divided into 5 groups on the basis of morphological characteristics. Chromatin structure, frequency of degenerative changes and the ability to maturation in vitro of different oocyte groups have been studied. The correlation of morphological characteristics of native oocytes and their ability to mature in vitro have been shown. The bovine follicular oocyte classification allows to pick out more homogeneous oocyte groups in comparison with the population as a whole and the oocyte group which is the best for maturation in vitro.

We have demonstrated that the mutagenic effect of oncovirus DNA injected into Drosophila embryos is of two-type locus specificity: the spectrum of mutations induced by the retroviral cDNA (RSV) changed in different recipient stocks and those induced by the adenoviral DNA (Sa7) did not differ in the stocks studied. The Sa7 DNA and the cDNA of RSV induce mutations in different groups of loci. Transpositions of the copia element were found in mutant lines obtained in both cases.

Transgenic mice containing in somatic (liver) cells a gene encoding hepatitis virus B surface antigen (HBsAg) were obtained and analysed. About 10(4)-10(5) copies of circular plasmid pSH21 with HBsAg gene under the control of the SV40 early promoter were microinjected into the cytoplasm (pronucleus region) of mouse zygotes. 10 of the 24 animals isolated after this treatment contained 1 to 5 copies of the HBsAg gene per genome of hepatocytes (7 males and 3 females). The Southern analysis of DNA from some of transgenic animals showed rearrangements of the HBsAg gene in most of them. In the liver of one female transcripts were found hybridizing with the probe on the HBsAg gene; progenies of this mouse expressed no HBsAg gene. Possible reasons for the high frequency HBsAg gene rearrangements in transgenic mice are discussed.

A selection system for isolating DNA sequences with transcription-promoting activity by their functioning in bacterial cells has been proposed. Tobacco nuclear DNA fragments were inserted in front of the promoterless neomycin 3'-phosphotransferase II (NPT-II) gene and promoter-like sequences were identified by their ability to restore NTP-II activity in E. coli cells. One of these recombinant plasmids was introduced in tobacco protoplasts by direct gene transfer and transformed calli were isolated by kanamycin selection. The NTP-II expression in regenerated transgenic plants were highest in root, slightly lower in stem and were practically absent in leaf. Sequence analysis of cloned segment showed the presence of conserved sequences essential for promoter activity in eukaryotic cells. A transcription start site was observed by S1 mapping. The size of protected fragments corresponds to the initiation of transcription 176 and 179 base pairs upstream the initiation codon in tobacco and 75 base pairs in E. coli.

Under the conditions of acute phenylhydrazine anemia in pigeons, early erythroblasts develop in reticulocytes with basophilic cytoplasm directly by passing the stages of polychromatophilic and ortochromic erythroblasts. During the maximum activity of bone marrow erythropoiesis stimulated by anemia over 80% of reticulocytes develop in such a way. A hypothesis is put forward to the effect that there exist in birds two alternative pathways of erythropoiesis: the main pathway which ensures the slow repopulation of blood by erythrocytes under normal conditions and the reserve pathway which opens for a short time under anemia and ensures rapid increase of the erythrocyte titer in blood up to its normal value.

We have studied the spectrum and nature of mutations induced by oncogenic virus DNA injections into wsn, T-007 line of embryos, and those of the first generation hybrids obtained after crossing the T-007 line males with the Oregon R wild line females (hybrid disgenesis). Each line is shown to have a special group of "hot" sites mutating with high frequency under the effect of the oncovirus DNA injected.

The structure of the transgenic mouse DNA region containing an integrated transgene (fragment of pBR322 sequence) was analysed. In one of the sequences flanking the transgene, short direct and inverted overlapping repeats were revealed at a distance of 60 bp from the integration site. In the same flanking sequence, there is an extended sequence (3.5 kbp) 0.3-1 kbp away from the transgene. It repeats 100-300 times in the mouse genome and is highly conservative (the homologs of the repeat have been revealed in other mammalian, bird, fish and insect genomes). This up-to-date unknown family of highly-conserved dispersed repeats has been denoted by T1. We believe that both the revealed short inverted repeats capable of forming hairpins with loops and the T1 repeat are structures involved in the process of non-homologous insertion of foreign DNA into the region of the transgenic mouse genome.

Using isolated nuclei of salivary grand cells of Chironomus plumosus larvae, it was revealed that the integrity of nuclei was a necessary condition for realization of protein synthesis in the nuclei. The involvement of nuclear particles in the above synthesis is supposed.

The paper covers experimental results of introducing exogenic genetic material, namely DNA sequences of the Rous sarcoma virus, by microinjections in mice zygotes and Drosophila early embryos. In a number of cases integration of viral DNA into genomes of these organisms was detected. Blot-hybridizations analysis of cell DNA proved that the inserted viral sequences undergo rearrangements in the course of integration.

The results of experiments on the transfer of bovine gene for growth hormone into mice and rabbits are presented. The gene was transferred by the technique of microinjection into the zygote. In all cases transgene in rabbits occurred to be changed. In two transgenic mice the bovine growth hormone gene represented some tandem arranged copies. One of the mice had accelerated growth. This phenotypic changes is found to be inheritable.

This review deals with the analysis of the conflinting situations that appear during the study of the translational apparatus in cell nuclei. Experimental approaches used to unravel this problem are surveyed.

Rapidly labelled mRNAs were isolated from informosomes and polyribosomes of imbibed wheat embryos. The distribution of poly(A) sequences in these fractions were studied by poly(U) Sepharose chromatography. It was shown that informosomes contain 11% polyadenylated mRNA while polyribosomes--38%. This fact suggests the important role of poly(A) sequences for translation of mRNA.

A perfusion device for life supporting in isolated reproductive organs is described. With the device, the following functions are possible: gas exchange in recirculating blood flow, perfusate replacement in the course of perfusion, blood flow generation in a circular circuit with simultaneous provision of hemodynamic parameters closely approximating native ones.

The ability of H5 and H1 histones, purified from immature or mature pigeon erythroid cells, to suppress RNA synthesis in vitro was compared. It was found that H1 histones from both sources as well as histone H5 from bone marrow suppress RNA synthesis to a comparable degree while H5 from the mature erythrocytes exhibits significantly higher suppression efficiency. H5 histone subfractions, differing in phosphate content, also had different ability to restrict the template activity of chromatin: the higher is the phosphorylation level of H5 histone, the weaker is its effect on the transcription.

In was shown earlier (Gazaryan & Kulminskaya, 1975; Kulminskaya & Gazaryan, 1976) that under the conditions of anemia a new (reserve) mechanism of the terminal differentiation of erythroid cells was induced. It was now found that in the course of cell development along this path the basophylic erythroblasts doubled the amount of DNA passed in the peripheral blood where they transformed into basophylic, polychromatophylic and orthochromic reticulocytes. Thereafter they entered the mitosis and transformed into the mature erythrocytes with diploid nuclei. It was shown for the first time that the cell delayed in the G2 phase could actively accumulate the specific product (hemoglobin) and keep its ability to enter the mitotic division.

The gene coding for the bovine growth hormone was isolated from a lambda-phage library. The restriction map of the 3'-region (about 10 kb) was determined by restriction analysis and by Southern blot analysis. A comparison of the 5'- and 3'-flanking regions of the bovine growth hormone gene revealed some patches of homology.

Some peculiarities of the technique of nuclear transplantation for teleostean fishes are described, the loach (Misgurnus fossilis) taken as an example. The cells of the late high blastula were used as donors and the activated non-enucleated and enucleated (by X-rays, 20 kR) eggs of the loach as recipients. Following the nuclear transplantation in the activated non-enucleated eggs, 33 (out of 128) normal blastulae were obtained, one of which developed until hatching. Following the nuclear transplantation in the activated enucleated eggs, 34 (out of 251) blastulae were obtained, 6 embryos hatched and 2 larvae attained the stage of active feeding.