[A short repeat in the genome of the DNA sequences flanking bovine growth hormone genes]

The phage clones containing a gene coding for bovine growth hormone were isolated from a bovine genomic library. Comparison of the 5' and 3' regions flanking the bovine growth hormone gene by Southern blot hybridization revealed that they share homology. Screening the bovine genomic library by nick-translated DNA fragment from 5' flanking region leads to conclusion that this sequence is present in 0.1% of clones. Each analysed clone carrying the sequence contains some copies of it.

[The gene for bovine growth hormone is flanked by homologous sequences]

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.

[Erythroid cells of the bone marrow of the mouse]

The bone marrow of three intact male mice of C57Bl/6 line, fixed by perfusion of isotonic fixative of Karnovsky, has been studied by means of the scanning electron microscopy method. The surface of erythroid cells, that are immediately connected with macrophages of the erythroblasts islets, is analysed. According to the surface form, the erythroid cells are devided into 5 types. Every maturation stage of the erythroid cells is characterized by a certain type of surface. For identification of basophilic and polychromatophilic proerythrocytes the combined method of light and electron scanning microscopy of the cells in suspension is used. The bone marrow cells, obtained from the two male mice of C57Bl/6 line are fixed with the same fixative on special glasses with grids traced on them, stained after Romanovsky-Giemsa method and in moist preparations are examined in the light microscope. After further treatment the surface of the same cells in studied in the scanning electron microscope.

[Elements of the genome regulating structural gene transcription in eukaryotes]

A constant fine regulation of gene expression is needed for the normal development to proceed and for the physiological homeostasis to be maintained. In many cases such a regulation in eukaryotes is realized at the level of transcription, involving various cis- and trans-regulatory genomic elements. The review provides the data on the structure of elements determining the level of gene transcription in response to the action of various environmental factors and effectors, responsible for coordinated expression of the genes which provide for tissue-specific transcription and self-regulation of gene transcription. The data were considered on regulation of gene activity by mobile genetic elements and a relationship between the mechanisms of regulation of gene expression and evolution has been formulated.

[DNA synthesis and content and the accumulation of total protein and hemoglobin during the differentiation of primary erythroid cells in chickens]

Using cytophotometric and autoradiographic methods, it was shown that on days 2-3 of embryogenesis primary erythroid cells (PEC) divided actively. The distribution of erythroblasts (EB) according to their DNA content is not, however, typical of a proliferating population: it contains an unusually large number of 4c cells resulting from the cell cycle arrest at the G2 phase. It is established that reticulocytes (RC) do not divide and are arrested at G1 or G2 phases, since they do not incorporate 3H-thymidine after their formation is complete and their DNA contents are strictly confined to either 2c or 4c. All types of PEC include a large number of cells containing H2c DNA which is due either to the cell cycle arrest at the S phase, or to the formation of accessory nuclei. All PECs have much higher contents of hemoglobin and total protein than do adult hen erythrocytes (EC). Hemoglobin and total protein contents of H2c and accessory nuclei containing cells are much higher than those in 2c-cells. We have calculated that adult birds and embryos contain the same amount of hemoglobin per gram of weight, but the quantity of red blood cells in the former is ten times higher. A conclusion is drawn that proliferation and cytodifferentiation regulation mechanisms are directed, in primary erythropoiesis, to intense hemoglobinization of the cells, and, in adult erythropoiesis, to increasing their number. In both the cases homeostatic regulation of erythropoiesis works.(ABSTRACT TRUNCATED AT 250 WORDS)

[Differentiation pathways of primary erythroid cells in chickens]

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.

[Introduction of DNA sequences of Rous sarcoma virus into Drosophila and mouse genomes by microinjections into ova]

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.

[Induction of unstable mutations in Drosophila melanogaster by the microinjection of oncogenic viruses and their DNA into early embryos]

RNA-containing Raus sarcoma virus, recombinant plasmid pBR322 inserted by kDNA RSV (pPrC11) and Sa7 adenovirus DNA were injected into the polar region of Drosophila melanogaster early embryons. The exogenic genetic material injected was shown to induce mutations, many of them unstable. In a number of cases, virus-specific sequences were found in DNA isolated from mutant flies. It is hypothesized that mutations induced by DNA of oncogenic viruses are of the insertion type.

[A perfusion device for the survival of isolated organs of the reproductive system]

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.

[Characteristics of the pathways of erythroid cell differentiation in birds in anemia]

A comparative study has been made of erythroid cell development pathways in the peripheral blood of pigeons during severe, moderate and weak forms of anaemia. Three modes of erythrocyte formation from bone marrow precursor are described: 1. A reserve erythropoiesis--the principal process during severe anaemia; the bone marrow precursors are basophylic erythroblasts which are reversibly blocked in phase G2 of the cell cycle; in results the rapid, increase of erythrocyte population above the normal level, although the cells have 25-30 per cent deficiency in haemoglobin content. 2) A mode of erythropoiesis, whose precursors are proliferating polychromatophylic erythroblasts; this is the principal mode of erythropoiesis at the moderate anaemia, leading to restoration of the normal quantity of erythrocytes with a normal haemoglobin content. 3) A mode of erythropoiesis with proliferating orthochromatic erythroblasts being precursors (which do not divide normally); this is the principal mode during the weak anaemia to result in a slow restoration of the number of erythrocytes with an excess in haemoglobin content. It is shown that regulation of the restoration processes during anaemia are characterized by a specific combination of cell proliferation and differentiation.

[Changes in the representation of repeating DNA sequences in nuclear RNAs of early loach embryos]

The hybridization kinetics of nuclear RNAs of loach embryos labelled with [3H]uridine for 1 hour with DNA excess shows that during embryogenesis (from the blastula to the gastrula stage) the number of newly formed RNA molecules transcribed from repeating DNA sequences in considerably reduced. This occurs both in the RNA fraction extracted from the nuclei with phenol pH 7.7 and having a low sedimentation coefficient and a low degree of polyadenylation, and in the RNA fraction extracted with phenol pH 9.0 having a higher sedimentation coefficient and a higher degree of polyadenylation.

[Size and organization of repetitive sequences in pigeon genome]

Organization of sequences in pigeon genome and the spectrum of their repetition frequencies were studied by means of DNA/DNA reassociation. Reassociation of 125I-labelled DNA fractions isolated from pigeon total DNA attested the presence of rare repetitions with an average of 50 copies within a gaploid genome. The disposition of repetitive and unique sequences was studied by reassociation of the labelled fragments of different length with an essential excess of short fragments of an unlabelled DNA. Additional evidence was provided by estimation of hyperchromicity and resistance to nuclease S1 of long DNA fragments, reassociated to the given C0t values. It was demonstrated that approximately one fourth of the pigeon genome consists of intermittent repetitive and unique sequences with individual elements of average length of 2 and 37 kb, respectively (1 kb = = 1000 nucleotide base pairs). A hypothetical organization of palindromic sequences in pigeon genome is discussed in terms of the dependence of the value of zero binding to hydroxyapatite on the fragment length.

[Globin-coding sequences in the nuclear 28S pre-mRNA and in the cytoplasmic RNA of pigeon erythroid cells]

The steady-state content of globin-coding sequences in nuclear and cytoplasmic RNA of pigeon erythroid cells was estimated by hybridization in the excess of nuclear 28S RNA and cytoplasmic poly(A) + RNA with [3H]DNA, synthesized on globin mRNA. Sequences of 9S globin mRNA are found in 0.06% of molecules of non-ribosomal 28S nuclear RNA (pre-mRNA) of erythroblasts and in 0.5% of molecules of non-ribosomal 28S nuclear RNA of reticulocytes. The content of globin mRNA in erythroblast cytoplasm is, respectively lower than in that of reticulocytes.

[Reassociation of rat DNA fractions]

A method for direct registration of the first derivative of DNA reassociation kinetics in spectrophotometric cuvettes is proposed. Using this method, the rat liver DNA obtained by chromatography on hydroxyapatite was studied. The differential curves of reassociation and changes in hyperchromic spectra revealed the presence in the rat genome of 4 types of repeating sequences differing in their GC-content. A scheme of preparative separation of DNA with respect to the reassociation rate was developed. Three types of sequences repeating 3.10(5), 600 and 1 times in the genomes with the GC-content of 50, 42, and 33%, respectively, were obtained in a homogeneous state. The advantages of the differential method of registration of the kinetic curves for the study of DNA structure and calculation of fractionation schemes are discussed.

[Proliferative activity of bone marrow and blood cells in rats with phenylhydrazine anemia]

Anemia was induced in rats by phenylhydrazine. There were found in the blood basophil erythroblasts, macrocytes, both ortochromatic and polychromatophil and basophil reticulocytes (the number of which could attain 60%). The role of macrocytosis in the reaction of the organism is discussed. The mitotic activity of erythroid cells increased in the bone marrow. On the basis of comparison of hemopoiesis in mammals (rats) and birds, by the previous authors' publication, a suggestion is put forward to the effect that during evolution "reserve" erythropoiesis is preserved only in the forms with nucleate erythrocytes (birds) or in the cells which have not lost the nucleus (in the bone marrow of rats).

[Molecular structure of pigeon genome. Revealing of clusters consisting of prolonged homopolymeric and short palindromic sequences]

Isolated from pigeon genome short (approximately 450 nucleotides) and long (approximately 8000 nucleotides) single-stranded DNA fragments containing prolonged (greater than or equal to 300 nucleotides) polydeoxyandenylic sequences have been studied. Based on the analysis carried out we come to the conclusion that for the pigeon genome the prolonged poly(dA)-sequences are located as clusters where a large amount of short palindromic sequences occur.

[Metabolically stable classes of messenger-like nuclear RNA. II. Existence of homology between the 28S fraction of nuclear RNA, giant non-polyadenylated molecules of heterogeneous nuclear RNA and polyadenylated molecules of cytoplasmic RNA]

The existence and extent of homology between the 28S fraction of messenger-like nuclear RNA on one hand, and giant (greater than 45S) molecules of heterogeneous nuclear RNA and various fractions of cytoplasmic RNA on the other hand were studied by the method of competitive hybridization. The results obtained lead to the conclusion that the poly(A)-subfraction of hnRNA molecules with the size of greater than 15 000 nucleotides contains molecules subjected to rapid but incomplete processing with the formation of chains approximately 5000 nucleotides long (approximately 28S), which are then stored in the nucleus for up to 30 hours. Later polyadenylated and non-polyadenylated molecules of cytoplasmic RNA with the size of less than or equal to 2000 nucleotides are formed from the stored precursors.

[Immunochemical analysis of histone H1 and H5 from pigeon erythroid cells]

An antiserum with the antibody titer of 1 : 4096 was obtained by immunization of rabbits with the tRNA-histone H5 complex from pigeon erythrocytes. The specificity of the antiserum was studied quantitatively from the reaction of the complement binding to a homologous antigen (histone H5) and its modifications (I, II, III), differing in the degree of phosphorylation. It was shown that phosphorylation of histone H5 increases the ability of the antigen to bind to antibodies, which is especially well-pronounced at the antiserum dilutions as high as 20480. The comparison of the antigenic properties of histones H5 from pigeon and chicken erythrocytes revealed beside structural differences of the proteins the presence of common antigenic determinants. A similar observation was made when histones H5 and H1 from pigeon erythrocytes were compared. Histone H1 from chicken erythrocytes and histone H1 from calf thymus did not produce criss-cross reactions with antiserum H5.