The review is concerned with a progress in genetic modification of a mammalian genome in vitro and in vivo at chromosomal level. Recently three new approaches for the chromosome biotechnology have been developed: Using Cre/loxP-system a researcher is able to produce targeted rearrangements of whole chromosomes or their segments or particular genes within the genome, and therefore to modify the set, position and copy number of the endogenous elements of the genome. Mammalian artificial chromosomes (MACs) provide a possibility to introduce into genome relatively large segments of alien chromosome material, either artificially constructed or derived from the genome of different species. Using ES-somatic cell hybrids allows to transfer whole chromosomes or their fragments between different genomes within and between species. Advantages and limitations of these approaches are discussed.

In evolutionary terms, insectivores are thought to be close to primates. Through ZOO-FISH analysis using human chromosome-specific painting probes, the syntenic relationship between the human and common shrew, Sorex araneus, karyotypes was studied. The human karyotype was found to be conserved in the shrew, with 32 autosomal segments of common synteny. Special arrangements, already known from similar studies on other species, were noted: fusions of HSA 16 and 19, HSA 3 and 21, and HSA 14 and 15. Only 10 breaks are necessary to transform the human karyotype into the karyotype of the common shrew. Together with known ZOO-FISH data from species belonging to other orders, this puts the human karyotype arrangement near the basis of all mammalian karyotypes. Human chromosome 2 was found to be conserved in its entirety as a single chromosome arm in the shrew. Evidence is presented that the same fusion of two original chromosomal segments formed the shrew chromosome ortholog of HSA 2 as the fusion that occurred during primate evolution to form human chromosome 2. This is a remarkable example of chromosomal coevolution.

This report extends the genetic map of the common shrew (Sorex αrαneus) by use of a clone panel of shrew-Chinese hamster and shrew-mouse hybrid cells (Pack et al., 1995; Matyakhina et al., 1996). This set of hybrid clones made it possible to assign the shrew genes for isocitrate dehydrogenase 2 (IDH2), inorganic pyrophosphatase (PP), glutamic-pyruvate transaminase (GPT), adenosine kinase (ADK), glucuronidase 2 (GUSB) and acid phosphatase 2 (ACP2) to chromosome ik, the genes for adenylate kinases 1 and 3 (AK1 and AK3) to chromosome af; the genes for glutamate-oxaloacetate transaminase 2 (GOT2), peptidase D (PEPD) and growth hormone (GH) to chromosome hn; the gene for phosphoglucomutase 2 (PGM2) to chromosome go, the gene for enolase 1 (ENOl) to chromosome jl, the gene for ornithine carbamoyl-transferase (OTC) to chromosome de, the gene for aminoacylase 1 (ACY1) to arm m (chromosome mp), the gene for glutamate-oxaloacetate transaminase 1 (GOT1) to arm q (chromosome qr). Thus, the genetic map of the common shrew now contains 33 genes and it is possible to compare the syntenic associations with other species.

We compared in detail the GTG-banding patterns of the chromosomes of cattle, sheep, and goat. Minor differences were revealed between the patterns of cattle on the one hand, and sheep/goat chromosomes on the other. These differences concerned mainly the pericentromeric regions of autosomes. Based on comparative data, we suggest how the contemporary cattle X chromosome might have arisen from the ancestral goat type as a result of rearrangements. No differences were found between the G-banded chromosomes of goat and sheep. Also, ideograms of the prometaphase GTG-banded chromosomes of cattle are given with descriptions of the chromosomes thought previously to be difficult to identify.

A cDNA library from the mink pituitary was screened using as probe a synthetic oligodeoxyribonucleotide, 5'-TTCATGACCTCCGA-3', corresponding to the endorphin region of bovine proopiomelanocortin (POMC) cDNA. As a result, several clones containing inserts complementary to POMC mRNA were identified. The sequence of one of the fragments (585 bp, 65% of the total length of mRNA) was determined. A high degree of homology (over 80%) among the primary structures of sequences from mink, man, and bovine cDNA POMC was established. With the cloned mink cDNA fragment as probe, the DNAs from mink-Chinese hamster hybrid clones were studied. The results of segregation analysis of mink POMC sequences and mink chromosomes in the mink-Chinese hamster panel allowed us to assign the POMC gene to mink chromosome 11.

The spectrum of LDH isozymes was studied at the successive stages of retinal regeneration from the pigment epithelium and lens cells from the iris margin in the adults Pleurodeles waltlii. The combination of two methods, electrophoresis and immunofluorescence, has revealed the slow and rapid LDH isozymes with different intensity of histochemical staining in cells of the tissues under study (pigment epithelium, retina, iris and lens). During the regeneration the spectra of LDH isozymes peculiar to the pigment epithelium and iris and characterized by the predominance of slow forms were substituted by those peculiar to the retina and iris and characterized by the predominance of rapid forms. The rearrangement is realized in the proliferative phase during the transformation of one cell type into another.

An improved method is described for the isolation of isozymes 1 and 5 of lactate dehydrogenase (LDH) from heart and skeletal muscles of foxes. The method includes salt fractionation with ammonium sulphate, chromatography on DEAE- and CM-celluloses and affinity chromatography on AMP-Sepharose. The preparations of LDH isozymes 1 and 5 turned out to be homogeneous both in 7,5% polyacrylamide gel electrophoresis and under immunodiffusion analysis. It is shown that the pH optimum for LDH-1 is 10.2-10.4 for LDH-5 it is 9.5-9.6 in the case of the direct reaction, and the pH optimum is 7.6-7.8 for LDH-1 and 7.3-7.4 for LDH-5 in the case of reverse reaction. The values of Mikhaelis constants were determined for substrates and coenzymes in direct and reverse reactions. It is found that the excess of lactate and pyruvate causes substrate inhibition of both LDH-1 and LDH-5. The activities of LDH-1 and LDH-5 showed an unexpected similar sensitivity to the inhibitory effect of high pyruvate concentrations.

Experimental conditions for the molecular hybridization in vitro between iodine and native subunits of isoenzymes 1 and 5 of lactate dehydrogenase (LDH) are described. It is also shown that the covalently fixed on the polyacrylamide beads rat J125 labelled LDH-5 and J125 labelled aldolase A, under conditions of complete dissociation of the quaternary structure of these enzymes, only one of the four subunits remain bound with the beads. Subunit of LDH-5, which is covalently bound with the polyacrylamide beads, is capable to hybridize (reassociated) with 3 native subunits. In addition, the immobilized LDH-5 subunits and aldolase A are capable to hybridize with J125 labelled subunits of these enzymes. Thus, when thyrosine, lysine and N-terminal amino acids are modified, subunits of LDH-5 and aldolase A retain their capacity to restore their quaternary structures.