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Results for “hybridization”

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At least 19 recordsLinked to original sources

PubMed1979

Production of serum proteins in normal diploid fibroblast-hepatoma cell hybrids and in A9-normal liver cell hybrids.

Two series of interspecific hybrids have been generated between liver cells (which actively secrete several serum proteins) and fibroblasts (which do not). In each series, one of the parental cells was a normal diploid cell: mouse hepatoma cells were fused with normal diploid rat fibroblasts, and normal rat liver cells were fused with mouse fibroblasts of the permanent line A9. The production of albumin, alpha-fetoprotein (AFP) transferrin and the third component of complement (C3) was analysed in these hybrids. Most hepatoma cell hybrids exhibit extinction of albumin, AFP and (to a lesser extent) transferrin; they retain the capacity to secrete C3. Normal liver cell hybrids are also characterized by the absence of albumin and transferrin production and by retention of C3 secretion. These results, when compared to previous results obtained with hybrids derived exclusively from different differentiated cells of permanent and transformed lines show that the phenotype of such hybrids is not determined by the abnormal character per se of the aneuploid parental cells. Amongst the rat fibroblast-mouse hepatoma cell hybrids, a few clones retain the capacity to actively secrete mouse albumin, AFP and transferrin, without the concomitant production of the rat serum proteins. These hybrids have lost more rat (fibroblast) chromosomes than the other clones and also have an increased number of mouse (hepatoma) chromosomes. Thus, their phenotype must result from either the complete loss of 'extinguisher' chromosomes, or gene dosage effects. The significance of the lack of rat serum protein production is also discussed, and it is suggested that retention, without concomitant activation, could be explained in terms of diffusible regulators and heritable differences in chromatin conformation.

Animals↗

PubMed1979

Genetic regulation of CFA expression in interspecific avian hybrids and somatic cell hybrids.

Chicken fetal-leukemic antigen (CFA) is an oncodevelopmental antigen present on embryonic and neonatal chicken peripheral red blood cells (RBCs) but is not restricted to fetal stages of development in other avian species. Crosses between white Leghorn chickens and Japanese quail resulted in adult hybrids whose peripheral RBCs were positive for CFA. Of the four CFA determinants normally found in adult quail RBCs, only two were present on quail-chicken hybrid RBCs. Adult quail--chicken hybrid RBCs also possessed on CFA determinant associated with early development in both quail and chicken and one chicken-specific CFA determinant. Evidence is presented for the possible association of CFA-positive adult peripheral RBCs and the level of circulating reticulocytes. Crosses between pheasant and turkey (both with CFA-positive adult RBCs) resulted in hybrid adult RBCs expressing only a portion of the parental CFA determinants. Through the formation of somatic cell hybrids between adult chicken and embryonic Japanese quail RBCs, it was possible to induce the appearance of CFA determinants normally restricted to embryonic chicken RBCs. Approximately 50% of the hybrid cells showed reexpression of CFA, and this induction was both time and temperature dependent. Hybridization between RBCs of adult chicken and those of either adult Japanese quail or adult turkey failed to elicit the reexpression of chicken-specific CFA.

Animals↗

PubMed1977

Human lymphocyte-mouse myeloma somatic cell hybrids: selective hybrid formation.

Fusion of unfractionated human lymphocytes with mouse myeloma cells resulted in proliferating hybrid colonies, almost all producting human Ig. We examined whether this high frequency of Ig production was the result of selective formation of human B lymphocyte-mouse myeloma hybrids, rather than induction of Ig genes in T lymphocytes. Unfractionated peripheral lymphocytes and B lymphocytes from patients with the common variable form of agammaglobulinemia formed proliferating somatic cell hybrid colonies. In contrast, peripheral lymphocytes from a patient with agammaglobulinema who lacked B lymphocytes, as well as albumin gradient fractions of peripheral blood which do not contain B lymphocytes, failed to produce somatic cell hybrids with three different myeloma parent cell lines. B, T, and precursor lymphocytes all had Sendai virus receptors, as witnessed by viral agglutination. We conclude that fusion of human lymphocytes with mouse myeloma cells results in selective hybrid formation, rather than activation of Ig genes in disparate cell types. Only B lymphocyte-mouse myeloma heterokaryons form hybrid cells.

Agammaglobulinemia↗

PubMed1979

Hybrid mammalian cells assemble hybrid ribosomes.

Hybrid cell lines formed by fusion of mouse 3T3 cells and Chinese hamster ovary (CHO) cells resistant to emetine, which have an altered 40S ribosomal protein, are generally sensitive to emetine. From most hybrid lines it was possible to select sublines resistant to emetine. The ribosomal components of three lines were studied: A34, an emetine-sensitive hybrid; A34/R3, an emetine-resistant derivative of A34; and A72, an emetine-sensitive hybrid that did not give rise to emetine-resistant sublines. Genetic and biochemical evidence suggests that in A34 both the mouse emetine sensitivity gene and the hamster emetine resistance gene are active, whereas in A34/R3 only the hamster emetine resistance gene is active and in A72 only the mouse emetine sensitivity gene is active. The ribosomes of all three sublines contained both mouse and hamster RNA, predominantly mouse. However, the 60S subunits had roughly equal amounts of the three mouse and hamster proteins that could be distinguished by two-dimensional electrophoresis, suggesting the association of mouse RNA with hamster ribosomal proteins. The emetine-resistant and emetine-sensitive 40S subunits could be separated by sedimentation in 0.5 M KCl. Resistant subunits contained predominantly mouse RNA, presumably associated with the hamster protein conferring emetine resistance. We conclude that hybrid cells can form hybrid ribosomes and that the amounts of ribosomal RNA and ribosomal protein of each species are not closely coupled.

Animals↗

PubMed1978

Pharmacologic responses of cells of a neuroblastoma X glioma hybrid clone and modulation of synapses between hybrid cells and mouse myotubes.

Cells of the hybrid clone NG108-15 responded to 5-hydroxytryptamine (5-HT), dopamine or acetylcholine with graded depolarizations involving membrane conductance increases. Responses desensitized during continuous application of the neurotransmitters, and responses to 5-HT and dopamine cross-desensitized: a desensitizing application of one neurotransmitter also desensitized the hybrd cell to the other neurotransmitter. 5-HT and acetylcholine did not cross-desensitize. The hybrid cell 5-HT response was not attenuated by D-LSD, and was blocked by 10(-5) M morphine, although not via binding to naloxone-sensitive opiate receptors. 5-HT or the prostaglandin PGF2alpha caused the release of acetylcholine at the synapses of hybrid cells with mouse myotubes. Application of 5-HT or PGF2alpha also facilitated the synaptic release elicited by hybrid cell action potentials. Following treatment with the antimitotic agent cytosine arabinoside, co-cultures of hybrid cells and mouse myotubes exhibited plentiful synaptic connections only if maintained in medium containing 1 mM dibutyryl cAMP (dBcAMP). After X-irradiation, co-cultures were synaptically active even in the absence of dBcAMP. Thus, methods have been found to regulate both the short-term and long-term synaptic activity of NG108-15 hybrid cells.

Acetylcholine↗

PubMed1975

Expression of differentiated functions in hepatoma cell hybrids: IX extinction and reexpression of liver-specific enzymes in rat hepatoma-Chinese hamster fibroblast hybrids.

Most of the hybrid clones derived from a cross of Chinese hamster fibroblasts (DON) with rat hepatoma cells (Faza 967) showed preferential loss of rat chromosomes. Two of the hybrid clones retained the rat chromosomes, and both showed extinction of 4 liver-specific enzymes: aldolase B, liver alcohol dehydrogenase, and the inducible enzymes tyrosine aminotransferase and alanine aminotransferase. Subcloning of 1 of these hybrids, which contained 2 sets of hepatoma chromosomes and 1 set of hamster chromosomes, permitted the isolation of some clones which reexpressed 1 or more of the liver-specific enzymes. Liver alcohol dehydrogenase was the most frequently reexpressed enzyme and aldolase B the least. Tyrosine aminotransferase inducibility was reexpressed independently of basal activity, and the enzyme produced by the reexpressing hybrid cells was precipitated by a specific antiserum. No correlation was detected between the presence or absence of the marker chromosomes (large metacentrics) of the hamster parent and the extinction and reexpression of the hepatic enzymes. The results reported confirm and extend to interspecific hybrids the observation of the stable and independent reexpression of tissue-specific enzymes.

Alanine Transaminase↗

PubMed1977

Genetics of the connective tissue proteins: assignment of the gene for human type I procollagen to chromosome 17 by analysis of cell hybrids and microcell hybrids.

Somatic cell hybrids between mouse and human cell lines have been used to identify the specific chromosome that governs the synthesis of type I procollagen. Fourteen hybrid clones and subclones were derived independently from crosses between mouse parents [LM (thymidine kinase-negative) or A9 (hypoxanthine phosphoribosyltransferase-negative)] and human cells (human diploid lung fibroblasts WI-38 or diploid skin fibroblasts GM5, GM17, and GM9). The cultures were labeled with [(3)H]proline in modified Eagle's medium without serum. Radioactive procollagens were purified from the medium by the method of Church et al. [(1974) J. Mol. Biol. 86, 785-799]. DEAE-cellulose chromatography was used to separate collagen and type I and type III procollagen. Human type I procollagen was assayed by double immunodiffusion analysis with type I procollagen antibodies prepared by immunizing rabbits with purified human type I procollagen. These analyses combined with karyology and isozyme analyses of each hybrid line have produced evidence for the assignment of the gene for human type I procollagen to chromosome 17. A human microcell-mouse hybrid cell line containing only human chromosome 17 was positive for human type I procollagen, lending further support to the assignment of the human type I procollagen gene to chromosome 17. Finally, by using a hybrid line containing only the long arm of human chromosome 17 translocated onto a mouse chromosome, the type I procollagen gene can be assigned more specifically to the long arm of chromosome 17.

Animals↗

PubMed1979

Tumor-specific immunity induced by somatic hybrids. I. Lack of relationship between immunogenicity and tumorigenicity of selected hybrids.

Hybrid clones were derived from fusion of TEPC-15 plasmacytoma cells of BALB/c mice with mouse L cells of C3H origin. The morphology, tumorigenicity, and immunogenicity of three representative clones were extensively studied. One clone (LTC-1) showed a morphology intermediate to that of either parental cell and possessed the highest tumorigenic and immunogenic properties. The other two clones displayed a "flat" morphology which differed significantly from that of either parent. One of these two, LTC-4, eventually induced tumors in some (BALB/c X C3H)F1 mice but failed to stimulate protective immunity against TEPC-15 tumor cells in BALB/c mice. The other hybrid clone, LTC-2, has a "very flat" morphology and did not induce tumors, although it was capable of stimulating a significant level of tumor immunity. Histologically, all the tumors induced by hybrid cells were fibrosarcomas rather than plasmacytomas. These results indicate that the morphology of hybrid cells may be correlated with the tumorigenicity as well as the histologic appearance of tumor. In addition, the degree of tumorigenicity of individual hybrid clones does not correspond to their immunogenicity in the host, suggesting that major antigens responsible for immunogenicity may not play an important role in induction of tumors.

Animals↗

PubMed1978

Hybridization properties of human X-chromosomal RNA transcripts from murine--human hybrids.

A human--mouse hybrid cell line which has retained the human X chromosome and a fragment of chromosome 2 contains RNA sequences transcribed from human DNA. Nuclear RNA enriched for human sequences was prepared from this hybrid cell line by a multistep hybridization procedure to mouse and human DNA immoblized on nitrocellulose filters. The properties of this RNA were analyzed by RNA--DNA hybridization techniques. The results indicate that we have prepared a RNA fraction enriched for sequences homologous to repeated DNA sequences of the human X chromosome.

Animals↗

PubMed1977

Genetic studies of hybrids between coliphage lambda and salmonella phage P22: genetic analysis of the P22-lambda hybrid class.

P22-lambda hybrids which retain the protein coat of P22 have been isolated and characterized into two types. Type 1 hybrids which have the c through O-P genes of lambda are unable to grow lytically on Salmonella typhimurium. On the other hand, type 2 hybrids which contain only the c region of lambda, plated on S. typhimurium. Both hybrid types retained the generalized transducing and antigenic conversion capabilities of P22.

Antigens, Viral↗

PubMed1977

Regional assignment of seven genes on chromosome 1 of man by use of man-Chinese hamster somatic cell hybrids. I. Results obtained after hybridization of human cells carrying reciprocal translocations involving chromosome 1.

Regional localization studies of genes coding for human PGD, PPH1, PGM1, UGPP, GuK1, Pep-C, and FH, which have been assigned to chromosome 1, were performed with man-Chinese hamster somatic cell hybrids, Informative hybrids that retained fragments of the human chromosome 1 were produced by fusion of hamster cells with human cells carrying reciprocal translocations involving chromosome 1. Analysis of the hybrids that retained one of the translocation chromosomes or de novo rearrangements involving the human 1 revealed the following gene positions: PGD and PPH1 in 1pter leads to 1p32, PGM1 in 1p32 leads to 1p22, UGPP and GuK1 in 1q21 leads to 1q42, FH in 1qter leads to 1q42, and Pep-C probably in 1q42.

Animals↗

PubMed1979

Cytogenetics of somatic cell hybrids. I. Progression of stemlines in continuous uncloned cultures of man-mouse cell hybrids.

Karyotypes of hybrid cells were studied in continuous uncloned cultures by Q- and C-bandings. Cultures were initiated by virus-mediated or spontaneous cell fusions from normal human diploid fibroblasts and mouse heteroploid RAG cells. Heterokaryons containing complete genomes of both parental cells randomly lost chromosomes from both species. The majority of cells in early growth stages, however, still possessed a nearly complete human genome. The rate of human chromosome loss in subsequent growth periods was not uniform, being gradual in some and rapid in others. The initially predominant 2n human-1s mouse (1h:1m) type was soon replaced by a less frequent 2n human-2s mouse (1h:2m) type. Over an increased period of time in mass culture, the number of stemlines decreased. One stemline, often a (1h:2m) type with a greatly reduced human complement, outgrew the others and occupied the entire culture. Therefore, the usual process of clonal isolation may confer a negative selection bias against cell hybrids retaining a large number of human chromosomes. Hybrid stemlines with stable karyotypes were established in the present HAT-agar selection system before 36 days after fusion had elapsed.

Animals↗

PubMedDate not supplied

[Analysis of the thermostability of the hybrid DNA molecules of microorganisms as a means of increasing the resolution of the molecular hybridization technic].

A comparative study of termostability of microorganisms DNA was performed in order to increase the resolution of the method of molecular hybridization. Molecular hybridization was carried out and the curve of hybrid DNA duplexes distribution, acccording to termostability of two groups of microorganisms, related to strains Echerichia coli B1 and Vibrio cholerae eltor 18647, were obtained. It was determined that the form of the curves is specie specific for the microorganisms investigated but there exists a similarity between the closely related strains which can not be distinguished by the percent of homology.

Base Sequence↗

PubMed1977

[Intergeneric conjugational hybridization of Escherichia coli and Salmonella typhimurium. 1. Obtaining a salmonella hybrid possessing greater recipient activity in crosses with Escherichia coli].

Intergeneric hybrids were selected from mating HfrH Escherichia coli with F- Salmonella typhimurium. The hybrid obtained from E. coli leu+ and pro+ genes possessed the increased recipient ability in the mating with E. coli HfrR1 (O--ilv--metE--ara). This hybrid lacked the ability to restrict the phage P1 DNA propagated on E. coli K-12. The replacement of mutated uvrA gene of Salmonella for uvrA+ gene of E. coli restore uvr+ phenotype of Salmonella mutant.

Coliphages↗

PubMed1975

Somatic cell hybrids between mouse peritoneal macrophages and simian-virus-40-transformed human cells: II. Presence of human chromosome 7 carrying simin virus 40 genome in cells of tumors induced by hybrid cells.

Cells derived from tumors induced in "nude" mice after injection of cells that were hybrids between mouse peritoneal macrophages and simian virus 40 (SV40)-transformed human cells were found to retain the human chromosome 7 carrying the SV40 genome, and indicate that the presence of human chromosome 7 carrying the SV40 genome is responsible for the expression of the tumorigenic phenotype in the hybrid cells.

Animals↗

PubMed1978

F1-hybrid anti-parental-strain reactivity. II. Proliferation of C3H X CBA hybrid lymphocytes in the spleens of irradiated CBA mice.

Experiments were conducted to explore whether C3H X CBA lymphocytes can react by proliferation when they meet parental CBA spleen cells. MLC tests could not detect such a reaction, but infusion of C3H X CBA lymph node cells into irradiated CBA hosts resulted in rapid cell proliferation in the host's spleen. Such a cell proliferation was also observed after infusion of T-cell-enriched lymph node cell preparations or thymic cells from C3H X CBA donors. Upon transfer to new irradiated mice these proliferating cells continued to proliferate in CBA mice but not in C3H X CBA mice. Further evidence that the injected T-cells were the proliferating emerged from experiments where AKR X CBA lymphocytes were found to proliferate in spleens of irradiated CBA mice and that most of these cells posessed the theta antigen determined by AKR. Proliferation of F1-hybrid lymphocytes in the spleens of its irradiated parental strains was found not to be a general phenomenon and is probably restricted to some Mls-antigen-compatible strain combinations. The possibility that the C3H X CBA hybrid lymphocytes are stimulated to proliferations by CBA lymphocytes reactive against the C3H-determined Mls antigen is discussed.

Animals↗

PubMed1978

Construction of a novel plasmid-phage hybrid: use of the hybrid to demonstrate ColE1 DNA replication in vivo in the absence of a ColE1-specified protein.

A hybrid bacteriophage, P420, was constructed in vitro; it contains part of bacteriophage P4 and a 3.6-kilobase derivative of plasmid ColE1. In Escherichia coli, the plasmid-phage hybrid can exist as a stable plasmid or can be packaged into infective bacteriophage particles. Replication of P420, directed by the ColE1 replicon, was found to occur after P420 phage infection of E. coli cells that had been incubated in the presence of chloramphenicol. Replication began without a lag period and resulted in the synthesis of covalently closed circles of P420 DNA. Like ColE1 DNA replication but unlike that of P4, replication was dependent on DNA polymerase I and was sensitive to rifampicin. The presence of a resident ColE1 plasmid in the infected cells resulted in an inhibition of the replication of the incoming P420 DNA. These results indicate that ColE1 does not require a plasmid-coded protein to replicate its DNA in vivo and demonstrate the utility of P4 bacteriophage for coupling bacteriophage properties to a plasmid replicon.

Bacterial Proteins↗

PubMed1979

Expermental hybridization within the genus Triturus (Urodela: Salamandridae). III. Evidence for crossing-over, true chiasmata and chomosomal homologies in the spermatogenesis of F1 species hybrids, T. cristatus carnifex female X T. marmoratus male.

Spermatogenesis in the F1 hybrid (2n=24=12 female + 12 male) between the closely related newt species T. cristatus carnifex and T. marmoratus was apparently normal up to pachytene. Many unpaired chromosomes were present at diplotene and a typical diakinesis was lacking. Primary spermatocytes at meta- and meta-anaphase contained up to 12 regular intergenomal bivalents and a corresponding number of univalents when less then 12 II. Most chiasmata were terminal or subterminal, some intercalary. Chiasmata between corresponding heterospecific chromosomes can be reported as true: real crossing over has taken place, proving the presence of primary chromosomal homologies between the 2 sets of the parental species. Evidence for recombination is based on the segregation of particular markers (i.e., subterminal C-bands and NORs) observed in certain chromosomes at metaphase II. One chromatid of single chromosomes can show the T. cristatus "pheno-type" and the other the T. marmoratus phenotype". A few primary spermatocytes contain a certain number of irregular associations (intragenomal or intrahaploid bivalents, irregular intergenomal bivalents, chromosome multivalents) joined by chiasmata which can be defined as anomalous. Other abnormalities concern the occurrence of interlocked bivalents which occasionally show an anomalous exchange between heterologous chromatids. Cytogenetic criteria useful to evaluate the taxonomic relationships between different species have been discussed as well as some possible trends in chromosome evolution and speciation within the genus Triturus.

Animals↗