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Biomedical subjects

C M Croce

Publications and source records attributed to C M Croce.

At least 505 records · Page 28Linked to original sources
PubMed1974

Restoration of the conversion of desmosterol to cholesterol in L-cells after hybridization with human fibroblasts.

Hybrids between different human cells (which synthesize cholesterol) and mouse cells (whose end-product of sterol synthesis is desmosterol) were analyzed for the ability to convert desmosterol to cholesterol. Conversion of [(14)C]desmosterol to cholesterol and incorporation of [(14)C]acetate into the end-product sterol were studied in the parental and hybrid cells. Concordant segregation of the conversion of desmosterol to cholesterol and the human chromosome F-20 was observed.

Acetates↗
PubMed1974

Chromosome assignment of the T-antigen gene of simian virus 40 in African green monkey cells transformed by adeno 7-SV40 hybrid.

Somatic cell hybrids between mouse cells deficient in thymidine kinase [ATP:thymidine 5'-phosphotransferase (EC 2.7.1.75)] and two different monkey cell lines transformed by an adeno 7-SV40 hybrid have been produced using both a semiselective and a double selective procedure. Concordant segregation of the expression of SV40 T antigen with a specific monkey chromosome has been observed in all the mouse-monkey hybrid clones examined. Subcloning of three SV40 T antigen positive hybrid clones resulted in their segregation into SV40 T antigen-positive and negative subclones. Positive correlation between the SV40 T antigen and the same monkey chromosome has been observed in all the subclones examined.

Adenoviridae↗
PubMed1974

Assignment of the human gene for hexose-1-phosphate uridylyltransferase to chromosome 3.

Mouse-human hybrid clones were tested for the presence of human hexose-1-phosphate uridylyl-transferase (EC 2.7.7.12;UDPglucose:alpha-D-galactose-1-phosphate uridylyltransferase). Two criteria, starch gel electrophoresis and double-immunodiffusion against a human transferase-specific antibody, were used to identify human enzyme in the hybrid clones. Seventeen of 33 hybrid clones analyzed were found to contain human transferase by both criteria. Karyological analysis of the hybrid clones showed concordant segregation of human transferase with human chromosome 3. Human galactokinase was asyntenic with human transferase. We thus assign this gene to human chromosome 3.

Animals↗
PubMed1973

Assignment of the T-antigen gene of simian virus 40 to human chromosome C-7.

Hybrid cell clones between mouse cells deficient in thymidine kinase (EC 2.7.1.21) and two different human cell lines transformed by simian virus 40 (SV40) and deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) were examined for SV40 tumor (T) antigen(s). Concordant segregation of the gene(s) for SV40 T antigen and human chromosome C-7 was observed in these hybrids. The human chromosome C-7 which contains the gene(s) for SV40 T antigen is preferentially retained by the majority of the hybrid clones tested. When hybrid clones positive and negative for SV40 T antigen, derived from the fusion of SV40-transformed Lesch-Nyhan fibroblasts with mouse cells, were fused with CV-1 permissive cells, SV40-specific V antigen was observed only in the cultures derived from fusion of the hybrid clones positive for T antigen. This result indicates a linkage relationship between human chromosome C-7, SV40 T-antigen gene(s), and SV40 genome(s) integrated in the human transformed cells.

Animals↗
PubMed1973

Effect of environmental pH on rescue of Simian virus 40.

Rescue of SV40 virus after Sendai virus-mediated fusion of transformed mouse or hamster cell lines with permissive monkey cells was strikingly dependent on pH in the range 6.4-8.8, with a maximum at pH 8.4. The titer of virus recovered at pH 8.4 was 2 logs higher than that at pH 7.6, and 4 logs higher than that at pH 6.4. The pH-sensitive step was neither the number of heterokaryocytes formed, which was essentially the same at pH 7.6 and 8.4, nor the degree of SV40 replication in the monkey cells, which was also unaffected by pH variation in the range 7.2-8.4.

Animals↗
PubMed1973

Human regulatory gene for inducible tyrosine aminotransferase in rat-human hybrids.

The inducibility of tyrosine aminotransferase (EC 2.6.1.5) by corticosteroid hormones in rat-human hybrid clones was studied. The presence of human X chromosome activity in the cells was always associated with the suppression of tyrosine aminotransferase inducibility in all the clones examined. Negative correlation between the human X chromosome and inducibility of the enzyme was clearly established. Corticosteroid receptor was present to the same extent in hybrid cell clones that either contained or lost the human X chromosome. The human repressor for inducible tyrosine aminotransferase has a linkage relationship with glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and hypoxanthine-guanine-phosphoribosyltransferase (EC 2.4.2.8) and, therefore, can be assigned to the X chromosome.

Animals↗
PubMed1973

Restoration of hypoxanthine phosphoribosyl transferase activity in mouse 1R cells after fusion with chick-embryo fibroblasts.

Fusion of the 1R mouse cell, which lacks activity of hypoxanthine phosphoribosyl transferase (EC 2.4.2.8), with chick-embryo fibroblasts yielded progeny cells that survived in hypoxanthine-aminopterin-thymidine selective medium. This property and the failure of the progeny to survive in 8-azaguanine indicated that hypoxanthine phosphoribosyl transferase activity was present. Electrophoretic analysis revealed that the enzyme was of mouse, not chick, origin. These observations are consistent with the operation of a regulator gene responsible for the absence of hypoxanthine phosphoribosyl-transferase activity in the 1R cell and its presence in the progeny.

Adenine↗
PubMed1973

Reexpression of the rat hypoxanthine phosphoribosyltransferase gene in rat-human hybrids.

Fusion of hypoxanthine phosphoribosyltransferase (HPRT)(-) rat hepatoma cells with HPRT(+) human fibroblasts yielded hybrid clones that grew in HAT selective medium and contained all the rat chromosomes and one to nine human chromosomes. Among the retained chromosomes was the human X chromosome. In all clones backselected in medium containing 8-azaguanine, human X chromosome was absent. Electrophoretic analysis revealed that, without exception, hybrid clones growing in HAT medium had an active HPRT enzyme, either human or rat, or both. When these clones were backselected in 8-azaguanine, they did not show HPRT enzyme activity. Hybrids that contained the human X chromosome also had human glucose-6-phosphate dehydrogenase. The observed reexpression of rat HPRT in hybrid cells derived from HPRT(-) rat cells suggests that a genetic factor from the human cell determined the expression of the rat structural gene for HPRT.

Adenine↗
PubMed1972

Effect of environmental pH on the efficiency of cellular hybridization.

The hybridization of a human and mouse cell was strikingly pH-dependent, with a well defined optimum at (about) pH 7.6-8.0. The yield of hybrid cell colonies (1 per 500-2000 heterokaryocytes) was several hundred times greater than that obtained at pH 6.8-7.2. Although there was a significant effect on the efficiency of cell fusion, the critical time for the pH effect was in the first 4-8 days after fusion, presumably while viable hybrids were being formed from the multinucleated heterokaryocytes.

Animals↗