Biomedical subjects

F H Ruddle

Publications and source records attributed to F H Ruddle.

At least 361 records · Page 20Linked to original sources

PubMed1975

Genetic analysis of the cell surface: association of human chromosome 5 with sensitivity to diphtheria toxin in mouse-human somatic cell hybrids.

Diphtheria toxin inhibits protein synthesis in eukaryotic cells by catalyzing inactivation of elongation factor 2. The 10,000-fold greater sensitivity in vitro to diphtheria toxin of human cells as compared to mouse cells seems to be attributable to a difference at the level of the cell membrane. Mouse-human cell hybrids are as sensitive to diphtheria toxin as human cells. We have shown that the sensitivity of the hybrid cells is due to a gene or genes located on human chromosome 5. Mouse-human hybrid cells in which chromosome 5 is present are as sensitive to the toxin as human cells, which hybrids without chromosome 5 are as resistant as mouse cells. Entry of toxin into cells seems to be a two-step process involvin, (1) binding of toxin to the cell surface and (2) endocytotic uptake of toxin. The difference in sensitivity between human and mouse cells and between hybrid cells with and without chromosome 5 does not appear to be due to a difference in endocytotic activity and may be due to presence or absence of toxin-specific receptor.

Animals↗

PubMed1975

Genetic complementation in heterokaryons of human fibroblasts defective in cobalamin metabolism.

Inherited methylmalonicacidemia due to deficiency of methylmalonyl-CoA mutase (methylmalonyl-CoA CoA-carbonylmutase; EC 5.4.99.2) activity results from at least three classes of biochemically distinct defects affecting cobalamin (Cbl: vitamin B12) metabolism (cbl A, cbl B, and cbl C mutants) and a fourth class producing a defective mutase apoenzyme. We have obtained genetic evidence in support of this biochemical heterogeneity, using heterokaryons prepared by Sendai-virus-mediated cell fusion. Nine fibroblast lines from patients with defective Cbl metabolism (4 cbl A, 3 cbl B, and 2 cbl C), two from patients with defective mutase apoenzyme, and two from controls were fused in pairwise combinations and tested for functional mutase holoenzyme using a radioautographic procedure which detects [14C]propionate incorporation into trichloroacetic-acid-precipitable material in fibroblast monolayers in situ. Each of the mutants incorporates negligible radioactivity compared to control cells. Activity is also negligible when different mutants are mixed without virus or when homokaryons are produced by self-fusion. Heterokaryons produced by fusing members of each of the four mutant classes with representatives of any other class recover the ability to incorporate [14C]propionate to levels comparable to those of control cells. However, heterokaryons produced between members of the same class fail to complement in all cases. We conclude that the mutants with defective Cbl metabolism (cbl A, cbl B, cbl C) comprise three complementation groups, that a fourth group corresponds to mutase apoenzyme deficiency, and that all four classes of mutations are recessively inherited.

Amino Acid Metabolism, Inborn Errors↗

PubMed1975

Mouse-human heterokaryon analysis with a 33258 Hoechst-Giemsa technique.

The bibenzimidazol derivative 33258 Hoechst can be used to distinguish microfluorometrically between mouse and human nuclei in heterokaryons. This affords a quick and accurate alternative to autoradiography in the analysis of such heterokaryons. The 33258 Hoechst fluorescence patterns can be converted after irradiation to a Giemsa rendition of the differential staining.

Animals↗

PubMed1975