Biomedical subjects
Publications and source records attributed to G Lüder.
The virulent Bacillus subtilis phage SPP1 transduces plasmid DNA. Plasmid-transducing phages contain only plasmid DNA. Such DNA represents a concatemer of monomeric plasmid molecules with the molecular weight of mature SPP1 DNA. Biological parameters of plasmid transduction are described.
41 genes of SPP1 have been delineated by using complementation analyses of 75 conditionally lethal (ts and sus) mutations. The physical locations of these genes on the SPP1 chromosome have been determined by transfection/marker rescue experiments in which restriction endonuclease generated fragments of SPP1 DNA were used as donor DNA. The physical order of these fragments has been previously established (Ratcliff et al., 1979).
Transfection with phi 29 DNA is predominantly caused by multimolecular, protease-sensitive aggregates of DNA. A minority of transfecting DNA molecules having properties of unit-length phi 29 genome molecules show a quadratic dose response in transfection.
A recF mutation renders Bacillus subtilis cells very sensitive to DNA-damaging agents. Such a recF defect is partially suppressed either by the presence of the recA73 mutation or by the presence of a plasmid-borne, heterologous, single-stranded DNA-binding (ssb) protein gene. Plasmids carrying ssb genes also suppressed the recR and recL defects. Our results suggest that suppression occurs by increasing recombinational repair. The effect of the suppressors may be at the level of induction of the SOS response.
A computer program is described for the collision technique by which data acquisition and data interpretation is possible. Paired stimuli with varying interstimulus times evoke a muscle action potential. The amplitude or the rectified area integral as a function of interstimulus times was used to define the scatter of conduction velocities within the ulnar nerve. In normal and slightly distorted EMG signals the amplitude and area produces the same scatter. In distorted potentials the integrated area is more sensitive. The technique was furthermore used to separate two different age groups of normal persons. Significant differences were seen as well as in an age matched group of patients with myotonic dystrophy. The collision technique and the computer program proved to be sensitive and applicable in routine examinations.