SV40 DNA and pSV2neo were microinjected into isolated nuclei of Acetabularia mediterranea. The injected nuclei were implanted into anucleate cell fragments of the same species. Such combinations not only survived but also formed progeny. The F1, F2 and F3 generations of these combinations were analyzed. In the case of SV40‐treated cells T‐antigen was expressed and accumulated in the nuclei of all three generations studied as shown by indirect immunofluorescence. Nuclear exchange experiments revealed expression of the T‐antigen only if a transformed nucleus but not if only a transformed cytoplasm was involved. Transformation by pSV2neo, a chimeric gene with a selectable marker was demonstrated by the induction of G‐418 resistance as well as immunofluorescence. Genomic DNA was isolated from gametes, originating in cysts from the F1, F2 and F3 generations of injected cells, and subjected to Southern analysis. These experiments demonstrated that both types of DNA are integrated into the host genome.

1. The occurrence of an as yet unidentified cytochrome P-450 in the microsomal fraction of the digestive gland of the snail, Lymnaea stagnalis was studied. 2. Studies in vivo and in vitro (digestive gland homogenates or the 170,000g fraction) of the cytochrome P-450-mediated metabolism of substrates such as biphenyl, pentoxy- and ethoxy-resorufin and aminopyrine have been made. 3. Cytochrome P-450 concentration in the digestive gland calculated from CO-difference spectra was 0.30 +/- 0.05 nmol/g tissue. This amount was not increased either by phenobarbital or by 3-methylcholanthrene. 4. Aniline binding spectra resembled normal type II spectra, while type I model substrates such as hexobarbital and 2,2'-dichlorobiphenyl showed type II- or reversed type I-like spectra. 5. O-Deethylation of 7-ethoxyresorufin did not occur, but 7-pentoxyresorufin O-depentylation activity (80.4 +/- 28.6 pmol resorufin/g per hour) and aminopyrine N-demethylation activity (375 +/- 96 pmol formaldehyde/g per minute) were demonstrated. 6. 4-Hydroxybiphenyl was the major metabolite of biphenyl, while minor amounts of 2-hydroxybiphenyl were formed (in vivo: 63.7 nmol 4-hydroxybiphenyl and 3.33 nmol 2-hydroxybiphenyl per snail per 24 h, after an oral dose of 778.2 nmol biphenyl; in vitro 118 +/- 21 pmol and 21 +/- 9 nmol, respectively (digestive gland homogenate/mg protein, per hour). 7. The results indicate that the isoenzymes involved in the observed MFO activities resemble isoenzymes P-450b/e.

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A variety of base-modified nucleotide analogues was prepared and characterized as their alpha-32P- or U-14C-labeled compounds. Carrier-linked nucleotide binding and carrier-catalyzed exchange across the inner membrane of rat liver mitochondria were measured by using an inhibitor (atractyloside) stop method. Kinetic data of carrier-specific bound analogues were evaluated from Dixon plots and indicate that these analogues are competitive inhibitors for mitochondrial [14C]ADP uptake. Km and Vmax values for carrier-mediated uptake of nucleotide analogues were calculated from Lineweaver-Burk plots. By means of the analogues, a systematic mapping of the essential chemical and steric interactions between the transporter protein and the heterocycle of its substrate in the course of the binding as well as transfer step was achieved. Prerequisites for carrier-specific binding (recognition) are (A) an anti- or syn-positioned beta-glycosyl-linked heterocycle, (B) a nitrogen ring atom in position 7 for syn-structured analogues, and (C) an electron-rich region at the N(1) position, i.e., a permanent dipole moment oriented toward N(1) for anti-structured analogues. Additional requirements for subsequent transport catalysis are (A) a non-fixed anti-positioned base moiety with a beta-glycosyl torsion angle of about -20 degrees, (B) a C(6)-positioned amino group, and (C) an unsubstituted C(2) atom. The complementary binding site at the carrier protein to the N(1)-C(6)(-NH2) amidine region is proposed to be represented by two juxtaposed and invariant bonding points, i.e., an asparagine or glutamine residue.

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