During serial passages of Herpes simplex virus (HSV) at high multiplicity of infection, virions containing defective viral DNA accumulate in the progeny. The defective DNA molecules are made up by repeats of restricted portions of the standard viral genome. Two different classes of defective DNA derived from HSV-1 Angelotti (ANG) in independent series of high MOI-passages were studied. The nucleotide sequences contained in the defective DNA were localized on the parental viral genome. One of the two classes contained sequences from non-contiguous sites mapping in unique and in redundant regions of the parental DNA, whereas the second class apparently originates from the S-terminal redundant region of the parental DNA. The localization of defective DNA sequences was complicated by the fact that there exists sequence homology between the S-terminal redundancy and various unique DNA sequences in the L-segment of the HSV-1 ANG genome.

Herpes simplex virus type 1 (HSV-1), strain ANG, was passaged serially at high MOI or undiluted on RC-37 cells. The yields of infectious virus decreased and increased periodically with a maximum of about 3 log units variation in titer. The amount of newly synthesized HSV-1 DNA, however, did not vary by more than a factor of 2. On the other hand, the fraction of total HSV-1 DNA associated with virions was reduced at passage numbers coinciding with the minima in the yields of infectious progeny virus. Apparently, low yields of infectious virus mainly reflected a reduced efficiency of packaging of viral DNA into mature virus particles. One step in the process of virus maturation which appeared to be impaired was the assembly of nucleocapsids. HSV-1 ANG was shown to be capable of generating different classes of defective particles in independent series of virus passages at high MOI.

Esterase D phenotypes were determined in a population sample of Berlin (West) by means of high voltage agarosegel electrophoresis. The gene frequencies were calculated with 0.8835 for Es D-1 and 0.1165 for Es D-2. This is consistent with other results obtained in German populations.

Two external metabolizing systems, S9 mix from Aroclor-induced rat livers and freshly isolated hepatocytes, were used for activation in cultures of human lymphocytes and V79 cells. 7, 12-dimethylbenzanthracene (DMBA) and aflatoxin B1 (AFB1) were employed as indirectly acting reference mutagens. Mutagenic effects were measured by induction of sister chromatid exchange (SCE). With DMBA, SCE-inducing effects were found to be quite similar after activation by S9 mix and activation by hepatocytes. In human lymphocytes nearly the same dose-effect relationships were found with both metabolizing systems; in V79 cells the hepatocyte-mediated induction of SCE was detectable at slightly lower concentrations than the S9-mediated SCE induction. In contrast with AFB1, S9 activation led to a stronger SCE induction than hepatocyte activation in both target cells. The induction of chromosomal aberrations by AFB1 after activation by the two metabolizing systems was also analysed in V79 cells. This experiment again revealed that AFB1 was more efficiently activated by S9 mix than by hepatocytes, and it appeared that AFB1 is a more potent inducer of chromosomal aberrations than of SCE. The different activation capacities of the two metabolizing systems for AFB1 may be due to the maintenance of inactivation mechanisms in hepatocytes or to the Aroclor induction of the S9 fraction. Our experiments have shown that the suitability of hepatocytes as an activation system is not restricted to microbial or eukaryotic point mutation assays, but that hepatocyte metabolism can also be successfully included in cytogenetic tests with short- and long-term cultures of mammalian target cells.