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J Hauser

Publications and source records attributed to J Hauser.

At least 91 records · Page 5Linked to original sources
PubMed1983

Adenovirus 2 early gene expression promotes susceptibility to effector cell lysis of hybrids formed between hamster cells transformed by adenovirus 2 and simian virus 40.

Weakly oncogenic adenovirus 2 (Ad2)-transformed LSH hamster cells are sensitive to lysis by spontaneously cytolytic lymphoid cells and activated macrophages, whereas highly oncogenic simian virus 40 (SV40)-transformed LSH cells are relatively resistant to these nonspecific effector cells. Somatic cell hybrids formed between Ad2- and SV40-transformed hamster cells, which expressed Ad2 tumor (T) antigens, exhibited an increased cytolytic susceptibility compared to Ad2 T antigen-negative cell hybrids or nonhybrid SV40-transformed cells. No correlation was found between the expression of SV40 T antigen in hybrid cells and cytolytic susceptibility. The results suggest the existence of a novel function for early Ad2 genome-encoded polypeptides (T antigens) expressed in transformed hamster cells--the induction of susceptibility to destruction mediated by immunologically nonspecific effector cells.

Adenoviruses, Human↗
PubMed1983

Suppression of the simian virus 40 tumorigenic phenotype in hybrid cells formed from simian virus 40- and adenovirus 2-transformed hamster embryo cells.

Hamster cells transformed by adenovirus 2 (Ad2) or simian virus 40 (SV40) have different tumorigenic phenotypes. In the present study, somatic cell hybrids formed from Ad2- and SV40-transformed hamster cells were used to determine whether possible interactions between the integrated viral genomes would influence the tumorigenic phenotype of hybrid transformed cells. These somatic cell hybrids were of two types, one expressing both Ad2 and SV40 T-antigens and the other expressing only SV40 T-antigens. Tumor induction by hybrid cells that expressed both Ad2 and SV40 T-antigens was reduced in adult syngeneic hamsters and abrogated in adult allogeneic hamsters. These results indicate that the tumorigenic phenotype of transformed somatic cell hybrids that contain both the Ad2 and SV40 genome is governed by the genetic expression of Ad2. This expression may alter the ability of SV40-transformed hamster cells to resist the immunologically nonspecific defenses of the host.

Adenoviridae↗
PubMed1982

Morphogenesis of regenerating fragments of Dugesia schubarti (Turbellaria tricladia).

An extensive study of regeneration processes from the point of view of the axial gradient theory and its corollary, the possibility of forming two heads from one fragment (the Janus head problem) was undertaken on the South American species Dugesia schubarti. Altogether 330 specimens were used, cut into 2,640 pieces and the regeneration of each of them was followed to the end result. Concerning the role of an axial gradient in the regeneration processes the results were not supportive. Anterior fragments often regenerated less completely (eyes and auricles without complete heads) than more posterior ones, although the differences were not sharp, due to individual variations of physiological nature. The Janus head regeneration, one of the postulates of the axial gradient theory, was analyzed both on preauricular (parts A) and postauricular fragments (part B). The regeneration of parts A was less perfect than that of parts B. ALthough a considerable number of the part A fragments regenerated normally, the majority of the cases remained incomplete for a long time and eventually disintegrated without completing the regeneration process. The only irregularity parts B proceeded more evenly and the death rate was also much lower. The only irregularity observed was a great number of cyclopic regenerates, i.e. heads with one single eye in the midline. Some of these cyclopic heads remained permanently in this condition but most of them later separated in two eyes but with a pigment between them, and in others the cyclopic eye separated in two normal eyes at the end of the regeneration. The Janus head phenomenon was never observed.

Animals↗
PubMed1981

Kinetics of inhibition of papovavirus DNA synthesis by superinfection with adenovirus 2 and non-defective adenovirus 2-simian virus 40 hybrid viruses.

Simian Virus 40 (SV40) DNA synthesis is inhibited in monkey cells by superinfection with adenovirus 2 (Ad2) and various non-defective Ad2-SV40 hybrid viruses. Similarly, BKV (a human papovavirus) DNA synthesis is inhibited in human cells by superinfection with Ad2. Kinetic studies indicate that inhibition begins during the early phase of the Ad2 lytic cycle. Superinfection with Ad2 does not significantly alter the formation of SV40 T antigen. Superinfection with Ad2 late in SV40 lytic cycle is less efficient in the inhibition of SV40 DNA synthesis, and the onset of Ad2 DNA synthesis is delayed, compared to superinfection early in the SV40 lytic cycle. These findings suggest that the Ad2 and SV40 genomes may compete to bind an early AD2 protein which is essential for Ad2 replication, but which blocks SV40 replication.

Adenoviruses, Human↗
PubMed1981

Regulation of viral transcription in cells infected with iododeoxyuridine-substituted simian virus 40 as a model for the activation by iododeoxyuridine of latent viral genomes.

5-Iododeoxyuridine (IdUrd) induces the expression of viruses in a variety of cell lines that harbor latent viral genomes. Moreover, IdUrd stimulates cellular as well as viral RNA synthesis in certain cells. In order to understand better the action of IdUrd on RNA metabolism, we have examined viral RNA synthesis in monkeys cell infected with IdUrd-substituted simian virus 40 (SV40). Extensively substituted SV40, in which 18 to 35% of the thymidine residues were substituted by IdUrd, was 100-fold less viable (by plaque analysis) than was unsubstituted SV40, although the substituted virus induced 30 to 50% as much viral-specific RNA as did the unsubstituted virus. In contrast, SV40, containing only 10 to 15% IdUrd, substitution was almost as viable as unsubstituted virus, and the substituted SV40 induced 5-fold more viral-specific RNA, as well as longer viral messenger RNA transcripts, than did the unsubstituted virus. These results suggest that the lightly substituted, mutagenized SV40 genome may produce defective proteins which fall to regulate their own transcription. Cellular DNA into which halogenated pyrimidines have been incorporated may also induce the synthesis of defective regulatory proteins, including cellular repressors of transcription which normally maintain the latent state of integrated viral genomes.

Animals↗
PubMed1979

Method for determining the extent and copy number of overlapping and nonoverlapping segments of integrated viral genomes.

We analyzed the method of exhaustive hybridization of single-stranded DNA and derived a general relationship between the fraction of the probe DNA hybridized and the sizes and copy numbers of the segments of the viral genome integrated in cellular DNA. The equations employed can be used to analyze integrated DNA comprised of overlapping and nonoverlapping segments of the viral genome. Using these equations, we analyzd the adenovirus type 2 DNA content of a series of hamster cell lines transformed by adenovirus type 2 and several adenovirus type 2-simian virus 40 hybrid viruses. We found no eividence that the integrated viral DNA is comprised of overlapsping segments. However, the number of copies of the integrated segments varies between lines cloned from the same transformed isolate, and copy numbers change during in vivo passage of transformed cells.

Adenoviruses, Human↗
PubMed1976

Content and expression of integrated viral DNA in hamster cells transformed by nondefective adenovirus type 2- simian virus 40 hybrid viruses.

Hamster cells transformed by adenovirus 2 (Ad2) and five nondefective Ad2-simian virus 40 (SV40) hybrid viruses are all of the Ad2-transformed phenotype. All lines accumulate Ad2 RNA and Ad2 T antigen; two hybrid-transformed lines accumulate SV40 RNA, but only one contains detectable amounts of SV40 antigens. We examines selected lines from this group of transformed hamster cells for Ad2 DNA content and viral RNA expression by using hydroxyapatite chromatography and separated strands of labeled viral DNA as probes. All lines studies contain 1 to 2 Ad2 genome equivalents per haploid equivalent of cell DNA. The expression of Ad2 RNA exhibits two distinct patterns. In one pattern, transcription of the heavy strand of Ad2 DNA is less than that of the light strand, whereas in the second pattern of Ad2 RNA expression the extent of heavy-strand transcription is greatly increased. In the two lines containing SV40 RNA, the entire SV40 (-) strand is transcribed; the (+) strand is not expressed in these cells. These patterns of viral RNA expression suggest the possibility that host promoters may play a role in regulating transcription of integrated viral DNA.

Adenoviridae↗