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Biomedical subjects

W G Verly

Publications and source records attributed to W G Verly.

At least 73 records · Page 4Linked to original sources
PubMed1976

Inactivation of the T7 coliphage by monofunctional alkylating agents. Action of phage adsorption and injection of its DNA.

Alkylation by ethyl or methyl methanesulfonate to an extent that inactivates more than 99.5% of T7 coliphages has no effect on phage adsorption on Escherichia coli B cells, but decreases the amount of phage DNA injected into the host cells. Depurination interferes with the injection of the phage DNA. Failure to inject the whole phage genome thus appears to be a cause of the immediate as well as of the delayed inactivation of the T7 coliphage treated by monofunctional alkylating agents; the hypothesis that it is the only cause of inactivation, although not very likely, cannot be excluded at the present time.

Binding Sites↗
PubMed1976

Action of ethyl and methyl methane sulfonates on DNA injection and genetic recombination in T7 bacteriophage.

After treatment with methyl or ethyl methane sulfonate, T7 amber mutants display a reduced capacity for recombination. Moreover, alkylation reduces recombination frequency involving markers on the right-hand side of the genetic map more than it reduces recombination frequency involving markers on the left-hand side. We interpret this to mean that alkylation can stop DNA injection at any point along the DNA molecule, and that T7 phage injects its DNA in a unique fashion starting from the end carrying the genes for early proteins.

Alkylation↗
PubMed1975

Purification of Escherichia coli endonuclease specific for apurinic sites in DNA.

The endonuclease specific for apurinic sites in DNA has been isolated from Escherichia coli B41 as a pure monomeric protein of 32,000 daltons. The enzyme hydrolyzes a phosphodiester bond near the apurinic sites in double-stranded DNA; it does not hydrolyze untreated DNA and its action on alkylated DNA is restricted to the apurinic sites always present. This enzyme is not endonuclease II which is most probably a mixture of two enzymes, one a glycosidase (Kirtikar, D. M., and Goldthwait, D. A. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 2022-2026), the other an endonuclease for apurinic sites which is the enzyme isolated in this work.

Amino Acids↗
PubMed1975

Maintenance of DNA and repair of Apurinic sites.

Escherichia coli cells contain an enzyme which hydrolyzes a phosphodiester bond near each apurinic site in double-stranded DNA. This endonuclease is specific for apurinic sites; it has no effect on normal DNA, and its action on alkylated DNA is restricted to apurinic sites. In vitro incubation with the endonuclease for apurinic sites, DNA polymerase I, and ligase permits repair of DNA containing apurinic sites. The endonuclease for apurinic sites might thus play a role in cell survival after a treatment with alkylating agents; as DNA spontaneously loses purines, the enzyme might also play a role in the maintance of a normal DNA in every cell. Indeed, an endonuclease for apurinic sites has been found not only in bacteria but also in animal and plant cells; it is very active in thermophilic bacteria.

Apurinic Acid↗
PubMed1975

The hepatic chalone. II. Chemical and biological properties of the rabbit liver chalone.

A factor has been purified from rabbit liver which decreases the incorporation of 3H-thymidine in DNA of regenerating rat liver slices. This effect is due mostly to an inhibition of DNA synthesis from the deoxynucleoside triphosphates. The purified rabbit liver factor thus interferes with the liver cell division cycle. This inhibitor of DNA synthesis is specific for liver cells; it is not toxic for cultured hepatocytes and its action on DNA synthesis is reversible: at low dose, the inhibition of DNA synthesis in regenerating liver slices is transitory. The purified rabbit liver inhibitor is thus a chalone. The purified rabbit liver chalone ultrafiltrates through 1.2 nm pores, is destroyed by trypsine and pronase, carries a negative charge at pH 8.8 and a positive charge at pH 4.6; it is thermostable and likely a small peptide. It also inhibits RNA and protein synthesis in regenerating liver slices. The inhibition of protein synthesis is immediately maximal then decreases with time, while the maximum inhibition of DNA and RNA synthesis appears after a delay. When a low dose of chalone is used (0.2 unit per 5 ml), the inhibition of DNA and RNA synthesis disappears after some time: this is not due to a destruction of the chalone, but to a loss of sensitivity of the slices incubated in Hanks solution. The inhibitor content of liver cells, normal or malignant, seems inversely correlated with their state of growth. It is much lower in the liver of a young animal or in regenerating liver than in adult liver. Hepatomas produced by feeding DAB contain three times less inhibitor than the normal liver. The purified liver chalone is 5-10 times less active on the incorporation of 3H-thymidine in DNA of DAB hepatoma slices than in DNA of regenerating liver slices. It has no apparent action on adult liver slices; this might be due to the fact that 3H-thymidine incorporation into DNA of the adult organ depends, for the greater part, on other processes than DNA replication in hepatocytes.

Aging↗
PubMed1974

Inhibition of cell proliferation in the livers of hepatectomized rats by a rabbit hepatic chalone.

A purified chalone isolated from rabbit liver was tested in vitro on regenerating rat liver slices incubated with tritiated thymidine to determine more precisely the phase of the normal cell cycle that was blocked by that substance. Biochemical and radioautographic studies showed that the inhibition of tritiated thymidine incorporation during chromosomal DNA replication resulted chiefly from a block in the G(1)-S transition in the normal cell cycle. Under these conditions the chalone had little inhibitory effect on hepatocytes that were in the S phase of the cell cycle. The inhibitory effects of the liver chalone appeared to be specific for hepatocytes and no significant inhibition of cell division was observed when that compound was tested against intestinal villi or tongue epithelial cells of the rat. When, on the other hand, the purified chalone was injected into rats following partial hepatectomy, not only was an inhibition observed during the G(1)-S transition but an increase in the ratio of metaphases to anaphases was found, suggesting that a block also occurs at metaphase as a result of the action of the purified liver chalone used in this study. The injection of a crude supernatant fluid obtained from rabbit liver homogenates into partially hepatectomized rats resulted not only in a more pronounced block at the G(1)-S transition than was observed when the purified chalone was used, but the supernatant liquid also affected significantly DNA synthesis during the S phase of the cell cycle. These inhibitory effects were observed not only in hepatocytes but in intestinal epithelium and tongue epithelial cells of the rat as well. The rabbit liver supernatant fluid thus appears to contain, in addition to the liver chalone, one or more nonspecific inhibitors of DNA synthesis.

Animals↗
PubMed1974

In vitro repair of apurinic sites in DNA.

Apurinic sites disappear from DNA during an incubation of the DNA with the Escherichia coli endonuclease specific for apurinic sites, DNA polymerase I (EC 2.7.7.7.), and T4 ligase (EC 6.5.1.1). Omission of any one of these three enzymes and, in particular, omission of the endonuclease specific for apurinic sites prevents this in vitro repair.

Binding Sites↗