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Biomedical subjects

P Volpe

Publications and source records attributed to P Volpe.

At least 163 records · Page 9Linked to original sources
PubMed1977

An electron paramagnetic resonance study of free radicals in cells.

An electron paramagnetic resonance study was performed on cell lines of the following strains: HeLa, 37RC, L, FLC, NRK/RSV, 3T3/SV40. Unsynchronized and synchronized HeLa cells were studied with particular attention paid to the relation between growth and free radical concentration. Free radical levels were shown to be a function of the growth stage and different phases of the cell cycle.

Cell Division↗
PubMed1975

Polysome translational state during the cell cycle.

HeLa cells were synchronized with a double thymidine block. Ribosomal subunits, monomers and polyribosomes have been quantitatively analysed at hourly intervals, during interphase, and every 15 min, during mitosis. This analysis was performed on linear 7-47% sucrose gradients. From the beginning of G1 up to the end of S phase, a certain equilibrium among ribosomal subunits, monomers and polyribosomes is maintained, while from the time of entering G2 to M the translation machinery appears to be mobilized in the sense of polysome formation. Under these conditions, the amount of polysomes per cell during the mitotic cycle is expressed by a bi-phasic pattern showing pre- and post-mitotic peaks with a falling-off during S. The G1 peak, meanwhile, is much lower than the G2 peak. The incorporation of [3H]leucine into nascent polypeptide chains on polysomes, as well as into bulk cell proteins and into nuclear and cytoplasmic proteins considered separately, is also represented by a bi-phasic curve which shows, however, a higher peak in G1 and a lower peak in G2, with two fallings-off during S and M, respectively. Since between the G1 and the G2 amino acid pools there are not strong differences of leucine concentration, the discrepancy between the amount of polysomes and the rate of labelling is discussed on the basis of the differences of polysome shape found at the different stages of the cycle. In young cells, in fact, there is an abundance of small polysomes, while in the old cell large polysomes predominate. It is suggested that, in the old cell, the rate of translation on large polysomes could be relatively lower or that among these heavy aggregates a given number of "frozen" polysomes could be present. The ribosome state is considered as a probable limiting-factor of translation, particularly in mitosis.

Cell Division↗
PubMed1974

A guanidine-sensitive step of the poliovirus RNA replication cycle.

It has been shown that the amount of viral RNA synthesized in synchronized HeLa cells 0-2 h after infection does not notably vary during the mitotic cycle. However, the amount of viral RNA synthesized 2-4.5 h after infection exhibited a sharp maximum in S-phase cells. Guanidine inhibited the incorporation of 3-H-uridine into the viral RNA synthesized 2-4.5 h after infection only in cells in the S-phase. It had no demonstrable effect on viral RNA synthesis 0-2 h after infection in cells in any phase of the mitotic cycle. Thus, additional indirect evidence has been presented in favor of the hypothesis that two different replicases or two different conformations of one enzyme are involved in poliovirus RNA replication. The one functioning 0-2 h after infection is cycle-independent and guanidine-sensitive, whereas the other functions exclusively in phase-S cells 2-4.5 h after infection and is inhibited by guanidine.

Cell Division↗