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M Crippa

Publications and source records attributed to M Crippa.

23 records · Page 2Linked to original sources
PubMed1976

DNA-dependent RNA polymerase C from Xenopus laevis ovaries. Ability to transcribe intact double-stranded DNA.

DNA-dependent RNA polymerase C, partially purified from Xenopus laevis ovaries, has been resolved by DEAE-Sephadex chromatography in two forms, eluting at 0.2 M and 0.3 M ammonium sulfate, respectively. Both are sensitive to high concentrations of alpha-amanitin (200 mug/ml). Their ionic strength dependence and divalent cation requirements are indistinguishable. Quantitatively, RNA polymerase C represents the major form of RNA polymerase activity solubilized from the ovaries. Both RNA polymerases C are able to transcribe efficiently either high-molecular-weight Xenopus DNA or intact adenovirus DNA, as compared to nicked DNA. In contrast, RNA polymerase A has little activity on an intact DNA template. The salt dependence of the RNA polymerases C activity is different on the two kinds of template. Nicked DNA is efficiently transcribed up to a salt concentration of 100 mM ammonium sulfate. On intact DNA, optimal transcription is obtained at 40 mM ammonium sulfate and is inhibited by higher salt concentrations.

Amanitins↗
PubMedDate not supplied

[Risk of exposure to metals in the production and processing of copper alloys].

A study was carried out in 3 copper alloy industries: a foundry for scrap of various origin producing brass and bronze alloys (foundry A) and 2 foundries that used these same alloys (foundries B and C). An environmental investigation and biological monitoring of the employees for Pb, ZPP, Cu, Zn, Be, Sb, Mn, Ni and Cr were performed in each foundry. The results of biological and environmental monitoring showed that the Pb exposure levels were distinctly higher than those of the other metals in all 3 foundries. The highest levels of PbA and PbB were observed in foundry A, especially during scrap grinding operations, where the limit values were exceeded. The environmental concentrations and the levels of the biological indicators for all other metals, except Pb, were within reasonable limits. Therefore, in the investigated working situations and for the metals under study, except Pb, it would appear that a situation exists of exposure to "microdoses" which, even though not implying a risk of appearance of the classic signs and symptoms of intoxication, raises the problem of the possibility of identifying early effects and interpreting the biological indicators. Biological monitoring of exposed subjects has shown that the levels of the indicators for Cu, Ni and Cr are markedly different from the reference values on a group basis, whereas in individual workers the values are generally below the "upper limits". A comparison with the "limit values'' was only possible for the biological indicators of Pb; for the others, although differences were observed indicating that absorption had taken place, no univocal interpretation criteria exist, considering also the relatively low mean increases observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗
PubMedDate not supplied

[Intraerythrocyte folates and leukocytic neutrophil segmentation in macrocytosis in patients with liver disease].

The problem of macrocytosis above all concerns deficiences and the study of these aspects is particularly important in hepatopathic patients for therapeutic purposes. A state of deficiency can also be revealed in morphological terms by the assessment of the hypersegmentation of polymorphonucleate neutrophil leucocytes. In the group of hepatopathic patients included in the study there was no significant differences in vitamin B12 concentrations in comparison to normal values, whereas mean levels of serum folates were decreased, although still within the normal range. It is worth underlining that to evaluate vitamin B12 it is necessary to measure analogous inefficient components from a metabolic point of view and the assessment of serum folates is not important as an index of normal erythropoietic activity. To overcome this limitation, we assayed intraerythrocytic folates which are vitamin-B12-dependent and these too proved to be within the normal range. Leucocyte hypersegmentation was also excluded by evaluating the mean of PMN lobes. A clearly normal RDW was also observed in macrocytic anemia in hepatopathic patients and this may represent a further difference from hepatocytic macrocytosis.

Erythrocytes↗