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Biomedical subjects

S Aho

Publications and source records attributed to S Aho.

At least 73 records · Page 4Linked to original sources
PubMed1983

Multiple 3' ends of the chicken pro alpha 2(I) collagen gene.

The precise location of the 3' ends of the chicken pro alpha 2(I) collagen gene have been identified by S1 nuclease protection of overlapping genomic fragments by calvaria poly A containing RNA and size determination of the protected fragments on DNA sequencing gels. The gene ends 300 and 306 bp and 754 and 777 bp from the translation stop codon. The two sets of ends explain the major and minor pro alpha 2(I) collagen mRNAs previously observed, which may result from either RNA polymerase readthrough of the first termination site and/or different processing sites.

Animals↗
PubMed1983

Fibroblast RNA and macrophage proteins (including the fibrogenic factor) in experimental silicosis.

A hypothesis is presented for the action of silica-treated macrophages on protein synthesis in fibroblasts and also a method for the isolation of silica-attached materials in lung tissue. The increased protein synthesis in the fibroblasts is due, at least partly, to an increase in mRNA. Silica prevents the suppressing "macrophage effect" of macrophage-originated ribonuclease on fibroblasts. However, under certain conditions, collagen synthesis is stimulated by silica-treated macrophage preparations to such an extent that the effect cannot be explained by the inhibition of macrophage ribonuclease alone. We therefore postulate the existence of a fibrogenic factor, which is released by the macrophages. This factor has been demonstrated and can be purified from lung homogenate of SiO2-treated rats.

Animals↗
PubMed1982

Penetration of macrophage ribonuclease into fibroblasts and the effects on nucleic acid and collagen metabolism.

RNAase isolated from macrophage culture medium was labelled with 3H-acetic anhydride. The acetylation density of 1.8 acetyl residues/10(4) dalton RNAase was achieved. After just 5 mins' incubation of granulation-tissue slices with 3H-Ac-RNAase, the enzyme had entered fibroblasts, and after 20 min there was only slight increase of the radioactivity. After 1 h incubation 32% of the ingested RNAse was in the nuclei, 23% in the cytosol and about 2% in RER. After the same period of incubation with 3H-Ac-RNAase, 47% of nuclear RNA of the fibroblasts was lost, as compared with the control incubation, and the amount of cytosol RNA increased by about 40%. During a 3-h incubation, in low concentrations, the biologically active macrophage RNAase stimulated. 3H-thymidine incorporation into DNA of proliferative granulation-tissue slices. Thus it was concluded that the fibrogenic effect of the macrophage RNAase on the granulation-tissue fibroblasts takes place through the RNA metabolism and the main target of the enzyme in the fibroblasts is the nuclear RNA.

Acetylation↗
PubMed1981

Penetration of various mononuclear ribonucleases into rat experimental granulation-tissue fibroblasts and their intracellular effects.

The penetration of five different mononuclear ribonucleases into the subcellular particles of rat experimental granulation-tissue fibroblasts was compared, along with the effects of the enzymes on the fibroblast RNA fractions. Ribonucleases from normal and silica-treated rat peritoneal macrophages have been shown before to regulate the nucleic acid and protein metabolism of rat experimental granulation-tissue fibroblasts. These biologically active enzymes were taken into the fibroblasts in a greater amount than the corresponding human monocyte enzymes and the biologically inactive rat macrophage ribonuclease. The biologically active macrophage enzymes were incorporated mainly into the nuclear fraction. The other three mononuclear ribonucleases were not found particularly in any subcellular compartment. Both biologically active macrophage enzymes degraded the nuclear RNA of fibroblasts and released it to the soluble fraction in contrast to the biologically inactive macrophage enzyme and ribonuclease from normal human monocytes. Instead the ribonuclease from normal human monocytes seemed to degrade RNA in the soluble fraction. There were no marked differences in the subcellular effects of ribonucleases from normal and silica-treated macrophages. However, the treatment of human monocytes with silica changed their ribonuclease so that it split the nuclear RNA of fibroblast and released it to the soluble fraction in the same way as the biologically active macrophage enzymes did.

Animals↗
PubMed1980

Involvement of ribonuclease in the interactions of macrophages and fibroblasts in experimental silicosis.

Decreased ribonuclease activity in the supernatant from silica-treated macrophages is associated with the enhanced protein synthesis in granulation-tissue slices incubated in this supernatant, and with the decreased degradation of polysomes in granuloma slices and of polysomes isolated from the granulation tissue. The phagocytized silica particles adsorb ribonuclease and perhaps other proteins and thus remove them from the macrophage supernatant.

Animals↗
PubMed1980

Effects of purified macrophage RNase on granuloma fibroblasts with reference to silicosis.

Two alkaline RNases, designated RNase 1 and RNase 2, were isolated from the culture media of silica-treated and non-treated macrophages. The yield of RNase from the medium of silica-treated macrophages was 30% of that from the non-treated control. The effects of these RNases on cultured granuloma fibroblasts and on granulation-tissue nuclei were studied. RNase 1 inhibited thymidine incorporation into fibroblasts except at low concentrations, where it was observed to be stimulatory. RNase 1 also inhibited the protein synthesis of fibroblasts. The incorporation of cytidine into RNA in cultured fibroblasts was not affected by RNase 1, but the incorporation into isolated nuclei was decreased. In pulse chase experiments RNase 1 increased the release of cytidine, but not that of thymidine, from the cells. RNase 2 had no effect on the protein or nucleic acid metabolism of the fibroblasts or on the RNA metabolism of isolated nuclei, perhaps because of impermeability. These experiments confirm that macrophage RNase activity is able to regulate the metabolism of granulation-tissue fibroblasts by increasing RNA degradation. Through this action it also regulates DNA and protein synthesis and other metabolic functions of those cells.

Animals↗
PubMed1980

Purification of two ribonucleases from macrophage culture medium and studies on their effect on granulation-tissue fibroblasts.

Two ribonuclease activities have been isolated from macrophage culture medium. SDS-electrophoresis gave a molecular weight of 26,000 for both RNAases. The two RNAases differ only slightly in their enzymic properties. They are optimally active at neutral and slightly alkaline pH, and are not activated by monovalent or divalent cations or by spermine. Cu(II), Zn(II), Mn(II) and heparine inactivate them but they are not affected by the RNAase inhibitor from rat liver. They both degrade RNA endonucleolytically to mono- and oligonucleotides. They react to synthetic polynucleotides, especially poly(C), but do not degrade the synthetic double-stranded RNA poly(I) . poly(C), or double or single-stranded DNA. RNAase 1 inhibits DNA synthesis and increases degradation of RNA in granulation-tissue fibroblasts but RNAase 2 at the same concentration does not have these effects.

Animals↗
PubMed1979

Ribonuclease activities in developing experimental granulation tissue with reference to polysomes.

The Mg2+-precipitable polysomes in experimental granulation tissue increase up to three weeks and decrease slowly thereafter. Polysomes from young granulation tissue are, on a weight basis, more active in cell-free protein synthesis than polysomes from old granulation tissue. RNase activity is highest in polysomes from 1-week tissue. The polysomes contain both acid and alkaline RNase, but the alkaline RNase is the latent form, manifested by the addition of p-chloromercuribenzoate (pCMB). The high RNase activity of granulation tissue renders the analysis of polysomal patterns and functions of the polysomes difficult. In the post-polysomal supernatant of granulation tissue the RNase activity is highest in 2-4 week old tissue; it is maximal at pH 7-8 and only slightly influenced by pCMB.

Animals↗
PubMed1978

Alkaline ribonuclease associated with polyribosomes in fibroblasts of experimental granulation tissue.

Alkaline ribonuclease (RNase) from polyribosomes derived from experimental granulation tissue has been purified 1900-fold through affinity chromatography. The preparation was homogeneous in sodium dodecyl sulfate (SDS) polyacrylamide-gel electrophoresis with an estimated molecular weight of 15 000. Purified RNase was completely inhibited in the presence of divalent ions Mg2+(100 mM) and Ca2+(100 mM) but activated slightly with Na+(50 mM). The enzyme is an endonuclease and the best substrates were poly(U), mixed RNA from yeast, rRNA from granulation tissue and poly(C). The estimated apparent Km-values were 0.037, 0.064, 0.13 and 0.27 g1-1, respectively. In polyribosomes RNase occurred in both free and p-chloromercuribenzoate (pCMB)-liberated forms. The total activity was at the highest but the proportion of the free activity minimal in the granulation tissue during the maximal synthesis of collagen.

Animals↗