Biosynthesis and secretion of alpha 1 acute-phase globulin in primary cultures of rat hepatocytes

Experimental inflammation in rats led to a sevenfold increase in serum levels of alpha 1 acute-phase globulin. This increase is correlated with elevated levels of translatable mRNA for alpha 1 acute-phase globulin in the liver. Biosynthesis and secretion of alpha 1 acute-phase globulin were studied in rat hepatocyte primary cultures. An intracellular form of alpha 1 acute-phase globulin with an apparent relative molecular mass of 63 500 and a secreted form of 68 000 were found. The intracellular form of alpha 1 acute-phase globulin could be deglycosylated by endoglucosaminidase H treatment indicating that its oligosaccharide chains were of the high-mannose type. The secreted form of alpha 1 acute-phase globulin was not sensitive to endoglucosaminidase H, but was susceptible to the action of sialidase reflecting carbohydrate side-chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the high-mannose and the complex type alpha 1 acute-phase globulin. In the hepatocyte medium newly synthesized alpha 1 acute-phase globulin was detected 30 min after the pulse. Unglycosylated alpha 1 acute-phase globulin was found in the cells as well as in the medium when the transfer of oligosaccharide chains onto the polypeptide chains was blocked by tunicamycin. Tunicamycin led to a marked delay in alpha 1 acute-phase globulin secretion.     

EBV-inducing factor from platelets exhibits growth-promoting activity for NIH 3T3 cells.

An Epstein-Barr virus-indicating factor (EIF) has been purified from serum and platelets. We show here that highly purified preparations of platelet EIF exhibit growth-promoting activity for NIH 3T3 cells maintained in platelet-poor plasma. The Epstein-Barr virus (EBV)-inducing activity and growth-promoting activity co-elute upon gel chromatography under non-dissociating as well as dissociating conditions and co-migrate in SDS-gel electrophoresis, supporting the notion that both activities reside on the same molecule. Furthermore, both activities require a pH shock for full activity and act in the same concentration range. The growth-promoting activity of EIF can be differentiated from that of platelet-derived growth factor (PDGF), biologically (on the basis of differential response of cell lines to both factors), biochemically (on the basis of differences in isoelectric points and mol. wts. and the requirement of EIF to become activated by a pH shock) and by the lack of inhibition of EIF by antibody to PDGF.     

Studies in Heterobasidiomycetes,Part 38*)Sphacelotheca polygoni-persicariae G. Demi & Oberw. spec. nov.

A new species, Sphacelotheca polygoni-persicariae, parasitizing the ovaries of Polygonum persicaria L. is described. This smut, collected several times in Madeira, Portugal, differs from other species of that genus, by its host plant and the reticulated teliospore ornamentation. On the basis of the morphological and ultrastructural characters of S. polygoni-persicariae, in connection with some recently published data on siderophore formation and 5S ribosomal RNA sequences it can be assumed that 1) members of the genus Sphacelotheca are separated from typical Ustilago species of Poaceae, 2) Sphacelotheca is restricted to species parasitizing Polygonaceae, and 3) species of Sphacelotheca and Microhotryum as well as those Ustilago species which parasitize in the flowers of Polygonaceae are closely related.     

Temperature dependence of the gel electrophoretic mobility of superhelical DNA.

We have determined the gel electrophoretic behavior of closed circular plasmid pSM1 DNA (5420 bp) as a function of both temperature and of linking number (Lk). At temperatures below 37 degrees, the electrophoretic mobility first increases, then becomes constant as Lk is decreased below that of the relaxed closed DNA. As the temperature is increased above 37 degrees the electrophoretic mobility first increases as Lk decreases and then varies in a cyclic manner with further decreases in Lk. As the temperature is increased over the range 37 degrees - 65 degrees the cyclic behavior is manifested at progressively smaller decreases in Lk and the amplitude of the cycles increases. We interpret the results in terms of the early melting of superhelical DNA, in which the free energy associated with superhelix formation is progressively transferred to local denaturation. Using a two state approximation, we estimate the free energy change in the first cyclic transition to be 35 Kcal/mole DNA at 37 degrees and to decrease linearly with temperature. The free energy becomes equal to zero at a temperature of 71.6 degrees, which lies within 3 degrees of the melting temperature for the corresponding nicked circular DNA. From the slope of this relationship we estimate the apparent entropy and enthalpy of the first mobility transition to be 6.0 Kcal/mole base pair and 17.3 cal/mole base pair/degree, values consistent with duplex melting.     

Increase of translational fidelity blocks sporulation in the fungus Podospora anserina

Summary AS7-1 and AS7-2 are antisuppressor mutations reducing the miscoding capacity of ribosomes. Strains carrying and AS7 mutation do not sporulate. We have investigated whether the sporulation deficiency is due to the decrease of translational ambiguity. Two major findings argue in favour of this assumption. First, a significant sporulation level is restored in the presence of paromomycin. Second, three mutations which restore the sporulation of AS7-2 increase the ribosomal misreading in vitro. They define two new loci for ribosomal suppressors, su11 and su12. The two ribosomal proteins altered by su11-1 and su12-1 have been identified by electrophoresis. The results are discussed in the context of a more general hypothesis proposed by Picard-Bennoun (1982).     

Evolution of a Vκ gene family

To examine the evolution of multigene families we have selected as an example an immunoglobulin light chain variable region subgroup (V24) which has been extensively characterized in inbred mice (Mus musculus domesticus). Homologous genes have been isolated and sequenced from Mus pahari, a genetically and geographically isolated species believed to be the oldest living representative of the genus. Southern blot analysis using probes corresponding to individual genes in this subgroup reveals changes in the overall size of the family occurring at the level of individual genes but not at the level of the entire family. Nucleotide sequence analysis indicates an absence of regulatory sequences such as the CAT and TATA boxes 5 to the coding region, but a decanucleotide sequence involved in light chain expression is highly conserved. Within coding regions highly complex patterns of variation are seen which appear to reflect quite different selective pressures on various subregions of the coding sequence. Complementarity determining regions (CDR) are conserved to different extents, with the first CDR region in all family members being among the most conserved segments of the molecule. Conservation is similarly variable among framework segments, indicating complex and variable evolutionary pressures not only at the level of individual genes or their products but also at subregions within homologous molecules.     

Ultrastructural localization of cell wall teichoic acids in Streptococcus faecalis by means of concanavalin A

Some teichoic acids are known to be partially substituted by α-D-glucopyranosyl residues such as the teichoic acids of Streptococcus faecalis NCIB 8191. They will, therefore, bind specifically the phytohemagglutinin concanavalin A. Concanavalin A labelled with mercury or colloidal gold coated with concanavalin A has been used to mark isolated cell walls in order to localize the teichoic acids at the ultrastructural level. Besides these two direct marking techniques, the indirect concanavalin A-peroxidase technique (localization of peroxidase by the diaminobenzidine method followed by postosmication) has been applied to thin sections of premarked cells. All three methods gave almost identical results, namely, a dense and homogeneous distribution of the cell wall teichoic acids. In control experiments total inhibition was achieved in the presence of methyl-α-D-mannopyranoside. After trichloroacetic acid or alkali extraction of the teichoic acids from isolated walls no marking could be detected.     

Ploidy effect on the radiation reaction of mammalian cells

Summary The variation of X-ray sensitivity was investigated during the cell cycle. The cells were most sensitive during the S phase and less sensitive during the G₂- and G₁ phase. Furthermore, the repair of X-ray damage was investigated in stationary (plateau phase) cells. The cells of both lines were able to repair damage to nearly the same extent.

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Zusammenfassung Die Variation der Strahlensensibilität während des Zellcyclus wurde untersucht. Die Zellen reagierten am sensibelsten in der S-Phase, weniger sensibel in der G₂-und G₁-Phase. Weiterhin wurde die Reparation von Strahlenschäden bei stationären (Plateauphase-)Zellen untersucht. Die Zellen beider Linien sind in etwa gleichem Maße reparationsfähig.

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Supported (I-IV) by the Deutsche Forschungsgemeinschaft (Mi/100, 1-7).     

Ribonuclease H activity present in purified DNA polymerase from avian myeloblastosis virus

The presence of ribonuclease H activity in the purified complex of DNA polymerase from avian myeloblastosis virus is described. Evidence includes co-chromatography of the two activities during all purification steps; the presence of ribonuclease H activity in the purified two-polypeptide complex of DNA polymerase; ion requirements for optimal activity of purified ribonuclease H are identical to those for the purified DNA polymerase; and monospecific antiserum against purified DNA polymerase neutralizes the ribonuclease H activity.