Modulation of globin gene expression by a tumor promoter during induced differentiation of Friend erythroleukemic cells

Friend erythroleukemic cells were induced to differentiate by dimethylsulfoxide (Me2SO) in the absence or presence of the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate. The effects of the latter on the molecular parameters related to globin mRNA metabolism were examined. When differentiation was scored by benzidine staining, it had an inhibitory effect on Me2SO-treated cells. On the other hand, when differentiation was followed by determination of globin mRNA accumulation, it had a pleiotropic effect on Me2SO-treated cells. At the early phase of differentiation (2--3 days) the rate of globin mRNA accumulation was higher in the promoter-treated cells than in the control. This unexpectedly high level of accumulation was followed by a sharp reduction and most of the globin RNA sequences disappeared at later stages of differentiation (days 4--5). The reduction can be related to the effect of the promoter on the stability of globin RNA in the cytoplasm which was reduced from a half-life of 16 h to that of 8 h only. Other parameters, such as the rate of globin mRNA synthesis and its capability to serve as a template for cell-free protein synthesis were not affected by treatment with the promoter throughout the differentiation process.     

Competitive Advantage Provided by Bacterial Motility in the Formation of Nodules by Rhizobium meliloti

The effect of motility on the competitive success of Rhizobium meliloti in nodule production was investigated. A motile strain formed more nodules than expected when mixed at various unfavorable ratios with either flagellated or nonflagellated nonmotile derivatives. We conclude that motility confers a selective advantage on rhizobia when competing with nonmotile strains.     

Occurrence and characterization of "avium-like" Mycobacteria isolated from animals in Sweden

431 cultures of "avium-like" mycobacteria (ALM) were isolated from wild and domestic animals during 1974--76 at the National Veterinary Institute, Stockholm. Of these, 50 isolates from pigs were studied by growth-chromogenicity, pathogenicity, and biochemical tests. Furthermore, thin-layer chromathography was performed, and on some isolates serotyping. All 50 isolates belonged to Runyon's group III and were pathogenic for chicken; none was capable of splitting oleic acid from Tween 80. 47 gave tellurite reduction within a period of three days; one was arylsulphatase-positive after three days and a further four after 14 days. The biological and biochemical tests permit assignation of the 50 isolates to the M. avium-intracellulare complex. The lipid patterns of the isolates examined were analysed by thin-layer chromatography. Thirty-five of the isolates showed a lipid pattern similar to that of A 2 of the fowl reference strain; three belonged to lipid type A 1 and four to A 3. Eight could not be typed. Of 22 isolates, 14 could be assigned to M. avium serotypes.     

Evaluation of several enrichment procedures for the isolation of recombinant plasmid DNA

A number of methods for the selective enrichment of recombinant plasmids were examined; these include alkaline phosphatase treatment of the restricted pBR322 vector, as well as a combination of this and S1 nuclease treatment of the ligated mixture of pBR322 and pCR1 plasmids orS. griseus DNA followed by D-cycloserine treatment to enrich for cells carrying recombinant molecules. The relative efficiencies of these methods were compared.     

Temporal relationship of translation and glycosylation of immunoglobulin heavy and light chains.

The initial glycosylation of MPC 11 gamma 2b heavy chains occurs quantitatively in vivo when the nascent heavy chains reach a size of approximately 38 000 daltons. Nonglycosylated, completed MPC 11 heavy chains cannot be glycosylated in these cells. Other classes of mouse heavy chains (i.e., mu, alpha, and gamma 1) also appear to be glycosylated as nascent chains; nonglycosylated, completed heavy chains cannot be glycosylated by the cell in any of these cases. In contrast, variant MPC 11 cells synthesizing a heavy chain with a carboxy-terminal deletion appear to glycosylate some heavy chains prior to chain completion and some heavy chains after chain completion and release from the polysomes. Similar to the variant MPC 11 cells, MOPC 46B cells (which synthesize a kappa light chain containing an oligosaccharide attached to an asparagine located 28 residues from the amino terminus) glycosylate the majority of light chains after prior to chain completion but also some light chains after chain completion and release from the polysomes. In addition, it appears that, although completed MOPC 46B light chains can be glycosylated if they are present in a monomeric form, they cannot be glycosylated if they are present in a covalent dimeric form.     

Epigenetic regulation of the Igf2/H19 gene cluster

Igf2 (insulin‐like growth factor 2) and H19 genes are imprinted in mammals; they are expressed unevenly from the two parental alleles. Igf2 is a growth factor expressed in most normal tissues, solely from the paternal allele. H19 gene is transcribed (but not translated to a protein) from the maternal allele. Igf2 protein is a growth factor particularly important during pregnancy, where it promotes both foetal and placental growth and also nutrient transfer from mother to offspring via the placenta. This article reviews epigenetic regulation of the Igf2/H19 gene‐cluster that leads to parent‐specific expression, with current models including parental allele‐specific DNA methylation and chromatin modifications, DNA‐binding of insulator proteins (CTCFs) and three‐dimensional partitioning of DNA in the nucleus. It is emphasized that key genomic features are conserved among mammals and have been functionally tested in mouse. ‘The enhancer competition model’, ‘the boundary model’ and ‘the chromatin‐loop model’ are three models based on differential methylation as the epigenetic mark responsible for the imprinted expression pattern. Pathways are discussed that can account for allelic methylation differences; there is a recent study that contradicts the previously accepted fact that biallelic expression is accompanied with loss of differential methylation pattern.     

Site factors are more important than management for indicator species in semi-natural grasslands in southern Sweden

Plant Ecology - Management of semi-natural grasslands is essential to retain the characteristic diversity of flora and fauna found in these habitats. To maintain, restore or recreate favourable...