Evidence for negative regulation of T cell growth by low affinity interleukin 2 receptors

Two experimental situations have been studied, and the results provide evidence for a negative regulatory role for the low affinity interleukin 2 receptor (LA-IL 2R). The IL 2-dependent T helper cell line L-14, deprived of IL 2, becomes quiescent and expresses comparable numbers of high affinity IL 2R (HA-IL 2R) and LA-IL 2R. After activation by recombinant IL 2, this cell line preferentially expresses LA-IL 2R. The IL 2 responsiveness of the L-14 cell line was found to vary according to the ratio of LA-IL 2R to HA-IL 2R: the relative predominance of the LA-IL 2R coincides with a hyporeactivity of cells to IL 2. In contrast, a predominance of HA-IL 2R is accompanied by an increase in cellular IL 2 reactivity. Treatment of three IL 2-dependent T cell lines (L-14, HT-2, and C30.1) with limited amounts of recombinant IL 2 and moderate concentrations of anti-IL 2R monoclonal antibodies stimulates T cell growth. This treatment was shown to selectively diminish the expression of membrane LA-IL 2R. The stimulation was attributed to the decrease of expression of LA-IL 2R.     

An acridine-linked oligodeoxynucleotide targeted to the common 5' end of trypanosome mRNAs kills cultured parasites

Anti-messenger oligodeoxynucleotides covalently linked to an intercalating agent were tested for their ability to inhibit translation of Trypanosoma brucei mRNAs in a cell-free system. The sequence of these oligodeoxynucleotides was complementary to part of the 35-nucleotide (nt) sequence which is present at the 5' end of all trypanosome mRNAs (the so-called mini-exon sequence). In a rabbit reticulocyte lysate, a nonadeoxynucleotide linked to an acridine derivative, specifically inhibited protein synthesis from T. brucei mRNAs much more efficiently than unmodified oligodeoxynucleotides of similar length. These oligodeoxynucleotides were tested on cultured trypanosomes. The acridine-linked nonadeoxynucleotide had a lethal effect on the parasites. No effect was observed with the homologous unmodified 9-mer nor with those 9-mers linked to the acridine derivative which were not complementary to the mini-exon sequence. These effects are probably a result of hybrid formation between the anti-messenger and mini-exon sequence. Trypanocidal activity of the acridine-modified nonadeoxynucleotide is most likely due to (i) increased affinity for its target, (ii) improved resistance to 3' exonucleases, and (iii) promoted membrane penetration of living parasites.     

Copy number and distribution of P and I mobile elements in Drosophila melanogaster populations

The distribution of the number of copies of P and I transposable elements per genome was investigated by in situ hybridization for a large set of Drosophila melanogaster strains. These included the P, Q and M types of the P-M system of hybrid dysgenesis. P element copy number varied widely (range 5–59). P and Q strains had around 40 copies whereas M strains generally had lower numbers (between 5 and 35) with one extreme value (52). The copy number of I elements appeared to be precisely regulated, as no strains were found outside the 15±5 range. The number of copies of the two families were independent. An excess of P copies on the X chromosome compared with the autosomes was found for the P and Q strains, but not for M strains. Among X-inserted P sites, a very high frequency of occupation was found at the tip of the X chromosome (cytological site 1A), especially for P and Q strains. The possible regulatory role in the P-M system of X-inserted P sites is discussed.     

Evidence for a novel growth factor in Xenopus oocytes

Xenopus oocytes contain a novel growth factor, as determined by its effect on the anchorage-dependent and -independent growth of various rat cells and on a Xenopus cell line; it is destroyed by trypsin, acidification (pH 2.0), heating (100 degrees C, 3 min), 8 M urea but not by dithiothreitol. Gel filtration of this activity in nondissociating conditions suggests the existence of aggregates and the presence of a very high (approximately 2000 Kd) and a much lower (approximately 30 Kd) form.     

Cystic fibrosis typing with DNA probes and screening for ΔF508 deletion in families from Southern France

Summary A sample of 235 individuals from 49 French cystic fibrosis (CF) families with at least one living affected child was typed with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CF gene, and was screened for the ΔF508 mutation. Using a combination of six probes, 44 out of the 49 families were sufficiently informative to enable prenatal diagnosis or carrier determination. As in many other populations, linkage disequilibrium was found between the CF locus and the haplotype B (XV2c: allele 1; KM19: allele 2), which accounts for about 78% of CF chromosomes in our families. The ΔF508 deletion was present in 64.3% of CF chromosomes.     

Somatic hybrid plants produced by electrofusion between dihaploid potatoes: BF15 (H1), Aminca (H6) and Cardinal (H3)

In order to regenerate somatic hybrids, mesophyll protoplasts from a dihaploid potato, BF15 (H1), were electrofused with those from two other dihaploid clones, Aminca (H6) and Cardinal (H3). Determination of the ploidy level by flow cytometry showed that 10% of plants regenerated from the fusion experiment with BF15 + Aminca were diploids, 14% triploids, 63% tetraploids and very few were mixoploids or had a higher ploidy level. Using morphological markers and vigour in plant growth, we were able to recover a total of 24 somatic hybrid plants, respectively 20 and 4 hybrids (accounting for 12% and 13% of regenerants) from the fusions BF15 + Aminca and BF15 + Cardinal. Most of the somatic hybrids were at the expected tetraploid level (2n=4x=48). The hybrid nature was confirmed by examining isoenzyme patterns for malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICD).     

A novel extracellular carbohydrase produced by Lipomyces tetrasporus

Summary The ascosporogenous yeast Lipomyces tetrasporus produced an unusual extracellular carbohydrase. It was purified to homogeneity using ammonium sulphate precipitation and DEAE Bio-gel A ion-exchange chromatography. While retaining highest activity on low-molecular-weight saccharides such as maltose and nigerose, it displays considerable activity towards polymeric substrates including soluble starch. It is particularly unusual in that it also hydrolyses dextran and has a very high affinity for this substrate. The enzyme has an exo-lytic mode of action with the only hydrolysis product, glucose, being released in the -anomeric form. Optimum activity occurs at pH 4.5 and at 50°C. It is a glycoprotein, and has an M _r value of 150 000 (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) — 183 000 (fast protein liquid chromatography) and a pI of 6.0. Offprint requests to: C. T. Kelly     

Comparison of the amino acid sequences of human protamines HP2 and HP3 and of intermediate basic nuclear proteins HPS1 and HPS2. Structural evidence that HPS1 and HPS2 are pro-protamines

Two intermediate nuclear basic proteins HPS1 and HPS2 were isolated from human sperm. They were characterized by their electrophoretic mobility in acid-urea gels, their amino acid composition, and their peptide maps after digestion by endoproteinase Lys-C and by endoproteinase Glu-C. Their amino-terminal amino acid sequences have also been determined. The structural data thus obtained suggest that HPS1 and HPS2 are precursors of human protamines HP2 and HP3.     

Pichia triangularis sp. nov., the teleomorph of Candida polymorpha Ohara et Nonomura,nom. nud.

The type strain of Candida polymorpha Ohara et Nonomura, nom. nud. was found to produce hat-shaped ascospores. On the basis of its morphology and physiology, it is considered a new species of the genus Pichia and is described as Pichia triangularis sp. nov.