An HLA-C-specific DNA probe

Analysis of available nucleotide sequence data for class I HLA genes has established that the seventh intron is one of the gene regions which expresses the highest degree of locus specificity (the percentage sequence divergence between nonallelic genes minus the percentage sequence divergence between allelic genes). We have subcloned short DNA sequences including this region from the HLA-Cw3 gene. Two clones, pC250 and pC800, were tested by hybridizing them at high stringency to a panel of clones containing class I HLA genes. Under conditions permitting a strong hybridization signal with a C-locus gene, pC800 also expressed a weak but significant hybridization to other class I genes, while pC250 appeared to hybridize exclusively to the C-locus gene. Hybridization of the pC250 probe at high stringency to Hind III-digested genomic DNA from a panel of unrelated individuals and homozygous typing cell lines revealed a single band in all cases. However, equivalent hybridization against Eco RI-digested DNA revealed two hybridization bands, one at 7.9 kb which correlated with the serologically defined Cw5 and Cw8 alleles, and one at 7.6 kb which correlated with the Cw1, Cw2, Cw3, Cw4, Cw6, and Cw7 alleles.     

Hydrogen-peroxide-scavenging systems within pea chloroplasts

The subcellular distribution of ascorbate peroxidase and glutathione reductase (EC 1.6.4.2) in pea leaves was compared with that of organelle markers. Enzyme distribution was found to be similar to that of the chloroplast enzyme NADPH-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13). Isolated chloroplasts showed a close correlation between intactness and the percentage of enzyme activity recovered. Chloroplasts of 85% intactness were found to contain a high proportion of leaf dehydroascorbate reductase activity (EC 1.8.5.1), 10% of leaf glutathione and 30% of leaf ascorbate. These results are discussed in relation to the potential role of chloroplast antioxidant systems in plant resistance to environmental and other stress conditions.Abbreviations GSH reduced glutathione - GSSG oxidized glutathione - NADPH-GPD glyceraldehyde-3-phosphate dehydrogenase - SOD superoxide dismutase     

Chromosome structure in the dinophyceae

Summary A large number of cytochemical staining techniques together with chemical and enzymic extractions have been used on Prorocentrum micans. The object of this study being to ascertain the main chemical components of the unusual chromosomes found in the Dinophyceae.DNA was the only major component which could be positively determined and unlike most other chromosomes these appeared to contain no protein or RNA. However, the chromosomes were embedded in a granular proteinaceous nuclear matrix, the function of which is as yet unknown. The similarity in the composition and structure of the chromosomes of Prorocentrum and the nuclei of Bacteria are discussed.     

International Society for Reef Studies

International Society for Reef Studies     

Role of the tubulin-microtubule system in lymphocyte activation

The role of the tubulin-microtubule system was examined in human peripheral blood leukocytes after activation with phytohemagglutinin (PHA). Soluble tubulin and microtubules were measured with a [(3)H]colchicine-binding assay. It was found that the tubulin content of PHA-activated lymphocytes was consistently increased relative to total protein content after 36 h of culture. There was no increase in the proportion of total tubulin synthesis which was present as microtubules at 36 h. Nevertheless, as a result of increased tubulin synthesis, there was a two-to three-fold increase in total microtubular mass. Colchicine, which disrupts microtubles, was used to assess the role of microtubule assembly in the sequence of events which follow lymphocyte activation, namely lymphokine release, protein synthesis, RNA synthesis, and DNA synthesis. Colchicine consistently inhibited DNA synthesis but did not inhibit release of the lymphokine, osteoclast activating factor (OAF). Protein and RNA syntheses were inhibited much less than DNA synthesis. The fact that some effects of PHA on lymphocytes appear to require intact microtubules and at least one does not suggest that the microtubule dependent step in PHA-stimulated lymphocyte activation occurs at a stage after propagation of the signal from the membrane to the cell interior.     

Evidence for a double-helically coiled toroidal chromonema in the dinoflagellate chromosome

The structure of the dinoflagellate chromosome is examined using spread whole mounts and serial sectioning. Evidence is presented that the chromosome is composed of a toroidal bundle of DNA strands which is coiled plectonemically into a tight double helix. This structure is apparent in interphase whole-mount chromosomes and by careful analysis of serial sectioning can be shown in all mitotic stages. It is particularly apparent in the arms of replicating Y shaped chromosomes which often uncoil slightly (either naturally or as a result of the fixation used). A model is presented which is based on these results and recent genetic and biochemical data.