The migration stage of Dictyostelium: Behavior without muscles or nerves

Abstract Glycoproteins are providing to be quite common in prokaryotes. Those is S-layers are the best understood in terms of structure. Numerous eubacteria produce non-S-layer glycoproteins about which relatively little is known. The glycans on such protein and the nature and sites of their linkages to protein are novel in those glycoproteins which have been examined in any detail. The possible functions of the glycans are mostly not understood. Eubacterial non-S-layer glycoproteins and the glycosylation systems producing them observe more attention.     

Revealing hidden interval graph structure in STS-content data.

MOTIVATION: STS-content data for genomic mapping contain numerous errors and anomalies resulting in cross-links among distant regions of the genome. Identification of contigs within the data is an important and difficult problem. RESULTS: This paper introduces a graph algorithm which creates a simplified view of STS-content data. The shape of the resulting structure graph provides a quality check - coherent data produce a straight line, while anomalous data produce branches and loops. In the latter case, it is sometimes possible to disentangle the various paths into subsets of the data covering contiguous regions of the genome, i.e. contigs. These straight subgraphs can then be analyzed in standard ways to construct a physical map. A theoretical basis for the method is presented along with examples of its application to current STS data from human genome centers. AVAILABILITY: Freely available on request.     

Cytofluorometric analysis of anti-lymphocyte antibodies in AIDS

Abstract Anti-lymphocyte antibodies (ALA) have been detected in the plasma of 53.8% of HIV-positive patients tested (CD4/CD8 ratios: mean 0.265; range 0.01 to 0.5) using analytical continuous-flow cytofluorometry. IgG from the AIDS plasma was seen to bind to normal PBL in 53.8% of cases (14/26). In double labelling experiments CD4 + lymphocytes, CD8 + lymphocytes, and B lymphocytes were all bound by the ALA, but monocytes were not bound. Pre-adsorption of the diluted AIDS plasma onto an excess of mouse spleen cells did not remove lymphocyte binding activity. No evidence was found for preferential binding to phytohaemagglutinin-stimulated lymphocytes.
ALA could not be detected in the plasma of normal subjects, patients with acute renal failure undergoing renal dialysis, or patients with high levels of circulating immune complexes.     

Grey seals, Halichoerus grypus, of the Dee Estuary and observations on a characteristic skin lesion in British seals

Grey seals on the West Hoyle Bank feed on a variety of fish and have a high incidence of dermal lesions, often associated with emaciation and nematode parasite infection. Corynebacterium phocae has been isolated from an active lesion. The significance of large numbers of seals in the Dee Estuary bearing lesions is discussed and the occurrence of seals with lesions elsewhere in British waters is reviewed. No evidence was found to associate the dermal lesions with any environmental factor and it is probable that lesions develop as a result of infection of minor wounds.     

Isolation of phytochrome from the alga mesotaenium and liverwort sphaerocarpos

Phytochrome has been isolated from the green alga Mesotaenium and the liverwort Sphaerocarpos. The Mesotaenium pigment had absorption peaks at 649 and 710 nm for the P_R and P_FR forms, respectively. Corresponding difference spectrum maxima for the Sphaerocarpos pigment were at 655 and 720 nm. While the absorption maxima differ, the reversibility and efficiency with which red and far-red light transform the Mesotaenium pigment are very similar to that reported for phytochrome isolated from etiolated seedlings of higher plants. Methods are described which allow efficient separation of phytochrome from highly pigmented light-grown material.     

Regulation of the anterior-like cell state by ammonia in Dictyostelium discoideum

Ammonia appears to be an important regulatory signal for several aspects of the Dictyostelium life cycle. The postulated role of ammonia in the determination of the prespore pathway in cells of the slug stage has led us to examine the effect of ammonia on the prestalk/prespore ratio of migrating slugs. In the presence of 10(-3) M ammonium chloride, the volume of the prestalk region decreases by 40.8%. The kinetics of the process make it unlikely that this is due to a shift in the differentiation pathway. A test of the hypothesis that the decrease in volume of the prestalk region is due to the conversion of prestalk cells to anterior-like cells shows that the percent of anterior-like cells in the posterior region increases by the amount predicted by the hypothesis. This suggests that ammonia may be the molecular signal, produced by the tip, that prevents anterior-like cells from chemotactically migrating to the tip and thereby becoming anterior cells. The effect of enzymatic removal of ammonia from vitally stained migrating slugs is the appearance of a series of dark stripes beginning at the posterior end and progressing forward. We interpret this as a result of progressive removal of anterior-like cells from tip dominance and essentially as the formation of new potential tips. Indeed, in a few cases one or even two of the stripes separate from the posterior of the cell mass and form small fruiting bodies. We consider the phenomenon of stripe formation further evidence that the tip acts on anterior-like cells through ammonia.