Terrestrial pollen record of recent land-use changes around nine North African lakes in the CASSARINA Project

Pollen analyses and related plant macrofossil records are presented from short cores from nine North African lakes in the EU-funded CASSARINA project. Terrestrial pollen reflects human impact on the vegetation and landscape over the last 150–100 years. Pollen changes, aided by radiometric dating, could be correlated with historical developments. The chronology of the landscape changes date other biostratigraphical records reflecting changes in the aquatic ecosystems.Three lakes in Morocco show gradually intensifying land-use over the last century. Accelerated technological development and landscape modification over the last 20 years culminated in one of the lakes being drained and cultivated during the project period. In Tunisia, a nationally unique acid-water lake is threatened by water withdrawal for increased catchment cultivation. The landscape around two other lakes is being increasingly cultivated and urbanised, and water withdrawal to support this has resulted in deleterious effects on the aquatic ecosystems, particularly at the internationally famous Garaet El Ichkeul where reed-marshes and macrophyte beds have been lost. The three lakes in the Egyptian Nile Delta are in the same hydrological system and show parallel changes in the balance between saltmarsh and reed-marsh. Control of Nile floods and year-round irrigation led to marked increases in cultivation in the delta region since ca. 1920. The Aswan High Dam (1964) had little detectable further effect. Documented planting of dates, palms, and olives and of introduced Casuarina and Eucalyptus trees provided a chronology to supplement the unsatisfactory radiometric dating of the sediments in this low-rainfall area.     

Frozen-etched septate junctions

Summary Freeze-etch replicas indicate that septate junctions are formed somewhat differently from the structures proposed on the basis of sectioning studies. The junction appears to be based on ridges on the external surface of the plasma membranes which completely surround the cell sealing off the intercellular space from the external environment of the epithelium. These ridges are reinforced by rows of particles within the two opposing membranes.     

On the hierarchical classification of G protein-coupled receptors

MOTIVATION: G protein-coupled receptors (GPCRs) play an important role in many physiological systems by transducing an extracellular signal into an intracellular response. Over 50% of all marketed drugs are targeted towards a GPCR. There is considerable interest in developing an algorithm that could effectively predict the function of a GPCR from its primary sequence. Such an algorithm is useful not only in identifying novel GPCR sequences but in characterizing the interrelationships between known GPCRs. RESULTS: An alignment-free approach to GPCR classification has been developed using techniques drawn from data mining and proteochemometrics. A dataset of over 8000 sequences was constructed to train the algorithm. This represents one of the largest GPCR datasets currently available. A predictive algorithm was developed based upon the simplest reasonable numerical representation of the protein's physicochemical properties. A selective top-down approach was developed, which used a hierarchical classifier to assign sequences to subdivisions within the GPCR hierarchy. The predictive performance of the algorithm was assessed against several standard data mining classifiers and further validated against Support Vector Machine-based GPCR prediction servers. The selective top-down approach achieves significantly higher accuracy than standard data mining methods in almost all cases.     

Differential modulation of annexin I binding sites on monocytes and neutrophils

Specific binding sites for the anti-inflammatory protein annexin I have been detected on the surface of human monocytes and polymorphonuclear leukocytes (PMN). These binding sites are proteinaceous in nature and are sensitive to cleavage by the proteolytic enzymes trypsin, collagenase, elastase and cathepsin G. When monocytes and PMN were isolated independently from peripheral blood, only the monocytes exhibited constitutive annexin I binding. However PMN acquired the capacity to bind annexin I following co-culture with monocytes. PMN incubation with sodium azide, but not protease inhibitors, partially blocked this process. A similar increase in annexin I binding capacity was also detected in PMN following adhesion to endothelial monolayers. We propose that a juxtacrine activation rather than a cleavage-mediated transfer is involved in this process. Removal of annexin I binding sites from monocytes with elastase rendered monocytes functionally insensitive to full length annexin I or to the annexin I-derived pharmacophore, peptide Ac2-26, assessed as suppression of the respiratory burst. These data indicate that the annexin I binding site on phagocytic cells may have an important function in the feedback control of the inflammatory response and their loss through cleavage could potentiate such responses.     

HLA-A3 supermotif defined by quantitative structure-activity relationship analysis

Activation of a cytotoxic T cell requires specific binding of antigenic peptides to major histocompatibility complex (MHC) molecules. This paper reports a study of peptides binding to members of the HLA-A3 superfamily using a recently developed 2D-QSAR method, called the additive method. Four alleles with high phenotype frequency were included in the study: A*0301, A*1101, A*3101 and A*6801. The influence of each of the 20 amino acids at each position of the peptide on binding was studied. A refined A3 supertype motif was defined in the study.     

Greater CD8+ TCR heterogeneity and functional flexibility in HIV-2 compared to HIV-1 infection

Virus-specific CD8(+) T cells are known to play an important role in the control of HIV infection. In this study we investigated whether there may be qualitative differences in the CD8(+) T cell response in HIV-1- and HIV-2-infected individuals that contribute to the relatively efficient control of the latter infection. A molecular comparison of global TCR heterogeneity showed a more oligoclonal pattern of CD8 cells in HIV-1- than HIV-2-infected patients. This was reflected in restricted and conserved TCR usage by CD8(+) T cells recognizing individual HLA-A2- and HLA-B57-restricted viral epitopes in HIV-1, with limited plasticity in their response to amino acid substitutions within these epitopes. The more diverse TCR usage observed for HIV-2-specific CD8(+) T cells was associated with an enhanced potential for CD8 expansion and IFN-gamma production on cross-recognition of variant epitopes. Our data suggest a mechanism that could account for any possible cross-protection that may be mediated by HIV-2-specific CD8(+) T cells against HIV-1 infection. Furthermore, they have implications for HIV vaccine development, demonstrating an association between a polyclonal, virus-specific CD8(+) T cell response and an enhanced capacity to tolerate substitutions within T cell epitopes.     

BK antibody and virus-specific IgM responses in renal transplant recipients,patients with malignant disease,and healthy people.

Haemagglutination-inhibition (HAI) antibodies to BK virus, including BK-virus-specific IgM, were determined before and after renal transplantation in 20 patients, in 57 patients with malignant disease, and in 66 healthy controls, Before transplantation 11 of the renal transplant recipients were seronegative, but eight later serocconverted, two before and six after transplantation. Twenty of the patients with malignant disease and 22 controls were also seronegative. The geometric mean titre of BK HAI antibodies was significantly higher among transplanted patients (1/180) than among controls (1/90). BK-virus-specific IgM antibody was detected in seven renal transplant recipients, six patients with malignant disease, and 13 healthy controls. In transplant recipients BK-virus-specific IgM antibody usually persisted throughout the duration of the study, and studies on controls from whom second serum samples were available suggested that they too had persistent BK-virus-specific IgM responses. The geometric mean titre of BK-virus-specific IgM HAI antibody was significantly greater in post-transplantation sera (1/223) than in control sera (1/28). The specificity of the detection of BK-virus-specific IgM HAI antibody was confirmed by direct visualisation of antibody by immune electron microscopy. The persistence of BK-virus-specific IgM suggested that BK virus continued to provide an antigenic stimulus. Nevertheless, there was no obvious association between the serological findings and any clinical features, and prospective studies will be needed to elucidate any such association.     

Crystallization and initial X-ray analysis of the C2-subunit of crustacyanin.

Crystals of the C2-subunit of crustacyanin have been grown from solutions containing ammonium sulphate and 2-methyl-2,4-pentanediol as co-precipitants. The crystals belong to space group P2(1)2(1)2(1) (a = 42.0 A, b = 80.9 A, c = 110.8 A) with two subunits per asymmetric unit and diffract beyond 2.2 A resolution.