Effects of hyperbaric gases on membrane nanostructure and function in neurons

This mini-review summarizes current ideas of how hyperbaric gases (>1-10 atmospheres absolute) affect neuronal mechanisms of excitability through molecular interaction with membrane components. The dynamic nature of the lipid bilayer, its resident proteins, and the underlying cytoskeleton make each respective nanostructure a potential target for modulation by hyperbaric gases. Depending on the composition of the gas mixture, the relative concentrations of O(2) and inert gas, and total barometric pressure, the net effect of a particular gas on the cell membrane will be determined by the gas' 1) lipid solubility, 2) ability to oxidize lipids and proteins (O(2)), and 3) capacity, in the compressed state, to generate localized shear and strain forces between various nanostructures. A change in the properties of any one membrane component is anticipated to change conductance of membrane-spanning ion channels and thus neuronal function.     

Proteolysis and deglycosylation of human C1 inhibitor. Effect on functional properties.

The effects of proteolysis and deglycosylation on C1 inhibitor (C1Inh) were tested with respect to both its ability to form complexes with C1s and its capacity to block C1 autoactivation. Limited proteolysis of C1Inh by Staphylococcus aureus V8 proteinase, proline-specific endopeptidase or elastase generated a major high-Mr (approximately 86,000) fragment. In contrast with the fragment produced by elastase, which was inactive, the fragments resulting from V8 proteinase and proline-specific endopeptidase treatment retained activity. Deglycosylation with N-glycanase or O-glycanase, or both, had no major effect on the functional activity of C1Inh.     

The complement system and its biological activities

The complement system is a non specific humoral defence mechanism which can be triggered by various effectors : immune-complexes, extrinsic proteases, bacterial cell-wall polysaccharides, viral membranes. Different peptides or multimolecular complexes are formed by a cascade of proteolytic cleavages; they take an active part in the inflammatory response and may contribute to different pathological manifestations.     

Cell-cycle studies by multiparametric automatic scanning of topographically preserved cells in culture

The authors have developed a new methodology for characterizing in situ the cell cycle of human mammary epithelial cell lines. Using a SAMBA 200 cell image processor (scanning cytometry), 15 densitometric and textural parameters were computed on each Feulgen-stained nucleus. Parameters computed from the grey level cooccurrence and run-length section matrices allowed assessment of the chromatin pattern. Multiparametric analysis of data defined: 1) the relative position of each cell; 2) the relative positions of groups of cells, each group corresponding to a definite phase of the cell cycle; and 3) the function of these parameters best separating these phases. Files then were constructed for each phase: G0/G1, S, G2/ and M. Using these three files as a reference to classify cells, it was possible to ascertain the phase of the cell cycle for each cell of a population. The MDA AG human cell line synchronized by mitotic selection was used as a model to develop this method. The criteria used to assign cells to G0/G1, S, or G2 was DNA content. Classification in M phase was achieved by visual identification of mitotic cells. This method was checked on unsynchronized MDA AG and then applied to other human cell lines (MDA MB231, MCF-7, T47D C111). Comparison of results obtained by scanning cytometry and flow cytometry showed the proportion of cells assigned to G0/G1, S, and G2/M by the two methods to be similar. This new method removes some of the limitations of flow cytometry by 1) allowing visual verification of each cell analyzed; 2) lowering the number of cells required for study; 3) discriminating between G2 and M; and 4) preserving cell topography.     

Systematic review and meta-analysis: rapid diagnostic tests versus placental histology, microscopy and PCR for malaria in pregnant women

Background

To prepare field sites for malaria vaccine trials, it is important to determine baseline antibody and T cell responses to candidate malaria vaccine antigens. Assessing T cell responses is especially challenging, given genetic restriction, low responses observed in endemic areas, their variability over time, potential suppression by parasitaemia and the intrinsic variability of the assays.

Methods

In Part A of this study, antibody titres were measured in adults from urban and rural communities in Ghana to recombinant Plasmodium falciparum CSP, SSP2/TRAP, LSA1, EXP1, MSP1, MSP3 and EBA175 by ELISA, and to sporozoites and infected erythrocytes by IFA. Positive ELISA responses were determined using two methods. T cell responses to defined CD8 or CD4 T cell epitopes from CSP, SSP2/TRAP, LSA1 and EXP1 were measured by ex vivo IFN-γ ELISpot assays using HLA-matched Class I- and DR-restricted synthetic peptides. In Part B, the reproducibility of the ELISpot assay to CSP and AMA1 was measured by repeating assays of individual samples using peptide pools and low, medium or high stringency criteria for defining positive responses, and by comparing samples collected two weeks apart.

Results

In Part A, positive antibody responses varied widely from 17%-100%, according to the antigen and statistical method, with blood stage antigens showing more frequent and higher magnitude responses. ELISA titres were higher in rural subjects, while IFA titres and the frequencies and magnitudes of ex vivo ELISpot activities were similar in both communities. DR-restricted peptides showed stronger responses than Class I-restricted peptides. In Part B, the most stringent statistical criteria gave the fewest, and the least stringent the most positive responses, with reproducibility slightly higher using the least stringent method when assays were repeated. Results varied significantly between the two-week time-points for many participants.

Conclusions

All participants were positive for at least one malaria protein by ELISA, with results dependent on the criteria for positivity. Likewise, ELISpot responses varied among participants, but were relatively reproducible by the three methods tested, especially the least stringent, when assays were repeated. However, results often differed between samples taken two weeks apart, indicating significant biological variability over short intervals.     

Phylogenetic relationships among prokaryotic and eukaryotic catalases

Seventy-four catalase protein sequences, including 29 bacterial, 8 fungal, 7 animal, and 30 plant sequences, were compiled, and 70 were used for phylogenetic reconstruction. The core of the resulting tree revealed unique, separate groups of plant and animal catalases, two groups of fungal catalases, and three groups of bacterial catalases. The only overlap of kingdoms occurred within one branch and involved fungal and bacterial large-subunit enzymes. The other fungal branch was closely linked to the group of animal enzymes. Group I bacterial catalases were more closely related to the plant enzymes and contained such diverse taxa as the Gram-positive Listeria seeligeri, Deinocococcus radiodurans, and gamma-proteobacteria. Group III bacterial sequences were more closely related to fungal and animal sequences and included enzymes from a broad range of bacteria including high- and low-GC Gram positives, proteobacteria, and a bacteroides species. Group II was composed of large-subunit catalases from diverse sources including Gram positives (low-GC Bacilli and high-GC Mycobacteria), proteobacteria, and species of the filamentous fungus Aspergillus. These data can be interpreted in terms of two gene duplication events that produced a minimum of three catalase gene family members that subsequently evolved in response to environmental demands. Horizontal gene transfer may have been responsible for the group II mixture of bacterial and fungal large-subunit catalases.      

Neutron scattering studies of subcomponent C1q of first component C1 of human complement and its association with subunit C1r2C1s2 within C1

Neutron scattering studies are reported on subcomponent C1q of component C1 of human complement, and on C1, the complex of C1q with subunit C1r₂C1s₂. For C1q, the molecular weight was determined as 460,000. The radius of gyration at infinite contrast R_c is 12.8 nm. The R_c values for the proteolytically cleaved forms of C1q, namely the heads and the stalks, are 1.5 to 2 nm and 11 nm, respectively, and thus the axis-to-arm angle of C1q is estimated at 45 °. Neutron data for subunit C1r₂C1s₂ are published elsewhere. The neutron data on C1 lead to an R_c value of 12.6 nm for proenzymic C1 and a molecular weight of 820,000. The wideangle scattering curve of C1q exhibits a minimum at Q = 0.28 nm^?1 and a maximum at 0.39 nm^?1; on the addition of C1r₂C1s₂, this minimum disappears. The neutron data on C1 indicate that C1q and C1r₂C1s₂ have complexed with a large conformational change in one or both parts. No conformational changes can be detected on the activation of C1 by this method.