Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expanded bed adsorption (EBA) is a primary recovery operation allowing the adsorption of proteins directly from unclarified feedstock, e.g. culture suspensions, homogenates or crude extracts. Thus solid-liquid separation is combined with adsorptive purification in a single step. The concept of integration requires that the solid components of the feed solution are regarded as a part of the process, which influences stability, reproducibility, and overall performance. This aspect is investigated here at the example of the influence of presence and concentration of intact yeast cells (S. cerevisiae) on the adsorption of model proteins (hen egg white lysozyme and bovine serum albumin) to various stationary phases (cation and anion-exchange, hydrophobic interaction, immobilised metal affinity). The interaction of the cells with the adsorbents is determined qualitatively and quantitatively by a pulse response method as well as by a finite bath technique under different operating conditions. The consequence of these interactions for the stability of expanded beds in suspensions of varying cell concentration is measured by residence time distributions (RTDs) after tracer pulse injection (NaBr, LiCl). Analysis of the measured RTD by the PDE model allows the calculation of the fraction of perfectly fluidised bed (phi), a parameter which may be regarded as a critical quantity for the estimation of the quality of fluidisation of adsorbents in cell containing suspensions. The correlation between bed stability and performance is made by analysing the breakthrough of model proteins during adsorption from unclarified yeast culture broth. A clear relationship is found between the degree of cell/adsorbent interaction, bed stability in terms of the phi parameter, and the sorption efficiency. Only beds characterised by a phi value larger than 0.8 in the presence of cells will show a conserved performance compared to adsorption from cell free solutions. A drop in phi, which is due to interactions of the fluidised adsorbent particles with cells from the feed, will directly result in a reduced breakthrough efficiency. The data presented highlight the importance of including the potential interaction of solid feedstock components and the expanded adsorbents into the design of EBA processes, as the interrelation found here is a key factor for the overall performance of EBA as a truly integrated operation.
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PMID:The influence of cell adsorbent interactions on protein adsorption in expanded beds. 1075 97

Photoreceptor degeneration in human photoreceptor dystrophies and in the relevant animal models has been thought to be executed by one common mechanism -- caspase-mediated apoptosis. However, recent experiments have challenged this concept. In previous experiments, analyzing gene expression in the degenerating rd/rd mouse retina, we have suggested that the gene defect leads to oxidative stress and altered metabolism, which may induce caspase-dependent and caspase-independent cell death mechanisms such as the activation of cystein-proteases, lysosomal proteases, autophagy and complement-mediated lysis. In this study we asked two questions. First, whether a temporal analysis of these different mechanisms during the course of degeneration would enable us to establish a causal relationship between these events; and second, whether photoreceptor degeneration in different models of photoreceptor dystrophies occurs by activating the same mechanisms. Three models of photoreceptor degeneration were chosen in which photoreceptor degeneration is caused by different events: the rd/rd mouse (calcium overload); the rds/rds mouse (structural defect); and light-damage (LD; oxidative stress). Marker genes were selected for the identified processes. PCR-analysis on laser capture microdissection samples was used to verify the expression of these genes in the rod photoreceptor layer. A temporal relationship between the processes was established at the mRNA level, using quantitative RT-PCR. The time course of gene expression was compared to that of cell loss (loss of rows of photoreceptor nuclei) and apoptosis (TUNEL labeling). Apoptosis and autophagy was analyzed using enzymatic assays. The time course of apoptosis and TUNEL labeling coincide in all three models. Complement-activated lysis was found to either parallel (rd/rd and rds/rds) or precede (LD) the development of TUNEL-positive cells. Autophagy was determined to parallel (rd/rd and LD) or lag (rds/rds) behind the development of TUNEL-positive cells. In all three models, glucose metabolism was found to be increased significantly prior to the onset of cell death, but then dropped in parallel with the loss of cells. The presence of the marker genes was verified by laser capture microdissection, and apoptosis (caspase activity) and autophagy (lysozyme and cathepsin activity) were verified in retina extracts. These results provide evidence that irrespective of whether photoreceptor degeneration is triggered by gene defects (lack of beta-PDE or rds/peripherin) or environmental stress (light-damage), a number of pro-apoptotic mechanisms are triggered leading to the degeneration of the photoreceptor cells. The temporal pattern of the different pathways suggests that the non-caspase-dependent mechanisms may actively participate in the demise of the photoreceptors, rather than represent a passive response of the retina to the presence of dying cells. Thus, unless the common upstream initiator for a given photoreceptor dystrophy is found, multiple rescue paradigms need to be used to target all active pathways.
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PMID:Multiple, parallel cellular suicide mechanisms participate in photoreceptor cell death. 1710 84