The rotorfermentor. I. Description of the apparatus,power requirements,and mass transfer characteristics

A novel fermentation device, the rotorfermentor, is described and some experimental results are presented on power requirements and oxygen mass transfer characteristics of the rotorfermentor. This fermentation device is designed to achieve high cell concentrations in batch and continuous cultures. Basically, the rotorfermentor consists of a rotating microporous membrane which is enclosed within a stationary fermentor vessel. The metabolic products in the broth are continuously removed by filtration through the rotating microporous membrane while the growing cells can be retained inside the fermentor. This dual function of cell growth and concentration with the simultaneous removal of metabolic products is the essential characteristic of the rotorfermentor.     

Mixing,mass transfer,and scale-up of polysaccharide fermentations

Microbial polysaccharides are rapidly emerging as a new and important source of polymeric materials. These biopolymers have novel and unique properties and already have found a wide range of applications in the food, pharmaceutical, and other industries. In view of the impending importance of polysaccharides as an industrial commodity, there is renewed interest in the area of product and process development. This paper summarizes the state-of-the art in polysaccharide fermentations. An attempt is being made to review the following areas: rheological characteristics of polysaccharide solutions, mixing and power requirements of polysaccharides and other highly viscous non-Newtonian systems, oxygen mass transfer, and scale-up problems encountered in polysaccharide fermentations.     

The effect of temperature on the growth and hydrogen production by Citrobacter intermedius

Summary Citrobacter intermedius was grown batchwise in a mineral salts medium with glucose as a carbon and energy source under anaerobic conditions and at different temperatures. The effect of temperature on the following parameters was studied: maximum specific growth rate, max, maximum rate of hydrogen gas production and maximum rate of total gas (H₂ + CO₂) production. Arrhenius plots were used to determine the activation energies associated with max and maximum rates of hydrogen gas production.     

Crystalline layer in Drosophila melanogaster eggshell: arrangement of components as revealed by negative staining and reconstruction

Eggshell formation in Drosophila melanogaster is used as a model system in studies of cellular differentiation. A detailed knowledge of eggshell structure is necessary for this purpose and also to permit correlation of eggshell structure with function. Unique among the eggshell layers, the innermost chorionic layer (ICL) was investigated by means of transmission electron microscopy of thin sections and whole mounts, utilizing conventional fixation. LaNO₃ impregnation and negative staining with uranyl acetate. Whole mount face views of negatively stained ICLs were processed by means of optical and computer reconstruction. The ICL, which almost fully covers the oocyte, consists of 4 5 bilaminar sublayers with a total thickness of 400–500 Å. It appears to be formed by crystallites 1– μm in size, containing roughtly spherical molecules which are 30 Å in diameter approximately. Each unit cell probably includes 8 molecules and also distinct vacant spaces, differing in size, ICL may be involved in the exchange of the respiratory gases during embryogenesis.     

Actin cytoskeleton reorganization of the apoptotic nurse cells during the late developmental stages of oogenesis in Dacus oleae

In the present study, we demonstrate the actin cytoskeleton reorganization during nurse cells apoptosis of the olive fruit fly Dacus oleae. At the developmental stage 9A of oogenesis, the actin microfilaments are assembled in numerous ring canals and subcortically support all the nurse cells, as is shown by phalloidin-FITC staining. During the following stages, 9B and 10A, this structural pattern remains the same. The developmental stage 10B is characterized by actin microfilament rearrangement and formation of actin cables that are symmetrically organized around the nurse cell nuclei. At stage 11, when the dumping process begins, these actin cables seem to retain each nurse cell nucleus in the cell center, away from blocking the ring canals. The early stage 12 is characterized by an asynchronous nurse cell nuclear chromatin condensation, while at late stage 12 the actin cables become very thick, as adjacent ones overlap one another and traverse the disorganized apoptotic nurse cell nuclei that already have fragmented DNA, as is demonstrated by acridine orange staining and TUNEL assay. Finally, during stage 13, the apoptotic nuclear remnants are phagocytosed by the neighboring follicle cells. The data presented herein compared to previous reported results in Drosophila [Nezis et al., 2000: Eur J Cell Biol 79:610-620], demonstrate that actin cytoskeleton reorganization during nurse cell apoptosis is a developmentally regulated physiological mechanism, phylogenetically conserved in higher Dipteran.     

Let-7, Mir-98 and Mir-181 as Biomarkers for Cancer and Schizophrenia

Recent evidence supports a role of microRNAs in cancer and psychiatric disorders such as schizophrenia and bipolar disorder, through their regulatory role on the expression of multiple genes. The rather rare co-morbidity of cancer and schizophrenia is an old hypothesis which needs further research on microRNAs as molecules that might exert their oncosuppressive or oncogenic activity in the context of their role in psychiatric disorders. The expression pattern of a variety of different microRNAs was investigated in patients (N = 6) suffering from schizophrenia termed control, patients with a solid tumor (N = 10) and patients with both schizophrenia and tumor (N = 8). miRNA profiling was performed on whole blood samples using the miRCURY LNA microRNA Array technology (6th & 7th generation). A subset of 3 microRNAs showed a statistically significant differential expression between the control and the study groups. Specifically, significant down-regulation of the let-7p-5p, miR-98-5p and of miR-183-5p in the study groups (tumor alone and tumorand schizophrenia) was observed (p<0.05). The results of the present study showed that let-7, miR-98 and miR-183 may play an important oncosuppressive role through their regulatory impact in gene expression irrespective of the presence of schizophrenia, although a larger sample size is required to validate these results. Nevertheless, further studies are warranted in order to highlight a possible role of these and other micro-RNAs in the molecular pathways of schizophrenia.     

The Fidelity of Dynamic Signaling by Noisy Biomolecular Networks

Cells live in changing, dynamic environments. To understand cellular decision-making, we must therefore understand how fluctuating inputs are processed by noisy biomolecular networks. Here we present a general methodology for analyzing the fidelity with which different statistics of a fluctuating input are represented, or encoded, in the output of a signaling system over time. We identify two orthogonal sources of error that corrupt perfect representation of the signal: dynamical error, which occurs when the network responds on average to other features of the input trajectory as well as to the signal of interest, and mechanistic error, which occurs because biochemical reactions comprising the signaling mechanism are stochastic. Trade-offs between these two errors can determine the system''s fidelity. By developing mathematical approaches to derive dynamics conditional on input trajectories we can show, for example, that increased biochemical noise (mechanistic error) can improve fidelity and that both negative and positive feedback degrade fidelity, for standard models of genetic autoregulation. For a group of cells, the fidelity of the collective output exceeds that of an individual cell and negative feedback then typically becomes beneficial. We can also predict the dynamic signal for which a given system has highest fidelity and, conversely, how to modify the network design to maximize fidelity for a given dynamic signal. Our approach is general, has applications to both systems and synthetic biology, and will help underpin studies of cellular behavior in natural, dynamic environments.     

Down-regulation of kallikrein-related peptidase 5 (<Emphasis Type="Italic">KLK5</Emphasis>) expression in breast cancer patients: a biomarker for the differential diagnosis of breast lesions

Background  

Kallikrein-related peptidase 5 (KLK5) is a secreted trypsin-like protease of the KLK family, encoded by the KLK5 gene. KLK5 has been found to cleave various extracellular matrix components, as well as to activate several other KLK proteases, triggering the stimulation of tissue microenvironment proteolytic cascades.     

Hydrodynamic and Mass Transfer Characteristics of Three-Phase Gaslift Bioreactor Systems

ABSTRACT:?

This review focuses on the hydrodynamic and mass transfer characteristics of various three-phase, gaslift fluidized bioreactors. The factors affecting the mixing and volumetric mass transfer coefficient (k_La), such as liquid properties, solid particle properties, liquid circulation velocity, superficial gas velocity, bioreactor geometry, are reviewed and discussed. Measurement methods, modeling and empirical correlations are reviewed and compared. To the authors' knowledge, there is no 'generalized' correlation to calculate the volumetric mass transfer coefficient, instead, only 'type-specific' correlations are available in the literature. This is due to the difficulty in modeling the gaslift bioreactor, caused by the variation in geometry, fluid dynamics, and phase interactions. The most important design parameters reported in the literature are: gas hold-up, liquid circulation velocity, 'true' superficial gas velocity, mixing, shear rate, aeration rate and volumetric mass transfer coefficient, k_La.     

Detrimental effects of proteasome inhibition activity in Drosophila melanogaster: implication of ER stress, autophagy, and apoptosis

In eukaryotes, the ubiquitin–proteasome machinery regulates a number of fundamental cellular processes through accurate and tightly controlled protein degradation pathways. We have, herein, examined the effects of proteasome functional disruption in Dmp53 ^+/+ (wild-type) and Dmp53 ^?/? Drosophila melanogaster fly strains through utilization of Bortezomib, a proteasome-specific inhibitor. We report that proteasome inhibition drastically shortens fly life-span and impairs climbing performance, while it also causes larval lethality and activates developmentally irregular cell death programs during oogenesis. Interestingly, Dmp53 gene seems to play a role in fly longevity and climbing ability. Moreover, Bortezomib proved to induce endoplasmic reticulum (ER) stress that was able to result in the engagement of unfolded protein response (UPR) signaling pathway, as respectively indicated by fly Xbp1 activation and Ref(2)P-containing protein aggregate formation. Larva salivary gland and adult brain both underwent strong ER stress in response to Bortezomib, thus underscoring the detrimental role of proteasome inhibition in larval development and brain function. We also propose that the observed upregulation of autophagy operates as a protective mechanism to “counterbalance” Bortezomib-induced systemic toxicity, which is tightly associated, besides ER stress, with activation of apoptosis, mainly mediated by functional Drice caspase and deregulated dAkt kinase. The reduced life-span of exposed to Bortezomib flies overexpressing Atg1_RNAi or Atg18_RNAi supports the protective nature of autophagy against proteasome inhibition-induced stress. Our data reveal the in vivo significance of proteasome functional integrity as a major defensive system against cellular toxicity likely occurring during critical biological processes and morphogenetic courses.