Physiological difference during ethanol fermentation between calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae

Calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae are compared for glucose fermentation. Immobilized C. tropicalis cells showed a slight morphological alteration during ethanol production at 40 degrees C, but their fermentation capacity was reduced by 25%. Under immobilization conditions, the two species demonstrated two different mathematical patterns when the relationship between growth rate, respiration rate, and ethanol tolerance was assessed. The interspecific difference in behavior of immobilized yeast cells is mainly due to their natural metabolic preference. The production of CO(2) by calcium alginate-immobilized C. tropicalis, as well as the lower supply of oxygen to the cells, are the major factors that reduce ethanol production.     

Catalytic activity and thermostability of enzymes immobilized on silanized surface: Influence of the crosslinking agent

In this work, we investigate the influence of crosslinkers on the operational and heat stability of immobilized enzymes on a silanized silicon surface. To this end, glucose-6-phosphate dehydrogenase (G6PDH), a model multimeric enzyme, was attached through bifunctional crosslinkers able to bind covalently the ?NH₂ in the silane layer and of amine residues in the enzyme. Five bifunctional crosslinkers in the form of “X-spacer-X” were used, differing by the reactive functional groups (X = aldehyde: ?CHO, isothiocyanate: ?NCS, isocyanate: ?NCO), by the nature of the spacer chain (aromatic or aliphatic) or by the geometry (bifunctional groups positioned in meta- or para- on an aromatic ring). A thermostability enhancement has been obtained for enzymes immobilized using 1,4-phenylene diisothiocyanate (PDC) and 1,4-phenylene diisocyanate (DIC). Moreover, using the latter crosslinker, activity was the mostly preserved upon successive uses, thus giving the best operational stability achieved. Changing the geometry of the cross-linker, i.e., 1,4- as compared to 1,3-phenylene diisothiocyanate (PDC and MDC, respectively), has a crucial effect on operational and thermal stabilities. Indeed, among all used crosslinkers, the most important loss was observed for MDC (residual activity after 6 times use is ~16%). Using dialdehyde crosslinkers: glutaraldehyde (GA) and terephtalaldehyde (TE), activity was significantly less well preserved than with DIC and PDC (for GA and TE, a loss of about 50% at 30 °C against no loss for PDC and DIC).These effects can be explained by a multipoint attachment model, in which a higher number of anchoring points stabilizes the three-dimensional structure and especially the binding of the two subunits in the active dimer, at the expense of a greater rigidity which is detrimental to the absolute activity. The differences observed with the crosslinkers are mainly due to steric hindrance at the interface which seems to be greatly influenced by the structure and the reactivity of the linkers.     

ARHGAP30 is a Wrch-1-interacting protein involved in actin dynamics and cell adhesion

It has previously been reported that shedding of the PTPκ ectodomain drives enhanced motility of colon cancer cells. Herein, we provide mechanism underlying the regulation of PTPκ shedding by galectin-3 binding protein. PTPκ was inarguably scissored by the processed form of proprotein convertase 5 (subtilisin/kexin type 5), and galectin-3 binding protein which is over-produced in colon cancer cells and tissues contributed to increased cancer cell motility by acting as a negative regulator of galectin-3 at the cell surface. The high expression ratio of galectin-3 binding protein to galectin-3 was clinically correlated to lymphatic invasion. These results suggest that galectin-3 binding protein may be a potential therapeutic target for treatment of, at least, colon cancer patients with high expression of galectin-3 binding protein.     

Expression of Dystrophins and the Dystrophin-Associated-Protein Complex by Pituicytes in Culture

The dystrophin-associated-protein complex (DAPC) has been extensively characterized in the central nervous system where it is localized both in neuronal and glial cells. Few studies have characterized this complex in the neurohypophysis. To further study this complex in pituicytes, the resident astroglia of the neurophypophysis, we used adult pituicyte cultures and determined the expression and localization of dystrophins/utrophins and the DAPC by RT–PCR, western blotting and immunofluorescence. Our data show that the pituicytes express dystrophins, utrophins and several members of the DAPC including dystroglycans, δ-, γ-sarcoglycans, α-dystrobrevin-1 and α1-syntrophin. Double immunofluorescence analysis shows that laminin colocalizes with dystroglycan, suggesting that similarly to muscle and astrocytes, the DAPC interacts with the extracellular matrix in pituicytes. Collectively these findings show that dystrophins/utrophins and members of the DAPC are expressed in pituicytes where they may form multiprotein complexes and play a role in the retraction-reinsertion of pituicyte endfeet during specific physiological conditions.     

A Mediterranean Holocene restricted coastal lagoon under arid climate: Case of the sedimentary record of Sabkha Boujmel (SE Tunisia)

The Holocene sedimentary record of Sabkha Boujmel (SE Tunisia) is expressed by a shallowing-upward carbonate lagoon-tidal flat cycle (2.3 m thick) unconformably overlying continental silt-sandy sediment, Late Würmian in age. The sedimentary package of this cycle starts with transgressive marginal shallow marine (intertidal to subtidal) bioclastic sands grading upwards to black mudstone, rich in organic matter (T.O.C. up to 1.3%) deposited within a lagoon protected from the sea by Upper Pleistocene lithified sand spits.The uppermost part of the cycle is represented by oobioclastic carbonate sands covered with dead biodegraded microbial mats and/or reddish sands of aeolian origin deposited in intertidal to supratidal environments. The facies arrangement, particularly the spatial distribution of the ancient and the more recent microbial mats, records the progressive infilling of the lagoon as well as the progradation of the shoreline during the last 2000 years. The organic-rich facies which provide an age varying between 4130 and 6800 yr B.P. were deposited when the Boujmel lagoon started to be progressively separated from the Mediterranean Sea.The main factors controlling the facies and the thickness variation are the local topographic sea-floor irregularities most likely controlled by the inheritance morphology resulting from an important fluviatile digging that occurred during the last glacial maximum, the relative sea-level fluctuations, the hydro-isostatic rebound and the climate.     

Cloning, gene expression and characterization of a novel bacterial NAD-dependent non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase from Neisseria meningitidis strain Z2491

Alignment of the amino acid sequence of some archaeal, bacterial and eukaryotic non-phosphorylating glyceraldehydes-3-phosphate dehydrogenases (GAPNs) and aldehyde dehydrogenases (ALDHs) with the sequence of a putative GAPN present in the genome of the Gram-negative bacterium Neisseria meningitidis strain Z2491 demonstrated the conservation of residues involved in the catalytic activity. The predicted coding sequence of the N. meningitidis gapN gene was cloned in Escherichia coli XL1-blue under the expression of an inducible promoter. The IPTG-induced GAPN was purified ca. 48-fold from E. coli cells using a procedure that sequentially employed conventional ammonium sulfate fractionation as well as anion-exchange and affinity chromatography. The purified recombinant enzyme was thoroughly characterized. The protein is a homotetramer with a 50-kDa subunit, exhibiting absolute specificity for NAD and a broad spectrum of aldehyde substrates. Isoelectric focusing analysis with the purified fraction showed the presence of an acidic polypeptide with an isoelectric point of 6.3. The optimum pH of the purified enzyme was between 9 and 10. Studies on the effect of increasing temperatures on the enzyme activity revealed an optimal value ca. 64 °C. Molecular phylogenetic data suggest that N. meningitidis GAPN has a closer relationship with archaeal GAPNs and glyceraldehyde dehydrogenases than with the typical NADP-specific GAPNs from Gram-positive bacteria and photosynthetic eukaryotes.     

Glycan Dependence of Galectin-3 Self-Association Properties

Human Galectin-3 is found in the nucleus, the cytoplasm and at the cell surface. This lectin is constituted of two domains: an unfolded N-terminal domain and a C-terminal Carbohydrate Recognition Domain (CRD). There are still uncertainties about the relationship between the quaternary structure of Galectin-3 and its carbohydrate binding properties. Two types of self-association have been described for this lectin: a C-type self-association and a N-type self-association. Herein, we have analyzed Galectin-3 oligomerization by Dynamic Light Scattering using both the recombinant CRD and the full length lectin. Our results proved that LNnT induces N-type self-association of full length Galectin-3. Moreover, from Nuclear Magnetic Resonance (NMR) and Surface Plasmon Resonance experiments, we observed no significant specificity or affinity variations for carbohydrates related to the presence of the N-terminal domain of Galectin-3. NMR mapping clearly established that the N-terminal domain interacts with the CRD. We propose that LNnT induces a release of the N-terminal domain resulting in the glycan-dependent self-association of Galectin-3 through N-terminal domain interactions.     

Cell therapy in the heart

Cell therapy is emerging as a new strategy to circumvent the adverse effects of heart disease. Many experimental and clinical studies investigating the transplantation of cells into the injured myocardium have yielded promising results. Moreover, data from these reports show that transplanted stem cells can engraft within the myocardium, differentiate into major cardiac cell types, and improve cardiac function. However, results from clinical trials show conflicting results. These trials demonstrate significant improvements in cardiac function for up to 6 months. However, these improved functions were diminished when examined at 18 months. In this review, we will discuss the current literature available on cell transplantation, covering studies ranging from animal models to clinical trials.     

Hsp70-2 gene polymorphism: susceptibility implication in Tunisian patients with coronary artery disease

ABSTRACT: Coronary artery disease (CAD) is a multifactorial disease where genetic and environmental factors interact in complex ways to cause the disease. Heat shock protein genes are involved in the progress of CAD. This implies that genetic variants of Hsp70-2 genes might contribute to the development of the disease. Aim of study The aim of this study was to characterize statistical correlation of linkage between lipid profiles, polymorphism PstI site of Hsp70-2 gene and coronary artery diseases. Patients and methods This study was carried out on Tunisian patients with CAD recruited from Hospital of Fattouma Bourguiba of Monastir-Tunisia. Polymerase chain reaction and restriction enzymes were used to determine the genotypic distributions in 252 unrelated patients and 151 healthy control subjects. Further, ApoA-I and ApoB as well as the serum total of cholesterol, HDL, triglyceride, and hs-CRP levels were measured. RESULTS: We showed a decreased level of ApoA-I, whereas the levels of each of ApoB and hs-CRP were increased in patients with CAD compared with control group. In addition our studies of a polymorphic PstI site of Hsp70-2 gene lying in the coding region at position 1267 of the Hsp70-2 gene have revealed that the frequency of P1/P2 heterozygote was 0.484 in patient group compared with control group (0.476, p = 0.046). Whereas, the frequency of the P2/P2 homozygote was 0.190 in patient group and only 0.099 in controls (P = 0.006). These results indicate that the odds ratio of CAD associated with the Hsp70-2 polymorphism is confined the P2/P2 homozygotes (OR 2.498; P = 0.006). CONCLUSION: Taken together, our results indicate that the high frequency of P2/P2 genotype is associated with elevated levels of biochemical parameters (LDL cholesterol, hs-CRP) in Tunisian patient group. The Hsp70-2 polymorphism has susceptibly implication in CAD. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1118340895703689.