Hollow-fiber enzyme reactor operating under nonisothermal conditions

A hollow-fiber enzyme reactor, operating under isothermal and nonisothermal conditions, was built employing a polypropylene hollow fiber onto which beta-galactosidase was immobilized. Hexamethylenediamine and glutaraldehyde were used as spacer and coupling agent, respectively. Glucose production was studied as a function of temperature, substrate concentration, and size of the transmembrane temperature gradient. The actual average temperature differences across the polypropylene fiber, to which reference was done to evaluate the effect of the nonisothermal conditions, were calculated by means of a mathematical approach, which made it possible to know, using computer simulation, the radial and axial temperature profiles inside the bioreactor and across the membrane. Percent activity increases, proportional to the size of the temperature gradients, were found when the enzyme activities under nonisothermal conditions were compared to those measured under comparable isothermal conditions. Percent reductions of the production times, proportional to the applied temperature gradients, were also calculated. The advantage of employing nonisothermal bioreactors in biotechnological industrial process was discussed.     

The plant pathogen Erwinia amylovora produces acyl-homoserine lactone signal molecules in vitro and in planta

We report for the first time the production of acyl homoserine lactones (AHLs) by Erwina amylovora, an important quarantine bacterial pathogen that causes fire blight in plants. E. amylovora produces one N-acyl homoserine lactone [a N-(3-oxo-hexanoyl)-homoserine lactone or a N-(3-hydroxy-hexanoyl)-homoserine lactone] quorum sensing signal molecule both in vitro and in planta (pear plant). Given the involvement of AHLs in plant pathogenesis, we speculate that AHL-dependent quorum sensing could play an important role in the regulation of E. amylovora virulence.     

Sound-driven synaptic inhibition in primary visual cortex

Multimodal objects and events activate many sensory cortical areas simultaneously. This is possibly reflected in reciprocal modulations of neuronal activity, even at the level of primary cortical areas. However, the synaptic character of these interareal interactions, and their impact on synaptic and behavioral sensory responses are unclear. Here, we found that activation of auditory cortex by a noise burst drove local GABAergic inhibition on supragranular pyramids of the mouse primary visual cortex, via cortico-cortical connections. This inhibition was generated by sound-driven excitation of a limited number of cells in infragranular visual cortical neurons. Consequently, visually driven synaptic and spike responses were reduced upon bimodal stimulation. Also, acoustic stimulation suppressed conditioned behavioral responses to a dim flash, an effect that was prevented by acute blockade of GABAergic transmission in visual cortex. Thus, auditory cortex activation by salient stimuli degrades potentially distracting sensory processing in visual cortex by recruiting local, translaminar, inhibitory circuits.     

2000 Year-old ancient equids: an ancient-DNA lesson from pompeii remains

Ancient DNA extracted from 2000 year-old equine bones was examined in order to amplify mitochondrial and nuclear DNA fragments. A specific equine satellite-type sequence representing 3.7%-11% of the entire equine genome, proved to be a suitable target to address the question of the presence of aDNA in ancient bones. The PCR strategy designed to investigate this specific target also allowed us to calculate the molecular weight of amplifiable DNA fragments. Sequencing of a 370 bp DNA fragment of mitochondrial control region allowed the comparison of ancient DNA sequences with those of modern horses to assess their genetic relationship. The 16S rRNA mitochondrial gene was also examined to unravel the post-mortem base modification feature and to test the status of Pompeian equids taxon on the basis of a Mae III restriction site polymorphism.     

Mitochondrial permeability transitions: how many doors to the house?

The inner mitochondrial membrane is famously impermeable to solutes not provided with a specific carrier. When this impermeability is lost, either in a developmental context or under stress, the consequences for the cell can be far-reaching. Permeabilization of isolated mitochondria, studied since the early days of the field, is often discussed as if it were a biochemically well-defined phenomenon, occurring by a unique mechanism. On the contrary, evidence has been accumulating that it may be the common outcome of several distinct processes, involving different proteins or protein complexes, depending on circumstances. A clear definition of this putative variety is a prerequisite for an understanding of mitochondrial permeabilization within cells, of its roles in the life of organisms, and of the possibilities for pharmacological intervention.     

Chaperone-like activity of alpha-crystallin toward aldose reductase oxidatively stressed by copper ion

The protective action of alpha-crystallin against copper-induced protein stress is studied using bovine lens aldose reductase (ALR2) as protein model. The oxidative inactivation of ALR2 induced by CuCl2 at the stoichiometric Cu2+/ALR2 ratio of 2/1 [I. Cecconi, M. Moroni, P.G. Vilardo, M. Dal Monte, P. Borella, G. Rastelli, L. Costantino, D. Garland, D. Carper, J.M. Petrash, A. Del Corso, U. Mura, Biochemistry 37 (1998) 14167-14174] is accompanied by protein aggregation phenomena when the metal ion concentration is increased (Cu2+/ALR2>3). Protein oxidation precedes protein precipitation. Both inactivation and precipitation of ALR2 are prevented by alpha-crystallin in a concentration-dependent manner. The rationale for the stabilization of ALR2 exerted by alpha-crystallin at low metal concentration is given on the basis of the ability of alpha-crystallin to chelate copper. However, the overall protective action exerted by alpha-crystallin at higher copper concentration may be explained invoking the contribution of the special features of alpha-crystallin to easily interact with target proteins undergoing structural rearrangement.     

Amine oxidases in apoptosis and cancer

Amine oxidases, the major enzymes of biogenic amines metabolism, are considered to be biological regulators, especially for cell growth and differentiation. A primary involvement of amine oxidases in cancer growth inhibition and progression, especially by means of aldehydes, H(2)O(2) and other reactive oxygen species, the amine oxidase-mediated products of biogenic amines oxidation, has been demonstrated. Amine oxidases are involved in cancer growth inhibition because of the higher content in tumour cells of biogenic amines in comparison to normal cells. The cytotoxic effect can be explained by a damage to cell membranes and/or nuclei or, indirectly, through modulation of membrane permeability transition and therefore apoptosis. The oxidation products of biogenic amines appears to be also carcinogenic, while acrolein, produced from the oxidation of spermine and spermidine, should be a key compound both carcinogenic and cytotoxic. The cancer inhibition/promotion effect of amine oxidases could be explained by taking into consideration the full pattern of the enzyme content of the cell. The balance of amine oxidases and antioxidant enzymes appear to be a crucial point for cancer inhibition or progression. A long lasting imbalance of these enzymes appears to be carcinogenic, while, for a short time, amine oxidases are cytotoxic for cancer cells.     

Proteomic analysis of liver tissues subjected to early ischemia/reperfusion injury during human orthotopic liver transplantation

Knowledge of early molecular events occurring upon ischemia/reperfusion (I/R) during liver transplantation (LT) is of great importance to improve the therapeutic intervention of surgical treatment. However, nowadays, few data are available on early protein targets of I/R injury. To identify these proteins, we used a differential proteomics approach in the characterization human liver biopsies during I/R upon LT. Analyses were performed on nine donor livers during LT. By using 2-DE and MALDI-TOF MS, we identified 36 proteins which resulted significantly altered upon I/R injury. The majority of these proteins are functionally involved in lipid and energy metabolism, in different metabolic pathways, in redox signalling and in oxidative-stress response. Our data represent the first global approach in the study of I/R injury in liver.