Distribution of human virus contamination in shellfish from different growing areas in Greece,Spain, Sweden,and the United Kingdom

Viral pollution in shellfish has been analyzed simultaneously across a wide range of geographical regions, with emphasis on the concomitant variations in physicochemical characteristics and social features. The methods for sample treatment and for the detection of human enteric viruses were optimized by the participating laboratories. The second part of this study involves the selection of a protocol for virus detection, which was validated by analyzing the distribution and concentration of human viral pathogens under diverse conditions during an 18-month period in four European countries. Shellfish-growing areas from diverse countries in the north and south of Europe were defined and studied, and the microbiological quality of the shellfish was analyzed. Human adenovirus, Norwalk-like virus, and enterovirus were identified as contaminants of shellfish in all the participating countries. Hepatitis A virus was also isolated in all areas except Sweden. The seasonal distribution of viral contamination was also described. Norwalk-like virus appeared to be the only group of viruses that demonstrated seasonal variation, with lower concentrations occurring during warm months. The depuration treatments currently applied were shown to be adequate for reducing Escherichia coli levels but ineffective for the elimination of viral particles. The human adenoviruses detected by PCR correlate with the presence of other human viruses and could be useful as a molecular index of viral contamination in shellfish.     

Malnutrition and its association with intestinal parasitism among children from a village in the Colombian Amazonian region

Intestinal parasites and malnutrition cause high morbidity among children in developing countries. A study to establish the associations between intestinal parasitism and undernourishment was undertaken in a village in the Colombian Amazon region. Two hundred thirty seven children each provided four stool samples for parasitic analysis. Anthropometric indices were calculated based on height and weight (HAZ), weight and age (WAZ) and height and weight (WHZ) using the international growth standards recommended by the World Health Organization. Of the 237 children, 86.1% were carrying parasites, 54% had 2 or more parasites, 30% were stunted, 10% were underweight, and 2.5% were wasting. HAZ and WAZ indices were inversely related to age and number of parasites. Socioeconomic status was positively correlated with the number of parasites and inversely related to the HAZ index (p < 0.05). In conclusion, frequencies of undernourishment and intestinal parasites among the sample population were higher than the national average for Colombia. As previous studies have indicated, age, intestinal parasitism and socio-economic level are variables significantly related to nutritional state.     

Stabilization of trypsin by chemical modification with β-cyclodextrin monoaldehyde

The monoaldehyde derivative of -cyclodextrin was attached to trypsin via reductive alkylation with NaBH₄. The thermostability was enhanced from 49.5 °C to 60 °C for modified trypsin. The activation free energy of thermal inactivation at 50 °C was increased by 3.2 kJ mol^–1. The conjugated enzyme retained 100% of its initial activity after 3 h incubation at pH 9.     

Correlation between electrical activity and intracellular Ca2+ oscillations in GH3 rat anterior pituitary cells

Simultaneous measurements of electrical activity and intracellular Ca(2+) levels were performed in perforated-patch current-clamped individual GH3 cells. Both in cells showing brief (<100 ms) and long action potentials (APs), we found a good correlation between the averaged intracellular Ca2+ concentration ([Ca2+]i) and AP frequency, but not between the mean [Ca2+]i and AP duration. Nevertheless, the magnitude of spontaneous Ca2+ oscillations was highly dependent on the size and duration of the APs. The decay of the Ca2+ transients was not slowed when the size of the oscillations was varied either spontaneously or after elongation of the AP with the K+ channel blocker tetraethyl ammonium. Furthermore, the recovery from Ca2+ loads similar to those induced by the APs was slightly retarded after treatment of the cells with intracellular store Ca2+-ATPase inhibitors. Among previous results showing that caffeine-induced [Ca2+]i increases are secondary to electrical activity enhancements in GH3 cells, these data indicate that the Ca2+ entry triggered via APs is the primary determinant of the [Ca2+]i variations, and that Ca2+-induced Ca2+ release has a minor contribution to Ca2+ oscillations recorded during spontaneous activity. They also point to modulation of electrical activity patterns as a crucial factor regulating spontaneous [Ca2+]i signalling, and hence pituitary cell functions in response to physiological secretagogues.     

Cutting edge: dynamic redistribution of tetraspanin CD81 at the central zone of the immune synapse in both T lymphocytes and APC

The tetraspanin CD81 has been involved in T-dependent B cell-mediated immune responses. However, the behavior of CD81 during immune synapse (IS) formation has not been elucidated. We determined herein that CD81 redistributed to the contact area of T cell-B cell and T cell-dendritic cell conjugates in an Ag-dependent manner. Confocal microscopy showed that CD81 colocalized with CD3 at the central supramolecular activation complex. Videomicroscopy studies with APC or T cells transiently expressing CD81-green fluorescent protein (GFP) revealed that in both cells CD81 redistributed toward the central supramolecular activation complex. In T lymphocytes, CD81-GFP rapidly redistributed to the IS, whereas, in the APC, CD81-GFP formed a large accumulation in the contact area that later concentrated in a discrete cluster and waves of CD81 accumulated at the IS periphery. These results suggest a relevant role for CD81 in the topography of the IS that would explain its functional implication in T cell-B cell collaboration.     

Chrysanthemum chlorotic mottle viroid RNA: dissection of the pathogenicity determinant and comparative fitness of symptomatic and non-symptomatic variants

Chrysanthemum chlorotic mottle viroid (CChMVd) is a small RNA (398-401nt) with hammerhead ribozymes in both polarity strands that mediate self-cleavage of the oligomeric RNA intermediates generated in a rolling-circle mechanism of replication. Within the in vivo branched RNA conformation of CChMVd, a tetraloop has been identified as a major determinant of pathogenicity. Here we present a detailed study of this tetraloop by site-directed mutagenesis, bioassay of the CChMV-cDNA clones and analysis of the resulting progenies. None of the changes introduced in the tetraloop, including its substitution by a triloop or a pentaloop, abolished infectivity. In contrast to observations for other RNAs, the thermodynamically stable GAAA tetraloop characteristic of non-symptomatic CChMVd-NS strains was not functionally interchangeable for other stable tetraloops of the UNCG family, suggesting that the sequence, rather than the structure, is the major factor governing conservation of this motif. In most cases, the changes introduced initially led to symptomless infections, which eventually evolved to be symptomatic concurrently with the prevalence in the progeny of the UUUC tetraloop characteristic of symptomatic CChMVd-S strains. Only in one case did the GAAA tetraloop emerge and eventually dominate the progeny in infected plants that were non-symptomatic. These results revealed two major fitness peaks in the tetraloop (UUUC and GAAA), whose adjacent stem was also under strong selection pressure. Co-inoculations with CChMVd-S and -NS variants showed that only when the latter was in a 100- or 1000-fold excess did the infected plants remain symptomless, confirming the higher biological fitness of the S variant and explaining the lack of symptom expression previously observed in cross-protection experiments.     

Development and evolution of inner ear sensory epithelia and their innervation

The development and evolution of the inner ear sensory patches and their innervation is reviewed. Recent molecular developmental data suggest that development of these sensory patches is a developmental recapitulation of the evolutionary history. These data suggest that the ear generates multiple, functionally diverse sensory epithelia by dividing a single sensory primordium. Those epithelia will establish distinct identities through the overlapping expression of genes of which only a few are currently known. One of these distinctions is the unique pattern of hair cell polarity. A hypothesis is presented on how the hair cell polarity may relate to the progressive segregation of the six sensory epithelia. Besides being markers for sensory epithelia development, neurotrophins are also expressed in delaminating cells that migrate toward the developing vestibular and cochlear ganglia. These delaminating cells originate from multiple sites at or near the developing sensory epithelia and some also express neuronal markers such as NeuroD. The differential origin of precursors raises the possibility that some sensory neurons acquire positional information before they delaminate the ear. Such an identity of these delaminating sensory neurons may be used both to navigate their dendrites to the area they delaminated from, as well as to help them navigate to their central target. The navigational properties of sensory neurons as well as the acquisition of discrete sensory patch phenotypes implies a much more sophisticated subdivision of the developing otocyst than the few available gene expression studies suggest.     

An oxidative stress-mediated positive-feedback iron uptake loop in neuronal cells

Intracellular reactive iron is a source of free radicals and a possible cause of cell damage. In this study, we analyzed the changes in iron homeostasis generated by iron accumulation in neuroblastoma (N2A) cells and hippocampal neurons. Increasing concentrations of iron in the culture medium elicited increasing amounts of intracellular iron and of the reactive iron pool. The cells had both IRP1 and IRP2 activities, being IRP1 activity quantitatively predominant. When iron in the culture medium increased from 1 to 40 microm, IRP2 activity decreased to nil. In contrast, IRP1 activity decreased when iron increased up to 20 microm, and then, unexpectedly, increased. IRP1 activity at iron concentrations above 20 microm was functional as it correlated with increased (55) Fe uptake. The increase in IRP1 activity was mediated by oxidative-stress as it was largely abolished by N-acetyl-L-cysteine. Culturing cells with iron resulted in proteins and DNA modifications. In summary, iron uptake by N2A cells and hippocampus neurons did not shut off at high iron concentrations in the culture media. As a consequence, iron accumulated and generated oxidative damage. This behavior is probably a consequence of the paradoxical activation of IRP1 at high iron concentrations, a condition that may underlie some processes associated with neuronal degeneration and death.     

Formation of carnosine-Cu(II) complexes prevents and reverts the inhibitory action of copper in P2X4 and P2X7 receptors

To further analyze the action of copper on brain synaptic mechanisms, the brain dipeptide carnosine (beta-alanyl-L-histidine) was tested in Xenopus laevis oocytes expressing the rat P2X4 or P2X7 receptors. Ten micromolar copper halved the currents evoked by ATP in both receptors; co-application of carnosine plus copper prevented the metal induced-inhibition with a median effective concentration of 12.1 +/- 3.9 and 12.0 +/- 5.5 microm for P2X4 and P2X7, respectively. Zinc potentiated only the P2X4 ATP-evoked currents; carnosine had no effect over this metal. The relative potency and selectivity of classical metal chelators to prevent the copper inhibition was compared between carnosine and penicillamine (PA), bathophenanthroline (BPh) or L-histidine (His). Their rank order of potency in P2X4 and P2X7 receptors was carnosine = PA = His > BPh > Glycine (Gly) and carnosine = BPh = His > PA > Gly, respectively. The potency to prevent the zinc-induced potentiation in the P2X4 receptor was BPh > PA > His; carnosine, Gly and beta-alanine were inactive. Whereas 1-100 microm carnosine or His alone did not modify the ATP-evoked currents, 10-100 microm PA augmented and 100 microm BPh decreased the ATP-evoked currents. Carnosine was able to revert the copper-induced inhibition restoring the maximal ATP gated current in a concentration-dependent manner. Electronic spectroscopy confirm the formation of carnosine-Cu(II) complexes, mechanism that can account for the prevention and reversal of the copper inhibition, revealing its potential in copper intoxication treatment.     

The degenerative effect of a single intranigral injection of LPS on the dopaminergic system is prevented by dexamethasone,and not mimicked by rh-TNF-alpha,IL-1beta and IFN-gamma

It is becoming widely accepted that the inflammatory response is involved in neurodegenerative disease. In this context, we have developed an animal model of dopaminergic system degeneration by the intranigral injection of lipopolysaccharide (LPS), a potent inductor of inflammation. To address the importance of the inflammatory response in the LPS-induced degeneration of nigral dopaminergic neurones, we carried out two different kinds of studies: (i) the possible protective effect of an anti-inflammatory compound, and (ii) the effect of the intranigral injection of inflammatory cytokines (TNF-alpha, IL-1beta and IFN-gamma) on dopaminergic neurones viability. Present results show that dexamethasone, a potent anti-inflammatory drug that interferes with many of the features characterizing pro-inflammatory glial activation, prevented the loss of catecholamine content, Tyrosine hydroxylase (TH) activity and TH immunostaining induced by LPS-injection and also the bulk activation of microglia/macrophages. Surprisingly, injection of the pro-inflammatory cytokines failed to reproduce the LPS effect. Taken together, our results suggest that inflammatory response is implicated in LPS-induced neurodegeneration. This damage may be due, at least in part, to a cascade of events independent of that described for TNF-alpha/IL-1 beta/IFN-gamma.