Inhibitory effect of interferon on the genetic and oncogenic transformation by viral and cellular genes.

The rodent established cell lines LTk- and NIH 3T3 have been used as recipients in gene transfer experiments to study the effect of interferon treatment on the genetic and oncogenic transformation by several genes of viral and cellular origin. Our results show that interferon severely inhibits, to a similar extent, the stable transformation of Ltk- and NIH 3T3 cells by the chicken thymidine kinase (tk) gene, Ecogpt gene, simian virus 40, v-Ha-ras, and human c-Ha-ras and c-Ki-ras oncogenes. These results are consistent with an inhibition by interferon at the level of stabilization or integration, or both, of exogenous DNA sequences in the recipient cells, with an apparent effect on gene expression.     

Improved protein identification through the use of unstained gels

In this work, a method for improved protein identification of low-abundance proteins using unstained gels, in combination with robotics and matrix-assisted laser desorption/ionization tandem mass spectrometry, has been developed and evaluated. Omitting the silver-staining process resulted in increased protein identification scores, an increase in the number of peptides observed in the MALDI mass spectrum, and improved quality of the tandem mass spectrometry data.     

Hepatitis C virus (HCV) circulates as a population of different but closely related genomes: quasispecies nature of HCV genome distribution.

Sequencing of multiple recombinant clones generated from polymerase chain reaction-amplified products demonstrated that the degree of heterogeneity of two well-conserved regions of the hepatitis C virus (HCV) genome within individual plasma samples from a single patient was consistent with a quasispecies structure of HCV genomic RNA. About half of circulating RNA molecules were identical, while the remaining consisted of a spectrum of mutants differing from each other in one to four nucleotides. Mutant sequence diversity ranged from silent mutations to appearance of in-frame stop codons and included both conservative and nonconservative amino acid substitutions. From the relative proportion of essentially defective sequences, we estimated that most circulating particles should contain defective genomes. These observations might have important implications in the physiopathology of HCV infection and underline the need for a population-based approach when one is analyzing HCV genomes.     

Subunit-specific rules governing AMPA receptor trafficking to synapses in hippocampal pyramidal neurons

AMPA-type glutamate receptors (AMPA-Rs) mediate a majority of excitatory synaptic transmission in the brain. In hippocampus, most AMPA-Rs are hetero-oligomers composed of GluR1/GluR2 or GluR2/GluR3 subunits. Here we show that these AMPA-R forms display different synaptic delivery mechanisms. GluR1/GluR2 receptors are added to synapses during plasticity; this requires interactions between GluR1 and group I PDZ domain proteins. In contrast, GluR2/GluR3 receptors replace existing synaptic receptors continuously; this occurs only at synapses that already have AMPA-Rs and requires interactions by GluR2 with NSF and group II PDZ domain proteins. The combination of regulated addition and continuous replacement of synaptic receptors can stabilize long-term changes in synaptic efficacy and may serve as a general model for how surface receptor number is established and maintained.     

Induction of increase in the heterocyst frequency of Anabaena sp. strain ATCC33047. Effect on ammonium photoproduction

Abstract Several approaches have been followed to increase the nitrogenase level in filaments of Anabaena ATCC33047. In a nitrogen-free medium lacking added molybdate and supplemented with 10 mM tungstate, growth was impaired as a result of decreased nitrogenase activity level. Under these conditions, the filaments exhibited nitrogen starvation symptoms and a high heterocyst frequency, with heterocysts being up to 28% of the total number of cells in the filaments, while a regular pattern of heterocyst distribution was maintained. Normal nitrogenase level and nitrogen status were recovered upon molybdate addition, with resumption of growth and decrease of the heterocyst frequency with time until reaching a value of about 10%. The yield of ammonium photoproduction from N₂ by filaments displaying different heterocyst frequencies and treated with l -methionine- d,l -sulfoximine (MSX) was determined. Maximal rates were obtained with filaments containing 16% of the cells differentiated as heterocysts. Results indicate that appropriate manipulation of the heterocyst frequency leads to an improvement in the efficiency of conversion of light energy into chemical energy through photoreduction of N₂ to ammonium.     

Role of endocannabinoids in brain development.

In addition to those functions that have been extensively addressed in this special issue, such as nociception, motor activity, neuroendocrine regulation, immune function and others, the endogenous cannabinoid system seems to play also a role in neural development. This view is based on a three-fold evidence. A first evidence emerges from neurotoxicological studies that showed that synthetic and plant-derived cannabinoids, when administered to pregnant rats, produced a variety of changes in the maturation of several neurotransmitters and their associated-behaviors in their pups, changes that were evident at different stages of brain development. A second evidence comes from studies that demonstrated the early appearance of elements of the endogenous cannabinoid system (receptors and ligands) during the brain development. The atypical location of these elements during fetal and early postnatal periods favours the notion that this system may play a role in specific molecular events related to neural development. Finally, a third evidence derives from studies using cultures of fetal glial or neuronal cells. Cannabinoid receptors are present in some of these cultured cells and their activation produced a set of cellular effects consistent with a role of this system in the process of neural development. All this likely supports that endocannabinoids, early synthesized in nervous cells, play a role in events related to development, by acting through the activation of second messenger-coupled cannabinoid receptors.