Correlation of pause sites in MDV-1 RNA replication with kinetic refolding of the growing chain. A Monte Carlo simulation of the Markov process

We consider a template-instructed MDV-1 RNA replication catalyzed by Q beta replicase. The relaxation of the effective binding of the growing chain to the enzyme is simulated, considering a Markov process where refolding events in the chain are concomitant with chain elongation events. When realistic transition probabilities are considered, it becomes evident that the pause sites in replication are due to relaxation of the binding by folding of the growing chain.     

Host Cell Poly(ADP-Ribose) Glycohydrolase Is Crucial for Trypanosoma cruzi Infection Cycle

Trypanosoma cruzi, etiological agent of Chagas’ disease, has a complex life cycle which involves the invasion of mammalian host cells, differentiation and intracellular replication. Here we report the first insights into the biological role of a poly(ADP-ribose) glycohydrolase in a trypanosomatid (TcPARG). In silico analysis of the TcPARG gene pointed out the conservation of key residues involved in the catalytic process and, by Western blot, we demonstrated that it is expressed in a life stage-dependant manner. Indirect immunofluorescence assays and electron microscopy using an anti-TcPARG antibody showed that this enzyme is localized in the nucleus independently of the presence of DNA damage or cell cycle stage. The addition of poly(ADP-ribose) glycohydrolase inhibitors ADP-HPD (adenosine diphosphate (hydroxymethyl) pyrrolidinediol) or DEA (6,9-diamino-2-ethoxyacridine lactate monohydrate) to the culture media, both at a 1 µM concentration, reduced in vitro epimastigote growth by 35% and 37% respectively, when compared to control cultures. We also showed that ADP-HPD 1 µM can lead to an alteration in the progression of the cell cycle in hydroxyurea synchronized cultures of T. cruzi epimastigotes. Outstandingly, here we demonstrate that the lack of poly(ADP-ribose) glycohydrolase activity in Vero and A549 host cells, achieved by chemical inhibition or iRNA, produces the reduction of the percentage of infected cells as well as the number of amastigotes per cell and trypomastigotes released, leading to a nearly complete abrogation of the infection process. We conclude that both, T. cruzi and the host, poly(ADP-ribose) glycohydrolase activities are important players in the life cycle of Trypanosoma cruzi, emerging as a promising therapeutic target for the treatment of Chagas’ disease.     

Synthesis and structure-activity relationship of 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives: a novel series of 5-HT(2A/2C) receptor antagonists. Part 2.

Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described.     

Commissural component of the stria terminalis: electrophysiological properties

The commissural component of the stria terminalis (S. T.) was studied in Equi-Thesin (92.7 mg/kg) anesthetized rats after their exposure in the caudothalamic surface of both hemispheres. Two types of connection between right and left S. T. across the anterior commissure are described: A "direct" connection set up by fibres that run through the S. T. and join the contralateral S. T., and another "indirect" component, formed by cell axons that receive excitatory synaptic contacts from fibres running in the S. T.     

Survey of metal tolerance in moderately halophilic eubacteria

The tolerance patterns, expressed as MICs, for 250 moderately halophilic eubacteria to 10 heavy metals were surveyed by using an agar dilution method. The moderate halophiles tested included 12 culture collection strains and fresh isolates representative of Deleya halophila (37 strains), Acinetobacter sp. (24 strains), Flavobacterium sp. (28 strains), and 149 moderately halophilic gram-positive cocci included in the genera Marinococcus, Sporosarcina, Micrococcus, and Staphylococcus. On the basis of the MICs, the collection strains showed, overall, similar responses to silver, cobalt, mercury, nickel, lead, and zinc. All were sensitive to silver, mercury, and zinc and tolerant of lead. The response to arsenate, cadmium, chromium, and copper was very heterogeneous. The metal susceptibility levels of the 238 freshly isolated strains were, in general, very heterogeneous among the four taxonomic groups as well as within the strains included in each group. The highest toxicities were found with mercury, silver, and zinc, while arsenate showed the lowest activity. All these strains were tolerant of nickel, lead, and chromium and sensitive to silver and mercury. Acinetobacter sp. strains were the most heavy-metal tolerant, with the majority of them showing tolerance of eight different metal ions. In contrast, Flavobacterium sp. strains were the most metal sensitive. The influence of salinity and yeast extract concentrations of the culture medium on the toxicity of the heavy metals tested for some representative strains was also studied. Lowering the salinity, in general, led to enhanced sensitivity to cadmium and, in some cases, to cobalt and copper. However, increasing the salinity resulted in only a slight decrease in the cadmium, copper, and nickel toxicities.(ABSTRACT TRUNCATED AT 250 WORDS)