A novel role for cyclic guanosine 3',5'monophosphate signaling in synaptic plasticity: a selective suppressor of protein kinase A-dependent forms of long-term potentiation.

At excitatory synapses onto hippocampal CA1 pyramidal cells, activation of cyclic AMP-dependent protein kinase and subsequent down-regulation of protein phosphatases has a crucial role in the induction of long-term potentiation by low-frequency patterns of synaptic stimulation. Because the second messenger cyclic guanosine 3',5'monophosphate can regulate the activity of different forms of the cyclic AMP degrading enzyme phosphodiesterase, we examined whether increases in cyclic guanosine 3',5'monophosphate can modulate long-term potentiation induction in the mouse hippocampal CA1 region through effects on cyclic AMP signaling. Using the cyclic guanosine 3',5'monophosphate-specific phosphodiesterase inhibitor zaprinast or the nitric oxide donor S-nitroso-D,L-penicillamine to elevate cyclic guanosine 3',5'monophosphate levels we found that increases in cyclic guanosine 3',5'monophosphate strongly inhibit the induction of long-term potentiation by low-frequency patterns of synaptic stimulation where protein kinase A activation is required for long-term potentiation induction. In contrast, zaprinast and S-nitroso-D,L-penicillamine had no effect on the induction of long-term potentiation by high-frequency patterns of synaptic stimulation that induce long-term potentiation in a protein kinase A-independent manner. Directly activating protein kinase A with the phosphodiesterase-resistant cyclic AMP analog 8-Br-cAMP, blocking all phosphodiesterases with 3-isobutyl-1-methylxanthine, or inhibiting protein phosphatases rescued long-term potentiation induction in zaprinast-treated slices. Together, these results suggest that increases in cyclic guanosine 3',5'monophosphate inhibit long-term potentiation by activating phosphodiesterases that interfere with the protein kinase A-mediated suppression of protein phosphatases needed for long-term potentiation induction. Consistent with the notion that this cyclic guanosine 3',5'monophosphate-mediated inhibitory pathway is recruited by some patterns of synaptic activity, blocking cyclic guanosine 3',5'monophosphate production strongly facilitated the induction of long-term potentiation by long trains of theta-frequency synaptic stimulation. Together, our results indicate that increases in cyclic guanosine 3',5'monophosphate can act as a long-term potentiation suppressor mechanism that selectively constrains the induction of protein kinase A-dependent forms of long-term potentiation induced by low-frequency patterns of synaptic stimulation.

Serological response to Helicobacter pylori recombinant antigens in Chilean infected patients with duodenal ulcer, non-ulcer dyspepsia and gastric cancer.

We have previously cloned 10 Helicobacter pylori antigen genes from a Chilean strain including: cytotoxin VacA, a truncated region of CagA (called A17), a species-specific protein (Ag26), urease subunits (UreA, UreB), a flagellin, (FlaB), heat shock proteins (HspA and HspB), an adhesin (HpaA) and a lipoprotein (Lpp20). Immunogenicity of these antigens was tested by immunoblot with sera of Chilean infected patients, revealing that HpaA, A17, HspB and VacA were more frequently recognized (86%, 82%, 68% and 68%, respectively). According to the clinical condition, it was determined that Lpp20 was preferentially recognized by sera from non-ulcer dyspepsia patients (80%), A17 and VacA by patients with duodenal ulcer (92% and 83% respectively), and HspB by patients with duodenal ulcer (83%) and gastric cancer (90%). An ELISA was developed with a purified mixture of A17 and VacA antigens to test the different groups of patients. It was found that sera from duodenal ulcer patients showed higher values than those from non-ulcer dyspepsia patients, but this difference was not significant (p<0.2). Moreover, sera from gastric cancer patients showed values lower than those from non-ulcer dyspepsia patients (p<0.019). These results indicate that, in the Chilean population, antibodies raised against VacA and A 7 are not markers either for duodenal ulcer or for gastric cancer.

Autopsias psicológicas de treinta suicidios en la IV región de Chile / Psychological autopsies of thirty suicides of the IV region of Chile

Background: Suicide is a relevant public health problem in Chile. This is the first Chilean study with the psychological autopsy method (PA). Aims: a) to identify risk factors for suicide in Chilean victims; b) to identify risk indicators for early intervention; c) to assess acceptability of the PA method by informants. Method: Sample consisted of 30 subjects (24 males, six females) who commited suicide in the IV Region of Chile (December 2008-September 2010). Data was collected from informant interviews. Main instrument was the Psychological Autopsy Interview Protocol. Results: Mean age at suicide was 35.8 years. Most victims communicated suicidal intent before consummation. Almost all experienced negative life events, in many cases shortly before suicide. One half had attempted suicide previously, some during the preceding month. Thirty-six percent were in mental health treatments at time of death. A quarter had recently visited mental health professionals. Psychiatric disorders (ICD-10) were identified in 90 percent, mainly depressive and substance use disorders. Personality disorders were evident in eight victims (33 percent): dissocial (4), emotionally unstable (2), paranoid (1), and anxious (avoidant) (1). Conclusions: A high rate of psychiatric disorders was confirmed. Previous suicide attempts are sensitive predictors of completed suicide. Communication of suicide intent is frequent, and may be an opportunity for intervention. Suicide is often preceded by negative life events. Prevention of suicide may be improved by effective treatment of psychiatric disorders, and focused psychosocial interventions. Intensive follow-up of attempters seems highly relevant. PA is an acceptable method for informants.

Introducción: El suicidio es un problema de salud pública relevante en Chile. Este es el primer estudio chileno con el método de la autopsia psicológica (AP). Objetivos: a) identificar factores de riesgo de suicidio en víctimas chilenas; b) identificar indicadores de riesgo para la intervención temprana; c) evaluar la aceptabilidad del método de la AP por los informantes. Método: La muestra consistió en 30 sujetos (24 hombres y 6 mujeres) que cometieron suicidio en la IV Región de Chile (diciembre de 2008-septiembre de 2010). La información fue recogida de entrevistas a informantes. El instrumento principal fue el Protocolo de Entrevista para Autopsia Psicológica. Resultados: La edad promedio fue 35,8 años. La mayoría comunicó intención suicida antes de consumarlo. Casi todos experimentaron eventos negativos, frecuentemente poco antes del suicidio. La mitad había intentado suicidarse previamente, algunos durante el mes precedente. El 36 por ciento estaba en tratamientos de salud mental al fallecer y un cuarto había visitado recientemente a profesionales de salud mental. Se identificó trastornos psiquiátricos (CIE-10) en el 90 por ciento, principalmente trastorno depresivo y por uso de sustancias. Los trastornos de personalidad fueron evidentes en ocho víctimas (33 por ciento): disocial (4), emocionalmente inestable (2), paranoide (1) y ansioso (evitativo) (1). Conclusiones: Se confirmó una elevada tasa de trastornos psiquiátricos. El antecedente de intentos previos es un predictor sensible de suicidio. La comunicación de intención suicida es frecuente y puede ser una oportunidad de intervención. El suicidio es frecuentemente precedido por eventos vitales negativos. La prevención del suicidio puede mejorar mediante el tratamiento efectivo de trastornos psiquiátricos e intervenciones psicosociales focalizadas. El seguimiento intensivo de intentadores parece altamente relevante. La AP es aceptable para los informantes.

Differential regulation by exercise of BDNF and NT-3 in rat spinal cord and skeletal muscle.

We have investigated the impact of neuromuscular activity on the expression of neurotrophins in the lumbar spinal cord region and innervating skeletal muscle of adult rats. Rats were exercised on a treadmill for 1 day or 5 consecutive days and euthanized at 0, 2 or 6 h after the last bout of exercise. By Day 1, there was no clear evidence of an increase in brain-derived neurotrophic factor (BDNF) mRNA in the spinal cord or the soleus muscle. By Day 5, there was a significant increase in BDNF mRNA in the spinal cord at 2 h post-training, and the soleus muscle showed a robust increase between 0 and 6 h post-training. Immunoassays showed significant increases in BDNF protein in the soleus muscle by training Day 5. Immunohistochemical analyses showed elevated BDNF levels in motoneuron cell bodies and axons in the ventral horn. Neurotrophin-3 (NT-3) mRNA was measured to determine whether selected neurotrophins respond with a selective pattern of induction to neuromuscular activity. In the spinal cord, there was a progressive post-training decrease in NT-3 mRNA following a single bout of training, while there was a significant increase in NT-3 mRNA at 2 h post-training by Day 5. The soleus muscle showed a progressive increase in NT-3 mRNA by Days 1 and 5 following training. These results show that neuromuscular activity has specific effects on the BDNF and NT-3 systems, and that repetitive exercise affects the magnitude and stability of these responses.

Subset of hybrid eukaryotic proteins is exported by the type I secretion system of Erwinia chrysanthemi.

Erwinia chrysanthemi exports degradative enzymes by using a type I protein secretion system. The proteases secreted by this system lack an N-terminal signal peptide but contain a C-terminal secretion signal. To explore the substrate specificity of this system, we have expressed the E. chrysanthemi transporter system (prtDEF genes) in Escherichia coli and tested the ability of this ABC transporter to export hybrid proteins carrying C-terminal fragments of E. chrysanthemi protease B. The C terminus contains six glycine-rich repeated motifs, followed by two repeats of the sequences DFLV and DIIV. Two types of hybrid proteins were assayed for transport, proteins with the 93-residue-protease-B C terminus containing one glycine-rich repeat and both hydrophobic terminal repeats and proteins with the 181-residue C terminus containing all repeat motifs. Although the shorter C terminus is unable to export the hybrids, the longer C terminus can promote the secretion of hybrid proteins with N termini as large as 424 amino acids, showing that the glycine-rich motifs are required for the efficient secretion of these hybrids. However, the secretion of hybrids occurs only if these proteins do not carry disulfide bonds in their mature structures. These latter results suggest that disulfide bond formation can occur prior to or during the secretion. Disulfide bonds may prevent type I secretion of hybrids. One simple hypothesis to explain these results is that the type I channel is too narrow to permit the export of proteins with secondary structures stabilized by disulfide bonds.

Patogenicidad y susceptibilidades a phoma exigua desm de tres portainjertos y dos variedades de limonero (citrus lemon l) / Patogenicity and susceptibility of phoma exigua desm to 3 rootstocks and 2 variety of lemon (citrus lemon l)

En la localidad de la Serena, IV región del país se detectaron plantas de limonero de dos años de edad con síntomas de atizonamiento a nivel de brotes y presencia de cancros en el tronco con abundante exudación de goma, produciendo en algunos casos la muerte de las plantas. A partir de la zona de avance de estas lesiones se aisló en forma consistente micelio correspondiente a phoma exigua desm. A partir de aislamientos puros de este hongo se inocularon frutos y plantas de limonero, obteniendose en estas últimas los mismos síntomas antes descritos. De este modo se demostró la patogenicidad de la cepa obtenida, la que fue recuperada a partir de las lesiones, manteniendose las mismas características del cultivo. Se realizaron además pruebas de susceptibilidad de dos variedades de limón crecidas sobre tres portainjertos y la de éstos por separado. Los resultados demostraron que todas las combinaciones fueron afectadas, existiendo diferencias en susceptibilidad, siendo la variedad génova más susceptible que la variedad eureka. Se concluye que esta sintomatología, sería una nueva enfermedad que afecta al cultivo del limón, la que denominamos "cancrosis y atizonamiento del limonero", causada por phoma exigua desm