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Se describe el comportamiento de la COVID-19 en la República Bolivariana de Venezuela durante el período febrero-junio 2020, mediante la caracterización epidemiológica según tiempo, espacio, persona y tipo de transmisión de los casos confirmados y fallecidos por esta enfermedad. Se identifican condiciones relacionadas con la mortalidad. Es un estudio descriptivo, observacional, retrospectivo que utilizó la base de datos de COVID-19 del Sistema Único de Información en Salud (SUIS) del Ministerio del Poder Popular para la Salud (MPPS). Se evidencia que después de la confirmación de los primeros casos, la incidencia se mantuvo estable hasta mediados de mayo, cuando la curva de casos confirmados presentó una inflexión abrupta, lo que se relacionó en gran medida con casos importados. La enfermedad ha afectado en su mayoría a personas del sexo masculino, menores de 40 años, con un elevado porcentaje de forma clínica asintomáticas. La letalidad registrada en el período es menos de 1% y está relacionada a la edad avanzada, presencia de comorbilidades como hipertensión arterial y/o diabetes. Se concluye que la COVID-19 ha afectado mayormente a personas menores de 40 años, con casos relacionados en su mayoría con el regreso de connacionales provenientes de países vecinos, con una proporción importante de casos asintomáticos, lo cual a su vez se encuentra asociado a la baja tasa de complicaciones y de mortalidad por esta enfermedad en Venezuela. &nbsp

Background: Neuroregeneration after nerve injury occurs via anterograde (proximal in the distal) regrowth. The purpose of this study was to demonstrate that nerve regeneration occurs not only proximally to distally as classically described, but also distally to proximally using a rat model with a left sciatic nerve injury, with or without repair, compared to a healthy uninjured control group. Methods: Fifteen rats were divided into 3 groups; a healthy control (Group 1, n=5), left sciatic nerve injury (Group 2, n=5), and left sciatic nerve injury and surgical retrograde nerve repair (Group 3, n=5). In Groups 2 and 3, complete surgical resection of the left sciatic nerve was performed and retrograde reconstruction of the nerve was done in Group 3 using an original, unique technique. Neuroconductive and histological variables were analyzed and compared between groups. Results: After 15 weeks, Groups 1 (control) and 3 (retrograde reinnervation) behaved similarly, with no significant differences (p

14 p.-3 fig., Plant transformation with tobamovirus gene sequences is one of a number of available strategies for the potential control of tobamovirus disease. In most cases, a complete, near immunity type of resistance can be induced in plants transformed with fragments or modified forms of the viral replicase gene and the strong resistance is exhibited against high concentrations of both virus and viral RNA inoculum. However, the transgenic plant exhibits a relatively narrow resistance spectrum, manifested only against the virus from which the transgene is derived or against very closely related virus strains. A more complete understanding of the molecular mechanisms involved in replicase-mediated transgenic resistance against tobamoviruses is needed, in order to increase its efficacy and reduce or eliminate the biosafety concerns related to its use in agriculture as a biotechnological tool for crop protection. ., Work contributing to this article was supported by project grants BIO97-0615-C02-01; BIO98- 0849; BIO2000-1605-C02-02 and BIO2000-0914 from CICYT and 07B/0026/1999 from Comunidad de Madrid (Spain).

11 páginas, 5 figuras -- PAGS nros. 5167-5177, In plants, small RNA-guided processes referred to as RNA silencing control gene expression and serve as an efficient antiviral mechanism. Plant viruses are inducers and targets of RNA silencing as infection involves the production of functional virus-derived small interfering RNAs (siRNAs). Here we investigate the structural and genetic components influencing the formation of Tobacco rattle virus (TRV)-derived siRNAs. TRV siRNAs are mostly 21 nucleotides in length and derive from positive and negative viral RNA strands, although TRV siRNAs of positive polarity are significantly more abundant. This asymmetry appears not to correlate with the presence of highly structured regions of single-stranded viral RNA. The Dicer-like enzyme DCL4, DCL3, or DCL2 targets, alone or in combination, viral templates to promote synthesis of siRNAs of both polarities from all regions of the viral genome. The heterogeneous distribution profile of TRV siRNAs reveals differential contributions throughout the TRV genome to siRNA formation. Indirect evidence suggests that DCL2 is responsible for production of a subset of siRNAs derived from the 3′ end region of TRV. TRV siRNA biogenesis and antiviral silencing are strongly dependent on the combined activity of the host-encoded RNA-dependent RNA polymerases RDR1, RDR2, and RDR6, thus providing evidence that perfectly complementary double-stranded RNA serves as a substrate for siRNA production. We conclude that the overall composition of viral siRNAs in TRV-infected plants reflects the combined action of several interconnected pathways involving different DCL and RDR activities, This work was supported by grants GEN2003-20222-C02-01 and BIO2006-13107 from the M.E.C. (Spain) and GR/SAL/0821/2004 from the C.A.M. (Spain). L.D. was the recipient of a predoctoral fellowship from the C.A.M.

Leída en la Universidad Complutense de Madrid. Facultad de Ciencias Biológicas. Departamento de Genética el 05-17-2005; 143 pp., La mayoría de virus son capaces de inducir en las plantas a las que infectan una respuesta de silenciamiento génico, que sirve en la planta huésped como mecanismo natural de defensa frente al virus. A la vez, muchos virus con capaces de contraatacar produciendo proteínas que interfieren con el mecanismo de silenciamiento génico. El balance entre la inducción de la defensa antiviral de la planta, basada en silenciamiento génico, y la supresión de esta defensa por parte de los virus, es probablemente uno de los factores que determinan el curso de una infección viral. En la presente tesis se han empleado plantas transgénicas que expresan secuencias correspondientes a la proteína supresora de silenciamiento génico postranscripcional (PTGS) HC-Pro del virus de la sharka o Plum pox virus (PPV), con el fin de estudiar el proceso de silenciamiento génico inducido frente a este transgén y el posible efecto de la proteína HC-Pro, codificada por el propio transgén, sobre el silenciamiento génico y la resistencia a virus. Con nuestro sistema hemos pretendido aportar información sobre el posible balance existente entre la inducción y supresión de silenciamiento génico por parte de los virus. Se transformaron plantas de Nicotiana benthamiana con construcciones derivadas del gen HC-Pro de PPV. Se empleó una versión traducible (HCt), diseñada para producir proteína HC-Pro, y otra versión no traducible (HCn). Se determinaron los niveles de expresión de proteína HC-Pro en varias de las líneas HCt obtenidas, así como la capacidad de la proteína HC-Pro expresada de suprimir silenciamiento génico.La proteína HC-Pro expresada en varias líneas HCt no manifestó capacidad para interferir con el silenciamiento génico ensayado en varios sistemas. Se estudió la resistencia a PPV en las plantas transgénicas HC-Pro. Se identificaron dos líneas HCt y otras dos HCn con una alta proporción de plantas resistentes a PPV y a PVX, Beca postgrado para la Formación del Profesorado Universitario del Ministerio de Educación y Ciencia

8 páginas, 6 figuras, 1 tabla -- PAGS nros. 894-901, The effects on symptom expression of single amino acid mutations in the central region of the Plum pox virus (PPV) helper component-protein- ase (HC-Pro) gene were analyzed in Nicotiana benthamiana using Potato virus X (PVX) recombinant viruses. PV X recombinant virus expressing the wild-type variant of PPV HC-Pro induced the expected enhancement of PVX pathogenicity, manifested as necrosis and plant death. Recombi- nant virus expressing a variant of PPV HC-Pro containing a single point mutation (HCL 134 H) was unable to induce this synergistic phenotype. The RNA silencing suppressor activity of PPV HC-Pro was demonstrated in a transient silencing suppression assay. In contrast, the HCL 134 H mu- tant showed no such activity. These results indicate that a unique point mutation in PPV HC-Pro impaired its ability to suppress RNA silencing and abolished its capacity to induce synergism, and clearly shows for the first time the link between these two functions in potyvirus HC-Pro. Additionally, we compared the effects on virus accumulation in N. ben- thamiana plants infected with either the PVX recombinant constructs or with native viruses in double infect ion experiments. PVX (+) and (–) strand genomic RNA accumulated at similar levels in plants infected with PVX recombinants, leading to an in crease in PVX pathology, compared with plants infected with PVX alone . This finding confirms that the en- hancement of pathogenicity associated with synergistic interaction is not a consequence of more efficient PVX replication due to RNA silencing suppression by PPV HC-Pro., P. González-Jara, F. A. Atencio, and D. Barajas were supported by doctoral fellowships from MECD-FPI (Spain), CONICET (Argentina), and the Comunidad de Madrid /MECD-FPU (Spain), respectively. B. Martínez-García is the recipient of a postdoctoral contract from the Comunidad de Madrid and the CSIC (Spain). This work was supported by grants BIO2003-03428 from the CICYT-MCyT and 07G/0043/2003 from the Comunidad de Madrid (Spain)