A High Incidence of Meiotic Silencing of Unsynapsed Chromatin Is Not Associated with Substantial Pachytene Loss in Heterozygous Male Mice Carrying Multiple Simple Robertsonian Translocations

Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC). Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., γH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR). These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading of Robertsonian translocations, explaining the multitude of natural Robertsonian populations described in the mouse

Influenza equina en Chile (1963- 1992)

 In this general article is presented the situation of equine influenza in Chile from 1963, when the first outbreak of this disease was described. Equine influenza has been reported several times from then; main outbreaks have occurred in 1977, 1985 and recently on march of 1992. The presentation of equine influenza in our country is discussed en relation to continental epizootics. Equine influenza virus has been isolated only in three oportu­nities: in 1977 it was isolated the strain A/equi/1/Santiago, Chile/1977 (H7 N7); in 1985 the strain A/equi/2/Santiago, Chile/1985 (H3 N8), and in 1992 the strain A/equi/2/Quillota, Chile/1992 (H3 N8). Beside, it is discussed different studies about the use of hemoagglu­tination inhibition test, viral seroneutralization and single radial hemolisis test; preliminary characterization of chilean strains of equine influenza virus and post vaccinal response to national and international vaccines against equine influenza.Key words: Virus, influenza, horses.Palabras claves: Virus, influenza,equino.

Influenza equina en Chile (1963- 1992)

 In this general article is presented the situation of equine influenza in Chile from 1963, when the first outbreak of this disease was described. Equine influenza has been reported several times from then; main outbreaks have occurred in 1977, 1985 and recently on march of 1992. The presentation of equine influenza in our country is discussed en relation to continental epizootics. Equine influenza virus has been isolated only in three oportu­nities: in 1977 it was isolated the strain A/equi/1/Santiago, Chile/1977 (H7 N7); in 1985 the strain A/equi/2/Santiago, Chile/1985 (H3 N8), and in 1992 the strain A/equi/2/Quillota, Chile/1992 (H3 N8). Beside, it is discussed different studies about the use of hemoagglu­tination inhibition test, viral seroneutralization and single radial hemolisis test; preliminary characterization of chilean strains of equine influenza virus and post vaccinal response to national and international vaccines against equine influenza.Key words: Virus, influenza, horses.Palabras claves: Virus, influenza,equino.

Estudio serológico de virus influenza y parainfluenza-3 en pequeños rumiantes del Zoológico Nacional de Santiago

En 200 sueros de pequeños rumiantes del Zoológico Nacional del Parque Metropolitano de Santiago, se estudió la infección causada por virus influenza y parainfluenza-3 mediante la prueba de inhibición de la hemoaglutinación. Las especies muestradas fue­ron 19 cabras anglo-nubian (Capra hircus), 32 cier­vos dama blanco (Dama dama var. albina), 10 ciervos dama negro (Dama dama var. melánica), 25 llamas (Lama glama), 30 muflones corso (Ovis musimon), 30 ovejas karakul (Ovis aries) y 54 ovejas somalí (Ovis aries steatopigas). Como antí­geno se utilizaron los virus parainfluenza-3 (cepas bovina y humana), influenza equina (H7N7) e in­fluenza humana A/Santiago/725/81 (H3N2) y A/Santiago/743/83 (H1 N1) .Todos los sueros resultaron negativos frente a los virus parainfluenza-3 e influenza equina (H7N7). Con el virus influenza humana se evidenciaron dos llamas positivas frente a la cepa H1 N1 y 17 ovejas somalí, dos muflones corso y dos ovejas karakul frente a la cepa H3N2.AbstractA serological survey of influenza and parainfluenza-3 viruses was done in 200 serum samples from small ruminants of the National Zoo of the Metropolitan Park of Santiago Chile. Nineteen anglo-nubian goats (Capra-hircus), 32 white deers (Dama dama var. albina), 10 black deers (Dama dama var. melanica), 25 llamas (Lama glama), 30 corsican rams (Ovis musimon), 30 karakul sheep (Ovis aries) and 54 somalian sheep (Ovis aries steatopigas) were sampled.Serum samples were analized through haemagglutination inhibition test with parainfluenza uenza-3 virus (bovine and human strains), equine influenza (H7N7) and human influenza virus A/Santiago/725/81 (H3N2) and A/Santiago/743/83 (HINI ).All samples were negative when challenged to parainfuenza-3 and equipe influenza viruses. Seventeen somalian sheep, two corsican rams and two karakul sheep were found positive to human influenza virus A/Santiago/725/81 (H3N2), and two llamas were positive to human influenza virus A/Santiago/743/83 (HINI )

Presencia de rotavirus en cerdos lactantes con síndrome diarreico

Se pesquisó la presencia de rotavirus en 100 muestras de contenido intestinal de cerdos lactantes que presentaban o habían muerto con signos de síndrome diarreico agudo, provenientes de 26 predios de explotación porcina de la Región Metropolitana; utilizándose la técnica inmunoenzimática ELISA (Rotazyme II, Abbott), microscopía electrónica, electroforesis en gel de poliacrilamida (Rotagel ISP), e inoculación en cultivos celulares de riñón porcino (PK–15) y de mono (MA–104).Mediante ELISA se detectaron antígenos rotavirales en 23 muestras; 18 muestras fueron consideradas como sospechosas y 59 negativas. En microscopía electrónica se observaron en 14 muestras partículas virales semejantes a rotavirus con morfología icosaédrica, doble cápside y un diámetro aproximado entre 60 y 70 nm. El estudio electroforético reveló la presencia de 11 bandas en cuatro muestras. En los cultivos celulares PK–15 y MA–104 no se detectó ECP atribuible a virus entéricos y rotavirus, respectivamente.Palabras claves: Rotavirus, cerdos lactantes, diarrea.AbstractThe presence of rotavirus was studied in 100 samples of intestinal content of pigs with history or showing signs of diarrheic syndrome, from the Metropolitan Region, Chile, by means of the ELISA test (Rotazyme 11, Abbott), electron microscopy, polyactylamide gel electrophoresis and inoculation in PK–15 and MA–104 cells.Twenty three positive samples were detected by the ELISA test, 18 were suspicious and 59 were negatives. The electron microscopy showed in 14 samples, icosahedrical particles with rotavirus wheel–like morphology and am estimated diameter of 60 to 70 nm. Using polyacrylamide gel electrophoresis only four samples showed 11 bands characteristic pattern of rotavirus RNA. It was notfound CPE in PK–15 or MA–104 inoculated with faecal materials.Key words: Rotavirus, piglet, diarrhea