Meiotic Arrest Compromises Pollen Fertility in an Interspecific Hybrid Between \u3cem\u3eBrachiaria Ruziziensis\u3c/em\u3e X \u3cem\u3eBrachiaria Decumbens\u3c/em\u3e (Gramineae)

Disruptions in meiosis, development of the free microspores, microspore mitosis, pollen differentiation or anthesis can result in male-sterile plants (Glover et al., 1998). An understanding of the meiotic process is pivotal to work on reproduction, fertility, genetics and breeding in plants, with serious implications in crop production (Armstrong & Jones, 2003). Some African species of Brachiaria are the most important for pastures in the American tropics due to good adaptation and production. Artificial hybridization is underway in Embrapa to improve production, quality and insect resistance (Valle & Miles, 2001). For a cultivar to be successfully adopted good seed production and pollen viability are required. This paper reports on meiotic abnormalities impairing pollen fertility in a hybrid between B. ruziziensis x B. decumbens

Analysis of Genomic Affinity Between \u3cem\u3eBrachiaria Ruziziensis\u3c/em\u3e and \u3cem\u3eB. Brizantha\u3c/em\u3e Through Meiotic Behaviour

Genetic divergence between polyploid hybrids is displayed in chromosome pairing and in the rate of chromosome elimination due to differences in cell cycle between the two combined genomes (Sundberg et al. 1991). In Brachiaria, a genus of African grasses reaching continental proportions as a tropical pasture in Latin America, genome analysis has never been performed. The majority of accessions in this genus is polyploid and apomictic, which restricts breeding. The relative ease of obtaining fertile interspecific hybrids once ploidy barriers are overcome (Pereira et al. 2001) confirms the phylogenetic proximity among B. ruziziensis, B. decumbens and B. brizantha. Hybrids were synthesised using sexual artificial 4x as the female genitor and natural apomictic 4x as the pollen donors. Genome affinity is a pre-requisite for chosen genitors to produce fertile hybrids and plenty of viable seed to assure adoption of the new cultivar. Microsporogenesis of a hybrid between B. ruziziensis and B. brizantha is described in this paper, focusing on the behaviour of both genomes

Depressive symptoms and childhood sleep apnea syndrome

BACKGROUND: The relationship between sleep and mood regulation is well known, and some reports suggest a key role of sleep-related breathing disorders (SRBD) in the development of the symptomatology of depression, even if no conclusive data are actually found in the clinical literature. The aim of this study was to assess the relationship between SRBD and depressive symptoms in a population of school-aged children. METHODS: The study population comprised 94 children affected by SRBD and 107 healthy children. To identify the severity of SRBD, an overnight respiratory evaluation was performed. All subjects filled out the Italian version of the Children Depression Inventory (CDI) to screen for the presence of depressive symptoms. RESULTS: The group with SRBD showed higher CDI scores than the group without SRBD, with a positive correlation found between CDI scores, apnea-hypopnea index, and oxygen desaturation index values. Logistic regression showed that an apnea-hypopnea index ≥ 3 and an oxygen desaturation index ≥ 1 could be risk factors for development of depressive symptoms. According to receiver-operating characteristic curve analysis, the cutoff point for the apnea-hypopnea index that could cause a pathological CDI score (≥19) was >5.66, and the cutoff point for the oxygen desaturation index was >4.2. The limitations of this study are that our data are derived from one single psychometric test and not from a complete psychiatric evaluation, and our subjects came from a small group in southern Italy. CONCLUSION: Our results suggest the importance of mood assessment in children affected by SRBD

Propaedeutic study for the delivery of nucleic acid-based molecules from PLGA microparticles and stearic acid nanoparticles

We studied the mechanism governing the delivery of nucleic acid-based drugs (NABD) from microparticles and nanoparticles in zero shear conditions, a situation occurring in applications such as in situ delivery to organ parenchyma. The delivery of a NABD molecule from poly(DL-lactide-co-glycolide) (PLGA) microparticles and stearic acid (SA) nanoparticles was studied using an experimental apparatus comprising a donor chamber separated from the receiver chamber by a synthetic membrane. A possible toxic effect on cell biology, as evaluated by studying cell proliferation, was also conducted for just PLGA microparticles. A mathematical model based on the hypothesis that NABD release from particles is due to particle erosion was used to interpret experimental release data. Despite zero shear conditions imposed in the donor chamber, particle erosion was the leading mechanism for NABD release from both PLGA microparticles and SA nanoparticles. PLGA microparticle erosion speed is one order of magnitude higher than that of competing to SA nanoparticles. Finally, no deleterious effects of PLGA microparticles on cell proliferation were detected. Thus, the data here reported can help optimize the delivery systems aimed at release of NABD from micro- and nanoparticles

Comportamento citológico atípico durante a microsporogênese em Brachiaria ruziziensis e B. decumbens.

Em gramíneas forrageiras do gênero Brachiaria, populações poliplóides naturais são abundantes e geralmente apomíticas, enquanto as diploídes, que se reproduzem sexualmente, são raras. Considerando-se a estreita correlação existente entre poloploidia e apomixia neste gênero, e a necessidade de identificação de genótipos sexuais compatíveis para o sucesso de hibridação, conhecimentos de características citológicas básicas como modo de reprodução, comportamento meiótico e nível de ploidia tornam-se essenciais para direcionar os programas de melhoramento. Durante análises desenvolvidas na Universidade Estadual de Maringá, com acessos de várias espécies de uma coleção de germoplasma, mantida na Embrapa Gado de Corte, três acessos, sendo um B. ruziziensis(BRA005568) e dois de B. decumbens (BRA007722 E BRA001058) apresentaram anormalidades meióticas incomuns e foram analisados com especial atenção. Inflorescências em estágio ideal para estudos meióticos foram coletadas, fixadas em uma mistura de etanol 95%, clorofórmio e ácido propiônico (6:3:2) durante 24 horas e armazenadas sob refrigeração. Os microsporócitos foram comportamento citológico atípico durante a microsporogênese em Brachiaria ruziziensis e B. decumbens. Preparados pela técnica de esmagamento e corados com carmim proiônico 0,5%. O acesso de B. ruziziensis (2n=2x=18) apresentou freqüência de produtos meióticos anormais não esperada, com base em sua condição diplóide. A meiose I apresentou baixa freqüência de anormalidades, enquanto na meiose II, a freqüência de anormalidade aumentou de forma inesperada. Alguns cromossomos não conseguiram alcançar a placa equatorial. As células com cromosossomos não alinhados na placa não receberam o sinal para prosseguir em divisão. Tais cromossomos deram origem a núcleos telofásticos de diferentes tamanhos, levando à formação de produtos meióticos anômalos. As observações sugerem a presença de um erro que afeta o "ponto de checagem do fuso", interrompendo a segunda divisão meiótica. Ciclo nucleolar anormal relacionado ao processo de desorganização do nucléolo e nuclologênese foi observado no acesso BRA007722 de B. decumbens (12n=4x=36). O acesso BRA001058de B. decumbens cv Basilisk (2n=4x=36) apresentou duas formas distintas de anormalidades quando coletado em diferentes épocas. Em uma das épocas, os micronúcleos formados na primeira divisão organizaram fusos na segunda divisão e sofreram citocineses adicionais que levaram à formação de micrócitos de diferentes tamanhos. Na outra época de coleta, algumas plantas apresentaram uma anormalidade que afetou o desenvolvimento do gametófito masculino. As mioses do grão de pólen não seguiram o padrão normal, comprometendo a formação das células vegetativa e generativa. As anormalidades encontradas no gênero Brachiaria representam um material biológico ímpar para o entendimento do controle genético da meiose. Algumas delas podem representar, também, ferramentas úteis para programa de melhoramento.bitstream/item/104572/1/Comportamento-citologico-atipico.pd

Candidate biomarkers from the integration of methylation and gene expression in discordant autistic sibling pairs

While the genetics of autism spectrum disorders (ASD) has been intensively studied, resulting in the identification of over 100 putative risk genes, the epigenetics of ASD has received less attention, and results have been inconsistent across studies. We aimed to investigate the contribution of DNA methylation (DNAm) to the risk of ASD and identify candidate biomarkers arising from the interaction of epigenetic mechanisms with genotype, gene expression, and cellular proportions. We performed DNAm differential analysis using whole blood samples from 75 discordant sibling pairs of the Italian Autism Network collection and estimated their cellular composition. We studied the correlation between DNAm and gene expression accounting for the potential effects of different genotypes on DNAm. We showed that the proportion of NK cells was significantly reduced in ASD siblings suggesting an imbalance in their immune system. We identified differentially methylated regions (DMRs) involved in neurogenesis and synaptic organization. Among candidate loci for ASD, we detected a DMR mapping to CLEC11A (neighboring SHANK1) where DNAm and gene expression were significantly and negatively correlated, independently from genotype effects. As reported in previous studies, we confirmed the involvement of immune functions in the pathophysiology of ASD. Notwithstanding the complexity of the disorder, suitable biomarkers such as CLEC11A and its neighbor SHANK1 can be discovered using integrative analyses even with peripheral tissues

Repaired tetralogy of Fallot: the roles of cardiovascular magnetic resonance in evaluating pathophysiology and for pulmonary valve replacement decision support

Surgical management of tetralogy of Fallot (TOF) results in anatomic and functional abnormalities in the majority of patients. Although right ventricular volume load due to severe pulmonary regurgitation can be tolerated for many years, there is now evidence that the compensatory mechanisms of the right ventricular myocardium ultimately fail and that if the volume load is not eliminated or reduced by pulmonary valve replacement the dysfunction might be irreversible. Cardiovascular magnetic resonance (CMR) has evolved during the last 2 decades as the reference standard imaging modality to assess the anatomic and functional sequelae in patients with repaired TOF. This article reviews the pathophysiology of chronic right ventricular volume load after TOF repair and the risks and benefits of pulmonary valve replacement. The CMR techniques used to comprehensively evaluate the patient with repaired TOF are reviewed and the role of CMR in supporting clinical decisions regarding pulmonary valve replacement is discussed