Relationship between leaf temperature and photosynthetic carbon in <i>Capsicum annuum </i>L. in controlled climates

528-533This study measures photosynthesis in Capsicum annuum L. by principles of gas analysis and expression of enzyme ribulose-1,5-biphosphate carboxylase/oxygenase (rubisco), and demonstrates that a relationship exists between leaf temperature and photosynthesis. Observed relationship between leaf temperature and photosynthesis may be applicable to other C3 plants

Identification of mutations in the S gene of hepatitis B virus in HIV positive Mexican patients with occult hepatitis B virus infection

Introduction and aim: Occult hepatitis B virus infection (OBI) is characterized by the presence of replication-competent hepatitis B virus (HBV) DNA in the liver and/or serum of patients with undetectable levels of the HBV surface antigen (HBsAg). Due to the shared infection routes HIV positive patients are at higher risk of developing OBI, thus, the aim of this study was to determine the frequency of OBI in Mexican HIV-infected patients and to identify mutations in the HBV S gene that could be associated to the development of OBI. Materials and methods: Plasma samples from 50 HIV-infected patients with undetectable levels of the HBsAg were obtained and analyzed. The Core, PreS and S genes were amplified by nested PCR and sequenced by the Sanger method. To analyze HBV diversity in the OBI-positive patients, ten sequences of 762 bp from the HBV S gene were selected, cloned, and subsequently sequenced for mutational analyses. Results: OBI infection was found with a frequency of 36% (18/50). All the HBV sequences corresponded to the H genotype. The most common mutations were: C19Y, Q129H, E164D, and I195M, with a frequency of 44%, 36%, 39% and 48% respectively. Conclusions: In this study, we report the presence of OBI in a cohort of Mexican HIV-infected patients with an overall prevalence of 36%. Mutational analyses revealed that four non-silent mutations were frequent in different regions of the HBsAg gene, suggesting that they might be associated to the development of OBI in this population, nevertheless, further studies are required to determine their role in the pathogenesis of OBI

Serum Dried Samples to Detect Dengue Antibodies: A Field Study

Background. Dried blood and serum samples are useful resources for detecting antiviral antibodies. The conditions for elution of the sample need to be optimized for each disease. Dengue is a widespread disease in Mexico which requires continuous surveillance. In this study, we standardized and validated a protocol for the specific detection of dengue antibodies from dried serum spots (DSSs). Methods. Paired serum and DSS samples from 66 suspected cases of dengue were collected in a clinic in Veracruz, Mexico. Samples were sent to our laboratory, where the conditions for optimal elution of DSSs were established. The presence of anti-dengue antibodies was determined in the paired samples. Results. DSS elution conditions were standardized as follows: 1 h at 4°C in 200 µl of DNase-, RNase-, and protease-free PBS (1x). The optimal volume of DSS eluate to be used in the IgG assay was 40 µl. Sensitivity of 94%, specificity of 93.3%, and kappa concordance of 0.87 were obtained when comparing the antidengue reactivity between DSSs and serum samples. Conclusion. DSS samples are useful for detecting anti-dengue IgG antibodies in the field

Clipped histone H3 is integrated into nucleosomes of DNA replication genes in the human malaria parasite Plasmodium falciparum

The fastq files supporting the results of this article are available in the EMBL‐EBI European Nucleotide Archive (ENA: PRJEB18114; Sample group: ERG011046): http://www.ebi.ac.uk/ena/data/view/PRJEB18114.International audiencePost‐translational modifications of histone H3 N‐terminal tails are key epigenetic regulators of virulence gene expression and sexual commitment in the human malaria parasite Plasmodium falciparum. Here, we identify proteolytic clipping of the N‐terminal tail of nucleosome‐associated histone H3 at amino acid position 21 as a new chromatin modification. A cathepsin C‐like proteolytic clipping activity is observed in nuclear parasite extracts. Notably, an ectopically expressed version of clipped histone H3, PfH3p‐HA, is targeted to the nucleus and integrates into mononucleosomes. Furthermore, chromatin immunoprecipitation and next‐generation sequencing analysis identified PfH3p‐HA as being highly enriched in the upstream region of six genes that play a key role in DNA replication and repair: In these genes, PfH3p‐HA demarcates a specific 1.5 kb chromatin island adjacent to the open reading frame. Our results indicate that, in P. falciparum, the process of histone clipping may precede chromatin integration hinting at preferential targeting of pre‐assembled PfH3p‐containing nucleosomes to specific genomic regions. The discovery of a protease‐directed mode of chromatin organization in P. falciparum opens up new avenues to develop new anti‐malarials