Search for Subsolar-Mass Binaries in the First Half of Advanced LIGO's and Advanced Virgo's Third Observing Run

We report on a search for compact binary coalescences where at least one binary component has a mass between 0.2  M_{⊙} and 1.0  M_{⊙} in Advanced LIGO and Advanced Virgo data collected between 1 April 2019 1500 UTC and 1 October 2019 1500 UTC. We extend our previous analyses in two main ways: we include data from the Virgo detector and we allow for more unequal mass systems, with mass ratio q≥0.1. We do not report any gravitational-wave candidates. The most significant trigger has a false alarm rate of 0.14  yr^{-1}. This implies an upper limit on the merger rate of subsolar binaries in the range [220-24200]  Gpc^{-3} yr^{-1}, depending on the chirp mass of the binary. We use this upper limit to derive astrophysical constraints on two phenomenological models that could produce subsolar-mass compact objects. One is an isotropic distribution of equal-mass primordial black holes. Using this model, we find that the fraction of dark matter in primordial black holes in the mass range 0.2  M_{⊙}<m_{PBH}<1.0  M_{⊙} is f_{PBH}≡Ω_{PBH}/Ω_{DM}≲6%. This improves existing constraints on primordial black hole abundance by a factor of ∼3. The other is a dissipative dark matter model, in which fermionic dark matter can collapse and form black holes. The upper limit on the fraction of dark matter black holes depends on the minimum mass of the black holes that can be formed: the most constraining result is obtained at M_{min}=1  M_{⊙}, where f_{DBH}≡Ω_{DBH}/Ω_{DM}≲0.003%. These are the first constraints placed on dissipative dark models by subsolar-mass analyses.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Sensor Noise in LISA Pathfinder: In-Flight Performance of the Optical Test Mass Readout

We report on the first subpicometer interferometer flown in space. It was part of ESA's Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0_{-1.7}^{+2.4}  fm/sqrt[Hz], significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.

Comparative analysis of the complete chloroplast genomes from six Neotropical species of Myrteae (Myrtaceae)

Myrteae is the largest and most diverse tribe within Myrtaceae and represents the majority of its diversity in the Neotropics. Members of Myrteae hold ecological importance in tropical biomes for the provision of food sources for many animal species. Thus, due to its several roles, a growing interest has been addressed to this group. In this study, we report the sequencing and de novo assembly of the complete chloroplast (cp) genomes of six Myrteae species: Eugenia brasiliensis, E. pyriformis, E. nitida, Myrcianthes pungens, Plinia edulis and Psidium cattleianum. We characterized genome structure, gene content, and identified SSRs to detect variation within Neotropical Myrteae. The six newly sequenced plastomes exhibit a typical quadripartite structure, gene content and organization highly conserved among Myrtaceae species. Some differences in genome length, protein-coding genes and non-coding regions were found. Besides, IR boundaries present structural changes among species. Increased sequence diversity was observed in some intergenic regions, suggesting their suitability for investigating intraand interspecific genetic diversity in populational studies. These data also contribute to the improvement of taxa sampling in further phylogenetic investigations to understand Myrtaceae evolution.

Transcriptomics analysis of Psidium cattleyanum Sabine (Myrtaceae) unveil potential genes involved in fruit pigmentation

Psidium cattleyanum Sabine is an Atlantic Forest native species that presents some populations with red fruits and others with yellow fruits. This variation in fruit pigmentation in this species is an intriguing character that could be related to species evolution but still needs to be further explored. Our goal was to provide genomic information for these morphotypes to understand the molecular mechanisms of differences in fruit colour in this species. In this study, we performed a comparative transcriptome analysis of red and yellow morphotypes of P. cattleyanum, considering two stages of fruit ripening. The transcriptomic analysis performed encompassing leaves, unripe and ripe fruits, in triplicate for each morphotype. The transcriptome consensus from each morphotype showed 301,058 and 298,310 contigs from plants with yellow and red fruits, respectively. The differential expression revealed important genes that were involved in anthocyanins biosynthesis, such as the anthocyanidin synthase (ANS) and UDP-glucose:flavonoid-o-glucosyltransferase (UFGT) that were differentially regulated during fruit ripening. This study reveals stimulating data for the understanding of the pathways and mechanisms involved in the maturation and colouring of P. cattleyanum fruits and suggests that the ANS and UFGT genes are key factors involved in the synthase and pigmentation accumulation in red fruits.

Transcriptional analyses of two soybean cultivars under salt stress

Soybean is an economically important plant, and its production is affected in soils with high salinity levels. It is important to understand the adaptive mechanisms through which plants overcome this kind of stress and to identify potential genes for improving abiotic stress tolerance. RNA-Seq data of two Glycine max cultivars, a drought-sensitive (C08) and a tolerant (Conquista), subjected to different periods of salt stress were analyzed. The transcript expression profile was obtained using a transcriptogram approach, comparing both cultivars and different times of treatment. After 4 h of salt stress, Conquista cultivar had 1400 differentially expressed genes, 647 induced and 753 repressed. Comparative expression revealed that 719 genes share the same pattern of induction or repression between both cultivars. Among them, 393 genes were up- and 326 down-regulated. Salt stress also modified the expression of 54 isoforms of miRNAs in Conquista, by the maturation of 39 different pre-miRNAs. The predicted targets for 12 of those mature miRNAs also have matches with 15 differentially expressed genes from our analyses. We found genes involved in important pathways related to stress adaptation. Genes from both ABA and BR signaling pathways were modulated, with possible crosstalk between them, and with a likely post-transcriptional regulation by miRNAs. Genes related to ethylene biosynthesis, DNA repair, and plastid translation process were those that could be regulated by miRNA.

Bioinformatic analysis of post-transmission viral readaptation in Argentine patients with acute HIV-1 infection

During the acute phase of HIV-1 infection, a strong readaptation occurs in the viral population. Our objective was to analyze the post-transmission mutations associated with escape to the cytotoxic immune response and its relationship with the progression of the infection. In this study, a total of 17 patients were enrolled during acute/early primary HIV infection and 8 subjects that were the HIV positive partner resulting in 8 transmission pairs. Genotyping of the genetic polymorphisms of HLA class I A and B was performed using PCR-SSOP. Viral RNA extraction was from plasma. 570 single Gag-gene amplifications were obtained by limiting-dilution RT-PCR. Epitope prediction was performed with NetMHC CBS prediction server for the 19 HLA-A and B alleles. Cytotoxic response prediction was performed by using the IEDB Analysis Resource. From our results, we deduce that the transmitted CTL / gag escape frequency in the founder virus was at least double compared to the post-transmission events. Additionally, by means of an algorithm that combines these frequencies, we observed that the founder viruses better adapted to the HLA A / B alleles of the recipient could contribute to a greater progression of the infection. Our results suggest that there is a large adaptation of HIV-1 to the HLA A / B alleles prevalent in our population. However, despite this adaptive advantage, the virus needs to make "readjustments" through new escape and compensatory mutations. Interestingly, according to our results, this readaptation could have a role in the progression of the infection.

Identification of root transcriptional responses to shoot illumination in Arabidopsis thaliana

The transcriptional profile of roots is highly affected by shoot illumination. Transcriptogram analysis allows the identification of cellular processes that are not detected by DESeq. Light is a key environmental factor regulating plant growth and development. Arabidopsis thaliana seedlings grown under light display a photomorphogenic development pattern, showing short hypocotyl and long roots. On the other hand, when grown in darkness, they display skotomorphogenic development, with long hypocotyls and short roots. Although many signals from shoots might be important for triggering root growth, the early transcriptional responses that stimulate primary root elongation are still unknown. Here, we aimed to investigate which genes are involved in the early photomorphogenic root development of dark grown roots. We found that 1616 genes 4 days after germination (days-old), and 3920 genes 7 days-old were differently expressed in roots when the shoot was exposed to light. Of these genes, 979 were up regulated in 4 days and 2784 at 7 days-old. We compared the functional categorization of differentially regulated processes by two methods: GO term enrichment and transcriptogram analysis. Expression analysis of nine selected candidate genes in roots confirmed the data observed in the RNA-seq analysis. Loss-of-function mutants of these selected differentially expressed genes suggest the involvement of these genes in root development in response to shoot illumination. Our findings are consistent with the observation that dark grown roots respond to the shoot-perceived aboveground light environment.

Transcriptome analysis of strawberry (Fragaria × ananassa) fruits under osmotic stresses and identification of genes related to ascorbic acid pathway

Strawberry (Fragaria ananassa Duch.) is an economically important fruit with a high demand owing to its good taste and medicinal properties. However, its cultivation is affected by various biotic and abiotic stresses. Plants exhibit several intrinsic mechanisms to deal with stresses. In the case of strawberry, the mechanisms highlighting the response against these stresses remain to be elucidated, which has hampered the efforts to develop and cultivate strawberry plants with high yield and quality. Although a virtual reference genome of F. ananassa has recently been published, there is still a lack of information on the expression of genes in response to various stresses. Therefore, to provide molecular information for further studies with strawberry plants, we present the reference transcriptome dataset of F. ananassa, assembled and annotated from deep RNA-Seq data of fruits cultivated under salinity and drought stresses. We also systematically arranged a series of transcripts differentially expressed during these stresses, with an emphasis on genes related to the accumulation of ascorbic acid (AsA). Ascorbic acid is the most potent antioxidant present in these fruits and highly considered during biofortification. A comparison of the expression profile of these genes by RT-qPCR with the content of AsA in the fruits verified a tight regulation and balance between the expression of genes, from biosynthesis, degradation and recycling pathways, resulting in the reduced content of AsA in fruits under these stresses. These results provide a useful repertoire of genes for metabolic engineering, thereby improving the tolerance to stresses.

Araucaria angustifolia chloroplast genome sequence and its relation to other Araucariaceae

Araucaria angustifolia is endemic to southern Brazil. Known as Brazilian pine, A. angustifolia is the only native conifer species with economic and social relevance in this country. Due to massive exploitation, it has suffered a significant population decline and currently is classified as critically endangered. This encouraged the scientific community to investigate genetic features in Brazilian pine to increase resources for management and preservation. In this work, RNA-Seq data was used to determine the complete nucleotide sequence of the A. angustifolia chloroplast genome (cpDNA). The cpDNA is 146,203 bp in length and contains 122 genes, including 80 protein-coding genes, 5 ribosomal RNA genes, and 37 tRNA genes. Coding regions comprise 45.02%, 4.96% correspond to rRNAs and tRNAs, and 50.02% of the genome encompasses non-coding regions. Genes found in the inverted repeat (IR) are present as single copy, with exception of the rrn5 and trnI-CAU loci. The typical LSC, SSC, IRa and IRb organization reported in several land-plant groups is not present in A. angustifolia cpDNA. Phylogenetic analyses using Bayesian and Maximum Likelihood methods clustered A. angustifolia in the Araucariaceae family, with A. heterophylla and A. columnaris as congeneric species. The screening of A. angustifolia cpDNA reveled 100 SSRs, 14 of them corresponding to tetrapolymer loci.

De novo assembly of Vriesea carinata leaf transcriptome to identify candidate cysteine-proteases

Vriesea carinata is an endemic bromeliad from the Brazilian Atlantic Forest. It has trichome and tank system in their leaves which allows to absorb water and nutrients. It belongs to Bromeliaceae family, which includes several species highly enriched of cysteine-proteases (CysPs). These proteolytic enzymes regulate processes as senescence, cell differentiation, pathogen-linked programmed cell death and mobilization of proteins. Although, their biological importance, there are not genomic resources in V. carinata that can help to identify and understand their molecular mechanisms involved in different biological processes. Thus high-throughput transcriptome sequencing of V. carinata is necessary to generate sequences for the purpose of gene discovery and functional genomic studies. In the present study, we sequenced and assembled the V. carinata transcriptome to the identification of CysPs. A total of 43,232 contigs were assembled for the leaf tissue. BLAST analysis indicated that 23,803 contigs exhibited similarity to non-redundant Viridiplantae proteins. 28.24% of the contigs were classified into the COG database, and gene ontology categorized them into 61 functional groups. A metabolic pathway analysis with KEGG revealed 9679 contigs assigned to 31 metabolic pathways. Among 16 full-length CysPs identified, 11 were evaluated in respect to their expression patterns in the leaf apex, base and inflorescence tissues. The results showed differential expression levels of legumain, metacaspase, pyroglutamyl and papain-like CysPs depending of the leaf region. These results provide a global overview of V. carinata gene functions and expression activities of CysPs in those tissues.

Novel and Conserved miRNAs Among Brazilian Pine and Other Gymnosperms

The knowledge about plant miRNAs has increased exponentially, with thousands of miRNAs been reported in different plant taxa using high throughput sequencing technologies and bioinformatic tools. Nevertheless, several groups of plants remain unexplored, and the gap of knowledge about conifer miRNAs is considerable. There is no sequence or functional information available on miRNAs in Araucariaceae. This group is represented in Brazil by only one species, Araucaria angustifolia, an endangered species known as Brazilian pine. In the present study, Brazilian pine has its transcriptome explored with respect to small RNAs, representing the first description in a member of the Araucariaceae family. The screening for conserved miRNAs in Brazilian pine revealed 115 sequences of 30 miRNA families. A total of 106 precursors sequences were predicted. Forty one comprised conserved miRNAs from 16 families, whereas 65 were annotated as novel miRNAs. The comparison of Brazilian pine precursors with sRNA libraries of other five conifer species indicates that 9 out 65 novel miRNAs are conserved among gymnosperms, while 56 seems to be specific for Brazilian pine or restricted to Araucariaceae family. Analysis comparing novel Brazilian pine miRNAs precursors and Araucaria cunninghamii RNA-seq data identified seven orthologs between both species. Mature miRNA identified by bioinformatics predictions were validated using stem-loop RT-qPCR assays. The expression pattern of conserved and novel miRNAs was analyzed in five different tissues of 3-month-old Araucaria seedlings. The present study provides insights about the nature and composition of miRNAs in an Araucariaceae species, with valuable information on miRNAs diversity and conservation in this taxon.

Development, characterization, and transferability of SSR markers for Vriesea carinata (Bromeliaceae) based on RNA sequencing

PREMISE OF THE STUDY

Expressed sequence tag-simple sequence repeat (EST-SSR) markers were isolated for Vriesea carinata, an endemic bromeliad from the Brazilian Atlantic Forest. These SSR loci may be used to investigate the genetic diversity and population structure of this species and related bromeliads.

METHODS AND RESULTS

Based on the transcriptome data of V. carinata, 30 primer pairs were designed and selected for initial validation. Of these primer pairs, 16 generated suitable SSR loci in 69 individuals. The number of alleles per locus ranged from one to 13; the levels of observed and expected heterozygosity per locus ranged from 0.000 to 1.000 and from 0.000 to 0.935, respectively. All loci produced heterologous amplification. Transferability of the loci was tested in 15 species belonging to three Bromeliaceae subfamilies.

CONCLUSIONS

The developed EST-SSR markers revealed polymorphism in the four studied populations and could be useful to investigate the genetic diversity of V. carinata and related species. The markers may also be suitable for novel gene annotation and discovery.

Molecular and genetic characterization of the Ryadg locus on chromosome XI from Andigena potatoes conferring extreme resistance to potato virus Y

KEY MESSAGE

We have elucidated the Andigena origin of the potato Ryadg gene on chromosome XI of CIP breeding lines and developed two marker assays to facilitate its introgression in potato by marker-assisted selection. Potato virus Y (PVY) is causing yield and quality losses forcing farmers to renew periodically their seeds from clean stocks. Two loci for extreme resistance to PVY, one on chromosome XI and the other on XII, have been identified and used in breeding. The latter corresponds to a well-known source of resistance (Solanum stoloniferum), whereas the one on chromosome XI was reported from S. stoloniferum and S. tuberosum group Andigena as well. To elucidate its taxonomic origin in our breeding lines, we analyzed the nucleotide sequences of tightly linked markers (M45, M6) and screened 251 landraces of S. tuberosum group Andigena for the presence of this gene. Our results indicate that the PVY resistance allele on chromosome XI in our breeding lines originated from S. tuberosum group Andigena. We have developed two marker assays to accelerate the introgression of Ryadg gene into breeding lines by marker-assisted selection (MAS). First, we have multiplexed RYSC3, M6 and M45 DNA markers flanking the Ryadg gene and validated it on potato varieties with known presence/absence of the Ryadg gene and a progeny of 6,521 individuals. Secondly, we developed an allele-dosage assay particularly useful to identify multiplex Ryadg progenitors. The assay based on high-resolution melting analysis at the M6 marker confirmed Ryadg plex level as nulliplex, simplex and duplex progenitors and few triplex progenies. These marker assays have been validated and can be used to facilitate MAS in potato breeding.

Inkjet printable-photoactive all inorganic perovskite films with long effective photocarrier lifetimes

Photoactive perovskite quantum dot films, deposited via an inkjet printer, have been characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The crystal structure and bonding environment are consistent with CsPbBr₃ perovskite quantum dots. The current-voltage (I-V) and capacitance-voltage (C-V) transport measurements indicate that the photo-carrier drift lifetime can exceed 1 ms for some printed perovskite films. This far exceeds the dark drift carrier lifetime, which is below 50 ns. The printed films show a photocarrier density 10⁹ greater than the dark carrier density, making these printed films ideal candidates for application in photodetectors. The successful printing of photoactive-perovskite quantum dot films of CsPbBr₃, indicates that the rapid prototyping of various perovskite inks and multilayers is realizable.

Complete sequence and comparative analysis of the chloroplast genome of Plinia trunciflora

Plinia trunciflora is a Brazilian native fruit tree from the Myrtaceae family, also known as jaboticaba. This species has great potential by its fruit production. Due to the high content of essential oils in their leaves and of anthocyanins in the fruits, there is also an increasing interest by the pharmaceutical industry. Nevertheless, there are few studies focusing on its molecular biology and genetic characterization. We herein report the complete chloroplast (cp) genome of P. trunciflora using high-throughput sequencing and compare it to other previously sequenced Myrtaceae genomes. The cp genome of P. trunciflora is 159,512 bp in size, comprising inverted repeats of 26,414 bp and single-copy regions of 88,097 bp (LSC) and 18,587 bp (SSC). The genome contains 111 single-copy genes (77 protein-coding, 30 tRNA and four rRNA genes). Phylogenetic analysis using 57 cp protein-coding genes demonstrated that P. trunciflora, Eugenia uniflora and Acca sellowiana form a cluster with closer relationship to Syzygium cumini than with Eucalyptus. The complete cp sequence reported here can be used in evolutionary and population genetics studies, contributing to resolve the complex taxonomy of this species and fill the gap in genetic characterization.

Identification and evaluation of reference genes for expression studies by RT-qPCR during embryonic development of the emerging model organism, Macrobrachium olfersii

RT-qPCR is a sensitive and highly efficient technique that is widely used in gene expression analysis and to provide insight into the molecular mechanisms underlying embryonic development. The freshwater prawn, Macrobrachium olfersii is an emerging model organism, but, the stable reference genes of this species need to be identified and validated for RT-qPCR analysis. Thus, the aim of this study was to evaluate the expression stability of six genes (β-act, GAPDH, EF-1α, RpL8, RpS6, AK) in embryos and in adult tissues (cerebral ganglia, muscle and hepatopancreas) of M. olfersii. The expression stabilities of these genes were evaluated using geNorm, NormFinder, BestKeeper, ΔCt method and integrated tool RefFinder. In the general ranking, RpL8 and RpS6 were the most stable genes in embryos, while RpS6 and RpL8 were the most stable in a combined adult tissue analysis. Analysis of the adult tissues revealed that β-act and AK were the most stable genes in cerebral ganglia, RpL8 and AK in muscle, and RpS6 and β-act in hepatopancreas. EF-1α and GAPDH were the least stable genes and as normalizer genes in RT-qPCR affected expression of the Distal-less gene during M. olfersii development. This study provides suitable reference genes for RT-qPCR analysis and allows future studies of the gene expression in M. olfersii for understanding the molecular mechanisms of their development. To our knowledge, this is the first published study that identifies and evaluates reference genes for RT-qPCR analysis in M. olfersii and could be useful as basis for evaluations of reference genes in other prawns.

Exploring developmental gene toolkit and associated pathways in a potential new model crustacean using transcriptomic analysis

The crustaceans are one of the largest, most diverse, and most successful groups of invertebrates. The diversity among the crustaceans is also reflected in embryonic development models. However, the molecular genetics that regulates embryonic development is not known in those crustaceans that have a short germ-band development with superficial cleavage, such as Macrobrachium olfersi. This species is a freshwater decapod and has great potential to become a model for developmental biology, as well as for evolutionary and environmental studies. To obtain sequence data of M. olfersi from an embryonic developmental perspective, we performed de novo assembly and annotation of the embryonic transcriptome. Using a pooling strategy of total RNA, paired-end Illumina sequencing, and assembly with multiple k-mers, a total of 25,636,097 pair reads were generated. In total, 99,751 unigenes were identified, and 20,893 of these returned a Blastx hit. KEGG pathway analysis mapped a total of 6866 unigenes related to 129 metabolic pathways. In general, 21,845 unigenes were assigned to gene ontology (GO) categories: molecular function (19,604), cellular components (10,254), and biological processes (13,841). Of these, 2142 unigenes were assigned to the developmental process category. More specifically, a total of 35 homologs of embryonic development toolkit genes were identified, which included maternal effect (one gene), gap (six), pair-rule (six), segment polarity (seven), Hox (four), Wnt (eight), and dorsoventral patterning genes (three). In addition, genes of developmental pathways were found, including TGF-β, Wnt, Notch, MAPK, Hedgehog, Jak-STAT, VEGF, and ecdysteroid-inducible nuclear receptors. RT-PCR analysis of eight genes related to embryonic development from gastrulation to late morphogenesis/organogenesis confirmed the applicability of the transcriptome analysis.

De novo assembly of Eugenia uniflora L. transcriptome and identification of genes from the terpenoid biosynthesis pathway

Pitanga (Eugenia uniflora L.) is a member of the Myrtaceae family and is of particular interest due to its medicinal properties that are attributed to specialized metabolites with known biological activities. Among these molecules, terpenoids are the most abundant in essential oils that are found in the leaves and represent compounds with potential pharmacological benefits. The terpene diversity observed in Myrtaceae is determined by the activity of different members of the terpene synthase and oxidosqualene cyclase families. Therefore, the aim of this study was to perform a de novo assembly of transcripts from E. uniflora leaves and to annotation to identify the genes potentially involved in the terpenoid biosynthesis pathway and terpene diversity. In total, 72,742 unigenes with a mean length of 1048bp were identified. Of these, 43,631 and 36,289 were annotated with the NCBI non-redundant protein and Swiss-Prot databases, respectively. The gene ontology categorized the sequences into 53 functional groups. A metabolic pathway analysis with KEGG revealed 8,625 unigenes assigned to 141 metabolic pathways and 40 unigenes predicted to be associated with the biosynthesis of terpenoids. Furthermore, we identified four putative full-length terpene synthase genes involved in sesquiterpenes and monoterpenes biosynthesis, and three putative full-length oxidosqualene cyclase genes involved in the triterpenes biosynthesis. The expression of these genes was validated in different E. uniflora tissues.

Identifying microRNAs and transcript targets in Jatropha seeds

MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant biological processes. Jatropha curcas L. has received significant attention as a potential oilseed crop for the production of renewable oil. Here, a sRNA library of mature seeds and three mRNA libraries from three different seed development stages were generated by deep sequencing to identify and characterize the miRNAs and pre-miRNAs of J. curcas. Computational analysis was used for the identification of 180 conserved miRNAs and 41 precursors (pre-miRNAs) as well as 16 novel pre-miRNAs. The predicted miRNA target genes are involved in a broad range of physiological functions, including cellular structure, nuclear function, translation, transport, hormone synthesis, defense, and lipid metabolism. Some pre-miRNA and miRNA targets vary in abundance between the three stages of seed development. A search for sequences that produce siRNA was performed, and the results indicated that J. curcas siRNAs play a role in nuclear functions, transport, catalytic processes and disease resistance. This study presents the first large scale identification of J. curcas miRNAs and their targets in mature seeds based on deep sequencing, and it contributes to a functional understanding of these miRNAs.

Identifying microRNAs and transcript targets in Jatropha seeds

MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant biological processes. Jatropha curcas L. has received significant attention as a potential oilseed crop for the production of renewable oil. Here, a sRNA library of mature seeds and three mRNA libraries from three different seed development stages were generated by deep sequencing to identify and characterize the miRNAs and pre-miRNAs of J. curcas. Computational analysis was used for the identification of 180 conserved miRNAs and 41 precursors (pre-miRNAs) as well as 16 novel pre-miRNAs. The predicted miRNA target genes are involved in a broad range of physiological functions, including cellular structure, nuclear function, translation, transport, hormone synthesis, defense, and lipid metabolism. Some pre-miRNA and miRNA targets vary in abundance between the three stages of seed development. A search for sequences that produce siRNA was performed, and the results indicated that J. curcas siRNAs play a role in nuclear functions, transport, catalytic processes and disease resistance. This study presents the first large scale identification of J. curcas miRNAs and their targets in mature seeds based on deep sequencing, and it contributes to a functional understanding of these miRNAs.

Identification of potential miRNAs and their targets in Vriesea carinata (Poales, Bromeliaceae)

The miRNAs play important roles in regulation of gene expression at the post-transcriptional level. A small RNA and RNA-seq of libraries were constructed to identify miRNAs in Vriesea carinata, a native bromeliad species from Brazilian Atlantic Rainforest. Illumina technology was used to perform high throughput sequencing and data was analyzed using bioinformatics tools. We obtained 2,191,509 mature miRNAs sequences representing 54 conserved families in plant species. Further analysis allowed the prediction of secondary structures for 19 conserved and 16 novel miRNAs. Potential targets were predicted from pre-miRNAs by sequence homology and validated using RTqPCR approach. This study provides the first identification of miRNAs and their potential targets of a bromeliad species.

Identifying conserved and novel microRNAs in developing seeds of Brassica napus using deep sequencing

MicroRNAs (miRNAs) are important post-transcriptional regulators of plant development and seed formation. In Brassica napus, an important edible oil crop, valuable lipids are synthesized and stored in specific seed tissues during embryogenesis. The miRNA transcriptome of B. napus is currently poorly characterized, especially at different seed developmental stages. This work aims to describe the miRNAome of developing seeds of B. napus by identifying plant-conserved and novel miRNAs and comparing miRNA abundance in mature versus developing seeds. Members of 59 miRNA families were detected through a computational analysis of a large number of reads obtained from deep sequencing two small RNA and two RNA-seq libraries of (i) pooled immature developing stages and (ii) mature B. napus seeds. Among these miRNA families, 17 families are currently known to exist in B. napus; additionally 29 families not reported in B. napus but conserved in other plant species were identified by alignment with known plant mature miRNAs. Assembled mRNA-seq contigs allowed for a search of putative new precursors and led to the identification of 13 novel miRNA families. Analysis of miRNA population between libraries reveals that several miRNAs and isomiRNAs have different abundance in developing stages compared to mature seeds. The predicted miRNA target genes encode a broad range of proteins related to seed development and energy storage. This work presents a comparative study of the miRNA transcriptome of mature and developing B. napus seeds and provides a basis for future research on individual miRNAs and their functions in embryogenesis, seed maturation and lipid accumulation in B. napus.

Identification of microRNAs from Eugenia uniflora by high-throughput sequencing and bioinformatics analysis

Background

microRNAs or miRNAs are small non-coding regulatory RNAs that play important functions in the regulation of gene expression at the post-transcriptional level by targeting mRNAs for degradation or inhibiting protein translation. Eugenia uniflora is a plant native to tropical America with pharmacological and ecological importance, and there have been no previous studies concerning its gene expression and regulation. To date, no miRNAs have been reported in Myrtaceae species.

Results

Small RNA and RNA-seq libraries were constructed to identify miRNAs and pre-miRNAs in Eugenia uniflora. Solexa technology was used to perform high throughput sequencing of the library, and the data obtained were analyzed using bioinformatics tools. From 14,489,131 small RNA clean reads, we obtained 1,852,722 mature miRNA sequences representing 45 conserved families that have been identified in other plant species. Further analysis using contigs assembled from RNA-seq allowed the prediction of secondary structures of 25 known and 17 novel pre-miRNAs. The expression of twenty-seven identified miRNAs was also validated using RT-PCR assays. Potential targets were predicted for the most abundant mature miRNAs in the identified pre-miRNAs based on sequence homology.

Conclusions

This study is the first large scale identification of miRNAs and their potential targets from a species of the Myrtaceae family without genomic sequence resources. Our study provides more information about the evolutionary conservation of the regulatory network of miRNAs in plants and highlights species-specific miRNAs.

Long‐term accumulation and microdistribution of uranium in the bone and marrow of beagle dog

The accumulation and microdistribution of uranium in the bone and marrow of Beagle dogs were determined by both neutron activation and neutron-fission analysis. The experiment started immediately after the weaning period, lasting till maturity. Two animal groups were fed daily with uranyl nitrate at concentrations of 20 and 100 microg g(-1) food. Of the two measuring techniques, uranium accumulated along the marrow as much as in the bone, contrary to the results obtained with single, acute doses. The role played by this finding for the evaluation of radiobiological long-term risks is discussed. It was demonstrated, by means of a biokinetical approach, that the long-term accumulation of uranium in bone and marrow could be described by a piling up of single dose daily incorporation.

In vitro effects of gamma radiation from 60Co and 137Cs on plasmid DNA

The effects of gamma radiation from (60)Co and (137)Cs on DNA in aqueous solution are studied experimentally. Using an improved plasmid purification protocol and improved electrophoretic gel analysis techniques provided results with relatively small uncertainties. The results are compared with both theoretical and experimental results. In particular, the results obtained here are discussed in the light of recent discussion on supposed differences of the effects induced by gamma radiation from (60)Co and (137)Cs. We find that the effects of both types of gamma radiation are similar.

Use of biodegradable PLGA microspheres as a slow release delivery system for the Boophilus microplus synthetic vaccine SBm7462

The synthetic anti-Boophilus microplus vaccine SBm7462 derived from the tick intestinal protein, Bm86, induced a protective immune response when emulsified in saponin and used in cattle. Using a mice model, and with the objective of improving the vaccine by continual peptide release, it was encapsulated in PLGA 50:50 microspheres and inoculated in BALB/c mice to assess the immunological response by detection of anti-peptide IgGs. Comparative studies were made with the peptide emulsified in saponin and with another synthetic vaccine, and the microsphere/peptide was characterized for efficiency of encapsulation, in vitro release profile, morphology, size, peptide integrity after encapsulation and stability in different pHs. The findings showed that saponin enhances a better immune response from SBm7462 and that the PLGA 50:50 microspheres are suitable for use with this peptide.

Immunization of cattle with synthetic peptides derived from the Boophilus microplus gut protein (Bm86)

Three synthetic peptides (SBm4912, SBm7462 and SBm19733), derived from the Bm86 glycoprotein from Boophilus microplus gut, were constructed and used to immunize cattle from a tick-free area. The immunized animals received three subcutaneous doses of the peptides, with saponin as adjuvant, at 30-day intervals. The immune response was evaluated by IgG elicited against the peptides by the detection of anti-Bm86 specific antibodies in situ and by Western blotting analysis. After tick challenge, reduction in the number, weight and oviposition capacity of engorged females was observed in the tick population that had fed on immunized animals. The results pointed a high efficacy (81.05%) for the SBm7462 synthetic peptide in relation to the others (p<0.01), demonstrating the efficiency of the immune response elicited by synthetic peptides to control the cattle tick B. microplus.

T-cell reactivity against streptococcal antigens in the periphery mirrors reactivity of heart-infiltrating T lymphocytes in rheumatic heart disease patients

T-cell molecular mimicry between streptococcal and heart proteins has been proposed as the triggering factor leading to autoimmunity in rheumatic heart disease (RHD). We searched for immunodominant T-cell M5 epitopes among RHD patients with defined clinical outcomes and compared the T-cell reactivities of peripheral blood and intralesional T cells from patients with severe RHD. The role of HLA class II molecules in the presentation of M5 peptides was also evaluated. We studied the T-cell reactivity against M5 peptides and heart proteins on peripheral blood mononuclear cells (PBMC) from 74 RHD patients grouped according to the severity of disease, along with intralesional and peripheral T-cell clones from RHD patients. Peptides encompassing residues 1 to 25, 81 to 103, 125 to 139, and 163 to 177 were more frequently recognized by PBMC from RHD patients than by those from controls. The M5 peptide encompassing residues 81 to 96 [M5(81-96) peptide] was most frequently recognized by PBMC from HLA-DR7+ DR53+ patients with severe RHD, and 46.9% (15 of 32) and 43% (3 of 7) of heart-infiltrating and PBMC-derived peptide-reactive T-cell clones, respectively, recognized the M5(81-103) region. Heart proteins were recognized more frequently by PBMC from patients with severe RHD than by those from patients with mild RHD. The similar pattern of T-cell reactivity found with both peripheral blood and heart-infiltrating T cells is consistent with the migration of M-protein-sensitized T cells to the heart tissue. Conversely, the presence of heart-reactive T cells in the PBMC of patients with severe RHD also suggests a spillover of sensitized T cells from the heart lesion.

Biodegradable PLGA microspheres as a delivery system for malaria synthetic peptide SPf66

SPf66 is the first chemically synthesised vaccine to elicit a partial protective immune response against malaria. The aluminium hydroxide (alum)-adsorbed SPf66 vaccine is weakly immunogenic and of poor to moderate efficacy in humans. To investigate the possibility of improving SPf66 vaccine immunogenicity, a delivery system based on poly-D,L-lactide-co-glycolide (PLGA) microspheres was developed and the immune response induced after its subcutaneous administration into mice was evaluated. Microspheres were prepared by a solvent extraction/double emulsion (w/o/w) method and characterised for morphology, size, peptide loading, release profile and peptide integrity. The in vitro and in vivo results obtained showed that there was no apparent effect of the encapsulation procedure on SPf66 integrity and immunogenicity. The subcutaneous administration of microspheres showed a significantly higher immune response (serum IgG levels) than that obtained with alum adsorbed SPf66 and it was comparable to that of SPf66 emulsified with Freund's adjuvant (FA). These observations illustrate the potential of PLGA microspheres as a delivery system for chemically synthesised antigens.

Transfer coefficient measurements of uranium to the organs of Wistar rats, as a function of the uranium content in the food

Groups of animals (Wistar rats) were fed with rations doped with uranyl nitrate at concentrations ranging from 0.5 to 100 ppm. The uranium content in the ashes of the organs was measured by the neutron-fission track counting technique. The most striking result is that the transfer coefficients, as a function of the uranium concentration, exhibit a concave shape with a minimum around 20 ppm-U for all organs. Explanations to interpret this finding are tentatively given.

Activation pattern and toxicity of the Cry11Bb1 toxin of Bacillus thuringiensis subsp. medellin

Bacillus thuringiensis protoxins undergo proteolytic processing in the midgut of susceptible insects to become active. The ability to process the Cry11Bb1 protoxin by trypsin and Culex quinquefasciatus larval gut extracts was tested. The protease activity indicated by the appearance of proteolytic products increased with an increment in pH, with the highest activity being observed at pH 10.6. A time course study showed the proteolysis of the 94-kDa Cry11Bb protein ending with the production of fragments of relative molecular mass of 30 and 35 kDa within 5 min. In vitro, gut proteases extract cleaved the solubilized toxin between Ser59 and Ile60 and between Ala395 and Asn396, generating a 30-kDa N-terminal and a 35-kDa C-terminal fragment, respectively. Similarly, mosquito larvae processed in vivo the parasporal inclusions, generating the same fragments as those observed in vitro. The Cry11Bb1 protoxin activated with trypsin or gut proteases showed larvicidal activity against C. quinquefasciatus first instar larvae. The data suggest that gut proteases participate in the activation of CryllBbl protoxin, generating at least two different fragments on which the activity could reside.

A GBP 130 derived peptide from Plasmodium falciparum binds to human erythrocytes and inhibits merozoite invasion in vitro

The malarial GBP 130 protein binds weakly to intact human erythrocytes; the binding sites seem to be located in the repeat region and this region's antibodies block the merozoite invasion. A peptide from this region (residues from 701 to 720) which binds to human erythrocytes was identified. This peptide named 2220 did not bind to sialic acid; the binding site on human erythrocyte was affected by treatment with trypsin but not by chymotrypsin. The peptide was able to inhibit Plasmodium falciparum merozoite invasion of erythrocytes. The residues F701, K703, L705, T706, E713 (FYKILTNTDPNDEVERDNAD) were found to be critical for peptide binding to erythrocytes.

Plasmodium falciparum EBA-175 kDa protein peptides which bind to human red blood cells

Solid experimental evidence indicates that EBA-175 is used as a ligand by the Plasmodium falciparum merozoite to bind to human RBC, via different binding processing fragments. Using synthetic peptides and specific receptor-ligand interaction methodology, we have identified 6 high-activity binding sequences from the EBA-175 CAMP strain; peptide 1758 (KSYGTPDNIDKNMSLIHKHN), located in the so-called region I for which no binding activity has been reported before, peptides 1779 (NIDRIYDKNLLMIKEHILAI) and 1783 (HRNKKNDKLYRDEWWKVIKK), located in region II, in a sub-region known as 5' Cys F2, previously reported as being a binding region, and peptides 1814 (DRNSNTLHLKDYRNEENERH), 1815 (YTNQNINISQERDLQKHGFH) and 1818 (NNNFNNIPSRYNLYDKKLDL), in region III-V where antibodies inhibit merozoite invasion of erythrocytes. The affinity constants were between 60 and 180 nM and the critical amino acids involved in the binding were identified. The binding of these peptides to enzyme-treated RBC was analysed; binding of peptide 1814, located in the III-V region, was found to be sialic acid dependent. Some of these high binding peptides were able to inhibit in vitro merozoite invasion and to block the binding of recombinant RII-EBA to RBC. Several of these peptides are located in regions recognized by protective immune clusters of merozoites (ICMs) eluted antibodies.

Isolation, characterization, molecular cloning and amplification of a species-specific M. leprae antigen

A polyclonal serum sample from a lepromatous leprosy (LL) patient, which presented a specific recognition pattern for leprosin, was used to screen a Mycobacterium leprae genomic library constructed with DNA isolated from human lepromas. One clone, designated ML4-1, which expressed a specific antigenic determinant of M. leprae as part of a beta-galactosidase fusion protein, was isolated. The 1.932 bp M. leprae-derived genomic fragment was sequenced, and it had an incomplete open-reading frame shown to code for a 644 amino-acid polypeptide (72.3 kDa). Some partial nucleotide homology to the M. tuberculosis MTCY9C4 cosmid and the M. leprae B1913 cosmid were found. Southern blot assays using the 584 bp Eco RI-Bam HI fragment excised from the ML4-1 clone revealed that this sequence is present only in the M. leprae genome and not in the 24 different mycobacterial DNA tested. Two oligonucleotides based on the genomic sequence were also synthesized and used as amplifiers for a polymerase chain reaction (PCR) test, giving a positive signal exclusively in M. leprae DNA. Furthermore, 32 sequential synthetic peptides, 20 amino-acids long, spanning the entire protein corresponding to the hypothetical ML4-1 clone sequence, were synthesized and evaluated by ELISA. A peptide included in the 221-240 region was significantly recognized by either lepromatous leprosy or healthy tuberculosis contact patient sera. Thus, PCR amplification of this fragment, along with the recognition of its protein sequence by leprosy patient sera, could be a useful tool for a potential diagnostic method in the detection of M. leprae infection in the future.

CD4(+) T-cell- and gamma interferon-dependent protection against murine malaria by immunization with linear synthetic peptides from a Plasmodium yoelii 17-kilodalton hepatocyte erythrocyte protein

Most work on protective immunity against the pre-erythrocytic stages of malaria has focused on induction of antibodies that prevent sporozoite invasion of hepatocytes, and CD8(+) T-cell responses that eliminate infected hepatocytes. We recently reported that immunization of A/J mice with an 18-amino-acid synthetic linear peptide from Plasmodium yoelii sporozoite surface protein 2 (SSP2) in TiterMax adjuvant induces sterile protection that is dependent on CD4(+) T cells and gamma interferon (IFN-gamma). We now report that immunization of inbred A/J mice and outbred CD1 mice with each of two linear synthetic peptides from the 17-kDa P. yoelii hepatocyte erythrocyte protein (HEP17) in the same adjuvant also induces protection against sporozoite challenge that is dependent on CD4(+) T cells and IFN-gamma. The SSP2 peptide and the two HEP17 peptides are recognized by B cells as well as T cells, and the protection induced by these peptides appears to be directed against the infected hepatocytes. In contrast to the peptide-induced protection, immunization of eight different strains of mice with radiation-attenuated sporozoites induces protection that is absolutely dependent on CD8(+) T cells. Data represented here demonstrate that CD4(+) T-cell-dependent protection can be induced by immunization with linear synthetic peptides. These studies therefore provide the foundation for an approach to pre-erythrocytic-stage malaria vaccine development, based on the induction of protective CD4(+) T-cell responses, which will complement efforts to induce protective antibody and CD8(+) T-cell responses.

Particulate Air Pollution in Mexico City: A Collaborative Research Project

PM₁₀, PM₂₅, precursor gas, and upper-air meteorological measurements were taken in Mexico City, Mexico, from February 23 to March 22, 1997, to understand concentrations and chemical compositions of the city's particulate matter (PM). Average 24-hr PM₁₀ concentrations over the period of study at the core sites in the city were 75 H g/m³. The 24-hr standard of 150 μ g/m³ was exceeded for seven samples taken during the study period; the maximum 24-hr concentration measured was 542 μ g/m³. Nearly half of the PM₁₀ was composed of fugitive dust from roadways, construction, and bare land. About 50% of the PM₁₀ consisted of PM_2.5, with higher percentages during the morning hours. Organic and black carbon constituted up to half of the PM_2.5. PM concentrations were highest during the early morning and after sunset, when the mixed layers were shallow. Meteorological measurements taken during the field campaign show that on most days air was transported out of the Mexico City basin during the afternoon with little day-to-day carryover.

A new statistical method for transfer coefficient calculations in the framework of the general multiple-compartment model of transport for radionuclides in biological systems

A new and simple statistical procedure (STATFLUX) for the calculation of transfer coefficients of radionuclide transport to animals and plants is proposed. The method is based on the general multiple-compartment model, which uses a system of linear equations involving geometrical volume considerations. By using experimentally available curves of radionuclide concentrations versus time, for each animal compartment (organs), flow parameters were estimated by employing a least-squares procedure, whose consistency is tested. Some numerical results are presented in order to compare the STATFLUX transfer coefficients with those from other works and experimental data.

Trypanosoma cruzi: conformational preferences of antigenic peptides bearing the immunodominant epitope of the B13 antigen

The Trypanosoma cruzi recombinant protein B13 contains tandemly repeated domains and shows high sensitivity in the serological diagnosis of Chagas' disease. It has been shown that the immunodominant epitope of B13 is contained in the GDKPSLFGQAAAGDKPSLF-NH(2) sequence and that the hexapeptide AAAGDK seems to be the "core" of that epitope. Three peptides containing that "core" sequence, one corresponding to the entire repeat motif GDKPSLFGQAAAGDKPSLF-NH(2), pB13, and two smaller fragments, FGQAAAGDK-NH(2), S4, and QAAAGDKPS-NH(2), S5, have been tested in competitive ELISA with recombinant protein B13 in the solid phase against 40 chagasic sera from Brazilian patients. The median percentage inhibition for pB13, S4, and S5 were, respectively, 91, 86, and 68%. The possibility that the distinct antigenic activity of those peptides correlates with the existence of preferential conformational properties has been investigated by CD and NMR spectroscopy. Results indicate their propensity to adopt a helical configuration, centered in the AAAGDK sequence, and whose extent and stability directly correlates with the peptides' antigenicity. The data are discussed in the light of the existence of conformational preferences involving immunodominant epitopes in tandemly repeated antigens.

Antigenicity of the Leishmania infantum histones H2B and H4 during canine viscerocutaneous leishmaniasis

In this study we show that sera from dogs naturally infected with Leishmania infantum contain antibodies that specifically react against the parasite H2B and H4 histones. The Leishmania H2B and the amino-terminal region of the histone H4, expressed as fusion proteins, when confronted with sera from canine viscerocutaneous leishmaniasis (VCL) dogs, were recognized by 63% and 47%, respectively. No reactivity was detected when sera from dogs naturally infected with pathogens other than Leishmania were used. Using a collection of synthetic peptides covering the complete sequence of both proteins, we have determined that the main linear antigenic determinants are located in the amino-terminal domains of these histones. The humoral response against histones H2B and H4 induced during canine leishmaniasis was found to be specific for Leishmania histones, since no cross-reactivity of the VCL sera with mammal histones was observed. Also, a comparative study of the prevalence of antibodies among VCL sera against the four core histones of L. infantum was performed. Although a large heterogeneity of the humoral responses against these proteins was found, histones H2A and H3 seem to be more prevalent immunogens than histones H2B and H4 during canine natural leishmaniasis. The origin of the anti-histone humoral response and its possible implications in the pathogenesis of Leishmania infection are discussed.

Mapping of the antigenic determinants of the Leishmania infantum gp63 protein recognized by antibodies elicited during canine visceral leishmaniasis

The gp63 gene encoding the major surface antigen of Leishmania infantum has been cloned and sequenced. In spite of the overall sequence homology with the gp63 genes from other Leishmania species, particularly with the constitutively expressed Leishmania chagasi Gp63 gene, the carboxy-terminal ends of these genes are clearly divergent (62% homology). To study the prevalence of anti-gp63 antibodies in the sera from dogs with visceral leishmaniasis, a recombinant L. infantum gp63 protein was expressed in Escherichia coli. It was found that 100% of the sera from these dogs recognized the recombinant gp63 protein, suggesting that it must function as a potent B cell immunogen during natural canine visceral leishmaniasis. However, heterogeneity in the level of response was observed. Fine mapping of the antigenic determinants was performed by means of 6 overlapping subfragments of the gp63 protein and by the use of a library of synthetic peptides. The data showed that there is some degree of immunological restriction in the recognition of the protein since reactivity was observed preferentially against the most divergent region. The epitope mapping of this region showed 2 immunodominant peptides the response to which seems to be preferentially of the IgG2 type.

Characterization of the antigenic determinants of the Leishmania infantum histone H3 recognized by antibodies elicited during canine visceral leishmaniasis

In the present study we show that sera from dogs naturally infected with the protozoan parasite Leishmania infantum contain antibodies that specifically react with the parasite histone H3. Using synthetic peptides covering the complete sequence of the protein we located the linear antigenic determinants within the 40 amino-terminal amino acids of the molecule. In addition to the complete form of the protein (rLiH3), two regions of the Leishmania histone H3 were expressed as recombinant proteins: the rLiH3-Nt fragment containing the 39 amino-terminal amino acids and the rLiH3-Ct fragment containing the 90 carboxyl-terminal residues. Competition experiments using the protein fragment rLiH3-Nt as competitor confirmed that the antigenic determinants of histone H3 are confined to the amino-terminal domain. This domain, which is believed to be exposed on the nucleosome surface, is also the most evolutionarily divergent region of the L. infantum histone H3. Visceral leishmaniasis (VL) sera do not react with mammalian histones, an indication that the anti-histone response elicited during Leishmania infection is triggered by the parasite histone. The results of the prevalence of anti-histone H3 antibodies in canine VL sera together with the sequence-specific characteristics of the amino-terminal region of L. infantum histone H3 indicate that the recombinant protein rLiH3-Nt may be of use for diagnosis of canine VL.

Comparison of prevalence of anti-hepatitis C virus antibodies in differing South American populations

Very little is known about the distribution of hepatitis C virus (HCV) within South America. To assess the exposure of the general population to this virus, a number of sera obtained from three distinct geographical and racial groups were screened using a combination of immunoassays. Initial screening was undertaken with an inhouse immunoassay (core-ELISA) using synthetic peptides based on the N-terminus of the HCV core protein. Sera which were repeatedly positive by core-ELISA were also assessed using a commercial third-generation assay. The highest prevalence rate (2.3%) was seen in sera taken from the Tumaco region of Colombia. Lower rates were found in sera taken from La T, Ecuador (0.7%) and Las Majadas, Venezuela (0.7%). This indicates significantly different prevalence in different racial and geographical groups within the region.