Host immune responses to enzootic and invasive pathogen lineages vary in magnitude, timing, and efficacy.

Infectious diseases of wildlife continue to pose a threat to biodiversity worldwide, yet pathogens are far from uniform in virulence or host disease outcome. Within the same pathogen species, virulence can vary considerably depending on strain or lineage, in turn eliciting variable host responses. One pathogen that has caused extensive biodiversity loss is the amphibian-killing fungus, Batrachochytrium dendrobatidis (Bd), which is comprised of a globally widespread hypervirulent lineage (Bd-GPL), and multiple geographically restricted, enzootic lineages. Whereas host immunogenomic responses to Bd-GPL have been characterized in a number of amphibian species, immunogenomic responses to geographically restricted, enzootic Bd lineages are less clear. To examine lineage-specific host immune responses to Bd, we exposed a species of pumpkin toadlet, Brachycephalus pitanga, which is endemic to Brazil's Southern Atlantic Forest, to either the Bd-GPL or the enzootic Bd-Asia-2/Brazil (hereafter Bd-Brazil) lineage. Using temporal samples from early, mid, and late infection stages, we quantified functional immunogenomic responses over the course of infection using differential gene expression tests and coexpression network analyses. Host immune responses varied significantly with Bd lineage. Relative to controls, toadlet responses to Bd-Brazil were weak at early infection (25 genes significantly differentially expressed), peaked by mid-stage infection (414 genes), and were nearly fully resolved by late-stage infection (nine genes). In contrast, responses to Bd-GPL were magnified and delayed; toadlets significantly differentially expressed 111 genes early, 87 genes at mid-stage infection, and 726 genes by late-stage infection relative to controls. Given that infection intensity did not vary between mid- and late-stage disease in either Bd-Brazil or Bd-GPL treatments, this suggests that pumpkin toadlets may be at least partially tolerant to the enzootic Bd-Brazil lineage. In contrast, late-stage immune activation against Bd-GPL was consistent with immune dysregulation previously observed in other species. Our results demonstrate that both the timing of immune response and the particular immune pathways activated are specific to Bd lineage. Within regions where multiple Bd lineages co-occur, and given continued global Bd movement, these differential host responses may influence not only individual disease outcome, but transmission dynamics at the population and community levels.

Habitat fragmentation in the Brazilian Atlantic Forest is associated with erosion of frog immunogenetic diversity and increased fungal infections.

Habitat fragmentation and infectious diseases threaten wildlife globally, but the interactions of these threats are poorly understood. For instance, while habitat fragmentation can impact genetic diversity at neutral loci, the impacts on disease-relevant loci are less well-studied. We examined the effects of habitat fragmentation in Brazil's Atlantic Forest on amphibian genetic diversity at an immune locus related to antigen presentation and detection (MHC IIB Exon 2). We used a custom high-throughput assay to sequence a fragment of MHC IIB and quantified Batrachochytrium dendrobatidis (Bd) infections in six frog species in two Atlantic Forest regions. Habitat fragmentation was associated with genetic erosion at MHC IIB Exon 2. This erosion was most severe in forest specialists. Significant Bd infections were detected only in one Atlantic Forest region, potentially due to relatively higher elevation. In this region, forest specialists showed an increase in both Bd prevalence and infection loads in fragmented habitats. Reduced population-level MHC IIB diversity was associated with increased Bd infection risk. On the individual level, MHC IIB heterozygotes exhibited a trend toward reduced Bd infection risk, although this was marginally non-significant. Our results suggest that habitat fragmentation increases Bd infection susceptibility in amphibians, mediated at least in part through erosion of immunogenetic diversity. Our findings have implications for management of fragmented populations in the face of emerging infectious diseases.

Development and characterization of a novel liquid crystalline system containing sodium alginate for incorporation of trans-resveratrol intended for treatment of buccal candidiasis.

Trans-resveratrol has antimicrobial effects; however, its hydrophobic properties hamper its incorporation into pharmaceutical formulations. The aim of this study was to develop liquid crystals and a liquid crystal precursor (microemulsion), a common nanotechnology-based drug delivery system using a surfactant, an oil phase, and a polymer dispersion, for topical administration against buccal candidiasis. A ternary diagram was constructed and a potential formulation was selected, in order to run characterization tests. We chose the formulation that presented microemulsion and crystal liquid characteristics through polarized light microscopy and smallangle X-ray scattering experiments. The stability and structural features of the formulations were observed by performing rheological assay, measuring mucoadhesion, and analyzing texture profiles. It was verified that the chosen system was capable of transiting from microemulsion to liquid crystals when added in aqueous phase; further, the presence of sodium alginate as the polymer increased its mucoadhesion strength. Microbiological assay of trans-resveratrol, using amphotericin B and fluconazole as controls against strains of Candida albicans, showed positive anti-microbiological effect; however, a high concentration of the compound was needed.

Globally invasive genotypes of the amphibian chytrid outcompete an enzootic lineage in coinfections.

Competition between genotypes is likely to be a key driver of pathogen evolution, particularly following a geographical invasion by distant strains. Theory predicts that competition between disease strains will result in the most virulent strain persisting. Despite its evolutionary implications, the role of strain competition in shaping populations remains untested for most pathogens. We experimentally investigated the in vivo competitive differences between two divergent lineages of the amphibian-killing chytrid fungus ( Batrachochytrium dendrobatidis, Bd). These Bd lineages are hypothesized to have diverged in allopatry but been recently brought back into secondary contact by human introduction. Prior studies indicate that a panzootically-distributed, global lineage of Bd was recently introduced into southern Brazil, and is competitively excluding enzootic lineages in the southern Atlantic Forest. To test for differences in competitive ability between invasive and enzootic Brazilian Bd isolates, we coinfected a model host frog system which we developed for this study ( Hymenochirus curtipes). We tracked isolate-specific zoospore production over the course of the coinfection experiment with chip-based digital PCR (dPCR). The globally invasive panzootic lineage had a competitive advantage in spore production especially during the first one to four weeks of infection, and on frogs that eventually succumbed to Bd infection. Our study provides new evidence that competitive pressure resulting from the human movement of pathogen strains can rapidly alter the genetics, community dynamics and spatial epidemiology of pathogens in the wild.

Virtual cystoscopy, computed tomography urography and optical cystoscopy for the detection and follow-up for bladder cancer. / Cistoscopia virtual, urografía por tomografía computarizada y uretrocistoscopia óptica en el diagnóstico y el seguimiento del cáncer de vejiga.

OBJECTIVES: To evaluate the utility of virtual cystoscopy (VC) performed with CT urography in patients being studied under gross hematuria or patients being followed-up after a previous bladder cancer and compare the results with those obtained with gold standard technique (optical cystoscopy). METHODS: Retrospective study of 117 patients who were referred for VC by the Urology Department between May 2014 and May 2015. Those patients presented with gross hematuria or they were previously treated patients from bladder cancer being followed up. These patients were evaluated with MDCT and virtual cystoscopy after distending the bladder with air. The results were compared with those obtained with optical cystoscopy which was performed no more than a week after. RESULTS: The global sensitivity and specificity of VC were 81,8 and 92,1%. Aditional findings detected in CT urography were an aortic dissection, urinary lithiasis and colonic metastasis. CONCLUSION: VC seems an useful technique in the diagnosis and follow-up for bladder cancer with a good correlation with OC. The main limitations are the impossibility of biopsy during the procedure and the detection of erythematous lesions. Collateral findings can be detected performed with CT urography although the high radiation exposure does not recommend their combined use.

Partitioning the net effect of host diversity on an emerging amphibian pathogen.

The 'dilution effect' (DE) hypothesis predicts that diverse host communities will show reduced disease. The underlying causes of pathogen dilution are complex, because they involve non-additive (driven by host interactions and differential habitat use) and additive (controlled by host species composition) mechanisms. Here, we used measures of complementarity and selection traditionally employed in the field of biodiversity-ecosystem function (BEF) to quantify the net effect of host diversity on disease dynamics of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd). Complementarity occurs when average infection load in diverse host assemblages departs from that of each component species in uniform populations. Selection measures the disproportionate impact of a particular species in diverse assemblages compared with its performance in uniform populations, and therefore has strong additive and non-additive properties. We experimentally infected tropical amphibian species of varying life histories, in single- and multi-host treatments, and measured individual Bd infection loads. Host diversity reduced Bd infection in amphibians through a mechanism analogous to complementarity (sensu BEF), potentially by reducing shared habitat use and transmission among hosts. Additionally, the selection component indicated that one particular terrestrial species showed reduced infection loads in diverse assemblages at the expense of neighbouring aquatic hosts becoming heavily infected. By partitioning components of diversity, our findings underscore the importance of additive and non-additive mechanisms underlying the DE.

Comparative application of direct sequencing, PCR-RFLP, and cytogenetic markers in the genetic characterization of Pimelodus (Siluriformes: Pimelodidae) species: possible implications for fish conservation.

Pimelodus (Pimelodidae) is a genus comprising a group of South American species with complex taxonomic relationships. Cytogenetics, polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), and sequencing data of mitochondrial genes were analyzed to characterize 4 Pimelodus species: P. fur, P. heraldoi, P. maculatus, and Pimelodus sp. All populations presented 2n=56 chromosomes and distinct karyotypic formulae. The heterochromatin distribution pattern and the number and location of 5S and 18S rDNA sites are discussed. The application of PCR-RFLP markers and sequencing of mitochondrial DNA genes provided species-specific haplotypes, which allowed us to differentiate the species studied. The mitochondrial gene sequences presented nucleotide mutations in the restriction sites and throughout the sequences, and they were mostly related to synonymous substitutions in the coded proteins; however, they did not affect the protein and its function. Comparing the data obtained using these 3 methodologies, the existence of a species complex in P. maculatus along the basins studied might be inferred, showing that cytogenetics is an important tool in studies focusing on the conservation or management of both natural and captive populations of these fishes.

Coevolution of a generalist pathogen with many hosts: the case of the amphibian chytrid Batrachochytrium dendrobatidis.

Generalist pathogens maintain infectivity in numerous hosts; how this broad ecological niche impacts host-pathogen coevolution remains to be widely explored. Batrachochytrium dendrobatidis (Bd) is a highly generalist pathogenic fungus that has caused devastating declines in hundreds of amphibian species worldwide. This review examines amphibian chytridiomycosis host-pathogen interactions and available evidence for coevolution between Bd and its numerous hosts. We summarize recent evidence showing that Bd genotypes vary in geographic distribution and virulence, and that amphibian species also vary in Bd susceptibility according to their geographic distribution. How much variation can be explained by phenotypic plasticity or genetic differences remains uncertain. Recent research suggests that Bd genotypes display preferences for specific hosts and that some hosts are undergoing evolution as populations rebound from Bd outbreaks. Taken together, these findings suggest the potential for coevolution to occur and illuminate a path for addressing open questions through integrating historical and contemporary genetic data.

An endogenous DNA virus in an amphibian-killing fungus associated with pathogen genotype and virulence.

The global panzootic lineage (GPL) of the pathogenic fungus Batrachochytrium dendrobatidis (Bd) has caused severe amphibian population declines, yet the drivers underlying the high frequency of GPL in regions of amphibian decline are unclear. Using publicly available Bd genome sequences, we identified multiple non-GPL Bd isolates that contain a circular Rep-encoding single-stranded (CRESS)-like DNA virus, which we named Bd DNA virus 1 (BdDV-1). We further sequenced and constructed genome assemblies with long read sequences to find that the virus is integrated into the nuclear genome in some strains. Attempts to cure virus-positive isolates were unsuccessful; however, phenotypic differences between naturally virus-positive and virus-negative Bd isolates suggested that BdDV-1 decreases the growth of its host in vitro but increases the virulence of its host in vivo. BdDV-1 is the first-described CRESS DNA mycovirus of zoosporic true fungi, with a distribution inversely associated with the emergence of the panzootic lineage.

MLL2 mutation detection in 86 patients with Kabuki syndrome: a genotype-phenotype study.

Recently, pathogenic variants in the MLL2 gene were identified as the most common cause of Kabuki (Niikawa-Kuroki) syndrome (MIM#147920). To further elucidate the genotype-phenotype correlation, we studied a large cohort of 86 clinically defined patients with Kabuki syndrome (KS) for mutations in MLL2. All patients were assessed using a standardized phenotype list and all were scored using a newly developed clinical score list for KS (MLL2-Kabuki score 0-10). Sequencing of the full coding region and intron-exon boundaries of MLL2 identified a total of 45 likely pathogenic mutations (52%): 31 nonsense, 10 missense and four splice-site mutations, 34 of which were novel. In five additional patients, novel, i.e. non-dbSNP132 variants of clinically unknown relevance, were identified. Patients with likely pathogenic nonsense or missense MLL2 mutations were usually more severely affected (median 'MLL2-Kabuki score' of 6) as compared to the patients without MLL2 mutations (median 'MLL2-Kabuki score' of 5), a significant difference (p < 0.0014). Several typical facial features such as large dysplastic ears, arched eyebrows with sparse lateral third, blue sclerae, a flat nasal tip with a broad nasal root, and a thin upper and a full lower lip were observed more often in mutation positive patients.

COVID-19 impedimetric biosensor based on polypyrrole nanotubes, nickel hydroxide and VHH antibody fragment: specific, sensitive, and rapid viral detection in saliva samples.

SARS-CoV-2 rapid spread required urgent, accurate, and prompt diagnosis to control the virus dissemination and pandemic management. Several sensors were developed using different biorecognition elements to obtain high specificity and sensitivity. However, the task to achieve these parameters in combination with fast detection, simplicity, and portability to identify the biorecognition element even in low concentration remains a challenge. Therefore, we developed an electrochemical biosensor based on polypyrrole nanotubes coupled via Ni(OH)2 ligation to an engineered antigen-binding fragment of heavy chain-only antibodies (VHH) termed Sb#15. Herein we report Sb#15-His6 expression, purification, and characterization of its interaction with the receptor-binding domain (RBD) of SARS-CoV-2 in addition to the construction and validation of a biosensor. The recombinant Sb#15 is correctly folded and interacts with the RBD with a dissociation constant (KD) of 27.1 ± 6.4 nmol/L. The biosensing platform was developed using polypyrrole nanotubes and Ni(OH)2, which can properly orientate the immobilization of Sb#15-His6 at the electrode surface through His-tag interaction for the sensitive SARS-CoV-2 antigen detection. The quantification limit was determined as 0.01 pg/mL using recombinant RBD, which was expressively lower than commercial monoclonal antibodies. In pre-characterized saliva, both Omicron and Delta SARS-CoV-2 were accurately detected only in positive samples, meeting all the requirements recommended by the World Health Organization for in vitro diagnostics. A low sample volume of saliva is needed to perform the detection, providing results within 15 min without further sample preparations. In summary, a new perspective allying recombinant VHHs with biosensor development and real sample detection was explored, addressing the need for accurate, rapid, and sensitive biosensors.

Molecular characterization and physical mapping of two classes of 5S rDNA in the genomes of Gymnotus sylvius and G. inaequilabiatus (Gymnotiformes, Gymnotidae).

The nucleotide sequences of the 5S rRNA multigene family and their distribution across the karyotypes in 2 species of Gymnotiformes, genus Gymnotus (G. sylvius and G. inaequilabiatus) were investigated by means of fluorescence in situ hybridization (FISH). The results showed the existence of 2 distinct classes of 5S rDNA sequences in both species: class I and class II. A high conservative pattern of the codifying region of the 5S rRNA gene was identified, contrasting with significant alterations detected in the nontranscribed spacer (NTS). The presence of TATA-like sequences along the NTS of both species was an expected occurrence, since such sequences have been associated with the regulation of the gene expression. FISH using 5S rDNA class I and class II probes revealed that both gene classes were collocated in the same chromosome pair in the genome of G. sylvius, while in that of G. inaequilabiatus, class II appeared more disperse than class I.

The contrasting role of heterochromatin in the differentiation of sex chromosomes: an overview from Neotropical fishes.

During the evolutionary process of the sex chromosomes, a general principle that arises is that cessation or a partial restriction of recombination between the sex chromosome pair is necessary. Data from phylogenetically distinct organisms reveal that this phenomenon is frequently associated with the accumulation of heterochromatin in the sex chromosomes. Fish species emerge as excellent models to study this phenomenon because they have much younger sex chromosomes compared to higher vertebrates and many other organisms making it possible to follow their steps of differentiation. In several Neotropical fish species, the heterochromatinization, accompanied by amplification of tandem repeats, represents an important step in the morphological differentiation of simple sex chromosome systems, especially in the ZZ/ZW sex systems. In contrast, multiple sex chromosome systems have no additional increase of heterochromatin in the chromosomes. Thus, the initial stage of differentiation of the multiple sex chromosome systems seems to be associated with proper chromosomal rearrangements, whereas the simple sex chromosome systems have an accumulation of heterochromatin. In this review, attention has been drawn to this contrasting role of heterochromatin in the differentiation of simple and multiple sex chromosomes of Neotropical fishes, highlighting their surprising evolutionary dynamism.

Reflex activity of the pubococcygeus muscle is modified throughout the estrous cycle in Wistar rats.

Pubococcygeus muscle reflex activity has been reported to be driven by specialized neuronal circuitry, including the participation of spinal cord interneurons. Both the reflex and elements of the circuit are known to be sensitive to gonadal hormones, but studies using female rats have not considered the potential effects of estrous phase. Hence, in the present study we used mechanical stimulation of the clitoris to produce reflex activity, and recorded across the different phases of the estrous cycle, including the dark and light periods during each phase. Afterdischarge activity was observed only during the light and dark periods of proestrus, and during the light period of estrus coincident with the receptivity period in the rat́s reproductive behavior. Moreover, this reflex activity comprises at least five different motor unit groups with different firing patterns that are dependent on gonadal hormones variation.

Development of polypyrrole (nano)structures decorated with gold nanoparticles toward immunosensing for COVID-19 serological diagnosis.

The rapid and reliable detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroconversion in humans is crucial for suitable infection control. In this sense, many studies have focused on increasing the sensibility, lowering the detection limits and minimizing false negative/positive results. Thus, biosensors based on nanoarchitectures of conducting polymers are promising alternatives to more traditional materials since they can hold improved surface area, higher electrical conductivity and electrochemical activity. In this work, we reported the analytical comparison of two different conducting polymers morphologies for the development of an impedimetric biosensor to monitor SARS-CoV-2 seroconversion in humans. Biosensors based on polypyrrole (PPy), synthesized in both globular and nanotubular (NT) morphology, and gold nanoparticles are reported, using a self-assembly monolayer of 3-mercaptopropionic acid and covalently linked SARS-CoV-2 Nucleocapsid protein. First, the novel hybrid materials were characterized by electron microscopy and electrochemical measurements, and the biosensor step-by-step construction was characterized by electrochemical and spectroscopic techniques. As a proof of concept, the biosensor was used for the impedimetric detection of anti-SARS-CoV-2 Nucleocapsid protein monoclonal antibodies. The results showed a linear response for different antibody concentrations, good sensibility and possibility to quantify 7.442 and 0.4 ng/mL of monoclonal antibody for PPy in the globular and NT morphology, respectively. The PPy-NTs biosensor was able to discriminate serum obtained from COVID-19 positive versus negative clinical samples and is a promising tool for COVID-19 immunodiagnostic, which can contribute to further studies concerning rapid, efficient, and reliable detections.

Comparative cytogenetics and molecular phylogeography in the group astyanax altiparanae--Astyanax aff. bimaculatus (Teleostei, Characidae).

The genus Astyanax comprises small characin fish of the neotropical region. The so-called 'yellow-tailed characins' compose one of the most widely distributed Astyanax groups. A. altiparanae and A. aff. bimaculatus, are evolutionarily closely related and commonly found in several Brazilian hydrographic basins. In the present work, chromosomal data of specimens of A. altiparanae and A. aff. bimaculatus from 4 hydrographic basins in the states of São Paulo (Upper Tietê, Paranapanema, Ribeira de Iguape) and Rio de Janeiro (Guapimirim) are shown. All the populations showed 50 chromosomes, with different karyotypic formula. Although only a single Ag-NOR bearing chromosome pair was observed, all populations possess multiple cistrons of 18S rDNA. FISH with the 5S rDNA probe showed single signals at the interstitial position of one metacentric chromosome pair. C-bands are distributed in the terminal and interstitial regions of several chromosomes. However, the As-51 satDNA are frugally located in a few chromosomes of fishes from Upper Tietê, Paranapanema and Guapimirim Rivers, being absent in individuals of A. aff. bimaculatus from Ribeira de Iguape River basin. Beside these 4 populations, molecular phylogeography studies were also performed in individuals from Middle and Lower Tietê River basin and from 2 additional collection sites in the Paranapanema and Ribeira de Iguape River basins. The phylogeographic analysis using 2 mtDNA regions (totalizing 1.314 bp of ND2 and ATPase6/8 genes) of 8 populations of the group of 'yellow-tailed characins' from 3 major hydrographic basins showed structuring of populations, suggesting a correlation between chromosomal (nuclear) and molecular (mitochondrial) data.

Independent fusions and recent origins of sex chromosomes in the evolution and diversification of glass knife fishes (Eigenmannia).

The genus Eigenmannia comprises several species groups that display a surprising variety of diploid chromosome numbers and sex-determining systems. In this study, hypotheses regarding phylogenetic relationships and karyotype evolution were investigated using a combination of molecular and cytogenetic methods. Phylogenetic relationships were analyzed for 11 cytotypes based on sequences from five mitochondrial DNA regions. Parsimony-based character mapping of sex chromosomes confirms previous suggestions of multiple origins of sex chromosomes. Molecular cytogenetic analyses involved chromosome painting using probes derived from whole sex chromosomes from two taxa that were hybridized to metaphases of their respective sister cytotypes. These analyses showed that a multiple XY system evolved recently (<7 mya) by fusion. Furthermore, one of the chromosomes that fused to form the neo-Y chromosome is fused independently to another chromosome in the sister cytotype. This may constitute an efficient post-mating barrier and might imply a direct function of sex chromosomes in the speciation processes in Eigenmannia. The other chromosomal sex-determination system investigated is shown to have differentiated by an accumulation of heterochromatin on the X chromosome. This has occurred in the past 0.6 my, and is the most recent chromosomal sex-determining system described to date. These results show that the evolution of sex-determining systems can proceed very rapidly.

Geography, Host Genetics, and Cross-Domain Microbial Networks Structure the Skin Microbiota of Fragmented Brazilian Atlantic Forest Frog Populations.

The host-associated microbiome plays a significant role in health. However, the roles of factors such as host genetics and microbial interactions in determining microbiome diversity remain unclear. We examined these factors using amplicon-based sequencing of 175 Thoropa taophora frog skin swabs collected from a naturally fragmented landscape in southeastern Brazil. Specifically, we examined (1) the effects of geography and host genetics on microbiome diversity and structure; (2) the structure of microbial eukaryotic and bacterial co-occurrence networks; and (3) co-occurrence between microeukaryotes with bacterial OTUs known to affect growth of the fungal pathogen Batrachochytrium dendrobatidis (Bd). While bacterial alpha diversity varied by both site type and host MHC IIB genotype, microeukaryotic alpha diversity varied only by site type. However, bacteria and microeukaryote composition showed variation according to both site type and host MHC IIB genotype. Our network analysis showed the highest connectivity when both eukaryotes and bacteria were included, implying that ecological interactions may occur among domains. Lastly, anti-Bd bacteria were not broadly negatively co-associated with the fungal microbiome and were positively associated with potential amphibian parasites. Our findings emphasize the importance of considering both domains in microbiome research and suggest that for effective probiotic strategies for amphibian disease management, considering potential interactions among all members of the microbiome is crucial.

Bowel habits in the first 24 months of life: preterm- versus term-born infants.

BACKGROUND AND AIM: New prospective studies concerning feeding and bowel habits of term and preterm infants from birth to 24 months of life are needed. The aim of the present study was to describe and compare feeding and bowel habits between term- and preterm-born infants starting from birth up to the age of 24 months. PATIENTS AND METHODS: Between August and November 2006 all of the infants admitted to an academic and nonacademic neonatal care unit with gestational age 25 to 42 weeks participated in the study. Bowel diaries were recorded 1 and 2 weeks, and 3, 6, 12, and 24 months after birth. Infants with gastrointestinal surgery, neurological diseases, metabolic diseases, or congenital abnormalities were excluded. RESULTS: A total of 199 (126 preterm) infants were eligible; 153 gave consent for participation. Although feeding frequency was higher in the first 3 months in the preterm born, overall feeding frequency decreased between the first 3 follow-up periods (P < 0.001) in both groups. In the first and second week, breast-fed infants had 2.41 more episodes of defecation per week compared with the formula-fed infants (P = 0.017 and P = 0.021, respectively). Higher median (10th percentile-90th percentile) defecation frequency was only found in week 1 in the term compared with the preterm group (24 [9.4-31.6] versus 16 [6.5-31]; P = 0.002). The overall median defecation frequency was 16 (7-30) per week from birth up to the age of 24 months over the total group of participating infants. CONCLUSIONS: Term and preterm infants have a comparable defecation frequency from the second week of life up to the age of 24 months.

Karyotypic evolution trends in Rhamdia quelen (Siluriformes, Heptapteridae) with considerations about the origin and differentiation of its supernumerary chromosomes.

Among catfish species of the genus Rhamdia reported for the Brazilian territory, R. quelen is the most widespread, being found in nearly all hydrographic basins of Brazil. Nowadays, R. quelen is a synonym for at least 47 other species in this genus, its taxonomic status still being controversial. The available cytogenetic reports show a wide variation in the karyotypic macrostructure, with the frequent presence of supernumerary chromosomes. The remarkable cytogenetic variability associated with taxonomic issues in this species indicates that R. quelen is actually a species complex. In order to carry out a wide comparative cytogenetic study in R. quelen from southern and southeastern Brazil and examine a species complex, we analyzed the chromosomes of 14 populations from the main hydrographic basins of these two regions. Using classic and molecular cytogenetic techniques, we found seven distinct karyotypic formulae, all bearing 2n = 58 chromosomes. Supernumerary chromosomes were present in most of the populations; their number, size and C-banding pattern allowed us to differentiate populations with similar karyotypic compositions. We examined patterns of chromosomal evolution as well as the probable mechanisms involved in the origin and morphological differentiation of their supernumerary chromosomes.