Genome-Wide Classification of Myb Domain-Containing Protein Families in Entamoeba invadens

Entamoeba histolytica, the causative agent of amebiasis, is the third leading cause of death among parasitic diseases globally. Its life cycle includes encystation, which has been mostly studied in Entamoeba invadens, responsible for reptilian amebiasis. However, the molecular mechanisms underlying this process are not fully understood. Therefore, we focused on the identification and characterization of Myb proteins, which regulate the expression of encystation-related genes in various protozoan parasites. Through bioinformatic analysis, we identified 48 genes in E. invadens encoding MYB-domain-containing proteins. These were classified into single-repeat 1R (20), 2R-MYB proteins (27), and one 4R-MYB protein. The in-silico analysis suggests that these proteins are multifunctional, participating in transcriptional regulation, chromatin remodeling, telomere maintenance, and splicing. Transcriptomic data analysis revealed expression signatures of eimyb genes, suggesting a potential orchestration in the regulation of early and late encystation-excystation genes. Furthermore, we identified probable target genes associated with reproduction, the meiotic cell cycle, ubiquitin-dependent protein catabolism, and endosomal transport. In conclusion, our findings suggest that E. invadens Myb proteins regulate stage-specific proteins and a wide array of cellular processes. This study provides a foundation for further exploration of the molecular mechanisms governing encystation and unveils potential targets for therapeutic intervention in amebiasis.

CDNF overexpression prevents motor-cognitive dysfunction by intrastriatal CPP-based delivery system in a Parkinson's disease animal model

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compact (SNpc), and no effective treatment has yet been established to prevent PD. Neurotrophic factors, such as cerebral dopamine neurotrophic factor (CDNF), have shown a neuroprotective effect on dopaminergic neurons. Previously, we developed a cell-penetrating-peptide-based delivery system that includes Asn194Lys mutation in the rabies virus glycoprotein-9R peptide (mRVG9R), which demonstrated a higher delivery rate than the wild-type. In this study, using a mouse PD-like model, we evaluated the intrastriatal mRVG9R-KP-CDNF gene therapy through motor and cognitive tests and brain cell analysis. The mRVG9R-KP-CDNF complex was injected into the striatum on days 0 and 20. To induce the PD-like model, mice were intraperitoneally administered Paraquat (PQ) twice a week for 6 weeks. Our findings demonstrate that mRVG9R-KP-CDNF gene therapy effectively protects brain cells from PQ toxicity and prevents motor and cognitive dysfunction in mice. We propose that the mRVG9R-KP-CDNF complex inhibits astrogliosis and microglia activation, safeguarding dopaminergic neurons and oligodendrocytes from PQ-induced damage. This study presents an efficient CDNF delivery system, protecting neurons and glia in the nigrostriatal pathway from PQ-induced damage, which is known to lead to motor and cognitive dysfunction in neurodegenerative diseases such as PD.

Human-induced metals accumulation in sediments of an industrialized bay of northern Chile. An enrichment and ecological risk assessment based on preindustrial values

Environmental assessment in marine systems is difficult because most of the time their preindustrial characteristics are not available. Four sediment cores taken in Mejillones bay (northern Chile) were used to establish preindustrial metals concentrations, and to assess the environmental status of this industrialized zone. According to historical documents, the beginning of the industrial era start in 1850 CE. Considering this, the preindustrial concentration of some metals was established, by mean of a statistical approach. Most of the metals increase their concentration from the preindustrial to the industrial period. Environmental assessment showed an enrichment of Zr and Cr, a moderately polluted condition, and a low probability of toxic effect on the biological communities. The preindustrial values derived from sediment cores are a good tool to evaluate the environmental condition of Mejillones bay. However new information (backgrounds with a higher spatial representativity, toxicological threshold, and others) it is necessary to improve the environmental assessment of this environment.

Enhanced antitumor activity induced by a DNA vaccine encoding E7 antigen fused to an ERAD-targeting sequence

The endoplasmic reticulum (ER) is a key organelle in cell homeostasis and cell health through antigen presentation to immune cells. Thus, the ER has become a therapeutic target to induce cellular immune responses. We previously reported the antitumor effect of a DNA vaccine that expresses the E7 antigen fused to the cyclooxygenase-2 (COX-2) protein. This inflammation-related enzyme contains a degradation cassette associated with the endoplasmic reticulum-associated degradation (ERAD) pathway. To avoid the use of full-length COX-2 and any risk of adverse effects due to the activity of its catalytic site, we designed new versions of the fusion protein. These new constructs encode the E7 antigen fused to the signal peptide and the ERAD sequence of COX-2 with or without the membrane-binding domain (MBD) as well as deletion of the catalytic site. We evaluated the antigen-specific antitumor effect of these DNA constructs in murine prophylactic and therapeutic cancer models. These assays showed that the ERAD cassette is the minimum sequence in the COX-2 protein that induces an antitumor effect when fused to the E7 antigen with the advantage of eliminating any potential adverse effects from the use of full-length COX-2.

External validation of a prediction model for estimating fat mass in children and adolescents in 19 countries: individual participant data meta-analysis

OBJECTIVE

To evaluate the performance of a UK based prediction model for estimating fat-free mass (and indirectly fat mass) in children and adolescents in non-UK settings.

DESIGN

Individual participant data meta-analysis.

SETTING

19 countries.

PARTICIPANTS

5693 children and adolescents (49.7% boys) aged 4 to 15 years with complete data on the predictors included in the UK based model (weight, height, age, sex, and ethnicity) and on the independently assessed outcome measure (fat-free mass determined by deuterium dilution assessment).

MAIN OUTCOME MEASURES

The outcome of the UK based prediction model was natural log transformed fat-free mass (lnFFM). Predictive performance statistics of R², calibration slope, calibration-in-the-large, and root mean square error were assessed in each of the 19 countries and then pooled through random effects meta-analysis. Calibration plots were also derived for each country, including flexible calibration curves.

RESULTS

The model showed good predictive ability in non-UK populations of children and adolescents, providing R² values of >75% in all countries and >90% in 11 of the 19 countries, and with good calibration (ie, agreement) of observed and predicted values. Root mean square error values (on fat-free mass scale) were <4 kg in 17 of the 19 settings. Pooled values (95% confidence intervals) of R², calibration slope, and calibration-in-the-large were 88.7% (85.9% to 91.4%), 0.98 (0.97 to 1.00), and 0.01 (-0.02 to 0.04), respectively. Heterogeneity was evident in the R² and calibration-in-the-large values across settings, but not in the calibration slope. Model performance did not vary markedly between boys and girls, age, ethnicity, and national income groups. To further improve the accuracy of the predictions, the model equation was recalibrated for the intercept in each setting so that country specific equations are available for future use.

CONCLUSION

The UK based prediction model, which is based on readily available measures, provides predictions of childhood fat-free mass, and hence fat mass, in a range of non-UK settings that explain a large proportion of the variability in observed fat-free mass, and exhibit good calibration performance, especially after recalibration of the intercept for each population. The model demonstrates good generalisability in both low-middle income and high income populations of healthy children and adolescents aged 4-15 years.

Plasmid DNA for Therapeutic Applications in Cancer

Recently, the interest in using nucleic acids for therapeutic applications has been increasing. DNA molecules can be manipulated to express a gene of interest for gene therapy applications or vaccine development. Plasmid DNA can be developed to treat different diseases, such as infections and cancer. In most cancers, the immune system is limited or suppressed, allowing cancer cells to grow. DNA vaccination has demonstrated its capacity to stimulate the immune system to fight against cancer cells. Furthermore, plasmids for cancer gene therapy can direct the expression of proteins with different functions, such as enzymes, toxins, and cytotoxic or proapoptotic proteins, to directly kill cancer cells. The progress and promising results reported in animal models in recent years have led to interesting clinical results. These DNA strategies are expected to be approved for cancer treatment in the near future. This review discusses the main strategies, challenges, and future perspectives of using plasmid DNA for cancer treatment.

An Unusual U2AF2 Inhibits Splicing and Attenuates the Virulence of the Human Protozoan Parasite Entamoeba histolytica

E. histolytica is the etiological agent of intestinal amebiasis and liver abscesses, which still poses public health threat globally. Metronidazole is the drug of choice against amebiasis. However, metronidazole-resistant amoebic clinical isolates and strains have been reported recently, challenging the efforts for amebiasis eradication. In search of alternative treatments, E. histolytica transcriptomes have shown the association of genes involved in RNA metabolism with the virulence of the parasite. Among the upregulated genes in amoebic liver abscesses are the splicing factors EhU2AF2 and a paralog of EhSF3B1. For this reason and because EhU2AF2 contains unusual KH-QUA2 (84KQ) motifs in its lengthened C-terminus domain, here we investigated how the role of EhU2AF2 in pre-mRNA processing impacts the virulence of the parasite. We found that 84KQ is involved in splicing inhibition/intron retention of several virulence and non-virulence-related genes. The 84KQ domain interacts with the same domain of the constitutive splicing factor SF1 (SF1KQ), both in solution and when SF1KQ is bound to branchpoint signal RNA probes. The 84KQ–SF1KQ interaction prevents splicing complex E to A transition, thus inhibiting splicing. Surprisingly, the deletion of the 84KQ domain in EhU2AF2 amoeba transformants increased splicing and enhanced the in vitro and in vivo virulence phenotypes. We conclude that the interaction of the 84KQ and SF1KQ domains, probably involving additional factors, tunes down Entamoeba virulence by favoring intron retention.

Mental health and associated factors among undergraduate students during Covid-19 pandemic in Chile

Introduction

Very few studies have explored mental health among undergraduate students in Chile, especially during the Covid-19 pandemic. International studies have estimated the prevalence of depression at around 28%.

Objectives

i) To determine the prevalence of mental health problems among undergraduate students at a private university in Chile; ii) to explore the associated factors in the context of the Covid-19 pandemic.

Methods

This was a cross-sectional study, approved by the Ethical Committee of the Universidad de los Andes, Santiago Chile (CEC201984). Undergraduate students completed an online survey between August and September 2020. Mental health was assessed using The Depression, Anxiety and Stress Scale-21; suicidality, using the Columbia Suicide Severity Rating Scale; insomnia using the Insomnia Severity Index; and several individual, family, and university factors. Variables regarding the Covid-19 were also assessed, such as personal and family history of covid-19 contagion and death of family members due to Covid-19. A multivariate logistic analysis was performed.

Results

5,037 students responded to the survey. 70.4% were female, mean age, 21 years. 37.1% had depression; 38%, anxiety; 54.6%, stress; 32.6%, insomnia; and 20.5%, suicidal ideation (last month). The most important risk factors were non-medical use of benzodiazepine and fear of contracting Covid-19; the most relevant protective factors were high family functionality and a high sense of university belonging.

Conclusions

This is one of the first studies that has evaluated mental health among undergraduate students in the context of the Covid-19 pandemic in Chile. The findings showed concerning levels of mental health problems.

Disclosure

No significant relationships.

Three-Dimensional 3D Culture Models in Gynecological and Breast Cancer Research

Traditional two-dimensional (2D) monolayer cell cultures have long been the gold standard for cancer biology research. However, their ability to accurately reflect the molecular mechanisms of tumors occurring in vivo is limited. Recent development of three-dimensional (3D) cell culture models facilitate the possibility to better recapitulate several of the biological and molecular characteristics of tumors in vivo, such as cancer cells heterogeneity, cell-extracellular matrix interactions, development of a hypoxic microenvironment, signaling pathway activities depending on contacts with extracellular matrix, differential growth kinetics, more accurate drugs response, and specific gene expression and epigenetic patterns. In this review, we discuss the utilization of different types of 3D culture models including spheroids, organotypic models and patient-derived organoids in gynecologic cancers research, as well as its potential applications in oncological research mainly for screening drugs with major physiological and clinical relevance. Moreover, microRNAs regulation of cancer hallmarks in 3D cell cultures from different types of cancers is discussed.

A Three-Dimensional Culture-Based Assay to Detect Early Stages of Vasculogenic Mimicry in Ovarian Cancer Cells

Vasculogenic mimicry is a cellular mechanism in which tumor cells grow and align forming complex three-dimensional (3D) channel-like structures in a hypoxic microenvironment. This phenomenon represents a novel oxygen, nutrient, and blood supply, in a similar way as occurs in classic angiogenesis. Vasculogenic mimicry has been described in numerous clinical tumors including breast, prostate, lung, and ovarian cancers where it is associated with poor prognosis; thus, it is considered as a hallmark of highly aggressive and metastatic tumors. Here, we describe a simple method to model the in vitro formation of three-dimensional cellular networks over Matrigel in SKOV3 ovarian cancer cells representing the early stages of vasculogenic mimicry.

Clinical characteristics and severity of COVID-19 among Mexican adults

Introduction

Obesity, diabetes, hypertension and age have been pointed at as factors that influence on the progression of COVID-19; however, evidence for other conditions is inconclusive.

Objective

To identify which clinical characteristics are related to COVID-19 severity and to determine whether age acts a modifier of the relationship between cardio-metabolic comorbidities (CMC) and COVID-19 progression.

Method

Data on ≥ 20-year-old confirmed cases (n = 159,017) were analyzed. Hospitalization, development of pneumonia, intubation requirement, intensive care unit admission and death were the dependent variables in Poisson regression models estimation, whereas the interaction between age and different CMCs were the independent variables.

Results

Having CMCs, as well as other comorbidities, was directly related to COVID-19 progression, whereas chronic obstructive pulmonary disease was only related to an increase in the risk of dying. The risk for COVID-19 severity was lower as age was more advanced. Asthma and smoking were not risk factors for the progression of COVID-19.

Conclusion

In the Mexican population, the risk of COVID-19 progression associated with comorbidities was higher in young adults.

In silico analysis of putative metal response elements (MREs) in the zinc-responsive genes from Trichomonas vaginalis and the identification of novel palindromic MRE-like motif

Zinc is an essential micronutrient that plays an important role as a co-factor to several proteins, including zinc-responsive transcription factors. Trichomonas vaginalis is able to survive in the presence of high zinc concentrations in the male urogenital tract. Several genes in T. vaginalis have been shown to respond to changes in zinc concentrations, however, the zinc-dependent mechanism remains undetermined. Recently, we identified in T. vaginalis the zinc finger protein, TvZNF1, which is an ortholog of the mammal metal transcription factor (MTF1). We searched for several of the zinc-responsive genes in T. vaginalis to determine whether if they contain metal response elements (MRE), cis-acting DNA elements that specifically bind MTF1. Six highly conserved over-represented sequence motifs (TvMREs), which share similarity with other eukaryotic MREs, were identified in the zinc-responsive genes in T. vaginalis. We also demonstrated that some of the TvMREs assemble as divalent complexes either as two closely spaced TvMREs or as two overlapping TvMREs forming a palindromic-like sequence: TGCC(N3)GGCA. Electrophoretic mobility shift assays were used to detect the zinc-dependent binding of TvZNF1 and nuclear proteins from T. vaginalis to this specific palindromic motif. Our results support a novel mechanism used by T. vaginalis for the transcriptional regulation of associated zinc-responsive genes through a MTF1/MRE-like system.

The metabolic pathway of sphingolipids biosynthesis and signaling in Entamoeba histolytica

Sphingolipids (SLs) synthesis involves a complex metabolic pathway occurring between the endoplasmic reticulum (ER) and Golgi apparatus, generating ceramide synthesis and complex lipids, respectively. Here we show that E. histolytica, apparently lacking cellular organelles (ER and Golgi apparatus), synthesizes a wide variety of sphingolipid subspecies, being particularly abundant those of long-chain fatty acids. In silico analysis showed five putative genes coding for ceramide synthases (CerS), all of them coding for proteins containing the TLC domain, a region conserved in CerS of multiple organisms. These genes are abundantly expressed in different growth phases. Silencing and overexpression of CerS C4M4U4 (the closest homolog of human CerS 2 and 3) demonstrated its involvement in the synthesis of ceramide. Additionally, we identify C4M4U4, SMS2 and PKC (α, βII) proteins and their subcellular localization of E. histolytica, suggesting that these subcellular compartments might be involved in the biosynthesis and signaling pathway of sphingolipids, and evidencing different sphingolipid synthesis pathways in Entamoeba.

Production and characterization of monoclonal antibodies against the DNA binding domain of the RE1-silencing transcription factor

The use of monoclonal antibodies for the detection of cellular biomarkers during carcinogenesis provides new strategies for cancer diagnosis or prognosis in patients. Loss of the Restrictive Element 1-Silencing Transcription (REST) factor has been observed in previous molecular and immunological approaches in aggressive breast cancer, small cell lung cancer, liver carcinoma, and colo-rectal cancer; however, for clinic diagnosis, monoclonal antibodies for REST recognition are unavailable. The goal of this work was to design, produce and characterize monoclonal antibodies against the REST DNA binding damain (DBD) that would be suitable for immunoassays. We searched for conserved domains, and immunogenic and antigenic sites in the REST structure via in silico analysis. For mice immunization, we used a recombinant REST DBD purified by affinity chromatography, and then Hybridomas were generated by mouse spleen fusion with myeloma cells. Finally, for monoclonal antibody characterization, we performed enzyme-linked immunosorbent (ELISA), western blot, dot blot, immunocytochemistry (ICC) and immunoprecipitation assays. Results showed that the DBD is conserved in REST isoforms and contains immunogenic and antigenic sites. We generated three clones producing monoclonal antibodies against REST DBD, one of them specifically recognized native REST and was suitable for ICC in samples from patients.

The mRVG-9R peptide as a potential therapeutic vector to the central nervous system cells

Our research group has developed a cell-penetrating peptide-based delivery system that includes the Asn194Lys mutation in the rabies virus glycoprotein-9R peptide (mRVG-9R). This system has the capacity to deliver DNA in astrocytes and SH-SY5Y cells. The aim of this study was to evaluate the ability of the mRVG-9R peptide to deliver DNA molecules to murine brain cells. The mRVG-9R peptide, a karyophilic peptide (KP) and a plasmid encoding green fluorescent protein (GFP) were bound by electrostatic charges to form the mRVG-9R complex. mRVG-9R complex was injected into the cerebral cortex, striatum and hippocampus of C57BL/6 mice by stereotactic surgery. After 2, 4, and 20 days, the animals were sacrificed and their brains were prepared for quantitative reverse-transcription polymerase chain reaction and histological analysis. We detected the GFP expression in neurons and glial cells in the cerebral cortex, striatum, and hippocampus of the murine brain. The results suggest that the mRVG-9R peptide has the ability to deliver DNA molecules to murine brain cells. Also, the expression of the reporter gene is maintained at least up to 20 days after injection in neurons, astrocytes, oligodendrocytes, and microglia cells. Thus, the in vivo transfection ability of the mRVG-9R peptide, makes it a promising candidate as a therapeutic gene delivery vector to the central nervous system cells.

De novo synthesis of sphingolipids plays an important role during in vitro encystment of Entamoeba invadens

Entamoeba invadens is a protozoan, which causes multiple damages in reptiles and is considered a prototype for the study of the Entamoeba encystment in vitro. Here we report for the first time the role of the de novo synthesis pathway of sphingolipids during the encystment of E. invadens. In silico analysis showed that this parasite has six putative genes coding for ceramide synthases (CerS), all of them coding for proteins containing the Lag1p motif, a region conserved in the ceramide synthases of multiple organisms, suggesting that they might be bona fide CerS. The six genes of E. invadens are differentially expressed at different time intervals in both stages trophozoite and cyst, based on the results obtained through qRT-PCR assays, the genes involved in the synthesis of sphingolipids with long-chain fatty acids CerS 2,3,4 (EIN_046610, EIN_097030, EIN_130350) have maximum points of relative expression in both stages of the E. invadens life cycle, which strongly suggest that the signaling exerted from the synthesis pathway of sphingolipids is essential for the encystment of E. invadens, since the generation of the more abundant sphingomyelin (SM) subspecies with long-chain fatty acids are fundamental for the parasite to reach its conversion from trophozoite to cyst. When myriocin was used as an inhibitor of serine palmitoyl CoA transferase (SPT), first enzyme in the de novo biosynthesis of sphingolipids, the trophozoites of E. invadens were unable to reach the encystment. Since the effect of myriocin was reversed with exogenous d-erythrosphingosine (DHS), it was demonstrated that the inhibition was specific and it was confirmed that the synthesis of sphingolipids play an essential role during the encystment process of E. invadens.

Telomeric Repeat-Binding Factor Homologs in Entamoeba histolytica: New Clues for Telomeric Research

Telomeric Repeat Binding Factors (TRFs) are architectural nuclear proteins with critical roles in telomere-length regulation, chromosome end protection and, fusion prevention, DNA damage detection, and senescence regulation. Entamoeba histolytica, the parasite responsible of human amoebiasis, harbors three homologs of human TRFs, based on sequence similarities to their Myb DNA binding domain. These proteins were dubbed EhTRF-like I, II and III. In this work, we revealed that EhTRF-like I and II share similarity with human TRF1, while EhTRF-like III shares similarity with human TRF2 by in silico approach. The analysis of ehtrf-like genes showed they are expressed differentially under basal culture conditions. We also studied the cellular localization of EhTRF-like I and III proteins using subcellular fractionation and western blot assays. EhTRF-like I and III proteins were enriched in the nuclear fraction, but they were also present in the cytoplasm. Indirect immunofluorescence showed that these proteins were located at the nuclear periphery co-localizing with Lamin B1 and trimethylated H4K20, which is a characteristic mark of heterochromatic regions and telomeres. We found by transmission electron microscopy that EhTRF-like III was located in regions of more condensed chromatin. Finally, EMSA assays showed that EhTRF-like III forms specific DNA-protein complexes with telomeric related sequences. Our data suggested that EhTRF-like proteins play a role in the maintenance of the chromosome ends in this parasite.

Postsplicing-Derived Full-Length Intron Circles in the Protozoan Parasite Entamoeba histolytica

Noncoding circular RNAs are widespread in the tree of life. Particularly, intron-containing circular RNAs which apparently upregulate their parental gene expression. Entamoeba histolytica, the causative agent of dysentery and liver abscesses in humans, codes for several noncoding RNAs, including circular ribosomal RNAs, but no intron containing circular RNAs have been described to date. Divergent RT-PCR and diverse molecular approaches, allowed us to detect bona fide full-length intronic circular RNA (flicRNA) molecules. Self-splicing reactions, RNA polymerase II inhibition with Actinomycin D, and second step of splicing-inhibition with boric acid showed that the production of flicRX13 (one of the flicRNAs found in this work, and our test model) depends on mRNA synthesis and pre-mRNA processing instead of self-splicing. To explore the cues and factors involved in flicRX13 biogenesis in vivo, splicing assays were carried out in amoeba transformants where splicing factors and Dbr1 (intron lariat debranching enzyme 1) were silenced or overexpressed, or where Rabx13 wild-type and mutant 5'ss (splice site) and branch site minigene constructs were overexpressed. Whereas SF1 (splicing factor 1) is not involved, the U2 auxiliary splicing factor, Dbr1, and the GU-rich 5'ss are involved in postsplicing flicRX13 biogenesis, probably by Dbr1 stalling, in a similar fashion to the formation of ciRNAs (circular intronic RNAs), but with distinctive 5'-3'ss ligation points. Different from the reported functions of ciRNAs, the 5'ss GU-rich element of flicRX13 possibly interacts with transcription machinery to silence its own gene in cis. Furthermore, introns of E. histolytica virulence-related genes are also processed as flicRNAs.

Unexplored Molecular Features of the Entamoeba histolytica RNA Lariat Debranching Enzyme Dbr1 Expression Profile

The RNA lariat debranching enzyme (Dbr1) has different functions in RNA metabolism, such as hydrolyzing the 2′-5′ linkage in intron lariats, positively influencing Ty1 and HIV-1 retrotransposition, and modulating snRNP recycling during splicing reactions. It seems that Dbr1 is one of the major players in RNA turnover. It is remarkable that of all the studies carried out to date with Dbr1, to our knowledge, none of them have evaluated the expression profile of the endogenous Dbr1 gene. In this work, we describe, for the first time, that Entamoeba histolytica EhDbr1 mRNA has a very short half-life (less than 30 min) and encodes a very stable protein that is present until trophozoite cultures die. We also show that the EhDbr1 protein is present in the nuclear periphery on the cytoplasmic basal side, contrary to the localization of human Dbr1. Comparing these results with previous hypotheses and with results from different organisms suggests that Dbr1 gene expression is finely tuned and conserved across eukaryotes. Experiments describing the aspects of Dbr1 gene expression and Dbr1 mRNA turnover as well as other functions of the protein need to be performed. Particularly, a special emphasis is needed on the protozoan parasite E. histolytica, the causative agent of amoebiasis, since even though it is a unicellular organism, it is an intron-rich eukaryote whose intron lariats seem to be open to avoid intron lariat accumulation and to process them in non-coding RNAs that might be involved in its virulence.

The Entamoeba histolytica Syf1 Homolog Is Involved in the Splicing of AG-Dependent and AG-Independent Transcripts

Syf1 is a tetratricopeptide repeat (TPR) protein implicated in transcription elongation, spliceosome conformation, mRNA nuclear-cytoplasmic export and transcription-coupled DNA repair. Recently, we identified the spliceosomal components of the human parasite Entamoeba histolytica, among them is EhSyf. Molecular predictions confirmed that EhSyf contains 15 type 1 TPR tandem α-antiparallel array motifs. Amoeba transformants carrying plasmids overexpressing HA-tagged or EhSyf silencing plasmids were established to monitor the impact of EhSyf on the splicing of several test Entamoeba transcripts. EhSyf Entamoeba transformants efficiently silenced or overexpressed the proteins in the nucleus. The overexpression or absence of EhSyf notably enhanced or blocked splicing of transcripts irrespective of the strength of their 3′ splice site. Finally, the absence of EhSyf negatively affected the transcription of an intron-less transcript. Altogether our data suggest that EhSyf is a bona fide Syf1 ortholog involved in transcription and splicing.

The Entamoeba histolytica TBP and TRF1 transcription factors are GAAC-box binding proteins, which display differential gene expression under different stress stimuli and during the interaction with mammalian cells

BACKGROUND

Entamoeba histolytica is the protozoan parasite responsible for human amebiasis. It causes up to 100,000 deaths worldwide each year. This parasite has two closely related basal transcription factors, the TATA-box binding protein (EhTBP) and the TBP-related factor 1 (EhTRF1). TBP binds to the canonical TATTTAAA-box, as well as to different TATA variants. TRF1 also binds to the TATTTAAA-box. However, their binding capacity to diverse core promoter elements, including the GAAC-element, and their role in gene regulation in this parasite remains unknown.

METHODS

EMSA experiments were performed to determine the binding capacity of recombinant TBP and TRF1 to TATA variants, GAAC and GAAC-like boxes. For the functional analysis under different stress stimuli (e.g. growth curve, serum depletion, heat-shock, and UV-irradiation) and during the interaction with mammalian cells (erythrocytes, MDCK cell monolayers, and hepatocytes of hamsters), RT-qPCR, and gene knockdown were performed.

RESULTS

Both transcription factors bound to the different TATA variants tested, as well as to the GAAC-boxes, suggesting that they are GAAC-box-binding proteins. The K _D values determined for TBP and TRF1 for the different TATA variants and GAAC-box were in the range of 10^-12 M to 10^-11 M. During the death phase of growth or in serum depletion, Ehtbp mRNA levels significantly increased, whereas the mRNA level of Ehtrf1 did not change under these conditions. Ehtrf1 gene expression was negatively regulated by UV-irradiation and heat-shock stress, with no changes in Ehtbp gene expression. Moreover, Ehtrf1 gene also showed a negative regulation during erythrophagocytosis, liver abscess formation, and a transient expression level increase at the initial phase of MDCK cell destruction. Finally, the Ehtbp gene knockdown displayed a drastic decrease in the efficiency of erythrophagocytosis in G3 trophozoites.

CONCLUSIONS

To our knowledge, this study reveals that these basal transcription factors are able to bind multiple core promoter elements. However, their immediate change in gene expression level in response to different stimuli, as well as during the interaction with mammalian cells, and the diminishing of erythrophagocytosis by silencing the Ehtbp gene indicate the different physiological roles of these transcription factors in E. histolytica.

Identification of repressive and active epigenetic marks and nuclear bodies in Entamoeba histolytica

Background

In human hosts, Entamoeba histolytica cysts can develop into trophozoites, suggesting that the life cycle of this parasite are regulated by changes in gene expression. To date, some evidence has suggested that epigenetic mechanisms such as DNA methylation and histone modification are involved in the regulation of gene expression in Entamoeba. Some post–translational modifications (PTMs) at the N-terminus of E. histolytica’s histones have been reported experimentally, including tri-methylation in the lysine 4 of histone H3 (H3K4me3) and dimethylation in the lysine 27 of histone H3 (H3K27me2), dimethylation of arginine 3 (H4R3me2) and the indirect acetylation of histone H4 in the N-terminal region. However, it is not known which residues of histone H4 are subject to acetylation and/or methylation or where in the nucleus these epigenetic marks are located.

Methods

Histones from trophozoites of E. histolytica were obtained and analyzed by LC-MS/MS. WB assays were performed using antibodies against epigenetic marks (acetylated lysines and methylated arginines). Immunofluorescence assays (IFA) were carried out to determine the distribution of PTMs and the localization of DNA methylation as a heterochromatin marker. Nuclear bodies such as the nucleolus were identified by using antibodies against fibrillarin and nucleolin and speckles by using anti-PRP6 antibody.

Results

Some new PTMs in histone H4 of E. histolytica, such as the acetylation of lysines 5, 8, 12 and 16 and the monomethylation of arginine 3, were identified by WB. IFA demonstrated that some marks are associated with transcriptional activity (such as acetylation and/or methylation) and that these marks are distributed throughout the E. histolytica nucleus. Staining with antibodies against anti-pan-acetylated lysine H4 histone and 5-methyl cytosine showed that the activation and transcriptional repression marks converge. Additionally, two nuclear bodies, the nucleolus and speckles, were identified in this parasite.

Conclusions

This study provides the first evidence that the nucleus of E. histolytica is not compartmentalized and contains two nuclear bodies, the nucleolus and speckles, the latter of which was not identified previously. The challenge is now to understand how these epigenetic marks and nuclear bodies work together to regulate gene expression in E. histolytica.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1298-7) contains supplementary material, which is available to authorized users.

Trace metal variability in coastal waters of San Jorge Bay, Antofagasta, Chile: An environmental evaluation and statistical approach to propose local background levels

Between 2008 and 2011, twelve metals from 384 coastal waters samples from San Jorge Bay (Antofagasta, northern Chile) were collected and analyzed. The goal was to evaluate the quality of the bay's water bodies according to the current Chilean Quality Guideline and to establish background levels for these metals. The result suggests that the coastal waters of San Jorge Bay are of very good quality suitable for recreational activities involving human body contact. The natural background thresholds established for this bay were significantly lower than primary and secondary water quality guidelines. The distribution of Cu, Zn and Pb, along the bay's coastline provides evidence of the effects of industrial activity. Both situations suggest that the threshold indicated in the environmental guidelines of the Chilean legislation may be overestimated and do not represent pollution-free environments.

Accuracy of body mass index for age to diagnose obesity in Mexican schoolchildren

OBJECTIVE

To compare the accuracy of three BMI-forage references (World Health Organization reference, WHO; the updated International Obesity Task Force reference, IOTF; and Centers for Disease Control and Prevention (CDC) growth charts) to diagnose obesity in Mexican children.

METHODS

A convenience sample of Mexican schoolchildren (n = 218) was assessed. The gold standard was the percentage of body fat estimated by deuterium dilution technique. Sensitivity and specificity of the classical cutoff point of BMI-for-age to identify obesity (i.e. > 2.00 standard deviation, SD) were estimated. The accuracy (i.e. area under the curve, AUC) of three BMI-for-age references for the diagnosis of obesity was estimated with the receiver operating characteristic (ROC) curves method. The optimal cutoff point (OCP) was determined.

RESULTS

The cutoff points to identify obesity had low (WHO reference: 57.6%, CDC: 53.5%) to very low (IOTF reference: 40.4%) sensitivities, but adequate specificities (91.6%, 95.0%, and, 97.5%, respectively). The AUC of the three references were adequate (0.89). For the IOTF reference, the AUC was lower among the older children. The OCP for the CDC reference (1.24 SD) was lower than the OCP for WHO (1.53 SD) and IOTF charts (1.47 SD).

CONCLUSIONS

The classical cutoff point for obesity has low sensitivity--especially for the IOTF reference. The accuracy of the three references was similar. However, to obtain comparable diagnosis of obesity different cutoff points should be used depending of the reference.

PTB binds to the 3' untranslated region of the human astrovirus type 8: a possible role in viral replication

The 3′ untranslated region (3′UTR) of human astroviruses (HAstV) consists of two hairpin structures (helix I and II) joined by a linker harboring a conserved PTB/hnRNP1 binding site. The identification and characterization of cellular proteins that interact with the 3′UTR of HAstV-8 virus will help to uncover cellular requirements for viral functions. To this end, mobility shift assays and UV cross-linking were performed with uninfected and HAstV-8-infected cell extracts and HAstV-8 3′UTR probes. Two RNA-protein complexes (CI and CII) were recruited into the 3′UTR. Complex CII formation was compromised with cold homologous RNA, and seven proteins of 35, 40, 45, 50, 52, 57/60 and 75 kDa were cross-linked to the 3′UTR. Supermobility shift assays indicated that PTB/hnRNP1 is part of this complex, and 3′UTR-crosslinked PTB/hnRNP1 was immunoprecipitated from HAstV-8 infected cell-membrane extracts. Also, immunofluorescence analyses revealed that PTB/hnRNP1 is distributed in the nucleus and cytoplasm of uninfected cells, but it is mainly localized perinuclearly in the cytoplasm of HAstV-8 infected cells. Furthermore, the minimal 3′UTR sequences recognized by recombinant PTB are those conforming helix I, and an intact PTB/hnRNP1-binding site. Finally, small interfering RNA-mediated PTB/hnRNP1 silencing reduced synthesis viral genome and virus yield in CaCo2 cells, suggesting that PTB/hnRNP1 is required for HAstV replication. In conclusion, PTB/hnRNP1 binds to the 3′UTR HAstV-8 and is required or participates in viral replication.

Proteomic analysis of Entamoeba histolytica in vivo assembled pre-mRNA splicing complexes

The genome of the human intestinal parasite Entamoeba histolytica contains nearly 3000 introns and bioinformatic predictions indicate that major and minor spliceosomes occur in Entamoeba. However, except for the U2-, U4-, U5- and U6 snRNAs, no other splicing factor has been cloned and characterized. Here, we HA-tagged cloned the snRNP component U1A and assessed its expression and nuclear localization. Because the snRNP-free U1A form interacts with polyadenylate-binding protein, HA-U1A immunoprecipitates could identify early and late splicing complexes. Avoiding Entamoeba's endonucleases and ensuring the precipitation of RNA-binding proteins, parasite cultures were UV cross-linked prior to nuclear fraction immunoprecipitations with HA antibodies, and precipitates were subjected to tandem mass spectrometry (MS/MS) analyses. To discriminate their nuclear roles (chromatin-, co-transcriptional-, splicing-related), MS/MS analyses were carried out with proteins eluted with MS2-GST-sepharose from nuclear extracts of an MS2 aptamer-tagged Rabx13 intron amoeba transformant. Thus, we probed thirty-six Entamoeba proteins corresponding to 32 cognate splicing-specific factors, including 13 DExH/D helicases required for all stages of splicing, and 12 different splicing-related helicases were identified also. Furthermore 50 additional proteins, possibly involved in co-transcriptional processes were identified, revealing the complexity of co-transcriptional splicing in Entamoeba. Some of these later factors were not previously found in splicing complex analyses.

BIOLOGICAL SIGNIFICANCE

Numerous facts about the splicing of the nearly 3000 introns of the Entamoeba genome have not been unraveled, particularly the splicing factors and their activities. Considering that many of such introns are located in metabolic genes, the knowledge of the splicing cues has the potential to be used to attack or control the parasite. We have found numerous new splicing-related factors which could have therapeutic benefit. We also detected all the DExH/A RNA helicases involved in splicing and splicing proofreading control. Still, Entamoeba is very inefficient in splicing fidelity, thus we may have found a possible model system to study these processes.

Frequency of family meals and childhood overweight: a systematic review

Energy balance is influenced by understudied genetic, social and other environmental factors. The frequency of family meals (FFM) may be one of these factors since it is associated with a healthier dietary pattern in children and adolescents. The objective of this review is to evaluate the scientific evidence on the association between FFM and the risk of childhood and adolescent overweight. The electronic literature search identified 394 articles published during 2005-2012. Of these, 15 studies gave precise information of the studied association, of which four were longitudinal. We found great variability regarding the measurement of FFM. Six out of 11 cross-sectional studies and 1 out of 4 longitudinal studies found statistically significant inverse associations between FFM and being overweight, mainly in children, with odds ratios ranging from 0.11 to 0.93. Of those, only one adjusted for all the potential confounding factors considering socio-demographic, physical activity- and diet-related variables. Therefore, this review found inconsistent and weak evidence of an inverse association between FFM and risk of childhood overweight. In conclusion, further research is needed to establish whether family meals have an effect on childhood overweight. These studies ideally should have longitudinal or experimental designs, a clear and standardized definition of the exposure under study, a measure of the exposure based on direct observation or validated questionnaires and an adequate adjustment for potential confounders.

Gonadotropin-releasing hormone receptor activates GTPase RhoA and inhibits cell invasion in the breast cancer cell line MDA-MB-231

Background

Gonadotropin-releasing hormone (GnRH) and its receptor (GnRHR) are both expressed by a number of malignant tumors, including those of the breast. In the latter, both behave as potent inhibitors of invasion. Nevertheless, the signaling pathways whereby the activated GnRH/GnRHR system exerts this effect have not been clearly established. In this study, we provide experimental evidence that describes components of the mechanism(s) whereby GnRH inhibits breast cancer cell invasion.

Methods

Actin polymerization and substrate adhesion was measured in the highly invasive cell line, MDA-MB-231 transiently expressing the wild-type or mutant DesK191 GnRHR by fluorometry, flow cytometric analysis, and confocal microscopy, in the absence or presence of GnRH agonist. The effect of RhoA-GTP on stress fiber formation and focal adhesion assembly was measured in MDA-MB-231 cells co-expressing the GnRHRs and the GAP domain of human p190Rho GAP-A or the dominant negative mutant GAP-Y1284D. Cell invasion was determined by the transwell migration assay.

Results

Agonist-stimulated activation of the wild-type GnRHR and the highly plasma membrane expressed mutant GnRHR-DesK191 transiently transfected to MDA-MB-231 cells, favored F-actin polymerization and substrate adhesion. Confocal imaging allowed detection of an association between F-actin levels and the increase in stress fibers promoted by exposure to GnRH. Pull-down assays showed that the effects observed on actin cytoskeleton resulted from GnRH-stimulated activation of RhoA GTPase. Activation of this small G protein favored the marked increase in both cell adhesion to Collagen-I and number of focal adhesion complexes leading to inhibition of the invasion capacity of MDA-MB-231 cells as disclosed by assays in Transwell Chambers.

Conclusions

We here show that GnRH inhibits invasion of highly invasive breast cancer-derived MDA-MB-231 cells. This effect is mediated through an increase in substrate adhesion promoted by activation of RhoA GTPase and formation of stress fibers and focal adhesions. These observations offer new insights into the molecular mechanisms whereby activation of overexpressed GnRHRs affects cell invasion potential of this malignant cell line, and provide opportunities for designing mechanism-based adjuvant therapies for breast cancer.

Expression of claudins -2 and -4 and cingulin is coordinated with the start of stratification and differentiation in corneal epithelial cells: retinoic acid reversibly disrupts epithelial barrier

Although tight junctions (TJ) have been extensively studied in simple epithelial cells, it is still unknown whether their organization is coupled to cell differentiation in stratified epithelia. We studied the expression of TJ in RCE1(5T5) cells, an in vitro model which mimics the sequential steps of rabbit corneal epithelial differentiation. RCE1(5T5) cells expressed TJ components which were assembled once cells constituted differentiated epithelia, as suggested by the increase of transepithelial electrical resistance (TER) which followed a similar kinetic to the expression of the early differentiation marker Pax-6. TJ were functional as indicated by the establishment of an epithelial barrier nonpermeable to ruthenium red or a biotin tracer. In immunostaining experiments, TJ were located at the superficial cells from the suprabasal layers; Western blot and RT-PCR suggested that TJ were composed of claudins (cldn) -1, -2, -4, cingulin (cgn), occludin (ocln) and ZO-1. Semi-quantitative RT-PCR and TER measurements showed that TJ became organized when cells began to form a 3–5 layers stratified epithelium; TER increased once cells reached confluence, with a time course comparable to the raise in the expression of cgn, cldn-2 and -4. Nevertheless, cldn-1, -2, ZO-1 and ocln were present in the cells from the beginning of cultivation, suggesting that TER increases mainly depend on TJ assembly. While EGF increased epithelial barrier strength, retinoic acid disrupted it, increasing paracellular flux about 2-fold; this effect was concentration dependent and completely reversible. Our results suggest that TJ assembly is tightly linked to the expression of corneal epithelial terminal phenotype.

Binding of hnRNP H and U2AF65 to respective G-codes and a poly-uridine tract collaborate in the N50-5'ss selection of the REST N exon in H69 cells

The splicing of the N exon in the pre-mRNA coding for the RE1-silencing transcription factor (REST) results in a truncated protein that modifies the expression pattern of some of its target genes. A weak 3'ss, three alternative 5'ss (N4-, N50-, and N62-5'ss) and a variety of putative target sites for splicing regulatory proteins are found around the N exon; two GGGG codes (G2-G3) and a poly-Uridine tract (N-PU) are found in front of the N50-5'ss. In this work we analyzed some of the regulatory factors and elements involved in the preferred selection of the N50-5'ss (N50 activation) in the small cell lung cancer cell line H69. Wild type and mutant N exon/β-globin minigenes recapitulated N50 exon splicing in H69 cells, and showed that the N-PU and the G2-G3 elements are required for N50 exon splicing. Biochemical and knockdown experiments identified these elements as U2AF65 and hnRNP H targets, respectively, and that they are also required for N50 exon activation. Compared to normal MRC5 cells, and in keeping with N50 exon activation, U2AF65, hnRNP H and other splicing factors were highly expressed in H69 cells. CLIP experiments revealed that hnRNP H RNA-binding occurs first and is a prerequisite for U2AF65 RNA binding, and EMSA and CLIP experiments suggest that U2AF65-RNA recognition displaces hnRNP H and helps to recruit other splicing factors (at least U1 70K) to the N50-5'ss. Our results evidenced novel hnRNP H and U2AF65 functions: respectively, U2AF65-recruiting to a 5'ss in humans and the hnRNP H-displacing function from two juxtaposed GGGG codes.

Health status of red mullets from polluted areas of the Spanish Mediterranean coast, with special reference to Portmán (SE Spain)

A suite of general physiological indicators and hepatic biomarker responses were determined in red mullet (Mullus barbatus) from priority pollution areas of W Mediterranean Sea, including the highly metal polluted area of Portmán (Cartagena, SE Spain). Concentrations of metals and persistent organic pollutants in fish muscle tissue and sediment samples were also analysed. Our results showed that fish from Portmán accumulated the highest concentrations of mercury, lead and arsenic and also of some polycyclic aromatic hydrocarbons and polychlorinated biphenyls congeners. In addition, they had significantly lower condition factor, muscle lipid content and gonadosomatic index, as well as the lowest levels of DNA integrity and the highest ethoxyresorufin-O-deethylase (EROD) activity in liver of the areas investigated. Contaminant body burden in fish only partly corresponded to chemical characteristics of the sediments in the areas in which they were collected. Our findings indicate that red mullets from Portmán had suboptimal health status that warrant further study.

The association of sexual orientation with self-rated health, and cigarette and alcohol use in Mexican adolescents and youths

Evidence of health inequities associated with sexual orientation has been gathered for industrialized countries. The situation for lesbians, gay males, and bisexuals (LGB) from middle- or low-income countries may be worse than those in industrialized nations. Here, we analyze the relationship of sexual orientation with self-rated health and cigarette and alcohol use among a representative sample of Mexican adolescents and youths between the ages of 12 and 29 years, in order to explore whether this association is mediated by discrimination and violence. Three dimensions of sexual orientation (affective attraction, sexual behavior, and identity) were assessed. The outcomes were self-rated health and cigarette and alcohol use. Compared to heterosexuals, LGB youths more frequently smoked >or=6 cigarettes per day, reported having experienced family violence, having crimes perpetrated against them, and having experienced violations of their rights. Among males, gays and bisexuals exhibited a higher risk of poor health than heterosexuals. Compared to heterosexual women, lesbians and bisexual women were more likely to consume alcohol. Many differences in self-rated health and substance use according to sexual orientation were explained by having experienced discrimination and violence. We concluded that lesbian and bisexual females have a higher prevalence of cigarette and alcohol use. It is necessary to develop policies and programs aimed at the reduction of substance abuse among LGB youths (focusing on females who engage in sexual contact with persons of the same gender) and to work against discrimination and violence experienced by LGB people, particularly against non-heterosexual males.

Evaluation of three-year monitoring with biomarkers in fish following the Prestige oil spill (N Spain)

A previous study using a suite of hepatic enzymatic biomarker in two demersal fish species (Lepidorhombus boscii and Callionymus lyra) indicated exposure of the fish to the hydrocarbons in the oil spilled by the Prestige five months after the accident. The main objective of this follow-up study is to determine whether the same biomarkers in both fish species show any significant variations in responses over the years following the Prestige oil spill. Detoxification and antioxidant enzyme measurements--of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), glutathione reductase (GR) and catalase (CAT)--were taken from immature specimens. The results show significant lowering of biomarker activity two and three-years after the oil spill, indicating a decreasing level of exposure of the fish to residual hydrocarbons associated with the spillage (p < 0.01) and a recovery to baseline levels existing before the accident. Overall, spatial biomarker patterns over time are in agreement with the oil slick trajectories and the spatial distribution of tar aggregates found on the bottom shelf after the accident. The results also indicate that the Prestige oil spill had an impact on sublethal responses in fish not only in inshore areas, but also in offshore areas along the middle/outer northern Iberian shelf. In both species, EROD activity was found to be the most discriminating biomarker.

Histopathologic study of long-bone growth plates confirms the basset hound as an osteochondrodysplastic breed

Osteochondrodysplasias are caused by abnormal development and growth of cartilage and bone. These abnormalities have been reported in both humans and animals with dwarfism. The basset hound is considered a breed with a disproportionate prevalence of dwarfism, the cause of which is unknown. To determine the type of osteochondrodysplasia in this breed, we analyzed histologically the growth plates from the long bones of a basset hound and a Doberman pinscher, both 2 mo old. Tissue was fixed in 4% paraformaldehyde, embedded in paraffin, sectioned at 5 microm, stained with hematoxylin and eosin, and analyzed by light microscopy. Our results suggest that by this method the basset hound can be defined only as a breed having osteochondrodysplasia due to a primary cartilage problem in the growth plate.

Monitoring biomarkers in fish (Lepidorhombus boscii and Callionymus lyra) from the northern Iberian shelf after the Prestige oil spill

Hepatic biomarker responses were measured in two demersal fish species (Lepidorhombus boscii and Callionymus lyra) from the northern Iberian shelf associated with the massive Prestige oil spill (POS), five months after the accident. The biomarkers selected were 7-ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), glutathione reductase (GR), catalase (CAT), and DNA integrity. Interspecies differences and spatial variations in biomarker responses were observed along the shelf. GST, GR and CAT activities were significantly elevated in L. boscii in the most oil impacted area (Finisterre) and positively correlated (p<0.05) with POS tar aggregate densities. The lack of previous data from the area together with the existence of chronic background pollution of the shelf implies that the observed biomarker responses cannot be solely attributed to the petroleum hydrocarbon components of the spilled oil. This first biological effect assessment showed that L. boscii is a potentially suitable target species to be used in future biomonitoring programmes along the northern Iberian shelf.

Circadian oscillations of RPCH gene expression in the eyestalk of the crayfish Cherax quadricarinatus

The RPCH and beta-actin cDNAs from the crayfish Cherax quadricarinatus were amplified, cloned and sequenced. The primary structure sequences of these cDNAs were compared to other members of the AKH/RPCH family. Fluctuations in the amount of the C. quadricarinatus RPCH and beta-actin mRNAs, as cDNAs, were quantified every 3h by RT-PCR. Single cosinor analysis supports the notion of beta-actin and RPCH mRNA circadian behavior in animals subjected to 12h:12h light/dark regimes. In constant darkness RPCH mRNA concentration changes to ultradian cycles.

Distribution and enrichment evaluation of heavy metals in Mejillones Bay (23 degrees S), Northern Chile: geochemical and statistical approach

A suite of 36 surface sediment samples, taken between 10 and 100 m water depth in Mejillones Bay (Northern Chile), were analyzed for mineralogy, grain size, total organic carbon, Al, and heavy metal content (Cd, Zn, Ni, Mn, V, Mo). Quartz and feldspars were the main lithogenic minerals and carbonate the predominant biogenic mineral. Sediments were fine sands in the shallow zone and organic silt in the deeper zone. Enrichment Factor and Factor Analysis approach showed that the presence of Mn in the marine sediment of Mejillones is due to a partial influence of continental input, while all other metals are not supported by lithogenic debris. Although all metals showed high concentrations in the marine sediment of Mejillones Bay, comparison between metal concentration in surface sediments and preindustrial levels in this bay, show that present values agree with natural levels.

Ventajas y peculiaridades del abordaje laparoscópico en el anciano

Both the age of the population and anesthetic and surgical techniques are advancing. Currently, 40% of surgical activity is performed in patients older than 65 years, who present a higher surgical risk than younger patients. The aim of treatment in the elderly is to provide the best possible quality of life, even though this represents a surgical challenge because of associated comorbidity and reduced cardiopulmonary reserve. From the moment at which laparotomy becomes an increased stress in the elderly, laparoscopic surgery can be particularly advantageous in this population. Therefore, minimally invasive surgery may have a greater impact in these individuals than in younger patients in reducing postoperative pain, cardiorespiratory complications, hospital stay, and recovery time before resuming physical activity. The recent advances in anesthesia, together with improved patient selection and perioperative cardiac care, and the general adoption of minimally invasive access have enabled more complex gastrointestinal procedures to be performed in the elderly. The factors that could influence the development of this type of approach in the elderly, as well as the precautions that should be taken, should be further analyzed.

Two exonic elements in the flanking constitutive exons control the alternative splicing of the alpha exon of the ZO-1 pre-mRNA

The 240-bp alpha exon of the tight junction (TJ) protein ZO-1 pre-mRNA is alternatively spliced. Expression of both ZO-1alpha+/ZO-1alpha- isoforms results in hermetic TJs, and these become leaky when ZO-1alpha- expression prevails. The alpha exon inclusion/skipping mechanism was studied by in vivo RT-PCR splicing assays in neural and epithelial cells, utilizing a canine minigene construct containing the alpha exon, and the flanking introns and exons. Inclusion of the alpha exon always occurs in wild-type MDCK cells and it is detectable in transfected HeLa cells. However, the alpha exon is skipped in transfected neural cells. Accordingly, both 5' and 3' splice sites surrounding the alpha exon appear to be suboptimal and no cis-acting splicing control elements were found in this exon. Deletion analysis revealed an 83-bp splicing enhancer in the downstream exon and a 35-bp splicing silencer at the beginning of the upstream exon. In epithelial cells all constructs rendered alpha exon inclusion. We conclude that, in neural cells, skipping of the alpha exon depends on two antagonistic exonic elements located in the flanking constitutive exons.

Nitric oxide and nitric oxide synthases in the fetal cerebral cortex of rats following transient uteroplacental ischemia

The effect of transient uteroplacental ischemia on nitric oxide (NO) levels, enzymatic activity, and expression of NO synthase (NOS) isoforms was studied in fetal rat brains. Fetuses were subjected to ischemia by clamping the uterine arteries for 5 min on gestational day 17 (GD17). At different times after ischemia, fetuses were delivered by Cesarean section under anesthesia to obtain the brains. Transient uteroplacental ischemia produced a time dependent increase in nitrite levels in the brain, reaching a maximum value (300 +/- 25% of baseline) 24 h after uterine artery occlusion and remaining elevated as long as 48 h. Significantly increased nitrite levels were found in the cerebral cortex but not in the mesencephalon and cerebellum. The ischemia-induced increment in nitrite levels was totally blocked by either L-NAME (10 mg/kg) or AMT (0.65 mg/kg) administered i.p. 1 h before uterine artery occlusion. Both Ca(2+)-dependent and Ca(2+)-independent NOS activities in the cerebral cortex remained significantly increased with respect to controls after 24 h following the ischemia. Reverse transcriptase-polymerase chain reaction showed augmented levels of mRNAs for both nNOS and iNOS when compared with controls at 8 h after ischemia. At 36 h, nNOS mRNA returned to basal levels whereas eNOS mRNA levels increased and iNOS mRNA remained elevated. Our results show that the three NOS isoforms participate in increasing NO levels after transient ischemia and suggest a biphasic and differential regulation of the expression of constitutive NOS isoforms in the rat cerebral cortex.

A possible molecular ancestor for mollusk APGWamide, insect adipokinetic hormone, and crustacean red pigment concentrating hormone

Precursor structures of various members of the neuropeptide family adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) of mandibular arthropods and the APGWamide family of mollusks were compared. Amino acid alignments showed a common overall architecture (signal peptide, active peptide, related peptide), with a similar alpha helix-random coil secondary structure. DNA sequence alignments revealed close similarities between the genes encoding for the peptides of the two families. The APGWamide genes are larger than the AKH/RPCH genes. The sequence environment occupied by introns is similar in AKH/RPCH and APGWamide genes. Such similarities suggest that these peptide families might have been originated by gene rearrangements from a common ancestor having either an AKH/RPCH/APGWamide-like structure or both an AKH/RPCH-like and an APGWamide-like structures. In the former model, DNA fragments could have been gained when the ancestor evolved to mollusks and it could have lost nucleotides when the progression to mandibular arthropods took place. In the second model, AKH/RPCH-like structures could have been fused during evolution toward mandibular arthropods, whereas in mollusks they could have been lost with the possible amplification of the APGWamide-like structure. Loss of domains in exon 1 may have originated the signal peptide and the first codon of the active RPCH. In exon 2, loss of domains possibly determined the junctions of codons 2 to 5 with the loss of a APGWamide copy; exon 3 underwent fewer variations. The similarity of the mollusk APGWamide precursors is closer to that of the RPCH family than the insect AKH family, indicating an earlier evolutionary departure.

The genomic organization of the open reading frame of the red pigment concentrating hormone gene in the blue crab Callinectes sapidus

The open reading frame (ORF) of the gene for the precursor of the octapeptide Red Pigment Concentrating Hormone (RPCH) from the blue crab Callinectes sapidus was cloned by PCR with oligonucleotides targeted to the initiation and the end of the translation coding sequences. A 272 bp intron was characterized between nucleotides 343 and 344 of the reported cDNA, present in the region coding for the last amino acids of the precursor related peptide of RPCH. The intron genomic structure here described is similar to that reported for the gene coding for the Adipokinetic Hormone (AKH) of the grasshopper Schistocerca nitans.

The low and high frequency auditory steady state responses mature at different rates

The age-related changes in the fast rate (70-110 Hz) auditory steady state response elicited by multiple-frequency tones (MSSR) that were amplitude-modulated (AM) are reported here. The MSSR was recorded in a sample of 64 well babies distributed into three age groups: 0-29 days (n = 25); 1-6 months (n = 26); 7-12 months (n = 13). Four simultaneously presented AM tones (0.5, 1, 2 and 4 kHz) were delivered monaurally through TDH 49 earphones, at different intensities (between 90 and 30 dB SPL). Clear developmental changes were found between birth and 12 months of age in response threshold, amplitude and detectability. Statistical analysis revealed that these changes occurred at different rates for low- and high- frequency responses. Nonetheless adult-like hearing thresholds were estimated reasonably well in most newborns and well babies, for all frequencies tested. Therefore the MSSR technique could be useful for objective frequency-specific audiometry beginning at birth.

Fructo-oligosaccharides production by the Gluconacetobacter diazotrophicus levansucrase expressed in the methylotrophic yeast Pichia pastoris

Levansucrase (LsdA) (EC 2.4.1.10) from Gluconacetobacter diazotrophicus (formerly Acetobacter diazotrophicus) yields high levels of fructo-oligosaccharides (FOS) from sucrose. A DNA fragment encoding the precursor LsdA lacking the first 57 amino acids was fused to the pho1 signal sequence under the control of the Pichia pastoris-alcohol oxidase 1 (AOX1) promoter. Methanol induction of a P. pastoris strain harboring a single copy of the lsdA expression cassette integrated in the genome resulted in the production of active levansucrase. After fermentation of the recombinant yeast, LsdA activity was detected in the periplasmic fraction (81%) and in the culture supernatant (18%) with an overall yield of 1% of total protein. The recombinant LsdA was glycosylated and displayed optimal pH and temperature for enzyme activity similar to those of the native enzyme, but thermal stability was increased. Neither fructosylpolymerase activity nor FOS production was affected. Incubation of recombinant LsdA in sucrose (500 g l(-1)) yielded 43% (w/w) of total sugar as 1-kestose, with a conversion efficiency about 70%. Intact recombinant yeast cells also converted sucrose to FOS although for a 30% efficiency.

[Child health care program in Mexico. Evaluation of the quality of the integrated health care given in training centers]

OBJECTIVE

To assess the quality of the integral care of children under five years old (AIMCA) at three first level care units, that without additional resources, were selected by the Child Health Care Program (PASN) to function as statewide training centers.

MATERIAL AND METHODS

Using matching list, structure, validated by a consensus of experts and a pilot test, six components of the AIMCA were assessed. The study included children under five years old outpatient clinic, during a period of a week: on the average 30 at each unit.

RESULTS

Although there were differences between each health unit, in a high number of cases, the score given to each component of the AIMCA was optimum or satisfactory. The most relevant deficiencies were those related to the mother's training. The assessment allowed for correcting deficiencies in the AIMCA and others related with the organization of Training Centers.

CONCLUSIONS

It is possible to have an AIMCA of good quality, at first level units without additional resources. We propose that the mother's training be given mainly by a nurse, especially in children with factors of poor prognosis. The methodology used can be employed to evaluate the AIMCA periodically at training centers.