Departamento Biomédico

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Comparison of Total Anaerobic Microbiota in Periodontitis Before and After the Subgingival Irrigation with Chlorhexidine at 0.12 %
(2019) Lorena Mejías; Diego Iriarte; Rodolfo Sanchez; Iván Neira; Joel Bravo
El objetivo del presente estudio fue determinar el efecto de la irrigaci n subgingival de la clorhexidina 0,12 % sobre la microbiota anaer bica total. Se tomaron muestras microbiol gicas a 30 sujetos con periodontitis estadio II grado B, en sacos periodontales con una profundidad de sondaje > 4 mm. Se realizó la irrigación subgingival con 5 mL. de clorhexidina en el grupo test y con 5 mL. de agua destilada en el grupo control. 24 horas después del procedimiento se obtuvo una segunda muestra a comparar. Se detectó que la irrigación subgingival con clorhexidina al 0,12 % logra disminuir en forma estadísticamente significativa la microbiota anaeróbica total (p< 0,05).
Observational cross-sectional study of Trichomonas tenax in patients with periodontal disease attending a Chilean university dental clinic
(2019) Casandra Bracamonte Wolf; Patricio R. Orrego; Christian Muñoz; Daniel Herrera; Joel Bravo; Jorge Gonzalez; Héctor Varela; Alejandro Catalán; Jorge E. Araya
Background: The oral flagellated protozoan Trichomonas tenax has been associated with patients with periodontal disease. However, no recent studies have been conducted on the prevalence of T. tenax in Chile. The aim of this study was to determine the presence of T. tenax in patients with periodontal disease, admitted to the Dental Clinic of the University of Antofagasta, Chile, through Polymerase Chain Reaction (PCR) amplification of the beta-tubulin gene. Methods: An observational, cross-sectional study was conducted on 50 patients diagnosed with periodontal disease, 20 of them with gingivitis and 30 with periodontitis. T. tenax was identified by PCR amplification of the beta-tubulin gene. Associations between the protozoan and periodontal disease or the presence of risk factors to establish T. tenax infection were determined using the chi-square test and binary logistic regression analysis. Results: T. tenax was present in 28 out of 50 (56%) of patients with periodontal disease, and was more prevalent when associated with periodontitis (21 out of 30; 70%) than dental plaque-induced gingivitis (7 out of 20; 35%). Non-statistically-significant associations were observed between the presence of T. tenax and age, gender, smoking habit or diabetes. Statistically significant associations were observed between the presence of T. tenax and periodontal disease, and between T. tenax and the Periodontal Screening and Recording (PSR) index. Conclusion: T. tenax showed a high presence in patients with progressive states of periodontal diseases. Consequently, T. tenax detection is strongly recommended in patients with periodontal disease diagnosis and with a PSR index greater than 3.
Immediate Small-Diameter Implants as Abutments for an Overdenture in the Edentulous Atrophic Mandible: Report of Immersion Endoscopic Bone in vivo, and Histologic Bone-Implant Evaluation After 6 Months of Function
(2019) Víctor Beltrán; Ricardo Lillo; Benjamín Weber; Iván Valdivia Gandur; María Cristina Manzanares-Céspedes; Wilfried Engelke
The aim of this report was to endoscopically evaluate bone quality in vivo in the immediate installation of temporary small-diameter implants, and again after 6 months of function, through an attachments system for overdenture, in the atrophic mandible of a patient. We also histologically evaluated bone-implant interaction in these temporary small-diameter implants, once the success of the osseointegration of the submerged implants was guaranteed. A patient received a total of 6 implants in the atrophic mandible, two of which were immediately loaded with a provisional prosthesis, and four were left to heal in a submerged way. Further, an immersion endoscopic evaluation was performed during bone drilling, and this showed a compact bone structure with limited vascularization and predominantly cortical structure.This immediate loading protocol involving an overdenture retained by two small-diameter implants of 2.9 mm in the atrophic mandible proved to be successful after 6 months of loading. Clinical and histologic osseointegration was consistently achieved for both of the retrieved immediately loaded implants. This modality allows the patient to be restored with a stable, functional, and aesthetic prosthesis during the osseointegration period of submerged implants and soft-tissue healing, before the removal of the provisional implants. The histological evaluation of bone-implant contact found that the space between the implant threads closer to the surface was filled with woven bone and lamellar bone, but the tissue in contact with the cervical portion of the implants was compatible with cortical bone organization. Also, the newly formed bone has a regular cell distribution and characteristics of advanced maturation after 6 months of function in the atrophic mandible. Anchored overdentures in 2 to 4 small-diameter implants (2.9 mm) for edentulous patients with severe atrophy of the mandible with cortical bone would be a minimally invasive alternative.
Development of a Bicistronic Vector for the Expression of a CRISPR/Cas9-mCherry System in Fish Cell Lines
(2019) Sebastian Escobar Aguirre; Duxan Arancibia; Amanda Escorza; Cristián Bravo; María Estela Andrés; Pedro Zamorano; Víctor Martínez
The clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) system has been widely used in animals as an efficient genome editing tool. In fish cells, the technique has been difficult to implement due to the lack of proper vectors that use active promoters to drive the expression of both small guide RNA (sgRNA) and the S. pyogenes Cas9 (spCas9) protein within a single expression platform. Until now, fish cells have been modified using co-transfection of the mRNA of both the sgRNA and the spCas9. In the present study, we describe the optimization of a new vector for the expression of a CRISPR/Cas9 system, designed to edit the genome of fish cell lines, that combines a gene reporter (mCherry), sgRNA, and spCas9 in a single vector, facilitating the study of the efficiency of piscine and non-piscine promoters. A cassette containing the zebrafish U6 RNA III polymerase (U6ZF) promoter was used for the expression of the sgRNA. The new plasmid displayed the expression of spCas9, mCherry, and sgRNA in CHSE/F fish cells. The results demonstrate the functionality of the mammalian promoter and the U6ZF promoter in fish cell lines. This is the first approach aimed at developing a unified genome editing system in fish cells using bicistronic vectors, thus creating a powerful biotechnological platform to study gene function
Characterization of LDLR rs5925 and PCSK9 rs505151 genetic variants frequencies in healthy subjects from northern Chile: Influence on plasma lipid levels
(2019) Claudio Rojas; Hugo Ramírez; Luis A. Salazar; Alexis M. Kalergis; Anita S. Gálvez; Jorge Escobar‐Vera
Background: Identification and characterization of genetic variants and their effects on human health may allow to establish relationships between genetic background and susceptibility to developing cardiovascular diseases. LDLR and PCSK9 polymorphisms have been associated with higher lipid levels and risk of cardiovascular diseases. Thus, the main aim of this study was to evaluate genotype distribution and relative allelic frequency of LDLR rs5925 (1959C > T) and PCSK9 rs505151 (23968 A > G) genetic variants and their effects on lipid levels of healthy subjects from northern Chile. Methods: A total of 178 healthy individuals were recruited for this study. The genotyping of rs5925 (LDLR) and rs505151 (PCSK9) polymorphisms was performed by PCR‐RFLP and qPCR, respectively. In addition, glucose and lipid levels were determined and associated with the genetic data. Results: Genotype distribution for LDLR rs5925 polymorphism was as follows: CC = 19%; CT = 53%; and TT = 28% (HWE: χ2 = 0.80; P = .37), and for PCSK9 rs505151 genetic variant was as follows: AA = 93%; AG = 7%; and GG = 0% (HWE: χ2 = 0.22; P = .64). The frequency of T (rs5925) and G (rs505151) mutated alleles was 0.55 and 0.03, respectively. Data showed that individuals carrying LDLR mutated allele (T) presented lower values of total cholesterol, triglycerides, and LDL‐cholesterol when compared to CC homozygous genotype (P < .05). Subgroup analysis revealed that women carrying the PCSK9 mutated allele (G) exhibited higher values of total cholesterol, triglycerides, HDL‐C, and LDL‐C when compared to male group carrying the same genotype (P<05). Conclusions: The effect of LDLR rs5925 and PCSK9 rs505151 gene polymorphisms on lipid levels is associated with gender among healthy subjects from northern Chile.
Draft Genome Sequence of Staphylococcus sciuri Strain LCHXa, a Lithium-Tolerant Bacterium Isolated from Laguna Chaxa, Salar de Atacama, Chile.
(2019) Claudia Vilo; Camila Salazar Ardiles; Tamara N. Caimanque,; Qunfeng Dong; Nataly Flores; Alexandra Galetović; Jorge E. Araya; Benito Gómez Silva
A Gram-positive, coagulase-negative, novobiocin resistant, and lithiumtolerant bacterium was isolated from Salar de Atacama. Strain LCHXa is closely related to Staphylococcus sciuri. Its genome is 3,013,090 bp long and contains 2,551 predicted protein genes. We observed 58 genes associated with stress response and 17 genes linked to osmoregulation, mainly related to glycine betaine metabolism.
A Regenerative Endodontic Approach in Mature Ferret Teeth Using Rodent Preameloblast-conditioned Medium
(2019) CRISTINA BUCCHI; ÁLVARO GIMENO SANDIG; IVÁN VALDIVIA-GANDUR; CRISTINA MANZANARES CÉSPEDES; JOSEP MARIA DE ANTA
Regenerative endodontics, revitalization, mature teeth, ferrets, pulp regeneration
Contribution of Fcy Receptor-Mediated Immunity to the Pathogenesis Caused by the Human Respiratory Syncytial Virus
(2019) Orlando A. Acevedo; Fabián E. Díaz; Tomas E. Beals; Felipe M. Benavente; Jorge A. Soto Pablo A. González Alexis M. Kalergis; Jorge Escobar Vera; Pablo A. González; Alexis M. Kalergis
The human Respiratory Syncytial Virus (hRSV) is the leading cause of severe acute lower respiratory tract infections (ALRTIs) in humans at all ages and is the main cause of hospitalization due to pneumonia, asthma, and bronchiolitis in infants. hRSV symptoms mainly develop due to an excessive host immune and inflammatory response in the respiratory tissue. hRSV infection during life is frequent and likely because of non-optimal immunological memory is developed against this virus. Vaccine development against this pathogen has been delayed after the detrimental effects produced in children by vaccination with a formalin-inactivated hRSV preparation (FI-hRSV), which caused enhanced disease upon natural viral infection. Since then, several studies have focused on understanding the mechanisms underlying such disease exacerbation. Along these lines, several studies have suggested that antibodies elicited by immunization with FI-hRSV show low neutralizing capacity and promote the formation of immune complexes containing hRSV (hRSV-ICs), which contribute to hRSV pathogenesis through the engagement of Fc gamma receptors (FcγRs) expressed on the surface of immune cells. Furthermore, a role for FcγRs is supported by studies evaluating the contribution of these molecules to hRSV-induced disease. These studies have shown that FcγRs can modulate viral clearance by the host and the inflammatory response triggered by hRSV infection. In addition, ICs can facilitate viral entry into host cells expressing FcγRs, thus extending hRSV infectivity. In this article, we discuss current knowledge relative to the contribution of hRSV-ICs and FcγRs to the pathogenesis caused by hRSV and their putative role in the exacerbation of the disease caused by this virus after FI-hRSV vaccination. A better understanding FcγRs involvement in the immune response against hRSV will contribute to the development of new prophylactic or therapeutic tools to promote virus clearance with limited inflammatory damage to the airways
Explorar la Construcción de la Identidad Docente en Profesionales de la Salud: Diseño y Validación de Instrumento
(2019) Catherine, R. Jara; Cristina Mayor Ruiz
El objetivo de esta investigación es diseñar y validar un instrumento para explorar la construcción de la identidad docente en profesionales de la salud. El diseño del instrumento se estableció según dimensiones establecidas por el marco teórico. La validación del contenido se efectuó por juicio de expertos y de constructo con Alfa de Cronbach y Análisis factorial. La muestra la formaron 25 docentes de las Facultades de salud de la Universidad de Antofagasta y de la Universidad de Sevilla. En los resultados se obtuvo un cuestionario con cuatro dimensiones: Formación, Reflexión del proceso, Desempeño profesional y Elementos afectivos de la Identidad. Se obtuvo un alfa de Cronbach superior en todos los casos a 0,72 y un factor Kaiser-Meyer-Olkin (KMO) entre 0,72 y 0,5. En conclusión, el instrumento presenta una adecuada validez de contenido y constructo, lo que permite utilizarlo en estudios relacionados con construcción de identidad docente.
Serine–Arginine Protein Kinase SRPK2 Modulates the Assembly of the Active Zone Sca olding Protein CAST1/ERC2
(2019) Duxan Arancibia; Matias Lira; Yocelin Cruz; Daniela P. Barrera; Carolina Montenegro Venegas; Juan A. Godoy; Craig C. Garner; Nibaldo C. Inestrosa; Eckart D. Gundelfinger; Pedro Zamorano; VivianaI.Torres
Neurons release neurotransmitters at a specialized region of the presynaptic membrane, the active zone (AZ), where a complex meshwork of proteins organizes the release apparatus. The formation of this proteinaceous cytomatrix at the AZ (CAZ) depends on precise homo- and hetero-oligomerizations of distinct CAZ proteins. The CAZ protein CAST1/ERC2 contains four coiled-coil (CC) domains that interact with other CAZ proteins, but also promote self-assembly, which is an essential step for its integration during AZ formation. The self-assembly and synaptic recruitmentoftheDrosophilaproteinBruchpilot(BRP),apartialhomologofCAST1/ERC2,ismodulated by the serine-arginine protein kinase (SRPK79D). Here, we demonstrate that overexpression of the vertebrate SRPK2 regulates the self-assembly of CAST1/ERC2 in HEK293T, SH-SY5Y and HT-22 cells and the CC1 and CC4 domains are involved in this process. Moreover, the isoform SRPK2 forms a complex with CAST1/ERC2 when co-expressed in HEK293T and SH-SY5Y cells. More importantly, SRPK2 is present in brain synaptic fractions and synapses, suggesting that this protein kinase might control the level of self-aggregation of CAST1/ERC2 in synapses, and thereby modulate presynaptic assembly.
Immediate Small-Diameter Implants as Abutments for an Overdenture in the Edentulous Atrophic Mandible: Report of Immersion Endoscopic Bone in vivo, and Histologic Bone-Implant Evaluation After 6 Months of Function
(2019) Víctor Beltrán; Ricardo Lillo; Benjamín Weber; Iván Valdivia Gandur; María Cristina Manzanares Céspedes; Wilfried Engelke
The aim of this report was to endoscopically evaluate bone quality in vivo in the immediate installation of temporary small-diameter implants, and again after 6 months of function, through an attachments system for overdenture, in the atrophic mandible of a patient. We also histologically evaluated bone-implant interaction in these temporary small-diameter implants, once the success of the osseointegration of the submerged implants was guaranteed. A patient received a total of 6 implants in the atrophic mandible, two of which were immediately loaded with a provisional prosthesis, and four were left to heal in a submerged way. Further, an immersion endoscopic evaluation was performed during bone drilling, and this showed a compact bone structure with limited vascularization and predominantly cortical structure.This immediate loading protocol involving an overdenture retained by two small-diameter implants of 2.9 mm in the atrophic mandible proved to be successful after 6 months of loading. Clinical and histologic osseointegration was consistently achieved for both of the retrieved immediately loaded implants. This modality allows the patient to be restored with a stable, functional, and aesthetic prosthesis during the osseointegration period of submerged implants and soft-tissue healing, before the removal of the provisional implants. The histological evaluation of bone-implant contact found that the space between the implant threads closer to the surface was filled with woven bone and lamellar bone, but the tissue in contact with the cervical portion of the implants was compatible with cortical bone organization. Also, the newly formed bone has a regular cell distribution and characteristics of advanced maturation after 6 months of function in the atrophic mandible. Anchored overdentures in 2 to 4 small-diameter implants (2.9 mm) for edentulous patients with severe atrophy of the mandible with cortical bone would be a minimally invasive alternative.
Halophilic microbial community compositional shift after a rare rainfall in the Atacama Desert
(2019) Gherman Uritskiy; Samantha Getsin; Adam Munn; Benito Gomez Silva; Alfonso Davila; Brian Glass; James Taylor; Jocelyne DiRuggiero
Understanding the mechanisms underlying microbial resistance and resilience to perturbations is essential to predict the impact of climate change on Earth’s ecosystems. However, the resilience and adaptation mechanisms of microbial communities to natural perturbations remain relatively unexplored, particularly in extreme environments. The response of an extremophile community inhabiting halite (salt rocks) in the Atacama Desert to a catastrophic rainfall provided the opportunity to characterize and de-convolute the temporal response of a highly specialized community to a major disturbance. With shotgun metagenomic sequencing, we investigated the halite microbiome taxonomic composition and functional potential over a 4-year longitudinal study, uncovering the dynamics of the initial response and of the recovery of the community after a rainfall event. The observed changes can be recapitulated by two general modes of community shifts —a rapid Type 1 shift and a more gradual Type 2 adjustment. In the initial response, the community entered an unstable intermediate state after stochastic niche re-colonization, resulting in broad predicted protein adaptations to increased water availability. In contrast, during recovery, the community returned to its former functional potential by a gradual shift in abundances of the newly acquired taxa. The general characterization and proposed quantitation of these two modes of community response could potentially be applied to other ecosystems, providing a theoretical framework for prediction of taxonomic and functional flux following environmental changes.
The activation of the chymotrypsin-like activity of the proteasome is regulated by soluble adenyl cyclase/cAMP/protein kinase A pathway and required for human sperm capacitation
(2019) Héctor Zapata Carmona; Lina Barón; Lidia M.Zuñiga; Emilce Silvina Díaz; Milene Kong; Erma Z.Drobnis; Peter Sutovsky; Patricio Morales
Metagenomics of Atacama Lithobiontic Extremophile Life Unveils Highlights on Fungal Communities, Biogeochemical Cycles and Carbohydrate-Active Enzymes
(2019) Benito Gómez-Silva; Claudia Vilo-Muñoz; Alexandra Galetović; Qunfeng Dong; Hugo G. Castelán Sánchez; Yordanis Pérez Llano; María del Rayo Sánchez Carbente; Sonia Dávila Ramos; Nohemí Gabriela Cortés López; Liliana Martínez Ávila; Alan D. W. Dobson; Ramón Alberto Batista García
Halites, which are typically found in various Atacama locations, are evaporitic rocks that are considered as micro-scaled salterns. Both structural and functional metagenomic analyses of halite nodules were performed. Structural analyses indicated that the halite microbiota is mainly composed of NaCl-adapted microorganisms. In addition, halites appear to harbor a limited diversity of fungal families together with a biodiverse collection of protozoa. Functional analysis indicated that the halite microbiome possesses the capacity to make an extensive contribution to carbon, nitrogen, and sulfur cycles, but possess a limited capacity to fix nitrogen. The halite metagenome also contains a vast repertory of carbohydrate active enzymes (CAZY) with glycosyl transferases being the most abundant class present, followed by glycosyl hydrolases (GH). Amylases were also present in high abundance, with GH also being identified. Thus, the halite microbiota is a potential useful source of novel enzymes that could have biotechnological applicability. This is the first metagenomic report of fungi and protozoa as endolithobionts of halite nodules, as well as the first attempt to describe the repertoire of CAZY in this community. In addition, we present a comprehensive functional metagenomic analysis of the metabolic capacities of the halite microbiota, providing evidence for the first time on the sulfur cycle in Atacama halites.
Sinus Floor Augmentation by Intraoral Endoscopic Approach for Biomaterial Study in a Rabbit Model
(2019) Ivan ValdiviaGandur; Víctor Beltrán; Eduardo Borie; Wilson Astudillo Rozas; Oscar Aceiturno Antezana; Nicolas Ferrer Valdivia; Wilfried Engelke
To develop a new surgical model for sinus floor augmentation (SFA) in rabbit for experimental purposes. Materials and Methods: Eight adult rabbits were used, two for a surgical design using the anatomical dissection study, and the other six for an endoscopically assisted intraoral approach of SFA unilaterally, creating a subantral space where an allograft biomaterial was deposited. SFA was verified through cone-beam computerized tomography. Healing, weight, food, feces, and behavior were evaluated for 4 weeks post operatively. Results: All animals survived. There was no bleeding or infection; inflammation was mild. No changes were observed in terms of feeding, weight, feces, or behavior. Tissue healing was normal. Conclusion: This model is a refinement of the experimental technique and is a real option for SFA, without compromising animal morbidity because of its conservative design. The minimally invasive approach with endoscopic assistance reduces bias and improves surgical predictability. Sinus floor augmentation (SFA) is a useful technique for treating severe sinus pneumatization before the placement of dental implants. The singular anatomy and physiology of this anatomical site, in addition to the clinical importance that it has acquired, makes it ideal for investigating biomaterials, which has led to the proposal of various animal models including the rabbit (1-3).
Syndecan-4/PAR-3 signaling regulates focal adhesion dynamics in mesenchymal cells
(2020) Alejandra Valdivia; Areli Cárdena; Marianne Brenet ; Horacio Maldonado; Milen Kong; Jorge Díaz; Keith Burridge; Pascal Schneider; Alejandra San Martín; Rafael García-Mata; Andrew F.G. Quest; Lisette Leyton
Background: Syndecans regulate cell migration thus having key roles in scarring and wound healing processes. Our previous results have shown that Thy-1/CD90 can engage both αvβ3 integrin and Syndecan-4 expressed on the surface of astrocytes to induce cell migration. Despite a well-described role of Syndecan-4 during cell movement, information is scarce regarding specific Syndecan-4 partners involved in Thy-1/CD90-stimulated cell migration. Methods: Mass spectrometry (MS) analysis of complexes precipitated with the Syndecan-4 cytoplasmic tail peptide was used to identify potential Syndecan-4-binding partners. The interactions found by MS were validated by immunoprecipitation and proximity ligation assays. The conducted research employed an array of genetic, biochemical and pharmacological approaches, including: PAR-3, Syndecan-4 and Tiam1 silencing, active Rac1 GEFs affinity precipitation, and video microscopy. Results: We identified PAR-3 as a Syndecan-4-binding protein. Its interaction depended on the carboxy-terminal EFYA sequence present on Syndecan-4. In astrocytes where PAR-3 expression was reduced, Thy-1-induced cell migration and focal adhesion disassembly was impaired. This effect was associated with a sustained Focal Adhesion Kinase activation in the siRNA-PAR-3 treated cells. Our data also show that Thy-1/CD90 activates Tiam1, a PAR-3 effector. Additionally, we found that after Syndecan-4 silencing, Tiam1 activation was decreased and it was no longer recruited to the membrane. Syndecan-4/PAR-3 interaction and the alteration in focal adhesion dynamics were validated in mouse embryonic fibroblast (MEF) cells, thereby identifying this novel Syndecan-4/PAR-3 signaling complex as a general mechanism for mesenchymal cell migration involved in Thy-1/CD90 stimulation. Conclusions: The newly identified Syndecan-4/PAR-3 signaling complex participates in Thy-1/CD90-induced focal adhesion disassembly in mesenchymal cells. The mechanism involves focal adhesion kinase dephosphorylation and Tiam1 activation downstream of Syndecan-4/PAR-3 signaling complex formation. Additionally, PAR-3 is defined here as a novel adhesome-associated component with an essential role in focal adhesion disassembly during polarized cell migration. These novel findings uncover signaling mechanisms regulating cell migration, thereby opening up new avenues for future research on Syndecan-4/PAR-3 signaling in processes such as wound healing and scarring
Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex
(2020) Matías Lira; Rodrigo G. Mira; Francisco J. Carvajal; Pedro Zamorano; Nibaldo C. Inestrosa; Waldo Cerpa
Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo tra cking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle tra cking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor tracking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor tracking and the exocyst complex in both basal and stimulated levels, comparing constitutive tracking and long-term potentiation-related tracking.
Uv-a irradiation increases scytonemin biosynthesis in cyanobacteria inhabiting halites at salar grande, atacama desert
(2020) Gabriela Orellana; Benito Gómez-Silva; Milton Urrutia; Alexandra Galetović
Microbial consortia inhabiting evaporitic salt nodules at the Atacama Desert are dominated by unculturable cyanobacteria from the genus Halothece. Halite nodules provide transparency to photosynthetically active radiation and diminish photochemically damaging UV light. Atacama cyanobacteria synthesize scytonemin, a heterocyclic dimer, lipid soluble, UV-filtering pigment (in vivo absorption maximum at 370 nm) that accumulates at the extracellular sheath. Our goal was to demonstrate if UV-A irradiations modulate scytonemin biosynthesis in ground halites containing uncultured Halothece sp. cyanobacteria. Pulverized halite nodules with endolithic colonization were incubated under continuous UV-A radiation (3.6 W/m2) for 96 h, at 67% relative humidity, mimicking their natural habitat. Scytonemin content and relative transcription levels of scyB gene (a key gene in the biosynthesis of scytonemin) were evaluated by spectrophotometry and quantitative RT-PCR, respectively. After 48 h under these experimental conditions, the ratio scytonemin/chlorophyll a and the transcription of scyB gene increased to a maximal 1.7-fold value. Therefore, endolithic Halothece cyanobacteria in halites are metabolically active and UV radiation is an environmental stressor with a positive influence on scyB gene transcription and scytonemin biosynthesis. Endolithobiontic cyanobacteria in Atacama show a resilient evolutive and adaptive strategy to survive in one of the most extreme environments on Earth.
Baroreflex Modulation During Acute High-Altitude Exposure in Rats
(2020) Ana Rosa Beltrán; Alexis Arce-Álvarez; Rodrigo Ramirez-Campillo; Manuel Vásquez-Muñoz; Magdalena von Igel; Marco Antonio Ramírez; Rodrigo Del Rio; David C. Andrade
Baroreflex (BR) control is critically dependent of sympathetic and parasympathetic modulation. It has been documented that during acute hypobaric hypoxia there is a BR control impairment, however, the effect of a natural hypoxic environment on BR function is limited and controversial. Therefore, the aim of this study was to determine the effect of acute High-Altitude exposure on sympathetic/parasympathetic modulation of BR control in normal rats. Male Sprague Dawley rats were randomly allocated into Sea-Level (n = 7) and High-Altitude (n = 5) (3,270 m above sea level) groups. The BR control was studied using phenylephrine (Phe) and sodium nitroprusside (SNP) through sigmoidal analysis. The autonomic control of the heart was estimated using heart rate variability (HRV) analysis in frequency domain. Additionally, to determine the maximum sympathetic and parasympathetic activation of BR, spectral non-stationary method analysis, during Phe (0.05 mg/mL) and SNP administration (0.10 mg/mL) were used. Compared to Sea-Level condition, the High-Altitude group displayed parasympathetic withdrawal (high frequency, 0.6–2.4 Hz) and sympathoexcitation (low frequency, 0.04–0.6 Hz). Regarding to BR modulation, rats showed a significant decrease (p < 0.05) of curvature and parasympathetic bradycardic responses to Phe, without significant differences in sympathetic tachycardic responses to SNP after High-Altitude exposure. In addition, the non-stationary analysis of HRV showed a reduction of parasympathetic activation (Phe) in the High-Altitude group. Our results suggest that acute exposure to High-Altitude produces an autonomic and BR control impairment, characterized by parasympathetic withdrawal after 24 h of high-altitude exposure.
Absence of Cyanotoxins in Llayta, Edible Nostocaceae Colonies from the Andes Highlands
(2020) Alexandra Galetović ; Joana Azevedo; Raquel Castelo-Branco; Falvio Oliveira; Bneito Gómez-Silva; Vitor Vasconselos
Edible Llayta are cyanobacterial colonies consumed in the Andes highlands. Llayta and four isolated cyanobacteria strains were tested for cyanotoxins (microcystin, nodularin, cylindrospermopsin, saxitoxin and -N-methylamino-L-alanine—BMAA) usingmolecular and chemicalmethods. All isolates were free of target genes involved in toxin biosynthesis. Only DNA from Llayta amplified the mcyE gene. Presence of microcystin-LR and BMAA in Llayta extracts was discarded by LC/MS analyses. The analysed Llayta colonies have an incomplete microcystin biosynthetic pathway and are a safe food ingredient.

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