Single-cell mechanical assay unveils viscoelastic similarities in normal and neoplastic brain cells.

Understanding cancer cell mechanics allows for the identification of novel disease mechanisms, diagnostic biomarkers, and targeted therapies. In this study, we utilized our previously established fluid shear stress assay to investigate and compare the viscoelastic properties of normal immortalized human astrocytes and invasive human glioblastoma (GBM) cells when subjected to physiological levels of shear stress that are present in the brain microenvironment. We used a parallel-flow microfluidic shear system and a camera-coupled optical microscope to expose single cells to fluid shear stress and monitor the resulting deformation in real time, respectively. From the video-rate imaging, we fed cell deformation information from digital image correlation into a three-parameter generalized Maxwell model to quantify the nuclear and cytoplasmic viscoelastic properties of single cells. We further quantified actin cytoskeleton density and alignment in immortalized human astrocytes and GBM cells via fluorescence microscopy and image analysis techniques. Results from our study show that contrary to the behavior of many extracranial cells, normal and cancerous brain cells do not exhibit significant differences in their viscoelastic properties. Moreover, we also found that the viscoelastic properties of the nucleus and cytoplasm as well as the actin cytoskeletal densities of both brain cell types are similar. Our work suggests that malignant GBM cells exhibit unique mechanical behaviors not seen in other cancer cell types. These results warrant future studies to elucidate the distinct biophysical characteristics of the brain and reveal novel mechanical attributes of GBM and other primary brain tumors.

Non-Woven Fibrous Polylactic Acid/Hydroxyapatite Nanocomposites Obtained via Solution Blow Spinning: Morphology, Thermal and Mechanical Behavior.

Polylactic acid (PLA) is widely used in tissue engineering and other biomedical applications. PLA can be modified with appropriate biocompatible ceramic materials since this would allow tailoring the mechanical properties of the tissues to be engineered. In this study, PLA-based non-woven fibrillar nanocomposites containing nanoparticles of hydroxyapatite (HA), a bioceramic commonly used in bone tissue engineering, were prepared via solution blow spinning (SBS). The compositions of the final materials were selected to study the influence of HA concentration on the structure, morphology, and thermal and mechanical properties. The resulting materials were highly porous and mainly constituted fibers. FTIR analysis did not reveal any specific interactions. The diameters of the fibers varied very little with the composition. For example, slightly thinner fibers were obtained for pure PLA and PLA + 10% HA, with fiber diameters of less than 400 nm, while the thicker fibers were found for PLA + 1% HA, with average diameters of 427 ± 170 nm. The crystallinity and stiffness of the PLA/HA composite increased with the HA content. Further, composites containing PLA fibers with slightly larger diameters were more ductile. Thus, with an appropriate balance between factors, such as the diameter of the solution-blow-spun PLA fibers, HA particle content, and degree of crystallinity, PLA/HA composites may be effectively used in tissue engineering applications.

Single-cell mechanical analysis reveals viscoelastic similarities between normal and neoplastic brain cells.

Understanding cancer cell mechanics allows for the identification of novel disease mechanisms, diagnostic biomarkers, and targeted therapies. In this study, we utilized our previously established fluid shear stress assay to investigate and compare the viscoelastic properties of normal immortalized human astrocytes (IHAs) and invasive human glioblastoma (GBM) cells when subjected to physiological levels of shear stress that are present in the brain microenvironment. We used a parallel-flow microfluidic shear system and a camera-coupled optical microscope to expose single cells to fluid shear stress and monitor the resulting deformation in real-time, respectively. From the video-rate imaging, we fed cell deformation information from digital image correlation into a three-parameter generalized Maxwell model to quantify the nuclear and cytoplasmic viscoelastic properties of single cells. We further quantified actin cytoskeleton density and alignment in IHAs and GBM cells via immunofluorescence microscopy and image analysis techniques. Results from our study show that contrary to the behavior of many extracranial cells, normal and cancerous brain cells do not exhibit significant differences in their viscoelastic behavior. Moreover, we also found that the viscoelastic properties of the nucleus and cytoplasm as well as the actin cytoskeletal densities of both brain cell types are similar. Our work suggests that malignant GBM cells exhibit unique mechanical behaviors not seen in other cancer cell types. These results warrant future study to elucidate the distinct biophysical characteristics of the brain and reveal novel mechanical attributes of GBM and other primary brain tumors.

Atomic Force Microscopy Methods to Measure Tumor Mechanical Properties.

Atomic force microscopy (AFM) is a popular tool for evaluating the mechanical properties of biological materials (cells and tissues) at high resolution. This technique has become particularly attractive to cancer researchers seeking to bridge the gap between mechanobiology and cancer initiation, progression, and treatment resistance. The majority of AFM studies thus far have been extensively focused on the nanomechanical characterization of cells. However, these approaches fail to capture the complex and heterogeneous nature of a tumor and its host organ. Over the past decade, efforts have been made to characterize the mechanical properties of tumors and tumor-bearing tissues using AFM. This has led to novel insights regarding cancer mechanopathology at the tissue scale. In this Review, we first explain the principles of AFM nanoindentation for the general study of tissue mechanics. We next discuss key considerations when using this technique and preparing tissue samples for analysis. We then examine AFM application in characterizing the mechanical properties of cancer tissues. Finally, we provide an outlook on AFM in the field of cancer mechanobiology and its application in the clinic.

Shear Assay Protocol for the Determination of Single-Cell Material Properties.

Irregular biomechanics are a hallmark of cancer biology subject to extensive study. The mechanical properties of a cell are similar to those of a material. A cell's resistance to stress and strain, its relaxation time, and its elasticity are all properties that can be derived and compared to other types of cells. Quantifying the mechanical properties of cancerous (malignant) versus normal (non-malignant) cells allows researchers to further uncover the biophysical fundamentals of this disease. While the mechanical properties of cancer cells are known to consistently differ from the mechanical properties of normal cells, a standard experimental procedure to deduce these properties from cells in culture is lacking. This paper outlines a procedure to quantify the mechanical properties of single cells in vitro using a fluid shear assay. The principle behind this assay involves applying fluid shear stress onto a single cell and optically monitoring the resulting cellular deformation over time. Cell mechanical properties are subsequently characterized using digital image correlation (DIC) analysis and fitting an appropriate viscoelastic model to the experimental data generated from the DIC analysis. Overall, the protocol outlined here aims to provide a more effective and targeted method for the diagnosis of difficult-to-treat cancers.

The peritumor microenvironment: physics and immunity.

Cancer initiation and progression drastically alter the microenvironment at the interface between healthy and malignant tissue. This site, termed the peritumor, bears unique physical and immune attributes that together further promote tumor progression through interconnected mechanical signaling and immune activity. In this review, we describe the distinct physical features of the peritumoral microenvironment and link their relationship to immune responses. The peritumor is a region rich in biomarkers and therapeutic targets and thus is a key focus for future cancer research as well as clinical outlooks, particularly to understand and overcome novel mechanisms of immunotherapy resistance.

Highly cited tropical medicine articles in the Web of Science from 1991 to 2020: A bibliometric analysis.

BACKGROUND: An adequate response to health needs to include the identification of research patterns about the large number of people living in the tropics and subjected to tropical diseases. Studies have shown that research does not always match the real needs of those populations, and that citation reflects mostly the amount of money behind particular publications. Here we test the hypothesis that research from richer institutions is published in better-indexed journals, and thus has greater citation rates. METHODS: The data in this study were extracted from the Science Citation Index Expanded database; the 2020 journal Impact Factor (IF2020) was updated to 30 June 2021. We considered places, subjects, institutions and journals. RESULTS: We identified 1041 highly cited articles with ≥100 citations in the category of tropical medicine. About a decade is needed for an article to reach peak citation. Only two COVID-19-related articles were highly cited in the last 3 y. The most cited articles were published by the journals Memorias Do Instituto Oswaldo Cruz (Brazil), Acta Tropica (Switzerland) and PLoS Neglected Tropical Diseases (USA). The USA dominated five of the six publication indicators. International collaboration articles had more citations than single-country articles. The UK, South Africa and Switzerland had high citation rates, as did the London School of Hygiene and Tropical Medicine in the UK, the Centers for Disease Control and Prevention in the USA and the WHO in Switzerland. CONCLUSIONS: About 10 y of accumulated citations is needed to achieve ≥100 citations as highly cited articles in the Web of Science category of tropical medicine. Six publication and citation indicators, including authors' publication potential and characteristics evaluated by Y-index, indicate that the currently available indexing system places tropical researchers at a disadvantage against their colleagues in temperate countries, and suggest that, to progress towards better control of tropical diseases, international collaboration should increase, and other tropical countries should follow the example of Brazil, which provides significant financing to its scientific community.

Do Tumor Mechanical Stresses Promote Cancer Immune Escape?

Immune evasion-a well-established cancer hallmark-is a major barrier to immunotherapy efficacy. While the molecular mechanisms and biological consequences underpinning immune evasion are largely known, the role of tissue mechanical stresses in these processes warrants further investigation. The tumor microenvironment (TME) features physical abnormalities (notably, increased fluid and solid pressures applied both inside and outside the TME) that drive cancer mechanopathologies. Strikingly, in response to these mechanical stresses, cancer cells upregulate canonical immune evasion mechanisms, including epithelial-mesenchymal transition (EMT) and autophagy. Consideration and characterization of the origins and consequences of tumor mechanical stresses in the TME may yield novel strategies to combat immunotherapy resistance. In this Perspective, we posit that tumor mechanical stresses-namely fluid shear and solid stresses-induce immune evasion by upregulating EMT and autophagy. In addition to exploring the basis for our hypothesis, we also identify explicit gaps in the field that need to be addressed in order to directly demonstrate the existence and importance of this biophysical relationship. Finally, we propose that reducing or neutralizing fluid shear stress and solid stress-induced cancer immune escape may improve immunotherapy outcomes.

Bibliometrics of Sudanese scientific publications: Subjects, institutions, collaboration, citation and recommendations / Bibliometría de publicaciones científicas sudanesas: temas, instituciones, colaboración, citas y recomendaciones

Abstract Introduction: Sudan is the third largest country in Africa and has rich reserves of petroleum and other ground resources, but its per capita Gross Domestic Product is only $808 and researchers work in insufficient institutional facilities and with little funding. Previous studies about its scientific productivity have been limited to specific subjects and relatively short periods, with no large analyses until now. Objective: To analyze the scientific output of Sudan in depth, considering all research areas and several decades of scientific activity. Methods: We retrieved the documents with "Sudan" in field country in the Science Citation Index Expanded for the period 1900-2019. Results: We retrieved over 9 000 publications and found that most were articles; that citation was higher for review articles and book chapters, and that this index mostly covered articles in English. Beginning in 1972, the number of publications in this database has increased rapidly. The citation lifespan indicates slow growth in the Sudanese scientific literature, and collaboration is frequent both nationally and internationally, possibly because the scarce resources make collaboration almost compulsory. Most external collaboration is done with Saudi Arabia but citation is higher for articles resulting from international megaprojects, led by Europe and the USA, in which Sudanese researchers play secondary roles. Research focusses on applied technological subjects with little innovation value. Women play a smaller role in Sudanese science. Conclusions: Our recommendations for Sudanese science include increasing the number of women in leading research positions; providing funding directly to researchers (i.e., bypassing bureaucratic bodies); increasing basic research to avoid stagnation; training Sudanese researchers for leading positions; and identifying specific research areas where Sudan can lead in its region.

Resumen Introducción: Sudán es el tercer país más grande de África y tiene ricas reservas de petróleo y otros recursos terrestres, pero su Producto Interno Bruto per cápita es de solo $ 808 y los investigadores trabajan en instalaciones institucionales deficientes y con poca financiación. Los estudios previos sobre su productividad científica se han limitado a temas específicos y períodos relativamente cortos. Objetivo: Analizar la producción científica de Sudán en profundidad, considerando todas las áreas de investigación y varias décadas. Métodos: Recuperamos los documentos con "Sudán" como país de origen en el Science Citation Index Expanded para el período 1900-2019. Resultados: Hallamos más de 9 000 publicaciones y encontramos que la mayoría eran artículos; que fueron más citados los artículos de revisión y capítulos de libros, y que esta base de datos cubría principalmente artículos en inglés; desde 1972, el número de publicaciones en ella ha aumentado rápidamente. La vida útil de las citas indica un crecimiento lento en la literatura científica sudanesa, y la colaboración es frecuente tanto a nivel nacional como internacional, posiblemente porque los escasos recursos hacen que la colaboración sea casi obligatoria. La mayor parte de la colaboración externa se realiza con Arabia Saudita, pero hay más citas para los artículos resultantes de megaproyectos internacionales, dirigidos por Europa y Estados Unidos, en los cuales los investigadores sudaneses desempeñan papeles secundarios. La investigación se centra en temas de tecnología aplicada con poco valor de innovación. Conclusiones: Nuestras recomendaciones para la ciencia sudanesa incluyen aumentar el número de mujeres en altos puestos; proporcionar financiación directamente a los investigadores (sin pasar por organismos burocráticos); ir más allá de la investigación aplicada para evitar el estancamiento; capacitar al personal sudanés para puestos de liderazgo; e identificar áreas de investigación específicas donde Sudán puede liderar en su región.

Half a century of Sri Lanka research: Subjects, researchers, institutions, journals and impact (1973-2019) / Medio siglo de investigación en Sri Lanka: temas, investigadores, instituciones, revistas e impacto (1973-2019)

Abstract Introduction: Bibliometric analyses of research in Sri Lanka, a lower-middle income island nation in South Asia, has focused mainly on medical research, concluding that there is a need for increased research productivity and impact, and for local solutions to health concerns. There has been no general bibliometric analysis across scientific disciplines in the nation, or any study that covers a long period of time to identify general time trends. Objective: To measure and analyse Sri Lanka research by focusing on subjects, authors, institutions, journals and citation for half a century. Methods: We used an advanced search method to extract publications with the word "Sri Lanka" in the SCI-EXPANDED, and calculated indicators such as total citations from Web of Science Core Collection since publication year to the end of 2019, citations in 2019, and mean citations per publication. Journal data were taken from 2019 Journal Citation Report. Affiliation re-classification was done to ensure consistency regarding the origin of all publications. Publications were further analysed based on collaboration, and first and corresponding authorship. Results: We retrieved 16 069 publications in 19 document types (77 % articles). Corrections had the highest number of authors per publication (616) followed by articles (116). Four articles had more than 5 000 authors and 593 articles had more than 1 000 authors. The highest citations in this database were for international megaprojects where Sri Lanka authors played minor roles. The UK had the most collaborative articles with Sri Lanka (19 %). The articles were published in 3 051 journals across 177 Web of Science categories. The category of Public, environmental and occupational health, with 193 journals, had 6.7 % of all articles, followed by environmental sciences (6.6 %). Conclusion: Sri Lanka has an unusually strong pattern of participating as small role players in international megaprojects about health and physics. Sri Lanka authors should be encouraged to expand their horizons by researching non-applied fields that are the basis of all innovation; to strengthen their own journals so that they have better visibility and impact, and to improve their positions in international projects that are published in larger journals.

Resumen Introducción: Los análisis bibliométricos de la investigación en Sri Lanka, una nación insular de ingresos mediano-bajos en el sur de Asia, se han centrado principalmente en la investigación médica, concluyendo que existe la necesidad de aumentar la productividad y el impacto de la investigación, y de soluciones locales a los problemas de salud. No ha habido un análisis bibliométrico general de disciplinas científicas o algún estudio que cubra un período largo de tiempo para identificar tendencias generales. Objetivo: Medir y analizar la investigación de Sri Lanka centrándose en temas, autores, instituciones, revistas y citas, durante medio siglo. Métodos: Utilizamos un método de búsqueda avanzada para extraer publicaciones con las palabras "Sri Lanka" en el SCI-EXPANDED, y calculamos indicadores como el total de citas de Web of Science Core Collection desde el año de publicación hasta finales de 2019, citas solo en 2019, y media de citas por publicación. Los datos de revistas son del Journal Citation Report 2019. Revisamos manualmente las afiliaciones para garantizar su coherencia, y, de todos los tipos de publicación, analizamos en detalle los artículos en función de la colaboración y la autoría. Resultados: Hallamos 16 069 publicaciones en 19 tipos de documentos (77 % artículos). Las correcciones tuvieron el mayor número de autores por publicación (616), seguidas de los artículos (116 autores en promedio); cuatro artículos tenían más de 5 000 autores y 593 artículos tenían más de 1 000 autores. Las citas más altas en esta base de datos fueron para megaproyectos internacionales en los que los autores de Sri Lanka desempeñaron papeles menores. El Reino Unido tuvo más artículos colaborativos con Sri Lanka (19 %). Los artículos se publicaron en 3 051 revistas de 177 categorías del Web of Science. La categoría d Salud pública, ambiental y ocupacional, con 193 revistas, tuvo el 6.7 % del total de artículos, seguida de Ciencias ambientales (6.6 %). Conclusión: En Sri Lanka hay una tendencia inusual a participar como pequeños actores en megaproyectos internacionales sobre salud y física. Debería alentarse a quienes hacen ciencia en Sri Lanka a ampliar sus horizontes investigando campos no aplicados, que son la base de la innovación; a fortalecer sus propias revistas para lograr mayor visibilidad e impacto, y a mejorar su ubicación en proyectos internacionales que se publican en revistas más grandes.

Cuba Publications in the Science Citation Index Expanded: publication characteristics, institutions and journals / Publicaciones de Cuba en el Science Citation Index: características de la publicación, instituciones y revistas

Abstract Introduction: In contrast with other tropical countries, Cuba has been frequently studied from the point of view of scientometrics. It has been reported that Cuban researchers often failed to cite other Cuban researchers or to collaborate with them and that 78 % of the Cuban scientific output is published in Cuban journals and mostly missed by Scopus and the Web of Science. However, there are no recent comprehensive studies of science in Cuba. Objective: To quantify the Cuban scientific output, in all disciplines, until the beginning of 2021. Methods: We analyzed publications from Cuba, dated 1900 to 2021, that reached the index Science Citation Index Expanded. Results: We retrieved a total of 23 576 publications, mostly articles. In this particular database, English is the dominant language, and, over time, articles have become longer and increased the number of authors and references. Numerically, the leading institution is Universidad de La Habana. Research is strongly concentrated around medical subjects. Collaboration teams led by foreign authors have more citations recorded by the database, where the number of Cuban articles has decreased strongly since 2008. Conclusion: Our conclussions only apply to the fraction of Cuban science covered by the Science Citation Index Expanded (under 22 %). We recommend three main improvements: to increase collaboration among Cuban scientists; to expand research areas beyond medical subjects; and to improve the quality of Cuban journals.

Resumen Introducción: A diferencia de otros países tropicales, Cuba ha sido frecuentemente estudiada desde el punto de vista de la cienciometría. Se ha informado que los investigadores cubanos citan poco a otros investigadores cubanos, no colaboraron entre sí, y que el 78 % de la producción científica cubana se publica en revistas cubanas sin llegar a Scopus y la Web of Science. Sin embargo, no existen estudios recientes y generales de la ciencia en Cuba. Objetivo: Cuantificar la producción científica cubana, en todas las disciplinas, hasta inicios de 2021. Métodos: Analizamos publicaciones con dirección autoral de Cuba, fechadas de 1900 a 2021, únicamente en el Science Citation Index Expanded. Resultados: Hallamos 23 576 publicaciones, en su mayoría artículos. En esta base de datos en particular, el inglés es el idioma dominante y, con el tiempo, los artículos se han vuelto más largos y han aumentado el número de autores y referencias. Numéricamente, la institución líder es la Universidad de La Habana. La investigación se concentra fuertemente en temas médicos. Los equipos de colaboración dirigidos por autores extranjeros tienen más citas registradas en esta base de datos estadounidense, donde el número de artículos cubanos ha disminuido fuertemente desde 2008. Conclusión: Nuestras conclusiones solo se aplican a la fracción de la ciencia cubana cubierta por el Science Citation Index Expanded (menos del 22 %) . Recomendamos tres mejoras principales: incrementar la colaboración entre los científicos cubanos; ampliar las áreas de investigación más allá de los temas médicos; y mejorar la calidad de las revistas cubanas.

Bibliometrics of Cambodian Science: subjects, researchers and impact in the Science Citation Index Expanded / Bibliometría de la ciencia camboyana: temas, investigadores e impacto en el Science Citation Index Expanded

Abstract Introduction: Cambodia is a small agricultural tropical country for which only two small scientometric studies, published five years ago, were available until now. Objective: To identify, for Cambodian research, subjects, outlets, authors, institutions, citations and recommendations. Methods: The data were retrieved from the Science Citation Index Expanded (January 04, 2021) using the word "Cambodia" for the period 1972 to 2019. Results: We retrieved 3 689 documents: for the half century covered, the yearly presence of Cambodia in the index has grown strongly, to 325 articles and 6 555 authors in 2019 alone. Most documents are articles in English about health, particularly infectious and tropical diseases. Most international collaboration is done, by country, with the USA, France, and Thailand; and by institution, with Mahidol University, the Pasteur Institute and Oxford University. The most productive institutions are the Cambodian Ministry of Health and the Cambodian National Center for Parasitology. The main outlets are PLoS One, Malaria and PLoS Neglected Tropical Diseases. Cambodian articles are cited for up to 33 years, with a peak of 4.5 citations within the first two years. Those in English, or from well-funded foreign projects, have more citations in this particular index; especially if they are about malaria, hepatitis or influenza. Conclusions: The nature and impact of Cambodian science outside the SCI-EXPANDED remain unknown, but publications in that index have increased, concentrate on solving local problems, and depend heavily on international collaboration, following a well-known pattern of science in tropical countries. We suggest a funding system based on international peers who assign funds to the most productive researchers with minimal bureaucracy, so that local research is done on a greater variety of topics and with less participation of Cambodian researchers as low-level members in foreign projects.

Resumen Introducción: Camboya es un país tropical asiático pequeño y "subdesarrollado", con una economía basada en la agricultura, para el que hasta ahora solo estaban disponibles dos pequeños estudios cienciométricos, publicados hace cinco años. Objetivo: Identificar, para la investigación camboyana, qué se estudia; quién hizo la investigación; dónde y cuándo se publicó; y los factores que afectan su citación. Métodos: Usamos el Science Citation Index Expanded (4 de enero de 2021) utilizando la palabra "Camboya" y se limitaron al período 1972 a 2019. Resultados: Hallamos 3 689 documentos; durante el medio siglo cubierto, la presencia anual de Camboya en el índice ha aumentado considerablemente, con 325 artículos y 6 555 autores incorporados tan solo en 2019. La mayoría son artículos en inglés sobre salud, particularmente enfermedades infecciosas y tropicales. La mayor parte de la colaboración internacional se realiza, por país, con EE. UU., Francia y Tailandia; y por institución, con la Universidad Mahidol, el Instituto Pasteur y la Universidad de Oxford. Las instituciones más productivas son el Ministerio de Salud de Camboya y el Centro Nacional de Parasitología de Camboya. Las principales revistas son PLoS One, Malaria y PLoS Neglected Tropical Diseases. Los artículos camboyanos se citan hasta por 33 años, con un máximo de 4.5 citas en los dos primeros años. Los que son en inglés, o de proyectos dirigidos por el extranjero, tienen más citas en esta base de datos; particularmente si se trata de malaria, hepatitis o influenza. Conclusiones: La naturaleza y el impacto de la ciencia camboyana fuera del SCI-EXPANDED siguen sin conocerse, pero las publicaciones en ese índice han aumentado, se concentran en resolver problemas locales y dependen en gran medida de la colaboración internacional, siguiendo un patrón bien conocido en los países tropicales. Sugerimos un sistema de financiación basado en pares internacionales que asignen, con burocracia mínima, fondos a los investigadores más productivos, de modo que la investigación local se realice en una mayor variedad de temas y con una menor participación de investigadores camboyanos como miembros de bajo nivel en proyectos extranjeros.

The geographic bias of mammal studies: a comparison of a half a century of research on Palearctic and Neotropical mammals / El sesgo geográfico en el estudio de los mamíferos: comparación de medio siglo de investigación sobre mamíferos paleárticos y neotropicales

Abstract Introduction: There are no studies that specifically compare research output of Palearctic and Neotropical mammalogy; such comparison would be useful for informed decisions in conservation and management. Objective: To compare the scientific documents and citations about Palearctic and Neotropical mammals over half a century. Methods: We compared 50 years (1970-2019) of documents on 60 medium and large-sized (heavier than 1 kg) mammal species, in Scopus and the Web of Science (WoS) Core Collection, considering number of documents and four citation indicators at the species level (h-index, citation rate, total citations, and citations per year). Results: We retrieved 13 274 documents in Scopus and 12 913 in WoS. We found that Palearctic mammals have 3.77 times more documents than Neotropical species in Scopus (3.91 times in WoS), and that the documents recorded 5.95 more total citations in Scopus (6.93 times more in WoS). Palearctic documents also record more yearly citations and a higher h-index in both Scopus and WoS. Scopus retrieved more articles for Neotropical species (2 782 vs. 2 631 in WoS) and had more citations (28 120 vs. 24 977 in WoS); differences for the citation indicators between regions were marker in WoS. The h-index and total citations are greatly affected by how many studies are published, i.e. the region with more production is the one with higher values. The Neotropical articles showed a greater growth rate in the last decade, decreasing the gap between both regions. Conclusion: There is a regional bias in WoS and Scopus, which retrieve more articles and citations about Palearctic mammals than about Neotropical mammals; this bias is worse in WoS and means that an urgent increase in indexed research about Neotropical species is needed to be on par with Palearctic research.

Resumen Introducción: No existen estudios que comparen, específicamente, la investigación de la mastozoología paleártica con la neotropical; pero tales comparaciones serían útiles para tomar decisiones informadas en conservación y manejo. Objetivo: Comparar los documentos científicos sobre mamíferos paleárticos y neotropicales, y su impacto en citas, durante medio siglo. Métodos: Comparamos 50 años (1970-2019) de documentos sobre 60 especies de mamíferos de tamaño mediano y grande (más de 1 kg), en Scopus y la colección principal del Web of Science (WoS), considerando el número de documentos y cuatro indicadores de citas a nivel de especie (índice h, tasa de citas, total de citas y citas por año). Resultados: Recuperamos 13 274 documentos en Scopus y 12 913 en WoS, y encontramos que los mamíferos paleárticos tienen 3.77 veces más documentos que las especies neotropicales en Scopus (3.91 veces en WoS), y que los documentos registran 5.95 más citas totales en Scopus (6.93 veces más en WoS). Los documentos paleárticos también registran más citas anuales y un índice h más alto, tanto en Scopus como en WoS. Scopus recuperó más artículos para especies neotropicales (2 782 vs. 2 631 en WoS) y tuvo más citas (28 120 vs. 24 977 en WoS). Las diferencias para los indicadores de citas entre regiones fueron más marcadas en WoS. El índice h y el total de citas se ven muy afectados por la cantidad de estudios publicados, es decir, la región con más producción será la que tenga indicadores más altos. Los artículos neotropicales mostraron una mayor tasa de crecimiento en la última década, disminuyendo la brecha entre ambas regiones. Conclusión: Existe un sesgo regional en WoS y Scopus, que recuperan más artículos y citas sobre mamíferos paleárticos que sobre mamíferos neotropicales; este sesgo es peor en WoS y significa que se necesita un aumento urgente en la investigación indexada sobre especies neotropicales para estar al nivel de la investigación paleártica.

Comparative Animal Mucomics: Inspiration for Functional Materials from Ubiquitous and Understudied Biopolymers.

The functions of secreted animal mucuses are remarkably diverse and include lubricants, wet adhesives, protective barriers, and mineralizing agents. Although present in all animals, many open questions related to the hierarchical architectures, material properties, and genetics of mucus remain. Here, we summarize what is known about secreted mucus structure, describe the work of research groups throughout the world who are investigating various animal mucuses, and relate how these studies are revealing new mucus properties and the relationships between mucus hierarchical structure and hydrogel function. Finally, we call for a more systematic approach to studying animal mucuses so that data sets can be compared, omics-style, to address unanswered questions in the emerging field of mucomics. One major result that we anticipate from these efforts is design rules for creating new materials that are inspired by the structures and functions of animal mucuses.

Are tropical reptiles really declining? A six-year survey of snakes in a tropical coastal rainforest: role of prey and environment

Introduction: Even though snake declines seem to be a reality in many parts of the world, some reports are based on anecdotal evidence and there is a need of prolonged and intensive studies, especially in the tropics, for corroboration. Objective: Toinvestigate if snake populations in Drake Bay are decreasing, and if there is a relationship with prey, time, temperature, rain and moonlight. Methods: We counted snakes seen per hour when walking along a single trail in the coastal forest of Drake Bay, Costa Rica. We walked the trail at night for a total of 842 nights (over 4 000 hours of observations), from 2012 through 2017 and recorded all the individual snakes we could see with head flashlights. We used ANOVA tests to check correlations among counts per hour with moonlight and rain; and graphic analysis for associations with diet, temperature, month and year. Results: We recorded 25 species (five families); which feed mostly on terrestrial vertebrates. Counts per hour have fallen over the years, especially for species that prey on amphibians and reptiles; Mastigodryas melanolomus has remained in similar numbers; and Siphlophis compressus has not been seen since May 2016. Temperature is relatively constant along the year in Drake, but month strongly affected the counts, which increased from August to September. Most species were seen more often in rainy nights (0.11 per hour versus only 0.03 per hour in nights without rain, ANOVA P 0.05). Conclusion: Night field counts of snakes in Drake Bay, Costa Rica, are not strongly affected by light or temperature, but are lower when there is no rain and show a strong decline from 2012 through 2017, particularly for species that feed on amphibians and reptiles. We have no reason to believe that the decline is an erroneous interpretation or that the snakes moved elsewhere, the decline of snakes in Drake seems to be real and needs attention from the conservation authorities.

Introducción: A pesar de que la disminución de serpientes parece ser una realidad en muchas partes del mundo, algunos informes se basan en evidencia anecdótica y existe la necesidad de estudios prolongados e intensivos, especialmente en los trópicos, para corroborar. Objetivo: Investigar si las poblaciones de serpientes en Bahía Drake están disminuyendo y si existe una relación con la presa, el tiempo, la temperatura, la lluvia y la luz de la luna. Metodología: Contamos las serpientes que se ven por hora al caminar por un sendero en el bosque costero de la Bahía Drake, Costa Rica. Recorrimos el sendero por la noche durante un total de 842 noches (más de 4 000 horas de observaciones), desde el 2012 hasta el 2017, y registramos todas las serpientes individuales que pudimos ver con linternas de cabeza. Utilizamos pruebas ANDEVA para verificar correlaciones entre conteos por hora con luz de luna y lluvia; y análisis gráfico para asociaciones con dieta, temperatura, mes y año. Resultados: Registramos 25 especies (cinco familias); se alimentan principalmente de vertebrados terrestres. Las cuentas por hora han disminuido a lo largo de los años, especialmente para especies que se alimentan de anfibios y reptiles; Mastigodryas melanolomus se ha mantenido en números similares; y Siphlophis compressus no se ha visto desde mayo de 2016. La temperatura es relativamente constante durante todo el año en Drake, pero el mes afectó fuertemente los conteos, que aumentaron de agosto a septiembre. La mayoría de las especies se observaron con mayor frecuencia en noches lluviosas (0.11 por hora versus solo 0.03 por hora en noches sin lluvia, ANDEVA P 0.05). Conclusión: El recuento nocturno de serpientes en la Bahía de Drake, Costa Rica, no se ve muy afectado por la luz o la temperatura, pero es más bajo cuando no llueve y muestra un fuerte descenso desde 2012 hasta 2017, particularmente para las especies que se alimentan de anfibios y reptiles. No tenemos ninguna razón para creer que la disminución sea una interpretación errónea o que las serpientes se mudaron a otra parte, la disminución de las serpientes en Drake parece ser real y necesita la atención de las autoridades de conservación.

Ecuador publications in the Science Citation Index Expanded: institutions, subjects, citation and collaboration patterns

Introduction: Ecuador, a country of 17 million inhabitants with a medium human development index of 0.75, has a small scientific productivity in relation to its size and population. Objective: To analyze Ecuador publications in the Science Citation Index Expanded, focusing on productivity, subjects, institutions, citations, and trends. Methods: We analyzed scientific publications by authors from Ecuador from 1900 to 2017 in the Science Citation Index Expanded and compared it with other tropical countries. Results: We found 16 document types (7 806 articles). The three most productive institutions were Universidad San Francisco de Quito, Pontificia Universidad Católica del Ecuador, and Escuela Politécnica Nacional. USA and Spain were the most frequent collaborating countries. Most articles were in English and ecology, botany, and zoology were common, but no field produced over 8 % of articles. However, ecology represents 11.3 % of the total citations. The most cited papers in the database were from large international biology and physics projects with minimal participation of Ecuadorean scientists. Article citations occurs mostly after the SCI stops counting. Conclusion: Science in Ecuador is growing but needs to greatly increase collaboration among Ecuadorean institutions to reduce its dependence on foreing projects. However, this study did not include articles published by the hundreds of Ecuadorean journals not covered by the SCI Expanded.

Introducción: Ecuador es un país con 17 millones de habitantes y un indice de desarrollo humano medio de 0.75, pero tiene una baja producción científica en relación con su tamaño y población. Objectivo: Analizar las publicaciones de Ecuador en el Índice de Citación de Ciencia enfocándose en la productividad, categorías, instituciones, citaciones y tendencias. Métodos: En la base de datos Science Citation Index analizamos las publicaciones científicas de autores con dirección ecuatoriana desde 1900 hasta 2017 y comparamos los resultados con otros países tropicales. Resultados: Encontramos 16 tipos de documentos (7 806 artículos). Las tres instituciones más productivas fueron Universidad San Francisco de Quito, Pontificia Universidad Católica del Ecuador, y Escuela Politécnica Nacional. Estados Unidos y España fueron los países con colaboración más frecuente. La mayoría de los artículos fueron escritos en inglés con Ecología, Botánica y Zoología como las categorías más comunes, pero ninguna supera una producción del 8 % del total de las publicaciones. Sin embargo, Ecología representa el 11.3 % del total de citaciones. Los artículos más citados en esa base de datos fueron de grandes equipos internacionales en Biología y en Física, con poca participación de científicos ecuatorianos. La mayoría de las citas se dan después de que el SCI detiene el conteo. Conclusión: La ciencia en Ecuador está creciendo, pero se necesita aumentar la colaboración entre las instituciones ecuatorianas para reducir la dependencia de proyectos extranjeros. Se debe considerar que este estudio no incluyó los artículos publicados por centenares de revistas ecuatorianas que no son cubiertas por el Science Citation Index.

Bibliometrics of Vietnam Publications in the Science Citation Index: general trends and comparison with other tropical countries / Bibliometría de las publicaciones de Vietnam en el Science Citation Index: tendencias generales y comparación con otros países tropicales

Introduction: The economy of Vietnam, a highly populated tropical country with a per capita gross domestic product of $ 8 000, is growing rapidly, but there are few recent studies of general scope about its scientific productivity and how it compares with other tropical countries. Objective: To identify trends in Vietnamese science and compare them with trends in other tropical countries. Methods: We extracted data about scientific papers, in all disciplines that had Vietnam as country in the Science Citation Index Expanded for the period 1991 to 2018, focusing on type of publication, language, subject, authorship, collaboration, and citations. Results: Vietnam publishes more document types than other tropical countries, and those in this particular database are mostly in English, albeit most Vietnamese science is published in Vietnamese and not covered by the index. The primary categories were multidisciplinary materials science, mathematics, and applied mathematics. Most collaboration was done with the USA, Japan, South Korea, and France. A large number of articles were published by the Vietnam Academy of Science and Technology, and the most frequent foreign collaboration was with the University of Oxford. Conclusion: The tropical countries of Latin America, Africa, and Asia studied in our project have some similarities but also crucial differences. Science is developing rapidly in Vietnam and the production of articles in Vietnamese, which represent the vast majority of research in the country but is not included in this database, should also be studied.

Introducción: La economía de Vietnam, un país tropical muy poblado con un producto interno bruto per cápita de $ 8000, está creciendo rápidamente, pero hay pocos estudios recientes y de enfoque general sobre su productividad científica y cómo se compara con la de otros países tropicales. Objetivo: Identificar tendencias en la ciencia vietnamita y compararlas con las tendencias en otros países tropicales. Métodos: Extrajimos datos sobre artículos científicos, en todas las disciplinas que tenían a Vietnam como "país" en el Science Citation Index Expanded para el período 1991 a 2018, centrándonos en el tipo de publicación, idioma, tema, autoría, colaboración y citas. Resultados: Vietnam publica más tipos de documentos que otros países tropicales, y los de esta base de datos en particular están principalmente en inglés, aunque la mayoría de la ciencia vietnamita se publica en vietnamita y no está cubierta por el índice. Las categorías principales fueron ciencia de materiales (estudios multidisciplinarios), matemáticas y matemáticas aplicadas. La mayor parte de la colaboración se realizó con EE. UU., Japón, Corea del Sur y Francia. La Academia de Ciencia y Tecnología de Vietnam publicó una proporción importante de estos artículos, y la colaboración extranjera más frecuente fue con la Universidad de Oxford. Conclusión: los países tropicales de América Latina, África y Asia estudiados en nuestro proyecto tienen tanto similitudes como diferencias importantes con Vietnam. La ciencia en Vietnam está en una etapa de crecimiento y convendría estudiar los artículos que se publican en vietnamita, los cuales representan la amplia mayoría de la ciencia del país, pero no se incluyen en esta base de datos.

Relative humidity, temperature, substrate type, and height of terrestrial lichens in a tropical paramo / Humedad relativa, temperatura, tipo de sustrato y altura de los líquenes del suelo en un páramo tropical

Abstract Lichens are traditionally divided into types such as "crustose", "foliose" and "fruticose", with different shapes and heights. Substrate, temperature and water are thought to affect lichen height, but there are few studies regarding tropical paramo lichens. Along 2015 I measured those variables in the terricolous lichens of the Cerro Buena Vista, paramo (Costa Rica, 9°33' N & 83°45' W). The measurements were taken inside the lichens and in the substrate under them, in 61 randomly located quadrats (50 x 50 cm). Lichens grew taller on (1) warmer ground, (2) wetter ground, (3) the moister Caribbean slope, and (4) the season with heavier rainfall, as expected. Apparently, atmospheric factors are more important than substrate in the determination of temperature, relative humidity and growth of lichens. Physiologically available water seems to be the main determinant of lichen vertical growth in the Buena Vista paramo.(AU)

Resumen Los líquenes se dividen tradicionalmente en morfotipos como "crustoso", "folioso" y "fruticoso", con diferentes formas y alturas. Se cree que el sustrato, la temperatura y el agua afectan la altura de los líquenes, pero existen pocos estudios con respecto a los líquenes tropicales. A lo largo del 2015, medí esas variables en los líquenes del suelo en el páramo de Cerro Buena Vista (Costa Rica, 9 ° 33'N; 83 ° 45'W). Las medidas se tomaron dentro de los líquenes y en el sustrato debajo de ellos, en 61 cuadrantes ubicados al azar (50 x 50 cm). Los líquenes fueron más altos en (1) suelo más cálido, (2) suelo más húmedo, (3) la pendiente del Caribe, que es más húmeda y (4) la temporada con lluvias más intensas, como se esperaba. Aparentemente, los factores atmosféricos son más importantes que el sustrato en la determinación de la temperatura, la humedad relativa y el crecimiento de los líquenes. El agua fisiológicamente disponible parece ser el principal determinante del crecimiento vertical de los líquenes en el páramo del Cerro Buena Vista.(AU)

Brunei Publications in the Science Citation Index Expanded (1973-2016): Bibliometrics and comparison with other tropical countries / Publicaciones de Brunei en el Science Citation Index Expanded (1973-2016): Bibliometría y comparación con otros países tropicales

Abstract Brunei is a small tropical country -located in Southeast Asia- for which there are no previous bibliometric studies. Here we analyze papers published by Brunei scientists from 1973 to 2016 in the Science Citation Index Expanded and compare results with other tropical countries. We identified 1 547 publications and 11 document types. The most productive categories were ecology, multidisciplinary geosciences, inorganic and nuclear chemistry, and environmental sciences. Singapore Medical Journal published most of these papers, and the three most productive institutions were Universiti Brunei Darussalam, RIPAS Hospital, and Universiti Teknologi Brunei. UK and Malaysia were the most frequent collaborating countries. M.A. Ali from the Universiti Brunei Darussalam was the most prolific author and a Brunei independent article written by C.K. Morley from the Universiti Brunei Darussalam in 2002 had the highest number of citations of the whole period and the highest number in 2016. The tropical countries of Central America and Asia have a few similarities but also important differences, and both are highly heterogeneous in scientific organization and productivity. Rev. Biol. Trop. 66(3): 1090-1100. Epub 2018 September 01.

Resumen Brunei es un pequeño país tropical del sudeste asiático, sobre el cual no hay estudios bibliométricos. Aquí analizamos los artículos publicados por científicos de Brunei de 1973 a 2016 y comparamos los resultados con otros países tropicales. Examinamos los documentos del Science Citation Index Expanded en la colección principal del Web of Science. Hallamos 1 547 publicaciones de Brunei con 11 tipos de documentos, donde las categorías más productivas fueron ecología, geociencias multidisciplinarias, química inorgánica y nuclear, y ciencias ambientales. Singapore Medical Journal publicó la mayoría, y las tres instituciones más productivas fueron: Universiti Brunei Darussalam, RIPAS Hospital y Universiti Teknologi Brunei. Reino Unido y Malasia fueron los países que más colaboraron con Brunei. M.A. Ali de la Universidad Brunei Darussalam fue el autor más prolífico. El mayor número total de citas, y el mayor número de citas en 2016, correspondieron a un artículo exclusivamente de Brunei, escrito por C. K. Morley de la Universiti Brunei Darussalam en 2002. Los países tropicales de América Central y Asia tienen algunas similitudes pero también diferencias importantes, siendo heterogéneos en su organización científica y productividad.

Road kills in tropical ecosystems: a review with recommendations for mitigation and for new research

Resumen Si bien los caminos son indispensables para la civilización moderna y benefician a muchas especies de vida silvestre, han estado causando mortalidad por atropello desde que se inventaron los carruajes de alta velocidad hace 4 000 años. La mayoría de trabajos científicos en el tema se han realizado en ecosistemas templados, pero algunos autores han sospechado que hay diferencias en ecosistemas tropicales. En esta revisión, resumo publicaciones que se centran en muertes en carretera en países tropicales de África, América, Asia y Oceanía. Encontré 73 estudios pertinentes. El número de artículos aumentó después del 2011 y los países más productivos, en artículos per capita son Costa Rica, Colombia y Brasil. En muchos estudios, los mamíferos aparecen como víctimas más frecuentes, pero los anfibios sufren mortalidad masiva durante la época reproductiva y la mortalidad de aves es unas 20 veces mayor de lo que se creía. Cada víctima es un pequeño ecosistema en sí, lleno de especies microscópicas, pero la microbiología de fauna atropellada aún no se desarrolla como rama nueva de la ciencia. No se puede generalizar sobre el papel de la temporada o el hábitat en la mortalidad en carreteras porque los datos mezclados ocultan patrones individuales. Para evitar conclusiones erróneas, hay que mantener registros separados por año, sexo, especie, hora del día, época y lugar. Muchas víctimas son movidas por los carroñeros, mueren fuera de la carretera, o son demasiado pequeñas para ser notadas, por lo que no hay un solo estudio, tropical o templado, que pueda responder con certeza y precisión cuántos animales mueren, dónde o cuándo: sólo tenemos aproximaciones. Las contribuciones importantes de los estudios tropicales incluyen el énfasis ético en aprovechar los especímenes atropellados para investigación, la inclusión de especies que no son de vida silvestre, el estudio de aspectos poco entendidos (como el efecto de la hora del día y tasas de éxito y fracaso al cruzar la carretera, así como la eficacia comprobada de reducir la velocidad para mitigar el problema). La llamada "ciencia ciudadana" puede identificar las especies más afectadas, pero aporta datos muy diferentes de los generados por científicos profesionales en cuanto a proporción de grupos afectados. La reducción de velocidad es la medida de mitigación más simple y efectiva. Respetando directrices éticas, los científicos tropicales deberían concentrarse en el monitoreo conservacionista, y en el trabajo experimental para entender mejor la ecología de los atropellos y hacer un aporte que compita con el de los países ricos.

Abstract While roads are indispensable for modern civilization and beneficial for many wildlife species, they have been causing mortality from collisions since high speed chariots were invented 4 000 years ago. Most scientific work about road kill has been done in temperate ecosystems, but some authors have suspected that they have different characteristics in tropical ecosystems. In this review, I summarize publications that focus on road kills in tropical countries from Africa, America, Asia and Oceania. I found 73 studies that focus on tropical road kills. Output increased after 2011 and the most productive countries, in articles per capita, are Costa Rica, Colombia and Brazil. Most studies report that mammals are the main victims, but bird deaths are severely underestimated and amphibians suffer mass mortality in reproductive concentrations. Every road victim is itself a small ecosystem that contains thousands of microscopic species, but "Road Kill Microbiology" is yet to be developed as a new branch of research. No generalization can be made about the role of season or habitat in road kills because pooled data hide individual trends: researchers should keep separate records by age, sex, species, time of day, season and place; otherwise important patterns will be missed. There is not a single study, tropical or temperate, that can completely answer how many animals are killed, where, or when, because many victims are removed by scavengers, end outside the road or are too small to be noticed. Significant contributions from the tropics include emphasis on the ethical use of road kill for research, inclusion of species other than wild vertebrates, study of often overlooked phenomena like hour of day and failed versus successful crossing attempts, and the value of speed control in mitigation. The so-called "citizen science" can identify the most affected species but produces data that are very different from those generated by professional scientists in terms of the proportion of affected groups. Real speed limitation is the simplest effective mitigation measure. Tropical scientists should concentrate on monitoring and experimental studies to fully understand the ecology of road kills and to make a contribution that matches what rich countries do. Rev. Biol. Trop. 66(2): 722-738. Epub 2018 June 01.