Esta pesquisa objetivou levantar concepções de estudantes de Ciências Biológicas sobre a Natureza da Ciência (NdC). Para isso foram utilizados os questionários VNOS-C, desenvolvido por Norman Lederman, Fouad Abd-El-Khalick, Randy Bell e Reneé S. Schwartz, em 2002, e o questionário VOSE, desenvolvido por Sufen Chen, em 2006. Os dois questionários foram aplicados em alunos ingressantes do Curso de Ciências Biológicas do Instituto de Biociências da Universidade de São Paulo em duas etapas, no início e final do primeiro semestre letivo. A fim de complementar os dados fornecidos a partir da aplicação dos questionários VNOS-C e VOSE, foi realizada uma triangulação de metodológica e de dados, onde buscamos: a partir do Questionário Sociocultural e de Opinião Sobre a Importância da NdC, traçar o perfil sociocultural e de opinião dos alunos a respeito das questões investigadas, e, a partir de entrevistas semiestruturadas com professores dos alunos investigados, conhecer possíveis abordagens, em sala de aula, sobre questões da NdC. Para a análise escolhemos alguns aspectos da NdC a saber: a criatividade e imaginação na construção do conhecimento científico, a inserção da ciência na cultura, o papel das teorias na construção do conhecimento científico...
This research aimed to understand how students at different terms of a Biological Sciences course deal with the themes of evolution and the origin of life. The research instrument was a questionnaire developed within the European project BIOHEAD-CITIZEN applied in several countries aiming at analysing the views of students and teachers about health, environment and evolution. For this study only evolution questions were selected, which were answered by 56 students of the course of Biological Sciences, of the University Centre of Formiga, Minas Gerais (UNIFOR/MG), Brazil. The Qui-square (χ2) and Pearsons statistical tests were applied to estimate the effect of being enrolled in the course, i.e. applied to the answers of the students attending the 2nd, 4th and 6th terms. Results showed that they accommodate new conceptions about biological evolution and human origin, which often are conflicting between science and religion views. The contradictions observed may be associated to the lack students’ definition about dogmatic and scientific views. Comparisons with answers obtained in other Brazil regions and other countries were established. The results obtained at the 2nd, 4th and 6th course terms showed that attending the course leads to students’ conceptual changes. It was noticed that the dogmatic views hinder the understanding and acceptance of the new scientific concepts for any students and it was concluded that attending the course makes the future biology teachers modify their conceptions. However...
As questões ambientais, atualmente, têm sido abordadas de maneira que vai além dos impactos naturais, abrangendo aspectos socioeconômicos, políticos e culturais. Neste trabalho faz-se uma descrição das tipologias das concepções sobre o saber ambiental, com especial referência às relações que o permeiam, e desenvolve-se um trabalho empírico, analisando as concepções sobre o saber ambiental de estudantes concluintes do curso de licenciatura em ciências biológicas, em uma universidade do Estado da Bahia. Os dados foram recolhidos através de pesquisa de cunho qualitativo, por meio da aplicação do questionário de perguntas abertas com respostas em texto e desenho. Os resultados evidenciaram um predomínio de concepções naturalistas, mas não foram encontradas concepções socioambientais do tipo metabólicas. Tal resultado conduz à necessidade de inserção dessas abordagens críticas da questão ambiental na formação do professor de Ciências e Biologia, enfatizando interação entre trabalho, natureza e sociedade. Por fim, emergem também algumas sugestões de pesquisas futuras, entre as quais a de analisar as concepções sobre o ambiente que têm professores universitários de cursos de licenciatura em ciências biológicas e uma pesquisa-ação com os licenciandos investigados quanto à abordagem crítica sobre ambiente.; Nowadays...
Paige, Lisa A.; Christensen, Dale J.; Grøn, Hanne; Norris, John D.; Gottlin, Elizabeth B.; Padilla, Karen M.; Chang, Ching-yi; Ballas, Lawrence M.; Hamilton, Paul T.; McDonnell, Donald P.; Fowlkes, Dana M.
Fonte: The National Academy of SciencesPublicador: The National Academy of Sciences
Estrogen receptor (ER) modulators produce distinct tissue-specific biological effects, but within the confines of the established models of ER action it is difficult to understand why. Previous studies have suggested that there might be a relationship between ER structure and activity. Different ER modulators may induce conformational changes in the receptor that result in a specific biological activity. To investigate the possibility of modulator-specific conformational changes, we have applied affinity selection of peptides to identify binding surfaces that are exposed on the apo-ERs α and β and on each receptor complexed with estradiol or 4-OH tamoxifen. These peptides are sensitive probes of receptor conformation. We show here that ER ligands, known to produce distinct biological effects, induce distinct conformational changes in the receptors, providing a strong correlation between ER conformation and biological activity. Furthermore, the ability of some of the peptides to discriminate between different ER α and ER β ligand complexes suggests that the biological effects of ER agonists and antagonists acting through these receptors are likely to be different.
The primary motivation behind the considerable effort in studying stratospheric ozone depletion is the potential for biological consequences of increased solar UVB (280–315 nm) radiation. Yet, direct links between ozone depletion and biological impacts have been established only for organisms of Antarctic waters under the influence of the ozone “hole;” no direct evidence exists that ozone-related variations in UVB affect ecosystems of temperate latitudes. Indeed, calculations based on laboratory studies with plants suggest that the biological impact of ozone depletion (measured by the formation of cyclobutane pyrimidine dimers in DNA) is likely to be less marked than previously thought, because UVA quanta (315–400 nm) may also cause significant damage, and UVA is unaffected by ozone depletion. Herein, we show that the temperate ecosystems of southern South America have been subjected to increasingly high levels of ozone depletion during the last decade. We found that in the spring of 1997, despite frequent cloud cover, the passages of the ozone hole over Tierra del Fuego (55° S) caused concomitant increases in solar UV and that the enhanced ground-level UV led to significant increases in DNA damage in the native plant Gunnera magellanica. The fluctuations in solar UV explained a large proportion of the variation in DNA damage (up to 68%)...
For the act of membrane fusion, there are two competing, mutually exclusive molecular models that differ in the structure of the initial pore, the pathway for ionic continuity between formerly separated volumes. Because biological “fusion pores” can be as small as ionic channels or gap junctions, one model posits a proteinaceous initial fusion pore. Because biological fusion pore conductance varies widely, another model proposes a lipidic initial pore. We have found pore opening and flickering during the fusion of protein-free phospholipid vesicles with planar phospholipid bilayers. Fusion pore formation appears to follow the coalescence of contacting monolayers to create a zone of hemifusion where continuity between the two adherent membranes is lipidic, but not aqueous. Hypotonic stress, causing tension in the vesicle membrane, promotes complete fusion. Pores closed soon after opening (flickering), and the distribution of fusion pore conductance appears similar to the distribution of initial fusion pores in biological fusion. Because small flickering pores can form in the absence of protein, the existence of small pores in biological fusion cannot be an argument in support of models based on proteinaceous pores. Rather, these results support the model of a lipidic fusion pore developing within a hemifused contact site.
Collagen is a key fibrous protein in biological systems, characterized by a complex structural hierarchy as well as the ability to self-assemble into liquid crystalline mesophases. The structural features of collagen influence cellular responses and material properties, with importance for a wide range of biomaterials and tissue architectures. The mechanism by which fibrillar collagen structures form from liquid crystalline mesophases is not well characterized. We report positive printing of collagen and a collagen-like peptide down to 30–50-nm line widths, using the atomic force microscopy technique of dip-pen nanolithography. The method preserved the triple-helical structure and biological activity of collagen and even fostered the formation of characteristic higher levels of structural organization. The “direct-write” capability of biologically relevant molecules, while preserving their structure and functionality, provides tremendous flexibility in future biological device applications and in proteomics arrays, as well as a new strategy to study the important hierarchical assembly processes of biological systems.
Kin-selection theory has thrived in the explanation of a wide variety of biological phenomena, chiefly the evolution of biological altruism as that found in sterile castes of eusocial insects. Much of the way in which it has been tested is based on the existence of conflicts over sex-ratio production within eusocial colonies. However, despite neatly showing eusocial colonies as arenas where selection at the gene level triggers the appearance of sophisticated disputes, these studies have only demonstrated the existence of genes that act by biasing sex ratios to promote their own spread. Here we argue that such genes depend on the social organization of the colonies where they are expressed, but that they are not, in any way, the precursors of these societies—the major implication being that unequivocal evidence that eusociality evolved through the action of kin-selected altruistic genes is still lacking. Additionally, we highlight the neglect of alternative theories on the explanation of both biological altruism and sex-ratio conflicts, and defend that the enthusiasm with the latter has, in some cases, led to its inappropriate use as a basis for the explanation of other biological characteristics of eusocial organisms, when accounts based on phylogenetic or physiological constraints are also available.
We present a general algorithm to detect genes differentially expressed between two nonhomogeneous time-series data sets. As increasing amounts of high-throughput biological data become available, a major challenge in genomic and computational biology is to develop methods for comparing data from different experimental sources. Time-series whole-genome expression data are a particularly valuable source of information because they can describe an unfolding biological process such as the cell cycle or immune response. However, comparisons of time-series expression data sets are hindered by biological and experimental inconsistencies such as differences in sampling rate, variations in the timing of biological processes, and the lack of repeats. Our algorithm overcomes these difficulties by using a continuous representation for time-series data and combining a noise model for individual samples with a global difference measure. We introduce a corresponding statistical method for computing the significance of this differential expression measure. We used our algorithm to compare cell-cycle-dependent gene expression in wild-type and knockout yeast strains. Our algorithm identified a set of 56 differentially expressed genes...
Quantitative protein bioanalysis in complex biological fluids presents considerable challenges in biological studies and disease diagnosis. The major obstacles are the background signals from both the probe and the biological fluids where the proteins reside. We have molecularly engineered light-switching excimer aptamer probes for rapid and sensitive detection of a biomarker protein, platelet-derived growth factor (PDGF). Labeled with one pyrene at each end, the aptamer switches its fluorescence emission from ≈400 nm (pyrene monomer) to 485 nm (pyrene excimer) upon PDGF binding. This fluorescence wavelength change from monomer to excimer emission is a result of aptamer conformation rearrangement induced by target binding. The excimer probe is able to effectively detect picomolar PDGF in homogeneous solutions. Because the excimer has a much longer fluorescence lifetime (≈40 ns) than that of the background (≈5 ns), time-resolved measurements were used to eliminate the biological background. We thus were able to detect PDGF in a cell sample quantitatively without any sample pretreatment. This molecular engineering strategy can be used to develop other aptamer probes for protein monitoring. Combined with lifetime-based measurements and molecular engineering...
Biopolymers exhibit rough energy landscapes, thereby allowing biological processes to access a broad range of kinetic and thermodynamic states. In contrast to proteins, the energy landscapes of nucleic acids have been the subject of relatively few experimental investigations. In this study, we use calorimetric and spectroscopic observables to detect, resolve, and selectively enrich energetically discrete ensembles of microstates within metastable DNA structures. Our results are consistent with metastable, “native” DNA states being composed of an ensemble of discrete and kinetically stable microstates of differential stabilities, rather than exclusively being a single, discrete thermodynamic species. This conceptual construct is important for understanding the linkage between biopolymer conformational/configurational space and biological function, such as in protein folding, allosteric control of enzyme activity, RNA and DNA folding and function, DNA structure and biological regulation, etc. For the specific DNA sequences and structures studied here, the demonstration of discrete, kinetically stable microstates potentially has biological consequences for understanding the development and onset of DNA expansion and triplet repeat diseases.
Biological ice nucleators (IN) function as catalysts for freezing at relatively warm temperatures (warmer than −10 °C). We examined the concentration (per volume of liquid) and nature of IN in precipitation collected from Montana and Louisiana, the Alps and Pyrenees (France), Ross Island (Antarctica), and Yukon (Canada). The temperature of detectable ice-nucleating activity for more than half of the samples was ≥ −5 °C based on immersion freezing testing. Digestion of the samples with lysozyme (i.e., to hydrolyze bacterial cell walls) led to reductions in the frequency of freezing (0–100%); heat treatment greatly reduced (95% average) or completely eliminated ice nucleation at the measured conditions in every sample. These behaviors were consistent with the activity being bacterial and/or proteinaceous in origin. Statistical analysis revealed seasonal similarities between warm-temperature ice-nucleating activities in snow samples collected over 7 months in Montana. Multiple regression was used to construct models with biogeochemical data [major ions, total organic carbon (TOC), particle, and cell concentration] that were accurate in predicting the concentration of microbial cells and biological IN in precipitation based on the concentration of TOC...
To understand the effects of temperature on biological systems, we compile, organize, and analyze a database of 1,072 thermal responses for microbes, plants, and animals. The unprecedented diversity of traits (n = 112), species (n = 309), body sizes (15 orders of magnitude), and habitats (all major biomes) in our database allows us to quantify novel features of the temperature response of biological traits. In particular, analysis of the rising component of within-species (intraspecific) responses reveals that 87% are fit well by the Boltzmann–Arrhenius model. The mean activation energy for these rises is 0.66 ± 0.05 eV, similar to the reported across-species (interspecific) value of 0.65 eV. However, systematic variation in the distribution of rise activation energies is evident, including previously unrecognized right skewness around a median of 0.55 eV. This skewness exists across levels of organization, taxa, trophic groups, and habitats, and it is partially explained by prey having increased trait performance at lower temperatures relative to predators, suggesting a thermal version of the life-dinner principle—stronger selection on running for your life than running for your dinner. For unimodal responses, habitat (marine...
As the world grows less biologically diverse, it is becoming less linguistically and culturally diverse as well. Biologists estimate annual loss of species at 1,000 times or more greater than historic rates, and linguists predict that 50–90% of the world’s languages will disappear by the end of this century. Prior studies indicate similarities in the geographic arrangement of biological and linguistic diversity, although conclusions have often been constrained by use of data with limited spatial precision. Here we use greatly improved datasets to explore the co-occurrence of linguistic and biological diversity in regions containing many of the Earth’s remaining species: biodiversity hotspots and high biodiversity wilderness areas. Results indicate that these regions often contain considerable linguistic diversity, accounting for 70% of all languages on Earth. Moreover, the languages involved are frequently unique (endemic) to particular regions, with many facing extinction. Likely reasons for co-occurrence of linguistic and biological diversity are complex and appear to vary among localities, although strong geographic concordance between biological and linguistic diversity in many areas argues for some form of functional connection. Languages in high biodiversity regions also often co-occur with one or more specific conservation priorities...
In May 2012, Yale University’s Graduate School of Arts and Sciences held a
reunion for all who have received doctorates from Yale in the biological
sciences. The proceedings began with two presentations on the history of
biological research at Yale: one focused on the Medical School, and the other
centered on the rest of the University. This essay is a lightly edited version
of my account of the history of the biological sciences outside the Medical
Childhood maltreatment is likely to influence fundamental biological processes and engrave long-lasting epigenetic marks, leading to adverse health outcomes in adulthood. We aimed to elucidate the impact of different early environment on disease-related genome-wide gene expression and DNA methylation in peripheral blood cells in patients with posttraumatic stress disorder (PTSD). Compared with the same trauma-exposed controls (n = 108), gene-expression profiles of PTSD patients with similar clinical symptoms and matched adult trauma exposure but different childhood adverse events (n = 32 and 29) were almost completely nonoverlapping (98%). These differences on the level of individual transcripts were paralleled by the enrichment of several distinct biological networks between the groups. Moreover, these gene-expression changes were accompanied and likely mediated by changes in DNA methylation in the same loci to a much larger proportion in the childhood abuse (69%) vs. the non-child abuse-only group (34%). This study is unique in providing genome-wide evidence of distinct biological modifications in PTSD in the presence or absence of exposure to childhood abuse. The findings that nonoverlapping biological pathways seem to be affected in the two PTSD groups and that changes in DNA methylation appear to have a much greater impact in the childhood-abuse group might reflect differences in the pathophysiology of PTSD...
Mental disorders are increasingly understood biologically. We tested the effects of biological explanations among mental health clinicians, specifically examining their empathy toward patients. Conventional wisdom suggests that biological explanations reduce perceived blameworthiness against those with mental disorders, which could increase empathy. Yet, conceptualizing mental disorders biologically can cast patients as physiologically different from “normal” people and as governed by genetic or neurochemical abnormalities instead of their own human agency, which can engender negative social attitudes and dehumanization. This suggests that biological explanations might actually decrease empathy. Indeed, we find that biological explanations significantly reduce clinicians’ empathy. This is alarming because clinicians’ empathy is important for the therapeutic alliance between mental health providers and patients and significantly predicts positive clinical outcomes.
Establishing quantitative relationships between molecular structure and broad biological effects has been a longstanding challenge in science. Currently, no method exists for forecasting broad biological activity profiles of medicinal agents even within narrow boundaries of structurally similar molecules. Starting from the premise that biological activity results from the capacity of small organic molecules to modulate the activity of the proteome, we set out to investigate whether descriptor sets could be developed for measuring and quantifying this molecular property. Using a 1,567-compound database, we show that percent inhibition values, determined at single high drug concentration in a battery of in vitro assays representing a cross section of the proteome, provide precise molecular property descriptors that identify the structure of molecules. When broad biological activity of molecules is represented in spectra form, organic molecules can be sorted by quantifying differences between biological spectra. Unlike traditional structure–activity relationship methods, sorting of molecules by using biospectra comparisons does not require knowledge of a molecule's putative drug targets. To illustrate this finding, we selected as starting point the biological activity spectra of clotrimazole and tioconazole because their putative target...
The dual-use dilemma arises in the context of research in the biological and other sciences as a consequence of the fact that one and the same piece of scientific research sometimes has the potential to be used for bad as well as good purposes. It is an e
One popular assumption regarding biological systems is that traits have
evolved to be optimized with respect to function. This is a standard goal in
evolutionary computation, and while not always embraced in the biological
sciences, is an underlying assumption of what happens when fitness is
maximized. The implication of this is that a signaling pathway or phylogeny
should show evidence of minimizing the number of steps required to produce a
biochemical product or phenotypic adaptation. In this paper, it will be shown
that a principle of "maximum intermediate steps" may also characterize complex
biological systems, especially those in which extreme historical contingency or
a combination of mutation and recombination are key features. The contribution
to existing literature is two-fold: demonstrating both the potential for
non-optimality in engineered systems with "lifelike" attributes, and the
underpinnings of non-optimality in naturalistic contexts.
This will be demonstrated by using the Rube Goldberg Machine (RGM) analogy.
Mechanical RGMs will be introduced, and their relationship to conceptual
biological RGMs. Exemplars of these biological RGMs and their evolution (e.g.
introduction of mutations and recombination-like inversions) will be
demonstrated using block diagrams and interconnections with complex networks
(called convolution architectures). The conceptual biological RGM will then be
mapped to an artificial vascular system...