RESUMO
A recent paper by Beretta-Blanco and Carrasco-Letelier (2021) claims that agricultural eutrophication is not one of the main causes for cyanobacterial blooms in rivers and artificial reservoirs. By combining rivers of markedly different hydrological characteristics e.g., presence/absence and number of dams, river discharge and geological setting, the study speculates about the role of nutrients for modulating phytoplankton chlorophyll-a. Here, we identified serious flaws, from erratic and inaccurate data manipulation. The study did not define how erroneous original dataset values were treated, how the variables below the detection/quantification limit were numerically introduced, lack of mandatory variables for river studies such as flow and rainfall, arbitrary removal of pH > 7.5 values (which were not outliers), and finally how extreme values of other environmental variables were included. In addition, we identified conceptual and procedural mistakes such as biased construction/evaluation of model prediction capability. The study trained the model using pooled data from a short restricted lotic section of the (large) Uruguay River and from both lotic and reservoir domains of the Negro River, but then tested predictability within the (small) Cuareim River. Besides these methodological considerations, the article shows misinterpretations of the statistical correlation of cause and effect neglecting basic limnological knowledge of the ecology of harmful algal blooms (HABs) and international research on land use effects on freshwater quality. The argument that pH is a predictor variable for HABs neglects overwhelming basic paradigms of carbon fluxes and change in pH because of primary productivity. As a result, the article introduces the notion that HABs formation are not related to agricultural land use and water residence time and generate a great risk for the management of surface waterbodies. This reply also emphasizes the need for good practices of open data management, especially for public databases in view of external reproducibility.
Assuntos
Negro ou Afro-Americano , Rios , Monitoramento Ambiental , Eutrofização , Proliferação Nociva de Algas , Humanos , Fósforo/análise , Reprodutibilidade dos Testes , UruguaiRESUMO
Microcystis aeruginosa complex (MAC) encompasses noxious colonial bloom forming cyanobacteria. MAC representatives bloom in eutrophic freshwater and brackish ecosystems with stagnant water, were temperature and salinity are the main variables modulating their distribution, biomass and toxicity. Cell abundance and biovolume of MAC colonies define regulatory standards for public health. These variables depend upon colony size that in turn changes with environmental conditions. Here, we conducted two series of experiments to evaluate the response of MAC colonies morphological traits (length, volume, mucilage and number of cells) to temperature and salinity. In two series of experiments in the laboratory, we exposed natural MAC communities to three different temperatures (10, 21 and 30 °C) and four salinity levels (0, 5, 10 and 25 ppt) typically found in estuaries. We found that average colony length, volume and mucilage thickness did not change with temperature, but the cell-free space inside the colonies was smaller at the highest evaluated temperature (30 °C). Salinity fostered an increase in colony length, volume and mucilage thickness, while cell-free space diminished, resulting in higher cell density. The number of cells per colony was significantly related to colony size (length and volume) and both, temperature and salinity, affected the parameters of the relationships. Based on present results we propose statistical models to predict cell number per colony based on length and volume and accounting for the effect of salinity and temperature on these traits. This is applicable to ecological studies and to the monitoring of estuarine aquatic environments, by means of a fast and more accurate estimation of cell numbers to define MAC toxic populations early warning systems. A protocol is suggested for its application while the analysis of the interaction of temperature and salinity, as well as the variability in natural environments are objectives for future researches.
Assuntos
Monitoramento Ambiental/métodos , Microcystis/fisiologia , Águas Salinas/química , Salinidade , Temperatura , Microbiologia da ÁguaRESUMO
Honeybees Apis mellifera are important pollinators of wild plants and commercial crops. For more than a decade, high percentages of honeybee colony losses have been reported worldwide. Nutritional stress due to habitat depletion, infection by different pests and pathogens and pesticide exposure has been proposed as the major causes. In this study we analyzed how nutritional stress affects colony strength and health. Two groups of colonies were set in a Eucalyptus grandis plantation at the beginning of the flowering period (autumn), replicating a natural scenario with a nutritionally poor food source. While both groups of colonies had access to the pollen available in this plantation, one was supplemented with a polyfloral pollen patty during the entire flowering period. In the short-term, colonies under nutritional stress (which consumed mainly E. grandis pollen) showed higher infection level with Nosema spp. and lower brood and adult bee population, compared to supplemented colonies. On the other hand, these supplemented colonies showed higher infection level with RNA viruses although infection levels were low compared to countries were viral infections have negative impacts. Nutritional stress also had long-term colony effects, because bee population did not recover in spring, as in supplemented colonies did. In conclusion, nutritional stress and Nosema spp. infection had a severe impact on colony strength with consequences in both short and long-term.
Assuntos
Fenômenos Fisiológicos da Nutrição Animal/fisiologia , Abelhas/microbiologia , Abelhas/fisiologia , Animais , Colapso da Colônia , Eucalyptus , Nosema , Pólen , Estresse Fisiológico , Trypanosomatina/genética , Trypanosomatina/patogenicidade , Varroidae/patogenicidadeRESUMO
The Microcystis aeruginosa complex (MAC) clusters many of the most common freshwater and brackish bloom-forming cyanobacteria. In monitoring protocols, biovolume estimation is a common approach to determine MAC colonies biomass and useful for prediction purposes. Biovolume (µm3 mL-1) is calculated multiplying organism abundance (orgL-1) by colonial volume (µm3org-1). Colonial volume is estimated based on geometric shapes and requires accurate measurements of dimensions using optical microscopy. A trade-off between easy-to-measure but low-accuracy simple shapes (e.g. sphere) and time costly but high-accuracy complex shapes (e.g. ellipsoid) volume estimation is posed. Overestimations effects in ecological studies and management decisions associated to harmful blooms are significant due to the large sizes of MAC colonies. In this work, we aimed to increase the precision of MAC biovolume estimations by developing a statistical model based on two easy-to-measure dimensions. We analyzed field data from a wide environmental gradient (800â¯km) spanning freshwater to estuarine and seawater. We measured length, width and depth from ca. 5700 colonies under an inverted microscope and estimated colonial volume using three different recommended geometrical shapes (sphere, prolate spheroid and ellipsoid). Because of the non-spherical shape of MAC the ellipsoid resulted in the most accurate approximation, whereas the sphere overestimated colonial volume (3-80) especially for large colonies (MLD higher than 300⯵m). Ellipsoid requires measuring three dimensions and is time-consuming. Therefore, we constructed different statistical models to predict organisms depth based on length and width. Splitting the data into training (2/3) and test (1/3) sets, all models resulted in low training (1.41-1.44%) and testing average error (1.3-2.0%). The models were also evaluated using three other independent datasets. The multiple linear model was finally selected to calculate MAC volume as an ellipsoid based on length and width. This work contributes to achieve a better estimation of MAC volume applicable to monitoring programs as well as to ecological research.
Assuntos
Monitoramento Ambiental/métodos , Microcystis/citologia , Microcystis/crescimento & desenvolvimento , Biomassa , Água Doce/microbiologia , Modelos Lineares , Água do Mar/microbiologia , UruguaiRESUMO
The study of the mammalian GnRH system has been greatly advanced by the development of immortalized cell lines. Of particular relevance are the so-called GT1 cells. Not only do they exhibit many of the known physiologic characteristics of GnRH neurons in situ, but in approximately one decade have yielded new insights regarding the intrinsic physiology of individual cells and networks of GnRH neurons, as well as the nature of central and peripheral signals that directly modulate their function. For instance, valuable information has been generated concerning intrinsic properties of the system such as the inherent pulsatile pattern of secretion displayed by networks of GT1 cells. Concepts regarding feedback regulation and autocrine feedback of GnRH neurons have been dramatically expanded. Likewise, the nature of the receptors and of the proximal and distal signal transduction mechanisms involved in the actions of multiple afferent signals has been identified. Understanding this neuronal system allows a better comprehension of the hypothalamic-pituitary-gonadal axis and of the regulatory influences that ultimately control reproductive competence.
Assuntos
Hormônio Liberador de Gonadotropina/metabolismo , Neurônios/metabolismo , Vias Aferentes/fisiologia , Animais , Neoplasias Encefálicas/patologia , Catecolaminas/fisiologia , AMP Cíclico/fisiologia , Retroalimentação , Feminino , Hormônios Esteroides Gonadais/fisiologia , Sistema Hipotálamo-Hipofisário/fisiologia , Masculino , Camundongos , Camundongos Transgênicos , Neuroglia/fisiologia , Neurotransmissores/fisiologia , Condutos Olfatórios/patologia , Ovário/fisiologia , Prosencéfalo/patologia , Fluxo Pulsátil , Ratos , Receptores de Neurotransmissores/efeitos dos fármacos , Receptores de Neurotransmissores/fisiologia , Taxa Secretória , Transdução de Sinais , Testículo/fisiologia , Células Tumorais CultivadasRESUMO
OBJECTIVE: Systemic lupus erythematosus (SLE) has been associated with high levels of prolactin in the circulation of some patients. Although prolactin stimulates immune responses, the relationship between hyperprolactinemia and the pathophysiology of SLE remains controversial. This study was undertaken to investigate whether circulating bioactive prolactin isoforms are associated with the activity of SLE. METHODS: The molecular heterogeneity of prolactin was studied in the plasma of patients with active and inactive SLE and in healthy volunteers by radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), Nb2-cell bioassay, and immunoprecipitation-Western blots. The specificity of the bioassay determinations was assessed by neutralization of growth-promoting effects with antiserum to human prolactin. RESULTS: Significantly higher prolactin levels were detected by bioassay and by ELISA than by RIA in both subsets of SLE patients and in normal individuals. Plasma prolactin levels in the SLE patients were significantly greater than those in the normal controls when measured by ELISA, but not by RIA or bioassay. The bioassay:ELISA and bioassay:RIA ratios were similar between SLE patients and controls, suggesting that prolactin biopotency was not altered with the disease, and none of the 3 assays detected a difference in prolactin levels between patients with active SLE and those with inactive SLE. However, the prolactin detected in plasma was associated with immunoreactive proteins of 130 kd and 23 kd, and the concentration of the 130-kd prolactin-like species was 10-fold higher in inactive SLE versus active SLE patients. CONCLUSION: Discrepancies among assays substantiate the molecular heterogeneity of circulating prolactin. The prolactin isotype that is found in association with inactive SLE could be of potential use as a marker for the inactive form of the disease and as an index for the efficacy of treatment.
Assuntos
Lúpus Eritematoso Sistêmico/sangue , Prolactina/sangue , Isoformas de Proteínas/sangue , Animais , Anticorpos Monoclonais/farmacologia , Western Blotting , Divisão Celular/efeitos dos fármacos , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Masculino , Testes de Precipitina , Prolactina/imunologia , Prolactina/farmacologia , Isoformas de Proteínas/imunologia , Isoformas de Proteínas/farmacologia , Radioimunoensaio , Ratos , Células Tumorais Cultivadas/citologia , Células Tumorais Cultivadas/efeitos dos fármacosRESUMO
Hypothalamic dopamine (DA) tonically inhibits prolactin (PRL) release from the anterior pituitary gland. Transient escapes from this DA tone elicit a pronounced potentiation of the PRL-releasing action of secretagogues such as thyrotropin-releasing hormone (TRH). Previous evidence has suggested that modulation of Ca(2+) channels can be involved in this potentiation. With a lactotropic cell line (GH(4)C(1)) expressing human D(2)-DA receptors, we tested the hypothesis that a brief escape from the tonic inhibitory action of DA triggers a facilitation of Ca(2+) influx through Ca(2+) channels. We initially found that in these cells, DA effectively and reversibly inhibited PRL secretion, and reversibly enhanced an inwardly rectifying K(+) current. The effects of DA administration and withdrawal on Ca(2+) currents were examined using the patch-clamp technique in the whole-cell configuration and Ba(2+) as a divalent charge carrier through Ca(2+) channels. Macroscopic Ba(2+) currents were significantly decreased by short term (1-10 min) applications of DA (500 nM), which further declined following 24 h of constant exposure to DA. After DA removal, a biphasic facilitation of the density of Ba(2+) currents was observed. An initial 2-fold enhancement of conductance was detected between 10 and 40 min, followed by a second facilitation of the same magnitude observed 24 h after DA withdrawal. The present results directly demonstrate that dissociation of DA from D(2)-receptors expressed in GH(4)C(1) lactotrope cells causes an increase of high-voltage-activated Ca(2+) channel function, which may play an important role in the cross-talking amplification of endocrine cascades such as that involved in the TRH-induced PRL-release potentiating action of DA withdrawal.
Assuntos
Canais de Cálcio Tipo L/metabolismo , Dopamina/fisiologia , Canais de Potássio Corretores do Fluxo de Internalização , Prolactina/metabolismo , Animais , Bário/metabolismo , Dopamina/farmacologia , Eletrofisiologia , Indicadores e Reagentes , Potenciais da Membrana/fisiologia , Técnicas de Patch-Clamp , Hipófise/citologia , Hipófise/efeitos dos fármacos , Hipófise/metabolismo , Canais de Potássio/efeitos dos fármacos , Canais de Potássio/metabolismo , Radioimunoensaio , Ratos , Hormônio Liberador de Tireotropina/farmacologiaRESUMO
Prolactin (PRL) release following the removal of tonic dopamine (DA) inhibition was investigated in superfused cultures of dispersed rat anterior pituitary cells. The removal of DA (500 nM) inhibition resulted in a rapid and sustained increased in PRL release as measured by RIA which occurred in an episodic manner. The first PRL pulse reached a maximum 15 to 30 min. after DA removal (20.6 +/- 1.1 min). The second pulse occurred 40 to 45 min. after DA removal and the mean interpulse period was 21.7 +/- 1.2 min. The amplitude of the first pulse was 1.6 to 13.5 higher than the value observed in the presence of DA. It was followed by a nadir that was 1.1 to 8.0 fold higher than the basal value. The second pulse was of slightly lower amplitude, reaching a maximum of 2.3 to 8.0 fold over the control value and 1.25 to 2.5 fold over the preceding nadir. This episodic pattern was observed in 16 independent experiments performed with cells cultured at a density of 0.7-2.8 x 10(6) cells/coverslip. We hypothesize that lactotrophs in vitro have an inherent 20 minute secretory rhythm as has been observed under certain circumstances in vivo. Tonic dopamine inhibition restrains the otherwise random secretory rhythms of lactotrophs thereby synchronizing the secretory phase of the cells upon its removal. Consistent with this hypothesis episodic PRL release was not observed when DA was constantly present or absent.