Phosphorus is frequently a limiting factor for phytoplankton in freshwater ecosystems, because algae and cyanobacteria are able to incorporate it only in a dissolved inorganic form. Phytoplankton evolved several mechanisms to overcome phosphorus limitation. One of them is the production of extracellular phosphatases. These enzymes are excreted on the surface of cells or released to the environment. They hydrolyze organic molecules containing phosphorus, which can be then incorporated by cells. This mechanism can influence the competitiveness of algae living in environments that are characterised by long-term phosphorus limitation (that is caused e.g. by the effect of low pH). In this study the influence of phosphorus concentration and form on extracellular phosphatase activity under laboratory conditions was investigated. The two experimental strains of the genus Coccomyxa (Chlorophyta) were isolated from acidified localities with different phosphorus availability  Plešné Lake and Hromnické Lake. Extracellular phosphatase activity on a single-cell level was measured using the FLEA technique and fluorescence microscopy. The FLEA technique allows direct visualization of phosphatases on the cell surface by incubating the samples with the artificial substrate ELF® 97 phosphate. Extracellular...

A fototerapia com laser em baixa intensidade (FTLBI) é capaz de aumentar o metabolismo celular, o que poderia influenciar na diferenciação ósseo/odontogênica das células-tronco da polpa dentária humada (hDPSCs). O PDGF e o BMP-2 são fatores de crescimento envolvidos na dentinogênese e na reparação tecidual. O PDGF tem papel importante durante o desenvolvimento embrionário, na proliferação e migração celular e na angiogênese, enquanto o BMP-2 está fortemente associado à diferenciação celular em tecidos mineralizados, como o osso e a dentina. Sendo assim, o objetivo do estudo foi analisar os efeitos da FTLBI e dos fatores de crescimento (PDGF-BB ou BMP-2), isolados ou em associação, na diferenciação ósseo/odontogênica das hDPSCs. Para o estudo hDPSCs foram cultivadas em meio regular (G1) e irradiadas (G2), meio mineralizante (G3) e irradiadas (G4), meio mineralizante contendo PDGF-BB (G5) e irradiadas (G6), meio mineralizante contendo BMP-2 (G7) e irradiadas (G8). Para os grupos irradiados, a FTLBI foi realizada no modo pontual e em contato, com um laser de diodo semi-condutor, com área de feixe de 0,028cm2 e comprimento de onda 660nm (InGaAlP-vermelho), utilizando-se os seguintes parâmetros: potência de 20mW, densidade de energia de 5J/cm2, tempo de irradiação de 7 segundos por ponto e 0,14J de energia por ponto. A expressão dos genes relacionados à diferenciação ósseo/odontogênica (DSPP, DMP-1 e OCN) através do PCR quantitativo em tempo real (qRT-PCR), a atividade da fosfatase alcalina e os depósitos de cálcio foram analisados em 3, 7 e 14 dias. Os dados obtidos foram comparados pelo teste ANOVA complementado pelo teste de Tukey (p<0,05). As culturas tratadas com meio mineralizante contendo BMP-2 e irradiadas (G8) foram as que mostraram os maiores índices de diferenciação ósseo/odontogênica nos testes realizados. As expressões de DSPP, OCN e DMP-1, ao menos em 14 dias, foram significantemente maiores no G8 que nos demais grupos experimentais, exceto os grupos G3 e G7. Estes grupos apresentaram expressões de DSPP e OCN semelhantes às do G8 em 14 dias. A maior atividade de ALP foi observada no G8 em 3 dias e a menor no mesmo grupo aos 14 dias. A maior quantidade de depósitos de cálcio também foi encontrada no G8 em 14 dias. A associação de FTLBI e BMP-2 se mostrou capaz de induzir a diferenciação ósseo/odontogênica em células-tronco de polpa dentária humana de forma mais marcante que as demais terapias isoladas ou associadas estudadas. Portanto, o uso de uma terapia associando FTLBI e BMP-2 poderia ser de relevância para o restabelecimento da fisiologia pulpar quando aplicada em casos de exposição deste tecido, uma vez que poderia favorecer a diferenciação das células indiferenciadas da polpa dentária. / Laser phototherapy (LPT) is able to increase cellular metabolism, which in turn could influence the odontogenic differentiation of dental pulp stem cells (hDPSCs). PDGF and BMP-2 are growth factors involved in dentinogenesis and tissue repair. PDGF plays a role in embryonic development, cell proliferation, cell migration, and angiogenesis, whereas BMP-2 is strongly associated with cell differentiation in mineralized tissues such as bone and dentin. The aim of this study was to analyze the effects of LPT and the growth factors PDGF-BB and BMP-2 combined or not on the odontogenic differentiation of hDPSCs. These cells were grown in regular medium (G1) and irradiated (G2), mineralizing medium (G3) and irradiated (G4), mineralizing medium containing PDGF-BB (G5) and irradiated (G6), mineralizing medium containing BMP-2 (G7) and irradiated (G8). For irradiated groups, LPT was performed in punctual and contact mode with a semiconductor diode laser, with a beam spot area of 0.028 cm2 and wavelength of 660nm (InGaAlP-visible red), using the following parameters: power of 20mW, energy density of 5J/cm2 and irradiation time of 7 seconds per point (0,14 J per point). Differentiation was assessed by the following analysis: expression of genes related to odontogenic differentiation (DSPP, DMP-1 and OCN) using quantitative real time PCR (qRT-PCR); alkaline phosphatase activity and calcium deposition using alizarin red staining in 3, 7 and 14 days. Data were compared by ANOVA and Tukey´s test (p<0.05). The cultures treated with mineralizing medium containing BMP-2 and irradiated (G8) showed the highest rate of odontogenic differentiation. The expressions of DSPP, DMP-1 and OCN genes, at least in 14 days, were significantly higher in G8 compared to all other groups, except for the groups G3 and G7. These groups showed similar expressions of DSPP and OCN than G8 in 14 days. G8 showed the highest ALP activity in 3 days and the lowest in 14 days compared to all other groups. The largest amount of calcium deposits was observed in G8 in 14 days. The most striking feature on induction of odontogenic differentiation of hDPSCs was observed when LPT was applied in association with BMP-2. Therefore, the use of a combined LPT and BMP-2 therapy could be of relevance for the re-establishment of pulp physiology when applied in cases of dental pulp exposure by promoting the differentiation of hDPSCs.

A fototerapia com laser em baixa intensidade (FTLBI) é capaz de aumentar o metabolismo celular, o que poderia influenciar na diferenciação ósseo/odontogênica das células-tronco da polpa dentária humada (hDPSCs). O PDGF e o BMP-2 são fatores de crescimento envolvidos na dentinogênese e na reparação tecidual. O PDGF tem papel importante durante o desenvolvimento embrionário, na proliferação e migração celular e na angiogênese, enquanto o BMP-2 está fortemente associado à diferenciação celular em tecidos mineralizados, como o osso e a dentina. Sendo assim, o objetivo do estudo foi analisar os efeitos da FTLBI e dos fatores de crescimento (PDGF-BB ou BMP-2), isolados ou em associação, na diferenciação ósseo/odontogênica das hDPSCs. Para o estudo hDPSCs foram cultivadas em meio regular (G1) e irradiadas (G2), meio mineralizante (G3) e irradiadas (G4), meio mineralizante contendo PDGF-BB (G5) e irradiadas (G6), meio mineralizante contendo BMP-2 (G7) e irradiadas (G8). Para os grupos irradiados, a FTLBI foi realizada no modo pontual e em contato, com um laser de diodo semi-condutor, com área de feixe de 0,028cm2 e comprimento de onda 660nm (InGaAlP-vermelho), utilizando-se os seguintes parâmetros: potência de 20mW, densidade de energia de 5J/cm2, tempo de irradiação de 7 segundos por ponto e 0,14J de energia por ponto. A expressão dos genes relacionados à diferenciação ósseo/odontogênica (DSPP, DMP-1 e OCN) através do PCR quantitativo em tempo real (qRT-PCR), a atividade da fosfatase alcalina e os depósitos de cálcio foram analisados em 3, 7 e 14 dias. Os dados obtidos foram comparados pelo teste ANOVA complementado pelo teste de Tukey (p<0,05). As culturas tratadas com meio mineralizante contendo BMP-2 e irradiadas (G8) foram as que mostraram os maiores índices de diferenciação ósseo/odontogênica nos testes realizados. As expressões de DSPP, OCN e DMP-1, ao menos em 14 dias, foram significantemente maiores no G8 que nos demais grupos experimentais, exceto os grupos G3 e G7. Estes grupos apresentaram expressões de DSPP e OCN semelhantes às do G8 em 14 dias. A maior atividade de ALP foi observada no G8 em 3 dias e a menor no mesmo grupo aos 14 dias. A maior quantidade de depósitos de cálcio também foi encontrada no G8 em 14 dias. A associação de FTLBI e BMP-2 se mostrou capaz de induzir a diferenciação ósseo/odontogênica em células-tronco de polpa dentária humana de forma mais marcante que as demais terapias isoladas ou associadas estudadas. Portanto, o uso de uma terapia associando FTLBI e BMP-2 poderia ser de relevância para o restabelecimento da fisiologia pulpar quando aplicada em casos de exposição deste tecido, uma vez que poderia favorecer a diferenciação das células indiferenciadas da polpa dentária. / Laser phototherapy (LPT) is able to increase cellular metabolism, which in turn could influence the odontogenic differentiation of dental pulp stem cells (hDPSCs). PDGF and BMP-2 are growth factors involved in dentinogenesis and tissue repair. PDGF plays a role in embryonic development, cell proliferation, cell migration, and angiogenesis, whereas BMP-2 is strongly associated with cell differentiation in mineralized tissues such as bone and dentin. The aim of this study was to analyze the effects of LPT and the growth factors PDGF-BB and BMP-2 combined or not on the odontogenic differentiation of hDPSCs. These cells were grown in regular medium (G1) and irradiated (G2), mineralizing medium (G3) and irradiated (G4), mineralizing medium containing PDGF-BB (G5) and irradiated (G6), mineralizing medium containing BMP-2 (G7) and irradiated (G8). For irradiated groups, LPT was performed in punctual and contact mode with a semiconductor diode laser, with a beam spot area of 0.028 cm2 and wavelength of 660nm (InGaAlP-visible red), using the following parameters: power of 20mW, energy density of 5J/cm2 and irradiation time of 7 seconds per point (0,14 J per point). Differentiation was assessed by the following analysis: expression of genes related to odontogenic differentiation (DSPP, DMP-1 and OCN) using quantitative real time PCR (qRT-PCR); alkaline phosphatase activity and calcium deposition using alizarin red staining in 3, 7 and 14 days. Data were compared by ANOVA and Tukey´s test (p<0.05). The cultures treated with mineralizing medium containing BMP-2 and irradiated (G8) showed the highest rate of odontogenic differentiation. The expressions of DSPP, DMP-1 and OCN genes, at least in 14 days, were significantly higher in G8 compared to all other groups, except for the groups G3 and G7. These groups showed similar expressions of DSPP and OCN than G8 in 14 days. G8 showed the highest ALP activity in 3 days and the lowest in 14 days compared to all other groups. The largest amount of calcium deposits was observed in G8 in 14 days. The most striking feature on induction of odontogenic differentiation of hDPSCs was observed when LPT was applied in association with BMP-2. Therefore, the use of a combined LPT and BMP-2 therapy could be of relevance for the re-establishment of pulp physiology when applied in cases of dental pulp exposure by promoting the differentiation of hDPSCs.

Les plantes se distribuent dans des habitats présentant une disponibilité variable en nutriment et s'y adaptent en ajustant leur taux de croissance relatif. Les espèces adaptées aux habitats infertiles, affichent un taux de croissance plus faible que celles adaptées aux habitats fertiles. Les adaptations expliquant cette distribution ont été identifiées, premièrement, au niveau des feuilles. Un fort taux de fixation du carbone et d’allocation de ce dernier à la croissance sont favorisés en investissant davantage dans des tissus foliaires contenant des enzymes photosynthétiques riches en azote, par rapport aux tissus structuraux riches en carbone. Inversement, les feuilles favorisant une croissance lente présentent une plus grande quantité de tissus structuraux que de tissus riches en enzymes photosynthétiques, ce qui prolonge leur longévité, mais restreint leur taux d'assimilation du carbone. Étant donné que les adaptations foliaires dépendent de l'utilisation des nutriments acquis par les racines, les adaptations de ces dernières sont essentielles pour comprendre la distribution des plantes. Le fonctionnement des racines est influencé par les mêmes variations dans le ratio entre les tissus à forte teneur en protéines riches en azote et les tissus structuraux. Les fortes valeurs de ce ratio améliorent l’acquisition des nutriments et soutiennent une croissance rapide, tandis que les faibles valeurs prolongent la longévité des racines, mais restreignent leur taux d'acquisition. Cependant, les racines doivent également explorer le sol dû à la mobilité limitée des nutriments. Cette fonction est réalisée en établissant des relations symbiotiques avec des champignons ou par l'allongement de leurs racines. Cependant, contrairement aux adaptations foliaires, la relation entre ces adaptations racinaires et la disponibilité des nutriments présente des résultats contradictoires. De plus, ces adaptations n'influencent pas l'acquisition des nutriments non directement disponibles, comme les nutriments organiques, qui peuvent représenter une proportion importante des nutriments du sol. Cela limite notre compréhension de la nutrition des plantes et entrave notre compréhension des mécanismes expliquant leur distribution. Afin de mieux comprendre la nutrition des plantes, des feuilles et des racines furent échantillonnées le long de gradients de fertilité. Les résultats ont montré que l'utilisation de nutriments organiques par le biais d'enzymes hydrolytiques augmentait à mesure que la fertilité des sols diminuait. De plus, une forte corrélation entre cette adaptation et les adaptations racinaires liées aux taux d'acquisition des nutriments a été observée, mais aucune corrélation n'a été constatée avec celles liées à l'exploration du sol. En revanche, dans un autre système d'étude, les résultats ont indiqué que les adaptations racinaires liées à l'exploration du sol, plutôt que celles associées aux taux d'acquisition des nutriments, s'alignaient avec la variation de la disponibilité des nutriments et se coordonnaient avec les adaptations foliaires qui permettent d’expliquer en partie la distribution des plantes. Dans l'ensemble, ces études ont approfondi notre compréhension de la nutrition des plantes et ont révélé différentes relations entre la variation de la disponibilité des nutriments et les adaptations racinaires influençant l'acquisition des nutriments et l'exploration du sol. Cela suggère qu’une généralisation des adaptations racinaires répondant systématiquement aux demandes nutritionnelles des feuilles est peu probable. / Plants are distributed across habitats of varying nutrient availability and adapt by adjusting, notably, their relative growth rates. Species adapted to nutrient-poor habitats exhibit lower growth rates than those adapted to nutrient-rich habitats. The adaptations explaining this distribution have been identified, first and foremost, at the leaf level. Leaves promoting rapid growth enhance net carbon assimilation by investing more in nitrogen-rich photosynthetic enzymes compared to carbon-rich structural tissues. This extends their lifespan, enhances their nutrient-use efficiency but limits carbon assimilation. Given that foliar adaptations depend on the utilization of nutrients acquired by roots, root adaptations are essential to understanding plant distribution. Plants possess also the ability to modify the ratio between nitrogen-rich protein tissues and carbonrich structural tissues in their roots. Similarly to leaf functioning, increasing this ratio enhances the efficiency of nutrient acquisition while minimizing carbon investment, enabling optimal carbon allocation for growth. On the other hand, they can decrease this ratio to prioritize nutrient conservation, which extends their longevity but restricts nutrient acquisition rate. However, roots must also explore the soil due to the limited mobility of nutrients. Soil exploration is achieved by establishing symbiotic relationships with fungi or through the elongation of their roots. Unlike leaf adaptations, the relationship between these root adaptations and nutrient availability yields contradictory results. Additionally, these adaptations do not directly influence the acquisition of non-readily available soil nutrients, such as organic nutrients, which can represent a significant proportion of the total nutrient pool. Thus, our understanding of plant nutrition is limited, impeding our understanding of the mechanisms explaining their distributions. To contribute to an enriched understanding of plant nutrition, leaves and roots were sampled along strong fertility gradients. The results revealed an increase in the utilization of organic nutrients through hydrolytic enzymes as the availability of directly accessible nutrients declined. Furthermore, a strong correlation between this adaptation and root adaptations related to nutrient acquisition rates has been observed, but no correlation was found with adaptations related to soil exploration. On the other hand, in another study system, the results indicated that root adaptations related to soil exploration, rather than those associated with nutrient acquisition rates, aligned with the variation in nutrient availability and coordinated with foliar adaptations influencing net carbon assimilation. As a result, a high degree of mycorrhizal symbiosis was associated with leaves favoring rapid growth in fertile soil. Overall, roots displaying a high density of structural tissues and a high degree of symbiotic association were associated with fertile soil across two different study systems. Altogether, these results have deepened our understanding of plant nutrition and revealed different possible relationships between nutrient availability variation and root adaptations influencing nutrient acquisition and soil exploration. This suggests that generalizing root adaptations that consistently meet the nutrient demands of leaves is unlikely.