Effects of phosphorus starvation versus limitation on the marine cyanobacterium Prochlorococcus†MED4 I: uptake physiology.

Recent measurements of natural populations of the marine cyanobacterium Prochlorococcus indicate this numerically dominant phototroph assimilates phosphorus (P) at significant rates in P-limited oceanic regions. To better understand uptake capabilities of Prochlorococcus under different P stress conditions, uptake kinetic experiments were performed on Prochlorococcus MED4 grown in P-limited chemostats and batch cultures. Our results indicate that MED4 has a small cell-specific Vmax but a high specific affinity (αP ) for P, making it competitive with other marine cyanobacteria at low P concentrations. Additionally, MED4 regulates its uptake kinetics in response to P stress by significantly increasing Vmax and αP for both inorganic and organic P (PO4 and ATP). The Michaelis-Menten constant, KM , for PO4 remained constant under different P stress conditions, whereas the KM for ATP was higher when cells were stressed for PO4 , pointing to additional processes involved in uptake of ATP. MED4 cleaves the PO4 moieties from ATP, likely with a 5'-nucleotidase-like enzyme rather than alkaline phosphatase. MED4 exhibited distinct physiological differences between cells under steady-state P limitation versus those transitioning from P-replete to P-starved conditions. Thus, MED4 employs a variety of strategies to deal with changing P sources in the oceans and displays complexity in P stress acclimation and regulatory mechanisms.

Impacto da evolução científica no ensino e na prática odontológica brasileira ao longo dos séculos / Impact of scientific development on Brazilian oral health education and practice through the centuries

A história da Odontologia no Brasil iniciou-se de maneira rudimentar com instrumentos primitivos e sem preocupações com higiene. Não havia nenhuma referência à ciência, apenas à prática da profissão. No século XVII, evidencia-se um aumento no número de cáries e maior demanda por serviços odontológicos estéticos. Porém, apenas em 1879 inicia-se o estudo da Odontologia, no Brasil, e outras faculdades começam a se instalar somente a partir do século XX. A comprovação da origem bacteriana da doença cárie e surgimento de mais estudos referentes às doenças bucais ocorreram somente a partir da década de 1940. A fluoretação da água de abastecimento público foi o primeiro procedimento preventivo realizado no Brasil e o primeiro estudo epidemiológico nacional foi realizado em 1986. O Ministério da Saúde declarou que no ano de 2012, a quantidade de atendimentos odontológicos oferecidos pelo Sistema Único de Saúde foi de 150 milhões de consultas no país, além disso, o governo ampliou o sistema para 90% das cidades brasileiras atingindo uma população de 92 milhões de beneficiados e implementou serviços de promoção, prevenção e recuperação da saúde bucal. Apesar desse grande avanço, o controle da doença cárie em todas as faixas etárias ainda está longe de ser alcançado. Fazer com que todos os progressos obtidos até o momento cheguem a todos os cidadãos deve ser a meta deste século. (AU)

The history of dentistry in Brazil initiated in a rudimentary way with primitive tools and no hygiene preoccupations. There was no reference to science, only the practice of the profession. In the seventeenth century there is evidence about the increase of the number of dental caries and demand for aesthetics dental services. However, only in 1879 began the study of Dentistry in Brazil and new faculties were installed on the twentieth century. Evidence of bacterial decay and the emergence of more studies about oral diseases only occurred since the 1940s. Fluoride supplies of public water was the first preventive procedure performed in Brazil and the first national epidemiological study was conducted in 1986. The Ministry of Health stated that in the year 2012, the amount of dental care offered by the National Health System was 150 million consultations in the country, besides the government expanded the system to 90% of Brazilian cities reaching a population of 92 million of beneficiaries and implemented health promotion, prevention and recovery of oral health services. Despite this breakthrough, the control of caries in all age groups is still far from being achieved. Make all the progress made so far reaching all citizens should be the goal of this century. (AU)