PubMed · 14202831
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O E AUFRANC, W N JONES, W H HARRIS. 1964-11-30. MULTIPLE PSEUDOFRACTURES.. https://doi.org/10.1001/jama.1964.03070220048011
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Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus, the two most abundant phototrophs on Earth, thrive in oligotrophic oceanic regions. While it is well known that specific lineages are exquisitely adapted to prevailing in situ light and temperature regimes, much less is known of the molecular machinery required to facilitate occupancy of these low-nutrient environments. Here, we describe a hitherto unknown alkaline phosphatase, Psip1, that has a substantially higher affinity for phosphomonoesters than other well-known phosphatases like PhoA, PhoX, or PhoD and is restricted to clade III Synechococcus and a subset of high light I-adapted Prochlorococcus strains, suggesting niche specificity. We demonstrate that Psip1 has undergone convergent evolution with PhoX, requiring both iron and calcium for activity and likely possessing identical key residues around the active site, despite generally very low sequence homology. Interrogation of metagenomes and transcriptomes from TARA oceans and an Atlantic Meridional transect shows that psip1 is abundant and highly expressed in picocyanobacterial populations from the Mediterranean Sea and north Atlantic gyre, regions well recognized to be phosphorus (P)-deplete. Together, this identifies psip1 as an important oligotrophy-specific gene for P recycling in these organisms. Furthermore, psip1 is not restricted to picocyanobacteria and is abundant and highly transcribed in some α-proteobacteria and eukaryotic algae, suggesting that such a high-affinity phosphatase is important across the microbial taxonomic world to occupy low-P environments.
Bioactive glass (BG) is an effective synthetic bone graft material. BG granules of narrow size range (300-355 mum) have the ability to form new bone tissue inside excavations produced by in vivo resorption. Previously, we demonstrated that BG stimulates the differentiation of cultured osteoblast precursors if the glass surface was biomimetically modified by the formation of bone-like apatite and adsorption of serum proteins. We now report that modified BG can also increase the rate at which multipotential rat bone marrow stromal cells (rMSC) will undergo osteogenesis. BG promoted rMSC osteogenesis both when cells were plated in contact with BG and when cells were not directly in contact with the BG. Alkaline phosphatase activity, a marker of bone cell differentiation, was used as an indicator for osteogenesis. Alkaline phosphatase activity of rMSCs exposed to osteoinducers such as ascorbate, dexamethasone, and BMP-2 was enhanced in the presence of BG. The stimulatory effect of BG was more pronounced in rMSC cultures with low basal alkaline phosphatase activity than in those with higher activity. The enhanced differentiation of rMSCs was associated with both a change in rMSC morphology and altered chemical composition of the cell culture media. rMSCs cultured on BG in the presence of BMP or dexamethasone exhibited a more rounded osteoblast-like appearance as compared with cells grown on tissue culture plastic. In the presence of BG, elevated levels of calcium and silicon in the culture medium were observed throughout the 7-day culture period, suggesting a continuous dissolution of surface-modified BG and resulting release of BG dissolution products. The data suggest that both surface- and solution-mediated events play a role in the osteogenic effect of BG.
DNA is a universal analyte found in almost every organism. It is the code that dictates our genetic make-up and it provides a vast library of information. DNA sequences can indicate genetic modification of foodstuffs, how we may metabolise pharmaceuticals and the likelihood of suffering particular diseases. The basis for many of these genetic tests would benefit greatly from procedures that can accurately quantitate DNA in an absolute manner. This would then provide a sound and universally consistent foundation for regulatory and diagnostic decision making. This work compares two different enzymatic digestion systems as precursor steps to high accuracy isotope dilution mass spectrometry (IDMS) quantitation of a 20mer oligonucleotide. In the first approach, snake venom phosphodiesterase (SVP) digests the oligonucleotide to its constituent deoxynucleotides (dNMPs), followed by liquid chromatography-IDMS (LC-IDMS) quantitation. The second enzyme digestion approach used a combination of snake venom phosphodiesterase and shrimp alkaline phosphatase (SAP) which reduces the oligonucleotide to its constituent deoxynucleosides (dNs). This was then followed by an alternative LC separation and equivalent IDMS measurements. Total phosphorous content of the 20mer oligonucleotide was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). This provided independent data for comparison with the two enzyme digestion-IDMS based procedures. The most appropriate method of quantitation was found to be the combined SVP and SAP digestion. This approach negates the need to consider and/or account for the lack of a 5' terminal phosphate residue. It also enables the use of positive ion mass spectrometry which simplifies the chromatographic requirements. Based on the exact matched IDMS of the adenine deoxynucleoside, the concentration of the original 20mer oligonucleotide was found to be 110+/-9 microg g(-1). This showed good agreement with the ICP-OES data based on the measurement of phosphorus which gave an equivalent value for the original 20mer oligonucleotide of 108+/-5microg g(-1) (uncertainties at the 95% confidence interval). It is intended that this high accuracy methodology should be used to produce high calibre reference standards. These, in turn, could then be used to underpin the quality and consistency of routine measurements involving a variety of more commonly encountered methodologies. It should be noted that the IDMS procedures are equally applicable to both sequenced and non-sequenced oligonucleotide materials.