The presence of the swirling phenomenon is useful to define platelet concentrates that are suitable for transfusion. If it is possible to identify donor-related factors which are related to persisting swirling during storage, it is possible to select platelet donors. Endogenous platelet serotonin content is stable and easily measured and related to agonist-induced serotonin secretion. During a 3-month period, the swirling in 825 single donor platelet concentrates was controlled before issue. Endogenous serotonin, % serotonin release and swirling were tested in 21 concentrates with poor or no swirling during storage. Sixty-three concentrates were randomly selected from the routinely prepared platelet concentrates and were routinely tested with the same analyses on days 1 and 7. To evaluate an obvious effect of endogenous serotonin on the swirling phenomenon, eight platelet concentrates prepared from buffy coat, each from four donors, were divided. One part was stored in the presence of 8.5 micromol serotonin L-1, and analysed as the control concentrates. The endogenous serotonin content in the 'low- swirling' concentrates was significantly lower than in the control group (P < 0.001). PCO2 and pH were significantly lower, and PO2 and MPV significantly higher than in the controls. In the control group, swirling after 7 days was significantly correlated with serotonin release. In the eight buffy-coat concentrates enriched in endogenous serotonin, both swirling and the percentage serotonin release were improved after storage for 10 days, compared with nonenriched concentrates. This study suggests that endogenous serotonin content and serotonin release are factors that may be of significance concerning preservation of the swirling phenomenon in platelet concentrates during storage.

The opportunistic pathogens Fusobacterium nucleatum and Porphyromonas gingivalis are Gram-negative bacteria associated with oral biofilm and periodontal disease. Although liquid cultures are often the preferred cultivation method in microbiology, bacterial cells in biofilm adopt a profoundly different phenotype reflecting the close cell-to-cell contact compare to their planktonic counterparts. To investigate F. nucleatum and P. gingivalis interactions relevant in biofilm formation, we applied liquid chromatography-tandem mass spectrometry to determine the expressed proteome of F. nucleatum and P. gingivalis cells that were grown either as biofilm or in planktonic culture, and individually or together.The proteomic analyses detected 1,322 F. nucleatum and 966 P. gingivalis proteins. We statistically compared the proteins label-free quantitative (LFQ) intensities between biofilm and planktonic culture and identified significant changes (p-value ≤0.05) in 0,4% F. nucleatum proteins, 7% P. gingivalis proteins, and more than 14% of all proteins in the dual-species model. For both species, proteins involved in vitamin B2 (riboflavin) metabolic process had significantly increased levels in the biofilm condition. In both mono- and dual-species biofilm models, P. gingivalis increased the production of proteins functional in translation, oxidation-reduction, and amino acid metabolism, when compared to planktonic cultures. However, when we compared LFQ intensities between mono- and dual-species models, over 90% of the significantly changed P. gingivalis proteins had their levels reduced in biofilm and planktonic settings of the dual-species model.Our findings suggest that the two bacteria interact with each other at the protein level and indicate that P. gingivalis reduces the production of multiple proteins because of more favourable growth conditions provided by F. nucleatum presence. The results highlight the complex interactions of bacteria contributing to oral biofilm, which need to be considered in the design of future prevention strategies.