Applicability of differential fluorescein diacetate and propidium iodide fluorescence staining for monitoring algal growth and viability

Microalgae can be cultivated for producing high-valued products through the production of enzymes to offset the cost of CO_(2) sequestration,providing financial incentives.The viability of algae in the photobioreactor needs to be monitored to ensure biologically active live cells.In this study,we explored a simple fluorometry method for differentiation of live and dead algal cells in photobioreactors by fluorescein diacetate(FDA)and propidium iodide(PI)fluorescence staining.FDA stains fluorescent green to the living cells while PI stains the dead cells,allowing the discrimination of live and dead cells.The method was evaluated using two green algae and two strains of cyanobacteria grown in shake flasks and a continuously stirred photobioreactor.The method was found applicable for Chlorella pyrenoidosa and Synechococcus 7002 but was not applicable for the cultures of Scenedesmus dimorphus and Synechococcus elongatus 7942.We conclude that FDA is a good stain for monitoring live algal cells in photobioreactors but its applicability to individual species of algae must be evaluated.

The Function and Meaning of Receptor Activator of NF-κB Ligand in Arterial Calcification

Osteoclast-like cells are known to inhibit arterial calcification. Receptor activator of NF-κB ligand（RANKL） is likely to act as an inducer of osteoclast-like cell differentiation. However,several studies have shown that RANKL promotes arterial calcification rather than inhibiting arterial calcification. The present study was conducted in order to investigate and elucidate this paradox. Firstly,RANKL was added into the media,and the monocyte precursor cells were cultured. Morphological observation and Tartrate resistant acid phosphatase（TRAP） staining were used to assess whether RANKL could induce the monocyte precursor cells to differentiate into osteoclast-like cells. During arterial calcification,in vivo and in vitro expression of RANKL and its inhibitor,osteoprotegerin（OPG）,was detected by real-time PCR. The extent of osteoclast-like cell differentiation was also assessed. It was found RANKL could induce osteoclast-like cell differentiation. There was no in vivo or in vitro expression of osteoclast-like cells in the early stage of calcification. At that time,the ratio of RANKL to OPG was very low. In the late stage of calcification,a small amount of osteoclast-like cell expression coincided with a relatively high ratio of RANKL to OPG. According to the results,the ratio of RANKL to OPG was very low during most of the arterial calcification period. This made it possible for OPG to completely inhibit RANKL-induced osteoclast-like cell differentiation. This likely explains why RANKL had the ability to induce osteoclast-like cell differentiation but acted as a promoter of calcification instead.