Responses of Marine Diatom Skeletonema marinoi to Nutrient Deficiency: Programmed Cell Death.

Diatoms are important phytoplankton and contribute greatly to the primary productivity of marine ecosystems. Despite the ecological significance of diatoms and the importance of programmed cell death (PCD) in the fluctuation of diatom populations, little is known about the molecular mechanisms of PCD triggered by different nutrient stresses. Here we describe the physiological, morphological, biochemical, and molecular changes in response to low levels of nutrients in the ubiquitous diatom Skeletonema marinoi The levels of gene expression involved in oxidation resistance and PCD strongly increased upon nitrogen (N) or phosphorus (P) starvation. The enzymatic activity of caspase 3-like protein also increased. Differences in mRNA levels and protein activities were observed between the low-N and low-P treatments, suggesting that PCD could have a differential response to different nutrient stresses. When cultures were replete with N or P, the growth inhibition stopped. Meanwhile, the enzymatic activity of caspase 3-like protein and the number of cells with damaged membranes decreased. These results suggest that PCD is an important cell fate decision mechanism in the marine diatom S. marinoi Our results provide important insight into how diatoms adjust phenotypic and genotypic features of their cell-regulated death programs when stressed by nutrient limitations. Overall, this study could allow us to better understand the molecular mechanism behind the formation and termination of diatom blooms in the marine environment.IMPORTANCE Our study showed how the ubiquitous diatom S. marinoi responded to different nutrient limitations with PCD in terms of physiological, morphological, biochemical, and molecular characteristics. Some PCD-related genes (PDCD4, GOX, and HSP90) induced by N deficiency were relatively upregulated compared to those induced by P deficiency. In contrast, the expression of the TSG101 gene in S. marinoi showed a clear and constant increase during P limitation compared to N limitation. These findings suggest that PCD is a complex mechanism involving several different proteins. The systematic mRNA level investigations provide new insight into understanding the oxidative stress- and cell death-related functional genes of diatoms involved in the response to nutrient fluctuations (N or P stress) in the marine environment.

[A high content screening method for detection of anaphylactoid reaction of injection formulations].

Anaphylactoid reaction (AR) is the most common adverse reaction of injection formulations, however, there are obvious drawbacks in available methods for AR detection. A novel in vitro detection method for AR was established based on fluorescent labeling and high content screen (HCS) system in present study. With the use of RBL-2H3 cells degranulation model, positive cell count was determined with specific cellular membrane fluorescent dye FM4-64 labeling vesicle recycle, and total cells count was determined with specific nucleus fluorescent dye Hochest 3334, and then the ratio of cells degranulation after drug stimulation was calculated. In order to verify the reliability of this HCS method, positive drug Compound 48/80 was first used to confirm the consistence of HCS method with the traditional ß-hexosaminidase release test and the Evans blue staining ears test in mice. The results showed high consistence between HCS method and traditional testing methods, and the HCS method showed higher sensitivity than the other two tests. Then 30 samples of Danhong injection (DHI) with clinical allergy symptoms further were used to confirm the reliability of this HCS method. The HCS results showed high consistence with the clinical report, and the HCS method had the advantage in reducing the interference by drug color. Therefore, this HCS method is reliable, sensitive, simple and high-throughput method in detection of AR, applicable for the AR evaluation of injection formulations, and can provide guidance for safety of clinical application in clinical practice.