SpectraMax Paradigm Multi-Mode Microplate Reader

Development of predictive in vitro assays suitable for safety and efficacy testing is of high interest for improving the drug development process and reducing drug attrition. Recently, there has been a great interest in using stem cells as tools for screening compounds during early drug development. Cardiomyocytes, neuronal progenitors, hepatocytes, and hematopoietic stem cells have all been shown to be attractive cell models for performing a variety of assays. Typically, such assays are performed using high content imaging and analysis (HCA) that allows individual assessment of cell response and multi-parametric outputs. However, there is a need for higher throughput methods with similar sensitivity. Here we present results obtained from the SpectraMax® Paradigm® Plate Reader for performing toxicity assessment of various compounds using stem cell derived cell models in a high throughput manner. The system is configured for cell-based assays with a highly sensitive direct bottom fluorescence read. Plates can be scanned using “Well Scan” or “On-The-Fly” read types. Several viability markers were evaluated including Calcein AM, actin, and mitochondrial stain. We have characterized a number of known hepatotoxic compounds and IC50 values were determined. Excellent agreement was found between plate reader and HCA results.

The γ-aminobutyric acid (GABA) shunt is closely associated with plant tolerance; however, little is known about its mechanism. This study aimed to decipher the responses of the GABA shunt and related carbon–nitrogen metabolism in poplar seedlings (Populus alba × Populus glandulosa) treated with different NaCl and CdCl₂ concentrations for 30 h. The results showed that the activities of glutamate decarboxylase (GAD) and GABA-transaminase (GABA-T) were activated, as well as α-ketoglutarate dehydrogenase (α-KGDH) and succinate dehydrogenase (SDH) activities were enhanced by NaCl and CdCl₂ stresses, except for SDH under CdCl₂ stress. Meanwhile, the expression levels of GADs, GABA-Ts SDHs, succinyl-CoA ligases (SCSs), and succinic acid aldehyde dehydrogenases (SSADHs) were also increased. Notably, significant increases in the key components of GABA shunt, Glu and GABA, were observed under both stresses. Soluble sugars and free amino acids were enhanced, whereas citrate, malate and succinate were almost inhibited by both NaCl and CdCl₂ stresses except that citrate was not changed or just increased by 50-mM NaCl stress. Thus, these results suggested that the carbon–nitrogen balance could be altered by activating the GABA shunt when main TCA-cycle intermediates were inhibited under NaCl and CdCl₂ stresses. This study can enhance the understanding about the functions of the GABA shunt in woody plants under abiotic stresses and may be applied to the genetic improvement of trees for phytoremediation.

The rise in antibiotic resistance has become a daunting concern in the last decade, including strains like methicillin-resistant Staphylococcus aureus (MRSA), causing significant health problems and extensive medical bills. It is important, then, to explore novel, non-drug antibiotics to reduce these life-threatening infections. Selenium nanoparticles (SeNP) have been shown to exhibit specific toxicity to bacteria while remaining non-toxic to healthy mammalian cells.