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Although quantitative analysis of biological images demands precise extraction of specific organelles or cells, it remains challenging in broad-field grayscale images, where traditional thresholding methods have been hampered due to complex image features. Nevertheless, rapidly growing artificial intelligence technology is overcoming obstacles. We previously reported the fine-tuned apodized phase-contrast microscopy system to capture high-resolution, label-free images of organelle dynamics in unstained living cells (Shimasaki, K. et al. (2024). Cell Struct. Funct., 49: 21–29). We here showed machine learning-based segmentation models for subcellular targeted objects in phase-contrast images using fluorescent markers as origins of ground truth masks. This method enables accurate segmentation of organelles in high-resolution phase-contrast images, providing a practical framework for studying cellular dynamics in unstained living cells.Key words: label-free imaging, organelle dynamics, apodized phase contrast, deep learning-based segmentation

Cell biologists have long sought the ability to observe intracellular structures in living cells without labels. This study presents procedures to adjust a commercially available apodized phase-contrast (APC) microscopy system for better visualizing the dynamic behaviors of various subcellular organelles in living cells. By harnessing the versatility of this technique to capture sequential images, we could observe morphological changes in cellular geometry after virus infection in real time without probes or invasive staining. The tune-up APC microscopy system is a highly efficient platform for simultaneously observing the dynamic behaviors of diverse subcellular structures with exceptional resolution.

Polio or poliomyelitis is a disabling and life-threatening disease caused by poliovirus (PV). As a consequence of global polio vaccination efforts, wild PV serotypes 2 and 3 have been eradicated around the world, and wild PV serotype 1-transmitted cases have been largely eliminated except for limited regions. However, vaccine-derived PV, pathogenically reverted live PV vaccine strains, has become a serious issue. For the global eradication of polio, the World Health Organization is conducting the third edition of the Global Action Plan, which is requesting stringent control of potentially PV-infected materials. To facilitate the mission, we generated a PV-nonsusceptible Vero cell subline, which may serve as an ideal replacement of standard Vero cells to isolate emerging/re-emerging viruses without the risk of generating PV-infected materials.

Classical- (C-) and atypical L-type bovine spongiform encephalopathy (BSE) prions cause different pathological phenotypes in cattle brains, and the disease-associated forms of each prion protein (PrPSc) has a dissimilar biochemical signature. Bovine C-BSE prions are the causative agent of variant Creutzfeldt-Jakob disease. To date, human infection with L-BSE prions has not been reported, but they can be transmitted experimentally from cows to cynomolgus monkeys (Macaca fascicularis), a non-human primate model. When transmitted to monkeys, C- and L-BSE prions induce different pathological phenotypes in the brain. However, when isolated from infected brains, the two prion proteins (PrPSc) have similar biochemical signatures (i.e., electrophoretic mobility, glycoforms, and resistance to proteinase K). Such similarities suggest the possibility that L-BSE prions alter their virulence to that of C-BSE prions during propagation in monkeys. To clarify this possibility, we conducted bioassays using inbred mice. C-BSE prions with or without propagation in monkeys were pathogenic to mice, and exhibited comparable incubation periods in secondary passage in mice. By contrast, L-BSE prions, either with or without propagation in monkeys, did not cause the disease in mice, indicating that the pathogenicity of L-BSE prions does not converge towards a C-BSE prion type in this primate model. These results suggest that, although C- and L-BSE prions propagated in cynomolgus monkeys exhibit similar biochemical PrPSc signatures and consist of the monkey amino acid sequence, the two prions maintain strain-specific conformations of PrPSc in which they encipher and retain unique pathogenic traits.

Although quantitative analysis of biological images demands precise extraction of specific organelles or cells, it remains challenging in broad-field grayscale images, where traditional thresholding methods have been hampered due to complex image features. Nevertheless, rapidly growing artificial intelligence technology is overcoming obstacles. We previously reported the fine-tuned apodized phase-contrast microscopy system to capture high-resolution, label-free images of organelle dynamics in unstained living cells (Shimasaki, K. et al. (2024). Cell Struct. Funct., 49:21-29). We here showed machine learning-based segmentation models for subcellular targeted objects in phase-contrast images using fluorescent markers as origins of ground truth masks. This method enables accurate segmentation of organelles in high-resolution phase-contrast images, providing a practical framework for studying cellular dynamics in unstained living cells.Key words: Label-free imaging, Organelle dynamics, Apodized phase contrast, Deep learning-based segmentation

Cell biologists have long sought the ability to observe intracellular structures in living cells without labels. This study presents procedures to adjust a commercially available apodized phase-contrast (APC) microscopy system for better visualizing the dynamic behaviors of various subcellular organelles in living cells. By harnessing the versatility of this technique to capture sequential images, we could observe morphological changes in cellular geometry after virus infection in real time without probes or invasive staining. The tune-up APC microscopy system is a highly efficient platform for simultaneously observing the dynamic behaviors of diverse subcellular structures with exceptional resolution.Key words: Label-free imaging, Organelle dynamics, Virus infections, Apodized phase contrast

Global efforts are underway to eliminate measles and rubella and active viral surveillance is key to achieving this goal. In addition to this, the World Health Organization announced guidelines for handling materials potentially infectious for poliovirus (PV) to minimize the risk of PV reintroduction and achieve PV eradication. To support the global efforts, we have established new PV-non-susceptible cell lines useful for the isolation of measles virus (MeV) and rubella virus (RuV) (Vero ΔPVR1/2 hSLAM+). In the cell lines, MeV and RuV replicated efficiently with no concern about PV replication.

Polio or poliomyelitis is a disabling and life-threatening disease caused by poliovirus (PV). As a consequence of global polio vaccination efforts, wild PV serotype 2 has been eradicated, and wild PV serotypes 1- and 3-transmitted cases have been largely eliminated except for in limited regions around the world. However, vaccine-derived PV, pathogenically reverted live PV vaccine strains in vaccinated humans, has become a serious issue. For the global eradication of polio, the World Health Organization is conducting the third edition of the Global Action Plan, which is requesting stringent control of potentially PV-infected materials. To facilitate the mission, we generated a PV-nonsusceptible Vero cell subline, which may serve as an ideal replacement of standard Vero cells to isolate emerging/re-emerging viruses without the risk of generating PV-infected materials. Competing Interest Statement The authors have declared no competing interest.