In recent years graphene has drawn considerable research interest for biomedical applications. However, applications of graphene in biological systems also raise concerns about its possible toxicity. Here, by using live cell imaging techniques, we investigate the effect of pristine graphene on the viability as well as stress of both nonneuronal and neuronal cells under physiological conditions. We find that graphene promotes cell adhesion and proliferation. Furthermore, we find that graphene has no detectable adverse effect on mitochondrial membrane potential and morphology, or autophagy levels in the cell, indicating that graphene does not induce cell stress. Our results highlight the potential of graphene to be used in biomedical applications by providing long-term and stable nonneural and neural interfaces.

SUMMARY In eukaryotic cells, lysosomes are distributed in the cytoplasm as individual membrane-bound compartments to degrade macromolecules and to control cellular metabolism. A fundamental yet unanswered question is whether and, if so, how individual lysosomes are organized spatially to coordinate and integrate their functions. To address this question, we analyzed their collective behavior in cultured cells using spatial statistical techniques. We found that in single cells, lysosomes maintain non-random, stable, yet distinct spatial distributions mediated by the cytoskeleton, the endoplasmic reticulum (ER), and lysosomal biogenesis. Throughout the intracellular space, lysosomes form dynamic clusters that significantly increase their interactions with endosomes. Cluster formation is associated with local increases in ER spatial density but does not depend on fusion with endosomes or spatial exclusion by mitochondria. Taken together, our findings reveal whole-cell scale spatial organization of lysosomes and provide insights into how organelle interactions are mediated and regulated across the entire intracellular space.

Associate Editor William E. Bentley oversaw the review of this article.

SummaryIn eukaryotic cells, lysosomes are distributed in the cytoplasm as individual membranebound compartments to degrade macromolecules and to control cellular metabolism. A fundamental yet unanswered question is whether and, if so, how individual lysosomes are spatially organized so that their functions can be coordinated and integrated to meet changing needs of cells. To address this question, we analyze their collective behavior in cultured cells using spatial statistical techniques. We find that in single cells, lysosomes maintain nonrandom, stable, yet distinct spatial distributions, which are mediated by the coordinated effects of the cytoskeleton and lysosomal biogenesis on different lysosomal subpopulations. Furthermore, we find that throughout the intracellular space, lysosomes form dynamic clusters that substantially increase their interactions with endosomes. Together, our findings reveal the spatial organization of lysosomes at the whole-cell scale and provide new insights into how organelle interactions are mediated and regulated over the entire intracellular space.peer-reviewed)

The constant body temperature of homeotherms is the net result of the balance between heat production and heat loss. This balance is achieved through changes in physical and chemical functions mediated by neural mechanisms.Body temperature can be measured at a number of sites on the animal body; e.g. oral, rectal and axillary temperatures are often used clinically to indicate the deep body temperature. However, Benzinger (1961) suggests that because of its considerable thermal inertia, rectal temperature is not a reliable index of deep body temperature and although it may be a useful clinical indicator, it is not truly representative of the temperature which stimulates the heat-production or heat-conservation mechanisms.While it is unlikely that the temperature of any one location is truly representative of the deep body temperature, that of the blood supplying the brain seems to provide a better measure of the changes which affect thermoregulatory mechanisms than do any of the sites where body temperature is commonly measured. However, it was not until Bligh (1957 a) successfully implanted thermocouples in the bicarotid trunk of sheep tbat it became possible to keep the temperature of the blood flowing to the brain under constant observation for prolonged periods in the intact, conscious animal. This procedure has the disadvantage of requiring surgery which limits its application to a small number of animals at any given time. On the other hand, the non-surgical technique of measuring the temperature of the tympanic membrane (Benzinger, 1959) does not readily lend itself to animal research because each animal must be thoroughly trained to permit this kind of treatment. Thus, an attempt was made in this study to find a readily accessible location on the body of sheep which closely follows the temperature of the internal carotid artery and which could be used under a variety of experimental conditions.