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  1. The use of fluorescence microscopy to study fate and transport of nanoparticles in the environment can be limited by the presence of confounding background signals such as autofluorescence and scattered light. The unique spin-related luminescence properties of nitrogen vacancy (NV) centers in diamond nanoparticles (NVND) enable new types of imaging modalities such as selective imaging of nanoparticles in the presence of background fluorescence. These techniques make use of the fact that the spin properties, which affect the fluorescence of NV centers, can be modulated using applied magnetic or radio-frequency fields. This work presents the use magnetic fields to modulate the fluorescence of NVND for background-subtracted imaging of nanoparticles ingested by a model organism, C. elegans . With the addition of modest time-modulated magnetic fields from an inexpensive “hobby” electromagnet, the fluorescence of 40 nm NVND can be modulated by 10% in a widefield imaging configuration. Herein, differential magnetic imaging is used to image and to isolate the fluorescence arising from nanodiamond within the gut of the organism C. elegans . This method represents a promising approach to probing the uptake of nanoparticles by organisms and to assessing the movement and interactions of nanoparticles in biological systems.
  2. Abstract

    Human cerebral organoids derived from induced pluripotent stem cells (iPSCs) provide novel tools for recapitulating the cytoarchitecture of human brain and for studying biological mechanisms of neurological disorders. However, the heterotypic interactions of neurovascular units, composed of neurons, pericytes, astrocytes, and brain microvascular endothelial cells, in brain-like tissues are less investigated. The objective of this study is to investigate the impacts of neural spheroids and vascular spheroids interactions on the regional brain-like tissue patterning in cortical spheroids derived from human iPSCs. Hybrid neurovascular spheroids were constructed by fusion of human iPSC-derived cortical neural progenitor cell (iNPC) spheroids, endothelial cell (iEC) spheroids, and the supporting human mesenchymal stem cells (MSCs). Single hybrid spheroids were constructed at different iNPC: iEC: MSC ratios of 4:2:0, 3:2:1 2:2:2, and 1:2:3 in low-attachment 96-well plates. The incorporation of MSCs upregulated the secretion levels of cytokines VEGF-A, PGE2, and TGF-β1 in hybrid spheroid system. In addition, tri-cultured spheroids had high levels of TBR1 (deep cortical layer VI) and Nkx2.1 (ventral cells), and matrix remodeling genes, MMP2 and MMP3, as well as Notch-1, indicating the crucial role of matrix remodeling and cell-cell communications on cortical spheroid and organoid patterning. Moreover, tri-culture system elevated blood-brain barrier genemore »expression (e.g., GLUT-1), CD31, and tight junction protein ZO1 expression. Treatment with AMD3100, a CXCR4 antagonist, showed the immobilization of MSCs during spheroid fusion, indicating a CXCR4-dependent manner of hMSC migration and homing. This forebrain-like model has potential applications in understanding heterotypic cell-cell interactions and novel drug screening in diseased human brain.

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  3. Abstract

    Cocaine is a highly abused drug that causes psychiatric and neurological problems. Its entry into neurons could alter cell-biochemistry and contribute in the manifestation of early pathological symptoms. We have previously shown the acute cocaine effects in rat C6 astroglia-like cells and found that these cells were highly sensitive to cocaine in terms of manifesting certain pathologies known to underlie psychological disorders. The present study was aimed to discern acute cocaine effects on the early onset of various changes in Neuro-2a (N2a) cells. Whole-cell patch-clamp recording of differentiated cells displayed the functional voltage-gated Na+and K+channels, which demonstrated the neuronal characteristics of the cells. Treatment of these cells with acute cocaine (1 h) at in vivo (nM to μM) and in vitro (mM) concentrations revealed that the cells remained almost 100% viable. Cocaine administration at 6.25 μM or 4 mM doses significantly reduced the inward currents but had no significant effect on outward currents, indicating the Na+channel-blocking activity of cocaine. While no morphological change was observed at in vivo doses, treatment at in vitro doses altered the morphology, damaged the neurites, and induced cytoplasmic vacuoles; furthermore, general mitochondrial activity and membrane potential were significantly decreased. Mitochondrial dysfunction enabled the cells switch to anaerobicmore »glycolysis, evidenced by dose-dependent increases in lactate and H2S, resulting unaltered ATP level in the cells. Further investigation on the mechanism of action unfolded that the cell’s resistance to cocaine was through the activation of nuclear factor E2-related factor-2 (Nrf-2) gene and subsequent increase of antioxidants (glutathione [GSH], catalase and GSH peroxidase [GPx]). The data clearly indicate that the cells employed a detoxifying strategy against cocaine. On a broader perspective, we envision that extrapolating the knowledge of neuronal resistance to central nervous system (CNS) diseases could delay their onset or progression.

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