Accessible and reliable neurometric testing in humans using a smartphone platform.

Tests of human brain circuit function typically require fixed equipment in lab environments. We have developed a smartphone-based platform for neurometric testing. This platform, which uses AI models like computer vision, is optimized for at-home use and produces reproducible, robust results on a battery of tests, including eyeblink conditioning, prepulse inhibition of acoustic startle response, and startle habituation. This approach provides a scalable, universal resource for quantitative assays of central nervous system function.

Transepithelial electrical resistance and tight junctions of human gingival keratinocytes.

Human gingival keratinocytes (HGKs) were studied by means of freeze-fracture technique, conventional electron microscopy and the transepithelial electrical resistance for the investigation of intercellular contacts. For the purpose of comparison, MDCK cells and HaCat cells were also included. An unexpected finding was the presence of tight junctions in the HGKs. In vivo the tight junctions, which were of low complexity and P-face-associated, were co-distributed with desmosomes; in one case, the strands ran directly through desmosomal plaques. Where tight junctions and desmosomes occurred together, no gap junctions were seen. In contrast, where no tight junctions were present, gap junctions and desmosomes were co-localized. However, the unfavourable fracture planes through the tissue did not allow a clearcut allocation of gap junction/tight junction occurrence to certain strata. In vitro, HGKs also expressed tight junctions which formed networks of low complexity and high P-face association. Whereas desmosomes were highly expressed, gap junctions were not observed in cultured keratinocytes. Transepithelial electrical resistances (TEER) of cultured HGKs were higher than the values in low resistance-MDCK cells and HaCat cells but considerably lower than the values in high resistance MDCK cells, supporting the fundamental correlation between tight junction morphology and TEER. The results with this cell culture model of the human gingiva provide some valuable information about in vitro differentation and concommittent changes in cellular contacts of human gingival keratinocytes.

Determination of hair cell degeneration and hair cell death in neomycin treated cultures of the neonatal rat cochlea.

The spatial-temporal course of hair cell degeneration and hair cell death was examined in the mammalian cochlea following aminoglycoside treatment. Organotypic cultures were established from postnatal rats (P3) and treated with 1 mM neomycin sulfate for 12-48 h and analyzed using a live/dead assay under epifluorescence microscopy. Live hair cells were labeled with calcein, a probe whose fluorescence and cellular retention depends upon intracellular esterase activity and cell-membrane integrity, respectively. Hair cell death was determined by ethidium homodimer-1, a probe that can enter cells with compromised cell membranes only. Inside the cell it binds to DNA. Hair cell morphology was also examined using phalloidin labeling, scanning electron microscopy and semi-thin section analysis. Results showed that hair cell degeneration and hair cell death occurred in a time dependent gradient from base to apex. After 48 h of neomycin treatment, most apical hair cells survived while most basal hair cells died. Calcein labeling provides a sensitive functional assay for measuring hair cell survival.

Gene disruption of p27(Kip1) allows cell proliferation in the postnatal and adult organ of corti.

Hearing loss is most often the result of hair-cell degeneration due to genetic abnormalities or ototoxic and traumatic insults. In the postembryonic and adult mammalian auditory sensory epithelium, the organ of Corti, no hair-cell regeneration has ever been observed. However, nonmammalian hair-cell epithelia are capable of regenerating sensory hair cells as a consequence of nonsensory supporting-cell proliferation. The supporting cells of the organ of Corti are highly specialized, terminally differentiated cell types that apparently are incapable of proliferation. At the molecular level terminally differentiated cells have been shown to express high levels of cell-cycle inhibitors, in particular, cyclin-dependent kinase inhibitors [Parker, S. B., et al. (1995) Science 267, 1024-1027], which are thought to be responsible for preventing these cells from reentering the cell cycle. Here we report that the cyclin-dependent kinase inhibitor p27(Kip1) is selectively expressed in the supporting-cell population of the organ of Corti. Effects of p27(Kip1)-gene disruption include ongoing cell proliferation in postnatal and adult mouse organ of Corti at time points well after mitosis normally has ceased during embryonic development. This suggests that release from p27(Kip1)-induced cell-cycle arrest is sufficient to allow supporting-cell proliferation to occur. This finding may provide an important pathway for inducing hair-cell regeneration in the mammalian hearing organ.

Variation in contact guidance by human cells on a microstructured surface.

Contact guidance induced by the surface topography of the underlying substratum influences the interaction of tissue cells with implanted material. It was the aim of this study to compare the reaction of different human cells on the same surface microtexture. After staining with fluoresceinediacetate, the orientation of human fibroblasts, gingival keratinocytes, neutrophils, monocytes, and macrophages on a regular surface microstructure of 1 microns pitch and 1 microns depth was analyzed by fluorescence microscopy. Contact guidance could not be observed in the experiments with keratinocytes and neutrophils, but 100% of the fibroblasts and approximately 20% of the monocytes and macrophages reacted with alignment. After 2 h some of the macrophages extended long dendritic cellular processes parallel to the long axis of the microstructures.

Fibroblast anchorage to microtextured surfaces.

The contact between tissue and the implanted biomaterial is influenced by the micromorphology of the implant surface as well as biomechanical reactions. This effect is mediated by subcellular morphological structures and can affect the anchorage of the material inside the body of the host. The aim of the present study was to ascertain by transmission electron microscopy how human gingival fibroblasts interact with surface events. A special replica technique was used to produce a line pattern of 1 micron pitch with a depth of 1 micron. It was demonstrated, by transmission electron microscopy, that cells seeded on this surface extended cellular processes into the grooves, leading to an intensive contact and probably to mechanical interlocking. The typical morphological structures at several points indicated the presence of focal adhesion sites.