Permeability changes of integrin-containing multivesicular structures triggered by picornavirus entry.

Cellular uptake of clustered α2β1-integrin induces the formation of membrane compartments that subsequently mature into a multivesicular body (MVB). Enhanced internalization mediated by clustered integrins was observed upon infection by the picornavirus echovirus 1 (EVI). We elucidated the structural features of virus-induced MVBs (vMVBs) in comparison to antibody-induced control MVBs (mock infection) by means of high-pressure cryo fixation of cells followed by immuno electron tomography during early entry of the virus.

Rapid 3D fluorescence imaging of individual optically trapped living immune cells.

We demonstrate an approach to rapidly characterize living suspension cells in 4 dimensions while they are immobilized and manipulated within optical traps. A single, high numerical aperture objective lens is used to separate the imaging plane from the trapping plane. This facilitates full control over the position and orientation of multiple trapped cells using a spatial light modulator, including directed motion and object rotation, while also allowing rapid 4D imaging.

Mechanism-based facilitated maturation of human pluripotent stem cell-derived cardiomyocytes.

Background: Human embryonic stem cells (hESCs) can be efficiently and reproducibly directed into cardiomyocytes (CMs) using stage-specific induction protocols. However, their functional properties and suitability for clinical and other applications have not been evaluated.

Methods And Results: Here we showed that CMs derived from multiple pluripotent human stem cell lines (hESC: H1, HES2) and types (induced pluripotent stem cell) using different in vitro differentiation protocols (embryoid body formation, endodermal induction, directed differentiation) commonly displayed immature, proarrhythmic action potential properties such as high degree of automaticity, depolarized resting membrane potential, Phase 4- depolarization, and delayed after-depolarization.

The Relationship between fenestrations, sieve plates and rafts in liver sinusoidal endothelial cells.

Fenestrations are transcellular pores in endothelial cells that facilitate transfer of substrates between blood and the extravascular compartment. In order to understand the regulation and formation of fenestrations, the relationship between membrane rafts and fenestrations was investigated in liver sinusoidal endothelial cells where fenestrations are grouped into sieve plates. Three dimensional structured illumination microscopy, scanning electron microscopy, internal reflectance fluorescence microscopy and two-photon fluorescence microscopy were used to study liver sinusoidal endothelial cells isolated from mice.

Cell-to-cell transfer of HIV-1 via virological synapses leads to endosomal virion maturation that activates viral membrane fusion.

HIV-1 can infect T cells by cell-free virus or by direct virion transfer between cells through cell contact-induced structures called virological synapses (VS). During VS-mediated infection, virions accumulate within target cell endosomes. We show that after crossing the VS, the transferred virus undergoes both maturation and viral membrane fusion.

Visualizing cell-to-cell transfer of HIV using fluorescent clones of HIV and live confocal microscopy.

By fusing the green fluorescent protein to their favorite proteins, biologists now have the ability to study living complex cellular processes using fluorescence video microscopy. To track the movements of the human immunodeficiency virus core protein during cell-to-cell transmission of human immunodeficiency virus, we have GFP-tagged the Gag protein in the context of an infectious molecular clone of HIV, called HIV Gag-iGFP. We study this viral clone using video confocal microscopy.

Tracking and quantitation of fluorescent HIV during cell-to-cell transmission.

The green fluorescent protein (GFP) is a powerful genetic marking tool that has enabled virologists to monitor and track viral proteins during HIV infection. Expression-optimized Gag-GFP constructs have been used to study virus-like particle (VLP) assembly and localization in cell types that are easily transfected. The development of HIV-1 variants carrying GFP within the context of the viral genome has facilitated the study of infection and has been particularly useful in monitoring the transfer of virus between cells following virological synapse formation.

Three-dimensional structured illumination microscopy of liver sinusoidal endothelial cell fenestrations.

Fenestrations are pores in liver sinusoidal endothelial cells that filter substrates and debris between the blood and hepatocytes. Fenestrations have significant roles in aging and the regulation of lipoproteins. However their small size (<200 nm) has prohibited any functional analysis by light microscopy.

Manipulating CD4+ T cells by optical tweezers for the initiation of cell-cell transfer of HIV-1.

Cell-cell interactions through direct contact are very important for cellular communication and coordination - especially for immune cells. The human immunodeficiency virus type I (HIV-1) induces immune cell interactions between CD4(+) cells to shuttle between T cells via a virological synapse. A goal to understand the process of cell-cell transmission through virological synapses is to determine the cellular states that allow a chance encounter between cells to become a stable cell-cell adhesion.

Quantitative 3D video microscopy of HIV transfer across T cell virological synapses.

The spread of HIV between immune cells is greatly enhanced by cell-cell adhesions called virological synapses, although the underlying mechanisms have been unclear. With use of an infectious, fluorescent clone of HIV, we tracked the movement of Gag in live CD4 T cells and captured the direct translocation of HIV across the virological synapse. Quantitative, high-speed three-dimensional (3D) video microscopy revealed the rapid formation of micrometer-sized "buttons" containing oligomerized viral Gag protein.

Absence of transverse tubules contributes to non-uniform Ca(2+) wavefronts in mouse and human embryonic stem cell-derived cardiomyocytes.

Mouse (m) and human embryonic stem cell-derived cardiomyocytes (hESC-CMs) are known to exhibit immature Ca(2+) dynamics such as small whole-cell peak amplitude and slower kinetics relative to those of adult. In this study, we examined the maturity and efficiency of Ca(2+)-induced Ca(2+) release in m and hESC-CMs, the presence of transverse (t) tubules and its effects on the regional Ca(2+) dynamics. In m and hESC-CMs, fluorescent staining and atomic force microscopy (AFM) were used to detect the presence of t-tubules, caveolin-3, amphiphysin-2 and colocalization of dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs).

Arginine deiminase as a novel therapy for prostate cancer induces autophagy and caspase-independent apoptosis.

Arginine deprivation as an anticancer therapy has historically been met with limited success. The development of pegylated arginine deiminase (ADI-PEG20) has renewed interest in arginine deprivation for the treatment of some cancers. The efficacy of ADI-PEG20 is directly correlated with argininosuccinate synthetase (ASS) deficiency.

Simultaneous forward and epi-CARS microscopy with a single detector by time-correlated single photon counting.

We present a novel scheme to simultaneously detect coherent anti-Stokes Raman scattering (CARS) microscopy signals in the forward (F) and backward (epi - E) direction with a single avalanche photodiode (APD) detector using time-correlated single photon counting (TCSPC). By installing a mirror at a well-defined distance above the sample the forward-scattered F-CARS signal is reflected back into the microscope objective leading to spatial overlap of the F and E-CARS signals. Due to traveling an additional distance the F-CARS signal is time delayed relative to the E-CARS signal.

Time-gated single photon counting enables separation of CARS microscopy data from multiphoton-excited tissue autofluorescence.

We demonstrate time-gated confocal imaging as a means to separate coherent anti-Stokes Raman scattering (CARS) microscopy data from multi-photon excited endogenous fluorescence in tissue. CARS is a quasi-instantaneous process and its signal decay time is only limited by the system's instrument response function (IRF). Signals due to two-photon-excited (TPE) tissue autofluorescence with excited state lifetimes on the nanosecond scale can be identified and separated from the CARS signal by employing time-gating techniques.