Transhemispheric cortex remodeling promotes forelimb recovery after spinal cord injury.

Understanding the reorganization of neural circuits spared after spinal cord injury in the motor cortex and spinal cord would provide insights for developing therapeutics. Using optogenetic mapping, we demonstrated a transhemispheric recruitment of neural circuits in the contralateral cortical M1/M2 area to improve the impaired forelimb function after a cervical 5 right-sided hemisection in mice, a model mimicking the human Brown-Séquard syndrome. This cortical reorganization can be elicited by a selective cortical optogenetic neuromodulation paradigm. Areas of whisker, jaw, and neck, together with the rostral forelimb area, on the motor cortex ipsilateral to the lesion were engaged to control the ipsilesional forelimb in both stimulation and nonstimulation groups 8 weeks following injury. However, significant functional benefits were only seen in the stimulation group. Using anterograde tracing, we further revealed a robust sprouting of the intact corticospinal tract in the spinal cord of those animals receiving optogenetic stimulation. The intraspinal corticospinal axonal sprouting correlated with the forelimb functional recovery. Thus, specific neuromodulation of the cortical neural circuits induced massive neural reorganization both in the motor cortex and spinal cord, constructing an alternative motor pathway in restoring impaired forelimb function.

Development of a diffraction imaging flow cytometer.

Diffraction images record angle-resolved distribution of scattered light from a particle excited by coherent light and can correlate highly with the 3D morphology of a particle. We present a jet-in-fluid design of flow chamber for acquisition of clear diffraction images in a laminar flow. Diffraction images of polystyrene spheres of different diameters were acquired and found to correlate highly with the calculated ones based on the Mie theory. Fast Fourier transform analysis indicated that the measured images can be used to extract sphere diameter values. These results demonstrate the significant potentials of high-throughput diffraction imaging flow cytometry for extracting 3D morphological features of cells.

Determination of complex refractive index of polystyrene microspheres from 370 to 1610 nm.

We introduce an inverse method for determining simultaneously the real and imaginary refractive indices of microspheres based on integrating sphere measurements of diffuse reflectance and transmittance, and Monte Carlo modelling in conjunction with the Mie theory. The results for polystyrene microspheres suspended in water are presented.

Transfected early growth response gene-1 DNA enzyme prevents stenosis and occlusion of autogenous vein graft in vivo.

The aim of this study was to detect the inhibitory action of the early growth response gene-1 DNA enzyme (EDRz) as a carrying agent by liposomes on vascular smooth muscle cell proliferation and intimal hyperplasia. An autogenous vein graft model was established. EDRz was transfected to the graft vein. The vein graft samples were obtained on each time point after surgery. The expression of the EDRz transfected in the vein graft was detected using a fluorescent microscope. Early growth response gene-1 (Egr-1) mRNA was measured using reverse transcription-PCR and in situ hybridization. And the protein expression of Egr-1 was detected by using western blot and immunohistochemistry analyses. EDRz was located at the media of the vein graft from 2 to 24 h, 7 h after grafting. The Egr-1 protein was mainly located in the medial VSMCs, monocytes, and endothelium cells during the early phase of the vein graft. The degree of VSMC proliferation and thickness of intima were obviously relieved compared with the no-gene therapy group. EDRz can reduce Egr-1 expression in autogenous vein grafts, effectively restrain VSMC proliferation and intimal hyperplasia, and prevent vascular stenosis and occlusion after vein graft.

Microgels: From responsive polymer colloids to biomaterials.

Microgels are network polymer colloid particles that can swell in a good solvent or as a result of electrostatic repulsion between charged groups produced by pH-triggered neutralisation. They have attracted considerable interest as both model colloids and for their potential applications. This discussion reviews the properties of microgel particles and the current understanding of their structure. The review concentrates on the period after an earlier microgel review by Saunders and Vincent [Adv. Coll. Interf. Sci., 1999, 80, 1]. A key challenge for microgel research has involved elucidation of the internal particle structure. Most microgels prepared by emulsion or precipitation polymerisation have a core-shell structure. The segment density is usually highest in the core. Here, we discuss relationships between microgel structure and dispersion stability. The reasons for the exceptional stability of microgel dispersions are considered. There are a number of favourable structural features that make microgels candidates for biomaterial applications and these are discussed. The main potential biomaterial applications that have been investigated for microgels to date are drug delivery and regenerative medicine. Poly(NIPAM) (N-isopropylacrylamide) microgels have been extensively studied in the context of drug delivery. Regenerative medicine research for microgels is an emerging area. Recent work involving the use of gelled microgel dispersions to support biomechanically meaningful loads is considered. We conclude with a discussion of promising directions for microgel research as biomaterials.

Diffraction imaging of spheres and melanoma cells with a microscope objective.

Diffraction imaging of polystyrene spheres and B16F10 mouse melanoma cells embedded in gel has been investigated with a microscope objective. The diffraction images acquired with the objective from a sphere have been shown to be comparable to the Mie theory based projection images of the scattered light if the objective is translated to defocused positions towards the sphere. Using a confocal imaging based method to reconstruct and analyze the 3D structure, we demonstrated that genetic modifications in these cells can induce morphological changes and the modified cells can be used as an experimental model for study of the correlation between 3D morphology features and diffraction image data.