Broad-band-enhanced plasmonic random laser in silver nanostar arrays.

As a novel optical device, the plasmonic random laser has unique working principle and emission characteristics. However, the simultaneous enhancement of absorption and emission by plasmons is still a problem. In this paper, we propose a broad-band-enhanced plasmonic random laser. Two-dimensional silver (Ag) nanostar arrays were prepared using a bottom-up method with the assistance of self-assembled nanosphere templates. The plasmon resonance of Ag nanostars contributes to the pump light absorption and photoluminescence (PL) of RhB. Coherent random lasing was achieved in RhB@PVA film based on localized surface plasmon resonance (SPR) dual enhancement and scattering feedback of Ag nanostars. Ag nanostars prepared with different nanosphere diameters affect the laser emission wavelength. In addition, the random laser device achieves wavelength tunability on a flexible substrate under mechanical external force.

Acetylation targets mutant huntingtin to autophagosomes for degradation.

Huntington's disease (HD) is an incurable neurodegenerative disease caused by neuronal accumulation of the mutant protein huntingtin. Improving clearance of the mutant protein is expected to prevent cellular dysfunction and neurodegeneration in HD. We report here that such clearance can be achieved by posttranslational modification of the mutant Huntingtin (Htt) by acetylation at lysine residue 444 (K444). Increased acetylation at K444 facilitates trafficking of mutant Htt into autophagosomes, significantly improves clearance of the mutant protein by macroautophagy, and reverses the toxic effects of mutant huntingtin in primary striatal and cortical neurons and in a transgenic C. elegans model of HD. In contrast, mutant Htt that is rendered resistant to acetylation dramatically accumulates and leads to neurodegeneration in cultured neurons and in mouse brain. These studies identify acetylation as a mechanism for removing accumulated protein in HD, and more broadly for actively targeting proteins for degradation by autophagy.

Analysis of adjacent vertebral fracture after percutaneous vertebroplasty: do radiological or surgical features matter?

PURPOSE: To report the incidence and risk factors of adjacent vertebral fracture (AVF) after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compression fractures (OVCFs). We focused to investigate effect of radiological or surgical features on AVF. METHODS: All patients with OVCFs who were treated with PVP between January 2016 and December 2019 were retrospectively reviewed. Patients were followed up at least 12 months after procedure according to treatment protocol. AVF was defined as postoperatively recurrent intractable back pain and subsequently presence of fracture on magnetic resonance imaging (MRI) in adjacent levels. Clinical, radiological, and surgical factors potentially affecting occurrence of AVF were recorded and analyzed using univariate and multivariate analysis. RESULTS: Totally, 1077 patients with 1077 fractured vertebrae who underwent PVP were enrolled in the study, after inclusion and exclusion criteria were met. Mean follow-up time was 24.3 ± 11.9 months (range, 12-59 months). AVF was identified in 98 (9.1%) patients. Univariate analysis showed that seven significant factors related to AVF were older age, non-traumatic fracture, cortical disruption on anterior wall, cortical disruption on lateral wall, basivertebral foramen, type-B leakage and type-C leakage. In multivariate analysis, two clinical factors, older age (P = 0.031) and non-traumatic fracture (P = 0.002), were significantly associated with AVF. However, any radiological or surgical factor did not reach significance in final model analysis. CONCLUSIONS: Incidence of AVF after PVP in patients with OVCFs was 9.1% (98/1077). Older age and non-traumatic fracture were two clinical risk factors for AVF. Neither radiological nor surgical feature was significantly correlated with AVF.

Plasmonic distributed feedback lasing in an anodic aluminum oxide/silver/polymer hybrid membrane.

A hybrid membrane is employed as a high-order plasmonic distributed feedback (DFB) cavity to reduce the lasing threshold of polymer lasers. The hybrid membrane consists of an anodic aluminum oxide (AAO) membrane, a 25 nm thick silver layer and a free-standing polymer membrane. The AAO membrane is fabricated by a low-cost, single chemical etching method. Then, a layer of silver with a thickness of 25 nm is sputtered on the surface of the AAO. Subsequently, a polymer membrane is directly attached to the silver-plated AAO membrane, forming an AAO/silver/polymer hybrid membrane. Under optical pumping conditions, low-threshold, three-order DFB lasing is observed. The proposed laser device exhibited a dual-threshold characteristic because of the evolution from amplified spontaneous emission to DFB lasing. And a significant shift from omnidirectional emission to directional emission lasing can be observed while the pump energy density is beyond the second threshold. Furthermore, the plasmonic enhancement sourced from silver corrugation reveals important improvement effects to the DFB lasing of AAO/silver/polymer hybrid membrane for decreasing threshold, narrowing full width at half maximum (FWHM), and an increasing Q factor. This work may promote the design and production of low-cost and large-area high-order plasmonic DFB polymer lasers.

Dynamic manipulation of WGM lasing by tailoring the coupling strength.

Miniaturized lasing with dynamic manipulation is critical to the performance of compact and versatile photonic devices. However, it is still a challenge to manipulate the whispering gallery mode lasing modes dynamically. Here, we design the quasi-three-dimensional coupled cavity by a micromanipulation technique. The coupled cavity consists of two intersection polymer microfibers. The mode selection mechanism is demonstrated experimentally and theoretically in the coupled microfiber cavity. Dynamic manipulation from multiple modes to single-mode lasing is achieved by controlling the coupling strength, which can be quantitatively controlled by changing the coupling angle or the coupling distance. Our work provides a flexible alternative for the lasing mode modulation in the on-chip photonic integration.

Colloidal quantum dots lasing and coupling in 2D holographic photonic quasicrystals.

Global research on the solution-processable colloidal quantum dots (CQDs) constitutes outstanding model systems in nanoscience, micro-lasers, and optoelectronic devices due to tunable color, low cost, and wet chemical processing. The two-dimensional (2D) CQDs quasicrystal lasers are more efficient in providing coherent lasing due to radiation feedback, high-quality-factor optical mode, and long-range rotational symmetry. Here, we have fabricated a 2D quasicrystal exhibiting 10-fold rotational symmetry by using a specially design pentagonal prism in the optical setup of a simple and low-cost holographic lithography. We developed a general analytical model based on the cavity coupling effect, which can be used to explain the underlying mechanism responsible for the multi-wavelength lasing in the fabricated 2D CQDs holographic photonic quasicrystal. The multi-wavelength surface-emitting lasers such as λ0 = 629.27 nm, λ1 = 629.85 nm, λ-1 = 629.06 nm, λ2 = 630.17 nm, and λ-2 = 628.76 with a coupling constant κ = 0.38 achieved from the 2D holographic photonic quasicrystal are approximately similar with the developed analytical model based on cavity coupling effect. Moreover, the lasing patterns of the 2D CQDs photonic quasicrystal laser exhibit a symmetrical polarization effect by rotating the axis of polarization with a difference of 1200 angle in a round trip. We expect that our findings will provide a new approach to customize the 2D CQDs holographic photonic quasicrystal lasers in the field of optoelectronic devices and miniature lasing systems.

The impact of intravertebral cleft on cement leakage in percutaneous vertebroplasty for osteoporotic vertebral compression fractures: a case-control study.

BACKGROUND: The impact of intravertebral cleft (IVC) on cement leakage in percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs) has been discussed. However, the results were conflicting, as the study population and cement leakage classification were heterogeneous. The aim of the study was to evaluate the impact of IVC on the incidence of leakage through vein, leakage through cortex as well as general leakage in PVP for OVCFs. METHODS: All patients with OVCFs who underwent PVP between January 2016 and June 2019 at our institution were retrospectively reviewed. Patients were eligible for this case-control study if they were diagnosed as single level fracture in spine. After inclusive and exclusive criteria were met, a total of 139 patients with IVC were enrolled as the study group. Non-IVC controls were matched in a 1:1 ratio in age (within 3 years), sex and fracture severity with patients in study group. Cement leakage were classified into four types [type B (through basivertebral vein), type S (through segmental vein), type-C (through a cortical defect), and type D (intradiscal leakage)], furtherly into two types [venous type (type-B or/and type S) and cortical type (type-C or/and type-D)]. A general leakage rate and a specific leakage rate per each type were compared between both groups. RESULTS: Each group included 139 patients. Groups were homogenous for age, sex, fracture severity, fracture location, fracture type, cement volume, puncture approach and property of cement. Compared with control group, IVC group had a significantly lower rate of type-B (20.9% vs. 31.7%, P = 0.041), type-S (24.5% vs. 52.5%, P = 0.000), and venous type leakage (37.4% vs. 67.6%, P = 0.000), a significantly higher rate of type-C (25.9% vs. 12.2%, P = 0.004), type-D (16.5% vs. 6.5%, P = 0.009), and cortical type leakage (40.3% vs. 16.5%, P = 0.000), no significant difference on the rate of general leakage (67.6% vs. 76.3%, P = 0.109). CONCLUSION: IVC decreased the risk of cement leakage through vein and increased the risk of cement leakage through cortex. However, it had no significant effect on the occurrence of general leakage.

Tunable polymer lasing in chirped cavities.

Continuously tunable polymer lasing was achieved in one-dimensional, two-dimensional, and compound chirped cavities. The chirped cavity was simply fabricated by using interference lithography and spin coating. Two-dimensional and compound chirped cavities were obtained by employing oblique exposure and double exposure, respectively. The tunability range of two-dimensional chirped cavities was much wider than that of one-dimensional chirped cavities, which varied from 557 nm to 582 nm. The interaction between lasing modes was studied in the compound cavity by introducing an additional nanostructure into the two-dimensional chirped cavities. The threshold of the compound chirped cavities changed with the coupling strength between lasing modes. These results may be helpful for designing compact polymer laser sources.

MiR-20a Plays a Key Regulatory Role in the Repair of Spinal Cord Dorsal Column Lesion via PDZ-RhoGEF/RhoA/GAP43 Axis in Rat.

Spinal cord injury (SCI) causes sensory dysfunctions such as paresthesia, dysesthesia, and chronic neuropathic pain. MiR-20a facilitates the axonal outgrowth of the cortical neurons. However, the role of miR-20a in the axonal outgrowth of primary sensory neurons and spinal cord dorsal column lesion (SDCL) is yet unknown. Therefore, the role of miR-20a post-SDCL was investigated in rat. The NF-200 immunofluorescence staining was applied to observe whether axonal outgrowth of dorsal root ganglion (DRG) neurons could be altered by miR-20a or PDZ-RhoGEF modulation in vitro. The expression of miR-20a was quantized with RT-PCR. Western blotting analyzed the expression of PDZ-RhoGEF/RhoA/GAP43 axis after miR-20a or PDZ-RhoGEF was modulated. The spinal cord sensory conduction function was assessed by somatosensory-evoked potentials and tape removal test. The results demonstrated that the expression of miR-20a decreased in a time-dependent manner post-SDCL. The regulation of miR-20a modulated the axonal growth and the expression of PDZ-RhoGEF/RhoA/GAP43 axis in vitro. The in vivo regulation of miR-20a altered the expression of miR-20a-PDZ-RhoGEF/RhoA/GAP43 axis and promoted the recovery of ascending sensory function post-SDCL. The results indicated that miR-20a/PDZ-RhoGEF/RhoA/GAP43 axis is associated with the pathophysiological process of SDCL. Thus, targeting the miR-20a/PDZ-RhoGEF /RhoA/GAP43 axis served as a novel strategy in promoting the sensory function recovery post-SCI.

Magnetic resonance diffusion tensor imaging of cervical spinal cord and lumbosacral enlargement in patients with cervical spondylotic myelopathy.

PURPOSE: To identify the correlations of diffusion tensor imaging (DTI) indices between the cervical spinal cord and lumbosacral enlargement in healthy volunteers and patients with cervical spondylotic myelopathy (CSM). MATERIALS AND METHODS: DTI was performed at the cervical spinal cord and lumbosacral enlargement in 10 CSM patients and 10 volunteers at 1.5T. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of were measured and compared between CSM patients and volunteers. DTI indices of different cervical segments in volunteers were compared. DTI indices of the cervical spinal cord were correlated with those of the lumbosacral enlargement. RESULTS: In healthy subjects, DTI indices of different cervical cord sections showed no significant difference (ADC: F = 0.62; P = 0.65; FA: F = 1.228; P = 0.312); there was no correlation between the DTI indices of the cervical spinal cord and those of the lumbosacral enlargement (ADC: r = 0.442, P = 0.201; FA: r = -0.054, P = 0.881). In the CSM patients, the ADC value significantly increased, while the FA value significantly decreased in the cervical spinal cord (ADC: P = 0.002; FA: P < 0.001) and lumbosacral enlargement (ADC: P = 0.003; FA: P < 0.001) compared with the healthy group. Both DTI indices showed no correlation between the cervical spinal cord and those of the lumbosacral enlargement in the CSM group (ADC: r = -0.052, P = 0.887; FA: r = 0.129, P = 0.722). CONCLUSION: The ADC value of the cervical spinal cord and lumbosacral enlargement in CSM patients showed significant increase compared with healthy volunteers, while the FA value significantly decreased. Both DTI indices of the cervical spinal cord had no linear correlation with those of the lumbosacral enlargement. J. Magn. Reson. Imaging 2016;43:1484-1491.

In vivo diffusion tensor imaging of chronic spinal cord compression : a rat model with special attention to the conus medullaris.

Background Few studies have focused on diffusion tensor imaging (DTI) parameters of the conus medullaris after chronic compression in the cervical spinal cord. Purpose To discuss the correlation of DTI parameters between the chronically compressed cervical spinal cord and the conus medullaris in a rat model at different time points. Material and Methods Fifty female Sprague-Dawley rats were randomized into five groups: control group (group A), sham group (group B), and test groups C, D, and E (1, 2, and 3 weeks after compression, respectively). Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of the cervical spinal cord and conus medullaris were compared among different groups. Correlations of ADC and FA values of the cervical spinal cord with those of the conus medullaris were performed in all groups. Results The ADC values at the cervical spinal cord and conus medullaris in all test groups were higher than those of group A and B, while the FA values were lower. The ADC value of the cervical spinal cord was linearly correlated with that of the conus medullaris only in group D. There were no linear correlations of FA values between the cervical spinal cord and the conus medullaris in all test groups. Conclusion After compression of the cervical spinal cord, ADC values of the cervical spinal cord and conus medullaris in test group were significantly increased, while FA values were significantly decreased. The ADC value of the cervical spinal cord was linearly correlated with that of the conus medullaris at 2 weeks after compression.

Accelerated neurodegeneration and neuroinflammation in transgenic mice expressing P301L tau mutant and tau-tubulin kinase 1.

Tau-tubulin kinase-1 (TTBK1) is a central nervous system (CNS)-specific protein kinase implicated in the pathological phosphorylation of tau. TTBK1-transgenic mice show enhanced neuroinflammation in the CNS. Double-transgenic mice expressing TTBK1 and frontotemporal dementia with parkinsonism-17-linked P301L (JNPL3) tau mutant (TTBK1/JNPL3) show increased accumulation of oligomeric tau protein in the CNS and enhanced loss of motor neurons in the ventral horn of the lumbar spinal cord. To determine the role of TTBK1-induced neuroinflammation in tauopathy-related neuropathogenesis, age-matched TTBK1/JNPL3, JNPL3, TTBK1, and non-transgenic littermates were systematically characterized. There was a striking switch in the activation phenotype and population of mononuclear phagocytes (resident microglia and infiltrating macrophages) in the affected spinal cord region: JNPL3 mice showed accumulation of alternatively activated microglia, whereas TTBK1 and TTBK1/JNPL3 mice showed accumulation of classically activated infiltrating peripheral monocytes. In addition, expression of chemokine ligand 2, a chemokine important for the recruitment of peripheral monocytes, was enhanced in TTBK1 and TTBK1/JNPL3 but not in other groups in the spinal cord. Furthermore, primary cultured mouse motor neurons showed axonal degeneration after transient expression of the TTBK1 gene or treatment with conditioned media derived from lipopolysaccharide-stimulated microglia; this was partially blocked by silencing of the endogenous TTBK1 gene in neurons. These data suggest that TTBK1 accelerates motor neuron neurodegeneration by recruiting proinflammatory monocytes and enhancing sensitivity to neurotoxicity in inflammatory conditions.

JBP1-seq: a fast and efficient method for genome-wide profiling of 5hmC.

We developed a novel approach, J-binding protein 1 sequencing (JBP1-seq), that combines the benefits of an improved recombinant JBP1 protein, Nextera-based library construction, and next-generation sequencing (NGS) for genome-wide profiling of 5-hydroxymethylcytosine (5hmC). Compared with the original JBP1, this new recombinant JBP1 was biotinylated in vivo and conjugated to magnetic beads via biotin-streptavidin interactions. These modifications allowed a more efficient and consistent pull-down of ß-glucosyl-5-hydroxymethylcytosine (ß-glu-5hmC), and sequence-ready libraries can be generated within 4.5h from DNA inputs as low as 50ng. 5hmC enrichment of human brain DNA using the new JBP1 resulted in over 25,000 peaks called, which is significantly higher than the 4003 peaks enriched using the old JBP1. Comparison of the technical duplicates and validations with other platforms indicated the results are reproducible and reliable. Thus, JBP1-seq provides a fast, efficient, and cost-effective method for accurate 5hmC genome-wide profiling.

[Radiological characteristics and clinical manifestation of isolated lumbar foraminal stenosis].

OBJECTIVE: To discuss radiological characteristics and clinical manifestation of isolated lumbar foraminal stenosis. METHODS: From March 2011 to March 2014, 21 patients with isolated degenerative lumbar foraminal stenosis accepted lumbar decompression and fusion in Beijing Luhe Hospital. Intervertebral disc space was evaluated by measuring the position of joint-body line on preoperative X-ray. Bilateral foraminal area of the corresponding segment in CT (sagittal view of 2D reconstruction) and MRI (T2W1 sagittal view) were measured by Surgimap software. For patients with unilateral symptoms, foraminal area of the affected side was compared with that of the contralateral side. Foraminal area of the same segment on CT was also compared with that on MRI. Preoperatively and at the final follow-up, visual analogue score (VAS) and Oswestry Disability Index (ODI) were used to evaluate clinical outcomes. RESULTS: All patients had a follow-up over 6 months and the average follow-up was 16.8 months (7-42 months). Of the 21 patients (26 segments), 12 segments showed gross narrowing and 14 segments showed slight narrowing. After preoperative measurement on MRI, 6 patients had foraminal stenosis of grade 2, and 15 patients had foraminal stenosis of grade 3, showing no significant difference in clinical outcomes. Compared with the foraminal area of the unaffected side, the affected side showed a decrease of 16% on CT and 28% on MRI, and the difference was statistically significant (t = 3.453, P < 0.05). The foraminal area measured on CT was larger than that measured on MRI (P < 0.05). Compared with that preoperatively, VAS (back pain), VAS (leg pain) and ODI showed significant improvement at the final follow-up (P < 0.05). CONCLUSIONS: Radiological examinations as X-ray, CT, MRI and intervertebral foramen block technique play an important role in the diagnosis of foraminal stenosis. Soft oppression caused by hyperplasia and hypertrophy of transforaminal ligment or joint capsule may be important promoters of degenerative lumbar foraminal stenosis. Lumbar foraminal decompression and interbody fusion can satisfactorily improve preoperative symptoms.

The Closer Vicinity to Treated Vertebrae in Percutaneous Vertebroplasty, the Higher Rate of New Vertebral Compression Fractures at Follow-up.

OBJECTIVE: To investigate whether risk of new vertebral compression fractures (NVCFs) was associated with vicinity to treated vertebrae in percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs). METHODS: All OVCF (T6-L5) patients treated with PVP between January 2016 and December 2020 were retrospectively reviewed. Vicinity to treated vertebrae was defined as the number of vertebrae between an untreated and its closest treated level. The closest treated level was chosen as reference vertebra. Clinical, radiologic, and surgical parameters were compared between groups of reference vertebrae for each vicinity NVCF. RESULTS: In total, 1348 patients with 1592 fractured and 14,584 normal vertebrae were enrolled. NVCF was identified in 20.1% (271 of 1348) patients in 2.2% (319 of 14584) vertebrae in a mean follow-up time of 24.3 ± 11.9 months. Rate of NVCF in vicinity 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 level were 4.6% (130 of 2808), 2.4% (62 of 2558), 1.8% (42 of 2365), 1.5% (31 of 2131), 1.3% (23 of 1739), 1.3% (17 of 1298), 0.8% (7 of 847), 0.9% (4 of 450), 0.8% (2 of 245), 0.9% (1 of 117), and 0% (0 of 26), respectively. Rate of NVCF in vicinity 1 level was significantly higher than that in vicinity 2, 3, 4, 5, 6, 7, 8, and 9 level, respectively. However, compared to reference vertebrae for vicinity 1 NVCF, any clinical, radiologic, or surgical parameters were not significantly different in those for vicinity 2, 3, and 4 NVCF, respectively. CONCLUSIONS: The closer vicinity to treated vertebrae in PVP, the higher rate of NVCF at follow-up. However, any clinical, radiologic, or surgical parameters might not matter in this phenomenon of vicinity-related NVCF.

Deep learning-driven diagnosis of multi-type vertebra diseases based on computed tomography images.

Background: Osteoporotic vertebral compression fractures (OVCFs) are the most common type of fragility fracture. Distinguishing between OVCFs and other types of vertebra diseases, such as old fractures (OFs), Schmorl's node (SN), Kummell's disease (KD), and previous surgery (PS), is critical for subsequent surgery and treatment. Combining with advanced deep learning (DL) technologies, this study plans to develop a DL-driven diagnostic system for diagnosing multi-type vertebra diseases. Methods: We established a large-scale dataset based on the computed tomography (CT) images of 1,051 patients with OVCFs from Luhe Hospital and used data of 46 patients from Xuanwu Hospital as alternative hospital validation dataset. Each patient underwent one examination. The dataset contained 11,417 CT slices and 19,718 manually annotated vertebrae with diseases. A two-stage DL-based system was developed to diagnose five vertebra diseases. The proposed system consisted of a vertebra detection module (VDModule) and a vertebra classification module (VCModule). Results: The training and testing dataset for the VDModule consisted of 9,135 and 3,212 vertebrae, respectively. The VDModule using the ResNet18-based Faster region-based convolutional neural network (R-CNN) model achieved an area under the curve (AUC), false-positive (FP) rate, and false-negative (FN) rate of 0.982, 1.52%, and 1.33%, respectively, in the testing dataset. The training dataset for VCModule consisted of 14,584 and 47,604 diseased and normal vertebrae, respectively. The testing dataset consisted of 4,489 and 15,122 diseased and normal vertebrae, respectively. The ResNet50-based VCModule achieved an average sensitivity and specificity of 0.919 and 0.995, respectively, in diagnosing four kinds of vertebra diseases except for SN in the testing dataset. In the alternative hospital validation dataset, the ResNet50-based VCModule achieved an average sensitivity and specificity of 0.891 and 0.989, respectively, in diagnosing four kinds of vertebra diseases except for SN. Conclusions: Our proposed DL system can accurately diagnose four vertebra diseases and has strong potential to facilitate the accurate and rapid diagnosis of vertebral diseases.

Does atlantoaxial dislocation influence the subaxial cervical spine?

INTRODUCTION: Previous studies have reported that the alignments of the occipital-cervical and subaxial spine were closely interrelated in asymptomatic individuals; however, none have focused on a population with atlantoaxial dislocation. MATERIAL AND METHODS: From 2007 to 2011, 298 patients with atlantoaxial dislocation and atlas occipitalization were studied. Angles formed between Occiput-C2 and C2-C7 were measured. The relationship between the alignment of the occipital-cervical junction and the subaxial cervical spine was evaluated. RESULTS: The range of values for the angles measured was as followed: the Occiput-C2 angles were -35.2° to 44.8°, and the C2-C7 angles were -17.4° to 77.8°. Statistically significant negative correlations were observed between the Occiput-C2 and C2-C7 angles. CONCLUSION: Anterior dislocations of the atlas are associated with diminished lordosis or even kyphosis of the occipital-cervical junction, and result in compensatory hyperlordosis of the subaxial cervical spine, collectively presenting as a "swan neck" deformity. Atlantoaxial dislocation may influence the global cervical alignment.

Peroxisome-proliferator-activated receptor gamma coactivator 1 α contributes to dysmyelination in experimental models of Huntington's disease.

The peroxisome-proliferator-activated receptor gamma coactivator 1 α (PGC1α) has been implicated in the pathogenesis of several neurodegenerative disorders, including Huntington's disease (HD). Recent data demonstrating white matter abnormalities in PGC1α knock-out (KO) mice prompted us to examine the role of PGC1α in CNS myelination and its relevance to HD pathogenesis. We found deficient postnatal myelination in the striatum of PGC1α KO mice, accompanied by a decrease in myelin basic protein (MBP). In addition, brain cholesterol, its precursors, and the rate-limiting enzymes for cholesterol synthesis, HMG CoA synthase (HMGCS1) and HMG CoA reductase (HMGCR), were also reduced in PGC1α KO mice. Moreover, knockdown of PGC1α in oligodendrocytes by lentiviral shRNA led to a decrease in MBP, HMGCS1, and Hmgcr mRNAs. Chromatin immunoprecipitations revealed the recruitment of PGC1α to MBP promoter in mouse brain, and PGC1α over-expression increased MBP and SREBP-2 promoter activity, suggesting that PGC1α regulates MBP and cholesterol synthesis at the transcriptional level. Importantly, expression of mutant huntingtin (Htt) in primary oligodendrocytes resulted in decreased expression of PGC1α and its targets HmgcS1, Hmgcr, and MBP. Decreased expression of MBP and deficient myelination were found postnatally and in adult R6/2 mouse model of HD. Diffusion tensor imaging detected white matter abnormalities in the corpus callosum of R6/2 mice, and electron microscopy revealed thinner myelin sheaths and increased myelin periodicity in BACHD [bacterial artificial chromosome (BAC)-mediated transgenic model for Huntington's disease] mice expressing full-length mutant Htt. Together, these data suggest that PGC1α plays a role in postnatal myelination and that deficient PGC1α activity in oligodendrocytes may contribute to abnormal myelination in HD.

Improved spatial learning performance of fat-1 mice is associated with enhanced neurogenesis and neuritogenesis by docosahexaenoic acid.

Docosahexaenoic acid (DHA), an n-3 long chain polyunsaturated fatty acid (LC-PUFA), highly enriched in the central nervous system, is critical for brain development and function. It has been shown that DHA deficiency impairs cognitive performance whereas DHA supplementation improves the condition. However, the mechanisms underlying the role of DHA in brain development and function remain to be elucidated. By using transgenic fat-1 mice rich in endogenous n-3 PUFA, we show that increased brain DHA significantly enhances hippocampal neurogenesis shown by an increased number of proliferating neurons and neuritogenesis, evidenced by increased density of dendritic spines of CA1 pyramidal neurons in the hippocampus. Concurrently, fat-1 mice exhibit a better spatial learning performance in the Morris water maze compared with control WT littermates. In vitro experiments further demonstrate that DHA promotes differentiation and neurite outgrowth of neuronal cells derived from mouse ES cells and increases the proliferation of cells undergoing differentiation into neuronal lineages from the ES cells. These results together provide direct evidence for a promoting effect of DHA on neurogenesis and neuritogenesis and suggest that this effect may be a mechanism underlying its beneficial effect on behavioral performance.

Electrically Tunable Polymer Whispering-Gallery-Mode Laser.

Microlasers hold great promise for the development of photonics and optoelectronics. At present, tunable microcavity lasers, especially regarding in situ dynamic tuning, are still the focus of research. In this study, we combined a 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) piezoelectric crystal with a Poly [9,9-dioctylfluorenyl-2,7-diyl] (PFO) microring cavity to realize a high-quality, electrically tunable, whispering-gallery-mode (WGM) laser. The dependence of the laser properties on the diameter of the microrings, including the laser spectrum and quality (Q) value, was investigated. It was found that with an increase in microring diameter, the laser emission redshifted, and the Q value increased. In addition, the device effectively achieved a blueshift under an applied electric field, and the wavelength tuning range was 0.71 nm. This work provides a method for in situ dynamic spectral modulation of microcavity lasers, and is expected to provide inspiration for the application of integrated photonics technology.