In vivo deep brain multiphoton fluorescence imaging emitting at NIR-I and NIR-II and excited at NIR-IV.

Multiphoton microscopy (MPM) enables deep brain imaging. Three optical windows: NIR-I, NIR-II, and NIR-III are widely used. Recently, NIR-IV (the 2200 nm window) has been demonstrated to be the last and longest window for deep tissue MPM. However, so far MPM covers only two optical windows labeled by single fluorescent probe, one for emission and one for excitation. Here we demonstrate in vivo deep brain MPM covering three optical windows, with emission at NIR-I, NIR-II, and excitation at NIR-IV, labeled by ICG. The innovations include: (1) characterizing both 3-photon excitation and emission properties of ICG emitting at both NIR-I and NIR-II, in water, plasma, and circulating blood; (2) a home-built multiphoton microscope with simultaneous dual channel detection, with which we demonstrate deep brain MPM 950 µm (NIR-I) and 850 µm (NIR-II) into the mouse brain in vivo, verifying that multi-optical window MPM is promising for deep brain imaging.

[Scenario Simulation and Effects Assessment of Co-control on Pollution and Carbon Emission Reduction in Beijing].

Focused on the key areas of energy, buildings, industry, and transportation, with 2020 as the base year and 2035 as the target year, we respectively designed the baseline scenario, policy scenario, and enhanced scenario, calculated the emission reduction potential of air pollutants and CO2 of Beijing, and constructed an assessment method of co-control effect gradation index to evaluate the co-control effect of air pollutants and CO2 in the policy scenario and enhanced scenario. The results showed that in the policy scenario and enhanced scenario, the reduction rates of air pollutants emissions will reach 11%-75% and 12%-94%, respectively, and reduction rates of CO2 emissions will reach 41% and 52%, respectively, compared with those from the baseline scenario. Optimizing vehicle structure had the largest contribution to the emission reduction of NOx, VOCs, and CO2, and the emission reduction rates will reach 74%, 80%, and 31% in the policy scenario and 68%, 74%, and 22% in the enhanced scenario, respectively. Replacing coal-fired with clean energy in rural areas had the largest contribution to the emission reduction of SO2; the emission reduction rates will reach 47% and 35% in the policy scenario and enhanced scenario, respectively. Improving the green level of new buildings had the largest contribution to the emission reduction of PM10; the emission reduction rates will reach 79% and 74% in the policy scenario and enhanced scenario, respectively. Optimizing travel structure and promoting green development of digital infrastructure had the best co-control effect. The co-control effect of replacing coal-fired with clean energy in rural areas, optimizing vehicle structure, and promoting green upgrading of the manufacturing industry will be improved to a better status in the enhanced scenario. More attention should be paid to improving the proportion of green trips, implementing the promotion of new energy vehicles, and the green transportation of goods to reduce emissions in the field of transportation. At the same time, with the continuous improvement in electrification level in the end energy consumption structure, the proportion of green electricity should be increased by expanding local renewable energy power production and increasing external green electricity transmission capacity, to enhance the co-control effect of pollution and carbon reduction.

In Vivo Deep-Brain 3- and 4-Photon Fluorescence Imaging of Subcortical Structures Labeled by Quantum Dots Excited at the 2200 nm Window.

Multiphoton microscopy (MPM) is an enabling technology for visualizing deep-brain structures at high spatial resolution in vivo. Within the low tissue absorption window, shifting to longer excitation wavelengths reduces tissue scattering and boosts penetration depth. Recently, the 2200 nm excitation window has emerged as the last and longest window suitable for deep-brain MPM. However, multiphoton fluorescence imaging at this window has not been demonstrated, due to the lack of characterization of multiphoton properties of fluorescent labels. Here we demonstrate technologies for measuring both the multiphoton excitation and emission properties of fluorescent labels at the 2200 nm window, using (1) 3-photon (ησ3) and 4-photon action cross sections (ησ4) and (2) 3-photon and 4-photon emission spectra both ex vivo and in vivo of quantum dots. Our results show that quantum dots have exceptionally large ησ3 and ησ4 for efficient generation of multiphoton fluorescence. Besides, the 3-photon and 4-photon emission spectra of quantum dots are essentially identical to those of one-photon emission, which change negligibly subject to the local environment of circulating blood. Based on these characterization results, we further demonstrate deep-brain vasculature imaging in vivo. Due to the superb multiphoton properties of quantum dots, 3-photon and 4-photon fluorescence imaging reaches a maximum brain imaging depth of 1060 and 940 µm below the surface of a mouse brain, respectively, which enables the imaging of subcortical structures. We thus fill the last gap in multiphoton fluorescence imaging in terms of wavelength selection.

Resolving arteriolar wall structures in mouse brain in vivo with three-photon microscopy.

The brain arteriolar wall is a multilayered structure, whose integrity is of key significance to the brain function. However, resolving these different layers in anmial models in vivo is hampered by the lack of either labeling or imaging technology. Here, we demonstrate that three-photon microscopy (3PM) is an ideal solution. In mouse brain in vivo, excited at the 1700-nm window, label-free third-harmonic generation imaging and three-photon fluorescence (3PF) imaging with Alexa 633 labeling colocalize and resolve the internal elastic lamina. Furthermore, Alexa Fluor 594-conjugated Wheat Germ Agglutinin (WGA-594) shows time-dependent labeling behavior. As time lapses, WGA-594 first labels endothelium, and then vascular smooth muscle cells, which are readily captured and resolved with 3PF imaging. Our results show that 3PM, in combination with proper labeling, is a promising technology for investigating the structures of brain arteriolar wall in vivo.

Research progress on occupational exposure to carbon nanotubes and carbon nanotubes-induced pulmonary fibrosis / 中国职业医学

Carbon nanotube (CNT), as a new nanomaterial, is widely used in commercial and industrial production. The occupational exposure of workers involved in CNT production and manufacturing is gradually increasing. CNT mainly enters the human body through the respiratory system, and mainly exerts toxic effects on the respiratory system, including decreased lung function, lung inflammation, and pulmonary fibrosis. Pulmonary fibrosis, as one of the important diseases caused by CNT exposure, has attracted attention and been studied. The process of pulmonary fibrosis induced by CNT has four stages: acute pulmonary inflammatory response, structural destruction and parenchymal injury of lung tissue, impaired lung tissue repair and pulmonary fibrosis. The molecular mechanisms of CNT induced pulmonary fibrosis may be related to cell proliferation, epithelial-mesenchymal transition, fibroblast-myofibroblast differentiation, pulmonary inflammation, immune response and oxidative stress. In the future, it is needed to explore the pathogenesis of pulmonary fibrosis caused by CNT through animal experiments, and carry out large sample and multi-center epidemiological studies for verification.

Galloway-Mowat Syndrome in an infant caused by OSGEP gene mutation: a case report and literature review / 中国新生儿科杂志

Objective:To summarize the clinical features and pathogenic gene mutation of Galloway-Mowat syndrome (GAMOS).Methods:We retrospectively collected the medical history, physical signs, laboratory findings, imaging, and molecular data of GAMOS in an infant diagnosed at the department of Pediatrics of Women and Children's Hospital, School of Medicine, Xiamen university. Relevant literature up to December 2021, retrieved from PubMed, Embase, Web of Science, the Cochrane Library, China National Knowledge Infrastructure, VIP, Wanfang and the Chinese Medical Journal Full Text database with the terms of "Galloway-Mowat syndrome", "infant", "WDR73", "LAGE3", "OSGEP", "TP53RK" and "TPRKB".Results:The male infant with dysmorphic facial features and microcephaly at birth gradually displayed growth restriction and developmental delay. He was admitted to hospital at 3 months and 1 day due to "tachypnea for a half day", and suffered from severe pneumonia, urinary tract infection, nephrotic syndrome, repetitive convulsion, septic shock, disseminated intravascular coagulation, acute renal damage and multiple organ failure during hospitalization. He died when his family had given up treatment. Whole exome sequencing revealed a homozygous mutation c.740G>A (p.Arg247Gln) in the OSGEP gene and both of his parents were heterozygous variation carriers. In the total 14 publications (13 were in English and only 1 in Chinese) that were retrieved, with 78 patients from 58 pedigrees. Together with the index case, there were 79 patients in total. The main clinical manifestations were craniofacial and skeletal dysmorphism, as well as nervous system, renal and eye impairment. Obstetric problems were detected in 15 cases (19.0%), including intrauterine growth restriction, microcephaly, oligohydramnios and fetal distress in utero. 49 cases (62.0%) died when reported. The genetic cause of GAMOS had been reported in 79 patients: OSGEP in 36 (45.6%), WDR73 in 29 (36.7%), TP53RK in 7(8.9%), LAGE3 in 5 (6.3%), and TPRKB in 2(2.5%).Conclusions:The main clinical manifestations of GAMOS were craniofacial and skeletal dysmorphism, development delay, leukoencephalopathy, myelination defect, proteinuria and nephrotic syndrome, and associated with poor prognosis. Prenatal findings may be useful for an early diagnosis.

Acceptance testing and clinical assessment of the in-vivo dose measurement EPIgray system / 中国医学装备

Objective:To assess the accuracy of dose reconstruction of the in-vivo dose verification EPIgray system in intensity-modulated radiation therapy(IMRT)and volumetric-modulated arc therapy(VMAT)through acceptance testing,and to explore the preliminarily clinical application of that.Methods:A total of 37 patients with cancer at various parts were selected for clinical testing.Referring to the suggestions of the acceptance manual of manufacturer and the American Association of Physicists in Medicine(AAPM)TG-119 report,the square field,strip field and intensity-modulated plan were adopted to test the precision of dose reconstruction of EPIgray system on phantom.The recognition ability of the system for error was researched through changed the thickness of homogeneous phantom and the skin distance of exposure source.A total of 37 patients with cancer at different parts who underwent VMAT were selected to conduct clinical test,and then,the consistence between the dose reconstruction of EPIgray system and the counted dose of treatment plan system were further analyzed.Results:In the tests of square field,EPIgray dose reconstruction demonstrated excellent linearity and higher accuracy.On the phantoms with different thicknesses of fields with different sizes,the highest precision of dose reconstruction of central axis of field was(0.10±0.39)%.The all precisions of dose reconstruction were within 3.0%besides the built region of dose and field edges.In the tests of IMRT and VMAT plan,the deviation of dose reconstruction was<5.0%.With the increasing of the complexity of plan and the heterogeneity of phantom,there was a slight decrease in the reconstruction precision,but all deviations of dose reconstruction were within the range of allowable deviations.In clinical testing of 37 patients,the average reconstruction deviation of the prescription dose point was(-0.6±4.8)%,and the average deviation of sampling points within the range of target area was(-2.1±2.7)%.The reconstruction deviations outside of field and that with large dose gradient were larger.Conclusion:The dose reconstructions of in-vivo dose verification system EPIgray has better consistency with treatment planning system in calculating dose,and the precision of dose reconstruction can meet the requirement of clinical application.

Research progress on biomarkers and detection methods for Alzheimer's disease diagnosis in vitro / 中华预防医学杂志

Alzheimer's disease (AD) is a neurodegenerative disease with insidious onset, posing a serious threat to human physical and mental health. The cognitive impairments caused by AD are generally diffuse and overlap symptomatically with other neurodegenerative diseases. Moreover, the symptoms of AD are often covert, leading to missed opportunities for optimal treatment after diagnosis. Therefore, early diagnosis of AD is crucial. In vitro diagnostic biomarkers not only contribute to the early clinical diagnosis of AD but also aid in further understanding the disease's pathogenesis, predicting disease progression, and observing the effects of novel candidate therapeutic drugs in clinical trials. Currently, although there are numerous biomarkers associated with AD diagnosis, the complex nature of AD pathogenesis, limitations of individual biomarkers, and constraints of clinical detection methods have hindered the development of efficient, cost-effective, and convenient diagnostic methods and standards. This article provides an overview of the research progress on in vitro diagnostic biomarkers and detection methods related to AD in recent years.

Research progress on biomarkers and detection methods for Alzheimer's disease diagnosis in vitro / 中华预防医学杂志

Alzheimer's disease (AD) is a neurodegenerative disease with insidious onset, posing a serious threat to human physical and mental health. The cognitive impairments caused by AD are generally diffuse and overlap symptomatically with other neurodegenerative diseases. Moreover, the symptoms of AD are often covert, leading to missed opportunities for optimal treatment after diagnosis. Therefore, early diagnosis of AD is crucial. In vitro diagnostic biomarkers not only contribute to the early clinical diagnosis of AD but also aid in further understanding the disease's pathogenesis, predicting disease progression, and observing the effects of novel candidate therapeutic drugs in clinical trials. Currently, although there are numerous biomarkers associated with AD diagnosis, the complex nature of AD pathogenesis, limitations of individual biomarkers, and constraints of clinical detection methods have hindered the development of efficient, cost-effective, and convenient diagnostic methods and standards. This article provides an overview of the research progress on in vitro diagnostic biomarkers and detection methods related to AD in recent years.

Artesunate inhibits development of breast cancer cells via affecting expression of Skp2 and CDKN1A / 中国药理学通报

Aim To explore the effect of artesunate (ART) on the function of breast cancer cells during the progression of breast cancer and the possible mechanism of action. Methods MCF-7 (30 μmol • L-

Artesunate inhibits development of esophageal squamous cell carcinoma via regulating expression of Skp2 and P21 / 中国药理学通报

Aim To clarify the regulatory effect of Artesunate(ART) on tumor cell function and cell cycle in the pathological process of esophageal squamous cell carcinoma(ESCC). Methods KYSE450 and TE14 cells were treated with different concentrations of ART. The cells treated with 0 mg •L

Oblique lumbar interbody fusion combined with percutaneous endoscopic decompression and posterior fixation for the treatment of lumbar spondylolisthesis accompanied with lumbar spinal stenosis / 中华骨科杂志

Objective:To investigate the efficacy of oblique lumbar interbody fusion (OLIF) combined with percutaneous transforaminal endoscopic decompression (PTED) and posterior pedicle fixation through Wiltse approach in the treatment of lumbar spondylolisthesis accompanied with lumbar spinal stenosis.Methods:From June 2017 to February 2022, 103 patients (50 males and 53 females) of lumbar spondylolisthesis accompanied with lumbar spinal stenosis were performed with OLIF combined with PTED and posterior pedicle fixation. The mean age was 64.1±5.2 years (range, 42-87 years). All involved cases were single-segment and included 83 cases of L 4, 5, 17 cases of L 3, 4, and 3 cases of L 2, 3. Among them, 94 cases were performed for the first time, and other 9 were revision surgery treated by posterior lumbar laminectomy previously. The visual analog scale (VAS) was used to evaluate the low back pain and leg pain, and the Oswestry disability index (ODI) was used to evaluate the lumbar function. The VAS and ODI scores were recorded respectively before the operation, at discharge, 1, 3, 6 months after the operation and at the last follow-up. Macnab criteria was used to evaluate the clinical efficacy at the last follow-up. At the same time, imaging measurements were conducted, including the anterior and posterior disc height, segmental lordotic angle, percentage of slip on lateral X-ray film and the vertebral canal area on axial MRI before and after surgery. Results:All of 103 patients were successfully operated in one stage with an average operation time of 177.7±21.5 min (range, 155-220 min), and an average intraoperative blood loss of 55.9±18.3 ml (range, 30-150 ml). The mean follow-up time were 15.1±2.6 months (range, 6-36 months). There were significant differences in both VAS scores of back and leg and ODI scores at each postoperative time point when compared with preoperative ( F=508.25, F=1524.82, F=1148.68, P<0.001). Macnab criteria of the last follow-up was evaluated as follow: excellent in 85 cases, good in 14, fair in 4, and the excellent and good rate was 96.1%. The radiographic results showed the mean immediate postoperative anterior disc height, posterior disc height, segmental lordotic angle, percentage of slip and axial area of the vertebral canal were 15.23±2.97 mm, 9.32±2.31 mm, 14.36°±4.18°, 3.89%±3.11%, 113.37±47.27 mm 2, and thus all of those increased significantly compared to the mean preoperative 11.93±3.17 mm, 7.21±2.03 mm, 6.15°±3.99°, 23.66%±7.79%, 57.63±28.91 mm 2, respectively ( t=7.84, t=7.07, t=14.91, t=27.62, t=9.68, P<0.001). All cases achieved bony fusion during 6-12 months after operation. The incidence of surgery-related complications was 10.7% (11/103). There were 3 cases of end plate fracture and 2 cases of dural injury, which had no complaint after operation. There was 1 case of pedicle screw entering into the spinal canal by mistake, and the symptoms of nerve damage appeared after operation. After 1 year it basically returned to normal. There were 2 cases of thigh numbness and 1 case of psoas major weakness after operation, all of which relieved after 4 weeks. There was 1 case continuous pain of abdominal incision after surgery. There was 1 case of cage subsidence at the last follow-up. Conclusion:OLIF combined with PTED and posterior pedicle fixation through Wiltse approach is a minimally invasive surgical method for the treatment of lumbar spondylolisthesis accompanied with lumbar spinal stenosis. With the combined minimally invasive techniques, the decompression, fusion and fixation of the lumbar spine can be fulfilled perfectly. It has the advantages of minimally invasive, good clical outcome, few complications and rapid rehabilitation.

Beyond diabetes mellitus: role of metformin in non-muscle-invasive bladder cancer

INTRODUCTION@#Usage of metformin is associated with improved survival in lung, breast and prostate cancer, and metformin has been shown to inhibit cancer cell growth and proliferation in in vitro studies. Given the lack of clinical data on metformin use in patients with bladder cancer, we aimed to evaluate the role of metformin in their oncological outcomes.@*METHODS@#Medication use data from a prospectively maintained database of 122 patients with non-muscle-invasive bladder cancer treated with intravesical Bacille Calmette-Guerin (BCG), who were recruited under a randomised, double-blinded, controlled clinical trial, was collected and analysed. Kaplan-Meier curves were used to assess overall survival (OS) and disease-specific survival (DSS).@*RESULTS@#At a median follow-up duration of 102 (range 3-357) months, 53 (43.4%) patients experienced disease recurrence and 21 (17.2%) experienced disease progression. There was no significant difference in mortality between patients with and without diabetes mellitus. There was significant difference in OS between patients without diabetes mellitus, patients with diabetes mellitus on metformin and patients with diabetes mellitus but not on metformin (p = 0.033); patients with diabetes mellitus on metformin had the best prognosis. Metformin use was associated with significantly lower DSS (p = 0.042). Other oral hypoglycaemic agents, insulin or statins were not associated with disease recurrence or progression.@*CONCLUSION@#Metformin use was associated with improved oncological outcomes in patients with non-muscle-invasive bladder cancer treated with intravesical BCG. Prospective studies with larger patient populations are needed to validate the role of metformin as potential therapy for bladder cancer.

Deep-skin multiphoton microscopy of lymphatic vessels excited at the 1700-nm window in vivo.

Visualization of lymphatic vessels is key to the understanding of their structure, function, and dynamics. Multiphoton microscopy (MPM) is a potential technology for imaging lymphatic vessels, but tissue scattering prevents its deep penetration in skin. Here we demonstrate deep-skin MPM of the lymphatic vessels in mouse hindlimb in vivo, excited at the 1700 nm window. Our results show that with contrast provided by indocyanine green (ICG), 2-photon fluorescence (2PF) imaging enables noninvasive imaging of lymphatic vessels 300 µm below the skin surface, visualizing both its structure and contraction dynamics. Simultaneously acquired second-harmonic generation (SHG) and third-harmonic generation (THG) images visualize the local environment in which the lymphatic vessels reside. After removing the surface skin layer, 2PF and THG imaging visualize finer structures of the lymphatic vessels: most notably, the label-free THG imaging visualizes lymphatic valves and their open-and-close dynamics in real time. MPM excited at the 1700-nm window thus provides a promising technology for the study of lymphatic vessels.

Decomposition of rock micro-fracture signals based on a singular value empirical mode decomposition algorithm.

Rock burst early warning technology is currently applied mainly in microseismic monitoring. Rock burst signals indicate the micro-fracture phenomena of a rock and can transmit earthquake waves through the rock before they are finally received by a detector. A characteristic decomposition of rock micro-fracture signals was conducted by the singular value Empirical Mode Decomposition (EMD) algorithm to effectively decompose the characteristic signals of a rock micro-fracture from mixed microseismic signals, with a low signal to noise ratio to ensure prediction precision. When comparing the proposed method with wavelet decomposition and EMD, it was found that the local characteristics of the signals were retained effectively. The proposed algorithm was verified by applying it in a laboratory simulation and to the decomposition of microseismic signals from a hydro-power station. It was concluded that the improved algorithm had a better decomposition precision than wavelet decomposition and EMD decomposition and could effectively separate the characteristic signals of micro-earthquakes. This could provide a significant basis for the identification of the abnormal microseismic signals of rock micro-fractures as well as a pre-warning of rock fractures. It is therefore of practical significance to study rock fracture early warning technology.

Deep-skin multiphoton microscopy in vivo excited at 1600 nm: A comparative investigation with silicone oil and deuterium dioxide immersion.

Multiphoton microscopy (MPM) excited at the 1700-nm window has enabled deep-tissue penetration in biological tissue, especially brain. MPM of skin may also benefit from this deep-penetration capability. Skin is a layered structure with varying refractive index (from 1.34 to 1.5). Consequently, proper immersion medium should be selected when imaging with high numerical aperture objective lens. To provide guidelines for immersion medium selection for skin MPM, here we demonstrate comparative experimental investigation of deep-skin MPM excited at 1600 nm in vivo, using both silicone oil and deuterium dioxide (D2 O) immersion. We specifically characterize imaging depths, signal levels and spatial resolution. Our results show that both immersion media give similar performance in imaging depth and spatial resolution, while signal levels are slightly better with silicone oil immersion. We also demonstrate that local injection of fluorescent beads into the skin is a viable technique for spatial resolution characterization in vivo.

Self-phase-modulated femtosecond laser source at 1603 nm and its application to deep-brain 3-photon microscopy in vivo.

3-photon microscopy (3PM) excited at the 1700 nm window enables deep-tissue imaging in vivo, especially in brain. PC rod soliton source has previously been exclusively used as the excitation source, which is rather costly and difficult to align. Here we demonstrate a novel nonlinear optical technique to build femtosecond laser source at the 1700 nm window, based on self-phase modulation (SPM) in a short span of large-mode-area fiber. The spectral broadening experienced by the pump pulse leads to the generation of a red-shifted sidelobe at 1603 nm. After spectral filtering, this sidelobe corresponds to 170-fs, 167-nJ pulses at 1603 nm. Using this SPM source, we further demonstrate deep-brain 3 PM to a depth of 1500 µm below the mouse brain surface in vivo. Our SPM femtosecond laser source thus provides a cost effective and easy-to-align alternative excitation source to the PC rod soliton source.

The value of peripheral blood component of T cells and neutrophil to lymphocyte ratio in thyroid cancer coexisted with Hashimoto’s thyroiditis / 中华内分泌外科杂志

Objective:To evaluate clincal value of preoperative peripheral blood CD4/CD8 and neutrophil to lymphocyte ratio (NLR) in papillary thyroid carcinoma (PTC) coexisted with Hashimoto’s thyroiditis (HT) .Methods:Clinicopathological data of 202 patients diagnosed as PTC treated with operation from Jul.2016 to Jun.2019 were retrospectively analyzed. They were divided into Treatment Group including 94 PTC coexisted with HT and Control Group including 108 thyroid cancer according to the postoperateive pathology report. CD4+ and CD8+ subsets in peripheral blood were analyzed by flowcytometer and blood counts were measured before surgery.Results:There was no significant difference in gender, tumor size, number of lesions or lymph node metastasis between the two goups. In comparison with Control Group, median age was lower (39.5 vs 50.5, P=0.001) and CD4/CD8 raito (1.9731.973 Cvs 1.24141973 CD P=0.001) was higher in Treatment group. There was a higher proportion of bilateral lobe thyroidectomy in Treatment Group (40/94 vs 26/108, P=0.005) . A multivariate model analysis identified CD4/CD8 raito as independent risk factor for incidence of PTC coexisted with HT [ OR=0.035, 95% CI (0.009-0.093) , P=0.001]. The NLR level of thyroid cancer patients was correlated with lateral lymph node metastasis negatively (correlation coefficients=-0.286, P=0.045) . Conclusions:PTC might have some connection with HT mediated by body inmune status. Preoperative NLR level is correlated with lateral lymph node metastasis.

In vivo deep-brain imaging of microglia enabled by three-photon fluorescence microscopy.

Microglia act as the first and main form of active immune defense in brain. However, in animal models, research on these cells is limited to the superficial layer of the brain, due to the lack of a deep-imaging technique. Here we break this depth limit using three-photon fluorescence (3PF) microscopy excited at the 1700-nm window. Three-photon action cross-section (ησ3) measurement lays the basis for dye selection and the resultant maximization of 3PF generation. 3PF imaging suppresses the surface background, leading to a much improved signal-to-background ratio compared to the commonly used two-photon microscopy (2PM). We can image microglia 1124 µm below the brain surface in vivo, 3.7 times deeper than previous results using 2PM for microglia imaging. This technique enables us to visualize microglia in the white matter layer in vivo for the first time.

3-photon microscopy of myelin in mouse digital skin excited at the 1700-nm window.

Myelin is a key component of the peripheral nervous system, whose structure anomaly in the digital skin is implicated in neuropathy. Here we demonstrate an in vivo labeling and imaging technique, capable of visualizing myelin sheaths deep in the mouse digital skin. Through material characterization, we verify that 3-photon fluorescence (3PF) can be generated from a commonly used dye- FluoroMyelin Red for labeling myelin, excited at the 1700-nm window. Topical injection of FluoroMyelin Red in the mouse digit leads to bright labeling of myelin sheaths. Harnessing the deep-penetration capability of 3-photon microscopy excited at the 1700-nm window, we demonstrate that 3PF imaging of FluoroMyelin Red-labeled myelin sheaths in the mouse digit in vivo can be achieved to a depth 340 µm below the skin surface, revealing both branching bundle of and individual myelin sheaths.