Automatic counting of retinal ganglion cells in the entire mouse retina based on improved YOLOv5.

Glaucoma is characterized by the progressive loss of retinal ganglion cells (RGCs), although the pathogenic mechanism remains largely unknown. To study the mechanism and assess RGC degradation, mouse models are often used to simulate human glaucoma and specific markers are used to label and quantify RGCs. However, manually counting RGCs is time-consuming and prone to distortion due to subjective bias. Furthermore, semi-automated counting methods can produce significant differences due to different parameters, thereby failing objective evaluation. Here, to improve counting accuracy and efficiency, we developed an automated algorithm based on the improved YOLOv5 model, which uses five channels instead of one, with a squeeze-and-excitation block added. The complete number of RGCs in an intact mouse retina was obtained by dividing the retina into small overlapping areas and counting, and then merging the divided areas using a non-maximum suppression algorithm. The automated quantification results showed very strong correlation (mean Pearson correlation coefficient of 0.993) with manual counting. Importantly, the model achieved an average precision of 0.981. Furthermore, the graphics processing unit (GPU) calculation time for each retina was less than 1 min. The developed software has been uploaded online as a free and convenient tool for studies using mouse models of glaucoma, which should help elucidate disease pathogenesis and potential therapeutics.

Inhibition of mTOR signaling by rapamycin protects photoreceptors from degeneration in rd1 mice.

Retinitis pigmentosa (RP) is an inherited retinal degenerative disease that begins with defective rod photoreceptor function, followed by impaired cone function, and complete blindness in its late stage. To date, however, there is no effective treatment for RP. By carrying a nonsense mutation in the Pde6b gene, rd1 mice display elevated cGMP in conjunction with higher intracellular Ca 2+ in their rod photoreceptors, resulting in fast retinal degeneration. Ca 2+ has been linked to activation of the mammalian target of rapamycin (mTOR) pathway. The mTOR pathway integrates extracellular and intracellular signals to sense the supply of nutrients and plays a central role in regulating protein and lipid synthesis as well as apoptosis and autophagy. In the present study, we showed that mTOR and phosphorylated mTOR (p-mTOR, activated form of mTOR) are up-regulated in rd1 photoreceptors at postnatal day 10 (P10), a pre-degenerative stage. Moreover, the downstream effectors of mTOR, such as pS6K and S6K, are also increased, suggesting activation of the mTOR signaling pathway. Intravitreal administration of rapamycin, a negative regulator of mTOR, inhibits the mTOR pathway in rd1 photoreceptors. Consequently, the progression of retinal degeneration is slower and retinal function is enhanced, possibly mediated by activation of autophagy in the photoreceptors. Taken together, these results highlight rapamycin as a potential therapeutic avenue for retinal degeneration.

Enabling Oxygen-Sulfur Exchange Reaction to Produce Semicrystalline Copolymers from Carbon Disulfide and Ethylene Oxide.

This work describes the first example of semicrystalline poly(thiocarbonate)s from carbon disulfide (CS2 ) and ethylene oxide (EO), two mass producible low-cost monomers. Lewis acid/base pairs (LPs) exhibit high activity (EO conversion up to >99%, 8 h) in catalyzing the copolymerization under low Lewis pair/monomer ratio of 1:1500. Oxygen-sulfur exchange reaction (O-S ER) during the copolymerization of CS2 and EO, the generation and mutual copolymerization with COS, CO2 , and episulfide, is harnessed to introduce crystallizable segments [SC(O)O and SC(S)S] in the copolymer. The type of Lewis base is found to have a great impact on the chain microstructure and the crystalline properties. The formed copolymers with melting point from 117.7 to 245.3 °C are obtained. The maximum crystallinity is estimated to be 78% based on the powder wide-angle X-ray diffraction pattern. This work provides a general method to prepare semicrystalline sulfur-containing polymers.

Simultaneous Improvement of Ionic Conductivity and Mechanical Strength in Block Copolymer Electrolytes with Double Conductive Nanophases.

The most daunting challenge of solid polymer electrolytes (SPEs) is the development of materials with simultaneously high ionic conductivity and mechanical strength. Herein, SPEs of lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI)-doped poly(propylene monothiocarbonate)-b-poly(ethylene oxide) (PPMTC-b-PEO) block copolymers (BCPs) with both blocks associating with Li+ ions are prepared. It is found that the PPMTC-b-PEO/LiTFSI electrolytes with double conductive phases exhibit much higher ionic conductivity (2 × 10-4 S cm-1 at r.t.) than the BCP electrolytes with a single conductive phase. Concurrently, the storage moduli of PPMTCn -b-PEO44 /LiTFSI electrolytes are ≈1-4 orders of magnitude higher than that of the neat PEO/LiTFSI electrolytes. Therefore, simultaneous improvement of ionic conductivity and mechanical properties is achieved by construction of a microphase-separated and disordered structure with double conductive phases.

An Investigation of the Organoborane/Lewis Base Pairs on the Copolymerization of Propylene Oxide with Succinic Anhydride.

The copolymerization of biorenewable succinic anhydride (SA) with propylene oxide (PO) is a promising way to synthesize biodegradable aliphatic polyesters. However, the catalytic systems for this reaction still deserve to be explored because the catalytic activity of the reported catalysts and the molecular weights of produced polyesters are unsatisfied. Herein, we investigate the copolymerization of SA with PO catalyzed by the organoborane/base pairs. The types of Lewis bases, organoboranes, and their loadings all have a large impact on the activity and selectivity of the copolymerization. High ester content of >99% was achieved when performed the PO/SA copolymerization using triethyl borane (TEB)/phosphazene base P1-t-Bu (t-BuP1) pair with a molar ratio of 1/1 at 30-80 °C. Using TEB/t-BuP1 pair with the molar ratio of 4/1 at 80 °C, the turnover of frequency (TOF) was up to 128 h-1 and clearly higher than the known TOF values (0.5-34 h-1) of the PO/SA copolymerization by previously reported catalysts. The number-average molecular weights (Mns) of the resultant polyesters reached up to 20.4 kg/mol when copolymerization was carried out using TEB/t-BuP1 (1/1, in molar ratio) at 30 °C.

DL-CNV: A deep learning method for identifying copy number variations based on next generation target sequencing.

Copy number variations (CNVs) play an important role in many types of cancer. With the rapid development of next generation sequencing (NGS) techniques, many methods for detecting CNVs of a single sample have emerged: (i) require genome-wide data of both case and control samples, (ii) depend on sequencing depth and GC content correction algorithm, (iii) rely on statistical models built on CNV positive and negative sample datasets. These make them costly in the data analysis and ineffective in the targeted sequencing data. In this study, we developed a novel alignment-free method called DL-CNV to call CNV from the target sequencing data of a single sample. Specifically, we collected two sets of samples. The first set consists of 1301 samples, in which 272 have CNVs in ERBB2 and the second set is composed of 1148 samples with 63 samples containing CNVs in MET. Finally, we found that a testing AUC of 0.9454 for ERBB2 and 0.9220 for MET. Furthermore, we hope to make the CNV detection could be more accurate with clinical "gold standard" (e.g. FISH) information and provide a new research direction, which can be used as the supplement to the existing NGS methods.

Precise synthesis of sulfur-containing polymers via cooperative dual organocatalysts with high activity.

Metal-free and controlled synthesis of sulfur-containing polymer is still a big challenge in polymer chemistry. Here, we report a metal-free, living copolymerization of carbonyl sulfide (COS) with epoxides via the cooperative catalysis of organic Lewis pairs including bases (e.g.: phosphazene, amidine, and guanidine) and thioureas as hydrogen-bond donors, afford well-defined poly(monothiocarbonate)s with 100% alternating degree, >99% tail-to-head content, controlled molecular weights (up to 98.4 kg/mol), and narrow molecular weight distributions (1.13-1.23). The effect of the types of Lewis pairs on the copolymerization of COS with several epoxides is investigated. The turnover frequencies (TOFs) of these Lewis pairs are as high as 112 h-1 at 25 °C. Kinetic and mechanistic results suggest that the supramolecular specific recognition of thiourea to epoxide and base to COS promote the copolymerization cooperatively. This strategy provides commercially available Lewis pairs for metal-free synthesis of sulfur-containing polymers with precise structure.

Highly Efficient One-Pot Synthesis of COS-Based Block Copolymers by Using Organic Lewis Pairs.

A one-pot synthesis of block copolymer with regioregular poly(monothiocarbonate) block is described via metal-free catalysis. Lewis bases such as guanidine, quaternary onium salts, and Lewis acid triethyl borane (TEB) were equivalently combined and used as the catalysts. By using polyethylene glycol (PEG) as the macromolecular chain transfer agent (CTA), narrow polydispersity block copolymers were obtained from the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO). The block copolymers had a poly(monothiocarbonate) block with perfect alternating degree and regioregularity. Unexpectedly, the addition of CTA to COS/PO copolymerization system could dramatically improve the turnover frequency (TOF) of PO (up to 240 h-1), higher than that of the copolymerization without CTA. In addition, the conversion of CTA could be up to 100% in most cases, as revealed by ¹H NMR spectra. Of consequence, the number-average molecular weights (Mns) of the resultant block copolymers could be regulated by varying the feed ratio of CTA to PO. Oxygen-sulfur exchange reaction (O/S ER), which can generate randomly distributed thiocarbonate and carbonate units, was effectively suppressed in all of the cases in the presence of CTA, even at 80 °C. This work presents a versatile method for synthesizing sulfur-containing block copolymers through a metal-free route, providing an array of new block copolymers.

Perfectly Alternating and Regioselective Copolymerization of Carbonyl Sulfide and Epoxides by Metal-Free Lewis Pairs.

The preparation of perfectly alternating and regioslective copolymers derived from the copolymerization of carbonyl sulfide (COS) and epoxides by metal-free Lewis pair catalysts composed of a Lewis base (amidine, guanidine, or quaternary onium salts) and a Lewis acid (triethyl borane) is described. Colorless and highly transparent copolymers of poly(monothiocarbonate) were successfully obtained with over 99 % tail-to-head content and high molecular weight (up to 92.5 kg mol-1 ). In most instances, oxygen-sulfur exchange reactions (O/S ERs), which would generate random thiocarbonate and carbonate units, were effectively suppressed. The turnover frequencies (TOF) of these Lewis pair catalyzed processes were as high as 119 h-1 at ambient temperature.