Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 5.666
Filtrar
1.
Talanta ; 221: 121463, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33076083

RESUMO

In this study, we describe the construction of an "off-on" fluorescent probe based on carbon dots (CDs) and silver nanoparticles (AgNPs) mixture for sensitive and selective detection of cysteamine. By mixing AgNPs with CDs solution, the fluorescence of CDs was significantly decreased due to the inner filter effect (IFE). Upon addition of cysteamine to the mixed aqueous of CDs and AgNPs, the silver-sulfur bond between cysteamine and AgNPs caused AgNPs to aggregate, and the quenched fluorescence of CDs could in turn be recovered. The probe was employed to quantitatively detect cysteamine, and the results showed that it could detect cysteamine in a concentration range of 2-16 µM with the detection limit of 0.35 µM (signal-to-noise ratio of 3). The detection of cysteamine spiked into bovine serum samples showed high recovery rates ranging from 95.5 to 111.7%. More importantly, the developed probe had low cytotoxicity and was successfully used for in vivo imaging of HepG2 cells.

2.
BMC Plant Biol ; 20(1): 448, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33003994

RESUMO

BACKGROUND: Agricultural yield is closely associated with nitrogen application. Thus, reducing the application of nitrogen without affecting agricultural production remains a challenging task. To understand the metabolic, physiological, and morphological response of wheat (Triticum aestivum) to nitrogen deficiency, it is crucial to identify the genes involved in the activated signaling pathways. RESULTS: We conducted a hydroponic experiment using a complete nutrient solution (N1) and a nutrient solution without nitrogen (N0). Wheat plants under nitrogen-deficient conditions (NDC) showed decreased crop height, leaf area, root volume, photosynthetic rate, crop weight, and increased root length, root surface area, root/shoot ratio. It indicates that nitrogen deficiency altered the phenotype of wheat plants. Furthermore, we performed a comprehensive analysis of the phenotype, transcriptome, GO pathways, and KEGG pathways of DEGs identified in wheat grown under NDC. It showed up-regulation of Exp (24), and Nrt (9) gene family members, which increased the nitrogen absorption and down-regulation of Pet (3), Psb (8), Nar (3), and Nir (1) gene family members hampered photosynthesis and nitrogen metabolism. CONCLUSIONS: We identified 48 candidate genes that were involved in improved photosynthesis and nitrogen metabolism in wheat plants grown under NDC. These genes may serve as molecular markers for genetic breeding of crops.

3.
Brain Behav ; : e01867, 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33022141

RESUMO

BACKGROUND AND PURPOSE: Although many functional magnetic resonance imaging (fMRI) studies have investigated the language architecture and neurobiological mechanism underlying poststroke aphasia (PSA), the pathophysiological mechanisms of PSA still remain poorly understood. In addition to a limited number of subjects (<20) tested with different methodologies and stimuli, inconsistent reports of the brain regions involved have been a major factor. Thus, we conducted a meta-analysis of 12 peer-reviewed studies of abnormal brain activation regions in PSA patients at rest using activation likelihood estimation (ALE). RESULTS: A meta-analysis was performed based on 24 experiments with 497 total participants in 12 studies to establish the ALE of regional activation in PSA. Through experiments with PSA patients and healthy controls, we found that hypoactivation in PSA converged on the left superior frontal gyrus and the left parietal postcentral gyrus, whereas there was hyperactivation in the right cerebellar anterior lobe, left fusiform gyrus, left superior parietal lobule, and right subgyral hippocampus. CONCLUSION: Our study verified that dominant and nondominant language networks play roles in the recovery of language function.

4.
Nat Prod Res ; : 1-7, 2020 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-33016130

RESUMO

One new xanthone, chryxanthone C (1), together with four known analogues (2-5), were isolated from the cultures of Paecilamyces sp. TE-540, an endophytic fungus obtained from the leaves of Nicotiana tabacum L. The structure of 1 was elucidated by comprehensive spectral analysis including HRESIMS and 1D/2D NMR, which were confirmed by Cu Kα X-ray crystallography. Compound 1 featured an unusual dihydropyran ring fused to an aromatic ring, rather than the commonly occurring prenyl moiety. The cytotoxicity of compounds 1-5 were evaluated against five human tumour cell lines and 4 exhibited moderate to strong cytotoxicities with IC50 values ranging from 5.6 to 14.2 µM.

5.
Plant Genome ; 13(2): e20019, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33016609

RESUMO

Mangroves is an umbrella term for plants located across the tropics and sub-tropics that live in the coastal region, between the sea and the land. All mangroves evolved from terrestrial plants, providing the opportunity to assess convergence, as well as the lineage-specific features, at the genetic level. In this study, we compared chloroplast genomes from 21 mangrove species, covering main phylogenetic clades. We demonstrate that chloroplast gene order, content, and genome size is largely conserved in mangroves. The exceptions are loss of the photosystem I gene psaZ in Acanthus ilicifolius and inversion of the ribosomal protein gene rpl23 in Avicennia germinans. The repeat content of mangrove chloroplast varied between species, but was conserved within species of the same order. Sequence diversity analysis revealed that the IR (invert repeat) region was highly conserved compared to the SC (single-copy) region in most phylogenetic clades, except clade core leptosporangiates (ferns). The ribosomal protein gene rps7 was under positive selection in Kandelia obovato, Rhizophora stylosa, Bruguiera sexangular and Rhizophora mangle, a monophyletic branch of clade fabids, while no evidence of positive selection was found in other mangrove lineages. Taken together, our data suggests that convergent evolutionary dynamics leaves no significant signal on the plastid genome of mangroves. The complete chloroplast genomes provided in this study shed light on the evolution of these important plastids and provides a valuable resource for further research efforts.

6.
Artigo em Inglês | MEDLINE | ID: mdl-33021942

RESUMO

We consider the problem of minimizing the sum of an average of a large number of smooth convex component functions and a possibly nonsmooth convex function that admits a simple proximal mapping. This class of problems arises frequently in machine learning, known as regularized empirical risk minimization (ERM). In this article, we propose mSRGTR-BB, a minibatch proximal stochastic recursive gradient algorithm, which employs a trust-region-like scheme to select stepsizes that are automatically computed by the Barzilai-Borwein method. We prove that mSRGTR-BB converges linearly in expectation for strongly and nonstrongly convex objective functions. With proper parameters, mSRGTR-BB enjoys a faster convergence rate than the state-of-the-art minibatch proximal variant of the semistochastic gradient method (mS2GD). Numerical experiments on standard data sets show that the performance of mSRGTR-BB is comparable to and sometimes even better than mS2GD with best-tuned stepsizes and is superior to some modern proximal stochastic gradient methods.

7.
Mech Ageing Dev ; : 111381, 2020 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-33045248

RESUMO

Saccharomyces cerevisiae MED2/YDL005C is a subunit of the mediator complex (Mediator), which is responsible for tightly controlling the transcription of protein-coding genes by mediating the interaction of RNA polymerase II with gene-specific transcription factors. Although a high-throughput analysis in yeast showed that the MED2 protein exhibits altered cellular localization under hypoxic stress, no specific function of MED2 has been described to date. In this study, we first provided evidence that MED2 is involved in the endoplasmic reticulum (ER) stress response and modulation of the replicative life span. We showed that deletion of MED2 leads to sensitivity to the ER stress inducer tunicamycin (TM) as well as a shortened replicative lifespan (RLS), accompanied by increased intracellular ROS levels and hyperpolarization of mitochondria. On the other hand, overexpression of MED2 in wild-type (WT) yeast enhanced TM resistance and extended the RLS. In addition, the IRE1-HAC1 pathway was essential for the TM resistance of MED2-overexpressing cells. Moreover, we showed that MED2 deficiency enhances ER unfolded protein response (UPR) activity compared to that in WT cells. Collectively, these results suggest the novel role of MED2 as a regulator in maintaining ER homeostasis and longevity.

8.
BMC Genomics ; 21(1): 701, 2020 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-33032518

RESUMO

BACKGROUND: Intrauterine growth restriction (IUGR) remains a major problem associated with swine production. Thus, understanding the physiological changes of postnatal IUGR piglets would aid in improving growth performance. Moreover, liver metabolism plays an important role in the growth and survival of neonatal piglets. RESULTS: By profiling the transcriptome of liver samples on postnatal Days 1, 7, and 28, our study focused on characterizing the growth, function, and metabolism in the liver of IUGR neonatal piglets. Our study demonstrates that the livers of IUGR piglets were associated with a series of complications, including inflammatory stress and immune dysregulation; cytoskeleton and membrane structure disorganization; dysregulated transcription events; and abnormal glucocorticoid metabolism. In addition, the abnormal liver function index in the serum [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total protein (TP)], coupled with hepatic pathological and ultrastructural morphological changes are indicative of liver damage and dysfunction in IUGR piglets. Moreover, these results reveal the sex-biased developmental dynamics between male and female IUGR piglets, and that male IUGR piglets may be more sensitive to disrupted metabolic homeostasis. CONCLUSIONS: These observations provide a detailed reference for understanding the mechanisms and characterizations of IUGR liver functions, and suggest that the potential strategies for improving the survival and growth performance of IUGR offspring should consider the balance between postnatal catch-up growth and adverse metabolic consequences. In particular, sex-specific intervention strategies should be considered for both female and male IUGR piglets.

9.
Theriogenology ; 158: 470-476, 2020 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-33049572

RESUMO

Signaling pathways and transcription factors are involved in porcine embryonic development. Here, we demonstrate that glycogen synthase kinase-3 (GSK3) inhibitor, CHIR99021 and recombinant porcine interleukin-6 (rpIL6) significantly promote porcine parthenogenetic blastocyst formation (49.23 ± 8.40% vs 32.34 ± 4.15%), with increased inner cell mass (ICM) cell numbers (7.72 ± 2.30 vs 4.28 ± 1.60) and higher expression of pluripotent genes, such as OCT4, SOX2 and NANOG. Furthermore, CHIR99021 and rpIL6 improve blastocyst quality with increased blastocyst hatching percentage (16.19 ± 1.96% vs 10.25 ± 1.12%) and subsequently porcine pluripotent stem cells (pPSCs) derivation efficiency. These results advance the understanding of porcine pre-implantation development and provide evidences in improving the blastocyst quality.

10.
BMC Gastroenterol ; 20(1): 334, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-33054747

RESUMO

BACKGROUND: We report a rare case of primary abdominal cocoon with bilateral cryptorchidism. CASE PRESENTATION: The patient had a history of laparoscopic surgery for bilateral cryptorchidism 6 years earlier. He was admitted to the hospital again due to intestinal obstruction. Surgery was performed on the patient after the failure of conservative treatment. The patient was diagnosed with primary abdominal cocoon. Instead of the greater omentum, many cocoon-like tissues surrounding the bowel were seen during operation. Abdominal surgery can increase the risk of intestinal adhesion, which is one of the main causes of intestinal obstruction, especially in patients with abdominal cocoon. We hypothesize that the surgery 6 years earlier to address transabdominal bilateral cryptorchidism accelerated the patient's intestinal obstruction. CONCLUSION: This case implies that it is important for urologists to evaluate whether their patients exhibit abdominal cocoon before cryptorchidism surgery, to choose better surgical methods and reduce the risks of poor prognosis.

11.
Matrix Biol ; 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-33068727

RESUMO

Disturbed flow leads to increased inflammatory responses of endothelial cells (ECs) prone to atherogenic state. Currently, little is known about the physiological mechanisms protecting vasculature against disturbed flow-activated ECs leading to atherosclerosis. Understanding the protective mediators involved in EC activation could provide novel therapeutic strategies for atherosclerosis. The extracellular matrix microenvironment profoundly regulates cellular homeostasis. A non-EC resident ECM protein, cartilage oligomeric matrix protein (COMP), has diverse protective roles in the cardiovascular system. To determine whether COMP could protect against disturbed flow-activated EC and atherosclerosis, we compared oscillatory shear stress (OSS) induced EC activation coated with various ECM proteins. Purified COMP inhibited EC activation caused by OSS. EC activation was upregulated in the aortic arch where the flow is disturbed in COMP-/- mice as compared with wild-type mice under physiological conditions or pathologically in partially ligated mouse carotid arteries. Mechanistically, co-immunoprecipitation, mammalian two-hybrid and FRET assay results suggest that COMP bound directly to integrin α5 via its C-terminus. We next synthesized a COMP-derived peptidomimetics (CCPep24) mimicking a specific COMP-integrin α5 interaction and found that CCPep24 protected against EC activation and atherogenesis in vivo. This study extends our current understanding of how ECM and flow coordinately fine-tune EC homeostasis and reveals the potential therapeutic effect of COMP or COMP-derived peptidomimetics on blocking aberrant integrin α5 activation, inflammatory EC activation and atherosclerosis pathogenesis.

12.
Planta ; 252(5): 75, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-33026530

RESUMO

MAIN CONCLUSION: Exogenous SA treatment at appropriate concentrations promotes adventitious root formation in cucumber hypocotyls, via competitive inhibiting the IAA-Asp synthetase activity of CsGH3.5, and increasing the local free IAA level. Adventitious root formation is critical for the cutting propagation of horticultural plants. Indole-3-acetic acid (IAA) has been shown to play a central role in regulating this process, while for salicylic acid (SA), its exact effects and regulatory mechanism have not been elucidated. In this study, we showed that exogenous SA treatment at the concentrations of both 50 and 100 µM promoted adventitious root formation at the base of the hypocotyl of cucumber seedlings. At these concentrations, SA could induce the expression of CYCLIN and Cyclin-dependent Kinase (CDK) genes during adventitious rooting. IAA was shown to be involved in SA-induced adventitious root formation in cucumber hypocotyls. Exposure to exogenous SA led to a slight increase in the free IAA content, and pre-treatment with the auxin transport inhibitor 1-naphthylphthalamic acid (NPA) almost completely abolished the inducible effects of SA on adventitious root number. SA-induced IAA accumulation was also associated with the enhanced expression of Gretchen Hagen3.5 (CsGH3.5). The in vitro enzymatic assay indicated that CsGH3.5 has both IAA- and SA-amido synthetase activity and prefers aspartate (Asp) as the amino acid conjugate. The Asp concentration dictated the functional activity of CsGH3.5 on IAA. Both affinity and catalytic efficiency (Kcat/Km) increased when the Asp concentration increased from 0.3 to 1 mM. In contrast, CsGH3.5 showed equal catalytic efficiency for SA at low and high Asp concentrations. Furthermore, SA functioned as a competitive inhibitor of the IAA-Asp synthetase activity of CsGH3.5. During adventitious formation, SA application indeed repressed the IAA-Asp levels in the rooting zone. These data show that SA plays an inducible role in adventitious root formation in cucumber through competitive inhibition of the auxin conjugation enzyme CsGH3.5. SA reduces the IAA conjugate levels, thereby increasing the local free IAA level and ultimately enhancing adventitious root formation.

13.
Clin Exp Immunol ; 2020 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-33030251

RESUMO

BACKGROUND: Hepatic inflammatory response is a risk factor for liver cancer initiation and progression. Interleukin (IL)-35 is the newest member of IL-12 cytokine family, and has been reported to play an essential role in the immunosuppressive liver microenvironment. Herein we focus on the expression profiles of IL-35 in hepatocellular carcinoma (HCC) and effects on local immune status. METHODS: HCC transcriptome array data were downloaded from GEO. Analysis was performed by BRB array tools and IPA software. Serum IL-35 level was detected by AimPlet bead-based immunoassay. In situ IL-35 detection was performed by immunohistochemical staining and western blot. In vitro effect of IL-35 on CD4+ or CD8+ T cell function was detected by flow cytometry. RESULTS: Our results showed that there were large amounts of IL-35 expressed in HCC serum and tumor tissues. IL-35 expression affects the transcript of thousands of genes, most differentially expressed genes (DEGs) in tumor tissues correlated with T-cell immunity. The IL-35 high-expression group exhibited enhancement of regulatory T cells (Tregs) and impairment of cytolytic T cells. In vitro experiments proved that exogenous IL-35 stimulated the expression of PD1 and LAG3 in CD4+ and CD8+ T cells. In addition, the stimulating effect was time-dependent. Furthermore, IL-35 inhibited interferon(IFN)-γ secretion by CD4+ and CD8+ T cells. CONCLUSIONS: Elevated IL-35 had an immune suppressive role in HCC tumor microenvironments through affecting inhibitor receptor expression and cytokine secretion of CD4+ and CD8+ T cells. Dissection of the precise targets and underlying molecular mechanisms would mean alternative treatments for HCC patients. (250 words).

14.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1485-1488, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018272

RESUMO

The susceptibility-based positive contrast MR technique was applied to estimate arbitrary magnetic susceptibility distributions of the metallic devices using a kernel deconvolution algorithm with a regularized L-1 minimization. Previously, the first-order primal-dual (PD) algorithm could provide a faster reconstruction time to solve the L-1 minimization, compared with other methods. Here, we propose to accelerate the PD algorithm of the positive contrast image using the multi-core multi-thread feature of graphics processor units (GPUs). The some experimental results showed that the GPU-based PD algorithm could achieve comparable accuracy of the metallic interventional devices in positive contrast imaging with less computational time. And the GPU-based PD approach was 4~15 times faster than the previous CPU-based scheme.Clinical Relevance-This can estimate arbitrary magnetic susceptibility distributions of the metallic devices with the processing efficacy of 4~15 times faster than before.

15.
Brain Res Bull ; 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-33049352

RESUMO

Neuropathic pain is caused by damage to the nervous system. Increasing studies have confirmed that jagged 1 (JAG1) plays a significant role in nervous system diseases. However, the regulatory mechanisms of JAG1 in neuropathic pain remain vague. In this study, a chronic constriction injury (CCI) rat model was performed. JAG1 was found to be upregulated in CCI rats. The recombinant lentiviruses containing sh-JAG1 were injected to the CCI rats for knockdown of JAG1 in rats. JAG1 knockdown improved the mechanical allodynia and thermal hyperalgesia in CCI rats, and decreased the concentrations and mRNA expression of inflammatory cytokines (IL-6, TNF-α and IL-1ß) in spinal cord dorsal horn of CCI rats, suggesting that JAG1 knockdown attenuated neuropathic pain. In addition, we explored for the upstream mechanism of JAG1. Through RNA pull down assay and luciferase reporter assay, we confirmed that miR-124-3p and miR-141-3p bound with JAG1. Long non-coding RNA (lncRNA) small nucleolar RNA host gene 6 (SNHG16) was verified to be the upstream molecule of miR-124-3p and miR-141-3p to negatively regulate miR-124-3p and miR-141-3p. SNHG16 positively regulated JAG1 expression through competitively binding with miR-124-3p and miR-141-3p. Moreover, SNHG16 was found to be upregulated in CCI rats. SNHG16 knockdown improved the mechanical allodynia and thermal hyperalgesia as well as reduced the concentrations and mRNA expression of inflammatory cytokines in CCI rats. Finally, SNHG16 was confirmed to aggravate neuropathic pain in CCI rats via upregulating JAG1. In conclusion, this study verified that SNHG16 aggravated neuropathic pain in CCI rats via binding with miR-124-3p and miR-141-3p to upregulate JAG1, which may provide new insights into the development of gene therapy for neuropathic pain.

16.
Carbohydr Polym ; 250: 116922, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-33049836

RESUMO

Natural hydrogels are widely investigated for biomedical applications because of their structures similar to extracellular matrix of native tissues, possessing excellent biocompatibility and biodegradability. However, they are often susceptible to mechanical disruption. In this study, self-healing hyaluronic acid (HA) hydrogels are fabricated through a facile dynamic covalent Schiff base reaction. Dialdehyde-modified HA (AHA) precursor was synthesized, and then the AHA/cystamine dihydrochloride (AHA/Cys) hydrogels were formed by blending AHA and Cys at acidic pH levels. By varying Cys to AHA ratio, the hydrogel morphology, swelling and kinetics of gelation could be controlled. Gelation occurred fast, which was predominantly attributed to Schiff base reaction between the dialdehyde groups on AHA and amimo groups on Cys. The hydrogel exhibited improved mechanical properties with increase in Cys content. Furthermore, due to dynamic imine bonds, this hydrogel demonstrated excellent self-healing ability based on the stress after mechanical disruption. Also, it was found to be pH-responsive and injectable. Taken together, this kind of hyaluronic acid hydrogel can provide promising future for various biomedical applications in drug delivery, bioprinting, smart robots and tissue regeneration.

17.
Artigo em Inglês | MEDLINE | ID: mdl-33052853

RESUMO

Online segmentation and recognition of skeletonbased gestures are challenging. Compared with offline cases, the inference of online settings can only rely on the current few frames and always completes before whole temporal movements are performed. However, incompletely performed gestures are ambiguous and their early recognition is easy to fall into local optimum. In this work, we address the problem with a temporal hierarchical dictionary to guide the hidden Markov model (HMM) decoding procedure. The intuition is that, gestures are ambiguous with high uncertainty at early performing phases, and only become discriminate after certain phases. This uncertainty naturally can be measured by entropy. Thus, we propose a measurement called "relative entropy map" (REM) to encode this temporal context to guide HMM decoding. Furthermore, we introduce a progressive learning strategy with which neural networks could learn a robust recognition of HMM states in an iterative manner. The performance of our method is intensively evaluated on three challenging databases and achieves state-ofthe- art results. Our method shows the abilities of both extracting the discriminate connotations and reducing large redundancy in the HMM transition process. It is verified that our framework can achieve online recognition of continuous gesture streams even when they are halfway performed.

18.
Rapid Commun Mass Spectrom ; : e8972, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-33053243

RESUMO

RATIONALE: Methicillin-resistant Staphylococcus aureus (MRSA) is one of major clinical pathogens responsible for both hospital- and community-acquired infections worldwide. The delay of targeted antibiotic treatment contributes to longer hospitalization stay, higher costs, and increasing in-hospital mortality. Matrix-assisted laser-desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been integrated into the routine workflow for microbial identification over the past decade, and it also showed promising functions in the detection of bacterial resistance. Therefore, we describe a rapid MALDI-TOF MS-based methodology for MRSA screening with machine learning algorithms. METHODS: A total of 452 clinical S. aureus isolates were included in this study, of which 194 were MRSA and 258 were methicillin-sensitive S. aureus (MSSA). The mass-to-charge ratio (m/z) features from MRSA and MSSA strains were binned and selected through Lasso regression. These features were then used to train a non-linear support vector machine (SVM) with radial basis function (RBF) kernels for evaluating the discrimination performance. The classifiers' accuracy, sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve (AUC) were evaluated and compared with those from the Random Forest (RF) model. RESULTS: 2601 unique spectral peaks of all isolates were identified in total and 38 m/z features were selected for the classifying model. The AUCs of the non-linear RBF-SVM model, RF model were 0.89, 0.87, respectively, and the accuracy ranged between 0.86 (RBF-SVM) and 0.82 (RF). CONCLUSIONS: Our study demonstrates that MALDI-TOF MS coupled with machine-learning algorithms could be used to develop a rapid and easy-to-use method to discriminate MRSA from MSSA. Considering that this method is easy to implement in routine microbiology laboratories, it suggests a cost-effective and time-efficient alternative to conventional resistance detection in the future to improve clinical treatment.

19.
Mol Ecol Resour ; 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-33053263

RESUMO

The reissner lamprey Lethenteron reissneri, belonging to the class Cyclostomata, serves as a bridge between invertebrates and jawed vertebrates, and is considered the sister group of jawed vertebrates. However, despite this evolutionary significance, the genetic mechanisms underlying the adaptive evolution of the lamprey lineage remain unclear. Here, we assembled a 1.06 Gb chromosome-level draft genome of L. reissneri, with 72 chromosomes (ranging in length from 4.5 Mb to 25.9 Mb) and a scaffold N50 length of 13.23 Mb. Genome quality comparisons revealed that the reissner lamprey genome has higher completeness and contiguity than the previously published sea lamprey and Japanese lamprey genomes. Moreover, reissner lamprey, sea lamprey, and Japanese lamprey species share similar transposable element profiles and Hox gene cluster compositions, suggesting that a burst of transposable element activity and whole genome duplication occurred before their divergence. Additionally, the Lip gene copy numbers, which have been studied for their functions in the host defense system, were found to be expanded uniquely in lamprey lineages, suggesting key roles for these genes in lamprey evolution and adaptation. We also identified two neural-related genes, Nrn1 and Unc13a, with copy number expansions in jawed vertebrates, which may be functionally relevant to the origin of lamprey brains. Hence, this study not only provides the first chromosome-level reference genome for Cyclostomata, but also highlights features of the unique biology and adaptive evolution of the lamprey lineage.

20.
Artigo em Inglês | MEDLINE | ID: mdl-33052624

RESUMO

In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo-differentiation of remote motifs away from the radical reaction site. We herein describe a copper-catalyzed asymmetric radical 1,4-carboalkynylation of 1,3-enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P-ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3-enynes as well as radical precursors with excellent functional group tolerance.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA