RESUMO
The past decade has witnessed a rapid progress in asymmetric C-H activation. However, the enantioselective C-H alkoxylation and amination with alcohols and free amines remains elusive. Herein, we disclose the first enantioselective dehydrogenative C-H alkoxylation and amination enabled by a simple cobalt/salicyloxazoline (Salox) catalysis. The use of cheap and readily available cobalt(II) salts as catalysts and Saloxs as chiral ligands provides an efficient method to access P-stereogenic compounds in excellent enantioselectivities (up to >99 % ee). The practicality of this protocol is demonstrated by gram-scale preparation and further derivatizations of the resulting P-stereogenic phosphinamides, which offering a flexible asymmetric alternative to access P-stereogenic mono- and diphosphine chiral ligands. Preliminary mechanistic studies on the enantioselective C-H alkoxylation reaction suggest that a cobalt(III/IV/II) catalytic cycle might be involved.
Assuntos
Cobalto , Aminação , Catálise , Ligantes , EstereoisomerismoRESUMO
Astrocytes, the most abundant cell population in the central nervous system (CNS), are essential for normal neurological function. We show that astrocytes are allocated to spatial domains in mouse spinal cord and brain in accordance with their embryonic sites of origin in the ventricular zone. These domains remain stable throughout life without evidence of secondary tangential migration, even after acute CNS injury. Domain-specific depletion of astrocytes in ventral spinal cord resulted in abnormal motor neuron synaptogenesis, which was not rescued by immigration of astrocytes from adjoining regions. Our findings demonstrate that region-restricted astrocyte allocation is a general CNS phenomenon and reveal intrinsic limitations of the astroglial response to injury.
Assuntos
Astrócitos/fisiologia , Encéfalo/citologia , Movimento Celular , Neurônios Motores/fisiologia , Medula Espinal/citologia , Sinapses/fisiologia , Animais , Proteínas de Bactérias/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Encéfalo/anormalidades , Encéfalo/fisiologia , Lesões Encefálicas/fisiopatologia , Proteínas de Fluorescência Verde , Proteína Homeobox Nkx-2.2 , Proteínas de Homeodomínio/metabolismo , Integrases/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Proteínas/metabolismo , RNA não Traduzido , Medula Espinal/anormalidades , Medula Espinal/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Fatores de Transcrição/metabolismo , Transcrição Gênica , Proteínas de Peixe-ZebraRESUMO
1,25-Dihydroxyvitamin D3, the physiologically active form of vitamin D3, exerts its functions through a receptor-mediated mechanism and plays an important role in the cell differentiation. This study investigated the effects of 1,25-dihydroxyvitamin D3 on the proliferation and differentiation of porcine preadipocyte. Stromal-vascular cells containing preadipocytes were prepared from dorsal subcutaneous adipose tissue of approximately 3-day-old Chinese male crossbred pigs. After confluence, the differentiation was induced by transferrin, dexamethasone and insulin for 2 days, and then subsequently cultured for 6 days. The cells were treated with 1,25-dihydroxyvitamin D3 during the induction of differentiation (the early phase of differentiation) or throughout the differentiation period. The terminal differentiation markers, such as glycerol-3-phosphate dehydrogenase activity and lipid accumulation were measured during the process of cultures. The treatment with 1,25-dihydroxyvitamin D3 severely affected the induction of all differentiation markers throughout the differentiation period. 1,25-Dihydroxyvitamin D3 suppressed the expression of peroxisome proliferator-activated receptor gamma mRNA and interfered with the induction of retinoid X receptor alpha mRNA. The mRNAs of the adipogenesis-related genes, lipoprotein lipase, stearoyl-CoA desaturase, phosphoenolpyruvate carboxykinase, glycerol-3-phosphate dehydrogenase and glucose transporter 4 were reduced when 1,25-dihydroxyvitamin D3 was added into differentiation medium. Also, 1,25-dihydroxyvitamin D3 inhibited preadipocyte differentiation in dose-dependent manner. These results suggested that 1,25-dihydroxyvitamin D3 inhibited porcine preadipocyte differentiation through suppressing PPAR gamma and RXR alpha mRNA expressions and then down regulating the expression of adipogenesis-related genes.
Assuntos
Adipócitos/efeitos dos fármacos , Calcitriol/farmacologia , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Adipócitos/citologia , Adipócitos/enzimologia , Adipócitos/metabolismo , Animais , Sequência de Bases , Primers do DNA , Técnicas In Vitro , Masculino , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The elucidation of the molecular mechanism of porcine adipocyte differentiation is important not only to domestic animal industry, but also to medical science because of the similarities in the trait of body lipid deposition between human and pigs. In this study, we investigated the roles of RXRalpha in porcine (Sus scrofa) adipocyte differentiation by using RNAi method and primary cultured porcine adipocytes. With the transfection of RXRalpha-siRNA, the gene and protein expressions of RXRalpha were successfully inhibited in differentiating porcine adipocytes. By the RXRalpha gene silencing, the adipocyte differentiation, as characterized by lipid accumulation and GPDH activity, was suppressed. Furthermore, in association with the decrease in RXRalpha gene expression level, PPARgamma and C/EBPalpha genes expression level also decreased, suggesting that RXRalpha is involved in their expression. Thus, our study clearly demonstrated the pivotal roles of RXRalpha in porcine adipocyte differentiation.
