植物氮素吸收与转运的研究进展

氮素是植物生长发育所必须的基本营养元素,在植物生长发育和形态建成中起着重要作用.土壤中植物所利用的主要氮素形式是铵态氮和硝态氮,在进化过程中植物形成不同的吸收和转运铵态氮和硝态氮的分子机制.该文对植物吸收与转运氮素的生理学特征、分子机制及涉及的相关基因等研究进行概括性综述,为研究水稻中氮素吸收、转运相关基因提供理论基础...     

TGF-beta mediated Msx2 expression controls occipital somites-derived caudal region of skull development

Craniofacial development involves cranial neural crest (CNC) and mesoderm-derived cells. TGF-beta signaling plays a critical role in instructing CNC cells to form the craniofacial skeleton. However, it is not known how TGF-beta signaling regulates the fate of mesoderm-derived cells during craniofacial development. In this study, we show that occipital somites contribute to the caudal region of mammalian skull development. Conditional inactivation of Tgfbr2 in mesoderm-derived cells results in defects of the supraoccipital bone with meningoencephalocele and discontinuity of the neural arch of the C1 vertebra. At the cellular level, loss of TGF-beta signaling causes decreased chondrocyte proliferation and premature differentiation of cartilage to bone. Expression of Msx2, a critical factor in the formation of the dorsoventral axis, is diminished in the Tgfbr2 mutant. Significantly, overexpression of Msx2 in Myf5-Cre;Tgfbr2flox/flox mice partially rescues supraoccipital bone development. These results suggest that the TGF-beta/Msx2 signaling cascade is critical for development of the caudal region of the skull.     

Electric-field-induced spin switch of endohedral dodecahedrane heterodimers H@C<Subscript>20</Subscript>H<Subscript>n</Subscript>–C<Subscript>20</Subscript>H<Subscript>n</Subscript>@M (M= Cu,Ag and Au,n = 15, 18, and 19): a theoretical study

We designed nine endohedral dodecahedrane heterodimers H@C₂₀H_n-C₂₀H_n@M (M = Cu, Ag, and Au, n = 15, 18, and 19) that may act as single-molecule spin switches, and we predicted theoretically that the ground states of the dimmers shift from low-spin states (S = 0) to the high-spin states (S = 1) under an external electric field applied parallel or perpendicular to the molecular symmetry axes, consisting well with the analyses of Stark effect. Molecular orbitals analyses provide an intuitive insight into the spin crossover behavior. This study expands the application of endohedral chemistry and provides new molecules for designing single-molecule spin switch.     

New amperometric and potentiometric immunosensors based on gold nanoparticles/tris(2,2'-bipyridyl)cobalt(III) multilayer films for hepatitis B surface antigen determinations

Two generic, fast, sensitive and novel electrochemical immunosensors have been developed. Initially, a layer of plasma-polymerized Nafion film (PPF) was deposited on the platinum electrode surface, then positively charged tris(2,2'-bipyridyl)cobalt(III) (Co(bpy)(3)(3+)) and negatively charged gold nanoparticles were assembled on the PPF-modified Pt electrode by layer-by-layer technique. Finally, hepatitis B surface antibody (HBsAb) was electrostatically adsorbed on the gold nanoparticles surface. Electrochemical behavior of the {Au/Co(bpy)(3)(3+)}(n) multilayer film-modified electrodes was studied. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS) were adopted to monitor the regular growth of the multilayer films. The performance and factors influencing the performance of the resulting immunosensors were studied in detail. The multilayer film-modified immunosensor was used for hepatitis B surface antigen (HBsAg) determination via the amperometric and potentiometric immunosensor systems, and both systems provided the same linear ranges from 0.05 to 4.5 microg/mL with different detection limits for the amperometric system 0.005 microg/mL and for the potentiometric system 0.015 microg/mL. The immunosensors were used to analyse HBsAg in human serum samples. Analytical results of clinical samples show that the developed immunoassay is comparable with the enzyme-linked immunosorbent assays (ELISAs) method, implying a promising alternative approach for detecting HBsAg in the clinical diagnosis. In addition, the multilayer films also showed better stability for 1 month at least.     

Stereoselective reduction of ketones by various vegetables

Reduction of (+)-and (−)-camphorquinones (1a, 1b) by various vegetables (carrot, potato, sweet potato, apple, Japanese radish, cucumber, burdock and onion) gave -hydroxycamphor selectively. Using burdock, (+)-camphorquinone was reduced to give (−)-3S-exo-hydroxycamphor (4a) as major product in high stereoselectivity with high yield. Moreover, 1,2-cyclohexanedione (1c) and 2-methylcyclohexanone (1d) with various vegetables afford enantiomerically pure trans- and/or cis-alcohol, respectively. Various vegetable reduction gave a new idea of a biotechnological process.     

USP10 exacerbates neointima formation by stabilizing Skp2 protein in vascular smooth muscle cells

The underlying mechanism of neointima formation remains unclear. Ubiquitin-specific peptidase 10 (USP10) is a deubiquitinase that plays a major role in cancer development and progression. However, the function of USP10 in arterial restenosis is unknown. Herein, USP10 expression was detected in mouse arteries and increased after carotid ligation. The inhibition of USP10 exhibited thinner neointima in the model of mouse carotid ligation. In vitro data showed that USP10 deficiency reduced proliferation and migration of rat thoracic aorta smooth muscle cells (A7r5) and human aortic smooth muscle cells (HASMCs). Mechanically, USP10 can bind to Skp2 and stabilize its protein level by removing polyubiquitin on Skp2 in the cytoplasm. The overexpression of Skp2 abrogated cell cycle arrest induced by USP10 inhibition. Overall, the current study demonstrated that USP10 is involved in vascular remodeling by directly promoting VSMC proliferation and migration via stabilization of Skp2 protein expression.     

Two new cytotoxic eudesmane sesquiterpenoids from Artemisia anomala

Two new eudesmane sesquiterpenoids artanoate (1) and eudesmanomolide (2) were isolated from the aerial parts of Artemisia anomala S. Moore. Their structures were elucidated as methyl (4R, 5S, 6S, 7S, 10R)-1-oxo-4, 6-dihydroxy-eudesma-2, 11 (13)-dien-12-oate (1) and (1R, 5R, 6R, 10R)-3, 13-diacetoxy-1-hydroxy-3, 7(11)-diene-12, 6-olide (2) on the basis of extensive spectroscopic analyses. Compound 1 showed cytotoxicity against HCT-8 cell lines with IC₅₀ value of 9.13 μM, and compound 2 exhibited inhibitory activities against HCT-8 and A549 cell lines with IC₅₀ values of 3.76 and 5.49 μM, respectively.     

Sympathetic-correlated c-Fos expression in the neonatal rat spinal cord in vitro

An isolated thoracic spinal cord of the neonatal rat in vitro spontaneously generates sympathetic nerve discharge (SND) at ~25°C, but it fails in SND genesis at ≤ 10°C. Basal levels of the c-Fos expression in the spinal cords incubated at ≤ 10°C and ~25°C were compared to determine the anatomical substrates that might participate in SND genesis. Cells that exhibited c-Fos immunoreactivity were virtually absent in the spinal cords incubated at ≤ 10°C. However, in the spinal cords incubated at ~25°C, c-Fos-positive cells were found in the dorsal laminae, the white matter, lamina X, and the intermediolateral cell column (IML). Cell identities were verified by double labeling of c-Fos with neuron-specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), or choline acetyltransferase (ChAT). The c-Fos-positive cells distributed in the white matter and lamina X were NeuN-negative or GFAP-positive and were glial cells. Endogenously active neurons showing c-Fos and NeuN double labeling were scattered in the dorsal laminae and concentrated in the IML. Double labeling of c-Fos and ChAT confirmed the presence of active sympathetic preganglionic neurons (SPNs) in the IML. Suppression of SND genesis by tetrodotoxin (TTX) or mecamylamine (MECA, nicotinic receptor blocker) almost abolished c-Fos expression in dorsal laminae, but only mildly affected c-Fos expression in the SPNs. Therefore, c-Fos expression in some SPNs does not require synaptic activation. Our results suggest that spinal SND genesis is initiated from some spontaneously active SPNs, which are capable of TTX- or MECA-resistant c-Fos expression.     

An Imported Case of Echinococcosis of the Liver in a Korean Who Traveled to Western and Central Europe

Echinococcus granulosus, an intestinal tapeworm of dogs and other canids, infects humans in its larval stage and causes human echinococcosis or hydatid disease. In the Republic of Korea, 31 parasite-proven human echinococcosis cases have been reported, most of which were imported from the Middle East. We recently examined a 61-year-old Korean man who had a large cystic mass in his liver. ELISA was negative for tissue parasitic infections, including echinococcosis, cysticercosis, paragonimiasis, and sparganosis. The patient underwent surgery to remove the cyst, and the resected cyst was processed histopathologically for microscopic examinations. In sectioned cyst tissue, necrotizing protoscolices with disintegrated hooklets of E. granulosus were found. In some areas, only freed, fragmented hooklets were detected. The patient had traveled to western and central Europe in 1996, and had no other history of overseas travel. We report our patient as a hepatic echinococcosis case which was probably imported from Europe.