Translational strategies in potexviruses: products encoded by clover yellow mosaic virus, foxtail mosaic virus, and viola mottle virus RNAs in vitro

We have examined the template properties of the genomic RNAs from three potexviruses: clover yellow mosaic virus (CYMV), foxtail mosaic virus (FMV), and viola mottle virus (VMV). All three RNAs encode a large (160,000 to 182,000 molecular weight) nonstructural protein when translated in the rabbit reticulocyte cell-free system. Only CYMV RNA is able to direct the synthesis of significant quantities of a product whose electrophoretic mobility, antigenic determinants, and partial peptide map resemble those of authentic coat protein. All three viral RNAs also encode a number of discrete polypeptide products whose molecular weights are intermediate between those of the large nonstructural proteins and those of their respective coat proteins. We have examined the kinetics of synthesis in vitro of these intermediate products. For each of the three viral templates, as well as for papaya mosaic virus RNA, pulse-chase experiments suggest that most, if not all, the intermediate polypeptides are incomplete ("paused") or prematurely terminated precursors to the corresponding large nonstructural protein. A partial proteolytic map of the in vitro products encoded by CYMV RNA supports this interpretation. Our data, and those of others, are consistent with a model in which all potexviruses would encode a large nonstructural protein.     

Central nervous system high-resolution magnetic resonance imaging: effect of increasing spatial resolution on resolving power

Resolving power is a useful measure of the magnetic resonance (MR) imager-determined ability to discriminate subtle disease. Optimizing the resolving power produces the best MR images. The resolving power improves with higher spatial resolution, signal-to-noise ratio, and object contrast. Resolving power degrades with increased patient motion, which can be associated with prolonged imaging times. High and low object contrast 0.35-T MR images of the central nervous system are compared at different levels of spatial resolution and signal-to-noise ratios. In systems that have a marginal signal-to-noise ratio, the resolving power can actually decrease when higher spatial resolution is used due to further lowering of signal-to-noise ratio and to increased motion resulting from longer imaging times. This decreases the conspicuity of small, low contrast lesions.     

Effect of methemoglobin formation on the MR appearance of subarachnoid hemorrhage

Subarachnoid hemorrhage has a much higher intensity in magnetic resonance (MR) images with the passage of time. Acute subarachnoid hemorrhage is difficult to see; within 1 week its appearance has become intensified on T1-weighted images. Different concentrations of blood and lysed red blood cells in cerebrospinal fluid (CSF) were examined spectroscopically but did not significantly alter T1 and T2 relaxation of CSF acutely. Ultraviolet visible spectroscopy of bloody CSF stored hypoxically for 3 days showed the presence of methemoglobin. The iron in methemoglobin is paramagnetic; in combination with water this facilitates T1 relaxation. It is concluded that methemoglobin formation with T1 shortening at least partially accounts for the increasing intensity of the MR appearance of subarachnoid hemorrhage over time in the central nervous system and may also explain the intense appearance of subacute hemorrhage in MR images elsewhere in the body.     

阿魏酸钠对花生四烯酸代谢的影响

利用放射薄层方法测定兔血小板花生四烯酸代谢产物TXB₂,PGE₂和PGF_2α。用放射免疫法测定兔血小板TXB₂及主动脉6-keto-PGF_1α。阿魏酸钠(SF,0.1～3.2 mmol/L),抑制¹⁴C-花生四烯酸转化为TXB₂,呈剂量效应关系,IC₅₀为0.762 mmol/L。SF在较高浓度(0.8～3.2mmol/L)时亦抑制PGE₂,PGF_2α的生成。用放免法观察到,SF对血小板TXB₂和动脉壁6-keto-PGF_1α的生成均有抑制作用,对TXB₂的作用较强。结果提示,SF可抑制兔血小板和动脉壁环氧酶活性。     

X-linked syndrome of platelet dysfunction, thrombocytopenia, and imbalanced globin chain synthesis with hemolysis

An unusual family is described with a congenital bleeding disorder present in four males belonging to three generations. Of the three surviving affected males, all had splenomegaly and petechiae. The three had moderate thrombocytopenia (55-90 X 10(9)/liter) and markedly prolonged Ivy-template bleeding times (greater than 30 min). They were also noted to have reticulocytosis and, upon further investigation, imbalanced globin chain synthesis resembling that of beta-thalassemia minor. Studies on nine additional family members in four generations were normal except for slight elevations of reticulocyte counts in female members, one of whom had the abnormal globin chain synthesis ratio. In male members, the bleeding tendency and clinical signs always occurred in the presence of the globin chain synthesis defect and reticulocytosis. This previously undescribed condition was apparently transmitted as an X-linked disorder.     

基于受体结构的药物分子设计系统:维甲类分子与其结合蛋白之间相互作用的研究

大分子解剖程序,配体分子契合适配和DOCK程序,以及计算化学的其它程序等,已集成为基于受体结构和分子间相互作用的进行分子设计的软件系统,定名为BIOS(Biomolecularinteractionsandorientationsimulator)。BIOS软件可在普通的微机上运行。使用BIOS分别剥离了细胞浆维甲结合蛋白(CRBP)和副睾维甲酸结合蛋白(E-RABP)两种蛋白的配体结合腔,剥离是围绕配体以同样的分子距离进行的。从而得到了芳香性残基分布相似的两个结合腔,其结合位点的几何排布却有相当差别。揭示出的结合腔已用于一系列的维甲类化合物的DOCK研究。E-RABP的结合腔可做为设计新维甲类分子的模板。     

Proton spectroscopic imaging (Dixon method) of the liver: clinical utility

The contribution of proton spectroscopic (PS) imaging to magnetic resonance (MR) imaging of the liver was assessed at 0.5 T in 55 patients with known or suspected hepatic malignancy. PS images were compared subjectively with T1- and T2-weighted spin-echo (SE) images for hepatic lesion detection and conspicuity. For hepatic metastases (n = 27), PS images were equal to T1-weighted images in lesion detection in 17 patients but showed fewer lesions in five patients and false-negative results in two. When compared with T2-weighted images, PS images depicted more lesions in six patients, an equal number of lesions in 18, and fewer lesions in two. Hepatomas (n = 8) were detected with each sequence in all patients. Hepatomas were often more conspicuous on PS images than on T2-weighted images; they were of equal conspicuity on PS and T1-weighted images in most cases. Whereas fatty infiltration (n = 16) appeared on PS images as areas of low signal intensity similar to that of paraspinal muscle, it produced no detectable abnormality on either T1- or T2-weighted images. PS imaging is inferior to T1-weighted SE imaging in the detection of hepatic metastases. The major role of PS imaging at intermediate field strength is to differentiate focal fatty infiltration from hepatic metastases.