De novo RNA synthesis catalyzed by HCV RNA-dependent RNA polymerase

The 65 kDa RNA-dependent RNA polymerase (NS5B), encoded by the hepatitis C virus (HCV) genome, is a key component involved in viral replication. Here we provide the direct evidence that purified HCV polymerase catalyzed de novo RNA synthesis in a primer-independent manner using homopolymers and HCV RNA as templates. The enzyme could utilize both polyC and polyU as templates for de novo RNA synthesis, suggesting that NS5B specifically recognized pyrimidine bases for initiation. More importantly, NS5B also catalyzed de novo RNA synthesis with an HCV RNA template; the resulting nascent RNA products, smaller than the template used, contained ATP as the first nucleotide. These results indicate that the newly synthesized RNAs did not result from template self-priming and suggest that a replication initiation site in the HCV RNA genome is a uridylate.     

Seasonal occurrence of helminths in the anadromous fish Coilia nasus (Engraulidae): parasite indicators of fish migratory movements

To understand the seasonal migration of the anadromous Coilia nasus , we attempted to identify the parasites infecting C. nasus and determine their seasonal occurrence. From June 2007 to July 2008, a survey of 775 C. nasus individuals from the estuary of the Yangtze River and the coast of the East China Sea revealed more than 7,300 parasites associated with the gills and alimentary tracts of C. nasus . The following 6 helminth taxa were identified, i.e., the monogeneans Heteromazocraes lingmueni and Helciferus tenuis, the digenean Elytrophallus coiliae, the acanthocephalan Acanthosentis cheni , and larvae of the nematodes Anisakis simplex and Contracaecum sp., all of which are marine or brackish-water parasites. The absence of freshwater helminths suggested that the parasites acquired in freshwater may have been accidentally, and easily, lost by the time the fish had reached the estuary and coast. Contrary to seasonal occurrence of the parasites' life cycles, the lowest mean abundance and prevalence of H. lingmueni and A. cheni occurred in August, which suggested the immigration of C. nasus from freshwater to the Yangtze estuary, with lower parasite burdens. The highest mean abundance and prevalence of the nematodes A. simplex and Contracaecum sp. in May and June, and the lowest in August, indicated the arrival of the fish from the coast and the Yangtze River, to the estuary, respectively. These findings suggested that a majority of the fish prepared for spawning migration in the estuary in spring and early summer and returned to the estuary after spawning in the lower and middle reaches of the Yangtze River in late summer.     

周围神经损伤后外源性GKNF对神经元的保护作用

采用硅管套接大鼠切断的坐骨神经模型,局部给予胶质细胞源性神经营养因子（ＧＤＮＦ）,应用尼氏染色、酶组织化学染色方法,观察到外源性ＧＤＮＦ能减少脊髓修复侧前角运动神经元死亡的数目,降低脊髓前角运动神经元及脊神经节感觉神经元中胆碱酯酶（ＣＨＥ）及酸性磷酸酶（ＡＣＰ）变化的幅度。这表明外源性ＧＤＮＦ能保护周围神经切断后引起的神经元损伤．     

应激对免疫功能的影响

应激(stress)可产生广泛的、复杂的生物学效应,如神经内分泌系统功能的改变、心血、管反应,以及心理和行为方面的变化等。长期在应激状态下生活可导致机体抗病能力下降,从而产生多种疾病,这可能是机体免疫功能下降的一种反映。近年来已有许多学者报道应激可通过神经内分泌系统的作用影响机体的免疫功能。一、应激与疾病的关系应激对于多种疾病的发病、演变以至结局都有密切的关系,这是由于应激可使机体产生复杂的生理和心理反应。关于机体在应激过程中所表现出的各种反应机制,众说不一,早期     

Corticofugal regulation of auditory sensitivity in the bat inferior colliculus

Under free-field stimulation conditions, corticofugal regulation of auditory sensitivity of neurons in the central nucleus of the inferior colliculus of the big brown bat, Eptesicus fuscus, was studied by blocking activities of auditory cortical neurons with Lidocaine or by electrical stimulation in auditory cortical neuron recording sites. The corticocollicular pathway regulated the number of impulses, the auditory spatial response areas and the frequency-tuning curves of inferior colliculus neurons through facilitation or inhibition. Corticofugal regulation was most effective at low sound intensity and was dependent upon the time interval between acoustic and electrical stimuli. At optimal interstimulus intervals, inferior colliculus neurons had the smallest number of impulses and the longest response latency during corticofugal inhibition. The opposite effects were observed during corticofugal facilitation. Corticofugal inhibitory latency was longer than corticofugal facilitatory latency. Iontophoretic application of γ-aminobutyric acid and bicuculline to inferior colliculus recording sites produced effects similar to what were observed during corticofugal inhibition and facilitation. We suggest that corticofugal regulation of central auditory sensitivity can provide an animal with a mechanism to regulate acoustic signal processing in the ascending auditory pathway. Accepted: 15 July 1998     

Cloning and characterization of full-length human ribosomal protein L15 cDNA which was overexpressed in esophageal cancer

The aim of this investigation was trying to identify the genes differentially expressed in esophageal cancer. By combining suppression subtractive hybridization (SSH) with reverse Northern high density blots, a gene named EC45 was obtained, which dramatically overexpressed in 70% esophageal cancer (18/26). EC45 was mapped to 3p12-3p11.2 by radiation hybrid mapping (RH mapping). The putative full length EC45 cDNA (1987 bp) was identified by cDNA libraries screening of esophageal cancer. EC45 encoded 204 amino acids, and it shared a 100% similarity with ribosomal protein L15 (635 bp, mRNA) in ORF, but no similarity in 5' UTR or 3' UTR. Northern blot panel of multiple adult human normal tissues showed EC45 distributed in almost normal tissues tested. All these data suggested that EC45, encoding ribosomal protein L15 and overexpressing in esophageal cancer might play a possible role in carcinogenesis of esophagus.     

Paradoxical effect on atherosclerosis of hormone-sensitive lipase overexpression in macrophages

Foam cells formed from receptor-mediated uptake of lipoprotein cholesterol by macrophages in the arterial intima are critical in the initiation, progression, and stability of atherosclerotic lesions. Macrophages accumulate cholesterol when conditions favor esterification by acyl-CoA:cholesterol acyltransferase (ACAT) over cholesteryl-ester hydrolysis by a neutral cholesteryl-ester hydrolase, such as hormone-sensitive lipase (HSL), and subsequent cholesterol efflux mediated by extracellular acceptors. We recently made stable transfectants of a murine macrophage cell line, RAW 264.7, that overexpressed a rat HSL cDNA and had a 5-fold higher rate of cholesteryl-ester hydrolysis than control cells. The current study examined the effect of macrophage-specific HSL overexpression on susceptibility to diet-induced atherosclerosis in mice. A transgenic line overexpressing the rat HSL cDNA regulated with a macrophage-specific scavenger receptor promoter-enhancer was established by breeding with C57BL/6J mice. Transgenic peritoneal macrophages exhibited macrophage-specific 7-fold overexpression of HSL cholesterol esterase activity. Total plasma cholesterol levels in transgenic mice fed a chow diet were modestly elevated 16% compared to control littermates. After 14 weeks on a high-fat, high-cholesterol diet, total cholesterol increased 3-fold, with no difference between transgenics and controls. However, HSL overexpression resulted in thicker aortic fatty lesions that were 2.5-times larger in transgenic mice. HSL expression in the aortic lesions was shown by immunocytochemistry. Atherosclerosis was more advanced in transgenic mice exhibiting raised lesions involving the aortic wall, along with lipid accumulation in coronary arteries occurring only in transgenics. Thus, increasing cholesteryl-ester hydrolysis, without concomitantly decreasing ACAT activity or increasing cholesterol efflux, is not sufficient to protect against atherosclerosis. hormone-sensitive lipase overexpression in macrophages.     

Expression of simple epithelial type cytokeratins in stratified epithelia as detected by immunolocalization and hybridization in situ

Multi-layered ("stratified") epithelia differ from one-layered ("simple") polar epithelia by various architectural and functional properties as well as by their cytoskeletal complements, notably a set of cytokeratins characteristic of stratified tissue. The simple epithelial cytokeratins 8 and 18 have so far not been detected in any stratified epithelium. Using specific monoclonal antibodies we have noted, in several but not all samples of stratified epithelia, including esophagus, tongue, exocervix, and vagina, positive immunocytochemical reactions for cytokeratins 8, 18, and 19 which in some regions were selective for the basal cell layer(s) but extended into suprabasal layers in others. In situ hybridization with different probes (riboprobes, synthetic oligonucleotides) for mRNAs of cytokeratin 8 on esophageal epithelium has shown, in extended regions, relatively strong reactivity for cytokeratin 8 mRNA in the basal cell layer. In contrast, probes to cytokeratin 18 have shown much weaker hybridization which, however, was rather evenly spread over basal and suprabasal strata. These results, which emphasize the importance of in situ hybridization in studies of gene expression in complex tissues, show that the genes encoding simple epithelial cytokeratins can be expressed in stratified epithelia. This suggests that continual expression of genes coding for simple epithelial cytokeratins is compatible with the formation of squamous stratified tissues and can occur, at least in basal cell layers, simultaneously with the synthesis of certain stratification-related cytokeratins. We also emphasize differences of expression and immunoreactivity of these cytokeratins between different samples and in different regions of the same stratified epithelium and discuss the results in relation to changes of cytokeratin expression during fetal development of stratified epithelia, in response to environmental factors and during the formation of squamous cell carcinomas.