Similarity among nucleotide sequences

In this work we report a simple way to measure the similarity between two nucleotide sequences by using graph theory and information theory. This method reported allows for theoretical comparisons of naturally occurring nucleotide sequences.     

Serum and urine chromium concentrations in elderly diabetics

The serum and urine chromium concentrations of 57 diabetics and 55 normal fasting subjects were determined by atomic absorption spectrometry (AAS). Our results indicate that the chromium concentration ranges of serum and urine for diabetics are 0.22–0.36 and 4.54–5.90 μg/L, respectively, significantly lower than 0.66–0.84 7.80–9.68 μg/L for the normal (P<0.001), which implies that the elderly diabetics probably lack chromium. Further, it was found that the urine chromium level of the female diabetics was substantially higher than that of the male in the same age group (P<0.01), whereas the serum chromium level was almost the same. However, the urine chromium concentration increases with aging, no matter who the diabetics or the controls are. The serum chromium concentrations of the 24 cases patients with 2-h oral glucose tolerance test (OGTT) were significantly lower than that of those with empty stomach, whereas the urine chromium exhibits a contrary tendency. Our data indicate that the chromium lost and excreted from human body increases with aging and is related to the diabetics. Thus, it is recommended to supplement a certain amount of chromium to the elderly diabetics according to their nutritional level.     

Negative phototropism of rice root and its influencing factors

Some characteristics of the rice (Oryza sativa L.) root were found in the experiment of unilaterally irradiating the roots which were planted in water: (i) All the seminal roots, adventitious roots and their branched roots bent away from light, and their curvatures ranged from 25° to 60°. The curvature of adventitious root of the higher node was often larger than that of the lower node, and even larger than that of the seminal root, (ii) The negative phototropic bending of the rice root was mainly due to the larger growth increment of root-tip cells of the irradiated side compared with that of the shaded side, (iii) Root cap was the site of light perception. If root cap was shaded while the root was irradiated the root showed no negative phototropism, and the root lost the characteristic of negative phototropism when root cap was divested. Rice root could resume the characteristic of negative phototropism when the new root cap grew up, if the original cells of root cap were well protected while root cap was divested, (iv) The growth increment and curvature of rice root were both influenced by light intensity. Within the range of 0–100 μmol · m² -s⁻¹, the increasing of light intensity resulted in the decreasing of the growth increment and the increasing of the curvature of rice root, (v) The growth increment and the curvature reached the maximum at 30°C with the temperature treatment of 10–40°C. (vi) Blue-violet light could prominently induce the negative phototropism of rice root, while red light had no such effect. (vii) The auxin (IAA) in the solution, as a very prominent influencing factor, inhibited the growth, the negative phototropism and the gravitropism of rice root when the concentration of IAA increased. The response of negative phototropism of rice root disappeared when the concentration of IAA was above 10 mg · L⁻¹     

A model of salmon louse production in Norway: effects of increasing salmon production and public management measures.

Salmon lice Lepeophtheirus salmonis Kr?yer have caused disease problems in farmed Atlantic salmon Salmo salar L. since the mid-1970s in Norway. High infection intensities and premature return of wild sea trout Salmo trutta L. were first reported in 1992. Later emaciated wild Atlantic salmon smolts carrying large amounts of lice have been observed both in fjords and offshore. The Norwegian Animal Health Authority regulations to control the problem, which came into operation in 1998, included compulsory louse level monitoring in farms and maximum legal numbers of lice per fish. Here, we present a model of salmon louse egg production in Norway and show that the effect of the current public management strategy is critically dependent on the yearly increase in salmon production. This is because the infection pressure is the product of the number of fish in the system, and the number of lice per fish. Due to the much larger number of farmed than wild salmonids, it is highly likely that lice originating from farmed salmon infect wild stock. Estimated tolerance limits for wild salmonids vary widely, and the level of louse egg production in farms which would be needed to decimate wild populations is not known. Two possible thresholds for total lice egg production are investigated: (1) 1986 to 1987 level (i.e. before adverse effects on sea trout were recorded), and (2) a level corresponding to a doubling of the estimated natural infection pressure. The farm lice per fish limits that would have to be observed to keep louse production within the 2 thresholds are calculated for the period 1986 to 2005. A steady decrease in the permitted number of lice per fish may keep the total louse production stable, but the number of salmon required for verification of lice numbers will increase as the prevalence to be verified is decreased. At threshold (2), the model estimated that lice limits should have been 0.05 louse per fish in 1999. This would require 60 fish from each pen to be collected, anaesthetised and examined for a good estimate at a confidence level of 95%. Such sample numbers are likely to be opposed by farmers. The use of national delousing programs to solve the problem is discussed.     

Internalization and transcytosis of pancreatic enzymes by the intestinal mucosa.

As early as the beginning of the twentieth century some data indicated that macromolecules are able to cross the intestinal mucosa to reach the blood. Further evidence was added over the years; however, pathways for this transport still remain to be established. We report here the transfer of two pancreatic enzymes, amylase and lipase, from the intestinal lumen to the blood. Both are present in higher concentrations in the intestinal mucosa and in blood of fed rats. Upon cholinergic stimulation of pancreatic secretion, there was not only an increase in blood enzyme concentrations, but evidence for internalization by duodenal enterocytes was obtained. Following insertion of fluorochrome-tagged amylase and lipase into the duodenal lumen of fasting rats, blood and intestinal tissues were sampled at different time points. Serum activities for both enzymes clearly increased with time. Light microscopy established internalization of both proteins by duodenal enterocytes, and immunogold outlined the pathway taken by both proteins across the enterocytes. From the intestinal lumen, enzymes are channeled through the endosomal compartment to the Golgi apparatus and to the basolateral membrane reaching the interstitial space and blood circulation. Transcytosis through the intestinal mucosa thereby represents an access route for pancreatic enzymes to reach blood circulation.     

Characterization of mutants of human immunodeficiency virus type 1 that have escaped neutralization by a monoclonal antibody to the gp120 V2 loop.

The biologically cloned human immunodeficiency virus type 1 (HIV-1) RF isolate is sensitive to neutralization by the murine monoclonal antibody (MAb) G3-4 to a conformationally sensitive epitope in the V2 loop of HIV-1 gp120. To assess how variation in the V2 amino acid sequence affects neutralization by this MAb, we cultured RF in the presence of G3-4 to select neutralization escape mutants. Three such mutants resistant to G3-4 neutralization were generated from three independent experiments. Solubilized gp120 from each of these escape mutants had a reduced affinity for G3-4 and also for two other V2 MAbs that were able to bind the wild-type RF gp120. PCR sequencing of the entire gp120 of the wild-type RF virus and the escape mutants showed that amino acid substitutions had occurred only at two positions, Y177H and L179P, both in V2. Experimental introduction of the Y177H substitution into the RF V2 loop in the context of the NL4-3 molecular clone re-created the G3-4-resistant phenotype. The L179P mutant was not viable. Thus, our findings confirm that the HIV-1 V2 loop contains the conformationally sensitive neutralization epitope recognized by G3-4 and that a single amino acid substitution within this region can result in escape variants that arise from immune selection pressure.     

向日葵AGO和DCL基因家族的鉴定和表达分析

为了解向日葵(Helianthus annuus)的Argonaute (AGO)和Dicer-like (DCL)的功能,利用拟南芥(Arabidopsis thaliana)的AGO和DCL基因序列在向日葵基因组数据库中进行同源比对,对向日葵AGO和DCL家族成员进行生物信息学分析。结果表明,从向日葵中鉴定到15个Ha AGOs和5个HaDCLs家族成员;这2类基因在染色体上的分布均不均匀。系统发育分析表明,与拟南芥相似,HaAGO家族成员可分为3个分支,HaDCL可分为4个分支;所有的HaAGO都具有保守的N domain、DUF1785、PAZ和PIWI结构域,Ha DCL家族成员都含有PAZ和RIBOc结构域。表达分析表明,Ha DCL3a和Ha DCL3b在茎和花序中高度表达;亚细胞定位表明Ha AGO多定位于细胞核。这表明向日葵中可能存在典型的RNAi干扰机制,并可能参与了协调向日葵的生长发育过程。     

芽孢杆菌DU-106裂解物对2,4-二硝基氟苯诱导的特应性皮炎小鼠的治疗作用

【背景】本团队前期研究发现芽孢杆菌DU-106具有良好的健康益处,但都是基于活菌的研究,对灭活菌的研究尚未开展。【目的】探究芽孢杆菌DU-106裂解物对特应性皮炎的治疗效果及作用机制。【方法】以2,4-二硝基氟苯诱导的特应性皮炎BALB/c小鼠为模型,通过病理学观察、免疫组化等手段研究其治疗效果,并测定NF-κB通路中基因与蛋白表达量,揭示其内在机制。【结果】芽孢杆菌DU-106裂解物有效缓解了特应性皮炎小鼠的病理学特征,减轻了肥大细胞的浸润,降低了免疫球蛋白E、肿瘤坏死因子-α(TNF-α)和干扰素-γ的含量(P<0.05)。芽孢杆菌DU-106裂解物可能是通过抑制NF-κB信号通路中TNF-α、IKKα和NF-κB基因表达水平和蛋白磷酸化而实现抗特应性皮炎效果。【结论】芽孢杆菌DU-106裂解物可作为一种后生元,对特应性皮炎具有积极的治疗作用。