Genome-wide analysis of codon usage bias patterns in an enterotoxigenic <Emphasis Type="Italic">Escherichia coli</Emphasis> F18 strain

Enterogenic Escherichia coli (ETEC) F18 strains are the main pathogenic bacteria causing severe diarrhea in humans and domestic animals. However, the information about synonymous codon usage pattern of ETEC F18 genome remains unclear. We conducted a genome-wide analysis of synonymous codon usage patterns in the ETEC F18 strain SRA: SAMN02471895. After filtering of the complete genome sequence, 4327 coding sequences were analyzed using multivariate statistical methods to calculate synonymous codon usage patterns and to evaluate the influence of various factors in shaping the codon usage. The mean GC content was 51.38%, with a slight preference for G/C-ending codons. Twenty-two codons were determined as ‘‘optimal codons”. ENC plots showed some of the genes were on or close to the expected curve, while only points with low-ENC values were below the curve. PR2 analysis showed that GC and AT were not used proportionally, suggesting major roles for mutational pressure and natural selection in shaping usage. Neutrality plots showed a significant correlation between GC12 and GC3, suggesting that mutational pressure is responsible for nucleotide composition in shaping the strength of codon usage. Translational selection was the main factor shaping the codon usage pattern of ETEC F18 genome, while other factors such as protein length, GRAVY and ARO values also influenced codon usage to some extent. We analyzed the codon usage pattern systematically and identified the factors shaping codon usage bias in the ETEC F18 genome. Such information further elucidates the mechanisms of synonymous codon usage bias and provides the basis of molecular genetic engineering and evolutionary studies.     

Oxazolopyridines and thiazolopyridines as monoamine oxidase B inhibitors for the treatment of Parkinson’s disease

In Parkinson’s disease, the motor impairments are mainly caused by the death of dopaminergic neurons. Among the enzymes which are involved in the biosynthesis and catabolism of dopamine, monoamine oxidase B (MAO-B) has been a therapeutic target of Parkinson’s disease. However, due to the undesirable adverse effects, development of alternative MAO-B inhibitors with greater optimal therapeutic potential towards Parkinson’s disease is urgently required. In this study, we designed and synthesized the oxazolopyridine and thiazolopyridine derivatives, and biologically evaluated their inhibitory activities against MAO-B. Structure–activity relationship study revealed that the piperidino group was the best choice for the R¹ amino substituent to the oxazolopyridine core structure and the activities of the oxazolopyridines with various phenyl rings were between 267.1 and 889.5 nM in IC₅₀ values. Interestingly, by replacement of the core structure from oxazolopyrine to thiazolopyridine, the activities were significantly improved and the compound 1n with the thiazolopyridine core structure showed the most potent activity with the IC₅₀ value of 26.5 nM. Molecular docking study showed that van der Waals interaction in the human MAO-B active site could explain the enhanced inhibitory activities of thiazolopyridine derivatives.     

A Complex Role of Herpes Viruses in the Disease Process of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system (CNS). Neither the antigenic target(s) nor the cell population(s) responsible for CNS tissue destruction in MS have been fully defined. The objective of this study was to simultaneously determine the antigen (Ag)-specificity and phenotype of un-manipulated intrathecal CD4⁺ and CD8⁺ T cells of patients with relapsing-remitting and progressive MS compared to subjects with other inflammatory neurological diseases. We applied a novel Ag-recognition assay based on co-cultures of freshly obtained cerebrospinal fluid T cells and autologous dendritic cells pre-loaded with complex candidate Ag''s. We observed comparably low T cell responses to complex auto-Ag''s including human myelin, brain homogenate, and cell lysates of apoptotically modified oligodendroglial and neuronal cells in all cohorts and both compartments. Conversely, we detected a strong intrathecal enrichment of Epstein-Barr virus- and human herpes virus 6-specific (but not cytomegalovirus-specific) reactivities of the Th1-phenotype throughout all patients. Qualitatively, the intrathecal enrichment of herpes virus reactivities was more pronounced in MS patients. This enrichment was completely reversed by long-term treatment with the IL-2 modulating antibody daclizumab, which strongly inhibits MS disease activity. Finally, we observed a striking discrepancy between diminished intrathecal T cell proliferation and enhanced cytokine production of herpes virus-specific T cells among progressive MS patients, consistent with the phenotype of terminally differentiated cells. The data suggest that intrathecal administration of novel therapeutic agents targeting immune cells outside of the proliferation cycle may be necessary to effectively eliminate intrathecal inflammation in progressive MS.     

Micropropagation of Cymbidium sinense using continuous and temporary airlift bioreactor systems

Airlift bioreactors were programmed for continuous and temporary immersion culture to investigate factors that affect the rhizome proliferation, shoot formation, and plantlet regeneration of Cymbidium sinense. During rhizome proliferation, the continuous immersion bioreactor system was used to explore the effects of activated charcoal (AC) in the culture medium, inoculation density, and air volume on rhizome differentiation and growth. The optimum conditions for obtaining massive health rhizomes were 0.3 g l^?1 AC in the culture medium, 7.5 g l^?1 inoculation density, and 150 ml min^?1 air. In addition, the temporary immersion bioreactor system was used for both shoot formation and plantlet regeneration. Supplementing 4 mg l^?1 6-benzylaminopurine and 0.2 mg l^?1 naphthalene acetic acid (NAA) to the culture medium promoted shoot induction from the rhizome. Cutting the rhizome explants into 1 cm segments was better for massive shoot formation than cutting into 0.25 and 0.5 cm explant segments. NAA promoted plantlet regeneration and the rooting rate (94.7 %), with whole plantlets growing well in culture medium containing 1.0 mg l^?1 NAA. Therefore, applying bioreactors in C. sinense micropropagation is an efficient way for scaling up the production of propagules and whole plantlets for the industrial production of high-quality seedlings.     

Low-power inductive RF plasma sources for technological applications

The objective of the present paper is to develop an analytic theory of cylindrical low-power RF plasma sources operating at an industrial frequency (f=13.56 MHz, ω=8.52×10⁷ s^?1). Inductive surface exciters of electromagnetic fields (exciting antennas) are considered that are positioned either at the side surface of the cylinder or at one of its end surfaces. In the latter case, the plasma flows out of the source through the opposite end surface of the cylinder. A study is made of elongated systems in which the length L of the cylinder exceeds its diameter 2R and of planar disk-shaped systems with L<2R. Simple analytic expressions are derived for electromagnetic fields excited by the antenna in the source plasma. The equivalent plasma resistance and the equivalent RF power deposited in the plasma are calculated for systems with prescribed parameters, i.e., in a non-self-consistent model. Up to now, such sources have been investigated mainly through the numerical solution of the complicated general electrodynamic equations. In the Introduction, the problem is formulated in general terms and the geometry of the sources, as well as the characteristic parameters of the source plasma, is discussed. In Section 2, plasma sources operating without an external magnetic field are investigated. In Section 3, helicon plasma sources in a sufficiently strong external magnetic field are considered. Analytic predictions are compared with the results from solving the problem numerically without using the helicon approximation. Section 4 gives a brief discussion of an electron cyclotron resonance-based RF plasma source. In the Conclusion, the main results of the paper are summarized and the technological efficiency of the sources under consideration is estimated at a qualitative level.     

利用聚鸟氨酸提高大豆原生质体外源基因的转化效率(简报)

有不少利用PEG法把外源基因导入到大豆原生质体,获得了转基因植株的报道,目前PEG的转化效率有所提高,但还是不能满足转化的需要,如何提高原生质体的转化效率是基因转化工作中的关键问题。本实验为了解决这个难题,以大豆幼子叶原生质体为材料,利用聚鸟氨酸(PLO:Poly-L-Ornithine,MW:114900,SIGMA)对Bt基因的转化进行了探讨。     

卤虫（Artemia salina）孵化腺细胞分化时相的免疫细胞化学研究（简报）

动物孵化酶(hatching enzyme HE)是早期胚胎在特定发育阶段由孵化腺细胞产生和分泌的,在动物早期胚胎孵化中具有关键性作用^[4]。孵化腺细胞(hatching gland cell,HGC)一般为单细胞腺体,是从胚胎发育到特定阶段(孵化前)出现、至胚胎孵出后的特定时期消失的一时性细胞(transient type of