Protective effects of green tea polyphenols on human HepG2 cells against oxidative damage of fenofibrate

The aim of this work was to investigate the protective effects of green tea polyphenols on the cytotoxic effects of hypolipidemic agent fenofibrate (FF), a peroxisome proliferator (PP), in human HepG2 cells. The results showed that high concentrations of FF induced human HepG2 cell death through a mechanism involving an increase of reactive oxygen species (ROS) and intracellular reduced glutathione (GSH) depletion. These effects were partially prevented by antioxidant green tea polyphenols. The elevated expression of PP-activated receptors alpha (PPARalpha) in HepG2 cells induced by FF was also decreased by treatment with green tea polyphenols. In conclusion, this result demonstrates that oxidative stress and PPARalpha are involved in FF cytotoxicity and green tea polyphenols have a protective effect against FF-induced cellular injury. It may be beneficial for the hyperlipidemic patients who were administered the hypolipidemic drug fenofibrate to drink tea or use green tea polyphenols synchronously during their treatment.     

Detection of mitochondrial DNA deletion by a modified PCR method in a 60Co radiation-exposed patient

A new PCR based method was developed to detect deleted mitochondrial DNA (mtDNA). Peripheral blood cell DNA was obtained from a victim who was accidently exposed to a 60Co radiation source in 1990. Using the DNA as template, first PCR was performed to generate multiple products including true deletions and artifacts. The full length product was recovered and used as template of secondary PCR. The suspicious deletion product of mtDNA could be confirmed only if it was yielded by first PCR. Using either original primers or their nested primers, the suspicious deletion product was amplified and authenticated as a true deletion product. The template was recovered and determined to be a deletion by sequencing directly. The results show that a new mtDNA deletion, which spans 889 bp from nt 11688 to nt 12576, was detected in the peripheral blood cells of the victim. It indicates that this new PCR-based method was more efficient at detecting small populations of mtDNA deletion than other routine methods. MtDNA deletion was found in the victim, suggesting the relationship between the deletion and phenotypes of the disease.     

Analysis of nucleolar pre-rRNA processing sites in pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>)

The location of rRNA processing was analyzed by usingin situ hybridization with ITS1 probe and immunolabeling of anti-fibrillarin mAb in pea (Pisum sativum) root pole cells. The results showed that rRNA processing sites were in dense fibrillar components (DFCs) and granular components (GCs), but not in fibrillar centers (FCs). Low doses of actinomycin D (AMD) treatment can selectively suppress pre-rRNA synthesis but cannot disturb the processing of preformed pre-rRNAs. With AMD treatment prolonged, the density of labeled signals gradually decreased, indicating the preformed pre-rRNAs were gradually processed.     

肾血管性高血压大鼠发病过程中心血管AT1-受体自身抗体的变化

实验观察了肾血管性高血压（RVH）大鼠血浆中抗AT1－受体自身抗体在发病过程中的作用及其变化规律。采用两肾一夹Goldblatt RVH模型,以合成的大鼠AT1－受体细胞外第二环165－191位氨基酸序列作为特慢性抗原,用SA－ELISA法检测大鼠血清中抗AT1-受体自身抗体。结果表明,RVH模型组术后2周时大鼠血清中抗AT1－受体自身抗体的阳性率和平均滴度与术前相比明显增高,较高的阳性率和平均滴度持续几周后逐渐下降,12周时下降到正常水平。结果提示,自身免疫机制参与了高血压的形成,抗AT1－受体自身抗体可能与心肌肥厚有关。     

Developmental changes in functional expression and beta-adrenergic regulation of I(f) in the heart of mouse embryo

The hyperpolarization-activated current (I(f)) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and beta-adrenergic regulation of I(f) in embryonic mouse heart. The expression of I(f) is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells. Beta-adrenergic agonist isoproterenol (ISO) stimulates I(f) in LDS but not in EDS cardiomyocytes, indicating that the beta-adrenergic regulation of I(f) is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of I(f) in EDS cells, indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore, the results demonstrate that I(f) is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells.     

Efficient isolation of total RNA from antibiotic-producing bacterium Amycolatopsis mediterranei

RNA extraction from antibiotic-producing actinomycetes can be a difficult and time-consuming process due to their special peptidoglycans cell wall composition and the short life of RNA. Hence, the rapidity of cellular lysis and complete inhibition of RNase are of particular importance for isolating intact RNA of high quality. The genus of Amycolatopsis mediterranei produces many clinically important antibiotics, such as rifamycin and vancomycin; however, the available methods for bacterial RNA isolation did not work very well with this genus. In this report, we described a new method for RNA isolation using the combination of LiCl, urea and guanidinium thiocyanate to disrupt the cell wall of Amycolatopsis. Compared with earlier published RNA isolation methods, the method gave higher yields of pure and intact RNA. About 1 microg total RNA free of DNA contamination can be obtained from 1 mg wet weight of A. mediterranei. The integrity of the RNA was demonstrated by formaldehyde agarose gel electrophoresis and Northern blot analyses.     

Structural design and biomechanics of friction-based releasable attachment devices in insects

Design of attachment devices in insects varies enormously inrelation to different functional loads. Many systems, locatedon different parts of the body, involve surfaces with particularfrictional properties. Such systems evolved to attach partsof the body to each other, or to attach an insect to the substratumby providing fast and reversible attachment/detachment. Amongthese systems, there are some that deal with predefined surfaces,and others, in which one surface remains unpredictable. Thefirst type of system occurs, for example, in wing-locking devicesand head-arresting systems and is called probabilistic fasteners.The second type is mainly represented by insect attachment padsof two alternative designs: hairy and smooth. The relationshipbetween surface patterns and/or mechanical properties of materialsof contact pairs results in two main working principles of thefrictional devices: mechanical interlocking, or maximizationof the contact area. We give an overview of the functional designof two main groups of friction-based attachment devices in insects:probabilistic fasteners and attachment pads.     

膜表面质子可能是ATP合成的主要驱动力

利用细胞压破碎仪破碎鼠肝线粒体,得到了具有良好生物活性的ＳＭＰ,其呼吸控制率为１．４。分别采用荧光探针ｏｘｏｎｏｌＶＩ和ａｃｒｉｄｉｎｅｏｒａｎｇｅ,利用荧光淬灭法测定了丙二酸滴定过程中,ＳＭＰΔΨ和ΔｐＨ的变化趋势,结果表明：当丙二酸浓度达到０．７５ｍｍｏｌ／Ｌ时,ΔΨ的建立完全被抑制,而ΔｐＨ仍然保持了８３．９％。当丙二酸浓度达到１．００ｍｍｏｌ／Ｌ时,ΔｐＨ的建立才完全被抑制。ＳＭＰＡＴＰ合成活性的测定显示,当ΔΨ的建立被完全抑制,而ΔｐＨ仍然存在时,仍有部分ＡＴＰ合成活性（３４．１％）。上述现象为膜表面高能质子是ＡＴＰ合成的主要驱动力的观点提供了又一佐证。此外,当丙二酸浓度从０ｍｍｏｌ／Ｌ增加到０．７５ｍｍｏｌ／Ｌ时,尽管ΔΨ与ΔｐＨ的变化不很大,但ＳＭＰＡＴＰ合成活性却出现明显降低,与氧化呼吸链活性的变化类似,二者呈对数关系,也表明ＡＴＰ合成很可能与ΔμＨ＋并不直接相关,而与膜表面质子流量呈更为紧密的关系     

Reorganization and condensation of chromatin in mitotic prophase nuclei of Allium cepa

This paper studies the process and features of chromosome construction in mitotic prophase cells of Allium cepa. The results showed that a prominent reorganization of chromatin occurred during G₂-early prophase. The 250–400 nm thick compact chromatin threads in G₂ nuclei began to disorganize into about 30, 100 and 220 nm chromatin fibres which constituted the loosely organized chromosome outlines in early prophase before chromosome condensation. In middle prophase, chromosome condensation was characterized by the formation of many condensed regions (aggregates of chromatin), which increased in size (1–1.5 m) when prophase proceeded. Meanwhile, the chromatin threads that constituted and connected the condensed regions became increasingly thicker (120–250 nm). In late prophase adjacent condensed regions fused to form cylinder-shaped chromosomes. Based on these observations, we come to the conclusion that the construction of prophase chromosomes is a two-step process, that is, the reorganization and condensation of chromatin. In addition, we report the study of silver-stained, DNA- and histone-depleted prophase chromosomes, describe morphological features of the non-histone protein (NHP) residue in early, middle and late prophase chromosomes, and discuss the roles of NHPs in chromosome construction.     

Recent structural variations in the Medicago chloroplast genomes and their horizontal transfer into nuclear chromosomes

Medicago is a genus of legumes (Fabaceae) that resemble common clovers with pinnately trifoliate leaves and spirally coiled seed pods, and Medicago sativa is a famous forage crop throughout the world. In this study, we systematically assembled the complete plastid genomes of 18 Medicago species, representing 35 Medicago accessions, whose genome size ranged from ~119 to 125 kb, and identified one novel inverted repeat (IR) in two accessions of Medicago soleirolii (PI537242 and PI537243), albeit of no IRs in the most accessions. We built a phylogenetic tree based on common protein-coding sequences of 55 Medicago accessions in 38 species, which were placed into five clades with a divergence since 9.37 million years ago. Global alignment revealed independent genome evolution events, including eight inversions in nine species and four intron losses (ILs) in 10 species, among which four inversions and two ILs have not been reported previously. Within 109–111 unique genes, ndhA, rpl2, and ycf3 were under positive selection in 54 Medicago accessions. Finally, by aligning chloroplast genes against the nuclear genome assembly of M. sativa cultivar “Zhongmu No.1”, we found that a large number of chloroplast gene fragments were horizontally transferred to nuclear chromosomes in alfalfa, especially on the chr3:47518422–48722257 coordinates of chromosome 3. Our comprehensive exploration of Medicago chloroplast genomes provided insights for the understanding of Medicago diversity and their genomic evolution events.