In vivo inhibition of cholesterol uptake in rabbit aortas by 7-ketocholesterol.

The iv injection of 7-ketocholesterol into rabbits, made soluble by combining with bile salts, inhibited cholesterol uptake by the aorta. However, the inhibition was not as marked or as uniform as previously demonstrated in in vitro experiments. This difference may have been the result of lower plasma concentrations of 7-ketocholesterol in the injected animals. Gastric feeding of 7-ketocholesterol failed to inhibit aortic cholesterol uptake, probably because of inadequate plasma concentrations of the inhibitory steroid. The results suggest that the mechanism of 7-ketocholesterol on aortic cholesterol uptake is through competitive inhibition.     

Mechanisms of chromatin-based epigenetic inheritance

Multi-cellular organisms such as humans contain hundreds of cell types that share the same genetic information(DNA sequences), and yet have different cellular traits and functions. While how genetic information is passed through generations has been extensively characterized, it remains largely obscure how epigenetic information encoded by chromatin regulates the passage of certain traits, gene expression states and cell identity during mitotic cell divisions, and even through meiosis. In this r...     

Cytoplasmic domain and enzymatic activity of ACE2 are not required for PI4KB dependent endocytosis entry of SARS-CoV-2 into host cells

The recent COVID-19 pandemic poses a global health emergency. Cellular entry of the causative agent SARS-CoV-2 is mediated by its spike protein interacting with cellular receptor-human angiotensin converting enzyme 2 (ACE2). Here, by using lentivirus based pseudotypes bearing spike protein, we demonstrated that entry of SARS-CoV-2 into host cells was dependent on clathrin-mediated endocytosis, and phosphoinositides played essential roles during this process. In addition, we showed that the intracellular domain and the catalytic activity of ACE2 were not required for efficient virus entry. Finally, we showed that the current predominant Delta variant, although with high infectivity and high syncytium formation, also entered cells through clathrin-mediated endocytosis. These results provide new insights into SARS-CoV-2 cellular entry and present proof of principle that targeting viral entry could be an effective way to treat different variant infections.     

供氮水平对落叶松幼苗光合作用的影响

为探讨落叶松光合作用对外界供氮环境变化的响应规律,采用砂培方法在温室内设置了4种供氮浓度(1、4、8mmol/L和16mmol/L),对生长在不同供氮水平下落叶松(Larixgmelinii)1年生幼苗的气体交换参数、叶绿素荧光参数以及一些生化指标进行了测定。结果显示,随供氮水平的提高,落叶松幼苗针叶氮含量、叶绿素含量、类胡罗卜素含量、可溶性蛋白(TSP)含量和光饱和净光合速率(Pmax)均显著增加,同时伴随着叶磷含量和胞间与外界CO2浓度之比(Ci/Ca)的降低。然而,当供氮水平超过8mmol/L增至16mmol/L时,TSP含量及Pmax不再增加,反而略有下降。供氮不足显著降低了幼苗针叶光系统最大光能转换效率(Fv/Fm)、光系统量子效率(ΦPS)和光化学猝灭系数(qP),却增加了非光化学猝灭系数(NPQ)。而增加供氮可使Fv/Fm和ΦPS回升,同时qP升高,NPQ下降,但当供氮水平超过8mmol/L后,各叶绿素荧光参数变化幅度较小。结果表明,增加供氮可显著提高落叶松幼苗的光合能力,增加光系统天线色素捕获的光能用于光化学电子传递的份额,减缓光抑制。然而,16mmol/L已经超过落叶松幼苗最适的供氮水平,过量供氮引起的负面效应可能主要与过低的叶磷含量导致的营养失衡有关。     

飞机草挥发油对真菌和昆虫的生物活性及其化学成分研究

研究结果表明 :飞机草挥发油在中等浓度 (80 0mg·l-1)时 ,对水稻稻瘟病菌 (Pryiculariagrisea)的抑制作用最强 ,对长春花疫病菌 (Phytophthoranicotianae)的抑制作用次之 ,对香蕉枯萎病菌(Fusariumoxysporum)的抑制作用最弱 ,其抑菌率分别为 6 1.4 0 %、2 9.2 7%和 14 .4 4 %。用 10～ 2 0 μl·株 -1的飞机草挥发油 ,对小菜蛾 (Plutellaxylostella)和黄曲条跳甲 (Phyllotretastriolata)有显著的驱避产卵作用。用GC/MS详细分析了飞机草挥发油的化学成分 ,共鉴定了 33个化合物。主要成分是萜类化合物 ,如反式 石竹烯 (16 5 8% )、δ 杜松烯 (15 .85 % )、α 可巴烯 (11.5 8% )、氧化石竹烯 (9.6 3% )、大根香叶烯 (4.96 % )和α 律草烯 (4.32 % )。     

蝙蝠携带病毒的研究进展

蝙蝠物种丰富,分布广泛,有很强的飞行能力,其中一些蝙蝠种类还有迁飞的习性,与人类接触密切.迄今为止,已在蝙蝠体内分离到80多种病毒,其中一些是多种重大人兽共患疾病的传染源,给人类公共健康和蝙蝠生物保护带来威胁.近年来,一些新病毒病的暴发,老病毒病的重返都与蝙蝠有关,如1994年澳大利亚爆发的亨德拉病毒(Hendra virus)[1,2],1997年澳大利亚爆发的梅南高病毒(Menangle virus)[3],1998年马来西亚爆发的尼巴病毒(Nipah virus)[4],以及Tioman病毒(Tioman virus)[5]等;而人类在防止蝙蝠传播病毒的同时,很可能由于采取的方法不当而对蝙蝠物种的保护构成潜在的威胁.     

玉米根细胞中类整合素蛋白与α-微管蛋白的共定位及其可能的相互作用

采用间接免疫荧光标记法对玉米根细胞中的类整合素蛋白和细胞骨架主要组分之一的α-微管蛋白进行了荧光定位。结果表明：类整合素蛋白主要分布在质膜上。与对照相比,用与类整合素蛋白特异结合的5肽GRGDS处理后,质膜上类整合素的分布更为均匀,微管的排列密度降低,而用不与类整合素蛋白特异结合的GRGDS类似物SDGRG处理则对类整合素蛋白分布和微管蛋白的排列均无明显影响。微管蛋白解聚剂或稳定剂处理改变类整合素在质膜上的分布。这些结果表明类整合素蛋白与微管蛋白间有复杂的相互作用。     

Regulation of the L-Type Ca2+ Channel Current in Rat Pinealocytes

Abstract : In the present study, the role of phosphoprotein phosphatase in the regulation of L-type Ca²⁺ channel currents in rat pinealocytes was investigated using the whole-cell version of the patch-clamp technique. The effects of three phosphatase inhibitors, calyculin A, tautomycin, and okadaic acid, were compared. Although all three inhibitors were effective in inhibiting the L-type Ca²⁺ channel current, calyculin A was more potent than either tautomycin or okadaic acid, suggesting the involvement of phosphoprotein phosphatase-1. To determine the kinase involved in the regulation of these channels, cells were pretreated with H7 (a nonspecific kinase inhibitor), H89 (a specific inhibitor of cyclic AMP-dependent kinase), KT5823 (a specific inhibitor of cyclic GMP-dependent kinase), or calphostin C (a specific inhibitor of protein kinase C). Pretreatment with either H7 or calphostin C decreased the inhibitory effect of calyculin A on the L-type Ca²⁺ channel current. In contrast, pretreatment with H89 or KT5823 had no effect on the inhibition caused by calyculin A. Based on these observations, we conclude that basal phosphatase activity, probably phosphoprotein phosphatase-1, plays an important role in the regulation of L-type Ca²⁺ channel currents in rat pinealocytes by counteracting protein kinase C-mediated phosphorylation.     

地方医科大学实验动物管理工作水平评价指标体系的构建

目的构建地方医科大学实验动物管理工作水平评价指标体系,为高校实验动物管理工作的评价提供参考。方法根据研究主题确定咨询专家人选37人,采用Delphi法进行问卷调查和统计分析。结果两轮咨询问卷回收率分别为70．27％和76．92％。权威系数为0．855;第二轮指标体系的协调系数为0．486。结论本次研究构成的地方医科大学实验动物管理工作水平评价指标体系是可靠的。     

菲菊头蝠回声定位信号特征及下丘神经元频率调谐

研究了菲菊头蝠自由飞行状态下的回声定位信号和下丘神经元的声反应特性。菲菊头蝠在自由飞行时发射的CF/FM型回声定位叫声含2-3个谐波,主频为105.3±1.7kHz,时程为39.5±9.6ms,脉冲间隔为73.9±16.0ms。在所记录到的159个下丘神经元中,E型(Echolocation)神经元为32.7%(52/159),其中CF1型(Constantfrequency)占11.3%(18/159),FM1型(Frequencymodulated)占20.1%(32/159),FM2型占1.3%(2/159);NE型(Nonecholocation)神经元的比例为67.3%(107/159)。这些神经元的最佳频率(Bestfrequency,BF)与记录深度之间存在线性关系(r=0.9471,P<0.01)。E型神经元的深度范围为349-1855(1027.5±351.6)μm,阈值范围为6-74(43.1±14.5)dBSPL,潜伏期范围为10.0-26.0(14.6±3.8)ms。NE型神经元的分别为93.0-1745.0(733.3±290.3)μm、2-70(36.5±23.8)dBSPL、5.0-23.0(13.5±3.7)ms。记录到的53个IC神经元的调谐曲线(Frequencytuningcurve,FTC)均为开放型,51个为单峰型,2个为双峰型。单峰型神经元中大部分为狭窄型(Q10dB>5),占70.6%(36/51),E型神经元全部为狭窄型,Q10dB为10.4±7.1(5.5-31.6),其中CF1型为18.3±11.2(5.5-31.6),FM1型为8.7±4.7(5.5-24.3),FM2型为6.9±0.3(6.7-7.1);NE型神经元既有宽阔型也有狭窄型,Q10dB为6.6±5.1(1.6-25.6)。两个双峰型FTC主、副峰分别偏向高、低频区,高频边对应的是E型神经元。