摄食水平对中华鳖稚鳖生长、氮排泄和能量收支的影响

在 30℃水温下进行摄食 -生长实验 (实验周期为 5 6d) ,设饥饿、1%、2 %、4 %和饱食 5个摄食水平 ,研究了中华鳖稚鳖 (39 5 4— 4 4 2 2g)的生长和能量收支。结果表明 ,中华鳖稚鳖的特定生长率随摄食水平的增加 ,其湿重、干物质、蛋白质和能量的特定生长率均呈二次曲线增加 ,其中干物质的特定生长率 (SGRdr)与摄食率 (Rl)的关系式为 :SGRdr=- 1 8799 1 0 795Rl- 0 0 832Rl2 (r=0 90 6 ,n =2 5 ,P <0 0 1) ;除干物质转化效率外 ,湿重、蛋白质和能量的转化效率在 2 %组均达到最大 ,分别为 36 31%、2 1 4 7%和 2 8 10 % ;除能量转化效率外 ,4 %组湿重、干物质和蛋白质的转化效率与最大值均无显著差异 ;摄食水平对中华鳖稚鳖总氮排泄率、氨氮排泄率、尿素氮排泄率以及氨氮占总氮排泄率的比例均有显著影响 (P <0 0 1) ,除氨氮占总氮比例外其他指标均随摄食水平的增加而增加 ,氨氮比例在饥饿组最高为 5 5 83% ,由饥饿到饱食其变化范围是 4 4 5 0 %— 5 5 83% ;总氮排泄率、氨态氮排泄率和尿素氮排泄率的变动范围分别是 19 81%— 6 5 87%、9 4 4 %— 36 31%和 8 2 4 %— 2 9 5 6 % ,回归分析表明 ,幼鳖的总氮排泄率 (μmol/g·d) (G N)、氨氮排泄率 (μmol/g·d) (NH3 N)及尿素氮排泄率 (μmol/g·     

膨化饲料动植物蛋白比对中华鳖稚鳖生长特性的影响

本实验设计了营养相近、不同动植物蛋白比的四种膨化饲料（饲料1,1.5∶1;饲料2,3∶1;饲料3,5∶1;饲料4,7∶1）,研究了动植物蛋白比对中华鳖稚鳖摄食、生长、饲料利用能力和营养组成的影响。饲料1组稚鳖的摄食率显著高于饲料2—4组。饲料1—4组稚鳖的特定生长率没有显著影响。饲料1组稚鳖的干物质和脂类消化率、饲料转化效率、蛋白贮积率和能量贮积率显著低于饲料2—4组。饲料1组稚鳖体脂肪含量显著低于饲料4组。稚鳖的上述指标在饲料2—4组间均无显著差异。结果表明,鳖膨化饲料动植物蛋白比对中华鳖稚鳖生长特性有明显的影响,适宜的动植物蛋白比为3∶1。     

摄食水平和投喂频率对大菱鲆幼鱼生长及生化成分的影响

以大菱鲆幼鱼(7.56±0.03 g)为试验对象,在水温17～19℃下,设计了4个摄食水平梯度(1.0％、1.5％、2.0％和饱食)和3个投喂频率梯度(1、2和3次·d-1),探讨了不同摄食水平和投喂频率对其生长及生化成分的影响.结果表明:随着摄食水平的升高,大菱鲆幼鱼的终末体重、相对增重率和摄食率显著升高(P＜0.05);特定生长率随摄食水平的增加呈线性升高;湿重、干重、蛋白质和能量转化效率出现先升高后降低的趋势;摄食水平对鱼体的体成分和组间表观消化率无显著影响(P＞0.05);不同投喂频率下,终末体重、相对增重率、特定生长率及转化效率呈先升高再降低的趋势,在2次·d-1时取得最大值;投喂频率对鱼体的体成分和组间表观消化率无显著影响(P＞O.05).     

光周期对中华鳖稚鳖摄食、生长和能量转换的影响

在水温２９±１℃,光照强度５００ｌｘ的条件下,研究了不同光周期对中华鳖稚鳖的最大日摄食量、最大日摄食率、特定生长率、同化效率、消化时间和生长效率的影响。结果表明,光周期对中华鳖稚鳖的上述各指标均无显著影响。随体重的增加,中华鳖稚鳖的最大日摄食量逐渐增大,而最大日摄食率则逐渐减少。在人工养殖中华鳖稚鳖过程中,光照周期的选择是次要的     

光照强度对中华鳖稚鳖摄食和生长的影响

在３０００，１０００，３００和１０１ｘ的光照强度下，测定了中华鳖稚鳖的最大日摄食量和特定生长率。结果表明，光照强度对中华鳖稚瞥珠最大日摄食量影响显著，随着光照强度的减弱，中华鳖稚鳖的最大日摄食量逐渐增加，二者之间呈线性负相关。     

温度对中华鳖卵孵化和胚胎发育的影响

在25℃,27．5℃,30℃,32．5℃和35℃条件下,分别研究了中华鳖（Trionyx sinensis)卵的孵化和胚胎的发育。卵黄和卵壳的湿重分别占卵重的85．10％和14．90％,含水量分别为76．63％和21．01％。中华鳖胚胎重随孵化时间呈逻辑斯谛曲线增长,孵化温度越高,胚胎发育速度r越大。25℃－30℃的胚胎发育仅表现为‘S’型生长曲线的前,中段,在孵化后期发育速度未受到明显的抑制,32．5℃和35℃温度条件下,后期发育速度受到了较大的影响。孵出稚鳖湿重和干重均与初始孵重存在极显著的经性相关关系。孵化温度对孵出稚鳖湿重没有显著影响,但对孵出稚鳖干重的影响极显著。随孵化温度的升高,孵出稚鳖干重吾‘U’形变化,在适中温度下,胚胎的生长效率最低。卵黄干重随孵化时间呈指数递减,温度越高,孵黄的利用速度越快。在孵化过程中,卵重,卵干重和卵内水总量都随孵化时间的延长,孵化温度的上升而略有下降。孵化期随温度升高呈双曲线缩短,其相关关系可用方程I＝30．6＋109／（T－22．5）来表示。中华鳖卵的最适孵化温度在32．5℃左右,胚胎孵化后期比早期对温度的需求可能要低一些。     

外源维生素C及冬眠对中华鳖稚鳖生长、维生素C合成和肝脏维生素C含量的影响

本文研究了饲料中维生素C(Vc)对中华鳖稚鳖冬眠前后Vc合成能力及肝脏中Vc含量的影响。将体重为29.41g±5.44g的稚鳖180只,按其饲料中Vc含量(0、500、2500mgVc/kg饲料)分为Vc0、Vc500和Vc2500共3组,每组6个平行,每平行10只鳖。实验开始前称重得各组初始平均体重。25℃±1℃下用实验饲料饲喂4周后,缓慢降温至7℃,人工诱导其进入冬眠,此时为冬眠期开始,每组取6只鳖,称重后快速处死,取其肝脏和肾脏。其余鳖全部称重。冬眠8周末取样,处理同上。用高效液相色谱(HPLC)法测定肝脏Vc含量和肝脏、肾脏古洛糖酸内酯氧化酶(GLO)活力。结果发现中华鳖自身能够合成Vc,且合成部位在肾脏。饲喂4周不同Vc水平的饲料后,各组间特定生长率差异不显著。冬眠8周后,各组体重均有所降低,组间冬眠期间特定生长率无显著性差异。冬眠开始时,稚鳖肝脏Vc蓄积量有随外源Vc浓度升高而递增的趋势,但差异未达到显著性水平;经历冬眠后各组稚鳖肝脏Vc含量降低,Vc500组下降不显著,而Vc0与Vc2500组显著下降;肾脏GLO活力在不同Vc梯度组间及冬眠前后均无显著差异。以上结果表明:中华鳖冬眠过程中要消耗较多的肝脏Vc,外源Vc和冬眠对肾脏Vc合成能力影响不显著。     

南方鲇继饥饿后的恢复生长

1996年1月至4月在27．5℃条件下,对南方鲇幼鱼（初始体重：73．65±9．82g）进行了不同时间的饥饿处理后再供食的恢复生长实验。实验鱼饥饿60d后,鱼体比能值、蛋白质含量及脂肪含量明显下降,灰分含量及含水量明显上升。分别将饥饿处理0（对照）、10、20、30、40、50和60d的南方鲇再恢复喂食,在饱足摄食水平下生长20d。各饥饿处理组的鱼体化学组成及比能值均接近,并恢复到对照生长组水平。饥饿处理50d组的干重及能量生长率,湿重、干重及能量摄食率显著高于对照组的相应值。通过讨论认为：（1）饥饿处理50d的南方鲇在恢复生长过程中产生了显著的补偿效应;（2）该补偿现象主要因摄食水平显著升高所致。     

完全或部分的食物剥夺对中华鳖(Pelodiscus sinensis)幼体补偿生长反应的影响:生长率的时间变化模式与体组成的变化

为了探究中华鳖（Pelodiscus sinensis）幼体的补偿生长能力,我们对中华鳖幼鳖（平均湿重9．56g）进行如下6种处理：饥饿0（对照）、1、2、3、4周,或者食物限制4周,即只投喂体湿重百分之一的食物;然后对各组进行饱食处理直到10周的实验结束为止。结果发现在饱食期的第一周各饥饿处理组的特殊生长率均显著高于对照组（P〈0．05）,但是终体重均没有赶上对照组。当饥饿或食物限制结束时,脂肪含量随着饥饿期的延长而降低,灰分和水分则表现出相反的变化趋势：脂肪含量显著低于对照（P〈0．05）,而灰分和水分则显著高于对照（P〈0．05）。蛋白含量则没有显著变化（P〉0．05）。实验结束时,除了灰分外（P〈0．05）,其他个体组成指标均恢复到对照组的水平。以上结果表明中华鳖幼体在饥饿胁迫下首先利用脂肪作为主要能源以维持生存,以及在该研究条件下完全的食物剥夺可以诱发其部分补偿生长反应．而部分食物剥夺则不能诱发此反应。     

蛋白质限制后恢复投喂对牙鲆幼鱼生长的影响

2004年4月4日~5月22日,在(23.0±0.5)℃条件下研究了牙鲆(平均体重,(8.80±0.18)g)继蛋白质限制后恢复投喂对其生长的影响。整个实验期间对照组(C组)连续48d饱食投喂含能17.29kJ/g,含粗蛋白50.00%的饵料。蛋白质限制阶段(1~18d)处理组T30和T40的饵料蛋白含量分别为27.95%和40.47%,但饵料含能与对照组相同,在恢复投喂阶段(19~48d)各处理组均投喂与对照组相同的饵料。实验结果表明,在蛋白质限制阶段,饵料蛋白质水平下降显著降低了处理组鱼的体重、特定生长率、饵料湿重、干重以及能量转化率(p<0.05),而摄食率、蛋白质效率和饵料蛋白质转化率随饵料蛋白水平降低而显著升高(p<0.05)。恢复投喂结束后,处理组上述各指标均恢复至对照组水平(p>0.05)。此外,除实验结束时T30组鱼体脂肪含量显著低于对照组(p<0.05)外,整个实验期间各处理组的表观消化率及鱼体成分与对照组相比均无显著差异(p>0.05)。实验结果表明,牙鲆幼鱼继蛋白质限制后的恢复投喂阶段出现了完全补偿生长效应。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.