外源核苷酸对动物肠道发育和免疫功能的影响

核苷酸（NT）是组成细胞的主要成分，是DNA和RNA的基本组成单位，在细胞结构、代谢、能量和功能调节等方面起重要作用。过去人们认为，动物机体能由内源从头合成各种核苷酸，而且又没有特异性的缺乏症．所以一直将其视为非必需营养素。但近年来对大鼠、小鼠的研究表明。机体许多生长代谢旺盛的组织（小肠、大肠、淋巴）和细胞（红细胞、白细胞、骨髓细胞）从头合成的核苷酸能力有限。尤其当动物处在受到免疫应激、肝损伤、饥饿及快速生长的情况下，内源合成的核苷酸不能满足机体的需要．需要补充外源核苷酸。研究发现，日粮核苷酸对维持免疫系统的正常功能、胃肠道的生长发育有重要作用。     

立用核苷酸对抗断奶仔猪应激

核苷酸对机体免疫系统、小肠生长发育、脂肪代谢及肝脏功能有一定效果（表1）。因为有机体能自身合成核苷酸,一般认为核苷酸不是必需营养素。动物在应激、快速生长或营养不足时,体内合成的核苷酸就不能满足其自身的需要,所以核苷酸被称为“半”或“条件性”必需营养素。     

外源核苷酸对动物的营养生理作用及应用

<正>核苷酸是生物体的一种重要组成成分,细胞增殖及其它一些生理过程都需要一定量的核苷酸,特别是在一些快速分裂的组织中,如淋巴组织和肠组织,它们都需要核苷酸以合成核酸,而复制一个DNA至少需要109个核苷酸分子(Roux,1973)[1]。由于动物体内能合成核苷酸,长期以来核苷酸被认为是一种非必需营养素。但内源核苷酸的合成是一个非常耗能的过程,且在某些组织如肠粘膜、骨髓、造血细胞及淋巴细胞中合成量有限。近期研究表明,对于动物快速生长时期或动物受到免疫应激、     

鱼类的核苷酸营养研究进展

健康动物的内源核苷酸在肝脏内可通过合成途径和补救途径两种途径合成,外源核苷酸大部分在肠细胞中很快被氧化,仅有少于5%的核苷酸能被组织利用。然而在特殊生理条件,如幼龄期、肝功能障碍时,内源核苷酸相对合成不足,需要来源于日粮的外源核苷酸加以补充。鱼类也能够从头合成核     

核苷酸在动物饲料中的应用

随着动物营养研究的深入,核苷酸在饲料中的功能和作用机理也逐步被人们重新认识。核苷酸作为细胞合成的必需物质,具有保护肠道黏膜、增强机体免疫力等生理功能。在正常情况下,成年动物可以通过内源性核苷酸来满足自身的需要,不需特意的补充。但近年来的一些研究表明,当机体迅速生长或受到免疫挑战时,内源性核苷酸就不能满足动物组织和细胞代谢的需要,此时必须补充外源性核苷酸,以保证组织的生长和正常生理功能。本文综述了在动物应激、快速生长和预防疾病等情况下,动物体内核苷酸的需求情况及其重要的生理功能,由此阐述了核苷酸作为新型饲料添加剂在生产中的作用。     

外源核苷酸对动物免疫功能及肠道发育的影响

人和动物能够以体内氨基酸为原料从头(内源)合成核苷苷酸(NT)，但某些组织、器官在特殊状况下，内源合成的核苷酸不能满足机体的需要，补充外源核苷酸可以适应机体的需要，保证机体正常功能的发挥。日粮来源的核苷酸对动物免疫系统、脂类代谢、肠道的微生物环境、肠道的形态、结构、功能有重要作用。本文介绍了日粮核苷酸在机体内消化吸收、代谢以及合成的主要途径，并对其免疫功能及对肠道发育的影响进行了综述。     

日粮核苷酸对动物免疫功能的影响研究进展

核苷酸（嘌呤和嘧啶）是组成DNA和RNA单体，在体内具有重要的生理生化作用。人和动物能从头合成核苷酸。在机体迅速生长、或动物受到免疫挑战时，一些器官、组织内源合成的不能满足机体的需要。补充日粮核苷酸对于动物免疫细胞、器官的发育及维持免疫系统正常功能有积极作用。     

尿中嘌呤衍生物是估测瘤胃微生物合成量的一种指示物

确定瘤胃微生物细胞净合成量对反刍动物营养十分重要。这是因为微生物蛋白质量是反刍动物宿主对蛋白质需要的重要来源。用标记物和在动物小肠安装瘘管的方法来测定瘤胃合成的净微生物细胞量或微生物细胞进入下一级消化道的数量不仅费时，且精度不高。Ｌｉｎｇ等（１９７８）研究了许多用以区分进入绵羊小肠食糜中微生物蛋白质的微生物标记物。食糜中ＲＮＡ与总氮比率是一种测定进入十二指肠食糜氮中微生物氮含量的适宜标记物。然而Ｂｒｏｄｅｒｉｃｋ等（１９９２）认为常用的微生物标记物（嘌呤、ＲＮＡ、ＤＮＡ、二氨基庚二酸及同位素标记…     

不同海拔地区牦牛血浆和组织中乳酸脱氢酶的比较

乳酸脱氢酶（lactate dehydrogenase，LDH）是与组织能量代谢过程密切相关的酶，目前已成为研究动物发生过程中基因表达与调控分析的良好模型。其活性的大小与组织细胞内氧分压的高低密切相关。在有氧条件下，LDH将乳酸转化成丙酮酸，进而促进整个机体的代谢过程；在无氧条件下，LDH催化丙酮酸还原成乳酸，从而完成葡萄糖的无氧酵解过程；同时在其过程中释放少量ATP分子，为缺氧情况下的机体生命活力提供一定的能量。Kaplan认为LDH还能调节烟酰胺腺嘌呤二核苷酸（NAD）和烟酰胺腺嘌呤二核苷酸磷酸（NADH）的比率，因而对细胞内的一系列生化反应起调节控制作用。牦牛世代生活在高原环境，对低氧、寒冷、强紫外线等恶劣环境有强大的适应能力，本文通过测定牦牛的血浆和组织LDH活性，进一步探讨高原牦牛适应高寒，缺氧环境的生理机制。     

鱼类的核苷酸营养:研究现状及应用展望

关于水产饲料中核苷酸及代谢产物的应用研究已开展了至少25年,结果表明,添加核苷酸能增加饲料的适口性,影响鱼类摄食行为和非必需氨基酸的合成.最新的研究表明,在水产养殖中,外源核苷酸的添加能显著增强鱼类机体免疫力、提高机体抗病力.也有研究发现,饲料中添加核苷酸能促进幼鱼早期组织发育,改变肠道结构、调节机体特异性和非特异性免疫来增强抗应激能力,也能通过增强亲鱼饵料的营养来强化幼鱼的体质.同时,饲料中添加核苷酸能增强鱼体对病毒、细菌和寄生虫的抗感染能力.尽管生理指标检测方面偶尔有不一致的表现,但饲料中添加核苷酸已经为诸多水产养殖品种带来效益.核苷酸营养在水产上的研究目前还处于初级阶段,尚有一些基础性问题没有得到解决.然而现有的研究结果足以表明,对于鱼类而言,核苷酸是半必需营养元素或条件性营养元素,还需要进一步开展更为深入的应用研究.核苷酸的作用体现在为合成能力有限的组织(如淋巴系统)提供原料,调节机体能量代谢和免疫内分泌作用,介导基因的表达模式调控等.因此,关于外源核苷酸在鱼类其它方面的应用研究如核苷酸消化、吸收、代谢及影响生理反应的方式(尤其是免疫相关基因的表达,免疫球蛋白的产生等),以及不同养殖品种的大小、阶段、使用剂量和添加时间等的研究都有待更为深入的研究.     

利用核苷类逆转录酶抑制剂去除疫苗毒种中禽网状内皮组织增生症病毒污染

使用污染有禽网状内皮组织增生症病毒(REV)的弱毒疫苗被认为是REV流行的原因之一,去除疫苗毒种中REV污染是生产合格疫苗的基础环节,本研究试图利用核苷类逆转录酶抑制剂类药物Azidothymidine(LAM)和Lamivudine(AZT)去除疫苗毒种中REV污染。首先通过在培养液中添加不同质量浓度AZT或LAM连续传代以及利用CCK-8测定细胞活性的方法,证实了在培养液中添加不超过5mg/L的抑制剂类药物对于DF-1细胞复制和活性没有影响。体外试验证实,当在培养液中分别添加5mg/L的AZT或LAM以及两者联合应用时均可以显著抑制REV在DF-1细胞上的复制,通过在新城疫弱毒疫苗中人为添加REV模拟AZT或LAM以及两者联合应用对疫苗毒种中REV污染的净化作用,结果显示经药物干预4代后即将REV去除,并且净化后毒种检验合格。本研究证实了AZT或LAM在体外对REV的抑制作用,并在人工模拟试验中成功净化了疫苗毒种中污染的REV。     

Histochemistry of nucleoside phosphatases and phosphoglucomutase in the small intestine during coccidiosis in piglets]

The first day after birth, 22 conventional piglets were experimentally infected with the oocysts of the coccidia of I. suis (infection dose 200,000 oocysts). The activity of 5-nucleotidase (5-ribonucleotide phosphohydrolase, EC.3.1.3.5) and phosphoglucomutase (alpha-D-glucoso-1-phosphate phosphotransferase, EC.5.4.2.2) was densitometrically assessed in the mucosa of the small intestines of these piglets. Enzyme activities were studied in the infected piglets during the 2nd to 10th day after infection. The same histochemical examination was simultaneously performed in the intestinal mucosa of five control conventional piglets at an age of 2-14 days. 5-nucleotidase and phosphoglucomutase were found to have a high density in the mucosa of the small intestine of the control piglets: the high-density locations of these enzymes include, first of all, the supranuclear area of the absorption cells, the microvillous zone of enterocytes and the smooth muscle elements of lamina muscularis mucosae. The experimentally infected piglets showed a marked decline of the density of both enzymes during the infection. The deficit affected, for a transient period, the microvillous zone and the supranuclear region of enterocytes; the musculature of the mucous layer was affected permanently. The inactivity was more protracted in the case phosphoglutamase (especially 5 to 9 days after infection). The density of 5-nucleotidase showed a partial return to the normal already the 7th day after infection, with an interruption of resumption of activity on the 10th day. Resumption of enzyme activity in the lamina muscularis mucosae was not recorded during the infection. In the three locations under study, the density of none of the enzymes did reach parameters comparable with the controls at the end of the trial (10 days after infection).     

尿中修饰核苷水平在膀胱移行细胞癌诊断及预测预后中的意义

目的 探讨尿中7种修饰核苷M1A、ac4C、A、06-MeG、MTA、1 -MeI、1-MeG检测在膀胱移行细胞癌(bladder transitional cell carcinoma,BTCC)诊断及预测预后中的意义.方法 选取经病理证实为膀胱移行细胞癌患者45例为膀胱癌组,其中初发32例,复发13例;组织学分级:Ⅰ级22例,Ⅱ级16例,Ⅲ级7例;浸润性癌16例,非浸润癌29例.选取16例正常人为对照组.应用高效液相色谱/电喷雾-四极杆-飞行时间质谱技术(HPLC/ESI-Q-TOF-MS)检测膀胱癌组和对照组尿液中M1A、ac4C、A、06-MeG、MTA、1-MeI、1-MeG 7种修饰核苷水平(核苷含量/肌酐).结果 BTCC组尿液M1A、ac4C、06-MeG和1-MeI水平[分别为(4.61±1.82)、(0.63±0.29)、(0.46±0.35)和(12.28±9.74)],均显著高于对照组[(2.85±0.68)、(0.35±0.15)、(0.21±0.11)和(5.39±2.41),P＜0.01];诊断准确度由大到小为1-MeI＞ M1A＞ ac4C＞ 06-MeG,且1-MeI与M1A联合检测可达到对膀胱癌最高的灵敏度和特异性,分别为92.45%和87.50%.BTCC组织学分级之间以及浸润性与非浸润性之间尿液修饰核苷水平差异均无统计学意义(P＞0.05).复发患者尿液M1A和ac4C水平分别为(6.74±1.23)、(0.83±0.41),均显著性高于初发患者[(3.93±1.43)、(0.57±0.20),P＜0.05],M1A与其复发时间呈负相关(r= -0.895,P＜0.01).结论 尿液M1A联合1-MeI检测在膀胱移行细胞癌诊断中意义重大,M1A和ac4C有助于预测膀胱移行细胞癌患者预后.     

Activities of adenine nucleotide and nucleoside degradation enzymes in platelets of rats infected by Trypanosoma evansi

Pigeons (Columba livia) cohabit with humans in urban and rural areas, representing a public health problem since microorganisms are transmitted through the inhalation of dust from their dry feces (chlamydiosis) and through ingestion of their undercooked or poorly refrigerated meat (toxoplasmosis). This study aimed to evaluate the presence of Chlamydophila psittaci and Toxoplasma gondii in pigeons from four cities in São Paulo State, Brazil. C. psittaci was evaluated through hemi-nested polymerase chain reaction (hnPCR) using cloacal and tracheal swabs, whereas T. gondii specific antibodies were assessed by means of modified agglutination test (MAT), mouse brain and muscle bioassay, and polymerase chain reaction (PCR). To confirm the infection in mice, T. gondii antibodies were assayed by using indirect fluorescent antibody test (IFAT). Considering C. psittaci, 40/238 (16.8%; 95%CI 12.6–22.1%) samples were positive according to hnPCR, especially for the cities of São Paulo (42.5%) and Bauru (35%). As regards T. gondii, 12/238 (5%; 95%CI 2.9–8.6%) serum samples were positive according to MAT. Of these, five samples had titer equal to 1:8; six samples, 1:16; and one sample, 1:32. Bioassay, IFAT and PCR were negative for mouse toxoplasmosis. The absence of T. gondii antibodies suggests that pigeons may be infected with a low concentration of the agent, not detected by the antigen test. Thus, C. psittaci represents an actual problem concerning bird health.     

Maternal pyrimidine nucleoside supplementation regulates fatty acid,amino acid and glucose metabolism of neonatal piglets

Pyrimidine nucleosides(PN) are abundant in mammalian milk and mainly involved in glycogen deposition and lipid metabolism. To investigate the effects of maternal supplementation with pyrimidine nucleoside on glucose, fatty acids(FAs), and amino acids(AAs) metabolism in neonatal piglets. Forty pregnant sows were randomly assigned into the control(CON) group(fed a basal diet, n = 20) or the PN group(fed a basal diet supplemented with PN at 150 g/t, n = 20). Litter size, born alive and birth litter...     

禽源NME/NM23核苷二磷酸激酶2(NME2)基因的克隆及表达鉴定

参照GenBank中禽源核苷二磷酸激酶2(NME2)基因序列,设计了NME2基因的特异性引物。采用RT-PCR扩增NME2基因,经双酶切后克隆到真核表达载体pEF1α-Myc,得到重组质粒pEF1α-Myc-NME2。将构建好的重组质粒pEF1α-Myc-NME2转染DF1细胞后,采用间接免疫荧光和Western blot技术对目的蛋白进行验证。结果表明,Myc-NME2融合蛋白在DF1细胞内得到了正确表达。本研究为后续研究禽源NME2基因的功能奠定了基础。     

Tunicamycins, a class of nucleoside antibiotics similar to corynetoxins of the Rathayibacter toxicus, increase susceptibility of mice to Neospora caninum

Neosporosis is the leading cause of abortion in cattle. Neospora caninum-associated abortion may exhibit both endemic and epidemic patterns. It was reported that the epidemic outbreaks took place in the form of "abortion storms" and were not significantly correlated with seasonal changes or consumption of any particular feeds; and thus, the mechanisms by which the epidemic "abortion storms" are triggered remain unclear. Annual ryegrass toxicity (ARGT) is a severe or fatal neurological disorder of livestock of Australia and South Africa. This disorder is caused by the ingestion of several plant genera (Lolium, Polypogon, and Agrostis) colonized by a nematode (Anguina sp.) and a bacterium, Rathayibacter toxicus. Corynetoxins (CTs) produced by R. toxicus contaminate plants which are in turn ingested by sheep and cattle, causing severe or often fatal hepatocerebral disorders in affected animals. We hypothesize that N. caninum-associated fetal deaths and abortions in cattle may be potentiated by pre-exposure of sublethal levels of CT-contaminated plants prior to N. caninum infection or reactivation of a latent infection. The exposure of sublethal CTs may not cause clinical diseases, but may increase susceptibility to pathogens such as N. caninum. Indeed, CT poisoning surviving pregnant sheep can have up to 10% abortions. The present study investigated whether animals pre-exposed to tunicamycins (TMs), a functional substitute for CTs, had a lowered resistance to sublethal experimental infection by N. caninum tachyzoites in mice. The results showed that sublethal doses of TMs or N. caninum alone did not cause significant deaths. Sublethal doses of N. caninum induced high mortality in TM-treated mice in a dose dependent manner. When mice were treated with a low dose of TMs (5 μg/mouse), as few as 2.5 × 10(6) tachyzoites were needed to induce more than 30% of mortality which is equivalent to the mortality rate caused by 40 × 10(6) tachyzoites. Spleen cells of mice treated with TMs had reduced (p<0.05) Neospora antigen-induced interferon-gamma (IFN-g) production and Con A-stimulated proliferation. The results suggest that CT contaminated plants, when exposed to animals under natural conditions, may contribute to lowered host resistance and increased N. caninum-associated fetal morbidity and mortality in affected animals.     

Clinical efficacy of the acyclic nucleoside phosphonate 9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine (PMPDAP) in the treatment of feline immunodeficiency virus-infected cats

In in vitro studies, the acyclic nucleoside phosphonate 9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine (PMPDAP) inhibited the replication of feline immunodeficiency virus (FIV). No information about its clinical efficacy is available so far. The aim of this prospective placebo-controlled, double-blinded study was to evaluate the antiviral efficacy of PMPDAP in cats naturally infected with FIV. Twenty cats were randomly assigned to two treatment groups receiving either PMPDAP (25 mg/kg) or placebo twice per week subcutaneously for 6 weeks. The general health status (Karnofsky's score), clinical signs, laboratory, immunological, and surrogate parameters were evaluated. No significant differences were found between PMPDAP- and placebo-treated cats, although cats treated with PMPDAP showed a tendency for improvement in their Karnofsky's score and clinical signs. Haematological side effects were noted in the PMPDAP-treated cats. Thus, PMPDAP may be an option in treating cats if it becomes available for veterinarians, but side effects have been monitored.