Studies on maternal transmission of scrapie in sheep by embryo transfer.

The technique of embryo transfer was used to investigate the maternal transmission of scrapie in sheep. Embryo donor ewes were experimentally infected with scrapie (all eventually developing the disease) and artificially inseminated six months later with semen from an uninfected scrapie-susceptible ram. Embryos were harvested five and six days after insemination and transferred by laparoscopy, unwashed, into recipient ewes which had been genetically selected for very low susceptibility to scrapie. Six of the 26 lambs born to these recipients developed scrapie.     

Effects of temperature on the migration of primordial germ cells in the chick embryo.

1. Incubating eggs at reduced temperatures leads to a decline in the rate of embryonic development. 2. All tissues do not respond equally and the migration of primordial germ cells is delayed in time, but occurs at an earlier stage of development than for normally incubated eggs. 3. The results are interpreted in relation to the integrated development of the gonad.     

Toxoplasmosis in sheep. Influence of various factors on the antibody contents.

The contents of toxoplasma antibodies were estimated by a micro-modification of the dye test for up to 3 years after the initial stage of infection both in ewes which had aborted and in ewes with normal pregnancies. During the first 2 years the titres in ewes which had aborted were significantly higher than in ewes with normal pregnancies. The investigation indicated that dye test titres ≥ 1/512 usually occur during the first stage of infection, and are mainly found in ewes with clinical toxoplasmosis.The dye test titres in lambs due to antibodies transferred with the colostrum were up to 4 twofold dilutions higher than in their dams during the first 2 days after birth. Later the titres declined, and at the age of about 2 months only 3 of 29 lambs had higher titres than their dams. After the age of about 3 months maternally derived antibodies were not detected.The contents of toxoplasma antibodies in sheep with listeric encephalitis were nearly the same as found by a serological survey of the local sheep population. The examination indicated that the dye test titres in sheep are little influenced by conditions that may affect the defence mechanism.Sheep with haemoglobin type B had significantly higher dye test titres than sheep with the haemoglobin types A and AB when examined less than about 6 months after they had acquired the infection. No association was found between the susceptibility to toxoplasma infection and the haemoglobin type. kw|Keywords|k]toxoplasma infection; k]antibody formation; k]sheep {fn1|This work was supported by grants from The Norwegian Research Council for Science and for the Humanities.}     

杜泊羊胚胎移植试验

48只杜泊绵羊供体用促卵泡素(FSH) 进行超排处理, 用手术法采胚, 39只羊共获250枚可用胚, 头均获可用胚为6 41 ( 250 /39 ) 枚,不同产地FSH及供体年龄对超排效果影响差异不显著(P>0 05)。将250枚可用胚植入209只小尾寒羊受体中, 产羔101只, 产双羔受体10只,产羔率为48 33% (101 /209)。结果表明: 移三胚、双胚的受体羊产羔率明显高于移单胚的产羔率, 差异极显著(P<0 01 ); 移植受体的移入侧卵巢上有3个及以上黄体的受胎率高于1个黄体和2个黄体, 但差异不显著(P>0 05); 不同饲养管理水平下羔羊初生重差异显著(P<0 05 ),但受胎率无显著差异。双羔平均初生重较单羔低0 58kg, 差异显著(P<0 05); 双羔成活率较单羔成活率低25 6%, 差异极显著(P<0 01 );单羔妊娠期较双羔长, 差异显著(P<0 05)。     

胚胎移植试验羊群发情规律的研究

为了有效提高绵羊体细胞克隆和转基因等研究工作的效率,缩短胚胎移植试验羊群中空怀个体的利用周期间隔,试验对采用不同移植方法的胚胎移植受体及供体绵羊进行了移植前后的发情规律研究。结果表明:采用自制孕激素海绵栓和进口阴道孕激素释放装置(CIDR)对绵羊进行同期发情处理时发情率均接近90%,且92%以上的个体发情起始时间均集中在撤栓后24～48 h。在胚胎移植试验结束后,未参加胚胎移植个体和子宫角法未移植受体第2情期发情起始时间主要集中在上次发情后的14～20 d,而输卵管法未移植受体和输卵管法冲卵供体的发情时间则比较分散,呈现明显延后状态。未参加胚胎移植个体和子宫角法未移植受体人工授精后的受胎率接近往年羊场的平均水平,输卵管法未移植受体的受胎率略有下降,且输卵管法冲卵供体的受胎率明显降低。     

The effect of an intrauterine viral infection on the skin follicles of sheep

Border disease of sheep is a transplacental viral infection of the foetus. In medium and fine fleeced breeds, the most consistent of the pathological changes is permanent primary follicle enlargement, first apparent at 115 days gestation and accompanied by increased fibre size and frequency of fibre medullation. A tendency for fewer secondary follicles to develop in Border disease is probably an indirect consequence of infection.Primary follicles are only susceptible to the effects of Border disease following maternal inoculation with standard inoculum up to 80 days gestation. The subsequent resistance of primary follicles may be related to a loss of susceptibility with differentiation or, more probably, to the development of a foetal immunological response to the agent.In coarse fleeced breeds, the skin appears to be unaffected by Border disease. It may be that Border disease de-inhibits follicle growth limiting mechanisms in finer fleeced breeds, causing reversion to a more primitive, coarser fleece type.     

Intrauterine migration of the porcine embryo: coordination of bead migration with estradiol

Forty crossbred gilts were used in three experiments to examine the effects of estradiol on embryo migration. Small, spherical beads of Silastic glue containing either cholesterol or estradiol-17 beta were used to mimic embryo migration. In the first experiment, 10 cholesterol- and 10 estradiol-impregnated beads were injected into the tip of the uterine horns, either on the same side (n = 5) or opposite from each other (n = 5). The second experiment consisted of a localized release of cholesterol or estradiol and observing migration of cholesterol-containing beads inserted 10 cm anterior and posterior to this site (n = 5). In the third experiment, 10 cholesterol-impregnated beads were injected into either the tip or base of one uterine horn. Additionally, these gilts were exposed to vehicle or exogenous estradiol in a 2 X 2 factorial arrangement of treatments (n = 5). Results of these experiments indicated that cholesterol-impregnated beads migrated further (P less than .05) when adjacent to estradiol-containing beads than when in an opposite uterine horn. Localized release of estradiol failed to induce movement of beads away from the site of steroid release. Finally, beads inserted at the base of the uterus moved anteriorly following treatment of gilts with estradiol. We suggest from these experiments that the porcine uterine horn cannot discriminate between estradiol- and cholesterol-releasing beads and, further, lacks a coordinated ability to displace adjacent beads. A site-dose dependent mechanism(s) of estrogenic induction of migration may exist such that porcine embryos become bilaterally intermixed following posterior, then anterior, waves of uterine contractions.     

Acephalous lamb from an in vitro-produced sheep embryo

This is the first report of an acephalous lamb from the transfer of an in vitro-produced sheep embryo. Twelve in vitro-fertilized embryos were transferred to 4 recipient ewes (3 embryos/ewe). Two ewes remained pregnant: one delivered a normal female lamb, the other a male acephalous lamb. Possible contributing factors are discussed.     

绵羊胚胎移植生殖内分泌调控及其效果研究

初产供体母羊（14月龄）德国美利奴15只、波德代15只、无角陶赛特18只分别用孕酮(CIDR)+促性腺激素(PMSG)+促卵泡素(FSH)进行处理,受体小尾寒羊母羊（2胎）124只用CIDR+PMSG进行处理,处理期测定供、受体外周血液中生殖激素孕酮（p4）、雌二醇（E2）、促卵泡素（FSH）和促黄体素（LH）的动态变化。结果显示：3个供体品种和受体各自发情同期化水平和效果达到非常理想的状态,但供、受体发情同步差相距1 d。黄体数德国美利奴（7.71）显著高于陶赛特（5.19）（P<0.05）;冲卵数德国美利奴（5.50）显著高于陶赛特（3.44）（P<0.05）;可用胚胎率德国美利奴、波德代、陶赛特分别为70.13%、55.74%、78.18%,陶赛特显著高于波德代（P<0.05）;德国美利奴、波德代、陶赛特胚胎移植受胎率分别为55.26%、54.17%、42.31%,德国美利奴显著高于陶赛特（P<0.05）。处理期供体和受体生殖激素动态变化的幅度大,第13天供、受体血清中p4达到峰值,小尾寒羊分别高于德国美利奴（5.37 ng/mL）、波德代（6.14 ng/mL）和陶赛特（5.37 ng/mL）;供体血清中E2于第14天开始发情达到峰值,小尾寒羊于第15天开始发情达到峰值;供体血清中FSH于第13天达到峰值,小尾寒羊第14天达到峰值;供体血清中LH于第14天开始发情达到峰值,小尾寒羊血清中LH于第15天开始发情达到峰值。     

Sperm migration in pigs after deep intrauterine and intraperitoneal insemination

Deep intrauterine insemination in pigs allows sperm deposition only into one uterine horn, but bilateral fertilization of oocytes occurs. How the sperm reach the contralateral oviduct remains disputable. The aim of this experiment was to study possible transperitoneal and/or transuterine sperm migration ways. Follicle growth and ovulation were induced in 24 peripubertal gilts with eCG and hCG 72 h after eCG. Endoscopic intrauterine insemination (IUI) was performed 32 h after hCG with 20 ml of extended semen (60 × 10(6) spermatozoa) as follows: Group CONTROL (n=8) received IUI into the right horn, and the left horn served as non-treated control; Group LIGATURE (n=8) received IUI into the right horn, and the left horn was closed by endoscopic double ligature close to the bifurcation; Group INTRAPERITONEAL (IPI; n=8) received IUI into the right uterine horn, the left horn was closed by double ligature and semen was deposited intraperitoneally at the surface of the left ovary. Genital tracts were removed 65-66 h after hCG, the oviducts were flushed and ova (n=299) were analyzed for fertilization and cleavage. Furthermore, the accessory spermatozoa count/oocyte was graded as 0, without spermatozoa, 1, <5 spermatozoa, 2, 5-50 spermatozoa, 3, 50-100 spermatozoa and 4, >100 spermatozoa. The results indicate that low dose IUI into one horn provides a lower grade of accessory spermatozoa in the contra-lateral side (1.6 vs. 2.8). No spermatozoa were found in ova flushed from oviducts of the ligated uterine horn, even after intraperitoneal insemination (P<0.05), and no fertilization occurred, respectively. Our results clearly indicate that after low dose IUI into one uterine horn, spermatozoa reach the contralateral oviduct via transuterine migration.     

Influence of selenium on antibody production in sheep

Three experiments were carried out, using sheep fed a marginally low selenium diet, to study the effect of selenium supplementation on the antibody response to tetanus toxoid and on the serum IgG concentration. Six groups of three six-month-old lambs were fed a basal diet containing 0.13 mg Se kg-1 supplemented with either 0.1, 0.5 or 1.0 mg Se kg-1, as sodium selenite or as selenomethionine. These animals generally showed enhanced antibody response to tetanus toxoid, parainfluenza-3 virus and Corynebacterium pseudotuberculosis, and their total serum IgG concentrations were higher than in unsupplemented control animals although few responses were statistically significant. In two field studies significantly higher titres to tetanus toxoid were detected in ewes injected with 100 mg selenium as barium selenate, although no influence on serum IgG concentrations was detected. Lambs from selenium supplemented ewes had significantly higher titres to tetanus toxoid than lambs from ewes in the control group. Dietary vitamin E supplementation had a similar effect on the antibody response to tetanus toxoid in ewes, though no additive effect was seen when vitamin E was given together with selenium.     

Estradiol-17 beta-oxytocin-induced cervical dilation in sheep: application to transcervical embryo transfer.

Experiments were conducted to determine whether exogenous estradiol-17beta (E2) and oxytocin (OT) can be used to improve transcervical (TC) embryo transfer (ET) procedures for sheep. Our concerns that the E2-OT treatment may alter luteal function prompted Exp. 1, in which 32 ewes were assigned to treatments in a 2x2 factorial array. On d 7 after onset of estrus, ewes received i.v. either 100 microg of E2 or diluent; 12 h later, ewes received i.v. either 400 USP units of OT or saline. To monitor luteal function, progesterone was measured in jugular blood collected from d 7 to 18. The treatments did not affect progesterone concentrations. Two trials were conducted in Exp. 2. In Trial 1, ewes were assigned to one of three treatments: TC transfer with E2-OT treatment to dilate the cervix, laparoscopic ET with E2-OT treatment, or laparoscopic ET with an equivalent diluent that did not dilate the cervix. In Trial 2, ewes were assigned to treatments in a 2x2 factorial array: TC or laparoscopic ET on d 6; E2-OT treatment for cervical dilation or diluents on d 6. Transferred embryos were recovered on d 12 in Trial 1 and d 14 in Trial 2, evaluated morphologically for development, and scored. Treatments did not affect the percentage of transferred embryos recovered. However, mode of transfer decreased (P<.01) the mean embryo development score. The E2-OT treatment increased (P<.01) the development score of embryos transferred transcervically, indicating that cervical dilation may improve the chances of embryos surviving after TC transfer. In conclusion, E2-OT treatment did not affect luteal function, and the E2-OT treatment can be used to enhance the success of TC embryo transfer in sheep.