Preventing experimental vertical transmission of scrapie by embryo transfer.

This study investigated whether the transmission of naturally occurring scrapie in sheep can be prevented using embryo transfer. Embryos were collected from 38 donor ewes in a Suffolk sheep flock with a high incidence of naturally occurring scrapie, treated with a sanitary procedure (embryo washing) recommended by the International Embryo Transfer Society and then transferred to 58 scrapie-free recipient ewes. Ninety-four offspring were produced. None of the offspring or the recipient ewes developed scrapie. Furthermore, offspring derived from embryos collected from donor ewes bred to the immunohistochemically positive ram did not develop scrapie. We conclude that scrapie was not transmitted to offspring via the embryo nor was the infective agent transmitted to recipient ewes during embryo transfer procedures.

PrP genotypes and experimental scrapie in orally inoculated Suffolk sheep in the United States.

One-hundred and three Unites States Suffolk sheep were inoculated orally with a scrapie agent preparation and monitored for clinical disease and histopathological lesions characteristic of scrapie. A retrospective study of the polymorphisms at codon 171 of the prion protein (PrP) gene was performed on these sheep. All 63 sheep that developed scrapie during the observation period were homozygous for the glutamine 171 (171-QQ) PrP allele. Twelve 171-QQ sheep failed to develop disease. All 5 sheep homozygous for arginine (171-RR) and all 23 heterozygous (171-QR) sheep remained free of scrapie.

Prevention of scrapie transmission in sheep, using embryo transfer.

Reciprocal embryo transfers were made between scrapie-inoculated and scrapie-free sheep (Cheviot and Suffolk breeds) to measure scrapie transmission via the embryo (using offspring from embryos of scrapie-inoculated donors and scrapie-free recipients) and via the uterus (using offspring from embryos of scrapie-free donors and scrapie-inoculated recipients taken by cesarean section). Two control groups of offspring, 1 from scrapie-free parents (negative) and 1 from scrapie-inoculated parents (positive), also were included. All sheep were observed for clinical signs of scrapie until death or for a minimum of 60 months. Final diagnosis was made on the basis of histopathologic findings or results of mouse inoculation and/or proteinase-K-resistant protein analysis. Thirty to 61% of the scrapie-inoculated donor/recipient sheep within groups developed scrapie within 8 to 44 months after inoculation. None of the scrapie-free donor/recipients, including those gestating embryos from scrapie-inoculated donors, developed scrapie. Also, none of the offspring observed to > or = 24 months of age from reciprocal cross, via embryo (0/67), or via the uterus (0/25), or from the negative-control group (0/33) developed scrapie. Fifty-six of the offspring via embryo, 19 of these via the uterus, and 31 negative controls survived to > or = 60 months of age. Of the 21 sheep in the positive-control group, 2 (9.5%) developed scrapie, 1 at 31 months of age and 1 at 42 months of age. In the Cheviot offspring, the percentage of sheep carrying the short incubation allele ranged from 24 to 44% and the percentage in the Suffolk offspring ranged from 61 to 83%.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphisms of a scrapie-associated fibril protein (PrP) gene and their association with susceptibility to experimentally induced scrapie in Cheviot sheep in the United States.

The duration of the incubation period for scrapie, a fatal transmissible neurodegenerative disorder of sheep and goats, is mainly determined by the Sip gene, which has 2 alleles (sA--susceptible and pA--resistant). A diagnostic test is not available to detect scrapie in live animals. We analyzed genomic DNA extracted from frozen sheep brains collected from Cheviot sheep of the United States that had been inoculated with the SSBP/1 scrapie inoculum. Digestion of the DNA with EcoRI or HindIII followed by the addition of a scrapie-associated fibril protein (PrP)-specific marker probe, yielded fragments of 6.8 (e1) and 4.0 (e3) kb, or 5.0 (h1) and 3.4 (h2) kb, respectively. Fragments e1 and h2 were associated with the histopathologic diagnosis of scrapie, and fragments e3 and h1 were associated with survival. A valine/alanine polymorphism within the PrP coding region that resulted in a BspHI site was further used to determine the genotype of these Cheviot sheep. Digestion of polymerase chain reaction fragments with BspHI resulted in an undigested fragment b- (0.840 kb), digested fragments b+ (0.460 and 0.380 kb), or both types of fragments. Survival time of b+/b+ homozygous sheep was significantly (P < 0.01) shorter (218 +/- 26.0 days) than survival time for b-/b- sheep (> 700 days after inoculation). Results indicated that b+ and b- are markers for the Sip sA and pA alleles, respectively. The intermediate duration of the incubation period for heterozygous sheep (b+/b-; 342.9 +/- 25.3 days) indicated that the Sip sA allele is expressed codominantly to the Sip pA allele.

Transferrin and haemoglobin polymorphism in domesticated goats in the USA.

The distribution of transferrin (Tf) and haemoglobin (Hb) polymorphisms in five goat breeds in the USA is reported. Two Tf types, A and B, were identified. A significant difference in frequency (P less than 0.05) was observed only between the Spanish and Alpine goats. Haemoglobin beta-globin variants, Hb beta A, Hb beta D and Hb beta E were observed with isoelectric focusing at pH ranges 5-8 and 6.7-7.7. Hb beta D was not found in the Alpine and Angora breeds. Haemoglobin allelic frequencies varied widely and differed significantly (P less than 0.05) among breeds.

Genetic variability in domesticated and wild sheep based on blood protein characters.

1. The study examined genetic variation, as indicated by eight blood proteins of 539 animals from 11 genotypes (14 flocks) of domesticated sheep and three genotypes of wild sheep. 2. The polymorphic distribution among the animal populations presented a random pattern with wide variation. 3. Genetic variability both between and within populations was larger in domesticated sheep than in their wild relatives. 4. This increased genetic variability observed in domesticated sheep may have resulted from the process of domestication through accelerated genetic drift and promoted gene flow.

The influence of culture and transport on pretransfer development and posttransfer survival of sheep embryos.

Sheep embryos were collected under sterile conditions in Dulbecco's Phosphate Buffered Saline (DPBS) + 10% Fetal Calf Serum (FCS) and cultured in DPBS + 20% FCS at 37 degrees C. They were classified according to their stage of development, from the lowest stage, 13 (less than a morula) to the highest stage, 20 (hatched blastocyst). Morphology was graded from 1 for excellent to 5 for degenerated. All embryos placed in the experiment had a development stage classification of 14 (morula) or higher and morphology classification of 1 to 3. Thirty-four embryos cultured in the laboratory for 24 h (Treatment B) and 32 embryos handled the same way except that they were transported for approximately 12 h (Treatment C) increased an average of 1.8 development classification scores and decreased -0.84 and -0.58 morphology classification scores for the two treatments, respectively. Twelve embryos in Treatment D (the same as Treatment C except that they were cultured in the laboratory for an additional 24 h) progressed 2.2 development classification scores during 48 h culture and did not change (-0.08) in the morphology classification score. The development estimates related to length of culture time but showed no affect of transport. Seventy-five percent of 20 embryos transferred in Treatment C and 42% of 12 embryos in Treatment D survived to parturition, demonstrating that the procedures used to transport and culture them for 24 and 48 h, respectively, maintained embryos capable of post transfer survival. Forty-one percent of the 22 embryos transferred in Treatment A (noncultured) and 20% of 20 embryos in Treatment B survived.

Effect of summer heat stress on serum luteinizing hormone and progresterone values in Holstein-Friesian cows in Arizona.

Serum-luteinizing hormone and progesterone values were measured in lactating and nonlactating Holstein-Friesian cows to evaluate their relationship with reduced fertility observed during hot summer months in Arizona. The stress of hot weather had no effect on frequency of preovulatory increase of luteinizing hormone nor on the interval between the preovulatory increase and ovulation in either lactating or nonlactating cows. Progesterone values were significantly (P less than 0.05) increased in lactating cows which became hyperthermic during hot weather, yet progesterone values did not change in nonlactating cows which had remained homeothermic. A similar relationship was observed between fertility and serum progesterone values, and between fertility and degree of thermal stress caused by hot weather. Decreased fertility and increased serum progesterone values were associated with increased environmental temperature and hyperthermia.

False-positive echocardiographic diagnosis of pericardial effusion. Result of tumor encasement of the heart simulating constrictive pericarditis.

A 46-year-old man had advanced squamous cell carcinoma of the lung and apparent constrictive pericarditis. Echocardiographic studies twice demonstrated apparent pericardial effusions, but pericardiocenteses were unsuccessful. Tumor encasement of the heart was diagnosed clinically and at necropsy. This entity is yet another cause of a false-positive echocardiographic diagnosis of pericardial effusion.

Chromosomes, hemoglobins, and transferrins of Iranian domestic sheep.

Twelve breeds of Iranian domestic sheep were cytogenetically analyzed. The diploid chromosome number of 2n = 54 is identical to that of most breeds of domestic sheep, which is comprised of 3 pairs of metacentric and 23 pairs of acrocentric autosomes. The sex chromosomes consist of a large acrocentric X and a small bi-armed Y. Hemoglobin analysis by isoelectric focusing for these 12 breeds resulted in the identification of 2 protein fractions: Hb AB and B. The A allele was observed in 7 percent of the 506 sheep sampled, in 6 of the 12 breeds, and then only in the heterozygous form. Transferrins were analyzed by starch-gel electrophoresis and comparisons made between breeds. Nine alleles, pooled frequency of occurrence in descending order, B, C, D, A, M, E, G, P, and I were identified and resulted in 19 phenotypes. Tfs A, B, C, and D were observed in all breeds, whereas I was found in 2,G in 1, M in 8, E in 6, and P in 2. Significant differences in allelic occurrence of Tfs A, B, C, and D were observed in seven breeds.

Translocations of acrocentric chromosomes and their implications in the evolution of sheep (Ovis).

Cytogenetic evidence suggests that the caprids (sheep and goats) evolved from a common ancestor with a 2n=60 karyotype. Although goats (Capra) retained the primitive 2n=60 karyotype, sheep (Ovis) underwent a sequential reduction in the number of chromosomes by means of acrocentric translocation. The formation of the first metacentric autosome (M1) occurred in the aoudad (Ammotragus) and urial (O. vignei), resulting in a 2n=58 karyotype. The G-bands are homologous, which implies both genotypes arose from a common ancestor, possibly a rupicaprid. Based on G-bands, acrocentric chromosomes 1 and 7 of the 2n=60 karyotype formed the M1. The X chromosome, which is the second longest acrocentric in the 2n=60 karyotype, became the longest acrocentric in Ammotragus and Ovis (2n=58). The second pair of metacentrics to evolve, which is ranked in the M3 position of the 2n=54 karotype, resulted from the translocations of acrocentric chromosomes 4 and 14 or 15 in the 2n=60 karyotype. The M2 was the third pair of metacentrics to be formed and resulted from the translocations of acrocentric chromosomes 3 and 12 or 13 in the 2n=60 karyotype. The G-bands of all 2n=54 karyotypes are homologous, which indicates origin from a common ancestor. Evidence is presented that suggests a prezygotic selection is bringing about a reduction in diploid chromosome numbers. The possible roles of fission and fusion in the karyotypic evolution of Ovis are discussed.