Near extinction of a large, widely distributed fish

Are extinctions of marine vertebrates as rare and unlikely as current data indicate? Long-term research surveys on the continental shelf between the Grand Banks of Newfoundland and southern New England reveal that one of the largest skates in the northwest Atlantic, the barndoor skate (Raja laevis), is close to extinction. Forty-five years ago, research surveys on St. Pierre Bank (off southern Newfoundland) recorded barndoor skates in 10% of their tows; in the last 20 years, none has been caught, and this pattern of decline is similar throughout the range of the species.     

Twin pregnancies following transfer of single embryos in three mares: A case report

Spontaneous development of identical or monozygotic twins is a rare event in the horse. Monozygotic twins develop after division of a single embryo. This report documents three cases in which twin embryos developed following surgical transfer of a single morula stage embryo into the uterus of a synchronized recipient mare.     

Association of cytochrome b5 with 16-androstene steroid synthesis in the testis and accumulation in the fat of male pigs.

The 16-androstene steroids, one of the principal causes of boar taint, are synthesized in the testis by the andien-beta synthase enzyme system. This system has been shown in vitro to involve both cytochrome P450c17 and cytochrome b5. The objective of this work was to investigate the relationship between the levels of cytochrome b5 in the testis, in vitro steroidogenesis, and the accumulation of 16-androstene steroids in the fat of pubertal boars. We found that the in vitro rate of 16-androstene steroidogenesis in testis microsomes was correlated with 16-androstene steroid concentrations in fat (r = .66, P < .01). Western blots were used to determine the amounts of cytochrome b5 and cytochrome P450c17 protein in testis, and two immunoreactive cytochrome b5 proteins of approximately 12 and 16 kDa were found. Levels of cytochrome P450c17 or the high molecular weight cytochrome b5 in testis were not significantly correlated to levels of 16-androstene steroids in fat. However, levels of total cytochrome b5 immunoreactive protein and levels of the low molecular weight immunoreactive cytochrome b5 were correlated to fat 16-androstene steroid concentrations (r = .59, P < .001; r = .72, P = .0001, respectively). Levels of the low molecular weight immunoreactive cytochrome b5 were also correlated to 16-androstene steroid synthesis rates in vitro (r = .62, P < .05). These results indicate that increased levels of a low molecular weight immunoreactive cytochrome b5 protein, and not of cytochrome P450c17, are related to increased testicular 16-androstene steroid production and accumulation in fat. These results support the hypothesis that selection for reduced levels of this low molecular weight immunoreactive cytochrome b5 protein in the testis may result in decreased levels of 16-androstene steroids in fat and reduced boar taint in uncastrated male pigs.     

Effect of dietary flax oil and hypobaric hypoxia on pulmonary hypertension and haematological variables in broiler chickens.

1. Three experiments were conducted with broiler chickens using hypobaric chambers and control pens, feeding diets containing 25 or 50 g flax oil/kg food or control diets with equivalent amounts of animal/vegetable (A/V) blend oil for 4 weeks. The effect of these diets on haematological variables and the extent of right ventricular hypertrophy (RVH) leading to ascites was determined. 2. Overall growth rate was not consistently affected by dietary treatment, although feeding the 25 g flax oil/kg diet reduced weight gain in week 4 of one experiment. Feeding the 50 g flax oil/kg diet but not the 25 g flax oil/kg diet reduced RVH in birds exposed to hypobaric conditions compared to feeding control diets. 3. Feeding the 50 g flax oil/kg diet under hypobaric conditions reduced the haematocrit and haemoglobin content, increased the erythrocyte deformability and the proportion of unsaturated fatty acids in the erythrocyte membranes, and reduced the whole blood viscosity compared to feeding control diets. These effects were not seen when the 25 g flax oil/kg diet was fed. The ratio of n-3 to n-6 fatty acids in erythrocyte membranes was increased in the 50 g flax oil/kg treatment group compared to controls. 4. Including 50 g flax oil/kg broiler diet reduces RVH in broiler chickens. This may be attributable in part to an increase in erythrocyte deformability from an increased proportion of unsaturated fatty acids in the erythrocyte membranes.     

Changes in Equine Reproduction: Have They Been Good or Bad for the Horse Industry?

In the past four decades there have been tremendous changes in equine reproduction. Most breeds now allow the use of artificial insemination with fresh, cooled and frozen semen. Artificial insemination has many advantages for the breeder, in particular the control of bacteria through the use of semen extenders containing antibiotics. Deposition of sperm in small volumes onto the uterotubal junction has allowed the use of relatively low numbers of sperm. Intracytoplasmic injection of sperm into oocytes allows older, subfertile stallions to be used as breeding stallions. Advances in mare reproduction have included developing tools for hastening the onset of the breeding season. Other advances include embryo transfer, oocyte collection and transfer, and cloning. The acceptance of reproductive technology depends on the success of the technology, the attitude of the breeders/veterinarians, and the cost/benefit ratio to the industry and breed registry.     

Transduction and Transplantation of Spermatogonia into the Testis of Ram Lambs through the Extra-testicular Rete

Spermatogonial transplantation will provide a new way to study spermatogenesis in domestic animals, disseminate male genetics and produce transgenic animals, if efficiency can be improved. We evaluated a 'surgical' method for transplanting donor cells into testes of ram lambs, where the head of the epididymis is reflected, and a catheter introduced into the extra-testicular rete testis. We also tested transduction of ram spermatogonia with a lentiviral (LV) vector as a means to identify permanent colonization, and introduce genes into donor cells. Eight ram lambs, 11- to 13-week olds, were the recipients: in five, spermatogonia were injected into one testis, and the contralateral testis was an un-manipulated control: in two, spermatogonia were injected into one testis and the contralateral was sham-injected: in one, both testes were injected. Six lambs received spermatogonia labelled with a cell-tracking dye and these were collected 1 or 2 weeks after transplantation; three lambs received spermatogonia transduced with a LV vector driving the expression of enhanced Green Fluorescence Protein and these were collected after 2 months. Donor cells were detected by immunohistochemistry in tubules of seven of nine recipient testes. Approximately 22% of tubule cross-sections contained donor cells immediately after transplantation, and 0.2% contained virally transduced cells 2 months after transplantation. The onset of spermatogenesis was delayed, and there were lesions in both injected and sham-injected testes. Despite the effects of the surgery, elongated spermatids were present in one recipient testis 2 months after surgery. The results suggest that, after modifying the surgical and transduction techniques, this approach will be a means to produce good colonization by donor spermatogonia in sheep testes.     

Isolation of Canine Mammary Cells With Stem Cell Properties and Tumour-Initiating Potential

Recent data suggest that mammary carcinogenesis may be driven by cancer stem cells (CSCs) derived from mutated adult stem cells, which have acquired aberrant cell self-renewal or by progenitor cells that have acquired the capacity for cell self-renewal. Spontaneous mammary cancers in cats and dogs are important models for the understanding of human breast cancer and may represent alternative species model systems that can significantly contribute to the study of human oncogenesis. With the goal of identifying markers for isolating human breast CSCs, we have generated a canine model system to isolate and characterize normal and CSCs from dog mammary gland. Insight into the hierarchical organization of canine tumours may contribute to the development of universal concepts in oncogenesis by CSCs. Cells with stem cell properties were isolated from normal and tumoural canine breast tissue and propagated as mammospheres and tumourspheres in long-term non-adherent culture conditions. We showed that cells obtained from spheres that display self-renewing properties, have multi-lineage differentiation potential, could generate complex branched tubular structures in vitro and form tumours in NOD/SCID mice. We analysed these cells for the expression of human stem and CSC markers and are currently investigating the tumour-initiating properties of these cells and the hierarchical organization of normal and neoplastic canine mammary tissue.