Maturation Status, Protein Synthesis and Developmental Competence of Oocytes Derived from Lambs and Ewes

The efficacy of oocyte selection for in vitro embryo production depends on the abundance and diameter of follicles, cumulus layers around the oocytes and subsequent fertilization. Application of `ovum pick-up' technique allows us to utilize partially matured oocytes for embryo production even from juvenile subjects. To compare their developmental competence, oocytes derived from lambs and ewes and cultured in maturation medium for up to 26 h were assessed at 2 h intervals by confocal microscopy after chromatin and microtubulin-specific fluorochrome labelling. Lamb oocytes reached second meiotic metaphase (MII) at lower numbers at 24 h (60.0%) and 26 h (28.6%) whereas 85.7% of adult-derived oocytes attained MII status by 24 h of maturation. Radiolabelling of oocyte proteins revealed higher incorporation of [³⁵S-]-methionine and [³⁵S]-cysteine in adult-derived oocytes compared to lamb oocytes. Although the cleavage rate of lamb oocytes was similar to that of ewe oocytes, the proportion reaching blastocyst stage was significantly lower (p < 0.05) in the lamb-derived oocytes. However, blastocysts from both types of oocytes displayed similar cell lineage allocations to inner cell mass and trophectoderm.     

The efficacy of a controlled-release albendazole capsule in suppressing nematode burdens in sheep

An experiment was undertaken between July and November 1985 in East Gippsland, Victoria, to determine the efficacy of an intra-ruminal controlled-release albendazole capsule against naturally acquired worm burdens and larval challenge in Merino hoggets. Two groups of 20 sheep, one group untreated, the other dosed with a capsule were grazed together; 5 sheep from each group were slaughtered for total worm counts 30 and 101 d after capsules were administered. Serum anthelmintic concentrations, faecal egg counts and body weights were monitored. Most capsules were exhausted within 91 d of administration. During the estimated 80 d for which they remained active the capsules were highly effective against the benzimidazole-susceptible worm populations. Faecal egg counts were reduced to zero and total worm populations were reduced by over 97% 30 d after administration. By 101 d egg counts were increasing and worm counts indicated that sheep were becoming reinfected. Sheep treated with the capsules grew faster than those not treated.     

Progressive ataxia associated with degenerative thoracic myelopathy in Merino sheep

A neurological disorder in Merino sheep, characterised clinically by progressive posterior ataxia and microscopically by Wallerian degeneration in thoracic segments of the spinal cord, is described. Animals of both sexes were affected, with the earliest onset of disease being at 5 months of age. Most affected animals died before 2 years of age. The clinical, pathological and epidemiological features suggest that this degenerative thoracic myelopathy is a previously unrecognised entity differing from other reported causes of ataxia in sheep in Australia.     

Tumour angiogenesis,anti‐angiogenic therapy and chemotherapeutic resistance

In order for a tumour to continue to grow and disseminate, it must acquire a new blood supply. Neovascularisation can be enacted by a number of different mechanisms. This dependence of tumour progression on an augmented vascular supply has been exploited by the development of anti‐angiogenic drugs, which are designed to inhibit new blood vessel formation or disrupt existing tumour‐associated vasculature, both leading to ischaemic–hypoxic tumour cell death. However, the clinical benefits of these therapeutic approaches are frequently variable and often transient, the neoplasm sometimes being able to use other neovascularisation mechanisms to maintain its blood supply and thus evade the current anti‐angiogenic therapy. Tumours may also develop a more malignant phenotype following this treatment. Clinical outcomes may be improved by simultaneously inhibiting different angiogenic pathways, abetted by more effective drug delivery regimens such as metronomic chemotherapy and the concurrent use of other antitumour modalities.     

Detection of Toxoplasma gondii DNA in Fresh and Frozen Semen from Rams in Brazil

The aim of this study was to estimate the prevalence of genomic DNA of Toxoplasma gondii in semen samples from commercial rams in artificial insemination centres in Brazil, as well as in fresh semen from rams in the northeast of Brazil. In total, 108 semen samples were obtained from artificial insemination centres, and genomic DNA of T. gondii was detected in 24 of 108 (22.2%). The prevalence of antibodies anti‐Toxoplasma gondii among sheep on rural properties was 9.2% (10/109), and 100% of the semen samples of these animals were positive in the PCR for T. gondii DNA. The molecular identity was confirmed through sequencing, which indicated 99.9% similarity with the T. gondii DNA sequences stored in the GenBank. This study reports the first occurrence of T. gondii DNA in the semen of rams, which came from artificial insemination centres in Brazil, as well as the occurrence of T. gondii DNA in the fresh semen of naturally infected rams in the northeast of Brazil.