Polyploid Abnormalities in Day 3 and Day 5 Merino Sheep Embryos

The chromosome complement was assessed in Merino sheep embryos collected at 3 and 5 days after the onset of oestrus. Donor ewe treatments were: untreated, or immunized against androstenedione (day 3); and untreated, or treated with follicle-stimulating hormone (FSH), or treated with FSH plus immunization against androstenedione (day 5). No significant differences in the frequency of chromosomally abnormal embryos between treatment groups within each age group were observed, so the data have been combined. Euploid abnormalities were observed in 10�8070 of the day-3 embryos (4/37), with the abnormalities being one In, one 3n and two 5n. Embryos with euploidy (10%) were also observed at day 5, with three 1n12n mosaics and a 3n embryo present in a sample of 40. These data suggest that chromosomally aberrant embryos are not lost before day 5 of development.

Inheritance of Tail Colour and White-spotting in Conilurus penicillatus (Muridae)

In the wild, Coni/urus penicillatus has two tail colour morphs, one entirely black and the other with a white distal brush of variable length. These colour morphs have been used in the past for taxonomic purposes. A small proportion (4'6%) of laboratory-reared animals have a white interstitial section. Pedigree data were collected from a laboratory colony (n = 173) established using seven wild-caught animals from the north Kimberley region, Western Australia. The hypothesis tested was that black tail is inherited as a Mendelian character recessive to white tip. Matings between black-tailed individuals always gave black offspring. Crosses between other colour morphs also supported this hypothesis.

The Heavy-chain Stoichiometry of Smooth Muscle Myosin is a Characteristic of Smooth Muscle Tissues

The stoichiometry of the two heavy chains of myosin in smooth muscle was determined by electrophoresing extracts of native myosin and of dissociated myosin on sodium dodecyl sulfate (SDS) 4%-polyacrylamide gels. The slower migrating heavy chain was 3�6 times more abundant in toad stomach, 2�3 in rabbit myometrium, 2�0 in rat femoral artery, 1�3 in guinea pig ileum, 0�93 in pig trachea and 0�69 in human bronchus, than the more rapidly migrating chain. Both heavy chains were identified as smooth muscle myosin by immunoblotting using antibodies to smooth muscle and nonmuscle myosin. The unequal proportion of heavy chains suggested the possibility of native isoforms of myosin comprised of heavy-chain homodimers. To test this, native myosin extracts were electrophoresed on non-dissociating (pyrophosphate) gels. When each band was individually analysed on SDS-polyacrylamide gel the slowest was found to be filamin and the other bands were myosin in which the relative proportion of the heavy chains was unchanged from that found in the original tissue extracts. Since this is incompatible with either a heterodimeric or a homodimeric arrangement it suggests that pyrophosphate gel electrophoresis is incapable of separating putative isoforms of native myosin.

Development of Sheep Embryos in vitro in a Medium Supplemented with Different Batches of Serum Albumin

Variability in different lots of commercial serum albumin affects mammalian embryo development in culture. The composition of commercial preparations of ovine, bovine and defatted bovine serum albumin and a fraction of ovine serum containing proteins with a mean molecular weight of 65 kDa (fraction 3) was examined by polyacrylamide gel electrophoresis. All preparations were heavily contaminated with serum proteins other than albumin. Day-6 sheep morulae were cultured for 48 h in a basal bicarbonate-buffered salt solution supplemented with the commercial preparations of ovine, bovine or defatted bovine serum albumin. These three albumin preparations differed in their abilities to support the development of morulae into expanded blastocysts, but these differences disappeared when the basal medium was also supplemented with a component of ovine serum containing substances with molecular weights of less than 10 kDa. In the latter case, the three commercial albumin preparations and fraction 3 of ovine serum all supported full development in about 40-60% of morulae.

Oestrogen Sulfotransferase: Molecular Cloning and Sequencing of cDNA for the Bovine Placental Enzyme

The female sex hormone, oestrogen, plays a central role in breast cell proliferation in both the normal and malignant state. It controls transcription from several genes, including that for the progesterone receptor, and in endometrial tissue, via this receptor, it controls the gene for the enzyme oestrogen sulfotransferase. This enzyme may control the level of the oestrogen receptor by sulfurylating free oestradiol. To study the mode of transcriptional control exercised by oestrogen, bovine oestrogen sulfotransferase cDNA has been cloned and the nucleotide sequence determined. The message, of which 1812 bases have been sequenced, contains an open reading frame of 885 bases which encode a protein of 295 amino acids and a maximum apparent molecular weight of 34 600. The deduced protein sequence is supported by existing peptide sequence data and appears to contain a steroid-binding region. Some physico-chemical characteristics of the enzyme appear to differ markedly from those previously reported.

Effects of Growth Hormone Administration on Wool Growth in Merino Sheep

The effects of daily administration of 10 mg of highly purified ovine growth hormone (GH) for a period of 4 weeks on wool growth have been measured in 12 Merino ewes fed either a calculated maintenance energy intake or 1�6 times this amount (six on each ration). Concentrations of hormones, glucose, urea, a-amino N and amino acids in the blood were monitored and faeces and urine collected for measurement of nitrogen balance.

Effect of Short-term and Long-term Lithium Treatment on Uptake and Retention of 10dine-131 in Rat Thyroid

No significant change occurred in the uptake by the thyroid of male Wistar rats of a standard dose of carrier-free 1311 administered intraperitoneally and its retention by the thyroid, as measured by biological and effective half-life, after feeding these rats a powdered pelleted diet containing lithium carbonate (I . I g per kg of diet) for 7 days. However, continuing this diet for 10 days inhibited thyroid uptake and increased the retention of 131 I. Uptake remained suppressed for up to 4 months after lithium treatment and continuing this treatment for 6 months did not result in any significant change in 1311 uptake by the thryoid. Lithium treatment for 10 days increased the biological and effective half-life of 13l I in the thyroid and this increase continued for the 6 months treatment period. The dose of 13l I delivered to the thyroid was significantly lower after 10 days and I month of lithium treatment but there was no change in this dose after 2 and 4 months of treatment. However, there was a significant increase after 6 months.

Insulin Affects Glucose Uptake by Muscle and Mammary Tissues of Lactating Ewes

Effects of insulin on exchanges of glucose across skeletal muscle and mammary tissue were measured in short-term studies in lactating ewes. Insulin secretion was suppressed by a primed/continuous infusion of somatostatin, then insulin was administered by continuous intravenous infusion of doses that were increased, in a step-wise manner, from 0 to 2 U h -I. Plasma glucose was maintained essentially constant by frequent monitoring and intravenous administration of exogenous glucose.

Development of a Radioimmunoassay for Plasma C-Peptide in Sheep: Kinetics of C-Peptide and Effects of Exogenous Growth Hormone and Glucose on Insulin and C-Peptide

An antiserum to purified bovine C-peptide was used to develop a sensitive radioimmunoassay for C-peptide in sheep. The assay was used to measure kinetics of C-peptide and insulin in non-pregnant and non-lactating sheep. Injected, purified C-peptide was distributed in pools comprising c. 11�4% of liveweight, the half time of C-peptide was estimated as 13�7 min and its clearance rate was c. 5 ml kg-I min-I. In lactating ewes exogenous recombinant bovine growth hormone (rebGH) increased both plasma insulin and C-peptide as did glucose challenge given before and during administration of rebGH. Estimates of insulin secretion rate in lactating ewes were c. 7 X 10-3 and 8�5 x 10-3 nmol kg-I min-I before and after glucose challenge prior to injections of rebGH. After 4 days of injection of rebGH, corresponding values were c. 8 x 10- 3 and 10 x 10-3 nmol min-I kg-I.