N.D. Costa

Effect of copper, zinc and cadmium on the promoter of selenoprotein W in glial and myoblast cells

Rat selenoprotein W (SeW) promoter activity was investigated using different concentrations of cadmium, copper, and zinc. Two fragments (404 and 1265 bp) of the SeW promoter, containing a single metal response element (MRE), were ligated into the multiple cloning site of a pGL3-Basic reporter plasmid. The constructs were transfected into cultured C6 (rat glial) and L8 (myoblast) cells and promoter activity measured by means of luciferase reporter gene fused to the SeW promoter fragments in the reporter plasmid. With post-transfection exposure of these cell lines to these metals, copper and zinc, but not cadmium, significantly increased promoter activity of the unmutated 1265 bp (not 404 bp) construct (p<0.05) only in the C6 cells. Mutation of the MRE sequence abolished promoter response to metal exposure but did not eliminate promoter activity. The results suggest that SeW expression in glial cells can be increased on exposure to copper and zinc and that this response is dependent on the MRE sequence present in the SeW promoter.

The composition and distribution of lipid granules in the rat ovary

Lipid granules in ovaries of immature rats were confined to the interstitial tissue, and comprised 70% cholesteryl esters and 20% triacylglycerols, the balance being phospholipid and free cholesterol. Following treatment with gonadotropin the interstitial granules disappeared as cholesteryl esters were hydrolysed, but reformed in the follicle as it developed, first in the theca, then in the outer granulosa and finally in the inner cells. The cholesteryl ester: triacylglycerol ratio fell during follicular growth, but in the corpus luteum the ratio in the widely distributed granules was 1:1. Esterified fatty acids in both cholesteryl esters and triacylglycerols became longer and more unsaturated as development progressed. The same progression of granules across the follicles was evident in ovaries of normal adult rats. We concluded that lipid granules in interstitial tissue supplied the substrates for synthesis of new cells in adjacent developing follicles, and those in corpora lutea were a prerequisite for steroidogenic competence.

Changes in coenzyme A and carnitine concentrations in superovulated rats

Changes in the concentrations of total coenzyme A, acetyl CoA, free carnitine and acetylcarnitine were measured in ovaries from immature rats before and after superovulation with 50 I.U. pregnant mares serum gonadotropin. In addition, the concentrations of total CoA and total acid-soluble carnitine were measured in liver, adrenal glands and skeletal muscle from the same rats. Ovarian concentrations of total CoA, free carnitine and acetylcarnitine increased 3-fold on gonadotropin stimulation, whereas there was no marked change in total CoA and acid-soluble carnitine concentrations in the other organs. In ovary, the ratio of free CoA to acetyl CoA was about 2:1 during the growth period of follicular development and during active steroidogenesis in the luteal phase, but less than 1 when replication stopped and ovulation occurred. These results show that during periods of high energy demand the ovary has a good capacity to accommodate fatty acid oxidation, and supports the evidence that fatty acids are the major source of reducing equivalents for steroidogenesis at these times.

Carnitine and the development of steroidogenesis in rat ovary

We have measured the concentrations of carnitine and the activities of the carnitine acyltransferases in immature rat ovaries which had been stimulated to develop with pregnant mare gonadotropin. The concentration of carnitine increased from 700 nmol/g wet wt. to 1 mumol/g wet wt. of ovary after hormonal administration and the activities of the acyltransferases also rose. These increases corresponded with cell division. After replication had ceased, when the new cells were emerging and actively making steroid hormones, the concentration of carnitine and activities of the transferases fell.

Associations between body condition, rumen fill, diarrhoea and lameness and ruminal acidosis in Australian dairy herds

AIMS: To investigate associations between ruminal acidosis and body condition score (BCS), prevalence of poor rumen fill, diarrhoea and lameness in dairy cows in New South Wales and Victoria, Australia. METHODS: This was a cross-sectional study conducted in 100 dairy herds in five regions of Australia. Feeding practices, diets and management practices of herds were assessed. Lactating cows within herds were sampled for rumen biochemistry (n = 8 per herd) and scored for body condition, rumen fill and locomotion (n = 15 per herd). The consistency of faecal pats (n = 20 per herd) from the lactating herd was also scored. A perineal faecal staining score was given to each herd. Herds were classified as subclinically acidotic (ACID), suboptimal (SO) and non-acidotic (Normal) when ≥3/8 cows per herd were allocated to previously defined categories based on rumen biochemical measures. Multivariate logistic regression models were used to examine associations between the prevalence of conditions within a herd and explanatory variables. RESULTS: Median BCS and perineal staining score were not associated with herd category (p >0.05). In the multivariate models, herds with a high prevalence of low rumen fill scores (≤2/5) were more likely to be categorised Normal than SO with an associated increased risk of 69% (p = 0.05). Herds that had a greater prevalence of lame cows (locomotion scores ≥3/5), had 103% higher risk of being categorised as ACID than SO (p = 0.034). In a multivariate logistic regression model, with herd modelled as a random effect, an increase of 1% of pasture in the diet was associated with a 5.5% increase in risk of high faecal scores (≥4/5) indicating diarrhoea (p = 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: This study confirmed that herd categories based on rumen function are associated with biological outcomes consistent with acidosis. Herds that had a higher risk of lameness also had a much higher risk of being categorised ACID than SO. Herds with a high prevalence of low rumen scores were more likely to be categorised Normal than SO. The findings indicate that differences in rumen metabolism identified for herd categories ACID, SO and Normal were associated with differences in disease risk and physiology. The study also identified an association between pasture feeding and higher faecal scores. This study suggests that there is a challenge for farmers seeking to increase milk production of cows on pasture to maintain the health of cattle.

Rural veterinary services in Western Australia: Part B. Rural practice

OBJECTIVE To determine the current status of rural veterinary services in Western Australia. PROCEDURE A questionnaire was sent to all eligible rural practitioners registered in 2006 and the replies were transferred to Microsoft Excel for analysis. RESULTS Of the rural practitioners invited to participate in the survey replies were received from 67%. There were equal numbers of females and males. Their mean age was 44 years. Ninety per cent of respondents considered knowledge gained as an undergraduate was sufficient to equip them for practice, but only 60% considered their practical skills adequate. Thirteen per cent of those in rural practices in 2005 had left by 2006. Eighty-nine per cent of respondents were in mixed practice, the balance in specific species practice, such as equine, large animal and production animal consultancy. The majority of rural practitioners relied on servicing companion animals for their viability; 7% earned their income from servicing production animals only. Seventy per cent utilised merchandising and the sale of pet foods to supplement the income received from the traditional veterinary services and 34% found it necessary to earn an independent income. A quarter considered that rural practice did not have a future. CONCLUSION The majority of rural practitioners in Western Australia depend on companion animals, not production animals, to remain viable, with very few operating production animal services. Poor remuneration is a major reason why veterinarians leave rural practice, and many find it necessary to supplement their income or develop an independent income.

Steroidogenesis despite a variant metabolism in primary cultures of pig granulosa cells

Enzymic changes in primary cultures of granulosa cells over 9 days were measured and compared with changes occurring during follicular development in vivo. Characteristic of in vivo development of granulosa cells was a large increase in activities of the NADP+-dependent isocitrate, glucose-6-phosphate dehydrogenases and malic enzyme, and smaller increases in the activities of the NAD+-dependent lactate and malate dehydrogenases. In vitro, the NAD+-dependent dehydrogenases increased in activity, while the NADP+-dependent enzymes showed transient or no changes. Despite the uncharacteristic metabolism, granulosa cells in culture could synthesize steroids. Our results suggest that the cells in vitro and in vivo use different metabolic pathways to support syntheses dependent on reducing equivalents.

Rural veterinary services in Western Australia: Part A. Government veterinary services.

OBJECTIVE To determine the status of rural veterinary services in Western Australia. PROCEDURE Two questionnaires were mailed to eligible, registered veterinary surgeons in Western Australia in 2006. The first was mailed to government veterinarians and the second to private practitioners in rural practice. Part A presents the replies from government veterinary officers and Part B the replies from rural practitioners. Replies were transferred to Microsoft Excel for analysis. RESULTS Sixty-seven per cent of government veterinary officers responded to the questionnaire. Eighty per cent of these had been in the service for 20 years or more and their average age was 54. Work with sheep and beef cattle occupied 75% of their time, with dairy cattle receiving 10% and pigs and poultry less than 10%. The majority of respondents reported changes in the attitude of farmers to the service as a result of rural recessions and the decision to make a direct charge for government veterinary services. Although most respondents thought that the government veterinary service would continue in the future there were differences of opinion as to what form that would take. CONCLUSION Government veterinary services in Western Australia are undergoing major changes, with the service decreasing in size and scope. Recently the Department of Agriculture has been renamed the Department of Agriculture and Food and it is likely that the role of its veterinary officers will change accordingly.

The Effect of Monensin Sodium on Trace Element Status of Cattle at Pasture

When fed to sheep and cattle the carboxylic ionophore, monensin sodium, can produce a wide variety of effects on ruminai function with the main effect being a decrease in the acetate:propionate ratio1. Monensin has been used to increase feed conversion efficiency in cattle and sheep fed high concentrate diets and also to improve average daily gain in cattle at pasture2. Although the improvement in performance has been attributed mainly to shifts in ruminal fermentation towards an increase in propionate production, this increase alone can not account for all the improvement in productivity1. More recently monensin has been shown to increase retention of Se and Zn in steers3. Monensin supplementation in sheep increases Mg, P and Zn retention and Zn absorption4 and also increases blood glutathione peroxidase activity5. The increase in retention of selenium in steers3 and of zinc in lambs4 observed during momensin supplementation is of sufficient magnitude to suggest that monensin may help alleviate problems of dietary deficiency of selenium and zinc. Ruminal delivery devices (RDD) designed to release 150 mgs of monensin per day for 150 days provided a means for assessing the hypothesis that monensin could significantly alter trace element status in cattle at pasture.

Lupinosis and reproduction reduce the wool growth of Merino ewes

Summary. Lupinosis was induced in Merino ewes by subcutaneous injections of phomopsins. Liver damage and impairment of liver function was measured by increases in plasma activities of glutamate dehydrogenase and gamma glutamyl transferase, plasma concentrations of bilirubin, and plasma clearance of bromosulfthalein. The wool growth of the ewes during and after exposure to phomopsins at different periods relative to mating was measured, and the impact of lupinosis on annual wool production assessed. Phomopsin administration decreased the length of staple grown during, and for at least 6 weeks after, exposure to phomopsins. Mean fibre diameter of wool grown during this time was also reduced. Annual wool production of the ewes was affected by exposure to phomopsins, with effects noted on fleece weight, yield, fibre diameter, strength and position of break. These effects were minor and varied between experiments. The adverse effects of reproduction on annual wool production were more significant than those of phomopsins.