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PubMed1997

Comparative aspects of glucose tolerance in camels, sheep, and ponies.

The aim of the study was to gain informations about factors responsible for the higher level of plasma glucose in camels as compared to sheep and ponies. An intravenous glucose tolerance test was carried out with four camels, four ponies, and four sheep by infusing 1 mmol glucose per kg body weight intravenously within 3 min. Concentrations of glucose, insulin, and non-esterified fatty acids (NEFA) were estimated in venous plasma samples taken before and within 6 hr after infusion. Basal glucose values were higher in camels (7.1 +/- 0.3 mmol/l) than in ponies (4.2 +/- 0.4 mmol/l) and sheep (3.4 +/- 0.2 mmol/l). The rate of glucose elimination was markedly lower in camels (0.270 +/- 0.018 hr-1) than in sheep (0.804 +/- 0.036 hr-1) and ponies (0.858 +/- 0.084 hr-1). The insulin response after glucose infusion was more pronounced in ponies and sheep than in camels. Concentrations of NEFA in plasma dropped 30 min after the infusion in all species, however, NEFA level decreased slower in camels than in sheep and ponies. It is concluded that the markedly higher plasma concentration of glucose in camels compared to sheep and ponies may be caused by a poorer insulin response and/or a reduced tissue sensitivity to insulin.

Animals↗
PubMed1997

A comparative study on the functional properties of the wild European mouflon and domestic sheep hemoglobins.

The functional properties of Hb B of the wild European mouflon (Ovis gmelini musimon), Hb B of domestic sheep (Ovis aries), and Hb C isolated from anemic mouflon were investigated. Mouflon and sheep Hbs appear to be very similar in their response to organic anions and protons, whereas sheep Hb B displays an oxygen affinity lower than that of mouflon Hb B and sheep Hb A. Mouflon Hb B and Hb C, like sheep Hb A and Hb C, have similar efficiencies in transporting oxygen to the tissues. As in other ruminant Hbs, the effect of temperature on the oxygen affinity is slight. Data suggest that mouflon Hb B is not only structurally, but even functionally, more similar to sheep Hb A than to sheep Hb B.

Animals↗
PubMed1999

Cloning and expression analysis of the sheep ceruloplasmin cDNA.

The cDNA encoding sheep ceruloplasmin (sCP) was isolated from a sheep liver cDNA library. The cDNA contig was 3530 nucleotides in length and encoded a protein of 1048 amino acids. The deduced amino acid sequence showed a high degree of conservation (87%) when compared to the human ceruloplasmin (hCP) sequence. Northern blot analysis of sheep tissue revealed that the sheep ceruloplasmin gene (sCP) was expressed primarily in the liver, but low levels of mRNA were detected in the hypothalamus, spleen and uterus. No sCP mRNA was detected in the cortex, heart, intestine or kidney. Expression was not significantly affected by hepatic copper content. Northern blot analysis of sheep liver during development demonstrated little sCP expression during fetal life, but significant levels of mRNA were observed after birth. Significantly, the developmental expression pattern of sCP was closely correlated with that of the sheep Wilson disease gene (sATP7B), suggesting that the expression of the two genes may be coordinated to ensure that copper is supplied to apoceruloplasmin. Overall, the structure and expression of sCP appeared similar to other mammals, suggesting that abnormalities in CP were not responsible for the unusual sheep copper phenotype.

Age Factors↗
PubMed2002

Duration of viraemia infectious to Culicoides sonorensis in bluetongue virus-infected cattle and sheep.

The duration of viraemia infectious to Culicoides sonorensis (C. sonorensis) was evaluated in bluetongue virus (BTV)-infected sheep and cattle by feeding laboratory-reared C. sonorensis directly on the skin of ruminants that previously were infected with BTV by insect inoculation. The intervals after infection when infectious BTV and BTV nucleic acids were present in the blood of infected cattle and sheep, respectively, were determined by virus isolation and reverse transcriptase (RT)-nested polymerase chain reaction (PCR) assays. The presence of BTV in vector insects that fed on the BTV-infected cattle and sheep at 7, 21, and 49 days post-infection (p.i.) was also determined by virus isolation and RT-PCR assays. BTV was isolated from the blood of infected cattle for up to 49 days p.i., whereas it was not isolated from the BTV-infected sheep after 11 days p.i. In contrast, BTV nucleic acids were detected in the blood of infected ruminants for 111-222 days p.i. The maximal duration of viraemia that was infectious to C. sonorensis was 21 days p.i. of both cattle and sheep and, with the notable exception of one sheep at 21 days p.i., only ruminants whose blood contained BTV as determined by virus isolation were able to infect C. sonorensis after oral feeding. Data from this and previous studies indicates that viraemia is transient in BTV-infected ruminants, and that the RT-nested PCR assay provides a very sensitive and conservative test for the screening of cattle and sheep for the presence of BTV.

Animals↗
PubMed1998

Effects of insulin-like growth factor-1 on luteinizing hormone secretion in sheep.

Circulating insulin-like growth factor-1 (IGF-1) may be involved in nutritional modulation of reproductive status. Acute effects of IGF-1 on luteinizing hormone (LH) secretion were studied in two experiments, each using eight castrate male sheep surgically prepared with an elevated carotid artery, four with (E+) and four without (E-) subcutaneous oestradiol implants. Blood samples were taken every 12 min for 8 h at weekly intervals, with IGF-1 given at 4 h. In Experiment 1, sheep were fed to maintain live weight (maintenance) and IGF-1 doses tested were 25, 50, 100 and 150 micrograms kg-1 given via the carotid (i.c.). Plasma LH concentrations were 6.2 +/- 0.35 (E-) and 4.2 +/- 0.49 (E+) ng ml-1 pre-IGF-1, were increased after 25 micrograms kg-1 IGF-1 (E-, 15%; E+, 11%) but were either unaltered (E-) or decreased (E+, -16%) after 150 micrograms kg-1; thus, mean LH response was negatively related to IGF-1 dose (E-, b = -0.007, P < 0.01; E+, b = -0.011, P < 0.05). LH pulse frequencies (p.f.) were 4.6 +/- 0.42 (E-) and 3.9 +/- 0.35 (E+) pulses per 4 h pre-IGF-1, were unaltered after 25 micrograms kg-1 IGF-1, but were decreased after 150 micrograms kg-1 (E-, -33%; E+, -51%); thus, p.f. was also negatively related to IGF-1 dose (E-, b = -0.016, P < 0.01; E+, b = -0.019, P > 0.05). LH pulse amplitude and baseline were not significantly altered by IGF-1. Plasma glucose concentrations decreased after 100 and 150 micrograms kg-1 IGF-1 from 3.40 to 2.50 and 2.34 mmol l-1, respectively (SED 0.314, P < 0.001), but were not significantly altered after lower doses. Thus, hypoglycaemia caused LH inhibition after higher doses of IGF-1, which counteracted (E-) or overcame (E+) the stimulatory effects on LH seen after lower doses. In Experiment 2, sheep were fed 50% maintenance; saline vehicle i.c., then IGF-1 doses 25 and 50 micrograms kg-1 given i.c. or i.v. were tested. In E- and E+ sheep, respectively, mean LH pre-IGF-1 was 8.7 +/- 0.97 and 1.9 +/- 0.16 ng ml-1, p.f. was 3.8 +/- 0.44 and 0.8 +/- 0.44 pulses per 4 h, and amplitude was 3.6 +/- 0.49 and 0.4 +/- 0.08 ng ml-1. Saline vehicle had no effect on LH. IGF-1 at both doses and by both administration routes in E- sheep increased mean LH (22-29%, P < 0.001), and in E+ sheep increased mean LH (12-36%, P < 0.001), p.f. (94-219%, P < 0.001) and amplitude (125-803%, P < 0.01). Thus, low doses of peripherally-administered IGF-1 stimulated LH output in sheep, consistent with its putative physiological role as a nutritional modulator of reproduction.

Animals↗
PubMed1999

Distribution of galanin immunoreactivity in the sheep diencephalon.

Although the physiological role of galanin has been demonstrated in several endocrine regulations in sheep, the anatomical characteristics of this neuronal system has never been studied. The distribution of galanin-containing neurones was described by immunohistochemistry using galanin antiserum in the diencephalon of adult ewes, both ovariectomized or treated with colchicine. Galanin-immunoreactivity was found throughout the diencephalon. In the ovariectomized ewes, galanin-immunoreactive neurones were mainly observed in the medial preoptic area and the infundibular nucleus. The highest density of immunoreactive fibres was found in the external layer of the median eminence. Numerous galanin-immunoreactive fibres were also observed in the preoptic area, the mediobasal hypothalamus, the periphery of the supraoptic and the paraventricular nuclei. With colchicine treatment, the number of labelled neurones increased, and additional galanin-immunoreactive perikarya were observed in the bed nucleus of the stria terminalis, the lateral septum, the supraoptic, the paraventricular and the periventricular nuclei and the paraventricular nucleus of the thalamus. In the caudal part of the diencephalon, the density of labelled neurones was lower in both groups of animals than in other species studied. Regardless of treatment, labelling was not seen in the suprachiasmatic nucleus and only rarely in the ventromedial nucleus. These results describe, for the first time, the distribution of galanin-immunoreactive neurones in the sheep diencephalon. Compared to other species studied, distribution in the sheep diencephalon has several distinct differences. In ovariectomized animals, the medial preoptic area presents more labelled neurones in sheep than in monkeys, whereas in the supraoptic nucleus the density of labelled neurones is lower in sheep than in humans or opossums. After colchicine treatment only very few differences were observed between sheep and rats, but in contrast to other species, the suprachiasmatic nucleus of the sheep does not contain labelled neurones.

Animals↗
PubMed2002

New in vivo and ex vivo models for the experimental study of sheep scrapie: development and perspectives.

Sheep scrapie is a prototypical transmissible spongiform encephalopathy (TSE), and the most widespread of these diseases. Experimental study of TSE infectious agents from sheep and other species essentially depends on bioassays in rodents. Transmission of natural sheep scrapie to conventional mice commonly requires one or two years. In an effort to develop laboratory models in which investigations on the sheep TSE agent would be facilitated, we have established mice and cell lines that were genetically engineered to express ovine PrP protein and examined their susceptibility to the infection. A series of transgenic mice lines (tgOv) expressing the high susceptibility allele (VRQ) of the ovine PrP gene from different constructs was expanded. Following intracerebral inoculation with natural scrapie isolates, all animals developed typical TSE neurological signs and accumulated abnormal PrP in their brain. The survival time in the highest expressing tgOv lines ranged from 2 to 7 months, depending on the isolate. It was inversely related to the brain PrP content, and essentially unchanged on further passaging. Ovine PrP transgene expression thus enhanced scrapie disease transmission from sheep to mice. Such tgOv mice may bring new opportunities for analysing the natural variation of scrapie strains and measuring infectivity. As no relevant cell culture models for agents of naturally-occurring TSE exist, we have explored various strategies in order to obtain stable cell lines that would propagate the sheep agent ex vivo without prior adaptation to rodent. In one otherwise refractory rabbit epithelial cell line, a regulable expression of ovine PrP was achieved and found to enable an efficient replication of the scrapie agent in inoculated cultures. Cells derived from sheep embryos or from tgOv mice were also used in an attempt to establish permissive cell lines derived from the nervous system. Cells engineered to express PrP proteins of a specified sequence may thus represent a promising strategy to further explore, at the cellular level, various aspects of TSE diseases.

Alleles↗
PubMedDate not supplied

CT-Scan sheep and human inner ear morphometric comparison.

INTRODUCTION: Studies about the use of sheep in surgical training and experimental otologic surgery are rare. This study intends to contribute to the knowledge on this field. AIM: To study sheep inner ear structures using computerized tomography and serial cross-sections to collect more accurate morphometric data to compare sheep and human ears. MATERIAL AND METHODS: This descriptive study compared the inner structures of sheep and human ears. Measurements were made using computerized tomography, and they were stored in a DICOM compact disc for later analysis and manipulation, with a program used for medical image analysis (Osíris 4.16). RESULTS: Mean measures for sheep and human ears were found to be similar in this morphological study. Most structures (10 out of 15) maintained the 2/3 ratio of sheep to human ear. CONCLUSION: The results of this morphometric study of sheep ear are an important contribution to the development of an animal model to be used for surgical training and experimental otologic surgeries.

Animals↗
PubMed1975

Energy exchanges associated with eating and rumination in sheep given grass diets of different physical forms.

1. Energy exchanges and other physiological functions associated with eating and rumination were determined in four experiments. Sheep were given chopped, dried grass (DGC), pelleted, dried grass (DGP) or fresh grass (FGC). 2. In Expt I a preliminary study was made using all three diets. The dry matter (DM) of DGP was eaten significantly faster than that of chopped diets. Sheep salivated most during eating and ruminated longest when given DGC. Rates of contraction for the reticulo-rumen did not differ significantly between diets during idling and rumination, but were significantly faster during eating with DGP. The apparent energy costs of eating were 17, 109 and 176 kJ/kg DM eaten for DGP, DGC and FGC respectively, but these probably underestimated the true energy cost. 3. Expt 2 compared DGP and DGC at two levels of intake. The mean energy costs of eating DGP and DGC were 23.5 and 267 kI/kg DM respectively. The mean energy costs of eating between the energy cost of eating and the duration of the meal. The proportion of time the sheep spent ruminating DGC was about 23% but less than 1% for DGP. There was no significant relationship between heat production and the time spent ruminating. 4. In Expt 3 four sheep were offered fresh grass and, later, an equivalent DM intake after the material had been dried. The sheep ate the dried meal significantly faster. The mean energy costs of eating were 208 and 346 kJ/kg DM for DGC and FGC respectively. In this experiment the sheep ruminated significantly longer when given FGC, and the energy cost of rumination was 0.11 kJ/min. 5. Increases in heat production during and after fistula-feeding only 2-8% of those obtained during eating, indicating that nearly all the increase in heat production during eating could be attributed to the energy cost of eating per se. 6. The contribution of the energy costs of eating and rumination to the heat increment of feeding and the energy requirement for maintenance of sheep are discussed.

Animal Feed↗
PubMed2006

Detection of transgenic and endogenous plant DNA in digesta and tissues of sheep and pigs fed Roundup Ready canola meal.

The persistence of plant-derived recombinant DNA in sheep and pigs fed genetically modified (Roundup Ready) canola was assessed by PCR and Southern hybridization analysis of DNA extracted from digesta, gastrointestinal (GI) tract tissues, and visceral organs. Sheep (n = 11) and pigs (n = 36) were fed to slaughter on diets containing 6.5 or 15% Roundup Ready canola. Native plant DNA (high- and low-copy-number gene fragments) and the cp4 epsps transgene that encodes 5-enolpyruvyl shikimate-3-phosphate synthase were tracked in ruminal, abomasal, and large intestinal digesta and in tissue from the esophagus, rumen, abomasum, small and large intestine, liver, and kidney of sheep and in cecal content and tissue from the duodenum, cecum, liver, spleen, and kidney of pigs. High-copy chloroplast-specific DNA (a 520-bp fragment) was detected in all digesta samples, the majority (89-100%) of intestinal tissues, and at least one of each visceral organ sample (frequencies of 3-27%) from sheep and swine. Low-copy rubisco fragments (186- and 540-bp sequences from the small subunit) were present at slightly lower, variable frequencies in digesta (18-82%) and intestinal tissues (9-27% of ovine and 17-25% of porcine samples) and infrequently in visceral organs (1 of 88 ovine samples; 3 of 216 porcine samples). Each of the five cp4 epsps transgene fragments (179-527 bp) surveyed was present in at least 27% of ovine large intestinal content samples (maximum = 64%) and at least 33% of porcine cecal content samples (maximum = 75%). In sheep, transgene fragments were more common in intestinal digesta than in ruminal or abomasal content. Transgene fragments were detected in 0 (esophagus) to 3 (large intestine) GI tract tissues from the 11 sheep and in 0-10 of the duodenal and cecal tissues collected from 36 pigs. The feed-ingested recombinant DNA was not detected in visceral tissues (liver, kidney) of lambs or in the spleen from pigs. Of note, however, one liver and one kidney sample from the pigs (different animals) were positive for a 278-bp fragment of the transgenic cp4 epsps (denoted F3). Examination of genomic libraries from these tissues yielded no conclusive information regarding integration of the fragment into porcine DNA. This study confirms that feed-ingested DNA fragments (endogenous and transgenic) do survive to the terminal GI tract and that uptake into gut epithelial tissues does occur. A very low frequency of transmittance to visceral tissue was confirmed in pigs, but not in sheep. It is recognized that the low copy number of transgenes in GM feeds is a challenge to their detection in tissues, but there was no evidence to suggest that recombinant DNA would be processed in the gut in any manner different from endogenous feed-ingested genetic material.

Animal Feed↗
PubMed1980

The binding of lectins to sheep tissues and circulating cells: peanut agglutinin, a marker for presumptive T-lymphocytes.

A study was undertaken into the binding of 7 fluorescein (FITC)-labelled, lectins to sheep tissues and cells. Wheat germ agglutinin (WGA), conconavalin A (con A) and Ricinus communis agglutinin (RCA) bound strongly to all sheep tissues and circulating cells, while Dolichos biflorus (DBA) and Ulex europaeus (UEA) did not bind at all. Peanut agglutinin (PNA) and soybean agglutinin (SBA) bound to thymus and lymph node cell suspensions and to a proportion of circulating cells, but only weakly to the other sheep tissues tested. PNA and SBA bound to polymorphs and monocytes, making it necessary to treat whole blood with carbonyl-iron and magnet to remove the phagocytic cells before purfication of the peripheral blood leucocytes (PBL). PNA bound to 40 to 50% of carbonyl-iron treated PBL and to 65 to 70% of the cells in efferent popliteal lymph. Using a rhodamine-labelled anti-sheep lg reagent greater than 98% of PNA + cells in lymph and carbonyl-iron treated PBL were sIg-. Furthermore, using an FITC-labelled F(ab')2 anti-sheep Ig reagent, the sum of the 0/0 PNA+cells and sIg+ cells in individually labelled preparations was equal to the percentage of cells labelled when both reagents were added simultaneously. Cells binding PNA were found in more dense regions of buoyant density gradients and were less adherent to nylon wool than cells having surface immunoglobulin (sIg). Approximately 20 to 30% of PBL and 10 to 20% of the cells in lymph were PNA-/sIg- and these were termed 'null' cells. Although Con A induced sheep PBL to transform in tissue culture, PNA, SBA and WGA all failed to stimulate the incorporation of 3H-thymidine at the concentrations tested. Sorting lymph cells from BCG vaccinated sheep into PNA+ and PNA- subpopulations showed that the cells able to transform in vitro to the specific antigen, purified protein derivative (PPD) or the mitogen phytohemagglutinin (PHA) were in the PNA+ but not PNA- population.

Age Factors↗
PubMed1996

The PCR typing of MHC-DRB genes in the sheep using primers for an intronic microsatellite: application to nematode parasite resistance.

The strong association between polymorphisms in an intronic microsatellite and the coding sequences for (BoLA)-DRB3 genes, previously described for demonstrating alleles of class II major histocompatibility complex (MHC) in the cow, was examined in sheep to see if similar polymorphisms could be demonstrated in the DRB region of the MHC. The bovine primes LA53 and LA54, previously used to amplify the bovine DRB3 microsatellites, were used with DNA from Australian sheep, eight DRB alleles were identified by length polymorphisms of polymerase chain reaction (PCR) products amplified from the DRB microsatellite region. Incomplete amplification of both alleles was sometimes found for sheep DNA samples using bovine primers, so a modified primer (LA53b) was used, and found to amplify the microsatellite next to intron 2 of the MHC more reliably than the LA53 primer. Two additional primers (LA31 and LA32), used in amplification of the exon 2 region of bovine DRB3, were used in the sheep, and the PCR products were analysed by single-stranded conformation polymorphism (SSCP). These primers successfully amplified the variable region of the ovine DRB region coded by exon 2, and the SSCP technique demonstrated polymorphisms with sheep DNA. Family studies demonstrated the segregation of alleles, by amplification both of intronic microsatellites and of the exon 2 variable region. Close correspondence was found between the two regions for several alleles, suggesting that the intronic microsatellites were closely linked to DRB-variable region alleles. Three families of Merino sheep with different antibody responses to intestinal nematode parasites were examined. The sire group with the highest antibody levels possessed two microsatellite alleles of closely similar length (alleles 3 and 4) inherited from the sire and present in high frequency in the lambs. In contrast, the other two sires did not possess these two alleles and the alleles were in low frequency in their progeny. Further studies are required in unrelated sheep to confirm whether these two alleles are associated with resistance to nematode parasites.

Alleles↗
PubMed1987

Glomerulonephritis induced in sheep by immunization with human glomerular basement membrane.

The specificity of the anti-glomerular basement membrane (GBM) antibodies in experimental nephritis in sheep (Steblay's nephritis) was studied and compared with the specificity of antibodies in human anti-GBM nephritis (Goodpasture's syndrome). Sheep were injected monthly with isolated human GBM and antibody reactivities with isolated human and sheep GBM proteins were quantified with ELISA. Expectedly, the sheep had high titers of antibodies against several human GBM antigens. These antibodies remained for the most part in the circulation. In contrast, circulating antibody levels against sheep GBM antigens remained low for a long period of time, but a significant and progressive increase coincided with the development of acute nephritis. These antibodies accumulated in the kidneys of the nephritic sheep and could be eluted from diseased kidneys. They represent auto-antibodies immunologically cross-reacting with antigens of both sheep and human GBM. The specificity of auto-antibodies eluted from the kidneys was analyzed by immunoblotting and ELISA. The major populations reacted with one subunit, termed M2, of the globular domain of collagen IV. The same subunit contains the major antigen in Goodpasture's syndrome. It is concluded that the M2 subunit of the globular domain of collagen IV is recognized by IgG antibodies that primarily bind to the glomerular basement membrane in both Steblay's nephritis and Goodpasture's syndrome, indicating that it is a main nephritogen in both diseases.

Animals↗
PubMed2004

Replacing cows' with sheep's dairy fat lowers plasma cholesterol concentration in participants consuming dairy fat-rich diets.

OBJECTIVE: To determine the effects on plasma cholesterol concentration of replacing cows' dairy fat with sheep's dairy fat. DESIGN: Randomised crossover dietary intervention. SETTING: General community, Dunedin, New Zealand. SUBJECTS: Volunteer sample of 41 healthy adults with initial plasma cholesterol concentration between 4.8 and 7.8 mmol/l. INTERVENTIONS: Participants were asked to follow a self-selected low-fat background diet throughout the study to which, during each of the 2, 3-week dairy diets, they were asked to add sheep's or cows' dairy products. MAIN OUTCOME MEASURES: Energy and nutrient intakes, plasma triacylglycerol fatty acids, and plasma cholesterol. RESULTS: Energy and nutrient intakes on the sheep-dairy and cow-dairy diets were very similar, with total, saturated, monounsaturated and polyunsaturated fat contributing 34, 18-19, 9, and 3% of total energy intake, respectively. Participants consumed approximately 50 g/day of dairy fat on each diet. Replacing cows' with sheep's dairy fat led to a 0.33 (0.11-0.56, 95% CI) mmol/l decrease (6%) in plasma total cholesterol concentration, from 5.53 (0.90, s.d.) to 5.20 (0.90) mmol/l. Plasma low-density lipoprotein (LDL) cholesterol was 0.18 (0.02-0.33) mmol/l lower on the sheep-dairy diet as was the concentration of plasma high-density lipoprotein (HDL) cholesterol, 0.11 (0.02-0.20) mmol/l. The LDL to HDL cholesterol ratio at the end of the sheep-dairy diet, 2.91 (1.10), was not significantly different (P>0.05) from the cow-dairy diet, 2.73 (0.83). CONCLUSIONS: Within the context of a diet high in dairy fat (50 g/day), replacing cows' milk fat with sheep's milk fat leads to a small reduction in plasma cholesterol concentration, but no change in the ratio of LDL to HDL cholesterol.

Adult↗
PubMed2005

Unfolding of population structure in Baltic sheep breeds using microsatellite analysis.

Studies of domestic animals are performed on breeds, but a breed does not necessarily equate to a genetically defined population. The division of sheep from three native and four modern Baltic sheep breeds was studied using 21 microsatellite loci and applying a Bayesian clustering method. A traditional breed-wise approach was compared to that relying on the pattern of molecular diversity. In this study, a breed was found to be inconsistent with a distinct genetic population for three reasons: (i) a lack of differentiation between modern Baltic breeds, since the majority of the studied sheep formed a single population; (ii) the presence of individuals of foreign ancestry within the breed; and (iii) an undefined local Saaremaa sheep was referred to as a breed, but was shown to consist of separate populations. In the breed-wise approach, only the clearly distinct Ruhnu sheep demonstrated low within-breed variation, although the newly identified Saaremaa populations also have low variability. Providing adequate management recommendations for the Saaremaa sheep is not possible without further studies, but the potential harmful effects of inbreeding in the Ruhnu sheep could be reduced through the use of two genetically related Saaremaa populations. In other breeds, excessive crossing appears to be a larger concern than inbreeding. Assigning individuals into populations based on the pattern of genetic diversity offers potentially unbiased means of elucidating the genetic population structure of species. Combining these genetic populations with phenotypic and aetiological data will enable formulation of the most informed recommendations for gene resource management.

Animals↗
PubMed1988

Roles of insulin and growth hormone in the adaptations of fatty acid synthesis in white adipose tissue during the lactation cycle in sheep.

1. Lactation results in a substantial fall in the rate of fatty acid synthesis in sheep adipose tissue. 2. Maintenance of adipose tissue from non-lactating sheep in tissue culture for 24 or 48 h with insulin increased the rate of fatty acid synthesis. Dexamethasone, a glucocorticoid analogue, alone inhibited the rate of fatty acid synthesis, but enhanced the stimulatory effect of insulin. Growth hormone (somatotropin) antagonized the increase in the rate of fatty acid synthesis induced by insulin or insulin plus dexamethasone. 3. Maintenance of adipose tissue from lactating sheep in tissue culture resulted in a small increase in the rate of fatty acid synthesis after 24 h, and then a large increase in rate between 24 and 48 h of culture. The increase during the second 24 h period was dependent on the presence of insulin; this effect was enhanced by dexamethasone and inhibited by growth hormone. 4. The increase in the rate of fatty acid synthesis in tissue from non-lactating sheep and in tissue from lactating sheep during the major increase in rate was prevented by actinomycin D, an inhibitor of transcription. 5. Effects of insulin and growth hormone were observed with physiological concentrations of the hormones. 6. The study suggests that known changes in the serum concentrations of insulin and growth hormone are the primary causes of the changes in fatty acid synthesis in adipose tissue during the lactation cycle in sheep. 7. During lactation, adipose tissue becomes refractory to insulin in sheep; responsiveness is partly restored by tissue culture in the presence of insulin and dexamethasone.

1-Methyl-3-isobutylxanthine↗
PubMed1996

The role of sheep stroma in human haemopoiesis in the human/sheep chimaeras.

We have previously reported on the successful engraftment and long-term expression of human HSC (haemopoietic stem cells) in sheep following transplantation into pre-immune fetuses. The mechanism(s) underlying the support/maintenance of human haemopoiesis in sheep is not understood. In these studies we examined the ability of sheep stroma to support human haemopoiesis in vitro and compared this with support provided by human stroma. We found that, overall, human stroma was significantly more effective than sheep stroma in supporting human haemopoiesis in vitro. Nevertheless, stroma established from bone marrow of normal sheep was capable of lower-level support of the proliferation and multilineage differentiation of highly purified (CD34+, CD38-) preparations of human HSC in vitro. At lower concentrations, sheep stroma conditioned media (CM) induced human bone marrow mononuclear cells enriched for the CD34-positive fraction to enter the cell cycle at levels comparable to that of human stroma CM. However, unlike human CM, at higher concentrations, sheep CM inhibited human cells from initiating the cell cycle. These results provide a possible explanation for the long-term maintenance of low levels of human haemopoietic cell activity in human/sheep chimaeras.

Animals↗
PubMed1997

Comparative pharmacokinetics of ampicillin trihydrate, gentamicin sulphate and oxytetracycline hydrochloride in Nubian goats and desert sheep.

In this investigation the pharmacokinetics of three commonly used antibiotics, ampicillin trihydrate (10 mg/kg), gentamicin sulphate (3 mg/kg) and oxytetracycline hydrochloride (5 mg/kg), given intravenously, were each studied in five Nubian goats and five desert sheep. The pharmacokinetic parameters were described by a two-compartment open model. The results indicated that there were significant differences between the two species in some kinetic parameters of ampicillin and oxytetracycline but not gentamicin. Ampicillin elimination half life (t[1/2beta]) in goats (1.20 h) was shorter than that in sheep (2.48 h), and its clearance (Cl) significantly higher in goats (2921 mL/h x kg) compared to sheep (262 mL/h x kg) (P < 0.01). Ampicillin volume of distribution (Vd[area]) was found to be significantly larger in goats (5673 mL/kg) than in sheep (992 mL/kg) (P < 0.01). For oxytetracycline, the t(1/2beta) in goats (3.89 h) was significantly shorter than that in sheep (6.30 h) and the Cl value in goats (437 mL/h x kg) was significantly higher than in sheep (281 mL/h x kg). The results suggest that when treating sheep and goats, the pharmacokinetic differences between the two species must be considered in order to optimize the therapeutic doses of ampicillin and oxytetracycline.

Ampicillin↗