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PubMed1992

Secondary cytotoxicity of cross-linked dermal sheep collagens during repeated exposure to human fibroblasts.

We investigated commercially available dermal sheep collagen either cross-linked with hexamethylenediisocyanate, or cross-linked with glutaraldehyde. In previous in vitro studies we could discriminate primary, i.e. extractable, and secondary cytotoxicity, due to cell-biomaterial interactions, i.e. enzymatic actions. To develop dermal sheep collagen for clinical applications, we focused in this study on the release, e.g. elimination, of secondary cytotoxicity over time. We used the universal 7 d methylcellulose cell culture with human skin fibroblasts as a test system. Hexamethylenediisocyanate-cross-linked dermal sheep collagen and glutaraldehyde-cross-linked dermal sheep collagen were tested, with intervals of 6 d, over a culture period of 42 d. With hexamethylenediisocyanate-cross-linked dermal sheep collagen, cytotoxicity, i.e. cell growth inhibition and deviant cell morphology, was eliminated after 18 d of exposure. When testing glutaraldehyde-cross-linked dermal sheep collagen, the bulk of cytotoxic products was released after 6 d, but a continuous low secondary cytotoxicity was measured up to 42 d. As a control, non-cross-linked dermal-sheep collagen was tested over a period of 36 d, but no secondary cytotoxic effects were observed. The differences in release of secondary cytotoxicity between hexamethylenediisocyanate-cross-linked dermal sheep collagen, glutaraldehyde-cross-linked dermal sheep collagen and non-cross-linked dermal sheep collagen are explained from differences in cross-linking agents and cross-links obtained. We hypothesize that secondary cytotoxicity results from enzymatic release of pendant molecules from hexamethylene-diisocyanate-cross-linked dermal sheep collagen, e.g. formed after reaction of hydrolysis products of hexamethylenediisocyanate with dermal sheep collagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Study on tandem repeat sequence variation in sheep mtDNA D-loop region.

The 75-nt-long tandem repeat sequence in the control region of mtDNA of 77 individuals, of which 69 were from different indigenous sheep breeds in China and 8 were from imported breeds, was sequenced and analyzed to investigate the origin and differentiation of Chinese indigenous sheep breeds and also the genetic diversities and relationships among them. A total of 28 variable sites were detected within 309 repeated sequences, among which 7 sites were singleton variable sites with two variants, 1 site was a singleton variable site with three variants, and 20 sites were parsimony informative sites with two variants. A total of 63 haplotypes were sorted from 28 polymorphic sites, among which two main and basic haplotypes, namely, Hap 1 and Hap 3 were present at a much higher proportion, at 12.94% and 30.42%, respectively. It could be inferred that Chinese indigenous sheep breeds originated from two maternal ancestors because of the maternal inheritance characteristics of the mtDNA. Altay sheep and Kazakstan sheep are closely related and do not differentiate significantly. Mongolian sheep and Ujumuqin sheep also share a close relationship. Tibetan sheep, Mongolian sheep, and Ujumuqin sheep have lower genetic diversity than Altay sheep and Kazakstan sheep.

Animals↗
PubMedDate not supplied

Biological and clinical responses of west African sheep to Crimean-Congo haemorrhagic fever virus experimental infection.

West African sheep appear to play a central role as virus hosts in the maintenance cycle of Crimean-Congo haemorrhagic fever (CCHF) virus in endemic areas and also because of their role as a principal host of the CCHF virus tick vector. In an effort to clarify CCHF epidemiological significance in sheep, we studied the biological and clinical aspects of sheep experimentally infected with CCHF virus. West African sheep breeds were infected either by intraperitoneal inoculation or by infestation with experimentally CCHF-virus-infected ticks (Hyalomma truncatum). A total of 17 sheep including controls as well as 5 lambs from their progeny were monitored. A moderate but constant fever was observed (39.7 degrees C +/- 0.3) which correlates with the viraemia. Virus was reisolated from blood samples taken from day 3 to day 9 postinfection (p.i.) at a mean titre of 3.3 log LD50/ml. The virus was detected for a period of time of 7 days in non-immune sheep and for less than 4 days in previously immunized sheep. In non-immune sheep, antibody detected by ELISA showed an IgM response on day 7 p.i., followed by an IgG response one day later. Five infected sheep, surveyed for liver and kidney biological markers, showed hepatic dysfunction with a moderate serum aspartate transferase rise to 210 U/l. Out of four sheep tested for blood markers, two showed an abnormal blood cell count, with marked neutrophilia of up to 63% lasting for two weeks. Infected pregnant ewes produced antibodies in their milk at a significant titre (1:1,000), and antibodies were recovered in the sera of nursing lambs from their first meal to 50 days after birth. These findings are discussed; they demonstrate that, in spite of a high turnover of local sheep herds (median age of 3 years) and long-term CCHF antibody persistence (> 3 years), sheep can be infected and efficiently transmit the virus at least once in a lifetime.

Africa, Western↗
PubMed2002

Genetic polymorphism of apolipoprotein C polypeptide in native Asian sheep.

The frequency distributions of apolipoprotein C alleles in native Asian sheep (Bengal, Kagi, Lampuchhre, Vietnamese, Myanmar, Baruwal, Bhyanglung, Khalkhas, and Kuwait) were determined using a one-dimensional polyacrylamide gel isoelectric-focusing immunoblotting technique. Among these Asian sheep, the genetic locus consisted mainly of two common APOC*1 and APOC*3 alleles. The Baruwal sheep most frequently possessed APOC*1 (0.9881), showing significant differences from all other Asian sheep in allele frequency (0.7195-0.9032, P < 0.02). Compared with European sheep tested previously, these Asian sheep had significantly higher frequencies of APOC*1 (0.7828 and 0.7127 averages, P < 0.0005) and APOC*3 (0.2162 and 0.11 averages, P < 0.0001). In particular, APOC*2 was detected at an extremely low frequency (0.0025) in the Khalkhas sheep only, and was uncommon in all Asian sheep (0.001 average), in contrast with the 0.1773 average of European sheep (P < 0.00001). This finding suggests that APOC*2 is exceedingly rare in Asian sheep. With the exception of triglycerides and VLDL cholesterol in the Vietnamese sheep, no phenotypic effects on plasma lipid and lipoprotein levels in the Asian sheep tested were seen.

Animals↗
PubMed1975

Purification, properties and kinetics of sheep and human renin substrates.

Sheep plasma renin substrate was purified 1,200-fold by using nephrectomised sheep plasma, followed by DEAE-Sephadex chromatography and gel filtration. The purified substrate contained 8 mu-g angiotensin II/mg protein and had an estimated molecular weight of 52,000. The kinetic characteristics of the purified substrate were identical both to those of unpurified nephrectomised sheep plasma and to normal sheep plasma substrates. At pH 7.5, K-m of the human renin-sheep substrate reaction was 0.29 mu-M and for sheep renin-sheep substrate, 2.0 mu-M. Sheep substrate was susceptible to peptic digestion with generation of pepsitensin. Human renin substrate was less readily purified. DEAE-Sephadex chromatography of plasma from pregnant women at 36-40 weeks' gestation produced a 70-fold increase in purity (0.9 mu-g angiotensin II/mg protein). No further increase was achieved with gel filtration. Human renin substrate behaved as a larger (mol. wt. 82,000) more anionic protein than sheep substrate and was resistant to the proteolytic actions of both pepsin and sheep renin. K-m for the human renin-human substrate reaction was high and could not be accurately determined (range 3-8 mu-M, mean 5.7 mu-M). The presence of human substrate in a human renin-sheep substrate system did not alter the measured initial velocity. In both sheep and man, the normal concentration of renin substrate is considerably less than K-m and must therefore be considered a determinant of angiotensin production rate in vivo.

Angiotensin II↗
PubMed2003

Induction of allergic inflammation in the lungs of sensitized sheep after local challenge with house dust mite.

BACKGROUND: Previous sheep models of asthma are based on sheep sensitized to nematode (Ascaris) allergens and these have been used to evaluate the physiological and pharmacological effects of potential anti-asthma agents. The immunological mechanisms associated with the allergic response in sheep lungs has not been examined in detail. OBJECTIVE: To develop an experimental sheep model of allergic lung inflammation based on a relevant major human allergen, house dust mite, and to define the immunological features of the allergic response in this model. METHODS: Sheep immunized subcutaneously with solubilized house dust mite extract were given a single bronchial challenge with house dust mite. Bronchoalveolar lavage (BAL) and peripheral blood leucocytes were collected before and after challenge for flow cytometry, and tissue samples were taken post-mortem (48 h post-challenge) for histology and immunohistochemical analyses. RESULTS: Immunizations with 50 microg house dust mite induced an allergen-specific IgE response in 50 to 60% of sheep (allergic sheep), with higher antigen doses increasing specific IgG1 but not IgE. Lung challenge of allergic sheep with house dust mite led to the initial recruitment of neutrophils (at 6 h post-challenge) followed by eosinophils and activated lymphocytes into the lung tissue and BAL, similar to the late-phase allergic response seen in human asthma. Eosinophil recruitment peaked at 48 h post-challenge, representing 10 to 33% of BAL leucocytes in allergen-challenged allergic sheep compared to 0 to 3% in allergen-challenged control (naïve) sheep. Lymphocytes recovered from the lung after allergen challenge were enriched for CD4+ T cells and were more activated than lymphocytes in blood. There was significant down-regulation of CD62L (L-selectin) and CD49d (VLA-4) expression after allergen challenge on BAL eosinophils and lymphocytes compared to blood. In addition, VCAM-1 (ligand for VLA-4) was up-regulated on blood vessels of allergen-challenged lungs. Eosinophils, CD4+ T cells and CD45R+ B cells were the most prominent leucocytes found in lung tissue 48 h after allergen challenge. CONCLUSION: This study demonstrates, for the first time, the ability of house dust mite to induce allergic responses in sheep lungs. This novel sheep model of allergic lung inflammation using relevant human allergens, exhibits similarities to human asthmatic disease and will be a useful tool for studies of the immunological and physiological mechanisms of allergic asthma.

Animals↗
PubMed2001

A previous infection with Toxoplasma gondii does not protect against a challenge with Neospora caninum in pregnant sheep.

Sheep immunized with Toxoplasma gondii (Toxovax) prior to pregnancy were tested for their ability to withstand a challenge at 90 days gestation with 107 Neospora caninum (NC1) tachyzoites. The antibody responses in sheep following immunization with T. gondii were specific for T. gondii whereas peripheral blood mononuclear cells responded to both T. gondii and N. caninum antigen in vitro. This suggested that there was induction of crossreactive immune recognition in the sheep, at least at the cellular level. Following challenge of sheep at mid-gestation with N. caninum, no febrile responses were recorded in the group of sheep which had previously received Toxovax while significant febrile responses were recorded in the group of sheep which received N. caninum challenge alone. Antibody responses to N. caninum developed in all sheep following N. caninum challenge and antibody responses to T. gondii were boosted in the group of sheep which had previously been immunized with Toxovax. No antibodies to T. gondii were observed in the sheep which received the N. caninum challenge alone. Peripheral blood mononuclear cells from both groups of sheep responded to T. gondii and N. caninum antigen in vitro and interferon gamma was present in the cell-free supernatant from activated cells. However despite evidence of the induction of crossreactive immunity between T. gondii and N. caninum, this was not sufficient to prevent foetal death. The group of sheep which had received Toxovax prior to pregnancy and the group of sheep which only received the N. caninum challenge experienced 100% foetal death compared with 0% in the unchallenged control group. Vaccination prior to pregnancy with Toxovax did protect against foetal death following oral challenge at 90 days with 2000 T. gondii oocysts which caused 100% foetal death in a control challenge group.

Animals↗
PubMed2002

Occurrence and distribution of infection-specific PrP in tissues of clinical scrapie cases and cull sheep from scrapie-affected farms in Shetland.

The prion protein (PrP) genotypes of all cull sheep originating from four scrapie-affected farms in Shetland in 1998-1999 were determined and a representative sample of the different genotypes was selected for necropsy. Samples of brain and selected viscera were removed from 159 such sheep aged 2-11 years. These samples were examined immunohistochemically and by Western blotting for infection-specific forms of PrP. None of the sheep bearing the following genotypes showed any evidence of PrP accumulation in brain, intestine, selected lymph nodes or the cranial mesenteric ganglia: ARQ/ARQ (n = 41), ARQ/ARH (n = 12), ARH/ARH (n = 2), ARQ/ARR (n = 24), ARR/ARR (n= 2). In five of 71 sheep bearing a single VRQ allele, PrP accumulation was detected immunohistochemically in viscera or brain, or both. These results suggested that only a small proportion of susceptible sheep showed evidence of infection (accumulation of PrP) on the farms studied, and that even sheep of the most susceptible genotype (VRQ/VRQ) did not invariably develop disease in an infected environment. Furthermore, there was no evidence that, in sheep of semi-resistant or fully resistant genotypes, infection could be sequestered within the lymphoreticular system or peripheral nervous system and thereby provide a possible "carrier" source of infection. Rather, the data suggested that some sheep, possibly because they had been exposed to a relatively low infective dose, became infected and accumulated the infective agent over a protracted pre-clinical phase of the disease. Such sheep might be potentially infective for many years. In two VRQ/ARR genotype sheep, PrP was confined to the brain. Infection-specific PrP was also confined to the brain in two of 24 clinical cases of VRQ/ARQ scrapie. Thus, direct neuroinvasion, apparently without a prior phase of replication in the lymphoreticular system, occurred in a proportion of VRQ/ARQ sheep. Possibly it may occur in all sheep of the VRQ/ARR genotype. The factors responsible for direct neuroinvasion are not understood. However, it cannot be attributed to genotype alone.

Animals↗
PubMed1988

Studies in sheep on the absorption of magnesium from a low molecular weight fraction of the reticulo-rumen contents.

1. Six sheep, three animals per diet, were prepared with rumen fistulas and fed on frozen grass or grass-maize pellets to give magnesium intakes of 1.79 and 2.23 g/d respectively. The mean apparent availabilities of Mg in sheep fed on frozen grass and grass-maize pellets were 0.31 and 0.36 respectively. 2. The rumen contents were fractionated by straining the digesta through linen cloth and then differentially centrifuged to give 20,000 g and 100,000 g supernatant fractions. 3. In all sheep, regardless of diet, at 4 and 16 h after a meal, 50 and 60% respectively of the total Mg in the rumen contents was found in strained rumen fluid while 30 and 38% respectively of the total Mg was found in the 100,000 g supernatant fraction. 4. The net absorption of Mg from the temporarily isolated and washed reticulo-rumen was studied using either 100,000 g supernatant fractions of rumen contents from sheep fed on one or other of the two diets, or inorganic buffers containing the same concentration of Mg and other macroelements. 5. The Mg was readily absorbed from the 100,000 g supernatant fraction placed in the rumen with the rate of absorption being 7.3 mumol/l per min (505 mg/d) from the supernatant fraction obtained from sheep fed on frozen grass and 11.3 mumol/l per min (781 mg/d) from the supernatant fraction from sheep fed on grass-maize pellets. In the same sheep, the previously described rates of Mg absorption from the 100,000 g supernatant fraction were similar to those obtained from the comparable inorganic buffers. 6. The effects of varying concentrations of potassium and sodium on the net absorption rate of Mg (as 24Mg) and on the one-way efflux of Mg (as 28Mg) from supernatant fractions or rumen fluid and inorganic buffers were investigated using the temporarily-isolated and washed rumen in three sheep. Although the net absorption rate of 24Mg from supernatant fractions or buffers containing similar K concentrations varied significantly between sheep, a similar percentage decrease in the absorption rates of both 24Mg and 28Mg was found for each sheep as the K concentration was increased. 7. One pair of sheep was fed on the frozen grass and the other pair was fed on the grass-maize pellets. Their daily intakes of K were then increased to 50 g/d for 14 d by intrarumen infusion of potassium chloride. In three of the four sheep the plasma Mg concentration fell within 12 h of the start of the KCl administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Absorption↗
PubMed1996

Digestion of 14C-labelled condensed tannins from Desmodium intortum in sheep and goats.

An experiment was conducted to investigate the metabolism of condensed tannin (CT) in sheep and goats offered a mixture of Digitaria decumbens (700 g/kg) and Desmodium intortum (300 g/kg) hay. Radioactive 14CO2 was used to label CT in young growing desmodium plants, [14C]CT was extracted, purified and infused intraruminally, and the metabolism of [14C]CT was followed in the rumen and lower digestive tract of both species. Digestion of DM, organic matter (OM), cell-wall constituents (CWC), N and the efficiency of rumen microbial synthesis were determined using a continuous intraruminal infusion of 51Cr EDTA, YbCl3 and Na235SO4. The measurements taken for sheep and goats respectively were: intake, 21 and 30 g/kg0.9 per d; digestibilities (g/g) of DM, 0.566 and 0.505; OM 0.578 and 0.508; neutral-detergent fibre, 0.584 and 0.532; and acid-detergent fibre, 0.535 and 0.435. None of these measurements was significantly different (P > 0.05) between animal species. There was an apparent net gain in lignin across the rumen and whole intestinal tract for both animal species (19 and 29% for sheep and goats respectively). There were no significant differences between sheep and goats (P > 0.05) detected for any measurements of N excretion and utilization. The overall efficiency of N digestion and utilization was also similar between species. The routes of CT metabolism were compared for both colorimetric estimates (butanol-HCl) of dietary CT (DCT) and the specific radioactivity of [14C]CT in digesta (abomasum) and excreta (urine and faeces) of both sheep and goats. [14C]CT showed total losses of 57 and 56% in sheep and goats respectively whilst losses of DCT of 71 and 70% were detected with butanol-HCl in sheep and goats respectively. The apparent losses of DCT across the rumen of sheep and goats were 12 and 9% whilst higher losses (49 and 42% for sheep and goats respectively) were observed for [14C]CT. Losses of DCT in the lower intestinal tract accounted for 69 and 71% of the total CT leaving the abomasum. By comparison, only 40 and 35% of [14C]CT was lost during intestinal passage in sheep and goats respectively. It was concluded that the infused free [14C]CT interacted with DCT and entered the protein and fibre-bound DCT pools. The loss of DCT during passage through the intestines was considered to be a consequence of either absorption of free CT or the degradation products of CT. It was assumed that free CT arose in the lower gastrointestinal tract from protein-CT and fibre-CT dissociation to be digested and/or absorbed. The higher recoveries of [14C]CT in faeces (32 and 35%) compared with DCT (27 and 26%) for sheep and goats respectively) were associated with the excretion of [14C] degradation products or conjugates which were not reactive to butanol-HCl. It was concluded that both methods (butanol-HCl and labelling CT with 14C) detected a substantial disappearance of CT (free, protein, and fibre-bound) during metabolism in the gastrointestinal tract in sheep and goats.

Animals↗
PubMed2003

Intravenous and intrapulmonary administration of honey solution to healthy sheep: effects on blood sugar, renal and liver function tests, bone marrow function, lipid profile, and carbon tetrachloride-induced liver injury.

Safety of intravenous (i.v.) or intrapulmonary administration of different concentrations of honey and their effects on blood sugar, renal and liver function tests, bone marrow function, lipid profile, and carbon tetrachloride (CCl(4))-induced liver damage were studied. Healthy sheep of either sex, 6-8 months old, were assigned randomly into the following groups: sheep received i.v. infusion of 5% honey in normal saline at 10-day intervals for 50 days and were compared with sheep that received 5% dextrose; sheep received higher doses of honey (50 g of honey) by i.v. infusion daily for 10 days; sheep received four higher doses of honey (80 g each dose) for 2 weeks; sheep received subcutaneous injection of CCl(4) after four doses of i.v. infusion of 80 g of honey, and estimations of serum gamma-glutamyl transpeptidase (SGGT), serum glutamic oxaloacetic transaminase (SGOT), and serum glutamate pyruvate transaminase (SGPT) were performed daily for 10 days postinjection; sheep received i.v. infusion of 40 g of honey, and blood sugar estimation was performed for 3 h at 30-min intervals after infusion and compared with sheep that received 5% dextrose; sheep received rapid i.v. injection of 40% honey or 40% dextrose, and blood sugar was estimated before and after injection; sheep received various concentrations of honey in distilled water (0.5 mL/1.5 mL, 0.75 mL/1.75 mL and 1.2 mL/2.2 mL), and blood sugar estimation was performed before and after inhalation. Results showed that i.v. or intrapulmonary administration of honey did not cause any adverse effect. Intravenous delivery of honey by slow infusion caused improvement of renal and hepatic function, bone marrow function, and lipid profile. It reduced SGOT, SGPT, triglyceride, cholesterol, blood urea nitrogen, and blood sugar and elevated serum protein, serum albumin, hemoglobin, white blood cell, and neutrophil percentage. Similar results were obtained with the use of higher doses of honey. CCl(4) caused mild elevation of SGPT and SGGT and lowering of SGOT in sheep that received repeated i.v. administration of honey before administration of CCl(4), whereas in control sheep CCl(4) caused significant elevation of all the liver enzymes. Intravenous infusion of 40 g of honey caused elevation of blood sugar for 90 min postinfusion, whereas it decreased blood sugar at 2 and 3 h postinfusion as compared with fasting blood sugar. Dextrose caused significant elevation of blood sugar at all time intervals. Similar results were obtained with the use of 10% dextrose or 80 g of honey. Addition of honey to dextrose caused less hyperglycemia as compared with dextrose alone. Acute injection of 20 mL of 40% dextrose significantly elevated blood sugar for 3 h postinjection, whereas little elevation in blood sugar was obtained after injection of 40% honey; the difference between honey and dextrose was significant. Inhalation of honey caused significant lowering of blood sugar during and after inhalation as compared with fasting blood sugar and water inhalation. The effect was greater with a higher concentration of inhaled honey. It might be concluded that slow i.v. infusion or rapid i.v. injection of honey in different concentrations was safe and could lower blood sugar and improve renal, hepatic, and bone marrow functions and lipid profile. Intravenous honey had a hepatoprotective effect against CCl(4)-induced liver injury. Inhaled honey was safe and reduced blood sugar significantly.

Administration, Inhalation↗
PubMedDate not supplied

Genetic distinctiveness of endangered dwarf blue sheep (Pseudois nayaur schaeferi): evidence from mitochondrial control region and Y-linked ZFY intron sequences.

To elucidate the controversial systematic relationship of blue sheep (Pseudois nayaur) and endangered dwarf blue sheep, we sequenced part of the mtDNA control region and Y-linked ZFY intron, and carried out phylogenetic analyses. Mitochondrial results revealed that the dwarf blue sheep is a strongly supported monophyletic group, with an average of 12.21% sequence divergence from the blue sheep. This is the first genetic evidence for the distinctness of the dwarf blue sheep. ZFY intron results showed an average of 0.51% sequence divergence, and one shared haplotype between the dwarf blue sheep and blue sheep. By analyzing an expanded data set that incorporated ZFY intron sequences of two additional Ovis (sheep) species-O. nivicola and O. ammon--we demonstrated that ZFY intron provides good resolution at the species and genus levels. The ZFY intron sequence divergence between dwarf blue sheep and blue sheep was comparable to that within the two Ovis species. Moreover, we found intraspecific sequence variation in ZFY intron for all three species examined. We propose that dwarf blue sheep be designated as a subspecies of blue sheep, P. n. schaeferi.

Animals↗
PubMed2005

Effects of tail fat on halothane biotransformation in fat-tailed sheep.

1. The aim of the present study was to evaluate the effects of tail fat on halothane biotransformation following similar anaesthetic exposure in intact sheep and sheep with a ligated median sacral artery. 2. A prospective randomized experimental study was performed using 12 healthy, 10-12-month-old female sheep. 3. Sheep were randomly divided into two groups of six animals each and were anaesthetized twice at 2 weekly intervals. After mask induction with halothane in 100% oxygen, sheep were intubated and anaesthesia was maintained for 3 h using a rebreathing system. Serum fluoride concentration (SFC) was measured at 0, 1, 3, 6, 12, 24, 48 and 72 h following the induction of anaesthesia. Serum biochemistry was also evaluated at baseline and 72 h after anaesthesia. Induction and extubation times and time to sternal recumbency were also recorded during anaesthetic induction and recovery. Prior to the second anaesthesia (2 weeks later), the median sacral artery (MSA) was ligated under epidural anaesthesia in the experimental group. Sheep in the control group underwent sham operation. All sheep were anaesthetized as before. 4. Following the first halothane anaesthesia, SFC was significantly increased from 3 to 48 h compared with baseline. In the second stage of the experiment, the increases in SFC in the control group were similar to those seen in the first stage of the experiment. However, in MSA-ligated sheep, the increases in SFC were only significant between 3 and 12 h compared with baseline. The SFC was significantly higher in intact sheep from 3 to 72 h compared with the MSA-ligated group. Extubation and sternal recumbency times were significantly longer in intact sheep. 5. Ligation of the MSA in fat-tailed sheep induced a significant reduction in SFC, suggesting that the presence of tail fat substantially affects halothane metabolism during the peri-anaesthetic period in sheep. The greater extent of halothane biotransformation may be clinically important in, otherwise normal, obese patients.

Administration, Inhalation↗
PubMed1997

Chronic hypoxia suppresses pharmacomechanical coupling of the uterine artery in near-term pregnant sheep.

1. The role of inositol 1,4,5-trisphosphate (InsP3) in the reduced vascular responsiveness to 5-hydroxytryptamine (5-HT) caused by chronic hypoxia was examined in uterine arteries obtained from normoxic (control) and chronically hypoxic pregnant sheep (approximately 140 days gestation) maintained at high altitude (3820 m; arterial PO2, 60 mmHg) from 30 days gestation. 2. Chronic hypoxia significantly decreased uterine artery contractile sensitivity in that pD2 (-logEC50) for the contractile response to 5-HT was 7.19 +/- 0.15 and 6.62 +/- 0.12 (P < 0.05) in uterine arteries from normoxic and chronically hypoxic sheep, respectively. The intrinsic efficacy of the agonist was reduced by 75%. Although 5-HT2A receptor density (Bmax) in the uterine artery was not changed in chronically hypoxic sheep compared with normoxic sheep (32.0 +/- 9.8 vs. 31.9 +/- 5.9 fmol (mg protein)-1, respectively) as assessed from the saturation binding of [3H]ketanserin, the agonist binding affinity (pKA, -log of dissociation constant) was decreased from 6.25 +/- 0.07 in normoxic sheep to 5.85 +/- 0.08 in chronically hypoxic sheep (P < 0.05). 3. Chronic hypoxia did not change the time course of 5-HT-induced InsP3 synthesis but decreased its potency in inducing InsP3 synthesis, with the pD2 being 6.09 +/- 0.11 and 5.51 +/- 0.08 (P < 0.05) in uterine arteries from normoxic and chronically hypoxic sheep, respectively. The maximal response of 5-HT-induced InsP3 generation in the uterine artery was decreased from 251.3 +/- 24.2 pmol (mg protein)-1 in normoxic sheep to 146.6 +/- 11.3 pmol (mg protein)-1 in chronically hypoxic sheep (P < 0.05). Furthermore, the ability of the activated 5-HT receptors to couple InsP3 synthesis was significantly decreased in chronically hypoxic compared with normoxic sheep (280 +/- 10 vs. 450 +/- 20 fmol InsP3 (fmol receptor)-1, P < 0.01). In addition, for a given amount of InsP3 generated, the contractile force of the uterine artery was significantly less in chronically hypoxic sheep (0.82 +/- 0.08 g tension (pmol InsP3)-1) than that in normoxic sheep (1.28 +/- 0.05 g tension (pmol InsP3)-1) (P < 0.05). 4. These results suggest that chronic hypoxia suppresses pharmacomechanical coupling of the ovine uterine artery by inhibiting the efficiency of receptor-effector-contraction coupling. This suppression of the InsP3 pathway may play an important role in the adjustment of vascular tone and uterine blood flow in response to the stress of chronic hypoxia in late pregnancy.

Animals↗
PubMed2004

Associations between the prion protein genotype and performance traits of meat breeds of sheep.

The prion protein (PrP) genotypes of four German meat breeds of sheep were examined in relation to their scores for muscle mass, conformation, wool quality, daily liveweight gain and ultrasonic measurements of the depth of back muscle and back fat. The dataset included 912 genotyped German texel sheep among 10,383 recorded sheep, 474 genotyped Suffolk sheep among 4079 recorded sheep, 271 genotyped German white-headed mutton sheep among 3393 recorded sheep, and 99 genotyped German black-headed mutton sheep among 1642 recorded sheep. The model included the fixed effects of PrP genotype, herd, year and season, test day, sex, rearing method, the regression coefficient of average age, and the random additive genetic effect of the animal. In all four breeds there were no statistically significant associations between these performance traits and the occurrence of ARR alleles and the ARR/ARR genotype except for the depth of back muscle and the daily liveweight gain of German black-headed mutton sheep; however, in this breed, the interpretation could be affected by the small number of animals involved. All the genotyped sheep had significantly better performance traits than the non-genotyped sheep.

Animals↗
PubMed1989

Effects of obesity and ovarian steroids on insulin secretion and removal in sheep.

The interactive effects of sex steroids and obesity on glucose metabolism and pancreatic secretion and organ removal of insulin were determined in multicatheterized lean and obese sheep by multiplying venoarterial concentration differences by plasma flows. Ovariectomized lean and dietary obese ewes received implants of progesterone and estradiol-17 beta that produced plasma concentrations of each equivalent to those during either anestrus (low progesterone), diestrus or pregnancy (high progesterone), or estrus (high estradiol). Sheep were exposed to each of the three steroid treatments for 2 days and fasted overnight before blood samples were collected for 5 h before (basal) and 90 min after injecting glucose (200 mg/kg) to simulate an intravenous glucose tolerance test (IVGTT). Regardless of steroid treatment, pancreatic secretory (18 vs. 5 mU/min) and hepatic (10 vs. 2 mU/min) and hindquarters (1.8 vs. 0.5 mU/min) removal rates of insulin in the basal state were greater (P less than 0.005) in obese than lean sheep. Obese sheep had greater (P less than 0.025) basal hepatic glucose output (66 vs. 47 mg/min) and similar hindquarters glucose removal (37 vs. 32 mg/min) as lean sheep even though arterial concentrations of insulin were fourfold higher (25 vs. 6 microU/ml; P less than 0.01) in the obese sheep. High progesterone increased (P less than 0.05) basal hepatic insulin removal in obese sheep. High progesterone and high estradiol increased insulin but decreased (P less than 0.05) glucose removal in hindquarters of obese sheep in the basal state. High progesterone potentiated significantly glucose-induced hyperinsulinemia in obese sheep, whereas high estradiol suppressed hepatic insulin removal but increased the removal of insulin by hindquarters during glucose stimulation in the obese sheep. We concluded that excessive insulin secretion, not decreased insulin removal, maintains the basal hyperinsulinemia in moderately obese sheep and that the progesterone-to-estradiol ratio has marked and divergent effects on insulin and glucose metabolism in individual tissues of sheep both in the basal state and during an IVGTT.

Animals↗
PubMed1984

Effect of calcitonin on salivary phosphorus and calcium excretion in sheep.

Three thyroidectomized sheep were infused intravenously with porcine calcitonin at a rate of 30 mi.u./h per kg and three sham-operated sheep were infused with vehicle for 5 h. Saliva was collected from the left parotid duct by cannulation for 10 min in every hour. Salivary secretion rates were not changed in either thyroidectomized or sham-operated sheep throughout the experiment. Before the infusion, salivary phosphorus excretion was less in thyroidectomized sheep than in sham-operated animals. Calcitonin infusion increased salivary phosphorus excretion and decreased serum phosphorus concentrations in thyroidectomized sheep. Vehicle infusion did not affect salivary phosphorus excretion in sham-operated sheep. Serum concentrations and salivary excretion of calcium were decreased by calcitonin infusion into thyroidectomized sheep but were not changed in sham-operated sheep infused with vehicle. Calcitonin infusion increased serum parathyroid hormone concentrations in thyroidectomized sheep after the decrease of serum calcium concentrations. However, vehicle infusion did not affect serum parathyroid hormone concentrations in sham-operated sheep. There was little change of cyclic AMP excretion during the experiment in either thyroidectomized or sham-operated sheep. It is concluded that calcitonin increases salivary phosphorus excretion in sheep.

Animals↗
PubMed2003

Effect of dimethyl sulfoxide in the treatment of sheep experimentally infected with Ehrlichia ruminantium.

OBJECTIVE: To evaluate the clinical response of sheep experimentally infected with Ehrlichia ruminantium to treatment with dimethyl sulfoxide (DMSO). ANIMALS: 32 Merino crossbred sheep. PROCEDURES: 16 sheep were infected with E ruminantium; 8 of these were treated twice daily with a 10% solution of DMSO (1 g/kg, i.v.) in polyionic fluid for 3 consecutive days. Treatment was initiated 2 days after the onset of clinical disease. Eight uninfected control sheep were similarly treated with DMSO. Placebo treatments (polyionic fluid administrations) were given to 8 infected and 8 uninfected sheep. Arterial and venous blood samples for blood gas and total plasma protein concentration measurements were collected daily (data from 5 days before until 6 days after onset of clinical disease were analyzed); physiologic variables and food consumption were also monitored. Gross pathologic findings and cytologic confirmation of the disease were recorded for the 16 infected sheep. RESULTS: Infected sheep treated with DMSO were able to maintain pulmonary gas exchange and had reduced pleural effusion and plasma protein loss, compared with infected untreated sheep that became hypoxic. Infected treated sheep developed an uncompensated metabolic acidosis. Uninfected treated sheep had reduced appetite, whereas uninfected untreated sheep maintained normal food intake. CONCLUSIONS AND CLINICAL RELEVANCE: Results of DMSO treatment in sheep with experimentally induced heartwater disease indicated that administration of this agent, in combination with specific antimicrobial treatment, may be of some benefit in treatment of naturally occurring disease.

Acidosis↗