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PubMed1983

Direct evidence for interaction between human erythroid progenitor cells and a hemoglobin switching activity present in fetal sheep serum.

An activity that induces Hb F to Hb A switching in human cells is present in fetal sheep serum. To test directly the role of cell-to-environment interactions in hemoglobin switching and to define the level of erythroid cell differentiation at which this activity operates, colony transfer experiments were done. Clones grown in the presence of switching activity-containing medium (fetal sheep serum) or control medium (fetal calf serum) were transferred, at the 16- to 30-cell stage, to either fetal sheep serum or fetal calf serum plates and Hb F synthesis was determined in the fully mature erythroid bursts. Fetal calf serum-to-fetal calf serum transfers produced colonies with the high Hb F levels characteristic of undisturbed fetal calf serum-grown clones. Fetal sheep serum-to-fetal calf serum transfers resulted in significant decrease in Hb F synthesis, revealing an interaction between hemoglobin switching activity and cells at an early stage of progenitor cell development. The reduction of Hb F synthesis in fetal calf serum-to-fetal sheep serum transfers indicated that hemoglobin switching activity interacts with cells at later stages of progenitor cell development. Maximal decrease in Hb F synthesis was observed in fetal sheep serum-to-fetal sheep serum transfers, indicating that optimal effects on Hb switching are obtained when the environment that induces Hb switching is present throughout the development of progenitor cells. By splitting single early clones into two parts and transferring them to either a fetal sheep serum or a fetal calf serum environment, these interactions were further demonstrated in the progeny of a single erythroid burst-forming unit. Since all clone transfers were done on cell-free plates, the results of fetal calf serum-to-fetal sheep serum and of fetal sheep serum-to-fetal sheep serum transfers indicated that the switching activity does not require helper cells for its action. These studies show directly that (i) Hb F synthesis is controlled at the level of progenitors and (ii) it involves interactions between progenitor cells and their environment.

Animals↗
PubMed1975

Nutritional studies on East African herbivores. 1. Digestibilities of dry matter , crude fibre and crude protein in antelope, cattle and sheep.

1. A series of digestibility trials was done using four animals of each of the following species: Friesian cattle (Bos taurus), Boran zebu cattle (Bos indicus), Corriedale sheep, fat-tailed sheep, eland (Taurotragus oryx Pallas), Coke's hartebeest (Alcelaphus buselaphus cokei Günther), Thomson's gazelle (Gazella thomsonii Günther) and bush duiker (Sylvicapra grimmia L.). 2. Two batches of pelleted food were prepared from ground maize cobs, cassava, whs (A-E) were prepared containing 65 (A)-135 (E) g crude protein (nitrogen times 6-25)/kg dry matter. The crude-fibre contents of all the diets were similar (120-138 g/kg dry matter). 3. The animals were given the high-protein diet (E), then given diets with decreasing protein contents finishing with the low-protein (A). The antelope and half the sheep were given diets from the first batch of pelleted food, the other four sheep and all the cattle were given diets from the second batch of food. 4. In sheep, there were significant differences in digestibility between the two batches of food. 5. There were no significant differences in the over-all mean digestibilities of all diets when given to cattle (both species) and sheep. However, with diet E, dry-matter digestibility was higher in sheep than in cattle (P smaller than 0-05): the reverse was true with diet A (P smaller than 0-001). Crude-fibre and crude-protein digestibilities followed a similar pattern. The differences between Corriedale and fat-tailed sheep were not significant. The only significant difference between the two species of cattle was the higher digestibility of crude protein in Borans given diet E (P smaller than 0-05). 6. The over-all mean digestibility of the dry matter was higher (P smaller than 0-001) in hartebeest and duiker than in sheep; in Thomson's gazelle (P smaller than 0-01) and eland (P smaller than 0-001) it was lower than in sheep. The values for crude-fibre digestibilities varied in a similar way. 7. The mean apparent digestibility of crude protein was higher (P smaller than 0-001) in eland, hartebeest and duiker than in sheep and gazelle. 8. The results are discussed in relation to the feeding habits and digestive physiology of the various species.

Africa, Eastern↗
PubMed1993

The effect of condensed tannins in Lotus pedunculatus on the digestion and metabolism of methionine, cystine and inorganic sulphur in sheep.

Two experiments were conducted with sheep fed on fresh Lotus pedunculatus containing 50-55 g condensed tannin (CT)/kg dry matter. Effects of CT were assessed by comparing control sheep (CT operating) with sheep receiving a continuous intraruminal infusion of polyethylene glycol (PEG) to bind and inactivate CT. Digestion of methionine and cystine was determined using a continuous intraruminal infusion of indigestible markers, whilst plasma irreversible loss (IRL) of methionine, cystine and inorganic sulphate was determined using 35S labelling. The proportion of microbial non-NH3-N (NAN) in whole rumen digesta NAN and the IRL of reducible S from the rumen were determined using a continuous intraruminal infusion of (NH4)2(35)SO4. The proportion of microbial NAN in whole rumen digesta NAN (0.44 v. 0.71) and the IRL of reducible S from the rumen (0.84 v. 2.49 g S/d) were lower in control than PEG sheep. PEG sheep lost 30% of ingested methionine and cystine across the rumen, whereas the control sheep lost no methionine and cystine across the rumen. Apparent absorption of methionine from the small intestine was 27% higher in control than PEG sheep, but both groups had a similar apparent absorption of cystine. The apparent digestibility of cystine in the small intestine was lower in control (0.42) than PEG (0.53) sheep, whereas the apparent digestibility of methionine was similar (0.78) for both groups. CT had no effect on plasma methionine IRL, but markedly increased the IRL of cystine (39.8 v. 22.4 mumol/min) and reduced the IRL of plasma inorganic sulphate (35.9 v. 50.2 mumol/min). A three-pool model comparing interconversions between the three plasma metabolites showed that CT increased the flow of cystine to body synthetic reactions (36.5 v. 17.3 mumol/min). This was due to trans-sulphuration of methionine to cystine being greater in control than in PEG sheep, whilst the oxidation of both methionine and cystine were reduced in control sheep. It was concluded that CT reduced the proteolysis of forage protein and the degradation of S amino acids to inorganic sulphide in the rumen, resulting in increased net absorption of methionine and increased utilization of cystine for body synthetic reactions in sheep with a high capacity for wool growth (and, hence, high cystine requirement).

Animal Feed↗
PubMed1986

Insulin and glucose responses to glucose injection in fed and fasted obese and lean sheep.

Effects of short-term fasting on the insulin and glucose responses to injected glucose were determined in obese (n = 6) and lean (n = 6) Dorset ewes that were fed a maintenance level of energy intake. Sheep were assigned by Latin-square design to be fasted for 0 (fed), 12 or 24 h before glucose (350 mg/kg) was injected via jugular cannula at 2000 h with at least 7 d between successive tests. Insulin and glucose were quantified in jugular plasma samples. Pretreatment concentrations of insulin were affected (P less than 0.005) only by body condition with higher mean values in obese (23.5 +/- 3.3 microU/ml) than in lean (9.4 +/- 1.0 microU/ml) sheep. Pretreatment concentrations of glucose (53.6 +/- 1.8 mg/dl) were unaffected by body condition and fasting. The insulin responses to glucose, whether determined as absolute levels or response areas above base-line levels, were greater (P less than 0.005) in obese than in lean sheep regardless of fasting period. Insulin and glucose concentrations after glucose injection in lean sheep were unaffected by fasting. In contrast, the insulin response to glucose was greater (P less than 0.005) in fed obese than 12- or 24-h fasted obese sheep while glucose levels in the fed sheep were similar to those in the fasted obese sheep. Thus, factors associated with feeding enhanced the insulin response to glucose in obese sheep. In addition, obesity in sheep was associated with insulin resistance because basal hyperinsulinemia coexisted with euglycemia and because fractional removal rates of injected glucose were similar in obese and lean sheep despite much greater concentrations of insulin in obese sheep.

Animals↗
PubMed2002

DNA tests in prolific sheep from eight countries provide new evidence on origin of the Booroola (FecB) mutation.

Recent discoveries that high prolificacy in sheep carrying the Booroola gene (FecB) is the result of a mutation in the BMPIB receptor and high prolificacy in Inverdale sheep (FecX(I)) is the result of a mutation in the BMP15 oocyte-derived growth factor gene have allowed direct marker tests to be developed for FecB and FecX(I). These tests were carried out in seven strains of sheep (Javanese, Thoka, Woodlands, Olkuska, Lacaune, Belclare, and Cambridge) in which inheritance patterns have suggested the presence of major genes affecting prolificacy and in the prolific Garole sheep of India, which have been proposed as the ancestor of Australian Booroola Merinos. The FecB mutation was found in the Garole and Javanese sheep but not in Thoka, Woodlands, Olkuska, Lacaune, Belclare, and Cambridge sheep. None of the sheep tested had the FecX(I) mutation. These findings present strong evidence to support historical records that the Booroola gene was introduced into Australian flocks from Garole (Bengal) sheep in the late 18th century. It is unknown whether Javanese Thin-tailed sheep acquired the Booroola gene directly from Garole sheep from India or via Merinos from Australia. The DNA mutation test for FecB will enable breeding plans to be developed that allow the most effective use of this gene in Garole and Javanese Thin-tailed sheep and their crosses.

Animals↗
PubMed1972

Electrolytes and water in the brain and cerebrospinal fluid of the foetal sheep and guinea-pig.

1. Samples of cisternal cerebrospinal fluid (c.s.f.) and blood plasma have been obtained nearly simultaneously from foetal sheep of different ages, the foetus having been exteriorized and maintained in a normal state with respect to its blood gases and arterial pH. The brains were removed from these foetuses and also from foetal guinea-pigs after exsanguination.2. A comprehensive study has been made of the concentrations of water, chloride, sodium, potassium, calcium and magnesium in blood plasma, c.s.f. and brain from foetal sheep and in brain from foetal guinea-pigs during development in utero. Maternal arterial blood plasma, cisternal c.s.f. and brain from the sheep and brain from the guinea-pig have been analysed for comparison.3. Concentrations of the ions analysed in foetal blood plasma are similar to those found by others in the sheep and other species. In the case of calcium, the results suggest an active maintenance of the concentration of this ion in foetal plasma by the placenta.4. The chloride concentration in c.s.f. at ages between 65 days and term (147 days) averaged 1.19 times that in foetal plasma, but only 1.08 at 45-50 days; the sodium concentration in c.s.f. was also slightly reduced at this time. The increase in the c.s.f./plasma ratios for chloride and sodium appears to coincide with the first development of the blood-brain and blood-c.s.f. barriers to non-electrolytes.5. Magnesium was at a slightly higher concentration in c.s.f. than in plasma at all foetal ages and did not vary with age. The concentrations of potassium and calcium in c.s.f. were high at early ages and fell to reach adult concentrations after birth: the mechanisms determining the concentrations of the various ions in c.s.f. develop at very different, largely independent, rates.6. The water content of the cerebral hemispheres of the foetal sheep was stable at 90% of the wet weight till 105 days and fell thereafter. The contents of chloride, sodium and potassium followed paraboloid relations with age. Chloride and sodium reached a peak of 62 and 81 m-equiv/kg respectively between 89 and 105 days in the sheep. Potassium was at a minimum of 65 m-equiv/kg at the same time. The content of water and these electrolytes in the cerebral hemispheres of the foetal guinea-pig underwent similar changes, the maxima and minimum occurring as in the sheep at two-thirds of the total length of the pregnancy, namely 65 days in the guinea-pig. At 46 days in the guinea-pig, chloride in brain reached 53 m-equiv/kg, sodium was 68 m-equiv/kg and potassium was 75 m-equiv/kg. In contrast to the sheep, no reversal of the sodium-potassium ratio occurred. These changes in water and electrolytes probably represent a rise, a peak and a decrease in the volume of the extracellular space of cerebral cortex, but changes in the volume occupied by a cell-type, containing much intracellular chloride and sodium, could also contribute to this phenomenon.7. The calcium content in the cerebral hemispheres of the foetal sheep remained at about 3.0 m-equiv/kg throughout pregnancy. Magnesium in the cerebral hemispheres of both the foetal sheep and the guinea-pig showed a trough in concentration during pregnancy which corresponded approximately in position to the minimum in potassium content and the maxima in chloride and sodium contents. Lowest values were 9.6 m-equiv/kg at 105 days in the sheep and 9.5 m-equiv/kg at 51 days in the guinea-pig.

Animals↗
PubMed1967

Effect of various essential oils isolated from Douglas fir needles upon sheep and deer rumen microbial activity.

The effects of essential oils isolated from Douglas fir needles on sheep and deer rumen microbial activity were tested by use of an anaerobic manometric technique. Rumen microorganisms were obtained from a sheep which had been fed mainly on alfalfa hay and dried range grass. One deer used in this study had access to Douglas fir trees the year around, whereas the other deer had no access to Douglas fir. All of the monoterpene hydrocarbons isolated from Douglas fir needles-alpha-pinene, beta-pinene, limonene, myrcene, camphene, Delta(3)-carene, and terpinolene-promoted only slightly or had no effect on deer rumen microbial activity, whereas all of them promoted activity in sheep rumen microbes, except Delta(3)-carene and terpinolene, which inhibited activity. Of the oxygenated monoterpenes, all monoterpene alcohols-alpha-terpineol, terpinen-4-ol, linalool, citronellol, and fenchyl alcohol-strongly inhibited the rumen microbial activity of both sheep and deer. Monoterpene esters (bornyl acetate) produced mild inhibition for both sheep and deer microbes, and citronellyl acetate inhibited rumen microbial activity in sheep, whereas it promoted activity in both deer. Monoterpene aldehyde (citronellal) inhibited the activity of rumen microbes from both sheep and deer having no access to Douglas fir from the Hopland Field Station, whereas they produced no effect upon the deer having access to Douglas fir from the Masonite forest. Rumen microbial activity for sheep and deer was promoted slightly with aliphatic ester (ethyl-n-caproate). There was a marked difference between sheep and deer rumen microbes as affected by addition of the various essential oils. The monoterpene hydrocarbons promoted activity more on sheep rumen microbes than on deer, and the monoterpene alcohols inhibited sheep rumen microbial activity more than that of deer. Furthermore, the deer rumen microbes from Hopland Field Station were affected more than the deer from Masonite forest.

Animals↗
PubMed1994

Renal perfusion pressure and renin secretion in bilaterally renal denervated sheep.

To further investigate the influence of renal nerves on renin secretion, the renin secretion responses to step reductions of renal perfusion pressure (RPP) were studied in conscious sheep with innervated kidneys (n = 5) and with bilaterally denervated kidneys (n = 5). The average basal level of RPP in sheep with denervated kidneys (82 +/- 4 mmHg; 1 mmHg = 133.3 Pa) was similar to that in sheep with innervated kidneys (83 +/- 3 mmHg). RPP was reduced in four sequential 15-min steps, to a final level of 54 +/- 2 mmHg in sheep with innervated kidneys and to 57 +/- 1 mmHg in denervated sheep. The renin secretion rate was increased as RPP was reduced in sheep with innervated kidneys. Baseline peripheral plasma renin activity was reduced and there was almost no response of renin secretion rate to reduction of RPP in sheep with denervated kidneys. Also, baseline renal blood flow, urine flow rate, sodium excretion rate, and potassium excretion rate were higher in sheep with denervated kidneys than those with innervated kidneys. Baseline plasma angiotensin II was similar in both groups of sheep. As RPP was decreased, plasma angiotensin II was increased in sheep with innervated kidneys, but was not RPP or renal denervation. In conclusion, hormonal factors, such as angiotensin II and atrial natriuretic factor, do not account for the dramatic suppression of renin secretion in response to the reduction of RPP in sheep with bilateral renal denervation. Renal nerves are a necessary component in the control of renin secretion during reduction of RPP and may contribute to the regulation of baseline plasma renin activity and sodium excretion rate in conscious ewes.

Angiotensin II↗
PubMed1981

Leukocytes are required for increased lung microvascular permeability after microembolization in sheep.

We studied the effects of uneven pulmonary artery obstruction by microemboli on steady state transvascular fluid and protein exchange in normal and leukopenic sheep. We measured pulmonary artery and left atrial pressures, cardiac output, lung lymph flow, and lymph plasma protein concentrations. Sheep were made profoundly leukopenic by administration of intra-arterial mechlorethamine hydrochloride (0.4 mg/kg, two doses) and colchicine (0.1-0.2 mg/kg, anesthetized sheep only). In anesthetized sheep, we injected glass beads 200 micrometers in diameter via the right atrium to raise pulmonary vascular resistance to 2-3 times baseline values. With normal levels of circulating leukocytes, sheep developed an increased protein-rich lymph flow from the lung characteristic of increased permeability edema. Leukopenic sheep had a significantly attenuated response after embolization for equivalent degrees of vascular obstruction. In unanesthetized sheep, we continuously infused air bubbles 1 mm in diameter via the right atrium to raise pulmonary vascular resistance to about 2 times baseline values. Each sheep served as its own control. With normal circulating leukocyte levels, there was an increase in protein-rich lymph flow from the lung during embolization. When the air infusion ended, the sheep recovered to the baseline condition in 24 hours. We induced emboli with the same amount of air when the sheep were profoundly leukopenic; lymph and protein flow from the lung were significantly less for equivalent degrees of obstruction. We conclude that circulating leukocytes are essential for the microvascular injury that results in increased permeability in the lungs of sheep after microembolization.

Animals↗
PubMed2005

Preliminary study of histological comparison on the growth patterns of long-bone cortex in young calf, pig, and sheep.

Some young large farm animals show a laminar bone formation in the long-bone cortex. Such a laminar bone is gradually replaced by Haversian bone with osteons during their growth periods. In this preliminary study, we observed the transverse ground samples of tibia cortex in young calves, pigs, and sheep by backscattered electron imaging. The cortex bones of all the newborn (NB) animals were basically formed with laminar bone structures. The NB and 1-month-old (1-M) calves had a typical concentric structure of laminar bone, whereas the NB and 1-M pigs showed a wire-netting bone with laminar-bone units. The NB sheep was similar to the calf rather than the pig. In the growth rate of bone volume, sheep was similar to calf up to 6 months after birth (6-M). Such calf and sheep showed a more rapid ratio of bone volume than pig. A few osteons had initially appeared in the innermost layer of the 6-M calf. A 1-year-old (1-Y) calf showed scattered osteons in the bone cortex, but many laminar-bone units were still retained in the outer layer. A 6-M pig had many osteons in the entire cortex but only a few osteons in the outermost layer. In the 6-M sheep, no osteons were observed, whereas a 1-Y sheep showed a relatively small number of osteons mainly in the middle layer but a higher osteon-volume than the 1-Y calf. In the 1-Y sheep, the more widely absorbed areas by bone-remodeling with osteons were observed as compared with the 1-Y calf, and the bone volume was decreased from the 6-M into the 1-Y sheep because of the remarkable bone-absorption. Thus, calf kept on possessing many laminar-bone units for a longer time in the growth period than sheep, while pig showed the earliest bone-remodeling with osteons. These results may be caused by their different body size and withers height in calf and sheep after growing and the difference of the dependence upon mother's body during juvenile period between pig and calf with sheep. The initial region of osteon formation may be distinguishable among their animals, respectively. However, further detailed investigations of their young animals at successive stages will be necessary.

Age Factors↗
PubMed1983

Suppressive effect of calcitonin on intestinal absorption of calcium and phosphorus in sheep.

This study was carried out to determine the effect of calcitonin on calcium and phosphorus absorption in sheep. Six sheep, which were prepared with a carotid loop and a portal venous catheter, were used. Thyroidectomized sheep were injected intramuscularly with porcine calcitonin at feeding time. Serum calcium concentrations did not change in intact or thyroidectomized sheep after feeding but calcium venoarterial blood differences in thyroidectomized sheep were higher than in intact sheep 8 h after feeding. Serum calcium concentrations and calcium veno-arterial blood differences were decreased by calcitonin injection into thyroidectomized sheep. Calcitonin injection also reduced the serum phosphorus concentrations. Phosphorus veno-arterial blood differences in thyroidectomized sheep were much less than in intact sheep before feeding although the blood differences were not affected by calcitonin injection in thyroidectomized sheep. The results indicated that calcitonin decreased calcium absorption, which caused a reduction in the serum calcium concentrations, and that calcitonin injection did not affect phosphorus absorption in thyroidectomized sheep.

Animals↗
PubMed1999

Neuropeptide Y restores appetite and alters concentrations of GH after central administration to endotoxic sheep.

The objective of this study was to determine whether neuropeptide Y (NPY) and recombinant human interleukin-1 receptor antagonist (IL-1ra) would: first, increase food intake; secondly, decrease concentrations of GH; thirdly, reduce GHRH-induced release of GH; and fourthly, reduce changes to concentrations of IGF-I in plasma during experimental endotoxemia in sheep. Six treatments were given to six castrated male sheep in a 6x6 Latin square treatment order. Osmotic mini-pumps were implanted at 0 h and a jugular vein was cannulated. Each sheep was continuously infused with saline (0.9%) or lipopolysaccharide (LPS) (20 micrograms/kg per 24 h, s.c.) at 10 microliters/h for 72 h via the osmotic mini-pumps. Blood samples (3 ml) were collected at 15-min intervals from 24 to 33 h. At 26 h, one of three treatments (artificial cerebrospinal fluid, NPY or IL-1ra) was injected i.c.v. within 30 s (0.3 microgram/kg), then infused i.c.v. from 26 to 33 h (600 microliters/h) at 0.3 microgram/kg per h. GHRH was injected i.v. (0.075 microgram/kg) at 32 h after which blood samples were collected at 5, 10, 15, 30, 45 and 60 min. Feed intake was reduced up to 50% for 48 h in LPS-treated compared with non-LPS-treated sheep. NPY restored feed intake in LPS-treated sheep and induced hyperphagia in non-LPS-treated sheep from 24 to 48 h. In contrast, IL-1ra did not affect appetite. Injection of NPY increased concentrations of GH from 26 to 27 h, while IL-1ra had no effect. Infusion of NPY suppressed GHRH-induced release of GH. However, no treatment altered pulse secretion parameters of GH. Concentrations of IGF-I were 20% higher at 72 h in LPS-treated sheep given NPY than in sheep treated with LPS alone, and this may reflect increased appetite from 24 to 48 h. We concluded that reduced appetite during endotoxemia is due to down-regulation of an NPY-mediated mechanism. Furthermore, NPY stimulates release of GH in healthy sheep, does not reduce pulse secretion parameters of GH, but does suppress GHRH-induced release of GH in endotoxic sheep. Therefore, NPY may be an important neurotransmitter linking appetite with regulation of GH during endotoxemic and healthy states in sheep.

Animals↗
PubMed2006

Retention of different sizes of electronic identification boluses in the forestomachs of sheep.

Twelve types of electronic identification ruminal boluses of different dimensions were used to obtain a model for predicting their retention in the forestomachs of sheep. Boluses (n = 1,662) were made of ceramic materials, and their dimensions varied in o.d. (9 to 21 mm), length (37 to 68 mm), volume (2.5 to 21.0 mL), and specific gravity (0.85 to 3.91). Each bolus contained a half-duplex, standardized, glass-encapsulated transponder (32 x 3.8 mm). Boluses were administered to sheep (n = 1,497) of different ages by using the appropriate balling guns, and their retention under semiintensive conditions was recorded for at least 2 yr. When a bolus was lost, the sheep was rebolused with a heavier bolus. All sheep wore 2 plastic ear tags: one for the official control of health programs and the other for farm use. To determine the anatomical limit for a bolus passing through the gastrointestinal tract, the size of the reticulo-omasal orifice was measured in 46 adult sheep (male, n = 14; female, n = 32) that died by causes not related to bolus administration during the experiment. No signs of disease or growth alteration were detected in the bolused sheep. Total ear tag losses during the experiment period were 7.5% on average. Bolus retention (5 to 100%) varied according to bolus features and age of the sheep, but it showed a plateau after 18 mo. Inadequately dimensioned boluses were regurgitated or passed through the gastrointestinal tract and were excreted with the feces. The diameter of the reticulo-omasal orifice in adult sheep differed between male and female (23.1 and 21.8 mm, respectively; P < 0.01) and was greater than the o.d. of the retained boluses. Retention rate was predicted from bolus weight and volume by a logistic regression (R2 = 0.997; P < 0.001). When retention data from the literature (59.0 to 100%) were included in the model, the adjustment was slightly lower (R2 = 0.967). As a result, the minimum bolus weight estimated to reach a 99.5% retention rate in sheep varied between 16 and 45 g when volume varied between 3 and 22 mL, for boluses with a specific gravity between 2.0 and 5.2. In conclusion, bolus retention rate in sheep varied dramatically according to their features. For safe and efficient retention of electronic identification boluses in sheep, boluses of small volume and diameter (e.g., < 15 mm) with specific gravity and weight greater than 3.0 and 20 g, respectively, are recommended.

Animal Identification Systems↗
PubMed1990

Mass, number and size of lung fibres in the pathogenesis of asbestosis in sheep.

After long-term asbestos inhalation, the lung tissue burden is much less for chrysotile (CHRY) than for crocidolite (CRO) exposure. Nonetheless CHRY does not appear to be less fibrogenic. To study mechanisms responsible for the low retention of CHRY and the relationships with fibrogenesis, 15 sheep received a single intratracheal injection of either CHRY or CRO. Exposures in 100 ml saline consisted of 100 mg of 1-micron latex beads for the five control sheep, 100 mg UICC CRO fibres for the five CRO sheep and 100 mg UICC B CHRY fibres for the five CHRY sheep. Bronchoalveolar lavage (BAL) was carried out at months 2, 4, 6 and 8 after exposure and necropsy at month 8. BAL and tissue samples were analysed for fibres by transmission electron microscopy. At month 2, mass concentration in BAL was 108 +/- 30 ng/ml for CRO and 0.6 +/- 0.1 ng/ml for CHRY. BAL CRO decreased afterward but BAL CHRY did not. The mass concentration in the lung at month 8 was 40.6 +/- 8.7 ng/mg dry tissue for CRO and 11.5 +/- 7.0 ng/mg for CHRY. BAL fibrogenic activity at month 8 assessed by macrophage fibronectin production was less than 0.2 ng/10(6) cells/24 h in control sheep, 5 +/- 2 in CRO sheep and 11 +/- 2 in CHRY sheep (P less than 0.05 CRO vs CHRY). Histologic score of tissue injury fibrosis was 0 in control sheep, 1.9 +/- 0.3 in CRO sheep and 2.8 +/- 0.1 in CHRY sheep (P less than 0.05). At necropsy, the number size distribution of fibres per microgram of tissue from the (CRO)/(CHRY) sheep was respectively: (127 +/- 54)/(15 +/- 14) for fibres less than 5 microns, (18 +/- 17)/(32 +/- 14) for fibres greater than 5 microns, (1.6 +/- 8)/(7 +/- 13) for fibres greater than 20 microns. This study documented that the low pulmonary retention of CHRY was largely related to the faster alveolar clearance rate of CHRY mass. Fibrogenicity of CHRY remained higher and appeared to be related at least in part to the preferential retention of long and very long CHRY fibres.

Animals↗
PubMed1986

Tracing the leukocyte marker protein in lung fluids and lung-draining lymph nodes during endotoxemia in sheep.

Infusion of Escherichia coli endotoxin into sheep produces a form of acute lung injury that resembles the adult respiratory distress syndrome (ARDS). A large portion of the physiologic derangements produced by E. coli endotoxin in this model is thought to be granulocyte-dependent. We measured the level of L1, a granulocyte and monocyte marker protein, in various tissues and fluids after infusion of E. coli endotoxin into sheep. In an acute study, sheep received saline or 1.25 microgram/kg E. coli endotoxin dissolved in saline, or endotoxin after hydroxyurea-induced granulocytopenia. L1 was measured by radioimmunoassay in efferent lymph from the caudal mediastinal lymph node collected between 5 and 6 h after infusion. In addition, L1 was visualized in both lung-draining and extrapulmonary lymph nodes by indirect immunofluorescence. In a chronic study, sheep were prepared with lung lymph fistulas, and L1 was measured in draining pulmonary lymph, plasma, and bronchoalveolar lavage (BAL) fluid, serially, over a 24-h period after infusion. Mean L1 level in pulmonary lymph in the acute study was 6 times higher by absolute concentration, and 19 times higher when lymph flow rates were taken into account, in the sheep that received endotoxin than in saline-infused sheep or endotoxin-infused, granulocytopenic sheep. Fluorescence was greater in the outer cortical region adjacent to subcapsular, afferent sinuses of lung draining-lymph nodes of endotoxin-treated sheep than in the comparable nodes of saline-infused sheep and endotoxin-infused granulocytopenic sheep. In endotoxin-treated sheep, extrapulmonary lymph nodes were less reactive than lung-draining nodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Renal excretion of urea in the Merino and Steppe fat-tailed breeds of sheep after a short period of fasting].

Urea excretion was studied in an experiment with two sheep breeds (steppe fat-tailed and merino) on the second day of fasting when the urea concentration in blood increases in fasting animals. The control group in the two breeds was given free-choice feed and water while fasting sheep were given ad libitum only water. Diuresis in both breeds was steady during the experiment. Glomerular filtration rate was not found to vary, in comparison with the control, although the plasma urea concentration rose in fat-tailed sheep (P less than 0.01) as well as in the sheep of merino breed (P less than 0.001). Fractional excretion of urea decreased in fat-tailed sheep (P less than 0.05) and also in the sheep of merino breed (P less than 0.02) while total output of urea remained steady in fat-tailed sheep but it increased in merino sheep (P less than 0.02). Tubular reabsorption of urea on the second day of fasting was observed to be higher by 65% in merino sheep (P less than 0.001), but in steppe fat-tailed sheep the increase was much higher--by up to 180% (P less than 0.001), in comparison with the control. It was demonstrated by the results that the increased tubular reabsorption of urea contributes to the rise of plasma urea concentration in sheep on the second day of fasting.

Animals↗
PubMed1997

Relation between serologic response and pathologic findings in sheep with naturally acquired paratuberculosis.

OBJECTIVE: To investigate the relation between lesions and serologic response in sheep with naturally acquired paratuberculosis and to evaluate the efficacy of agar gel immunodiffusion (AGID) and ELISA as diagnostic tests. ANIMALS: 134 adult sheep, culled by the owner from flocks with history of severe chronic weight loss. PROCEDURE: Before euthanasia, blood samples were collected and serum was obtained. AGID and ELISA were performed, using a protoplasmic antigen of Mycobacterium paratuberculosis. Sensitivity and specificity of these techniques were evaluated, using histopathologic findings as a reference. Histologic studies were carried out focusing on specimens containing intestinal organized lymphoid tissue. RESULTS: Of the sheep examined, 46.3% had lesions that were classified in 5 categories, according to their location, extension, cellular types, and presence of acid-fast bacilli. Regarding serologic test results, 37.1% of sheep with lesions had a positive AGID result, and all sheep without lesions had negative results. However, ELISA positivity was slightly greater--48.4% of sheep with lesions; however, by use of ELISA, 11.1% of sheep without lesions had positive results. CONCLUSION: A close relation between pathologic findings and serologic response was determined, especially between presence of acid-fast bacilli (potentially heavily shedding sheep) in the intestinal lesions and positivity to serologic tests, especially AGID. CLINICAL RELEVANCE: On the basis of these results, together with its high specificity, reliability, and the difficulty of fecal specimen culture in sheep, AGID is proposed as a useful tool for seeking evidence of paratuberculosis in live sheep, and therefore, is suggested as the basis for control programs in areas in which the disease is a serious threat to sheep production.

Animals↗
PubMed1995

Specification of pen rail spacing and trough heights to prevent escape and enable good access to feed by sheep during sea shipments from New Zealand.

A trial was carried out to determine the optimal height of feeding troughs above floor level and the spacing between pen railings which would enable sheep to access feed troughs but prevent them from getting out of pens during sea voyages. The trial involved a group of 16 large (79 kg) wether sheep and 24 small (30 kg) wether lambs which were held in pens and trained to eat lucerne pellets. Feed troughs similar to those used on ships were constructed 260 mm deep and 220 mm wide. A system of adjustable railings were used to alter the trough height and to determine the optimal spacing to allow the large sheep to get their heads through, but to prevent small sheep from escaping. In order that sheep of various sizes can access feed from the bottom of feed troughs, the height of the top edge of the trough should not exceed 360 mm above floor level for 30 kg sheep or 460 mm for mature sheep. This range is due to differences between the groups in their shoulder height, and variation between individuals within each group. Shoulder heights of the small sheep used in this trial ranged from 505 to 590 mm, and for the 16 mature animals the range was 610-715 mm. It is important that the feed troughs are low enough for all animals to access the feed on offer. Mature sheep were able to pass their heads between rails spaced at 200 mm without difficulty, but some difficulty was experienced when the space was reduced to 180 mm. The maximum rail spacing which prevented the escape of 30 kg lambs could not be determined with certainty because they could pass through a space of only 180 mm when laid on their side, but the smallest space through which they passed voluntarily was 220 mm. Hence the optimal spacing between railings which would allow all sheep good access to feed and would prevent almost all small sheep from escaping is about 190-210 mm.

Journal Article↗