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PubMed1997

Autonomic control of bronchial circulation in awake sheep during rest and behaviour.

1. We tested the hypothesis that the pattern and the intensity of autonomic mechanisms causing vasoconstriction in the resting bronchial circulation of awake dogs also exists in awake sheep. It was also postulated that sighing behaviour and the associated bronchovascular dilatation induced by non-adrenergic, non-cholinergic (NANC) mechanisms observed in the dog exist in sheep. 2. Bronchial arterial blood flow to lower airways of both lungs of awake sheep was measured continuously using pulsed Doppler flow probes mounted on the bronchial artery at prior thoracotomy. 3. Cumulative and factorial analysis of responses to randomized combinations of autonomic alpha 1-, alpha 2-, beta 1- and beta 2-adrenoceptors and cholinoceptor autonomic blockade suggests that resting vasoconstrictor activity is less in sheep than in dogs. At normal aortic pressure, the autonomic activity of these receptor groups in the sheep lowers bronchial blood flow and conductance by 30%, whereas in the awake dog, the corresponding autonomic effect is 50%. 4. Tonic autonomic control of bronchial conductance can be partitioned in sheep to show significant and separate alpha- and beta-adrenoceptor vasoconstrictor activity at a ratio of 1.8:1, an effect normally offset by a weaker vasodilator alpha-/beta-adrenoceptor interaction. In contrast to the situation in awake dogs, cholinoceptors do not play a role in awake sheep. 5. Nitric oxide (NO) synthase inhibition in sheep using NG-nitro-L-arginine following blockade of alpha- and beta-adrenoceptors and cholinoceptors causes hypertension, but minor changes, if any, in pulmonary pressures or heart rate. Bronchial flow and conductance, however, fall from a higher resting conductance by approximately 50%, suggesting that, normally, resting bronchial flow conductance is dominated by strong tonic NO vasodilator effects that interact with weaker tonic autonomic vasoconstrictor effects. 6. Superimposed (respiratory) behaviours of sighing, sneezing and coughing, which involve negative swings in intrathoracic pressure and the movement of inspired air, evoke large active bronchovascular dilator effects. These appear to be largely NANC in origin and appear to be dependent, in part, on mechanisms associated with NO release. It is postulated that the C-fibre axon reflex using substance P, calcitonin gene-related peptide and neurokinin A may be involved. Vocalization and eructation do not evoke bronchovascular effects.

Adrenergic alpha-Antagonists↗
PubMed1998

Oxygen-dependent K+ fluxes in sheep red cells.

1. This study was designed to investigate the O2 dependence of K+ influx in sheep red cells. Influx was determined using 86Rb+ as a tracer for K+; glass tonometers coupled to a gas mixing pump were used to equilibrate cell samples to the requisite oxygen tension (PO2). 2. Both volume- and H(+)-stimulated K+ influxes in low potassium-containing (LK) sheep red cells were approximately doubled on equilibration with O2 relative to influxes measured in N2.O2-dependent influxes were abolished when Cl- was replaced with NO3-, consistent with mediation by the KCl cotransporter. At pH 7, PO2 required for half-maximal stimulation was 56 +/- 1 mmHg (mean +/- S.E.M., 3 sheep) for the O2-dependent component of K+ influx: thus PO2 values over the physiological range affected K+ influx. 3. K+ influx in fully deoxygenated sheep red cells showed substantial volume and H+ sensitivity. These residual components in N2 were also Cl- dependent, indicating that the KCl cotransporter of LK sheep red cells was active in the absence of O2. 4. Volume-sensitive K+ influxes in high potassium-containing (HK) sheep red cells responded in a similar way to those in cells from LK sheep, although much smaller in magnitude, showing that intracellular [K+] had no significant effect on the O2 dependence of the cotransporter. 5. Intracellular [Mg2+] ([Mg2+]i) was altered by incubating sheep red cells with A23187 (20 microM) and different values of extracellular [Mg2+] ([Mg2+]o). Total [Mg2+]i was determined by atomic absorption spectroscopy and free [Mg2+]i from [Mg2+]o and the Donnan ratio. Total [Mg2+]i was 1.29 +/- 0.08 mM (mean +/- S.E.M., n = 5), similar to that reported in the literature. Estimates of free [Mg2+]i showed an increase from 0.39 +/- 0.05 in oxygenated cells to 0.52 +/- 0.04 mM (mean +/- S.E.M., n = 5; P < 0.05) in deoxygenated ones. 6. Finally, although K+ influxes were altered by pharmacological loading or depletion of cells with Mg2+, the free [Mg2+]i required to affect influxes significantly was outside the physiological range. Results are difficult to reconcile with PO2 modulating KCl cotransport activity directly via changes in free [Mg2+]i or [Mg(2+)-ATP]i.

Animals↗
PubMed1999

A novel role for cyclic nucleotide-gated cation channels in lung liquid homeostasis in sheep.

1. Sheep lungs were artificially perfused in situ with warmed whole oxygenated sheep blood. The airspaces of the lungs were filled with liquid containing an impermeant tracer, to allow measurement of the rate of net transepithelial liquid movement under various conditions. 2. Dichlorobenzamil (1.5 x 10-5 M), a blocker of cyclic nucleotide-gated cation channels, inhibited the resting absorption of lung liquid in sheep aged 6 months (n = 5) (from -36.47 +/- 4.62 to -4.36 +/- 5.27 ml h-1, means +/- s.e.m.; P < 0.005, paired t test). Amiloride (10-4 M), a blocker of epithelial sodium channels, had no additive effect to that of dichlorobenzamil. 3. In the lungs of sheep aged 6 months (n = 4), amiloride (10-4 M) partially inhibited the resting absorption of liquid (from -35.21 +/- 8.57 to -11.05 +/- 4.91 ml h-1; P < 0.05, one-tailed paired t test), and dichlorobenzamil (1.5 x 10-5 M) exerted an additive effect to that of amiloride resulting in secretion at +6.29 +/- 3.05 ml h-1 (P < 0. 01, paired t test). 4. In the lungs of sheep aged 6 weeks (n = 3), amiloride (10-4 M) also inhibited the resting absorption of liquid (from -26.36 +/- 14.05 to -5.17 +/- 8.27 ml h-1; P < 0.05, one-tailed paired t test); however, dichlorobenzamil (1.5 x 10-5 M) did not exert an additive effect to that of amiloride. 5. In the lungs of sheep aged 6 months (n = 4), amiloride (10-4 M) partially inhibited the resting absorption of liquid (from -35.70 +/- 8.58 to -6.79 +/- 4.28 ml h-1; P < 0.05, paired t test), and pimozide (1.5 x 10-4 M), another blocker of cyclic nucleotide-gated cation channels, also exerted an additive effect to that of amiloride, resulting in secretion of lung liquid at +15.36 +/- 9.14 ml h-1 (P < 0.05, paired t test). 6. We conclude that cyclic nucleotide-gated cation channels mediate a component of lung liquid absorption in sheep aged 6 months (but not in sheep aged 6 weeks), and that a mechanism for lung liquid secretion (present in fetuses) is retained at 6 months of age.

Absorption↗
PubMed1979

Attempted cross-transmission of coccidia between sheep and goats and description of Eimeria ovinoidalis sp. n.

Attempted infection of 2 young lambs with oocysts of Eimeria christenseni from a goat was unsuccessful. Negative results were obtained also when young kids were fed oocysts of Eimeria ninakohlyakimovae from sheep. There was no difficulty in infecting lambs with the sheep coccidium resembling E. ninakohlyakimovae nor goats with the goat coccidium E. christenseni. Oocysts from the goat measured 38.4 X 26.7 microns, but were easily distinguished from Eimeria ahsata from the sheep by sporocyst size and shape, and from Eimeria ovina by oocyst size. Eimeria ninakohlyakimovae-like oocysts from sheep averaged 23.0 X 18.2 microns and were morphologically indistinguishable from previously reported goat coccidia. Since no cross infections of sheep and goats could be accomplished with oocysts of Eimeria sp. characteristic of one or the other host, I concluded that sheep coccidia previously known as E. ninakohlykimovae are distinct from morphologically similar goat coccidia and therefore constitute a separate species. Since the name E. ninakohlyakimovae was first used for coccidia from the goat, the sheep coccidium is renamed Eimeria ovinoidalis with oocyst structure and endogenous stages similar to those previously described from the sheep.

Animals↗
PubMed1996

Contagious ecthyma in the live sheep export industry.

OBJECTIVE: To investigate control options for contagious ecthyma (scabby mouth) in Australian sheep exported live to the Middle East. DESIGN: Prevalence, vaccination and modelling studies. PROCEDURE: One hundred and forty weaner sheep (less than 1 year old) on each of 106 farms in Western Australia (WA) and 18 farm groups of adult wethers received at a WA commercial feedlot were examined for lesions of scabby mouth. Sheep on a total of 26 farms in 3 States were divided into treatment and control groups for the vaccination study. A simple deterministic compartmental model was developed to establish which parameters had the greater effect on disease prevalence. RESULTS: The proportion of farms with evidence of scabby mouth in weaner sheep was 23.6% and, on those farms with the disease, the overall prevalence was 6.1%. At the feedlot, 4 out of 18 farm groups had 5 or more sheep with lesions on arrival. The overall prevalence in the 4 diseased groups was 5.2%. Sheep vaccinated on farm before trucking to the feedlot had a lower prevalence of scabby mouth at the end of simulated shipping than controls. The main determinant of scabby mouth prevalence was the proportion of sheep immune to the disease. CONCLUSION: A program of vaccination for scabby mouth will reduce the prevalence of disease during live export. However, using current technology it is not possible to deliver shipments of sheep to the Middle East that are guaranteed completely free of scabby mouth.

Animals↗
PubMed1978

The effects of two analogues of arginine-vasopressin (ornithine-vasopressin and desamino-D-arginine-vasopressin) on kidney function in sheep.

The effects of intravenous infusion of ornithine-vasopressin (OVP) and desamino-D-arginine-vasopressin (dDAVP) were studied in normal and hydrated Merino sheep. In normal sheep, OVP resulted in a diuresis, increased urinary sodium and potassium excretion, and a fall in the plasma potassium concentration. Renal plasma flow remained constant but glomerular filtration rate and filtration fraction rose markedly. dDAVP in normal sheep was antidiuretic, but its only significant effect was a small decrease in plasma osmolality. In the hydrated sheep OVP was antidiuretic and resulted in increased urinary excretion of sodium and potassium, and a fall in the plasma potassium level. Renal plasma flow fell, but glomerular filtration and filtration fraction tended to rise. dDAVP in the hydrated sheep was also antidiuretic but urinary sodium and potassium excretion was reduced. Renal plasma flow and glomerular filtration fell, with a small decrease in filtration fraction. These results suggest that the diuretic effect in normal sheep and the electrolyte-excreting effects in both normal and hydrated sheep of OVP are related to the increase in glomerular filtration, which in turn is dependent on the vasopressor activity of the hormone. The increase in glomerular filtration caused by OVP is due to an increase in the filtration fraction of an unchanged renal plasma flow, which could be brought about by an increase in renal efferent arteriolar tone. The effects of hydration of the sheep were the conventional increased urine flow, decreased urine osmolality and decreased solute-free water reabsorption. Sodium and potassium excretion rose slightly and plasma osmolality fell. Renal plasma flow and glomerular filtration both increased with little change in filtration fraction. These effects could be brought about by suppression of endogenous vasopressin and a decrease in both afferent and efferent renal arteriolar tone.

Animals↗
PubMed1990

Measurement of plasma osteocalcin in sheep: assessment of circadian variation, the effects of age and nutritional status and the response to perturbation of the adrenocortical axis.

An assay for plasma osteocalcin (BGP) in ruminants is described. Satisfactory cross-reaction was obtained for bovine BGP in several species, namely ovine, cervine, caprine and human. Sample stability at room temperature, after freezing and thawing and after lyophilization and reconstitution is described. Sheep of both sexes have been used throughout and no significant sex effect has been noted. A series of experiments showed a lack of circadian rhythm of plasma BGP concentration in sheep. Plasma BGP values from sheep ranging in age from 0.25 to 7 years fell exponentially from 300 ng/ml at 0.25 years to approximately 50 ng/ml at 1.25 years of age where it remained until the end of the study at 7 years. Long-term administration of adrenocorticotrophic hormone (ACTH) depressed plasma BGP concentrations, although plasma BGP levels were not affected sufficiently by short-term administration of ACTH to increase plasma cortisol concentrations 10-fold during a period of 4 h. It was confirmed that dietary phosphate deficiency depressed plasma BPG concentrations. It is concluded that neither circadian variation nor the short-term stress of handling and bleeding untrained animals need be considered in sampling sheep for measurement of plasma BGP concentration and that the change with age reflected the pattern of development of skeletal maturity in sheep. Values in both growing and mature sheep were at least 6 times higher than in human subjects, which may reflect the 10-fold higher skeletal growth rate in sheep than in humans. This high skeletal activity in sheep may have been selected for in the development of highly productive breeds.

Adrenocorticotropic Hormone↗
PubMed1995

Responses to reduced water intake, including dehydration natriuresis, in sheep excreting sodium predominantly in urine or in faeces.

Sheep which were predominantly urinary excretors (U) or faecal excretors (F) of sodium were exposed to a 75% reduction of water intake for 72 h. The experiment was performed on moderate, low or high sodium intakes (0.4, 0.05 or 1.2 mmol kg-1 day-1) to test the hypothesis that dehydration natriuresis was not a cause of sodium depletion but a defence against hypernatraemia. Dehydration caused elevation of plasma sodium concentration, osmolality, antidiuretic hormone (ADH) and oxytocin but, as in other experiments, a fall in haematocrit. The two higher levels of sodium intake were associated with dehydration natriuresis but also a smaller increase in faecal sodium excretion in both U and F sheep. On low sodium intake, however, neither urinary nor faecal sodium excretion increased in either group of sheep although the rise in plasma sodium concentration caused by dehydration was similar. Thus, when there is a risk of sodium depletion, due to low sodium intake, dehydration natriuresis does not occur, consistent with the hypothesis. Active sodium transport inhibitor (ASTI) and atrial natriuretic peptide (ANP) fell rather than rose during dehydration. Since aldosterone is suppressed by the higher levels of sodium intake, none of these hormones is likely to mediate dehydration natriuresis in sheep. F sheep showed more effective renal and faecal water conservation when dehydrated. During water restriction, the urinary potassium excretion of U sheep was significantly reduced, unlike that of F sheep; moreover, the latter maintained an identical plasma potassium concentration between baseline and restriction period, whereas in U sheep it was 0.3 mmol l-1 higher during water restriction. Increased drinking rather than reduced urine output was the basis of rehydration when ad lib. water intake was restored.

Animals↗
PubMed1975

Rate of flow of digesta and electrical activity of the small intestine in dogs and sheep.

1. Spiking activity of the small intestine in the conscious dog and sheep was recorded continuously from electrodes chronically implanted on the jejunum and summed at intervals of 20 sec. The activity was related to the transit time and flow rate of intestinal contents as estimated by phenol red and by dilution of continuous marker infusions respectively. Also in some sheep the flow of digesta was measured directly from a cannula in the proximal part of the jejunum, and also by use of an electromagnetic flow meter. 2. In the fasted dog and in sheep on a normal diet the intestinal activity was characterized by a migrating myo-electric complex comprising an irregular phase followed by a regular phase. These migrating myo-electric complexes occurred regularly after a period of inactivity at a frequency of 15-20/24 hr. In dogs after feeding, a continuous spiking activity appeared and persisted for periods of 7-8 hr. This was associated with much higher rates of flow and shorter transit times than were observed during fasting. In sheep, continuous spiking activity could be induced by intravenous injection of 5-hydroxytryptophan and this, similarly, was accompanied by a more rapid flow and a shorter transit time than recorded during the control period. 3. In both species the longest transit time occurred when a phenol red bolus was injected during the period of electrical inactivity. Relatively short transit times were observed when the bolus was administered just before the period of regular spiking activity. 4. When relaxation of the bowel was induced by intraperitoneal injection of hypertonic saline there was no spiking activity and the transit time for the infused solution was greatly lengthened, especially in the sheep. A noticeable flow of digestive contents persisted in the dog. 5. In the sheep the intestinal contents flowed intermittently during periods of 10-15 min and at the same frequency as the migrating myo-electric complex. Two thirds of this flow took place in the 4-6 min immediately preceding the periods of irregular spiking activity. 6. It is concluded that in the fasted dog and in the sheep the migrating myo-electric complex controls the pressure gradients on which the flow of intestinal contents depends. This is accomplished in the main by the prolonged phase of irregular spiking activity, and it is suggested that the regular spiking activity which follows it, though not in itself propulsive, serves as a barrier to prevent backflow of digesta into the quiescent part of the intestine. When continuous spiking activity is induced, by feeding in the dog and by injection of 5-hydroxytryptophan in the sheep, no part of the intestine is quiescent and the transit time is shortened by the incessant irregular spiking activity.

5-Hydroxytryptophan↗
PubMed1988

Effects of tracheostomy breathing on brain and body temperatures in hyperthermic sheep.

1. We measured rectal and hypothalamic temperature in sheep breathing nasally and via a tracheostomy, during hyperthermia resulting from exposure to a hot environment, exercise and fever. 2. In normothermic and hyperthermic sheep hypothalamic temperature was up to 1.0 degree C lower than rectal temperature when the sheep breathed nasally. Tracheostomy breathing abolished the rectal-hypothalamic temperature difference. 3. In sheep breathing via the tracheostomy and exposed to a dry-bulb temperature of 45-50 degrees C for 2 h, hypothalamic temperature exceeded rectal temperature by about 0.4 degrees C, and was significantly higher than that in sheep breathing nasally in the same environment. 4. During exercise on a treadmill and in the post-exercise period, the difference between hypothalamic and rectal temperature was abolished in the sheep while breathing through the tracheostomy, and rectal temperature rose to higher levels compared to those evident in the same activity while breathing nasally. 5. After an I.V. injection of 0.4 micrograms/kg lipopolysaccharide (LPS), the difference between hypothalamic and rectal temperature again was abolished in the sheep when breathing through the tracheostomy, but rectal temperature rose significantly less compared to when breathing nasally. 6. Our results indicate that selective brain cooling depends on upper respiratory tract cooling in normo- and hyperthermic states in sheep.

Animals↗
PubMed1992

Staphylococcal alpha toxin: a study with chronically instrumented awake sheep.

The in vivo responses to staphylococcal alpha toxin are reported for 15 chronically instrumented awake yearling sheep. The data obtained from a total of 30 experiments are grouped into four categories of response: no response, noted in seven experiments done on 5 sheep; pressor response, obtained seven times in 4 sheep; fluid and solute exchange, noted on six occasions in 3 sheep; and acute heart failure and death, which occurred in 10 of the 15 sheep. "No response" denoted no change in any of the measured outcome variables. The group of sheep labeled as showing "pressor response" responded to alpha toxin infusion with an increase in pulmonary artery pressure, unaccompanied by changes either in lung lymph flow or in lung mechanics. "Changes in lung fluid and solute exchange" involve increases in lung lymph flow. The harbinger of the last category, acute left heart failure leading to death, was a marked elevation in left atrial pressure. The threshold response dose in sheep is approximately 21 micrograms/kg. A very steep dose-response curve is observed, with only a narrow window of doses, 15 to 25 micrograms/kg, between the group showing no response and the group showing death from acute heart failure. The data obtained in these studies indicate that the lethal effects of alpha toxin in sheep include acute heart failure, which may be due to direct toxicity to heart muscle and/or the coronary vasculature endothelium.

Animals↗
PubMed2000

Transforming growth factor beta(2) (TGF beta(2)) produces effective pleurodesis in sheep with no systemic complications.

BACKGROUND: We have recently shown that transforming growth factor (TGF)beta(2) induces effective pleurodesis in rabbits. However, rabbits have a thin pleura while humans have a thick visceral pleura. The effect of intrapleural administration of TGF beta(2) in animals with a thick pleura and its associated systemic effects have not been investigated. This study was undertaken (1) to develop a new animal model for the study of pleurodesis using sheep which have a thick pleura resembling that of humans; (2) to study the efficacy of TGF beta(2) as a pleurodesis agent in the sheep model; and (3) to assess whether histological changes occur in extrapulmonary organs after intrapleural administration of TGF beta(2). METHODS: Twelve sheep were divided into four groups and were given a single intrapleural injection of TGF beta(2) in a concentration of 1.0 microg/kg, 0.5 microg/kg, 0.25 microg/kg or 0.125 microg/kg to the right pleural cavity via a chest tube. The left pleural cavity served as the control. Any pleural fluid that accumulated after the intrapleural TGF beta(2) injection was collected and analysed. The degree of pleurodesis was graded from 1 (no adhesions) to 8 (complete symphysis >50% of chest wall) at day 14 when the sheep were killed. Biopsy specimens were taken from the lungs and extrapulmonary organs. RESULTS: All sheep that received > or = 0.25 microg/kg TGF beta(2) developed excellent pleurodesis (score = 8) while those that received 0.125 microg/kg had a median score of 6. The pleurodesis score did not exceed 2 in the control (left) side of any sheep. Sheep receiving > or = 0.50 microg/kg TGF beta(2) developed large exudative pleural effusions while those receiving a lower dose did not. The production of effusions neither hindered nor was necessary for inducing pleurodesis. There were no significant fibrotic changes in any of the extrapulmonary organs. CONCLUSION: Intrapleural injection of 0.25-1.0 microg/kg TGF beta(2) produces excellent pleurodesis in a new sheep model with no evidence of extrapulmonary fibrosis.

Animals↗
PubMed1987

Injection site reactions and antibody responses in sheep and goats after the use of multivalent clostridial vaccines.

Uncertainty concerning the use, efficacy and possible adverse effects of clostridial vaccination in goats prompted a study of the injection site reactions and antibody responses in 40 goats and 40 sheep. The vaccines used were Covexin 8, Heptavac and Tasvax 8. In all the animals swellings averaging 2.5 cm in diameter were present at the injection site seven days after vaccination and were still apparent 28 days after vaccination. The injection site reactions could not be attributed to faulty vaccination technique because they did not occur in a control group injected with sterile water. By 14 days the reactions were significantly larger in sheep than in goats and by 28 days the reactions to Covexin 8 were larger than those to the other vaccines in sheep and goats. Serum antibody was present in all groups before vaccination and, with the exception of the goats vaccinated with Heptavac, increased 14 days after vaccination. The increase was greater in sheep than in goats. By 28 days antibody levels had declined in all but the sheep vaccinated with Heptavac in which a further increase occurred. At that time, the antibody levels in vaccinated sheep were still higher than in the unvaccinated sheep whereas the antibody levels in vaccinated goats were no longer different from those in the control goats. These results suggest that there is a difference between the vaccines used and between the responses of the two species and support the clinical observation that the protection afforded to goats by multivalent clostridial vaccines is poorer than that afforded to sheep.

Animals↗
PubMed2002

Discriminant value of blood and urinary corticoids for the diagnosis of scrapie in live sheep.

The mean (sd) concentration of plasma 20beta-dihydrocortisol in 126 scrapie-affected sheep was 5-5 (7.0) ng/ml compared with 1.1 (0.7) ng/ml in 52 healthy sheep. The mean (sd) concentration of creatinine in the urine of 93 scrapie-affected sheep was 2.43 (1.56) microg/ml compared with 0.94 (0.86) pg/ml in 49 healthy sheep and 1.10 (0-95) pg/ml in 25 sheep with other diseases. These discriminant analyses carried out on healthy and scrapie-affected sheep showed that plasma 20beta-dihydrocortisol and urinary creatinine were the best predictors of the disease, and classified correctly 98 per cent of healthy sheep and 82 per cent of scrapie-affected sheep.

Animals↗
PubMed2004

Programming of adult cardiovascular function after early maternal undernutrition in sheep.

The prenatal nutritional environment influences the subsequent risk of hypertension in adulthood. Animal studies have used, generally, the rat as a model species to illustrate the association between maternal nutrient intake and blood pressure in the resulting adult offspring. No study to date has shown programming of adult cardiovascular function in the sheep through maternal dietary intervention. We therefore fed pregnant sheep to either 100% recommended intake from day 0 of gestation to term [ approximately 147 days gestational age (dGA); controls n = 8] or to 50% recommended intake from day 0 to 95 dGA and thereafter to 100% intake (NR; n = 9). Sheep lambed naturally, offspring were weaned at 16 wk, and the male offspring were reared on pasture until 3 yr of age. At this time, cardiovascular catheters were inserted under halothane anesthesia and sheep were allowed 2-4 days recovery. Basal cardiovascular status and pressor responses to infusion of norepinephrine, angiotensin II, and captopril were then assessed alongside basal plasma concentrations of glucose, cortisol, and leptin. NR sheep were of similar birth weight to controls but at 3 yr of age had higher blood pressure before, but not after, feeding. Peripheral sensitivity to vasoconstrictor infusion was similar between dietary groups, although a reflex bradycardia was not apparent in NR sheep during norepinephrine infusion. Circulating leptin correlated well with fat mass and increased more after vasoconstrictor infusion in NR sheep. In conclusion, early NR has been shown to program aspects of cardiovascular control and adipocyte function in adult sheep.

Algorithms↗
PubMed1986

Angiotensin and Na appetite of sheep.

The effect of both intravenous (iv; 24 micrograms/h) and intracerebroventricular (ivt; 3.8 micrograms/h) infusion over 1-2 days of angiotensin II (ANG II) on Na intake of both Na-replete and -deplete sheep (i.e., 22 h loss of parotid saliva) was observed. In Na-replete sheep with continuous access to water and 2-h daily access to 0.5 M NaCl solution, both iv and ivt ANG II caused an increase in Na intake. The increase in Na intake caused by iv or ivt ANG II was preceded by a Na deficit due to increased urinary Na excretion. The increase in Na intake was eliminated by the continuous return of urine. In Na-deplete sheep with continuous access to water and 2-h daily access to 0.6 M NaHCO3 solution, iv ANG II caused no change in Na loss but a small increase in Na intake during the 1st day of infusion. The ivt ANG II caused no change in Na loss or in Na intake. The iv ANG II caused a small and inconsistent increase in water intake in Na-replete sheep but did not cause any change in water intake of Na-deplete sheep. The ivt ANG II caused a large increase in water intake in both Na-replete and -deplete sheep. In both Na-replete and -deplete sheep, iv ANG II did not alter cerebrospinal fluid or plasma [Na] or osmolality but decreased plasma [K]. The ivt ANG II decreased both cerebrospinal fluid and plasma [Na] and osmolality. The results of the present experiments are consistent with the proposition that the ANG II-induced Na appetite in sheep is largely due to an ANG II-induced Na loss preceding the development of appetite.

Angiotensin II↗
PubMed1989

Glucose metabolism in pregnant sheep when placental growth is restricted.

The effect of restricting placental growth on glucose metabolism in pregnant sheep in late gestation was determined by primed constant infusions of D-[U-14C]- and D-[2-3H]glucose and antipyrine into fetuses of six control sheep and six sheep from which endometrial caruncles had been removed before pregnancy (caruncle sheep). In the latter, placental and fetal weights were reduced, as was the concentration of glucose in fetal arterial blood. Fetal glucose turnover in caruncle sheep was only 52-59% of that in controls, largely because of lower umbilical loss of glucose back to the placenta (38-39% of control) and lower fetal glucose utilization (61-74% of control). However, fetal glucose utilization on a weight-specific basis was similar in control and caruncle sheep. Significant endogenous glucose production occurred in control and caruncle fetal sheep. Maternal glucose production and partition of glucose between the gravid uterus and other maternal tissues were similar in control and caruncle sheep. In conclusion, when placental and fetal growth are restricted, fetal glucose utilization is maintained by reduced loss of glucose back to the placenta and mother and by maintaining endogenous glucose production.

Animals↗
PubMed1975

Effects of topical and general anesthetic agents on tracheal mucous velocity of sheep.

Tracheal mucous velocity was estimated in eleven sheep by means of cine-bronchofiberscopic technique in which Teflon discs placed on the tracheal mucosa were filmed as markers. The procedure was done using a transnasal approach in conscious nonanesthetized sheep, and in the same sheep using topical and/or general anesthetic agents. The average mucous velocity in conscious sheep was 17.3 plus or minus 6.2 (SD) mm/min; in sheep anesthetized with intravenous pentobarbital or thioamylal, the average velocity was significantly depressed to 11.1 plus or minus 3.6 mm/min. No Significant differences in tracheal mucous velocity were found when 10 ml of 2 percent lidocaine was instilled into the tracheas of either conscious sheep or sheep under general anesthesia. Sheep as an animal model appear to be ideal in the study of the responses of tracheal mucous velocity to physical and chemical agents since they tolerate bronchofiberscopy quite well without the use of topical or general anesthetic agents. The basis for the depression of tracheal mucous velocity by barbiturates cannot be ascertained from the present study but the model should be useful for comparing different types of anesthetic agents.

Anesthesia, General↗