Regional myocardial oxygen consumption determined noninvasively in humans with [1-11C]acetate and dynamic positron tomography.

Experimental studies of animals have previously demonstrated the validity of [1-11C]acetate as a tracer of oxidative metabolism for use with positron emission tomography. The present study was undertaken to define in normal human volunteers the relation between myocardial clearance kinetics of [1-11C]acetate, and the rate-pressure product as an index of myocardial oxygen consumption. Twenty-two studies were performed of 12 volunteers.

Trial of a novel experimental Toxoplasma iscom vaccine in pregnant sheep.

Fifteen vaccinated ewes (group 1) and 13 unvaccinated ewes (group 2) were each challenged orally with 2000 sporulated Toxoplasma gondii oocysts at 91 (+/- 1) days' gestation. Another four pregnant ewes acted as unvaccinated unchallenged controls. Lamb mortality in group 1 was 36.

Isolation and characterisation of lymphoblastoid cells from cattle and deer affected with 'sheep-associated' malignant catarrhal fever.

Cells with the histological and ultrastructural characteristics of large granular lymphocytes (LGL) have been obtained in culture from both cattle and red deer (Cervus elaphus) reacting with 'sheep-associated' malignant catarrhal fever (MCF). Such cells have been derived from thymus, lymph node and spleen suspensions as well as from cerebrospinal fluid cells and cultured cornea. On most occasions their presence was observed only transitorily but by providing the cells with feeder monolayers and, or, interleukin-2, several lines were maintained indefinitely, and some became independent of these factors after prolonged culture.

Noninvasive quantitation of regional myocardial oxygen consumption in vivo with [1-11C]acetate and dynamic positron emission tomography.

The usefulness of [1-11C]acetate as a tracer of overall myocardial oxidative metabolism for use with positron emission tomography has been investigated in 12 closed-chest dogs. Myocardial 11C activity clearance kinetics after intravenous administration of [1-11C]acetate in dogs have been determined noninvasively by positron emission tomography. Biexponential fitting of regional myocardial 11C time-activity curves was performed to give clearance half-times and fractional distribution.

Serodiagnosis of ovine toxoplasmosis: an assessment of the latex agglutination test and the value of IgM specific titres after experimental oocyst-induced infections.

The antibody response of 20 pregnant ewes to oocyst infection with Toxoplasma gondii was determined by the latex agglutination test (LAT) and compared with the indirect fluorescent antibody test (IFAT) and a commercially available indirect haemagglutination test (IHAT). The LAT and IFAT showed a similar rapid response with antibody first appearing by two to three weeks after infection and titres that correlated closely (r = 0.81, P less than 0.

Modulation of growth hormone-releasing factor stimulated growth hormone secretion by plasma glucose and free fatty acid concentrations in sheep.

Effects of plasma glucose and free fatty acid (FFA) concentrations on bovine growth hormone-releasing factor (bGRF)-induced release of growth hormone (GH) were examined in ovariohysterectomized sheep. In experiment 1, the effects of an infusion of insulin (0.025 U/kg BW.

Titration of Toxoplasma gondii oocysts in non-pregnant sheep and the effects of subsequent challenge during pregnancy.

Fifty-nine ewes, seronegative to Toxoplasma gondii, were allocated to four groups which received 2000, 200, 20 or no M1 strain toxoplasma oocysts 56 days before mating. Fifty-one of them subsequently became pregnant and were challenged with 10,000 oocysts between 78 and 83 days of gestation. Infection with 2000 oocysts induced a pyrexia, seroconversion and protective immunity in all the recipient animals.

Radiolabeled acetate as a tracer of myocardial tricarboxylic acid cycle flux.

The kinetics of [1-14C]acetate oxidation in isolated perfused rat hearts have been determined over a range of perfusion conditions. Effluent measurements demonstrated that 14CO2 cleared biexponentially over 50 minutes after bolus injection of [1-14C]acetate into normoxic hearts perfused with 5 mM glucose and 10 mU/ml insulin. The clearance half-time (t1/2) for the predominant initial clearance phase was 3.

Insights into coronary artery disease gained from metabolic imaging.

Positron emission tomography offers the possibility of evaluating and quantifying regional myocardial blood flow and metabolism. Used in patients with coronary artery disease, positron emission tomography has demonstrated sustained metabolic activity in regions with reduced blood flow and impaired contractile function, and it thereby enables differentiation between viable myocardium and myocardium that has succumbed to necrosis and scar formation. Viable myocardial regions identified by metabolic rather than functional or blood-flow criteria are frequently observed in patients after an acute coronary event and in patients with stable coronary artery disease.

Acute regulation of the branched-chain 2-oxo acid dehydrogenase complex by adrenaline and glucagon in the perfused rat heart.

Rates of transamination and decarboxylation of [1-14C]leucine at a physiological concentration (0.1 mM) were measured in the perfused rat heart. In hearts from fasted rats, metabolic flux through the branched-chain 2-oxo acid dehydrogenase reaction was low initially, but increased gradually during the perfusion period.

Further studies in the use of monensin in the control of experimental ovine toxoplasmosis.

Monensin was fed to 69 pregnant ewes from 81 to 84 days gestation until lambing, at an estimated rate of nil, 16.8 or 27.9 mg per head per day.

The pathology of "sheep-associated" malignant catarrhal fever in the hamster.

Lesions induced in hamsters by inoculation with the "sheep-associated" agents of malignant catarrhal fever (SA-MCF) isolated from a red deer (Cervus elaphus), designated D/1 and of bovine origin (C/2), are described. Clinical signs in hamsters inoculated with the D/1 isolate occurred as early as 13 days after infection although the mean incubation period in animals that developed signs was 27 days. Increased numbers of polymorphonuclear leucocytes were present in the blood of clinically affected hamsters.

Potentiation of the glycogenolytic and haemodynamic actions of adenosine in the perfused rat liver by verapamil.

The effects of calcium channel blockers on the glycogenolytic and haemodynamic responses to adenosine were determined in perfused rat liver. Verapamil, 5-25 microM, potentiated the increased glucose output and vasoconstriction observed in response to adenosine. In the absence of perfusate calcium, adenosine responses were inhibited and verapamil was without effect.

The pathology of wildebeest-associated malignant catarrhal fever in hamsters, rats and guinea-pigs.

Lesions typical of malignant catarrhal fever were found in hamsters, rats and guinea-pigs inoculated with a rabbit-passaged strain (C-500) of alcelaphine herpesvirus-1. Lesions found during primary passage included proliferation of lymphoid tissues, multisystemic mononuclear cell infiltrates, vasculitis and necrosis, especially in the alimentary tract. The character, severity and distribution of lesions remained stable in affected hamsters during serial passage of disease, whereas lympho-proliferation became dominant in rats.

Transmission of wildebeest-associated and sheep-associated malignant catarrhal fever to hamsters, rats and guinea-pigs.

Wildebeest-derived malignant catarrhal fever (WD-MCF) was transmitted to hamsters, rats and guinea-pigs by inoculation of rabbit lymphoid cells infected with alcelaphine herpesvirus-1, strain C-500. Sheep-associated MCF (SA-MCF) was transmitted to hamsters by inoculation of lymphoid cells from rabbits affected with SA-MCF derived from deer. Mice were refractory to both forms of the disease.

Measurement of branched-chain alpha-keto acid dehydrogenase flux rates in perfused heart and liver.

The methods described here represent a flexible set of procedures for investigating the metabolism of the branched-chain alpha-keto acids and other substances in perfused organs, notably the rat heart and liver. These procedures have been used to investigate many aspects of the metabolism of the branched-chain alpha-keto acids not discussed here, such as the effects on branched-chain alpha-keto acid metabolism by exposure to alpha-adrenergic agents, by inhibition of the monocarboxylate translocator, and by the coinfusion of other metabolites.

Functional mechanisms and histologic composition of the lingual appendage in the alligator snapping turtle, Macroclemys temmincki (Troost) (Testudines: Chelydridae).

Gross and microscopic examination of the lingual appendages of juvenile and adult alligator snapping turtles, Macroclemys temmincki, shows that it is divided into an anterior horn, a body, and a posterior horn. Lingual appendages of adults usually are more darkly pigmented than those of juveniles and melanocyte distribution is variable, resulting in a mottled appearance. The musculoskeletal components of the hyoid apparatus, presumably responsible for most of the motion displayed by the appendage, are described here.

Stimulation of glycogenolysis and vasoconstriction by adenosine and adenosine analogues in the perfused rat liver.

Infusion of adenosine into perfused rat livers resulted in transient increases in glucose output, portal-vein pressure, the effluent perfusate [lactate]/[pyruvate] ratio, and O2 consumption. 8-Phenyltheophylline (10 microM) inhibited adenosine responses, whereas dipyridamole (50 microM) potentiated the vasoconstrictive effect of adenosine. The order of potency for adenosine analogues was: 5'-N-ethylcarboxamidoadenosine (NECA) greater than L-phenylisopropyladenosine greater than cyclohexyladenosine greater than D-phenylisopropyladenosine greater than 2-chloroadenosine greater than adenosine, consistent with adenosine actions modulated through P1-purine receptors of the A2-subtype.

Studies on ovine efferent lymph following infection with Toxoplasma gondii.

Cell output was monitored in efferent popliteal lymphatics of sheep following subcutaneous injection into the lateral tarsus of either 100 T. gondii tissue cysts or control inoculum. Sheep undergoing a primary infection developed a substantially increased lymphoblast output which reached a peak of more than 50 per cent of all cells.

Activation of hepatic glycogenolysis by phagocytic stimulation.

Infusion of latex beads into isolated perfused rat livers transiently increased glucose output, perfusate lactate/pyruvate ratio and portal vein pressure, mimicking hepatic effects of heat-aggregated IgG (HAG). Indomethacin attenuated hepatic responses to latex beads, and extracellular calcium was required for full expression of hepatic responses. Prior infusion of HAG inhibited the glycogenolytic response to latex beads, supporting a common mechanism of action for the two agents.