Bone mineral measurements and Tc-99m IDP retention in the dog.

The reproducibility of various procedures for the noninvasive assessment of the skeleton in dogs has been measured. In one animal, dual photon measurements of bone mineral mass were made in the whole body, the lumbar spine, and the proximal femur on 10 occasions during a 15-week period. In two other dogs, repeat measurements of Tc-99m imidodiphosphate (IDP) retention were made. For the total body and the proximal femur, the reproducibilities were 2 and 2.5%, respectively. The reproducibility of the lumbar spine was approximately 10% and was influenced by the variable fraction of the posterior spinous processes included in the measurement. The reproducibility of IDP retention measurements was not established. It was about 8% when all 10 measurements were considered but fell to 1.5% when three consecutive measurements were excluded. Dual photon measurements of the whole body and the proximal femur can be used to assess bone mass changes in the canine skeleton.

Hemopoietic stem cells in murine embryonic yolk sac and peripheral blood.

Disaggregated embryonic yolk sac cells and circulating peripheral blood cells were obtained from normal murine day 9 embryos, prior to the formation of the fetal liver. These cells were microinjected transplacentally into days 11-15 W mutant anemic fetuses, when the fetal liver was the major hemopoietic organ. In a small proportion of the recipient animals examined after birth, long-term repopulation by the embryonic donor hemopoietic cells was observed. The donor hemopoietic stem cells proliferated and differentiated in the hosts as evidenced by the presence of donor hemoglobins in the growing recipient host animals. Some mothers of the pups were also repopulated by the donor stem cells. These results provide direct evidence that, during early murine embryogenesis, there are functional hemopoietic stem cells which are capable of colonizing the adult hemopoietic organs and probably the fetal liver and spleen to initiate hemopoiesis in these tissues.

Use of human adenovirus-based vectors for antigen expression in animals.

An infectious recombinant human adenovirus type 5 (Ad5) vector, AdG12, which carries the glycoprotein gene of vesicular stomatitis virus (VSV) and expresses that gene in cultured HeLa cells was used to examine the host range of insert expression by human Ad vectors. The VSV glycoprotein was expressed in bovine, canine and murine cells when infected with AdG12 in culture. These cell lines are respectively permissive, non-permissive and semi-permissive for human Ad5 replication. Administration of the AdG12 vector to calves, piglets or dogs by either the subcutaneous or oral route resulted in the production of high titres of neutralizing antibodies to VSV. Mice injected intraperitoneally with the vector produced neutralizing antibodies and were protected against subsequent intravenous challenge with normally lethal doses of VSV. This work demonstrates the utility of human adenoviral vectors for antigen expression in a number of non-human cell lines and for the induction of an immune response to the delivered antigen in a number of species.

Measurement of absolute bone blood flow by positron emission tomography.

A method of measuring bone blood flow has been developed using 18F sodium fluoride and positron emission tomography. The blood flow levels are in line with those obtained experimentally from microsphere embolisation. This investigative method could be applied to elucidate a number of clinical questions involving bone perfusion.

Hypobaric hypoxia does not affect lung fluid or protein exchange in awake adult sheep at rest.

We measured pulmonary artery (Ppa) and left atrial (Pla) pressures, lung lymph flow, and lymph/plasma protein concentrations in four adult sheep at a barometric pressure of 380 Torr (1 Torr = 133.322 Pa) for 22 h. Hypobaric hypoxia caused an immediate increase in Ppa from 20 to 39 Torr. There was no significant change in Pla, lymph flow, or lymph protein concentrations. We conclude that hypobaric hypoxia does not affect lung fluid or protein exchange in awake adult sheep at rest.

Early changes in venous arterial autografts: a scanning electron microscope study.

The use of autogenous vein as an arterial substitute has been advocated for many years. Methods of harvesting generally cause spasm of the vein and it has been shown that preventing the spasm by applying papaverine improves long-term patency. The present study was undertaken to see if the reported long-term patency of such grafts was associated with improved short-term appearance of the venous endothelium as viewed with the scanning electron microscope. Two groups of dogs were studied; those sacrificed at 3 hours and those at 24 hours after replacing excised segments of the carotid and femoral arteries with cephalic veins. One of the veins was removed in the standard manner allowing spasm followed by distension back to its pre-spasm state; in the other, spasm was prevented by the topical application of papaverine before removal. The study shows that venous endothelial integrity is preserved by the use of papaverine and this improved appearance of the endothelium persists for the first 24 hours after insertion into an arterial milieu. But the study also demonstrated that there was extensive activity of polymorphonuclear leukocytes associated with the endothelium in the early hours after arterialization and that they appeared to have a deleterious effect on the endothelium.

Lipid accumulation in the neointima formed in normally fed rabbits in response to one or six removals of the aortic endothelium.

In previous experiments it was shown that repeated mechanical or immunologic injury to the arterial intima of normally fed rabbits induced lesions morphologically identical with human atherosclerosis. These regressed in size and lipid content when the injury stimulus was removed. By contrast, repeated injury directed to removal of only the endothelial layer induced lesions in which lipid accumulated in areas of endothelial regeneration and increased with time. In the present report the lesions associated with multiple and with a single episode of endothelial removal, using a Fogarty balloon catheter, are compared. Lipid accumulates in areas of endothelial regrowth following one endothelial injury and is similar in amount to that at comparable time intervals following the first of multiple balloon removals of the endothelium. There is much more lipid in areas of endothelial regrowth than in areas that remain uncovered by endothelium, the lipid tends to increase with time, and there is more lipid in the abdominal aortic than in the thoracic aortic lesions. A correlation was found between lipid content and thickness of lesions, especially in response to multiple removals of the endothelium. Multiple removals resulted in thicker lesions than a single injury. There appeared to be a positive relationship between the level of blood cholesterol and the amount of lipid deposited in areas of endothelial regrowth. This is consistent with trapping of low density lipoprotein by glycosaminoglycans in the neointima covered by regenerated endothelium.

Soft-tissue necrosis induced by extravasated cancer chemotherapeutic agents.

The inadvertent extravasation of anticancer drugs in clinical use may result in the development of indolent lesions at the site of injection. Investigation of this phenomenon in Hartley guinea pigs showed that the pathogenesis was based on direct tissue toxicity and not on sensitization. The risk of a serious reaction appeared to be related to the localization of the injurious agent within the dermis rather than at the subcutaneous site.

Effects of complete or partial occlusion of a coronary artery.

We investigated the effects of a partial compared to a complete thrombotic occlusion of the left anterior descending coronary artery in dogs. A completely occlusive thrombus was associated with a full thickness myocardial infarction. Mural thrombus was associated with focal areas of myocardial injury, mainly subendocardial in location. The findings are compatible with the concept that mural thrombus can give rise to platelet or platelet-fibrin emboli in the microcirculation which cause focal areas of ischemic damage. This pathogenesis was further explored using a thrombogenic wire placed in the left anterior descending coronary artery by indirect technique. Five of 10 dogs had developed a completely occlusive thrombus, whereas five had a mural thrombus at death, which occurred within 2 days. Three of the five dogs with mural thrombus had focal ischemic myocardial damage and platelet-fibrin thrombi; the other two that died early showed only platelet fibrin masses in the microcirculation. When platelets were labeled with 111Indium, there was increased radioactivity in the territory of the myocardium served by the artery containing a developing thrombus.

Levamisole reduces the thrombocytopenia associated with myxovirus vaccination.

Mature dogs were vaccinated with a myxovirus vaccine. At this time, half of the dogs were also given a subcutaneous injection of levamisole hydrochloride (2.2 mg/kg). Blood platelets were counted daily. The dogs that had received only the vaccine showed, after 48 hours, a 48% decrease in platelets. Levamisole reduced the thrombocytopenia associated with myxovirus vaccination. Levamisole could have a protective effect on platelets by preventing their aggregation induced by viral neuraminidase.

[18F]fluoro-dopa, an analogue of dopa, and its use in direct external measurements of storage, degradation, and turnover of intracerebral dopamine.

3,4-Dihydroxy-5-fluorophenylalanine, fluorodopa, was injected into rats in which unilateral lesions of the nigrostriatal pathway had been made. The rats rotated towards the side with the lesions, thus providing further evidence that fluoro-dopa is an analogue of dopa. [(18)F]Fluoro-dopa was then injected intravenously into fully conscious baboons. A well-collimated scintillation detector, aligned along the occipitomental axis, recorded the accumulation of (18)F in the brain. Control animals accumulated (18)F continuously for 100 min. This accumulation represents net transport of [(18)F]fluoro-dopa from blood to brain, decarboxylation to [(18)F]fluoro-dopamine, storage, and degradation of [(18)F]fluoro-dopamine. alpha-Methyl-dopa, a competitive inhibitor of dopa transport and decarboxylation, prevented the accumulation of (18)F; reserpine, known to release stored intracerebral dopamine, discharged (18)F; pargyline, a monoamine oxidase inhibitor, and haloperidol, a known augmentor of intracerebral dopamine turnover, increased the rate of accumulation of (18)F. These changes in the accumulation of intracerebral (18)F, after [(18)F]fluoro-dopa, were commensurate with the known action of the drugs used to induce them and demonstrate the use of a gamma-emitting precursor of a neurotransmitter to monitor simply, atraumatically, and externally the intracerebral metabolism of the transmitter in fully conscious primates. When applied to man, the same technique should be able to provide more conclusive evidence than is presently available for the role of catecholamines in schizophrenia and depression. It should also provide further insight into the natural history of nigrostriatal diseases and the action of drugs used in their treatment.

Testosterone production by ovarian follicles of the domestic cat (Felis catus).

In order to determine whether the ovarian follicles of the domestic cat which normally ovulates following copulation, were similar to those of the rabbit steroidogenically, the following experiments were carried out. Follicles were dissected out of ovaries from nine estrous cats throughout the year and incubated in medium alone or with luteinizing hormone (LH) or human chorionic gonadotropin (HCG). Media were removed every 15 min and stored frozen until analyzed for testosterone using established radioimmunoassay procedures. Although LH and HCG caused slight increases in testosterone production the amounts produced were much less than that produced by rabbit follicles under identical conditions. However, when follicles were incubated for a total of 8 h without removal of media, marked changes in testosterone and estradiol production occurred. These data suggest that the ovarian follicles of the estrous cat are steroidogenically active.

Splanchnic and hepatic triglyceride secretion during hypercaloric intravenous glucose infusion in conscious swine.

We have validated a radiochemical technique for measuring the rate of secretion of plasma triglycerides from the liver and/or splanchnic region during the consumption of glucose under isotopic steady-state conditions. Values obtained with this technique correlated closely with those based on transhepatic or transsplanchnic chemical gradients (r = 0.95). Likewise, values for secretion of triglycerides obtained with the radiochemical technique correlated closely with those obtained for extrahepatic or extrasplanchnic triglyceride clearance. Values for mean net splanchnic and hepatic secretion of plasma triglyceride fatty acids, transported essentially in very low density lipoproteins, were 1.9 and 2.0 mumoles/min.kg body wt0.75, respectively, about one-half of the rate of transport of free fatty acids. However, the fraction of triglyceride fatty acids of plasma very low density lipoproteins that was derived from plasma free fatty acids averaged 9% and that derived from glucose, though increasing with time, reached only 2% after constant intravenous infusion of radioglucose for 5 hr. Porcine hepatic secretion of plasma triglycerides is large in the glucose-fed state, and the secreted triglyceride fatty acids evidently are derived from stored fat or glycon.