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Biomedical subjects

E B Wheeldon

Publications and source records attributed to E B Wheeldon.

At least 19 recordsLinked to original sources
PubMed1997

Intracranial administration of adenovirus expressing HSV-TK in combination with ganciclovir produces a dose-dependent, self-limiting inflammatory response.

Replication-defective adenovirus expressing the herpes simplex thymidine kinase gene (H5.010RSVtk) may be useful in treating human gliomas. To determine the toxicity of this therapeutic strategy, we injected H5.010RSVtk stereotactically into the normal brain of Wistar rats, cotton rats, and rhesus monkeys in conjunction with systemic ganciclovir (GCV) at 10 mg/kg per day. In the Wistar rat, 5.7 x 10(9) pfu resulted in histopathologic injury consisting of localized necrosis, mild gliosis, marked malacia, and focal astrocytosis; however, 1.0 x 10(8) pfu resulted in only mild gliosis and trace meningitis and approximates a "no toxic effect" dose. A dose of 1.0 x 10(9) pfu in both adenoviral immune and adenoviral naive cotton rats resulted in similar findings. In the rhesus monkey, doses ranging from 1.4 x 10(8) pfu to 1.5 x 10(11) pfu resulted in localized gliosis, necrosis, perivascular cuffing, meningitis, and roughly correlated in severity with increasing dose. No histologic evidence of toxicity was found in non-central nervous system (CNS) tissues, and no virus could be cultured from cerebrospinal fluid (CSF), blood, urine, and stool samples. All animals survived to prescribed end points without signs of general toxicity or neurologic symptoms, except for 2 of the rhesus monkeys, one of which became febrile and the other of which developed a grand mal seizure (both subsequently resolved). These toxicology studies define the parameters for developing a phase I clinical trial.

Adenoviridae↗
PubMed1996

Safety of intrapleurally administered recombinant adenovirus carrying herpes simplex thymidine kinase DNA followed by ganciclovir therapy in nonhuman primates.

Preclinical safety and toxicity studies of intrapleural administration of recombinant adenovirus carrying the herpes simplex thymidine kinase gene (H5.010RSVtk) were performed. Previously reported experimental evidence has demonstrated the efficacy of this approach in animal models of a localized thoracic cancer, malignant mesothelioma. H5.010RSVtk was delivered at high dose (10(12) pfu) into the pleural cavity of three non-human primates followed by systemic administration of ganciclovir. No clinical toxicity was noted. Although an inflammatory reaction observable by microscopy was noted in the serosal spaces of the chest cavity, these changes were reversible and were not associated with radiographic sequelae. Extrathoracic viral dissemination was minimal and detectable only by sensitive polymerase chain reaction techniques. This low level of viral dissemination was not associated with detectable clinical, biochemical, or pathologic abnormalities.

Adenoviridae↗
PubMed1996

Treatment of advanced CNS malignancies with the recombinant adenovirus H5.010RSVTK: a phase I trial.

Primary CNS malignancies are responsible for approximately 12,000 deaths annually in the United States. There has been little change in the outcome for adults with malignant brain tumors over the past few decades, despite improvements in surgical techniques and advances in radiation therapy. These tumors are uniformly fatal one to two years after diagnosis. The morbidity and mortality of this disease arise from the effects of a locally invasive, non-metastasizing lesion. The patients may suffer from seizures, paralysis, incoordination, aphasia, confusion, memory loss, sensory deficits or visual loss, depending on the regions of the brain affected. In addition, they usually require large doses of corticosteroids early and late in their illness, and may experience disabling side effects of this treatment, such as edema, proximal myopathy, diabetes, fungal infections or deep vein thrombosis. Few patients in the older age group are able to work after the diagnosis. Most of the patients are incapable of self-care for several months before death. The localized transfer of new genes into cancer cells potentially permits the expression of proteins with specific biologic functions that may provide a means to alter the biology of tumor growth through a variety of mechanisms including increasing tumor immunogenicity, inducing the local expression of toxic agents, and sensitization of tumors to chemotherapeutic agents. Gene therapy with the transfer of the drug susceptibility gene Herpes virus thymidine kinase (HSV-TK) has shown promise in a number of animal models, including CNS tumors. This study will evaluate the use of adenovirus-mediated transfer of the HSV-TK gene into primary human brain tumors followed by systemic treatment with ganciclovir. The goals of this phase I study are to evaluate the overall safety and efficacy of this treatment and to gain insight into the parameters that may limit the general applicability of this approach. In this phase I study, patients with recurrent gliomas will receive stereotactic-guided injections of the virus into the brain tumor, followed by intravenous ganciclovir for 14 days. Patients eligible to undergo a palliative debulking procedure will receive the same treatment followed by resection on day 7. At the time of resection a second dose of virus will be administered intra-operatively into the residual, unresectable portion of the tumor, and intravenous ganciclovir will be continued for additional 14 days. Tissue removed at the time of resection will be analyzed for evidence of adenovirus infection, thymidine kinase expression and signs of inflammation. The size and metabolic activity of all tumors will be followed by volumetric MRI scans and Position Emission Tomography Scans, respectively. Patients will be enrolled in groups of three, with each group receiving successively larger doses of adenovirus. This study will quantify the toxicity of this therapy, and provide evidence as to the duration of transgene expression and virus induced inflammation.

Adenoviridae Infections↗
PubMed1995

Dosing-induced stress causes hepatocyte apoptosis in rats primed by the rodent nongenotoxic hepatocarcinogen cyproterone acetate.

It has been proposed that several nongenotoxic compounds act as hepatocarcinogens by suppressing the apoptosis that would normally act to remove damaged or potentially initiated cells from the liver. During our investigations of this hypothesis using a widely applied protocol, we have found that the stress induced by the process of gavage dosing can induce massive apoptosis in livers uniquely primed by withdrawal of the hepatomitogen cyproterone acetate from the hyperplastic rat liver. This effect of gavage dosing was not seen in livers of naive animals. Apoptosis was measured by both in situ end labeling (ISEL) of the DNA damage associated with programmed cell death and conventional hematoxylin and eosin (H&E) staining of apoptotic morphology. Apoptotic rates measured by H&E increased significantly from 0.005 +/- 0.010% on Day 11 to 0.657 +/- 0.315% of hepatocytes on Day 15, 4 days after cessation of 10 days dosing with CPA (120 mg/kg). The readministration of CPA suppressed > 89% of this Day 15 apoptosis. However, the readministration of vehicle alone (corn oil) caused a 390% increase in apoptosis to 2.56 +/- 1.31% of hepatocytes. Similar results were obtained using ISEL. Measurements of liver to body weight ratios and total DNA per liver reflected these changes in cell loss by apoptosis. In a second experiment, CPA was administered for 10 days as before then animals were subjected to readministration of CPA in corn oil, CPA in saline, corn oil, saline, or sham dosed. Again, apoptosis was dramatically suppressed by the readministration of CPA in either vehicle but was dramatically increased to around 2% of hepatocytes in all other groups, including the sham dosed group. Data on food consumption provided no evidence for a reduction in food intake as a causative agent but rather pointed to a less efficient usage of food in the stressed animals. The ability of stress to induce liver apoptosis should be borne in mind in the design and interpretation of future toxicological studies aimed at understanding the putative suppression of apoptosis by liver nongenotoxic carcinogens and other toxicants.

Animals↗
PubMed1995

Non-genotoxic hepatocarcinogens stimulate DNA synthesis and their withdrawal induces apoptosis, but in different hepatocyte populations.

Non-genotoxic hepatocarcinogenesis may involve suppression of the hepatocyte apoptosis that would normally remove damaged or initiated cells. These protected hepatocytes could then remain as preferential targets for promotion by this class of compounds. Here we demonstrate clearly that the non-genotoxic liver carcinogens and hepatomitogens cyproterone acetate (CPA) and nafenopin, a peroxisome proliferator, both suppress the basal level of rat liver apoptosis in vivo. After 10 days of dosing with CPA (120 mg/kg/day) or nafenopin (25 mg/kg/day) there were 0.005 +/- 0.010 and 0.002 +/- 0.021 apoptotic bodies/100 hepatocytes respectively, compared with 0.031 +/- 0.008 per 100 in controls. Concomitant with this suppression of apoptosis, bromodeoxyuridine (BrdU) labelling indices and mitotic figures rose, confirming a perturbation of both sides of the growth equation between cell death and replication. Withdrawal of CPA or nafenopin resulted in a 100- to 200-fold elevation in apoptosis. This was inhibited by the re-administration of either compound. To investigate if cells protected from apoptosis by non-genotoxic carcinogens are targets for replication, we examined the replicative history of the apoptotic bodies generated upon withdrawal of CPA or nafenopin. Rats were administered BrdU during the hyperplastic phase of compound administration (0-10 days). Livers were examined 5 days after compound withdrawal. With both CPA and nafenopin, apoptotic bodies and S phase were predominantly in the periportal region. However, despite this zonal co-localization, very few (< 10%) of the apoptotic bodies were labelled with BrdU. Overall, our data provide in vivo evidence to support the hypothesis that non-genotoxic hepatocarcinogens such as CPA and the peroxisome proliferators suppress apoptosis. Surprisingly, the majority of the hepatocytes generated during compound-induced hyperplasia were protected from apoptosis during liver regression. These data contribute to our understanding of clonal selection and promotion during non-genotoxic hepatocarcinogenesis.

Animals↗
PubMed1994

Image analysis of bromodeoxyuridine (BrdU) staining for measurement of S-phase in rat and mouse liver.

We developed a system for quantifying the numbers of bromodeoxyuridine (BrdU)-labeled hepatocyte nuclei in rat and mouse liver with an automated image analysis system. We began by developing a protocol for BrdU staining that would provide consistently intense staining to facilitate identification of both labeled and unlabeled nuclei by image analysis. Preliminary studies detected and characterized hepatocyte nuclei and differentiated them from non-hepatocyte nuclei using area and form factors. The parameters were selected to optimize discrimination between the two populations, selecting 90% of hepatocyte and 5% non-hepatocyte nuclei. Finally, we developed a program for automatic counting of BrdU-labeled hepatocyte and total hepatocyte nuclei. Results obtained from this method correlated well with data collected by a microscopist over a wide range of labeling indices. The automated system reduces interobserver variation and should minimize intraobserver error, as well as reducing the tedium of measuring labeling indices in the liver. Moreover, the techniques described should be applicable to other tissues.

Animals↗
PubMed1993

Therapeutic intervention in a rat model of ARDS: IV. Phosphodiesterase IV inhibition.

The following study was performed to determine the effects of phosphodiesterase IV (PDE-IV) inhibition and its attenuation of tumor necrosis factor (TNF alpha) production in a rat model of the Adult Respiratory Distress Syndrome (ARDS). Rats were either unexposed (n = 8), pretreated orally with vehicle prior to intratracheal saline exposure (n = 11), pretreated with vehicle prior to 7 mg/kg intratracheal endotoxin (LPS) administration (n = 22), or pretreated with 5 or 50 mg/kg rolipram prior to LPS exposure (n = 6 and 7, respectively). Blood was sampled 1 and 3 hr post LPS exposure and assayed for plasma TNF alpha concentrations. Twenty-four hours after LPS exposure, blood was sampled again for hematologic measurements. The rats were then anesthetized and exsanguinated. Bronchoalveolar lavage (BAL) was performed after the lung of each rat was removed and weighed. Rolipram pretreatment was protective against LPS-induced mortality and also resulted in reduced plasma TNF alpha concentrations. LPS induced pulmonary edema, as indicated by wet/dry lung weight ratio (W/D) and total BAL protein content (TP) was attenuated by rolipram pretreatment. LPS-induced alveolar hemorrhage was reduced by rolipram pretreatment, but LPS-induced pulmonary neutrophilia was not. The hemoconcentration induced by LPS was reduced by rolipram, as was the LPS-induced thrombocytopenia. However, LPS-induced changes in circulating leukocyte populations were actually exacerbated by rolipram. LPS-induced alterations in renal and hepatic function, indicated by increased blood urea nitrogen (BUN), alanine aminotransferase (ALT), and aspartate aminotransferase (AST), were inhibited by rolipram.(ABSTRACT TRUNCATED AT 250 WORDS)

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1992

Intratracheal aerosolization of endotoxin in the rat: a model of the adult respiratory distress syndrome (ARDS).

A technique is described for the intratracheal aerosolization of endotoxin into the rat. Using a miniaturized nozzle within the tracheal lumen to optimize uniform distribution 0.5 ml of an endotoxin solution (7 mg/kg) was aerosolized and dispersed throughout the lung. Time course studies of pulmonary function and histological changes revealed marked functional and morphological changes by 24 h. Histopathologic changes consisted of widespread pulmonary oedema and a diffuse neutrophilic alveolitis. At the same time, there were significant decreases in tidal volume, minute ventilation and lung compliance. Haematologic changes were also seen, including profound thrombocytopaenia and leukopaenia together with an increased haematocrit, indicating systemic effects in this model. Bronchoalveolar lavage (BAL) at 24 h revealed significant increases in BAL protein, erythrocytes and neutrophils. The functional, cytological and histological changes observed after endotoxin challenge mimic those seen in the Adult Respiratory Distress Syndrome in humans and can thus be used as a model to compare the efficacy of a variety of therapeutic interventions for this syndrome.

Administration, Inhalation↗
PubMed1991

Therapeutic intervention in a rat model of adult respiratory distress syndrome: II. Lipoxygenase pathway inhibition.

The present study was designed to investigate the role of 5-lipoxygenase (5LO) metabolites in an endotoxin (LPS)-induced model of the adult respiratory distress syndrome (ARDS) in the rat. The therapeutic value of two 5LO inhibitors and a specific LTB4 and a LTD4 receptor antagonist were examined. Rats were treated 1 hr prior to administration of aerosolized LPS. Rats were either unexposed (n = 11), or pretreated with vehicle sham (n = 63), 50 mg/kg phenidone t.i.d. (n = 7, n = 10 for assessment of mortality), 30 mg/kg SK&F 103842 b.i.d. (n = 6), 50 mg/kg SK&F 106203 t.i.d. (n = 11), or 5 mg/kg SK&F 107324 b.i.d. (n = 6) 1 hr prior to the administration of aerosolized endotoxin (LPS, 7 mg/kg) or phosphate-buffered saline (PBS, n = 22). Twenty-four hours later, blood samples were collected for hematologic evaluation and after wet lung weight was determined, broncho-alveolar lavage (BAL) was performed to measure cells counts and total protein (TP). 5LO inhibition and LTD4 receptor antagonism reduced LPS-induced mortality to zero compared to 35% in rats pretreated with vehicle sham. Pretreatment with the LTD4 receptor antagonist attenuated the LPS-induced increased in wet/dry lung weight (W/D) whereas 5LO inhibition reduced TP increases. Both 5LO inhibition and LTD4 receptor antagonism attenuated the LPS-induced BAL erythrocyte increase. The LPS-induced thrombocytopenia was attenuated by phenidone, the 5LO receptor antagonist. We conclude that the increased microvascular permeability was associated with the formation of 5LO products since 5LO inhibition lessened the severity of the LPS-induced increase in W/D and TP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Therapeutic intervention in a rat model of adult respiratory distress syndrome: III. Cyclooxygenase pathway inhibition.

Current strategies for the treatment of ARDS have been unsuccessful in reducing mortality. In the present study, we have evaluated the role of cyclooxygenase (CO) products in a rat model of ARDS by testing naproxen, indomethacin, ibuprofen, and a thromboxane A2 (TXA2) receptor antagonist (SK&F 96148). Rats were treated 1 hr prior to endotoxin (LPS) exposure and 24 hr later, survival, body weight changes, wet/dry lung weight (W/D), total protein content (TP) of the bronchoalveolar lavage (BAL) fluid, and total erythrocyte and differential leukocyte counts of the BAL fluid were measured. In addition, the following hematologic measurements were taken: hemoglobin (Hb), hematocrit (Hct), circulating erythrocyte, differential leukocyte, and platelet counts. Treatment with the TXA2 receptor antagonist reduced mortality to zero after 24 hr after LPS administration. Other compounds had no significant effect on LPS-induced mortality. Pretreatment with CO inhibitors or the TXA2 receptor antagonist attenuated the LPS-induced increase in TP and W/D. Although all compounds tended to reduce the LPS-induced increase in BAL erythrocytes, only the TXA2 receptor antagonist did so significantly. The LPS-induced increase in BAL neutrophil counts was significantly reduced by 30 mg/kg ibuprofen, but not by the other compounds. In fact, the TXA2 receptor antagonist actually exacerbated BAL neutrophil counts, but diminished the peripheral neutrophilia and lymphopenia induced by LPS. None of the CO inhibitors tested significantly affected LPS-induced hematologic responses. We conclude that by virtue of its protection against LPS-induced mortality, the TXA2 receptor antagonist was the most effective compound in this model. However, it did cause certain negative side effects such as increased pulmonary inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Microwave fixation of the lung.

A technique for microwave fixation of inflated rat lung is described. Conventional intratracheal fixation with instillation of fixative into the airways at a constant pressure results in pressure artifacts as well as flushing and disruption of cells and exudates. Microwave fixation fixes these elements in situ without disruption and thus is valuable when evaluating the distribution of inflammatory infiltrates. Exudative pneumonitis was produced in the rat using intratracheal instillations of either endotoxin or silica and comparisons were made between histologic sections fixed using either standard formalin fixation or microwave fixation.

Animals↗
PubMed1990

Therapeutic intervention in a rat model of ARDS: I. Dual inhibition of arachidonic acid metabolism.

The protective effects of altered arachidonic acid metabolism, using either methylprednisolone or a dual cyclooxygenase and 5-lipoxygenase inhibitor (SK&F 86002), were compared in a rat model of adult respiratory distress syndrome (ARDS). Rats were either unexposed (n = 9) or pretreated with vehicle (n = 25), 100 mg/kg SK&F 86002 (n = 8) or 30 mg/kg methylprednisolone (MP, n = 7) 1 h prior to the intratracheal administration of 7 mg/kg aerosolized endotoxin (LPS) or phosphate buffered saline (PBS). Twenty-four hours later, blood samples were collected and the rats were anesthetized and exsanguinated. The lungs were surgically removed, weighed and bronchoalveolar lavage (BAL) was performed. LPS caused 30-35% mortality and induced significant differences in body weight, BAL erythrocyte and neutrophil counts, lung wet/dry weight ratio (W/D), total BAL protein (TP), hemoglobin (Hb), hematocrit (HCT), and circulating leukocyte and platelet counts as compared with controls. Pretreatment with MP reduced mortality to zero and also attenuated the LPS-induced alterations in body weight, W/D, TP, BAL erythrocyte count, and circulating platelet count. However, MP exacerbated LPS-induced increases in Hb, HCT and circulating neutrophil counts while enhancing lymphopenia. Pretreatment with SK&F 86002 also reduced mortality to zero and attenuated LPS-induced alterations in W/D, TP, HCT and circulating platelet count. Like MP, SK&F 86002 exacerbated the LPS-induced lymphopenia, and increased circulating neutrophils above baseline values. We conclude that both MP and SK&F 86002 provided protection against LPS-induced responses in this model of ARDS. Mechanistically, this indicates the critical role of eicosanoid mediators in this model. Therapeutically, SK&F 86002, or a similar compound, may be beneficial in preventing the acute phase responses so harmful to ARDS patients.

Animals↗
PubMed1989

Cardiovascular and pulmonary effects of human recombinant tumor necrosis factor in the conscious rat.

The purpose of this study was to examine the dose response to a highly purified human recombinant tumor necrosis factor (TNF alpha) preparation (1-2 x 10(7) U/mg; less than 0.05 ng endotoxin/mg TNF alpha) in the conscious rat. Rats received intravenous bolus injections of 0.3 mg/kg (n = 6), 1.0 mg/kg (n = 17), 3.0 mg/kg (n = 11), or 10 mg/kg (n = 15) of TNF alpha, 30 mg/kg (n = 7) Salmonella enteritidis endotoxin (LPS), or isotonic saline (n = 11). Upon termination of the experiment, the lungs were removed for lavage or histology. Survival was 0% 24 hr after the injection of LPS and 83, 59, 73, and 73% after the lowest to highest doses of TNF alpha, respectively. As with endotoxin, TNF alpha caused a dose-dependent increase in heart rate (HR) (P less than 0.05) within 0.5 hr of administration, which remained elevated throughout the 24 hr period. TNF alpha had no effect on mean arterial blood pressure (MABP) acutely, but it caused a 15-20% decrease in MABP 24 hr post exposure (P less than 0.05). TNF alpha increased hematocrit within 0.5 to 3 hr in all dose groups by 10-15%. Furthermore, TNF alpha produced a thrombocytopenia in all dose groups, although the decrease in platelet count was less than that produced by endotoxin. TNF alpha doses of 1-10 mg/kg caused leukopenia within 0.5 hr (P less than 0.05). Lavage and histology revealed no changes in the number of pulmonary neutrophils. These results suggest that TNF alpha stimulated dose-dependent responses, which were consistent with those produced by LPS. However, these responses to TNF alpha were appreciably smaller than those reported for either LPS or for TNF alpha from other sources.

Animals↗
PubMed1988

The effect of human recombinant tissue-type plasminogen activator on clinical and laboratory parameters of hemostasis and systemic plasminogen activation in the dog and the rat.

The effect of human recombinant tissue-type plasminogen activator (rt-PA) on parameters of hemostasis and systemic plasminogen activation was studied in the dog and rat. Effects on screening coagulation times, fibrinogen concentration, fibrin/fibrinogen degradation products, and plasminogen and alpha 2-antiplasmin (alpha 2-AP) activities in plasma were examined following single bolus injections of 0.5-5.0 mg/kg, single and repeated 3 hr infusions of 0.75-7.5 mg/kg and 24 hr infusions of 6.0 and 30.0 mg/kg administered intravenously to dogs. Rats receiving single or 14 daily injections of 5.0-30.0 mg/kg i.v. were similarly monitored. Systemic fibrinogenolysis (greater than 50% decrease in fibrinogen, plasminogen or alpha 2-AP values) was observed in dogs receiving greater than or equal to 1.0 mg/kg as a bolus, greater than or equal to 3.75 mg/kg (20.8 micrograms or 1.19 x 10(4) IU kg-1min-1) as a 3 hr infusion and greater than or equal to 6 mg/kg (4.2 micrograms or 2.42 x 10(3) IU kg-1min-1) as a 24 hr infusion; and in rats treated with bolus injections of 30 mg/kg rt-PA. Clinical and laboratory indications of impaired hemostasis and bleeding (anemia, prolonged coagulation times and post-mortem evidence of hemorrhage) were associated with these effects, which together were dose-dependent and influenced by the rate of infusion. The incidence of major hemorrhage was variable and limited to animals receiving prolonged (24 hr) or repeated infusions.

Animals↗
PubMed1988

Central nervous system malformations induced by triamcinolone acetonide in nonhuman primates: pathogenesis.

The pathogenetic sequence for TAC-induced encephalocele is in agreement with hypotheses proposing that neural tube closure is followed by protrusion of the mesencephalon, with subsequent growth and development resulting in herniation of the cerebrum and cerebellum. This model could serve to clarify the pathogenesis of encephalocele and to stimulate further study in comparing this defect to other dysraphic states. Triamcinolone acetonide (TAC) was administered intramuscularly (10 mg/kg) to 16 pregnant rhesus monkeys (Macaca mulatta) for 5 alternate days of pregnancy, beginning on gestational day (GD) 23. Conceptuses were removed by hysterotomy at GD 35, 42, 50, or 70 and examined grossly and histologically. Length, area, and perimeter of the tectum and aqueduct area and perimeter were measured with an image analyzer. Changes in treated specimens were suggestive of forces within or ventral to the tectum resulting in dorsal protrusion, rostral-posterior stretching, and attenuation. The angle of the cephalic, pontine, and cervical flexures was also measured. The more acute angle of the cephalic flexure and less acute cervical flexure of treated specimens could represent altered orientation secondary to a mesenchymal deficiency. However, the less acute angle of the pontine flexure in treated specimens suggests an intrinsic alteration in the neural tube. This suggests that encephalocele may result from a combination of mesenchymal and neural tube abnormalities.

Animals↗
PubMed1988

Pulmonary angiotensin-converting enzyme activity in the oxygen-toxic sheep.

Despite the potential utility of endothelial metabolic substrates for the early clinical detection of acute lung injury, the relationship between lung capillary injury and pulmonary endothelial metabolic function remains incompletely understood. Previous studies have shown that lung capillaries are damaged by oxygen toxicity in the sheep; however, metabolic functions of the pulmonary endothelium have not been examined in this otherwise well-characterized animal model of lung injury. Therefore, we studied the activity of pulmonary endothelial angiotensin-converting enzyme (ACE) in five unanesthetized adult sheep that breathed 100% O2 via tracheostomy for 3 days and in four other sheep that breathed compressed air. In contrast to the sheep that breathed air, the sheep that breathed O2 developed substantial arterial hypoxemia and hypercapnia, an increased alveolar-to-arterial O2 gradient and a slight respiratory acidosis. Morphological examination of lungs from sheep that breathed O2 revealed a multifocal distribution of injury, including interstitial edema, capillary endothelial damage, and alveolar epithelial damage. Indicator-dilution methods were used to assess first-pass pulmonary metabolism of the ACE substrate [3H]Benzoyl-Phe-Ala-Pro (BPAP) and the apparent kinetics (KM and Vmax) of ACE activity. Pulmonary metabolism of BPAP exhibited saturability, was reduced by an ACE inhibitor (enalaprit), and did not result from the activity of circulating plasma ACE. There was no difference between the 2 groups of sheep in the percent metabolism of either 0.1 mumol BPAP/kg or 1.0 mumol BPAP/kg or in the KM of BPAP metabolism. In both groups, the Vmax and Vmax/KM decreased as a result of reductions in cardiac output and volume distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Intravascular macrophages in the sheep lung.

The presence of a resident population of intravascular macrophages in the sheep lung was investigated. Injection of fluorescent microspheres into the sheep results in uptake by a population of large phagocytic cells scattered within the alveolar capillaries of the lung. By contrast, the rat lung has no uptake of these fluorescent microspheres into the alveolar walls. The cells are large, extremely irregular in shape, often exceed 30 micron in length, and lie within the vascular lumen, apposed to the underlying endothelium. They have several features characteristic of mature macrophages including numerous pseudopodia, a partially preserved cell coat, wormlike bodies ("micropinocytosis vermiformis"), and numerous phagosomes that often contain erythrocytes. Unlike other species such as the rat, in which the mononuclear phagocyte system is distributed primarily in the liver and spleen, the sheep lung has a significant clearance function. Moreover, the presence of these cells in the lung may have important implications for studies of the inflammatory response to pulmonary vascular injury in the sheep.

Animals↗