Tyrphostin AG 556 improves survival and reduces multiorgan failure in canine Escherichia coli peritonitis.

Tyrosine kinase-dependent cell signaling is postulated to be a pivotal control point in inflammatory responses initiated by bacterial products and TNF. Using a canine model of gram-negative septic shock, we investigated the effect of tyrosine kinase inhibitors (tyrphostins) on survival. Animals were infected intraperitoneally with Escherichia coli 0111: B4, and then, in a randomized, blinded fashion, were treated immediately with one of two tyrphostins, AG 556 (n = 40) or AG 126 (n = 10), or with control (n = 50), and followed for 28 d or until death. All animals received supplemental oxygen, fluids, and antibiotics. Tyrphostin AG 556 improved survival times when compared to controls (P = 0.05). During the first 48 h after infection, AG 556 also improved mean arterial pressure, left ventricular ejection fraction, cardiac output, oxygen delivery, and alveolar-arterial oxygen gradient compared to controls (all P < or = 0.05). These improvements in organ injury were significantly predictive of survival. Treatment with AG 556 had no effect on clearance of endotoxin or bacteria from the blood (both P = NS); however, AG 556 did significantly lower serum TNF levels (P = 0.03). These data are consistent with the conclusion that AG 556 prevented cytokine-induced multiorgan failure and death during septic shock by inhibiting cell-signaling pathways without impairing host defenses as determined by clearance of bacteria and endotoxin.

In vivo bypass of hemophilia A coagulation defect by factor XIIa implant.

Hemophilia A and B coagulation defects, which are caused by deficiencies of Factor VIII and Factor IX, respectively, can be bypassed by administration of recombinant Factor VIIa. However, the short half-life of recombinant Factor VIIa in vivo negates its routine clinical use. We report here an in vivo method for the continuous generation of Factor VIIa. The method depends on the implantation of a porous chamber that contains Factor Xa or XIIa, and continuously generates Factor VIIa bypass activity from the subject's own Factor VII, which enters the chamber by diffusion. Once inside, the Factor VII is cleaved to Factor VIIa by the immobilized Factor Xa or XIIa. The newly created Factor VIIa diffuses out of the chamber and back into the circulation, where it can bypass the deficient Factors VIII or IX, and enable coagulation to occur. In vitro, this method generates sufficient Factor VIIa to substantially correct Factor VIII-deficient plasma when assessed by the classical aPTT coagulation assay. In vivo, a Factor XIIa peritoneal implant generates bypass activity for up to one month when tested in rhesus monkeys. Implantation of such a chamber in a patient with hemophilia A or B could eventually provide a viable alternative to replacement therapies using exogenous coagulation factors.

Liberation of Printed Circuit Assembly (PCA) and dust generation in relation to mobile phone design in a size reduction process.

Complex electronic devices entering our recycling systems often generate losses in the whole treatment chain. For better liberation, crucial for the mechanical separation process, the devices are crushed which also generates dusts that are not recovered. This study investigated the relation between the liberation of Printed Circuit Assembly (PCA) and dust generation in the crushing process of two different types of mobile phone samples. The results revealed that the overall PCA grade in both samples was approximately 70% with around 3.4% dust generation. However, the liberation distribution of PCAs differed between mobile phones resulting in better distribution for sophisticated mobile phones due among other things to the initial size of the phones. Further, the dust fractions comprised both noble and valuable metals but also contaminants that need to be taken into account when further processing is planned. A higher gold concentrate was detected in dusts from regular phones since the protective plastic casing crushed more easily thus exposing the PCA surface for grinding.

Conversion of the severe to the moderate disease phenotype with donor leukocyte microchimerism in canine leukocyte adhesion deficiency.

Leukocyte adhesion deficiency-1 (LAD-1), a genetic immunodeficiency disease characterized by life-threatening bacterial infections, results from the defective adherence and migration of leukocytes due to mutations in the leukocyte integrin CD18 molecule. Canine LAD (CLAD) represents the canine homologue of the severe phenotype of LAD-1 in children. In previous studies we demonstrated that non-myeloablative stem cell transplantation from matched littermates resulted in mixed donor-host chimerism and reversal of the disease phenotype in CLAD. In this study, we describe two CLAD dogs with less than 2% donor leukocyte chimerism following non-myeloablative transplant. Both dogs are alive more than 24 months after transplant with an attenuated CLAD phenotype resembling the moderate deficiency phenotype of LAD. The improvement in the CLAD phenotype with very low levels of donor CD18(+) leukocytes correlated with the preferential egress of the CD18(+) neutrophils into extravascular sites. The clinical response with very low levels of donor CD18(+) leukocytes in CLAD supports using this model for testing gene therapy strategies since the low levels of gene-corrected hematopoietic cells expected with hematopoietic gene therapy would likely have a therapeutic effect in CLAD.

Rescue of experimental intrathecal methotrexate overdose with carboxypeptidase-G2.

The carboxypeptidase G class of enzymes rapidly hydrolyze methotrexate (MTX) into the inactive metabolites 4-deoxy-4-amino-N10-methylpteroic acid (DAMPA) and glutamate. This study evaluated the use of carboxypeptidase-G2 (CPDG2) as a potential intrathecal (IT) rescue agent for massive IT MTX overdose. The CSF pharmacokinetics of MTX with and without CPDG2 rescue was studied in adult rhesus monkeys (Macaca mulatta) using a nontoxic IT 5 mg dose (equivalent to 50 mg in humans). Without CPDG2 rescue, peak CSF MTX concentration was 2,904 +/- 340 mumol/L. Within 5 minutes of administration of 30 U IT CPDG2, CSF MTX concentrations decreased greater than 400-fold to 6.55 +/- 6.7 microM. Subsequently, groups of three monkeys received either 25 mg IT MTX (equivalent to 250 mg in humans) followed by 150 U IT CPDG2 or 50 mg IT MTX (equivalent to 500 mg in humans) followed by 300 U IT CPDG2. All animals survived without neurotoxicity. Our studies suggest that CPDG2 may prove to be an important addition to the currently recommended strategy for the management of IT MTX overdose.

In vivo imaging of insulin receptors in monkeys using 18F-labeled insulin and positron emission tomography.

We previously described a prosthetic group methodology for incorporating 18F into peptides and showed that 18F-labeled insulin (18F-insulin) binds to insulin receptors on human cells (IM-9 lymphoblastoid cells) with affinity equal to that of native insulin (1). We now report studies using 18F-insulin with positron emission tomography to study binding to insulin receptors in vivo. Positron emission tomography scans were performed in six rhesus monkeys injected with 0.3-1.4 mCi of 18F-insulin (approximately 0.1 nmol, SA 4-11 Ci/mumol). Integrity of the tracer in blood, determined by immunoprecipitation, was 94% of control for the first 5 min and decreased to 31% by 30 min. Specific, saturable uptake of 18F was observed in the liver and kidney. Coinjection of unlabeled insulin (200 U, approximately 1 nmol) with the 18F-insulin reduced liver and increased kidney uptake of the labeled insulin. Liver radioactivity was decreased by administration of unlabeled insulin at 3 min, but not 5 min, after administration of the tracer, while some kidney radioactivity could be displaced 5 min after injection. Clearance of 18F was predominantly in bile and urine. 18F-insulin is a suitable analogue for studying insulin receptor-ligand interactions in vivo, especially in the liver and kidney.

Mechanical pre-treatment of mobile phones and its effect on the Printed Circuit Assemblies (PCAs).

The recycling of Waste Electrical and Electronic Equipment (WEEE) has attracted a notable amount of interest during the last few decades due to the high metal concentrations and substantial increase in the growth rate of WEEE. In addition, higher recovery and recycling rates required by the European Union demand more comprehensive treatment of WEEE. However, complex product design and the presence of harmful substances together with low concentrations of special metals present challenges for processing. This study examines the effect of mechanical treatment of mobile phones on metal concentrations in the printed circuit assembly (PCA) fraction compared to manual dismantling. The designed mechanical treatment process including crushing, sieving, magnetic-, eddy current- and sensor-based separation was able to separate plastics, ferrous metals, PCA and stainless steel for further treatment. The process separated PCA with an efficiency of 85%. However, the quality of the separated PCAs was poor compared with "pure" manually dismantled PCAs. The primary crushing of mobile phones destroys PCAs thus resulting in the loss of especially precious metals used in the connector coatings and in the surface-mounted components. As a result, the theoretical value of the produced PCA fraction is only half compared to using manual dismantling. However, high labour costs in western countries and low capacity may hinder the feasibility of hand dismantling.

Linear growth in the rabbit is continuous, not saltatory.

A recent report in Science suggests that human growth occurs in brief bursts, up to 1.65 cm in a single day, separated by extended periods of stasis, lasting up to 63 days. Thus, the organism is proposed to alternate between two states, one with a growth velocity of zero, the other with a mean annualized growth velocity greater than 350 cm/yr. These observations, if correct, suggest the existence of a previously unsuspected hormonal mechanism capable of abruptly switching growth plate cell division on and off and of synchronizing cellular growth not only throughout the growth plate, but presumably throughout all the growth plates in the organism. However, the experimental assessment of short-term growth velocity in the human faces the formidable obstacle of a technical error of measurement that exceeds the mean daily growth rate. Accordingly, we tested the saltatory growth hypothesis by measuring proximal tibial growth in the rabbit, a model in which daily growth rate could be measured more than 15 times more accurately than in the human. The model of saltation and stasis predicts a majority of daily growth velocities clustered around zero, and a minority of high growth velocities, that is, a bimodal distribution. The frequency distribution of observed daily growth velocities instead approximated a single Gaussian distribution, indicating continuous growth. We conclude that linear growth, in the most accurate mammalian system yet studied, is continuous, not saltatory.

Human chorionic gonadotropin maintains plasma progesterone at pregnancy levels in rhesus monkeys.

Peripheral plasma progesterone (P) levels in the rhesus monkey remain relatively constant both during the latter half of pregnancy and for long periods after fetectomy (removal of the fetus with the placenta left in situ) or ovariectomy. The constancy is maintained despite what appears to be reciprocal changes in the relative contributions of ovary and placenta. Placental regulation of the corpus luteum is likely, but it is not known if the corpus luteum responds to a gonadotropic stimulus in the later stages of pregnancy. In this study, we have investigated the effects of hCG administration in postdelivery monkeys (normally pregnant, fetectomized, ovariectomized and sham ovariectomized animals) and have determined if hCG administration maintains plasma P at pregnancy levels. hCG maintained P at pregnancy levels after surgical removal of the conceptus near term in both normally pregnant and previously fetectomized monkeys over a 7-day treatment period. hCG treatment after normal delivery maintained P levels in sham-ovariectomized but not in ovariectomized monkeys over an 8-day treatment period. The magnitude of the response to hCG declines over the treatment period in all groups except fetectomized monkeys, although hCG levels in the peripheral plasma are quite constant. These results indicate that the ovary of late pregnancy is fully capable of producing P at normal values and is responsive to this gonadotropin.

Catch-up growth after glucocorticoid excess: a mechanism intrinsic to the growth plate.

In humans and other mammals, the release from growth-inhibiting conditions, such as glucocorticoid excess, leads to supranormal linear growth. The prevailing explanation for this catch-up growth involves a central nervous system mechanism that compares actual body size to an age-appropriate set-point and adjusts growth rate accordingly via a circulating factor. Although such a neuroendocrine "sizostat" was hypothesized more than 30 yr ago, its existence has never been confirmed experimentally. Here we show that suppression of growth within a single growth plate by locally administered glucocorticoid is followed by local catch-up growth that is restricted to the affected growth plate. Thus, the catch-up growth cannot be explained by neuroendocrine mechanism but, rather, must arise from a mechanism intrinsic to the growth plate. To explain this finding, we propose that the normal senescent decline in growth plate function depends not on age per se, but on the cumulative number of stem cell divisions, and that glucocorticoid administration, by suppressing stem cell proliferation, delays senescence, resulting in catch-up growth after the growth-inhibiting agent is removed.

Induction of growth plate cartilage ossification by basic fibroblast growth factor.

In mammals, longitudinal bone growth results from the precise coupling of chondrogenesis and osteogenesis within the epiphyseal growth plate, a process termed endochondral ossification. The mechanisms coupling chondrogenesis and osteogenesis are unknown. Previous studies have shown that both basic fibroblast growth factor (bFGF) and acidic FGF are expressed by growth plate chondrocytes. Here we show that bFGF, infused directly into the rabbit proximal tibial growth plate, accelerates vascular invasion and ossification of growth plate cartilage. Our results suggest the possibility that bFGF (or a related member of the FGF family) couples osteogenesis to chondrogenesis by attracting vascular and bone cell invasion from the adjacent metaphyseal bone.

Effects of pituitary-testicular axis suppression in utero and during the early neonatal period with a long-acting luteinizing hormone-releasing hormone analog on genital development, somatic growth, and bone density in male cynomolgus monkeys in the first 6 months of life.

The specific role of late fetal and early neonatal gonadotropins and/or sex steroids on genital development, linear growth, and bone mass accretion remains unclear. To investigate this, we attempted to selectively suppress pituitary-testicular activation from midgestation through early infancy with a long-acting LHRH agonist (LHRHA), D-Trp6,Pro9-NEt-LHRH, in microspheres. The agonist was injected sc on days 72-81 in utero, on day 1 of life, and 3 months postnatally in male cynomolgus monkeys. Control animals were treated with placebo. We then examined the consequences of such an intervention in the first 6 months of life. In the LHRHA-treated animals, marked suppression of plasma testosterone and gonadotropin levels were evident in the first 3 months of life compared to control values. The mean testicular volumes of the LHRHA group were significantly lower at birth and in the first 2 months of life than those of the placebo group (P less than 0.05). However, by 4 months of age, the mean testicular volumes of the two groups were comparable. Similarly, the mean stretched phallic lengths of the LHRH approximately A group were significantly lower than those of the placebo group throughout the first 6 months of life (P less than 0.05). By contrast, LHRHA treatment had no effect on somatic growth, as mean body weights, total body lengths, and trunk lengths of the two groups were similar over the first 6 months of life. Mean bone widths and densities of the distal third of the left radius and the left midfemur were similar in the two groups at 1 and 6 months of life. We conclude that pituitary-testicular axis suppression with a long-acting LHRHA in utero and during early infancy results in markedly stunted penile and testicular growth without affecting general somatic growth and bone density of appendicular cortical bone in the cynomolgus monkey in the first 6 months of life. Thus, an intact fetal and neonatal pituitary-testicular axis is critical for normal genital growth. However, the sex steroid requirement for maintenance of bone mineral content of appendicular cortical bone may be lower than that necessary for normal genital development.

Brain metabolic correlates of hypoxic-ischemic cerebral necrosis in mid-gestational sheep fetuses: significance of hypotension.

Mid-gestational sheep fetuses exposed to marked hypoxia for 2 h remain brain intact if MABP is maintained above 30 mm Hg. On the other hand, similarly hypoxic fetuses, if they experience reductions in MABP below 30 mm Hg, develop foci of necrosis that predominantly affect hemispheric white matter and neostriatum. Cortex damage is more restricted and is usually associated with more massive underlying white matter damage. The present study examines the brain metabolic basis for the important role of hypotension in brain injury development in marked hypoxia. Sheep fetuses rendered hypoxic by respiring their ewes with 11% oxygen (fetal PaO2 = 8-12 mm Hg) in which MABP was maintained above 30 mm Hg showed increases in brain lactic acid concentrations to 7-13 mumol/g but unaltered energy charge. In contrast, fetuses that sustained MABP reductions below 30 mm Hg showed increases in lactic acid concentrations in vulnerable structures to 16-24 mumol/g accompanied by marked decreases in energy charge. The vulnerable structures also showed reductions in fructose concentrations but a variable behavior of other brain metabolites including phosphocreatine, glycogen, and glucose. Thus, the present findings suggest a relation between hypotension during marked hypoxia, low energy charge, lactic acid accumulation in brain at high concentrations, and fetal brain injury. The ewes of hypoxic hypotensive fetuses received pentobarbital at lower doses than did those of fetuses that maintained blood pressure. This suggests that pentobarbital plays an important role in protecting the fetal brain from asphyxia by extending the hypoxic fetus's ability to maintain blood pressure in addition to reducing its brain metabolism.

Hemodynamic effect of the nitroxide superoxide dismutase mimics.

Reactive oxygen species play critical roles in a number of physiologic and pathologic processes. Nitroxides are stable free radical compounds that possess superoxide dismutase (SOD) mimetic activity and have been shown to protect against the toxicity of reactive oxygen species in vitro and in vivo. Tempol, a cell-permeable hydrophilic nitroxide, protects against oxidative stress and also is an in vitro and in vivo radioprotector. In the course of evaluating the pharmacology and toxicity of the nitroxides, Tempol and another nitroxide, 3-carbamoyl-PROXYL (3-CP), were administered intravenously in various concentrations to miniature swine. Tempol caused dose-related hypotension accompanied by reflex tachycardia and increased skin temperature. Invasive hemodynamic monitoring with Swan Ganz catheterization (SGC) confirmed the potent vasodilative effect of Tempol. However, 3-CP had no effect on porcine blood pressure. The hemodynamic effects of Tempol and 3-CP are discussed in the context of differential catalytic rate constants for superoxide disumation that may impact systemic nitric oxide (NO) levels and lead to vasodilation. These findings are consistent with a role for the superoxide ion in the modulation of blood pressure and have potential implications for the systemic use of nitroxides.

Toxicity studies and distribution dynamics of retroviral vectors following intrathecal administration of retroviral vector-producer cells.

The use of intrathecal, retroviral-mediated transfer of the herpes simplex thymidine kinase (HStk) gene and subsequent ganciclovir (GCV) administration has recently been shown to improve survival in a rat model of leptomeningeal carcinomatosis. Clinical application of this approach is attractive because access to the cerebrospinal fluid (CSF) space is relatively noninvasive and distribution of producer cells and vectors may be facilitated by circulation of CSF, overcoming distribution problems inherent in solid tumors. However, meningeal inflammation, transduction and injury to normal CNS tissue, proliferation of the xenogeneic producer cells in the subarachnoid space, immune-mediated injury, and development of hydrocephalus are possible complications of intraventricular or intrathecal administration of vector-producer cells. In addition, the dynamics of producer cell and vector distribution in the CSF are unknown. To address these issues, we evaluated the safety of this approach for gene delivery and assessed the dynamics of distribution of producer cells and retroviral vectors in rats and non-human primates. In rats, transduction of normal central nervous system (CNS) structures surrounding the subarachnoid space was evaluated after intrathecal and intraventricular injections of beta-galactosidase and HStk vector-producer cells, with and without GCV. In primates, beta-galactosidase and HStk vector-producer cells were injected intraventricularly and GCV was administered either intrathecally or intravenously. Toxicity was evaluated by neurologic examination, serial gadolinium-enhanced MRI scans of the brain, and blood and CSF profiles. A subgroup of monkeys received repeated intraventricular injection of vector-producer cells and intravenous GCV. The titer of retroviral-vector was measured in cisternal and lumbar CSF samples after repeated producer cell injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical seizure lateralization in mesial temporal lobe epilepsy: differences between patients with unitemporal and bitemporal interictal spikes.

OBJECTIVE: To compare the reliability of clinical seizure lateralization in temporal lobe epilepsy patients with unitemporal and bitemporal independent interictal spikes and unilateral hippocampal atrophy or sclerosis (HA/HS) on MRI scan. PATIENTS AND METHODS: We studied 11 patients with unitemporal and 10 patients with bitemporal interictal spikes. We calculated a spike ratio by dividing the number of spikes ipsilateral to the side of HA/HS by those occurring contralaterally. RESULTS: Clinical seizure lateralization was correct, i.e., ipsilateral to the side of HA/HS, significantly more often in the unitemporal group. Spike ratios were significantly higher in seizures that were lateralized correctly as compared with both incorrectly and nonlateralized seizures. Within the individual patients, a significant positive correlation between spike ratios and the proportion of correctly lateralized seizures was found. We identified three categories of symptoms according to lateralization accuracy. Category 1 symptoms (version, postictal paresis, and early ictal vomiting/retching) lateralized to the side of HA/HS in 100% of patients in the uni- and bitemporal groups. Category 2 symptoms (dystonic posturing, mouth deviation, postictal dysnomia/dysphasia, and ictal speech) provided a 100% correct lateralization in the unitemporal but not in the bitemporal patients. Category 3 symptoms (nonversive early head turning and unilateral upper extremity automatisms) yielded erroneous lateralization in both patient groups. CONCLUSIONS: We conclude that reliable clinical seizure lateralization in mesial temporal lobe epilepsy can only be achieved in patients with unitemporal interictal spikes, whereas clinical lateralization in patients with bitemporal spikes must be viewed cautiously.

Genital automatisms in complex partial seizures.

OBJECTIVE: To determine which brain region is responsible for the generation of sexual automatisms. METHODS: Ninety consecutive patients with medically refractory focal epilepsy (74 with temporal lobe and 16 with frontal lobe epilepsy) referred to an epilepsy monitoring unit were studied. The occurrence of the following sexual automatisms was assessed during prolonged video-EEG monitoring: 1) repeatedly grabbing or fondling the genitals and 2) pelvic or truncal thrusting or similar movements. RESULTS: Five patients repeatedly fondled or grabbed their genitals during or immediately after some of their seizures. All five had temporal lobe epilepsy, as evidenced from prolonged video-EEG monitoring, high-resolution MRI, and good to excellent outcome after epilepsy surgery. Sexual automatisms did not occur with frontal lobe epilepsy. CONCLUSION: Sexual automatisms cannot be related exclusively to frontal lobe seizures. As previously proposed, apparently sexual hypermotoric pelvic or truncal movements are common in frontal lobe seizures, but this study suggests that discrete genital automatisms, like fondling and grabbing the genitals, are more common in seizures evolving from the temporal lobe.

Long term tolerance of thoracic organs to intraoperative radiotherapy.

The tolerance of mediastinal structures to intraoperative radiotherapy (IORT) was investigated in 3 separate animals trials using 49 adult foxhounds and one limited Phase I trial in 4 patients with Stage II or III non-small cell lung cancer (NSCLC). The 1- to 2-year results of these trials have been previously reported with significant toxicity found at dose levels over 20 Gy. We now report the results of five dogs reserved for long term studies and one Stage II NSCLC patient alive at 5 years. Two dogs received 20 Gy IORT and one received 30 Gy IORT to the esophagus, all three to a single 6 cm field with 9 MeV electrons. One control dog underwent surgery without irradiation. One dog received 20 Gy IORT to a single 5 cm mediastinal field with 13 MeV electrons following left pneumonectomy. At 5 years, all five dogs reserved for a long term evaluation were alive and evaluable with minimal endoscopic and radiographic abnormalities. The one patient alive at 5 years for evaluation received 25 Gy IORT to two matched 6 cm fields with 13 MeV electrons. She has stable dyspnea on exertion and there is no evidence of cancer by endoscopy. We conclude, based on these limited data, that IORT in the mediastinum may be safe at dose levels that do not exceed 20 Gy, and further careful evaluation at these lower treatment doses is warranted to determine efficacy.

Clinical toxicity of peripheral nerve to intraoperative radiotherapy in a canine model.

PURPOSE: The clinical late effects of intraoperative radiotherapy (IORT) on peripheral nerve were investigated in a foxhound model. METHODS AND MATERIALS: Between 1982 and 1987, 40 animals underwent laparotomy with intraoperative radiotherapy of doses from 0-75 Gy administered to the right lumbosacral plexus. Subsequently, all animals were monitored closely and sacrificed to assess clinical effects to peripheral nerve. This analysis reports final clinical results of all animals, with follow-up to 5 years. RESULTS: All animals treated with > or = 25 Gy developed ipsilateral neuropathy. An inverse relationship was noted between intraoperative radiotherapy dose and time to neuropathy, with an effective dose for 50% paralysis (ED50) of 17.2 Gy. One of the animals treated with 15 Gy IORT developed paralysis, after a much longer latency than the other animals. CONCLUSIONS: Doses of 15 Gy delivered intraoperatively may be accompanied by peripheral neuropathy with long-term follow-up. This threshold is less than that reported with shorter follow-up. The value of ED50 determined here is in keeping with data from other animal trials, and from clinical trials in humans.

Effects of intraoperative radiotherapy on vascular grafts in a canine model.

PURPOSE: The effects of intraoperative radiotherapy +/- external beam radiotherapy on prosthetic vascular grafts were investigated in a canine model. METHODS AND MATERIALS: In 1986 and 1987, 30 adult beagles underwent laparotomy with transection and segmental resection of the infrarenal aorta followed by immediate reconstruction with a prosthetic graft. Intraoperative radiotherapy at varying doses from 0-30 Gy was then administered to all animals. Half of the dogs received 36 Gy external beam radiotherapy in 10 fractions postoperatively. Animals were sacrificed and necropsied at predetermined intervals and as clinically indicated to assess early (< or = 6 months) and late (> 6 months) effects to the vascular graft and surrounding normal tissue. RESULTS: Histopathologic analyses of irradiated vascular structures were performed and correlations were made with the clinical outcome. The most frequent early clinical toxicity was graft thrombosis, occurring in 7 of 10 animals followed for < or = 6 months. Early graft thrombus formation appeared unrelated to radiotherapy dose and probably represented a technical surgical complication. Anastomotic stenosis of varying severity occurred in most animals followed > 6 months. Late (> 6 months) graft stenosis was correlated with intraoperative radiotherapy dose. At < or = 20 Gy of intraoperative irradiation, 3 of 14 animals developed late graft occlusion; at > 25 Gy, five of six animals developed late occlusion. On histopathologic review, increasing intraoperative dose and increasing total radiotherapy dose (intraoperative+external beam) appeared to correspond with increasing severity of graft changes seen after 6 months of follow-up. CONCLUSIONS: Thrombus formation is a frequent early complication of vascular graft placement of the infrarenal aorta in our beagle dog model. Intraoperative doses up to 20 Gy appear to contribute minimally to late graft occlusion, while doses > or = 25 Gy contribute to late occlusion with high likelihood. Both intraoperative dose and total radiotherapy dose correlated with late graft occlusion, and with histopathologic changes in the graft and anastomoses.