Nancy R. Clendenon

Boron neutron capture therapy of a rat glioma.

The purpose of the present study was to utilize a well-established rat glioma to evaluate boron neutron capture therapy for the treatment of malignant brain tumors. Boron-10 (10B) is a stable isotope which, when irradiated with thermal neutrons, produces a capture reaction yielding high linear energy transfer particles (10B + 1nth----[11B]----4He(alpha) + 7Li + 2.79 MeV). The F98 tumor is an anaplastic glioma of CD Fischer rat origin with an aggressive biological behavior similar to that of human glioblastoma multiforme. F98 cells were implanted intracerebrally into the caudate nuclei of Fischer rats. Seven to 12 days later the boron-10-enriched polyhedral borane, Na2B12H11SH, was administered intravenously at a dose of 50 mg/kg body weight at varying time intervals ranging from 3 to 23.5 hours before neutron irradiation. Pharmacokinetic studies revealed blood 10B values ranging from 0.33 to 10.5 micrograms/ml depending upon the time after administration, a T1/2 of 6.2 hours, normal brain 10B concentrations of 0.5 microgram/g, and tumor values ranging from 1.1 to 12.8 micrograms/g. No therapeutic gain was seen if the capture agent was given at 3 or 6 hours before irradiation with 4 x 10(12) n/cm2 (10 MW-min; 429 cGy). A 13.5-hour preirradiation interval resulted in a mean survival of 37.8 days (P less than 0.01), compared to 30.5 days (P less than 0.03) for irradiated controls and 22.1 days for untreated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of lysosomal hydrolases of dog spinal cord and cerebrospinal fluid to experimental trauma

Spinal cord damage was induced in dogs by a 400 gm-centimeter force injury to assess an early release of lysosomal enzymes from traumatized cord. In whole cord homogenates, an early decrease in total acid phosphatase and beta-glucuronidase was observed, approaching control levels by 2 hours. With acid phosphatase, total activity increased to 11 7 percent of control by 4 hours. Beta-glucuronidase showed no significant change in free activity at any time up to 4 hours. Dissected gray and white matter trauma samples displayed free, soluble, and total activities similar to controls. Cisternal CSF showed increased beta-glucuronidase and acid phosphatase activity at 30 and 60 minutes, while lumbosacral values were decreased. By 2 hours, acid phosphatase was increased in lumbar fluid and remained elevated for the 24-hour interval studied. Cisternal CSF protein was unchanged throughout the 24-hour period, while lumbosacral values increased at 4 and 24 hours. In traumatized adjacent and control cord segments a significant drop in total acid phosphatase activity in the trauma core samples was noted by 30 minutes and remained lower than control for the 24-hour period. The early drop in total activity in the area of maximal injury suggests enzyme inactivation by free radicals or some unknown inhibitor. The late increase in acid phosphatase activity in surrounding white matter may be due to accumulation of lysosomes within axis cylinders of partially injured nerve fibers. We conclude that lysosomal enzyme release does not appear to play a role in the early phases of the pathophysiologic process of spinal cord trauma.

Ultrastructural microvascular response to boron neutron capture therapy in an experimental model

A CD 344 rat glioma model currently used to investigate boron neutron capture therapy (BNCT) was used to demonstrate an increased survival rate after thermal neutron irradiation enhanced by administration of 10B-enriched polyhedral borane, Na2B12H11SH. To investigate the possible effects of BNCT on normal and tumor microvasculature, we subjected animals to sublethal neutron irradiation with and without intravenous injection of 50 mg/kg of enriched 10B and performed histological and ultrastructural analyses. In the rats that did not undergo tumor transplantation, minimal detectable morphological changes in the microvasculature of the central nervous system were observed after treatment, both in the immediate posttreatment phase and at 10 months. Light microscopy of cerebral cortex and caudate nucleus showed normal cytoarchitecture with no evidence of vessel occlusion, hyalinization, thickening, or reactive gliosis. Electron microscopy demonstrated that the junctional complexes of the endothelial cells, the basal lamina, and the perivascular glia were comparable in both treated and control animals. In those animals examined at 18 months, pathological membrane-bound clusters of electron-dense vesicles were seen in pericytes. In the rats implanted with gliomas, vascular proliferation with evidence of breakdown of the blood-brain barrier and vasogenic edema occurred. In the irradiated animals, we noted increased peritumoral edema 3 days after treatment. At seven days, both increased peritumoral edema and necrosis were noted in the rats treated with BNCT. These observations show that the normal microvasculature of the central nervous system tolerates BNCT at the treatment parameters used in our experimental model; the progressive edema and necrosis found in the peritumoral region after BNCT indicate a pathological endothelial response.

Inhibition of tumor growth in a glioma model treated with boron neutron capture therapy

This investigation attempts to determine whether increased survival time seen when the F98 glioma model is treated with boron neutron capture therapy (BNCT) is a result of inhibition of tumor growth caused by radiation-induced alterations in endothelial cells and normal tissue components. This indirect effect of radiation has been called the tumor bed effect. A series of tumor-bearing rats was studied, using a standardized investigational BNCT protocol consisting of 50 mg/kg of Na2B12H11SH injected intravenously 14 to 17 hours before neutron irradiation at 4 x 10(12) n/cm2. Ten rats, serving as controls, received no treatment either before or after tumor implantation. A second group of 10 rats was treated with BNCT 4 days before tumor implantation; these animals received no further treatment. The remaining group of 10 rats received no pretreatment but was treated with BNCT 10 days after implantation. Histological and ultrastructural analyses were performed in 2 animals from each group 17 days after implantation. Survival times of the untreated control animals (mean, 25.8 days) did not differ statistically from the survival times of the rats in the pretreated group (mean, 25.5 days). The rats treated with BNCT after implantation survived significantly longer (P less than 0.02; mean, 33.2 days) than the controls and the preirradiated animals. Tumor size indices calculated from measurements taken at the time of death were similar in all groups. These results indicate that, with this tumor model, BNCT does not cause a tumor bed effect in cerebral tissue. The therapeutic gains observed with BNCT result from direct effects on tumor cells or on the peritumoral neovascularity.

Acid hydrolase and cytochrome oxidase activities in nitrosourea induced tumors of the nervous system

SummaryNitrosourea induced tumors of the nervous system in rats have proven useful for biochemical studies combined with morphological approaches.The pattern of enzyme activities for acid hydrolases and cytochrome oxidase resemble those previously observed in spontaneous nervous system tumors of man.The activities of 4 acid hydrolases were generally high in the gliomas. This could not be attributed solely to zones of regression or necrosis but was a general characteristic of the neoplasms. The activities were predominantly particulate and most likely lysosomal in localization.In schwannomas a similar increase in hydrolases was found in comparison with normal neural tissues but aryl-sulfatase was not increased.Cytochrome oxidase activities were markedly reduced in all tumors studied. The proportionate reduction with respect to normal brain was comparable to that noted in man. No differences were found with respect to fairly well differentiated gliomas.

Experimental alterations of the bound state of cerebral lysosomal enzymes.

I N IIIS LYSOSOMAL HYPOTHESIS of cell injury, de Duvel proposed that the acid hydrolases, ordinarily bound within the lysosomes, might be released into the cell sap and surrounding tissues under various injurious conditions, resulting in local destruction of cellular components and adjacent tissue. Leighty and coworkers,2 using canine heart muscle, and de Duve and Beaufay,3 with rat liver, have presented evidence that this may occur as a result of anoxia. Excess vitamin A was employed by Weissmann and Thomas4 and Dingle5 to obtain similar results in rabbit cartilage and rat liver. Abraham et a1.6 have recently presented histochemical evidence that oxygen toxicity may also produce an alteration in the permeability of rat liver lysosomal membranes. Their work complemented the biochemical evidence This study was undertaken to evaluate the effects of these labilizers upon lysosomal enzyme distribution in brain and to assess the possible role of hydrolase release in the pathogenesis of experimental brain injury. The study utilized the techniques of enzyme latency measurements and nonsedimentable fraction determinations, and many of the results were compared with parallel studies on rat liver.

Pre-clinical studies on boron neutron capture therapy.

The present report provides an overview of the multidisciplinary research effort on BNCT that currently is in progress at The Ohio State University. Areas under investigation include the preparation of boron containing monoclonal antibodies, the synthesis of boron containing derivatives of promazines and phathalocyanines, the development of a rat model for the treatment of glioblastoma by means of BNCT, the design of an accelerator-based neutron irradiation facility, and 10B concentration measurements using alpha track autoradiographic methods. Progress in each of these areas is described and the direction of future research is indicated.

Theoretical Basis and Clinical Methodology for Stereotactic Interstitial Brain Tumor Irradiation Using Iododeoxyuridine as a Radiation Sensitizer and 145Sm as a Brachytherapy Source

A technique to produce radiation enhancement during interstitial brain tumor irradiation by using a radiation sensitizer (iododeoxyuridine-IdUrd) and by stimulation of Auger electron cascades through absorption of low-energy photons in iodine is described. Clinical studies using iododeoxyuridine, 192Ir as a brachytherapy source, and external radiation have produced promising results. Substituting 145Sm for 192Ir in this protocol is planned to evaluate the enhanced dose resulting from photon activation therapy.

Delayed Effects of Neutron Irradiation on Central Nervous System Microvasculature in the Rat

Pathologic examination of a series of 14 patients with malignant gliomas treated with BNCT showed well demarcated zones of radiation damage characterized by coagulation necrosis. Beam attenuation was correlated with edema, loss of parenchymal elements, demyelination, leukocytosis, and peripheral gliosis. Vascular disturbances consisted of endothelial swelling, medial and adventitial proliferation, fibrin impregnation, frequent thrombosis, and perivascular inflammation. Radiation changes appeared to be acute and delayed. The outcome of the patients in this series was not significantly different from the natural course of the disease, even though two of the patients had no residual tumor detected at the time of autopsy. The intensity of the vascular changes raised a suspicion that boron may have sequestered in vessel walls, resulting in selectively high doses of radiation to these structures (Asbury et al., 1972), or that there may have been high blood concentrations of boron at the time of treatment. The potential limiting effects of a vascular ischemic reaction in Boron Neutron Capture Therapy (BNCT) prompted the following study to investigate the delayed response of microvascular structures in a rat model currently being used for pre-clinical investigations.

Lysosomal Acid Hydrolases in Primary Monolayer Cultures Derived from Neonatal Brains Exposed Transplacentally to Ethylnitrosourea

Summary The effect of transplacental exposure of the fetal rat brain to the carcinogen ethylnitrosourea (ENU) on lysosomal acid hydrolase activities in glial cells has been reported. Primary monolayer cultures of brain cells derived from the brains of newborn rats exposed transplacentally to ENU and from unexposed newborn brains were used to provide concentrated samples of glial cells for hydrolase assay. The hydrolases assayed were β-glucuronidase, N-acetyl-β-D-glucosaminidase, arylsulfatase A and B and acid phosphatase and data were expressed as micromoles of substrate hydrolyzed per hour per milligram of protein. Experimental and control cultures were prepared, incubated and assayed contemporaneously and the ratios between treated and control hydrolase activities were used to evaluate the effect of transplacental ENU exposure. Results showed that there was no effect on the activities of the lysosomal acid hydrolases measured in primary monolayer cultures of brain cells derived from newborn rat brains exposed transplacentally to ENU. Glucosaminidase activities increased through the 49 day incubation period, while maximum activities of β-glucuronidase, arylsulfatase and acid phosphatase were observed after 21 to 35 days incubation. Hydrolase activities in the brain cell cultures were markedly higher than activities previously reported in neonatal whole brain.