Carotid artery injections in 40- to 99-g Fischer rats: technical note and evaluation of blood flow by various injection techniques

Novel microcatheter-based intracarotid delivery approach for MCAO/R mice

The intra-arterial (IA) model by microcatheter administration was an effective way to deliver drugs or cells to the brain. All of these models were carried out introduced in rat rather than mice for the difficult and technically challenging due to their small caliber. In 2014, Alejandro Santillan first introduced this model in mice and we found that most of the operational steps were similar with the middle cerebral artery occlusion and reperfusion (MCAO/R) model. We attempted to combine these two techniques into a single model in mice and discovered that this technique was indeed possible. In our work, 12C57Bl/6J male mice were carried on middle cerebral artery occlusion for 60min and then the intra-arterial microcatheter was placed into the internal carotid artery (ICA) from the external carotid artery (ECA). GFP-Luc-Pro labeled mNSCs were infused through the microcatheter and then the blood flow perfusion was reestablished subsequently. The results showed that all 12 mice were carried on successfully the model of middle cerebral artery occlusion, and the placement of the microcatheter and the mNSCs perfusion were completed smoothly without exception. Which means that it is logical to combine the two models into one in order to facilitate studying of stroke. Meanwhile, during the dissection, we found the variation of occipital artery (OA) was noticeable and we classified first time this variation into four categories to attempt to protect the OA.

Cannulation of the internal carotid artery in mice: a novel technique for intra-arterial delivery of therapeutics

We have developed a novel minimally invasive technique for the intra-arterial delivery of therapeutics to the mouse brain. CD-1 mice were anesthetized and placed in a lateral decubitus position. A 10mm midline longitudinal incision was made over the thyroid bone. The omohyoid and sternomastoid muscles were retracted to expose the common carotid artery and external carotid artery (ECA). To maximize delivery of administered agents, the superior thyroid artery was ligated or coagulated, and the occipital artery and the pterygopalatine artery (PPA) were temporarily occluded with 6-0 prolene suture. The ECA was carefully dissected and a permanent ligature was placed on its distal segment while a temporary 6-0 prolene ligature was placed on the proximal segment in order to obtain a flow-free segment of vessel. A sterilized 169 μm outer diameter polyimide microcatheter was introduced into the ECA and advanced in retrograde fashion toward the carotid bifurcation. The catheter was then secured and manually rotated so that the microcatheter tip was oriented cephalad in the internal carotid artery (ICA). We were able to achieve reproducible results for selective ipsilateral hemispheric carotid injections of mannitol mediated therapeutics and/or gadolinium-based MRI contrast agent. Survival rates were dependent on the administered agent and ranged from 78 to 90%. This technique allows for reproducible delivery of agents to the ipsilateral cerebral hemisphere by utilizing anterograde catheter placement and temporary ligation of the PPA. This method is cost-effective and associated with a low rate of morbimortality.

Blood-brain barrier opening to large molecules does not imply blood-brain barrier opening to small ions

Neuroimaging of exogenous tracer extravasation has become the technique of choice in preclinical and clinical studies of blood-brain barrier permeability. Such tracers have a larger molecular weight than small ions, neurotransmitters and many drugs. Therefore, it is assumed that tracer extravasation indicates both permeability to these and the cancelation of the electrical polarization across the barrier. Electrophysiological anomalies following intracarotideal administration of dehydrocholate, a bile salt causing extravasation of the albumin-binding tracer Evans blue, seemingly supported this. By contrast, electron microscopic studies suggested a different hierarchical pattern of blood-brain barrier dysfunction, a milder degree of impairment being characterized by increased function of the transcellular pathway and a severe degree by opening of the tight junctions. This would imply that the extravasation of macromolecules can occur before disruption of the electrical barrier. However, functional evidence for this has been lacking. Here, we further investigated the electrophysiological anomalies following intracarotideal application of dehydrocholate in rats and found that it caused focal cerebral ischemia by middle cerebral artery thrombosis, the electrophysiological recordings being characteristic of long-lasting spreading depolarization. These observations indicated that intracarotideal dehydrocholate is not a suitable model to study the isolated dysfunction of the blood-brain barrier. Second, we studied the topical application of dehydrocholate to the brain and the application of mannitol into the carotid artery. In both models, we found significant extravasation of Evans blue but no changes in either extracellular potassium or the CO(2)-dependent intracortical direct current deflection. The latter is assumed to depend on the proton gradient across the barrier in rats which we confirmed in additional experiments in vivo and in vitro. The stability of the extracellular potassium concentration and the CO(2)-dependent direct current deflection are two functional tests which indicate the integrity of the electrical barrier. Hence, our results provide functional evidence that the blood-brain barrier opening to large molecules does not necessarily imply the opening to small ions consistent with the hierarchy of damage in the previous electron microscopic studies.

Prolonged survival of Fischer rats bearing F98 glioma after iodine-enhanced synchrotron stereotactic radiotherapy

PURPOSE

Heavy-atom-enhanced synchrotron stereotactic radiotherapy (SSR) is a treatment that involves selective accumulation of high-Z elements in tumors followed by stereotactic irradiation with X-rays from a synchrotron source. The purpose of this study was to determine whether the efficacy of iodine-enhanced SSR could be further improved in the F98 rodent glioma model, by using a concomitant injection of an iodinated contrast agent and a transient blood-brain barrier opener (mannitol) during irradiation.

METHODS AND MATERIALS

Fourteen days after intracerebral inoculations of F98 cells, the rats were irradiated with 50-keV X-rays while receiving an infusion of hyperosmotic mannitol with iodine, either intravenously or via the carotid (9 to 15 rats per group, 117 rats total).

RESULTS

For doses<or=15 Gy, the intracarotid infusion of mannitol and iodine improved the rats' survival compared with intravenous injection or irradiation alone. The percentage-increased life spans (ILS) were 91%, 116%, and 169% without iodine, after infusion of iodine and mannitol intravenously, and intracarotid, respectively (15 Gy). At 25 Gy, the rats irradiated without iodine had the longest survival (ILS=607%), but no additional benefit was obtained with iodine and mannitol.

CONCLUSIONS

Iodine-enhanced SSR is significantly improved with concomitant intracarotid infusion of iodine and mannitol for radiation doses<or=15 Gy.

129Xe spectra from the heads of rats with and without ligation of the external carotid and pterygopalatine arteries

After rats inhaled hyperpolarized (129)Xe gas, in vivo spectra from their heads revealed a dominant peak around 195 ppm, another easily resolvable peak near 189 ppm, a broad peak around 210 ppm, and two minor peaks around 198 ppm and 192 ppm. However, the source of each peak remains controversial. To further study the origin of each peak, we compared spectra obtained from the heads of normal rats with spectra taken from the heads of rats that had undergone ligation of the external carotid (ECA) and pterygopalatine (PPA) arteries, the major feeding vessels of nonbrain tissue in the rat head. The amplitude of the peak at around 189 ppm was greatly reduced in the ECA/PPA-ligated rats, while the peak around 195 ppm persisted. We conclude that the signal that originates from the rat brain after inhalation of (129)Xe gas is overwhelmingly dominated by the single resonance at 195 ppm.

Enhanced delivery of iodine for synchrotron stereotactic radiotherapy by means of intracarotid injection and blood–brain barrier disruption: Quantitative iodine biodistribution studies and associated dosimetry

PURPOSE

Synchrotron stereotactic radiotherapy (SSR) is a binary cancer treatment modality that involves the selective accumulation of a high Z element, such as iodine, in tumors, followed by stereotactic irradiation with kilovoltage X-rays from a synchrotron source. The success of SSR is directly related to the absolute amount of iodine achievable in the tumor. The purposes of this preclinical study were to determine whether the delivery of iodine to brain tumor models in rats could be enhanced by the means of its intracarotid injection with or without a hyperosmotic solution and to evaluate corresponding absorbed X-ray doses.

METHODS AND MATERIALS

Experiments were performed on four groups of F98 glioma-bearing rats, which received either intracarotid (IC) or intravenous (IV) infusions of a mixture (6 mL in 12 min) of an iodinated contrast agent associated or not with a transient blood-brain barrier opener (mannitol). The mixture volumetric proportions were 8/13 of Iomeron (C = 350 mg/mL) for 5/13 of mannitol or saline, respectively. Absolute iodine concentration kinetic was measured in vivo in the tumor, blood, contralateral and ipsilateral brain, and muscle by monochromatic computed tomography. Associated dosimetry was performed by computing the iodine dose enhancement factor (DEF) in each region and building dose distribution maps by analytical simulations.

RESULTS

Infusion of mannitol significantly enhanced iodine tumor uptake compared with the control values (p < 0.0001 and p = 0.0138, for IC and IV protocols, respectively). The mean iodine concentrations (C) reached 20.5 +/- 0.98 mg/mL (DEF = 4.1) after administration of iodine and mannitol vs. 4.1 +/- 1.2 mg/mL i.c. with serum (DEF = 1.6). The tumor iodine uptakes after jugular injection with mannitol (C = 4.4 +/- 2.1 mg/mL, DEF = 1.7) were not significantly different from IC injection of iodine without mannitol (p = 0.8142). The IV injection of iodine with saline led to an iodine concentration in the tumor of 1.2 +/- 0.98 mg/mL and a DEF of 1.2.

CONCLUSIONS

This study established that optimizing the delivery of iodine by means of IC injection combined with a blood-brain barrier opener (mannitol) significantly increases the iodine uptake of F98 rat gliomas. This infusion protocol could potentially enhance the efficacy of SSR treatment, because the radiation dose is proportional to the iodine amount present in the irradiation bed.

Improved survival after boron neutron capture therapy of brain tumors by Cereport-mediated blood-brain barrier modulation to enhance delivery of boronophenylalanine

OBJECTIVE

Cereport (Alkermes, Inc., Cambridge, MA), or, as it has been previously called, RMP-7 (receptor-mediated permeabilizer-7), is a bradykinin analog that has been shown to produce a transient, pharmacologically mediated opening of the blood-brain barrier. The purpose of the present study was to determine whether the efficacy of boron neutron capture therapy (BNCT) could be enhanced by means of intracarotid (i.c.) infusion of Cereport, in combination with intravenous (i.v.) injection or i.c. infusion of boronophenylalanine (BPA) in the F98 rat glioma model.

METHODS

For biodistribution studies, Fischer rats bearing intracerebral implants of the F98 glioma received i.v. or i.c. injections of 300 or 500 mg/kg body weight (b.w.) of BPA with or without i.c. infusion of 1.5 microg/kg b.w. of Cereport. For therapy studies, BNCT was initiated 14 days after intracerebral implantation of 10(3) F98 cells. The i.v. or i.c. injection of BPA (500 mg/kg b.w.) was given with or without Cereport, and the animals were irradiated 2.5 hours later at the Brookhaven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head.

RESULTS

At a BPA dose of 500 mg/kg b.w., tumor boron concentrations (mean +/- standard deviation) were 55.7 +/- 9.6 microg/g with Cereport versus 33.6 +/- 3.9 microg/g without Cereport at 2.5 hours after i.c. infusion of BPA, and concentrations were 29.4 +/- 9.9 microg/g with Cereport versus 15.4 +/- 3.5 microg/g without Cereport (P < 0.05) after i.v. injection of BPA. After i.c. administration of BPA and Cereport, the tumor-to-blood ratio was 5.4 +/- 0.6, and the tumor-to-brain ratio was 5.2 +/- 2.4. After BNCT with BPA at a dose of 500 mg/kg, the survival time was 50 +/- 16 days for i.c. administration of BPA with Cereport versus 40 +/- 6 days without Cereport (P = 0.05), 38 +/- 4 days for i.v. administration of BPA with Cereport versus 34 +/- 3 days without Cereport (P = 0.02), 28 +/- 5 days for irradiated controls, and 23 +/- 3 days for untreated controls. Compared with untreated controls, there was a 117% increase in lifespan in rats that received an i.c. infusion of Cereport and then BPA, and an 86% increase in lifespan in rats that received i.c. administration of BPA without Cereport.

CONCLUSION

These studies have established that i.c. administration of Cereport can not only increase tumor uptake of BPA, but also enhance the efficacy of BNCT.

Relationship between drug delivery and the intra-arterial infusion rate of SarCNU in C6 rat brain tumor model

The influences of the flow rate on the concentration and distribution of drug in the rat brains and brain tumors after intra-arterial (intra-carotid) administration of [3H]SarCNU (sarcosinamide chloroethyl-1-nitrosourea) were examined. Results obtained at three flow rates via intra-carotid route were compared to those obtained with intravenous administrations. Adult female Wistar rats bearing C6 brain tumor were randomized into four-groups. Groups 1 (G.1) to 3 (G.3) received intra-arterial injection and Group 4 (G.4) received intravenous administration of [3H]SarCNU. G.1 (slow infusion rate) was administered 1 ml of [3H]SarCNU solution over 60 min (0.017 ml/min), Group 2 (G.2; medium infusion rate): 0.2 ml over 5 min (0.04 ml/min), G.3 (fast infusion rate): 1 ml over 5 min (0.2 ml/min), and G.4 (intravenous infusion): 1 ml intravenously over 5 min. Quantitative autoradiographic method was used to measure the concentration and the distribution of [3H]SarCNU in the brain and the brain tumors. The tissue uptake constant of SarCNU in both viable (tumor tissue excluding necrosis) and peak regions (the area of tumor containing top 20% of the tracer concentration) of the intra-arterial injection groups were significantly higher (p < 0.0001) than those in the intravenous group. The mean concentrations of the viable tumor in the intra-arterial groups were 2.92 (G.1), 16.06 (G.2), and 20.8 (G.3) times higher than those of intravenous group. Between the intra-arterial groups, the mean concentration in the viable tumors of G.1 (slow flow rate) was significantly (p < 0.0001) lower than in G.2 and G.3. However, there was no significant difference between G.2 and G.3. In three intra-arterial groups the mean concentration delivery ratios of the brain tumors were high and ranged from 3.07 (G.3) to 3.87 (G.2), but there was no significant difference between them. Only G.4, intravenous group, showed significantly (p < 0.005) lower concentration delivery ratio, 1.26. These results suggest that higher infusion rate in the intra-arterial chemotherapy could have an effect not only on the streaming phenomenon which results in the brain toxicities, but also on the increase in the concentration and the sufficient distribution of a drug in tumors. By finding chemotherapeutic agents to which tumors show high sensitivity and using intra-arterial administration of these agents at more effective flow rate, better clinical results could be achieved in the treatment of patients with malignant brain tumors.

Enhanced survival of glioma bearing rats following boron neutron capture therapy with blood-brain barrier disruption and intracarotid injection of boronophenylalanine

Boronophenylalanine (BPA) has been used for boron neutron capture therapy (BNCT) of brain tumors in both experimental animals and humans. The purpose of the present study was to determine if the efficacy of BNCT could be enhanced by means of intracarotid (i.c.) injection of BPA with or without blood-brain barrier disruption (BBB-D) and neutron irradiation using a rat brain tumor model. For biodistribution studies, F98 glioma cells were implanted stereotactically into the brains of Fischer rats, and 12 days later BBB-D was carried out by i.c. infusion of 25% mannitol (1.373 mOsmol/ml), followed immediately by i.c. administration of 300, 500 or 800 mg of BPA/kg body weight (b.w.). At the 500 mg dose a fourfold increase in tumor boron concentration (94.5 micrograms/g) was seen at 2.5 hours after BBB-D. compared to 20.8 micrograms/g in i.v. injected animals. The best composite tumor to normal tissue ratios were observed at 2.5 hours after BBB-D, at which time the tumor: blood (T: Bl) ratio was 10.9, and the tumor: brain (T:Br) ratio was 7.5, compared to 3.2 and 5.0 respectively for i.v. injected rats. In contrast, animals that had received i.c. BPA without BBB-D had T : Bl and T:Br ratios of 8.5 and 5.9, respectively, and the tumor boron concentration was 42.7 micrograms/g. For therapy experiments, initiated 14 days after intracerebral implantation of F98 glioma cells, 500 mg/kg b.w. of BPA were administered i.v. or i.c. with or without BBB-D, and the animals were irradiated 2.5 hours later at the Brook-haven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head. The mean survival time for untreated control rats was 24 +/- 3 days, 30 +/- 2 days for irradiate controls, 37 +/- 3 days for those receiving i.v. BPA, 52 +/- 15 days for rats receiving i.c. BPA without BBB-D, and 95 +/- 95 days for BBB-D followed by i.c. BPA and BNCT. The latter group had a 246% increase in life span (ILS) compared to untreated controls and a 124% ILS compared to that of i.v. injected animals. These survival data are the best ever obtained with the F98 glioma model and suggest that i.c. administration of BPA with or without BBB-D may be useful as a means to increase the efficacy of BNCT.

Enhanced delivery of boronophenylalanine for neutron capture therapy by means of intracarotid injection and blood-brain barrier disruption

There has been increasing interest in the possible use of boronophenylalanine as a capture agent for boron neutron capture therapy of brain tumors. The purpose of the present study was to determine whether the uptake of boronophenylalanine in F98 glioma-bearing rats could be enhanced by means of intracarotid (i.c.) injection with or without blood-brain barrier disruption (BBB-D). Glioma cells (10(5)) were stereotactically implanted into the right cerebral hemisphere of Fischer rats, and 12 days later, BBB-D was performed by infusing 25% mannitol (1.373 mOsmol/ml) into the right carotid artery and then immediately injecting L-boronophenylalanine (300 mg/kg of body weight) intracarotidly. The animals were killed 0.5, 1, 2.5, and 4 hours later, and the brains were removed for boron determination by direct current plasma atomic emission spectroscopy. BBB-D was assessed by the intravenous injection of Evans blue or horseradish peroxidase, and the barrier-disrupted hemispheres and tumors showed intense staining with each. The mean tumor boron concentration after i.c. injection and BBB-D was 34.8 +/- 6.8 micrograms/g at 2.5 hours compared with 20.3 +/- 6.2 micrograms/g after i.c. injection without BBB-D and 10.7 +/- 0.7 micrograms/g after intravenous injection. No significant differences in boron concentration in muscle, skin, and eye were observed among the different groups. Boron concentrations in the ipsilateral, disrupted hemisphere increased transiently but rapidly returned to background levels by 2.5 hours after BBB-D. The tumor:brain and tumor:blood ratios were 5.2 and 5.6, respectively, compared to 3.2 and 2.1 for intravenous injection groups at 2.5 hours. The present study is the first to show that BBB-D combined with i.c. injection can enhance the tumor uptake of boron compounds for boron neutron capture therapy.

Optimization of epoxyeicosatrienoic acid syntheses to test their effects on cerebral blood flow in vivo

Epoxyeicosatrienoic acids (EETs), normally present in brain and blood, appear to be released from atherosclerotic vessels in large amounts. Once intravascular, EETs can constrict renal arteries in vivo and dilate cerebral and coronary arteries in vitro. Whether EETs in blood will alter cerebral blood flow (CBF) in vivo is unknown. In the present study, the chemical synthesis of four EET regioisomers was optimized, and their identity and structural integrity established by chromatographic and mass spectral methods. The chemically labile EETs were converted to a sodium salt, complexed with albumin, and infused into anesthetized rats via the common carotid. The objective was to test whether sustained, high levels of intravascular EETs alter CBF. The CBF (cortical H2 clearance) was measured before and 30 min after the continuous infusion of 14,15- (n = 5), 11,12- (n = 5), 8,9- (n = 7) and 5,6-EET (unesterified or as the methyl ester, n = 5 for each). Neither the CBF nor the systemic blood pressure was affected by EETs. Because the infusions elevated the plasma concentrations of EETs about 700-fold above normal levels (1.0 nM), it is unlikely that EETs released from atherosclerotic vessels will alter CBF.

Effect of phorbol myristate acetate on cerebral blood flow in normal and neutrophil-depleted rats

BACKGROUND AND PURPOSE

Recent evidence suggests a possible role for leukocytes in ischemic brain injury. This study examined the effect of activation of endogenous circulating leukocytes on cerebral blood flow in normal and neutrophil-depleted rats.

METHODS

Leukocytes were activated by rapid injection of either 50 micrograms/kg phorbol 12-myristate 13-acetate, a protein kinase C activator, or an equimolar amount of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine, into the right carotid artery. Control rats received an equal volume of dimethyl sulfoxide in saline vehicle. H2-clearance cerebral blood flow was measured in each of the three groups and in vinblastine-treated, neutrophil-depleted rats after carotid artery injection of phorbol.

RESULTS

Phorbol 12-myristate 13-acetate dramatically decreased circulating leukocyte and platelet counts from 5 to 120 minutes after infusion and decreased regional cerebral blood flow in the ipsilateral parietal cortex from a baseline of 119 +/- 14 mL.min-1.100 g-1 (mean +/- SEM) to 49 +/- 5 mL.min-1.100 g-1 at 30 minutes (P < .05). Decreased flow persisted for the 2-hour study. Neither N-formyl-methionyl-leucyl-phenylalanine or vehicle had an effect on cerebral blood flow. In the neutrophil-depleted rats the initial decrease in cerebral blood flow at 30 and 60 minutes after infusion of phorbol was observed, but cerebral blood flow was restored to 70% to 80% of its baseline value (P > .05 versus baseline) by 90 to 120 minutes.

CONCLUSIONS

The early phorbol 12-myristate 13-acetate-induced decrease in cerebral blood flow may be due to the effects of protein kinase C activation on vascular smooth muscle or on platelet aggregation, whereas the persistent decrease in cerebral blood flow appears to be mediated in part by neutrophil activation.

Delivery of a novel nitrosourea, MCNU, to the brain tissue in glioma-bearing rats. Intracarotid versus intravenous infusion

We observed the tissue delivery of a novel water-soluble nitrosourea, 1-(2-chloroethyl)-3-(methyl-alpha-D-glucopyranos-6-yl)-1-nitros our ea (MCNU) in rats bearing experimental brain tumors by conducting autoradiography on all. Prior to this study, the development of a streaming phenomenon was ascertained (and thus finding the optimum velocity for intra-arterial infusion) by 14C-iodoantipyrine (IAP) autoradiography. Furthermore, a single pass extraction value of MCNU was measured. At an arterial infusion rate of 0.2 ml/min., the streaming phenomenon was recognized but the tracer was fairly evenly distributed at a rate of 1.0 ml/min. On the other hand, the single pass extraction value for MCNU was 0.18 +/- 0.036 (mean +/- S.D., n = 3, under pentobarbital anesthesia). It was suggested that MCNU is very unlikely to be transported into the normal rat brain. We conducted 14C-MCNU autoradiography to observe tissue distribution of MCNU following its intra-arterial and intravenous infusions in a brain tumor model using rats. The normal side (the side where no infusions were given) and the cerebral cortex at the side affected by the tumor (the side where the infusion was given) showed hardly any uptake of 14C-MCNU in both the intra-arterial and intravenous infusion groups. The tumorous section was divided into the periphery and the center to measure tissue concentration of the tracer in each section. Compared against the cortical section, the periphery and the center showed significant increases in the concentration (approximately 11 to 15 times and 3 to 7 times, respectively, the figure for the cortical region) for both the intra-arterial and intravenous groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravascular streaming and variable delivery to brain following carotid artery infusions in the Sprague-Dawley rat

Intracarotid artery infusions in animals are commonly performed in studies of the blood-brain barrier and in chemotherapy trials. Implicit in the analysis of these experiments is that the infusate will be distributed to the territory of the internal carotid artery in a manner that is proportional to blood flow. Fifteen Sprague-Dawley rats were studied to determine if poor infusate mixing with blood due to intravascular streaming occurred during intracarotid artery drug infusions and if it could be eliminated with fast retrograde infusion. In three experimental groups, a radiolabeled flow tracer--14C-iodoantipyrine (IAP)--was infused retrograde through the external carotid artery into the common carotid artery at slow, medium, and fast rates (0.45, 1.5, and 5.0 ml/min). In a control group, IAP was injected intravenously (i.v.). Local isotope concentrations in the brain were determined by quantitative autoradiography, and the variability of isotope delivery was assessed in the frontoparietal cortex, temporal cortex, and caudate putamen of all animals. Streaming phenomena were manifest in all selected anatomic areas after the slow and medium rates of intraarterial infusion. After fast intracarotid infusion or i.v. injection, there was uniform distribution of isotope in the same brain regions.

Applications of monoclonal antibodies in the diagnosis and treatment of primary brain tumors

The development of monoclonal antibodies has resulted in marked expansion in understanding the central nervous system (CNS). This has been especially true in the study of human neuroectodermal tumors where monoclonal antibodies have been used as physiological probes to define and characterize human neuroectodermal tumor-associated antigens. Utilizing monoclonal antibodies, neuroectodermal tumor-associated antigens have been described in four broad categories; biochemically defined markers, shared nervous system-lymphoid cell markers, shared neuroectodermal-oncofetal markers, and putative restricted tumor markers. Preliminary data have demonstrated the ability to localize animal and human tumors in vitro, ex vivo, and in vivo. Early application of monoclonal antibody technology to neuroimmunology and neuro-oncology has resulted in a new awareness of the complex relationships that exist within the CNS. Their specificity and reproducibility may provide the means to qualitatively and quantitatively define the phenotypic heterogeneity of human neuroectodermal tumors. Potentially, monoclonal antibodies, alone or as carriers of radionuclides, drugs, or toxins, may allow successful diagnosis and treatment of human neuroectodermal tumors.

Comparison of various methods for delivering radiolabeled monoclonal antibody to normal rat brain

Different methods were evaluated for delivering iodine-125 monoclonal antibodies (Mab's) to the central nervous system in 40- to 99-gm Fischer rats. By evaluating interhemispheric, interregional, and brain:blood ratios of Mab's, the efficacy of intracarotid (IC) or intravenous (IV) administration of Mab's with and without prior IC perfusion with 0.9% NaCl (normal saline, NS), 1.4 M mannitol, or 1.6 M arabinose, or of femoral artery perfusion with 1.4 M mannitol was evaluated. No difference was seen between IC and IV administration of Mab's with or without prior perfusion. Intracarotid perfusion with hyperosmolar agents was required to disrupt the blood-brain barrier (BBB) and to significantly elevate brain levels of Mab's. The brain and blood levels of Mab's were elevated in all regions of the brain following hyperosmolar BBB disruption. However, the levels were significantly higher in the ipsilateral hemisphere, with cross-over occurring primarily in the vascular distribution of the contralateral anterior cerebral artery. Intracarotid hyperosmolar perfusion produced 450% to 500% increases in ipsilateral and 240% to 280% increases in contralateral hemispheric brain:blood Mab ratio levels compared to those achieved with NS perfusion. For IC perfusion of mannitol or arabinose, flow rates ranging from 0.017 to 0.052 ml/sec were equally effective in disrupting the BBB. Insignificant morbidity and mortality rates were noted up to 2 weeks following BBB disruption. Additional ligation of major extracranial branches of the external and internal carotid arteries prior to IC perfusion did not result in a selective increase in hemispheric Mab levels. Temporally, following hyperosmolar BBB disruption, brain:blood Mab ratios remained elevated bilaterally at 7 days after Mab delivery, with the ipsilateral hemispheric levels remaining significantly elevated compared with the contralateral hemispheric levels until Day 5, when the ratio returned to the nonperfused range. Catheterization was required in the small animals and was performed under magnification in 10 to 20 minutes, with less than an 8% overall morbidity and mortality. The methodology developed should prove helpful in delivery of Mab's or other agents in rat tumor models and experimental models for other disease entities.