Improving delivery of agents to the brain will play a major role in the therapeutic outcome of brain neoplasms. As techniques for gene therapy are advanced, manipulation of the BBB also may be important in the treatment of central nervous system genetic disorders.

BBBD resulted in global delivery of a variety of agents in a wide range of sizes. In this human brain tumor xenograft model, bradykinin was not effective at increasing delivery to the tumor of any agent tested.

The volume of distribution in tissue (Vt) that can be achieved by direct interstitial infusion of therapeutic agents into brain is limited. The maintenance of a pressure gradient during interstitial infusion to establish fluid convection has been shown to increase the Vt of small, medium, and large molecules. We have used monocrystalline iron oxide nanocompounds, superparamagnetic particles of sizes the same order of magnitude as virions, to investigate the effect of dose, the volume of infusate, and the time of infusion on the distribution of large molecules in rodent brain. Our initial study in rats (n = 6) replicated the results of a previously described report of convection-enhanced delivery in cats. At a constant rate and concentration, the Vt increased in a linear fashion, proportional to the increases in time, volume, and dose. When using a constant rate and a constant concentration, however, it is unclear which variable or variables (dose, volume, infusion time) have the greatest influence on this effect. Therefore, we assessed each variable independently (n = 12). When the iron dose was increased from 5.3 to 26.5 micrograms, there was a three- to fivefold increase in the Vt, depending on the volume and time of infusion (2 Microliters/20 min, 24 microliters/20 min, or 24 microliters/120 min) (P < 0.001). When the volume of infusate was increased from 2 to 24 microliters, at an infusion time of 20 minutes and a dose of either 5.3 or 26.5 micrograms, there was a 43 or 52% decline in the Vt, respectively (P = 0.018). When the time for the infusion of 24 microliters was increased from 20 to 120 minutes, there was a 79% increase in the Vt at a dose of 26.5 micrograms but no change in the Vt at a dose of 5.3 micrograms. The effect associated with infusion time was not significant (P = 0.113). Magnetic resonance imaging was performed to document the distribution of monocrystalline iron oxide nanocompounds in vivo, and histochemical staining for iron was used to document the distribution of monocrystalline iron oxide nanocompounds in tissue sections. The Vt for both methods was calculated by computer image analysis, and the correlation between magnetic resonance and histological volumes was determined (r2 = 0.93). On the basis of this model, we suggest that dose, rather than convection, might be the most important variable in maximizing the Vt and improved distribution might be achieved by administering an increased concentration of agent.

Dysautonomia was diagnosed in 11 young (median age, 14-months), predominantly medium-to large-breed dogs from 1988 to 1995. Clinical signs caused by autonomic dysfunction of the urinary, alimentary, and ocular systems were most common. Dysuria, mydriasis, absence of pupillary light reflexes, decreased tear production, dry mucous membranes, weight loss, and decreased anal tone were present in over 75% of affected dogs. Ocular pharmacological testing with a dilute (0.1%) solution of pilocarpine was used to demonstrate iris sphincter receptor function in all dogs. A low-dose 10.0375 mglkg SC) bethanechol test and pharmacological ysautonomia is a general term for dysfunction of the D autonomic nervous system. It can be secondary to other systemic or neurological diseases,'-6 but primary dysautonomias are relatively rare in both people and animals. Equine dysautonomia (grass sickness) is the most common of the dysautonomias in animals and was described in horses in the British Isles during the early twentieth centu~-y.~-~ Dysautonomia has since been reported in nondomestic equines and in wild European hares.''-'' Dysautonomia was described in cats in the United Kingdom in 1982.''-15 Additional affected cats, were later identified throughout Europe, Scandinavia, New Zealand, and the United States.''-*' The first case of canine dysautonomia was reported in England in 1983." Since then, 9 other dogs with dysautonomia have been reported from Scotland:' Belgium,".25 Nor~ay:~,'~ and France?' In 1991, a dog with suspected dysautonomia was reported in the United States, but the diagnosis was not confirmed histol~gically.~~ The purpose of this report is to describe and correlate the clinical and pathological findings associated with this neurological disorder, describe diagnostic tests of the autonomic nervous system that are helpful in obtaining an antemortern diagnosis of dysautonomia, and compare canine dysautonomia with other known dysautonomias in animals. Patients and MethodsTen of the 11 dogs studied were presented to the University of Missouri for evaluation of autonomic dysfunction ( Table 1). Physical and neurological examinations, and ocular pharmacological testing were performed by the authors in these 10 dogs. Dog 3 died before referral, and for this patient the results of the physical and neurological examinations and of ocular pharmacological testing obtained by the referring veterinarian were recorded. Necropsies were performed at the University of Missouri on all 11 dogs. Electrocardiographic, radiographic, clinicopathologic, cerebrospinal fluid (CSF) analysis, and ultrasonographic findings were reviewed when available. Cisternal CSF was analyzed for total nucleated cell count, RBC, protein concentration, Pandy reaction, and color and transparency prior to and after centrifugation.Physiological and pharmacological testing was performed in patients prior to euthanasia or death. One to 2 drops of a 0. so that urinary bladder distention was subjectively quantified ultrasonographically before and after voluntary ...

The delivery of viral vectors to the brain for treatment of intracerebral tumors is most commonly accomplished by stereotaxic inoculation directly into the tumor. However, the small volume of distribution by inoculation may limit the efficacy of viral therapy of large or disseminated tumors. We have investigated mechanisms to increase vector delivery to intracerebral xenografts of human LX-1 small-cell lung carcinoma tumors in the nude rat. The distribution of Escherichia coli lacZ transgene expression from primary viral infection was assessed after delivery of recombinant virus by intratumor inoculation or intracarotid infusion with or without osmotic disruption of the blood-brain barrier (BBB). These studies used replication-compromised herpes simplex virus type 1 (HSV; vector RH105) and replication-defective adenovirus (AdRSVlacZ), which represent two of the most commonly proposed viral vectors for tumor therapy. Transvascular delivery of both viruses to intracerebral tumor was demonstrated when administered intraarterially (i.a.) after osmotic BBB disruption (n = 9 for adenovirus; n = 7 for HSV), while no virus infection was apparent after i.a. administration without BBB modification (n = 8 for adenovirus; n = 4 for HSV). The thymidine kinase-negative HSV vector infected clumps of tumor cells as a result of its ability to replicate selectively in dividing cells. Osmotic BBB disruption in combination with i.a. administration of viral vectors may offer a method of global delivery to treat disseminated brain tumors.