A four-hour topotecan infusion achieves cytotoxic exposure throughout the neuraxis in the nonhuman primate model: implications for treatment of children with metastatic medulloblastoma.

The purpose of this study was to define the length of topotecan (TPT) i.v. infusion necessary to attain a cytotoxic exposure for medulloblastoma cells throughout the neuraxis. In vitro studies of human medulloblastoma cell lines (Daoy, SJ-Med3) were used to estimate the length and extent of TPT systemic exposure associated with inhibition of tumor cell growth or the exposure duration threshold (EDT). We evaluated TPT systemic and cerebrospinal fluid (CSF) disposition in six male rhesus monkeys (8-12 kg) that received TPT 2.0 mg/m2 i.v. as a 30-min or 4-h infusion. Plasma and CSF samples were assayed for TPT lactone by high-performance liquid chromatography, and the CSF exposures were compared with the estimated EDT. Results of the in vitro studies defined an EDT as a TPT lactone concentration of > 1 ng/ml for 8 h (IC99) daily for 5 days. The mean +/- SD for systemic clearance (CL(SYS)), penetration into fourth ventricle (%CSF(4th)), and penetration into lumbar space (%CSF(LUM)) were similar for the 30-min and the 4-h infusions. At a TPT lactone systemic exposure (AUC(PL)) of 56.7 +/- 19.9 ng/ml x h, time above 1 ng/ml in the fourth ventricle was 1.4-fold greater for a 4-h infusion compared with a 30-min infusion. At a TPT lactone AUC(PL) of 140 ng/ml x h, the 4-h infusion achieved the desired TPT exposure throughout the neuraxis (lateral and fourth ventricles and lumbar space), whereas the 30-min infusion failed to achieve it in the lumbar space. In conclusion, prolonging TPT i.v. infusion from 30-min to 4-h at a targeted AUC(PL) achieves the EDT throughout the neuraxis and represents an alternative method of TPT administration that will be tested prospectively in patients with high-risk medulloblastoma.

Reduction of peridural fibrosis after lumbar laminotomy and discectomy in dogs by a resorbable gel (ADCON-L).

STUDY DESIGN: A canine lumbar laminotomy and discectomy model was used to evaluate the effects of a resorbable gel, ADCON-L (Gliatech Inc., Cleveland, OH), in reducing peridural scar formation and to assess the healing progress of immediately adjacent normal structures. OBJECTIVES: To compare peridural scar formation and anulus fibrosis healing with and without the use of ADCON-L in an animal model that closely replicates the common human surgical procedure. SUMMARY OF BACKGROUND DATA: ADCON-L has been shown to reduce the development of peridural scars in rat, rabbit, and canine laminectomy models in previous investigations; discectomies were not performed in these previous studies, however, and thus anular healing could not be assessed. METHODS: Seven adult mongrel dogs underwent a three-level unilateral lumbar hemilaminotomy and anular fenestration. In each dog, the ADCON-L was applied to two randomly assigned sites around the discectomy, the nerve roots, and the hemilaminotomy. The third site underwent surgery, but was left untreated (sham surgery only). The canines were killed 8 weeks after surgery, and a gross anatomic assessment of scar formation was done using microdissection by an observer blinded to treatment. A numerical rating system was developed to assess the relative amount and tenacity of the anterior scarring (discectomy site) and posterior scarring (hemilaminotomy site). The healing of the anular defect was assessed histologically. RESULTS: ADCON-L significantly reduced peridural fibrosis in this lumbar discectomy model compared with the sham treated sites (p < 0.05). Further, the superficial layers, the posterior longitudinal ligament, and the anulus fibrosus healed well in the ADCON-L treated sites. CONCLUSIONS: ADCON-L reduced local peridural fibrosis after lumbar laminotomy and discectomy without impacting the healing of the surrounding tissues.

Early assessment of neurologic deficits in the fluid percussion model of brain injury.

This study was designed to quantify the early neurologic effects of brain injury elicited by fluid percussion to the dura of cats. Propofol was used for surgical anesthesia because recovery in normal animals from an intravenous infusion was found to be nearly complete within 2 h of cessation and absolutely complete by 4 h. In addition, a cat coma scale (CCS) was developed that reflects normal (CCS, 14) to moribund (CCS, 3) behavior. The CCS values at 6 h were compared with the force of injury expressed in atmospheres (atm), maximum blood pressure change, and gross neuropathology to ascertain which parameter might best account for the behavior observed after brain injury. The results showed that decreasing neurologic scores correlated well with increasing atmospheres of injury (Pearson's r 0.71, p < 0.001) but not with the rise in systolic blood pressure caused by the trauma (n = 29). Coma scores did correlate with the cross sectional area of ponto-mesencephalic lesions (Pearson's r = 0.51, p < 0.01) and proved to be significantly different in animals grouped according to lesion size of less or more than 3 mm in length (t test, p < 0.01). Thus the CCS and the pharmacologic properties of propofol permit an early analysis of the neurologic status in the feline fluid percussion model of brain injury. These procedures could facilitate the evaluation of early biochemical changes that affect behavior and of therapies designed to ameliorate the deleterious effects of head injury.

Ubiquitin marks the reactive swellings of diffuse axonal injury.

Ubiquitin is a protein that targets proteins for non-lysosomal degradation. It has been found to be present in a number of inclusions characteristic of neurodegenerative diseases. Using the fluid percussion model of closed head injury in the cat, a well-established model of diffuse axonal injury (DAI), we now report that the reactive axonal swellings and the retraction balls produced in this model stain positively with anti-ubiquitin immunohistochemistry. Furthermore, the affected axons become ubiquitin positive quickly (within the first 6 h after injury). Anti-ubiquitin immunohistochemistry compares well with the recently reported ability of antibodies to low molecular weight neurofilament proteins to demonstrate reactive axonal change in DAI, and it could provide additional clues to the pathogenesis of axonal transection.