Infant rat model of the shaken baby syndrome: preliminary characterization and evidence for the role of free radicals in cortical hemorrhaging and progressive neuronal degeneration.

Infants subjected to repeated episodes of violent shaking develop brain damage characterized by intracranial hemorrhage and progressive cortical atrophy. We have developed an animal model that mimics this pathological state and investigated its etiology and treatment. Anesthetized male rats, 6 days of age, were subjected to one episode of shaking per day for 3 consecutive days. Separate groups of rats were sacrificed 1 h postinjury on the third day of shaking for HPLC quantification of cortical .OH and vitamin E levels, and histological assessment of cortical hemorrhaging. Additional groups were sacrificed 7 or 14 days postinjury to demonstrate progressive neuronal degeneration via cortical wet weight comparisons. In comparison to noninjured shams, the results indicated that cortical vitamin E and .OH levels rose 53.7% (p < 0.005) and 457.1% (p < 0.001), respectively, in shaken infant rats. Brain histologies revealed a moderate-to-severe degree of cortical hemorrhaging in these animals 1 h postinjury. By 7 and 14 days postinjury, there was a 13.3% and 28.7% (p < 0.0001 vs. sham) loss of cortical tissue in shaken infants, respectively, indicating progressive neuronal degeneration. Treatment with 10 mg/kg (ip) of the 21-aminosteroid antioxidant, tirilazad mesylate, 10 min before and 2 h after each episode of shaking, resulted in a 53.1% attenuation of cortical .OH levels and a 34.9% decrease in brain hemorrhaging (p < 0.05 vs. vehicle). Tirilazad treatment did not, however, significantly effect cortical vitamin E concentrations at 1 h postinjury or the extent of progressive neuronal degeneration at either 7 or 14 days postinjury. The present animal model mimics the brain pathology seen in abused children. Our observation that tirilazad mesylate, an antioxidant-lipid peroxidation inhibitor, significantly reduces cortical .OH levels and brain hemorrhaging in shaken infant rats supports a role for oxygen radicals in the pathophysiology of this type of CNS injury. The failure of tirilazad to block progressive cortical degeneration suggests that mechanisms other than free radicals may be of prime importance in the mediation of this aspect of the pathology.

Human buccal absorption of flurbiprofen.

The buccal absorption of flurbiprofen was studied in normal men to quantify the transport from the oral cavity in humans and to evaluate the closed-perfusion cell apparatus as a means to study drug transport across externally accessible biologic membranes. Flurbiprofen was buccally absorbed by a passive diffusional mechanism and the rate of absorption was pH dependent. Membrane permeability coefficients for flurbiprofen were 4.3 x 10(-4) cm/sec at pH 5.5 and 2.1 x 10(-5) cm/sec at pH 7.0. These findings are in agreement with the pH relationship for buccal transport observed in dog experiments. Delineation of the effective permeability coefficients into components for the aqueous boundary layer and the lipoidal buccal membrane allowed for the prediction of the extent of absorption of the drug over a period of time. It was concluded that the buccal membranes of the human and dog were essentially lipoidal membranes with equivalent permeabilities and no evident aqueous pore pathways.

Laboratory automation of high-pressure liquid chromatography.

An automated system for high-pressure liquid chromatography was developed. The system is built around commercial modules wherever possible, modified to varying degrees. An automatic sampler, a sample pump, a high-pressure sampling valve, a recorder with an integrator, and a high-pressure liquid chromatograph comprise the commercial instruments. Relays, solenoid valves, and timers control chromatographic events, i.e., duration of sampling and rinse, mobile phase pump refill, sample injection, and chromatographic time. The automated system is dependable over long periods of unattended operation. With the 40-sample capacity of the sample tray and the last sample stop capability, the automated system produces, for example, 40 20-min chromatograms in approximately 13 hr of unattended operation. Data demonstrate the reliability and utility of the system.