Magnetic resonance imaging and 31P spectroscopy of an interictal cortical spike focus in the rat

Magnetic resonance imaging (MRI) has proven to be an effective noninvasive technique for identifying lesions in patients with temporal lobe epilepsy. It has also been suggested that MRI may be sensitive to transient functional or metabolic changes in brain tissue. Increased brain electrical activity as monitored by electroencephalography causes changes in cerebral metabolism that may be responsible for focal or regional alterations in signal in the MRI of some patients. To test this hypotheses, experimental interictal cortical foci were produced in rats by topical application of penicillin to one hemisphere of the brain. In vivo MRI and phosphorous-31 (31P) spectroscopy of the focal and contralateral hemifield were performed in a 30-cm bore 1.89-T Bruker MSL system. 31P spectroscopy revealed no quantifiable differences in pH or in phosphocreatinine and ATP levels between the focal area and the contralateral hemisphere or between experimental and saline-treated control animals. There were also no differences in proton MRI. Similar areas of prolonged T2 were found near the cortex and in the deeper parenchyma in 55% of the experimental animals and 50% of the controls. These results suggest that the electrical activity from an interictal cortical spike focus is not severe enough to perturb cerebral metabolism sufficiently to be detectable by 31P spectroscopy or proton imaging techniques.

Comparison of Tirilazad Mesylate (U-74006F) and Methyl Prednisolone Sodium Succinate Treatments in Experimental Allergic Encephalomyelitis in the Guinea Pig

The effects of the non-glucocortioid 21-aminosteroid, tirilazad mesylate (U-74006F), on MRI and clinical findings in guinea pigs with experimental allergic encephalomyelitis were compared to treatment with methylprednisolone sodium succinate (MPSS). A dose response experiment for U-74006F was performed 1, 3 and 10 mg/kg/day IP on day 0–12 after immunization. Additionally, the 3 mg/kg/day IP dose was extended to 24 and 35 days. MPSS was given in three different protocols at doses ranging from 0.8 to 3.2 mg/kg/day. Abnormalities in T2-weighted images were assessed as measures of edema and inflammation and gadolinium-DTPA enhanced TI-weighted images were used to determine blood-brain barrier integrity. U-74006F improved the clinical status at doses of 3 and 10 mg/kg. For example, maximum clinical score was halved at 10 mg/kg/day (P < 0.01). The presence of gadolinium-DTPA in the parenchyma was also decreased at 3 and 10 mg/kg/day U-74006F although maximum MRI scores were decreased only in the 10 mg/kg U-74006F group. Clinical disease suppression seen with 3 mg/kg treatment on days 0–12 reverted to control at > 24 days of dosing. MPSS treatment considerably worsened the clinical outcome of EAE Mean clinical scores for vehicle and the highest MPSS dose were 0.94 ± 0.66 versus 2.64 ± 1.49 (P < 0.05). The combination of decreased T2-weighted abnormalities, clinical signs and gadolinium-DTPA permeation in the U-74006F treated animals suggested protection of the blood–brain barrier without the severe glucocorticoid effects associated with steroid therapy.

Baseline consideration of liposomal contrast agent. CNS transport by macrophages in experimental allergic encephalomyelitis

The purpose of this study was to investigate a specialized liposomal contrast agent for magnetic resonance imaging (MRI), as part of a program to examine infiltrating immune cells in lesions of experimental allergic encephalomyelitis (EAE). A potent investigational liposomal contrast agent, phosphatidylethanolamine-DTPA-gadolinium, was chosen which has been shown to remain tightly liposomal-associated, with long persistence in vivo. Europium (Eu3+), a fluorescent paramagnetic metal, was also utilized in these experiments in place of gadolinium. This material is avidly taken up by monocytes in vivo. Thirty-four animals received some form of liposomal material either before or during the opening of the blood-brain barrier (BBB). Twenty-seven Hartley guinea pigs were inoculated for EAE with homogenized brain and Complete Freunds Adjuvant (CFA) and seven control animals received CFA alone. Eighty-two percent of the experimental animals exhibited degeneration of the BBB with inflammation and edema in the brain, while all control animals had normal brain scans. T1-weighted MRI, performed to detect the presence of liposomal contrast material in experimental animals, was not different from untreated animals. Fluorescent microscopy revealed no characteristic changes associated with Eu3+ presence in the brains of treated or control animals. Therefore, it would seem that insufficient material crosses the disrupted BBB, either in free form or subsequent to macrophage ingestion, to be detected by MRI or fluorescent microscopic examination.

Comparison of tirilazad mesylate (U-74006F) and methylprednisolone sodium succinate treatments in experimental allergic encephalomyelitis in the guinea pig

The effects of the non-glucocorticoid 21-aminosteroid, tirilazad mesylate (U-74006F), on MRI and clinical findings in guinea pigs with experimental allergic encephalomyelitis were compared to treatment with methylprednisolone sodium succinate (MPSS). A dose response experiment for U-74006F was performed 1, 3 and 10 mg/kg/day i.p. on day 0-12 after immunization. Additionally, the 3 mg/kg/day i.p. dose was extended to 24 and 35 days. MPSS was given in three different protocols at doses ranging from 0.8 to 3.2 mg/kg/day. Abnormalities in T2-weighted images were assessed as measures of edema and inflammation and gadolinium-DTPA enhanced T1-weighted images were used to determine blood-brain barrier integrity. U-74006F improved the clinical status at doses of 3 and 10 mg/kg. For example, maximum clinical score was halved at 10 mg/ kg/day (P < 0.01). The presence of gadolinium-DTPA in the parenchyma was also decreased at 3 and 10 mg/kg/day U-74006F although maximum MRI scores were decreased only in the 10 mg/kg U-74006F group. Clinical disease suppression seen with 3 mg/kg treatment on days 0-12 reverted to control at > 24 days of dosing. MPSS treatment considerably worsened the clinical outcome of EAE. Mean clinical scores for vehicle and the highest MPSS dose were 0.94 +/- 0.66 versus 2.64 +/- 1.49 (P < 0.05). The combination of decreased T2-weighted abnormalities, clinical signs and gadolinium-DTPA permeation in the U-74006F treated animals suggested protection of the blood-brain barrier without the severe glucocorticoid effects associated with steroid therapy.