Jeannette J. Townsend

Pre- and Postsynaptic Neurotoxic Effects of Dopamine Demonstrated by Intrastriatal Injection

Considerable evidence indicates that dopamine (DA) may play a neurotoxic role in brain in certain pathologic circumstances. To investigate this issue, dopamine (1000 nmol/1 microliter) was directly injected into the striatum of anesthetized Sprague-Dawley rats. Control animals received equal-volume injections of gamma-aminobutyric acid (GABA) or NaCl at identical concentrations (diluted in distilled H2O, pH 7.0-7.7). Brains were removed 7 to 9 days later and frozen or fixed and sectioned for histologic and autoradiographic analysis. Dopamine injection resulted in a small-volume (3.3-mm3) lesion in comparison to control GABA and NaCl injections which produced only a needle track < 0.6 mm3 in volume (P < 0.01). Dose dependency of DA toxicity was demonstrated, with substantial parenchymal damage requiring an injection of 500 nmol/1 microliter. Within the lesion, marked neuronal loss, macrophage invasion, and capillary and glial proliferation were present. Acetylcholinesterase staining and D1 receptor binding were markedly reduced as well. [3H]RO5-4864 binding to peripheral benzodiazepine receptors (on astrocytes) was increased in the periphery of the lesion. The binding of 1-[3H]benzo[b]cyclohexylthiophenylpiperidine to dopamine uptake sites was also reduced, but over a wider striatal area in comparison to local parenchymal damage. Prior interruption of the dopaminergic nigrostriatal pathway (by injection of 6-hydroxydopamine) appeared to potentiate the toxicity of intrastriatal dopamine injection. The findings indicate that local injection of dopamine produces both post- and presynaptic damage to nigrostriatal structures, and support the contention that dopamine may act as a low-potency neurotoxin.

A phase II evaluation of tamoxifen in unresectable or refractory meningiomas: a southwest oncology group study

Twenty-one patients with nonresectable refractory meningiomas were registered on a study giving tamoxifen 40 mg per M2 b.i.d. for four days, then 10 mg b.i.d. thereafter. Nineteen were eligible and evaluated for response. One patient (5%) achieved an MRI-documented partial response while two had a minor response measured on CT scan which was of short duration (4 and 20 months). Six patients (32%) remained stable for a median duration of 31 + months while ten (53%) demonstrated progression. Twenty-two percent (22%) reported subjective improvement though this did not correlate with objective improvement in all cases. At present, a definite recommendation for the use of tamoxifen in refractory meningiomas cannot be made. Further evaluation of hormonal therapy of meningiomas with a concensus for definition of endpoints for evaluation of response in view of the difficulty of evaluating radiologic findings with clinical outcome, is needed.

Neurenteric cysts of the posterior fossa: recognition, management, and embryogenesis.

Neurenteric cysts are endothelium-lined structures most commonly encountered in the lower cervical or upper thoracic spinal cord. The occurrence of neurenteric cysts within the cranial vault is unusual. We present three patients with neurenteric cysts located within the posterior fossa: one near the jugular foramen deforming the 4th ventricle, a second in the cerebellopontine angle, and a third in the prepontine cistern. Several different theories have been advanced to explain the embryogenesis of neurenteric cysts. We review these theories and conclude that cranial neurenteric cysts may arise from a disturbance of early gastrulation, shortly after the onset of primitive streak regression.

Anaplastic Oligodendrogliomas: Prognostic Factors for Tumor Recurrence and Survival

Objectives: Anaplastic oligodendrogliomas (AO) are uncommon primary brain tumors whose natural history, prognosis, and optimal management are not yet fully understood. However, they are associated with a better prognosis and response to multimodality therapy based on specific molecular changes. In this multicenter retrospective study, we analyzed the clinical characteristics of patients with AO to identify prognostic factors that influence time to progression (TTP) and survival. Methods: A retrospective search of the brain tumor databases of three institutions (the University of Texas M. D. Anderson Cancer Center, the University of California at San Francisco, and the University of Utah) for patients between 1977 and 1995 with histologically confirmed AO identified a cohort of 106 patients that was further analyzed in this study. Initial treatment included surgery alone (n = 12) or surgery followed by one of the following: radiotherapy (RT) alone (n = 49), chemotherapy alone (n = 4), chemotherapy followed by RT (n = 10), RT followed by chemotherapy (n = 20), and others (n = 11). Results: The median age at diagnosis was 43 years, and the median Karnofsky performance score (KPS) was 90. The overall median survival was 7.3 years, and the 5-year survival rate was 62%. Univariate analysis of several clinical variables showed that only age (p < 0.0001) and KPS (p = 0.04) correlated significantly with survival. Fifty patients had disease progression after initial therapy. The median TTP was 48 months. Age at diagnosis was the only variable that correlated significantly with TTP. Conclusions: A trend towards longer survival with a greater extent of resection was evident. The relative efficacy of various treatment modalities could not be definitively determined because of the heterogeneity of the therapies used. Overall, patients with AO have a better prognosis after therapy compared with those who have other malignant gliomas.

Augmentation of adoptively transferred experimental allergic encephalomyelitis by administration of a monoclonal antibody specific for LFA-1α

We investigated the effect of an anti-leukocyte function antigen 1 (LFA-1 alpha) monoclonal antibody, M17/4.2, on murine relapsing experimental allergic encephalomyelitis (EAE). In vitro investigations demonstrated that M17/4.2 inhibited proliferation with concanavalin A or myelin basic protein. Control mice treated with phosphate buffered saline (PBS) developed a mild to moderate disease at 7-10 days followed by a long-term relapsing clinical course. With administration of M17/4.2, the time of disease onset was unchanged; however, the severity of the disease was greatly augmented, resulting in early mortality. The pathology correlated well with the clinical course. M17/4.2 mice showed more inflammation and demyelination than PBS or anti-CD4 treated mice. Therefore, this anti-LFA-1 specific monoclonal antibody augmented EAE.

Central nervous system susceptibility to herpes simplex infection.

Four days after inoculation of herpes simplex virus (HSV) on the rabbit cornea, distinctive and reproducible lesions appear in the trigeminal root entry zone. These viral lesions, situated in the central nervous system (CNS) portion of the root, consist of severe myelin destruction accompanied by mononuclear cell infiltration and partial sparing of axons. Immunofluorescent study demonstrated abundant viral antigen, and by electron microscopy viral nucleocapsids were found to be numerous within astrocytes and were rarely found in other cell types. In contrast, the adjacent peripheral nervous system (PNS) tissue appears unaffected by the presence of virus. The mechanism for this marked difference in response of the central nervous system and the peripheral nervous system may depend upon the susceptibility of astrocytes to viral infection and replication. The selective nature of the lesion provides an easily reproducible model for further investigation of the response of nervous system tissue to HSV.

Subependymomas: An analysis of clinical and imaging features

OBJECTIVE:Subependymomas are slow-growing, benign tumors usually found incidentally in the fourth ventricle at autopsy. They are typically associated with the ventricular system and become apparent clinically only when symptoms of hydrocephalus or mass effect develop. We review clinical, histological, and contemporary radiographic presentations of 16 subependymomas, including 2 intraparenchymal tumors. METHODS:We retrospectively evaluated eight patients with pathologically proven subependymomas. Initial magnetic resonance imaging and magnetic resonance spectroscopy were reviewed when available. Imaging was also available on eight outside subependymoma cases reviewed by our radiology department. RESULTS:Twelve of these subependymomas were intraventricular, one was in the posterior fossa, two were intraparenchymal, and one was an intramedullary spinal cord tumor. These lesions were hypo- to hyperintense on T1- and T2-weighted magnetic resonance imaging, with minimal to moderate enhancement. Initial complaints included headache, seizures, tingling sensations, and weakness. Among our eight patients who underwent gross total resection with no adjuvant therapy, no recurrences have been noted on follow-up magnetic resonance imaging. CONCLUSION:Subependymomas are rare, representing only 0.51% of all central nervous system tumors operated on during an 8-year period at the University of Utah. Clinical symptoms were associated with tumor location: intracranial masses caused headaches, seizures, and neurological complaints, and spinal cord locations resulted in neurological deficit. The authors review the clinical presentation, management, and contemporary radiographic appearance of this rare tumor.

Case reportsNeurenteric Cysts of the Posterior Fossa: Recognition, Management, and Embryogenesis

Neurenteric cysts are endothelium-lined structures most commonly encountered in the lower cervical or upper thoracic spinal cord. The occurrence of neurenteric cysts within the cranial vault is unusual. We present three patients with neurenteric cysts located within the posterior fossa: one near the

Ataxin-7 expression analysis in controls and spinocerebellar ataxia type 7 patients.

Abstract Expansion of polymorphic CAG repeats encoding polyglutamine cause at least eight inherited neurodegenerative diseases, including Huntington disease and the spinocerebellar ataxias. However, the pathways by which proteins containing expanded polyglutamine tracts cause disease remain unclear. To gain insight into the function of the SCA7 gene product, ataxin-7, as well as its contribution to cell death in spinocerebellar ataxia type 7 (SCA7), polyclonal antibodies were generated and ataxin-7 expression was examined within neuronal tissues from controls and three SCA7 patients. Immunoblotting demonstrates that ataxin-7 is widely expressed but that expression levels vary between tissues. Immunohistochemical analyses indicate that ataxin-7 is expressed within neurons both affected and unaffected in SCA7 pathology and that subcellular localization varies depending upon the neuronal subtype. Additionally, ataxin-7 staining was detected throughout control retina, including intense staining within the cell bodies and photosensitive outer segments of cone photoreceptors. Anti-ataxin-7 antibodies revealed intranuclear inclusions within surviving inferior olivary and cortical pyramidal neurons, as well as within surviving photoreceptor and ganglion cells of SCA7 patients harboring either 42 or 66 CAG repeats at the SCA7 locus. In contrast, inclusion formation was not detected within neurons of a patient with 41 repeats. This study broadens the current understanding of ataxin-7 localization and incorporates for the first time analysis of late-onset SCA7 patients where polyglutamine tract lengths are relatively shorter and disease course less severe than in previously described infantile-onset cases.

Comparison of clinical and neuropathologic diagnoses of Alzheimer’s disease in 3 epidemiologic samples

Studies of dementia in populations avoid many of the selection biases in clinical samples but require special evaluation and diagnostic methods to obtain high participation rates. To address this issue, we developed a unique in‐home dementia assessment. We assessed validity of these assessments using neuropathologic confirmation of the clinical diagnosis in 3 epidemiologic samples.