Thomas A. Eskin

Divergent differentiation in pleomorphic xanthoastrocytoma. Evidence for a neuronal element and possible relationship to ganglion cell tumors.

We report the detection of cytoplasmic immunoreactivity for neuronal/neuroendocrine antigens in a subpopulation of tumor cells within seven pleomorphic xanthoastrocytomas (PXAs). The expression of glial and neuronal polypeptides was examined in routinely prepared surgical resections by immunohistochemistry using well-characterized antibodies that recognize glial fibrillary acidic protein (GFAP), synaptophysin (SYN), and neurofilament triplet polypeptides (NFPs) in microwave-enhanced single- and double-immunolabelling experiments. Each neoplasm contained cells that were immunoreactive for SYN and/or NFPs, GFAP, and occasionally for both GFAP and either NFP or SYN. We conclude that abortive neuronal/neuroendocrine differentiation may occur in PXAs, suggesting a relationship between PXA and other developmental neoplasms that reveal a more overt neuronal phenotype, such as ganglioglioma, dysembryoplastic neuroepithelial tumor, and desmoplastic ganglioglioma, and with tumors expressing ambiguous glial/neuronal lineage, such as the subependymal giant cell tumor of tuberous sclerosis. These findings suggest that aberrant expression and accumulation of neuronal intermediate filaments may account for the large, pleomorphic cell morphology observed in many of these tumors.

β-Catenin is expressed aberrantly in tumors expressing shadow cells: Pilomatricoma, craniopharyngioma, and calcifying odontogenic cyst

We studied the beta-catenin immunohistochemical profile in tumors expressing shadow cells: pilomatricoma, 10 cases; calcifying odontogenic cyst, 6 cases; and craniopharyngioma, 9 cases. There was strong membranous, cytoplasmic, and nuclear staining of the immature basaloid cells in all of these tumors. Shadow cells were negative in all tumors. It has been documented that rising levels of free beta-catenin drive the formation of complexes with T-cell factor/lymphoid enhancer factor (TCF-Lef) and up-regulate the wingless-Wnt cell-cell signals. The end result is an abnormality of beta-catenin degradation and, thus, a buildup of free beta-catenin in the cytoplasm and/or nucleus, resulting in the stimulation of cellular proliferation and/or inhibition of cell death. beta-Catenin seems to have an important role in the oncogenesis of these tumors. The similar pattern of keratinization in these tumors and the similar pattern of beta-catenin immunoreactivity in the cytoplasm and the nucleus are important findings. It seems that the activation of a common cellular pathway, namely Wnt-beta-catenin-TCF-Lef, has a role in the pathogenesis of these tumors. The latter could be related to their shared method of keratinization or shared dysfunction of the cellular adhesion complex leading to tumorigenesis.

Altered mRNA expression for brain-derived neurotrophic factor and type II calcium/calmodulin-dependent protein kinase in the hippocampus of patients with intractable temporal lobe epilepsy

The expression of brain‐derived neurotrophic factor and the α subunit of calcium/calmodulin‐dependent protein kinase II mRNA in hippocampi obtained during surgical resections for intractable temporal lobe epilepsy were examined. Both calcium/calmodulin‐dependent protein kinase II and brain‐derived neurotrophic factor are localized heavily within the hippocampus and have been implicated in regulating hippocampal activity (Kang and Schuman [1995] Science 267:1658–1662; Suzuki [1994] Intl J Biochem 26:735–744). Also, the autocrine and paracrine actions of brain‐derived neurotrophic factor within the central nervous system make it a likely candidate for mediating morphologic changes typically seen in the epileptic hippocampus. Quantitative assessments of mRNA levels in epileptic hippocampi relative to autopsy controls were made by using normalized densitometric analysis of in situ hybridization. In addition, correlations between clinical data and mRNA levels were studied. Relative to autopsy control tissue, decreased hybridization to mRNA of the α subunit of calcium/calmodulin‐dependent protein kinase II and increased hybridization to brain‐derived neurotrophic factor mRNA were found throughout the granule cells of the epileptic hippocampus. There also was a significant negative correlation between the duration of epilepsy and the expression of mRNA for brain‐derived neurotrophic factor. These results are similar qualitatively to those found in animal models of epilepsy and suggest that chronic seizure activity in humans leads to persistent alterations in gene expression. Furthermore, these alterations in gene expression may play a role in the etiology of the epileptic condition. J. Comp. Neurol. 418:411–422, 2000.

Topical Review Article: Brainstem Glioma: I. Pathology, Clinical Features, and Therapy

Gliomas that arise in the brain stem have been associated with a poor prognosis. Diagnostic neuroimaging readily identifies the tumor as it extends between normal brainstem structures. Histologic sampling of tumor with stereotactic methods is notoriously unreliable in establishing a definitive prognosis. Clinical trials that incorporate high-dose chemotherapy, autologous bone marrow rescue, and irradiation hold promise of better tumor control by overcoming the inaccessibility of the central nervous system to standard doses of chemotherapy. We review the pathology, clinical features, neuroimaging features, and current therapeutic concepts relative to brainstem glioma. The pediatric neurologist has a pivotal role in identifying and monitoring children with this malignancy. (J Child Neurol 1993;8:112-128).

Characteristics of Human Fetal Spinal Cord Grafts in the Adult Rat Spinal Cord: Influences of Lesion and Grafting Conditions ☆

The present study evaluated the growth potential and differentiation of human fetal spinal cord (FSC) tissue in the injured adult rat spinal cord under different lesion and grafting conditions. Donor tissue at 6-9 weeks of gestational age was obtained through elective abortions and transplanted either immediately into acute resection (solid grafts) or into chronic contusion (suspension and solid grafts) lesions (i.e., 14-40 days after injury) in the thoracic spinal cord. The xenografts were then examined either histologically in plastic sections or immunocytochemically 1-3 months postgrafting. Intraspinal grafts in acute lesions demonstrated an 83% survival rate and developed as well-circumscribed nodules that were predominantly composed of immature astrocytes. Solid-piece grafts in chronic contusion lesions exhibited a 92% survival rate and also developed as nodular masses. These grafts, however, contained many immature neurons 2 months postgrafting. Suspension grafts in chronic contusion lesions had an 85% survival rate and expanded in a nonrestrictive, diffuse pattern. These transplants demonstrated large neuronally rich areas of neural parenchyma. Extensive neuritic outgrowth could also be seen extending from these grafts into the surrounding host spinal cord. These findings show that human FSC tissue reliably survives and differentiates in both acute and chronic lesions. However, both the lesion environment and the grafting techniques can greatly influence the pattern of differentiation and degree of host-graft integration achieved.

Rabbit study of an in situ forming hydrogel vitreous substitute.

PURPOSEnAn in situ forming hydrogel was evaluated as a potential vitreous substitute in rabbits.nnnMETHODSnThe hydrogel used a disulfide cross-linker that was then reduced to produce an injectable thiol-containing polymer solution. The disulfide cross-links reformed by air oxidation of the thiols and produced a stable hydrogel once inside the eye. The polymer was clear, autoclavable, and could be stored easily in the presence of nitrogen gas. Capillary rheometry was used to measure the viscoelastic properties of the hydrogels and the porcine vitreous. Fourteen black rabbits underwent a pars plana, 25-gauge, three-port vitrectomy by a single surgeon with injection of a vitreous substitute.nnnRESULTSnThe refractive indices of the hydrogels were measured by refractometry and were shown to be close to 1.33, and the 2% hydrogel matched the mechanical properties of the natural vitreous humor. The reduced polymeric hydrogel was easily injectable through a small-gauge needle into the vitreous cavity and did not show any fragmentation. The material underwent gelation within the eye, remained optically clear, and appeared well tolerated clinically. Slit lamp examination, dilated fundus examination, and electroretinograms showed no evidence of vitritis, uveitis, or endophthalmitis after 1 week. Histopathologic evaluation did not reveal any overt toxicity or gross morphologic changes in the retina.nnnCONCLUSIONSnThe fact that this process of in situ gelation gives rise to hydrogels that are biocompatible and physically and optically similar to the natural vitreous suggests its suitability as a permanent vitreous substitute. Hydrogel candidates will be further studied to evaluate long-term biocompatibility and degradation in vivo.

Distinct neurodevelopmental patterns of bcl-2 and bcl-x expression are altered in glioneuronal hamartias of the human temporal lobe.

Bcl-2 and bcl-xL are homologous proteins that inhibit cell death and are expressed in the nervous system. We tested the hypothesis that aberrant expression of such “death suppressor” molecules may promote the survival of abnormal cells in glioneuronal lesions associated with temporal lobe epilepsy. The normal pattern of bcl-2 and bcl-x expression was studied in postmortem human fetal and adult temporal lobes. Formalin-fixed, paraffin-embedded tissue sections were probed for bcl-2 and bcl-x in immunohistochemical studies using well-characterized primary antibodies that had been raised against epitopes that are not shared by these proteins. Strong staining for both proteins was observed in the ventricular zone and in migrating, postmitotic and postmigratory young neurons of the neocortex, hippocampus, and entorhinal cortex from 6 to 20 weeks gestational age (GA). However, bcl-2 immunoreactivity gradually decreased to weak or nondetectable levels between 20 and 39 weeks GA, while strong bcl-x staining of neurons persisted throughout fetal development and into adulthood. Twenty-eight temporal lobe resections from children and adults ranging in age from 1 to 45 years (mean=19 years) with intractable epilepsy were then screened for differences in the pattern of bcl-2 and bcl-x expression compared to normal controls. Bcl-2 (but not bcl-x) was strongly immunoreactive in small, immature-appearing cells that were components of microscopic glioneuronal aggregates (hamartias) and that have been shown previously to express an embryonic form of the neural cell adhesion molecule. These immature cells were immunonegative for standard markers of neuronal and glial lineage and were negative for Ki67, suggesting that they are post-mitotic. The persistent expression of bcl-2 and apparent downregulation of bcl-x in these cells represent deviations from the normal ontogeny of these molecules in the human nervous system. These data suggest that dysregulation of bcl-2 and related proteins may be involved in the pathogenesis of some temporal lobe malformative lesions.

Fatality in a case of envenomation byCrotalus adamanteus initially successfully treated with polyvalent ovine antivenom followed by recurrence of defibrinogenation syndrome

IntroductionRecurrences of clinical or laboratory manifestations of North American pit viper envenomation may happen despite control of the envenomation syndrome by prompt and adequate antivenom therapy. Recurrences of coagulopathy in victims of Eastern diamondback rattlesnake envenomation are generally regarded as benign. The vast majority suffer no actual bleeding despite florid coagulation laboratory abnormalities due to selective defibrinogenation.Case ReportWe report what we believe to be the first fatality following successful control of the envenomation syndrome following ovine antivenom treatment resulting from envenomation by a bite from the Eastern diamondback rattlesnake. This case raises the question of whether such recurrences are in fact benign, causal, or coincidental. This patient sustained significant brain hemorrhage and death ensued due to generalized cerebral edema. Defibrinogenation occurred 4 days after treatment with ovine antivenom.DiscussionCoagulation abnormalities following Eastern diamondback rattlesnake envenomation are due to selective defibrinogenation. This is separate from disseminated intravascular coagulation (DIC). Thrombin generation, thus hemostasis, are generally considered normal. This case may cause reexamination of this belief.

Granulomatous Angiitis of the Spinal Cord: A Case Report

A 12-year-old caucasian boy presented with a thoracic myelopathy. Magnetic resonance T1-weighted images revealed an enhancing lesion infiltrating the lower thoracic spinal cord to the level of the conus. Evaluation of the lesion by open biopsy revealed granulomatous angiitis of the spinal cord. Granulomatous angiitis is a rare vasculitic process that typically involves the brain and, less frequently, the spinal cord. Diagnosis must be established early by histopathological examination so that treatment with corticosteroids and/or cytotoxic agents may be instituted. When left untreated, patients with granulomatous angiitis of the spinal cord have developed fatal intracranial manifestations.

Developmental Patterns of BCL-2 and BCL-X Polypeptide Expression in the Human Spinal Cord

The cell death suppressors bcl-2 and bcl-x are developmentally regulated and may modulate physiologic cell death in the central nervous system (CNS). However, little data are currently available on the expression patterns of these polypeptides in the human CNS. We examined the ontogeny of bcl-2 and bcl-x in 12 human spinal cords of gestational ages (GA) between 5 and 39 weeks and in 3 adult cords. Paraffin sections were probed by immunohistochemistry using well-characterized, commercially available antibodies that had been raised against poorly conserved epitopes of these homologous proteins. Between 5 and 10 weeks GA, bcl-2 immunoreactivity was identified in primitive neuroepithelial cells of the ventricular zone. Individual cells of the mantle zone were stained including clusters of early anterior horn cells. Bcl-x immunoreactivity was most prominent in differentiating neurons of the mantle zone and less pronounced in the ventricular zone. Between 10 and 14 weeks GA, bcl-2 staining was observed in cells lining the central canal, neurons of the dorsal horn (especially laminae I and II), and in anterior horn cells. The latter exhibited a range of staining intensities from moderate to nondetectable. Bcl-2 immunoreactivity became markedly reduced between 15 and 25 weeks GA, persisting only in ependymal cells. In contrast, strong bcl-x staining was observed in most neurons throughout development and into adulthood. The period of apparent bcl-2 down-regulation overlaps with a peak in physiologic motoneuron death and the establishment of functional neuromuscular synapses in the human spinal cord. These findings suggest that bcl-2 and bcl-x may both be required for survival of early postmitotic neurons before appropriate synaptic connections have been established. Continued neuronal survival (after bcl-2 is down-regulated) may require persistent bcl-x expression in addition to target-derived neurotrophic factors made available through the formation of appropriate synapses.