Does astroglial protein S100B contribute to West Nile neuro-invasive syndrome?

The clinical spectrum of West Nile Virus (WNV) infection ranges from a flu-like febrile condition to a more severe neuro-invasive disease that can cause death. The exact mechanism of neurodegeneration in neuro-invasive form of WNV infection has not been elucidated; however, a destructive role played by glial cells in promoting WNV mediated neurotoxicity has widely been speculated. The clinical studies revealed that the astroglial protein S100B is significantly elevated in the blood and CSF of patients with WNV infection, even in the absence of neuro-invasive disease. Therefore, the present study was designed to explore the potential role of S100B in the pathophysiology of WNV infection. The overarching hypothesis was that WNV primes astroglia to release S100B protein, which leads to a cascade of events that may have deleterious effects in both acute and chronic stages of WNV disease. To justify our hypothesis, we first ascertained increased levels of S100B in post-mortem tissue samples from WNV patients. Next, we looked at the effects of UV-inactivated WNV particles on astroglia using astroglial cell lines or primary cultures. Astroglial activation was measured as an increase in the expression of S100B and was analyzed by immunofluorescence and real-time PCR. Further, the in vitro effects of purified S100B protein on neutrophil migration and glutamate uptake were also determined in astroglial cell lines or primary cultures. We found that incubation of cultured astroglial cells with UV-inactivated WNV particles caused induction of S100B both at the mRNA and protein levels. Varying concentrations of S100B stimulated neutrophil migration in vitro. In addition, varying amounts of S100B caused inhibition of glutamate uptake in astroglia in a dose-dependent manner. Our data suggest that inactivated WNV particles are capable of inducing S100B synthesis in astroglia in vitro. We speculate that S100B release by activated astroglia may have multiple roles in the pathophysiology of WNV neuro-invasive disease, including induction of neutrophil migration to the sites where blood brain barrier is disrupted as well as glutamate neurotoxicity. To further elucidate the WNV-S100B neurotoxic pathway, in vivo studies using mouse models are warranted.

A novel ryanodine receptor gene mutation causing both cores and rods in congenital myopathy.

BACKGROUND: Central core disease (CCD) and nemaline rod myopathy are generally considered two genetically and histologically distinct disorders. CCD is defined by the presence of well-demarcated round cores within most myofibers. Nemaline rod myopathy is distinguished by the presence of characteristic nemaline bodies within myofibers. The simultaneous occurrence of both cores and rods in the same muscle biopsy has been described, but no gene mutations have been reported yet for this condition. OBJECTIVE: To describe a family containing 16 affected individuals in six generations with an autosomal dominant congenital myopathy that shows clinical and histologic features of both CCD and nemaline myopathy, and to determine the genetic etiology and protein composition of the cores/rods in this family. METHODS AND RESULTS: The results of linkage analyses excluded involvement of the two autosomal dominant nemaline myopathy loci on chromosome 1, but were consistent with a localization of the disease gene at the CCD locus on chromosome 19q13.1 (ryanodine receptor). SSCP analysis and DNA sequencing identified a novel Thr4637Ala mutation in the transmembrane region of the ryanodine receptor protein. Immunofluorescence studies of patient muscle biopsies showed the central cores to stain for ryanodine receptor. CONCLUSIONS: These data suggest that the occurrence of nemaline bodies can be a secondary feature of CCD, and that genetic studies on previously reported core/rod families should be targeted to the ryanodine receptor locus. The results of the immunofluorescence studies suggest that the cores contain excess abnormal ryanodine receptor protein.

Desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in piglets.

OBJECTIVE: Desmethyl tirilazad is a lipid-soluble free radical quencher. Deferoxamine reduces free radicals by chelating iron and reducing hydroxyl formation. Free radical inhibitors have shown promise in several hypoxic ischemic brain injury models, and we wished to see if this work could be extended to our newborn piglet model. DESIGN: Randomized controlled trial. SUBJECTS: Piglets (0 to 3 days old). INTERVENTION: Carotid snares and arterial and venous catheters were placed under 1.5% isoflurane anesthesia. In Experiment 1, piglets were randomly assigned to receive either 3 mg/kg desmethyl tirilazad or vehicle at -15 and 90 mins. In Experiment 2, piglets were randomly assigned to receive either 20 mg/kg desmethyl tirilazad at -15 mins followed by 8 mg/kg/hr for 90 mins or 100 mg/kg deferoxamine at -15 mins or vehicle. At time 0, both carotid arteries were clamped and blood was withdrawn to reduce the blood pressure to two-thirds normal. At 15 mins, inspired oxygen was reduced to 6%. At 30 mins, the carotid snares were released, the withdrawn blood was reinfused, and the oxygen was switched to 100%. On the third day after the hypoxic ischemic injury, the animals were killed by perfusing their brains with 10% formalin. We tested the timing of lipid peroxidation and inhibition of lipid peroxidation by these agents by freezing the brains of a subset of pigs in liquid nitrogen. MEASUREMENTS: Neurologic examination and brain pathology were scored by blinded observers. Thiobarbituric acid-reactive substance and oxidized and reduced glutathione were measured on frozen brains. MAIN RESULTS: Desmethyl tirilazad (20 mg/kg) and 100 mg/kg deferoxamine inhibit lipid peroxidation. Desmethyl tirilazad (20 mg/kg) improves neurologic exam, but 3 mg/kg Desmethyl tirilazad or 100 mg/kg deferoxamine does not. Neither desmethyl tirilazad nor deferoxamine improves pathologic results. CONCLUSIONS: High-dose desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in the newborn piglet.

Reduced nitric oxide is involved in prenatal ischemia-induced tolerance to neonatal hypoxic-ischemic brain injury in rats.

To explore the role of nitric oxide (NO) in the hypoxic-ischemic (HI) tolerance phenomenon, NO production and brain injury following neonatal hypoxia-ischemia (induced by unilateral common carotid artery ligation followed by hypoxic exposure) were assessed in rat pups with or without HI preconditioning. A previously demonstrated prenatal HI rat model of preconditioning was used in this study. On G17, rat fetuses were subjected to either HI in utero (PreHI) for 30 min or a sham operation (SH). The PreHI treatment provided significant protection against neonatal HI-induced brain injury, as indicated by decreased ipsilateral brain weight reduction, less severe tissue damage, and decreased activation of caspase-3. Concomitant with the protective effect of prenatal HI preconditioning, elevation of nitrite/nitrate content in the ipsilateral cortex of the brain, as an indirect measure of NO production, was significantly lower in the PreHI group than in the SH group following neonatal HI. The protective effect of prenatal HI preconditioning could be reversed by sodium nitroprusside (SNP), a spontaneous NO donor, while SNP had no effect on neonatal HI-induced brain injury in the SH group. Intraperitoneal administration of SNP to pups from the PreHI group (2 mg/kg, 24 and 1.5 h before neonatal HI) increased neonatal HI-induced brain injury similar to that observed in the SH group. On the other hand, L-N(G)-nitro-arginine (2 mg/kg, i.p., 1.5 h before the hypoxic exposure), an NO synthase inhibitor, significantly attenuated neonatal HI-induced brain injury in the SH group. The overall results indicate that reduced NO production in the preconditioned rat brain contributes to prenatal HI-induced tolerance to neonatal HI brain injury.

Relationship between ataxin-1 nuclear inclusions and Purkinje cell specific proteins in SCA-1 transgenic mice.

Spinocerebellar ataxia-1 (SCA-1), like other polyglutamine diseases, is associated with aggregation of mutant protein ataxin-1 in the nuclei of susceptible neurons. The role of ataxin-1 aggregates in the pathogenesis of susceptible neurons, especially cerebellar Purkinje cells, is unknown. The present study was initiated to determine the temporal relationship between ataxin-1 aggregation and the sequence of specific biochemical changes in Purkinje cells in SCA-1 transgenic mice (TM). Earlier, we demonstrated that SCA-1 TM with no Purkinje cell loss and no alterations in home cage behavior show decreased expression of calcium-binding proteins calbindin-D28k (CaB) and parvalbumin (PV) in Purkinje cells. To determine if increased expression of mutant ataxin-1 in TM is also associated with earlier biochemical changes in Purkinje cells, both heterozygous and homozygous (B05 line of SCA-1) TM were used. The age of onset of ataxia in SCA-1 TM was at 12 weeks in heterozygotes and 6 weeks in homozygotes. In 6 week old heterozygous TM, Western blot analysis of growth associated protein 43 (GAP-43) and synaptophysin revealed no significant alterations as compared with the age-matched nontransgenic mice (nTM), whereas CaB was significantly reduced. beta-III-Tubulin was used as a specific Purkinje cell marker protein, immunohistochemical localization showed strong beta-III-tubulin immunoreactivity (IR) in Purkinje cells in 6 week old heterozygous TM, whereas CaB and PV IR were markedly reduced in the same neurons (double immunofluorescence staining). Most Purkinje cells from heterozygous (12 weeks old) and homozygous (6 weeks old) TM contained ataxin-1 nuclear inclusions (NIs). Cells with and without visible NIs revealed reduced PV and CaB IR; however, the changes were overtly more severe in cells with visible NIs. In contrast, the same cells were strongly immunoreactive to beta-III-tubulin. CaB, which is also present in the nucleus, colocalized with ataxin-1 and ubiquitin positive NIs. Further, RT-PCR analysis of CaB mRNA in the cerebellum in 6 week old heterozygous TM demonstrated a significant decrease in mRNA in comparison with the aged-matched nTM. These data suggest that there are selective alterations in the expression of CaB and PV in Purkinje cells which possibly occur earlier than ataxin-1 aggregation. Further, we speculate that ataxin-1 aggregates may not be toxic in general; however, they may deplete specific proteins essential for Purkinje cell viability in SCA-1 TM.

N-tosyl-L-phenylalanyl-chloromethylketone reduces hypoxic-ischemic brain injury in rat pups.

N-tosyl-L-phenylalanyl-chloromethylketone (TPCK) in vitro blocks apoptotic pathways leading to cell death. We wished to see if TPCK would reduce brain injury in vivo. Seven-day-old rat pups had the right carotid artery ligated and then received either vehicle or TPCK (5 to 100 mg/kg i.p.). They were then given 8% oxygen for 2.25 h. Twenty-two days later, the cerebral hemispheres were weighed to determine the reduction in size in the right hemisphere. TPCK decreased the reduction in right hemisphere weight from 15+/-3% (vehicle, n=20), to 4+/-2% (10 mg/kg, n = 19, P<0.01). TPCK reduced the number of cells staining for DNA breaks 3 days after injury from 1729+/-275 mm(-2) (vehicle, n = 8) to 550+/-236 mm(-2) (10 mg/kg TPCK, n = 9, P<0.01), decreased the amount of DNA fragmentation 3 days after injury by gel electrophoreses (20 mg/kg, n = 16, P<0.01) and eliminated the increase in nitric oxide metabolites 6 h after injury (vehicle 1.5+/-0.4, n = 10; and 20 mg/kg TPCK 0.0+/-0.1 nM/mg protein, n = 10, P<0.001). TPCK pretreatment in the newborn rat model of hypoxic-ischemic brain injury reduces DNA fragmentation, nitric oxide production and brain injury.

Protection of neonatal rat brain from hypoxic-ischemic injury by LY379268, a Group II metabotropic glutamate receptor agonist.

Neuroprotective effects of a Group II metabotropic glutamate receptor agonist, LY379268, were examined in a neonatal rat model of hypoxia-ischemia (unilateral common carotid artery ligation followed by hypoxic exposure for 1.5h in 7-day-old rat pups). LY379268 administered 5 min after hypoxic exposure (2, 5, or 10 mg/kg, i.p.) significantly reduced brain injury as measured by reductions in the ipsilateral brain weight and in CA1 hippocampal neuron density. The significant neuroprotective effects were also observed when this compound (5 mg/kg) was administered 30 min, but not 60 min, after hypoxic exposure. The neonatal hypoxia-ischemia (HI) procedure significantly increased caspase-3 activity and induced DNA fragmentation in the ipsilateral cortex compared with that in the contralateral cortex 24 and 72h after the insult, respectively. LY379268 did not prevent this increase in caspase-3 activity and DNA fragmentation in the ipsilateral cortex. These results suggest that activation of Group II metabotropic glutamate receptors may provide neuroprotection against HI brain injury. However, blockade of caspase-3 activation and the apoptotic pathway appears not to be involved in the neuroprotective effects of LY379268 observed in the neonatal rat model of HI.

Solitary choroid plexus metastasis from a renal cell carcinoma.

Metastatic tumors to the choroid plexus are rare. We report a case of renal cell carcinoma metastasizing to the choroid plexus of the lateral ventricular atrium. This tumor was shown by magnetic resonance imaging, followed by craniotomy and histologic confirmation. Computed tomography of the abdomen showed the primary tumor. We also reviewed 40 years of the literature and found 14 cases of metastasis to the choroid plexus. We discuss the clinical features of this intraventricular metastasis.

Surgical removal of subfoveal iatrogenic choroidal neovascular membranes.

OBJECTIVE: To present the cases of two patients with laser-induced iatrogenic subfoveal choroidal neovascular membranes (CNVMs) who underwent surgical removal of the membranes with favorable outcomes. DESIGN: Interventional case reports. PARTICIPANTS: Two patients with iatrogenic subfoveal CNVM. One case developed after laser treatment for macular edema due to branch retinal vein occlusion, and the second case developed after focal laser photocoagulation for diabetic retinopathy. INTERVENTION: Surgical removal by pars plana vitrectomy. MAIN OUTCOME MEASURES: Visual acuity, scotoma, retinal examination with fundus photography, and fluorescein angiography before surgery and during the postoperative period. RESULTS: Both patients underwent surgical removal after progression of the membrane with severe visual loss of 20/200 was noted. At present follow-up, there is a significant improvement in visual acuity and a reduction in the size of the scotoma. No recurrence of CNVM is noted. CONCLUSION: Both patients with laser-induced iatrogenic subfoveal CNVM achieved a good visual outcome after surgical removal of the membrane. The reasons for a good surgical result are thought to be twofold. First, the origin of the CNVM is extrafoveal at the site of laser application. The chance for foveal cone cell damage during the surgery is reduced. Second, the degree of cellular destruction in iatrogenic CNVM is usually focal without extensive retinal photoreceptor cell and retinal pigment epithelial damage. Therefore, a better chance of postoperative visual recovery is anticipated.

Reduced immunoreactivity to calcium-binding proteins in Purkinje cells precedes onset of ataxia in spinocerebellar ataxia-1 transgenic mice.

Earlier we have shown alterations in immunoreactivity (IR) to the calcium-binding proteins parvalbumin (PV) and calbindin D-28k (CaB) in surviving Purkinje cells of patients with spinocerebellar ataxia-1 (SCA-1). In the present study we determined PV and CaB expression (by immunohistochemical and immunoblot analyses) in Purkinje cells of transgenic mice (TM) expressing the human SCA-1 gene with an expanded (line B05) and normal (line A02) CAG tract, as well as in age-matched nontransgenic mice (nTM). Heterozygotes in the B05 line develop progressive ataxia beginning around 12 weeks of age. A02 animals are phenotypically indistinguishable from wild-type (nontransgenic) animals. In the cerebella of 8-, 9-, and 12-week-old TM-B05 there was a progressive decrease in PV IR in Purkinje cells compared with nTM and TM-A02. Parvalbumin immunostaining in interneurons was well preserved in all groups. A progressive decrease was also observed in CaB IR in Purkinje cells of 8-, 9-, and 12-week-old TM-B05. Cerebellar Purkinje cells of 6-week-old TM-B05, which exhibit no ataxia and even lack demonstrable Purkinje cell loss, also revealed reduction in PV IR. This change was matched by a significant decrease in the amount of cerebellar PV in 6-week-old TM-B05 as determined by Western blot analysis. Calbindin D-28K immunohistochemistry did not detect any marked changes in CaB IR within Purkinje cells at 4 weeks. However, at 6 weeks immunostaining and immunoblot analysis revealed a significant decrease in CaB in TM-B05 compared with controls. These data suggest that decreased levels of calcium-binding proteins in Purkinje cells in SCA-1 transgenic mice may cause alteration in Ca2+ homeostasis.

Prenatal ischemia reduces neuronal injury caused by neonatal hypoxia-ischemia in rats.

To determine whether 'ischemic tolerance', first described in adult rodents, exists in fetal and neonatal rats, a comparison of brain injury was made between two groups of rat pups following neonatal hypoxia-ischemia (HI). One group of rat pups had previously been subjected to HI in utero (HI + HI); the other had been subjected to a sham operation (SH + HI). Brain infarct size and neuronal injury were measured 24 h after the neonatal HI insult. As indicated by 2,3,5-triphenyltetrazolium chloride staining and pathological examination, cerebral damage was significantly less in the HI+ HI group than in the SH + HI group. Induction of heat shock protein 70 (hsp70) was immunohistochemically detectable in both groups 24 h after the neonatal HI, and was proportional to the extent of tissue damage. The ischemic tolerance phenomenon observed in immature rats does not appear to be a result of induction of hsp70.

Should endolymphatic sac tumors be considered part of the von Hippel-Lindau complex? Pathology case report.

OBJECTIVE: Von Hippel-Lindau (vHL) disease is an inherited disorder characterized by numerous cystic and solid neoplasms. Because of the recent identification of the vHL gene, other investigators have demonstrated genetic mutations in this gene in several of the neoplasms associated with the disease. We describe a patient with an endolymphatic sac (ELS) tumor and vHL disease. The purpose of this study was to identify a similar genetic mutation within the vHL gene of the ELS tumor. METHODS: Using the patient's archival pathological slides, neoplastic cells were microdissected to yield a purely neoplastic cell population. The deoxyribonucleic acid of these cells was then extracted and amplified via polymerase chain reaction. After sufficient amplification, the specimen was analyzed on a single-strand conformation polymorphism gel system to detect putative changes in the base sequence. RESULTS: Single-strand conformation polymorphism gel system analysis yielded two bands representing the two single strands of deoxyribonucleic acid that were amplified. The upper band of the specimen was shifted down (compared with controls), representing a conformational change as a result of genetic mutation. CONCLUSION: ELS tumors are uncommon, and, to our knowledge, only seven cases associated with vHL disease have been reported in the literature. Although this association has been previously mentioned, no definitive studies have linked the two together. We report the eighth case of ELS tumor and vHL disease. We have demonstrated through molecular biological techniques, that, in our patient's tumor, a genetic mutation occurred, and that this mutation is similar to mutations previously reported in other neoplasms associated with vHL. We therefore suggest that ELS tumors be considered among the neoplasms associated with vHL.

Three-dimensional reconstruction of melanotic neuroectodermal tumor of infancy involving the occipital bone and dura.

A rare case of melanotic neuroectodermal tumor of infancy involving the right occipital bone in an 11-month-old infant is described. The bone tumor and its dural extension were surgically removed. Three-dimensional reconstruction of the tumor and brain from neuroimaging data added worthwhile information for preoperative planning. Microscopic examination revealed melanotic and neuroblastic tissue in a fibrillary matrix involving the expanded bone and superficial dura. A focal osteoblastic cranial mass in an infant should alert the clinician to consider this tumor.

Decreased parvalbumin immunoreactivity in surviving Purkinje cells of patients with spinocerebellar ataxia-1.

The distribution of two calcium-binding proteins, calbindin D28k (CaBP) and parvalbumin (PV), was investigated by immunohistochemistry in the brains of three individuals dying of nonneurologic illness and three patients with spinocerebellar ataxia-1 (SCA-1). SCA-1 has recently been proven to be due to an unstable CAG repeat mutation on chromosome 6. In the cerebellum of control individuals the Purkinje cells showed strong immunoreactivity to CaBP. Other cells were CaBP-negative. Parvalbumin was highly localized to Purkinje, basket, stellate, and Golgi cells. All surviving Purkinje cells in SCA-1 were strongly immunoreactive to CaBP. The number of PV-immunoreactive Purkinje cells was markedly reduced in SCA-1. In addition, there was a significant decrease in the intensity of PV immunostaining within the individual Purkinje cells compared with controls. However, in the hippocampus, temporal cortex, and lateral geniculate scattered PV-positive neurons were seen in SCA-1 patients, similar to those in controls. The present results suggest that the decreased PV-immunoreactivity in the surviving Purkinje cells in SCA-1 may reflect biochemical alterations preceding Purkinje cell degeneration.

Dominantly inherited cerebello-olivary atrophy is not due to a mutation at the spinocerebellar ataxia-I, Machado-Joseph disease, or Dentato-Rubro-Pallido-Luysian atrophy locus.

The dominantly inherited ataxias are characterized both by phenotypic variability (phenotypic heterogeneity) within the same genotype and overlapping phenotypes from different genotypes (genotypic heterogeneity). Therefore it is important to characterize specific clinical-neuropathologic phenotypes as precisely as possible at the genetic level. We describe a family with dominantly inherited ataxia of late adult onset with relatively "pure" cerebellar signs. Neuropathologic examination in two individuals from this family revealed findings consistent with cerebello-olivary atrophy, suggesting that this neuropathologic phenotype many run true within f families. Mutations at the spinocerebellar ataxia-I, Machado-Joseph disease, and dentatorubropallidoluysian atrophy loci were excluded by direct DNA analysis on the leukocytes of one living affected member. Thus we provide evidence that these mutations are not responsible for this particular phenotype of dominantly inherited ataxia.

Magnetic resonance imaging of massive intracranial invasion by an ethmoidal adenoid cystic carcinoma (cylindroma).

Magnetic resonance imaging showed a massive intracranial invasion by an adenoid cystic carcinoma (cylindroma) originating from an ethmoid sinus. The tumor was excised and follow-up radiation therapy was planned because of bone involvement and superficial invasion of the right olfactory tract area.

Scavenging of Alzheimer's amyloid beta-protein by microglia in culture.

Deposits of amyloid beta-protein (A beta) form the cores of the pathological plaques which characterize Alzheimer's disease. The mechanism of formation of the deposits is unknown; one possibility is failure of a clearance mechanism that would normally remove the protein from brain parenchyma. This study has investigated the capacity of the central nervous system (CNS) phagocytes, microglia cells, to clear exogenous A beta 1-42 from their environment. Cultured microglia from adult rat CNS have a high capacity to remove A beta from serum-free medium, shown by immunoblotting experiments. A beta from incubation medium was attached to the cell surface and could be identified by immunocytochemistry at the light or electron microscopic (EM) level; by EM, A beta also appeared in phagosome-like intracellular vesicles. Light microscopic immunocytochemistry combined with computer-assisted image analysis showed that cells accumulated A beta within 24 hr. from culture medium containing from 1 to 20 micrograms/ml A beta. Microglial accumulation of A beta was substantially reduced in the presence of fetal bovine serum. Addition of the protease inhibitor leupeptin to incubation medium with serum resulted in accumulation of A beta in a membrane-bound intracellular compartment, but not at the cell surface. The increase in intracellular accumulation in the presence of the protease inhibitor indicates a microglial capacity for intracellular degradation of A beta in the absence of inhibition. The change from predominantly cell-surface accumulation in serum-free medium to predominantly intracellular accumulation with serum may be explained by the presence in serum of carrier proteins that complex with A beta and target it to cell surface receptors capable of stimulating endocytosis. Microglia were also cultured on unfixed cryostat sections of human brain tissue containing Alzheimer's plaques. Very little A beta from the tissue was accumulated by the cells, although cultured microglia were found in direct contact with anti-A beta immunopositive plaques. Possibly A beta in tissue sections was complexed with other proteins which either inhibited its uptake by microglia or enhanced its proteolysis, preventing cellular accumulation of immunostainable A beta. The results indicate that cultured microglia effectively remove A beta from tissue culture medium and from the surface of the dish and concentrate monomer and aggregates of A beta either on the cell surface or intracellularly. This process may be modified by proteins present in Alzheimer's brain sections.

Developmental changes in cerebellar endothelin-1 receptors in the neurologic mouse lurcher mutant.

In order to elucidate the role of neuromodulator endothelin-1 (ET-1) in cerebellar degeneration we determined ET-1 receptor binding in the control and lurcher mice cerebella at different postnatal (P) ages. The lurcher mutant is a suggested animal model for human cerebellar ataxias. The cerebellar membranes were prepared from 5 to 20 day old lurcher mice and littermate controls. ET-1 receptor binding was determined using radioligand assay and affinity cross-linking. There was a significant decrease in [125I]ET-1 receptor binding with increasing postnatal age in the control and lurcher mice cerebella. Lurcher mice showed a significant increase in [125I]ET-1 receptor binding at P 9 to P 20 as compared with the controls. Whereas, at P5 to P7 no significant change was observed. By autoradiography, ET-1 receptors were localized in tile granule cell layer of 15 day old control and lurcher mice cerebella. Whereas, the lUrcher mice showed an increase in [125I]ET-1 binding in the cerebellum as compared with the littermate controls. The results of the present study suggest that the increase in ET-1 receptor binding as early as P9 (when neuronal loss is minimal) in the lurcher mutant may reflect upregulation of ET-1 receptors in the degenerating neurons. At P 15 to P 20, when about 50% to 75% neurons are lost respectively, these changes may also reflect astrogliosis.