bluuebunny/crossref_metadata_2025 huggingface dataset:
Primary Chemotherapy for Intracranial Nongerminomatous Germ Cell Tumors: Results of the Second International CNS Germ Cell Study Group Protocol
Authors: Kellie Stewart J , Boyce Hayden , Dunkel Ira J , Diez Blanca , Rosenblum Marc , Brualdi Lynette , Finlay Jonathan L
Published: February 2004

Purpose

The optimum therapy for intracranial nongerminomatous germ cell tumors (NGGCT) remains controversial. The primary objective of this study was to determine whether intensive cisplatin and cyclophosphamide-based combination chemotherapy was effective in patients with intracranial NGGCT.

Patients and Methods

Twenty patients were enrolled, aged 5 to 41 years (median, 13 years). Initial therapy included two courses of Regimen A (cisplatin, etoposide, cyclophosphamide, and bleomycin). Patients achieving a complete remission (CR) then received two courses of Regimen B (carboplatin, etoposide, and bleomycin). Those in CR after four courses of treatment received one additional course of Regimen A and Regimen B, while those not in CR after four treatment courses underwent second-look surgery and/or irradiation.

Results

Sixteen of 17 patients assessable for response after two courses of treatment achieved a CR or partial response (CR + partial response, 0.94; 95% CI, 0.73 to 1.0). With a median follow-up of 6.3 years, 14 of 20 patients are alive without disease; eight patients were without relapse or progression, of whom three received local irradiation in first complete remission in violation of protocol, and six patients were in durable second or third complete remission after further chemotherapy and/or irradiation. The 5-year overall survival and event-free survival were 0.75 (95% CI, 0.56 to 0.94) and 0.36 (95% CI, 0.13 to 0.59), respectively.

Conclusion

Intensive chemotherapy was effective in one-third of patients in this study. Salvage therapy, including irradiation, was feasible in patients with recurrent disease.
Phase I and Pharmacokinetic Study of Topotecan Administered Orally Once Daily for 5 Days for 2 Consecutive Weeks to Pediatric Patients With Refractory Solid Tumors
Authors: Daw Najat C. , Santana Victor M. , Iacono Lisa C. , Furman Wayne L. , Hawkins Dana R. , Houghton Peter J. , Panetta J. Carl , Gajjar Amar J. , Stewart Clinton F.
Published: February 2004

Purpose

We conducted a phase I trial of the injectable formulation of topotecan given orally once daily for 5 days for 2 consecutive weeks (qd × 5 × 2) in pediatric patients with refractory solid tumors.

Patients and Methods

Cohorts of two to six patients received oral topotecan at 0.8, 1.1, 1.4, 1.8, and 2.3 mg/m2/d every 28 days for a maximum of six courses. Twenty patients (median age, 10.6 years) received a total of 51 courses. Eight patients received topotecan capsules during course 2 only.

Results

Dose-limiting toxicity occurred at 2.3 mg/m2/d and consisted of prolonged grade 4 neutropenia (n = 2), grade 3 stomatitis as a result of radiation recall (n = 1), grade 3 hemorrhage (epistaxis) in the presence of grade 4 thrombocytopenia (n = 1), and grade 3 diarrhea in the presence of Clostridium difficile infection (n = 1). Dose-limiting, prolonged grade 4 neutropenia and thrombocytopenia occurred in one patient at 1.4 mg/m2/d. Infrequent toxicities were mild nausea, vomiting, elevated liver ALT or AST, and rash. The maximum-tolerated dosage was 1.8 mg/m2/d; the mean (± standard deviation) area under the plasma concentration-time curve for topotecan lactone at this dosage was 20.9 ± 8.4 ng/mL · h. The population mean (± standard error) oral bioavailability of the injectable formulation was 0.27 ± 0.03; that of capsules was 0.36 ± 0.06 (P = .16). Disease stabilized in nine of 19 assessable patients for 1.5 to 6 months.

Conclusion

Oral topotecan (1.8 mg/m2/d) on a qd × 5 × 2 schedule is well tolerated and warrants additional testing in pediatric patients.
Pelvic Irradiation With Concurrent Chemotherapy Versus Pelvic and Para-Aortic Irradiation for High-Risk Cervical Cancer: An Update of Radiation Therapy Oncology Group Trial (RTOG) 90-01
Authors: Eifel Patricia J. , Winter Kathryn , Morris Mitchell , Levenback Charles , Grigsby Perry W. , Cooper Jay , Rotman Marvin , Gershenson David , Mutch David G.
Published: February 2004

Purpose

To report mature results of a randomized trial that compared extended-field radiotherapy (EFRT) versus pelvic radiotherapy with concomitant fluorouracil and cisplatin (CTRT) in women with locoregionally advanced carcinomas of the uterine cervix.

Patients and Methods

Four hundred three women with cervical cancer were randomly assigned to receive either EFRT or CTRT. Patients were eligible if they had stage IIB to IVA disease, stage IB to IIA disease with a tumor diameter ≥ 5 cm, or positive pelvic lymph nodes. Patients were stratified by stage and by method of lymph node evaluation.

Results

The median follow-up time for 228 surviving patients was 6.6 years. The overall survival rate for patients treated with CTRT was significantly greater than that for patients treated with EFRT (67% v 41% at 8 years; P < .0001). There was an overall reduction in the risk of disease recurrence of 51% (95% CI, 36% to 66%) for patients who received CTRT. Patients with stage IB to IIB disease who received CTRT had better overall and disease-free survival than those treated with EFRT (P < .0001); 116 patients with stage III to IVA disease had better disease-free survival (P = .05) and a trend toward better overall survival (P = .07) if they were randomly assigned to CTRT. The rate of serious late complications of treatment was similar for the two treatment arms.

Conclusion

Mature analysis confirms that the addition of fluorouracil and cisplatin to radiotherapy significantly improved the survival rate of women with locally advanced cervical cancer without increasing the rate of late treatment-related side effects.
Gefitinib in Combination With Paclitaxel and Carboplatin in Advanced Non–Small-Cell Lung Cancer: A Phase III Trial—INTACT 2
Authors: Herbst Roy S. , Giaccone Giuseppe , Schiller Joan H. , Natale Ronald B. , Miller Vincent , Manegold Christian , Scagliotti Giorgio , Rosell Rafael , Oliff Ira , Reeves James A. , Wolf Michael K. , Krebs Annetta D. , Averbuch Steven D. , Ochs Judith S. , Grous John , Fandi Abderrahim , Johnson David H.
Published: February 2004

Purpose

Preclinical studies indicate that gefitinib (Iressa, ZD1839; AstraZeneca, Wilmington, DE), an orally active epidermal growth factor receptor tyrosine kinase inhibitor, may enhance antitumor efficacy of cytotoxics, and combination with paclitaxel and carboplatin had acceptable tolerability in a phase I trial. Gefitinib monotherapy demonstrated unparalleled antitumor activity for a biologic agent, with less toxicity than docetaxel, in phase II trials in refractory, advanced non–small-cell lung cancer (NSCLC). This phase III, randomized, placebo-controlled, double-blind trial evaluated gefitinib plus paclitaxel and carboplatin in chemotherapy-naive patients with advanced NSCLC.

Patients and Methods

Patients received paclitaxel 225 mg/m2and carboplatin area under concentration/time curve of 6 mg/min/mL (day 1 every 3 weeks) plus gefitinib 500 mg/d, gefitinib 250 mg/d, or placebo. After a maximum of six cycles, daily gefitinib or placebo continued until disease progression. End points included overall survival, time to progression (TTP), response rate (RR), and safety evaluation.

Results

A total of 1,037 patients were recruited. Baseline demographic characteristics were well balanced. There was no difference in overall survival (median, 8.7, 9.8, and 9.9 months for gefitinib 500 mg/d, 250 mg/d, and placebo, respectively; P = .64), TTP, or RR between arms. Expected dose-related diarrhea and skin toxicity were observed in gefitinib-treated patients, with no new significant/unexpected safety findings from combination with chemotherapy. Subset analysis of patients with adenocarcinoma who received ≥ 90 days' chemotherapy demonstrated statistically significant prolonged survival, suggesting a gefitinib maintenance effect.

Conclusion

Gefitinib showed no added benefit in survival, TTP, or RR compared with standard chemotherapy alone. This large, placebo-controlled trial confirmed the favorable gefitinib safety profile observed in phase I and II monotherapy trials.
Clinical and Outcome Characteristics of Children With Adrenocortical Tumors: A Report From the International Pediatric Adrenocortical Tumor Registry
Authors: Michalkiewicz E. , Sandrini R. , Figueiredo B. , Miranda E.C.M. , Caran E. , Oliveira-Filho A.G. , Marques R. , Pianovski M.A.D. , Lacerda L. , Cristofani L.M. , Jenkins J. , Rodriguez-Galindo C. , Ribeiro R.C.
Published: February 2004

Purpose

We created a registry for pediatric adrenocortical tumors (ACTs), which are rare and are not well characterized. We provide a descriptive analysis of 254 patients registered on the International Pediatric Adrenocortical Tumor Registry.

Patients and Methods

Between January 1990 and December 2001, 254 patients younger than 20 years of age with newly diagnosed or previously treated ACTs were registered. A histologic diagnosis of ACT was required, although central review was not mandatory. Follow-up information was periodically requested from the referring physician. Treatment was chosen by the primary physician.

Results

The overall female-male ratio was 1.6:1, but it varied widely among age groups. The most common presenting sign (84.2%) was virilization. Cushing's syndrome without virilization was uncommon (5.5%). Tumors were completely resected in 83% of patients. Patients with disseminated or residual disease received mitotane, cisplatin, etoposide, and/or doxorubicin, and rarely, radiation therapy. At a median follow-up of 2 years and 5 months, 157 patients (61.8%) survived without evidence of disease and 97 patients (38.2%) had died. The 5-year event-free survival estimate was 54.2% (95% CI, 48.2% to 60.2%). In a multivariate analysis, disease stage, presenting signs of endocrine dysfunction, and age were independently associated with prognosis.

Conclusion

Childhood ACTs occur predominantly in females and almost always causes clinical signs. Complete resection is required for cure. Residual or metastatic disease carries a poor prognosis. Our results demonstrate the feasibility of a disease-specific database for obtaining meaningful clinical and outcome information.
Modelling the entrainment and motion of particles in a gap: Application to abrasive wear
Authors: Kusano Y , Hutchings I. M.
Published: February 2004

The microscale abrasion or ball-cratering test is being increasingly applied to a wide range of bulk materials and coatings. The response of materials to this test depends critically on the nature of the motion of the abrasive particles in the contact zone: whether they roll and produce multiple indentations in the coating, or slide causing grooving abrasion. Similar phenomena also occur when hard contaminant particles enter a lubricated contact. This paper presents simple quantitative two-dimensional models which describe two aspects of the interaction between a hard abrasive particle and two sliding surfaces.

The first model treats the conditions under which a spherical abrasive particle of size d can be entrained into the gap between a rotating sphere of radius R and a plane surface. These conditions are determined by the coefficients of friction between the particle and the sphere, and the particle and the plane, denoted by μs and μp respectively. This model predicts that the values of (μs + μp) and 2μs should both exceed √2d/R for the particles to be entrained into the contact. If either is less than this value, the particle will slide against the sphere and never enter the contact.

The second model describes the mechanisms of abrasive wear in a contact when an idealized rhombus-sectioned prismatic particle is located between two parallel plane surfaces separated by a certain distance, which can represent either the thickness of a fluid film or the spacing due to the presence of other particles. It is shown that both the ratio of particle size to the separation of the surfaces and the ratio of the hardnesses of the two surfaces have important influences on the particle motion and hence on the mechanism of the resulting abrasive wear. Results from this model are compared with experimental observations, and the model is shown to lead to realistic predictions.
Bearing condition assessment. Part 1: Size and frequency of surface roughness interactions in impulsive vibration measurements
Authors: Ho M , Birch D. J. , Brunn P. J.
Published: February 2004

Impulsive vibrations generated during the operation of a rolling Hertzian line contact under elastohydrodynamic lubrication (EHL) conditions, typically found in tapered rolling bearings, are analysed using two-dimensional surface roughness profiles containing spherical asperities. The cause of these vibrations is modelled as a series of collisions between the asperities forming the surfaces in contact. Asperity heights are considered to vary according to a Gaussian distribution, and an innovative method, based upon probability, is developed so that the rates and the magnitudes of collisions between asperities of various heights under different lubrication conditions can be studied. The magnitude of individual collisions are predicted to allow them to be compared with those measured using a calibrated master piezoelectric transducer.
Influence of non-Newtonian fluids on the performance of a soft elastohydrodynamic lubrication contact with surface roughness
Authors: Bohan M. F. J. , Fox I. J. , Claypole T. C. , Gethin D. T.
Published: February 2004

The paper focuses on the development and results of a numerical model to evaluate the fluid transfer behaviour for non-Newtonian fluids in a rough soft elastohydrodynamic nip contact. The solution required coupling of the fluid and elastomer regimes, with a multi-gridding technique to facilitate the high mesh densities required to capture the rough surface representation. The non-Newtonian fluid behaviour was modelled using a power-law model. The study evaluated circumferential and longitudinal roughness forms. The introduction of longitudinal roughness introduced significant shear in the nip with the resultant large change to the viscosity profile. This also removed the stagnation point in the centre of the nip. The longitudinal roughness had a large impact on the film thickness and flow through the nip while the circumferential affected the local performance of the nip but not its overall pumping capacity.
Elastohydrodynamic analysis of lip seals with microundulations
Authors: Hajjam M , Bonneau D
Published: February 2004

The finite element method and the realistic structure analysis are used to develop an accurate model of lip seals based on elastohydrodynamic analysis. This original model, very close to reality, helps to predict most of the working features of seals. Lubrication characteristics such as lubricant film thickness, rubbing torque and cavitation zones, hydrodynamic field pressure and inverse pumping leakage are investigated.
Fourier analysis of a single transverse ridge passing through an elastohydrodynamically lubricated rolling contact: A comparison with experiment
Authors: Félix-Quiñonez A , Ehret P , Summers J. L. , Morales-Espejel G. E.
Published: February 2004

An image analysis technique is employed to measure lubricant film thickness fluctuations introduced by a single flat-top transverse ridge passing under pure rolling conditions through an elastohydrodynamically lubricated contact. The experimental observations are compared with the film thickness profiles predicted by the discrete Fourier transform method for real surface roughness given by Morales-Espejel et al. in 2000. The results show that the theoretical approach adequately predicts the overall film thickness, thus giving credence to its potential practical application. On a local scale, however, important differences are seen regarding the deformed shape of the feature.
Benefits of Skill Chaining in Serial Production Lines with Cross-Trained Workers
Authors: Hopp Wallace J. , Tekin Eylem , Van Oyen Mark P.
Published: February 2004

To gain insight into the potential logistical benefits of worker cross-training and agile workforce policies, we study simple models of serial production systems with flexible servers operating under a constant work-in-process (CONWIP) release policy. Two important and interrelated issues are: (a) how to decide which skill(s) are strategically most desirable for workers to gain, and (b) how to coordinate these workers to respond dynamically to congestion. We address these by considering two cross-training strategies: a straightforward capacity-balancing approach, which we call cherry picking (CP), and an innovative overlapping zone strategy that we call skill chaining. Our comparison shows that skill-chaining strategies have the potential to be robust and efficient methods for implementing workforce agility in serial production lines.
Channel Performance Under Consignment Contract with Revenue Sharing
Authors: Wang Yunzeng , Jiang Li , Shen Zuo-Jun
Published: February 2004

Under a consignment contract with revenue sharing, a supplier decides on the retail price and delivery quantity for his product, and retains ownership of the goods; for each item sold, the retailer deducts a percentage from the selling price and remits the balance to the supplier. In this paper we show that, under such a contract, both the overall channel performance and the performance of individual firms depend critically on demand price elasticity and on the retailer's share of channel cost. In particular, the (expected) channel profit loss, compared with that of a centralized system, increases with demand price elasticity and decreases with retailer's cost share, while the profit share extracted by the retailer decreases with price elasticity and increases with retailer's cost share. With an iso-price-elastic demand model, we show that the channel profit loss cannot exceed 26.4%, and that the retailer's profit share cannot be below 50%. When price elasticity is low, or when the retailer's cost share approaches 100%, or both, the retailer can extract nearly all the channel profit that is almost equal to the centralized channel profit.
Fifty Years of Management Science
Authors: Hopp Wallace J.
Published: February 2004

This issue marks the start of the 50th volume of Management Science. As is customary on such “round number” occasions, we will be taking time for a bit of retrospective review and soul-searching speculation. We begin here with an overall assessment of the journal's performance relative to its original mission. In subsequent articles, which will appear in issues throughout Volume 50, we will take more detailed disciplinary looks at the past, present, and future of Management Science and the management subfields it represents.
L1/Laminin Modulation of Growth Cone Response to EphB Triggers Growth Pauses and Regulates the Microtubule Destabilizing Protein SCG10
Authors: Suh Leejee H. , Oster Stephen F. , Soehrman Sophia S. , Grenningloh Gabriele , Sretavan David W.
Published: February 2004

During development, EphB proteins serve as axon guidance molecules for retinal ganglion cell axon pathfinding toward the optic nerve head and in midbrain targets. To better understand the mechanisms by which EphB proteins influence retinal growth cone behavior, we investigated how axon responses to EphB were modulated by laminin and L1, two guidance molecules that retinal axons encounter duringin vivopathfinding. Unlike EphB stimulation in the presence of laminin, which triggers typical growth cone collapse, growth cones co-stimulated by L1 did not respond to EphB. Moreover, EphB exposure in the presence of both laminin and L1 resulted in a novel growth cone inhibition manifested as a pause in axon elongation with maintenance of normal growth cone morphology and filopodial activity. Pauses were not associated with loss of growth cone actin but were accompanied by a redistribution of the microtubule cytoskeleton with increased numbers of microtubules extending into filopodia and to the peripheral edge of the growth cone. This phenomenon was accompanied by reduced levels of the growth cone microtubule destabilizing protein SCG10. Antibody blockade of SCG10 function in growth cones resulted in both changes in microtubule distribution and pause responses mirroring those elicited by EphB in the presence of laminin and L1. These results demonstrate that retinal growth cone responsiveness to EphB is regulated by co-impinging signals from other axon guidance molecules. Furthermore, the results are consistent with EphB-mediated axon guidance mechanisms that involve the SCG10-mediated regulation of the growth cone microtubule cytoskeleton.
Integrated Memory for Object, Place, and Context in Rats: A Possible Model of Episodic-Like Memory?
Authors: Eacott Madeline J. , Norman Gillian
Published: February 2004

We report an investigation into memory for an object, its spatial location, and the context in which it appeared in rats. A novel task based on the spontaneous recognition paradigm is presented that requires memory for these three aspects. This task is performed easily by intact rats at delays of up to 1 hr. However, performance of the task is severely and selectively disrupted by transection of the fornix. Ability to perform this task is discussed in relation to models of episodic memory in animals, and we suggest that this task provides a simple and useful animal model of episodic memory for use with rats.
Caspase-11 Mediates Inflammatory Dopaminergic Cell Death in the 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Mouse Model of Parkinson's Disease
Authors: Furuya Tsuyoshi , Hayakawa Hideki , Yamada Masanori , Yoshimi Kenji , Hisahara Shin , Miura Masayuki , Mizuno Yoshikuni , Mochizuki Hideki
Published: February 2004

The present study was designed to elucidate the inflammatory and apoptotic mechanisms of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in a model of Parkinson's disease. Our results showed that mutant mice lacking thecaspase-11gene were significantly more resistant to the effects of acute treatment with MPTP than their wild-type mice. Thus, the neurotoxicity of MPTP seems to be mediated by the induction of both mitochondrial dysfunction and free radical generation. Previously, we showed that overexpression of the Apaf-1 dominant-negative inhibitor inhibited the mitochondrial apoptotic cascade in chronic MPTP treatment but not in acute MPTP treatment. The present results indicate that MPTP neurotoxicity may be mediated via activation of the caspase-11 cascade and inflammatory cascade, as well as the mitochondrial apoptotic cascade.
Attention to Features Precedes Attention to Locations in Visual Search: Evidence from Electromagnetic Brain Responses in Humans
Authors: Hopf Jens-Max , Boelmans Kai , Schoenfeld Mircea Ariel , Luck Steven J. , Heinze Hans-Jochen
Published: February 2004

Single-unit recordings in macaque extrastriate cortex have shown that attentional selection of nonspatial features can operate in a location-independent manner. Here, we investigated analogous neural correlates at the neural population level in human observers by using simultaneous event-related potential (ERP) and event-related magnetic field (ERMF) recordings. The goals were to determine (1) whether task-relevant features are selected before attention is allocated to the location of the target, and (2) whether this selection reflects the locations of the relevant features. A visual search task was used in which the spatial distribution of nontarget items with attended feature values was varied independently of the location of the target. The presence of task-relevant features in a given location led to a change in ERP/ERMF activity beginning ∼140 msec after stimulus onset, with a neural origin in the ventral occipito-temporal cortex. This effect was independent of the location of the actual target. This effect was followed by lateralized activity reflecting the allocation of attention to the location of the target (the well known N2pc component), which began at ∼170 msec poststimulus. Current source localization indicated that the allocation of attention to the location of the target originated in more anterior regions of occipito-temporal cortex anterior than the feature-related effects. These findings suggest that target detection in visual search begins with the detection of task-relevant features, which then allows spatial attention to be allocated to the location of a likely target, which in turn allows the target to be positively identified.
The Hippocampal/Parahippocampal Regions and Recognition Memory: Insights from Visual Paired Comparison versus Object-Delayed Nonmatching in Monkeys
Authors: Nemanic Sarah , Alvarado Maria C. , Bachevalier Jocelyne
Published: February 2004

Recognition memory was assessed by submitting the same adult monkeys to visual paired comparison (VPC) with mixed delays (10-120 sec), followed by three consecutive versions of object-delayed nonmatching-to-sample (DNMS): increasing delays (10-600 sec), lengthened lists (3-10 objects), and intervening distractors in the delays (light at 10 sec, motor task at 30-600 sec, or context change at 600 sec). Four groups were tested: normal controls, monkeys with ibotenic acid lesions of the hippocampal formation (H), and monkeys with aspiration lesions of either the perirhinal (PRh) or parahippocampal (areas TH/TF) cortex. Group H was impaired on VPC at delays ≥60 sec but had difficulty on DNMS only at 600 sec delays with distraction. In group TH/TF, the VPC impairment emerged earlier (30 sec); yet, once the nonmatching rule was mastered, no significant change occurred on any DNMS condition. Only group PRh behaved congruently on VPC and DNMS, exhibiting a deficit at the easiest condition that worsened with increasing delays as well as in DNMS lengthened list and distraction conditions. These results led us to postulate that VPC and DNMS, as previously administered to monkeys, were not equivalent visual recognition memory probes. Specifically, we propose that, for VPC, because of passive (incidental) encoding, the animal's performance rests on both item familiarity and event recollection, whereas, for DNMS, because of active (purposeful) encoding, performance relies more on item familiarity. This proposal converges with current models postulating distinct, but interactive, mnemonic roles for the hippocampal and adjacent TH/TF regions.
Enhanced Relative Expression of Glutamate Receptor 1 Flip AMPA Receptor Subunits in Hippocampal Astrocytes of Epilepsy Patients with Ammon's Horn Sclerosis
Authors: Seifert Gerald , Hüttmann Kerstin , Schramm Johannes , Steinhäuser Christian
Published: February 2004

Astrocytes express ionotropic glutamate receptors (GluRs), and recent evidence suggests that these receptors contribute to direct signaling between neurons and glial cellsin vivo. Here, we have used functional and molecular analyses to investigate receptor properties in astrocytes of human hippocampus resected from patients with pharmacoresistant temporal lobe epilepsy (TLE). Histopathological analysis allowed us to distinguish two forms of epilepsy: Ammon's horn sclerosis (AHS) and lesion-associated TLE. Human hippocampal astrocytes selectively expressed the AMPA subtype of ionotropic glutamate receptors. Single-cell RT-PCR found preferential expression of the subunits GluR1 and GluR2 in human astrocytes, and the expression patterns were similar in patients with AHS and lesion-associated epilepsy. The AMPA receptor-specific modulators, cyclothiazide (CTZ) and 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), were used to investigate splice variant expression. Astrocytes of sclerotic specimens displayed a slower dissociation of CTZ from the receptor and a lower ratio of current potentiation by PEPA to potentiation by CTZ, suggesting enhanced expression of flip receptor variants in AHS versus lesion-associated epilepsy. Real-time PCR and restriction analysis substantiated this presumption by identifying elevated flip-to-flop mRNA ratios of GluR1 in single astrocytes of AHS specimens. These findings imply that in AHS, glutamate may lead to prolonged depolarization of astrocytes, thereby facilitating the generation or spread of seizure activity.
Monitoring Clathrin-Mediated Endocytosis during Synaptic Activity
Authors: Mueller Veronika J. , Wienisch Martin , Nehring Ralf B. , Klingauf Jurgen
Published: February 2004

To visualize clathrin redistribution during endocytosis in hippocampal boutons, we used a fusion protein of clathrin light chain with enhanced green fluorescent protein. Both high potassium and electric field stimulation lead after a stimulus-dependent delay to a transient increase of fluorescence in synapses, but a slight and transient decrease in adjacent axonal segments. We conclude that the rise and fall of the signal in boutons, with decay kinetics remarkably similar to previous estimates of the endocytic time course, reflects coat assembly and disassembly. Thus, we could selectively measure clathrin-mediated endocytosis and separate its kinetics from other modes of membrane retrieval in CNS synapses. A long-lasting delay preceding the fluorescent transients shows that endocytosis during the first few seconds of continuing stimulation cannot be mediated by newly formed clathrin-coated pits. Therefore, a fast mode of endocytosis is either clathrin-independent or involves preassembled (easily retrievable) clathrin lattices at sites of endocytosis.
Reelin and Cyclin-Dependent Kinase 5-Dependent Signals Cooperate in Regulating Neuronal Migration and Synaptic Transmission
Authors: Beffert Uwe , Weeber Edwin J. , Morfini Gerardo , Ko Jane , Brady Scott T. , Tsai Li-Huei , Sweatt J. David , Herz Joachim
Published: February 2004

Neuronal migration and positioning in the developing brain require the coordinated interaction of multiple cellular signaling pathways. The extracellular signaling molecule Reelin and the cytoplasmic serine/threonine kinase Cdk5 (cyclin-dependent kinase 5) are both required for normal neuronal positioning, lamination of the neocortex, and foliation of the cerebellum. They also modulate synaptic transmission in the adult brain. It is not known, however, to what extent Cdk5 participates in Reelin signaling and whether both pathways interact on the genetic or biochemical level. We have used genetically altered mice to generate compound functional defects of Reelin and Cdk5 signaling. Differential neurohistochemical staging combined with the biochemical analysis of Reelin- and Cdk5-dependent signaling in primary embryonic neurons and electrophysiology in hippocampal slices reveals evidence for genetic and functional interaction between both pathways. Inhibition of Reelin or Cdk5 signaling had no discernible biochemical effect on each other. Taken together, these findings suggest that both pathways function together in a parallel, rather than a simple, linear manner to coordinate neuronal migration and neurotransmission in the developing and mature brain.
DRAGON: A Member of the Repulsive Guidance Molecule-Related Family of Neuronal- and Muscle-Expressed Membrane Proteins Is Regulated by DRG11 and Has Neuronal Adhesive Properties
Authors: Samad Tarek A. , Srinivasan Ashok , Karchewski Laurie A. , Jeong Sung-Jin , Campagna Jason A. , Ji Ru-Rong , Fabrizio David A. , Zhang Ying , Lin Herbert Y. , Bell Esther , Woolf Clifford J.
Published: February 2004

DRG11, a transcription factor expressed in embryonic dorsal root ganglion (DRG) and dorsal horn neurons, has a role in the development of sensory circuits. We have used a genomic binding strategy to screen for the promoter region of genes regulated by DRG11. One gene with a promoter region binding to the DNA binding domain of DRG11 encodes a novel membrane-associated [glycosyl-phosphatidylinositol (GPI)-anchored] protein that we call DRAGON. DRAGON expression is transcriptionally regulated by DRG11, and it is coexpressed with DRG11 in embryonic DRG and spinal cord. DRAGON expression in these areas is reduced in DRG11 null mutants. DRAGON is expressed, however, in the neural tube before DRG11, and unlike DRG11 it is expressed in the brain and therefore must be regulated by other transcriptional regulatory elements. DRAGON shares high sequence homology with two other GPI-anchored membrane proteins: the mouse ortholog of chick repulsive guidance molecule (mRGM), which is expressed in the mouse nervous system in areas complementary to DRAGON, and DRAGON-like muscle (DL-M), the expression of which is restricted to skeletal and cardiac muscle. A comparative genomic analysis indicates that the family of RGM-related genes—mRGM, DRAGON, and DL-M—are highly conserved among mammals, zebrafish, chick, andCaenorhabditis elegansbut notDrosophila. DRAGON, RGM, and DL-M mRNA expression in the zebrafish embryo is similar to that in the mouse. Neuronal cell adhesion assays indicate that DRAGON promotes and mRGM reduces adhesion of mouse DRG neurons. We show that DRAGON interacts with itself homophilically. The dynamic expression, ordered spatial localization, and adhesive properties of the RGM-related family of membrane-associated proteins are compatible with specific roles in development.
Estimating Target Speed from the Population Response in Visual Area MT
Authors: Priebe Nicholas J. , Lisberger Stephen G.
Published: February 2004

To guide behavior, perceptual and motor systems must estimate properties of the sensory environment from the responses of populations of cortical neurons. In the domain of visual motion, estimates of target speed are derived from the responses of motion-sensitive neurons in the middle temporal (MT) area of the extrastriate visual cortex and are used to drive smooth pursuit eye movements and perceptual judgments of speed. We have asked how these behavioral systems estimate target speed from the population response in area MT. We found that increasing the spatial frequency of a sine wave grating caused decreases in the target speed estimated by both pursuit and perception and commensurate changes in the identity of the active neurons in area MT. Decreasing the contrast of a sine wave grating caused decreases in the target speed estimated by both pursuit and perception, while altering only the response amplitude of MT neurons and not the identity of the active neurons. Applying a modified vector-averaging computation to the population response measured in area MT allowed us to predict the effects of both spatial frequency and contrast on speed estimation for both perception and pursuit. The modification biased the speed estimation toward low target speeds when responses across the population of neurons were small.
Distinct Roles of Different Neural Cell Adhesion Molecule (NCAM) Isoforms in Synaptic Maturation Revealed by Analysis of NCAM 180 kDa Isoform-Deficient Mice
Authors: Polo-Parada Luis , Bose Christian M. , Plattner Florian , Landmesser Lynn T.
Published: February 2004

Mice that lack all three major isoforms of neural cell adhesion molecule (NCAM) (180 and 140 kDa transmembrane, and 120 kDa glycosylphosphatidylinositol linked) were previously shown to exhibit major alterations in the maturation of their neuromuscular junctions (NMJs). Specifically, even by postnatal day 30, they failed to downregulate from along their axons and terminals an immature, brefeldin A-sensitive, synaptic vesicle-cycling mechanism that used L-type Ca2+channels. In addition, these NCAM null NMJs were unable to maintain effective transmitter output with high-frequency repetitive stimulation, exhibiting both severe initial depression and subsequent cyclical periods of total transmission failures that were of presynaptic origin. As reported here, mice that lack only the 180 kDa isoform of NCAM downregulated the immature vesicle-cycling mechanism on schedule, implicating either the 140 or 120 kDa NCAM isoforms in this important maturational event. However, 180 NCAM-deficient mice still exhibited many functional transmission defects. Although 180 NCAM null NMJs did not show the severe initial depression of NCAM null NMJs, they still had cyclical periods of complete transmission failure. In addition, several presynaptic molecules were expressed at lower levels or were more diffusely localized. Thus, the 180 kDa isoform of NCAM appears to play an important role in the molecular organization of the presynaptic terminal and in ensuring effective transmitter output with repetitive stimulation. Our results also suggest that PKC and MLCK (myosin light chain kinase) may be downstream effectors of NCAM in these processes. Together, these results indicate that different isoforms of NCAM mediate distinct and important events in presynaptic maturation.
Disease Progression Despite Early Loss of Polyglutamine Protein Expression in SCA7 Mouse Model
Authors: Helmlinger Dominique , Abou-Sleymane Gretta , Yvert Gaël , Rousseau Stéphane , Weber Chantal , Trottier Yvon , Mandel Jean-Louis , Devys Didier
Published: February 2004

Nine neurodegenerative diseases including Huntington's disease (HD) and spinocerebellar ataxia type 7 (SCA7) are caused by an expansion of a polyglutamine (polyQ) stretch in the respective proteins. Aggregation of expanded polyQ-containing proteins into the nucleus is a hallmark of these diseases. Recent evidence indicates that transcriptional dysregulation may contribute to the molecular pathogenesis of these diseases. Using SCA7 and HD mouse models in which we recently described a retinal phenotype, we investigated whether altered gene expression underlies photoreceptor dysfunction. In both models, rhodopsin promoter activity was early and dramatically repressed, suggesting that downregulation of photoreceptor-specific genes plays a major role in polyQ-induced retinal dysfunction. Because the rhodopsin promoter drives mutant ataxin-7 expression in our SCA7 mice, we also assessed whether downregulation of mutantSCA7transgene would reverse retinopathy progression and aggregate formation. Although residual expression of mutant ataxin-7 was found negligible from 9 weeks of age, SCA7 transgenic mice showed a progressive decline of photoreceptor activity leading to a complete loss of electroretinographic responses from 1 year of age. At this age, aggregates were cleared in only half of the photoreceptors, indicating that their formation is not fully reversible in this model. We demonstrate here that abolishing full-length mutant ataxin-7 expression did not reverse retinopathy progression in SCA7 mice, raising the possibility that some polyQ-induced pathological events might be irreversible.
Calmodulin Regulates Transglutaminase 2 Cross-Linking of Huntingtin
Authors: Zainelli Gina M. , Ross Christopher A. , Troncoso Juan C. , Fitzgerald John K. , Muma Nancy A.
Published: February 2004

Striatal and cortical intranuclear inclusions and cytoplasmic aggregates of mutant huntingtin are prominent neuropathological hallmarks of Huntington's disease (HD). We demonstrated previously that transglutaminase 2 cross-links mutant huntingtin in cells in culture and demonstrated the presence of transglutaminase-catalyzed cross-links in the HD cortex that colocalize with transglutaminase 2 and huntingtin. Because calmodulin regulates transglutaminase activity in erythrocytes, platelets, and the gizzard, we hypothesized that calmodulin increases cross-linking of huntingtin in the HD brain. We found that calmodulin colocalizes at the confocal level with transglutaminase 2 and with huntingtin in HD intranuclear inclusions. Calmodulin coimmunoprecipitates with transglutaminase 2 and huntingtin in cells transfected with myc-tagged N-terminal huntingtin fragments containing 148 polyglutamine repeats (htt-N63-148Q-myc) and transglutaminase 2 but not in cells transfected with myc-tagged N-terminal huntingtin fragments containing 18 polyglutamine repeats. Our previous studies demonstrated that transfection with both htt-N63-148Q-myc and transglutaminase 2 resulted in cross-linking of mutant huntingtin protein fragments and the formation of insoluble high-molecular-weight aggregates of huntingtin protein fragments. Transfection with transglutaminase 2 and htt-N63-148Q-myc followed by treatment of cells withN-(6-aminohexyl)-1-naphthalenesulfonamide, a calmodulin inhibitor, resulted in a decrease in cross-linked huntingtin. Inhibiting the interaction of calmodulin with transglutaminase and huntingtin protein could decrease cross-linking and diminish huntingtin aggregate formation in the HD brain.
The Nitric Oxide-Guanylyl Cyclase Signaling Pathway Modulates Membrane Activity States and Electrophysiological Properties of Striatal Medium Spiny Neurons RecordedIn Vivo
Authors: West Anthony R. , Grace Anthony A.
Published: February 2004

Nitric oxide (NO)-releasing interneurons are believed to regulate the activity of striatal medium spiny neurons (MSNs) that contain the NO effector enzyme guanylyl cyclase (GC). The involvement of NO-GC signaling in modulating steady-state membrane activity of striatal MSNs was examined usingin vivointracellular recordings in rats. Intrastriatal infusion of a neuronal NO synthase inhibitor or a NO scavenger via reverse microdialysis consistently decreased the amplitude of spontaneously occurring depolarized plateau potentials (up events). Intrastriatal infusion of a NO scavenger also decreased the amplitude of EPSPs evoked during electrical stimulation of the orbital prefrontal cortex. The effect of the NO scavenger on spontaneous up events was partially reversed by coperfusion with a cell-permeable cGMP analog. Intracellular injection of MSNs with a soluble GC inhibitor resulted in large decreases in the following: (1) spontaneous up-event amplitude, (2) responsiveness to depolarizing current, (3) action potential amplitude, and (4) input resistance. These effects were partially reversed by coinjection of cGMP. Conversely, intracellular injection of a phosphodiesterase inhibitor increased MSN neuron membrane excitability. These results indicate that, in the intact animal, the NO signaling pathway exerts a powerful tonic modulatory influence over the membrane activity of striatal MSNs via the activation of GC and stimulation of cGMP production.
Friedreich Ataxia Mouse Models with Progressive Cerebellar and Sensory Ataxia Reveal Autophagic Neurodegeneration in Dorsal Root Ganglia
Authors: Simon Delphine , Seznec Hervé , Gansmuller Anne , Carelle Nadège , Weber Philipp , Metzger Daniel , Rustin Pierre , Koenig Michel , Puccio Hélène
Published: February 2004

Friedreich ataxia (FRDA), the most common recessive ataxia, is characterized by degeneration of the large sensory neurons of the spinal cord and cardiomyopathy. It is caused by severely reduced levels of frataxin, a mitochondrial protein involved in iron-sulfur cluster (ISC) biosynthesis. Through a spatiotemporally controlled conditional gene-targeting approach, we have generated two mouse models for FRDA that specifically develop progressive mixed cerebellar and sensory ataxia, the most prominent neurological features of FRDA. Histological studies showed both spinal cord and dorsal root ganglia (DRG) anomalies with absence of motor neuropathy, a hallmark of the human disease. In addition, one line revealed a cerebellar granule cell loss, whereas both lines had Purkinje cell arborization defects. These lines represent the first FRDA models with a slowly progressive neurological degeneration. We identified an autophagic process as the causative pathological mechanism in the DRG, leading to removal of mitochondrial debris and apparition of lipofuscin deposits. These mice therefore represent excellent models for FRDA to unravel the pathological cascade and to test compounds that interfere with the degenerative process.
Loss of Kv3.1 Tonotopicity and Alterations in cAMP Response Element-Binding Protein Signaling in Central Auditory Neurons of Hearing Impaired Mice
Authors: von Hehn Christian A. A. , Bhattacharjee Arin , Kaczmarek Leonard K.
Published: February 2004

The promoter for thekv3.1potassium channel gene is regulated by a Ca2+-cAMP responsive element, which binds the transcription factor cAMP response element-binding protein (CREB). Kv3.1 is expressed in a tonotopic gradient within the medial nucleus of the trapezoid body (MNTB) of the auditory brainstem, where Kv3.1 levels are highest at the medial end, which corresponds to high auditory frequencies. We have compared the levels of Kv3.1, CREB, and the phosphorylated form of CREB (pCREB) in a mouse strain that maintains good hearing throughout life, CBA/J (CBA), with one that suffers early cochlear hair cell loss, C57BL/6 (BL/6). A gradient of Kv3.1 immunoreactivity in the MNTB was detected in both young (6 week) and older (8 month) CBA mice. Although no gradient of CREB was detected, pCREB-immunopositive cells were grouped together in distinct clusters along the tonotopic axis. The same pattern of Kv3.1, CREB, and pCREB localization was also found in young BL/6 mice at a time (6 weeks) when hearing is normal. In contrast, at 8 months, when hearing is impaired, the gradient of Kv3.1 was abolished. Moreover, in the older BL/6 mice there was a decrease in CREB expression along the tonotopic axis, and the pattern of pCREB labeling appeared random, with no discrete clusters of pCREB-positive cells along the tonotopic axis. Our findings are consistent with the hypothesis that ongoing activity in auditory brainstem neurons is necessary for the maintenance of Kv3.1 tonotopicity through the CREB pathway.
Regulation of Dopaminergic Loss by Fas in a 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Model of Parkinson's Disease
Authors: Hayley Shawn , Crocker Stephen J. , Smith Patrice D. , Shree Tanaya , Jackson-Lewis Vernice , Przedborski Serge , Mount Matthew , Slack Ruth , Anisman Hymie , Park David S.
Published: February 2004

Accumulating evidence suggests that apoptotic and inflammatory factors contribute to the demise of dopaminergic neurons. In this respect, Fas, a member of the tumor necrosis factor receptor family with proapoptotic and inflammatory functions, was reported to be elevated within the striatum and substantia nigra pars compacta (SNc) of Parkinson's disease (PD) patients. Accordingly, the present investigation evaluated the function of Fas in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD. Injection of MPTP increased nigral Fas expression, and mice lacking Fas displayed attenuated MPTP-induced SNc dopaminergic loss and microglial activation. In addition, Fas induction was blocked by expression of a dominant-negative c-Jun adenovirus that also protected dopamine neurons from MPTP-induced damage. Together, these data suggest the critical nature of the c-Jun-Fas signaling pathway in MPTP-induced neuronal loss. Although critical for degeneration of the soma, Fas deficiency did not significantly prevent the reduction of dopaminergic terminal fibers within the striatum or normalize the activation of striatal microglia and elevation of the postsynaptic activity marker ΔFosB induced by denervation. Interestingly, Fas-deficient mice displayed a pre-existing reduction in striatal dopamine levels and locomotor behavior when compared with wild-type mice. Despite the reduced terminals, dopamine levels were not further suppressed by MPTP treatment in mutant mice, raising the possibility of a compensatory response in basal ganglia function in Fas-deficient mice.