bluuebunny/crossref_metadata_2025 huggingface dataset:
A statistical-mechanical model of polymer liquid crystals subjected to external deformations
Authors: Brostow Witold , Walasek Janusz
Published: July 2004

We consider the nematiclike system of polymer liquid crystal (PLC) macromolecules represented by the Flory semiflexible chain model. Segments of the flexible (F) spacers are shorter than the LC hard-rod sequences. We investigate effects of imposition of external deformations. The behavior of LC sequences is largely governed by orienting interactions while for F spacers the short-range interactions determined by the chemical structure are the most important. The stress-strain relation is obtained in addition to the orientation-deformation relations. Orientational order phase transitions caused by the external deformations of the system are recognized and described.
Solvation effects in near-critical binary mixtures
Authors: Onuki Akira , Kitamura Hikaru
Published: July 2004

A Ginzburg-Landau theory is presented to investigate solvation effects in near-critical polar fluid binary mixtures. Concentration dependence of the dielectric constant gives rise to a shell region around a charged particle within which solvation occurs preferentially. As the critical point is approached, the concentration has a long-range Ornstein-Zernike tail representing strong critical electrostriction. If salt is added, strong coupling arises among the critical fluctuations and the ions. The structure factors of the critical fluctuations and the charge density are calculated and the phase transition behavior is discussed.
Raman spectra of (He)N-Br2(X) clusters: The role of boson/fermion statistics in a quantum solvent
Authors: López-Durán D. , de Lara-Castells M. P. , Delgado-Barrio G. , Villarreal P. , Di. Paola C. , Gianturco F. A. , Jellinek J.
Published: July 2004

The aim of this paper is to elucidate the role played by the bosonic/fermionic character of N He atoms solvating a Br2(X) molecule. To this end, an adiabatic model in the molecular stretching coordinate is assumed and the ground energy levels of the complexes are searched by means of Hartree (or Hartree-Fock) Quantum Chemistry calculations for 4He (or 3He) solvent atoms. Simulations of vib-rotational Raman spectra point at the spin multiplicity as the main feature responsible for the drastic difference in the rotational structures of molecules embedded in boson or fermion helium drops as already observed by the experiments of Grebenev et al. [S. Grebenev, J. P. Toennies, and A. F. Vilesov, Science 279 (1998) 2083].
The role of molecular shape in bilayer elasticity and phase behavior
Authors: Brannigan Grace , Tamboli Adele C. , Brown Frank L. H.
Published: July 2004

A previously developed molecular level model for lipid bilayers [G. Brannigan and F. L. H. Brown, J. Chem. Phys. 120, 1059 (2004)] is extended to allow for variations in lipid length and simulations under constant surface tension conditions. The dependence of membrane elasticity on bilayer thickness is obtained by adjusting lipid length at constant temperature and surface tension. Additionally, bilayer fluidity at various lipid lengths is quantified by analysis of a length versus temperature phase diagram at vanishing tension. Regions of solid, gel-like (hexatic) and fluid bilayer behavior are established by identification of phase boundaries. The main melting transition is found to be density driven; the melting temperature scales inversely with lipid length since thermal expansion increases with lipid aspect ratio.
Resonant enhancement of two-photon absorption in substituted fluorene molecules
Authors: Hales Joel M. , Hagan David J. , Van Stryland Eric W. , Schafer K. J. , Morales A. R. , Belfield K. D. , Pacher P. , Kwon O. , Zojer E. , Bredas J. L.
Published: July 2004

The degenerate and nondegenerate two-photon absorption (2PA) spectra for a symmetric and an asymmetric fluorene derivative were experimentally measured in order to determine the effect of intermediate state resonance enhancement (ISRE) on the 2PA cross section δ. The ability to tune the individual photon energies in the nondegenerate 2PA (ND-2PA) process afforded a quantitative study of the ISRE without modifying the chemical structure of the investigated chromophores. Both molecules exhibited resonant enhancement of the nonlinearity with the asymmetric compound showing as much as a twentyfold increase in δ. Furthermore, the possibility of achieving over a one order of magnitude enhancement of the nonlinearity reveals the potential benefits of utilizing ND-2PA for certain applications. To model ISRE, we have used correlated quantum-chemical methods together with the perturbative sum-over-states (SOS) expression. We find strong qualitative and quantitative correlation between the experimental and theoretical results. Finally, using a simplified three-level model for the SOS expression, we provide intuitive insight into the process of ISRE for ND-2PA.
Hydrogen motions in the α-relaxation regime of poly(vinyl ethylene): A molecular dynamics simulation and neutron scattering study
Authors: Narros A. , Alvarez F. , Arbe A. , Colmenero J. , Richter D. , Farago B.
Published: July 2004

The hydrogen motion in poly(vinyl ethylene) (1,2-polybutadiene) in the α-relaxation regime has been studied by combining neutron spin echo (NSE) measurements on a fully protonated sample and fully atomistic molecular dynamics simulations. The almost perfect agreement between experiment and simulation results validates the simulated cell. A crossover from Gaussian to non-Gaussian behavior is observed for the intermediate scattering function obtained from both NSE measurements and simulations. This crossover takes place at unusually low Q values, well below the first maximum of the static structure factor. Such anomalous deviation from Gaussian behavior can be explained by the intrinsic dynamic heterogeneity arising from the differences in the dynamics of the different protons in this system. Side group hydrogens show a markedly higher mobility than main chain protons. Taking advantage of the simulations we have investigated the dynamic features of all different types of hydrogens in the sample. Considering each kind of proton in an isolated way, deviations from Gaussian behavior are also found. These can be rationalized in the framework of a simple picture based on the existence of a distribution of discrete jumps underlying the atomic motions in the α process.
Thermodynamic length in a two-dimensional thermodynamic state space
Authors: Santoro Manuel
Published: July 2004

The main goal of this paper is to reach an explicit formulation and possible interpretation of thermodynamic length in a thermodynamic state space with two degrees of freedom. Using the energy and entropy metric in a general form, we get explicit results about thermodynamic length along isotherms, its relation with work and with speed of sound. We also look at the relation between the determinants of the energy and entropy metrics and find that they differ by a factor of T4.
Optical excitation and absorption spectra of C50Cl10
Authors: Xie Rui-Hua , Bryant Garnett W. , Cheung Chiu Fung , Smith Vedene H. , Zhao Jijun
Published: July 2004

C 50 Cl 10 [S. Y. Xie et al., Science 304, 699 (2004)] has been synthesized in large quantities enabling the capture of the labile fullerene C50. In this Communication, we report ab initio calculations on the optical excitation and absorption spectra of C50Cl10. We successfully explain and assign the measured UV-visible absorption spectrum of C50Cl10. The first singlet excitation for C50Cl10 is optically forbidden, and its optical absorption gap is redshifted by 0.6 eV (110 nm) relative to that of C60. We demonstrate that passivating C50 with 10 hydrogen atoms and replacing one Cl in C50Cl10 by one methoxy group lead to 100 nm blueshift and 90 nm redshift of the optical gap predicted for C50Cl10, respectively, suggesting C50 derivatives are suitable for tunable optical applications.
The Ethical Complex of Corporate Food Power
Authors: Freidberg Susanne
Published: July 2004

In this paper I explore how nongovernmental organizations (NGOs) and the popular media in Britain have been able to pressure Britain's top supermarkets to undertake ‘ethical’ reforms of their global supply chains. I argue that, although the ‘ethical complex’ of British supermarkets is the product of unique historical and geographic circumstances, it also testifies to the capacity of agro-food activists to amplify their influence through the popular media. More broadly, it complicates assumptions about the demise of the Habermasian ‘public sphere’ at a time when massive corporations control both the media and the food supply. Three case studies of NGO campaigns illustrate this point. At the same time, however, they point to tensions between the international scope of certain NGO campaigns for supermarket ‘ethical reform’ and the more localized concerns of their constituencies.
Transnational Hegemony and US Labor Foreign Policy: Towards a Gramscian International Labor Geography
Authors: Glassman Jim
Published: July 2004

In this paper I explore the use of Gramsci's notion of hegemony in analyzing the relationships between US labor unions, the US foreign policy establishment, and workers in the global South. The hegemonic position of US capitalists, in relation to both US workers and states in the global South, heavily conditioned the development of American Federation of Labor–Congress of Industrial Organizations foreign policy during the cold war, with path-dependent effects that have carried over into the post-cold-war era of ‘globalization’. Although recent changes in the relationships between US capitalists and US labor unions have undermined the US ‘labor accord’ that reigned during the cold war, the new, ascendant transnational neoliberal hegemony has not as yet completely transformed the relationships of labor unions in the United States to those elsewhere in the world, which poses ongoing challenges for international labor solidarity, even in a context of new possibilities.
Serve and Certify: Paradoxes of Service Work in Organic-Coffee Certification
Authors: Mutersbaugh Tad
Published: July 2004

In this paper I argue that certified-organic inspection agents play a key role in reworking transnational organic-product certification standards to the unique conditions found within Mexican (Oaxacan) organic-coffee producer villages. First, I document the steps through which transnational product-certification norms, under the International Organization for Standardization guide 65 rubric, are codified as practical standards by organic-product certifying agencies. These standards are found to embed contradictions between inclusiveness and transparency that lead to difficulties in field-level implementation: in essence, practices required to make organic production legible to transnational certifiers often have the opposite effect of making certification unintelligible at the village level. Second, I show how field-level certification inspectors, working under contract to certifying agencies, cooperate with village organic extension agents to make certification legible both to villagers and to transnational certifiers (thereby helping to ensure its success). A corollary methodological argument is made to the effect that the importance of field-level work becomes evident when inspectors are viewed—through the optic of labor-process ethnography—as ‘interactive service employees’. This work thus points to a need to understand with greater clarity how standards are enacted in local contexts and support the efforts of field-level workers with the often-difficult task of making standards legible.
Corporate Citizenship? Elites, Labor, and the Geographies of Work in Guatemala
Authors: Oglesby Elizabeth
Published: July 2004

In this paper I critically assess the World Bank's adoption of discourses of corporate social responsibility in Latin America. I argue that the turn to private-sector associations as ‘agents of development’ or ‘corporate citizens’ is a logical extension of the neoliberal policy repertoire, allowing capital to position itself as the key actor within the arena of civil society and permitting the World Bank to resolve some of its internal debates around the role of institutions in development more broadly. At the same time, through a case study of the Guatemalan sugar industry, I argue that these initiatives are constructed in differentiated ways that are rooted in particular class trajectories and geographies of production and social reproduction. Looking at these so-called ‘strategic development alliances’ as arising at least in part from specific geographies of work may allow us to see where possibilities exist to push for more inclusive social and political participation.
Multiprotein complex containing succinate dehydrogenase confers mitochondrial ATP-sensitive K
+
channel activity
Authors: Ardehali Hossein , Chen Zhenhui , Ko Young , Mejía-Alvarez Rafael , Marbán Eduardo
Published: July 2004

The mitochondrial ATP-sensitive K
+
(mitoK
ATP
) channel plays a central role in protection of cardiac and neuronal cells against ischemia and apoptosis, but its molecular structure is unknown. Succinate dehydrogenase (SDH) is inhibited by mitoK
ATP
activators, fueling the contrary view that SDH, rather than mitoK
ATP
, is the target of cardioprotective drugs. Here, we report that SDH forms part of mitoK
ATP
functionally and structurally. Four mitochondrial proteins [mitochondrial ATP-binding cassette protein 1 (mABC1), phosphate carrier, adenine nucleotide translocator, and ATP synthase] associate with SDH. A purified IM fraction containing these proteins was reconstituted into proteoliposomes and lipid bilayers and shown to confer mitoK
ATP
channel activity. This channel activity is sensitive not only to mitoK
ATP
activators and blockers but also to SDH inhibitors. These results reconcile the controversy over the basis of ischemic preconditioning by demonstrating that SDH is a component of mitoK
ATP
as part of a macromolecular supercomplex. The findings also provide a tangible clue as to the structural basis of mitoK
ATP
channels.
Inhibition of apoptosis in acute promyelocytic leukemia cells leads to increases in levels of oxidized protein and LMP2 immunoproteasome
Authors: Khan Mohammed A. S. , Oubrahim Hammou , Stadtman Earl R.
Published: July 2004

On reaching maturity, animal organs cease to increase in size because of inhibition of cell replication activities. It follows that maintenance of optimal organ function depends on the elimination of oxidatively damaged cells and their replacement with new cells. To examine the effects of oxidative stress and apoptosis on the accumulation of oxidized proteins, we exposed acute promyelocytic leukemia cells to arsenic trioxide (As2O3) in the presence and absence of a general caspase inhibitor (benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone), which is known to inhibit caspase-induced apoptosis. We confirm that treatment of cells with As2O3induces apoptosis and leads to the accumulation of oxidized proteins. Furthermore, inhibition of caspase activities prevented As2O3-induced apoptosis and led to a substantial increase in accumulation of oxidized proteins. Moreover, inhibition of caspase activity in the absence of As2O3led to elevated levels of the LMP2 immunoproteasome protein. We also show that caspase inhibition leads to increases in the levels of oxidized proteins obtained by treatments with hydrogen peroxide plus ferrous iron. Collectively, these results suggest the possibility that an age-related loss in capacity to carry out apoptosis might contribute to the observed accumulation of oxidized proteins during aging and in age-related diseases.
Plasma carotenoid concentrations in relation to acute respiratory infections in elderly people
Authors: van der Horst-Graat Judith M. , Kok Frans J. , Schouten Evert G.
Published: July 2004

A high plasma carotenoid concentration could improve the immune response and result in decreased risk of infectious diseases. However, data on the relationship of plasma carotenoid concentration with acute respiratory infections, which occur frequently in elderly people, are scarce. We investigated, therefore, the relationship of plasma concentrations of six major carotenoids (β-carotene, α-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin) with the incidence and severity of acute respiratory infections. Baseline data from an intervention trial were used. Participants were 652 non-institutionalized elderly people (≥60 years old) enrolled via two community-based sampling strategies in the Wageningen area of The Netherlands in 1998–99. Plasma carotenoid concentrations were divided into quartiles, the lowest being the reference. Frequency and severity of episodes during the previous 1 year, i.e. staying in bed, medical consultation and episode-related medication, were self-reported by means of a questionnaire. On average 1·6 episodes per person were recorded. The incidence rate ratio of acute respiratory infections at high β-carotene status was 0·71 (95% CI 0·54–0·92) as compared with the low β-carotene concentration group. No association was observed between β-carotene and illness severity. α-Carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin were not related to incidence or severity of the infections. We conclude that elderly people with a high plasma β-carotene concentration may have a lower occurrence of acute respiratory infections.
Dietary plant-protein substitution affects hepatic metabolism in rainbow trout (Oncorhynchus mykiss)
Authors: Vilhelmsson Oddur T. , Martin Samuel A. M. , Médale Françoise , Kaushik Sadasivam J. , Houlihan Dominic F.
Published: July 2004

The high dietary protein requirements of salmonid fish are met with fishmeal-based feed in commercial aquaculture. The sustainability of this practice is questionable and, therefore, the feasibility of substituting fishmeal with plant-based products needs to be investigated. We investigated growth and metabolism in rainbow trout (Oncorhynchus mykiss) fed a diet composed of a mixture of plant proteins compared with those fed a fishmeal-based diet. Using two-dimensional gel electrophoresis of liver protein extracts, we showed that the liver protein profile changed in response to the alteration in the diet. A number of metabolic pathways were identified as sensitive to the protein source substitution. These included pathways involved in primary energy generation, maintenance of reducing potential, bile acid synthesis, and transport and cellular protein degradation. Interestingly, the pathways shown to be affected in the present study were somewhat different from those identified in our previous work with soyabean-based-protein replacement of fishmeal, with the effects on the abundance of several stress response proteins notably absent. We conclude, therefore, that the metabolic effects of plant protein replacement in aquaculture feed varies with plant-protein source.
Inhibitory effect of yoghurt and soya yoghurt containing bifidobacteria on the proliferation of Ehrlich ascites tumour cells in vitro and in vivo in a mouse tumour model
Authors: Abd El-Gawad I. A. , El-Sayed E. M. , Hafez S. A. , El-Zeini H. M. , Saleh F. A.
Published: July 2004

The effect of yoghurt and soya yoghurt containing Bifidobacterium lactis Bb-12 or B. longum Bb-46 on Ehrlich ascites tumour cell proliferation was investigated in vitro and in vivo. Tumour cells were incubated with B. lactis Bb-12 or B. longum Bb-46 cultivated in de Mann Rogosa Sharpe (MRS) broth medium, or with their centrifuged supernatant fractions or sediments, for 2 h at 37°C. Treatment resulted in the inhibition of tumour cell proliferation by 85·42 (sd 0·78) and 85·10 (sd 1·28) % by intact micro-organisms, 77·61 (sd 0·29) and 71·43 (sd 1·75) % by their supernatant fractions, but only 4·00 (sd 0·19) and 9·09 (sd 1·24) % by the two sedimented bacteria, respectively. The incubation of tumour cells with yoghurt and soya yoghurt containing Bb-12 for 2 h resulted in 83·01 (sd 0·11) and 88·23 (sd 0·06) % inhibition, respectively, while it was 83·82 (sd 0·24) and 86·36 (sd 0·06) %, respectively for the same products containing Bb-46. Corresponding values for plain yoghurt and soya milk (without bifidobacteria) were 32·81 (sd 0·14) and 5·55 (sd 0·12) %, respectively. The differences between yoghurt or soya yoghurt containing Bb-12 or Bb-46 and plain yoghurt, soya milk or control treatments were statistically significant (n 3; P>0·05). Female Swiss albino mice were injected intraperitoneally with the same tumour cells. The lifespan of mice fed diets supplemented with yoghurt or soya yoghurt containing Bb-12 or Bb-46 was prolonged by 16, 23, 34 and 39%, respectively compared with that of the positive control group (n 6; P>0·05). The lifespan of groups fed plain yoghurt or soya milk was prolonged by 15 and 8%, respectively. Prolongation of lifespan was positively correlated with faeces bifidobacterial count in the groups fed yoghurt or soya yoghurt containing bifidobacteria (r 0·917; P>0·05).
Ontologies for Behavior
Authors: Midford Peter E.
Published: July 2004

Summary: Although dozens of biological ontologies have been created and deployed, relatively little attention has been given to using ontologies to represent behavior. Ontologies for two different behavior systems are described here. One ontology was a translation of a published ethogram, and the second was coded from video clips in a comparative study of jumping spider courtship.

Availability:  http://mesquiteproject.org/ontology/
CLANS: a Java application for visualizing protein families based on pairwise similarity
Authors: Frickey Tancred , Lupas Andrei
Published: July 2004

Summary: The main source of hypotheses on the structure and function of new proteins is their homology to proteins with known properties. Homologous relationships are typically established through sequence similarity searches, multiple alignments and phylogenetic reconstruction. In cases where the number of potential relationships is large, for example in P-loop NTPases with many thousands of members, alignments and phylogenies become computationally demanding, accumulate errors and lose resolution. In search of a better way to analyze relationships in large sequence datasets we have developed a Java application, CLANS (CLuster ANalysis of Sequences), which uses a version of the Fruchterman–Reingold graph layout algorithm to visualize pairwise sequence similarities in either two-dimensional or three-dimensional space.

Availability: CLANS can be downloaded at http://protevo.eb.tuebingen.mpg.de/download
Advances to Bayesian network inference for generating causal networks from observational biological data
Authors: Yu Jing , Smith V. Anne , Wang Paul P. , Hartemink Alexander J. , Jarvis Erich D.
Published: July 2004

Motivation: Network inference algorithms are powerful computational tools for identifying putative causal interactions among variables from observational data. Bayesian network inference algorithms hold particular promise in that they can capture linear, non-linear, combinatorial, stochastic and other types of relationships among variables across multiple levels of biological organization. However, challenges remain when applying these algorithms to limited quantities of experimental data collected from biological systems. Here, we use a simulation approach to make advances in our dynamic Bayesian network (DBN) inference algorithm, especially in the context of limited quantities of biological data.

Results: We test a range of scoring metrics and search heuristics to find an effective algorithm configuration for evaluating our methodological advances. We also identify sampling intervals and levels of data discretization that allow the best recovery of the simulated networks. We develop a novel influence score for DBNs that attempts to estimate both the sign (activation or repression) and relative magnitude of interactions among variables. When faced with limited quantities of observational data, combining our influence score with moderate data interpolation reduces a significant portion of false positive interactions in the recovered networks. Together, our advances allow DBN inference algorithms to be more effective in recovering biological networks from experimentally collected data.

Availability: Source code and simulated data are available upon request.

Supplementary information:  http://www.jarvislab.net/Bioinformatics/BNAdvances/
Choroid Plexus Tumors in Children: Significance of Stromal Invasion
Authors: Levy Michael L. , Goldfarb Amy , Hyder Douglas J. , Gonzales-Gomez Ignacio , Nelson Marvin , Gilles Floyd H. , McComb J. Gordon
Published: July 2004

OBJECTIVE

A group of choroid plexus tumors fit the cellular criteria for choroid plexus papilloma (CPP) except for invasion into the adjacent parenchyma, with associated loss of the normal villus architecture at the site of invasion. These tumors retain a benign cellular appearance. In the existing literature, it is unclear whether these tumors are classified as choroid plexus carcinomas or as CPPs. In our experience, although evidence of invasion is present, these tumors tend to exhibit benign behavior. We suggest that stromal invasion of this type remains consistent with a benign clinical course, although surgical results may demonstrate higher morbidity rates, given the invasive nature of the tumors. The failure to classify these tumors as CPPs may explain some of the variability in outcomes reported for various studies.

METHODS

To study this question, clinical and histological data for children diagnosed with CPPs (either with or without stromal invasion) between 1985 and 1995 were examined. Only cases with pre- and postoperative magnetic resonance imaging data were included in the series.

RESULTS

A total of 12 patients with CPPs were identified, with 4 tumors being notable for stromal invasion. After gross total tumor removal, none of the eight children with CPPs received adjuvant therapy at our institution; all are alive without evidence of tumor recurrence after surgical excision (mean, 108 mo). Of the four patients with stromal invasion, three underwent gross total resection. The one patient who underwent subtotal resection received chemotherapy at another facility. All four of these patients are alive, after a mean of 100 months of follow-up monitoring.

CONCLUSION

It is recommended that CPPs with a benign cellular appearance but with evidence of local parenchymal invasion and loss of the normal villus architecture at the site of invasion be classified as CPPs. Patients with these tumors respond to surgical therapy alone, without the need for adjuvant treatment.
Prodromal Signs and Clinical Factors Influencing Outcome in Patients with Intraventricular Rupture of Purulent Brain Abscess
Authors: Takeshita Mikihiko , Kawamata Takakazu , Izawa Masahiro , Hori Tomokatsu
Published: July 2004

OBJECTIVE

To elucidate prodromal signs and clinical factors influencing the prognosis in patients with intraventricular rupture of brain abscess (IVROBA) to prevent and manage this catastrophic condition.

METHODS

In this study, 33 consecutive patients with IVROBA diagnosed by computed tomography (CT) were treated. Basic and therapeutic parameters were evaluated as independent predictive factors of a poor prognosis by using univariate analysis. The factors were statistically analyzed based on the interval between initial symptoms and IVROBA.

RESULTS

Patients with a good outcome were younger (<21 yr old) (P < 0.003) and had fewer complications after IVROBA (P < 0.03). For the most part, these patients had undergone aspiration for brain abscess with ventricular drainage combined with the immediate administration of appropriate intravenous and intrathecal antibiotics (P < 0.02). In just a short time, abscesses located in the parieto-occipital region ruptured into the ventricle (P < 0.004), and those with nonsterile cultures (P < 0.01) developed into IVROBA. Just before IVROBA, patients had severe headaches, signs of meningeal irritation, and a rapidly deteriorating clinical condition within 10 days after the signs of meningeal irritation developed. A CT scan obtained before IVROBA ascertained localized enhancement of the ventricular wall adjacent to the abscess.

CONCLUSION

Our findings suggest that signs of meningeal irritation and localized enhancement of the ventricular wall adjacent to the abscess, as observed on CT scans, preceded IVROBA. To decrease the mortality rate associated with purulent brain abscesses, signs forewarning of IVROBA should be recognized, and aggressive management of IVROBA should be initiated. Aggressive CT-guided aspiration of deep-seated abscesses, particularly in the parieto-occipital region, at the time forewarning signs of IVROBA are observed lead to the prevention of IVROBA and an improvement in outcome.
Utility of Three-dimensional Computed Tomographic Angiography for Assessment of Relationships between the Vertebrobasilar System and the Cranial Base
Authors: Villavicencio Alan T. , Gray Linda , Leveque Jean-Christophe , Fukushima Takanori , Kureshi Sohaib , Friedman Allan H.
Published: July 2004

OBJECTIVE

The optimal surgical exposure for basilar tip aneurysms is dictated by the relationship of the basilar bifurcation to the cranial base. This study was designed to evaluate three-dimensional computed tomographic angiography as a means of obtaining detailed anatomic information on the basilar artery and the surrounding cranial base in individual patients before surgery.

METHODS

We studied 30 patients using three-dimensional computed tomographic angiographic reconstructions from 1-mm computed tomographic slices. Detailed anatomic measurements were performed to define the relationship between the basilar artery and the cranial base. Particular attention was paid to the height of the dorsum sellae and its relationship to the basilar bifurcation.

RESULTS

The heights of the basilar apex and the vertebrobasilar junction, relative to the cranial base, were extremely variable. Considerable asymmetries in the heights of the left and right posterior clinoid processes were identified; in one case, this difference was more than 1 cm (mean difference in height, 0.9 mm; range, 0–10.3 mm). The heights of the posterior clinoid processes above the sellar floor ranged from 5.8 to 14.1 mm (mean height, 9.5 mm). We were able to determine the feasibility of the pterional/orbitozygomatic, middle fossa/anterior petrosal, and presigmoid retrolabyrinthine approaches to an individual basilar bifurcation. We also estimated the amount of bone removal required and determined the operative distances via those approaches.

CONCLUSION

Three-dimensional computed tomographic angiography is a useful tool for assessing critical anatomic relationships and represents an adjunct to conventional angiography in the planning of individualized, precisely tailored, cranial base approaches to the vertebrobasilar system.
Anterior Lumbar Microdiscectomy and Interbody Fusion for the Treatment of Recurrent Disc Herniation
Authors: Giancarlo Vishteh A. , Dickman Curtis A.
Published: July 2004

OBJECTIVE

To demonstrate the feasibility of anterior lumbar microdiscectomy in patients with recurrent, sequestered lumbar disc herniations.

METHODS

Between 1997 and 1999, six patients underwent a muscle-sparing “minilaparotomy” approach and subsequent microscopic anterior lumbar microdiscectomy and fragmentectomy for recurrent lumbar disc extrusions at L5–S1 (n = 4) or L4–L5 (n = 2). A contralateral distraction plug permitted ipsilateral discectomy under microscopic magnification. Effective resection of the extruded disc fragments was accomplished by opening the posterior longitudinal ligament. Interbody fusion was performed by placing cylindrical threaded titanium cages (n = 4) or threaded allograft bone dowels (n = 2).

RESULTS

There were no complications, and blood loss was minimal. Follow-up magnetic resonance imaging revealed complete resection of all herniated disc material. Plain x-rays revealed excellent interbody cage position. Radicular pain and neurological deficits resolved in all six patients (mean follow-up, 14 mo).

CONCLUSION

Anterior lumbar microdiscectomy with interbody fusion provides a viable alternative for the treatment of recurrent lumbar disc herniations. Recurrent herniated disc fragments can be removed completely under direct microscopic visualization, and interbody fusion can be performed in the same setting.
Malignant Giant-cell Tumor of the Parietal Bone: Case Report and Review of the Literature
Authors: Leonard Jeffrey , Gökden Murat , Kyriakos Michael , Derdeyn Colin P. , Rich Keith M.
Published: July 2004

OBJECTIVE AND IMPORTANCE

Giant-cell tumors (GCTs) are primary bone tumors that involve long bones in 75 to 90% of patients. They seldom develop in the cranium and are very rare in patients older than 60 years of age. A GCT rarely occurs with Paget's disease; when it does, however, it is most commonly associated with the polyostotic form and tends to involve the craniofacial bones. Pagetic GCTs are less aggressive than GCTs that are not associated with Paget's disease.

CLINICAL PRESENTATION

We report the case of an 81-year-old woman with a painless left parietal mass and asymptomatic monostotic parietal Paget's disease.

INTERVENTION

Surgical resection was performed, and histological examination of the lesion demonstrated Paget's disease with a malignant GCT. An incidental, low-grade, small-cell lymphocytic lymphoma also was noted. The patient experienced local recurrence of the malignant GCT and eventually died after developing pulmonary metastases of the malignant GCT.

CONCLUSION

This case is the first reported example of a patient with a malignant GCT of the cranium associated with monostotic Paget's disease. It provides evidence that not all pagetic GCTs in the cranium are benign, as has been reported.
Stereotactic Radiosurgery for Recurrent Central Neurocytoma: Case Report
Authors: Pollock Bruce E. , Stafford Scott L.
Published: July 2004

OBJECTIVE AND IMPORTANCE

Neurocytomas are typically benign tumors that have high local control rates after gross total resection. Nevertheless, tumor recurrence is possible, and some patients have aggressive tumors.

CLINICAL PRESENTATION

A 26-year-old woman had a recurrent, asymptomatic neurocytoma 3 years after gross total resection.

INTERVENTION

The patient underwent stereotactic radiosurgery for the tumor recurrence. Thirty-four months later, the patient remained neurologically intact, and the tumor had decreased significantly in size.

CONCLUSION

Radiosurgery may be a viable treatment option for patients with recurrent neurocytomas or for patients whose tumor resections were subtotal.
Preservation of Large Bridging Veins of the Cranial Base: Technical Note
Authors: Kyoshima Kazuhiko , Oikawa Susumu , Kobayashi Shigeaki
Published: July 2004

OBJECTIVE

Sacrifice of a bridging vein in the cranial base occasionally may cause significant postoperative morbidity. We report a simple method for preserving large bridging veins of the cranial base by reflecting the dura when a subtemporal or transsylvian approach is used.

METHODS

In the subtemporal approach, when a larger bridging vein enters the dura attached to the bone of the temporal base before it empties into the dural sinus, the dura is dissected widely from the bone and is cut vertically toward the medial side of the temporal base in front of the entrance of the vein into the dura. The dura, which includes part of the entrance and interdural course of the vein, is reflected and retracted over the brain. In the transsylvian approach, when the bridging segment of the superficial sylvian vein becomes taut because of retraction of the temporal lobe, the dura is incised along the sphenoid ridge and is dissected and freed from the sphenoid bone.

RESULTS AND CONCLUSION

This dura-reflecting technique facilitates brain retraction without exerting tension on the bridging vein of the cranial base and is expected to help avoid injury to bridging veins during neurosurgical procedures.
Treating Complex Nervous System Vascular Disorders through a “Needle Stick”: Origins, Evolution, and Future of Neuroendovascular Therapy
Authors: Hopkins L. Nelson , Lanzino Giuseppe , Guterman Lee R.
Published: July 2004

IN THE PAST few decades, dramatic improvements have occurred in the field of neuroendovascular surgery. Endovascular therapy today is a well-established treatment modality for a variety of cerebrovascular and nonvascular central nervous system diseases. The foundation of this spectacular evolution was laid by the efforts of pioneering visionaries who often worked alone and under difficult, almost impossible, conditions. Ongoing device development and refinement have revolutionized the field at a dizzying, exhilarating pace. With a better understanding of the molecular basis of diseases and further advancements in gene therapy, neuroendovascular techniques have an enormous potential for application to the entire spectrum of central nervous system diseases as a minimally invasive vehicle for the delivery of biological factors.
Is the Aspect Ratio a Reliable Index for Predicting the Rupture of a Saccular Aneurysm?
Authors: Ujiie Hiroshi , Tamano Yoshinori , Sasaki Kuri , Hori Tomokatsu
Published: July 2004

OBJECTIVE

The present retrospective study was undertaken to prove the reliability of the aspect ratio (aneurysm depth to aneurysm neck width) for predicting an aneurysmal rupture. The aspect ratio is considered a better geometric index than aneurysm size for determining the intra-aneurysmal blood flow.

METHODS

We measured the aspect ratios and the sizes of aneurysms, as determined by examining angiographic films magnified 1.4×, in 129 patients with ruptured aneurysms and in 72 patients with 78 unruptured aneurysms. After categorizing the aneurysms into four groups on the basis of their locations (aneurysms of the anterior communicating artery, middle cerebral artery, internal carotid artery-posterior communicating artery [ICA-PComA], and other aneurysms), a statistical analysis of ruptured and unruptured aneurysms was performed.

RESULTS

The mean aneurysm size was found to be statistically significant in the aneurysms at the ICA-PComA and in locations excluding the anterior communicating artery, the middle cerebral artery, and the ICA-PComA. However, the mean aspect ratio was statistically significant at all four locations. In patients with ruptured aneurysms, no ruptured aneurysms with an aspect ratio of less than 1.0 were found. The distribution of the ruptured group versus the unruptured group with an aspect ratio of less than 1.6 at each location was 13 versus 79%, respectively, at the anterior communicating artery, 11 versus 58% at the middle cerebral artery, 11% versus 85% at the ICA-PComA, and 7 versus 81% at other locations.

CONCLUSION

The aspect ratio between ruptured aneurysms and unruptured aneurysms was found to be statistically significant, and almost 80% of the ruptured aneurysms showed an aspect ratio of more than 1.6, whereas almost 90% of the unruptured aneurysms showed an aspect ratio of less than 1.6. This study therefore suggests that the aspect ratio may be useful in predicting imminent aneurysmal ruptures.
Spontaneous Resolution of Chiari I Malformation and Syringomyelia: Case Report and Review of the Literature
Authors: Klekamp Jörg , Iaconetta Giorgio , Samii Madjid
Published: July 2004

OBJECTIVE AND IMPORTANCE

Indications for surgery and the surgical technique of foramen magnum decompression for patients with Chiari I malformation and syringomyelia are controversial issues. This case report supports the view that observation may be adequate for patients without progressive symptoms or with mild clinical symptoms.

CLINICAL PRESENTATION

A 37-year-old woman presented with a 3-month history of burning dysesthesias and hypesthesia in her right arm. A neurological examination revealed hypesthesia in the right trigeminal distribution. A magnetic resonance imaging scan revealed a Chiari I malformation with syringomyelia between C2 and T2. No hydrocephalus was observed.

CLINICAL COURSE

Because the patient's symptoms regressed spontaneously, surgery was not performed. Thirty-two months after her initial examination, the patient was asymptomatic. A second magnetic resonance imaging scan was obtained, which demonstrated complete spontaneous resolution of the Chiari I malformation and syringomyelia.

CONCLUSION

We attribute the regression of the patient's symptoms to spontaneous recanalization of cerebrospinal fluid pathways at the foramen magnum, which most likely was due to rupture of the arachnoid membranes that had obstructed cerebrospinal fluid flow.
A Posterior Tibial Nerve Neurilemoma Unrecognized for 10 Years: Case Report
Authors: Ghaly Ramsis F.
Published: July 2004

OBJECTIVE AND IMPORTANCE

Neoplasms of peripheral nerves can be obscured, especially during the early phase. The author reports a patient with a posterior tibial nerve neurilemoma (schwannoma). For a decade, the tumor was misdiagnosed as nonspecific S1 radiculopathy and psychogenic chronic pain syndrome. The patient's presentation and initial management are unique.

CLINICAL PRESENTATION

A 40-year-old woman reported severe left foot and calf pain, numbness, and weakness. The symptoms were evident during three pregnancies, and they gradually progressed. The neuropathic pain was protracted, despite implantation of a dorsal column stimulator and administration of a wide variety of medications and therapies. The symptoms were unresponsive to both inpatient and outpatient treatments, which resulted in a misdiagnosis of psychogenic pain for more than a decade. Diagnostic scans obtained by computed tomography, ultrasonography, and nuclear scintigraphy confirmed a popliteal fossa mass.

INTERVENTION

A high, large posterior tibial nerve neurilemoma was found intraoperatively, positioned just below the sciatic nerve bifurcation with extensive degenerative features and hemorrhages. Surgical resection provided immediate recovery.

CONCLUSION

Peripheral nerve tumors are rarely acknowledged clinical entities. Chronic unexplained foot and calf pain and a positive Tinel's sign should raise suspicion of posterior tibial nerve neurilemoma. Even in patients who have had such tumors for a decade, surgical resection remains the treatment of choice.
Cord Compression Secondary to Cervical Disc Herniation Associated with Calcification of the Ligamentum Flavum: Case Report
Authors: Ugarriza L. Fernando , Cabezudo José M. , Porras Luis F. , Rodríguez-Sánchez José A.
Published: July 2004

OBJECTIVE AND IMPORTANCE

Calcification of the ligamentum flavum is a rare disease that occurs almost exclusively in elderly Japanese people. We report the case of a young Caucasian woman who presented with a C5–C6 disc herniation associated with a cervical calcified ligamentum flavum.

CLINICAL PRESENTATION

The patient presented with a cord compression syndrome of 76 hours' evolution. At exploration, a Brown-Séquard syndrome at the C6 level was found. Magnetic resonance imaging and computed tomography led to a correct diagnosis and planning for decompression.

INTERVENTION

We operated on the patient through a combined anterior and posterior approach. After the patient underwent anterior discectomy with intersomatic arthrodesis, we performed posterior decompression. During the operation, we observed that the dura mater could not be separated from the ligamentum, so an en bloc excision of both structures was performed. Microscopic examination indicated that the excised ligamentum had calcification, and total integration of the dura mater into the structure of the ligamentum was demonstrated. To our knowledge, this circumstance has never been described before. A posterior C3–C7 arthrodesis was performed to prevent postoperative kyphosis. Recovery was successful, with total recovery from neurological deficits 4 months later.

CONCLUSION

Calcification of the ligamentum flavum is a progressive disease that starts early in life and becomes symptomatic later in life when spinal stenosis occurs. Magnetic resonance imaging and computed tomography provide adequate diagnosis and allow proper surgical planning for decompression. The presence of hyperintense areas within the spinal cord parenchyma, in the absence of a traumatic antecedent, does not preclude a complete recovery.
Intrasellar Rhabdomyosarcoma: Case Report
Authors: Arita Kazunori , Sugiyama Kazuhiko , Tominaga Atushi , Yamasaki Fumiyuki
Published: July 2004

OBJECTIVE AND IMPORTANCE

There has been only one reported case of an intrasellar rhabdomyosarcoma, the origin of which was in the paranasal sinus. The authors encountered a patient with an intrasellar rhabdomyosarcoma with no evidence of tumor at any additional sites.

CLINICAL PRESENTATION

A 28-year-old otherwise healthy man complaining of headache exhibited left abducent nerve palsy and left visual disturbance. The patient was diagnosed as having a sellar tumor invading the left cavernous sinus.

INTERVENTION

Near total removal of the tumor was achieved via a transsphenoidal approach. Histologically, the tumor was composed of small, round-to-elongated undifferentiated cells and large spindle cells with myoblastic features. Immunohistochemically, tumor cells were positive for antibodies against desmin, myoglobin, and α-smooth muscle actin. The tumor was identified as an embryonal rhabdomyosarcoma on the basis of the above pathological findings. Systemic investigation, including the nasal and paranasal regions, failed to detect any additional tumors. Postoperative local radiation therapy and chemotherapy with the use of ifosfamide, etoposide, and vincristine brought about complete initial remission.

CONCLUSION

Rhabdomyosarcoma should be considered in the differential diagnosis of a primary intrasellar neoplasm.
What Factors Are Related to Impairment of Cerebrovascular Reserve before and after Arteriovenous Malformation Resection? A Cerebral Blood Flow Study Using Xenon-enhanced Computed Tomography
Authors: Roost Dirk Van , Schramm Johannes
Published: July 2004

OBJECTIVE

To examine the incidence and possible determinants of impaired vascular reserve in arteriovenous malformation (AVM)-affected brain, before and after surgery.

METHODS

In a prospective study of 30 patients, the regional cerebrovascular reserve capacity (rCRC) and the vasodilated regional cerebral blood flow (rCBF) were assessed during an acetazolamide challenge, using xenon-enhanced computed tomography, before and after complete AVM resection. Single brain slices at the level of the basal ganglia were examined, and scanning through the AVMs was avoided. Five regions of interest in the AVM-bearing hemisphere were compared with their counterparts in the unaffected hemisphere. Vasodilated rCBF reductions of at least 20% in one or more regions of interest and rCRC values of less than 10 ml/100 g/min were considered to be significant.

RESULTS

Ipsilateral vasodilated rCBF was significantly reduced in 17 patients before surgery and 15 patients after surgery. Ipsilateral rCRC was impaired in 14 patients before surgery and 12 patients after surgery. Large AVM size, venous congestion, and AVM-related vascular territories were correlated with impaired vascular reserve in AVM-nonadjacent brain tissue before surgery. Similar correlations were observed after surgery, except that not AVM size but a large number of AVM-supplying vascular territories was correlated. Moreover, the smallest AVMs and those supplied by a single vascular territory, as well as hemorrhage and nonhemorrhagic neurological deficits as presenting symptoms, were correlated with reduced ipsilateral vasodilated rCBF before surgery. Among patients with AVMs and nonhemorrhagic epilepsy, a trend of impaired cerebrovascular reserve was observed. In the only case of postresectional “breakthrough,” the preoperative rCRC was not impaired but abnormally high.

CONCLUSION

Among the determinants of impaired cerebrovascular reserve, AVM size is already a constituent of current grading scales and decision-making paradigms, whereas factors such as venous congestion have been less closely considered or less obvious but may deserve increased attention in the future. Nonhemorrhagic epilepsy in patients with AVMs may constitute the clinical equivalent of chronic cerebral ischemia in a murine model. Postresectional breakthrough may be partly attributable to individual predisposition to excessive vasoreactivity in the whole brain.