bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conversion of 3‐Arylazo‐5‐phenyl‐2(3H)‐furanones into Other Heterocycles of Anticipated Biological Activity
Authors: Sayed Hayam H. , Hashem Ahmed I. , Yousif Nabil M. , El‐Sayed Waled A. 
Published: June 2007

Abstract3‐Arylazo‐5‐phenyl‐2(3H)‐furanones 3 were prepared and converted into a variety of heterocyclic systems of synthetic and biological importance. Hydrazine hydrate reacted with furanones as nucleophiles and gave the corresponding acid hydrazides 4. The latter products were used as starting materials for the synthesis of 1,3,4‐oxadiazoles 6, 9, and the 1,2,4‐triazoles 8. Evaluation of the antiviral activity of selected compounds obtained was performed using two viruses: HAV and HSV‐1. Some of the tested compounds showed promising activities.
Finding treasures in frozen cells: new centriole intermediates
Authors: Dutcher Susan K. 
Published: June 2007

AbstractCentriole duplication has been an area of interest since the late 1800s when Boveri suggested that these structures were central organizers for mitosis and cell division. Two groups1, 2 have delineated a linear pathway for centriole assembly. In C. elegans, Pelletier and coworkers1 have identified intermediates in the pathway using cryo‐electron tomography. Surprising, the first intermediate is a hollow tube of 60 nm that increases in diameter and then elongates before acquiring microtubules. Similar structures have not been observed to date in other centrioles. BioEssays 29:630–634, 2007. © 2007 Wiley Periodicals, Inc.
Organizing chordates with an organizer
Authors: Garcia‐Fernàndez Jordi , D'Aniello Salvatore , Escrivà Hector 
Published: June 2007

AbstractUnderstanding how the chordate body plan originated and evolved is still controversial. The discovery by Spemann and Mangold in 1924 of the vertebrate organizer and its inductive properties in patterning the AP and DV axis was followed by a long gap until the 1960s when scientists started characterizing the molecular events responsible for such inductions. However, the evolutionary origin of the organizer itself remained obscure until very recently; did it appear together with the origin and radiation of vertebrates, or was it a chordate affair? A recent study by Yu and collaborators,1 which analyses the expression of several organizer‐specific genes in amphioxus together with recent phylogenetic data that reversed the position of invertebrate extant chordates (e.g. urochordates and cephalochordates), indicates that the organizer probably appeared in early chordates. It likely had separate signalling centres generating BMP and Wnt signalling gradients along the DV and AP axis. The organizer was then lost in the urochordate lineage, most probably as an adaptation to a rapid and determinate development. BioEssays 29:619–624, 2007. © 2007 Wiley Periodicals, Inc.
Evolution of the cytoskeleton
Authors: Erickson Harold P. 
Published: June 2007

AbstractThe eukaryotic cytoskeleton appears to have evolved from ancestral precursors related to prokaryotic FtsZ and MreB. FtsZ and MreB show 40–50% sequence identity across different bacterial and archaeal species. Here I suggest that this represents the limit of divergence that is consistent with maintaining their functions for cytokinesis and cell shape. Previous analyses have noted that tubulin and actin are highly conserved across eukaryotic species, but so divergent from their prokaryotic relatives as to be hardly recognizable from sequence comparisons. One suggestion for this extreme divergence of tubulin and actin is that it occurred as they evolved very different functions from FtsZ and MreB. I will present new arguments favoring this suggestion, and speculate on pathways. Moreover, the extreme conservation of tubulin and actin across eukaryotic species is not due to an intrinsic lack of variability, but is attributed to their acquisition of elaborate mechanisms for assembly dynamics and their interactions with multiple motor and binding proteins. A new structure‐based sequence alignment identifies amino acids that are conserved from FtsZ to tubulins. The highly conserved amino acids are not those forming the subunit core or protofilament interface, but those involved in binding and hydrolysis of GTP. BioEssays 29:668–677, 2007. © 2007 Wiley Periodicals, Inc.
Possible role of mitochondrial dysfunction in central neurodegeneration of ovariectomized rats
Authors: Shi Chun , Xu Xiao Wu , Forster E. Lucy , Tang Li Feng , Ge ZhenYing , Yew David T. , Xu Jie 
Published: June 2007

AbstractIn the present study, ovariectomized Sparague‐Dawley rats were used to mimic the pathological changes of post‐menopausal females with genistein and estradiol benzoate (EB) as substitutes for endogenous estradiol. Measurements of hippocampal ATP content, mitochondrial ATP content and the rate of mitochondrial ATP synthesis in the hippocampus indicated that after ovariectomy, brain energy metabolism of the rats presented a transient change in hippocampal ATP content which was significant from the 6th to the 8th day after ovariectomy. The change on the 6th day was the most noteworthy. Mitochondrial ATP content and the rate of mitochondrial ATP synthesis of the hippocampus were also lowered. However, after using EB or genistein, the three indicators returned to normal. It is suggested that mitochondrial dysfunction may play a key role in Alzheimer's disease (AD) of the post‐menopausal female, and may serve as the target for endogenous estrogen and exogenous phytoestrogen. In addition, genistein, which possesses the properties of estrogen but not its side effects such as carcinogenicity, could reverse the bioenergetic defects of ovariectomized rats and perhaps be used as a substitute for estradiol to prevent or treat central neurodegeneration in post‐menopausal women. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis of the 2,4,5‐Tri‐tert‐butyl‐1,3‐diphospholide Anion by Phosphinidene Elimination from 2,4,6‐Tri‐tert‐butyl‐1,3,5‐triphosphabenzene on Treatment with the Amide Li[NPh(SiMe3)]
Authors: Clendenning Scott B. , Hitchcock Peter B. , Lappert Michael F. , Merle Philippe G. , Nixon John F. , Nyulászi László 
Published: June 2007

AbstractTreatment of the lithium amide Li[NPh(SiMe3)] with 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene, P3C3tBu3, in a 1:2 ratio afforded equimolar amounts of the lithium salt of the five‐membered 2,4,5‐tri‐tert‐butyl‐1,3‐diphospholide anion, LiP2C3tBu3 (isolated as its N,N,N′,N′‐tetramethylethylenediamine (TMEDA) adduct), and the tricyclic compound 6‐[phenyl(trimethylsilyl)amino]‐3,5,7‐tri‐tert‐butyl‐1,2,4,6‐tetraphosphatricyclo[3.2.0.02,7]hept‐3‐ene. Both compounds have been structurally characterised by single‐crystal X‐ray diffraction studies. The mechanism of this remarkable reaction has been elucidated by theoretical methods at the B3LYP/6‐311+G** level of theory. The reaction involves a hitherto unobserved aminophosphinidene, which was formed by abstraction of a phosphorus atom from triphosphabenzene. The intermediate aminophosphinidene, which is further stabilised by the solvent THF, shows, in agreement with previous theoretical predictions, enhanced stability and reacts then with a second molecule of triphosphabenzene.
Scope and Limitations of Baird's Theory on Triplet State Aromaticity: Application to the Tuning of Singlet–Triplet Energy Gaps in Fulvenes
Authors: Ottosson Henrik , Kilså Kristine , Chajara Khalil , Piqueras Mari Carmen , Crespo Raül , Kato Haruhisa , Muthas Daniel 
Published: June 2007

AbstractUtilizing Baird's theory on triplet state aromaticity, we show that the singlet–triplet energy gaps (ΔEST) of pentafulvenes are easily varied through substitution by as much as 36 kcal mol−1. This exploits the fact that fulvenes act as aromatic chameleons in which the dipoles reverse on going from the singlet ground state (S0) to the lowest ππ* triplet state (T1); thus, their electron distributions are adapted so as to achieve some aromaticity in both states. The results are based on quantum chemical calculations with the OLYP density functional theory method and the CASPT2 ab initio method, as well as spectroscopic determination of ΔEST by triplet sensitization. The findings can also be generalized to fulvenes other than the pentafulvenes, even though the effect is attenuated as the size of the fulvene increases. Our studies thus reveal that triplet‐state aromaticity can greatly influence the properties of conjugated compounds in the T1 state.
Das Ozonloch und seine Ursachen
Authors: Dameris Martin , Peter Thomas , Schmidt Ulrich , Zellner Reinhard 
Published: June 2007

AbstractDas Ozon in der Atmosphäre gehört zu dem am längsten und am umfassendsten beobachteten Spurengasen. Das Muster seiner Verteilung über den Globus und mit der Höhe – vom Boden bis in ca. 80 km Höhe – ist gut bekannt. Seine Bedeutung in den verschiedenen Schichten der Atmosphäre ist allerdings sehr unterschiedlich. Während das Ozon in der Troposphäre als Quelle von Photooxidantien (wie dem OH‐Radikal) wirkt und zur Erwärmung des Globus aufgrund seines Treibhauseffektes beiträgt, ist das Ozon in der Stratosphäre hauptsächlich für den Schutz der Biosphäre vor der kurzwelligen Strahlung der Sonne verantwortlich. In beiden Regionen wird das Ozon auch durch unterschiedliche Mechanismen gebildet und verbraucht.Das Ozon in der Stratosphäre wird durch Photochemie des Sauerstoffs gebildet. In der reinen Sauerstoffatmosphäre stellt sich deshalb eine bestimmte Konzentration ein. Die Gegenwart von anthropogen emittierten Spurengasen wie N2O oder die FCKW hat diese Konzentration aufgrund einer Beschleunigung seiner Abbaureaktionen verringert. Besonders starke Ausprägungen hat diese Ozonabnahme in den Polarregionen im Winter erfahren. Als Ursache wurde neben der reinen Gasphasenchemie die Oberflächenchemie von chlorhaltigen Komponenten an sog. polaren stratosphärischen Wolken (PSCs) identifiziert. Damit wird das jährliche Ausmaß des Ozonverlustes in den Polarregionen auch von den mikrophysikalischen Vorraussetzungen (Temperatur, Geschwindigkeit der Partikelbildung) in der polaren Stratosphäre abhängig. Diese sind im Süden über der Antarktis regelmäßig intensiver als im Norden über der Arktis. Aufgrund der Beschlüsse des Montrealer Protokolls zum Schutz der Ozonschicht sowie dem Verbot der Produktion von FCKW und anderer halogenierter Spurengase wird das Ozonloch in einigen Jahrzehnten wieder verschwunden sein. Die spannende Frage ist allerdings, wie der bevorstehende Klimawandel, der sich mit umgekehrten Vorzeichen – nämlich einer Abkühlung der Luft – auch in der Stratosphäre auswirkt, die Erholung der Ozonschicht beeinflussen bzw. verzögern könnte.
Biosphäre und Atmosphäre: Bedeutung biogener Kohlenwasserstoffe
Authors: Steinbrecher Rainer , Koppmann Ralf 
Published: June 2007

AbstractDie Biosphäre steuert maßgeblich den Spurenstoffaustausch zwischen Erdoberfläche und Atmosphäre. Biogene flüchtige Verbindungen (BVOC) sind sehr reaktiv und werden in großem Umfang von Wäldern produziert. Deshalb sind BVOC wesentlich an Oxidationsprozessen in der Atmosphäre beteiligt. In den letzten Jahren haben zahlreiche nationale und internationale Forschungsprojekte die Wissenslage stark verbessert, insbesondere zu Oxidationspfaden in der Waldatmosphäre, zur biochemischen Bildung von Isoprenoiden und ihrer genetischen Grundlage sowie zum Spektrum der emittierten Verbindungen und ihrer Kontrolle durch Umgebungsfaktoren. Darüber hinaus wurde in Landschaften erstmals mit hoher räumlicher und zeitlicher Auflösung die Verteilung der biogenen Emissionsquellen analysiert und Variationsmuster abgeleitet. Dazu wurden Geräte und analytische Verfahren sowie Modelle neu entwickelt beziehungsweise weiterentwickelt. Trotz des großen Fortschrittes in den letzten Jahren bestehen große Kenntnislücken, insbesondere in der Emission von Sesquiterpenen und sauerstoffhaltigen VOC durch die Biosphäre. Darüber hinaus ist die Luftchemie im Innern von Wäldern erst in Ansätzen verstanden. Deshalb werden in Zukunft aufregende neue Erkenntnisse über den komplexen reaktiven Kohlenstoffumsatz im Erdsystem zu erwarten sein – insbesondere in der Rückkopplung mit Landnutzungsänderungen und dem Klimasystem der Erde.
Screening of Protease Inhibitors as Antiplasmodial Agents. Part I: Aziridines and Epoxides
Authors: Schulz Franziska , Gelhaus Christoph , Degel Björn , Vicik Radim , Heppner Saskia , Breuning Alexander , Leippe Matthias , Gut Jiri , Rosenthal Philip J. , Schirmeister Tanja 
Published: June 2007

AbstractA broad protease‐based and cell‐based screening of protease inhibitors yielded the aziridine‐2‐carboxylic acid derivative 2 a and the N‐acylated aziridine‐2,3‐dicarboxylic acid derivatives 32 a and 34 b as the most potent inhibitors of falcipain‐2 and falcipain‐3 (IC50 falcipain‐2: 0.079–5.4 μM, falcipain‐3: 0.25–39.8 μM). As the compounds also display in vitro activity against the P. falciparum parasite in the submicromolar and low micromolar range, these compound classes are leads for new antiplasmodial falcipain inhibitors.
Insurance status and stage of cancer at diagnosis among women with breast cancer
Authors: Halpern Michael T. , Bian John , Ward Elizabeth M. , Schrag Nicole M. , Chen Amy Y. 
Published: June 2007

AbstractBACKGROUNDIndividuals without medical insurance or with limited insurance are less likely than those with broader insurance coverage to receive preventive services and to seek timely medical care. The authors examined the associations of insurance status with stage at diagnosis among women with breast cancer.METHODSThis study included women age ≥40 years who were diagnosed with invasive breast cancer from 1998 to 2003 and who were reported to the National Cancer Data Base. Multivariable logistic regression analyses were used to examine the associations of insurance status with more advanced‐stage breast cancer at diagnosis while controlling for other patient characteristics.RESULTSAmong the 533,715 women with breast cancer who were included in the current analysis, the proportions with advanced‐stage (III/IV) cancer at diagnosis ranged from 8% among privately insured patients to 18% among uninsured patients and 19% among Medicaid patients; differences in the proportions of women with advanced‐stage cancer were statistically significant (P < .0001). Regression analyses indicated that, compared with privately insured patients, uninsured patients and Medicaid patients had a greater likelihood of diagnosis at stage II (odds ratio [OR], ∼≈1.5) or at stages III/IV (OR, 2.4) versus stage I (P < .001). Black and Hispanic patients also were significantly more likely than white patients to be diagnosed at a more advanced stage (P < .001).CONCLUSIONSThe results from this study provided strong evidence that patients without health insurance or with Medicaid coverage, as well as black and Hispanic patients, were more likely to present with advanced‐stage breast cancer. These results are consistent with other reports that have documented less use of preventive services, including mammography, among uninsured women and delays in diagnosis and treatment for black and Hispanic women. Cancer 2007. © 2007 American Cancer Society.
The impact of health insurance status on stage at diagnosis of oropharyngeal cancer
Authors: Chen Amy Y. , Schrag Nicole M. , Halpern Michael T. , Ward Elizabeth M. 
Published: June 2007

AbstractBACKGROUND.Although patients who have early‐stage oropharyngeal cancer can be treated with little impairment of function, the treatment of advanced disease can result in decreased quality of life and mortality. Patients without insurance and with other barriers to access to care may delay seeking medical attention for early symptoms, resulting in more advanced disease at presentation. In this study, the authors examined whether patients who had no insurance or who were covered by Medicaid insurance were more likely to present with advanced oropharyngeal cancer.METHODS.In this retrospective cohort study from the National Cancer Database from 1996 to 2003, patients with known insurance status who were diagnosed with invasive oropharyngeal cancer at Commission on Cancer facilities (n = 40,487) were included. Adjusted and unadjusted logistic regression models were used to analyze the likelihood of presenting with more advanced stage disease.RESULTS.After controlling for other sociodemographic characteristics, patients with advanced oropharyngeal cancer at diagnosis were more likely to be uninsured (odds ratio [OR], 1.37; 95% confidence interval [95% CI], 1.21–1.25) or covered by Medicaid (OR, 1.31; 95% CI, 1.19–1.46) compared with patients who had private insurance. Similarly, patients were most likely to present with the largest tumors (T4 disease) if they were uninsured (OR, 2.82; 95% CI, 2.46–3.23) or covered by Medicaid (OR, 2.95; 95% CI, 2.63–3.31). They also were more likely to present with the greatest degree of lymph node involvement (N3) if they were uninsured (OR, 2.06; 95% CI, 1.76–2.40) or covered by Medicaid (OR, 1.66; 95% CI, 1.45–1.90).CONCLUSIONS.Individuals who lacked insurance or had Medicaid coverage were at the greatest risk for presenting with advanced oropharyngeal cancer. In the current study, the results for the Medicaid group may have been influenced by the postdiagnostic enrollment of uninsured patients. Insurance coverage appeared to be a highly modifiable predictor of cancer stage. The findings indicated that it is important to consider the impact of insurance coverage on disease stage at diagnosis and associated morbidity, mortality, and quality of life. Cancer 2007. © 2007 American Cancer Society.
Asymptotic behavior of smooth solutions for partially dissipative hyperbolic systems with a convex entropy
Authors: Bianchini Stefano , Hanouzet Bernard , Natalini Roberto 
Published: June 2007

AbstractWe study the asymptotic time behavior of global smooth solutions to general entropy, dissipative, hyperbolic systems of balance laws in m space dimensions, under the Shizuta‐Kawashima condition. We show that these solutions approach a constant equilibrium state in the Lp‐norm at a rate O(t− (m/2)(1 − 1/p)) as t → ∞ for p ∈ [min{m, 2}, ∞]. Moreover, we can show that we can approximate, with a faster order of convergence, the conservative part of the solution in terms of the linearized hyperbolic operator for m ≥ 2, and by a parabolic equation, in the spirit of Chapman‐Enskog expansion in every space dimension. The main tool is given by a detailed analysis of the Green function for the linearized problem. © 2007 Wiley Periodicals, Inc.
Androgen modulates the kinetics of the delayed rectifying K+ current in the electric organ of a weakly electric fish
Authors: McAnelly M. Lynne , Zakon Harold H. 
Published: June 2007

AbstractWeakly electric fish such as Sternopygus macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi‐sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time‐varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Presynaptic plasticity and associative learning are impaired in a Drosophila presenilin null mutant
Authors: Knight David , Iliadi Konstantin , Charlton Milton P. , Atwood Harold L. , Boulianne Gabrielle L. 
Published: June 2007

AbstractAlzheimer's disease is a neurodegenerative disorder characterized by progressive memory and cognitive decline that is associated with changes in synaptic plasticity and neuronal cell loss. Recent evidence suggests that some of these defects may be due to a loss of normal presenilin activity. Here, we have examined the effect of loss of Drosophila presenilin (psn) function on synaptic plasticity and learning. Basal transmitter release was elevated in psn mutants while both paired pulse synaptic plasticity and post‐tetanic potentiation were impaired. These defects in synaptic strength and plasticity were not due to developmental defects in NMJ morphology. We also found that psn null terminals take up significantly less FM 4‐64 than control terminals when loaded with high frequency stimulation, suggesting a defect in synaptic vesicle availability or mobilization. To determine whether these reductions in synaptic plasticity had any impact on learning, we tested the larvae for defects in associative learning. Using both olfactory and visual learning assays, we found that associative learning is impaired in psn mutants compared with controls. Both the learning and synaptic defects could be rescued by expression of a full length psn transgene suggesting the defects are specifically due to a loss of psn function. Taken together, these results provide the first evidence of learning and synaptic defects in a Drosophila psn mutant and strongly suggest a presynaptic role for presenilin in normal neuronal function. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Endothelial cell‐matrix interactions determine maturation of dendritic cells
Authors: Methe Heiko , Hess Shmuel , Edelman Elazer R. 
Published: June 2007

AbstractThe fate of allo‐ and xenogeneic endothelial cell (EC) implants is regulated by EC‐matrix interactions. While free EC are destroyed by a vigorous immune reaction, EC embedded within 3D collagen cells are well tolerated. Given the critical role DC serve in immune reactivity, we hypothesized that EC‐driven DC maturation depends on EC‐matrix contact. In marked contrast to DC co‐cultured with a cytokine cocktail or with allo‐ and xenogeneic EC grown to confluence on 2D tissue culture plates, DC exposed to 3D matrix‐embedded allo‐ and xenogeneic EC failed to mature, retaining their endocytic activity and exhibiting significantly reduced expression of maturation markers (costimulatory molecules, HLA‐DR, CD83; p <0.01). Matrix‐embedded EC also limited cytokine‐induced maturation and activity of DC. Incubation with matrix‐embedded EC inhibited DC induction of allogeneic lymphocyte proliferation (p <0.002) and EC cross‐activation (ICAM‐1, VCAM‐1, HLA‐DR, TLR2 and 4; p <0.01). The endothelium in its quiescent state is confluent and substrate adherent. The former ensures secretion of growth inhibitors rather than promoters, and the latter may ensure immune acceptance. We now demonstrate for the first time that interactions of EC with an underlying 3D matrix affect the ability of EC to drive DC maturation.