bluuebunny/crossref_metadata_2025 huggingface dataset:
Substituted Pyrazolo[3,4‐b]pyridines as Potent A1 Adenosine Antagonists: Synthesis, Biological Evaluation, and Development of an A1 Bovine Receptor Model
Authors: Tuccinardi Tiziano , Schenone Silvia , Bondavalli Francesco , Brullo Chiara , Bruno Olga , Mosti Luisa , Zizzari Alessandra Tania , Tintori Cristina , Manetti Fabrizio , Ciampi Osele , Trincavelli Maria Letizia , Martini Claudia , Martinelli Adriano , Botta Maurizio
Published: March 2008

Sixty‐eight new substituted pyrazolo[3,4‐b]pyridine derivatives were synthesized and tested for enriching a library of active A1 adenosine receptor (AR) antagonists belonging to the same class. These compounds were also used as an external test set to check the reliability of a 3D QSAR model recently reported by us. To investigate the binding mode of pyrazolopyridine derivatives, a model of the bovine A1AR (bA1AR) was developed by a novel homology modeling approach and used to evaluate the main interactions of the ligands with the receptor through docking studies. Results suggest important interactions of the ligands mainly with L3.33(88), T3.36(91), Q3.37(92) and H6.52(251), in agreement with mutagenesis data. The racemic mixture of the most active compound was separated into the corresponding enantiomers which showed a bA1AR affinity in the nanomolar range, with the R enantiomer sevenfold more active than the S enantiomer, according to results derived from calculations on the receptor model. Analysis of the bovine/human A1AR affinity profile of ligands supported the hypothesis that such receptors should be characterized by a different size of their binding site, responsible for the different affinity of the antagonists.
Molecular basis explanation for imatinib resistance of BCR‐ABL due to T315I and P‐loop mutations from molecular dynamics simulations
Authors: Lee Tai‐Sung , Potts Steven J. , Kantarjian Hagop , Cortes Jorge , Giles Francis , Albitar Maher
Published: March 2008

BACKGROUND

Computational simulations have become powerful tools for understanding detailed interactions in biologic systems. To the authors' knowledge to date, the mechanism of imatinib resistance in BCR‐ABL has not been clarified at the atomic level, and computational studies are required.

METHODS

Molecular dynamics (MD) simulations on the complex of imatinib with the wild‐type, T315I mutant, and 10 other P‐loop mutants of the tyrosine kinase BCR‐ABL were performed to study the mechanism of imatinib resistance.

RESULTS

Simulations suggested that imatinib resistance of T315I results mainly comes from the breakdown of interactions between imatinib and both E286 and M290, contradictory to what was believed previously, in that the missing hydrogen bonding is the main contribution. The current results also demonstrated that the unfavorable electrostatic interaction between P‐loop and imatinib is the main reason for resistance for the P‐loop mutations. Furthermore, in Y253H, protonation of the histidine at the ε position is essential for rendering this mutation resistant to imatinib.

CONCLUSIONS

The current results indicated that large‐scale simulations may offer insight and information that other simple modeling methods cannot provide regarding the problem of BCR‐ABL imatinib resistance, especially in the case of conformational changes because of remote mutations. Imatinib resistance mechanisms that were not anticipated previously were revealed by analyzing the interactions between imatinib and individual residues based on simulation results. This results demonstrated that MD is a powerful way to verify and predict the clinical response or resistance to imatinib and to other potential drugs. Cancer 2008. © 2008 American Cancer Society.
Pretreatment prostate‐specific antigen velocity is associated with development of distant metastases and prostate cancer mortality in men treated with radiotherapy and androgen‐deprivation therapy
Authors: Palma David , Tyldesley Scott , Pickles Tom ,   for the Prostate Cohort Outcomes Initiative
Published: March 2008

BACKGROUND

In men with prostate cancer, pretreatment prostate‐specific antigen (PSA) velocity (PSAV) has been demonstrated as a predictor of biochemical and survival outcomes in patients undergoing radical prostatectomy (RP). The utility of pretreatment PSAV in predicting outcomes after radiotherapy (RT), with or without androgen‐deprivation therapy (ADT), is less certain. This study was undertaken to determine whether pretreatment PSAV is associated with biochemical disease‐free survival, patterns of recurrence, and survival outcomes in men treated with radiation therapy and ADT.

METHODS

Two hundred seventy‐seven patients with intermediate‐ and high‐risk prostate cancer treated with RT and ADT formed the study cohort. Kaplan‐Meier survival estimates and Cox regression analyses were used to evaluate whether PSAV was associated with disease outcomes.

RESULTS

The median age of diagnosis was 70 years, and the median follow‐up was 6.8 years. Men with a PSAV in the highest quartile tended to have higher risk disease at presentation (P = .028). After adjustment for known prognostic factors and duration of ADT, men who had a PSAV in the highest quartile had an increased risk of distant metastasis (hazard ratio [HR], 4.0; 95% confidence interval [95% CI], 1.61–9.9 [P = .003]) and prostate cancer‐specific mortality (HR, 2.75; 95% CI, 1.27–5.95 [P = .01]) compared with men who had a lower PSAV, but had no increase in the risk of local recurrence (P = .76).

CONCLUSIONS

A high pretreatment PSAV was associated with distant metastasis and prostate cancer‐specific mortality but not with local recurrence. A high pretreatment PSAV may signify the presence of occult metastatic disease. Randomized trials are needed to determine whether more aggressive intervention is required in men who present with high pretreatment PSAV. Cancer 2008. © 2008 American Cancer Society.
Cardiovascular risk in long‐term survivors of testicular cancer
Authors: Vaughn David J. , Palmer Steven C. , Carver Joseph R. , Jacobs Linda A. , Mohler Emile R.
Published: March 2008

BACKGROUND

Long‐term survivors of testicular cancer (TC) who received cisplatin‐based chemotherapy have an increased risk of cardiovascular disease. A cross‐sectional study was performed to objectively assess cardiovascular risk, subclinical atherosclerosis, and endothelial function in long‐term survivors of TC.

METHODS

Long‐term survivors of TC underwent evaluation including determination of body mass index (BMI), Framingham relative risk (RR), brachial artery flow‐mediated dilatation (FMD), carotid artery intima‐media thickness (IMT), soluble intercellular adhesion molecule‐1 (sICAM‐1), high sensitivity C‐reactive protein (hs‐CRP), and flow cytometric analysis of peripheral blood for levels of endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs). TC survivors who received chemotherapy were compared with a chemotherapy naive cohort.

RESULTS

Twenty‐four patients received cisplatin‐based chemotherapy (CBCT) and 15 were chemotherapy‐naive (CN). The CBCT cohort demonstrated more impairment of brachial artery FMD than the CN group (5.6% vs 8.8%; P = .05). The mean sICAM was also found to be higher in the CBCT cohort compared with the CN group (P = .04). No significant differences between the groups were noted with regard to BMI, Framingham RR, carotid IMT, or hs‐CRP. In a subset of patients, TC survivors who received chemotherapy had a significantly increased level of CECs compared with CN patients (P = .04). No significant difference in EPC levels was detected.

CONCLUSIONS

Long‐term survivors of TC who received chemotherapy demonstrate objective evidence of endothelial injury and dysfunction, a potential mechanism for increased cardiovascular risk. Cancer 2008. © 2008 American Cancer Society.
Breast cancer adjuvant chemotherapy dosing in obese patients
Authors: Greenman Christopher G. , Jagielski Christina H. , Griggs Jennifer J.
Published: March 2008

BACKGROUND

Substantial variation in adjuvant breast cancer chemotherapy dosing in obese women suggests that there is uncertainty about optimal practices. The purpose of this study was to investigate variations in dose determinations in clinical trial protocols and publications over the last 3 decades as potential sources of this uncertainty.

METHODS

The National Cancer Institute database was used to identify protocols of breast cancer adjuvant chemotherapy conducted by cooperative groups between 1970–2000, and these protocols were then obtained directly from the cooperative groups. Dose determinations were categorized in each protocol and in published reports from each clinical trial. Fisher exact tests were used to compare the proportions of protocols that used full weight‐based doses over time.

RESULTS

Protocol‐specified chemotherapy dosing was obtained for all of 44 eligible trials. A significant increase was identified in the use of full weight‐based doses in the later time period compared with the earlier (P = .004; 2‐sided Fisher exact test). A notable exception was 1 cooperative group that continues to require dose limitations for doxorubicin and cyclophosphamide in patients with a body surface area of more than 2.0 m2. Regardless of publication date, published reports of clinical trials rarely provide information on use of full or limited weight‐based doses.

CONCLUSIONS

Variations in dose determinations among clinical trial protocols and lack of information on use of full weight‐based doses in most publications are 2 likely sources of variation in chemotherapy dosing in obese women. Developing consensus and disseminating information on optimal chemotherapy dosing will likely reduce such variation and may improve survival among obese patients with breast cancer. Cancer 2008. © 2008 American Cancer Society.
Prednisone, etoposide, procarbazine, and cyclophosphamide (PEP‐C) oral combination chemotherapy regimen for recurring/refractory lymphoma: Low‐dose metronomic, multidrug therapy
Authors: Coleman Morton , Martin Peter , Ruan Jia , Furman Richard , Niesvizky Ruben , Elstrom Rebecca , George Patricia , Kaufman Thomas P. , Leonard John P.
Published: March 2008

BACKGROUND

Many patients with recurrent lymphoma are unable to tolerate intensive therapies, or have disease that is refractory. Metronomic chemotherapy offers a novel, potentially less toxic yet effective treatment strategy.

METHODS

An analysis was performed on 75 lymphoma patients who were treated with the PEP‐C regimen at a single institution. The program consisted of oral prednisone 20 mg after breakfast, cyclophosphamide 50 mg after lunch, etoposide 50 mg after dinner, and procarbazine 50 mg at bedtime with an oral antiemetic. All medications were administered daily until the white blood cell count fell to less than 3.0 × 109/L, whereupon treatment was withheld until recovery from the nadir. Therapy was then reinstituted on a daily, alternate day, or fractionated weekly basis (eg, 5 of 7 days), depending on patient tolerance. Doses given per day were held constant.

RESULTS

Eighty percent of patients had previously received 2 or more treatments. Overall, 69% achieved an objective response after PEP‐C treatment, with 36% complete responses and 33% partial responses. Subjects with indolent histologies had superior overall responses, complete responses, and time on therapy relative to those with aggressive histologies. The regimen was generally well tolerated.

CONCLUSIONS

Metronomic therapy with low‐dose oral agents administered in combination for continuous, prolonged periods with minimal drug‐free intervals represents a novel, active, easily tolerated approach to management of patients with recurrent lymphoma, particularly those with indolent histologies. Cancer 2008. © 2008 American Cancer Society.
Platelet‐derived growth factor receptor as a prognostic marker and a therapeutic target for imatinib mesylate therapy in osteosarcoma
Authors: Kubo Tadahiko , Piperdi Sajida , Rosenblum Jeremy , Antonescu Cristina R. , Chen Wen , Kim Han‐Soo , Huvos Andrew G. , Sowers Rebecca , Meyers Paul A. , Healey John H. , Gorlick Richard
Published: March 2008

The purpose of this review was to determine whether imatinib mesylate (STI571, Gleevec) has a role in the treatment of osteosarcoma. The expression of platelet‐derived growth factor (PDGF) receptor and its ligand was examined in a panel of surgical specimens obtained from 54 osteosarcoma patients, and then the expression was compared with prognosis. The effects of imatinib mesylate on growth and molecular events in 10 patient‐derived osteosarcoma cell cultures were investigated. Immunohistochemical studies demonstrated frequent expression of PDGF‐AA (80.4%) and PDGF‐α receptor (79.6%) and their correlation with inferior event‐free survival (P < .05). PDGF‐B–B and PDGF‐β–receptor expressions were also frequent (75.4% and 86%, respectively); however, statistically significant inferior event‐free survival was not demonstrated (P = .15). In vitro studies demonstrated that imatinib mesylate had a variable cytotoxic effect on various osteosarcoma primary cultures, with an IC50 of 5.6 μM to 9.5 μM, and blocked the PDGF‐induced intracellular signal transduction as well as inhibition of downstream Akt phosphorylation. Mitogen‐activated protein kinase (MAPK) was constitutively activated despite PDGF stimulation and imatinib mesylate treatment in 7 of 10 osteosarcoma cultures, perhaps explaining uncontrolled proliferation and relative unresponsiveness to imatinib. Imatinib mesylate could not be viewed as having a role as a single agent at current conventional doses for the treatment of osteosarcoma. These findings predicted activity in osteosarcoma clinical trials and suggested that in vitro model systems predict clinical behavior and that PDGF and its receptor expression could potentially be used for determining prognosis of osteosarcoma. Cancer 2008. ©2008 American Cancer Society.
Changes in causes of death over time after treatment for invasive aspergillosis
Authors: Wingard John R. , Ribaud Patricia , Schlamm Haran T. , Herbrecht Raoul
Published: March 2008

BACKGROUND

Assessment of response to invasive aspergillosis (IA) therapy has been challenging in treatment trials.

METHODS

The causes of death over 12 weeks were categorized prospectively by a blinded data review committee using a priori defined criteria in participants in a randomized comparative trial of voriconazole versus amphotericin B as first‐line therapy of proven or probable IA.

RESULTS

Death occurred in 98 of 277 patients during the 12‐week course of study. Seventy‐three of the 98 deaths (74%) occurred in the first 6 weeks; 25 deaths occurred during the second 6 weeks. Of the 73 deaths during the first 6 weeks, 50 (68%) were judged to be attributable to IA. Of the 25 deaths during the second 6 weeks, only 6 (24%) were judged to be attributable to IA. Fifty of the 56 deaths (89%) attributable to IA occurred during the first 6 weeks.

CONCLUSIONS

These data suggest that most deaths due to IA occur during the first 6 weeks after the start of therapy and 6 weeks may be a better interval to judge the effectiveness of antifungal therapy because most deaths after 6 weeks are due to causes related to the underlying disease and its treatment rather than due to IA. Attributable mortality when assessed using a priori definitions and conducted in a blinded manner by a central data review committee can be useful in the assessment of IA therapy. Cancer 2008. © 2008 American Cancer Society.
Molecular Diffusion Measurement in Lipid Bilayers over Wide Concentration Ranges: A Comparative Study
Authors: Guo Lin , Har Jia Yi , Sankaran Jagadish , Hong Yimian , Kannan Balakrishnan , Wohland Thorsten
Published: March 2008

Molecular diffusion in biological membranes is a determining factor in cell signaling and cell function. In the past few decades, three main fluorescence spectroscopy techniques have emerged that are capable of measuring molecular diffusion in artificial and biological membranes at very different concentration ranges and spatial resolutions. The widely used methods of fluorescence recovery after photobleaching (FRAP) and single‐particle tracking (SPT) can determine absolute diffusion coefficients at high (>100 μm−2) and very low surface concentrations (single‐molecule level), respectively. Fluorescence correlation spectroscopy (FCS), on the other hand, is well‐suited for the intermediate concentration range of about 0.1–100 μm−2. However, FCS in general requires calibration with a standard dye of known diffusion coefficient, and yields only relative measurements with respect to the calibration. A variant of FCS, z‐scan FCS, is calibration‐free for membrane measurements, but requires several experiments at different well‐controlled focusing positions. A recently established FCS method, electron‐multiplying charge‐coupled‐device‐based total internal reflection FCS (TIR‐FCS), referred to here as imaging TIR‐FCS (ITIR–FCS), is also independent of calibration standards, but to our knowledge no direct comparison between these different methods has been made. Herein, we seek to establish a comparison between FRAP, SPT, FCS, and ITIR–FCS by measuring the lateral diffusion coefficients in two model systems, namely, supported lipid bilayers and giant unilamellar vesicles.
Quantitative data analysis methods for bead‐based DNA hybridization assays using generic flow cytometry platforms
Authors: Corrie S. R. , Lawrie G. A. , Battersby B. J. , Ford K. , Rühmann A. , Koehler K. , Sabath D. E. , Trau M.
Published: March 2008

Bead‐based assays are in demand for rapid genomic and proteomic assays for both research and clinical purposes. Standard quantitative procedures addressing raw data quality and analysis are required to ensure the data are consistent and reproducible across laboratories independent of flow platform. Quantitative procedures have been introduced spanning raw histogram analysis through to absolute target quantitation. These included models developed to estimate the absolute number of sample molecules bound per bead (Langmuir isotherm), relative quantitative comparisons (two‐sided t‐tests), and statistical analyses investigating the quality of raw fluorescence data. The absolute target quantitation method revealed a concentration range (below probe saturation) of Cy5‐labeled synthetic cytokeratin 19 (K19) RNA of c.a. 1 × 104 to 500 × 104 molecules/bead, with a binding constant of c.a. 1.6 nM. Raw hybridization frequency histograms were observed to be highly reproducible across 10 triplex assay replicates and only three assay replicates were required to distinguish overlapping peaks representing small sequence mismatches. This study provides a quantitative scheme for determining the absolute target concentration in nucleic acid hybridization reactions and the equilibrium binding constants for individual probe/target pairs. It is envisaged that such studies will form the basis of standard analytical procedures for bead‐based cytometry assays to ensure reproducibility in inter‐ and intra‐platform comparisons of data between laboratories. © 2008 International Society for Advancement of Cytometry
A framework to determine the optimal weight parameter of RED in next‐generation Internet routers
Authors: Zheng Bing , Atiquzzaman Mohammed
Published: March 2008

Active buffer management can improve the performance of Transmission Control Protocol/Internet Protocol‐based networks. Random early detection (RED), an active queue management scheme, has been proposed by the Internet Engineering Task Force for next‐generation Internet routers. RED uses a number of parameters, such as buffer thresholds, a packet drop probability and a weight parameter. RED suffers from low throughput and large delay/jitter and induces instability in networks. Previous attempts to improve the performance of RED were based on modifying the thresholds and drop probabilities. In this paper, we show that an optimal value of the weight parameter can improve the performance of RED, and then develop a framework to determine the optimal value of the weight parameter. We show that the optimal weight parameter obtained from our framework improves the performance of RED. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis and Isomerisation Reactions of Tetranuclear and Octanuclear (Carbamato)zinc Complexes
Authors: Haywood Peter F. , Hill Matthew R. , Roberts Nicholas K. , Craig Donald C. , Russell Jennifer J. , Lamb Robert N.
Published: March 2008

A new series of (diisopropylcarbamato)(oxido)zinc complexes were obtained by innovative synthetic approaches. The (carbamato)zinc clusters [Zn4(μ4‐O)(O2CNiPr2)6] (1) and [Zn8(μ4‐O)2(O2CNiPr2)12] (2) were synthesised by an identical reaction procedure involving protolysis of ZnEt2 with iPr2NH/CO2 and followed by stoichiometric hydrolysis. Recrystallisation of the reaction product from nitrile solvents yielded the tetrazinc complex 1. Conversely, recrystallisation from alkane solvents yielded crystals of the octazinc complex 2. The two structural isomers were readily interconverted simply by recrystallisation from the appropriate solvent. Both complexes were structurally characterised by X‐ray crystallography. The tetrazinc complex 1 has the quintessential basic zinc acetate type structure. Its dimer, the octazinc complex 2 is a new derivative of the [M8(μ4‐O)2(O2CNiPr2)12] class, examples of which are known for all other first‐row transition metals. The solution chemistry was investigated using variable‐temperature NMR spectroscopy and ESI‐MS. The new synthetic approach offers a route to other similar complexes. Thus, using Et2NH in place of iPr2NH yielded the known complex [Zn4(μ4‐O)(O2CNEt2)6] (3).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Studies on Nickel(II) Complexes with Amide‐Based Ligands: Syntheses, Structures, Electrochemistry and Oxidation Chemistry
Authors: Singh Jyoti , Hundal Geeta , Gupta Rajeev
Published: March 2008

The present work discusses the nickel chemistry in a set of amide‐based open‐chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square‐planar geometry. Absorption spectra and NMR studies reveal that the solid‐state square‐planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Prion decontamination during the oleochemical process of fat hydrogenation
Authors: Müller Henrik , Stitz Lothar , Riesner Detlev
Published: March 2008

The human food and animal feed industry and even oleochemical manufacturing processes might be exposed to contamination from products of BSE‐infected cattle. Although the most important oleochemical raw material, i.e. tallow, is not considered to be a causal factor for BSE, the potential risk associated with tallow‐derived products has to be evaluated in the light of the specific production process. The main production process for oleochemicals, i.e. hydrolytic fat splitting of tallow yielding glycerol and a mixture of crude fatty acids, guarantees prion‐free products, safe for human consumption [1]. Fatty acids, however, are not necessarily produced by hydrolytic fat splitting. In order to evaluate these fatty acids with regard to prion safety, we analysed the industrial conditions of catalytic fat hydrogenation, which is widely applied to improve storage and flavour stability of fatty acids. Quantitative data for the degradation of the pathological prion protein and the inactivation of prion infectivity are presented. A risk assessment calculation demonstrates that the industrial conditions of fat hydrogenation are sufficiently effective to reduce the risk of BSE contamination to an acceptable minimum.
Retention behavior of trans isomers of eicosapentaenoic and docosahexaenoic acid methyl esters on a polyethylene glycol stationary phase
Authors: Mjøs Svein A.
Published: March 2008

A polyethylene glycol (PEG) stationary phase was evaluated for the separation of mono‐trans isomers of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) methyl esters. The resolution patterns were compared to patterns achieved with previously applied conditions on a cyanopropyl phase. There were no overlaps between all‐cis EPA/DHA and their mono‐trans isomers on the PEG phase. Because of overlap between 22:0 and 22:1 isomers, the PEG column is not a good choice for analyses of EPA trans isomers in crude fish oils. However, if the saturated and monounsaturated fatty acids are not present in significant amounts, PEG can be a better choice than cyanopropyl columns.
Conjugated linoleic acid (CLA) production and lipase‐catalyzed interesterification of purified CLA with canola oil
Authors: Goli Sayyed Amir Hossein , Kadivar Mahdi , Keramat Javad , Fazilati Mohammad
Published: March 2008

In this study, two important isomers of CLA, i.e. c9,t11 and t10,c12, were produced up to ca. 73% of total fatty acids, employing alkali isomerization of safflower oil, followed by purification with only one‐step urea crystallization to 85.6%, while the recovery of the purification process was 35%. Interesterification (acidolysis) of purified CLA with canola oil was then conducted by Thermomyces lanuginosus lipase. The CLA content incorporated into the triacylglycerols (TG) was 26.6 mol‐% after 48 h of reaction time. Physical and chemical properties of the TG were then changed according to the degree of substitution of oleic acid in canola oil with CLA.
Virgin grape seed oil: Is it really a nutritional highlight?
Authors: Matthäus Bertrand
Published: March 2008

In comparison to refined grape seed oil which is neutral in taste and smell, the virgin oil is characterized by a pleasant vinous and fruity aroma, which also reminds of raisins if high‐quality raw material is used for the production. Difficulties arise from the susceptibility of the raw material to microbial and enzymatic deterioration as a result of the high moisture content after pressing the juices from the grapes. Grape seed oil has a high content (70%) of linoleic acid, whereas the total part of unsaturated fatty acids amounts to about 90%. In comparison to other edible oils, the oil contains, in addition to tocopherols, antioxidant‐effective tocotrienols. During the oil pressing process, only a small amount of phenolic compounds is transferred into the oil (0.01 mg/g), while most of these nutritionally interesting components remain in the press cake. Here, the content of phenolic compounds is about 2000 times higher. During storage of virgin grape seed oil, the pleasant sensory attributes change, and more and more degradation products like ethyl acetate, acetic acid or ethanol are detectable. Parts of the seed material, which come into the oil during pressing, result in a faster impairment of the oil.
All vertebrates started out with a glial blood‐brain barrier 4–500 million years ago
Authors: Bundgaard Magnus , Abbott N. Joan
Published: March 2008

All extant vertebrates have a blood‐brain barrier (BBB), a specialized layer of cells that controls molecular traffic between blood and brain, and contributes to the regulation (homeostasis) of the brain microenvironment. Such homeostasis is critical for the stable function of synapses and neural networks. The barrier is formed by vascular endothelial cells in most groups, but by perivascular glial cells (astrocytes) in elasmobranch fish (sharks, skates, and rays). It has been unclear which is the ancestral form, but this information is important, as it could offer insights into the roles of the endothelium and perivascular glia in the modern mammalian BBB. We have used electron microscopic techniques to examine three further ancient fish groups, with intravascular horseradish peroxidase as permeability tracer. We find that in bichir and lungfish the barrier is formed by brain endothelial cells, while in sturgeon it is formed by a complex perivascular glial sheath, but with no detectable tight junctions. From their BBB pattern, and position on the vertebrate family tree, we conclude that the ancestral vertebrate had a glial BBB. This means that an endothelial barrier would have arisen independently several times during evolution, and implies that an endothelial barrier gave strong selective advantage. The selective advantage may derive partly from greater separation of function between endothelium and astrocytic glia. There are important implications for the development, physiology, and pathology of the mammalian BBB, and for the roles of endothelium and glia in CNS barrier layers. © 2008 Wiley‐Liss, Inc.
IGF‐1 receptor‐mediated ERK/MAPK signaling couples status epilepticus to progenitor cell proliferation in the subgranular layer of the dentate gyrus
Authors: Choi Yun‐Sik , Cho Hee‐Yeon , Hoyt Kari R. , Naegele Janice R. , Obrietan Karl
Published: March 2008

Adult progenitor cell proliferation in the subgranular zone (SGZ) of the dentate gyrus is a dynamic process that is modulated by an array of physiological process, including locomotor activity and novel environmental stimuli. In addition, pathophysiological events, such as ischemia and status epilepticus (SE), have been shown to stimulate neurogenesis. Currently, limited information is available regarding the extracellular stimuli, receptors, and downstream intracellular effectors that couple excitotoxic stimulation to progenitor cell proliferation. Here we show that pilocarpine‐induced SE triggers a set of signaling events that impinge upon the p42/44 mitogen‐activated protein kinase (MAPK) pathway to drive progenitor cell proliferation in the SGZ at 2‐days post‐SE. Increased proliferation was dependent on insulin‐like growth factor‐1 (IGF‐1), which was localized to activated microglia near the SGZ. Using a combination of techniques, we show that IGF‐1 is a CREB‐regulated gene and that SE triggered CRE‐dependent transcription in microglia at 2‐days post‐SE. Together, these data identify a potential signaling program that couples SE to progenitor cell proliferation. SE triggers CREB‐dependent transcription in reactive microglia. As a CREB‐target gene, IGF‐1 expression is upregulated, and by 2‐days post‐SE, IGF‐1 triggers MAPK pathway activation in progenitor cells and, in turn, an increase in progenitor cell proliferation. © 2008 Wiley‐Liss, Inc.
Hyperoxia promotes astrocyte cell death after oxygen and glucose deprivation
Authors: Danilov Camelia A. , Fiskum Gary
Published: March 2008

Astrocyte dysfunction and death accompany cerebral ischemia/reperfusion and possibly compromise neuronal survival. Animal studies indicate that neuronal death, neurologic injury, and oxidative molecular modifications are worse in animals exposed to hyperoxic compared to normoxic ventilation during reperfusion after global cerebral ischemia. It is unknown, however, whether ambient O2 affects brain cell survival using in vitro ischemia paradigms where mechanisms of injury to specific cell types can be more thoroughly investigated. This study tested the hypothesis that compared with the supraphysiological level of 20% O2 normally used in cell culture, lower, more physiological O2 levels protect astrocytes from death following oxygen and glucose deprivation. Primary rat cortical astrocytes were cultured under either 7 or 20% O2, exposed to O2, and glucose deprivation for 4 h, and then exposed to normal medium under either 7 or 20% O2. Cell death and 3‐nitrotyrosine and 8‐hydroxy‐2‐deoxyguanosine immunoreactivities were assessed at different periods of reoxygenation. Astrocytes exposed to low levels of O2 during reoxygenation undergo less death and exhibit lower levels of protein nitration and nucleic acid oxidation when compared with those under high levels of O2 during reoxygenation. These results support the hypothesis that the 20% O2 normally used in cell culture exacerbates astrocyte death and oxidative stress in an in vitro ischemia/reperfusion model compared to levels that more closely approximate those that exist in vivo. © 2008 Wiley‐Liss, Inc.
Ca2+ entry through TRPC1 channels contributes to intracellular Ca2+ dynamics and consequent glutamate release from rat astrocytes
Authors: Malarkey Erik B. , Ni Yingchun , Parpura Vladimir
Published: March 2008

Astrocytes can respond to a variety of stimuli by elevating their cytoplasmic Ca2+ concentration and can in turn release glutamate to signal adjacent neurons. The majority of this Ca2+ is derived from internal stores while a portion also comes from outside of the cell. Astrocytes use Ca2+ entry through store‐operated Ca2+ channels to refill their internal stores. Therefore, we investigated what role this store‐operated Ca2+ entry plays in astrocytic Ca2+ responses and subsequent glutamate release. Astrocytes express canonical transient receptor potential (TRPC) channels that have been implicated in mediating store‐operated Ca2+ entry. Here, we show that astrocytes in culture and freshly isolated astrocytes from visual cortex express TRPC1, TRPC4, and TRPC5. Indirect immunocytochemistry reveals that these proteins are present throughout the cell; the predominant expression of functionally tested TRPC1, however, is on the plasma membrane. Labeling in freshly isolated astrocytes reveals changes in TRPC expression throughout development. Using an antibody against TRPC1 we were able to block the function of TRPC1 channels and determine their involvement in mechanically and agonist‐evoked Ca2+ entry in cultured astrocytes. Blocking TRPC1 was also found to reduce mechanically induced Ca2+‐dependent glutamate release. These data indicate that Ca2+ entry through TRPC1 channels contributes to Ca2+ signaling in astrocytes and the consequent glutamate release from these cells. © 2008 Wiley‐Liss, Inc.
Hyperglycemia and downregulation of caveolin‐1 enhance neuregulin‐induced demyelination
Authors: Yu Cuijuan , Rouen Shefali , Dobrowsky Rick T.
Published: March 2008

Neuregulins (NRGs) are growth factors which bind to Erb receptor tyrosine kinases that localize to Schwann cells (SCs). Although NRGs can promote cell survival, mitogenesis, and myelination in undifferentiated SCs, they also induce demyelination of myelinated co‐cultures of SCs and dorsal root ganglion (DRG) neurons. We have shown previously that Erb B2 activity increased in premyelinating SCs in response to hyperglycemia, and that this correlated with the downregulation of the protein caveolin‐1 (Cav‐1). As myelinated SCs undergo substantial degeneration in diabetic neuropathy, we used myelinated SC/DRG neuron co‐cultures to determine if hyperglycemia and changes in Cav‐1 expression could enhance NRG‐induced demyelination. In basal glucose, NRG1 caused a 2.4‐fold increase in the number of damaged myelin segments. This damage reached 3.8‐fold under hyperglycemic conditions, and was also associated with a robust decrease in the expression of Cav‐1 and compact myelin proteins. The loss of Cav‐1 and compact myelin proteins following hyperglycemia and NRG treatment was not due to neuronal loss, since the axons remained intact and there was no loss of PGP 9.5, an axonal marker protein. To examine if changes in Cav‐1 were sufficient to alter the extent of NRG‐induced demyelination, SC/DRG neurons co‐cultures were infected with antisense or dominant‐negative Cav‐1(P132L) adenoviruses. Either antisense‐mediated downregulation or mis‐localization of endogenous Cav‐1 by Cav‐1(P132L) resulted in a 1.5‐ to 2.4‐fold increase in NRG‐induced degeneration compared to that present in control cultures. These data support that hyperglycemia and changes in Cav‐1 are sufficient to sensitize myelinated SC/DRG co‐cultures to NRG‐induced demyelination. © 2008 Wiley‐Liss, Inc.
VEGF‐D promotes tumor growth and lymphatic spread in a mouse model of hepatocellular carcinoma
Authors: Thelen Armin , Scholz Arne , Benckert Christoph , von Marschall Zofia , Schröder Maik , Wiedenmann Bertram , Neuhaus Peter , Rosewicz Stefan , Jonas Sven
Published: March 2008

Lymphatic spread is an important clinical determinant for the prognosis of hepatocellular carcinoma (HCC), but little is known about the control of lymphangiogenesis in HCC. We addressed expression and biological role of the pro‐(lymph), angiogenic protein VEGF‐D in this tumor entity. Using immunohistochemistry and in situ hybridization on specimens of HCC, cirrhotic and normal liver we found abundant expression of VEGF‐D exclusively in the tumor cells. The cognate receptor VEGFR‐3 was detected on blood and lymphatic vessels. By clinicopathological analysis VEGF‐D expression was correlated with pT‐stage of the primary, lymph node metastasis and lymphangiosis carcinomatosa. Three out of 4 human HCC cell lines expressed and secreted VEGF‐D. To approach its biological function, VEGF‐D deficient SKHep‐1 cells were stably transfected with VEGF‐D cDNA and effects on tumor progression were determined in vivo. Compared to mock‐transfected controls, subcutaneous tumors derived from VEGF‐D expressing cells were larger and more frequently metastasized to regional lymph nodes. VEGF‐D expressing tumors exhibited increased microvessel density and increased abundance of peri‐ and intratumoral lymphatics, as assessed by immunostaining for CD31 and for LYVE‐1 and/or podoplanin, respectively. Furthermore, coexpression of the soluble extracellular VEGFR‐3 domain blocked VEGF‐D‐induced tumor growth and lymphatic spread via reduction of angiogenesis and lymphangiogenesis. In the orthotopic approach, VEGF‐D expression resulted in an increased rate of intra‐ and extrahepatic as well as lymph node metastasis. In conclusion, our study suggests that expression of VEGF‐D is involved in growth and lymphatic spread of HCC. Therefore, VEGF‐D might represent a therapeutic target in HCC. © 2008 Wiley‐Liss, Inc.
Cervical cancer screening program integrating Pap smear and HPV DNA testing: A population‐based study
Authors: Chao Angel , Hsu Kuang‐Hung , Lai Chyong‐Huey , Huang Huei‐Jean , Hsueh Swei , Lin Sheue‐Rong , Jung Shih‐Ming , Chao Fang‐Yu , Huang Shang‐Lang , Huang Chu‐Chun , Yang Jung‐Erh , Chang Ting‐Chang
Published: March 2008

We conducted a population‐based cohort study to evaluate the complementary value of HPV testing to Papanicolaou (Pap) smear and the prevalence and genotype distribution of HPV in Taiwan. In this report, we described the design of the whole study and analyzed the cross‐sectional results. Female residents (age ≥ 30 years) of Taoyuan, Taiwan were invited. After signing informed consent, every participant had a Pap smear and a HPV testing. Patients with Pap ≥ atypical squamous cell of undetermined significance (Group I) or those with HPV‐positive but normal cytology (Group II) were referred for a colposcopic examination. A total of 10,014 women were eligible. The overall HPV prevalence was 10.8% (95% confidence interval 10.5%–11.4%) in the study population. A total of 37 types of HPV were identified and the leading three were HPV‐52, ‐18 and ‐58. There was a significant positive correlation of HPV prevalence with older age, postmenopausal status, current‐user of oral contraceptives and never‐user of hormone replacement therapy. Past users of oral contraceptives and never users of Pap were associated with higher risk of abnormal Pap, while age 40–49 strata had lower risk. Fifty‐nine cases of cervical intraepithelial neoplasia (CIN) 2 from Group I and additional 11 from Group II were identified. The improvement of sensitivity with additional HPV testing was 15.3%. Besides, no specific subgroup was found to most benefit from the combined strategy. The value of adding HPV test to conventional Pap smear has to be evaluated after longer‐term follow‐up of this population‐based cohort. © 2008 Wiley‐Liss, Inc.
HDPE‐Al2O3‐HAp composites for biomedical applications: Processing and characterizations
Authors: Nath Shekhar , Bodhak Subhadip , Basu Bikramjit
Published: March 2008

The objective of this work is to demonstrate how the stiffness, hardness, as well as the biocompatibility property, of bioinert high‐density polyethylene (HDPE) can be significantly improved by the combined addition of both bioinert and bioactive ceramic fillers. For this purpose, different volume fractions of hydroxyapatite and alumina, limited to a total of 40 vol %, have been incorporated in HDPE matrix. All the hybrid composites and monolithic HDPE were developed under optimized hot pressing condition (130°C, 0.5 h, 92MPa pressure). The results of the mechanical property characterization reveal that higher elastic modulus (6.2 GPa) and improved hardness (226.5 MPa) could be obtained in the developed HDPE‐20 vol %‐HAp‐20 vol % Al2O3 composite. Under the selected fretting conditions against various counterbody materials (steel, Al2O3, and ZrO2), an extremely low COF of (0.07–0.11) and higher wear resistance (order of 10−6 mm3/Nm) are obtained with the HDPE/20 vol % HAp/20 vol % Al2O3 composite in both air and simulated body fluid environment. Importantly, in‐vitro cell culture study using L929 fibroblast cells confirms favorable cell adhesion properties in the developed hybrid composite. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
Mandibular arch muscle identity is regulated by a conserved molecular process during vertebrate development
Authors: Knight Robert D. , Mebus Katharina , Roehl Henry H.
Published: March 2008

Vertebrate head muscles exhibit a highly conserved pattern of innervation and skeletal connectivity and yet it is unclear whether the molecular basis of their development is likewise conserved. Using the highly conserved expression of Engrailed 2 (En2) as a marker of identity in the dorsal mandibular muscles of zebrafish, we have investigated the molecular signals and tissues required for patterning these muscles. We show that muscle En2 expression is not dependent on signals from the adjacent neural tube, pharyngeal endoderm or axial mesoderm and that early identity of head muscles does not require bone morphogenetic pathway, Notch or Hedgehog (Hh) signalling. However, constrictor dorsalis En2 expression is completely lost after a loss of fibroblast growth factor (Fgf) signalling and we show that is true throughout head muscle development. These results suggest that head muscle identity is dependent on Fgf signalling. Data from experiments performed in chick suggest a similar regulation of En2 genes by Fgf signalling revealing a conserved mechanism for specifying head muscle identity. We present evidence that another key gene important in the development of mouse head muscles, Tbx1, is also critical for specification of mandibular arch muscle identity and that this is independent of Fgf signalling. These data imply that dorsal mandibular arch muscle identity in fish, chick and mouse is specified by a highly conserved molecular process despite differing functions of these muscles in different lineages. J. Exp. Zool. (Mol. Dev. Evol.) 310B:355–369, 2008. © 2008 Wiley‐Liss, Inc.
Enantiomeric radiochemical synthesis of R and S (1‐(6‐amino‐9H‐purin‐9‐yl)‐3‐fluoropropan‐2‐yloxy)methylphosphonic acid (FPMPA)
Authors: Kiesewetter Dale O. , Knudson Kathleen , Collins Matt , Srinivasula Sharat , Lim Esther , Di Mascio Michele
Published: March 2008

Therapy for human immunodeficiency virus (HIV)‐infected patients requires chronic multidrug administration. The eventual failure of therapy in some patients has brought into question the tissue concentration of the drugs. With an appropriately radiolabeled compound, we could utilize positron emission tomography to provide quantitative time–activity curves for various tissues. We have developed a fluorine‐18 labeled analog of Tenofovir, the active metabolite of Tenofovir DF, a commonly prescribed component of multidrug therapy. Because (1‐(6‐amino‐9H‐purin‐9‐yl)‐3‐fluoropropan‐2‐yloxy)methylphosphonic acid (FPMPA) has a chiral center, we prepared both enantiomers and confirmed that the S‐isomer exhibited significantly higher antiviral activity than the R‐isomer. In viral replication inhibition assays in human MT4 cells infected with SHIVDH12R, S‐FPMPA had an IC50 of 1.85 µM (95% CI; 0.8–5.53), while the R‐isomer was inactive. An appropriate chiral precursor was prepared to allow the incorporation of fluorine‐18. The [18F]FPMPA in racemic, R, or S form was prepared in a 50 min synthesis in 38±5% yield (n=23, corrected for decay). The product was of high radiochemical and enantiomeric purity. The specific activity of the final product was 4.0±1.8 Ci/µmol at EOB (end of bombardment). This product may provide information about drug tissue distribution in animal models under chronic drug treatment. Copyright © 2008 John Wiley & Sons, Ltd.
Cell‐specific actions of HIV‐Tat and morphine on opioid receptor expression in glia
Authors: Turchan‐Cholewo Jadwiga , Dimayuga Filomena O. , Ding Qunxing , Keller Jeffrey N. , Hauser Kurt F. , Knapp Pamela E. , Bruce‐Keller Annadora J.
Published: March 2008

HIV‐1 patients who abuse opiate‐based drugs, including heroin and morphine, are at a higher risk of developing HIV dementia. The effects of opiates are mediated predominantly through opioid receptors, which are expressed on glial cells. As HIV‐1 infection in the CNS is restricted to glial cells, experiments were designed to measure the cell‐specific effects of HIV Tat and morphine exposure on opioid receptor expression in both astrocytes and microglia. Specifically, the cell‐type‐specific pattern of mu opioid receptor (MOR), delta opioid receptor (DOR), and kappa opioid receptor (KOR) localization (surface vs. intracellular) and expression of opioid receptor mRNA were determined after exposure to morphine in the presence and the absence of Tat in primary cultured microglia and astrocytes. Data show that morphine treatment caused significantly decreased cell surface expression of opioid receptors in microglia but not in astrocytes. However, morphine treatment in the presence of Tat significantly increased intracellular expression of opioid receptors and prevented morphine‐induced cell surface opioid receptor down‐regulation in microglia. These findings document that cell surface opioid receptor expression is divergently regulated by morphine in microglia compared with in astrocytes, and further suggest that HIV‐Tat could exacerbate opioid receptor signaling in microglia by increasing receptor expression and/or altering ligand‐induced trafficking of opioid receptors. © 2008 Wiley‐Liss, Inc.