bluuebunny/crossref_metadata_2025 huggingface dataset:
Activated Akt promotes increased resting T cell size, CD28‐independent T cell growth, and development of autoimmunity and lymphoma
Authors: Rathmell Jeffrey C. , Elstrom Rebecca L. , Cinalli Ryan M. , Thompson Craig B.
Published: July 2003

The mechanisms that regulate basal T cell size and metabolic activity are uncertain. Since the phosphatidylinositol‐3 phosphate kinase (PI3 K) and Akt (PKB) pathway has been shown in model organisms to regulate both cell size and metabolism, we generated transgenic mice expressing a constitutively active form of Akt (myristoylated Akt, mAkt) in T cells. Naive transgenic T cells were enlarged and had increased rates of glycolysis compared to control T cells. In addition, mAkt transgenic T cells resisted death‐by‐neglect upon in vitro culture. Upon activation, mAkt‐transgenic T cells were less dependent than control cells on costimulation through CD28 and could both grow rapidly and secrete cytokines in the absence of CD28 ligation. In addition, transgenic expression of mAkt led to the accumulation of CD4 T cells and B cells with age. Many aged mAkt‐transgenic mice also developed autoimmunity with immunoglobulin deposits on kidney glomeruli and displayed increased incidence of lymphoma. Together, these data show that Akt activation is sufficient to increase basal T cell size and metabolism. Enhancement of T cell metabolism by Akt and more rapid CD28‐independent T cell growth may contribute to the accumulation of excess immune cells and the development of lymphoma and autoimmunity.
The mer receptor tyrosine kinase: expression and function suggest a role in innate immunity
Authors: Behrens Edward M. , Gadue Paul , Gong Shun‐you , Garrett Stacey , Stein Paul L. , Cohen Philip L.
Published: July 2003

The mer receptor tyrosine kinase mediates phagocytosis of apoptotic cells and modulates cytokine production; it is also required for prevention of systemic autoimmune disease. Using a mer‐specific antibody, we have confirmed the presence of mer on macrophages and now report its expression on NK cells, NKT cells, and dendritic cells (DC). We found that DC do not require mer for ingestion of apoptotic cells, as DC from mer‐deficient mice phagocytose apoptotic cells normally. Mer was observed in splenic sections on cells outside follicular areas, probably representing DC and macrophages. Mer apparentlyparticipates in NKT‐cell antigen‐induced signaling, as NKT cells from mer‐deficient mice evinced much lower cytokine production after in vivo α‐galactosylceramide stimulation; this defect was intrinsic to the mer‐deficient NKT cells. Taken together, these studies show mer expression on cells of the innate immune system. Mer, through its binding of lipid antigens, may not only mediate ingestion of apoptotic cells, but also signal events in NK cells, NKT cells, and DC.
Structural Characterization of N‐Methylpyridoxine (MePN; PN = Vitamin B6) and Its Diorganotin Complexes [SnR2(MePN‐H)]I (R = Me, Et, Bu and Ph)
Authors: Casas José S. , Castiñeiras Alfonso , Condori Félix , Couce María D. , Russo Umberto , Sánchez Agustín , Sordo José , Varela José M.
Published: July 2003

For comparison with the corresponding pyridoxine complexes we have prepared dimethyl‐, diethyl‐, dibutyl‐ and diphenyltin(IV) complexes of N‐methylpyridoxine (MePN). The compounds [SnMe2(MePN−H)]I (1), [SnEt2(MePN−H)]I (2), [SnBu2(MePN−H)]I (3) and [SnPh2(MePN−H)]I·H2O (4) were isolated and characterized by IR, Raman, Mössbauer, 1H, 13C and 119Sn NMR spectroscopy, and by EI and FAB mass spectrometry. The crystal structures of [HMePN]I and of compounds 1, 2·2H2O and 3 were determined by X‐ray diffractometry. Their lattices contain dimeric [SnR2(MePN−H)]22+ units (R = Me, Et, Bu) in which two bridging‐chelating methylpyridoxinato anions link pentacoordinate Sn atoms with coordination polyhedra closer to square pyramids than to trigonal bipyramids. NMR results show that the dimeric cations persist in (CD3)2SO. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Degradation of the Second‐Generation Grubbs Metathesis Catalyst with Primary Alcohols and Oxygen − Isomerization and Hydrogenation Activities of Monocarbonyl Complexes
Authors: Dinger Maarten B. , Mol Johannes C.
Published: July 2003

Reaction of the second‐generation Grubbs metathesis catalyst [RuCl2(=CHPh)(H2IMes)(PCy3)] (2) (H2IMes = 1,3‐dimethyl‐4,5‐dihydroimidazol‐2‐ylidene) with primary alcohols in the presence of a base produced the complexes [RuClH(CO)(PCy3)2] (3) and [RuClH(CO)(H2IMes)(PCy3)] (5). When benzyl alcohol was used, the ruthenium phenyl complexes [RuClPh(CO)(PCy3)2] (4) and [RuClPh(CO)(H2IMes)(PCy3)] (7) were formed in addition to 3 and 5. Complex 7, characterised by an X‐ray structure analysis, was also formed on exposure of 2 to oxygen. The isomerization and hydrogenation activity of 7 was determined and compared with that of 3 and 4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Remote Rotamer Control: The Effect of a 4‐tert‐Butyl Group on the Coordination Chemistry of TpR Ligands
Authors: Rheingold Arnold L. , Liable‐Sands Louise M. , Golan James A. , Trofimenko Swiatoslaw
Published: July 2003

Three novel homoscorpionate ligands containing a tert‐butyl group in the 4‐position have been synthesized: hydrotris(4‐tert‐butylpyrazol‐1‐yl)borate (Tp4tBu), hydrotris(4‐tert‐butyl‐3‐p‐tolylpyrazol‐1‐yl)borate (TpTol,4tBu), and hydrotris(4‐tert‐butyl‐3‐isopropylpyrazol‐1‐yl)borate (TpiPr,4tBu). The 4‐tert‐butyl group does not alter the coordination chemistry of the first two ligands, relative to their 4‐H analogues, however, the coordination chemistry of the third ligand is dramatically changed, making it a “tetrahedral enforcer”. The complexes Co[Tp4tBu][TpNp] (1), Tl[TpTol,4tBu] (2), Rh[TpTol,4tBu](CO)2 (3), Co[TpiPr,4tBu]Cl (4), Co[TpiPr,4tBu]N3 (5) and Co[TpiPr,4tBu]NCS (6) have been structurally characterized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Pyrene‐Bridged Bis(phenanthroline) Ligands and Their Dinuclear Ruthenium(II) Complexes
Authors: Chouai Latif , Wu Feiyue , Jang Youngchan , Thummel Randolph P.
Published: July 2003

The Friedländer condensation of 8‐amino‐7‐quinolinecarbaldehyde with a series of four isomeric diacetylpyrenes provides the corresponding 1,3‐, 1,6‐, 1,8‐, and 2,7‐bis(2′‐[1′,10′]phenanthrolinyl)pyrenes. These ligands, along with the tetrahydro analogue to the 2,7‐pyrene‐bridged isomer, have been treated with [Ru([D8]bpy)2Cl2], where [D8]bpy = [D8]2,2′‐bipyridine, to afford the dinuclear RuII complexes, 1H NMR and X‐ray crystallographic analysis of which indicate that the bridging pyrene is layered between a [D8]bpy auxiliary ligand coordinated to each metal atom. Although well situated for π−π interactions, little such effect is seen on the photophysical and electrochemical properties of these complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Ferromagnetism in [Mn(Cp*)2]+‐Derived Complexes: the “Miraculous” Stacking in [Mn(Cp*)2][Ni(dmit)2]
Authors: Faulmann Christophe , Rivière Eric , Dorbes Stéphane , Senocq François , Coronado Eugenio , Cassoux Patrick
Published: July 2003

The synthesis and characterisation (X‐ray structure and magnetism) of metal complexes (Ni, Au) with the [Mn(Cp*)2]+ cation and the dmit2− and dmid2− ligands are reported. [Mn(Cp*)2][Ni(dmit)2] (1) and [Mn(Cp*)2][Au(dmit)2] (2) exhibit the same structural arrangement, built on stacks of [Ni(dmit)2]− pairs separated by two [Mn(Cp*)2]+ cations, showing a ···D+D+A−A−D+D+A−A−··· motif. On the contrary, the dmid2− derivative [Mn(Cp*)2][Ni(dmid)2]·CH3CN (3) exhibits a totally different structure, built on mixed layers composed of one [Ni(dmid)2]− unit separated by two [Mn(Cp*)2]+ cations, showing a ···D+D+A−D+D+A−···motif. The layers are separated from each other by perpendicular [Ni(dmid)2]− units and solvent molecules. Compound 2 exhibits antiferromagnetic interactions, whereas 1 and 3 exhibit ferromagnetic interactions at low temperature. Moreover, as confirmed by AC and DC magnetic susceptibility measurements, 1 is a ferrimagnet, the first ever derived from a 1,2‐bis‐dithiolene ligand. The ferromagnetic interactions in 1 and 3 are explained using the McConnell I mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
General equilibrium pricing of nonredundant forward contracts
Authors: Lioui Abraham , Poncet Patrice
Published: July 2003

We derive the general equilibrium of a dynamic financial market in which the investors' opportunity set
includes nonredundant forward contracts. We show that Breeden's (1979) consumption‐based
CAPM equation for forward contracts contains an extra term relative to that for cash assets. We name this term a
strategy risk premium. It compensates investors for the (systematic) risk that stems from their very
portfolio strategies when the latter involve nonredundant forward contracts. We also show that Merton's
(1973) multibeta intertemporal CAPM must be amended for forward contracts to exhibit
adjusted risk premia for the market portfolio and all relevant state variables, as opposed to
the usual risk premia for cash assets. Our results are shown not to depend on the usual
cash‐and‐carry relationship, which, in general, does not hold. We, nevertheless, provide a
well‐known special case where it does hold, albeit not grounded on the usual no‐arbitrage
argument. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:817–840, 2003
An examination of the effectiveness of static hedging in the presence of stochastic volatility
Authors: Fink Jason
Published: July 2003

Toft and Xuan (1998) use simulation evidence to demonstrate that the static hedging method of Derman
et al. (1995) performs inadequately when volatility is stochastic. Particularly, the greater the
“volatility of volatility,” the poorer the static hedge. This article presents an alternative static
hedging methodology, denoted the generalized static hedge, that appears to perform more reliably. Specifically,
the value, delta, and vega of the static hedges closely approximate those values of the barrier option being
hedged. Further, simulation evidence indicates that when volatility of volatility is large, the standard
deviation of simulated cash flows from the generalized static hedge position is less than the standard deviation
of simulated cash flows from previously defined static hedge positions. © 2003 Wiley Periodicals, Inc. Jrl
Fut Mark 23:859–890, 2003
The effect of spot and futures trading on stock index market volatility: A nonparametric approach
Authors: Illueca M. , Lafuente J. A.
Published: July 2003

This article provides empirical evidence on the intraday relation between
spot volatility and trading volume in the Spanish stock index futures
market. GARCH methodology is used to estimate spot volatility. We analyze
the potential relation between spot and futures trading volume and
spot volatility by estimating the corresponding conditional density functions
as proposed in Quah (1997). Our results reveal no significant link
between those variables. Similar findings arise when expected and unexpected
volume is considered. Our results suggest that derivative market is
not a force behind episodes of significant spot jump volatility. © 2003
Wiley Periodicals, Inc. Jrl Fut Mark 23:841–858, 2003
Voidable preference reform: a New Zealand perspective on shifting standards and goalposts
Authors: Telfer Thomas G. W.
Published: July 2003

While there is consensus that some form of avoiding power is required in the context of a bankruptcy or company liquidation, there is little agreement on the means to implement a voidable preference regime. The New Zealand experience of the past eight years illustrates the inherent difficulties in designing a workable voidable preference regime. The New Zealand Companies Act 1993 replaced the debtor's intention with a test premised on the overall effect of the transaction with an exception for transactions in the ordinary course of business. The ordinary course of business exception became the most litigated and controversial aspect of the 1993 reforms and recently the government has announced its intention to abandon the ordinary course safe harbour in the pending round of insolvency reform. The paper examines the origins of the 1993 reforms and offers an explanation for the failure of the effects based regime. The New Zealand regime placed too much power in the hands of the liquidator with the result that creditors bore the cost and burden of justifying why the transaction should be saved. Although Parliament enacted the effects based regime with a view to promoting better equality of treatment amongst creditors the regime failed because it achieved too much equality. Copyright © 2003 John Wiley & Sons, Ltd.
Characteristics of the oestrous cycle of Iberian red deer (Cervus elaphus hispanicus) assessed by progesterone profiles
Authors: Garcia Andres Jose , Landete‐Castillejos Tomas , Gomez‐Brunet Amelia , Garde Jose Julian , Gallego Laureano
Published: July 2003

This study examines the length of the oestrous cycle in 16 Iberian red deer females assessed by means of changes in progesterone concentrations, along with the changes in the profile of this hormone. Samples were collected three occasions per week from the week after calving (15 May to 15 June) up to May of the following year. The oestrous cycle lasted 19.57±0.29 days (range 10–27 d) calculated in 130 oestrous cycles examined. Progesterone titres did not rise above 0.5 ng/ml in the follicular phase, except in four samples. The maximum peak in progesterone concentration during the luteal phase remained above 1 ng/ml in most cases. Twenty‐five percent of the individuals studied (4 out of 16) showed an oestrous cycle lasting shorter than the mean (15.2±0.30 days) before the start of the reproductive season, followed by a period of sexual inactivity. The standard progesterone profile in natural oestrous cycles rose from basal levels to those above 0.5 ng/ml four days after onset of oestrus, reached a peak of 1.71±0.07 ng/ml and then declined to less than 0.2 ng/ml after day 20. Following the rapid decline of progesterone after day 14, the concentration remained around the baseline level of 0.1 to 0.2 ng/ml during the immediate pre‐ and post‐ovulatory phase of the cycle. J. Exp. Zool. 298A:143–149, 2003. © 2003 Wiley‐Liss, Inc.
Chloride cell responses to ion challenge in two tropical freshwater fish, the erythrinids Hoplias Malabaricus and Hoplerythrinus Unitaeniatus
Authors: Moron Sandro Estevan , Oba Eliane Tie , De Andrade Cássio Arilson , Fernandes Marisa Narciso
Published: July 2003

Chloride cell (CC) responses to ion challenge and plasma ion concentration were evaluated in two ecologically distinct erythrinids, Hoplias malabaricus, an exclusively water‐breathing species, and Hoplerythrinus unitaeniatus, a facultative air‐breathing fish, at one, two, seven, and 15 days of exposure to deionized water and to ion‐rich water. H. malabaricus displayed high CC proliferation on filament and lamellar epithelium during exposure to deionized water and significant CC proliferation in the filament epithelium on the first day of exposure to water rich in NaCl and Ca2+ and in the lamellar epithelium on the first, second, and seventh day of exposure to such water. CC proliferation in H. unitaeniatus occurred only in the lamellar epithelium of fish exposed to deionized water. CC proliferation on both species was not accompanied by significant increase of CC density in contact with the external medium. The increase in the CC fractional area (CCFA) resulted from the increase of individual CC apical surface area on the first and second days of exposure to deionized water in H. malabaricus and only on the first day in H. unitaeniatus. Plasma ions in both erythrinid species showed transitory changes and, on the fifteenth day of exposure to the two types of experimental water, the plasma ion concentration was similar to the control fish. The CC responses of these erythrinid fish showed that CC proliferation depends on previous CC density in the gill and is not related solely to exposure to ion‐poor water. Furthermore, CC proliferation in gill epithelium did not always involve an increase of CC density in contact with the external medium. J. Exp. Zool. 298A:93–104, 2003. © 2003 Wiley‐Liss, Inc.
Calcitonin‐like immunoreactivity in serum and tissues of the bonnethead shark, Sphyrna tiburo
Authors: Nichols Stephanie , Gelsleichter James , Manire Charles A. , Cailliet Gregor M.
Published: July 2003

Calcitonin is a 32‐amino acid peptide hormone that is best known for its actions in maintaining skeletal integrity and calcium homeostasis in mammals. Calcitonin also appears to function in regulating certain aspects of animal reproduction, but the nature of this role remains unclear, particularly in nonmammalian vertebrates. The present study investigated the relationship between calcitonin and reproduction in the bonnethead shark (Sphyrna tiburo), a well‐studied member of the oldest living vertebrate group (i.e. elasmobranchs) known to possess a calcitonin‐producing organ. Serum calcitonin concentrations were measured in 28 reproductively mature female S. tiburo using a heterologous enzyme‐linked immunosorbent assay (ELISA) system. Sites of calcitonin immunoreactivity were detected in tissues of mature female and embryonic S. tiburo using immunocytochemistry. Significant increases in serum calcitonin concentrations of mature female S. tiburo occurred during early stages of gestation, a period characterized by yolk‐dependency of developing embryos. Immunoreactive calcitonin was detected in the duodenum and pancreas of embryonic S. tiburo sampled during the same period. The results from this study suggest that calcitonin obtained from endogenous and/or maternal sources may function in regulating yolk digestion in embryonic S. tiburo. Therefore, the association between calcitonin and reproduction in elasmobranchs may reflect an important role for this hormone in embryonic development. J. Exp. Zool. 298A:150–161, 2003. © 2003 Wiley‐Liss, Inc.
Comparative characteristic of Mytilus muscle cells developed in vitro and in vivo
Authors: Plotnikov Serguei V. , Karpenko Alexander A. , Odintsova Nelly A.
Published: July 2003

The mussel cells from premyogenic larval stages are capable of differentiation into smooth muscle cells in vitro. However, the behavior and protein composition of these cells are not completely identical to those of smooth muscle cells of adult mussels. In this study we compared some properties of mussel muscle cells forming from cells of trochophore (premyogenic larval stage) in vitro with those of muscle cells of veliger and adult mussel. We found a substantial difference between the contractile apparatus protein composition of veliger muscle and cultivated cells. Myorod, one of the molecular markers of the phenotype of mollusc smooth muscle cells (Shelud'ko et al., 1999, Comp Biochem Physiol 122:277–285), is not a constituent of the contractile apparatus of veliger muscle. At the same time the protein composition of contractile apparatus in cultivated cells was similar to that of adult Mytilus muscles. There were only few quantitative differences between them. The contractile activity of cultivated cells was changing in time. The kinetic parameters of first spontaneous contractions were similar to those of phasic contractions, while their period was close to that of tonic contractions. After 50–55 hrs cultivation the cells produced both phasic and tonic contractions, but the character of contractile activity of cultivated cells was regulated after six days of cultivation only. However, there were no muscle cells in vitro, whose contractile activity was similar to that of veliger muscle cells. So, we concluded that properties of muscle cells forming from premyogenic larval mussel cells in culture are similar to those of muscle cells of the adult mussel, but not of veliger. J. Exp. Zool. 298A:77–85, 2003. © 2003 Wiley‐Liss, Inc.
Farnesyl pyrophosphate promotes and is essential for the binding of RACK1 With β‐tubulin
Authors: Huang Chein‐Fuang , Fan Jun‐Huei , Chuang Nin‐Nin
Published: July 2003

Receptors for activated C kinase (RACKs) are a group of protein kinase C (PKC) binding proteins that have been shown to be crucial in the translocation and subsequent functioning of PKC on activation. RACK1 isolated from BALB/3T3 cells transformed with S‐ras(Q61K) exhibits receptor activity for PKCγ as competent as that of RACK1 from BALB/3T3 cells without transformation. However, the ability of RACK1 from transformed cells to bind with β‐tubulin peptide specific for Taxol (PEPtaxol) is defective. Interestingly, when farnesyl pyrophosphate was added at the submicrogram level, the association between RACK1 and PEPtaxol was enhanced significantly in a dosage‐dependent manner. A parallel finding for the enhanced effect of farnesyl pyrophosphate on tubulin binding was established with mice RACK1 expressed in vitro. On the other hand, geranylgeranyl pyrophosphate, and retinoic acid failed to modulate the binding between RACK1 and tubulin. The dissociation of RACK1 and tubulin was not effective at damaging the binding between RACK1 and membrane receptor integrin β1 in transformed cells. These findings indicate that depletion of farnesyl pyrophosphate provides a mechanism to seal PKC signaling on the membrane with immobile RACK1 and to divert cells to aberrant growth, such as transformation. J. Exp. Zool. 298A:119–127, 2003. © 2003 Wiley‐Liss, Inc.
Proton MR spectroscopic studies of chronic alcohol exposure on the rat brain
Authors: Lee Haakil , Holburn George H. , Price Ronald R.
Published: July 2003

Purpose:

To better understand the long‐term pathophysiologic mechanisms of alcoholism‐related organic brain damage by serially assessing brain metabolites in chronically exposed rats using both in vivo magnetic resonance spectroscopy (MRS) and high‐resolution nuclear magnetic resonance (NMR) from brain extracts.

Materials and Methods:

The alcoholic regimen was continued up to 60 weeks. In vivo proton MRS studies were performed at 200 MHz using a small animal imaging/spectrometer. In vitro rat brain extracts were also examined using a 500 MHz vertical bore magnet. Comparison measurements were also obtained in an age‐matched control group.

Results:

In vivo results showed that there is a significant increase in the Cho/NAA ratio in the chronic alcohol‐exposed group that reached a maximum around 16 weeks. After 44 weeks of alcohol exposure, Cho/NAA in the alcohol group decreased significantly from its maximum value to a value that was significantly lower than those from the control groups. Brain extract studies demonstrated that PC and GPC were the main components responsible for the observed in vivo spectral changes after 16 and 60 weeks of alcohol consumption, respectively.

Conclusion:

The fluctuation of choline‐containing metabolites during alcohol intoxication could explain sometimes seemingly conflicting and confusing results from MRS studies in human and animal studies in which the duration of alcohol consumption and amount are varied widely. J. Magn. Reson. Imaging 2003;18:147–151. © 2003 Wiley‐Liss, Inc.
Quantitative perfusion mapping of the human lung using 1H spin labeling
Authors: Wang Tungte , Schultz Georg , Hebestreit Helge , Hebestreit Alexandra , Hahn Dietbert , Jakob Peter M.
Published: July 2003

Purpose:

To evaluate the feasibility and reproducibility of a noninvasive, rapid and quantitative pulmonary perfusion mapping method using a two‐compartment tissue model in combination with a 1H spin labeling technique.

Materials and Methods:

Ten healthy volunteers and three patients with cystic fibrosis (CF) were examined on a 1.5‐T whole‐body scanner. Global and selective lung T1 maps based on an inversion recovery Snapshot FLASH technique were acquired from each subject with breath‐holds at end‐expiration. For comparison, corresponding Gd‐DTPA‐enhanced 1H MR perfusion images were also obtained from each CF patient.

Results:

Quantitative perfusion maps were calculated from the global and selective T1 maps. The measured perfusion rates of the upper right lung in volunteers ranged from 400 to 600 mL/100 g/minute. The method showed a high intra‐study reproducibility and low relative errors. In CF‐patients, perfusion defects detected using Gd‐DTPA‐enhanced MR imaging were also detected using the spin labeling method. The perfusion rates of diseased lung tissues were less than 200 mL/100 g/minute.

Conclusion:

Noninvasive, robust and quantitative 1H MR mapping of pulmonary perfusion was successfully performed using a rapid lung T1 mapping in combination with spin labeling within the imaging slice. The proposed method has the potential to provide both important qualitative functional information and quantitative pulmonary perfusion rates in various lung diseases at various stages without the need of contrast agents. J. Magn. Reson. Imaging 2003;18:260–265. © 2003 Wiley‐Liss, Inc.
Fat suppression gradient‐echo magnetic resonance imaging of experimental articular cartilage lesions: Comparison between phase‐contrast method at 0.23T and chemical shift selective method at 1.5T
Authors: Palosaari Kari , Ojala Risto , Blanco‐Sequeiros Roberto , Tervonen Osmo
Published: July 2003

Purpose:

To evaluate the diagnostic performance of a newly developed single‐scan phase‐contrast water‐fat imaging technique for fat suppression at 0.23T open magnet, compared to the conventional chemical shift selective fat suppression method at 1.5T, in the detection of experimental articular cartilage lesions.

Materials and Methods:

Sixty regions of 20 knee joint specimens of pigs with artificially created articular cartilage lesions were examined with 0.23T and 1.5T MR scanners. Sagittal fat‐suppressed three‐dimensional gradient‐echo (3D GRE) images, obtained with the phase‐contrast method at 0.23T, and fat‐suppressed three‐dimensional spoiled gradient recalled echo (3D SPGR) images, obtained with a chemical shift selective method at 1.5T, were evaluated. Diagnostic performance was analyzed. The conspicuity of the lesions, the amount of artifacts, and the uniformity of fat suppression were evaluated. The contrast‐to‐noise (CNR) values of cartilage‐to‐bone marrow, and cartilage‐to‐infrapatellar fat were calculated.

Results:

At 0.23T, sensitivity and specificity were 80% and 95% for partial cartilage lesions (grade 2), and 91% and 100% for full‐thickness lesions (grade 3). At 1.5T, sensitivity and specificity were 85% and 95% for grade 2 lesions, and 96% and 97% for grade 3 lesions. No significant difference was detected in the conspicuity of lesions. The uniformity of fat suppression was more constant with 3D SPGR images compared to 3D GRE images. More susceptibility artifacts, derived from the procedure of creating lesions, were detected at 1.5T. The cartilage‐to‐fat CNRs were significantly higher with high‐field images.

Conclusion:

Phase‐contrast method for fat suppression at 0.23T is a useful technique in detecting articular cartilage lesions. J. Magn. Reson. Imaging 2003;18:225–231. © 2003 Wiley‐Liss, Inc.
Serial MR imaging with MS‐325 for evaluating female sexual arousal response: Determination of intrasubject reproducibility
Authors: Maravilla Kenneth R. , Cao Yunyu , Heiman Julia R. , Garland Patricia A. , Peterson Barry T. , Carter Wayne O. , Weisskoff Robert M.
Published: July 2003

Purpose

To determine if a similar sexual arousal response in normal, healthy women could be obtained and monitored by serial magnetic resonance (MR) imaging at two separate sessions.

Materials and Methods

Serial imaging of the external genitalia was performed on nine healthy, sexually functional women at two separate MR sessions after administration of the contrast agent, MS‐325. Images were obtained every three minutes during a 45‐minute study period during each MR session. The second MR session began approximately 45 minutes after the end of the first MR session. While undergoing imaging, subjects viewed videotapes that contained neutral and sexually‐explicit material through an audiovisual system. Analysis performed at each time point consisted of visual evaluation of the images, clitoral and femoral vein signal intensity measurements, relative regional blood volume calculations, and clitoral volume measurements. Statistical analysis of the results consisted of calculating correlation coefficients of the two MR sessions by using the least square fit method.

Results

All nine subjects reported sexual arousal on subjective questionnaires at each MR session. Post‐contrast MS‐325 MR images showed strong enhancement of the external genitalia at each session. There was excellent correlation between the two sessions for the clitoral volume measurements of all nine subjects. The correlation coefficient, r2, was 0.95.

Conclusion

The sexual arousal response in normal, healthy women can be monitored by serial imaging combined with the use of the contrast agent, MS‐325, and similar results can be reproduced at two different MR sessions. This method holds promise for future studies of women with female sexual arousal dysfunction. J. Magn. Reson. Imaging 2003;18:216–224. © 2003 Wiley‐Liss, Inc.
Automated unwrapping of MR phase images applied to BOLD MR‐venography at 3 Tesla
Authors: Rauscher Alexander , Barth Markus , Reichenbach Jürgen R. , Stollberger Rudolf , Moser Ewald
Published: July 2003

Purpose:

To improve the diagnostic value of BOLD MR‐Venography by removing artifacts related to phase wrapping, particularly in regions of large background susceptibilities at high magnetic field strengths.

Materials and Methods:

High resolution, T‐weighted, single echo images were acquired on a 3 T system (Medspec 30/80 Avance, Bruker Medical, Ettlingen, Germany) with a three‐dimensional, first order velocity compensated gradient echo sequence using a quadrature transmit/receive birdcage head coil. Data of nine healthy subjects and 19 patients were evaluated (age range: 27 to 76 years). To achieve improved MR‐venograms, a fully automated region‐growing phase unwrapping algorithm and subsequent high pass filtering were applied to phase images prior to the computation of minimum intensity projections.

Results:

Considerably improved visualization of venous structures in regions of large background susceptibility‐induced field inhomogeneities is demonstrated in healthy subjects and patients with brain tumors.

Conclusion:

BOLD MR venograms are improved compared to previous post‐processing algorithms. It is now feasible to obtain high‐resolution images also in inhomogeneous regions, which increases the clinical potential of BOLD MR‐Venography. J. Magn. Reson. Imaging 2003;18:175–180. © 2003 Wiley‐Liss, Inc.
Acute infarct of the corpus callosum: Appearance on diffusion‐weighted MR imaging and MR spectroscopy
Authors: Riedy Gerard , Melhem Elias R.
Published: July 2003

Few reports of corpus callosum infarction are published in the radiologic literature. We present a case of an atypical infarction of the corpus callosum and adjacent gyri involving both anterior cerebral artery territories. Standard magnetic resonance (MR) imaging was performed including diffusion weighted imaging. In addition, perfusion‐weighted imaging and MR spectroscopy were employed to further characterize the patient's corpus callosal lesion. On MR imaging and spectroscopic examination, the lesion demonstrated T2 hyper‐intensity, restricted diffusion, and the metabolite lactate. While the MR imaging appearance of this bilateral infarction has some characteristics that mimic tumor, employment of the full range of MR techniques can obviate the need for biopsy in acute infarcts of the corpus callosum. J. Magn. Reson. Imaging 2003;18:255–259. © 2003 Wiley‐Liss, Inc.
Improvement in the quantification of myocardial perfusion using an automatic spline‐based registration algorithm
Authors: Dornier Christophe , Ivancevic Marko K. , Thévenaz Philippe , Vallée Jean‐Paul
Published: July 2003

Purpose:

To improve the quantification of myocardial perfusion by registering the time series of magnetic resonance (MR) images with injection of gadolinium.

Materials and Methods:

Eight patients underwent MR scans to perform myocardial perfusion exam. Two short axis views of the left ventricle (LV) were acquired in free breathing. Two masks for performing the spatial registration of the images were evaluated. The registration was based on pixel intensity in a multi‐resolution scheme. The efficiency of this correction was evaluated by calculating geometric residual displacement of the LV and by fitting the data to a compartment model fit with two parameters: K1, the blood‐to‐myocardium transfer coefficient, and Vd, the distribution volume of the contrast media.

Results:

The registration stage allowed a decrease in the observed motion of the LV from more than 1.98 ± 0.68 mm to less than 0.56 ± 0.18 mm (mean ± SD). Variability obtained in the perfusion analysis decreased from 46 ± 103% to 5± 4% for K1 parameter and from 18 ± 21% to 5 ± 5% for Vd parameter.

Conclusion:

As with manual correction, this automatic motion correction leads to accurate perfusion parameters in dynamic cardiac MR imaging after contrast agent injection. This automatic stage requires placing only one mask over one frame of the perfusion study instead of manually shifting each image to fit a reference image of the perfusion study. J. Magn. Reson. Imaging 2003;18:160–168. © 2003 Wiley‐Liss, Inc.
Dendritic polymers: from efficient catalysis to drug delivery
Authors: Kakkar Ashok K.
Published: July 2003

Dendritic polymers constitute an intriguing class of macromolecules that offer tremendous potential in designing new materaisl for applications in areas such as catalysis and small molecule loading and delivery. Synthesis of a variety of dendritic polymers using a simple and highly versatile synthetic methodology has enabled us to carry out a detailed investigation of dendritic effects in transition metal catalyzed organic transformations. Small dye molecules such as p‐nitroaninline and DR1 could be loaded into the intrinsic cavities of the backbone of 3,5‐dihydroxybenzyl alcohol based dendrimers, leading to a change in physical properties of both the dye and the dendrimer. We are also exploring the use of dendrimers as templates to prepare network carriers containing cavities of predetermined size and disposition.
Electron transport in conjugated metallopolymers
Authors: Cameron Colin G. , MacLean Brian J. , Pickup Peter G.
Published: July 2003

Superexchange interactions between metal centers coordinated to various conjugated polymer backbones have been shown to enhance the rate of electron transport through the polymer. Results for Ru and Os bipyridine moieties complexed to polybenzimidzoles and poly(bithiophene‐co‐bithiazole)s are reviewed. The evidence for superexchange mediated electron transport, and the factors that influence the rate of electron hopping between metal centers, are discussed.
Phosphine‐based coordination cages and nanoporous coordination polymers
Authors: James Stuart L. , Xu Xingling , Law Robert V.
Published: July 2003

Recent findings in the use of multidentate phosphines to synthesise porous coordination polymers (metal‐organic frameworks) and their possible precursor cages are reviewed. Additional recent investigations into using large adamantoid Age cages as polymer vertices in giant diamandoid structures are also presented. The results are discussed in terms of possible strategies for the controled synthesis of porous coordination polymers.
Nano‐scale metallodendritic complexes in electron‐transfer processes and catalysis
Authors: Astruc Didier , Blais Jean‐Claude , Daniel Marie‐Christine , Martinez Victor , Nlate Sylvain , Ruiz Jaime
Published: July 2003

Nano‐sized metallodendrimers in which the equivalent metal fragments are located at the periphery can be assembled covalently, by H‐bonding (supramolecular) or onto dendronized nanoparticles. They can be used as electron‐reservoirs, i.e. molecular batteries, redox catalysts and sensors for the recognition of biologically relevant anions. They can also be deposited on metal surfaces or electrodes, which optimizes their use as recoverable sensors.
Iridium(III) complexes as polymer bound oxygen sensors
Authors: DeRosa Maria C. , Mosher Peter J. , Evans Christopher E.B. , Crutchley Robert J.
Published: July 2003

New luminescent oxygen sensors have been prepared by covalent attachment of iridium complex luminophores to a silicone polymer. The oxygen sensor properties of these novel materials were compared to related sensors in which the luminophore is dispersed within the polymer matrix. Covalently bound luminophore materials showed increased sensitivity to oxygen over dispersions in pure silicone polymer as well as in blends with polystyrene, which was added to improve the mechanical properties of the material.
Synthesis and properties of new phosphorus‐functionalized bithiophene materials
Authors: Baumgartner Thomas
Published: July 2003

The synthesis and reactivity of the novel dithieno[3,2‐b:2′,3′‐d]‐phosphole system and its potential use in polymeric sensory materials was investigated. Due to the nucleophilic nature of the phosphorus atom, these materials were found to be easily tunable. Classical reactions at the phosphorus center were performed to modify the electronic structure of the system and the corresponding changes were detected by UV/Vis and fluorescence spectroscopy. Depending on the oxidation state of the central phosphorus atom or its substitution pattern, the dithieno[3,2‐b:2′,3′‐d]‐phospholes show varying wavelengths for absorption and emission allowing to distinguish between different compounds by means of optical spectroscopy.
Organometallic conducting polymers synthesized by metallacycling polymerization
Authors: Nishihara Hiroshi , Kurashina Masashi , Murata Masaki
Published: July 2003

The study on the synthesis of π‐conjugated polymers using cobaltacyclopentadiene formation reaction of CpCo(PPh3)2 and conjugated diacetylene and the structure and physical properties of the polymers is overviewed. The substituents on the diacetylene affect crucially the solubility, the degree of polymerization, redox properties, and electronic structures and so on. Recent synthesis of a ruthenacyclopentatriene polymers by metallacyling polymerization is also described.
Hybrid inorganic/organic crosslinked resins containing polyhedral oligomeric silsesquioxanes
Authors: Pittman Jr. Charles U. , Li Gui‐Zhi , Ni Hanli
Published: July 2003

The incorporation of both monofunctional and multifunctional polyhedral oligomeric silsesquioxane (POSS) derivatives into crosslinked resins has been conducted as a route to synthesize hybrid organic/inorganic nanocomposites. The central cores of POSS molecules contain an inorganic cage with (SiO1.5)n stoichiometry where n=8,10 and 12. Each Si atom is capped with one H or R function giving an organic outer shell surrounding the nanometer‐sized inorganic inner cage. By including polymerizable functions on the R groups, a hybrid organic/inorganic macromer is obtained which can be copolymerized with organic monomers to create thermoplastic or thermoset systems. We have focused on incorporating POSS derivatives into crosslinking resins of the following types: (1) dicyclopentadiene (2) epoxies (3) vinyl esters (4) styrene‐DVB (5) MMA/1,4‐butane dimethacrylate (6) phenolics and (7) cyanate esters. One goal has been to determine if molecular dispersion of the POSS macromers has been achieved or if various degrees of aggregation occur during crosslinked resin formation. As network formation proceeds, a kinetic race between POSS molecular incorporation into the network versus phase separation into POSS‐rich regions (which then polymerize) occurs. Ultimately, we hope to determine the effects of such microstructural features on properties. Combustion of these hybrids creates a SiO2‐like surface layer that retards flame spread. Dynamic mechanical properties have been studied.
Exploiting catalytic dehydrogenative coupling in the synthesis and study of polysilanes
Authors: Rosenberg Lisa
Published: July 2003

A reinvestigation of the catalytic activity of Wilkinson's catalyst, (Ph3P)3RhCl (1), for the dehydrogenative coupling reactions of secondary silanes has pointed the way toward the synthesis of key oligosilane reagents for structure property correlation studies of polysilanes. Implications are discussed for understanding the mechanisms of coupling and redistribution reactions of silanes mediated by such late metal centres. Also described are attempts to derivatize Si‐H bonds in the resulting oligosilanes, which is highly relevant to the development of improved methods for the post‐polymerization functionalization of polysilanes containing Si‐H bonds.
Polymer science with main group elements and transition metals
Authors: Manners Ian
Published: July 2003

The efficient formation of soluble, processable polymers with main chains containing inorganic elements provides a synthetic challenge but represents potentially important approach to new macromolecular and supramolecular materials with interesting properties. This talk will survey some of the recent research performed in our group concerning the development of controlled routes to a variety of different inorganic polymer systems and the use of the resulting materials in self‐assembly processes.
Towards photonic ink (P‐ink): a polychrome, fast response metallopolymer gel photonic crystal device
Authors: Arsenault André C. , Míguez Hernán , Kitaev Vladimir , Ozin Geoffrey A. , Manners Ian
Published: July 2003

We demonstrate here a new kind of planarized and oriented colloidal photonic crystal device whose optical stop‐band position, width and intensity can be reversibly redox and solvent tuned over a broad wavelength range by an anisotropic expansion of the photonic lattice. The material is composed of silica microspheres in a matrix of crosslinked polyferrocenylsilane[1], a metallopolymer network with a continuously variable state of oxidation[2]. Optical data was fitted using a scalar wave approximation, with a congruence to experimental data, allowing facile extraction of information concerning polymer swelling behaviour. The chemomechanical polychrome optical response of the material was exceptionally fast, attaining its fully swollen state from the dry shrunken state on a sub‐second time‐scale.
Lithographic applications of highly metallized polyferrocenylsilanes
Authors: Clendenning Scott B. , Manners Ian
Published: July 2003

Organometallic polymers are excellent candidates for the introduction of metals into nanostructures using lithographic techniques due to their inherently high and uniform metal loadings and processibility. Soluble, high molecular weight polyferrocenylsilanes possess unique physical properties and function as excellent ceramic precusors. Recent advances in the use of lithographic techniques with a highly metallized PFS resist to form new nanopatterned materials will be presented.
A Computational Study of the Polymerization‐Induced Phase Separation Phenomenon in Polymer Solutions under a Temperature Gradient
Authors: Lee Kam‐Wa D. , Chan Philip K. , Feng Xianshe
Published: July 2003

This paper studied the polymerization‐induced phase separation phenomenon (spinodal decomposition) in a model binary polymer solution under a linear spatial temperature gradient for the purpose of fabricating anisotropic polymeric materials by using mathematical modeling and computer simulation. Reaction kinetics were incorporated with the non‐linear Cahn‐Hilliard theory and the Flory‐Huggins free energy expression in the model. Moreover, the slow mode theory and Rouse law were used to account for polymer diffusion. It was found that an anisotropic morphology was obtained when a temperature gradient was imposed along the polymer solution sample. The direction of the structural anisotropy, however, depended significantly on the overall phase separation time. The presence of a temperature gradient along the polymer solution sample generated a spatial variation in polymerization rate, which resulted in a spatial variation of quench depth. Consequently, at a given instant, the phase separation at different locations of the polymer solution was at different stages of spinodal decomposition. The droplet size formed along the polymer solution was therefore dependent on the polymerization rate, the quench depth and the stage of spinodal decomposition. Furthermore, the spatial temperature gradient produced a spatial variation in the process induction time, which contains the polymerization induction time and phase separation induction time. It was also found that the polymerization induction time played a significant role on the spatial variation in the overall process induction time.

image
Free Radical Bulk Polymerization of Styrene: Simulation of Molecular Weight Distributions to High Conversion Using Experimentally Obtained Rate Coefficients
Authors: Zetterlund Per B. , Yamazoe Hirotomo , Yamada Bunichiro
Published: July 2003

Previously obtained experimental conversion‐dependences of the propagation rate coefficient (kp), the termination rate coefficient (kt) and the initiator efficiency (f) for the free‐radical bulk polymerization of styrene at 70 °C have been used to simulate the full molecular weight distributions (MWD) to high conversion using the software package PREDICI, providing a robust test of the kinetic model adopted. Satisfactory agreement with the experimental MWD's (GPC) was obtained up to approximately 70% conversion. Beyond 70% conversion, the high MW shoulder that appears was correctly predicted, although the amount of such polymer was somewhat underestimated. This discrepancy is believed to probably have its origin in experimental error in the conversion‐dependences of kp, kt and f, in particular kt, that were employed in the simulations, rather than indicate a more fundamental short‐coming of the model employed.

image
Simulation of Molecular Weight Distributions Obtained by Pulsed Laser Polymerization (PLP): New Analytical Expressions Including Intramolecular Chain Transfer to the Polymer
Authors: Nikitin Anatoly N. , Castignolles Patrice , Charleux Bernadette , Vairon Jean‐Pierre
Published: July 2003

A new approach for the simulation of PLP (pulsed laser polymerization) is presented. This approach allows one to obtain new analytical solutions for different polymerization schemes, including either chain transfer to the monomer or intramolecular chain transfer to the polymer. The first results of the simulation of PLP experiments on n‐butyl acrylate at 20 °C and ambient pressure are presented.

MWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).

image

MWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).