bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential expression of TGFβ‐stimulated clone 22 in normal prostate and prostate cancer
Authors: Rentsch Cyrill A. , Cecchini Marco G. , Schwaninger Ruth , Germann Markus , Markwalder Regula , Heller Manfred , van der Pluijm Gabri , Thalmann George N. , Wetterwald Antoinette
Published: August 2005

The transforming growth factor‐β (TGFβ) superfamily and its downstream effector genes are key regulators of epithelial homeostasis. Altered expression of these genes may be associated with malignant transformation of the prostate gland. The cDNA array analysis of differential expression of the TGFβ superfamily and functionally related genes between patient‐matched noncancerous prostate (NP) and prostate cancer (PC) bulk tissue specimens highlighted two genes, namely TGFβ‐stimulated clone‐22 (TSC‐22) and Id4. Verification of their mRNA expression by real‐time PCR in patient‐matched NP and PC bulk tissue, in laser‐captured pure epithelial and cancer cells and in NP and PC cell lines confirmed TSC‐22 underexpression, but not Id4 overexpression, in PC and in human PC cell lines. Immunohistochemical analysis showed that TSC‐22 protein expression in NP is restricted to the basal cells and colocalizes with the basal cell marker cytokeratin 5. In contrast, all matched PC samples lack TSC‐22 immunoreactivity. Likewise, PC cell lines do not show detectable TSC‐22 protein expression as shown by immunoblotting. TSC‐22 should be considered as a novel basal cell marker, potentially useful for studying lineage determination within the epithelial compartment of the prostate. Conversely, lack of TSC‐22 seems to be a hallmark of malignant transformation of the prostate epithelium. Accordingly, TSC‐22 immunohistochemistry may prove to be a diagnostic tool for discriminating benign lesions from malignant ones of the prostate. The suggested tumour suppressor function of TSC‐22 warrants further investigation on its role in prostate carcinogenesis and on the TSC‐22 pathway as a candidate therapeutic target in PC. © 2005 Wiley‐Liss, Inc.
Scaled interfacial activity of proteins at a hydrophobic solid/aqueous‐buffer interface
Authors: Krishnan Anandi , Liu Yi‐Hsiu , Cha Paul , Allara David , Vogler Erwin A.
Published: August 2005

Contact‐angle goniometry confirms that interfacial energetics of protein adsorption to the hydrophobic solid/aqueous‐buffer (solid–liquid, SL) surface is not fundamentally different than adsorption to the aqueous‐buffer/air (liquid–vapor, LV) interface measured by pendant‐drop tensiometry. Adsorption isotherms of 9 globular blood proteins with molecular weight (MW) spanning from 10 to 1000 kDa on methyl‐terminated self‐assembled monolayer surfaces demonstrate that (i) proteins are weak surfactants, reducing contact angles by no more than about 15° at maximum solution concentrations (∼10 mg/mL); (ii) the corresponding dynamic range of spreading pressure Πa < 20 mN/m; and (iii) the maximum spreading pressure Π for these diverse proteins falls within a relatively narrow 5 mN/m band. As with adsorption to the LV interface, we find that concentration scaling substantially alters perception of protein interfacial activity measured by Πa. Proteins appear more similar than dissimilar on a weight/volume basis whereas molarity scaling reveals a systematic ordering by MW, suggesting that adsorption is substantially driven by solution concentration rather than diversity in protein amphilicity. Scaling as a ratio‐to‐physiological‐concentration demonstrates that certain proteins exhibit Π at‐and‐well‐below physiological concentration whereas others require substantially higher solution concentration to attain Π. Important among this latter category of proteins is blood factor XII, assumed by the classical biochemical mechanism of plasma coagulation to be highly surface active, even in the presence of overwhelming concentrations of other blood constituents such as albumin and immunoglobulin that are shown by this work to be among the class of highly surface‐active proteins at physiologic concentration. The overarching interpretation of this work is that water plays a dominant, controlling role in the adsorption of globular‐blood proteins to hydrophobic surfaces and that energetics of hydration control the amount of protein adsorbed to poorly water‐wettable biomaterials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Interfacial chemistry of class II composite restoration: Structure analysis
Authors: Wang Yong , Spencer Paulette
Published: August 2005

The gingival margins of class II composite restorations are particularly vulnerable to marginal leakage and secondary caries. In identifying the factors contributing to caries development, the molecular structure and differences in the structure at the proximal and gingival margins have been largely overlooked. The purpose of this study was to compare the molecular structure at the adhesive/dentin interface of the proximal and gingival walls of class II composite restorations. Class II preparations were cut in 12 unerupted third molars with a water‐cooled high‐speed dental handpiece. The prepared teeth were randomly selected for treatment with Single Bond (SB) + Z100 (3M). Teeth were restored, per manufacturer's directions, under humidity and temperature characteristic of the oral cavity. Restored teeth were kept in sterile Delbecco's phosphate saline for 48 h. The samples were sectioned occluso‐gingivally and micro‐Raman spectra were acquired at ∼1.5‐μm spatial resolution across the composite/adhesive/dentin interfaces. Samples were wet throughout spectral acquisition. Raman spectral characteristics at the proximal and gingival margins were distinctly different; the depth of demineralized dentin was 6–7 μm at proximal margin, 12–13 μm at gingival margin. SB adhesive penetrated the depth of demineralized dentin in a gradient at the proximal margin. The “single bottle” adhesive used in this study, gradually penetrated the depth of the demineralized dentin at the proximal margin but failed to infiltrate the depth at the gingival margin, leaving a thick exposed collagen layer. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
The effect of limited lateral resolution in the measurement of implant surface roughness: A computer simulation
Authors: Hansson S. , Hansson K. N.
Published: August 2005

The surface roughness of dental implants affects the bone response elicited. Surface roughness is generally described by a range of surface texture parameters. The aim of the present study was to use computerized simulation to investigate the extent to which the lateral resolution of an instrument/method limits the accuracy of certain surface roughness parameters. The lateral resolution was defined as the pixel size of a profiling system. A surface roughness was simulated by a trigonometric function with random periodicity and amplitude. The function was divided into an array of pixels simulating the pixels of the profiling system. The mean height value for each pixel was used to calculate the surface roughness parameters. It was found that the accuracy of all the surface roughness parameters investigated decreased with increasing pixel size. This tendency was most pronounced for mean slope and developed length ratio; amounting to about 80% of their true values for a pixel size of 20% of the true mean high‐spot spacing. It was concluded that the lateral resolution of an instrument/method severely compromises the precision of surface roughness parameters measured for roughness features with a mean high‐spot spacing less than five times the lateral resolution. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Fault tolerant forwarding and optical indexes: A design theory approach
Authors: Gupta Arvind , Maňuch Ján , Stacho Ladislav
Published: August 2005

We study the problem of designing fault tolerant routings in both complete and complete bipartite optical networks. We show that this problem has strong connections to various fundamental problems in design theory. Using a design theory approach, we find optimal f‐fault tolerant arc‐forwarding indexes for all complete networks and all complete balanced bipartite networks. Similarly, we find almost exact values for f‐fault tolerant optical indexes for these networks. © 2005 Wiley Periodicals, Inc. J Combin Designs
Steiner triple systems with two disjoint subsystems
Authors: Bryant Darryn , Horsley Daniel
Published: August 2005

It is shown that there exists a triangle decomposition of the graph obtained from the complete graph of ordervby removing the edges of two vertex disjoint complete subgraphs of ordersuandwif and only ifu,w, andvare odd,${{v}\choose 2}-{u\choose 2}- {w\choose 2}\equiv 0$(mod 3), and${v}\ge w + u +{\rm max} \{ u,w\}$. Such decompositions are equivalent to group divisible designs with block size 3, one group of sizeu, one group of sizew, andv–u–wgroups of size 1. This result settles the existence problem for Steiner triple systems having two disjoint specified subsystems, thereby generalizing the well‐known theorem of Doyen and Wilson on the existence of Steiner triple systems with a single specified subsystem. © 2005 Wiley Periodicals, Inc. J Combin Designs
Bioleaching of acid‐consuming low‐grade nickel ore with elemental sulfur addition and subsequent acid generation
Authors: Salo‐Zieman Virpi LA , Kinnunen Päivi H‐M , Puhakka Jaakko A
Published: August 2005

The bioleaching of a nickel concentrate and an acid‐consuming nickel ore was studied using a co‐culture of Acidithiobacillus ferrooxidans and A. thiooxidans, as well as a thermophilic enrichment culture, VS2. The VS2 was dominated by a Sulfolobus species related to Sulfolobus metallicus. Nickel concentrate was readily solubilized with A. ferrooxidans and the VS2, resulting in nickel yields of 56% and 100%, respectively. Low‐grade nickel ore required 350 g H2SO4 kg−1 ore for maintaining the pH of the leaching solution below 3. To overcome the high acid demand, biological elemental sulfur oxidation was combined with the ore leaching. Leaching of a 2% (wt/vol) nickel ore with a co‐culture of A. thiooxidans and A. ferrooxidans resulted in nickel yield of up to 86% with acid supplementation of 290 g H2SO4 kg−1 ore. When coupled with biological sulfur oxidation, an 86% nickel recovery was achieved with 0.5% (wt/vol) ore concentration without further sulfuric acid addition. The VS2 oxidized sulfur at a rate of 0.063 g L−1 d−1 and the simultaneous nickel ore leaching resulted in 100% nickel yield. In summary, the potential of using elemental sulfur addition and subsequent biological acid generation to maintain the low pH during bioleaching of an acid‐consuming nickel ore was demonstrated. Copyright © 2005 Society of Chemical Industry
Phenoxymethylpenicillin–intercalated hydrotalcite as a bacteria inhibitor
Authors: Li Wen‐Zhuo , Lu Jun , Chen Jie‐Sheng , Li Guo‐Dong , Jiang Yu‐Sheng , Li Lian‐Sheng , Huang Bai‐Qu
Published: August 2005

Phenoxymethylpenicillin (PMP) has been reversibly intercalated into a layered double hydroxide, and the resulting composite exhibits effective anti‐bacterial activity. Powder X‐ray diffraction studies indicate that the PMP molecules are interdigitated between the inorganic layers, and under mild acidic media, the molecules are released gradually. Therefore a sustained‐release anti‐bacterial medication is envisioned on the basis of this inorganic–drug composite. Copyright © 2005 Society of Chemical Industry
Extraction of essential oil from geranium (Pelargonium graveolens) with supercritical carbon dioxide
Authors: Peterson Amelia , Machmudah Siti , Roy Bhupesh C , Goto Motonobu , Sasaki Mitsuru , Hirose Tsutomu
Published: August 2005

This study investigated the supercritical fluid extraction (SFE) of geranium essential oil from geranium (Pelargonium graveolens) using supercritical carbon dioxide solvent. The extraction yield was measured as a function of pressure, temperature and carbon dioxide flow rate. At low pressure (10 MPa) and high temperature (343 K), waxes were co‐extracted with the essential oil, resulting in artificially elevated essential oil extraction yields as no method was available with the SFE apparatus used to separate co‐extracted waxes and oil. At high pressure (30 MPa) and low temperature (313 K), the amount of wax co‐extracted decreased. Under these ‘optimum’ conditions, the extraction yield increased with decrease in flow rate giving a maximum extraction yield of 2.53%. All samples were analyzed by gas chromatography–mass spectrometry and the effect of pressure and extraction time on oil composition was studied. The percentage compositions of terpene hydrocarbons, terpenols, geraniol and geranyl esters were significantly affected by pressure and extraction time. The oil samples obtained by SFE were also compared with commercially obtained steam distilled samples. All major components of the commercially obtained oils were present in the SFE‐obtained oils; however, the percentage composition of the major components differed greatly between steam distilled and SFE oils. Copyright © 2005 Society of Chemical Industry
Characterization of paired helical filaments by scanning transmission electron microscopy
Authors: Ksiezak‐Reding Hanna , Wall Joseph S.
Published: August 2005

Paired helical filaments (PHFs) are abnormal twisted filaments composed of hyperphosphorylated tau protein. They are found in Alzheimer's disease and other neurodegenerative disorders designated as tauopathies. They are a major component of intracellular inclusions known as neurofibrillary tangles (NFTs). The objective of this review is to summarize various structural studies of PHFs in which using scanning transmission electron microscopy (STEM) has been particularly informative. STEM provides shape and mass per unit length measurements important for studying ultrastructural aspects of filaments. These include quantitative comparisons between dispersed and aggregated populations of PHFs as well as comparative studies of PHFs in Alzheimer's disease and other neurodegenerative disorders. Other approaches are also discussed if relevant or complementary to studies using STEM, e.g., application of a novel staining reagent, Nanovan. Our understanding of the PHF structure and the development of PHFs into NFTs is presented from a historical perspective. Others goals are to describe the biochemical and ultrastructural complexity of authentic PHFs, to assess similarities between authentic and synthetic PHFs, and to discuss recent advances in PHF modeling. Microsc. Res. Tech. 67:126–140, 2005. © 2005 Wiley‐Liss, Inc.
Amyloid‐β aggregates formed at polar–nonpolar interfaces differ from amyloid‐β protofibrils produced in aqueous buffers
Authors: Nichols Michael R. , Moss Melissa A. , Reed Dana Kim , Hoh Jan H. , Rosenberry Terrone L.
Published: August 2005

The deposition of aggregated amyloid‐β (Aβ) peptides in the brain as senile plaques is a pathological hallmark of Alzheimer's disease (AD). Several lines of evidence indicate that fibrillar and, in particular, soluble aggregates of these 40‐ and 42‐residue peptides are important in the etiology of AD. Recent studies also stress that amyloid aggregates are polymorphic and that a single polypeptide can fold into multiple amyloid conformations. Here we review our recent reports that Aβ(1‐40) in vitro can form soluble aggregates with predominant β‐structures that differ in stability and morphology. One class of aggregates involved soluble Aβ protofibrils, prepared by vigorous overnight agitation of monomeric Aβ(1‐40) in low ionic strength buffers. These aggregates were quite stable and disaggregated to only a limited extent on dilution. A second class of soluble Aβ aggregates was generated at polar–nonpolar interfaces. Aggregation in a two‐phase system of buffer over chloroform occurred more rapidly than in buffer alone. In buffered 2% hexafluoroisopropanol (HFIP), microdroplets of HFIP were formed and the half‐time for aggregation was less than 10 minutes. Like Aβ protofibrils, these interfacial aggregates showed increased thioflavin T fluorescence and were rich in β‐structure by circular dichroism. However, electron microscopy and atomic force microscopy revealed very different morphologies. The HFIP aggregates formed initial globular clusters that progressed over several days to soluble fibrous aggregates. When diluted out of HFIP these aggregates initially were very unstable and disaggregated completely within 2 minutes. However, their stability increased as they progressed to fibers. It is important to determine whether similar interfacial Aβ aggregates are produced in vivo. Microsc. Res. Tech. 67:164–174, 2005. © 2005 Wiley‐Liss, Inc.
Characterization of Alzheimer paired helical filaments by electron microscopy
Authors: Hernández Félix , Engel Tobias , Gómez‐Ramos Alberto , Pérez Mar , Avila Jesús
Published: August 2005

We show how electron microscopy can be used to answer several critical issues in neurodegenerative disorders that course with the formation of aberrant filamentous structures. Thus, electron microscopy is a useful technique to study in vitro assembly of pathogenic proteins, to map the regions involved in filament formation, as well as to detect by immunoelectron microscopy which proteins bind to the filaments. Furthermore, electron microscopy is the main technique used to discover if an animal model develops fibrillar pathology and if those filaments are similar to those found in human patients. This review focuses on Alzheimer's disease and related tauopathies, although similar studies have been done with other neurodegenerative disorders as, for example, Huntington's disease. Microsc. Res. Tech. 67:121–125, 2005. © 2005 Wiley‐Liss, Inc.
Paired helical filaments (PHFs) are a family of single filament structures with a common helical turn period: Negatively stained PHF imaged by TEM and measured before and after sonication, deglycosylation, and dephosphorylation
Authors: Ruben George C. , Wang Jian‐zhi , Iqbal Khalid , Grundke‐Iqbal Inge
Published: August 2005

Isolated paired helical filaments (PHFs) were visualized on glutaraldehyde vapor‐treated thin ∼10‐nm thick indirect carbon films using high‐resolution transmission electron microscopy (TEM) and the negative stain, phosphotungstate acid (PTA) at near neutral pH of 6.8. PHF preparations were prepared with and without 1 minute of sonication. These same PHF were also deglycosylated with endoglycosidase F/N‐glycosidase F for 1 hour or the PHF were dephosphorylated with PP‐2A for 1 hour. The negatively stained PHF filaments were quantitatively studied by measuring their wide regions (W) their thin regions (T) and their helical turn period (L) and these separate parameters were averaged for each filament. In the unsonicated PHF preparation there were PHF, cylindrical filaments with periodic thin regions (CF‐PT), cylindrical filaments (CF), as well as 2.0‐nm tau polymer‐like filaments. The CF‐PT were characterized by W, T, and L measurements and the CF were characterized by diameter measurements. The paired helical filament model proposed by Kidd (1963, Nature 197:192–193) of two ∼10 nm filaments twisting around each other every ∼80 nm with a thin region of 10 nm and a wide region of 25 nm does not correspond to the PHF structures found. None of the PHF we observed were composed of a pair of filaments and all of the PHF appear to be a single filament. The wide regions ranged from 12.5–27 nm and the thin regions ranged from 4.5–12.3 nm. The helical turn periods ranged from 76–85 nm and were generally about 80 nm. Only the helical turn period of ∼80 nm was a common property of the whole family of PHF structures. The CF‐PT appear to be a PHF precursor filament. Deglycosylation of the PHF and CF‐PT reduced their sizes by 0.5–0.6 nm and 0.7–1.0 nm, respectively, and the right‐hand helicity of the PHF was lost after deglycosylation. Dephosphorylation with PP‐2A reduced the PHF wide regions by 6.0 nm and the thin regions by 2.6 nm. Microsc. Res. Tech. 67:175–195, 2005. © 2005 Wiley‐Liss, Inc.
Alzheimer paired helical filaments (PHFs) studied by high‐resolution TEM: What can vertical Pt‐C replication tell us about the organization of the pronase‐digested PHF core?
Authors: Ruben George C. , Novak Michal , Edwards Patricia C. , Iqbal Khalid
Published: August 2005

Untreated paired helical filaments (PHFs) and pronase‐digested PHF‐core filaments were stereoscopically imaged with a freeze‐drying vertical platinum‐carbon replication preparation method for TEM. The untreated PHF have an average wide region (W) = 22.8 ± 2.4 nm, a narrow region (T) = 10.6 ± 1.7 nm, and a helical turn period (L) = 78.6 ± 13.4. The surfaces of the untreated PHF's fuzzy coat appears disorganized. The widths of the pronase‐treated PHF‐core filaments were significantly reduced (Wd = 14.8 ± 1.2 nm, Td = 5.7 ± 1.0 nm, and Ld = 75.4 ± 17 nm). The surfaces of the untreated PHF contained ∼1.1 nm strands, the same size as tau monomer (∼1.0 nm). The pronase‐digested PHF cores mostly contained ∼1.6 ± 0.3 nm strands although strand diameters ranged from 0.6–2.5 nm. The strands sometimes appear to be wrapped around the filament axis; less often, they appear to be roughly parallel to the PHF axis, and otherwise appear to be randomly oriented. Images of pronase‐digested PHF core images are discussed in relation to the core's biochemical composition, its proposed beta structure, and structural subunit models. Images of the untreated and the pronase‐digested PHF support a helical ribbon morphology. Microsc. Res. Tech. 67:196–209, 2005. © 2005 Wiley‐Liss, Inc.
Retrospective motion compensation using variable‐density spiral trajectories
Authors: Leung General , Plewes Donald B.
Published: August 2005

Purpose

To develop a method of retrospectively correcting for motion artifacts using a variable‐density spiral (VDS) trajectory.

Materials and Methods

Each VDS interleaf was designed to adequately sample the same center region of k‐space. This central overlapping region can then be used to measure rigid body motion between the acquisition of each VDS interleaf. By applying appropriate phase shifts and rotations of the k‐space data, rigid body motion artifacts can be removed, resulting in images with less motion corruption.

Results

Both phantom and volunteer experiments are shown, demonstrating the technique's ability to further reduce artifacts in images acquired with an already motion‐resistant acquisition trajectory. Registration accuracy is highly dependent on the trajectory design parameters. This space was explored to find an optimal design of VDS trajectories for motion compensation.

Conclusion

Using appropriately designed VDS trajectories, residual motion artifacts can be significantly reduced by retrospectively correcting for in‐plane rigid body motion. An overlapping region of approximately 8% of the central region of k‐space and approximately 70 interleaves were found to be near‐optimal parameters for retrospective correction using VDS trajectories. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Detection of acute renal ischemia in swine using blood oxygen level‐dependent magnetic resonance imaging
Authors: Alford Sara K. , Sadowski Elizabeth A. , Unal Orhan , Polzin Jason A. , Consigny Daniel W. , Korosec Frank R. , Grist Thomas M.
Published: August 2005

Purpose

To determine the feasibility and sensitivity of blood oxygen level‐dependent (BOLD) magnetic resonance imaging (MRI) to detect acute renal ischemia, using a swine model, and to present the causes of variability and assess techniques that minimize variability introduced during data analysis.

Materials and Methods

BOLD MRI was performed in axial and coronal planes of the kidneys of five swine. Color R2* maps were calculated and mean R2* values and 95% confidence intervals (CIs) for the cortex and medulla were determined for baseline, renal artery occlusion and reperfusion conditions. Paired Student's t‐tests were used to determine significance.

Results

Mean R2* measurements increased from baseline during renal artery occlusion in the cortex (axial, 13.8–24.6 second−1; coronal, 14.4–24.7 second−1) and medulla (axial, 19.3–32.2 second−1; coronal, 20.1–30.7 second−1). These differences were significant for both the cortex (axial, P < 0.04; coronal, P < 0.005) and medulla (axial, P < 0.02; coronal, P < 0.0005). No significant change was observed in the contralateral kidney.

Conclusion

R2* values were significantly higher than baseline for medulla and cortex during renal artery occlusion. More variability exists in R2* measurements in the medulla than the cortex and in the axial than the coronal plane. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Functional magnetic resonance imaging activation detection: Fuzzy cluster analysis in wavelet and multiwavelet domains
Authors: Jahanian Hesamoddin , Soltanian‐Zadeh Hamid , Hossein‐Zadeh Gholam‐Ali
Published: August 2005

Purpose

To present novel feature spaces, based on multiscale decompositions obtained by scalar wavelet and multiwavelet transforms, to remedy problems associated with high dimension of functional magnetic resonance imaging (fMRI) time series (when they are used directly in clustering algorithms) and their poor signal‐to‐noise ratio (SNR) that limits accurate classification of fMRI time series according to their activation contents.

Materials and Methods

Using randomization, the proposed method finds wavelet/multiwavelet coefficients that represent the activation content of fMRI time series and combines them to define new feature spaces. Using simulated and experimental fMRI data sets, the proposed feature spaces are compared to the cross‐correlation (CC) feature space and their performances are evaluated. In these studies, the false positive detection rate is controlled using randomization. To compare different methods, several points of the receiver operating characteristics (ROC) curves, using simulated data, are estimated and compared.

Results

The proposed features suppress the effects of confounding signals and improve activation detection sensitivity. Experimental results show improved sensitivity and robustness of the proposed method compared to the conventional CC analysis.

Conclusion

More accurate and sensitive activation detection can be achieved using the proposed feature spaces compared to CC feature space. Multiwavelet features show superior detection sensitivity compared to the scalar wavelet features. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
The impact of partial‐volume effects in dynamic susceptibility contrast magnetic resonance perfusion imaging
Authors: Chen Jean J. , Smith Michael R. , Frayne Richard
Published: August 2005

Purpose

To demonstrate the degree of the cerebral blood flow (CBF) estimation bias that could arise from distortion of the arterial input function (AIF) as a result of partial‐volume effects (PVEs) in dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI).

Materials and Methods

A model of the volume fraction an artery occupies in a voxel was devised, and a mathematical relationship between the amount of PVE and the measured baseline MR signal intensity was derived. Based on this model, simulation studies were performed to assess the impact of PVE on CBF. Furthermore, the effectiveness of linear PVE compensation approaches on the concentration function was investigated.

Results

Simulation results showed a nonlinear relationship between PVE and the resulting CBF measurement error. In addition to AIF underestimation, PVE also causes distortions of AIF frequency characteristics, leading to CBF errors varying with mean transit time (MTT). An uncorrected AIF measured at a voxel with a partial‐volume fraction of ≤50% could produce a CBF overestimation of more than fourfold. Linear compensation of the concentration curves did not produce correct CBF estimates.

Conclusion

PVE can induce significant CBF estimation biases. In addition, the MTT dependence of CBF accuracy raises doubts of the validity of adopting a single cross‐calibration factor (i.e., setting normal white matter to 22 mL minute−1 (100 g)−1) to obtain CBF values with absolute units. The impact of PVE may be reduced by decreasing the maximum arterial signal drop in the perfusion images. To correct the AIF distortions introduced by PVE, the nonlinear relationship between the impact of PVE on MR signal intensity and contrast concentration function must be considered. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Comparison of Gd [DTPA‐bis (2‐aminoethoxy) ethane] polymeric contrast agent with gadodiamide injection for interstitial MR lymphography: Experimental study with rabbits
Authors: Zhou Zhengyang , Guo Jian , Yu Haiping , Zhu Bin , Liu Changjian , Jiang Xiqun , Zhang Ming , Chen Junkun
Published: August 2005

Purpose

To compare the differences between macromolecular and small molecular contrast agents in interstitial magnetic resonance (MR) lymphography.

Materials and Methods

In two groups of rabbits (N = 12 each), 0.5‐mL volumes of 0.5 M and 0.1 M gadodiamide, respectively, were injected subcutaneously into the dorsal feet of both hind legs. After a 24‐hour interval, 0.5 mL of Gd [DTPA‐bis (2‐aminoethoxy) ethane] polymeric contrast agent (Gd‐poly‐DTPA‐EOEA) injection (0.1 M) was injected into the same sites in each rabbit. T1‐weighted three‐dimensional gradient‐echo and maximum intensity projection (MIP) images were obtained before and after the administration of each agent. The nodal maximum short‐axis diameter (MSAD) and signal‐to‐noise ratio (SNR) at each time point were measured. Postmortem measurements of nodal MSADs were also performed. The nodal MSAD measurements obtained by MR lymphography were compared with the postmortem measurements. As an additional control experiment, six rabbits received a subcutaneous injection of 0.5 mL of 0.1 M gadodiamide at the same sites as those described above. This procedure was repeated after a 24‐hour interval to determine whether the first injected gadodiamide had any effect on the performance of the subsequently injected agent, by comparing the differences in nodal MSADs obtained by MR lymphography after each injection.

Results

Gd‐poly‐DTPA‐EOEA showed a significantly longer enhancement plateau compared to gadodiamide. In comparison with postmortem measurements, nodal measurements by MR lymphography with Gd‐poly‐DTPA‐EOEA at the peak‐enhancement phase revealed no significantly different MSADs (P > 0.05), whereas nodal measurements by MR lymphography with gadodiamide showed significantly smaller MSADs (P < 0.05). A comparison of the nodal MSADs measured in two gadodiamide‐enhanced MR examinations after the 24‐hour interval showed no significant difference (P > 0.05).

Conclusion

Interstitial MR lymphography with polymeric Gd‐poly‐DTPA‐EOEA enhancer enables more sufficient and reliable visualization of lymph nodes compared to small molecular gadodiamide. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Quantitative analysis of regional airways obstruction using dynamic hyperpolarized 3He MRI—Preliminary results in children with cystic fibrosis
Authors: Koumellis Panos , van Beek Edwin J.R. , Woodhouse Neil , Fichele Stan , Swift Andrew J. , Paley Martyn N.J. , Hill Catherine , Taylor Chris J. , Wild Jim M.
Published: August 2005

Purpose

To investigate regional airways obstruction in patients with cystic fibrosis (CF) with quantitative analysis of dynamic hyperpolarized (HP) 3He MRI.

Materials and Methods

Dynamic radial projection MRI of HP 3He gas was used to study respiratory dynamics in a group of eight children with CF. Signal kinetics in a total of seven regions of interest (ROIs; three in each lung, and one in the trachea) were compared with the results of spirometric pulmonary function tests (PFTs). The tracheal signal intensity was used as a form of “input function” to normalize for input flow effects.

Results

A pattern of low flow rate in the upper lobes was observed. When the flow measurements from the peripheral ROIs were averaged to obtain an index of flow in the peripheral lung, a good correlation was found (P = 3.74 × 10−5) with the forced expired volume in one second (FEV1).

Conclusion

These results suggest that a quantitative measurement of localized airways obstruction in the early stages of CF may be obtained from dynamic 3He MRI by using the slope of the signal rise as a measure of air flow into the peripheral lung. This study also demonstrates that children can cooperate well with the 3He MRI technique. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Combined T1‐T2 mapping of human femoro‐tibial cartilage with turbo‐mixed imaging at 1.5T
Authors: Van Breuseghem Iwan , Palmieri Francesco , Peeters Ronald R. , Maes Frederik , Bosmans Hilde T.C. , Marchal Guy J.
Published: August 2005

Purpose

To evaluate the influence of Gd‐DTPA on cartilage T2 mapping using turbo‐mixed (tMIX) imaging, and to show the possible usefulness of the tMIX technique for simultaneously acquiring T1 and T2 information in cartilage.

Materials and Methods

Twenty volunteers underwent MRI of the knee using the tMIX sequence before and after gadolinium administration. T1 and T2 maps were calculated. The mean T1 was determined on the pre‐ and postcontrast T1 maps. T2 relaxation values before and after gadolinium administration were statistically analyzed.

Results

The obtained relaxation values are in correspondence with previously published data. The mean T1 before gadolinium administration was 449 msec ± 34.2 msec (SD), and after gadolinium administration it was 357 msec ± 55.8 msec (SD). The postcontrast T1 relaxation range was 221.5–572.8 msec. The mean T2 of the precontrast T2 maps was 34.2 msec ± 3.1 msec (SD), and the mean T2 of the postcontrast T2 maps was 32.5 msec ± 3.1 msec (SD). These are statistically significant different values. A correction for the postcontrast T2 values, using a back‐calculation algorithm, yielded a 98% correlation with the precontrast T2 values.

Conclusion

The absolute difference of pre‐ and postcontrast T2 is very small and is ruled out using the back‐calculation algorithm. Combined T1‐T2 tMIX cartilage mapping is a valuable alternative for separate T1 and T2 cartilage mapping. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Electron ionization and methane chemical ionization mass spectrometry study of some 2,2‐disubstituted 1,3‐dioxolanes, 1,3‐dithiolanes, 1,3‐oxathiolanes and 1,3‐dioxanes. Gas‐phase lactone and thiolactone formation
Authors: Pakarinen Jaana M. H. , Kolehmainen Jaana , Yrjölä Sari , Vainiotalo Pirjo
Published: August 2005

The electron ionization and methane chemical ionization mass spectra of some 2,2‐disubstituted 1,3‐dioxolanes, 1,3‐dithiolanes and 1,3‐oxathiolanes were studied. Especially, the effect of the length of the side chain in ring position 2 of these compounds and the ease of formation of possible lactone/thiolactone ion as a fragmentation product were examined. In addition, two 2,2‐disubstituted 1,3‐dioxanes were studied to see the effect of the bigger ring size. The formation of lactone ions was more favorable under methane chemical ionization than under electron ionization conditions. The structures of fragment ions and the ions generated from model compounds were carefully studied using both high‐ and low‐energy collision‐induced dissociation. Also ab initio molecular orbital calculations up to the HF/6–31G** level of theory for protonated 2‐methyl‐2‐propanoic acid ethyl ester of 1,3‐dioxolane, 1,3‐oxathiolane and 1,3‐dithiolane and for two isomeric bicyclic ions were carried out. The theoretical results obtained favor the formation of the lactone ion. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of molecular weight distributions of styrene‐methyl methacrylate copolymers using size exclusion chromatography data
Authors: Matusinović Zvonimir , Tomić Tatjana , Šegudović Nikola , Rogošić Marko
Published: August 2005

Size exclusion chromatography (SEC) is a common method for the determination of molecular weight distributions (MWD) of polymers. Using appropriate normalization procedures, MWD data may be put in a form suitable for the description by different theoretical distribution functions. In this paper such a procedure is described and applied to a model system. Statistical copolymers of styrene and methyl methacrylate (SMMA) of different compositions were synthesized by radical copolymerization in a batch isothermal reactor with toluene as solvent and azobisisobutyronitrile as initiator. Copolymer MWDs were obtained by SEC and average copolymer composition by elemental analysis. MWDs of SMMA copolymers were correlated with the lognormal, Flory, Schulz, and Tung theoretical function. The best match between experimental and calculated data was obtained by the Schulz distribution. The α‐parameter of Schulz's function was related to the average molecular weight and showed its maximum at the midpoint of the copolymer composition range, in connection with the observed minimal copolymerization rate. The variation of the b‐parameter was found to be less pronounced; the parameter was related to the polydispersity index. This feature indicated that there was no significant change in the copolymerization reaction mechanism throughout the entire copolymer composition range.
Ion chromatographic method development for monitoring of seawater quality used in over‐the‐counter pharmaceutical industry
Authors: Bolanča Tomislav , Cerjan‐Stefanović Štefica , Regelja Melita , Štanfel Danijela
Published: August 2005

A methodology is developed for the analysis of inorganic anions (fluoride, chloride, bromide, sulphate) in seawater used for over‐the‐counter (OTC) nasal spray production. The eluent flow rate and concentration of eluent competing ions are optimised by using an artificial neural network resolution model in combination with normalised resolution product criterion function. The developed artificial neural network resolution model shows good predictive ability R 2 ⪈ 0.9973. The determined ion chromatographic parameters enable baseline separation of all components of interest. By performing a validation procedure and a number of statistical tests, it is shown that the developed ion chromatographic method has superior performance characteristics: linearity R 2 ⪈ 0.9993, recovery = 99.77–100.65%, repeatability RSD ⪇ 1.85%. This result proves that the proposed method can be used for routine quality assurance analysis in OTC pharmaceutical industry.
Application of artificial neural networks for gradient elution retention modelling in ion chromatography
Authors: Bolanča Tomislav , Cerjan‐Stefanović Štefica , Regelja Melita , Regelja Hrvoje , Lončarić Sven
Published: August 2005

Gradient elution in ion chromatography (IC) offers several advantages: total analysis time can be significantly reduced, overall resolution of a mixture can be increased, peak shape can be improved (less tailing) and effective sensitivity can be increased (because there is little variation in peak shape). More importantly, it provides the maximum resolution per time unit. The aim of this work was the development of a suitable artificial neural network (ANN) gradient elution retention model that can be used in a variety of applications for method development and retention modelling of inorganic anions in IC. Multilayer perceptron ANNs were used to model the retention behaviour of fluoride, chloride, nitrite, sulphate, bromide, nitrate and phosphate in relation to the starting time of gradient elution and the slope of the linear gradient elution curve. The advantage of the developed model is the application of an optimized two‐phase training algorithm that enables the researcher to make use of the advantages of first‐ and second‐order training algorithms in one training procedure. This results in better predictive ability, with less time required for the calculations. The number of hidden layer neurons and experimental data points used for the training set were optimized in terms of obtaining a precise and accurate retention model with respect to minimization of unnecessary experimentation and time needed for the calculation procedures. This study shows that developed ANNs are the method of first choice for retention modelling of inorganic anions in IC.
An efficient slurry packing procedure for the preparation of columns applicable in capillary electrochromatography and capillary electrochromatography‐electrospray‐mass spectrometry
Authors: Lynen Frederic , Buica Astrid , de Villiers Andre , Crouch Andrew , Sandra Pat
Published: August 2005

A procedure is described for the slurry packing of 50‐μm ID fused silica capillaries with 3‐μm octadecyl silica (ODS) particles for capillary electrochromatography (CEC) and its hyphenation with electrospray ionisation mass spectrometry (ESI/MS). A homogeneous packed bed is obtained by using a slow packing process in an upward direction with a balanced density slurry solvent and MeOH as packing solvent. Special attention was paid to the in‐ and outlet frit preparation in order to avoid gas bubble formation which renders CEC‐ESI/MS problematic. Frits were made out of the packed bed itself, sintered in water, by using a perforated heating ribbon; they were not longer than 1 mm. In CEC‐UV, column efficiencies up to 300,000 plates per meter were obtained. Absence of gas bubbles was ascertained by the straightforward coupling to ESI/MS. A make‐up flow of 3 μL/min H2O/MeOH containing 0.1% HCOOH was used in the sheath flow interface. Steroids and carbamates were analysed with a 0.1% triethylamine‐acetic acid buffer (pH 8.9) containing varying amounts of acetonitrile. In CE‐ESI/MS, efficiencies dropped by ca. 20% but spectral data were excellent.
HPLC‐PDA characterisation ofDaphne gnidiumL. (Thymemeacea) dyeing extracts using two different C‐18 stationary phases
Authors: Nowik Witold
Published: August 2005

Raw aqueous extracts and acid‐hydrolysed extracts from leaves and stems ofDaphne gnidiumL. were investigated by HPLC‐PDA under two different separation conditions. This approach provides improved characterisation of natural compounds, especially those with similar structures, thanks to better resolution of critical pairs which can be difficult to separate by modification of gradient parameters only. In the leaf extracts, the presence of luteolin‐3′,7‐di‐O‐glucoside was found according to the results obtained for a standard sample. This compound is reported for the first time in this species. The presence of some other, previously reported flavonoids is confirmed. The stem extract is rich in coumarins and seems not to contain any significant amounts of flavonoids. Further investigation of hydrolysed extracts is a useful additional step in the indirect identification of flavonoid and coumarin glycosides.
Injector‐internal thermal desorption from edible oils. Part 1: Visual experiments on sample deposition on the liner wall
Authors: Biedermann Maurus , Fiselier Katell , Grob Koni
Published: August 2005

Injector‐internal thermal desorption from edible oils or fats enables the analysis of a wide range of compounds in oils or extracts of fatty food without prior removal of the sample matrix. The oil or fat is deposited onto the wall of the injector liner. The solutes of interest are evaporated, leaving behind the sample matrix. The injector is kept at a temperature volatilizing the solutes of interest, but minimizing evaporation of the bulk material of the oil. This technique was optimized regarding sample deposition on the liner wall (Part 1) and desorption of high boiling compounds, such as migrants from food packaging materials into simulant D (olive oil) or fatty food (Part 2). The sample liquid should be transferred to the liner wall and spread to a thin film in order to facilitate the release of high boiling components. Visual experiments with perylene‐containing solutions showed that the oil must be diluted to reduce the viscosity (separation from the needle tip). The oil concentration should not exceed 20% in order to rule out that squirting sample liquid drops to the bottom of the vaporizing chamber. Further dilution to about 10% oil improves spreading of the liquid to a thin film. A rather high boiling solvent should be used, such as n‐butyl acetate, to prevent thermospray at the needle exit and violent evaporation from the liner wall with sputtering liquid. Using a 5‐mm ID liner, 5–10‐μL injections of 10–20% oil solutions were at the upper limit.
High‐performance liquid chromatography of some basic drugs on a n‐octadecylphosphonic acid modified magnesia‐zirconia stationary phase
Authors: He Hai‐Bo , Feng Yu‐Qi , Da Shi‐Lu , Hu Zhi‐Xiong , Qu Li
Published: August 2005

The high‐performance liquid chromatographic behavior of some basic drugs was studied on a n‐octadecylphosphonic acid modified magnesia‐zirconia (C18PZM) stationary phase. The effect of mobile phase variables such as methanol content, ionic strength, and pH on their chromatographic behavior was investigated. The retention mechanism of basic drugs on the stationary phase was elucidated. The results indicate that both hydrophobic and cation‐exchange interactions contribute to solute retention under most chromatographic conditions. The inherent Brönsted‐acid sites and also the adsorbed Lewis base anionic buffer constituents on accessible ZM surface Lewis acid sites play a role in the retention of ionized solutes by cation‐exchange interaction. However, especially at high mobile phase pH, the retention of basic drugs depends mainly on hydrophobic interactions between solutes and support. Separations of the basic drugs on the C18PZM phase by a predominantly reversed‐phase retention mode were very promising. The mixed‐mode retention feature on this phase, as a result of the adsorbed Lewis base anionic buffer constituents acting as sites for cation‐exchange, could also be very useful, e.g. for enhancing the chromatographic selectivity of such analytes. The C18PZM seems to be an excellent alternative to silica‐based reversed‐phase stationary phase for the separation of strongly basic solutes.
Chromatographic determination of itopride hydrochloride in the presence of its degradation products
Authors: Kaul Neeraj , Agrawal Himani , Maske Pravin , Ramchandra Rao Janhavi , Mahadik Kakasaheb Ramoo , Kadam Shivajirao S.
Published: August 2005

Two sensitive and reproducible methods are described for the quantitative determination of itopride hydrochloride (IH) in the presence of its degradation products. The first method is based on HPLC separation on a reversed phase Kromasil column [C18 (5‐μm, 25 cm×4.6 mm, ID)] at ambient temperature using a mobile phase consisting of methanol and water (70:30, v/v) adjusted to pH 4.0 with orthophosphoric acid with UV detection at 258 nm. The flow rate was 1.0 mL per min with an average operating pressure of 180 kg/cm2. The second method is based on HPTLC separation on silica gel 60 F254 using toluene:methanol:chloroform:10% ammonia (5.0:3.0:6.0:0.1, v/v/v/v) as mobile phase at 270 nm. The analysis of variance (ANOVA) and Student's t‐test were applied to correlate the results of IH determination in dosage form by means of HPLC and HPTLC methods. The drug was subjected to acid and alkali hydrolysis, oxidation, dry heat, wet heat treatment, UV, and photodegradation. The proposed HPLC method was utilized to investigate the kinetics of the acidic, alkaline, and oxidative degradation processes at different temperatures and the apparent pseudo‐first‐order rate constant, half‐life, and activation energy were calculated. In addition the pH‐rate profile of degradation of IH in constant ionic strength buffer solutions in the pH range 2–11 was studied.