bluuebunny/crossref_metadata_2025 huggingface dataset:
Genesis of Dioctahedral Phyllosilicates During Hydrothermal Alteration of Volcanic Rocks: I. The Golden Cross Epithermal Ore Deposit, New Zealand
Authors: Tillick David A. , Peacor Donald R. , Mauk Jeffrey L.
Published: June 2006

To characterize the evolution of dioctahedral interstratified clay minerals in the Golden Cross epithermal deposit, New Zealand, hydrothermally altered volcanic rocks containing the sequence smectite through illite-smectite (I-S) to muscovite were examined by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission and analytical electron microscopies (TEM/AEM).

XRD analyses of 30 oriented clay samples show a broad deposit-wide trend of increasing illite content in I-S with increasing depth and proximity to the central vein system. Six representative samples were selected for SEM/TEM study on the basis of petrographic observations and XRD estimates of I-S interstratification. Ca and Na are the dominant interlayer cations in smectite, but as the proportion of illite layers in I-S increases, so does the K content and (IVAl + VIAl)/Si ratio. Layers and packets tend to flatten and form larger arrays, reducing the amount of pore space. Smectite coexists with (R = 1) I-S, rather than being (R = 0) I-S where R is the Reichweite parameter. The highest alteration rank samples contain discrete packets of mica to ∼300 Å thick, but a limited chemical and structural gap exists between illite, which is intermediate in composition between common illite and muscovite, and illite-rich I-S. Selected-area electron diffraction (SAED) patterns of mica show that the 1M polytype dominates, rather than the common 2M1 polytype.

Petrographic, SEM, and TEM data imply that all phyllosilicates formed via neoformation directly from fluids. Relatively mature I-S and micas form simultaneously, without progressing through the series of transformations that are commonly assumed to characterize diagenetic sequences during burial metamorphism in mud-dominated basins. Although the overall distribution of clay minerals is consistent with temperature as a controlling variable, local heterogeneities in the distribution of clay minerals were controlled by water/rock ratio, which varied widely owing to different rock types and fracture control.
Genesis of Dioctahedral Phyllosilicates During Hydrothermal Alteration of Volcanic Rocks: II. The Broadlands-Ohaaki Hydrothermal System, New Zealand
Authors: Yan Yonghong , Tillick David A. , Peacor Donald R. , Simmons Stuart F.
Published: June 2006

The clay mineral textures, assemblages, formation mechanisms, and controlling geological parameters relating to alteration of silicic volcanic rocks by hydrothermal solutions, in core samples from the Broadlands-Ohaaki hydrothermal system, New Zealand, were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission and analytical electron microscopy (TEM/AEM). Mineralogical and textural relations of this active hydrothermal system, for which temperatures and fluid relations are well known, are equivalent to those in the Golden Cross hydrothermal gold deposit as described in Part 1.

XRD data show a sequence of clay minerals from smectite to a range of interstratified I-S to mica with increasing depth and temperature, on average. TEM observations are in general agreement with XRD data, especially with respect to relative proportions of illite (I)- and smectite (S)- like layers. TEM data also show that: (1) Smectite packets contain no discrete illite-like layers in samples identified as (Reichweite, R = 0) I-S by XRD. They coexist with separate packets of (R = 1) I-S. (2) A continuous range in I-S occurs from (R = 1) I-S with increasing proportion of illite-like layers, but at high illite-like layer contents there is a gap between I-S and illite. (3) 1M and 2M1 polytypes of mica coexist in separate packets, but the rare 1M polytype has a larger VIMg content.

The data imply that clay minerals formed by dissolution and neocrystallization directly from volcanic phases, although multiple reaction events can not be ruled out. Such “episodic” alteration produces a sequence of clay minerals identical to those of prograde diagenesis of pelitic sediments. This result implies that the presence of a continuous sequence is not definitive proof of continuous sequences of transformation as a function of time and continuous burial. Reaction progress of the clay-mineral sequence is in general accord with the known temperature gradient, but with significant and common exceptions. High porosity and permeability, both inherent in rock texture and local structure, are inferred to foster local reaction progress, as consistent with metastability of phases and the Ostwald step rule.
Illite “Crystallinity” Revisited
Authors: Jaboyedoff M. , Bussy F. , Kübler B. , Thelin Ph.
Published: June 2006

The Kübler Index (KI) is defined as the full width at half-maximum height (FWHM) of the 10-Å X-ray diffraction peak of illite-smectite interstratified (I-S) clay minerals. The only parameters controlling the Kübler Index are assumed to be the mean number of layers (N) in the coherent scattering domains (CSD), the variance of the distribution of the number of layers of the CSD, the mean percentage of smectite layers in I-S (%S), and the probability of layer stacking (Reichweite).

The Kübler-Index measurements on air-dried (KIAD) and ethylene-glycolated (KIEG) samples were compared to N and %S using the NEWMOD computer program to simulate X-ray diffraction patterns. Charts of KIADversusKIEG corrected for instrumental broadening were made and isolines were mapped for constant N and %S. Isolines allow a direct and rapid determination of N and %S from KI measurements.

The method allows quantification of the metamorphic anchizone limits by considering mean thickness of fundamental particles in MacEwan crystallites. The transition from diagenesis to the anchizone and from the anchizone to the epizone of low-grade metamorphism corresponds to thicknesses of 20- and 70-layer fundamental particles, respectively.
Formation and Growth of Smectites In Bentonites: A Case Study From Kimolos Island, Aegean, Greece
Authors: Christidis George E.
Published: June 2006

The low-temperature alteration of a rhyolitic rock from Kimolos Island, Aegean, Greece, yielded an alteration profile characterized by gradual transition from fresh glass to bentonite containing homogeneous Chambers-type montmorillonite and then to a mordenite-bearing bentonite. Both mordenite and smectite were formed from poorly crystalline precursors, which probably had compositions comparable to that of the crystalline end-product. However, their composition may have been modified to some degree after reaction with the fluid phase. Particle length and width measurements of smectite crystals yielded lognormal profiles, which suggest supply-controlled crystal growth in an open system or random ripening in a closed system. The former mechanism is in accordance with the observed sustained supply of Mg and Fe by the fluid phase throughout the alteration profile and is believed to be the dominant formation mechanism of smectites in bentonites in general. In the mordenite-bearing zone, random ripening is expected in domains with low permeability, in which the system was essentially closed, favoring the formation of mordenite. The level of supersaturation with respect to smectite was probably lower in the mordenite-bearing zone. Smectite probably affected pore-fluid chemistry either through ion exchange or via dissolution of initially formed K-bearing smectite. The latter process raised the K+/(Na+ + Ca2+) activity ratio of the pore-fluid favoring K-bearing mordenite.
Methylene Blue Interactions with Reduced-Charge Smectites
Authors: Bujdák Juraj , Janek Marián , Madejová Jana , Komadel Peter
Published: June 2006

The objective of this work was to prepare series of reduced-charge materials from different parent Li-saturated dioctahedral smectites, to investigate the effects of temperature, chemical composition and charge location in smectites on the charge reduction and to characterize reduced-charge smectites (RCSs) using methylene blue (MB) adsorption. The layer charge decrease, induced by Li fixation, is correlated with the trends in the spectra of MB-RCS dispersions in the visible region (VIS) spectra. Distribution of the negative surface charge of the clay minerals controls the distance between the adsorbed MB cations and thus affects the formation of MB dimers and higher agglomerates. Because each form of MB (monomer, dimer, higher agglomerate, J-aggregates) absorbs light at a different wavelength, the VIS spectra of MB depend sensitively on the charge density at the clay surface. Both cation exchange capacity (CEC) values and spectra of MB-clay dispersions clearly detect extensive reduction of the layer-charge density in reduced-charge montmorillonites (RCMs) upon Li-thermal treatment. The extent of charge reduction depends on the temperature of the thermal treatment, as well as on the octahedral charge of the montmorillonite. Reduction of the layer charge proceeds to a much lesser extent for smectites with mainly tetrahedral charge and high Fe content (Fe-rich beidellite and ferruginous smectite). Both CEC data and MB spectra detect only a slight decrease of the layer charge density, which relates to the low octahedral charge of these minerals. Following heating at higher temperatures (120-160°C), slightly higher Li fixation is indicated by CEC values; however, no charge reduction is confirmed by MB spectra. Release of protons accompanying Li+ fixation in Fe-rich smectites heated at 180 or 200°C was detected in the spectra of MB-clay dispersions and confirmed by potentiometric titrations.
Influence of Ionic Environment and pH on the Electrokinetic Properties of Ball Clays
Authors: Galassi Carmen , Costa Anna Luisa , Pozzi Paolo
Published: June 2006

Three ball clays (SP from England, TSMA from France and UK from the Ukraine) were characterized for their dry and wet colloidal properties. On the basis of X-ray diffraction and chemical analyses the clays were classified as kaolinite-rich clay, smectitic kaolinite-rich clay and illitic kaolinite-rich clay. The ζ (zeta) potential at the clay-water interface as a function of pH, in three different electrolytes, was investigated using an electroacoustic technique. Starting from measurements of dynamic mobility, the calculated ζ potential was found to be almost constant as a function of pH for the TSMA and UK clays, while it increased from −20 to −60 for the SP clay, when potassium nitrate was used as an electrolyte. The behavior of the three clays in calcium and magnesium nitrate was slightly different: SP showed a smaller increase in ζ potential, while a small deviation from the constant behavior of the UK clay was found. The results are explained in terms of the surrounding-ion atmosphere in light of the chemical-physical properties measured. Our results may well be of use to those involved in ceramic processing.
Effect of KCl and CaCl2 as Background Electrolytes on the Competitive Adsorption of Glyphosate and Phosphate on Goethite
Authors: Gimsing Anne Louise , Borggaard Ole K.
Published: June 2006

Competitive adsorption between glyphosate and phosphate on goethite was evaluated. The influence of background electrolyte on the adsorption of glyphosate and phosphate was also investigated by using 0.01 M KCl, 0.1 M KCl and 0.01 M CaCl2 as background electrolytes. Experiments showed that phosphate displaced adsorbed glyphosate from goethite, whereas glyphosate did not displace phosphate. Results also showed that the background electrolyte had a strong effect on phosphate adsorption, but little effect on glyphosate adsorption. Thus, there are differences between the adsorption of glyphosate and phosphate. The study also showed that 0.01 M KCl caused dispersion of goethite, resulting in inefficient filtering, and that phosphate precipitated as calcium phosphates in 0.01 M CaCl2 background electrolyte solutions. The results suggest that 0.1 M KCl is a more suitable background electrolyte to determine competitive adsorption processes involving glyphosate and phosphate.
Thickness and Surface Characteristics of Colloidal 2:1 Aluminosilicates Using an Indirect Fourier Transform of Small-Angle X-Ray Scattering Data
Authors: Shang Chao , Rice James A. , Lin Jar-Shyong
Published: June 2006

An indirect Fourier transformation applied to small-angle X-ray scattering data has been used to determine the thickness and surface properties of two common clay minerals. For an illite system, the particle density distribution function (PDDF) generated by the analysis gave a correct description of particle geometry, and the calculated electron density profile was in accordance with the theoretical electron density distribution for this mineral. This approach provides the opportunity to determine the thickness of fundamental particles of illite while avoiding the difficulties encountered in other methods. Both the PDDF and the electron density profile accurately predict the thickness of Na-montmorillonite layers, and the results suggest that an electron inhomogeneity exists at the interface of this mineral.
Rheology of Na-Rich Montmorillonite Suspension as Affected by Electrolyte Concentration and Shear Rate
Authors: Heller Hadar , Keren Rami
Published: June 2006

Rheological measurements were used to evaluate the particle-particle associations of Na-rich montmorillonite in suspensions, under various electrolyte concentrations. A 2% free electrolyte clay suspension showed pseudoplastic flow behavior and had a high apparent viscosity, attributed at low shear rates to the high volume fraction of the suspended clay platelets, the flexibility of the platelets, and the presence of edge-to-edge association. The breaking of edge-to-edge associations and the progressive orientation of the individual platelets in the direction of flow contribute to the reduction in viscosity with increasing shear rate.

The compression of the diffuse double layer at a NaCl concentration of 10 mEq L-1 contributes to the free movement of the individual platelets, even at low shear rates. The flow behavior changed from pseudoplastic to plastic at an NaCl concentration of 100 mEq L-1. At this electrolyte concentration, face-to-face associations of specific junction points at certain areas of the planar surface are probably occurring.

The apparent viscosity of the clay suspension for the two particle-size ranges (<2 and <0.02 μm) at all shear rates converged to a minimum value of 4.5 mPa s at NaCl concentrations of 10–20 mEq L-1. On both sides of the minimum, the lower the shear rate, the greater the slope. The apparent viscosity of a 2% suspension of Na-rich montmorillonite <0.02 μm particles, however, was significantly greater than that observed for a suspension of <2 u,m particles. This high apparent viscosity is attributed to the increase in edge surface area and the number of clay particles in a unit volume.

We suggest that edge-to-edge association between Na-rich montmorillonite platelets prevails when the NaCl concentration is below the electrolyte critical concentration, for which the apparent viscosity of the suspension is at its minimum value, whereas face-to-face association prevails at NaCl concentrations above this critical value.
Possible Role of Microbial Polysaccharides in Nontronite Formation
Authors: Ueshima Masato , Tazaki Kazue
Published: June 2006

Nontronite and microbes were detected in the surface layers of deep-sea sediments from Iheya Basin, Okinawa Trough, Japan. Nontronite, an Fe-rich smectite mineral, was embedded in acidic polysaccharides that were exuded by microbial cells and electron microscopy showed that the nontronite layers were apparently oriented in the polysaccharide materials. We propose that the formation of nontronite was induced by the accumulation of Si and Fe ions from the ambient seawater and that extracellular polymeric substances (EPS) served as a template for layer-silicate synthesis. Experimental evidence for this hypothesis was obtained by mixing a solution of polysaccharides (dextrin and pectin) with ferrosiliceous groundwater. After stirring the mixture in a sealed vessel for two days, and centrifuging, Fe-rich layer silicates were identified within the precipitate of both the dextrin and pectin aggregates, whereas rod-shaped or spheroidal Si-bearing iron hydroxides were found in the external solution. Microbial polysaccharides would appear to have affected layer-silicate formation.
Baseline Studies of the Clay Minerals Society Source Clays: Preface
Authors: Costanzo P. A. , Guggenheim S.
Published: June 2006

The Source Clays Program of The Clay Minerals Society was initiated in 1972 to distribute a set of reference clays, so that distributed clays could be identical for all recipients. Because most clays do not consist of a single phase, the immediate objective was not to produce a pure product consisting of one clay mineral, but to provide a uniform product. These materials were collected and processed carefully, and sufficient amounts were collected so that material was available for researchers for many years, Large numbers of researchers were thereby assured of working on identical material. Initial descriptions of these materials were presented in the Data Handbook (van Olphen and Fripiat, 1979). An updated version of this book was suggested several years ago because of the availability of new analytical techniques and to provide descriptions of material added to the reference set since 1979.
Baseline Studies of the Clay Minerals Society Source Clays: Introduction
Authors: Costanzo Patricia M.
Published: June 2006

Clay minerals share a basic set of structural and chemical characteristics (e.g. they are largely aluminosilicates with layer structures) and yet each clay mineral has its own unique set of properties that determine how it will interact with other chemical species. The variation, in both chemistry and structure, among the clays leads to their applications in extremely diverse fields. Common and important industrial applications of clays are in the manufacture of paper, paint, plastics and rubber. One of their more recent and most economically important applications is in the petlitter industry where their adsorptive and deodorizing properties are used. Specialty uses include clay additive to chicken feed to boost nutritional uptake by the chicken, and in using clay as fillers and major ingredients in pharmaceuticals and cosmetics. Clays are used for their catalytic properties and for their ability to adsorb greases, fats and other organic materials. Those who exist with scarce resources frequently collect clays from local deposits and ingest them as a source of dietary minerals. It is difficult for a day to go by without using a product incorporating clay minerals, as we all use ceramics such as dinnerware and sanitaryware.
Baseline Studies of the Clay Minerals Society Source Clays: Chemical Analysis by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS)
Authors: Kogel Jessica Elzea , Lewis Susan A.
Published: June 2006

Inductively coupled plasma-mass spectrometry (ICP-MS) is ideally suited for the rapid and simultaneous analysis of multiple elements in geological materials, including soils, organic substances and most rock types (Eggins et al., 1997; Long erich et al., 1990; Jenner et al., 1990). The application to clay minerals is more recent (Jain et al., 1994). This technique is highly sensitive, and is capable of analyzing a wide range of isotopes covering the entire mass spectrum Consequently, ICP-MS is used to measure directly rare earth and platinum group elements at ppb levels without preconcentration.
Human kallikrein 10, a predictive marker for breast cancer
Authors: Zhang Ying , Bhat Ishfaq , Zeng Musheng , Jayal Goyal , Wazer David E. , Band Hamid , Band Vimla
Published: June 2006

Our laboratory is involved in identifying genes that can be used as early diagnostic or prognostic markers in breast cancer. We previously identified a gene (NES1) that is expressed in normal but not in transformed mammary epithelial cells (MECs).NES1is located on chromosome 19q13.4 within the kallikrein locus and thus was designated as human kallikrein 10 (hK10), although we have been unable to detect any protease activity. Importantly,hK10expression is decreased in a majority of breast cancer cell lines. Transfection ofhK10intohK10-negative breast cancer cells reduces the tumorigenicity. Using methylation-specific PCR and subsequent sequencing, we demonstrate a strong correlation between hypermethylation ofhK10and loss of mRNA expression. Further analysis showed that essentially 100% of normal breast specimens hadhK10expression, whereas 46% of ductal carcinomain situ(DCIS) and the majority of infiltrating ductal carcinoma (IDC) samples lacked thehK10 mRNA. Importantly,hK10-negative DCIS diagnosed at the time of biopsy were subsequently diagnosed as IDC at the time of definitive surgery. It has been shown that hK10 protein expression is regulated by steroids. In addition to breast cancers, hK10 is downregulated in cervical cancer, prostate cancer and acute lymphocytic leukemia, whereas it is upregulated in ovarian cancers. These results point to the paradoxical role of hK10 in human cancers and underscore the importance of further studies of this kallikrein.
Improved prostate cancer detection with a human kallikrein 11 and percentage free PSA-based artificial neural network
Authors: Stephan Carsten , Meyer Hellmuth-Alexander , Cammann Henning , Nakamura Terukazu , Diamandis Eleftherios P. , Jung Klaus
Published: June 2006

Human kallikrein 11 (hK11) was evaluated in a percentage free PSA-based artificial neural network (ANN) to reduce unnecessary prostate biopsies. Serum samples from 357 patients with (n=132) and without (n=225) prostate cancer (PCa) were analyzed and ANN models were constructed and compared to all parameters. The discriminatory power of hK11 was lower than that of PSA, but receiver operator characteristic (ROC) analyses demonstrated significantly larger areas under the curves for the ANN compared to all other parameters. ANNs with hK11 may lead to a further reduction in unnecessary prostate biopsies, especially when analyzing patients with less than 15% free PSA.
A Robust Structural Stress Parameter for Evaluation of Multiaxial Fatigue of Weldments
Authors: Dong P , Hong JK
Published: June 2006

In this paper, the applicability of a new mesh-insensitive structural stress method is examined for the evaluation of multiaxial fatigue behaviors in welded joints. The mesh-insensitive structural stress method proves to be effective in characterizing stress concentration effects in multi-axial fatigue of welded components. In seeking an effective structural stress based fatigue parameter, some well-known published test data were analyzed. These include those published by researchers, e.g., from the Electric Power Research Intitute (EPRI), the Fraunhofer-Institute for Structural Durability (LBF), the University of Illinois at Urbana-Champaign (UIUC), and the Welding Institute (TWI) under bending, torsion, and in-phase and out-of-phase loading combinations. An effective structural stress parameter has then been formulated in a form of a proposed modified Gough's ellipse for considering both in-phase and out-of-phase multiaxial loading conditions. The aforementioned multiaxial fatigue data from a total of five independent sources can be effectively correlated with a structural stress based parameter presented in this paper, without introducing any other material-related empirical parameters. The present method is rather simple to use for day-to-day finite element based fatigue evaluation of welded joints in actual structures subjected to multiaxial loading conditions.
Feasibility Study on a Simple Method of Retrospective Neutron Dosimetry for Reactor Internals and Reactor Vessel
Authors: Hayashi K , Tayama R , Watanabe Y , Nakamura T , Kubota I , Hayashi H , Yamasaki T , Yuya H
Published: June 2006

Nondestructive and simple retrospective dosimetry method was developed. Mercuric iodide or cadmium zinc telluride detector was used as a detector to measure 54Mn, 58Co, and 60Co that were created in reactor internals and vessels. Detector is surrounded by tungsten collimator which shield background gamma rays and detect gamma rays from desired measuring point. Photopeak count rate of this detector were calculated using the mcnp-4c code. This response was calculated for each reactor internal geometry that was irradiated by unit neutron flux which energy spectrum was calculated by the tort code. Neutron fluence is calculated using precalculated response, measuring time, decay time and reactor power history. We can also get Displacement per Atom (DPA), hydrogen and helium production simultaneously using neutron spectrum precalculated in reactor vessel. Because the time and cost of this method are much less than the sampling method, we can measure at many positions and even get a contour map.
IT Projects Performance Indices and Evaluation
Authors: Akinyokun OC , Chiemeke SC
Published: June 2006

Information Technology (IT) is the fastest growing technology in the world today. Investment on IT projects in all the sectors of the world economy has been on the increase in the past ten years. This paper proposes 50 performance indices of IT projects and a tool for evaluating them. Some popular IT projects in Nigeria were surveyed by administering questionnaires and holding meetings with their principal actors. The performance indices were subjected to factor analysis by principal components using Statistical Package for Social Scientists (SPSS). Eleven factors were extracted and the percentage contribution of each factor to the success of IT projects was estimated. The total sum of the percentage contributions of all the factors was found to be less than 100. This revealed that there were some extraneous factors whose related performance indices were not considered in the administered questionnaire which were liable to play a significant role in the success of IT projects. Moreover, a factor scores coefficient matrix that can be used to estimate and rank the assessment of each Assessor of IT projects was generated.
Mechanism of G‐protein Activation by Rhodopsin†
Authors: Shichida Yoshinori , Morizumi Takefumi
Published: June 2006

Rhodopsin is a member of the family of G‐protein‐coupled receptors (GPCRs), and is an excellent molecular switch for converting light signals into electrical response of the rod photoreceptor cells. Light initiates cis–trans isomerization of the retinal chromophore of rhodopsin and leads to the formation of several thermolabile intermediates during the bleaching process. Recent investigations have identified spectrally distinguishable two intermediate states that can interact with the retinal G‐protein, transducin, and have elucidated the functional sharing of these intermediates. The initial contact with GDP‐bound G‐protein occurs in the meta‐Ib intermediate state, which has a protonated Schiff base as its chromophore. The meta‐Ib intermediate in the complex with the G‐protein converts to the meta‐II intermediate with releasing GDP from the α‐subunit of the G protein. Meta‐II has a de‐protonated Schiff base chromophore and induces binding of GTP to the α‐subunit of the G‐protein. Thus, the GDP–GTP exchange reaction, namely G‐protein activation, by rhodopsin proceeds through at least two steps, with conformational changes in both rhodopsin and the G‐protein.
A Glucose Sensor Role for Glucokinase in Anterior Pituitary Cells
Authors: Zelent Dorothy , Golson Maria L. , Koeberlein Brigitte , Quintens Roel , van Lommel Leentje , Buettger Carol , Weik-Collins Heather , Taub Rebecca , Grimsby Joseph , Schuit Frans , Kaestner Klaus H. , Matschinsky Franz M.
Published: June 2006

Enzymatic activity of glucokinase was demonstrated, quantitated, and characterized kinetically in rat and mouse pituitary extracts using a highly specific and sensitive spectrometric assay. A previously proposed hypothesis that the glucokinase gene might be expressed in the pituitary corticotrophic cells was therefore reexamined using mRNA in situ hybridization and immunohistochemical techniques. No evidence was found that corticotrophs are glucokinase positive, and the identity of glucokinase-expressing cells remains to be determined. The findings do, however, suggest a novel hypothesis that a critical subgroup of anterior pituitary cells might function as glucose sensor cells and that direct fuel regulation of such cells may modify the classical indirect neuroendocrine pathways that are known to control hormone secretion from anterior pituitary cells.
The Relationship Between Plasma Osteoprotegerin and Endothelium-Dependent Arterial Dilation in Type 2 Diabetes
Authors: Xiang Guang-da , Xu Lin , Zhao Lin-shuang , Yue Ling , Hou Jie
Published: June 2006

Osteoprotegerin is a recently identified inhibitor of bone resorption. Recent studies indicate that osteoprotegerin also acts as an important regulatory molecule in the vasculature. The purpose of this study was to investigate the relationship between plasma osteoprotegerin levels and endothelium-dependent arterial dilation in type 2 diabetic patients. The study subjects included 40 newly diagnosed type 2 diabetic patients and 46 healthy subjects. All patients were given insulin therapy for 6 months. Plasma osteoprotegerin concentration was measured in duplicate by a sandwich enzyme-linked immunosorbent assay method, and high-resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia, and after sublingual glyceryltrinitrate. The plasma osteoprotegerin level in patients before treatment was 3.36 ± 0.32 ng/l, which was significantly higher than that in control subjects (2.38 ± 0.25 ng/l, P < 0.001). After 6 months of treatment, osteoprotegerin levels decreased markedly (2.83 ± 0.34 ng/l, P < 0.001). Flow-mediated endothelium-dependent arterial dilation in patients before treatment was 3.21 ± 0.52%, which was significantly lower than that in control subjects (4.46 ± 0.56%, P < 0.01), and it improved markedly after 6 months of treatment (4.03 ± 0.49%, P < 0.01). In multivariate analysis, osteoprotegerin was significantly associated with endothelium-dependent arterial dilation, fasting blood glucose (FBG), HbA1c (A1C), and ultrasensitive C-reactive protein (CRP) at baseline (P < 0.01). The absolute changes in osteoprotegerin showed significant correlation with changes in endothelium-dependent arterial dilation, FBG, A1C, and CRP in diabetic patients during the course of treatment (P < 0.01). This study shows that plasma osteoprotegerin levels are elevated in newly diagnosed diabetic patients and are significantly associated with endothelial function.
IGF-Binding Protein-1 Levels Are Related to Insulin-Mediated Glucose Disposal and Are a Potential Serum Marker of Insulin Resistance
Authors: Maddux Betty A. , Chan Adelene , Mandarino Lawrence J. , Goldfine Ira D. , De Filippis Elena A.
Published: June 2006

OBJECTIVE—IGF-binding protein (IGFBP)-1 is negatively regulated by insulin. We determined whether the measurement of IGFBP-1 in serum is a useful marker of insulin resistance.

RESEARCH DESIGN AND METHODS—Twenty-three subjects underwent a euglycemic insulin clamp. Glucose disposal rates (M) were then correlated with measurements of IGFBP-1, fasting insulin levels, homeostasis model assessment (HOMA), and BMI.

RESULTS—IGFBP-1 levels more strongly correlated with M (R = 0.73) than the other parameters such as BMI or HOMA. The level of this protein decreased in individuals who became more insulin sensitive by exercise training.

CONCLUSIONS—These studies show a strong correlation between insulin sensitivity and the serum levels of IGFBP-1. These studies suggest, therefore, that measurement of this protein may be valuable in identifying those individuals with insulin resistance and those individuals who respond to interventional strategies.
Short Stature and the Risk of Adiposity, Insulin Resistance, and Type 2 Diabetes in Middle Age
Authors: Asao Keiko , Kao W.H. Linda , Baptiste-Roberts Kesha , Bandeen-Roche Karen , Erlinger Thomas P. , Brancati Frederick L.
Published: June 2006

OBJECTIVE—To investigate the association between stature-related measurements (height, leg length, and leg length–to–height ratio) and adiposity, insulin resistance, and glucose intolerance.

RESEARCH DESIGN AND METHODS—We conducted a cross-sectional analysis of a nationally representative sample of 7,424 adults aged 40–74 years, from the Third National Health and Nutrition Examination Survey (1988–1994). The main outcome measures were percent body fat, homeostasis model assessment of insulin resistance (HOMA-IR), and glucose intolerance based on the World Health Organization’s 1985 criteria for an oral glucose tolerance test.

RESULTS—Shorter height and leg length, and lower leg length–to–height ratio, were associated with higher percent body fat, especially in women. Lower leg length–to–height ratio was associated with greater insulin resistance estimated by HOMA-IR. In multinomial regression models adjusting for potential confounders, including percent body fat, the relative prevalence of type 2 diabetes per 1-SD lower values in height, leg length, and leg length–to–height ratio were 1.10 (95% CI 0.94–0.29), 1.17 (0.98–1.39), and 1.19 (1.02–1.39), respectively.

CONCLUSIONS—Our study supports the hypothesis that adult markers of prepubertal growth, especially leg length–to–height ratio, are associated with adiposity, insulin resistance, and type 2 diabetes in the general U.S. population.
Assessing the Impact of Visual Acuity on Quality of Life in Individuals With Type 2 Diabetes Using the Short Form-36
Authors: Clarke Philip M. , Simon Judit , Cull Carole A. , Holman Rury R.
Published: June 2006

OBJECTIVE—We sought to ascertain quality-of-life measures and utility values associated with visual acuity in type 2 diabetes.

RESEARCH DESIGN AND METHODS—The Medical Outcome Study Short Form with 36 items (SF-36) was administered to 4,051 individuals with type 2 diabetes who were enrolled in the Lipids in Diabetes Study, and their best attainable vision was determined using an Early Treatment of Diabetic Retinopathy Study chart, expressed as a LogMAR score. Eight domain scores and a utility value representing an overall quality-of-life score were calculated using predefined algorithms. The associations between quality of life measured and best-eye visual acuity were assessed graphically and by regression analysis.

RESULTS—All eight SF-36 domain scores were negatively associated with reduced visual acuity. The impact of lower levels of visual acuity ranged from a decline of 1.3 units for a 0.1-LogMAR increase for physical functioning and 0.6 units in mental health. Regression analysis indicated a negative association (P < 0.001) between utility and reduced visual acuity after controlling for sex, BMI, smoking status, and history of diabetes complications. Patients whose LogMAR scores equated to legally blind had, on average, 0.054 (95% CI 0.034–0.074) lower utility compared with patients with normal visual acuity.

CONCLUSIONS—Reduced visual acuity is negatively associated with quality of life. The utility scores estimated here should inform studies quantifying the burden of diabetes and those evaluating potential therapies for treating or preventing diabetic eye diseases.
Efficacy and Safety of Atorvastatin in the Prevention of Cardiovascular End Points in Subjects With Type 2 Diabetes
Authors: Knopp Robert H. , d’Emden Michael , Smilde Johan G. , Pocock Stuart J. ,   on behalf of the ASPEN Study Group
Published: June 2006

OBJECTIVE—Cardiovascular disease (CVD) risk is increased in type 2 diabetes. The purpose of this study was to assess the effect of 10 mg of atorvastatin versus placebo on CVD prevention in subjects with type 2 diabetes and LDL cholesterol levels below contemporary guideline targets.

RESEARCH DESIGN AND METHODS—Subjects were randomly assigned to receive 10 mg of atorvastatin or placebo in a 4-year, double-blind, parallel-group study. The composite primary end point comprised cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, recanalization, coronary artery bypass surgery, resuscitated cardiac arrest, and worsening or unstable angina requiring hospitalization.

RESULTS—A total of 2,410 subjects with type 2 diabetes were randomized. Mean LDL cholesterol reduction in the atorvastatin group over 4 years was 29% versus placebo (P < 0.0001). When we compared atorvastatin versus placebo, composite primary end point rates were 13.7 and 15.0%, respectively (hazard ratio 0.90 [95% CI 0.73–1.12]). In the subset of 1,905 subjects without prior myocardial infarction or interventional procedure, 10.4% of atorvastatin- and 10.8% of placebo-treated subjects experienced a primary end point (0.97 [0.74–1.28]). In the 505 subjects with prior myocardial infarction or interventional procedure, 26.2% of atorvastatin- and 30.8% of placebo-treated subjects experienced a primary end point (0.82 [0.59–1.15]). Relative risk reductions in fatal and nonfatal myocardial infarction were 27% overall (P = 0.10) and 19% (P = 0.41) and 36% (P = 0.11) for subjects without and with prior myocardial infarction or interventional procedure, respectively.

CONCLUSIONS—Composite end point reductions were not statistically significant. This result may relate to the overall study design, the types of subjects recruited, the nature of the primary end point, and the protocol changes required because of changing treatment guidelines. For these reasons, the results of the Atorvastatin Study for Prevention of Coronary Heart Disease Endpoints in Non-Insulin-Dependent Diabetes Mellitus (ASPEN) did not confirm the benefit of therapy but do not detract from the imperative that the majority of diabetic patients are at risk of coronary heart disease and deserve LDL cholesterol lowering to the currently recommended targets.
Ethnicity, Obesity, and Risk of Type 2 Diabetes in Women
Authors: Shai Iris , Jiang Rui , Manson JoAnn E. , Stampfer Meir J. , Willett Walter C. , Colditz Graham A. , Hu Frank B.
Published: June 2006

OBJECTIVE—To examine ethnic differences in risk of type 2 diabetes, taking dietary and lifestyle risk factors into account.

RESEARCH DESIGN AND METHODS—A prospective (1980–2000) cohort (from The Nurses’ Health Study) including 78,419 apparently healthy women (75,584 whites, 801 Asians, 613 Hispanics, and 1,421 blacks) was studied. Detailed dietary and lifestyle information for each participant was repeatedly collected every 4 years.

RESULTS—During 1,294,799 person-years of follow-up, we documented 3,844 incident cases of diabetes. Compared with whites, the age-adjusted relative risks (RRs) were 1.43 (95% CI 1.08–1.90) for Asians, 1.76 (1.32–2.34) for Hispanics, and 2.18 (1.82–2.61) for blacks. After adjustment for BMI, the RRs changed to 2.26 (1.70–2.99) for Asians, 1.86 (1.40–2.47) for Hispanics, and 1.34 (1.12–1.61) for blacks. For each 5-unit increment in BMI, the multivariate RR of diabetes was 2.36 (1.83–3.04) for Asians, 2.21 (1.75–2.79) for Hispanics, 1.96 (1.93–2.00) for whites, and 1.55 (1.36–1.77) for blacks (P for interaction <0.001). For each 5-kg weight gain between age 18 and the year 1980, the risk of diabetes was increased by 84% (95% CI 58–114) for Asians, 44% (26–63) for Hispanics, 38% (28–49) for blacks, and 37% (35–38%) for whites. A healthy diet high in cereal fiber and polyunsaturated fat and low in trans fat and glycemic load was more strongly associated with a lower risk of diabetes among minorities (RR 0.54 [95% CI 0.39–0.73]) than among whites (0.77 [0.72–0.84]).

CONCLUSIONS—The risk of diabetes is significantly higher among Asians, Hispanics, and blacks than among whites before and after taking into account differences in BMI. Weight gain is particularly detrimental for Asians. Our data suggest that the inverse association of a healthy diet with diabetes is stronger for minorities than for whites.
Blood Pressure and Hematocrit in Diabetes and the Role of Endothelial Responses in the Variability of Blood Viscosity
Authors: Salazar-Vazquez Beatriz Y. , Intaglietta Marcos , Rodríguez-Morán Martha , Guerrero-Romero Fernando
Published: June 2006

OBJECTIVE—To investigate the relationship between mean arterial blood pressure and hematocrit in a population of treated diabetic patients and a control population of healthy individuals.

RESEARCH DESIGN AND METHODS—Data on hematocrit and blood pressure were obtained from 129 diabetic subjects (87 women and 42 men) and 103 healthy subjects (76 women and 27 men) enrolled in a cross-sectional study. Alcohol consumption, ischemic heart disease, stroke, neoplasia, renal, hepatic, and chronic inflammatory disease were exclusion criteria.

RESULTS—The hematocrit of diabetic patients ranged from 0.35 to 0.52, and blood pressure had a bimodal distribution described by a second-order polynomial (P < 0.001), whereby elevated pressures correlated with low and high hematocrit, while the minimum average pressure was at hematocrit 0.43. Hematocrit of normal control subjects (range 0.28–0.55) was uncorrelated to blood pressure (averaged 99.7 ± 9.7 mmHg). High blood pressure, low hematocrit diabetic subjects up to the minimum average hematocrit of 0.43 had a negative correlation (P < 0.0001) between these variables.

CONCLUSIONS—Our findings are compatible with the hypothesis that diabetic patients present normal responses to hematocrit variation and therefore blood viscosity and shear stress in mediating the release of vasodilators and lack the ability to autoregulate blood pressure relative to differences in hematocrit by comparison to nondiabetic subjects. These findings also suggest that the treatment of diabetes should target maintaining an optimal hematocrit in order to lower cardiovascular risk.
Glucose Control Influences Glomerular Filtration Rate and Its Prediction in Diabetic Subjects
Authors: Rigalleau Vincent , Lasseur Catherine , Raffaitin Christelle , Perlemoine Caroline , Barthe Nicole , Chauveau Philippe , Combe Christian , Gin Henri
Published: June 2006

OBJECTIVE—Hyperglycemia increases glomerular filtration rate (GFR), but the influence of HbA1c (A1C) on GFR and GFR’s prediction by recommended equations remains to be determined.

RESEARCH DESIGN AND METHODS—In 193 diabetic patients, we searched for an association between A1C and isotopically measured GFR (51Cr-EDTA) and their predictions by the Cockcroft and Gault formula (CG) and the modification of diet in renal disease (MDRD) equation. Their accuracy for the diagnosis of moderate (GFR <60 ml/min per 1.73 m2) or severe (GFR <30 ml/min per 1.73 m2) renal failure was compared from receiver operating characteristic (ROC) curves, before and after categorizing the patients as well (A1C ≤8%) or poorly controlled.

RESULTS—The mean GFR was 57.0 ± 34.8 ml/min per 1.73 m2 and was well correlated with both estimations (CG r = 0.75, MDRD r = 0.83; P < 0.05). The areas under the ROC curves were higher with the MDRD (P < 0.05). A1C was correlated (P < 0.001) with the GFR (r = 0.29), MDRD (r = 0.38), CG (r = 0.26), and the absolute differences between the GFR and their CG but not MDRD estimations (r = 0.17, P < 0.05). Each +1% A1C was associated with +6.0 ml/min per 1.73 m2 GFR (CG +5.6, MDRD +5.3). After separating well-controlled (n = 88, A1C 7.0 ± 0.7%) and poorly controlled (n = 105, 9.6 ± 1.3%) patients, the diagnostic accuracies were better (P < 0.05) for the MDRD, except for the diagnosis of moderate renal failure in well-controlled patients (NS).

CONCLUSIONS—GFR and its estimations correlate with A1C. Although the relations between GFR and its estimations were not affected by the degree of glucose control, the precision and diagnostic accuracy of the CG formula were diminished for A1C >8%. The MDRD equation was more accurate and robust in diabetic patients with impaired renal function.
Prospective Study of Diabetes and Risk of Hip Fracture
Authors: Janghorbani Mohsen , Feskanich Diane , Willett Walter C. , Hu Frank
Published: June 2006

OBJECTIVE—The purpose of this study was to determine whether women with type 1 and type 2 diabetes are at higher risk of hip fractures.

RESEARCH DESIGN AND METHODS—A total of 109,983 women aged 34–59 years in 1980 were followed through 2002 for the occurrence of hip fracture. At baseline and through biennial follow-up, women were asked about their history and treatment of diabetes and other potential risk factors for hip fracture.

RESULTS—During 2.22 million person-years of follow-up, 1,398 women had a hip fracture. Compared with women without diabetes, the age-adjusted relative risk (RRs) of hip fracture was 7.1 (95% CI 4.4–11.4) for women with type 1 diabetes and 1.7 (1.4–2.0) for those with type 2 diabetes. After further adjustment for BMI, smoking, physical activity, menopausal status, daily intake of calcium, vitamin D, protein, and postmenopausal hormone use, the multivariate RR of incident hip fracture in individuals with type 1 diabetes compared with individuals without diabetes was 6.4 (3.9–10.3) and with type 2 diabetes was 2.2 (1.8–2.7). The RRs increased with longer duration of type 2 diabetes (3.1 [2.3–4.0] for ≥12 years compared with no diabetes, P for trend < 0.001) and ever use of insulin.

CONCLUSIONS—These data indicate that both type 1 and type 2 diabetes are associated with an increased risk of hip fracture. The results of this study highlight the need for fracture-prevention strategies in women with diabetes.
Are Obesity-Related Metabolic Risk Factors Modulated by the Degree of Insulin Resistance in Adolescents?
Authors: Bacha Fida , Saad Rola , Gungor Neslihan , Arslanian Silva A.
Published: June 2006

OBJECTIVE—Obesity is often associated with insulin resistance and the components of the metabolic syndrome. However, wide variations in insulin sensitivity are noted in obese youth. It is not clear if greater insulin resistance confers a higher risk of cardiovascular comorbidities and risk for type 2 diabetes.

RESEARCH DESIGN AND METHODS—We investigated physical and metabolic features of 54 obese adolescents. Subsequently, we pair matched 17 moderately insulin-resistant (MIR group) to 17 severely insulin-resistant (SIR group) youth based on cut points for insulin sensitivity (MIR group insulin sensitivity within 2 SDs and SIR group <2 SDs of normal-weight adolescent values). We evaluated differences in body composition (dual-energy X-ray absorptiometry), abdominal fat (computed tomography scan), cardiorespiratory fitness (CRF) (Vo2max on a treadmill), insulin sensitivity and secretion (hyperinsulinemic-euglycemic and hyperglycemic clamps), substrate utilization (indirect calorimetry), and fasting adiponectin and lipid profile.

RESULTS—SIR youth had higher visceral adiposity (78.3 ± 6.9 vs. 60.3 ± 6.9 cm2, P = 0.017) and waist-to-hip ratio (0.91 ± 0.01 vs. 0.86 ± 0.02, P = 0.026) and lower HDL (1.0 ± 0.03 vs. 1.16 ± 0.06 mmol/l, P = 0.015) than pair-matched MIR subjects. There was a tendency for adiponectin (6.1 ± 0.5 vs. 8.6 ± 1.1 μg/ml, P = 0.079) and CRF (49.9 ± 3.2 vs. 55.2 ± 3.5 ml · min−1 · kg−1 fat-free mass, P = 0.09) to be lower in SIR subjects. SIR youth also had an impaired balance between insulin sensitivity and β-cell compensation with a lower glucose disposition index.

CONCLUSIONS—Despite similar BMI, the degree of insulin resistance impacts the risk for obesity-related metabolic comorbidities. The SIR youth are at greater risk for type 2 diabetes and cardiovascular disease.