scispace - formally typeset
Search or ask a question

Showing papers by "Yi Chen published in 1993"


Journal ArticleDOI
TL;DR: Insulin resistant pattern B subjects are insulin resistant, have higher glucose, insulin, and TG, lower HDL-cholesterol levels, and higher blood pressure than those with pattern A or intermediate.
Abstract: Subjects characterized by a predominance of small LDL particles (pattern B) have changes in plasma triglyceride (TG) and HDL-cholesterol concentrations consistent with the presence of resistance to insulin-mediated glucose uptake. To pursue this issue, plasma glucose and insulin responses to oral glucose, insulin-mediated glucose disposal, and lipoprotein concentrations were measured in subjects categorized on the basis of LDL peak diameter measured by gradient gel electrophoresis. Subjects with pattern B had higher (P < 0.05-0.001) total integrated plasma glucose (20.7 +/- 1.0 mmol/liter.h) and insulin (1,743 +/- 293 pmol/liter.h) responses to oral glucose compared with glucose (16.3 +/- 0.4 and 19.2 +/- 0.8 mmol/liter.h) and insulin (856 +/- 60 and 1,222 +/- 168 pmol/liter.h) responses in those with either pattern A or an intermediate pattern. Pattern B individuals were shown to be more insulin resistant on the basis of higher steady state plasma glucose concentrations (SSPG, 10.4 +/- 1.0, P < 0.002, vs. 7.5 +/- 0.7 and 6.0 +/- 0.4 mmol/liter) after a constant infusion of somatostatin, glucose, and insulin than those with either the intermediate or pattern A subclass. Pattern B subjects also had higher concentrations of (P < 0.001) TG (1.98 +/- 0.15 vs. 1.33 +/- 0.17 and 0.77 +/- 0.05 mmol/liter) and lower (P < 0.01-0.001) HDL cholesterol (1.12 +/- 0.06 vs. 1.34 +/- 0.05 vs. 1.45 +/- 0.05 mmol/liter) than those with either the intermediate or pattern A. Finally, significant (P < 0.001) correlation coefficients existed between LDL diameter and SSPG (r = -0.44); glucose (r = -0.41) and insulin (r = -0.38) responses; TG (r = -0.65) and HDL-cholesterol (r = 0.42) concentrations; and systolic (r = -0.34) and diastolic (r = -0.34) blood pressure. Thus, pattern B subjects are insulin resistant, have higher glucose, insulin, and TG, lower HDL-cholesterol levels, and higher blood pressure than those with pattern A or intermediate.

691 citations


Journal ArticleDOI
TL;DR: The postprandial RP concentration in the Sf 20-400 lipoprotein fraction was higher than normal in patients with NIDDM, and associations have been defined in patients without diabetes mellitus between postPRandial insulin response, fasting TG and high density lipop Protein-cholesterol concentrations, and magnitude of postpr andial increase in TG-rich lipoproteins of intestinal origin.
Abstract: In this paper we have compared the postprandial increase in triglyceride (TG) rich lipoproteins of intestinal origin in 10 patients with noninsulin-dependent diabetes mellitus (NIDDM) and 10 subjects with normal glucose tolerance. The two groups were matched for age, sex distribution, body mass index, and plasma TG concentration. Breakfast was consumed at 0800 h and lunch at 1200 h, at which time vitamin A was also administered. Blood was sampled frequently from 1200 h to 2400 h, and measurements made of glucose, insulin, and TG concentrations. Furthermore, the retinyl palmitate (RP) content of plasma, the Sf > 400 lipoprotein fraction, and the Sf 20-400 lipoprotein fraction was also determined, and differences compared by two-way analysis of variance. Fasting and postprandial (from 1200 h to 2400 h) TG concentrations in the plasma and the two lipoprotein fractions were not significantly different in normal subjects and patients with NIDDM. In addition, the postprandial RP concentration of the two groups ...

151 citations


Journal ArticleDOI
TL;DR: Evidence is provided that, in a backcross between strains Mus spretus and C57BL/6J, apoAII levels correlate with plasma FFA concentrations on both chow and high-fat diets and that apoCII levels are linked to the apo AII gene, a gene that controls plasma apo aII levels, and that APOAII influences, by an unknown mechanism, plasma F FA levels.
Abstract: Although it has been hypothesized that the synteny between mouse and human genes provides an approach to the localization of genes that determine quantitative traits in humans, this has yet to be demonstrated We tested this approach with two quantitative traits, plasma apolipoprotein A-II (apoAII) and free fatty acid (FFA) levels ApoAII is the second most abundant protein of high density lipoprotein particles, but its function remains largely unknown We now show that, in a backcross between strains Mus spretus and C57BL/6J, apoAII levels correlate with plasma FFA concentrations on both chow (P < 00001) and high-fat (P < 00003) diets and that apoAII levels are linked to the apoAII gene (P < 00002) To test whether variations of the apoAII gene influence plasma lipid metabolism in humans, we studied 306 individuals in 25 families enriched for coronary artery disease The segregation of the apoAII gene was followed by using an informative simple sequence repeat in the second intron of the gene and two nearby genetic markers Robust sib-pair linkage analysis was performed on members of these families using the SAGE linkage programs The results suggest linkage between the human apoAII gene and a gene controlling plasma apoAII levels (P = 003) Plasma apoAII levels were also significantly correlated with plasma FFA levels (P = 0007) Moreover, the apoAII gene exhibited linkage with a gene controlling FFA levels (P = 0003) Evidence for nonrandom segregation was seen with markers as far as 6-12 centimorgans from the apoAII structural locus These data provide evidence, in two species, that the apoAII gene is linked to a gene that controls plasma apoAII levels and that apoAII influences, by an unknown mechanism, plasma FFA levels The results illustrate the utility of animal studies for analysis of complex traits

71 citations


Journal ArticleDOI
TL;DR: A new method of detecting structured changes in trabecular bone, such as those associated with osteoporosis, was evaluated on magnetic resonance images of the wrist based on gray‐scale morphological granulometries, which classify image texture by iteratively filtering an image and measuring the rate of change of structural diminution in a filtered‐image sequence.
Abstract: A new method of detecting structured changes in trabecular bone, such as those associated with osteoporosis, was evaluated on magnetic resonance images of the wrist. The method was based on gray-scale morphological granulometries which classify image texture by iteratively filtering an image and measuring the rate of change of structural diminution in a filtered-image sequence. A classification scheme capable of distinguishing structural changes in trabecular bone starting from normal trabeculae through sclerotic, cystic, and grossly porotic bone is presented. Results of the application of this technique to the evaluation of high resolution magnetic resonance images of the wrist are presented.

49 citations


Journal ArticleDOI
TL;DR: It is reported that a simple hydrophobic purification scheme separates intact hCG from nicked hCG as well as from hCG beta core fragment, and it should now be possible to make reference preparations of these forms of hCG directly from the raw urine of normal pregnant patients and those with trophoblastic disease.
Abstract: hCG is found in pregnancy urine and in urine from some cancer patients in a variety of forms whose concentrations have clinical importance. Recently, concerns about accurate measurement of these forms have been raised because of the finding that hCG with peptide bond cleavages within the beta-subunit is not recognized by commonly used antibodies. Such nicked forms of hCG are biologically inactive or of very low activity. They are present in normal pregnancy urine and to varying extents in the urine of patients with trophoblastic disease. International reference preparations of hCG contain nicked forms of hCG. Previously, it was not possible to separate nicked hormone from the intact form of hCG. This was a serious impediment to producing improved reference standards from natural pregnancy hormone. We now report that a simple hydrophobic purification scheme separates intact hCG from nicked hCG as well as from hCG beta core fragment. This scheme is a modification of the method of Hiyama et al. The order of elution from low to high hydrophobicity is hCG beta core fragment, nicked hCG, and lastly, intact hCG. Nicking of the putative amphipathic helix loop, hCG beta 38-57, apparently renders the hormone significantly less hydrophobic despite the equal molar content of sialic acid. The hCG CR 127 nicked preparation was only 10% as potent as the reference preparation in a heterodimer-directed assay. The nicked-depleted hCG CR 127 was 30% more potent in this assay. Improved hCG reference standards should display similar increases in immunopotency (20-30%) with most antiheterodimeric antibodies and similar increases in bio-potency assays. It should now be possible to make reference preparations of these forms of hCG directly from the raw urine of normal pregnant patients and those with trophoblastic disease.

28 citations


Journal ArticleDOI
TL;DR: The finding of a discrete hLH beta core fragment in a tissue extract suggests that it may be produced within pituitary tissue, rather than by a peripheral degradation process, and may allow development of assays that distinguish it from its hCG analog.
Abstract: A fragment of the hCG beta-subunit is present in high concentrations in the urine of pregnant women and the urine from individuals with ovarian or other cancers. The utility of immunoreactive measurement of this fragment to monitor therapy of such cancers is compromised, however, because high concentrations of the molecule are also detected in the urine of healthy postmenopausal women. It has been suggested that the latter observations may be due to a cross-reacting human (h) LH beta core fragment, presumably of pituitary origin, but no such fragment had ever been isolated. We have now isolated a hLH beta core fragment from a pituitary tissue extract. Its structure is exactly analogous to that of the hCG beta core fragment. The finding of a discrete hLH beta core fragment in a tissue extract suggests that it may be produced within pituitary tissue, rather than by a peripheral degradation process. We have also found that the same immunoaffinity method used to extract the hLH beta core fragment from the pit...

27 citations


Journal ArticleDOI
TL;DR: In this article, the relation between the catalytic performance and the composition of the catalyst surface has been studied by means of X-ray diffraction, CO2 temperature-programmed desorption, O2 temperature programmable desorcization, and laser Raman spectroscopy techniques.
Abstract: Alkaline earth metal titanates used as catalysts for methane oxidative coupling have been prepared by (1) solid state reaction and (2) spray combustion methods. It has been established that the bulk phase of all the samples prepared have a perovskite-like structure and that the surface composition and hence the catalytic performance for methane oxidative coupling of the samples differ considerably and are dependent on the preparation method. The relation between the catalytic performance and the composition of the catalyst surface has been studied by means of X-ray diffraction, CO2 temperature-programmed desorption, O2 temperature-programmed desorption. X-ray photoelectron spectroscopy, and laser Raman spectroscopy techniques. A high surface concentration of Ti4+ cations leads to the complete oxidation of methane, and a high surface concentration of alkaline earth metal cations facilitates the formation of C2 hydrocarbons. Surface basicity is necessary for methane oxidative coupling and the oxygen adsorbed on the basic site is also indispensable; in fact, the adsorbed electron deficient species, i.e. O− and O−2, on the surface play a crucial role in methane conversion and C2 selectivity. The adsorption of carbon dioxide could compete for the adsorption site of oxygen, and exerts an unfavorable influence in methane oxidative coupling.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present an optical and force microscopy system using a glass probe, which is capable of monitoring the sample topography and optical parameters using the light guiding properties of the tip.
Abstract: Operational aspects of a newly developed simultaneous near‐field optical and force microscope are considered. Using a glass probe, the technique is capable of monitoring the sample topography, through its force microscopy capability, as well as the sample’s optical parameters, using the light guiding properties of the tip. In addition, the force signal can be used reliably as a feedback signal, thus allowing a crash‐free detection of optical fields in the vicinity of opaque steps on the sample. Results are presented on imaging a variety of samples including biological and nonbiological objects and thin film structures. In each instance, results obtained with different modalities are compared. It is shown that the simultaneity of the images obtained with different modalities can be very useful in, and sometimes necessary for, sample identification.

21 citations


Journal ArticleDOI
Zheng Hu1, Jianyi Shen1, Yi Chen1, Mu Lu1, Yuanfu Hsia1 
TL;DR: In this article, a new chemical method for preparing ultrafine amorphous Ni85P15 alloy particles with uniform size and spherical shape is reported, which consists of primary nucleation of NiB followed by autocatalytic deposition of the components.
Abstract: A new chemical method for preparing ultrafine amorphous Ni85P15 alloy particles with uniform size and spherical shape is reported. The particles were prepared by reduction of nickel chloride with sodium hypophosphite initiated with a drop of potassium borohydride solution at room temperature. The preparation mechanism, which consists of primary nucleation of NiB followed by autocatalytic deposition of the components, is discussed. The amorphous structure of the particles was identified by X-ray diffraction and selected area electron diffraction. X-ray photoelectron spectroscopy indicated that nickel and phosphorus are present as an alloy. Transmission election microscopy revealed that the particles are uniform and spherical with a diameter of about 100 nm.

17 citations



Journal ArticleDOI
Weiyan Guan1, Yi Chen1, J.Y.T. Wei1, Yunhui Xu1, Maw-Kuen Wu1 
TL;DR: In this paper, the magnetic ordering temperatures T m of Pr ions in (R 1−x Pr x )Ba 2 Cu 3 O 7 systems (R = Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm, Nd and Y) were measured.
Abstract: The magnetic ordering temperatures T m of Pr ions in (R 1−x Pr x )Ba 2 Cu 3 O 7 systems (R = Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm, Nd and Y) with x = 0.5 – 1.0 were measured. We observe that T m decreases monotonically with increasing R concentration. At constant x, T m is R ion-size dependent. The slope in the T m vs. x is steeper for ion with smaller ionic radius. In comparison with the ion-size effect on the superconducting transition temperatures T c in these systems, the observed results can be qualitatively interpreted in terms of the hybridization between the local states of Pr ion and the conduction band states of the CuO 2 planes.

Journal ArticleDOI
TL;DR: A new phase of a gas of pairs of electrons bounded in a singlet state is found in the one-dimensional t-J model for J>2t and the density of electrons less than 0.2.
Abstract: A new phase of a gas of pairs of electrons bounded in a singlet state is found in the one-dimensional t-J model for J>2t and the density of electrons less than 0.2. This phase was conjectured in the study of the diagonalization of small lattices [Phys. Rev. Lett. 66, 2388 (1991)]. The existence of this new phase for much larger lattice sizes is demonstrated by a combination of two numerical methods, the variational Monte Carlo and the power method. A trial wave function for this phase is proposed and shown to be in good agreement with the ground state obtained by the power method

Journal ArticleDOI
TL;DR: In this article, the chemical reduction method was used for the preparation of ultrafine amorphous alloy particles and the crystallization process of Fe35Ni15B26 sample was investigated by Mossbauer spectroscopy, and the electron irradiation effect of Fe82P11B7 sample was reported.
Abstract: FeNiB and FePB ultrafine amorphous alloy particles were prepared by the chemical reduction method. The crystallization process of Fe35Ni15B26 sample was investigated by Mossbauer spectroscopy, and the electron irradiation effect of the Fe82P11B7 sample was reported. Some comparisons of these two samples were presented.

Journal ArticleDOI
Jianyi Shen1, Zhiyu Li1, Yining Fan1, Zheng Hu1, Yi Chen1 
TL;DR: In this article, the reaction process, monitored by the change in pH value during the reaction, and the effect of addition rate of KBH 4 solution, i.e., the reaction time, was investigated.


Journal ArticleDOI
TL;DR: In this article, the 3D photoelectron spectra of lanthanum in the SrZrO 3 crystal lattice were investigated in terms of coexcitations of charge transfer type, namely O 2p → La 4f transitions.

Journal ArticleDOI
TL;DR: In this paper, two equations for justifying whether a FIA peak is a gamma peak or an exponentially modified Gaussian (EMG) peak or neither of them have been presented were presented. From these two equations, the peaks of flow injection extraction and FIA with single-line and two-line manifolds obtained in this paper are gamma peaks.
Abstract: Two equations for justifying whether a FIA peak is a gamma peak or an exponentially modified Gaussian (EMG) peak or neither of them have been presented. From these two equations, the peaks of flow injection extraction and FIA with single-line and two-line manifolds obtained in this paper are gamma peaks.

Journal ArticleDOI
TL;DR: In this article, it was shown that the spin-S exchange interaction model and the (2 S + 1)-state Potts model have the same thermodynamic properties in mean field theory.

Book ChapterDOI
Qijie Yan1, Y. S. Jin1, Yuhong Wang1, Yi Chen1, Xiancai Fu1 
TL;DR: In this paper, the catalytic performance of complex layered oxides with K 2 NiF 4 structure composing of alternating perovskite (ABO 3 ) and rock salt (AO) layers was studied for the oxidative coupling of methane to C 2 hydrocarbons.
Abstract: The catalytic performance of complex layered oxides with K 2 NiF 4 structure composing of alternating perovskite (ABO 3 ) and rock salt (AO) layers was studied for the oxidative coupling of methane to C 2 hydrocarbons. The partial substitution of transition metal ions in B position of the oxide by low valence metal ions such as Li, Zn and Mg ions was found to greatly improve the C 2 selectivity. A C 2 yield of 22% was obtained under 1073 K over Ca(Sr,Ba)LaFeLiO catalyst. Study of the deactivition showed that the CaLaFeLiO sample can maintain a C 2 yield of 19.2% after 420 hr on stream. The results are discussed on the basis of catalyst structure, valence state of transition metal ions in B site, and surface oxygen species.