PubMed Health⌕ Search

Biomedical subjects

J W Chen

Publications and source records attributed to J W Chen.

At least 19 recordsLinked to original sources
PubMed2005

Homozygous and heterozygous expression of a novel insulin-like growth factor-I mutation.

IGF-I is a key factor in intrauterine development and postnatal growth and metabolism. The secretion of IGF-I in utero is not dependent on GH, whereas in childhood and adult life, IGF-I secretion seems to be mainly controlled by GH, as revealed from studies on patients with GHRH receptor and GH receptor mutations. In a 55-yr-old male, the first child of consanguineous parents, presenting with severe intrauterine and postnatal growth retardation, microcephaly, and sensorineural deafness, we found a homozygous G to A nucleotide substitution in the IGF-I gene changing valine 44 into methione. The inactivating nature of the mutation was proven by functional analysis demonstrating a 90-fold reduced affinity of recombinantly produced for the IGF-I receptor. Additional investigations revealed osteoporosis, a partial gonadal dysfunction, and a relatively well-preserved cardiac function. Nine of the 24 relatives studied carried the mutation. They had a significantly lower birth weight, final height, and head circumference than noncarriers. In conclusion, the phenotype of our patient consists of severe intrauterine growth retardation, deafness, and mental retardation, reflecting the GH-independent secretion of IGF-I in utero. The postnatal growth pattern, similar to growth of untreated GH-deficient or GH-insensitive children, is in agreement with the hypothesis that IGF-I secretion in childhood is mainly GH dependent. Remarkably, IGF-I deficiency is relatively well tolerated during the subsequent four decades of adulthood. IGF-I haploinsufficiency results in subtle inhibition of intrauterine and postnatal growth.

Heterozygote↗
PubMed2004

Data evaluations and quantitative predictive models for vapor pressures of polycyclic aromatic hydrocarbons at different temperatures.

Polycyclic aromatic hydrocarbons (PAHs) are typical and ubiquitous organic pollutants. Vapor pressures, which can be classified as solid vapor pressure (P(S)) and (subcooled) liquid vapor pressure (P(L)), are key physicochemical properties governing the environmental fate of organic pollutants. It is of great importance to develop predictive models of vapor pressures. In the present study, partial least squares (PLS) regression together with 15 theoretical molecular structural descriptors was used to develop quantitative predictive models for vapor pressures of PAHs at different temperatures. Two procedures were adopted to develop the optimal predictive models by eliminating redundant molecular structural descriptors. The cross-validated Q2(cum) values for the obtained models have been found higher than 0.975, indicating good predictive ability and robustness of the models. It has been shown that the intermolecular dispersive interactions played a leading role in governing the values of log P(L). In addition to dispersive interactions, dipole-dipole interactions also played a secondary role in determining the magnitude of log P(S). In view of the scarceness of chemical standards for some PAHs, the difficulty in experimental determinations, and the high cost involved in experimental determinations, the obtained models should serve as a fast and simple first approximation of the vapor pressure values for PAHs at different environmental temperatures.

Environmental Pollutants↗
PubMed2003

Quantitative predictive models for octanol-air partition coefficients of polybrominated diphenyl ethers at different temperatures.

Quantitative predictive models for octanol-air partition coefficients of polybrominated diphenyl ethers at different environmental temperatures (T) were developed. Partial least squares (PLS) regression was used for model development. A list of 18 theoretical molecular structural descriptors was screened by PLS analysis. The optimal model was selected from the one containing nine theoretical molecular descriptors and 1/T as predictor variables. The cross-validated Q(2)(cum) value for the optimal model is 0.975, indicating a good predictive ability and stability of the model. Intermolecular dispersive interactions play a leading role in governing the magnitude of logK(OA). The lower the E(LUMO) (the energy of the lowest unoccupied molecular orbital), the greater the intermolecular interactions between octanol and PCB molecules, and thus the greater the logK(OA) values.

Environmental Pollutants↗
PubMed2003

Quantitative relationships between molecular structures, environmental temperatures and octanol-air partition coefficients of polychlorinated biphenyls.

A quantitative model that incorporates information on both environmental temperatures (T) and molecular structures, for logarithm of octanol-air partition coefficient to base 10 (logK(OA)) of polychlorinated biphenyls (PCBs) was developed. Partial least squares (PLS) analysis together with 16 theoretical molecular structural descriptors was used to develop the Quantitative relationships between structures, environmental temperatures and properties (QRSETP) model. The cross-validated Q(cum)(2) value for the optimal QRSETP model is 0.976, indicating a good predictive ability for logK(OA) of PCBs at different environmental temperatures. T, E(LUMO) (the energy of the lowest unoccupied molecular orbital), molecular size or average molecular polarizability (alpha), and the net atomic charges on chlorine, hydrogen and carbon atoms of PCB molecules, are major factors governing logK(OA). The lower the E(LUMO), the greater the intermolecular interactions between octanol and PCB molecules, and thus the greater the logK(OA) values. Because of intermolecular dispersive forces, the more chlorine atoms in PCB molecules, the greater the molecular size or alpha, the greater the logK(OA). The largest negative net atomic charge on a carbon atom (q(C)(-)) and molecular size or average molecular polarizability (alpha) are major factors governing temperature dependence of logK(OA). PCB molecules with low q(C)(-) values and more chlorines (big size or alpha) tend to have strong temperature dependence, due to intermolecular electrostatic interactions and dispersive forces, respectively.

Journal Article↗
PubMed2003

Quantitative structure-property relationships for vapor pressures of polybrominated diphenyl ethers.

Based on quantum chemical descriptors, by the use of partial least squares regression, quantitative structure-property relationship models for subcooled liquid vapor pressures (PL) of polybrominated diphenyl ether (PBDE) congeners were developed. The Q2cum value of the optimal model obtained is as high as 0.993, indicating a good predictive ability and robustness of the model. Although disagreements were observed between the predicted log PL values and log PL values of validation set, the model obtained can still be used for estimating PL of other PBDE congeners, considering the fact that accurate PL values for compounds with low volatility are extremely difficult to determine experimentally. Intermolecular dispersive interactions play a leading role in governing the values of PL, followed by electrostatic, dipole-dipole and dipole-induced dipole interactions. Intermolecular dispersive interactions also govern the values of enthalpies of vaporization.

Chemical Phenomena↗
PubMed2003

Free and total insulin-like growth factor (IGF)-I, -II, and IGF binding protein-1, -2, and -3 serum levels in patients with active thyroid eye disease.

To determine whether serum levels of total (T) and free (F) IGF-I and -II and IGF binding protein (IGFBP),-1, -2, and -3 are normal in euthyroid patients with Graves' disease and active thyroid ophthalmopathy, we investigated the above-mentioned parameters in 21 patients (11 male, 10 female) aged 50.8 +/- 11.8 yr (range 35-70) and 19 healthy individuals matched for age, gender, and body mass index. All patients had active thyroid eye disease (TED) with clinical activity scores > or = 4 and positive orbital octreoscan in both eyes. Serum T and F IGF-I and IGF-II were determined using noncompetitive time-resolved monoclonal immunofluorometric assays, IGFBP-1 was determined by an in-house RIA, IGFBP-2 by a novel in-house time-resolved immunofluorometric assay, whereas IGFBP-3 by an immunoradiometric assay. All data are expressed as mean +/- SD. Our results show that T and F IGF-I, -II, and IGFBP-1, -2, and -3 levels in patients were similar to controls and did not show any significant difference. Specifically, mean T IGF-I for patients group was 131 (61), F IGF-I was 0.47 (0.16), T IGF-II was 1056 (300), F IGF-II was 1.45 (0.54), IGFBP-1 was 33 (14), IGFBP-2 was 848 (377), and finally IGFBP-3 was 3953 (1422). For controls, mean T IGF-I was 146 (51), F IGF-I was 0.85 (0.43), T IGF-II was 939 (197), F IGF-II was 1.53 (0.53), IGFBP-1 was 44 (24), IGFBP-2 was 764 (316) and finally IGFBP-3 was 3721 (1017). Furthermore, no statistically differences emerged in the ratio between molar weights of T IGF-I/IGFBP-3 and T IGF-II/IGFBP-3, as well as to the F/T IGF-I and F/T IGF-II. Finally, no relationship was found between the levels of the above-mentioned parameters and clinical activity scores, octreoscan scores, and thyroid hormones. Our data demonstrate for the first time that serum levels of IGFs (including free fractions) and IGFBPs are not increased in euthyroid Graves' patients with active TED. The increased IGF levels in retrobulbar tissues previously described, appear to be independent of serum IGFs concentration and probably represent autocrine and/or paracrine activity.

Adult↗
PubMed2002

Quantitative relationships between molecular structures, environmental temperatures and octanol-air partition coefficients of PCDD/Fs.

A concise quantitative model that incorporates information on both environmental temperature (T) and molecular structures, for logarithm of octanol-air partition coefficient (K(OA)) to base 10 (logK(OA)) of PCDDs, was developed. Partial least squares (PLS) analysis together with 14 quantum chemical descriptors were used to develop the quantitative relationships between structures, environmental temperatures and properties (QRSETP) model. It has been validated that the obtained QRSETP model can be used to predict logK(OA) of other PCDDs. Molecular size, environmental temperature (T), q+ (the most positive net atomic charge on hydrogen or chlorine atoms in PCDD molecules) and E(LUMO) (the energy of the lowest unoccupied molecular orbital) are main factors governing logK(OA) of PCDD/Fs under study. The intermolecular dispersive interactions and thus the size of the molecules play a leading role in governing logK(OA). The more chlorines in PCDD molecules, the greater the logK(OA) values. Increasing E(LUMO) values of the molecules leads to decreasing logK(OA) values, implying possible intermolecular interactions between the molecules under study and octanol molecules. Greater q+ values results in greater intermolecular electrostatic repulsive interactions between PCDD and octanol molecules and smaller logK(OA) values.

Journal Article↗
PubMed2001

Endothelin-1 induces contraction of human and Australian possum gallbladder in vitro.

BACKGROUND: Endothelin-1 (ET-1) stimulates guinea pig gallbladder (GB) muscle strip contractility; however, the role and source of ET-1 in the GB remains to be elucidated. AIMS: To determine the effect of ET-1 on human and possum GB muscle strip contractility and evaluate whether ET-1 is present in GB tissue. METHODS: GB muscle strips were mounted in organ baths to measure isometric tension. ET-1 was added cumulatively with and without pretreatment with the neural blocker tetrodotoxin (TTX) or the ET receptor antagonists BQ-123, BQ-788, and tezosentan. Immunohistochemical localization of ET was performed on freshly fixed and cultured GBs. RESULTS: ET-1 induced concentration-dependent increases in tone in human and possum GB strips (p<0.05). This response was unaffected by BQ-123, BQ-788, and TTX but antagonized by BQ-123+BQ-788 in the human tissue only. Tezosentan (10(-4) mol/l) blocked the ET-1-induced response in human and possum GB strips (p<0.001). Although ET immunoreactivity was absent in freshly fixed possum GB, immunoreactivity was observed in the GB epithelium of freshly fixed human tissue and in both possum and human tissue following 24 h of organ culture. CONCLUSION: ET-1 acts directly on human and possum GB smooth muscle producing contractions, possibly via ET-B receptors. ET may be present under pathophysiological conditions altering GB function.

Animals↗
PubMed2001

Constructing parton convolution in effective field theory.

Parton convolution models have been used extensively in describing the sea quarks in the nucleon and explaining quark distributions in nuclei (the EMC effect). From the effective field theory point of view, we construct the parton convolution formalism which has been the underlying conception of all convolution models. We explain the significance of scheme and scale dependence of the auxiliary quantities such as the pion distributions in a nucleon. As an application, we calculate the complete leading nonanalytic chiral contribution to the isovector component of the nucleon sea.

Journal Article↗
PubMed2001

Influence of cholesterol on the biophysical properties of the sphingomyelin/DOPC binary system.

The influence of cholesterol on the sphingomyelin (SM)/dioleoylphosphatidylcholine (DOPC) binary system was investigated in various respects. Electron spin resonance (ESR) measurements reveal that the order parameter of 5DS (5-doxyl stearic acid) in SM/DOPC bilayers increases notably when the concentration of cholesterol is over 30 mol%. Membrane potential measurements indicate that the K+ permeability of the SM/DOPC bilayer decreases steeply at 40 mol% cholesterol concentration. Both these experiments suggest that cholesterol reduces the motion amplitude of hydrocarbon chains abruptly above 30 mol%. In contrast to the ordering effects on the hydrocarbon chains, (31)P-NMR results indicate that cholesterol slightly increases the motion of phosphate groups of the lipids. (31)P-NMR also raises the possibility of domain formation in the presence of cholesterol. Fluorescence-quenching experiments verified that solid domains appear in the binary system when cholesterol is present, and percolation threshold occurs at 50 mol% cholesterol concentration. The solid domains bear the properties of liquid ordered phase, which is the basic structure of caveolae and functional rafts. So this work provides an artificial model for the study of rafts and caveolae on biological membranes.

Animals↗
PubMed2001

Measuring the P-odd pion-nucleon coupling h((1))(piNN) in pi(+)-photoproton production near threshold.

We show that gamma-->p-->pi(+)n in the threshold region is an excellent candidate for measuring the leading parity-violating pion-nucleon coupling h((1))(piNN) to an uncertainty of 20% if it has a natural size from dimensional analysis. The conclusion is based on a large unpolarized cross section, a new low-energy theorem for the photon polarization asymmetry at the threshold A(gamma)/(th) = square root of 2 f(pi)(mu(p)-mu(n))h((1))(piNN)/g(A)m(N) approximately h((1))(piNN)/2, and its strong dominance at forward and backward angles in the threshold region.

Journal Article↗
PubMed2001

Salvianolic acid B attenuates VCAM-1 and ICAM-1 expression in TNF-alpha-treated human aortic endothelial cells.

Attachment to, and migration of leukocytes into the vessel wall is an early event in atherogenesis. Expression of cell adhesion molecules by the arterial endothelium may play a major role in atherosclerosis. It has been suggested that antioxidants inhibit the expression of adhesion molecules and may thus attenuate the processes leading to atherosclerosis. In the present study, the effects of a potent water-soluble antioxidant, salvianolic acid B (Sal B), and an aqueous ethanolic extract (SME), both derived from a Chinese herb, Salvia miltiorrhiza, on the expression of endothelial-leukocyte adhesion molecules by tumor necrosis factor-alpha (TNF-alpha)-treated human aortic endothelial cells (HAECs) were investigated. When pretreated with SME (50 and 100 microg/ml), the TNF-alpha-induced expression of vascular adhesion molecule-1 (VCAM-1) was notably attenuated (77.2 +/- 3.2% and 80.0 +/- 2.2%, respectively); and with Sal B (1, 2.5, 5, 10, and 20 microg/ml), 84.5 +/- 1.9%, 78.8 +/- 1.2%, 58.9 +/- 0.4%, 58.7 +/- 0.9%, and 57.4 +/- 0.3%, respectively. Dose-dependent lowering of expression of intercellular cell adhesion molecule-1 (ICAM-1) was also seen with SME or Sal B. In contrast, the expression of endothelial cell selectin (E-selectin) was not affected. SME (50 microg/ml) or Sal B (5 microg/ml) significantly reduced the binding of the human monocytic cell line, U937, to TNF-alpha-stimulated HAECs (45.7 +/- 2.5% and 55.8 +/- 1.2%, respectively). SME or Sal B significantly inhibited TNF-alpha-induced activation of nuclear factor kappa B (NF-kappaB) in HAECs (0.36- and 0.48-fold, respectively). These results demonstrate that SME and Sal B have anti-inflammatory properties and may explain their anti-atherosclerotic properties. This new mechanism of action of Sal B and SME, in addition to their previously reported inhibition of LDL, may help explain their efficacy in the treatment of atherosclerosis.

Antioxidants↗
PubMed2001

Seroprevalence and demographic characteristics of HTLV-I among blood donors in Taiwan: 1996-1999.

Screening for the human T-cell lymphotropic virus type I (HTLV-I) and-II in blood donors was implemented in Taiwan beginning in February 1996. The purpose of the present study was to investigate the changes in HTLV-I seroprevalence in all unpaid blood donors in Taiwan during the period from February 1996 to December 1999 and to determine the influence of age and sex on the HTLV-I seropositivity of donors. HTLV-I and HTLV-II screening was performed using combined HTLV-I/II immunoassay. Repeated reactive samples were confirmed by Western blot analysis. Of a total of 3,701,087 donors in all 6 blood centers in Taiwan, 2,311 (0.058%) were seropositive for HTLV-I. The HTLV-I seropositivity was 0.130%, 0.063%, 0.044%, and 0.032% in the years 1996, 1997,1998, and 1999, respectively. There was a linear increase of HTLV-I seropositivity with advancing age. The HTLV-I carrier rate for female donors was twice that for the male donors. Ninty-seven percent of HTLV-I seropositive results came from first-time donors. Our findings suggest that Taiwan is a low-prevalence nonendemic area for HTLV-I infection. The large-scale HTLV-I screening program has decreased HTLV-I seropositivity among blood donors and is useful for preventing HTLV-I transmission via blood transfusion.

Adolescent↗