Biomedical subjects

J R Chen

Publications and source records attributed to J R Chen.

At least 19 recordsLinked to original sources

PubMed2005

MHC class I chain-related gene A (MICA) polymorphism and the different histological types of cervical cancer.

Cervical cancer has been one of the most important gynecologic cancer in Taiwan with incidence of 24/100,000 and mortality of 8.7/100,000 annually. About 70-80% are squamous cell carcinoma; the remainder are composed of various types of adenocarcinoma, adenosquamous carcinoma and undifferentiated carcinoma. The Major Histocompatibility Complex (MHC) class I chain-related gene A (MICA) is expressed by keratinocytes and epithelial cells and interacts with gamma-delta T cells. Although MICA was not associated with cervical cancer in the study of Northern Sweden, there are no further studies about the association of MICA polymorphism and the different histological types of cervical cancer. We analyzed the MICA polymorphism in 110 cervical cancer cases (88 squamous cell carcinoma, 12 adenocarcinoma and 10 adenosquamous carcinoma) and 82 randomly selected unrelated controls from 1994 to 2000 in the Mackay Memorial Hospital, Taipei, Taiwan. DNA was extracted part from leukocytes of peripheral blood, part from tumor tissue and 5 polymorphic microsatellite alleles (A4,A5,A5.1,A6,A9) of MICA were identified by a polymerase chain reaction-based (PCR) technique using ABI Prism 377-18 DNA sequencer (Applied Biosystems, Foster City, CA, USA). The phenotypes, alleles and genotypes of MICA gene were calculated. There was no association with cervical cancer patients and non-cervical cancer patients (p=0.337, 0.356 and 0.414). After dividing the cervical cancer patients into 3 major histological types (squamous cell carcinoma, adenocarcinoma and adenosquamous carcinoma), the result was still the same (p=0.598, 0.172 and 0.617) in our study. We found no association between MICA gene polymorphism and cervical cancer in Taiwan. Different histological types of cervical cancer also have no significant correlation with MICA gene polymorphism. It demonstrates that polymorphism of MICA gene bears no relation to cervical cancer and the different histological types of cervical cancer in Taiwan. We need further studies for identifying the factors causing the differentiation of cancer cells of the uterine cervix.

Adenocarcinoma↗

PubMed2004

Optimizing the error term in direct-method SAD phasing.

The probability formula of the direct-method SAD (single-wavelength anomalous diffraction) phasing proposed by Fan & Gu (1985, Acta Cryst. A41, 280-284) contains an error term which is related to the lack-of-closure error. This error term is used as a weighting function in the phase derivation and in the subsequent calculation of electron-density maps. Previously, there has been a constant in the error term that has had to be determined empirically for each particular case. It has been found that improper choice of the constant often leads to failure of the direct-method SAD phasing. The problem is resolved by introducing a modified error term and a method of automatically tuning the associated scaling factor.

Algorithms↗

PubMed2004

Direct-method SAD phasing with partial-structure iteration: towards automation.

The probability formula of direct-method SAD (single-wavelength anomalous diffraction) phasing proposed by Fan & Gu (1985, Acta Cryst. A41, 280-284) contains partial-structure information in the form of a Sim-weighting term. Previously, only the substructure of anomalous scatterers has been included in this term. In the case that the subsequent density modification and model building yields only structure fragments, which do not straightforwardly lead to the complete solution, the partial structure can be fed back into the Sim-weighting term of the probability formula in order to strengthen its phasing power and to benefit the subsequent automatic model building. The procedure has been tested with experimental SAD data from two known proteins with copper and sulfur as the anomalous scatterers.

Automation↗

PubMed2004

SAD phasing by combination of direct methods with the SOLVE/RESOLVE procedure.

In the initial stage of SAD phasing, the essential point is to break the intrinsic phase ambiguity. The presence of two kinds of phase information enables the discrimination of phase doublets from SAD data prior to density modification. One is from the heavy atoms (anomalous scatterers), while the other is from the direct-methods phase relationships. The former can be expressed by the Sim distribution, while the latter can be expressed by the Cochran distribution. Typically, only the Sim distribution has been used to yield initial phases for subsequent density modification. However, it has been demonstrated that using direct-methods phases based on the product of the Sim and Cochran distributions can lead to improved initial phases. In this paper, the direct-methods phasing procedure OASIS has been improved and combined with the SOLVE/RESOLVE procedure. Experimental SAD data from three known proteins with expected Bijvoet ratios / in the range 1.4-7.0% were used as test cases. In all cases, the phases obtained using the program RESOLVE beginning with initial phases based on experimental phases plus Sim and direct-methods information were more accurate than those based on experimental plus Sim phase information alone.

Azurin↗

PubMed2002

Reversal of bone loss in mice by nongenotropic signaling of sex steroids.

We show that sex steroids protect the adult murine skeleton through a mechanism that is distinct from that used to preserve the mass and function of reproductive organs. The classical genotropic actions of sex steroid receptors are dispensable for their bone protective effects, but essential for their effects on reproductive tissues. A synthetic ligand (4-estren-3alpha,17beta-diol) that reproduces the nongenotropic effects of sex steroids, without affecting classical transcription, increases bone mass and strength in ovariectomized females above the level of the estrogen-replete state and is at least as effective as dihydrotestosterone in orchidectomized males, without affecting reproductive organs. Such ligands merit investigation as potential therapeutic alternatives to hormone replacement for osteoporosis in both women and men [corrected].

Animals↗

PubMed2001

Synthesis and photodynamic action of diphenyl-2,3-dihydroxychlorin: a potential tumor photosensitizer.

The synthesis, photophysical properties of diphenyl-2,3-dihydroxychlorin (DPCOH) and its photocytotoxicity to tumor cells are described. DPCOH exhibits photodynamic activity in terms of type I and type II mechanisms under irradiation. The quantum yield of (1)O(2) in CHCl(3) is 0.7. For the photocytotoxicity to tumor cells, DPCOH proved to be 200 times more potent than HPD, and the dark toxicity is low (dark IC(90)>32 microg/mL).

Biphenyl Compounds↗

PubMed2001

Dual control of LIF expression and LIF receptor function regulate Stat3 activation at the onset of uterine receptivity and embryo implantation.

Leukemia inhibitory factor (LIF) expression in the uterus is essential for embryo implantation in mice. Here we describe the spatial and temporal regulation of LIF signaling in vivo by using tissues isolated from uteri on different days over the implantation period. During this time, LIF receptors are expressed predominantly in the luminal epithelium (LE) of the uterus. Isolated epithelium responds to LIF by phosphorylation and nuclear translocation of signal transducer and activator of transcription (Stat) 3, but not by an increase in mitogen-activated protein kinase levels. The related cytokines Il-6, ciliary neurotrophic factor, as well as epidermal growth factor, do not activate Stat3, although epidermal growth factor stimulates mitogen-activated protein kinase. In vivo Stat3 activation is induced by LIF alone, resulting in the localization of Stat3 specifically to the nuclei of the LE coinciding with the onset of uterine receptivity. The responsiveness of the LE to LIF is regulated temporally, with Stat activation being restricted to day 4 of pregnancy despite the presence of constant levels of LIF receptor throughout the preimplantation period. Uterine receptivity is therefore under dual control and is regulated by both the onset of LIF expression in the endometrial glands and the release from inhibition of receptor function in the LE.

Animals↗

PubMed2001

A recombinant chimera composed of repeat region RR1 of Mycoplasma hyopneumoniae adhesin with Pseudomonas exotoxin: in vivo evaluation of specific IgG response in mice and pigs.

Using the binding and translocation domain of Pseudomonas exotoxin A [domain III deleted PE termed PE(DeltaIII)] as a vehicle, this study characterized and evaluated a novel application of PE toxin in Mycoplasma hyopneumoniae adhesin used as an immunogen. PCR and sequence analysis revealed that 16 copies of AAKPV(E) in tandem repeat region 1 (RR1) of M. hyopneumoniae 97kDa adhesion were successfully fused to the downstream of PE(DeltaIII) to create a subunit vaccine, i.e. PE(DeltaIII)-RR1. This chimeric protein, over-expressed in inclusion bodies of E. coli BL21(DE3)pLysS, was characterized by a monoclonal antibody (MAb) F2G5 prepared against RR1 of the 97kDa adhesin and was readily purified. The data indicated that the epitope recognized by MAb F2G5 was located in the structure of PE(DeltaIII)-RR1. Using ELISA and Western blot analyses, the specific IgG immune response against RR1 and whole adhesin in mice immunized with PE(DeltaIII)-RR1 was found more marked than that in mice immunized with the M. hyopneumoniae whole cells. Similarly, PE(DeltaIII)-RR1 also stimulated a remarkable IgG response against RR1 in pigs compared to that in pigs immunized with the conventional M. hyopneumoniae vaccine. The PE(DeltaIII)-RR1 would be potentially useful for the future development of a M. hyopneumoniae adhesin vaccine.

ADP Ribose Transferases↗

PubMed2001

Semipreparative capillary electrochromatography.

Capillaries with inner diameters of 550 microm have successfully been packed with 1.5-microm octadecyl silica particles using frits made of macroporous polymers by the UV photopolymerization of a solution of glycidyl methacrylate and trimethylolpropane trimethacrylate. This type of frit is found superior to one made of low-melting point poly(styrene-co-divinylbenzene) beads. Bubble formation is not observed to occur within these capillary columns under our experimental conditions. Separations can be achieved with sample injection volumes as high as 1 microL. To demonstrate its semipreparative use, a mixture of 500 nL of taxol (20 mM) and its precursor, baccatin III (30 mM), is separated using such a column with a Tris buffer.

Alkaloids↗

PubMed2001

Identification of antihypertensive peptides from peptic digest of two microalgae, Chlorella vulgaris and Spirulina platensis.

The peptidic fractions that inhibited angiotensin I-converting enzyme (ACE) were separated from the peptic digests of 2 microalgae, Chlorella vulgaris and Spirulina platensis, by ion exchange chromatography and gel filtration. Oral administration of peptidic fractions into spontaneously hypertensive rats at 200 mg/kg of body weight resulted in marked antihypertensive effects. Further separation of the peptidic fractions by ODS high-performance liquid chromatography furnished the following active peptides: Ile-Val-Val-Glu (inhibitory against ACE with an IC(50) of 315.3 microM), Ala-Phe-Leu (63.8 microM), Phe-Ala-Leu (26.3 microM), Ala-Glu-Leu (57.1 microM), and Val-Val-Pro-Pro-Ala (79.5 microM) from C. vulgaris; Ile-Ala-Glu (34.7 microM), Phe-Ala-Leu, Ala-Glu-Leu, Ile-Ala-Pro-Gly (11.4 microM), and Val-Ala-Phe (35.8 microM) from S. platensis.

Journal Article↗

PubMed2001

Comparison of transcranial color-coded sonography and magnetic resonance angiography in acute ischemic stroke.

BACKGROUND AND PURPOSE: This study was designed to assess the accuracy of transcranial color-coded sonography (TCCS) as compared to magnetic resonance angiography (MRA) for detecting intracranial arterial stenosis in patients with acute cerebral ischemia. METHODS: The authors prospectively identified 120 consecutive patients admitted with acute ischemic stroke and performed both TCCS and MRA with a mean interval of 1 day. TCCS data (sampling depth, peak systolic and end diastolic angle-corrected velocity, mean angle-corrected velocity, and pulsatility index) for middle cerebral arteries (MCAs) were compared to MRA data and classified into 4 grades: normal (grade 1): normal caliber and signal; mild stenosis (grade 2): irregular lumen with reduced signal; severe stenosis (grade 3): absent signal in the stenotic segment (flow gap) and reconstituted distal signal; and possible occlusion (grade 4): absent signal. The cutoffs were chosen to maximize diagnostic accuracy. RESULTS: Interobserver agreement for MRA grading resulted in a weighted-kappa value of 0.776. The rate of poor temporal window was 37% (89/240). Doppler signals were obtained in 135 vessels, and the angle-corrected velocities (peak systolic, end diastolic, mean) were significantly different (P = .001, P = .006, and P < .001) among the MRA grades: grade 1 (100, 47, 68 cm/s), grade 2 (171, 72, 110 cm/s), grade 3 (226, 79, 134 cm/s), grade 4 (61, 26, 39 cm/s). Additionally, an angle-corrected MCA peak systolic velocity > or = 120 cm/s correlates with intracranial stenosis on MRA (grade 2 or worse) with high specificity (90.5%; 95% confidence interval = 78.5%-96.8%) and positive predictive value (93.9%) but relatively low sensitivity (66.7%; 95% confidence interval = 61.2%-69.5%) and negative predictive value (55.1%). CONCLUSION: Elevated MCA velocities on TCCS correlate with intracranial stenosis detected on MRA. An angle-corrected peak systolic velocity > or = 120 cm/s is highly specific for detecting intracranial stenosis as defined by significant MRA abnormality.

Acute Disease↗

PubMed2001

Population-based, case-control study of blood C-peptide level and breast cancer risk.

Insulin resistance has been suggested to be associated with an increased risk of breast cancer. Insulin sensitivity can be measured using blood C-peptide, a marker of insulin secretion. It is thus conceivable that blood C-peptide levels may be associated with breast cancer risk. To evaluate this hypothesis, we analyzed data from a subset (143 case-control pairs matched by age and status of menopause) of women who participated in the Shanghai Breast Cancer Study, a population-based, case-control study conducted in Shanghai during 1996-1998. Fasting blood samples were collected from study subjects to measure C-peptide levels. For cancer patients, the samples were collected before any cancer therapy. Conditional logistic regression was used to estimate adjusted odds ratios and 95% confidence intervals related to C-peptide levels. Breast cancer risk was increased with increasing levels of C-peptide (trend test, P = 0.01), with an odds ratio of 2.7 (95% confidence interval = 1.2-5.9) observed for the highest compared with the lowest tertile of C-peptide concentration after adjusting for body mass index and age at the first live birth. The risk was not altered after fully adjusting for other traditional risk factors for breast cancer. This positive association was observed in both pre and postmenopausal women and regardless of the levels of waist-to-hip ratio or body mass index. The results from this study were consistent with the insulin-resistance hypothesis for breast cancer and suggest that increased levels of C-peptide may contribute to the development of breast cancer.

Adult↗

PubMed2000

Identification of the copper-zinc superoxide dismutase activity in Mycoplasma hyopneumoniae.

Copper-zinc superoxide dismutase (Cu/ZnSOD), a key enzyme in defense against toxic oxygen-free radicals, is widespread in eukaryotes and several species of gram-negative bacteria. The presence of this enzyme in Mycoplasma hyopneumoniae (M. hyopneumoniae), the primary pathogen of mycoplasmal pneumonia in pigs, was examined since the polyclonal antibody against bovine Cu/ZnSOD was dominantly cross-reactive with the M. hyopneumoniae Cu/ZnSOD from whole cellular proteins. In situ activity staining on SDS-PAGE showed that the molecular mass of M. hyopneumoniae Cu/ZnSOD in reducing form was approximately 17kDa. The presence of Cu and Zn ions at the active site of the enzyme was confirmed on the basis of inhibition by KCN and by H(2)O(2). The activity of M. hyopneumoniae Cu/ZnSOD on both SDS- and native-polyacrylamide gels was completely inhibited by 2mM KCN and the gels showed no iron-containing SOD (FeSOD) or manganese-containing SOD (MnSOD) in the crude extracts. The activity of M. hyopneumoniae Cu/ZnSOD in crude extract was 70units/mg protein and was 55% inhibited by 5mM KCN and 56% inactivated by 40mM H(2)O(2). This enzyme was growth-stage dependent and evidenced markedly higher production during the early log phase. Different expression levels of Cu/ZnSOD activity in field isolates were also detected. Taken together, the presence of Cu/ZnSOD in M. hyopneumoniae was identified for the first time.

Animals↗

PubMed2000

Direct detection of crosslinks of collagen and elastin in the hydrolysates of human yellow ligament using single-column high performance liquid chromatography.

Collagen and elastin are recognized as two major connective tissue proteins of human yellow ligament. In both collagen and elastin there are many kinds of intra- or intermolecular crosslinks. Pyridinoline (Pyr) and deoxypyridinoline (Dpyr) are mature crosslinks which maintain the structure of the collagen fibril. Desmosine (Des) and isodesmosine (Isodes) represent the major crosslinking components of elastin. Pentosidine (Pen), which is a senescent crosslink and one of the advanced glycation end products, accumulates with age in tissue proteins including collagen. We developed a direct and one-injection HPLC method to measure Pyr, Dpyr, Des, Isodes, and Pen in the hydrolysate of human yellow ligament. This method used one column and two detectors. Recovery rates of Pyr, Dpyr, Pen, Des, and Isodes were 86.4-98.3, 83.6-96.8, 78.7-95.6, 83.6-97.9, and 85.6-99.3%, respectively (n = 8). The intraassay coefficients of variation for Pyr, Dpyr, Pen, Des, and Isodes were 3.7, 4.1, 5.4, 4.5, and 4.7%, respectively (n = 8), and the interassay coefficients of variation for Pyr, Dpyr, Pen, Des, and Isodes were 4.4, 5.1, 4.9, 4.6 and 4.1%, respectively. Linear regression analysis showed the linearity (r = 0.99, P = 0.0001) of calibration line for each Pyr, Dpyr, Pen, Des, and Isodes. Using this method, we investigated age-related changes in the crosslinks of collagen and elastin in human yellow ligament. There was a significant correlation between Pen and age, but no correlations with Pyr, Dpyr, Des, and Isodes. We believe that this method is useful for investigating the content of these crosslinks in both collagen and elastin under various conditions.

Chromatography, High Pressure Liquid↗

PubMed2000

Softening of fused-silica capillaries during particle packing.

When a semipreparative capillary electrochromatography (CEC) capillary is packed with silica particles and exposed to solvent, its mechanical strength is markedly reduced. In our studies, a fused-silica capillary (internal diameter > 200 microm and wall thickness < 150 microm) was packed under pressure (approximately 200 psi) with spherical silica particles (1.5-5 microm) suspended in water or various common organic solvents. After one hour of exposure, the capillary can be readily deformed, and it keeps its deformed shape upon release of the force causing deformation. It is suggested that capillary softening is promoted through the propagation of internal microcracks that have been caused by action of the particles during packing in the presence of solvent. Application of a protective coating to the inside of the capillary is found to reduce or eliminate capillary softening.

Chromatography, Liquid↗

PubMed2000

Leukemia inhibitory factor can substitute for nidatory estrogen and is essential to inducing a receptive uterus for implantation but is not essential for subsequent embryogenesis.

A stage critical in mammalian development is embryo implantation. At this point, the blastocyst establishes a close interaction with the uterine tissues, a step necessary for its continued embryonic development. In many mammalian species, including man, uterine expression of the cytokine, leukemia inhibitory factor (LIF) is coincident with the onset of implantation and in mice LIF is essential to this process. The reasons for implantation failure have not been established. Here we show in LIF-deficient mice that up to the onset of implantation, changes in uterine cell proliferation, hormone levels, blastocyst localization, as well as expression of lactoferrin and Muc-1, do not differ from wild-types. However, the uterus fails to respond to the presence of embryos or to artificial stimuli by decidualizing. In mice, implantation and decidualization are induced by nidatory estrogen. We show that uterine expression of LIF is up-regulated by estrogen and LIF can replace nidatory estrogen at inducing both implantation and decidualization in ovariectomized mice. Implantation of LIF-deficient embryos in the LIF-deficient females, with normal development to term is rescued by i.p. injection of LIF. Transient expression of LIF on D4 of pregnancy is therefore only required to induce a state of receptivity in the uterus permitting embryo implantation and decidualization. LIF is neither required by the embryo for development nor for the maintenance of pregnancy.

Animals↗

PubMed1999

Miller Fisher syndrome with central involvement: successful treatment with plasmapheresis.

Miller Fisher syndrome is characterized by external ophthalmoplegia, ataxia, and areflexia. Most researchers favor a peripheral origin while others suggest a brainstem inflammatory lesion or a combination of central and peripheral demyelination. We report 2 cases of Miller Fisher syndrome with the typical triad of ataxia, areflexia, and ophthalmoplegia. Strong clinical evidence of central involvement included initial drowsiness, bilateral Babinski sign, and quadriparesis. Evoked potential studies showed prolongation of central conduction time. Plasmapheresis was performed to relieve respiratory failure in Patient 1 and to shorten the duration of nasogastric tube feeding due to severe bulbar palsy in Patient 2. Significant improvement of electrophysiologic parameters was recorded after plasmapheresis. Abnormal evoked potentials, together with clinical evidence of central nervous system abnormalities, support the hypothesis that there is a combination of peripheral and central involvement in Miller Fisher syndrome in our patients. Plasmapheresis is highly effective in relieving the profound neurological deficits of this atypical syndrome.

Adult↗

PubMed1999

Metastable polymorph of etoposide with higher dissolution rate.

Etoposide, an anticancer drug, has low oral bioavailability because of low aqueous solubility, slow dissolution rate, and instability in acidic pH. Our objective was to enhance the aqueous solubility and dissolution rate of etoposide by polymorph formation. Preparation of various polymorphs of etoposide was attempted by crystallizing etoposide from organic solvents. Physicochemical properties of the crystals, namely, crystal habit, thermal behavior with hot-stage microscopy, thermal analysis by differential scanning calorimetry, IR spectrum, and solubility and dissolution rates, were examined. Based on the physicochemical characteristics, a metastable polymorph of etoposide was identified when it was crystallized from isopropanol. The metastable polymorph had an equilibrium solubility and intrinsic dissolution rate of 221 micrograms/ml and 16.3 micrograms/min/cm2, respectively; 1.9 and 1.7 times that of etoposide powder at 25 degrees C, respectively.

2-Propanol↗