Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 55 records · Page 3Linked to original sources

PubMed2001

Modulation of aromatase expression in human breast tissue.

Aromatase plays an important role in breast cancer development through its role in the synthesis of estrogen. Aromatase expression in breast tissue can be regulated by several mechanisms. The major promoter usage for aromatase expression in breast tumors (i.e. cAMP-stimulated promoters I.3 and II) is different from that in normal breast tissue (i.e. glucocorticoid-stimulated promoter I.4). Recent characterization of transcription factors that interact with the two important regulatory elements near promoters I.3 and II, i.e. S1 and CREaro, helps us better understand the mechanism of the switch of promoter usage between normal breast tissue and cancer tissue. It is thought that in normal breast tissue, the function of promoters I.3 and II is suppressed through the binding of EAR-2, COUP-TFI, and EARgamma to S1, and through the binding of Snail/Slug proteins to their binding site that quenchs the CREaro activity. In cancer tissue, the expression levels of EAR-2, COUP-TFI, EARgamma, Snail, and Slug decrease, and aromatase expression is then up regulated through the binding of ERRalpha-1 to S1 and the binding of CREB or related factors to CREaro. Results from this and other laboratories reveal that aromatase activity in aromatase expressing cells can also be modified by treatment with aromatase inhibitors and the antiestrogen ICI 182, 780. While aromatase inhibitors are used to treat breast cancer, the treatment has been found to increase the level of aromatase in the breast tissue of some patients. The enhancement of aromatase activity by aromatase inhibitors is thought to be due to a decrease of aromatase protein degradation by enzyme-inhibitor complex formation, up-regulation of the aromatase gene transcription through a cAMP-mediated mechanism, and an induction of aromatase expression by gonadtropins that are released from the pituitary in response to a reduction of estrogen levels in circulation in premenopausal women. Antiestrogen ICI 182, 780 has been found to suppress aromatase expression, but the mechanism has not yet been determined. In addition, aromatase activity and expression can be affected by environmental chemicals. A detailed structure-function study has revealed that flavones, but not isoflavones, are inhibitors of aromatase. It was found that flavones bind to the active site of aromatase in an orientation in which their rings-A and -C mimic rings-D and -C of the androgen substrate. The modulation of aromatase expression by endocrine disrupting chemicals is exemplified by two organochlorine pesticides (i.e. toxaphene and chlordane) that have been found to be antagonists of ERRalpha-1 orphan receptor. These compounds reduce ERRalpha-1 activity, resulting in a suppression of aromatase expression.

Aromatase↗

PubMed2001

Sonochemical degradation for toxic halogenated organic compounds.

This paper describes the degradation of p-chlorophenol using three different ultrasonic devices. The dissipated power in the reaction matrix was measured based on calorimetric method. The study showed that hydrogen peroxide can improve the sonochemical reaction and gases dissolved in reaction matrix can affect the process to a small extent. The reaction mechanism and kinetics of degradation were also investigated.

Calorimetry↗

PubMed2001

Volatiles from Ficus hispida and their attractiveness to fig wasps.

Volatile compositions of receptive (ready to be pollinated), postpollinated, and postparasitized figs. and leaves of Ficus hispida were analyzed. Differences among them were examined, and the specificity of fig wasp attractiveness was investigated. Linalool was the major constituent of steam-distilled oil of either male or female receptive figs, while dibutyl phthalate was the major compound of the oils of postparasitized and postpollinated figs. In petroleum ether extracts, palmitic oil, and 9,12-octadecadienoic acid were the main constituents of male and female receptive figs, while hexadecanoic acid ethyl ester was the major compound of postparasitized and postpollinated figs. In dichloromethane extracts, linalool was the major constituent of male and female receptive figs, 1-hydroxylinalool was the major component of male postparasitized figs, and 1-hydroxylinalool and benzyl alcohol were the major constituents of female postpollinated figs. Bioassays with sticky traps showed that Ceratosolen solmsimarchal was attracted to dichloromethane extracts of male and female receptive figs and to petroleum ether extracts of female receptive figs, but was not attracted to dichloromethane and petroleum ether extracts of male postparasitized and female postpollinated figs. Figs were attractive to pollinating wasps only at the receptive stage. The volatile constituents of receptive figs were different from those of postpollinated or postparasitized figs. From a receptive to a postpollinated state, figs changed in their volatile composition. Some compounds disappeared or decreased in amount. These include linalool, linalool oxide, alpha-terpeneol, and 2,6-dimethyl-1,7-octadiene-3,6-diol, which may act as the attractants of the wasps. Others increased in amount, or several additional chemicals appeared. These include dibutyl phthalate, 1-hydroxylinalool, and benzyl alcohol, which may be repellents of the wasps. That dichloromethane extracts of male and female receptive figs showed similar activities in attracting fig wasps indicates that receptive figs of both sexes are similarly attractive to fig wasps, which is further supported by their similar volatile composition. Leaf extract was not attractive to the wasps.

Animals↗

PubMed2001

Experimental validation of a computational fluid dynamics model for IAQ applications in ice rink arenas.

Many ice rink arenas have ice resurfacing equipment that uses fossil fuel as power. The combustion byproducts are a major source of contamination. Ventilation along with other pollution source control measures is the most widely applied strategy to lower the contaminant level below the threshold limit and maintain acceptable indoor air quality (IAQ). A computational fluid dynamics (CFD) model has been developed and used to predict the contaminant concentrations, air velocity, and air temperature distributions in ice rinks. The numerical results agree reasonably with the corresponding experimental data for both steady-state and transient conditions. The CFD model is a useful and inexpensive tool to investigate ventilation parameters, such as air distribution methods, ventilation effectiveness, air exchange rates, and various ventilation control strategies.

Air Movements↗

PubMed2001

Determination of diphenylamine stabilizer and its nitrated derivatives in smokeless gunpowder using a tandem MS method.

A novel method for determination of diphenylamine (DPA) and its nitrated derivatives, which are considered as characteristic components in smokeless powder and gunshot residues, is described. A tandem mass spectrometric method is established and mass spectrometer parameters optimized for each compound to obtain higher sensitivity. Under optimum conditions, quantitative analysis was carried out. The linear ranges are 5.0-200.0, 2.0-200.0 and 5.0-250.0 ng ml-1 and the detection limits are 1.0, 0.5 and 2.5 ng ml-1 for diphenylamine (DPA), N-NO-diphenylamine (N-NO-DPA) and 4-NO2-diphenylamine (4-NO2-DPA), respectively. Intra-assay and inter-assay precision and accuracy of analysis of these three samples were investigated. Based on the regression lines obtained above, smokeless samples were analyzed. It was found that there are 0.952% DPA, 0.384% N-NO-DPA and 0.128% 4-NO2-DPA in smokeless powder. Recovery tests showed that using cotton swabs, 80.3 +/- 4.9% DPA, 79.6 +/- 3.1% N-NO-DPA and 83.1 +/- 5.4% 4-NO2-DPA could be recovered from human hands.

Journal Article↗

PubMed2001

Evaluation of a single stage nitroglycerin tilt table test for diagnosis of neurally mediated syncope.

The purpose of this study was to compare clinical outcomes between a single stage head-up tilt table test (HUT) with infusion of 3.44 microg/kg per hour of nitroglycerin and a conventional multistage test with infusion of nitroglycerin from 1.72 microg/kg per hour to 5.16 microg/kg per hour in five successive stages. Thirty-seven patients with recurrent syncope underwent both tests in a prospective, randomized, crossoverfashion. During single stage HUT, a positive response occurred in 24 (64.9%) patients with unexplained syncope, an exaggerated response occurred in 3 (8.1%), a negative response in 7 (18.9%), and drug intolerance in 3 (8.1%). During the multistage HUT, these percentages were 62.2%, 16.2%, 13.5%, and 8.1%, respectively. Twenty healthy control subjects were involved in both tests, One of the control subjects had a positive response to single stage HUT, and two (10%) patients to multistage HUT. The duration of the test in single stage HUT was shorter than that in multistage HUT (8.6 +/- 10.3 vs 38.6 +/- 32.1 minutes, P < 0.01). The results showed that the single stage HUT was a fairly sensitive, specific, and a time-efficient test for provoking neurally mediated syncope.

Adolescent↗

PubMed2001

Osteoid osteoma of the eminence of the temporomandibular joint.

We describe an osteoid osteoma in the articular eminence of the left temporomandibular joint of a 24-year-old woman. This is an uncommon tumour of the jaws, and has not previously been reported in this location. The mass was removed, she made a good recovery, and there are not signs of recurrence four years later.

Adult↗

PubMed2001

Effect of honey and sugars on the metabolism and disposition of naringin in rabbits.

To investigate the effect of honey and sugars on the metabolism and disposition of naringin, rabbits were administered naringin alone and naringin with honey or its component sugars - fructose, glucose and sucrose in crossover designs. An HPLC method was developed to determine naringenin in serum after enzymatic hydrolysis. Our results indicate that honey, fructose and sucrose significantly reduced AUC(0-t) of naringenin by 41 %, 61 % and 45 %, respectively. In vitro studies using a rabbit feces suspension to incubate naringin without or with honey or the respective sugars were employed to investigate the mechanism of this interaction. The results indicated that honey and its component sugars did not affect the rate and extent of naringin hydrolysis, whereas the degradation of naringenin was significantly enhanced in the presence of honey and fructose. It could be concluded that concomitant intake of honey, fructose and sucrose resulted in the reduction of naringin absorption which could be attributable in part to the enhanced preabsorption degradation of absorbable naringenin in the large intestine.

Animals↗

PubMed2001

The effect of calcium phosphate implant coating on osteoconduction.

OBJECTIVE: The purpose of this study was to determine whether a calcium phosphate (CaP) coating would have a significant impact on osteoconduction. STUDY DESIGN: In this investigation, porous-surfaced titanium alloy (Ti-6Al-4V) implants were prepared with or without the addition of a thin surface layer of CaP applied by means of sol-gel coating and implanted into the tibiae of 16 rabbits. Implant sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment by using backscatter scanning electron microscopy and the Bioquant Image Analyzer. RESULTS: The absolute contact length was significantly (P <.01) higher for CaP-coated implants (1.18 mm) than for the noncoated implants (0.74 mm), as were the contact length fraction (40.4% vs 27.0%; P <.01) and the straight-line bone growth (1.19 mm vs 1.04 mm; P <.01). CONCLUSION: On the basis of the findings in this study, the addition of a thin layer of CaP to the implant promotes accelerated bone healing around porous-surfaced implants-even after only 2 weeks of initial healing.

Alloys↗

PubMed2001

Structure and dynamics of calcium-activated calmodulin in solution.

Two 4-ns molecular dynamics simulations of calcium loaded calmodulin in solution have been performed, using both standard nonbonded cutoffs and Ewald summation to treat electrostatic interactions. Our simulation results are generally consistent with solution experimental studies of calmodulin structure and dynamics, including NMR, cross-linking, fluorescence and x-ray scattering. The most interesting result of the molecular dynamics simulations is the detection of large-scale structural fluctuations of calmodulin in solution. The globular N- and C-terminal domains tend to move approximately like rigid bodies, with fluctuations of interdomain distances within a 7 A range and of interdomain angles by up to 60 deg. Essential dynamics analysis indicates that the three dominant types of motion involve bending of the central helix in two perpendicular planes and a twist in which the domains rotate in opposite directions around the central helix. In the more realistic Ewald trajectory the protein backbone remains mostly within a 2-3 A root-mean-square distance from the crystal structure, the secondary structure within the domains is conserved and middle part of the central helix becomes disordered. The central helix itself exhibits limited fluctuations, with its bend angle exploring the 0-50 degrees range and the end-to-end distance falling in 39-43 A. The results of the two simulations were similar in many respects. However, the cutoff trajectory exhibited a larger deviation from the crystal, loss of several helical hydrogen bonds in the N-terminal domain and lack of structural disorder in the central helix.

Amino Acid Motifs↗

PubMed2001

Metastatic meningioma to the lung with multiple pleural metastases.

Meningiomas with both malignant clinical behavior and cytology are rare. Meningiomas comprise approximately 15% of the primary brain tumors. The majority are benign; less than 1% metastasize, most commonly to the lung (61%) followed by liver, lymph node, and bone. Approximately 130 cases of extracranial metastatic meningiomas have been described. Only 13% had more than three metastases, with few cases reported with extensive pleural involvement. We report an interesting case of a malignant meningioma that invaded through the skull in the frontal sinus that later metastasized to the left lung with multiple pulmonary and pleural nodules.

Aged↗

PubMed2001

The G to C polymorphism at -174 of the interleukin-6 gene is rare in a Southern Chinese population.

Interleukin-6 is thought to be involved in the pathogenesis of coal workers' pneumoconiosis. Recently, a functional G to C polymorphism at position -174 of the promoter of the IL-6 gene has been described. We examined the -174 polymorphisms in 259 retired Chinese men from Guangxi province (all retired coal miners). Only one GC heterozygous and no CC homozygous variants were found. Our results suggest that the frequency of the C allele in this Chinese population is lower than in Caucasian and east Indian populations.

5' Untranslated Regions↗

PubMed2001

A case of Kaposi's sarcoma associated with pemphigoid nodularis.

Pemphigoid nodularis is a rare variant of bullous pemphigoid. Bullous pemphigoid complicated by internal malignancy has been well documented. There have been only a few reported cases of bullous pemphigoid associated with Kaposi's sarcoma. We described a case of pemphigoid nodularis who later developed Kaposi's sarcoma that might be related to immunosupressive therapy, a situation that has not been reported previously.

Aged↗

PubMed2001

Steady flow and wall compression in stenotic arteries: a three-dimensional thick-wall model with fluid-wall interactions.

Severe stenosis may cause critical flow and wall mechanical conditions related to artery fatigue, artery compression, and plaque rupture, which leads directly to heart attack and stroke. The exact mechanism involved is not well understood. In this paper a nonlinear three-dimensional thick-wall model with fluid-wall interactions is introduced to simulate blood flow in carotid arteries with stenosis and to quantify physiological conditions under which wall compression or even collapse may occur. The mechanical properties of the tube wall were selected to match a thick-wall stenosis model made of PVA hydrogel. The experimentally measured nonlinear stress-strain relationship is implemented in the computational model using an incremental linear elasticity approach. The Navier-Stokes equations are used for the fluid model. An incremental boundary iteration method is used to handle the fluid-wall interactions. Our results indicate that severe stenosis causes considerable compressive stress in the tube wall and critical flow conditions such as negative pressure, high shear stress, and flow separation which may be related to artery compression, plaque cap rupture, platelet activation, and thrombus formation. The stress distribution has a very localized pattern and both maximum tensile stress (five times higher than normal average stress) and maximum compressive stress occur inside the stenotic section. Wall deformation, flow rates, and true severities of the stenosis under different pressure conditions are calculated and compared with experimental measurements and reasonable agreement is found.

Aortic Valve Stenosis↗

PubMed2001

Mutations in the cytoplasmic tail of murine leukemia virus envelope protein suppress fusion inhibition by R peptide.

During viral maturation, the cytoplasmic tail of the murine leukemia virus (MuLV) envelope (Env) protein undergoes proteolytic cleavage by the viral protease to release the 16-amino-acid R peptide, and this cleavage event activates the Env protein's fusion activity. We introduced Gly and/or Ser residues at different positions upstream of the R peptide in the cytoplasmic tail of the Friend MuLV Env protein and investigated their effects on fusion activity. Expression in HeLa T4 cells of a mutant Env protein with a single Gly insertion after I619, five amino acids upstream from the R peptide, induced syncytium formation with overlaid XC cells. Env proteins containing single or double Gly-Ser insertions after F614, 10 amino acids upstream from the R peptide, induced syncytium formation, and mutant proteins with multiple Gly insertions induced various levels of syncytium formation between HeLa T4 and XC cells. Immunoprecipitation and surface biotinylation assays showed that most of the mutants had surface expression levels comparable to those of the wild-type or R peptide-truncated Env proteins. Fluorescence dye redistribution assays also showed no hemifusion in the Env proteins which did not induce fusion. Our results indicate that insertion mutations in the cytoplasmic tail of the MuLV Env protein can suppress the inhibitory effect of the R peptide on membrane fusion and that there are differences in the effects of insertions in two regions in the cytoplasmic tail upstream of the R peptide.

Amino Acid Sequence↗

PubMed2001

VAMP3 null mice display normal constitutive, insulin- and exercise-regulated vesicle trafficking.

To investigate the physiological function of the VAMP3 vesicle SNARE (v-SNARE) isoform in the regulation of GLUT4 vesicle trafficking, we generated homozygotic VAMP3 null mice by targeted gene disruption. The VAMP3 null mice had typical growth rate and weight gain, with normal maintenance of fasting serum glucose and insulin levels. Analysis of glucose disposal and insulin sensitivity demonstrated normal insulin and glucose tolerance, with no evidence for insulin resistance. Insulin stimulation of glucose uptake in isolated primary adipocytes was essentially the same for the wild-type and VAMP3 null mice. Similarly, insulin-, hypoxia-, and exercise-stimulated glucose uptake in isolated skeletal muscle did not differ significantly. In addition, other general membrane trafficking events including phagocytosis, pinocytosis, and transferrin receptor recycling were also found to be unaffected in the VAMP3 null mice. Taken together, these data demonstrate that VAMP3 function is not necessary for either regulated GLUT4 translocation or general constitutive membrane recycling.

Adipocytes↗

PubMed2001

Syntaxin 4 heterozygous knockout mice develop muscle insulin resistance.

To investigate the physiological function of syntaxin 4 in the regulation of GLUT4 vesicle trafficking, we used homologous recombination to generate syntaxin 4-knockout mice. Homozygotic disruption of the syntaxin 4 gene results in early embryonic lethality, whereas heterozygous knockout mice, Syn4(+/-), had normal viability with no significant impairment in growth, development, or reproduction. However, the Syn4(+/-) mice manifested impaired glucose tolerance with a 50% reduction in whole-body glucose uptake. This defect was attributed to a 50% reduction in skeletal muscle glucose transport determined by 2-deoxyglucose uptake during hyperinsulinemic-euglycemic clamp procedures. In parallel, insulin-stimulated GLUT4 translocation in skeletal muscle was also significantly reduced in these mice. In contrast, Syn4(+/-) mice displayed normal insulin-stimulated glucose uptake and metabolism in adipose tissue and liver. Together, these data demonstrate that syntaxin 4 plays a critical physiological role in insulin-stimulated glucose uptake in skeletal muscle. Furthermore, reduction in syntaxin 4 protein levels in this tissue can account for the impairment in whole-body insulin-stimulated glucose metabolism in this animal model.

Adipocytes↗

PubMed2001

The MEF2A and MEF2D isoforms are differentially regulated in muscle and adipose tissue during states of insulin deficiency.

Previously we have demonstrated that striated muscle GLUT4 gene expression decreased following streptozotocin-induced diabetes due to a loss of MEF2A transcription factor expression without any significant effect on the MEF2D isoform (Mora, S. and J. E. Pessin (2000) J Biol Chem, 275:16323-16328). In contrast to both cardiac and skeletal muscle, adipose tissue displays a selective decrease in MEF2D expression in diabetes without any significant alteration in MEF2A protein content. Adipose tissue also expresses very low levels of the MEF2 transcription factors and nuclear extracts from white adipose tissue exhibit poor in vitro binding to the MEF2 element. However, addition of in vitro synthesized MEF2A to adipose nuclear extracts results in the formation of the expected MEF2/DNA complex. More importantly, binding to the MEF2 element was also compromised in the diabetic condition. Furthermore, in vivo overexpression of MEF2A selectively in adipose tissue did not affect GLUT4 or MEF2D expression and was not sufficient to prevent GLUT4 down-regulation that occurred in insulin-deficient states.

Adipose Tissue↗