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Biomedical subjects

X R Yang

Publications and source records attributed to X R Yang.

12 recordsLinked to original sources
PubMed2006

Influence of glutathione-S-transferase (GSTM1, GSTP1, GSTT1) and cytochrome p450 (CYP1A1, CYP2D6) polymorphisms on numbers of basal cell carcinomas (BCCs) in families with the naevoid basal cell carcinoma syndrome.

BACKGROUND: The naevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant multisystem disorder with variable expression. NBCCS patients have variable susceptibility to development of basal cell carcinoma (BCC). Previous studies have shown that polymorphisms of some metabolic genes encoding the cytochrome p450 (CYP) and glutathione-S-transferase (GST) enzymes influenced the numbers of BCCs in sporadic BCC cases. OBJECTIVE: To determine whether allelic variants of these genes contribute to the variation in numbers of BCCs observed in NBCCS families. METHODS: Genotyping and analysis was carried out in 152 members (69 affected and 83 unaffected) of 13 families with NBCCS for seven polymorphisms in five metabolic genes including CYP1A1, CYP2D6, GSTM1, GSTP1, and GSTT1. RESULTS: GSTP1 Val105 and GSTP1 Val114 alleles were significantly associated with fewer BCC numbers (odds ratio (OR)105 = 0.55 (95% confidence interval, 0.35 to 0.88); OR114 = 0.20 (0.05 to 0.88)). The Val(105) allele showed a dose dependent effect (OR(Ile/Val) = 0.58 (0.34 to 0.88); OR(Val/Val) = 0.34 (0.14 to 0.78)). In addition, fewer jaw cysts were observed in carriers of the three p450 polymorphisms (CYP1A1m1, CYP1A1m2, and CYP2D6*4) (OR(CYP1A1m1) = 0.27 (0.12 to 0.58); OR(CYP1A1m2) = 0.25 (0.08 to 0.78); OR(CYP2D6*4) = 0.33 (0.18 to 0.60)). CONCLUSIONS: Genetic variants might contribute to the variation in numbers of BCCs and jaw cysts observed in NBCCS families.

Adult↗
PubMed2001

[Application of surface plasmon resonance in molecular biology].

The application of surface plasmon resonance (SPR) in molecular biology was reviewed. The biomolecular interaction can be detected with SPR in real time and in situ without the use of labels, the association and dissociation can be monitored continuously, and multi-component complex interaction can be followed step by step. The applications of the SPR in the fields of molecular biology, demonstrated the advantage of this technique that couldn't achieved by the routine techniques.

DNA Replication↗
PubMed2000

[Effects of total flavones of metasequosia on left ventricular hypertrophy due to pressure overload in rats].

OBJECTIVE: To determine the preventive and regressive effects of total flavones of metasequosia (TFM) on left ventricular hypertrophy in rats. METHOD: Left ventricular hypertrophy was inducedin by partial ligation of abdominal aorta. The rats were given ig TFM(4, 40, 400 mg.kg-1.d-1) for six weeks. RESULT: TFM markedly reduced the HW/BW, LVW/BW, myofibril diameter and Ca2+ content in left ventricles but the systolic blood pressure (SBP) in rats wasn't obviously influenced. CONCLUSION: TFM can prevent and reverse the left ventricular hypertrophy due to pressure overload in rats. The mechanism may be related to its calcium antagonistic properties.

Animals↗
PubMed1998

Flow-injection determination of total ammonia and total carbon dioxide in blood based on gas-diffusion separation and with a bulk acoustic wave impedance sensor.

A novel flow-injection (FIA) system, for the rapid and direct determination of both total ammonia (T[NH3]) and total carbon dioxide (T[CO2]) in clinical blood samples, has been developed. Samples were injected into a carrier stream of H2O, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h(-1), the proposed system exhibited a linear frequency response up to 200 micromol l(-1) ammonium and 20 mmol l(-1) bicarbonate with a detection limit of 1.0 and 10 micromol l(-1), respectively. Results obtained for T(NH3) in serum and T(CO2) in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals were also discussed.

Acoustics↗
PubMed1995

Detection of D-aspartate in tau proteins associated with Alzheimer paired helical filaments.

Paired helical filaments (PHF) characteristic of Alzheimer neurofibrillary lesions are known to contain a modified form of microtubule associated protein tau. These proteins, PHF-tau, differ from normal tau in the extent and the site of phosphorylation. To determine whether PHF-tau, tau proteins from normal adult brains (N-tau), tau proteins from Alzheimer brains not associated with PHF (A-tau), and tau proteins from fetal brains (F-tau) differ in racemization, these proteins were compared for their D-aspartate content. The results demonstrated that PHF-tau contain more D-aspartate than N-tau, A-tau and F-tau. The average percentage D-aspartate for these proteins, after a correction for background, are 4.9%, 2.8%, 1.6%, and 1% for PHF-tau, N-tau, A-tau and F-tau, respectively. It remains to be determined if the increase in D-aspartate is a consequence of PHF formation. It is also unknown if the change in D-aspartate content in PHF-tau is associated with phosphorylation, which alters the susceptibility of tau to proteolysis.

Alzheimer Disease↗
PubMed1994

The effect of elevated plasma phenylalanine levels on protein synthesis rates in adult rat brain.

Increasing the plasma phenylalanine concentration to levels as high as 0.560-0.870 mM (over ten times normal levels) had no detectable effect on the rate of brain protein synthesis in adult rats. The average rates for 7-week-old rats were: valine, 0.58 +/- 0.05%/h, phenylalanine, 0.59 +/- 0.06%/h, and tyrosine, 0.60 +/- 0.09%/h, or 0.59 +/- 0.06%/h overall. Synthesis rates calculated on the basis of the specific activity of the tRNA-bound amino acid were slightly lower (4% lower for phenylalanine) than those based on the brain free amino acid pool. Similarly, the specific activities of valine and phenylalanine in microdialysis fluid from striatum were practically the same as those in the brain free amino acid pool. Thus the specific activities of the valine and phenylalanine brain free pools are good measures of the precursor specific activity for protein synthesis. In any event, synthesis rates, whether based on the specific activities of the amino acids in the brain free pool or those bound to tRNA, were unaffected by elevated levels of plasma phenylalanine. Brain protein synthesis rates measured after the administration of quite large doses of phenylalanine (> 1.5 mumol/g) or valine (15 mumol/g) were in agreement (0.62 +/- 0.01 and 0.65 +/- 0.01%/h respectively) with the rates determined with infusions of trace amounts of amino acids. Thus the technique of stabilizing precursor-specific activity, and pushing values in the brain close to those of the plasma, by the administration of large quantities of precursor, appears to be valid.

Animals↗
PubMed1990

Scanning tunneling microscopy of the enzymes of muscle glycogenolysis.

Scanning tunneling microscopy (STM) has been used to examine the structures of the skeletal muscle enzymes phosphorylase and phosphorylase kinase. The interaction of these two proteins represents the last step in the process of signal transduction which results in muscle glycogen being converted into metabolic energy for use in muscle contraction. Phosphorylase b has a molecular weight of 97,000 and the dimer is seen by STM to have dimensions of 11 X 5.7 nm. Phosphorylase b has a tendency to form linear arrays of dimers on the graphite surface used as the support for STM imaging. Phosphorylase kinase is imaged as a butterfly-like object with lateral dimensions of 36 X 27 nm. The molecular thicknesses given by scanning tunneling microscopy for these two non-conducting molecules is significantly less than expected. The height measurement in STM is dependent not only on the surface topology of the object being imaged, but also on the electronic work function of the object compared to that of the graphite surface on which it lies. In addition to the individual proteins, a complex between phosphorylase and phosphorylase kinase has been observed by scanning tunneling microscopy.

Animals↗
PubMed1990

Direct visualization of phosphorylase-phosphorylase kinase complexes by scanning tunneling and atomic force microscopy.

In skeletal muscle the activation of phosphorylase b is catalyzed by phosphorylase kinase. Both enzymes occur in vivo as part of a multienzyme complex. The two enzymes have been imaged by atomic force microscopy and the results compared to those previously found by scanning tunneling microscopy. Scanning tunneling microscopy and atomic force microscopy have been used to view complexes between the activating enzyme phosphorylase kinase and its substrate phosphorylase b. Changes in the size and shape of phosphorylase kinase were observed when it bound phosphorylase b.

Animals↗
PubMed1990

Viewing molecules with scanning tunneling microscopy and atomic force microscopy.

Two new microscopic techniques make it possible to obtain images of biologically interesting molecules directly in air, vacuum, or under water. Scanning tunneling microscopy and atomic force microscopy both have the capacity to visualize atoms on the surface of rigid structures and provide details of molecular structure for lipids, proteins, carbohydrates, and nucleic acids. In addition to providing visualizations of individual molecules, these scanning probe techniques allow direct imaging of complexes between molecules or between molecules and higher-order subcellular structures such as membranes and cytoskeletal components. Both microscopes can be operated under a variety of ambient conditions ranging from high vacuum to above atmospheric pressure. Specimens need not be dry; both techniques have been used to image molecules in aqueous media under nearly physiological conditions. It is proposed that as these techniques mature they will allow direct observation of many molecular interactions under physiological conditions or even in vivo while they are occurring within the cell.

Brain↗
PubMed1990

Scanning tunneling microscopic images show a laminated structure for glycogen molecules.

Scanning tunneling microscopy (STM) has been used to examine glycogen molecules. Individual molecules were approximately ellipsoidal with dimensions in the 20- to 60-nm range. Images of the glycogen molecular surfaces have a laminar appearance. The layered features seen on the surfaces of the molecules suggest that glycogen may grow from one edge as a laminar structure to form an ellipsoid rather than originating at a central point with radial growth of the oligosaccharide chains to form a sphere. The results of these studies indicate that STM can be used to determine details of polysaccharide structures.

Animals↗
PubMed1990

[Inhibitory action of peruvoside and neriifolin on Na+, K(+)-ATPase].

Effects of peruvoside and neriifolin, main components of neriperside, a tevetoside extracted from Thevitia neriifolia Juss, on Na+, K(+)-ATPase activities and on [3H] ouabain binding to the Na+, K(+)-ATPase isolated from hearts of guinea pigs, dogs and cats and kidneys of guinea pigs and cats were compared with digoxin and ouabain. It was found that peruvoside and neriifolin inhibited Na+, K(+)-ATPase activities and they showed a strong competitive inhibition on [3H] ouabain binding to the enzymes isolated from various tissues. A marked species difference existed as great as that of digitalis. The mechanism of action of these 2 drugs may be similar to that of digitalis. Their inhibitory effects on the enzyme activity were stronger than their positive inotropic effects, while both actions of digitalis were parallel quantitatively. There may be some differences in the modulation of the intracellular Ca2+ between neripersides and digitalis.

Animals↗