Biomedical subjects

D S Yang

Publications and source records attributed to D S Yang.

At least 55 records · Page 3Linked to original sources

PubMed1995

Overexpression, purification, and crystallization of the DNA binding and dimerization domains of the Epstein-Barr virus nuclear antigen 1.

The Epstein-Barr virus nuclear antigen (EBNA) 1 binds to and activates DNA replication from the latent origin of Epstein-Barr virus. Six different fragments of EBNA1 that retain DNA binding activity were expressed in bacteria, purified, and crystallized. Two fragments, EBNA470-619 and EBNA470-607, formed well ordered crystals that diffracted beyond 2.5-A resolution. Two different EBNA470-619 crystals were grown from sodium formate, pH 6-6.5. One crystal belonged to the trigonal space group P3 with unit cell dimensions a = b = 86.5 A and c = 31.8 A and with two molecules in the asymmetric unit. The other crystal, which appeared only twice and was likely related to the P3 crystal form, belonged to the trigonal space group P312 with cell dimensions a = b = 86.7 A and c = 31.8 A. Crystals of EBNA470-607 were grown by lowering the salt concentration to 0-100 mM NaCl at pH 6.0. These crystals belonged to the orthorhombic space group P2(1)2(1)2(1) and had cell dimensions a = 59 A, b = 66.9 A, and c = 69.8 A with two molecules in the asymmetric unit.

Antigens, Viral↗

PubMed1995

Ice-binding structure and mechanism of an antifreeze protein from winter flounder.

Antifreeze proteins provide fish with protection against the freezing effect of polar environments by binding to ice surfaces and inhibiting growth of ice crystals. We present the X-ray crystal structure at 1.5 A resolution of a lone alpha-helical antifreeze protein from winter flounder, which provides a detailed look at its ice-binding features. These consist of four repeated ice-binding motifs, the side chains of which are inherently rigid or restrained by pair-wise side-chain interactions to form a flat binding surface. Elaborate amino- and carboxy-terminal cap structures are also present, which explain the protein's rich alpha-helical content in solution. We propose an ice-binding model that accounts for the binding specificity of the antifreeze protein along the <0112> axes of the (2021) ice planes.

Amino Acid Sequence↗

PubMed1995

The mechanism of protein crystal growth from lipid layers.

Two-dimensional (2D) crystals of proteins on lipid monolayers can initiate the formation of large three-dimensional (3D) crystals suitable for X-ray diffraction studies. The role of the 2D crystals in this process has not been firmly established. While it is likely that the 2D crystals serve as nuclei for epitaxial crystal growth, other mechanisms, such as non-specific nucleation induced by the high local concentration of the protein at the surface of the lipid layer, cannot be excluded. Using streptavidin as a model system, we have now firmly established that 3D crystal growth from 2D crystals on lipid layers occurs by epitaxy. We show that 2D crystals of streptavidin (space group C222) on biotinated lipid layers nucleate the growth of a 3D crystal form (space group I4I22) that possesses a structural similarity with the 2D crystal, but have no effect on the growth of 3D crystal forms (I222 and P2(1)) that are unrelated to the 2D crystal. At lower pH, a new 3D crystal form (space group P1), unrelated to the previously described 2D crystals, grew from lipid layers. This discovery initially raised concern about the validity of the epitaxial mechanism, but these concerns were alleviated with the subsequent discovery of a structurally related 2D P1 crystal that grew in similar solution conditions. Some parameters affecting epitaxial growth of both the P1 and I4I22 crystals were investigated, revealing several noteworthy features of the epitaxial growth. (1) 2D crystals are very effective nucleating agents; for instance, the P1 2D crystals can direct the growth of P1 3D crystals even under conditions that favour the growth of other crystal forms. (2) The epitaxial 3D crystal grow very rapidly and at amazingly low protein concentrations; P1 3D crystals can be grown from solutions as low as 10 microM streptavidin. (3) There is no obligate requirement for the deposition of pre-formed 2D crystals; lipid layers alone are equally effective at promoting epitaxial crystal growth.

Bacterial Proteins↗

PubMed1995

Antifreeze proteins in winter rye are similar to pathogenesis-related proteins.

The ability to control extracellular ice formation during freezing is critical to the survival of freezing-tolerant plants. Antifreeze proteins, which are proteins that have the ability to retard ice crystal growth, were recently identified as the most abundant apoplastic proteins in cold-acclimated winter rye (Secale cereale L.) leaves. In the experiments reported here, amino-terminal sequence comparisons, immuno-cross-reactions, and enzyme activity assays all indicated that these antifreeze proteins are similar to members of three classes of pathogenesis-related proteins, namely, endochitinases, endo-beta-1,3-glucanases, and thaumatin-like proteins. Apoplastic endochitinases and endo-beta-1,3-glucanases that were induced by pathogens in freezing-sensitive tobacco did not exhibit antifreeze activity. Our findings suggest that subtle structural differences may have evolved in the pathogenesis-related proteins that accumulate at cold temperatures in winter rye to confer upon these proteins the ability to bind to ice.

Adaptation, Biological↗

PubMed1994

Single crystals of a type III antifreeze polypeptide from ocean pout.

Antifreeze protein (HPLC-2) from ocean pout was purified from serum using column chromatography on Sephadex G75 and reverse-phase HPLC columns. Single crystals were grown by batch methods at 4 degrees C from a 1.5 M solution of ammonium sulphate (pH 7.1). The crystals diffracted to about 2.5 A resolution at 4 degrees C and belong to the monoclinic space group P2(1), with cell parameters: a = 39.77 A, b = 58.51 A, c = 30.27 A, beta = 102.28 degrees, with two molecules of 6000 M(r) per asymmetric unit.

Animals↗

PubMed1994

The utero-placental circulation, eugenics and the prevention and treatment of high risk pregnancies.

Through systematic experimental and clinical studies, the physiological regulation of utero-placental circulation and the relation of the disturbance in this acirculation to pathogenic mechanisms of high risk pregnancies-Intrauterine Growth Retardation (IUGR) and Pregnancy-induced hypertension (PIH) were explored. The pharmacological effects and mechanism of a Chinese herbal medicine-Qingxintong in improving, the utero-placental circulation and the therapeutic efficacy in treatment of IUGR and PIH, both accompanied by disturbance of utero-placental circulation, were investigated as well.

Acetophenones↗

PubMed1994

[Stereoscopic visual evoked potential elicited by static random dot stereogram].

Using 16.56' visual disparity stimulation produced by television random dot stereogram (TVRDS), we recorded visual evoked potentials (VEPs) elicited from 35 normal subjects with and without breaking their stereopsis and 28 stereoblind subjects. The results showed that a constant negative-positive wave complex was observed in 33 of 35 normal subjects; this negative-positive wave-complex disappeared when the stereopsis was artificially inhibited by a prism and in the stereoblind group, and no VEP wave was elicited in all of the stereoblind patients except in one with paralytic strabismus. The results revealed that under this condition the VEPs elicited by TVRDS were specific VEPs related to visual disparity stimulation and were stereoscopic ones. The TVRDS is an effective electro-physiological means to examine the stereopsis objectively and a new way to approach the occurrence and development of stereopsis.

Adolescent↗

PubMed1994

[Protective effect of tetrandrine on pancreatic islet cells damaged by alloxan in rats].

Tetrandrine (TET, 100 mg/kg) injected intraperitoneally could prevent rats from diabetes induced by alloxan. After 48 h of injection of alloxan, the blood sugar of the preventive group decreased from the control value of 25.46 +/- 1.21 mmol/L to 7.63 +/- 0.44 mmol/L (P < 0.001) while the serum insulin level increased to 11.33 +/- 1.97 microU/ml and the plasma glucagon concentration to 66.85 +/- 5.07 pg/ml respectively from the control group's value of 7.13 +/- 0.45 microU/ml and 90.35 +/- 8.33 pg/ml. In glucose tolerance test, TET 100 mg/kg showed that the abnormal glucose tolerance induced by alloxan could be improved. The blood sugar area under the glucose tolerance curve of the preventive group decreased from the control groups level of 113.28 +/- 5.02 mmol.h/L to 29.45 +/- 1.63 mmol.h/L (P < 0.001). Immunohistochemical observation of islet beta cells confirmed that TET could markedly prevent beta cells from injuries induced by alloxan and there was no obvious change in the appearance of islet beta cells in the preventive group. The above results suggested that TET could protect pancreatic islet beta cells from injuries caused by Alloxan.

Alkaloids↗

PubMed1994

National field trial of the Chinese classification and diagnostic criteria of mental disorders: comprehensibility, acceptability and applicability.

The Chinese Neurology and Psychiatry Association conducted a national field trial of its Chinese Classification and Diagnostic Criteria of Mental Disorders (CCMD-2) involving 26 provinces and municipalities, 80 psychiatric institutes, and 224 professionals. The results were as follows: (1) 95.2% of researchers considered the comprehensibility of the CCMD-2 diagnostic criteria good. Within the ten major categories, comprehensibility ranged from 85.7% to 100%. (2) Of those surveyed concerning the acceptability of the CCMD-2 diagnostic criteria, 85.9% considered them acceptable. In individual classifications, the rate ranged from 74.1% to 95.2%. (3) 1498 cases were tested. The overall applicability rate which indicated the consistency between the CCMD-2 result and the actual clinical diagnoses was found to be 87.6%, (averaging Kappa = 0.82, P < 0.01), better than those obtained from non-Chinese systems of diagnosis.

Adult↗

PubMed1993

Direct evidence for the partial dehydration of phosphatidylethanolamine bilayers on approaching the hexagonal phase.

X-ray diffraction studies on oriented multilayers of 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE) in the lamellar gel (L beta) and inverted hexagonal (HII) phases at various temperatures (5-50 degrees C) and relative humidities (0-100%) are reported. One-dimensional electron density profiles of the L beta phase bilayers were constructed to a resolution of better than 4 A using direct methods to solve for the phase problem. In addition, the electron density profiles were fitted favorably using a model in which the atomic groups were assumed to be Gaussian distributed [Wiener, M. C., & White, S. H. (1992) Biophys. J. 61, 434-447]. The X-ray data clearly demonstrate that, at 100% relative humidity (RH), POPE samples exist in two distinct L beta phases, differing primarily in the amount of water between the lamellae. As the hexagonal phase transition temperature is approached, 100% RH POPE samples partially dehydrate, releasing approximately 5 water molecules per phospholipid and experiencing on average a 3-A decrease in repeat spacing. The lower temperature hydrated L beta phase POPE electron density distribution resembles that obtained from the L beta phase 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) bilayers and is unlike the partially dehydrated POPE bilayers.

Desiccation↗

PubMed1993

Crystallization of Bacillus subtilis tryptophanyl-tRNA synthetase.

Tryptophanyl-tRNA synthetase from Bacillus subtilis was overexpressed in Escherichia coli and was purified using column chromatography on DEAE-Sephacel and hydroxyapatite columns. Single crystals of the synthetase were grown by vapor diffusion at 4 degrees C from pH 5.5 solutions of polyethylene glycol 8000 containing magnesium ATP and L-tryptophan. The crystals diffracted to about 4.0 A resolution at -150 degrees C and appeared to belong to the orthorhombic space group P2(1)2(1)2 with unit cell dimensions: a = 143.6 A, b = 111.6 A, c = 50.6 A with one dimer in the asymmetric unit.

Bacillus subtilis↗

PubMed1993

[A nationwide field trial of the Chinese classification and diagnostic criteria of mental disorders: application and evaluation].

To test the quality and feasibility of the Chinese Classification and Diagnostic Criteria of Mental Disorders (CCMD-2), a nationwide field trial was carried out by 224 professionals from 80 psychiatric facilities. The results showed that the diagnostic criteria of CCMD-2 was clearly understandable and acceptable reported by 95.2% and 85.2% of the researchers. From a survey sample of 1,489 cases of mental disorders, the interrater agreement of criteria diagnosis was 0.96 (K) and the concordance between the diagnosis from clinical records and that based upon the criteria was 0.84(K) indicating the excellent reliability and validity of CCMD-2.

Adolescent↗

PubMed1992

3,4-Dihydroquinolin-2(1H)-ones as combined inhibitors of thromboxane A2 synthase and cAMP phosphodiesterase.

A series of 1H-imidazol-1-yl- and 3-pyridyl-substituted 3,4-dihydroquinolin-2(1H)-ones was designed and synthesized as combined inhibitors of thromboxane (TXA2) synthase and cAMP phosphodiesterase (PDE) in human blood platelets. A number of structures, e.g. 4b, 7a, 7e, 13a, and 21-25, were superior to dazoxiben 26 as inhibitors of TXA2 synthase in in vitro ADP-induced aggregation experiments with human blood platelets. The TXA2 synthase inhibitory activity was confirmed by measurement of the prostanoid metabolites derived from 14C-labeled arachidonic acid. Three compounds (7a, 7e, and 25) demonstrated in vitro inhibition of human platelet cAMP PDE at micromolar concentrations in conjunction with their TXA2 synthase inhibitory activity. Synergistic enhancement of antiaggregatory and antithrombotic actions was expected when simultaneous stimulation of adenylate cyclase (through increased PGI2 production) and inhibition of platelet cAMP PDE were possible from the same compound. Ex vivo and in vivo experiments were conducted in rats and mice, respectively, to evaluate the effects of compounds 7e and 23 on platelet aggregation and thrombotic events within these animals. Compound 7e, which has a comparable level of TXA2 synthase (IC50 1.2 microM) and human platelet cAMP PDE (IC50 6.4 microM) inhibitory activities, was found to be orally bioavailable with a long duration of action and offered effective protection against mortality in a collagen-epinephrine-induced pulmonary thromboembolism model in mice. Significant blood pressure and heart rate effects were observed for several compounds, e.g. 7e, 9e, 13a, 13d, 18, 20, 21, and 23, when dosed orally in conscious spontaneously hypertensive rats.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1992

Protein interaction with ice.

Many organisms have evolved novel mechanisms to minimize freezing injury due to extracellular ice formation. This article reviews our present knowledge on the structure and mode of action of two types of proteins capable of ice interaction. The antifreeze proteins inhibit ice crystal formation and alter ice growth habits. The ice nucleation proteins, on the other hand, provide a proper template to stimulate ice growth. The potential applications of these proteins in different industries are discussed.

Antifreeze Proteins↗

PubMed1992

Binding of secretory component to protein 511, a pIgA mouse protein lacking 36 amino acid residues of the C alpha 3 domain.

Protein 511, a murine IgA protein described previously by Robinson and Appella [Proc. natn. Acad. Sci. U.S.A. 77, 4909-4913 (1980)] which lacks 36 amino acids in the C alpha 3 domain, was tested for its ability to bind to radiolabelled secretory component (125I-rat SC) and to be transported from blood to bile in the rat, a function described previously to be mediated by the poly Ig receptor (pIg R). When compared to other mouse pIgA proteins, the naturally occurring mutant protein 511 bound 125I-rat SC and was transported from blood to bile in a manner indistinguishable from wild-type pIgA protein. We conclude that the region of Fc alpha which is missing in protein 511, is not involved in mediating the binding of pIgA to the pIg R.

Animals↗

PubMed1992

Estrogen-induced uterine vasodilatation is antagonized by L-nitroarginine methyl ester, an inhibitor of nitric oxide synthesis.

OBJECTIVES: Our study was designed to determine whether nitric oxide mediates estrogen-induced increases in uterine blood flow. STUDY DESIGN: Six nonpregnant oophorectomized ewes were instrumented with uterine artery flow probes and catheters. Ewes received estradiol-17 beta 1 microgram/kg, which maximally increased uterine blood flow by 120 minutes. Each animal then received local bolus injections of the nitric oxide synthetase inhibitor L-nitroarginine methyl ester. RESULTS: Estradiol-17 beta increased uterine blood flow from 16 +/- 6 to 139 +/- 32 ml/min by 120 minutes. Local uterine artery administration of L-nitroarginine methyl ester (1 to 30 mg) caused a dose-related decrease in uterine blood flow, which reached a maximum of 59% +/- 6% inhibition. Higher doses of L-nitroarginine methyl ester less than or equal to 10 mg/kg (330 to 460 mg) given locally led to a maximum inhibition of 79% +/- 3% but showed systemic responses. CONCLUSION: Estradiol-17 beta-induced increases in uterine blood flow are mediated mainly by nitric oxide; the observed vasodilation can be antagonized by the intraaterial administration of nitric oxide synthetase inhibitor L-nitroarginine methyl ester.

Animals↗

PubMed1992

Fatty-acid chain tilt angles and directions in dipalmitoyl phosphatidylcholine bilayers.

X-ray diffraction has been applied to determine the various tilt angles and directions (if any) which can be assumed by oriented gel phase multilayers of dipalmitoyl phosphatidylcholine (DPPC) as a function of hydration. We report for the first time that oriented DPPC multilayers with a repeat spacing (d-spacing) of 55.2A at 25 degrees C and 0% relative humidity (RH) have hydrocarbon chains tilted at an angle theta of 21.5 degrees with respect to the bilayer normal. In addition, the chains are tilted along one of the bisectors (omega = 0 degrees) of the hexagonal lattice (8 wide-angle maxima, 2 unique), a phase not previously reported in DPPC studies. At 100% RH, the chain tilt angle and d-spacing increased to approximately 29.0 degrees and 58.9A, respectively. Since at 100% RH only 4 wide-angle maxima are observed, we analyze the data on the assumption that the hydrocarbon chains may rotate independently of the hexagonal lattice (omega = 0-30 degrees), at a fixed chain tilt angle theta (Stamatoff, J.B., et al. 1979. Biophys. J. 25:253-262). The largest observed angle phi made by the wide-angle maxima with the equator is 29.5 degrees corresponding to a theta of approximately 32.6 degrees (omega avg. = 24 degrees) and the sample having a d-spacing of 64.0 A (excess water condition). Finally, theta remains relatively constant (approximately 21.5 degrees) up to a RH of approximately 45% and a d-spacing of 57.8A, after which, with increases in RH, theta increases to a maximum of 32.6 degrees.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1992

Antifreeze protein produced endogenously in winter rye leaves.

After cold acclimation, winter rye (Secale cereale L.) is able to withstand the formation of extracellular ice at freezing temperatures. We now show, for the first time, that cold-acclimated winter rye plants contain endogenously produced antifreeze protein. The protein was extracted from the apoplast of winter rye leaves, where ice forms during freezing. After partial purification, the protein was identified as antifreeze protein because it modified the normal growth pattern of ice crystals and depressed the freezing temperature of water noncolligatively.

Journal Article↗