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Y Wei

Publications and source records attributed to Y Wei.

At least 325 records · Page 18Linked to original sources
PubMed1994

Current progress in crystallographic studies of new lipases from filamentous fungi.

Lipases from filamentous fungi have been studied extensively over many years. They exhibit properties attractive for industrial applications, e.g. in laundry detergents, tanning and paper industries and stereospecific organic synthesis. Enzymes from the fungi Rhizomucor miehei and Geotrichum candidum have been among the first neutral lipases to be characterized structurally by X-ray diffraction methods. In this paper we report a preliminary account of crystallographic studies of three other fungal lipases homologous to that from R. miehei and obtained from Humicola lanuginosa, Penicillium camembertii and Rhizopus delemar. These newly characterized structures have important implications for our understanding of structure-function relationships in lipases in general and the molecular basis of interfacial activation.

Amino Acid Sequence↗
PubMed1994

Early afterdepolarization formation in cardiac myocytes: analysis of phase plane patterns, action potential, and membrane currents.

INTRODUCTION: Early afterdepolarizations (EADs) are among the mechanisms proposed to underlie ventricular arrhythmias. Sea anemone toxin, ATXII, known to delay Na inactivation and to induce plateau level voltage oscillations, was used to study the formation of EADs. METHODS AND RESULTS: Action potential and membrane currents were studied in rat ventricular myocytes using whole cell current and voltage clamp techniques. Phase plane trajectories were generated by plotting membrane potential (V) versus the first time derivative of membrane potential (dV/dt). Under current clamp conditions, ATXII (40 nM) consistently prolonged the action potential and induced EADs. The EADs developed at a plateau voltage between -10 and -40 mV. Calcium channel blockers, verapamil 10 microM and cobalt 4 mM, and the sarcoplasmic reticulum modulator, ryanodine (1 microM), did not antagonize ATXII effects on the action potential and EADs. However, Na channel blockers, tetrodotoxin 0.3 microM and lidocaine 40 microM, and rapid stimulation consistently shortened the prolonged action potential and suppressed EADs. Under voltage clamp conditions in the presence of ATXII, a slowly decaying inward current followed the fast inward current during depolarizing pulses. Membrane currents flowing at or later than 100 msec after the test pulse were analyzed. The control isochronal current-voltage (I-V) curves showed no late inward currents. In the presence of ATXII, all the isochronal I-V curves showed an inward current that was more prominent between -40 and 0 mV. The ATXII-induced current at the 100-msec isochrone activated at a potential of approximately -60 mV, peaked at about -20 mV, and reversed at +40 mV consistent with the Na current I-V curve. The isochronal I-V curves obtained after lidocaine superfusion resembled those of the control. The phase plane trajectory of the action potential obtained with ATXII showed an oscillatory behavior corresponding to the EAD range of potential; within this voltage range, the isochronal I-V curves were shown to cross the abscissa three times instead of once. CONCLUSION: These results suggest that, in this experimental model, neither sarcolemmal L-type Ca current nor sarcoplasmic reticulum Ca release plays a significant role in the genesis of ATXII-induced EADs. EADs are generated by a voltage-dependent balance between a markedly prolonged Na inward current and K outward currents within the voltage plateau range of the action potential but not by Ca current reactivation and inactivation.

Action Potentials↗
PubMed1994

[The study of metaphasic chromosome pellicle].

Among 12 antichromosome antisera from scleroderma patients, four were found to be the antisera against the pellicle of metaphase chromosomes. Western blotting with these sera were achieved on the protein bands resolved by SDS-PAGE of the whole cell lysate and nuclear lysate of the ascites cells. The result showed 11 bands of the nuclear lysate reacted with antisera. Moreover, additional 8 were obtained in the whole cell lysate.

Animals↗
PubMed1994

Conformational lability of lipases observed in the absence of an oil-water interface: crystallographic studies of enzymes from the fungi Humicola lanuginosa and Rhizopus delemar.

Considerable controversy exists regarding the exact nature of the molecular mechanism of interfacial activation, a process by which most lipases achieve maximum catalytic activity upon adsorption to an oil water interface. X-ray crystallographic studies show that lipases contain buried active centers and that displacements of entire secondary structure elements, or "lids," take place when the enzymes assume active conformations [Derewenda, U., A. M. Brzozowski, D. M. Lawson, and Z. S. Derewenda. 1992. Biochemistry: 31: 1532-1541; van Tilbeurgh, H., M-P. Egloff, C. Martinez, N. Rugani, R. Verger, and C. Cambillau. 1993. Nature: 362: 814-820; Grochulski, P., L. Yunge, J. D. Schrag, F. Bouthillier, P. Smith, D. Harrison, B. Rubin, and M. Cygler. 1993. J. Biol. Chem. 268: 12843-12847]. A simple two-state model inferred from these results implies that the "closed" conformation is stable in an aqueous medium, rendering the active centers inaccessible to water soluble substrates. We now report that in crystals of the Humicola lanuginosa lipase the "lid" is significantly disordered irrespective of the ionic strength of the medium, while in a related enzyme from Rhizopus delemar, crystallized in the presence of a detergent, the two molecules that form the asymmetric unit show different "lid" conformations. These new results call into question the simplicity of the "enzyme theory" of interfacial activation.

Amino Acid Sequence↗
PubMed1993

Fast algorithm for exact rendering of space-filling molecular models with shadows.

An algorithm for accurate rendering of space-filling molecular models with shadows is presented. The intensity of light and cast shadows are computed to generate realistic pictures. Arbitrary numbers of light sources, which may be at infinite or finite distances can be applied. Hidden-surface removal, lighting, and shadowing are presented in detail.

Algorithms↗
PubMed1993

[The ultrastructural changes of infiltrating gastric carcinoma cells and their surrounding structures].

The ultrastructural changes of infiltrating gastric carcinoma cells and their surrounding structures, including extracellular matrix and tissues of target organ were observed under electron microscope. Foot-like processes with abundant microfilaments extended from one side of the surface of cancer cell were found. The microfilaments were lost with the disappearance of foot-like processes. It hinted that there might be some relationship between the presence of microfilaments and the movement of cancer cells. Around the foot-like processes of infiltrating cancer cell, the local basal lamina always disappeared, and a zone of amorphous matrix was shown. It may result from the action of collagenase. Sometimes the basal lamina may reappear, even on the surface of metastating cancer cell. No direct evidence of destruction of smooth muscle cell by the cancer cell was found. The atrophy and degeneration of smooth muscle cells may be the changes indirectly caused by the infiltrating cancer cells.

Actin Cytoskeleton↗
PubMed1993

Parentage determination on placental tissues through deoxyribonucleic acid fingerprints.

Investigation of genomic polymorphisms detected by a mini-satellite "Myo" probe gives distinct and different Deoxyribonucleic Acid (DNA) fingerprints of chorionic villus and decidual membrane in the same placenta. The chorionic villus, which is regarded as the extra-embryonal tissue, represents the essential embryonal DNA fingerprint pattern, while the decidual membrane reveals the maternal pattern. A comparison between the DNA fingerprints from the chorionic villus and from the blood sample of the suspected father provides the possibility of setting a paternity test in the early gestational stage. Twenty-eight cases of paternity test on aborted placental tissues by DNA fingerprints were analysed.

Abortion, Induced↗
PubMed1992

Crystallization and preliminary crystallographic data of a Streptomyces scabies extracellular esterase.

X-ray quality single crystals of an extracellular esterase from pathogenic Streptomyces scabies were obtained by the hanging drop method. The crystals are monoclinic (space group C2, a = 161.1 A, b = 51.2 A, c = 124.2 A, beta = 100.6 degrees) with two molecules related by a noncrystallographic dyad in the asymmetric unit, with a solvent content of approximately 64%. The diffraction pattern from fresh crystals extends beyond 2 A resolution using sealed tube CuK alpha radiation. The study has been initiated in order to elucidate the mechanism of this unusual non-serine-dependent esterase, and to gain better understanding of the molecular basis of the pathogenesis of the scab disease.

Crystallization↗
PubMed1992

Alpha 1- and beta-adrenergic interactions on L-type calcium current in cardiac myocytes.

We investigated the mechanism by which alpha 1-adrenergic activation regulates basal and stimulated whole cell L-type Ca current (ICa) in rat ventricular myocytes using the physiological neurotransmitter, norepinephrine (NE, 10 microM). Stimulation of alpha 1-adrenoceptors, achieved by NE + 10 microM esmolol (a beta-receptor antagonist), had no significant effect on basal ICa. alpha 1-adrenergic activation had a marked inhibitory effect on ICa elevated by beta activation (NE + 1 microM) prazosin, an alpha 1-receptor antagonist) or activation of adenylyl cyclase by forskolin (25 microM); the inhibitory effect was reversible upon washout. However, alpha 1-adrenergic stimulation had no significant effect on ICa previously increased by intracellular application of cAMP (25 microM). The inhibitory effect seen on ICa elevated by NE showed no significant shift of either I-V or inactivation curves. It is unlikely that the inhibitory effect of alpha 1-adrenergic stimulation on NE or forskolin-elevated ICa is mediated through activation of Ca-dependent protein kinase C or changes in intracellular free Ca (pCa = 8.5, EGTA 5 mM) or cAMP-dependent phosphodiesterase. We conclude that alpha 1-adrenergic inhibition of beta-adrenergic stimulated-ICa is probably mediated through an as yet unknown G-protein. This inhibitory effect could serve as a regulatory feedback mechanism in physiological and pathophysiological settings.

Adrenergic beta-Antagonists↗
PubMed1992

Neural modeling with dynamically adjustable threshold and refractory period.

A variant of the FitzHugh-Nagumo model is proposed in order to fully make use of the computational properties of intraneuronal dynamics. The mechanisms of threshold and refractory periods resulting from the double dynamical processes are qualitatively studied through computer simulation. The results show that the variant neuron model has the property that its threshold, refractory period and response amplitude are dynamically adjustable. This paper has also discussed some problems relating to collective property, learning and implementation of the neural network based on the neuron model proposed. It is noted that the implicit way to describe threshold and refractory period is advantageous to adaptive learning in neural networks and that molecular electronics probably provides an effective approach to implementing the above neuron model.

Animals↗
PubMed1992

Hepadnavirus integration: mechanisms of activation of the N-myc2 retrotransposon in woodchuck liver tumors.

In persistent hepadnavirus infections, a distinctive feature of woodchuck hepatitis virus (WHV) is the coupling of frequent viral integrations into myc family genes with the rapid onset of primary liver tumors. We have investigated the patterns of WHV DNA insertion into N-myc2, a newly identified retroposed oncogene, in woodchuck hepatomas resulting from either natural or experimental infections. In both cases, integrated viral sequences were preferentially associated with the N-myc2 locus. In more than 40% of the woodchuck tumors analyzed, viral insertion sites were clustered in a 3-kb region upstream of N-myc2 or in the 3' noncoding region. Insertion of WHV sequences homologous to the human hepatitis B virus enhancers, either upstream or downstream of the N-myc2 coding domain, was associated with the production of normal N-myc2 mRNA or hybrid N-myc2-WHV transcripts, initiated at the normal N-myc2 transcriptional start site. Transient-transfection assays with different N-myc2-WHV constructs in HepG2 cells demonstrated that the viral enhancers could efficiently activate the N-myc2 promoter. These results, showing that cis activation of preferred cellular targets through enhancer insertion is a common strategy for tumor induction by WHV, emphasize the previously noted similarities between hepadnaviruses and nonacute oncogenic retroviruses.

Animals↗
PubMed1992

[Hypotensive effects of safflower yellow in spontaneously hypertensive rats and influence on plasma renin activity and angiotensin II level].

Safflower yellow (SY) is a mixture of chalconoid compounds extracted from Carthamus tinctorius L. Ig SY 1-2 g.kg-1.d-1 lowered the blood pressure of spontaneously hypertensive rats (SHR), for about 1.86-3.86 kPa. Five weeks after administration of SY, the plasma renin activity and angiotensin II level diminished in the SHR experimental groups. These suggest that the decrease of blood pressure is mediated by the renin-angiotensin system.

Angiotensin II↗
PubMed1992

[A study on the relationship between pathologic morphology and clinical prognosis of renal cell carcinoma].

One hundred and six cases of renal cell carcinoma (RCC) were studied with an objective to investigate the effects of clinical stages, histological patterns (grading), cell types, nuclear grading and tumor sizes on the postoperative survival time of the patients. The results showed that there were no statistical differences in the postoperative survival time among different histological patterns and among different cellular types, such as clear cell, granular cell and mixed cell. But those with either diffuse sarcomatoid pattern or undifferentiated cell type had poor prognosis. The patients with tumor size greater than 10 cm in diameter had poor prognosis. The prognosis-deciding factors for RCC patients were the clinical staging and nuclear grading. We suggest that the nuclear grading of RCC be noted in every pathological report, so as to provide reference for clinical evaluation of the prognosis and further treatment.

Carcinoma, Renal Cell↗