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Biomedical subjects

X Xie

Publications and source records attributed to X Xie.

At least 181 records · Page 10Linked to original sources
PubMed1995

Human papillomavirus type 18 DNA in gestational trophoblastic tissues and choriocarcinomas.

The objectives of our study were to better understand carcinogenesis of gestational trophoblastic tumors and to investigate the possible presence of human papillomavirus types 16 and 18 DNA sequences in these tumors. Amplification-based DNA methodology was used on 11 hydatidiform moles, 5 invasive moles, 8 choriocarcinomas and 9 normal early placental tissues. Human papillomavirus type 16 DNA was not found in any of these tissues. Although human papillomavirus type 18 DNA was also not found in the 9 normal placentas and 5 invasive moles, it was present in 2 of the 11 (18%) hydatidiform moles and in 4 of the 8 (50%) choriocarcinomas.

Base Sequence↗
PubMed1995

Single crystal X-ray structures of the two 4-heptadecyl derivatives of (1R,5S)-3,6,8-trioxabicyclo[3.2.1]octane.

The single crystal structures of the two diastereomeric 4-heptadecyl derivatives of (1R,5S)-3,6,8-trioxabicyclo[3.2.1]octane have been determined by X-ray diffraction to be (1R,4R,5S)-heptadecyl-3,6,8-trioxabicyclo[3.2.1]octane (I) and (1R,4S,5S)-4-heptadecyl[3,6,8-trioxabicyclo[3.2.1]octane (II), respectively, which have an exo or axial 4-heptadecyl group, and an endo or equatorial 4-heptadecyl group, respectively. The structures of I and II had been suggested by their phase-sensitive 2D NOESY 1H-NMR spectra, but are now established unambiguously. These optically pure non-ionic lipid-like amphipathic molecules (I and II) represent the first 3,6,8-trioxabicyclo[3.2.1]octanes for which single crystal structures have been solved. Crystals of both isomer I and isomer II were orthorhombic with space group P2(1)2(1)2(1), and had unit cell dimensions of a = 9.586, b = 43.14, c = 5.289 A, and a = 7.34, b = 51.8, c = 5.636 A, respectively. The structures of I and II were both solved by using direct methods to R = 0.045 and R = 0.086, respectively. Both I and II pack in stacked bilayers with interdigitating and tilting hydrocarbon chains. The molecular and hydrocarbon cross sections are I: S = 50.70 A2, sigma = 19.00 A2; and II: S = 41.37 A2, sigma = 18.26 A2.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed1995

Interaction of the antiepileptic drug lamotrigine with recombinant rat brain type IIA Na+ channels and with native Na+ channels in rat hippocampal neurones.

Actions of the new antiepileptic drug lamotrigine (LTG, Lamictal) were characterised using recombinant rat brain type IIA Na+ channels expressed in Chinese hamster ovary (CHO) cells and native Na+ channels in rat hippocampal pyramidal neurones, using whole-cell recording and intracellular recording techniques. In CHO cells, LTG caused a tonic inhibition of Na+ currents in a concentration-dependent and voltage-dependent manner. The half-maximal inhibitory concentration (IC50) of approximately 500 microM was obtained at a holding potential (Vh) of -90 mV compared with an IC50 of 100 microM at a Vh of -60 mV. LTG (50 microM) caused a 10-mV negative shift in the slow, steady-state inactivation curve and delayed considerably the recovery from inactivation, but had no significant effects on the voltage dependence of activation or fast inactivation, suggesting that LTG acts mainly on the slow inactivated state. The affinity for the inactivated channels was estimated at 12 microM. The tonic inhibition was augmented by a use-dependent action in which a further inhibition by the drug developed during rapid repetitive stimulation using a train of 20-ms duration pulses (11 Hz). These results were consistent with the drug action being on firing properties of pyramidal neurones. Only in those epilepti-form bursts which caused cumulative inactivation of Na+ spikes did LTG produce a potent inhibition. Our data suggest that the inactivated channel is a primary target for LTG action at therapeutic concentrations.

Action Potentials↗
PubMed1995

An isochromosome of the long arm of chromosome 18 in a patient with myelodysplastic syndrome with myelofibrosis.

A case of myelodysplastic syndrome (MDS) with myelofibrosis and i(18q) is reported. The patient, a 29-year-old Chinese man, was noted to be anemic over a 10-year period. Recently, his spleen became progressively massive and bone marrow aspirates yielded "dry taps" on several occasions. Hematologic investigation disclosed pancytopenia, numerous nucleated red cells, and slightly increased myeloblasts (8%) in the peripheral blood. Bone marrow aspirate and biopsy revealed hypercellular marrow, trilineage dysplasia, and significant reticulin fibrosis, but without collagen formation. Bone marrow karyotypic analysis with R-banding showed an isochromosome 18q as a sole abnormality in 20 of 24 metaphases analysed. The patient died of severe anemia and bleeding due to bone marrow failure. We believe that i(18q) and myelofibrosis may be related to his poor prognosis.

Adult↗
PubMed1995

Cardiac function in smokers and nonsmokers: the CARDIA study. The Coronary Artery Risk Development in Young Adults Study.

OBJECTIVES: This study assessed clinical and echocardiographic measures of cardiac function at rest in smokers and nonsmokers to determine the associations of cigarette smoking with various measures of left and right ventricular performance. BACKGROUND: Whereas the immediate cardiovascular effects of cigarette smoking have been well described, the long-term effects in an otherwise healthy cohort have not. Of particular interest were associations with heart rate, left ventricular end-systolic stress and left ventricular mass because higher levels of these measures would suggest increased myocardial oxygen consumption. METHODS: In year 5 of the Coronary Artery Risk Development in Young Adults (CARDIA) study, 3,366 smokers and nonsmokers (ex-smokers were excluded) underwent echocardiography as well as assessment of heart rate, anthropometric measurements and blood pressure. Participants ranged in age from 23 to 35 years and were equally distributed by race and gender. Echocardiographic measures included pulsed Doppler pulmonary artery acceleration time (a decrease suggests increased pulmonary artery pressure), left ventricular mass, left ventricular end-systolic stress and left ventricular fractional shortening. RESULTS: All comparisons were between smokers and nonsmokers. Heart rate at rest was significantly higher in smokers by 1.5 to 5 beats/min in all race/gender groups except black men. In men who smoked, pulmonary artery acceleration time was significantly lower by 4 to 8 ms. Except for black male smokers, there was a trend toward increased left ventricular mass (3 to 8 g) in all race/gender groups, significant in black women. Left ventricular end-systolic stress was significantly higher in women who smoked (4 to 6 dynes/cm2). There were no differences for systolic blood pressure or left ventricular fractional shortening. CONCLUSION: In an assessment of cardiovascular function at rest in young adults, quantifiable differences between smokers and nonsmokers that predict increased rest myocardial oxygen consumption in smokers were found. Some of these differences were gender specific.

Adolescent↗
PubMed1995

Microvascular mechanisms of histamine-induced potentiation of leukocyte adhesion evoked by chemoattractants.

1. Intravital microscopy of the rat mesentery was used to examine interactions between histamine and the chemoattractant leukotriene B4 (LTB4) with regard to leukocyte adhesion in postcapillary venules. 2. Topical administration of histamine caused a four fold potentiation of LTB4-induced leukocyte adhesion. 3. Histamine significantly increased the rolling leukocyte flux by 25%, and this effect of histamine on rolling was strictly blood flow-dependent, i.e. we found significant positive correlations between both blood flow and total leukocyte flux and between total and rolling leukocyte flux, while no changes in leukocyte rolling fraction or rolling velocity were observed. Furthermore, histamine caused a clear-cut increase in venular plasma protein leakage. 4. The platelet-activating factor (PAF) receptor antagonist WEB 2086, which effectively inhibited adhesion of leukocytes evoked by exogenous PAF, did not reduce the potentiating effect of histamine on LTB4-induced leukocyte adhesion. 5. The vasodilator acetylcholine (ACh) caused a moderate enhancement of LTB4 induced leukocyte adhesion in proportion to its blood flow-dependent 40% increase in rolling leukocyte flux. In contrast to histamine, ACh did not provoke vascular leakage of plasma proteins. 6. Taken together, our findings suggest that histamine plays an important pro-inflammatory role in tissues where leukocyte rolling is already present, by potentiating chemoattractant-induced firm leukocyte adhesion through a combination of microcirculatory changes such as increased rolling leukocyte flux and vascular permeability.

Amino Acid Sequence↗
PubMed1995

Purpose in life, boredom, and volunteerism in a group of retirees.

In a pilot study of 40 retirees, those who volunteered more than 10 hours per week scored significantly higher on the Purpose In Life test than those who volunteered 10 or fewer hours per week. A significant negative correlation of -.75 was obtained between scores on purpose in life and boredom proneness.

Aged↗
PubMed1995

[Abnormal expression and clinical significance of mutation p53 gene on human bladder cancer].

In order to study the relationships between the mutant p53 gene and human bladder cancer, the authors used in situ hybridization to detect 30 of bladder cancer and 4 of normal bladder samples. The results showed that p53 gene positive rate of mRNA was 23.3% in cancer patient, and all negative in normal-bladder. The positive rate was significantly different in pathological grading and clinical stages of carcinoma (P < 0.05). It suggests that the mutant p53 gene participats in transformation of carcinoma and may be used as a tumor marker for determinating invasiveness and prognosis of bladder carcinoma.

Carcinoma, Transitional Cell↗
PubMed1995

[A preliminary study on etiology of atrophic rhinitis in Zunyi].

200 cases (households with atrophic rhinitis (AR) diagnosed from outpatients and mobile medical team as the AR group were studied. Another 200 cases (households) served as the control group, who were residents of countryside and members of a factory in Zunyi, and they have lived in Zunyi for more than 20 years. The subjects between the two groups were similar in age and sex. Each of these two groups was further divided into two groups, the opentype stove group (100 cases) and the closetype stove group (100 cases). The heritability (h2, 59.4 +/- 0.032%) was estimated by using the method of Falconer liability threshold. The concentration of SO2 in living environment was monitored with Parafuchsin colorimetry. The daily average SO2 concentrations have been drawn for comparison. The result showed that the SO2 concentration of living environment in AR group was significantly higher than that in control group (P < 0.01). We believe that the contraction and development of AR were determined by the combination of inheritance with environment. This fact suggests that AR may be transmitted in a multigenic and multifacterial modes.

Adolescent↗
PubMed1994

Cloning and expression of a new mammalian chaperonin gene from a multipotent hematopoietic progenitor clone.

Molecular chaperones assist in the folding and assembly of proteins in cells. Although chaperonins have been shown in prokaryotes, mitochondria, and chloroplasts long-ago, a cytoplasmic heteromeric chaperonin complex was isolated only recently and found to contain at least five to six polypeptides, one of which was identified as the product of the T complex polypeptide-1 (TCP-1) gene. We have isolated and cloned a novel gene called A45 from a cDNA library constructed from poly (A)+ RNA of a multipotent hematopoietic progenitor clone. The A45 cDNA encodes a predicted polypeptide of M(r) 58,118 that exhibits 32% overall amino acid sequence identity to TCP-1 and contains the putative adenosine triphosphate-binding domain and two characteristic consensus regions that are conserved in all chaperonins. The A45 gene is expressed in hematopoietic precursors cells at a much higher level than in nonhematopoietic cells and tissues. We conclude that A45 represents a new member of the mammalian chaperonins that is involved in the folding and assembly of polypeptides.

Amino Acid Sequence↗
PubMed1994

Modulation of GABA-mediated synaptic transmission by endogenous zinc in the immature rat hippocampus in vitro.

1. Intracellular recordings from postnatal 2- to 12-day-old (P2-12) rat hippocampal CA3 pyramidal neurones exhibited spontaneous synaptic potentials mediated by GABAA receptors. These potentials can be separated on the basis of amplitude into two classes which are referred to as small and large. 2. The large depolarizing potentials were reversibly inhibited by the Zn2+ chelator 1,2-diethyl-3-hydroxypyridin-4-one (CP94). The small inhibitory postsynaptic potentials. (IPSPs) were apparently unaffected. 3. Stimulation of the mossy fibre pathway evoked composite excitatory postsynaptic potentials (EPSPs) and IPSPs. Threshold stimulus-evoked synaptic potentials were mediated by GABAA receptors and were reversibly blocked by CP94. The responses evoked by suprathreshold stimulation and persisting in the presence of bicuculline or CP94 were partially inhibited by 2-amino-5-phosphonopropionic acid (AP5) and were completely blocked with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). 4. L-Histidine, which preferentially forms complexes with Cu2+ > Zn2+ > Fe2+ > Mn2+, inhibited both naturally occurring spontaneous and evoked GABAA-mediated large synaptic potentials without affecting the neuronal resting membrane properties. Exogenously applied Zn2+ induced large spontaneous synaptic potentials and prolonged the duration of the evoked potentials. These effects were reversibly blocked by histidine. 5. The metal chelating agent diethyldithiocarbamate had little effect on the large amplitude synaptic potentials. 6. The transition metal divalent cations Fe2+ and Mn2+ did not initiate large synaptic potentials in CA3 neurones; however, Cu2+ depolarized the membrane and enhanced both excitatory and inhibitory synaptic transmission, resulting in a transient increase in the frequency of the large amplitude events. In comparison, zinc increased the frequency of the large potentials and also induced such events in neurons (P4-21) where innate potentials were absent. The postsynaptic response to ionophoretically applied GABA was either unaffected or slightly enhanced by Zn2+. 7. Under conditions favouring the activation of non-NMDA receptors, excitatory synaptic transmission was unaffected by CP94 but was depressed by Zn2+. Responses to ionophoretically applied glutamate were not inhibited by Zn2+, indicating that Zn2+ affects excitatory synaptic transmission via a presynaptic mechanism. 8. We conclude that the naturally occurring large synaptic potentials in young CA3 neurones are apparently induced by endogenous Zn2+ which can promote or synchronize the release of GABA in the immature hippocampus.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1994

Structure of the regulatory domain of scallop myosin at 2.8 A resolution.

The regulatory domain of scallop myosin is a three-chain protein complex that switches on this motor in response to Ca2+ binding. This domain has been crystallized and the structure solved to 2.8 A resolution. Side-chain interactions link the two light chains in tandem to adjacent segments of the heavy chain bearing the IQ-sequence motif. The Ca(2+)-binding site is a novel EF-hand motif on the essential light chain and is stabilized by linkages involving the heavy chain and both light chains, accounting for the requirement of all three chains for Ca2+ binding and regulation in the intact myosin molecule.

Amino Acid Sequence↗
PubMed1994

Ethnic differences in electrocardiographic left ventricular hypertrophy in young and middle-aged employed American men.

In the United States population, black men have higher prevalence rates of electrocardiographic (ECG) high QRS voltage, more ST-segment and T-wave abnormalities, and more ECG left ventricular hypertrophy (LVH) than do white men. Reasons for these differences have not been fully elucidated. The prevalence rate of ECG LVH and associated characteristics were compared in black and white men in the Chicago Heart Association Detection Project in Industry population study. Data were from 1,391 black men and 19,126 white men (age range 20 to 64 years) employed by 84 Chicago organizations. ECG LVH was defined by the presence of both high QRS (Minnesota code 3.3) and ST-T abnormality (code 4.1-4.3 or 5.1-5.3). Black men had a significantly higher prevalence rate of ECG LVH than did white men in each 15-year age group (15.9 vs 2.4, 14.6 vs 2.8, and 35.7 vs 12.5/1,000 in the 20- to 34-, 35- to 49-, and 50-to 64-year age groups, respectively; p < 0.01 for each comparison). Multiple logistic regression analyses indicated that systolic blood pressure and age were associated positively with ECG LVH (p < 0.01) in both black and white men. Men with history of hypertension and receiving drug treatment had a greater likelihood of having ECG LVH than did those with history of hypertension but not receiving drug treatment, possibly because those with more severe hypertension were more likely to have been prescribed medication. Serum cholesterol, cigarettes smoked/day, 1-hour post-load plasma glucose and education were not consistently related to ECG LVH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Coiled-coil packing in spermine-induced tropomyosin crystals. A comparative study of three forms.

Electron microscope images of highly ordered spermine-induced microcrystals of tropomyosin have been analyzed to determine the packing of the molecular filaments. Negatively stained microcrystals terminate in a distinctive "double fringe", which reveals the location of the molecular ends. This information, together with the symmetry of the structure in projection, shows that the microcrystals can be accounted for by a packing scheme of four layers of molecules in the unit cell. Knowing the position of the symmetry elements relating the layers then allows the three-dimensional space group of the microcrystals to be established as C222(1). Using cryo-electron microscopy and simulation studies, the run of the filaments and their packing in the C222(1) form have been shown to be related to those in the spermine-induced C2 crystal of tropomyosin whose structure has been solved to 9 A by X-ray crystallography. This result allows us to infer the location of the molecular ends in the C2 crystal as well, and this inference has been confirmed by analysis of thin sections of the C2 crystal. The C222(1) microcrystal has also been shown to be closely related to the classical divalent cation tropomyosin paracrystal. Based on knowledge of the molecular packing in the divalent cation paracrystal, the polarity of the molecules has been deduced in the other two crystal forms. The tropomyosin filament packing in all these forms may be accounted for by coiled-coil close packing and specific cationic bridging of negatively charged zones on the molecule. Taken together the results reveal a hierarchy of interactions in these close-packed crystalline forms, whose principles may apply to the packing in other fibrous proteins. This study also shows the usefulness of co-ordinating results from cryo-electron microscopy with negative staining in the structure analysis of such ordered arrays, and how these findings can complement the results of low resolution X-ray crystallographic studies.

Animals↗