Biomedical subjects

X Zheng

Publications and source records attributed to X Zheng.

At least 91 records · Page 5Linked to original sources

PubMed2001

[The survey of HIV prevalence among children between 0 to 7 years old in one county in China].

OBJECTIVE: To estimate the HIV prevalence among children between 0 to 7 years old in one county with HIV epidemic. METHODS: In September 2000, finger tip blood samples were collected from 619 children between 0 to 7 years old in three districts of one county with high HIV prevalence and tested for HIV antibody and HBV antigen. RESULTS: Among those 619 children, 11 were found HIV positive, with the prevalence of 1.8% (11/169). The HIV prevalence of three districts were 5.9% (10/169), 0.5% (1/206), and 0% (0/244), respectively. The possible channel associated with the HIV infection was mother-to-child transmission since none of the infected children had the history of blood transfusion. Twenty-four tested children were found HBV positive and the prevalence was 4.3 (24/619). CONCLUSION: There was higher HIV prevalence in children between 0 to 7 years old in certain areas. More intervenes are needed in the future to prevent the HIV spreading through mother-to-child transmission.

Child↗

PubMed2001

[Anatomy structures of nasal cavity and paranasal sinus on virtual endoscopy and coronal image].

OBJECTIVE: To evaluate normal and bony anatomy of nasal cavity and paranasal sinus on the spiral CT virtual endoscopy(VE) and coronal scanning image. METHOD: After patients were scanned on axial or coronal position by spiral CT, data were transferred to workstation. Structures such as ostium-meatal complex(OMC) were viewed by navigator software when threshold was changing. RESULT: Turbinates, meatus and ostium-meatal complex were better viewed by virtual endoscopy compared with by coronal scanning image. To some extent, bony anatomy was clearer. CONCLUSION: Virtual endoscopy is of value in realizing characteristics of nasal cavity and paranasal sinus anatomy.

Adolescent↗

PubMed2001

Effect of 0.2% brimonidine on retinal blood flow.

PURPOSE: To analyze the effect of 0.2% brimonidine eye drops on retinal blood flow of patients with glaucoma. METHODS: Using self-control method and Heidelberg Retina Flowmeter (HRF), we examined the volume, flow and velocity of the superior nasal and temporal, the inferior nasal and temporal artery of retina at baseline and 2 hours after single instillation of 0.2% brimonidine. RESULTS: There were no significant changes in volume, flow and velocity of four vessels before and after the administration of 0.2% brimonidine. CONCLUSIONS: There are no significant ocular haemodynamic benefits associated with Brimonidine therapy to the glaucoma patients.

Adrenergic alpha-Agonists↗

PubMed2001

[The role of Anopheles anthropophagus in malaria transmission in in Xinyang City of Henan Province].

OBJECTIVE: To study the role of Anopheles anthropophagus in malaria transmission and transmission threshold so as to provide basis for vector surveillance and malaria control strategy. METHODS: Parasitological and entomological methods were used in the investigation at 5 villages of Xinyang City, Henan Province. RESULTS: From July to August, 1999, 74 febrile cases (10.9% of the total population) were examined. Among them 50 were infected, the incidence in the population of surveyed spots was 7.4%. Active detection was made in another randomly selected two villages and found that the parasite rate in the inhabitants was 2.0%, and the positive rate of IFA was 8.4%. Only vivax malaria was detected. An. anthropophagus and An. sinensis were collected, with An. anthropophagus as the predominant one in human dwellings. The estimated man-biting rate and the human blood index were 4.9388 and 0.7858 respectively. The vectorial capacity of An. anthropophagus was 5.5296. The critical man-biting rate of An. anthropophagus was 0.2407 as calculated by the formula (ma = -rlnP/abPh) according to Macdonald's model. The local man-biting rate was 20 times higher than that of the critical man-biting rate. CONCLUSION: The results demonstrated that An. anthropophagus is the principal vector in malaria transmission in the area. The findings imply that the critical man-biting rate is of practicable importance in vector surveillance.

Animals↗

PubMed2001

[Study on the direct interaction between alkaline phophatase and Cu(II) ions by spectral analysis].

In this paper, the results of EPR, VIS and enzyme activity show that alkaline phophatase from calf intrest directly interacted with additional Cu(II). The added Cu(II) enter into A site of active sites of AKP which decrease enzyme activity. With increase of pH value, the decrease in the intensity of the Cu(II) EPR signal and the change of place signal in VIS were observed. These results suggest that Cu(II) migrate in the active center of the enzyme.

Alkaline Phosphatase↗

PubMed2001

[Study on interaction between the metal ion in the active site of cytochrome C and trace elements by ultraviolet spectroscopy].

The direct interaction between the metal ion in the active center of cytochrome C(Fecyt-C) and four trace elements in pH 7.1 phosphate buffer by UV spectrometry has been studied. As a result, part of the metal ion Fe(II) in Fecyt-C was replaced and the corresponding cytochrome C derivatives were produced. The Soret absorption maximum is blue-shifted and the absorption coefficient of the alpha band relative to that of the beta band is decreased in comparison to the Fecyt-C.

Copper↗

PubMed2001

[Interaction between the metal ion in the active site of cytochrome C and copper sulfate by ultraviolet spectroscopy].

The direct interaction between the metal ion in the active center of cytochrome C (Fecyt-C) and inorganic copper sulfate in pH 7.1 phosphate has been studied by UV spectrometry. As a result, part of the metal ion Fe(II) in Fecyt-C was replaced by Cu(II) and the corresponding cytochrome C derivatives Cucyt-C were produced, in addition, the interaction was increased with amount of copper sulfate added. The direct interaction between the CuSO4 and metal ion of cytochrome C was verified for the first time.

Cations↗

PubMed2001

[Dynamic observation of serum cytokines in patients receiving hand transplantation].

OBJECTIVE: To investigate the changes of serum levels of cytokines in patients receiving hand transplantation. METHODS: The serum levels of IL-2, IL-10, TNF-alpha, and IFN-gamma in 2 hand transplant recipients were measured by enzyme-linked immunosorbent assays (ELISA). RESULTS: The serum levels, IL-2, TNF-alpha, and IFN-gamma in the 2 patients decreased significantly during the first posttransplant week, then increased gradually to the pretransplant levels, and finally decreased and maintained the low level. The serum level of IL-10 in the patients increased significantly during the first posttransplant week, and decreased gradually to the low level. At 5 posttransplant months, the serum level of IL-10 increased moderately again. CONCLUSION: The predominance of Th2 over Th1 confirms the efficiency of immunosuppressive drug regimens, which contribute to the survival of hand transplant. Hand transplantation does not elicit significant immune rejection. The dynamic determination of cytokines helps judge the prognosis and diagnosis of rejection in hand transplantation.

Adult↗

PubMed2000

Straightening of bulged RNA by the double-stranded RNA-binding domain from the protein kinase PKR.

The human interferon-induced protein kinase, PKR, is an antiviral agent that is activated by long stretches of double-stranded (ds)RNA. PKR has an N-terminal dsRNA-binding domain that contains two tandem copies of the dsRNA-binding motif and interacts with dsRNA in a nonsequence-specific fashion. Surprisingly, PKR can be regulated by certain viral and cellular RNAs containing non-Watson-Crick features. We found that RNAs containing bulges in the middle of a helix can bind to p20, a C-terminal truncated PKR containing the dsRNA-binding domain. Bulges are known to change the global geometry of RNA by bending the helical axis; therefore, we investigated the conformational changes of bulged RNA caused by PKR binding. A 66-mer DNA-RNA(+/- A(3) bulge)-DNA chimera was constructed and annealed to a complementary RNA strand. This duplex forces the protein to bind in the middle. A 66-mer duplex with a top strand composed of DNA-DNA(+/-A(3) bulge)-RNA was used as a control. Gel mobility-shift changes among the RNA-protein complexes are consistent with straightening of bulged RNA on protein binding. In addition, a van't Hoff analysis of p20 binding to bulged RNA reveals a favorable DeltaDeltaH degrees and an unfavorable DeltaDeltaS degrees relative to binding to straight dsRNA. These thermodynamic parameters are in good agreement with predictions from a nearest-neighbor analysis for RNA straightening and support a model in which the helical junction flanking the bulge stacks on protein binding. The ability of dsRNA-binding motif proteins to recognize and straighten bent RNA has implications for modulating the topology of RNAs in vivo.

Base Sequence↗

PubMed2000

Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide.

A simple apparatus for collecting methane emission from a simulated rice field ecosystem was formed. With no wheat straw powder amended all treatments with inhibitor(s) had so much lower methane emission during rice growth than the treatment with urea alone (control), which was contrary to methane emission from the cut rice-soil system. Especially for treatments with dicyandiamide (DCD) and with DCD plus hydroquinone (HQ), the total amount of methane emission from the soil system and intact rice-soil system was 68.25-46.64% and 46.89-41.78% of the control, respectively. Hence, DCD, especially in combination with HQ, not only increased methane oxidation in the floodwater-soil interface following application of urea, but also significantly enhanced methane oxidation in rice root rhizosphere, particularly from its tillering to booting stage. Wheat straw powder incorporated into flooded surface layer soil significantly weakened the above-mentioned simulating effects. Regression analysis indicated that methane emission from the rice field ecosystem was related to the turnover of ammonium-N in flooded surface layer soil. Diminishing methane emissions from the rice field ecosystem was significantly beneficial to the growth of rice.

Agriculture↗

PubMed2000

Retroviral transduction of cancer cell lines with the gene encoding Drosophila melanogaster multisubstrate deoxyribonucleoside kinase.

Nucleoside kinases from several species are investigated as "suicide genes" for treatment of malignant tumors by combined gene/chemotherapy. We have recently cloned a multisubstrate deoxyribonucleoside kinase of Drosophila melanogaster (Dm-dNK), and we have shown that the enzyme phosphorylates cytotoxic pyrimidine and purine nucleoside analogs. The broad substrate specificity of the enzyme, as well as its very high catalytic rate, makes it a unique member of the nucleoside kinase enzyme family. In the present study, we evaluated Dm-dNK as a suicide gene by constructing a replication-deficient retroviral vector that expresses the enzyme. The human pancreatic adenocarcinoma cell line MIA PaCa-2 and a thymidine kinase-deficient osteosarcoma cell line were transduced with the recombinant virus. We showed that Dm-dNK can be expressed in human cells, that the enzyme retained its enzymatic activity, and that it is localized in the cell nuclei due to a nuclear localization signal in its C-terminal region. The cells expressing Dm-dNK exhibited increased sensitivity to several cytotoxic nucleoside analogs, such as 1-beta-d-arabinofuranosylcytosine, 1-beta-d-arabinofuranosylthymine, (E)-5-(2-bromovinyl)-2'-deoxyuridine, 2-chloro-2'-deoxyadenosine, and 2',2'-difluorodeoxycytidine. These findings suggest that Dm-dNK may be used as a suicide gene in combined gene/chemotherapy of cancer.

Adenocarcinoma↗

PubMed2000

Syntheses and structures of Mg(C5H5BMe)2, Mg(3,5-Me2C5H3BNMe2)2, the 2,2'-bipyridine adduct Mg(C5H5BMe)2(bipy), and the N-bonded aminoboratabenzene species Mg(3,5-Me2C5H3BNMe2)2(THF)2.

The donor-free magnesocene analogues bis(1-methylboratabenzene)magnesium (1) and bis[3,5-dimethyl-1- (dimethylamino)boratabenzene]magnesium (2) are synthesized in good yields by the reactions of dimethylmagnesium with (trimethylstannyl)dihydroborinine precursors 3 and 4. In the crystalline state, both 1 and 2 possess sandwich structures with eta 6-coordinated boratabenzene ligands and display crystallographic centrosymmetry. Compound 1 reacts with the nitrogen donor 2,2'-bipyridine to give the Lewis base adduct (1)(bipy) (identical to 5). In the crystal structure of 5, one boratabenzene ligand is eta 6-bonded to the central metal while the other ligand adopts an eta 1-bonding mode. Crystallization of compound 2 from THF produces the solvate (2)(THF)2 (identical to 6), which exhibits a distorted tetrahedral N2O2 coordination environment around the magnesium atom. The average Mg-N bond distance is 2.141(3) A, and the N-Mg-N angle is 148.0(1) degrees. The observation of an aminoboratabenzene that is solely sigma-bonded to a metal is without precedent.

Journal Article↗

PubMed2000

Reduction of atrial defibrillation threshold with an interatrial septal electrode.

BACKGROUND: The standard lead configuration for internal atrial defibrillation consists of a shock between electrodes in the right atrial appendage (RAA) and coronary sinus (CS). We tested the hypothesis that the atrial defibrillation threshold (ADFT) of this RAA-->CS configuration would be lowered with use of an additional electrode at the atrial septum (SP). METHODS AND RESULTS: Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and continuous pericardial infusion of acetyl-ss-methylcholine. Defibrillation electrodes were situated in the RAA, CS, pulmonary artery (PA), low right atrium (LRA), and across the SP. ADFTs of RAA-->CS and 4 other lead configurations were determined in random order by use of a multiple-reversal protocol. Biphasic waveforms of 3/1-ms duration were used for all single and sequential shocks. The ADFT delivered energies for the single-shock configurations were 1.27+/-0.67 J for RAA-->CS and 0. 86+/-0.59 J for RAA+CS-->SP; the ADFTs for the sequential-shock configurations were 0.39+/-0.18 J for RAA-->SP/CS-->SP, 1.16+/-0.72 J for CS-->SP/RAA-->SP, and 0.68+/-0.46 J for RAA-->CS/LRA-->PA. Except for CS-->SP/RAA-->SP versus RAA-->CS and RAA-->CS/LRA-->PA versus RAA+CS-->SP, the ADFT delivered energies of all of the configurations were significantly different from each other (P:<0. 05). CONCLUSIONS: The ADFT of the standard RAA-->CS configuration is markedly reduced with an additional electrode at the atrial SP.

Animals↗

PubMed2000

Synthesis and calpain inhibitory activity of alpha-ketoamides with 2,3-methanoleucine stereoisomers at the P2 position.

A series of novel ketoamides incorporating all four 2,3-methanoleucine stereoisomers at the P2 position was synthesized. The compounds displayed a wide variation in Ki values for inhibition of calpain I depending on the configuration of the P2 methanoleucine residue. However, similar variation in cathepsin B inhibition was not observed suggesting that the S2 pocket of calpain I is more stereosensitive than that of cathepsin B.

Amides↗

PubMed2000

Differentiation-independent retinoid induction of folate receptor type beta, a potential tumor target in myeloid leukemia.

Folate receptor (FR) type beta is expressed in the myelomonocytic lineage, predominantly during neutrophil maturation and in myeloid leukemias. FR-beta expression was elevated up to 20-fold by all-trans retinoic acid (ATRA) in KG-1 myeloid leukemia cells in a dose-dependent and reversible manner in the absence of terminal differentiation or cell growth inhibition. ATRA also increased FR-beta expression in vitro in myeloid leukemia cells from patient marrow. FR-beta was not up-regulated in KG-1 cells treated with phorbol ester, dexamethasone, 1,25-dihydroxy vitamin D(3), or transforming growth factor beta. ATRA did not induce FR-beta expression in receptor negative cells of diverse origin. The ATRA-induced increase in FR-beta expression in KG-1 cells occurred at the level of messenger RNA synthesis, and in 293 cells containing a stably integrated FR-beta promoter-luciferase reporter construct, ATRA induced expression of the reporter. From experiments using retinoid agonists and antagonists and from cotransfection studies using the FR-beta promoter and expression plasmids for the nuclear receptors retinoic acid receptor (RAR)alpha, RARbeta, or RARgamma, it appears that the retinoid effect on FR-beta expression could be mediated by ligand binding to RARs alpha, beta, or gamma, but not to retinoid X receptors. Furthermore, there was apparent cross-talk between RARalpha and RARgamma selective agonists or antagonists, suggesting a common downstream target for RAR isoforms in inducing FR-beta expression. Thus, blocks in the RARalpha-specific pathway of retinoid-induced differentiation may be bypassed during retinoid induction of FR-beta expression. The results suggest that to facilitate FR-targeted therapies, retinoids may be used to modulate FR-beta expression in myeloid leukemia cells refractory to retinoid differentiation therapy.

Antineoplastic Agents↗

PubMed2000

G-Protein types involved in calcium channel inhibition at a presynaptic nerve terminal.

The inhibition of presynaptic calcium channels via G-protein-dependent second messenger pathways is a key mechanism of transmitter release modulation. We used the calyx-type nerve terminal of the chick ciliary ganglion to examine which G-proteins are involved in the voltage-sensitive inhibition of presynaptic N-type calcium channels. Adenosine caused a prominent inhibition of the calcium current that was totally blocked by pretreatment with pertussis toxin (PTX), consistent with an exclusive involvement of G(o)/G(i) in the G-protein pathway. Immunocytochemistry was used to localize these G-protein types to the nerve terminal and its transmitter release face. We used two approaches to test for modulation by other G-protein types. First, we treated the terminals with ligands for a variety of G-protein-linked neurotransmitter receptor types that have been associated with different G-protein families. Although small inhibitory effects were observed, these could all be eliminated by PTX, indicating that in this terminal the G(i) family is the sole transmitter-induced G-protein inhibitory pathway. Second, we examined the kinetics of calcium channel inhibition by uncaging the nonselective and irreversible G-protein activator GTPgammaS, bypassing the receptors. A large fraction of the rapid GTPgammaS-induced inhibition persisted, consistent with a G(o)/G(i)-independent pathway. Immunocytochemistry identified G(q), G(11), G(12), and G(13) as potential PTX-insensitive second messengers at this terminal. Thus, our results suggest that whereas neurotransmitter-mediated calcium channel inhibition is mainly, and possibly exclusively, via G(o)/G(i), other rapid PTX-insensitive G-protein pathways exist that may involve novel, and perhaps transmitter-independent, activating mechanisms.

Adenosine↗

PubMed2000

Left ventricular apex ablation decreases the upper limit of vulnerability.

BACKGROUND: After shocks with an approximately 50% probability of success for the upper limit of vulnerability (ULV(50)) of strength, the first few activations appear focally on the epicardium at almost the same site at the left ventricular (LV) apex in both successful and failed induction of ventricular fibrillation (VF). We tested the hypothesis that subendocardial ablation at this early site would decrease the shock strength required for the ULV(50). METHODS AND RESULTS: Ten S1 stimuli were delivered from the right ventricular apex at a 300-ms coupling interval in 5 pigs. Biphasic shocks were delivered from right ventricular-superior vena cava electrodes after the last S1 stimulus. The ULV(50) was determined using an up/down protocol with T-wave scanning. Radiofrequency ablation was performed endocardially at the apical LV. The ULV(50) was determined again 30 minutes after ablation. To determine the importance of the ablation region, this protocol was repeated in another 5 pigs with ablation at the LV base. Delivered voltage (401+/-60 versus 323+/-50 V) and energy (11+/-3 versus 7+/-2 J) for the ULV(50) were significantly decreased after LV apex ablation by 19% and 34%, respectively. However, no difference existed in ULV(50) before and after LV base ablation. Lesions at both the LV apex and base were subendocardial and ranged from 0.8 to 1.1 cm in diameter. CONCLUSIONS: Subendocardial ablation at the apical LV markedly decreases ULV(50), which suggests that the activation originating from this postshock early site is responsible for VF initiation and that interventions to electrically silence this site can influence the outcome of VF induction by ULV shocks.

Animals↗

PubMed2000

Pathological effects of extensive radiofrequency energy applications in the pulmonary veins in dogs.

INTRODUCTION: The long-term complications of catheter ablation within the pulmonary veins are unknown. The development of pulmonary vein stenosis has recently been described after catheter ablation to treat either chronic or paroxysmal atrial fibrillation. The purpose of this study was to examine the pathological and hemodynamic effects of radiofrequency (RF) energy application within the pulmonary veins. METHODS AND RESULTS: Right heart and transseptal catheterization were performed in 9 anesthetized mongrel dogs. The pulmonary vein ostia were cannulated and pulmonary venous pressure was measured before RF energy application in up to 4 separate pulmonary veins. Animals were euthanized at intervals of 2 to 4 weeks (n=3), 6 to 8 weeks (n=3), or 10 to 14 weeks (n=3) after ablation. Repeat catheterization before euthanasia demonstrated statistically significant differences in pulmonary capillary wedge pressure, cardiac output, pulmonary vascular resistance, and systemic vascular resistance (P<0.05) compared with the baseline. Luminal narrowing was observed in 22 of 33 pulmonary veins to which RF energy was applied. Of these, 7 were totally occluded, 7 had severe stenosis, and 8 were only minimally narrowed. Histological examination revealed intimal proliferation with organizing thrombus, necrotic myocardium in various stages of collagen replacement, endovascular contraction, and a proliferation of elastic lamina. CONCLUSIONS: Applications of RF current within the pulmonary veins may result in pulmonary vein narrowing or complete occlusion. These observations should be considered in treatment of arrhythmias originating within the pulmonary veins.

Animals↗