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Biomedical subjects

X Yang

Publications and source records attributed to X Yang.

At least 937 records · Page 52Linked to original sources
PubMed1995

Investigation on breastfeeding and lactational amenorrhoeic women in mountainous areas of Pengxian County, Southwest China.

OBJECTIVE: To determine the distributions of the duration of postpartum breastfeeding, amenorrhoea, and contraceptive use, a community-based epidemiological investigation was carried out in Pengxian County, Southwest China in March 1992. METHODS: 1,040 women who had given live births during the reference period were interviewed. A current-status life table analysis was used. RESULTS: At 1 month postpartum, 100% infants were breastfed, at 6 months 95%, and at 12 months 82%. The level of amenorrhoea at 1 month postpartum was 90%, at 3 months 74%, at 6 months 62%, and at 12 months 36%. Contraceptive use was initiated at the second month postpartum with 19% of users, at 6 months 48%, and at 12 months 91%. CONCLUSION: The results indicate that at population level advising women to begin using contraceptives in 3 months postpartum is fairly reasonable, and the non-medicated IUD is recommended to be the first choice for the lactating women.

Adult↗
PubMed1995

Biological activity of human immunodeficiency virus type 1 Vif requires membrane targeting by C-terminal basic domains.

Human immunodeficiency virus type 1 (HIV-1) encodes a Vif protein which is important for virus replication and infectivity. Vif is a cytoplasmic protein which exists in both membrane-associated and soluble forms. The membrane-associated form is an extrinsic membrane protein which is tightly associated with the cytoplasmic side of membranes. We have analyzed the mechanism of membrane targeting of Vif and its role in HIV-1 replication. Mutagenesis studies demonstrate that C-terminal basic domains are required for membrane association. Vif mutations which disrupt membrane association also inhibit HIV-1 replication, indicating that membrane localization of Vif is likely to be required for its biological activity in vivo. Membrane binding of Vif is almost completely abolished by trypsin treatment of membranes. These results demonstrate that membrane localization of Vif requires C-terminal basic domains and interaction with a membrane-associated protein(s). This interaction may serve to direct Vif to a specific cellular site, since immunofluorescence staining and plasma membrane fractionation studies show that Vif is localized predominantly to an internal cytoplasmic compartment rather than to the plasma membrane. The mechanism of membrane targeting of Vif is different in some respects from that of other extrinsic membrane proteins, such as Ras, Src, and MARCKS, which utilize a basic domain together with a lipid modification for membrane targeting. Membrane targeting of Vif is likely to play an important role in HIV-1 replication and thus may be a therapeutic target.

Amino Acid Sequence↗
PubMed1995

The lethal effects of cytokine-induced nitric oxide on cardiac myocytes are blocked by nitric oxide synthase antagonism or transforming growth factor beta.

Inducible nitric oxide (NO) produced by macrophages is cytotoxic to invading organisms and has an important role in host defense. Recent studies have demonstrated inducible NO production within the heart, and that cytokine-induced NO mediates alterations in cardiac contractility, but the cytotoxic potential of nitric oxide with respect to the heart has not been defined. To evaluate the role of inducible nitric oxide synthase (iNOS) on cardiac myocyte cytotoxicity, we exposed adult rat cardiac myocytes to either cytokines alone or to activated J774 macrophages in coculture. Increased expression of both iNOS message and protein was seen in J774 macrophages treated with IFN gamma and LPS and cardiac myocytes treated with TNF-alpha, IL-1 beta, and IFN gamma. Increased NO synthesis was confirmed in both the coculture and isolated myocyte preparations by increased nitrite production. Increased NO synthesis was associated with a parallel increase in myocyte death as measured by CPK release into the culture medium as well as by loss of membrane integrity, visualized by trypan blue staining. Addition of the competitive NO synthase inhibitor L-NMMA to the culture medium prevented both the increased nitrite production and the cytotoxicity observed after cytokine treatment in both the isolated myocyte and the coculture experiments. Because transforming growth-factor beta modulates iNOS expression in other cell types, we evaluated its effects on cardiac myocyte iNOS expression and NO-mediated myocyte cytotoxicity. TGF-beta reduced expression of cardiac myocyte iNOS message and protein, reduced nitrite production, and reduced NO-mediated cytotoxicity in parallel. Taken together, these experiments show the cytotoxic potential of endogenous NO production within the heart, and suggest a role for TGF-beta or NO synthase antagonists to mute these lethal effects. These findings may help explain the cardiac response to sepsis or allograft rejection, as well as the progression of dilated cardiomyopathies of diverse etiologies.

Amino Acid Oxidoreductases↗
PubMed1995

Absence of molecular defect in the type II 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) gene in premature pubarche children and hirsute female patients with moderately decreased adrenal 3 beta-HSD activity.

To date the molecular basis and hormonal criteria for inherited mild late-onset 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency congenital adrenal hyperplasia (CAH) have not been defined. We have thus investigated the presence or absence of mutation in the type II 3 beta-HSD gene encoding adrenal/gonadal 3 beta-HSD in each of five premature pubarche children and hirsute female patients manifesting moderately decreased adrenal 3 beta-HSD activity. ACTH-stimulated hormonal levels in all patients compared with mean levels in pubertal stage-matched normal subjects were between 2.5 and 6.5 SD for 17-hydroxypregnenolone levels, and between 2.5 and 7 SD for dehydroepiandrosterone levels in all except one patient. 17-Hydroxypregnenolone to cortisol ratios were between 2.5 and 4.3 SD, and dehydroepiandrosterone to androstenedione ratios were between 3 and 8.6 SD. The type II 3 beta-HSD gene regions of a putative promoter, exons I, II, III, and IV, and exon-intron boundaries in all subjects were amplified by polymerase chain reaction and then sequenced. All patients had normal sequences of the type II 3 beta-HSD gene in both alleles. Three female patients heterozygotic for severe 3 beta-HSD deficiency CAH with one allele mutation of the gene demonstrated normal ACTH-stimulated hormone profiles. These data indicate that moderately decreased adrenal 3 beta-HSD activity resulting in modestly increased delta 5 precursor steroid levels and delta 5 to delta 4 steroid ratios in premature pubarche and hirsute patients is not caused by a mutation in the type II 3 beta-HSD gene.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

Diagnosis of occlusion site in the left anterior descending coronary artery in patients with anterior myocardial infarction--comparison of thallium-201 myocardial scintigraphy and 12-lead electrocardiography.

To evaluate whether the site of occlusion/stenosis in the left anterior descending coronary artery (LAD) could be diagnosed by noninvasive techniques, thallium-201 myocardial scintigraphy (TMS), 12-lead electrocardiography (ECG), and coronary arteriography were performed in 33 patients with anterior acute myocardial infarction (AMI). The subjects were divided into two groups according to the location of stenosis: ie, either proximal to the first diagonal branch (PRO, n = 18), or beyond the first diagonal branch (NON-PRO, n = 15). The location of the anterior interventricular groove was defined as 0 degrees. The extent of persistent perfusion defect was greater in the PRO group than in the NON-PRO group (0.43 +/- 0.12 vs 0.31 +/- 0.14, p < 0.01). The left margin of the defect in the basal short-axis layer was at 75 +/- 30 degrees in the PRO group and at -19 +/- 43 degrees in the NON-PRO group (p < 0.001). A defect with a left margin at > 30 degrees in the basal layer was found in 94% (17/18) of the patients in the PRO group and in 6% (1/15) of the patients in the NON-PRO group (p < 0.001). An abnormal Q wave in leads a VL/I was found in 78% (14/18) of the patients in the PRO group and in 20% (3/15) of the patients in the NON-PRO group (p < 0.001). The sensitivity, specificity and total predictive accuracy of detection of proximal lesions of the LAD were 94%, 93% and 94% by TMS, and 78%, 80% and 79% by ECG, respectively. A significant difference in accuracy existed between TMS and ECG (p < 0.05). These data suggest that it is possible to diagnose the site of occlusion/stenosis of the LAD as either proximal or non-proximal in patients with anterior AMI by TMS and ECG.

Coronary Angiography↗
PubMed1995

Radiofrequency catheter ablation for the treatment of common atrial flutter in humans.

Endocardial catheter ablation has been recently been proposed for the treatment of arrhythmias originating in the right atrium. In this study, we used this technique in 5 patients with paroxysmal common atrial flutter and 3 patients with paroxysmal uncommon atrial flutter. Various antiarrhythmic agents had failed to prevent the recurrence of these episodes. In each procedure, we used a large-tip 7 F quadripolar catheter electrode that was introduced via the femoral vein into the lower part of the right atrium. The two distal electrodes were used to record double-spike potentials or fragmented electrograms. A unipolar electrogram recording from a distal electrode of the same catheter was also used to identify local activation. The targets for ablation were sites which showed double-spike potential and fragmented electrogram 40-60 msec earlier than the onset of the F wave. Application of radiofrequency (RF) energy (25-40 watts) (3-17 applications) terminated atrial flutter and prevented reinduction of atrial flutter in the 5 patients with common atrial flutter. However, atrial flutter could not be terminated with the application of RF energy in the 3 patients with uncommon atrial flutter. The sites at which ablation was successful were located inferior or posterior to the coronary sinus ostium between the inferior vena cava and the tricuspid valve annulus, and were characterized by double-spike potentials and fragmented electrograms with activation times > or = 40 msec before the onset of the F wave. This area may represent the exit site from the area of slow conduction, since pacing from this site showed concealed entrainment of the F wave, and a local electrogram to the onset of the F wave coincided with the pacing spike to the onset of the F wave. Follow-up of these 5 patients (19.4 +/- 10.4 weeks) revealed recurrence of the original atrial flutter in 1 patient and a new type of atrial flutter in 1 patient. The other 3 patients have been episode-free, although an antiarrythmic agent was given for the treatment of paroxysmal atrial fibrillation in 2 patients. We conclude that the application of RF energy to the presumed critical area in the atrial flutter reentrant circuit seems to be effective in terminating and preventing common atrial flutter. Long-term follow-up is required for the recurrence of atrial flutter.

Adolescent↗
PubMed1995

Nuclear transfer of putative rabbit embryonic stem cells leads to normal blastocyst development.

Rabbit embryonic stem-like cells, characterized by embryoid body formation and differentiation into cell types representative of all three germ layers, were studied for their ability to promote early embryonic development after nuclear transfer. After culture of the reconstructed embryos, 23% (n = 35) developed successfully into morulae or blastocysts, compared with 34% (n = 62) for cloned embryos derived from nuclear transfer with embryonic blastomeres. The cloned embryos from the embryonic stem-like cells appeared normal, with an average of 26% inner cell mass cells, similar to that of control non-manipulated embryos (25%) or cloned embryos from blastomeres (25%). Thus, nuclear transfer of rabbit embryonic stem-like cells leads to early embryonic development that is indistinguishable from blastomere fusion. These results have implications for the development of gene targeting in a species (rabbit) that may be a more suitable model for studying certain human diseases. In addition, this technique may be applicable to other species from which putative embryonic stem cells have been derived, particularly agriculturally important animals.

Animals↗
PubMed1995

[A study of errors of radiography in 10000 intraoral periapical radiographs]

A total of 10000 full-mouth radiographs (10000 periapical radiographs were evaluated for radiographic errors.The result showed that four major types of errors were found in this study,They are cone cutting(5.59%),incorrect vertical angulation(38.84%),incorrect horizontal angulation(37.16%),and incorrect film placement (14.16%).The incidence of radiographic technique errors was 0.096%.Most errors were caused by incorrect vertical angulation and incorrect horizontal angulation(76%).Most errors were found in the cuspid premolar regions(70.6%)

Journal Article↗
PubMed1995

[Radiographic image analysis of root canal in anterior teeth.].

The aim of this study was to determine the number and morphology of anterior dental root canals,and their different types.1200 permanent anterior teeth were examined with radiographs.Each tooth was radiographed with two methods.The results showed there were four types of canals configulation in these teeth,two canals were present in less than one canal,the incidence of two canals was 9.6%.Author indicated that good quality of radiograph get an obvious value in determining both external and internal anatomy of teeth.The radiographs should be taken from two of several different angles.If a radiolucent line was located at mesial to distal of main canal,two canals should be suspected.

English Abstract↗
PubMed1995

[Analysis of pressure-volume-hysteresis in rabbit].

UNLABELLED: The pressure-volume (PV) relationships of respiratory, lung and chest wall (Prs-V, PL-V and Pcw-V) were studied in 11 white rabbits. The relaxation pressure induced by Hering-Breuer reflex was measured on inflating certain volume of air. Four groups of inflation experiments were performed in each rabbit. (1) Inflations of incremental tidal air with 10 ml in each increment were performed from functional residual capacity (FRC) to 70 ml, then inflations of decremental tidal air with 10 ml in each decrement were done from 70 ml to FRC. (2) 70 ml of air was inflated just before each incremental and decremental inflation. (3) 10 ml more air was inflated before each predicted incremental inflation. (4) The first group inflation was repeated. THE RESULTS: The P-V curves showed a "S" shape in all 4 groups. There was an obvious hysteresis on the Prs-V and PL-V curves in the 1st group between the incremental and decremental inflations; it disappeared in the 2nd and 3rd groups. Hysteresis reappeared in the 4th group, but it was smaller than that in the 1st group. These results substantiate the theory proposed by Frazer that pulmonary hysteresis mainly comes from sequential opening and closing of lung units during inflation and deflation.

Animals↗
PubMed1995

[Study on determination of gentamycin in serum by enhanced chemiluminesent immunoassay based on immobilized antibody and biotin-avidin system].

Gentamycin was determined by competition with biotin labeled gentamycin in the presence of an immobilized antibody to gentamycin. Microcrystalline cellulose was first coupled with sheep anti-rabbit antibody, then the anti-gentamycin antibody was conjugated and the competition reaction conducted. After separation, HRP-avidin was added to the precipitation and the amount of HRP conjugate determined by enhanced chemiluminescene. The limit of detection for gentamycin in serum was 63-78 ng/tube and the average recovery of gentamycin 103%. The correlation coefficient of the log-log regression equation. Magnitude of r was 0.991 +/- 0.006.

Animals↗
PubMed1995

[Establishment and biological characteristics of the nude mice xenograft model from human hepatocellular carcinoma].

The human hepatocellular carcinoma was successfully heterotrasplanted into nude mice and 10 passages were made seriously during 11 months. Initial take rate was 14.3% and then the take rate increased to 100% after the 3rd passage. Histological, morphological, ultrastructural and biological investigation and chromosome analysis showed that the characteristic of transplanted tumor was identical to that of characteristics of human donor tumor. Through serial passages no metastatic signs were found grossly and under the microscope in the lymph nodes, liver and lung of the nude mice. Result also showed that the model retained some functions of the original tumor. The transplanted tumor could secret a-fetoprotein (AFP), r-glufamyl transpeptidase (r-GT). Acidic isoferritin (AIF) also could be detected. The tumor tissue of xenograft model was cultured in vitro in order to develop a permanent cell line. We found that the tumor specimen of the later passages grew more rapidly than the earlier ones. Up to now 3 cell passages were made. In this paper, a reliable animal model of human hepatocellular carcinoma is provided for studies of clinical diagnosis, treatment, antitumor drug screen test, etc.

Aged↗
PubMed1995

Carbon dioxide in vascular imaging and intervention.

Angiography with iodinated contrast agents is bound up with the risks of contrast-induced nephrotoxicity and hypersensitivity, which led to the idea of using carbon dioxide (CO2) gas as a negative contrast medium to eliminate these drawbacks. During the last decade, refinements and experiences have proved carbon dioxide digital subtraction angiography (CO2-DSA) to be an accurate, safe, and clinically promising vascular imaging modality, with the advantages of no hypersensitivity and no nephrotoxicity as well as minimal patient discomfort. In this article, we have reviewed the history, physical and chemical aspects, techniques, and pathophysiologic changes with the use of CO2-DSA as well as some clinical trials. Applications of CO2 gas in vascular interventions and other imagings, and the advantages and limitations of using CO2 gas in DSA are also discussed.

Angiography↗
PubMed1995

[Analysis of the causes of recurrence of atrioventricular reentry tachycardia in patients treated with radiofrequency current ablation].

The recurrence rate of atrioventricular reentry tachycardia (AVRT) after radiofrequency current ablation (RFCA) of 124 accessory atrioventricular pathways (AP) in 122 patients were reported and the possible causes of recurrence of AVRT were analyzed. Of the 122 patients, 81 were male, 41 female. The average age of the patients was 46.3 +/- 14.4 (14-71) hears. There were 81 manifest AP in 80 patients, 43 concealed AP in 42 patients. 13 of the 124 AP were located in left anterior wall, 59 left lateral wall, 8 left posterior wall, 10 left posterior interventricular septum. 14 right anterior interventricular septum, 2 mid-septum, 14 righy posterior interventricular septum and 4 right free wall. All patients had no organic heart disease. The total recurrence rate of 124 AP in the 122 patients during a follow-up period of 2-25 (13.5 +/- 7.1) months was 4.03% (5/124), with manifest and concealed AP 1.23% (1/81) and 9.30% (4/43), respectively (P < 0.05); left free wall and interventricular septum AP were 2.5% (2/80) and 7.5% (3/40), respectively (P > 0.05); left and right AP were 3.3% (3/90) and 3.1% (1/32), respectively (P > 0.05). The recurrence time was from 0.5 to 60 (15.4 +/- 25.4) days. The recurrence may be related to inaccurate ablation target site, functional and anatomical characteristics of AP, locations of AP, and insufficient ablation energy, etc. It is suggested that AVRT patients receiving RFCA should be followed up for a certain period.

Adolescent↗