Biomedical subjects

X Yan

Publications and source records attributed to X Yan.

At least 127 records · Page 7Linked to original sources

PubMed1997

Cytokine-dependent gp130 receptor subunit regulates human fetal pituitary adrenocorticotropin hormone and growth hormone secretion.

We have shown recently that leukemia inhibitory factor (LIF) and oncostatin M (OSM), two members of the gp130-dependent cytokine family, stimulate murine proopiomelanocortin (POMC) transcription and adrenocorticotropin hormone (ACTH) secretion. LIF and corticotropin-releasing hormone (CRH) also synergistically induced in vivo ACTH secretion in fetal nonhuman primates. To elucidate the role of the gp130-related cytokines in human pituitary hormone regulation, we tested expression of gp130-related cytokine receptors in human fetal pituitaries. Using RT-PCR, mRNA expression of receptors for LIF, IL-6, and CRH, and the gp130 subunit, were all detected in fetal pituitaries of 18- and 31-wk gestation. Recombinant human IL-6, LIF, and OSM treatments of primary human fetal pituitary cultures (16-31 wk) increased ACTH secretion by up to 48% (P < 0.05) using doses of 1 nM, and when fetal cultures were cotreated with CRH, ACTH was induced five- to sixfold as compared to CRH alone (three- to fourfold; P = 0.01). Incubation with gp130-specific antibody suppressed basal and cytokine-stimulated ACTH secretion (alone or with CRH) from human fetal cells. Human POMC promoter -879/+6 fused to the luciferase reporter gene and transfected into AtT-20 cells, was stimulated by LIF (7-fold), which also exerted strong (22-fold) synergy with CRH on POMC transcription. Growth hormone (GH) release from fetal cultures was modestly stimulated (15-31%, P < 0.05), while other anterior pituitary hormones were not altered by these cytokines. Thus, physiologic concentrations of the gp130-related cytokines have direct effects on ACTH and GH regulation in the human pituitary, indicating that gp130-dependent signals serve as a paracrine system controlling early human pituitary function.

Adrenocorticotropic Hormone↗

PubMed1997

Structure-based identification of a ricin inhibitor.

Ricin is a potent cytotoxin which has been used widely in the construction of therapeutic agents such as immunotoxins. Recently it has been used by governments and underground groups as a poison. There is interest in identifying and designing effective inhibitors of the ricin A chain (RTA). In this study computer-assisted searches indicated that pterins might bind in the RTA active site which normally recognizes a specific adenine base on rRNA. Kinetic assays showed that pteroic acid could inhibit RTA activity with an apparent Ki of 0.6 mM. A 2.3 A crystal structure of the complex revealed the mode of binding. The pterin ring displaces Tyr80 and binds in the adenine pocket making specific hydrogen bonds to active site residues. The benzoate moiety of pteroic acid binds on the opposite side of Tyr80 making van der Waals contact with the Tyr ring and forming a hydrogen bond with Asn78. Neopterin, a propane triol derivative of pterin, also binds to RTA as revealed by the X-ray structure of its complex with RTA. Neither pterin-6-carboxylic acid nor folic acid bind to the crystal or act as inhibitors. The models observed suggest alterations to the pterin moiety which may produce more potent and specific RTA inhibitors.

Antidotes↗

PubMed1997

Effects of the herbicide molinate on mixotrophic growth, photosynthetic pigments, and protein content of Anabaena sphaerica under different light conditions.

The effects of the carbamate herbicide molinate on growth and chlorophyll a, biliprotein, and protein content of the nitrogen-fixing cyanobacterium Anabaena sphaerica grown mixotrophically under 3000- and 300-lux light intensity were studied. Under two light intensities, the three concentrations of molinate tested (5, 25, and 50 microg ml-1) can significantly inhibit algal growth in a dose-dependent manner. The high concentration of molinate (50 microg ml-1) stimulated the synthesis of chlorophyll a and protein, but inhibited the formation of biliprotein, and these effects appear to be greater at 3000 lux than at 300 lux. The effects of the other two concentrations of molinate (5 and 25 microg ml-1) on chlorophyll a and biliprotein varied with time, but 5 microg ml-1 molinate had an inhibitory effect on the synthesis of protein. It was demonstrated that different concentrations of molinate had different effects on chlorophyll a, biliprotein, and protein content, which varied with light intensity. The results support the suggestion that the physiological mode of molinate toxicity to A. sphaerica is related to its interference with the metabolism of protein, particularly the formation and functional effectiveness of some special protein.

Anabaena↗

PubMed1997

Study on the migrant labour force of China in recent years--a case study of Nanhai City, Guangdong Province.

"This paper, taking Nanhai City of Guangdong Province as an example, focuses on five interrelated aspects of the migrant labour force of China in recent years. Attention is initially paid to the background of the labour migration from inland towards coastal areas. Then, the demographic characteristics of the migrant labour force are analysed before turning to the analysis [of] the reasons for the migration. Fourthly, the impacts of the migrant workers on the socio-economic development of Nanhai City and the problems are examined. Finally, the prospects and some suggestions for... labour migration are put forward."

Asia↗

PubMed1997

New spirostanol glycosides from Anemarrhena asphodeloides.

Two new spirostanol saponins, named anemarsaponin F (2b) and G (4b), along with six known spirostanol saponins were obtained from the rhizomes of Anemarrhena asphodeloides Bunge. On the basis of spectral analyses and chemical evidence, the structures of 2b and 4b were established as neogitogenin 3-O-beta-glucopyranosyl-(1-->2) [beta-xylopyranosyl-(1-->3)]-beta-glucopyranosyl (1-->4)-beta-galactopyranoside) and lilagenin 3-O-beta-glucopyranosyl-(1-->2)-[beta-xylopyranosyl-(1-->3)]-beta- glucopyranosyl-(1-->4)-beta-galactopyranoside, respectively.

Carbohydrate Conformation↗

PubMed1997

Gene fusions of signal sequences with a modified beta-glucuronidase gene results in retention of the beta-glucuronidase protein in the secretory pathway/plasma membrane.

Signal sequences and endoplasmic reticulum (ER) retention signals are known to play central roles in targeting and translocation in the secretory pathway, but molecular aspects about their involvement are poorly understood. We tested the effectiveness of deduced signal sequences from various genes (hydroxyproline-rich glycoprotein [HRGP] from Phaseolus vulgaris; Serpin from Manduca sexta) to direct a modified beta-glucuronidase (GUS) protein into the secretory pathway in transgenic tobacco (Nicotiana tabacum L.). The reporter protein was not secreted to the cell wall/extracellular space as monitored using extracellular fluid analysis (low- or high-ionic-strength conditions) but occurred in membranes with a density of 1.16 to 1.20 g/mL. Membrane-bound GUS equilibrated with the plasma membrane (PM) and the ER on linear sucrose gradients with or without ethylenediaminetetraacetic acid, suggesting that GUS associates with the ER and the PM. Confocal microscopy of fixed cultured cells prepared from GUS control and HRGP signal peptide (SP)-GUS-expressing plants suggested only cytosolic localization in GUS-expressing plants but substantial peripheral localization in HRGP SP-GUS plants, which is consistent with GUS being associated with the PM. Aqueous two-phase partitioning of microsomal membranes from HRGP SP-GUS and Serpin SP-GUS transgenic leaves also indicated that GUS activity was enriched in the ER and the PM. These observations, together with hydrophobic moment plot analysis, suggest that properties of the SP-GUS protein result in its retention in the secretory pathway and PM.

Animals↗

PubMed1997

[Rapid bioluminescence method for pathogen detection of nephropyelitis patient].

ATP is a kind of necessary metabolites in the living cells. We detected ATP contents in 222 bacteriuria or the urine germ by bioluminescence method. The results showed that the patient had been infected when the mean value was > 130.9 +/- 11.38 and had not when the mean value was < 32.9 +/- 2.26. The results were the same with the Gram Stain, L-form bacteriuria culture and the common bacteriuria culture. The mean values of positive specimens are higher than that of the negative specimens by the bioluminescence. Thus, it is indicated that the bioluminescence method has high sensitivity. This method can be used to detect L-form bacteriuria in the urine germ quickly and is important for early diagnosis by the doctors.

Adenosine Triphosphate↗

PubMed1997

[Analysis of 24-hour ambulatory EEG monitoring in 315 children with paroxysmal diseases].

The 24-hour ambulatory electroencephalography monitoring (AEEG) of 315 children with various paroxysmal diseases were monitored. Among them 224 cases (71.11%) were lightly abnormal including 142 cases (45.08%) recorded as epilepsy burst; the absence seizures and convulsions were the highest positive rates in these patients who have been recorded epilepsy burst. We found that AEEG was more accurate to get abnormal burst wave or epilepsy burst wave than EEG. These data may indicate that AEEG is more accurate in children with paroxysmal diseases.

Adolescent↗

PubMed1997

Predictive value of clinic blood pressure variability for pressure changes during placebo in elderly hypertensives.

OBJECTIVES: Syst-China is the ongoing placebo-controlled double-blind outcome trial in older (aged 60 years or more) Chinese patients with isolated systolic hypertension (systolic blood pressure 160-219 mmHg and diastolic blood pressure < 95 mmHg). This article is based on the data accumulated until 31 August 1992. Its purpose is to investigate the extent to which the variability in the clinic blood pressure readings at baseline could predict the blood pressure changes observed in the placebo arm of the trial. METHODS: From 2379 patients recruited into the trial, 728 [455 men and 273 women, aged 66.7+/-5.5 years (mean +/- SD)] were selected, because their blood pressure readings for the three run-in visits as well as 3, 6 and 12 months after random allocation were available. Overall and between-visit blood pressure variabilities at baseline were estimated from the two readings obtained with the subject seated during the first and second run-in visits. The baseline blood pressure used to calculate the blood pressure changes during follow-up was the average of the two readings during the third run-in visit. RESULTS: The blood pressure variability at baseline was larger for women than it was for men. For all of the subjects combined, the blood pressure had decreased by 4.1+/-14.4 mmHg (P < 0.001) systolic and 0.5+/-6.7 mmHg (P < 0.06) diastolic by the 3-month follow-up visit, by 8.5+/- 15.2 and 1.4+/-7.5 mmHg, respectively, after 6 months and by 10.3+/-15.7 and 1.9+/-7.9 mmHg, respectively, after 1 year (p < 0.001 for all). Stepwise multiple regression analysis showed that sex, age, alcohol intake and the blood pressure at baseline were significant determinants of the long-term (1 year) blood pressure changes. Aftger adjustment for the aforementioned covariates, the between-visit variability was a significant predictor of the changes in the diastolic blood pressure after 1 year of placebo treatment for the men (partial r+/-SEM -0.36+/-0.12, P < 0.01) and for all of the subjects (-0.19+/-0.09, P < 0.05). For men, the partial regression coefficient between the overall variability and the changes in the diastolic blood pressure also attained statistical significance (-0.39+/- 0.14, P < 0.01). CONCLUSION: For older Chinese patients with isolated systolic hypertension, in particular for men, a higher blood pressure variability at baseline was associated with a larger decrease in diastolic blood pressure during 1-year follow-up on placebo, explaining up to 2% of the variance of the observed changes. Similar associations were not observed for systolic blood pressure.

Journal Article↗

PubMed1997

[Effects of sterigmatocystin on ras p21 expression and ultrastructure of human lung fibroblasts in vitro].

Effects of Sterigmatocystin (ST) on ras p21 expression and ultrastructure of human lung fibroblasts in vitro were studied with immunological flow cytometry and electron microscopy. The results showed that ras p21 expression in the ST treated cells was dramatically increased and the ultrastructural features of malignant cells, such as enlarged nuclei with bizzar nuclear membranne folds and predominant nucleoli, could be seen.

Carcinogens↗

PubMed1997

[DNA content correlation with the prognosis of pheochromocytoma: 10 cases report].

We investigated the relationship between DNA ploidy and the prognosis of pheochromocytoma. DNA ploidy studies on paraffin-embedded archival specimens from ten cases of pheochromocytoma were performed by flow cytometry according to Hedley's method. Clinical features and pathological results were investigated and follow-up was made. The values of DNA content in assessment of the prognosis of the tumor were discussed. Flow cytometry examination showed that seven cases had aneuploid, two deploid and one tetraploid. The malignent case was tetraploid, and died from matastasis to the bone. The other cases had a benign process. The examination of DNA content is of value in the assessment of the prognosis of pheochromocytoma.

Adrenal Gland Neoplasms↗

PubMed1997

[New digital carotid compressor].

Since 1979, many cases of paraganliomas in the neck have been successfully treated in Tianjin Cancer Hospital. All patients who would be subjected to this operation should undergo preoperative compressing exercises of the carotid artery to promote better circulation of collateral cerebral crossflow. Therefore, a reliable and compact instrument is necessary for the compressing exercises of the carotid artery and the long-term ambulatory monitoring of the compressing effect. This paper introduces our developed instrument, Adjustable and Digital Carotid compressor, which is based on the principle of volume-oscillometric method. During the gradual change in cuff pressure, the amplitude of consecutive arterial volume pulsation associated with pulse pressure shows change characteristically due to the nonlinearity of arterial pressure-volume (P-V) relation. Arterial pressure can be determined by detecting this change in the amplitude, while the arterial volume change can be noninvasively obtained as a function of this transmural pressure, provided that the state of blood flow are determined during this pressure measurement. Considering the simplicity and practicability of this instrument, we have designed a new portable one which consists of pulse pressure transducer, signal amplifier, peak voltage locking circuit and liquid crystal displayer. The validity and accuracy of this instrument and a few examples of its clinical application are presented.

Blood Pressure↗

PubMed1997

[A study on the counteracting effect of hypoxia and Qigong on simulated weightlessness and orthostatic tolerance after bedrest].

-6 degrees head down bed rest (-6 degrees HDBR) 21d were used to simulate weightlessness. 15 healthy males, aged 19-22, were divided into 3 groups with 5 people in each group: control group (-6 degrees HDBR), hypoxia group (-6 degrees HDBR + Low Oxygen), Qigong group (-6 degrees HDBR + Qigong). The results showed that the reduction of weight, perimeter of shank, daily average cardic output, basal cardic output and the pulse pressure of the Qigong group were lower than those of the control group (P<0.05). The basal cardic output and the perimeter of shank of the Hypoxia group reduced significantly than those of the control group (P<0.05). However, the reduction of the other physiological functions of the Hypoxia group were not significantly lower than that of the control group (P>0.05). During HUT +75 degrees 20 min orthostatic tolerance test after HDBR, the parameters in the Hypoxia group were better than those in the other groups. The average standing time was also longer, and no presyncopal symptom occured.

Adaptation, Physiological↗

PubMed1997

Analysis of heart rate variability and its application.

Heart rate variability (HRV) has considerable potentials in assessing the role of autonomic nervous system fluctuations in healthy individuals and patients. This paper reviews the analytical methods of HRV and its application. HRV is a useful parameter for predicting cardiac risk after acute myocardial infarction, and an early warning sign of diabetes neuropath in clinical medicine. In space medical studies, HRV analysis have been used to assess changes in autonomic regulation after weightlessness or simulated weightlessness, evaluate tolerance in various stress test, study regulatory mechanisms of cardiovascular system, and assess the effect of countermeasure against weightlessness.

Aerospace Medicine↗

PubMed1997

[Detection of Chlamydia trachomatis and Ureaplasma urealyticum from aborted tissues by polymerase chain reaction technique].

OBJECTIVE: To study the prevalence of Chlamydia trachomatis (CT) and Ureaplasma urealyticum (UU) infection in spontaneous abortion patients. METHODS: CT and UU in aborted tissues were determined by polymerase chain reaction (PCR) technique in 45 spontaneous abortion patients (abortion group) and 25 artificial abortion cases (control group). RESULTS: The detective rate of CT and UU was 42.2% and 33.3% respectively in the abortion group. As compared with the control group significant difference (P < 0.01, P < 0.025) was shown. The detection rate of mixed CT and UU is 8.9%. CONCLUSION: CT and UU are important infection factors which may cause spontaneous abortion. PCR examination of the aborted tissue can submit an accurate, rapid microorganic diagnosis of CT and (or) UU infection.

Abortion, Spontaneous↗

PubMed1997

[Applying correlation dimension of R-R intervals to the analysis of heart rate variability].

This paper addresses the correlation dimension of R-R intervals under Heart Rate Variability (HRV) conditions according to chaos theory. We calculate the R-R interval dimensions of normal people's waking and sleeping status, and of different status of a 24-hour clinical Holter recording. The results show that the bigger the HRV is, the smaller the dimension of R-R interval is. This method needs small data and costs little time to calculate, so probably it can be of clinical use in the analysis of HRV.

Electrocardiography, Ambulatory↗

PubMed1997

[Study on the inactivated vaccine of Gardnerella vaginalis of fox. VI. Experimental development of the inactivated vaccine of Gardnerella vaginalis of fox].

The aluminum hydroxide gel, propolis and oil adjuvant inactivated vaccines were developed by silecting good immunity, representing principal epidemic serotype I GVF44 of Gardnerella vaginalis of fox in civil. The results showed that the aluminum hydroxide gel vaccine in safety was better than propolis and oil adjuvant vaccines, the most optimal inactivated concentration of formalin is 0.1%. Efficient immunity doses are 4 billon bacteria/1 ml. There were on any bad influences to occur for fox after the aluminum hydroxide gel of three times immunity doses were injected. The inoculated foxes could resist challenge of a hundred ID50 virulent strains after the vaccine was injected to foxes for 21 d. Immunity period of the vaccine is 6 months storage period is 10 months at 4-10 degrees C. The field experiments confirmed that the vaccine possessed accuracy, stability and reliability.

Animals↗

PubMed1997

[Endocardial endothelium modulates lysophosphatidylcholine induced positive inotropism].

In isolated guinea pig papillary muscles, the endocardial endothelium (EE) was selectively damaged by exposing the muscles to a flow of dry air for 30s for removal of function EE. The results showed that LPC induced positive inotropic effect on papillary muscles was observed in a concentration-and time-dependent manner [PT after 15 mins' exposure to 5, 10 and 20 mumol.L-1 lysophosphatidylcholine (LPC) was increased by 104 +/- 7%, 110 +/- 6% and 124 +/- 10%, respectively]. The positive inotropic effect of 10 mmol.L-1 LPC on papillary muscles denuded of EE was significantly enhanced (PT: 163 +/- 23% vs 130 +/- 17% after exposing to LPC for 30 min). Scanning and transmission electronic microscopic studies exhibited signs of EE damage of papillary muscles incubated with LPC 10 mumol.L-1 for 30 minutes, such as disruption of gap junction between overlapping EE cells, retraction of the cell borders, fenestration on the EE, and denudation of the subjacent basal lamina. The present study suggests that the EE may affect the LPC-induced contractibility of papillary muscle via its barrier function signs, in addition, the present data provides further evidence that LPC may be a trigger for some kind of biological active factor release form EE.

Animals↗