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Biomedical subjects

H Yan

Publications and source records attributed to H Yan.

At least 181 records · Page 10Linked to original sources
PubMed1997

[Expression and distribution of bFGF in rat lung tissue of chronic hypoxic pulmonary hypertension].

OBJECTIVE: To evaluate the role of bFGF in the development of hypoxic pulmonary hypertension. METHOD: Rat models with chronic hypoxia induced pulmonary hypertension were established, the pulmonary hemodynamics were measured and the pulmonary arterioles change were studied with morphometric analysis under light microscopes, immunohistochemical staining with monoclonal antibody against human recombinant bFGF was performed in the paraffin section of rat lung. RESULT: (1) The mean pulmonary artery pressure (mPAP), and the ratio of the thickness of pulmonary arteriolar wall to external diameter of pulmonary arterioles (MT%) were 3.96 +/- 0.47 kPa and 33.8% +/- 3.5% in rats exposed to hypoxia for 3 weeks respectively, both were significant higher than those in normal control group, P < 0.01. (2) The positive staining for bFGF in the wall of pulmonary arterioles in hypoxic rats was stronger than that of control group (P < 0.01), there was a statistical relationship between increase of staining for bFGF and MT% in rats exposed to hypoxia. CONCLUSION: (1) Hypoxia can induce formation of pulmonary hypertension and structual remodeling of pulmonary arterioles. (2) bFGF may modulate the structure remodeling of pulmonary arterioles in chronic hypoxic pulmonary hypertension.

Animals↗
PubMed1997

[Pathological type of liposarcoma and its effects of clinical treatment].

To study the pathological type of liposarcoma and it effects of clinical treatment, reviewed 21 cases of liposarcoma. Since Oct. 1976 to Dec. 1995, 21 cases of liposarcoma were treated by operation. 15 cases were male and 6 cases female. The onset of the disease occurred between 6-79 years of age with an average of 49.9 years. 13 cases were well-differentiated, 4 Myxoid, 4 cases of andifferentiaed. All cases were followed up with an average of 8.9 years. The 5-, 10-year survival rate was 94%, the 5-, 10-year unrecurernce rate was 72% and 52%. Among the malignant soft tissue tumors liposarcoma, was most common. The survival rate was related to the pathological type, the site and the size. Good clinical results were well-differentiated and myxoid. The poor was retroperitoneal liposarcoma. The smaller the tumor, the better the result. For the treatment, wide margin excision is a good method of choice.

Adolescent↗
PubMed1997

[Comparison of radiographs and magnetic resonance imaging in the detection of sacroiliitis in patients with ankylosing spondylitis].

The role of radiography and magnetic resonance (MR) imaging in the detection of sacroiliitis in patients with ankylosing spondylitis (AS) was compared in this study. Thirty-six sacroiliac joints in 18 patients with AS were examined with radiography and MR scan. MR images were performed with the sequence of the coronal T1 weighted image, T2 weighted image, and T2* weighted image. Images of all patients were graded according to the modified New York criteria. Statistical results showed that significant differences existed between MR imaging and radiography in the detection of sacroiliitis (P < 0.01). MR imaging was superior to plain film radiographs in visualising erosions (P < 0.01). Radiography cannot reveal the cartilage changes and bone marrow oedema, which can only be seen in MR images. In the absence of radiographic changes, MR imaging can provide objective and complementary findings of sacroiliitis in patients with AS. Due to the ability to image cartilage changes and bone marrow oedema directly, MR imaging may be particularly useful in early diagnosis of sacroiliitis. For patients without any changes on sacroiliac joint radiograph, further examination of MR imaging may be advisable.

Adolescent↗
PubMed1997

[The residue and degradation of herbicide ammonium 2,4-dichloro-6-nitrophenate in the system of wheat and soil].

To study the residue and degradation of ammonium 2, 4-dichloro-6-nitrophenate (a herbicide) in wheat and soil, a field test was made in Wuxi Jiangsu of East China and Chengdu Sichuan of West Chain during 1985-1992. The results showed that ammonium 2,4-dichloro-6-nitrophenate was unstable with a half-life of 12-18 days in soil. The residue in wheat was less than 0.05 mg/kg on the field doses recommended. These results may be used as a basis for the hygienic evaluation of ammonium, 2,4-dichloro-6-nitrophenate.

Herbicides↗
PubMed1997

[Evaluation of enhanced CT examination in the differential diagnosis of local recurrence and postradiation fibrosis in nasopharyngeal carcinoma].

OBJECTIVE: To evaluate enhanced CT examination in the differential diagnosis of local tumor recurrence and postradiation fibrosis when a mass appeared is observed after radiation therapy of carcinoma of nasopharynx. METHODS: 159 cases of nasopharyngeal carcinoma were examined by CT, including 37 cases of local recurrence(RT) after radiation therapy and 54 cases of postradiation fibrosis (RF) 68 cases of nasopharyngeal carcinoma (PT) before radiation therapy sened as comparison. Elscint sprint 2000 CT machine was used. The CT number of plain and enhanced examination of the mass appearing after radiation therapy were measured. Variance analysis was used as statistical management for CT number difference of different kinds of mass lesions before and after contrast enhancement. RESULTS: In the RT cases, the average CT number of the mass lesion for plain scan were 50.40 +/- 8.10 Hu, and for enhanced scan it was 73.74 +/- 7.37 Hu. In the RF cases plain scan 48.62 +/- 10.15 Hu, enhanced scan 56.74 +/- 8.69 Hu, In the control cases (PT), the CT number in the plain scan of lesion was 48.32 +/- 9.20 Hu, and 72.38 +/- 7.75 Hu in the enhanced examination. These measurement showed obvious enhancement of recurrence tumor. The CT number of contrast scan of RT and RF was obviousy different (P < 0.01). CONCLUSION: If a mass lesion appears after radiation therapy in carcinoma of nasopharyx, enhancement of the lesion in CT scan is an important criterion for differential diagnosis.

Adult↗
PubMed1997

PCR amplification, molecular cloning, DNA sequence analysis and immuno/protection in BALB/C mice of the 33 kDa endoflagellar protein of L. interrorgans serovar lai.

A pair of oligonucleotide primers were designed to amplify the endoflagella gene of L. interrogans serovar lai. An approximately 840 bp fragment was generated with PCR and inserted into plasmid pUC8, after the fragment and pUC8 were digested respectively with BamHI and PstI. A recombinant plasmid (designated as pLF1) was obtained. SDS-PAGE analysis indicated that a 33 kDa was expressed in E. coli JM103 harboring pLF1 and the expression level of the protein was 11% of the total bacterial soluble proteins. Western blot analysis showed that the protein band could be recognized by the antiserum against the endoflegella (Axial filament) of Leptospira interrogans serover lai. Nucleotide sequence data showed an open reading frame encoding 282 aminoacids residues, corresponding to a protein of molecular weight 33.6 kDa. Comparison of the deduced endoflagellar subunit protein (flaB) amino acid sequence with flagellins from other bacteria revealed a high level of identity with the Treponema pallidum flaB proteins. Immunization/protection experiment was performed on the model of BALB/C mice and showed that there was higher survival rate in the group JM103-pLE1 than in the group JM103-pUC8.

Amino Acid Sequence↗
PubMed1997

Magnetic resonance images of the hypothalamic-pituitary area in idiopathic growth deficiency.

In order to describe the magnetic resonance imaging (MRI) findings in hypothalamic-pituitary area and its clinical relevance in patients with idiopathic growth hormone deficiency (IGHD), the MR imagings of 26 patients with IGHD were analyzed. On MRI, 24 out of 26 cases (92.3%) showed apparent pituitary upper margin depression; 8 out of 26 cases (30.8%) showed definite pituitary stalk transection; 22 out of 26 cases (84.6%) showed absence of the normal posterior pituitary bright spot. The bright lipidlike signal on T1W1 images at the median eminence distal to the breaking point (so-called ectopic posterior lobe) was found in 4 out of 26 cases (15.4%). According to the MRI findings of the pituitary stalks, the 26 cases were divided into three groups; group A of 8 cases (31%) characterized by the definite transaction of stalk; group B of 13 cases (50%) defined by the possible stalk transection; and group C of 5 cases (19%) with no definite stalk transection. MRI findings were consistent with the clinical and endocrine tests. The stalk transection was statistically significantly difference in insulin test, L-dopa/p test, and height standard deviation score (P < 0.05). The MRI of hypothalamic-pituitary area may differentiate partial IGHD form stalk-transected, doubtful transection and without transection.

Adolescent↗
PubMed1997

[Effect of body position changes and circadian rhythm on cerebral blood flow velocity].

To study the effects of -6 degrees head down tilt (HDT), upright posture and 24 h circadian rhythm on cerebral blood flow (CBF) velocity in humans, the CBF velocity was measured by use of transcranial Doppler technique in the middle cerebral artery (MCA) of 12 healthy male subjects. The results showed that the mean CBF velocity increased significantly during -6 degrees HDT and decreased during upright posture, and CBF velocity was higher in day time than at night.

Blood Flow Velocity↗
PubMed1997

[Construction of recombinant vaccinia virus expressing HSV-2 gD gene as live recombinant vaccine strain].

We had reported that the recombinant vaccinia virus expressing glycoprotein D of herpes simplex virus type 2 (HSV-2 gD) protected mice against lethal HSV-2 challenge. Following the succeed in animal model, we continue the research to construct the recombinant vaccinia virus expressing HSV-2 gD gene as live recombinant vaccine strain in strict accordance with the guideline for human vaccine research. A PCR-modified HSV-2 gD gene was inserted into the plasmid pJSB1175, under the control of P7.5K early/late promoter of vaccinia virus. The recombinant plasmid was used, with lipofectin reagent, to transfect 2BS cells which had been infected by wild type of TK+ vaccinia virus (Tian Tan 761 strain). The recombinant vaccinia virus harboring HSV-2 gD gene was selected out by using in situ hybridization employing 32P-1a-belled HSV-2 gD fragment as probe, together with three cycles of plaque purification. Dot and Southern blot confirmed HSV-2 gD gene had been integrated into the TK region of vaccinia virus genome, as expected. Indirect immunofluorescent assay using anti-HSV-2 gD monoclonal antibody showed HSV-2 gD was expressed effectively in the recombinant virus infected cells.

Animals↗
PubMed1997

[Determination of trace rare earth in fossil of dinosaurian egg by laser thermal lens spectrometry].

Determination of trace rare earth in fossil of dinosaurian egg by LTLS (Laser thermal lens spectrometry) is presented in this paper. The trace rare earth in fossil of dinosaurian egg was separated and concentrated with ion exchange method. The measure conditions and effect factors are discussedian. The LTLS was applied to the determination of trace rare earth in fossil of dinosaurian egg with satisfactory results. It provides the reference data for the studies on the fossil of dinosaurian egg and an analytical method for the determination of rare earth in geochemical sample.

Animals↗
PubMed1997

Programmed stimulation for simulation of atrial tachyarrythmias.

Swine have become the preeminent non-human animal model for testing of cardiac assistance devices. Such devices must be robust to perturbations in the EKG; therefore it is expeditious, as part of cardiac assistance device testing, to simulate arrhythmias such as atrial flutter and fibrillation in swine. Methods for producing atrial tachyarrythmias include surgical ablation or crushing of atrial tissue and the administration of drugs. These are dangerous, unreliable and usually irreversible; in varying combinations and degrees. When we applied rapid evenly spaced electrical atrial pacing in swine, the variability of ventricular response was less than expected from the corresponding arrhythmia in man. We will describe efforts to produce reversible atrial tachyarrythmias in swine, using programmed stimulation, with the desired degree of ventricular response variability.

Animals↗
PubMed1996

Kinetic and thermodynamic characterizations of yeast guanylate kinase.

Yeast guanylate kinase was expressed at high level in Escherichia coli using pET-17b vector. It was purified to homogeneity by a simple two-column procedure with an average yield of approximately 100 mg/liter. The steady-state kinetic parameters for both forward and reverse reactions were determined by initial velocity measurements. The turnover numbers (kcat) were 394 s-1 for the forward reaction (formation of ADP and GDP) and 90 s-1 for the reverse reaction (formation of ATP and GMP). Km values were 0.20, 0. 091, 0.017, and 0.097 mM for MgATP, GMP, MgADP, and GDP, respectively. Analysis of the initial velocity patterns indicated a sequential mechanism. GMP was found to have partial substrate inhibition. The substrate inhibition was not competitive with MgATP and could be attributed to formation of the abortive complex guanylate kinase.MgADP.GMP. The equilibrium constant of the reaction was measured under various conditions by NMR and a radiometric assay. The results showed that the steady-state kinetic parameters were consistent with the thermodynamic constant. NMR titration and equilibrium dialysis showed that both substrates and products could bind to free guanylate kinase. The dissociation constants were 0.090, 0.18, 0.029, 0.084, and 0.12 mM for MgATP, ATP, GMP, MgADP, and GDP, respectively. Viscosity-dependent kinetics was used to identify the rate-limiting steps of the reaction. The results indicated that the reaction rate is largely controlled by the chemical step.

Adenosine Diphosphate↗
PubMed1996

Dimerization of a chimeric CD4-interferon-alpha receptor reconstitutes the signaling events preceding STAT phosphorylation.

Interferon-alpha induces the rapid tyrosine phosphorylation of a number of molecules, including the cognate receptors, JAK-family kinases (Jak1 and tyk2), and latent transcription factors (STATs 1 and 2). Here, we describe the use of chimeric molecules composed of the extracellular domain of CD4 fused to the intracellular domain of the interferon-alpha receptor subunit 1 (IFNaR1). Antibody mediated crosslinking dimerizes the transfected chimeras, activates tyk2 and induces a tyk2-dependent tyrosine phosphorylation of the intracellular domain of the chimera. We further define the major site of IFNaR1 phosphorylation, and show that phosphorylation of this site is required for association with STAT2. Finally, we show that homodimerization of IFNaR1 is not sufficient to activate the STATs, suggesting a role for the IFNaR2 subunit and Jak1 in the transduction of the interferon-alpha signal.

Amino Acid Sequence↗
PubMed1996

Cloning and functional expression of cDNAs encoding human and rat pancreatic polypeptide receptors.

PCR was used to isolate nucleotide sequences that may encode novel members of the neuropeptide Y receptor family. By use of a PCR product as a hybridization probe, a full-length human cDNA was isolated that encodes a 375-aa protein with a predicted membrane topology identifying it as a member of the G-protein-coupled receptor superfamily. After stable transfection of the cDNA into human embryonic kidney 293 cells, the receptor exhibited high affinity (Kd = 2.8 nM) for 125I-labeled human pancreatic polypeptide (PP). Competition binding studies in whole cells indicated the following rank order of potency: human PP = bovine PP > or = human [Pro34]peptide YY > rat PP > human peptide YY = human neuropeptide Y. Northern blot analysis revealed that human PP receptor mRNA is most abundantly expressed in skeletal muscle and, to a lesser extent, in lung and brain tissue. A rat cDNA clone encoding a high-affinity PP receptor that is 74% identical to the human PP receptor at the amino acid level was also isolated. These receptor clones will be useful in elucidating the functional role of PP and designing selective PP receptor agonists and antagonists.

Amino Acid Sequence↗
PubMed1996

Phosphorylated interferon-alpha receptor 1 subunit (IFNaR1) acts as a docking site for the latent form of the 113 kDa STAT2 protein.

Interferon-alpha (IFN alpha) induces rapid tyrosine phosphorylation of its receptors, two JAK kinases and three STAT transcription factors. One kinase, p135tyk2, is complexed with the IFNaR1 receptor, and may catalyze some of these phosphorylation events. We demonstrate that, in vitro, p135tyk2 phosphorylates two tyrosines on IFNaR1. A phosphopeptide corresponding to the major phosphorylation site (Tyr466) binds STAT2, but not STAT1, in an SH-2-dependent manner. Furthermore, only latent, non-phosphorylated STAT2 interacts with this phosphopeptide. When this phosphopeptide is introduced into permeabilized cells, the IFN alpha-dependent tyrosine phosphorylation of both STATs is blocked. Finally, mutant versions of IFNaR1, in which Tyr466 is changed to phenylalanine, can act in a dominant negative manner to inhibit phosphorylation of STAT2. These observations are consistent with a model in which IFNaR1 mediates the interaction between JAK kinases and the STAT transcription factors.

Amino Acid Sequence↗
PubMed1996

The SH2 domains of Stat1 and Stat2 mediate multiple interactions in the transduction of IFN-alpha signals.

Analysis of the ability of IFN-alpha to rapidly stimulate genes has led to the identification of a new family of signal transducing factors (STFs). The STF activated by IFN-alpha consists of two members of the STAT (Signal Transducers and Activators of Transcription) family of signaling proteins, Stat1 and Stat2. Sequence comparison of these STATs has determined that they share several conserved domains, the most notable of which is an SH2 domain. Recently, studies have determined that these SH2 domains can mediate a specific association between a STAT and the cytoplasmic domain of the appropriate receptor. Once associated with the receptor, the STATs become activated by an associated tyrosine kinase, whereupon they dissociate from the receptor and dimerize to form active STFs. The SH2 domain has also been implicated in the formation of STAT dimers found in STFs, suggesting it may play multiple roles in signaling. We have carried out a detailed analysis on the role of the Stat1 and Stat2 SH2 domains in the mediation of IFN-alpha stimulated signals. These studies, which have determined that the SH2 domain of Stat1 and Stat2 can mediate homo- as well as heterodimerization, suggest that a single SH2 domain-phosphotyrosyl interaction is sufficient for dimerization. Moreover, they provide the first direct evidence that the target of the SH2 domain is the STAT tyrosine activation site. In addition, these studies implicate the SH2 domain in another step in the signaling cascade, namely mediation of the interaction between STATs and their activating kinases (i.e. the JAKs).

Animals↗
PubMed1996

In vivo studies of cadmium-induced apoptosis in testicular tissue of the rat and its modulation by a chelating agent.

In vivo CdCl2-induced apoptotic DNA fragmentation in the testes of the male Wistar rat has been demonstrated on agarose gel. Characteristic DNA migration patterns (laddering) provide evidence of apoptosis (programmed cell death) in testicular tissue of rats administered CdCl2 at a level of 0.03 mmol/kg 48 h previously. Evidence that administration of an appropriate cadmium chelating agent within the first 24 h can suppress some or all of the apoptotic changes in testicular DNA has also been obtained for the first time. A greater reduction in apoptosis is observed as the interval between the administration of the cadmium and that of the chelating agent is shortened. Administration of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to male Wistar rats given CdCl2 is effective in the modulation of the typically apoptotic DNA fragmentation and associated histopathologic injury when the antagonist is given within approximately 1 h after the CdCl2 exposure. When the antagonist is given at later times there is a progressively more pronounced degradation of the DNA into oligonucleotides as seen in the typical electrophoretic DNA ladder pattern found with apoptosis. There is also a progressive increase in histopathological tissue changes as the antagonist is administered at progressively greater intervals after the cadmium.

Animals↗