Biomedical subjects

H Yuan

Publications and source records attributed to H Yuan.

At least 109 records · Page 6Linked to original sources

PubMed1998

A biomechanical evaluation of graft loading characteristics for anterior cervical discectomy and fusion. A comparison of traditional and reverse grafting techniques.

STUDY DESIGN: A biomechanical study of graft loading characteristics for anterior cervical discectomy and fusion comparing the amount and location of transmitted forces. OBJECTIVES: To evaluate the difference between traditional iliac grafting and reverse iliac grafting used for anterior cervical discectomy and fusion in the amount and location of forces applied to the grafts. SUMMARY OF BACKGROUND DATA: Traditional fusion after anterior cervical discectomy involves placing a tricortical iliac crest strut into the disc space with the cortical portion facing anteriorly and the cancellous portion posteriorly. Recently, reverse iliac grafting has been introduced in which the cortical portion is placed in the posterior disc space and the cancellous portion in the anterior disc space. There is no biomechanical or clinical study showing an advantage of using one technique over the other. This study is the first to produce data supporting one technique as biomechanically superior. METHODS: Five fresh cadaveric cervical spines were tested using pressure-sensitive film placed between the bone graft and the vertebral endplate after an anterior discectomy was performed. A 10-pound load was applied to the cervical spine at predetermined sagittal positions. Recordings were made at neutral, 10 degrees of flexion, and 10 degrees and 20 degrees of extension after traditional and reverse iliac grafting. RESULTS: Graft forces were identical in both traditional and reverse grafting in the location and amount of force applied. Total force increased to the maximum in flexion and gradually decreased in more extended positions. The location of the forces was completely anterior with flexion, moving to the posterior portion of the graft with positions of extension. With 10 degrees of flexion, the load applied to the grafts was 20.4 N. In the neutral position, the load was 12 N. The loads decreased further with extension with forces of 11 N in 10 degrees extension, and 4 N in 20 degrees of extension. CONCLUSIONS: The optimal position of the tricortical iliac graft for an anterior cervical fusion is with the stronger cortical portion placed in the anterior disc space and the weaker cancellous portion placed in the posterior disc space. In this traditional position, the graft will best resist the loads applied to the cervical spine, preventing graft collapse.

Adult↗

PubMed1998

Guanine nucleotide exchange factor GEF115 specifically mediates activation of Rho and serum response factor by the G protein alpha subunit Galpha13.

Signal transduction pathways that mediate activation of serum response factor (SRF) by heterotrimeric G protein alpha subunits were characterized in transfection systems. Galphaq, Galpha12, and Galpha13, but not Galphai, activate SRF through RhoA. When Galphaq, alpha12, or alpha13 were coexpressed with a Rho-specific guanine nucleotide exchange factor GEF115, Galpha13, but not Galphaq or Galpha12, showed synergistic activation of SRF with GEF115. The synergy between Galpha13 and GEF115 depends on the N-terminal part of GEF115, and there was no synergistic effect between Galpha13 and another Rho-specific exchange factor Lbc. In addition, the Dbl-homology (DH)-domain-deletion mutant of GEF115 inhibited Galpha13- and Galpha12-induced, but not GEF115 itself- or Galphaq-induced, SRF activation. The DH-domain-deletion mutant also suppressed thrombin- and lysophosphatidic acid-induced SRF activation in NIH 3T3 cells, probably by inhibition of Galpha12/13. The N-terminal part of GEF115 contains a sequence motif that is homologous to the regulator of G protein signaling (RGS) domain of RGS12. RGS12 can inhibit both Galpha12 and Galpha13. Thus, the inhibition of Galpha12/13 by the DH-deletion mutant may be due to the RGS activity of the mutant. The synergism between Galpha13 and GEF115 indicates that GEF115 mediates Galpha13-induced activation of Rho and SRF.

3T3 Cells↗

PubMed1998

Specific involvement of G proteins in regulation of serum response factor-mediated gene transcription by different receptors.

Regulation of serum response factor (SRF)-mediated gene transcription by G protein subunits and G protein-coupled receptors was investigated in transfected NIH3T3 cells and in a cell line that was derived from mice lacking Galphaq and Galpha11. We found that the constitutively active forms of the alpha subunits of the Gq and G12 class of G proteins, including Galphaq, Galpha11, Galpha14, Galpha16, Galpha12, and Galpha13, can activate SRF in NIH3T3 cells. We also found that the type 1 muscarinic receptor (m1R) and alpha1-adrenergic receptor (AR)-mediated SRF activation is exclusively dependent on Galphaq/11, while the receptors for thrombin, lysophosphatidic acid (LPA), thromboxane A2, and endothelin can activate SRF in the absence of Galphaq/11. Moreover, RGS12 but not RGS2, RGS4, or Axin was able to inhibit Galpha12 and Galpha13-mediated SRF activation. And RGS12, but not other RGS proteins, blocked thrombin- and LPA-mediated SRF activation in the Galphaq/11-deficient cells. Therefore, the thrombin, LPA, thromboxane A2, and endothelin receptors may be able to couple to Galpha12/13. On the contrary, receptors including beta2- and alpha2-ARs, m2R, the dopamine receptors type 1 and 2, angiotensin receptors types 1 and 2, and interleukin-8 receptor could not activate SRF in the presence or absence of Galphaq/11, suggesting that these receptors cannot couple to endogenous G proteins of the G12 or Gq classes.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1998

Tec/Bmx non-receptor tyrosine kinases are involved in regulation of Rho and serum response factor by Galpha12/13.

A transient transfection system was used to identify regulators and effectors for Tec and Bmx, members of the Tec non-receptor tyrosine kinase family. We found that Tec and Bmx activate serum response factor (SRF), in synergy with constitutively active alpha subunits of the G12 family of GTP-binding proteins, in transiently transfected NIH 3T3 cells. The SRF activation is sensitive to C3, suggesting the involvement of Rho. The kinase and Tec homology (TH) domains of the kinases are required for SRF activation. In addition, kinase-deficient mutants of Bmx are able to inhibit Galpha13- and Galpha12-induced SRF activation, and to suppress thrombin-induced SRF activation in cells lacking Galphaq/11, where thrombin's effect is mediated by G12/13 proteins. Moreover, expression of Galpha12 and Galpha13 stimulates autophosphorylation and transphosphorylation activities of Tec. Thus, the evidence indicates that Tec kinases are involved in Galpha12/13-induced, Rho-mediated activation of SRF. Furthermore, Src, which was previously shown to activate kinase activities of Tec kinases, activates SRF predominantly in Rho-independent pathways in 3T3 cells, as shown by the fact that C3 did not block Src-mediated SRF activation. However, the Rho-dependent pathway becomes significant when Tec is overexpressed.

3T3 Cells↗

PubMed1998

Heme and the endothelium. Effects of nitric oxide on catalytic iron and heme degradation by heme oxygenase.

We studied the effects of nitric oxide (NO) on the control of excess cellular heme and release of catalytically active iron. Endothelial cells (ECs) exposed to hemin followed by a NO donor have a ferritin content that is 16% that of cells exposed to hemin alone. Hemin-treated ECs experience a 3.5-fold rise in non-heme, catalytic iron 2 h later, but a hemin rechallenge 20 h later results in only a 24% increase. The addition of a NO donor after the first hemin exposure prevents this adaptive response, presumably due to effects on ferritin synthesis. NO donors were found to reduce iron release from hemin, while hemin accumulated in cells. A NO donor, in a dose-dependent fashion, inhibited heme oxygenase activity, measured by bilirubin production. Using low temperature EPR spectroscopy, heme oxygenase inhibition correlated with nitrosylation of free heme in microsomes. Nitrosylation of cellular heme prevented iron release, for while there was heme oxygenase-dependent release of iron in cells incubated with hemin for 24 h, the addition of a NO donor blocked iron release. This indicates that NO readily nitrosylates intracellular free heme and prevents its degradation by heme oxygenase. Nitrosylation of heme was found to reduce sensitization of cells to oxidative injury.

Adaptation, Physiological↗

PubMed1998

Complexation of type 2 copper by cytochrome c oxidase: probing of metal-specific binding sites by electron paramagnetic resonance.

Cytochrome c oxidase, CcO, contains at least four, probably five type 2 copper binding sites per monomer in addition to the mixed valence [CuA(1.5+)CuA(1.5+)], S = 1/2 center and the EPR-silent CuB. Electron paramagnetic resonance (EPR) parameters for these site are g parallel = 2.22 and A parallel = 195 G. Nitrogen superhyperfine structure is observed in the g perpendicular region, with A perpendicular N of around 15 G. The EPR parameters for Cu(2+) bound to a synthetic peptide, AHGSVVKSEDYALPS, are similar to the parameters for the type 2 sites in CcO. The lines in the EPR spectrum of the type 2 site in the synthetic peptide are better resolved at low microwave frequency (3.4 GHz). Resolved lines in the expansion of the MI = -1/2 line in the g parallel region of the low frequency spectrum are attributed to superhyperfine structure from three almost equivalent nitrogen donor atoms bound to Cu(2+) in a square planar configuration. The MI = -1/2 line in the g parallel region for excess Cu(2+) bound to CcO is not as well resolved as for the synthetic peptide, presumably because the four or five binding sites per monomer are similar, but not exactly equivalent. These binding sites are proposed to be at the N-terminus of subunits of CcO, for example, at subunit IV where the sequence is AHGS-. Nitrogen donor atoms from the alpha-amino group of the amino terminal residue, the imidazole group of histidine, and a peptide nitrogen are predicted to comprise the binding site.

Binding Sites↗

PubMed1998

Concentration of Cu, EPR-detectable Cu, and formation of cupric-ferrocyanide in membranes with pMMO.

EPR spectra were obtained for the type 2 Cu(2+) site in particulate methane monooxygenase, pMMO, from membrane fractions of Methylomicrobium album BG8. In addition to the EPR signal with g parallel = 2.24 and A parallel = 185 G found in both cells and membrane fractions, a second EPR signal with g parallel = 2.29 and A parallel = 146 G was found in membrane fractions and attributed to oxidation of cuprous sites. Comparison of EPR-detectable Cu(2+) with total copper determined by atomic absorption suggests that there are two or three EPR-silent coppers for every EPR-detectable copper and that there are approximately four coppers per enzyme composed of the 47, 27, and 25 kDa subunits. Treatment of membrane fractions loaded with pMMO with Fe(CN)6(3-) results in a new EPR signal that is attributed to CuFe(CN)6(2-), not to an intrinsic trimeric copper cluster as previously reported in studies with a related bacterium.

Cell Membrane↗

PubMed1998

Osteoinduction by calcium phosphate biomaterials.

Different materials were implanted in muscles of dogs to study the osteoinduction of calcium phosphate biomaterials. Bone formation was only seen in calcium phosphate biomaterials with micropores, and could be found in hydroxyapatite (HA) ceramic, tricalcium phosphate/hydroxyapatite ceramic (BCP), beta-TCP ceramic and calcium phosphate cement. The osteoinductive potential was different in different materials. The results indicate that osteoinduction can be a property of calcium phosphate biomaterials when they exhibit specific chemical and structural characteristics.

Journal Article↗

PubMed1998

Bone morphogenetic protein and ceramic-induced osteogenesis.

To investigate the relationship between bone morphogenetic proteins (BMP) and calcium phosphate ceramic-induced osteogenesis in soft tissues, in vitro and in vivo experiments were performed. In an in vitro study, the ability of different calcium phosphate ceramics to absorb bovine BMP (bBMP) from a bBMP solution was tested. In vivo studies included immunohistochemical BMP staining before bone formation in the ceramics was detected, and the enhancement of bone formation in calcium phosphate ceramics by bBMP. The results were: (1) calcium phosphate ceramics have a strong ability to absorb bBMP; (2) a high BMP concentration reaches inside the ceramic implants before bone formation in soft tissues of domestic pig occurs; (3) by 56% at 50 d and by 23% at 100 d, bBMP enhances bone formation in calcium phosphate ceramics implanted in soft tissues of dogs. The results indicate the BMP plays an important role in calcium phosphate ceramic-induced osteogenesis and that adsorption of native BMP from the body fluids to ceramic implants may be a key step in osteoinduction by calcium phosphate ceramics.

Journal Article↗

PubMed1998

Glycine-valine dimorphism at the 86th amino acid of HLA-DRB1 influenced the prognosis of postschistosomal hepatic fibrosis.

Chinese patients (n = 113) with schistosomal hepatic fibrosis diagnosed by ultrasonography (grade I, II, or III) and 184 age- and sex-matched persons with no clinical information of schistosomal infection were typed for their HLA-DRB1 alleles by DNA typing. There was no single allele that conferred susceptibility or resistance to fibrosis. However, there were three groups of alleles that showed decreased (resistant), increased (susceptible), or neutral frequency in the patients with fibrosis. The susceptible alleles, DRBI *1202, DRB1 *1404, and DRBI *1405, shared a valine at amino acid residue 86, whereas the resistant alleles, DRB1*11011, DRB1*0409, and DRB1*0701, all had glycine at position 86. Therefore, this study focused on the glycine-valine dimorphism at aa 86, which influences the depth of the P1 pocket in the antigen binding groove, and found that the 86th valine allele was significantly increased in the patients with fibrosis (odds ratio = 2.2; 95% CI = 1.34-3.61, corrected P < .05).

Alleles↗

PubMed1998

Characterization of anion exchangers in an inner medullary collecting duct cell line.

Although the inner medullary collecting duct (IMCD) plays a major role in urinary acidification, the molecular identification of many of the specific components of the transport system in this nephron segment are lacking. A cultured line of rat IMCD cells was used to characterize the mediators of cellular HCO3 exit. This cell line functionally resembles alpha-intercalated cells. Physiologic experiments document that HCO3- transport is a reversible, electroneutral, Cl dependent, Na+-independent process. It can be driven by Cl-gradients and inhibited by stilbenes such as 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid. Immunohistochemical analysis, using a rabbit polyclonal antibody against the carboxy-terminal 12 amino acids of anion exchanger 1 (AE1), revealed a distribution of immunoreactive protein that is consistent with a basolateral localization of AE in cultured cells and in alpha-intercalated cells identified in sections of rat kidney cortex. Immunoblot revealed two immunoreactive bands (approximately 100 and 180 kD in size) in membranes from cultured IMCD cells, rat renal medulla, and freshly isolated IMCD cells. The mobility of the lower molecular weight band was similar to that of AE1 in red blood cell ghosts and kidney homogenate and therefore probably represents AE1. The mobility of the 180-kD band is similar to that for rat stomach and kidney AE2 and therefore probably represents AE2. Selective biotinylation of the apical or basolateral membrane proteins in cultured IMCD cells revealed that both AE1 and AE2 are polarized to the basolateral membrane. Northern blot analysis documented the expression of mRNA for AE1 and AE2 but not AE3. Furthermore, the cDNA sequence of AE1 and AE2 expressed by these cells was found to be virtually identical to that reported for kidney AE1 and rat stomach AE2. It is concluded that this cultured line of rat IMCD cells expresses two members of the anion exchanger gene family, AE1 and AE2, and both of these exchangers probably mediate the electroneutral Cl--dependent HCO3-transport observed in this cell line.

Animals↗

PubMed1998

[Clinical epidemiological research of antigastroesophageal reflux after cardiac plasty by anastomosis of esophageal mucosa and gastric wall].

A new operative method was designed for preventing gastroesophageal reflux after esophageal and cardiac cancer operation. From April, 1994 to December, 1995, sixty-one patients after resection of esophageal and cardiac cancer were randomly divided into two groups: experimental group with 34 patients and control group with the others. All patients were observed, monitored and followed up. It was found that no case in the experimental group showed symptoms of gastroesophageal reflux or marked reflux by esophagoscopy and barium meal examination. 10 patients (37%) in the control group had the symptoms of heartburn and regurgitation and inflammation and obvious gastroesphageal reflux were observed under esophagoscopy and barium meal examination. The pH values of anastomotic ostium were 7.0249 +/- 0.9996 and 4.6667 +/- 2.4573 in the experimental and control groups, respectively. Significant difference (P < 0.01) was observed between two groups with t test. The results showed that the advancement of operative method plays a key rolein prevention of gastroesophageal reflux.

Anastomosis, Surgical↗

PubMed1998

[Distribution of Mg2+ and Ca2+ in serum and lymphocyte of the patients with arrhythmia].

The distributions of Mg2+ and Ca2+ in serum and lymphocyte from 51 arrhythmic patients (15 cases of atrial premature beat, 12 cases of atrial fibrillation, 24 cases of ventricular premature beat) and 30 healthy subjects were detected by flame atomic absorption spectrophotometry. The results showed that the distribution of Mg2+ of the arrhythmia cases was significantly lower than that of the control group (P < 0.01) and the concentration of Ca2+ in lymphocytes of arrhythmia case group was significantly higher than that of the control group (P < 0.01). The above distribution of Mg2+ and Ca2+ was somewhat related to the degree of heart failure. It is suggested that the lower distribution of Mg2+ in lymphocytes may cause arrhythmias.

Arrhythmias, Cardiac↗

PubMed1998

[Effect on endothelin and cytokines on the pathogenesis of coronary heart disease].

The plasma levels of endothelin(ET), serum levels of tumor necrosis factor(TNF) and interleukin-6(IL-6) in 35 patients with coronary heart disease(CHD) and 20 healthy people were studied by radioimmunoassay and enzymebinded immunosorbent assay(ELISA). The results showed that the plasma ET level and the serum TNF level in the CHD group, especially the acute myocardial infarction(AMI) group, were much higher than those of the control group (P < 0.01). There was no obvious statistical difference on IL-6 levels between the narrowed coronary artery group and the control group (P > 0.05). But the serum level of IL-6 in the AMI group was significantly higher than that of the other groups (P < 0.01). These findings indicate that ET and cytokine levels may play an important role on the pathogenesis of coronary heart disease.

Adult↗

PubMed1998

[Screening for the 1555G mutation in mitochondrial DNA in pedigrees with aminoglycoside antibiotic induced deafness].

OBJECTIVE: To identify the relationship between the 1555G mutation in mitochondrial DNA and aminoglycoside antibiotic induced deafness and provide theoretical evidence for establishing diagnostic method. METHODS: Blood samples were obtained from three pedigrees with aminoglycoside antibiotic induced deafness. DNA was extracted from the isolated leukocytes. The mitochondrial DNA fragments were amplified by PCR, 1555G mutation was detected by Alw26 I restriction endonuclease digestion, allele-specific oligonucleotide hybridization and DNA sequencing. RESULTS: Seven individuals from pedigrees A and C carried homoplasmic 1555G mutation, six individuals from pedigree B did not have 1555G mutation. CONCLUSION: 1555G mutation is not the only pathologic mitochondrial DNA mutation associated with aminoglycoside antibiotic induced deafness. This is the first finding of aminoglycoside antibiotic induced deafness pedigree without 1555G mutation.

Anti-Bacterial Agents↗

PubMed1998

[Study on the in vitro and in vivo thrombolytic efficacy of bispecific antifibrin-antiurokinase monoclonal antibodies].

OBJECTIVE: To evaluate the thrombolytic efficacy of bispecfic antifibrin-antiurokinase monoclonal antibodies. METHODS: Murine hybrid hybridomas secreting bispecific monoclonal antibodies (bsMcAbs) were prepared by fusing a mutant hybridomas secreting antifibrin McAbs with spleen cells of murine immunized with urokinase. The binding power of bsMcAbs with fibrin or urokinase was determined by ELISA method. The in vitro thrombolytic efficacy was measured by the dissolving rate of 131I-plasma clot. The in vivo thrombolytic efficacy was measured by using the rabbit jugular vein thrombus model. RESULTS: 8 strains of bsMcAbs have been obtained. ELISA experiments showed that bsMcAbs have very strong binding power with fibrin or urokinase. The bsMcAbs bound with urokinase increased the in vitro thrombolytic efficacy of urokinase by 15.5%. The in vivo thrombolytic efficacy of bsMcAbs bound with urokinase was 1.6-2.1 times as high as urokinase. CONCLUSIONS: Monoclonal antibody-directed thrombolytic agents have advantages of high specificity and strong local thrombolytic efficacy. It is well worth going on further study.

Animals↗

PubMed1998

[The study of normal occlusion's perioral muscle pressure].

OBJECTIVE: To measure the perioral muscle pressure, to realize the relationship between the morphology of dent, occlusion, skeleton and muscle pressure, moreover we established the measuring system and the mini-pressure transducers. METHODS: Thirty volunteers of normal occlusions aging 18.4-20.2 years old were selected. Mini-pressure transducer were bonded on the surface of the tooth. We measured the muscle pressure at rest and during swalling. The collection, handing, statistics of muscle pressure were finished automatically by the computer system. RESULTS: Normal occlusion's muscle pressure is related with sex; there isn't large variation in the intra-individual, but there is great variation in the inter-individual; there isn't a force balance between the buccal and lingual sides of the dentition in normal occlusion subjects. CONCLUSION: No matter which kind of occlusion, it has its own stable character of perioral muscle pressure. The buccal and lingual sides force are not equal, the perioral muscle pressure is related with the type of occlusion.

Adolescent↗

PubMed1998

[Microbial succession on lignite along with weathering].

Six different weathered lignite samples were examined by scanning electron microscopy. Few microorganisms were observed on lignit just excavated and only spores and short hyphae were observed on lignite samples excavated 5 months, 1 year and 4 years before sampling. When lignite samples were moistened with distilled water and incubated for 10 days, actinomycetes proliferated significantly on lignite samples that were just excavated or excavated 5 months before sampling. The growth of bacteria was observed on lignite samples excavated 1 year before sampling. Fungi increased in length and in number on lignite samples excavated 4 years before sampling. These findings of microbial succession on lignite samples along with weathering were consistent with results of the plate count method; actinomycetes are the first colonizers, then bacteria and fungi are the last degrader. The dominant microorganisms were Actinosynnema sp., Streptomyces sp. and Nocardia sp. among actinomycetes, two Arthrobacter sp. among bacteria and two Aspergillus sp. among fungi.

Actinomycetales↗