Biomedical subjects

X Gong

Publications and source records attributed to X Gong.

At least 91 records · Page 5Linked to original sources

PubMed1997

[Penetrating keratoplasty combined with pupilloplasty].

OBJECTIVE: To investigate the effect of penetrating keratoplasty combined with pupilloplasty. METHOD: The penetrating keratoplasty combined with pupilloplasty was performed on 48 eyes. They had been followed-up for 6-89 months postoperatively. RESULTS: The rate of clarity was 79.2%, and the visual acuity of 0.1 or better was restored in 64.6% after an average follow-up of 19.4 months. The pupil was repaired to approximately normal in 89.6%, and the incidence of postoperative complications, anterior synechia and glaucoma, was lowered. CONCLUSION: The results show that the combined operation can reduce the postoperative complications, improve the prognosis of grafts and vision, and is valuable for the patients with corneal opacity and gappy iris.

Adolescent↗

PubMed1997

[Unambiguous turbulence measurement method and system using transverse Doppler techniques].

This paper introduces the principle of Doppler ambiguity process and the ambiguity reduction techniques using dual-sample volume. An unambiguous fluid turbulence measurement method using transverse Doppler and dual-sample volume cross-correlation techniques is described. An experimental turbulence detection system is designed. Theoretical and experimental results show that this method can eliminate the Doppler ambiguity spectra produced by transit-time effect, turbulence and velocity gradient in sample volume.

Equipment Design↗

PubMed1997

[Culture of human corneal epithelial cells].

PURPOSE: To select culture technique of human epithelial cells for grafts. METHODS: Epithelial cells of limbus were collected by improved enzymatic disaggregation or explant technique growth curves and to calculate doubling time. DNA synthesis of cells were measured with 3H-thymidine incorporation and liquid scintillation techniques. RESULTS: Doubling time of cells which were collected by enzymatic disaggregation and by explant technique were 54.15 +/- 4.28 h and 67.88 +/- 1.96 h (P < 0.01). Cellular DNA synthesis of the former was more active (P < 0.01). CONCLUSIONS: Epithelial cells which were collected by improved enzymatic disaggregation from limbus include stem cells of corneal epithelium. These cells show more active cellulde proliferation and are fitter for use as grafts.

Cell Culture Techniques↗

PubMed1997

[The combined procedure of limbal transplantation (LT) and penetrating keratoplasty (PK) for severe ocular obsolete chemical or thermal burns].

PURPOSE: To improve the prognosis of grafts for obsolete ocular chemical or thermal burns. METHODS: LT + PK or PK were performed in 28 eyes with severe chemical or thermal burns. The effects of the two groups were compared. RESULTS: In LT + PK group(12 eyes), during 5 to 28 months of follow-up, the results showed improved visual acuity in 9 eyes (75%), maintained stable epithelial adhesion without recurrent erosion or persistent epithelial defect in 11 eyes (91.67%), graft transparent in 9 eyes (75%). Nine eyes (75%) showed prevented neovascularization and conjunctival tissue from growing into graft. Allograft rejection were identified in 4 eyes (33.33%). In routine PK group (16 eyes), during 3 to 22 months of follow-up, the results showed improved visual acuity in 4 eyes (25%), maintained stable epithelial adhesion without recurrent erosion or PCED in 8 eyes (50%), graft transparent in 4 eyes (25%). Four eyes (25%) showed prevented neovascularization and conjunctival tissue from growing into cornea. CONCLUSIONS: Combined procedure of LT and PK is an effective treatment for severe ocular chemical or thermal burns. It can reduce persistent corneal epithelial defect and prevent neovascularization and conjunctival epithelial from growing into cornea thus maintaining graft transparent and improving visual acuity.

Adolescent↗

PubMed1997

[Simultaneous determination of carotenoids and chlorophylls in algae by high performance liquid chromatography].

An isocratic reversed-phase HPLC method for the simultaneous determination of carotenoids and chlorophylls in algae is presented. Both carotenoids and chlorophylls were separated by using a C18 column and a mobile phase consisting of dichloromethane/acetonitrile/methanol/water (22.5:9.5:67.5:0.5). The flow rate was 1.0mL/min. These pigments were detected by a UV-VIS absorbance detector set at 450nm. The average recoveries of these pigments by standard addition method were 99.1% for lutein, 98.5% for alpha-carotene, 99.4% for beta-carotene, 100.6% for chlorophyll a and 99.9% for chlorophyll b. The relative standard deviations of these pigments were 2.4% for lutein, 5.6% for alpha-carotene, 6.0% for beta-carotene, 4.1% for chlorophyll a and 4.0% for chlorophyll b. The calibration curves for these pigments gave good linearity over a wide range of 0-50mg/L (r = 0.9992-0.9999). The retention times were 3.0 min for lutein, 4.7 min for chlorophyll b, 6.3 min for chlorophyll a, 14.1 min for alpha-carotene, and 14.7 min for beta-carotene. Using this method, carotenoids and chlorophylls were determined in Spirulina platensis, Chlorella vulgaris and Haematococcus lacustris. Chlorella vulgaris and Haematococcus lacustris samples were ground in a B. Braun homogenizer. Spirulina platensis sample was smashed by supersonic wave. Acetone was used as extractant.

Carotenoids↗

PubMed1997

[Causes and influential factors of spectral broadening in Doppler flow signal].

Signals received are the resultant of the blood flow phasors in CW Doppler system and there are spectral broadening phenomena in it, in other words, frequency of signals corresponding to a moving RBC is not single. A model is presented that enables the detailed effects of spectral broadening to be calculated for a CW Doppler system by using geometric boundary argument. Results are given for the circular geometry.

Blood Flow Velocity↗

PubMed1997

[Effects of a high-pass filter on the Doppler blood flow signal].

A high-pass filter is used to remove the large signals scattered or reflected from stationary and slow moving objects in many clinical CW Doppler units. theoretical results are presented that such a filter will lead to overestimate of the mean velocity of Doppler blood flow. As for different frequency signals, high-pass filter have different amplitudes and phase responses, consequently, nonlinear phase shift is produced. It is proved by computer experiment that nonlinear phase shift caused by high-pass filter hardly has any effects on Doppler flow power spectrum if the high-pass filter does not affect the amplitudes of signals.

Blood Flow Velocity↗

PubMed1996

Effects of calorie restriction and aging on the expression of antioxidant enzymes and ubiquitin in the liver of Emory mice.

We studied the effect of age and calorie restriction on the expression of genes involved in antioxidant defenses in livers of young (4.5-6 months) and old (22 months) Emory mice fed a control (C) or restricted (R) diet. Specifically examined were catalase (CAT), glutathione peroxidase (Gpx), Cu/Zn and Mn superoxide dismutase (Cu/ZnSOD and MnSOD). As an indicator of oxidative damage to the tissues we measured lipid peroxidation. As indicators of oxidative stress we determined ubiquitin mRNA levels and endogenous high molecular weight (HMW) ubiquitin conjugates. Lower mRNA levels of ubiquitin (P < 0.05), CAT (P < 0.01) and Gpx (P < 0.01) were observed in tissues from young R versus C animals. The old C group had a lower CAT mRNA level (P < 0.0001) compared with young C. In the R group, age did not affect the CAT mRNA levels or Gpx mRNA levels; however, ubiquitin mRNA levels were higher (P < 0.05). No significant changes in Cu/Zn or MnSOD mRNA were observed with age or diet. Cu/ZnSOD protein levels were lower in the young R at 4.5 months (P < 0.05) than young C, and higher in the old R group versus old C (P < 0.05). CAT protein levels were higher in the old C versus old R (P < 0.05). Changes of HMW ubiquitin conjugates with age r diet were not significant. Of the four groups, the old R group showed the highest levels of lipid peroxidation.

Aging↗

PubMed1996

Probing the basis of antibody reactivity with a panel of constrained peptide libraries displayed by filamentous phage.

The structural requirements for peptide binding to an antibody may be elucidated by probing it with a variety of peptides having different constraints. To this end, we have constructed and screened a panel of peptide libraries displayed by filamentous bacteriophage. The peptides in most of the libraries have the potential for constraint by fixed Cys residues, which have been placed at different sites within a randomized amino acid sequence of varying length. When taken together, the binding data obtained from screening the panel with a given antibody allow one to determine the types of constraints that promote binding, as well as the residues that are critical for binding. We describe the construction of 11, pVIII-displayed, peptide libraries, whose sizes range from 150 million to 10 billion clones. The libraries were screened with a number of polyclonal and monoclonal antibodies against peptides, proteins and carbohydrates. Cross-reactivity with peptides was always found for antibodies produced against peptides, linear epitopes on folded proteins and, surprisingly, carbohydrates, whereas antibodies against discontinuous epitopes on proteins were found less frequently. The implications of these results are discussed in terms of the structural basis for cross-reactivity with peptides.

Amino Acid Sequence↗

PubMed1996

A library of organic landscapes on filamentous phage.

A billion-clone library of filamentous phage with different surface structures ("landscapes') was generated by fusing random octapeptides to the N-terminus of all 4000 copies of the major coat protein. Such a "landscape library' might include clones exhibiting emergent properties that inhere in the entire surface architecture, not in the peptides by themselves. Because the diverse surface landscapes are displayed on viable phage, they can be surveyed for exceedingly rare functions using microbiological selection methods. Clones with several emergent properties of the sort envisioned were successfully selected, suggesting that landscape libraries have promise as a novel source of nanomaterials with exploitable surface properties.

Amino Acid Sequence↗

PubMed1996

Acoustic nonlinearity parameter tomography for biological specimens via measurements of the second harmonics.

The acoustic nonlinearity parameter B/A is a new parameter in ultrasound tissue characterization. In this paper, on the basis of a theoretical analysis of finite amplitude ultrasonic wave propagation in fluidlike media, an experimental system for nonlinearity parameter tomography is developed. Using this system, the amplitude of the second harmonic wave cumulated in the propagation path of the primary wave is measured and the finite amplitude insert-substitution method is used in the conventional computer tomography (CT) technique. The filtered convolution algorithm is implemented using the amplitude of the second harmonic as the projection data, then the B/A tomography can be reconstructed. The B/A images for several biological samples are obtained. Besides, the image of porcine pathological liver tissue is studied and is compared with that of porcine normal liver tissue. These results show the potential applications of the nonlinearity parameter B/A in medical diagnosis.

Animals↗

PubMed1996

[Effect of combining EGF with KGF on proliferation of human corneal epithelial cells].

OBJECTIVE: To select effective drugs for enhancing corneal epithelial wound healing and treating persistent corneal epithelial defect. METHODS: Epidermal growth factor (EGF) and keratinocyte growth factor (KGF) were added to cultures of human corneal epithelial cells and DNA synthesis in corneal epithelial cells were measured with [3H]-thymidine incorporation and liquid scintillation techniques. The cells were counted in a hemocytometer to determine the doubling time. RESULTS: 10 ng/ml EGF, 10 ng/ml KGF enhanced cellular proliferation effectively (P < 0.01). EGF in combination with KGF, the enhancement was more effective (P < 0.05) and reduced the doubling time. CONCLUSIONS: Our results suggest that exogenous EGF with KGF can stimulate proliferation of human corneal epithelial cells and it may be of potential use clinically for treatment of persistent corneal epithelial

Cell Division↗

PubMed1995

Activation of a G protein complex by aggregation of beta-1,4-galactosyltransferase on the surface of sperm.

Fertilization is initiated by the species-specific binding of sperm to the extracellular coat of the egg. One sperm receptor for the mouse egg is beta-1,4-galactosyltransferase (GalTase), which binds O-linked oligosaccharides on the egg coat glycoprotein ZP3. ZP3 binding induces acrosomal exocytosis through the activation of a pertussis toxin-sensitive heterotrimeric guanine nucleotide-binding protein (G protein). The cytoplasmic domain of sperm surface GalTase bound to and activated a heterotrimeric G protein complex that contained the Gi alpha subunit. Aggregation of GalTase by multivalent ligands elicited G protein activation. Sperm from transgenic mice that overexpressed GalTase had higher rates of G protein activation than did wild-type sperm, which rendered transgenic sperm hypersensitive to their ZP3 ligand. Thus, the cytoplasmic domain of cell surface GalTase appears to enable it to function as a signal-transducing receptor for extracellular oligosaccharide ligands.

Acrosome↗

PubMed1995

Site-directed photo-cross-linking of rRNA transcription initiation complexes.

Site-specific photo-cross-linking of the rRNA committed transcription complex was carried out by using 5-[N-(p-azidobenzoyl)-3-aminoallyl]-dUMP-derivatized promoter DNA. Putative TAFIs of 145, 99, 96, and 91 kDa, as well as TATA-binding protein (TBP), were found to specifically photo-cross-link to different positions along the promoter. These had been identified as potential subunits of the fundamental transcription initiation factor TIF-IB (also known as SL1, factor D, and TFID) from Acanthamoeba castellanii by purification to apparent homogeneity. No other polypeptides attributable to the rRNA architectural transcription factor UBF were identified, suggesting that this protein is not part of the committed complex. Scanning transmission electron microscopy of the complexes was used to estimate the mass of the complex and the contour length of the DNA in the complex. This showed that a single molecule of TIF-IB is in each committed complex and that the DNA is not looped around the protein, as would be expected if UBF were in the complex. A circular permutation analysis of DNA bending resulting from TIF-IB binding revealed a 45 +/- 3.1 degrees (n = 14) bend centered 23 bp upstream of the transcription initiation site. This degree of bending and the position of the bend relative to the site of TBP photo-cross-linking are consistent with earlier data showing that the TBP TATA box-binding domain is not utilized in the assembly of the rRNA committed complex (C. A. Radebaugh, J. L. Mathews, G. K. Geiss, F. Liu, J. Wong, E. Bateman, S. Camier, A. Sentenac, and M. R. Paule, Mol. Cell. Biol. 14:597-605, 1994).

Acanthamoeba↗

PubMed1995

[Effect of glucocorticoid receptor blockade on pulmonary and renal vascular permeability in scalded rats].

With glucocorticoid receptor (GR) blockade by RU38486, a competitive antagonist of GR, the change in contents of FITC labeled albumin (FITC-albumin) in pulmonary and renal tissue in scalded rats have been measured to study the changes in vascular permeability. The result showed that the contents of FITC-albumin in pulmonary and renal tissue in the scalded rats were markedly higher than those of the controls (lung: P < 0.05, kidney: P < 0.001). When the scalded rats were given GR blockade, the contents of FITC-albumin in pulmonary and renal tissue were significantly higher than those of rats with scald only (P < 0.05). The results indicated: (1) the pulmonary and renal vascular permeability in scalded rats was markedly enhanced; (2) GR blockade might aggravate the increase in vascular permeability caused by scald, so that the protective effect of glucocorticoid (GC) on vascular permeability seemed to be reversed.

Animals↗

PubMed1995

[Effects of glucocorticoid on PMN adhesion induced by TNF].

TNF was used as a stimulating factor to study the effects of glucocorticoid (GC) on polymorphonuclear leucocyte (PMN) adhesion. The results showed that tumor necrosis factor (TNF) could increase the PMN adhesion markedly, and Dex could not inhibit the PMN adhesion induced by TNF, but it had a certain effect of prevention. PMN adhesion was increased prominently when Dex and RU 38486 were given after TNF pretreatment.

Animals↗

PubMed1995

[The effects of glucocorticoid on rabbit polymorphonuclears during inflammation].

The CD18 expression on rabbit polymorphonuclears (PMNs) and adhesion rate of rabbit PMNs to ICAM-1 coated magnetic beads were determined, and the correlationship was analysed between CD18 expression and adhesion rate. The results showed that glucocorticoid inhibited the rise of CD18 expression on rabbit PMNs caused by tumor necrosis factor (TNF) and that the inhibitory effect reversed when glucocorticoid receptor (GR) was blocked by RU 38486. There was a positive correlationship (r = 0.966) after PMNs were cultured with a range concentration of dexamethasone (Dex). The data indicate that GC inhibits the rise of CD18 expression on rabbit PMNs caused by TNF which is mediated by GR, and plays an important role in inhibition of PMNs adhesion.

Animals↗

PubMed1995

[Cardial myxoma: analysis of cardiopulmonary bypass perfusion in 95 cases].

From 1980 to 1993, 95 patients with cardial myxoma (male 32 and female 63) were treated surgically. The myxoma located on left-atrium in 88 patients, right-atrium in 5, left-ventricle in 1, and pulmonary in 1. All the operations were carried out under cardiopulmonary bypass. After operations, 12 patients had dyspnea and 8 died of pulmonary infection and heart or respiratory failure. The hemoglobin level was 118.02 +/- 16.7 g/L, 72.33 +/- 8.82 g/L, and 105.75 +/- 5.91 g/L respectively for pre-dilution, post-dilution, and post-operation. The patients with cardial myxoma often complicated with anemia (56), hepatic enlargement (36), and history of heart failure (64), and embolism (12). Combined with clinical characteristics mentioned above, the preparation of prime solution and the management of perfusion were discussed.

Adolescent↗