Biomedical subjects

X M Gong

Publications and source records attributed to X M Gong.

14 recordsLinked to original sources

PubMed2000

Role of metal ions in coupling between chemical catalysis and conformational changes in ATP synthase.

Isolated chloroplast ATP synthase (CF0F1) was used for determination of the structure-function relation by measuring the effect of divalent metal ions on the properties of ATPase. Mg2+ ions were more efficient catalysts than Ca2+ ions as indicated by Kcat/Km of 55.2 and 5.4, respectively. Other activity parameters related to binding, such as the Km of MATP and Ki of MADP, indicated a stronger binding in the presence of Mg2+ as seen from a Mg2+/Ca2+ ratio of 2.8 and 3.8, respectively. Strong binding of Ca2+ ions with a Kd of 0.03 +/- 00.6 microM-1 was detected only in the presence of ADP probably because of the positive interactive effect of CaADP as indicated in the inhibition properties. Mg2+ ions were more efficient catalysts also in other forms of the enzyme such as in the thylakoid membrane, in isolated CF0F1 and in CF1. The Mg2+/Ca2+ ratio of Kcat/Km was 5.3, 10.2 and 1.5 for the thylakoid membrane enzyme, the isolated CF0F1 and the soluble CF1 respectively. This indicated that Ca2+ ions became less efficient catalysts in the more intact and integrated enzyme while Mg2+ ions were as efficient in all forms of the enzyme. Unlike Mg2+, Ca2+ ions also did not support proton-coupled ATP synthesis and ATP driven proton pumping. It is suggested that the differences in the ligand structure of these two ions might be the reason for the differential function. An average 0.3 A shorter bond length of octahedral first coordination in Ca2+ ions caused a weaker binding of CaATP than that of MgATP. The effect of differential binding is discussed in relation to the binding of the transition state intermediate and to the rate of product release.

Catalysis↗

PubMed1994

[Effects of contact lens wear on the corneal endothelium and sensitivity].

The corneal endothelium of 38 contact lens wearers (74 eyes) and 74 normal eyes for control was photographed and analyzed with specular microscopy and the graphic processing system. The central corneal sensitivity and thickness were also measured. The results showed that the frequency rate of hexagonal cells that reflected the changes in endothelial cell morphology and size, the coefficient of variation of cell area, and the ratio of largest to smallest cell areas differed significantly from those of the control eyes comparable in age and sex distribution. The central corneal sensitivity declined while the corneal thickness was not affected. The causes and clinical significance of endothelial changes were discussed.

Adult↗

PubMed1994

[Penetrating keratoplasty in the treatment of corneal perforation].

166 patients of corneal perforation from HSK, suppurative corneal ulcer and chemical or thermal burn were treated by penetrating keratoplasty. In the group of HSK, 69.8% of the grafts remained transparent and vision was restored to 0.05-1.0 in 81 cases (69.8); in the group of suppurative corneal ulcer, 40% of the grafts were transparent and vision was restored to 0.05 or better in 15 cases (37.5%); while in the group of burns, the grafts were clear only in 20% and vision was 0.05-0.6 in 3 cases (30%). The complications and causes for failure were similar to those in patients without perforation. These results indicate that timely penetrating keratoplasty is recommendable for the treatment of corneal perforations of various etiology.

Adolescent↗

PubMed1992

[Recovery of corneal sensitivity following keratoplasty and corneal diseases].

Corneal sensitivity (CS) was tested in 201 eyes with clear plastic grafts and in 193 eyes with corneal diseases, using the Cochet-Bonnet Aesthesiometer. After keratoplasty, the CS returned to normal in 40.0% and 50.0% of the eyes with non-HSK in 5-6 years and 7-22 years respectively, while only 17.2% of the eyes with HSK showed normal CS in 7-22 years postoperative. The corneas of HSK patients were markedly hypoesthetic all over, whereas in non-HSK patients, the corneal hypoesthesia involved only the morbid area. The examination of CS is useful in the diagnosis of corneal diseases and evaluation of nerve regeneration after keratoplasty.

Adolescent↗

PubMed1991

Systematic morphogenesis of the viral haemorrhagic disease virus in infected rabbits and in adapted cell culture.

The morphogenesis of viral haemorrhagic disease virus (VHDV) of rabbits in infected cell cultures and in tissues and cells from infected animals has been observed systematically by electron microscopy. Viral particles have been found to assemble through a condensation process within the nucleus of infected cells, having passed partially into the cytoplasm through disrupted nuclear membranes, enlarged nuclear pores or perinuclear space. Late in infection, both mature and immature virions are observed in the cytoplasm; these are often aggregated or interspersed and remain cell-associated long after infection. Release of the virus occurs when the cell finally lyses. In studies of the localisation and development of VHDV antigens, the viral antigens have been observed to appear first in the nucleus of infected cells and often thereafter in the cytoplasm. This finding is very similar to observations made by electron microscopy.

Animals↗

PubMed1989

Study in cytotoxicity of gentamycin to corneal epithelium and endothelium in tissue culture.

A study in cytotoxicity of gentamycin to tissue-cultured bovine corneal endothelial cells and rabbit corneal epithelial cells is reported. When the cultured cells reached confluence, they were exposed to tissue culture media containing gentamycin for 6 hours. We found that 0.5% gentamycin caused significant damage to corneal epithelial cells--diffuse plasmolysis, with scattered cell necrosis and 5% loss. While corneal endothelial cells were exposed to 1.6 mg/ml gentamycin, extensive cell loss (approximately 15%) was observed. The damaged cells recovered their normal morphology after 24 hours. When the concentration of gentamycin increased twice, serious damage to cells occurred. The area of cell loss reached 40%, and the recovery of cellular morphology was much slower. This study demonstrates that gentamycin potential cytotoxicity to corneal epithelium and endothelium, suggesting that gentamycin should be rationally used in the treatment of ocular diseases.

Animals↗

PubMed1989

[Infections in the early postoperative period following keratoplasty--a report of seven cases].

Keratoplasty was performed on 3482 eyes from 1965 to 1986 in our hospital. Five eyes (0.14%) were infected in the early postoperative period. Two eyes had endophthalmitis. These seven eyes were operated on again and with local and systemic antibiotics treated as well. Followed up for 36 days to 7 years, six eyes remained safe (5 eyes transparent and 1 eye semi-transparent.) The visual acuity reached 0.3 in two eyes, 0.2 in one eye and finger counting to 0.1 in three eyes. The seventh eye was enucleated because of serious infection. Several factors of infection in the early postoperative period following keratoplasty, causative organisms, the relations between the types of operation in the early postoperative period following keratoplasty were also discussed.

Adolescent↗

PubMed1988