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Biomedical subjects

C F Zhang

Publications and source records attributed to C F Zhang.

At least 19 recordsLinked to original sources
PubMed1992

Conformational energetics and excited state level ordering in 11-cis retinal.

Semiempirical molecular orbital theory and semiclassical solvent effect theory are used to analyze the conformational and electronic properties of the 12-s-cis and 12-s-trans conformers of 11-cis retinal. The goal is to examine the influence of solvent environment on the equilibrium geometries of these conformers as well as to provide a perspective on the electronic transitions that contribute to the four band systems that are observed in the 200-500 nm region of the optical spectrum. We conclude that the 12-s-cis isomer is more stable in vacuum, but that the 12-s-trans conformer is preferentially stabilized in both polar and nonpolar solvent environment due to dispersive as well as electrostatic interactions. This observation is in substantial agreement with previous literature results. In contrast, our analysis of the excited state manifold indicates that the spectral features observed in the absorption spectrum are associated with a complex set of overlapping transitions. A total of 18 pi*<--pi transitions contribute to the four bands, and in some cases, conformation changes the relative contribution of the individual transitions that define the overall band shape. This study provides the first definitive assignments for all four band systems.

Molecular Conformation↗
PubMed1992

[Contrast sensitivity in the fellow eye of unilateral age-related macular degeneration].

The VCTS 6000 Contrast Sensitivity Test System was used in testing the fellow eyes of 20 cases of unilateral age-related macular degeneration (ARMD), with age-matched normal controls. Among the patients, 25% of the fellow eyes showed minor contrast sensitivity reduction at medium and high spatial frequencies. This test may be useful in the diagnosis of subclinical ARMD.

Age Factors↗
PubMed1992

A clinical study on diabetic retinopathy.

A clinical research on the diabetic retinopathy(DR) is reported. In the 662 cases of diabetes mellitus examined, the prevalence of DR was 51.3%, of which 7.6% were preproliferative and 7% proliferative. The study showed that when the disease progressed to the preproliferative and proliferative DR, laser photocoagulation could be the best treatment of choice, and panretinal photocoagulation was also quite effective in the treatment of pregnant patients with proliferative diabetic retinopathy.

Adult↗
PubMed1992

[Parafoveal retinal telangiectasis and changes of the capillary free zone in non-diabetic patients].

Microaneurysms, hard exudates, hemorrhages and/or edema in the macular region were observed in 10 eyes of 10 non-diabetic patients. By fluorescein angiography, parafoveal retinal telangiectasis was found in all cases. Deformation, enlargement and boundary disruption of the foveolar avascular zone were discernible in most cases, as were unevenness of capillary spacing, small areas of non-perfusion and leakage of dye in some cases. Analysis and calculations of the foveolar avascular zone were done with the Model-970 Quantmet computerized image analysis system. The data showed that the values of circumference, vertical diameter and roundness of the avascular zone differed significantly from those of the 10 normal control eyes.

Adult↗
PubMed1992

Anti-shock effect of cyproheptadine in rabbit.

Twenty four New Zealand rabbits were equally divided into a cyproheptadine (Cyp) treated group and a control group. Profound hemorrhagic shock was produced by exsanguination via carotid artery until mean arterial pressure (MAP) = 5.3 kPa (40 mm Hg) for a period of 90 min. After given Cyp 10 mg.kg-1, the MAP and central venous pressure (CVP) of the treated group rose obviously (P less than 0.01) and the mesenteric microcirculation improved markedly. After 1 h, all indices returned nearly to the preshock state. The survival rate 2 h after Cyp increased to 12 (P less than 0.01) in comparison with the control group (7). The results showed that Cyp, which dilates the vasculature and improves the microcirculation through blocking serotonin S2 and histamine H1 receptors, has a beneficial anti-shock effect.

Animals↗
PubMed1990

Mitochondrial gene mutation: the ageing process and degenerative diseases.

Polymerase chain reaction (PCR) amplification was carried out on total DNA from a range of autopsy tissues from deceased human subjects with no known mitochondrial disease, aged from birth (80 minutes) to 87 years. We report the finding of an age-related 5 kb deletion in the mitochondrial genomes of these subjects. The deletion occurs between nucleotide positions 8470 and 13459 of the mitochondrial genome, and is flanked by a 13 bp direct repeat. All tissues from adult subjects showed the presence of mitochondrial DNA molecules with the deletion after a 30 cycle PCR amplification; by contrast the deletion was not similarly detected in any of the infant tissues analysed. However, the occurrence of the deletion was detected in the infant tissues after 60 PCR cycles of MtDNA amplification. It is concluded that such deletions are not necessarily associated with particular mitochondrial diseases but occur naturally, and with increasing frequency with age. A consequence of the accumulation of this deletion could be a progressive decrease with age of bioenergetic capacity which in turn could influence the rate of ageing and predispose to age-associated degenerative diseases.

Adenosine Triphosphatases↗
PubMed1990

Choroidal osteoma. Clinical characteristics and long-term follow-up of five cases.

We studied the clinical characteristics and long-term follow-up of 5 patients with choroidal osteoma. All the patients but one were female. The choroidal lesions were unilateral in 3 patients and bilateral in 2. During the follow-up, the lesions enlarged somewhat, but the progression was very slow and inconspicuous. Clinical diagnosis and treatment are briefly discussed.

Adult↗
PubMed1989

[Clinical study on preproliferative and proliferative diabetic retinopathy].

A long-term follow-up study was carried out on 159 cases (245 eyes) of pre-proliferative and proliferative diabetic retinopathy. In 75 percent of the series, diabetic retinopathy progressed and visual acuity markedly decreased. Argon Iaser panretinal photocoagulation was performed and followed-up in 80 of the cases (138 eyes). 50.72% of these obtained good results, visual acuity improved by more than 2 lines. Only 10.14% of the treated series showed progression of the disorder. There were 10 cases of diabetic mellitus associated with pregnancy. Argon laser panretinal photocoagulation just prior to and after delivery was effective against preproliferative and proliferative diabetic retinopathy. The prognosis of pregnant patients was greatly enhanced.

Adult↗
PubMed1989

[Electrophysiological changes of the retina after hypothermic vitreous surgery].

Local ocular hypothermia has been introduced as a possible alternative to performing intraocular surgery at the room temperature. The authors evaluated experimentally the effect of prolonged local hypothermia on the ERG. 22 rabbits underwent pars plana vitrectomy followed by continuous irrigation of the vitreous cavity for 1 hour. In the right eye, the temperature of the irrigating solution was 7 degrees C which lowered the intravitreal temperature to 15 degrees C; in the left eye, the solution was at room temperature and the intravitreal temperature was 24 degrees C. Flash ERG was performed pre-operatively and one week postoperatively on all eyes. There was no statistically significant difference in the post-operative ERG changes between the right and left eyes. The authors concluded that no harmful ERG changes were detected as near as 1 week following exposure to hypothermia for 1 hour.

Analysis of Variance↗
PubMed1989

[Laser treatment for pre-proliferative and proliferative diabetic retinopathy].

105 cases of pre-proliferative and proliferative diabetic retinopathy were treated with argon laser panretinal photocoagulation mainly on the mid-periphery and posteriorly 1.5-2 DD from the optic disc. The posterior fundus, i.e. the area temporal to the optic disc between the superior and inferior temporal vascular arches and 1-2 DD temporal to the macula, was spared. The treatment was completed in 3-4 sessions of 300-800 shots each. Among 80 cases (138 eyes) followed up for over 1 year, 50.7% obtained good results, with visual acuity improved by 2 lines on Snellen's chart, resorption of retinal exudates and hemorrhages, and regression of microaneurysms and neovascularization; 39.7% showed middling effects, with visual acuity up or down by 1 line and the lesions of diabetic retinopathy still visible; and 10.1% deteriorated, with visual acuity drops of over 2 lines and fundus lesions worsened or obscured by vitreous bleeding. The causes of failure were discussed.

Adult↗
PubMed1989

[The discovery and study on invasive strain of Escherichia coli O121].

A strain of Enteroinvasive Escherichia coli was isolated from the stool with blood and mucus of a child suffering from acute diarrhea. The strain shows the following characteristics: rapid fermentation of glucose (with gas), no fermentation of lactose, beta-galactosidase reaction positive, growth in acetate media, lysine decarboxylase negative, non-motility causing keratoconjunctivitis in guinea pigs and invading into epithelial cells, with a plasmid of 140 Md, Serotype is O121:H- which is a new serotype of Enteroinvasive Escherichia coli.

Child↗
PubMed1989

[Postabortion complications and recovery of ovarian function in nulliparous women].

Induced abortions performed in 481 cases of nulliparous women were carefully investigated. The incidence of complications during operation was 2.1%, of which the majority was the induced abortion syndrome. The early postabortal complication rate was 6.4% and the majority was mild pelvic inflammatory disease. The late complication rate was 10.2% and manifested mainly by menstrual disturbance. Ovulation occurred in 67.4% of the first postabortal cycles. It is suggested that the induced abortion is not a safe procedure for nulliparous women.

Abortion, Induced↗
PubMed1987

Purification of a lectin from the hemolymph of Chinese oak silk moth (Antheraea pernyi) pupae.

A lectin with affinity to galactose was purified to homogeneity from the hemolymph of diapausing pupae of the Chinese oak silk moth, Anteraea pernyi. The molecular mass of this lectin was 380,000 and it formed an oligomeric structure of a subunit with a molecular mass of 38,000. The hemagglutinating activity in the hemolymph was found to increase with time after immunization with E. coli. Studies with antibody against the purified lectin showed that increase in the hemagglutinating activity was due to the same lectin, suggesting that the amount of the lectin increased in response to intrusion of foreign substances. The function of this lectin in the defence mechanism is discussed.

Animals↗