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Biomedical subjects

H Cheng

Publications and source records attributed to H Cheng.

At least 505 records · Page 28Linked to original sources
PubMed1981

Intraocular melanoma, diabetes, and Turner's syndrome: presentation with proptosis.

A patient with Turner's syndrome and untreated diabetes mellitus presented with a blind, painful, glaucomatous eye and progressive unilateral proptosis. Although a computerised tomographic scan failed to show evidence of a retroocular extension of the presumed choroidal melanoma, the clinical features were so suggestive of extraocular extension that an orbital exenteration was considered. Examination of the enucleated eye for histological conformation of the presence of malignant melanoma showed no extraocular extension, and histology of the retroocular connective tissue revealed only haemorrhage and fibroblastic activity. There are 3 other reported cases of malignant melanoma presenting as proptosis without extraocular extension, so that extreme caution is required when exenteration is deemed necessary on clinical grounds but where computerised scanning fails to reveal direct tumour spread.

Adult↗
PubMed1981

Contact and noncontact specular microscopy.

A contact specular microscope was compared with a noncontact endothelial camera on 20 eyes of 10 consecutive patients presenting for cataract surgery. No difference was found in the percentage of photographs acceptable for cell counting or the time for photography by one or other camera. A close correlation was found in cell density estimations by the 2 methods. Most patients prefer the noncontact mode of examination.

Adult↗
PubMed1981

A band of alkaline phosphatase activity in the crypts of mouse duodenal epithelium.

Isolated mouse duodenal epithelium, in the form of structurally intact crypt-villus units, was used to study the distribution of alkaline phosphatase with histochemistry. The tissue was incubated on ice in the medium of Hugon and Borgers (J Histochem Cytochem 14:629, 1966), with constant stirring to ensure uniform reaction. Continuous activity was observed frm the crypt mouth to the villus tip. A single band of alkaline phosphatase activity, 2-03 cell in height, was observed in the mid-crypt region in about 80% of crypts studied. Control studies (no substrate control, no lead control, pH control, inhibitor control, inactivated enzyme control, no enzyme control, and stimulator indeed due to alkaline phosphatase. The narrow band of activity in the crypt was also observed in vibratome sections of nonfrozen tissue. When isolated epithelium was subjected to a freeze-thaw cycle and then incubated in Hugon's medium, reaction product was observed continuously from the mid-crypt region to the villus tip. This pattern was similar to that observed with frozen sections. We conclude that alkaline phosphatase is present in an active form in epithelial cells in the region of the band. In epithelial cells above the band, e.e., in the upper crypt, alkaline phosphatase is present in an inactive form which may be activated by a freeze-thaw cycle.

Alkaline Phosphatase↗
PubMed1981

Longitudinal study of intraocular lens implants after intracapsular cataract extraction. Complete follow-up of the first 7 years.

Lens implant surgery has a significant complication rate, although most complications are treatable and occur within the first 2 months after operation. The short-term visual results are comparable with the published results of intracapsular extraction alone. Six cases of bullous keratopathy developed in 138 cases in 7 1/2 years. When endothelial cell density fell below 500/mm2, corneal oedema developed within the year. However, a more recent study showed that endothelial cell loss was much reduced by the closed chamber technique of insertion and by serum coating of the implant.

Aged↗
PubMed1980

Erythrocyte glyceraldehyde-reductase levels in diabetics with retinopathy and cataract.

The activity levels of glyceraldehyde reductase, an aldose-reductase-like enzyme present in the erythrocyte, were determined in 104 subjects, who were divided into five groups--diabetics with retinopathy and cataract, diabetics with retinopathy and no cataract, diabetics with no retinopathy and no cataract, non-diabetics with senile cataract, and non-diabetic normal controls. Diabetics with retinopathy and cataract had significantly higher mean enzyme activity levels than normal control subjects (2.5 fold increase, p < 0.001); so had diabetics with retinopathy but no cataract (2 fold, p < 0.01) and patients with senile cataract (1.5 fold, p < 0.05). Juvenile diabetics had a significantly higher enzyme level than maturity onset diabetics. There was no significant difference in glyceraldehyde reductase between normal controls and diabetics without retinopathy or cataract, and no significant difference in polyol-dehydrogenase activity levels between any group studied. Enzyme activity did not correlate with age or glycosylated haemoglobin (HbA1c) levels. The increase in levels of erythrocyte glyceraldehyde reductase were due to increased amounts of active enzyme, rather than to elaboration of new kinetic pathways.

Aged↗
PubMed1978

Photocoagulation in diabetic retinopathy: II. Methodology.

There is now evidence from clinical trials that patients with diabetic retinopathy have their visual lives prolonged by photocoagulation. However, the exact indications for treatment have not yet been established and are undergoing continuous reevaluation. For many years, the presence of fibrous tissue either on the optic disc or the retina was considered to be a contraindication to treatment. However, recently treatment has been possible using gentle photocoagulation. It is hoped that over the next few years the exact indications for treatment will be established. It may be found in the future that the treatment of patients with maculopathy by panretinal photocoagulation and focal treatment and similarly patients with a few peripheral new vessels, by panretinal photocoagulation may prevent further progression and remove the necessity for treatment. It is important to limit as much as possible the number of visits to the opththalmologist that the patient must make. It is therefore important to establish a technique that requires as few treatment sessions as possible. Ultimately, follow up should be done by the well trained physician. The difficulty with the development of this type of technique is that diabetic retinopathy is a progressive disease and therefore new abnormal areas may well develop in patients who have had seemingly adequate treatment. Also, relatively mild background retinopathy or maculopathy may progress ultimately to proliferative retinopathy. However, with improvements in technique and establishment of safe treatment regimens, the goal of single treatment may be achieved.

Diabetic Retinopathy↗
PubMed1978

Photocoagulation in diabetic retinopathy: III. Complications.

We have reviewed the unwanted effects that follow the treatment of diabetic retinopathy with photocoagulation. Complications are uncommon, and those side effects that occur regularly are acceptable in relation to the benefits to be gained from treatment.

Diabetic Retinopathy↗
PubMed1977

Endothelial cell loss and corneal thickness after intracapsular extraction and iris clip lens implantation: a randomised controlled trial (interim report).

Patients in a randomised controlled trial were chosen either to have iris clip lens implantation after intracapsular cataract extraction or intracapsular extraction only. They were assessed in terms of corneal thickness, postoperative epithelial oedema, and endothelial cell counts. All patients had 1 eye submitted to operation, which was carried out by the same surgeon. There was significantly greater increase in corneal thickness (P less than 0.05) on the 5th postoperative day in eyes which had lens implants (23 patients with intracapsular extraction and 19 with implant), but the difference between the 2 groups became insignificant at 1 month (17 patients in each group). Daily corneal thickness measurements and observations of epithelial oedema in a subgroup (20 patients divided equally into 2 groups) showed that postoperatively there was greater and more widespread corneal oedema after implant surgery. When the operated eye was compared with the unoperated eye, endothelial cell loss was significantly greater in those with implants (P less than 0.01) than in those with simple intracapsular extraction.

Aged↗
PubMed1977

Corneal oedema and endothelial cell loss after iris-clip lens implantation.

Lens implantation as a form of replacement surgery has some clear advantages over other forms of aphakic correction. The most feared complication of this type of operation is bullous keratopathy. A short-term study was carried out in two comparable groups of patients to assess corneal oedema and endothelial cell loss after simple cataract extraction and after iris-clip lens implantation following intracapsular extraction as a primary procedure. All patients were randomly chosen to have one or other procedure. The results indicate that lens implantation causes greater postoperative corneal oedema and greater endothelial cell loss. It is therefore important for implant surgeons to bear in mind the possible harm they may be inflicting and the need both for stringent criteria of selection and for the adoption of techniques which will minimize endothelial trauma.

Cell Count↗
PubMed1977

Corneal edema: iris-clip lens implantation and simple intracapsular extraction compared.

Corneal edema following intracapsular lens extraction and iris-clip lens implantation was compared by assessing corneal thickness and epithelial edema. In a retrospective study the corneal thickness of twenty patients who had intracapsular lens extraction in one eye only was compared with twenty-six patients with iris-clip lens implants in one eye. There was no significant increase in corneal thickness in the operated eye in either group. In a prospective randomized controlled study, a smaller number of patients, had serial measurements of corneal thickness pre- and postoperatively. There was an increase in thickness in the immediate postoperative period for both groups. However, there was no significant difference between eyes which had simple extraction and those which had implants. The implanted eyes however had greater mean increase endothelial trauma in the initial period, compared to eyes with cataract extraction alone.

Aged↗
PubMed1976

Presence of adenylate cyclase activity in Golgi and other fractions from rat liver. I. Biochemical determination.

The distribution of adenylate cyclase (AC) in Golgi and other cell fractions from rat liver was studied using the Golgi isolation procedure of Ehrenreich et al. In liver homogenate the AC activity was found to decay with time, but addition of 1 mM EGTA reduced the rate of enzyme loss. The incorporation of 1 mM EGTA into the sucrose medium used in the initial two centrifugal steps of the Golgi isolation method stabilized the enzyme activity throughout the entire procedure and resulted in good enzyme recovery. In such preparations, AC activity was demonstrated to be associated not only with plasma membranes but also with Golgi membranes and smooth microsomal membranes as well. Furthermore, under the conditions used, enzyme activity was also associated with the 105,000 g x 90 min supernatant fraction. The specific activity of the liver homogenate was found to be 2.9 pmol-mg protein-1-min-1, the nonsedimentabel and microsomal activity was of the same order of magnitude, but the Golgi and plasma membrane activities were much higher. The specific activity of plasma membrane AC was 29 pmol-mg proten-1-min-1. The Golgi activity varied in the three fractions, with the highest activity (14 pmol) in GF1 lowest activity (1.8) in GF2, and intermediate activity (5.5) in GF3, when the Golgi activity was corrected for the presence of content protein, the activity in GF1 became much higher (9 x) than that of the plasma membrane while the activities in GF2 and GF3 were comparable to that of plasma membrane. In all locations studied, the AC was sensitive to NaF stimulation, especially the enzyme associated with Golgi membranes. The activities in plasma and microsomal membranes were stimulated by glucagon, whereas the Golgi and nonsedimentable AC were not.

Adenylyl Cyclases↗
PubMed1976

Presence of adenylate cyclase activity in Golgi and other fractions from rat liver. II. Cytochemical localization within Golgi and ER membranes.

The presence of adenylate cyclase (AC) in liver Golgi and microsomal fractions from ethanol-treated rats was tested cytochemically using 5'-adenylyl imidodiphosphate (AMP-PNP) lead phosphate method. Parallel biochemical assays showed that rat liver Golgi AC was only partially inhibited by lead: in the presence of 1 mM Pb++ 80% of the enzyme was preserved, while when 2 mM Pb++ was used 25% remained. No cAMP was formed when the AMP-PNP medium was incubated in the presence of 1 or 2 mM Pb++ but in the absence of cell fractions, indicating that at these concentrations Pb++ does not cause the nonenzymatic hydrolysis of AMP-PNP. Therefore, the reaction product observed by cytochemical localization is not due to the nonenzymatic hydrolysis of AMP-PNP by Pb++. In Golgi subfractions, lead phosphate reaction product was widely distributed among Golgi elements: it was seen in association with the majority of the very low density lipoprotein-filled secretory droplets which predominated in the two lightest Golgi fractions (GF1 and GF2) as well as within the majority of the cisternae found in the heaviest Golgi fraction (GF3). In the latter, reaction product was heaviest along the dilated peripheral rims of the cisternae. In all cases, the reaction product was localized to the outside or cytoplasmic face of the Golgi membranes. When microsomes were incubated cytochemically for AC, deposits were found on the cytoplasmic surface of smooth endoplasmic reticulum (ER) membranes, but none were observed on rough ER membranes. The results confirm the biochemical data reported previously indicating the presence of AC in Golgi and smooth microsomal fractions from rat liver and further demonstrate that the activity is indeed indigenous to Golgi elements and not due to plasma membrane contaminants. They also indicate that AC is widely distributed among Golgi and smooth ER elements. Thus, AC is not restricted in its distribution to plasma membranes as usually assumed.

Adenylyl Cyclases↗
PubMed1976

Lymphocyte and macrophage responses after vaccinia virus infections.

Using a semimicromethod with washed whole blood, in vitro lymphocyte responses of rabbits to intradermal infection with vaccinia virus was studied. Peritoneal exudate macrophages were infected with vaccinia in vitro to determine the time of appearance of activated macrophages. After primary infection, an increase in spontaneous incorporation of thymidine by blood cultures was found as early as 2 days postinfection. This effect was at a maximum at 7 to 10 days, with counts up to 100-fold higher than before infection. Incubation of these cultures with concanavalin A showed a marked decrease in stimulation index as compared with normals. Although only a transient stimulation with vaccinia was found during the acute infection, stimulation indexes of 2 to 3 were obtained during convalescence. Macrophages from rabbits early after infection supported vaccinia replication, whereas those at day 6 or later resisted infection. Macrophage resistance persisted for 2 to 3 weeks. The response of lymphocytes from rabbits reinfected with vaccinia after 15 weeks differed, with a small increase in spontaneous thymidine uptake, a smaller depression in concanavalin A stimulation, and a greater specific response to vaccinia. Macrophage activation occurred earlier and persisted for a longer time after secondary infection.

Animals↗
PubMed1976

Response of proliferative diabetic retinopathy to xenon-arc photocoagulation. A multicentre randomized controlled trial. Second interim report.

Patients with proliferative diabetic retinopathy had one eye chosen by a randomization procedure to have treatment by xenon-arc photocoagulation. 100 patients were followed for at least 1 year, 58 patients for 2 years, and 23 for 3 years. The patients form roughly two equal subgroups: those with new vessels on both optic discs and those without new vessels on either disc. There was a significant difference between the visual acuity of the treated and the untreated eyes in the former group, i.e. with disc new vessels, after 1, 2, and 3 years, but there was no difference in the latter group. Eleven patients were blind in one or both eyes for two consecutive yearly assessments. No treated eye became blind without concomitant blindness in the fellow eye but eight untreated eyes did so. This difference was statistically significant.

Adult↗