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Biomedical subjects

H Cheng

Publications and source records attributed to H Cheng.

At least 433 records · Page 24Linked to original sources
PubMed1988

Positive correlation of corneal thickness and endothelial cell loss. Serial measurements after cataract surgery.

A significant linear correlation was found between increase in corneal thickness (delta CT) in the immediate postoperative period and percentage of cell loss one and six months after surgery in a prospective study on cataract surgery. Eyes were grouped according to delta CT, and the groups were compared according to the percentage of cell loss. Eyes with delta CT of 0.1 mm or more at five days lost significantly more cells at one and six months than eyes with delta CT of less than 0.025 mm. Eyes were then regrouped according to the percentage of cell loss. Those with cell loss of 30% or more were found to have significantly greater delta CT at 48 hours and five days than eyes with cell loss of less than 30%. The derived probability of cell loss of 30% or more increases the greater the value of delta CT. For delta CT of 100 micron or more at five days, the probability of high cell loss is 30%; this is nearly three times the likelihood that high cell loss had occurred when delta CT is less than 100 micron. Our results suggest that delta CT could be a useful clinical indicator of endothelial cell loss.

Cataract Extraction↗
PubMed1988

Variation of mouse intestinal epithelial whole population cell kinetics during the estrous cycle.

There are contradictory reports on the effect of the estrous cycle on cell proliferation in the intestinal epithelium. We reexamined estrous-cycle-related changes in the epithelium by using flow cytometry and Coulter particle counting. We found significant estrous-cycle-related variations in both the distribution of epithelial cells through the cell cycle as well as the number of epithelial cells per unit area in mouse jejunal and colonic epithelium.

Animals↗
PubMed1988

Changes in the pattern of intercellular transfer of lucifer yellow between villus epithelial cells during postnatal development.

We demonstrate the pattern of intercellular transfer of Lucifer yellow between villus epithelial cells during postnatal development. Epithelial cells in all villi from newborn mice demonstrate high dye transfer efficiency. The efficiency of dye transfer decreases with the age of the mouse and with villus size, until in adult mice, dye transfer is observed only in what are presumably newly forming villi. We suggest that the development of an osmolality gradient in taller villi, a result of sodium pumps and a countercurrent multiplier, may be responsible for the changes in the pattern of dye transfer observed.

Animals↗
PubMed1988

Variation in crypt size and its influence on the analysis of epithelial cell proliferation in the intestinal crypt.

The standard model of epithelial cell renewal in the intestine proposes a gradual transition between the region of the crypt containing actively proliferating cells and that containing solely terminally differentiating cells (Cairnie, Lamerton and Steel, 1965 a, b). The experimental justification for this conclusion was the gradual decrease towards the crypt top of the measured labeling and mitotic indices. Recently, however, we have proposed that intestinal crypts normally undergo a replicative cycle so that at any time in any region of the intestine, crypts will be found to have a wide range of sizes. We show here that if this intrinsic size variation is taken into account, then a sharp transition between the proliferative and nonproliferative compartments of individual intestinal crypts is consistent with the labeling and mitotic index distributions of mouse and rat jejunal crypts. Thus there is no need to invoke the region of gradual transition from proliferating to nonproliferating cells as is done in the standard model. The position of this sharp transition is estimated for both the mouse and rat. Experiments to further test our model are suggested and the significance of the results discussed.

Animals↗
PubMed1988

An area function method for estimating the apparent absorption rate constant.

A new method for calculation of the apparent absorption rate constant of a drug has been derived based on the relationship between the plasma concentrations after an oral dose and the area intervals under both the oral and the intravenous plasma concentration-time curves. The method is a noncompartmental technique evolved from the convolution integral and does not use any theoretical approximation. It has been evaluated and compared with nonlinear regression analysis using NONLIN84 and moment analysis using both errorless and errant data. The approach is as adequate as nonlinear regression analysis under a variety of conditions but offers ease and simplicity in handling experimental data.

Administration, Oral↗
PubMed1988

Treatment of cataract in diabetics with and without retinopathy.

The results of cataract surgery in diabetic patients was reviewed. The visual outcome was good in the absence of retinopathy and was not significantly different from that of non-diabetic patients. Eyes with retinopathy achieved significantly worse visual results and the prognosis was related to the severity of retinopathy. Clinical cystoid macular oedema occurred significantly more frequently in eyes with retinopathy than without and there were significantly more eyes with retinopathy which became blind or partially sighted. The use of a Projectoscope for assessing the amount of degradation of an image was tested. A good correlation was found between the amount of blurring of the test target and the drop in visual acuity. The optimal type of cataract surgery is discussed and lines of management outlined.

Blindness↗
PubMed1988

Lamicel is more effective in preparing the cervix for midtrimester termination of pregnancy than Laminaria japonicum.

Laminaria tents are often used prior to prostaglandin termination of midtrimester pregnancy to reduce the induction-abortion interval. Natural laminaria suffers from a number of disadvantages and, recently, a synthetic form Lamicel (Cabot Medical, PA), has been produced. Uncontrolled evaluation has suggested that it is effective for dilating the cervix but scepticism remains because Lamicel does not exert radial force on the cervical canal. One hundred women who requested abortion between 12 and 24 weeks of pregnancy were studied. They were randomly divided into group A who had a Lamicel inserted for 6 hours and group B who had a laminaria tent inserted for 8 hours. The cervical dilatation was assessed at the end of this period and the patients were then given up to 6 injections of sulprostone at 4-hourly intervals. All patients in Group A aborted, but 7 of those in Group B did not. The mean cervical dilatation in Group A was 7.47 +/- 1.46 mm compared with 4.71 +/- 1.76 mm in Group B (p less than 0.001). The mean induction-abortion interval in Group A was also significantly shorter (p less than 0.05) than that in Group B: 11.79 +/- 7.24 hours compared with 12.51 +/- 6.52 hours in Group B (excluding 7 patients who failed to abort in Group B). The results of the study suggest that the degree of cervical dilatation that can be achieved using Lamicel is significantly greater than that by laminaria tents.

Abortifacient Agents, Nonsteroidal↗
PubMed1988

Panretinal cryotherapy in neovascular disease.

Panretinal cryotherapy (PRC) was used to treat 15 eyes with rubeosis, nine of which had established neovascular glaucoma, and seven eyes with proliferative diabetic retinopathy. The rubeosis regressed, with preservation of vision and return to normal of intraocular pressure, in all but one eye. With one exception all eyes with proliferative retinopathy also showed new vessel regression after treatment. PRC may be considered an effective alternative to retinal photocoagulation in the treatment of advanced rubeosis, early rubeotic glaucoma, and in certain circumstances proliferative diabetic retinopathy.

Adult↗
PubMed1988

Bullous keratopathy: a study of endothelial cell morphology in patients undergoing cataract surgery.

Preoperative and postoperative endothelial cell morphology was examined in three types of patients participating in a randomised, controlled trial of cataract surgery. The first sustained modest endothelial cell loss and served as controls, the second and third sustained high cell loss, but only the latter progressed to bullous keratopathy. The technique of examining endothelial cell morphology is described and its validity assessed. Measures of cell area, number of sides, side length, and variation in cell size and cell shape were utilised. No significant differences were found between the three groups by any of the preoperative morphological measures. Furthermore, postoperative values of variation in cell shape and cell size did not differ significantly between the groups. No evidence was found in our patients to support the hypothesis that eyes at particular risk of developing bullous keratopathy may be differentiated on the basis of their preoperative or early postoperative endothelial cell morphology.

Aged↗
PubMed1987

Liquid chromatographic determination of 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one in human plasma with fluorescence detection.

A simple and sensitive assay for quantitating 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one (1; BMY 26517) in human plasma was developed using high-performance liquid chromatography with fluorescence detection. The method involves precipitation of protein and reversed-phase chromatography. The method is linear in the range of 4.3-429 ng/mL of 1, and the limit of detection is 0.4 ng/mL. The day-to-day precision values of this method at 25.7 and 386 ng/mL are 2.1 and 2.6%, respectively. The day-to-day accuracy values at these concentrations are 99.7 and 99.8%, respectively. The recovery of 1 is 98.3%.

Anti-Ulcer Agents↗
PubMed1987

Three-dimensional reconstruction of biological objects using a graphics engine.

A common problem in the study of biological material is the determination of three-dimensional structure from serial sections. The large number of sections required to obtain sufficient internal detail of a structure results in enormous processing requirements. These requirements can now be satisfied by current graphics engine technology in combination with image-digitizing hardware. The previously onerous tasks of manipulating and displaying 3D objects become routine with this combination of technologies. We report a computer-assisted reconstruction system on a graphics engine-based workstation. The system accepts images from any video source and includes a utility for aligning adjacent video images. Also available is an editor for geometric object entry and editing. More novel in our approach is the use of video interiors in 3D displays in addition to contours and tiled surfaces. Video interiors is a form of display in which digitized pixels interior to objects are revealed by cutaway blocks.

Algorithms↗
PubMed1987

DNA and protein components of nuclear acceptor sites for androgen receptors in the rat prostate.

Androgen receptor-acceptor complexes in nuclei from rat ventral prostates were cross-linked in situ with formaldehyde and partially purified using affinity chromatography. To isolate acceptor DNA, the cross-linked receptor-acceptor complexes in formaldehyde-treated chromatin samples were adsorbed to dihydrotestosterone-17 beta-succinyl agarose, eluted with 75 microM dihydrotestosterone-1% SDS, digested with proteinase K and extracted with phenol-chloroform. After 32P end-labelling and PAGE, this DNA contained two distinct bands of DNA (about 300 and 400 base pairs respectively) which were unique relative to the total prostatic DNA. As an alternative approach for characterizing acceptor DNA, the DNA in prostatic nuclei and cross-linked chromatin was labelled with 32P by nick translation and analysed in glycerol density gradients for associations with cross-linked androgen receptors. A symmetrical 7s peak of 32P-DNA with a small amount of coincident receptor was observed in the gradients after mild trypsin treatment. In the absence of trypsin treatment, both the cross-linked receptors and the labelled DNA sedimented to the bottom of the gradients. Isolation of acceptor proteins involved iodination of cross-linked chromatin with 125I and androgen affinity chromatography. A comparison of the relative efficiency of retention and elution of 125I-proteins from different affinity columns revealed that testosterone-17 beta-succinyl agarose was potentially most suitable for purification of acceptor proteins. After electrophoresis on SDS-polyacrylamide gels, the eluates from this type of affinity matrix were found to contain two major peaks of 125I-labelled proteins--one corresponding to a protein with a similar molecular weight as the nuclear androgen receptor (33,000 Da); the other having a molecular weight of 20,000 Da. While the precise identity of this latter entity is unknown, its enrichment and retention by the affinity gel implies that it is closely associated with the androgen receptor and may be a component of the acceptor sites.

Animals↗
PubMed1987

The crypt cycle. Crypt and villus production in the adult intestinal epithelium.

We propose a model for the growth of individual crypts that is able to account for the observed changes in the number of cells in crypts under normal conditions, after irradiation, and after 30% resection. Parameter values for this model are estimated both for mouse and man, and detailed predictions of crypt growth rates are made. This model does not predict a steady-state crypt size; rather it suggests that crypts grow until they bifurcate. We therefore propose a crypt cycle (analogous to the cell cycle) and present evidence that most if not all crypts in the adult mouse are cycling asynchronously and independently. This evidence consists of four experiments that indicate that branching crypts are randomly distributed over the intestinal epithelium, that the plane of bifurcation of branching crypts is randomly oriented with respect to the villus base, and that the size distribution of crypts is consistent with an expanding crypt population. We also report for the first time evidence of villus production in the adult mouse intestinal epithelium. We conclude that the crypt and villus populations in the adult mouse are not in a steady state.

Adult↗
PubMed1987

Current status of cataract surgery--a review of personal experience.

One hundred and five eyes treated consecutively over a 5 year period for senile cataract by extracapsular extraction and posterior chamber lens (PC) implantation were compared with 112 consecutive eyes taken from a prospective study which had extracapsular surgery and iridocapsular lens implantation and had been followed from 4 to 7 years. At 1 year the visual acuity of eyes of the two groups were similar but a trend suggests better results in the PC groups. The PC group also had fewer serious complications and less endothelial cell loss.

Cataract↗