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Biomedical subjects

K L Chung

Publications and source records attributed to K L Chung.

At least 19 recordsLinked to original sources
PubMed2004

Use of ophthalmic medications during pregnancy.

OBJECTIVES: To review potential risks of eye medications to the mother and her foetus. DATA SOURCES: PubMed search for all relevant articles (1966 to 2003). STUDY SELECTION: All types of publication that documented potential risks of eye medications during pregnancy. The following key words were used: pregnancy, fetus, teratogenicity, eye, ocular, ophthalmic, glaucoma, antibiotics, anti-inflammatory, and corticosteroids. DATA EXTRACTION: All relevant articles including original articles, review papers, case studies, and relevant book chapters were extracted and reviewed. DATA SYNTHESIS: Whether ophthalmic medications can be used during pregnancy is a very important issue; yet, limited information on the subject exists in the literature. Topically applied eye medications that give rise to systemic side-effects are of particular concern to both patients and doctors. Various ophthalmic anti-infective preparations and ophthalmic corticosteroids have shown to cause teratogenicity in animal studies. Furthermore, anti-glaucoma drugs pose potential risks to the foetus if they are absorbed systemically. This article examines the association between the main groups of ophthalmic medication and their possible adverse effects on the mother and the foetus. Recommendations for the treatment of pregnant patients with eye diseases are also discussed. CONCLUSION: The risk of giving ophthalmic drugs to pregnant women is low. Doctors should be cautious when prescribing drugs for pregnant women and consult experts in the field when in doubt.

Adrenal Cortex Hormones↗
PubMed1996

Task analysis for computer-aided design (CAD) at a keystroke level.

The purpose of this research was to develop a new model to describe and predict a computerized task. AutoCAD was utilized as the experimental tool to collect operating procedure and time data at a keystroke level for a computer aided design (CAD) task. Six undergraduate students participated in the experiment. They were required to complete one simple and one complex engineering drawing. A model which characterized the task performance by software commands and predicted task execution time using keystroke-level model operators was proposed and applied to the analysis of the dialogue data. This task parameter model adopted software commands, e.g. LINE, OFFSET in AutoCAD, to describe the function of a task unit and used up to five parameters to indicate the number of keystrokes, chosen function for a command and ways of starting and ending a command. Each task unit in the task parameter model can be replaced by a number of primitive operators as in the keystroke level model to predict the task execution time. The observed task execution times of all task units were found to be highly correlated with the task execution times predicted by the keystroke level model. Therefore, the task parameter model was proved to be a usable analytical tool for evaluating the human-computer interface (HCI).

Journal Article↗
PubMed1996

[The study on the in-vitro stability of Tc(V)-99m dimercaptosuccinic acid].

Tc(V)-99m DMS, developed by Yokoyama et al. in 1981, has been recognized to be advantageous for the scintigraphic diagnosis of various malignant tumors and their metastasis, the aim of this study is to assess the in-vitro stability of Tc(V)-99m DMS. Thin-layer chromatography, including paper chromatography and silica gel thin layer chromatography, is performed to determine the change of radiochemical species presented in the reconstituted solution of Tc(V)-99m DMS prepared from the DMS kit (Institute of Nuclear Energy Research, Atomic Energy Council R.O.C.) and the commercial DMSA kit (Nephroscint, IRE CELLTARG Radiopharmaceuticals Japan). The bioscan imaging scanner is used to measure the Rf value and labeling efficiency of radiochemical species on the chromatographic strip. The in-vitro stability of Tc(V)-99m DMS prepared from the DMS kit and the commercial DMSA kit is studied by examining various parameters which include temperature(degree C) and time(hr) after reconstitution. The results show that the in-vitro stability of Tc(V)-99m DMS prepared from the DMS kit is actually better than that from the commercial DMSA kit. The one-step labeling method of DMS kit is much simpler than the two-step labeling method of DMSA kit.

Drug Stability↗
PubMed1995

The E-SCREEN assay as a tool to identify estrogens: an update on estrogenic environmental pollutants.

Estrogens are defined by their ability to induce the proliferation of cells of the female genital tract. The wide chemical diversity of estrogenic compounds precludes an accurate prediction of estrogenic activity on the basis of chemical structure. Rodent bioassays are not suited for the large-scale screening of chemicals before their release into the environment because of their cost, complexity, and ethical concerns. The E-SCREEN assay was developed to assess the estrogenicity of environmental chemicals using the proliferative effect of estrogens on their target cells as an end point. This quantitative assay compares the cell number achieved by similar inocula of MCF-7 cells in the absence of estrogens (negative control) and in the presence of 17 beta-estradiol (positive control) and a range of concentrations of chemicals suspected to be estrogenic. Among the compounds tested, several "new" estrogens were found; alkylphenols, phthalates, some PCB congeners and hydroxylated PCBs, and the insecticides dieldrin, endosulfan, and toxaphene were estrogenic by the E-SCREEN assay. In addition, these compounds competed with estradiol for binding to the estrogen receptor and increased the levels of progesterone receptor and pS2 in MCF-7 cells, as expected from estrogen mimics. Recombinant human growth factors (bFGF, EGF, IGF-1) and insulin did not increase in cell yields. The aims of the work summarized in this paper were a) to validate the E-SCREEN assay; b) to screen a variety of chemicals present in the environment to identify those that may be causing reproductive effects in wildlife and humans; c) to assess whether environmental estrogens may act cumulatively; and finally d) to discuss the reliability of this and other assays to screen chemicals for their estrogenicity before they are released into the environment.

Animals↗
PubMed1994

The pesticides endosulfan, toxaphene, and dieldrin have estrogenic effects on human estrogen-sensitive cells.

Estrogenic pesticides such as DDT and chlordecone generate deleterious reproductive effects. An "in culture" bioassay was used to assess the estrogenicity of several pesticides. The E-screen test uses human breast estrogen-sensitive MCF7 cells and compares the cell yield achieved after 6 days of culture in medium supplemented with 5% charcoal-dextran stripped human serum in the presence (positive control) or absence (negative control) of estradiol and with diverse concentrations of xenobiotics suspected of being estrogenic. Among the organochlorine pesticides tested, toxaphene, dieldrin, and endosulfan had estrogenic properties comparable to those of DDT and chlordecone; the latter are known to be estrogenic in rodent models. The E-screen test also revealed that estrogenic chemicals may act cumulatively; when mixed together they induce estrogenic responses at concentrations lower than those required when each compound is administered alone.

Biological Assay↗
PubMed1983

Analysis of a mutant of Autographa california nuclear polyhedrosis virus with a defect in the morphogenesis of the occlusion body macromolecular lattice.

A mutant (m-29) of Autographa californica nuclear polyhedrosis virus (AcMNPV) grew in Spodoptera frugiperda and Trichoplusia ni cells but did not form typical intranuclear occlusion bodies (OB); instead, small particles (95 to 180 nm diam.) were produced in copious amounts within nuclei. Ultrastructural studies showed that the particles did not occlude enveloped nucleocapsids and that they lacked a macromolecular paracrystalline lattice and a structure equivalent to the occlusion body envelope. The particles within nuclei stained in an immunofluorescence test with antipolyhedrin antibody and when extracted from cells the major polypeptide of a particle preparation was indistinguishable from polyhedrin when examined on SDS--polyacrylamide gels and had an identical peptide pattern following proteolysis with V8 protease. Other elements believed to be implicated in OB morphogenesis such as a proliferation of intranuclear membranes, enveloped bundles of nucleocapsids, patches of fibrous material and fibrous sheets were present in normal amounts. No alteration in the synthesis or processing of polypeptides was seen in mutant-infected cells. Analysis of m-29 DNA with BamHI, EcoRI and HindIII restriction endonucleases revealed that the HindIII restriction site at the F/V junction of viral DNA was absent in the mutant. No other modifications in the restriction patterns were detected. It is proposed that an alteration in the amino acid sequence of polyhedrin towards the--NH2 terminus of the polypeptide may account for the growth characteristics of the mutant.

Animals↗
PubMed1982

Effects of hemolymph from immune and non-immune larvae of Galleria mellonella on the ultra-structure of Pseudomonas aeruginosa.

The ultrastructure of Pseudomonas aeruginosa, a pathogen of Galleria mellonella is rapidly altered after in vitro exposure to the hemolymph of vaccinated larvae. The bacteria were treated with normal and immune hemolymph for periods of time ranging from 7 to 28 min at 28 degrees C. In contrast to the apparent non-damaging effects of normal hemolymph, the immune hemolymph caused progressive damage to the cells within 7 min. The initial attack was directed towards the cell wall. Complete degradation was observed after 14 to 28 min exposure to the immune hemolymph.

Animals↗
PubMed1977

The effect of rifampicin on the developmental phases of germinating spores of Clostridum sp., MSp+.

The effect of rifampicin on the developmental phases of germinating spores of Clostridium botulinum, MSp+, has been studied. At sublethal concentrations of rifampicin (0.05 ng/ml) the time periods required for outgrowth and vegetative growth was significantly prolonged because of the inhibition of RNA and protein synthesis. However, rifampicin had essentially no effect on DNA synthesis or on subsequent spore formation. Chemical analyses showed that the amount of protein present in vegetative cells of the rifampicin-treated cultures was twice as great as in the untreated cultures but the total protein content of endospores was the same in both cases. It was revealed in ultrastructural studies of rifampicin (0.1 ng/ml) treated cultures, examined after 22 h, that septum formation and normal cell division of the emerging cell was blocked and a few cells showed constriction which produced one normal and one protoplast-like daughter cell.

Bacterial Proteins↗
PubMed1976

The effect of sublethal doses of rifampin on the sporulation of Clostridium botulinum.

Sublethal doses of rifampin (0-005 mug/ml), added to vegetatively growing cultures of a sporogenic mutant of Clostridium botulinum at inoculation time or after 4 h, resulted in a decrease of growth and in blockage of spore formation. But when rifampin was added 6 to 24 h after inoculation, normal growth and sporulation occurred, indicating that the time of addition was critical and that rifampin was most effective on rapidly dividing, exponential-phase cells. Ultrastructural studies showed that when rifampin was added at the time of inoculation, endospore development was blocked at stage III. During subsequent incubation (greater than 10 h) the cells lost their rigidity, and lysis of the mother cell was followed by that of the forespore. When the cultures were treated with rifampin at 4 h, about 40% of the cells were blocked at stage III and about 60% reached stages IV and V. Some showed excessive elongation and contained developing spores at each pole. They appeared to be derived from two daughter cells unable to form a division septum because of a specific inhibitory effect of rifampin on division. It would seem, therefore, that two daughter cells which are genetically coded to form endospores will do so irrespective of the development of a division septum, and the spores are formed at the 'old' polar regions.

Clostridium botulinum↗