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Biomedical subjects

E Chang

Publications and source records attributed to E Chang.

At least 127 records · Page 7Linked to original sources
PubMed1988

Xeroderma pigmentosum group E cells lack a nuclear factor that binds to damaged DNA.

The disease xeroderma pigmentosum is characterized by deficient repair of damaged DNA. Fusions of cells from different patients have defined nine genetic complementation groups (A through I), implying that DNA repair in humans involves multiple gene products. In this report, an extension of the gel electrophoresis binding assay was used to identify at least one nuclear factor that (i) bound to DNA damaged by ultraviolet radiation or the antitumor drug cisplatin, but (ii) was notably absent in cells from complementation group E. Therefore, the factor appears to participate in a versatile DNA repair pathway at the stage of binding and recognition.

Cell Line↗
PubMed1988

Angiotensinogen mRNA. Regulation by cell cycle and growth factors.

The components of the renin-angiotensin system have been colocalized in many tissues suggesting that local generation of angiotensin II can regulate blood flow in specific organs or tissues. This in combination with the fact that proliferating tissues require angiogenesis and increased blood flow to develop have led us to study the relationship of angiotensinogen mRNA production to cell cycle regulation. Reuber H35 (H4IIE) cells were growth-arrested by serum deprivation. Cells were then treated with 10% fetal calf serum, depleted serum, or insulin. Insulin and serum were equally potent at increasing beta-actin mRNA levels, depressing angiotensinogen mRNA levels, and in increasing [3H]methyl thymidine incorporation. The half-maximal insulin effect occurred at 5 x 10(-9) M. Insulin-like growth factor I and II had no effect on any of the parameters measured. 12-O-tetradecanoyl phorbol 13-acetate (TPA) also induced beta-actin mRNA, decreased angiotensinogen mRNA, and caused an increase in [3H]methyl thymidine incorporation. The TPA effects were of shorter duration and of lower magnitude than those caused by insulin or serum. Inactivation of protein kinase C by preincubation with TPA did not block the insulin response. TPA has been shown to induce angiogenesis in vitro. Thus, these studies suggest that inhibition of angiotensinogen gene activity may be part of the proliferative or angiogenic process. Our experimental data may provide a model for further experimental dissection of the biochemical steps involved in angiogenesis.

Actins↗
PubMed1987

Multiple hormones regulate angiotensinogen messenger ribonucleic acid levels in a rat hepatoma cell line.

Angiotensinogen is regulated by both hormones and changes in cardiovascular and electrolyte status. We have used the Reuber H35 (H4IIE) rat hepatoma cell line to study the regulation of angiotensinogen mRNA levels by dexamethasone, aldosterone, L-T3, and 17 beta-estradiol. Using the Acc I (1097 basepairs) fragment of our angiotensinogen cDNA clone, we have studied, by Northern and slot blot analysis, the accumulation of angiotensinogen mRNA in this cell culture system. Angiotensinogen mRNA of approximately 1800 bases was identified in these cells. It was identical in size to angiotensinogen mRNA from rat liver. Cells grown in medium containing serum depleted of thyroid and steroid hormones for up to 72 h showed a progressive decrease in angiotensinogen mRNA. Dexamethasone treatment resulted in a time- and dose-dependent increase in angiotensinogen mRNA. The half-maximal response occurred at 10(-9) M dexamethasone, with a maximal response of approximately 4-fold (serum-free conditions). Aldosterone induced a dose-dependent increase in mRNA. Half-maximal levels were obtained at 5 X 10(-8) M. Competition studies using the glucocorticoid antagonist RU38486 (Roussel-UCLAF) confirmed that dexamethasone was acting through the glucocorticoid receptor and suggested that aldosterone was acting through the same receptor. L-T3 treatment caused a dose and time-dependent increase in angiotensinogen mRNA levels. The half-maximal response occurred at 5 X 10(-8) M, and the maximal response was a 2-fold increase. Combined treatment with dexamethasone and L-T3 triiodothyronine resulted in a synergistic increase in angiotensinogen mRNA levels. 17 beta-Estradiol failed to elicit a change in angiotensinogen mRNA levels consistent with the observation that these cells lack estrogen receptors. Our results indicate that hepatic angiotensinogen mRNA levels are regulated in a complex fashion by several hormones. These cells provide a useful system for studying the hormonal regulation of the angiotensinogen gene.

Adrenal Cortex Hormones↗
PubMed1987

The effect of intramammary antibiotic therapy at calving on udder health traits.

The effect of intramammary antibiotic therapy at calving on mastitis infection prevalence, linear score milk somatic cell count, and milk NAGase activity, 30 d postpartum, and on milk production, 90 to 120 d postpartum, was tested. Cows (n = 175) were split into treatment and control groups at drying off. All cows received commercial dry cow therapy. At calving, treated cows received commercial lactating cow therapy in all quarters after the first two milkings; control cows were not treated. Composite milk samples were aseptically collected from all cows at drying off, calving, and 30 d postpartum. Udder health traits: linear score milk SCC, NAGase activity, and bacterial content in milk, were determined on all samples. The first three DHI milk weights were recorded for all cows. Treatment and control cows had similar prevalences of intramammary infections during the dry and 30-d postpartum periods. Least squares means of linear score milk SCC and NAGase activities were similar at drying off and calving. Cell count scores were similar between groups; NAGase activities were higher in control cows at 30 d postpartum. Control cows tended to produce more milk postpartum. Results demonstrated no advantage of intramammary therapy at calving in improving milk production or udder health.

Acetylglucosaminidase↗
PubMed1985

Prenatal diagnosis of neuronal ceroid-lipofuscinoses.

We report on the successful prenatal diagnosis of the late infantile "Jansky-Bielschowsky" variant of the neuronal ceroid-lipofuscinoses (NCL). The fetus was studied at 16 weeks of gestation because of an affected sib. Uncultured amniotic fluid cells were studied by conventional electron microscopic techniques. About one-third of a subpopulation of dark, elongated cells contained one or more deposits of curvilinear cytosomes bound by a single unit membrane. These findings were considered typical of the late infantile variant of NCL. After delivery at term, a skin punch biopsy and a buffy coat preparation from the baby were examined and found to have similar characteristic inclusions, which confirmed our prenatal diagnosis.

Biopsy↗
PubMed1983

Microbial growth associated with granular activated carbon in a pilot water treatment facility.

The microbial dynamics associated with granular activated carbon (GAC) in a pilot water treatment plant were investigated over a period of 16 months. Microbial populations were monitored in the influent and effluent waters and on the GAC particles by means of total plate counts and ATP assays. Microbial populations between the influent and effluent waters of the GAC columns generally increased, indicating microbial growth. The dominant genera of microorganisms isolated from interstitial waters and GAC particles were Achromobacter, Acinetobacter, Aeromonas, Alcaligenes, Bacillus, Chromobacterium, Corynebacterium, Micrococcus, Microcyclus, Paracoccus, and Pseudomonas. Coliform bacteria were found in small numbers in the effluents from some of the GAC columns in the later months of the study. Oxidation of influent waters with ozone and maintenance of aerobic conditions on the GAC columns failed to appreciably enhance the microbial growth on GAC.

Adsorption↗
PubMed1977

Fine structure of cutaneous nerves in ganglioside storage disease.

Skin punch biopsies of six children suffering from infantile or late onset Tay-Sachs disease, juvenile Sandhoff disease, or GM gangliosidosis type I, contained axons which, when viewed with the electron microscope, were distended by large amorphous black deposits. These are nonspecific residual bodies. Their large numbers indicate severe disturbance of the nerve cell and may be part of the dying back process. The three cases with Tay-Sachs disease had also axonal zebra or complex membranous bodies which appeared to be specific. Cytoplasmic vacuolation of other cells was a feature in the patient with GM1 gangliosidosis. Biopsies of three parents were negative.

Axons↗
PubMed1975

Skin punch biopsies and lymphocytes in the diagnosis of lipidoses.

Skin punch biopsies and buffy coats of white blood cells were examined electron microscopically in patients suffering from a variety of storage diseases. No specific abnormalities could be detected in Gaucher's disease and adreno-leucodystrophy. While characteristic deposits were found in cutaneous nerves in globoid and metachromatic leucodystrophy, this method was deemed inferior to sural nerve biopsy. In gangliosidoses, on the other hand, pathognomonic membranous cytoplasmic bodies were common in axons of cutaneous nerves, and in generalized gangliosidoses marked vacuolation of many other cells was prominent. Specific deposits were found in various cells in skin punch biopsies and in lymphocytes of children suffering from ceroid lipofuscinoses, and in lymphocytes of their parents. This constitutes the easiest diagnostic laboratory procedure in such cases.

Adolescent↗