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Biomedical subjects

T Y Chang

Publications and source records attributed to T Y Chang.

104 records · Page 6Linked to original sources
PubMed1978

Mammalian cell mutant requiring cholesterol and unsaturated fatty acid for growth.

A mutant requiring both cholesterol and oleate for growth has been isolated from mutagenized Chinese hamster ovary cells. By comparison with wild-type cells, sterol and unsaturated fatty acid biosynthetic activities in the mutant cells grown in fetal calf serum medium appear to be nearly intact. However, whole-cell radioactive acetate, mevalonate, dihydrolanosterol, and stearate incorporation studies show that sterol synthesis from acetate, lanosterol demethylation, and fatty acid desaturation are defective in the mutant cells grown in delipidated serum medium. In vitro enzyme assays with crude cell extracts demonstrated that beta-hydroxy-beta-methylglutaryl-coenzyme A reductase is not induced in the mutant. These experiments were substantiated by gas/liquid chromatographic analyses which showed the sterol content and the percentage unsaturated fatty acids in mutant cells to be drastically reduced when the cells are grown in delipidated serum medium. A spontaneous revertant exhibiting prototrophic growth in lipid-free medium has been isolated from 50 X 10(6) mutant cells. All three defects in this revertant reverted back in parallel, which suggests that these three biosynthetic activities may be controlled by a common regulatory mechanism.

Cell Division↗
PubMed1977

Isolation and partial characterization of a cholesterol-requiring mutant of Chinese hamster ovary cells.

A sterol-requiring mutant has been isolated from mutagenized Chinese hamster ovary cells. This mutant grows normally only when cholesterol is present in the medium. Cell lysis occurs within 3 days in the absence of cholesterol. The frequency of reversion of this mutant to prototrophic growth is low (less than or equal to 10(-6). Whole cell pulse experiments with [14C]acetate or [3H]mevalonate indicate that the rate of synthesis of digitonin-precipitable material is greatly diminished in the mutant cells as compared to that in normal Chinese hamster ovary cells. Enzyme assays in vitro with crude cell extracts show that the biosynthetic conversion of mevalonate to squalene and the conversion of squalene to lanosterol are not impaired in the mutant cells. Gas-liquid chromatographic analyses of radioactive sterol composition after whole cell pulse experiments with [3H]squalene and with [3H]anosterol suggest that the fundamental enzymatic defect of the mutant is at the stage of lanosterol demethylation. When cells were grown in serum-free medium, lanosterol and dihydrolanosterol accumulated intracellularly in the mutant cells before cell lysis occurred; neither of these two intermediary sterols was detected in the wild-type cells grown under the same condition.

Animals↗
PubMed1976

Isolation and characterization of an unsaturated fatty acid-requiring mutant of cultured mammalian cells.

An unsaturated fatty acid-requiring mutant derived from Chinese hamster ovary (CHO) cells has been isolated and characterized. This mutant grows normally when oleate or other unsaturated fatty acids are supplemented in the growth medium. Unlike the wild-type CHO cells, growth stops when medium is deprived of unsaturated fatty acid. Whole cell pulse experiments with [14C]acetate or [14C]stearate indicate that the mutant is defective in unsaturated fatty acid synthesis. Enzyme assays in vitro show that the enzymatic defect of the mutant is localized to the microsomal stearoyl-CoA desaturase.

Acetates↗
PubMed1975

Mechanized enzymatic determination of triglycerides in serum.

A procedure for enzymatic determination of serum triglycerides [Clin. Chem. 19, 476 (1973)] has been adapted for use in continuous-flow analysis (Technicon AutoAnalyzer). A very simple manifold is used; serum is incubated at 37 degrees C with the lipase and alpha-chymotrypsin in potassium phosphate buffer (0.1 mol/liter, pH 7, containing 1.50 g of bovine serum albumin per liter). The liberated glycerol is dialyzed against the complete glycerol reagent. The change in absorbance at 340 nm resulting from oxidation of NADH is proportional to the dialyzed glycerol. The same manifold can be used to determine preformed glycerol if the hydrolyzing enzymes are omitted. The hydrolysis is complete, as shown by the use of equivalent glycerol standards. No prior treatment of the samples is necessary. Assays are run at 60 per hour in the AutoAnalyzer l, 80 per hour in the AutoAnalyzer ll. Results with both instruments for 150 samples correlated well with those obtained by the same enzymatic manual method and by the AutoAnalyzer fluorometric procedure.

Autoanalysis↗
PubMedDate not supplied

Synthetic peptide-based vaccine and diagnostic system for effective control of FMD.

We have designed synthetic peptides corresponding to two different regions of the genome of foot-and-mouth disease virus (FMDV) that are effective as (a) a vaccine or (b) a diagnostic reagent which differentiates convalescent from vaccinated animals, respectively. The peptide vaccine is based on a sequence from the prominent G-H loop of VP1, one of the four capsid proteins. The sequence was optimized by the inclusion of a cyclic constraint and adjoining sequences, and broader immunogenicity was obtained by the incorporation of consensus residues at hypervariable positions. The peptide also included a promiscuous T-helper epitope for effective immunogenicity in outbred populations of large animals.The diagnostic reagent, a peptide based on non-structural (NS) protein 3B, is used in immuno-assays for the detection of antibodies. Antibodies to this NS protein are present in the sera of infected animals but not in the sera of vaccinated animals. The VP1 peptide can be used in complementary immuno-assays for confirmation of NS test results and to monitor for vaccination. This system for differential diagnosis is important to establish the disease-free status of a country.

Amino Acid Sequence↗
PubMedDate not supplied

[Prevalence of Chlamydia trachomatis infection in infants & children].

To understand the prevalence of Chlamydial infection in children in the central area of Taiwan, 220 cases were surveyed in the hospital nursery and pediatric ward from September 1985 to June 1986. In these 10 months, using the enzyme immunoassay (EIA) method, the patients were divided into two groups. Group A included 98 newborn cases, in the nursery, whose conjunctival secretions were collected within two hours after birth. All cases were then treated with erythromycin ophthalmic ointment. Group B included 122 cases, from the pediatric ward, who suffered from symptoms of respiratory tract disease; aspirated secretions from the trachea-were studied. The antigen positive rate in Group A was 12.2% (12 cases), male to female ratio was 1:5. However, in Group B the antigen positive ratio was 26.2% (32 cases), with male to female ratio of approximating 5:3. Children under two years old had the highest incidence of infection, around 77.2% (34 cases). In conclusion, the younger is the case, the higher the positive rate is. However, most of them probably are carriers. Newborns weighed more than 3 Kg and infants older than one month were not treated by erythromycin, but with supportive methods, the clinical symptoms and signs still improved gradually. However in newborn with symptoms of respiratory problem antibiotic treatment is usually indicated, and at present erythromycin is very effective.

Antigens, Bacterial↗