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Biomedical subjects

C C Chang

Publications and source records attributed to C C Chang.

At least 685 records · Page 38Linked to original sources
PubMed1976

Relaxin concentrations in pig plasma following the administration of prostaglandin F2alpha during late pregnancy.

Concentrations of relaxin in peripheral plasma were measured following the injection of 10 mg of PGF2alpha to pregnant sows on day 112 of gestation. The mean concentrations of relaxin before injection of PGF2alpha were less than 13 ng/ml. Relaxin concentrations increased sharply to a mean of 104 ng/ml by 45 min following injection of PGF2alpha and then fell rapidly to a mean of 40 ng/ml 4 h later. Following this initial peak of relaxin, there was a gradual rise and fall of relaxin concentrations during the day preceding parturition. The levels of relaxin during this period were also influenced by PGF2alpha administration since the mean levels of relaxin were significantly lower from the 22nd through the 10th h before parturition in pigs given PGF2alpha, than in pigs given saline.

Animals↗
PubMed1975

Mutant hamster cells exhibiting a pleiotropic effect on carbohydrate metabolism.

Sixty-seven galactose negative (Gal minus) clones were established from survivors after treatment of Chinese hamster lung (V79) cells with 5-bromodeoxyuridine and black light. The mutational origin of these clonal isolates was inferred on the basis of the previously demonstrated mutagenic action of the combined treatment, persistence of the Gal minus phenotype in cell progeny in the absence of selection, conditional lethality of three isolates, interallelic complementation, and assignment of a homologous human gene to chromosome A2. In contrast to the parental cells, Gal minus mutants could not utilize exogenous galactose, mannose, fructose, galactose 1-phosphate, glucose 1-phosphate, or glucose 6-phosphate. Permeation of galactose into mutant cells appeared unimpaired. In intra- and interspecific cell hybrids, the mutation causing the Gal minus phenotype behaved like a recessive character. The pleiotropic nutritional response was due not to deficiency of any one specific enzyme in the Leloir pathway but to significant reduction in activities of phosphoglucomutase, NADP-dependent isocitrate dehydrogenase, and perhaps other enzymes. In temperature-sensitive Gal minus mutants grown at permissive temperature or in complementing intra- and interspecific cell hybrids, the activities of these enzymes were restored to normal levels, accompanied by a regained ability to use the particular hexoses or hexose monophosphates. We postulate that the change from Gal + to Gal minus phenotype in hamster cells could be due to mutations at a regulatory gene locus, or at a yet unknown locus with enzymic defect that causes secondary metabolic imbalances.

Animals↗
PubMed1975

Effects of chronic treatment with various neuromuscular blocking agents on the number and distribution of acetylcholine receptors in the rat diaphragm.

1. Acetylcholine receptors in the end-plate and non-end-plate areas of the rat diaphragm, after treating the animal with hemicholinium-3, alpha- or beta-bungarotoxin in vivo, were studied by their specific binding of labelled alpha-bungarotoxin. 2. Subcutaneous injection of maximum tolerable doses of hemicholinium-3 (50 mug/kg) twice daily for 7 days increased the number of extrajunctional receptors along the whole length of muscle fibre, the approximate density of receptor on muscle membrane being increased from 6/mum2 in normal diaphragm to 38/mum2. Junctional receptors were also increased in number from 2-2 x 10(7) to 2-8 x 10(7) per end-plate. 3. Five days after denervation, there were approximately 153/mum2 extrajunctional receptors and the number of receptors on the end-plate was increased by 220%. 4. Intrathoracic injection of beta-bungarotoxin (50 mug/kg) also increased the density of extrajunctional receptors to approximately 104/mum2, and the number of end-plate receptors by 140% in 5 days. The neuromuscular block was extensive and prolonged. 5. [3H]Diacetyl alpha-bungarotoxin (150 mug/kg) injected into thoracic cavity caused complete neuromuscular blockade for 12 hr. At 24 hr, the synaptic transmission was restored in 80% of the junctions with less than 10% end-plate receptors freed, whereas the safety factor for transmission in normal diaphragm was 3-5. Extrajunctional receptors appeared to increase within 24 hr. This increase continued despite the restoration of neuromuscular transmission, and the receptor density at 5 days was approximately 5l/mum2. The number of junctional receptors, however, was not increased. Repeated injection of the toxin gave the same result. 6. It is concluded that the numbers of junctional and extrajunctional acetylcholine receptors are regulated in different ways, and the possible role of acetylcholine is discussed.

Animals↗
PubMed1975

Stability of aflatoxin B-1 and ochratoxin A in brewing.

The stability of aflatoxin B-1 and ochratoxin A in brewing was investigated by adding the purified toxins to the raw materials at 1 and 10 mug/g levels during mashing in a conventional micro-brewing process. The results indicate that both toxins are stable to heat and are insensitive to cooker mash treatment. Both mycotoxins were partially removed in the mashing and brewing processes. About 14 to 18% and 27 to 28% of the added toxins were found in the final beers brewed from starting materials containing 1 and 10 mug, respectively, of either toxin per g. The possible route of transmission of mycotoxins into beer is discussed.

Aflatoxins↗
PubMed1975

Radioimmunoassay of plasma relaxin levels throughout pregnancy and at parturition in the pig.

Relaxin concentrations in peripheral plasma have been measured throughout pregnancy and immediately following parturition in the pig by radioimmunoassay. Gestation ranged from 114-117 days. Relaxin concentrations remained below 2 ng/ml during the first 100 days of pregnancy and then rose gradually to a mean of 11.9 ng/ml by 3 days before parturition. At this time, relaxin levels began to rise more rapidly and over the next 2 days increased to a mean concentration of 44.0 ng/ml by 30 h before parturition. Relaxin concentrations then increased sharply to a mean of 145.6 ng/ml by 14 h before parturition. This maximum was followed be a rapid decrease to a mean of 42.4 ng/ml by 2 h before parturition. At one day following parturition, relaxin levels were less than 1 ng/ml.

Animals↗