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T T Liu

Publications and source records attributed to T T Liu.

48 records · Page 3Linked to original sources
PubMed1983

Effects of polybrominated biphenyls on the concentration and clearance of steroids from blood.

Hepatic microsomal mixed-function oxidases have been stimulated when cattle were experimentally fed polybrominated biphenyls (PBB; fireMaster BP-6). These changes provide mechanisms for alteration of the metabolism and clearance of steroid hormones that might then affect reproductive function. This study was conducted to examine the effects of PBB on the clearance of radiolabel from injected estradiol-17 beta and progesterone along with daily determinations of concentrations of endogenous estradiol-17 beta and progestins in blood plasma. Toxicity was induced by dosing two Holstein cows with 25 g of fireMaster BP-6/d for 39 or 50 d. Single iv injections of 35 microCi [4-14C] progesterone and 400 microCi [2,4,6,7-3H] estradiol-17 beta were given on d -5, 10, 30 and 38 or 48 relative to dosing. Last injections were given when severe toxic symptoms were observed in each animal. Clinical signs, blood constituents, and necropsy findings confirmed the toxic syndrome. Clearance of 14C from progesterone was described by a biexponential function of time, while 3H from estradiol was cleared more slowly with a triexponential function. The total clearance rate for radiolabel from progesterone was approximately four times greater than estradiol throughout the experiments. The total clearance rates were similar for both steroids before and 10 d after dosing with PBB. A toxic syndrome was well developed by d 30 of PBB dosing and the total clearance rate of both steroids decreased approximately 50% with precipitous decreases when animals were terminally toxic. Despite the developing toxic syndrome, plasma concentrations of estradiol-17 beta and total progestins were normal and the periodicity of estrous cycles was maintained.

Animals↗
PubMed1982

Performance and health of offspring of cows experimentally exposed to polybrominated biphenyls.

Offspring of cows experimentally given polybrominated biphenyls(fire-Master BP-6) were studied from May 1976 through January 1981. Daily doses were 0,.25, and 250 mg for 60 days for Groups I, II, and III, and 250 mg for 180 or 202 days for Group V. Concentrations of polybrominated biphenyls in fat of dosed animals in Groups I, II, and III, and V were .05, .20, 25, and 30 micrograms/g at the end of dosing. Residue concentrations in body fat declined with a half life of about 1 yr. Seventy-five calves were born to these cows and their offspring, representing first through fifth parturition. Fifteen calves died, 10 of which were in Groups III and V. All deaths in Groups III and V were attributable to dystocia. Incidence od dystocia and calf mortality were related to birth weight of the calf which in turn was correlated with concentrations of polybrominated biphenyls in blood and tissues of the dam. Other variables that influenced birth weight were sex of calf, length of gestation, and parturition number of dam. There were no significant differences in growth and performance of calves from the four dosed groups. Clinical signs of polybrominated biphenyl toxicosis were not evident, and general health of offspring was not influenced. Number of inseminations for conception was greater among offspring from Groups III and V. Mechanisms for this dysfunction have not been determined.

Animals↗
PubMed1981

A Nonaqueous Procedure for Isolating Starch Granules with Associated Metabolites from Maize (Zea mays L.) Endosperm.

A nonaqueous procedure using glycerol and 3-chloro-1,2-propanediol was developed for the isolation from maize of starch granules with associated metabolites. In this procedure, immature endosperm tissue was quickly frozen at -156 C, freeze-dried, homogenized in cold glycerol, filtered through Miracloth, and centrifuged through a higher density medium of 3-chloro-1,2-propanediol. The procedure was used to isolate starch granules from the endosperm of normal and the mutant amylose-extender dull waxy. Starch and water-soluble polysaccharide recovery was high with low cytoplasmic (RNA) and nuclear (DNA) contamination.Electron microscopic examination of the isolated starch granules failed to demonstrate the presence of the amyloplast's membrane. However, based on an examination of fresh, freeze-dried, and rehydrated freeze-dried normal endosperm, it is suggested that the amyloplast membrane and enclosed stroma metabolites were dried onto the surface of the starch granules during the freeze-drying procedure. Chemical analysis of the glycerol-propanediol isolated granules showed the presence of alcohol-soluble sugars, inorganic phosphate, and phosphate-containing compounds. These soluble metabolites may represent amyloplast stroma metabolites which became bound to the starch granules during freeze-drying. Thus, this isolation procedure should be useful when metabolites closely associated with starch granules in situ are to be evaluated.

Journal Article↗
PubMed1981

Measurement of Metabolites Associated with Nonaqueously Isolated Starch Granules from Immature Zea mays L. Endosperm.

Starch granules with associated metabolites were isolated from immature Zea mays L. endosperm by a nonaqueous procedure using glycerol and 3-chloro-1,2-propanediol. The soluble extract of the granule preparation contained varying amounts of neutral sugars, inorganic phosphate, hexose and triose phosphates, organic acids, adenosine and uridine nucleotides, sugar nucleotides, and amino acids. Based on the metabolites present and on information about translocators in chloroplast membranes, which function in transferring metabolites from the chloroplast stroma into the cytoplasm, it is suggested that sucrose is degraded in the cytoplasm, via glycolysis, to triose phosphates which cross the amyloplast membrane by means of a phosphate translocator. It is further postulated that hexose phosphates and sugars are produced from the triose phosphates in the amyloplast stroma by gluconeogenesis with starch being formed from glucose 1-phosphate via pyrophosphorylase and starch synthase enzymes. The glucose 1-phosphate to inorganic phosphate ratio in the granule preparation was such that starch synthesis by phosphorylase is highly unlikely in maize endosperm.

Journal Article↗