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Biomedical subjects

Y Ku

Publications and source records attributed to Y Ku.

At least 181 records · Page 10Linked to original sources
PubMed1985

Uptake, translocation, and transformation of pentachlorophenol in soybean and spinach plants.

Soybean plants were grown for 90 days and spinach plants for 64 days in a mixture of sterilized greenhouse soil and sand containing 10 ppm pentachlorophenol. All plant parts and soil samples were extracted and separated into nonpolar and polar fractions. Major nonpolar and polar metabolites were identified by gas-liquid chromatography and mass spectrometry. Nonpolar fractions from both soybean and spinach plants were found to contain pentachlorophenol and its metabolites, 2,3,4,6-tetrachlorophenol, methoxytetrachlorophenol, 2,3,4,6-tetrachloroanisole, and pentachloroanisole. Cleavage of polar metabolites from the soybean plants by acid hydrolysis yielded organic solvent-extractable products. These products were identified as pentachlorophenol, 2,3,4,6-tetrachlorophenol, and methoxytetrachlorophenol. Cleavage of polar materials from spinach plants yielded only pentachlorophenol. The polar metabolites from the soybean plants were also subjected to enzymatic cleavage by beta-glucosidase. The conjugates consisted mostly of O-glucosides of the same metabolites released by acid hydrolysis. Failure of hydrolysis by aryl sulfatase indicated that very little or no sulfates were present. The metabolites found in the plants were not detected in soil samples obtained from pots immediately after the plants were harvested.

Biotransformation↗
PubMed1983

Screening of fresh water fish extracts for enzyme-inducing substances by an aryl hydrocarbon hydroxylase induction bioassay technique.

A sensitive biological test to detect the presence of certain contaminants, such as highly toxic halogenated dioxins, dibenzofurans, and biphenyls in foods, was applied to extracts of fresh water fish that had been prepared by a food extraction-cleanup procedure developed by the Food and Drug Administration for pesticides and industrial chemicals. Aryl hydrocarbon hydroxylase (AHH) activity in a rat hepatoma cell line was used as the biological detection system for residues that induce enzyme activity. The induction of AHH activity by the extracts was compared with a standard AHH-induction curve for the most active compound known, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and results were computed as TCDD equivalents. Several dilutions of fish extracts were used to produce AHH-induction curves from which an optimal dose-response range was determined and used to estimate TCDD equivalents. Cleaned-up extracts of fish obtained from different water bodies in the United States were examined for AHH activity. The samples which had low levels of polyhalogenated contaminants produced low biological activity, while a higher activity was obtained from fish that contained higher levels of polyhalogenated contaminants. The results suggest that the fish extracts can be screened for AHH inducers before chemical analysis.

Animals↗
PubMed1982

Biodegradation of [C]Tri-p-Cresyl Phosphate in a Laboratory Activated-Sludge System.

Biodegradation of [C]tri-p-cresyl phosphate was studied in a laboratory model sewage treatment system to develop information on the nature of its transformation products. In 24-h experiments, 70 to 80% of tri-p-cresyl phosphate added at the 1-mug/ml level was degraded. The remaining parent compound was associated with the sludge solids. The major metabolite extracted with ethyl ether from the aqueous phase was identified as p-hydroxybenzoic acid by gas chromatography-mass spectrometry. Two unstable ether-extractable metabolites were not identified. The half-life of [C]tri-p-cresyl phosphate was estimated to be 7.5 h.

Journal Article↗
PubMed1981

A new possible regulatory system for protein phosphorylation in human peripheral lymphocytes. II. Possible relation to phosphatidylinositol turnover induced by mitogens.

Ca++-activated, phospholipid-dependent protein kinase present in human peripheral lymphocytes requires a small amount of diacylglycerol in addition to phospholipid, particularly at lower concentrations of Ca++. It is necessary that such diacylglycerol contain unsaturated fatty acid at least at position 2. Saturated diacylglycerols such as dipalmitin and distearin are far less effective. Kinetic analysis indicates that unsaturated diacylglycerol greatly increases the apparent affinity of the enzyme for phospholipid, and sharply decreases the Ca++ concentration to the micromolar range that gives rise to the maximum enzyme activation. Among various phospholipids tested, phosphatidylserine is most active in supporting enzymatic activity. Phosphatidylinositol and phosphatidylethanolamine are less effective. Phosphatidylcholine, phosphatidic acid, sphingomyelin, and lysophosphatidylcholine are inert. It is most likely, therefore, that various lymphocyte mitogens induce specific hydrolysis of phosphatidylinositol to produce such an active unsaturated diacylglycerol, which in turn serves as a second messenger for the selective activation of this unique protein kinase. Dibucaine and chlorpromazine appear to interact with phospholipid and thereby inhibit the activation process of this enzyme. Cyclic nucleotide-dependent protein kinases are not susceptible to these phospholipid-interacting drugs.

Chlorpromazine↗
PubMed1980

Multiplicity of phosphate acceptor proteins for muscle glycogen phosphorylase kinase.

Although muscle glycogen phosphorylase kinase reacts preferentially with an inactive form of phosphorylase, the enzyme is able to phosphorylate in vitro multiple species of unidentified endogenous proteins in mammalian tissues such as liver. The reactions absolutely require Ca2+. Phosphate acceptor proteins are most abundant in the soluble and microsomal fractions. Sodium lauryl sulfate-slab gel electrophoresis analysis has revealed that the spectrum of phosphate acceptor proteins entirely differs from that for cyclic AMP-dependent protein kinase, although the biological significance of these reactions is unclear. Nevertheless, it is suggested that the enzyme is potentially multifunctional and plays roles in controlling some of the Ca2+-dependent processes. In contrast, myosin light chain kinase which is another species of calmodulin-dependent protein kinase seems to be strictly specific for this particular protein, and does not utilize any other endogenous protein so far tested.

Animals↗
PubMed1979

A comment on the functional specificities of cyclic AMP-dependent and cyclic GMP-dependent protein kinases.

Cyclic AMP-dependent and cyclic GMP-dependent protein kinases (protein kinases A and G, respectively) utilize the same phosphate acceptor proteins when assayed in in vitro systems. Nevertheless, protein kinase A phosphorylates preferentially free histone, whereas protein kinase G greatly favors the histone which is associated with polydeoxyribonucleotide. On the other hand, when cytoplasmic soluble substrates such as phosphorylase kinase are used, the reactions are always more favorable for protein kinase A rather than for protein kinase G. Available evidence implies that the topographic relationship between enzyme and substrate may be an important determining factor for the functional specificities of these two classes of protein kinases.

Cyclic AMP↗
PubMed1978

Comparative effects of feeding lead acetate and phospholipid-bound lead on blood and tissue lead concentrations in young and adult rats.

Two different forms of lead, lead acetate and phospholipid-bound lead, were fed to young and adult male rats for 10 weeks at the 300 ppm dietary level. Based on the lead concentrations found in selected tissues, our results indicate that the bioavailability of phospholipid-bound lead is similar to that of lead acetate at the 300 ppm level. Young rats had higher concentrations of lead in tissues than did adult rats.

Aging↗
PubMedDate not supplied

Measurement of sugars and starches in foods by a modification of the AOAC total dietary fiber method.

A separation scheme for the determination of sugars and starch in processed food was developed. It is based on AOAC Method 985.29 for total dietary fiber with these modifications: carbohydrate starches are separated into soluble and insoluble fractions before they are hydrolyzed; acetonitrile is used instead of ethanol to separate sugars from enzyme-resistant carbohydrates, proteins, and other macromolecules; and a solid-phase extraction filter is included to remove substances that interfere with high-performance liquid chromatography (HPLC). Recovery studies indicate a > 97% sugar recovery. Twenty foods were analyzed. After enzymatic hydrolysis, fructose, glucose, sucrose, maltose, and lactose were extracted and determined by HPLC using a refractive index detector. Starch content was calculated from the increase in the amount of glucose. The results were compared with values listed on the "Nutrition Facts" panel for that food. The analyzed amounts of sugars and starches were 73-96% of declared values.

Acetonitriles↗