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Biomedical subjects

C Wu

Publications and source records attributed to C Wu.

At least 559 records · Page 31Linked to original sources
PubMed1985

Behavioral and emotional factors and treatment responses in a study of anovulatory infertile women.

In a controlled treatment study of 49 anovulatory infertile women, responses to clomiphene citrate (CC) and placebo treatments were compared and associations of behavioral and emotional factors with treatment responses were investigated. In the first treatment series, ovulation occurred in 20 of 24 women in the CC group and 8 of 22 women in the placebo group. Pregnancy was achieved by 11 women during CC treatment and 3 women during placebo treatment. Overall, 28 women completed the protocol and 21 withdrew. Those who achieved pregnancy (n = 14) did not differ significantly from the ovulation-only group (n = 22) on pretreatment measures of emotional, behavioral, and personality factors including the Hopkins Symptom Checklist (HSCL-90), Eysenck Personality Inventory, Langner Screening Scale, Mood Analog Scale, Social Adjustment Scale, Mooney Problem Checklist, and the Minnesota Multiphasic Personality Inventory (MMPI). Conclusions were that a placebo response was observed in both ovulation and pregnancy, but psychologic factors as measured in this sample were not associated with these treatment outcomes.

Adult↗
PubMed1985

Electron microscopic evidence for externalization of the transferrin receptor in vesicular form in sheep reticulocytes.

Using ferritin-labeled protein A and colloidal gold-labeled anti-rabbit IgG, the fate of the sheep transferrin receptor has been followed microscopically during reticulocyte maturation in vitro. After a few minutes of incubation at 37 degrees C, the receptor is found on the cell surface or in simple vesicles of 100-200 nm, in which the receptor appears to line the limiting membrane of the vesicles. With time (60 min or longer), large multivesicular elements (MVEs) appear whose diameter may reach 1-1.5 micron. Inside these large MVEs are round bodies of approximately 50-nm diam that bear the receptor at their external surfaces. The limiting membrane of the large MVEs is relatively free from receptor. When the large MVEs fuse with the plasma membrane, their contents, the 50-nm bodies, are released into the medium. The 50-nm bodies appear to arise by budding from the limiting membrane of the intracellular vesicles. Removal of surface receptor with pronase does not prevent exocytosis of internalized receptor. It is proposed that the exocytosis of the approximately 50-nm bodies represents the mechanism by which the transferrin receptor is shed during reticulocyte maturation.

Animals↗
PubMed1984

Age-related irreversible decrease in glutamine synthetase following liver cell proliferation.

The apparently permanent decrease in glutamine synthetase activity following partial hepatectomy in young adult rats has been studied further to include weanling and aged rats and other procedures that induced liver cell proliferation. In contrast to young adult rats, partial hepatectomy in weanling and aged rats did not produce a lasting decrease in liver glutamine synthetase activity. In addition to the surgical procedure, dietary regimentation and CCl4 poisoning also resulted in a lasting decrease in the liver enzyme in young adult rats. The enzyme activity present exclusively in the parenchymal cells of the liver declined progressively following each successive surgical operation. A combination of these procedures may be applicable to the production of a liver parenchymal cell line essentially devoid of the enzyme activity.

Aging↗
PubMed1983

Indomethacin inhibition of glutathione S-transferases.

Indomethacin inhibited rat liver glutathione S-transferases (EC 2.5.1.18). Its inhibition was non-competitive with respect to 3,4-dichloronitrobenzene with an apparent Ki of 5.3 X 10(-5) M and uncompetitive with respect to glutathione with an apparent Ki of 4.0 X 10(-5) M. 4-Chlorobenzoic acid and 5-methoxy-2-methylindole-3-acetic acid, two metabolites of indomethacin, were weak inhibitors of the enzymes. On the other hand, meclofenamic acid was a competitive inhibitor of the enzymes with an apparent Ki of 3.0 X 10(-4) M. Possible significance of these findings in arachidonic acid metabolism is discussed.

Animals↗
PubMed1982

Nucleoside phosphorothioates as probes of the nucleotide binding site of brain pyridoxal kinase.

N-Dansyl-2-oxopyrrolidine, a competitive inhibitor with respect to ATP, was used as a probe of the nucleotide binding site of pyridoxal kinase. It binds to an hydrophobic region of the catalytic site with a KD = 6 microM. Time emission anisotropy measurements yielded a rotational correlation time of 38 ns for the bound inhibitor. N-Dansyl-2-oxopyrrolidine is immobilized by strong interactions with the nucleotide binding site. Protein fluorescence quenching was used to determine the dissociation constants of the diastereomers of ATP beta S. Both diastereomers bind with a dissociation constant KD = 25 microM. The kinetic parameters Km and Vmax for the pyridoxal kinase reaction were determined for ATP and the diastereomers of ATP beta S in the presence of Mg(II), Co(II), Zn(II), and Cd(II). With Mg(II), pyridoxal kinase exhibits stereoselectivity for the A diastereomer of ATP beta S, Vmax ratio, A/B = 30. In the presence of Cd(II), the stereoselectivity is reversed and the B diastereomer of ATP beta S is the preferred substrate. As the divalent cations were varied in the series Mg(II), Co(II), Zn(II), and Cd(II), the A/B ratio was progressively lowered to the value of 0.2 found for Cd(II). These data indicate that the divalent cations coordinate to the beta-phosphate group of the nucleoside triphosphate substrates. The results obtained with the diastereomers of ATP alpha S suggest that pyridoxal kinase uses the divalent cation, delta,beta,gamma-bidentate nucleotide chelate as substrate.

Adenosine Triphosphate↗
PubMed1982

Isolation of platelet glycocalicin by affinity chromatography on thrombin-sepharose.

Platelet glycocalicin has been purified to homogeneity by a two step procedure involving affinity chromatography on WGA-Sepharose and then on thrombin-Sepharose using selective elution with heparin. The procedure is more rapid (3-4 days), more reproducible and gives about twice the yield (10 mg/40 units platelets) of the previous method (Okumura et al. J. Biol. Chem. 251, 5950-5955, 1976). The two preparations showed identical inhibition of aggregation of gel filtered platelets induced by thrombin and by ristocetin. Glycocalicin was cleaved in a controlled fashion by trypsin-Sepharose over 3hr to yield the macroglycopeptide and peptide "tail" fragments and there was no apparent further degradation with 18 hrs digestion.

Blood Platelets↗
PubMed1982

Effect of chronic irradiation of 60Co-gamma-ray at low dose rate on rhesus monkey - effect on peripheral blood and testis.

The authors have demonstrated that after a long-term chronic irradiation of 2.17 rad/day for 2 months, the testis of the experimental monkey (Macaca mulatta) is extremely atrophied with a loss of reproductive ability. But the effect on peripheral blood is not apparent even after irradiation for 57 months. It should be noted that rhesus monkeys, being as sensitive to irradiation and similar in evolutionary steps as human beings, could be used as experimental animals to further study the dose rate for aspermatogenesis, the morphological injuring effect on the reproductive system and the cytogenetic effect of irradiation, and this is highly important to working out a standard of promised dose of irradiation for X-ray workers and an index or radiation protection monitoring.

Animals↗
PubMed1981

Brain pyridoxal kinase. Mechanism of substrate addition, binding of ATP, and rotational mobility of the inhibitor pyridoxaloxime.

The inhibition kinetic patterns obtained when ATP and pyridoxal analogues are used as inhibitors of the reaction catalyzed by pyridoxal kinase are consistent with a rapid equilibrium random Bi Bi, in which binary complexes, i.e. enzyme . ATP and enzyme . pyridoxal, are formed in kinetically significant amounts. Protein fluorescence quenching was used to determine the dissociation constant (Kd = 25 microM) of ATP . Zn bound to the nucleotide site of the kinase. The binding of ATP to the kinase induces a conformational change which is transmitted to other areas of the macromolecule. Pyridoxaloxime, a competitive inhibitor of pyridoxal, was used as a probe of the pyridoxal-binding site. It binds to the kinase with Ki = 2 microM and displays a fluorescent decay time of 7.8 ns. Time emission anisotropy measurements yield a rotational correlation time for bound pyridoxaloxime of approximately 2 ns, which is considerably shorter than the rotational correlation time of the protein (phi = 38 ns). The fast rotation of pyridoxaloxime remains unaffected by the binding of ATP.

Adenosine Triphosphate↗
PubMed1981

Tissue-specific exposure of chromatin structure at the 5' terminus of the rat preproinsulin II gene.

The 5' terminus of the rat preproinsulin II gene exhibits a tissue-dependent DNase I sensitivity. Only in the chromatin froma pancreatic beta-cell tumor, but not in liver, spleen, kidney, or brain chromatin, is a region at and before the 5' end of the gene exposed to cleavage. The region of exposure extends 250-300 base pairs upstream from the 5' terminus of the preproinsulin mRNA. Such a region may allow control sequences special access to regulatory proteins.

Adenoma, Islet Cell↗
PubMed1980

The distribution of collagen:glucosyltransferase in human blood cells and plasma.

Collagen:glucosyltransferase (UDP-glucose:5-hydroxylysine-collagen glucosyltransferase, EC 2.4.1.66) present in platelets, plasma, granulocytes and lymphocytes has been compared in order to determine whether the platelet enzyme has unique properties or distribution which would support a possible role in platelet-collagen interaction. The enzyme was purified 5400-fold from human plasma and 4400 from human platelets. The two enzymes were similar in terms of Km values for reacting with galactosylhydroxylysine (2.75 mM) and UDPglucose (7.4 microM), optimal Mn2+ concentration (10--15 mM) and pH optimum (7.0). The enzyme was not detectable in red cells. As in platelets, the enzyme was detected in membrane-bound and soluble forms in lymphocytes and granulocytes. Identical mobilities were obtained after elution following polyacrylamide gel electrophoresis of the enzymes from plasma, platelets, granulocytes and lymphocytes. These studies do not support a unique role for the collagen:glucosyltransferase of platelets in platelet-collagen interaction.

Blood Platelets↗