PubMed Health⌕ Search

Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 1,009 records · Page 56Linked to original sources
PubMed1988

The effects of a mandatory child restraint law on injuries requiring hospitalization.

Using data on all inpatients in 16 Michigan hospitals from 1980 through 1985, the clinical effects of a mandatory child restraint law were examined. Time-series analytic techniques revealed a 36% decline in hospitalization for all injuries, with a 25% decline for head injuries, and a 20% decline for extremity injuries for children younger than 4 years. In addition, length of stay declined for children hospitalized secondary to motor vehicle crashes. This study confirms the effectiveness of the child restraint law in Michigan, previously demonstrated by analyses of police records. Current hospital databases may be able to serve as one component for the implementation of comprehensive injury surveillance systems.

Accidents, Traffic↗
PubMed1988

Molecular cloning and sequencing of DNA complementary to chicken liver fatty acid synthase mRNA.

The cDNA corresponding to 4.18 kilobases (kb) of the mRNA of chicken liver fatty acid synthase has been cloned and sequenced. The cDNA corresponds to the 3' end of the mRNA and consists of a 1.87-kb noncoding tail and a 2.31-kb region encoding 769 amino acids of the C terminus of the enzyme. The thioesterase at the C terminus, preceded by the acyl carrier protein, can be identified from known amino acid sequences. However, the identity of the enzymes N terminal to the acyl carrier protein could not be ascertained. The partial amino acid sequence of the chicken liver fatty acid synthase shows greater than 70% similarity with the rat mammary gland enzyme.

Amino Acid Sequence↗
PubMed1988

Mechanism of action of Escherichia coli heat stable enterotoxin in a human colonic cell line.

Escherichia coli heat stable enterotoxin (STa) caused Cl- secretion across T84 cell monolayers in a dose-dependent manner only when applied to the apical membrane surface and not when applied to the basolateral surface. Measurement of cAMP, cGMP, and free cytosolic Ca2+ in response to STa suggested that cGMP alone mediated the Cl- secretory response. Studies utilizing blockers of the Na+,K+-ATPase pump, a Na+,K+,Cl- cotransport system, a K+ channel, and a Cl- channel suggest that all of them participate in the Cl- secretory process induced by STa. The results suggest that the Cl- secretory response induced by STa is mediated by cGMP after the enterotoxin binds to its receptor on the apical membrane. The enterotoxin, by increasing cGMP, opens a K+ channel on the basolateral membrane as well as a Cl- channel on the apical membrane. The activation of these ion exit mechanisms, together with activations of the Na+,K+,Cl- cotransporter and the Na+,K+-ATPase pump drives Cl- exit through the Cl- channel on the apical membrane.

Bacterial Toxins↗
PubMed1987

Activity change during unfolding of bovine pancreatic ribonuclease A in guanidine.

Bovine pancreatic ribonuclease A loses almost completely its activity in 2-3 M guanidine, whereas only very slight conformational changes can be detected when following its unfolding by changes in its intrinsic fluorescence at 305 nm and ultraviolet absorbance at 287 nm. Reactivation on diluting out the denaturant is a time-dependent process, indicating that the inactivation is not due to inhibition by a reversible association of the enzyme with guanidine. The kinetic method of following the substrate reaction, in the presence of the denaturant previously proposed for use in the study of rapid inactivation reactions (Tian, W.X. and Tsou, C.-L. (1982) Biochemistry 21, 1028-1032), is applied to examine the inactivation rates of this enzyme during guanidine denaturation, and these have been compared with the unfolding rates as followed by fluorescence and absorbance changes. It is shown that during the unfolding of this enzyme in guanidine, the inactivation of the enzyme occurs within the dead time of mixing in a stopped-flow apparatus and is at least several orders of magnitude faster than the unfolding reaction as detected by the optical parameters. It appears that, as in the case of creatine kinase reported previously, the active site of a small enzyme stabilized by multiple disulfide linkages, such as ribonuclease A, is also situated in a region which is much more liable to being perturbed by denaturants than is the molecule as a whole.

Algorithms↗
PubMed1987

Kinetics of reactivation during refolding of guanidine-denatured pancreatic ribonuclease A.

The method aforementioned (Liu, W. and Tsou, C.L. (1987) Biochim. Biophys. Acta 916, 455-464) for the study of the kinetics of irreversible modification of enzyme activity has been applied to the reactivation of guanidine-denatured ribonuclease A, by following the hydrolysis of cyclic CMP during refolding upon diluting a guanidine-denatured enzyme with a substrate-containing buffer. Appropriate equations have been derived to deal with the kinetics of the substrate reaction during the course of activation, while the product formed, 3'CMP, is a competitive inhibitor. When the overall process consists of multiple first-order reactions, the individual rate constants could be obtained by suitable semilogarithmic plots. Moreover, in certain cases, it can be distinguished from the shapes of the plots, whether the overall process consists of parallel or consecutive first-order reactions. The kinetics for the reactivation reaction has been compared to that for the refolding of the substrate binding site, as indicated by complex formation with the competitive inhibitor, 2'CMP, and for the refolding of the molecule as a whole. At pH 6.0 and 25 degrees C, only monophasic first-order reactions could be detected by manual mixing for both the reactivation and the refolding processes. At lower temperatures (0-10 degrees C), both processes consist of two first-order reactions. In all cases, the same rate constants have been obtained for the refolding and reactivation reactions.

Algorithms↗
PubMed1987

Diferric transferrin reduction stimulates the Na+/H+ antiport of HeLa cells.

Proton release from HeLa cells is stimulated by external oxidants for the transplasmalemma electron transport enzymes. These oxidants, such as ferricyanide and diferric transferrin, also stimulate cell growth. We now present evidence that proton release associated with the reduction of ferricyanide and diferric transferrin is through the Na+/H+ antiport. The stoichiometry of H+/e- release with diferric transferrin is over 50 to 1, which is greater than expected for oxidation of a protonated transmembrane electron carrier. Diferric transferrin induced proton release depends on external sodium and is inhibited by amiloride. Proton release is also inhibited when diferric transferrin reduction is inhibited by apotransferrin. A tightly coupled association between the redox system and the antiport is shown by sodium dependence and amiloride inhibition of diferric transferrin reduction. The results indicate a new role for ferric transferrin in growth stimulation by activation of the sodium-proton antiport.

Carrier Proteins↗
PubMed1987

Effect of (D-Trp6, Pro9-NEt)-GnRH on the function and ultrastructure of pituitary and testis in male rats.

Groups of ten adult male Wistar rats were treated chronically with GnRH agonist for different durations. The responses of pituitary and testis to GnRH agonist were evaluated by serum and testicular testosterone, serum and pituitary LH, and testicular LH receptors. Testicular testosterone and LH receptors were decreased very significantly under our experimental regimen, irrespective of the duration of the treatment Serum testosterone levels were reduced after 10 and 15 injections, but only rats receiving 10 injections showed a significant increase in serum LH levels and decrease of pituitary LH content. The type II gonadotropes of the pars distalis of pituitary were increased in number but showed a higher degree of dilated smooth endoplasmic reticulum with few secretory granules. Many large lipid droplets appeared in the cytoplasms of the Leydig cells. Degenerative changes were observed in most seminiferous tubules following GnRH agonist treatment. Obvious abnormal acrosome and nuclear caps of some spermatids were also observed. The functional changes caused by GnRH agonist coincided with their ultrastructural appearance.

Animals↗
PubMed1986

Determination of rate constants for the irreversible inhibition of acetylcholine esterase by continuously monitoring the substrate reaction in the presence of the inhibitor.

The kinetics of the irreversible inhibition of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) by diisopropyl fluorophosphate and paraoxon have been studied by the approach of following the substrate reaction continuously in the presence of both the substrate and the inhibitor based on kinetic equations previously derived (Tsou, C.-L. (1965) Acta Biochim. Biophys. Sinica 5, 387-417). From determinations of the effects of different concentrations of substrate and the inhibitors on the apparent rate constants for the irreversible inhibition reactions it can be shown that these inhibitors are of the competitive complexing type. Both the reversible dissociation constant for the enzyme inhibitor complex and the rate constant for the subsequent phosphorylation step can be obtained from suitable plots of the experimental data.

Acetylcholinesterase↗