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T L Wu

Publications and source records attributed to T L Wu.

At least 109 records · Page 6Linked to original sources
PubMed1982

Purification and properties of pyruvate dehydrogenase phosphatase from bovine heart and kidney.

Pyruvate dehydrogenase phosphatase was purified to apparent homogeneity from bovine heart and kidney mitochondria. The phosphatase has a sedimentation coefficient (S20,w) of about 7.4 S and a molecular weight (Mr) of about 150 000 as determined by sedimentation equilibrium and by gel-permeation chromatography. The phosphatase consists of two subunits with molecular weights of about 97 000 and 50 000 as estimated by sodium dodecyl sulfate--polyacrylamide gel electrophoresis. Phosphatase activity resides in the Mr 50 000 subunit, which is sensitive to proteolysis. The phosphatase contains approximately 1 mol of flavin adenine dinucleotide (FAD) per mol of protein of Mr 150 000. FAD is apparently associated with the Mr 97 000 subunit. The function of this subunit remains to be established. The phosphatase binds 1 mol of Ca2+ per mol of enzyme of Mr 150 000 at pH 7.0, with a dissociation constant (Kd) of about 35 microM as determined by flow dialysis. Use of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate (EGTA) at pH 7.6 in conjunction with flow dialysis gave a Kd value for Ca2+ of about 8 microM. In the presence of both the phosphatase and the dihydrolipoyl transacetylase (E2) core of the pyruvate dehydrogenase complex, two equivalent and apparently non-interacting CA2+-binding sites were detected per unit of Mr 150 000, with a Kd value of about 24 microM in the absence and about 5 microM in the presence of EGTA. In the presence of 0.2 M KCl, which inhibits phosphatase activity about 95%, the phosphatase exhibited only one Ca2+-binding site, even in the presence of E2. The phosphatase apparently possesses an "intrinsic" Ca2+-binding site, and a second Ca2+-binding site is produced in the presence of E2. The second site is apparently altered by increasing the ionic strength. It is proposed that the second site may be at the interface between the phosphatase and E2, with Ca2+ acting as a bridging ligand for specific attachment of the phosphatase to E2.

Animals↗
PubMed1982

Effect of atropine on escape mechanism of the subsidiary pacemakers in patients with dysfunction of the sinus node.

Effects of intravenous atropine on postpacing impulse recovery time of the subsidiary pacemakers were studied by incremental atrial pacing in 9 patients with sinus nodal (SN) dysfunction. Patients having either or both of the following anomalies are used: 1) persistent sinus bradycardia (sinus cycle length greater than 1000 msec), or documented episodes of sinoatrial block or arrest and/or 2) maximum corrected SN recovery time of longer than 525 msec before and after atropine. Seven patients had a history of cerebral ischemic symptoms. The mean +/- SEM of the maximum A-V junctional recovery times (MJRTs) before and after atropine, measured in 5 patients, were 2,485 +/- 825 msec and 1,164 +/- 281 msec, respectively (p less than 0.01). The average percent reduction of the junctional escape times in these 5 patients was 53.2%. In all 9 patients MJRT shortened to less than 1,610 msec after atropine. Moreover, a low atrial pacemaker also was the escape mechanism following pacing in 2 patients after atropine; the maximum atrial recovery times were 2,500 msec and 1,220 msec, respectively. We conclude that atropine can markedly enhance escape mechanism of the subsidiary pacemakers in patients with SN dysfunction.

Adult↗