[Non-pharmacological treatment of arrhythmia]

During the past decade, a variety of innovative procedures and devices for non-pharmacological treatment of tachyarrhythmias have been proposed. Recent improvements in the implantable cardioverter/defibrillators and transcatheter ablative techniques have resulted in a revolution of the therapeutic approach in ventricular and supraventricular tachyarrhythmias, respectively, providing a valuable alternative to conventional antiarrhythmic surgery. Indeed, the selection criteria for surgery for tachyarrhythmias have been revised, and this therapeutic option is considered appropriate only for selected patients with postinfarction ventricular tachycardia. Ther implantable cardioverter/defibrillator has proved effective in conversion of life-threatening tachyarrhythmias, leading a dramatic decrease in the incidence of sudden death in high risk subjects. Thus, with further refinements, a wide use of this therapeutic modality can be anticipated. Transcatheter ablation has become the first-line option in the most common forms of supraventricular tachycardias, such as accessory pathway-mediated tachycardia and AV nodal reentry. More recently, encouraging results of this technique in common atrial flutter and ectopic atrial tachycardia have been reported, although confirmation with larger series and longer follow-up is needed. In general, results of catheter ablation in ventricular tachycardia have been disappointing, with the exception of bundle branch reentry and idiopathic ventricular tachycardia, in which a high success rate is reported. An increasingly important role of these therapeutic modalities is expected. In the meanwhile, due to their evolutional character and the specific competence required for their use, such procedures should be performed exclusively in well trained centers.

[The applied anatomy of human right posterior hepatic veins]

The right posterior hepatic veins (RPHV) were investigated using the stripped specimens of 55 cadaver adult livers and the corrosion casts of portal and hepatic venous system of 45 embryos and newborns. RPHV were found in 88 livers (88%). RPHV of 6 livers (6%) was thicker than the right hepatic vein. There were 4 types of RP-HV and they could be grouped under three anatomical locations: superior, intermedial and inferior RPHV. According to our observation, RPHV with calibre more than 0.50 cm was mainly in the group of inferior RPHV (72%). RPHV in 23 (41.82%) adult livers had extrahepatic course with a Length of 1.72 +/- 0.88 cm. The application of RPHV in hepatectomy and image diagnosis was also discussed.

[Prediction of one second forced expiratory volume after lung resection using multiple view lung perfusion images and "regions of interest" quantitative analysis]

In 17 patients mostly with bronchial carcinoma undergoing pneumonectomy (N = 2) or lobectomy (N = 15) multiple view lung perfusion images with 99mTc-MAA and "regions of interest" quantitative analysis of functional distributions to each lung or lobe (MV-ROI) were used for predicting postoperative FEV1. For comparison, other two methods were also conducted, i.e. the split function study by lung perfusion images combined with subtraction of segmental function (SF+SS) and the simple subtraction of segmental function (SSS). The correlation between predicted postoperative FEV1 and actual FEV1 measured 3-6 months after lung resection was better by MV-ROI method than by the other two. In all patients the correlation coefficient (r) was 0.957, 0.923 and 0.887 by three methods respectively; in lobectomy patients the (r) was 0.948, 0.907 and 0.869 by three methods respectively (all P less than 0.001). The mean error (liters), mean percent error and median of percent error between predicted and observed FEV1 in MV-ROI were less than in SF+SS or SSS. The difference between error of MV-ROI and error of SF+SS or SSS was significant, while the difference between error of SF+SS and error of SSS was insignificant. The number of cases having the error greater than 10% was 3,5,8 in all patients and 3,5,7 in lobectomy patients by three methods respectively. There was a tendency of overestimation in MV-ROI, which was attributed to the old age of our patients whose pulmonary functions recovered slowly and to the short period of the follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of apolipoprotein B-100 of human low density lipoproteins

We have analyzed low density lipoproteins (LDL) apolipoprotein (apop) B structure by direct sequence analysis of LDL apo B-100 tryptic peptides. Native LDL were digested with trypsin, and the products were fractionated on a Sephadex G-50 column. The partially digested apo B-100 still associated with lipids was recovered in the void volume (designated trypsin-nonreleasable, TN, peptides). The released peptides (designated trypsin-releasable, TR, peptides) in subsequent peaks were repurified on two successive high-performance liquid chromatography (HPLC) columns. The TN peak was delipidated and redigested with trypsin, and the resulting peptides were purified on two successive HPLC columns. Using this approach, we sequenced over 88% of LDL apo B-100, extending and refining our previous study (Nature 1986;323:738-742) which covered 52% of the protein. TN peptides made up 31%, and the TR peptides, 34% of the apo B-100 sequence; 23.7% were found under both TN and TR categories. Based on its differential trypsin releasability, apo B-100 can be divided into five domains: 1) residues 1----1000, largely TR; 2) residues 1001----1700, alternating TR and TN; 3) residues 1701----3070, largely TN; 4) residues 3071----4100, mainly TR and mixed; and 5) residues 4101----4536, almost exclusively TN. Domain 1 contained 14 of the 25 Cys residues in apo B. Domain 4 encompassed seven N-glycosylation sites, and contained the putative receptor binding domains. All 19 potential N-glycosylation sites were directly sequenced: 16 were found to be glycosylated and three were not. Three pairs of disulfide bridges were also mapped. Finally, a combination of cDNA sequencing, direct mRNA sequencing, and comparison of published apo B-100 sequences allowed us to identify specific amino acid residues within apo B-100 that seem to represent bona fide allelic variations. Our study provides information on LDL apo B-100 structure that will be important to our understanding of its conformation and metabolism.

Human hepatic lipase. Cloned cDNA sequence, restriction fragment length polymorphisms, chromosomal localization, and evolutionary relationships with lipoprotein lipase and pancreatic lipase

Human hepatic lipase is an important enzyme in high density lipoprotein (HDL) metabolism, being implicated in the conversion of HDL2 to HDL3. Three human hepatic lipase cDNA clones were identified in two lambda gt11 libraries from human liver. The cDNA-derived amino acid sequence predicts a protein of 476 amino acid residues, preceded by a 23-residue signal peptide. Four potential N-glycosylation sites are identified, two of which are conserved in rat hepatic lipase. On alignment with human, mouse, and bovine lipoprotein lipase, the same two sites were also conserved in lipoprotein lipase in all three species. Stringent conservation of the cysteine residues was also evident. Comparative analysis of amino acid sequences shows that hepatic lipase evolves at a rapid rate, 2.07 x 10(-9) substitutions/site/year, about four times that in lipoprotein lipase and half that in pancreatic lipase. Further, hepatic lipase and pancreatic lipase appear to be evolutionarily closer to each other than either of them is to lipoprotein lipase. Southern blot analysis revealed high frequency restriction fragment length polymorphisms of the hepatic lipase gene for the enzymes HindIII and MspI. these polymorphisms will be useful for haplotype and linkage analysis of the hepatic lipase gene. Using cloned human hepatic lipase cDNA as a hybridization probe, we performed Southern blot analysis of a panel of 13 human-rodent somatic cell hybrids. Concordance analysis of the various hybrid clones indicates that the hepatic lipase gene is located on the long arm of human chromosome 15. Analysis of hybrids containing different translocations of chromosome 15 localized the gene to the region 15q15----q22.

Construction and characterization of a library of metallothionein coding sequence mutants

New possibilities for experimental investigation of the metallothionein system at the DNA, RNA, and protein levels are now available via a library of metallothionein coding sequence mutants. Appropriate treatment in vitro with sodium bisulfite of the sense or antisense DNA strands in M13 phage vectors and propagation in Escherichia coli BD1528 (ung-) produced two unique collections in the library containing either C to T or G to A transition mutations in the codons at low and high frequencies. The strategy for mutagenesis takes advantage of degeneracy in the genetic code so that no cysteine codons are replaced in the CT mutants while all are subject to change in the GA collection. Two hundred and sixty-four clones from the library have been sequenced and G to A transitions affecting each of the 20 cysteine codons in metallothionein have been detected. Other mutations in codons for amino acids proposed to be important for metallothionein function have also been identified.

Purification and characterization of Escherichia coli guanine-xanthine phosphoribosyltransferase produced by a high efficiency expression plasmid utilizing a lambda PL promoter and CI857 temperature-sensitive repressor

The gene for Escherichia coli guanine-xanthine phosphoribosyltransferase was placed after the high efficiency lambda phage leftward promoter in plasmid pHEGPT also containing the lambda CI857 temperature-sensitive repressor. Guanine-xanthine phosphoribosyltransferase increases 780-fold when cells containing pHEGPT are shifted from 30 to 42 degrees C. Guanine-xanthine phosphoribosyltransferase represents approximately 5% of the protein in a crude extract of induced cells. Guanine-xanthine phosphoribosyltransferase may be purified to apparent homogeneity by ammonium sulfate fractionation, Sephadex G-100, and DEAE-cellulose column chromatography. The enzyme has a subunit molecular weight of 18,600 determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and behaves as a trimer during Sephadex G-100 column chromatography. Guanine-xanthine phosphoribosyltransferase is active from pH 7.5 to 10.5 with maximum activity at pH 9.5. The enzyme is protected from heat inactivation by phosphoribosylpyrophosphate (PRPP). At 65 degrees C, the enzyme has a half-life of 2 min in the absence of PRPP and 90 min in the presence of PRPP. The enzyme displays Michaelis-Menten kinetics with apparent Michaelis constants for guanine, xanthine, hypoxanthine, and PRPP of 2.6, 39, 167, and 95 microM, respectively. The activity of the enzyme with guanine is 2-fold greater than that with xanthine and 3-fold greater than that with hypoxanthine.