眼镜蛇科蛇毒对S180,EAC腹水癌治疗作用研究

本文报道金环蛇、扁颈蛇、眼镜蛇、银环蛇蛇毒及其细胞毒对小鼠S180,EAC腹水癌的治疗作用。结果表明,蛇毒及其细胞毒在体外有明显杀灭癌细胞作用,体内有较明显的治疗作用,动物存活时间延长,接种率降低。肿瘤细胞呈现不同程度形态变化,主要为膜破裂,坏死等。治疗效应由强到弱为金环蛇毒,扁颈蛇毒,金环蛇细胞毒,眼镜蛇毒,眼镜蛇细胞毒。银环蛇毒无作用。     

Studies on compound I formation of the lignin peroxidase from Phanerochaete chrysosporium

Ligninase, isolated from the wood-destroying fungus Phanerochaete chrysosporium, catalyzes the oxidation of lignin and lignin-related compounds. Ligninase reacts with H2O2 to form the classical peroxidase intermediates Compounds I and II. We have determined the activation energy of ligninase Compound I formation to be 5.9 kcal/mol. The effect of pH and ionic strength on the rate of ligninase Compound I formation was studied. In contrast to all other peroxidases, no pH effect was observed. This is despite homology of active-site amino acids residues (Tien, M., and Tu, C.-P. D. (1987) Nature 326, 520-523) which are proposed to affect the pH profile of Compound I formation. Ligninase Compound I formation can also be supported by organic peroxides. The second-order rate constants with the organic peroxides are lower, suggesting that H2O2 is the preferred substrate.     

A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera

Levels of mitochondrial DNA (mtDNA) sequence divergence between species within each of several avian (Anas, Aythya, Dendroica, Melospiza, and Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were compared. An analysis of digestion profiles generated by 13-18 restriction endonucleases indicates little overlap in magnitude of mtDNA divergence for the avian versus nonavian taxa examined. In 55 interspecific comparisons among the avian congeners, the fraction of identical fragment lengths (F) ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these translate into estimates of nucleotide sequence divergence (p) ranging from 0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater than 0.070. The small mtDNA distances among avian congeners are associated with protein-electrophoretic distances (D values) less than approximately 0.2, while the mtDNA distances among assayed fish and amphibian congeners are associated with D values usually greater than 0.4. Since the conservative pattern of protein differentiation previously reported for many avian versus nonavian taxa now appears to be paralleled by a conservative pattern of mtDNA divergence, it seems increasingly likely that many avian species have shared more recent common ancestors than have their nonavian taxonomic counterparts. However, estimates of avian divergence times derived from mtDNA- and protein-calibrated clocks cannot readily be reconciled with some published dates based on limited fossil remains. If the earlier paleontological interpretations are valid, then protein and mtDNA evolution must be somewhat decelerated in birds. The empirical and conceptual issues raised by these findings are highly analogous to those in the long-standing debate about rates of molecular evolution and times of separation of ancestral hominids from African apes.      

Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes

Statistical methods for computing the standard errors of the branching points of an evolutionary tree are developed. These methods are for the unweighted pair-group method-determined (UPGMA) trees reconstructed from molecular data such as amino acid sequences, nucleotide sequences, restriction-sites data, and electrophoretic distances. They were applied to data for the human, chimpanzee, gorilla, orangutan, and gibbon species. Among the four different sets of data used, DNA sequences for an 895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979) gave the least reliable one. The DNA sequence data suggested that the chimpanzee is the closest and that the gorilla is the next closest to the human species. The orangutan and gibbon are more distantly related to man than is the gorilla. This topology of the tree is in agreement with that for the tree obtained from chromosomal studies and DNA-hybridization experiments. However, the difference between the branching point for the human and the chimpanzee species and that for the gorilla species and the human-chimpanzee group is not statistically significant. In addition to this analysis, various factors that affect the accuracy of an estimated tree are discussed.      

Ligninase of Phanerochaete chrysosporium. Mechanism of its degradation of the non-phenolic arylglycerol beta-aryl ether substructure of lignin.

This study examined the ligninase-catalysed degradation of lignin model compounds representing the arylglycerol beta-aryl ether substructure, which is the dominant one in the lignin polymer. Three dimeric model compounds were used, all methoxylated in the 3- and 4-positions of the arylglycerol ring (ring A) and having various substituents in the beta-ether-linked aromatic ring (ring B), so that competing reactions involving both rings could be compared. Studies of the products formed and the time courses of their formation showed that these model compounds are oxidized by ligninase (+ H2O2 + O2) in both ring A and ring B. The major consequence with all three model compounds is oxidation of ring A, leading primarily to cleavage between C(alpha) and C(beta) (C(alpha) being proximal to ring A), and to a lesser extent to the oxidation of the C(alpha)-hydroxy group to a carbonyl group. Such C(alpha)-oxidation deactivates ring A, leaving only ring B for attack. Studies with C(alpha)-carbonyl model compounds corresponding to the three basic model compounds revealed that oxidation of ring B leads in part to dealkoxylations (i.e. to cleavage of the glycerol beta-aryl ether bond and to demethoxylations), but that these are minor reactions in the model compounds most closely related to lignin. Evidence is also given that another consequence of oxidation of ring B in the C(alpha)-carbonyl model compounds is formation of unstable cyclohexadienone ketals, which can decompose with elimination of the beta-ether-linked aromatic ring. The mechanisms proposed for the observed reactions involve initial formation of aryl cation radicals in either ring A or ring B. The cation radical intermediate from one of the C(alpha)-carbonyl model compounds was identified by e.s.r. spectroscopy. The mechanisms are based on earlier studies showing that ligninase acts by oxidizing appropriately substituted aromatic nuclei to aryl cation radicals [Kersten, Tien, Kalyanaraman & Kirk (1985) J. Biol. Chem. 260, 2609-2612; Hammel, Tien, Kalyanaraman & Kirk (1985) J. Biol. Chem. 260, 8348-8353].     

Phytanic acid alpha-oxidation and complementation analysis of classical Refsum and peroxisomal disorders

Summary We have measured the production of ¹⁴CO₂ from exogenous [1-¹⁴C] phytanic acid in fibroblast monolayers from patients with classical Refsum's disease and peroxisomal disorders. Activities in the different disorders were (percentage of control): classical Refsum's disease (5%), isolated peroxisomal acyl-CoA oxidase deficiency (75%), Zellweger syndrome (4%), neonatal adrenoleukodystrophy (5%), and rhizomelic chondrodysplasia punctate (3%). Absence of complementation was demonstrated between Zellweger syndrome and infantile Refsum's disease lines after polyethylene glycol fusion, with decreases of average activity of 11% relative to unfused cell mixtures. Classical Refsum's disease, rhizomelic chondrodysplasia punctata, and neonatal adrenoleukodystrophy lines all complemented one another, and Zellweger syndrome or infantile Refsum's disease lines, with average activity increases of 522%–772%. No intragenic complementation was observed within either group. Four complementation groups were detected suggesting that at least four genes are involved in phytanic acid -oxidation: one gene for the enzyme phytanic acid -hydroxylase (probably mitochondrial); one gene for a regulatory factor for the expression of phytanic acid -decarboxylation activity and two membrane-bound peroxisomal enzymes involved in the synthesis of plasmalogens; two genes for the assembly of functional peroxisomes and/or import of proteins into peroxisomes.