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1.
Stephen M. Reilly 《Journal of morphology》1987,191(2):205-214
Comparison of metamorphosis of skull and hyobranchial system in two species of neotenic salamanders reveals two different types of neoteny. Ambystoma talpoideum is completely neotenic owing to delayed metamorphosis. Notophthalmus viridescens exhibits limited neoteny as a result of incomplete metamorphosis. Morphological details of neoteny are compared to life history in both species in order to discuss the ecological morphology of the two neotenic strategies. Comparisons to Taricha granulosa, Triturus vulgaris, and Ambystoma gracile indicate that these two strategies are widely employed and may represent familial patterns. 相似文献
2.
Published gene frequency data, checked for consistency of allele definitions across laboratories and for comparability of
geographically identical samples, were pooled into a data set containing frequencies at nine loci for each of 20 populations
that encompassed 10 macaque species. Genetic distances were calculated by the methods of Kidd and Cavalli-Sforza (1974). These
distances were used to construct phylogenetic trees and to evaluate the relationships between divergence times and effective
population sizes. Inter-and intraspecific genetic distances and the groupings defined by phenetic tree analyses support Fooden’s
(1976) classification of the genus Macacainto four species groups. A paleozoogeographical model of Asia including the known times of major sea-level changes allows
us to explain Macacainto four species groups. A paleozoogeographical model of Asia including the known times of major sea-level changes allows
us to explain qualitatively the inferred evolutionary relationships among macaque species. Many assumptions are required in
order to estimate the variables necessary in the quantitative prediction of genetic differences for a comparison between any
two populations. Examination of those assumptions demonstrates the need for more accurate genetic as well as paleozoogeographic
information.
An erratum to this article is available at . 相似文献
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Don Trinh Nguyen Jens Christian G?pfert Nobuhiro Ikezawa Gillian MacNevin Meena Kathiresan Jürgen Conrad Otmar Spring Dae-Kyun Ro 《The Journal of biological chemistry》2010,285(22):16588-16598
Sesquiterpene lactones are characteristic natural products in Asteraceae, which constitutes ∼8% of all plant species. Despite their physiological and pharmaceutical importance, the biochemistry and evolution of sesquiterpene lactones remain unexplored. Here we show that germacrene A oxidase (GAO), evolutionarily conserved in all major subfamilies of Asteraceae, catalyzes three consecutive oxidations of germacrene A to yield germacrene A acid. Furthermore, it is also capable of oxidizing non-natural substrate amorphadiene. Co-expression of lettuce GAO with germacrene synthase in engineered yeast synthesized aberrant products, costic acids and ilicic acid, in an acidic condition. However, cultivation in a neutral condition allowed the de novo synthesis of a single novel compound that was identified as germacrene A acid by gas and liquid chromatography and NMR analyses. To trace the evolutionary lineage of GAO in Asteraceae, homologous genes were further isolated from the representative species of three major subfamilies of Asteraceae (sunflower, chicory, and costus from Asteroideae, Cichorioideae, and Carduoideae, respectively) and also from the phylogenetically basal species, Barnadesia spinosa, from Barnadesioideae. The recombinant GAOs from these genes clearly showed germacrene A oxidase activities, suggesting that GAO activity is widely conserved in Asteraceae including the basal lineage. All GAOs could catalyze the three-step oxidation of non-natural substrate amorphadiene to artemisinic acid, whereas amorphadiene oxidase diverged from GAO displayed negligible activity for germacrene A oxidation. The observed amorphadiene oxidase activity in GAOs suggests that the catalytic plasticity is embedded in ancestral GAO enzymes that may contribute to the chemical and catalytic diversity in nature. 相似文献
5.
The catalytic mechanism of porcine pancreatic alpha-amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) has been examined by nuclear magnetic resonance (NMR) at subzero temperatures by using [1-13C]maltotetraose as substrate. Spectral summation and difference techniques revealed a broad resonance peak, whose chemical shift, relative signal intensity and time-course appearance corresponded to a beta-carboxyl-acetal ester covalent enzyme-glycosyl intermediate. This evidence supports a double-displacement covalent mechanism for porcine pancreatic alpha-amylase-catalyzed hydrolysis of glycosidic linkages, based on the presence of catalytic aspartic acid residues within the active site of this enzyme. 相似文献
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Don Ross 《Biology & philosophy》2012,27(2):287-297
The revised edition of Paul Seabright’s The Company of Strangers is critically reviewed. Seabright aims to help non-economists participating in the cross-disciplinary study of the evolution
of human sociality appreciate the potential value that can be added by economists. Though the book includes nicely constructed
and vivid essays on a range of economic topics, in its main ambition it largely falls short. The most serious problem is endorsement
of the so-called strong reciprocity hypothesis that has been promoted by several prominent economists, but does not pass muster
with biologists. 相似文献
9.
Baby hamster kidney cells were seeded onto Western blots of fetal serum proteins which had been extracted from several foreign surfaces. This revealed that the major cell adhesive proteins adsorbed onto these surfaces from fetal serum were (1) fibronectin of Mr 220,000 Da and (2) vitronectin of Mr 65,000 and 78,000 Da. Two minor bands of cell attachment were observed at Mr 153,000 and Mr 134,000 Da in the fetal serum proteins extracted from heparin-agarose and serotonin-agarose. However, by exposing the Western blots of separated proteins to a second round of serum proteins, prior to cell blotting, very strong cell adhesive bands were revealed at Mr 153,000, 134,000, and 120,000 Da. By (i) modifying the composition of the serum proteins used to treat the Western blots, (ii) using specific antibodies to fibronectin, and (iii) using radiolabeled fibronectin, it was conclusively demonstrated that the new cell adhesive bands owed their increased cell attachment activity to secondary binding of fibronectin. The new bands were shown (i) to be trypsin sensitive and collagenase sensitive and therefore to be collagen-like proteins and (ii) to react negatively in immunoblots using anti-fibronectin, anti-vitronectin, anti-fibrinogen, anti-fetuin or anti-thrombospondin. In SDS-PAGE (i) the Mr 120,000-Da protein comigrated with the alpha 2-chain of Type I collagen, (ii) the Mr 134,000-Da protein comigrated with the alpha 1-chain of Type I collagen, and (iii) the Mr 153,000-Da protein comigrated with the pN-alpha 1-chain of Type III collagen. Since the novel collagen-like proteins acted as strong sites of cell attachment on nitrocellulose blots by binding fibronectin, they might well promote cell attachment on the foreign surfaces from which they were extracted. 相似文献
10.