Evolution and the nature of time.

The concept of time is critical in evolutionary thought, but rarely has it been considered as an object of theoretical research by evolutionary biologists. Evolution is an organism's possibility of access to the future; in other words, evolutionary reward is paid out as increased time. Replicating entities are granted time, but for them, time only serves to allow replication and evolution, and to further expand the frontier of time. The present review discusses the possible influence of considering time not as a pure dimension (or an a priori intuitive condition of human experience) but as an object in itself. At least as a metaphor, time can be considered as a self-replicating entity rooted in physical (including biological) beings, with the result of producing dimensional time. Time self-replication forces beings to replicate, which, in turn, further sustains the replication of time. In that sense, time-replication may constitute the driving force, i.e., the basic engine, providing directional energy to the evolutionary process. The philosophical roots, caveats, and perspectives of this hypothesis are presented here. The metaphor of replicating-time plays with the possibility of viewing time not as a merely regulatory component of scientific inquiry but instead, as a real and creative constituent of nature and, for this reason, an object worthy of research in the natural sciences.     

谷子茎尖体外遗传转化体系的建立与优化

以谷子(Seteria italica)豫谷一号为实验材料,建立了一套简便、稳定的体外茎尖遗传转化体系。通过根癌农杆菌(Agrobacterium tumefaciens)介导的茎尖转化法,对转化受体采取不同的处理方式,待拟转化株长到三叶期后进行PCR鉴定。探明了草丁膦(Basta)喷施处理用于谷子转基因幼苗筛选的最适...     

Universal common ancestry,LUCA, and the Tree of Life: three distinct hypotheses about the evolution of life

Common ancestry is a central feature of the theory of evolution, yet it is not clear what “common ancestry” actually means; nor is it clear how it is related to other terms such as “the Tree of Life” and “the last universal common ancestor”. I argue these terms describe three distinct hypotheses ordered in a logical way: that there is a Tree of Life is a claim about the pattern of evolutionary history, that there is a last universal common ancestor is an ontological claim about the existence of an entity of a specific kind, and that there is universal common ancestry is a claim about a causal pattern in the history of life. With these generalizations in mind, I argue that the existence of a Tree of Life entails a last universal common ancestor, which would entail universal common ancestry, but neither of the converse entailments hold. This allows us to make sense of the debates surrounding the Tree, as well as our lack of knowledge about the last universal common ancestor, while still maintaining the uncontroversial truth of universal common ancestry.     

A bioremediation approach using natural transformation in pure-culture and mixed-population biofilms

Bacterial transformation by naked DNA is thought to contribute to gene transfer and microbial evolution within natural environments. In nature many microbial communities exist as complex assemblages known as biofilms where genetic exchange is facilitated. It may be possible to take advantage of natural transformation processes to modify the phenotypes of biofilm communities giving them specific and desirable functions. Work described here shows that biofilms composed of either pure cultures or mixed populations can be transformed with specific catabolic genes such that the communities acquire the ability to degrade a particular xenobiotic compound. Biofilms were transformed by plasmids bearing genes encoding green fluorescent protein (mut2) and/or atrazine chlorohydrolase (atzA). Confocal microscopy was used to quantify the number of transformants expressing mut2 in the biofilms. Degradation of atrazine by expressed atzA was quantified by tandem mass spectrometry. PCR analysis was performed to confirm the presence of atzA in transformed biofilms. These results indicate that it should be possible to use natural transformation to enhance bioremediation processes performed by biofilms.     

Open systems living in a closed biosphere: a new paradox for the Gaia debate

While energetically open, the biosphere is appreciably closed from the standpoint of matter exchange. Matter cycling and recycling is hence a necessary and emergent property of the global-scale system known as Gaia. But how can an aggregate of open-system life forms have evolved and persisted for billions of years within a planetary system that is largely closed to matter influx and outflow? The puzzling nature of a closed yet persistent biosphere draws our attention to the course of evolution of fundamental metabolic strategies and matter-capture techniques. It suggests a facet of the Gaia hypothesis, framed in terms of persistence. The oceans, atmosphere, soils and biota constitute a complex system which maintains and adjusts matter cycling and recycling within the constraints of planetary closure such that open-system forms of life can persist. This weaker version of the Gaia hypothesis may be useful because it readily lends itself to at least one form of test. What is the solution to the closed biosphere puzzle, and does it indicate that Gaia merits status as a discrete entity? We suggest several disciplines within the field of biology that might provide tools and perspectives toward reaching a solution. These disciplines include artificial closed ecosystems, prokaryote evolution, the nexus of thermodynamics and evolutionary biology, and hierarchy theory in ecosystem modeling and evolution theory.     

Altered matrix metalloproteinase expression associated with oncogene-mediated cellular transformation and metastasis formation

Matrix metalloproteinase expression was examined in a series of mammalian cell lines of varying degrees of malignant progression. The expression of MMP-2 and MMP-9 was found to correlate with ras-mediated cellular transformation and as a function of malignant potential. Altered MMP-2 and MMP-9 expression was found to correlate also in other oncogene transformed cell lines and the level of expression of both MMP-2 and MMP-9 correlated with metastatic potential. Increased expression of both MMP-2 and MMP-9 was also found in cells which constitutively over-express MAP kinase kinase suggesting that one of the consequences of the persistent activation of the MAP kinase pathway is elevated expression of MMP-2 and MMP-9. Additionally, this study demonstrated a correlation between the expression of MMP-3 (stromelysin-1) and the level of ras expressed in cells and with the cells' ability to form tumors and with malignant potential. The existence of a novel 80 kDa caseinase activity which correlates with ras expression and the ability of the cell to form tumors was also demonstrated. The growth status of transformed cells was also found to be important in determining the expression of MMP-2 mRNA but not MMP-9 mRNA expression, and this expression was cell-type specific. This study also demonstrates that oncogenes can interact to influence and to determine the nature of the matrix metalloproteinases expressed and that this interaction results in a tumorigenic phenotype and, most importantly, contributes to the metastatic phenotype. Alterations in the expression and the regulation of MMPs, particularly MMP-2 and MMP-9, constitute an integral part of the altered growth regulatory program found within transformed cells and in particular, in transformed cells capable of malignant progression.     

Acquisition of a potential marker for insect transformation: isolation of a novel alcohol dehydrogenase gene from Bactrocera oleae by functional complementation in yeast

The alcohol dehydrogenase genes make up one of the best studied gene families in Drosophila, both in terms of expression and evolution. Moreover, alcohol dehydrogenase genes constitute potential versatile markers in insect transformation experiments. However, due to their rapid evolution, these genes cannot be cloned from other insect genera by DNA hybridization or PCR-based strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast genes have evolved independently, acquiring their enzymatic function convergently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementation in yeast can be used to clone alcohol dehydrogenase genes that are unrelated in sequence to those of yeast, thus providing a powerful tool for isolation of dominant insect transformation marker genes. Received: 29 June 1999 / Accepted: 27 October 1999     

Evolutionary Trends of External Morphology in the Marine Mite Genus Rhombognathides (Acari: Halacaridae: Rhombognathinae)

A morphology-based phylogenetic analysis of the eight species of Rhombognathides (Acari: Halacaridae) demonstrated some evolutionary tendencies of character transformation. In the course of the evolution of Rhombognathides, idiosomal plates increased in size or fused. Simple filiform setae transformed into spiniform or bipectinate setae. The number of tarsal claws, the length of median claw and leg chaetotaxy of telofemora and tibiae were reduced. The fusion or expansion of dorsal plates, transformation from filiform to other setal forms, and reduction of leg setae would have recurrently occurred in halacarid evolution. The claw structure most likely reflects adaptation to specific habitat.     

Tumor cells can evade dependence on autophagy through adaptation

The autophagy-lysosome and the proteasome constitute the two major intracellular degradation systems. Suppression of the proteasome promotes autophagy for compensation and simultaneous inhibition of autophagy can selectively increase apoptosis in transformed cells, but not in untransformed or normal cells. Transformed cells are thus more dependent on autophagy for survival. However, it is unclear whether long-term autophagy inhibition/insufficiency would affect such dependency. To address this question, we transformed wild-type and autophagy-deficient cells lacking a key autophagy-related gene Atg5 with activated Ras. We found that such transformation did not make the autophagy-deficient tumor cells more susceptible to proteasome inhibitors than the wild type tumor cells, although the transformed cells were in general more sensitive to proteasome inhibition. We then compared the effect of acute versus constitutive knock-down of a key autophagy initiating molecule, Beclin 1, in an already transformed cancer cell line. In a wild-type U251 glioblastoma cell line (autophagy intact), increased sensitivity to proteasome inhibition was induced immediately after the knock-down of Beclin 1 expression with a specific siRNA (acute autophagy deficiency). On the other hand, when the tumor cell line was selected over a long period to achieve constitutive knock-down of Beclin 1, its sensitivity to proteasome inhibitors was no higher than that of the wild-type tumor cells. These results suggest that long-term autophagy deficiency either before or after oncogenic transformation can render the tumor cell survival independent of the autophagic activity, and the response to chemotherapy is no longer affected by the manipulation of the autophagy status.     

Surface Membrane Glycopeptides Which Coincide with Virus Transformation and Tumorigenesis

Glycopeptides from the surface of clones of hamster embryo cells were examined at various intervals after infection with polyoma virus. Two types of transformed cells were examined: (i) clones that showed delayed transformation or an initially low tumorigenicity, and (ii) clones that were rapidly transformed showing an initially high tumorigenicity. The glycopeptides were removed from the cell surface by trypsin and, after Pronase digestion, were examined by filtration through Sephadex G-50. With delayed transformation, a specific group of glycopeptides was increasingly evident over an 85-day period as the cells showed phenotypic properties of transformation and the ability to form tumors. In the other series, all but one clone of hamster embryo cells showed rapid transformation after infection with polyoma virus. This clone was less tumorigenic and showed little of the specific glycopeptides. In all cases of delayed or rapid transformation examined, the specific group of glycopeptides increased proportionately to the ability of the cells to form tumors. All of the cells derived from progressively growing tumors formed by injection of these transformed hamster cells into adult animals showed an abundance of this group of glycopeptides. These results suggest that specific surface membrane glycopeptides accompany viral transformation and tumorigenesis.     

水稻OsRab7耐盐功能的初步鉴定及其表达载体的构建

Rab7是一个GTP结合蛋白,隶属于Rab家族,该家族在调控膜泡的运输、结合以及细胞内膜结构的组织中行使重要作用。本实验通过RT-PCR技术从盐敏感水稻品种‘日本晴’(‘Nipponbare’)获得了OsRab7基因全长序列,成功构建了原核表达载体pET-32a-OsRab7。在IPTG诱导下,该蛋白高效表达,并明显缓解了高盐环境(4.5% ～8.5% NaCl)对大肠杆菌的生长胁迫。为进一步研究该基因的功能,将OsRab7在大肠杆菌中的表达蛋白纯化,并利用p1301B(pCAMBIA1301改造载体)构建了植物表达载体,成功转化来源于水稻株系‘中花11’(盐敏感)的愈伤组织,为探讨其在水稻中的表达模式和功能分析及应用于水稻耐盐品种的改良奠定了一定的基础。     

Electrodes modified with nitrofluorenone derivatives as a basis for new biosensors

We report about the electrocatalytic properties of electrodes modified by adsorption of nitro-fluorenone derivatives. The stable, adherent monolayer of these catalyst precursors can be transformed electrochemically into the corresponding hydroxylamine compounds (R-NO₂+4e+4H⁺R-NHOH+H₂O). The completely reversible two electron oxidation of the hydroxylamine leads to the nitroso compounds (R-NHOHR-NO+2e+2H⁺) that exhibit high catalytic activity in the electrooxidation of NADH at low overpotentials (−30 mV vs. Ag/AgCl) and therefore constitute a new family of efficient redox mediators for biosensor applications. A significant increase in catalytic activity (up to 500%) is observed after addition of calcium ions to the electrolyte. This is explained by a specific and bridging complexation between the coenzyme's phosphate groups and a carboxyl group present in the catalyst molecule. The interaction favours the contact between NADH and the surface confined catalyst, leading to a higher electron transfer efficiency. This interaction can be used in an approach of molecular level design for controlled monolayer deposition of catalyst, Ca²⁺, NAD⁺ and enzyme. A very simple and inexpensive modification scheme, essentially based on electrostatic attraction, leads to electrodes that can be employed as reagentless biosensors for the electrochemical detection of common and commercially interesting analytes like glucose.     

Regarding zygotes as persons: implications for public policy

In this paper, we examine the notion put forward by certain groups (largely as a consequence of their opposition to elective abortion) that the immediate post-fertilization cellular entity - the zygote - is a person and should be given full moral status. Because the zygote has none of the inherent characteristics necessary to be regarded as a person in the traditional philosophical sense (e.g., John Locke or Immanuel Kant), some advocates of this position attempt to advance their case with arguments based on the genetic potential of the human zygote to develop into a person. We argue that this position represents a flawed use of human genetics and ignores the extraordinarily inefficient and wasteful nature of human reproduction. We then explore the public policy consequences that would follow from granting the zygote full moral status. We conclude that the logical consequences of granting the zygote full moral status would require a revolutionary restructuring of many basic social institutions, especially the health care system. The social, political, and economic changes that would be required if the zygote is enshrined as a person in law constitute a convincing reductio ad absurdum that demonstrates the danger in taking this position seriously.     

The evolutionary origins of tensed language and belief

I outline the debate in metaphysics between those who believe time is tensed and those who believe it is tenseless. I describe the terms in which this debate has been carried out, and the significance to it of ordinary tensed language and widespread common sense beliefs that time is tensed. I then outline a case for thinking that our intuitive beliefs about tense constitute an Adaptive Imaginary Representation (Wilson, in Biol Philos 5:37–62, 1990; Wilson, in Biol Philos 10:77–97, 1995). I also outline a case for thinking that our ordinary tensed beliefs and tensed language owe their tensed nature to its being adaptive to adopt a temporally self-locating perspective on reality. If these conclusions are right, then common sense intuitions and temporal language will be utterly misleading guides to the nature of temporal reality.     

High frequency transformation of Streptomyces niveus protoplasts by plasmid DNA

H.A. HUSSAIN AND D.A. RITCHIE. 1991. A procedure has been developed for transforming protoplasts of the novobiocin producing strain Streptomyces niveus at high frequency. This required the isolation of strains LH13 and LH20 defective in DNA restriction from the wild type (ATCC 19793) which is transformed at very low frequencies. The LH13 and LH20 derivatives were obtained by curing pIJ702 DNA from the few S. niveus transformed protoplasts obtained by transformation of the wild type with high concentrations of pIJ702 DNA. Protoplasts of S. niveus strains LH13 and LH20 produced about 10⁶ transformants/μg DNA with modified pIJ702 DNA derived by replication in S. niveus. Unmodified DNA (derived from replication in S. lividans ) from a series of pIJ101, SCP2 and pSN2-based derivatives, gave transformation frequencies in the range of 10²-10³ transformants/μg DNA. Optimal conditions for the formation and transformation of S. niveus protoplasts are described.     

Effect of cytokines, dexamethasone and the A/T-signal peptide polymorphism on the expression of alpha(1)-antichymotrypsin in astrocytes: significance for Alzheimer's disease

Proinflammatory cytokines and acute phase proteins, such as ₁-antichymotrypsin, are over expressed in microglia and astrocytes in brain regions with abundant mature amyloid plaques, suggesting a glial cell-led brain acute phase response in the Alzheimer neuropathology. In this paper, we show that ₁-antichymotrypsin gene expression in human astrocytes is elevated by interleukin-1 and interleukin-6, and further enhanced by glucocorticoid, while the homologous contrapsin gene in rat astrocytes is unaffected by these cytokines. These distinct gene regulation mechanisms might help to explain the differential susceptibility of humans and rodents to amyloid formation of the Alzheimer's type. In addition, we demonstrate that the ₁-antichymotrypsin A-allele that encodes a different signal peptide and is a suggested risk factor for Alzheimer's disease gives rise to a reduced level of immature ₁-antichymotrypsin in transfected cells. The physiological result would be an enhanced ability of the A-encoded ₁-antichymotrypsin protein to become secreted and promote extracellular amyloid formation. We discuss our findings in terms of a model in which cytokine-induced ₁-antichymotrypsin synthesis in astrocytes constitutes a specific inflammatory pathway that accelerates the development of Alzheimer's disease and could at least partly underlie the regional specificity and species restriction of the neuropathology.     

Development of transformation vectors based upon a modified plant alpha-tubulin gene as the selectable marker

A plant transformation and selection system has been developed utilizing a modified tubulin gene as a selectable marker. The vector constructs carrying a mutant alpha-tubulin gene from goosegrass conferring resistance to dinitroaniline herbicides were created for transformation of monocotyledonous and dicotyledonous plants. These constructs contained beta- and/or mutant alpha-tubulin genes driven either by ubiquitin or CaMV 35S promoter. The constructs were used for biolistic transformation of finger millet and soybean or for Agrobacterium-mediated transformation of flax and tobacco. Trifluralin, the main representative of dinitroaniline herbicides, was used as a selective agent in experiments to select transgenic cells, tissues and plantlets. Selective concentrations of trifluralin estimated for each species were as follows: 10 microM for Eleusine coracana, Glycine max, Nicotiana plumbaginifolia and Nicotiana sylvestris; 3 microM for Linum usitatissimum. PCR and Southern blotting analyses of transformed lines with a specific probe to nptII, alpha-tubulin or beta-tubulin genes were performed to confirm the transgenic nature of regenerated plants. Band specific for the mutant alpha-tubulin gene was identified in transformed plant lines. Results confirmed the stable integration of the mutant tubulin gene into the plant genomes. The present study clearly demonstrates the use of a plant mutant tubulin as a selective gene for plant transformation.