共查询到20条相似文献,搜索用时 15 毫秒
1.
Island birds and isolation: Lack revisited 总被引:1,自引:0,他引:1
Timothy M. Reed 《Biological journal of the Linnean Society. Linnean Society of London》1987,30(1):25-29
David Lack's theory of island biology was published in 1976. In this he stated that isolation was of little consequence as a barrier to bird dispersal. Lack's theory was singular for his lack of statistical support of his assertions. One reviewer indicated from his data that statistically significant isolation effects might be present. Here data for the Bahamas and Gulf of Guinea islands were examined. In both cases isolation from the mainland colonisation source was significantly inversely correlated with the number of breeding bird species on the islands. 相似文献
2.
Hudson RG 《History and philosophy of the life sciences》2003,25(2):167-191
In his recent article, Nicolas Rasmussen (2001) is harshly critical of what he terms 'empirical philosophy of science', a philosophy that takes seriously the history of science in advancing philosophical pronouncements about science. He motivates his criticism by reflecting on recent history in microbiology involving the 'discovery' of a new bacterial organelle, the mesosome, during the 1950's and 1960's, and the subsequent retraction of this discovery by experimental microbiologists during the late 1970's and early 1980's. In particular, he argues that there was a lack of constancy in the methods microbiologists used in approaching the issue of the existence of mesosomes, and that in fact a similar sort of 'methodological flux' pervades all experimental work. My goal here is to refute Rasmussen's doctrine of flux, and in turn to re-establish order in our understanding of the methods and strategies of experimenters. My strategy in achieving this goal is to re-visit the same crucial research articles in the history of the mesosome episode that Rasmussen (2001) visits; and what I find upon returning to this literature is not flux, as Rasmussen seems to find, but a constancy of method in experimental reasoning, a constancy codified by what I call 'reliable process reasoning'. 相似文献
3.
Despite the tension between the United States and the Soviet Union in the early 1920's, the Rockefeller Foundation and the Rockefeller Institute for Medical Research found ways to assist I.P. Pavlov. In addition to providing scientific literature and financial aid, these institutions and their officers rendered important moral support to the scientific career of Pavlov during his later years. In 1923, as a guest of the Rockefeller Institute, Pavlov visited American scientific laboratories. In 1924, he requested and received a number of books on physiology, and during the 1930's the Foundation helped him to acquire equipment for his Leningrad laboratory. 相似文献
4.
5.
Abstract Archie (1990) prefers his "homoplasy excess ratio" HER to Farris' (1989) 1 ensemble retention index R . HER, he writes, lacks R 's defects: R 's minimum is not zero, and varies with number of terminals or characters.
HER has those defects. Archie has misunderstood the permutation method on which HER rests, and mistaken the properties of R as well. After explaining those points, I describe other permutation-based indices and briefly consider their utility. These provide relative measures of congruence among the characters of the data; one corresponds to a significance test. 相似文献
HER has those defects. Archie has misunderstood the permutation method on which HER rests, and mistaken the properties of R as well. After explaining those points, I describe other permutation-based indices and briefly consider their utility. These provide relative measures of congruence among the characters of the data; one corresponds to a significance test. 相似文献
6.
Aronson JD 《History and philosophy of the life sciences》2002,24(3-4):441-465
In this paper, I analyze George Gaylord Simpson's response to the molecularization of evolutionary biology from his unique perspective as a paleontologist. I do so by exploring his views on early attempts to reconstruct phylogenetic relationships among primates using molecular data. Particular attention is paid to Simpson's role in the evolutionary synthesis of the 1930s and 1940s, as well as his concerns about the rise of molecular biology as a powerful discipline and world-view in the 1960s. I argue that Simpson's belief in the supremacy of natural selection as the primary driving force of evolution, as well as his view that biology was a historical science that seeks ultimate causes and highlights contingency, prevented him from acknowledging that the study of molecular evolution was an inherently valuable part of the life sciences. 相似文献
7.
Palmer Pete 《古生物学报》2014,(4):前插9-前插9
Professor Chang was a long-time friend and colleague.We began exchanging reprints in the 1950's and finally,in 1976 I was able to visit Nanjing and we met for the first time.Subsequently he came to the U.S.and I was able to show him some of our spectacular desert Cambrian exposures in the west.Later,he was a most gracious host as we toured much of eastern China,following an International Cambrian Symposium in Novosibirsk,dividing our time between Cambrian exposures and famous tourist sites.Our final personal meeting was in 2002 at his apartment following a Cambrian conference in Nanjing,where he was still pursuing research on Cambrian trilobites.He was the leader of his generation in Cambrian studies and his work provided important demonstrations of the significant differences between contemporaneous faunas in Laurentia and what was then eastern Gondwana.This work contributed significantly to our understanding of the biogeography of the Cambrian world,and is a lasting addition to global knowledge of the Cambrian of eastern Asia. 相似文献
8.
Modulation of types I and III procollagen synthesis at various stages of arterial smooth muscle cell growth in vitro 总被引:3,自引:0,他引:3
Collagen synthesis was monitored in cultures of rabbit arterial smooth muscle cells (SMC). Both the rate of collagen synthesis per cell and collagen synthesis as a percent of total protein synthesis were measured at specific intervals from 1 to 14 days after inoculation of smooth muscle cells. The proportions of types I and III collagen present in the conditioned incubation medium and in the cell layer were also examined. After inoculation the cells displayed population expansion typical of SMC in which growth slowed but did not cease after the cells attained confluence. Collagen synthesis rates, expressed as [14C]hydroxyproline per cell, were eight-fold higher in preconfluent cells. In these cultures collagen accounted for more than 20% of the newly synthesized, 14C-labeled protein present as trichloroacetic acid (TCA)-insoluble material in 24 h culture media. In post-confluent cultures, this percentage was reduced to about 7% of the total protein synthesized. Synthesis rates of both collagen and non-collagen protein decreased with increasing time after inoculation. However, the rate of decline of collagen synthesis was three times greater than that seen for non-collagen protein. Early cultures synthesized relatively more type I than type III procollagen. The type I to type III ratio was highest at day 3 and declined after that time to day 14. While the synthesis of both types decreased with increasing age, type I declined at a greater rate resulting in a predominance of type III procollagen secretion by older cultures. We conclude that protein synthesis in general and collagen synthesis in particular are quantitatively and qualitatively dependent upon the growth stage of SMC in vitro. 相似文献
9.
Activation of group I metabotropic glutamate receptors leads to long-term depression (mGluR-LTD). Alterations in this form of plasticity have been linked to drug addiction and cognitive disorders. A key characteristic of mGluR-LTD is its dependence on rapid protein synthesis; however, the identities of the proteins mediating LTD remain elusive. Here, we identify the X-linked mental retardation protein OPHN1 as a molecule essential for mGluR-LTD in the hippocampus. mGluR-LTD induction elicits rapid dendritic OPHN1 synthesis, which is dependent on mGluR1 activation and independent of fragile X mental retardation protein (FMRP). This response is essential for mGluR-LTD, as acute blockade of OPHN1 synthesis impedes LTD. mGluR-induced OPHN1 mediates LTD and associated persistent decreases in surface AMPARs via interactions with endophilin A2/3. Importantly, this role of OPHN1 is separable from its effects on basal synaptic strength, which require OPHN1's Rho-GAP activity and interaction with Homer1b/c. Thus, our data establish a role for rapid OPHN1 synthesis in mGluR-LTD. VIDEO ABSTRACT: 相似文献
10.
Gísli Pálsson 《Ethnos》2013,78(3-4):413-440
A lively debate has taken place in anthropology in recent years on field‐work and its representation in ethnographic accounts. At the same time, historians and cultural critics have dissected the ideology and rhetoric of early explorations. Here I examine the writings of the anthropologist and explorer Vilhjalmur Stefans‐son (1879–1962) in the light of current debates about textual representation, drawing upon recent discussions of ethnography, gender, and the power relations of early twentieth‐century explorations. Stefansson went on lengthy expeditions into the Alaskan and Canadian Arctic and wrote extensively on his encounters with indigenous groups, I argue that while Stefansson was a perceptive ethnographer and explorer, he was silent in both his publications and his diaries about important aspects pertaining to his fieldwork, in particular the ethnographic contributions of his Inuit companions and his intimate relations with a native woman named Pannigabluk. This silence, I suggest, contradicts the narrative trope Stefansson generally adopted, summed up in his concept of the friendly Arctic’ 相似文献
11.
A recent model of parental provisioning (the tradeoff model) suggests that the maximum delivery rate of food to nestlings represents a tradeoff between parental residual reproductive value and nestling survival. In contrast, Lack's hypothesis suggests that maximum provisioning rate determines brood size and therefore delivery rates are limited by shortages of food or foraging time, not by tradeoffs of parental investment. Several authors have examined the shape of the per-nestling feeding curves to test the tradeoff model against Lack's hypothesis. We show that Lack's hypothesis can produce per-nestling feeding curves consistent with the tradeoff model. Therefore, the shape of the per-nestling feeding curve cannot be used to distinguish between the models. 相似文献
12.
Graham CF 《The International journal of developmental biology》2008,52(2-3):171-178
An informal account records the remaining traces of Tarkowski's research visits to the United Kingdom and France. The account has many authors and it should not be regarded as an exact history. The early 1960s began with the dramatic production of chimaeras at the University of Bangor and the long term exchange of information with Anne McLaren's Edinburgh laboratory. The techniques of parthenogenesis and nuclear transfer became the obsession of the 1970's and Tarkowski pursued the problem in Oxford (U.K.), in France, and with his group in Warsaw (Poland). A variant of this theme emerged during the 1980's and this was attempts to produce interspecies hybrids in Oxford and Warsaw. During the 1990's, the Warsaw laboratory became sufficiently well funded to make his trips unnecessary and his pupils became a Polish Diaspora of Embryologists. 相似文献
13.
An incubation medium is described which supports RNA synthesis in isolated oocyte nuclei of the newt Notophthalmus, and which permits subsequent autoradiographic examination of the lampbrush chromosomes and nucleoli. By using different
concentrations of α-amanitin we distinguish RNA synthesis due to RNA polymerases I, II and III. All RNA synthesis on loops
is inhibited by 0.5 μ/ml of α-amanitin and is therefore due to polymerase II. Polymerase III is responsible for RNA synthesis
at a small number of discrete sites in condensed chromatm. These include the centromere bars of three of four chromosomes,
which probably represent 5S RNA synthesis, as well as 15–20 lesser sites scattered elsewhere. Polymerase I activity is confined
to the nucleoli.
Dedicated to Professor W. Beermann on the occasion of his 60th birthday 相似文献
14.
Erik Krag 《Bioethics》2014,28(8):427-435
Drawing on Christopher Boorse's Biostatistical Theory (BST), Norman Daniels contends that a genuine health need is one which is necessary to restore normal functioning – a supposedly objective notion which he believes can be read from the natural world without reference to potentially controversial normative categories. But despite his claims to the contrary, this conception of health harbors arbitrary evaluative judgments which make room for intractable disagreement as to which conditions should count as genuine health needs and therefore which needs should be met. I begin by offering a brief summary of Boorse's BST, the theory to which Daniels appeals for providing the conception of health as normal functioning upon which his overall distributive scheme rests. Next, I consider what I call practical objections to Daniels's use of Boorse's theory. Finally I recount Elseljin Kingma's theoretical objection to Boorse's BST and discuss its impact on Daniels's overall theory. Though I conclude that Boorse's view, so weakened, will no longer be able to sustain the judgments which Daniels's theory uses it to reach, in the end, I offer Daniels an olive branch by briefly sketching an alternative strategy for reaching suitably objective conclusions regarding the health and/or disease status of various conditions. 相似文献
15.
MATS ENVALL 《Biological journal of the Linnean Society. Linnean Society of London》2008,94(1):217-220
About 50 years ago, the German entomologist Willi Hennig presented a new approach in biological systematics that he called a phylogenetic systematics. The main difference between his approach and traditional Linnean systematics was that he distinguished two new kinds of groups that he called mono- and paraphyletic groups, and whereof he considered only monophyletic groups to be natural groups. However, almost immediately after publication of his approach in English, some biological systematists commented that his monophyletic groups rather ought to be called holophyletic groups. The comment sparked a heated debate about the definition of the concept 'monophyletic groups', but the debate never reached consensus. In this paper, I claim that the controversy does not concern the definition of the concept monophyletic groups per se , but instead conceptualization of phylogenies (i.e. dichotomously branching processes) in a general sense. I discuss the relation between mono-, holo- and paraphyletic groups, and conclude that Hennig's conceptualization of phylogenies is both inconsistent and empirically wrong, whereas Linné's instead is consistent and correct. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 217–220. 相似文献
16.
Changes in the synthesis of minor cartilage collagens after growth of chick chondrocytes in 5-bromo-2'-deoxyuridine or to senescence 总被引:6,自引:0,他引:6
R Mayne B W Elrod P M Mayne R D Sanderson T F Linsenmayer 《Experimental cell research》1984,151(1):171-182
Analyses were made of the minor collagens synthesized by cultures of chondrocytes derived from 14-day chick embryo sterna. Comparisons were made between control cultures, cultures grown for 9 days in 5-bromo-2'-deoxyuridine (BrdU) and clones of chondrocytes grown to senescence. Separation of minor collagens from interstitial collagens was achieved by differential salt precipitation in the presence of carrier collagens in acid conditions. The precipitate at 0.9 M NaCl 0.5 M acetic acid from control cultures was shown by CNBr peptide analysis to contain only the alpha 1(II) chain of type II collagen, whereas after BrdU treatment or growth to senescence synthesis of only alpha 1(I) and alpha 2(I) chains occurred. The synthesis of type III collagen was not detected. Analysis of the precipitate at 2.0 M NaCl, 0.5 M HAc from control cultures demonstrated the synthesis of 1 alpha, 2 alpha and 3 alpha chains together with the synthesis of short chain (SC) collagen of Mr 43000 after pepsin digestion. After BrdU treatment or growth to senescence alpha chains were isolated which possessed the migration positions on polyacrylamide gel electrophoresis (PAGE), or the elution positions on CM-cellulose chromatography, of the alpha 1(V) and alpha 2(V) chains of type V collagen. In addition, for BrdU-treated but not for control cultures, intracellular immunofluorescent staining was observed with a monoclonal antibody which specifically recognizes an epitope present in the triple helix of type V collagen. Synthesis of short chain (SC) collagen was not detected after BrdU treatment or growth to senescence. These results suggest that chick chondrocytes grown in conditions known to cause switching of collagen synthesis from type II to type I collagen also undergo a switch from the synthesis of 1 alpha, 2 alpha and 3 alpha chains to the synthesis of the alpha 1(V) and alpha 2(V) chains of type V collagen. It appears that there are several cartilage-specific collagens which together undergo a regulatory control to the synthesis of collagens typical of other connective tissues. 相似文献
17.
A brief survey and appreciation ofK. H. Rechinger's manifold activities is given on the occasion of his 80th birthday—as plant taxonomist, phyto-geographer specializing in the flora of Greece and SW. Asia, author of Flora Aegaea and editor of Flora Iranica, plant collector, head of the Department of Botany and later Director-General of the Natural History Museum in Vienna and as academic teacher at Vienna University.English version of a speech given in the Institute of Botany, University of Vienna on October 18th, 1986 on the occasion ofK. H. Rechinger's 80th birthday. 相似文献
18.
Brandon Kendhammer 《Ethnic and racial studies》2013,36(1):51-71
While W.E.B. DuBois's importance as a political activist and writer is well-documented, a ‘DuBoisian’ political theory has proved illusory. I argue that the key to change and continuity in DuBois's work is his pan-Africanism, which he used to develop a broad theory of anti-colonial nationalism. This reading of his legacy emphasizes DuBois's singular role in shaping anti-colonial discourse in the postwar era, especially in Africa, as well as in theorizing African nationalism and the African diaspora. It also allows us to understand the contradiction of the early, liberal DuBois's views on race and his later preoccupation with Communism. I suggest that across both positions, DuBois's actual political arguments remained over-determined by his positionality within the colonial world, producing a set of anti-colonial arguments that while rooted in the economic exploitation of the colonies, appeal to liberal universalizing standards of progress and modernity. 相似文献
19.
Prebble JN 《Journal of the history of biology》2001,34(3):433-460
Mitchell's formulation of the chemiosmotic theory of oxidative phosphorylation in 1961 lacked any experimental support for
its three central postulates. The path by which Mitchell reached this theory is explored. A major factor was the role of Mitchell's
philosophical system conceived in his student days at Cambridge. This system appears to have become a tacit influence on his
work in the sense that Polanyi understood all knowledge to be generated by an interaction between tacit and explicit knowing.
Early in his life Mitchell had evolved a simple philosophy based on fluctoids, fluctids and statids which was developed in
a thesis submitted for the z at the University of Cambridge, England. This aspect of his work was rejected by the examiners
and became a tacit element in his intellectual development. It is argued from his various publications that this philosophy
can be traced as an underlying theme behind much of Mitchell's theoretical writing in the 50's leading, through his notion
of vectorial metabolism, to the formulation and amplification of the chemiosmotic theory in the sixties. This philosophy formed
the basis for Mitchell of his understanding of biological systems and gave him his unique approach to cell biology.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Adrian Desmond 《Journal of the history of biology》1984,17(2):189-223
Conclusion Wakley in 1846 called Grant at once the most eloquent, the most accomplished, the most self-sacrificing, and the most unrewarded man in the profession.128 I have shown some of the reasons why this was so, and I have suggested that his Lamarckism was one of a number of factors that served to alienate him from the conservative scientific community in the 1830's and 1840's. I have further shown the need for a fundamental rethinking of Grant's position in the history of biology. There is little profit in seeing him as a precursor of Darwin. His importance lies as a teacher of philosophical anatomy and as the disseminator of Geoffroy's views in London. With the recent interest of historians in the emergence of a non-Paleyite approach to design in the 1830's (that is, an approach stemming from a unity of plan), a reassessment of Grant along these lines seems in order.Also, by understanding Grant's professional and transmutational threat, we can more fully appreciate the anti-Lamarckian ploys of leading scientists like Owen and Lyell. These scientific and social tactics reinforced the isolation Grant suffered as a result of his radical, materialistic, and antimonopolist views. Together with the laissez-faire arrangements at the joint-stock university, they led to his financial collapse — and to the decline of his scientific output that Darwin found so inexplicable. Beddoe described Grant as a disappointed man. Alas! wrote Wakley. Who would be an English Cuvier?129 相似文献