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1.
In the period 1875–1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
1. Rates of entry and oxidation of a range of metabolites have been measured in tracheostomized sheep (diet, 800g. of lucerne chaff and 100g. of maize/day) by combining isotope-dilution techniques with the continuous measurement of total respiratory gas exchange, and 14CO2 production during the intravenous or intraruminal infusion of 14C-labelled substrates. 2. Mean entry rates in fed and starved (24hr.) sheep respectively, expressed as mg./min./kg. body wt.0·75, were: glucose, 5·0 (range 4·8–5·1, 2 observations) and 3·8 (3·2–4·2, 4); acetate, 10·8 (9·1–13·5, 4) and 5·8 (1); d(−)-β-hydroxybutyrate, 1·4 (1) and 1·5 (0·8–2·4, 4); palmitate, oleate and stearate (starved sheep only) 1·0 (0·6–1·9, 7), 0·9 (0·2–1·6, 10) and 0·9 (0·5–1·1, 11) respectively. 3. Production rates of propionate and butyrate in continuously feeding sheep were 6·4 (4·7–8·3, 4) and 4·3 (3·4–6·1, 4) mg./min./kg.0·75 respectively, and in starved (24hr.) sheep were 2·5 (2·2–2·9, 2) and 1·0 (0·8–1·2, 2) mg./min./kg.0·75 respectively. 4. Calculated terminal values for the specific radioactivity of respiratory 14CO2 during measurements of entry rates and production rates were used to calculate the contributions of individual substrates to overall oxidative metabolism. Mean values for fed and starved sheep respectively were: glucose, 9·1 (8·6–9·6, 2) and 11·2 (5·9–15·1, 4)%; acetate, 31·6 (26·8–38·1, 4) and 22·1 (1)%; d(−)-β-hydroxybutyrate, 10·4 (1) and 4·8 (1·9–7·7, 4)%; propionate, 23·0 (13·8–29·9, 4) and 7·1 (6·8–7·4, 2)%; butyrate, 16·5 (13·7–20·5, 4) and 5·3 (5·2–5·3, 2)%; palmitate, oleate and stearate (starved sheep only), 4·7 (2·0–7·7, 7), 4·0 (1·2–6·6, 10) and 4·4 (3·8–5·8, 9)% respectively. The sum of these values for individual substrates in fed and starved sheep, excluding that of β-hydroxybutyrate and after correction of the glucose value for the known interrelations of this substrate with propionate, accounted for 76% and 58% respectively of total production of carbon dioxide. 5. Calculations based on the proportion of substrate entry directly oxidized indicated that the substrates studied accounted for 63% (fed sheep) and 43% (starved sheep) of total energy expenditure measured by oxygen uptake. The contribution of β-hydroxybutyrate was excluded, and corrections were made for glucose–propionate interrelations, and for the different rates of oxidation of the methyl and carboxyl fragments of acetate. 6. The present results have been combined with those obtained earlier in this Laboratory to examine the relationships between rates of substrate entry and oxidation, and concentrations of substrate in blood. Rates of entry of acetate, glucose, d(−)-β-hydroxybutyrate, palmitate and oleate (but not stearate) were well correlated with concentration in blood, and substrate contribution to production of carbon dioxide showed a similar correlation to blood concentration, except with glucose. 7. It was concluded that the general technique is of potential value in providing valid quantitative parameters of animal metabolism.  相似文献   

3.
This article revisits the development of the protoplasm concept as it originally arose from critiques of the cell theory, and examines how the term “protoplasm” transformed from a botanical term of art in the 1840s to the so-called “living substance” and “the physical basis of life” two decades later. I show that there were two major shifts in biological materialism that needed to occur before protoplasm theory could be elevated to have equal status with cell theory in the nineteenth century. First, I argue that biologists had to accept that life could inhere in matter alone, regardless of form. Second, I argue that in the 1840s, ideas of what formless, biological matter was capable of dramatically changed: going from a “coagulation paradigm” (Pickstone, 1973) that had existed since Theophrastus, to a more robust conception of matter that was itself capable of movement and self-maintenance. In addition to revisiting Schleiden and Schwann’s original writings on cell theory, this article looks especially closely at Hugo von Mohl’s definition of the protoplasm concept in 1846, how it differed from his primordial utricle theory of cell structure two years earlier. This article draws on Lakoff and Johnson’s theory of “ontological metaphors” to show that the cell, primordial utricle, and protoplasm can be understood as material container, object, and substance, and that these overlapping distinctions help explain the chaotic and confusing early history of cell theory.  相似文献   

4.
Fusarium, graminearum KF 370 isolate is able to simultaneous biosynthesis of three toxic metabolites, namely: fusarenone-X (FUS), nivalenol (NIV) and zearalenone (F-2). After metabolites extraction with methanol — water (3:1) and defatting with n-heptane toxins were partitioned into chloroform layer. Purification of the? compounds was performed on Celite 545 — charcoal — Aluminiumoxid 90 column then metabolites were separated on Kieselgel 60 (200–300 mesh) column with developing solvent chloroform — methanol. This way FUS, NIV and F-2 were obtained as crystalline or high purity standards.  相似文献   

5.
Human immunodeficiency virus (HIV) is the infectious agent causing acquired immu-nodeficiency syndrome (AIDS),a deadliest scourge of human society. Hepatitis C virus (HCV) is a major causative agent of chronic liver disease and infects an estimated 170 million people worldwide,resulting in a serious public health burden. Due to shared routes of transmission,co-infection with HIV and HCV has become common among individuals who had high risks of blood exposures. Among hemophiliacs the co-infection rate accounts for 85%; while among injection drug users (IDU) the rate can be as high as 90%. HIV can accelerate the progression of HCV-related liver disease,particularly when immunodeficiency has developed. Although the effect of HCV on HIV infection is controversial,most studies showed an increase in mortality due to liver disease. HCV may act as a direct cofactor to fasten the progression of AIDS and decrease the tolerance of highly active antiretroviral therapy (HARRT). Conversely,HAART-related hepatotoxicity may enhance the progression of liver fibrosis. Due to above complications,co-infection with HCV and HIV-1 has imposed a critical challenge in the management of these patients. In this review,we focus on the epidemiology and transmission of HIV and HCV,the impact of the two viruses on each other,and their treatment.  相似文献   

6.
Conservation of mass and energy are essential to physical accounting, just as price and market balances are essential to economic accounting. These principles guide data collection and inventory compilation in industrial ecology. The resulting balanced surveys, however, can rarely be used directly for life cycle assessment (LCA) or environmentally extended input‐output (EEIO) analysis; some modeling is necessary to recast coproductions by multifunctional activities as monofunctional unit processes (a.k.a. Leontief production functions or technical “recipes”). This modeling is done with allocations in LCA and constructs in input‐output. In this article, we ask how these models respect or perturb the balances of the original inventory. Which allocations or constructs, applied to what type of data set, have the potential to simultaneously respect its multiple physical, financial, and market balances? Our analysis builds upon the recent harmonization of allocations and constructs and the ongoing development of multilayered supply and use inventory tables. We derive the necessary and sufficient conditions for balanced models, investigate the role of data aggregation, and clarify these models' relation to system expansion. We find that none of the modeling families in LCA and EEIO are balanced in general, but special data characteristics can allow for the respect of multiple balances. An analysis of these special cases allows for clear guidance for data compilation and methods integration.  相似文献   

7.
Computer based sequence comparisons indicate partial sequence homology between human c-myc, Rous sarcoma virus, adenovirus 7, and simian sarcoma virus proteins and the cytoskeletal proteins desmin, keratin and vimentin. In addition, sections of the oncogene proteins showed partial but significant homology to and subunits of transducin, -II and -BP crystallins showed partial but significant homology to the cytoskeletal proteins keratin, vimentin, desmin, and -tubulin, and to adenovirus 7 and simian sarcoma virus transforming gene proteins. -BP crystallin showed partial but significant homology to Rous sarcoma virus protein, and to and y subunits of transducin. Both crystallins showed partial sequence homology to the GTP-binding protein elongation factor TU fromEscherichia coli . These sequence homologies suggest a link between the mechanisms of normal lens cell differentiation, involving modifications to the cytoskeleton and subsequent changes to the pattern of protein synthesis, and mechanisms of neoplastic transformation. Furthermore the transducin-like region on -crystallin may be important for its interaction with lens membranes and the maintenance of short-range order for lens transparency.  相似文献   

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In nature, no single plant completes its life cycle withoutencountering environmental stress. When plant cells surpassstress threshold stimuli, chemically reactive oxygen species(ROS) are generated that can cause oxidative damage or act assignals. Plants have developed numerous ROS-scavenging systemsto minimize the cytotoxic effects of ROS. The role of sucrosyloligosaccharides (SOS), including fructans and the raffinosefamily oligosaccharides (RFOs), is well established during stressphysiology. They are believed to act as important membrane protectorsin planta. So far a putative role for sucrose and SOS duringoxidative stress has largely been neglected, as has the contributionof the vacuolar compartment. Recent studies suggest a link betweenSOS and oxidative defence and/or scavenging. SOS might be involvedin stabilizing membrane-associated peroxidases and NADPH oxidases,and SOS-derived radicals might fulfil an intermediate role inoxido-reduction reactions taking place in the vicinity of membranes.Here, these emerging features are discussed and perspectivesfor future research are provided. Key words: Fructan, oxidative stress, raffinose, ROS, sucrose, sucrosyl oligosaccharides Received 25 September 2008; Revised 20 October 2008 Accepted 23 October 2008  相似文献   

11.
The purpose of this paper is to describe some parallels and theoretical affinities between biosemiotics and biolinguistics. In particular, this paper examines the importance of Uexküll's Umwelt and Peircean abduction as foundational concepts for Sebeok's biosemiotics and Chomsky's biolinguistic program. Other affinities touched upon in this paper include references to concepts articulated by Immanuel Kant, Konrad Lorenz, Marcel Florkin, François Jacob, C.H. Waddington, D'Arcy Thomson and Ernst Haeckel. While both programs share theoretical influences and historiographical parallels in their mid-century origins continuing throughout the late twentieth century, recent articulations of biosemiotics and biolinguistics privilege different intellectual styles and methods of inquiry that define their future objectives as intellectual movements. The goal of this paper is to show that, in spite of the different scholarly agendas of biosemiotics and biolinguistics, both movements share a theoretical and philosophical core in Peirce and Uexküll.  相似文献   

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The lactoperoxidase (LPO), retinoblastoma (RB1), and -lactalbumin (LALBA) genes have been mapped by fluorescent in situ hybridization respectively to cattle Chromosomes (Chrs) 19, 12, 5; goat Chrs 19, 12, 5; and sheep Chrs 11, 10, 3. The results confirm the homologies among cattle, sheep, and goat chromosomes, previously reported, and provide more information for the comparison between the bovine and human karyotypes and gene maps.  相似文献   

15.
Advances in proteogenomic technologies have revealed hundreds to thousands of translated small open reading frames (sORFs) that encode microproteins in genomes across evolutionary space. While many microproteins have now been shown to play critical roles in biology and human disease, a majority of recently identified microproteins have little or no experimental evidence regarding their functionality. Computational tools have some limitations for analysis of short, poorly conserved microprotein sequences, so additional approaches are needed to determine the role of each member of this recently discovered polypeptide class. A currently underexplored avenue in the study of microproteins is structure prediction and determination, which delivers a depth of functional information. In this review, we provide a brief overview of microprotein discovery methods, then examine examples of microprotein structures (and, conversely, intrinsic disorder) that have been experimentally determined using crystallography, cryo-electron microscopy, and NMR, which provide insight into their molecular functions and mechanisms. Additionally, we discuss examples of predicted microprotein structures that have provided insight or context regarding their function. Analysis of microprotein structure at the angstrom level, and confirmation of predicted structures, therefore, has potential to identify translated microproteins that are of biological importance and to provide molecular mechanism for their in vivo roles.  相似文献   

16.
Thorens B 《Cell metabolism》2011,14(4):439-440
The molecular mechanisms linking diet, obesity, and type 2 diabetes are still poorly understood. In a recent paper, Ohtsubo et?al. (2011) show that high lipid levels induce nuclear exclusion of Foxa2 and HNF1α in β cells, leading to impaired expression and glycosylation of proteins controlling glucose-stimulated insulin secretion.  相似文献   

17.
Babic M  Zinsmaier KE 《Neuron》2011,69(6):1039-1041
In this issue of Neuron, two studies by Pielage et?al. and Bednarek and Caroni suggest that the cytoskeleton regulator β-Adducin provides an activity-dependent switch controlling synapse disassembly and assembly at the Drosophila neuromuscular junction (NMJ) and the mouse hippocampus. In mice, the β-Adducin switch is required for the improvement of learning and memory induced by enriched environments.  相似文献   

18.
Caveolin,Cholesterol, and Lipid Droplets?   总被引:11,自引:0,他引:11       下载免费PDF全文
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19.
Although some studies have shown that cognitive training can produce improvements to untrained cognitive domains (far transfer), many others fail to show these effects, especially when it comes to improving fluid intelligence. The current study was designed to overcome several limitations of previous training studies by incorporating training expectancy assessments, an active control group, and “Mind Frontiers,” a video game-based mobile program comprised of six adaptive, cognitively demanding training tasks that have been found to lead to increased scores in fluid intelligence (Gf) tests. We hypothesize that such integrated training may lead to broad improvements in cognitive abilities by targeting aspects of working memory, executive function, reasoning, and problem solving. Ninety participants completed 20 hour-and-a-half long training sessions over four to five weeks, 45 of whom played Mind Frontiers and 45 of whom completed visual search and change detection tasks (active control). After training, the Mind Frontiers group improved in working memory n-back tests, a composite measure of perceptual speed, and a composite measure of reaction time in reasoning tests. No training-related improvements were found in reasoning accuracy or other working memory tests, nor in composite measures of episodic memory, selective attention, divided attention, and multi-tasking. Perceived self-improvement in the tested abilities did not differ between groups. A general expectancy difference in problem-solving was observed between groups, but this perceived benefit did not correlate with training-related improvement. In summary, although these findings provide modest evidence regarding the efficacy of an integrated cognitive training program, more research is needed to determine the utility of Mind Frontiers as a cognitive training tool.  相似文献   

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