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1.
At a wide range of synapses, synaptic vesicles reside in distinct pools that respond to different stimuli. The recycling pool supplies the vesicles required for release in response to modest stimulation, whereas the reserve pool is mobilized only by strong stimulation. Multiple pathways have been proposed for the recycling of synaptic vesicles after exocytosis, but the relationship of these pathways to the different synaptic vesicle pools has remained unclear. Synaptic vesicle proteins have also been assumed to undergo recycling as a unit. However, emerging data indicate that differences in the association with distinct endocytic adaptors such as the heterotetrameric adaptor AP3 influence the trafficking of individual synaptic vesicle proteins, affecting the composition of synaptic vesicles and hence their functional characteristics. These observations might begin to account for differences in the properties of different vesicle pools. 相似文献
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Hulbert AJ Turner N Hinde J Else P Guderley H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(2):93-105
Mitochondria were isolated from the liver, kidney and mixed hindlimb skeletal muscle of three vertebrate species; the laboratory
rat Rattus norvegicus, the bearded dragon lizard Pogona vitticeps, and the cane toad Bufo marinus. These vertebrate species are approximately the same body mass and have similar body temperatures. The content of cytochromes
B, C, C1, and A were measured in these isolated mitochondria by oxidised–reduced difference spectra. Adenine nucleotide translocase
(ANT) was measured by titration of mitochondrial respiration with carboxyactractyloside and the protein and phospholipid content
of isolated mitochondria were also measured. Fatty acid composition of mitochondrial phospholipids was measured. Mitochondrial
respiration was measured at 37°C under states III and IV conditions as well as during oligomycin inhibition. Species differed
in the ratios of different mitochondrial cytochromes. Muscle mitochondria differed from kidney and liver mitochondria by having
a higher ANT content relative to cytochrome content. Respiration rates were compared relative to a number of denominators
and found to be most variable when expressed relative to mitochondrial protein content and least variable when expressed relative
to mitochondrial cytochrome A and ANT content. The turnover of cytochromes was calculated and found to vary between 1 and
94 electrons s−1. The molecular activity of mitochondrial cytochromes was found to be significantly positively correlated with the relative
polyunsaturation of mitochondrial membrane lipids. 相似文献
4.
Hyland ME 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2011,366(1572):1828-1837
This paper challenges the common assumption that the mechanisms underlying short-term placebo paradigms (where there is no motivation for health improvement) and long-term placebo paradigms (where patients value improvement in their health) are the same. Three types of motivational theory are reviewed: (i) classical placebo motivation theory that the placebo response results from the desire for therapeutic improvement; (ii) goal activation model that expectancy-driven placebo responses are enhanced when the placebo response satisfies an activated goal; and (iii) motivational concordance model that the placebo response is the consequence of concordance between the placebo ritual and significant intrinsic motives. It is suggested that current data are consistent with the following theory: response expectancy, conditioning and goal activation are responsible for short-term placebo effects but long-term therapeutic change is achieved through the effects of goal satisfaction and affect on the inflammatory response system and hypothalamic-pituitary-adrenal axis. Empirical predictions of this new theory are outlined, including ways in which placebo effects can be combined with other psychologically mediated effects on short-term and long-term psychological and physiological state. 相似文献
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Non-tree-based ("surrogate") methods have been used to identify instances of lateral genetic transfer in microbial genomes but agreement among predictions of different methods can be poor. It has been proposed that this disagreement arises because different surrogate methods are biased towards the detection of certain types of transfer events. This conjecture is supported by a rigorous phylogenetic analysis of 3776 proteins in Escherichia coli K12 MG1655 to map the ages of transfer events relative to one another. 相似文献
6.
Emergence of drug resistance is a major problem in the treatment of many diseases including tuberculosis. To tackle the problem
from a wholistic perspective, it is essential to understand the molecular mechanisms by which bacteria acquire drug resistance
using a systems approach. Availability of genome-scale data of expression profiles under different drug exposed conditions
and protein–protein interactions, makes it feasible to reconstruct and analyze systems-level models. A number of proteins
involved in different resistance mechanisms, referred to as the resistome are identified from literature. The interaction
of the drug directly with the resistome is unable to explain most resistance processes adequately, including that of increased
mutations in the target’s binding site. We recently hypothesized that some communication might exist from the drug environment
to the resistome to trigger emergence of drug resistance. We report here a network based approach to identify most plausible
paths of such communication in Mycobacterium tuberculosis. Networks capturing both structural and functional linkages among various proteins were weighted based on gene expression
profiles upon exposure to specific drugs and betweenness centrality of the interactions. Our analysis suggests that different
drug targets and hence different drugs could trigger the resistome to different extents and through different routes. The
identified paths correlate well with the mechanisms known through experiment. Some examples of the top ranked hubs in multiple
drug specific networks are PolA, FadD1, CydA, a monoxygenase and GltS, which could serve as co-targets, that could be inhibited
in order to retard resistance related communication in the cell. 相似文献
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Iris Fry 《Biology & philosophy》1995,10(4):389-417
This paper calls attention to a philosophical presupposition, coined here the continuity thesis which underlies and unites the different, often conflicting, hypotheses in the origin of life field. This presupposition, a necessary condition for any scientific investigation of the origin of life problem, has two components. First, it contends that there is no unbridgeable gap between inorganic matter and life. Second, it regards the emergence of life as a highly probable process. Examining several current origin-of-life theories. I indicate the implicit or explicit role played by the continuity thesis in each of them. In addition, I identify the rivals of the thesis within the scientific community — the almost miracle camp. Though adopting the anti-vitalistic aspect of the continuity thesis, this camp regards the emergence of life as involving highly improbable events. Since it seems that the chemistry of the prebiotic stages and of molecular self-organization processes rules out the possibility that life is the result of a happy accident, I claim that the almost miracle view implies in fact, a creationist position. 相似文献
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Prey evolve antipredator strategies against multiple enemies in nature. We examined how a prey species adopts different predation avoidance tactics against pursuit or sit‐and‐wait predators. As prey, we used three strains of Tribolium beetles artificially selected for short (short strain) or long (long strain) duration of death feigning, and a stock culture (base population). Death feigning is known to be effective for evading a jumping spider in the case of the long strains, while the present study showed that the long‐strain beetles used freezing against a sit‐and‐wait type predator, Amphibolus venator, in this study. The short‐ strain beetles were more easily oriented toward predators. The time to predation was also shorter in the short strains compared to the long strains. The results showed that, as prey, the short strains displayed the same behavior, escaping, against both types of predators. Traditionally, death feigning has been thought to be the last resort in a series of antipredator avoidance behaviors. However, our results showed that freezing and death feigning were not parts of a series of behaviors, but independent strategies against different predators, at least for long‐strain beetles. We also examined the relationship between a predator''s starvation level and its predatory behavior. In addition, the orientation behavior toward and predation rate on the prey were observed to determine how often the predatory insect attacked the beetles. 相似文献
11.
Jan Lukáš Carlos Bernstein Hainan Gu Silvia Dorn 《Entomologia Experimentalis et Applicata》2010,136(1):80-88
In the parasitoid Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae), asexual and sexual wasps coexist in the field in the Mediterranean basin, but only the asexual strain is present indoors. The sexual strain dominates outdoors despite the demographic costs associated with the production of males and mate location. The present study tests whether females of the sexual and asexual strains of V. canescens differ in flight characteristics in line with the differences of their preferred habitats and enquires whether these differences might contribute to the persistence of sexually reproducing individuals in the vicinity of asexual counterparts. The results show that sexual female wasps are smaller than their asexual counterparts. The size of wasps has a strong influence on flight parameters, with larger animals generally being better fliers. In wasps of approximately the same size, sexual wasps fly faster than their asexual counterparts under experimental laboratory conditions, in terms of both the average speed over the observation period as well as the longest single flight. Sexual wasps also perform fewer flights to cover the same distance. Sexual wasps have higher wing loading than asexual ones of the same size, which could have contributed to the observed differences in speed between individuals of both reproductive modes. There are no significant differences between the two reproductive modes in the parameters related to the distance traversed or the time spent in flight. This study shows clear differences in the flight behaviour of sexual and asexual V. canescens. Together with previous results, this finding suggests differential adaptations to their preferred habitats. These differences might ease the competition between modes of reproduction through niche and habitat differentiation and might help to explain their coexistence on a geographical scale. 相似文献
13.
IL-1α and IL-1β recruit different myeloid cells and promote different stages of sterile inflammation
Rider P Carmi Y Guttman O Braiman A Cohen I Voronov E White MR Dinarello CA Apte RN 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(9):4835-4843
The immune system has evolved to protect the host from invading pathogens and to maintain tissue homeostasis. Although the inflammatory process involving pathogens is well documented, the intrinsic compounds that initiate sterile inflammation and how its progression is mediated are still not clear. Because tissue injury is usually associated with ischemia and the accompanied hypoxia, the microenvironment of various pathologies involves anaerobic metabolites and products of necrotic cells. In the current study, we assessed in a comparative manner the role of IL-1α and IL-1β in the initiation and propagation of sterile inflammation induced by products of hypoxic cells. We found that following hypoxia, the precursor form of IL-1α, and not IL-1β, is upregulated and subsequently released from dying cells. Using an inflammation-monitoring system consisting of Matrigel mixed with supernatants of hypoxic cells, we noted accumulation of IL-1α in the initial phase, which correlated with the infiltration of neutrophils, and the expression of IL-1β correlated with later migration of macrophages. In addition, we were able to show that IL-1 molecules from cells transfected with either precursor IL-1α or mature IL-1β can recruit neutrophils or macrophages, respectively. Taken together, these data suggest that IL-1α, released from dying cells, initiates sterile inflammation by inducing recruitment of neutrophils, whereas IL-1β promotes the recruitment and retention of macrophages. Overall, our data provide new insight into the biology of IL-1 molecules as well as on the regulation of sterile inflammation. 相似文献
14.
Mate choice for neutral and MHC genetic characteristics in Alpine marmots: different targets in different contexts?
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Mariona Ferrandiz‐Rovira Dominique Allainé Marie‐Pierre Callait‐Cardinal Aurélie Cohas 《Ecology and evolution》2016,6(13):4243-4257
Sexual selection through female mate choice for genetic characteristics has been suggested to be an important evolutionary force maintaining genetic variation in animal populations. However, the genetic targets of female mate choice are not clearly identified and whether female mate choice is based on neutral genetic characteristics or on particular functional loci remains an open question. Here, we investigated the genetic targets of female mate choice in Alpine marmots (Marmota marmota), a socially monogamous mammal where extra‐pair paternity (EPP) occurs. We used 16 microsatellites to describe neutral genetic characteristics and two MHC loci belonging to MHC class I and II as functional genetic characteristics. Our results reveal that (1) neutral and MHC genetic characteristics convey different information in this species, (2) social pairs show a higher MHC class II dissimilarity than expected under random mate choice, and (3) the occurrence of EPP increases when social pairs present a high neutral genetic similarity or dissimilarity but also when they present low MHC class II dissimilarity. Thus, female mate choice is based on both neutral and MHC genetic characteristics, and the genetic characteristics targeted seem to be context dependent (i.e., the genes involved in social mate choice and genetic mate choice differ). We emphasize the need for empirical studies of mate choice in the wild using both neutral and MHC genetic characteristics because whether neutral and functional genetic characteristics convey similar information is not universal. 相似文献
15.
Timo Muotka 《Oecologia》1990,85(2):281-292
Summary Guild structure and coexistence of filter feeding caddis larvae was studied in three lake-outlet streams in northern Finland. Natural stones were used as sampling units, and for each stone measurements of six microhabitat variables were taken. Species and species instar relationships in the multivariate microhabitat space were analyzed by a method based on Principal Components Analysis. Seven species of filtering caddis larvae were found at the study sites, but detailed analysis was restricted to the four most abundant ones (Polycentropus flavomaculatus, Hydropsyche angustipennis, H. pellucidula, H. saxonica). P. flavomaculatus was the microhabitat generalist of the guild, whereas all the hydropsychids were narrowly specialized in at least one larval instar. In all species, different instars utilized the microhabitat somewhat differentially. Moss content and Froude number were significantly different between instar microhabitats in all comparisons. Ontogenetic niche changes not only separated species instars from each other, but also profoundly changed the biotic as well as abiotic environment of the species at different phases of larval development. This may have important effects on the dynamics of interacting species and, consequently, on the guild structure. While some of the more classical models of coexistence may also be relevant for understanding coexistence in this guild of sessile stream insects, ontogenetic niche changes clearly need to be taken into consideration in future studies of guild structure and species interactions of filter feeding caddisfly larvae. 相似文献
16.
Jane R Allison Marlen M��ller Wilfred F van Gunsteren 《Protein science : a publication of the Protein Society》2010,19(11):2186-2195
The right‐handed α‐helix is the dominant helical fold of α‐peptides, whereas the left‐handed 314‐helix is the dominant helical fold of β‐peptides. Using molecular dynamics simulations, the properties of α‐helical α‐peptides and 314‐helical β‐peptides with different C‐terminal protonation states and in the solvents water and methanol are compared. The observed energetic and entropic differences can be traced to differences in the polarity of the solvent‐accessible surface area and, in particular, the solute dipole moments, suggesting different reasons for their stability. 相似文献
17.
Toxoplasma gondii is a protozoan parasite that is globally widespread and causes a common infection of many warm-blooded animals. It has an unusual population structure with a few clonally reproducing strains apparently dominating in many of its hosts, which include humans. In mice, the various strains of the parasite differ enormously in their virulence and disease presentation. In humans, disease manifestations are highly variable, ranging from asymptomatic to severe, especially in cases of brain and eye infection. Recent data suggest that, as with mice, at least part of this variability in human infection may be tied to the type of strain that causes the infection. Improvements in our knowledge of this parasite's population biology and ways to determine the genotype of an infecting strain should make it possible to test this relationship in various disease scenarios. Clear correlations will substantially affect the management of human disease, matching an aggressive infection with an equally aggressive treatment. 相似文献
18.
Young KD 《Current opinion in microbiology》2007,10(6):596-600
The fact that bacteria have different shapes is not surprising; after all, we teach the concept early and often and use it in identification and classification. However, why bacteria should have a particular shape is a question that receives much less attention. The answer is that morphology is just another way microorganisms cope with their environment, another tool for gaining a competitive advantage. Recent work has established that bacterial morphology has an evolutionary history and has highlighted the survival value of different shapes for accessing nutrients, moving from one place to another, and escaping predators. Shape may be so important in some of these endeavors that an organism may change its morphology to fit the circumstances. In short, if a bacterium needs to eat, divide or survive, or if it needs to attach, move or differentiate, then it can benefit from adopting an appropriate shape. 相似文献
19.
Caveolae, discovered by electron microscope in the 1950s, are membrane invaginations that accommodate various molecules that are involved in cellular signaling. Caveolin, a major protein component of caveolae identified in 1990s, has been known to inhibit the function of multiple caveolar proteins, such as kinases, which are involved in cell growth and proliferation, and thus considered to be a general growth signal inhibitor. Recent studies using transgenic mouse models have suggested that insulin signal may be exempted from this inhibition, which rather requires the presence of caveolin for proper signaling. Caveolin may stabilize insulin receptor protein or directly stimulate insulin receptors. Other studies have demonstrated that caveolae provide the TC10 complex with cellular microdomains for glucose transportation through Glut4. These findings suggest that caveolin plays an important role in insulin signal to maintain glucose metabolism in intact animals. However, the role of caveolin in insulin signal may differ from that in other transmembrane receptor signals. 相似文献
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W H Fuchsman C R Barton M M Stein J T Thompson R M Willett 《Biochemical and biophysical research communications》1976,68(2):387-392
The ratio of leghemoglobin c content to leghemoglobin a content in soybean (Glycine max) root nodules drops in the early stages of plant growth and becomes constant during flowering and fruiting. These data bring into question the assumption that leghemoglobin components have a single biochemical role in nitrogen fixation. 相似文献