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61.
HYUK JE LEE ELIZABETH G. BOULDING 《Biological journal of the Linnean Society. Linnean Society of London》2010,100(3):494-505
Natural populations of widely‐distributed animals often exhibit clinal variation in phenotypic traits or in allele frequencies of a particular gene over their geographical range. A planktotrophic intertidal snail, Littorina keenae is broadly distributed along the north‐eastern Pacific coast through a large latitudinal range (24°50′N–43°18′N). We tested for latitudinal clines in two complex phenotypic traits – thermal tolerance and body size – and one single locus trait – heat shock cognate 70 (HSC70) – in L. keenae along almost its entire geographical range. We found only weak evidence for a latitudinal cline in the thermal tolerance and no evidence for a cline in allele frequencies at HSC70. However, as predicted by Bergmann's rule, we detected a strong latitudinal cline that accounted for 60% of the variance in body size (R2 = 0.598; P < 0.001). In contrast, body size did not significantly affect thermal tolerance. HSC70 showed no genetic differentiation among the populations, supporting our previous mitochondrial gene‐based estimate of high gene flow during this snail's free‐swimming larval stage. Given that L. keenae experiences panmixia along its species range, the observed size cline may be partially or entirely caused by a phenotypically plastic response to local thermal environments rather than by genetic divergence in body size among populations in response to locally optimizing natural selection. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 494–505. 相似文献
62.
Jane E. Libbey Nikki J. Kirkman Karen S. Wilcox H. Steve White Robert S. Fujinami 《Journal of virology》2010,84(13):6452-6460
Complement, part of the innate immune system, acts to remove pathogens and unwanted host material. Complement is known to function in all tissues, including the central nervous system (CNS). In this study, we demonstrated the importance of the complement system within the CNS in the development of behavioral seizures following Theiler''s murine encephalomyelitis virus (TMEV) infection. C57BL/6 mice, deficient in complement component C3, developed significantly fewer behavioral seizures following TMEV infection, whereas mice depleted of complement component C3 in the periphery through treatment with cobra venom factor had a seizure rate comparable to that of control mice. These studies indicate that C3 participates in the induction of acute seizures during viral encephalitis.The complement system, a component of the innate immune system, functions to recognize and eliminate pathogens and unwanted host material (1). Activation of complement can occur by the classical, alternative, lectin, and terminal pathways (1). The classical pathway is activated by antigen-antibody complexes, some viruses, Gram-negative bacteria, or C-reactive protein complexes (4). The alternative pathway is activated by lipopolysaccharides and polysaccharides on the surfaces of viruses, bacteria, fungi, and parasites. The lectin pathway is activated by mannose or N-acetylglucosamine on the surfaces of bacteria and other pathogens (4). The complement system, consisting of >40 proteins, is highly regulated by the expression of complement inhibitors and complement receptors, as the complement system can have deleterious effects when unregulated (1). Two important steps in the complement cascade are the cleavage of the multifunctional complement proteins C3 and C5 into C3a and C3b proteins and C5a and C5b proteins, respectively. The anaphylatoxins C3a and C5a function to recruit leukocytes and induce inflammation. C3b functions in opsonization, the process of coating pathogens or particulate material with opsonin and thus making it more susceptible to phagocytosis. C5b functions to initiate the assembly of the C5b-C9 complex, the membrane attack complex (MAC), leading to pathogen lysis. Proteins of the complement system are found throughout all tissues and bodily fluids. Although primarily produced by hepatocytes in the liver, other cell types constitutively express low levels of complement proteins (1).Complement proteins are constitutively produced by neurons, microglia, astrocytes, and oligodendrocytes in the central nervous system (CNS) (14, 16, 44; reviewed in references 1 and 13). Astrocytes, the predominant glial cell type in the brain, are comparable to hepatocytes in terms of the number of complement components they produce (4). The levels of various complement mRNAs and proteins are markedly increased in the CNS following viral infection; for example, C1q and C3 proteins and mRNAs are increased in the rat brain following infection with Borna disease virus (11), and C1q protein and mRNA are increased in the rhesus macaque brain following infection with simian immunodeficiency virus (10). In both cases, the increase in the production of C1q in the brain was localized to microglia/macrophages (10, 11). Complement activation has also been shown to be involved in the control of other viral infections, such as the spread of West Nile virus to the CNS (24).We have been studying the role of the innate immune system in the development of acute behavioral seizures following CNS infection of C57BL/6 mice with a neurotropic virus (19, 23). Infection with Theiler''s murine encephalomyelitis virus (TMEV) results in acute seizures developing in more than 50% of C57BL/6 mice (both male and female) generally between days 3 and 10 postinfection (p.i.) (23). Two proinflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6), and concomitant inflammatory changes in the brain (perivascular cuffing comprised of infiltrating mononuclear cells, infiltration of macrophages, and/or activation of microglial cells and gliosis) were implicated as contributors to the development of acute seizures (19). In contrast, the proinflammatory cytokine IL-1, TMEV-specific CD8+ T cells, and viral persistence were discounted as playing a role in seizures (19). It was found that both the pattern of days on which the mice were observed to have seizures and the seizure score (Racine scale) for any given day varied from mouse to mouse (23). Typically, day 3 p.i. was the first day on which a few mice were observed to have seizures, day 6 p.i. was the peak of behavioral seizure activity, and the majority of seizures had a seizure score of 3 (forelimb clonus) and above (score of 4, rearing; score of 5, rearing and falling). The seizures were afebrile and appeared limbic in nature (23). The seizure frequency was observed to be one per mouse per 2-h observation period, and the duration of the seizures was typically 1 to 2 min (23, 31). Mice experiencing seizures were impaired in both coordination and motor function (23).The role of complement in the development of seizures has been studied in humans with Rasmussen''s encephalitis (RE) (41). Although several different viruses have been detected in the tissues of humans with RE by PCR and in situ hybridization, these results are still controversial. Instead it is thought that an autoimmune process underlies RE. Notwithstanding the unknown etiology of RE, the activation of the complement cascade is thought to be a critical component of disease pathogenesis. Several activated components of the complement system (C4, C8, and MAC) were shown to be present in discrete patches of neurons in the cortex of three out of five patients with active RE by immunohistochemistry (41). As a means of demonstrating in vivo that MAC deposition on neurons could trigger seizures, the individual components of the MAC (C5b6, C7, C8, and C9) were sequentially infused into the rat hippocampus, and assembly of the MAC triggered both behavioral and electrographic seizures as well as cytotoxicity (42).In our current study, we examined the role that complement may play in the development of behavioral seizures in the TMEV-induced seizure model. Through the use of mice deficient in complement component C3 and through depletion of complement component C3 in the periphery, we were able to demonstrate the importance of the complement system within the CNS in the development of seizures in the TMEV-induced seizure model. 相似文献
63.
Dogs, in the age range 1–3 years old, were randomly selected from the largest animal insurance database in Sweden for inclusion in the study. The study was performed in 1997, and a total of 680 dog owners were selected for the study. A total of 461 dog owners completed the survey, at an overall response rate of 68%. Data was compared to a recent gallup performed on a sample of all dogs in Sweden. The demographic statistics of the insured dog population were in many aspects similar to the total dog population of Sweden. Typical for both insured dogs and the total population of dogs were a low proportion of neutered dogs, that many dogs were bought at an early age, that many dogs were in contact with a "breeder" when sold, and a similar profile of health status. However, "dog breeders" seemed to have their dogs insured to a higher extent than the general dog owner. It was concluded that as the populations were alike in many respects, it is reasonable to use the insurance database for epidemiological studies on diet and exercise in Swedish dogs. 相似文献
64.
W H Cooke I V Ames JE A A Crossman J F Cox T A Kuusela K U Tahvanainen L B Moon J Drescher F J Baisch T Mano B D Levine C G Blomqvist D L Eckberg 《Journal of applied physiology》2000,89(3):1039-1045
We studied three Russian cosmonauts to better understand how long-term exposure to microgravity affects autonomic cardiovascular control. We recorded the electrocardiogram, finger photoplethysmographic pressure, and respiratory flow before, during, and after two 9-mo missions to the Russian space station Mir. Measurements were made during four modes of breathing: 1) uncontrolled spontaneous breathing; 2) stepwise breathing at six different frequencies; 3) fixed-frequency breathing; and 4) random-frequency breathing. R wave-to-R wave (R-R) interval standard deviations decreased in all and respiratory frequency R-R interval spectral power decreased in two cosmonauts in space. Two weeks after the cosmonauts returned to Earth, R-R interval spectral power was decreased, and systolic pressure spectral power was increased in all. The transfer function between systolic pressures and R-R intervals was reduced in-flight, was reduced further the day after landing, and had not returned to preflight levels by 14 days after landing. Our results suggest that long-duration spaceflight reduces vagal-cardiac nerve traffic and decreases vagal baroreflex gain and that these changes may persist as long as 2 wk after return to Earth. 相似文献
65.
MOTIVATION: Recently, we described a Maximum Weighted Matching (MWM) method
for RNA structure prediction. The MWM method is capable of detecting
pseudoknots and other tertiary base-pairing interactions in a
computationally efficient manner (Cary and Stormo, Proceedings of the Third
International Conference on Intelligent Systems for Molecular Biology, pp.
75-80, 1995). Here we report on the results of our efforts to improve the
MWM method's predictive accuracy, and show how the method can be extended
to detect base interactions formerly inaccessible to automated RNA modeling
techniques. RESULTS: Improved performance in MWM structure prediction was
achieved in two ways. First, new ways of calculating base pair likelihoods
have been developed. These allow experimental data and combined statistical
and thermodynamic information to be used by the program. Second, accuracy
was improved by developing techniques for filtering out spurious base pairs
predicted by the MWM program. We also demonstrate here a means by which the
MWM folding method may be used to detect the presence of base triples in
RNAs. AVAILABILITY: http://www.cshl.org/mzhanglab/tabaska/j axpage. html
CONTACT: tabaska@cshl.org
相似文献
66.
Single-copy nuclear DNAs (scnDNAs) of eight species of arvicoline and six
species of murine rodents were compared using DNA-DNA hybridization. The
branching pattern derived from the DNA comparisons is congruent with the
fossil evidence and supported by comparative biochemical, chromosomal, and
morphological studies. The recently improved fossil record for these
lineages provides seven approximate divergence dates, which were used to
calibrate the DNA-hybridization data. The average rate of scnDNA divergence
was estimated as 2.5%/Myr. This is approximately 10 times the rate in the
hominoid primates. These results agree with previous reports of accelerated
DNA evolution in muroid rodents and extend the DNA-DNA hybridization data
set of Brownell.
相似文献
67.
Structural comparison of fibroblast growth factor-specific heparan sulfates derived from a growing or differentiating neuroepithelial cell line 总被引:3,自引:1,他引:2
Brickman YG; Nurcombe V; Ford MD; Gallagher JT; Bartlett PF; Turnbull JE 《Glycobiology》1998,8(5):463-471
Heparan sulfate (HS) glycosaminoglycans are essential modulators of
fibroblast growth factor (FGF) activity both in vivo and in vitro, and
appear to act by cross-linking particular forms of FGF to appropriate FGF
receptors. We have recently isolated and characterized two separate HS
pools derived from immortalized embryonic day 10 mouse neuroepithelial 2.3D
cells: one from cells in log growth phase, which greatly potentiates the
activity of FGF-2, and the other from cells undergoing contact-inhibition
and differentiation, which preferentially activates FGF-1. These two pools
of HS have very similar functional activities to those species isolated
from primary neuroepithelial cells at corresponding stages of active
proliferation or differentiation. We present here a structural comparison
between these cell line HS species to establish the nature of the changes
that occur in the biosynthesis of HS. A combination of chemical and
enzymatic cleavage, low pressure chromatography and strong anion-exchange
HPLC were used to generate full chain models of each species. Overall, the
HS pools synthesized in the dividing cell line pools possessed less complex
sulfation than those derived from more differentiated, growth arrested
cells.
相似文献
68.
Carbohydrates have been suggested to account for some IgE cross- reactions
between various plant, insect, and mollusk extracts, while some IgG
antibodies have been successfully raised against plant glycoproteins. A rat
monoclonal antibody raised against elderberry abscission tissue (YZ1/2.23)
and rabbit polyclonal antiserum against horseradish peroxidase were
screened for reactivity in enzyme-linked immunosorbent assay against a
range of plant glycoproteins and extracts as well as neoglycoproteins, bee
venom phospholipase, and several animal glycoproteins. Of the
oligosaccharides tested, Man3XylFucGlcNAc2(MMXF3) derived from horseradish
peroxidase was the most potent inhibitor of the reactivity of both YZ1/2.23
and anti- horseradish peroxidase to native horseradish peroxidase
glycoprotein. The reactivity of YZ1/2. 23 and anti-horseradish peroxidase
against Sophora japonica lectin was most inhibited by a neoglycoconjugate
of bromelain glycopeptide cross-linked to bovine serum albumin, while the
defucosylated form of this conjugate was inactive as an inhibitor. A wide
range of plant extracts was found to react against YZ1/2.23 and
anti-horseradish peroxidase, with particularly high reactivities recorded
for grass pollen and nut extracts. All these reactivities were inhibitable
with the bromelain glycopeptide/bovine serum albumin conjugate. Bee venom
phospholipase and whole bee venom reacted weakly with YZ1/2.23 but more
strongly with anti-horseradish peroxidase in a manner inhibitable with the
bromelain glycopeptide/bovine serum albumin conjugate, while hemocyanin
from Helix pomatia reacted poorly with YZ1/2.23 but did react with
anti-horseradish peroxidase. It is concluded that the alpha1, 3-fucose
residue linked to the chitobiose core of plant glycoproteins is the most
important residue in the epitope recognized by the two antibodies studied,
but that the polyclonal anti-horseradish peroxidase antiserum also contains
antibody populations that recognize the xylose linked to the core mannose
of many plant and gastropod N-linked oligosaccharides.
相似文献
69.
70.