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1.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
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2.
G. E. Silvey D. C. Sandeman 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1976,108(1):67-73
1. | Intracellular recordings from identified eye muscle motoneurons provide evidence that they are monosynaptically driven by the primary sensory axons from the thread hair receptors in the statocyst. |
2. | The eye muscle motoneurons are either depolarized or actively hyperpolarized following irrigation of the Statocyst canals. The hyperpolarization of the motoneurons is brought about by the Statocyst receptors themselves either acting directly on the motoneurons or via inhibitory neurons. |
3.
High voltage-activated (HVA) Cav channels form complexes with KCa1.1 channels, allowing reliable activation of KCa1.1 current through a nanodomain interaction. We recently found that low voltage-activated Cav3 calcium channels also create KCa1.1-Cav3 complexes. While coimmunoprecipitation studies again supported a nanodomain interaction, the sensitivity to calcium chelating agents was instead consistent with a microdomain interaction. A computational model of the KCa1.1-Cav3 complex suggested that multiple Cav3 channels were necessary to activate KCa1.1 channels, potentially causing the KCa1.1-Cav3 complex to be more susceptible to calcium chelators. Here, we expanded the model and compared it to a KCa1.1-Cav2.2 model to examine the role of Cav channel conductance and kinetics on KCa1.1 activation. As found for direct recordings, the voltage-dependent and kinetic properties of Cav3 channels were reflected in the activation of KCa1.1 current, including transient activation from lower voltages than other KCa1.1-Cav complexes. Substantial activation of KCa1.1 channels required the concerted activity of several Cav3.2 channels. Combined with the effect of EGTA, these results suggest that the Ca2+ domains of several KCa1.1-Cav3 complexes need to cooperate to generate sufficient [Ca2+]i, despite the physical association between KCa1.1 and Cav3 channels. By comparison, Cav2.2 channels were twice as effective at activating KCa1.1 channels and a single KCa1.1-Cav2.2 complex would be self-sufficient. However, even though Cav3 channels generate small, transient currents, the regulation of KCa1.1 activity by Cav3 channels is possible if multiple complexes cooperate through microdomain interactions. 相似文献
4.
5.
Role of immunoglobulin A in protection against reovirus entry into Murine Peyer's patches 总被引:8,自引:0,他引:8
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Reovirus type 1 Lang (T1L) infects the mouse intestinal mucosa by adhering specifically to epithelial M cells and exploiting M-cell transport to enter the Peyer's patches. Oral inoculation of adult mice has been shown to elicit cellular and humoral immune responses that clear the infection within 10 days. This study was designed to determine whether adult mice that have cleared a primary infection are protected against viral entry upon oral rechallenge and, if so, whether antireovirus secretory immunoglobulin A (S-IgA) is a necessary component of protection. Adult BALB/c mice that were orally inoculated on day 0 with reovirus T1L produced antiviral S-IgA in feces and IgG in serum directed primarily against the reovirus sigma1 attachment protein. Eight hours after oral reovirus challenge on day 21, the Peyer's patches of previously exposed mice contained no detectable virus whereas Peyer's patches of naive controls contained up to 2,300 PFU of reovirus/mg of tissue. Orally inoculated IgA knockout (IgA(-/-)) mice cleared the initial infection as effectively as wild-type mice and produced higher levels of reovirus-specific serum IgG and secretory IgM than C57BL/6 wild-type mice. When IgA(-/-) mice were rechallenged on day 21, however, their Peyer's patches became infected. These results indicate that intestinal S-IgA is an essential component of immune protection against reovirus entry into Peyer's patch mucosa. 相似文献
6.
Aravinthan DT Samuel Venkatesh N Murthy Michael O Hengartner 《BMC developmental biology》2001,1(1):8-6
Background
Of the animals typically used to study fertilization-induced calcium dynamics, none is as accessible to genetics and molecular biology as the model organism Caenorhabditis elegans. Motivated by the experimental possibilities inherent in using such a well-established model organism, we have characterized fertilization-induced calcium dynamics in C. elegans.Results
Owing to the transparency of the nematode, we have been able to study the calcium signal in C. elegans fertilization in vivo by monitoring the fluorescence of calcium indicator dyes that we introduce into the cytosol of oocytes. In C. elegans, fertilization induces a single calcium transient that is initiated soon after oocyte entry into the spermatheca, the compartment that contains sperm. Therefore, it is likely that the calcium transient is initiated by contact with sperm. This calcium elevation spreads throughout the oocyte, and decays monotonically after which the cytosolic calcium concentration returns to that preceding fertilization. Only this single calcium transient is observed.Conclusion
Development of a technique to study fertilization induced calcium transients opens several experimental possibilities, e.g., identification of the signaling events intervening sperm binding and calcium elevation, identifying the possible roles of the calcium elevation such as the completion of meiosis, the formation of the eggshell, and the establishing of the embryo's axis of symmetry. 相似文献7.
Responses of foliage‐living spider assemblage composition and traits to a climatic gradient in Themeda grasslands
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H. Gibb D. Muscat M. R. Binns C. J. Silvey R. A. Peters D. I. Warton N. R. Andrew 《Austral ecology》2015,40(3):225-237
For speciose, but poorly known groups, such as terrestrial arthropods, functional traits present a potential avenue to assist in predicting responses to environmental change. Species turnover is common along environmental gradients, but it is unclear how this is reflected in species traits. Community‐level change in arthropod traits, other than body size, has rarely been explored across spatial scales comparable to those examined here. We hypothesized that the composition and morphological traits of spider assemblages would differ across a gradient of climate and habitat structure. We examined foliage‐living spider assemblages associated with Themeda triandra grasslands along a 900 km climatic gradient in south‐eastern Australia. We used sweep‐netting to collect T. triandra‐associated spiders and counted juveniles and identified adults. We also measured morphological traits of adult spiders and noted their hunting mode. Associations with measures of habitat structure were less consistent than relationships with climate. Both juvenile and adult spiders were more abundant in warmer sites, although species richness was not affected by temperature. We found distinct turnover in species composition along the climatic gradient, with hunting spiders, particularly crab spiders (Thomisidae), making up a greater proportion of assemblages in warmer climates. A range of traits of spiders correlated with the climatic gradient. For example, larger spider species and species that were active hunters were more common in warmer climates. Changes in morphological traits across species, rather than within species drove the morphology‐climate relationship. Strong climate‐trait correlations suggest that it may be possible to predict changes in functional traits of assemblages in response to anthropogenic disturbances such as climate change. 相似文献
8.
Gut-associated lymphoid tissue (GALT) is an early target of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) and a site for severe CD4+ T-cell depletion. Although antiretroviral therapy (ART) is effective in suppressing HIV replication and restoring CD4+ T cells in peripheral blood, restoration in GALT is delayed. The role of restored CD4+ T-cell help in GALT during ART and its impact on antiviral CD8+ T-cell responses have not been investigated. Using the SIV model, we investigated gut CD4+ T-cell restoration in infected macaques, initiating ART during either the primary stage (1 week postinfection), prior to acute CD4+ cell loss (PSI), or during the chronic stage at 10 weeks postinfection (CSI). ART led to viral suppression in GALT and peripheral blood mononuclear cells of PSI and CSI animals at comparable levels. CSI animals had incomplete CD4+ T-cell restoration in GALT. In PSI animals, ART did not prevent acute CD4+ T-cell loss by 2 weeks postinfection in GALT but supported rapid and complete CD4+ T-cell restoration thereafter. This correlated with an accumulation of central memory CD4+ T cells and better suppression of inflammation. Restoration of CD4+ T cells in GALT correlated with qualitative changes in SIV gag-specific CD8+ T-cell responses, with a dominance of interleukin-2-producing responses in PSI animals, while both CSI macaques and untreated SIV-infected controls were dominated by gamma interferon responses. Thus, central memory CD4+ T-cell levels and qualitative antiviral CD8+ T-cell responses, independent of viral suppression, were the immune correlates of gut mucosal immune restoration during ART. 相似文献
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10.
Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular‐based phylogenetic inferences
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Michael D. Amor Mark D. Norman Alvaro Roura Tatiana S. Leite Ian G. Gleadall Amanda Reid Catalina Perales‐Raya Chung‐Cheng Lu Colin J. Silvey Erica A. G. Vidal Frederick G. Hochberg Xiaodong Zheng Jan M. Strugnell 《Zoologica scripta》2017,46(3):275-288
Cryptic species are common in the ocean, particularly among marine invertebrates such as octopuses. Delineating cryptic species is particularly problematic in octopus taxonomy where the plasticity recorded among taxonomic characters often results in low resolution at the species level. This study investigated the morphological relationships among seven phylogenetic clades (identified using cytochrome c oxidase subunit I) of the broadly distributed Octopus vulgaris species complex and close relatives. Morphological analyses in this study were successful in delimiting O. sinensis, Brazilian O. vulgaris and O. vulgaris sensu stricto, which was congruent with the molecular findings of this study. Analyses based on male morphology were successful in distinguishing 14 of 15 total pairwise comparisons and proved to be a more reliable indicator of species‐level relationships in comparison with female morphology. The majority of characters with the greatest discriminatory power were male sexual traits. Significant morphological differences were also recorded among sampling localities of conspecifics, with phenotype showing correlation with local environmental data. The findings of this study support the hypothesis that multiple O. vulgaris‐like species are currently being incorrectly treated under a single species name, O. vulgaris. Octopuses being exported globally under the name O. vulgaris are of extremely high fisheries market value and profile. Our findings have potentially significant implications for the naming and conservation of commercially harvested members of this species complex throughout their ranges. 相似文献