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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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大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
6.
Mark Richard McNeill Chikako van Koten Stephen Latham Goldson 《Journal of Applied Entomology》2021,145(6):587-600
Listronotus bonariensis (Kuschel) is a pest of agriculturally important graminaceous species, with mining larvae that kill the stems of the host plants. In this study, larval populations were measured in spring and summer in irrigated dairy grassland comprising Lolium perenne L. (cv. Nui) with and without the endophyte Epichloë festucae var. lolii Latch, M.J. Chr. and Samuels and Poa annua L.. Larvae were extracted from tillers taken from the swards of these two grass species and extracted from turves, and L. bonariensis population densities were estimated from tiller and turf larval counts on a m−2 basis. Over the study period, the total number of larvae and larval densities extracted from turves was on average 2× greater than indicated from tillers. In most seasons, larval densities from turves were significantly higher than those from the tillers, though there was no correlation between tiller and turf larval densities. Mean head capsule widths of larvae emerging from turf samples showed significant seasonal effects compared with tillers, while mean head capsule widths of all four instars were significantly greater when extracted from tillers compared with turves. There was a significant endophyte effect on head capsule widths of larvae collected in summer, but the effect was not consistent across instars or source. Conversely, no significant endophyte effect on head capsule width was found in spring populations from either tillers or turves. This study shows that in irrigated dairy pasture, a high proportion of L. bonariensis larvae can live externally of tillers, presumably among the organic matter around the base of grasses in irrigated dairy pasture, and that density estimates based only on tiller populations will have significantly underestimated actual numbers. Having a precise indication of larval population densities is essential when developing life tables or determining economic damage threshold levels. 相似文献
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Garcia-Conesa MT Crepin VF Goldson AJ Williamson G Cummings NJ Connerton IF Faulds CB Kroon PA 《Journal of biotechnology》2004,108(3):227-241
Several extracellular feruloyl esterases were produced by the mesophilic fungus Talaromyces stipitatus when grown on selective carbon sources in liquid media. Type-A and Type-B feruloyl esterases, as defined by their substrate specificity against methyl hydroxycinnamates, were produced during growth on wheat bran and sugar beet pulp, respectively. In addition, Tal. stipitatus produced a new type of esterase (TsFaeC) during growth on sugar beet pulp with a broader spectrum of activity (Type-C) against the (hydroxy)cinnamate esters than those previously described. All three enzymes were purified and N-terminal amino acid sequences and internal peptide sequences determined. The TsFaeC sequences were used to amplify a gene fragment from Tal. stipitatus genomic DNA. The flanking sequences were identified with the aid of RACE-RTPCR, and a full-length clone constructed. The faeC gene is present as a single copy and contains a single intron. The complete cDNA fragment contains an ORF of 1590bp, faeC, which is predicted to encode a 530 amino acid pre-protein, including a 25-residue signal peptide, and to produce a mature protein of M(R) 55 340Da. There was no evidence for a carbohydrate-binding domain in TsFaeC. 相似文献
9.
Black AP Bhayani H Ryder CA Pugh MT Gardner-Medwin JM Southwood TR 《Arthritis research & therapy》2003,5(5):R277-R284
The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients
with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to
a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients
with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients:
a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested;
and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial
fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients
without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association
between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence
recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses
to enteric bacteria and the presence of αEβ7 T cells in synovial fluid may reflect accumulation of gut associated T cells
in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association
between the acute phase response and the T cell population recruited to an inflammatory site. 相似文献
10.
Rates and patterns of evolution in partial sequences of five mitochondrial
genes (cytochrome b, ATPase 6, NADH dehydrogenase subunit 5, tRNA(Glu), and
the control region) were compared among taxa in the passerine bird genera
Fringilla and Carduelis. Rates of divergence do not vary significantly
among genes, even in comparisons with the control region. Rate variation
among lineages is significant only for the control region and NADH
dehydrogenase subunit 5, and patterns of variation are consistent with the
expectations of neutral theory. Base composition is biased in all genes but
is stationary among lineages, and there is evidence for directional
mutation pressure only in the control region. Despite these similarities,
patterns of substitution differ among genes, consistent with alternative
regimes of selective constraint. Rates of nonsynonymous substitution are
higher in NADH dehydrogenase subunit 5 than in other protein-coding genes,
and transitions exist in elevated proportions relative to transversions.
Transitions appear to accumulate linearly with time in tRNA(Glu), and
despite exhibiting the highest overall rate of divergence among species,
there are no transversional changes in this gene. Finally, for resolving
phylogenetic relationships among Fringilla taxa, the combined
protein-coding data are broadly similar to those of the control region in
terms of phylogenetic informativeness and statistical support.
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