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31.
The murid rodent subfamily Sigmodontinae contains 79 genera which are
distributed throughout the New World. The time of arrival of the first
sigmodontines in South America and the estimated divergence time(s) of the
different lineages of South American sigmodontines have been controversial
due to the lack of a good fossil record and the immense number of extant
species. The "early-arrival hypothesis" states that the sigmodontines must
have arrived in South America no later than the early Miocene, at least 20
MYA, in order to account for their vast present-day diversity, whereas the
"late-arrival hypothesis" includes the sigmodontines as part of the
Plio-Pleistocene Great American Interchange, which occurred approximately
3.5 MYA. The phylogenetic relationships among 33 of these genera were
reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3,
ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the
same rate. A molecular clock was calibrated for these genes using published
fossil dates, and the genetic distances were estimated from the DNA
sequences in this study. The molecular clock was used to estimate the dates
of the South American sigmodontine origin and the main sigmodontine
radiation in order to evaluate the "early-" and "late-arrival" scenarios.
We estimate the time of the sigmodontine invasion of South America as
between approximately 5 and 9 MYA, supporting neither of the scenarios but
suggesting two possible models in which the invading lineage was either (1)
ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to
the akodonts and phyllotines and accompanied by the oryzomyines. The
sigmodontine invasion of South America provides an example of the advantage
afforded to a lineage by the fortuitous invasion of a previously
unexploited habitat, in this case an entire continent.
相似文献
32.
Previously, treatment of Tamm-Horsfall glycoprotein (THp) from different
donors with endo-beta-galactosidase has been shown to liberate a tetra- and
a Sd(a)-active pentasaccharide, concluding the presence of N-linked
carbohydrate chains containing additional N - acetyllactosamine units.
These type of oligosaccharides were not found in a detailed structure
elucidation of the carbohydrate moiety of THp of one male donor, suggesting
a donor-specific feature for these type of structures. Therefore, THp was
isolated from four healthy male donors and each subjected to
endo-beta-galactosidase treatment in order to release these tetra- and
Sd(a)-active pentasaccharide. Differences were observed in the total amount
of released tetra- and Sda-active pentasaccharide of the used donors (42,
470, 478, 718 microg/100 mg THp), indicating that the presence of repeating
N-acetyllactosamine units incorporated into the N-glycan moiety of THp is
donor specific. Furthermore, a higher expression of the Sd(a) determinant
on antennae which display N-acetyllactosamine elongation was observed,
suggesting a better accessibility for the
beta-N-acetylgalactosaminyltransferase. In order to characterize the
N-glycans containing repeating N- acetyllactosamine units, carbohydrate
chains were enzymatically released from THp and isolated. The
tetraantennary fraction, which accounts for more than 33% of the total
carbohydrate moiety of THp, was used to isolate oligosaccharides containing
additional N - acetyllactosamine units. Five N-linked tetraantennary
oligosaccharides containing a repeating N-acetyllactosamine unit were
identified, varying from structures bearing four Sd(a) determinants to
structures containing no Sd(a) determinant (see below). One compound was
used in order to specify the branch location of the additional N-
acetyllactosamine unit, and it appeared that only the Gal-6' and Gal-8'
residues were occupied by a repeating N -acetyllactosamine unit.
相似文献
33.
Wingfield BD; Grant WS; Wolfaardt JF; Wingfield MJ 《Molecular biology and evolution》1994,11(3):376-383
The genus Ceratocystis sensu stricto includes important fungal pathogens of
woody and herbaceous plants. This genus is distinguished from species in
Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore
shape has been used extensively in delineating Ceratocystis taxa, which
show a large variety of ascospore shapes. Sequence analysis of one region
of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA
subunit showed that there was a majority of multiple substitutions at
nucleotide sites and that there was a low transition/transversion ratio, T
= 0.72. Both of these results suggest that these are well established, old
species. Ascospore morphology, for the most part, was not congruent with
the molecular phylogeny, and the use of morphological characters may be
misleading in the taxonomy of these species.
相似文献
34.
Membrane compartmentalized ATP and its preferential use by the Na, K-ATPase of human red cell ghosts
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This paper describes work which begins to define the molecular organization in the region of the membrane that comprises the functional domain of the Na:K pump. The membrane-bound phosphoglycerate kinase (PGK) and Na, K-ATPase appear to be directly linked via a compartmentalized form of ATP. Evidence for the membrane pool of ATP is based on the labeling characteristics of the phosphoproteins by [γ-(32)P]ATP of ghosts incubated under various conditions. Preincubation of ghosts in the presence of ATP at 37 degrees C, but not at 0 degrees C, completely obscures the formation of the Na-phosphoprotein in ghosts washed and subsequently incubated in the presence of [gamma-(32)P]ATP. In contrast to the Na component, the Mg component of phosphorylation is only slightly altered by preincubation with ATP. ATPase activity measured as (32)P(i) liberated during the subsequent incubation at 0 degrees C, reflects completely the differential effects of preincubation with ATP on (32)P incorporation into phosphoprotein. ATP placed within the pool by preincubation can be removed by operating the Na, K-ATPase or the PGK reaction in the reverse direction by use of exogenous substrates. Alternatively, the membrane pool of ATP can be formed also from exogenous substrates by running the PGK reaction in the forward direction. These results, while providing direct support for a membrane compartment of ATP, also indicate the location of this compartment in relation to the PGK and the Na, K-ATPase. In addition, these results also imply that the Mg and Na components are different enzymatic entities since substrate ATP can be derived from separate sources. 相似文献
35.
Histogenesis of human extraparenchymal Leydig cells 总被引:2,自引:0,他引:2
From 64 consecutive autopsies of patients with neither testicular nor hormonal pathology, 26 showed extraparenchymal Leydig cells, located mainly in the epididymis and in the spermatic cord. The ultrastructural study of these specimens plus those obtained from 2 patients affected with functional testicular tumors leads to the following conclusions: (1) The origin of ectopic Leydig cells is not interstitial Leydig cells having infiltrated the testicular nerves and migrated along them towards ectopic locations. (2) The ectopic Leydig cells are considered to develop from undifferentiated precursor cells, located extraparenchymally, mainly inside and beside the testicular nerves. These precursor cells are similar to those observed in the testicular interstitium and have an ovoid shape and some cytoplasmic projections. The cytoplasm contains vesicles of smooth endoplasmic reticulum, lysosomes, lipid droplets and abundant microfilament bundles. The transformation from these cells into mature Leydig cells implies a progressive differentiation of the cytoplasmic components involved in steroid biosynthesis. 相似文献
36.
M Nistal R Paniagua A Herruzo 《Virchows Archiv. B, Cell pathology including molecular pathology》1977,26(2):111-118
A case is presented of an infertile male whose spermatozoa showed low mobility, a high percentage of irregular large heads and a variable number of tails (between 0 and 4). In the spermatozoa with several tails each axoneme, surrounded by its own outer fibres and mitochondrial sheath, arose from its own basal plate. Throughout the middle piece of every spermatozoon all the axonemes were arranged in parallel and were enclosed by the same plasma membrane. Usually, at the beginning of the principal piece, the axonemes became separated. At this level each of them constituted a different tail. In most spermatozoa the fine structure of the tail or tails was normal. The alterations of the inner structure of the tail or tails was normal. The alterations of the inner structure of the flagellum observed in some spermatozoa (enlargement of the fibrous sheath, duplication of the outer fibres and of some peripheral doublets) were independent of the number of tails present. In some cases, an intracytoplasmic coiling of the tail or tails could be observed. 相似文献
37.
Niels Reinmuth Nadine Payer Thomas Muley Hans Hoffmann Felix JF Herth Matthias Villalobos Michael Thomas 《Respiratory research》2013,14(1):139
Background
Most patients with metastatic non-small cell lung cancer (NSCLC) will face treatment with systemic therapy. Current clinical studies are demonstrating improvements in chemotherapy and overall survival. However, it remains unclear whether these results are translated into clinical practice.Methods
We reviewed all stage IV NSCLC patients without second malignancies that were diagnosed from 2004 to 2006 at our institution. 493 consecutive patients were included into this retrospective analysis and were followed-up until end of 2011.Results
352 patients (71.4%) received systemic therapy for up to 7 lines. For most patients, adjustments of dosages or applications had to be made at some point of the treatment, but the total applied dose remained generally close to the intended dose. The best disease control (BDC) rate decreased with increasing therapy lines from 59.7% to about 35%. Patients with palliative local therapy but no systemic treatment demonstrated inferior survival (median 2.9 versus 8.7 months, p < 0.001). The median interval between last treatment and death was 50 days and 15 days for chemotherapy and anti-EGFR therapy, respectively. BDC to the previous therapy lines was predictive for improved BDC to third- but not second-line therapy. Performing multivariate analysis, BDC to previous therapy, never-/ former-smoking status, and age > 70 years were associated with improved survival performing third-line therapy.Conclusions
Stage IV NSCLC patients may receive substantial systemic therapy resulting in response and median survival rates that are comparable to data from clinical studies. However, preselection factors are increasingly important to improve therapy outcome and life quality. 相似文献38.
López-Iglesias P Blázquez-Martínez A Fernández-Delgado J Regadera J Nistal M Miguel MP 《World journal of stem cells》2011,3(6):53-62
AIM:To study the ability of human adipose-derived mesenchymal stem cells(AMSCs)to survive over the short and long term,their biodistribution and their biosafety in vivo in tumor-prone environments.METHODS:We subcutaneously injected human AMSCs from different human donors into immunodeficient SCID mice over both short-(2 and 4 mo)and long-(17 mo)term in young,and aged tumor-prone mice.Presence of human cells was studied by immunohistochemistry and polymerase chain reaction analysis in all organs of injected mice.RESULTS:Subcutaneously injected AMSCs did not form teratomas at any time point.They did not migrate but remained at the site of injection regardless of animal age,and did not fuse with host cells in any organ examined.AMSCs survived in vivo for at least 17 mo after injection,and differentiated into fibroblasts of the subdermic connective tissue and into mature adipocytes of fat tissue,exclusively at the site of injection.CONCLUSION:Our results support the assertion that AMSC may be safe candidates for therapy when injected subcutaneously because of their long term inability to form teratomas. 相似文献
39.
Alena S Gsell Lisette N de Senerpont Domis Koen JF Verhoeven Ellen van Donk Bastiaan W Ibelings 《The ISME journal》2013,7(10):2057-2059
Contrary to expectation, populations of clonal organisms are often genetically highly diverse. In phytoplankton, this diversity is maintained throughout periods of high population growth (that is, blooms), even though competitive exclusion among genotypes should hypothetically lead to the dominance of a few superior genotypes. Genotype-specific parasitism may be one mechanism that helps maintain such high-genotypic diversity of clonal organisms. Here, we present a comparison of population genetic similarity by estimating the beta-dispersion among genotypes of early and peak bloom populations of the diatom Asterionella formosa for three spring-blooms under high or low parasite pressure. The Asterionella population showed greater beta-dispersion at peak bloom than early bloom in the 2 years with high parasite pressure, whereas the within group dispersion did not change under low parasite pressure. Our findings support that high prevalence parasitism can promote genetic diversification of natural populations of clonal hosts. 相似文献
40.
The trefoil factor (TFF) family, which comprises TFF1, TFF2 and TFF3, plays an essential role in epithelial regeneration within the gastrointestinal tract. All three TFFs are present in human saliva; TFF3 is the predominant trefoil peptide. Little is known about the expression and tissue distribution of TFFs in rats, which are commonly used as a model system for human studies. We investigated the localization of the TFF genes that encode secretory peptides in rat submandibular glands (SMG). All three TFFs were expressed in rat SMG, although their location varied. Substantial amounts of TFF1 were detected only in the cytoplasm of epithelial cells in the SMG granular convoluted tubules (GCT), while TFF2 and TFF3 were widely distributed in the cytoplasm of epithelial cells of intercalated ducts (ID), striated ducts (SD) and interlobular ducts (ILD). The three TFFs also were detected especially in the lumens of the SD and ILD. Semi-quantitative RT-PCR and in situ hybridization experiments confirmed TFF1, TFF2 and TFF3 mRNA expressions in the SMG. Greater expression of TFF peptides and mRNA was observed in male rats than in females. The broad expression of TFFs in rat SMG cells and lumens suggests that TFFs function in this organ by their secretion into the duct lumens. We also found differences in TFF expression profiles between rat and human SMG; therefore, caution should be exercised when using rats as a model for human TFF studies. 相似文献