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61.
Skeletal adaptations and phylogeny of the oldest mole Eotalpa (Talpidae,Lipotyphla, Mammalia) from the UK Eocene: the beginning of fossoriality in moles 下载免费PDF全文
Jerry J. Hooker 《Palaeontology》2016,59(2):195-216
The oldest talpid, Eotalpa, was previously known only from isolated cheek teeth from the European late Middle Eocene to earliest Oligocene. Screenwashing of Late Eocene sediments of the Hampshire Basin, UK, has yielded cranial and postcranial elements: maxilla, dentary, ulna, metacarpals, distal tibia, astragalus, calcaneum, metatarsals and phalanges. In addition to M1–2 myotodonty, typical talpid features are as follows: ulna with long medially curved olecranon and deep abductor fossa and astragalar body with lateral process. However, Eotalpa retains certain soricid‐like primitive states (M1 preparacrista, P4 with prominent mesiolingual protocone lobe, strongly angled astragalar neck and calcaneum with no space for a cuboid medial process) not found in modern talpids. Eotalpa is more derived than the most primitive living talpid Uropsilus in having lost the M1–2 talon shelf, developed a convex radial facet on the ulna, an incipient proximal olecranon crest, relatively shorter metapodials and depressed manual unguals. Its astragalus with medial trochlear ridge taller than the lateral one and massive medial plantar process is typical of the Lipotyphla. Eotalpa lacks synostosis of tibia and fibula, found in other Talpidae, Soricidae and Erinaceidae, suggesting that synostosis in these groups has been independently acquired. Cladistic analysis places Eotalpa as stem member of the Talpidae and shows that much homoplasy arose during the early evolution of the family. Ground dwelling in Eotalpa is indicated by the following: astragalus with a medially dipping head, curved in a single plane; calcaneum with distal peroneal process and strongly overlapping ectal and sustentacular facets; and matching sized ectal and sustentacular facets on calcaneum and astragalus. These features would have restricted ankle mobility. Ungual and metatarsal shape and ulnar structure suggest a primitive stage in fossorial evolution and argue against a semiaquatic precursor stage in talpid fossoriality. Shrew‐moles may represent a reversal to surface foraging rather than an intermediate stage in fossoriality. 相似文献
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Goswami N Batzel JJ Loeppky JA Hinghofer-Szalkay H 《Advances in physiology education》2011,35(4):330-335
Hypovolemic and orthostatic challenge can be simulated in humans by the application of lower body negative pressure (LBNP), because this perturbation leads to peripheral blood pooling and, consequently, central hypovolemia. The classic paper by Foux and colleagues clearly shows the effects of orthostasis simulated by LBNP on fluid shifts and homeostatic mechanisms. The carefully carried out experiments reported in this paper show the interplay between different physiological control systems to ensure blood pressure regulation, failure of which could lead to critical decreases in cerebral blood flow and syncope. Here, a teaching seminar for graduate students is described that is designed in the context of this paper and aimed at allowing students to learn how Foux and colleagues have advanced this field by addressing important aspects of blood regulation. This seminar is also designed to put their research into perspective by including important components of LBNP testing and protocols developed in subsequent research in the field. Learning about comprehensive protocols and carefully controlled studies can reduce confounding variables and allow for an optimal analysis and elucidation of the physiological responses that are being investigated. Finally, in collaboration with researchers in mathematical modeling, in the future, we will incorporate the concepts of applicable mathematical models into our curriculum. 相似文献
63.
Quantitative trait loci affecting the difference in pigmentation between Drosophila yakuba and D. santomea 下载免费PDF全文
Using quantitative trait locus (QTL) mapping, we studied the genetic basis of the difference in pigmentation between two sister species of Drosophila: Drosophila yakuba, which, like other members of the D. melanogaster subgroup, shows heavy black pigmentation on the abdomen of males and females, and D. santomea, an endemic to the African island of S?o Tomé, which has virtually no pigmentation. Here we mapped four QTL with large effects on this interspecific difference in pigmentation: two on the X chromosome and one each on the second and third chromosomes. The same four QTL were detected in male hybrids in the backcrosses to both D. santomea and D. yakuba and in the female D. yakuba backcross hybrids. All four QTL exhibited strong epistatic interactions in male backcross hybrids, but only one pair of QTL interacted in females from the backcross to D. yabuka. All QTL from each species affected pigmentation in the same direction, consistent with adaptive evolution driven by directional natural selection. The regions delimited by the QTL included many positional candidate loci in the pigmentation pathway, including genes affecting catecholamine biosynthesis, melanization of the cuticle, and many additional pleiotropic effects. 相似文献
64.
The morphological distribution of oligosaccharides is determined in the egg jelly surrounding Xenopus laevis eggs. This biological system is used to illustrate a method for readily identifying and quantifying oligosaccharides in specific tissues. The extracellular matrix surrounding X. laevis eggs consists of a vitelline envelope and a jelly coat. The jelly coat contains three morphologically distinct layers designated J1, J2, and J3 from the innermost to the outermost and is composed of 9-11 distinct glycoproteins. Each jelly layer is known to have specific functions in the fertilization of the egg. We developed a rapid method to separate and identify the oligosaccharides from X. laevis egg jelly layers. Identification was based on the retention times in high-performance liquid chromatography (porous graphitized carbon column), exact masses, and tandem mass spectrometry. Over 40 neutral and 30 sulfated oligosaccharides were observed in the three jelly layers. Neutral oligosaccharide structures from different jelly layers were both unique and overlapping, while sulfated oligosaccharides were detected only in layers J1 and J2. Neutral oligosaccharides unique to jelly layer J3 and the combined layers J1+J2 had similar core structures and similar residues. However, differences between these two sets of unique oligosaccharides were also observed and were primarily due to the branching carbohydrate moieties rather than the core structures. 相似文献
65.
CXC chemokine ligand 10 controls viral infection in the central nervous system: evidence for a role in innate immune response through recruitment and activation of natural killer cells 下载免费PDF全文
Trifilo MJ Montalto-Morrison C Stiles LN Hurst KR Hardison JL Manning JE Masters PS Lane TE 《Journal of virology》2004,78(2):585-594
How chemokines shape the immune response to viral infection of the central nervous system (CNS) has largely been considered within the context of recruitment and activation of antigen-specific lymphocytes. However, chemokines are expressed early following viral infection, suggesting an important role in coordinating innate immune responses. Herein, we evaluated the contributions of CXC chemokine ligand 10 (CXCL10) in promoting innate defense mechanisms following coronavirus infection of the CNS. Intracerebral infection of RAG1(-/-) mice with a recombinant CXCL10-expressing murine coronavirus (mouse hepatitis virus) resulted in protection from disease and increased survival that correlated with a significant increase in recruitment and activation of natural killer (NK) cells within the CNS. Accumulation of NK cells resulted in a reduction in viral titers that was dependent on gamma interferon secretion. These results indicate that CXCL10 expression plays a pivotal role in defense following coronavirus infection of the CNS by enhancing innate immune responses. 相似文献
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Wen-Han Chuang Arivajiagane Arundhathi Ching Lu Chang-Chiang Chen Wan-Chen Wu Hendra Susanto Jerry D. T. Purnomo Chih-Hong Wang 《Metabolomics : Official journal of the Metabolomic Society》2016,12(6):108
Introduction
Dysregulation of acylcarnitines (AcylCNs) and amino acids metabolism have implicated in abnormality of fatty acid oxidation in type 2 diabetes (T2D). However, it is not well known whether altered plasma AcylCN, and amino acid profiles are associated with albuminuria or diabetic nephropathy (DN) in T2D.Objective
The aim of this study was to elucidate alterations in plasma levels of AcylCNs and amino acids with respect to the T2D patients with various stages of albuminuria.Methods
We recruited 52 healthy subjects as control, and 156 T2D patients which were divided into 52 normoalbuminuria, 52 microalbuminuria, and 52 macroalbuminuria. Plasma 37 AcylCNs and 12 amino acids were analyzed by tandem mass spectrometry.Results
We found that T2D with normoalbuminuria and microalbuminuria had lower shot-, medium-, and long-chain AcylCNs, whereas T2D with macroalbuminuria had higher short-and medium-chain AcylCNs and lower long-chain AcylCNs than healthy subjects. Moreover, estimated glomerular filtration rate (eGFR) was a negative, independent and significant predictor of albumin to creatinine ratio (ACR) levels (β = ?0.376, P < 0.001), whereas plasma Low-density lipoprotein cholesterol (LDL-C) was significantly and positively associated with ACR levels (β = 0.169, P = 0.049). Furthermore, multivariate ordinal logistic regression analysis revealed that isobutyrylcarnitine (C4) was a positive, independent, and significant predictor of ACR levels with higher odds of having T2D patients with progression normoalbuminuria to microalbuminuria [OR = 9.93, 95 % CI (3.51–28.05), P < 0.001].Conclusions
The findings suggest that plasma C4 may serve as a potential biomarker for the early stages of DN.69.
Jennifer C. Jenkins David W. Kicklighter Scott V. Ollinger John D. Aber Jerry M. Melillo 《Ecosystems》1999,2(6):555-570
Because model predictions at continental and global scales are necessarily based on broad characterizations of vegetation,
soils, and climate, estimates of carbon stocks and fluxes made by global terrestrial biosphere models may not be accurate
for every region. At the regional scale, we suggest that attention can be focused more clearly on understanding the relative
strengths of predicted net primary productivity (NPP) limitation by energy, water, and nutrients. We evaluate the sources
of variability among model predictions of NPP with a regional-scale comparison between estimates made by PnET-II (a forest
ecosystem process model previously applied to the northeastern region) and TEM 4.0 (a terrestrial biosphere model typically
applied to the globe) for the northeastern US. When the same climate, vegetation, and soil data sets were used to drive both
models, regional average NPP predictions made by PnET-II and TEM were remarkably similar, and at the biome level, model predictions
agreed fairly well with NPP estimates developed from field measurements. However, TEM 4.0 predictions were more sensitive
to regional variations in temperature as a result of feedbacks between temperature and belowground N availability. In PnET-II,
the direct link between transpiration and photosynthesis caused substantial water stress in hardwood and pine forest types
with increases in solar radiation; predicted water stress was relieved substantially when soil water holding capacity (WHC)
was increased. Increasing soil WHC had little effect on TEM 4.0 predictions because soil water storage was already sufficient
to meet plant demand with baseline WHC values, and because predicted N availability under baseline conditions in this region
was not limited by water. Because NPP predictions were closely keyed to forest cover type, the relative coverage of low- versus
high-productivity forests at both fine and coarse resolutions was an important determinant of regional NPP predictions. Therefore,
changes in grid cell size and differences in the methods used to aggregate from fine to coarse resolution were important to
NPP predictions insofar as they changed the relative proportions of forest cover. We suggest that because the small patches
of high-elevation spruce-fir forest in this region are substantially less productive than forests in the remainder of the
region, more accurate NPP predictions will result if models applied to this region use land cover input data sets that retain
as much fine-resolution forest type variability as possible. The differences among model responses to variations in climate
and soil WHC data sets suggest that the models will respond quite differently to scenarios of future climate. A better understanding
of the dynamic interactions between water stress, N availability, and forest productivity in this region will enable models
to make more accurate predictions of future carbon stocks and fluxes.
Received 19 June 1998; accepted 25 June 1999. 相似文献
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