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1.
In 1897, Salvador Calderón y Arana published a study of the first vertebrate footprint from Spain. It was found in the Buntsandstein of Rillo de Gallo (Guadalajara), probably in the Rillo Mudstone and Sandstone Formation (middle Anisian-Landian). This isolated left pes imprint was classified as “Cheirotherium” sp. We conducted a historical study of this specimen, mentioned by several authors for more than a century, but never analyzed in detail. This well-preserved footprint, in which skin marks are present, is described here. Its characters are compared with those of valid chirotheriid ichnogenera. This work is complemented with a bibliographic analysis of the chirotheriid footprints recorded in Spain. This record is remarkable for its abundance and ichnodiversity.  相似文献   

2.
Monoclonal antibody M90 recognizes a specific epitope of the ras-encoded p21 protein. This region comprises amino acids 107-130 containing the residues 116-119, which are related to GTP binding. This antibody strongly reacts on Western Blots with a 22kDa protein from human erythroleukemia (HEL) cells. Treatment of HEL cells with iloprost, an agonist that increases cellular cyclic AMP levels, produces the appearance of a protein with an apparent molecular mass of 24kDa. This protein is also recognized by antiserum M90 on Western Blots; its appearance parallels a decrease of the 22kDa protein, and it can be labeled with 32P. This effect is also observed with dibutyryl cyclic AMP, which indicates phosphorylation of the 22kDa protein by cyclic AMP-dependent protein kinase. This phosphorylation produces an electrophoretic mobility change of the 22kDa protein to a 24kDa region on gels. The change of mobility of the 22kDa protein induced by iloprost in HEL cells is also observed when the protein is labeled with [35S]methionine and immunoprecipitated with antiserum M90. This information indicates a coupling mechanism involving phosphorylation of an oncogene product in HEL cells.  相似文献   

3.
乳腺浸润性微乳头状癌(IMPC)是乳腺浸润性癌的一种特殊类型,其发生率低,临床表现及影像学特征与普通的乳腺浸润性导管癌没有显著区别。这种病理类型可与普通浸润性导管癌混合出现,也可表现为单纯的浸润性微乳头状癌。但浸润性微乳头状癌具有独特的组织学形态及分子结构,决定了其病理学分级较高、易于发生淋巴结转移的侵袭性生物学行为特点。多数浸润性微乳头状癌在影像学上表现为边缘不清的不规则肿块影,常伴有微小钙化。其特征性病理形态为细胞膜上皮抗原(EMA)在肿瘤细胞簇外周的细胞和基质中腔隙边缘特异性染色,同时显微镜下瘤细胞表面发现微绒毛结构,说明了瘤细胞簇周围的空隙样结构实际上是管状腔隙,瘤细胞呈"极向倒转"方式排列。IMPC具有高度淋巴血管浸润倾向,局部复发率高,是一种预后较差的类型。本文对近年来关于乳腺浸润性微乳头状癌的研究进展进行了综述。  相似文献   

4.
Two hearts beat in every liberal breast. One is the heart of non-discrimination – the commitment to propounding equal chances for all. Such a principle, built around individuals and their free choices, ought to be applicable everywhere and to everyone. This perspective currently dominates human-rights discourse and is associated with the ‘global left’ and with the politics of ‘recognition’. The second liberal heart is communitarian social justice. Redistribution, effected primarily through the state, is owed the poor and exploited, and it can be accomplished best in one's own society, for one's own countrymen. This vision has lost a great deal of ground, especially among elites and critical intellectuals. This view is associated with the ‘sovereignty left’ and with the politics of ‘redistributive justice’. This paper examines the manifestations of these tensions in recent US immigration debates, particularly over issues of labour market competition between immigrants and the domestic poor.  相似文献   

5.
This paper is concerned with the statistical aspects of the phenomenon of disease occurring more frequently in individuals with some genotypes than in individuals with others. A correlation coefficient is defined to quantify association between disease and genotype. A distinction is made between the concepts of independence of allele and disease and independence of genotype and disease. This distinction is used to define two components of association which describe separate aspects of association of disease with genotype. One component is a measure of the association of disease with allele; the other a measure of the effect of allele interaction on association of disease and genotype. One aspect of the usefulness of the partition into components which is discussed is in expressing the recurrence risk of disease for a relative of an affected individual. A chi-squared analysis is provided to test hypotheses about the components of association and other hypotheses of genetic interest. This analysis is illustrated using a study done to determine the effect of the sex-linked dwarfing gene in male chickens on resistance to E. coli infection. This analysis shows a significant allele interaction effect on resistance to disease but no association of disease with alleles. In conclusion, some extensions and limitations of the proposed concepts and procedures are discussed.  相似文献   

6.
Translation of encephalomyocarditis virus RNA in a cell-free system from uninfected Krebs ascites cells results in the synthesis of a major polypeptide product with a molecular weight of approximately 112,000. In contrast, when the viral RNA is translated in a cell-free system from virus-infected cells, this polypeptide is absent and the largest polypeptide produced has a molecular weight of about 100,000. This latter polypeptide comigrates on sodium dodecyl sulfate-gels with in vivo virus capsid precursor A, and the two have identical patterns of CNBr-generated peptides. A polypeptide having a molecular weight of 12,500 is also a major translation product in the system from infected cells (but not from uninfected cells). This polypeptide appears to be generated by cleavage of the NH-2-terminal portion of the viral RNA-dependent polypeptides by a proteolytic activity present in the infected cell-free system. This proteolytic activity copurifies with the 23,000-molecular weight viral capsid protein gamma, found in infected cells, through chromatography on DEAE-cellulose and cellulose phosphate. This suggests that gamma is itself a proteolytic enzyme involved in maturation of the viral capsid precursor.  相似文献   

7.
Large scale genomic studies are generating significant amounts of data on the structure of cellular networks. This is in contrast to kinetic data, which is frequently absent, unreliable or fragmentary. There is, therefore, a desire by many in the community to investigate the potential rewards of analyzing the more readily available topological data. This brief review is concerned with a particular property of biological networks, namely structural conservations (e.g. moiety conserved cycles). There has been much discussion in the literature on these cycles but a review on the computational issues related to conserved cycles has been missing. This review is concerned with the detection and characterization of conservation relations in arbitrary networks and related issues, which impinge on simulation simulation software writers. This review will not address flux balance constraints or small-world type analyses in any significant detail.  相似文献   

8.
Cultures of foetal human pituitary cells excrete and synthetize different molecular forms of proteins with HGH immunological activity. These cells incorporate tritiated-leucine in these proteins. Gel chromatography on sephadex using different length of column allow us to separate: One form excluded in front of the dead volume and which has a high molecular weight. This form is not dissociated by treatment with urea 8 M, guanidine 6 M and dithiothreitol. Nor this form is modified by treatment by ribonuclease. One form excluded within the dead volume and which is probably a dimere. This form is no more modified by the different treatments. One form which is excluded like a monomere--it is the more important form--. This form is dissociated in fragments of lower molecular weight by urea 8 M. This dissociation is partially reversible by dialysis.  相似文献   

9.
T. G. Dewey 《Biopolymers》1990,29(14):1793-1799
A ligand binding model of counterion association in finite length polyelectrolytes is presented. This model introduces counterion condensation features into a binding formalism. It agrees well with the predictions of other finite length models and is consistent with experimental data on helix–coil melting transitions for short nucleic acid oligomers. This model uses a discrete charge distribution for the polyelectrolyte. An expression for the electrostatic self-energy of finite length polyelectrolytes is derived using the Euler–Maclaurin sum formula. This sum is shown to be accurate over a wide range of salt concentrations. This electrostatic term is used in an energy minimization analysis. The energy minimization is solved analytically using a Lagrange inversion formula. This general procedure gives a rapidly convergent series and requires no assumptions with regard to “limiting law” behavior. However, when used in the Manning minimization formalism [(1977) Biophysical Chemistry, 24 , 2086], the volume of the condensed phase becomes unrealistically large at low ionic strength. The ligand binding model does not have a condensed phase volume as a parameter. It provides a single expression that agrees both with Manning's theory and with the theory of Ramanathan and Woodbury [(1982) Journal of Chemical Physics 77 , 4133] under the respective conditions of these theories.  相似文献   

10.
We have developed a method for detecting a transgene and its protein product in maize endosperm that allows the kernel to be germinated after analysis. This technique could be highly useful for several monocots and dicots. Our method involves first sampling the endosperm with a hand-held rotary grinder so that the embryo is preserved and capable of germination. This tissue is then serially extracted, first with SDS-PAGE sample buffer to extract proteins, then with an aqueous buffer to extract DNA. The product of the transgene can be detected in the first extract by SDS-PAGE with visualization by total protein staining or immuno-blot detection. The second extract can be purified and used as template DNA in PCR reactions to detect the transgene. This method is particularly useful for screening transgenic kernels in breeding experiments and testing for gene silencing in kernels.  相似文献   

11.
Abstract: Using optical and scanning electron microscopy, we completed a palynological study of the subtribe Artemisiinae (Asteraceae, Anthemideae), which we started in a previous paper. This subtribe contains different genera with a systematic position that, in many cases, has been controversial. There is a group of genera closely related to Artemisia, and another one more related to Chrysanthemum sensu lato. We confirm the existence of two pollen morphological patterns - concerning exine ornamentation - in the tribe Anthemideae and in the subtribe Artemisiinae as currently considered: one with long spines ( Anthemis type) and the other with short spinules ( Artemisia type). This feature is a good taxonomic marker, well correlated with other morphological and with molecular characters. This enables a new delimitation of the subtribe Artemisiinae, which is characterized by pollen grain ornamentation constituted by short spinules (microechinate pollen), and should be restricted to Artemisia and the closely related genera that share this trait.  相似文献   

12.
It is commonly observed that reproduction decreases with age, often at a different rate in males and females. This phenomenon is generally interpreted as senescence. Such reproductive declines may stem from at least two sources: a change in resource allocation and a decline in the ability to convert resources into offspring. This distinction is important because a shift in resource allocation may be favoured by selection, while reduced efficiency is purely deleterious. We propose a way to distinguish whether a decline in reproduction is purely deleterious based on estimating reproductive investment, output, and their ratio, efficiency. We apply this approach to the hermaphroditic snail Physa acuta and demonstrate that both male and female functions decline with age. The male decline largely stems from reduced investment into male activity while female decline is due to increased reproductive inefficiency. This shows that age‐related declines in reproduction can occur for a number of different reasons, a distinction that is usually masked by the general term ‘senescence’. This approach could be applied to any species to evaluate age‐related reproductive decline. We advocate that future studies measure age trajectories of reproductive investment and output to explore the potential processes hidden behind the observation that reproduction declines with age.  相似文献   

13.
The genus Dysoxylum is a large genus comprising of about a dozen species, distributed in India. This is the genus which is rich in compounds like terpenoids and alkaloids. The isolated compounds from the genus were reported to have interesting biological activities. This review contains the chemical structures, along with their biological activities reported in the literature.  相似文献   

14.
著: 《生物信息学》2019,26(2):53-62
学名为Phytolacca dioica的树种将会贯穿全文。此树种在乌拉圭的通用名叫做树商陆,是本研究缘起的核心。它是潘帕斯大草原的标志性物种,也是乌拉圭景观特质的基础。树商陆在研究和教育工作领域的目标和意义在于将艺术、人类、社会和自然科学联系起来。对树商陆在潘帕斯大草原湿润气候下所表现出的景观价值进行研究。提高了公众对自然元素同景观价值、地方故事间关系的认知度和敏感度。这加强了对遗产以及领土和文化融合的集体责任感。理论往往需要适用于方法论,并协作实践性的工作。例如现场活动与ICT(门户网站http://www.ombues.edu.uy)的相互关联,这便如不断往返于科学文化的普及与流行文化的智慧, 用跨学科的方式建构知识。  相似文献   

15.
16.
濒危植物——长喙毛茛泽泻的受精作用及胚和胚乳的发育   总被引:4,自引:0,他引:4  
长喙毛茛泽泻Ranalisma rostratum Stapf的配子融合开始较早,但精核与极核融合速度较快。精核与珠孔极核融合后即移向胚囊合点端与另一极核再融合形成初生胚乳核。初生胚乳核第一次分裂后形成两个细胞,以后珠孔端胚乳细胞再进行游离核分裂,胚乳发育属于沼生目型。开花后两天,合子分裂,八分体呈4层,每层呈两个细胞方式排列胚胎发生属于石竹型。  相似文献   

17.
This article advocates a crucial role for economic anthropology in the twenty‐first century. The use of anthropological techniques for primary data collection is essential for understanding the complexity of diverse local economies. This is demonstrated with reference to a remote Aboriginal economy in Arnhem Land, Northern Australia, using a ‘hybrid economy’ model that includes the customary sector as well as market and state sectors. This empirically grounded model is contrasted with a very different theoretical construct: the ‘real’ economy that is dominating Indigenous affairs policy discourse. Although the hybrid economy model is currently subordinated, mainly for ideological reasons, examples are provided to demonstrate its policy and legal influences.  相似文献   

18.
EmrE is a member of the small multidrug resistance family of proteins and functions as a efflux transporter of lipophilic cations. This integral membrane protein is composed of 110 amino acids and is very hydrophobic with small loops exposed to the aqueous environment. This protein has been purified in a variety of ways including extraction with chloroform:methanol mixtures. This study explored culture growth and induction conditions, the parameters of organic solvent extraction, running conditions of a lipophilic column for lipid removal, as well as solubilization conditions. Optimal expression and purification protocols are crucial to the characterization goals of this protein. The experiments presented here led to an improvement in the yield of pure EmrE obtained by organic solvent extraction methods at a level of 0.9+/-0.2mg/L of culture. This is on the order of a 60% improvement over previous reports.  相似文献   

19.
Ranalisma rostratum Stapf is a rare and endangered species. This paper deals with the fertilization and the development of embryo and endosperm in this plant.The embryogenesis is of Caryophyllad type and the development of endosperm belongs to Heobial type.Before fertilization,the two polar nuclei are located respectively at both ends of embryo sac. In most angiosperms with two polar nuclei,the polar nuclei may fuse eiher before fertilization to form a secondary nucleus or during fertilization called triple fusion. In Ranalisma rostratum Stapf, however, it is found that only in case when the micropylar polar nucleus is fertilized,it can move to the chalazal end and fuse with the chalazal polar nucleus.This phenomenon is very rare and the process must take more time to fulfil fertilization both polar nuclei. This feature of fusion of polar nuclei is therefore thought as a primitive character from the view of phylogeny.  相似文献   

20.
The incidence of testicular cancer is highest among young men, and then decreases sharply with age. This points towards a frailty effect, where some men have a much greater risk of testicular cancer than the majority of the male population. Those with the highest risk get cancer, drain the group of individuals at risk, and leave a healthy male population which has approximately zero risk of testicular cancer. This leads to the observed decrease in incidence. We discuss a frailty model, where the frailty is compound-Poisson-distributed. This allows for a non-susceptible group (of zero frailty). The model is successfully applied to incidence data from the Danish and Norwegian registries. It is indicated that there was a decrease in incidence for males born during World War II in both countries. Bootstrap analysis is used to find the degree of variation in the estimates. In the Armitage-Doll multistage model, the estimated number of transitions needed for a cell to become malignant is close to 3 for non-seminomas and 4 for seminomas in both the Danish and Norwegian data. This paper demonstrates that a model including a frailty effect fits the incidence data well and gives interesting results and interpretations, although this is no proof of the effect's truth.  相似文献   

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