排序方式: 共有63条查询结果,搜索用时 203 毫秒
31.
A characteristic feature of the sperm P1 protamines of eutherian mammals is
the constant presence of six to nine cysteine residues per molecule. During
spermiogenesis these residues become oxidized to form a three-dimensional
network of disulfide bridges between, and within, protamine molecules in
the sperm chromatin. This covalent cross linking strongly stabilizes
eutherian sperm nuclei. In contrast, protamines sequenced from teleost
fish, birds, monotremes, and marsupials all lack cysteine residues and
their sperm nuclei, without the stabilizing cross links, are easily
decondensed in vitro. We have now found that one genus of tiny, shrewlike
dasyurid marsupials, the Planigales, possess P1 protamines containing five
to six cysteine residues. These residues appear to have evolved since the
divergence of Planigales from other members of the family Dasyuridae, such
as the marsupial mouse, Sminthopsis crassicaudata. We believe this
constitutes a case of convergent evolution in a subfamily of dasyurid
marsupials toward the cysteine-rich eutherian form of sperm protamine P1.
相似文献
32.
Ponnappan RK Markova DZ Antonio PJ Murray HB Vaccaro AR Shapiro IM Anderson DG Albert TJ Risbud MV 《Arthritis research & therapy》2011,13(5):R171
Introduction
Back pain, a significant source of morbidity in our society, is related to the degenerative changes of the intervertebral disc. At present, the treatment of disc disease consists of therapies that are aimed at symptomatic relief. This shortcoming stems in large part from our lack of understanding of the biochemical and molecular events that drive the disease process. The goal of this study is to develop a model of early disc degeneration using an organ culture. This approach is based on our previous studies that indicate that organ culture closely models molecular events that occur in vivo in an ex vivo setting. 相似文献33.
Hernández-Quintero JD MH Reyes-Valdés DV Mendoza-Rodríguez M Gómez-Martínez R Rodríguez-Herrera 《Phyton》2015,84(1):107-112
The genus Dasylirion is a group of plants typically present in the Chihuahuan Desert, perennial, with a dioecious sexual behavior and commonly called sotoles. This genus has been little studied from the biological point of view, and the bases of its reproductive response remain unknown. In this work we studied the chromosome number and meiotic response of Dasylirion cedrosanum in the county of Saltillo, Coahuila, located at the North East of Mexico. For the preparation of mitotic chromosomes, we used a technique based on enzymatic treatment with pectolyase and cellulase, as well as staining with acetocarmin dye. For the study of meiosis, male flower buds were collected, fixed and stained for analysis with the same dye. As a result, the gametic (n = x = 19) and somatic chromosome (2n = 38) numbers of D. cedrosanum are reported for the first time, being consistent with previous findings in other Dasylirion species, which points to a constant ploidy level across the genus. Variation was observed in the morphology and size of the somatic chromosomes, with types ranging from submetacentric to subtelocentric, and sizes oscillating in a range of 4.43 µm, with an average total length of 112.38 µm for the diploid chromosome complement. This shows that the chromosome complement of D. cedrosanom would belong to a 3B classification of Stebins, with a medium variation between chromosome lengths and low chromosome asymmetry. This variation indicates the feasibility of constructing a chromosome ideotype for this species. The meiotic chromosome pairing showed a chromosome behavior consistent with a disomic inheritance characteristic of a diploid species, with prevalence of ring and chain bivalents, typically without pairing abnormalities. Bivalent configurations in all cases were symmetrical.The normal and symmetrical meiotic pairing indicates a balanced production of gametes, and suggests the absence of heteromorphic sex determination. 相似文献
34.
35.
Paolo Puccetti Francesca Fallarino Antoine Italiano Isabelle Soubeyran Gaetan MacGrogan Marc Debled Valerie Velasco Dominique Bodet Sandrine Eimer Marc Veldhoen Georges C. Prendergast Michael Platten Alban Bessede Gilles J. Guillemin 《PloS one》2015,10(4)
Tumor immune escape mechanisms are being regarded as suitable targets for tumor therapy. Among these, tryptophan catabolism plays a central role in creating an immunosuppressive environment, leading to tolerance to potentially immunogenic tumor antigens. Tryptophan catabolism is initiated by either indoleamine 2,3-dioxygenase (IDO-1/-2) or tryptophan 2,3-dioxygenase 2 (TDO2), resulting in biostatic tryptophan starvation and l-kynurenine production, which participates in shaping the dynamic relationship of the host’s immune system with tumor cells. Current immunotherapy strategies include blockade of IDO-1/-2 or TDO2, to restore efficient antitumor responses. Patients who might benefit from this approach are currently identified based on expression analyses of IDO-1/-2 or TDO2 in tumor tissue and/or enzymatic activity assessed by kynurenine/tryptophan ratios in the serum. We developed a monoclonal antibody targeting l-kynurenine as an in situ biomarker of IDO-1/-2 or TDO2 activity. Using Tissue Micro Array technology and immunostaining, colorectal and breast cancer patients were phenotyped based on l-kynurenine production. In colorectal cancer l-kynurenine was not unequivocally associated with IDO-1 expression, suggesting that the mere expression of tryptophan catabolic enzymes is not sufficiently informative for optimal immunotherapy. 相似文献
36.
37.
The cryptochromes are a family of blue light photoreceptors that play important roles in the control of plant development.
We have characterised the cryptochrome gene family in the model legume garden pea (Pisum sativum L.). Pea contains three expressed cryptochrome genes; a single CRY1 orthologue, and two distinct CRY2 genes that we have termed CRY2a and CRY2b. Genomic southern blots indicate that there are unlikely to be more CRY genes in pea. Each of the three genes encodes a full-length CRY protein that contains all the major domains characteristic
of other higher plant cryptochromes. Database searches have identified Medicago truncatula expressed sequence tags (ESTs) corresponding to all three genes, whereas only a single CRY2 is represented in EST collections from the more distantly related legumes soybean and Lotus japonicus. The proteins encoded by the pea and Medicago CRY2b genes are distinguished from other CRY2 proteins by their shorter C-terminus. Expression analyses have identified marked
differences in the regulation of the three genes, with CRY2b expression in particular distinguished by high-amplitude diurnal cycling and rapid repression in seedlings transferred from
darkness to blue light. 相似文献
38.
Rampant horizontal transfer and duplication of rubisco genes in eubacteria and plastids 总被引:16,自引:2,他引:14
Previous work has shown that molecular phylogenies of plastids,
cyanobacteria, and proteobacteria based on the rubisco (ribulose-1,5-
bisphosphate carboxylase/oxygenase) genes rbcL and rbcS are incongruent
with molecular phylogenies based on other genes and are also incompatible
with structural and biochemical information. Although it has been much
speculated that this is the consequence of a single horizontal gene
transfer (of a proteobacterial or mitochondrial rubisco operon into
plastids of rhodophytic and chromophytic algae), neither this hypothesis
nor the alternative hypothesis of ancient gene duplication have been
examined in detail. We have conducted phylogenetic analyses of all
available bacterial rbcL sequences, and representative plastid sequences,
in order to explore these alternative hypothesis and fully examine the
complexity of rubisco gene evolution. The rbcL phylogeny reveals a
surprising number of gene relationships that are fundamentally incongruent
with organismal relationships as inferred from multiple lines of other
molecular evidence. On the order of six horizontal gene transfers are
implied by the form I (L8S8) rbcL phylogeny, two between cyanobacteria and
proteobacteria, one between proteobacteria and plastids, and three within
proteobacteria. Alternatively, a single ancient duplication of the form I
rubisco operon, followed by repeated and pervasive differential loss of one
operon or the other, would account for much of this incongruity. In all
probability, the rubisco operon has undergone multiple events of both
horizontal gene transfer and gene duplication in different lineages.
相似文献
39.
Nonparametric regression in the presence of measurement error 总被引:4,自引:0,他引:4
40.
Ming Luo ;Damien Platten ;Abed Chaudhury ;W.J. Peacock ;Elizabeth S. Dennis 《植物生理学报》2009,(4):711-723
Polycomb group proteins (PcG) play important roles in epigenetic regulation of gene expression. Some core PeG proteins, such as Enhancer of Zeste (E(z)), Suppressor of Zeste (12) (Su(z)12), and Extra Sex Combs (ESC), are conserved in plants. The rice genome contains two E(z)-Iike genes, OsiEZ1 and OsCLF, two homologs of Su(z)12, OsEMF2a and OsEMF2b, and two ESC-like genes, OsFIE1 and OsFIE2. OsFIE1 is expressed only in endosperm; the maternal copy is expressed while the paternal copy is not active. Other rice PcG genes are expressed in a wide range of tissues and are not imprinted in the endosperm. The two E(z)-Iike genes appear to have duplicated before the separation of the dicots and monocots; the two homologs of Su(z)12 possibly duplicated during the evolution of the Gramineae and the two ESC- like genes are likely to have duplicated in the ancestor of the grasses. No homologs of the Arabidopsis seed-expressed PcG genes MEA and FIS2 were identified in the rice genome. We have isolated T-DNA insertion lines in the rice homologs of three PcG genes. There is no autonomous endosperm development in these T-DNA insertion lines. One line with a T-DNA insertion in OsEMF2b displays pleiotropic phenotypes including altered flowering time and abnormal flower organs, suggesting important roles in rice development for this gene. 相似文献