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排序方式: 共有96条查询结果,搜索用时 15 毫秒
1.
H Padh J J Aleo 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1987,185(2):153-157
Ascorbic acid is transported into 3T6 fibroblasts by a carrier-mediated, energy-dependent saturable active process with a Km of 112 microM and Vmax of 158 pmole/min/mg protein. The transport is dependent on extracellular Na+ concentration which reduces the Km. It was recently observed in this laboratory that bovine serum contained a heat-labile factor which, after interaction with bacterial endotoxin (lipopolysaccharides), inhibited ascorbic acid transport (J.J. Alleo and H. Padh, Proc Soc Exp Biol Med 179:128-131, 1985). We report here that the inhibition of ascorbic acid transport by endotoxin is mediated by the activation of serum complement. This was done by examining the activation of complement by other activators like zymosan and immunocomplexes (e.g., albumin and antibodies to albumin). Ascorbate transport was inhibited by the mixture of unheated serum and the activators. No inhibition was observed with serum devoid of C3 (component 3 of the complement). When C3-deficient serum was reconstituted by the addition of purified C3, the endotoxin-induced inhibition of ascorbate transport was restored. The implication of these findings is that in spite of a normal intake and blood level of the vitamin, tissues may not be getting adequate vitamin C during disease states when the complement in serum is activated. In other words, what may be considered an adequate intake of vitamin C under health conditions may not be adequate under disease conditions. 相似文献
2.
3.
For several species of lepidoptera, most of the approximately 350-bp
mitochondrial control-region sequences were determined. Six of these
species are in one genus, Jalmenus; are closely related; and are believed
to have undergone recent rapid speciation. Recent speciation was supported
by the observation of low interspecific sequence divergence. Thus, no
useful phylogeny could be constructed for the genus. Despite a surprising
conservation of control-region length, there was little conservation of
primary sequences either among the three lepidopteran genera or between
lepidoptera and Drosophila. Analysis of secondary structure indicated only
one possible feature in common--inferred stem loops with higher-than-random
folding energies-- although the positions of the structures in different
species were unrelated to regions of primary sequence similarity. We
suggest that the conserved, short length of control regions is related to
the observed lack of heteroplasmy in lepidopteran mitochondrial genomes. In
addition, determination of flanking sequences for one Jalmenus species
indicated (i) only weak support for the available model of insect 12S rRNA
structure and (ii) that tRNA translocation is a frequent event in the
evolution of insect mitochondrial genomes.
相似文献
4.
MF Perutz 《Current opinion in structural biology》1996,6(6):848-858
Several dominantly inherited, late onset, neurodegenerative diseases are due to expansion of CAG repeats, leading to expansion of glutamine repeats in the affected proteins. These proteins are of very different sizes and, with one exception, show no sequence homology to known proteins or to each other; their functions are unknown. In some, the glutamine repeat starts near the N-terminus, in another near the middle and in another near the C-terminus, but regardless of these differences, no disease has been observed in individuals with fewer than 37 repeats, and absence of disease has never been found in those with more than 41 repeats. Protein constructs with more than 41 repeats are toxic to E. coli and to CHO cells in culture, and they elicit ataxia in transgenic mice. These observations argue in favour of a distinct change of structure associated with elongation beyond 37–41 glutamine repeats. The review describes experiments designed to find out what these structures might be and how they could influence the properties of the proteins of which they form part. Poly-
-glutamines form pleated sheets of β-strands held together by hydrogen bonds between their amides. Incorporation of glutamine repeats into a small protein of known structure made it associate irreversibly into oligomers. That association took place during the folding of the protein molecules and led to their becoming firmly interlocked by either strand- or domain-swapping. Thermodynamic considerations suggest that elongation of glutamine repeats beyond a certain length may lead to a phase change from random coils to hydrogen-bonded hairpins. Possible mechanisms of expansion of CAG repeats are discussed in the light of looped DNA model structures. 相似文献
5.
Glycine-induced cytoprotection of renal proximal tubules exposed to chemical- or hypoxic/anoxic-induced cell death is shared by a few amino acid agonists of the neuronal strychnine-sensitive glycine receptor. The goal of this study was to determine if antagonists of the strychnine-sensitive glycine receptor attenuated the cytoprotective effects of glycine. Strychnine did not antagonize the cytoprotective effects of glycine in proximal tubules exposed to antimycin A. In contrast, strychnine was cytoprotective, was equipotent as glycine (EC50 = 0.4 mM), and the combination of strychnine and glycine was additive. Likewise, bicuculline and norharmane were cytoprotective but 20-50% less potent than glycine. These results suggest that glycine and strychnine act as a common site to produce proximal tubule cytoprotection, but this site does not share the same potency and agonist/antagonist properties as the neuronal strychnine-sensitive glycine receptor. 相似文献
6.
S Marchesini A Preti M F Aleo A Casella A Dagan S Gatt 《Chemistry and physics of lipids》1990,53(2-3):165-175
Fluorescent derivatives of cerebroside sulfate (sulfogalactosyl ceramide, sulfatide) containing long-wavelength-emission fluorophores were synthesized. For this purpose a procedure was developed for preparing a cerebroside 3-sulfate derivative with an amino group on the terminal carbon atom of its fatty acyl residue. The latter compound has been used to prepare cerebroside 3-sulfate, coupled to lissamine-rhodamine, fluoresceine, eosine and NBD. The spectroscopic properties of these compounds, in different solvent systems and when incorporated into micelles of a non-ionic detergent or liposomes of a phospholipid, are reported. Incubation of these respective sulfatides with a human leukocyte preparation, resulted in the formation of the corresponding fluorescent cerebrosides. 相似文献
7.
8.
Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life. 相似文献
9.
Mohammed O. Abdelaziz Celestino Bonura Aurora Aleo Teresa Fasciana Cinzia Calà Caterina Mammina 《Microbiology and immunology》2013,57(5):391-395
Cephalosporin‐resistant Escherichia coli has been increasingly reported worldwide. In this study, 32 cephalosporin resistant E. coli isolates identified from cancer patients in Cairo, Egypt in 2009–2010 were analyzed. Twenty‐three were of phylogenetic group D, seven A and one each B1 and B2. By rep‐PCR 15 phylogroup D isolates were grouped in four clusters, one with sequence type (ST) 405 and three ST68. Seventeen isolates showed single patterns. blaCTX‐M‐15 and aac(6')‐Ib‐cr were the most common resistance determinants. blaOXA‐48 and blaVIM were also detected. Multidrug resistant E. coli seriously affects healthcare, especially in immunocompromised hosts, such as cancer patients. 相似文献
10.
B30.2-like domain proteins: update and new insights into a rapidly expanding family of proteins 总被引:5,自引:0,他引:5
Henry J; Mather IH; McDermott MF; Pontarotti P 《Molecular biology and evolution》1998,15(12):1696-1705
The B30.2 domain is a conserved region of around 170 amino acids associated
with several different protein domains, including the immunoglobulin folds
of butyrophilin and the RING finger domain of ret finger protein. We
recently reported several novel members of this family as well as
previously undescribed protein families possessing the B30.2 domain. Many
proteins have subsequently been found to possess this domain, including
pyrin/marenostrin and the midline 1 (MID1) protein. Mutations in the B30.2
domain of pyrin/marenostrin are implicated in familial Mediterranean fever,
and partial loss of the B30.2 domain of MID1 is responsible for Opitz G/BBB
syndrome, characterized by developmental midline defects. In this study, we
scrutinized the available sequence data bases for the identification of
novel B30.2 domain proteins using highly sensitive database-searching
tools. In addition, we discuss the chromosomal localization of genes in the
B30.2 family, since the encoded proteins are likely to be involved in other
forms of periodic fever, autoimmune, and genetic diseases.
相似文献