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排序方式: 共有119条查询结果,搜索用时 46 毫秒
91.
Diminished production of monocyte proinflammatory cytokines during human immunodeficiency virus viremia is mediated by type I interferons 总被引:1,自引:0,他引:1 下载免费PDF全文
92.
93.
The uterine horns and utero-ovarian veins of nine crossbred mature gilts were bilaterally cannulated on day 9 of the estrous cycle (day 0 - first day of estrus). Each uterine horn in treated gilts (N=5) was infused with 150 μg PGE2 in 3 ml of saline at 0900 h on day 12, 15 and 18 of the estrous cycle. Control gilts (N=4) received 3 ml saline intrauterine infusions on the corresponding day. Blood samples were collected from the utero-ovarian veins 15 min before each infusion and for the following 6 h with 15, 30 and 60 min intervals through the first, second and third two-hour periods, respectively. Venous concentrations of PGE2 and PGF2α were determined by radioimmunoassay procedures. Infusion of PGE2 resulted in an immediate elevation in PGE2 concentration in utero-ovarian venous drainage. Coincident elevations of PGF2α utero-ovarian venous concentrations were observed after PGE2 infusion. Plasma PGF2α concentrations in the utero-ovarian veins were elevated (P<.01) in PGE2 treated gilts for one hour post-treatment. The duration of PGE2 and PGE2α elevations as well as the peak values were influenced by day of the cycle. 相似文献
94.
A 96 picosecond dynamics trajectory of myoglobin with five xenon-probe ligands in internal cavities is examined to study the effect of protein motions on ligand motion and internal cavity fluctuations. Average structural and energetic properties indicate that the simulation is well behaved. The average protein volume is similar to the volume of the X-ray model and the main-chain atom root-mean-square deviation between the X-ray model and the average dynamical structure is 1.25 A. The protein volume oscillates 3 to 4% around the volume of the X-ray structure. These fluctuations lead to changes in the internal free volume and in the size, shape and location of atom-sized cavity features. Transient cavities produced in the simulation have a crucial role in the movement of two of the ligands. One of the ligands escapes to the protein surface, whilst a second ligand travels through the protein interior. Complex gating processes involving several protein residues are responsible for producing the necessary pores through which the ligand passes between transient cavities or packing defects. 相似文献
95.
Reassembly of flagellar B (alpha beta) tubulin into singlet microtubules: consequences for cytoplasmic microtubule structure and assembly 下载免费PDF全文
B(alpha beta) tubulin was obtained from a homogeneous class of microtubules, the incomplete B subfiber of sea urchin sperm flagellar doublet microtubules, by thermal fractionation. The thermally derived soluble B tubulin fraction (100, 000 g-h) repolymerizes in vitro, yielding microtubule-like structures. The microtubule-associated protein (MAP) composition and certain assembly parameters of thermally derived B tubulin are different from those reported for sonication- derived flageller tubulin and purified vertebrate tubulin. The "microtubules" reassembled from thermally prepared B tubulin are composed of 12-15 protofilaments (73% possess 14 protofilaments). A certain number possess a single "adlumenal component" applied to their inside walls, regardless of the number of protofilaments. Following the first cycle of polymerization, 81% of the B tubulin and essentially 100% of the MAPs remain cold insoluble. Evidence suggests that B tubulin assembles faithfully into a B lattice, creating a j seam between two protofilaments that are laterally bonded in a A-lattice configuration. The significance of these seams is discussed in relation to the mechanism of microtubule assembly, the stability of observed ribbons of protofilaments, and the three-dimensional organization of microtubule-associated components. 相似文献
96.
Varien R. Tilton 《American journal of botany》1981,68(7):980-993
Mature embryos of Zea mays L. (inbred A188) were used in this study, which was undertaken to investigate three questions: 1) do all embryonic tissues of Zea, viz., coleoptile, scutellum, epicotyl, mesocotyl, hypocotyl, and coleorhiza, influence germling morphology and growth; 2) if a given tissue does exert an influence, what is it, and 3) what effect does removal of one tissue have on that tissue and on the tissues remaining? Experimental results revealed growth of isolated epicotyls was greater than that of epicotyls still attached to the scutellum, but it was less than that of whole embryo controls. Isolated hypocotyls grew less than any other tissue except scutella, which seemed to have no growth response. Hypocotyls still attached to the scutellum had the greatest growth response of all tissues. Intact embryo axes had a response intermediate to whole embryo controls and isolated epicotyls. Growth of the epicotyl is influenced most strongly by the hypocotyl, and growth of the hypocotyl, by the scutellum. The mesocotyl does not appear to have a regulatory influence on other tissues. It is proposed that the scutellum synthesizes or otherwise provides a growth factor (nutrients, growth regulator, or combination thereof) which is the initial stimulus for hypocotyl and root growth during germination, and that the epicotyl has a regulating influence on this factor in germlings and young seedlings. 相似文献
97.
Utilizing single or double pulses of gonadotropin-releasing hormone (GnRH), with or without progesterone pretreatment, we induced ovulation in dairy cows on day 14 postpartum. In experiment 1, neither progesterone priming nor repetitive injection of GnRH enhanced pituitary LH or FSH secretion compared to a single GnRH injection. However, pretreatment with 100 mg progesterone tended (P<0.1) to enhance luteal progesterone secretion during the induced cycle. We confirmed this observation in a second experiment by utilizing a larger number of cows. Cows given 100 mg progesterone prior to a single 200 mug injection of GnRH exhibited higher (P<0.05) concentrations of serum progesterone on days 12 and 16 of the induced cycle (days 26 and 30 postpartum). These results suggest that progesterone pretreatment may influence luteal progesterone secretion following ovulation. This appears to occur via an ovarian mechanism which is independent of pituitary gonadotropin secretion. 相似文献
98.
Administration of human chorionic gonadotropin (hCG) to promote ovarian steroid secretion near the time of recognition of pregnancy was evaluated. Neither 500 or 1000 IU of hCG caused a significant increase in luteal function as determined by progesterone (P(4)) concentrations in peripheral blood following treatment on Day 12. Estradiol concentrations were elevated (P<0.01) for the 500 IU hCG group on Days 13, 14, 15 and 16 versus the control group. The 1000 IU of hCG group had three-to five-fold greater (P<0.01) estradiol concentrations than controls on Days 14, 15 and 16 post mating. Treatment with hCG also reduced (P<0.05) the number of resorbed embryos. The results suggest that hCG treatment on Day 12 of pregnancy reduced embryo loss and influenced peripheral estradiol secretion patterns. 相似文献
99.
A model of the carbohydrate recognition domain CRD, residues 111-245, of
hamster galectin-3 has been made using homology modeling and dynamics
minimization methods. The model is based on the known x-ray structures of
bovine galectin-1 and human galectin-2. The oligosaccharides
NeuNAc-alpha2,3-Gal-beta1,4-Glc and GalNAc-alpha1, 3-
[Fuc-alpha1,2]-Gal-beta1,4-Glc, known to be specific high-affinity ligands
for galectin-3, as well as lactose recognized by all galectins were docked
in the galectin-3 CRD model structure and a minimized binding conformation
found in each case. These studies indicate a putative extended
carbohydrate-binding subsite in the hamster galectin- 3 involving Arg139,
Glu230, and Ser232 for NeuNAc-alpha2,3-; Arg139 and Glu160 for
fucose-alpha1,2-; and Arg139 and Ile141 for GalNAc-alpha1,3- substituents
on the primary galactose. Each of these positions is variable within the
whole galectin family. Two of these residues, Arg139 and Ser232, were
selected for mutagenesis to probe their importance in this newly identified
putative subsite. Residue 139 adopts main-chain dihedral angles
characteristic of an isolated bridge structural feature, while residue 232
is the C-terminal residue of beta- strand-11, and is followed immediately
by an inverse gamma-turn. A systematic series of mutant proteins have been
prepared to represent the residue variation present in the aligned
sequences of galectins-1, - 2, and -3. Minimized docked models were
generated for each mutant in complex with NeuNAc-alpha2,3-Gal-beta1,4-Glc,
GalNAc-alpha1, 3-[Fuc- alpha1,2]-Gal-beta1,4- Glc, and Gal-beta1,4-Glc.
Correlation of the computed protein-carbohydrate interaction energies for
each lectin- oligosaccharide pair with the experimentally determined
binding affinities for fetuin and asialofetuin or the relative potencies of
lactose and sialyllactose in inhibiting binding to asiolofetuin is
consistent with the postulated key importance of Arg139 in recognition of
the extended sialylated ligand.
相似文献
100.
Java language has been demonstrated to be an effective tool in supporting medical image viewing in Russia. This evaluation was completed by obtaining a maximum of 20 images, depending on the client's computer workstation from one patient using a commercially available computer tomography (CT) scanner. The images were compared against standard CT images that were viewed at the site of capture. There was no appreciable difference. The client side is a lightweight component that provides an intuitive interface for end users. Each image is loaded in its own thread and the user can begin work after the first image has been loaded. This feature is especially useful on slow connection speed, 9.6 Kbps for example. The server side, which is implemented by the Java Servlet Engine works more effective than common gateway interface (CGI) programs do. Advantages of the Java Technology place this program on the next level of application development. This paper presents a unique application of Java in telemedicine. 相似文献