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排序方式: 共有8082条查询结果,搜索用时 15 毫秒
61.
62.
Mario L. Rocci William J. Jusko 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1981,224(2):221-227
A high-performance liquid chromatographic technique primarily developed for use on samples from kidney perfusion studies is presented for simultaneous determination of prednisone, prednisolone and their 20β-hydroxylated metabolites. The technique employs 6β-hydroxycortisol as the internal standard. Samples are extracted with ethyl acetate, washed with sodium hydroxide and water and injected onto a silica gel column with UV detection at 254 nm. Inter- and intraday variability of the assay was determined at two concentrations of each steroid and was less than 10%. Assay steroid recovery ranged from 54.1% for prednisone to 63.2% for 20β-hydroxyprednisone. Sensitivity is 4–10 ng/ml for the steroids measured. The chromatographic conditions may be modified to permit quantitation of these steroids from plasma samples. This method may alternatively be used for quantitation of 6β-hydroxycortisol, an endogenous indicator of enzyme induction. A perfusate concentration-time profile is presented from a kidney perfusion study using prednisolone. 相似文献
63.
A method of retrograde perfusion of the myocardium has been developed in dogs. It consists of a double lumen balloon-tipped catheter inserted transvenously into the coronary sinus, with one lumen connected to a roller pump, the other to a helium counterpulsing pump. Oxygenated heparinized blood is obtained from the femoral artery and pumped continuously into the coronary sinus at a pressure of 50-75 mm Hg. The balloon is inflated during diastole, sealing the coronary sinus and promoting retrograde flow, and is deflated during systole, allowing blood drainage into the right atrium and preventing venous congestion. Thirteen anesthetized open-chest dogs were subjected to 15 minutes of proximal LAD artery occlusion and 30 minutes of diastolic coronary sinus perfusion (DCSP). The area of ischemia was mapped by means of platinum electrodes capable of simultaneously measuring myocardial tissue oxygen tension M(p)O(2)) and electrograms. Reduction of M(p)O(2) with simultaneous elevation of the ST segment on the corresponding electrogram was considered an indication of ischemia. Diastolic coronary sinus perfusion improved myocardial oxygen tension in the ischemic myocardium, reduced ST segment elevation, and tended to restore arterial blood pressure. Histologically, there was no intramyocardial hemorrhage. 相似文献
64.
Mario Maggi Guido Fantoni Alessandro Peri Stefano Giannini Maria Luisa Brandi Claudio Orlando Mario Serio 《The Journal of steroid biochemistry and molecular biology》1991,40(4-6):481-491
Oxytocin (OT) and V1 vasopressin (VP) receptors are present simultaneously in several tissues, including the uterus. In myometrium these receptors mediate contractility, while in endometrium they mediate the release of other uterotonic substances as endothelin (ET). In rabbit myometrium, estrogens increase, while progesterone blunts neurohypophysial hormone receptors. However, the action of sex steroids on OT and V1 VP receptors differs in terms of the ED50 and maximal effect. Therefore, at parturition, only OT receptors show a dramatic rise, while V1 VP receptors do not change, suggesting a major role for OT in labor. ET is a potent stimulator of uterine activity acting through specific receptors present on myometrial cells. These receptors as well as the endometrial localization of ET are modulated by sex steroids, indicating that ET might represent a paracrine regulator of uterine activity. In humans, OT but not V1 VP receptors increase as pregnancy progresses, confirming the primary relevance of OT in timing delivery. 相似文献
65.
Susceptibility of inbred strains of mice to murine AIDS (MAIDS) correlates with target cell expansion and high expression of defective MAIDS virus. 下载免费PDF全文
Murine AIDS (MAIDS) is readily induced by the Duplan strain of defective murine leukemia virus in susceptible C57BL/6 mice. To identify mouse strains resistant to MAIDS, and to understand the genetic factors controlling susceptibility to the disease, we screened more than 20 inbred strains of mice for their susceptibility to MAIDS. For this study, mice of the Fv-1n/n, Fv-1b/b, or Fv-1n/b genotype were inoculated with stocks of defective MAIDS virus pseudotyped with N-tropic, B-tropic, or NB-tropic helper murine leukemia virus, respectively. Strains could be classified as susceptible, resistant, or moderately resistant. None of the individual H-2 haplotypes examined appears to explain resistance to MAIDS by itself. However, a very good correlation between the susceptibility or resistance phenotype and the presence or absence of defective proviral DNA and RNA in the spleen of these animals was found. Since the presence of defective proviral DNA and RNA reflects the oligoclonal proliferation of the cells infected by the defective MAIDS virus, our results strongly suggest that this target cell expansion is genetically controlled and is necessary and perhaps even sufficient for the development of the disease. 相似文献
66.
67.
L. Mario Amzel Mario A. Bianchet Peter L. Pedersen 《Journal of bioenergetics and biomembranes》1992,24(5):429-433
It has been proposed that during ATP synthesis/hydrolysis F1 ATPases experience a complex pattern of nucleotide binding and release during the catalytic cycle (binding change mechanism). This type of mechanism has implications that can be correlated with the structure of the enzyme. F1-ATPases (stoichiometry 33) are essentially a symmetrical trimer of pairs of the major subunits ( and ); the minor subunits (, and ) are in single copies and interact with the trimer in an asymmetrical fashion. The asymmetry introduced by the minor subunits has important structural and functional consequences: (1) it introduces differences between the potentially equivalent binding and catalytic sites in the major subunits, (2) it restricts the ways in which a binding change mechanism can occur, and (3) it governs the way in which the F1 interacts with the (asymmetrical) F0 sector. 相似文献
68.
69.
Mario Díaz Antonio Lorenzo 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(2):189-196
Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I
sc), as well as in the mucosa-to-serosa (J
m-s
Na
) and net sodium flux (J
net
Na
). In AT tissues, aldosterone did not change net chloride flux (J
net
Cl
) but did so in CT tissues. Amiloride reduced the aldosterone-increased I
sc in AT and CT tissues, inhibited J
net
Na
in AT tissues and abolished it in CT colons. J
net
Cl
was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na+ absorption and totally inhibited Cl- absorption in the AT tissues, but did not change I
sc. However, in CT tissues neither Na+ nor Cl- transport were affected by DIDS. A good relationship between I
sc and J
m-s
Na
was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J
net
Na
and reduced I
sc to untreated control values. Addition of serosal ouabain abolished I
sc and Na+ absorption in AT and CT colons, but Cl- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT
acutely treated
- CT
chronically treated animals
- DIDS
4-4-diisothiocyanatostibene-2-2-disulfonic acid
- DMSO
dimethylsulphoxide
-
G
t
tissue conductance
-
I
sc
short circuit current
- PD
transepithelial potential difference
- SITS
4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid
- UC
untreated controls
Preliminary results of this paper were presented at the X
th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990 相似文献
70.
Lessonia trabeculata is one of the major kelps found along the northern coast of Chile. In addition to its ecological and economic importance, L. trabeculata may be severely affected by environmental disturbances such as El Níño, which during 1982–1983 cleared wide areas along the coast of Peru and Chile. The main goal of this work was to mass culture L. trabeculata and to observe the growth of sporophytes obtained in the laboratory and cultured in the sea. Juvenile sporophytes obtained in the laboratory were attached between 1 and 6 m in depth. The linear growth rate, as blade elongation, was recorded weekly for seven months. No significant differences (p < 0.05) were found in sporophyte blade linear growth at different depths. The best elongation growth rate was 7.5 ± 1.6 mm d–1 at 3 m during March. This preliminary work suggests that L. trabeculata follows an annual growth cycle similar to that of other Laminariales with a high rate of blade elongation during the summer and decreasing towards autumn. This species can be considered a potential candidate for aquaculture to increase the availability of raw material and aid in repopulation of overexploited areas. 相似文献