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排序方式: 共有282条查询结果,搜索用时 16 毫秒
1.
2.
Inhibition of follicle-stimulating hormone-induced ovulation by indomethacin in the perfused rat ovary 总被引:1,自引:0,他引:1
J H Sogn T E Curry M Br?nnstr?m W J Lemaire R D Koos H Papkoff P O Janson 《Biology of reproduction》1987,36(3):536-542
In isolated, perfused ovaries of rats treated with pregnant mare's serum gonadotropin (PMSG), purified preparations of ovine follicle-stimulating hormone (FSH) (oFSH-211B) and rat FSH (rFSH-I-6), 100 ng/ml, were found to induce ovulations (4.8 +/- 0.9, n = 4, and 6.4 +/- 2.0, n = 5, ovulations per ovary, respectively). Indomethacin (5 micrograms/ml) added to the perfusate inhibited this ovulatory effect and exogenous prostaglandin F2 alpha (PGF2 alpha) (1 microgram/ml), or prostaglandin E2 (PGE2) (0.5 microgram/ml), reversed the blockade. Ovine FSH and rFSH had only a weak stimulatory effect on estradiol release, and only rFSH caused a significant increase in progesterone accumulation. Indomethacin reduced the stimulatory effect of rFSH on progesterone release, and this effect was reversed by PGE2 but not by PGF2 alpha. In a 6-h incubation experiment with preovulatory rat follicles, we tested the biological activity of gonadotropins used to induce oocyte maturation. The concentration of FSH used in the perfusion experiments induced oocyte maturation in more than 88% of the oocytes studied. The data confirm earlier findings that FSH can induce ovulations and show that prostaglandins are involved in this process. The data also indicate that prostaglandins might be involved in the FSH-induced increase of progesterone levels. 相似文献
3.
Subunit interaction during catalysis. ATP modulation of catalytic steps in the succinyl-CoA synthetase reaction 总被引:3,自引:0,他引:3
A new approach for assessing of catalytic cooperativity may occur between subunits has been applied to succinyl-CoA synthetase. This is based on the extent of oxygen exchange between medium [18O]Pi and succinate per molecule of ATP cleaved during steady state succinyl-CoA synthesis. Suitable traps are used to remove succinyl-CoA and ADP as soon as they are released to the medium. With the Escherichia coli enzyme, which has an alpha 2 beta 2 structure, a pronounced increase in oxygen exchange per ATP cleaved occurs as ATP concentration is lowered. In contrast, when the CoA concentration is varied, the oxygen exchange per molecule of product formed remains constant. Also, with the pig heart enzyme, which is shown to retain its alpha beta structure during catalysis and thus has only one catalytic site, no modulation of oxygen exchange by ATP concentration is observed. These experimental findings show that the binding of an ATP either promotes the dissociation of bound succinyl-CoA or decreases its participation in exchange. Measurement of the distribution of [18O]Pi species found as exchange occurs shows that only one catalytic sequence is involved in exchange at various ATP concentrations. These observations along with other controls and results eliminate most other explanations of the ATP modulation of the exchange and suggest that binding of ATP at one catalytic site promotes catalytic site promotes catalytic events at an alternate catalytic site. 相似文献
4.
Animals respond to novel stimuli via explorative or neophobic behavior or both. The coexistence of these responses toward novel foods may be a successful adaptive strategy for a generalist species such as Cebus apella, because it allows the gradual introduction of new foods into the diet and reduces the risk of poisoning by ingestion of large amounts of toxic compounds (Glander, 1982; Milton, 1993; Visalberghi, 1994). Neophobia has been studied mostly in captivity. We investigated responsiveness to novelty in a group of 25–30 wild tufted capuchins (Cebus apella) in Iguazü National Park (Argentina). They had been habituated to visiting sites where bananas were provided on three elevated platforms. We presented novel stimuli on an adjacent platform. There were 4 experimental conditions with 10 sessions each: the Novel Food condition, the Novel Object condition, the Control condition, in which the platform was empty, and the Banana condition. In the Novel Food and Novel Object conditions, a new stimulus—food or object—was on the platform during each session. The Banana condition provided information on capuchin response to a familiar preferred food. Overall, capuchins were less responsive toward novel objects than toward novel foods; however, although cautious, they ate small amounts of the novel foods. Age affected individual responsiveness toward novel foods, whereas sex affected responsiveness toward novel objects. Capuchins ignored the empty platform. Our findings are in agreement with the idea that tufted capuchins can adapt to new habitats by gradually exploiting new food sources. 相似文献
5.
Marco P. Boks Eske M. Derks Daniel J. Weisenberger Erik Strengman Esther Janson Iris E. Sommer René S. Kahn Roel A. Ophoff 《PloS one》2009,4(8)
Cytosine-5 methylation within CpG dinucleotides is a potentially important mechanism of epigenetic influence on human traits and disease. In addition to influences of age and gender, genetic control of DNA methylation levels has recently been described. We used whole blood genomic DNA in a twin set (23 MZ twin-pairs and 23 DZ twin-pairs, N = 92) as well as healthy controls (N = 96) to investigate heritability and relationship with age and gender of selected DNA methylation profiles using readily commercially available GoldenGate bead array technology. Despite the inability to detect meaningful methylation differences in the majority of CpG loci due to tissue type and locus selection issues, we found replicable significant associations of DNA methylation with age and gender. We identified associations of genetically heritable single nucleotide polymorphisms with large differences in DNA methylation levels near the polymorphism (cis effects) as well as associations with much smaller differences in DNA methylation levels elsewhere in the human genome (trans effects). Our results demonstrate the feasibility of array-based approaches in studies of DNA methylation and highlight the vast differences between individual loci. The identification of CpG loci of which DNA methylation levels are under genetic control or are related to age or gender will facilitate further studies into the role of DNA methylation and disease. 相似文献
6.
7.
Luykx JJ Bakker SC Lentjes E Boks MP van Geloven N Eijkemans MJ Janson E Strengman E de Lepper AM Westenberg H Klopper KE Hoorn HJ Gelissen HP Jordan J Tolenaar NM van Dongen EP Michel B Abramovic L Horvath S Kappen T Bruins P Keijzers P Borgdorff P Ophoff RA Kahn RS 《PloS one》2012,7(2):e30497
Background
Animal studies have revealed seasonal patterns in cerebrospinal fluid (CSF) monoamine (MA) turnover. In humans, no study had systematically assessed seasonal patterns in CSF MA turnover in a large set of healthy adults.Methodology/Principal Findings
Standardized amounts of CSF were prospectively collected from 223 healthy individuals undergoing spinal anesthesia for minor surgical procedures. The metabolites of serotonin (5-hydroxyindoleacetic acid, 5-HIAA), dopamine (homovanillic acid, HVA) and norepinephrine (3-methoxy-4-hydroxyphenylglycol, MPHG) were measured using high performance liquid chromatography (HPLC). Concentration measurements by sampling and birth dates were modeled using a non-linear quantile cosine function and locally weighted scatterplot smoothing (LOESS, span = 0.75). The cosine model showed a unimodal season of sampling 5-HIAA zenith in April and a nadir in October (p-value of the amplitude of the cosine = 0.00050), with predicted maximum (PCmax) and minimum (PCmin) concentrations of 173 and 108 nmol/L, respectively, implying a 60% increase from trough to peak. Season of birth showed a unimodal 5-HIAA zenith in May and a nadir in November (p = 0.00339; PCmax = 172 and PCmin = 126). The non-parametric LOESS showed a similar pattern to the cosine in both season of sampling and season of birth models, validating the cosine model. A final model including both sampling and birth months demonstrated that both sampling and birth seasons were independent predictors of 5-HIAA concentrations.Conclusion
In subjects without mental illness, 5-HT turnover shows circannual variation by season of sampling as well as season of birth, with peaks in spring and troughs in fall. 相似文献8.
M Br?nnstr?m B M Boberg J T?rnell P O Janson K Ahrén 《Journal of reproduction and fertility》1989,85(2):451-459
The effects of two different protein synthesis inhibitors (cycloheximide and puromycin) on the ovulatory process were examined in vitro using a perfused rat ovary model. Ovaries of PMSG (20 i.u.)-primed rats were perfused for 21 h. Release of cyclic adenosine 3',5'-monophosphate (cAMP) and steroids (progesterone, testosterone, and oestradiol) was measured and the number of ovulations was estimated by counting released oocytes. Unstimulated control ovaries did not ovulate whereas addition of LH (0.1 microgram/ml) plus 3-isobutyl-1-methylxanthine (IBMX; 0.2 mM) resulted in 16.7 +/- 3.5 ovulations per treated ovary. Cycloheximide (5 micrograms/ml) totally inhibited the ovulatory effect of LH + IBMX when present from the beginning of the perfusions and also when added 8 h after LH + IBMX. No inhibition was seen when cycloheximide was added 10 h after LH + IBMX (1-1.5 h before the first ovulation; 15.2 +/- 4.4 ovulations per treated ovary). Puromycin (200 micrograms/ml) completely blocked ovulation when present from the beginning of the perfusions and the inhibition was congruent to 60% (6.5 +/- 2.2 ovulations per treated ovary) when the compound was added 8 h after LH + IBMX. Both inhibitors increased LH + IBMX-stimulated cAMP release substantially, but decreased the release of progesterone, testosterone and oestradiol. These results indicate that de-novo protein synthesis is important late in the ovulatory process for follicular rupture to occur. 相似文献
9.
D C Anderson W C van Schooten A Janson M E Barry R R de Vries 《Journal of immunology (Baltimore, Md. : 1950)》1990,144(7):2459-2464
A systematic series of 89 single residue substitution analogs of the Mycobacterium leprae 65-kDa protein-derived peptide LQAAPALDKL were tested for stimulation of two HLA-DR2 restricted 65 kDa-reactive T cell clones from a tuberculoid leprosy patient. Some analogs with substitutions outside a "core" region showed enhanced stimulation of the T cell clones. This core region of seven or eight residues was essential for recognition, whereas substitution of amino acids outside this region did not affect T cell recognition although these residues could not be omitted. Thus these core residues interact directly with the presenting HLA-DR2 molecule and/or the TCR. Except for analogs of position 419 for clone 2B6, the majority of the nonstimulatory substitution analogs did not inhibit the presentation of LQAAPALDKL and thus probably failed to bind to the HLA-DR2 molecule. Unless all of the core residues are physically involved in binding to DR2, substitution at a position not directly involved in binding appears to have an influence on other residues that do bind to the DR2 molecule. Active peptide analogs with two or more internal prolines suggest that not all analogs need be helical for activity with clone 2F10. 相似文献
10.
A Mycobacterium leprae-specific gene encoding an immunologically recognized 45 kDa protein 总被引:1,自引:0,他引:1
Tobias F. Rinke de Wit Josephine E. Clark-Curtiss Feseha Abebe Arend H. J. Kolk Anneke A. M. Janson Miranda van Agterveld Jelle E. R. Thole 《Molecular microbiology》1993,10(4):829-838
By screening a Mycobacterium leprae lambda gt11 expression library with a serum from an Ethiopian lepromatous leprosy (LL) patient a clone was isolated (LL4) belonging to hybridization group III of a panel of previously isolated M. leprae clones. Members of this hybridization group encode a serologically recognized 45 kDa protein. The complete DNA sequences of the partially overlapping clones LL4 and L1 (hybridization group III) are presented and these revealed the presence of an open reading frame (ORF) predicting a protein with a molecular size of 42 448 Da. Southern hybridizations on total genomic DNA of M. Ieprae, Mycobacterium tuberculosis and eight atypical mycobacteria showed that the LL4 DNA fragment is specific for M. Ieprae DNA even under low-stringency conditions. The M. Ieprae specificity of LL4 DNA was further confirmed by the polymerase chain reaction using four different sets of primers. Western blotting analyses showed that the M. Ieprae 45 kDa protein is frequently recognized by antibodies from leprosy patients and that this recognition is specific since no antibodies could be detected in sera of tuberculosis patients. T-cell proliferation assays also demonstrated T-cell recognition by leprosy patients and healthy contacts of the M. Ieprae 45 kDa protein. The specificity of the LL4 DNA region and the 45 kDa antigen that is encoded by hybridization group III could provide unique tools for the development of M. Ieprae-specific immunological and DNA reagents. 相似文献