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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Erica Raspelli Corinne Cassani Elena Chiroli Roberta Fraschini 《The Journal of biological chemistry》2015,290(1):1-12
Cyclin-dependent kinase (Cdk1) activity is required for mitotic entry, and this event is restrained by an inhibitory phosphorylation of the catalytic subunit Cdc28 on a conserved tyrosine (Tyr19). This modification is brought about by the protein kinase Swe1 that inhibits Cdk1 activation thus blocking mitotic entry. Swe1 levels are regulated during the cell cycle, and they decrease during G2/M concomitantly to Cdk1 activation, which drives entry into mitosis. However, after mitotic entry, a pool of Swe1 persists, and we collected evidence that it is involved in controlling mitotic spindle elongation. We also describe that the protein phosphatase Cdc14 is implicated in Swe1 regulation; in fact, we observed that Swe1 dephosphorylation in vivo depends on Cdc14 that, in turn, is able to control its subcellular localization. In addition we show that the lack of Swe1 causes premature mitotic spindle elongation and that high levels of Swe1 block mitotic spindle elongation, indicating that Swe1 inhibits this process. Importantly, these effects are not dependent upon the role of in Cdk1 inhibition. These data fit into a model in which Cdc14 binds and inhibits Swe1 to allow timely mitotic spindle elongation. 相似文献
32.
《Harmful algae》2015
A differential screening study using high-resolution (HR)-hydrophilic interaction chromatography (HILIC)-electrospray ionization (ESI)–quadrupole time-of-flight mass spectrometry (Q-TOF MS) was conducted to identify saxitoxin (STX) analogues in the marine dinoflagellate toxic sub-clone Alexandrium tamarense Axat-2 and the non-toxic sub-clone UAT-014-009 derived from the same Japanese isolate. One unknown compound was identified only in the toxic sub-clone and was found to have the molecular formula C9H16N6O2. This structure differed from that of decarbamoyl STX (dcSTX; C9H16N6O3) by the loss of a single oxygen. A 12-deoxy-dcSTX standard (a mixture of 12α- and β-deoxy-dcSTX) was chemically prepared from dcSTX by reduction with sodium borohydride. The unknown compound in the toxic strain of A. tamarense was identified as 12β-deoxy-dcSTX by comparison of its HR-HILIC-LC–MS retention time and HR–MS/MS spectrum with those of the chemically prepared standard, and the identification was confirmed by high-sensitivity HPLC analysis with post-column fluorescent derivatization. Moreover, two Japanese isolates of A. catenella showing toxin profiles different from that of A. tamarense were also found to contain 12β-deoxy-dcSTX. Previously, 12β-deoxy-dcSTX was isolated from the freshwater cyanobacterium Lyngbya wollei, which produces a unique set of STX analogues. This study is the first evidence of the presence of 12β-deoxy-dcSTX in marine dinoflagellates. 相似文献
33.
Ryota Masuzaki Sophia Zhao M. Todd Valerius Daisuke Tsugawa Yuki Oya Kevin C. Ray Seth J. Karp 《The Journal of biological chemistry》2016,291(7):3346-3358
After significant injury, the liver must maintain homeostasis during the regenerative process. We hypothesized the existence of mechanisms to limit hepatocyte proliferation after injury to maintain metabolic and synthetic function. A screen for candidates revealed suppressor of cytokine signaling 2 (SOCS2), an inhibitor of growth hormone (GH) signaling, was strongly induced after partial hepatectomy. Using genetic deletion and administration of various factors we investigated the role of SOCS2 during liver regeneration. SOCS2 preserves liver function by restraining the first round of hepatocyte proliferation after partial hepatectomy by preventing increases in growth hormone receptor (GHR) via ubiquitination, suppressing GH pathway activity. At later times, SOCS2 enhances hepatocyte proliferation by modulating a decrease in serum insulin-like growth factor 1 (IGF-1) that allows GH release from the pituitary. SOCS2, therefore, plays a dual role in modulating the rate of hepatocyte proliferation. In particular, this is the first demonstration of an endogenous mechanism to limit hepatocyte proliferation after injury. 相似文献
34.
《Saudi Journal of Biological Sciences》2016,23(4):462-466
The present study is to determine the prevalence and implication of coeliac disease (CD) among adult Saudis and compared to those with diagnosed irritable bowel syndrome. This prospective study was conducted among 980 adults. Out of that, 482 subjects (staff and students of Riyadh Health Science College) were designated as control cohorts for undetected coeliac disease. Furthermore, another contingent of 498 subjects diagnosed with irritable bowel syndrome (IBS) at Prince Salman Hospital and Al-Iman General Hospital also constituted a segment of the overall initial 1020 subjects. Both cases and control were tested for serological markers of coeliac disease (tissues transglutaminase (tTGAs) and endomysial autoantibody (EMAs) and were confirmed by histopathology test. All the positive for cases of coeliac disease were screened for iron deficiency anaemia, Vitamin D deficiency, and osteoporosis and weight assessment. The percentage of coeliac disease in control subjects and patients diagnosed with irritable bowel syndrome (IBS) were found to be 1.9% and 9.6% respectively, about 38% of the total coeliac disease patients are among females of middle age (20–39-years) and 16% of the males in the same age range. Whereas, 20% and 25% of all coeliac disease cases with ages of 40–59 were remarked as females and males respectively. The identical nature and overlap of symptoms of the two conditions could possibly result in misdiagnosis of coeliac diseases or over-diagnosis of irritable bowel syndrome. The findings of the study might also give considerable implications of the disease in the nutritional level which is noticeable. 相似文献
35.
A.C. Gonçalves T.D. Matos H.R. Simões-Teixeira M. Pimenta Machado M. Simão Ó.P. Dias M. Andrea G. Fialho H. Caria 《Gene》2014
Low-frequency sensorineural hearing loss (LFSNHL) is an unusual type of HL in which frequencies at 2000 Hz and below are predominantly affected. Most of the families with LFSNHL carry missense mutations in WFS1 gene, coding for wolframin. 相似文献
36.
LOURDES M. DE LA GARZA GOVINDAN BHASKARAN PUNNEE BARRERA KARL H. DAHM 《Physiological Entomology》1991,16(2):163-172
Abstract Larvae of the tobacco hornworm moth Manduca sexta starved for the first 3 days of the last (fifth) stadium undergo a supernumerary moult. If they are provided with sucrose during the starvation period, they develop into normal pupae although pupation is delayed. The activities of the corpora allata (CA) from normal, starved, and sucrose fed larvae were followed through the fifth stadium with a radiochemical assay for Juvenile Hormone (JH) biosynthesis. An attempt was made to correlate CA-activity with CA cell number, size, and protein content.
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated. 相似文献
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated. 相似文献
37.
Stefano Carenini Dirk Montag Harold Cremer Melitta Schachner Rudolf Martini 《Cell and tissue research》1996,287(1):3-9
We have previously shown that mice deficient in the gene for the myelin-associated glycoprotein (MAG) develop normal myelin
in the peripheral nerves, but show axon and myelin degeneration at eight months of age, suggesting that MAG is involved in
the maintenance of axon-Schwann cell integrity. The search for molecules that might replace MAG during myelination revealed
an overexpression of the neural cell adhesion molecule (N-CAM) at those aspects where MAG is detectable in wild type mice.
To test whether N-CAM might compensate for MAG during myelination in MAG-deficient mice, double mutants deficient in both
MAG and N-CAM (MAG−/N-CAM−mice) were generated by cross-breeding the single mutants. Whereas alterations of myelin development were not detectable in
either of the single or double mutants, degeneration of myelin and axons occurred approximately 4 weeks earlier in MAG−/N-CAM−than in MAG−mutants. Furthermore, at 8 weeks of age, single fiber preparation and electron microscopy revealed that the number of profiles
indicative of degeneration was substantially increased in MAG−/N-CAM−mutants when compared to MAG−mice. These data suggest that in MAG-deficient mice N-CAM does not compensate for MAG in myelin formation but partially substitutes
for it in the maintenance of axon-myelin integrity.
Received: 20 May 1996 / Accepted: 19 July 1996 相似文献
38.
Huan-Chen Li Chitra Mani David Kupfer 《Journal of biochemical and molecular toxicology》1993,8(4):195-206
Methoxychlor, a currently used pesticide, is demethylated and hydroxylated by several hepatic microsomal cytochrome P450 enzymes. Also, methoxychlor undergoes metabolic activation, yielding a reactive intermediate (M*) that binds irreversibly and apparently covalently to microsomal proteins. The study investigated whether methoxychlor could inhibit or inactivate certain liver microsomal P450 enzymes. The regioselective and stereoselective hydrox-ylation of testosterone and the 2-hydroxylation of estradiol (E2) were utilized as markers of the P450 enzymes inhibited by methoxychlor. Both reversible and time-dependent inhibition were examined. Coincubation of methoxychlor and testosterone with liver microsomes from phenobarbital treated (PB-microsomes) male rats, yielded marked diminution of 2α- and 16α-testosterone hydroxylation, indicating strong inhibition of P4502C11 (P450h). Methoxychlor moderately inhibited 2β-, 7α-, 15α-, 15β-, and 16β-hydroxylation and androstenedi-one formation. There was only a weak inhibition of 6β-ydroxylation of testosterone. The methox-ychlor-mediated inhibition of 6β-hydroxylation was competitive. By contrast, when methoxychlor was permitted to be metabolized by PB-microsomes or by liver microsomes from pregnenolone-16α-car-bonitrile treated rats (PCN-microsomes) prior to addition of testosterone, a pronounced time-dependent inhibition of 6β-hydroxylation was observed, suggesting that methoxychlor inactivates the P450 3A isozyme(s). The di-demethylated methoxychlor (bis-OH-M) and the tris-hydroxy (ca-techol) methoxychlor metabolite (tris-OH-M) inhibited 6β-hydroxylation in PB-microsomes competitively and noncompetitively, respectively; however, these methoxychlor metabolites did not exhibit a time-dependent inhibition. Methoxychlor inhibited competitively the formation of 7α-hydroxytestosterone (7α-OH-T) and 16α-hydroxy-testosterone (16α-OH-T) but exhibited little or no time-dependent inhibition of generation of these metabolites, indicating that P450s 2A1, 2B1/B2, and 2C11 were inhibited but not inactivated. Methoxychlor inhibited in a time-dependent fashion the 2-hydroxylation of E2 in PB-microsomes. However, bis-OH-M exhibited solely reversible inhibition of the 2-hydroxylation, supporting our conclusion that the inactivation of P450s does not involve participation of the demethylated metabolites. Both competitive inhibition and time-dependent inactivation of human liver P450 3A (6β-hydroxylase) by methoxychlor, was observed. As with rat liver microsomes, the human 6β-hydroxylase was inhibited by bis-OH-M and tris-OH-M competitively and noncompetitively, respectively. Testosterone and estradiol strongly inhibited the irreversible binding of methoxychlor to microsomal proteins. This might explain the “clean” competitive inhibition by methoxychlor of the 6β-OH-T formation when the compounds were coin-cubated. Glutathione (GSH) has been shown to interfere with the irreversible binding of methoxychlor to PB-microsomal proteins. The finding that the coincubation of GSH with methoxychlor partially diminishes the time-dependent inhibition of 6β-hydroxylation provides supportive evidence that the inactivation of P450 3A isozymes by methoxychlor is related to the formation of M*. 相似文献
39.
The hypothesis that resource monopolization and defense increaseas the spatial clumping of resources increases was tested usinggroups of three convict cichlids competing for 120 Daphnia magnaprey. Spatial clumping was manipulated by varying the distance(3, 20, or 40 cm) between three tubes through which the preyappeared. As predicted, monopolization of prey (percentage eatenby the dominant fish) and frequency of aggression (chases perminute) by dominant fish increased significantly as the distancebetween the tubes decreased. However, there was no evidenceof individual flexibility in the aggressiveness (percentageof conspecifics chased) of dominant fish across treatments.Differences among dominant fish in aggressiveness were positivelycorrelated with their ability to monopolize prey, but the strengthof the correlation decreased as the distance between the tubesincreased. Aggression appears to be a more effective mechanismof interference competition when resources are clumped thanwhen resources are dispersed. 相似文献
40.
Soybean hypocotyl segments were treated in the dark with 24-epibrassinolide (BR) at a range of concentrations for different durations. The maximum effect on adventitious root induction, both in terms of number and length was obtained at very low concentration (0.0001 ppm) of BR applied for 8 h. Higher concentrations were supraoptimal unless applied for a shorter period (4 h). BR was ineffective when applied at low concentration in continuous light. 相似文献