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201.
The synthesis of juvenile hormone-III by corpora allata of the cockroach Diploptera punctata is dependent under in vitro conditions upon a supply of exogenous methionine. Radiolabelled S-adenosylmethionine was identified by HPLC in extracts of corpora allata incubated with either [methyl-3H]methionine or [35S]methionine. Juvenile hormone (JH) synthesis by intact glands in vitro was inhibited by cycloleucine and selenomethionine, but this inhibition could be relieved by increasing the concentration of methionine. S-adenosylhomocysteine or sinefungin had little or no inhibitory effect on JH synthesis by intact glands, but 5′-deoxy-5′-methylthioadenosine was inhibitory. Adenosine and homocysteine synergistically inhibited JH synthesis. These results show that JH-III synthesis by intact glands can be inhibited by interfering with the S-adenosylmethionine-dependent transmethylation, and suggest that the product and inhibitor of that reaction, S-adenosyl-homocysteine, is rapidly hydrolyzed to adenosine and homocysteine in the corpora allata. 相似文献
202.
Yingjie Yu Shailender S Kanwar Bhaumik B Patel Jyoti Nautiyal Fazlul H Sarkar Adhip PN Majumdar 《Translational oncology》2009,2(4):321-328
5-Fluorouracil (5-FU) or 5-FU plus oxaliplatin (FOLFOX) remains the backbone of colorectal cancer chemotherapeutics but with limited success. This could partly be due to the enrichment of cancer stem cells (CSCs) that are resistant to conventional chemotherapy. Therefore, validation of a nontoxic agent that can either cause reversal of chemoresistance or promote the killing of CSCs would be highly desirable. The current study examines whether curcumin, the major active ingredient of turmeric, either alone or together with FOLFOX, would be an effective strategy to eliminate colon CSCs. Exposure of colon cancer HCT-116 or HT-29 cells to FOLFOX that inhibited their growth led to the enrichment of CSC phenotype as evidenced by increased proportion of CD133-, CD44-, and/or CD166-positive cells and epidermal growth factor receptor (EGFR) levels. Treatment of FOLFOX-surviving colon cancer cells with either curcumin alone or together with FOLFOX resulted in a marked reduction in CSCs, as evidenced by the decreased expression of CD44 and CD166 as well as EGFR and by their ability to form anchorage-dependent colonies. They also caused disintegration of colonospheres. Increased expression of EGFR in FOLFOX-surviving cells could be attributed to hypomethylation of the EGFR promoter, whereas an opposite phenomenon was observed when the FOLFOX-surviving cells were treated with curcumin and/or FOLFOX. These changes were accompanied by parallel alterations in the levels of DNA methyltransferase 1. In conclusion, our data suggest that curcumin by itself or together with the conventional chemotherapeutic could be an effective treatment strategy for preventing the emergence of chemoresistant colon cancer cells by reducing/eliminating CSCs. 相似文献
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A capacity to predict the effects of fire on biota is critical for conservation in fire‐prone regions as it assists managers to anticipate the outcomes of different approaches to fire management. The task is complicated because species’ responses to fire can vary geographically. This poses challenges, both for conceptual understanding of post‐fire succession and fire management. We examine two hypotheses for why species may display geographically varying responses to fire. 1) Species’ post‐fire responses are driven by vegetation structure, but vegetation – fire relationships vary spatially (the ‘dynamic vegetation’ hypothesis). 2) Regional variation in ecological conditions leads species to select different post‐fire ages as habitat (the ‘dynamic habitat’ hypothesis). Our case study uses data on lizards at 280 sites in a ~ 100 000 km2 region of south‐eastern Australia. We compared the predictive capacity of models based on 1) habitat associations, with models based on 2) fire history and vegetation type, and 3) fire history alone, for four species of lizards. Habitat association models generally out‐performed fire history models in terms of predictive capacity. For two species, habitat association models provided good discrimination capacity even though the species showed geographically varying post‐fire responses. Our results support the dynamic vegetation hypothesis, that spatial variation in relationships between fire and vegetation structure results in regional variation in fauna–fire relationships. These observations explain how the widely recognised ‘habitat accommodation’ model of animal succession can be conceptually accurate yet predictively weak. 相似文献
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Nadya I. Tarasova Terry D. Copeland David W. Farnsworth Stephen A. Wank Eric A. Hudson James H. Resau Christopher J. Michejda 《Letters in Peptide Science》1995,1(5):221-228
Summary Seven synthetic peptides, between 7–22 residues long, corresponding to six different parts of the gastrin/CCKB receptor molecule which are conserved among the species, were used for raising antibodies. The peptides were coupled to keyhole limpet hemocyanine and injected into rabbits. ELISA analysis demonstrated that all peptides produced an immune response after three to six injections given at biweekly intervals. The titer ranged from 1:104 to 1:105. All antibodies recognized a 78 kDa protein on immunoblots of NIH 3T3 cells stably transfected with human gastrin/CCKB receptor cDNA, as well as human and guinea pig stomach mucosal extracts. Preincubation of the sera with the corresponding peptides abolished the staining. Indirect immunofluorescence staining revealed that four antibodies out of the seven tested recognized the receptor in fixed COS-7 cells transiently transfected with human gastrin/CCKB receptor cDNA. The reactive antibodies were raised against the peptides corresponding to receptor residues 40–58, 153–160, 288–294 and 356–372. Immunohistochemical staining of guinea pig stomach using these antisera resulted in intense staining of parietal cells in the fundus and cardia regions.Abbreviations CCK
cholecystokinin
- GR
gastrin/CCKB receptor
- TFA
trifluoroacetic acid
- BSA
bovine serum albumin
- PBS
phosphate-buffered saline
- PAGE
polyacrylamide gel electrophoresis
- ELISA
enzyme-linked immunosorbent assay
- EDTA
ethylenediamino tetraacetic acid
- CLSM
confocal laser scanning microscopy
- KLH
keyhole limpet hemocyanine 相似文献
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Alice H. Cavanaugh Wells E. Farnsworth Hebe B. Greizerstein Caryn Wojtowicz 《Life sciences》1979,26(1):19-28
Human prostate tissue has been found to be an excellent organ for synthesizing and metabolizing prostaglandin F2 alpha. Employing 3H-arachidonic acid as substrate, tritium incorporation into PGF2 alpha and three different metabolites, namely, 15-keto-PGF2 alpha, 13, 14-dihydro-PGFP2 alpha, and 13, 14-dihydro-15-keto-PGF2 alpha, has been shown. The identity of these substances was corroborated by gas chromatography and chemical ionization mass spectrometry. Indomethacin has been widely reported as an inhibitor of PGF2 alpha synthesis. In our experiments, upon adding indomethacin, slight to no inhibition of PGF2 alpha synthesis was seen. Instead, we found a highly significant increase in the incorporation of the tritium of arachidonic acid into 15-keto-PGF2 alpha. We interpret these findings as evidence that the indomethacin may block not PGF2 alpha synthetase, but the Δ13-reductase, thus causing the accumulation of this enzyme's substrate, 15-keto-PGF2 alpha. 相似文献
210.