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131.
Diers JA Bowling JJ Duke SO Wahyuono S Kelly M Hamann MT 《Marine biotechnology (New York, N.Y.)》2006,8(4):366-372
Several aaptamine derivatives were selected as potential zebra mussel (Dreissena polymorpha) antifoulants because of the noteworthy
absence of fouling observed on Aaptos sponges. Sponges of the genus Aaptos collected in Manado, Indonesia consistently produce
aaptamine-type alkaloids. To date, aaptamine and its derivatives have not been carefully evaluated for their antifoulant properties.
Structure–activity relationship studies were conducted using several aaptamine derivatives in a zebra mussel antifouling assay.
From these data, three analogs have shown significant antifouling activity against zebra mussel attachment. Aaptamine, isoaaptamine,
and the demethylated aaptamine compounds used in the zebra mussel assay produced EC50 values of 24.2, 11.6, and 18.6 μM, respectively. In addition, neither aaptamine nor isoaaptamine produced a phytotoxic response
(as high as 300 μM) toward a nontarget organism, Lemna pausicostata, in a 7-day exposure. The use of these aaptamine derivatives
from Aaptos sp. as potential environmentally benign antifouling alternatives to metal-based paints and preservatives is significant,
not only as a possible control of fouling organisms, but also to highlight the ecological importance of these and similar
biochemical defenses. 相似文献
132.
Tetraspanins on the surface of Schistosoma mansoni are protective antigens against schistosomiasis 总被引:8,自引:0,他引:8
Tran MH Pearson MS Bethony JM Smyth DJ Jones MK Duke M Don TA McManus DP Correa-Oliveira R Loukas A 《Nature medicine》2006,12(7):835-840
Schistosomes are blood-dwelling flukes that infect 200 million people worldwide and are responsible for hundreds of thousands of deaths annually. Using a signal sequence trap, we cloned from Schistosoma mansoni two cDNAs, Sm-tsp-1 and Sm-tsp-2, encoding the tetraspanin (TSP) integral membrane proteins TSP-1 and TSP-2. We raised antibodies to recombinant TSP fusion proteins and showed that both proteins are exposed on the surface of S. mansoni. Recombinant TSP-2, but not TSP-1, is strongly recognized by IgG1 and IgG3 (but not IgE) from naturally resistant individuals but is not recognized by IgG from chronically infected or unexposed individuals. Vaccination of mice with the recombinant proteins followed by challenge infection with S. mansoni resulted in reductions of 57% and 64% (TSP-2) and 34% and 52% (TSP-1) for mean adult worm burdens and liver egg burdens, respectively, over two independent trials. Fecal egg counts were reduced by 65-69% in both test groups. TSP-2 in particular provided protection in excess of the 40% benchmark set by the World Health Organization for progression of schistosome vaccine antigens into clinical trials. When coupled with its selective recognition by naturally resistant people, TSP-2 seems to be an effective vaccine antigen against S. mansoni. 相似文献
133.
J A Alberta K R Auger D Batt P Iannarelli G Hwang H L Elliott R Duke T M Roberts C D Stiles 《The Journal of biological chemistry》1999,274(43):31062-31067
134.
The effects of neurotensin on pancreatic exocrine secretion were examined in fasted, conscious White Leghorn hens. A cannula was surgically implanted in the central duct serving the ventral lobe of the pancreas in order to collect pure pancreatic juice. Following recovery, neurotensin was infused intravenously at 3.6 or 10.8 pmol/kg*min. The volume and pH of the pancreatic secretions were recorded and total pancreatic protein concentration, amylase, lipase, trypsin, and chymotrypsin activity were measured every 30 min for 2 hr and compared to secretions following the infusion of 0.9% saline. Our results demonstrated that neurotensin did not affect the pH nor the pancreatic juice protein concentration, but did increase secretion rate following neurotensin infusion at 3.6 pmol/kg*min. Amylase activity was significantly depressed during neurotensin infusions, while lipase (both pancreatic and carboxylester lipase) activity was significantly elevated. The ratio of amylase to lipase activity was especially depressed by neurotensin infusion at 10.8 pmol/kg*min. Insufficient secretory activity prevented a balanced statistical analysis of chymotrypsin activity, but from a pooled analysis, neurotensin had no effect on protease activity in the pancreatic juice. These results support our current research indicating that neurotensin may be a hormonal regulator of postprandial lipid digestion in chickens. 相似文献
135.
Kuo WL Duke CJ Abe MK Kaplan EL Gomes S Rosner MR 《The Journal of biological chemistry》2004,279(22):23073-23081
ERK7 is a unique member of the extracellular signal-regulated kinase (ERK) subfamily of MAP kinases. Although ERK7 shares a TEY motif in the activation loop of the kinase, it displays constitutive activation, nuclear localization, and growth inhibitory properties that are regulated by its C-terminal domain. Because ERK7 is expressed at low levels compared with ERK2 and its activity is dependent upon its expression level, we investigated the mechanism by which ERK7 expression is regulated. We now show that ERK7 expression is regulated by ubiquitination and rapid proteosomal turnover. Furthermore, both the kinase domain and the C-terminal tail are independently degraded at a rate comparable with that of the intact protein. Analysis of a series of chimeras between ERK2 and ERK7 reveal that the N-terminal 20 amino acids of the kinase domain are a primary determinant of ERK7 degradation. Fusion of the N-terminal 20 amino acids is both necessary and sufficient to cause proteolytic degradation of both ERK2 and green fluorescent protein. Finally, ERK7 is stabilized by an N-terminal mutant of Cullin-1 suggesting that ERK7 is ubiquitinated by the Skip1-Cullin-F box complex. These results indicate that ERK7 is a highly regulated enzyme whose cellular expression and kinase activation level is tightly controlled by the ubiquitin-proteosome pathway. 相似文献
136.
We investigate the isometric transient response of muscle using a quantitative stochastic model of the actomyosin cycle based on the swinging lever-arm hypothesis. We first consider a single pair of filaments, and show that when values of parameters such as the lever-arm displacement and the cross-bridge elasticity are chosen to provide effective energy transduction, the T(2) curve (the tension recovered immediately after a step displacement) displays a region of negative slope. If filament compliance and the discrete nature of the binding sites are taken into account, the negative slope is diminished, but not eliminated. This implies that there is an instability in the dynamics of individual half sarcomeres. However, when the symmetric nature of whole sarcomeres is taken into account, filament rearrangement becomes important during the transient: as tension is recovered, some half sarcomeres lengthen whereas others shorten. This leads to a flat T(2) curve, as observed experimentally. In addition, we investigate the isotonic transient response and show that for a range of parameter values the model displays damped oscillations, as recently observed in experiments on single muscle fibers. We conclude that it is essential to consider the collective dynamics of many sarcomeres, rather than the dynamics of a single pair of filaments, when interpreting the transient response of muscle. 相似文献
137.
Ecophysiological aspects of allelopathy 总被引:37,自引:0,他引:37
Allelochemicals play an important role in explaining plant growth inhibition in interspecies interactions and in structuring the plant community. Five aspects of allelochemicals are discussed from an ecophysiological perspective: (i) biosynthesis, (ii) mode of release, (iii) mode of action, (iv) detoxification and prevention of autotoxicity, and (v) joint action of allelochemicals. A discussion on identifying a compound as an allelochemical is also presented. 相似文献
138.
139.
The nematode shows responses to acute ethanol exposure that are similar to those observed in humans, mice, and Drosophila, namely hyperactivity followed by uncoordination and sedation. We used in this report the nematode Caenorhabditis elegans as a model system to identify and characterize the genes that are affected by ethanol exposure and to link those genes functionally into an ethanol-induced gene network. By analyzing the expression profiles of all C. elegans ORFs using microarrays, we identified 230 genes affected by ethanol. While the ethanol response of some of the identified genes was significant at early time points, that of the majority was at late time points, indicating that the genes in the latter case might represent the physiological consequence of the ethanol exposure. We further characterized the early response genes that may represent those involved directly in the ethanol response. These genes included many heat shock protein genes, indicating that high concentration of ethanol acts as a strong stress to the animal. Interestingly, we identified two non-heat-shock protein genes that were specifically responsive to ethanol. glr-2 was the only glutamate receptor gene to be induced by ethanol. T28C12.4, which encodes a protein with limited homology to human neuroligin, was also specific to ethanol stress. Finally, by analyzing the promoter regions of the early response genes, we identified a regulatory element, TCTGCGTCTCT, that was necessary for the expression of subsets of ethanol response genes. 相似文献
140.
Differentiation-associated modulation of heparan sulfate structure and function in CaCo-2 colon carcinoma cells 总被引:3,自引:2,他引:1
Salmivirta M; Safaiyan F; Prydz K; Andresen MS; Aryan M; Kolset SO 《Glycobiology》1998,8(10):1029-1036
Heparan sulfate species expressed by different cell and tissue types differ
in their structural and functional properties. Limited information is
available on differences in regulation of heparan sulfate biosynthesis
within a single tissue or cell population under different conditions. We
have approached this question by studying the effect of cell
differentiation on the biosynthesis and function of heparan sulfate in
human colon carcinoma cells (CaCo-2). These cells undergo spontaneous
differentiation in culture when grown on semipermeable supports; the
differentiated cells show phenotypic similarity to small intestine
enterocytes. Metabolically labeled heparan sulfate was isolated from the
apical and basolateral media from cultures of differentiated and
undifferentiated cells. Compositional analysis of disaccharides, derived
from the contiguous N-sulfated regions of heparan sulfate, indicated a
greater proportion of 2-O- sulfated iduronic acid units and a smaller
amount of 6-O-sulfated glucosamine units in differentiated than in
undifferentiated cells. By contrast, the overall degree of sulfation, the
chain length and the size distribution of the N-acetylated regions were
similar regardless the differentiation status of the cells. The structural
changes were found to affect the binding of heparan sulfate to the long
isoform of platelet-derived growth factor A chain but not to fibroblast
growth factor 2. These findings show that heparan sulfate structures change
during cell differentiation and that heparan sulfate-growth factor
interactions may be affected by such changes.
相似文献