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101.
102.
1. As trees age, they undergo significant physiological and morphological changes. Nevertheless, tree ontogeny and its impacts on herbivores are often overlooked as determinants of plant–herbivore population dynamics and the strength of plant–herbivore interactions. 2. Juniperus (Cupressaceae) is a dominant, long‐lived conifer that serves as the sole host to a specialised assemblage of caterpillars. Over the past 150 years, several juniper species in western North America have expanded their geographic occupancy at local and regional scales, which has resulted in an increase in the number of immature trees on the landscape. Using assays in the laboratory, the effects of tree ontogeny on caterpillar performance and oviposition preference for two juniper specialist caterpillars, Callophrys gryneus (Lycaenidae) and Glena quinquelinearia (Geometridae), were examined. The study considered whether responses to tree ontogeny were consistent across caterpillar species and juniper host species. 3. Tree age was found to be a reliable predictor of caterpillar performance, with caterpillars developing more quickly and growing larger when fed foliage from young trees. Differences in the phytochemical diversity between foliage from trees of different ages might help to explain observed differences in caterpillar performance. Interestingly, the specialist butterfly, C. gryneus, displayed an oviposition preference for foliage from old‐growth Juniperus osteosperma trees, despite the fact that larvae of this species performed poorly on older trees. 4. It is concluded that young juniper trees are an important resource for the specialised Lepidopteran community and that tree ontogeny is an important component of intraspecific variation, which contributes to the structure of plant–herbivore communities. 相似文献
103.
Isolation and characterization of monkey interphotoreceptor retinoid-binding protein, a unique extracellular matrix component of the retina 总被引:6,自引:0,他引:6
T M Redmond B Wiggert F A Robey N Y Nguyen M S Lewis L Lee G J Chader 《Biochemistry》1985,24(3):787-793
The interphotoreceptor retinoid-binding protein (IRBP) has been isolated from monkey interphotoreceptor matrix (IPM). Following gentle washing of the IPM from the retinal surface, the protein was purified to homogeneity by concanavalin A-Sepharose affinity chromatography, ion-exchange high-performance liquid chromatography (HPLC), and size-exclusion HPLC. Bovine IRBP was purified similarly and compared with the monkey protein. Sedimentation equilibrium analysis yielded a molecular weight of 106 000 +/- 2900 for the native monkey protein. Sedimentation velocity analysis gave a sedimentation coefficient of 5.4 +/- 0.3 S and a frictional ratio of 1.59, indicating an asymmetrical molecular shape. IRBP contains neutral sugar, including fucose, and sialic acid; the glycoprotein nature of the proteins probably accounts for the microheterogeneity observed in the electrofocusing pattern of both bovine and monkey IRBP. Both IRBPs have isoelectric points between 6.0 and 7.0. The fluorescence emission lambda max of the bound ligand was 470 nm with excitation at 340 nm, while the excitation lambda max was 333 nm with emission at 470 nm, for monkey IRBP incubated with exogenous all-trans-retinol. The amino acid compositions of the monkey and bovine proteins are similar; nonpolar amino acids account for over 50% of the residues, which may explain the apparent hydrophobic nature of the isolated proteins. The amino-terminal analyses indicated considerable homology between the monkey and bovine IRBPs in this region and verified the purity of the isolated proteins. IRBP thus appears to be a unique, conserved glycoprotein of the retinal extracellular matrix that could serve as a retinoid-transport vehicle. 相似文献
104.
The structure, biochemical properties, and immunogenicity of neurofilament peripheral regions are determined by phosphorylation state 总被引:31,自引:0,他引:31
Treatment of freshly isolated, bovine neurofilaments with Escherichia coli alkaline phosphatase removes over 90% of the phosphate groups from serine residues of the Mr 200,000 and 150,000 polypeptide components (NF200 and NF150). Dephosphorylated NF200 and NF150 remain associated with filaments, but migrate in sodium dodecyl sulfate gels with reduced apparent molecular weights. Unusual migration appears to be due to modification at regions of these polypeptides that are peripheral to the neurofilament backbone as defined by limited chymotryptic digestion. Over 90 monoclonal antibodies recognizing epitopes located within the peripheral domain of native NF200 all show reduced affinity for dephosphorylated NF200. A single monoclonal antibody binds within the filament-associated domain of NF200 and its recognition of NF200 is unaffected upon treatment of neurofilaments with phosphatase. Around 50% of our monoclonal antibodies that bind NF150 monospecifically and at epitopes within its peripheral domain have reduced affinities for NF150 from phosphatase-treated filaments, while the remaining 50% bind native and dephosphorylated NF150 equally well. The smallest neurofilament component (NF70) contains few phosphate groups, most of which remain after treatment of neurofilaments with phosphatase. The resulting form of NF70 migrates normally in gels and its recognition by antibodies is unchanged. We conclude that phosphorylation modifies the structure of the two larger neurofilament polypeptides along domains that are peripheral to the filamentous backbone and that these effects are more pronounced for NF200 than for NF150. 相似文献
105.
S C Lee J Y Shew F H Chang M J Chou C S Yang 《Proceedings of the National Science Council, Republic of China. Part B, Life sciences》1984,8(2):143-147
Protein kinase activity has been found in hepatitis B virions (Dane particles) purified from the plasma of hepatitis B surface antigen carriers [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302]. Dane particles were purified from the pooled, HBeAg-positive plasma. When this preparation was incubated with [gamma 32P]ATP in the presence of 10mM MnCl2 and 0.5% NP-40 for 15 seconds at 30 degrees C, several phosphorylated polypeptides of 20,000, 42,000, 48,000, 50,000 and 56,000 daltons were detected in sodium dodecyl sulfate-polyacrylamide gels. When the Dane particles were incubated with [gamma 32P]ATP, 10 mM MnCl2, and 0.5% NP-40 in the presence of human hepatoma cell (J-5) particulate fraction at 30 degrees C, 15 seconds, the 42,000, 48,000 and 50,000 daltons phosphorylated polypeptides were not found. When human peripheral blood lymphocytes particulate fraction was incubated with Dane particles under the same conditions, no change of Dane particle phosphorylated polypeptides was detected. Previous publications [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302; Gerlich, W.H. et al. (1982) J. Virol. 42, 761-766] showed that when hepatitis B core particles purified from hepatoma tissues contained protein kinase activity, only phosphorylated polypeptide was 20,000 daltons. Our data suggested that when Dane particles were put in an environment of hepatoma cells (or tissues), the protein kinase could only phosphorylate selected polypeptides in these particles. 相似文献
106.
I Lee V E Gould J A Radosevich A Thor Y X Ma J Schlom S T Rosen 《Virchows Archiv. B, Cell pathology including molecular pathology》1987,53(3):146-152
We undertook an immunohistochemical analysis of human bronchopulmonary epithelial neoplasms and pleural mesotheliomas using a monoclonal antibody which recognizes ras oncogene products (p21ras). The monoclonal antibody, RAP-5, recognizes both unaltered and certain mutated p21ras. Formalin fixed and paraffin embedded tissue samples of 187 lung epithelial tumors and 27 pleural mesotheliomas were investigated; normal and bronchiectatic lungs were similarly studied. Normal lung and pleural tissue did not immunostain except for occasional type II pneumocytes. Reactive type II pneumocytes adjacent to carcinomas and bronchiectasis immunostained consistently. Twenty four/34 (71%) squamous carcinomas immunostained. Only 8/50 (16%) adenocarcinomas immunostained focally and weakly whereas 19/24 (79%) bronchioloalveolar carcinomas immunostained. Eleven/18 (61%) large cell carcinomas immunostained with variable intensity. Eleven/13 (85%) carcinoids, 6/7 (85%) well differentiated neuroendocrine carcinomas, and 18/21 (86%) intermediate cell neuroendocrine carcinomas immunostained while none of 20 small cell neuroendocrine carcinomas immunostained. Only a few mesotheliomas were immunostained focally. Two/14 (14%) epithelial type and 1/9 (11%) biphasic type mesotheliomas immunostained weakly; none of 4 spindle cell mesotheliomas immunostained. We conclude that while at least occasional cases of most types of pulmonary epithelial neoplasms express p21ras, the frequency and intensity of the expression are distinctly greater in certain tumor types such as squamous, bronchioloalveolar, and neuroendocrine neoplasm except for the small cell type. Contrary to these lung epithelial neoplasms, most mesotheliomas did not immunostain for p21ras. Whether the enhanced p21ras expression may point to a different mechanism of transformation or may merely reflect differentiation features remains undetermined. 相似文献
107.
B S Yoo S B Kim J H Lee K H Yang 《Biochemical and biophysical research communications》1988,153(2):748-752
The subunit composition of isolated polymeric forms of Portunus trituberculatus hemocyanin were analysed by immunological techniques. The dodecamers contain four monomeric subunits corresponding to subunits I, II, III and IV, whereas the hexamers are devoid of subunit IV. These results suggest that subunit IV is required as a joining piece for the assembly of dodecamers. 相似文献
108.
C G Lee Y K Ip 《Comparative biochemistry and physiology. A, Comparative physiology》1987,87(4):1009-1014
1. In both Periophthalmus chrysospilos and Boleophthalmus boddaerti, T4 was involved in enabling the fish to cope with terrestrial stress and not in osmoregulation in waters of different salinities. In B. boddaerti, however, 3,5,3'-triiodo-L-thyronine (T3) played a more significant role in osmoregulation under the various aquatic conditions. 2. The control of osmoregulation mechanisms in P. chrysospilos kept in waters of different salinities was taken over by prolactin instead, whereas prolactin was only involved in osmoregulation in B. boddaerti under extreme osmotic stress (100% SW). Prolactin is also involved in the terrestrial adaptations of P. chrysospilos. 3. Plasma cAMP levels in P. chrysospilos increased with increasing salinity of the external environment (Tables 4 and 5) implicating its role in the stimulation of chloride secretion and in intracellular isosmotic regulation. 4. Significant increase in the plasma cAMP level of B. boddaerti submerged in 100% SW was also observed. However, the plasma cAMP levels of B. boddaerti fully submerged in 30% and 50% SW were not significantly different from the control as these conditions simulated those of their natural habitats. 相似文献
109.
State of aggregation of the (Ca2+ + Mg2+)-ATPase studied using saturation-transfer electron spin resonance 总被引:1,自引:0,他引:1
The state of aggregation of the (Ca2+ + Mg2+)-ATPase in the membrane of sarcoplasmic reticulum and in reconstituted membrane systems has been studied using saturation-transfer electron spin resonance (ST-ESR). Saturation-transfer ESR spectra show that in the sarcoplasmic reticulum, the ATPase is relatively free to rotate, with an effective rotational correlation time of approx. 33 microseconds at 4 degrees C, consistent with a monomeric or dimeric structure. The rate of rotation is observed to decrease with decreasing molar ratio of lipid to protein. In reconstituted systems, rotational motion of the ATPase on the millisecond time scale ceases when the lipids are in the gel phase. Addition of decavanadate, which causes the formation of crystalline arrays in negatively stained electron micrographs, results in only a small reduction in rotation rate for the ATPase in the membrane. The experiments are interpreted in terms of a short-lived (on the millisecond time scale) protein-protein interaction, with the formation of crystalline clusters of ATPase molecules which form and melt rapidly. 相似文献