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201.
Ikuzawa M Yasumasu S Inokuchi T Kobayashi K Nomura K Iuchi I 《Journal of biochemistry》2003,134(3):385-394
Cathepsin E (CE) was purified from the foregut of Xenopus laevis tadpoles as a mature dimeric form. The purified enzyme was a typical CE among aspartic proteinases with respect to pH dependence of proteolytic activity, susceptibility to pepstatin, and having N-linked high-mannose type oligosaccharide chains. We isolated two cDNAs for the CE (CE1 and CE2) from adult stomach. The amino acid sequence of the N-terminal region of the purified CE coincided with the corresponding sequence predicted from CE1. Northern blot analysis and in situ hybridization were performed. The CE1 mRNA was highly expressed in surface mucous cells and gland cells constituting the larval epithelium of the foregut of pro-metamorphic tadpoles. As metamorphosis began and progressed, CE1 mRNA drastically decreased in amount, and subsequently both CE1 and CE2 mRNAs gradually increased. The increase in CE2 mRNA was detected shortly after the increase in CE1 mRNA. The decrease in CE1 expression correlated with degeneration of the larval type epithelium, while the increases in both CE1 and CE2 expression correlated with formation of the adult type epithelium. Thus, cathepsin E gene expression was differentially regulated during metamorphosis-associated remodeling of the larval to adult type epithelium in stomach. 相似文献
202.
Kwak MK Wakabayashi N Itoh K Motohashi H Yamamoto M Kensler TW 《The Journal of biological chemistry》2003,278(10):8135-8145
203.
Saito K Sarai A Oda M Azuma T Kozono H 《The Journal of biological chemistry》2003,278(17):14732-14738
The differential scanning calorimetry analysis of the murine major histocompatibility complex class II molecule, I-E(k), in complex with an antigenic peptide derived from mouse hemoglobin, showed that the thermal stability at the mildly acidic pH is higher than that at the neutral pH. Although the thermal unfolding of I-E(k)-hemoglobin was irreversible, we extracted the equilibrium thermodynamic parameters from the kinetically controlled heat capacity curves. Both the denaturation temperatures and the enthalpy changes were almost independent of the heating rate over 1 degrees C per min. The linear relation between the denaturation temperature and the calorimetric enthalpy change provided the heat capacity changes, which are classified into one for the mildly acidic pH region and another for the neutral pH region. The equilibrium thermodynamic parameters showed that the increased stability at the mildly acidic pH is because of the entropic effect. These thermodynamic data provided new insight into the current structural model of a transition to an open conformation at the mildly acidic pH, which is critical for the peptide exchange function of major histocompatibility complex class II in the endosome. 相似文献
204.
Hyaluronan oligosaccharides induce CD44 cleavage and promote cell migration in CD44-expressing tumor cells 总被引:9,自引:0,他引:9
Sugahara KN Murai T Nishinakamura H Kawashima H Saya H Miyasaka M 《The Journal of biological chemistry》2003,278(34):32259-32265
CD44 is an adhesion molecule that serves as a cell surface receptor for several extracellular matrix components, including hyaluronan (HA). The proteolytic cleavage of CD44 from the cell surface plays a critical role in the migration of tumor cells. Although this cleavage can be induced by certain stimuli such as phorbol ester and anti-CD44 antibodies in vitro, the physiological inducer of CD44 cleavage in vivo is unknown. Here, we demonstrate that HA oligosaccharides of a specific size range induce CD44 cleavage from tumor cells. Fragmented HA containing 6-mers to 14-mers enhanced CD44 cleavage dose-dependently by interacting with CD44, whereas a large polymer HA failed to enhance CD44 cleavage, although it bound to CD44. Examination using uniformly sized HA oligosaccharides revealed that HAs smaller than 36 kDa significantly enhanced CD44 cleavage. In particular, the 6.9-kDa HA (36-mers) not only enhanced CD44 cleavage but also promoted tumor cell motility, which was completely inhibited by an anti-CD44 monoclonal antibody. These results raise the possibility that small HA oligosaccharides, which are known to occur in various tumor tissues, promote tumor invasion by enhancing the tumor cell motility that may be driven by CD44 cleavage. 相似文献
205.
An age-related pigment, lipofuscin (LF), which accumulates in postmitotic, long-lived cells, is formed by the oxidative degradation of cellular macromolecules by oxygen-derived free radicals. In the present study we show that LF is accumulated in some myofibres, myosatellite cells and interstitial cells in the diaphragm muscles of the X chromosome-linked muscular dystrophic (mdx) mice at the age of 10 weeks when repetitive cycles of de- and regeneration of myofibres occur. In contrast, LF is virtually absent in diaphragm muscles of age-matched C57BL/10 (C57) normal control mice. Therefore, mdx muscle is more susceptible to oxidative stress than normal muscle. We hypothesise that gene-regulated cell death (apoptosis) occurs in dystrophic muscle cells that accumulate LF as a consequence of either oxidative stress or injury. We found that 74-79% of apoptotic myosatellite cells, interstitial cells and myofibres in mdx diaphragm contain accumulated or dotted LF granules, but only 12-20% of non-apoptotic cells contain LF. Apoptotic cells are very rare in the diaphragm of age-matched C57 control mice. This suggests that the regeneration of mdx diaphragm muscle initiated from myosatellite cells is impaired by their apoptosis as the result of either oxidative stress or a product of oxidative injury. 相似文献
206.
A study was made of cambial activity, the localization of storage starch around the cambium, and the localization and occurrence
of microtubules in cambial cells from dormancy to reactivation in locally heated (22–26 °C) stems of the evergreen conifer
Abies sachalinensis. Heating induced localized reactivation of the cambium in the heated portions of the stem. Erect ray cambial cells resumed
cell division 1 d prior to the reactivation of fusiform cambial cells and procumbent ray cambial cells. The re-initiation
of the division of fusiform cambial cells occurred first on the phloem side. During the heat treatment, the amount of storage
starch decreased in procumbent ray cambial cells and in the phloem parenchyma adjacent to the cambium but increased in fusiform
cambial cells. Preprophase bands of microtubules, spindle microtubules and phragmoplast microtubules were observed both in
erect ray cambial cells and in procumbent ray cambial cells. By contrast, no evidence of the presence of such preprophase
bands of microtubules was detected in fusiform cambial cells. The results suggest that the localized heating of stems of evergreen
conifers might provide a useful experimental model system for studies of the dynamics of cambial reactivation in intact trees.
Received: 25 May 2000 / Accepted: 12 July 2000 相似文献
207.
Masayuki Saigusa 《Ecological Research》2001,16(1):1-28
Many small invertebrates inhabit the shallow subtidal zone and some of them emerge at times into the water column. The daily timing of their emergence is affected by the day/night and tidal cycles, and shows various patterns of synchrony with these cyclical factors, depending on the species. To detect possible regional differences in their emergence patterns, sampling was carried out at four locations in Japan: a boreal sea (Akkeshi), a temperate sea (Sugashima), an inland sea (Ushimado) and a subtropical sea (Iriomote-jima). The emergence patterns of major taxa were examined by visual inspection and by two statistical methods (periodogram and autocorrelogram). The composition of the taxa collected by the pump system, mostly crustaceans, was similar in each location. The number of taxa that emerged revealed a day/night rhythm in every location. This characteristic was clearest at Iriomote-jima and least clear at Sugashima. The daily fluctuation in the number of individuals in each taxon varied widely, from very clearly nocturnal to weakly diurnal patterns. In Iriomote-jima, the major taxa all showed well-demarcated nocturnal patterns, so these patterns were classified as either level N2 or N3 with regard to the degree of synchrony with the day/night cycle. With regard to the synchrony with the tide, the majority of patterns in all locations showed a double-tidal interval. Many patterns were slightly modified by the tidal cycle. These patterns were classified as level T1 or T2 with regard to the degree of synchrony with the tidal cycle. The synchrony with the tide was comparatively strong at Ushimado. The synchrony with day/night and tidal cycles varied even within the same species or closely related species. In benthic invertebrates, hiding or resting in the bottom substrates and swimming in the water column would occur alternatively. In planktonic animals, aggregation near the bottom and dispersal in the water column would occur alternatively. The daily timing of such activities may be synchronized with the day/night and tidal cycles to various degrees among species or populations, resulting in a wide variety of emergence patterns in subtidal small invertebrates. This type of behavior is not daily (diel) vertical migration; it should rather be called daily emergence/dispersal. Strong winds, rough waves and unknown seasonal factors would also affect emergence patterns. Furthermore, the transparency of the seawater may also strongly affect these patterns. Nocturnal patterns may be an adaptation to avoid vulnerability to sighted predators. Variation of synchrony with the tide indicates that by definition, the tidal rhythm can only be distinguished from the day/night rhythm. Hence, the daily patterns that are weakly modified by the tides (levels T1 and T2) should be called the tidal rhythms. As the period of such rhythms cannot be determined exactly by using statistical methods, lengthy field investigations and visual inspection of each pattern is essential to assess the influence of tides. 相似文献
208.
Komatsu M Kawagishi T Emoto M Shoji T Yamada A Sato K Hosoi M Nishizawa Y 《American journal of physiology. Heart and circulatory physiology》2002,283(2):H557-H561
The association between endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism and vascular endothelial function has not been clarified. We investigated the impact of ecNOS gene polymorphism on endothelial function in 95 patients with Type 2 diabetes (ecNOS genotype: 4b/b, n = 62; 4b/a, n = 30; 4a/a, n = 3). Flow-mediated (endothelium dependent, FMD) and nitroglycerin-induced (endothelium independent, NTG) vasodilations of the right brachial artery were studied using a phase-locked echotracking system. There were no significant differences in clinical characteristics among the ecNOS genotypes. The FMD was significantly lower in the patients with ecNOS4a allele than in those without ecNOS4a allele (P < 0.05). Multiple regression analysis showed that ecNOS4a allele and mean blood pressure were significant independent determinants for reduced FMD in all patients (R(2) = 0.122, P = 0.0025). The ecNOS4a allele was an independent determinant for reduced FMD in smokers but not in nonsmokers. These results suggest that ecNOS4a allele is a genetic risk factor for endothelial dysfunction in diabetic patients, especially in smokers. 相似文献
209.
An anhydrous polymorphic form of trehalose 总被引:1,自引:0,他引:1
An anhydrous polymorphic form of alpha,alpha-trehalose was prepared from trehalose dihydrate by two different drying methods: (1) heating under vacuum; and (2) heating in hot air. Preparation of this anhydrous form by vacuum heating showed good reproducibility. This form was characterized by X-ray powder diffraction analysis and differential scanning calorimetry. This anhydrous form was converted to an amorphous phase at 127 degrees C and was found to be hygroscopic. At 43% relative humidity at 25 degrees C, this form rapidly reverted to dihydrate, while the amorphous phase remained unchanged. When an amorphous phase coexisted with this form, the rate of water adsorption to the amorphous phase was slower than that to the amorphous phase alone. These properties of this anhydrous form of alpha,alpha-trehalose may explain the effects of trehalose in dehydration tolerance of plants and insects in the desert. 相似文献
210.