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21.
Microcystin-LR is a liver tumor promoter in the okadaic acid class, a group of potent inhibitors of protein phosphatases 1 and 2A. Because of inhibition of protein phosphatases, microcystin-LR induces hyperphosphorylation of cellular proteins, including cytoskeletal proteins—cytokeratins 8 and 18—and causes morphological changes in mouse hepatocytes in primary culture. We studied the effects of carotenoids to antagonize microcystin-LR-induced morphological changes in hepatocytes. β-Carotene (100 nM to 100 μM), suppressed the morphological changes induced by 100 nM microcystin-LR in a dose-dependent manner. Other carotenoids tested exerted similar suppressive effects, although retinoids, such as all-trans retinol, all-trans retinoic acid, and 9-cis retinoic acid, were only weakly suppressive. The relative potency of the suppression correlated significantly with the number of conjugated double bonds in thetrans configuration. β-Carotene strongly suppressed the hyperphosphorylation of cellular proteins induced by microcystin-LR without significant changes in the basal phosphorylation level. Other antioxidants, such as α-tocopherol, did not protect the cells against microcystin-LR. Taken together, the antagonistic effects of carotenoids against microcystin-LR are difficult to explain by their antioxidant or provitamin A activities. Suppression of the hyperphosphorylation of cellular proteins may be a novel mechanism by which carotenoids inhibit tumor promotion.  相似文献   
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Protein tyrosine phosphatase zeta (PTPzeta/RPTPbeta) is a receptor-like protein tyrosine phosphatase specifically expressed in the brain. Alternative splicing produces three isoforms of this molecule: PTPzeta-A, the full-length form of PTPzeta; PTPzeta-B, the short form of PTPzeta; and PTPzeta-S, an extracellular variant. Here, we identified all these isoforms, including PTPzeta-B, as chondroitin sulfate proteoglycans, and characterized their carbohydrate modification and expression profiles in the rat brain. The level of PTPzeta-A expression was maintained during the prenatal period and decreased rapidly after birth. PTPzeta-S was expressed in a similar manner, although the postnatal decrease was gradual. In contrast, relatively constant amounts of PTPzeta-B were observed from embryonic day 13 (E13) through adulthood. PTPzeta-A and -S were constantly expressed only as proteoglycans during development, but a substantial amount of PTPzeta-B was detected in a non-proteoglycan form at E13-15. Moreover, PTPzeta-B did not contain LeX, HNK-1 carbohydrate, or keratan sulfate, although PTPzeta-A and -S were generally modified with these carbohydrates. L cells transfected with PTPzeta-A and -B cDNAs expressed these proteins as enzymatically active chondroitin sulfate proteoglycans. The PTPzeta-A and -B in L cells showed essentially similar localizations in cell cortical structures on immunofluorescence microscopy, although immature or processed forms of PTPzeta-A were accumulated additively in intracellular patchy structures. These results show that the three isoforms of PTPzeta are differentially regulated during development, and that the extracellular deleted region in PTPzeta-B is important for determination of carbohydrate modification.  相似文献   
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In an effort to clarify the etiology of milk allergy from the standpoint of allergen-specific immune reactions, we investigated the determinants of IgE, IgG4, and T cells specific for bovine alpha(s)1-casein from the same individual patients by using its synthetic peptides and cyanogen bromide-digested fragments. Alpha(s)1-casein is a major allergen in cow's milk, and its unique conformation enabled us to investigate the determinants of antibodies without consideration about missing the reactivities because of conformational changes. Nine patients were selected as subjects from among 129 milk-sensitive infants screened by ELISA to assess the anti-alpha(s)1-casein IgE levels in their sera. By using ELISA for epitope mapping, a C-terminal region of alpha(s)1-casein was identified as a common binding site for IgE from all of these patients, whereas those for anti-alpha(s)1-casein IgG4 were located in multiple regions of alpha(s)1-casein. We determined the specificities of seven alpha(s)1-casein-specific T-cell lines established from peripheral blood mononuclear cells of two of the patients. These T cells have been shown to secrete IL-4. All of the T-cell lines had different specificities to alpha(s)1-casein. However, a common amino acid residue use was found among the determinants of various T-cell lines from each patient. The results suggest that patients allergic to cow's milk have characteristic B cells recognizing a limited region of alpha(s)1-casein and secreting alpha(s)1-casein-specific IgE. These B cells may interact particularly with T cells recognizing determinants with a common structure.  相似文献   
26.
To suppress reignition overvoltages caused when a 500-kV shunt reactor current is interrupted by a 550-kV one-break circuit breaker (CB), a study was carried out on controlled switching. Using a full-scale test circuit, reactor current interruption tests were carried out to obtain the relation between opening phase angle and generation of reignition. The results showed that even with the dispersion of CB operations taken into account, there were contact separation points free from high reignition overvoltages. It was also proved that no voltage escalations were caused by reignition and high-frequency arc extinction, and that overvoltages due to current chopping were at a safe level in terms of equipment insulation.  相似文献   
27.
PURPOSE: To report a method to evaluate leukocyte dynamics in the choroidal circulation with indocyanine green (ICG) angiography. METHODS: Nonpigmented and pigmented rats were administered ICG solution intravenously. The fundus image was obtained with a scanning laser ophthalmoscope and recorded on magnetic tapes at a video rate (30 frames/second). The images were analyzed with a personal computer-based image analysis system. RESULTS: On ICG angiography, hyperfluorescent dots were seen moving along the choroidal vessels and in the retinal vessels several minutes after injection. These fluorescent dots were thought to be circulating leukocytes stained with ICG. The micrographs of blood smears after ICG injection showed intense fluorescence of leukocytes. Computer-assisted image analysis allowed tracing of these fluorescent dots using a frame-by frame method. CONCLUSIONS: Results of this study indicated that ICG can be used for vital staining of leukocytes and that it is possible to evaluate leukocyte movement in the choroidal circulation in vivo in rats.  相似文献   
28.
CPM spectra of the fullerene film was measured to obtain the below gap absorption. The optical energy gap Eo was obtained by using the Tauc's plots. Eo did not change so much with the intercalated impurities. The absorption due to intercalated impurities was found below 1.6eV.  相似文献   
29.
A new type of translucent amorphous silicon (a-Si) solar cell, called the see-through a-Si solar cell, is developed. It has multiple microscopic holes within its effective area to transmit light and it generates electric power. A series of technical data on the fabrication processing with various patterning and photovoltaic performance are presented. Some examples of application systems such as car sunroof and home interior are introduced and discussed on a wide variety of new areas of PV applications. The see-through a-Si solar cell was mounted on a car sunroof to drive the car's ventilating system or to charge its battery. The ventilating system reduced the interior temperature of the car from 61 to 47°C during daytime parking.  相似文献   
30.
Boron nitride (BN) nanocage clusters of B12N12 were synthesized, and detected by laser desorption time-of-flight mass spectrometry. The B12N12 clusters consisted of 4- and 6-membered BN rings satisfying the isolated tetragonal rule, which was optimized by molecular orbital calculations. The electronic structure showed a bandgap energy of 5.1 eV, which is a little smaller than that of B36N36 cluster.  相似文献   
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