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741.
The Arabidopsis Ca(2+)/H(+) antiporters cation exchanger (CAX) 1 and 2 utilise an electrochemical gradient to transport Ca(2+) into the vacuole to help mediate Ca(2+) homeostasis. Previous whole plant studies indicate that activity of Ca(2+)/H(+) antiporters is regulated by pH. However, the pH regulation of individual Ca(2+)/H(+) antiporters has not been examined. To determine whether CAX1 and CAX2 activity is affected by pH, Ca(2+)/H(+) antiport activity was measured in vacuolar membrane vesicles isolated from yeast heterologously expressing either transporter. Ca(2+) transport by CAX1 and CAX2 was regulated by cytosolic pH and each transporter had a distinct cytosolic pH profile. Screening of CAX1/CAX2 chimeras identified an amino acid domain within CAX2 that altered the pH-dependent Ca(2+) transport profile so that it was almost identical to the pH profile of CAX1. Results from mutagenesis of a specific His residue within this domain suggests a role for this residue in pH regulation. 相似文献
742.
Takashi Osumi Atsushi Imamura Toshiro Tsukamoto Chiharu Fujivara Noriho Hashiguchi Nobuyuki Shimozawa Yasuyuki Suzuki Naomi Kondo 《Cell biochemistry and biophysics》2000,32(1-3):165-170
Peroxisome biogenesis disorders (PBDs) contain various clinical phenotypes; Zellweger syndrome (ZS), neonatal adrenoleukodystrophy
(NALD), and infantile Refsum disease (IRD), decreasing in the clinical severity in this order. We found that all IRD cell
lines and some NALD lines belonging to several different complementation groups are temperature-sensitive in peroxisome assembly;
that is, they lacked catalase-positive peroxisomes at 37°C, but do gain the peroxisomes at 30°C. We identified heterozygous
mutations E55K/R119Stop in the PEX2 gene of an IRD patient of complementation group F. The E55K mutation was the direct cause
of the temperature-sensitivity because similar phenotypes could be transferred to PEX2-defective CHO cells by transfecting
the mutant gene. Thus, temperature-sensitive peroxisome assembly is representative of milder forms of PBDs.
The main part of this study was published by Imamura et al. (1). 相似文献
743.
Toshiro Yadomae Iwao Suzuki Yoshio Kumazawa Toshio Miyazaki 《Microbiology and immunology》1979,23(10):997-1008
A water-soluble mitogen was extracted with hot-water from the fruiting bodies of a fungus, Peziza vesiculosa, collected in the wild. The active substance, named vesiculogen, was able to stimulate selectively murine B cells because mitogenic activity was observed in the spleen cell cultures of congenitally athymic nude mice, but not in the thymus cell cultures. The possibility that the mitogenicity of vesiculogen was due to lipopolysaccharide was denied completely by the following evidence: 1) lipopolysaccharide in vesiculogen was undetectable (less than 0.001% in the Limulus test), 2) vesiculogen was able to stimulate strongly DNA synthesis of spleen cells from C3H/HeJ mice, and 3) the mitogenic activity of vesiculogen was not inhibited by polymyxin B. Vesiculogen increased antigen-nonspecifically the number of direct plaque forming cells to sheep erythrocytes, horse erythrocytes, and trinitrophenylated-horse erythrocytes. This result shows that vesiculogen acts as a polyclonal B cell activator on murine spleen cells. 相似文献
744.
The attenuance (apparent absorbance), angular distribution oftransmitted light (scattering) and reflectance of paradermalsections of Camellia leaves were measured spectrophotometricallyand the data for the palisade and spongy tissues were compared. Attenuance in tissues could be expressed by Beer's law onlyfor wavelengths of strong absorption. At 680 nm, the apparentextinction coefficient of chlorophyll (e) for the spongy tissuewas about 1.4 times that for the palisade tissue. The largere for the spongy tissue is attributable mostly to the more effectiveincrease in the pathlength of light due to scattering at theinterfaces between the air space and cells because the differencebetween e for the two tissues was minimized by infiltrationof the air space in the tissues with a medium whose refractiveindex was similar to the index of the leaf cells. Scatteringwas larger for wavelengths of weak absorption, and the relativeincrease in attenuance caused by elongating the optical pathlengthwas even more prominent. Based on these data, we report an ecophysiological discussionof the internal light environment of a leaf and the meaningof the differentiation of mesophyll into the palisade and spongytissues. (Received May 18, 1983; Accepted September 21, 1983) 相似文献
745.
Cell wall preparations of Bacillus anthracis, strain Pasteur No. 2-H, were treated with heat or with acetone and ether. Both of the treated cell walls preparations inactivated γ phage. The centrifuged supernatant of the heat-treated cell walls was fractionated on Sephadex G-200, and four fractions containing reducing sugars were obtained. The first fraction had the phage-inactivating activity. On the other hand, the fourth fraction had no phage-inactivating activity, but strongly inhibited phage adsorption to the cell walls. In the fourth fraction, glutamic acid, alanine, 2, 6-diaminopimelic acid and glucosamine were detected by paper chromatography after acid hydrolysis. Authentic D,L -2, 6-diaminopimelic acid and D -glucosamine markedly inhibited phage adsorption to the cell walls. D -Galactosamine, D -mannosamine and L -lysine also showed similar activities. Results suggest the possibility that one or a combination of these substances defines the characteristics of phage adsorption to the cell walls of B. anthracis, strain Pasteur No. 2-H. 相似文献
746.
Ken Nishihara Toshiro Futami Kazuho Hosoda Toshiaki Gomi 《Journal of electromyography and kinesiology》2005,15(1):93-101
To estimate muscle fiber conduction velocity (MFCV), the normalized peak-averaging technique was developed along with complementary software and reported in a previous study. Electromyograms were recorded from the vicinity of end-plate zones (EMG data 1) and a site farther from the end-plates and distal tendons (EMG data 2) of biceps brachii muscles using surface array electrodes during 50% maximal voluntary isometric contractions in ten healthy volunteers. The MFCV values obtained with normalized peak-averaging technique were compared to those obtained with the cross-correlation technique and examined by computer simulation of the MFCV distribution. The MFCV values obtained with normalized peak-averaging technique highly correlated with those obtained with cross-correlation technique in both EMG data 1 and EMG data 2. It was also confirmed that MFCV values obtained from EMG data 1 were distributed much more widely than those obtained from EMG data 2. These results show the clinical usefulness of normalized peak-averaging technique for the detailed assessment of MFCV. 相似文献
747.
Multicellular cells were efficiently induced in Staphylococcus haemolyticus by the addition of protease to exponentially growing cultures at 30 C. Electron microscopy revealed the formation of tetrad-shaped multicells that were septated but not separated from each other. Incubation of the multicells with extract from the cells grown without protease resulted in a fourfold increase in the number of colony-forming units as compared with the untreated control. An electrophoretic analysis showed that protease caused a loss of cell wall-lytic activity of the cell, which possibly led to the formation of multicells through cessation of cross wall separation. 相似文献
748.
In freshwater systems, contributions of chemosynthetic products by sulfur-oxidizing bacteria in sediments as nutritional resources in benthic food webs remain unclear, even though chemosynthetic products might be an important nutritional resource for benthic food webs in deep-sea hydrothermal vents and shallow marine systems. To study geochemical aspects of this trophic pathway, we sampled sediment cores and benthic animals at two sites (90 and 50 m water depths) in the largest freshwater (mesotrophic) lake in Japan: Lake Biwa. Stable carbon, nitrogen, and sulfur isotopes of the sediments and animals were measured to elucidate the sulfur nutritional resources for the benthic food web precisely by calculating the contributions of the incorporation of sulfide-derived sulfur to the biomass and of the biogeochemical sulfur cycle supporting the sulfur nutritional resource. The recovered sediment cores showed increases in 34S-depleted sulfide at 5 cm sediment depth and showed low sulfide concentration with high δ34S in deeper layers, suggesting an association of microbial activities with sulfate reduction and sulfide oxidation in the sediments. The sulfur-oxidizing bacteria may contribute to benthic animal biomass. Calculations based on the biomass, sulfur content, and contribution to sulfide-derived sulfur of each animal comprising the benthic food web revealed that 58%–67% of the total biomass sulfur in the benthic food web of Lake Biwa is occupied by sulfide-derived sulfur. Such a large contribution implies that the chemosynthetic products of sulfur-oxidizing bacteria are important nutritional resources supporting benthic food webs in the lake ecosystems, at least in terms of sulfur. The results present a new trophic pathway for sulfur that has been overlooked in lake ecosystems with low-sulfate concentrations. 相似文献
749.
Masao Ota Takeshi Seki Kendo Kiyosawa Seiichi Furuta Kunihiko Hino Toshiro Kondo Hirofumi Fuskushima Kimiyoshi Tsuji Hidetoshi Inoko 《Immunogenetics》1992,36(1):49-55
Fifty-one patients with autoimmune hepatitis have been studied for HLA association by conventional serology and also by modified polymerase chain reaction-restriction fragment lenght polymorphism (PCR-RFLP) genotyping.HLA-DR4 was significantly associated with autoimmmune hepatitis (46 of 51 patients, 90.2%). DNA typing of the DRB1 gene for 43 DR4-positive patients by using the PCR-RFLP technique revealed that of 43 patients, 33 had DRB1
*
0405 (Dw15), five had DRB1
*
0406 (DwKT2), four had DRB1
*
0403 (Dw13a), two had DRB1
*
0401 (Dw4), two of 43 had DRB1
*
0407 (Dw13b) and one had DRB1
*
0408 (Dw14b). Thus, there was no significant difference in Dw frequencies between DR4-positive patients and DR4-positive healthy subjects. These findings suggest that the DR4-specific sequence (Val 11 and His 13 at amino acid positions 11 and 13, respectively), but not particular Dw-associated DR4 sequence, in the first domain of the DRB1 chain contributes to susceptibility to autoimmune hepatitis among Japanese. Interestingly, all five of the DR4-negative patients had the DR2 specificity (DRB1
1502 or 1601). Taken together, these results imply that the basic amino acids at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), are most important for determining the predisposition to autoimmune hepatitis.
Address correspondence and offprint requests to: M. Ota. 相似文献
750.
Toshiro Okazaki Tadakazu Kondo Toshiyuki Kitano Masaro Tashima 《Cellular signalling》1998,10(10):685-692
Sphingolipid ceramide has emerged as a lipid messenger of cell functions including differentiation and apoptosis. Diverse kinds of stresses (ultraviolet, irradiation, heat shock and hypoxia) and biological factors (TNF-, IFN-γ and Fas antibody) require ceramide generation to execute apoptosis. The review summarises the diversity and complexity of up- and downstream of ceramide signalling in apoptosis and clinical implications of ceramide-induced apoptosis. 相似文献