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Summary The presence of a Ca2+ channel in the plasmalemma of tonoplast-freeNitellopsis obtusa cells was demonstrated and its characteristics were studied using current- and voltage-clamp techniques. A long-lasting inward membrane current (I
m
), recorded using a step voltage clamp, consisted of a single component without time-dependent inactivation. Increasing either [Ca2+]
o
or [Cl–]
o
1) enhanced the maximum amplitude of inwardI
m
((I
m
)
p
) and 2) shifted the peak voltage ((V
m
)
p
) at(I
m
)
p
to more positive values under ramp-shaped voltage clamping and 3) depolarized the peak value of action potentials. This behavior is consistent with predictions based on the Nernst equation for Ca2+ but not for Cl–. DIDS (4,4-diisothiocyano-2,2-disulfonic acid stilbene) did not suppress(I
m
)
p
in tonoplast-free cells, in contrast with its effect on normal cells. La3+ and nifedipine blocked(I
m
)
p
irreversibly. On the other hand, Ca2+ channel agonist, BAY K 8644 irreversibly enhanced(I
m
)
p
. Both Sr2+ influx and K+ efflux increased upon excitation. The charge carried by Sr2+ influx was compensated for by K+ efflux. It is concluded that only the Ca2+ channel is activated during plasmalemma excitation in tonoplast-free cells. In terms of the magnitude of(I
m
)
p
, Sr2+ could replace Ca2+, but Mn2+, Mg2+ and Ba2+ could not. External pH affected(I
m
)
p
and the membrane conductance (g
m
) at(I
m
)
p
((g
m
)
p
). Increasing the external ionic strength caused increases in both(I
m
)
p
and(g
m
)
p
, and shifted(V
m
)
p
to positive values. At the same time, Sr2+ influx increased. Thus Ca2+ channel activation seems to be enhanced by increasing external ionic strength. The possible involvement of surface potential is discussed. 相似文献
5.
Masayuki Sasaki Kenji Sugio Jun-Ichi Soejima Tatsuro Ikeuchi Akira Tonomura Takeo Iwama Joji Utsunomiya Takehiko Sasazuki 《Human genetics》1987,77(1):36-39
Summary We investigated possible association of and linkage between HLA and familial polyposis coli (FPC). In 182 individuals from 66 pedigrees of FPC and 108 individuals from a normal population, HLA-A,-B, and-C antigens were determined. When the frequencies of HLA antigens in 66 unrelated patients and in normal controls were compared, no association of FPC with HLA was observed. For the linkage analysis, HLA haplotypes of 17 affected sib pairs were investigated by the affected sib pair method. The number of pairs which shared two, one, and no haplotypes identical by descent was not significantly different from the number expected with random occurrence (P>0.95). Finally, seven families were analyzed using Morton's sequential test. A maximum lod score of-0.056 at a recombination fraction of 0.4, and a lod of-3.089 at a recombination fraction of 0.05 were obtained. Therefore, there is neither an association of nor linkage between FPC and HLA. 相似文献
6.
Kazumasa Matsuki M.D. Hiroo Maeda Takeo Juji Hidetoshi Inoko Asako Ando Kimiyoshi Tsuji Yutaka Honda 《Immunogenetics》1988,27(2):87-90
Taq I-generated HLA-DQrestriction fragment length polymorphism was examined in Japanese patients with narcolepsy. All patients were DR2 positive and shared a 6.0 kb fragment, although this fragment was found only in 54 % of the healthy DR2-positive Japanese. This finding added the DQ
gene to the list of candidates for the possible narcolepsy-susceptibility gene. In contrast, there was no complete association between narcolepsy and DXrestriction fragment length polymorphism. These findings suggest that a narcolepsy-susceptibility gene is located closer to the DQ locus than to the DX locus. 相似文献
7.
Day-night changes in production of carbohydrate and protein by natural phytoplankton population from Lake Biwa, Japan 总被引:2,自引:0,他引:2
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1988,10(5):941-955
The 13C and gas chromatography-mass spectrometry (13C-GC-MS)method was applied to determine the day-night changes in thecomposition of photosynthetic products of the natural phytoplanktonpopulation from Lake Biwa, Japan. Glucose is the most abundantmonosaccharide in acid-hydrolyzable carbohydrate. The contributionof glucose was high in incubatesd samples in daytime and decreasedduring the night. Other monosaccharides (rhamnose, fucose, ribose,arabinose, xylose, mannose and galactose) and amino acids tendedto be produced throughout both day- and night-time. These resultssuggested that the carbon flows from glucose, which might constitutereserve glucan, to other monosaccharides and amino acids duringnight-time. The disproportionate production of glucose (reservedglucan) during daytime was thus partly cancelled out at night. 相似文献
8.
Summary In order to demonstrate the presence of a Ca2+-activated Cl–-channel in theNitellopsis plasmalemma, tonoplast-free cells were prepared and their intracellular Ca2+ concentration was modified by internal perfusion. An increase in the Ca2+ concentration caused a large Cl– efflux with a concomitant depolarization of the membrane potential. These changes were for the most part reversible. The critical Ca2+ concentration was about 4.0 m. Neither the Cl– efflux nor the membrane depolarization showed a time-dependent inactivation. A Cl–-channel blocker, A-9-C (9-anthracenecarboxylic acid) reduced both the Cl– efflux and the magnitude of the membrane potential depolarization. A small increase in the intracellular Ca2+ concentration, which is caused by membrane excitation of tonoplast-free cells is not sufficient to activate this Ca2+-dependent Cl–-channel. 相似文献
9.
Akira Kurosaka Ikuo Funakoshi Mutsushi Matsuyama Takeo Nagayo Ikuo Yamashina 《FEBS letters》1985,190(2)
GalNAc transferase activities of 6 human intestinal cancerous tissues were examined using bovine submaxillary gland mucin and its desialylated derivative, asialomucin, as acceptors. A Triton X-100 extract of these tissues was used as an enzyme source. All the tissues examined had GalNAc transferase that catalyzes the transfer of GalNAc from UDP-GalNAc to serine or threonine residues of the polypeptide chain. One of 6 specimens showed in addition UDP-GalNAc:GalNAc-mucin α-GalNAc transferase activity, synthesizing a disaccharide unit, GalNAcα→ GalNAc, when asialomucin was used as an acceptor. This carbohydrate structure was deduced on the basis of results of gel filtration, exoglycosidase digestion, and high-voltage paper electrophoresis.GalNAc transferaseHuman intestinal cancerous tissueBovine submaxillary gland mucin O-Glycosidically linked sugar chain 相似文献
10.
Sadao Yasugi Susumu Matsusbita Takeo Mizuno 《Differentiation; research in biological diversity》1985,30(1):47-52
Abstract. Allantoic and small-intestinal endoderms of chick and quail embryos were associated with the proventricular mesenchyme of chick embryos and then cultivated on chorioallantoic membrane. This resulted in the induction of complex glands, but the recombinates never produced embryo-specific pepsinogens; also, glandular cells developed a brush border, expressed sucrase antigen on their apical surface, and sometimes differentiated into goblet cells, thus indicating that both endoderms have the tendency to differentiate into an intestinal epithelium. In the recombinates composed of allantoic endoderm and proventricular mesenchyme, acid-protease activity was detected, but biochemical analysis revealed that this activity was not due topepsinogens. These results indicate that the gland formation induced in allantoic and small-intestinal endoderms by the proventricular mesenchyme is not accompanied by the expression of pepsinogens, suggesting that independent mechanisms are responsible for the morphogenesis and cyto chemical differentiation of the endoderm. 相似文献