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11.
Fujita Yuichi; Takahashi Yasuhiro; Shonai Fumio; Ogura Yutaka; Matsubara Hiroshi 《Plant & cell physiology》1991,32(7):1093-1106
The frxC gene, found in liverwort chloroplast DNA, encodes aprotein of unknown function. The deduced amino acid sequenceof the protein shows significant homology to that of ni-trogenaseFe-protein encoded by the nifH gene. We have cloned the frxCand nifH genes from the nitrogen-fixing cyanobacterium Plectonemaboryanum, using frxC- and nifH-specific probes, and have determinedtheir nucleotide sequences. The amino acid sequence deducedfrom the frxC gene of P. boryanum exhibits 83% homology to thatof the protein encoded by the/rxCgene from liverwort, whereasit exhibits only 34% homology to that encoded by the nifH genefrom the same organism, namely, P. boryanum. Northern blot analysisshowed that the frxC gene was transcribed more actively undernitrogenase-repressed conditions than under nitrogenase-inducedconditions, suggesting that the FrxC protein has a functiondistinct from nitrogen fixation. These results, together withthe phylogenetic relationship between the nifH and frxC genes,indicate that the frxC and nifH genes are derived from a commonancestral gene but have evolved independently to encode proteinswith different functions. (Received April 27, 1991; Accepted August 12, 1991) 相似文献
12.
Synaptosomes isolated from the rat cerebral cortex were mixed with sonicated phospholipid vesicles and subjected to freezing-thawing to acquire giant proteoliposomes. Membranes of these giant proteoliposome could thus be studied using patch-clamp techniques. Single-channel currents were measured with the inside-out patch of the membrane, in KCl solutions. Three different potassium channels were detected and unit conductances were 15.1, 28.6 and 91.0 pS, respectively, in a symmetrical 150 mM KCl solution. All these channels are more permeable to potassium than to sodium ions, the permeability ratio being about 2:1. Tetraethylammonium ions blocked these channels. The gating of these potassium channels is independent of the membrane potential, Presumably, these channels play a role in the resting membrane potential of presynaptic nerve terminals. 相似文献
13.
K Takahashi T Imaeda Y Kawazoe 《Biochemical and biophysical research communications》1988,157(3):1124-1130
Induction of the adaptive response was quantified by analysis of beta-galactosidase released after the treatment of Escherichia coli CHS26/pYM3 (ada'-lacZ') with N-methyl-N-nitrosourea (MNU). Of the 15 metal ions examined, only Cd++ and Hg++ inhibited induction of the adaptive response with neither severe suppression of cell growth nor inhibition of the induction of the SOS response by MNU. Mutagenicity of MNU was potentiated by the presence of these metal ions in an E. coli strain. These results suggest that the inhibition mechanism involves a specific interaction of Cd++ or Hg++ with O6-methyl-guanine-DNA methyltransferase. 相似文献
14.
Noritsugu Yabe Yutaka Matsuya Isao Yamane Mitsuru Takada 《In vitro cellular & developmental biology. Plant》1986,22(7):363-368
Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized
mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without
the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium
NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the
presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently
established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is
dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in
serum- and HAT-containing medium or are masked by serum. 相似文献
15.
Chromosomal localization of the Epstein-Barr virus (EBV) genome in Bloom's syndrome B-lymphoblastoid cell lines transformed with EBV 总被引:3,自引:0,他引:3
The localization of the Epstein-Barr virus (EBV) genome in chromosomes of human B-lymphoblastoid cell lines (LCLs) transformed with EBV, and the effect of EBV DNA on the level of sister chromatid exchange (SCE) in Bloom's syndrome (BS) B-LCLs, were examined with chromosomal in situ hybridization techniques using a 3H-EBV DNA probe. EBV DNA was detected in chromosomes 1–5 and 13–15 at specific G band regions in BS as well as in normal B-LCLs, regardless of SCE. Several chromosomal sites (1p31, 1q31, 4q22–24, 5q21, 13q21, 14q21) carrying EBV DNA seemed to be very characteristic in normal as well as in BS B-LCLs. There was no statistically significant difference in silver grain counts due to EBV DNA and their distribution in different chromosomes or groups among normal and BS B-LCLs with normal and high SCE. These findings strongly indicate that EBV infection did not introduce a correcting factor for BS SCE. 相似文献
16.
In order to determine whether the usual feeding pattern actually modifies the circadian rhythms of urinary excretion of water and electrolytes, we compared the circadian rhythm characteristics in patients receiving total parenteral nutrition (TPN group) with those in patients on an ordinary hospital diet (control group). Statistically significant circadian rhythms were detected in all of the urinary variables investigated herein by using the population mean-cosinor method in both groups. In addition, there were no statistically significant differences of the mesor, the %-amplitude and the acrophase between the two groups. These results suggest that the usual feeding pattern is not a main determinant in forming the circadian rhythm characteristics of human urinary variables. 相似文献
17.
Diazepam action onγ-aminobutyric acid-activated chloride currents in internally perfused frog sensory neurons 总被引:3,自引:0,他引:3
The Cl- current (ICl) in gamma-aminobutyric acid (GABA)-sensitive frog sensory neuron was separated from other Na+, Ca2+, and K+ currents using a suction pipette technique which allows internal perfusion under a single-electrode voltage clamp. Diazepam (DZP) itself evoked no response but facilitated the dose- and time-dependently GABA-induced ICl without changing the GABA equilibrium potential (EGABA) at concentrations ranging widely, from 3 X 10(-9) to 10(-4) M. In the presence of DZP, the GABA dose-response curve shifted to the left without changing the maximum current, indicating that DZP modifies the interaction between GABA and its receptor rather than affecting directly the channel activation step. The enhancement of the GABA-induced ICl by DZP depended neither on the membrane voltage nor on the inward or outward direction of the ICl. DZP also potentiated the ICl elicited by GABA agonists such as beta-alanine, taurine, homotaurine, 5-aminovaleric acid, l-GABOB, d-GABOB, glycine, and muscimol. The GABA response enhanced by pentobarbital (PB) was further enhanced by adding DZP, indicating that DZP and PB do not act in the same way. Ro5-3663, a diazepam analogue, enhanced the GABA-induced ICl only in a narrow range of the concentrations but inhibited the current at concentrations higher than 2 X 10(-6) M. 相似文献
18.
Akira Inokuchi Yasunobu Tomida Chizuko Yanaihara Ryogo Yui Yutaka Oomura Hiroshi Kimura Takanobu Hase Tomoaki Matsumoto Noboru Yanaihara 《Cell and tissue research》1986,246(1):71-75
Summary Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism. 相似文献
19.
Diurnal K+ and Anion Transport in Phaseolus Pulvinus 总被引:1,自引:0,他引:1
Diurnal movement of Phaseolus leaf is caused by deformationof the laminar pulvinus located at the joint of the leaf bladeand the petiole. The plants were cultured in solutions withvarious ion compositions, and changes of K+, Na+, Ca2+, Mg2+,Cl, NO3 and P1 concentrations both in the upperand lower parts of the laminar pulvinus were measured. Culturein 10 mM KCl solution caused an increase in K+ and Clconcentrations both in the upper and lower parts without anysignificant change in the concentration of NO3; culturein 10 mM KNO3 solution caused an increase in K+ and NO3concentration without any significant change in the concentrationof Cl; and culture in 10 mM KH2PO4 solution caused anincrease in K+ and P1 concentrations without any significantchange in the concentrations of NO3- and Cl. K+ moved from the upper to lower parts or from the lower toupper parts diurnally in all plants cultured in any solutionmentioned above. The main inorganic anion that accompanied thisK+ movement was Cl in KCl solution, and NO3 inKNO3 solution. When the seedlings were cultured in distilledwater or in KH2PO4 solution, neither Cl NO3 norP1 accompanied this K+ movement. In these cases, mainly H+ and/ororganic anions are supposed to move in exchange for and/or incombination with K+ movement. (Received November 8, 1982; Accepted June 13, 1983) 相似文献
20.
Hiroshi Iijima Yutaka Ebizuka Ushio Sankawa Etsuo Yamamoto G.H.N. Towers 《Phytochemistry》1983,22(2):371-374
The metabolism of vulpinic acid by an unclassified soil micro-organism was studied. A new compound, 2,5-diphenyl-3-hydroxy-4-oxo-2-hexendioic acid (DHOHA) was isolated from the reaction mixture of a cell-free preparation and pulvinic acid. The existence of a hydrolase which catalyses the conversion of vulpinic acid to pulvinic acid was detected in cell-free preparation, and an inducible lactone hydrolase capable of converting pulvinic acid to DHOHA was purified 130-fold and characterized. This enzyme had a MW of ca 34 000, a Km for pulvinic acid at pH optimum (pH 7.0) less than 10 ? 6 M, pI = 5.0, and was inhibited by p-chloromercuriphenylsulfonate and diethylpyrocarbonate. The enzyme was highly specific for pulvinic acid. The initial degradative steps proposed for this organism are vulpinic acid → pulvinic acid → DHOHA. 相似文献