共查询到20条相似文献,搜索用时 31 毫秒
1.
The effect of cisapride on L-type Ca2+ current (I
Ca,L) was studied in guinea pig ventricular myocytes using a whole-cell voltage-clamp technique and a conventional action potential recording method. Myocytes were held at –40 mV, and internally dialyzed and externally perfused with Na+- and K+-free solutions; cisapride elicited a concentration-dependent block of peakI
Ca,L, with a half-maximum inhibition concentration (IC50) of 46.9 µM. There was no shift in the reversal potential, nor any change in the shape of the current-voltage relationship ofI
Ca,L in the presence of cisapride. Inhibition of cisapride was not associated with its binding to serotonin or to -adrenergic receptors because ketanserin, SB203186, and prazosin had no effect on the inhibitory action of cisapride onI
Ca,L. Cisapride elicited a tonic block and a use-dependent block ofI
Ca,L. These blocking effects were voltage dependent as the degree of inhibition at –40 mV was greater than that at –70 mV. Cisapride shifted the steady-state inactivation curve ofI
Ca,L in the negative direction, but had no effect on the steady-state activation curve. Cisapride also delayed the kinetics of recovery ofI
Ca,L from inactivation. At a slow stimulation frequency (0.1 Hz), the action potential duration in guinea pig papillary muscles showed biphasic effects; it was prolonged by lower concentrations of cisapride, but shortened by higher concentrations. These findings suggest that cisapride preferentially binds to the inactivated state of L-type Ca2+ channels. The inhibitory effect of cisapride onI
Ca,L might play an important role in its cardiotoxicity under pathophysiological conditions, such as myocardial ischemia. 相似文献
2.
Nitrate, nitrite and nitrous oxide were denitrified to N2 gas by washed cells ofRhizobium japonicum CC706 as well as by bacteroids prepared from root nodules ofGlycine max (L.) Merr. (CV. Clark 63). Radiolabelled N2 was produced from either K15NO3 or Na15NO2 by washed cells ofRh. japonicum CC705 grown with either nitrate only (5 mM) or nitrate (5 mM) plus glutamate (10 mM). Nitrogen gas was also produced from N2O. Similar results were obtained with bacteroids ofG. max. The stoichiometry for the utilization of15NO
3
-
or15NO
2
-
and the produciton of15N2 was 2:1 and for N2O utilization and N2 production it was 1:1. Some of the15N2 gas produced by denitrification of15NO
3
-
in bacteroids was recycled via nitrogenase into cell nitrogen. 相似文献
3.
A miniaturized, porometer-compatible cuvette for measurements of CO2 efflux from woody plant parts at controlled temperature conditions is described. A copper cuvette equipped with a PID-controlled Peltier element regulates cortex temperature in three modes: (1) synchronized with ambient air temperature; (2) at a constant difference in the range of ±10°C from air temperature; and (3) constant at a temperature in a range of ±25°C difference from ambient air. This method allows investigation of (a) respiratory capacity of woody plant parts dependent on short-term temperature variations, (b) CO2 release from woody plant parts following exposure to the sun, and (c) acclimation of woody plant parts to long-term changes of temperature. By use of the copper cuvette, temperature gradients in the cortex are drastically reduced. Therefore, studies on the effect of metabolically and physico-chemically based processes on diurnal variations of CO2 efflux from woody plant parts can be carried out. Field experiments were carried out on trees of Betula pendula, B. ermanii, and B. litwinowii. At synchronized temperatures of ambient air and woody plant tissue, daytime reductions of CO2 efflux relative to night-time rates at a given temperature from branches of B. pendula and B. ermanii were observed. In July, CO2 efflux from branches of B. litwinowii under controlled temperature conditions from 3 to 27°C showed a characteristic exponential increase from 0.6 to 7.2 µmol CO2 m–2 s–1. During dormancy, long-term warming of branches of B. ermanii failed to increase metabolic activity. 相似文献
4.
The adaptation ofCamellia rusticana, an evergreen broad-leaved shrub found in areas of heavy snowfall in Japan, to heavy snowfall environments, and the mechanisms
by which it is damaged in winter above the snow, were investigated. The stomatal response and photosynthetic characteristics
ofC. rusticana were compared to those ofCamellia japonica found in areas of light snowfall. In field conditions, the mean net photosynthesis ofC. rusticana at photon flux density (PFD) over 200 μmol m−2s−1 (Pn(>200). was 50% larger than that ofC. japonica, but in both light saturated and CO2 saturated conditions, the O2 evolution rate (Pc) ofC. rusticana was not different from that ofC. japonica. Mean leaf conductance at PFD over 200 μmol m−2s−1 (gl(>200)) was about 100% larger than that ofC. japonica in the field. The Pn(>200)) was 50% ratio ofC. rusticana was 37% higher than that ofC. japonica which suggests thatC. rusticana's larger Pn(>200) can be explained by its larger gl(>200). WhenC. rusticana trees wintering underneath the snow were projected above it, the leaves of these plants showed serious drought within five
days in non-freezing conditions. Their Pc and the maximum stomatal conductance decreased by half and did not recover. The
leaves ofC. rusticana showed larger gl(>200) and a less sensitive stomatal response to the decrease of leaf water potential than that ofC. japonica. The stomata characteristics ofC. rusticana caused larger net photosynthesis than that ofC. japonica during the no snow period, and caused the need for snow cover in winter as protector from winter drought. 相似文献
5.
An effective transformation procedure for Kitasatospora setae was established based on transconjugation from Escherichia coli ET12567 (pUZ8002) using a C31-derived integration vector, pSET152, containing oriT and attP fragments. While no transconjugation was observed under the standard transconjugation conditions for Streptomyces species, sufficient transconjugation (>1×10-6) was achieved on ISP4 medium containing 30 mM MgCl2 using a 25- to 125-fold excess of E. coli donor cells. In addition, the sequence and location of the chromosomal integration site attB of K. setae was identified for the first time in genera of non-Streptomyces actinomycetes. K. setae contains a single C31 attB site. Similar to the case of Streptomyces species, the attB site of K. setae is present within an ORF encoding a pirin-homolog, but the K. setae-attB sequence deviates slightly from the consensus sequence of Streptomyces attB sequences. 相似文献
6.
The pmm gene from Vibrio furnissii, which encodes phosphomannomutase (PMM), was cloned and sequenced. The open reading frame consisted of 1,434 bp, encoding a polypeptide of 477 amino acids with a molecular mass of 53,325 Da. The predicted amino acid sequence of V. furnissii PMM showed high similarity with PMMs from other enteric bacteria, such as V. cholerae, Salmonella sp. and Escherichia coli. The PMM protein was overexpressed in E. coli as a His6-tagged recombinant protein. The estimated apparent Km and kcat values of the purified recombinant protein for mannose 1-phosphate were about 60 M and 800 min–1, respectively. To investigate the biochemical functions and the role of pmm in the virulence of V. furnissii, a pmm knock-out mutant was constructed by homologous recombination mutation. Under the various physical conditions, cell numbers of the wild-type and the mutant did not differ. Oral introduction of bacterial suspensions to a mouse model showed that the pmm-deficient mutant decreased in viability at the intestine. Microscopy of the isolated intestines from mice revealed significant damage after 3 days in intestinal mucosa infected with the wild-type as compared with the mutant. The pmm-deficient mutant caused a reduction of virulence in mice and the loss of O-antigen polysaccharide, and showed low resistance relative to the wild-type when incubated with normal human serum. 相似文献
7.
Somatic embryogenesis and plant regeneration from immature zygotic embryos of<Emphasis Type="Italic"> Cryptomeria japonica</Emphasis> D. Don 总被引:2,自引:0,他引:2
Igasaki T Sato T Akashi N Mohri T Maruyama E Kinoshita I Walter C Shinohara K 《Plant cell reports》2003,22(4):239-243
This report describes the successful plant regeneration via somatic embryogenesis from immature zygotic embryos of Cryptomeria japonica D. Don. For the induction of embryogenic tissue, we determined that the optimal medium contained N6-benzyladenine and 2,4-dichlorophenoxyacetic acid. Immature zygotic embryos that were collected at the end of June yielded embryogenic tissue at the highest frequency. Embryogenic tissues that had proliferated in liquid medium included small and loosely packed cells and elongating or elongated cells. We used ten cell lines to determine the optimal medium for the development of somatic embryos. Induced somatic embryos germinated with synchronous sprouting of cotyledons, hypocotyls and roots. Gibberellin A3 in the germination medium had a positive effect on both the elongation of hypocotyls and the survival of seedlings. The frequencies of induction and germination of somatic embryos differed among the cell lines examined. Most of the seedlings grew normally. This system of somatic embryogenesis required 4–5 months for the regeneration of C. japonica plantlets from immature zygotic embryos.Abbreviations ABA Abscisic acid - BA N6-Benzyladenine - 2,4-D 2,4-Dichlorophenoxyacetic acid - GA3 Gibberellin A3Communicated by F. Sato 相似文献
8.
Ji Young Hyun Kodiveri Muthukalianan Gothandam Nam Kwon Baek Gongwei Wang Yong-Yoon Chung 《Journal of Plant Biology》2007,50(2):161-166
InBrassica, self-incompatibility (SI) can be overcome by CO2 application, an effective method for obtaining numerous inbred lines for F, commercial seed. We previously reported two different
S-alleles ofBrassica campestris, S733 and S734, with extremely different degrees of susceptibility to this gas. In the current study, we raised a cross-population between
those two genetic lines, and analyzed their reaction level of self-incompatibility to CO2 (RLSICO2). Here, all 40 of our progeny from the F1 cross-population were susceptible, maintaining high values of RLSICO2. This suggests that the susceptible line, S734, is dominant to the insusceptible line, S733. We also generated an F2 selfing-population of each crossed progeny, S733♀ S734♂ and S733♂ S734♀, to assess the RLSICO2 of each individual. PCR-RFLP analysis was performed to determine the S-genotype of the F2 population. The S734 allele segregated in a theoretical ratio of the dominant trait, and the RLSICO2 was consistent with the dominance relationship. Therefore, we have now demonstrated that high RLSICO2 in β.campestris is controlled by a dominant gene.
Both authors contributed equally to this work 相似文献
9.
The effect of the supernatants obtained from the liquid culture medium ofSporothrix schenkii andCandida albicans on the generation of superoxide anion (O
2
–
and hydroxyl radicals OH., the elements of reactive oxygen species (ROS), and chemilimunescence (CL), a measure of several ROS, by polymorphonuclear leukocytes (PMNs) was examined. In our study, it was shown that the supernatant ofS. schenkii increased all types of ROS generation examined and CL, while that ofC. albicans increased OH. generation and CL. The effect of the supernatants ofS. schenkii on OH. generation and CL and that ofC. albicans on CL were most remarkable when the supernatant obtained 8 weeks after the inoculation was used. The supernatant ofS. schenkii was shown to be a much more potent stimulant than the supernatant ofC. albicans. This ROS-stimulating effect of the supernatant ofS. schenkii was heat stable but not dialyzable. These findings suggest the possible role of ROS produced by infiltrated PMNs in the inflammatory skin lesions induced byS. schenkii. 相似文献
10.
Jyotsna Verma Santosh Pasha Sharad V. Gangal 《Molecular and cellular biochemistry》1994,131(2):157-166
A component ofFusarium solani (F. solani), identified as the major allergen,Fus sI3596
* was purified to homogeneity from culture filtrate (CF) by means of anion-exchange column chromatography, gel filtration and FPLC. The homogeneity ofFus sI3596
* was assessed by IEF, PAGE, SDS-PAGE (non-reducing), immunoblot and HPLC.Fus sI3596
* was isolated as a glycoprotein of MW 65 kd and pI 3.6. The IgE ELISA-inhibition assay after periodate treatment of the fraction showed a lower IgE binding capacity suggesting involvement of carbohydrate moiety in IgE binding reactions of the allergen. Peptide fragments ofFus sI3596
* obtained after CNBr and trypsin treatment were analysed by immunoblotting for their allergenicity. This study indicated that there could be at least 3 allergenic determinants in the major allergen,Fus sI3596
* ofF. solani CF.Abbreviations DEAE
diethyl aminoethyl
- HPLC
high performance liquid chromatography
- SDS
sodium dodecyl sulphate
- PBS-Tween
phosphate buffer saline containing 0.1% tween
- DTT
dithiothreitol
- TFA
triflouroacetate
- FPLC
fast protein liquid chromatography 相似文献
11.
Previous reports have suggested that high-doseL-arginine could be used in diabetic patients as a prophylactic blocker for the initial glycation reaction of proteins by methylglyoxal (MG), a reactive dicarbonyl compound of glucose metabolism. Here, we present several lines of evidence to substantiate that this prophylactic intervention may be inappropriate and should be used with care. First, we demonstrated that when various concentrations ofL-arginine (2.0–8.0 mM) were added to a fixed concentration of MG (1.56 µM) in a buffered lucigenin solution, dose-dependent generation of superoxide anion (O
2
–
)-mediated ultraweak chemiluminescence (uwCL) occurs. The suppression of uwCL generation by exogenously added superoxide dismutase further substantiated that the interaction between MG andL-arginine generated O
2
–
. This phenomenon can also be demonstrated in a serum-based system. Furthermore, when a fixed concentration ofL-arginine (8.0 mM) was added exogenously to a group of sera obtained from either diabetic patients (n=10) or their matched nondiabetic controls (n=10), a marked discrepancy in the generation of O
2
–
-mediated uwCL could be demonstrated (12,534 ± 3,147 vs. 950 ± 350 counts; p<0.001). Taken together, this evidence demonstrates that the appropriateness of using high-doseL-arginine for prophylactic measures in diabetic patients may be questioned, because the inhibition of the glycation reaction between MG and proteins by high-doseL-arginine unexpectedly produces plethoric O
2
–
as a by-product, which may subsequently aggravate the preexisting oxidative stress status of diabetic patients. 相似文献
12.
The class II fructose-1,6-bisphosphatase gene of Corynebacterium glutamicum, fbp, was cloned and expressed with a N-terminal His-tag in Escherichia coli. Purified, His-tagged fructose-1,6-bisphosphatase from C. glutamicum was shown to be tetrameric, with a molecular mass of about 140 kDa for the homotetramer. The enzyme displayed Michaelis-Menten kinetics for the substrate fructose 1,6-bisphosphate with a Km value of about 14 µM and a Vmax of about 5.4 µmol min–1 mg–1 and kcat of about 3.2 s–1. Fructose-1,6-bisphosphatase activity was dependent on the divalent cations Mg2+ or Mn2+ and was inhibited by the monovalent cation Li+ with an inhibition constant of 140 µM. Fructose 6-phosphate, glycerol 3-phosphate, ribulose 1,5-bisphosphate and myo-inositol-monophosphate were not significant substrates of fructose-1,6-bisphosphatase from C. glutamicum. The enzymatic activity was inhibited by AMP and phosphoenolpyruvate and to a lesser extent by phosphate, fructose 6-phosphate, fructose 2,6-bisphosphate, and UDP. Fructose-1,6-bisphosphatase activities and protein levels varied little with respect to the carbon source. Deletion of the chromosomal fbp gene led to the absence of any detectable fructose-1,6-bisphosphatase activity in crude extracts of C. glutamicum WTfbp and to an inability of this strain to grow on the carbon sources acetate, citrate, glutamate, and lactate. Thus, fbp is essential for growth on gluconeogenic carbon sources and likely codes for the only fructose-1,6-bisphosphatase in C. glutamicum. 相似文献
13.
Both hypotonic exposure (185 mOsmol/l) and infusion of glutamine plus glycine (2 mmol/l each) along with the isotonic medium
caused a significant increase of14CO2 production from [1-14C]glucose by 110 and 70%, respectively, from the basal level of 18.4 ± 1.2 nmol/g liver/min from the perfused liver ofClarias batrachus. Conversely, hypertonic exposure (345 mOsmol/l) caused significant decrease of14CO2 production from [1-14C]glucose by 34%.14CO2 production from [6-14C]glucose was largely unaffected by anisotonicity. The steady-state release of oxidized glutathione (GSSG) into bile was 1.18
±0.09 nmol/g liver/min, which was reduced significantly by 36% and 34%, respectively, during hypotonic exposure and amino
acid-induced cell swelling, and increased by 34% during hypertonic exposure. The effects of anisotonicity on14CO2 production from [1-14C]glucose and biliary GSSG release were also observed in the presence of t-butylhydroperoxide (50 (Amol/1). The oxidative
stress-induced cell injury, caused due to infusion of t-butylhydroperoxide, was measured as the amount of lactate dehydrogenase
(LDH) leakage into the effluent from the perfused liver; this was found to be affected by anisotonicity. Hypotonic exposure
caused significant decrease of LDH release and hypertonic exposure caused significant increase of LDH release from the perfused
liver. The data suggest that hypotonically-induced as well as amino acid-induced cell swelling stimulates flux through the
pentose-phosphate pathway and decreases loss of GSSG under condition of mild oxidative stress; hypotonically swollen cells
are less prone to hydroperoxide-induced LDH release than hypertonically shrunken cells, thus suggesting that cell swelling
may exert beneficial effects during early stages of oxidative cell injury probably due to swelling-induced alterations in
hepatic metabolism. 相似文献
14.
Molecular analysis of a genomic region of Bacillus megaterium, a polyhydroxybutyrate (PHB)-producing microorganism, revealed the presence of a gene coding for the enzyme phosphotransbutyrylase (Ptb). Enzyme activity was measured throughout the different growth phases of B. megaterium and was found to correlate with PHB accumulation during the late-exponential growth phase. Ptb expression was repressed by glucose and activated by the branched amino acids isoleucine and valine. Overexpression of ActBm, a 54 regulator from B. megaterium whose gene is located upstream from ptb, caused an increase in Ptb activity and PHB accumulation in B. megaterium. 相似文献
15.
P-fimbriae, S-fimbriae and AFA-adhesins are virulence factors responsible for adherence ofEscherichia coli strains to extraintestinal host-cell surface. Detection ofpap-,sfa- andafa-specific sequences performed by PCR revealed 74%pap
+, 65%sfa
+, and 8.3%afa
+ strains in a group of 84 extraintestialE. coli isolates. Detection in a group of fecal strains showed 29%pap
+, 21%sfa
+ and 4%afa
+ strains.pap together withsfa were found as the most frequent combination (56%) among extraintestinal isolates probably due to localization ofpap-andsfa-operons on a common pathogenicity island. The occurrence ofafa-specific sequence among 56 urine strains was 11%, although noafa
+ strain was detected among 28 gynecological isolates. No strains with detected adhesin operons were found among twenty (24%)
extraintestinalE. coli strains. 相似文献
16.
G. W. M. Barendse 《Planta》1971,99(4):290-301
Summary Developing seeds ofPharbitis nil accumulate free as well as bound gibberellins until a maximum level is reached at approximately 25 days after anthesis. Seeds from CCC-treated parent plants have a strongly reduced level of free as well as bound gibberellins. When different spray reagents were used it was found that trichloroacetic acid in particular was suitable to locate non-hydrolysed bound GA fractions on thin-layer plates. Chromatography showed two major bound GA fractions, determined with spray reagents as well as by means of hydrolysis.3H-GA1 applied to youngPharbitis plants was converted to two water-soluble compounds present in the aqueous phase. The rate of conversion was significantly enhanced when3H-GA1 and14C-glucose were applied to the same plants. Chromatography indicated that one of the conversion products of3H-GA1 became at least partly associated with the applied14C-glucose (or its products). This suggestion was also supported by the fact that mild acid hydrolysis of the aqueous fraction resulted in the reappearance of3H-GA1 and a conversion product of3H-GA1, including a14C-radioactivity peak cochromatographing with14C-glucose. However, the conversion products obtained with3H-GA1 applied to plants appeared to be chromatographycally different from any of the bound-GA fraction established by means of hydrolysis or spray reagents in developing seeds.Abbreviation GA(s)
gibberellin(s). 相似文献
17.
E. I. Solntseva 《Neurophysiology》1993,25(6):354-358
A low-threshold outward current was studied in the neurons ofHelix pomatia at –70 to –30 mV using a two-electrode voltage clamp technique. In addition to the well-known A current (I
A), a slower outward current calledI
As (slow) was revealed. Activation and inactivation times ofI
As at –40 mV ranged from 90 to 120 msec and from 3 to 5 sec, respectively. The current recovered within 2 to 5 sec after inactivation at –120 mV. Analysis of changes in the reversal potential ofI
As caused by an increase in external potassium concentration suggests a potassium origin forI
As. The curves ofI
As stationary activation and inactivation fit the Boltzmann equation. Deriving from an activation curve, the activation potential for a half-maximum current,, is –40 mV, and the slope factor,k, is –9.8 mV, while those values for the inactivation curve are –84 mV (a half-maximum inactivation) and 7.5 mV.I
As is blocked by 4-aminopyridine (1–30 µM), tetraethylammonium (1 mM), and Ba2+ (1 mM), but is resistant to Cs+ (1 mM). PeakI
As is not affected either by substitution of external Ca2+ for Mg2+ or by application of Cd2+ (0.5–1.0 mM). The results suggest that activation ofI
As does not require Ca2+ entry into the cell.Neirofiziologiya/Neurophysiology, Vol. 25, No. 6, pp. 427–432, November–December, 1993. 相似文献
18.
Sutrisno A Ueda M Abe Y Nakazawa M Miyatake K 《Applied microbiology and biotechnology》2004,63(4):398-406
A moderately thermophilic bacterium, strain A-471, capable of degrading chitin was isolated from a composting system of chitin-containing waste. Analysis of the 16S rDNA sequence revealed that the bacterium belongs to the genus Ralstonia. A thermostable chitinase A (Ra-ChiA) was purified from culture fluid of the bacterium grown in colloidal chitin medium. Purification of the enzyme was achieved mainly by exploiting its binding to the colloidal chitin. The molecular mass of the enzyme was estimated to be 70 kDa and the isoelectric point approximately 4.7. N-terminal amino acid sequencing revealed a sequence of ADPYLKVAYYP, which had high homology (66% identity) with that of chitinase A1 from Bacillus circulans WL-12. The pH and temperature optima were determined to be 5.0 and 70°C, respectively. The enzyme was classified as a retaining glycosyl hydrolase and was most active against partially N-acetylated chitosans. Its activities towards the partially N-acetylated chitosans, i.e. chitosan 7B, chitosan 8B, and chitosan 9B, were about 11-fold, 9-fold, and 5-fold higher than towards colloidal chitin, respectively. Ra-ChiA cleaved (GlcNAc)6 almost exclusively into (GlcNAc)2. Activation of Ra-ChiA was observed by the addition of 1 mM Cu2+, Mn2+, Ca2+, or Mg2+. Degradation of the partially N-acetylated chitosan produced oligosaccharides with a degree of polymerization ranging from 1–8; these are products that offer potential application for functional oligosaccharide production. 相似文献
19.
Corynebacterium acetoacidophilum RYU3161 was cultivated in al-histidine-limited fed-batch culture. To investigate the effect of cell growth on thel-proline production, 5l fed-batch culture was performed using an exponential feeding rate to obtain the specific growth rates (μ) of 0.04, 0.06,
0.08, and 0.1 h−1. The results show that the highest production ofl-proline was obtained at μ=0.04 h−1. The specificl-proline production rate (Qp) increased proportionally as a function of the specific growth rate, but decreased after it revealed the maximum value at
μ=0.08 h−1. Thus, the highest productivity ofl-proline was 1.66 g L−1 h−1 at μ=0.08 h−1. The results show that the production of L-proline inC. acetoacidophilum RYU3161 has mixed growth-associated characteristics. 相似文献
20.
Cytological and genetical studies are reported on the hybrid and later generations ofGossypium herbaceum (A1 genome) xG. triphyllum (Hg genome). Chromosome pairing between the two genomes was high, and their chromosomes are considered, with minor exceptions,
to be strueturally similar. Studies of the F1 and segregating families showed thatG. triphyllum carries the complementary factorsR
inf2
supΘS
R
infa
supGO
for petal spot,Y
a(Yb) Y
infc
supP
for cream petal,pa for cream pollen, andY
ap for depression of yellow petal pigment. Leaf ahape ofG. triphyllum was dominant to the leaf shape ofG. herbaceum. The blue petal color ofG. triphyllum was recovered only in the backeross of the F1 to this species.
Contribution from the Agricultural Experiment Stations of Arizona and Texas. Part of this work was done under Regional Research
Project S-1 of the Hatch Act (Amended). 1. Address of first author; 2. Address of second author. 相似文献