共查询到20条相似文献,搜索用时 15 毫秒
1.
ATP-sensitive K+ (KATP) channels have been characterized in pituitary GH3 cells with the aid of the patch-clamp technique. In the cell-attached configuration, the presence of diazoxide (100 μm) revealed the presence of glibenclamide-sensitive KATP channel exhibiting a unitary conductance of 74 pS. Metabolic inhibition induced by 2,4-dinitrophenol (1 mm) or sodium cyanide (300 μm) increased KATP channel activity, while nicorandil (100 μm) had no effect on it. In the inside-out configuration, Mg-ATP applied intracellularly suppressed the activity of KATP channels in a concentration-dependent manner with an IC50 value of 30 μm. The activation of phospholipase A2 caused by mellitin (1 μm) was found to enhance KATP channel activity and further application of aristolochic acid (30 μm) reduced the mellitin-induced increase in channel activity. The challenging of cells with 4,4′-dithiodipyridine (100 μm) also induced KATP channel activity. Diazoxide, mellitin and 4,4′-dithiodipyridine activated the KATP channels that exhibited similar channel-opening kinetics. In addition, under current-clamp conditions, the application of
diazoxide (100 μm) hyperpolarized the membrane potential and reduced the firing rate of spontaneous action potentials. The present study clearly
indicates that KATP channels similar to those seen in pancreatic β cells are functionally expressed in GH3 cells. In addition to the presence of Ca2+-activated K+ channels, KATP channels found in these cells could thus play an important role in controlling hormonal release by regulating the membrane
potential.
Received: 19 June 2000/Revised: 13 September 2000 相似文献
2.
Helena Ceretti Diana Vullo Anita Zalts Silvana Ramírez 《World journal of microbiology & biotechnology》2010,26(5):847-853
The aim of this study was to evaluate complexing capacity (CC) accompanying microbial growth in a metal supplemented culture
medium. A combined strategy of square wave anodic stripping voltammetry (SWASV) monitored titration and ion-exchange resins
treatment (Chelex 100) has been applied. Culture medium, supplemented with Cd(II) in excess to ligands, was inoculated with
an indigenous bacterial culture; total ligand concentration and stability constants were determined at different bacterial
growth stages. As far as known, determination of CC in such conditions has not been reported (usually ligands in natural or
wastewaters exceed metal concentration). HIDA, (N-(2-hydroxyethyl)iminodiacetic acid), was used as a model ligand to mimic
soluble products derived from the resin treatment and bacterial metabolism. Ligand concentration, Lt (1.3 ± 0.1 μM), and the
conditional stability constant, K′, (log K′ = 5.7 ± 0.2) were in good agreement with expected values (1.0 ± 0.1 μM and log K′ = 6.1). In the supplemented culture medium, total ligand concentration in the micromolar range (60–80 μM) and conditional
stability constants (5.5 < log K′ < 6.5) were determined. Cd(II) complexes detected in the different stages of microbial growth are labile from an electrochemical
point of view. Results were compared to the case of Cd(II) non-supplemented broth. 相似文献
3.
Plant regeneration via somatic embryogenesis was achieved from leaf petioles of Pelargonium sp. `Frensham' cultured on Murashige and Skoog medium containing 15 μM N6-benzyladenine, and 5 μM α-naphthaleneacetic acid (NAA). More than 80% of these somatic embryos converted into plants when
isolated and cultured on Murashige and Skoog medium supplemented with 15 μM NAA. Stable transgenic plants were obtained by
co-cultivation of the petioles (prior to culture) with Agrobacterium tumefaciens strains LBA4404 (harbouring a binary vector pBI121 carrying the nptII and gus genes) and LBG66 (harbouring a binary plasmid pJQ418 carrying the gus/int:nptII fusion gene). Transformants were selected using kanamycin and transformation was verified by β-glucuronidase histochemical
assay and polymerase chain reaction. Southern analysis further confirmed the integration of these genes into the genome of
transgenic plants. We report here for the first time, an Agrobacterium-mediated model transformation system coupled with regeneration via somatic embryogenesis for production of transgenics in
Pelargonium sp.
Received: 20 September 1996 / Accepted: 13 November 1996 相似文献
4.
Tarasova MV Kuznetsov VV Netesova NA Gonchar DA Degtyarev SKh 《Biochemistry. Biokhimii?a》2010,75(12):1484-1490
A restriction-modification system from Bacillus psychrodurans AC (recognition sequence 5′-CCGC-3′) comprises two DNA methyltransferases: M1.BspACI and M2.BspACI. The bspACIM1 gene was cloned in the pJW2 vector and expressed in Escherichia coli cells. High-purity M1.BspACI preparation has been obtained by chromatography on different carriers. M1.BspACI has a temperature
optimum of 30°C and demonstrates maximum activity at pH 8.0. M1.BspACI modifies the first cytosine in the recognition sequence
5′-CCGC-3′. The kinetic parameters of M1.BspACI DNA methylation are as follows: K
m for phage λ DNA is 0.053 μM and K
m for S-adenosyl-L-methionine is 5.1 μM. The catalytic constant (k
cat) is 0.095 min−1. 相似文献
5.
Effects of exogenous adenosine 5′-triphosphate (ATP) on dissociated guinea pig ileum submucous neurons were studied using
a conventional whole-cell patch-clamp technique. With the holding potential of −50 mV, application of 50–1,000 μM ATP evoked
an inward current (ATP-induced current) in most (90%) of the tested neurons (n-35). ATP-induced currents were observed regardless of whether or not guanosine 5′-triphosphate (GTP, 0.2 mM) and ATP (2 mM)
were present in the intracellular solution, or GTP was replaced with equimolar concentration of guanosine 5′-O-3-thiotriphosphate
(n-5). In 26 of 29 neurons studied, which responded to ATP, applications of 50–1,000 μM ATP induced slowly declining currents.
ATP receptors did not appear to be completely desensitized during a long pulse (up to 4 min) of 200 μM ATP. Suramin (200 μM)
accelerated an increase to peak of the current induced by 200 μM ATP without affecting the maximum response amplitude (n−4_. In about 10% of the neuronsn−3), 50 μM ATP evoked rapidly declining (about 1 sec) currents. Application of 100 μM α,β-Me-ATP to these neurons evoked similar
responses. The above results suggest that submucous neurons express two specific subtypes of ionotropic P2x-purinoceptors, which might be involved in distinct excitatory processes in these neurons. 相似文献
6.
7.
Bacteroids formed by Mesorhizobium ciceri CC 1192 in symbiosis with chickpea plants (Cicer arietinum L.) contained a single form of citrate synthase [citrate oxaloacetate-lyase (CoA-acetylating) enzyme; EC 4.1.3.7], which
had the same electrophoretic mobility as the enzyme from the free-living cells. The citrate synthase from CC 1192 bacteroids
had a native molecular mass of 228 ± 32 kDa and was activated by KCl, which also enhanced stability. Double reciprocal plots
of initial velocity against acetyl-CoA concentration were linear, whereas the corresponding plots with oxaloacetate were nonlinear.
The K
m value for acetyl-CoA was 174 μM in the absence of added KCl, and 88 μM when the concentration of KCl in reaction mixtures
was 100 mM. The concentrations of oxaloacetate for 50% of maximal activity were 27 μM without added KCl and 14 μM in the presence
of 100 mM KCl. Activity of citrate synthase was inhibited 50% by 80 μM NADH and more than 90% by 200 μM NADH. Inhibition by
NADH was linear competitive with respect to acetyl-CoA (K
is = 23.1 ± 3 μM) and linear noncompetitive with respect to oxaloacetate (K
is = 56 ± 3.8 μM and K
ii = 115 ± 15.4 μM). NADH inhibition was relieved by NAD+ and by micromolar concentrations of 5′-AMP. In the presence of 50 or 100 mM KCl, inhibition by NADH was apparent only when
the proportion of NADH in the nicotinamide adenine dinucleotide pool was greater than 0.6. In the microaerobic environment
of bacteroids, NADH may be at concentrations that are inhibitory for citrate synthase. However, this inhibition is likely
to be relieved by NAD+ and 5′-AMP, allowing carbon to enter the tricarboxylic acid cycle.
Received: 14 July 1999 / Accepted: 20 September 1999 相似文献
8.
Koszela-Piotrowska I Choma K Bednarczyk P Dołowy K Szewczyk A Kunz WS Malekova L Kominkova V Ondrias K 《Cellular & molecular biology letters》2007,12(4):493-508
Ion channels selective for chloride ions are present in all biological membranes, where they regulate the cell volume or membrane
potential. Various chloride channels from mitochondrial membranes have been described in recent years. The aim of our study
was to characterize the effect of stilbene derivatives on single-chloride channel activity in the inner mitochondrial membrane.
The measurements were performed after the reconstitution into a planar lipid bilayer of the inner mitochondrial membranes
from rat skeletal muscle (SMM), rat brain (BM) and heart (HM) mitochondria. After incorporation in a symmetric 450/450 mM
KCl solution (cis/trans), the chloride channels were recorded with a mean conductance of 155 ± 5 pS (rat skeletal muscle) and 120 ± 16 pS (rat brain).
The conductances of the chloride channels from the rat heart mitochondria in 250/50 mM KCl (cis/trans) gradient solutions were within the 70–130 pS range. The chloride channels were inhibited by these two stilbene derivatives:
4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) and 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid (SITS).
The skeletal muscle mitochondrial chloride channel was blocked after the addition of 1 mM DIDS or SITS, whereas the brain
mitochondrial channel was blocked by 300 μM DIDS or SITS. The chloride channel from the rat heart mitochondria was inhibited
by 50–100 μM DIDS. The inhibitory effect of DIDS was irreversible. Our results confirm the presence of chloride channels sensitive
to stilbene derivatives in the inner mitochondrial membrane from rat skeletal muscle, brain and heart cells. 相似文献
9.
Masłyk M Kochanowicz E Zieliński R Kubiński K Hellman U Szyszka R 《Molecular and cellular biochemistry》2008,312(1-2):61-69
Since Svf1 is phosphoprotein, we investigated whether it was a substrate for protein kinase CK2. According to the amino acid
sequence Svf1 harbours 20 putative CK2 phosphorylation sites. Here, we have reported cloning, overexpression, purification
and characterization of yeast Svf1 as a substrate for three forms of yeast CK2. Svf1 serves as a substrate for both the recombinant
CK2α (K
m 0.35 μM) and CK2α′ (K
m 0.18 μM) as well as CK2 holoenzyme (K
m 1.1 μM). Different K
m values argue that CK2β(β′) subunit has an inhibitory effect on the activity of both CK2α and CK2α′ towards surviving factor
Svf1. Reconstitution of α′2ββ′ isoform of CK2 holoenzyme shows that β/β′ subunits have regulatory effect depending on the kind of CK2 catalytic subunit.
This effect was not observed in the case of α2ββ′ isoform, which may be due to interaction between Svf1 and regulatory CK2β subunit (shown by co-immunoprecipitation experiments).
Interactions between CK2 subunits and Svf1 protein may have influence on ATP as well as ATP-competitive inhibitors (TBBt and
TBBz) binding. CK2 phosphorylates up to six serine residues in highly acidic peptide K199EVIPESDEEESSADEDDNEDEDEESGDSEEESGSEEESDSEEVEITYED248 of the Svf1 protein in vitro. Presented data may help to elucidate the role of protein kinase CK2 and Svf1 in the regulation
of cell survival pathways. 相似文献
10.
Antimicrobial Butyrolactone I Derivatives from the Ecuadorian Soil Fungus Aspergillus terreus Thorn. var terreus 总被引:1,自引:0,他引:1
M. E. Cazar G. Schmeda-Hirschmann L. Astudillo 《World journal of microbiology & biotechnology》2005,21(6-7):1067-1075
Summary The fungus Aspergillus terreus Thorn var. terreus isolated from an Ecuador soil sample was cultured in liquid and solid media and yielded three main metabolites identified
as terreic acid (1), butyrolactone I (2) and lovastatin (3). The natural products as well as three synthetic butyrolactone I derivatives were assessed for antimicrobial activity against
Gram-positive and Gram-negative bacteria and fungi as well as for seed germination and seedling growth. Furthermore, the compounds
were assessed as inhibitors towards the enzymes acetylcholinesterase, β-glucosidase, and β-glucuronidase. Terreic acid, butyrolactone I, butyrolactone 4′,4′′-diacetate (2.1), and 3′-(3-methylbutyl)-butyrolactone II (2.2) were active towards the phytopathogenic bacteria Erwinia carotovora with IC50 of 5 and 4–18 μg/ml, respectively. Under the same experimental conditions, the IC50 of streptomycin was 1.9 μg/ml. 3′-(3-Methylbutyl)-butyrolactone II was moderately active against Pseudomonas syringae and Botrytis cinerea with IC50 of 21μg/ml and MIC of 15.6 μg/ml, respectively. Butyrolactone I also inhibited germination of the dicot Lactuca sativa with an IC50 of 5 × 10−5 M. The IC50 of reference herbicide acetochlor was 1 × 10−5 M. The effect of 2.2 and 2.3, known as butyrolactone III on Panicum millaceum germination and growth was stronger than that of 2 and 2.1. Reduction of the double bond in the isoprenyl side chain of butyrolactone I increased the antibacterial effect against E. carotovora as well as acetylation. To our best knowledge, this is the first report on the antibacterial effect of butyrolactone derivatives
towards Erwinia carotovora and the phytopathogenic fungus Botrytis cinerea. The butyrolactone I derivative 2.2 presented a moderate inhibitory effect against the enzyme acetylcholinesterase with an IC50 of 47 μg/ml. Under the same experimental conditions, the reference inhibitor galanthamine had an IC50 of 3 μg/ml. 相似文献
11.
Dacil Zurita Isabelle Gautier-Luneau Stéphane Ménage J.-L. Pierre Eric Saint-Aman 《Journal of biological inorganic chemistry》1997,2(1):46-55
Copper(II) complexes derived from the tripodal ligand bis(3′-t–butyl-2′-hydroxybenzyl)(2-pyridylmethyl)amine (LH2) have been studied in order to mimic the redox active site of the free radical-containing copper metalloenzyme galactose
oxidase. In non-coordinating solvents such as dichloromethane, only an EPR-silent dimeric complex was obtained (L2Cu2). The crystal structure of L2Cu2 revealed a "butterfly" design of the [Cu(μOR)2Cu] unit, which is not flattened and leads to a short Cu–Cu distance, the t–butyl groups being localized on the same side of the [Cu(μOR)2Cu] unit. The dimeric structure was broken down by acetonitrile or by alcohols, leading quantitatively to a brown mononuclear
copper(II) complex. UV-visible and EPR data indicated the coordination of the solvent in these mononuclear complexes. Electrochemical
as well as chemical (silver acetate) one-electron oxidation of acetonitrile solutions of the monomeric complex led to a yellow-green
solution. Based on EPR, UV-visible and resonance Raman spectroscopy, the one-electron oxidation product was identified as
a cupric phenoxyl radical system. It slowly decomposes into a product where the ligand has been substituted (dimerization)
in the para position of the hydroxyl group, for one of the phenolic groups. The data for the one-electron oxidized species provides strong
evidence for a free-radical copper (II) complex.
Received: 19 July 1996 / Accepted: 16 October 1996 相似文献
12.
J. E. Tomilova V. V. Kuznetsov M. A. Abdurashitov N. A. Netesova S. Kh. Degtyarev 《Molecular Biology》2010,44(4):606-615
The M1.Bst19I DNA-methyltransferase gene from restriction-modification system Bst19I (recognition sequence 5′-GCATC-3′) in
Bacillus stearothermophilus 19 has been cloned in the expressing vector pJW that carries a tandem of thermo inducible promoters P
R
/P
L
from phage λ. Highly purified enzyme has been isolated by chromatography on various resins from Escherichia coli cells where it is accumulated in a soluble form. The study of M1.Bst19I properties has revealed that the enzyme has a temperature
optimum at 50°C and demonstrates maximal activity at pH 8.0. M1.Bst19I modifies adenine in sequence 5′-GCATC-3′. Kinetic parameters
of M1.Bst19I DNA methylation reaction have been determined as follows: Km for λ DNA is 0.68 ± 0.07 μM, Km for S-adenosyl-L-methionine is 2.02 ± 0.31 μM. Catalytical constant (k
cat) is 1.8 ± 0.05 min−1. Comparative analysis of Target Recognition Domain amino acid sequences for M1.Bst19I and other α-N6-DNA-methyltransferases
has allowed us to suggest the presence of two types of the enzymes containing ATG or ATC triplets in the recognition sequence. 相似文献
13.
Müller F Aschenbach JR Gäbel G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):337-343
This study sought to investigate effects of short-chain fatty acids and CO2 on intracellular pH (pHi) and mechanisms that mediate pHi recovery from intracellular acidification in cultured ruminal epithelial cells of sheep. pHi was studied by spectrofluorometry using the pH-sensitive fluorescent indicator 2′,7′-bis (carboxyethyl)-5(6′)-carboxyfluorescein
acetoxymethyl ester (BCECF/AM). The resting pHi in N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES)-buffered solution was 7.37 ± 0.03. In HEPES-buffered solution,
a NH4
+/NH3-prepulse (20 mM) or addition of butyrate (20 mM) led to a rapid intracellular acidification (P < 0.05). Addition of 5-(N-ethyl-N-isopropyl)-amiloride (EIPA; 10 μM) or HOE-694 (200 μM) inhibited pHi recovery from an NH4
+/NH3-induced acid load by 58% and 70%, respectively. pHi recovery from acidification by butyrate was reduced by 62% and 69% in the presence of EIPA (10 μM) and HOE-694 (200 μM),
respectively. Changing from HEPES- (20 mM) to CO2/HCO3
−-buffered (5%/20 mM) solution caused a rapid decrease of pHi (P < 0.01), followed by an effective counter-regulation. 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS; 100 μM) blocked
the pHi recovery by 88%. The results indicate that intracellular acidification by butyrate and CO2 is effectively counter-regulated by an Na+/H+ exchanger and by DIDS-sensitive, HCO3
−-dependent mechanism(s). Considering the large amount of intraruminal weak acids in vivo, both mechanisms are of major importance
for maintaining the pHi homeostasis of ruminal epithelial cells.
Accepted: 8 March 2000 相似文献
14.
Thioredoxin reductase (TrxR, EC 1.6.4.5) of Deinococcus radiophilus was purified by steps of sonication, ammonium sulfate fractionation, 2′5′ ADP Sepharose 4B affinity chromatography, and Sephadex
G-100 gel filtration. The purified TrxR, which was active with both NADPH and NADH, gave a 368 U/mg protein of specific activity
with 478-fold purification and 18% recovery from the cell-free extract. An isoelectric point of the purified enzymes was ca.
4.5. The molecular weights of the purified TrxR estimated by PAGE and gel filtration were about 63.1 and 72.2 kDa, respectively.
The molecular mass of a TrxR subunit is 37 kDa. This suggests that TrxR definitely belongs to low molecular weight TrxR (L-TrxR).
The Km and Vmax of TrxR for NADPH are 12.5 μM and 25 μM/min, whereas those for NADH are 30.2 μM and 192 μM/min. The Km and
Vmax for 5, 5′-dithio-bis-2-nitrobenzoic acid (DTNB, a substituted substrate for thioredoxin) are 463 μM and 756 μM/min, respectively.
The presence of FAD in TrxR was confirmed with the absorbance peaks at 385 and 460 nm. The purified TrxR was quite stable
from pH 3 to 9, and was thermo-stable up to 70°C. TrxR activity was drastically reduced (ca. 70%) by Cu2+, Zn2+, Hg2+, and Cd2+, but moderately reduced (ca. 50%) by Ag+. A significant inhibition of TrxR by N-ethylmaleimide suggests an occurrence of cysteine at its active sites. Amino acid
sequences at the N-terminus of purified TrxR are H2N-Ser-Glu-Gln-Ala-Gln-Met-Tyr-Asp-Val-Ile-Ile-Val-Gly-Gly-Gly-Pro-Ala-Gly-Leu-Thr-Ala-COOH. These sequences show high similarity
with TrxRs reported in Archaea, such as Methanosarcina mazei, Archaeoglobus fulgidus etc. 相似文献
15.
M. V. Tarasova V. V. Kuznetsov N. A. Netesova D. A. Gonchar S. Kh. Degtyarev 《Moscow University Biological Sciences Bulletin》2011,66(2):76-78
DNA methyltransferases genes of the BspACI restriction-modification system from Bacillus psychrodurans AC have been cloned in E. coli cells. Analysis of amino acid sequences of the proteins showed that both of these genes belong to C5 DNA methyltransferases.
Gene M1.BspACI has been subcloned in pJW2 vector. A high-purity recombinant enzyme has been obtained using chromatography on different carriers.
It has been shown that M1.BspACI modifies the first cytosine residue in the sequence 5′-CCGC-3′. Kinetic parameters of DNA
methylation by the enzyme have been determined. Catalytic constant appears to be 0.095 ± 0.002 min−1. K
mphage is λ DNA—0.053 ± 0.007 μM, and K
mSAM is 5.1 ± 0.3 μM. 相似文献
16.
Siu Wah Wong-Deyrup Youngbae Kim Sonya J. Franklin 《Journal of biological inorganic chemistry》2006,11(1):17-25
The DNA-binding behavior and target sequences of two designed metallopeptides have been investigated with an iterative electrophoresis
mobility shift assay followed by PCR amplification, and by circular dichroism spectroscopy. Peptides P3W and P5b were designed
based on the structural similarity of the helix–turn–helix motif of homeodomains and the EF-hand motifs of calmodulin, as
previously described for P3W. Like P3W, P5b binds both Eu(III) (K
d=12.6±1.9 μM) and Ca(II) (K
d=70±8 μM) with reasonable affinity. Binding selection from a library of randomized 8-mer DNA oligonucleotide sequences identified
one target family for CaP5b [5′-pur-T-pur-G-(G/C)-3′], and two target sites for CaP3W [5′-(A/T)-G-G-G-(T/C)-3′ and 5′-A-T-(G/T)-T-G-3′].
Circular dichroism studies indicate that unlike EuP3W, EuP5b is poorly folded in the absence of DNA. In the presence of DNA
containing target-binding sites for both peptides, both EuP3W and EuP5b increase in helical content, in the latter case significantly.
These results suggest that EuP5b binding to target DNA involves an induced-fit mechanism. These small chimeric metallopeptides
have been found to bind selectively to DNA targets, analogous to natural protein–DNA interactions. This corroborates our earlier
conclusions (J. Am. Chem. Soc. 125:6656, 2003) that sequence-preferential DNA cleavage by Ce(IV)P3W was due to sequence recognition.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
17.
Victor Asensi Francisco Parra Joshua Fierer Eulalia Valle Carmen Bordallo Paz Rendueles Santiago Gascón José A. Carton José A. Maradona José M. Arribas 《Current microbiology》1997,34(1):61-66
Bacillus subtilis is a ubiquitous soil bacterium used for measuring the β-lysin activity and in other bioassays. We observed a complete bactericidal
effect of ADP on B. subtilis at concentrations of 50–100 μM at pH values <5.5, which disappeared at pH values above 6. The effect was also found for acetic
acid at concentrations >17.4 μM and similar pH values. ATP, adenosine, and HCl were not bactericidal. We used BCECF-AM, a
pH-sensitive probe, and found that the killing of B. subtilis was due to a change in the intracellular pH caused by the passage across the cell membrane of these weak organic acids when
incubated with B. subtilis at pH values near the pK. More experiments are needed to determine the biological meaning of these in vitro findings.
Received: 14 June 1996 / Accepted: 19 July 1996 相似文献
18.
Sze-Tin Von Hoi-Ling Seng Hong-Boon Lee Seik-Weng Ng Yusuke Kitamura Makoto Chikira Chew-Hee Ng 《Journal of biological inorganic chemistry》2012,17(1):57-69
Abstract
By inhibiting only two or three of 12 restriction enzymes, the series of [M(phen)(edda)] complexes [M(II) is Cu, Co, Zn; phen is 1,10-phenanthroline; edda is N,N′-ethylenediaminediacetate] exhibit DNA binding specificity. The Cu(II) and Zn(II) complexes could differentiate the palindromic sequences 5′-CATATG-3′ and 5′-GTATAC-3′, whereas the Co(II) analogue could not. This and other differences in their biological properties may arise from distinct differences in their octahedral structures. The complexes could inhibit topoisomerase I, stabilize or destabilize G-quadruplex, and lower the mitochondrial membrane potential of MCF7 breast cells. The pronounced stabilization of G-quadruplex by the Zn(II) complex may account for the additional ability of only the Zn(II) complex to induce cell cycle arrest in S phase. On the basis of the known action of anticancer compounds against the above-mentioned individual targets, we suggest the mode of action of the present complexes could involve multiple targets. Cytotoxicity studies with MCF10A and cisplatin-resistant MCF7 suggest that these complexes exhibit selectivity towards breast cancer cells over normal ones. 相似文献19.
Epidermal ultrastructure of Seison nebaliae and Seison annulatus, and a comparison of epidermal structures within the Gnathifera 总被引:3,自引:0,他引:3
W. H. Ahlrichs 《Zoomorphology》1997,117(1):41-48
The epidermis of both species of Seison is syncytial and has a characteristic internal layer divided into two distinct sublayers. Sublayer I is very thin (0.03 μm)
and bounded to the outer cell membrane of the epidermis. Sublayer II is 0.5 μm thick and separated from sublayer I by a thin
layer of cytoplasm. Intrusions of the outer cell membrane of the epidermis perforate the internal layer, before terminating
within the cytoplasm. The intrusions of the cell membrane of S. annulatus are coated by an electron-dense material, the annulus, when passing through the internal layer. Bundles of filaments are present
in the epidermis of S. nebaliae. A comparison of epidermal structures within the Gnathifera Ahlrichs, 1995, confirms phylogenetic relationships earlier proposed
by the author.
Accepted: 19 December 1996 相似文献
20.
1. The effects of three metabotropic glutamate receptor (mGluR) agonists were tested in two pathways of rat piriform cortex. The group I, II and III mGluR agonists used were RS-3,5-dihydroxyphenenylglycine (DHPG) (10–100 μM), (2S,1′S,2′S)-2-Carboxycyclopropyl (L-CCG) (20–100 μM) and L(+)-2-amino-4-phosphonobutyric acid (L-AP4) (5–500 μM), respectively.2. The effects of the three groups of agonists on synaptic transmission in the two piriform cortex pathways also were examined. All three agonists reduced the amplitude of the monosynaptic EPSPs generated by stimulation of the lateral olfactory tract (LOT) or of the association fiber pathway (ASSN). This was always accompanied by an increase in paired pulse facilitation.3. Group I and II mGluR agonists had similar synaptic effects on the two pathways, while the group III mGluR agonist suppressed the LOT pathway more than the association pathway.4. The group II and III mGluR agonists had no effect on passive membrane properties of pyramidal neurons. Group I agonists depolarized the pyramidal neuron membrane potential, and enhanced both membrane resistance and noise.5. Our data suggest that all three types of mGluRs modulate synaptic transmission in both of these pathways in piriform cortex. Only group I agonists alter post-synaptic membrane properties, while all three types of receptor regulate synaptic transmission. Groups I and II are equally potent in the LOT and association fiber pathways, while group III receptors are more potent in the LOT than the association fiber pathways. 相似文献