共查询到20条相似文献,搜索用时 15 毫秒
1.
Sarigüllü Ozgüney I Yeşim Karasulu H Kantarci G Sözer S Güneri T Ertan G 《AAPS PharmSciTech》2006,7(4):E39-E45
The aim of this study was to evaluate and compare the in vitro and in vivo transdermal potential of w/o microemulsion (M)
and gel (G) bases for diclofenac sodium (DS). The effect of dimethyl sulfoxide (DMSO) as a penetration enhancer was also examined
when it was added to the M formulation. To study the in vitro potential of these formulations, permeation studies were performed
with Franz diffusion cells using excised dorsal rat skin. To investigate their in vivo performance, a carrageenan-induced
rat paw edema model was used. The commercial formulation of DS (C) was used as a reference formulation. The results of the
in vitro permeation studies and the paw edema tests were analyzed by repeated-measures analysis of variance. The in vitro
permeation studies found that M was superior to G and C and that adding DMSO to M increased the permeation rate. The permeability
coefficients (Kp) of DS from M and M+DMSO were higher (Kp=4.9×10−3±3.6×10−4 cm/h and 5.3×10−3±1.2×10−3 cm/h, respectively) than the Kp of DS from C (Kp=2.7×10−3±7.3×10−4 cm/h) and G (Kp=4.5×10−3±4.5×10−5 cm/h). In the paw edema test, M showed the best permeation and effectiveness, and M+DMSO had nearly the same effect as M.
The in vitro and in vivo studies showed that M could be a new, alternative dosage form for effective therapy. 相似文献
2.
M. M. Flawia A. R. Kornblihtt D. de Mendoza H. N. Torres 《Molecular and cellular biochemistry》1981,34(3):185-190
Summary Cytosolic adenylate cyclase activity from rat seminiferous tubules is inhibited by L-triiodothyronine (L-T3). In a typical dose-response curve, using Mn-ATP as substrate, no effect is observed at 10−10 M L-T3; about 15 to 25% inhibition is found in the range between 10−9 and 10−6 M L-T3 and finally a sharp enzyme inhibition is evident at increasing hormone concentrations from 10−6 to 10−4 M. Incubation of decapsulated testes with L-T3 leads to a decrease of intracellular cyclic AMP levels. Dose-response relationships for such effect are similar to those
found for adenylate cyclase activity. In this case a clear response is observed at 10−8 M L-T3. 相似文献
3.
O. M. Tsivileva E. A. Loshchinina O. E. Makarov V. E. Nikitina 《Applied Biochemistry and Microbiology》2012,48(3):280-289
The auxin formation in a submerged culture of the xylotrophic basidiomycete Lentinus edodes (Berk.) Sing (Lentinula edodes (Berk.) Pegler) (shiitake) is studied. Biologically active substances of an indole nature are identified, “the effect of
small doses” of which lies in not only the stimulation of growth of the mycelium (indole-3-acetic acid, 2 × 10−7–2 × 10−4 g/l), but also in the induction of tryptophan-independent paths of auxin biosynthesis. The above-mentioned path is realized
in the presence of exogenous indole (1 × 10−3–1 × 10−4 g/l), as well as while inducing the biosynthesis of indole-3-acetic acid by its microadditives (1 × 10−5−1 × 10−8 g/l), and is accompanied by the formation of anthranilic acid (up to 1.5 mg/l). Induction of the generative development stage
of shiitake by indole derivatives is revealed. It was found that among the studied compounds only indoleacetamide at a concentration
of an order of ×10−4 g/l in the culture fluid of L. edodes had a pronounced stimulatory effect on the formation of shiitake’s brown mycelial film. 相似文献
4.
Tatiana G. Sazykina A. I. Kryshev K. D. Sanina 《Radiation and environmental biophysics》2009,48(4):391-404
Databases on effects of chronic low-LET radiation exposure were analyzed by non-parametric statistical methods, to estimate
the threshold dose rates above which radiation effects can be expected in vertebrate organisms. Data were grouped under three
umbrella endpoints: effects on morbidity, reproduction, and life shortening. The data sets were compiled on a simple ‘yes’
or ‘no’ basis. Each data set included dose rates at which effects were reported without further details about the size or
peculiarity of the effects. In total, the data sets include 84 values for endpoint “morbidity”, 77 values for reproduction,
and 41 values for life shortening. The dose rates in each set were ranked from low to higher values. The threshold TDR5 for
radiation effects of a given umbrella type was estimated as a dose rate below which only a small percentage (5%) of data reported
statistically significant radiation effects. The statistical treatment of the data sets was performed using non-parametric
order statistics, and the bootstrap method. The resulting thresholds estimated by the order statistics are for morbidity effects
8.1 × 10−4 Gy day−1 (2.0 × 10−4–1.0 × 10−3), reproduction effects 6.0 × 10−4 Gy day−1 (4.0 × 10−4–1.5 × 10−3), and life shortening 3.0 × 10−3 Gy day−1 (1.0 × 10−3–6.0 × 10−3), respectively. The bootstrap method gave slightly lower values: 2.1 × 10−4 Gy day−1 (1.4 × 10−4–3.2 × 10−4) (morbidity), 4.1 × 10−4 Gy day−1 (3.0 × 10−4–5.7 × 10−4) (reproduction), and 1.1 × 10−3 Gy day−1 (7.9 × 10−4–1.3 × 10−3) (life shortening), respectively. The generic threshold dose rate (based on all umbrella types of effects) was estimated
at 1.0 × 10−3 Gy day−1. 相似文献
5.
Enzymatic synthesis of arbutin undecylenic acid ester and its inhibitory effect on mushroom tyrosinase 总被引:1,自引:0,他引:1
A novel tyrosinase inhibitor, an arbutin derivative having undecylenic acid at the 6-position of its glucose moiety, was enzymatically
synthesized. Its inhibitory activity was studied in vitro by using catechol and phenol as substrates. The IC50 value of the arbutin ester on tyrosinase using catechol (4 × 10−4 M) was 1% of that when arbutin (4 × 10−2 M) was used. Using phenol, IC50 of the arbutin ester (3 × 10−4 M) as substrate was 10% of that of arbutin (3 × 10−3 M). These results suggest that the arbutin ester inhibits the latter part of the tyrosinase reaction, which consists of hydroxylation
and oxidation. 相似文献
6.
Denis V. Abramochkin Natalia V. Tennova Elizaveta E. Hirazova Anna V. Pizgareva Vladislav S. Kuzmin Galina S. Sukhova 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(5):645-651
Standard microelectrode technique was used to study electrical activity of the isolated heart of the polychaete annelid, Arenicola marina. Typical pacemaker activity with slow diastolic depolarization was observed in all recordings. The average maximum diastolic
potential (−58.4 ± 3.2 mV), the average amplitude of the action potential (28.7 ± 4.7 mV) and the average total duration of
the action potential (2,434 ± 430 ms) were determined. There has been no gradient of automaticity observed in our studies,
which suggests that all regions of the Arenicola heart could possess pacemaker functions. Acetylcholine (ACh) produced a concentration dependent (5 × 10−8–5 × 10−5 M) increase of the beating rate via increase in the rate of the diastolic depolarization. ACh (5 × 10−5 M) increased beating rate by 2.5-fold compared to the control rate. A stronger action of ACh resulted in depolarization,
block of action potential generation and contracture of the heart. The non-hydrolysable ACh analog carbacholine (10−8–10−6 M) produced similar effects. All effects of ACh and carbacholine were abolished by 5 × 10−6 M atropine. d-Tubocurarine (5 × 10−5 M) did not significantly alter effects of ACh or carbacholine. Epinephrine (10−8–10−6 M) caused the slowing of pacemaker activity and marked decrease of action potential duration. 10−6 M epinephrine produced complete cardiac arrest. The effects of epinephrine were not significantly altered by the β-blocker
propranolol (5 × 10−6 M). The β-agonist isoproterenol (10−7–10−5 M) and the α-agonist xylometazoline (10−6–10−5 M) did not produce significant effects. Thus, cholinergic effects in the Arenicola heart are likely to be mediated via muscarinic receptors, while the nature of adrenergic effects needs further investigation. 相似文献
7.
Adam H. Balen Jovita Er Brian Rafferty Matthew Rose 《In vitro cellular & developmental biology. Animal》1995,31(4):316-322
Summary We have described the protocols and characterization of a pituicyte culture, which became established as a reliable and reproducible
bioassay for the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The bioassay was used to measure
the bioactivity of factors that inhibit and stimulate gonadotrophin secretion. The protocol that was used involved the culling
of female Wistar rats (200 to 250 g weight), at random stages of their cycle, and dispersal of their pituicytes in a concentration
of 0.4 × 106 cells · ml−1 · well−1 in serum-free medium (Dulbecco’s modified Eagle’s medium/Ham’s F12 mixture, supplemented with insulin and transferrin) in
Falcon 3047 24-well culture plates. After 24 h of pre-culture, the medium was changed and the cells cultured for a further
48 h. The supernatant was removed and assayed for basal secretion of FSH and LH. The cells were then stimulated with 10−8
M GnRH for 4 h and the supernatant assayed for gonadotrophin-releasing hormone (GnRH)-stimulated FSH and LH secretion. All
samples were assayed as pairs of duplicates (i.e. quadruplicate samples) which were randomly added to the plates to minimize
plate effects. Random number tables were used to achieve this randomization. 相似文献
8.
Kabir ME Krishnaswamy S Miyamoto M Furuichi Y Komiyama T 《Applied microbiology and biotechnology》2011,90(2):553-564
Phage-display and competitive panning elution leads to the identification of minimum-sized antigen binders together with conventional
antibodies from a mouse cDNA library constructed from HM-1 killer toxin neutralizing monoclonal antibody (nmAb-KT). Antigen-specific
altered camelid-like single-domain heavy chain antibody (scFv K2) and a conventional antibody (scFv K1) have been isolated
against the idiotypic antigen nmAb-KT. The objectives of the study were to examine (1) their properties as compared to conventional
antibodies and also (2) their antifungal activity against different pathogenic and non-pathogenic fungal species. The alternative
small antigen-binder, i.e., the single-domain heavy chain antibody, was originated from a conventional mouse scFv phage library
through somatic hyper-mutation while selection against antigen. This single-domain antibody fragment was well expressed in
bacteria and specifically bound with the idiotypic antigen nmAb-KT and had a high stability and solubility. Experimental data
showed that the binding affinity for this single-domain antibody was 272-fold higher (K
d = 1.07 × 10−10 M) and antifungal activity was three- to fivefold more efficient (IC50 = 0.46 × 10−6 to 1.17 × 10−6 M) than that for the conventional antibody (K
d = 2.91 × 10−8 M and IC50 = 2.14 × 10−6 to 3.78 × 10−6 M). The derived single-domain antibody might be an ideal scaffold for anti-idiotypic antibody therapy and the development
of smaller peptides or peptide mimetic drugs due to their less complex antigen-binding site. We expect that such single-domain
synthetic antibodies will find their way into a number of biotechnological or medical applications. 相似文献
9.
Barbara Duquenne Tom Eeckhaut Stefaan Werbrouck Johan Van Huylenbroeck 《Plant Cell, Tissue and Organ Culture》2007,91(2):165-173
Vital protoplasts from Spathiphyllum wallisii ‘Alain’ and Anthurium scherzerianum ‘238’ were isolated from both somatic embryos and leaves. The highest yields were obtained when 1.5% cellulase, 0.5% macerase
and 0.5% driselase were used for Spathiphyllum wallisii leaves and 0.5% cellulase, 0.3% macerase and 0.5% driselase for Anthurium scherzerianum embryos. About 1 × 106 protoplasts g−1 and 1 × 105 protoplasts g−1 could be isolated from leaves and embryos, respectively. For protoplast fusion Spathiphyllum wallisii ‘Alain’ and Anthurium scherzerianum ‘238’ were mixed in a 1:1 ratio in a fusion solution containing 1 mM CaCl2·2H2O, 1 mM MES and 0.5 M mannitol. Fusion was performed by protoplast alignment under 500 V cm−1 alternating current for 60 s and subsequent generation of two pulses of 4500 V cm−1 direct current during 50 μs. Development until colony stage was achieved using agarose beads for protoplast culture. 相似文献
10.
Paolo Ascenzi Alessandro Bolli Alessandra di Masi Grazia R. Tundo Gabriella Fanali Massimo Coletta Mauro Fasano 《Journal of biological inorganic chemistry》2011,16(1):97-108
Human serum heme–albumin (HSA-heme) displays globin-like properties. Here, the allosteric inhibition of ferric heme [heme-Fe(III)]
binding to human serum albumin (HSA) and of ferric HSA–heme [HSA-heme-Fe(III)]-mediated peroxynitrite isomerization by isoniazid
and rifampicin is reported. Moreover, the allosteric inhibition of isoniazid and rifampicin binding to HSA by heme-Fe(III)
has been investigated. Data were obtained at pH 7.2 and 20.0 °C. The affinity of isoniazid and rifampicin for HSA [K
0 = (3.9 ± 0.4) × 10−4 and (1.3 ± 0.1) × 10−5 M, respectively] decreases by about 1 order of magnitude upon heme-Fe(III) binding to HSA [K
h = (4.3 ± 0.4) × 10−3 and (1.2 ± 0.1) × 10−4 M, respectively]. As expected, the heme-Fe(III) affinity for HSA [H
0 = (1.9 ± 0.2) × 10−8 M] decreases by about 1 order of magnitude in the presence of saturating amounts of isoniazid and rifampicin [H
d = (2.1 ± 0.2) × 10−7 M]. In the absence and presence of CO2, the values of the second-order rate constant (l
on) for peroxynitrite isomerization by HSA-heme-Fe(III) are 4.1 × 105 and 4.3 × 105 M−1 s−1, respectively. Moreover, isoniazid and rifampicin inhibit dose-dependently peroxynitrite isomerization by HSA-heme-Fe(III)
in the absence and presence of CO2. Accordingly, isoniazid and rifampicin impair in a dose-dependent fashion the HSA-heme-Fe(III)-based protection of free l-tyrosine against peroxynitrite-mediated nitration. This behavior has been ascribed to the pivotal role of Tyr150, a residue
that either provides a polar environment in Sudlow’s site I (i.e., the binding pocket of isoniazid and rifampicin) or protrudes
into the heme-Fe(III) cleft, depending on ligand binding to Sudlow’s site I or to the FA1 pocket, respectively. These results
highlight the role of drugs in modulating heme-Fe(III) binding to HSA and HSA-heme-Fe(III) reactivity. 相似文献
11.
Yamada T Matsuda K Uchiyama M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(3):203-212
The effects of atrial natriuretic peptide (ANP) and cGMP on transepithelial ion transport were examined in the urinary bladder
of the Japanese tree frog, Hyla japonica, using Ussing chamber voltage-clamp and whole-cell patch-clamp techniques. When the bladders were exposed to 4.4×10−11 to 10−6 M ANP or 10−7 to 3×10−4 M 8-Br-cGMP, both the transepithelial potential difference (PD) and the short-circuit current (Isc) were significantly increased
in a concentration-response manner. The cGMP-dependent responses were inhibited in a Na+-free bath solution and in the presence of amiloride. The cGMP-dependent increases in Isc were significantly inhibited by
specific PKA inhibitors (5×10−7 M KT-5720 and >10−5 M H-89), but not by a specific PKG inhibitor (5×10−7 M KT-5823). ANP-dependent increases in Isc were also significantly inhibited by KT-5720. In the patch-clamp study, ANP and
cGMP significantly increased in inward currents involving Na+ uptake. These results suggest that a cross-talk mechanism exists between cAMP and cGMP signaling pathways, which leads to
Na+ transport in the frog urinary bladder. In addition, the cGMP-dependent increases in Isc were partially inhibited by 10−4 M l-cis-diltiazem, a specific inhibitor of cyclic nucleotide-gated (CNG) channels. These results also suggest a relation between
CNG channels and the cGMP-dependent increases in Na+ absorption of the frog urinary bladder. 相似文献
12.
Fabiana R. X. Batista Carlos A. Pereira Ronaldo Z. Mendon?a Angela M. Moraes 《Cytotechnology》2005,49(1):1-9
Animal cells can be cultured both in basal media supplemented with fetal bovine serum (FBS) and in serum-free media. In this
work, the supplementation of Grace’s medium with a set of nutrients to reduce FBS requirements in Spodoptera frugiperda (Sf9) cell culture was evaluated, aiming the production of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) at a cost lower than those for the production using Sf900 II medium. In Grace’s medium supplemented
with glucose, Pluronic F68 (PF68) and yeast extract (YE), the effects of FBS and milk whey ultrafiltrate (MWU) on cell concentration
and viability during midexponential and stationary growth phase were evaluated. In spite of the fact that FBS presented higher
statistical effects than MWU on all dependent variables in the first cell passage studies, after cell adaptation, AgMNPV polyhedra
production was comparable to that in Sf900 II. Batch cultivation in Grace’s medium with 2.7 g l−1 glucose, 8 g l−1 YE and 0.1% (w/v) PF68 supplemented with 1% (w/v) MWU and 3% (v/v) FBS increased viable cell concentration to about 5-fold
(4.7×106 cells ml−1) when compared to Grace’s containing 10% (v/v) FBS (9.5×105 cells ml−1). AgMNPV polyhedra (PIBs) production was around 3-fold higher in the MWU supplemented medium (1.6×107 PIBs ml−1) than in Grace’s medium with 10% FBS (0.6×107 PIBs ml−1). This study therefore shows a promising achievement to significantly reduce FBS concentration in Sf9 insect cell media,
keeping high productivity in terms of cell concentration and final virus production at a cost almost 50% lower than that observed
for Sf900 II medium.
C.A. Pereira is recipient of a CNPq fellowship. 相似文献
13.
Li WB Gerstmann U Giussani A Oeh U Paretzke HG 《Radiation and environmental biophysics》2008,47(1):101-110
The mysterious death of Mr. Alexander Litvinenko who was most possibly poisoned by Polonium-210 (210Po) in November 2006 in London attracted the attention of the public to the kinetics, dosimetry and the risk of this high
radiotoxic isotope in the human body. In the present paper, the urinary excretion of seven persons who were possibly exposed
to traces of 210Po was monitored. The values measured in the GSF Radioanalytical Laboratory are in the range of natural background concentration.
To assess the effective dose received by those persons, the time-dependence of the organ equivalent dose and the effective
dose after acute ingestion and inhalation of 210Po were calculated using the biokinetic model for polonium (Po) recommended by the International Commission on Radiological
Protection (ICRP) and the one recently published by Leggett and Eckerman (L&E). The daily urinary excretion to effective dose
conversion factors for ingestion and inhalation were evaluated based on the ICRP and L&E models for members of the public.
The ingestion (inhalation) effective dose per unit intake integrated over one day is 1.7 × 10−8 (1.4 × 10−7) Sv Bq−1, 2.0 × 10−7 (9.6 × 10−7) Sv Bq−1 over 10 days, 5.2 × 10−7 (2.0 × 10−6) Sv Bq−1 over 30 days and 1.0 × 10−6 (3.0 × 10−6) Sv Bq−1 over 100 days. The daily urinary excretions after acute ingestion (inhalation) of 1 Bq of 210Po are 1.1 × 10−3 (1.0 × 10−4) on day 1, 2.0 × 10−3 (1.9 × 10−4) on day 10, 1.3 × 10−3 (1.7 × 10−4) on day 30 and 3.6 × 10−4 (8.3 × 10−5) Bq d−1 on day 100, respectively. The resulting committed effective doses range from 2.1 × 10−3 to 1.7 × 10−2 mSv by an assumption of ingestion and from 5.5 × 10−2 to 4.5 × 10−1 mSv by inhalation. For the case of Mr. Litvinenko, the mean organ absorbed dose as a function of time was calculated using
both the above stated models. The red bone marrow, the kidneys and the liver were considered as the critical organs. Assuming
a value of lethal absorbed dose of 5 Gy to the bone marrow, 6 Gy to the kidneys and 8 Gy to the liver, the amount of 210Po which Mr. Litvinenko might have ingested is therefore estimated to range from 27 to 1,408 MBq, i.e 0.2–8.5 μg, depending
on the modality of intake and on different assumptions about blood absorption. 相似文献
14.
Yamaguchi M Hamamoto R Uchiyama S Ishiyama K 《Molecular and cellular biochemistry》2007,303(1-2):83-88
The effect of various flavonoids, which are present in food and plants, on bone calcium content and osteoclastogenesis were
investigated to compare action of flavonoid on bone formation and bone resorption in vitro. Rat femoral-diaphyseal (cortical
bone) and -metaphyseal (trabecular bone) tissues were cultured for 48 h in Dulbecco’s modified Eagle’s medium (high glucose)
supplemented with antibiotics and bovine serum albumin. Amoung quercetin, myricetin, kaempferol, isorhamnetin, curcumin, hesperidin,
or astaxanthin in the range of 10−7–10−5 M, culture with quercetin (10−6 or 10−5 M) caused a significant increase in diaphyseal calcium content. Such an effect was not seen in other compounds. Mouse bone
marrow cells were cultured for 7 days in the presence of parathyroid hormone (PTH; 10−7 M), a bone-resorbing factor, in vitro. Culture with PTH caused a significant increase in osteoclast-like cell formation. This
increase was significantly inhibited in the presence of quercetin, myricetin, kaempferol, isorhamnetin, or curcumin in the
range of 10−8–10−6 M. Such an effect was not seen in the case of hesperidin or astaxanthin. In addition, culture with PTH (10−7 M) caused a significant decrease in diaphyseal calcium content. This decrease was completely prevented in the presence of
quercetin, myricetin, kaempferal, or isorhamnetin of 10−6 M. This study demonstrates that various flavonoids have a potent inhibitory effect on osteoclastogenesis and bone resorption
rather than bone formation in vitro. Among various flavonoids, quercetin had a stimulatory effect on bone formation and an
inhibitory effect on bone resorption in vitro. 相似文献
15.
Zanaty R. Komy Rabei M. Gabar Ahmed A. Shoriet Rehab M. Mohammed 《World journal of microbiology & biotechnology》2006,22(9):975-982
Summary The ability of Pseudomonas
aeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pK
i
=1.66±3.26×10−3, 1.92±1.63×10−4 and 2.16±3.79×10−4) and binding constant of cadmium metal ions (pK
M1=1.99±2.45×10−3 and pK
M2=1.67±4.08×10−3) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pK
f) constant is 2.04±2.1×10−5 suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (q
max) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10−3± 2.10×10−3, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains. 相似文献
16.
Changes of polyol contents in the mycelium and fruit-bodies ofFlammulina velutipes were measured. The results suggested that arabinitol is accumulated in the fruit-bodies as the end-product after its translocation
from the mycelium, while mannitol in the fruit-bodies is converted into fructose by the action of mannitol dehydrogenase (MDH).
The development of fruit-bodies was promoted by feeding of mannitol to the mycelial colony. A14C tracer experiment indicated that half of mannitol translocated from mycelium to fruit-bodies was utilized for fruit-body
development. NAD-linked MDH andd-arabinitol dehydroganase (D-ADH) were detected in both mycelium and fruit-bodies. The activities of MDH and ADH in the mycelium
reached their maximum levels in the inital stage of fruit-body development and decreased thereafter. In contrast, the activity
of MDH in the fruit-bodies showed a peak in the middle stage of development. The activity of ADH in the fruit-bodies was less
than half of that of MDH. MDH showed a lower Km value for mannitol (1.3 ×10−3M) than for fructose (6.0×10−2 M). The Km value of ADH for arabinitol was extremely high (1.3×10−1M). 相似文献
17.
Natalia A. Prissadova Mariana D. Argirova Athanas D. Krastev Valentin I. Turiiski Rayna I. Ardasheva 《Central European Journal of Biology》2011,6(1):16-22
Tacrine, a well-known acetylcholinesterase inhibitor, applied in concentrations higher than 2×10−5 mol/l promoted Ca2+-independent relaxation of rat gastric smooth muscles in experiments in vitro. The relaxation was not cholinergic and was
a result of influence of tacrine over intracellular signaling pathways regulating smooth muscle contraction/relaxation. The
nature of this untypical muscle relaxation was studied by using smooth muscle strips isolated from rat stomach. Their bioelectrical
and mechanical responses were recorded after treatment with tacrine and different activators or blockers of intracellular
pathways involved in muscle contractility. Following the activation of adenylate cyclase with 1×10−6 mol/l forskolin and increase in the concentration of cyclic adenosine monophosphate (cAMP) after application of 4×10−5 mol/l SQ22536, a significant decrease in the muscle relaxation was observed. Theophylline (2×10−4 mol/l), a phosphodiesterase inhibitor, had no effect on the amplitude of tacrine-induced relaxation. The latter was also
reduced by inhibition of protein kinase A (PKA) with 5×10−6 mol/l KT5720. These findings support the assumption that tacrine promoted smooth muscle relaxation through PKA-induced phosphorylation
and inhibition of myosin light chain kinase activity. The reduction of spike-linked Ca2+ influx provoked by tacrine was probably a secondary contributing process, associated with an influence of increased cAMP
level on Ca2+ channels. 相似文献
18.
Serge Ostrovidov Patricia Franck Josette Capiaumont Brigitte Dousset Francine Belleville 《In vitro cellular & developmental biology. Animal》1998,34(3):259-264
Summary The effect of low concentrations of hydrogen peroxide (H2O2) (5 × 10−7−9.5 × 10−7
M) on cell growth and antibody production was investigated with murine hybridoma cells (Mark 3 and anti-hPL) in culture. Cell
growth, measured by flow cytometry with morphological parameters, was significantly stimulated by H2O2 (8 × 10−7
M) but H2O2 concentration of 7 × 10−6
M and above increased cell death. H2O2 stimulation of antibody production was nonsignificant. The metabolism of cells treated with 8 × 10−7 or 1 × 10−5
M H2O2 was similar to that of the control in terms of glucose and glutamine consumption, lactate and ammonia production, and amino
acid concentrations in the medium. The concentrations of lactate dehydrogenase, a marker of cell death, in test and control
cells were similar. However, concentrations of intracellular free radicals measured by flow cytometry with dihydrorhodamine
123 (DHR 123) and dichlorofluorescein diacetate (DCFH-DA) as fluorochromes were different. The reactive oxygen species content
of cells in 8 × 10−7
M H2O2 was similar to that of the controls, but there was a sudden, marked production of superoxide anions (detected with DHR 123)
and H2O2 or peroxides (detected with DCFH-DA) by cells incubated with 1 × 10−5
M H2O2 which increased with increasing H2O2 until cell death. 相似文献
19.
O. N. Yermakova A. M. Yermakov Kh. P. Tiras V. V. Lednev 《Russian Journal of Developmental Biology》2009,40(6):382-385
The melatonin effect on the anterior and posterior ends of a free-living flatworm Girardia tigrina was studied, as well as the variability of the mitotic activity of the stem cells (neoblasts) in the anterior and posterior
postblasteme. This hormone may inhibit the regeneration of the anterior end of the animal in the physiologic-friendly concentrations
of 10−10–10−5 M by suppressing the mitotic activity of the neoblasts. This hormone does not affect the posterior end’s regeneration; thus,
its regeneration effect is significantly elective. 相似文献
20.
Ikonomopoulou MP Bradley AJ Whittier JM Ibrahim K 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(8):775-782
We report for the first time the presence of a sex steroid-binding protein in the plasma of green sea turtles Chelonia mydas, which provides an insight into reproductive status. A high affinity, low capacity sex hormone steroid-binding protein was identified in nesting C. mydas and its thermal profile was established. In nesting C. mydas testosterone and oestradiol bind at 4°C with high affinity (K
a = 1.49 ± 0.09 × 109 M−1; 0.17 ± 0.02 × 107 M−1) and low binding capacity (B
max = 3.24 ± 0.84 × 10−5 M; 0.33 ± 0.06 × 10−4 M). The binding affinity and capacity of testosterone at 23 and 36°C, respectively were similar to those determined at 4°C. However, oestradiol showed no binding activity at 36°C. With competition studies we showed that oestradiol and oestrone do not compete for binding sites. Furthermore, in nesting C. mydas plasma no high-affinity binding was observed for adrenocortical steroids (cortisol and corticosterone) and progesterone. Our results indicate that in nesting C. mydas plasma temperature has a minimal effect on the high-affinity binding of testosterone to sex steroid-binding protein, however, the high affinity binding of oestradiol to sex steroid-binding protein is abolished at a hypothetically high (36°C) sea/ambient/body temperature. This suggests that at high core body temperatures most of the oestradiol becomes biologically available to the tissues rather than remaining bound to a high-affinity carrier. 相似文献