共查询到20条相似文献,搜索用时 687 毫秒
1.
Skoblina MN 《Ontogenez》2000,31(5):382-387
The inhibitor of cAMP-dependent protein kinase N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) (12.5-50 microM) decreased the rate of ovulation of the follicle-enclosed Rana temporaria oocytes induced by the homologous pituitary extract in amphibian Ringer solution and in a chloride-free medium. The inhibitor of voltage-dependent calcium channels diltiazem (10 and 100 microM) decreased the rate of ovulation in Ringer solution but did not affect it in a chloride-free medium or decreased the ovulation inhibitory effect of this medium. It was concluded that cAMP-dependent protein kinase and intracellular free calcium ions were involved as second messengers in the gonadotropin regulation not only in maturation of amphibian oocytes but also in ovulation. 相似文献
2.
The concentration of intracellular free calcium ions in the follicle wall cells and in the follicle cells of Rana temporaria in Ringer solution is 150 +/- 10 and in the follicle wall cells of Xenopus laevis, 220 +/- 10 nM. In a chloride-free saline, its concentration in the same cells is 2.5-3 times that in Ringer solution. Voltage-dependent Ca(2+)-channel blockers diltiazem and verapamil (100 microM) reduce the level of intracellular free calcium ions in R. temporaria follicle wall cells cultivated in a chloride-free saline to 170 +/- 20 nM, which practically does not differ from the level in Ringer solution. Inhibitors (100 microM) decrease the rate of "spontaneous" maturation of R. temporaria follicle-enclosed oocytes both in chloride-free and Ringer solutions. It was concluded that an increased level of intracellular free calcium ions in the follicle cells, among other factors, may determine the stimulating effect of the medium (Ringer or chloride-free solution) on "spontaneous" maturation of follicle-enclosed amphibian oocytes. Voltage-dependent calcium channels appear to be involved in Ca2+ influx into the cells. 相似文献
3.
M. N. Skoblina 《Russian Journal of Developmental Biology》2006,37(6):382-388
The influence of diluted Ringer solution on ovulation and maturation of common frog oocytes stimulated in vitro by homologous pituitary extract (0.005 pit/ml) or progesterone (1 μg/ml) was studied. During hibernation, the dilution of Ringer solution led to a decreased percentage of oocytes ovulated and matured under the influence of both inducers. As the season of reproduction approached, the dependence of oocyte maturation and ovulation on the Ringer solution dilution was reduced. Possible causes of different dependence of the ovulation of amphibian and sturgeon oocytes stimulated by gonadotropic hormones or progesterone on the culture medium osmolality is discussed. 相似文献
4.
Skoblina MN 《Ontogenez》2006,37(6):457-464
The influence of diluted Ringer solution on ovulation and maturation of common frog oocytes stimulated in vitro by homologous pituitary extract (0.005 pit/ml) or progesterone (1 pg/ml) was studied. During wintering, the dilution of Ringer solution led to a decreased percentage of oocytes ovulated and matured under the influence of both inducers. As the season of reproduction approached, the dependence of oocyte maturation and ovulation on the Ringer solution dilution weakened. Possible causes of different dependence of the ovulation of amphibian and sturgeon oocytes stimulated by gonadotropic hormones or progesterone on the culture medium osmolality is discussed. 相似文献
5.
Rat forebrain- and heart-derived mRNA were used to express Ca2+ channels inXenopus oocytes to study their cAMP-dependent regulation. Forebrain and heart mRNA-directed Ca2+ channel currents (I
Ba, 40 mM Ba2+ were used as a charge carrier) showed similar voltage dependence and macroscopic kinetics but different pharmacology, which
allowed us to attribute them to N- and L-type, respectively. Brain mRNA-directedI
Ba was insensitive to the dihydropyridine (DHP) antagonist nitrendipine and the agonist Bay K 8644, but could be inhibited by
70% by 1 μM of ω-conotoxin GVIA, whileI
Ba directed by cardiac mRNA was extremely sensitive to DHP. Neither forebrain, nor heart mRNA-directedI
Ba could be augmented by the external applications of the β-agonist isoproterenol (ISO, 10 μM), the adenylate cyclase (AC) activator
forskolin (FSK, 10 μM), the phosphodiesterase inhibitor IBMX (200 μM), or their mixtures. “Cardiac”I
Ba was also unresponsive to the external applications of a membrane-permeable cAMP analog 8-(4-chlorophenylthio)-cAMP (500 μM),
as well as to the direct intracellular infusion of cAMP (300 μM). Blockade of cAMP-dependent phosphorylation pathway by intracellular
perfusion of the oocytes with 200 μM Rp-cAMP plus 200 μM of a synthetic protein kinase A (PKA) inhibitor peptide also exerted
no effect on the basal level ofI
Ba, suggesting that the expressed Ca2+ channels are not fully phosphorylated in the resting state. Measurements of the concentration of cAMP in the control and
heart mRNA-injected oocytes, using an enzyme-immunoassay system, showed that they display a similar basal cAMP concentration
(2.0–2.5 μM); however, application of ISO + FSK increased the cAMP concentration 2- to 3-fold in mRNA-injected oocytes, but
not in control oocytes. Thus, our data demonstrate that injection of rat cardiac mRNA intoXenopus oocytes results in the expression of receptor-stimulated AC and L-type Ca2+ channels, which do not respond to cAMP or PKA inhibitors. Unresponsiveness to cAMP-dependent regulation is not channel type-specific,
since N-type Ca2+ channels expressed by means of forebrain mRNA are also insensitive to such regulation. Unresponsiveness of the channels to
cAMP-mediated regulation is most probably due to lack/inaccessibility of PKA-dependent phosphorylation site(s), or loss of
functional significance of phosphorylation. 相似文献
6.
Cell swelling is associated with the activation of an increase in the osmosensitive taurine release (OTR) rate, which serves
to decrease cell volume as part of a process known as regulatory volume decrease. OTR, which is sensitive to many pharmacological
agents including anion channel blockers and signalling pathway modulators, has also been suggested to play a role in cell
cycle progression. At non-cytotoxic concentrations, the anion channel blocker NPPB (25 μM), the extra-cellular signal-regulated
kinase inhibitor PD98059 (50 μM), and the c-Jun NH2-terminal kinase inhibitor SP 600125 (5 μM) each decreased the OTR rate
by ≥50%, decreased cell proliferation, and increased G0/G1 cell cycle arrest. 相似文献
7.
Mature zygotic embryos of recalcitrant Christmas tree species eastern white pine (Pinus strobus L.) were used as explants for Agrobacterium tumefaciens strain GV3101-mediated transformation using the uidA (β-Glucuronidase) gene as a reporter. Influence of the time of sonication and the concentrations of protein phosphatase inhibitor
(okadaic acid) and kinase inhibitor (trifluoperazine) on Agrobacterium-mediated transformation have been evaluated. A high transformation frequency was obtained after embryos were sonicated for
45–50 s, or treated with 1.5–2.0 μM okadaic acid or treated with 100–200 μM trifluoperazine, respectively. Protein phosphatase
and kinase inhibitors enhance Agrobacterium-mediated transformation in eastern white pine. A 2–3.5-fold higher rate of hygromycin-resistant callus was obtained with
an addition of 2 μM okadaic acid or 150 μM trifluoperazine or sonicated embryos for 45 s. Stable integration of the uidA gene in the plant genome of eastern white pine was confirmed by polymerase chain reaction (PCR), Southern and northern blot
analyses. These results demonstrated that a stable and enhanced transformation system has been established in eastern white
pine and this system would provide an opportunity to transfer economically important genes into this Christmas tree species.
Communicated by W. H. Wu 相似文献
8.
M. Schnizler W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(4):295-302
Voltage clamp studies were performed on the dorsal integument of Hirudo medicinalis. Under apical calcium-free conditions an inward-directed component of transepithelial current was activated by changes of
transepithelial voltage. Depolarization caused up to 50% increase of the transepithelial sodium current. Hyperpolarization
had no comparable effects. With calcium (1.8 mM) or amiloride (100 μM) in the apical solution and in sodium-free solutions
the inward-directed current failed to increase after depolarization. Activation also occurred under chloride-free conditions.
Permeabilization of the apical membrane by nystatin (5 μM) increased the current activation significantly. After nystatin,
calcium as well as amiloride lost their inhibitory effects. This indicates a basolateral localization of the voltage-dependent
conductance. Vesicle insertion or cytoskeletal structures are probably not involved in regulation, as seen by the lack of
effects of brefeldin A and the cytochalasins B and D. However, serosal hyposmolar solutions (170 mosmol · l−1) caused a reinforced activation of the current. Our results indicate a voltage-dependent conductance in a tight sodium-absorbing
epithelium.
Accepted: 22 January 1998 相似文献
9.
Regulation of calcium current through L-type calcium channels (I
Ca,L) of the guinea pigtaenia coli smooth muscle cell (SMC) membrane by cyclic nucleotides and protein kinase C (PKC) was studied using a voltage-clamp technique
with intracellular dialysis or membrane patch perforation with amphotericin B. Non-selective blockers of serine/threonine
kinase, staurosporine and H-7 reduced theI
Ca,L amplitude in a dose-dependent manner. Dose-dependent suppression ofI
Ca,L was also produced by a selective PKC blocker, chelerythrine, and a cAMP-and cGMP-dependent protein kinase (PKA, PKG), blocker
H-8. Forskolin, which increases the intracellular level of cAMP, as well as membrane-permeant cAMP analogs, dibutyryl-cAMP
(db-cAMP) and 8-bromo-cAMP, exerted complex effects onI
Ca,L. The latter increased at their concentrations below 10 μM and decreased at their higher concentrations. 8-Bromo-cGMP reducedI
Ca,L in all cases. Addition of 50 μM GTPγS to the micropipette solution caused a marked and slowly developing increase inI
Ca,L. 8-Bromo-cAMP (1 μM) increasedI
Ca,L by 30%, both in the control and during the action of GTPγS. The blockade of PKC by 10 μM chelerythrine removed the effect
of GTPγS onI
Ca,L. The results suggest that basal activity of L-type calcium channels in SMC of the guinea pigtaenia coli depends on PKC- and PKA-dependent phosphorylation. PKC can increase theI
Ca,L amplitude provided G proteins are activated. cAMP at low concentrations likewise increasesI
Ca,L (probably through activation of PKA). PKG apparently mediatesI
Ca,L drops evoked by cAMP at high concentrations and by cGMP. 相似文献
10.
D.B. Light M.R. Adler J.K. Ter Beest S.A. Botsford R.T. Gronau 《The Journal of membrane biology》1998,166(2):119-132
This study examined whether protein kinase C (PKC) stimulates K+ efflux during regulatory volume decrease (RVD) in Necturus maculosus (mudpuppy) red blood cells (RBCs). The limit of osmotic fragility increased with the general protein kinase inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine
(H-7, 10 μm), but not with the cyclic nucleotide-dependent kinase antagonists N-(2′-guanidinoethyl)-5-isoquinolinesulfonamide (HA-1004,
10 μm) and N-2-(methylamino)ethyl-5-isoquinoline-sulfonamide (H-8, 5 μm). Consistent with these results, osmotic fragility also increased with the PKC antagonists bisindolylmaleimide I (GF-109203X
or bis I, 100 nm), bisindolylmaleimide II (bis II, 100 nm), and chelerythrine (10 μm). The effect of these three antagonists and H-7 was reversed with gramicidin (5 μm in a choline Ringer), indicating PKC was linked to K+ efflux (gramicidin is a cationophore that was used to ensure a high K+ permeability). We also measured cell volume recovery from hypotonic shock (0.5× Ringer) with a Coulter counter and estimated
cell volume from the hematocrit. The percent RVD compared to control decreased with H-7 (10 μm), sphingosine (100 nm), chelerythrine (10 μm), bis I (100 nm), and bis II (100 nm), but not with HA-1004 (10 μm) nor H-8 (5 μm). Inhibition of RVD by H-7, chelerythrine, bis I, and bis II was reversed with gramicidin (5 μm). Furthermore, using the patch clamp technique, we found H-7 (10 μm) reduced a whole cell conductance that was activated during cell swelling. In addition, a conductance responsible for K+ efflux during cell swelling was inhibited by bis I (100 nm) and bis II (100 nm). These results indicate that a conductive pathway mediating K+ loss during RVD is regulated, at least in part, by protein kinase C.
Received: 20 January 1998/Revised: 2 September 1998 相似文献
11.
In experiments on transversal slices of the dorsal hippocampus of rats, we found that low-frequency stimulation of the mossy
fibers (MF) against the background of pre-settled long-term post-tetanic potentiation in the MF-CA3 pyramidal neuron (PN) dendrites synaptic system evoked depotentiation in all studied slices. Depotentiation was considerably
decreased by a non-competitive blocker of the NMDA glutamate receptors, ketamine (100 μM), as well as by an inhibitor of calmodulin,
trifluoroperazine (10 μM), and an inhibitor of calcineurin, cyclosporin A (250 μM). At the same time, depontentiation was
not changed by 50 μM polymixin B, an inhibitor of protein kinase C. Long-term potentiation of synaptic transmission in the
Schaffer collaterals (SchC)-CA1 PN dendrites system, which was evoked by 2.5-min-long anoxia/aglycemia episodes, resulted exclusively from enhancement of
the NMDA component of population EPSP, while their AMPA component was not modified, i.e., in this case potentiation was of
a postsynaptic nature. Under these conditions, low-frequency stimulation of SchC resulted in a further increase in the intensity
of synaptic transmission due to increases in both the NMDA and AMPA components of population EPSP. The above form of potentiation
could be suppressed by 100 μM ketamine, 10 μM trifuoroperazine, 250 μM cyclosporin A, or 10 μM N-nitro-L-arginine. Weak (near-threshold)
high-frequency stimulation of SchC induced long-lasting potentiation of synaptic transmission due to an isolated increase
in the AMPA component of population EPSP, i.e., this potentiation was of a postsynaptic nature. In the latter case, low-frequency
SchC stimulation resulted in further facilitation of synaptic transmission. Intensive tetanic high-frequency stimulation of
the above fibers induced long-term potentiation of a presynaptic nature, while their low-frequency stimulation depotentiated
synaptic transmission. 相似文献
12.
Xiaohong Liu Junwei Zeng Yandong Zhao Zhi Xiao Chuanqing Fang Huaizhen Ruan 《Neurochemical research》2010,35(5):804-810
In addition to the classic genomic effects, it is well known that glucocorticoids also have rapid, nongenomic effects on neurons.
In the present study, the effect of corticosterone (CORT) on ATP-induced Ca2+ mobilization in cultured dorsal root ganglion (DRG) neurons were detected with confocal laser scanning microscopy using fluo-4/AM
as a calcium fluorescent indicator that could monitor real-time alterations of intracellular calcium concentration ([Ca2+]i). ATP, an algesic agent, caused [Ca2+]i increase in DRG neurons by activation of P2X receptor. Pretreatment with CORT (1 nM–1 μM for 5 min) inhibited ATP-induced
[Ca2+]i increase in DRG neurons. The rapid inhibition of ATP-induced Ca2+ response by CORT was concentration-dependent, reversible and could be blocked by glucocorticoid receptor antagonist RU38486
(10 μM). Furthermore, the inhibitory effect of CORT was abolished by protein kinase A inhibitor H89 (10 μM), but was not influenced
by protein kinase C inhibitor Chelerythrine chloride (10 μM). On the other hand, membrane-impermeable bovine serum albumin-conjugated
corticosterone had no effect on ATP-induced [Ca2+]i transients. These observations suggest that a nongenomic pathways may be involved in the effect of CORT on ATP-induced
[Ca2+]i transients in cultured DRG neurons. 相似文献
13.
Brian Christensen Sridevy Sriskandarajah Margrethe Serek Renate Müller 《Plant Cell, Tissue and Organ Culture》2008,93(2):151-161
Some factors influencing in vitro cultures of potted Hibiscus rosa-sinensis L. using nodal cuttings were investigated. A protocol using a modified MS medium helped to overcome chlorosis, shoot tip necrosis
(STN) and leaf drop. These disorders have been caused by mineral imbalance associated with calcium and iron deficiency. STN
and leaf drop were overcome by increasing calcium level from 3 mM (MS standard concentration) to 9 mM, and this increase,
in addition, enhanced shoot dry weight and shoot extension. The chlorophyll content and leaf area increased by increasing
the iron concentration 3-fold from 98 μM to 295 μM. Furthermore, substituting Fe-EDTA with Fe-EDDHA resulted in an increase
in chlorophyll content, leaf area and shoot extension. The most suitable multiplication medium for H. rosa-sinensis L. was demonstrated to be a modified MS medium containing 2.2 μM BAP and increased concentrations of calcium at 9 mM and
iron at 295 μM provided as Fe-EDDHA. The shoots were rooted in half-strength modified MS medium containing 2.7 μM NAA. Acclimatization
was successful with all shoots with or without roots. 相似文献
14.
Dell'Aquila ME Casavola V Reshkin SJ Albrizio M Guerra L Maritato F Minoia P 《Molecular reproduction and development》2002,63(2):210-222
Bovine cumulus-oocyte complexes (COCs) and mural granulosa cells express the mRNA coding for the micro-opioid receptor. The addition of beta-endorphin (beta-end) to oocytes cultured in hormonally-supplemented in vitro maturation (IVM) medium had no effect on the rates of oocytes reaching the metaphase II (MII) stage, but significantly decreased the maturation rate (P < 0.05) and arrested oocytes at metaphase I (MI) after culture in hormone-free medium (P < 0.001). Naloxone (Nx) reverted this inhibitory effect of beta-end. Moreover, Nx "per se" showed a dose-dependent dual effect. When added at high concentration (10 x (-3) M), it significantly reduced the rate of oocytes in MII (P < 0.001), thus increasing the rate of oocytes arrested in MI. However, Nx added at low concentration (10 x (-8) M) significantly increased oocyte maturation (P < 0.001). High concentration of Nx induced an increase in both intracellular calcium concentration ([Ca(2+)](i)) and in the activity of the mitogen-activated protein kinase (MAPK) also called extracellular-regulated kinase (ERK) in cumulus cells of bovine COCs. Blocking the rise in [Ca(2+)](i) with the calcium chelator acetoxymethylester-derived form of bis (o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) reversed the Nx-dependent inhibition of meiotic maturation observed at high Nx concentrations. Whereas blocking ERK with the MAPK/ERK kinase (MEK) inhibitor, PD98059, had no effect on this process. Therefore, we concluded that the mocro-opioid receptor, by inducing [Ca(2+)](i) increase, participates in the cumulus-oocyte coupled signaling associated with oocyte maturation. 相似文献
15.
Iliyana V. Sazdova Bilyana M. Ilieva Ignat B. Minkov Rudolf Schubert Hristo S. Gagov 《Central European Journal of Biology》2009,4(3):327-334
The aim of this study is to investigate the mechanism of positive inotropic effect of obestatin on in vitro heart preparations of Rana ridibunda frog. The application of increasing amounts of obestatin in the concentration range from 1 μmol/l to 1 μmol/l significantly
enhances the force of contraction of excised and cannulated frog hearts. This effect was partially reduced in the presence
of prazosin (3 μmol/l). Propranolol (30 μmol/l), pertussis toxin (2 ng/ml) and the specific inhibitor of cAMP-dependent protein
kinase (PKA) Rp-adenosine 3′,5′-cyclic monophosphothioate triethylamine (30 μmol/l) completely blocked the obestatin-induced
increase of the force of frog heart contractions. It is concluded that, via its receptor molecule, obestatin activates neuronal pertussis toxin sensitive G-protein(s) that further enhance the secretion
of epinephrine from sympathetic neurons. This epinephrine activates mainly the myocardial β-adrenoreceptors and PKA downstream
targets, and is responsible for the observed positive inotropic effect of obestatin. An alternative explanation of our data
is that obestatin directly enhances the effect of myocardial β-adrenergic signaling. 相似文献
16.
We investigated the effects of selenium (Se) deficiency on differentiation, protein degradation, and cell lysis in cultured
skeletal muscle cells, using L8 rat skeletal muscle cells cultured in serum-free (SF) medium to induce differentiation and
to maintain myotubes. Creatine kinase activity was reduced (p < 0.05) by approximately 15% without Se supplementation for 96 h. Confluent myoblasts were treated with SF media with four
different levels of vitamin E (0,10, 35, and 100 μM) in the absence and presence of Se (0 and 0.25 μM, respectively). After
96 h, vitamin E at a high dose (100 μM) was effective in the prevention of the decrease of differentiation caused by Se deficiency
(p < 0.05). Following differentiation, the effects of three Se concentrations (0, 0.25, and 2.5 μM) on degradation of proteins
as assessed by release of3H-labeled free amino acids secreted into the media were studied. Selenium supplementation did not affect (p > 0.05) total protein degradation. However, Se deficiency increased (p < 0.05) lactate dehydrogenase released from lyzed dead cells. The results indicate that Se is required to maintain an optimal
rate of muscle cell differentiation and health of myotube cultures. 相似文献
17.
I. I. Abramets Yu. V. Kuznetsov I. M. Samoilovich L. Ya. Zin’kovskaya 《Neurophysiology》1999,31(4):227-232
In experiments performed on rat transversial slices of the rat dorsal hippocampus, we found that high-frequency tetanic stimulation
of the mossy fibers (MF) and short-term action of 1 μM kainic acid on the slices resulted in long-term potentiation of the
population spikes evoked inCA3 pyramidal neurons by single stimuli applied to the MF. The tetanus-and kainate-induced potentiations of synaptic transmission
were accompanied by a decrease in the degree of paired facilitation at a 50-msec-long interstimulus interval; they were additive,
prevented by 10 μM CNQX, a competitive antagonist of AMPA/kainate receptors, and insensitive to 100 μM ketamine, a noncompetitive
antagonist of NMDA-glutamate receptors. Both types of potentiation were enhanced by 10 μM (1S, 3R)-ACPD, an agonist of metabotropic
glutamate receptors, as well as by 1 μM pyracetam or 50 μM dichlothiazide, substances weakening AMPA/kainate receptor desensitization.
The effects produced by high-frequency tetanic stimulation of the MF and by kainic acid were prevented by 50 μM polymixin
B, a protein kinase C blocker, and weakened by 10 μM trifluoroperazine, a calmodulin inhibitor, or 1 μM pirenzepine, an M1
acetylcholine receptor blocking agent. In total, the above data suggest that the tetanus- and kainate-induced potentiations
of transmission in the synapses formed by the MF and dendrites ofCA3 pyramidal neurons are due to the combined activation of pre-synaptic high-affinity kainate-preferring receptors, located
in the membranes of the MF varicosities, and post-synaptic phosphoinositide metabolism-coupled metabotropic glutamate receptors
and 1 and M1 acetylcholine receptors. This activation results in a significant increase in the activity of epsilon-form protein
kinase C, phosphorylation of protein substrates involved in vesicular glutamate release from the MF varicosities, and long-term
enhancement of presynaptic glutamate release. 相似文献
18.
Hehai Wang Michael L. Looper Zelpha B. Johnson Rick W. Rorie Charles F. RosenkransJr 《In vitro cellular & developmental biology. Animal》2009,45(8):483-489
There is evidence that ergot alkaloids can directly interact with mammalian spermatozoa affecting sperm functions. Ergot alkaloids
exert their toxic or pharmaceutical effects through membrane receptor-mediated activities. This study investigated the signaling
pathways involved in the in vitro inhibitory effects of both ergotamine (ET) and dihydroergotamine (DEHT) on the relative
motility of bovine spermatozoa using specific inhibitors. Motile bovine spermatozoa were prepared using a Percoll gradient
and incubated with ergot alkaloids with and without signaling pathway inhibitors. Co-incubation of ET or DHET with 100 μM
prazosin (alpha 1-adrenergic receptor inhibitor) decreased (p < 0.05) relative motility of spermatozoa when compared with controls. In addition, preincubation of spermatozoa with 10 or
20 μM prazosin and DHET also reduced (p < 0.05) the number of motile spermatozoa. Relative sperm motility (motility of treated spermatozoa normalized to control sperm
motility) was increased (p < 0.05) when co-incubations included ET and yohimbine (alpha 2-adrenergic receptor inhibitor); conversely, co-incubation of
yohimbine (100 μM) and DHET decreased (p < 0.05) the percentage of motile spermatozoa when compared with controls. Pertussis toxin and cholera toxin (effectors of
inhibitory and stimulatory G-proteins, respectively) altered (p < 0.05) relative sperm motility in a concentration dependent manner; however, co-incubation of pertussis or cholera toxin
with ergot alkaloids had no interactive (p = 0.83) effects on the relative motility of spermatozoa. Co-incubation of Rp-cAMP (a membrane-permeable cAMP inhibitor) with
50 μM DHET had no effect (p > 0.05) on relative sperm motility; whereas, the co-incubation of 22.4 or 44.8 μM Rp-cAMP with 50 μM ET increased (p < 0.05) the percentage of motile spermatozoa when compared with 0 or 224 μM Rp-cAMP (49%, 65%, 59%, and 54%, respectively,
for 0, 22.4, 44.8, and 224 μM of Rp-cAMP. An interaction between BAPTA-AM (a chelator of intracellular calcium) and alkaloids
also impacted (p < 0.05) relative sperm motility. Generally, co-incubating spermatozoa with BAPTA-AM and ET increased the percentage of motile
spermatozoa; however, co-incubation with DHET decreased relative sperm motility except with 41 μM BAPTA-AM. Collectively,
these observations suggest that ET and DHET decreased the percentage of motile bovine spermatozoa via alpha adrenergic receptors.
However, the second messenger systems involved with ergot alkaloid inhibition of relative motility of bovine spermatozoa remain
to be elucidated. 相似文献
19.
In in vitro studies on superfused slices obtained from the rat hippocampus and cortex, we found that 50 μM N-methyl-D-aspartate (NMDA)
applied to the slices in the presence of 10 μM glycine for 15 min exerts a significant damaging action to neurons of these
structures. One hour after termination of the action of NMDA, this was manifested in more than a twofold decrease in the synaptic
reactivity of pyramidal neurons of the hippocampal СА1 area and layers II/III of the cerebral cortex. The excitotoxic effect of NMDA was prevented by application of competitive
(D-2-amino-5-phosphonovaleric acid, 50 μM) and noncompetitive (ketamine, 100 μM) blockers of NMDA receptors. A blocker of
glycine-binding sites of NMDA receptors (compound ТСВ 24.15, 10 μM) weakened NMDA-induced damage to the neurons. A competitive
blocker of glutamate АМРА receptors, 6,7-dinitroquinoxaline-2,3-dione (DNQX, 10 μM), and a local anesthetic, lidocaine hydrochloride
(50 μM), did not modify the excitotoxic effect of NMDA. A blocker of voltagedependent L-type calcium channels, verapamil (20
μM), demonstrated some trend to intensification of NMDA excitotoxic action. An inhibitor of tyrosine-protein phosphatases,
sodium vanadate, when i.p. injected into rats in a dose of 15 mg/kg 6 h prior to the electrophysiological experiment, decreased
the damaging action of NMDA. Two-hour-long treatment of cerebral slices with 1 μM genistein, an inhibitor of tyrosine kinases,
weakened the neuroprotective effect of sodium vanadate. Chronic injections (14 days in daily doses of 20 mg/kg) of antidepressants
belonging to different functional classes (imipramine, fluoxetine, and pyrazidol) into rats decreased (similarly to blockers
of NMDA receptors) the excitotoxic action of NMDA receptors. Neuroprotective effects of antidepressants were weakened upon
the action of genistein. We conclude that the neuroprotective activity of antidepressants under conditions of excitotoxic
action of NMDA is mainly determined by an increase in the activity of tyrosine kinases in the cytoplasm and/or neuronal nucleus. 相似文献
20.
Regulation of pharyngeal motility by FMRFamide and related peptides in the medicinal leech, Hirudo medicinalis 总被引:1,自引:0,他引:1
Bruce A. O'Gara P. Leon Brown Deborah Dlugosch Ahmed Kandiel Joanna W. Ku Jamie K. Geier Nicole C. Henggeler Ahlam Abbasi Nicole Kounalakis 《Invertebrate neuroscience : IN》1999,4(1):0041-0053