Concentrations Of A23187 Research Articles

Evaluationof the novel vaginal contraceptive agent PPCM in preclinical studies using sperm hyaluronan binding and acrosome status assays.

BackgroundPolyphenylene carboxymethylene (PPCM) sodium salt is a promising multipurpose technology for prevention of both sexually transmitted infections (STIs) and pregnancy. In preclinical studies, PPCM has demonstrated significant (1) antimicrobial activity against several important viral and bacterial pathogens and (2) contraceptive activity associated with premature acrosome loss.ObjectiveTo further evaluate a vaginal antimicrobial compound as a contraceptive agent in preclinical studies utilizing a repurposed hyaluronan binding assay (HBA).Materials and methodsSemen samples containing either neat semen or washed spermatozoa were treated with increasing concentrations of PPCM or calcium ionophore A23187 (positive control). Sperm inactivation was measured by two methods: (1) double acrosome staining (AS), and (2) a hyaluronan binding assay (HBA®). Percentage of inactivated sperm was compared between untreated control sperm and those treated with PPCM or A23187.ResultsPPCM had a significant (p < 0.05) and dose‐dependent effect on sperm inactivation in both assays, with HBA detecting a higher proportion of inactivated sperm than AS. PPCM did not affect sperm motility and exhibited equivalent responses in the neat and washed samples.DiscussionBoth HBA and AS confirmed that spermatozoa were rapidly inactivated at PPCM concentrations likely present in the vagina under actual use conditions and in a time‐frame comparable to in vivo migration of spermatozoa out of seminal plasma into cervical mucus.ConclusionPPCM vaginal gel may provide contraceptive protection as well as help with STI prevention. HBA may be a sensitive and much needed biomarker for sperm activity in future contraceptive development.

Factors affecting intracellular calcium influx in response to calcium ionophore A23187 in equine sperm.

Exposure to the calcium ionophore A23187 may present a "universal" sperm treatment for IVF, as it bypasses capacitation pathways. However, success in utilizing A23187 is variable, especially in equine spermatozoa. Notably, albumin is used during A23187 treatment but paradoxically is thought to suppress A23187 action. Essentially no critical data are available on the effects of A23187 and albumin concentrations, ratios, or addition protocols on changes in intracellular calcium ([Ca]i ) in any cell type. To determine factors that affect the action of A23187 on [Ca]i in equine and murine spermatozoa. Spermatozoa were loaded with Fluo-4 and changes in fluorescence after A23187 treatment were measured under various conditions using a microplate reader. Concentrations of bovine serum albumin (BSA) and A23187, type of BSA, makeup of A23187stock solutions (i.e., 1° stock (DMSO) or 2° stock made with medium, water or DMSO), order of addition of spermatozoa and A23187, incubation of media before sperm addition, species of spermatozoa, and time of addition of BSA all affected [Ca]i in response to A23187 treatment. In equine spermatozoa already exposed to 10µM A23187, addition of BSA to 33mg/ml to "quench" the A23187 did not affect [Ca]i . When this concentration of BSA was added to spermatozoa exposed to 1µM A23187, [Ca]i in murine spermatozoa returned to baseline, however, equine spermatozoa continued to exhibit increased [Ca]i . Addition of BSA to 33mg/ml to media containing 1µM A23187, prior to addition of spermatozoa, completely inhibited change in [Ca]i in both murine and equine spermatozoa. These results represent some of the first critical data on the effects of albumin and other procedural factors on A23187-induced changes in [Ca]i in any cell type. Our findings help to explain the variability in reported response of spermatozoa to A23187 among species and among laboratories.

139 Effect of protein and calcium ionophore A23187 concentration on hyperactivated motility and acrosome status of stallion sperm

In vitro fertilization does not occur readily in the horse. Fertilization can be achieved using sperm treated with the calcium ionophore A23187 (CaI), but rates are low and variable. In order to fertilize, it is thought that the sperm must show hyperactivated motility and undergo the acrosome reaction. The presence of protein in the media is thought to suppress the effect of CaI, but protein is needed for maintenance of sperm motility. Therefore, the objective of this study was to assess the effect of CaI in the presence or absence of protein on the acrosome and on hyperactivated motility of equine sperm. For this purpose, sperm from 4 stallions were exposed for 10min at 37°C to vehicle or to 1 (C1), 5 (C5) or 10 (C10) μM CaI, with (BSA) or without (N) 7mg mL−1 BSA. The sperm were then washed and incubated at 37°C for 2h. Total and hyperactivated motility were measured by computer-assisted semen analysis. Sperm were considered hyperactivated if curvilinear velocity was &amp;gt;180μm s−1, amplitude of lateral head displacement was &amp;gt;12μm, linearity was &amp;lt;30% and fractal dimension value was &amp;gt;1.3. The percentage of live acrosome-reacted sperm was measured by flow cytometry after staining with propidium iodide and Pisum sativum agglutinin. Data were analysed by repeated-measures 2-way ANOVA. Results were expressed as mean±standard error. Total motility in C5 and C10 treatments was significantly decreased in relation to control (BSA-vehicle) starting at 30min of incubation (35.42±13.57 to 28.20±13.10% v. 71.72±9.21%, respectively; P&amp;lt;0.05). Hyperactivated motility was significantly lower in C10, C5 and N-C1 than in control after 2h of incubation (1.46±0.64v. 3.10±0.58%, respectively). Live acrosome-reacted sperm were significantly higher (P&amp;lt;0.05) for BSA-C5 (14.04±1.99%) and BSA-C10 (14.85±2.52%) than for control (7.50±1.62%) after 2h of incubation. The exposure to sperm of concentrations ≥5μM CaI was associated with loss of motility from 30min of incubation on. However, 2h of incubation after ≥5 μM CaI in the presence of BSA were needed to increase the percentage of live acrosome-reacted sperm. This mismatch between motility and acrosome response helps to clarify the reasons for the variable effect of sperm CaI treatment on equine IVF. Further studies measuring calcium influx and assessing the effect of sperm pre-incubation on CaI response are needed to explore mechanisms for equine in vitro sperm capacitation.

Intracellular Ca2+ threshold reversibly switches flagellar beat off and on.

Sperm motility is essential for fertilization. The asymmetry of flagellar beat in spermatozoa is finely regulated by intracellular calcium concentration ([Ca2+]i). Recently, we demonstrated that the application of high concentrations (10-20 μM) of the Ca2+ ionophore A23187 promotes sperm immobilization after 10 min, and its removal thereafter allows motility recovery, hyperactivation, and fertilization. In addition, the same ionophore treatment overcomes infertility observed in sperm from Catsper1-/-, Slo3-/-, and Adcy10-/-, but not PMCA4-/-, which strongly suggest that regulation of [Ca2+]i is mandatory for sperm motility and hyperactivation. In this study, we found that prior to inducing sperm immobilization, high A23187 concentrations (10 μM) increase flagellar beat. While 5-10 μM A23187 substantially elevates [Ca2+]i and rapidly immobilizes sperm in a few minutes, smaller concentrations (0.5 and 1 μM) provoke smaller [Ca2+]i increases and sperm hyperactivation, confirming that [Ca2+]i increases act as a motility switch. Until now, the [Ca2+]i thresholds that switch motility on and off were not fully understood. To study the relationship between [Ca2+]i and flagellar beating, we developed an automatic tool that allows the simultaneous measurement of these two parameters. Individual spermatozoa were treated with A23187, which is then washed to evaluate [Ca2+]i and flagellar beat recovery using the implemented method. We observe that [Ca2+]i must decrease below a threshold concentration range to facilitate subsequent flagellar beat recovery and sperm motility.

Effect of heparin, caffeine and calcium ionophore A23187 on in vitro induction of the acrosome reaction of fresh ram spermatozoa

Abstract Objective To determine the effect of different concentrations of heparin, caffeine or calcium ionophore and incubation time on motility, hyperactivity (HA) and acrosome reaction (AR) of ram sperm in vitro. Methods Semen samples were collected by artificial vagina from three mature ram. Split fractions (0.1 mL) of the pooled semen were layered under 1 mL of S-TALP medium supplemented with either heparin (10, 25, 50, 75 and 100 μg/mL), caffeine (0.5, 0.75, 1, 2 mg/mL), or calcium ionophore A23187 (0.5, 0.75, 1, 1.55 mM/mL). Individual motility, hyperactivity percentage and acrosomal status were recorded at 0, 1, 2, 3 and 4 h post-incubation for all treatments and control. Moreover, they were examined for ability to fertilize sheep oocyte in vitro. Results Heparin, caffeine and calcium ionophore A23187 at a concentration of 75 μg/mL, 1 mg/mL, and 1.55 mM/mL respectively can be used as a protocol to provide the best results for in vitro cap citation and acrosome reaction in ram. The penetration rates of rate of oocytes inseminated with spermatozoa treated with calcium ionophore A23187, and heparin were higher as compared with caffeine. Moreover, heparin achieved higher fertilization rates but without significant difference with others. Conclusion The best concentration of heparin, caffeine and ionophore A23187 are 75 μg/mL, 1 mg/mL, 1.55 mM/mL for 3, 1, 4 h incubation respectively and can be used for in vitro fertilization in sheep.

Live birth rates and miscarriage rates with the use of calcium ionophore in patients with prior failed or poor fertilization

Live birth rates and miscarriage rates with the use of calcium ionophore in patients with prior failed or poor fertilization

Platelet Apoptosis in Adult Immune Thrombocytopenia. Relationship with Auto-Antibodies, Platelet Function and Treatment

Similarly to nucleated cells, platelet life span is also controlled by an intrinsic apoptotic program that triggers collapse of the mitochondrial inner membrane potential, activation of caspases-3, -8 and -9, phosphatidylserine (PS) externalization and microparticle shedding. The aim of the present study was to investigate platelet apoptosis in adult patients with immune thrombocytopenia (ITP) under different treatment conditions and to search for its relationship with the type of auto-antibody and the platelet-activation status.Twenty-four patients with chronic ITP, age 42 (21-80) years (median and range) diagnosed according to current criteria (Rodeghiero et al, 2009) were included after written informed consent in accordance with the Declaration of Helsinki. The study was approved by the Ethics Committee from Instituto de Investigaciones Medicas Alfredo Lanari. Platelet count was 38x109/L (6-85). Platelet apoptosis was evaluated by phosphatidylserine (PS) exposure on the platelet surface using FITC-conjugated Anexin-V, mitochondrial electrochemical potential changes (ΔΨm) using the cell penetrating lipophilic cationic fluorochrome JC-1, and activated caspase-3 (a-casp3) measured by the cell-penetrating carboxyfluorescein-labelled fluoromethyl ketone tetrapeptide (FAM-DEVD-FMK). These parameters were studied in resting platelets and after stimulation with calcium ionophore (A23187). Platelet activation was evaluated by FITC-PAC-1 binding to activated GPIIb-IIIa and GPIb-IX internalization using PE-CD42b, in resting conditions and after stimulation either with ADP or TRAP. Apoptosis and activation parameters were evaluated by flow cytometry.In resting conditions, platelets from ITP patients showed increased PS expression and a- casp3 and abnormal ΔΨm (table 1). TablePSΔΨma-casp3Patients19.6 (1.9-82.0)31.2 (5.8-92.4)11.3 (1.8-40.9)Controls4.7 (1.9-10.8)10.3 (2.2-27.5)4.3 (1.9-8.2)p (Mann-Whitney)0.002<0.00010.012n212312After stimulation with A23187, ITP platelets had similar levels of PS expression (p=0.305, n=20) and ΔmΨ (p=0.383, n=25) compared to normal controls. However, an increased sensitivity to the apoptotic stimulus was evidenced by elevated levels of a-casp3 at low and high A23187 concentrations (1-3 mM, p=0.097; 6-10 mM, p=0.002). Platelet apoptosis was not related to platelet activation, as PAC-1 binding was not increased in ITP platelets (basal p=0.847, ADP-induced p=0.059, TRAP-induced p=0.103, n=16). Besides, internalization of GPIb-IX after ADP and TRAP stimulation was also normal (p=NS, n=9 for both agonists). Platelets from ITP patients bearing two of the most frequently found auto-antibodies (5 with anti-GPIIb-IIIa and 1 with anti-GPIb-IX) had similar levels of PS expression and ΔmΨ at resting conditions than those who were negative for these auto-antibodies (n=14) (p=0.265 and 0.148, respectively). There were no differences in apoptosis markers either in resting platelets or after stimulation when comparing untreated patients (n=9) vs patients under any kind of treatment (n=15) (resting conditions, PS p=0.737; ΔmΨ p=0.270; stimulated, PS p=0.966; ΔmΨ p=0.987), although platelet count was similar in both groups. Normal platelets incubated during 1 hour with plasma from ITP had higher a-casp3 than those incubated with normal plasma (n=12 and 9, respectively, p=0.027), suggesting a plasmatic component could be responsible for the apoptotic stimulus.In conclusion, increased platelet apoptosis in ITP patients could be induced by a plasmatic factor, contributing to thrombocytopenia in this entity. DisclosuresRiveros:Roche: Speakers Bureau.

246 USE OF IONOPHORE A23187 ON BOVINE FROZEN SPERM INCREASES HYPERACTIVATED MOTILITY

Sperm capacitation is critical for oocyte fertilization in mammals. The capacitated state is acquired by the spermatozoon during its passage through the female reproductive tract and can be induced in vitro. At a functional level, sperm capacitation is associated with changes in the motility pattern – the hyperactivated state (HA) – and terminates with the acrosome reaction (AR). These events are characteristically regulated by different Ca2+-signalling pathways. For this reason, Ca2+ ionophores, such as A23187, are commonly used in sperm capacitation studies. The induction of AR and IVF, as well as the assessment of protein phosporylation of tyrosine substrates are useful methods for the evaluation of the capacitation state of spermatozoa. Although the increase of protein tyrosine phosphorylation via PKA is associated with sperm capacitation, in the mouse, A23187 capacitates the spermatozoa, thus bypassing this pathway. The aim of the present work was to test the effect of the ionophore A23187 on acquisition of the capacitated state by evaluation of HA motility and protein phosphorylation pattern in frozen bovine spermatozoa. Motile bovine spermatozoa were isolated by gradient centrifugation (Percoll) from frozen/thawed samples and treated with different concentrations of A23187 (0.05, 0.1, 0.2, and 0.3 µM) in H-TYH medium without BSA. After 10 min of treatment, spermatozoa were washed in medium with BSA (11.2%) and incubated in H-TYH with BSA (6%) for 30 min. For control groups, sperm were incubated in H-TYH medium and DMSO. The motility pattern was visually identified and quantified using a computer-assisted sperm analysis system. The motile/immotile spermatozoa and the HA motility patterns of each group were statistically analysed by applying Fisher's tests. The protein tyrosine phosphorylation pattern was evaluated by a Western immunoblotting assay using heparin as a positive control of sperm capacitation. Our results showed that spermatozoa treated with A23187 had a significant increase in HA motility. The proportions of HA spermatozoa were 10.92, 31.27, and 75.4% for 0.1, 0.2, and 0.3 µM A23187, respectively (P &lt; 0.05). On the other hand, the pattern of PKA-tyrosine phoshorylation characteristic of capacitated spermatozoa was absent after incubation with A23187, similar to the response seen in mouse spermatozoa. The percentage of motile spermatozoa in the control groups (H-TYH medium: 36% and DMSO: 27.95%; P &lt; 0.05) was reduced as compared with that of the basal sperm suspension (65.4%, P &lt; 0.05) after 30 to 40 min of incubation. Motility in the spermatozoa treated with 0.1 and 0.2 µM ionophore was similar – 65.9 and 68.1%, respectively, but it was reduced in the 0.3 group – 57.5% (P &lt; 0.05). Thus, treatment with A23187 increased the percentage of spermatozoa with HA motility, probably suggesting an improvement in fertilizing capacity. Nevertheless, these promising results remain to be confirmed by IVF assay.

Acrosome reaction in the epididymal sperm of Chinchilla lanigera. Effect of progesterone, A23187 and stimulation of a GABAA-like receptor.

Little is known about the reproductive biology of Chinchilla lanigera in captivity. Currently there are no parameters to evaluate the quality of the semen of males that are sold as breeding stock, so they are selected according to their phenotypic characteristics, which cannot guarantee their reproductive efficiency. We worked with sexually mature males; the sperm were collected from the cauda epididymis by puncture. Capacitated sperm were incubated at 37 °C with different concentrations of progesterone. The results showed a biphasic behavior, where the increase in the percentage of the acrosome reaction (AR) was significant between 2.5-5 μM, and a maximum response with a dose of 20 μM. Also the suspension of sperm incubated with different concentrations of ionophore A23187 inducing response is obtained with a concentration of 10 μM. Stimulation of the Gamma-aminobutyric acid (GABA)A -like receptor by treating the sperm with different concentrations of muscimol, a specific receptor agonist, also induce acrosome reaction. The dose-response curve showed a biphasic effect with a maximum response at a concentration of 2.5 μM. The pretreatment of sperm suspension with a specific receptor antagonist, picrotoxin, a decrease was observed in the percentage of reacted perm. These studies represent a first step towards the establishment of standard parameters to determine the functionality and fertilizing capacity of Chinchilla sperm. In addition, our results indicate that the Chinchilla spermatozoa can undergo the AR when treated with A23187 or progesterone at high percentages. It also shows a clear involvement of GABAA -like receptors in acrosome exocytosis in sperm obtained by epididymal cauda.

Persistance et voie de l’inhibition de la production de superoxyde par les neutrophiles induite par isoflurane

Our previous work has demonstrated that treatment with isoflurane has a preconditioning-like inhibitory effect on superoxide production (SOP) by polymorphonuclear neutrophils. The current objectives were to determine persistency of this effect and to clarify where in the signalling pathway this inhibition of SOP occurred. The latter was accomplished using two receptor-dependent neutrophil agonists, platelet activating factor (PAF) and formyl-methionyl-leucyl-phenylalanine (fMLP), and two receptor-independent neutrophil stimuli, the protein-kinase C stimulator, phorbol myristate acetate (PMA), and the calcium ionophore, A23187. Arterial blood samples were obtained from eight dogs under baseline condition (conscious state), during isoflurane (1 MAC) administration, and 24 and 48 hr post-isoflurane (also in conscious state). Neutrophils were isolated and stimulated with 1 muM concentrations of PAF, fMLP, PMA, and A23187. SOP was measured spectrophotometrically. Isoflurane administration caused (1) an approximate 50% decrease in SOP during PAF or fMLP (P < 0.01 vs baseline), which remained evident from 24 to 48 hr following isoflurane; (2) an initial 29% decrease in SOP during PMA (P < 0.05 vs baseline), which returned to baseline by 24 hr following isoflurane; and (3) no change in SOP during A23187 (P > 0.05 vs baseline). Isoflurane administration caused prolonged (from 24 to 48 hr) decreases in agonist-induced SOP by neutrophils. This effect involved inhibition at site(s) in the signalling pathway upstream from protein kinase C. The current findings suggest that the intraoperative use of isoflurane may result in an extended impairment to the antibacterial host defense mechanism and that neutrophil inhibition may play a role in the delayed tissue protection afforded by treatment with volatile anesthetics.

Effect of Transient and Permanent Permeability Transition Pore Opening on NAD(P)H Localization in Intact Cells

To study the effect of mitochondrial permeability transition pore (PTP) opening on NAD(P)H localization, intact cells were exposed to the Ca(2+) ionophore A23187. PTP opening, mitochondrial membrane potential, mitochondrial volume, and NAD(P)H localization were assessed by time-lapse laser confocal microscopy using the calcein-cobalt technique, tetramethylrhodamine methyl ester, MitoTracker, and NAD(P)H autofluorescence, respectively. Concomitant with PTP opening, NAD(P)H fluorescence increased outside mitochondria. These events occurred in all cells and were prevented by cyclosporin A. Mitochondrial membrane potential was not systematically collapsed, whereas mitochondrial volume did not change, confirming that A23187 induced transient PTP opening in a subpopulation of cells and suggesting that mitochondrial swelling did not immediately occur after PTP opening in intact cells. NAD(P)H autofluorescence remained elevated after PTP opening, particularly after membrane potential had been collapsed by an uncoupler. Extraction of nucleotide for NAD(P)H quantification confirmed that PTP opening led to an increase in NAD(P)H content. Because the oxygen consumption rate decreased, whereas the lactate/pyruvate ratio increased after PTP opening in intact cells, we conclude that PTP opening inhibits respiration and dramatically affects the cytosolic redox potential in intact cells.

Translation Regulation by Eukaryotic Initiation Factor-2 Kinases in the Development of Latent Cysts in Toxoplasma gondii

A key problem in the treatment of numerous pathogenic eukaryotes centers on their development into latent forms during stress. For example, the opportunistic protist Toxoplasma gondii converts to latent cysts (bradyzoites) responsible for recrudescence of disease. We report that Toxoplasma eukaryotic initiation factor-2alpha (TgIF2alpha) is phosphorylated during stress and establish that protozoan parasites utilize translation control to modulate gene expression during development. Importantly, TgIF2alpha remains phosphorylated in bradyzoites, explaining how these cells maintain their quiescent state. Furthermore, we have characterized novel eIF2 kinases; one in the endoplasmic reticulum and a likely regulator of the unfolded protein response (TgIF2K-A) and another that is a probable responder to cytoplasmic stresses (TgIF2K-B). Significantly, our data suggest that 1) the regulation of protein translation through eIF2 kinases is associated with development, 2) eIF2alpha phosphorylation is employed by cells to maintain a latent state, and 3) endoplasmic reticulum and cytoplasmic stress responses evolved in eukaryotic cells before the early diverging Apicomplexa. Given its importance to pathogenesis, eIF2 kinase-mediated stress responses may provide opportunities for novel therapeutics.

Effects of dehydroepiandrosterone on aldosterone release in rat zona glomerulosa cells

The present study was to investigate the effects and action mechanisms of dehydroepiandrosterone (DHEA) on steroidogenesis in rat adrenal zona glomerulosa cells (ZG). ZG cells were incubated with DHEA in the presence or absence of angiotensin II (AngII), a high concentration of potassium, 8-Br-cAMP, forskolin, 25-OH-cholesterol, pregnenolone, progesterone, deoxycorticosterone, corticosterone, A23187, or cyclopiazonic acid (CPA) at 37 degrees C for 1 h. The concentration of aldosterone or pregnenolone in the culture medium was then measured by radioimmunoassay (RIA). The cells were used to determine the cellular cAMP content. The data demonstrated that: (1) DHEA inhibited AngII-, high concentration of KCl-, forskolin-, 8-Br-cAMP-, 25-OH-cholesterol-, pregnenolone-, progesterone-, deoxycorticosterone-, corticosterone-, A23187-, or CPA-stimulated aldosterone release; (2) DHEA increased 25-OH-cholesterol-stimulated pregnenolone release but not when 25-OH-cholesterol was combined with trilostane; (3) DHEA noncompetitively inhibited aldosterone synthase but showed uncompetitive inhibition of P450scc. These results suggest that DHEA acts directly on rat ZG cells to diminish aldosterone secretion by inhibition of a post-cAMP pathway or by acting on intracellular Ca2+ mobilization. In addition it affects the function of post-P450scc steroidogenic enzymes.

Differential regulation of platelet aggregation and aminophospholipid exposure by calpain

Aggregation, exposure of procoagulant phospholipids and shedding of microparticles are platelet responses that depend on activating conditions. To determine how these different responses are interconnected, we simultaneously measured fibrinogen (Fg) binding and aminophospholipid exposure on activated platelets by means of flow cytometry. Low calcium ionophore (A23187) concentrations induced Fg binding but not annexin V binding. In contrast, high A23187 concentrations induced annexin V binding but not Fg binding. Collagen, both alone and in the presence of thrombin, induced both Fg and annexin V binding. Dual labelling was found on 38 +/- 9% of platelets stimulated by thrombin plus collagen. The regulatory role of calpain in these platelet functions was investigated. When calpain was partially inhibited by 2 microg/ml calpeptin, Fg binding still occurred but aminophospholipid exposure was limited. By contrast, complete inhibition of calpain by 100 microg/ml calpeptin or E64d decreased Fg binding but enhanced aminophospholipid exposure. In these latter conditions, cytosolic calcium-extruding systems were inhibited. The results suggest that (i) conditions that favour aminophospholipid exposure tend to decrease the aggregation process and (ii) calpain determines the switch to either aggregation or aminophospholipid exposure by controlling intracellular calcium.

Protease-Activated Receptor-2 Activation: A Major Role in the Pathogenesis of Porphyromonas gingivalis Infection

Protease-Activated Receptor-2 Activation: A Major Role in the Pathogenesis of Porphyromonas gingivalis Infection

Inhibitory effects of calcium ionophore pretreatment of porcine oocytes on polyspermic fertilization

The present study examined the inhibitory effects of various pretreatment concentrations (0-100 microM) of the calcium ionophore A23187 on polyspermic fertilization and then examined the effect of the maturation period and the time between calcium ionophore treatment and fertilization on the inhibitory effect of calcium ionophore on polyspermic fertilization. In experiment 1, a high concentration of calcium ionophore (100 microM) increased the rate of activated oocytes, but the rate of fertilization declined. On the other hand, when oocytes were treated with a low concentration of calcium ionophore (10 microM), monospermic fertilization was significantly increased (10 microM; 31.3%) (p < 0.05). In experiment 2, oocytes were cultured for various times (0, 0.5, 3, 6 h) after calcium ionophore treatment (10 microM) before fertilization. The highest rate of monospermic fertilization was detected in the oocytes cultured for 6 h after calcium ionophore treatment before fertilization. In experiments 3 and 4, we examined the effect of the maturation period (40 h or 44 h) on the rate of fertilization and blastulation of oocytes pretreated with calcium ionophore. The treatment of oocytes with calcium ionophore significantly decreased the rate of polyspermic fertilization regardless of the maturation period (44 h: with calcium ionophore 26.25% vs without 78.8%; 40 h: with calcium ionophore 37.5% vs without 77.5%); however, calcium ionophore treatment increased the rates of monospermic fertilization and blastulation of the oocytes matured for 44 h, but not those matured for 40 h. In conclusion, activation with a low concentration of calcium ionophore (10 microM) and a further 6 h of culture before fertilization improved the rate of monospermic fertilization and blastulation.

Intracellular calcium changes trigger connexin 32 hemichannel opening

Connexin hemichannels have been proposed as a diffusion pathway for the release of extracellular messengers like ATP and others, based on connexin expression models and inhibition by gap junction blockers. Hemichannels are opened by various experimental stimuli, but the physiological intracellular triggers are currently not known. We investigated the hypothesis that an increase of cytoplasmic calcium concentration ([Ca2+]i) triggers hemichannel opening, making use of peptides that are identical to a short amino-acid sequence on the connexin subunit to specifically block hemichannels, but not gap junction channels. Our work performed on connexin 32 (Cx32)-expressing cells showed that an increase in [Ca2+]i triggers ATP release and dye uptake that is dependent on Cx32 expression, blocked by Cx32 (but not Cx43) mimetic peptides and a calmodulin antagonist, and critically dependent on [Ca2+]i elevation within a window situated around 500 nM. Our results indicate that [Ca2+]i elevation triggers hemichannel opening, and suggest that these channels are under physiological control.

Optimization of assay conditions for leukotriene B 4 synthesis by neutrophils or platelets isolated from peripheral blood of monogastric animals

Neutrophils are involved in inflammation through leukotriene (LT) production. The predominant proinflammatory leukotriene released from neutrophils is LTB 4, which serves as a biological marker of inflammation. The purpose of this study was to optimize the conditions ex vivo for LTB 4 production by neutrophils from horses and dogs, and platelets from chickens. Optimal production of LTB 4 was characterized by incubation time (2.5, 5, 10, 15 or 20 min), temperature (25 or 37 °C), and calcium ionophore A23187 concentration (0.1, 1, 10 or 20 μM). Incubation longer than 2.5 min did not increase production of LTB 4 in chickens or horses; in dogs, incubation for 2.5 and 10 min resulted in the highest concentrations of LTB 4 ( P ⩽ 0.05 ). In all species, incubation at 37 °C resulted in optimal LTB 4 production ( P ⩽ 0.05 ). Production of LTB 4 was highest when neutrophils or platelets were stimulated with 20 μM calcium ionophore in all species ( P ⩽ 0.05 ). These results indicate that neutrophils isolated from horses and dogs, and platelets isolated from chickens, are capable of producing LTB 4. Optimum conditions for LTB 4 production are similar in all three species.

Effect of Cleome arabica leaf extract, rutin and quercetin on soybean lipoxygenase activity and on generation of inflammatory eicosanoids by human neutrophils

The effects of Cleome arabica leaf extract, rutin and quercetin on soybean lipoxygenase (Lox) activity and on calcium ionophore (A23187)-stimulated generation of the leukotriene B 4 and prostaglandin E 2 by human neutrophils were examined. The extract (25 μg/ml), rutin (25 μM) and quercetin (25 μM) inhibited LTB 4 synthesis at all concentrations of A23187 used. The extract at 1–100 μg/ml and rutin at 1–100 μM inhibited LTB 4 generation by neutrophils stimulated with 1 μM A23187 by about 50%. PGE 2 production in response to different concentrations of A23187 was affected in a biphasic manner by the extract and rutin. Quercetin at 1–100 μM caused concentration-dependent inhibition of LTB 4 and PGE 2 production. The extract, rutin and quercetin caused concentration-dependent inhibition of soybean Lox activity. These results indicate that rutin, quercetin and an extract of C. arabica containing these compounds inhibit Lox activity, consequently decreasing LTB 4 production. Thus, these compounds or extracts containing them may be beneficial for the treatment of inflammatory conditions, particularly those characterised by excessive leukotriene generation.

Gene transfer of extracellular superoxide dismutase improves relaxation of aorta after treatment with endotoxin.

Lipopolysaccharide (LPS) impairs vascular function, in part by generation of reactive oxygen species. One goal of this study was to determine whether gene transfer of extracellular SOD (ECSOD) improves vascular responsiveness in LPS-treated rats. A second goal was to determine whether effects of ECSOD are dependent on the heparin-binding domain of the enzyme, which facilitates binding of ECSOD to the outside of cells. Adenoviruses containing ECSOD (AdECSOD), ECSOD with deletion of its heparin-binding domain (AdECSOD-HBD), or a control virus (AdLacZ) were injected intravenously into rats. Three days later, vehicle or LPS (10 mg/kg ip) was injected. After 24 h, vascular reactivity was examined in aortic rings in vitro. Maximum relaxation to acetylcholine was 95 +/- 1% (means +/- SE) after AdlacZ plus vehicle and 77 +/- 3% after AdlacZ plus LPS (P < 0.05). Responses to calcium ionophore A-23187 and submaximal concentrations of nitroprusside also were impaired by LPS. Gene transfer of ECSOD, but not AdECSOD-HBD, improved (P < 0.05) relaxation to acetylcholine and A-23187 after LPS. Maximum relaxation to acetylcholine was 88 +/- 3% after LPS plus AdECSOD. Superoxide was increased in aorta after LPS, and the levels were reduced after AdECSOD but not AdECSOD-HBD. LPS-induced adhesion of leukocytes to aortic endothelium was reduced by AdECSOD but not by AdECSOD-HBD. We conclude that after gene transfer in vivo, binding of ECSOD to arteries effectively decreases the numbers of adherent leukocytes and levels of superoxide and improves impaired endothelium-dependent relaxation produced by LPS.