Altered expression of phospholipase D1 in spontaneously hypertensive rats

To clarify the involvement of phospholipase D (PLD) in the mechanism underlying genetically-induced hypertension, we investigated the activity and expression levels of PLD in tissues taken from spontaneously hypertensive rats (SHR), and their normotensive controls, Wistar-Kyoto rats (WKY). The ADP-ribosylation factor 3 (ARF3)-dependent PLD activity and protein levels of PLD1 from SHR increased significantly in the brain and liver, but not in the heart and kidney, compared to those of WKY. The activity and expression of PLD were the same between the homogenated whole kidneys of the two strains; however, there were topographical differences in the expression and activity of PLD between the kidneys of the two strains. The activity and expression level of PLD gradually increased from the cortex to the inner medulla of WKY. The enzyme activity, and amount of PLD in the inner stripe of the outer medulla and in the inner medulla, was significantly lower in SHR than in WKY. Taken together, these results suggest that the distinctly distributed patterns of PLD in the kidney may be associated with differential signal transduction pathways that are involved in hypertension in conjunction with an increase of PLD activity in the brain and liver.

The involvement of phospholipase A(2) in ethanol-induced gastric muscle contraction

To understand the underlying mechanism of ethanol in tonic contraction, the effect of ethanol on phospholipase A(2) and phospholipase C activities and the effects of phospholipase inhibitors on ethanol-induced contraction of cat gastric smooth muscle were tested. Circular muscle strips (2.0 x 0.2 cm) obtained from the fundus of cat stomach were used to measure isometric contraction. Ethanol elicited tonic contraction and activated phospholipase A(2) activity in a dose-dependent manner. Phospholipase A(2) inhibitors, manoalide (0.1--10 microM) and oleyloxyethyl phosphorylcholine (1--10 microM), significantly inhibited ethanol-induced contraction. Furthermore, 342 mM ethanol-induced contraction was significantly inhibited by cyclooxygenase inhibitors, ibuprofen (10--100 microM) and indomethacin (10--100 microM), but not by lipoxygenase inhibitors. On the other hand, phospholipase C inhibitors had no effect on ethanol-induced contraction, indicating that phospholipase C is not involved in ethanol-induced contraction. It is suggested from the above results that ethanol-induced contraction in cat gastric smooth muscle is, in part, mediated by phospholipase A(2) and cyclooxygenase pathways.

Distributional patterns of phospholipase C isozymes in rat pancreas

Phospholipase C (PLC) isozymes are believed to play a role in regulating pancreatic exocrine and endocrine secretion. In an attempt to investigate the role of PLC, we examined the distribution patterns of PLC isozymes in the normal rat pancreas by Western blot analysis and immunohistochemistry. Western blot analysis was performed on pancreatic acinar tissues and the islet of Langerhans, which were separated from each other. PLC-beta isozymes (beta1, beta2, beta3, and beta4), delta1, and delta2 were detected in both acinar and islet cells, whereas PLC-gamma1 and gamma2 were observed only in acinar tissues. On immunohistochemistry, the immunoreactivities of PLC isozymes except for PLC-gamma1 were observed as follows: PLC-beta1, in both the exocrine and endocrine tissues; PLC-beta2, mainly in the periphery of the islet and acinar cells; PLC-beta3, in the periphery of the islet and in some ductal epithelium; PLC-beta4, through the islet of Langerhans and ductal epithelium; PLC-gamma1, not detected in pancreatic tissue; PLC-gamma2, mainly in acinar cells; PLC-delta1 and delta2, in the islet and in ductal epithelium. These results suggest that the intrapancreatic site-specific existence of PLC isozymes may modulate pancreatic exocrine and endocrine functions through a PLC-mediated signal transduction.

Involvement of cyclic GMP in nitric-oxide-induced gastric relaxation Comparison of the actions of cyclic GMP and cyclic AMP

BACKGROUND

Smooth muscle relaxation induced by various agents that increase the cellular levels of cyclic nucleotides (cAMP and cGMP) is accompanied by a decrease in intracellular Ca2+ concentration. However, little is known about the differences between the inhibitory effects of cAMP and cGMP on the contraction of smooth muscle.

OBJECTIVE

To compare the effects and underlying mechanisms of cAMP and cGMP on the inhibition of gastric smooth muscle contraction, cyclic nucleotide promoting agents, as well as cell membrane permeable cyclic nucleotides were used.

METHODS

Isometric contraction was measured from circular muscle strips prepared from the fundus of cat stomach in a cylinder-shaped chamber filled with Krebs-Ringer solution (pH 7.4, temperature 36 degrees C) bubbled with 5% CO2 in O2. The level of inositol phosphates (IPs) was measured.

RESULTS

Forskolin and sodium nitroprusside significantly inhibited acetylcholine (ACh)-induced gastric smooth muscle contraction and increased the cellular levels of cAMP and cGMP, respectively. Direct application of 8-Br-cAMP and 8-Br-cGMP also significantly inhibited ACh-induced contraction. Both verapamil and TMB-8 inhibited ACh-induced contraction. The combined inhibitory effect of verapamil and TMB-8 was significantly greater than the effect of either one, separately. Forskolin or sodium nitroprusside similarly augmented the effect of verapamil. However, the inhibitory effect of TMB-8 was augmented only by 8-Br-cGMP or sodium nitroprusside but not by 8-BrcAMP or forskolin. Forskolin and 8-Br-cAMP significantly inhibited the formation of inositol phosphates stimulated by ACh.

CONCLUSIONS

cAMP inhibits the contraction mechanism associated with intracellular Ca2+ mobilization as well as extracellular Ca2+ influx, while cGMP inhibits contraction by inhibiting the mechanism associated with extracellular Ca2+ influx.

Analysis of the interventricular pressure waveform in the moving-actuator total artificial heart

Right and left filling pressures are important parameters in the automatic control of a total artificial heart (TAH) within normal physiologic ranges. Our TAH is composed of a moving actuator, right and left ventricles, and an interventricular space (IVS) enclosed by a semirigid housing. During operation of the TAH, the IVS volume is changed dynamically by the difference between the ejection volume of one ventricle and the inflow volume of the other. We measured the interventricular pressure (IVP) waveform by using a pressure sensor and analyzed the relationship between the IVP and the preload condition. From in vitro and in vivo experiments, we found that the measured filling pressures were linearly related to the negative peak value of the IVP. Additionally, we found that we could use the time interval from actuator start to the positive peak value of the IVP (outflow valve opening) as a useful parameter to estimate the blood filling volume of the diastole ventricle.

Tissue-engineered heart valve leaflets: an effective method for seeding autologous cells on scaffolds

BACKGROUND

A precondition for the successful formation of tissue-engineered heart valves is the generation of a proper matrix on biodegradable scaffolds over a limited period of time. The aim of this study was to find an effective method of seeding autologous cells on these scaffolds to create a new matrix for heart valves.

METHODS

Myofibroblasts and endothelial cells were isolated and cultured from an ovine artery. A synthetic biodegradable scaffold consisting of polyglycolic and polylactic acids was seeded first with the myofibroblasts, then coated with endothelial cells. Three different methods of myofibroblast seeding were compared: I) daily seeding of myofibroblasts (1x10(6)) for ten days and culture for four days; II) seeding of myofibroblasts (1x10(7)) and culture for 14 days with the use of a simple medium; III) seeding of myofibroblasts (1x10(7)) with the use of a medium containing collagen and culture for 14 days. Light and electron microscopic analyses were performed.

RESULTS

The group that used the medium containing collagen showed the best results in terms of seeding efficiency.

CONCLUSION

Seeding autologous cells with a medium containing collagen onto the scaffold showed the largest cell population and might generate the best matrix on the scaffold.

Implantation of one piece biventricular assist device by left thoracotomy in an ovine model

In this report, we describe an operative procedure for our implantable 1 piece biventricular assist device (BiVAD) based on a moving actuator mechanism, using an ovine model. Our implantable BiVAD is a volumetric coupled 1 piece unit including right and left blood sacs and an actuator assembly based on the moving actuator mechanism. The BiVAD was controlled by fixed rate control with 75 bpm for the most part. Both the left and the right full ejection modes with the maximum stroke angle were selected to minimize blood stasis in the blood sacs because of low assist flow condition. Three Corriedale sheep were used for the device implantation by a left thoracotomy incision. Cannulation was successfully performed in all cases. Although exposability of the right atrial appendage varied from animal to animal, the insertion of the cannula was easily performed. The cannulas were connected to the pump-actuator assembly in the preperitoneal pocket. All 3 animals survived the experimental procedure. During implantation of the device, in the 1 month survival animal, pump flow was maintained between 2.0 L/min and 2.5 L/min, mean aortic pressure was 90-110 mm Hg, and mean pulmonary artery pressure was 20-30 mm Hg. The left and right atrial pressure were maintained between 0 and 5 mm Hg. In conclusion, this ovine model for implantation of the 1 piece BiVAD can be an effective alternative for testing in vivo biocompatibility of the device although it needs more consideration for anatomical fittability for future human application.

Cellular distribution of isozymes of protein kinase C in septal olfactory epithelium of mice

To determine the presence of protein kinase C (PKC) isozymes in the septal olfactory epithelium of mice (mSOE), western blotting and immunohistochemistry were performed using antibodies against PKC isozymes. With the exception of PKC-betaI, all of the PKC isozymes were detected in the whole lysate of septal tissue layer and apparent molecular weights for each isoform were found. PKC-alpha, PKC-gamma and PKC-epsilon were detected in the olfactory glandular cells of the lamina propria, and PKC-betaI and PKC-betaII were located in the microvillar cells. Neither novel PKC nor atypical PKC was detected in olfactory glandular cells or microvillar cells, except for PKC-epsilon. PKC-lambda was localized in the mucous layer of the mSOE. Meanwhile, PKC-delta and PKC-xi were distributed in the receptor cells in the mSOE. These data demonstrate the isoform-specific expression of PKC in mSOE and suggest a role for the novel and atypical types of PKC in olfactory transduction.

Phospholipase C, protein kinase C, Ca(2+)/calmodulin-dependent protein kinase II, and tyrosine phosphorylation are involved in carbachol-induced phospholipase D activation in Chinese hamster ovary cells expressing muscarinic acetylcholine receptor of Caenorhabditis elegans

Recently, we have isolated a cDNA encoding a muscarinic acetylcholine receptor (mAChR) from Caenorhabditis elegans. To investigate the regulation of phospholipase D (PLD) signaling via a muscarinic receptor, we generated stable transfected Chinese hamster ovary (CHO) cells that overexpress the mAChR of C. elegans (CHO-GAR-3). Carbachol (CCh) induced inositol phosphate formation and a significantly higher Ca(2+) elevation and stimulated PLD activity through the mAChR; this was insensitive to pertussis toxin, but its activity was abolished by the phospholipase C (PLC) inhibitor U73122. Western blot analysis revealed several apparent tyrosine-phosphorylated protein bands after CCh treatment. The CCh-induced PLD activation and tyrosine phosphorylation were significantly reduced by the protein kinase C (PKC) inhibitor calphostin C and down-regulation of PKC and the tyrosine kinase inhibitor genistein. Moreover, the Ca(2+)-calmodulin-dependent protein kinase II (CaM kinase II) inhibitor KN62, in addition to chelation of extracellular or intracellular Ca(2+) by EGTA and BAPTA/AM, abolished CCh-induced PLD activation and protein tyrosine phosphorylation. Taken together, these results suggest that the PLC/PKC-PLD pathway and the CaM kinase II/tyrosine kinase-PLD pathway are involved in the activation of PLD through mAChRs of C. elegans.

Upregulation of phospholipase D in astrocytes in response to transient forebrain ischemia

Previous in vitro studies using cell cultures or brain slices have demonstrated that phospholipase D (PLD) in the nervous system is involved in the signaling mechanism in response to a variety of agonists. However, little is known about the pathophysiological role of PLD-mediated signaling in the adult brain. We examined the changes in the expression of a PLD isozyme, PLD1, in the adult rat hippocampus, using immunological approaches and an assay for PLD activity after transient forebrain ischemia (four-vessel occlusion model) that results in the selective delayed death of CA1 pyramidal cells and induces reactive astrocytes in the CA1 subfield. In the control hippocampus, PLD1 the level of immunoreactivity was very low. After ischemia, in parallel with the results of Western blot analysis and the PLD activity assay, immunohistochemical analysis of PLD1 demonstrated that the immunoreactive proteins peaked at 7-14 days and were most prominent in the CA1 and the dentate hilar region. The temporal and spatial patterns of immunoreactivity of both PLD1 and glial fibrillary acidic protein (GFAP) were very similar, indicating that reactive astrocytes express PLD1, confirmed by double staining for PLD1 and GFAP. These results demonstrate that reactive astrocytes upregulate PLD in vivo after injury in the adult rat hippocampus.

Direct block by bisindolylmaleimide of rat Kv1.5 expressed in Chinese hamster ovary cells

The interaction of bisindolylmaleimide (BIM), widely used as a specific protein kinase C (PKC) inhibitor, with rat brain Kv1.5 (rKv1.5) channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. BIM (I) and its inactive analog, BIM (V), inhibited rKv1.5 currents at +50 mV in a reversible concentration-dependent manner with an apparent K(d) value of 0.38 and 1.70 microM, respectively. BIM (I) accelerated the decay rate of inactivation of rKv1.5 currents but did not significantly modify the kinetics of current activation. Other specific PKC inhibitors, chelerythrine and PKC 19-36, had no effect on rKv1.5 and did not prevent the inhibitory effect of BIM (I). The inhibition of rKv1.5 by BIM (I) and BIM (V) was highly voltage-dependent between -30 and 0 mV (voltage range of channel opening), suggesting that both drugs interact preferentially with the open state of the channel. The additional inhibition by BIM (I) displayed a voltage dependence (delta = 0.19) in the full activation voltage range positive to 0 mV, but was not shown in BIM (V) (delta = 0). The rate constants of association and dissociation for BIM (I) were 9.63 microM(-1) s(-1) and 5.82 s(-1), respectively. BIM (I) increased the time constant of deactivation of tail currents from 26. 35 to 45.79 ms, resulting in tail crossover phenomenon. BIM (I) had no effect on the voltage dependence of steady-state inactivation. BIM (I) produced use-dependent inhibition of rKv1.5, which was consistent with the slow recovery from inactivation in the presence of drug. These results suggest that BIM (I) directly inhibits rKv1.5 channels in a phosphorylation-independent, and state-, voltage-, time-, and use-dependent manner.

Mechanism of fluoxetine block of cloned voltage-activated potassium channel Kv1.3

The effects of fluoxetine (Prozac), a widely used antidepressant drug, on Kv1.3 stably expressed in Chinese hamster ovary cells were examined using the whole-cell and excised inside-out configurations of the patch-clamp technique. In whole-cell recordings, fluoxetine accelerated the decay rate of inactivation of Kv1.3 and thus decreased the current amplitude at the end of the pulse in a concentration-dependent manner with an IC(50) value of 5.9 microM. The inhibition displayed a weak voltage dependence, increasing at more positive potentials. Neither the activation nor the steady-state inactivation curve was affected by fluoxetine. In addition, fluoxetine reduced the tail current amplitude and slowed the deactivation of the tail current, resulting in a crossover phenomenon. When applied to the internal side of the membrane in inside-out recordings, the inhibition by fluoxetine was much faster and more potent with an IC(50) value of 1.7 microM compared with whole-cell recordings. Norfluoxetine, the major metabolite of fluoxetine, also inhibited Kv1.3 in a concentration-dependent manner (IC(50) = 1.4 microM) in whole-cell recordings. To check whether the fluoxetine-induced inhibition demonstrated in cloned Kv1.3 could also be observed in native T lymphocytes, the effects of fluoxetine were investigated on human T lymphocytes. Fluoxetine also inhibited outward K(+) current in human T lymphocytes. Our results indicate that fluoxetine produced a concentration- and voltage-dependent inhibition of Kv1.3 that can be interpreted as an open channel block and that a binding site for fluoxetine is more accessible from the intracellular side.

Molecular cloning and expression analysis of a mouse phospholipase C-delta1

We describe here the molecular cloning and expression analysis of mouse PLC-delta1 (mPLC-delta1), a key enzyme in cell signal transduction. A mouse brain cDNA library was screened in order to isolate the mPLC-delta1 cDNA. The mPLC-delta1 cDNA was 2660 bp in length. The predicted open reading frame encodes a protein of 756 amino acids with an estimated molecular mass of 85 kDa. The deduced amino acid sequence exhibits 96.9% and 92.7% identity with the sequence of rat and human PLC-delta1, respectively. The mPLC-delta1 mRNA was highly expressed in brain, heart, lung, and testis. We found that transcripts of mPLC-delta1 are present in almost all regions of mouse brain examined, implying that the enzyme may play a role in some fundamental cellular process in brain. In male reproductive tract, mPLC-delta1 mRNA was widely expressed in the epididymis as well as in the testis. In situ hybridization studies indicate that distribution of mPLC-delta1 mRNA in mouse testis is discrete and unique. The expression of mPLC-delta1 mRNA was defined in the periphery of each seminiferous tubule, especially in spermatogonia, which might imply that mPLC-delta1 plays a role in proliferation of spermatogonia. To the best our knowledge, this is the first report to demonstrate the high expression of mPLC-delta1 mRNA in spermatogonia of testis. Taken together, these results suggest that mPLC-delta1 may carry out fundamental roles in almost all of mouse tissues, especially in brain and specific roles in testis.

Down-regulation of phospholipase D during differentiation of mouse F9 teratocarcinoma cells

Phospholipase D has been recognized as playing an important role in signal transduction in many types of cells. We investigated the expression of phospholipase D during the differentiation of F9 embryonal teratocarcinoma cells. The ADP ribosylation factor-dependent phospholipase D activity, as measured by an in vitro assay, and H2O2-induced phospholipase D activity and phospholipase D protein content in whole cells were decreased during the differentiation of F9 cells induced by a combination of dibutyryl cyclic AMP and all-trans retinoic acid. In contrast, these changes were not observed when cells were induced by retinoic acid. These results suggest that down-regulation of phospholipase D protein is associated with differentiation of F9 cells to a parietal endoderm lineage.

In vivo experiment leading to clinical application of an electrohydraulic ventricular assist device with magnetic coupling

We developed an electrohydraulic ventricular assist device with magnetic coupling. The integrated system consists of a blood pump, a water conduit for pressure transmission, a bellows type pumping sac, an actuator for transforming the circular motion of a motor to the linear motion of a pusher plate attached to the pumping sac with magnetic coupling, and a controller. The purpose of the coupling was to prevent excessive sucking against the atrial wall. Number 21 Medtronic Hall (Irvine, CA) mechanical valves were used in the inflow and outflow ports of the blood pump. Maximum dynamic stroke volume was 48 ml, and against a mean afterload of 100 mm Hg, maximum pump output was 7 L/min. Chronic in vivo experiments were performed in three sheep, and during these evaluations the system showed no noticeable problems related to mechanical or electronic devices. When left atrial pressure decreased below 0 mm Hg, the magnetic coupling system decoupled the pumping sac and pusher plate with satisfactory reliability. The device was clinically applied in a postoperative patient with chronic dilating cardiomyopathy, and no significant device related problems ensued. These results prove that the electrohydraulic ventricular assist system with magnetic coupling is a suitable ventricular assist device.

Staurosporine directly blocks Kv1.3 channels expressed in Chinese hamster ovary cells

The effects of staurosporine (ST), a widely used protein kinase C (PKC) inhibitor, were examined on Kv1.3 channels stably expressed in Chinese hamster ovary (CHO) cells using the whole-cell and excised inside-out configurations of the patch clamp technique. In whole-cell recordings, ST, at external concentrations from 300 nM to 10 microM, accelerated the rate of inactivation of Kv1.3 currents and thereby reduced the current at the end of the depolarizing pulse in a concentration-dependent manner with an IC50 of 1.2 microM. The actions of ST were unaffected by pretreatment with another selective PKC inhibitor, chelerythrine, or by including the PKC pseudosubstrate peptide inhibitor, PKC 19-36, in the intracellular solution. Rp-cAMPS, a specific protein kinase A inhibitor, included in intracellular solution did not affect the effects of ST. Furthermore, the same effects of ST on Kv1.3 were also observed in excised inside-out patches when applied to the internal face of the membrane. These effects were completely reversible upon washing. Current-voltage relations for Kv1.3 currents at the end of voltage steps indicated that ST reduced Kv1.3 currents over a wide voltage range. The blockade exhibited a shallow voltage dependence between -10 mV and +40 mV, increasing at more positive potentials. ST had no effect on the voltage dependence of steady-state inactivation. It reduced the tail current amplitude and slowed the deactivation time course, resulting in a crossover phenomenon. These results suggest that the action of ST on Kv1.3 is independent of PKC and PKA inhibition. ST blocks the open state of Kv1.3 channels to produce an apparent acceleration of the inactivation rate.

Synaptic corelease of ATP and GABA in cultured spinal neurons

In the spinal dorsal horn (DH), transmission and modulation of peripheral nociceptive (pain-inducing) messages involve classical neurotransmitters and neuropeptides. We show that approximately half of DH neurons use ATP as a fast excitatory neurotransmitter acting at ionotropic P2X postsynaptic receptors. ATP was not codetected with glutamate but was coreleased with the inhibitory neurotransmitter GABA. Moreover, adenosine, probably generated by extracellular metabolism of ATP, finely tuned GABAergic inhibitory postsynaptic currents. Differential modulation of excitatory versus inhibitory components of this mixed cotransmission may help to explain changes in sensory message processing in the DH during mechanical hyperalgesia and neuropathic pain.

Inhibition by fluoxetine of voltage-activated ion channels in rat PC12 cells

The effects of fluoxetine (Prozac) on voltage-activated K+, Ca2+ and Na+ channels were examined using the whole-cell configuration of the patch clamp technique in rat pheochromocytoma (PC12) cells. When applied to the external bath solution, fluoxetine (1, 10, 100 microM) decreased the peak amplitude of K+ currents. The K+ current inhibition by fluoxetine (10 microM) was voltage-independent and the fraction of current inhibition was 39.7-51.3% at all voltages tested (0 to +50 mV). Neither the activation and inactivation curves nor the reversal potential for K+ currents was significantly changed by fluoxetine. The inhibition by fluoxetine of K+ currents was use- and concentration-dependent with an IC50 of 16.0 microM. The inhibition was partially reversible upon washout of fluoxetine. The action of fluoxetine was independent of the protein kinases, because the protein kinase C or A inhibitors (H-7, staurosporine, Rp-cAMPS) did not prevent the inhibition by fluoxetine. Intracellular infusion with GDPbetaS or pretreatment with pertussis toxin did not block the inhibitory effects of fluoxetine. The inhibitory action of fluoxetine was not specific to K+ currents because it also inhibited both Ca2+ (IC50 = 13.4 microM) and Na+ (IC50 = 25.6 microM) currents in a concentration-dependent manner. Our data indicate that when applied to the external side of cells, fluoxetine inhibited voltage-activated K+, Ca2+ and Na+ currents in PC12 cells and its action on K+ currents does not appear to be mediated through protein kinases or G proteins.

Somatostatin potentiates voltage-dependent K+ and Ca2+ channel expression induced by nerve growth factor in PC12 cells

It has been proposed that neurotransmitters and neuromodulators may function as neurotrophic factors during the development of the nervous system. Somatostatin (SS) was known to increase neurite outgrowth in PC12 cells, rat pheochromocytoma cell line, and cerebellar granule cells as well as Helisoma neuron. To further investigate a neurotrophic role of SS, voltage-dependent K+ and Ca2+ channel expression was studied using whole-cell patch-clamp in PC12 cells and the effect of SS was compared to that of nerve growth factor (NGF). Cyclic AMP (cAMP) level and mitogen-activated protein (MAP) kinase phosphorylation were also studied following the treatment with SS and/or NGF. Whereas NGF (50 ng/ml) increased continually the current density of the voltage-dependent K+ channel throughout 8 days treatment, SS (1 microM) increased the K+ current density on day 2 to the peak. K+ current density was decreased thereafter and was not different on day 6 from that of undifferentiated cells. Although SS did not increase voltage-dependent Ca2+ current density, it potentiated NGF-induced increase of voltage-dependent Ca2+ channel current density as well as the K+ current density. cAMP level was decreased by NGF and/or SS treatment. An increased phosphorylation of MAP kinase induced by NGF was not changed by SS treatment. These results support functionally that SS may function as a neurotrophic factor in developing nervous system.

Static state hemodynamic variables estimation model for the moving-actuator type total artificial heart. Part II - Aortic pressure estimation

Aortic pressure (AoP) estimation is a very important study for the artificial heart. In this paper, we developed a AoP estimation model for the moving-actuator type total artificial heart (MH-TAH) that was being developed at Seoul National University Hospital. The proposed model is simple and provides beat-by-beat mean AoP estimation. Moreover, it uses non-invasively acquired signals. Model parameters were adjusted with in vitro data by least mean square (LMS) algorithm. Results showed that the proposed scheme gives a mean estimation error of about 8 (mmHg). This ensures the suitability of the proposed model. The proposed approach can also be applied to the model setup of pulmonary arterial pressure (PAP) estimation by using the symmetric characteristics between AoP and PAP.

Oxytocin modulates glutamatergic synaptic transmission between cultured neonatal spinal cord dorsal horn neurons

The functional characteristics of binding sites for the neuropeptide oxytocin (OT) detected by radioautography in laminae I and II of the dorsal horn (DH) and on cultured neonatal DH neurons were studied on the latter using perforated patch-clamp recordings. The neurons were identified by their spike discharge properties and on the basis of the presence of met-enkephalin-like and glutamate decarboxylase-like immunoreactivities. OT (100 nM) never induced any membrane current at a holding potential of -60 mV but increased the frequency of spontaneously occurring AMPA receptor-mediated EPSCs or the mean amplitude of electrically evoked EPSCs in a subset (35%) of neurons. The frequency of miniature EPSCs (m-EPSCs) recorded in the presence of 0.5 microM tetrodotoxin was also increased by OT (100 nM) without any change in their mean amplitude, indicating an action at a site close to the presynaptic terminal. The decay kinetics of any type of EPSC were never modified by OT. The effect of OT was reproduced by [Thr4, Gly7]-OT (100 nM), a selective OT receptor agonist, and blocked by d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH29]-ornithine vasotocin (100 nM), a specific OT receptor antagonist. Reducing the extracellular Ca2+ concentration from 2.5 to 0.3 mM in the presence of Cd2+ (100 microM) reversibly blocked the effect of OT on m-EPSCs. The OT receptors described here may represent the substrate for modulatory actions of descending hypothalamo-spinal OT-containing pathways on the nociceptive system.

Electrophysiological properties of cultured neonatal rat dorsal horn neurons containing GABA and met-enkephalin-like immunoreactivity

We have developed a culture of neurons dissociated from the most superficial laminae of the neonatal rat spinal cord dorsal horn (DH). By using the perforated patch-clamp technique, we distinguished four types of neurons based on their firing properties in response to intracellular injection of 900 ms lasting current pulses. Type 1 neurons were characterized by a tonic firing. Type 2 neurons displayed marked spike accommodation and fired brief (<500 ms) bursts of action potentials, whereas type 3 neurons fired a single spike. Type 4 neurons exhibited different types of firing patterns, but all of them possessed a time-dependent inwardly rectifying current activated by membrane hyperpolarization. Met-enkephalin-like immunoreactivity (met-ENK-LI) and glutamic acid decarboxylase-like immunoreactivity (GAD-LI) were colocalized in 42% of the neurons (n = 59), which were previously identified electrophysiologically. Type 1-4 neurons represented respectively 4, 64, 20, and 12% of the population of neurons colocalizing met-ENK-LI and GAD-LI. We conclude that the electrophysiological properties of DH neurons present in our cultures are similar to those described in acute slice or hemisected spinal cord preparations and that met-ENK-LI and GABA-LI are preferentially colocalized in type 2 neurons.

Regulation of protein kinases in steady-state contraction of cat gastric smooth muscle

Cat gastric smooth muscle strips were used to investigate the involvement of protein kinases in the steady-state contraction induced by 1 microM acetylcholine or 20 mM KCI. The steady-state contraction induced by acetylcholine or KCl was inhibited by EGTA dose dependently. Voltage-dependent Ca2+ channel antagonists dose dependently inhibited the contractions induced by KCI as well as by acetylcholine. Inhibitory effects of voltage-dependent Ca2+ channel antagonists were significantly more prominent on KCI-induced contractions than on acetylcholine-induced contractions. The acetylcholine-induced contraction was dose dependently inhibited by 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8, a blocker of intracellular Ca2+ release), but the KCl-induced contraction was not inhibited at all. Therefore both intracellular Ca2+ release and extracellular Ca2+ influx seem to be necessary for the acetylcholine-induced contraction, but intracellular Ca2+ release is not necessary for the KCl-induced contraction. Protein kinase C inhibitors, 10 microM 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine 2HCl (H-7) and 1 microM staurosporine, significantly inhibited the contraction induced by acetylcholine or KCl. Calmodulin antagonists, 30 microM trifluoperazine and 50 microM N-(6-aminohexyl)-5-chloro-2-naphthalenesulfonamide HCI (W-7), however, significantly inhibited the contraction induced by acetylcholine but not by KCl. A tyrosine kinase inhibitor, 50 microM genistein, did not affect the acetylcholine-induced contraction but significantly inhibited the KCl-induced contraction. These results strongly suggest that the involvement of protein kinases in regulation of the steady-state contraction may be agonist-dependent.

Electrophysiological characterization of non-NMDA glutamate receptors on cultured intermediate lobe cells of the rat pituitary

Glutamate is the major excitatory neurotransmitter in the central nervous system, yet little is known about its actions on endocrine cells. We have investigated the membrane effects of glutamate in cultured neonatal rat pituitary intermediate lobe (IL) cells using the whole-cell configuration of the patch-clamp technique. In a standard Na(+)-based extracellular solution, glutamate failed to induce a detectable membrane current at a holding potential (HP) of -60 mV (n = 40). However, when cyclothiazide (50 microM), a benzothiazide that blocks desensitization of alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazole-propanoic acid (AMPA)-type receptors, was added to the extracellular solution, glutamate (0.5-1 mM) induced an inward current at a HP of -60 mV in 65% of the cells tested (n = 72). This response was usually small in amplitude (mean amplitude: 28.6 +/- 37.5 pA, n = 47). The glutamate-induced current reversed polarity close to 0 mV and was reversibly blocked when extracellular Na+ was replaced by the impermeant cation N-methyl-D-glucamine, suggesting that this current was a nonselective cation current. The response to glutamate (1 mM) was reproduced by AMPA (50 microM), kainate (200 microM), and quisqualate (200 microM). N-Methyl-D-aspartate (NMDA, 100 microM) in the presence of 10 microM glycine did not induce any membrane current in cells responding to glutamate (n = 8). The non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) reversibly inhibited the response to glutamate (0.5 mM) by 85 +/- 14% (n = 7), whereas D(-)-2-amino-5-phosphonopentanoic acid (20 microM), an antagonist of NMDA receptors, had no effect on the glutamate-induced current (n = 3). Moreover, we show that although the amplitude of the glutamate currents was small, the latter induced large (30-mV) membrane depolarizations and triggered the firing of action potentials. Taken together, our results indicate that neonatal rat IL cells possess AMPA-type glutamate receptors that could possibly underlie a fast excitatory glutamatergic synaptic input to these cells.

Stimulatory role of the dorsal motor nucleus of the vagus in gastrointestinal motility through myoelectromechanical coordination in cats

This study was undertaken to investigate the effect of stimulation of the dorsal motor nucleus of the vagus (DMV) on myoelectric activity and motility of the gastric antrum and duodenum in normal and in vagotomized cats. 37 cats were starved for 24 h and then anesthetized with alpha-chloralose (70-80 mg/kg, iv). Electrical stimulation (0.1 mA, 0.2 ms, 50 Hz) of the left DMV was performed through a stereotaxically inserted electrode in 19 of the cats. The remaining 18 cats were injected in the left DMV with a glutamate solution (1 M, 200 nl) through an inserted 3-barreled micropipette. The myoelectric activity (slow wave) and the motility of the gastric antrum (2 cm proximal to the pylorus) and duodenum (3 cm distal to the pylorus) were measured using serosal bipolar electrodes and intraluminal balloons. Both the electrical and the glutamate stimulations of the DMV markedly increased the occurrence of spike potentials on the antral and duodenal myoelectric activity; however, the stimulations significantly decreased the frequency of the antral slow wave. The stimulations also produced increases in the motility of the antrum and duodenum which corresponded to the changes in the myoelectric activity. All the changes in the myoelectric activity and the motility were not observed after the ipsilateral vagotomy. Thus, these results strongly suggest that the dorsal motor nucleus of the vagus has a stimulatory influence on antral and duodenal motility through myoelectromechanical coordination via the vagus nerve in cats.