Differential expression of VAMP2/synaptobrevin-2 after antidepressant and electroconvulsive treatment in rat frontal cortex

The biological basis for the therapeutic mechanisms of depression is still unknown. We have previously performed expressed-sequence tag (EST) analysis to identify some molecular machinery responsible for antidepressant effect. Then, we developed our original cDNA microarray, on which cDNA fragments identified as antidepressant-related genes/ESTs were spotted. In this study, with this microarray followed by Western blot analysis, we have demonstrated the induction of vesicle-associated membrane protein 2(VAMP2/synaptobrevin-2) in rat frontal cortex not only after chronic antidepressant treatment, but also after repeated electroconvulsive treatment. On the other hand, expression of SNAP-25 and syntaxin-1 was not changed by these treatments. These components make a soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor complex with VAMP2 and mediate the synaptic vesicle docking/fusion machinery. In conclusion, it is suggested that VAMP2/synaptobrevin-2 plays important roles in the antidepressant effects. Our results may contribute to a novel model for the therapeutic mechanism of depression and new molecular targets for the development of therapeutic agents.

Corticotropin-releasing factor as well as opioid and dopamine are involved in tail-pinch-induced food intake of rats

Several kinds of stress such as psychological stress, restraint, and foot shock inhibit feeding behavior through corticotropin-releasing factor (CRF). In contrast, a mild tail pinch increases food intake in rats. Although dopamine and opioid are thought to be involved in tail-pinch-induced food intake, it is unknown whether CRF participates in this phenomenon. Therefore, we attempted to clarify this issue using rats. A 30-s tail pinch increased food intake in 30 min after the tail pinch, and this increase was blocked by intraperitoneal injection of CRF receptor type 1 selective antagonist. CRF increased food intake in 30 min after intracerebroventricular injection at a dose of 2 or 10 ng, and this increase was also blocked by CRF receptor type 1 antagonist. Tail-pinch- or CRF-induced food intake was blocked by naloxone, pimozide, and spiperone. These results suggest that CRF, through CRF receptor type 1 as well as opioid and dopaminergic systems, are involved in the mechanism of tail-pinch-induced food intake. The results also suggest that brain CRF has dual effects on food intake, hyperphagia and anorexia, in a stress-dependent manner.

Changes in calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide in patients undergoing coronary artery bypass grafting

The initiation of cardiopulmonary bypass creates significant derangements in cardiovascular volume status and both endocrine and autonomic nervous system function. To examine whether such derangements might differ in patients with different pre-operative physical status scores, we measured the plasma concentrations of calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide, catecholamines and antidiuretic hormone, as well as haemodynamic variables, during and after cardiopulmonary bypass in 27 consecutive patients undergoing coronary artery bypass grafting. The pre-operative levels of atrial natriuretic peptide and brain natriuretic peptide differed significantly between ASA II patients and III and IV patients [mean (SD) brain natriuretic peptide levels = 14 (8.2) vs. 129 (51) pg.ml-1]. Plasma calcitonin gene-related peptide increased significantly in both groups after the initiation of cardiopulmonary bypass, and remained increased throughout cardiopulmonary bypass. The changes in plasma epinephrine, norepinephrine and antidiuretic hormone were similar to those reported previously. The changes in plasma calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide did not correlate with any changes in haemodynamic variables before or after cardiopulmonary bypass. Measurement of plasma brain natriuretic peptide might usefully be included in the pre-operative evaluation of patients with cardiac disease.

Ketamine, not propofol, attenuates cerebrovascular response to carbon dioxide in humans with isoflurane anesthesia

STUDY OBJECTIVES

To investigate the effects of ketamine and propofol on the cerebrovascular response to carbon dioxide (CO(2)) in humans during isoflurane anesthesia.

DESIGN

Randomized clinical investigation.

SETTINGS

University hospital of a medical school.

PATIENTS

30 ASA physical status I and II adult, elective surgical patients.

INTERVENTIONS AND MEASUREMENTS

With each patient given air/oxygen/isoflurane anesthesia, the flow velocity in the middle cerebral artery (Vmca) and pulsatility index were measured using the transcranial Doppler method under hypocapnic [arterial CO(2)tension (PaCO(2)) 28-32 mmHg], normocapnic (PaCO(2) 38-42 mmHg), and hypercapnic conditions (PaCO(2) 48-52 mmHg). PaCO(2) was altered by supplementing the inspired gas with CO(2) without changing the respiratory conditions. Patients were then randomly assigned to receive either ketamine 1 mg. kg(-1) or propofol (2 mg. kg(-1)followed by an infusion of 6-10 mg. kg(-1). hr(-1)) (n = 15 for each drug), and the measurements were repeated.

MAIN RESULTS

Ketamine reduced both absolute and relative cerebrovascular reactivity to CO(2) significantly [2.9 +/- 0.8 (control) vs. 2.6 +/- 1.0 (ketamine) cm. sec(-1). mmHg(-1): p < 0.05; and 3.5 +/- 0.7 (control) vs. 2.8 +/- 0.9 (ketamine) %. mmHg(-1): p < 0.01, respectively]. However, ketamine did not reduce Vmca during hypercapnic conditions (117 +/- 29 cm. sec(-1)) compared with controls (120 +/- 28 cm. sec(-1)). Although propofol decreased Vmca during all conditions, it did not cause any change in either absolute or relative CO(2) reactivity [2.5 +/- 0.8 (control) vs. 2.5 +/- 1.0 (propofol) cm. sec(-1). mmHg(-1), and 3.3 +/- 1.3 (control) vs. 4.1 +/- 1.0 (propofol) %. mmHg(-1), respectively].

CONCLUSIONS

In humans given isoflurane anesthesia, a) ketamine reduced cerebrovascular response to CO(2), but cerebral blood flow (CBF) during hypercapnic conditions was comparable with controls, and b) although propofol decreases CBF, it maintains the cerebrovascular response to CO(2).

The differential effects of stereoisomers of ropivacaine and bupivacaine on cerebral pial arterioles in dogs

We investigated whether the stereoisomers of ropivacaine and bupivacaine exert differential effects on the cerebral microcirculation. Pentobarbital-anesthetized dogs (n = 16) were prepared for measurement of cerebral pial vessel diameters by using a closed cranial window preparation. We administered three different concentrations (10(-7), 10(-5), and 10(-3) M) of each of three drug solutions [R(+), racemic, and S(-) forms of ropivacaine (n = 8) or bupivacaine (n = 8)] under the window in a randomized manner and measured cerebral pial arteriolar diameters. Various physiologic data were obtained before and after topical application of each test solution. All three forms of ropivacaine constricted cerebral pial arterioles, each in a concentration-dependent manner. The rank order for degree of vasoconstriction was S(-) ropivacaine > racemic ropivacaine > R(+) ropivacaine. In contrast, R(+) and racemic bupivacaine dilated, but S(-) bupivacaine constricted, cerebral pial arterioles, each in a concentration-dependent manner. We could find no difference in vascular reactivity to these drugs between large (> or = microm) and small (<100 microm) arterioles. Topical application of these drugs induced no changes in mean blood pressure or heart rate. The observed differences in the microvascular alterations induced by the stereoisomers of ropivacaine and bupivacaine suggest that the vasoactive effects of these drugs on cerebral arterioles could, at least in part, depend on their chirality.

IMPLICATIONS

The differential effects of the stereoisomers of ropivacaine and bupivacaine on cerebral pial vessels could, at least in part, depend on their chirality.

Lysophosphatidic acid enhances airway response to acetylcholine in guinea pigs

Inhalation of lysophosphatidic acid (LPA, 1-100 microg/ml) for 2 min enhanced the airway response induced by intravenous injection of ACh in guinea pigs. At 30 min after inhalation of LPA, the airway response to ACh was two fold higher than that before inhalation. This enhancement of airway response to ACh was partially inhibited by capsaicin desensitization or bilateral vagotomy. These results suggested that the enhancement of airway response to ACh induced by LPA may be due to the activation of capsaicin-sensitive fibers. It can be also contribute to bronchial asthma or other types of pulmonary disease such as cough variant asthma and atopic cough.

Physiological and pharmacological role of lysophosphatidic acid as modulator in mechanotransduction

The mechanotransduction mechanism is believed to play an important role in maintenance of cellular homeostasis in a wide variety of cell types. In particular, the mechanotransduction system in vascular endothelial cells may be an essential mechanism for local hemodynamic control. Elevations in intracellular free Ca2+ concentration ([Ca2]i) are an important signal in the initial step of mechanotransduction and mechanosensitive (MS) cation channels are thought to be a putative pathway; however, the molecular mechanisms remain unclear. We found that lysophosphatidic acid (LPA), a bioactive phospholipid, sensitizes the response of [Ca2+]i to mechanical stress in several cell types. Employing real-time confocal microscopy, local increases in [Ca2+]i in several regions within the cell during application of mechanical stress were clearly visualized in bovine lens epithelial and endothelial cells in the presence of LPA. The phenomenon was termed "Ca2+ spots". Pharmacological studies revealed that Ca2+ spots arise due to influx through MS channels. In this report, our data indicating the possible significance of LPA as an endogenous factor involved in regulation of mechanotransduction is reviewed. Furthermore, our findings suggest that the Ca2+ spot is a novel phenomenon occurring as an elementary Ca2+-influx event through MS channels directly coupled with the initial step in mechanotransduction.

A mechanism of Ca2+ release from Ca2+ stores coupling to the Na+/Ca2+ exchanger in cultured smooth muscle cells

We previously observed Ca2+ release from intracellular Ca2+ stores caused by reduction in extracellular Na+ concentration ([Na+]o). The purpose of this study was to determine whether lowering [Na+]o can elicit Ca2+ release from Ca2+ stores via the Na+/Ca2+ exchanger and to elucidate the mechanisms related to the Ca2+ release pathway in cultured longitudinal smooth muscle cells obtained from guinea pig ileum. Low [Na+]o-induced Ca2+ release was inhibited by antisense oligodeoxynucleotides for Na+/Ca2+ exchanger type 1 (anti-NCX). Application of anti-NCX to cells attenuated both the number of Ca2+ responding cells and the expression of the exchanger. Moreover, microinjection of heparin, a blocker of inositol 1,4,5-trisphosphate (IP3) receptors, into the cells inhibited low [Na+]o-induced Ca2+ release. These findings suggest that low [Na+]o-induced Ca2+ release occurs through an IP3-induced Ca2+ release mechanism due to changes in the Ca2+ flux regulated by the Na+/Ca2+ exchanger.

Effect of tributyltin chloride on the release of calcium ion from intracellular calcium stores in rat hepatocytes

The effects of tri-n-butyltin chloride (TBT), an environmental pollutant, on the release of Ca(2+) from intracellular stores were investigated in isolated rat hepatocytes. Isolated hepatocytes permeabilized with digitonin were suspended in solution, and the concentration of extracellular Ca(2+) was measured, using a fluorescent Ca(2+) dye, fura-2. In the solution containing permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min, the extracellular Ca(2+) concentration was high, but the inositol 1,4,5-trisphosphate (InsP(3))-induced increase in Ca(2+) concentration was suppressed, suggesting that the extracellular release of Ca(2+) in response to TBT treatment was from intracellular stores. Images of the Ca(2+) concentration in the intracellular stores of primary cultured hepatocytes loaded with fura-2 were obtained after digitonin-permeabilization, using digitalized fluorescence microscopy. The permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min had a very low fura-2 fluorescence ratio (340/380 nm), suggesting that stored Ca(2+) was released. When the hepatocytes were treated with 4.0 microM TBT after digitonin-permeabilization, the decrease in the fura-2 fluorescence ratio was very small. However, when the permeabilized hepatocytes were incubated with 4.0 microM TBT and 2.0 microM NADPH, the decrease was enhanced, raising the possibility that TBT might be metabolized to the active form(s), thus releasing Ca(2+) from intracellular stores. When the hepatocytes were preincubated with 0.1 microM TBT for 30 min and then were permeabilized, the fura-2 fluorescence ratio was almost the same as that in the control permeabilized hepatocytes. However, the InsP(3)-induced decrease in the fluorescence ratio was suppressed significantly in the permeabilized hepatocytes. These results suggest that TBT released Ca(2+) from the intracellular stores at high concentrations, and suppressed the InsP(3)-induced Ca(2+) release at non-toxic low concentrations. It is probable that the latter effect was responsible for the previously reported suppression of Ca(2+) response induced by hormonal stimulations (Kawanish et al., Toxicol Appl Pharmacol 1999;155:54-61).

The effects of topical and intravenous ketamine on cerebral arterioles in dogs receiving pentobarbital or isoflurane anesthesia

To evaluate the effects of ketamine on cerebral arterioles, we used a closed cranial window technique in mechanically ventilated, anesthetized dogs. Fourteen dogs were assigned to one of the following two basal-anesthesia groups: pentobarbital 2 mg. kg(-1). h(-1) or isoflurane 0.5 MAC (n = 7 each). We administered three different concentrations of ketamine (10(-7), 10(-5), and 10(-3) M) under the window and measured arteriolar diameters. For comparison, in another 14 dogs we examined the effect of systemic (IV) ketamine (1 mg/kg and 5 mg/kg) using the same two basal anesthetics. We measured diameters before and after ketamine administration, and we evaluated the effect of ketamine on CO(2) reactivity of the cerebral arterioles. Neither topical nor systemic ketamine dilated pial arterioles in either basal-anesthesia group. CO(2) reactivity of pial arterioles was reduced under systemic ketamine in both basal-anesthesia groups. The results indicate that although ketamine does not dilate pial arteriolar diameters when topically or IV administered, IV ketamine does attenuate hypercapnic vasodilation in dogs under basal pentobarbital or isoflurane anesthesia. These results provide some insight that ketamine is suitable for supplementary neurosurgical anesthesia.

Lysophosphatidic acid positively regulates the fluid flow-induced local Ca(2+) influx in bovine aortic endothelial cells

Using real-time confocal microscopy, we have demonstrated that lysophosphatidic acid (LPA), a bioactive phospholipid existing in plasma, positively regulates fluid flow-induced [Ca(2+)](i) response in fluo 4-loaded, cultured, bovine aortic endothelial cells. The initial increase in [Ca(2+)](i) was localized to a circular area with a diameter of <4 microm and spread concentrically, resulting in a mean global increase in [Ca(2+)](i). The local increase often occurred in a stepwise manner or repetitively during constant flow. The percentage of cells that responded and the averaged level of increase in [Ca(2+)](i) were dependent on both the concentration of LPA (0.1 to 10 micromol/L) and the flow rate (25 to 250 mm/s). The response was inhibited by removing extracellular Ca(2+) or by the application of Gd(3+), an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticular Ca(2+)-ATPASE: It was also inhibited by 8-bromo-cGMP, and the inhibition was completely reversed by KT5823, an inhibitor of protein kinase G (PKG). These results suggest that the [Ca(2+)](i) response arises from Ca(2+) influx through Gd(3+)-sensitive MS channels, which are negatively regulated by the activation of PKG. The spatiotemporal properties of the [Ca(2+)](i) response were completely different from those of a Ca(2+) wave induced by ATP, a Ca(2+)-mobilizing agonist. Therefore, we called the phenomenon Ca(2+) spots. We conclude that LPA positively regulates fluid flow-induced local and oscillatory [Ca(2+)](i) increase, ie, the Ca(2+) spots, in endothelial cells via the activation of elementary Ca(2+) influx through PKG-regulating MS channels. This indicates an important role for LPA as an endogenous factor in fluid flow-induced endothelial function.

Visualization of elementary mechanosensitive Ca2+-influx events, Ca2+ spots, in bovine lens epithelial cells

Local increases in the intracellular Ca2+ concentration ([Ca2+]i) in several regions within the bovine lens epithelial cell during application of mechanical stress were clearly visualized in the presence of lysophosphatidic acid (LPA), a bioactive lysophospholipid, using real-time confocal microscopy. We called the phenomenon 'Ca2+ spots'. Ca2+ spots started in a circular area with a radius of about 1.5 m. These Ca2+ spots spread concentrically, resulting in a mean global increase in [Ca2+]i. The local increase often occurred in a stepwise manner or repetitively at the same region. The spatiotemporal properties of the Ca2+ spots were completely different from those of the Ca2+ wave induced by ATP, a Ca2+-mobilizing agonist. Ca2+ spots were inhibited by decreasing the extracellular Ca2+ concentration or by the presence of Gd3+, an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, suggesting that Ca2+ spots arise from Ca2+ influx through Gd3+-sensitive MS channels. On the assumption that, in lens epithelial cells, the open probability of the MS channel is 0.4, the membrane potential is 56 mV and the channel conductance is 50 pS, the estimated maximum flux of Ca2+ in a Ca2+ spot (0.4 x 10-17 to 4.7 x 10-17 mol x s(-1)) was comparable to currents of one or a few MS channels. On real-time three-dimensional confocal imaging analysis, which permitted simultaneous imaging of basal and apical planes of cells at 37.6 ms intervals, Ca2+ spots on the apical plane were more clearly visualized than those on the basal plane. From these results, we propose that the Ca2+ spot is an elementary Ca2+-influx event through MS channels directly coupled with the first step in mechanoreception In addition, our results strongly suggest that LPA functions as an endogenous factor affecting mechanotransduction systems.

Changes in Ca2+ signaling and contractile protein isoforms in smooth muscle cells from guinea pig ileum during culture

Single smooth muscle cells (SMCs) isolated from guinea pig ileum using collagenase and papain were cultured on laminin-coated dishes in MEM containing fetal calf serum. Temporal changes in intracellular calcium ion concentration in response to carbachol and to ATP were investigated using fluo-3/AM and fluorescence microscopy. It was observed that carbachol caused an increased intracellular calcium ion in freshly isolated single SMCs but a reduced or negative response of cultured SMCs before confluence. On the other hand, ATP was observed to cause an increase in the calcium ion content of SMCs throughout the culture. SDS-PAGE and Western blot analyses revealed changes in the expression of contractile proteins as follows. l-Caldesmon and non-muscle type myosin heavy chain (NMHC) (considered to be marker molecules for dedifferentiation in smooth muscle cells) and non-muscle type tropomyosin were not observed in freshly isolated single SMCs. l-Caldesmon and NMHC appeared in the cultured SMCs within 2 days and the tropomyosin isoform was observed 6 days following seeding. Simultaneously, smooth muscle type myosin heavy chain (SMHC) decreased strikingly and the 41 kDa tropomyosin monomer was lost. The content of alpha-actin decreased gradually to a minimum on day 6 when non-muscle type tropomyosin appeared, and the cells began to proliferate rapidly. These results suggest that the loss of contractility in cultured smooth muscle cells is more closely related to changes in contractile protein profiles than to receptor-mediated signal transduction and that in addition to NMHC and l-caldesmon, non-muscle type tropomyosin may be useful as a marker molecule for de-differentiation of smooth muscle cells.

[Silent myocardial ischemia and exercise-induced arrhythmia detected by the exercise test in the total health promotion plan (THP)]

We investigated the prevalence and characteristics of ischemic heart disease especially silent myocardial ischemia (SMI) and arrhythmia in need of careful observation in the exercise stress tests in the Total Health Promotion Plan (THP), which was conducted between 1994-96 for the purpose of measuring cardiopulmonary function. All workers (n = 4,918, 4,426 males) aged 18-60 yr old in an occupational field were studied. Exercise tests with an ergometer were performed by the LOPS protocol, in which the maximal workload was set up as a presumed 70-80% maximal oxygen intake, or STEP (original multistage protocol). ECG changes were evaluated with a CC5 lead. Two hundred and fifteen people refused the study because of a common cold, lumbago and so on. Of 4,703 subjects, 17 with abnormal rest ECG and 19 with probable anginal pain were excluded from the exercise tests. Of 4,667 who underwent the exercise test, 37 (0.79%) had ischemic ECG change, and 155 (3.32%) had striking arrhythmia. These 228 subjects then did a treadmill exercise test with Bruce protocol. Twenty-two (0.47% of 4,703) showed positive ECG change, 9 (0.19%) of 22 had abnormal findings on a 201Tl scan. 8 (0.17%) were diagnosed as SMI (Cohn I), in which the prevalence of hypertension, hyperlipidemia, diabetes mellitus, smoker and positive familial history of ischemic heart disease was greater than that of all subjects. In a 15-30 month follow up, none has developed cardiac accidents. Exercise-induced arrhythmia was detected in 11 (0.23%) subjects. Four were non-sustained ventricular tachycardia without any organic disease, 4 were ventricular arrhythmia based on cardiomyopathy detected by echocardiography, 2 were atrial fibrillation and another was WPW syndrome. It is therefore likely that the ergometer exercise test in THP was effective in preventing sudden death caused by ischemic heart disease or striking arrhythmia.

Spontaneous and flow-induced Ca2+ transients in retracted regions in endothelial cells

Changes in intracellular calcium concentration ([Ca2+]i) and focal adhesion sites of cultured bovine aortic endothelial cells (BAECs) were simultaneously visualized in real time. Local [Ca2+]i transients were observed at the rear edges of spontaneously migrating BAECs. Furthermore, the majority of starting regions of [Ca2+]i transients retracted continuously. Frequency of [Ca2+]i transients increased with the application of fluid flow. The majority of starting regions of flow-induced [Ca2+]i transients retracted following the occurrence of [Ca2+]i transients. In addition, retracted areas were distributed in the upstream regions of the cell. Application of GdCl3, a mechanosensitive cation channel blocker, resulted in a clear reduction of [Ca2+]i transients and rear retractions in cases of spontaneous and flow-induced BAEC migration. Flow-induced directional rear retractions were also inhibited. Consequently, we conclude that local [Ca2+]i transients play an important role in the migration of BAECs with respect to rear retraction. Furthermore, flow-induced [Ca2+]i transients regulate directional rear retraction under flow conditions.

[Molecular structure and function of mechanosensor mechanisms: an alternative prospect for the development of new drugs]

Mechanical stress to cells induces various physiological cellular responses and pathophysiological changes in many cell types. However, the molecular mechanisms remain unclear. Clarification of the mechanosensor mechanisms on the molecular level may provide an alternative approach for the development of new drugs. In the 73rd Annual Meeting of The Japanese Pharmacological Society, the latest studies performed by the following five departments were reported and discussed: 1) Expression of putative stretch sensitive nonselective cation channels of mammal, by M. Suzuki et al. (Department of Pharmacology, Jichi Medical School); 2) Mechanosensitive ATP release in aortic endothelial cells, by M. Oike et al. (Department of Pharmacology, Graduate School of Medical Science, Kyushu University); 3) Lysophosphatidic acid acts as an endogenous modulator on mechanotransduction, by H. Ohata et al. (Department of Pharmacology, School of Pharmaceutical Sciences, Showa University); 4) Stretch-induced myosin light chain phosphorylation without force development in canine basilar artery, by K. Obara et al. (Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka); and 5) Transcriptional regulation of smooth muscle phenotypic modulation, by R. Nagai (Department of Cardiovascular Medicine, University of Tokyo). This article reviews these reports.

Urocortin in the ventromedial hypothalamic nucleus acts as an inhibitor of feeding behavior in rats

Urocortin (UCN), a member of the corticotropin-releasing factor (CRF) family, inhibits food intake when it is injected intracerebroventricularly in rats. To explore the site of action of UCN in feeding behavior, we examined the effects of injection of UCN into various hypothalamic nuclei on food and water intake in 24-h fasted rats. Injection of UCN into the ventromedial hypothalamic nucleus (VMH) significantly inhibited food and water intake over 3 h without sedative effect, but no significant effect was observed following injection either into the lateral hypothalamic area, or the paraventricular nucleus of the hypothalamus. To further explore the physiological significance of endogenous UCN of the VMH in feeding behavior, the effect of immunoneutralization of hypothalamic UCN on food intake was examined. Injection of anti-rat UCN rabbit gamma-globulin into the bilateral VMH in freely fed rats significantly potentiated food and water intake compared with rats that received normal rabbit gamma-globulin. These results suggest that endogenous UCN in the VMH exert inhibitory control on ingestive behavior.

Optical recording study of granule cell activities in the hippocampal dentate gyrus of kainate-treated rats

In the epileptic hippocampus, newly sprouted mossy fibers are considered to form recurrent excitatory connections to granule cells in the dentate gyrus and thereby increase seizure susceptibility. To study the effects of mossy fiber sprouting on neural activity in individual lamellae of the dentate gyrus, we used high-speed optical recording to record signals from voltage-sensitive dye in hippocampal slices prepared from kainate-treated epileptic rats (KA rats). In 14 of 24 slices from KA rats, hilar stimulation evoked a large depolarization in almost the entire molecular layer in which granule cell apical dendrites are located. The signals were identified as postsynaptic responses because of their dependence on extracellular Ca(2+). The depolarization amplitude was largest in the inner molecular layer (the target area of sprouted mossy fibers) and declined with increasing distance from the granule cell layer. In the inner molecular layer, a good correlation was obtained between depolarization size and the density of mossy fiber terminals detected by Timm staining methods. Blockade of GABAergic inhibition by bicuculline enlarged the depolarization in granule cell dendrites. Our data indicate that mossy fiber sprouting results in a large and prolonged synaptic depolarization in an extensive dendritic area and that the enhanced GABAergic inhibition partly masks the synaptic depolarization. However, despite the large dendritic excitation induced by the sprouted mossy fibers, seizure-like activity of granule cells was never observed, even when GABAergic inhibition was blocked. Therefore, mossy fiber sprouting may not play a critical role in epileptogenesis.

Attenuated additional hypocapnic constriction, but not hypercapnic dilation, of spinal pial arterioles during spinal ropivacaine

Ropivacaine constricts spinal vessels. Because the CO2 response of spinal vessels is similar to that of cerebral vessels, we tested to see if hypocapnia would cause further spinal vasoconstriction during ropivacaine administration. In 12 pentobarbital-anesthetized dogs, spinal pial arteriolar diameter was measured using a closed spinal window preparation. Either ropivacaine solution (0.1%; n = 6) or artificial cerebrospinal fluid (n = 6) was infused continuously into the spinal window. After a period of hypocapnia (Paco2, 20-25 mm Hg) had been induced, inspired CO2 levels were adjusted to produce normocapnia (35-40 mm Hg) followed by hypercapnia (55-60 mm Hg). When the desired Paco2 was reached, measurements were made of the arteriolar diameter and physiological variables. During normocapnia, ropivacaine infusion produced a significant constriction of pial arterioles, whereas artificial cerebrospinal fluid caused no change. Hypocapnia induced a much smaller (almost nonexistent) additional vasoconstriction in the ropivacaine group than in the control group (P < 0.01). The final hypercapnic vasodilation was somewhat greater during ropivacaine (P < 0.05 versus control group). Topical ropivacaine induced no change in hemodynamic variables. We conclude that hypocapnia of the magnitude tested did not cause further constriction in spinal vessels during spinal ropivacaine.

IMPLICATIONS

During topical application of the local anesthetic ropivacaine in dogs, hypocapnia (Paco2, 20-25 mm Hg) induced almost no additional constriction of spinal arterioles, and the hypercapnic vasodilation was maintained. These data suggest that an additional constriction in spinal vessels is unlikely when hypocapnia occurs during spinal ropivacaine.

Prevention of reactive oxygen-induced endothelial cell injury by blocking its process

Endothelial cell (EC) injury induced by reactive oxygen species (ROS) was investigated and effects of Ca(2+) channel blockers, agents which elevate intracellular cAMP levels ([cAMP](i)), and protein kinase inhibitors on H(2)O(2)-induced EC injury were analyzed using human umbilical vein EC cultures. Exposure to H(2)O(2) increased intracellular Ca(2+) levels and decreased [cAMP](i). Ca(2+) channel blockers, [cAMP](i)-elevating agents, and protein kinase inhibitors significantly inhibited H(2)O(2)-induced EC injury. Data suggest that H(2)O(2)-induced EC injury is mediated by extracellular Ca(2+) influx, intracellular cAMP efflux, and intracellular signaling, each of which is blocked by Ca(2+) channel blockers, [cAMP](i)-elevating agents, or protein kinase inhibitors. It is suggested that ischemia/reperfusion injury induced by ROS may be prevented by Ca(2+) channel blockers, [cAMP](i)-elevating agents, and protein kinase inhibitors.

Hemodynamic responses induced by dopamine and dobutamine in anesthetized patients premedicated with clonidine

To test the hypothesis that the pharmacological effects of dopamine (DOA) and dobutamine (DOB) are altered when there is inhibition of the release of norepinephrine from nerve endings, we examined the hemodynamic responses to DOA and DOB in anesthetized patients premedicated with oral clonidine. Seventy adult patients were assigned to one of two groups (oral premedication with clonidine 5 microg/kg or no premedication). After the induction of general anesthesia, heart rate and systemic blood pressure (BP) were measured for 10 min after each of five IV infusions (3 and 5 microg x kg(-1) x min(-1) of DOA; 0.5, 1, and 3 microg x kg(-1) x min(-1) of DOB) in a randomized, double-blind manner. In patients given clonidine, the mean BP increases induced by DOA 5 microg x kg(-1) x min(-1) were significantly attenuated (P < 0.01), whereas the mean BP increases induced by DOB-0.5, 1, or 3 microg x kg(-l) x min(-1) were significantly enhanced (P < 0.01 or 0.05). The heart rate responses to DOA and DOB did not differ between patients with or without clonidine. Premedication with clonidine alters the effects on BP to both DOA and DOB. When small doses of DOA or DOB are used in clonidine-premedicated patients, differences of pharmacological profiles need to be considered for perioperative management.

IMPLICATIONS

Our randomized, double-blind study suggests that premedication with clonidine may enhance the effect on blood pressure response to a small dose of dobutamine (direct-acting) and attenuate that to a small dose of dopamine (mixed direct-and indirect-acting) in patients anesthetized with fentanyl and nitrous oxide.

Sensitizing effect of lysophosphatidic acid on Ca2+ response to hypotonic stress in cultured lens epithelial cells

The effects of lysophosphatidic acid (LPA), a bioactive phospholipid, on the response of the cytosolic free Ca2+ concentration ([Ca2+]i) to hypotonic stress were studied in cultured bovine lens epithelial cells, to test whether LPA affects cellular swelling-mediated increase in [Ca2+]i, which may relate to formation of sugar cataracts. Exposure of the cells to a 30% hypotonic stress caused only a slight increase in [Ca2+]i. Pretreatment with LPA (10 microM) significantly augmented the hypotonic stress-induced [Ca2+]i response, whereas addition of LPA to the cells did not affect [Ca2+]i. The hypotonic stress-induced increase in [Ca2+]i in the presence of LPA was inhibited by Gd3+, a blocker of mechanosensitive cation channels, but not by nicardipine, a L-type Ca2+ channel blocker, or thapsigargin, an inhibitor of endoplasmic reticulum-ATPase pump. These results show that LPA sensitizes the response to hypotonic stress via increase in Ca2+ influx through Gd3+-sensitive stretch-activated ion channels, and not via Ca2+ release from intracellular stores. On the other hand, LPA did not affect the [Ca2+]i response to ATP, a Ca2+ mobilizing agonist. Therefore, LPA sensitizes the hypotonic stress-induced [Ca2+]i response in lens epithelial cells, suggesting that LPA potentiates the development of cataracts induced by cellular swelling such as sugar cataract.

Effect of amino acids on the plasma concentration and urinary excretion of uric acid and uridine

To determine the effect of amino acids on the plasma level and urinary excretion of uric acid and uridine, 200 mL 12% amino acid solution, and 2 weeks later, 100 mL physiological saline solution containing glucagon (1.2 microg/kg weight), was infused into five healthy men. Both increased the urinary excretion of uric acid and the concentration of glucagon, insulin, and glucose in plasma and pyruvic acid in blood, whereas they decreased the concentration of uridine and inorganic phosphate in plasma. However, neither the amino acid infusion nor glucagon infusion affected the concentration of purine bases (hypoxanthine, xanthine, and uric acid), cyclic adenosine monophosphate (cAMP) in plasma, or lactic acid in blood or the urinary excretion of oxypurines (hypoxanthine and xanthine), uridine, or sodium. These results suggest that glucagon may have an important role in the amino acid-induced increase in urinary excretion of uric acid and decrease in plasma uridine.

Direct effects of alpha1- and alpha2-adrenergic agonists on spinal and cerebral pial vessels in dogs

BACKGROUND

The effects of adrenergic agonists, often used as local anesthetic additives or spinal analgesics, on spinal vessels have not been firmly established. The authors investigated the effects of alpha2- and alpha1-adrenergic agonists on spinal and cerebral pial vessels in vivo.

METHODS

Pentobarbital-anesthetized dogs (n = 28) were prepared for measurement of spinal pial-vessel diameter in a spinal-window preparation. The authors applied dexmedetomidine, clonidine, phenylephrine, or epinephrine in three different concentrations (0.5, 5.0, and 50 microg/ml; [2.1, 1.9, 2.5, and 2.3] x [10(-6), 10(-5), and 10(-4)] M, respectively) under the window (one drug in each dog) and measured spinal pial arteriolar and venular diameters in a sequential manner. To enable the comparison of their effects on cerebral vessels, the authors also administered these drugs under a cranial window.

RESULTS

On topical administration, each drug constricted spinal pial arterioles in a concentration-dependent manner. Phenylephrine and epinephrine induced a significantly larger arteriolar constriction than dexmedetomidine or clonidine at 5 microg/ml (8%, 11%, 0%, and 1%, respectively). Spinal pial venules tended to be less constricted than arterioles. In cerebral arterioles, greater constrictions were induced by dexmedetomidine and clonidine than those induced by phenylephrine and epinephrine (14%, 8%, 0%, and 1%, respectively). Cerebral pial venules tended to exhibit larger constrictions than cerebral arterioles (unlike in spinal vessels).

CONCLUSION

Dexmedetomidine and clonidine constricted spinal vessels in a concentration-dependent manner, but such vasoconstrictions were smaller than those induced by phenylephrine and epinephrine.

Intravenous dexmedetomidine inhibits cerebrovascular dilation induced by isoflurane and sevoflurane in dogs

Our aim in this study, performed using a closed cranial window preparation, was to investigate the effect of systemic pretreatment with dexmedetomidine on cerebrovascular response to isoflurane or sevoflurane. After instrumentation under pentobarbital anesthesia, 48 dogs were assigned to one of two groups: the isoflurane group or the sevoflurane group (n = 24 each). Twenty-four dogs received saline (n = 6) or one of three different doses of dexmedetomidine (0.5, 1.0, or 2.0 micrograms/kg) (n = 6 each) i.v. Animals were then exposed to three different minimum alveolar anesthetic concentrations (MACs; 0.5, 1.0, and 1.5) of either isoflurane or sevoflurane. Cerebrovascular diameters were measured at each stage. Pretreatment with dexmedetomidine decreased pial vessel diameters. Both isoflurane and sevoflurane significantly dilated both arterioles and venules in a concentration-dependent manner. Isoflurane- and sevoflurane-induced dilation of cerebral arterioles was significantly attenuated in the presence of dexmedetomidine. The dexmedetomidine-induced attenuation of the vascular responses was not dependent on the dose of dexmedetomidine and was not different between isoflurane and sevoflurane. The vasodilation of cerebral pial vessels induced by isoflurane and sevoflurane could be attenuated by the systemic administration of dexmedetomidine, and this interaction between dexmedetomidine and volatile anesthetics showed no evidence of dose-dependency.

IMPLICATIONS

The systemic administration of dexmedetomidine attenuates the dilation of cerebral vessels induced by isoflurane and sevoflurane in pentobarbital-anesthetized dogs. This interaction was not dependent on the clinical (0.5-2.0 micrograms/kg) dose of dexmedetomidine and was not different between isoflurane and sevoflurane anesthesia.

'Pseudohypouricosuria' in alcaptonuria: homogentisic acid interference in the measurement of urinary uric acid with the uricase-peroxidase reaction

Urinary excretion of uric acid was found to be extremely low in a 58-year-old female patient with alcaptonuria. This was due to interference with the uricase-peroxidase method used, because analysis using high-performance liquid chromatography (HPLC) showed a normal urinary concentration of uric acid. In vitro experiments demonstrated that a high concentration of homogentisic acid in the patient's urine inhibited the peroxidase reaction, possibly due to inhibition of the colour development of 3-methyl-N-ethyl-N-(beta-hydroxyethyl)aniline (MEHA) and 4-aminoantipyrine, via the peroxidase reaction. A homogentisic acid concentration equivalent to that in plasma did not affect the uricase-peroxidase reaction. This result suggests that any assay based on a peroxidase method is affected by a high urinary concentration of homogentisic acid in patients with alcaptonuria.

Suppression of calcium oscillation by tri-n-butyltin chloride in cultured rat hepatocytes

The effects of tri-n-butyltin chloride (TBT), an environmental pollutant, on cytoplasmic free calcium ion concentration ([Ca2+]i) were investigated in primary cultured rat hepatocytes. A high concentration (4.0 microM) of TBT increased resting levels of [Ca2+]i and then induced cell blebs resulting in cell death within 2 h. The increase in [Ca2+]i, but not the cell death, depended on the presence of extracellular Ca2+, suggesting that the increase in [Ca2+]i is not critical for the cytotoxicity of TBT. A low concentration (0.1 microM) of TBT did not have any toxic effect (decrease in ATP content, decrease in viability, and shape change) on cultured hepatocytes and did not change [Ca2+]i. However, the calcium responses induced by phenylephrine, [Arg8]-vasopressin, and ATP were suppressed in the cells pretreated with 0.1 microM TBT for 30 min. The suppression was not observed in the cells pretreated with 0.1 microM TBT for only 1 min. Pretreatment with 0.1 microM TBT for 30 min had no effect on the inositol 1,4,5-triphosphate content or its increase in response to hormonal stimulation. These results suggest that TBT suppresses hormone-induced calcium responses at nontoxic low concentrations.

Pulmonary arterial and right ventricular responses to prophylactic albumin administration before aortic unclamping during abdominal aortic aneurysmectomy

During abdominal aortic aneurysmectomy (AAAectomy) and before aortic unclamping (XU), we studied the effects of albumin administration on pulmonary arterial and right ventricular responses in 39 anesthetized patients using a modified thermodilution technique. Group 1 patients (n = 18) were given no extra IV fluids. Group 2 patients (n = 21) were given additional albumin administration (5% albumin at 10 mL/kg) before XU. After XU, mean arterial blood pressure (MAP) decreased significantly in each group, and MAP and stroke volume index (SVI) were not significantly higher in Group 2 than in Group 1. At 5 min after XU, the patients in Group 2 had a higher mean pulmonary arterial pressure and pulmonary vascular resistance index and a lower right ventricular ejection fraction than those in Group 1 (P < 0.05), but their SVIs were well maintained. These results indicate that albumin administration before XU may not always prevent post-XU hypotension. It caused a significant increase in right ventricular afterload and a significant dilation of the right ventricular cavity; however, right ventricular function was almost equally maintained in both groups. However, because SVI did not increase in some patients (Group 2) with the increase in right ventricular end-diastolic volume index after XU, albumin administration should be performed carefully before XU during AAAectomy.

IMPLICATIONS

We studied the effects of albumin administration before aortic unclamping on pulmonary arterial and right ventricular responses during abdominal aortic aneurysmectomy using a modified thermodilution technique. Albumin administration before aortic unclamping may not always prevent hypotension, and it may cause a higher pulmonary arterial pressure than in patients without albumin administration.

Clonidine premedication modifies responses to adrenoceptor agonists and baroreflex sensitivity

PURPOSE

To evaluate the effects of clonidine on responses to adrenoceptor agonists and baroreflex sensitivity, we examined arterial blood pressure (AP) responses to phenylephrine and heart rate (HR) responses to isoproterenol and baroreflex sensitivity (HR response to AP changes due to phenylephrine or nitroglycerin).

METHODS

We studied 60 anaesthetized patients who either did or did not receive 5 micrograms.kg-1 clonidine po before they were anaesthetized. After induction of general anaesthesia, the patients received 3 micrograms.kg-1 phenylephrine, 0.02 microgram.kg-1 isoproterenol, or 2-3 micrograms.kg-1 nitroglycerin, and haemodynamic measurements were taken. Baroreflex sensitivity was expressed as the slope of the linear regression line (msec.mmHg-1; in msec of R-R interval change vs mmHg change in systolic arterial pressure) following the administration of phenylephrine and nitroglycerin.

RESULTS

Patients who received clonidine had greater augmented responses in AP to phenylephrine and in HR to isoproterenol (47.2 +/- 15.6% vs 23.7 +/- 11.9% for increase in systolic AP and 59.8 +/- 22.6% vs 26.2 +/- 11.0% for increase in HR, P < 0.05 respectively). There were no differences between the baroreflex sensitivities in the pressor (phenylephrine) test groups (3.77 +/- 1.08 vs 4.41 +/- 1.66 msec.mmHg-1). In contrast, the slopes of depressor (nitroglycerin) test groups were decreased in patients receiving clonidine (1.98 +/- 0.73 vs 3.68 +/- 1.72 msec.mmHg-1, P < 0.05).

CONCLUSION

The results suggest that premedication with clonidine might enhance critical hypotension during anaesthesia and surgery, but restoration both of AP and HR decrease can be achieved effectively by phenylephrine and isoproterenol i.v., respectively.

Non-peptidic corticotropin-releasing hormone receptor type 1 antagonist reverses restraint stress-induced shortening of sodium pentobarbital-induced sleeping time of rats: evidence that an increase in arousal induced by stress is mediated through CRH receptor type 1

Stress shortens sodium pentobarbital (PbNa)-induced sleeping time through corticotropin-releasing hormone (CRH) in rats. We investigated whether this effect of brain CRH is mediated by CRH receptor type 1 (CRHR1) using a non-peptidic CRHR1 antagonist in rats. A 60 min period of restraint significantly shortened PbNa-induced sleeping time. This shortening was completely reversed by peripheral administration of CRHR1 antagonist. These results suggest that the stress-induced increase in arousal is mediated by CRHR1.

Contractile protein isoforms of single and cultured smooth muscle cells from guinea pig ileum

Single smooth muscle cells isolated from guinea pig ileum using collagenase and papain produce contractile response to muscarinic agents, while the cultured cells do not. Using fluo-3/AM and a confocal laser scanning fluorescence microscope, it was observed that carbachol, a muscarinic agent, caused an increase in the intracellular Ca2+ of both single and cultured cells. SDS-PAGE and Western Blot analyses revealed the expression of myosin heavy chain isoforms of SM1 (204 kDa) and SM2 (200 kDa) in single smooth muscle cells, and non muscle isoform (196 kDa) of myosin heavy chain only in the cultured cells. With respect to actin isoforms, alpha-actin was predominant in single cells and beta-actin was major in the cultured cells. Two types of tropomyosin monomer, 39 kDa and 41 kDa, were detected in single cells, while the 41 kDa monomer was lost in cultured cells. These differences in contractile protein profiles between single and cultured cells were collaborated with the observation of cells using immunofluorescence microscope with responsible antibodies to isoforms of myosin heavy chain, actin and tropomyosin. These results suggest that the loss of contractility in cultured smooth muscle cells is profoundly related to changes in contractile protein profiles from smooth muscle type to non muscle type.

Isoflurane and sevoflurane induce vasodilation of cerebral vessels via ATP-sensitive K+ channel activation

BACKGROUND

Activation of adenosine triphosphate-sensitive K+ channels causes cerebral vasodilation. To assess their contribution to volatile anesthetic-induced cerebral vasodilation, the effects of glibenclamide, an adenosine triphosphate-sensitive K+ channel blocker, on the cerebral vasodilation induced by isoflurane and sevoflurane were studied.

METHODS

Pentobarbital-anesthetized dogs (n = 24) assigned to one of two groups were prepared for measurement of pial vessel diameter using a cranial window preparation. Each dog received three minimum alveolar concentrations (MAC; 0.5, 1, and 1.5 MAC) of either isoflurane or sevoflurane, and the pial arteriolar diameters were measured in the presence or absence of glibenclamide (10(-5) M) infused continuously into the window. Mean arterial pressure was maintained with phenylephrine. Furthermore, to assess the direct effect of isoflurane and sevoflurane on cerebral vessels, artificial cerebrospinal fluid was administered topically by being bubbled with isoflurane or sevoflurane. The blocking effect of glibenclamide on the vasoactive effects of these anesthetics also were evaluated.

RESULTS

Isoflurane and sevoflurane both significantly dilated large (> or = 100 microm) and small (< 100 microm) pial arterioles in a concentration-dependent manner (6% and 10%, 3% and 8% for 0.5 MAC; 10% and 19%, 7% and 14% for 1 MAC; 17% and 28%, 13% and 25% for 1.5 MAC). Glibenclamide attenuated the arteriolar dilation induced by these anesthetics (not significant in isoflurane). Topical application of isoflurane or sevoflurane dilated large and small arterioles both in a concentration-dependent manner. Such vasodilation was inhibited completely by glibenclamide.

CONCLUSION

The vasodilation of cerebral pial vessels induced by isoflurane and sevoflurane appears to be mediated, at least in part, via activation of adenosine triphosphate-sensitive K+ channels.

Effect of bucladesine sodium on the plasma concentrations and urinary excretion of purine bases and uridine

To examine whether bucladesine sodium affects the plasma concentrations of purine bases (hypoxanthine, xanthine, and uric acid) and uridine, 100 mL of physiological saline containing bucladesine sodium (6 mg/kg weight) was administered intravenously to eight healthy subjects for 1 hour after overnight fast except for water. Blood was drawn 30 minutes before, and 30 minutes and 1 hour after the beginning of the infusion, and 1-hour urine was collected before and after the beginning of the infusion. Two weeks later, 100 mL of only physiological saline was administered under the same protocol. Bucladesine sodium decreased the plasma concentrations of hypoxanthine by 36% and by 37%, and of xanthine by 16% and 33%, and of uridine by 17% and 30%, 30 minutes and 1 hour after the beginning of the infusion, respectively, and increased the urinary excretion of hypoxanthine and uric acid by 140% and 30%, respectively, after the beginning of the infusion. However, it did not affect the plasma concentration of uric acid or the urinary excretion of xanthine, and the urinary excretion of uridine was less than 0.2 micromol/h before or after bucladesine sodium infusion. On the other hand, physiological saline alone did not affect any of the values described. These results suggest that bucladesine sodium acts on the secretory process of the renal transport of hypoxanthine, resulting in the increased urinary excretion of hypoxanthine, and further suggest that bucladesine sodium enhances the uptake of uridine in plasma to liver cells.

Discrepant intracellular pH changes following intracellular Ca2+ increases induced by glutamate and Ca2+ ionophores in rat hippocampal neurons

We investigated changes in intracellular pH (pHi) in relation to intracellular Ca2+ concentration ([Ca2+]i) in primary cultured hippocampal neurons treated with glutamate. [Ca2+]i and pHi were imaged with fluorescent dyes and confocal microscopy. Exposure to 1 mM glutamate for 10 min increased [Ca2+]i and evoked acidosis. These changes persisted for at least 60 min, even after removal of glutamate. The increase in [Ca2+]i and the acidosis were not observed in Ca2+-free solution and were attenuated in the presence of MK-801, an NMDA receptor antagonist. We also found that the increase in [Ca2+]i and acidosis could be induced by addition of Ca2+ to the extracellular solution in the cells pretreated with glutamate in Ca2+-free solution, even if glutamate did not exist in the extracellular solution. On the other hand, ionomycin and Br-A23187, calcium ionophores, increased [Ca2+]i to almost the same level as glutamate and increased pHi. Extracellular Ca2+ was also indispensable for the increase in [Ca2+]i and the alkalosis. These results suggest the followings: 1) intracellular acidosis by glutamate is dependent on the presence of extracellular Ca2+; 2) the acidosis does not result from only the increase in [Ca2+]i; and 3) glutamate induces the irreversible disorder of regulatory mechanisms of [Ca2+]i not only by Ca2+-dependent process, but also by Ca2+-independent process.

Induction of DNA fragmentation by nicotine in human myelogenous leukemic cell lines

The effect of nicotine, a component of tobacco, on the cytokine production and cell growth of various cultured cells was investigated. Nicotine did not stimulate, but rather inhibited the tumor necrosis factor production by human peripheral blood mononuclear cells at higher doses. Cytotoxic concentrations of nicotine did not induce the monocytic and granulocytic differentiation of human myelogenous leukemic cell lines (HL-60, ML-1). Nicotine induced internucleosomal DNA cleavage in these leukemic cell lines but not in human peripheral blood lymphocytes and polymorphonuclear cells. The fragmentation-inducing activity of nicotine was not prevented by simultaneous addition of ascorbic acid. Flow cytometry showed a slight increase in the number of G2 + M phase cells, before the appearance of the apoptosis peak. Nicotine transiently increased the intracellular calcium concentration to higher levels in leukemic cells than in normal leukocytes. These data suggest that the induction of DNA fragmentation requires elevation of intracellular calcium concentration above a certain threshold level.

Calcium mobilization during nicotine-induced cell death in human glioma and glioblastoma cell lines

Nicotine dose-dependently induced cytotoxicity in human glioma (KG-1-C) and glioblastoma (GBS-1, T98G) cell lines, but could not induce internucleosomal DNA cleavage, in contrast to apoptosing human myelogenous leukemic cell lines. Human glioma/glioblastoma cell lines thus might have a chromatin structure resistant to endonuclease digestion. Nicotine induced a rapid increase in the intracellular calcium concentration. Confocal experiments with Fluo-3 fluorescence revealed that nicotine elevated the free Ca2+ concentration in both nuclear and cytoplasmic regions of the cells, and the elevation of Ca2+ in the nuclear region was more pronounced than that of the cytoplasmic region. The present study suggests that nuclear accumulation of Ca2+ is an important initial step for cell death induction by nicotine.

Effect of glucagon on the plasma concentration of uridine

To determine whether glucagon affects the plasma concentration of uridine, we administered 100 mL physiological saline containing 1 mg glucagon or 100 mL physiological saline alone intravenously over 1 hour to healthy subjects. Glucagon decreased the plasma concentration of uridine from 5.72 +/- 1.05 to 4.80 +/- 0.60 micromol/L but increased the concentrations of cyclic adenosine monophosphate (cAMP) in plasma and pyruvic acid and lactic acid in blood 59-, 1.4-, and 1.3-fold, respectively. Although glucagon increased urinary excretion of uric acid, it did not affect the plasma concentration of purine bases (hypoxanthine, xanthine, and uric acid) or urinary excretion of oxypurines and uridine, indicating that glucagon does not affect purine degradation and suggesting that glucagon does not affect adenosine triphosphate (ATP) consumption-induced pyrimidine degradation. In contrast, physiological saline did not affect any of the measured variables. These results suggest that glucagon enhanced Na+-dependent uridine uptake from the blood into the cells, since glucagon stimulates Na+-dependent uridine uptake into cells in vitro.

Mitochondrial Ca2+ transients in cardiac myocytes during the excitation-contraction cycle: effects of pacing and hormonal stimulation

Using laser scanning confocal microscopy, our objective was to measure mitochondrial, nuclear, and cytosolic free ionized Ca2+ in adult rabbit cardiac myocytes loaded with Ca2+-indicating fluorophores. When myocytes were loaded with Fluo 3 at 37 degrees C, the fluorophore was loaded extensively into the cytosol and nucleus, but poorly into mitochondria, and Fluo 3 fluorescence transients after field stimulation were confined to the cytosol and nucleus. In contrast, after loading at 4 degrees C, Fluo 3 also entered mitochondria, and large transients of mitochondrial Fluo 3 fluorescence then occurred after stimulation. Isoproterenol (1 microM) increased the magnitude of Ca2+ transients and their subsequent rate of decay, an effect more marked in the cytosol and nucleus than in mitochondria. As pacing frequency was increased from 0.5 to 2 Hz, diastolic mitochondrial Ca2+ rose markedly in the absence but not in the presence of isoproterenol. Resting Ca2+ estimated by Indo 1 ratio imaging using UV/visible laser scanning confocal microscopy was about 200 nM in all compartments. During field stimulation, Ca2+ transiently increased to 671, 522, and 487 nM in cytosol, interfibrillar mitochondria, and perinuclear mitochondria, respectively. Isoproterenol increased these respective peak values to 1280, 750, and 573 nM. These results were consistent with those obtained in Fluo 3 experiments. We conclude that rapid mitochondrial Ca2+ transients occur during excitation-contraction coupling in adult rabbit cardiac myocytes, which may be important in matching mitochondrial metabolism to myocardial ATP demand during changes in cardiac output.

The optimal test dose of epinephrine for epidural injection with lidocaine solution in awake patients premedicated with oral clonidine

We attempted to determine the optimal test dose of epinephrine for use with epidural anesthesia in awake patients premedicated with clonidine. Eighty-eight adult patients were randomized into two groups [oral premedication with clonidine 5 microg/kg (CLON) or no premedication (CONT)]. Before induction of general anesthesia, heart rate (HR) and blood pressure (BP) were measured for 3 min after the i.v. injection of 3 mL of 1.5% lidocaine containing epinephrine (0, 1.25, 2.5, 5, 7.5, or 15 microg) in a randomized, double-blind manner. We calculated 95% confidence intervals for the peak HR and BP increases induced by each dose of epinephrine. At 7.5 microg, epinephrine induced a significantly greater increase in HR and BP in CLON than in CONT. The 95% confidence interval for the HR change induced by 7.5 microg of epinephrine in CLON was nearly the same as the accepted standard dose of epinephrine (15 microg) in CONT. We conclude that premedication with clonidine enhances HR and BP responses to the i.v. administration of epinephrine-containing epidural test solutions. Consequently, 7.5 microg of epinephrine may be sufficient to enable detection of accidental injection into a blood vessel in awake patients premedicated with clonidine 5 microg/kg.

IMPLICATIONS

Clonidine, a commonly used preanesthetic medication, alters patients' cardiovascular responses to drugs such as epinephrine. Our randomized, double-blind study suggests that, in awake patients receiving oral clonidine premedication, 7.5 microg of epinephrine (half the usual dose) is adequate as an indicator of accidental injection into the epidural vessels during epidural anesthesia.

Lysophosphatidic acid sensitises Ca2+ influx through mechanosensitive ion channels in cultured lens epithelial cells

We investigated the effect of lysophosphatidic acid (LPA), a bioactive phospholipid, on the response in cytosolic free Ca2+ concentration ([Ca2+]i) to mechanical stress in cultured bovine lens epithelial cells. Spritzing of bath solution onto cells as mechanical stress caused marked increase in [Ca2+]i in the presence of LPA and this increase was concentration-dependent (1-10 microM), whereas neither addition of LPA alone nor the mechanical stress in the absence of LPA affected [Ca2+]i. The mechanical stress-induced increase in [Ca2+]i in the presence of LPA was inhibited by removing extracellular Ca2+ or by addition of Gd3+, a blocker of mechanosensitive cation channels, but not by nicardipine, thapsigargin, an inhibitor of endoplasmic reticulum-ATPase pump, or U73122, a phospholipase C inhibitor. These results show that LPA sensitises Ca2+ influx through cation-selective mechanosensitive channels, but does not sensitise Ca2+ release from intracellular stores, triggered by changes in mechanical stress. On the other hand, phosphatidic acid had less of a sensitising effect than LPA, and neither lysophosphatidylcholine nor chlorpromazine had any effect. Also Ca2+ mobilising agonists, ATP, histamine and carbachol, did not sensitise Ca2+ response to the mechanical stress. These results show that LPA sensitises mechanoreceptor-linked response in lens epithelial cells, suggesting that it plays a role in the development of cataracts due to increases in [Ca2+]i induced by mechanical stress.

Determination of acetaldehyde in biological samples by gas chromatography with electron-capture detection

A simple specific assay was developed for the determination of acetaldehyde in biological samples. Acetaldehyde was derivatized to 2,4-dinitrophenylhydrazone, which was determined by gas chromatography with electron-capture detection. The use of this detection method is an important device to which no one drew notice. This procedure was very simple and so sensitive that as little as 500 fmol of acetaldehyde could be measured in aqueous solution. The calibration curve of acetaldehyde was linear at least up to 40 microM. Its recoveries from human plasma and rat liver homogenate were 96.5 and 95.7%, respectively.