Characterization of oxidized low-density lipoprotein-induced hormesis-like effects in osteoblastic cells

Epidemiological studies indicate that patients suffering from atherosclerosis are predisposed to develop osteoporosis. Atherogenic determinants such as oxidized low-density lipoprotein (oxLDL) particles have been shown both to stimulate the proliferation and promote apoptosis of bone-forming osteoblasts. Given such opposite responses, we characterized the oxLDL-induced hormesis-like effects in osteoblasts. Biphasic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reductive activity responses were induced by oxLDL where low concentrations (10-50 microg/ml) increased and high concentrations (from 150 microg/ml) reduced the MTT activity. Cell proliferation stimulation by oxLDL partially accounted for the increased MTT activity. No alteration of mitochondria mass was noticed, whereas low concentrations of oxLDL induced mitochondria hyperpolarization and increased the cellular levels of reactive oxygen species (ROS). The oxLDL-induced MTT activity was not related to intracellular ROS levels. OxLDL increased NAD(P)H-associated cellular fluorescence and flavoenzyme inhibitor diphenyleneiodonium reduced basal and oxLDL-induced MTT activity, suggesting an enhancement of NAD(P)H-dependent cellular reduction potential. Low concentrations of oxLDL reduced cellular thiol content and increased metallothionein expression, suggesting the induction of compensatory mechanisms for the maintenance of cell redox state. These concentrations of oxLDL reduced osteoblast alkaline phosphatase activity and cell migration. Our results indicate that oxLDL particles cause hormesis-like response with the stimulation of both proliferation and cellular NAD(P)H-dependent reduction potential by low concentrations, whereas high concentrations lead to reduction of MTT activity associated with the cell death. Given the effects of low concentrations of oxLDL on osteoblast functions, oxLDL may contribute to the impairment of bone remodeling equilibrium.

Incidence and characteristics of type 2 hepatorenal syndrome in patients with cirrhosis and refractory ascites

BACKGROUND AND AIM

Type 2 hepatorenal syndrome (HRS) is a well described progressive impairment of renal function in patients with cirrhosis but its natural history, especially in patients with refractory ascites, is not well known. The aim of this study was to assess the incidence, predictive factors and outcome of type 2 HRS in patients with cirrhosis and refractory ascites.

PATIENTS AND METHODS

Thirty patients with refractory ascites were followed-up for 17.5 +/- 26.3 months. The clinical characteristics, biological findings and outcome were analysed. The occurrence of renal dysfunction, and type 2 HRS in particular, was systematically analysed.

RESULTS

Twenty-five patients (83.3%) developed renal dysfunction. Type 2 HRS was diagnosed in 16 patients (53.3%). Patients with type 2 HRS were older than patients without (64.8 +/- 9.1 yr vs 52.8 +/- 9.0 yr ; p < 0.001). All the others studied variables were similar between type 2 HRS and non-type 2 HRS patients. There was no significant difference in the overall probability of survival between these 2 groups.

CONCLUSIONS

In patients with cirrhosis and refractory ascites, the development of type 2 HRS is frequent but does not occur in more severe liver disease and does not affect prognosis.

Capacitative calcium entry and proliferation of human osteoblast-like MG-63 cells

Adult bone tissue is continuously being remodelled and bone mass is maintained by a balance between osteoclastic bone resorption and osteoblastic bone formation. Alteration of osteoblastic cell proliferation may account in part for lack of balance between these two processes in bone loss of osteoporosis. There is calcium (Ca2+) control in numerous cellular functions; however, involvement of capacitative Ca2+ entry (CCE) in proliferation of bone cells is less well investigated.

OBJECTIVES

The study described here was aimed to investigate roles of CCE in the proliferation of osteoblast-like MG-63 cells.

MATERIALS AND METHODS

Pharmacological characterizations of CCE were undertaken in parallel, with evaluation of the expression of transient receptor potential canonical (TRPC) channels and of cell proliferation.

RESULTS

Intracellular Ca2+ store depletion by thapsigargin induced CCE in MG-63 cells; this was characterized by a rapid transient increase of intracellular Ca2+ followed by significant CCE, induced by conditions that stimulated cell proliferation, namely serum and platelet-derived growth factor. Inhibitors of store-operated Ca2+ channels (2-APB and SKF-96365) prevented CCE, while voltage-dependent Ca2+ channel blockers had no effect. Expression of various TRPC channels was shown in the cells, some having been shown to be responsible for CCE. Voltage-dependent Ca2+ channel blockers had no effect on osteoblast proliferation while thapsigargin, 2-APB and SKF-96395, inhibited it. Cell cycle analysis showed that 2-APB and SKF-96395 lengthen the S and G2/M phases, which would account for the reduction in cell proliferation.

CONCLUSIONS

Our results indicate that CCE, likely attributed to the activation of TRPCs, might be the main route for Ca2+ influx involved in osteoblast proliferation.

Importance of melastatin-like transient receptor potential 7 and cations (magnesium, calcium) in human osteoblast-like cell proliferation

Bone tissue in the adult is continuously being remodelled, and overall bone mass is maintained constant by the balance between osteoclastic bone resorption and osteoblastic bone formation. Adequate osteoblastic proliferation is essential for both appropriate formation and for regulation of resorption, and thereby the maintenance of bone remodelling equilibrium.

OBJECTIVES

Here, we have investigated the roles of melastatin-like transient receptor potential 6 and 7 (TRPM6, TRPM7), which are calcium (Ca2+) and magnesium (Mg2+) conducting channels, during proliferation of human osteoblasts.

RESULTS

Genetic expression of TRPM6 and TRPM7 was shown in human osteoblast-like MG-63, SaOS and U2-OS cells, and reduction of extracellular Mg2+ or Ca2+ led to a decrease of cell proliferation. Concomitant reduction of both ions further accentuated reduction of cell proliferation. Expression of TRPM7 channels was increased under conditions of reduced extracellular Mg2+ and Ca2+ levels whereas expression of TRPM6 was not modified, suggesting compensatory mechanisms afforded by TRPM7 in order to maintain intracellular ion homeostasis. Pre-incubation of cells in reduced extracellular Mg2+ conditions led to activation of Ca2+ and Mg2+ influx. Reduction of TRPM7 expression by specific siRNA prevented latter influx and inhibited cell proliferation.

CONCLUSIONS

Our results indicate that extracellular Mg2+ and Ca2+ deficiency reduces the proliferation of human osteoblastic cells. Expression and activity of TRPM7 is modulated by extracellular Mg2+ and Ca2+ availability, indicating that TRPM7 channels are involved in intracellular ion homeostasis and proliferation of osteoblasts.

Design of a medical simulator for subcutaneous contraceptive implant insertion

New contraceptive methods like the subcutaneous implant offers a new kind of comfort for women with an efficiency similar to the contraceptive pill. Unfortunately, the few numbers of unintended pregnancies that have been reported, are generally due to a bad insertion of the implant. In order to give more security to patients, we have designed, in close collaboration with physicians, a new kind of medical simulator. This simulator can be used for two purposes: one for training novice physicians in the correct gesture and the other for doctor certification which will help to determine if they are capable of inserting the implant in vivo. This paper describes the approach which has led to the design of this simulator. It describes its functionalities, its several components but also methods used to analyze the gesture of the implant insertion inside the patient. Finally, first experimental results are reported and discussed.

Relationship between the Fibrotest and portal hypertension in patients with liver disease

BACKGROUND

The best technique to estimate portal hypertension (PHT) is to measure the hepatic venous pressure gradient (HVPG), which is an invasive method.

AIM

To assess the relationship between the Fibrotest (Biopredictive, Paris, France) and the presence and degree of PHT in patients with liver disease, and to determine if the Fibrotest can diagnose severe PHT, defined by HVPG >or= 12 mmHg, in cirrhotic patients.

METHODS

Patients who underwent a transjugular liver biopsy were prospectively included. HVPG was measured, and classification of histological lesions assessed. The same day, blood samples for Fibrotest were performed.

RESULTS

A total of 130 patients were included (no or minimal fibrosis: 12%, moderate fibrosis 17%, cirrhosis 71%). There was a significant correlation between Fibrotest and HVPG (Pearson correlation coefficient = 0.58, P < 0.0001), also weaker in cirrhotic patients (Pearson correlation coefficient = 0.24, P = 0.02). In cirrhotic patients, Fibrotest was significantly higher when there was a severe PHT (0.87 +/- 0.15 vs. 0.73 +/- 0.14, respectively, P = 0.02). The areas under the receiver operating characteristic curves for the diagnosis of severe PHT was 0.79 +/- 0.07, not different from that of platelets and Child-Pugh score.

CONCLUSION

In patients with liver disease or cirrhosis, Fibrotest is correlated with the presence and degree of PHT. Other studies are needed to confirm these results, especially in non-decompensated cirrhotic patients.

Evaluation of obstetric gestures: an approach based on the curvature of 3-D positions

This paper presents a method to evaluate a gesture carried out by a resident obstetrician doctors by comparing it to a gesture carried out by an expert obstetrician doctors. The studied gesture is the forceps blade placement. Residents were recorded on a childbirth simulator while placing forceps blades. Their paths were compared in order to evaluate how similar they are to a reference path defined by an expert. The comparison method is developed with respect to expert requests: time independence and in considering the whole set of data and not only particular points. In order to respect these requests, the developed method lies on the correlation coefficient between the path curvatures. Residents have been trained on a simulator and their gestures were evaluated by comparing their path curvatures to reference path curvatures. Quantitative results confirm the qualitative analysis, residents become more similar to the reference while training on simulator.

[Obstetrical forceps: yesterday, today and tomorrow. Toward a new classification of obstetrical forceps]

OBJECTIVE

Obstetrical forceps are used worldwide since more than 400 years. In 2003 forceps deliveries accounted for 6.3% of all deliveries of the AURORE Grand-Lyon perinatal network. Although more than 400 different forceps have been described, obstetrics handbooks neither describe experimental forceps nor provide any chapter dedicated to instrumental delivery training. Our aim was to provide junior obstetricians with information that will allow them to select the best instrument and to let them know about experimental as well as pedagogic forceps.

PATIENTS AND METHODS

International literature review using the terms "forceps" and "delivery" and a four year experimental work involving a close collaboration between obstetricians and biomechanics of the INSA engineering school.

RESULTS

Two instruments are presented as well as a new forceps classification.

DISCUSSION AND CONCLUSION

This classification distinguishes between three types of forceps: operational forceps designed to delivers neonates, experimental forceps designed to study biomechanics and training forceps designed for resident training. For the first time the classic blind forceps procedure is transformed in a full screen real time procedure.

Rapidité d’extraction respective des césariennes et des forceps réalisés en urgence

AIM

Comparison of the decision to delivery interval in cases of forceps delivery and in cases of cesarean sections.

MATERIAL AND METHOD

A retrospective analysis was performed on 137 cases of forceps deliver (n = 63) and cesarean section (n = 74) indicated for abnormal fetal heart rhythm. All cases were observed in a level 3 maternity unit between October 2003 and August 2004.

RESULTS

The mean decision-to-delivery interval was significantly shorter in the forceps group (14.84 min +/- 6.54 versus 29.31 min +/- 11.79 p < 0.0001). Maternal and neonatal morbidity were comparable.

CONCLUSION

This study suggest that once the fetal head is engaged, forceps delivery can significantly reduced the decision-to-delivery interval.

Sepsis in cirrhosis: report on the 7th meeting of the International Ascites Club

Sepsis is a systemic inflammatory response to the presence of infection, mediated via the production of many cytokines, including tumour necrosis factor (TNF-), interleukin (IL)-6, and IL-1, which cause changes in the circulation and in the coagulation cascade. There is stagnation of blood flow and poor oxygenation, subclinical coagulopathy with elevated D-dimers, and increased production of superoxide from nitric oxide synthase. All of these changes favour endothelial apoptosis and necrosis as well as increased oxidant stress. Reduced levels of activated protein C, which is normally anti-inflammatory and antiapoptotic, can lead to further tissue injury. Cirrhotic patients are particularly susceptible to bacterial infections because of increased bacterial translocation, possibly related to liver dysfunction and reduced reticuloendothelial function. Sepsis ensues when there is overactivation of pathways involved in the development of the sepsis syndrome, associated with complications such as renal failure, encephalopathy, gastrointestinal bleed, and shock with decreased survival. Thus the treating physician needs to be vigilant in diagnosing and treating bacterial infections in cirrhosis early, in order to prevent the development and downward spiral of the sepsis syndrome. Recent advances in management strategies of infections in cirrhosis have helped to improve the prognosis of these patients. These include the use of prophylactic antibiotics in patients with gastrointestinal bleed to prevent infection and the use of albumin in patients with spontaneous bacterial peritonitis to reduce the incidence of renal impairment. The use of antibiotics has to be judicious, as their indiscriminate use can lead to antibiotic resistance with potentially disastrous consequences.

Transjugular intrahepatic portosystemic shunt in refractory ascites: a meta-analysis

Transjugular intrahepatic portosystemic shunt (TIPS) is a more effective treatment for refractory ascites than large volume paracentesis (LVP), but the magnitude of its effect in terms of control of ascites, encephalopathy and survival has not been established.

AIM

This meta-analysis compare TIPS to LVP in terms of control of ascites at 4 and 12 months, encephalopathy and survival at 1 and 2 years.

RESULTS

Five randomized controlled trials involving 330 patients were included. In the TIPS group, control of ascites was more frequently achieved at 4 months (66% vs 23.8%, mean difference: 41.4%, 95% confidence interval (CI): 29.5-53.2%, P < 0.001) and 12 months (54.8% vs 18.9%, mean difference: 35%, 95% CI: 24.9-45.1%, P < 0.001), whereas encephalopathy was higher (54.9% vs 38.1%, mean difference: 17%, 95% CI: 7.3-26.6%, P < 0.001). Survival at 1 year (61.7% vs 56.5%, mean difference: 3.2%, 95% CI: -14.7 to 21.9%) and 2 years (50% vs 42.8%, mean difference: 6.8%, 95% CI: -10 to 23.6%) were not significantly different.

CONCLUSIONS

TIPS is a more effective treatment for refractory ascites than LVP. However, TIPS increase encephalopathy and does not improve survival.

Tezosentan, an endothelin receptor antagonist, limits liver injury in endotoxin challenged cirrhotic rats

BACKGROUND/AIMS

Lipopolysaccharide (LPS) induces liver injury which is associated with upregulated endothelin (ET)-1 production. The aim of this study was to investigate the effects of tezosentan, a non-selective ETA and ETB receptor antagonist, in LPS challenged rats with cirrhosis.

METHODS

Rats with cirrhosis received LPS and then tezosentan or placebo one hour later. Four hours after LPS administration, rats were killed to measure serum transaminase activity and plasma tumour necrosis factor alpha (TNF-alpha) levels. Hepatic inducible nitric oxide synthase (iNOS), myeloperoxidase (MPO), a marker of neutrophil infiltration, and cyclooxygenase (COX)-2 expression were also measured.

RESULTS

LPS administration significantly decreased arterial pressure and significantly increased plasma endothelin levels. Following LPS and tezosentan administration, serum aspartate aminotransferase and alanine aminotransferase activities were similar to those in the control group while they were increased by more than 700% with LPS alone. Plasma TNF-alpha levels were significantly lower in rats receiving LPS and tezosentan (182 (38) pg/ml) compared with those receiving LPS alone (821 (212) pg/ml). Tezosentan significantly decreased hepatic MPO activity and hepatic neutrophils but had no effect on LPS induced iNOS or COX-2. Survival rate was significantly higher in rats receiving LPS plus tezosentan (80%) than in rats receiving LPS alone (50%).

CONCLUSION

In LPS challenged cirrhotic rats, tezosentan administration prevents LPS induced liver injury by decreasing intrahepatic neutrophil infiltration. In addition, tezosentan increases survival in these rats.

Rubber Tree (Hevea brasiliensis) Bark Necrosis Syndrome II: First Comprehensive Report on Causal Stresses

Bark necrosis (BN), described and first studied in Côte d'Ivoire in the 1980s (2), affects most modern rubber plantations (i.e., grafted trees with high-yielding clones, intensive exploitation due to tapping frequency, and use of Ethrel as a yield stimulant) worldwide with a wide range of severity across sites. While previous (3) and recent (4) etiological analyses remain inconclusive, environmental factors were shown associated with BN. Numerous epidemiological surveys conducted in various African and Asian plantations on recently tapped blocks (less than 10-year-old trees) revealed the nonrandom location of the earliest single diseased trees. These risky areas are mainly characterized by the proximity of a swamp, plantation road, windrow, old bulldozer track, residual forest stump, or slope break. In BN emergence areas, while no significant correlation was found with chemical soil parameters, physical soil analyses (e.g., penetrometer) revealed higher soil compaction often associated with poorer rhizogenesis in BN trees (comparative root counts made in pits close to healthy or BN trees). Furthermore, initial BN symptoms were preferentially observed near the grafted bud at the rootstock/scion junction (RS/S). Numerous comparative ecophysiological measurements of leaf water potential, stem water potential, and predawn base potential using a plant moisture stress (PMS) pressure chamber indicated water stress in BN trees. These results and preliminary dye transfer studies at the RS/S junction suggested a nonoptimal vascular relation between the root system and the trunk of BN trees. In conclusion, compaction-associated reduced water availability of the soil and poor root capacity to meet the water demand during drier dry seasons combined with disturbed sap flows and recurrent local water drainage (latex flows) are now suspected to jointly act as the main exogenous causal stresses that induce the BN process at the RS/S bud zone before spreading upward to the tapping cut. This multidisciplinary approach gives a new comprehensive scenario for the emergence of this multifactorial physiological disease, now suspected to involve cyanide release (1) into the inner phloem of the rubber tree. References: (1) H. Chrestin. Plant Dis. 88:1047, 2004. (2) D. Nandris et al. Eur. J. For. Pathol. 21:325, 1991. (3) D. Nandris et al. Eur. J. For Pathol. 21:340, 1991. (4) F. Pellegrin et al. Plant Dis. 88:1046, 2004.

Review article: hepatorenal syndrome--definitions and diagnosis

Hepatorenal syndrome (HRS) is a severe complication of cirrhosis that develops in the final phase of the disease. Two types of HRS exist. Type 1 is defined by a rapid reduction of renal function and in type 2 HRS the reduction of renal function is slowly progressive. Type 1 HRS is diagnosed when the serum creatinine level increases by more than 50% of the baseline value to above 133 micromol/L. According to the International Ascites Club, HRS is defined by the presence of five criteria: (1) severe cirrhosis; (2) glomerular hypofiltration; (3) no other functional or organic causes; (4) failure of plasma volume expansion; (5) no proteinuria. Additional diagnostic criteria may be present. The diagnosis of HRS may be difficult in patients with severe cirrhosis. Other types of acute renal failure may occur. For example, ischaemic or toxic tubular necrosis or sepsis may cause renal failure in these patients. Furthermore, uncontrolled HRS may lead to ischaemic tubular necrosis; thus, these patients must be managed as soon as possible in an intensive care unit.

Nosocomial and community-acquired spontaneous bacterial peritonitis: comparative microbiology and therapeutic implications

In order to compare the microbiological characteristics of nosocomial and community-acquired episodes of bacterial peritonitis, 95 consecutive, spontaneous episodes were reviewed. Seventy of these episodes were bacteriologically documented. Fifty-three (55.8%) episodes were nosocomial and 42 (44.2%) were community acquired. A total of 78 pathogens were isolated, including 40 gram-positive cocci (34 streptococci, 6 Staphylococcus aureus), 35 gram-negative bacilli (including 23 Escherichia coli), 2 gram-positive bacilli and 1 yeast. Streptococci were found more frequently in community-acquired episodes (53.8%) than in nosocomial episodes (33.3%). Gram-negative bacilli were significantly more frequent in nosocomial episodes than in community-acquired episodes (56.4% vs. 33.3%, P<0.05). Nosocomial isolates were significantly more resistant to amoxicillin-clavulanic acid (48.7% vs. 18.4%, P<0.01) and cefotaxime (33.3% vs. 13.2%, P<0.05) than community-acquired isolates, but no difference was detected regarding resistance to ciprofloxacin. The results indicate that the empirical treatment of spontaneous bacterial peritonitis should differ for nosocomial and community-acquired cases.

Comparison of the effect of terlipressin and albumin on arterial blood volume in patients with cirrhosis and tense ascites treated by paracentesis: a randomised pilot study

BACKGROUND

Patients with cirrhosis and tense ascites treated by paracentesis alone have a decrease in effective arterial blood volume after ascites removal. Although intravenous albumin is effective in preventing paracentesis induced decreased arterial blood volume, its clinical use is controversial. As paracentesis induces arteriolar vasodilation which plays a role in the development of decreased effective arterial blood volume, administration of a vasoconstrictor (terlipressin) could prevent circulatory alterations due to paracentesis.

AIMS

To perform a pilot study comparing the effects of terlipressin and albumin on effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites.

METHODS

Twenty patients with cirrhosis and tense ascites were randomly assigned to be treated by either paracentesis and terlipressin or paracentesis and albumin. Terlipressin (3 mg) or albumin (8 g/l of removed ascites) were administered on the day of paracentesis. Effective arterial blood volume was assessed by measuring plasma renin concentrations at baseline and on the day of hospital discharge (4-6 days after treatment). Decreased effective arterial blood volume was defined as an increase in plasma renin concentrations on the day of hospital discharge of more than 50% of baseline values.

RESULTS

Irrespective of the treatment group, mean values for plasma renin concentrations at hospital discharge did not differ from their respective baseline values (p=0.10). Baseline plasma levels of renin concentrations did not differ between the terlipressin and albumin groups (p=0.61). Changes from baseline in plasma renin concentrations did not differ between groups (p=0.39). Three patients in the terlipressin group and three in the albumin group developed decreased arterial blood volume.

CONCLUSIONS

This randomised pilot study suggests that terlipressin may be as effective as intravenous albumin in preventing a decrease in effective arterial blood volume in patients with cirrhosis treated by paracentesis for tense ascites.

Role of small-conductance Ca2+-dependent K+ channels in in vitro nitric oxide-mediated aortic hyporeactivity to alpha-adrenergic vasoconstriction in rats with cirrhosis

BACKGROUND/AIMS

In vitro studies have shown that cirrhotic aortas are hyporeactive to the contractile effect of vasoconstrictors because upregulated endothelial nitric oxide-synthase (NOS) overproduces nitric oxide (NO). Although stimulation of endothelial small-conductance Ca2+-dependent K+ (SK(Ca)) channels may elicit vasorelaxation in normal arteries, the role of these channels in cirrhosis-induced hyporeactivity is unknown. Thus, the aim of the present study was to investigate the role of endothelial SK(Ca) channels in cirrhosis-induced, NO-mediated, in vitro aortic hyporeactivity to alpha1-adrenergic vasoconstrictors.

METHODS

Isolated thoracic aortas from cirrhotic and normal rats were used. The effects of apamin, a selective SK(Ca) channel blocker, were measured on the vascular reactivity to phenylephrine. In addition, SK(Ca) channel protein expression was studied. The effects of iberiotoxin and charybdotoxin, blockers of other K(Ca) channels, were also studied in cirrhotic aortas.

RESULTS

Apamin suppressed cirrhosis-induced aortic hyporeactivity to phenylephrine in an endothelium-dependent, NOS-inhibitor-sensitive manner. SK(Ca) channel protein was overexpressed in cirrhotic aortic walls. Iberiotoxin abolished cirrhosis-induced aortic hyporeactivity to phenylephrine in an endothelium-dependent but NOS-inhibitor-resistant manner. Charybdotoxin did not induce any significant increase in phenylephrine-elicited contraction.

CONCLUSIONS

In cirrhotic aortas, the overexpression and overactivity of endothelial SK(Ca) channels contributes to in vitro NO-mediated hyporeactivity to the contractile action of alpha1-adrenergic agonists.

Characteristics of calcium uptake by BeWo cells, a human trophoblast cell line

Placental transfer of maternal calcium (Ca(2+)) is a crucial process for fetal development although the biochemical mechanisms responsible for this transfer are largely unknown. We have investigated the characteristics of Ca(2+)uptake by the human placental trophoblast cell line BeWo. The kinetics studies revealed an active extracellular Ca(2+)uptake by BeWo cells, which was rapid in the first 2 min (initial velocity (V(i)) of 4.17+/-0.25 nmol/mg/min), and showed a subsequent plateau. Uptake experiments performed at V(i)with increasing concentrations of Ca(2+)resulted in a typical saturation curve (K(m)of 0.54+/-0.07 m m and V(max)of 7.07+/-0.28 nmol/mg protein/min). Lowering the pH of the incubation medium from 7.4 to 5.5 led to Ca(2+)uptake inhibition of 40-50 per cent. The presence of voltage-sensitive (l -type) Ca(2+)channels in BeWo cells was demonstrated by Western blot. Therefore, the implication of such channels in basal Ca(2+)uptake of BeWo cells was investigated. Cell depolarization with extracellular high potassium concentration (40 m m), and hyperpolarization with extracellular high chloride concentration (60 m m) or with valinomycin (10 microm) did not influence the basal Ca(2+)uptake of BeWo cells. The L-type Ca(2+)channel modulators (Bay K 8644 and Nitrendipine) had no effect on the Ca(2+)uptake. An antagonist of receptor-mediated, store-operated and voltage-gated Ca(2+)channels (SKF-96365) also did not modulate the Ca(2+)uptake of BeWo cells. Therefore, our results indicate that the basal Ca(2+)uptake of BeWo cells is inhibited by lowering pH of the incubation medium, is voltage independent, and is not influenced by l -type Ca(2+)channel and capacitative Ca(2+)conductance modulators.

Role of nitric oxide in hepatopulmonary syndrome in cirrhotic rats

The hepatopulmonary syndrome (HPS) is characterized by intrapulmonary vascular dilatations and an increased alveolar-arterial oxygen difference (AaPO(2)). Exhaled nitric oxide (NO) concentrations are elevated, suggesting that pulmonary NO overproduction may be the mechanism underlying HPS. We investigated whether common bile duct ligation in rats results in lung NO overproduction and whether normalization of NO synthesis by a 6-wk course of N(G)-nitro-L-arginine methyl ester (L-NAME) (5 mg x kg(-)(1) x d(-)(1)) prevents HPS. Untreated cirrhotic rats showed increases in AaPO(2) and in cerebral uptake of intravenous (99m)Tc-labeled albumin macroaggregates (indicating intrapulmonary vascular dilatations), with decreases in pulmonary vascular resistance and in pulmonary vasoconstriction induced by angiotensin II and hypoxia. Increases were found in exhaled NO; pulmonary total and calcium-dependent NO synthase (NOS) activities; and pulmonary expression of inducible and, to a lesser extent, endothelial NOS. Accumulation of intravascular macrophages accounted for the inducible NOS expression. L-NAME normalized AaPO(2), brain radioactivity, pulmonary vascular resistance, reactivity to hypoxia and angiotensin II, exhaled NO, and NOS activities. These findings suggest that HPS and the associated reduced response to pulmonary vasoconstrictors seen in untreated cirrhotic rats are related to increased pulmonary NO production dependent primarily on increases in the expression and activities of inducible NOS within pulmonary intravascular macrophages.

Pathogenesis of portal hypertension

Portal hypertension is defined by an elevation in portal pressure and is associated with haemodynamic alterations. Haemodynamic changes are characterized by a hyperdynamic circulation in the splanchnic and systemic territories and a reduced pressure effect of vasoconstrictive substances. They were observed in both patients and animals with different types of portal hypertension. In this review, the main results and their mechanisms of the splanchnic and systemic haemodynamic alterations in portal hypertension are discussed.