Time-dependent modulation of muscarinic m1/m3 receptor signalling by local anaesthetics.

BACKGROUND: Signalling of several G-protein-coupled receptors of the Gq/11 family is time-dependently inhibited by local anaesthetics (LAs). Since LA-induced modulation of muscarinic m1 and m3 receptor function may explain their beneficial effects in clinical practice, such as decreased postoperative cognitive dysfunction or less bronchoconstriction, we studied how prolonged exposure affects muscarinic signalling (Wang D, Wu X, Li J, Xiao F, Liu X, Meng M. The effect of lidocaine on early postoperative cognitive dysfunction after coronary artery bypass surgery. Anesth Analg 2002; 95: 1134-41; Groeben H, Silvanus MT, Beste M, Peters J. Combined lidocaine and salbutamol inhalation for airway anesthesia markedly protects against reflex bronchoconstriction. Chest 2000; 118: 509-15). METHODS: A two-electrode voltage clamp was used to assess the effects of lidocaine or its permanently charged analogue QX314 on recombinantly expressed m1 and m3 receptors in Xenopus oocytes. Antisense knock-down of functional Gαq-protein and inhibition of protein kinase C (PKC) served to define mechanisms and sites of action. RESULTS: Lidocaine affected muscarinic signalling in a biphasic way: an initial decrease in methylcholine bromide-elicited m1 and m3 responses after 30 min, followed by a significant increase in muscarinic responses after 8 h. Intracellularly injected QX314 time-dependently inhibited muscarinic signalling, but had no effect in Gαq-depleted oocytes. PKC-antagonism enhanced m1 and m3 signalling, but completely abolished the LA-induced increase in muscarinic responses, unmasking an underlying time-dependent inhibition of m1 and m3 responses after 8 h. CONCLUSIONS: Lidocaine modulates muscarinic m1 and m3 receptors in a time- and Gαq-dependent manner, but this is masked by enhanced PKC activity. The biphasic time course may be due to interactions of LAs with an extracellular receptor domain, modulated by PKC activity. Prolonged exposure to LAs may not benefit pulmonary function, but may positively affect postoperative cognitive function.

Current knowledge and practice of Candida auris screening in France: A nationwide survey from the French Society of Medical Mycology (SFMM).

Due to large outbreaks observed worldwide, Candida auris has emerged as a major threat to healthcare facilities. To prevent these phenomena, a systematic screening should be performed in patients transferred from regions where the pathogen is highly endemic. In this study, we recorded and analyzed French mycologists' current knowledge and practice regarding C. auris screening and diagnosis. Thirty-six centers answered an online questionnaire. Only 11 (30.6 %) participants were aware of any systematic screening for C. auris for patients admitted to their hospital. In the case of post-admission screening, axillae/groins (n = 21), nares (n = 7), rectum (n = 9), and mouth (n = 6) alone or various combinations were the body sites the most frequently sampled. Only six centers (8.3 %) reported using a commercially available plate allowing the differentiation of C. auris colonies from that of other Candida species, while five laboratories (13.8 %) had implemented a C. auris-specific qPCR. Considering the potential impact on infected patients and the risk of disorganization in the care of patients, it is crucial to remember to biologists and clinicians the utmost importance of systematic screening on admission.

Ketamine induces apoptosis via the mitochondrial pathway in human lymphocytes and neuronal cells.

BACKGROUND: Ketamine has been shown to have neurotoxic properties, when administered neuraxially. The mechanism of this local toxicity is still unknown. Therefore, we investigated the mechanism of cytotoxicity in different human cell lines in vitro. METHODS: We incubated the following cell types for 24 h with increasing concentrations of S(+)-ketamine and racemic ketamine: (i) human Jurkat T-lymphoma cells overexpressing the antiapoptotic B-cell lymphoma 2 protein, (ii) cells deficient of caspase-9, caspase-8, or Fas-associated protein with death domain and parental cells, and (iii) neuroblastoma cells (SHEP). N-Methyl-d-aspartate (NMDA) receptors and caspase-3 cleavage were identified by immunoblotting. Cell viability and apoptotic cell death were evaluated flowcytometrically by Annexin V and 7-aminoactinomycin D double staining. Mitochondrial metabolic activity and caspase-3 activation were measured. RESULTS: Ketamine, in a concentration-dependent manner, induced apoptosis in lymphocytes and neuroblastoma cell lines. Cell lines with alterations of the mitochondrial pathway of apoptosis were protected against ketamine-induced apoptosis, whereas alterations of the death receptor pathway did not reduce apoptosis. S(+)-Ketamine and racemic ketamine induced the same percentage of cell death in Jurkat cells, whereas in neuroblastoma cells, S(+)-ketamine was slightly less toxic. CONCLUSIONS: Ketamine at millimolar concentrations induces apoptosis via the mitochondrial pathway, independent of death receptor signalling. At higher concentrations necrosis is the predominant mechanism. Less toxicity of S(+)-ketamine was observed in neuroblastoma cells, but this difference was minor and therefore unlikely to be mediated via the NMDA receptor.

[Value of double reading of whole body CT in polytrauma patients]. / Intérêt de la double lecture du scanner corps entier dans la prise en charge des polytraumatisés.

PURPOSE: To assess the value of standard double reading of whole body CT in the management of polytrauma patients. MATERIALS AND METHODS: Prospective study between January and July 2005. Two senior radiologists with expertise in trauma imaging, blinded to clinical findings, reviewed 105 initial CT examinations of polytrauma patients. These examinations had initially been interpreted by the on-call radiologist. The second interpretations were performed within 12 hours of admission, and were considered the gold standard. RESULTS: A total of 105 patients were included with 82 males (78%) and 23 females (22%), aged between 2 and 83 years. The level of admission was graded III (n=64), II (n=30) and I (n=11). The second reading identified 3 lesions that were not initially described, each requiring a change in management, including splenic rupture (n=1), thoracic spine fracture (n=1) and epidural hematoma (n=1), with no unfavorable impact on mortality. Additional errors in the initial interpretation were identified: peripheral fractures (n=38), chest (n=36), brain (n=31), abdominal (n=28), spine (n=19) and maxillofacial (17) lesions and contrast extravasation (n=6). CONCLUSION: Based on the large number and severity of some lesions missed at initial interpretation of whole body CT of polytrauma patients, we recommend standard double reading of these examinations.

[Value of MRCP with Mangafodipir Trisodium (Teslascan) injection in the diagnosis and management of bile leaks]. / Intérêt de la cholangio-IRM avec perfusion de Mangafodipir Trisodium (Teslascan) dans le diagnostic topographique et la prise en charge des fuites biliaires.

PURPOSE: To assess the value of MRCP with Mangafodipir Trisodium (Teslascan) injection in the diagnosis and management of bile leaks. PATIENTS AND METHODS: Retrospective study of 25 patients (18 males, 7 females) with a mean age of 49.7 years and high clinical suspicion of bile leak who underwent MRCP with Mangafodipir Trisodium (Teslascan) injection between 2002 and 2006. The suspected etiology for bile leak was surgical (n=17), traumatic (n=7) or medical (n=1). The clinical suspicion was based on a combination of clinical, laboratory and imaging findings. RESULTS: MRCP with Teslascan injection demonstrated a bile leak in 20 patients. The site of leak was depicted in 17 cases: second order of smaller bile duct, (n=9), hepatic duct (n=3), confluence (n=2), cystic duct (n=1), bilioenteric anastomosis (n=2). Management based on MR findings included biloma drainage (n=7), biliary drainage (n=5), endoscopic management (n=2), repeat surgery (n=3), expectant management (n=1), and medical management (n=1). Outcome was favourable in 18 cases. Two patients died from infectious complications. CONCLUSION: In addition to confirming a diagnosis of bile leak, MRCP with Teslascan injection depicts the site of leak allowing optimal management.

[Radiological management of vascular lesions secondary to pelvic injuries]. / Prise en charge radiologique des lésions vasculaires secondaires aux traumatismes du bassin.

Pelvic injuries are serious, with mortality higher than 40% if the patient is in shock upon arrival at the hospital. These injuries are generally secondary to traffic accidents with violent kinetics, which explains the frequency of the associated extrapelvic lesions. With the vital prognosis at stake, management of these patients is a true challenge from both the radiographic and emergency care points of view. The objectives of this review are to present the epidemiological and physiological issues involved in pelvic injuries and the place of imaging today, necessarily integrated within a multidisciplinary team associating emergency physicians, surgeons, radiologists, and biologists.

Lumbar spinal muscles and spinal canal study by MRI three-dimensional reconstruction in adult lumbar spinal stenosis.

BACKGROUND: Lumbar spinal stenosis is degenerative disc disease most common manifestation. If stenosis degree seems poorly related to symptom severity, lumbar muscles role is recognized. Many studies report imaging methods, to analyze muscle volumes and fat infiltration (FI), but remain limited due to the difficulty to represent entire muscle volume variability. Recently a 3D muscle reconstruction protocol (using the deformation of a parametric specific object method (DPSO) and three-point Dixon images) was reported. It offers the ability to evaluate, muscles volumes and muscle FI. PURPOSE: To describe, in a lumbar spinal stenosis population, muscle volumes, muscle FI and lumbar spinal canal volume with 3D MRI images reconstructions. MATERIALS AND METHODS: Ten adults presenting L4-L5 lumbar stenosis, were included. After specific MRI protocol, three-dimensional, muscle and spinal canal, reconstructions were performed. Muscle (psoas and paraspinal muscles) volumes and fat infiltration (FI), the spinal canal volume, age, and height were correlated one to each other with Spearman correlation factor. An ANOVA was performed to evaluate the intervertebral level influence (P≤0.05). RESULTS: Muscle volumes correlated with height (r=0.68 for psoas). Muscles FI correlated with age (r=0.66 for psoas) and lumbar spinal canal volume (r=0.91). Psoas and paraspinal volumes were maximum at L3-L4 level whereas FI increased from L1-L2 to L5-S1 level. DISCUSSION: These first results illustrate the importance to consider muscles entirely and report correlations between muscles FI, lumbar spinal canal volume and age; and between muscle volumes and patients height. Muscle degeneration seems more related to muscle FI than muscle volume. LEVEL OF EVIDENCE: 3.

Quantification of cerebral perfusion with "Real-Time" contrast-enhanced ultrasound.

BACKGROUND: No noninvasive technique is currently capable of "real-time" assessment and monitoring of cerebral blood flow (CBF). We hypothesized that cerebral perfusion could be accurately measured and monitored in "real time" with contrast-enhanced ultrasound (CEU). METHODS AND RESULTS: Cerebral perfusion was assessed in 9 dogs through a craniotomy with CEU at baseline and during hypercapnia and hypocapnia while normoxia was maintained. Cerebral microvascular blood volume (A), microbubble velocity (beta), and blood flow (Axbeta) were calculated from time-versus-acoustic intensity relations. Compared with baseline, hypercapnia and hypocapnia significantly increased and decreased CBF, respectively, as measured by CEU. These changes in blood flow were mediated by changes in both A and beta. A good correlation was found between Axbeta derived from CEU and CBF measured by radiolabeled microspheres (y=0.67x-0.04, r=0.91, P<0.001). CONCLUSIONS: Changes in both cerebral microvascular blood volume and red blood cell velocity can be accurately assessed with CEU. Thus, CEU has the potential for bedside measurement and monitoring of cerebral perfusion in real time in patients with craniotomies or burr holes.

Signalling properties of lysophosphatidic acid.

Lysophosphatidic acid (LPA) is the simplest natural phospholipid, primarily known as a membrane component and metabolic intermediate. However, a remarkable variety of biological effects of this compound have come to light, seemingly pointing to an additional role for LPA as a signalling molecule. In this review, Marcel Durieux and Kevin Lynch integrate the recent information that indicates that LPA could be an intercellular messenger, possibly acting through a G protein-coupled receptor, and with a role in cell growth and motility.

MS lesions are better detected with 3D T1 gradient-echo than with 2D T1 spin-echo gadolinium-enhanced imaging at 3T.

BACKGROUND AND PURPOSE: In multiple sclerosis, gadolinium enhancement is used to classify lesions as active. Regarding the need for a standardized and accurate method for detection of multiple sclerosis activity, we compared 2D-spin-echo with 3D-gradient-echo T1WI for the detection of gadolinium-enhancing MS lesions. MATERIALS AND METHODS: Fifty-eight patients with MS were prospectively imaged at 3T by using both 2D-spin-echo and 3D-gradient recalled-echo T1WI in random order after the injection of gadolinium. Blinded and independent evaluation was performed by a junior and a senior reader to count gadolinium-enhancing lesions and to characterize their location, size, pattern of enhancement, and the relative contrast between enhancing lesions and the adjacent white matter. Finally, the SNR and relative contrast of gadolinium-enhancing lesions were computed for both sequences by using simulations. RESULTS: Significantly more gadolinium-enhancing lesions were reported on 3D-gradient recalled-echo than on 2D-spin-echo (n = 59 versus n = 30 for the junior reader, P = .021; n = 77 versus n = 61 for the senior reader, P = .017). The difference between the 2 readers was significant on 2D-spin-echo (P = .044), for which images were less reproducible (κ = 0.51) than for 3D-gradient recalled-echo (κ = 0.65). Further comparisons showed that there were statistically more small lesions (<5 mm) on 3D-gradient recalled-echo than on 2D-spin-echo (P = .04), while other features were similar. Theoretic results from simulations predicted SNR and lesion contrast for 3D-gradient recalled-echo to be better than for 2D-spin-echo for visualization of small enhancing lesions and were, therefore, consistent with clinical observations. CONCLUSIONS: At 3T, 3D-gradient recalled-echo provides a higher detection rate of gadolinium-enhancing lesions, especially those with smaller size, with a better reproducibility; this finding suggests using 3D-gradient recalled-echo to detect MS activity, with potential impact in initiation, monitoring, and optimization of therapy.

Magnetic resonance arthrography of the wrist with axial traction: An iconographic review.

Stress maneuvers inspired by arthroscopic techniques have been previously studied for MRA of shoulder, hip, knee and wrist. Axial traction in MRA of the wrist is advantageous to study intrinsic ligaments and cartilage, but seems useless to assess tendons or nerves disorders. Based on our experience and a well-chosen iconography, we would like to emphasize the contribution of axial traction in MRA of wrist disorders.

Saralasin dilates arterioles in SHR but not WKY rats.

Microvascular responses to topical or intravascular saralasin were determined in the cremaster muscle arterioles of adult spontaneously hypertensive rats (SHR, n = 19) and Wistar-Kyoto (WKY, n = 16) normotensive rats. Animals were anesthetized with chloralose and urethane, and they breathed room air spontaneously. Mean arterial pressure was obtained from a catheter in a carotid artery, and microvascular diameters were determined by video microscopy. Plasma renin activity was measured in animals that were treated identically except that saralasin was not administered. For all animals, mean arterial pressure averaged 126 +/- 4 mm Hg in SHR and 82 +/- 4 mm Hg (p less than 0.001) in WKY rats. Topical saralasin, 10(-6)M, was applied to the cremaster muscles of SHR (n = 9) or WKY (n = 8) rats while internal diameters of first-through fourth-order arterioles (A1, A2, A3, A4) were measured. Topical saralasin did not alter arteriolar diameters (A1 through A4) in WKY rats, but A3 and A4 vessels dilated significantly (29% +/- 5% and 38% +/- 7% respectively; p less than 0.01) in SHR. Fourth-order diameters were measured in other SHR (n = 10) and WKY (n = 8) rats while saralasin was administered intraarterially (300 micrograms bolus into the hypogastric artery) or intravenously (10 micrograms/kg/min for 30 minutes). Intraarterial or intravenous saralasin caused significant dilation (32% +/- 12% and 20% +/- 4%, respectively; p less than 0.01) of A4 arterioles in SHR, but no dilation occurred in the arterioles of WKY rats. Arteriolar responses were significantly different (p less than 0.001) in SHR vs WKY rats for both the topical and the intravascular administration of saralasin.(ABSTRACT TRUNCATED AT 250 WORDS)

Trypsin induces Ca(2+)-activated Cl- currents in X. laevis oocytes.

The protease trypsin induces Ca(2+)-activated Cl- currents when applied in concentrations as low as 0.1 mg/ml to defolliculated, voltage clamped X. laevis oocytes. The response is dose-dependent and specific, as other proteases (chymotrypsin, Lys-C and Arg-C), or trypsin pretreated with soybean trypsin inhibitor, did not induce currents. Intracellular trypsin injection did not induce responses. The current does not appear to result from proteolytic activation of the endogenous receptor for lysophosphatidic acid, the only known Ca(2+)-mobilizing receptor consistently present in oocytes. These results suggest the presence on the oocyte membrane of a specific receptor for trypsin.

Macrophage function in vitamin C-deficient guinea pigs.

Guinea pigs were fed a vitamin C-deficient diet and at various time periods thereafter their peritoneal cells were tested for biological activity. The serum levels of vitamin C in the deficient animals indicated a progressive state of ascorbic acid deficiency with time and this correlated well with clinical signs and symptoms of scurvy. Fewer macrophages were obtained from the peritoneal cavities of deficient animals and in structural appearance under the phase contrast and light microscope they were smaller in size. They showed no significant impairment in phagocytosis of bacterial cells. The macrophages, however, exhibited significantly reduced migration on glass as compared to the normal cells. In vitro addition of vitamin C partially reversed this reduced migration.

Inhibition of m3 muscarinic acetylcholine receptors by local anaesthetics.

1. Muscarinic m1 receptors are inhibited by local anaesthetics (LA) at nM concentrations. To elucidate in more detail the site(s) of LA interaction, we compared these findings with LA effects on m3 muscarinic receptors. 2. We expressed receptors in Xenopus oocytes. Using two-electrode voltage clamp, we measured the effects of lidocaine, QX314 (permanently charged) and benzocaine (permanently uncharged) on Ca(2+)-activated Cl(-)-currents (I(Cl(Ca))), elicited by acetyl-beta-methylcholine bromide (MCh). We also characterized the interaction of lidocaine with [(3)H]-quinuclydinyl benzylate ([(3)H]-QNB) binding to m3 receptors. Antisense-injection was used to determine the role of specific G-protein alpha subunits in mediating the inhibitory effects of LA. Using chimeric receptor constructs we investigated which domains of the muscarinic receptors contribute to the binding site for LA. 3. Lidocaine inhibited m3-signalling in a concentration-dependent, reversible, non-competitive manner with an IC(50) of 370 nM, approximately 21 fold higher than the IC(50) (18 nM) reported for m1 receptors. Intracellular inhibition of both signalling pathways by LA was similar, and dependent on the G(q)- protein alpha subunit. In contrast to results reported for the m1 receptor, the m3 receptor lacks the major extracellular binding site for charged LA. The N-terminus and third extracellular loop of the m1 muscarinic receptor molecule were identified as requirements to obtain extracellular inhibition by charged LA.

Volatile anesthetic inhibition of neuronal Ca channel currents expressed in Xenopus oocytes.

The genes encoding the alpha(1A), alpha(1B), alpha(1C) and alpha(1E) subunits of neuronal high voltage-gated Ca channels (HVGCCs) were separately expressed with beta(1B) and alpha(2)/delta subunits in Xenopus oocytes to determine the effects of volatile anesthetics (VAs) on currents through each specific channel. VA effects were determined on currents carried by Ba(2+) (I(Ba)) using the two electrode voltage clamp technique. Although time to peak was unaffected, both halothane (0.59 mM) and isoflurane (0.70 mM) reversibly inhibited peak I(Ba) by 25-35% and late current (at 830 ms) by 50-60%. A hyperpolarizing shift in steady-state inactivation of alpha(1E)-current was found which could contribute up to one third of observed decrease in the peak current. The rate of inactivation of I(Ba) seen with alpha(1A), alpha(1B) and alpha(1E)-type Ca channels was consistently increased by halothane and isoflurane. To more clearly quantify these effects, I(Ba) inactivation was fit by a single exponential function. The anesthetics depressed both the inactivating and non-inactivating residual components of I(Ba) and decreased the time constant of inactivation. In the case of I(Ba) through alpha(1C)-type channels, inactivation was minimal; however, the average current was inhibited by VAs. Similar inhibition of all these HVGCCs by halothane and isoflurane suggests that a common structural component may be involved. Furthermore, the inhibition of such neuronal HVGCCs in situ could alter synaptic neurotransmitter release and contribute to the anesthetic state.

Influence of anesthetics on endogenous and recombinantly expressed G protein-coupled receptors in the Xenopus oocyte.

1. The oocyte of the African clawed toad (Xenopus laevis) offers a reliable, sensitive and disease resistant system to investigate recombinantly and endogenously expressed Ca2+ signaling G protein-coupled receptors and their intracellular signaling pathways. 2. To study receptor induced Ca2+ release, two-electrode voltage clamping can quantify a Ca2+-activated transmembrane Cl- current. Intracellular steps of the signaling pathway can be inhibited by injections of EDTA or heparin into the oocyte. Components of the intracellular pathway can be activated directly by GTPgammaS or IP3 injection. 3. We have investigated the effects of volatile, local and i.v. anesthetics on the signaling properties of the endogenous lysophosphatidate receptor and on mammalian receptors expressed recombinantly by intracellular injection of the encoding mRNA or cDNA. A number of receptors are sensitive to these anesthetics. Anesthetics interact with muscarinic, thromboxane A2 and lysophosphatidate signaling. 4. Investigations of the intracellular pathways revealed that the receptor or the receptor-G protein coupling is affected primarily and that mechanisms further downstream are not influenced by the various types of anesthetics.