Excitatory action of low frequency depolarizing GABA/glycine synaptic inputs is prevalent in prenatal spinal SOD1G93A motoneurons

Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset neurodegenerative disease characterized by progressive motor neuron degeneration and muscle paralysis. Recent evidence suggests the dysfunction of inhibitory signalling in ALS motor neurons. We have shown that embryonic day (E)17.5 spinal motoneurons (MNs) of the SOD1G93A mouse model of ALS exhibit an altered chloride homeostasis. At this prenatal stage, inhibition of spinal motoneurons (MNs) is mediated by depolarizing GABAergic/glycinergic postsynaptic potentials (dGPSPs). Here, using an ex vivo preparation and patch clamp recording from MNs with a chloride equilibrium set below spike threshold, we report that low input resistance (Rin ) E17.5 MNs from the SOD1G93A ALS mouse model do not correctly integrate dGPSPs evoked by electrical stimulations of GABA/glycine inputs at different frequencies. Indeed, firing activity of most wild-type (WT) MNs with low Rin was inhibited by incoming dGPSPs, whereas low Rin SOD1G93A MNs were excited or exhibited a dual response (excited by low frequency dGPSPs and inhibited by high frequency dGPSPs). Simulation highlighted the importance of the GABA/glycine input density and showed that pure excitation could be obtained in SOD-like MNs by moving GABA/glycine input away from the cell body to dendrites. This was in agreement with confocal imaging showing a lack of peri-somatic inhibitory terminals in SOD1G93A MNs compared to WT littermates. Putative fast ALS-vulnerable MNs with low Rin are therefore lacking functional inhibition at the near-term prenatal stage. KEY POINTS: We analysed the integration of GABAergic/glycinergic synaptic events by embryonic spinal motoneurons (MNs) in a mouse model of the amyotrophic lateral sclerosis (ALS) neurodegenerative disease. We found that GABAergic/glycinergic synaptic events do not properly inhibit ALS MNs with low input resistance, most probably corresponding to future vulnerable MNs. We used a neuron model to highlight the importance of the GABA/glycine terminal location and density in the integration of the GABAergic/glycinergic synaptic events. Confocal imaging showed a lack of GABA/glycine terminals on the cell body of ALS MNs. The present study suggests that putative ALS vulnerable MNs with low Rin lack functional inhibition at the near-term stage.

From real-time single to multicompartmental Hodgkin-Huxley neurons on FPGA for bio-hybrid systems

Modeling biological neural networks has been a field opening to major advances in our understanding of the mechanisms governing the functioning of the brain in normal and pathological conditions. The emergence of real-time neuromorphic platforms has been leading to a rising significance of bio-hybrid experiments as part of the development of neuromorphic biomedical devices such as neuroprosthesis. To provide a new tool for the neurological disorder characterization, we design real-time single and multicompartmental Hodgkin-Huxley neurons on FPGA. These neurons allow biological neural network emulation featuring improved accuracy through compartment modeling and show integration in bio-hybrid system thanks to its real-time dynamics.

Chloride Homeostasis in Developing Motoneurons

Maturation of GABA/Glycine chloride-mediated synaptic inhibitions is crucial for the establishment of a balance between excitation and inhibition. GABA and glycine are excitatory neurotransmitters on immature neurons that exhibit elevated [Cl^-]_i. Later in development [Cl^-]_i drops leading to the occurrence of inhibitory synaptic activity. This ontogenic change is closely correlated to a differential expression of two cation-chloride cotransporters that are the Cl^- channel K⁺/Cl^- co-transporter type 2 (KCC2) that extrudes Cl^- ions and the Na⁺-K⁺-2Cl^- cotransporter NKCC1 that accumulates Cl^- ions. The classical scheme built from studies performed on cortical and hippocampal networks proposes that immature neurons display high [Cl^-]_i because NKCC1 is overexpressed compared to KCC2 and that the co-transporters ratio reverses in mature neurons, lowering [Cl^-]_i. In this chapter, we will see that this classical scheme is not true in motoneurons (MNs) and that an early alteration of the chloride homeostasis may be involved in pathological conditions.

Two opposite voltage-dependent currents control the unusual early development pattern of embryonic Renshaw cell electrical activity

Renshaw cells (V1^R) are excitable as soon as they reach their final location next to the spinal motoneurons and are functionally heterogeneous. Using multiple experimental approaches, in combination with biophysical modeling and dynamical systems theory, we analyzed, for the first time, the mechanisms underlying the electrophysiological properties of V1^R during early embryonic development of the mouse spinal cord locomotor networks (E11.5–E16.5). We found that these interneurons are subdivided into several functional clusters from E11.5 and then display an unexpected transitory involution process during which they lose their ability to sustain tonic firing. We demonstrated that the essential factor controlling the diversity of the discharge pattern of embryonic V1^R is the ratio of a persistent sodium conductance to a delayed rectifier potassium conductance. Taken together, our results reveal how a simple mechanism, based on the synergy of two voltage-dependent conductances that are ubiquitous in neurons, can produce functional diversity in embryonic V1^R and control their early developmental trajectory.

Elective late open conversion after endovascular aneurysm repair is associated with comparable outcomes to primary open repair of abdominal aortic aneurysms

OBJECTIVE

Three of four patients with infrarenal abdominal aortic aneurysm are now treated with endovascular aneurysm repair (EVAR). The incidence of secondary procedures and surgical conversions is increasing for a population theoretically unfit for open surgery. The indications and outcomes of late open surgical conversions after EVAR in a high-volume tertiary vascular unit are reported.

METHODS

This retrospective single-center study includes all patients who underwent a late open conversion between January 1996 and July 2018. Data were collected from records on patient demographics, operative indications, surgical strategy, perioperative outcomes, and medium-term survival.

RESULTS

Sixty-two consecutive patients (88.7% male) with a mean age of 77.5 years are included. The median duration since index EVAR was 38.5 months; 65% of stent grafts requiring late open conversion had suprarenal fixation. Indications included 22.6% type IA, 16.1% type IB, and 45.2% type II endoleaks; 12.9% graft thrombosis; and 14.5% endoprosthesis infection. Complete endograft explantation was performed in 37.1% of patients and a partial explantation in 54.8%, whereas 8.1% of stent grafts were wholly preserved in situ. Overall 30-day mortality was 12.9% (n = 8) in the cohort and 2.7% for elective patients. The all-cause morbidity rate was 40.1%, and the median length of hospital stay was 9 days. After follow-up of 28.4 months (range, 1.8-187.3 months), all-cause survival was 58.8%. Avoidance of aortic clamping (P = .006) and elective procedures (P = .019) were associated with a significant reduction in the length of hospital stay. Moreover, the 30-day mortality (P = .002), occurrence of postoperative renal dysfunction (P = .004), and intestinal ischemia (P = .017) were increased in the emergency setting. Excluding cases with rupture or infection, survival estimates were 97%, 97%, and 71% at 1 year, 2 years, and 5 years, respectively.

CONCLUSIONS

Technically more complex than primary open surgery, late open conversion is a procedure that generates an acceptable perioperative risk when it is performed in a high-volume aortic surgical center. Elective open conversion is associated with excellent early and late outcomes. Endograft preservation strategies decrease perioperative morbidity.

Implication of 5-HT in the Dysregulation of Chloride Homeostasis in Prenatal Spinal Motoneurons from the G93A Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron degeneration and muscle paralysis. The early presymptomatic onset of abnormal processes is indicative of cumulative defects that ultimately lead to a late manifestation of clinical symptoms. It remains of paramount importance to identify the primary defects that underlie this condition and to determine how these deficits lead to a cycle of deterioration. We recently demonstrated that prenatal E17.5 lumbar spinal motoneurons (MNs) from SOD1G93A mice exhibit a KCC2-related alteration in chloride homeostasis, i.e., the EGABAAR is more depolarized than in WT littermates. Here, using immunohistochemistry, we found that the SOD1G93A lumbar spinal cord is less enriched with 5-HT descending fibres than the WT lumbar spinal cord. High-performance liquid chromatography confirmed the lower level of the monoamine 5-HT in the SOD1G93A spinal cord compared to the WT spinal cord. Using ex vivo perforated patch-clamp recordings of lumbar MNs coupled with pharmacology, we demonstrated that 5-HT strongly hyperpolarizes the EGABAAR by interacting with KCC2. Therefore, the deregulation of the interplay between 5-HT and KCC2 may explain the alteration in chloride homeostasis detected in prenatal SOD1G93A MNs. In conclusion, 5-HT and KCC2 are two likely key factors in the presymptomatic phase of ALS, particular in familial ALS involving the SOD1G93A mutation.

Relaxation of synaptic inhibitory events as a compensatory mechanism in fetal SOD spinal motor networks

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease affecting motor neurons (MNs) during late adulthood. Here, with the aim of identifying early changes underpinning ALS neurodegeneration, we analyzed the GABAergic/glycinergic inputs to E17.5 fetal MNs from SOD1G93A (SOD) mice in parallel with chloride homeostasis. Our results show that IPSCs are less frequent in SOD animals in accordance with a reduction of synaptic VIAAT-positive terminals. SOD MNs exhibited an EGABAAR10 mV more depolarized than in WT MNs associated with a KCC2 reduction. Interestingly, SOD GABAergic/glycinergic IPSCs and evoked GABAAR-currents exhibited a slower decay correlated to elevated [Cl-]i. Computer simulations revealed that a slower relaxation of synaptic inhibitory events acts as compensatory mechanism to strengthen GABA/glycine inhibition when EGABAAR is more depolarized. How such mechanisms evolve during pathophysiological processes remain to be determined, but our data indicate that at least SOD1 familial ALS may be considered as a neurodevelopmental disease.

[Acute and chronic pathologies of the thoracic aorta: From diagnosis to treatment]

Aortic pathologies benefit from imaging innovation and interventional radiology developments in order to improve patient management. At the early phase, vital risk should be considered. Whole body CT scan evaluate the complete aorta and its branches to assess the pathology and to choose the best approach between surgery or interventional radiology (fenestration, stentgraft, peripheral stenting). Algorithms, based on the understanding of the complications mechanisms and evolutive risk, modified the management specifically for aortic dissection. At chronic phase, GPs and angiologists should follow their patients in order to detect aortic complications and to treat cardiovascular risk factors. MRA is well indicated if possible.

Nonsynaptic glycine release is involved in the early KCC2 expression

The cation-chloride co-transporters are important regulators of the cellular Cl(-) homeostasis. Among them the Na(+) -K(+) -2Cl(-) co-transporter (NKCC1) is responsible for intracellular chloride accumulation in most immature brain structures, whereas the K(+) -Cl(-) co-transporter (KCC2) extrudes chloride from mature neurons, ensuring chloride-mediated inhibitory effects of GABA/glycine. We have shown that both KCC2 and NKCC1 are expressed at early embryonic stages (E11.5) in the ventral spinal cord (SC). The mechanisms by which KCC2 is prematurely expressed are unknown. In this study, we found that chronically blocking glycine receptors (GlyR) by strychnine led to a loss of KCC2 expression, without affecting NKCC1 level. This effect was not dependent on the firing of Na(+) action potentials but was mimicked by a Ca(2+) -dependent PKC blocker. Blocking the vesicular release of neurotransmitters did not impinge on strychnine effect whereas blocking volume-sensitive outwardly rectifying (VSOR) chloride channels reproduced the GlyR blockade, suggesting that KCC2 is controlled by a glycine release from progenitor radial cells in immature ventral spinal networks. Finally, we showed that the strychnine treatment prevented the maturation of rhythmic spontaneous activity. Thereby, the GlyR-activation is a necessary developmental process for the expression of functional spinal motor networks. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 764-779, 2016.

Endovascular Repair for Acute Rupture of the Descending Thoracic Aorta

Purpose:

To report the endovascular treatment of acute descending thoracic aortic rupture as an alternative to open surgery in high-risk patients.

Methods:

Between November 1999 and April 2001, 10 patients (7 men; median age 75 years) underwent endovascular stent-grafting of the descending thoracic aorta for acute rupture from an aneurysm (n = 7) or blunt trauma (n = 3). All patients were evaluated as high operative risk. The aortic rupture was associated with isolated mediastinal hematomas (n = 7), left hemothorax (n = 2), or aortobronchial fistula (n = 1). The Excluder Thoracic Endoprosthesis was used predominantly.

Results:

The mean interval to the endovascular repair was 45.3 ± 28.4 hours. All stent-grafts were successfully deployed. Two patients required common iliac artery access, and 2 needed covered stents for iatrogenic iliac artery rupture. There was 1 postoperative death (myocardial infarction) and no renal failure, neurological complications, embolization, stent-graft migration, or perigraft leak. One patient died 4 months later from an unrelated cause. At a mean follow-up of 7.9 ± 5.1 months, all aneurysms and rupture sites were excluded with no evidence of endoleak or hematoma.

Conclusions:

Endoluminal treatment is a feasible technique for the management of acute rupture of the descending thoracic aorta. Long-term studies are required to assess the effectiveness and durability of this technique in comparison to open repair.

[Tunnelled internal jugular vein catheters with taurolidine lock: an acceptable challenge to arterio-venous fistula in 70 years old haemodialyzed patients: a prospective pilot study]

Arteriovenous fistula (AVF) is still in 2010 the gold standard of vascular(2) access in haemodialysis (HD) patients. Nevertheless it may be difficult to obtain and/or to use AVF in elderly. With this prospective randomised pilot study, we compare two strategies of vascular access in 70 years old or more new HD patients. AVF were compared to tunnelled jugular vein catheters (TIJC) with taurolidine as bacterial lock solution. Results were as follow: [table: see text] The responses with the visual analogic scale of comfort was 8/10 for TIJC and 5/10 with AVF * P<0.05. In five TIJC patients, heparin was added with success to taurolidine because of partial clotting of catheters. Albuminemia was significantly lower in AVF failure patients compared to AVF success patients (24.8g/L vs 31.1g/L). This pilot study allows to conclude that TIJC is an acceptable challenge to AVF in haemodialysed patients of 70 years or more in a two years long use.

GABA(A) receptor and glycine receptor activation by paracrine/autocrine release of endogenous agonists: more than a simple communication pathway

It is a common and widely accepted assumption that glycine and GABA are the main inhibitory transmitters in the central nervous system (CNS). But, in the past 20 years, several studies have clearly demonstrated that these amino acids can also be excitatory in the immature central nervous system. In addition, it is now established that both GABA receptors (GABARs) and glycine receptors (GlyRs) can be located extrasynaptically and can be activated by paracrine release of endogenous agonists, such as GABA, glycine, and taurine. Recently, non-synaptic release of GABA, glycine, and taurine gained further attention with increasing evidence suggesting a developmental role of these neurotransmitters in neuronal network formation before and during synaptogenesis. This review summarizes recent knowledge about the non-synaptic activation of GABA(A)Rs and GlyRs, both in developing and adult CNS. We first present studies that reveal the functional specialization of both non-synaptic GABA(A)Rs and GlyRs and we discuss the neuronal versus non-neuronal origin of the paracrine release of GABA(A)R and GlyR agonists. We then discuss the proposed non-synaptic release mechanisms and/or pathways for GABA, glycine, and taurine. Finally, we summarize recent data about the various roles of non-synaptic GABAergic and glycinergic systems during the development of neuronal networks and in the adult.

Serotonin controls the maturation of the GABA phenotype in the ventral spinal cord via 5-HT1b receptors

Serotonin (5-hydroxytryptamine or 5-HT) is a pleiotropic neurotransmitter known to play a crucial modulating role during the construction of brain circuits. Descending bulbo-spinal 5-HT fibers, coming from the caudal medullary cell groups of the raphe nuclei, progressively invade the mouse spinal cord and arrive at lumbar segments at E15.5 when the number of ventral GABA immunoreactive (GABA-ir) interneurons reaches its maximum. We thus raised the question of a possible interaction between these two neurotransmitter systems and investigated the effect of 5-HT descending inputs on the maturation of the GABA phenotype in ventral spinal interneurons. Using a quantitative anatomical study performed on acute and cultured embryonic mouse spinal cord, we found that the GABAergic neuronal population matured according to a similar rostro-caudal gradient both in utero and in organotypic culture. We showed that 5-HT delayed the maturation of the GABA phenotype in lumbar but not brachial interneurons. Using pharmacological treatments and mice lacking 5-HT(1B) or 5-HT(1A), we demonstrated that the 5-HT repressing effect on the GABAergic phenotype was specifically attributed to 5-HT(1B) receptors.

Preoperative assessment of anatomical suitability for thoracic endovascular aortic repair

Endovascular treatment of descending thoracic aortic pathologies requires a preoperatively determined interventional strategy. Its feasibility depends mainly on anatomic factors: the morphology of the proximal and distal fixation sites, the diameter and disease state of the access vessels. These factors represent important predictors of success and the most important exclusion criteria. Current diagnostic evaluation of aortic aneurysm for endovascular repair relies primarily on CT scan associated with 3D-reconstruction to assess the anatomical suitability for endograft implantation. In patients with an inadequate length of the proximal or distal neck, the left subclavian artery or the coeliac trunk can be overstented to effectively exclude thoracic aortic lesions. Deliberate coverage of aortic side branches should be decided prior to the procedure (guided by a extensive anatomical assessment) or carefully be avoided in order to reduce major morbidity, especially cerebral embolization, spinal cord ischemia and ischemic abdominal complications.

Multi-stability and pattern-selection in oscillatory networks with fast inhibition and electrical synapses

A model or hybrid network consisting of oscillatory cells interconnected by inhibitory and electrical synapses may express different stable activity patterns without any change of network topology or parameters, and switching between the patterns can be induced by specific transient signals. However, little is known of properties of such signals. In the present study, we employ numerical simulations of neural networks of different size composed of relaxation oscillators, to investigate switching between in-phase (IP) and anti-phase (AP) activity patterns. We show that the time windows of susceptibility to switching between the patterns are similar in 2-, 4- and 6-cell fully-connected networks. Moreover, in a network (N = 4, 6) expressing a given AP pattern, a stimulus with a given profile consisting of depolarizing and hyperpolarizing signals sent to different subpopulations of cells can evoke switching to another AP pattern. Interestingly, the resulting pattern encodes the profile of the switching stimulus. These results can be extended to different network architectures. Indeed, relaxation oscillators are not only models of cellular pacemakers, bursting or spiking, but are also analogous to firing-rate models of neural activity. We show that rules of switching similar to those found for relaxation oscillators apply to oscillating circuits of excitatory cells interconnected by electrical synapses and cross-inhibition. Our results suggest that incoming information, arriving in a proper time window, may be stored in an oscillatory network in the form of a specific spatio-temporal activity pattern which is expressed until new pertinent information arrives.

NKCC1 cotransporter inactivation underlies embryonic development of chloride-mediated inhibition in mouse spinal motoneuron

Early in development, GABA and glycine exert excitatory action that turns to inhibition due to modification of the chloride equilibrium potential (E(Cl)) controlled by the KCC2 and NKCC1 transporters. This switch is thought to be due to a late expression of KCC2 associated with a NKCC1 down-regulation. Here, we show in mouse embryonic spinal cord that both KCC2 and NKCC1 are expressed and functional early in development (E11.5-E13.5) when GABA(A) receptor activation induces strong excitatory action. After E15.5, a switch occurs rendering GABA unable to provide excitation. At these subsequent stages, NKCC1 becomes both inactive and less abundant in motoneurons while KCC2 remains functional and hyperpolarizes E(Cl). In conclusion, in contrast to other systems, the cotransporters are concomitantly expressed early in the development of the mouse spinal cord. Moreover, whereas NKCC1 follows a classical functional extinction, KCC2 is highly expressed throughout both early and late embryonic life.

Expression of the glycinergic system during the course of embryonic development in the mouse spinal cord and its co-localization with GABA immunoreactivity

To understand better the role of glycine and gamma-aminobutyric acid (GABA) in the mouse spinal cord during development, we previously described the ontogeny of GABA. Now, we present the ontogeny of glycine-immunoreactive (Gly-ir) somata and fibers, at brachial and lumbar levels, from embryonic day 11.5 (E11.5) to postnatal day 0 (P0). Spinal Gly-ir somata appeared at E12.5 in the ventral horn, with a higher density at the brachial level. They were intermingled with numerous Gly-ir fibers reaching the border of the marginal zone. By E13.5, at the brachial level, the number of Gly-ir perikarya sharply increased throughout the whole ventral horn, whereas the density of fibers declined in the marginal zone. In the dorsal horn, the first Gly-ir somata were then detected. From E13.5 to E16.5, at the brachial level, the density of Gly-ir cells remained stable in the ventral horn, and after E16.5 it decreased to reach a plateau. In the dorsal horn, the density of Gly-ir cells increased, and after E16.5 it remained stable. At the lumbar level, maximum expression was reached at E16.5 in both the ventral and dorsal horn. Finally, the co-localization of glycine and GABA was analyzed, in the ventral motor area, at E13.5, E15.5, and E17.5. The results showed that, regardless of developmental stage studied, one-third of the stained somata co-expressed GABA and glycine. Our data show that the glycinergic system matures 1 day later than the GABAergic system and follows a parallel spatiotemporal evolution, leading to a larger population of glycine cells in the ventral horn.

Ontogenic changes of the spinal GABAergic cell population are controlled by the serotonin (5-HT) system: implication of 5-HT1 receptor family

During the development of the nervous system, the acquisition of the GABA neurotransmitter phenotype is crucial for neural networks operation. Although both intrinsic and extrinsic signals such as transcription factors and growth factors have been demonstrated to govern the acquisition of GABA, few data are available concerning the effects of modulatory transmitters expressed by axons that progressively invade emerging neuronal networks. Among such transmitters, serotonin (5-HT) is a good candidate because serotonergic axons innervate the entire CNS at very early stages of development. We have shown previously that descending 5-HT slows the maturation of inhibitory synaptic transmission in the embryonic mouse spinal cord. We now report that 5-HT also regulates the spatiotemporal changes of the GABAergic neuronal population in the mouse spinal cord. Using a quantitative confocal study performed on acute and cultured spinal cords, we find that the GABAergic population matures according to a similar rostrocaudal temporal gradient both in utero and in organotypic culture. Moreover, we show that 5-HT delays the appearance of the spinal GABAergic system. Indeed, in the absence of 5-HT descending inputs or exogenous 5-HT, the GABAergic population matures earlier. In the presence of exogenous 5-HT, the GABA population matures later. Finally, using a pharmacological approach, we show that 5-HT exerts its action via the 5-HT1 receptor family. Together, our data suggest that, during the course of the embryonic development, 5-HT descending inputs delay the maturation of lumbar spinal motor networks relative to brachial networks.

‘Pole Test’ Measurements in Critical Leg Ischaemia

BACKGROUND

For the quantification of critical limb ischaemia (CLI) most vascular surgery units use sphygmo-manometric and transcutaneous oxygen pressure (TcPO2) measurements. However, measurements obtained by cuff-manometry can be overestimated especially in diabetic patients because of medial calcification that makes leg arteries less compressible. TcPO2 measurements present a considerable overlap in the values obtained for patients with different degrees of ischaemia and its reproducibility has been questioned. Arterial wall stiffness has less influence on the pole test, based on hydrostatic pressure derived by leg elevation, and this test seems to provide a reliable index of CLI.

OBJECTIVE

The objective of this study was to evaluate the pole pressure test for detection of critical lower limb ischaemia, correlating results with cuff-manometry and transcutaneous oxygen pressure.

DESIGN

University hospital-prospective study.

MATERIALS AND METHODS

Seventy-four patients (83 legs) with rest pain or gangrene were evaluated by four methods: pole test, cuff-manometry, TcPO2 and arteriography. CLI was present if the following criteria were met: (a) important arteriographic lesions+rest pain with an ankle systolic pressure (ASP) < or = 40 mmHg and/or a TcPO2 < or = 30 mmHg, or (b) important arteriographic lesions+tissue loss with an ASP < or = 60 mmHg and/or a TcPO2 < or = 40 mmHg. Fifty-seven lower limbs met the criteria for CLI.

RESULTS

Measurements obtained by cuff-manometry were significantly higher to those obtained by pole test (mean pressure difference: 40 mmHg, p<0.001). The difference between the two methods remained statistically significant for both diabetics (50.73, p<0.001) and non-diabetics (31.46, p<0.001). Mean TcPO2 value was 15.51 mmHg and there was no important difference between patients with and without diabetes. Overall, there was a correlation between sphygmomanometry and pole test (r = 0.481). The correlation persisted for patients without diabetes (r = 0.581), but was not evident in patients with diabetes. Correlation between pole test and TcPO2 was observed only for patients with diabetes (r = 0.444). There was no correlation between cuff-manometry and TcPO2. The pole test offered an accuracy of 88% for the detection of CLI. The sensitivity of this test was 95% and the specificity 73%.

Acute Carotid Artery Thrombosis: Description of 12 Surgically Treated Cases

The morbidity and mortality of stroke secondary to acute internal carotid artery thrombosis range from 40 to 69% and from 15 to 55%, respectively, after purely medical treatment. This report describes a series of 12 patients who underwent urgent surgical treatment for primary acute carotid artery thrombosis between January 1999 and December 2002. Upon admission, all patients had severe neurologic deficits contralateral to carotid artery thrombosis. One patient experienced ongoing changes in the level of consciousness. The interval between the onset of symptoms and admission was less than 6 hr in all cases. Initial work-up in all patients included a brain computed tomographic scan with contrast injection and carotid duplex scan. The operative procedure consisted of carotid thomboemdarterectomy after shunt placement with prosthetic patch closure. Intraoperative angiography was performed in all cases. Following treatment, we observed deterioration of neurologic status leading to death in one case; improvement with partial regression of initial neurologic deficit in two cases, including one patient who died from causes unrelated to carotid artery disease; and full neurologic recovery in nine cases. The delay to revascularization was longer than 6 hr in both patients who died. These data support surgical intervention for carotid artery thrombosis in selected patients without major disturbances of consciousness or hemorrhagic infarction, provided that the delay to revascularization is less than 6 hr.

Multiple Spontaneous Rhythmic Activity Patterns Generated by the Embryonic Mouse Spinal Cord Occur Within a Specific Developmental Time Window

Spontaneous rhythmic activity is a ubiquitous phenomenon in developing neural networks and is assumed to play an important role in the elaboration of mature circuitry. Here we describe the day-by-day evolution of spontaneous activity in the embryonic mouse spinal cord and show that, at a specific developmental stage, 2 distinct rhythms coexist. On embryonic days E12.5 and E13.5, we observed a single type of regularly recurring short spike-episodes synchronized across cervical, thoracic, and lumbar levels. By E14.5, in addition to this motor rhythm, another type of spontaneous synchronous activity appeared, characterized by much longer lasting episodes separated by longer time intervals. On E15.5, these long episodes disappeared. Short episodes were less numerous and more irregular except at the cervical level where a rhythm was occasionally observed. By E16.5, this cervical rhythm became more robust, whereas the lumbar level fell almost silent. Surprisingly, at E17.5, spontaneous activity resumed at caudal levels, now characterized by numerous erratic short episodes. A striking ontogenetic feature of spontaneous activity was the occurrence of long episodes only at E14.5. Although concomitant at all levels of the spinal cord, long episodes displayed different patterns along the spinal cord, with tonic firing at the thoracic level and rhythmic discharge with occasional sequences of left/right alternation at the lumbar level. Thus at E14.5, the originally synchronized network has started to segregate into more specialized subnetworks. In conclusion, this work suggests that ongoing spontaneous rhythms do not follow a smooth evolution during maturation, but rather undergo profound changes at very specific stages.

Ontogenic changes of the GABAergic system in the embryonic mouse spinal cord

Numerous studies have demonstrated an excitatory action of GABA early in development, which is likely to play a neurotrophic role. In order to better understand the role of GABA in the mouse spinal cord, we followed the evolution of GABAergic neurons over the course of development. We investigated, in the present study, the ontogeny of GABA immunoreactive (GABA-ir) cell bodies and fibers in the embryonic mouse spinal cord at brachial and lumbar levels. GABA-ir somata were first detected at embryonic day 11.5 (E11.5) exclusively at brachial level in the marginal zone. By E13.5, the number of GABAergic neurons sharply increased throughout the extent of the ventral horn both at brachial and lumbar level. Stained perikarya first appeared in the future dorsal horn at E15.5 and progressively invaded this area while they decreased in number in the presumed ventral gray matter. At E12.5, E13.5 and E15.5, we checked the possibility that ventral GABA-ir cells could belong to the motoneuronal population. Using a GABA/Islet-1/2 double labeling, we did not detect any double-stained neurons indicating that spinal motoneurons do not synthesize GABA during the course of development. GABA-ir fibers also appeared at the E11.5 stage in the presumptive lateral white matter at brachial level. At E12.5 and E13.5, GABA-ir fibers progressively invaded the ventral marginal zone and by E15.5 reached the dorsal marginal zone. At E17.5 and postnatal day 0 (P0), the number of GABA-ir fibers declined in the white matter. Finally, by P0, GABA immunoreactivity that delineated somata was mainly restricted to the dorsal gray matter and declined in intensity and extent. The ventral gray matter exhibited very few GABA-ir cell bodies at this neonatal stage of development. The significance of the migration of somatic GABA immunoreactivity from ventral to the dorsal gray matter is discussed.

Endovascular repair for acute traumatic rupture of the thoracic aorta

BACKGROUND

We report endovascular treatment of acute traumatic rupture of the thoracic aorta as a potential alternative to open surgery for high-risk patients.

METHODS

Between January 2001 and July 2002, 9 patients with acute traumatic rupture of the thoracic aorta were treated with a stent-graft. In all cases the endovascular management was selected because of age, associated polytrauma, or comorbidities. Preoperative workup included chest computed tomography scan, transoesophageal echography, and angiography. The devices used were the Excluder and the Talent stent-grafts.

RESULTS

Eight patients underwent immediate repair and 1 patient was treated within 5 days of the accident because of delayed diagnosis of aortic rupture after surgical management of spleen rupture. The stent-graft was successfully expanded in all patients through the common femoral artery (n = 7) or the common iliac artery (n = 2). There was no perioperative death, renal failure, or neurologic complication (paraplegia or stroke). In 1 patient the computed tomography scan at 7 days postoperatively showed proximal endoleak requiring placement of a second stent-graft. Follow-up ranged from 4 to 20 months. All spiral computed tomography scans performed during follow-up revealed no evidence of endoleak, migration, or alteration of the stent-graft.

CONCLUSIONS

Endovascular repair in the acute phase of traumatic rupture of the thoracic aorta is technically feasible and safe, and may represent an alternative to open surgery for high-risk patients.

Ruptured aneurysm of the infrarenal abdominal aorta: impact of age and postoperative complications on mortality

Between 1985 and 2000, a total of 871 patients underwent surgical treatment for infrarenal abdominal aortic aneurysm (AAA), including 98 (11.2%) presenting with ruptured abdominal aortic aneurysms (RAAA). An optimized operative protocol was used to treat 77 RAAA starting in January 1989. The main features of the optimized protocol are routine use of intraoperative autotransfusion, revascularization by aortoaortic bypass, absence of systemic heparinization, and use of a collagen-impregnated prosthesis. Intraoperative mortality (IOM) was 3.8%. Postoperative mortality at 1 month (POM1) was 25.9% and postoperative mortality at 3 months (POM3) was 33.7%. Heart failure (p <0.001), hemodynamic shock (p <0.001), and hemorrhage (p = 0.04) were the only complications correlated with POM1. Pneumonia (p = 0.01) and sepsis (p = 0.01) were the only complications correlated with POM3. Isolated acute renal insufficiency was not a significant risk factor for postoperative mortality. Using a cutoff of 75 years, there was a significant age-related difference (p = 0.025) for POM1 but not for IOM and POM3. The findings of this study show that optimizing the operative protocol decreases mortality related to RAAA. The main predictor of POM1 was hemodynamic status while the main predictor of POM3 was infection. Isolated acute renal insufficiency was not a risk factor for mortality. Age should not be considered a contraindication for operative treatment.

A porcine model of systemic and renal haemodynamic responses to infrarenal aortic cross-clamping

OBJECTIVES

cross-clamping of the infrarenal aorta is associated with complex haemodynamic disturbances. Several experimental models of aortic cross-clamping (AXC) have been described with heterogeneous results. The main purpose of this study was to establish an animal model in which infrarenal AXC could reproduce similar systemic and renal haemodynamic changes to those observed in humans.

METHODS

eleven anaesthetised pigs underwent AXC just below the renal arteries. Renal blood flow was measured using clearance of (131)I hippuran. Systemic and renal parameters were collected at 3 consecutive 30-min periods.

RESULTS

AXC did not alter the extraction fraction of (131)I hippuran but was accompanied by significant (13%) decrease in cardiac index (p = 0.005) and a 23% increase in mean arterial pressure (p = 0.005). AXC induced significant 135% increase in renal vascular resistance (p = 0.012) and a 35% decrease in renal blood flow (p = 0.016). This worsened after removal of the aortic clamp, whereas systemic variables returned to baseline levels.

CONCLUSIONS

this AXC animal model reproduces the changes observed in humans. It provides a reliable animal model which allows to investigate the underlying mechanisms of renal vasoconstriction and the effect of new drugs.

Video-assisted thoracoscopic sympathectomy for palmar hyperhidrosis: results in 102 cases

The purpose of this retrospective study was to evaluate the immediate and long-term outcome of video-assisted thoracoscopic sympathectomy for idiopathic palmar hyperhidrosis. Between January 1996 and December 2000, a total of 67 patients underwent 102 sympathectomy procedures with excision of the sympathetic chain between the second and fourth sympathetic ganglion. The mean duration of hospitalization was 1.7 +/- 0.6 days. Five patients were lost to follow-up. Mean duration of follow-up for the 96 sympathectomy procedures in the remaining 62 patients was 38 +/- 6.3 months. Patient outcome showed that video-assisted thoracoscopic sympathectomy is the treatment of choice for idiopathic palmar hyperhidrosis. Long-term patient satisfaction is excellent.

Outcome of common iliac arteries after aortoaortic graft placement during elective repair of infrarenal abdominal aortic aneurysms

PURPOSE

The purpose of this study was determination of the expansion rates relative to the size of the common iliac artery (CIA) after elective placement of a straight aortic tube graft for an infrarenal abdominal aortic aneurysm (AAA).

METHODS

Between January 1993 and December 1997, 74 men (mean age, 69 years) with AAA underwent surgical repair with a straight tube graft. All patients underwent preoperative and postoperative computed tomography (CT) scans. The mean follow-up period was 68.3 months. The preoperative CT scan revealed a dilatation of at least one of the two CIAs in 32 patients (43.2%; group A). Within this group, the CIA was ectatic (12 mm < diameter < 18 mm) in 13 patients (subgroup A1) and aneurysmal (diameter >/=18 mm) in 19 patients (subgroup A2). The diameters of both CIAs were normal (diameter </=12 mm) in the other 42 patients (56.8%; group B).

RESULTS

Two patients (2.7%) in group A2 needed reoperation because of expansion of the diameter of the CIA; the preoperative diameter of the CIA in both patients was 30 mm. The diameters of the CIA aneurysms in the 17 other patients in subgroup A2 were smaller than 30 mm on the preoperative CT scan. After aortic surgery, the sizes of these aneurysms remained stable the first 5 years and reached a diameter of 30 mm on the CT scans obtained 7 to 8 years after surgery. Overall, 10 of the 74 patients (13.5%) had a CIA aneurysm develop that was smaller than 30 mm in diameter (mean diameter, 19.2 mm) 7 to 8 years after aortic surgery. The presence of a celiac aorta dilatation greater than or equal to 25 mm was the only statistically significant factor predictive of postoperative expansion of a CIA dilatation (P =.03).

CONCLUSION

Straight aortoaortic tube grafts are indicated for CIAs with diameters smaller than 18 mm. Aorta biiliac bifurcated grafts are justified when the CIA diameter is between 18 and 30 mm, when the patient's life expectancy is longer than 8 years, or when the diameter of the celiac aorta is greater than or equal to 25 mm. A CIA aneurysm greater than or equal to 30 mm should be repaired during the same operative session as the AAA with placement of an aorta biiliac bifurcated graft.

Ontogeny of descending serotonergic innervation and evidence for intraspinal 5-HT neurons in the mouse spinal cord

Neuronal networks in the mouse spinal cord express serotonin (5-HT)-induced rhythmic motor activity at early developmental stages (embryonic day (E) 12.5). Later in development, by post-natal day (P) 10, the 5-HT-evoked rhythmic motor activity matures and acquires an adult locomotor-like pattern. With the view to establishing a relationship between the ontogeny of locomotor networks and the maturation of spinal 5-HT systems, we have traced 5-HT immunoreactivity in the mouse spinal cord from E12.5 to PN10. By E12.5, descending 5-HT immunoreactive (5-HT-ir) fibers that likely originate from raphe nuclei were detected in the ventral and lateral funiculi, at anterior cervical spinal levels, but not at more caudal levels. Descending 5-HT-ir axons reached thoracic levels at E14.5 and lumbar levels at E16.5. Some 5-HT-ir fibers could be detected in the ventral and intermediate gray matter by E16.5, whereas the dorsal gray matter was not invaded before PN0. At PN10, a dense serotonergic innervation was restricted to the gray matter with a high concentration of 5-HT-ir fibers in three areas: dorsal horn, ventral horn (where motoneurons are located) and intermediate area. Surprisingly, from E16.5 to PN10, 5-HT-ir intraspinal neurons were found, exclusively at sacral levels. Their somata lay in the gray matter around the central canal and preferentially in the ventro-median part of the ventral horn. The functional significance of these sacral 5-HT-ir neurons is discussed.

Endovascular repair for acute rupture of the descending thoracic aorta

PURPOSE

To report the endovascular treatment of acute descending thoracic aortic rupture as an alternative to open surgery in high-risk patients.

METHODS

Between November 1999 and April 2001, 10 patients (7 men; median age 75 years) underwent endovascular stent-grafting of the descending thoracic aorta for acute rupture from an aneurysm (n=7) or blunt trauma (n=3). All patients were evaluated as high operative risk. The aortic rupture was associated with isolated mediastinal hematomas (n=7), left hemothorax (n=2), or aortobronchial fistula (n=1). The Excluder Thoracic Endoprosthesis was used predominantly.

RESULTS

The mean interval to the endovascular repair was 45.3+/-28.4 hours. All stent-grafts were successfully deployed. Two patients required common iliac artery access, and 2 needed covered stents for iatrogenic iliac artery rupture. There was 1 postoperative death (myocardial infarction) and no renal failure, neurological complications, embolization, stent-graft migration, or perigraft leak. One patient died 4 months later from an unrelated cause. At a mean follow-up of 7.9+/-5.1 months, all aneurysms and rupture sites were excluded with no evidence of endoleak or hematoma.

CONCLUSIONS

Endoluminal treatment is a feasible technique for the management of acute rupture of the descending thoracic aorta. Long-term studies are required to assess the effectiveness and durability of this technique in comparison to open repair.

Carotid artery stenting for stenosis following revascularization or cervical irradiation

PURPOSE

To assess the safety and efficacy of carotid artery stenting (CAS) for stenosis following revascularization or cervical irradiation.

METHODS

Twenty-two CAS procedures performed on 21 patients (20 men; mean age 69.3 years, range 58-87) from June 1997 to June 2000 were retrospectively reviewed. There were 5 radiation-induced carotid stenoses in 4 patients and 17 postsurgical restenoses. The mean interval between carotid revascularization and CAS was 48.1 months (range 6-264), while the elapsed time from irradiation to CAS was always >8 years (range 8-28). Seven patients screened during this period were excluded from CAS because of a duplex-defined >50% hypoechoic lesion and/or angiographic documentation of an irregular ulcerated stenosis.

RESULTS

Four Palmaz and 16 Wallstents were successfully deployed in 20 arteries; 1 access failure prompted conversion to surgery and a stent delivery failure resulted in 1 patient receiving balloon dilation only (technical success 91%). No complications were encountered in the periprocedural period, and no neurological events were observed during a mean follow-up of 16.6 months (range 3-36). One patient died at 20 months from an unrelated cause. One (4.8%) restenosis was detected after 1 year in the patient who did not receive a stent.

CONCLUSIONS

CAS is a safe alternative to conventional surgery in patients with carotid artery stenosis following surgical revascularization or cervical irradiation provided preoperative testing excludes stenoses at risk for embolism.

Surgical exposure of superior sulcus lung tumors with vascular involvement

Choice of exposure route for surgical excision of superior sulcus lung tumors depends on involvement at the thoracic inlet. From December 1985 to September 1999, we performed surgical treatment of superior sulcus tumors in 42 patients, including 22 with vascular involvement. Various exposure techniques were used, including a novel technique combining transverse supraclavicular cervicotomy and posterolateral thoracotomy in 11 cases, anterior transclavicular cervicothoracotomy in 7 cases, isolated posterolateral thoracotomy in 3 cases, and cervicosternotomy in 1 case. Vascular procedures consisted of subadventitial dissection of the subclavian artery in 5 patients, arterial resection-anastomosis in 7, and prosthetic bypass in 10. Postoperative mortality was 11.9% in the overall series of 42 patients (n = 5) and 9% (n = 2) in the subgroup of patients with vascular involvement. During follow-up, 13 patients died of tumor recurrence and 1 patient died of respiratory insufficiency. Actuarial 5-year survival was 22.7 +/- 17.5% overall and 18 +/- 17.9% in the subgroup of patients with vascular involvement. This study indicates that the combined exposure route with transverse supraclavicular cervicotomy and posterolateral thoracotomy was useful for treatment of superior sulcus lung tumors requiring lobectomy and pneumonectomy.

Development of lumbar rhythmic networks: from embryonic to neonate locomotor-like patterns in the mouse

Different aspects of spinal locomotor organization have been studied in the mouse during embryonic and neonatal development using in vitro preparations of isolated lumbosacral cords. The first consideration was the embryonic development of an alternating bilateral pattern. From embryonic day (E) 12, perfusion of serotonin could induce relatively synchronous lumbar bursts across the cord. Bilateral activity became progressively alternate at E15 due to the appearance of glycinergic inhibitory interactions (revealed by strychnine application). Strictly alternating patterns were expressed at E18 and were maintained after birth. In a second step, we investigated cellular properties involved in lumbar rhythmogenesis in postnatal day 0-2 preparations which displayed spontaneous locomotor-like activity. Perfusion of receptor antagonists showed the co-operative involvement of N-methyl-D-aspartate (NMDA)- and non-NMDA-receptors for excitatory amino acids-mediated operation of locomotor networks. In a final step we investigated the localization of locomotor networks within the lumbar cord. Data obtained from preparations exhibiting spontaneous or Mg2+-free induced bursts revealed that the networks are present throughout the lumbar cord and that rhythmogenesis is distributed throughout all segmental levels.