Biomedical subjects

J Zentner

Publications and source records attributed to J Zentner.

At least 19 recordsLinked to original sources

PubMed2005

Thoracoabdominal aortic aneurysm repair: interplay of spinal cord protecting modalities.

BACKGROUND: The purpose of this study was to assess the complementary use of different methods of measuring spinal cord perfusion during thoracoabdominal aortic surgery. METHODS: The spinal cords of 28 patients undergoing surgery on the thoracoabdominal aorta were monitored with transcranial electrical stimulation (tcMEP) and somatosensory-evoked potentials (SSEP). Available approaches of spinal cord-protection included: Moderate systemic hypothermia, constant cerebrospinal fluid (CSF) drainage and pressure monitoring, reimplantation of segmental arteries, cardiopulmonary bypass (CPB), and staged clamping. RESULTS: Fourteen of 19 patients (75%) undergoing open surgical treatment (Group I) exhibited loss of tcMEP after proximal aortic clamping. In nine cases (47%), we observed recovery of tcMEP after intraoperative interventions, while two patients subsequently developed paraplegia and three died. Seventeen of 19 patients showed loss of SSEP, with recovery in 12 cases (63%). During stent-graft implantation (Group II), one of nine patients (11%) demonstrated tcMEP loss with intraoperative, intervention-related recovery. The SSEP-recording course remained stable. CONCLUSIONS: tcMEP/SSEP monitoring has proved to be an excellent means of detecting spinal cord ischaemia during surgery on thoracoabdominal aortic aneurysms. The prognostic value of tcMEP monitoring should be considered superior to that of SSEP measurements, because of its direct and rapid response to spinal malperfusion. Through combined neurophysiological monitoring, vital parameter balancing and intraoperative interventions, spinal cord perfusion improves and recovery of tcMEP and SSEP is achievable, reducing the prevalence of postoperative paraplegia.

Adult↗

PubMed2005

Setup of neurophysiological monitoring with tcMEP/SSEP during thoracoabdominal aneurysm repair.

OBJECTIVES: The article describes a procedure for the intraoperative neurophysiological placement of electrodes to control the spinal cord function during thoracoabdominal aortic aneurysm repair. MATERIAL AND METHODS: Intraoperative monitoring is performed by motor-evoked myogenic potentials after transcranial electric stimulation (tcMEP) and somatosensory-evoked potentials (SSEP). In tcMEP, the stimulating percutaneous needle electrodes are placed at C3 and C4 according to the 10 - 20 system for EEG recordings. TcMEP are recorded from the anterior tibial and gastrocnemius muscles on both sides. The SSEP electrodes are placed laterally and caudally onto the malleolus medialis in order to stimulate the tibial nerve. The stimulus is documented via electrodes attached to the scalp within the sensory cortex region. RESULTS: The application of the electrodes is both easy to learn and can be performed without further difficulties. Once attached, the electrodes provide a quick assessment and interpretation of spinal cord function. The identification of external sources of disturbance during the monitoring (e. g. insufficient impedance, unfavourable electrode positioning, and technical interference caused by medical equipment) enables the supervisor to differentiate between normal and abnormal neurological responses. CONCLUSIONS: TcMEP and SSEP allow an adequate, direct, and reliable intraoperative assessment of spinal cord function, enabling the surgeon to diagnose an impending ischaemia and act accordingly. This measurement technique provides the surgical team with a means of integrating neurological aspects during thoracoabdominal aneurysm repair.

Aortic Aneurysm, Abdominal↗

PubMed2005

Improved spinal cord perfusion during thoracoabdominal aortic repair.

OBJECTIVES: The study's aim is to evaluate whether intraoperative neurophysiological monitoring with transcranial motor-evoked potentials (tcMEP) permits early recognition of neuronal lesions, thus making interventions to prevent irreversible spinal cord damage possible. MATERIAL AND METHODS: TcMEP monitoring was carried out in twelve patients (mean age 60 years) during open surgical thoracoabdominal aortic replacement. Current approaches for corrective, spinal cord-protecting interventions consist of: raising distal perfusion by increasing cardiopulmonary bypass (CPB) flow, catecholamine application, reducing central venous pressure, reimplantation of segmental arteries, and cerebrospinal fluid (CSF) drainage. RESULTS: Nine patients exhibited loss of tcMEP after segmental aorta clamping. In five patients we observed a recovery of tcMEP through counteractive measures. Three patients died intraoperatively, one patient presented with postoperative paraplegia and loss of tcMEP. CONCLUSION: TcMEP loss is associated with spinal cord ischaemia, causing postoperative paraplegia. TcMEP monitoring is an excellent method to detect spinal cord ischaemia at an early stage.

Aortic Aneurysm, Abdominal↗

PubMed2005

Pediatric farm injuries involving non-working children injured by a farm work hazard: five priorities for primary prevention.

OBJECTIVES: To describe pediatric farm injuries experienced by children who were not engaged in farm work, but were injured by a farm work hazard and to identify priorities for primary prevention. DESIGN: Secondary analysis of data from a novel evaluation of an injury control resource using a retrospective case series. DATA SOURCES: Fatal, hospitalized, and restricted activity farm injuries from Canada and the United States. SUBJECTS: Three hundred and seventy known non-work childhood injuries from a larger case series of 934 injury events covering the full spectrum of pediatric farm injuries. METHODS: Recurrent injury patterns were described by child demographics, external cause of injury, and associated child activities. Factors contributing to pediatric farm injury were described. New priorities for primary prevention were identified. RESULTS: The children involved were mainly resident members of farm families and 233/370 (63.0%) of the children were under the age of 7 years. Leading mechanisms of injury varied by data source but included: bystander and passenger runovers (fatalities); drowning (fatalities); machinery entanglements (hospitalizations); falls from heights (hospitalizations); and animal trauma (hospitalizations, restricted activity injuries). Common activities leading to injury included playing in the worksite (all data sources); being a bystander to or extra rider on farm machinery (all data sources); recreational horseback riding (restricted activity injuries). Five priorities for prevention programs are proposed. CONCLUSIONS: Substantial proportions of pediatric farm injuries are experienced by children who are not engaged in farm work. These injuries occur because farm children are often exposed to an occupational worksite with known hazards. Study findings could lead to more refined and focused pediatric farm injury prevention initiatives.

Adolescent↗

PubMed2005

Farm health surveillance in the Marshfield Epidemiologic Study Area: a pilot study.

Surveillance of agricultural work-related illness and non-fatal injuries is limited and considered to be a major gap in prevention and policy-making capacity. This pilot study evaluated the utility of the Marshfield Epidemiologic Study Area (MESA) and its farm residency cohort to identify and monitor potential priorities for prevention and control. MESA is a defined geographic region that serves as a resource for conducting population-based health research. Nearly all of the residents receive their health care from the Marshfield Clinic and affiliated hospitals, providing archived electronic medical information to characterize past and present diagnoses. Based on scientific literature and national research priorities, five broad health issues (injuries, back problems, hearing loss, respiratory conditions, and dermatologic conditions) were selected. To estimate age-specific and age-adjusted incidence and prevalence, we followed a fixed cohort of 1995 MESA residents through 2002. Standardized incidence ratios and standardized prevalence ratios were also estimated to quantify the potential impact of farm residency. Linking MESA, its farm residency cohort, and the clinic's data archives allowed successful identification of significant associations with agricultural exposure for a few conditions and subconditions related to consensus priorities in agricultural health, particularly among men. These included extrinsic alveolitis, organic dust toxic syndrome, back pain, osteoarthrosis, and certain injuries. However, the system was generally not able to demonstrate strong influence of farm residency on disease occurrence for many conditions specifically selected for their likely capacity to show such influence. Future surveillance systems should supplement clinical data with other sources of information on health events and should be adequately powered to focus on narrower ranges of health conditions.

Adult↗

PubMed2004

Cannabinoid CB1 receptor-mediated modulation of evoked dopamine release and of adenylyl cyclase activity in the human neocortex.

1. The present study investigated the binding characteristics of various ligands to cannabinoid CB(1) receptors in human neocortex and amygdala. In addition, the functionality of CB(1) receptors in the human neocortex was assessed by examining the effects of CB(1) receptor ligands on evoked [(3)H]-dopamine (DA) release in superfused brain slices and on synaptosomal cAMP accumulation. 2. Saturation-binding assays in human neocortical and amygdala synaptosomes using a radiolabelled cannabinoid receptor agonist ([(3)H]-CP55.940) revealed pK(d) values of 8.96 and 8.63, respectively. The numbers of binding sites (B(max)) were 3.99 and 2.67 pmol (mg protein)(-1), respectively. 3. Various cannabinoid receptor ligands inhibited [(3)H]-CP55.940 binding with rank order potencies corresponding to those of previous studies in animal tissues. 4. Electrically evoked [(3)H]-DA release from human neocortical slices was inhibited by CP55.940 (IC(50) 6.76 nm, I(max) 65%) and strongly enhanced by the cannabinoid receptor antagonist AM251. However, [(3)H]-DA release was not influenced in rat neocortex. In human tissue, the estimated endocannabinoid concentration in the biophase of the release-modulating CB(1) receptors was 1.07 nm, expressed in CP55.940 units. 5. K(+)-evoked [(3)H]-DA release in the presence of tetrodotoxin (TTX) was strongly inhibited by CP55.940 in humans, but not in rats. 6. In human tissue, CP55.940 inhibited forskolin-stimulated cAMP accumulation (IC(50) 20.89 nm, I(max) 35%). AM251 blocked this effect and per se increased forskolin-stimulated cAMP accumulation by approximately 20%. 7. In conclusion, cannabinoids modulate [(3)H]-DA release and adenylyl cyclase activity in the human neocortex. CB(1) receptors are located on dopaminergic nerve terminals and seem to be tonically activated by endocannabinoids.

Adenylyl Cyclases↗

PubMed2004

[Impaired cerebral autoregulation in asymptomatic patients with carotid artery stenosis: comparison of acetazolamide-SPECT and transcranial CO(2)-dopplersonography].

PURPOSE: The indication for operation in patients with asymptomatic high-grade carotid artery stenosis is still under debate. Since impaired cerebrovascular autoregulation is associated with an increased risk for ischaemic events, assessment of cerebral vascular reactivity might be a valuable selection criterion for surgery. The aim of our study was therefore to evaluate the incidence of impaired autoregulation in asymptomatic patients with acetazolamide-single photon emission computed tomography (ACZ-SPECT) and transcranial CO (2)-dopplersonography (CO (2)-TCD). Furthermore, both methods were compared in regard to results and clinical practicability. METHODS: In 42 patients with high-grade (> 70 %) asymptomatic carotid artery stenosis, cerebral perfusion and vascular reactivity were assessed with resting and ACZ-enhanced SPECT scans. In 31 of these patients the CO (2) reactivity of cerebral perfusion was determined by TCD and expressed as normalized autoregulation reserve (NAR). RESULTS: Cerebral perfusion was decreased in 14.3 %. In ACZ-SPECT 26 % and in CO (2)-TCD 28 % revealed an impaired vascular reactivity. Conformity of both methods was high (kappa = 0.93). TCD was superior in practicability, but only applicable in 81 % due to a missing temporal bone window for insonation. CONCLUSION: In accordance ACZ-SPECT and CO (2)-TCD could detect impaired vascular reactivity in a quarter of asymptomatic patients. Both TCD and SPECT could be of value for preoperative selection in this group of patients, whereby sonography is recommended for daily diagnostic work-up.

Acetazolamide↗

PubMed2004

Evaluation of the North American Guidelines for Children's Agricultural Tasks using a case series of injuries.

OBJECTIVE: To evaluate the potential for the North American Guidelines for Children's Agricultural Tasks (NAGCAT) to prevent the occurrence of pediatric farm injuries. This evaluation focuses upon farm injuries experienced when children were engaged in farm work. DESIGN: Novel outcome evaluation involving primary review of three retrospective case series. SETTING: Fatal, hospitalized, and restricted activity injuries from the United States and Canada. SUBJECTS: Nine hundred and thirty four pediatric farm injury cases. METHODS: The applicability of NAGCAT to each case was rated. For injuries where NAGCAT were applicable, recurrent injury patterns were described and the potential for NAGCAT to prevent their occurrence was assessed. RESULTS: A total of 283 (30.3%) cases involved children engaged in farm work. There was an applicable NAGCAT guideline in 64.9% of the work related cases. Leading individual guidelines applicable to the injury events were: (1) working with large animals; (2) driving a farm tractor; and (3) farm work with an all-terrain vehicle. In the judgment of the research team, 59.6% of these injuries were totally preventable if the principles espoused by NAGCAT had been applied. CONCLUSIONS: NAGCAT are a set of consensus guidelines aimed at the prevention of pediatric farm injuries. The findings suggest that NAGCAT, if applied, would be efficacious in preventing many of the most serious injuries experienced by children engaged in farm work. However, work related injuries represent only a modest portion of pediatric farm injuries. This new information assists in the refinement of NAGCAT as an injury control resource and puts its potential efficacy into context.

Accidents, Occupational↗

PubMed2003

Evidence for strychnine-sensitive glycine receptors in human amygdala.

Recent studies suggested the existence of strychnine-sensitive glycine-receptors in mammalian amygdala. In the present study, we investigated the amino acid concentrations as well as immunocytochemical and pharmacological properties of glycine-receptors in fresh human amygdala tissue obtained from epilepsy surgery. High pressure liquid chromatography revealed a considerable amount of glycine and its precursors and glycine-receptors agonists L-serine and taurine in this tissue. Immunohistochemistry using the monoclonal antibody mAb4a, recognizing an epitope common to all alpha-subunit variants of glycine receptors, displayed a specific labeling at the soma and on proximal dendrites of mostly tripolar, large-sized neurons of irregular distribution and arrangement. To elucidate the pharmacological properties of the glycine-receptors found slices of human amygdala were preloaded with [(3)H]-choline and superfused. Glycine induced an overflow of [(3)H]-acetylcholine, which was inhibited by strychnine in a concentration-dependent manner. Furthermore, the glycine-induced release of [(3)H]-acetylcholine was significantly inhibited by furosemide, indicating glycine-induced actions to be attributed to chloride channels. These actions of glycine were not influenced by MK-801, D-CP-Pene or bicuculline. Thus, the effects of glycine did not seem to be mediated through NMDA or GABA receptors. These observations indicate that strychnine-sensitive, chloride-conducting glycine receptors, which elicit the release of [(3)H]-acetylcholine, are present at the soma and on proximal dendrites of neurons in human amygdala. It is hypothesized that glycine may display a regulatory role in amygdaloid functions, probably via cholinergic interneurons.

Acetylcholine↗

PubMed2003

Modulation of electrically evoked acetylcholine release through cannabinoid CB1 receptors: evidence for an endocannabinoid tone in the human neocortex.

Cannabinoids are known to inhibit neurotransmitter release in the CNS through CB1 receptors. The present study compares the effects of synthetic cannabinoids on acetylcholine (ACh) release in human and mice neocortex. We further investigated a possible endocannabinoid tone on CB1 receptors in human neocortex caused by endogenous agonists like anandamide or 2-arachidonylglycerol. Brain slices, incubated with [3H]-choline, were superfused and stimulated electrically under autoinhibition-free conditions to evoke tritium overflow assumed to represent ACh release. The first series of experiments was performed with 26 pulses, 60 mA, at 0.1 Hz. In mice neocortical slices, the cannabinoid receptor agonist WIN55212-2 decreased ACh release (pIC50=6.68, I(max)=67%). In the human neocortex the concentration-response curve of WIN55212-2 was bell-shaped and flat (I(max observed) approximately 30%). The estimated maximum possible inhibition, however, was much larger: I(max derived)=79%. Lec, the negative logarithm (lg) of the biophase concentration of endocannabinoids in 'WIN55212-2 units,' was -6.52, the pKd of WIN55212-2 was 7.47. The CB1 receptor antagonist/inverse agonist SR141716 enhanced ACh release in the human neocortex (by 38%) and prevented the inhibitory effect of WIN55212-2. The concentration-response curve of WIN55212-2 was changed in its shape including a shift to the right due to the presence of SR141716. A pA2 of this antagonist between 11.60 and 11.18 was obtained. SR141716 alone had no effect in mice neocortical slices. A partial agonist without inverse agonistic activity, O-1184, enhanced ACh release in the human neocortex. The endocannabinoid uptake-inhibitor AM404 decreased ACh release in human, but not in mice, neocortical slices. Change of the stimulation parameters (eight trains of pseudo-one-pulse bursts (4 pulses, 76 mA, 100 Hz), spaced by 45 s intervals) led to a stronger inhibitory effect of WIN55212-2, and abolished the disinhibitory effect of SR141716 and O-1184. The results show that activation of CB1 cannabinoid receptors leads to inhibition of ACh release in the human and mouse neocortex. The endocannabinoid tone is high in the human, but not in the mouse neocortex and is dependent on neuronal activity. SR141716 acts as a competitive CB1 receptor antagonist.

Acetylcholine↗

PubMed2003

Shutting down operating theater ventilation when the theater is not in use: infection control and environmental aspects.

OBJECTIVE: In hospital operating rooms (ORs), specially conditioned air is supplied to protect patients from airborne agents that may cause infections. This study investigated whether it is hygienically safe to shut down the air supply at night if measures are taken to ensure a timely restart before surgery is performed. DESIGN: Experimental study. SETTING: Neurosurgical OR of a German university hospital. METHODS: The ventilation system was switched off and restarted after 10 hours. Particles suspended in the air near the operating table were counted, OR temperature was measured, and settle plates were exposed and incubated. RESULTS: In 13 investigations, a median of 1.3 x 10(4) particles 0.5 microm/m3 or greater (range, 5.8 x 10(3) to 1.1 x 10(5)) were documented immediately after restart in the morning. After 10 minutes and subsequently, no test showed a particle count exceeding the threshold limit of 1.0 x 10(4) particles 0.5 microm/m3 or greater recommended by the German Society of Hygiene and Microbiology. Only a few colony-forming units (CFU) were detected per settle plate (median, 0 CFU/60 cm2; range, 0 to 8) and OR temperatures quickly reached normal levels. CONCLUSIONS: Shutting down OR ventilation during off-duty periods does not appear to result in an unacceptably high particle count or microbial contamination of the OR air shortly after the system is restarted. Because substantial energy and cost savings are likely, this should be considered in hygienically safe heating, ventilation, and air conditioning systems. However, normal ventilation should be established at least 30 minutes before surgical activity.

Academic Medical Centers↗

PubMed2002

MR arthrography: pharmacology, efficacy and safety in clinical trials.

OBJECTIVE: A meta-analysis was carried out of clinical trials published between 1987 and 2001 in respect of the clinical pharmacology and safety as well as the diagnostic efficacy of gadolinium-DTPA (Gd-DTPA) for direct intra-articular injection before MRI examination. DESIGN: Scientific papers (clinical, postmortem and experimental studies) and information from the manufacturer regarding intra-articular injection of Gd-DTPA that addressed questions of mode of action, optimal concentration and dose, elimination and safety were reviewed. Clinical studies were classified according to their study design. The sensitivity, specificity and accuracy of MR arthrography (MRA) were compared with a "gold standard" (arthroscopy, arthrotomy) and other radiological evidence for different joints. RESULTS: Fifty-two clinical studies of the overall 112 studies addressed aspects of diagnostic efficacy of MRA in patients or in healthy volunteers. The shoulder was the most assessed joint (29 of 52 studies). Good (>80%) or even excellent (90-100%) sensitivity, specificity and accuracy were found for MRA in most indications, especially for the shoulder and knee joints and induced extension of rotator cuff lesions, labrum abnormalities and postoperative meniscal tears. Two millimoles per liter has proven to be the best concentration for intra-articular administration of Gd-DTPA. After passive complete diffusion from the joint within 6-24 h, complete and rapid renal elimination takes place after intra-articular injection. Local safety proved to be excellent after intra-articular administration of Gd-DTPA. Regarding systemic tolerance almost no side effects have been reported, but the same safety considerations apply for intra-articular administration of Gd-DTPA as for intravenous injection. CONCLUSIONS: The diagnostic efficacy of intra-articular MRA in most clinical conditions affecting major joints is greater than that of plain MRI. In some diagnostic problems MRA achieves almost the same sensitivity and specificity as the surgical gold standard. Given a sterile application, the intra-articular administration of Gd-DTPA in a concentration of 2 mmol/l prior to MRI is a safe procedure.

Arthrography↗

PubMed2002

Surgical treatment of epilepsies.

Epilepsy is characterized by recurrent epileptic seizures. Surgical interventions represent a reasonable alternative to long-term antiepileptic drug treatment in those patients destined to achieve incomplete seizure control. The presurgical work-up aims at identifying appropriate surgical candidates. Surgical options with a curative goal include temporal and extratemporal resections and hemispherectomy. With these procedures complete seizure control can be achieved in approximately 2/3 of patients. With palliative procedures such as callosotomy, multiple subpial transections, and vagal nerve stimulation, approximately half of the patients will significantly improve after surgery. In all, epilepsy surgery has proven to be a highly effective treatment option. Major problems include the definition of the epileptogenic area with respect to optimal seizure control and minimum neurological and neuropsychological impairment after surgery.

Brain Diseases↗

PubMed2002

Effect of skin disinfection with octenidine dihydrochloride on insertion site colonization of intravascular catheters.

BACKGROUND: We investigated the efficacy of two commercially available, alcohol-based antiseptic solutions in decontaminating the insertion site of central lines. One solution contained the bispyridine octenidine dihydrochloride. PATIENTS AND METHODS: Inpatients receiving either a central venous catheter (CVC) or a peripherally inserted central catheter (PICC) were alternately assigned to different skin disinfection regimens at the insertion site: (A) 0.1% octendine dihydrochloride with 30% 1-propanol and 45% 2-propanol, (B) 74% ethanol with 10% 2-propanol. Quantitative skin cultures were obtained from the insertion site at predetermined intervals. RESULTS: A total of 60 patients received 12 CVCs and 47 PICCs (no significant difference with respect to gender, age and catheter type). In total, 90 cultures were assessed in each group. The median colony-forming unit (cfu) counts per 24 cm(2) (group A vs B) were 2,270 vs 2,950 before, 20 vs 40 following and 860 vs 1,210 24 h after catheter insertion, respectively. A statistically significant difference in the efficacy of skin decontamination was seen between groups in culture set (3) and in the difference between culture sets (2) and (3) (Wilcoxon rank sum test). CONCLUSION: Octenidine/propanol appears to be more effective than alcohol (ethanol/propanol) alone in reducing microflora of the skin at the PICC/CVC insertion site over a 24-h period.

1-Propanol↗

PubMed2002

Error analysis in cranial neuronavigation.

Neuronavigation systems are now an important component of many modern neurosurgical treatment strategies. Their support facilities intraoperative orientation and makes neurosurgical operations more precise and less traumatic. Computer-aided neurosurgery is definitively not a temporary fashionable phenomenon, the concept of neuronavigation is here to stay. This report summarizes a ten-years-long experience and presents an error analysis of 108 failures (12.4 %) in a total of 874 image-guided cranial neurosurgical procedures with an arm-linked (mechanical) system and two different infrared-light emitting (optical) systems. The application of neuronavigation incurs multiple reasons for pitfalls because of the complex man-machine interface. Principally, we have to differentiate two types of errors: "machine made errors" due to soft- or hardware failure and "man made errors" generally, due to inadequate handling of the navigation system. The error analysis demonstrated that the so-called human interface plays the main role causing a high error rate.

Bias↗

PubMed2002

Calvarial sclerosing osteomyelitis.

We report a 15-year-old boy who suffered from calvarial sclerosing osteomyelitis and presented with painful head swelling. X-rays of the skull revealed areas of irregular radiolucency. MR imaging and CT showed a well-demarcated intradiploic lesion with thickening of the skull extending from the frontal to the parietal calvarium with a low signal on T1-weighted images, strong but heterogeneous enhancement after gadolinium application and a mixed signal on T2-weighted images. Computer-navigated neurosurgery was planned, and the craniotomy defect was reconstructed by a preformed titanium implant. Sclerosing osteomyelitis of the calvarium has to be included in the differential diagnosis of osteolytic and sclerosing lesions of the skull coinciding with persistent swelling of the head.

Adolescent↗

PubMed2001

Modulation of K+-evoked [3H]-noradrenaline release from rat and human brain slices by gabapentin: involvement of KATP channels.

To elucidate the mechanism of action of the anticonvulsant gabapentin (GBP), we compared its effects on K+-evoked [3H]-noradrenaline ([3H]-NA) release from rat hippocampal and human neocortical slices with those of the KATP channel opener pinacidil and the Na+ channel blockers phenytoin, carbamazepine and lamotrigine. Rat hippocampal and human neocortical slices were loaded with [3H]-NA and superfused. [3H]-NA release was evoked by increasing the extracellular [K+] from 3 to 15 mM. GBP decreased [3H]-NA release from rat hippocampal with a pIC50 of 5.59 and a maximum inhibition of 44%. Concentration-dependent inhibition was also seen in human neocortical slices (39% inhibition with 100 microM GBP). These inhibitory effects were antagonized by the KATP channel antagonist glibenclamide, yielding a pA2 of 7.50 in the rat. The KATP channel opener pinacidil (10 microM), like GBP, decreased [3H]-NA release from rat hippocampal slices by 27% and this effect was also antagonized by glibenclamide. In human neocortical slices the inhibition by pinacidil (10 microM) was 31%. Although phenytoin (10 microM), carbamazepine (100 microM) and lamotrigine (10 microM) also decreased [3H]-NA release (by 25%, 57% and 22%, respectively), glibenclamide did not antagonize the effects of these classical Na+ channel blockers. These findings suggest that GBP inhibits K+-evoked [3H]-NA release through activation of KATP channels. To establish whether the KATP channels under investigation were located on noradrenergic nerve terminals or on other neuronal elements, the effects of GBP were compared in the absence and in the presence of tetrodotoxin (TTX 0.32 microM) throughout superfusion. Since the functional elimination of the perikarya of interneurons by TTX reduced the inhibitory effect of GBP, the KATP channels mediating the effect of GBP may be located on nerve terminals, probably on both noradrenergic and glutamatergic nerve endings.

Acetates↗

PubMed2001

Cortical current density reconstruction of interictal epileptiform activity in temporal lobe epilepsy.

OBJECTIVE: To investigate the value of cortical current density (CCD) reconstruction in localizing intracranial generators of interictal epileptiform activity in mesial and lateral temporal lobe epilepsy (TLE). METHODS: Non-linear minimum L(1)-norm CCD reconstruction (with current sources restricted to the individual cortical surface and a realistic boundary element method (BEM) head model) was used to localize and to study the propagation of interictal epileptiform EEG activity in 13 pre-surgical patients with TLE. RESULTS: In all but one patient with mesial temporal lesions, an initial activation maximum corresponding to the ascending part of averaged sharp waves was found in the ipsilateral anterior basolateral temporal lobe, mostly extending up to the affected mesial structures whose resection rendered the patients seizure-free. In all 3 patients with lateral temporal lesions, the activation was initially confined to temporal neocortex immediately adjacent to the epileptogenic lesion. Towards the peak of sharp waves, two patients showed a propagation of interictal activity to anterior and posterior and partly contralateral temporal regions. A conventional EEG analysis based on amplitude maxima or phase reversal would have missed the initial onset zone. CONCLUSIONS: The findings demonstrate that CCD reconstruction can be a valuable additional non-invasive component in the multimodal pre-surgical evaluation of epilepsy patients.

Adolescent↗