Cortical Wedge Research Articles

Renal Histopathological Changes in Children With Congenital Ureteropelvic Junction Obstruction

Renal histologic changes in congenital ureteropelvic junction obstruction (UPJO), although well documented, are sparsely studied in children. This study aims to establish a histological grading depending on the glomerular and tubulo-interstitial changes in hydronephrotic kidneys and determine correlation with age at surgery and impact on function post-pyeloplasty. A renal cortical wedge biopsy was obtained after pyeloplasty and histological changes were graded from 1 to 4. A total of 47 viable biopsies from 57 children showed grade 1 changes in 10, grade 2 in 7, grade 3 in 27, and grade 4 in 3. Age at surgery, histological grade, and changes in differential renal function (DRF) were statistically analyzed. Younger age, near normal histology, and those with changes in 1 domain had preserved DRF pre-operatively. Renal histology and overall grade showed positive correlation with pre-operative DRF. However, no statistically significant association was noted with age at surgery or change in post-operative DRF.

Prediction of Intracranial Atherosclerotic Disease-Related Large-Vessel Occlusion Stroke on the Basis of Novel Cerebral Blood Volume Parameters.

Mechanical thrombectomy is an effective treatment method for large-vessel occlusion stroke (LVOS); however, it has limited efficacy for intracranial atherosclerotic disease (ICAD)-related LVOS. We investigated the use of cerebral blood volume (CBV) maps for identifying ICAD as the underlying cause of LVOS before the initiation of endovascular treatment (EVT). We reviewed clinical and imaging data from patients who presented with LVOS and underwent endovascular treatment between January 2011 and May 2021. The CBV patterns were analyzed to identify an increase in CBV within the hypoperfused area and estimate infarct patterns within the area of decreased CBV. Comparisons were made between the patients with an increase in CBV and those without, and among the estimated infarct patterns: territorial, cortical wedge, basal ganglia-only, subcortical, and normal CBV. Overall, 243 patients were included. CBV increase in the hypoperfused area was observed in 23.5% of patients. A significantly higher proportion of ICAD was observed in those with increased CBV than in those without (56.4% versus 19.8%; P<0.001). Regarding the estimated infarct patterns on the CBV, ICAD was most frequently observed in the normal CBV group (territorial, 14.9%; cortical wedge, 10.0%; basal ganglia-only, 43.8%; subcortical, 35.7%; normal, 61.7%). CBV parameters, including "an increase in CBV," "normal CBV infarct pattern," and "an increase in CBV or normal CBV infarct pattern composite," were independently associated with ICAD. An increased CBV or normal CBV pattern may be associated with ICAD LVOS on the pretreatment perfusion imaging.

Lateral Meniscal Allograft Transplantation With Distal Femoral Osteotomy

Background: Meniscal allograft transplantation improves functional and patient-reported outcomes in patients with meniscal deficiency without significant osteoarthritis. In addition, it is known that valgus malalignment of the knee can lead to meniscal and chondral damage, and surgery is often indicated to restore the mechanical axis and slow progression of osteoarthritis. Indications: Indications for this procedure include patients with symptomatic lateral meniscal deficiency with associated valgus deformity of the knee. Patient’s age must be less than 50 years, body mass index less than 35 kg/m2, meniscal deficiency, and ipsilateral pain with or without swelling. Ligament tears, focal cartilage loss, and malalignment are not contraindications if also corrected. Technique Description: We begin by removing the remaining lateral meniscus, taking care to leave a small peripheral rim of meniscus. A transpatellar tendon arthrotomy is performed, and the meniscal allograft is passed through the arthrotomy and into the knee. An inside-out repair is performed using vertical mattress sutures. The sutures are tightened and tied with the knee at 30° to 40° of flexion. The distal femoral osteotomy is then performed. An approach is made to the lateral femur, where initial guidewires are placed using fluoroscopic guidance. The initial saw cut is made about 75% of the way across the femur, and an osteotome is used to complete the osteotomy. Care is taken to preserve the far medial cortex. An adjustable wedge osteotome is placed to open the lateral cortex in accordance with the preoperative template. The cortical wedge is fashioned using the tibial allograft from the meniscal transplant and is placed into the osteotomy. The osteotomy is secured using a locking plate with locking screws, and this is confirmed in safe position using fluoroscopy prior to the conclusion of the case. Results: Patients will have effective deformity correction and alleviation of pain. Many patients can return to sport without restrictions following appropriate rehabhilitation. Conclusion: Lateral meniscal allograft transplantation with distal femoral opening wedge osteotomy is an effective treatment for symptomatic lateral meniscal insufficiency with associated valgus deformity of the knee in patients without osteoarthritis. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

An On-Demand Drug Delivery System for Control of Epileptiform Seizures.

Drug delivery systems have the potential to deliver high concentrations of drug to target areas on demand, while elsewhere and at other times encapsulating the drug, to limit unwanted actions. Here we show proof of concept in vivo and ex vivo tests of a novel drug delivery system based on hollow-gold nanoparticles tethered to liposomes (HGN-liposomes), which become transiently permeable when activated by optical or acoustic stimulation. We show that laser or ultrasound simulation of HGN-liposomes loaded with the GABAA receptor agonist, muscimol, triggers rapid and repeatable release in a sufficient concentration to inhibit neurons and suppress seizure activity. In particular, laser-stimulated release of muscimol from previously injected HGN-liposomes caused subsecond hyperpolarizations of the membrane potential of hippocampal pyramidal neurons, measured by whole cell intracellular recordings with patch electrodes. In hippocampal slices and hippocampal–entorhinal cortical wedges, seizure activity was immediately suppressed by muscimol release from HGN-liposomes triggered by laser or ultrasound pulses. After intravenous injection of HGN-liposomes in whole anesthetized rats, ultrasound stimulation applied to the brain through the dura attenuated the seizure activity induced by pentylenetetrazol. Ultrasound alone, or HGN-liposomes without ultrasound stimulation, had no effect. Intracerebrally-injected HGN-liposomes containing kainic acid retained their contents for at least one week, without damage to surrounding tissue. Thus, we demonstrate the feasibility of precise temporal control over exposure of neurons to the drug, potentially enabling therapeutic effects without continuous exposure. For future application, studies on the pharmacokinetics, pharmacodynamics, and toxicity of HGN-liposomes and their constituents, together with improved methods of targeting, are needed, to determine the utility and safety of the technology in humans.

Abstract WMP69: Imaging Analysis to Assess Stroke Mechanism in Aortic Dissection

Introduction: Stroke is a frequent complication in patients having surgery for Acute Type A Aortic Dissection (ATAAD) where a variety of neurocirculatory techniques are used to reconstruct the arch. In order for surgeons to prevent stroke, first an understanding of the dynamic hemodynamic processes that cause stroke is required. Objective of this study is to determine radiological characteristics and mechanisms of stroke in ATAAD. So far, surgical literature has only reported on incidence. Methods: From 2006-2016, of 189 ATAAD patients at a single centre, 42 had a stroke. Charts and brain imaging were reviewed by 2 Neurologists. Great vessel pathology along with willisian collateral status was identified. Stroke territory (anterior or posterior circulation), distribution (unilateral or bilateral) and number of lesions were identified. Mechanism of stroke was classified as hypoperfusion (water-shed, borderzone pattern), embolic (cortical multiple or wedge shaped) or combined. Results: All strokes were ischemic. Mean patient age 60.1 +/- 13.1 years. Stroke was diagnosed a median 3.0 days (IQR = 5.1) post operatively. NIHSS classification was mild in 7%, moderate in 81% and 12% had severe. Most strokes were multiple (65%) and in the anterior circulation (88% vs. 32 % posterior). Most patients had an embolic pattern of stroke (45% vs. 36% hypoperfusion vs 17% mixed). Detailed clinical and radiologic data are shown in Table 1. Conclusion: Stroke after ATAAD is ischemic, predominantly embolic, involves both hemispheres and results in significant morbidity. It remains unclear if stroke is a result of the dissection disease process extending to the brain vs. iatrogenically caused by choice and methodology of intraoperative surgical neurocirculatory management strategies used to reconstruct the aorta. Further studies will look for associations between pre-operative cerebrovascular abnormalities, intra-operative management, and mechanisms of stroke.

Can zero-hour cortical biopsy predict early graft outcomes after living donor renal transplantation?

The aim of this study was to identify relevance of subclinical pathological findings in the kidneys of living donors and correlate these with early graft renal function. This was a prospective study on 84 living donor kidney transplant recipients over a period of two years. In all the donors, cortical wedge biopsy was taken and sent for assessment of glomerular, mesangial, and tubule status. The graft function of patients with normal histology was compared with those of abnormal histological findings at one, three, and six months, and one year post-surgery. Most abnormal histological findings were of mild degree. Glomerulosclerosis (GS, 25%), interstitial fibrosis (IF, 13%), acute tubular necrosis (ATN 5%), and focal tubal atrophy (FTA, 5%) were the commonly observed pathological findings in zero-hour biopsies. Only those donors who had histological changes of IF and ATN showed progressive deterioration of renal function at one month, three months, six months, and one year post-transplantation. In donors with other histological changes, no significant effect on graft function was observed. Zero-hour cortical biopsy gave us an idea of the general status of the donor kidney and presence or absence of subclinical pathological lesions. A mild degree of subclinical and pathological findings on zero-hour biopsy did not affect early graft renal function in living donor kidney transplantation. Zero-hour cortical biopsy could also help in discriminating donor-derived lesions from de novo alterations in the kidney that could happen subsequently.

Diagnosis and treatment of autoimmune pancreatitis

Diagnosis and treatment of autoimmune pancreatitis

Abstract TMP13: Baseline DWMRI Characteristics In Patients With Cryptogenic Stroke And Patent Foramen Ovale: Results From The Closure I Trial

Background: Cryptogenic stroke may have several etiologies including paradoxical embolism through a patent foramen ovale (PFO). A cardiac source of embolism may be suggested by multiple infarcts, sometimes hemorrhagic, in different vascular distributions or a cortical wedge shaped infarct. We report the baseline diffusion weighted MRI (DWMRI) characteristics in patients with cryptogenic stroke and a patent foramen ovale (PFO) from the CLOSURE I trial. Methods: CLOSURE I compared device closure versus medical therapy for secondary prevention in patients with cryptogenic TIA or stroke and a PFO. Of 909 patients randomized, 562 patients demonstrated acute infarcts on baseline DWMRI and are included in this analysis. Multivariate proportional hazard Cox regression compared imaging subgroups with remaining randomized patients Results: Single infarcts were found in 62% of patients. Of these, 61% were anterior circulation, 30% posterior, and 8.5% were of uncertain territory. Of the anterior circulation infarcts, 40% were cortical, 36% subcortical, and 24% affected both the cortical and subcortical regions. Of the posterior circulation infarcts, 45% were thalamic or cerebellar. Of 562 patients, 18.5% had a single subcortical lesion &lt;1.5cm in diameter and met the radiological definition of an acute lacunar infarct. Multiple infarcts were found in 38%. Infarcts in a single vascular territory were found in 23%, often in the anterior circulation (66%). Infarcts in multiple vascular territories were found in 15%. Hemorrhagic infarction was present in 9%. Adjusting for patient characteristics, no significant difference in 2 year rate of TIA, stroke or death was found compared to remaining randomized patients. Discussion: The specificity of infarct patterns for embolism in patients with cryptogenic stroke and a PFO is uncertain. We found no significant relationship between lacunar or subcortical infarction and the risk of recurrent TIA or stroke. Baseline infarct patterns on DWMRI in patients with cryptogenic stroke and PFO may not be useful in predicting recurrent stroke risk or determining best prevention therapy.

Does brain slices from pentylenetetrazole-kindled mice provide a more predictive screening model for antiepileptic drugs?

The cortical wedge is a commonly applied model for in vitro screening of new antiepileptic drugs (AEDs) and has been extensively used in characterization of well-known AEDs. However, the predictive validity of this model as a screening model has been questioned as, e.g., carbamazepine has been reported to lack effect in this model. The neuroplastic changes induced in acute and chronic animal models of epilepsy are known to affect the pharmacological profile of AEDs in vivo. Hence, we investigated whether brain slices from pentylenetetrazole (PTZ)-kindled animals could provide a more predictive screening model for AEDs. To this end, we compared the in vitro and in vivo pharmacological profile of several selected AEDs (phenobarbital, phenytoin, tiagabine, fosphenytoin, valproate, and carbamazepine) along with citalopram using the PTZ-kindled model and brain slices from naïve, saline-injected and PTZ-kindled mice. Our data suggest that the use of slices from PTZ-kindled mice in the cortical wedge does not increase the predictive validity of the model as an in vitro screening model for AEDs. Traditionally, the incidence of certain seizure types is widely used as a measure to characterize drug action in animal models of epilepsy. In our study, the anticonvulsant effect of the AEDs was investigated in vivo using several observational parameters (i.e., incidence and duration of convulsions, latency to clonic convulsions, and severity of convulsions). We found that including the observational parameter “severity” offered important additional information about the drug profile that would otherwise be lost if only a single parameter as “incidence” was used.

GAD65 is essential for synthesis of GABA destined for tonic inhibition regulating epileptiform activity

GABA is synthesized from glutamate by glutamate decarboxylase (GAD), which exists in two isoforms, that is, GAD65 and GAD67. In line with GAD65 being located in the GABAergic synapse, several studies have demonstrated that this isoform is important during sustained synaptic transmission. In contrast, the functional significance of GAD65 in the maintenance of GABA destined for extrasynaptic tonic inhibition is less well studied. Using GAD65-/- and wild type GAD65+/+ mice, this was examined employing the cortical wedge preparation, a model suitable for investigating extrasynaptic GABA(A) receptor activity. An impaired tonic inhibition in GAD65-/- mice was revealed demonstrating a significant role of GAD65 in the synthesis of GABA acting extrasynaptically. The correlation between an altered tonic inhibition and metabolic events as well as the functional and metabolic role of GABA synthesized by GAD65 was further investigated in vivo. Tonic inhibition and the demand for biosynthesis of GABA were augmented by injection of kainate into GAD65-/- and GAD65+/+ mice. Moreover, [1-(13) C]glucose and [1,2-(13) C]acetate were administered to study neuronal and astrocytic metabolism concomitantly. Subsequently, cortical and hippocampal extracts were analyzed by NMR spectroscopy and mass spectrometry, respectively. Although seizure activity was induced by kainate, neuronal hypometabolism was observed in GAD65+/+ mice. In contrast, kainate evoked hypermetabolism in GAD65-/- mice exhibiting deficiencies in tonic inhibition. These findings underline the importance of GAD65 for synthesis of GABA destined for extrasynaptic tonic inhibition, regulating epileptiform activity.

ChemInform Abstract: Heterocyclic Excitatory Amino Acids. Synthesis and Biological Activity of Novel Analogues of AMPA.

The novel acidic amino acids 6a-c, 7, and 8 have been synthesized via 1,3-dipolar cycloadditions, using nitrile oxides and alkynes. The prepared compounds are heterocyclic analogues of glutamic acid with differing chain lengths. One of these compounds, (RS)-2-amino-3-(3-carboxy-5-methyl-4- isoxazolyl)propionic acid (ACPA, 8), was shown in [3H]AMPA binding studies to be more active than AMPA itself (IC50 = 20 nM compared to IC50 = 79 nM for AMPA). No affinity for NMDA receptors (NMDA-sensitive [3H]glutamic acid binding) was found, and only weak affinity in [3H]kainic acid binding (IC50 = 6.3 microM) was detected. The excitatory activity in rat cortical wedge also showed that ACPA was more potent than AMPA (EC50 = 1.0 microM compared to EC50 = 3.5 microM for AMPA). The depolarizing effect of ACPA could be fully antagonized by the selective non-NMDA antagonist 6-cyano-7-nitro-quinoxazoline-2,3-dione (CNQX), but was unaffected by the selective NMDA antagonist D-2-amino-5-phosphonovaleric acid (AP5).

Pharmacological screening of Malian medicinal plants used against epilepsy and convulsions

Ethnopharmacological relevance Several medicinal plants are used in Mali to treat epilepsy and convulsions. So far, no studies have investigated the pharmacological effect of these plants. Aims The aim of this study was to investigate the in vitro and in vivo antiepileptic potential of the ethanolic extracts of 11 Malian medicinal plants. Materials and methods The extracts were screened for antiepileptic properties in the mouse cortical wedge preparation and in the [ 3H]-flumazenil binding assay. Two of the plant extracts were investigated for anticonvulsive properties in the pentylenetetrazol (PTZ) kindling model in mice. Possible side effects on motor impairment were evaluated using the rota-rod test. Results Extracts of 10 of the 11 medicinal plants showed affinity to the benzodiazepine binding site on the GABA A receptor. Seven of the 11 extracts inhibited the spontaneous discharges (SEDs) in the mouse cortical wedge preparation, with the extracts of Flueggea virosa and Psorospermum senegalense being the most potent. However, when tested for in vivo anticonvulsive properties these two extracts failed to show any effect on PTZ-induced seizures in mice. Conclusions The pharmacological screening of the ethanolic extracts of 11 Malian medicinal plants in vitro lead to the identification of several extracts with potential anticonvulsant properties.

Immune Reconstitution Associated With Progressive Multifocal Leukoencephalopathy in Human Immunodeficiency Virus

To report the neuropathological findings of a patient with immune reconstitution syndrome associated with progressive multifocal leukoencephalopathy (PML) in human immunodeficiency virus (HIV) and to review the literature. A 38-year-old man was presented with a rapidly evolving brainstem syndrome. Serology for HIV was positive with an initial CD4 count of 130 cells/mL3. Magnetic resonance imaging showed widespread high signal changes within the brainstem bilaterally, the cerebellum, inferior cerebellar peduncle, and the frontal lobe on the right. Opportunistic infections were excluded from blood and cerebrospinal fluid samples. Despite treatment with antiretrovirals, he continued to deteriorate neurologically, and a repeat magnetic resonance imaging scan showed progression of his lesions. Cortical wedge frontal lobe brain biopsy showed features characteristic of PML, but was associated with an exaggerated inflammatory response. Polymerase chain reaction analysis of the specimen demonstrated the presence of JC virus (JCV) DNA, confirming the pathologic impression of PML. The patient made a rapid (within 24 hours) improvement with pulsed methylprednisolone and has maintained a clinical response 7 months later. These features clinically, radiologically, and histopathologically suggest an added component in the form of immune reconstitution syndrome to PML. This report highlights the need to carefully evaluate the clinical syndrome in patients with HIV-associated leukoencephalopathy. It also substantiates the role of corticosteroids in carefully considered cases of HIV with leukoencephalopathy secondary to immune reconstitution.

The effect of extracts of Searsia species on epileptiform activity in slices of the mouse cerebral cortex

Ethnopharmacological relevance Searsia dentata and Searsia pyroides are used in traditional South African medicine to treat convulsions and epilepsy. Previous studies have demonstrated that extracts of these plants comprise compounds that bind to the flumazenil-sensitive site on the GABA A receptor. However, their use as anticonvulsant medicinal plants cannot be adequately explained by these findings. Aims The aim of this study was to examine the possible involvement of the glutamatergic system of extracts from the plants. Materials and methods The mouse cortical wedge preparation was used for functional characterization of the extracts. The affinity towards the NMDA and the AMPA receptor was investigated using classical [ 3H]-GP39653 and [ 3H]-AMPA binding assays, respectively. Results The extracts of Searsia dentata and Searsia pyroides inhibited the spontaneous epileptiform discharges in mouse cerebral cortical slices with ED 50 of 0.62 and 1.67 mg dry extract/mL, respectively. Both extracts displaced [ 3H]-GP39653 binding and significantly inhibited the NMDA-induced response during co-administration in cortical slices. Conclusion In this study, the NMDA receptor antagonistic effect of the crude ethanolic extracts of these two South African medicinal plants was demonstrated.

3-Hydroxypyridazine 1-oxides as carboxylate bioisosteres: A new series of subtype-selective AMPA receptor agonists

Three positional isomers (compounds 1, 2, and 3) of 1-uracilylalanine (willardiine) based on a 3-hydroxypyridazine 1-oxide scaffold with an alanine side-chain at positions 4 ( 1), 5 ( 2) or 6 ( 3) were tested for binding to recombinant homomeric AMPA receptor (AMPA-R) subtypes GluR1-4, as well for excitatory activity on the rat cortical wedge preparation. 1 had approximately 30 times higher affinity than willardiine while showing a similar selectivity profile, i.e. 22-fold selectivity for GluR1/2 over GluR3/4. The GluR1-4 affinities of 3 were similar to 1, however, its 31-fold selectivity for GluR1/2 over GluR3/4 is the highest yet observed among azine-based glutamate analogues. The non-isosteric congener 2 showed weaker binding to AMPA-Rs. In the cortical wedge, 1 evokes similar responses to AMPA, while 3 and 2 are 10- and 100-fold weaker, respectively. Dose–response curves on Xenopus lævis oocytes expressing GluR1-4( flip) confirmed that 1 and 3 are potent GluR1/2 receptor agonists (EC 50s from 0.26 to 1.7 μM) but are 10- to 160-fold less potent at GluR3/4. The structures, potencies and selectivities of this new class of AMPA agonists are compared with those of willardiine, 5-fluorowillardiine and azawillardiine, referring to the binding mode observed in the crystal structure of willardiine bound to GluR2-S1S2. The results indicate that the 3-hydroxypyridazine 1-oxide moiety can function as an outstanding carboxylate mimic at AMPA-Rs, leading the way to further fine-tuning of subtype selectivity. This little-explored molecular motif may find wider application in medicinal chemistry.

Effect of spermine and N 1-dansyl-spermine on epileptiform activity in mouse cortical slices

N 1-dansyl-spermine is a novel polyamine analogue, which has been demonstrated to have an antagonist action at the stimulatory polyamine site on the N-methyl- d-aspartate (NMDA) receptor macrocomplex. Cortical wedges from genetically epilepsy-prone DBA/2 mice demonstrate spontaneous epileptiform activity when perfused with Mg 2+-free artificial cerebrospinal fluid (aCSF). This epileptiform activity has been demonstrated to be primarily mediated through the NMDA receptor. N 1-dansyl-spermine reduced the spontaneous epileptiform activity at a high dose (100 μM) but had no effect at a lower dose (50 μM). The polyamine, spermine (300 μM) caused an increase in the rate of the spontaneous epileptiform discharges. This effect of spermine was antagonised by administration of the low dose of N 1-dansyl-spermine (50 μM). This further demonstrates the role of the NMDA receptor in the production of spontaneous epileptiform discharges in the cortical wedge preparation and clearly illustrates both the facilitatory action of spermine and the polyamine antagonist action of N 1-dansyl-spermine at the stimulatory polyamine site on the NMDA receptor.

On the neurotoxicity of glutaric, 3-hydroxyglutaric, and trans-glutaconic acids in glutaric acidemia type 1.

Glutaric acidemia type 1 (GA1) is an autosomal recessively inherited deficiency of glutaryl-CoA dehydrogenase. Accumulating metabolites, 3-hydroxyglutaric (3-OH-GA), glutaric (GA), and trans-glutaconic (TG) acids, have been proposed to be involved in the development of the striatal degeneration seen in children with GA1 via an excitotoxic mechanism. We have studied the extent to which 3-OH-GA, GA, and TG are neurotoxic and whether neurotoxicity is caused by an excitotoxic mechanism in which 3-OH-GA, GA, or TG overactivates N-methyl-D-aspartate (NMDA) receptors. In cultured mouse neocortical neurons, all three compounds were weakly neurotoxic, possibly through activation of NMDA receptors. However, further studies in the rat cortical wedge preparation and with NMDA receptors expressed in Xenopus oocytes could not confirm an interaction of the compounds with NMDA receptors. It is concluded that the metabolites 3-OH-GA, GA, and TG are only weak neurotoxins and that the neurodegenerative cascade destroying the striatum in patients with GA1 involves mainly mechanisms other than excitoxicity.

Synthesis, theoretical and structural analyses, and enantiopharmacology of 3-carboxy homologs of AMPA.

We have previously used homologation of (S)-glutamic acid (Glu) and Glu analogs as an approach to the design of selective ligands for different subtypes of Glu receptors. (RS)-2-Amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic acid (ACPA), which is an isoxazole homolog of Glu, is a very potent agonist at the (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) subgroup of Glu receptors and a moderately potent ligand for the kainic acid (KA) subgroup of Glu receptors. The enantiomers of ACPA were previously obtained by chiral HPLC resolution. Prompted by pharmacological interest in ACPA, we have now prepared the (S)- and (R)-enantiomers of ACPA by stereocontrolled syntheses using (1R,2R,5R)- and (1S,2S,5S)-2-hydroxy-3-pinanone, respectively, as chiral auxiliaries. Furthermore, the 5-ethyl analog of ACPA, Ethyl-ACPA, was synthesized, and (S)- and (R)-Ethyl-ACPA were also prepared using this method. The absolute configurations of (S)- and (R)-ACPA were established by X-ray crystallographic analysis of a protected (1S,2S,5S)-2-hydroxy-3-pinanone imine derivative of (R)-ACPA. The absolute stereochemistry of (S)- and (R)-Ethyl-ACPA was assigned on the basis of a comparison of their properties with those of the enantiomers of ACPA, employing elution order on chiral HPLC columns, as well as circular dichroism (CD) spectroscopy in combination with time-dependent density functional theory. The structural and electronic basis for the Cotton effect observed for such analogs is examined. The lower homolog of ACPA, (RS)-2-amino-2-(3-carboxy-5-methyl-4-isoxazolyl)acetic acid (1), which is a Glu analog, was also synthesized. Affinities and neuroexcitatory effects were determined using rat brain membranes and cortical wedges, respectively, at native AMPA, KA, and N-methyl-D-aspartic acid (NMDA) receptors. The molecular pharmacology of (S)- and (R)-ACPA and (S)- and (R)-Ethyl-ACPA was evaluated at homomeric cloned subtypes of AMPA receptors (iGluR1o,3o,4o) and of KA receptors (iGluR5,6), expressed in Xenopus laevis oocytes. The cloned receptors mGluR1alpha, mGluR2, and mGluR4a, expressed in CHO cell lines, were used to study the effects of the five compounds at metabotropic Glu receptors. In accordance with ligand-receptor complexes known from X-ray crystallography, the conformationally restricted Glu analog 1 was inactive at all Glu receptors studied, and the R-forms of ACPA and Ethyl-ACPA were very weak or inactive at these receptors. At AMPA receptor subtypes, (S)-ACPA and (S)-Ethyl-ACPA showed equally potent agonist effects at iGluR1o and iGluR3o, whereas (S)-Ethyl-ACPA was 6-fold more potent than (S)-ACPA at iGluR4o. (S)-ACPA and (S)-Ethyl-ACPA were approximately an order of magnitude less potent at iGluR5 than at AMPA receptor subtypes, and neither compound showed detectable effects at iGluR6. The binding mode of (S)-Ethyl-ACPA at iGluR2 was examined by docking to the (S)-ACPA-iGluR2 complex.

Effects of Cyperus articulatus compared to effects of anticonvulsant compounds on the cortical wedge

Cyperus articulatus L. (Cyperaceae) is a plant commonly used in traditional medicine in Africa and Latin America to treat many diseases. The water extract from rhizomes of Cyperus articulatus concentration-dependently reduced spontaneous epileptiform discharges and NMDA-induced depolarisations in the rat cortical wedge preparation at concentrations at which AMPA-induced depolarisations are not affected. The two antiepileptic compounds, valproate and ethosuximide, possessed effect neither on epileptiform discharges nor on AMPA- and NMDA-induced depolarisations. Phenobarbital, pentobarbital and phenythoin inhibited both AMPA- and NMDA-induced depolarisations and spontaneous epileptiform discharges. The effects of Cyperus articulatus were very close to the effect of d-CPPene. d-CPPene also inhibited spontaneous epileptiform discharges and antagonised NMDA- but not AMPA-induced depolarisations. The extract of Cyperus articulatus could contain components acting as NMDA antagonists.

Gaboxadol: in vitro interaction studies with benzodiazepines and ethanol suggest functional selectivity

The interaction of gaboxadol (THIP; 4,5,6,7-tetrahydroisoxazolo-[5,4- c]pyridin-3-ol), ethanol and a series of benzodiazepine site agonists including diazepam, flunitrazepam, lorazepam, indiplon, zaleplon and zolpidem has been characterized at human α 1β 3γ 2S γ-aminobutyric acid type A (GABA A) receptors expressed in Xenopus oocytes and in the rat cortical wedge preparation. At the expressed receptors, gaboxadol and the benzodiazepine site agonists interacted synergistically and ethanol did not further enhance this potentiation. In contrast, in the rat cortical wedge preparation, where the inhibition of spontaneous activity was assessed, much weaker effects of the benzodiazepine site agonists were seen. Furthermore, ethanol did not further potentiate the effects of gaboxadol. These findings suggest that gaboxadol in functionally intact tissue may interact with a receptor population, which is insensitive to the modulation by benzodiazepines.