Takayasu Fukudome

Seronegative Lambert-Eaton myasthenic syndrome Study of 110 Japanese patients

The authors characterized the clinical and immunologic features of 110 patients with Lambert-Eaton myasthenic syndrome (LEMS). Anti-P/Q-type voltage-gated calcium channels (VGCC) antibodies were detected in 85% of the patients (seropositive) but not in the rest (seronegative). Except for the indication that small cell lung carcinoma is less common in seronegative patients, no significant differences were found in the clinical characteristics of patients who had or did not have anti-P/Q-type VGCC antibodies. The results of passive transfer experiments suggest that seronegative LEMS is also an autoantibody-mediated disorder.

Myopathy, myasthenic syndrome, and epidermolysis bullosa simplex due to plectin deficiency

Plectin, an intermediate filament linking protein, is normally associated with the sarcolemma, nuclear membrane, and intermyofibrillar network in muscle, and with hemisdesmosomes in skin. A 20-year-old female with epidermolysis bullosa simplex since birth had progressive ocular, facial, limb, and trunkal weakness and fatigability since age 9, fivefold CK elevation, a 25% decrement with myopathic motor unit potentials and increased electrical irritability on electromyography, and no anti-acetylcholine receptor (AChR) antibodies. Plectin expression was absent in muscle and severe plectin deficiency was noted in skin. Morphologic studies revealed necrotic and regenerating fibers and a wide spectrum of ultrastructural abnormalities: large accumulations of heterochromatic and lobulated nuclei, rare apoptotic nuclei, numerous cytoplasmic and few intranuclear nemaline rods, disarrayed myofibrils, thick-filament loss, vacuolar change, and pathologic alterations in membranous organelles. Many endplates (EPs) had an abnormal configuration with chains of small regions over the fiber surface and a few displayed focal degeneration of the junctional folds. The EP AChR content was normal. In vitro electrophysiologic studies showed normal quantal release by nerve impulse, small miniature EP potentials, and fetal as well as adult AChR channels at the EP. Our findings support the notion that plectin is essential for the structural integrity of muscle and skin, and for normal neuromuscular transmission.

Quinidine normalizes the open duration of slow-channel mutants of the acetylcholine receptor

QUINIDINE is a long-lived open-channel blocker of the wild-type endplate acetylcholine receptor (AChR). To test the hypothesis that quinidine can normalize the prolonged channel opening events of slow-channel mutants of human AChR, we expressed wild-type AChR and five well characterized slow-channel mutants of AChR in HEK 293 cells and monitored the effects of quinidine on acetylcholine-induced channel currents. Quinidine shortens the longest component of channel opening burst (τ3b) of both wild-type and mutant AChRs in a concentration-dependent manner, and 5 μM quini-dine reduces τ3b of the mutant AChRs to that of wild-type AChRs in the absence of quinidine. Because this concentration of quinidine is attainable in clinical practice, the findings predict a therapeutic effect for quinidine in the slow-channel congenital myasthenic syndrome.

Congenital myasthenic syndrome caused by low-expressor fast-channel AChR δ subunit mutation

Objective: To determine the molecular basis of a disabling congenital myasthenic syndrome (CMS) observed in two related and one unrelated Arab kinship. Background: CMS can arise from defects in presynaptic, synaptic basal lamina–associated, or postsynaptic proteins. Most CMS are postsynaptic, and most reside in the AChR ε subunit; only two mutations have been reported in the AChR δ subunit to date. Methods: Cytochemistry, electron microscopy, α-bungarotoxin binding studies, microelectrode and patch-clamp recordings, mutation analysis, mutagenesis, and expression studies in human embryonic kidney cells were employed. Results: Endplate studies showed AChR deficiency, fast decaying, low-amplitude endplate currents, and abnormally brief channel opening events. Mutation analysis revealed a novel homozygous missense mutation (δP250Q) of the penultimate proline in the first transmembrane domain (TMD1) of the AChR δ subunit. Expression studies indicate that δP250Q (1) hinders δ/α subunit association during early AChR assembly; (2) hinders opening of the doubly occupied closed receptor (A2R); and (3) speeds the dissociation of acetylcholine from A2R. Mutagenesis studies indicate that δP250L also has fast-channel effects, whereas ε P245L and ε P245Q, identical mutations of the corresponding proline in the ε subunit, have mild slow-channel effects. Conclusions: δP250Q represents the third mutation observed in the AChR δ subunit. The severe phenotype caused by δP250Q is attributed to endplate AChR deficiency, fast decay of the synaptic response, and lack of compensatory factors. That the penultimate prolines in TMD1 of the δ and ε subunits exert a reciprocal regulatory effect on the length of the channel opening bursts reveals an unexpected functional asymmetry between the two subunits.

Protein-anchoring Strategy for Delivering Acetylcholinesterase to the Neuromuscular Junction

Acetylcholinesterase (AChE) at the neuromuscular junction (NMJ) is anchored to the synaptic basal lamina via a triple helical collagen Q (ColQ). Congenital defects of ColQ cause endplate AChE deficiency and myasthenic syndrome. A single intravenous administration of adeno-associated virus serotype 8 (AAV8)-COLQ to Colq(-/-) mice recovered motor functions, synaptic transmission, as well as the morphology of the NMJ. ColQ-tailed AChE was specifically anchored to NMJ and its amount was restored to 89% of the wild type. We next characterized the molecular basis of this efficient recovery. We first confirmed that ColQ-tailed AChE can be specifically targeted to NMJ by an in vitro overlay assay in Colq(-/-) mice muscle sections. We then injected AAV1-COLQ-IRES-EGFP into the left tibialis anterior and detected AChE in noninjected limbs. Furthermore, the in vivo injection of recombinant ColQ-tailed AChE protein complex into the gluteus maximus muscle of Colq(-/-) mice led to accumulation of AChE in noninjected forelimbs. We demonstrated for the first time in vivo that the ColQ protein contains a tissue-targeting signal that is sufficient for anchoring itself to the NMJ. We propose that the protein-anchoring strategy is potentially applicable to a broad spectrum of diseases affecting extracellular matrix molecules.

Effect of Dietary Fatty Acid Composition on Th1/Th2 Polarization in Lymphocytes

BACKGROUND It has become increasingly clear that polyunsaturated fatty acids (PUFAs) have immunomodulatory effects. However, the intake of these fatty acids used in animal studies often greatly exceeds dietary human intake. Whether differences in the composition of fatty acids that are consumed in amounts consistent with normal dietary intake can influence immune function remains uncertain. METHODS We manufactured 3 types of liquid diet, related to modified fatty acid composition (omega-6/omega-3 = 0.25, 2.27 and 42.9), but excluding eicosapentaenoic acid and docosahexaenoic acid, based upon a liquid diet used clinically in humans. We assessed CD3-stimulated cytokine production of splenocytes in female BALB/c mice (n = 4 per group) fed 1 of 3 liquid diets for 4 weeks. We also measured the cytokine production of peripheral blood mononuclear cells stimulated with phorbol myristate acetate and ionomycin in humans at the end of a 4-week period of consumption of 2 different liquid diets (omega-6/omega-3 = 3 and 44). RESULTS We found that the ratio of interfero omega-gamma (IFN-gamma) / interleukin-4 (IL-4) was significantly higher in mice fed the omega-3 rich diet than in others. In humans, IFN-gamma / IL-4 was significantly higher after the omega-3 versus the omega-6 enhanced diet. CONCLUSIONS Differences in the composition of omega-3 and omega-6 PUFAs induces a shift in the Th1/Th2 balance in both mouse and human lymphocytes, even when ingested in normal dietary amounts. An omega-3 rich diet containing alpha-linolenic acid modulates immune function.

Neuroleptic malignant syndrome (parkinsonism-hyperpyrexia syndrome) after deep brain stimulation of the subthalamic nucleus

Neuroleptic malignant syndrome (NMS), also called parkinsonism-hyperpyrexia syndrome (PHS), is a severe, general, sometimes fatal, physical reaction, induced by sudden and strong blockade of dopamine receptors. When subthalamic nucleus (STN)-deep brain stimulation (DBS) is used on patients with Parkinson disease (PD), dopaminergic medications are transiently stopped prior to the procedure, and a reduction in the use of drugs is routinely attempted after the procedure. Although a sudden stop or abrupt reduction of dopaminergic medications may set the stage for NMS/PHS, only three cases have been reported after STN-DBS surgery. Here, we describe a 75-year-old woman with PD who experienced delayed onset, yet fatal, PHS after STN-DBS. Although STN-DBS might prevent or suppress PHS, its protective effect is not always complete. We must be aware that fatal PHS can occur when the use of medication for PD is reduced or altered, even when patients are under continuous STN stimulation.

R-spondin 2 promotes acetylcholine receptor clustering at the neuromuscular junction via Lgr5

At the neuromuscular junction (NMJ), acetylcholine receptor (AChR) clustering is mediated by spinal motor neuron (SMN)-derived agrin and its receptors on the muscle, the low-density lipoprotein receptor-related protein 4 (LRP4) and muscle-specific receptor tyrosine kinase (MuSK). Additionally, AChR clustering is mediated by the components of the Wnt pathway. Laser capture microdissection of SMNs revealed that a secreted activator of Wnt signaling, R-spondin 2 (Rspo2), is highly expressed in SMNs. We found that Rspo2 is enriched at the NMJ, and that Rspo2 induces MuSK phosphorylation and AChR clustering. Rspo2 requires Wnt ligands, but not agrin, for promoting AChR clustering in cultured myotubes. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5), an Rspo2 receptor, is also accumulated at the NMJ, and is associated with MuSK via LRP4. Lgr5 is required for Rspo2-mediated AChR clustering in myotubes. In Rspo2-knockout mice, the number and density of AChRs at the NMJ are reduced. The Rspo2-knockout diaphragm has an altered ultrastructure with widened synaptic clefts and sparse synaptic vesicles. Frequency of miniature endplate currents is markedly reduced in Rspo2-knockout mice. To conclude, we demonstrate that Rspo2 and its receptor Lgr5 are Wnt-dependent and agrin-independent regulators of AChR clustering at the NMJ.

The Cross-Sectional Area of Paraspinal Muscles Predicts the Efficacy of Deep Brain Stimulation for Camptocormia

BACKGROUND Camptocormia, a disturbance of posture, is a well-described clinical feature of PD and other parkinsonian syndromes. Previous reports have shown that DBS of the subthalamic nucleus (STN) or globus pallidus internus is effective in treating camptocormia. However, the efficacy of DBS for camptocormia varies. OBJECTIVE To determine a clinical marker for selecting an appropriate therapy for camptocormia, a disabling manifestation of Parkinsons disease (PD) that has a variable response to systemic and local therapies. METHODS We obtained pre-operative lumbar magnetic resonance imaging of 14 consecutive PD patients with camptocormia who underwent subthalamic nucleus deep brain stimulation (STN-DBS) in this retrospective-designed study. Lumbar MRI was performed three to six months prior to the operation. We measured the cross-sectional area (CSA) and width of each participants paraspinal muscles. RESULTS Four (28.6%) patients were effective (EF), five (35.7%) were partially effective (PE), and five (35.7%) were non-effective (NE) to STN-DBS. The lumbar paraspinal CSA and width were significantly larger in the EF group than in the PE and NE groups. CONCLUSIONS The CSA of paraspinal muscles and erector spinae width can be good predictive markers for improving camptocormia in patients with PD after deep brain stimulation.

[Left-sided metamorphopsia of the face and simple objects caused by an infarction at the right side of the splenium of the corpus callosum].

A 78-year-old woman noticed that peoples eyes and the right nasal foramens located in her left visual field looked smaller than those observed in the right. The woman reported no change in shape regarding facial outlines or scenic objects. Magnetic resonance imaging revealed an acute infarction of the right side of the splenium of the corpus callosum. Close examination revealed that her metamorphopsia affected the left side of her visual field, especially influencing facial components, particularly the eye. The woman had similar reactions to photographs of several kinds of animals, realistic portraits of humans, and caricatured humans. Meanwhile, presentings caricature human face at a 90° rotation elicited metamorphopsia in eyebrows located on the left side of a picture, but not the eyes. She also reported a change of shape or color tone for geometric objects. The patients only symptom was metamorphopsia, and she did not show any other neurological defects such as callosal disconnection syndrome. Furthermore, objects that were affected by the patients metamorphopsia (e.g. facial component especially the eye, and simple geometric figures) may be easy images to use in order to detect this type of distorted vision.