Anti-MuSK autoantibodies block binding of collagen Q to MuSK.

OBJECTIVE: Muscle-specific receptor tyrosine kinase (MuSK) antibody-positive myasthenia gravis (MG) accounts for 5%-15% of autoimmune MG. MuSK mediates the agrin-signaling pathway and also anchors the collagenic tail subunit (ColQ) of acetylcholinesterase (AChE). The exact molecular target of MuSK-immunoglobulin G (IgG), however, remains elusive. As acetylcholine receptor (AChR) deficiency is typically mild and as cholinesterase inhibitors are generally ineffective, we asked if MuSK-IgG interferes with binding of ColQ to MuSK. METHODS: We used 3 assays: in vitro overlay of the human ColQ-tailed AChE to muscle sections of Colq-/- mice; in vitro plate-binding assay to quantitate binding of MuSK to ColQ and to LRP4; and passive transfer of MuSK-IgG to mice. RESULTS: The in vitro overlay assay revealed that MuSK-IgG blocks binding of ColQ to the neuromuscular junction. The in vitro plate-binding assay showed that MuSK-IgG exerts a dose-dependent block of MuSK binding to ColQ by but not to LRP4. Passive transfer of MuSK-IgG to mice reduced the size and density of ColQ to ∼10% of controls and had a lesser effect on the size and density of AChR and MuSK. CONCLUSIONS: As lack of ColQ compromises agrin-mediated AChR clustering in Colq-/- mice, a similar mechanism may lead to AChR deficiency in MuSK-MG patients. Our experiments also predict partial AChE deficiency in MuSK-MG patients, but AChE is not reduced in biopsied NMJs. In humans, binding of ColQ to MuSK may be dispensable for clustering ColQ, but is required for facilitating AChR clustering. Further studies will be required to elucidate the basis of this paradox.

Effect of L-phenylalanine supplementation and a high-protein diet on pharmacokinetics of cefdinir in healthy volunteers: an exploratory study.

BACKGROUND: Upregulation of oligopeptide transport activity by dietary protein, certain dipeptides and amino acids has been reported in the rat intestine and a human intestinal cell line. OBJECTIVE: In this study, the pharmacokinetics of cefdinir were investigated after L-phenylalanine supplementation and a high-protein diet (HPD) in humans to explore changes in the activities of intestinal and renal oligopeptide transporters. METHODS: A normal-protein diet (NPD, 73.2 +/- 2.6 g/day), NPD + l-phenylalanine (7.5 g/day), or HPD (141.3 +/- 3.7 g/day) was given to six male healthy volunteers for 12 days followed by a single dose of cefdinir after an overnight fast in a randomized three-way crossover study with a 22-day washout. Blood and urine were collected over a 12-h period after administration of cefdinir. Concentrations of cefdinir in plasma and/or urine were measured by high-performance liquid chromatography. RESULTS: Plasma concentrations and urinary excretion of the drug did not change throughout the study. Physiological variables and laboratory values did not reveal any differences between the three periods except for serum and urinary nitrogen levels and serum triglyceride. DISCUSSION: A reason for the unchanged pharmacokinetics of cefdinir may be due to lower doses of L-phenylalanine and protein in humans than in animals when converting animal effective doses to humans. CONCLUSION: In humans, L-phenylalanine supplementation and HPD do not seem to upregulate intestinal and renal oligopeptide transport in the ranges of duration and dose examined.

Progressive myopathy with circulating autoantibody against giantin in the Golgi apparatus.

A woman aged 59 years with adult-onset progressive myopathy had anti-Golgi (giantin) autoantibody in the serum. Limb-muscle biopsy revealed chronic myopathy with paucity of cellular reactions and reduced immunostaining for alpha-dystroglycan. The similarity of the current patient with cases of hereditary alpha-dystroglycanopathies (Fukuyama-type congenital muscular dystrophy, Walker-Warburg syndrome, muscle-eye-brain disease, congenital muscular dystrophy type 1C, and limb-girdle muscular dystrophy type 2I) suggests that the Golgi apparatus is the target organelle in a subset of myopathies.

Anti-Ma2 antibody related paraneoplastic limbic/brain stem encephalitis associated with breast cancer expressing Ma1, Ma2, and Ma3 mRNAs.

A 69 year old woman presented with cognitive impairment and supranuclear gaze palsy caused by paraneoplastic limbic/brain stem encephalitis associated with atypical medullary breast carcinoma. The cerebrospinal fluid from the patient harboured an anti-neuronal cell antibody against Ma2 antigen, but not against Ma1 or Ma3 antigen. Despite the antibody being restricted to the Ma2 antigen, the patient's cancer tissue expressed Ma1, Ma2, and Ma3 mRNAs. These results, and the expression of Ma2 mRNA in an atypical medullar breast carcinoma in another patient without paraneoplastic encephalitis, indicate that the induction of anti-Ma2 antibody depends on host immunoreponsiveness and not on the presence of the antigen itself in the cancer.

Dysferlin mutations in Japanese Miyoshi myopathy: relationship to phenotype.

OBJECTIVE: To study dysferlin gene mutations and genotype-phenotype correlations in Japanese patients with Miyoshi myopathy (MM). BACKGROUND: MM is an autosomal recessive distal muscular dystrophy that arises from mutations in the dysferlin gene. This gene is also mutated in families with limb girdle muscular dystrophy 2B. METHODS: The authors examined 25 Japanese patients with MM. Genomic DNA was extracted from the peripheral lymphocytes of the patients. The PCR products of each of 55 exons were screened by single strand conformation polymorphism or direct sequencing from the PCR fragments. RESULTS: The authors identified 16 different mutations in 20 patients with MM; 10 were novel. Mutations in Japanese patients are distributed along the entire length of the gene. CONCLUSIONS: Four mutations (C1939G, G3370T, 3746delG, and 4870delT) are relatively more prevalent in this population, accounting for 60% of the mutations in this study. This study revealed that the G3370T mutation was associated with milder forms of MM and the G3510A mutation was associated with a more severe form.

[A case of LGMD2A identified with both western blot analysis and immunostaining of calpain 3 in biopsied muscle].

A 45-year-old housewife had proximal dominant limb muscle weakness from around 25 years of age. Her parents were cousins. None of family members was affected. Progressive muscle weakness and atrophy were prominent at the posterior compartments of legs and trunk. Serum CK was moderately elevated. Muscle pathology revealed variation in fiber size, moderate increase in numbers of internal nuclei and abundant lobulated fibers. On immunostaining using by monoclonal antibody against human calpain 3 (NCL-CALP-2 C4; Novocastra) to the biopsied muscle, calpain 3 was completely absent in the sarcoplasm, while granular debris and in part positive striation were noted in control muscle. By Western blot analysis, a band corresponding to 94 kDa of calpain 3 was not detected. A genetic analysis of calpain 3 revealed homozygous C-565-G mutation (Leu189Val). From the present study. Western blot analysis and immunostaining by using calpain 3 antibody were suggested to be useful to diagnose LGMD2A in LGMD patients.

[A case of myasthenia gravis following sarcoidosis and Hashimoto's thyroiditis].

Here, we report on an elderly woman with sarcoidosis and Hashimoto's disease who later developed myasthenia gravis. She was 68-year-old with a long history of Hashimoto's disease who had a clinical diagnosis of sarcoidosis with uveritis at the age of 66 years. On laboratory examination, angiotensin-converting enzyme, lysozyme and gamma-globulin were elevated and there was bilateral hilar lymphoadenopathy. She was admitted to our hospital because of left blepharoptosis and mild fatigability in the proximal muscles at the age of 68 years. Myasthenia gravis, type IIa, was confirmed by elevated titer of anti-acetylcholine receptor antibody in serum (0.8 nmol/l, normal < 0.6), positive edrophonium test and decremental EMG response. Oral prednisolone therapy was effective. Her muscle biopsy revealed HLA ABC-positive fibers in all fascicles, and HLA-DR positive fibers in the perifascicular areas. Myasthenia gravis complicated by sarcoidosis and Hashimoto's thyroiditis is extremely rare, suggesting that the common underlying immunological abnormalities for the three disorders such as a certain defective cellular immunity are responsible for the pathomechanism to induce the patient condition.

Renin-producing adrenal tumor: report of a case.

A 19-year-old man with an adrenal tumor associated with hypertension is herein described. The plasma renin activity (PRA) was markedly elevated and the plasma aldosterone level was also increased. The catecholamine level was within the normal range and the glucagone-regitine test was negative. An angiogram revealed the left renal artery to have no stenotic segments, but instead was curved caudally. Magnetic resonance imaging showed a tumor measuring about 8 cm in diameter to be clearly recognized from the left kidney. The blood pressure did not drop when a calcium-channel blocker was used, but was gradually stabilized with the angiotensin converting enzyme (ACE) antagonist. The adrenal tumor was then removed surgically. Normal adrenal tissue was scarcely recognized to the left of the tumor. After surgery, the PRA decreased and blood pressure stabilized rapidly without the ACE antagonist. The possibility of massive renal renin secretion due to suppression by the adrenal tumor was excluded by a method using an antibody to purified human renin.

(R)salsolinol N-methyltransferase activity increases in parkinsonian lymphocytes.

Recently, an endogenous catechol isoquinoline, 1(R),2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [N-methyl(R)salsolinol], was proved to be a neurotoxin specific for dopamine neurons by in vivo and in vitro experiments. This N-methyl(R)salsolinol was found to increase significantly in the cerebrospinal fluid of untreated parkinsonian patients, suggesting its possible involvement in the pathogenesis of Parkinson's disease. To clarify the mechanism of the increase, the activity of enzymes related to the metabolism of the neurotoxin was examined in lymphocytes prepared from parkinsonian patients and controls. In patients with Parkinson's disease, the activity of a neutral N-methyltransferase, measured by using (R)salsolinol as a substrate, was found to increase significantly (100.2 +/- 81.8 pmol/min/mg of protein) in comparison with that in controls (18.9 +/- 15.0 pmol/min/mg of protein). The distribution of the activity was bimodal in the parkinsonian patients, whereas it was singular in controls. The activity of other related enzymes, an alkaline N-methyltransferase and N-methyl(R)salsolinol oxidase, in parkinsonian lymphocytes was the same as in controls. Increase of the neutral N-methyltransferase may be an endogenous factor in the pathogenesis of Parkinson's disease.

[Clinico-pathological analysis of vesiculotubular myopathy of adult onset].

The patient was a 50-year-old house wife. There were complicated consanguineous marriages in the family tree. Since 30 years of age, she had suffered from progressive limb muscle weakness, but without myalgia and myasthenia. At present, she was wheelchair-bound. Physical examinations showed obesity, congenital livedo racemosa, epicanthus palpebrae and left renal defect. Neurologically, facial, anterior cervical, and iliopsoas muscles were well preserved, but others were severely involved. Laboratory examinations revealed mildly elevated myogenic serum enzymes, and myogenic changes on needle EMG. In her muscle biopsy from the left rectus femoris muscle, there were no inflammatory changes, but marked variations of the fiber size as well as adipose tissue replacement were recognized. Strickingly, basophilic masses located in the center of the sarcoplasm were present in about 10% of the fibers. Histochemically, the masses were present in both type 1 and 2 fibers, and exhibited almost similar stained patterns to the tubular aggregates, but were dystrophin-, GRP78- and clathrin-positive. Under electron microscopy, the masses consisted of aggregates of the vesiculotubular structure, measuring approximately from 60 nm to more than 6 microns in diameter, which were continuous with T system/sarcoplasmic reticulum and were clearly segregated from myofilaments. This is a chronic progressive muscular disorder of adult onset with the peculiar pathological finding of vesiculotubular structure.