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Biomedical subjects

K Arahata

Publications and source records attributed to K Arahata.

At least 73 records · Page 4Linked to original sources
PubMed1996

Effect of artificial (CTG) repeat expansion on the expression of myotonin protein kinase (MtPK) in COS-1 cells.

A major challenge in the study of a new genetic entity called triplet-repeat disease is to identify the role of triplet repeats in the pathogenesis of the disease. We have developed a strategy to demonstrate the effect in the 3'-untranslated end of the (CTG) repeats in myotonic dystrophy gene (MtPK) and found that repeat expansion (CTG46) causes a slight decrease in the translation rate of MtPK cDNA which correlates with the finding in patients with myotonic dystrophy of a low amount of MtPK protein in muscle. These results provide an important clue for characterizing the genetic abnormality in other triplet-repeat diseases.

Animals↗
PubMed1996

Reduction of serum IgG level and peripheral T-cell counts are correlated with CTG repeat lengths in myotonic dystrophy patients.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder associated with expansion of the CTG repeat within the 3' non-coding region of the myotonin protein kinase (MT-PK) gene. CTG repeat length has been shown to correlate with the clinical category and age at onset of the disease. The relationship between CTG repeat length and immunological parameters were analyzed in this study. We determined CTG repeat length in 14 DM patients and 15 normal controls using Southern and PCR analyses, and then correlated their CTG repeat lengths with their serum immunoglobulin (IgG, IgA, IgM) levels and the number of peripheral white blood cells, including lymphocyte subsets. In DM patients, increasing CTG repeat lengths correlated significantly with decreasing serum IgG levels, decreasing total lymphocyte counts, and decreasing CD2+, CD3+, and CD4+ cell counts. Immunological parameters were also influenced by the expansion of CTG repeat in DM patients.

Adult↗
PubMed1996

Emerin deficiency at the nuclear membrane in patients with Emery-Dreifuss muscular dystrophy.

Mutations in the STA gene at the Xq28 locus have been found in patients with X-linked Emery-Dreifuss muscular dystrophy (EDMD). This gene encodes a hitherto unknown protein named 'emerin'. To elucidate the subcellular localization of emerin, we raised two antisera against synthetic peptide fragments predicted from emerin cDNA. Using both antisera, we found positive nuclear membrane staining in skeletal, cardiac and smooth muscles in the normal controls and in patients with neuromuscular diseases other than EDMD. In contrast, a deficiency in immunofluorescent staining of skeletal and cardiac muscle from EDMD patients was observed. A 34 kD protein is immunoreactive with the antisera--the protein is equivalent to that predicted for emerin. Together, our findings suggest the specific deficiency of emerin in the nuclear membrane of muscle cells in patients with EDMD.

Adolescent↗
PubMed1996

Identification of an interleukin-1 beta converting enzyme-like activity that increases upon treatment of P19 cells with retinoic acid as the proteasome.

We examined changes in proteinase activities in P19 embryonal carcinoma cells during retinoic acid-induced differentiation. The interleukin-1 beta converting enzyme (ICE)-like Ac-YVAD-MCA hydrolytic activity was increased about 6-fold by treatment with retinoic acid. This activity was inhibited by N-ethylmaleimide and Ac-YVAD-H but not by E-64, EDTA, PMSF, or amastatin. The ICE-like activity in P19 cells eluted as a single peak just after the void volume on gel filtration. No ICE-like activity was observed at a molecular mass of 30-50 kDa. Enzymatic purification, Western blot analysis, and an immunoabsorption study demonstrated that the ICE-like activity in P19 cells is caused by the proteasome, and is stimulated during retinoic acid-induced differentiation. The proteasome purified from mouse liver also cleaved Ac-YVAD-MCA. These results strongly suggest that the proteasome is a major ICE-like proteinase in P19 cells and may be involved in the neural differentiation and the apoptotic pathway.

Animals↗
PubMed1996

Congenital muscular dystrophy: Clinical and pathologic study of 50 patients with the classical (Occidental) merosin-positive form.

We studied 50 patients with the merosin-positive form of congenital muscular dystrophy (MP-CMD) clinically and pathologically. The frequency of MP-CMD in our laboratory was approximately one-half that of the Fukuyama type and one-sixth that of Duchenne muscular dystrophy. The early signs of MP-CMD included decreased fetal movement during pregnancy (14%) and poor suck (42%), floppiness (30%), and respiratory difficulty (16%) in early infancy. Eighty-six percent of the patients had delayed motor development. Ninety-two percent of the patients followed beyond age 4 years had learned to walk. The disease was relatively slowly progressive, except in six patients who rapidly lost ambulation. Almost all patients had normal IQ, except four who were mildly to moderately retarded. Of the patients examined by cranial CT/MRI, 24% showed cerebral atrophy and 11% had areas of white matter lucency. Muscle biopsy results in those younger than 5 years showed mild dystrophic changes consisting of variation in fiber size and scattered necrotic and regenerating fibers. In older children, there were additional chronic dystrophic changes, including fiber splitting (32%), moth-eaten appearance (32%), marked fatty replacement (46%), and abnormal fiber type distribution (59%). The manifestations of MP-CMD were generally milder and more slowly progressive than those of the Fukuyama type and merosin-negative form of congenital muscular dystrophy.

Adolescent↗
PubMed1996

Myotonia congenita with painful muscle cramps.

A sporadic Japanese case of myotonia congenita with painful muscle cramps is reported. Electromyographic examinations disclosed myotonic discharge with dive bomber sounds at insertion, and high-amplitude, high-frequency motor unit potentials during the muscle cramps. Biopsied muscle specimens and EMG findings showed non-specific mild myopathic changes. There was no abnormal expansion of CTG repeat within the myotonic dystrophy gene. This patient's disorder closely resembles Becker's myotonia congenita Type II though the family history of was non contributory.

Biopsy↗
PubMed1995

Absence of extraocular muscle pathology in Duchenne's muscular dystrophy: role for calcium homeostasis in extraocular muscle sparing.

Duchenne muscular dystrophy (DMD) is characterized by clinical weakness and progressive necrosis of striated muscle as a consequence of dystrophin deficiency. While all skeletal muscle groups are thought to be affected, enigmatically, the extraocular muscles (EOM) appear clinically unaffected. Here we show that dystrophin deficiency does not result in myonecrosis or pathologically elevated levels of intracellular calcium ([Ca2+]i) in EOM. At variance with a previous report, we find no evidence for dystrophin-related protein/utrophin up-regulation in EOM. In vitro experiments demonstrate that extraocular muscles are inherently more resistant to necrosis caused by pharmacologically elevated [Ca2+]i levels when compared with pectoral musculature. We believe that EOM are spared in DMD because of their intrinsic ability to maintain calcium homeostasis better than other striated muscle groups. Our results indicate that modulating levels of [Ca2+]i in muscle may be of potential therapeutic use in DMD.

Animals↗
PubMed1995

Regulation of alternative splicing in the amyloid precursor protein (APP) mRNA during neuronal and glial differentiation of P19 embryonal carcinoma cells.

Cell-specific alteration in the splicing of exons 7, 8 and 15 of the amyloid precursor protein gene was investigated in differenting P19 EC cells into neuronal and glial cells. Exons 7 and 8 were skipped in the neuronal state and exon 15 was skipped in the glial state. Expression of U2AF, one of the essential factor for splicing in mammalian cells, was down-regulated during cellular differentiation. The skipping of exon 15 was suppressed in the glial cells transfected with U2AF. Thus, a reduction in U2AF is believed to play a crucial role in glial-specific splicing of the APP gene.

Alternative Splicing↗
PubMed1995

Hepatocyte growth factor specifically expressed in microglia activated Ras in the neurons, similar to the action of neurotrophic factors.

Hepatocyte growth factor (HGF) mRNA and its receptor (c-Met) mRNA were detected in the fetal and adult rat brain. Expression of c-Met mRNA was increased after birth. HGF mRNA was preferentially expressed in the microglia of the rat brain, while c-Met mRNA was expressed in neurons as well as astrocytes and microglia. Most of the neurons were c-Met positive, and HGF stimulated tyrosine phosphorylation of c-Met (140-kDa) in the neurons. HGF as well as bFGF also activated Ras in the neurons. These results suggest that HGF plays a biological role as one of the neurotrophic factors in the brain.

Animals↗
PubMed1995

Limb-girdle muscular dystrophy: clinical and pathologic reevaluation.

To better define limb-girdle muscular dystrophy (LGMD), we examined 58 patients clinically and pathologically who fulfilled the criteria for LGMD and had normal dystrophin expression in their muscle biopsies. Only 27.6% of patients had evidence of inheritance. The onset of disease varied from 2 to 58 years of age, averaging 17.2 years. The disease progression also differed from patient to patient. In addition to evidence of muscle fiber necrosis and regeneration, in all muscle biopsies there were fibers with architectural changes of disorganized intermyofibrillar networks including moth-eaten (100%), lobulated (40%), whorled (17%) and targetoid (8%) fibers. The lobulated fibers which have never been reported in Duchenne muscular dystrophy (DMD) were seen in the advanced stages of LGMD, although the significance of such fibers remains unknown. On immunohistochemical examination, dystrophin-associated proteins (DAPs) and laminin were normally expressed along the surface membrane of muscle fibers, including the lobulated fibers.

Adult↗
PubMed1995

DNA rearrangements in Japanese facioscapulohumeral muscular dystrophy patients: clinical correlations.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscular disorder in which the disease locus has been mapped to chromosome 4q35-qter. In most patients, the DNA rearrangements associated with FSHD have been found in the EcoRI fragment detected by the p13E-11 probe, and deletions of the 3.2 kb repeat units within the fragment are thought to cause the disease. To examine FSHD-associated DNA rearrangements in the Japanese population, we performed Southern blot analysis of the genomic DNA, using the p13E-11 and pFR-1 probes, in 158 Japanese individuals, including 38 FSHD patients from 19 families. We found that all but one (a possible affected recombinant) of the Japanese FSHD patients (97.4%) had specific smaller (< 28 kb) EcoRI fragments which cosegregated with the disease; this included four patients who had severe inflammatory changes in the muscle and eight patients with de novo DNA rearrangements. We found no FSHD patient who had a fragment larger than 28 kb. By contrast, only two of 35 Japanese controls (5.7%) had EcoRI fragments smaller than 28 kb. Our patients showed anticipation, i.e. decreased size of the EcoRI fragment in parallel with earlier onset of the disease (r = 0.531, P = 0.003, with younger age at onset in children (17.8 +/- 7.0) than their affected parents (31.5 +/- 14.8) (P = 0.019). However, since each family had a specific small EcoRI fragment associated with the disease, the differing clinical severity within a family cannot be explained by the size of the fragment alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

A severe muscular dystrophy patient with an internally deleted very short (110 kD) dystrophin: presence of the binding site for dystrophin-associated glycoprotein (DAG) may not be enough for physiological function of dystrophin.

We report a 4-yr and 5-month-old boy with severe clinical features of an early-onset Duchenne muscular dystrophy, who had a very short (110 kDa) dystrophin at the sarcolemma. The patient had a large deletion (exons 2-44) of the dystrophin gene which was predicted to cause a reading frame shift. Sequence analysis of dystrophin mRNA in muscle revealed an alternatively spliced gene product from exons 1 to 51 that caused restoration of the reading frame, in addition to an mRNA corresponding to the DNA deletion. A consistent result was obtained by immunocytochemical analysis of muscle; i.e. positive staining for dystrophin at the sarcolemma using antibodies against the C-terminus, cysteine-rich region and last three of 24 repeat units of the central rod-domain, but not for the remaining antibodies for dystrophin that recognize the N-terminal and proximal rod-domains. Immunostaining for dystrophin-associated glycoproteins (DAGs: 43 and 50 K) and merosin were preserved. Utrophin staining was positive but fainter than other DMD muscles. These results suggest that an extremely short dystrophin lacking the entire actin-binding site in the N-terminus cannot function properly even if the protein possesses the putative DAG-binding cysteine-rich and the C-terminal domains, and still has an ability to associate with sarcolemmal membrane.

Base Sequence↗
PubMed1995

Congenital muscular dystrophies.

Considerable advances in the understanding of congenital muscular dystrophy made during the past year may allow a new clinical classification of this disease. In particular, (1) evidence has accumulated to suggest that a laminin alpha2-chain (alpha2 subunit of laminin-2 or merosin) deficiency causes a type of congenital muscular dystrophy, and (2) it has been postulated that Fukuyama-type congenital muscular dystrophy and Walker-Warburg syndrome (but not Finnish muscle-eye-brain disease) are genetically identical diseases.

Disease Models, Animal↗
PubMed1995

The frequency of patients with 50-kd dystrophin-associated glycoprotein (50DAG or adhalin) deficiency in a muscular dystrophy patient population in Japan: immunocytochemical analysis of 50DAG, 43DAG, dystrophin, and utrophin.

The 50-kd dystrophin-associated glycoprotein (50DAG or adhalin) in the skeletal muscle has been shown to be deficient in patients with severe childhood autosomal recessive muscular dystrophy prevalent in North Africa. To elucidate the frequency of patients having the 50DAG deficiency in a muscular dystrophy population in Japan, we immunocytochemically examined 50DAG, 43DAG, dystrophin, and utrophin. A total of 243 patients with muscular dystrophy, among 1,035 diagnostic muscle biopsies during the past 2.5 years, were analyzed. We identified five unrelated patients (three females and two males who have no family history) with 50DAG deficiency in the sarcolemma. Thus, 2.1% (5/243) of our muscular dystrophy patient population had 50DAG deficiency.

Adolescent↗
PubMed1995

Cloning and mapping of a very short (10-kb) EcoRI fragment associated with facioscapulohumeral muscular dystrophy (FSHD).

Facioscapulohumeral muscular dystrophy (FSHD) is a dominantly inherited muscular disorder and the gene for FSHD has been mapped to chromosome 4q35. Recently, the DNA rearrangements associated with the disease were found in the EcoRI fragment detected by the probes p13E-11 and pFR-1, and deletions of the 3.3-kb KpnI repeat units within the EcoRI fragment are thought to cause the disease. In this study, we cloned the FSHD-associated EcoRI fragments (the shortest fragments identified to date: 10 kb) from 2 severely affected patients (unrelated). Restriction enzyme maps of the genomic fragments in the 2 patients revealed that the 10 kb fragments were identical and contained only one 3.3-kb KpnI repeat unit. These results suggest that deletions of the 3.3-kb KpnI repeat units are likely to associate with FSHD, and that the 10 kb fragments may provide a means of understanding the molecular details involved at the site of the chromosomal rearrangements in FSHD.

Adolescent↗