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Biomedical subjects

T Kitaguchi

Publications and source records attributed to T Kitaguchi.

At least 19 recordsLinked to original sources
PubMed2003

Pathological changes of the myonuclear fibrous lamina and internal nuclear membrane in two cases of autosomal dominant limb-girdle muscular dystrophy with atrioventricular conduction disturbance (LGMD1B).

Mutations in the lamin A/C gene have been reported in a variety of disorders including autosomal dominant Emery-Dreifuss muscular dystrophy and autosomal dominant limb girdle muscular dystrophy with cardiac conduction block or limb girdle muscular dystrophy type 1B (LGMD1B). However, how these mutations are involved in developing these diseases is not known. We examined morphological changes of the skeletal muscle in two cases of LGMD1B in a family, directing our attention to the nuclear envelope and its underlying structures where lamin A/C is located. Although conventional fluorescence microscope revealed no discernible abnormality in the distribution of emerin and lamin A/C, a serial multi-layer scanning with confocal laser scanning microscope showed an attenuated and uneven distribution of lamin A/C. Furthermore, under an electron microscope, the nuclear fibrous lamina and inner nuclear membrane were relatively indistinct compared to controls. These changes in the myonuclei may be related to pathomechanisms of the present cases.

Adult↗
PubMed2001

Experimental allergic myositis in SJL/J mouse. Reappraisal of immune reaction based on changes after single immunization.

SJL/J mice have been subjected to immunization with wide varieties of antigens to produce models of autoimmune disorders including experimental myositis. They also have a defect in dysferlin gene and spontaneously develop muscle fiber degeneration, a condition akin to limb-girdle type muscular dystrophy and Miyoshi myopathy. To know whether muscle inflammation of SJL mice after immunization with muscle fractions really represents immune-mediated myositis or no more than an epiphenomenon of muscle degeneration due to dysferlin defect, we studied immunological parameters after immunization with rabbit myosin B fraction. Initial infiltration of macrophages and CD4+ lymphocytes on day 11 was followed by increase in number of CD8+ cells. Such increase was not observed in the nontreated and adjuvant controls. Some infiltrating cells were interferon gamma (IFN-gamma) positive. Furthermore, increased expression of the signal transducers and activator of transcription 1 (STAT-1) and interferon regulatory factor 1 (IRF-1) mRNA was shown in the first 2 weeks. These results indicate Th1 system activity in the muscle, rather than simple dysferlin deficiency, particularly 1-3 weeks after immunization. Thus it is concluded that an immune-mediated myositis is taking place at this stage. This model can be helpful in understanding pathomechanisms involved in the early stage of human myositides. It has also important implications concerning immune reactions associated with transplantation or gene therapy for muscular dystrophies.

Animals↗
PubMed2001

Xenopus Polycomblike 2 (XPcl2) controls anterior to posterior patterning of the neural tissue.

A novel gene, Xenopus Polycomblike 2 (XPcl2), which encodes a protein similar to Drosophila Polycomblike was cloned and characterized. Polycomblike belongs to the Polycomb group proteins, which maintain stable expression patterns for the clustered homeotic genes in the Drosophila embryo by forming multimeric complexes on chromatin. XPcl2 shows greater amino acid sequence homology to human and mouse M96 (hPcl2, mPcl2) than Xenopus Pcl1 (XPcl1), mouse Tctex3 (mPcl1) and human PHF1 (hPcl1), indicating that at least two types of Polycomblike genes are conserved between amphibians and mammals. XPcl2 mRNA is present both maternally and zygotically, and the temporal expression profile is distinct from XPcl1, another member of the Polycomblike family in Xenopus. XPcl2 is highly expressed in the anterior-dorsal region of Xenopus following the neurula stage in a manner similar to XPcl1. Overexpression of XPcl2 disturbs the development of the anterior central nervous system, eye and cement gland. In the XPcl2-overexpressing embryo, a hindbrain marker, Krox20, and a spinal cord marker, HoxB9, are expressed more posteriorly, suggesting an alteration in the anterior-posterior patterning of the neural tissue. In addition, XPcl2 represses Zic3- and noggin-induced anterior neural markers, but not neural crest markers in animal cap explants. These results indicate that XPcl2 regulates anterior neural tissue development and the anterior-posterior patterning of the neural tissue.

Amino Acid Sequence↗
PubMed2001

A missense mutation in the exon 8 of lamin A/C gene in a Japanese case of autosomal dominant limb-girdle muscular dystrophy and cardiac conduction block.

A case of autosomal dominant limb-girdle muscular dystrophy with atrioventricular conduction block (LGMD1B) has been documented. In this family, 13 members, nine males and four females, had cardiac arrhythmia requiring pacemakers. The proband, a 67-year-old male, had longstanding proximal muscle weakness later associated with cardiac arrhythmia but showed neither rigid spine nor joint contracture. His muscle enzymes were within normal range and muscle biopsy showed myopathic changes. Gene analysis of the proband revealed Tyr481His mutation in the exon 8 of lamin A/C (LMNA) gene which is adjacent to the codon mutated in reported cases of familial partial lipodystrophy. This is the first report of muscular dystrophy shown to have a mutation of LMNA in a Japanese family as well as the first case of missense mutation in the exon 8 with LGMD1B phenotype.

Aged↗
PubMed2000

Zic3 is involved in the left-right specification of the Xenopus embryo.

Establishment of left-right (L-R) asymmetry is fundamental to vertebrate development. Several genes involved in L-R asymmetry have been described. In the Xenopus embryo, Vg1/activin signals are implicated upstream of asymmetric nodal related 1 (Xnr1) and Pitx2 expression in L-R patterning. We report here that Zic3 carries the left-sided signal from the initial activin-like signal to determinative factors such as Pitx2. Overexpression of Zic3 on the right side of the embryo altered the orientation of heart and gut looping, concomitant with disturbed laterality of expression of Xnr1 and Pitx2, both of which are normally expressed in the left lateral plate mesoderm. The results indicate that Zic3 participates in the left-sided signaling upstream of Xnr1 and Pitx2. At early gastrula, Zic3 was expressed not only in presumptive neuroectoderm but also in mesoderm. Correspondingly, overexpression of Zic3 was effective in the L-R specification at the early gastrula stage, as revealed by a hormone-inducible Zic3 construct. The Zic3 expression in the mesoderm is induced by activin (beta) or Vg1, which are also involved in the left-sided signal in L-R specification. These findings suggest that an activin-like signal is a potent upstream activator of Zic3 that establishes the L-R axis. Furthermore, overexpression of the zinc-finger domain of Zic3 on the right side is sufficient to disturb the L-R axis, while overexpression of the N-terminal domain on the left side affects the laterality. These results suggest that Zic3 has at least two functionally important domains that play different roles and provide a molecular basis for human heterotaxy, which is an L-R pattern anomaly caused by a mutation in human ZIC3.

Animals↗
PubMed1999

Characterization of liposomes carrying von Willebrand factor-binding domain of platelet glycoprotein Ibalpha: a potential substitute for platelet transfusion.

Platelet glycoprotein (GP) Ib/IX/V complex is a receptor for von Willebrand factor (vWf), which plays a crucial role in primary hemostasis by mediating platelet adhesion to injured blood vessels. We have expressed in CHO cells a fragment of GPIba that retained a vWf-binding function. The recombinant fragment (rGPIba) was incorporated into liposomes and evaluated their functions in vitro. rGPIba on the liposome surface was detectable by flow cytometric analysis. Addition of vWf and ristocetin caused specific agglutination of rGPIbalpha-liposomes, as evaluated by an aggregometer or a fluorescent microscopy. When ristocetin was added to platelet-rich plasma (PRP) pre-mixed with rhodamine-labeled rGPIbalpha-liposomes, platelets aggregated and rhodamine-fluorescence was strongly positive in the platelet thrombi, suggesting that heterologous aggregation (attachment of liposomes to platelets) occurred. Platelet aggregation in PRP at low platelet concentration (20-80 x 10(6)/ml) was enhanced by rGPIbalpha-liposomes in a dose-dependent manner. Thus, rGPIbalpha-liposomes may accumulate on vWf-exposed subendothelial tissues and enhance platelet function in vivo, supporting hemostasis in thrombocytopenic individuals.

Animals↗
PubMed1999

Changes in the cytoskeletal proteins, sarcoplasmic reticulum, and capillaries in acute relaxant-steroid myopathy (ARSM) in contrast to the corticosteroid myopathy.

Since we reported a case of acute relaxant-steroid myopathy (ARSM) in 1994, we continued histological studies and compared the findings with those in a case of corticosteroid myopathy (CM). It was revealed that (1) dystrophin, spectrin, beta dystroglycan, and sarcoglycans on the cell surface were decreased, (2) regular arrangement of the sarcoplasmic reticulum was lost, and (3) some capillaries were degenerated. Since none of these changes were seen in CM, it became clear that ARSM is different from CM. It was estimated that continuous administration of non-depolarizing muscle relaxant produces a state akin to denervation. Combination of denervation, immobilization and circulatory disturbance in ARSM not only augments the effects of corticosteroids, but they produce changes different from CM, namely impairment of the cell membrane system (both internal and external) and capillary degeneration.

Capillaries↗
PubMed1999

Fukuyama-type congenital muscular dystrophy: close relation between changes in the muscle basal lamina and plasma membrane.

Despite the recent advance in genetic study of Fukuyama-type congenital muscular dystrophy (FCMD), the mechanism of muscle degeneration in the disease remains unclear. To clarify it, muscle biopsies from six cases of FCMD were subjected to immunohistochemical and ultrastructural studies. On the muscle cell surface, decreased expression of laminin alpha2 subunit was seen along with aberrant expression of laminin alpha5 and neural cell adhesion molecule. Electron microscopy revealed breach of muscle basal lamina. The electron density of plasma membrane was significantly lower at the places without identifiable basal lamina. Thus in FCMD changes of laminin and other proteins on the cell surface involve a process common to developing muscles, and loss of normal structure of the basal lamina is closely associated with changes of the plasma membrane. This suggests that the primary cause of FCMD is related to formation and maintenance of the basal lamina.

Adult↗
PubMed1998

Characterization of cDNA encoding full-length mouse platelet glycoprotein IX.

Glycoprotein (GP) IX is a platelet membrane 20 kD protein, which is associated with GPIbalpha, GPIb beta, and GPV to form GPIb/IX/V complex. GPIb/IX/V complex is a major receptor for von Willebrand factor, which mediates platelet adhesion and aggregation under high shear stress conditions. The relevance of this receptor for hemostasis has been implicated by a congenital bleeding disorder lacking the receptor, Bernard-Soulier syndrome. All subunits for the human receptor have been cloned and characterized. However, the function of GPIX is still elusive. To obtain further information of GPIX, we have determined a cDNA sequence of mouse GPIX (811 bp). The deduced amino-acid sequence (177aa) was 71% identical to the human GPIX protein. All cysteine residues in extracytoplasmic domain and putative N-linked glycosylation site (Asn44) were conserved. Mouse GPIX contained a leucine-rich glycoprotein sequence composed of 24 amino acids, as did human GPIX.

Amino Acid Sequence↗
PubMed1997

Characterization of the gene encoding mouse platelet glycoprotien Ib beta.

Platelet glycoprotein (GP) Ib/IX/V complex is a major receptor for von Willebrand factor (vWF), which mediates platelet adhesion and aggregation under high shear stress conditions. It is composed of GPIb alpha, GPIb beta, GPIX, and GPV. All subunits for the human receptor have been cloned and characterized. However, the function of GPIb beta is still elusive. To obtain further information of GPIb beta, we have determined the genomic sequence of mouse GPIb beta (1466 bp). The deduced amino acid sequence (206aa) was 88% identical to the human GPIb beta protein. All cysteine residues, putative N-linked glycosylation site (Asn41), and putative phosphorylation site (Ser166) were conserved. The promoter region contained putative GATA and ets binding motif implicated in megakaryocytic expression. Mouse GPIb beta also contained a leucine-rich glycoprotein (LRG) sequence of 24 amino acids same as human GPIb beta.

Amino Acid Sequence↗
PubMed1997

Expression and functional characterization of an abnormal platelet membrane glycoprotein Ib alpha (Met239 --> Val) reported in patients with platelet-type von Willebrand disease.

Platelet-type von Willebrand disease (vWD) is a congenital bleeding disorder characterized by heightened ristocetin-induced platelet aggregation caused by abnormally high affinity between the platelet membrane glycoprotein (GP) Ib/IX complex and von Willebrand factor (vWF). Two distinct point mutations, Gly233 to Val and Met239 to Val, have been reported in GPIb alpha. We have constructed a recombinant GPIb alpha fragment containing the latter mutation, Met239 to Val (M239V) and characterized the mutant molecule using two methods, ie, interaction between soluble vWF and immobilized M239V and inhibition of platelet aggregation by purified soluble M239V. Spontaneous binding (ie, binding without any inducers) was observed between 125I-vWF and immobilized M239V but not between 125I-vWF and immobilized wild-type (WT) GPIb alpha. The addition of low concentrations of ristocetin (0.2 mg/mL) induced specific 125I-vWF binding to immobilized M239V, but not to WT GPIb alpha. At high concentrations of ristocetin (1.2 mg/mL), both WT GPIb alpha and M239V specifically bound to 125I-vWF. Thus, M239V reproduced the unique functional abnormality of the GPIb/IX complex in platelet-type vWD. Moreover, the purified soluble M239V inhibited platelet aggregation induced by low concentration of ristocetin (0.3 mg/mL) in platelet-rich plasma from a patient having Met239 to Val mutation, whereas purified WT did not. These results provide direct evidences that the reported point mutation is the responsible molecular basis of this disorder.

Analysis of Variance↗
PubMed1997

High shear stress attenuates agonist-induced, glycoprotein IIb/IIIa-mediated platelet aggregation when von Willebrand factor binding to glycoprotein Ib/IX is blocked.

High shear stress facilitates von Willebrand factor (vWF) binding to platelet glycoprotein (GP) Ib/IX, causing activation of GPIIb/IIIa to induce platelet aggregation. Here we report that activated GPIIb/IIIa, even occupied by ligands, is not sufficient to mediate platelet aggregation under high shear stress conditions when vWF binding to GPIb/IX is blocked. Platelet rich plasma or washed platelet suspension supplemented with purified human fibrinogen at a concentration of 2 mg/mL were treated with an anti-vWF monoclonal antibody NMC-4 which blocks the binding of vWF to GPIb/IX. After addition of 10 mumol/L ADP, aggregation was continuously monitored under various shear stress conditions (0-108 dyne/cm2) using a cone-plate type aggregometer previously described (Ikeda Y et al J Clin Invest 1991; 87:1234). The extent of maximal aggregation of agonist-stimulated platelets in the presence of NMC-4 correlated inversely with the level of shear stress applied, with the virtual absence of aggregation at 108 dyne/cm2. Once aggregated by 10 mumol/L ADP under low shear stress (12 dyne/cm2), platelets could be disaggregated, in part, by the application of high shear stress (108 dyne/cm2), and reaggregated when shear stress was returned to 12 dyne/cm2. Flow cytometric analysis revealed that platelets stimulated with 10 mumol/L ADP at 108 dyne/cm2 bound fluorescein isothiocyanate (FITC)-labeled fibrinogen, although aggregation was absent in this experimental condition. These results demonstrate the dual effect of shear stress on platelet functions; a pro-aggregating activity that induces vWF-GPIb/IX interaction leading to platelet activation, and an anti-aggregating force to prevent the growth of platelet thrombi. It is suggested that the efficacy of vWF blockade is greater under high shear than low shear stress conditions, and that a selective inhibition of platelet functions can be possible.

Adenosine Diphosphate↗
PubMed1996

Establishment and characterization of transgenic mice expressing human platelet glycoprotein Ib alpha.

The platelet glycoprotein (GP) Ib/IX/V is a hetero-oligomeric receptor complex for von Willebrand factor (vWF) and mediates platelet adhesion and aggregation under high shear stress conditions. It is composed of alpha and beta chain of GP Ib, GP IX, AND and GP V. To establish transgenic mice carrying human GP Ib alpha, we injected into mouse zygotes a 6 kb DNA fragment containing human GP Ib alpha gene that included entire coding sequence and putative promoter region. One hundred and thirteen offsprings were screened, and only one was found to express human GP Ib alpha protein and has passed the human GP Ib alpha gene as well as the expression of the gene to next generation. The expression of human GP Ib alpha in transgenic mice was limited to platelets and megakaryocytes. Glycocalicin, a proteolytic fragment of human GP Ib alpha found in normal human plasma, was not detected in transgenic mouse plasma. Human vWF in the presence of ristocetin supported agglutination of transgenic mouse platelets, but not of control mouse platelets.

Animals↗
PubMed1996

Analysis of roles of natural killer cells in defense against Plasmodium chabaudi in mice.

Mice that have recovered from a primary infection with Plasmodium chabaudi have been shown to resist a secondary infection. In the present study the authors investigated how natural killer (NK) cells were involved in this resistance. Spleen cells from P. chabaudiprimed C57BL/6 mice could transfer protection against P. chabaudi infection into naive syngeneic mice, but spleen cells from unprimed mice could not. T-enriched cells purified from primed spleen cells could also transfer such protection. Transfer of NK cells from primed spleen cells failed to protect against challenge infection. However, depletion of NK cells in host mice by injection of an anti-NK1.1 monoclonal antibody resulted in higher mortality relative to controls. The possible protective roles of NK cells in P. chabaudi infection are discussed.

Animals↗
PubMed1993

Neurite promoting activity of collagens on embryonic neurons: decreased effect at the postnatal stage.

We studied the in vitro neurite outgrowth activity of fibronectin, laminin, heparan sulfate proteoglycan, type I collagen, type IV collagen, and type VIII collagen in cholinergic neuronal cell lines and primary cultured neurons. All these substances had high neurite promoting activity on primary cultured neurons from embryonic mouse brain. However, collagens had no such an effect on primary cultured neurons from postnatal brain. When neuronal cell lines were used, collagens and other extracellular matrix substances were equally and highly effective on cells originated from embryonic brain, but collagens were less effective on cells from postnatal brain. These findings suggest that postnatal neurons lose the neuritic responsiveness to collagens earlier than that of other ECM.

Animals↗
PubMed1990

Beta-protein immunoreactivity in brains of patients with neuronal ceroid lipofuscinosis: ultrastructural and biochemical demonstration.

The storage pigment in neuronal ceroid lipofuscinoses (NCL) has a close similarity to age pigment lipofuscin. We studied immunoreactivity of isolated neuronal pigments from the juvenile form of NCL and aging control, using monoclonal antibodies (mAbs) against amyloid beta-protein. Ultrastructural localization of the immunoreactivity demonstrated that in NCL the epitopes are distributed mainly in curvilinear multilamellar arrays of the storage pigments and less in fingerprint profiles, while in aging control they are more homogeneously distributed on age pigment lipofuscin. The different distribution of the epitopes may reflect some catabolic as well as morphologic differences in lysosomes. A unique 31-kDa polypeptide detected on Western blots in NCL possibly derives from the same precursor, amyloid beta-protein precursor (ABPP). ABPP processing may be aberrant in NCL brains, and this can be detected as a 31-kDa polypeptide reactive with the mAbs.

Adolescent↗
PubMed1990

Topographic heterogeneity of amyloid B-protein epitopes in brains with various forms of neuronal ceroid lipofuscinoses suggesting defective processing of amyloid precursor protein.

To verify our hypothesis of defective protease inhibitor domains that are encoded by abnormal processing of amyloid precursor protein (APP) in brains of patients with neuronal ceroid lipofuscinoses (NCL), immunohistochemical and cytochemical studies were performed with monoclonal antibodies (mAbs) directed against various domains of APP. For the studies, 22 autopsy brains were used: 12 with different forms of NCL, and 10 control brains. The staining procedure for the avidin-biotin complex (ABC) technique and the postembedding gold-labelled procedure for electron microscopy (EM) were employed. Of all mAbs used for the study, only mAbs generated against amyloid B-protein bound to neural tissue were affected with NCL. The strongest immunostaining of neurons and of some reactive glial cells was found in brains with the juvenile form of NCL. Only in the infantile form of the disease were some neurons overloaded with storage material weakly immunoreactive. In brains of patients with the adult form of NCL, immunoreactivity was found in affected neurons and in extracellularly deposited material of senile plaques. The results of EM study showed that the immunoreactivity was restricted to lysosomal cytosomes in neural tissue with any form of NCL selectively localized on the curvilinear and fingerprint proteinaceous component of ceroid lipofuscin. Studies performed on control aging brains and Alzheimer's disease (AD) brains confirmed previous observations of immunoreactivity being found diffusely in the protein component of some neurons containing lipopigment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗