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Biomedical subjects

A Chiba

Publications and source records attributed to A Chiba.

At least 109 records · Page 6Linked to original sources
PubMed1995

Magnesium is essential for formation of an active complex of a hammerhead ribozyme with its substrate: an investigation by NMR spectroscopy.

The effects of magnesium ions on a 32-mer ribozyme (R32) were examined by high-resolution NMR spectroscopy. In solution, R32 (without its substrate) consisted of a GAAA loop, stem II, a non-Watson Crick three-base-paired duplex and a four-base-paired duplex that included a wobble base pair. When an uncleavable substrate RNA (RdC11) was added to R32 without Mg2+ ions, a complex did not form between R32 and RdC11 because the substrate-recognition regions of R32 formed intramolecular base pairs (the recognition arms were closed). By contrast, in the presence of Mg2+ ions, the R32-RdC11 complex was formed. Moreover, titration of mixtures of R32 and RdC11 with Mg2+ ions also induced the ribozyme-substrate interaction. These data suggest that Mg2+ ions are not only important as the true catalysts in the function of ribozyme-type metalloenzymes but they also induce the structural change in the R32 hammerhead ribozyme that is necessary for establishment of the active form of the ribozyme-substrate complex.

Base Sequence↗
PubMed1994

Ontogenetic development of gonadotropin-releasing hormone-like immunoreactive neurons in the brain of the chum salmon, Oncorhynchus keta.

In the chum salmon, gonadotropin-releasing hormone-immunoreactive (GnRH-ir) cells were first detected in the olfactory placode of embryos at 16 days after fertilization, and then appeared sequentially in the olfactory nerve and the distal part of the forebrain by hatching. Four months after hatching, the terminal nerve was differentiated along the olfactory nerve, and GnRH-ir fibers extended to the hypothalamus and hypophysis. GnRH-ir cells occurred later in the preoptic area in about 1-year-old juveniles. These data suggest that GnRH neurons originate in the olfactory placode and then migrate into the brain along the olfactory nerve.

Aging↗
PubMed1994

Unique localization of fucosyl GM1 in rabbit spinal cord and peripheral nerve: immunohistochemical study using monoclonal anti-fucosyl GM1 antibody CRD73-6.

We generated a murine monoclonal antibody (CRD73-6) for ganglioside fucosyl GM1 using a homogenate of rabbit dorsal root ganglia as an immunogen. CRD73-6 immunostained a subset of neurons and the satellite cells surrounding them in rabbit dorsal root ganglia, unmyelinated fibers in the dorsal root, and dorsal horn of the spinal cord. After the tissue sections had been treated with acetone, CRD73-6 also immunostained large neurons and the perineuronal area around them in the ventral horn, and axons and myelin of the small myelinated fibers in the dorsal root. Unique localization of fucosyl GM1 implicates its possible role in cell adhesion and recognition in the nervous system.

Acetone↗
PubMed1994

N-acetylgalactosaminyl GD1a is a target molecule for serum antibody in Guillain-Barré syndrome.

Serum antibodies against such major glycolipids as GM1, GD1b, and LM1 have been reported in patients in the acute phase of Guillain-Barré syndrome (GBS). Because minor unidentified glycolipids also may be targets of antibodies in GBS sera, we assayed serum antibody against a crude ganglioside fraction using thin-layer chromatogram immunostaining. Antibody activity was detected against a band that migrated just below GD1a in 6 of the 50 patients with GBS tested. Antibody titer, as determined by enzyme-linked immunosorbent assay, decreased during the course of the disease. All 6 patients had suffered gastrointestinal infection before the neurological onset of GBS and showed low amplitudes for the compound muscle action potentials and normal or only slightly decreased nerve conduction velocities. Thin-layer chromatogram immunostaining did not show this antibody activity in any of the 16 normal and 119 disease controls. The unidentified glycolipid was isolated by DEAE-Sephadex A-25 column chromatography, sialidase treatment, and Iatrobeads column chromatography. Fast atom bombardment-mass spectra showed it to be N-acetyl-galactosaminyl GD1a.

Adult↗
PubMed1994

Cerebellar ataxia and polyneuropathy in a patient with IgM M-protein specific to the Gal(beta 1-3)GalNAc epitope.

A 79-year-old man with sensory dominant polyneuropathy, cerebellar ataxia, and palatal myoclonus had serum IgM M-protein that specifically bound to GM1, GD1b, and asialo-GM1. IgM with the same specificity was detected in his cerebrospinal fluid. Results of immunohistochemical studies showed specific binding of this monoclonal IgM to the cerebellar granular layer, dentate nucleus, inferior olive, and gray matter of the cerebrum and spinal cord. Monoclonal antibody GGR12, monospecific to GD1b, had an immunostaining distribution similar to that of the patient's IgM M-protein. The binding of M-protein may be associated with the development of cerebellar ataxia and palatal myoclonus in this patient.

Aged↗
PubMed1994

Effects of pinealectomy and melatonin on the timing of the proestrous luteinizing hormone surge in the rat.

Effects of pinealectomy and melatonin replacement on the timing of the preovulatory luteinizing hormone (LH) surge were examined in female rats housed under a light-dark cycle (lights on 06:30-18:30 h). Animals were pinealectomized or sham-operated 21-28 days before bleeding. They were sequentially bled in the afternoon of proestrus through the indwelling cardiac cannula without anesthesia. Proestrous LH surges were observed in all pinealectomized rats, but the onset times of the LH surge in these animals showed a significantly greater variance than those in sham-operated controls. A single melatonin injection at 18:00 or 21:00, shortly before or after the light-dark transition, on the day before proestrus (diestrus II) reduced the variance in the LH surge onset in pinealectomized rats in a dose-dependent manner. In contrast, melatonin injected at 14:00 or 23:00 on diestrus II or at 04:00 on proestrus was ineffective. These results showed that the pineal gland is involved in controlling the timing of the proestrous LH surge in the rat. The pineal signal may be transmitted by melatonin, a major product of the gland.

Animals↗
PubMed1994

Neuropeptide Y-immunoreactive structures in the telencephalon and diencephalon of the white sturgeon, Acipenser transmontanus, with special regard to the hypothalamo-hypophyseal system.

An immunohistochemical study using a streptavidin-biotin method demonstrated the extensive distribution of neuropeptide Y (NPY)-like immunoreactivity in the brain of the white sturgeon, Acipenser transmontanus, with the highest density in the basal telencephalon and diencephalon. Two labeled cell groups were found in the telencephalon, in mediobasal and dorsocaudal locations. Labeled fibers were considerably dense in the ventral area. The epithalamus displayed dense networks of varicose fibers in the ganglion habenulae, but only a few fibers were seen in the organon subcommissurale. In the thalamus, two groups of labeled cells were discerned in the periventricular gray matter: an anteroventral group largely composed of cerebrospinal fluid (CSF)-contacting neurons, and a dorsocaudal group consisting of non-CSF-contacting large neurons. The hypothalamus also contained a number of CSF-contacting neurons in the periventricular areas including the nucleus lobi inferioris, the nucleus lateralis tuberis and the nucleus recessus posterioris. Labeled varicose fibers were closely associated with the hypothalamo-hypophyseal complex, the organon vasculosum hypothalami, and the saccus vasculosus. Immunoreactive cells and fibers were also detected in the dorsal region of the adenohypophysis. These results suggest that NPY or a related molecule is involved in the hypothalamic neuroendocrine mechanisms of this primitive bony fish.

Animals↗
PubMed1994

[Fisher syndrome and anti-GQ1b antibody].

Serum anti-GQ1b IgG antibody is specifically detected in almost all the patients with Fisher syndrome and those with Guillain-Barré syndrome with ophthalmoplegia in the acute phase. An anti-GQ1b mouse monoclonal antibody immunostained the paranodal regions of the extramedullary portion of the human oculomotor, trochlear and abducens nerves. Such immunostaining was not observed in the other cranial and peripheral nerves. Anti-GQ1b IgG antibody may be involved in the pathogenetic mechanism of ophthalmoplegia in Fisher syndrome and Guillain-Barré syndrome by binding to the paranodal regions of the oculomotor, trochlear and abducens nerves. Investigation of serum anti-GQ1b antibody is considered to be a useful diagnostic marker in Fisher syndrome and Guillain-Barré syndrome with ophthalmoplegia.

Autoantibodies↗
PubMed1993

Generation of a monoclonal antibody specific for a new class of minor ganglioside antigens, GQ1b alpha and GT1a alpha: its binding to dorsal and lateral horn of human thoracic cord.

We have established a monoclonal antibody, GGR41, specific for a new class of minor gangliosides, such as GQ1b alpha and GT1a alpha, by immunizing mice with a GQ1b-rich ganglioside fraction extracted from bovine brain. Each of those minor gangliosides has been reported to be one of the cholinergic-specific gangliosides (Chol-1). Careful examination of binding specificity of the antibody by both an enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatograms showed that the antibody recognizes three sialyl residues separately attaching to the gangliotetraosyl backbone structure. Immunohistochemical analysis revealed that GGR41 immunostained lamina I and III of dorsal horn and lateral horn of human thoracic cord but motor neurons were not immunostained. Except for negative staining of motor neurons, this distribution is similar to the distribution pattern of staining as reported in rats and humans using a polyclonal antibody against Chol-1. Thus, the antibody obtained in this study should be a useful reagent to study the function of a unique new class of the minor gangliosides.

Animals↗
PubMed1993

Localization of GM1 and GD1b antigens in the human peripheral nervous system.

Serum antibodies against ganglioside GM1 and/or GD1b are frequently detected in autoimmune neuropathies such as multifocal motor neuropathy, IgM paraproteinemic neuropathy and Guillain-Barré syndrome. Some of them bind to GM1 or GD1b monospecifically but others cross-react with both of the antigens. In order to investigate the respective localizations of GM1 and GD1b antigens in the human peripheral nervous system, an immunohistochemical study was performed using two mouse monoclonal antibodies, each monospecific to GM1 and GD1b. GGR12, monospecific to GD1b, bound to neurons in dorsal root ganglia and sympathetic ganglia, and some parts of the peripheral myelin, mainly the paranodal areas. However GMB16, monospecific to GM1, did not bind to either neurons or myelin. GD1b antigen present on neurons and paranodal myelin in the peripheral nervous system can be a target antigen of serum antibodies in autoimmune neuropathies. Further effort should be made to reveal the localization of GM1 antigen in the human peripheral nervous system.

Antibodies, Monoclonal↗
PubMed1993

Cellular mechanisms governing synaptic development in Drosophila melanogaster.

The neuromuscular connections of Drosophila are ideally suited for studying synaptic function and development. Hypotheses about cell recognition can be tested in a simple array of pre- and postsynaptic elements. Drosophila muscle fibers are multiply innervated by individually identifiable motoneurons. The neurons express several synaptic cotransmitters, including glutamate, proctolin, and octopamine, and are specialized by their synaptic morphology, neurotransmitters, and connectivity. During larval development the initial motoneuron endings grow extensively over the surface of the muscle fibers, and differentiate synaptic boutons of characteristic morphology. While considerable growth occurs postembryonically, the initial wiring of motoneurons to muscle fibers is accomplished during mid-to-late embryogenesis (stages 15-17). Efferent growth cones sample multiple muscle fibers with rapidly moving filopodia. Upon reaching their target muscle fibers, the growth cones rapidly differentiate into synaptic contacts whose morphology prefigures that of the larval junction. Mismatch experiments show that growth cones recognize specific muscle fibers, and can do so when the surrounding musculature is radically altered. However, when denied their normal targets, motoneurons can establish functional synapses on alternate muscle fibers. Blocking synaptic activity with either injected toxins or ion channel mutants does not derange synaptogenesis, but may influence the number of motor ending processes. The molecular mechanisms governing cellular recognition during synaptogenesis remain to be identified. However, several cell surface glycoproteins known to mediate cellular adhesion events in vitro are expressed by the developing synapses. Furthermore, enhancer detector lines have identified genes with expression restricted to small subsets of muscle fibers and/or motoneurons during the period of synaptogenesis. These observations suggest that in Drosophila a mechanism of target chemoaffinity may be involved in the genesis of stereotypic synaptic wiring.

Animals↗
PubMed1993

Neuromuscular development in Drosophila: insights from single neurons and single genes.

How a neuron finds its synaptic target is one of the key questions of developmental neurobiology. It is a problem that must, at least in part, be explained in molecular terms. In light of this, several groups have recently examined the synapses that are made between individual motoneurons and muscle fibers in the embryos and larvae of the fruit fly Drosophila melanogaster. The work combines the traditions of small system neurobiology, which is founded on the analysis of singly identified cells, with those of developmental genetics. An important insight emerging from the work is that many of the familiar features of vertebrate synaptogenesis occur in Drosophila, where a rich array of genetic and molecular methods may be readily applied.

Animals↗
PubMed1993

The expression of rat GAP-43 cDNA in transgenic carp.

To understand more about growth-associated protein-43 (GAP-43), we produced transgenic carp by introduction of a rat GAP-43 cDNA linked to the Rous sarcoma virus-long terminal repeat into fertilized eggs. Of 180 eggs microinjected with exogenous gene, 59 embryos hatched and 4 fish were found to contain the exogenous gene sequences in the genomic DNA. From a mature female transgenic carp, parthenogenetically, 126 progeny were derived and 52 of them survived for more than 90 days. The exogenous gene sequences were detected in 22 F1 progeny, and its messenger RNA was detected in all of 10 transgenic F1 carp examined. In serum-free medium, cultured retinal ganglion cells isolated from transgenic carp elongated their axons, while non-transgenic cells did not elongate axons.

Animals↗
PubMed1993

Serum anti-GQ1b IgG antibody is associated with ophthalmoplegia in Miller Fisher syndrome and Guillain-Barré syndrome: clinical and immunohistochemical studies.

To determine the significance of serum anti-GQ1b IgG antibody, we studied the disease spectrum associated with this antibody and GQ1b epitope in the human nervous system. We examined sera from 19 patients with typical Miller Fisher syndrome (MFS), five patients with acute postinfectious ophthalmoplegia without ataxia (atypical MFS), six patients with Guillain-Barré syndrome (GBS) with ophthalmoplegia (GBS-OP[+]), and 23 patients with GBS without ophthalmoplegia (GBS-OP[-]). We also examined sera from 84 patients with other neurologic or non-neurologic disorders and from 16 normal control subjects. Eighteen of the 19 patients with typical MFS, all the patients with atypical MFS, and five of the six patients with GBS-OP(+) had increased anti-GQ1b IgG activity in ELISA, but none of the patients in the other groups, including GBS-OP(-), had it. All the patients' sera that had anti-GQ1b IgG antibody showed anti-GT1a IgG activity. Results of absorption studies suggested that the same antibody reacted with GQ1b and GT1a. An anti-GQ1b mouse monoclonal antibody immunostained the paranodal regions of the extramedullary portion of the human oculomotor, trochlear, and abducens nerves. Biochemical analysis showed that the human oculomotor nerve contained a larger amount of GQ1b than did the ventral and dorsal roots of the spinal cord. We conclude that serum IgG antibody against GQ1b is very closely associated with acute postinfectious ophthalmoplegia in MFS and GBS.

Ataxia↗
PubMed1993

31P-NMR study on effects of electric shock on swimming leeches, Hirudo medicinalis.

1. We evaluated the effect of electric shock on swimming leeches by measuring changes in high-energy phosphate metabolism using in vivo 31P-NMR. 2. Leeches electrically stimulated during swimming showed anodal galvanotaxis and stopped swimming with stimulation at strong current. 3. Comparison of the concentrations of high-energy phosphate metabolites before and after electric shock using 31P-NMR revealed a marked decrease in beta-ATP and an increase in that of Pi. 4. Electric shock apparently induces excessive muscle fatigue in leeches, resulting in transient paralysis.

Animals↗
PubMed1993

Phosphate metabolism during muscular contraction in starved frogs (Rana catesbeiana).

1. The muscle tension and the state of high-energy phosphate metabolism during contraction of the sartorius muscle in frogs (Rana catesbeiana) starved for 1-5 months was studied by in vivo 31P-NMR spectrometry. 2. Muscle tension began to decrease after 2-month starvation compared with the control group and decreased to about one-third of the control value after a 5-month starvation. 3. Muscle contraction induced by electrical stimulation or the use of anaerobic perfusion fluid did not decrease the concentration of creatine phosphate (PCr) or beta-ATP, and only negligibly changed the PCr/Pi ratio from starvation. 4. These results suggest a decrease in creatine kinase activity in the muscle of starved frogs.

Animals↗
PubMed1993

[Biopsy diagnosis for gastric lymphoma--usefulness and limitation of AgNOR staining].

Sixteen cases of resected gastric lymphoma were classified into 3 groups based on the easiness of the diagnosis; mucosa associated lymphoid tissue lymphoma (MALToma) 4 cases, superficial type lymphoma 5 cases and ulcerative (mass forming) type lymphoma 7 cases. Sixty seven of pre-operative biopsy reports and 44 biopsy specimens were analyzed. Although lymphoma cells retrospectively obtained in 92%, 69% and 88% of biopsy specimens, the definite diagnosis was only made in 7%, 24% and 38% of endoscopic biopsy. Mean AgNOR number per nucleus in resected specimens were as follows; chronic inflammation 1.20 +/- 0.02, MALToma 1.39 +/- 0.23, superficial lymphoma 2.44 +/- 0.50 and ulcerative lymphoma 3.44 +/- 0.55. They correlated well to proliferating cell nuclear antigen positive rates (r = 0.776, p < 0.01). Supposing that lesions showing 2.0 or more AgNOR dots in biopsy specimens are lymphoma, diagnostic rate improves to 69% in superficial lymphoma and to 88% in ulcerative lymphoma. Biopsy specimens from MALToma never showed 2.0 or more AgNOR dots. These results suggest that application of AgNOR to the biopsy diagnosis is useful in superficial and ulcerative lymphoma and has limitation in MALToma of the stomach.

Biopsy↗