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A Y Chiu

Publications and source records attributed to A Y Chiu.

9 recordsLinked to original sources
PubMed1992

Early stages in the development of spinal motor neurons.

In order to identify early events in the differentiation of motor neurons, the expression of several developmentally regulated, neuronal molecules was investigated by immunohistochemistry on consecutive sections of cervical spinal cord. Motor neurons are among the first neurons to be born and to differentiate within the embryonic rat spinal cord. They undergo their terminal mitosis on embryonic days 10 and 11 (E10-11) and acquire detectable levels of the transmitter synthesizing enzyme, choline acetyltransferase, by E11.5. Staining with antibodies to the 68 kD neurofilament protein revealed motor neurons extending processes out the ventral root as early as E10.5. Monoclonal antibodies to two different epitopes on the cell adhesive molecule, NCAM, bound to myotomes on E10.5, and began to recognize ventral horn neurons by E11. Two other markers of developing neurons, the growth-associated protein, GAP-43, and the surface glycoprotein, TAG-1, were clearly detected on young motor neurons by E11.5. Thus, during the 36 hours following the final mitosis of their precursors, motor neurons acquire cytoskeletal, enzymatic, and cell surface components that distinguish them from other developing cells within the spinal cord. Not all of the newly acquired molecules continue to be expressed by motor neurons. Immunoreactivity for TAG-1 was lost by E12.5, followed by a gradual reduction of immunoreactivity for GAP-43 and the highly polysialylated form of NCAM. By E15, only antibodies to choline acetyltransferase (Phelps et al., J. Comp. Neurol. 307:1-10, 1990), and to neurofilaments, selectively stained motor neurons within the embryonic spinal cord. The transient presence of GAP-43, TAG-1, and the embryonic form of NCAM coincides with a period of vigorous axonal growth and declines when motor neurons reach their targets. This report describes the temporal sequence of early stages in the differentiation of the rodent motor neuronal phenotype. Some of these changes may be related to interactions with their synaptic partners.

Animals↗
PubMed1992

Purification and lectin-binding properties of s-laminin, a synaptic isoform of the laminin B1 chain.

The extracellular matrix (ECM) at the vertebrate neuromuscular junction is a repository of functionally important molecules, some of which can regulate the formation of synapses during regeneration. One candidate molecule is s-laminin, a 185-kDa homologue of the laminin B1 chain. Whereas several members of the laminin family are present throughout the ECM ensheathing muscle fibers, immunoreactivity for s-laminin is found selectively at synaptic sites in adult and embryonic rats, and is detectable at a time when synaptogenesis is taking place during development. We have reported previously that a rat schwannoma cell line, D6P2T, produces and releases large amounts of s-laminin in culture. We have now purified s-laminin from medium conditioned by these cells by using a simple three-step procedure. Serum-free, conditioned medium is separated by ion-exchange chromatography on DEAE-Sephacel, followed by size-exclusion chromatography on 500 HR-Sephacryl. Finally, s-laminin is dissociated from other ECM components by agarose gel electrophoresis under reducing conditions and recovered in solution by extracting slices of agarose gel. The purified preparation displays one silver-stained band that is recognized by three monoclonal antibodies known to bind to different epitopes on s-laminin. Lectin-binding studies demonstrate that s-laminin is a glycoprotein and bears many of the carbohydrate moieties present on the B1 and B2 chains of laminin. Thus, the three 185-220-kDa members of the laminin family are related in both their protein and carbohydrate domains.

Animals↗
PubMed1991

Laminin and s-laminin are produced and released by astrocytes, Schwann cells, and schwannomas in culture.

Components of the extracellular matrix (ECM) have been implicated in the regulation of neuronal migration, axonal growth, and synaptogenesis. We have examined cultures of glial cells, Schwann cells, and schwannomas for the expression of two components of the ECM, laminin and s-laminin, using immunohistochemical and Western blot techniques. Laminin is a potent promotor of neurite outgrowth in cultures of both central and peripheral neurons, and is present in all ECMs. In contrast, s-laminin (for synaptic laminin), a recently described homolog of laminin, is highly localized at the neuromuscular synaptic cleft (Sanes and Chiu, Cold Spring Harbor Symp. Quant. Biol. 1983;48:667-678; Chiu and Sanes, Dev. Biol. 1984;103:456-467) and shows selective adhesivity for motor neurons (Hunter et al. Cell 1989;59:905-913). While the distribution of these ECM components have been well documented in situ, the sources of these extracellular molecules are unclear. We report that astrocytes cultured in serum-free medium maintain an organized ECM that only bears laminin immunoreactivity; s-laminin appears to be sequestered intracellularly. However, both molecules are found in the astrocyte conditioned medium. Thus, under these growth conditions, astrocytes produce and release laminin and s-laminin, but only incorporate the former into an ECM. In contrast, neither molecule is present in comparable cultures of oligodendrocytes. Although no established ECM is seen in cultures of Schwann cells or schwannomas, laminin and s-laminin immunoreactivity are present within cells and in the conditioned media. These results indicate that certain populations of non-neuronal support cells and cell lines can produce and release both synaptic and extrasynaptic components of the ECM. The assembly of these different molecules into an organized basal lamina may require the presence of additional factors or interaction with neurons.

Animals↗
PubMed1990

A monoclonal antibody that recognizes somatic motor neurons in the mature rat nervous system.

In order to obtain markers selective for motor neurons, an in vitro immunization was carried out using a crude homogenate of embryonic rat ventral spinal cord. We have generated a monoclonal antibody, MO-1, that binds selectively to the cell bodies of somatic motor neurons in the brain stem and spinal cord of the adult rat nervous system. In a survey of both peripheral and central nervous systems, intense labeling by MO-1 appears exclusive to this class of cholinergic neuron. Immunoreactivity is predominantly intracellular and is detectable within the somata as well as the proximal regions of processes but is absent along fiber tracts and at neuromuscular junctions. This staining pattern indicates that MO-1 does not recognize other molecules known to be present in motor neurons, such as choline acetyltransferase, acetylcholinesterase, agrin, or the calcitonin-gene-related-peptide. In the spinal cord, antibody binding begins to be detectable in motor neurons late in development, during the second postnatal week. Thus, MO-1 appears to recognize a novel cellular component that accumulates in somatic motor neurons during terminal stages of differentiation.

Aging↗
PubMed1989

Combination immunosuppressive therapy after factor VIII infusion for acquired factor VIII inhibitor.

STUDY OBJECTIVE: To evaluate the effectiveness of combined cyclophosphamide, vincristine, and prednisone (CVP) therapy after antigenic stimulation with factor VIII in the eradication of factor VIII inhibitor. DESIGN: Factor VIII activity and inhibitor titer were measured before and after FVIII-CVP therapy and patients with factor VIII inhibitor were followed for at least 2 years. SETTING: The first course of therapy was carried out in the hospital when nonhemophiliac patients were admitted for bleeding. Otherwise, treatment was administered at the outpatient clinic. PATIENTS: From 1975 to 1986 we studied 12 nonhemophiliac and 5 hemophiliac patients with factor VIII inhibitor treated with FVIII-CVP and followed at our clinic. INTERVENTION: Patients were infused with one dose of factor VIII concentrate, 50 to 100 U/kg body weight, followed by cyclophosphamide, 500 mg on day 1 and 200 mg/d on days 2 to 5; vincristine, 2 mg on day 1; and prednisone, 100 mg/d on days 1 to 5. This regimen was repeated every 3 to 4 weeks. RESULTS: Of 12 nonhemophiliac patients, 11 responded after 1 to 3 courses of FVIII-CVP with complete disappearance of the inhibitor without recurrence. Among 5 patients with hemophilia who were given 3 to 8 courses, only 1 patient responded with a transient disappearance of inhibitor. Mild neutropenia and infection occurred in 3 patients and required antibiotic treatment. CONCLUSION: Factor VIII-CVP therapy is highly effective in the eradication of factor VIII inhibitor in nonhemophiliac patients but not in patients with hemophilia.

Adult↗
PubMed1979

Purification and primary structure of the neuropeptide egg-laying hormone of Aplysia californica.

Egg-laying hormone (ELH), a neuropeptide synthesized by the bag cell neurons, induces egg laying and its correlated behavior in Aplysia californica. In the present study, ELH has been purified to homogeneity and its primary structure has been determined. We find this molecule to have 36 amino acid residues with a M(r) of 4385 and a calculated isoelectric point of 9.7. Direct microsequence analysis revealed a single amino acid sequence that is in agreement with the amino acid composition determined after acid hydrolysis of ELH: H-Ile-Ser-Ile-Asn-Gln-Asp-Leu-Lys-Ala-Ile-Thr-Asp-Met-Leu-Leu-Thr-Glu-Gln- Ile-Arg-Glu-Arg-Gln-Arg-Tyr-Leu-Ala-Asp-Leu-Arg-Gln-Arg-Leu-Leu-Glu-Lys-OH. Enzyme data indicate that the COOH-terminal lysine may be modified but its exact nature remains to be determined. There is no similarity between the amino acid sequence of ELH and that of presently known vertebrate neuropeptides. The two-step purification procedure, starting with a homogenate of bag cell clusters, consisted of cation exchange chromatography on SP C25 (Sephadex) followed by gel filtration on Bio-Gel P-6. Our purification results in a 100-fold enrichment of ELH from bag cell homogenates and a 36% recovery of purified radiolabeled marker ELH. Analysis of purified ELH radiolabeled with [(35)S]methionine or [(3)H]leucine on isoelectric focusing gels and on 8 M urea/sodium dodecyl sulfate gels showed only a single peak containing 90% of the radiolabel. Radiolabeled ELH migrated with a pI of 9.0-9.2 and an apparent M(r) of 3500-5700. ELH retained egg-laying bioactivity when eluted from this segment of the gel. We find that 2.5 nmol of pure ELH consistently induces egg laying at 20 degrees C.

Amino Acid Sequence↗
PubMed1975

Mechanism of axonal transport: a proposed role for calcium ions.

In vitro axonal transport of tritiated protein decreased 40 to 60 percent when neuronal cell bodies were incubated in calcium-free medium, but was not affected when only nerve trunks were exposed to calcium-free conditions. In addition, calcium-45 was transported along axons at a rate similar to that of rapidly transported tritiated protein. These data are interpreted to suggest that calcium ions are involved in the initiation of axonal transport and in the coupling of transported proteins to the transport system.

Animals↗