Ultrastructural subtypes of glutamate-immunoreactive terminals on rat trigeminal motoneurones and their relationships with GABA-immunoreactive terminals

Electron-microscopic immunolabelling methods were used to study the relationships between glutamate-immunoreactive and gamma-aminobutyric acid (GABA)-immunoreactive synapses on trigeminal motoneurones labelled by the retrograde transport of horseradish peroxidase. Serial sections were cut through the motor nucleus, alternate sections were incubated with antibodies to glutamate and GABA, and the immunopositive nerve terminal profiles were recognized using a quantitative, post-embedding immunogold method. Boutons exhibiting high levels of glutamate immunoreactivity and GABA-immunoreactive boutons both formed axo-dendritic and axo-somatic synaptic contacts on labelled motoneurones. Boutons strongly immunopositive for glutamate were not immunopositive for GABA, and vice versa. Strongly glutamate immunoreactive boutons received axo-axonic synaptic contacts but did not form such contacts, while GABA-immunoreactive boutons formed axo-axonic synapses but did not receive them. The presynaptic elements at all axo-axonic synapses on to glutamate-immunoreactive boutons sampled were GABA-immunopositive. These data provide ultrastructural evidence in support of the roles of glutamate and GABA as transmitters at synapses on trigeminal motoneurones, and for presynaptic control of transmission at glutamatergic synapses by GABA acting at receptors at axo-axonic synapses. The vast majority (more than 90%) of strongly glutamate immunoreactive boutons contained spherical synaptic vesicles, in contrast to GABA-immunoreactive boutons, which contained pleomorphic vesicles. Most of the glutamate-immunoreactive boutons (67%) formed asymmetrical synaptic active zones, many of which (47% of total) were associated with subsynaptic dense "Taxi" bodies (T-terminals), while a smaller population of boutons (21%) formed symmetrical synapses, and a few (11%) made synapses associated with subsynaptic cisternae (C-terminals). The heterogeneity of active zone ultrastructure of boutons identified as being glutamatergic on the basis of their high levels of immunolabelling is discussed in relation to possible differences in co-transmitters released, origins of the synaptic input or post-synaptic receptor subtypes activated.

Glycine-immunoreactive terminals in the rat trigeminal motor nucleus: light- and electron-microscopic analysis of their relationships with motoneurones and with GABA-immunoreactive terminals

Post-embedding immunolabelling methods were applied to semi-thin and ultrathin resin sections to examine the relationships between glycine- and gamma-aminobutyric acid (GABA)-immunoreactive terminals on trigeminal motoneurones, which were identified by the retrograde transport of horseradish peroxidase injected into the jaw-closer muscles. Serial sections were cut through boutons and alternate sections were incubated with antibodies to glycine and GABA. Light-microscopic analysis of semi-thin sections revealed a similar pattern of glycine and GABA-immunoreactive boutons along the motoneurone soma and proximal dendrites, and of immunoreactive cell bodies in the parvocellular reticular and peritrigeminal areas surrounding the motor nucleus. Immunoreactive synaptic terminals on motoneurones were identified on serial ultrathin sections at electron-microscopic level using a quantitative immunogold method. Three populations of immunolabelled boutons were recognized: boutons immunoreactive for glycine alone (32%), boutons immunoreactive for GABA alone (22%), and boutons showing co-existence of glycine and GABA immunoreactivities (46%). Terminals which were immunoreactive for glycine only contained a higher proportion of flattened synaptic vesicles than those which were immunoreactive for GABA only, which contained predominantly spherical vesicles. Terminals which exhibited both immunoreactivities contained a mixture of vesicle types. All three classes of terminal formed axo-dendritic and axo-somatic contacts onto retrogradely labelled motoneurones. A relatively high proportion (25%) of boutons that were immunoreactive for both transmitters formed synapses on somatic spines. However, only GABA-immunoreactive boutons formed the presynaptic elements at axo-axonic contacts: none of these were found to contain glycine immunoreactivity. These data provide ultrastructural evidence for the role of glycine and GABA as inhibitory neurotransmitters at synapses onto jaw-closer motoneurones, but suggest that presynaptic control of transmission at excitatory (glutamatergic) synapses on motoneurones involves GABAergic, but not glycinergic inhibition.

High-level production of recombinant human lysosomal acid alpha-glucosidase in Chinese hamster ovary cells which targets to heart muscle and corrects glycogen accumulation in fibroblasts from patients with Pompe disease

Infantile Pompe disease is a fatal genetic muscle disorder caused by a deficiency of acid alpha-glucosidase, a glycogen-degrading lysosomal enzyme. We constructed a plasmid containing a 5'-shortened human acid alpha-glucosidase cDNA driven by the cytomegalovirus promoter, as well as the aminoglycoside phosphotransferase and dihydrofolate reductase genes. Following transfection in dihydrofolate reductase-deficient Chinese hamster ovary cells, selection with Geneticin, and amplification with methotrexate, a cell line producing high levels of the alpha-glucosidase was established. In 48 hr, the cells cultured in Iscove's medium with 5 mM butyrate secreted 110-kDa precursor enzyme that accumulated to 91 micrograms.ml-1 in the medium (activity, > 22.6 mumol.hr-1.ml-1). This enzyme has a pH optimum similar to that of the mature form, but a lower Vmax and Km for 4-methylumbelliferyl-alpha-D-glucoside. It is efficiently taken up by fibroblasts from Pompe patients, restoring normal levels of acid alpha-glucosidase and glycogen. The uptake is blocked by mannose 6-phosphate. Following intravenous injection, high enzyme levels are seen in heart and liver. An efficient production system now exists for recombinant human acid alpha-glucosidase targeted to heart and capable of correcting fibroblasts from patients with Pompe disease.

Genetic clinical markers of human neuroblastoma with special reference to N-myc oncogene: amplified or not amplified?--An overview

Neuroblastoma is the most common extracranial tumor in children, and cytogenetically, chromosome 1p deletions, extrachromosomal double minutes, and homogeneously staining regions (HSRs) are commonly observed in cell lines and in tumors in advanced stages. It is found that an HSR represents genomic amplification of N-myc, which plays a key role in determining the aggressiveness of neuroblastoma. However, stage IV neuroblastomas or cell lines which lack N-myc amplification are also progressive, and some of them show evidence of N-myc expression in terms of mRNA and/or N-Myc oncoprotein. It was recently shown that a small proximal locus mapped between 1p35-36.1 and 1p36.23 may function as a suppressor gene of N-myc amplification. In neuroblastoma, a pattern of diploidy is associated with rapid tumor growth and poor survival. Expression of bcl-2 proto-oncogene is strongly associated with unfavorable histology, while expressions of Ha-ras and trk-A proto-oncogenes indicate a favorable prognosis. trk-A proto-oncogene encodes a receptor for nerve growth factor. Genetic characteristics of neuroblastomas found by urinary catecholamine mass screening are also discussed.

Experimental studies on the application of a porcelain-light-cured resin matrix system to the porcelain margin of metal-ceramic crowns

Application of a light-cured porcelain margin is a technique which has been developed recently. In this study, we compared the porcelain margin properties of the porcelain-light-cured resin matrix system and the traditional porcelain-water system, in terms of volumetric shrinkage, density, compressive strength, surface characteristics, internal porosity, separability of the condensed porcelain from the stone die, and the marginal integrity. The experimental resin matrix was composed of BDMA or EGDMA as a base monomer, CQ as a photoinitiator, DEAEMA as a polymerization accelerator, and TEGDMA as a diluent. Compared with the conventional system, the porcelain of the resin matrix system tended to show a larger volumetric shrinkage, a smaller density and a lower compressive strength. The experimental groups containing the diluent and the traditional control group demonstrated smoother surfaces and less internal porosity than those without the diluent. The photoinitiator was thought to play an important role on the separability from the stone die and the marginal integrity; the higher the ratio of the photoinitiator (1.0 wt%), the better the separability and the fit.