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Biomedical subjects

W L Liu

Publications and source records attributed to W L Liu.

62 records · Page 4Linked to original sources
PubMed1985

(3H) glycine-accumulating neurons of the human retina.

Isolated human retinas were incubated in physiological saline containing micromolar (3H) glycine. The types, distributions, and synaptologies of glycine-accumulating neurons were determined by light and electron microscope autoradiography. Two types of amacrine cells were discriminated on the bases of number of processes descending into the inner plexiform layer, density of label in light-microscope autoradiographs, size, and synaptic features: (1) Gly1 amacrine cells have moderate labeling, several oblique dendrites arising from the soma, and electron lucent synaptic terminals containing large presynaptic specializations, nd (2) Gly2 amacrine cells have dense labeling, a single proximal dendrite, and moderately electron-dense terminals with small presynaptic specializations. Gly1 amacrine cells constitute approximately 15% and Gly2 amacrine cells approximately 38% of all cells in the amacrine cell layer. The laminar distribution of label in the inner plexiform layer was measured by scanning microdensitometry, which provided a format for categorizing types of synaptic contacts. Many features of glycine-accumulating amacrine cell contacts were similar to those of cat AII/Gly2 amacrine cells: a diffuse yet bisublaminar distribution of label, concentration of synaptic output in sublamina a, rod bipolar cell input in sublamina b and gap junctions in mid-inner plexiform layer involving labeled cells. The evidence seems to indicate that human Gly2 amacrine cells and cat AII/Gly2 amacrine cells are homologous cell types. finally, some cone bipolar cells were labeled.

Autoradiography↗
PubMedDate not supplied

Mast cell heterogeneity in man: unique functional properties of skin mast cells in response to a range of polycationic stimuli.

Human mast cell heterogeneity was assessed by histochemical and detailed functional criteria using mast cells isolated from foreskin, uterine myometrium and lung parenchyma. The skin mast cells were histochemically distinct from their counterparts in the other two tissues by being predominantly insensitive to blockage of dye-binding following formalin fixation (ca. 80%). Functionally, a wide range of structurally diverse polycationic compounds induced selective histamine release from the skin mast cells (ca. 10% at top concentrations) although these cells were less responsive to immunological ligands and calcium ionophores when compared with the uterine and lung cells. The basic compounds, polyarginine and histone, proved to be more generalised histamine liberators as compared with their structural analogues, polylysine and protamine sulphate, probably by virtue of their high content of arginine residues and hydrophobic nature (histone). Studies with the anaphylatoxin, C3a, and its analogues 21R and C3ades Arg on skin mast cells emphasized the importance of basic amino acids for histamine-liberating peptides. Skin mast cells also proved more susceptible than their uterine counterparts to lysis by the detergents, Triton X-100 and Tween 20, suggesting that fundamental differences in membrane structure and/or fluidity might account for functional heterogeneity within the human mast cell population.

Amino Acids↗
PubMedDate not supplied

Immunocytochemical localization of excitatory and inhibitory neurotransmitters in the zebrafish retina.

The patterns of glutamate, gamma-aminobutyric acid (GABA), and glycine distribution in the zebrafish retina were determined using immunocytochemical localization of antisera at the light-microscope level. The observed GABA immunoreactivity (GABA-IR) patterns were further characterized using antibodies to both isoforms of glutamic acid decarboxylase (GAD65 and GAD67), the synthetic enzyme for GABA. Glutamate-IR was observed in all retinal layers with photoreceptors, bipolar cells, and ganglion cells prominently labeled. Bipolar cells displayed the most intense glutamate-IR and bipolar cell axon terminals were clearly identified as puncta arranged in layers throughout the inner plexiform layer (IPL). These findings suggest the presence of multiple subtypes of presumed OFF- and ON-bipolar cells, including some ON-bipolar cells characterized by a single, large (9 microm X 6 microm) axon terminal. GABA-, GAD-, and glycine-IR were most intense in the inner retina. In general, the observed labeling patterns for GABA, GAD65, and GAD67 were similar. GABA- and GAD-IR were observed in a population of amacrine cells, a few cells in the ganglion cell layer, throughout the IPL, and in horizontal cells. In the IPL, both GABA- and GAD-IR structures were organized into two broad bands. Glycine-IR was observed in amacrine cells, interplexiform cells, and in both plexiform layers. Glycine-positive terminals were identified throughout the IPL, with a prominent band in sublamina 3 corresponding to an immunonegative region observed in sections stained for GAD and GABA. Our results show the distribution of neurons in the zebrafish retina that use glutamate, GABA, or glycine as their neurotransmitter. The observed distribution of neurotransmitters in the inner retina is consistent with previous studies of other vertebrates and suggests that the advantages of zebrafish for developmental studies may be exploited for retinal studies.

Animals↗
PubMedDate not supplied

Horizontal cell synapses onto glycine-accumulating interplexiform cells.

Horizontal cells mediate lateral transmission of signals in the outer plexiform layer of the vertebrate retina, and are presumed to contribute to surround properties of photoreceptors and bipolar cells by chemical transmission. The cell bodies and dendrites of fish horizontal cells possess presynaptic specializations characteristic of conventional chemical synapses. Horizontal cell axon terminals have not so far been shown to contain presynaptic specializations nor have the targets of the somatic and dendritic synapses been fully characterized. Using electron microscope autoradiography of retinas labelled by high-affinity 3H-glycine uptake, we show here that goldfish horizontal cells make somatodendritic and axodendritic synapses on glycinergic interplexiform cells (Gly-IPCs) as apposed to dopaminergic interplexiform cells. Thus, horizontal cells have at least three postsynaptic targets: photoreceptors, bipolar cells and Gly-IPCs. Gly-IPCs may constitute a major alternative pathway for horizontal cell signals to reach the inner plexiform layer.

Animals↗
PubMedDate not supplied

Mechanical restraint use among residents of skilled nursing facilities. Prevalence, patterns, and predictors.

The patterns of and risk factors for mechanical restraint use were determined in 12 skilled nursing facilities. Restraints were being used for 59% of residents at the beginning of the study; 31% of remaining residents were restrained during the follow-up year. No facility characteristic was associated with restraint use. The resident characteristics independently associated with initiation of restraints were older age, disorientation, dependence in dressing, greater participation in social activities, and nonuse of antidepressants. Unsteadiness (72%), disruptive behavior such as agitation (41%), and wandering (20%) were the most frequently cited reasons for initiation of restraints.

Aged↗