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Biomedical subjects

Y Y Su

Publications and source records attributed to Y Y Su.

At least 19 recordsLinked to original sources
PubMed2001

Growth inhibition of cultured smooth muscle cells by corrosion products of 316 L stainless steel wire.

The potential cytotoxicity on vascular smooth muscle cells of corrosion products from 316 L stainless steel, one of most popular biomaterials of intravascular stents, has not been highlighted. In this investigation, 316 L stainless steel wires were corroded in Dulbecco's modified eagle's medium with applied constant electrochemical breakdown voltage, and the supernatant and precipitates of corrosion products were prepared as culture media. The effects of different concentrations of corrosion products on the growth of rat aortic smooth muscle cells were conducted with the [3H]-thymidine uptake test and cell cycle sorter. Both the supernatant and precipitates of corrosion products were toxic to the primary culture of smooth muscle cells. The growth inhibition was correlated well with the increased nickel ions in the corrosion products when nickel concentration was above 11.7 ppm. The corrosion products also changed cell morphology and induced cell necrosis. The cell growth inhibition occurred at the G0/G1 to S transition phase. Similar to our recent study of nitinol stent wire, the present investigation also demonstrated the cytotoxicity of corrosion products of 316 L stainless steel stent wire on smooth muscle cells, which might affect the poststenting vascular response.

Animals↗
PubMed2000

Increased corrosion resistance of stent materials by converting current surface film of polycrystalline oxide into amorphous oxide.

Current efforts of new stent technology have been aimed largely at the improvement of intravascular stent biocompatibility. Among the chemical characteristics of metallic stents, surface oxide corrosion properties are paramount. Using our unique technique, the currently marketed 316 L stainless steel and nitinol stent wires covered with polycrystalline oxide were chemically etched and then passivated to form amorphous oxide. Excellent metallic-stent corrosion resistance with an amorphous oxide surface was demonstrated in our previous in vitro study. For in vivo validation, we compared the corrosion behavior of different oxide surfaces on various forms of test wires in the abdominal aorta of mongrel dogs using open-circuit potential and cyclic anodic polarization measurements. After conduction, the retrieved test wires were observed under scanning electron microscope. No passivity breakdown was found for wires covered with amorphous oxide, while wires with polycrystalline oxide showed breakdown at potentials between +0.2 to + 0.6 V. It has been proven that severe pitting or crevice corrosion occurred on the surface of polycrystalline oxide, while the surface of amorphous oxide was free of degradations in our experiment. We have demonstrated that this amorphous oxide coating on metallic material provides better corrosion resistance, not only in vitro but also in vivo, and it is superior not only in strength safety but also in medical device biocompatibility.

Alloys↗
PubMed2000

The cytotoxicity of corrosion products of nitinol stent wire on cultured smooth muscle cells.

Although nitinol is one of most popular materials of intravascular stents, there are still few confirmative biocompatibility data available, especially in vascular smooth muscle cells. In this report, the nitinol wires were corroded in Dulbecco's modified Eagle's medium with constant electrochemical breakdown voltage and the supernatant and precipitates of corrosion products were prepared as culture media. The dose and time effects of different concentrations of corrosion products on the growth and morphology of smooth muscle cells were evaluated with [(3)H]-thymidine uptake ratio and cell cycle sorter. Both the supernatant and precipitate of the corrosive products of nitinol wire were toxic to the primary cultured rat aortic smooth muscle cells. The growth inhibition was correlated well with the increased concentrations of the corrosion products. Although small stimulation was found with released nickel concentration of 0.95 +/- 0.23 ppm, the growth inhibition became significant when the nickel concentration was above 9 ppm. The corrosion products also altered cell morphology, induced cell necrosis, and decreased cell numbers. The cell replication was inhibited at the G0-G1 to S transition phase. This was the first study to demonstrate the cytotoxicity of corrosion products of current nitinol stent wire on smooth muscle cells, which might affect the postimplantation neointimal hyperplasia and the patency rate of cardiovascular stents.

Alloys↗
PubMed2000

Computerized rotational vestibular testing in normal subjects.

BACKGROUND: As an integral part of the contemporary vestibular testing battery, computerized vestibular rotational testing provides physiologic stimuli and quantitative evaluation of the vestibulo-ocular reflex function of the horizontal semicircular canals. Clinically, it is most commonly used in the sinusoidal harmonic acceleration test (SHAT) and velocity step test. Because the results for a given subject may vary when tested using different facilities, the purpose of this study is to establish the normative data for our laboratory. METHODS: Fifty-six normal subjects underwent the SHAT and velocity step test. Three parameters of SHAT--gain, phase and symmetry--were measured and recorded at 0.02, 0.05, 0.09 and 0.10 Hz. In the velocity step test, the three parameters of postrotatory nystagmus-time constant, maximum slow component eye velocity and directional preponderance were measured and recorded. RESULTS: The means +/- standard deviations of gain in the SHAT were 0.47 +/- 0.16 at 0.02 Hz, 0.50 +/- 0.16 at 0.05 Hz, 0.50 +/- 0.16 at 0.09 Hz and 0.53 +/- 0.17 at 0.10 Hz. The coefficient of variation for SHAT gain was 0.32. The time constant means and standard deviations in the velocity step test were 13.44 +/- 3.53 and 13.52 +/- 3.69 for clockwise and counterclockwise rotations, respectively. CONCLUSIONS: We conclude that computerized rotational vestibular testing is precise.

Adolescent↗
PubMed1994

[Analytical study on processing of Scutellaria baicalensis Georyl by HPLC].

This paper deal with the effect of processing on Scutellaria baicalensis. A HPLC method for the determination of baicalin in the drug processed in four different ways has been established. The method is simple, specific and accurate. The recovery is 99.5% and relative standard deviation 0.99%.

Chromatography, High Pressure Liquid↗
PubMed1987

Interaction between enkephalin and dopamine in the avian retina.

Biochemical and pharmacological techniques were utilized to investigate the interaction between the enkephalinergic and dopaminergic systems in the chicken retina. Exogenously applied enkephalin and its analogues were observed to inhibit the release of preloaded dopamine from the retina. This inhibition was concentration-dependent and was suppressed by the opiate antagonist, naloxone. The relationship between enkephalinergic and dopaminergic amacrine cells was studied in retinas which were subjected to 6-hydroxydopamine (6-OHDA) treatments. 6-OHDA degenerated approximately 80-90% of those cells which exhibit high affinity uptake of [3H]dopamine. In 6-OHDA-treated retinas, the capacity of 3H-labelled [D-Ala2]methionine enkephalinamide to bind specifically to opiate receptors was substantially reduced (only 70-75% of the control). Scatchard analyses and ligand displacement studies indicated that this decrease in binding was due to a reduction in the number of opiate receptors. Taken together, these observations strongly indicate that a fraction of the opiate receptors in the chicken retina (25-30%) are closely associated with the population of dopaminergic amacrine cells.

Animals↗
PubMed1986

Enkephalin in the goldfish retina.

Enkephalin-like immunoreactive amacrine cells were visualized using the highly sensitive avidin-biotin method. The somas of these cells were situated in the inner nuclear and ganglion cell layers. Enkephalin-stained processes were observed in layers 1, 3, and 5 of the inner plexiform layer. The biosynthesis of sulfur-containing compounds in the goldfish retina was studied by means of a pulse-chase incubation with 35S-methionine. A 35S-labeled compound, which comigrated with authentic Met5-enkephalin on high-performance liquid chromatography (HPLC), was synthesized and was bound competitively by antibodies to enkephalin and by opiate receptors. This compound was tentatively identified as "Met5-enkephalin." The newly synthesized 35S-Met5-enkephalin was released upon depolarization of the retina with a high K+ concentration. This K+-stimulated release was greatly suppressed by 5 mM Co2+, suggesting that the release was Ca2+ dependent. Using a double-label technique, enkephalin immunoreactivity and gamma-aminobutyric acid (GABA) uptake were colocalized to some amacrine cells, whereas others labeled only for enkephalin or GABA. The possible significance of enkephalin-GABA interactions is also discussed.

Animals↗
PubMed1986

The self-regulating synapse: a functional role for the co-existence of neuroactive substances.

Although the co-localizations of neuroactive substances, such as transmitters and peptides, in identified neurons is now a common histochemical phenomenon, the physiological roles and functional significance of such co-existence are largely unknown. Using the vertebrate retina as a model for the central nervous system, we have examined the relationship between co-existence and co-function. We propose here that the co-localization of neuroactive substances in a synaptic terminal provides the structural configuration to ensure the co-release of two or more predetermined substances into the same synaptic cleft, resulting in the capability of the presynaptic neuron to stringently regulate its own activities and output.

Animals↗
PubMed1985

A monoclonal antibody specific for retinal ganglion cells of mammals.

The development of specific markers for retinal ganglion cells is an area of great interest in retinal research. In this study we report on a monoclonal antibody (AB5) which specifically labels ganglion cells in rabbit, cat and monkey, as well as a variety of other mammalian species. Labelling of ganglion cells was also observed in isolated cell preparations of rabbit retina.

Animals↗
PubMed1985

The signature hypothesis: co-localizations of neuroactive substances as anatomical probes for circuitry analyses.

The recent discoveries that a neuron in the vertebrate retina may contain more than one neuroactive substance (transmitter or neuropeptide) raise the possibility that within each class of neurons, every morphologically and physiologically distinct cell type may be uniquely identified and categorized by the neuroactive substances that it contains. This article examines the evidence to-date for such a conjecture and discusses some of its potential applications and implications.

Animals↗
PubMed1985

Isolation and purification of an endogenous brain ligand for benzodiazepine receptor(s).

An endogenous brain ligand which competes with 3H-flunitrazepine for the binding to benzodiazepine receptor has been isolated and purified to homogeneity. The purification procedures involve the liberation of the ligand into the high speed supernatant followed by ultrafiltration through a PM10 membrane (exclusion limit: 10,000-dalton) column chromatographies on Sephadex G-50, Bio-Rad P2 and finally with three times reversed phase HPLC using C18 columns. The purified endogenous ligand is heat stable, insensitive to DNAase or RNAase and contains about 5-10% amino acid residues. It has an absorption maximum at 220 nm and a minor peak at 313 nm. The exact chemical structure is unknown.

Animals↗
PubMed1985

Opioid pathways in an avian retina. I. The content, biosynthesis, and release of Met5-enkephalin.

By means of an enzyme-linked immunosorbent assay, the concentration of enkephalin-immunoreactive substances was estimated to be about 25 nM in the chicken retina. The biosynthesis of 3H-Met5-enkephalin in this retina was studied by a pulse-chase incubation technique. Isolated retinas were incubated with 0.2 ml of oxygenated Ringer's solution containing 40 microCi of [3H]methionine and trasylol, a peptidase inhibitor, for 30 min at room temperature. The tissue was then rinsed three times in large volumes of Ringer's solution and incubated in the same solution containing unlabeled methionine (100 micrograms/ml) and trasylol for at least another hour. The products synthesized were extracted in acetic acid and assayed by high performance liquid chromatography (HPLC) and immunoassay. A peak of radioactivity that comigrated with Met5-enkephalin on HPLC and cross-reacted with antibodies against enkephalins was detected. The level of 3H-Met5-enkephalin radioactivity increased approximately 10-fold as the chase-incubation period increased from 0 to 120 min, suggesting that, as in other tissues, Met5-enkephalin may be synthesized as part of a larger precursor. The newly synthesized Met5-enkephalin could be released by depolarization of the retina with high extracellular K+ concentration. Furthermore, this K+-stimulated release was greatly suppressed by 5 mM Co2+ in the medium, suggesting that this release is Ca2+-dependent and may be synaptically mediated.

Animals↗
PubMed1985

Opioid pathways in an avian retina. II. Synaptic organization of enkephalin-immunoreactive amacrine cells.

Peroxidase-antiperoxidase immunocytochemistry was utilized to investigate the synaptic organization of enkephalin-like immunoreactive amacrine (Enk-amacrine) cells in the chicken retina. An initial light microscopic analysis revealed that immunostained cell bodies were situated in either the second or third tier of cells from the border of the inner nuclear and inner plexiform layers. The processes of such cells extended into the inner plexiform layer where they ramified as a fine plexus in sublaminae 1 and 3 to 5. At the ultrastructural level, enkephalin-positive somas exhibited a rather dense and evenly distributed peroxidase reaction product throughout their cytoplasm. Furthermore, the nucleus of Enk-amacrine cells was characterized by a round, unindented nuclear membrane. Immunoreactive processes of such cells were found to receive synaptic input from unstained amacrine and bipolar cells. Immunolabeled varicosities formed conventional synaptic contacts onto other vesicle-filled, nonimmunoreactive profiles tentatively suggested to originate from amacrine cells. Bipolar cell terminals did not receive synaptic input from stained varicosities of enkephalin-immunoreactive amacrine cells. Moreover, each of the above synaptic relationships were identified in each of sublaminae 1, and 3 to 5 of the inner plexiform layer. In addition, labeled varicosities of Enk-amacrine cells synapsed upon unstained processes which lacked synaptic vesicles and possibly arise from ganglion cells. Enkephalin-positive processes were also observed to synapse upon the vitreal pole of unstained somas situated in the innermost cell row of the inner nuclear layer. Lastly, large immunoreactive varicosities of Enk-amacrine cells were often characterized by the presence of large dense-core vesicles in addition to typical, small agranular synaptic vesicles.

Animals↗