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Biomedical subjects

S J Lin

Publications and source records attributed to S J Lin.

At least 37 records · Page 2Linked to original sources
PubMed2001

Possible source of tetrodotoxin in the starfish Astropecten scoparius.

The seasonal variations of toxicity and stomach contents in toxic starfish Astropecten scoparius were detected. The average highest specimen toxicity, expressed as tetrodotoxin (TTX), was 16,821 mouse units (MU). The toxin was composed of TTX only, except April's sample containing mainly TTX along with minor paralytic shellfish poisons. The composition in the stomach of less and more toxic starfish was mainly Veremolpa scabra and Umborium suturale, respectively. The toxicities of U. suturale and V. scabra, found in the starfish stomach were 65 and 33 MU, respectively. For those collected from the coastal waters, U. suturale was toxic with average toxicity value of 77 MU/g, but V. scabra was nontoxic. The toxin in the specimens of U. suturale collected from either the digestive gland of starfish or the coastal waters, was TTX and anhydroTTX only. It indicates that the starfish A. scoparius might mainly accumulate high amount of TTX from U. suturale. Furthermore, both small gastropods U. suturale and Natica psuestes are first reported to contain TTX.

Animals↗
PubMed2001

Effect of orthographic and phonological similarity on false recognition of drug names.

Health professionals and patients tend to confuse drugs with similar names, thereby threatening patient safety. One out of four medication errors voluntarily reported in the US involves this type of drug name confusion. Cognitive psychology offers insight into how and why these errors occur. The objective of this investigation was to examine the effect of orthographic (i.e., spelling) and phonological (i.e., sound) similarity on the probability of making recognition memory errors (i.e., false recognitions). Prospective, computer-based, recognition memory experiments on 30 pharmacists and 66 college students were conducted. Participants viewed a study list of drug names and then a test list. The test list was twice as long as the study list and contained distractor names at progressively increasing levels of similarity to the study words. The task was to identify which test names were on study list and which were new. The main outcome measure was probability of making a false recognition error (i.e., of saying a new name was on the study list). Among pharmacists and college students, there was a strong and significant effect of similarity on the probability of making a false recognition error. It was concluded that both orthographic (i.e., spelling) and phonological (i.e., sound) similarity increase the probability that experts and novices will make false recognition errors when trying to remember drug names. Similarity is easily and cheaply measured, and therefore, steps should be taken to monitor and reduce similarity as a means of reducing the likelihood of drug name confusions.

Humans↗
PubMed2001

Stress analysis of the distal locking screws for femoral interlocking nailing.

In femoral locked nailing, the distal locking screws are vulnerable to mechanical failure. Biomechanical studies have shown that the stress on these screws is substantially affected by the fit of the nail in the medullary canal. In this study, a "closed form" mathematical model based on elastic beam-column theory was developed to investigate how the nail-cortical contact, which was simulated by a linear elastic foundation, affected the stress on the distal locking screws. Providing data for the model was a construct of a fractured femur with an intramedullary locked nail loaded by an eccentric vertical load. The stress on the locking screw was analyzed as a function of the distance from the fracture to the locking screw in the distal fragment under two situations: with and without nail-cortical contact in the distal fragment. With nail-cortical contact, the screw stress decreased as the length of nail-cortical contact and the distance between the distal locking screw and the fracture site increased, but this stress contrarily increased when the nail reached the femoral region at which the screw length increased. The screw stress was much higher without nail-cortical contact than with contact and continued to increase as the nail was inserted further. The mathematical model developed here can be a convenient means of rapid stress evaluation and parametric analysis for locked femoral nailing. It may be used to improve the design of interlocking nails and surgical technique.

Biomechanical Phenomena↗
PubMed2001

Phenotypic changes of T-lymphocyte subsets induced by interleukin-12 and interleukin-15 in umbilical cord vs. adult peripheral blood mononuclear cells.

The decreased incidence of graft-vs.-host disease found following umbilical cord blood (CB) transplantation, and the increased susceptibility of newborns to infections, have been attributed, in part, to functional and phenotypic immaturity of neonatal T cells. We investigated the phenotypic changes of CB T cells induced by two immunoregulary cytokines, interleukin (IL)-12 and IL-15, alone or in combination. Adult peripheral blood (APB) mononuclear cells (MNCs) were also tested for comparison. Prior to culture, the percentages of CD3+ CD8+, CD3+ CD25+, and CD3+ CD56+ cells were significantly lower in CB MNCs than in APB MNCs. IL-15, but not IL-12, significantly increased CD3+ CD8+ expression among the CB MNCs after 1 week of culture. Combining IL-12 and IL-15, however, resulted in decreased CB CD3+ CD8+ expression compared with IL-15 alone. The percentage of CD3+ CD25+ cells in CB MNCs spontaneously increased in the absence of cytokines, while that of CD3+ CD56+ cells in CB MNCs could not be enhanced with cytokines. In contrast, the percentages of CD3+ CD25+ and CD3+ CD56+ cells among the APB MNCs could be increased with IL-12, IL-15, and further with IL-12 and IL-15 combined. Thus, different patterns of T-cell subset changes were demonstrated between CB MNCs and APB MNCs in response to IL-12 and/or IL-15. These data may serve as a foundation for using cytokine therapy in newborns and children receiving CB transplants.

Adult↗
PubMed2001

Interleukin-15 enhances CD4(+) CD45RA(+) expression on umbilical cord blood mononuclear cells.

The reduced incidence of graft-vs.-host disease following umbilical cord blood (CB) transplantation may be related to the functional immaturity of newborn T cells expressing mainly the naive CD45RA phenotype. Expansion of CD4(+) CD45RA(+) T cells using cytokines may benefit neonates and infants with human immunodeficiency virus (HIV) infection, as a preferential decline in CD4(+) CD45RA(+) cells has been noted as HIV disease progresses. The aim of the study was to investigate the effect of interleukin (IL)-15, a novel cytokine similar to IL-2 in biological activities, on CD45RA/RO expression and apoptosis in umbilical cord blood (CB) and adult peripheral blood (APB) mononuclear cells (MNCs). Prior to culture, CB MNCs contained a greater number of CD4(+) CD45RA(+) cells and fewer CD4(+) CD45RO(+) cells than did APB MNCs. When incubated with RPMI-1640 containing 10% fetal calf serum for 7 days, the percentage of CD45RA(+) cells within CD4(+) T cells (%CD45RA(+)/CD4(+)) significantly decreased compared to that of fresh CB MNCs. IL-15 exerted a dose-dependent increase of %CD45RA(+)/CD4(+) and a corresponding decrease of %CD45RO(+)/CD4(+) in CB MNCs, an effect not observed with APB MNCs treated with IL-15. The percentages of CD45RA(+) and CD45RO(+) expression within CD8(+) cells, however, were not influenced by IL-15, in either CB or APB MNCs. A greater number of CB MNCs underwent apoptosis than did APB MNCs after 7 days of culture in RPMI-1640 containing 10% fetal calf serum. IL-15 did not inhibit apoptosis but induced proliferation comparable to that achieved in APB MNCs. The ability of IL-15 to preferentially enhance the proliferation of CD4(+) CD45RA(+) cells in CB MNCs suggests a role for immunomodulative therapy in HIV-infected newborns and infants.

Adult↗
PubMed2001

Effect of interleukin (IL)-12 and IL-15 on apoptosis and proliferation of umbilical cord blood mononuclear cells.

Decreased graft-versus-host disease (GVHD) in cord blood (CB) transplantation may be attributed to the immunological immaturity and susceptibility to apoptosis of CB mononuclear cells (MNCs). Cytokines like interleukin (IL)-12 and IL-15 may be used for in vivoadministration or ex vivo expansion of lymphoid cells for more rapid recovery following stem cell transplant, and for providing a graft-versus-leukemia (GVL) effect. We investigated the effects of IL-12 and IL-15, alone or in combination on apoptosis and proliferation of both CB and adult peripheral blood (APB) MNCs, with particular emphasis on CB CD4+, CD8+ and CD56+ lymphocyte subpopulations. The results of our study indicated that: (1) the combination of IL-12+IL-15 resulted in a greater degree of CB and APB apoptosis than either cytokine alone; (2) the level of both spontaneous and cytokine-induced apoptosis by IL-12 and/or IL-15 are greater in CB MNCs than in APB MNCs using TUNEL assays; (3) IL-15 is superior to IL-12 in enhancing the proliferative response in CB and APB MNCs; (4) the combination of IL-12+IL-15, but not either cytokine alone, significantly enhanced apoptosis in CD8+ and CD56+ CB subsets, but not in CD4+ CB subsets; (5) IL-12 or IL-15 alone resulted in increased proliferation in CD4+, CD8+ and CD56+ CB subsets, with IL-12+IL-15 producing the greatest increase of proliferation in all three CB subsets; and (6) IL-15 and/or IL-12 significantly upregulate Fas (CD95) expression on CB T and NK cells. These findings may have therapeutic implications when designing cytokine therapy in patients receiving CB transplant.

Adult↗
PubMed2001

Lack of age-associated LFA-1 up-regulation and impaired ICAM-1 binding in lymphocytes from patients with Down syndrome.

To investigate the role of LFA-1 in the immune defects in DS patients, we analysed lymphocytes from DS patients in LFA-1 expression and LFA-1 mediated cell adhesion. DS patients less than 2 years of age expressed a higher level of LFA-1 when compared with age-matched controls. The difference in LFA-1 expression was much less significant in older DS patients when compared with age-matched children. Although older children (2-15-year-old groups) without DS tend to increase their expression of lymphocyte LFA-1 when compared with younger normal children (0-2 years old), DS patients showed no age-associated increase in lymphocyte LFA-1 expression. Two-colour analysis with CD4/CD8 and LFA-1 in patients and controls showed that proportions of CD4 + lymphocytes were comparable in DS patients and controls, while the proportion of CD8 + lymphocytes was higher in older DS patients. Expression levels of LFA-1 on both CD4 + and CD8 + lymphocytes in younger DS patients were higher when compared with age-matched controls and close to the expression levels in the older DS group. Proportions of memory lymphocytes expressing the CD45RO isoform were higher in both younger and older DS patients when compared with age-matched control groups. Noticeably, the LFA-1 expression levels on CD45RO lymphocytes from younger DS patients were higher than the levels of the controls and declined in the older DS group. We tested lymphocytes (EBV transformed B cells, resting and anti-CD3 stimulated T cells) for cellular adhesion to recombinant ICAM-1 and found that lymphocytes from DS patients were less adhesive, even though their beta2 integrin expression was comparable with that of normal controls. These results suggest that more generalized pathological processes, such as early senescence of the immune system or ineffective lymphocyte activation, and subsequent integrin dysfunction may underlie the immune defects in DS patients.

Adolescent↗
PubMed2001

Bending strength and holding power of tibial locking screws.

The bending strength and holding power of two types of specially designed tibial locking devices, a both-ends-threaded screw and an unthreaded bolt, were studied and compared with four types of commercially available tibial interlocking screws: Synthes, Howmedica, Richards, and Osteo AG. To test bending strength, the devices were inserted into a high molecular weight polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three point bending test. Single loading yielding strength and cyclic loading fatigue life were measured. To test holding power, the devices were inserted into tubes made of polyurethane foam, and their tips were loaded axially to measure pushout strength. The devices were tested with two different densities of foam materials and two different sizes of pilot holes. Insertion torque and stripping torque of the screws were measured first. Pushout tests were performed with each screw inserted with a tightness equal to 60% of its stripping torque. Test results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the screws. The stripping torque predicted the pushout strength more reliably than did the insertion torque. All tested devices showed greater holding power in the foam with the higher density and with the smaller pilot holes. The both-ends-threaded screw had the highest pushout strength and a satisfactory fatigue strength. The unthreaded bolt had the highest fatigue strength but only fair holding power. Clinical studies of the use of these two types of locking devices are worthwhile.

Bone Screws↗
PubMed2001

An effective strategy of using molecular testing to screen mentally retarded individuals for fragile X syndrome.

Fragile X syndrome (FXS) is the most common form of familial mental retardation (MR). It is caused by the expansion of the CGG repeat in the FMR1 gene on the X chromosome. To date, FXS is not treatable, but can be prevented by prenatal genetic examination. Identifying women who carry a full mutation or premutation FMR1 gene is thus very important, and can be done by tracing family members of FXS subjects. However, most of the FXS subjects in Taiwan as well as those in many other countries have not been identified. In this study the authors attempt to develop reliable and inexpensive tests suitable for a large-scale screen of subjects with MR for FXS. Together with their previous study, a total of 311 male and 160 female subjects with MR were screened with nonradioactive Southern blot assay using mixed deoxyribonucleic acid from three subjects of the same sex. From these subjects, nine male subjects and one female FXS subject were diagnosed. All male subjects were also screened with nonradioactive polymerase chain reaction (PCR). These nine male FXS subjects were also detected on the basis of PCR amplification failure. No false-negative results were discerned. The PCR procedure was simplified further by combining it with an analysis of a blood spot on filter paper, which is a much simpler and cheaper method for sample collection and DNA preparation. This method was then used to screen 104 boys with MR. Two of them were suspected, and later confirmed with Southern blot assay, as subjects with FXS. This study suggests that simple PCR combined with blood spot analysis could be a reliable, inexpensive test that is feasible for a large-scale screening of male subjects with MR for FXS. However, Southern blot assay with mixed deoxyribonucleic acid is appropriate for screening female subjects. Based on this strategy, most FXS subjects could be identified easily for further management.

Blotting, Southern↗
PubMed2001

A salvianolic acid B-rich fraction of Salvia miltiorrhiza induces neointimal cell apoptosis in rabbit angioplasty model.

Apoptosis has been suggested to participate in stabilizing cell number in restenosis. Salvia miltiorrhiza (SM) Bunge which is a Chinese herb widely used for the treatment of cardiovascular disorders contains a potent antioxidant, Salvianolic acid B. To determine whether the antioxidant affects vascular apoptosis, the present study examined the frequency of apoptotic cell death in atherosclerotic plaques and in restenotic lesions of cholesterol-fed rabbits. New Zealand White rabbits were treated with a normal diet (normal), a 2% cholesterol diet (HC), a 2% cholesterol diet and endothelial denudation (HC-ED), a 2% cholesterol diet with 5% water-soluble extract of SM (4.8 g/Kg B.W./day) and endothelial denudation (HC-ED-SM), or with a 2% cholesterol diet containing probucol (0.6 g/kg B.W./day) and endothelial denudation (HC-ED-probucol). Apoptosis and associated cell types were examined in serial paraffin sections by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and immunohistochemistry. The expression of p53, an apoptosis-related protein, was also examined. Apoptosis was mainly detected in the neointima of the three groups with endothelial denudation. The percentage of apoptotic cells in SM-treated group (68.5+/-5.9%) was significantly higher than that of normal (0%), HC (1.9+/-1.2%), HC-ED (46.1+/-5.4%), and probucol-treated (32.8+/-3.9%) groups. The SM treatment markedly reduced the thickness of the neointima which was mainly composed of smooth muscle cells with few macrophages. In accordance with the apoptotic cell counts, positive immunoreactivity for p53 was observed in restenotic lesions from HC-ED, SM-treated and probucol-treated groups but not in the intima of the other two groups. These results suggest that the treatment with salvianolic acid B-rich fraction of SM induces apoptosis in neointima which in turn may help prevent the neointimal thickening.

Angioplasty↗
PubMed2000

Y-chromosome microdeletion and its effect on reproductive decisions in taiwanese patients presenting with nonobstructive azoospermia.

OBJECTIVES: To investigate the position, extent, and frequency of Y chromosome microdeletions in Taiwanese patients presenting with nonobstructive azoospermia, and to investigate the effect of microdeletions on reproductive decisions. METHODS: We studied 176 consecutive men with azoospermia in our urology clinic. Polymerase chain reaction tests were performed in 94 patients with nonobstructive azoospermia, and a series of 27 sequence-tagged sites (STSs) mapped within intervals 5 and 6 of Yq11 was selected for analysis. Clinical genetics counseling was provided to couples with microdeletions, and these couples made their own choices about further treatment modalities. RESULTS: Among 94 patients screened for microdeletion, 11 (11.7%) showed microdeletions of one or more STSs. One had a deletion confined to the azoospermia factor b (AZFb) region (encompassing the RBM gene). Two were found to have deletions of both the AZFb and AZFc regions. Eight patients had deletions in the AZFc region (encompassing the DAZ gene). Five had deletions distal to the DAZ gene family. One had multiple, noncontiguous deletions. In 8 patients with testicular histology available, a lack of genotype/phenotype correlation was noted. Of the 11 couples with deletions, 3 thought microdeletion was a serious defect and opted for an artificial insemination of donor or adoption, 5 chose intracytoplasmic sperm injection, and the other 3 decided to undergo treatment with Chinese medicinal herbs. CONCLUSIONS: The most commonly deleted region in the Taiwanese population is AZFc. The genes implicated in Taiwanese spermatogenesis defects are the DAZ and RBM gene families. Twenty-seven percent of couples with microdeletions deferred assisted reproductive technologies because of concern about their underlying genetic defects.

Adoption↗
PubMed2000

Requirement of NAD and SIR2 for life-span extension by calorie restriction in Saccharomyces cerevisiae.

Calorie restriction extends life-span in a wide variety of organisms. Although it has been suggested that calorie restriction may work by reducing the levels of reactive oxygen species produced during respiration, the mechanism by which this regimen slows aging is uncertain. Here, we mimicked calorie restriction in yeast by physiological or genetic means and showed a substantial extension in life-span. This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide). These findings suggest that the increased longevity induced by calorie restriction requires the activation of Sir2p by NAD.

Cyclic AMP-Dependent Protein Kinases↗
PubMed2000

Impaired forearm reactive hyperemia is related to late restenosis after coronary stenting.

To investigate whether systemic endothelial function on forearm resistance vessels is related to angiographic restenosis after coronary stenting, 47 men who underwent elective coronary stenting were divided into 2 groups according to the presence (n = 20) or absence (n = 27) of in-stent restenosis 6 months after the procedure. Another 19 risk factor-matched men with normal coronary angiograms served as the control group. Forearm blood flow was assessed by venous occlusive plethysmography. Basal forearm blood flow was similar between restenosis, nonrestenosis, and control groups (2.63 +/- 0.19, 2.58 +/- 0.14, and 3.23 +/- 0.13 ml/100 ml forearm tissue per minute, respectively). In all 3 groups, forearm blood flow increased significantly during reactive hyperemia (5.75 +/- 0.7, 11. 32 +/- 1.23, and 14.52 +/- 1.36 ml/100 ml forearm tissue per minute, p <0.05, respectively) and remained unchanged after sublingual administration of nitroglycerin. The percentage change of forearm blood flow during reactive hyperemia was significantly lower in the restenosis group (117.3 +/- 18.3%) than in the nonrestenosis group (354.2 +/- 46.5%, p <0.01). This difference was still present after sublingual nitroglycerin (37.6 +/- 21.2% vs 226.4 +/- 40.5%, p <0. 01). In contrast, percentage change of hyperemic forearm blood flow was significantly lower in patients with angina (117.5 +/- 49.5%) than in those without angina (290.1 +/- 37.4%, p <0.05) at follow-up. In all patients, the angiographic loss index was correlated negatively to the percentage change of hyperemic forearm blood flow (r = -0.33, p <0.01) and positively to the percentage change of forearm vascular resistance during reactive hyperemia (r = 0.33, p <0.01). In patients with angiographic restenosis after coronary stenting, forearm reactive hyperemia was more impaired compared with those without angiographic restenosis. Systemic endothelial dysfunction might be either a marker or one of the confounding factors in the development of late restenosis after coronary stenting.

Aged↗
PubMed2000

Metal-metal interactions in weakly coupled mixed-valence E- and Z-diferrocenylethylene complexes.

To study metal-to-metal interactions in mixed-valence states of two weakly coupling ferrocenyl groups assembled in E or Z conformation on an ethylenic double bond, E-1,2-dimethyldiferrocenylethylene (1), Z-1,2-dimethyldi-ferrocenylethylene (2), and 1,2-diferrocenylcyclohexene (3) were synthesized and structurally characterized. Crystals of 1 are triclinic, P1, with a = 7.494(9) A, b = 10.801(3) A, c = 11.971(2) A, alpha = 102.17(2) degrees, beta = 106.12(9) degrees, gamma = 90.42(2) degrees, V = 907.8 A3, and Z = 2. Crystals of 2 are monoclinic, P2(1)/c, with a = 13.601(8) A, b = 11.104(4) A, c = 13.732(1) A, beta = 114.26(7) degrees, V = 1890.8(3) A3, and Z = 4. Crystals of 3 are orthorhombic, P2(1)2(1)2(1), with a = 5.766(2) A, b = 13.090(1) A, c = 26.695(2) A, V = 2014.9(3) A3, and Z = 4. Intervalence transition spectra (IT) and electrochemical data have been determined and compared with those of diferrocenyl-benzene (para, ortho, and meta). The comproportionation constants in nitrobenzene at 25 degrees C were found to be 490 and 813 for 1 and 3, respectively. That of 2 was not measured because of the fact that 2+ isomerizes rapidly in all solvents tested, yielding nearly a racemic mixture of E and Z conformers. This finding helps to clear the paradoxical phenomenon between experimental results of mixed-valence complexes of E- and Z-1,2-bis(1'-ethyl-1-ferrocenyl)-1,2-dimethylethylene and theories. The stability of the mixed-valence species was discussed in terms of resonance delocalization, Coulomb repulsion energy, inductive effect, magnetic interaction, structural factors, and statistical factor. According to our analysis based on the Hush formalism, the contribution due to Coulomb repulsion energy dominates the overall stability of the mixed-valence state in 1+, 2+, and 3+. Stabilization that arises from resonance delocalization is only minor and contributes less than 4% to the overall stability, even in 3+ where linked Cp rings and the ethylenic plane are coplanar. In calculating the resonance contribution, crystallographic Fe-Fe distances of 7.44 A (1) and 6.68 A (3) were used for 1+, and 3+, respectively.

Journal Article↗
PubMed2000

Tuning metal-to-metal charge transfer of mixed-valence complexes containing ferrocenylpyridine and rutheniumammines via solvent donicity and substituent effects.

A homogeneous series of heterobimetallic complexes of [R-Fc(4-py)Ru(NH3)5](PF6)2 (R = H, Et, Br, acetyl; Fc(4-py) = 4-ferrocenylpyridine) have been prepared and characterized. The mixed-valence species generated in situ using ferrocenium hexafluorophosphate as the oxidant show class II behavior, and the oxidized sites are ruthenium centered. deltaE(1/2), E(1/2)(Fe(III)/Fe(II)) - E(1/2)(Ru(III)/Ru(II)), an upper limit for deltaGo that is an energetic difference between the donor and acceptor sites, changes sharply and linearly with Gutmann solvent donor number (DN) and Hammett substituent constants (sigma). The solvent-dependent and substituent-dependent intervalence transfer bands were found to vary almost exclusively with deltaE(1/2). The activation energy for the optical electron transfer versus deltaE(1/2) plot yields a common nuclear reorganization energy (lambda) of 0.74 +/- 0.04 eV for this series. The equation that allows one to incorporate the effect of both solvent donicity and substituents on optical electron transfer is Eop = lambda + deltaGo, where deltaGo = (deltaGo)intrinsic + (deltaGo)solvent donicity + (deltaGo)substituent effect (deltaGo )intinnsic with a numerical value of 0.083 +/- 0.045 eV was obtained from the intercept of the deltaE(1/2) of [H-Fc(4-py)Ru(NH3)5]2+,3+,4+ versus DN plot. (deltaGo)solvent donicity was obtained from the average slopes of the deltaE(1/2) of [R-Fc-(4-py)Ru(NH3)5]2+,3+,4+ versus DN plot, and (deltaGo)substituent effect was obtained from the average slopes of the corresponding deltaE(1/2) versus sigma plot. The empirical equation allows one to finely tune Eop of this series to Eop = 0.82 + 0.019(DN) + 0.44sigma eV at 298 K, and the discrepancy between the calculated and experimental data is less than 6%.

Journal Article↗
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↗