Biomedical subjects

H Liao

Publications and source records attributed to H Liao.

At least 37 records · Page 2Linked to original sources

PubMed1999

A failure model for ligaments.

We propose a failure model for ligament which assumes that sequential uncrimping and stretching of collagen fibers is responsible for the mechanical response of ligament. We further assume that the fibers rupture sequentially and in a brittle, strain-limited manner. The model was fit to stress strain curves obtained from medial collateral ligaments of New Zealand White rabbits from two age groups (4 and 7 months). The model indicated that collagen modulus values ranged from 300 to 680 MPa and that fiber failure strains ranged from 6 to 22%. The model provides a convenient means of describing the elastic and failure response of ligament using four structurally based parameters.

Aging↗

PubMed1999

Membrane stabilization in harvested vein graft storage: effects on adhesion molecule expression and nitric oxide synthesis.

OBJECTIVE: Expression of cellular adhesion molecules in human saphenous vein grafts may occur even during harvesting and storage, before the grafts have been implanted as bypass conduits. This may play a role in graft adaptation to arterial flow conditions, which may play an important role in late graft patency. In this study, ketotifen, a mast cell membrane stabilizing agent was studied for its effects on reducing endothelial reactivity during storage of harvested vein graft segments. METHODS: Human saphenous vein grafts, obtained from seven patients and then divided into two equal parts of control and study specimens, were stored in either heparinized blood (Group A) or heparinized blood containing 100 microg/ml ketotifen (Group B) for 1 h at room temperature. Specimens were analyzed by Western blotting to quantify ICAM-1, E-selectin, P-selectin, VCAM-1, and inducible nitric oxide synthase (NOS-2) expression, as well as tissue cGMP levels in response to topical application of an endothelium-independent vasodilator. RESULTS: ICAM-1, E-selectin and P-selectin expression did not differ between the groups. However, VCAM-1 expression was significantly lower in Group B (460 +/- 29 vs. 289 +/- 50, P = 0.01). NOS-2 expression (488 +/- 64 vs. 577 +/- 38, P = 0.02) and tissue cGMP levels (2.2 +/- 0.6 pmol/ml vs. 5.7 +/- 1.7 pmol/ml, P = 0.01) in response to nitroglycerin (24 +/- 10% vs. 11 +/- 5%, P = 0.02) were higher in Group B. CONCLUSIONS: Of all of the adhesion receptors studied, only VCAM-1 expression was reduced by a mast cell membrane-stabilizing agent, perhaps because of activation of the venous endothelium during harvest prior to ketotifen exposure. However, ketotifen also augmented NOS-2 expression, increased tissue cGMP levels in response to nitroglycerin. These actions may improve vascular homeostasis in the venous graft, suggesting the possibility that this strategy may improve long-term graft patency.

Anticoagulants↗

PubMed1999

CD18-mediated neutrophil recruitment contributes to the pathogenesis of reperfused but not nonreperfused stroke.

BACKGROUND AND PURPOSE: Neutrophil (PMN) recruitment mediated by increased expression of intercellular adhesion molecule-1 expression (ICAM-1, CD54) in the cerebral microvasculature contributes to the pathogenesis of tissue injury in stroke. However, studies using blocking antibodies against the common beta2-integrin subunit on the PMN, the counterligand for ICAM-1 (CD18), have demonstrated equivocal efficacy. The current study tested the hypothesis that mice deficient in CD18 would be protected in the setting of reperfused but not nonreperfused stroke. METHODS: Two groups of mice were studied, those whose PMNs could express CD18 (CD18 +/+) and those mice hypomorphic for the CD-18 gene (CD18 -/-). PMNs obtained from CD18 -/- or CD18 +/+ mice were fluorescently labeled and tested for binding to murine brain endothelial monolayers. Using a murine model of focal cerebral ischemia in which an occluding suture placed in the middle cerebral artery (MCA) is removed after 45 minutes (transient ischemia, reperfused stroke) or left in place (permanent ischemia, nonreperfused stroke), cerebral infarct volumes (% ipsilateral hemisphere by TTC staining), cerebral blood flow (CBF, % contralateral hemisphere by laser-Doppler flowmetry), and survival (%) were examined 24 hours after the initial ischemic event. Adoptive transfer studies used 111In-labeled PMNs (from either CD18 +/+ or CD18 -/- mice) to examine the relative accumulation of PMNs in the ischemic region. RESULTS: PMNs obtained from CD18 -/- mice exhibit reduced adhesivity (compared with CD18 +/+ PMNs) for both quiescent and cytokine-activated endothelial monolayers. CD18 -/- mice (n=14) subjected to transient focal cerebral ischemia demonstrated a 53% decrease in infarct volumes versus CD18 +/+ mice (n=26, P<0.05), improved penumbral CBF at 24 hours (1.8-fold, P=0.02), and a 3.7-fold decrease in mortality (P=0.02). However, when CD18 -/- mice (n=12) were subjected to permanent focal cerebral ischemia, no differences were noted in infarct volume, mortality, or CBF versus similarly treated CD18 +/+ mice (n=10). There was a greater accumulation of CD18 +/+ PMNs in the ischemic zone of CD18 +/+ animals than CD18 -/- animals subjected to reperfused stroke (82% increase, P=0.02), although there was no difference between groups when subjected to permanent MCA occlusion. CONCLUSIONS: Deficiency for the CD18 gene confers cerebral protection in a murine model of reperfused stroke, but this benefit does not extend to CD18-deficient animals subjected to permanent MCA occlusion. These data suggest that anti-PMN strategies should be targeted to reperfused stroke and may perhaps be used in conjunction with thrombolytic therapy that establishes reperfusion.

Animals↗

PubMed1999

[A study on the pathogenicity of acute hepatitis G infection].

OBJECTIVE: To study the infection due to hepatitis G virus (HGV) in liver tissues of patients with acute hepatitis and to investigate its pathogenicity. METHODS: HGV NS5 antigen was detected by using immunohistochemical method in the liver biopsy tissues of patients with acute hepatitis but serologically negative to hepatitis virus antigens from A to E. The clinical and pathological data were also analysed. RESULTS: 37 samples were tested, HGV NS5 antigen was detected in 14 (37.8%). 4 of the 14 were positive for HGV NS5 antigen alone (acute hepatitis G group) and 10 other cases were also positive for HBsAg, hepatitis C virus (HCV) NS3 antigen or EB virus antigen (superinfection group). 7 cases were HBsAg positive alone (acute hepatitis B group) and the remaining 16 cases were negative for all the antigens mentioned above (non-A - G hepatitis group). There was no difference among the 4 groups in the detecting rate of Fas antigen, histological activity index (HAI), serum alanine transferase (ALT) and total bilirubin (TBil). CONCLUSION: It is suggested that HGV appears to play some role in the pathogenesis of acute viral hepatitis and the degree of liver injury in acute hepatitis G may be as severe as that of hepatitis caused by other types of viruses.

Acute Disease↗

PubMed1999

[Effect of plasminogen activator inhibitor 1 gene transfer into mesangial cells on Extracellular matrix accumulation].

OBJECTIVE: To observe the influence of plasminogen activator inhibitor 1 (PAI-1) overexpression on extracellular matrix (ECM) accumulation of rat mesangial cells. METHODS: PAI-1/GFP green fluorescent protein fusion gene eukaryotic expression vector pCMX-PAI-1-GFP was constructed and delivered into cultured rat mesangial cells by liposome. PAI-1/GFP expression was observed by fluorescent microscope. FN, LN and Type IV collagen levels were measured by Northern blot analysis and ELISA method. RESULTS: Northern blot analysis, SDS-PAGE analysis and Western blot analysis demonstrated that PAI-1/GFP gene can be transcripted and translated in rat mesangial cells. PAI-1/GFP gene can express a specific protein. The recombinant PAI-1/GFP had significant inhibition activity on urokinase-type plasminogen activator and displayed autonomous fluorescence. The PA activity of cell supernatants decreased markedly in gene transfer group. FN, LN and Type IV collagen levels were higher than in a control group. CONCLUSION: Over-expression of PAI-1 gene leads to mesangial ECM accumulation. The changes of PA/PAI-1 activity in supernatants of cultured rat mesangial cells might be the key factor in ECM accumulation regulation.

Animals↗

PubMed1999

[Experimental study on pharmacological action of fukean tablet on gastrointestinal tract].

The pharmacological effects of FuKean Tablet(FKT) on gastrointestinal tract were studied. The results showed FKT cured the diarrhea induced by rhubarb or senna, prominently reduced the quantity of feces and delayed the time of excreting charcoal powder in the diarrhea induced by rhubarb or senna model NIH mice; FKT inhibited intestinal propelling-movement in diarrhea induced by senna mmodel NIH mice. FKT inhibited the automatic contraction and Ach induced spasmodic contraction of isolated rabbit intestine(decreased the frequency and intensity of contraction). The above results revealed that the pharmacological base of curing the urgent disease in gastrointestinal tract may be curing the diarrhea, inhibiting intestinal propelling-movement and inhibiting the contraction of intestine.

Animals↗

PubMed1999

[Otoacoustic emissions for newborn hearing screening].

OBJECTIVE: To evaluate the validity of transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) in newborn hearing screening and to establish the feasible pass/fail criteria of screening. METHODS: One hundred and eight newborns (216 ears) were screened by TEOAE and DPOAE with Celesta 503 Cochlear Emission Analyzer. The outcome of OAE screening was compared with that of auditory brainstem response(ABR) test. RESULTS: When the criterion of passing TEOAE screening was based on the correlation coefficient of waveforms equal to or greater than 0.60 (r > or = 0.60), the co-positivity and co-negativity to the ABR results were 100% and 93.8% respectively. When the pass criterion of DPOAE was set as that the response levels were greater than the 5th percentile (P5) of the normal newborns in more than five out of eight frequencies, the co-positivity and co-negativity were 100% and 94.3% respectively. The outcome of TEOAE and DPOAE screening between r > or = 0.60 and P5 showed the best correlation, r = 0.6583 (n = 216, P = 0.0001). CONCLUSION: r > or = 0.60 and P5 were the feasible pass criteria of TEOAE and DPOAE for newborn hearing screening respectively. OAE proved to be an objective tool for rapid and effective test in universal newborn hearing screening.

Acoustic Stimulation↗

PubMed1998

A homeobox gene with potential developmental control function in the meristem of the conifer Picea abies.

Many homeobox genes control essential developmental processes in animals and plants. In this report, we describe the first cDNA corresponding to a homeobox gene isolated from a gymnosperm, the HBK1 gene from the conifer Picea abies (L.) Karst (Norway spruce). The sequence shows distinct similarities specifically to the KNOX (knotted-like homeobox) class of homeobox genes known from different angiosperm plants. The deduced amino acid sequence of HBK1 is strikingly similar within the homeodomain (84% identical) to the maize gene Knotted1 (Kn1), which acts to regulate cell differentiation in the shoot meristem. This similarity suggested that the phylogenetic association of HBK1 with the KNOX genes might be coupled to a conservation of gene function. In support of this suggestion, we have found HBK1 to be expressed in the apical meristem in the central population of nondifferentiated stem cells, but not in organ primordia developing at the flanks of the meristem. This pattern of expression is similar to that of Kn1 in the maize meristem. We show further that HBK1, when expressed ectopically in transgenic Arabidopsis plants, causes aberrations in leaf development that are similar to the effects of ectopic expression of angiosperm KNOX genes on Arabidopsis development. Taken together, these data suggest that HBK1 has a role, similar to the KNOX genes in angiosperms, in the control of cellular differentiation in the apical meristem of spruce. The data also indicate that KNOX-gene regulation of vegetative development is an ancient feature of seed plants that was present in the last common ancestor of conifers and angiosperms.

Amino Acid Sequence↗

PubMed1998

Coordinated induction of plasminogen activator inhibitor-1 (PAI-1) and inhibition of plasminogen activator gene expression by hypoxia promotes pulmonary vascular fibrin deposition.

Oxygen deprivation, as occurs during tissue ischemia, tips the natural anticoagulant/procoagulant balance of the endovascular wall to favor activation of coagulation. To investigate the effects of low ambient oxygen tension on the fibrinolytic system, mice were placed in a hypoxic environment with pO2 < 40 Torr. Plasma levels of plasminogen activator inhibitor-1 (PAI-1) antigen, detected by ELISA, increased in a time-dependent fashion after hypoxic exposure (increased as early as 4 h, P < 0.05 vs. normoxic controls), and were accompanied by an increase in plasma PAI-1 activity by 4 h (P < 0.05 vs. normoxic controls). Northern analysis of hypoxic murine lung demonstrated an increase in PAI-1 mRNA compared with normoxic controls; in contrast, transcripts for both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) decreased under hypoxic conditions. Immunocolocalization studies identified macrophages as the predominant source of increased PAI-1 within hypoxic lung. Using a transformed murine macrophage line, striking induction of PAI-1 transcripts occurred under hypoxic conditions, due to both increased de novo transcription as well as increased mRNA stability. Consistent with an important role of the fibrinolytic system in hypoxia-induced fibrin accumulation, PAI-1 +/+ mice exposed to hypoxia exhibited increased pulmonary fibrin deposition based upon a fibrin immunoblot, intravascular fibrin identified by immunostaining, and increased accumulation of 125I-fibrinogen/fibrin in hypoxic tissue. In contrast, mice deficient for the PAI-1 gene (PAI-1 -/-) similarly exposed to hypoxic conditions did not display increased fibrin accumulation compared with normoxic PAI-1 +/+ controls. Furthermore, homozygous null uPA (uPA -/-) and tPA (tPA -/-) mice subjected to oxygen deprivation showed increased fibrin deposition compared with wild-type controls. These studies identify enhanced expression of PAI-1 as an important mechanism suppressing fibrinolysis under conditions of low oxygen tension, a response which may be further amplified by decreased expression of plasminogen activators. Taken together, these data provide insight into an important potential role of macrophages and the fibrinolytic system in ischemia-induced thrombosis.

Animals↗

PubMed1998

Protein phosphatase 1 is targeted to microtubules by the microtubule-associated protein Tau.

Phosphorylation has been implicated in the regulation of microtubule (MT) stability and function by controlling the interactions between MTs and MT-associated proteins. We found previously that protein phosphatase inhibitors selectively break down stable MTs, suggesting that protein phosphatases may be involved in regulating MT stability. To identify the protein phosphatases involved, we examined purified calf brain MTs and found a protein phosphatase activity that copurified with MTs to constant stoichiometry. Western blot analysis and inhibitor profiles demonstrated that the MT-associated phosphatase was a type 1 protein phosphatase (PP1), which we named PP1MT. Recombinant PP1 catalytic subunit (PP1c) did not bind to MTs, whereas PP1MT did bind, suggesting the presence of proteins that target PP1 to MTs. By Sepharose CL-6B chromatography, the phosphatase activity of PP1MT eluted as a large protein complex of approximately 400 kDa. High salt (2 M NaCl) treatment followed by CL-6B chromatography dissociated PP1MT into PP1c and the MT-targeting subunit(s). The MT-targeting subunit was shown to be the MT-associated protein tau by PP1 blot overlays and other assays. Also, recombinant tau reconstituted the binding of PP1c to MTs. These results identify PP1 as the first tau binding protein and suggest that tau is a novel PP1-targeting subunit.

Animals↗

PubMed1998

A reduction-pyrolysis-catalysis synthesis of diamond

Diamond powder was synthesized through a metallic reduction-pyrolysis-catalysis route with the reaction of carbon tetrachloride and sodium at 700 degreesC, in which the sodium was used as reductant and flux. This temperature is much lower than that of traditional methods. The x-ray powder diffraction patterns showed three strong peaks of diamond. The Raman spectrum showed a sharp peak at 1332 inverse centimeters, which is characteristic of diamond. Although the yield was only 2 percent, this method is a simple means of forming diamond.

Journal Article↗

PubMed1998

Cardiac graft intercellular adhesion molecule-1 (ICAM-1) and interleukin-1 expression mediate primary isograft failure and induction of ICAM-1 in organs remote from the site of transplantation.

During the first few hours after heart transplantation, the occurrence of graft failure is unpredictable and devastating. An explosive cascade of inflammatory events within the reperfused graft vasculature is likely to be mediated, at least in part, by the local expression of the leukocyte adhesion receptor intercellular adhesion molecule-1 (ICAM-1, CD54). Furthermore, although proinflammatory cytokines such as interleukin-1 (IL-1) are known to autoinduce their own (and ICAM-1) expression in vitro, there are no data to identify their functional in vivo cross talk in the setting of isograft transplantation. To determine the role of ICAM-1 in primary graft failure, we used an isogeneic vascularized model of heterotopic cardiac transplantation. ICAM-1 mRNA and protein increased in grafts during the early posttransplant period and were predominantly localized in the endothelium. The functional significance of this was established using donor hearts obtained from either ICAM-1-deficient (ICAM-1 -/-) or control (ICAM-1 +/+) mice. ICAM-1 +/+ grafts exhibited increased neutrophil infiltration, reduced left ventricular compliance, and poorer survival than did ICAM-1 -/- grafts. Increased ICAM-1 expression was not limited to ICAM-1 +/+ grafts but also occurred in unmanipulated recipient organs located remote from the site of surgery (but only after transplantation of ICAM-1 +/+, not ICAM-1 -/-, cardiac grafts). This expression of ICAM-1 in remote organs appeared to be triggered by IL-1alpha released from the graft, because (1) in situ hybridization revealed increased IL-1 mRNA within cells of the reperfused graft, including myocytes and endothelial cells; (2) ICAM-1 expression in remote organs coincided with a significant increase in serum levels of IL-1alpha after transplantation of ICAM-1 +/+ grafts; both remote organ ICAM-1 expression and IL-1alpha levels were blunted by implantation of ICAM-1 -/- grafts; and (3) remote organ ICAM-1 expression and neutrophil infiltration and IL-1 levels could be blocked by the administration of an IL-1 receptor antagonist. These data demonstrate an apparent positive-feedback loop in which local ICAM-1 and IL-1 expression leads to a mutual amplification of each other's expression within the reperfused graft, promulgating inflammatory events that are likely to be an important cause of primary cardiac graft failure. Because IL-1 receptor blockade reduces the IL-1-mediated autoinduction of IL-1, reduces the expression of ICAM-1 in both the graft and remote organs, and improves graft survival, it may provide a new and effective strategy to prevent the occurrence of primary cardiac graft failure.

Animals↗

PubMed1998

Mechanism of phosphatidylinositol-specific phospholipase C: a unified view of the mechanism of catalysis.

The mechanism of phosphatidylinositol-specific phospholipase C (PI-PLC) has been suggested to resemble that of ribonuclease A. The goal of this work is to rigorously evaluate the mechanism of PI-PLC from Bacillus thuringiensis by examining the functional and structural roles of His-32 and His-82, along with the two nearby residues Asp-274 and Asp-33 (which form a hydrogen bond with His-32 and His-82, respectively), using site-directed mutagenesis. In all, twelve mutants were constructed, which, except D274E, showed little structural perturbation on the basis of 1D NMR and 2D NOESY analyses. The H32A, H32N, H32Q, H82A, H82N, H82Q, H82D, and D274A mutants showed a 10(4)-10(5)-fold decrease in specific activity toward phosphatidylinositol; the D274N, D33A, and D33N mutants retained 0. 1-1% activity, whereas the D274E mutant retained 13% activity. Steady-state kinetic analysis of mutants using (2R)-1, 2-dipalmitoyloxypropane-3-(thiophospho-1d-myo-inositol) (DPsPI) as a substrate generally agreed well with the specific activity toward phosphatidylinositol. The results suggest a mechanism in which His-32 functions as a general base to abstract the proton from 2-OH and facilitates the attack of the deprotonated 2-oxygen on the phosphorus atom. This general base function is augmented by the carboxylate group of Asp-274 which forms a diad with His-32. The H82A and D33A mutants showed an unusually high activity with substrates featuring low pKa leaving groups, such as DPsPI and p-nitrophenyl inositol phosphate (NPIPs). These results suggest that His-82 functions as the general acid with assistance from Asp-33, facilitating the departure of the leaving group by protonation of the glycerol O3 oxygen. The Bronsted coefficients obtained for the WT and the D33N mutant indicate a high degree of proton transfer to the leaving group and further underscore the "helper" function of Asp-33. The complete mechanism also includes activation of the phosphate group toward nucleophilic attack by a hydrogen bond between Arg-69 and a nonbridging oxygen atom. The overall mechanism can be described as "complex" general acid-general base since three elements are required for efficient catalysis.

Alcohols↗

PubMed1998

Variation of oxide films on titanium induced by osteoblast-like cell culture and the influence of an H2O2 pretreatment.

Variations of titanium oxide films induced by osteoblast-like cells in a rat calvaria culture system and the influence of an H2O2 pretreatment have been investigated by using X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. For abraded titanium, the results revealed that phosphate and calcium ions may incorporate into the surface oxide film during the cell culture, forming a precipitate with a Ca/P ratio near that of hydroxyapatite. Oxidized carbon also was found in the surface layer, most likely precipitated hydroxylcarbonated apatite (HCA). The H2O2 pretreatment of titanium in a phosphate-buffered saline solution results in a 10-fold thickened porous oxide film and large amounts of surface hydroxyl groups as well as a certain amount of phosphate ions inside the oxide film. During the cell culture, the H2O2-treated titanium surface favors the ion incorporation and precipitation of the HCA-like compound, which probably is inlaid into the oxide film. Osteoblast-like cells on the H2O2-treated titanium showed a more active morphology during the initial stage compared with cells on abraded titanium. Moreover, bone-like nodule formation and mineralization appear to be related to the precipitation of the HCA-like compound on the surface. The results are discussed with respect to corrosion resistance, ion incorporation and precipitation of the HCA-like compound on the surface, osseointegration, and bioactivity of titanium implants.

Animals↗

PubMed1998

Crystal structure of calsequestrin from rabbit skeletal muscle sarcoplasmic reticulum.

Calsequestrin, the major Ca2+ storage protein of muscle, coordinately binds and releases 40-50 Ca2+ ions per molecule for each contraction-relaxation cycle by an uncertain mechanism. We have determined the structure of rabbit skeletal muscle calsequestrin. Three very negative thioredoxin-like domains surround a hydrophilic center. Each monomer makes two extensive dimerization contacts, both of which involve the approach of many negative groups. This structure suggests a mechanism by which calsequestrin may achieve high capacity Ca2+ binding. The suggested mechanism involves Ca2+-induced collapse of the three domains and polymerization of calsequestrin monomers arising from three factors: N-terminal arm exchange, helix-helix contacts and Ca2+ cross bridges. This proposed structure-based mechanism accounts for the observed coupling of high capacity Ca2+ binding with protein precipitation.

Animals↗

PubMed1998

Osteonectin RNA and collagen alpha1(I) RNA in the developing rat maxilla.

The sequence of rat osteonectin mRNA was determined. Comparison with osteonectin (ON) mRNA sequences of other vertebrates showed a great similarity, but a stretch of codons deviated with respect to another rat strain, suggesting the possibility of two ON variants in rats. Northern blots exhibited one band of ON mRNA only. The expression of ON and collagen alpha1(I) RNA in tissues of the developing rat maxilla was studied by in situ hybridization. Both ON and collagen alpha1(I) RNA were observed concomitantly in osteoblasts, starting from the onset of bone formation at day 17 post coitum through the oldest age examined, day 20 after birth. A strict co-expression of the two sequences was also observed in odontoblasts as well as in fibroblasts of the periodontal ligament. In ameloblasts, neither ON nor collagen alpha1(I) RNA was detected under stringent hybridization conditions, but lower stringency led to an ON signal. Considering that ON is a secretory protein and the high stability of the ON mRNA, the co-expression of collagen alpha1(I) and ON RNA sequences in matrix-forming cells provided evidence that ON is a substantial component of collagen matrices.

Ameloblasts↗

PubMed1998

Indentation creep behavior of a direct-filling silver alternative to amalgam.

Amalgam creep has been identified as a key parameter associated with marginal breakdown and corrosion. The aim of this study was to evaluate the time-dependent deformation (creep) of a novel silver filling material as an alternative to amalgam. We made the silver specimens by pressing a precipitated powder at room temperature to a density that can be achieved in clinical hand consolidation. The surface of the silver was either polished or burnished. To examine local contact creep and the effect of surface finishing, we used an indentation creep method in which a Vickers indenter was loaded on the specimen surface at a load of 10 N with dwell times of 5 sec to 6x10(4) sec. We used a bonded-interface technique to examine subsurface creep mechanisms. The flexural strength (mean+/-SD; n = 10) was 86+/-20 MPa for amalgam, 180+/-21 MPa for polished silver, and 209+/-19 MPa for burnished silver-values which are significantly different from each other (family confidence coefficient = 0.95; Tukey's multiple-comparison test). Indentation creep manifested as hardness number decreasing with increased dwell time. With dwell time increasing from 5 sec to 6x10(4) sec, the hardness number of amalgam was reduced by approximately 80%; that of the polished silver and the burnished silver was reduced by only 40%. Subsurface creep in amalgam consisted of the shape change of the alloy particles from spherical to elongated shapes, and the separation of matrix grains from each other, possibly due to grain-boundary sliding. Creep of the polished silver occurred by densification reducing porosity and increasing hardness; that of the burnished silver occurred by the displacement of the burnished layer. These results suggest that, due to creep-induced subsurface work-hardening and densification, the consolidated silver exhibits a higher resistance to indentation creep than does amalgam. The hardness number of silver approaches that of amalgam after prolonged indentation loading.

Analysis of Variance↗

PubMed1998

[Indigenous hydroxyapatite as a successful anophthalmic orbital implant].

OBJECTIVE: The aim of the work was to improve the operative result of eye socket reconstruction after enucleation. METHODS: The hydroxyapa tite implant of eyeball shape was buried in the scleral shell, which was stitched to the extraocular muscles at the points of muscle attachment so as to create a rotatable eye seat connector. RESULTS: One hundred and two patients have received eye socket reconstruction of this method with improved results. The prosthetic eyes move freely. Follow-up for 6 to 38 months reveals that the results are stable and satisfactory. CONCLUSION: The indigenous hydroxyapa tite implant is a good biomaterial for socket reconstruction.

Adolescent↗