Biomedical subjects

L Hao

Publications and source records attributed to L Hao.

At least 19 recordsLinked to original sources

PubMed2006

Wettability modification and the subsequent manipulation of protein adsorption on a Ti6Al4V alloy by means of CO2 laser surface treatment.

Improvements in the wettability of the Ti6Al4V alloy following CO(2) laser treatment were identified as being due mainly to the increase in surface roughness, surface oxygen content and surface energy of the material. Untreated and mechanically roughened samples had higher amounts of adsorbed albumin and lower amounts of adsorbed fibronectin than CO(2) laser treated samples. Moreover, as the wettability of the Ti6Al4V alloy increased the adsorbed amounts of fibronectin increased, while the adsorbed amounts of albumin decreased--indicating the controllability of the CO(2) laser process. From this finding it is possible to assert that the wettability of the Ti6Al4V alloy was the prime influence on the observed changes in in vitro protein adsorption. Further, the noted considerable change in the polar component of surface energy, [Formula: see text], on the protein adsorption implied that the protein adsorption on the Ti6Al4V alloy was probably due to the polar and chemical interactions. This work has demonstrated that CO(2) laser radiation could be a suitable means to modify the wettability of the Ti6Al4V alloy and thereby manipulate protein adsorption and consequently render the material more bone cell responsive.

Adhesiveness↗

PubMed2006

The cysteinyl-leukotriene type 1 receptor polymorphism 927T/C is associated with atopy severity but not with asthma.

BACKGROUND: The cysteinyl-leukotriene receptor type 1 (CysLT1) mediates the bronchoconstrictor and pro-inflammatory actions of cysteinyl-leukotrienes (LTC4, LTD4, LTE4) in asthma and is the molecular target of the lukast class of oral anti-leukotriene drugs. We screened the CYSLTR1 gene on chromosome Xq13-21 for coding region polymorphisms, and investigated their associations with allergy and asthma. METHODS: Solid-phase chemical cleavage was used to screen polymorphisms in the coding region of CYSLTR1. A TaqMan allelic discrimination assay was used to genotype a 927T/C SNP and oligonucleotide ligation assays were used to genotype the previously reported 617T/C and 898G/A SNPs of CYSLTR1 in 341 asthmatic families from the UK. Associations with asthma diagnosis, atopic status, serum-specific IgE and severity of allergy and asthma were examined. RESULTS: Family-based association tests showed that the 927 T allele was associated with atopy severity, especially in female subjects, but not with asthma diagnosis or severity, atopic status, bronchial hyper-responsiveness to methacholine or forced expiratory volume in 1 s. CONCLUSION: Mutation screening identified only one polymorphism, 927T/C, in the coding region of the CysLT1 receptor. This polymorphsim is predictive of atopy severity, but not associated with asthma.

Adolescent↗

PubMed2006

Albumin and fibronectin protein adsorption on CO2-laser-modified biograde stainless steel.

The surface properties of a biomaterial play an essential role in protein adsorption, which in turn determines the cellular response to the adsorbed surface. In order to obtain a surface that would yield favourable protein adsorption for successful cellular response, the surface properties of a biograde stainless steel were modified by CO2 laser treatment. An investigation of the CO2-laser-modified surface properties and the effects thereof on the adsorption of human serum albumin (no-cell adhesive) and human plasma fibronectin (cell adhesive) was conducted. It was found that the thickness of the adsorbed fibronectin layer increased with increasing CO2 laser power density, while the thickness of the adsorbed albumin layer decreased with increasing CO2 laser power density. The surface roughness and wettability characteristics contributed to the observed changes in protein adsorption. The wettability characteristics of the biograde stainless steel were found to be the predominant mechanism governing the observed change in protein adsorption. Since the wettability characteristics of the biograde stainless steel can be modified in an efficient and controllable way with the CO2 laser, it is believed that this work presents a demonstrable alternative to the techniques currently available for enhancing the biocompatibility of biograde stainless steels.

Adsorption↗

PubMed2006

Selective laser sintering of hydroxyapatite reinforced polyethylene composites for bioactive implants and tissue scaffold development.

Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using composites of high-density polyethylene (HDPE) reinforced with hydroxyapatite (HA) with the aim of achieving the rapid manufacturing of customized implants. Single-layer and multilayer block specimens made of HA-HDPE composites with 30 and 40 vol % HA were sintered successfully using a CO2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS-fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products but also to produce appropriate features for their application as bioactive implants and tissue scaffolds.

Biocompatible Materials↗

PubMed2006

Population dynamics of anaerobic microbial consortia in thermophilic methanogenic sludge treating paper-containing solid waste.

To maintain a stable thermophilic (55 degrees C) anaerobic digestion treating toilet paper-containing garbage, it is necessary to operate the digester at long hydraulic retention time (HRT) and low organic loading rate (OLR). Critical conditions of the digestion were investigated by operating the digester at HRT 23 days and OLR 3.4 gCOD(Cr)/L/d (R1) or HRT 14 days and OLR 5.6 gCOD/Cr)/L/d (R2) separately. Characteristics of methanogenesis of the two digesters were examined by measuring gas generation volume and volatile fatty acids (VFA) concentration, and the populations of four anaerobic acidogens and three methanogens were analyzed using quantitative PCR method. In digester R1, methanogenic activity was unstable but it could be recovered by stopping feeding as though VFA accumulation occurred. The population of acidogens and two methanogens were maintained at 10(11) - 10(13) copies/L, however, the population of Methanoculleus could not be recovered after methanogenesis recovering. In digester R2, the period of methanogenesis was significantly shorter than that in digester R1. Both the acidogens and the methanogens could not be maintained at a stable concentration. It is suggested that the critical HRT to sustain the population of acidogens in this process should be longer than 14 days and for all kinds of methanogens, HRT should be longer than 23 days.

Acids↗

PubMed2005

Accumulation of advanced glycation end products in women with preeclampsia: possible involvement of placental oxidative and nitrative stress.

Advanced glycation end products (AGEs) are known to cause oxidative damage in various cells by binding with its receptor, RAGE. We measured the serum level of AGEs and examined the AGEs, RAGE, and the other biomarkers of oxidative stress in the placentas from preeclamptic women. Competitive ELISA was carried out to measure the AGEs in serum. Western blotting was performed to analyze AGEs and RAGE in the placenta. Immunohistochemical analyses were performed to examine the localization of AGEs, RAGE, and other biomarkers of oxidative stress in the placenta. The mean level of serum AGEs in preeclamptic women was significantly higher than that in healthy non-pregnant women or healthy pregnant women. Western blotting revealed that the level of AGEs or RAGE in preeclamptic placenta was significantly higher than that in normal placenta. Immunohistochemical analyses showed that levels of nitrotyrosine and nitroguanosine, which are formed by reactive nitrogen species, in preeclamptic placenta were higher than those in normal placenta. Accumulation of 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine indicated enhanced oxidative modifications of lipids and DNA in preeclamptic placenta. The AGE-RAGE system, which is upregulated in preeclampsia, is likely to be involved in the oxidative stress of preeclampsia.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2005

Enhanced human osteoblast cell adhesion and proliferation on 316 LS stainless steel by means of CO2 laser surface treatment.

An effective and novel technique for improving the biocompatibility of a biograde 316 LS stainless steel through the application of CO(2) laser treatment to modify the surface properties of the material is described herein. Different surface properties, such as surface roughness, surface oxygen content, and surface energy for CO(2) laser-treated 316 LS stainless steel, untreated, and mechanically roughened samples were analyzed, and their effects on the wettability characteristics of the material were studied. It was found that modification of the wettability characteristics of the 316 LS stainless steel following CO(2) laser treatment was achieved. This improvement was identified as being mainly due to the change in the polar component of the surface energy. One-day cell adhesion tests showed that cells not only adhered and spread better, but also grew faster on the CO(2) laser-treated sample than on either the untreated or mechanically roughened sample. Further, compared with the untreated sample, MTT cell proliferation analysis revealed that the mechanically roughed surface resulted in a slight enhancement, and CO(2) laser treatment brought about a significant increase in cell proliferation. An increase in the wettability of the 316 LS stainless steel was observed to positively correlate with the cell proliferation.

Biocompatible Materials↗

PubMed2005

Osteoblast cell adhesion on a laser modified zirconia based bioceramic.

Due to their attractive mechanical properties, bioinert zirconia bioceramics are frequently used in the high load-bearing sites such as orthopaedic and dental implants, but they are chemically inert and do not naturally form a direct bond with bone and thus do not provide osseointegration. A CO2 laser was used to modify the surface properties with the aim to achieve osseointegration between bioinert zirconia and bone. The surface characterisation revealed that the surface roughness decreased and solidified microstructure occurred after laser treatment. Higher wettability characteristics generated by the CO2 laser treatment was primarily due to the enhancement of the surface energy, particularly the polar component, determined by microstructural changes. An in vitro test using human fetal osteoblast cells (hFOB) revealed that osteoblast cells adhere better on the laser treated sample than the untreated sample. The change in the wettability characteristics could be the main mechanism governing the osteoblast cell adhesion on the YPSZ.

Biocompatible Materials↗

PubMed2004

On the role of CO2 laser treatment in the human serum albumin and human plasma fibronectin adsorption on zirconia (MGO-PSZ) bioceramic surface.

The nature of the surface strongly influences the composition and recognizability of the adsorbed protein layer, which in turn affects the subsequent cellular interactions. Thus, to understand the biological response to a material, especially in vitro, one must fully understand the nature of the adsorbed protein film that forms on the material. This study investigates the fundamental interactions between the human serum albumin (no-cell adhesive) and human plasma fibronectin and bioinert ceramic following CO(2) laser treatment. The analysis of the albumin and fibronectin adsorption was conducted on the untreated and CO(2) laser-modified magnesia partially stabilized zirconia (MgO-PSZ) bioceramic using an ellipsometry. It was found that the adsorptions of albumin and fibronectin were influenced by the surface properties. The albumin adsorption was affected by the surface roughness and wettability characteristics of the MgO-PSZ and decreased with these properties, while the fibronectin adsorption was increased with wettability characteristics and predominantly governed by this property. Moreover, the considerable change in the polar component of surface energy, gamma(sv) (p), and its effect on protein adsorption implied that the albumin and fibronectin adsorption on the MgO-PSZ surfaces was probably due to the polar and chemical interactions. The value of this work is to provide a novel technique and useful information for manipulating protein adsorption and thereof cellular interactions.

Biocompatible Materials↗

PubMed2004

The adsorption of human serum albumin (HSA) on CO2 laser modified magnesia partially stabilised zirconia (MgO-PSZ).

Magnesia partially stabilised zirconia (MgO-PSZ), a bioinert ceramic, exhibits high mechanical strength, excellent corrosion resistance and good biocompatibility, but it does not naturally form a direct bond with bone resulting in a lack of osteointegration. The surface properties and structure of a biomaterial play an essential role in protein adsorption. As such, changes in the surface properties and structure of biomaterials may in turn alter their bioactivity. So, the fundamental reactions at the interface of biomaterials and tissue should influence their integration and bone-bonding properties. To this end, CO2 laser radiation was used to modify the surface roughness, crystal size, phase and surface energy of the MgO-PSZ. The basic mechanisms active in improving the surface energy were analysed and found to be the phase change and augmented surface area. The adsorption of human serum albumin (HSA), which is a non-cell adhesive protein, was compared on the untreated and CO2 laser modified MgO-PSZ. It was observed that the thickness of the adsorbed HSA decreased as the polar surface energy of the MgO-PSZ increased, indicating that HSA adsorbed more effectively on the hydrophobic MgO-PSZ surface than the hydrophilic surface. The current study provided important information regarding protein-biomaterial interactions and possible mechanisms behind the cell interaction and in vivo behaviour.

Adsorption↗

PubMed2004

The formation of a hydroxyl bond and the effects thereof on bone-like apatite formation on a magnesia partially stabilized zirconia (MgO-PSZ) bioceramic following CO2 laser irradiation.

For the purpose of improving the bioactivity of a magnesia partially stabilized zirconia (MgO-PSZ) and to explore a new technique for inducing OH group and apatite formation, a CO(2) laser has been used to modified the surface properties. The bioactivity of the CO(2) laser modified MgO-PSZ has been investigated in stimulated human fluids (SBF) with ion concentrations almost equal to those in human blood plasma. Some hydroxyl groups were found on the MgO-PSZ following CO(2) laser treatment with selected power densities. The surface melting on the MgO-PSZ induced by CO(2) laser processing provides the Zr(4+) ion and OH(-) ion, in turn, the incorporation of the Zr(4+) ion and the OH(-) ion creates the Zr-OH group on the surface. After 14 days of SBF soaking, the apatites formed on the MgO-PSZ with relatively high amount of hydroxyl groups generated by the CO(2) laser treatment, while no apatite was observed on the untreated with few hydroxyl groups. It exhibits that the Zr-OH groups on the MgO-PSZ surface is the functional groups to facilitate the apatite formation. The increased surface roughness provides more active sites, meantime, increased surface energy benefits to the adsorption and reaction on the surface.

Adsorption↗

PubMed2004

Effects of CO2 laser irradiation on the surface properties of magnesia-partially stabilised zirconia (MgO-PSZ) bioceramic and the subsequent improvements in human osteoblast cell adhesion.

In order to acquire the surface properties favouring osseo-integration at the implant and bone interface, human foetal osteoblast cells (hFOB) were used in an in vitro test to examine changes in cell adhesion on a magnesia-partially stabilised zirconia (MgO-PSZ) bioceramic after CO(2) laser treatment. The surface roughness, microstructure, crystal size and surface energy of untreated and CO(2) laser-treated MgO-PSZ were fully characterised. The in vitro cell evaluation revealed a more favourable cell response on the CO(2) laser-treated MgO-PSZ than on the untreated sample. After 24-h cell incubation, no cell was observed on the MgO-PSZ, whereas a few cells attached on the CO(2) laser-treated MgO-PSZandshowedwellspreadandgood attachment. Moreover, the cell coverage density indicating cell proliferation generally increases with CO(2) laser power densities applied in the experiments. The enhancement of the surface energy of the MgO-PSZ, especially its polar component caused by the CO(2) laser treatment, was found to play a significant role in the initial cell attaching, thus enhancing the cell growth. Moreover, the change in topography induced by the CO(2) laser treatment was identified as one of the factors influencing the hFOB cell response.

Bone Substitutes↗

PubMed2001

Electrocorticographic gamma activity during word production in spoken and sign language.

OBJECTIVE: To investigate the functional-neuroanatomic substrates of word production using signed versus spoken language. METHODS: The authors studied single-word processing with varying input and output modalities in a 38-year-old woman with normal hearing and speech who had become proficient in sign language 8 years before developing intractable epilepsy. Subdural electrocorticography (ECoG) was performed during picture naming and word reading (visual inputs) and word repetition (auditory inputs); these tasks were repeated with speech and with sign language responses. Cortical activation was indexed by event-related power augmentation in the 80- to 100-Hz gamma band, and was compared with general principles of functional anatomy and with subject-specific maps of the same or similar tasks using electrical cortical stimulation (ECS). RESULTS: Speech outputs activated tongue regions of the sensorimotor cortex, and sign outputs activated hand regions. In addition, signed word production activated parietal regions that were not activated by spoken word production. Posterior superior temporal gyrus was activated earliest and to the greatest extent during auditory word repetition, and the basal temporal-occipital cortex was activated similarly during naming and reading, reflecting the different modalities of input processing. With few exceptions, topographic patterns of ECoG gamma were consistent with ECS maps of the same or similar language tasks. CONCLUSIONS: Spoken and signed word production activated many of the same cortical regions, particularly those processing auditory and visual inputs; however, they activated different regions of sensorimotor cortex, and signing activated parietal cortex more than did speech. This study illustrates the utility of electrocorticographic gamma for studying the neuroanatomy and processing dynamics of human language.

Brain Mapping↗

PubMed2001

Induced electrocorticographic gamma activity during auditory perception. Brazier Award-winning article, 2001.

OBJECTIVE: To define the spatial, temporal, and functional characteristics of induced gamma (>30 Hz) activity during functional activation of the left superior temporal gyrus. METHODS: Electrocorticographic (ECoG) recordings were made in 4 clinical subjects during auditory tone and phoneme discrimination tasks, and event-related changes in the ECoG band power were calculated. The topography and temporal sequence of event-related power changes in different gamma bands were contrasted with those of auditory evoked potentials (AEPs), and with those of event-related power changes in the alpha band (8-12 Hz). RESULTS: Auditory stimuli induced a broadband power augmentation that included 40 Hz, as well as higher (80-100 Hz) gamma frequencies. The topography of gamma augmentation was similar, but not identical, to that of the AEP, and was more focused than that of alpha power suppression. Its temporal onset coincided with the N100, but outlasted it. Phonemes produced greater gamma augmentation than tones, while a similar difference was not observed in the N100. CONCLUSIONS: Auditory perception induces ECoG gamma activity not only at 40 Hz, but also in higher gamma frequencies. This activity appears to be an index of cortical activation that reflects task-specific processing in the human auditory cortex more closely than the AEP or alpha power suppression.

Adolescent↗

PubMed2001

Immigrants' welfare use and opportunity for contact with co-ethnics.

In this article we examine the relationship between immigrants' welfare use and their social capital, using the 1990 census. We measure community social capital using contact with co-ethnics and co-ethnics' economic inactivity, and examine the use of AFDC and SSI in two subpopulations: single-mother families and elderly units. Major findings are that the effects of social capital differ between immigrant single-mother families and elderly units; the effects of social capital differ between the young-at-arrival elderly and the old-at-arrival elderly; and the process of AFDC use is similar for immigrants and for natives, whereas the process of SSI use is more complicated for immigrants than for natives.

Age Factors↗

PubMed2001

[Establishment of trans-inactivation system for haloalkane dehalogenase gene in Arabidopsis thaliana].

With haloalkane dehalogenase gene (dhlA) of Xanthobacter autothophicus as a negative selection marker, a novel trans-inactivation system for transgenes in plants was developed. After the Arabidopsis plants were transformed with dhlA, one plant was shown dhlA post-transcriptional silencing by nuclear run-off transcriptional analysis. The Arabidopsis plants containing silencing locus were crossed to those efficiently expressed dhlA, referred as a homologous transgenic locus, and 96% of F1 plants became the homologous dhlA inactivated in trans. When the F1 plants were selfed, and the silencing locus and the homologous locus were separated in some progenies, 42 of the 200 progenies exhibited DhlA activity, and 158 no DhlA activity, and the proportion of the DhlA-expressing plants to the dhlA-silencing ones was 3.76 to 1, which suggested that the silencing locus inactivated in trans the homologous transgenic locus as a Mendelian dominant factor.

Arabidopsis↗

PubMed2000

A gold(I) mononuclear complex and its association into binuclear and cluster compounds by hydrogen bonding or metal ion coordination.

The mononuclear Au(I) complex, Au(Spy)(PPh2py) (1), has been synthesized and characterized structurally. The complex possesses the expected linear coordination geometry with a S-Au-P bond angle of 176.03(6) degrees and no evidence of aurophilic interactions between nearest neighbor Au(I) ions in the solid state. Protonation of the pendant pyridyl groups of 1 leads to the formation of the H-bonded dimer [(Au(SpyH)(PPh2py))2](PF6)2 (2), which has also been structurally characterized. A linear coordination geometry at the Au(I) ions in 2 with a S-Au-P bond angle of 173.7(2) degrees is augmented by evidence of a strong aurophilic interaction with a Au...Au distance of 2.979(1) A. The pendant pyridyl groups of 1 have also been used to bind Cu(I) by reactions with [Cu(NCMe)4](PF6) and Cu(P(p-tolyl)3)2(NO3) leading to the formation of the heterobimetallic complexes [(AuCu(mu-Spy)(mu-PPh2py))2](PF6)2 (3) and [AuCu(P(p-tolyl)3)2(mu-Spy)(mu-PPh2py)](NO3) (4), respectively. A structure determination of 3 reveals a tetranuclear complex composed of two AuCu(mu-Spy)(mu-PPh2py)+ units held together by bridging thiolate ligands. A strong metal-metal interaction is noted between the two different d10 ions with nearest Au-Cu distances averaging 2.6395 A. The S-Au-P bond angles in 3 deviate slightly from linearity due to the Au...Cu interactions, while the coordination geometries at Cu(I) are distorted tetrahedral consisting of the two pyridyl nitrogen atoms, a bridging thiolate sulfur, and the interacting Au(I) ion. While mononuclear complex 1 is only weakly emissive in the solid state and in fluid solution, complexes 2-4 show stronger photoluminescence in the solid state and rigid media at 77 K, and in fluid solution. The emission maxima for 2-4 in ambient temperature fluid solution are 470, 635, and 510 nm, respectively. A tentative assignment of the emitting state as a S(p pi)-->Au LMCT transition is made on the basis of previous studies of Au(I) thiolate phosphine complexes. Shifts of lambda em result from the influence of H bonding or Cu(I) coordination on the filled thiolate orbital energy, or on the effect of metal-metal interaction on the Au(I) acceptor orbital energy. Crystal data for Au(Spy)(PPh2py) (1): triclinic, space group P1 (No. 2), with a = 8.3975(4) A, b = 11.0237(5) A, c = 12.4105(6) A, alpha = 98.6740(10) degrees, beta = 105.3540(10) degrees, gamma = 110.9620(10) degrees, V = 995.33(8) A3, Z = 2, R1 = 3.66% (I > 2 sigma(I)), wR2 = 9.04% (I > 2 sigma(I)) for 2617 unique reflections. Crystal data for [(Au(SpyH)(PPh2py))2](PF6)2 (2): triclinic, space group P1 (No. 2), with a = 14.0284(3) A, b = 14.1093(3) A, c = 15.7027(2) A, alpha = 97.1870(10) degrees, beta = 96.5310(10) degrees, gamma = 117.1420(10) degrees, V = 2692.21(9) A3, Z = 2, R1 = 7.72% (I > 2 sigma(I)), wR2 = 15.34% (I > 2 sigma(I)) for 5596 unique reflections. Crystal data for [(AuCu(mu-Spy)(mu-PPh2py))2](PF6)2 (3): monoclinic, space group P2(1)/c (No. 14), with a = 19.6388(6) A, b = 16.3788(4) A, c = 17.2294(5) A, beta = 91.48 degrees, V = 5540.2(3) A3, Z = 4, R1 = 3.99% (I > 2 sigma(I)), wR2 = 8.38% (I > 2 sigma(I)) for 10,597 unique reflections.

Journal Article↗

PubMed2000

A role for complement in antibody-mediated inflammation: C5-deficient DBA/1 mice are resistant to collagen-induced arthritis.

Collagen-induced arthritis (CIA) represents an animal model of autoimmune polyarthritis with significant similarities to human rheumatoid arthritis that can be induced upon immunization with native type II collagen. As in rheumatoid arthritis, both cellular and humoral immune mechanisms contribute to disease pathogenesis. Genotypic studies have identified at least six genetic loci contributing to arthritis susceptibility, including the class II MHC. We have examined the mechanism of Ab-mediated inflammation in CIA joints, specifically the role of complement activation, by deriving a line of mice from the highly CIA-susceptible DBA/1LacJ strain that are congenic for deficiency of the C5 complement component. We show that such C5-deficient DBA/1LacJ animals mount normal cellular and humoral immune responses to native type II collagen, with the activation of collagen-specific TNF-alpha-producing T cells in the periphery and substantial intra-articular deposition of complement-fixing IgG Abs. Nevertheless, these C5-deficient mice are highly resistant to the induction of CIA. These data provide evidence for an important role of complement in Ab-triggered inflammation and in the pathogenesis of autoimmune arthritis.

Animals↗