Biomedical subjects

S H Li

Publications and source records attributed to S H Li.

At least 19 recordsLinked to original sources

PubMed2006

Cancellous bone from porous Ti6Al4V by multiple coating technique.

A highly porous Ti6Al4V with interconnected porous structure has been developed in our previous study. By using a so-called "Multiple coating" technique, the porous Ti6Al4V can be tailored to resemble cancellous bone in terms of porous structure and mechanical properties. A thin layer of Ti6Al4V slurry was coated on the struts of base porous Ti6Al4V to improve the pore structure. After two additional coating, pore sizes ranged from 100 microm to 700 microm, and the porosity was decreased from approximately 90% to approximately 75%, while the compressive strength was increased from 10.3 +/- 3.3 MPa to 59.4 +/- 20.3 MPa and the Young's modulus increased from 0.8 +/- 0.3 GPa to 1.8 +/- 0.3 GPa. The pore size and porosity are similar to that of cancellous bone, meanwhile the compressive strength is higher than that of cancellous bone, and the Young's modulus is between that of cancellous bone and cortical bone. Porosity, pore size and mechanical properties can be controlled by the parameters in such multiple coating processes. Therefore the porous Ti6Al4V with the characteristics of cancellous bone is expected to be a promising biomaterial for biomedical applications.

Alloys↗

PubMed2005

A novel porous Ti6Al4V: characterization and cell attachment.

For the first time, a highly porous strong Ti6Al4V was produced by using a "polymeric sponge replication" method. A polymeric sponge, impregnated with a Ti6Al4V slurry prepared from Ti6Al4V powders and binders, was subjected to drying and pyrolyzing to remove the polymeric sponge and binders. After sintering at a high temperature and under high vacuum, a porous Ti6Al4V was produced. Optical microscopical observation, environmental scanning electron microscopy observation (with energy-dispersive micro X-ray analysis), mechanical tests, and metallurgical analyses were performed on the obtained porous Ti6Al4V with regard to the porous structure (both macropores and micropores), mechanical properties, chemical composition, phase compositions, and cell attachment behavior. The porous Ti6Al4V made by this method had a three-dimensional trabecular porous structure with interconnected pores mainly ranging from 400 to 700 microm and a total porosity of about 90%. The compressive strength was 10.3 +/- 3.3 MPa and the elastic constant 0.8 +/- 0.3 GPa. MC3T3-E1 cells attached and spread well in the inner surface of pores. Being similar to cancellous bone with regard to both interconnected porous structure and mechanical properties, the resulting porous Ti6Al4V is expected to be a promising biomaterial for biomedical applications.

3T3 Cells↗

PubMed2005

DHEAS and POMS measures identify cocaine dependence treatment outcome.

UNLABELLED: Early attrition is a significant problem in the treatment of cocaine dependence, but it is unclear why some patients succeed in treatment while others relapse or drop out of treatment without a demonstrated relapse. The goal of this study was to determine whether baseline levels of select hormones, including the adrenal hormone and excitatory neurosteroid dehydroepiandrosterone sulfate (DHEAS), would distinguish between treatment outcome groups. Based on the literature, completion of 90 days of treatment was established as a key outcome variable. METHODS: Quantitative urine levels of the cocaine metabolite benzoylecgonine (BE) and other substance of abuse analytes, plasma levels of DHEAS, DHEA, cortisol, and prolactin, and the profile of mood states (POMS) were serially measured in 38 male cocaine-dependent (DSM-IV) patients and in 28 controls of similar gender and age over a six month study. Exclusion criteria for the patients and controls included Axis I mood, anxiety or psychotic disorders. The patients could not manifest substance dependence except to cocaine. The patients and controls received remuneration for urine and blood collection. Blood samples for hormone levels were obtained between 8 and 10 a.m. on days 1, 14 and 21 of a 21-day inpatient treatment program and throughout 6 months of outpatient study visits at 45-day intervals. RESULTS: Attrition from treatment and study appointments occurred predominately at the junction between inpatient and outpatient programs. Forty percent of patients made the transition to outpatient treatment and remained abstinent and in treatment for a median of 103 days (ABST). Forty-two percent of patients dropped out of treatment during the inpatient stay or never returned after completing the inpatient program (DO) and 18% had a documented relapse either during, or within the first week after, the inpatient stay (REL). POMS total scores were elevated at treatment entry for both the ABST and DO groups. Plasma DHEAS levels in the DO patients were decreased compared to controls and increased in the ABST patients. POMS total scores for the REL patients at baseline were at control levels. Baseline cortisol levels were not statistically different between the outcome groups, though they were elevated for all cocaine patient groups. When treatment outcome was collapsed into whether patients completed (ABST) or did not complete 90 days of treatment (90N), ABST plasma DHEAS and cortisol were significantly elevated compared to the 90N patients and controls across the first 3 weeks of cocaine withdrawal. CONCLUSIONS: At treatment entry, each of the three patient outcome groups was identified by levels of circulating DHEAS and distressed mood. In the ABST patients, distressed mood during withdrawal may have been mitigated through antidepressant-like actions of enhanced endogenous DHEAS activity, thus contributing to improved abstinence and treatment retention. Patients, such as the DO group, with high levels of distressed mood at treatment entry and low DHEAS levels may benefit from adjunctive pharmacotherapy that targets DHEAS and POMS measures. Patients, such as the REL group, who lack distressed mood at treatment entry, may require intense application of motivational approaches plus residential treatment.

Adult↗

PubMed2005

Utilization of the metal-cyano complex tetracyanonickelate (II) by Azotobacter vinelandii.

AIMS: The ability of Azotobacter vinelandii, a N(2)-fixing bacterium, to biodegrade tetracyanonickelate (TCN) was evaluated. METHODS AND RESULTS: The amounts of TCN were measured spectrophotometrically. Ammonia was determined colorimetrically by the indophenol method. The produced methane from TCN conversion by A. vinelandii was detected by gas chromatography. Results showed that A. vinelandii was able to biodegrade 1 mmol l(-1) of TCN. Ammonia and methane were detected during the process of TCN degradation. Effects of exogenous nitrogen sources on TCN degradation were addressed in this study. Results revealed that the addition of ammonia (1, 5 and 10 mmol l(-1)) into the reaction mixtures caused decrease of TCN degradation rate during a 24-h incubation period. This inhibition was also observed when nitrite (5 and 10 mmol l(-1)) was added, whereas TCN degradation still proceeded after the addition of nitrate at the same concentrations. Furthermore, the rate of TCN utilization was strikingly enhanced when 0.8% of glucose was added. CONCLUSIONS: Azotobacter vinelandii can degrade 1 mmol l(-1) of TCN into ammonia and methane. However, the inhibitory effects of exogenous ammonia and nitrite on TCN degradation by this bacterium were found in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report defining the capability of A. vinelandii to degrade TCN. This bacterium might have potential value in applied strategies for removing metal-cyano wastes. Furthermore, these findings would be helpful in designing a practical system inoculated with A. vinelandii for the treatment of TCN.

Ammonia↗

PubMed2004

Alteration of the copy number and deletion of mitochondrial DNA in human hepatocellular carcinoma.

Somatic mutations in mitochondrial DNA (mtDNA) have been detected in hepatocellular carcinoma (HCC). However, it remains unclear whether mtDNA copy number and mitochondrial biogenesis are altered in HCC. In this study, we found that mtDNA copy number and the content of mitochondrial respiratory proteins were reduced in HCCs as compared with the corresponding non-tumorous livers. MtDNA copy number was significantly reduced in female HCC but not in male HCC. Expression of the peroxisome proliferator-activated receptor gamma coactivator-1 was significantly repressed in HCCs (P<0.005), while the expression of the mitochondrial single-strand DNA-binding protein was upregulated, indicating that the regulation of mitochondria biogenesis is disturbed in HCC. Moreover, 22% of HCCs carried a somatic mutation in the mtDNA D-loop region. The non-tumorous liver of the HCC patients with a long-term alcohol-drinking history contained reduced mtDNA copy number (P<0.05) and higher level of the 4977 bp-deleted mtDNA (P<0.05) as compared with non-alcohol patients. Our results suggest that reduced mtDNA copy number, impaired mitochondrial biogenesis and somatic mutations in mtDNA are important events during carcinogenesis of HCC, and the differential alterations in mtDNA of male and female HCC may contribute to the differences in the clinical manifestation between female and male HCC patients.

Alcohol Drinking↗

PubMed2004

Genetic testing in spinocerebellar ataxia in Taiwan: expansions of trinucleotide repeats in SCA8 and SCA17 are associated with typical Parkinson's disease.

DNA tests in normal subjects and patients with ataxia and Parkinson's disease (PD) were carried out to assess the frequency of spinocerebellar ataxia (SCA) and to document the distribution of SCA mutations underlying ethnic Chinese in Taiwan. MJD/SCA3 (46%) was the most common autosomal dominant SCA in the Taiwanese cohort, followed by SCA6 (18%) and SCA1 (3%). No expansions of SCA types 2, 10, 12, or dentatorubropallidoluysian atrophy (DRPLA) were detected. The clinical phenotypes of these affected SCA patients were very heterogeneous. All of them showed clinical symptoms of cerebellar ataxia, with or without other associated features. The frequencies of large normal alleles are closely associated with the prevalence of SCA1, SCA2, MJD/SCA3, SCA6, and DRPLA among Taiwanese, Japanese, and Caucasians. Interestingly, abnormal expansions of SCA8 and SCA17 genes were detected in patients with PD. The clinical presentation for these patients is typical of idiopathic PD with the following characteristics: late onset of disease, resting tremor in the limbs, rigidity, bradykinesia, and a good response to levodopa. This study appears to be the first report describing the PD phenotype in association with an expanded allele in the TATA-binding protein gene and suggests that SCA8 may also be a cause of typical PD.

Age of Onset↗

PubMed2002

Luminescence isochron dating: a new approach using different grain sizes.

A new approach to isochron dating is described using different sizes of quartz and K-feldspar grains. The technique can be applied to sites with time-dependent external dose rates. It is assumed that any underestimation of the equivalent dose (De) using K-feldspar is by a factor F, which is independent of grain size (90-350 microm) for a given sample. Calibration of the beta source for different grain sizes is discussed, and then the sample ages are calculated using the differences between quartz and K-feldspar De from grains of similar size. Two aeolian sediment samples from north-eastern China are used to illustrate the application of the new method. It is confirmed that the observed values of De derived using K-feldspar underestimate the expected doses (based on the quartz De) but, nevertheless, these K-feldspar De values correlate linearly with the calculated internal dose rate contribution, supporting the assumption that the underestimation factor F is independent of grain size. The isochron ages are also compared with the results obtained using quartz De and the measured external dose rates.

Alpha Particles↗

PubMed2001

Huntingtin aggregate-associated axonal degeneration is an early pathological event in Huntington's disease mice.

Huntington's disease (HD) is characterized by the selective loss of striatal projection neurons. In early stages of HD, neurodegeneration preferentially occurs in the lateral globus pallidus (LGP) and substantia nigra (SN), two regions in which the axons of striatal neurons terminate. Here we report that in mice expressing full-length mutant huntingtin and modeling early stages of HD, neuropil aggregates form preferentially in the LGP and SN. The progressive formation of these neuropil aggregates follows intranuclear accumulation of mutant huntingtin and becomes prominent from 11 to 27 months after birth. Neuropil aggregates, but no intranuclear inclusions, were observed in the LGP and SN, suggesting that huntingtin aggregates are formed in the axons of striatal projection neurons. In the LGP and SN, we observed degenerated axons in which huntingtin aggregates were associated with dark, swollen organelles that resemble degenerated mitochondria. Neuritic aggregates also form in cultured striatal neurons expressing mutant huntingtin, block protein transport in neurites, and cause neuritic degeneration before nuclear DNA fragmentation occurs. These findings suggest that the early neuropathology of HD originates from axonal dysfunction and degeneration associated with huntingtin aggregates.

Aging↗

PubMed2001

Chaperone suppression of cellular toxicity of huntingtin is independent of polyglutamine aggregation.

Polyglutamine protein aggregation is associated with eight inherited neurodegenerative disorders. In Huntington's disease, N-terminal fragments of mutant huntingtin form intracellular aggregates and mediate cellular toxicity. Recent studies have shown that chaperones inhibit polyglutamine-mediated aggregation and cellular toxicity. Because chaperones also inhibit caspase activation to protect cells from death, it remains unclear whether the protective effect of chaperones on polyglutamine-mediated cellular toxicity is dependent on their inhibition of protein aggregation. In this study, we show that several chaperones including HSP 40, HSP 70, and N-ethylmaleimide-sensitive factor can inhibit cellular toxicity caused by N-terminal mutant huntingtin fragments. However, only HSP 40 is able to inhibit huntingtin aggregation. Furthermore, time-course study suggests that the protection of chaperones against huntingtin toxicity is not the result of their suppression of huntingtin aggregation. Chaperones inhibit caspase-3 and caspase-9 activation mediated by mutant huntingtin, and this inhibition is independent of huntingtin aggregation. We propose that the inhibition of caspase activity by chaperones is involved in their suppression of polyglutamine toxicity.

Amino Acid Sequence↗

PubMed2001

Nuclear aggregation of huntingtin is not prevented by deletion of chaperone Hsp104.

Polyglutamine expansion causes the disease proteins to aggregate, resulting in stable insoluble aggregates in the nucleus. The in vitro aggregation and cellular toxicity of polyglutamine proteins are reduced by chaperone heat shock proteins (Hsp). In polyglutamine disease animal models, however, polyglutamine inclusions remain in the nucleus despite the suppression of neurodegeneration by Hsp. Studies using yeast genetic approach revealed that the balance of Hsp is important for regulating protein aggregation in the cytoplasm of yeast cells. Here we report that N-terminal fragments of huntingtin with an expanded polyglutamine tract form aggregates only in the cytoplasm of yeast cells and, when tagged with nuclear localization sequences (NLS), are able to aggregate in the nucleus. Deletion of the Hsp104 gene prevents the aggregation of huntingtin in the cytoplasm but is unable to eliminate the aggregation of NLS-tagged huntingtin in the nucleus. The inhibitory effect of Hsp104 deletion on the cytoplasmic aggregation of huntingtin only occurs in viable yeast cells, as aggregates can be formed in Hsp104 deletion cells that have been frozen for 72 h. Fresh cytosolic extracts of the Hsp104 deletion strain inhibit the aggregation of huntingtin in vitro, suggesting that the deletion of Hsp104 may alter the activities of other cytoplasmic factors to inhibit polyglutamine aggregation in the cytoplasm. We propose that the regulatory effects of chaperones may mainly be restricted to the cytoplasm and have much less influence on polyglutamine-containing aggregates in the nucleus.

Cell Nucleus↗

PubMed2001

Magnetic field exposure induces DNA degradation.

In our earlier experiments, we discovered that magnetic field exposure could bring both stabilizing and destabilizing effects to the DNA of Escherichia coli, depending on our parameters of assessment, and both of these effects were associated with the induced synthesis of the heat shock proteins Hsp70/Hsp40 (DnaK/DnaJ). These contradicting results prompted us to explore in this study the effect of magnetic field exposure on the DNA stability in vivo when the heat shock response of the cell was suppressed. By using plasmid pUC18 in E. coli as the indicator, we found that without the protection of the heat shock response, magnetic field exposure indeed induced DNA degradation and this deleterious effect could be diminished by the presence of an antioxidant, Trolox C. In our in vitro test, we also showed that the magnetic field could potentiate the activity of oxidant radicals.

Antioxidants↗

PubMed2001

Migration of radionuclides in porous rock in the presence of colloids: effects of kinetic interactions.

This work investigates the colloid-facilitated migration of radionuclides with radioactive decay in porous media. The sorption processes for radionuclides with both the solid matrix and colloids are treated as equilibrium or nonequilibrium. An analytical solution is obtained from a simplified linear equilibrium interaction mechanism. In addition, the adsorption processes for radionuclides with colloids and porous rock can be assumed as nonequilibrium and modeled by the linear kinetic adsorption. The numerical method is employed to solve the coupled colloid and radionuclide transport equations under nonequilibrium sorption assumption. Moreover, the reaction rates of the adsorption processes for radionuclides with the solid matrix and colloids affect the transport characteristics of radionuclides. The fast reaction rate of radionuclides with colloids causes a higher concentration of radionuclides adsorbed on colloids in a dispersed phase and enlarges acceleration caused by colloids. However, the fast reaction rate for radionuclides with solid matrix increases the retardation effect caused by the solid matrix. This work developed a predictive model for the transport of colloid-facilitated radionuclides in porous medium and to assess the importance of various phenomenological coefficients, particularly parameters for the adsorption interactions.

Adsorption↗

PubMed2001

Effects of hydrodynamic chromatography on colloid-facilitated migration of radionuclides in the fractured rock.

The performance assessment of high level radioactive waste disposal has emphasized the role of colloids in the migration of radionuclides in the geosphere. Previous literature [Nagasaki S, Tanaka S, Suzuki A. Fast transport of colloidal particles through quartz-packed columns. J. Nucl. Sci. Technol. 1975;30(11):1136] indicates that owing to hydrodynamic chromatography the colloid velocity may not be equal to that of groundwater. Using hydrodynamic chromatography, this work investigates the effects of the size of colloidal particles on the radionuclide migration facilitated by colloids in a single fractured porous rock. Also, a methodology is proposed to develop a predictive model to assess transport within the fracture rock as well as various other phenomenological coefficients, particularly the size of colloidal particles. In addition, a fully developed concentration profile for non-reactive colloids in the fracture is developed to elucidate hydrodynamic chromatography of colloids in geological media. The external forces acting on colloidal particles hypothesized in the model proposed herein include inertial force, van der Waals attractive force, double layer force as well as gravitational force. The dispersion coefficient of colloids and the distribution coefficient for radionuclides with colloids are also considered as they pertain to the size of the colloid. In addition, the size distributions of colloids are utilized to investigate the effects of polydispersed colloids.

Chromatography↗

PubMed2001

Megastigmane glycosides and an acylated triterpenoid from Eriobotrya japonica.

Two new megastigmane glycosides, eriojaposides A (1) and B (2), and a new acylated triterpenoid (3) were isolated along with nine known compounds from a leaf extract of Eriobotrya japonica. The structures of 1--3 were characterized as (6R,9R)-3-oxo-alpha-ionyl-9-O-beta-xylopyranosyl-(1' '-->6')-beta-glucopyranoside, (6R,9R)-3-oxo-alpha-ionyl-9-O-alpha-rhamnopyranosyl-(1' '-->6')-beta-glucopyranoside, and 3 alpha-trans-feruloyloxy-2 alpha-hydroxyurs-12-en-28-oic acid, respectively, on the basis of spectral and chemical evidence.

Asia↗

PubMed2001

In vivo effects of vanadium on GLUT4 translocation in cardiac tissue of STZ-diabetic rats.

The effect of vanadium treatment on insulin-stimulated glucose transporter type 4 (GLUT4) translocation was studied in cardiac tissue of streptozotocin (STZ)-induced diabetic rats by determining the subcellular distribution of GLUT4. Four groups of rats were examined: control and diabetic, with or without bis(maltolato)oxovanadium(IV) (BMOV, an organic form of vanadium) treatment for 8 weeks. The effect of vanadium on insulin-induced GLUT4 translocation was studied at 5 min as the early insulin response and at 15 min after insulin injection as the maximal insulin response. At 5 min after insulin injection, plasma membrane GLUT4 level in the diabetic-treated group was not different from the control groups and was significantly higher than that of the insulin-stimulated diabetic group, indicating an enhancement of insulin response on GLUT4 translocation brought about by vanadium treatment. In contrast to that at 5 min after insulin injection, no significant difference in the plasma membrane GLUT4 level was observed between the diabetic and the diabetic-treated groups at 15 min after insulin injection. GLUT4 mobilization from the intracellular pool in response to insulin was also investigated at 15 min after insulin injection. Basal intracellular GLUT4 content was significantly higher in the diabetic-treated group when compared to the diabetic group under the same condition. However, the increased basal intracellular GLUT4 in the diabetic-treated group did not result in more insulin-mediated GLUT4 translocation at 15 min after insulin injection. In conclusion, the finding that plasma membrane GLUT4 in the diabetic-treated group is significantly higher than that of the diabetic group at 5 min but not at 15 min post-insulin injection indicates that vanadium treatment enhances insulin-mediated GLUT4 translocation in cardiac tissue by enhancing its early response.

Animals↗

PubMed2001

Constituents from Limonia crenulata.

A new indole alkaloid, crenulatine (1), along with twenty known compounds, was isolated from the stems of Limonia Crenulata. Their structures were identified by spectral means. Those compounds include four alkaloids, four coumarins, two flavanones, three tetranortriterpenoids, one triterpenoid, three steroids, two lignans and two aromatic compounds.

Alkaloids↗

PubMed2001

[Studies of FISH and karyotype of Gossypium barbadense].

Based on the fluorescent in situ hybridization (FISH) of somatic chromosome of Gossypium barbadense with the probe of genomic DNA (gDNA) of Gossypium arboreum, two sets of chromosomes were easily distinguished by signals hybridized or not. The FISH directly proved that G. barbadense originated from two different diploid species, but was not in concordance with the former point that every chromosome of A sub-genome of tetraploid species was bigger than that of other sub-genome (D genome). The karyotype formula of G. barbadense based on its FISH was 2n = 4x = 52 = 38 m + 14sm(6sat). There were three pairs of satellite chromosomes which were all sm types. Their satellites located in short arms but originated differently from their chromosomes of sub-genome. Fragment translocations occured in the long arms of homologous chromosomes of number 5, 6 and 9 of A sub-genome. It was suggested that the translated fragments come from D sub-genome. The fragments are fairly large with the relative lengths of 19.21%, 17.69% and 12.88% of their whole chromosomes, respectively. At least five pairs of chromosomes in D sub-genome show some hybridized signals of gDNA probe of G. arboreum in their centromere regions, which indicated that there would be chromatin introgressions from A sub-genome.

Gossypium↗

PubMed2001

Effect of ligustrum fruit extract on reproduction in experimental diabetic rats.

AIM: To study the effect of ligustrum fruit on spermatogenesis and blood gonadal hormones in diabetic rats. METHODS: Experimental diabetes was induced in male Wistar rats with streptozotocin. Ligustrum fruit extract was given by gastric gavage at a dose of crude drug 30 g x kg(-1) x d(-1) for 110 days. The serum gonadadotropic hormones and testosterone were determined on d 60 and testicular histology examined on d 110. RESULTS: In the control diabetic rats, the seminiferous tubules were dilated and the spermatogenic cells irregularly arranged. Spermatogenesis was arrested with the number of spermatids highly reduced and spermatozoa not observed. In the treated rats, all types of spermatogenic cells were practically normal. The serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone levels were higher in the treated than in the control rats, but the difference was insignificant. CONCLUSION: In experimental diabetic rats, ligustrum fruit extract protects the damaging effect of experimental diabetes on spermatogenesis.

Animals↗