Biomedical subjects

Kai Zhang

Publications and source records attributed to Kai Zhang.

At least 73 records · Page 4Linked to original sources

PubMed2005

Systematic variation of interfacial phase reactivity in dental nanocomposites.

This study was designed to determine the effect of varying the chemistry of the interfacial phase on critical composite properties in dental nanocomposite materials. Silica nanoparticles were silanized with varying ratios of 3-methacryloxypropyltrimethoxysilane (MPTMS) and octyltrimethoxysilane (OTMS) while keeping the total amount of silane constant at 10% by mass fraction relative to the mass of filler. The silanized nanoparticles were mixed into a dimethacrylate resin (60% filler by mass fraction). The mechanical properties of the uncured pastes were assessed by compression testing between parallel plates. The composites were photo-cured and tested by biaxial flexure and three-point bend flexure testing. Fracture surfaces were analyzed by field-emission scanning electron microscopy (FE-SEM). At maximized filler mass fractions, the workabilities of the uncured pastes were better maintained as the fraction of OTMS in the interphase increased relative to MPTMS. The flexure strengths and moduli of the MPTMS silanized and dual silanized composites were similar but decreased as OTMS mass fractions in the silane mixture increased to 7.5% and 10%. FE-SEM images revealed evidence for phase separation in the composites containing silica silanized with high fractions of OTMS. Among the potential practical benefits of dual silanized nanoparticles are the improved workability of composite pastes with higher filler loadings that should lead to higher modulus composites with lower polymerization shrinkage.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2005

A tale of two hospitals: assessing cultural landscapes and compositions.

Clinical directorate service structures (CDs) have been widely implemented in acute settings in the belief that they will enhance efficiency and patient care by bringing teams together and involving clinicians in management. We argue that the achievement of such goals depends not only on changing its formalized structural arrangements but also the culture of the organisation concerned. We conducted comparative observational studies and questionnaire surveys of two large Australian teaching hospitals similar in size, role and CD structure. Martin's conceptualization of culture in terms of integration, differentiation and fragmentation was applied in the analysis of the data. The ethnographic work revealed that compared to Metropolitan Hospital, Royal Hospital was better supported and more favourably viewed by its staff across six categories identified in both settings: leadership, structure, communication, change, finance and human resource management. Royal staff were more optimistic about their organisation's ability to meet future challenges. The surveys revealed that both staff groups preferred CD to traditional structures and shared some favourable and critical views of them. However Royal staff were significantly more positive, reporting many more benefits from CDs e.g. improved working relations, greater accountability and efficiency, better cost management, more devolvement of management to clinicians and a hospital more strategically placed and patient focused. Metropolitan staff were more likely to claim that CDs failed to solve problems and created a range of others including disunity and poor working relationships. There was greater consensus of views among Royal staff and more fragmentation at Metropolitan where both intensely held and uncertain attitudes were more common. The outcomes of implementing CDs in these two similar organisations differed considerably indicating the need to address cultural issues when introducing structural change. Martin's framework provides a useful antidote to researchers' tendency to focus at only one level of culture.

Anthropology, Cultural↗

PubMed2005

Assay and functional properties of PrBP(PDEdelta), a prenyl-binding protein interacting with multiple partners.

A 17-kDa prenyl-binding protein, PrBP(PDEdelta), is highly conserved among various species from human to Caenorhabditis elegans. First identified as a putative regulatory delta subunit of the cyclic nucleotide phosphodiesterase (PDE6) purified from mammalian photoreceptor cells, PrBP(PDEdelta) has been hypothesized to reduce activation of PDE6 by the heterotrimeric G-protein, transducin, thereby desensitizing the photoresponse. However, recent work shows that PrBP(PDEdelta) interacts with numerous prenylated proteins at their farnesylated or geranylgeranylated C-termini, as well as with non-prenylated proteins. These polypeptides include small GTPases such as Rab13, Ras, Rap, and Rho6, as well as components involved in phototransduction (e.g., rod and cone PDE6, rod and cone opsin kinases). Expression of PrBP(PDEdelta) in tissues and organisms not expressing PDE6, the demonstration of multiple interacting partners with PrBP(PDEdelta), and its low abundance in rod outer segments all argue against it being a regulatory PDE6 subunit. This raises intriguing questions as to its physiological functions. In this chapter, we review the current status of PrBP(PDEdelta) and describe some of the assays used to determine these interactions in detail. In mammalian photoreceptors, the results are consistent with a role of PrBP(PDEdelta) in the transport of prenylated proteins from their site of synthesis in the inner segment to the outer segment where phototransduction occurs.

Amphibians↗

PubMed2005

Leishmania salvage and remodelling of host sphingolipids in amastigote survival and acidocalcisome biogenesis.

Sphingolipids (SLs) play essential roles in most eukaryotes, but in the trypanosomatid protozoan Leishmania major their functions differ significantly. Previously we showed that null mutants defective in de novo sphingoid base synthesis (spt2-) lacked SLs but grew well and retained lipid rafts while replicating as promastigotes in vitro. However, they experienced catastrophic defects in membrane trafficking on entry into stationary phase, and failed to differentiate to the infective metacyclic form. Here we showed this mutant retained the ability to enter macrophages silently and inhibit activation, although as expected most parasites were destroyed. However, in mouse infections, after a delay rapidly progressive lesions appeared, and purified amastigotes were fully virulent to macrophages and mice. Mass spectrometry of spt2- amastigote lipids revealed the presence of high levels of parasite-specific inositol phosphorylceramides (IPCs) not synthesized by the mammalian hosts. Inhibitor studies showed that salvage occurs at the level of complex SLs, suggesting that parasites carry out 'headgroup' remodelling. Additionally, we describe a new defect of the spt2- promastigotes involving 'empty' acidocalcisomes (ACs), which may point to the origin of this organelle from the lysosome-related organelle/multivesicular body biogenesis pathway. However, ACs in spt2- amastigotes appeared quantitatively and morphologically normal. Thus salvage of SLs and other molecules by intracellular amastigotes play key roles in AC biogenesis and parasite survival in the host.

Animals↗

PubMed2005

Synthesis of SiO2-coated ZnMnFe2O4 nanospheres with improved magnetic properties.

A core-shell structured composite, SiO2 coated ZnMnFe2O4 spinel ferrite nanoparticles (average diameter of approximately 80 nm), was prepared by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of ZnMnFe2O4 nanoparticles (average diameter of approximately 10 nm) synthesized by a hydrothermal method. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate that the core-shell samples possess better magnetic properties at room temperature, compared with paramagnetic colloids with a magnetic core by a coprecipitation method. These core-shell nanospherical particles with self-assembly under additional magnetic fields could have potential application in biomedical systems.

Coated Materials, Biocompatible↗

PubMed2005

Measurement of total disc replacement radiographic range of motion: a comparison of two techniques.

OBJECTIVE: Current methods used to measure total disc replacement (TDR) radiographic range of motion (ROM) have not been previously evaluated. Sagittal ROM is measured by determining the change in the Cobb angle of the prosthesis from the flexion to the extension radiographs. Either the metallic endplates or the keels of the TDR prosthesis can be used as radiographic landmarks in measuring ROM. We hypothesized that use of the prosthesis keels as radiographic landmarks, when compared with the use of prosthesis endplates, might lead to more precise measurements of TDR sagittal ROM. METHODS: Two observers (a fifth-year orthopedics resident and an attending orthopedic spine surgeon) measured the ROM of 51 Prodisc II TDRs on standard flexion and extension lumbar spine radiograph sets. Repeated measurements were made on two occasions using either the keels or the endplates as landmarks. Precision was defined as the mean of the absolute differences between measurements. RESULTS: For observer A, the mean absolute difference between two measurements was 1.4 degrees with the keel method compared with 3.0 degrees with the endplate method (P < 0.001). For observer B, the mean absolute difference between two measurements was 1.8 degrees with the keel method and 3.3 degrees with the endplate method (P < 0.001). When the interobserver differences were examined, the mean absolute difference was 1.8 degrees with the keel method and 3.3 degrees with the endplate method (P < 0.001). CONCLUSIONS: Our results show that the use of TDR prosthesis keels as radiographic landmarks, when compared with the use of prosthesis endplates, yields greater precision in ROM measurement. For TDR prostheses with a keel, we recommend using the keel to measure ROM.

Adult↗

PubMed2005

[Study on the relationship between methylene tetrahydrofolate reductase gene (677C-->T) mutation and skin lesions in endemic arsenic poisoning].

OBJECTIVE: Methylene tetrahydrofolate reductase (MTHFR) is the key enzyme in folate metabolism. We examined whether single nucleotide 677 C-->T mutation in the MTHFR gene could affect the occurrence of skin lesions in endemic arsenic poisoning. METHODS: Fifty individuals with arsenic-induced skin lesions were identified as cases, and 35 individuals without skin lesions from the same village were selected as controls. The MTHFR C677T polymorphism was analyzed by PCR-RFLP method, serum folic acid and Vitamin B12 were determined by microbiological assay and the electrochemiluminescence immunoassay, respectively. RESULTS: The frequencies of TT genotype and T allele in case group were 34.0% and 56.0%, respectively, and were not significantly different from those in controls. There was no significant difference between case and control group in the levels of folic acid and Vitamin B12 in serum. Compared to subjects carrying the CC genotype and having the level of folic acid above 10.5 nmol/L, other subjects were at elevated risk of skin lesions, but the 95% CI of both crude OR and adjusted OR (controlled for age, gender, smoking and arsenic level in drinking water) include 1. CONCLUSION: This study did not find the relationship between MTHFR gene (677C-->T) mutation and skin lesions in endemic arsenic poisoning.

Adult↗

PubMed2005

[Correlation between ATP bioluminescence tumor chemosensitivity assay and clinical response in ovarian cancer].

OBJECTIVE: To determine the correlation between results of ATP bioluminescence tumor chemosensitivity assay (ATP-TCA) of human ovarian cancer specimens in vitro and clinical chemo-therapeutic responses of patients. METHODS: Thirty-four freshly taken ovarian cancer specimens (28 cases) and ascites (6 cases) and 9 chemotherapeutic drugs were tested in vitro for cancer chemosensitivity by ATP-TCA. RESULTS: Among the 34 ovarian cancer cases, the efficacy of ATP-TCA is 94.0%, the sensitivity, the specificity, the positive and negative predicting values, and an overall predicting value in vitro and vivo were 90.0%, 91.7%, 94.7%, 84.6% and 90.6%, respectively. CONCLUSION: The results of ATP-TCA assay are correlated well with clinical treatment responses. The assay may be an important and useful method for individual-based chemotherapy of cancers.

Adenosine Triphosphate↗

PubMed2005

[Long-term efficacy of TRUS-guided transperineal needle aspiration and irrigation on persistent hematospermia].

OBJECTIVE: To evaluate the long-term efficacy of transrectal ultrasonography (TRUS)-guided transperineal needle aspiration and irrigation for persistent hematospermia. METHODS: Included in the study were 12 patients with persistent hematospermia, aged (36.4 +/- 10.8) years, and with a course of the disease of (13.9 +/- 6.4) months. After the expressed prostatic secretion (EPS) by prostatic massage cultured, the patients received TRUS-guided transperineal needle aspiration for seminal vesicle fluid (SVF) for bacteriological examination. For the EPS positive patients, antibiotics were selected according to the drug sensitivity assay and injected into the abnormal seminal vesicle (SV) via TRUS-guided transperineal needle puncture. The treatment was repeated one month later for those still with hematospermia. The patients were followed up every three months. RESULTS: Abnormal images were found in the SV and/or ejaculatory duct in 9 cases, including SV and/or ejaculatory duct dilation, SV wall thickening, calcification or calculi of SV, and müllerian duct cyst. SVF cultures were positive in 7 cases, including 4 cases of methicillin-resistant Staphylococcus aurous (MRSA), 1 case of methicillin-resistant coagulase-negative staphylococcus (MRCNS), 1 case of E. Coli, and 1 case of Proteus mirabili. All the patients were treated by TRUS-guided transperineal injection of certain antibiotics into SV. Ten of them were followed up for (31.4 +/- 5.7) months. Hematospermia disappeared in 3 cases and relapsed at least once in the other 7. The last follow-up showed hematospermia recurrence in 2 cases. CONCLUSION: TRUS-guided transperineal irrigation of antibiotics into SV is effective to a certain extent for persistent hematospermia.

Adult↗

PubMed2005

[Changes of serum leptin level in pulmonary infection-induced multiple organ dysfunction syndrome].

OBJECTIVE: To determine serum levels of leptin and some related cytokines in severely ill patients, including severe pulmonary infection-induced multiple organ dysfunction syndrome (MODS), acute myocardial infarction (AMI) and arrhythmia (AR), and to explore the possible role of leptin in the pathogenesis and diagnosis of MODS. METHODS: Radioimmunoassay was used to determine leptin, fatty acid binding protein (FABP), transferrin (Ferr) and interleukin-1beta (IL-1beta), and enzyme-linked immuno adsorbent assay (ELISA) was used to assess C reactive protein (CRP). RESULTS: Compared with normal individuals, leptin levels in MODS, AMI and AR patients increased significantly (all P<0.01). CRP and IL-1beta levels also increased significantly in MODS, AMI and AR patients, but the changes were more marked (all P<0.05) in MODS patients than in the patients of other two diseases (both P<0.05). Though FABP and Ferr levels of patients in all the three groups of patients showed a trend toward increase, especially in MODS patients, there was no significant difference between them and normal individuals. CONCLUSION: Serum leptin level increases significantly in pulmonary infection-induced MODS patients with a simultaneous increase of CRP and IL-1beta levels, and the result suggests that leptin plays a possible role in the pathogenesis and prognosis of MODS.

C-Reactive Protein↗

PubMed2005

[Effect of captopril on the nervous function in rabbits exposed to vibration].

OBJECTIVE: To study the effect of captopril on the nervous function in rabbits exposed to vibration. METHODS: Rabbits were divided into vibration group, intervention group, and control group. Vibration group and intervention group were exposed to (tested by) vibration. Captopril was given to intervention group from the 11th day of vibration exposure. Somatosensory evoked potential (SEP) and motor nervous conduction function (MCF) were measured and analyzed in each group before and after vibration exposure. RESULTS: The latent periods of N1, P1 and N2 of SEP in vibration group after vibration exposure were (30.76 +/- 4.26), (41.91 +/- 6.67), and (45.29 +/- 5.81) ms respectively, and in intervention group after vibration exposure were (27.00 +/- 3.04), (35.07 +/- 4.20) and (41.15 +/- 3.19) ms respectively. Compared with intervention group before and after exposure, and control group, the latent periods of each wave of SEP were delayed significantly (P < 0.05). The nervous conduction velocity, the distant wave amplitude, and the distant potential period of sciatic nerve in vibration group after vibration exposure were significantly different from those in intervention group [(35.69 +/- 4.37) m/s, (1.55 +/- 0.73) microV, (8.16 +/- 0.71) ms respectively vs (52.20 +/- 5.13) m/s, (2.89 +/- 0.36) microV, (7.26 +/- 0.77) ms respectively (P < 0.01)]. CONCLUSION: Captopril may improve the impairment of nervous functions to a certain degree in rabbits exposed to vibration.

Animals↗

PubMed2005

[Correlation analysis of increase in serum level of leptin with that of C reactive protein, troponin T and endothelin in patients with acute myocardial infarction].

OBJECTIVE: To determine serum leptin levels in patients with acute myocardial infarction (AMI) and coronary atherosclerosis (CS), and to analyze its correlation with C reactive protein (CRP), troponin T (TnT) and endothelin (ET). METHODS: Serum samples from confirmed AMI and CS patients were collected. Leptin and ET were assayed with high sensitive radioimmunoassay, TnT was determined with automatic biochemical analyser, and CRP was determined with enzyme-linked immunosorbant assay (ELISA). RESULTS: Compared with normal control group, serum leptin, TnT, CRP and ET levels increased significantly (all P<0.01) in AMI patients. Serum levels of other cytokines, except TnT in CS patients, increased significantly compared with normal control group (all P<0.01). Correlation analysis showed that all the changes were not correlated with each other, each being an independent factor. Only serum TnT levels of AMI and CS patients showed a significant difference (P<0.01). CONCLUSION: Serum leptin levels of both AMI and CS patients increase significantly without a significant difference between each other, and there is no correlation for leptin with CRP, TnT and ET.

C-Reactive Protein↗

PubMed2005

[From better erection to better sex: viagra updates 2005].

Viagra (sildenafil citrate) has been proven as the first choice of treatment for erectile dysfunction (ED) due to its producing rigid, sustained erection and rapid onset of action. In recent years, more and more studies on efficacy of Viagra focused on the improvement of overall sex life, as well as the psychological impact on the ED patients. Using several psychological assessment tools such as erectile dysfunction inventory of treatment satisfaction (EDITS), self-esteem and relationship (SEAR) questionnaire, psychological impact of erectile dysfunction (PIED) scores, these studies found that Viagra treatment significantly improved the following psychological factors: satisfaction of both ED patients and their partners with sexual intercourse and sexual relationship, confidence and self-esteem of the patients, desire for intimacy and sexual intercourse. The significant increased frequency of sexual intercourse attempts and improvement of health-related quality of life were also seen in the patients receiving Viagra treatment. Thus, Viagra produces the better erection and then promotes the better sex cycle.

Erectile Dysfunction↗

PubMed2005

[Effects of sildenafil on erectile dysfunction in the aged men with diabetes].

OBJECTIVE: To evaluate the efficacy and safety of sildenafil on erectile dysfunction in the aged men with diabetes. METHODS: One hundred and ten patients aged 55 years old above with type I or II diabetes and a minimum 3-month history of ED were studied. Patients were instructed to take one dose of their treatment orally at any time before anticipated sexual activity. Changes from baseline in mean scores on the erectile function domain of the International index of Erectile Function and changes from baseline in the proportion of "yes" responses to question 2, and 3, of the Sexual Encounter Profile were coprimary outcome measures. RESULTS: Treatment with sildenafil significantly improved all primary efficacy variables. CONCLUSION: Sildenafil therapy significantly enhanced erectile function and was well tolerated by men with diabetes and ED.

Aged↗

PubMed2005

[Effect of testosterone propionate on the distribution pattern of calcitonin gene-related peptide in different motoneuron pools].

OBJECTIVE: To study the effect of testosterone propionate (TP) on the distribution pattern of calcitonin gene-related peptide (CGRP) in two types of motoneuron (Mn) pools in rats. METHOD: The double labeling of cholera toxin B subunit coupled with colloidal gold (CB-Au) retrograde identification combining with immunocytochemistry was mainly used to reveal the distribution pattern of CGRP-like immunoreactivity (CGRP-LI) and its changes in the motoneuron pools labeled by CB-Au. RESULT: TP injected intramuscularly 28 days later significantly decreased CGRP expression in Mn pool innervating extensor digitorum longus (EDL, fast-twitch), comparing with corresponding control and castration group respectively (P < 0.001), while no significant effect on Mn pools innervating soleus (SOL, slow-twitch, P > 0.05) was observed. CONCLUSION: EDL-Mn pool is more sensitive to testosterone propionate than SOL-Mn pool in regulating CGRP expression.

Animals↗

PubMed2004

Hollow titania spheres with movable silica spheres inside.

We demonstrate a flexible method for preparing hollow TiO2 nanospheres with movable silica nanoparticles inside (HTNMSNs). In this method, we used monodisperse silica--polystyrene core--shell nanospheres (SiO2-PS-CSNs) sulfonated as templates and prepared the composite shell consisting of TiO2 and sulfonated polystyrene (SPS) through adsorbing or depositing tetrabutyl titanate gel into the SPS shell. Finally the HTNMSNs were obtained after removal of all polymers in the composite nanospheres by dissolution or calcinations. We investigated the dependence of the morphologies of HTNMSNs on the thickness of PS shells and the size of SiO2 cores and prepared rare earth doped HTNMSNs by a sol-gel process.

Journal Article↗

PubMed2004

Microcontact printing of colloidal crystals.

Patterned two-dimensional (2D) colloidal crystals have been transferred by a modified mucp technique that was based on the use of polymer film as "glue" to provide an efficient interaction between the microsphere "ink" and substrate. The versatility of this method has been demonstrated by the patterning of colloidal crystal on a nonplanar substrate and heterogeneously structured colloidal crystal film. The table of contents graphic shows an SEM image of the ordered parallel lines of 2D colloidal crystals on a polymer-coated glass tube with a 3.7 mm radius of curvature.

Journal Article↗

PubMed2004

The effect of megestrol acetate on growth of HepG2 cells in vitro and in vivo.

PURPOSE: Hepatocellular carcinoma (HCC) is generally considered as a sex hormone-dependent tumor, and hormonal therapy has been proposed as a strategy for the treatment of HCC. The aim of the study is to investigate the effect of megestrol acetate, a synthetic progesteronal agent, on growth of HepG2 cells in vitro and in vivo. EXPERIMENTAL DESIGN: Cell growth in vitro was assessed by a colormetric method, and cell growth in vivo was assessed by tumor volumetrics. RESULTS: Megestrol acetate was shown to inhibit the growth of HepG2 cells in vitro in dose- and time-dependent manners with an IC (50) of 260 microm (24-h incubation). The growth of HepG2 cell-transplanted tumors in nude mice was also inhibited by i.p. injection of megestrol acetate (10 mg/kg/day). The tumor volumes of the megestrol acetate-treated group regressed to 59% of controls by week 6 and to 41% of controls by week 13. Apoptosis following G(1) arrest was observed in megestrol acetate-treated cells and may be a mechanism through which megestrol acetate inhibits HepG2 cells. Megestrol acetate was also demonstrated to have a beneficial effect on the weight gain of tumor-bearing nude mice, and the mean weight of the megestrol acetate-treated animals was higher than that of controls from week 4 of the treatment period, and the differences were statistically significant in week 5 and 6 (P < 0.05, compared with controls). No significant survival advantage was, however, demonstrated in the treatment group. CONCLUSIONS: This study showed that megestrol acetate inhibited the growth of HepG2 cells grown in vitro and in vivo. These data provide useful information for clinical study of megestrol acetate for the treatment of HCC.

Animals↗