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Biomedical subjects

Kai Zhang

Publications and source records attributed to Kai Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2006

[Aildenafil citrate: a new potent and highly selective phosphodiesterase type 5 inhibitor for the treatment of erectile dysfunction].

OBJECTIVE: To evaluate the efficacy and safety of aildenafil citrate, an oral phosphodiesterase type 5 inhibitor, in the treatment of erectile dysfunction. METHODS: Integrated analyses were made of 8-week, randomized, double-blind, placebo-controlled phase 2 clinical trials involving 250 men with mild-to-severe erectile dysfunction of various etiologies who received aildenafil citrate 30 or 60 mg (n = 167) or placebo (n = 83). RESULTS: The statistic results of International Index of Erectile Function, Patient Sexual Encounter Profile (SEP) diaries and Global Assessment Question (GAQ) were significantly higher in the aildenafil citrate patients than in the placebo controls. The main drug-related adverse events were flushing, headache, dizziness and naupathia, which were mild and could be self-relieved. CONCLUSION: The aildenafil citrate therapy significantly ameliorated erectile function and was well tolerated by a wide range of patients with erectile dysfunction.

Administration, Oral↗
PubMed2005

Photon-by-photon determination of emission bursts from diffusing single chromophores.

One of the difficulties in diffusion-type single-molecule experiments is the determination of signal amid photon-counting noise. A commonly used approach is to further average the noisy time trace by binning, followed by placing a threshold to discriminate signal from background. The choice of smoothing parameters and the placement of the threshold may impact on the efficiency with which the information-rich region can be harvested, among other potential complications. Here we introduce a procedure that operates on the data sequence photon by photon, thereby relieving the incertitude in choosing binning-thresholding parameters. We characterize this procedure by detecting the two-photon emission bursts from diffusing single gold nanoparticles. The results support our burst-finding procedure as a reliable and efficient way of detecting and harvesting photon bursts from diffusing experiments.

Diffusion↗
PubMed2005

Occurrence and photochemical degradation of 17alpha-ethinylestradiol in Acushnet River Estuary.

17alpha-Ethinylestradiol (EE2), a major constituent of common contraceptive pills, and three other estrogenic hormones, estrone (E1), 17beta-estradiol (E2) and mestranol (MeEE2) have been determined in Acushnet River Estuary seawater using a GC-MS technique. Among three estrogenic compounds detected, EE2 has the highest concentration, up to 4.7 ng/l, at which EE2 may affect lobster and other fish abundance in the coastal seawater due to its high biological activity on fish feminization. Two natural estrogenic hormones, E1 and E2 have also been found in the estuary at concentrations up to 1.2 ng/l and 0.83 ng/l, respectively. Although EE2 is persistent to microbial degradation, it can undergo a rapid photodegradation in estuarine seawater under natural sunlight irradiation, with a half-life of less than 1.5 days in spring sunny days.

Estradiol↗
PubMed2005

Effect of activated sludge properties and membrane operation conditions on fouling characteristics in membrane bioreactors.

Biofouling control is considered to be a major challenge in operating membrane bioreactors (MBRs) for the treatment of wastewater. This study examined the impact of biological, chemical, and physical properties of activated sludge on membrane filtration performance in laboratory-scale MBRs. Sludges with different microbial communities were produced using pseudo-continuous stirred-tank reactors and pseudo-plug flow reactors treating a synthetic paper mill wastewater. Various filtration resistances were used to investigate membrane fouling characteristics, and molecular biology tools targeting 16S ribosomal DNA gene sequences were used to identify predominant bacterial populations in the sludges or attached to the fouled membranes. Filtration experiments using axenic cultures of Escherichia coli, Acinetobacter calcoaceticus, and Gordonia amarae were also performed to better understand the initiation and development of biofouling. The results showed that the tendency of membranes to biofoul depended upon membrane operating conditions as well as the properties of the activated sludge in the MBR systems. Specific bacterial populations, which were not dominant in the activated sludges, were selectively accumulated on the membrane surface leading to the development of irreversible biofouling.

Bacteria↗
PubMed2005

Hemoglobin/colloidal silver nanoparticles immobilized in titania sol-gel film on glassy carbon electrode: direct electrochemistry and electrocatalysis.

By vapor deposition method, both hemoglobin (Hb) and colloidal silver nanoparticles (CSNs) were entrapped in a titania sol-gel matrix on the surface of a glassy carbon electrode (GCE). CSNs could greatly enhance the electron transfer reactivity of Hb and its catalytic ability toward nitrite. Direct fast electron transfer between Hb and the GCE was achieved, and a pair of well-defined, quasi-reversible redox peaks was observed. The anodic and cathodic peak potentials are located at -0.298 V and -0.364 V (vs. Ag/AgCl), respectively. The dependence of the formal potential on solution pH indicated that the direct electron transfer reaction of Hb was a one-electron transfer coupled with a one-proton transfer reaction process. Meanwhile, the catalytic ability of Hb toward the reduction of NO2- was also studied. Accordingly, a NO2- biosensor was prepared, with a linear range from 0.2 mM to 6.0 mM and a detection limit of 34.0 microM. The apparent Michaelis-Menten constant was calculated to be 7.48 mM. Moreover, the biosensor had good long-term stability.

Carbon↗
PubMed2005

Angiotensin I-converting enzyme inhibitors block protein kinase C epsilon by activating bradykinin B1 receptors in human endothelial cells.

Angiotensin I-converting enzyme (ACE) inhibitors are widely used to treat patients with cardiovascular and kidney diseases, but inhibition of ACE alone does not fully explain the beneficial effects. We reported that ACE inhibitors directly activate bradykinin B1 receptor at the canonical Zn2+ binding site, leading to prolonged nitric oxide (NO) production in endothelial cells. Protein kinase C (PKC) epsilon, a novel PKC isoform, is up-regulated in myocardium after infarction, suggesting a role in the development of cardiac dysfunction. In cytokine-treated human lung microvascular endothelial cells, B1 receptor activation by ACE inhibitors (enalaprilat, quinaprilat) or peptide ligands (des-Arg10-Lys1-bradykinin, des-Arg9-bradykinin) inhibited PKC epsilon with an IC50 = 7 x 10(-9) M. Despite the reported differences in binding affinity to receptor, the two peptide ligands were equally active, even when inhibitor blocked the cleavage of Lys(1), thus the conversion by aminopeptidase. The synthetic undecapeptide (LLPHEAWHFAR) representing the binding site for ACE inhibitors on human B(1) receptors reduced PKC epsilon inhibition by enalaprilat but not by peptide agonist. A combination of inducible and endothelial NO synthase inhibitors, 1400W [N-(3(aminomethyl) benzyl) acetamidine dihydrochloride] and N omega-nitro-L-arginine (2 microM), significantly reduced inhibition by enalaprilat (100 nM), whereas the NO donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate (100 microM) inhibited PKC epsilon activity just as the B1 ligands did. In conclusion, NO generated by B1 receptor activation inhibits PKC epsilon.

Amino Acid Sequence↗
PubMed2005

Kallikrein activates bradykinin B2 receptors in absence of kininogen.

Kallikreins cleave plasma kininogens to release the bioactive peptides bradykinin (BK) or kallidin (Lys-BK). These peptides then activate widely disseminated B2 receptors with consequences that may be either noxious or beneficial. We used cultured cells to show that kallikrein can bypass kinin release to activate BK B2 receptors directly. To exclude intermediate kinin release or kininogen uptake from the cultured medium, we cultured and maintained cells in medium entirely free of animal proteins. We compared the responses of stably transfected Chinese hamster ovary (CHO) cells that express human B2 receptors (CHO B2) and cells that coexpress angiotensin I-converting enzyme (ACE) as well (CHO AB). We found that BK (1 nM or more) and tissue kallikrein (1-10 nM) both significantly increased release of arachidonic acid beyond unstimulated baseline level. An enzyme-linked immunoassay for kinin established that kallikrein did not release a kinin from CHO cells. We confirmed the absence of kininogen mRNA with RT-PCR to rule out kininogen synthesis by CHO cells. We next tested an ACE inhibitor for enhanced BK receptor activation in the absence of kinin release and synthesized an ACE-resistant BK analog as a control for these experiments. Enalaprilat (1 microM) potentiated kallikrein (100 nM) in CHO AB cells but was ineffective in CHO B2 cells that do not bear ACE. We concluded that kallikrein activated B2 receptors without releasing a kinin. Furthermore, inhibition of ACE enhanced the receptor activation by kallikrein, an action that may contribute to the manifold therapeutic effects of ACE inhibitors.

Animals↗
PubMed2005

Complete tumor response following intratumoral 32P BioSilicon on human hepatocellular and pancreatic carcinoma xenografts in nude mice.

PURPOSE: 32P BioSilicon is a new, implantable, radiological medical device that comprises particles of highly pure silicon encapsulating 32phosphorus (32P) for the treatment of unresectable solid tumors. Prior to administration, the device particles are suspended in a formulant which provides an even suspension of the intended dose for implantation. The primary objective of this animal trial study was to investigate the effects of intratumoral injection of 32)P BioSilicon on human hepatocellular (HepG2) and pancreatic carcinoma (2119) xenografts implanted in nude mice (BALB/c). A secondary objective was the histopathologic examination of the tumor foci and surrounding tissue during the study. METHODS: Cultured human carcinoma cells (HepG2 and 2119) were injected s.c. into the gluteal region of nude mice. When the implanted tumors were approximately 1 cm in diameter, 32P BioSilicon (0.5, 1.0, and 2.0 MBq) or formulant was injected into the tumors. Implanted tumor size was measured once a week for 10 weeks. At study termination, the tumor and surrounding normal tissue were collected and fixed in 10% formalin and processed for histopathologic analysis. RESULTS: 32P BioSilicon produced a reduction in HepG2 tumor volume when compared with formulant control, and complete response was observed among tumors in the 1.0 and 2.0 MBq treatment groups after week 8. There was also significant reduction in 2119 tumor volume in all treated groups, with the complete response rate of 67% in the 2.0 MBq group. CONCLUSION: 32P BioSilicon suppressed the growth of both human hepatocellular and pancreatic carcinoma xenografts implanted in nude mice and complete responses were also observed in tumors at higher radiation doses.

Animals↗
PubMed2005

[Capsule endoscopic diagnosis and treatment with intraoperative endoscopic assistance of vascular malformation of small intestine with bleeding].

OBJECTIVE: To evaluate the effect of capsule endoscopic examination in the diagnosis of vascular malformation of small intestine and discuss the operative method of this disease. METHODS: The clinical data of 11 cases of vascular malformation of small intestine by the capsule endoscopic diagnosis were analyzed retrospectively. RESULTS: All of the 11 cases received operation with the assistance of intra-operative endoscopic examination, and 10 cases were confirmed to suffer from vascular malformation of small intestine postoperatively. The methods of operation included dot-resection, wedge-shaped resection and segmental resection. CONCLUSIONS: The capsule endoscopic examination is optimal for the diagnosis of vascular malformation of small intestine. Dot-resection, wedge-shaped resection and segmental resection with the assistance of intra-operative endoscopic examination for the surgical intervention of this disease are recommendable.

Adult↗
PubMed2005

Irreducible anterior atlantoaxial dislocation: one-stage treatment with a transoral atlantoaxial reduction plate fixation and fusion. Report of 5 cases and review of the literature.

STUDY DESIGN: Retrospective report of five surgical cases and review of the literature. OBJECTIVES: To report the clinical application of a novel internal fixation device in the treatment of irreducible atlantoaxial dislocation with ventral spinal cord compression. SUMMARY AND BACKGROUND DATA: Irreducible atlantoaxial dislocation with ventral spinal cord compression is difficult to treat. Traction is not uniformly successful at either reducing the dislocation or decompressing the spinal cord. Direct anterior decompression of the spinal cord may be necessary, in addition to the need for surgical stabilization of the upper cervical spine. Numerous methods have been described for surgical stabilization following transoral decompression, which generally require a second-stage posterior instrumentation and fusion procedure. Complication rates remain noteworthy for any of these strategies. METHODS: A novel transoral atlantoaxial reduction plate (TARP) system was designed to facilitate a one-stage anterior operation capable of simultaneously decompressing the ventral spinal cord as well as reducing and fusing the atlantoaxial segment. The procedure and TARP implant has been employed for five patients with irreducible atlantoaxial dislocation because of trauma or congenital disorders. Following transoral decompression and excision of scar, ligament and osteophytes, the TARP was used to affect reduction and fixation of the atlantoaxial joints. The decorticated atlantoaxial joint surfaces were grafted with autogenous iliac crest bone. The histories of these cases were reported in detail. RESULTS: The five case examples demonstrate the efficacy of this one-stage approach to the surgical treatment of irreducible anterior atlantoaxial dislocation with spinal cord compression. The role of the TARP in affecting and maintaining the reduction while promoting successful fusion is illustrated. CONCLUSION: The authors' one-stage anterior procedure employing their TARP for the surgical treatment of irreducible anterior atlantoaxial subluxation was effective in these five cases. This method was able to avoid the need for interval traction and/or a second stage posterior instrumentation and fusion procedure.

Adult↗
PubMed2005

A simple and controlled method of preparing uniform Ag midnanoparticles on Tollens-soaked silica spheres.

Ag midnanoparticles (midnanoparticles are those particles whose diameters are in the range from 20 to 80 nm) with average size of 30-50 nm and tunable packing densities were formed on the surface of preformed Tollens-soaked silica spheres by a simple and controlled method. The process mainly involved two steps. In the first step the absorption of Ag(NH3)2(+) ions occurred on the silica spheres and in the second step Ag(NH3)2(+) ions on the silica spheres were reduced to Ag midnanoparticles in the presence of glucose solution. The amount of Ag midnanoparticles on the silica spheres could easily be tuned by varying the washing times in the process of preparing the Tollens-soaked silica spheres. The washing process also effectively avoided the reduction of Ag(NH3)2(+) ions and the nucleation of Ag particles in solution and easily produced more uniform Ag midnanoparticles on the silica spheres. Attributing to the uniform Ag midnanoparticles, the Ag midnanoparticle-coated silica spheres show unique optical properties in the UV-vis absorption spectra. The resulting Ag midnanoparticle-coated silica spheres were characterized with transmission electron microscopy, UV-vis-IR recording spectrophotometry, and X-ray photoelectron spectroscopy.

Journal Article↗
PubMed2005

Lead contamination in tea leaves and non-edaphic factors affecting it.

Recent tests have detected high lead (Pb) concentrations in some commercial brands of tea leaves and this finding has raised concerns due to the possible health-related problems associated with Pb poisoning. In present research, we investigated the Pb contamination in tea leaves produced in Zhejiang province in China. Pb concentrations in all tea leaves sampled were below 5 mg/kg, the permissible levels given by Chinese Ministry of Agriculture, indicating that Pb contamination in this province is not excessive. We then investigated the non-edaphic factors that may potentially contribute to Pb accumulation in tea leaves. Pb concentration in tea leaves was found to be positively correlated with the industrialization level of a district (R = 0.83, the significant level at P < 0.05), and greater amounts of Pb were washed from the leaves of plants in districts with more industrial activity. This suggests that Pb accumulation in tea leaves could, in part, be attributed to industrial activity through the precipitation of atmospheric Pb. Furthermore greater amounts of Pb were washed from the leaves of plants growing near road than those growing farther away from road. This trend indicates that automobile activity was another likely contributor to Pb accumulation in tea. Pb content of green tea was also affected by the processing of the leaves in the factory. In particular the twisting and water-removal stages caused increases in Pb content in the tea product. This study suggests that non-edaphic factors also contribute to the Pb accumulation in tea.

Air Pollutants↗
PubMed2005

Fluorescence image-guided brain tumour resection with adjuvant metronomic photodynamic therapy: pre-clinical model and technology development.

Fluorescence-guided resection (FGR) and photodynamic therapy (PDT) have previously been investigated separately with the objectives, respectively, of increasing the extent of brain tumour resection and of selectively destroying residual tumour post-resection. Both techniques have demonstrated trends towards improved survival, pre-clinically and clinically. We hypothesize that combining these techniques will further delay tumour re-growth. In order to demonstrate technical feasibility, we here evaluate fluorescence imaging and PDT treatment techniques in a specific intracranial tumour model. The model was the VX2 carcinoma grown by injection of tumour cells into the normal rabbit brain. An operating microscope was used for white light imaging and a custom-built fluorescence imaging system with co-axial excitation and detection was used for FGR. PDT treatment light was applied by intracranially-implanted light emitting diodes (LED). The fluorescent photosensitizer used for both FGR and PDT was ALA-induced PpIX. For PDT, ALA (100 mg kg(-1)) and low light doses (15 and 30 J) were administered over extended periods, which we refer to as metronomic PDT (mPDT). Eighteen tumour bearing rabbits were divided equally into three groups: controls (no resection); FGR; and FGR followed by mPDT. Histological whole brain sections (H&E stain) showed primary and recurrent tumours. No bacteriological infections were found by Gram staining. Selective tumour cell death through mPDT-induced apoptosis was demonstrated by TUNEL stain. These results demonstrate that the combined treatment is technically feasible and this model is a candidate to evaluate it. Further optimization of mPDT treatment parameters (drug/light dose rates) is required to improve survival.

Aminolevulinic Acid↗
PubMed2005

Techniques for delivery and monitoring of TOOKAD (WST09)-mediated photodynamic therapy of the prostate: clinical experience and practicalities.

Photodynamic therapy of solid organs requires sufficient PDT dose throughout the target tissue while minimizing the dose to proximal normal structures. This requires treatment planning for position and power of the multiple delivery channels, complemented by on-line monitoring during treatment of light delivery, drug concentration and oxygen levels. We describe our experience in implementing this approach in Phase I/II clinical trials of the Pd-bacteriophephorbide photosensitizer TOOKAD (WST09)-mediated PDT of recurrent prostate cancer following radiation failure. We present several techniques for delivery and monitoring of photodynamic therapy, including beam splitters for light delivery to multiple delivery fibers, multi-channel light dosimetry devices for monitoring the fluence rate in the prostate and surrounding organs, methods of measuring the tissue optical properties in situ, and optical spectroscopy for monitoring drug pharmacokinetics of TOOKAD in whole blood samples and in situ in the prostate. Since TOOKAD is a vascular-targeted agent, the design and implementation of the techniques are different than for cellular-targeted agents. Further development of these delivery and monitoring techniques will permit full on-line monitoring of the treatment that will enable real-time, patient-specific and optimized delivery of PDT.

Bacteriochlorophylls↗
PubMed2005

Effect of intestinal ischemia-reperfusion injury on protein levels of leptin and orexin-A in peripheral blood and central secretory tissues.

AIM: To explore the effect of intestinal ischemia-reperfusion injury on protein levels of leptin and orexin-A in peripheral blood and their central secretory tissues and to find out the role leptin and orexin-A play in acute inflammatory responses. METHODS: An intestinal ischemia-reperfusion (I/R) injury model of rats was established and rats were divided randomly into six groups: sham-operation group, 60 min ischemia/30 min reperfusion group (I60'R30'), I60'R90', I60'R150', I60'R240' and I60'R360', 9 rats each group. Two highly-sensitive radioimmunoassays for leptin and orexin-A were established and used to check the change of their concentrations in peripheral blood and central secretory tissues before and after intestinal I/R injury. RESULTS: Compared with the serum leptin level before injury, it decreased significantly in I60'R30' group and increased significantly in I60'R360' group; compared to sham-operation group after injury, serum leptin level increased significantly in I60'R360' group; compared to sham-operation group after injury, adipose leptin levels decreased significantly in I60'R30' and I60'R90' groups, while increased significantly in I60'R360' group. There was no significant difference between the expression levels of orexin-A before and after I/R injury. CONCLUSION: Leptin has a time-dependent response and orexin-A has a delayed response to acute inflammatory stimuli such as intestinal I/R injury and they may participate in metabolic disorders in injury as inflammatory cytokines.

Adipose Tissue↗
PubMed2005

Cytotoxicity of three-dimensionally ordered macroporous sol-gel bioactive glass (3DOM-BG).

In this study, 80% SiO(2)-20% CaO (mole fraction) three-dimensionally ordered macroporous sol-gel bioactive glass (3DOM-BG, average pore size: 345 nm) particles were prepared and characterized. Since the 3DOM-BGs have a novel microstructure and ion-releasing profile, the cytotoxicity of 3DOM-BG particles was tested. The cytotoxicity tests were performed using MC3T3-E1 osteoblast-like cells: (1) Wst-1 assay for cell viability after culture in extracts from 3DOM-BG particles; (2) phase contrast microscopy for cell morphology after culture with 3DOM-BG particles; and (3) fluorescence microscopy for imaging cells cultured directly on 3DOM-BG particles. The results showed that 3DOM-BG particles were not cytotoxic, and that cells attached, spread and proliferated on and around 3DOM-BG particles.

3T3 Cells↗
PubMed2005

Preparation and characterization of C16 monolithic columns for capillary electrochromatography.

A series of methacrylamide-based C16 monolithic columns were prepared and characterized to determine how their porous structural properties and chromatographic behavior are affected by the percentages of functional monomer, base monomer, and cross-linker in the polymerization solution. Baseline separation of 6 neutral compounds can be readily obtained in an optimized column. Furthermore, the effects of organic additive in the mobile phase, operating voltages, and temperature on retention behaviors and separation efficiencies were also studied. The separation mechanism is also discussed. High column efficiency and good reproducibility indicate that the monolithic columns hold considerable promise.

Journal Article↗