A highly enantio- and diastereoselective Cu-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with nitroalkenes.
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Journal Article↗
Biomedical subjects
Kai Zhang
Publications and source records attributed to Kai Zhang.
Glucose oxidase/colloidal gold nanoparticles immobilized in Nafion film on glassy carbon electrode: Direct electron transfer and electrocatalysis.
The direct electron transfer of glucose oxidase (GOD) was achieved based on the immobilization of GOD/colloidal gold nanoparticles on a glassy carbon electrode by a Nafion film. The immobilized GOD displayed a pair of well-defined and nearly reversible redox peaks with a formal potential (Eo ') of -0.434 V in 0.1 M pH 7.0 phosphate buffer solution and the response showed a surface-controlled electrode process. The dependence of Eo ' on solution pH indicated that the direct electron transfer reaction of GOD was a two-electron-transfer coupled with a two-proton-transfer reaction process. The experimental results also demonstrated that the immobilized GOD retained its electrocatalytic activity for the oxidation of glucose. So the resulting modified electrode can be used as a biosensor for detecting glucose.
Biosensing Techniques↗
Polynucleotide adsorption to negatively charged surfaces in divalent salt solutions.
Polynucleotide adsorption to negatively charged surfaces via divalent ions is extensively used in the study of biological systems. We analyze here the adsorption mechanism via a self-consistent mean-field model that includes the pH effect on the surface-charge density and the interactions between divalent ions and surface groups. The adsorption is driven by the cooperative effect of divalent metal ion condensation along polynucleotides and their reaction with the surface groups. Although the apparent reaction constants are enhanced by the presence of polynucleotides, the difference between reaction constants of different divalent ions at the ideal condition explains why not all divalent cations mediate DNA adsorption onto anionic surfaces. Calculated divalent salt concentration and pH value variations on polynucleotide adsorption are consistent with atomic force microscope results. Here we use long-period x-ray standing waves to study the adsorption of mercurated-polyuridylic acid in a ZnCl2 aqueous solution onto a negatively charged hydroxyl-terminated silica surface. These in situ x-ray measurements, which simultaneously reveal the Hg and Zn distribution profiles along the surface normal direction, are in good agreement with our model. The model also provides the effects of polyelectrolyte line-charge density and monovalent salt on adsorption.
Adsorption↗
Continuous distribution of emission states from single CdSe/ZnS quantum dots.
The photoluminescence dynamics of colloidal CdSe/ZnS/streptavidin quantum dots were studied using time-resolved single-molecule spectroscopy. Statistical tests of the photon-counting data suggested that the simple "on/off" discrete state model is inconsistent with experimental results. Instead, a continuous emission state distribution model was found to be more appropriate. Autocorrelation analysis of lifetime and intensity fluctuations showed a nonlinear correlation between them. These results were consistent with the model that charged quantum dots were also emissive, and that time-dependent charge migration gave rise to the observed photoluminescence dynamics.
Cadmium Compounds↗
Tannic acid, a potent inhibitor of epidermal growth factor receptor tyrosine kinase.
Increasing evidence supports the hypothesis that tannic acid, a plant polyphenol, exerts anticarcinogenic activity in chemically induced cancers. In the present study, tannic acid was found to strongly inhibit tyrosine kinase activity of epidermal growth factor receptor (EGFr) in vitro (IC50 = 323 nM). In contrast, the inhibition by tannic acid of p60(c-src) tyrosine kinase (IC50 = 14 microM) and insulin receptor tyrosine kinase (IC50 = 5 microM) was much weaker. The inhibition of EGFr tyrosine kinase by tannic acid was competitive with respect to ATP and non-competitive with respect to peptide substrate. In cultured cells, growth factor-induced tyrosine phosphorylation of growth factor receptors, including EGFr, platelet-derived growth factor receptor, and basic fibroblast growth factor receptor, was inhibited by tannic acid. No inhibition of insulin-induced tyrosine phosphorylation of insulin receptor and insulin-receptor substrate-1 was observed. EGF-stimulated growth of HepG2 cells was inhibited in the presence of tannic acid. The inhibition of serine/threonine-specific protein kinases, including cAMP-dependent protein kinase, protein kinase C and mitogen-activated protein kinase, by tannic acid was only detected at relatively high concentration, IC50 being 3, 325 and 142 microM respectively. The molecular modeling study suggested that tannic acid could be docked into the ATP binding pockets of either EGFr or insulin receptor. These results demonstrate that tannic acid is an in vitro potent inhibitor of EGFr tyrosine kinase.
3T3 Cells↗
Identifying pioneer bacterial species responsible for biofouling membrane bioreactors.
More effective control of membrane biofouling in membrane bioreactors (MBRs) lies in the fundamental understanding of the pioneer microorganisms responsible for surface colonization that leads to biofilm formation. In this study, the composition of the planktonic and sessile microbial communities inhabiting four laboratory-scale MBR systems were compared using amplified ribosomal DNA restriction analysis (ARDRA) and 16S ribosomal DNA gene sequencing. The ARDRA results suggest that the microbial communities on membrane surfaces could be very different from the ones in the suspended biomass. Phylogenetic analysis based on the 16S rRNA gene sequences provided a list of bacteria that might be the pioneers of surface colonization on microfiltration membranes. The results further suggested that research on the mechanisms of cell attachment in such an engineering environment could be critical for future development of appropriate biofouling control strategies.
Bacteria↗
A constitutive model of the human vocal fold cover for fundamental frequency regulation.
The elastic as well as time-dependent mechanical response of the vocal fold cover (epithelium and superficial layer of the lamina propria) under tension is one key variable in regulating the fundamental frequency. This study examines the hyperelastic and time-dependent tensile deformation behavior of a group of human vocal fold cover specimens (six male and five female). The primary goal is to formulate a constitutive model that could describe empirical trends in speaking fundamental frequency with reasonable confidence. The constitutive model for the tissue mechanical behavior consists of a hyperelastic equilibrium network in parallel with an inelastic, time-dependent network and is combined with the ideal string model for phonation. Results showed that hyperelastic and time-dependent parameters of the constitutive model can be related to observed age-related and gender-related differences in speaking fundamental frequency. The implications of these findings on fundamental frequency regulation are described. Limitations of the current constitutive model are discussed.
Adolescent↗
Transoral atlantoaxial reduction plate fixation for irreducible atlantoaxial dislocation.
OBJECTIVE: To design a clinically applicable transoralpharyngeal atlantoaxial reduction plate (TARP), introduce the operation procedure, and evaluate its preliminary clinical effects. METHODS: A novel TARP system, including butterfly titanium alloy plate, self-locking screws, atlantoaxial reductor and other operational instruments was developed. This system was applied clinically on five patients with irreducible atlantoaxial dislocation of congenital or traumatic origin. During operation, the reduction was completed by the combined action of the plate and the atlantoaxial reductor after transoral joint release and cord decompression. Bone graft granules were implanted between the bilateral atlantoaxial joints and TARP was used to immobilize subsequently the atlas and axis. RESULTS: Clinical application demonstrated that TARP could induce instant reduction and that the method was operationally feasible and its postoperational effect was satisfactory. CONCLUSIONS: The design of TARP is novel. The operational procedure is simple and easy to use. Furthermore, instant reduction can be completed during the operation and the fixation is relatively stable. TARP is an ideal alternative for irreducible atlantoaxial dislocation and may have excellent prospects for further clinical applications.
Adolescent↗
[Effect of long tubular bone fracture on serum levels of leptin, acute phase proteins and biochemical markers for organ functions].
OBJECTIVE: To investigate the effect of long tubular bone fracture (LTBF) on serum levels of leptin, acute phase proteins and biochemical markers for organ functions, and to look for the role of leptin in traumatic inflammatory responses. METHODS: Serum samples of LTBF patients and normal controls were collected, and immunoassays were used to determine serum levels of leptin and three acute phase proteins, including C-reactive protein (CRP), interleukin-1 (IL-1) and IL-2, and 21 biochemical markers for organ and metabolic functions were measured simultaneously with automatic biochemical analyzer. Correlation between leptin and all the markers was then analyzed. RESULTS: Compared with normal control, serum levels of leptin, CRP, IL-1 and IL-2 increased significantly (all P<0.05), with various degrees of changes in the markers for hepatic, cardiac, renal and metabolic functions. Leptin was independent to all the markers investigated, and it seemed to exert its unique roles. CONCLUSION: Leptin increases significantly in LTBF-induced acute traumatic inflammatory response, showing a comparatively strong responsiveness to the stimulation, and it may play a role as an anti-inflammatory cytokine.
Acute-Phase Proteins↗
[The value of dynamic color duplex scanning in the diagnosis of vascular erectile dysfunction].
OBJECTIVE: To evaluate deep penile arterial flow after an intracavernosal injection with prostaglandin E1 in patients with erectile dysfunction (ED). METHODS: 527 patients with ED were evaluated using Color Doppler Ultrasonography. Diagnostic tests were undertaken after an intracavernosal injection with 20 microg prostaglandin El. The peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI) were analysed. RESULTS: There were 112 patients (26.99%) with nonvasculogenic ED, 207 patients (49.88%) with arteriogenic ED, 144 patients (34.70%)with venogenic ED, 64 patients (15.42%)with mixed ED. CONCLUSION: The Color Doppler Ultrasonography technique allows accurate location and evaluation of deep penile arteries. Vascular pathology may be differentiated after an intracavernosal injection with a vasomotor agent. Recognising the pathological pattern assists in choosing the best method of treatment.
Adult↗
[Changes in serum leptin levels in patients with surgically induced stress responses].
OBJECTIVE: To explore the effect of operative trauma induced stress responses on serum leptin levels. METHODS: Serum samples of patients who had undergone resection of hepatic tumors or cholecystectomy were collected, and highly sensitive radioimmunoassay and enzyme-linked immunoadsorbent assay (ELISA) were used to determine serum levels of leptin, granulocyte-clone stimulating factor (G-CSF), C-reactive protein (CRP) and adrenocorticotropin hormone (ACTH) in the blood of these patients. RESULTS: Compared with self-control before operation, serum leptin levels decreased slightly right after an abdominal operation (T0), it reached the highest level 1 day after operation (T1), and began to decrease from 2 days (T2) to 4 days after operation (T4), but the level was still higher than that before operation. Serum leptin levels of patients undergoing laparoscopic operation showed no significant difference when compared with that of laparotomy patients. G-SF levels decreased significantly after operation in both groups, and didn't recover to the levels before operation from T1 to T4. CRP levels slightly decreased in both groups at T0, but increased significantly higher than the levels before operation from T1 to T4. ACTH levels of decreased significantly in laparotomy patients from T0 to T1, and began to recover on T2, while that of laparoscopic operation patients showed no significant difference before and after operation. CONCLUSION: Serum leptin levels of patients increase significantly and constantly subsequent to operative trauma induced stress responses, but this change has no correlation with that of CRP, G-SF and ACTH.
Adrenocorticotropic Hormone↗
Blastic natural killer (NK) cell leukemia (agranular CD4+CD56+ leukemia).
Blastic NK cell lymphoma is a rare hematolymphoid neoplasm. This report illustrates an unusual presentation of this entity, namely as a primary leukemia, but without skin lesions.
Aged, 80 and over↗
[Semantic extension to DICOM standard].
The Digital Imaging and Communications in Medicine (DICOM) Standard was developed by National Electrical Manufacturers Association (NEMA) and the American College of Radiology (ACR) for medical image archiving and communication. The Standard is widely used in medicine now. But it does not define image semantic content sufficiently, so there is a difficulty in the implementation based on semantic content. In this article are discussed the semantic hierarchy structure in medical image and the method to describe the image content used in the DICOM Standard. We point out the limitations of DICOM in image semantic content description, and then set forth a way to extend the semantic content description by using DICOM private attributes.
Computer Communication Networks↗
[Effect of intestinal ischemia/reperfusion injury on leptin and orexin-A levels].
OBJECTIVE: To explore the effect of intestinal ischemia/reperfusion (I/R) injury on leptin and orexin-A levels in peripheral blood and central secretory tissues, and investigate the roles of leptin and orexin-A in acute inflammatory responses. METHODS: An intestinal I/R injury rat model was established, and the rats were grouped according to duration of the reperfusion time following a 60-min ischemia. Radioimmunoassay was used to examine the protein levels of leptin in the serum and adipose tissue, and the protein levels of orexin-A in the plasma and hypothalamus. Reverse transcriptase-polymerase chain reaction was also performed to detect the mRNA expressions of adipose leptin and hypothalamus orexin-A. RESULTS: Compared with that before injury, serum leptin level of 60-min ischemia with 30-min reperfusion (I60'R30') group decreased significantly and that of I60'R360' increased significantly. Compared with the sham-operation group (sham) after injury, serum leptin level of I60'R360' group increased significantly, and adipose leptin protein levels of I60'R30' and I60'R90' groups decreased significantly, whereas that of I60'R360' group increased obviously. Compared with sham group after injury, adipose leptin mRNA expressions of I60'R30', I60'R240' and I60'R360' groups all increased significantly, while that of I60'R150' showed significant decrease. No significant changes were noted in the protein levels of orexin-A either in the plasma or hypothalamus after I/R injury. In comparison with sham group after injury, hypothalamus orexin-A mRNA expressions of I60'R30' and I60'R90' groups showed gradual but significant decrease, and till 150 min of reperfusion, the expression reached its lowest, followed then by slow recovery at 240 and 360 min, though still remaining significantly lower than that of sham group. CONCLUSION: Leptin and orexin-A have a time-dependent response to intestinal I/R injury, but the former appears to exhibit a faster response, and they may play a certain role in the metabolic disorders of acute inflammation.
Animals↗
[Water-soluble chloride in aerosol PM10 in Beijing].
Water-soluble chloride is one of the most important components in aerosols. The chloride in PM10 measured from January to December 2004 in Beijing was determined using a system by combing rapid collection of fine particles and ion chromatography (RCFP-IC). The results showed that the annual average concentration of water-soluble chloride at the urban area in Beijing was about (3.1 +/- 1.7) microg x m(-3); the average concentration of chloride during the heating period was (4.6 +/- 2.1) microg m(-3) while it was (2.6 +/- 1.6) microg x m(-3) during the period no heating. The lowest concentration of (1.3 +/- 0.8) microg x m(-3) appeared in May, and the highest concentration appeared of (5.8 +/- 5.3) microg x m(-3) in December. Trends of the diurnal variation of water-soluble chloride depended on seasons. In autumn and winter, the higher concentration appeared in the daytime and the lower concentration appeared at night. In spring and summer, the higher concentration appeared at forenoon and the lower appeared at afternoon. Overall, the concentration of chloride in autumn and winter was higher than in spring and summer.
Aerosols↗
[Effect of intestinal ischemia/reperfusion injury on protein and mRNA levels of orexin-A].
OBJECTIVE: To investigate the effect of intestinal ischemia/reperfusion (I/R) injury on orexin-A levels in plasma and hypothalamus, and to find out the role of orexin-A in acute inflammatory responses. METHODS: Fifty-four SD rats were randomly divided into a sham-operation group and 5 experiment groups. Then we established the intestinal I/R injury model of rats and setup the 5 experiment groups of 60 min ischemia followed by different periods of time for reperfusion. Protein levels of orexin-A in plasma and hypothalamus were measured by radioimmunoassay, and the changes of orexin-A mRNA expression in hypothalamus were detected by RT-PCR. RESULTS: By analyses on the orexin-A levels in plasma of rats before and after injury, no significant change was observed in the 5 experiment groups (P > 0.05), and the 5 groups' post-injury orexin-A levels in plasma and hypothalamus were not significantly different from the sham-operation group's (P > 0.05). However, by comparison with the sham-operation group after injury, the experiment groups were found to have orexin-A mRNA levels in hypothalamus significantly decreased step by step from 60 min ishchemia/30 min reperfusion (160' R30') to 160'R150'; the lowest level was seen at 160'R150'; and at 160'R240' and I60'R360', the level recovered slowly, but it was still lower than that seen in the sham-operation group. CONCLUSION: Orexin-A makes a delayed response to intestinal I/R injury and may function as inflammatory cytokine in the metabolic disorders caused by acute inflammation.
Animals↗
[Whole rehabilitation: a new goal of erectile dysfunction therapy].
Phosphodiesterase type 5 (PDE5) inhibitors effectively enhance the erectile function of the patients with erectile dysfunction (ED). The use of sildenafil citrate is expanding to a broader extent. Pulmonary artery hypertension has become a new indication of sildenafil. Sildenafil could improve the epithelial function in several vascular conditions in clinical trials. This article reviews the recent advances on basic and clinical studies of ED and sildenafil. On animal models, sildenafil could resume the cavernous epithelial function, up-regulate the protein expression of phosphorylated endothelial NO synthase (eNOS), reverse the decreased intracavernosal pressure (ICP) induced by pudendal artery blood flow restriction or hypoxia. In clinical studies, over 50% of ED patients receiving sildenafil got a fully rigid erection (grade 4 erection). And the same percentage of post-nerve-sparing radical prostatectomy patients receiving sildenafil obtained penile rehabilitation and spontaneously resumed erection sufficient for sexual intercourse. Sildenafil treatment has contributed to the normalization of self-esteem, confidence and sexual harmony in men with ED. All this suggests that a whole rehabilitation from erectile to psychosocial function may become a new goal of ED therapy.
Animals↗
[Leptin protects sepsis-induced renal injury and research for its mechanism].
OBJECTIVE: To detect the effect of sepsis on renal function and corresponding enzymes in mice, and to explore the role of leptin in acute inflammation. METHODS: Sepsis was reproduced by cecum ligation and puncture in mice. Serum uric acid (UA) and four enzymes related with synthesis of free radicals in kidney homogenized fluids, myeloperoxidase (MPO), glutathione-S-transferase (GST), xanthine oxidase (XOD) and superoxide dismutase (SOD) were determined with spectrophotometry, and leptin level in kidney was detected by radioimmunoassay. Histopathologic changes in kidney were observed with hematoxylin-eosin staining. RESULTS: Twelve hours after leptin (0.08 mg/kg, i.p.) and indomethacin (8 mg/kg, i.p.) injection, serum UA was significantly decreased [(295.79+/-80.86) micromol/L and (281.78+/-46.35) micromol/L, respectively, vs. sepsis group (474.03+/-75.22) micromol/L]. At the same time, renal leptin levels in leptin injection group [(196.00+/-134.30) microg/g] 12 hours after sepsis and in indomethacin injection group [(169.30+/-132.00) microg/g] 6 hours after sepsis were also significantly higher than sepsis group [(61.65+/-27.29) microg/g]. Six and 12 hours after leptin and indomethacin injection, renal MPO, GST, XOD and SOD activities were affected to certain extent, as the results were not completely inhibited or enhanced. Nevertheless, leptin and indomethacin could promote scavenge and deactivation of free radicals. CONCLUSION: Low dose leptin can ameliorate sepsis-induced renal injury, which may be related with scavenge and deactivation of free radicals in renal cells, and this mechanism is similar with that of indomethacin.
Animals↗