Biomedical subjects

Kai Zhang

Publications and source records attributed to Kai Zhang.

At least 91 records · Page 5Linked to original sources

PubMed2004

[Sigma rectum pouch for urinary diversion].

OBJECTIVE: To investigate the clinical outcome of sigma rectum pouch as a continent form of urinary diversion. METHODS: The clinical data of 38 patients, 32 males and 7 females, aged 53.2 (42 - 68) with muscle-invading bladder carcinoma who underwent a Mainz pouch II procedure after radical cystectomy 1996 - 2001 were analyzed. The intestine was incised over a length of 20 - 24 cm with the junction of sigmoid colon and rectum as the midpoint so as to create a low-pressure reservoir for urine and side-to-side anastomosis was performed on the posterior borders of the rectosigmoid wall. Submucosal tunnel technique was employed in antireflux urethral implantation. The patients were followed up for 7 - 60 months with a mean of 30 months postoperatively. RESULTS: Continence has been achieved in all the 38 patients with a micturition frequency of 3 - 5 times during daytime and 0 - 3 times at night. The mean volume of pouch was 515.6 ml (400 - 650 ml). The basal intra-reservoir pressure was 8 - 23 cm H(2)O (mean 16.5 cm H(2)O, 1 cm H(2)O = 0.098 kPa), the highest peak pressure was 12 - 33 cm H(2)O (mean 21.3 cm H(2)O). CONCLUSION: A modified sigmoid rectal pouch procedure provides a reservoir with a higher capacity and lower pressure without a reflux to the upper urinary tract and descending colon with lower incidence of complication, it is also a better alternative diversion procedure that would be easily accepted by surgeons and patients.

Adult↗

PubMed2004

[Design and preliminary clinical application of transoralpharyngeal atlantoaxial reduction plate].

OBJECTIVE: To design transoralpharyngeal atlantoaxial reduction plate (TARP), evaluate its biomechanical performance and observe its preliminary clinical effect. METHODS: A brand-new TARP system was designed, including butterfly titanium alloy plate, self-locking screws, atlantoaxial reductor and other operation instruments. Twelve fresh occipital bone-C(3) specimen were designed for biomechanical test including range of motion (ROM) (n = 6) and screw pull-out strength (n = 12). Preliminary clinical application of TARP was reported. RESULTS: The reduction mechanism of the TARP system was designed cleverly. TARP had equal effect with Magerl + Brooks and it was more stable than the other three clinically widely used atlantoaxial fixators: Magerl, Brooks and anterior transarticular screw fixation through C(2) vertebral body. TARP's C(1) and C(2) screws were strong enough for atlantoaxial arthrodesis and their antipull-out performance was excellent. Clinical application on irreducible atlantoaxial dislocation proved that TARP had the function of instant reduction, the operation was feasible and the operation effect was significant. CONCLUSION: TARP's design is novel and it has excellent biomechanical performance. The operation procedure is simple and reasonable. Furthermore, instant reduction could be completed during the operation and the fixation is strong. Above all, TARP is creative and will have excellent prospect.

Adolescent↗

PubMed2004

GC-MS determination of flavonoids and phenolic and benzoic acids in human plasma after consumption of cranberry juice.

A GC-MS method was developed for the determination of various flavonoids and phenolic and benzoic acids in human plasma. The procedure involved the extraction of flavonoids and phenolic and benzoic acids with ethyl acetate, followed by the derivatization of the phenolic and benzoic compounds with BSTFA (N,O-bis(trimethylsilyl) trifluoroacetamide) + TMCS (trimethylchlorosilane) reagent. The trimethylsilyl derivatives formed were separated and quantitated using GC-MS. Twenty flavonoids and phenolic and benzoic compounds have been well separated in the spiked human plasma without any interference. The average recovery was 79.3%. Several phenolic acids such as o-hydroxybenzoic, p-hydroxyphenylacetic, 2,3-dihydroxybenzoic, 2,4-dihydroxybenzoic, ferulic, sinapic, and benzoic acid were identified and quantified in human plasma after consumption of a cranberry juice. This developed method provides a simple, specific, and sensitive technique for the simultaneous determination of flavonoids and phenolic and benzoic acids in human plasma and is suitable for bioavailability and pharmacokinetic studies.

Benzoates↗

PubMed2004

Processing and properties of porous poly(L-lactide)/bioactive glass composites.

Porous poly(L-lactide)/bioactive glass (PLLA/BG) composites were prepared by phase separation of polymer solutions containing bioactive glass particles (average particle size: 1.5 microm). The composite microstructures consist of a porous PLLA matrix with glass particles distributed homogeneously throughout. Large pores (>100 microm) are present in a network of smaller (<10 microm) interconnected pores. The porous microstructure of the composites was not significantly influenced by glass content (9 or 29 vol%), but silane pretreatment of the glass resulted in better glass incorporation in the matrix. Mechanical tests showed that an increase in glass content increased the elastic modulus of the composites, but decreased their tensile strength and break strain. Silane pretreatment enhanced the increase in modulus and prevented the decrease in tensile strength with increasing glass content. Composites soaked in simulated body fluid (SBF) at body temperature formed bone-like apatite inside and on their surfaces. The silane pretreatment of glass particles delayed the in vitro apatite formation. This bone-like apatite formation demonstrates the composites' potential for integration with bone.

Biocompatible Materials↗

PubMed2004

Temperature and pH-responsive polymeric composite membranes for controlled delivery of proteins and peptides.

This work was focused on the investigation of temperature and pH-responsive polymeric composite membranes and their permeability to proteins and peptides in response to environmental stimuli. The composite membranes were prepared from nanoparticles of poly(N-isopropylacrylamide-co-methacrylic acid) of various NIPAAm:MAA ratios dispersed in a matrix of a hydrophobic polymer. N-Benzoyl-L-tyrosine ethyl ester HCl, momany peptide, Leuprolide, vitamin B(12), insulin, and lysozyme were used as model solutes. The morphology of the membranes was examined with SEM and permeation of the solutes was measured using side-by-side diffusion cells at varied temperatures and pH. Permeability of the solutes across the membranes increased with increasing temperature or particle concentration, while decreased with increasing pH and molecular size of the solutes. Membranes containing nanoparticles of more NIPAAm units exhibited higher thermal sensitivity, and those with higher MAA content showed more pH responsiveness, which was in line with the temperature and pH-responsive volume change of the nanoparticles. The change in permeability was quickly detected following the application of the stimuli. These results and partition study using vitamin B(12) supported the proposed gel-pore mechanism of solute permeation through these composite membranes.

Acrylamides↗

PubMed2004

The LPG1 gene family of Leishmania major.

In Leishmania major, the core of the abundant surface lipophosphoglycan (LPG) is structurally related to that of the smaller glycosylinositolphospholipids (GIPLs) in containing galactosylfuranose (Gal(f)) residues in a Gal(f) (beta1, 3)Man motif. However, deletion of the putative Gal(f)-transferase (Gal(f)T) LPG1 affected Gal(f) incorporation in LPG but not GIPLs. We hypothesized that the presumptive GIPL Gal(f)-transferases could be homologous to LPG1, and identified three related genes in the L. major genome. These were termed LPG1L, LPG1R, and LPG1G, the latter of which was found in three identical copies located at the telomeres of chromosomes 5, 19, and 32 based on Leishmania genome project data. Neither LPG1 nor its homologues LPG1L and LPG1R were involved in the biosynthesis of GIPLs, as an lpg1(-)/lpg1l(-)/lpg1r(-) triple knockout (the first such in Leishmania) grew normally and made wild-type levels of Gal(f) -containing GIPLs. In contrast, overexpression of these three led to elevated galactose incorporation in glycoproteins. Gal(f)-containing glycoproteins had not been described in Leishmania but occur at high levels in other closely related trypanosomatids including Trypanosoma cruzi, Crithidia, Leptomonas, and Endotrypanum, and LPG1L and LPG1R homologs were detected in these species. These data suggest that the glyco-synthetic capabilities of Leishmania and perhaps other trypanosomatids may be larger than previously thought, with some activities being 'cryptic' in different lineages and potentially serving as reservoirs for glycoconjugate variation during evolution. Future tests will address whether the LPG1G family encodes the hypothesized GIPL-specific Gal(f)T.

Amino Acid Sequence↗

PubMed2004

Leptin fluctuates in intestinal ischemia-reperfusion injury as inflammatory cytokine.

As leptin is an active mediator mainly secreted by adipose tissue and is closely related with energy metabolism, we evaluate both the changes of leptin levels in serum and adipose tissue with a concise radioimmunoassay and the changes of leptin mRNA expression in adipose tissue with RT-PCR, during the severe metabolic impediment in rat intestinal ischemia-reperfusion (I/R) injury. Results show that not only leptin levels in serum and adipose tissue but also its mRNA expression in adipose tissue undergo a fluctuation according to different injury times. Therefore, we conclude that leptin has a time-dependent response to acute inflammatory stimuli and acts as an anti-inflammatory cytokine.

Adipose Tissue↗

PubMed2004

Establishment and primary application of a highly-sensitive orexin-A radioimmunoassay.

Orexin-A was labeled by 125I using the chloramine-T method, and was purified with a Sephadex G-25 chromatographic column. The reaction between antigen and antibody was carried out by a one-step balance method and was incubated at 4 degrees C for 24 hours, then bonded and free antigen were separated by PR reagent. The detection range of this RIA is 21-2000 pg/mL; the lowest detection level is 21 pg/mL. The intra-assay and inter-assay variations were 7.8% and 9.7%, respectively. Plasma orexin-A levels of 30 normal individuals and 30 patients with hyperlipidemia (serum triglyceride > 1.7 mmol/L and serum total cholesterol > 5.7 mmol/L) were detected by this RIA, while orexin-A levels of plasma and hypothalamus in rat intestinal ischemia-reperfusion injury model were also measured. Plasma orexin-A levels of normal individuals was 338.48 +/- 20.24 pg/mL, while those of patients with hyperlipidemia were 343.51 +/- 15.49 pg/mL; there were no significant differences between these two groups t = -0.1976; P = 0.8441. We also found that orexin-A levels of rat plasma and hypothalamus did not express a significant change during the early stages of intestinal ischemia-reperfusion injury. These results have shown that this orexin-A radioimmunoassay is stable, simple, and specific, being sensitive enough to test orexin-A levels in human plasma, rat plasma, and hypothalamus.

Animals↗

PubMed2004

On the stability of insulin delivered through a new glucose-responsive polymeric composite membrane.

A new glucose-responsive polymeric composite membrane that provided pulsatile insulin release was developed in our laboratory previously. To develop a clinically useful insulin delivery system, this study was designed to investigate factors influencing insulin stability during delivery by this membrane. The effects of stirring, release duration, insulin concentration and surfactant on insulin stability were studied under both incubation and delivery conditions in a buffer solution at 37 degrees C. The structural change of insulin was characterized by reverse-phase HPLC and circular dichroism. Hydrophobicity of various contact surfaces was determined by contact angle measurement. The results indicated that insulin concentration played an important role in the insulin stability, followed by stirring. Treating the membrane with a non-ionic surfactant prevented insulin denaturation during delivery through the membrane.

Acrylamides↗

PubMed2004

Plasmablastic lymphoma of the cervical lymph nodes in a human immunodeficiency virus-negative patient: a case report and review of the literature.

We report a case of plasmablastic lymphoma presenting in cervical lymph nodes in an 82-year-old, human immunodeficiency virus-negative man. Cytologic and histologic examinations demonstrated a large cell lymphoma with plasmacytic differentiation. The tumor cells were positive for CD138, CD38, epithelial membrane antigen, CD30, and lysozyme, but lacked expression of leukocyte common antigen, T-cell, and B-cell markers. Abundant Epstein-Barr virus-encoded RNA transcripts were identified by in situ hybridization. A monoclonal rearrangement of kappa-light- chain gene was demonstrated. The cytologic, histologic, immunohistochemical, and molecular features of plasmablastic lymphoma are reviewed. The potential diagnostic pitfalls and differential diagnoses, especially in a fine-needle aspiration specimen, are addressed.

Aged↗

PubMed2004

[Gene expression changes of cartilage matrix of condylar cartilage with anterior disc displacement].

OBJECTIVE: To study the gene expression changes in extracellular matrix of condylar cartilage following disc anterior displacement of rabbit TMJ. METHODS: The right sides of 28 joints in 40 rabbits were subjected to surgical operation of disc displacement. The condylar Collagen II and Aggrecan mRNA expression were detected by in situ hybridization. RESULTS: Collagen II and Aggrecan mRNA mainly expressed in the lower zone of condylar chondrocyte. Aggrecan mRNA decreased faster than collagen II following disc displacement, and adjusted to normal later. CONCLUSION: Anterior disc displacement leads to alteration of extracellurar matrix gene expression in the condylar chondrocyte, which means the start of remodeling.

Aggrecans↗

PubMed2004

[Effect of intestinal ischemia/reperfusion injury on protein and mRNA levels of Leptin in rats].

OBJECTIVE: To investigate the effect of intestinal ischemia/reperfusion injury on Leptin levels in serum and adipose tissue, and evaluate the potential role of Leptin in acute inflammatory response. METHODS: An intestinal ischemia/reperfusion injury model of rats was reproduced. Serum and adipose tissue Leptin concentrations and Leptin mRNA expression in adipose tissue were determined by a highly-sensitive murine Leptin radioimmunoassay and reverse transcription-polymerase chain reaction (RT-PCR), respectively. RESULTS: Compared with animals prior to injury, serum Leptin level decreased significantly in ischemia for 60 minutes followed by reperfusion for 30 minutes (I60R30), but it tended to increase in I60R150 and significantly increased in I60R360. Compared with sham group, serum Leptin level tended to increase in I60R240 and elevated significantly in I60R360; Leptin levels in adipose tissue significantly decreased in I60R30 and I60R90, while they increased significantly in I60R360. Compared with sham group, Leptin mRNA levels elevated significantly in I60R30, I60R240 and I60R360, but lowered significantly in I60R150. CONCLUSION: Leptin has a time-dependent response to acute inflammatory stimuli such as intestinal ischemia/reperfusion injury, and it migh play a role as an inflammatory cytokine.

Adipose Tissue↗

PubMed2003

Sphingolipids are essential for differentiation but not growth in Leishmania.

Sphingolipids (SLs) play critical roles in eukaryotic cells in the formation of lipid rafts, membrane trafficking, and signal transduction. Here we created a SL null mutant in the protozoan parasite Leishmania major through targeted deletion of the key de novo biosynthetic enzyme serine palmitoyltransferase subunit 2 (SPT2). Although SLs are typically essential, spt2- Leishmania were viable, yet were completely deficient in de novo sphingolipid synthesis, and lacked inositol phosphorylceramides and other SLs. Remarkably, spt2- parasites maintained 'lipid rafts' as defined by Triton X-100 detergent resistant membrane formation. Upon entry to stationary phase spt2- failed to differentiate to infective metacyclic parasites and died instead. Death occurred not by apoptosis or changes in metacyclic gene expression, but from catastrophic problems leading to accumulation of small vesicles characteristic of the multivesicular body/multivesicular tubule network. Stage specificity may reflect changes in membrane structure as well as elevated demands in vesicular trafficking required for parasite remodeling during differentiation. We suggest that SL-deficient Leishmania provide a useful biological setting for tests of essential SL enzymes in other organisms where SL perturbation is lethal.

Acyltransferases↗

PubMed2003

Photoreceptor cGMP phosphodiesterase delta subunit (PDEdelta) functions as a prenyl-binding protein.

Bovine PDEdelta was originally copurified with rod cGMP phosphodiesterase (PDE) and shown to interact with prenylated, carboxymethylated C-terminal Cys residues. Other studies showed that PDEdelta can interact with several small GTPases including Rab13, Ras, Rap, and Rho6, all of which are prenylated, as well as the N-terminal portion of retinitis pigmentosa GTPase regulator and Arl2/Arl3, which are not prenylated. We show by immunocytochemistry with a PDEdelta-specific antibody that PDEdelta is present in rods and cones. We find by yeast two-hybrid screening with a PDEdelta bait that it can interact with farnesylated rhodopsin kinase (GRK1) and that prenylation is essential for this interaction. In vitro binding assays indicate that both recombinant farnesylated GRK1 and geranylgeranylated GRK7 co-precipitate with a glutathione S-transferase-PDEdelta fusion protein. Using fluorescence resonance energy transfer techniques exploiting the intrinsic tryptophan fluorescence of PDEdelta and dansylated prenyl cysteines as fluorescent ligands, we show that PDEdelta specifically binds geranylgeranyl and farnesyl moieties with a Kd of 19.06 and 0.70 microm, respectively. Our experiments establish that PDEdelta functions as a prenyl-binding protein interacting with multiple prenylated proteins.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2003

Effects of materials parameters on mineralization and degradation of sol-gel bioactive glasses with 3D-ordered macroporous structures.

Bioactive glasses (BGs) with three-dimensionally ordered macroporous (3DOM) structures were prepared by combining a sol-gel synthesis with colloidal crystal templating. 3DOM sol-gel BGs with two compositions (20 mol % CaO-80% SiO2 and 20 mol % CaO-4% P2O5-76% SiO2) and three macropore sizes (average: 345, 440, and 790 nm) were prepared. Glasses were separated into two particle sizes (212 microm< small < 355 microm and 600 microm < large < 1000 microm). The glasses were soaked in simulated body fluid at 37 degrees C for 2 or 4 days and the effects of composition, particle size, and macropore size on the formation of apatite and glass degradation were characterized. Within the parameter range of the experiments, several comparisons could be made. First, the formation of apatite and degradation of the glass were slightly enhanced for the phosphate containing composition. Second, large particles formed less apatite and degraded less completely compared with small particles. Lastly, an increase in macropore size slowed down the glass degradation and apatite formation processes, an effect related to the decreased internal surface area of the larger pore materials.

Gels↗

PubMed2003

Effects of single and repeated prolonged stress on mu-opioid receptor mRNA expression in rat gross hypothalamic and midbrain homogenates.

This study tested the hypothesis that stress-induced opioid peptides may have stimulative and inhibitive influence on mu opioid receptor (MOR) mRNA expression and hypothalamus. Several studies have investigated the effects of stress on MOR mRNA expression in rat brain, but almost none compared the response to single versus repeated stresses. Here, we examined the effects of single and repeated stress on MOR mRNA expression in different rat brain regions using reverse transcriptase-polymerase chain reaction (RT-PCR). Following a single episode of restraint stress for 4 h (1R) or 4 h per day on 2 (2R) or 3 (3R) consecutive days, the hypothalamus and midbrain were removed immediately and MOR mRNA levels in both regions were determined by RT-PCR. Blood samples were also collected for simultaneous measurement of serum adrenocorticotropic hormone (ACTH) and corticosterone (CS). MOR mRNA expression was significantly higher in both regions in the 2R group, whereas expression levels in the 3R group did not differ from controls. In the 1R group, hypothalamic MOR expression was equivalent to that in controls, but expression was significantly higher in the midbrain. Serum ACTH levels were significantly higher only in the 1R group, whereas serum CS was significantly higher in both the 1R and 3R groups. Our findings indicate that the influence of restraint stress on MOR mRNA expression in the hypothalamus is different than in the midbrain region in rats. Endogenous opioid peptides released in response to stress may paradoxically have an effect on the HPA axis.

Animals↗

PubMed2003

Increased expression of corticotropin-releasing factor receptor mRNA in the locus coeruleus of stress-induced rat model of depression.

Hypersecretion of corticotropin-releasing factor (CRF) has been hypothesized to occur in depression. To investigate CRF receptor (CRFR) response to the increased production of CRF in chronically stressed rats, we measured by in situ hybridization the expression of CRFR mRNA in the locus coeruleus (LC) concomitant with measuring plasma adrenocorticotropin (ACTH). The expression of both CRFR mRNA in the LC and the plasma level of ACTH increased significantly in "depression-model rats" which exhibit reduced activity following exposure to 14 days forced walking stress (FWS), but not in "spontaneous recovery rats" whose activity was restored after the long-term stress. These results suggest that the LC neurons continue to be stimulated by CRF, and that the hypothalamic-pituitary-adrenal (HPA) axis is hyperfunctioning in the depression-model rats.

Adrenocorticotropic Hormone↗

PubMed2003

Conjugation of chlorambucil with GSH by GST purified from human colon adenocarcinoma cells and its inhibition by plant polyphenols.

Chlorambucil (CMB) combines with glutathione (GSH) spontaneously in vitro to form monochloromonoglutathionyl CMB (MG-CMB). This was identified and quantified by an HPLC-UV method. Glutathione S-transferase (GST) purified from human colon adenocarcinoma cells increased the formation of the conjugate significantly. The GST-mediated conjugation, represented by the difference between total and spontaneous conjugation showed Michaelis-Menten kinetics with apparent Km and Vmax values of 0.2 mM and 75.8 nmol/min/mg for CMB and 5.2 mM and 127.0 nmol/min/mg for GSH respectively. Unexpectedly, we found in our study that both the spontaneous and the enzymatic conjugation of chlorambucil with GSH were affected markedly by a change in pH from 6.0 to 8.0. The optimum for the enzymatic conjugation was about 7.0, above which the spontaneous conjugation increased rapidly, while the enzymatic conjugation became lower. The plant polyphenols namely tannic acid, butein, quercetin, morin, 2-hydroxychalcone and 2'-hydroxychalcone at 40 microM inhibited the GST-mediated conjugation of CMB with GSH by 38 to 62%. Their action in this respect may contribute to sensitisation of tumour cells to anticancer drugs.

Adenocarcinoma↗