Biomedical subjects

X C Zhou

Publications and source records attributed to X C Zhou.

13 recordsLinked to original sources

PubMed2001

Microgravimetric DNA sensor based on quartz crystal microbalance: comparison of oligonucleotide immobilization methods and the application in genetic diagnosis.

We report on the study of immobilization DNA probes onto quartz crystal oscillators by self-assembly technique to form variety types of mono- and multi-layered sensing films towards the realization of DNA diagnostic devices. A 18-mer DNA probe complementary to the site of genetic beta-thalassaemia mutations was immobilized on the electrodes of QCM by covalent bonding or electrostatic adsorption on polyelectrolyte films to form mono- or multi-layered sensing films by self-assembled process. Hybridization was induced by exposure of the QCMs immobilized with DNA probe to a test solution containing the target nucleic acid sequences. The kinetics of DNA probe immobilization and hybridization with the fabricated DNA sensors were studied via in-situ frequency changes. The characteristics of QCM sensors containing mono- or multi-layered DNA probe constructed by direct chemical bonding, avidin-biotin interaction or electrostatic adsorption on polyelectrolyte films were compared. Results indicated that the DNA sensing films fabricated by immobilization of biotinylated DNA probe to avidin provide fast sensor response and high hybridization efficiencies. The effects of ionic strength of the buffer solution and the concentration of target nucleic acid used in hybridization were also studied. The fabricated DNA biosensor was used to detect a set of real samples. We conclude that the microgravimetric DNA sensor with its direct detection of amplified products provide a rapid, low cost and convenient diagnostic method for genetic disease.

Biosensing Techniques↗

PubMed2001

The Peutz-Jegher gene product LKB1 is a mediator of p53-dependent cell death.

Here, we investigate the mechanism and function of LKB1, a Ser/Thr kinase mutated in Peutz-Jegher syndrome (PJS). We demonstrate that LKB1 physically associates with p53 and regulates specific p53-dependent apoptosis pathways. LKB1 protein is present in both the cytoplasm and nucleus of living cells and translocates to mitochondria during apoptosis. In vivo, LKB1 is highly upregulated in pyknotic intestinal epithelial cells. In contrast, polyps arising in Peutz-Jegher patients are devoid of LKB1 staining and have reduced numbers of apoptotic cells. We propose that a deficiency in apoptosis is a key factor in the formation of multiple benign intestinal polyps in PJS patients, and possibly for the subsequent development of malignant tumors in these patients.

AMP-Activated Protein Kinase Kinases↗

PubMed2001

Enantioselective sensor based on microgravimetric quartz crystal microbalance with molecularly imprinted polymer film.

We report a novel quartz crystal microbalance sensor that provides enantioselectivity to dansylphenylalanine enantiomers by using a molecularly imprinted polymer film as a recognition element. The polymeric recognition thin film, imprinted with chiral dansyl-L-phenylalanine, was immobilised on a gold electrode modified with a photoactive precursor monolayer via a self-assembly process using photopolymerization. The fabricated sensor was able to discriminate between L- and D-dansylphenylalanine enantiomers in solution owing to the enantioselectivity of the imprinted sites. The enantiomeric composition of L- and D-enantiomeric mixtures could be quantitatively determined by the fabricated sensor. The detection limit is 5 micrograms mL-1 with a response range of 5-500 micrograms mL-1 at pH 10.0. The influence of the template concentration on the sensitivity and selectivity of the synthesised polymer membranes was investigated and optimised. The surface characteristics of the polymer coating were studied by varying the pH value of the buffer solution, and a convenient regeneration process was proposed to increase the reproducibility and reusability of the sensor by flushing with pH 2.0 buffer. The selectivity and recognition mechanism of the imprinted polymer film were studied with compounds that are structurally related to the template. The method presented in this work provides a novel means of preparing highly selective and sensitive chemical sensors via self-assembly and molecularly imprinting techniques.

Journal Article↗

PubMed2001

High sensitivity microgravimetric biosensor for qualitative and quantitative diagnostic detection of polychlorinated dibenzo-p-dioxins.

A piezoelectric immunosensor system was developed for the rapid detection of polychlorinated dibenzo-p-dioxins (PCDDs). The system uses a competitive inhibition enzyme immunoassay (EIA) based on a mouse monoclonal antibody that is specific for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and a conjugate of a dioxin-like competitor coupled to the enzyme horseradish peroxidase (HRP). The anti-dioxin antibody was deposited on a 10 MHz AT-cut quartz crystal resonator modified with a self-assembly monolayer of dithiobis-N-succinimidyl propionate. PCDDs at different concentrations in the range 0.001-10 ng mL-1 were mixed with a constant amount of HRP-conjugated competitor. The frequency responses due to the adsorption of the mixed samples on the biosensor surface were measured. The results show that 2,3,7,8-TCDD can be quantitatively detected with the developed immunosensor in the concentration range 0.01-1.3 ng mL-1. Cross-reactivities of the biosensor to various PCDD congeners were also investigated. The sensitivity and selectivity of the quartz crystal microbalance (QCM) biosensor is comparable to EIA and ELISA methods in the detection of polychlorinated dibenzo-p-dioxins. The developed QCM immunosensing system offers significant improvements in speed, sample throughout and cost for the qualitative and quantitative detection of PCDDs compared with GC-MS.

Journal Article↗

PubMed2001

Expression of Hsp70-2 in unilateral cryptorchid testis of rhesus monkey during germ cell apoptosis.

We investigated the possible role of Hsp70-2 in germ cell apoptosis induced by heat stress in monkey unilateral cryptorchid testis. The study focused on in situ analysis of the testicular cell DNA fragmentation and on the possible relationship between Hsp70-2 expression and germ cell apoptosis. The TUNEL result showed that most of the germ cells were labeled in the cryptorchid testis on d 5 after induction of cryptorchidism; that with most of the apoptotic germ cells depleted, only a few germ cells were labeled on d 10; and that almost no apoptotic signal was observed in the cryptorchid testis on d 15 and thereafter. This indicates that the increasing germ cell degeneration in cryptorchid testis may take the form of apoptosis. Using in situ hybridization, immunohistochemistry, and Northern blot, we examined the changes of Hsp70-2 expression in the monkey cryptorchid testis. The level of Hsp70-2 mRNA decreased slightly, while the expression of HSP70-2 protein was almost unchanged at the early stage of germ cell apoptosis in the cryptorchid testis on d 5 and dropped dramatically along with the loss of apoptotic germ cells in the cryptorchid testis on d 10 after operation. It is therefore suggested that Hsp70-2 might not take part in inhibiting the apoptosis of germ cells at the early stage during operation-induced cryptorchid testis, and that Hsp70-2 gene does not belong to the immediate early related gene responsible for germ cell apoptosis induced by heat stress.

Animals↗

PubMed2001

Mifepristone regulates expression of apoptosis related genes Fas and FasL in mouse endometrium.

AIM: To investigate the anti-implantation mechanism of mifepriston. METHODS: In situ hybridization and immunohistochemistry were applied to determine mRNA and protein. RESULTS: After mifepriston injection, the number of implantation sites were obviously reduced, mifepriston could inhibit the embryo implantation in mouse. The expression of apoptosis related genes, Fas and FasL, in mouse endometrium was also decreased after mifepriston treatment. CONCLUSION: The expression of apoptosis related genes Fas and FasL is regulated by mifepriston and the inhibitory effect of mifepriston on the embryo implantation may be mediated by action on the Fas/FasL system.

Abortifacient Agents, Steroidal↗

PubMed2001

Role of Fas/FasL genes in azoospermia or oligozoospermia induced by testosterone undecanoate in rhesus monkey.

AIM: To investigate role of apoptosis related genes Fas/FasL in azoospermia or oligozoospermia induced by testosterone undecanoate. METHODS: TUNEL was used to detect the apoptotic signal of testicular cells. Immunohistochemistry and Western blot were used to quantitatively or qualitatively analyze the expression of these apoptosis-related proteins. RESULTS: After injection of testosterone undecanoate, both the apoptotic signal in germ cells and the expression of Fas/FasL in testis increased correlatively in a time-dependent manner, reaching a maximum level on day 30. CONCLUSION: Fas system may initiate and regulate the germ cell apoptosis induced by testosterone undecanoate.

Animals↗

PubMed1998

The bis-azo compound FP-21399 inhibits HIV-1 replication by preventing viral entry.

The bis-azo compound FP-21399 inhibits HIV-1 infection. We now show that FP-21399 acts on the HIV-1 envelope glycoprotein to prevent viral replication. This compound targets the entry step of the HIV-1 replication cycle as demonstrated by time-of-addition and single cycle viral entry assays. The entry of SIVmac239, which uses the same coreceptors (CD4/CCR5) as HIV-1, was not inhibited by FP-21399, indicating that the antiviral effect of FP-21399 is specific for the HIV-1 envelope glycoprotein and is not dependent upon the cellular receptors CD4 and CCR5. FP-21399 inhibits neither the activity of HIV-1 reverse transcriptase nor the expression of HIV-1 early mRNA. Finally, this compound inhibits gp120 shedding of the T-tropic virus. Our results suggest that the anti-HIV activity of FP-21399 is due to its interaction with HIV-1 gp120/41 complex during viral entry.

Animals↗

PubMed1995

Experience with repair of hypospadias using bladder mucosa in adolescents and adults.

From July 1984 to January 1994, 113 hypospadias operations were performed using a free bladder mucosa graft. There were 31 primary cases and 82 secondary cases in which prior operations had been done. The meatus was penile in 33 patients, penoscrotal in 72 and perineal in 8. The cosmetic and functional results were satisfactory. Postoperative complications included 8 fistulas that required closure and 6 cases of stenosis treated by dilation. Our results suggest that hypospadias repair with a bladder mucosa graft is feasible and reliable. The technique has been performed successfully in the most complex as well as simple cases in adults and adolescents.

Adolescent↗

PubMed1994

Effect of the extracts of pumpkin seeds on the urodynamics of rabbits: an experimental study.

Pumpkin seeds were prepared into oil n-butyle alcohol and ether extracts. The effects of the three extracts on the urodynamics of rabbits were observed. It was concluded that the oil preparation could remarkably reduce the bladder pressure, increase the bladder compliance, reduce the urethral pressure. Other two kinds of preparations had no effect in this experimental. The mechanisms of the effect of oil preparation on the urodynamics and the prospect of clinical use was discussed.

Animals↗

PubMed1994

The relationship between the energy levels of shock waves and the degree of renal damage after ESWL: a prospective clinical matching trail.

In an attempt to understand the effects of high energy shock wave (HESW) on renal function, we studied prospectively 40 patients with nephrolithiasis in 4 groups, using same voltage with different numbers of shock wave therapy to identify the difference of effects on renal function. Stone burdens and position were similar in these groups. Each group received 1500, 2000, 2500 or 3000 pulses at 12.5 KV on JT-3 lithotripotor respectively. All the groups had significantly increased the levels of urinary NAG, beta 2MG, ALB and serum beta 2MG, which reached the highest values on 1-3 days after ESWL (P < 0.001), and then decreased to the pre-ESWL levels except urinary NAG in group C and D and serum beta 2MG which were still significantly higher (P < 0.05) than those before-ESWL on the 7th day after ESWL. There was significant correlation between either urinary NAG (gamma = 0.977, P < 0.05) or beta 2MG (gamma = 0.933, P < 0.001) with the number of shock wave. In addition, urinary NAG and beta 2MG increased significantly when the number of shock waves was over 2500 shots. These above findings suggest that shock wave had induced acute changes in renal functions and transient renal tubular damages, although these functional changes recovered within one week, and the tubular damage might last longer than 7 days, In order to avoid serious renal damage, it's necessary to limit the energy level of shock waves under 12.5 KV x 2500 shots by using JT-3 lithotriptor.

Acetylglucosaminidase↗

PubMed1992

Inhibitory effect of fluoride on renal stone formation in rats.

The effect of fluorine (F) on stone formation induced by ethylene glycol (EG) was studied in rats. For different groups, the drinking water was supplemented with EG, sodium fluoride (NaF), EG+NaF, or nothing as control. An isotope-tracing method was used to evaluate experimental stone formation in the kidneys by introducing 45Ca intraperitoneally into rats and then measuring the radioactivity of the kidney. At the end of the 4-week experiment, rats of the EG+NaF group showed a significantly lower incidence of gross urinary stones and lower 45Ca activity in their kidneys compared to the EG group of rats. Both the EG group and EG+NaF group had markedly increased urinary oxalate excretion, with the latter significantly lower than the former (p less than 0.05). Urinary oxalate excretion was relatively lower in the NaF group than in the control group. This study indicates that NaF can inhibit renal stone formation induced by EG by decreasing oxalate synthesis and urinary oxalate excretion, and suggests a possible clinical therapeutic value of NaF in the prevention of oxalate kidney stones.

Animals↗

PubMedDate not supplied

Expression of HSP70-2 gene during germ cell apoptosis in rat unilateral cryptorchid testes.

To investigate the role of Hsp70-2 gene in germ cell apoptosis induced by heat stress, its expression changes were examined in rat normal and unilateral cryptorchid testes by using in situ hybridization, immunohistochemistry, and northern blot analysis techniques. The results showed that the expression level of Hsp70-2 gene declined slightly at the early stage of germ cell apoptosis, and dropped dramatically when most of the germ cells were undergoing apoptosis on day 7.5 after the induction of cryptorchidism. This report suggests for the first time that Hsp70-2 gene might not inhibit the apoptosis of germ cells at the early stage in cryptorchid testes. Hsp70-2 gene does not belong to the immediate early related genes that are responsible for germ cell apoptosis induced by heat stress.

Animals↗