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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 325 records · Page 18Linked to original sources
PubMed2001

[Studies on synthesis and degradation of collagen at transcription level in liver fibrosis of rabbits with schistosomiasis japonica].

OBJECTIVE: To study the synthesis and degradation of collagen at the transcription level during liver fibrosis in rabbits with schistosomiasis japonica. METHODS: New Zealand rabbits infected with Schistosoma japonicum cercariae were served as animal models of liver fibrosis. The liver specimens were collected through operations at 4, 6, 8, 10, 12, 16, 20, 24 and 28 weeks after infection. Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels of liver tissue were detected by RT-PCR plus dot blotting, and the size of egg granulomas and the degree of liver fibrosis were measured by histopathological examinations. RESULTS: Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased simultaneously in the early stage after the infection, mostly reaching their peaks at 10 weeks after infection. Compared with normal controls, type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased by 12.0-, 11.0-, 6.6-, 10.0- and 11.0-fold, respectively, coinciding with the changes of egg granulomas. Thereafter, both collagen and collagenase mRNA levels decreased. Types I, III and IV collagen mRNA levels declined to 2-fold to 3-fold compared with normal controls (P < 0.05), while MMP-1 and MMP-9 mRNA levels declined to normal level (P > 0.05) at 28 weeks. This study showed that the synthesis and degradation of collagen remained dynamic balance in the early stage of schistosomiasis, while in the later stage the metabolism of collagen synthesis was higher than that of collagen degradation. CONCLUSION: It was confirmed at the transcription level that when the metabolism of collagen synthesis was higher than that of collagen degradation in rabbits with schistosomiasis japonica, liver fibrosis might be produced.

Animals↗
PubMed2001

[Determination of phospholipid in Cibotium barometz by supercritical fluid extraction and RP-HPLC].

A supercritical fluid extraction (SFE) method was used to extract phospholipids in Cibotium barometz. After a homogeneous design experiment, SFE conditions were obtained which were pressure at 31.5 MPa, temperature at 46.2 degrees C and a 0.37 L/kg modifier in supercritical fluid. The sample was extracted for 2 hours. A RP-HPLC method was developed for the determination of phosphatidylcholine. RP-HPLC conditions included a RP-HPLC column packed with Waters Symmetry C18(5 microns), a mobile phase composed of methanol-1% phoshporic acid(90:10) and the detection wavelength at 206 nm. The content of phosphatidylcholine was 0.198%(RSD 4.2%), and the method can be a measure of quality control for Cibotium barometz and its preparations.

Chromatography, High Pressure Liquid↗
PubMed2001

[Studies on the chemical compound of volatile oils from various species of Citrus grandis].

The volatile oils in Citrus grandis from various species were compared by GC-MS. The results showed that the content of volatile oil from Citrus grandis and Citrus grandis (L.) Osbek var. tomentosa Hort. was from 0.7% to 0.9%. Over 30 chemical compounds were identified from the volatile oils and the types of the compounds were almost the same. But gamma-terpinen could not be identified from Citrus grandis which was rich in Citrus gransis (L.) Osbeck var. tomentosa Hort.

Citrus↗
PubMed2001

Modification of urinary secretion of 8-hydroxy-2'-deoxyguanosine and serum ACTH concentration following repetitive parabolic flights.

It is important to clarify the molecular mechanisms of physiological responses of the human body to changes in gravity. Previous reports demonstrated that gravity-changing stress increases the human urinary concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG). However, it has yet to be clarified whether repetitive parabolic flight modulates the urinary concentration of 8-OHdG after exposure to gravity-changing stress. In the present study, the effects of the number of previous experiences with parabolic flight on urinary excretion of 8-OHdG and concentration of serum ACTH were examined in 12 healthy volunteers.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

[Study on the chemosensitivity test of human gastric cancer using the MTT assay].

OBJECTIVE: This study was conducted to investigate the chemosensitivity of gastric carcinoma. METHODS: 112 cases of fresh human gastric cancer samples were obtained for drug sensitivity testing using MTT. RESULTS: The sensitivity sequence of antitumor agents was 5-Fu, DDP, MMC, etc. On the other hand, the sensitivity was relative to pathology and individual differences. CONCLUSION: The MTT assay is an accurate system for determination of the chemosensitivity of tumor cells.

Adenocarcinoma↗
PubMed2001

[Diagnosis and treatment of horizontal canal benign paroxysmal positional vertigo].

OBJECTIVE: To explore effective methods for the diagnosis and treatment of horizontal-canal benign paroxysmal positional vertigo (HC-BPPV). METHODS: Medical records from nine patients with HC-BPPV, treated between July 1996 and March 2000, were retrospectively analyzed. Data of complete history, audiograms, positional tests and neuro-otological examinations were collected. All patients were treated with a particle repositioning maneuver called the "barbecue rotation" which starts with the patient in the supine position and consists of three 90-degree head rotations towards the unaffected ear. RESULTS: HC-BPPV was characterized by brief attacks of intense vertigo that were induced mainly by rolling over in bed (9/9) and turning the head to either side while upright (5/9). In most cases, rotation to the pathological side from supine position caused a very intense horizontal nystagmus beating towards the undermost ear. Findings such as latency and fatigability, which are common features of posterior-canal BPPV (PC-BPPV), were not present. After the barbecue rotation, all patients had immediate and sustained relief of their attacks during the 4 to 15 months' follow up. CONCLUSION: HC-BPPV is different from PC-BPPV and other vertiginous diseases in typical presentations and positional testing results. The barbecue rotation is a successful method for curing the disorder.

Adult↗
PubMed2001

[Effects of growth regulator, full exposure and mist spray on the cutting of Eucommia ulmoides].

OBJECTIVE: To study the effects of growth regulator on the cutting method of Eucommia ulmoides seedlings. METHODS: Treated with H2O (CK), NAA, 6-BA and NAA + 6-BA for 4 hours, respectively, cuttings of 4-year and 20-year trees were cultured for 45-60 days under the shed or full exposure and mist spray. The growth of the cuttings was observed periodically. The number of the roots, the root length, the callus and the death rate were investigated after harvest. RESULTS: Compared with the cutting from 4-year-old tree, the cutting from 20-year-old tree developed better. The rate of stroking root in treated group was 14 times as much as CK group. Other agronomic traits such as the number of the roots, the root length, the callus, the number of the leaves and the death rate of the cuttings in treated group were all better than that of the cuttings in CK group. The cultural time in treated group reduced by 15 days than that of CK group. CONCLUSIONS: The present study shows that both full exposure mist spray and growth regulators have remarkable effects on cuttings of tree with different ages for rooting or forming callus.

Eucommiaceae↗
PubMed2001

[The comparisons of fluorescence quenching between perylene and pyrene].

The fluorescence quenching of perylene and pyrene by dimethyl terephthalate (DMTP) and N,N-dimethylaniline (DMA) have been investigated. The results show that pyrene can form exciplex with DMTP or DMA at room temperature and perylene can only form exciplex with DMA. The fluorescence quenching date is in conformity with the Stern-Volmer equation: F0/F = 1 + KSV[Q] = 1 + Kq.tau 0[Q], the F0/F-[Q] straight lines are drawn. The Stren-Volmer constants and fluorescence quenching rate constants (KSV and Kq) are obtained. The Stern-Volmer quenching constants of pyrene is larger than that of perylene. The differences is due to the molecular structure of perylene which is not a typical large conjugated system and less coplanar configuration than pyrene.

Aniline Compounds↗
PubMed2001

[Immunolocalization of laminin during reparative dentinogenesis].

OBJECTIVE: To investigate the immunolocalization of laminin in the process of dental pulp injury and repair. METHODS: One cavity was prepared on the mesial surface of the first molars of Wistar rats. The animals were sacrificed in 3, 15, and 30 days of post-operation. After histological process, the paraffin sections were reacted with monoclonal antibodies against rat laminin using SABC method. RESULTS: Immunolocalization demonstrated positive staining for laminin in the different stages of dental pulp repair. In 3 days group, no reparative dentin were observed. The positive staining was located in odontoblasts and in predentin. After 15 days, reparative dentin and odontoblasts were observed. The odontoblast like cells and dental pulp cells were stained positively. 30 days later, the stronger staining intensity was observed in odontoblast like cells, pulp cells and in reparative dentin. Immunological reaction was particularly located among the interface of reparative dentin and dental pulp. CONCLUSION: The localization feature of laminin suggested that laminin may be a favored factor for the adhesion of dental pulp cell during reparative dentinogenesis.

English Abstract↗
PubMed2001

[A retroviral bicistronic strategy for efficient coexpression of ALDH1 and mdr1].

OBJECTIVE: To elucidate the feasibility of coexpression of human class 1 aldehyde dehydrogenase (ALDH1) and multidrug resistance gene (mdrl) by a retroviral bicistronic vector containing an internal ribosome entry site (IRES). METHODS: The constructed retroviral bicistronic vector G1Na-ALDH1-IRES-mdr1 (G1Na-AIM) was transduced into amphotropic packaging cells PA317 by electroporation. Selection was performed by using 15 ng/ ml vincristine. The titer of retrovirus was elevated by ping-pong transduction. K562 cells were transfected with retroviral producing cell supernatant. The integration of the transferred gene and its expression and the efficiency of transfection were determined by polymerase chain reaction (PCR), Southern blot, MTT assay, flow cytometry (FCM) and colony forming assay, respectively. RESULTS: The retroviral titer reached 1.0 x 10(5) cfu/ml in the supernatant of the PA317/ AIM cells after cross-infection with ecotropic GP + E86 cells. The transfected K562 cells exhibited a 3 - 10-fold increase of resistance to 4-hydroperoxycyclophosphamide (4-HC) and vincristin (VCR) and 62% of them expressed P-gp. The integration of both ALDH1 and mdr1 was confirmed by PCR and Southern blot analysis. CONCLUSION: The IRES containing bicistronic retroviral vector allows functional coexpression of two different kinds of drug resistance genes. This strategy could be applicable to the transfer of other combinations of drug resistance gene and dominant selection of transfectant cells in vivo.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2001

[Enhancement of bacillus Calmette-Guerin attachment to the bladder wall: experimental study].

OBJECTIVE: To provide experimentally a scientific basis for enhancement of bacillus Calmette-Guerin (BCG) antineoplastic effect. METHODS: Thirty rabbits were equally divided into five groups (groups A, B, C, D, and E) and the bladder mucosa of every rabbit was injured by electrocautery, cryocautery and incision on the left lateral wall, right lateral wall and posterior wall respectively. Then different drugs were instilled into bladders. Group A: pure phosphate-buffered sodium instillation (PBS); group B: PBS and radiolabeled BCG (3H-BCG) instillation; group C and group D: epsilon-aminocaproic acid or para-aminomethyl benzoic acid and 3H-BCG instillation; group E: heparin and 3H-BCG instillation. After instillation, every injured bladder wall and non-injured wall (anterior wall of bladder) were surgically removed and digested. The quantity of BCG adherence was determined by liquid scintillation counter. RESULTS: The quantity of BCG attached to injured bladder wall was significantly higher than that of non-injured wall (P < 0.001). The mean level of group C or group D was significantly higher than that of group B (P < 0.001) while the mean level of group E was significantly lower than that of group B (P < 0.001). CONCLUSION: For experimental rabbits, intravesical instillation of fibrin clot stabilizer EACA or PAMBA can enhance BCG attachment to the bladder wall while fibrin clot inhibitor heparin inhibits it.

Administration, Intravesical↗
PubMed2001

[Comparative effects of carvedilol, losartan and their combination in preventing left ventricular remodeling after acute myocardial infarction in rats].

OBJECTIVE: To compare the effects of carvedilol, losartan and their combination in preventing from left ventricular remodeling (LVRM) after acute myocardial infarction(AMI) in rats. METHODS: Twenty-four hours after ligating left coronary artery, 100 surviving AMI female SD rats were randomly assigned to: (1) AMI control (n = 25), (2) carvedilol (1 mg x kg(-1) x d(-1)) (C1) (n = 25); (3) losartan (3 mg x kg(-1) x d(-1)) (L3)(n = 25); and (4) carvedilol (1 mg x kg(-1) x d(-1)) + losartan (3 mg x kg(-1) x d(-1)) (C1 + L3) (n = 25) groups. Sham-operated group (n = 17) were selected randomly as non-infarction control. After 4 weeks of therapy with the drugs by gastric gavage, hemodynamic studies were performed, then the rat hearts were fixed and pathologically analyzed. Exclusive of the rats with MI size < 35% or > 55%, complete data were obtained in 65 rats, which were comprised of AMI control (n = 13), C1 (n = 12), L3 (n = 13), C1 + L3 (n = 14) and sham-operated (n = 13) groups. RESULTS: There were no significant differences in MI size among the four AMI groups (45.8% - 46.7%, P > 0.05) . Compared with sham-operated group, Left ventricular (LV) end diastolic pressure (LVEDP), volume (LVV), weight (LVW), septal thickness (STh) and right ventricular weight (RVW) were all significantly increased (all P < 0.01 ) in AMI group, while the left ventricular pressure maximal rate of rise and fall (dp/dt) were significantly decreased (all P < 0.01). In comparison with AMI group, LVEDP, LVV, LVW, STh and RVW were all significantly decreased (all P < 0.01), while +/- dp/dt and +/- dp/dt/LVSP were significantly increased (P < 0.05 - 0.01) in all three therapy groups, with LVEDP decreasing more in the combination and L3 groups than in C1 group (P < 0.05 - 0.01) and STh decreasing more in the combination group than in C1 group (P < 0.01), but there were no significant differences in other variables among the three therapy groups. CONCLUSION: Carvedilol, losartan and their combination all can prevent from LVRM after AMI in rats, improve hemodynamics and LV function, with the combination superior.

Adrenergic beta-Antagonists↗
PubMed2000

The C-terminal polylysine region and methylation of K-Ras are critical for the interaction between K-Ras and microtubules.

After synthesis in the cytosol, Ras proteins must be targeted to the inner leaflet of the plasma membrane for biological activity. This targeting requires a series of C-terminal posttranslational modifications initiated by the addition of an isoprenoid lipid in a process termed prenylation. A search for factors involved in the intracellular trafficking of Ras has identified a specific and prenylation-dependent interaction between tubulin/microtubules and K-Ras. In this study, we examined the structural requirements for this interaction between K-Ras and microtubules. By using a series of chimeras in which regions of the C terminus of K-Ras were replaced with those of Ha-Ras and vice versa, we found that the polylysine region of K-Ras located immediately upstream of the prenylation site is required for binding of K-Ras to microtubules. Studies in intact cells confirmed the importance of the K-Ras polylysine region for microtubule binding, as deletion or replacement of this region resulted in loss of paclitaxel-induced mislocalization of a fluorescent K-Ras fusion protein. The additional modifications in the prenyl protein processing pathway also affected the interaction of K-Ras with microtubules. Removal of the three C-terminal amino acids of farnesylated K-Ras with the specific endoprotease Rce1p abolished its binding to microtubules. Interestingly, however, methylation of the C-terminal prenylcysteine restored binding. Consistent with these results, localization of the fluorescent K-Ras fusion protein remained paclitaxel-sensitive in cells lacking Rce1, whereas no paclitaxel effect was observed in cells lacking the methyltransferase. These studies show that the polylysine region of K-Ras is critical for its interaction with microtubules and provide the first evidence for a functional consequence of Ras C-terminal proteolysis and methylation.

Amino Acid Sequence↗
PubMed2000

Reexamination of the role of the leucine/isoleucine zipper residues of phospholamban in inhibition of the Ca2+ pump of cardiac sarcoplasmic reticulum.

Phospholamban is a small phosphoprotein inhibitor of the Ca(2+)-pump in cardiac sarcoplasmic reticulum, which shows a distinct oligomeric distribution between monomers and homopentamers that are stabilized through Leu/Ile zipper interactions. A two-faced model of phospholamban inhibition of the Ca(2+)-pump was proposed, in which the Leu/Ile zipper residues located on one face of the transmembrane alpha-helix regulate the pentamer to monomer equilibrium, whereas residues on the other face of the helix bind to and inhibit the pump. Here we tested this two-faced model of phospholamban action by analyzing the functional effects of a new series of Leu/Ile zipper mutants. Pentameric stabilities of the mutants were quantified at different SDS concentrations. We show that several phospholamban mutants with hydrophobic amino acid substitutions at the Leu/Ile zipper region retain the ability to form pentamers but at the same time give the same or even stronger (i.e. L37I-PLB) inhibition of the Ca(2+)-pump than do mutants that are more completely monomeric. Steric constraints prevent the Leu/Ile zipper residues sequestered in the interior of the phospholamban pentamer from binding to the Ca(2+)-pump, leading to the conclusion that the zipper residues access the pump from the phospholamban monomer, which is the active inhibitory species. A modified model of phospholamban transmembrane domain action is proposed, in which the membrane span of the phospholamban monomer maintains contacts with the Ca(2+)-pump around most of its circumference, including residues located in the Leu/Ile zipper region.

Animals↗
PubMed2000

Magnetic resonance imaging of the membranous labyrinth during in vivo gadolinium (Gd-DTPA-BMA) uptake in the normal and lesioned cochlea.

MRI with a T1 contrast agent was used to investigate the normal and noise-damaged cochlea. The time course and distribution of the in vivo uptake of the gadodiamide chelate bound paramagnetic Gd ion (GdDTPA-BMA) throughout the membranous labyrinth of normal and impulse noise-damaged guinea pig cochleae were measured by MRI at 4.7T. Simultaneous signal enhancement of the basal, medial and apical scala tympani (ST) and scala vestibuli (SV) was observed within 10 min following i.v. injection, reaching maximum levels at around 100 min. ANOVA and post hoc paired t-tests showed statistically significant differences in the levels and rates of Gd uptake-enhancement between the scalae. The ST revealed the most rapid and extensive enhancement throughout the period of active Gd uptake, while the SV showed comparatively slower and less enhancement, and the intact scala media (SM) indicated insignificant enhancement. The in vivo Gd penetration and enhancement of the membranous SM increased significantly in the noise-damaged cochlea, suggesting lesioning of the cochlear membranes.

Acoustic Stimulation↗