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Biomedical subjects

Z G Chen

Publications and source records attributed to Z G Chen.

At least 19 recordsLinked to original sources
PubMed2001

Diffusion tensor trace mapping in normal adult brain using single-shot EPI technique. A methodological study of the aging brain.

PURPOSE: To quantify age-related changes of the average diffusion coefficient value in normal adult brain using orientation-independent diffusion tensor trace mapping and to address the methodological influences on diffusion quantification. MATERIAL AND METHODS: Fifty-four normal subjects (aged 20-79 years) were studied on a 1.5-T whole-body MR medical unit using a diffusion-weighted single-shot echo-planar imaging technique. Orientation-independent diffusion tensor trace maps were constructed for each subject using diffusion-weighted MR measurements in four different directions using a tetrahedral gradient combination pattern. The global average (including cerebral spinal fluid) and the tissue average of diffusion coefficients in adult brains were determined by analyzing the diffusion coefficient distribution histogram for the entire brain. Methodological influences on the measured diffusion coefficient were also investigated by comparing the results obtained using different experimental settings. RESULTS: Both global and tissue averages of the diffusion coefficient are significantly correlated with age (p<0.03). The global average of the diffusion coefficient increases 3% per decade after the age of 40, whereas the increase in the tissue average of diffusion coefficient is about 1% per decade. Experimental settings for self-diffusion measurements, such as data acquisition methods and number of b-values, can slightly influence the statistical distribution histogram of the diffusion tensor trace and its average value. CONCLUSION: Increased average diffusion coefficient in adult brains with aging are consistent with findings regarding structural changes in the brain that have been associated with aging. The study also demonstrates that it is desirable to use the same experimental parameters for diffusion coefficient quantification when comparing between different subjects and groups of interest.

Adult↗
PubMed2001

The POU homeodomain protein Oct-1 binds Cis-regulatory element essential for the human GnRH upstream promoter activity in JEG-3 cells.

In previous studies, we have localized four specific nuclear protein-binding elements in the human GnRH upstream promoter. To test whether these four elements are reproductive tissue specific, we placed the four elements upstream to a thymidine kinase (TK) promoter/luciferase reporter gene, and transfected the constructs into human placental choriocarcinoma (JEG-3) cells. The 272-bp fragment (-994 to -723) containing the four elements can drive heterologous TK promoter expression in JEG-3 cells about 15 times more than that of basal TK promoter activity. Deletion of element 4 (E4, -987/-968) significantly decreased (4-fold) the luciferase activity. Further deletion of the other elements (E3 individual, -960/-940 or E3 and E2 in combination, -919/-896) only slightly decreased the luciferase activity. In contrast, deletion of element 1 (E1, -876/-851) caused a 2-fold loss of luciferase activity and elimination of E2 and E3 only lost less than 2-fold of the luciferase activity. Study performed with 5' end deletion of this region confirmed these observations. Furthermore, E4 DNA-protein complex can be supershifted by Oct-1 antibody, indicating that Oct-1 binds to E4. These results clearly demonstrated that all four elements are required to confer tissue-specific expression of the hGnRH gene in JEG-3 cells. However, the E4 is the most important for the tissue-specific expression of the hGnRH gene in JEG-3 cells. Oct-1 factor binds with E4 element and may be involved in the mediation of the human GnRH upstream promoter activity.

DNA-Binding Proteins↗
PubMed2001

[Repair of humeral fracture and non-union with transfer of vascularized periosteal flap].

OBJECTIVE: To study the results of humeral fracture and non-union repaired by vascularized periosteal flap transfer. METHODS: The clinical data of humeral fracture and non-union in 23 cases were analysized retrospectively since 1995. Among them, minuted or several segmental fracture in 12 cases, non-union in 11 cases, and following injury of radial nerve in 7 cases. The operative method was open reduction, inner or external fixation with vascularized periosteal flap transfer. RESULTS: The period of follow-up was 6 months to 2 years. The repair result of all patients was excellent and good, but elbow joint motion in 2 cases of non-union was not satisfactory. The periosteal flap had good osteogenic ability. The period of bone union was 2 to 5 months in humeral fracture and non-union. And function of radial nerve was recovery. CONCLUSION: Transfer of distal humeral periosteal flap pedicled with radial collateral vessels is a better method for humeral fracture and non-union.

Adolescent↗
PubMed2000

[Heart morphologic state in retired fighter pilots].

Objective. To study the heart morphology in the retired fighter pilots, and to provide clinical evidence for protection combined G-loads (+ Gz), heat, noise, hypoxic and vibration stress induced cardiac structural damage. Method. Parameters of heart morphology were studied using Doppler echocardiography in 40 retired fighter pilots with 40 veteran cadres as control. Result. LVDd, LVDs, LADs, LVEDV, LVPWs and LVM in pilot group were somewhat higher than those in control group (NS); while IVSs and LVMI in pilot group were slightly lower than those in control group (NS); LVESV, aortic valve area, internal diameter of the ring and sinus in pilot group were significantly higher than those in control group (P < 0.05). Conclusion. Analysis of the results revealed no pathomorphologic damage of the heart. It suggest that all the variations can be regarded as adaptive changes due to the effects of the combined environmental factors experienced in long time flying.

Acceleration↗
PubMed2000

[The applied anatomy of transposition of the distal dorsal ulna bone flap pedicled with dorsal metacarpal artery].

OBJECTIVE: To investigate the anatomic basis for transposition of the distal dorsal ulna bone flap pedicled with dorsal metacarpal artery to repair the defect of the 3rd or 4th and 5th metacarpal bone head. METHODS: In 30 adult cadaveric upper limbs, the branches and constitutions of the dorsal carpal arterial networks were observed. RESULTS: The dorsal carpal arterial networks were consisted of the dorsal carpal branches of ulnar and radial arteries, the terminal branches of posterior interosseous artery and the dorsal carpal branch of anterior interosseous artery, and then the 2nd, 3rd, 4th dorsal metacarpal branches were originated from the networks. The dorsal metacarpal branches were anastomosed with the deep branches of deep palmar arch to constitute the dorsal metacarpal artery. CONCLUSION: Transposition of the distal dorsal ulna bone flap pedicled with the 3rd, 4th dorsal metacarpal arteries can be used in repairing the defect of 3rd, 4th and 5th metacarpal bone head.

Adult↗
PubMed2000

[Separation model of small molecules with SEC columns and micellar mobile phase].

Small alkanol molecules were successfully separated with SEC method in combination with a micellar mobile phase. The separation model has been given in this system. The separation is based on the differential migration of the micelle and the surrounding water and the differential distribution of the solute between the micelle and aqueous phase, therefore, the separation mechanism is very similar to that of micella electrokinetic chromatography (MEKC). The retention volume of solute is related to the micellar concentration by theoretical treatment, through which the solute distribution coefficient between micelle and aqueous phase could be obtained. Two different SEC columns were employed for separation of some alkanols and the theoretical model is supported by the experimental results. The distribution coefficients obtained were in good agreement for these two columns.

Azo Compounds↗
PubMed1999

Estrogen receptor-mediated repression of gonadotropin-releasing hormone (gnRH) promoter activity in transfected CHO-K1 cells.

To examine the transcriptional regulation of gonadotropin-releasing hormone (GnRH) gene in reproductive tissues, the expression of human GnRH gene promoter in cultured human granulosa cells and a Chinese hamster ovary-derived CHO-K1 tumor cells was studied. Transfection of luciferase reporter gene construct containing either upstream (hU) or downstream (hD) human GnRH gene promoter into both human granulosa and CHO-K1 cells showed that the upstream promoter, hU, was more active than hD in directing luciferase expression in these ovarian tissues. CHO-K1 cells transfected with either hU or hD construct showed insignificant changes in luciferase activity in response to 17beta-estradiol and GnRH. However, cotransfection of hU construct with a vector expressing a human estrogen receptor-alpha (ER-alpha) cDNA results in dose-dependent decreases in luciferase activity in response to both 17beta-estradiol and a GnRH agonist. By functional analysis of a series of deletion constructs, the ER-mediated suppression of GnRH promoter activity by 17beta-estradiol was localized to a region between -169 and -548 bp 5' of the upstream transcription start site of the human GnRH gene. Results of this study demonstrated that estrogen receptor can mediate the negative feedback regulation of human GnRH upstream promoter activity by both estrogen and GnRH in the ovary.

Animals↗
PubMed1999

A 30-residue fragment of the carp granulin-1 protein folds into a stack of two beta-hairpins similar to that found in the native protein.

Upon air oxidation, a peptide corresponding to the 30-residue N-terminal subdomain of carp granulin-1 spontaneously formed the disulfide pairing observed in the native protein. Structural characterization using NMR showed the presence of a defined secondary structure within this peptide. The chemical shifts for most of the alphaCH protons of the peptide and the protein are very similar, and the observed NOE contacts of the peptide strongly resemble those in the protein. A structure calculation of the peptide using NOE distance constraints indicates that the peptide fragment adopts the same conformation as formed within the native protein. The 30-residue N-terminal peptide of carp granulin-1 is the first example of an independently folded stack of two beta-hairpins reinforced by two interhairpin disulfide bonds. Two key areas of the structure show a clustering of hydrophobic residues that may account for its exceptional conformational stability.

Amino Acid Sequence↗
PubMed1999

[Applied anatomy of bone flap pedicled with spina scapular branch of transverse cervical artery for mandibular reconstruction].

OBJECTIVE: To study the anatomical basis of vascularized spina scapular bone flap, which was used in mandibular reconstruction. METHODS: Fifteen adult cadavers were adopted in this study. The two common carotid arteries of each cadaver were intubed and perfused with red emulsion respectively. Then the course and distribution of the transverse cervical artery(TCA) and its spina scapular branches were observed on 30 sides. RESULTS: The TCA was divided into two segments: the cervical segment originated from the origin of the artery to the superior margin of the trapezius muscle, and the dorsal segment originated from the superior margin of the trapezius muscle to the site where the TCA bifurcated into the superficial and deep branches. The average length and original caliber of the cervical segment were(4.7 +/- 0.1) cm and (4.0 +/- 0.1) mm. The average length and original caliber of the dorsal segment were (5.88 +/- 0.63) cm and (3.30 +/- 0.35) mm. 86.7% spina scapular branches originated from the superficial branch of TCA and 13.3% from TCA. The length of the spina scapular branch was (4.97 +/- 1.68) cm and its external diameter was (2.08 +/- 0.27) mm. It constantly sent 4-8 periosteal branches to spina with 0.20-1.25 mm in caliber. CONCLUSION: The spina scapular branch of TCA is one of the main blood supplier to the spina scapular area. The spina scapular flap pedicled with spina scapular branch of TCA may provide a new operation for mandibular reconstruction, whose circumpoint locates at the origin of the dorsal segment and the average length of the pedicle is 10.85 cm which enough to transposite to mandibular area.

Arteries↗
PubMed1998

Diffusion-weighted MR imaging of acute cerebral ischemia.

Diffusion-weighted MR imaging has been used in studies on experimental animal models and on patients with acute cerebral ischemia. Compared with CT and conventional MR techniques, diffusion-weighted imaging can provide earlier and more precise detection of the location and the extent of an ischemic lesion during the critical first few hours after the onset of stroke. Quantitative apparent diffusion coefficient (ADC) mapping of the brain water can also be carried out by recording a series of diffusion-weighted images with different amplitudes of the displacement encoding gradients. ADC maps can provide important information about the extra- and intracellular water homeostasis. ADC reduction of the tissue water is one of the early signals of the pathophysiological cascade resulting from ischemic tissue injury. Diffusion MR imaging has become a valuable tool in stroke research. It may also prove a valuable tool in monitoring the efficiency of therapeutic effects in stroke patients. It is our intention to provide an overview of the recent development in this area with emphasis on the diffusion-weighted MR techniques, and to discuss the possible underlying biophysical mechanisms responsible for the contrast of diffusion-weighted imaging.

Acute Disease↗
PubMed1998

Glucocorticoids modulate human gonadotrophin releasing hormone upstream promoter activity in transfected human placental cells (JEG-3).

A human gonadotrophin releasing hormone (GnRH) upstream promoter/luciferase reporter gene construct (H2 construct) was generated by inserting a 1.7 kb XbaI/AflII fragment containing the human GnRH upstream promoter region only into a promoter-less luciferase reporter vector. When JEG-3 cells were transiently transfected with this construct and treated with cortisol or its synthetic analogue dexamethasone, a stimulatory effect on the upstream promoter activity was observed. This stimulation was dependent on the cotransfection of a glucocorticoid receptor (GR) cDNA expression vector due to the low level of GR in JEG-3 cells and could be completely abolished by RU486, a glucocorticoid antagonist. Moreover, the cortisol actions could be modulated to a different extent by oestradiol. Thus, since the human placenta contains GRs and the increase in cortisol metabolism near term is regulated by oestrogen, the current findings suggest that cortisol may be physiologically involved in the regulation of GnRH gene expression in the human placenta.

Cell Line↗
PubMed1997

Characterization of multiple promoters directing tissue-specific expression of the human gonadotropin-releasing hormone gene.

Two promoters directing tissue-specific expression of GnRH gene in neuronal and reproductive tissues were characterized by functional analyses of GnRH promoter-luciferase (LUC) constructs in transfected placental cells (JEG) and hypothalamic neuronal cells (GT1-7). Results indicate that the downstream promoter directs the expression in a neuronal cell-specific manner, whereas the upstream promoter is fully active in the nonneural placental cell line. Transfection studies carried out in several tumor cell lines derived from human reproductive tissues verified that the upstream GnRH promoter construct was much more active in directing luciferase expression in reproductive tissue. The use of both upstream and downstream promoters in various human tumor cell lines derived from reproductive tissues were demonstrated by RT-PCR. Our studies also demonstrate that the reproductive tissue-specific messenger RNA transcribed from upstream promoter is capable of directing synthesis of preproGnRH protein. Serial deletion studies localized a cell-specific upstream promoter region that directs reproductive tissue expression. DNase I footprint analysis using nuclear extract obtained from the JEG cells indicated DNA/protein interactions in four specific sequence elements of the upstream promoter region. The interaction between nuclear binding proteins present in the JEG cells (but not the GT1-7 cells) and the four specific sequences in the upstream promoter region was confirmed by gel mobility shift analysis.

Animals↗
PubMed1996

Evidence for estrogen receptor-mediated regulation of human gonadotropin-releasing hormone promoter activity in human placental cells.

Two fragments of the human gonadotropin-releasing hormone (GnRH) promoter, one containing 0.6 kb of the downstream promoter sequence (H-1) and another 1.8 kb fragment (H-2) containing the upstream promoter region with a deletion of the downstream promoter sequence, were fused to a promoterless luciferase (Luc) reporter construct and transfected into the human placental (JEG) cells. JEG cells transfected with both constructs showed insignificant changes in luciferase activity in response to estradiol. However, cotransfection of H-2-Luc construct with a vector expressing a human estrogen receptor (ER) cDNA results in dose-dependent decreases in luciferase activity in response to estradiol. This ER mediated down-regulation of promoter activity was retained in constructs with the GnRH promoter deleted to position 548 bp 5' to the upstream transcription start site. Further deletion of upstream promoter sequence to 169 bp reversed the estrogen responsiveness from inhibitory to stimulatory. Thus, this study demonstrated that the upstream GnRH promoter region can be regulated by estrogen in transfected JEG cells.

Dose-Response Relationship, Drug↗
PubMed1995

[Influence of calcium concentration on 4-aminopyridine induced histamine release from isolated peritoneal mast cells].

4-Aminopyridine (4-AP) has been shown to induce histamine release from isolated peritoneal mast cells (PMC) in mice and rats. In the presence of extracellular calcium at normal level (0.9 mmol.L-1) histamine release induced by 4-AP (13.6 mmol.L-1) from mice PMC was 33.0% +/- 4.6%, while at low calcium concentration (0.5 mmol.L-1) and in calcium-free medium this parameter decreased to 25.5% +/- 4.2% and 16.3% +/- 3.7% respectively. Histamine release in response to 4-AP (10 mmol.L-1) from rat PMC was 39.1% +/- 6.7% (0.9 mmol.L-1 calcium), while at low calcium concentration (0.5 mmol.L-1) and in calcium-free medium this parameter decreased to 29.3% +/- 4.7% and 20.2% +/- 2.9% respectively. Results of statistical analysis indicate that 4-AP induced histamine release is related to Ca2+ concentration. When rat PMC were preincubated in calcium-free medium with EDTA 0.1 mmol.L-1 for 180 min 4-AP induced histamine release was 13.8% +/- 1.6%. This shows that 4-AP also elicited mobilization of endogenous calcium stores in mast cells. The mechanism of 4-AP induced histamine release was discussed.

4-Aminopyridine↗
PubMed1995

[Potassium channel openers antagonize 4-aminopyridine induced histamine release from rat peritoneal mast cells].

4-Aminopyridine (4-AP) was shown to promote histamine release from isolated rat peritoneal mast cells (PMC) in a dose-dependent manner. Potassium channel openers, minoxidil (Min) 200 mg.kg-1 ig, diazoxide (Dia) 500 mumol.L-1 in vitro and calcium antagonist nifedipine (Nif) 125 mg.kg-1 ig were found to inhibit 4-AP induced histamine release from rat PMC. Electron microscopy revealed that 4-AP caused partial degranulation of PMC and extrusion of granules and Min 200 mg.kg-1 ig retarded this phenomenon. These results provide evidence that potassium channels are present in rat mast cell membrane and indicate that the mechanism of histamine release by 4-AP may be related to its potassium channel blocking effect. As a result of this effect, the calcium channels open and Ca2+ influx to the mast cells increases, thus eliciting histamine release. Potassium channel openers seemed to be a new group of inhibitors of histamine release from mast cells.

4-Aminopyridine↗
PubMed1994

Specific overexpression of P53 in sarcoma derived from Rat-1 cells transformed by cigarette smoking condensate-treated human fetal lung DNA.

The p53 protein is highly expressed in fibrosarcoma derived from Rat-1 cells transfected with cigarette smoke condensate-treated human fetal lung DNA but expressed low in the counterparts of nitroso-N-methylurea and dimethyl sulfoxide groups. Our results denoted that a high expression of p53 protein specifically contributes to the initiation of human lung carcinogenesis induced by cigarette smoke condensate. High expression and missense mutation of p53 may probably be a potential biomarker of initiation of human lung carcinogenesis.

Animals↗
PubMed1994

[Transposing the great trochanter bone flap pedicaled with the deep branch of the medial circumflex artery in repair of necrotic femoral head].

The transposition of the greater trochanter bone flap pedicled with the deep branch of the medial circumflex artery was designed as a new therapeutic method for the treatment of early ischemic necrosis of the femoral head in adults. Bone flap was successfully used in 15 limbs of 13 patients. Applied anatomy, operative indications and procedure of the bone flap was introduced.

Adult↗