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Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 487 records · Page 27Linked to original sources
PubMed1998

Coexpression of multiple metabotropic glutamate receptors in axon terminals of single suprachiasmatic nucleus neurons.

Glutamate is the primary excitatory transmitter in axons innervating the hypothalamic suprachiasmatic nucleus (SCN) and is responsible for light-induced phase shifts of circadian rhythms generated by the SCN. By using self-innervating single neuron cultures and patch-clamp electrophysiology, we studied metabotropic glutamate receptors (mGluRs) expressed by SCN neurons. The selective agonists for group I (3,5-dihydroxy-phenylglycine), group II ((S)-4-carboxy-3-hydroxyphenylglycine), and group III ((+)-2-amino-4-phosphonobutyric acid) mGluRs all depressed the evoked IPSC in a subset (33%) of single autaptic neurons, suggesting a coexpression of all three groups of mGluRs in the same axon terminals of a single neuron. Other neurons showed a variety of combinations of mGluRs, including an expression of only one group of mGluR (18%) or coexpression of two groups of mGluRs (27%). Some neurons had no response to any of the three agonists (22%). The three mGluR agonists had no effect on postsynaptic gamma-aminobutyric acid (GABA) receptor responses, indicating a presynaptic modulation of GABA release by mGluRs. We conclude that multiple mGluRs that act through different second messenger pathways are coexpressed in single axon terminals of SCN neurons where they modulate the release of GABA presynaptically, usually inhibiting release.

Animals↗
PubMed1998

Contractile responses to allergen and cholinergic stimulation in bronchus and trachea of cockroach allergen-sensitized guinea pigs.

Airway hyperreactivity is a hallmark of asthma. Yet, the role of allergic sensitization in the hyperreactivity remains controversial. This study examined the effects of airborne cockroach allergen (CRa) sensitization on the contractility of bronchial (BSM) and tracheal (TSM) smooth muscle rings to cholinergic stimulations, and to specific antigen, in vitro. Guinea pigs were actively immunized with CRa, 5 mg (high dose, HD), 0.5 mg (low dose, LD), or saline aerosols (2x/day, 5 days/week, for 4 weeks) and challenged by CRa inhalation 5 days after last exposure. Twenty-four hours postchallenge, the contractions of the TSM and BSM to electrical field stimulation (EFS), acetylcholine (ACh), and to CRa were measured in vitro. In addition, the contraction to these stimuli were also examined in the passively sensitized TSM with the sera of CRa-immunized guinea pigs. The contractile responses of actively immunized and passively sensitized tissues to EFS and ACh were very similar to those of control tissues. CRa induced dose-dependent contractions in both actively immunized and passively sensitized, but not in control, tissues. The CRa-induced contraction was stronger in the HD group than in the LD group (p<0.0001). Leukotriene C4/D4 receptor antagonist LY-171883 inhibited the CRa-induced contraction by 86% in actively immunized TSM, and by 9% in the passively sensitized TSM. Pyrilamine inhibited the contraction by 57% in actively immunized TSM and 70% in passively sensitized TSM. The results indicate that CRa sensitization does not cause increased airway smooth muscle contractility to cholinergic stimulations, but induces antigen-specific contractions in vitro. Leukotrienes appear to play a significant role in the CRa-specific contractions, more in the actively immunized than those in the passively sensitized tissues, while histamine exerts a moderate effect on the CRa-induced contractions.

Acetophenones↗
PubMed1998

Artificial juxtacrine stimulation for tissue engineering.

To endow biomaterials with the ability to regulate cell functions such as proliferation, differentiation, and apoptosis, growth factor proteins were covalently immobilized. The proteins were immobilized on various matrices using different chemical methods. It was shown that insulin and epidermal growth factor stimulated cellular functions even after immobilization. Pattern-immobilization of growth factor proteins clearly demonstrated the stimulation by immobilized proteins. In other words, this type of stimulation by non-diffusional growth factors enabled us to regulate tissue formation with artificial biomaterials. The stimulation was enhanced by coimmobilization with adhesion factors. These stimulations due to the immobilized growth factors may mimic juxtacrine stimulation of membrane-anchored growth factors such as heparin-binding epidermal growth factor, transforming growth factor-alpha, and tumor necrosis factor-alpha.

Animals↗
PubMed1998

Vectors for expressing T7 epitope- and His6 affinity-tagged fusion proteins in S. cerevisiae.

We have constructed a series of vectors (YGALSETs) for the expression of epitope- and affinity-tagged fusion proteins in yeast cells using the regulated GAL10 promoter. Fusion proteins produced from YGALSET plasmids include a leader peptide at the N terminus that encodes both a T7 gene 10 epitope tag and a His6 affinity tag. The YGALSET vector series includes centromere plasmids for low-copy plasmid maintenance and 2 micron episomal plasmids for multicopy plasmid maintenance and four different selectable markers: TRP1, URA3, LEU2 and HIS3. We also provide a convenient approach for transferring cloned genes from a bacterial expression vector into YGALSET vectors by in vivo recombination and a rapid method to screen directly for clones that express the fusion protein of interest.

Affinity Labels↗
PubMed1998

Immunophenotype of myeloid cells in myelodysplastic syndromes and its clinical implications.

OBJECTIVE: To explore the immunophenotype of myeloid cells in myelodysplastic syndyomes (MDS) and its clinical implications. METHODS: A panel of monoclonal antibody was used to detect CD13+, CD33+, CD15+ and CD14+ antigens on the membrane surfaces of myeloid cells in the bone marrow from 51 MDS, 21 aplastic anemia (AA), 21 paroxysmal nocturnal hemoglobinuria (PNH) patients. 10 acute myeloblastic leukemia (AML) patients and 15 normal subjects by immunoenzymatic assay. The morphology and chromosome karyotype of bone marrow cells of MDS patients were also examined. RESULTS: CD14+, CD13+ and CD33+ cells in the bone marrow were more in MDS patients than in normal controls, AA patients and PNH patients. CD15+ cells in the bone marrow were less in MDS patients than in normal controls. CONCLUSIONS: The percentages of CD14+, CD13+ and CD33+ positive cells in the bone marrow of MDS patients were related to the percentage of myeloblasts, the chromosomal aberrations and the response to treatment. It indicated that there is immunophenotypic misexpression of myeloid cells in MDS patients. Immunophenotype analysis of myeloid cells might be useful for the diagnosis and treatment of MDS patients.

Adolescent↗
PubMed1998

Pharmacokinetics of theophylline metabolites in 8 Chinese patients.

AIM: To study theophylline metabolites pharmacokinetics in patients after a therapeutic dose. METHODS: Eight adult patients with mild bronchial asthma and normal liver function were infused aminophylline intravenously (6.6 mumol.kg-1). The plasma concentrations of theophylline and its 4 metabolites: 1,3-dimethyluric acid (DMUA), 3-methylxanthine (3-MX), 1-methyluric acid (MUA), and the intermediate 1-methylxanthine (1-MX) were monitored by HPLC throughout 24 h. RESULTS: The plasma concentration of DMUA was the highest one among the 4 metabolites. 3-MX showed the slowest elimination rate. The plasma concentration of 1-MX throughout a 24-h period showed that there was a picking up of 1-MX (from 0.04 mumol.L-1 to 1.05 mumol.L-1) in the next morning. CONCLUSION: The formation of DMUA was the main metabolites. During night there was an accumulation of 1-MX.

Adult↗
PubMed1998

[Arterialization of the great saphenous vein for treating severe ischemia of lower limbs].

This study was to observe the result in patients suffering from severe ischemia of legs with arterialization of the great saphenous vein. Eighty nine patients suffering from the disease were treated by bridging the autogenous cephalic vein or Gore-Tex artificial vessel between the great saphenous vein and the femoral or external iliac arteries. The results showed that the blood supply of the affected legs was increased immediately after operation. The ulcers of the toes and the plantar areas were healed gradually and the pain relieved. It was concluded that this method did not interfere with the reflux of the venous blood in the diseased limbs. This method was simple, safe and effective for treating severe ischemia of the lower limbs.

Adolescent↗
PubMed1998

Study on acupuncture and moxibustion therapy for female urethral syndrome.

Among 180 patients with female urethral syndrome, 128 were treated by acupuncture and moxibustion and 52 by western medicine as controls. The short-term effective rate in the acupuncture and moxibustion group was 90.6% and the long-term effective rate, 80.4%; whereas the short-term effective rate of the control group was 26.9% (P < 0.01). The maximal uroflow rate increased by an average of 4.6 ml/s, after acupuncture and moxibustion treatment (P < 0.001) and the mean uroflow rate increased by an average of 3.1 ml/s (P < 0.001); on the contrary, no changes were found in the control group (P > 0.05). Sixty-nine cases from the acupuncture and moxibustion group and 39 from the control group were subjected before and after treatment to determinations of the maximal bladder pressure, maximal abdominal pressure, bladder-neck pressure, and maximal urethral closure pressure during urination. All these indexes were decreased remarkably in the acupuncture and moxibustion group, while no changes were observed in the control group.

Acupuncture Therapy↗
PubMed1998

[Cleft palate repair with bilateral buccal musculomucosal flaps].

OBJECTIVE: A method for cleft palate repair was used for the purpose of diminishing surgical interference with maxillary growth. METHOD: Sixteen cases of cleft palate were repaired with bilateral buccal musculomucosal flaps. RESULT: The operation results in all cases were satisfactory. CONCLUSION: It is concluded: 1. The method does not traumatize the periosteum of the hard palate, thus alleviating postoperative maxillary deformity; 2. The buccal musculomucosal flap is generally long enough to reach across the incisive foramen and maintain good blood circulation; 3. The method benefits reconstruction of the levator sling and facilitates velopharyngeal closure.

Cheek↗
PubMed1998

[Experimental study on hypoglycemic effect of YTY granules].

OBJECT: To perform experimental pharmacodynamic evaluation of a new TCM antidiabetic drug Yitangyin (YTY). METHODS: Experimkental streptozotocin induced rat diabetes models were subjected YTY treatment and the hypoglycemic effect was evaluated. The proved TCM Yusanxiao (YSX) was used as contrast. RESULTS: The low, middle and high dose YTY groups exhibited significant hypoglycemic effects on the model rats. The efficiency was comparable with YSX. CONCLUSION: The TCM YTY granule is an effective hypoglycmeic agent.

Animals↗
PubMed1998

[Comparative study of left ventricular morphology and function of patients with left ventricular systolic and diastolic heart failure on echocardiography].

Left ventricular pathology and pathophysiological characteristics of fifty patients with left ventricular diastolic heart failure (LVDHF), and 35 patients with left ventricular systolic heart failure (LVSHF) diagnosed by clinical manifestations and radionuclide ventriculography, were examined by echocardiography and 20 healthy persons were served as control group. Left atrial diameter (LAD), interventricular septum thickness (IVST) and posterior wall thickness (PWT) and left ventricular mass index (LVMI) were significantly increased in the patients with LVDHF, while left ventricular diameter (LVD) was significantly increased in the patients with LVSHF. Left ventricular ejection fraction (LVEF), cardiac index (CI) were significantly decreased in the patients with LVSHF. Early peak filling velocity (EPFV), atiral peak filling velocity (APFV), deceleration of early peak filling velocity (DC) and isovolumic relaxation time (IRT) in the patients with LVDHF and LVSHF observed no significant difference.

Adult↗
PubMed1998

[Clinical study on left ventricular diastolic heart failure in the aged patients].

Forty aged patients with LVDHF and 30 with left ventricular systolic heart failure (LVSHF), confirmed by radionuclide ventriculography were studied by clinical, echocardiography and treadmill test. Twenty healthy aged persons were served as control group. Compared with LVSHF, short duration and less severe manifestations of heart failure in LVDHF were observed. Compared with the control, left atrium was enlarged but not the left ventricular chamber, and LV wall was thickened in LVDHF, while enlargement of LV chamber was only found in LVSHF. However, LV systolic function was remained normal in LVDHF. The exercise tolerance was decreased in both LVDHF and LVSHF groups, but more marked in LVSHF.

Aged↗
PubMed1998

[Experimental study of FZBZ decoction enhancing chemotherapy efficacy for mice bearing with tumors].

To study the mechanism of the increasing effect of Fuzheng Baozhen decoction (FZBZD) on chemotherapy. The BALB/C mice with transplanted human lung adenocarcinoma (SPC-A-1), sarcoma (S180) were treated in different groups. Comparing the group treated with chemotherapy (CTX), and the group treated with CTX plus FZBZD, the inhibiting tumor rate was higher (P < 0.01), the cAMP/cGMP ratio was increased by adding cAMP level in cancer tissue (P < 0.05), the level of serum TNF-alpha and MDA was decreased (P < 0.01), the activity of total SOD was improved (P < 0.01), the G0/G1 phase cells enhanced and S phase cells decreased in tumor tissue (P < 0.05). It suggested that FZBZD increased the effect of chemotherapy in different ways.

Adenocarcinoma↗
PubMed1998

[Detection of microcystins in source and tap water from a lake].

The microcystins in source and tap water collected from seven waterworks around a lake in summer, 1996 were detected by enzyme-linked immunosorbent assay (ELISA). Microcystins were determined in the source water from all the seven waterworks, and the concentrations ranged from 280 to 35,300 ng/L. Low concentrations of microcystins were also detected in the tap water of three waterworks. The results suggest that microcystins in source water could not be removed completely by conventional adding bleaching powder treatment.

Bacterial Toxins↗
PubMed1998

[A study of the adenosine deaminase polymorphism in a Chinese Han population by the PCR method].

The study of genetic polymorphism of adenosine deaminase (ADA) has not been reported in China and abroad. The target DNA was amplified by PCR. The amplified product was then digested with Pst I, and run on a 9% polyacrylamide gel electrophoresis and followed by AgNO3 staining. ADA polymorphism, was determined in 80 unrelated individuals Chinese Han polulation. Five alleles and 14 genotypes were detected. The gene frequencies were ADA * 10 = 0.15625, ADA * 11 = 0.31875, ADA * 12 = 0.23750, ADA * 13 = 0.23125 and ADA * 14 = 0.05625 respectively. The heterozygosity was 0.8 and the discrimination power (DP) was 0.89. The distribution of observed genotypes frequencies was in good agreement with the Hardy-Weinberg law. The study of three families demonstrated that this locus was inherited according to Mendelian law. The technique is quite simple, fast, extremely sensitive, and it does not require the use of radioisotopes. This new method may be used for the forensic identification and paternity testing.

Adenosine Deaminase↗
PubMed1998

[Morphologic changes of red blood cells in various conditions under scanning electron microscope].

To study the changes of RBC in various conditions, blood clots elapsed 6 days in water and air and bloodstains stored in variant time were observed under Scanning Electron Microscope (SEM). The results showed that the morphology of RBC elapsed 6 days in water and air seemed to retain their integrity. They were measured 5, 48-5, 88 microns in diameter, whereas the RBC in the bloodstains stored 14 years were obviously disfigured and some appeared membrane cracking. However, the structure of RBC membrane was well recognized under the SEM. The morphological changes under the SEM and the forensic significance of the RBC were discussed.

Blood Stains↗