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Biomedical subjects

K Chen

Publications and source records attributed to K Chen.

At least 217 records · Page 12Linked to original sources
PubMed1999

In vitro and in vivo studies of the effect of a Chinese herb medicine on osteoclastic bone resorption.

OBJECTIVE: To study the effect of a Chinese herb on osteoclastic bone resorption and osteoporosis. MATERIALS AND METHODS: Osteoclasts were isolated and cultured for in vitro study of the effect of the Chinese herb Guizhou epimedium (Epimedium Leptorrhizum Stearn). The in vivo effect of this Chinese herb was also investigated in rats in whom osteoporosis was induced by ovariectomy; these results were then compared with the effects of estradiol in the same group of rats. RESULTS: The in vitro study showed that the epimedium inhibited the osteoclastic resorption of bone. The in vivo investigation demonstrated that both the epimedium and estradiol were able to increase mineral content and promote bone formation. CONCLUSION: The Chinese herb Guizhou epimedium is of potential use in the treatment of osteoporosis.

Animals↗
PubMed1999

MAO-A and -B gene knock-out mice exhibit distinctly different behavior.

MAO-A and -B are key isoenzymes that degrade biogenic and dietary amines. MAO-A preferentially oxidizes 5-HT and NE, whereas MAO-B preferentially oxidizes PEA. However, the substrate and inhibitor selectivity overlap depending on the concentration of the enzyme and substrate. A line of transgenic mice has been generated in which the gene that encodes MAO-A is disrupted. MAO-A KO mice have elevated brain levels of 5-HT, NE and DA and manifest aggressive behavior similar to men with a deletion of MAO-A. We have also generated mice deficient in MAO-B by homologous recombination. Interestingly, MAO-B KO mice do not exhibit aggression and only levels of PEA are increased. MAO-B-deficient mice are resistant to the Parkinsongenic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Thus, studies of MAO-A and -B KO mice have clearly shown that MAO-A and -B have distinct functions in neurotransmitter metabolism and behavior. MAO KO mice are valuable models for investigating the role of monoamines in aggression and neurodegenerative and stress-related disorders.

Aggression↗
PubMed1999

Glutathione antagonized cyclophosphamide- and acrolein-induced cytotoxicity of PC3 cells and immunosuppressive actions in mice.

AIM: To study the antagonistic effect of glutathione (GSH) on toxicity of PC3 cell induced by cyclophosphamide (Cyc) and acrolein (Acr) and on immunosuppressive actions caused by Cyc. METHODS: Splenocyte, PC3 cell proliferation and cell protein content were measured by tetrazolium (MTT) assay and Coomassie brilliant blue assay. Serum anti-SRBC hemolysin, agglutinin, and splenocyte proliferation were measured in normal and S-180-bearing mice. Tumors were weighed. RESULTS: Pretreatment with GSH 2 mmol.L-1 reduced splenocyte proliferation inhibition from 18.64%, 49.72% to 6.78%, 18.36% (induced by Cyc 1, and 5 mmol.L-1), and PC3 cell proliferation inhibition from 27.7%, 45.3%, and 74.6% to 14.6%, 18.8%, and 49.1% (induced by Cyc 1, 3, and 5 mmol.L-1), and from 62.6%, 85.4%, and 90.6% to 41.9%, 57.7%, and 86.4% (induced by Acr 10, 25, and 50 mumol.L-1), respectively. In normal mice, s.c. GSH 75 or 150 mg.kg-1 b.i.d. x 5 d after i.p. Cyc 40 mg.kg-1, the hemolysin and the splenocyte proliferation were higher than those in normal mice i.p. Cyc 40 mg.kg-1 alone. Hemolysin, serum agglutinin, and splenocyte proliferation in S-180-bearing mice given s.c. GSH 150 mg.kg-1 b.i.d. x 10 d after i.p. Cyc 40 mg.kg-1 were also markedly higher than those in S-180-bearing mice given i.p. Cyc alone. But, according to tumor weight, GSH did not interfere the antitumor activity of Cyc in S-180-bearing mice. CONCLUSION: GSH exhibited protective effects against Cyc and Acr, but had no effect on the antitumor action of Cyc.

Acrolein↗
PubMed1999

[Efficacy of Chinese recipes of replenishing kidney and activating blood circulation in female rats with osteoporosis induced by ovariectomy].

OBJECTIVE: To investigate the efficacy of Chinese recipe of replenishing Kidney and activating blood circulation (RKABC) in female rats with osteoporosis induced by ovariectomy. METHODS: Fifty female SD rats at 12 months of age were chosen, and were divided into 5 groups; control, model, model plus nylestriol, RKABC (high dose) and RKABC (low dose). The model of osteoporosis was established by ovariectomy in rats for 12 weeks, and then was given different kinds of liquid and administered approximately for 12 weeks. General bone mineral density (GBMD), femur bending strength (FBS), serum-BGP and urine-Hyp/Cr were measured. RESULTS: GMBD, FBS in 3 treatment groups were significantly higher than those in the model group (P < 0.05), but lower than those in the normal control group (P < 0.05); GBMD, FBS in 2 RKABC groups were slightly higher than those in nylestriol's group (P > 0.05). Compared with model group, levels of serum BGP in 2 RKABC groups increased (P < 0.05) and in RKABC (H) treatment group increased almost the same as those in the control group (P > 0.05). In comparison with model group, levels of U-Hyp/Cr in 3 treatment groups decreased (P < 0.05, P < 0.01) but 2 RKABC treatment groups still significantly higher than those in the normal control group (P < 0.05). CONCLUSION: It indicated that RKABC could control osteoporosis in female rats induced by ovariectomy and seems to promote bone formation.

Animals↗
PubMed1999

[Direct determination of serum content of ferulic acid treated with boiling water in HPLC in volunteers after oral Administration of Coronary Heart No. II decoction].

OBJECTIVE: To develop a new method for clinical pharmacokinetic detection of chemical component of Coronary Heart NO. II in serum after oral administration in healthy person. METHODS: Content of ferulic acid (FA) in serum, which had been treated with boiling water bath, was determined directly by high performance liquid chromotography (HPLC) and spectrophotometer. After qualitative detection performed by using Bi- and tri-dimensional HPLC and ultraviolet spectrophotometer, the quantitative detection was determined with the internal standard (coumarin). RESULTS: When eluted by mobile phase of a mixture of methanol, acetic acid and water (38:0.3:61.7 in ratio), and stationary phase of C18(ODS2), column (150 mm x 4.6 mm, 5 microns), the minimal detectable limit of free methanol FA was 6 ng (N/S = 3), and the minimal detectable serum FA concentration, after 10 min of boiling water bath, was 20.2 micrograms/L, with a linearity of 33.7-2156.8 micrograms/L, r = 0.9993. The mean recovery of serum FA was (93.59 +/- 2.36) micrograms/L. The RSD within day and day-to-day were all less than 8.44%. CONCLUSION: In comparing with sample Preparation of acetonitrile, this method is simple, rapid, sensitive, cheap, accurate, specific, reproducible and no toxic.

Adolescent↗
PubMed1999

[The thumb reconstruction by transferring the injured index finger with pedicles].

OBJECTIVE: In order to inquire the methods of thumb reconstruction by transferring the index finger with incomplete conditions of nerve or blood vessels. METHODS: From April 1987 to October 1997, 6 cases were treated by 3 kinds of operative methods according to the damage type of thumb and complications injures of the rest of hand: 1. transferring the index finger with pedicle without proximal phalanx, 2. transferring the index finger with palmar nerve and blood vessels, and dorsal skin pedicle, 3. transferring the index finger with compound pedicle. RESULTS: All 6 cases of thumb reconstruction were successful. Followed up 6 months to 2 years, the pinching and gribing functions in 6 cases were completely recovered, and the sensation were partly recovered. CONCLUSION: The operative method of thumb reconstruction had following advantages: Simple operation, high survival rate and certain function recovery. It can enlarge the indications of thumb reconstruction.

Adult↗
PubMed1999

[Study on chemical constituents of essential oil of Michelia leaves by gas chromatography-mass spectrometry].

The essential oil in Michelia leaves was extracted by steam distillation. The oil obtained was dried with anhydrous magnesium sulfate. The chemical constituents were analyzed by GC-MS. Thirty three peaks were separated by GC, and 27 of them were identified by MS with NBS mass spectral data and Wiley/NBS registry of mass spectral data. The structure of linalool was further verified by GC/FTIR. The identified constituents represent 97% of the peak area of the essential oil on FID. The major chemical constituent of them are linalool, trans-caryophyllene and diethyl-o-phthalate.

Acyclic Monoterpenes↗
PubMed1998

Transcription factor binding to the core promoter of the human monoamine oxidase B gene in the cerebral cortex and in blood cells.

Many studies show that monoamine oxidase B in blood cells is a biological marker for personality characteristics such as sensation seeking. The mechanism underlying this association is so far not explored. In the present study we have performed electrophoretic mobility-shift assays to investigate the pattern of protein binding to a 150 bp fragment of the proximal 5'-flanking region of the human monoamine oxidase B gene. We compared the pattern using nuclear extracts from human brain and lymphocytes. Interestingly, a correlation was observed between monoamine oxidase B enzyme activity in blood cells (platelets) and the binding pattern of two uncharacterized transcription factors. These data are well in line with the long-standing notion that interindividual differences in platelet monoamine oxidase may represent differences in expression of the enzyme rather than genotypic variation.

Blood Platelets↗
PubMed1998

Morphologic characteristics of physiologically defined neurons in the cat trigeminal nucleus principalis.

Although the principalis nucleus (Vp) contains trigeminothalamic and internuclear tract cells, the functional and morphologic differences between the two kinds of neurons have remained unsettled. The present study was aimed to address these problems by using the intracellular horseradish peroxidase injection technique in the cat. Of 20 neurons stained, 7 and 13 were located in the dorsomedial subnucleus (Vpd) and ventrolateral subnucleus (Vpv) of Vp, respectively. The Vpd neurons received input from the intraoral structures only but the Vpv neurons from the intraoral or facial structures. Nineteen neurons could be divided as class I and class II, based on the branching pattern of their stem axons. Class I (eight neurons) had an ascending stem axon without branching. Class II was divided into two subclasses (IIa and IIb). Class IIa (eight neurons) had an ascending stem axon from which branches were given off. Their branches formed a local-circuit restricted to the lower brainstem. Class IIb (three neurons) had a stem axon that formed the local-circuit only. The dendritic morphology was indistinguishable between different classes of neurons and between the subdivisions. Although the dendritic arborization pattern was governed by the location of the somata, it was suggested to be also important elements for determining primary afferent arborizations. In the brainstem nuclei, the jaw-closing motor nucleus received the highest density of projections from class II neurons with the receptive field involving the periodontal ligaments. The present study provides new findings that Vp neurons could be divided into three distinct populations and suggests that each population exerts a distinct function with respect to sensory discrimination, sensorimotor reflexes, or both.

Anatomy, Artistic↗
PubMed1998

Protease-activated receptor 1 (PAR-1) is required and rate-limiting for thrombin-enhanced experimental pulmonary metastasis.

Thrombin-treated tumor cells induce a metastatic phenotype in experimental pulmonary murine metastasis. Thrombin binds to a unique protease-activated receptor (PAR-1) that requires N-terminal proteolytic cleavage for activation by its tethered end. A 14-mer thrombin receptor activation peptide (TRAP) of the tethered end induces the same cellular changes as thrombin. Four murine tumor cells (Lewis lung, CT26 colon CA, B16F10 melanoma, and CCL163 fibroblasts) contain PAR-1, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR). B16F10 cells did not contain the two other thrombin receptors, PAR-3 and glycoprotein Ib. TRAP-treated B16F10 tumor cells enhance pulmonary metastasis 41- to 48-fold (n = 17). Thrombin-treated B16F10 cells transfected with full-length murine PAR-1 sense cDNA (S6, S7, S14, and S22) enhanced their adhesion to fibronectin 1.5- to 2.4-fold (n = 5, P <.04), whereas thrombin-treated wild-type cells do not. S6 (adhesion index, 1.5-fold) and S14 (index, 2.4-fold) when examined by RT-PCR and Northern analysis showed minimal expression of PAR-1 for S6 over wild-type and considerable expression for S14. Immunohistochemistry showed greater expression of PAR-1 for S14 compared with wild-type or empty-plasmid transfected cells. In vivo experiments with the thrombin-treated S14 transfectant showed a fivefold to sixfold increase in metastases compared with empty-plasmid transfected thrombin-treated naive cells or S6 cells (n = 20, P =.0001 to .02). Antisense had no effect on thrombin-stimulated tumor mass. Thus, PAR-1 ligation and expression enhances and regulates tumor metastasis.

Animals↗
PubMed1998

Simulation of Particle Adsorption onto a Polymer-Coated Surface Using the Dissipative Particle Dynamics Method.

Dissipative particle dynamics (DPD) was originated as a tool for performing fluid dynamics simulations of complex fluids and among other things has been used to simulate dilute polymer solutions. This report describes a new application of the technique-modeling the adsorption of colloidal particles onto a polymer-coated surface. This type of simulation would be beyond the scope of molecular dynamics but is effectively modeled with DPD. The preliminary results of these investigations, presented here, show good agreement with what might be predicted theoretically. They show that the colloidal particles would be less likely to adsorb onto the surface as the size of the polymer relative to the particle is increased, or similarly as the density of the polymers is increased. They also show that particle adsorption is reduced when the polymer is well solvated. They demonstrate how particles that have agglomerated with each other find it more difficult to penetrate a polymer barrier because of their greater size. Further investigation is required to understand the effects of temperature. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

H+ISFET-based biosensor for determination of penicillin G.

A biosensor based on an H+ ion sensitive field effect transistor (H+(-)ISFET) and penicillin G acylase has been developed. The response time of the sensor to different concentrations of penicillin G was 30 s. In a 20 mM phosphate buffer at pH 7.0, the linear range of the calibration curve was from 0.5 to 8 mM. The coefficients of variation for three samples with 20 repeated measurements were below 5%. Stability of the sensor could reach about 6 months and more than 1000 runs were performed without a significant decrease of the output value. The sensor was tested for measurement of the penicillin G content in penicillin fermentation both. Forty samples with low and high concentrations of penicillin G were chosen for the correlation test. The values assayed by the sensor method were compared with the values assayed by HPLC method, the correlation coefficient (r) was 0.9944 and the regression equation was y = 1.034X - 2083.7, respectively. The different measuring methods are discussed in the text.

Biosensing Techniques↗
PubMed1998

Role of Mxi1 in ageing organ systems and the regulation of normal and neoplastic growth.

Mxi1 belongs to the Mad (Mxi1) family of proteins, which function as potent antagonists of Myc oncoproteins. This antagonism relates partly to their ability to compete with Myc for the protein Max and for consensus DNA binding sites and to recruit transcriptional co-repressors. Mad(Mxi1) proteins have been suggested to be essential in cellular growth control and/or in the induction and maintenance of the differentiated state. Consistent with these roles, mxi1 may be the tumour-suppressor gene that resides at region 24-26 of the long arm of chromosome 10. This region is a cancer hotspot, and mutations here may be involved in several cancers, including prostate adenocarcinoma. Here we show that mice lacking Mxi1 exhibit progressive, multisystem abnormalities. These mice also show increased susceptibility to tumorigenesis either following carcinogen treatment or when also deficient in Ink4a. This cancer-prone phenotype may correlate with the enhanced ability of several mxi1-deficient cell types, including prostatic epithelium, to proliferate. Our results show that Mxi1 is involved in the homeostasis of differentiated organ systems, acts as a tumour suppressor in vivo, and engages the Myc network in a functionally relevant manner.

Aging↗