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Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 721 records · Page 40Linked to original sources
PubMed1995

[Detection of serum procollagen III peptide in tuberculous patients].

The serum procollagen peptide (PIIIP) levels of 132 cases of tuberculosis and 37 healthy persons have been detected with RIA. The results showed that the serum PIIIP level in tuberculous patients is significantly higher than that of healthy persons (P < 0.001) and strongly related to the severe degree of activity and the size of pathological change of tuberculosis and patient condition. It suggests that there might be some significance in assessing serum PIIIP in tuberculous patients for evaluating the severity and prognosis of the illness.

Adolescent↗
PubMed1995

Effects of toquipidine on ionic channels of cultured embryonic Xenopus laevis myoblasts and neurons.

AIM: To study the effects of toquipidine (1-p-methyl-phenyl-2-(alpha-piperidinoacetyl)-1, 2, 3, 4-tetrahydroisoquinoline hydrochloride, Toq), a new anti-arrhythmic agent first synthesized in China, on ionic channels. METHODS: Ionic channel currents were recorded by whole-cell patch clamp technique in cultured embryonic Xenopus laevis myoblasts and neurons. RESULTS: Toq (0.1, 1, 10, and 100 mumol L-1) caused a concentration-dependent inhibition of the Na+ currents with IC50 7.2 mumol L-1 (5.3-9.8 mumol L-1). Toq (10 mumol L-1) also suppressed the high-voltage-activated Ca2+ currents in neurons. But the steady-state outward K+ currents in myoblasts were activated by Toq (10 mumol L-1). CONCLUSION: Toq blocked the Na+ and Ca2+ channels and opened the steady-state outward K+ channels.

Animals↗
PubMed1995

[Mentoplasty for common congenital mandibular deformities].

Since 1987, the authors have performed mentoplasty for congenital mandibular deformities in 46 patients with the assistance of X-ray pantomoscanning. Mandibular deformities include: 1) Bilateral hyperplasia of mandibular angles and massetter hypertrophy; 2) Retrognathia or micrognathia; 3) Asymmetric mandibular deformity. In this paper, following problems are discussed: 1) The advantages of an extraoral approach in mentoplasty; 2) The importance of the X-ray pantomoscanning; 3) The specific feature of asymmetric chin; 4) The improvement of the silicon implant used in mentoplasty; 5) Evaluation of the composite operative result.

Adolescent↗
PubMed1995

[Analysis of 110 cases of sacrococcygeal lesions in children].

110 cases of sacrococcygeal lesions seen in the Guangzhou Children's hospital were reviewed. 42 cases were anomalies, 66 cases were tumors and 2 were inflammatory granulomas. As compared to data in western literatures, the morbidity of anomalies in this series was lower than that of tumors, whereas in western reports the morbidity of anomalies was much higher than that of tumors. Another interesting point was that the morbidity of meningocele (MC) in this series was much higher than that of myelomeningocele (MMC) of spina bifida (7:1). According to a study in Australia, the MC:MMC was 1:5. We suggest that endodermal sinus tumor should be considered as an independent entity of there was no other tissue component (organlike component) found in tumor section. We also suggest that if neuroblastoma and/or other immature neuroectodermal component is observed in a teratoma, it should be classified as malignant rather than benign.

Child, Preschool↗
PubMed1995

Interaction of BiP with substance P and nucleotides.

A rapid and simple spin column assay has been used to study interactions of BiP with substance P (SP) and ATP. At 4 degrees C, the binding of SP to BiP requires ATP and a stable SP-BiP.ATP complex is formed. Nonhydrolyzable ATP analogues or ADP cannot replace ATP. Although ATP converts BiP dimers to monomers, the requirement for ATP for SP binding is not solely due to BiP dissociation, because purified BiP monomers also require ATP for peptide binding. At 37 degrees C, there is rapid binding of SP to BiP even in the absence of ATP and, in fact, ATP at concentrations above 5 microM causes release of SP from BiP. At this higher temperature, there is also rapid hydrolysis of ATP bound to BiP. These results extend our previous results (Brot et al., 1994) that indicated the formation, at low ATP concentrations, of a labile SP.BiP.ATP complex that, after ATP hydrolysis, resulted in a stable SP.BiP.ADP complex.

Adenosine Triphosphate↗
PubMed1995

[Observation of compensatory head posture in superior oblique muscle paralysis].

PURPOSE: Superior oblique muscle paralysis is the most common disease in clinic. We analysed the cause, machanism and regularity of compensatory head posture in superior oblique muscle paralysis. METHODS: All of 27 cases with superior oblique muscle paralysis aere examined regularly, and special muscle, binocular single vision function with synoptophore examined. Bielschowsky test was made. RESULTS: In our cases, the incidence rate of compensatory head posture was 40.7%, which had relations with age when a patient had disease, period and function of binocular single vision. CONCLUSION: The existance of binocular single vision function is the physiological bases leading to compensatory head posture, and the patients whose ages are older than 3 years and the course is less than 10 years may present the compensatory head posture. So we should pay attention to early diagnosis and training to restore the binocular single vision function.

Adolescent↗
PubMed1994

Search for linkage to schizophrenia on the X and Y chromosomes.

Markers for X chromosome loci were used in linkage studies of a large group of small families (n = 126) with at least two schizophrenic members in one sibship. Based on the hypothesis that a gene for schizophrenia could be X-Y linked, with homologous loci on both X and Y, our analyses included all families regardless of the pattern of familial inheritance. Lod scores were computed with both standard X-linked and a novel X-Y model, and sib-pair analyses were performed for all markers examining the sharing of maternal alleles. Small positive lod scores were obtained for loci pericentromeric, from Xp11.4 to Xq12. Lod scores were also computed separately in families selected for evidence of maternal inheritance and absence of male to male transmission of psychosis. The lod score for linkage to the locus DXS7 reached a maximum of 1.83 at 0.08% recombination, assuming dominant inheritance on the X chromosome in these families (n = 34). Further investigation of the X-Y homologous gene hypothesis focussing on this region is warranted.

Chromosome Mapping↗
PubMed1994

Cloning sequencing and expression of the gene encoding the VP2 protein of the human group B rotavirus, ADRV.

Adult diarrheal rotavirus, ADRV, is a noncultivable human group B rotavirus. A complete cDNA copy of ADRV gene segment 2 has been cloned and sequenced. Gene segment 2 contains 2844 bases and encodes one long open reading frame beginning at base 14 and terminating at base 2812. Gene 2 encodes a protein containing 933 amino acids with a calculated molecular weight of 105.6 kDa and a pl of 5.5. The gene 2 polypeptide contains significant homology with the VP2 protein which comprises the core of group A rotavirus strains. The gene 2 protein has been expressed in a rabbit reticulocyte lysate in vitro and is identical in molecular mass with a protein previously demonstrated to be present on iodinated EDTA-treated virions and from in vitro translations of total ADRV mRNA. A recombinant baculovirus containing gene segment 2 has been constructed and used to express the encoded VP2 equivalent protein. The expressed VP2 protein is immunoprecipitable by hyperimmune anti-ADRV serum, porcine group B infection serum, and human convalescent serum but not by hyperimmune serum to group A rotavirus. Our results suggest that ADRV gene segment 2 encodes the VP2 protein equivalent to group A rotavirus strains present in the core of the group B virion.

Amino Acid Sequence↗
PubMed1994

Role of cellular glutathione and glutathione S-transferase in the expression of alkylating agent cytotoxicity in human breast cancer cells.

Glutathione (GSH) and glutathione S-transferases (GSTs) play an important role in the protection of cells against toxic effects of many electrophilic drugs and chemicals. Modulation of cellular GSH and/or GST activity levels provides a potentially useful approach to sensitizing tumor cells to electrophilic anti-cancer drugs. In this study, we describe the interactions of four representative alkylating agents (AAs), melphalan, 4-hydroperoxy-cyclophosphamide (4HC), an an activated form of cyclophosphamide, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and cisplatin, with GSH and GST in the human breast cancer cell line MCF-7. Depletion of cellular GSH pools by approximately 80% by treatment of the cells with the GSH synthesis inhibitor buthionine sulfoximine (BSO) sensitized the tumor cells to each AA to a different extent, with dose-modifying factors of 2.39, 2.21, 1.64, and 1.27 observed for melphalan, 4HC, cisplatin, and BCNU, respectively. Treatment of the cells with the GST inhibitor ethacrynic acid (EA) failed to show any significant effects on the cytotoxicity of these AAs. However, EA did potentiate the cytotoxicity of melphalan when given in combination with BSO, an effect that may be due to a more complete depletion of cellular GSH levels by the combined modulator treatment. Following a 1-hr exposure to cytotoxic-equivalent concentrations of these AAs, GSH levels decreased substantially in the case of 4HC and BCNU, but increased by 30-50% in the case of cisplatin and melphalan. BSO pretreatment largely blocked this effect of cisplatin and melphalan on cellular GSH, while it further enhanced the GSH-depleting activity of both 4HC and BCNU. On the basis of these results, it is concluded that (a) GSH affects the cytotoxicity of different AAs to different extents, (b) basal GST expression in MCF-7 cells does not play a major role in AA metabolism, (c) EA can potentiate the enhancing effect of BSO on melphalan cytotoxicity in MCF-7 cells, and (d) depletion of cellular GSH by pretreatment with BCNU or cyclophosphamide may correspond to a useful strategy for enhancing the anti-tumor activity of other AAs given in a sequential combination.

Alkylating Agents↗
PubMed1994

Separation of mouse crushed muscle extract into distinct mitogenic activities by heparin affinity chromatography.

Extracts from gently crushed adult mouse skeletal muscles (CMEs) contain potent myoblast mitogens, and may be used as a model system to investigate myotrophic factors released by adult muscles following injury. CME was separated into four peaks of mitogenic activity by heparin affinity chromatography. The fraction of CME that did not bind to heparin contained transferrin (Tf). Three peaks of mitogenic activity were eluted from the heparin-agarose columns at NaCl concentrations of 0.4 M, 0.9 M, and 2.0 M. A 46 kDa protein that shared antigenicity with the BB isoform of platelet-derived growth factor (PDGF-BB) was present in the 0.4 M NaCl eluant. Mitogenic activity in the 2.0 M NaCl peak eluted identically to purified basic fibroblast growth factor (bFGF), did not act additively to saturating amounts of purified bFGF, and was neutralized by anti-bFGF antibodies. The 0.9 M NaCl eluant acted additively to the combination of three known growth factors for myoblasts, bFGF, insulin-like growth factor 1, and epidermal growth factor, to stimulate C2 myoblast proliferation, suggesting this fraction contains a mitogenic activity which does not utilize (and hence compete for) receptors for the known mitogens for myoblasts. Additionally, the 0.9 M NaCl eluant did not stimulate proliferation of fibroblast-like cells derived from muscle tissue. The unbound, 0.4 M NaCl, 0.9 M NaCl, and 2.0 M NaCl eluants from the heparin-agarose column acted additively to one another to stimulate myoblast proliferation. Our data suggest that Tf, PDGF-BB-like molecules, bFGF-like activity, and an uncharacterized heparin-binding myoblast mitogen could be released after muscle injury and act to stimulate satellite cell proliferation.

Animals↗
PubMed1994

Extracts from mdx and normal mouse skeletal muscle contain similar levels of mitogenic activity for myoblasts.

The mdx mouse has been used as an animal model for human Duchenne muscular dystrophy (DMD). Unlike DMD, skeletal muscles of mdx mice undergo successful regeneration and do not show extensive fibrosis and functional impairment. Growth factors have been proposed to be involved in muscle growth and regeneration. We compared mitogenic activity for skeletal myoblasts released after injury in mdx and control mice, using crushed muscle extract (CME) as a model system. We found that CMEs from normal and mdx mice contained similar mitogenic activities per microgram protein, and produced similar maximal levels of mitogenic stimulation. Skeletal muscles from mdx mice, however, released higher amounts of CME protein per gram of muscle weight compared to controls, possibly as a result of histological or physiological alterations in mdx muscle tissue. Adequate mitogenic activity in CME from mdx muscles may be related to successful muscle regeneration in mdx mice.

Animals↗
PubMed1994

Transforming growth factor-beta 1 lowers the CD14 content of monocytes.

Marked elevation of transforming growth factor-beta 1 (TGF-beta 1) has been demonstrated clinically following injury and in sepsis. While alterations in the monocyte binding site (CD14) for the lipopolysaccharide (LPS)-lipopolysaccharide binding protein (LBP) complex have been noted with exposure to LPS, immune complexes, gamma-interferon, and IL-4, it is not known whether TGF-beta 1 can alter CD14 expression. To study the effect of TGF-beta 1 on monocyte CD14 expression, human leukocytes were isolated from healthy donors with discontinuous gradient centrifugation and incubated at 37 degrees C for 2 and 24 hr with increasing doses of purified human platelet TGF-beta 1. Monocytes were immunofluorescently stained with monoclonal antibodies recognizing CD14 and CD16. The cells were analyzed by flow cytometry. At 2 hr, 50 ng/ml TGF-beta 1 significantly lowered CD14 expression (51%, P = 0.043). At 24 hr, there was no significant difference between cells stimulated by TGF-beta 1 and control cells. To confirm that TGF-beta 1 was active at 24 hr, we examined levels of CD16. CD16 expression was increased by 10 ng/ml of TGF-beta 1. These observations suggest that high physiologic concentrations of TGF-beta 1 cause early monocyte suppression of CD14. Thus, CD14 may be marker for the transition of monocytes to macrophages and TGF-beta 1 may be responsible for the down-regulation of CD14 expression observed in monocytes obtained from septic patients.

Antigens, CD↗
PubMed1994

Rice tungro bacilliform virus: transcription and translation in protoplasts.

Protoplasts from cell suspension cultures of Oryza sativa (monocot) and Orychophragmus violaceus (dicot) support transcription from the rice tungro bacilliform virus (RTBV) promoter and translation of the resulting mRNA despite the presence of a long leader sequence with strong secondary structure and 12 short open reading frames. Transcriptional elements located both upstream and downstream of the transcription initiation site are defined by deletion analysis and the functional TATA motif is determined. Expression of an open reading frame downstream of the entire leader is more efficient than that downstream of truncated derivatives. For optimal expression sequences in the 5' and 3' parts of the leader are required.

Base Sequence↗
PubMed1994

Tumor suppressor genes and their roles in breast cancer.

Tumor suppressor genes have been identified by the occurrence of mutations in many families with hereditary forms of cancer, exposed during development of the tumor by loss of heterozygosity. They have a number of diverse functions. For example, both the RB gene of retinoblastoma and the p53 gene, which is commonly mutated in breast and colon cancer among others, produce proteins involved in distinct steps of cell cycle control, while the nm23 product prevents metastasis. Here we review the data developed until now on the possible presence and role of mutations in these and other tumor suppressor genes in breast cancer. A more complete understanding of the tumor suppressor genes could not only provide diagnostic information, but could lead to specific gene therapy to replace suppressor functions lost in individual tumors.

Animals↗