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Biomedical subjects

W Luo

Publications and source records attributed to W Luo.

At least 181 records · Page 10Linked to original sources
PubMed1995

[The relationship between H2 receptor and the pathogenesis of bronchial asthma in guinea-pigs].

UNLABELLED: H2 receptor (H2R) is one of the three histamine receptor subtypes. In order to explore the relationship between H2R and the pathogenesis of bronchial asthma, we investigated the effects of H2R agonist impromidine on guinea-pig isolated tracheal smooth muscle and the effects of dimaprit on the lung function of guinea-pigs provoked by antigen. RESULTS: (1) Impromidine (10(6) mol/L) relaxed partly the guinea-pig isolated tracheal spirals contricted by histamine challenge. After pretreating the spirals with impromidine, the maximum response to histamine was reduced in a dose-dependent manner and the cumulative dose-response curve to histamine was shifted to right. (2) Dimaprit (3mg/kg) given by intravenous injection protected the lung function from damage caused by antigen. These results suggest that H2R agonist produces relaxation of guinea-pig tracheal smooth muscle and inhibits the release of inflammatory mediators in anaphylactic reaction. We concluded that H2R plays some protective roles in the pathogenesis of bronchial asthma.

Animals↗
PubMed1994

Regulation of the Msx2 homeobox gene during mouse embryogenesis: a transgene with 439 bp of 5' flanking sequence is expressed exclusively in the apical ectodermal ridge of the developing limb.

Msx2, a member of the highly conserved and widely distributed msh homeobox gene family, is expressed in a variety of sites in the vertebrate embryo, including craniofacial structures, heart, limb buds and otic and optic vesicles. In many of these sites, its expression is regulated by tissue interactions. Here we address the cis-trans regulatory interactions that direct Msx2 expression to specific regions of the embryo and enable it to respond to tissue interactions. We created a series of Msx2-lacZ fusion constructs with varying amounts of Msx2 genomic sequences. These were introduced into mouse embryos and their expression monitored by staining for beta-galactosidase activity. A construct bearing 5.2 kb of 5' flanking sequence, the intron, both exons and 3 kb of 3' flanking sequence was expressed in a pattern that closely resembled that of the endogenous Msx2 gene. In the E12.5 embryo, sites of expression included craniofacial mesenchyme, portions of the neural ectoderm, mesoderm in the distal limb bud and the overlying apical ectodermal ridge (AER). Removal of intronic and 3' UTR sequences slightly altered the pattern of Msx2 expression in the neural ectoderm of the E12 embryo. Deletion of 5' flanking sequences to -0.5 kb eliminated Msx2 expression in all sites except the AER. The proximal Msx2 promoter, including sequences required for the AER-specific expression of the -0.5 lacZ transgene, is highly conserved between mouse and human, one stretch exhibiting 100% identity over 72 bp. This conservation suggests that the AER element is under remarkably tight evolutionary constraint.

Amino Acid Sequence↗
PubMed1994

High affinity binding of thyrotropin (TSH) and thyroid-stimulating autoantibody for the TSH receptor extracellular domain.

There have been some controversial data as to whether the extracellular domain of the thyrotropin receptor (TSHR) is sufficient for constituting the high affinity binding site(s) for TSH and thyroid-stimulating antibody (TSAb). The present study was, therefore, designed to further evaluate the functional significance of the TSHR extracellular domain. The new chimeric receptor (designated TSHEX-LHTMR) consisting of the human (h) TSHR extracellular domain and the rat lutropin/choriogonadotropin (LH/CG) receptor transmembrane region was constructed, stably expressed in Chinese hamster ovary cells, and tested for its abilities to bind TSH and hCG and to increase intracellular cAMP production in response to hormone and TSAb stimulation. The binding affinity for TSH and the ability to produce cAMP in response to TSH stimulation in the chimeric receptor TSHEX-LHTMR was comparable to those in the wild-type (wt) TSHR (Kd = approximately 0.3 nM and EC50 = approximately 3 nM). The TSHEX-LHTMR and the wt-TSHR also demonstrated similar TSAb activity. However, the TSHEX-LHTMR, unlike the wt-LH/CGR, did not bind hCG or respond to hCG stimulation. These results demonstrate that the functional properties of the TSHR are not affected by the replacement of the receptor transmembrane region with the corresponding region of the LH/CGR, suggesting, together with other previous reports, that the TSHR extracellular domain appears to be of primary importance for the high affinity binding for TSH and TSAb, although the TSHR transmembrane region can contribute to high affinity binding and also bioactivity for TSH and TSAb.

Animals↗
PubMed1994

Targeted ablation of the phospholamban gene is associated with markedly enhanced myocardial contractility and loss of beta-agonist stimulation.

Phospholamban is the regulator of the Ca(2+)-ATPase in cardiac sarcoplasmic reticulum (SR), and it has been suggested to be an important determinant in the inotropic responses of the heart to beta-adrenergic stimulation. To determine the role of phospholamban in vivo, the gene coding for this protein was targeted in murine embryonic stem cells, and mice deficient in phospholamban were generated. The phospholamban-deficient mice showed no gross developmental abnormalities but exhibited enhanced myocardial performance without changes in heart rate. The time to peak pressure and the time to half-relaxation were significantly shorter in phospholamban-deficient mice compared with their wild-type homozygous littermates as assessed in work-performing mouse heart preparations under identical venous returns, afterloads, and heart rates. The first derivatives of intraventricular pressure (+/- dP/dt) were also significantly elevated, and this was associated with an increase in the affinity of the SR Ca(2+)-ATPase for Ca2+ in the phospholamban-deficient hearts. Baseline levels of these parameters in the phospholamban-deficient hearts were equal to those observed in hearts of wild-type littermates maximally stimulated with the beta-agonist isoproterenol. These findings indicate that phospholamban acts as a critical repressor of basal myocardial contractility and may be the key phosphoprotein in mediating the heart's contractile responses to beta-adrenergic agonists.

Animals↗
PubMed1994

[The effect of acute pulmonary alveolar hypoxia on canine plasma endothelin-1 levels].

The effect of acute pulmonary alveolar hypoxia on plasma endothelin (ET)-1 levels was observed in 10 anesthetized dogs (hypoxic group). Plasma ET-1 like immunoreactivity (-LI) levels increased significantly at the fifth, fifteenth, sixtieth minute after hypoxia (fractional inspiratory O2 concentration 10%), but they had no remarkable change at the thirtieth minute. It was suggested that the first peak of ET-1-LI levels (the fifth minute) might be caused by the release of endothelin-1 which was formed before hypoxia and the second peak could be associated with the secretion of ET-1 after hypoxia. The effect of ligustrazine on plasma ET-1-LI levels during hypoxia was also investigated in other 8 anesthetized dogs. Plasma ET-1-LI levels reduced significantly at the fifth minute after the injection of ligustrazine, compared with the hypoxic group. The result demonstrated that ligustrazine can inhibit the release of ET-1, which could be correlated with the blockade of calcium channel caused by ligustrazine.

Animals↗
PubMed1994

[Effects of ligustrazine and nitroglycerine on acute hypoxic pulmonary hypertension in anesthetized dogs].

The effects of ligustrazine and nitroglycerine on acute hypoxic pulmonary hypertension were observed in 10 anesthetized dogs. The results showed that ligustrazine (40 mg/kg) significantly reduced the hypoxic mean pulmonary artery pressure (PAPm) and pulmonary vascular resistance (PVR) the 10th and 15th minute after its injection into the right atrium, respectively. Its action was blocked by the continuous intravenous injection of methylene blue (1 mg/kg/min). It was suggested that the action of ligustrazine could be mediated by endothelium-derived relaxing factor. It was also discovered that nitroglycerine (40 micrograms/kg) could quickly decrease PAPm and PVR, indicating that nitroglycerine can be used to treat acute pulmonary hypertension and the aggravation of chronic cor pulmonale.

Acute Disease↗
PubMed1994

[Facial nerve repairs: a comparative experimental study of epineural and perineural techniques].

This paper reports the comparative study results of perineural and epineural techniques in facial nerve (FN) transection injuries of 16 rabbits. We found little difference in recovery of FN function and histology between epineural and perineural repairs. Both epineural and perineural sutures on FN have not yet solved the problem of misdirection growth of nerve fibers. It is possible to cause the synkinesis movement by using epineural or perineural sutures in human FN. The epineural repair method should be used at the site of FN trunk which is present as a structure of mixed fasciolae giving out branches. The recovery degree of-eye-openings, ENoG and anastomotic pass-rate of regenerating myelinated axons could reflect the recovery degree of FN transection objectively. The three parameters show a parallel relationship. We suggest that either epineural suture or perineural suture should be carried out after FN transection injury.

Animals↗
PubMed1993

Structure and function of C-CAM1. The first immunoglobulin domain is required for intercellular adhesion.

Cell-CAM105 proteins (also called C-CAM) are epithelial cell adhesion molecules of the immunoglobulin (Ig) superfamily. The sequences of C-CAM are highly homologous to those of human carcinoembryonic antigen (CEA)-family proteins. In previous studies using baculoviral vectors, we showed that expression of the L-form cell-CAM105 (also called C-CAM1) in insect cells resulted in cell aggregation (Cheung, P. H., Thompson, N. L., Earley, K., Culic, O., Hixson, D., and Lin, S. H. (1993) J. Biol. Chem. 268, 6139-6146). This result indicates that the insect-cell system is suitable for studying the adhesion function of C-CAM. Since C-CAM1 contains four extracellular Ig-domains, the structural features directly responsible for C-CAM1 adhesion function were investigated by site-directed deletion and expression in the baculovirus/insect cell system. Results from these studies indicated that the first Ig domain located in the NH2-terminal of C-CAM plays a crucial role in intercellular adhesion. Site-directed deletion producing mutants lacking the second, third, or fourth Ig domains had no effect on the adhesion function. In addition, adhesion function was retained when both the third and fourth Ig domains were deleted, although the adhesion activity was reduced to half that in control cells. However, simultaneous deletion of the second, third, and fourth domains abolished adhesion, suggesting that these domains affect the accessibility of the binding site localized in the first domain. In our previous studies, we showed that the cytoplasmic domains of C-CAM play a significant role in the isoforms' adhesion activity since expression of a C-CAM isoform containing only 6 instead of 71 amino acids intracellularly failed to show the adhesion phenotype (Cheung, P. H., Culic, O., Qiu, Y., Earley, K., Thompson, N., Hixson, D. C., and Lin, S.-H. (1993) Biochem. J. 295, in press). These results together suggest that both the cytoplasmic domain and the first N-terminal Ig-like domain are required for C-CAM-mediated cell adhesion activity.

Adenosine Triphosphatases↗
PubMed1993

A mutation in the homeodomain of the human MSX2 gene in a family affected with autosomal dominant craniosynostosis.

Craniosynostosis, the premature fusion of calvarial sutures, is a common developmental anomaly that causes abnormal skull shape. The locus for one autosomal dominant form of craniosynostosis has been mapped to chromosome 5qter. The human MSX2 gene localizes to chromosome 5, and a polymorphic marker in the MSX2 intron segregates in a kindred with the disorder with no recombination. Moreover, a histidine substitutes for a highly conserved proline at position 7 of the MSX2 homeodomain exclusively in affected members. In the mouse, transcripts of the Msx2 gene are localized to calvarial sutures. These results provide compelling evidence that the mutation causes this craniosynostosis syndrome.

Acrocephalosyndactylia↗
PubMed1993

Genomic structure, chromosomal location, and evolution of the mouse Hox 8 gene.

We isolated genomic clones containing the mouse Hox 8 gene, a member of the msh gene family. We show that Hox 8 comprises two exons of approximately 600 and 691 bp separated by a 3.5-kb intron, and that it cosegregates with previously mapped markers in the distal region of mouse chromosome 13. In midgestation embryos, the Hox 8 gene produces transcripts of 1.4 and 2.2 kb. Both transcripts are present in facial tissues of the newborn mouse, though the ratio of the 2.2-kb transcript to the 1.4-kb transcript is reduced relative to the ratio observed for midgestation embryos. An alignment of the homeobox sequences of previously characterized members of the msh family revealed three subclasses: Hox 7-like genes, Hox 8-like genes, and msh-like genes. Both the Hox 7-like genes and Hox 8-like genes are present throughout the vertebrates. Representatives of the third subclass, the msh-like genes, are found in a protostome (Drosophila) and a deuterostome (Ciona) and are thus likely to be phylogenetically widespread. To investigate the distribution of Hox 8-like genes outside the chordates, we used the polymerase chain reaction and degenerate Hox 8 primers to screen genomic DNA of the purple sea urchin (Strongylocentrotus purpuratus, Phylum Echinodermata). We isolated a gene with greater sequence similarity to mouse Hox 8 than to members of the Hox 7 or msh subfamilies, demonstrating that the Hox 8 subfamily has been in existence at least since the echinoderms diverged from the lineage that gave rise to the chordates.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

A novel protein encoded by small RNAs of parvovirus B19.

A second small ORF contained within the parvovirus B19 genome has been shown to direct synthesis of a small 7.5-kDa protein. These results extend our previous studies in which we identified a family of 11-kDa proteins (J. St. Amand, C. Beard, K. Humphries, and C.R. Astell, Virology 183, 133-142, 1991; J. St. Amand and C.R. Astell, Virology, 192, 121-131, 1993). The presumed ORF encoding the 7.5-kDa protein was discovered on the left side of the viral genome and was identified by expression of the protein and in vitro mutagenesis. Two small RNA transcripts of B19 virus were demonstrated to be able to direct the synthesis of this 7.5-kDa protein by in vitro translation using rabbit reticulocyte lysates. Expression of 7.5-kDa protein was also observed in COS-7 cells transfected with a plasmid containing the B19 genome as well as in human peripheral mononucleocytes infected with B19 virus. In both cases the 7.5-kDa protein was detected by immunoprecipitation of cell lysates with polyclonal antibodies raised against a synthetic peptide corresponding to a portion of the predicted protein sequence. These data partially reveal the function of the abundant small RNA transcripts produced by parvovirus B19.

Amino Acid Sequence↗
PubMed1993

Effect of polyunsaturated fatty acids on the drug sensitivity of human tumour cell lines resistant to either cisplatin or doxorubicin.

Growth of cells in vitro in the presence of fatty acids can alter the membrane composition and hence fluidity and permeability. Exposure of both doxorubicin (2780AD) and cisplatin (2780CP) resistant human ovarian cell lines to non-toxic concentrations of polyunsaturated fatty acids (gamma-linolenic acid and eicosapentaenoic acid) either before or during exposure to the cytotoxic drug did not modulate drug sensitivity. However, the fatty acids were toxic in their own right. Whilst the ovarian cell lines 2780AD and 2780CP showed a small degree of cross resistance to both fatty acids the doxorubicin resistant breast cell line MCF7/Adr was slightly more sensitive than MCF7. When the interactions between the polyunsaturated fatty acids and cytotoxic drugs were analysed by the isobologram method the toxicities were shown to be additive. The combination of polyunsaturated fatty acids and cytotoxic drugs may have clinical potential provided that the normal tissue toxicities of the two treatments are not additive.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1993

Immunohistochemical analysis of expression of nm23-H1/nucleoside diphosphate kinase in human thyroid carcinomas: lack of correlation between its expression and lymph node metastasis.

The nm23 gene that encodes nucleoside diphosphate (NDP) kinase has been proposed as a candidate tumor metastasis suppressor in rodent experimental carcinoma models and several types of human carcinomas. The present studies were designed to investigate, by immunohistochemical analysis, whether thyroid tissues express the nm23-H1/NDP kinase and, if so, whether the nm23-H1/NDP kinase expression is correlated to tumor metastasis suppressor potential in thyroid tumors. We found that normal thyroid epithelial cells were stained weakly but homogeneously by mouse monoclonal anti-nm23-H1/NDP kinase antibody. The staining intensity of the nm23-H1/NDP kinase in benign thyroid tumors tended to be weaker than that in normal thyroid tissues. In contrast, a series of malignant thyroid tumors expressed differently the nm23-H1/NDP kinase: the intensity of the nm23-H1/NDP kinase staining was stronger in 22 of 49 malignant tumors (45%), similar in 24 (49%), and weaker in 3 (6%) compared to that in normal tissues. The comparison of the staining intensity of the nm23-H1/NDP kinase in primary lesions of tumors with lymph node metastases and those without metastases revealed no statistically significant difference. In addition, there was also no significant difference in the nm23-H1/NDP kinase staining intensity of primary and metastatic lymph node lesions of tumors with lymph node metastases. These data indicate that the nm23-H1/NDP kinase may not be a good predictive marker for tumor regional metastatic potential in malignant thyroid tumors. We conclude that in thyroid tumors the nm23-H1/NDP kinase expression may be dissociated from metastasis suppressor activity.

Adenocarcinoma↗
PubMed1993

Steroidogenic factor 1, an orphan nuclear receptor, regulates the expression of the rat aromatase gene in gonadal tissues.

In a concerted analysis of the genes encoding three mouse steroid hydroxylases, we identified and characterized a transcriptional regulatory protein, designated steroidogenic factor 1 (SF-1), that contributes to the coordinate expression in adrenocortical cells. SF-1, an orphan member of the nuclear receptor family, binds to PyCAAGGPyCPu motifs upstream of the steroid hydroxylases to regulate their expression. In the present study, we extend these findings by examining the role of SF-1 in regulation of the rat P450 aromatase gene in gonadal tissues. The 5'-flanking region of the rat aromatase gene was isolated by a polymerase chain reaction-based approach, using primers corresponding to the 5'- and 3'-ends of a published aromatase sequence. DNA sequence analysis revealed three differences between our sequence and the previously published sequence, including a 44-base pair (bp) insertion. Moreover, the transcription initiation site, as determined by primer extension analysis, differed from that previously proposed. The new transcription initiation site is located 23 bp 3' of a putative TATA box. When a revised rat sequence was compared to that of the human aromatase PII promoter by BEST-FIT analysis, a region of about 300 bp was identified that was 80% conserved between the two promoters. A potential SF-1 site, CCAAGGTCA, was identified at position -82 within this region. An oligonucleotide probe containing this putative SF-1 site was used in gel mobility shift assays. Consistent with previous studies, a specific complex was observed with nuclear extracts from gonadal steroidogenic tissues but was absent with nuclear extracts from nonsteroidogenic tissues. The role of SF-1 in this steroidogenic cell-specific complex was next addressed more directly. Bacterial extracts containing an SF-1-glutathione S-transferase fusion protein interacted specifically with the putative SF-1 site, and polyclonal antisera against SF-1-glutathione S-transferase specifically abolished the complex formed with nuclear extracts from rat ovaries or R2C rat Leydig tumor cells. Finally, the aromatase SF-1 element increased expression of an SV40 promoter/luciferase construct in transient transfection experiments in a steroidogenic cell-selective manner. Collectively, these studies implicate SF-1 in the regulation of steroid hydroxylase gene expression in nonadrenal tissues, significantly extending previous studies in adrenocortical cells.

Amino Acid Sequence↗