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Biomedical subjects

S Guo

Publications and source records attributed to S Guo.

At least 163 records · Page 9Linked to original sources
PubMed1996

A non-muscle myosin required for embryonic polarity in Caenorhabditis elegans.

Daughter cells with distinct fates can arise through intrinsically asymmetrical divisions. Before such divisions, factors crucial for determining cell fates become asymmetrically localized in the mother cell. In Caenorhabditis elegans, PAR proteins are required for the early asymmetrical divisions that establish embryonic polarity, and are asymmetrically localized in early blastomeres, although the mechanism of their distribution is not known. Here we report the identification in C. elegans of nonmuscle myosin II heavy chain (designated NMY-2) by means of its interaction with the PAR-1 protein, a putative Ser/Thr protein kinase. Furthermore, injections of nmy-2 antisense RNA into ovaries of adult worms cause embryonic partitioning defects and lead to mislocalization of PAR proteins. We therefore conclude the NMY-2 is required for establishing cellular polarity in C. elegans embryos.

Animals↗
PubMed1996

Molecular genetics of asymmetric cleavage in the early Caenorhabditis elegans embryo.

Asymmetric cleavage plays an important role in Caenorhabditis elegans embryogenesis. In addition to generating cellular diversity, several early asymmetric cleavages contribute to the spatial organization of the embryo. Genetic and molecular analyses of several genes, including six par genes and the mex-1 and mes-1 genes, together with experimental embryological studies, have provided insights into mechanisms controlling polarity and spindle orientations during these cleavages. In particular, these studies focus attention on microfilament-based motility and changing protein distributions at the cell cortex.

Animals↗
PubMed1996

PAR-2 is asymmetrically distributed and promotes association of P granules and PAR-1 with the cortex in C. elegans embryos.

The par genes participate in the process of establishing cellular asymmetries during the first cell cycle of Caenorhabditis elegans development. The par-2 gene is required for the unequal first cleavage and for asymmetries in cell cycle length and spindle orientation in the two resulting daughter cells. We have found that the PAR-2 protein is present in adult gonads and early embryos. In gonads, the protein is uniformly distributed at the cell cortex, and this subcellular localization depends on microfilaments. In the one-cell embryo, PAR-2 is localized to the posterior cortex and is partitioned into the posterior daughter, P1, at the first cleavage. PAR-2 exhibits a similar asymmetric cortical localization in P1, P2, and P3, the asymmetrically dividing blastomeres of germ line lineage. This distribution in embryos is very similar to that of PAR-1 protein. By analyzing the distribution of the PAR-2 protein in various par mutant backgrounds we found that proper asymmetric distribution of PAR-2 depends upon par-3 activity but not upon par-1 or par-4. par-2 activity is required for proper cortical localization of PAR-1 and this effect requires wild-type par-3 gene activity. We also find that, although par-2 activity is not required for posterior localization of P granules at the one-cell stage, it is required for proper cortical association of P granules in P1.

Animals↗
PubMed1996

par-6, a gene involved in the establishment of asymmetry in early C. elegans embryos, mediates the asymmetric localization of PAR-3.

The generation of asymmetry in the one-cell embryo of Caenorhabditis elegans is necessary to establish the anterior-posterior axis and to ensure the proper identity of early blastomeres. Maternal-effect lethal mutations with a partitioning defective phenotype (par) have identified several genes involved in this process. We have identified a new gene, par-6, which acts in conjunction with other par genes to properly localize cytoplasmic components in the early embryo. The early phenotypes of par-6 embryos include the generation of equal-sized blastomeres, improper localization of P granules and SKN-1 protein, and abnormal second division cleavage patterns. Overall, this phenotype is very similar to that caused by mutations in a previously described gene, par-3. The probable basis for this similarity is revealed by our genetic and immunolocalization results; par-6 acts through par-3 by localizing or maintaining the PAR-3 protein at the cell periphery. In addition, we find that loss-of-function par-6 mutations act as dominant bypass suppressors of loss-of-function mutations in par-2.

Alleles↗
PubMed1996

[C-myc activation by translocation in human primary non-small cell lung cancer].

OBJECTIVE: Lung cancer is one of the most common human neoplasms. The carcinogenesis and development of lung cancer are related to activation and inactivation of many oncogenes and tumor-suppressor genes. We reported c-myc activation by translocation in SV40T-transformed human bronchial epithelial cells and lung cancer cell line before. In order to confirm that c-myc translocation exists in human primary non-small cell lung cancer, we continued our studies in 12 primary human lung cancers. METHODS: We applied major fluorescence in situ hybridization (FISH) in combination with immunohistochemistry. RESULTS: c-myc translocation was detected in two cases of the 12 primary lung cancers. Overexpression of c-myc was detected in the two cases by means of immunohistochemistry. CONCLUSION: These results suggest that c-myc can be activated by translocation in human primary lung cancer.

Adenocarcinoma↗
PubMed1996

[Transbronchial needle aspiration under CT guide for enlarged mediastinal lymph node biopsy].

To ascertain the nature of enlarged mediastinal lymph nodes transbronchial needle aspiration (TBNA) was performed under CT guide through bronchoscopy. Forty-five enlarged mediastinal lymph nodes from 33 lung cancer patients were biopsied. The results indicated that 25 enlarged lymph nodes from 20 patients were due to cancer metastasis while 15 enlarged lymph nodes from 8 cases were due to inflammation, and those from the remaining 5 cases were normal. Therefore, about 33.3% of the enlarged mediastinal lymph nodes in lung cancer patients result from noncancerous inflammatory changes. TBNA under CT guide has the advantage of accurate localization, is easy to perform and safe.

Adenocarcinoma↗
PubMed1996

[Studies on the septal ultrastructure of Armilaria mellea].

The structure and development of septum in Armillaria mellea were studied under the electronmicroscope. Hyphal septum was developed by inside wall of hyphae in cross direction, leaving a small pore in the center. Then the septal plate arround the pore became swollen, and formed a septal pore apparatus called dolipore septum. With subsequent development of endoplasmic reticulum septal pore caps appeared on each side of the pore. Organelles, such as mitochondrium and Golgi body in hyphal cells were all related with the development of septa. Thin-walled narrow hyphae of the medualla in mature rhizomorph were in a state of dormancy, and their septa were similar to those of the hyphae growing from liquid fermentation. Both of them were short of septal pore caps, but the latter had larger septal pores, the protoplasm flow from cell to cell through the pore was visible, and fusion rate between the hyphae was much higher. The relationship between the structural changes and functions of septa in A. mellea was also systematically discussed in this paper.

Agaricales↗
PubMed1996

[A legionella pneumophila strain serologically cross-reacting with thirteen serogroups of this species].

A bacterial strain, designated as Jin-1, was isolated from a water sample taken from the Jinyang Lake located in the suburbs of Taiyuan City, Shanxi Province. Its morphologic and tinctorial properties, nutritional requirements, growth characteristics, biochemical reactions, as well as results of DNA and peptide analysis overall met the criteria for identification of Legionella pneumophila. In serogrouping, extensive cross-reactions between Jin-1 and the type strains of L. pneumophila serogroup 1 through 14 were observed in both slide and tube agglutination tests mediated by the IgM antibodies. However, Jin-1 revealed the L. pneumophila serogroup 5 specificity in IFA, ELISA and dot-ELISA, all mediated by the IgG antibodies. Jin-1 was finally identified as a strain of L. pneumophila serogroup 5 with the more complex antigenic composition than the ATCC type strain of this serogroup. The taxonomic conclusion has been confirmed by CDC. A Legionella pneumophila strain which serologically cross-reacting with so many serogroups of this species has never been reported in the published articles. It is presumed that the cross-reacting antigen of Jin-1 belongs to the thymus-independent antigen by nature.

Antigens, Bacterial↗
PubMed1995

Asymmetrically distributed PAR-3 protein contributes to cell polarity and spindle alignment in early C. elegans embryos.

The par-3 gene is required for establishing polarity in early C. elegans embryos. Embryos from par-3 homozygous mothers show defects in segregation of cytoplasmic determinants and in positioning of the early cleavage spindles. We report here that the PAR-3 protein is asymmetrically distributed at the periphery of the zygote and asymmetrically dividing blastomeres of the germline lineage. The PAR-3 distribution is roughly the reciprocal of PAR-1, another protein required for establishing embryonic polarity in C. elegans. Analysis of the distribution of PAR-3 and PAR-1 in other par mutants reveals that par-2 activity is required for proper localization of PAR-3 and that PAR-3 is required for proper localization of PAR-1. In addition, the distribution of the PAR-3 protein correlates with differences in cleavage spindle orientation and suggests a mechanism by which PAR-3 contributes to control of cleavage pattern.

Animals↗
PubMed1995

par-1, a gene required for establishing polarity in C. elegans embryos, encodes a putative Ser/Thr kinase that is asymmetrically distributed.

The first cleavage of C. elegans is asymmetric, generating daughter cells with different sizes, cytoplasmic components, and fates. Mutations in the par-1 gene disrupt this asymmetry. We report here that par-1 encodes a putative Ser/Thr kinase with similarity to kinases from yeasts and mammals. Two strong alleles have mutations in the kinase domain, suggesting that kinase activity is essential for par-1 function. PAR-1 protein is localized to the posterior periphery of the zygote and is distributed in a polar fashion preceding the asymmetric divisions of the germline lineage. Because PAR-1 distribution in the germline correlates with the distribution of germline-specific P granules, it is possible that PAR-1 functions in germline development as well as in establishing embryonic polarity.

Amino Acid Sequence↗
PubMed1995

A 10-amino-acid sequence in the N-terminal A/B domain of thyroid hormone receptor alpha is essential for transcriptional activation and interaction with the general transcription factor TFIIB.

The effects of the thyroid hormone (3,5,3'-triiodo-L-thyronine [T3]) on gene transcription are mediated by nuclear T3 receptors (T3Rs). alpha- and beta-isoform T3Rs (T3R alpha and -beta) are expressed from different genes and are members of a superfamily of ligand-dependent transcription factors that also includes the receptors for steroid hormones, vitamin D, and retinoids. Although T3 activates transcription by mediating a conformational change in the C-terminal approximately 220-amino-acid ligand-binding domain (LBD), the fundamental mechanisms of T3R-mediated transcriptional activation remain to be determined. We found that deletion of the 50-amino-acid N-terminal A/B domain of chicken T3R alpha (cT3R alpha) decreases T3-dependent stimulation of genes regulated by native thyroid hormone response elements about 10- to 20-fold. The requirement of the A/B region for transcriptional activation was mapped to amino acids 21 to 30, which contain a cluster of five basic amino acids. The A/B region of cT3R alpha is not required for T3 binding or for DNA binding of the receptor as a heterodimer with retinoid X receptor. In vitro binding studies indicate that the N-terminal region of cT3R alpha interacts efficiently with TFIIB and that this interaction requires amino acids 21 to 30 of the A/B region. In contrast, the LBD interacts poorly with TFIIB. The region of TFIIB primarily involved in the binding of cT3R alpha includes an amphipathic alpha helix contained within residues 178 to 201. Analysis using a fusion protein containing the DNA-binding domain of GAL4 and the entire A/B region of cT3R alpha suggests that this region does not contain an intrinsic activation domain. These and other studies indicate that cT3R alpha mediates at least some of its effects through TFIIB in vivo and that the N-terminal region of DNA-bound cT3R alpha acts to recruit and/or stabilize the binding of TFIIB to the transcription complex. T3 stimulation could then result from ligand-mediated changes in the LBD which may lead to the interaction of other factors with cT3R alpha, TFIIB, and/or other components involved in the initiation of transcription.

Amino Acid Sequence↗
PubMed1995

[Study on Bian Que's tomb and temple].

The historical archives and records and the existed Bian Que's tombs and temples in over a dozen of locations, including Hebei, Shandong, Henan, Shanxi, have aroused controversies as to which is the authentic one. So far, no conclusion can be drawn. By combining the burial and offering customs and rituals at the end of Spring-Autumn period, analyses are made on Bian Que's tombs, temples, former residence, Bian Que Village, Bian Que town, historical remains of Prince Guo and legends on location of Bian Que's activity for making immortal pills etc., it is claimed by the authors that, besides a few places related to Bian Que's life, all the others are tombs and temples built by local people where Bian Que's visited for his memory, and his merits, reflecting the historical facts about Bian Que's activities. All these historical and cultural remains are precious evidences for the historic appraisal of Bian Que by modern scholars.

China↗
PubMed1995

[Modifications of gene expression by tumor promoters].

The modifications of gene expression by tumor promoters were analyzed in vitro and in vivo. The results of slot blot hybridizations showed that tumor promoter TPA induced c-fos and c-myc expressions in mouse fibroblast cell line BALB/3T3 and rat liver, decreased the levels of Rb RNA in BALB/3T3 cell line and of alpha 1-I3 RNA in rat liver. It was also demonstrated that tumor promoter phenobarbital influenced c-fos and c-myc expressions and decreased alpha 1I3 mRNA level in rat liver during a long term experiment. Phenobarbital was found to have no effect on c-fos and c-myc expressions in rat liver during a short experiment. Tumor promoters induced the expressions of c-fos and c-myc which were positively-related to cancer formation and inhibited the expressions of Rb and alpha 1-I3 which were negatively-related to cancer formation. This implied that tumor promotion played an important role in cancer development and tumor promoters exerted their effects selectively according to the attributes of different genes.

3T3 Cells↗