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Biomedical subjects

S Jin

Publications and source records attributed to S Jin.

At least 73 records · Page 4Linked to original sources
PubMed2001

Enhancer-binding proteins HrpR and HrpS interact to regulate hrp-encoded type III protein secretion in Pseudomonas syringae strains.

In Pseudomonas syringae strains, the hrp-hrc pathogenicity island consists of an HrpL-dependent regulon that encodes a type III protein translocation complex and translocated effector proteins required for pathogenesis. HrpR and HrpS function as positive regulatory factors for the hrpL promoter, but their mechanism of action has not been established. Both HrpR and HrpS are structurally related to enhancer-binding proteins, but they lack receiver domains and do not appear to require a cognate protein kinase for activity. hrpR and hrpS were shown to be expressed as an operon: a promoter was identified 5' to hrpR, and reverse transcriptase PCR detected the presence of an hrpRS transcript. The hrpR promoter and coding sequence were conserved among P. syringae strains. The coding sequences for hrpR and hrpS were cloned into compatible expression vectors, and their activities were monitored in Escherichia coli transformants carrying an hrpL'-lacZ fusion. HrpS could function as a weak activator of the hrpL promoter, but the activity was only 2.5% of the activity detected when both HrpR and HrpS were expressed in the reporter strain. This finding is consistent with a requirement for both HrpR and HrpS in the activation of the hrpL promoter. By using a yeast two-hybrid assay, an interaction between HrpR and HrpS was detected, suggestive of the formation of a heteromeric complex. Physical interaction of HrpR and HrpS was confirmed by column-binding experiments. The results show that HrpR and HrpS physically interact to regulate the sigma(54)-dependent hrpL promoter in P. syringae strains.

Bacterial Proteins↗
PubMed2001

Immortalization of rat middle ear epithelial cells by adeno 12-SV40 hybrid virus.

Rat middle ear epithelial cells were infected with the adeno 12-SV40 hybrid virus. The cell line thus obtained displays features of primary cultured epithelial cells in both light microscopic and ultrastructural examinations. The immortalized cells have been in continuous proliferation for 40 passages and more than 17 months. Immunohistochemical analysis of the immortalized cells was positive for the SV40 T antigen and the tumor suppressor protein p53. The cells also stained positive for cytokeratin, an epithelial cell marker, and negative for vimentin, a fibroblast marker. These results, together with karyotype analysis, indicate that this cell line originated from rat middle ear epithelial cells and retains the characteristics of epithelial cells. This cell line will be useful for studying the normal cellular biology of middle ear epithelial cells, as well as the cellular and molecular mechanisms involved in the bacteria-middle ear epithelial cell interaction.

Animals↗
PubMed2001

[Studies of localization of black streak body gene in Drosophila melanogaster].

Mutation type of body color shows frequently yellow (y), black (b) and ebony (e) in Drosophila melanogaster and locates on X, second and third chromosom respectively. A mutant of black streak (bsr) is a spontaneous mutation strain building in the laboratory in 1991. Whether this mutation strain is rediscovered on the primary style or not. We have discussed this problem with general cross breeding and complementation test. The result of complementation test indicated that it is a mutant in first filial generation with trans heterozygote and that it is few wild in second filial generation with cis teterozygote due to crossing over in crossing bsr and e. But, we believe that bsr and e is located same loci (93D2) but not the same sites. This report discussed for correlation inter-gene body color and ruleless of heredity passing down for black streak body.

Animals↗
PubMed2001

[A case of Mycobacterium intracellulare infection complicated by immotile cilia syndrome].

A 25-year-old woman with a history of immotile cilia syndrome (ICS) was admitted to our hospital with dyspnea. Chest roentgenography revealed dense infiltrates in both lower lung fields in addition to bronchiectasis and small nodular opacities, which had been observed previously. Transbronchial lung biopsy demonstrated evidence of non-caseating epithelioid cell granuloma. Sputum specimens were examined, and isolates were identified as Mycobacterium intracellulare. The patient was given antituberculous therapy and clarithromycin, which induced clinical improvement. It is well known that bronchial mucociliary transport is severely impaired in patients with ICS. However, to our knowledge, cases of M. intracellulare infection complicated by ICS have not been reported in Japan. We must pay close attention to the concurrence of these diseases.

Adult↗
PubMed2001

[The adhesive and migrating function of human epithelial cells opsonized by fibronectin].

OBJECTIVE: To investigate the adhesive and migrating function of human epithelial keratiocytes during in vitro culture. METHODS: The adhesive and migrating function was determined in freshly isolated EKCs and those cultured for 7 similar 10 days after being opsonized by fibronectin (FN). The expressions of alpha(5)beta(1) receptors in EKC were examined with indirect immunofluorescence staining methods before and after culture. RESULTS: (1) The adhesive and migrating indices after FN opsonization of EKCs freshly isolated EKCs were obviously lower than those cultured for 7 similar 10 days (P < 0.01). (2) There exhibited positive staining of the expression of alpha(5)beta(1) receptors in the EKC after 1 day culture and in the proliferative epithelia after in vitro culturing of a tissue mass. While there exhibited strongly positive staining of the peripheral proliferative epithelia of the EKCs and tissue mass after 7 days of culture, negative or weakly positive stainings were found in freshly isolated EKCs. CONCLUSION: (1) There existed significant difference of biological function between the freshly isolated EKCs and those cultured for 7 similar 10 days. (2) The strongest expression of alpha(5)beta(1) receptors was observed at the active proliferative site (peripheral proliferative epithelia of a tissue mass) and in the biological active period (cultured for 7 days) of EKCs. (3) The adhesive and migrating function of EKCs could be effectively induced and activated by in vitro culture, which enabled the EKC to alter from a relatively biologically functional static state to an actively functional state.

Cell Adhesion↗
PubMed2001

[An experimental study on demineralization of several beverages on bovine enamel].

OBJECTIVE: The aim of this study is to investigate the demineralization effects of several beverages on bovine enamel. METHODS: The concentration of calcium and phosphate in these beverages were measured by using EL 312e Micro-Plate after the bovine enamel was exposed to beverages for a period of 7 days. RESULTS: The data indicated that almost all of these beverages could cause demineralization of bovine enamel, except mineral water, and the concentration of calcium and phosphate in these beverages changed after the bovine enamel was exposed to beverages. There were great significant differences in demineralization abilities among different beverages (P < 0.01). The concentration of calcium and phosphate in beverages also changed with time (P < 0.01). CONCLUSION: All these beverages, except mineral water have erosive effects on bovine enamel. Demineralization degree varied with kinds of beverages. The fruit juice has the highest erosive effect on the enamel, and the calcium milk has the lowest erosive effect on the bovine enamel, when comparing with other beverages.

Animals↗
PubMed2001

[Measurement of serum neopterin levels in patients with nasopharyngeal carcinoma and its significance].

OBJECTIVE: To evaluate the relationship between serum neopterin levels and nasopharyngeal carcinoma and its clinical significance. METHOD: The serum neopterin levels were determined in 54 patients with nasopharyngeal carcinoma (NPC group) and 32 healthy adults (normal group) by ELISA. RESULT: The serum neopterin levels in NPC group were significantly higher than that of in normal group (P < 0.001). The serum neopterin levels in UICC-TNM stages were undifferentiated (P > 0.05). The serum neopterin levels in patients with no lymph node metastasis were lower than that of in lymph node metastasis (P < 0.05). The serum neopterin levels decreased significantly after disappearance of tumor and its lymph node treated by radiotherapy (P < 0.01). CONCLUSION: Cellular immunity mediated by macrophages might be involved in the pathogenesis of nasopharyngeal carcinoma and the measurement of the serum neopterin may be a useful objective index to evaluate cellular immunological functions and curative effects.

Adult↗
PubMed2000

Activation of the transcription factor Oct-1 in response to DNA damage.

Mammalian cells exhibit complex cellular responses to genotoxic stress, including cell cycle checkpoint, DNA repair, and apoptosis. Inactivation of these important biological events will result in genomic instability and cell transformation. It has been demonstrated that gene activation is a critical initial step during the cellular response to DNA damage. A number of investigations have shown that transcription factors are involved in the regulation of stress-inducible genes. These transcription factors include p53, c-Myc, and AP-1 (c-fos and c-jun). However, the role for the octamer-binding transcription factor Oct-1 in the DNA damage-activated response is unknown. In this report, we have presented the novel observation that the transcription factor Oct-1 is induced after cells are exposed to multiple DNA-damaging agents and therapeutic agents, including UV radiation, methylmethane sulfonate, ionizing radiation, etoposide, cisplatin, and camptothecin. The induction of the Oct-1 protein is mediated through a posttranscriptional mechanism and does not require the normal cellular function of the tumor suppressor p53, indicating that the Oct-1 protein, as a transcription factor, may play a role in p53-independent gene activation. In addition to increased protein level, the activity of Oct-1 DNA binding to its specific consensus sequence is also enhanced by DNA damage. Therefore, these results have implicated that the transcription factor Oct-1 might participate in cellular response to DNA damage, particularly in p53-independent gene activation.

DNA Damage↗
PubMed2000

Crucial role of kainate receptors in mediating striatal kainate injection-induced decrease in acetylcholine M(1) receptor binding in rat forebrain.

We investigated the roles of kainate-, alpha-amino-3-hydroxy-5-methylisoxazol-4-propionate (AMPA)- and N-methyl-D-aspartate (NMDA)-receptors in mediating striatal kainate injection-induced decrease in the binding of acetylcholine M(1) receptors in rat forebrain. After unilateral intrastriatal injection of kainate (4 nmol), the bindings of [3H]kainate (10 nM), [3H]MK-801 (4 nM) and [3H]pirenzepine (4 nM) to the rat ipsilateral forebrain membranes declined, reaching the lowest on day 2 to 4 and recovering on day 8. Saturation binding studies, performed on day 2 post-injection, showed that kainate (1, 2, 4 nmol) dose-dependently decreased B(max) and K(d) of the three ligands. (+)-5-Methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801), a selective NMDA receptor channel blocker, antagonised (from a dose of 4 nmol) kainate-induced decreases in the bindings of [3H]kainate (up to approximately 20%), [3H]MK-801 (up to approximately 90%) and [3H]pirenzepine (up to approximately 70%). In contrast, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a selective non-NMDA receptor antagonist, almost completely abolished (from a dose of 12 nmol) kainate-induced decreases in the bindings of all the three ligands (up to approximately 95-98%). Cyclothiazide, a selective potentiator that enhances AMPA receptor-mediated responses, significantly enhanced (from a dose of 4 nmol) kainate-induced decrease in the binding of [3H]kainate but not that of [3H]pirenzepine or [3H]MK-801. In summary, these results indicate that striatal kainate injection-induced decrease in the binding of acetylcholine M(1) receptors in rat forebrain is dependent on activation of kainate receptors and, to a certain extent, a consequent involvement of NMDA receptors. These and previous studies provide some evidence showing that kainate receptors might play a crucial role in regulating excitatory amino acids (EAA)-modulated cholinergic neurotransmission in the central nervous system (CNS).

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2000

c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process.

Differentiation of 3T3-L1 preadipocytes into adipocytes is induced by a combination of inducers, including a glucocorticoid, an agent that elevates cellular cAMP, and a ligand of the insulin-like growth factor-1 receptor. Previous studies have implicated protein-tyrosine phosphatase (PTPase) HA2, a homologue of PTPase 1B, in the signaling cascade initiated by the differentiation inducers. Vanadate, a potent PTPase inhibitor, blocks adipocyte differentiation at an early stage in the program, but has no effect on the mitotic clonal expansion required for differentiation. Exposure of preadipocytes to vanadate along with the inducing agents led to the accumulation of pp35, a phosphotyrosyl protein that is a substrate for PTPase HA2. pp35 was purified to homogeneity and shown by amino acid sequence and mass analyses of tryptic peptides to be c-Crk, a known cytoplasmic target of the insulin-like growth factor-1 receptor tyrosine kinase. Transfection of 3T3-L1 preadipocytes with a c-Crk antisense RNA expression vector markedly reduced c-Crk levels and prevented differentiation into adipocytes. Studies with C3G, a protein that binds to the SH3 domain in c-Crk, showed that phosphorylation of c-Crk rendered the SH3 domain inaccessible to C3G. Taken together, these findings indicate that locking c-Crk in the phosphorylated state with vanadate prevents its participation in the signaling system that initiates adipocyte differentiation.

3T3 Cells↗
PubMed2000

Activation of RhoA by association of Galpha(13) with Dbl.

RhoA is a small G protein that is implicated in the regulation of the actin cytoskeleton, gene expression, and cell cycle progression. It is activated by many agonists whose receptors are linked to heterotrimeric G proteins, but the mechanisms are incompletely understood. In this study, we show that the constitutively active alpha-subunit of the heterotrimeric G protein G(13) associated with the Rho family guanine nucleotide exchange factor Dbl in NIH 3T3 cells and that this resulted in activation of RhoA. This activation was not seen with wild-type Galpha(13) or if Dbl and active Galpha(13) were expressed separately and mixed. In contrast, coexpression of constitutively active Galpha(q) with Dbl did not lead to their association and caused a weak activation of RhoA that was no greater than that observed with wild-type Galpha(q). These findings illustrate that activated Galpha(13) and Dbl can associate in vivo and that this leads to Rho activation.

3T3 Cells↗
PubMed2000

BRCA1 activation of the GADD45 promoter.

Breast cancer susceptibility gene BRCA1 has been implicated in the control of gene regulation and such regulated genes are thought to mediate the biological role of BRCA1. Overexpression of BRCA1 induces GADD45, a p53-regulated and stress-inducible gene. However, the molecular mechanism by which BRCA1 induces the expression GADD45 remains unclear. In this report, we have shown that the GADD45 promoter is strongly activated following expression of wild-type BRCA1. In contrast, both the tumor-derived BRCA1 mutants (p1749R and Y1853insA) and truncated BRCA1 mutant protein (Delta500 - 1863 BRCA1), which lack transactivation activity, were unable to activate the GADD45 promoter, indicating that the BRCA1-mediated activation of the GADD45 promoter requires normal transcriptional properties of BRCA1. BRCA1 did not induce the c-Jun and c-fos promoters, which rules out a general effect of BRCA1 on other immediate-responsive genes. Expression of the human papillomavirus E6 and the dominant-negative mutant p53 proteins had no effect on the induction of the GADD45 promoter by BRCA1, suggesting that activation of the GADD45 promoter by BRCA1 is independent of cellular p53 function. With the 5'-deletion analysis, the BRCA1-responsive element of the GADD45 promoter was mapped at the region from -121 to -75. Disruption of this region resulted in the abrogation of BRCA1 activation of the GADD45 promoter. Taken together, these results demonstrate that the mechanism by which BRCA1 induces GADD45 is mainly through the transactivation of the GADD45 promoter, further demonstrating the evidence that GADD45 acts as one of the BRCA1-regulated genes. Oncogene (2000) 19, 4050 - 4057.

Adenocarcinoma↗
PubMed2000

The O(2) binding pocket of myohemerythrin: role of a conserved leucine.

A conserved O(2) binding pocket residue in Phascolopsis gouldii myohemerythrin (myoHr), namely, L104, was mutated to several other residues, and the effects on O(2) association and dissociation rates, O(2) affinity, and autoxidation were examined. The L104V, -F, and -Y myoHrs formed stable O(2) adducts whose UV-vis and resonance Raman spectra closely matched those of wild-type oxymyoHr. The L104V mutation produced only minimal effects on either O(2) association or dissociation, whereas the L104F and -Y mutations resulted in 100-300-fold decreases in both O(2) association and dissociation rates. These decreases are attributed to introduction of steric restrictions into the O(2) binding pocket, which are not present in either wild-type or L104V myoHrs. The failure to observe increased O(2) association or dissociation rates for L104V indicates that the side chain of leucine at position 104 does not sterically "gate" O(2) entry into or exit from the binding pocket in the rate-determining step(s). L104V myoHr autoxidized approximately 3 times faster than did wild type, whereas L104T autoxidized >10(6) times faster than did wild type. The latter large increase is attributed to increased side chain polarity, thereby increasing water occupancy in the oxymyoHr binding pocket. These results indicate that L104 contributes a hydrophobic barrier that restricts water entry into the oxymyoHr binding pocket. Thus, a leucine at position 104 in myoHr appears to have the optimal combination of size and hydrophobicity to facilitate O(2) binding while simultaneously inhibiting autoxidation.

Amino Acid Sequence↗
PubMed2000

The central region of Gadd45 is required for its interaction with p21/WAF1.

Cell cycle arrest represents an important response to genotoxic stress and the tumor suppressor p53 has been described to act as a critical effector in this biological event. Upon stress, p53 becomes transcriptionally active and up-regulates the transcription of downstream effector genes, which contain p53 recognition sites in their regulatory regions. Among the genes activated are p21 and GADD45, each of which independently exhibits growth-suppressive activity. The Gadd45 protein has been described to form a complex with p21, and thus, work was undertaken to map the regions of Gadd45 involved in this interaction and to examine the roles of those two proteins in growth suppression. In this report, a Gadd45 overlapping peptide library and a series of Gadd45 deletion mutants were used to define the domains of Gadd45 involved in the association with p21. Results using both in vitro and in vivo methods have shown that the interaction of Gadd45 with p21 involves a central region of Gadd45. Interestingly, the p21-binding domain of Gadd45 also encodes the Cdc2-binding activity, indicating that the central region of Gadd45 may serve as an important "core," through which Gadd45 protein is able to present cross-talk with other cell cycle regulators. In addition, GADD45 inhibition of Cdc2 kinase activity was compared with Myd118 and CR6, two other members of the GADD45 family. GADD45 was shown to generate the strongest inhibitory effect on Cdc2 activity. Finally, results from short-term survival assays further demonstrated that p21 and GADD45 act upon different cellular pathways to exert their growth-suppressive function.

Binding Sites↗
PubMed2000

Ligand substitution reactions of W6S8L6 with tricyclohexylphosphine (L = 4-tert-butylpyridine or n-butylamine): 31P NMR and structural studies of W6S8(PCy3)n(4-tert-butylpyridine)6-n (0 < n < or = 6) complexes.

The substitution reactions by bulky tricyclohexylphosphine (PCy3) ligands on W6S8L6 (L = 4-tert-butylpyridine or n-butylamine) clusters were investigated to prepare clusters with mixed axial ligands for low-dimensional cluster linking. When 4-6 equiv of PCy3 are used to react with W6S8(4-tert-butylpyridine)6 (4) in THF, cis-W6S8(PCy3)4(4-tert-butylpyridine)2 (1) is preferentially formed. But when starting with W6S8(n-butylamine)6 (2), only W6S8(PCy3)6 (3) is produced with 6 equiv of PCy3. Other conditions with fewer equivalents of PCy3 led to mixtures of partially substituted complexes in the W6S8L6-n(PCy3)n (0 < or = n < or = 6, L = 4-tert-butylpyridine or n-butylamine) series. A significantly distorted structure for 1 helps to explain its preferential formation. 1H NMR spectra were collected for clusters 1 and 2 and 31P NMR spectra for 1 and W6S8(4-tert-butylpyridine)6-n(PCy3)n complexes. P-P coupling through P-W-W-P is reported for the first time in octahedral metal clusters and shown to be very useful in identifying nearly all the W6S8L6-n(PR3)n complexes and their stereoisomers in the mixtures even before individual species are isolated.

Journal Article↗