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Biomedical subjects

Y Su

Publications and source records attributed to Y Su.

At least 127 records · Page 7Linked to original sources
PubMed1998

In vitro cytotoxic activity of 1-decarboxy-3-oxo-ceanothic acid in a human ovarian adenocarcinoma cell line.

The effect of a novel pentacyclic triterpene, 1-decarboxy-3-oxo-ceanothic acid (DOCA) on DNA synthesis, DNA degradation and programmed cell death was examined in human ovarian adenocarcinoma (OVCAR-3) cells. OVCAR-3 cells exposed to various concentrations of DOCA for 30 h displayed a dose-dependent inhibition of DNA synthesis. Morphologically, treatment with 10 microg/ml of DOCA for 24 h and 72 h resulted respectively in reduction in cell volume and condensation of nuclear structures. By agarose gel analysis, DNA fragmentation with the characteristic pattern of inter-nucleosomal ladder was observed after cells were treated with 2.5 microg/ml of DOCA for 24 h. Both cell death and DNA fragmentation caused by this compound were partially inhibited by the protein synthesis inhibitor cycloheximide, suggesting that the apoptotic process caused by DOCA requires synthesis of new proteins. On the other hand, no apparent double-stranded DNA breaks were detected after cells were incubated with 2.5 microg/ml of DOCA for 24 h, indicating that DNA damage was not a preceding event for apoptosis induced by this compound. Taken together, our results demonstrate that the cytotoxic effect of DOCA is mediated, at least in part, by the induction of apoptosis.

Adenocarcinoma↗
PubMed1997

Thyroid hormone induces apoptosis in primary cell cultures of tadpole intestine: cell type specificity and effects of extracellular matrix.

Thyroid hormone (T3 or 3,5,3'-triiodothyronine) plays a causative role during amphibian metamorphosis. To investigate how T3 induces some cells to die and others to proliferate and differentiate during this process, we have chosen the model system of intestinal remodeling, which involves apoptotic degeneration of larval epithelial cells and proliferation and differentiation of other cells, such as the fibroblasts and adult epithelial cells, to form the adult intestine. We have established in vitro culture conditions for intestinal epithelial cells and fibroblasts. With this system, we show that T3 can enhance the proliferation of both cell types. However, T3 also concurrently induces larval epithelial apoptosis, which can be inhibited by the extracellular matrix (ECM). Our studies with known inhibitors of mammalian cell death reveal both similarities and differences between amphibian and mammalian cell death. These, together with gene expression analysis, reveal that T3 appears to simultaneously induce different pathways that lead to specific gene regulation, proliferation, and apoptotic degeneration of the epithelial cells. Thus, our data provide an important molecular and cellular basis for the differential responses of different cell types to the endogenous T3 during metamorphosis and support a role of ECM during frog metamorphosis.

Animals↗
PubMed1997

Analysis of exon/intron structure and 400 kb of genomic sequence surrounding the 5'-promoter and 3'-terminal ends of the human glypican 3 (GPC3) gene.

GPC3, the gene modified in the Simpson-Golabi-Behmel gigantism/overgrowth syndrome (SGBS), is shown to span more than 500 kb of genomic sequence, with the transcript beginning 197 bp 5' of the translational start site. The Xq26.1 region containing GPC3 as the only known gene has been extended to > 900 kb by sequence analysis of flanking BAC clones. Two GC isochores (40.6 and 42.6% GC) are observed at the 5' and 3' ends of the locus, with a large repertoire of repetitive sequences that includes an unusual cluster of four L1 elements > 92% identical over 2.8 kb. Eight exons, accounting for the full 2.4-kb GPC3 cDNA, have been sequenced along with neighboring intronic regions. PCR assays have been developed to amplify each exon and exon/intron junction sequence, to help discriminate instances of SGBS among individuals with overgrowth syndromes and to facilitate mutational analysis of lesions in the gene.

Amino Acid Sequence↗
PubMed1997

Characterization of a Drosophila proximal-sequence-element-binding protein involved in transcription of small nuclear RNA genes.

In a wide variety of eukaryotic organisms, transcription of small nuclear RNA (snRNA) genes is dependent upon a proximal sequence element (PSE) located upstream of position -40 relative to the transcription start site. There is little or no existent knowledge concerning the PSE-binding proteins of organisms other than human. Here, we report the purification of a fraction enriched in the Drosophila melanogaster PSE-binding protein (DmPBP). DmPBP forms a highly specific complex with the PSE. The protein stimulates transcription from the U1 gene promoter by RNA polymerase II and from the U6 gene promoter by RNA polymerase III in Drosophila nuclear extracts, and activation is dependent upon the presence of a PSE. The molecular mass of native DmPBP as measured by gel-filtration chromatography is 375 kDa. Two polypeptides (apparent molecular masses 59 kDa and 61 kDa) appear to be in close contact with the DNA in that they can be very efficiently and specifically crosslinked to the PSE sequence by ultraviolet irradiation.

Animals↗
PubMed1997

Cloning and expression of a rat brain interleukin-1beta-converting enzyme (ICE)-related protease (IRP) and its possible role in apoptosis of cultured cerebellar granule neurons.

Several members of the IL-1beta-converting enzyme (ICE) family of proteases recently have been implicated in the intracellular cascade mediating the apoptotic death of various cell types. It is unclear, however, whether ICE-related proteases are involved in apoptosis of mammalian neurons and, if so, how they are activated. Here we report the cloning of an ICE-related protease (IRP) from rat brain, which displays strong sequence identity to human CPP32. In situ hybridization histochemistry reveals that this IRP mRNA is expressed in neuron-enriched regions of the developing and adult rat brain but is profoundly downregulated in the adult (compared with developing) brain. To investigate whether this IRP is involved in the death of neurons in the developing brain, we studied IRP expression in cultured cerebellar granule neurons. In cultured cerebellar granule neurons, reduction of extracellular K+ reliably induces apoptosis and stimulates overexpression of IRP mRNA. The latter is especially prominent 4 hr after switching from high K+ to low K+ medium. The expression of IRP mRNA was maintained at this level for at least 8 hr and was followed by apoptotic death of these neurons. Induction of IRP mRNA and cell death are blocked completely by adding depolarizing concentrations of K+ </=90 min after switching to low K+ medium (i.e., before the commitment point for apoptosis) and partially blocked by brain-derived neurotrophic factor (BDNF), which also partially rescues granule neurons from low K+-induced apoptosis. In addition, overexpression of IRP cDNA in HeLa cells results in cell death accompanied by strong internucleosomal cleavage of DNA, a typical feature of apoptosis. Finally, we detected cleavage of the putative death substrate poly (ADP-ribose) polymerase (PARP), beginning 8 hr after changing from high K+ to low K+ medium, coinciding with the time course of induced expression of the IRP gene. Our data suggest that transcriptional activation of IRP could be one of the mechanisms involved in the apoptotic death of cerebellar granule neurons.

Amino Acid Sequence↗
PubMed1997

Substrate inhibition of nitric oxide synthase in pulmonary artery endothelial cells in culture.

The effects of arginine on nitric oxide synthase (NOS) activity and NO production were studied in pulmonary artery endothelial cells (PAEC). Incubation of PAEC with 0-100 microM arginine increased NO production, detected as nitrite in the culture medium, in a dose-dependent manner. In contrast, incubation with concentrations of arginine in excess of 100 microM resulted in a reversible dose-dependent inhibition of NO production, even though intracellular arginine content increased in these cells. The NOS enzyme kinetics were studied in a total membrane preparation and in purified NOS protein and revealed that the Km of arginine as a substrate for NOS is 3-5 microM, the Vmax occurred at 100 microM arginine, and substrate inhibition occurred at >100 microM arginine. Oxyhemoglobin, carboxy-PTIO, catalase, SOD, citrulline, hydroxyarginine, and D-arginine did not change NOS kinetics. These results indicate that substrate inhibition of eNOS exists in porcine PAEC in vitro.

Animals↗
PubMed1997

Determining surface areas of marine alga cells by acid-base titration method.

A new method for determining the surface area of living marine alga cells was described. The method uses acid-base titration to measure the surface acid/base amount on the surface of alga cells and uses the BET (Brunauer, Emmett, and Teller) equation to estimate the maximum surface acid/base amount, assuming that hydrous cell walls have carbohydrates or other structural compounds which can behave like surface Brönsted acid-base sites due to coordination of environmental H2O molecules. The method was applied to 18 diverse alga species (including 7 diatoms, 2 flagellates, 8 green algae and 1 red alga) maintained in seawater cultures. For the species examined, the surface areas of individual cells ranged from 2.8 x 10(-8) m2 for Nannochloropsis oculata to 690 x 10(-8) m2 for Dunaliella viridis, specific surface areas from 1,030 m2.g-1 for Dunaliella salina to 28,900 m2.g-1 for Pyramidomonas sp. Measurement accuracy was 15.2%. Preliminary studies show that the method may be more promising and accurate than light/electron microscopic measurements for coarse estimation of the surface area of living algae.

Cell Division↗
PubMed1997

Construction of a cell-based high-flux assay for the rev protein of HIV-1.

The Rev of HIV-1 is essential for the replication of the viruses and is therefore a very attractive target for the development of antiviral drugs. To establish a cell-based high-flux assay system for random screening of Rev inhibitors, cells carrying both the Rev-expressing gene and a Rev-inducible SeAP gene were generated by permanent transfection. SeAP produced by these cells was 5-10-fold higher than that synthesized by cells not carrying the Rev gene. Northern blot analysis demonstrated that the increase in SeAP was due mainly to an increase in SeAP transcripts, indicating the effect of Rev proteins synthesized by the transfected cells. The assay system reported in this study should be useful for screening novel Rev inhibitors.

Alkaline Phosphatase↗
PubMed1997

Bisbenzylisoquinoline alkaloids from Stephania cepharantha and their effects on proliferation of cultured cells from the murine hair apparatus.

Bisbenzylisoquinoline alkaloids were isolated from Stephania cepharantha Hayata and their proliferative activities on cultured hair cells from the murine skin were evaluated. Cepharanthine (1), cepharanoline (9), isotetrandrine (2), and berbamine (7) showed significant activities in the range of 0.01-0.1 microgram/ml, but had no activity on cultured keratinocytes or fibroblasts from the murine skin.

Alkaloids↗
PubMed1997

Cyclosporin A but not FK506 inhibits thyroid hormone-induced apoptosis in tadpole intestinal epithelium.

Amphibian metamorphosis and mammalian T cell development represent two of the best known systems where developmental programmed cell death through apoptosis takes place. Two immunosuppressants, cyclosporin A (CsA) and FK506, have been demonstrated to inhibit activation-induced cell death in immature T cells and T cell hybridomas. In this study, we have established an in vitro system in which isolated primary tadpole intestinal epithelial cells undergo typical apoptosis upon treatment with thyroid hormone (T3), the causative agent of metamorphosis. It is surprising that this T3-induced apoptosis was found to be inhibited only by CsA but not by FK506, whereas both immunosuppressants block activation-induced apoptosis in T cells. Since T3 exerts its effect primarily by regulating gene transcription through direct binding to nuclear thyroid hormone receptors, our results strongly suggest that except for their similarity in the T cell receptor-mediated signal transduction process, CsA, but not FK506, also blocks another yet-unidentified step during the induction of apoptosis. The identification of this novel function of CsA may provide an important clue toward the understanding of the mechanism of apoptosis and helps in designing better clinical applications of the immunosuppressants.

Animals↗
PubMed1997

Analysis of a 103 kbp cluster homology region from the left end of Saccharomyces cerevisiae chromosome I.

The DNA sequence and preliminary functional analysis of a 103-kbp section of the left arm of yeast chromosome I is presented. This region, from the left telomere to the LTE1 gene, can be divided into two distinct portions. One portion, the telomeric 29 kbp, has a very low gene density (only five potential genes and 21 kbp of noncoding sequence), does not encode any "functionally important" genes, and is rich in sequences repeated several times within the yeast genome. The other portion, with 37 genes and only 14.5 kbp of noncoding sequence, is gene rich and codes for at least 16 "functionally important" genes. The entire gene-rich portion is apparently duplicated on chromosome XV as an extensive region of partial gene synteney called a cluster homology region. A function can be assigned with varying degrees of precision to 23 of the 42 potential genes in this region; however, the precise function is know for only eight genes. Nineteen genes encode products presently novel to yeast, although five of these have homologs elsewhere in the yeast genome.

Base Sequence↗
PubMed1997

Hypoxia inhibits the induction of argininosuccinate synthetase by endotoxin in lung endothelial cells.

Pulmonary artery endothelial cells (PAEC) possess a two-step pathway for synthesizing L-arginine from L-citrulline. The first and rate-limiting step is catalyzed by argininosuccinate synthetase (AS). We have previously shown that hypoxia inhibits synthesis of L-arginine from L-citrulline in PAEC. In this study, we examined the effect of hypoxia on the induction of AS in PAEC. Porcine PAEC were incubated with or without endotoxin under normoxia (air-5% CO2) or hypoxia (0% O2-95% N2-5% CO2) for 24 h, and then AS activity and AS mRNA content were determined. Incubation with endotoxin resulted in increases in AS activity and mRNA, and the latter was blocked by actinomycin D. Exposure to hypoxia for 24 h decreased AS activity and mRNA content and stability, and it also abolished the increases in AS activity and mRNA induced by endotoxin. These results indicate that hypoxia inhibits endotoxin-mediated induction of AS. This inhibition might reduce the availability of intracellular L-arginine and thereby limit immunostimulant-induced nitric oxide production by lung endothelial cells.

Animals↗
PubMed1997

Patterns of Fos-Immunoreactivity in the CNS Induced by Repeated Hemorrhage in Conscious Rats: Correlations with Pituitary-Adrenal Axis Activity.

While the present understanding of pituitary-adrenal function predicts attenuation of responses to a repeated stressor, experimental observations often show occurrence of potentiation rather than inhibition. The role of the CNS in this phenomenon was investigated in rats sustaining either a single (S-HEM) or a double episode (R-HEM) of hemorrhage. For S-HEM, blood was withdrawn over 3min and retransfused at 10min; for R-HEM, the stimulus was repeated at 90 min. S-HEM elicited 26- and 9-fold increases in circulating adrenocorticotropin (ACTH) and corticosterone, respectively. After R-HEM the plasma ACTH response was potentiated by 82%. Sixty min after S-HEM, Fos-like immunoreactivity (Fos-IR) was increased in medullary (solitary nucleus, NTS and ventrolateral medulla, VLM), pontine (locus coeruleus, LC and parabrachial nucleus, PBN), limbic (central amygdala, CNA and bed nucleus, BNST), and hypothalamic (supraoptic nucleus, SON and paraventricular nucleus, PVN) regions activated by hemodynamic stimuli. However after R-HEM, the Fos-IR response was significantly potentiated only in the VLM and PVN, while only a moderate increase was evident in the NTS. In other brain regions (LC, PBN, CNA, BNST, HPC and SON), Fos-IR either did not change or the increases were less than those observed after S-HEM. It is suggested that this plasticity in the pattern of neuronal activation following repetition of a stimulus may account for the maintenance of pituitary-adrenal secretory responses and its potentiation after R-HEM.

Journal Article↗
PubMed1997

[Plasma and skin tissue endothelin in patients with psoriasis vulgaris].

The levels of plasma endothelin in 46 patients with psoriasis vulgaris and the levels of endothelin in skin tissue of 25 cases were determined by RIA. The results showed that: (1) The plasma levels of endothelin in patients with psoriasis vulgaris was significantly increased compared with that of the controls (P < 0.01), so was the active stage group compared with the stable stage group (P < 0.01); (2) The level of endothelin in skin lesions of patients was significantly higher than that of the uninvolved skin. These findings suggest that endothelin might play a role in the pathogenesis of psoriasis vulgaris.

Adolescent↗
PubMed1997

[Survey on nutritional knowledge, attitude and practice among the residents in Beijing, Guangzhou and Shanghai].

A survey on nutritional knowledge, attitude and practice (K-A-P) was carried out among 965 residents aged between 20 and 50 and randomly selected in Beijing, Guangzhou and Shanghai. The results showed that subjects' knowledge level was not high, and their knowledge scores were significantly correlated with their education levels (r = 0.3011, P < 0.010). Subjects aged above 35 had a higher knowledge level than that of younger ones. Subjects from three cities held a positive and favorable attitude towards the acquisition of nutritional knowledge, reasonable dietary pattern and healthy diet habits. Results of food frequency survey indicated that the consumption of rice/flour, meat/poultry, vegetables, fruits, milk and milk products was relatively high. In addition, 89.5%, 78.8% and 47.8% of subjects selected newspaper, TV and broadcast as their main sources of nutritional information respectively. This survey provided basis on content and method for future nutrition education.

Adult↗
PubMed1997

[The diagnosis and surgical treatment in rectal endometriosis].

From Jun 1975 to Mar 1995, 26 cases of endometriosis in the rectum (RE) were admitted. Local resection was performed in 16 and Dixon's operation in 10. The result showed 21 cases were symptomatically cured and 5 with remission. 2 cases were reoperated because of recurrence in 5 years after the first operation and cured. RE is difficult in distiguishing from rectal cancer. It is characterized by tenesmus, bursting pain, hematochezia in young and middle aged women during periods. The diagnosis can be made by tipycal history and vaginal examination, rectal examination, barium enema, proctoscopy and so on. The indications of operation include severe clinic symptoms and failed conservative therapy. Wedge resection was suitable in cases with small lession in rectum, while large, deep seated lessions in lower rectum were treated with Dixon's operation in order to prevent recurrence.

Adult↗
PubMed1997

[MA891--an established spontaneous mouse mammary adenocarcinoma cell line and its immunologic characteristics].

OBJECTIVE: To characterize the immunologic properties of an established mouse mammary tumor cell line MA891. METHODS: From a spontaneous mouse mammary adenocarcionma (TA2 MA891) of TA2 mouse origin, an in vitro passaged cell line MA891 was maintained in RPMI1640 with 10% new born calf serum. The immunogenecity of MA891 was studied by classical tumor transplantation rejection assay, generation of cytotoxic T lymphocytes (CTL) by syngeneic secondary mixed lymphocyte-tumor cell culture (MLTC) and cytotoxic assay of tumor infiltrating lymphocytes (TIL). RESULTS: MA891 maintained the high metastatic potential of the parental TA2 MA891 tumor passaged in vivo. Transplantation rejection studies indicated that amputation of a hind limb with growing tumor in the footpad did not protect the mice from a second subcutaneous challenge of the same tumor. The cytotoxic activities of both CTL and TIL were shown to be very weak. CONCLUSION: MA891 is a mouse tumor of very low immunogenecity. It can be used as a mouse tumor model for studying cancer metastasis in humans.

Adenocarcinoma↗