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Biomedical subjects

K Shen

Publications and source records attributed to K Shen.

At least 55 records · Page 3Linked to original sources
PubMed1999

Functional analysis of DNA sequences located within a cluster of DNase I hypersensitive sites colocalizing with a MAR element at the upstream border of the chicken alpha-globin gene domain.

We have cloned and sequenced a genomic DNA fragment of chicken containing a cluster of DNase I hypersensitive sites (DHS) located 11-15 kb upstream from the first gene of the alpha-globin gene domain and including a constitutive DHS flanked by two erythroid-specific ones. A 1.2-kb subfragment of the DNA fragment under study located upstream to the constitutive DHS and colocalizing roughly with one of the erythroid-specific DHS was shown to possess the properties of a matrix association region (MAR). The cloned DNA sequences were tested for their ability to serve as promoters and/or influence transcription from the promoter of the alphaD globin gene. In the region studied, we did not find any promoters or enhancers that were active in erythroid cells. The whole DNase I hypersensitive region and some of its subfragments showed a silencing effect when placed downstream from the reporter gene. The expression of the reporter gene was completely abolished, however, when these DNA fragments were placed between the alphaD promoter and the reporter gene. Thus, they seem to act as transcription "terminators." Numerous polyadenylation signals (AATAAA) and an AT-rich palindrome were found within the sequenced DNA fragment. These observations are discussed within the frame of the hypothesis postulating that continuous transcription is essential for maintaining the active status of genomic domains. Furthermore, it is suggested that the DNA fragment studied contains a negative control element that keeps globin genes silent within the chromatin domain permanently open in nonerythroid cells.

Animals↗
PubMed1999

Dynamic control of CaMKII translocation and localization in hippocampal neurons by NMDA receptor stimulation.

Calcium-calmodulin-dependent protein kinase II (CaMKII) is thought to increase synaptic strength by phosphorylating postsynaptic density (PSD) ion channels and signaling proteins. It is shown that N-methyl-D-aspartate (NMDA) receptor stimulation reversibly translocates green fluorescent protein-tagged CaMKII from an F-actin-bound to a PSD-bound state. The translocation time was controlled by the ratio of expressed beta-CaMKII to alpha-CaMKII isoforms. Although F-actin dissociation into the cytosol required autophosphorylation of or calcium-calmodulin binding to beta-CaMKII, PSD translocation required binding of calcium-calmodulin to either the alpha- or beta-CaMKII subunits. Autophosphorylation of CaMKII indirectly prolongs its PSD localization by increasing the calmodulin-binding affinity.

Actins↗
PubMed1999

Potent and highly selective inhibitors of the protein tyrosine phosphatase 1B.

Several protein tyrosine phosphatases (PTPases) have been implicated as regulatory agents in the insulin-stimulated signal transduction pathway, including PTP1B, PTPalpha, and LAR. Furthermore, since all three enzymes are suggested to serve as negative regulators of insulin signaling, one or more may play a pivotal role in the pathogenesis of insulin resistance. We report herein the acquisition of highly selective PTP1B-targeted inhibitors. We recently demonstrated that PTP1B contains two proximal aromatic phosphate binding sites [Puius, Y. A., Zhao, Y., Sullivan, M., Lawrence, D. S., Almo S. C., and Zhang, Z. Y. (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 13420-5], and we have now employed this structural feature to design and synthesize an array of bis(aryldifluorophosphonates). Not only do the lead compounds serve as potent inhibitors of PTP1B but, in addition, several exhibit selectivities for PTP1B versus PTPalpha, LAR, and VHR that are greater than 2 orders in magnitude.

Catalytic Domain↗
PubMed1999

[Recurrent epithelial ovarian cancer].

OBJECTIVE: To evaluate the factors of influence on recurrent epithelial ovarian cancer and to make strategy of treatment. METHODS: Retrospective study of 189 cases of ovarian cancer admitted in our hospital from Jan, 1987 to Dec, 1997. All of these cases had postoperative pathological diagnosis. RESULTS: Of 31 recurrent cases, 19 cases had first cytoreductive surgery in our hospital, while other 12 cases were done in other hospitals. According to FIGO criteria, stage I, II 4 cases (12.9%), III, IV 27 cases (87.1%). The mean recurrent time of no-residual disease was 17.2 months, while that of residual disease < or = 2 cm was 10.1 months (P < 0.01). The mean recurrent time of those having chemotherapy > or = 6 cycles was 13.1 months, while that of those having chemotherapy < 6 cycles was 10.1 months (P > 0.05). The five-year survival rate of 18 cases having secondary cytoreductive surgery was 27.3%, while that of 4 cases having chemotherapy only was 7.1% (P < 0.01). The five-year survival rate of 7 cases abandoning any therapy was 4.8% (P < 0.01). 2 cases had only irradiation therapy. CONCLUSIONS: Histology, stage, degree of tumor differentiation, chemotherapy and the residual disease of cytoreductive surgery all influence recurrence of epithelial ovarian cancer. Secondary cytoreductive surgery along with chemotherapy can raise recurrent epithelial ovarian cancer's five-year survival rate.

Antineoplastic Agents↗
PubMed1999

[Diagnosis and treatment of endodermal sinus tumor of the vagina].

OBJECTIVES: To describe the clinical characteristics and the role of chemotherapy in endodermal sinus tumor of the vagina. METHOD: Two patients with endodermal sinus tumor of the vagina were presented focusing on the clinical manifestations and outcome of the chemotherapy. RESULTS: Patient's age was quite young, 2 and 3 years old respectively. Vaginal bleeding and a polypoid and fragile tumor of the vagina were main clinical features. Elevated serum alpha-FP was found before chemotherapy and dropped dramatically to normal if the tumor was sensitive to chemotherapy. Diagnosis was made by pathology and alpha-FP immunohistochemical staining. Both two patient was well responded to cisplatin vincristine bleomycin (PVB) and cisplatin etoposide bleomycin (PEB) chemotherapy. Clinical and pathological complete remission was obtained after 2-3 courses of chemotherapy without radical surgery and radiotherapy. CONCLUSIONS: Endodermal sinus tumor of vagina in infant was very sensitive to the chemotherapy. Serum alpha-FP was very useful in diagnosis and monitoring of the disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

[Diagnosis, treatment and prevention of postoperative deep venous thrombosis in gynecologic onocology].

OBJECTIVE: To describe the clinical profile of deep venous thrombosis (DVT) after operation on pelvic tumours and to study how to choose the methods of diagnosis, treatment and prevention of DVT. METHODS: The clinical characteristics, the methods of diagnosis, treatment and prevention of 11 cases with DVT and 18 cases with the tendency to DVT were analyzed retrospectively. RESULTS: Old age, fatness and oringinal pelvic malignant tumours were the high risk factors for postoperative DVT. Especially the patients with endometrial carcinoma were with the high incidence of DVT. Colour-code Doppler ultrasonography was the best choice to diagnose DVT. Heparin or low molecule weight heparin (LMWH) anticoagulation was effective treatment in postoperative DVT. CONCLUSIONS: Old age, fatness and gynecologic malignant tumours should be considered as highrisk factors for postoperative DVT. Preoperative or postoperative prophylatic treatment of DVT should be considered in high risk population. Anticoagulation was effective in postoperative DVT.

Adult↗
PubMed1999

[The effect of hydroxycamptothecin and topotecan to SKOV3 and CAOV3 in vitro].

OBJECTIVE: To examine the effect of hydroxycamptothecin (HCPT) and topotecan, two kinds of derivative of camptothecin, to two ovarian cancer cell lines, SKOV3 and CAOV3. METHODS: Methyl thiazolyl tetrazolium (MTT) was used to establish the dose-effect curves. The ability of these two drugs to induce apoptosis of the two cell lines was determined by the method of terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) and DNA Ladder. The morphological changes of the cells were observed by electronic microscope. Expression of c-myc, bcl-2, and fas was estimated by the immunohistochemical staining. RESULTS: The inhibition of HCPT and topotecan to the growth of SKOV3 and CAOV3 was dose-dependent. 50% inhibiting concentration (IC50) of HCPT and topotecan to SKOV3 was 72 ng/ml and 160 ng/ml, respectively; IC10 of HCPT and topotecan to CAOV3 was 141 ng/ml and 12 ng/ml, respectively. The inhibition of HCPT and topotecan to clone forming rate of two cell lines was significant. The growing curves of SKOV3 and CAOV3 treated by HCPT and topotecan were significantly lower than controls. HCPT and topotecan of 5 ng/ml can elongate the double time of SKOV3 for 49.00 and 1.75 times, respectively. They can elongate the double time of CAOV3 for 2.77 and 1.94 times, respectively. After treated by HCPT or topotecan, SKOV3 generated DNA Ladder. Positive rates of TUNEL of SKOV3 and CAOV3 were elevated by HCPT and topotecan notably. HCPT and topotecan did not affect the expression of c-myc, bcl-2, fas of SKOV3 and CAOV3. Observed by electronic microscope, heterochromatin of SKOV3 and CAOV3 coagulated after treated by HCPT. Micro villi of SKOV3 and CAOV3 were damaged, and some vacuoles appeared in the cytoplasm. CONCLUSIONS: HCPT and topotecan can inhibit growth of SKOV3 and CAOV3 significantly. HCPT and topotecan can induce apoptosis of SKOV3 and CAOV3.

Antineoplastic Agents↗
PubMed1998

Chromosome 2 sequence of the human malaria parasite Plasmodium falciparum.

Chromosome 2 of Plasmodium falciparum was sequenced; this sequence contains 947,103 base pairs and encodes 210 predicted genes. In comparison with the Saccharomyces cerevisiae genome, chromosome 2 has a lower gene density, introns are more frequent, and proteins are markedly enriched in nonglobular domains. A family of surface proteins, rifins, that may play a role in antigenic variation was identified. The complete sequencing of chromosome 2 has shown that sequencing of the A+T-rich P. falciparum genome is technically feasible.

Amino Acid Sequence↗
PubMed1998

[Role of CAAT/enhancer binding protein in IL-6 regulation of angiotensinogen gene expression].

OBJECTIVE: Angiotensinogen is the only known precursor of vasoactive angiotensin II and also one of the acute phase proteins. This study was intended to understand the regulation of angiotensinogen gene expression induced by IL-6. METHODS: Northern hybridization, electrophoretic mobility shift assay and transient transfections were conducted. RESULTS: Northern hybridization showed increase of angiotensinogen mRNA treated by IL-6 in Hep3B cells. Electrophoretic mobility shift assay further indicated the HAG IL-6RE homologous to IL-6 responsive element at -568 site of the angiotensinogen promoter binds C/EBP(CAAT/Enhancer Binding Protein). Consistent with this binding studies were the transient transfections of the expression vector in which 6 copies of HAG-IL-6RE linked to TK core promoter and fused to CAT reporter gene, revealing that C/EBPalpha was a transactivator under IL-6-induced condition. CONCLUSION: These observations suggest that C/EBP plays regulatory role in IL-6-induced angiotensinogen gene expression.

Angiotensinogen↗
PubMed1998

CaMKIIbeta functions as an F-actin targeting module that localizes CaMKIIalpha/beta heterooligomers to dendritic spines.

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a serine/threonine protein kinase that regulates long-term potentiation and other forms of neuronal plasticity. Functional differences between the neuronal CaMKIIalpha and CaMKIIbeta isoforms are not yet known. Here, we use green fluorescent protein-tagged (GFP-tagged) CaMKII isoforms and show that CaMKIIbeta is bound to F-actin in dendritic spines and cell cortex while CaMKIIalpha is largely a cytosolic enzyme. When expressed together, the two isoforms form large heterooligomers, and a small fraction of CaMKIIbeta is sufficient to dock the predominant CaMKIIalpha to the actin cytoskeleton. Thus, CaMKIIbeta functions as a targeting module that localizes a much larger number of CaMKIIalpha isozymes to synaptic and cytoskeletal sites of action.

3T3 Cells↗
PubMed1998

In vivo and in vitro characterization of the sequence requirement for oligomer formation of Ca2+/calmodulin-dependent protein kinase IIalpha.

Ca2+/calmodulin-dependent protein kinase II (CaMK II) is a multifunctional serine/threonine protein kinase that regulates ion channels, metabolic enzymes, cytoskeletal proteins, and possibly transcription factors. CaMK II holoenzymes have been shown to be large oligomers built from eight or more subunits. The oligomeric structure of CaMK II is required for a critical trans-autophosphorylation step by which each subunit traps bound calmodulin and renders the enzyme partially active in the absence of Ca2+/calmodulin. Here we define a minimal C-terminal domain of alphaCaMK II that is necessary and sufficient for oligomerization. The oligomeric structure of alphaCaMK II deletion mutants was investigated in vitro by gel filtration chromatography and in living cells by measuring nuclear exclusion and diffusion coefficients of green fluorescent protein-tagged mutants. These studies showed that a C-terminal region of alphaCaMK II of 135 amino acids is sufficient for oligomer formation. Oligomer formation was abolished by further C-terminal and N-terminal deletions, indicating that the same region is not only sufficient but also necessary for oligomerization. Thus, an oligomerization domain of only 15 kDa is sufficient to build the circular structure of CaMK II holoenzyme.

Amino Acid Sequence↗
PubMed1998

Cellular composition and anatomic distribution in nonfunctioning pancreatic endocrine tumors: immunohistochemical study of 30 cases.

OBJECTIVE: To investigate the cytological pattern and distribution in nonfunctioning pancreatic endocrine tumors. METHODS: Using labeled streptavidin-biotin (LSAB), immunohistochemical staining for insulin, glucagon, somatostatin, pancreatic polypeptide and gastrin was performed on 30 nonfunctioning pancreatic endocrine tumors from 30 patients. The cellular composition and anatomic distribution in these tumors were analyzed. RESULTS: Of 30 tumor tissues, 22 (73.3%) were found to contain cells immunoreactive to 1-4 kinds of peptide hormones; 17 (56.7%) showed positive staining for more than one peptide and up to 4 peptides; and 8 (26.7%) showed negative immunoreaction to all antiserum applied. No tumor was found to contain immunoreactive gastrin. Among 17 multihormonal tumors, 4 contained 2 kinds of peptide hormones, 8 had 3 kinds, and 5 harbored 4 kinds of peptide hormones. In addition, the difference in the number and type of positive endocrine cells between the tumors arising from the head of the pancreas and those arising from the body and tail of the pancreas were statistically significant (P < 0.05). CONCLUSIONS: Immunohistochemically, the high positive rate to peptide hormones suggests that the nonfunctioning pancreatic endocrine tumors are actually not nonfunctioning; they are asymptomatic pancreatic endocrine tumors. Moreover, an uneven distribution of positive endocrine cells in the nonfunctioning pancreas endocrine tumors within the pancreas was identified.

Adenoma, Islet Cell↗
PubMed1998

[Effect of vasectomy on apoptosis in spermatogenic cells of the male rat].

To explore the effect of vasectomy on apoptosis of spermatogenic cells, we have detected apoptosis in the testis of vasectomized and sham-operated adult rats within a period of 12 postoperative weeks by means of flow cytometry and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuride triphosphate nick-end labeling) method. Flow cytometry found that, in vasectomized rat, the sub-haploid peak was higher and the percentage of cells with sub-haploid was increased. The total number of positive TUNEL cells in the vasectomized group was greater than that in the sham-operated group (P < 0.001). Compared with the same time-phased sham-operated subgroups, the number of apoptotic spermatogonia and primary spermatocytes in the testes of the subgroups 2 weeks, 6 weeks and 10 weeks after vasectomy as well as the number of spermatogonia of the subgroup 12 weeks after vasectomy were significantly higher (P < 0.05). These findings demonstrate that vasectomy could enhance the apoptosis of spermatogenic cells.

Animals↗
PubMed1998

[The comparison of biological characteristics between tumor-infiltrating lymphocytes and tumor-associated lymphocytes in ascites of epithelial ovarian carcinoma].

OBJECTIVE: To compare biological charicteristics between tumor-infiltrating lymphocytes (TIL) and tumor-associated lymphocytes (TAL) in epithelial ovarian carcinomas. METHODS: The surgical samples of four ovarian specimens and eight cancer ascites from epithelial ovarian carcinoma were collected, and ascites were divided into bloody and non-bloody groups. The cancer tissue was dissected to yield single cells suspensions. TIL and TAL were grown in coculture with autologous tumor cells and 500 U/ml recombinant interleukin-2 (rIL-2). Phenotype was studied using flow cytometry for a varity of human immunocompetent cell surface markers (CD3, CD4, CD8, CD25). Cytotoxicity was investigated using 4-hr 51Cr-release assays with primary ovarian carcinoma cell cultures and the CAOV3 cell line and the K562 cell line as target cells in cultured period. RESULTS: (1) There was no significant difference in CD3, CD4, CD8 and CD25 expression among the three groups (P > 0.05). CD4 to CD8 (CD4/CD8) ratio was consistently more than 1 in cultured period. (2) In all three groups, Natural killer (NK) acitivity was high and no difference among them (P > 0.05). (3) In all twelve cases, TIL and TAL in the non-bloody ascites possess higher potential to lyse the autologous tumor target than TAL in the bloody ascites (P < 0.01) when effector cell to target cell (E:T) was 50 to 1 (50:1). Lytic activity was 30.2%-51.0% and 10.8%-15.8% respectively. CONCLUSIONS: TIL and TAL in non-bloody ascites in epithelial ovarian cancer have the same biological characteristics.

Ascitic Fluid↗
PubMed1998

Effects of proglumide, a gastrin receptor antagonist, on human large intestine carcinoma SW480 cell line.

OBJECTIVE: To explore the effects of proglumide, a gastrin receptor antagonist, on the amount of viable cells, synthesis of DNA and protein, and cell proliferation cycle in human large intestine carcinoma SW480 cell line in order to provide experimental basis for treatment of large intestine carcinoma using proglumide. METHODS: Large intestine carcinoma SW480 cells at logarithmic growth stage were cultivated with different concentrations of proglumide for different periods of time, then the amount of viable cells was determined by MTT colorimetric analysis. The SW480 cells were cultivated with proglumide, pentagastrin, proglumide + pentagastrin for the same period of time, then the contents of DNA and protein and the cell proliferation cycle were determined by flow-cytometry. RESULTS: The amount of viable cells, synthesis of DNA and protein, distribution of cell cycle, and proliferation index (PI) in the proglumide group did not differ significantly from those in the pentagastrin group (P > 0.05). The amount of viable cells in the pentagastrin group was significantly higher than that in the pentagastrin group (P < 0.01). In the proglumide + pentagastrin group the amount of viable cells, synthesis of DNA and protein, amount of S and G2M phase cells, and PI were all significantly lower than those in the pentagastrin group (all P < 0.01), and the amount of G0/G1 phase cells was significantly higher than that in the pentagastrin group (P < 0.01), but none of the above differed from those in the control group (all P > 0.05). CONCLUSIONS: Proglumide has no obvious effect on the growth of human large intestine carcinoma SW480 cell line, but can inhibit the growth-promoting effect of pentagastrin on large intestine carcinoma cells. The mechanism may be that proglumide inhibits the promoting effect of pentagastrin on the synthesis of DNA and protein of carcinoma cells, and then inhibits carcinoma cell growth from G0/G1 phase to S and G2M phase.

Antineoplastic Agents↗
PubMed1998

[Effect of xueling on relating substances of renal hypertension in rats].

Xueling(p.o.) obviously reduces the aldosterone content of renal hypertension rats, but not affecting markedly the endothelin, atrial natriuretic factor, calcitonin gene-related peptide, thromboxane B2 and 6-keto-prostaglandin F1 alpha. The content reduction of aldosterone is one of the mechanisms to lower blood pressure.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

The mammalian Rad24 homologous to yeast Saccharomyces cerevisiae Rad24 and Schizosaccharomyces pombe Rad17 is involved in DNA damage checkpoint.

Cell cycle checkpoint proteins play critical roles in maintaining genomic stability and integrity to prevent the development of cancer and hereditary diseases. Here we report the isolation of a novel mouse gene encoding the protein MmRad24 [MmRad24 is the mouse homologue of HRad17, which was described recently by A. E. Parker et al. (J. Biol. Chem., 273: 18340-18346, 1998)], which shares significant sequence and structural homology with the budding yeast Rad24 and its fission yeast counterpart Rad17, both of which are required for DNA damage checkpoints. Confocal microscopy revealed that the green fluorescent protein-tagged MmRad24 protein is localized to the nucleus in living cells. Fluorescence-activated cell-sorting analysis showed that overexpression of the wild-type MmRad24 in diploid fibroblast WI-38 cells caused a significant G2 arrest of the cell cycle, whereas overexpression of a mutant MmRad24 (mutated on the nucleotide-binding site) that likely functions as a dominant-negative protein resulted in a defect in cell cycle arrest after DNA damage treatment as measured by bromodeoxyuridine pulse-chase labeling experiments. Taken together, these results suggest that the mammalian Rad24 protein may function as a critical gatekeeper in DNA damage checkpoint control.

Amino Acid Sequence↗