Biomedical subjects

J Shou

Publications and source records attributed to J Shou.

At least 19 recordsLinked to original sources

PubMed2000

Dickkopf-1, an inhibitor of the Wnt signaling pathway, is induced by p53.

Dickkopf-1 (Dkk-1), a secreted glycoprotein, has been found to be necessary and sufficient for inducing amphibian head formation. Interestingly, the mechanism by which Dkk-1 does this is the ability of Dkk-1 to antagonize the Wnt signaling pathway. Wnt, itself a proto-oncoprotein, can promote cell proliferation and transformation when mutated or overexpressed, leading to tumor formation. p53 is a tumor suppressor and loss of p53 function accelerates mammary tumorigenesis by Wnt. In this study, we found that Dkk-1 is induced by wild-type p53 but not mutant p53(R249S). In addition, DNA damage upregulates Dkk-1 in cell lines that harbor an endogenous wild-type p53 gene but not in cell lines that are p53-null or harbor an endogenous mutant p53 gene. We also found a potential p53 responsive element located approximately 2100 nucleotides upstream of the Dkk-1 transcription start site and we show that p53 binds specifically to this element both in vitro and in vivo. Furthermore, we have established several cell lines derived from H1299 lung carcinoma and U118 glioma cells that inducibly express Dkk-1 under a tetracycline-regulated promoter. We found that Dkk-1 has no effect on proliferation of cells that are not transformed by Wnt. Taken together, these results suggest that Dkk-1 may mediate p53 tumor suppression by antagonizing the Wnt signaling pathway.

Camptothecin↗

PubMed2000

Protein phosphorylation is a regulatory mechanism for O6-alkylguanine-DNA alkyltransferase in human brain tumor cells.

The biochemical regulation of human O6-alkylguanine-DNA alkyltransferase (AGT), which determines the susceptibility of normal tissues to methylating carcinogens and resistance of tumor cells to many alkylating agents, is poorly understood. We investigated the regulation of AGT by protein phosphorylation in a human medulloblastoma cell line. Incubation of cell extracts with [gamma-32P]ATP resulted in Mg(2+)-dependent phosphorylation of the endogenous AGT. Immunoprecipitation after exposure of the cells to 32P-labeled inorganic phosphate showed that AGT exists as a phosphoprotein under physiological conditions. Western analysis and chemical stability studies showed the AGT protein to be phosphorylated at tyrosine, threonine, and serine residues. Purified protein kinase A (PKA), casein kinase II (CK II), and protein kinase C (PKC) phosphorylated the recombinant AGT protein with a stoichiometry of 0.15, 0.28, and 0.44 (mol phosphate incorporated/mol protein), respectively. Residual phosphorylation of the endogenous AGT by the PKs present in cell homogenates and phosphorylation of the recombinant AGT by purified serine/threonine kinases, PKA, PKC, and CK II reduced AGT activity by 30-65%. Conversely, dephosphorylation of cell extracts by alkaline phosphatases stimulated AGT activity. We also identified consensus phosphorylation motifs for many cellular kinases, including PKA and CK II in the AGT protein. These data provide the first and conclusive evidence of AGT phosphorylation and suggest that reversible phosphorylation may control the activity of this therapeutically important DNA repair protein in human normal and cancer cells.

Adenosine Triphosphate↗

PubMed1999

p53 induces TAP1 and enhances the transport of MHC class I peptides.

The transporter associated with antigen processing (TAP) 1 is required for the major histocompatibility complex (MHC) class I antigen presentation pathway, which plays a key role in host tumor surveillance. Since more than 50% of tumors have a dysfunctional p53, evasion of tumor surveillance by tumor cells may be linked to loss of p53 function. Here we found that TAP1 is strongly induced by p53 and DNA-damaging agents through a p53-responsive element. We also found that p73, which is homologous to p53, is capable of inducing TAP1 and cooperates with p53 to activate TAP1. Furthermore, we found that by inducing TAP1, p53 enhances the transport of MHC class I peptides and expression of surface MHC-peptide complexes, and cooperates with interferon gamma to activate the MHC class I pathway. These results suggest that tumor surveillance may be a mechanism by which p53 and/or p73 function as tumor suppressors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

BMPs inhibit neurogenesis by a mechanism involving degradation of a transcription factor.

Bone morphogenetic proteins (BMPs), negative regulators of neural determination in the early embryo, were found to be potent inhibitors of neurogenesis in olfactory epithelium (OE) cultures. BMPs 2, 4 or 7 decreased the number of proliferating progenitor cells and blocked production of olfactory receptor neurons (ORNs). Experiments suggested that this effect was due to an action of BMPs on an early-stage progenitor in the ORN lineage. Further analysis revealed that progenitors exposed to BMPs rapidly (< 2 h) lost MASH1, a transcription factor known to be required for the production of ORNs. This disappearance was due to proteolysis of existing MASH1 protein, but new gene expression was required to trigger it. The data suggest a novel mechanism of BMP action, whereby the induced degradation of an essential transcription factor results in premature termination of a neuronal lineage.

Animals↗

PubMed1998

Factors regulating neurogenesis and programmed cell death in mouse olfactory epithelium.

To identify factors regulating neurogenesis and programmed cell death in mouse olfactory epithelium (OE), and to determine the mechanisms by which these factors act, we have studied mouse OE using two major experimental paradigms: tissue culture of embryonic OE and cell types isolated from it; and ablation of the olfactory bulb ('bulbectomy') of adult mice, a procedure that induces programmed cell death of olfactory receptor neurons (ORNS) and a subsequent surge of neurogenesis in the OE in vivo. Such experiments have been used to characterize the cellular stages in the ORN lineage, leading to the realization that there are at least two distinct stages of proliferating neuronal progenitor cells interposed between the ORN and the stem cell that ultimately gives rise to it. The identification of a number of different factors that act to regulate proliferation and survival of ORNs and progenitor cells suggests that these multiple cell stages may each serve as a control point at which neuron number in the OE is regulated. Our recent studies of neuronal colony-forming progenitors (putative stem cells) of the OE suggest that even these cells, at the earliest stage in the ORN lineage so far identified, are subject to such regulation: if colony-forming progenitors are cultured in the presence of a large excess of differentiated ORNs, then the production of new neurons by progenitors is dramatically inhibited. This result suggests that differentiated ORNs produce a signal that feeds back to inhibit neurogenesis by their own progenitors, and provides a possible explanation for the observation that ORN death, consequent to bulbectomy, results in increased neurogenesis in the OE in vivo: death of ORNs may release neuronal progenitor cells from this inhibitory signal, produced by the differentiated ORNs that lie near them in the OE. Our current experiments are directed toward identifying the molecular basis of this inhibitory signal, and the cellular mechanism(s) by which it acts.

Animals↗

PubMed1998

The murine Fhit locus: isolation, characterization, and expression in normal and tumor cells.

The murine Fhit locus maps near the centromere nu proximal Ptprg locus on mouse chromosome 14. The cDNA sequence and structure are similar to those of the human gene, with exons 5-9 encoding the protein. The predominant mRNA in the tissues and cell lines tested was an alternatively spliced form missing exon 3. Most murine cell lines tested, including lines established from normal mouse embryos and tumors, expressed very low or undetectable levels of Fhit mRNA. Most normal mouse tissues expressed wild-type Fhit mRNA, whereas approximately 40% of murine lung carcinomas expressed wild-type and aberrant Fhit RT-PCR products that lacked various exons. Several tumorigenic mouse cell lines exhibited homozygous deletions of Fhit exons. We conclude that the murine Fhit gene, like its human counterpart, is a target of alterations involved in murine carcinogenesis.

Acid Anhydride Hydrolases↗

PubMed1998

Altered macrophage intracellular signaling induced by protein-calorie malnutrition.

Protein-calorie malnutrition (PCM) contributes to increased morbidity and mortality through impairment of host defense mechanisms and reduced macrophage function. The present study examined alterations in macrophage intracellular signaling associated with the impairment in host defense capabilities. Mice were randomized to either control (regular diet) or protein-free diets (PCM) and pair-fed for 1 week. Following endotoxin stimulation, peritoneal macrophages from PCM mice produce significantly less TNF-alpha and IL-6 product and had significantly less cell-associated IL-6 when compared to macrophages from control mice. Similarly, macrophages from PCM mice had a significant reduction in mRNA levels for both TNF-alpha and IL-6. Other macrophage intracellular signaling mechanisms, such as calcium flux and tyrosine kinase phosphorylation were also altered by PCM. The etiology of PCM-induced defects in macrophage function and intracellular signaling remain unknown but may be related to the neuroendocrine response to PCM.

Animals↗

PubMed1998

The neuronal stem cell of the olfactory epithelium.

The vertebrate olfactory epithelium (OE) is a system in which behavior of neuronal progenitor cells can be observed and manipulated easily. It is morphologically and functionally similar to embryonic germinal neuroepithelia, but is simpler in that it produces large numbers of a single type of neuron, the olfactory receptor neuron (ORN). The OE is amenable to tissue culture, gene transfer, and in vivo surgical approaches, and these have been exploited in experiments aimed at understanding the characteristics of OE neuronal progenitor cells. This has led to the realization that the ORN lineage contains at least three distinct stages of proliferating neuronal progenitor cells (including a stem cell), each of which represents a point at which growth control can be exerted. Neurogenesis proceeds continually in the OE, and studies in vivo have shown that this is a regulated process that serves to maintain the number of ORNs at a particular level. These studies suggest that OE neuronal progenitors-which are in close physical proximity to ORNs-can "read" the number of differentiated neurons in their environment and regulate production of new neurons accordingly. Putative neuronal stem cells of the OE have been identified in vitro, and studies of these cells indicate that ORNs produce a signal that feeds back to inhibit neurogenesis. This inhibitory signal may be exerted at the level of the stem cell itself. Recent studies to identify this signal, as well as endogenous stimulatory signals that may be important in regulating OE neurogenesis, are also discussed.

Animals↗

PubMed1996

Colony-forming progenitors from mouse olfactory epithelium: evidence for feedback regulation of neuron production.

The mammalian olfactory epithelium (OE) supports continual neurogenesis throughout life, suggesting that a neuronal stem cell exists in this system. In tissue culture, however, the capacity of the OE for neurogenesis ceases after a few days. In an attempt to identify conditions that support the survival of neuronal stem cells, a population of neuronal progenitors was isolated from embryonic mouse OE and cultured in defined serum-free medium. The vast majority of cells rapidly gave rise to neurons, which died shortly thereafter. However, when purified progenitors were co-cultured with cells derived from the stroma underlying the OE, a small subpopulation (0.07-0.1%) gave rise to proliferative colonies. A morphologically identifiable subset of these colonies generated new neurons as late as 7 days in vitro. Interestingly, development of these neuronal colonies was specifically inhibited when purified progenitors were plated onto stromal feeder cells in the presence of a large excess of differentiated OE neurons. These results indicate that a rare cell type, with the potential to undergo prolonged neurogenesis, can be isolated from mammalian OE and that stroma-derived factors are important in supporting neurogenesis by this cell. The data further suggest that differentiated neurons provide a signal that feeds back to inhibit production of new neurons by their own progenitors.

Animals↗

PubMed1996

Neurogenesis and cell death in olfactory epithelium.

The olfactory epithelium (OE) of the mammal is uniquely suited as a model system for studying how neurogenesis and cell death interact to regulate neuron number during development and regeneration. To identify factors regulating neurogenesis and neuronal death in the OE, and to determine the mechanisms by which these factors act, investigators studied OE using two major experimental paradigms: tissue culture of OE; and ablation of the olfactory bulb or severing the olfactory nerve in adult animals, procedures that induce cell death and a subsequent surge of neurogenesis in the OE in vivo. These studies characterized the cellular stages in the olfactory receptor neuron (ORN) lineage, leading to the realization that at least three distinct stages of proliferating neuronal precursor cells are employed in generating ORNs. The identification of a number of factors that act to regulate proliferation and survival of ORNs and their precursors suggests that these multiple developmental stages may serve as control points at which cell number is regulated by extrinsic factors. In vivo surgical studies, which have shown that all cell types in the neuronal lineage of the OE undergo apoptotic cell death, support this idea. These studies, and the possible coregulation of neuronal birth and apoptosis in the OE, are discussed.

Animals↗

PubMed1996

Oncogenic transformation of Syrian hamster embryo cells by 5.3-MeV alpha particles and a tumor promoter phorbol ester.

The primary Syrian hamster embryo (SHE) cells were used to study the oncogenic transformation by 238pu alpha particles or X-rays alone or in combination with a chemical promoter phorbol ester. Survival curves of SHE cells following exposure to alpha-particles or X-rays were fitted to single-or multi-target models, respectively. Model parameters were: Do = 0.55 Gy, n = 1 for alpha particles; Do = 1.44 Gy, Dq = 3.0 Gy, n = 7.7 for X-rays. Incidence of alpha particles or X-rays induced cell transformation was dose-dependent. alpha particles were more efficient in inducing cell transformation than that of X-rays. The enhancement of SHE cell transformation by phorbol 12-myristate 13-acetate (PMA) following exposure to alpha particles of 0.25-1.00 Gy was observed.

Animals↗

PubMed1996

Partial deletion of p53 gene in alpha particle-induced transformant of Syrian hamster embryo cells.

The mutation of p53 gene was detected in Syrian hamster embryo (SHE) cells neoplastically initiated with alpha particles. The level of the p53 mRNA in transformant was obviously higher than that in non-irradiated counterpart, as measured by Northern blot analysis of total RNA. A pair of primers were designed based on p53 cDNA sequence to produce the whole length of coding sequence about 1.2 kilobase (Kb) by reverse transcription of mRNA followed by the polymerase chain reaction (RT-PCR), but the length of fragment amplified from transformant mRNA was about 0.3 Kb, remarkably shorter than that from normal SHE cells. Immunohistochemical analysis of p53 protein showed that no heavy staining was found on slice of tumor derived from transformant inoculated in nude mice with hamster specific p53 monocloned antibody HD200. The results implied that p53 gene had been mutated by deletion, which might lead to loss of p53 protein expression but the increased expression of p53 remained in alpha particle-induced SHE transformant.

Animals↗

PubMed1996

[DNA damage induced by fotemustine in cultured HL60 cells].

AIM: To detect DNA damage caused by fotemustine (Fot). METHODS: DNA damage in HL60 cells was evaluated by modified alkaline elution technique. DNA interstrand crosslink (ISC) and DNA-protein crosslink (DPC) were determined. Carmustine (Car) was used as control. Drug treatment time was 1 h. RESULTS: After treatment with Fot 300 mumol.L-1, ISC and DPC index were 5.4 and 6.1 at 6 h, 2.7 and 1.2 at 12 h, respectively. ISC reached the maximum at about 6 h. For Fot 100 mumol.L-1, ISC and DPC index at ISC peak time were 2.1 +/- 0.9 and 3.55 +/- 0.23, 5.0 +/- 0.5 and 7.7 +/- 1.1 for Car 100 mumol.L-1, respectively. Single strand break (SSB) was induced by Fot. CONCLUSION: Fot caused HL60 cell DNA ISC, DPC, and SSB. ISC was formed more quickly by Fot than that by Car.

Antineoplastic Agents↗

PubMed1995

Antimicrobial effects of granulocyte-macrophage colony-stimulating factor in protein-energy malnutrition.

OBJECTIVES: To evaluate, in a murine model of protein-energy malnutrition, whether granulocyte-macrophage colony-stimulating factor (GM-CSF) improves the host response to a septic challenge and to determine the potential mechanisms involved. DESIGN: Nonblinded study of GM-CSF in mice with protein-energy malnutrition. SETTING: A university-based surgical laboratory and animal facility. INTERVENTION: In study 1, malnourished mice were randomized to receive either GM-CSF (120 micrograms/kg subcutaneously to receive either GM-CSF (120 micrograms/kg subcutaneously from day 4 to 7 of the protein-free diet) or saline vehicle as a control. On day 7, all mice were given Candida albicans (5 x 10(5) organisms intravenously). In study 2, malnourished mice received the same dose of GM-CSF or saline vehicle for 7 days of the protein-free diet. MAIN OUTCOME MEASURES: In study 1 mice were followed up for survival. In study 2, after 7 days of diets, splenic macrophages were harvested and were assayed for interleukin-6, superoxide anion, and nitric oxide production. Splenocytes were stimulated with concanavalin A (5 micrograms/mL) for interleukin-4, interleukin-10, and interferon-gamma production. RESULTS: Treatment with GM-CSF significantly enhanced survival in malnourished mice infected with C albicans. Treatment with GM-CSF was associated with increased production from splenic macrophages of interleukin-6, superoxide anion, and nitric oxide as well as decreased interleukin-4 production from splenocytes. CONCLUSIONS: This study suggests a beneficial role for GM-CSF in the malnourished host predisposed to infection. The antimicrobial properties of GM-CSF may function through enhanced production of nitric oxide and superoxide anion.

Animals↗

PubMed1995

Antigen presentation in protein-energy malnutrition.

Protein-energy malnutrition is associated with intrinsic defects in macrophage (MO) microbicidal function, but effects on MO-CD4+ cell interaction are unclear. This study examined the effect of protein-energy malnutrition on components of Ag presentation (AP) by peritoneal macrophages (PMO) and splenocyte responses (MLR) in the naive (resident) and infected state (mycobacterium-BCG), and assessed the potential role of prostaglandin (PGE2) and L-arginine-derived nitric oxide (NO) as regulatory mechanisms in these immune interactions. Mice were randomized to receive either a control (24% casein, RD) or low-protein (2.5% casein, LPD) diets for 8 weeks. PMO and splenocytes were harvested and AP function and MLR assessed +/- NG-mono-methyl-L-arginine (NMMA; competitive inhibitor of NO. synthesis) or indomethacin (PGE2 inhibitor). PMO components of AP were evaluated, including phagocytic function, MHC-class II (Ia) expression, and interleukin-1 (IL-1) and interleukin-6 (IL-6) production. PGE2 production and NO. (measured as NO-2) synthesis were also assessed. AP and MLR were preserved in protein-energy malnutrition in both resident and activated states. BCG infection in RD was associated with PMO activation as measured by increased O-2 and NO-2 release, but impaired AP and MLR responses. NMMA and indomethacin enhanced AP and MLR in RD groups only. Individual components of PMO AP (phagocytosis, IL-1 and IL-6 production) were defective during protein-energy malnutrition, as were NO-2 and PGE2 production. Thus, AP and MLR were preserved in LPD groups which may be related to a loss of prostaglandin- and L-arginine-mediated suppressor mechanisms.

Animals↗

PubMed1995

Glucocorticoids mediate macrophage dysfunction in protein calorie malnutrition.

BACKGROUND: In hospitalized patients protein calorie malnutrition substantially increases the incidence of infection and death. Protein calorie malnutrition results in significant macrophage dysfunction. Whether a primary nutrient deficit or elevated glucocorticoids levels mediate this dysfunction is unclear. The aim of this study was to evaluate the neuroendocrine response to protein calorie malnutrition and its effects on macrophage function. METHODS: By use of a murine model of protein calorie malnutrition, mice were randomized to (1) a standard 24% casein diet (control), (2) protein-free diet (PFD), (3) PFD in adrenalectomized mice, (4) PFD plus the glucocorticoid receptor antagonist RU486 (10 mg/kg), or (5) a standard 24% casein diet plus a 50 mg corticosterone pellet implanted subcutaneously for 7 days. Mice were killed after 7 days, and body weight and serum albumin and corticosterone levels were measured. Peritoneal macrophages were obtained, and stimulated superoxide and interleukin-6 productions were measured. RESULTS: Protein calorie malnutrition significantly impaired macrophage function and elevated serum glucocorticoid levels. Blocking the stress corticosterone response with adrenalectomy or using RU486 to block corticosterone receptors prevented the impairment of macrophage function without restoring nutritional indexes (body weight and serum albumin level). Administration of glucocorticoids via a subcutaneous pellet reproduced macrophage impairment without leading to nutritional deficits. CONCLUSIONS: The neuroendocrine systemic response to protein calorie malnutrition with elevated serum corticosterone levels is a major determinant of macrophage dysfunction in protein calorie malnutrition.

Animal Nutritional Physiological Phenomena↗

PubMed1995

Enteral nutrition during multimodality therapy in upper gastrointestinal cancer patients.

OBJECTIVE: The objective of this study was to evaluate long-term enteral nutrition support in postoperative cancer patients. BACKGROUND: Multimodality therapy for surgical patients with upper gastrointestinal malignancies may improve survival, but often results in substantial malnutrition, immunosuppression, and morbidity. The benefits of combined inpatient and outpatient enteral feeding with standard diets or diets supplemented with arginine, RNA + omega-3 fatty acids are unclear. METHODS: Sixty adult patients with esophageal (22), gastric (16), and pancreatic (22) lesions were stratified by disease site and percent usual weight and randomized to receive supplemental or standard diet via jejunostomy beginning on the first postoperative day (goal = 25 kcal/kg/day) until hospital discharge. Patients also were randomized to receive (n = 37) or not receive (n = 23) enteral jejunostomy feedings (1000 kcal/day overnight) for the 12- to 16-week recovery and radiation/chemotherapy periods. Plasma and peripheral white blood cells were obtained for fatty acid levels and PGE2 production measurements. RESULTS: Mean plasma and cellular omega 3/omega 6 fatty acid levels (percent composition) increased significantly (p < 0.05) in the arginine + omega-3 fatty acid group by postoperative day 7 (0.30 vs. 0.13) and (0.29 vs. 0.14) and continued to increase over time. Mean PGE2 production decreased significantly (p < 0.05) from 2760 to 1600 ng/10(6) cells/mL at day 7 in the arginine + omega-3 fatty acid group, whereas no significant change over time was noted in the standard group. Infectious/wound complications occurred in 10% of the supplemented group compared with 43% of the standard group (p < 0.05); mean length of hospital stay was 16 vs. 22 (p < 0.05) days, respectively. Of the patients who received postoperative chemoradiation therapy, only 1 (6%) of the 18 patients randomized to receive tube feeding did not continue, whereas 8 (61%) of the 13 patients not randomized to tube feedings required crossover to jejunostomy nutritional support. CONCLUSIONS: Supplemental enteral feeding significantly increased plasma and peripheral white blood cell omega 3/omega 6 ratios and significantly decreased PGE2 production and postoperative infectious/wound complications compared with standard enteral feeding. For outpatients receiving adjuvant therapy, those initially randomized to oral feedings alone required rehospitalization more frequently, and 61% crossed over to supplemental enteral feedings.

Aged↗

PubMed1995

[Clinical value of renal radionuclide imaging for diagnosis of urinary tract tumor].

Combined use of 99mTc-diethylenetriaminepentaacetic acid (DTPA) radionuclide angiography, and 99mTc-gluconate renal venography plus single photo computed tomography (SPECT) were employed for clinical diagnosis of urinary tract tumor. This is what we call serial renal radionuclide imaging (SRI). From Aug, 1989 to May, 1993, 63 patients with urinary tract tumor accepted this examination, including 52 cases with renal space-occupying lesion, 5 cases with retroperitoneal mass outside of kidney, 4 cases with bladder cancer (all 61 cases were confirmed by surgery and pathology) and 2 cases suspected of anastomotic leakage after total cystectomy and Bricker's operation. The results show that 1. The renal space-occupying lesion could be accurately localized by SRI and benign lesions could be differentiated from malignancy. 2. SRI could asertain if a retroperitoneal mass was in or outside of the kidney. 3. Urinary fistula could be demonstrated by SRI, while IVU detection failed.

Adolescent↗