Low Basal Levels (low + basal_level)

Distribution by Scientific Domains


Selected Abstracts


Differential control of apoptosis by DJ-1 in prostate benign and cancer cells

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2004
Yaacov Hod
Abstract DJ-1 is a conserved protein reported to be involved in diverse cellular processes ranging from cellular transformation, control of protein,RNA interaction, oxidative stress response to control of male infertility, among several others. Mutations in the human gene have been shown to be associated with an autosomal recessive, early onset Parkinson's disease (PARK7). The present study examines the control of DJ-1 expression in prostatic benign hyperplasia (BPH-1) and cancer (PC-3) cell lines in which DJ-1 abundance differs significantly. We show that while BPH-1 cells exhibit low basal level of DJ-1 expression, stress-inducing agents such as H2O2 and mitomycin C markedly increase the intracellular level of the polypeptide. In contrast, DJ-1 expression is relatively high in PC-3 cells, and incubation with the same cytotoxic drugs does not modulate further the level of the polypeptide. In correlation with the expression of DJ-1, both cytotoxic agents activate the apoptotic pathway in the prostatic benign cells but not in PC-3 cells, which are resistant to their action. We further demonstrate that incubation of BPH-1 cells with TNF-related-apoptosis-inducing-ligand/Apo-2L (TRAIL) also enhances DJ-1 expression and that TRAIL and H2O2 act additively to stimulate DJ-1 accumulation but synergistically in the activation of the apoptotic pathway. Time-course analysis of DJ-1 stimulation shows that while DJ-1 level increases without significant lag in TRAIL-treated cells, there is a delay in H2O2 -treated cells, and that the increase in DJ-1 abundance precedes the activation of apoptosis. Unexpectedly, over-expression of DJ-1 de-sensitizes BPH-1 cells to the action of apoptotic-inducing agents. However, RNA-interference-mediated silencing of DJ-1 expression results in sensitization of PC-3 cells to TRAIL action. These results are consistent with a model in which DJ-1 is involved in the control of cell death in prostate cell lines. DJ-1 appears to play a differential role between cells expressing a low but inducible level of DJ-1 (e.g., BPH-1 cells) and those expressing a high but constitutive level of the polypeptide (e.g., PC-3 cells). © 2004 Wiley-Liss, Inc. [source]


Tyrosine aminotransferase and gamma-glutamyl transferase activity in human fetal hepatocyte primary cultures under proliferative conditions

CELL BIOCHEMISTRY AND FUNCTION, Issue 2 2004
Khaja K. Rehman
Abstract The ontogeny of gamma-glutamyl transferase (GGTase; E.C.2.3.2.2) and tyrosine aminotransferase (TAT; E.C.2.6.1.5) activities in 14 to 36 weeks gestational and neonatal hepatocytes during development of human fetal liver was studied. Subsequently, 20,24 weeks gestational hepatocytes were cultured in media supplemented with epidermal growth factor (EGF) and insulin with or without glucagon and dexamethasone to investigate the proliferation and differentiation of fetal hepatocyte in vitro using GGTase and TAT as biochemical markers. During the development of the liver, the activity of GGTase increased continuously from the first trimester through the third trimester and decreased (p,<,0.001) in neonates. A low basal level of TAT activity was seen only during the third trimester, which then increased significantly (p,<,0.001) in neonates. Fetal hepatocytes, in the presence of EGF and insulin, undergo proliferation from the fourth to 10th day with an increase in cell number (p,<,0.001) and concomitant increase (p,<,0.001) in GGTase activity. As the cells attain confluence, enzyme activity decreased significantly (p,<,0.001) from the 10th to 16th day. Maximal TAT activity (p,<,0.001) was observed at 48,h of culture, which decreased, but not significantly, during cell proliferation and the enzyme activity was regained as the cultures attained confluence. Furthermore, TAT activity was induced synergistically (p<0.001) in the presence of glucagon and dexamethasone, while GGTase was inhibited (p<0.001). These results indicate that GGTase increases with proliferation, whereas TAT, once it has been expressed, is not suppressed during cell proliferation. In conclusion, human fetal hepatocytes undergo enzymic differentiation by 48,h of culture, and proliferate with an increase in GGTase in the presence of growth factors with maintenance of differentiated status up to the studied 16 days of culture. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Molecular cloning of cytochrome P4501A cDNA of medaka (Oryzias latipes) and messenger ribonucleic acid regulation by environmental pollutants

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2004
Jisung Ryu
Abstract The sequence of cytochrome P4501A (CYP1A) cDNA of medaka (Oryzias latipes) was determined, and its messenger ribonucleic acid (mRNA) regulation by ,-naphthoflavone (,NF) was evaluated. The determined cDNA sequence contained 2,349 base pairs (bp), and the open reading frame contained a total of 1,563 bp encoding 521 predicted amino acids. The induction of CYP1A mRNA in medaka was evaluated using reverse transcription,polymerase chain reaction. The concentration,dependent induction of CYP1A mRNA in the liver was observed after exposure to ,NF at nominal concentrations of 20, 100, and 500 ,g/ L for 2 d. Time-dependent changes of CYP1A mRNA levels were also observed in the liver, gill, gut, and caudal fin tissues of medaka exposed to 100 ,g/L of ,NF for 7 d. Our results showed that the degree of CYP1A mRNA induction in the gill, gut, and caudal fin after exposure to ,NF was relatively higher than that in the liver, possibly because of low basal levels of CYP1A mRNA in the gill, gut, and caudal fin of nonexposed fish. The induction of medaka CYP1A mRNA was also observed after exposure to an environmental sample, landfill leachate. The CYP1A mRNA inductions in the gill, gut, and caudal fin were also higher than that in the liver as shown in the ,NF-treated groups. These results show that CYP1A mRNA determination in the gill, gut, and caudal fin, which are in direct contact with the polluted water, may become a useful method for monitoring CYP1A-inducible chemicals. [source]


Sub-lethal heat shock induces plasma membrane translocation of 70-kDa heat shock protein in viable, but not in apoptotic, U-937 leukaemia cells

APMIS, Issue 3 2010
ELENA B. LASUNSKAIA
Lasunskaia EB, Fridlianskaia I, Arnholdt AV, Kanashiro M, Guzhova I, Margulis B. Sub-lethal heat shock induces plasma membrane translocation of 70-kDa heat shock protein in viable, but not in apoptotic, U-937 leukaemia cells. APMIS 2010; 118: 179,87. Heat shock protein 70 kDa, Hsp70, is an important intracellular factor that protects cells from stress. Unusual plasma membrane expression of Hsp70, observed in some cancer cells, contributes to the cell's recognition and elimination by the immune system. Induction of apoptosis in cancer cells was demonstrated to increase Hsp70 translocation to the surface membrane, enhancing immunogenic effects through the stimulation of dendritic cells. As hyperthermia is proposed as a method of choice for anti-cancer therapy, we examined whether apoptosis induction by heat shock enhances Hsp70 membrane translocation in U-937 leukaemia cells. Cells were exposed to sub-lethal heat shock, and intracellular and membrane-bound Hsp70 expression was evaluated in apoptotic and viable cell sub-populations, employing flow cytometry and immunofluorescence. Heat shock induced Hsp70 membrane translocation in the viable cells that were able to enhance Hsp70 production upon heating, but not in the cells undergoing apoptosis that continued to express low basal levels of the intracellular protein. Data suggest that the protein translocation was associated with the increasing Hsp70 content rather than the apoptotic process. Apoptosis does not contribute to externalization of Hsp70, at least in the cells with low levels of this protein. [source]


Effect of obesity and morbid obesity on the growth hormone (GH) secretion elicited by the combined GHRH + GHRP-6 test

CLINICAL ENDOCRINOLOGY, Issue 6 2006
Fahrettin Kelestimur
Summary Objective, Obesity is characterized by low basal levels of growth hormone (GH) and impeded GH release. However, the main problem arises in the diagnosis of GH deficiency in adults, as all accepted cut-offs in the diagnostic tests of GH reserve are no longer valid in obese subjects. In this work, the role of obesity in the GH response elicited by the GHRH + GHRP-6 test was assessed in a large population of obese and nonobese subjects. Patients, GHRH + GHRP-6-induced GH peaks were evaluated in 542 subjects. One hundred and five were healthy obese, 50 were morbid obese, and 261 were nonobese (both normal weight and overweight). One hundred and seventy-six GH-deficient patients (obese and nonobese) were also studied. Results, A regression analysis of the 366 subjects with normal pituitary function indicated that adiposity had a negative effect on the elicited GH peak (r = ,0·503, P < 0·0001). A receiver operating characteristic (ROC) curve analysis showed that in subjects with a BMI 35, the currently accepted cut-offs of the GHRH + GHRP-6 test (GH peaks 20 µg/l: normal secretion; GH peaks 10 µg/l: GH deficiency), were fully operative. However, in subjects with a BMI > 35, normality was indicated by GH peaks 15 µg/l and GH deficiency by peaks 5 µg/l (1 µg/l = 2·6 mU/l). Conclusions, This study confirms: (a) that the combined provocative test is adequate to separate normal and GH-deficient subjects; (b) the negative effect of obesity on GH secretion; (c) that obesity accounts for 25% of the reduction of GH release; and (d) that present cut-off values are applicable to normal weight, overweight and grade I obesity subjects, whereas in obese subjects with a BMI exceeding 35, all the normative limits of the GHRH-GHRP +6 test must be reduced by 5 µg/l. [source]