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Biomedical subjects

E Papadimitriou

Publications and source records attributed to E Papadimitriou.

28 records · Page 2Linked to original sources
PubMed1997

Cholera toxin stimulates human B-cell DR antigen biosynthesis at the level of translation.

Cholera toxin (CT) exerts many diverse regulatory effects on cells of the immune system and is considered a potent adjuvant on gut mucosal immune responses to orally presented antigens. It has been previously described that CT induces surface DR expression in human resting B-cells. As a further step toward understanding this phenomenon, the molecular mechanisms underlying the regulation of DR expression were investigated. By the use of Western analysis, it is shown that CT increases the total levels of DR protein in highly purified human tonsillar cells. [35S]Methionine incorporation studies show that the aforementioned increase is due to de novo biosynthesis of DR protein at as early as 6 hr after CT stimulation and is completed by 24 hr. [3H]Uridine uptake experiments, nuclear transcription runoff assays, and Northern analysis show that CT does not exert its effect at a transcriptional level, indicating translational regulation. Anti-IgM, which mimics B-cell antigen binding, behaves in a manner similar to CT. The B subunit of CT (B-CT) and prostaglandin E2, either alone or in combination, do not induce DR protein biosynthesis nor do they exert any effect on the transcription of DR beta 1 gene. These results show that cAMP elevation as well as binding of B-CT to GM-1 ganglioside, by themselves, do not lead to DR protein biosynthesis suggesting that other activation pathways may be involved.

Antibodies, Anti-Idiotypic↗
PubMed1997

Thrombin modulates vectorial secretion of extracellular matrix proteins in cultured endothelial cells.

We have identified a novel cellular action of thrombin on cultured rat adrenal medullary endothelial cells (RAMEC). Five-minute incubation of RAMEC with physiological concentrations of thrombin (<1 U/ml) caused within 3 h an increase in the basolateral deposition of the extracellular matrix (ECM) proteins fibronectin, laminin, and collagens IV and I, concomitant with a corresponding decrease in the apical release of these proteins into the medium. This shift in vectorial secretion of ECM proteins, quantitated with enzyme-linked immunoassays, was time dependent. Maximal stimulation of ECM protein deposition was observed after incubation of cells with thrombin for 5-15 min. Prolonged exposure (>1 h) to thrombin resulted in loss of proteins from the ECM. Thrombin-stimulated ECM protein deposition exhibited a bell-shaped dose dependence, peaking for all proteins at 0.25 U/ml of thrombin, and was independent of de novo mRNA or protein synthesis. Maximal amounts of deposited proteins increased between 2.5-fold (fibronectin) and 4-fold (collagen I) over baseline values. Similar results were obtained with thrombin receptor agonist peptide (TRAP), proteolytically active gamma-thrombin, and, to a lesser extent, other serine proteases such as trypsin and plasmin. A scrambled TRAP, proteolytically inactive PPACK-thrombin, DIP-thrombin, and type IV collagenase were ineffective. Together, these results suggest that the thrombin effects are mediated by proteolytic activation of the thrombin receptor. Possible involvement of the phospholipase C-signaling pathway in thrombin-mediated ECM protein deposition was also investigated. Inhibition or downregulation of protein kinase C (PKC) and chelation of intracellular or extracellular Ca2+ did not suppress, but rather enhanced, basal and thrombin-stimulated ECM protein deposition. Quantitative differences in augmentation of basolateral deposition by these treatments suggest differential regulatory pathways for individual ECM proteins. Our data indicate that, in cultured RAMEC, short-term activation of the thrombin receptor causes an increase in amounts of deposited ECM protein by a cellular signaling pathway that is independent of PKC activation and/or elevation of intracellular Ca2+.

Adrenal Medulla↗
PubMed1996

Myoglobinuria due to quail poisoning.

Quail poisoning is known to produce an acute myoglobinuric syndrome. The cause of this syndrome is still unknown. It has been suggested that a toxic effect or a genetic sensitivity plays a major role. Ten patients with a history of quail poisoning were examined to determine their present state and the course of the disease. A muscle biopsy was performed in 2 of these patients who complained of muscle cramps after exercise. The activities of several glycolytic mitochondrial and lipolytic enzymes were estimated. In all 10 patients the physical examination, electromyogram findings and conduction velocities were normal. Serum levels of CK, aldolase and lactic acid were also within normal range. In the 2 patients with cramps, all enzyme activities were normal in muscle tissue. Our findings possibly exclude a preexisting enzyme defect as a cause of myoglobinuria in quail poisoning. Considering that 4 of our patients continued the consumption of quails without further problems, we suggest that the major factor contributing to quail poisoning must be toxic.

Adolescent↗
PubMed1993

Measurement of cell numbers in microtiter culture plates using the fluorescent dye Hoechst 33258.

A sensitive fluorimetric assay based on DNA binding of the fluorescent dye Hoechst 33258 was developed to quantitate cell numbers in microtiter plates. The cells were fixed and incubated with the dye solution. The bound dye was extracted with ethanol and fluorescence was measured in a spectrofluorimeter. The method is sensitive for as little as a thousand cells and is particularly useful for the normalization of enzyme-linked immunoassay (ELISA) data obtained from the same cells. Another major advantage of this new technique is that in contrast to previously described methods, it requires commonly available, inexpensive equipment.

Adrenal Medulla↗
PubMed1990

McArdle's disease: two clinical expressions in the same pedigree.

Two patients with McArdle's disease within the same pedigree and with two different clinical forms are presented. The first patient suffered from progressive muscle weakness and atrophy. Muscle morphology was that of myopathy. Residual activity of phosphorylase was 28% and sodium dodecyl sulphate electrophoresis showed decreased protein. The second case was typical of McArdle's disease, clinically and biochemically. It was concluded that the first patient was a heterozygote (residual activity 28% of normal) and the second was a homozygote, the genetic transmission being autosomal recessive.

Adult↗
PubMedDate not supplied

X-rays affect the expression of genes involved in angiogenesis.

BACKGROUND: We have previously shown, using the chicken embryo chorioallantoic membrane (CAM) model of in vivo angiogenesis, that X-rays act on the extracellular matrix and enhance normal and tumor-induced angiogenesis. In the present work, we studied the effect of X-rays on the gene expression of three proteins that are important regulators of angiogenesis: vascular endothelial growth factor (VEGF), heparin affin regulatory peptide (HARP) and inducible nitric oxide synthase (iNOS). MATERIALS AND METHODS: An area of 1 cm2 of the CAM, restricted by a plastic ring was irradiated at room temperature. The expression of the genes was studied using RT-PCR and the amounts of the mRNAs were quantified using image analysis of the corresponding agarose gels of the RT-PCR products. RESULTS: VEGF mRNA was decreased 6 h after irradiation. However, at later time points, VEGF expression was significantly increased compared with the nonirradiated tissue. Similarly, X-rays down-regulated both HARP and iNOS expression 6 h after irradiation and the effect was reversed at later time points, similarly to the effect of X-rays on VEGF. CONCLUSION: These data support the notion that X-rays increase the expression of genes that favor angiogenesis.

Animals↗
PubMedDate not supplied

Effect of heparin affin regulatory peptide on the expression of vascular endothelial growth factor receptors in endothelial cells.

BACKGROUND: Heparin affin regulatory peptide (HARP) is an 18-kDa secreted protein that has been implicated in tumor growth and angiogenesis, although the mechanisms involved remain largely unknown. In the present work, the effect of human recombinant HARP on the expression of the vascular endothelial growth factor (VEGF) receptors KDR, Flt-1 and neuropilin-1 was studied in cultured human umbilical vein endothelial cells (HUVEC). MATERIALS AND METHODS: The mRNA and protein levels of VEGF receptors were estimated by semi-quantitative RT-PCR and Western blot, respectively. Cell proliferation and migration were measured by MTT, direct counting of the cells and modified Boyden chamber assays. RESULTS: HARP decreased the expression of KDR but increased the expression of Flt-1 and neuropilin-1 at both the mRNA and protein level. The effect reached a maximum 4 h after the addition of HARP into the cell culture medium and was reversed at later time-points. When HARP was added to the culture medium 4 h before the addition of VEGF165, it inhibited VEGF165-induced proliferation and migration of HUVEC. CONCLUSION: These data suggest that HARP affects the expression of VEGF receptors and inhibits VEGF165-induced activation of HUVEC.

Carrier Proteins↗
PubMedDate not supplied

[Organization of a central supply system for nursing units].

The provision of supplies for a hospital, wards and nursing units, must be undertaken carefully. The financial side as well as the suitability and the quality of the equipment must be taken into consideration for an effective patient nursing care. A central supply system for a hospital is considered as a more economical and effective one. By this way nursing staff relieved from no nursing duties, thus they can devote more time to direct patient care in the unit.

Central Supply, Hospital↗