Biomedical subjects

E Spanakis

Publications and source records attributed to E Spanakis.

23 records · Page 2Linked to original sources

PubMed1990

Triethyllead-induced inhibition of proliferation of normal human lymphocytes through decreased expression of the Tac chain of interleukin 2 receptor.

Triethyllead (Et3Pb+) in concentrations 10(-5) to 10(-6) M has been shown to inhibit several key cellular molecular systems. In order to evaluate the effect of Et3Pb+ on the human immune system, the mitogen-induced cell proliferation of peripheral blood mononuclear cells was studied in the presence of Et3Pb+. Preincubation of normal T-lymphocytes with 10(-6) M Et3Pb+ for 1-4 h, which has been shown to be non-cytotoxic, was sufficient to inhibit subsequent mitogenic-induced cell growth. The Et3Pb(+)-induced impairement of the in vitro proliferation of mitogen-activated normal T-cells was due to a dose-dependent decreased expression of the p55 polypeptide chain (Tac molecule) of the interleukin-2 receptor (IL-2-R), which could not be enhanced by exogeneously added recombinant interleukin 2 (rIL-2). Conversely, the same concentrations of Et3Pb+ could not inhibit the mitogen-induced expression of MHC class II molecules and the transferin receptor on activated T-cells. The impaired membrane expression of p55 on T-cells induced by Et3Pb+ was due to a decrease of Tac mRNA transcripts as showed by Northern blot analysis. This effect seems to be specific since in parallel experiments Et3Pb+ could not inhibit both the accumulation of actin mRNA and the production of IL-2 by Et3Pb(+)-treated mitogen-activated cells. The effect of this organolead compound was also associated with a dose-dependent decrease of the Na(+)-K(+)-ATPase activity of normal lymphocytes. These results indicate that Et3Pb+ could affect specifically T-cell proliferative responses through an imbalance of the IL-2/IL-2-R system.

Blotting, Northern↗

PubMed1990

[Osprovit: hydroxylapatite ceramic for the reconstruction of blow-out fractures of the orbital floor].

Common polymeric implantations, in use for the orbital floor reconstruction, form usually a surrounding fissural space and thus tend to dislocations. With the conservative methods that have been available up to now, the Dura Mater cannot be definitely sterilised so that a transmission of a virus may be possible, which causes the Creutzfeld-Jacob Encephalopathy. As an appropriate alternative-both for primary and secondary reconstruction of the orbital floor-an implantation of dense hydroxylapatite ceramics (Osprovit), anatomically shaped, is indicated. According to x-ray techniques of evaluation it presents itself without artifacts. It does not dislocate because it coalesces physiologically with the surrounding tissues and because of its biocompatibility, it is undoubtedly suitable as a permanent implantation. Post-operative examinations of 20 patients showed neither enophthalmus nor diplopia. All patients were without subjective symptoms.

Adult↗

PubMed1990

[Conservative therapy of mandibular fractures in children with operatively secured splints].

In the treatment of mandibular fractures in children offering no adequate possibility for attaching splints to the teeth, we use prosthetic splints fixed with four circumferential wires. This monomaxillary fixation is sufficient to stabilize fractures of the mandibular anterior segment. Fractures situated distal to the canines require additional intermaxillary fixation, i.e. zygomaticomaxillary suspension of the mandible. When functional therapy is needed at the same time, we use an activator instead of the prosthetic splint. 59 patients treated in this way were reevaluated within a period of 10 years. The results of this reevaluation are reported.

Child↗

PubMed1990

Intracytoplasmic detection of the Tac (p55) chain of interleukin-2 receptor in pre-B leukemic cells associated with a constitutive expression of Tac mRNA.

The pre-B Reh-6 leukemic cells do not express membrane interleukin-2 (IL-2)-R alpha (Tac or p55) chain; however, their incubation with PMA induces the expression of both high and low affinity IL-2-R. Northern analysis of nonstimulated Reh-6 as well as leukemic cells from patients with acute B cell precursor lymphoblastic leukemia displayed a constitutive expression of p55 mRNA transcripts, which could be enhanced by PMA. Both actinomycin-D and cycloheximide could abrogate PMA-induced p55 membrane expression, suggesting the need for de novo mRNA and protein synthesis. The increased PMA-induced p55 mRNA accumulation was an early event (4 hr) and could be enhanced, specifically, by rIL-2 because anti-Tac moAb inhibited this rIL-2-mediated effect. Immunofluorescence and cross-linking studies using 125I-rIL-2 failed to reveal membrane-associated p55 protein on both Reh-6 and patients' leukemic cells. Conversely, immunogold staining and electron microscopy studies, revealed p55 immunoreactive molecules in the cytoplasm but not in the nucleus of all Reh-6 cells. Using a sensitive EIA, p55 molecules could be detected in cell lysates but not the culture supernatants of Reh-6 cells, suggesting that p55 was not released into the culture medium. These results indicate that constitutively expressed p55 mRNA on pre-B leukemic cells is translated into a relative immunoreactive protein that cannot be expressed on cell surface for unknown, yet, reasons.

Blotting, Northern↗

PubMed1987

Co-adaptation of Escherichia coli and coliphage lambda vir in continuous culture.

Populations of the bacterium Escherichia coli and of its phage lambda vir appeared to equilibrate in continuous cultures. The bacterial end-populations were heterogeneous in respect of their resistance to lambda vir and their ability to utilize maltose. The most competitive of the selected bacteria were mutants which had a reduced rate of synthesis of lambda-receptor so as to become highly, but not totally, resistant to the phage. The coexisting phage had an increased affinity for the receptor and an altered antigenic specificity, suggesting adaptation of its adsorption site in response to the evolution of resistance in the bacteria.

Adaptation, Physiological↗