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D Dekegel

Publications and source records attributed to D Dekegel.

At least 19 recordsLinked to original sources
PubMed1993

Molecular characterization of resistance plasmids in epidemiologically unrelated strains of multiresistant Haemophilus influenzae.

Thirty-three epidemiologically unrelated strains of ampicillin-chloramphenicol-resistant isolates of Haemophilus influenzae (22 type b, 11 unencapsulated), isolated over 10 years in Belgium, were compared with 53 ampicillin-resistant chloramphenicol-susceptible isolates (22 type b, 31 unencapsulated). All ampicillin-chloramphenicol-resistant and 76% of ampicillin-resistant chloramphenicol-susceptible strains were resistant to tetracycline, kanamycin, or both. Resistance to these antibiotics was specified by a 37- to 44-MDa conjugative plasmid. The genetic relatedness of these plasmids and of those in multiresistance strains from Spain was investigated. Plasmids specifying ampicillin-chloramphenicol-tetracycline-kanamycin resistance in Belgium or in Spain had highly related restriction fragment patterns. By homoduplex analysis, they had similar molecular organization and contained a structure identical to Tn10-TnCm, a transposon previously identified in chloramphenicol-tetracycline-resistant H. influenzae. Plasmids coding for different resistance phenotypes had less resemblance by restriction endonuclease analysis; however, study of heteroduplex molecules indicated they shared a high proportion of core sequences. These findings support the hypothesis of independent transposition events resulting in resistance plasmids of close molecular organization.

Belgium↗
PubMed1993

Evidence of poxvirus in dusky dolphin (Lagenorhynchus obscurus) and Burmeister's porpoise (Phocoena spinipinnis) from coastal Peru.

In 1990, 74 dusky dolphins (Lagenorhynchus obscurus) and 10 Burmeister's porpoises (Phocoena spinipinnis) were examined for the presence of hyperpigmented marks and pinhole lesions on the skin (tattoo lesions) at the fishing terminal of Pucusana, central Peru. Prevalences of tattoo lesions were 8.1% and 30% in the dolphins and porpoises, respectively. Intracytoplasmic poxviruses were demonstrated by transmission electron microscopy in ultrathin sections of three of eight samples of infected epidermis from both species. The reason for the negative results in others is unclear but may be related to stages of infection with low virus density or even incorrect classification of some lesions as genuine viral tattoos. An irregular arrangement of tubules on the outer viral membrane, similar to those in orthopoxviruses, was visible in negative contrast preparations for P. spinipinnis. This is the first record of poxvirus in porpoises (Phocoenidae) and also the first report for dusky dolphins, and generally for cetaceans of the southern hemisphere.

Animals↗
PubMed1991

The lymphocytosis promoting action of pertussis toxin can be mimicked in vitro. Holotoxin but not the B subunit inhibits invasion of human T lymphoma cells through fibroblast monolayers.

Pertussis toxin is known to elicit lymphocytosis in whooping cough patients and experimental animals, by blocking the extravasation of lymphocytes and stimulating their release from lymphoid organs such as the thymus. The mechanisms responsible for these unique effects of PT are not fully understood. The effect of pertussis toxin (PT) on the invasive behavior of human CCRF-CEM T lymphoma cells has been investigated with the use of a monolayer invasion assay (MIA). We had previously found that invasion of murine T lymphoma cells in this model system was correlated with their ability to extravasate and form metastases after i.v. injection in syngeneic animals. We now show that human CEM cells can also penetrate through a precultured confluent monolayer of murine 10T1/2 fibroblast-like cells within a few hours. In a quantitative MIA run over 24 h, PT at concentrations above 10(-14) M inhibited invasion of the CEM cells. In addition, PT stimulated the release ('evasion') of CEM cells that had invaded under the monolayer before the toxin was added. The A subunit of PT was totally inactive, the B subunit had a small residual effect, and reconstitution of the AB complex partially restored the activity. The invasion-inhibiting activity of two different holotoxin preparations and of the subunits perfectly matched their activity in the Chinese hamster ovary cell clustering assay, which is known to depend on a functional AB complex. We suggest that inhibition of monolayer invasion by PT can be used as an in vitro model system to investigate the cellular and molecular mechanisms underlying the lymphocytosis-promoting action of the toxin. Furthermore, the method is sufficiently sensitive to be used for titration of toxin activity. Our data indicate that the ADP-ribosylating activity of the A subunit is indeed required, and that the promotion of lymphocytosis is not elicited by the binding of the B subunit alone.

Cells, Cultured↗
PubMed1990

Virosomes reconstituted from human immunodeficiency virus proteins and lipids.

Purified Human Immunodeficiency Virus (HIV) was solubilized in octylglucopyranoside. After centrifugation, the supernatant was added to lipid-detergent mixed micelles. Formation of virosomes occurred during overnight dialysis. Centrifugation on a continuous glycerol gradient showed that envelope glycoproteins (gp120 and gp41) and matrix protein p17 but not core protein p25 were associated to virosomes. Proteolytic treatment of virosomes indicates that gp120 is oriented toward the outside as in the virus particles, whereas p17 protein is anchored on both sides of the liposomal membrane. Virosomes are spherical vesicles with approximately the size of the virus as shown by electron microscopy.

Blotting, Western↗
PubMed1989

Identification of virus-like particles in Eimeria stiedae.

When nucleic acid samples purified from sporozoites of Eimeria stiedae were analyzed by agarose gel electrophoresis, an ethidium-stainable band with an apparent electrophoretic mobility of 6.5 kb was consistently observed. The band was readily degradable upon RNAse treatment, and its susceptibility towards ribonuclease A on a decreasing ionic strength was suggestive of double-stranded RNA (dsRNA). Electron microscopy revealed spherical, probably icosahedral, virus-like particles (VLP) with a diameter of 35 nm in sporozoite lysates. The VLP were purified by CsCl buoyant density gradient centrifugation. Upon extraction, these particles yielded dsRNA molecules of a uniform length of 1.63 microns. The presence of the VLP was investigated in different Eimeria strains. All E. stiedae isolates contained the RNA virus, whereas the Eimeria intestinalis and Eimeria magna isolates tested did not. RNA/RNA hybridization experiments where the E. stiedae VLP dsRNA was probed to the genomes of the dsRNA viruses of Trichomonas vaginalis and Giardia intestinalis revealed a strong relatedness of the E. stiedae virus to the G. intestinalis virus, in contrast with the T. vaginalis virus, where no homology could be detected.

Animals↗
PubMed1989

The in vitro invasive behavior of human myelomonocytic cell lines is modulated by HuIFN-gamma and pertussis toxin.

Using an in vitro monolayer invasion assay (MIA), we analyzed the interaction of human myeloid cell lines representing different maturation stages with murine fibroblastic monolayers. After 24 h of coculture, only promonocytic U937 cells invaded the monolayer to an appreciable extent in contrast to less-differentiated KG1a, KG1, and HL-60 cells and more mature THP-1 cells. Human interferon-gamma (HuIFN-gamma) treatment was found to induce maturation in the U937 line and resulted in a considerable reduction of interaction with the monolayer. Thus, the capacity of myeloid cells to interact with a fibroblastic monolayer is restricted to a specific maturation stage. Interaction of U937 cells was also abolished when they were treated with pertussis toxin (PT), an agent known to induce monocytosis in vivo, indicating that the MIA may serve as an in vitro simulation of the extravasation of blood borne cells. Finally, although both HuIFN-gamma and PT are able to block cell spreading in the MIA, no effect could be seen on the capacity of U937 cells to phagocytose.

Humans↗
PubMed1988

Difference in motile behavior between lymphoma variants with different invasive and metastatic capabilities.

The motile behavior of two tumor cell variants of the murine BW 5147 lymphosarcoma line, displaying different metastatic capabilities, was analyzed. When placed on top of a confluent monocellular layer of fibroblastic cells, the nonmetastatic lymphoma cells did not carry out any appreciable translocation or shape modification, whereas the metastatic cells displayed intense pseudopodal activity and performed positional shifts. Both these aspects of cell motility were approached through quantitative assays, demonstrating a highly significant difference between the two variant lines. In addition, the metastatic cells were shown to penetrate underneath the fibroblastic monolayer, whereas the nonmetastatic cells were unable to invade. We suggest that the difference in motile behavior is at the basis of the different invasive potencies of the variants. Since in vitro monolayer invasion assays mimic the extravasation of blood-borne cells, we further speculate that in this particular model system, cell motility is the discriminating property that determines whether disseminated tumor formation will occur after intravenous injection of either cell line.

Animals↗
PubMed1987

Changes in intraocular pressure associated with the administration of propofol.

The effect of propofol on intraocular pressure (IOP) was measured in 25 patients presenting for elective non-ophthalmological surgery when propofol was used for the induction and maintenance of anaesthesia (together with 67% nitrous oxide in oxygen, and vecuronium). Normocapnia was maintained. After induction of anaesthesia, intraocular pressure was significantly lower than the baseline value; during maintenance IOP never exceeded the preinduction value. There was a temporary decrease in arterial pressure after induction. In nine patients a cutaneous flush was observed and in seven patients there was discomfort on injection. Spontaneous movement in 20% and hiccup in 12% of the patients were observed at the time of tracheal intubation.

Adult↗
PubMed1987

Development of a monolayer invasion assay for the discrimination and isolation of metastatic lymphoma cells.

A new in vitro invasion model system, based on monolayers of 10T1/2 fibroblastic mouse embryo cells, is presented. When inoculated onto such a confluent monolayer, cells from a nonmetastatic T-cell lymphoma line remained on top, whereas cells from metastatic derivative lines penetrated through the monolayer. Combined differential interference contrast and interference reflection microscopy were used to follow the relative vertical cell positions in the co-cultures. The number of underlying lymphoma cells per unit area can be used as a quantitative invasion index, allowing a systematic comparison between cell lines. Moreover, since the invasive cells could be recovered separately, this invasion system allowed the isolation of minor subpopulation of invasive cells from a 1000-fold excess of noninvasive cells.

Animals↗
PubMed1985

Selecting, accelerating and suppressing interactions between macrophages and tumor cells.

Studies were carried out to test whether thioglycollate-induced macrophages (T-PM phi) exert a selective effect on 3LL tumor cells. One million 3LL tumor cells and 10 X 10(6) thioglycollate-elicited peritoneal macrophages were admixed and inoculated subcutaneously in C57BL/6 mice. This procedure was repeated for a series of 6-15 consecutive transplant generations. After 6 generations, the tumor cells which were selected in this manner (3LLR6) grew faster in vivo and in vitro when admixed with T-PM phi than 3LL cells which were not selected by T-PM phi. However, in vivo, this T-PM phi-mediated acceleration of 3LLR6 tumor growth was followed by tumor rejection and induction of anti-3LL immunity. Intravenous inoculation of T-PM phi enhanced the growth of pulmonary metastases in mice subsequently inoculated intravenously with 3LL cells. Such T-PM phi-mediated augmentation of metastases was not observed with 3LLR6 cells. Homing of 3LL and 3LLR6 cells to the lungs after pretreatment with T-PM phi was similar, indicating that these cells did not differ in their capacity to colonize the lungs but rather in subsequent tumor growth. Additional transplantations of 3LLR6 cells with T-PM phi led, after 9 further transplant generations, to a different tumor cell, 3LLR15, with completely new morphological, tumorigenic and metastatic properties. Unlike the 3LLR6 cells, this variant was not sensitive to the growth promoting effects of T-PM phi. Furthermore, it expressed the H-2K-and H-2D-encoded antigens of the H-2b haplotype, whereas the 3LL and 3LLR6 cells expressed only the H-2D alloantigens. This indicates that macrophages may either exert a selective effect on tumor cells or play a role in the induction of new tumor cells.

Animals↗
PubMed1984

Nonmetastatic tumor cells acquire metastatic properties following somatic hybridization with normal cells.

Somatic cell hybridization between nonmetastatic tumor cells and normal cells of the lymphoreticular system results in hybrid cells manifesting metastatic properties of defined target organ specificity. Thus, fusion of the nonmetastatic BALB/c originated NSI plasmacytoma with C57BL B lymphocytes resulted in hybridomas, each of which were metastatic. Of 10 hybridomas, 7 generated metastases in the spleen and liver, whereas 3 generated liver metastases. The generation of liver metastases by hybridomas which homed to both spleen and liver, but not by those which homed to the liver only, was controlled by the spleen. The acquisition of metastatic properties via somatic cell fusion seems to represent a general principle, in which the normal partner determines the target organ specificity for the metastatic growth. Thus, fusion of SP2/O myeloma cells with syngeneic B lymphocytes also resulted in a hybrid cell metastasizing to the spleen and liver, yet a somatic hybrid between NSI and a macrophage or dendritic-like cell metastasized to the lung. Cell surface molecules encoded by the genome of the normal partner was demonstrated to control the target organ specificity: antibodies against MHC-encoded antigens of the normal B cell partner prevented the generation of metastases by hybridomas metastasizing to the spleen and liver, but not by those metastasizing to the liver only. This is in accordance with the function of MHC molecules on lymphocytes in controlling their homing to lymphoid organs. Hybridomas of T cell lymphomas also manifested metastatic properties. Analysis of the cell surface Thy-1 antigens of a hybridoma (DCH10), produced via somatic fusion between BW5145 lymphoma and a putative macrophage cell indicated that cells of liver metastases (DCH10-Li) generated by the hybrid cells might have undergone further somatic cell fusion in vivo with host (T?) cells. These cells have acquired new metastatic properties, generating metastases in spleen, liver and kidneys. In fact, even the inoculation of the parental BW lymphoma cells resulted in a case of liver metastasis (BW-Li). Such BW-Li cells, upon reinoculation, also generated metastases in the spleen, liver and kidneys. Analysis of the Thyl phenotype indicated that BW-Li cells may also have undergone somatic cell fusion in vivo with host (T?) cells, resulting in the acquisition of metastatic properties. The pattern of cell-cell interactions (adhesion, infiltration) with liver cell monolayers of BW-Li cells and of DCH10-Li (T-cell lymphomas) was identical, and differed from cells of liver metastases of the myeloma-B cell hybridomas which might be based on responses to liver growth signals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Isolation of orthoreoviruses from psittacine birds.

Orthoreoviridae were regularly isolated from imported psittacine birds in the absence of other pathogens or in combination with salmonella. These viruses grew in embryonated eggs, in chicken embryo fibroblasts and in hepatic cell cultures. The viral isolates were classified as orthoreoviridae on the basis of their morphological and physico-chemical properties.

Animals↗
PubMed1983

Neutralization of poliovirus by antibody-mediated polymerization.

The neutralization of type 1 poliovirus by a monoclonal antibody was studied. The antibody caused polymerization of the virions as observed by sucrose gradient centrifugation and electron microscopy. Dimers, trimers, and higher polymers were formed. No antibody was found in association with the monomeric virions remaining after neutralization, which retained full infectivity. The specific infectivities of dimers, trimers, and higher polymers decreased in that order.

Antibodies, Monoclonal↗
PubMed1980

[The alveolar macrophage and its anti-infectious function (author's transl)].

The alveolar macrophage belongs to the "Mononuclear Phagocytic System". The medullary promonocyte is its stem-cell. It has a kidneyshaped nucleus, a developed vesicular Golgi apparatus, numerous mitochondriae, lysosomes, phagosomes, and a rough or smooth ergastoplasm. It can survive several weeks in vitro, when cultivated on a porous membrane in contact with a nutrient medium and incubated in a gaseous phase (5 per cent carbon dioxide in water saturated air). Mitotic activity is questionable. Oxygen consumption is high during endocytosis. Metabolic energy is derived from direct oxidative glucose breakdown. Its anti-infectious property is based on phagocytosis as well as on cytoplasmic germicidal or lytic systems (hydrogen peroxide, catalase, free oxygen radicals, hydrogen ion, lysozyme and other lysosomial hydrolases). This function is stimulated by T lymphocyte and by endocytosis of digestible material. In vitro, the alveolar macrophage is capable of inhibiting intra-cellular development of Candida albicans, Klebsiella pneumoniae, Listeria monocytogenes, Staphlylococcus albus and Staphylococcus aureus.

Animals↗