Biomedical subjects

J Endert

Publications and source records attributed to J Endert.

7 recordsLinked to original sources

PubMed2004

Both lamin A and lamin C mutations cause lamina instability as well as loss of internal nuclear lamin organization.

We have applied the fluorescence loss of intensity after photobleaching (FLIP) technique to study the molecular dynamics and organization of nuclear lamin proteins in cell lines stably transfected with green fluorescent protein (GFP)-tagged A-type lamin cDNA. Normal lamin A and C proteins show abundant decoration of the inner layer of the nuclear membrane, the nuclear lamina, and a generally diffuse localization in the nuclear interior. Bleaching studies revealed that, while the GFP-tagged lamins in the lamina were virtually immobile, the intranuclear fraction of these molecules was partially mobile. Intranuclear lamin C was significantly more mobile than intranuclear lamina A. In search of a structural cause for the variety of inherited diseases caused by A-type lamin mutations, we have studied the molecular organization of GFP-tagged lamin A and lamin C mutants R453W and R386K, found in Emery-Dreifuss muscular dystrophy (EDMD), and lamin A and lamin C mutant R482W, found in patients with Dunnigan-type familial partial lipodystrophy (FPLD). In all mutants, a prominent increase in lamin mobility was observed, indicating loss of structural stability of lamin polymers, both at the perinuclear lamina and in the intranuclear lamin organization. While the lamin rod domain mutant showed overall increased mobility, the tail domain mutants showed mainly intranuclear destabilization, possibly as a result of loss of interaction with chromatin. Decreased stability of lamin mutant polymers was confirmed by flow cytometric analyses and immunoblotting of nuclear extracts. Our findings suggest a loss of function of A-type lamin mutant proteins in the organization of intranuclear chromatin and predict the loss of gene regulatory function in laminopathies.

Animals↗

PubMed1991

The effect of virus infection on the adherence of leukocytes or platelets to endothelial cells.

It has been reported that atherosclerotic lesions contain genomic material belonging to members of the herpes family. This suggests that latent viral infection may be one of the atherogenic triggers. In this study we show that early infection of endothelial cell monolayers with Herpes Simplex virus type 1 (HSV-1) or Cytomegalovirus (CMV) results in an increased monocyte (MC) and polymorphonuclear leukocyte (PMN) adherence, but not in an increased platelet adhesion. Further, is demonstrated that MC and PMN respond differently to virus infected endothelial cell monolayers: PMN adhesion to CMV infected cells is approximately 430% of the control adherence, while the MC adherence is increased to 160%. Also, a difference in virus acting is observed: the adherence of MC or PMN to HSV-1 infected endothelial cells is caused by a secreted adherence promoting factor, while the adherence of MC or PMN to CMV infected endothelial cells seems to be a cell-bound phenomenon. In addition, it was demonstrated that the augmentation of MC or PMN adherence to virus infected endothelial cells is sensitive to tunicamycin, suggesting that both virus infections induce the expression of glycoproteins on the endothelial cell membrane, which is responsible for the MC and PMN adhesion. Thus, HSV-1 and CMV infection of endothelium results in an increased adherence of leukocytes which is suggested, irrespective of the precise nature of the mechanism of virus induced atherosclerosis, to be the earliest event associated with endothelium cell damage.

Arteriosclerosis↗

PubMed1989

Virus induced adherence of monocytes to endothelial cells.

In this study we have demonstrated that infection of human umbilical vein endothelial cells (HUVEC) with Herpes simplex virus type 1 (HSV-1) resulted in an increased adherence of monocytes (MC). This enhanced adherence occurred at 3 h post infection (p.i.) when about 20% of the monolayer is infected and when there is no cytopathic effect observable in the monolayer. The adherence of human MC to virus-infected HUVEC monolayers proved to be effective and reproducible if a multiplicity of infection (MOI) of ten and a ratio of number of MC to number of HUVEC of 5 was used. The increased adherence was also induced by incubating non-infected HUVEC with the 'supernatant medium' of the HSV-1 infected cells, showing that soluble factors induced by viral infection are responsible for the increased adherence. The augmentation of MC adherence to infected endothelium was sensitive to tunicamycin treatment, suggesting that the MC adherence is probably mediated by glycoproteins expressed on the HUVEC membranes by virus infection.

Cell Adhesion↗

PubMed1987

Influence of intracellular Ca2+-overload in eicosanoid synthesis of the myocardium.

Intracellular Ca2+-overload in the myocardium can be induced not only after readmission of Ca2+-containing fluid to rat hearts previously perfused with a Ca2+-free buffer, a phenomenon called "the calcium paradox", but also during administration of a Ca2+-ionophore to cardiac tissue. In rat hearts, the myocardial damage induced by the Ca2+ paradox was more pronounced than that after administration of the Ca2+-ionophore A23187, as indicated by the amount of lactate dehydrogenase released. The accumulation of NEFA, and especially arachidonic acid, was greater during the Ca2+ paradox than after the administration of the Ca2+-ionophore. Administration of the Ca2+-ionophore resulted in a considerable release of 6-keto-F1 alpha (the stable breakdown product of prostacylclin), and LTD4 and LTE4 (breakdown products of LTC4). In contrast, the formation of eicosanoids was absent during the Ca2+ paradox. It is concluded that the relation between Ca2+-overload and accumulation of arachidonic acid is ambiguous and that there is no close relation between the amount of arachidonic acid accumulated and the formation of eicosanoids in Ca2+-overloaded tissue. The absence of eicosanoid formation during the Ca2+ paradox might be explained by compartmentation of the arachidonic acid accumulation and its converting enzymes or impairment of the enzymatic machinery required for eicosanoid synthesis.

Animals↗

PubMed1987

Treatment of experimental cytomegalovirus infections with acyclovir.

Subcutaneous (s.c.) administration of Acyclovir (ACV) (100 mg/1 kg bodyweight) resulted in an ACV blood level of 80 microM at 2 h post infection. Thereafter the level declined rapidly reaching undetectable levels at 12 h post infection. Administration of pro-ACV (100 mg/kg body weight) by s.c. or intravenous (i.v.) route resulted in ACV levels of 75 microM and 160 microM respectively after 30 min. But here again the blood level of ACV declined rapidly and was completely disappeared after 12 h. Continuous administration of pro-ACV in daily doses of 100, 250 and 350 mg/kg body weight resulted in ACV blood levels of 15 microM, 19 microM and 39 microM, respectively. The effect of ACV and pro-ACV on the replication of CMV was measured in immunesuppressed rats. In rats inoculated with RCMV the daily administration of 25 to 50 mg ACV per kg body weight by s.c. injections twice daily, did not result in a reduction of virus titers in spleen and liver, but when the RCMV-infected rats were treated by 100 mg pro-ACV per kg body weight virus titers in the spleen and liver were significantly reduced as compared with those in sham-treated animals.

Acyclovir↗

PubMed1985

A quantitative method for assessing the third complement factor (C3) attached to the surface of opsonized Pseudomonas aeruginosa: interrelationship between C3 fixation, phagocytosis and complement consumption.

A direct enzyme-linked immunoassay is described for the determination of C3 that becomes attached to the surface of bacteria upon incubation in serum. The assay uses horseradish peroxidase-conjugated rabbit antiserum specific for human C3. In this study various Pseudomonas aeruginosa strains, Escherichia coli and Staphylococcus aureus were opsonized under different conditions and the amount of C3 fixed to the bacterial surface was measured directly. The extent of C3 fixation was compared with the percentage of phagocytosis by human polymorphonuclear leukocytes and with the complement consumption in the fluid phase. It was demonstrated that C3 fixation closely correlated with the percentage of phagocytosis but not with complement consumption. The method can be performed with relatively simple equipment and could be used in routine laboratories in order to determine the extent of opsonization of Pseudomonas aeruginosa and other bacteria and to detect opsonic defects in the sera of patients.

Complement Activation↗

PubMed1985

Role of lipopolysaccharide in opsonization and phagocytosis of Pseudomonas aeruginosa.

When the opsonization of various Pseudomonas aeruginosa strains--PAC 1, its O-chain-deficient mutant PAC 605, and an intermediate strain, P14--was measured either directly by determination of the amount of C3b attached to the bacterial surface or indirectly by assessing phagocytosis by human polymorphonuclear leukocytes and the responses of chemiluminescence, it was demonstrated that PAC 1 was opsonized and phagocytized to a lower extent than P14 and PAC 605. In contrast to PAC 605, PAC 1 showed an increased consumption of complement in the fluid phase and a rapid release of lipopolysaccharide antibodies bound to the bacterial surface due to the alternative pathway of the complement system. Furthermore, it was shown that with respect to PAC 1 and PAC 605, the lack of an O-chain resulted in increased sensitivity to serum and decreased virulence. From both in vivo and in vitro experiments, we concluded that the structure of the O-antigen polysaccharide chain of lipopolysaccharide is an important virulence factor of P. aeruginosa against the defense mechanisms of the host.

Complement Activation↗