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Biomedical subjects

V Enzmann

Publications and source records attributed to V Enzmann.

32 records · Page 2Linked to original sources
PubMed1998

Secretion of cytokines by human choroidal melanoma cells and skin melanoma cell lines in vitro.

The selective secretion of interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 10 (IL-10), basic fibroblast growth factor (b-FGF) and transforming growth factor beta 1 (TGF beta-1) in tissue culture of choroidal melanomas and two established skin melanoma cell lines was investigated with ELISA analysis. Values of choroidal melanoma cells were compared with the melanoma cell lines and human fibroblasts as a physiological control. High secretion of IL-6 was detectable in choroidal melanoma cultures but not in the cell lines. IL-8 secretion was found in all melanoma cultures. However, IL-10 was only secreted by one skin melanoma cell line and in choroidal melanoma cell cultures. B-FGF secretion by choroidal melanomas was higher than by cell lines. No differences were seen in the amounts of TGF beta-1 produced by melanoma cells. Human fibroblasts produce higher amounts of IL-6 and IL-8 but lower of b-FGF in vitro in contrast to the melanoma cells. The secretion of cytokines by choroidal melanoma cells suggests an important role of these soluble factors in the interaction of tumour and healthy tissue.

Choroid Neoplasms↗
PubMed1997

Modification of glutamine synthetase expression by mammalian Müller (glial) cells in retinal organ cultures.

One of the key enzymes in glial-neuronal transmitter recycling is glutamine synthetase (GS). In the retina, GS is exclusively expressed by glial (Müller) cells where it serves to convert neuron-released active transmitter substances (glutamate and GABA) into glutamine. Experiments on avian retinae have shown that GS expression is developmentally regulated by glucocorticoid hormones and, to a lesser extent, by a non-hormonal control mechanism(s). Much less is known about GS regulation in mammalian retinae, although either increases or decreases of GS immunoreactivity have been observed in Müller cells in different forms of retinal pathologies. We studied GS expression in postnatal rabbit retinae both in vivo and explanted as wholemounts in vitro, using immunocytochemistry and Western immunoblotting. GS expression was detectable in vivo from the fourth postnatal day, and increased rapidly within the first weeks of life. Levels were lower in vitro than in vivo by an order of magnitude, and could be significantly stimulated (> 60-110%) in vitro by application of hydrocortisone, conditioned medium from cultured retinal pigment epithelium and glutamate or ammonia, but not GABA. It is concluded that GS expression in mammalian Müller cells is dependent on systemic control by glucocorticoid hormones, as observed in birds, but environmental (activity-dependent) factors may play a more important role in mammals.

Animals↗
PubMed1997

Porcine iris pigment epithelial cells can take up retinal outer segments.

This study investigates the ability of iris epithelial cells (IPE) to ingest rod outer segments (ROS) and compares the amount of phagocytosis of porcine RPE and IPE cells by the use of a pH sensitive fluorescent dye (carboxy SNAFL) at the light microscopic level. The dye allowed investigation of ingestion separately from binding of rod outer segments. In a second set of experiments, after exposing ferritin-labeled ROS to the cultured cells, phagosomes were also counted in electron microscopic sections. Additionally immunocytochemical staining was performed with IPE and RPE cells. Both cell types stained positive with polyclonal NaK-ATPase antibodies against the alpha 1 subunit from rat brain and kidney. The epithelial nature of the cultured cells was determined by monoclonal anti-human-cytokeratin antibodies. Moreover, the ultrastructure of the cells revealed high amounts of phagosomes smaller than 1 micron in diameter present in both RPE and IPE cells. The iron label of the phagosomes was determined by EELS spectra taken from individual phagosomes. Electron and light microscopic quantification shows that cultured IPE cells have 64% of the phagocytic capacity of the RPE with respect to phagosomes larger than 1 micron in diameter.

Animals↗
PubMed1997

Mechanisms of graft rejection in the transplantation of retinal pigment epithelial cells.

PURPOSE: The role of activated retinal pigment epithelium (RPE) cells was investigated in the rejection after subretinal transplantation. METHODS: RPE cells from 7 pigmented rabbits were separated and evaluated regarding their MHC class II expression as the sign of activation. The activation of the RPE cells was augmented with a treatment of 1,000 U/ml interferon gamma (IFN-gamma) for 8 days. These cells were then transplanted into 7 albino rabbits. As control, RPE transplantations without a pretreatment were performed in 7 albino rabbits. Six weeks after the transplantation, the transplanted eyes were enucleated and histology was performed. RESULTS: In culture, without IFN-gamma addition, 11.38 +/- 0.94% of the RPE cells presented MHC class II. After IFN-gamma treatment, this quantity increased to 78.26 +/- 1.46% of the RPE cells. These cells transplanted into the rabbits caused an obvious rejection in the transplantation area which was verified histologically. The control group presented a transplantation area without signs of rejection or inflammation. CONCLUSION: In culture, some of the adult RPE cells are activated. These cells may accelerate the rejection cascade after transplantation. An elimination of activated RPE cells from the transplant should be recommended before transplantation.

Animals↗
PubMed1997

The Müller (glial) cell in normal and diseased retina: a case for single-cell electrophysiology.

In the retina of most vertebrates there exists only one type of macroglia, the Müller cell. Müller cells express voltage-gated ion channels, neurotransmitter receptors and various uptake carrier systems. These properties enable the Müller cells to control the activity of retinal neurons by regulating the extracellular concentration of neuroactive substances such as K+, GABA and glutamate. We show here how electrophysiological recordings from enzymatically dissociated mammalian Müller cells can be used to study these mechanisms. Müller cells from various species have Na(+)-dependent GABA uptake carriers, but only cells from primates have additional GABA receptors that activate Cl- channels. Application of glutamate analogues causes enhanced membrane currents recorded from Müller cells in situ but not from isolated cells. We show that mammalian Müller cells have no ionotropic glutamate receptors but respond to increased K+ release from glutamate-stimulated retinal neurons. This response is involved in extracellular K+ clearance and is mediated by voltage-gated (inwardly rectifying) K+ channels which are abundantly expressed by healthy Müller cells. In various cases of human retinal pathology, currents through these channels are strongly reduced or even extinguished. Another type of voltage-gated ion channels, observed in Müller cells from many mammalian species, are Na+ channels. In Müller cells from diseased human retinae, voltage-dependent Na+ currents were significantly increased in comparison to cells from control donors. Thus, the expression of glial ion channels seems to be controlled by neuronal signals. This interaction may be involved in the pathogenesis of retinal gliosis which inevitably accompanies any degeneration of retinal neurons. In particular, Müller cell proliferation may be triggered by mechanisms requiring the activation of Ca(2+)-dependent K+ channels. Ca(2+)-dependent K+ currents are easily elicitable in Müller cells from degenerating retinae and can be blocked by 1 mM TEA (tetraethylammonium). In purified Müller cell cultures, the application of 1 mM TEA greatly reduces the proliferative activity of the cells. These data clearly show that Müller cells are altered in cases of neuronal degeneration and may be crucially involved in pathogenetic mechanisms of the retina.

Animals↗
PubMed1996

Arginine-vasopressin influences the mitogen-induced development of T and B effector cells.

Using a solid phase enzyme-linked immunospot assay (ELISPOT) for enumerating antibody and interleukin secreting cells it could be demonstrated that arginine-vasopressin (AVP) inhibits the activation process of in vitro cultivated murine spleen lymphocytes. Lipopolysaccharide stimulated B cells could be influenced by high AVP concentrations (10[-5] M), while ConA induced Th1 cells respond also to a lower AVP level (10[-8] M) and such response by the IL-4 secreting Th2 cells may be demonstrated only after the activation with suboptimal doses of Con A. These observations suggest that AVP is not only able to suppress immunological reactions by stimulating proopiomelanocortin processing and secretion of adrenocorticotropic hormone, but also by a direct binding to lymphocytes and, moreover, that the susceptibility in monitoring this signal among the murine lymphocyte subpopulations is different.

Journal Article↗
PubMed1994

An improved MTT assay using the electron-coupling agent menadione.

A modification of the MTT based tetrazolium colorimetric assay is described. Using the electron-coupling agent menadione formazan formation by murine splenocytes and P-815 cells was significantly increased whereas dye reduction by macrophages was hardly influenced. These observations suggest that it should be possible to improve the tetrazolium based cytotoxicity assays of murine macrophages against cells of the syngeneic tumour cell line P-815.

Animals↗
PubMed1994

Immunohistochemical detection of substance P and vasoactive intestinal peptide fibres in the auricular lymph nodes of sensitized guinea pigs and mice.

The presence of substance P (SP) and vasoactive intestinal peptide (VIP) in auricular lymph nodes of normal and sensitized guinea pigs and mice has been investigated using polyclonal antibodies directed against these neurotransmitters and the unlabelled peroxidase-antiperoxidase procedure. Positive immunoreactivity could be observed only in draining lymph nodes of sensitized animals. SP-immunoreactivity was found in mice and guinea pigs but a VIP-positive reaction only in mice. The immunopositive sites were always associated with blood vessels. The present study suggests that the neurotransmitters SP and VIP are involved in mechanisms of sensitization taking place in secondary lymphoid organs.

Animals↗
PubMed1983

[A new plastic-bag transfusion set for dilution of erythrocyte concentrates].

A new transfusion set which contains 100 ml of 0.9% sodium chloride solution to resuspend packed red blood cells is described. The advantages of the system are--the technique is simple and hygienic, it contains an optimal quantity of suspension solution, and there is no danger of air embolus occurring. The rheologic properties of the then diluted red cell concentrates are very good, and allow for a mass transfusion. This new system affords the wider use of packed red blood cells, and it will probably contribute to the abolition of the practically obsolete transfusion of whole blood even for surgical patients.

Blood Transfusion↗
PubMed1982

[Complications of fluorescence angiography of the retina. Symptoms, prophylaxis and therapy].

The pathomecanism of the fluorescein incident is described. The anaphylactic reaction is, in accordance with the "all-or-nothing law", independent of the dose. Antihistamines and corticosteroides should be given prophylactically. Severe reactions require anesthesiological treatment. Fluorescein angiography of the retina should be performed only if an anesthesiologist is available. Fluorescein incidents - anaphylactic or anaphylactoid reactions - are very rare (0.1-1.1%). It is estimated that in every 20 000 procedures only one incident endangering life occurs. Fluorescein angiography of the retina should be performed only when the indication is utterly justified and then only if it will provide a guide for treatment. If prophylactic and therapeutic measures can be taken immediately the risk of fluorescein angiography is acceptable.

Anaphylaxis↗
PubMed1980

[The placing and the correcting of the position of central venous catheters with Seldinger's technique (author's transl)].

The Seldinger technique for placing and correcting the position of central venous catheters with a J-shaped guide wire has proved to be a valuable improvement on the technique available at present. The technique allows us to negotiate otherwise impassable "blocks" in the venous system and to correct problematic malpositioned catheters. The success rate in 135 cases of malpositioning was 81.5%. If in addition one had the help of X-ray scan, the catheters could be corrected in nearly every case. The Seldinger technique is particularly valuable in cases of tumours of the neck and upper mediastinum, in anticoagulant and thrombolytic therapy, in burns and for small children. No complications occurred.

Catheterization↗