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  • 1
    Electronic Resource
    Electronic Resource
    Atomic force microscopy of peritoneal macrophages after particle phagocytosis (1994)
    Springer
    The journal of membrane biology 140 (1994), S. 197-204 
    Details
    ISSN: 1432-1424
    Keywords: Atomic force microscope (AFM) ; Peritoneal macrophages ; Particle phagocytosis ; Force vs. distance curves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The atomic force microscope was used to image peritoneal macrophages after phagocytosis of latex beads with 0.45 μm in diameter and of zymosan particles. The rigidity of the phagocytosed material allowed to image the live membrane at forces below 2 nn. Repeated scanning of the membrane unavoidably caused the protrusion of the beads and increased their virtual height. The influence of fixation by glutaraldehyde on the image and the corresponding force vs. distance curves were analyzed and compared. Short treatment with Triton X-100 enabled us to identify intracellular components, such as embedded latex beads, cell nucleus and cytoskeletal strands. The data demonstrate that it is possible to image living cells if they are bolstered by stiff material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233708
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  • 2
    Electronic Resource
    Electronic Resource
    Thiamine triphosphate activates an anion channel of large unit conductance in neuroblastoma cells (1993)
    Springer
    The journal of membrane biology 136 (1993), S. 281-288 
    Details
    ISSN: 1432-1424
    Keywords: Thiamine triphosphate ; Anion channel ; Oxythiamine ; Neuroblastoma ; Patch clamp ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In neuroblastoma cells, the intracellular thiamine triphosphate (TTP) concentration was found to be about 0.5 μ m, which is several times above the amount of cultured neurons or glial cells. In inside-out patches, addition of TTP (1 or 10) μ m to the bath activated an anion channel of large unit conductance (350–400 pS) in symmetrical 150 mm NaCl solution. The activation occurred after a delay of about 4 min and was not reversed when TTP was washed out. A possible explanation is that the channel has been irreversibly phosphorylated by TTP. The channel open probability (P o) shows a bell-shaped behavior as a function of pipette potential (V p). P o is maximal for −25 mV〈V p〈10 mV and steeply decreases outside this potential range. From reversal potentials, permeability ratios of PCl/ PNa = 20 and PCl/Pgluconate = 3 were estimated. ATP (5 mm) at the cytoplasmic side of the channel decreased the mean single channel conductance by about 50%, but thiamine derivatives did not affect unit conductance; 4,4′ -diisothiocyanostilbene-2,2′-disulfonic acid (0.1 mm) increased the flickering of the channel between the open and closed state, finally leading to its closure. Addition of oxythiamine (1 mm), a thiamine antimetabolite, to the pipette filling solution potentiates the time-dependent inactivation of the channel at V p=−20 mV but had the opposite effect at +30 mV. This finding corresponds to a shift of P o towards more negative resting membrane potentials. These observations agree with our previous results showing a modulation of chloride permeability by thiamine derivatives in membrane vesicles from rat brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233667
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of gap junctional coupling in isolated pancreatic acinar cell pairs by cholecystokinin-octapeptide, vasoactive intestinal peptide (VIP) and a VIP-antagonist (1994)
    Springer
    The journal of membrane biology 139 (1994), S. 127-136 
    Details
    ISSN: 1432-1424
    Keywords: Gap junctions ; Double whole cell ; Cholecystokinin-octapeptide ; Vasoactive intestinal peptide (VIP) ; VIP antagonist ; Pancreatic acinar cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Cholecystokinin-octapeptide (CCK-OP) induces a time- and dose-dependent decrease of gap Junctional conductance in isolated pairs of pancreatic acinar cells. In double whole-cell experiments, the time course could be described by the latency and the half-life time (t 1/2 ) of cell-to-cell uncoupling. The latency shows a biphasic dependence on [CCK-OP] with a minimum of about 50 sec at 10−9 m CCK-OP. In the presence of vasoactive intestinal peptide (VIP), the biphasic relationship is shifted to lower CCK-OP concentrations. The increase of latency at high concentrations of CCK-OP (〉 1009 m) was blocked by addition of a VIP-antagonist. t 1/2 decreases monophasically with increasing [CCKOP]. Addition of GTPγS to the pipette solution suppresses the [CCK-OP] dependence of the latency and potentiates the uncoupling phase. The kinetic data are discussed in terms of CCK binding to receptors of high and low affinity. Evidence is presented that secretion and cell-to-cell coupling are not related by an all-ornone process, but that for physiological CCK-OP concentrations, gap junctional uncoupling follows secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232431
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  • 4
    Electronic Resource
    Electronic Resource
    Follow-up of cyclosporin A treatment in Type 1 (insulin-dependent) diabetes mellitus: lack of long-term effects (1991)
    Springer
    Diabetologia 34 (1991), S. 429-434 
    Details
    ISSN: 1432-0428
    Keywords: Cyclosporin A ; Type 1 (insulin-dependent) diabetes mellitus ; immunotherapy ; C-peptide ; islet function ; remission of Type 1 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the Canadian/European randomized controlled study on cyclosporin A (CsA) in recent onset Type 1 (insulin-dependent) diabetes, treatment with the immunosuppressive drug had increased and maintained Beta-cell function and clinical remission during the first 12 months. Following discontinuation of the study drug and double-blinding after a mean of 13.8 months former CsA patients doubled the daily insulin dose within 6 months reaching the level of former placebo patients. The difference in Beta-cell function between the two groups was also lost. Metabolic control (HbA1c) was transiently worse in the former CsA group. Adverse effects of cyclosporin A on systolic blood pressure, haemoglobin levels, serum potassium and creatinine levels also remitted during that time. We conclude that treatment with cyclosporin A for a mean of 13.8 months had no long-lasting effect on the course of Type 1 diabetes persisting beyond drug discontinuation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403182
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  • 5
    Electronic Resource
    Electronic Resource
    Cytotoxicity of activated rat macrophages against syngeneic islet cells is arginine-dependent, correlates with citrulline and nitrite concentrations and is identical to lysis by the nitric oxide donor nitroprusside (1993)
    Springer
    Diabetologia 36 (1993), S. 17-24 
    Details
    ISSN: 1432-0428
    Keywords: Activated macrophages ; nitric oxide ; nitroprusside ; cytotoxic activity ; islet cells ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lysis of rat islet cells by syngeneic activated macrophages in vitro can be completely inhibited by the nitric oxide-synthase-inhibitor NG-methyl-l-arginine. This inhibition can be reversed by an excess of l-arginine. Time-dependent lysis of islet cells by activated macrophages is accompanied by increasing concentrations of nitrite and citrulline in the culture medium both of which are measures of nitric oxide formation derived from l-arginine. Lysis of isolated islet cells and disintegration of isolated whole islets is also obtained within 15 h by culture in the presence of the nitric oxide generating vasodilator sodium nitroprusside. We thus conclude that nitric oxide is extremely toxic for islet cells and that nitric oxide alone and in the absence of other macrophage-generated potentially toxic products can rapidly and completely kill islet cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399088
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  • 6
    Electronic Resource
    Electronic Resource
    Inflammatory islet damage in patients bearing HLA-DR 3 and/or DR 4 haplotypes does not lead to islet autoimmunity (1994)
    Springer
    Diabetologia 37 (1994), S. 471-475 
    Details
    ISSN: 1432-0428
    Keywords: Key words IDDM, chronic pancreatitis, islet cell antibodies, autoimmunity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The hypothesis was tested that islet autoimmunity is induced by ongoing islet cell destruction in subjects with susceptibility genes HLA-DR 3 and/or DR 4. Sixty-one patients with confirmed chronic pancreatitis were analysed, 30 of whom expressed HLA-DR 3 and/or DR 4. Electron microscopy studies in 10 patients showed that the inflammatory process also affected islets, as recognisable from islet cell lysis, intrainsular fibrosis and immune cell infiltrates. None of the sera tested contained any of three markers of islet autoimmunity, ICA, IAA or GAD antibodies. A correlation was seen between the loss of exocrine function, as determined by the ALTAB-test, and of beta-cell function, as determined by the C-peptide response to i. v. glucagon. However, there was no preferential loss of beta-cell function in patients with HLA-DR 3 and/or DR 4. We conclude that islet cell destruction occurs during chronic pancreatitis, but does not trigger islet autoimmunity, even in the presence of HLA-DR 3 and/or DR 4. [Diabetologia (1994) 37: 471–475]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050134
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  • 7
    Electronic Resource
    Electronic Resource
    Increasing incidence of IDDM a consequence of improved hygiene? (1994)
    Springer
    Diabetologia 37 (1994), S. 729-729 
    Details
    ISSN: 1432-0428
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417700
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  • 8
    Electronic Resource
    Electronic Resource
    Macrophage cytotoxicity towards isolated rat islet cells: neither lysis nor its protection by nicotinamide are Beta-cell specific (1991)
    Springer
    Diabetologia 34 (1991), S. 232-238 
    Details
    ISSN: 1432-0428
    Keywords: Islet cell lysis ; macrophage cytotoxicity ; nicotinamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In animal models of Type 1 (insulin-dependent) diabetes mellitus macrophages were shown to be the first immunocytes that infiltrate the pancreatic Langerhans islets in the autoimmune process. We now show direct macrophage cytotoxicity against isolated rat islet cells in an electron microscopical study, which permits investigation of the specificity of this process. Freshly isolated islet cells were co-incubated with syngeneic peritoneal macrophages at a target∶effector-cell ratio of 1∶2. After various time periods, the cells were directly fixed and embedded; the ratio of live and dead cells was evaluated by electron microscopy. Our results demonstrate that activated but not resident macrophages lyse islet cells in a time-dependent manner. After 15 h of co-incubation lysis of islet cells is complete. No islet cell-macrophage contacts and no differences between the lysis of Beta cells or non-Beta cells were observed during the observation period. Islet cells encapsulated in alginate were also lysed by macrophages as a direct proof for soluble mediator(s) of cytotoxicity. Nicotinamide protected islet cells from lysis in a dosedependent manner. As a result of this electron microscopic study we conclude that even at very low target∶effector ratios, activated macrophages lyse syngeneic islet cells regardless of islet cell type via secretion of humoral mediator(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00405081
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  • 9
    Electronic Resource
    Electronic Resource
    Tumour necrosis factor alpha production is upregulated in diabetes prone BB rats (1990)
    Springer
    Diabetologia 33 (1990), S. 573-575 
    Details
    ISSN: 1432-0428
    Keywords: BB rat ; autoimmunity ; tumour necrosis factor alpha ; macrophages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following activation peritoneal macrophages from diabetes prone BB rats secreted strikingly higher amounts of tumour necrosis factor alpha than found for macrophages from diabetes resistant or normal Wistar rats. Enhanced tumour necrosis factor alpha production was detected prior to the occurrence of insulitis. Cultures of macrophages derived from precursor cells in diabetes prone BB rat bone marrow also showed upregulated tumour necrosis factor alpha secretion upon challenge with endotoxin and interferon gamma. Tumour necrosis factor alpha hypersecretion may contribute to autoimmune diabetes by affecting thymic and post-thymic T-cell maturation and by promoting pancreatic islet inflammation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404147
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  • 10
    Electronic Resource
    Electronic Resource
    Oxygen radicals generated by the enzyme xanthine oxidase lyse rat pancreatic islet cells in vitro (1992)
    Springer
    Diabetologia 35 (1992), S. 1028-1034 
    Details
    ISSN: 1432-0428
    Keywords: Autoimmune diabetes mellitus ; oxygen radicals ; xanthine oxidase ; islet cell lysis ; nicotinamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The endothelium-associated enzyme xanthine oxidase is known to generate reactive oxygen intermediates which may damage the surrounding tissue. We investigated whether reactive oxygen intermediates released by xanthine oxidase exert a toxic effect on isolated rat islet cells. The xanthine oxidase (25 mU/ml)/hypoxanthine (0.5 mmol/1) system released reactive oxygen intermediates in vitro as detected by luminol in a chemiluminescence analysing system. The addition of nicotinamide inhibited the release of reactive oxygen intermediates in a dose-dependent manner (50 % inhibition at 20 mmol/1). Exposure of islet cells to enzyme generated reactive oxygen intermediates caused lysis of 39% of the cells within 15 h. Monitoring the mitochondrial function of islet cells by the conversion of tetrazolium bromide to its formazan product revealed a significant reduction of the respiratory activity down to 51 % of that of the controls by 30 min after the initiation of the xanthine oxidase reaction. Mitochondrial dysfunction preceded plasma membrane damage. The addition of nicotinamide, a radical scavenger and inhibitor of the DNA repair enzyme poly(ADP-ribose) synthetase protected the islet cells from lysis and partially preserved their mitochondrial activity in the presence of reactive oxygen intermediates. We conclude that activation of the endothelial enzyme xanthine oxidase, known to be induced by mediators of immune cells or by episodes of ischaemia and reperfusion causes islet cell damage with subsequent cell death in early phases of pancreatic islet cell destruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221677
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