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M Nałecz

Publications and source records attributed to M Nałecz.

7 recordsLinked to original sources
PubMed2000

In vivo brain microdialysis as a tool in studies of neuroprotective effects of cyclosporin A in acute excitotoxicity.

The mitochondrial permeability transition (MPT) resulting from calcium-induced opening of cyclosporin A (CsA)-sensitive megachannels, leading to deenergisation of mitochondria and release of pro-apoptotic cytochrome c, has been implicated in the pathomechanism of excitotoxic neurodegeneration. The aim of this work was to test neuroprotective potential of CsA in the model of N-methyl-D-aspartate-(NMDA)-induced excitotoxicity in vivo, and to verify utility of microdialysis of the rabbit hippocampus in vivo for these mechanistic studies. In vitro experiments demonstrated that the early rapid phase of Ca(2+)-induced swelling of isolated brain mitochondria, and of accompanying cytochrome c release, was strongly inhibited by 0.5 microM CsA. In the in vivo experiments 1 mM NMDA was applied for 20 min to the hippocampus in a control, or 5 microM CsA-containing dialysis medium via transhippocampal microdialysis probes, and changes in extracellular Ca2+ concentration and in NO release were monitored. Application of NMDA induced a prolonged decrease in the extracellular concentration of Ca2+, reflecting influx of Ca2+ to stimulated neurones. CsA only slightly enhanced this effect. NMDA induced also release of NO to the dialysis medium. Morphological examination 30 min after NMDA application visualised swelling of dendritic mitochondria and cisternae of endoplasmatic reticulum of pyramidal neurones in the CA1 sector of the hippocampus in the vicinity of microdialysis probes. CsA prevented mitochondrial swelling. After 24 h degeneration of the CA1 pyramidal neurones close to a microdialysis probes was observed, which was partially prevented in CsA-treated rabbits. These results indicate that the mechanism of CsA nuroprotection may be at least in part ascribed to prevention of MPT. Microdialysis of the rabbit hippocampus combined with NMDA excitotoxicity appeared to be useful in mechanistic studies of CsA neuroprotection.

Animals↗
PubMed1985

Development of catalytic platinum-binder electrodes for glucose determination.

Compact catalytic platinum-binder glucose sensors were developed, provided for the artificial beta-cell. These consist of three electrodes: the working electrode, a 0.5 mm diameter glass-sheathed platinum wire, covered with a mixture of platinum black and binder (PMMA, PVC) at the face, the reference electrode and the rejuvenating or counter electrode. Measurements were carried out either by a non-equilibrium method within the anodic range or by determination of the current at the anodically directed peak during the cathodic scan. In the first case a periodical switching between rejuvenating and measuring potential takes place and, in the second case, the whole voltammogram is cycled between +1.2 V and -1.2 V (vs. Ag/AgCl). For measurements in phosphate-buffered saline at 37 degrees C the calibration curves exhibit an approximately linear dependence up to a glucose concentration of 30 mM; the sensitivity amounts to 0.3 microA mM-1 and the response times t90% are between 6 and 10 min. A urea concentration of 2.5 mM causes a decrease of the non-equilibrium current of 11.5%-3.0%, and a mixture of amino acids causes a current rise of 11.4%-2.7% with increasing glucose concentration. During the cathodic scan the amino acids affect the peak current negligibly, and the influence of urea reaches saturation for concentrations higher than 6.7 mM. Preliminary in vivo measurements permit the conclusions that after appropriate pretreatment the catalytic glucose sensors can be used for short-time blood glucose monitoring.

Animals↗
PubMed1978

Bioengineering aspects of the artificial pancreas.

In this paper, results of work aimed at the development of artificial beta-cells are presented. An electrolytically driven pump is considered to be a proper device for insulin injection. The transient characteristics of the simplified version of such a pump make it suitable for application in open-loop devices. Methods for electrical control of the injection rate of this pump for application in closed-loop artificial beta-cells are given. An essential component of a closed-loop artificial beta-cell is a glucose sensor. A modified version of the glucose sensor has been developed and its performance is described. Considerations of some control problems related to the artificial pancreas are briefly discussed.

Animals↗
PubMedDate not supplied

Amperometric glucose sensor: short-term, in vivo test.

The influence of selected physiologic coreactants on current-voltage scans of a (Pt-pvc) Pt electrode (the working electrode of the amperometric glucose sensor) was tested. It was shown that the electrode is sufficiently sensitive to glucose even in a case when a strong interference of tested substances was observed. On the basis of the preliminary in vivo measurements it was concluded that after the proper pretreatment, the amperometric glucose sensor can be used for short-term blood glucose monitoring.

Amino Acids↗