Dimitrolos Krajčí

An electron microscopy study of keratin degradation by the fungus Microsporum gypseum in vitro.

Summary: The authors examined by means of transmission electron microscopy the keratin degradation in human hair invaded by the dermatophyte Microsporum gypseum in vitro. Initial growth of the fungus in hair was intercellular; later on, the hyphae were found mostly inside the cells. The digestion showed all features of an enzymatic breakdown. Mechanical action of penetrating mycelia on surrounding cells could be observed in the cuticle only. The sequence of degradation of the individual hair components corresponded to their degrees of keratinization viz. to the cystine content. In the cuticle, the structures first invaded were the nonkeratinous cell membrane complex and the endocuticle containing cytoplasmic remnants. The exocuticle and especially its A‐layer were more resistant. A similar resistant layer was found below the inner membrane of cuticular cells. In the cortex, the cell membrane complex and cytoplasmic residues inside the cells were again digested first. Macrofibril bundles were disintegrated from the surface as well as from the centre. Marked increase of overall osmiophilia was typical of the places of the most intensive degradation. The fungus digested both structural components of the “hard” keratin‐microfibrils (filaments) and matrix. However, in the final phases of keratinolysis the remnants of the matrix retained their form a little longer.

Ki-1-positive anaplastic large cell lymphoma initially diagnosed as Hodgkin's disease by fine needle aspiration (FNA) cytology.

A 45‐year‐old male presented with a large mass in the left axilla. FNA cytology was interpreted as Hodgkins disease (HD), lymphocyte depletion (LD) type, but histopathologic and immunohistochemical examination showed features of Ki‐1‐positive anaplastic large cell lymphoma. Unrepresentative sampling by the FNA from the tumour periphery resulted in a false impression of dual reactive and neoplastic cell populations. which together with the frequent Reed‐Sternberg‐like cells led to the initial erroneous impression of HD. Therefore, the cytologic diagnosis of HD, LD should be approached with caution.

NMDA preconditioning and neuroprotection in vivo: Delayed onset of kainic acid-induced neurodegeneration and c-Fos attenuation in CA3a neurons

Intraventricular (i.c.v.) kainic acid (KA) causes an acute excitotoxic lesion to the CA3 region of rodent hippocampus. Recent evidence implicated c-fos gene in regulating neuron survival and death following an excitotoxic insult. In this study we attempted to prevent KA-induced damage in CA3 neurons with NMDA preconditioning, which produced a marked expression of c-fos in the hippocampus. NMDA (0.6-6 microg, i.c.v.) was injected to anesthetized rats alone or 1 h before KA (0.15 microg, i.c.v.). Following KA injection, vibratome sections were processed for immunohistochemistry/electron microscopy. c-Fos and Nissl staining were used to estimate the extent of neuronal excitation and damage, respectively. Quantitative evaluation of c-Fos-labeled cells showed significantly less c-Fos in CA3a than in neighboring CA3b and CA2 from 1 to 4 h after KA alone. Attenuation of expressed c-Fos in CA3a was accompanied by damage of neurons with more apoptotic than necrotic signs. NMDA preconditioning elevated CA3a c-Fos expression and at 1 and 2 h exceeded markedly that after KA alone. However, at 4 h after KA, NMDA-preconditioned c-Fos induction in CA3a diminished to the same level as that seen after KA alone. The onset of neuronal degeneration was delayed in similar way. While NMDA-induced c-Fos expression in CA3a could be blocked by MK-801 completely, MK-801 and CNQX were both without significant effect on KA-induced c-Fos expression and neuronal damage. In conclusion, inhibition of c-Fos expression and onset of neuronal damage in CA3a following icv KA injection might be transiently delayed by i.c.v. NMDA preconditioning.

Neurogenic control of the ovine gallbladder: ultrastructural and functional study.

The purpose of this study was to investigate the ultrastructure of the local nerve supply of ovine gallbladders as well as the functional characteristics of inhibitory nerves. We used electron microscopy of thin sections of ovine gallbladders and in vitro isometric tension recording using gallbladder strips. Specifically, we measured contractile and inhibitory responses induced by transmural electrical field stimulation (EFS). We found a ganglionated plexus with intramural nerve cells and interconnecting axons. Clear and large dense-core vesicles colocalized in axons close to smooth muscle cells. EFS elicited gallbladder contractions which were converted to relaxation after atropine. EFS-induced relaxation was reduced by the nitric oxide (NO) synthase inhibitor, L-NOARG and blocked by propranolol and/or tetrodotoxin. In conclusion, enteric ganglia and neurones with synaptic vesicles (clear and dense core) were detected close to smooth muscle bundles. Neural inhibition of gallbladder contraction was mediated by β-adrenoceptors coupled to NO generation.

Application and evaluation of teaching practical histology with the use of virtual microscopy

Virtual slides provide many benefits over observation of classical glass histology slides. We have developed an electronic teaching system of histology practical in a networked classroom of 30 student’s computers and one teachers. The teachers PC (personal computer) runs our own database of histology practical designed in MS Excel format that contains virtual slides organized into thematic sessions. The virtual slides are complemented with supporting documents and other explanatory visuals. A PC-based testing of identification of structures in histology slides has also been introduced.

Modulation of Porphyrin Derivatives Accumulation in C6 Glioma Cells by Drugs Acting on β-Adrenergic Receptors. A Spectrofluorometric Study

The pharmacological modulation of the uptake of porphyrin derivatives in cultured C6 glioma cells was investigated by means of spectrofluorometric analysis both in single cells and in cell homogenates. The influence of drugs acting as β‐receptor agonists or antagonists was studied in cells grown to semiconfluency. Isoproterenol (ISO), a β‐receptor agonist, enhanced the intracellular fluorescence intensity of both Photofrin and protoporphyrin IX (PpIX). A treatment with a β‐receptor antagonist I‐propranolol (PRO), simultaneous with ISO, resulted in an intracellular Photofrin fluorescence signal comparable to that of the control cells, indicating the specificity of the pharmacological action. The pharmacological treatment seemed particularly effective with the aggregated species. This is suggested by the relative increase of the band at 670 nm, being greater than that in the 630 nm band in the emission spectra of Photofrin and PpIX, and by the comparison of the fluorescence intensity on cell homogenates measured both in the absence and in the presence of cetyltrimethyl‐ammonium bromide as a detergent.