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Biomedical subjects

J Pokorný

Publications and source records attributed to J Pokorný.

At least 19 recordsLinked to original sources
PubMed2007

Morphological changes in the hippocampus following nicotine and kainic acid administration.

Using histochemical analysis (NADPH-diaphorase, Fluoro-Jade B dye and bis-benzimide 33,342 Hoechst) we studied the influence of intraperitoneal administration of nicotine (NIC), kainic acid (KA) and combination of both these substances on hippocampal neurons and their changes. In experiments, 35-day-old male rats of the Wistar strain were used. Animals were pretreated with 1 mg/kg of nicotine 30 min prior to the kainic acid application (10 mg/kg). After two days, the animals were transcardially perfused with 4 % paraformaldehyde under deep thiopental anesthesia. Cryostat sections were stained to identify NADPH-diaphorase positive neurons that were then quantified in the CA1 and CA3 areas of the hippocampus, in the dorsal and ventral blades of the dentate gyrus and in the hilus of the dentate gyrus. Fluoro-Jade B positive cells were examined in the same areas in order to elucidate a possible neurodegeneration. In animals exposed only to nicotine the number of NADPH-diaphorase positive neurons in the CA3 area of the hippocampus and in the hilus of the dentate gyrus was higher than in controls. In contrast, KA administration lowered the number of NADPH-diaphorase positive cells in all studied hippocampal areas and in both blades of the dentate gyrus. Massive cell degeneration was observed in CA1 and CA3 areas of the hippocampus and in the hilus of the dentate gyrus after kainic acid administration. Animals exposed to kainic acid and pretreated with nicotine exhibited degeneration to a lesser extent and the number of NADPH-diaphorase positive cells was higher compared to rats, which were exposed to kainic acid only.

Animals↗
PubMed2006

Early rehabilitation model shows positive effects on neural degeneration and recovery from neuromotor deficits following traumatic brain injury.

This study used an experimental early rehabilitation model combining an enriched environment, multisensory (visual, acoustic and olfactory) stimulation and motor training after traumatic brain injury (via fluid-percussion model) to simulate early multisensory rehabilitation. This therapy will be used by brain injured patients to improve neural plasticity and to restore brain integration functions. Motor dysfunction was evaluated using a composite neuroscore test. Direct structural effects of traumatic brain injury were examined using Fluoro-Jade staining, which allows identification of degenerating neural cell bodies and processes. Animals in the rehabilitation model group performed significantly better when tested for neuromotor function than the animals in standard housing in the 7-day and 15-day interval after injury (7d: p=0.005; 15d: p<0.05). Statistical analysis revealed significantly lower numbers of Fluoro-Jade positive cells (degenerating neurons) in the rehabilitation model group (n=5: mean 13.4) compared to the standard housing group (n=6: mean 123.8) (p<0.005). It appears that the housing of animals in the rehabilitation model led to a clear functional increase in neuromotor functions and to reduced neural loss compared with the animal group in standard housing.

Animals↗
PubMed2006

Alcohol abuse in mothers during gravidity and breastfeeding brings changes of hippocampal neurons in their offspring.

Neurotoxic effect of ethanol on the CNS of laboratory rats in the prenatal and postnatal period was studied. Another aim of the experiment was to analyse structure of the hippocampus after the prenatal and postnatal exposure to alcohol and to identify the most vulnerable hippocampal regions. Pregnant Wistar rats of our own breed received 20% alcohol p.o. ad libitum every day since the conception to the 18th day of postnatal life of their offspring. Since the birth (the day 1) till the age of 18 days offspring were kept together with their mother and were exposed to postnatal alcohol effect (alcohol in the breast milk). At the age of 18 days animals were perfused under deep thiopental anaesthesia with buffered solution of paraformaldehyde. Serial sections were stained with Fluoro-Jade B and DNA specific dye bis-benzimide (Hoechst No 33258). Brains of young rats aged 18 days were analysed under the light microscope Olympus Provis AX-70 with epifluorescence. In CA1 and CA3 areas and in Gyrus dentatus of the hippocampus, groups of degenerating cells were observed. In all offspring some cells with fine granulated karyons were identified, which were accompanied with high numbers of glial cells. Our results demonstrate the neurotoxic effects of alcohol and the high vulnerability of the developing CNS. The identification of cells with segmented karyons indicates the role of apoptotic mechanism in the cell death.

Animals↗
PubMed2006

Effect of magnesium pre-treatment on the hippocampal NOS activity during long-lasting intermittent hypoxia.

Influence of magnesium pre-treatment during repetitive hypoxia was studied in the hippocampus of rats by histochemical analysis (NADPH-diaphorase staining). NADPH-diaphorase occurs concurrently with NO-synthase that is responsible for NO synthesis. Rat pups were kept together with their mother for 8 hours a day in a hypobaric chamber at a simulated altitude of 7,000 m since the day of birth till the 17th day. The first group of animals was exposed to the repeated hypoxia; the second group under the same conditions was pre-treated by magnesium before the exposition to the hypoxia. Both groups were compared with intact control animals and intact animals treated with magnesium. The experimental and control animals were the transaortically perfused with 4% buffered neutral formaldehyde under thiopental anaesthesia at the age of 35 days. Brains were processed for NADPH-d staining. We estimated the density of NADPH-d positive neurons in CA1 and CA3 areas of the hippocampus and in the dentate gyrus. Intermittent hypoxia brings about higher numbers of NADPH-diaphorase positive neurons of CA1 and CA3 of the hippocampus and of the dorsal blade of dentate gyrus, in the comparison with either group of control animals. In the hilus and ventral blade of the dentate gyrus, on the contrary, the number of NADPH-d positive neurons was smaller. Magnesium pre-treatment during hypoxia decreased number of nitrergic neurons in all areas of the hippocampus except CA1 area, where the effect of magnesium was not significant. These results demonstrate that magnesium can probably have a neuroprotective effect.

Animals↗
PubMed2006

Changes in the number of nitrergic neurons in rats hippocampus following nicotine administration.

Nicotine is a very widely used drug of abuse, which exerts a number of neurovegetative behavioural effects by interacting with the neuronal nicotinic acetylcholine receptor. Using histochemical analysis (NADPH-diaphorase and Fluoro-Jade B dye), the influence of intraperitoneal administration of nicotine on neurons of the hippocampus in 35-day-old male rats of the Wistar strain was studied. At the age of 37 days, the animals were transcardially perfused with 4% paraformaldehyde under deep thiopental anaesthesia. Cryostat sections were stained to identify NADPH-diaphorase positive neurons that were then quantified in CA1 and CA3 areas of the hippocampus, in the dorsal and ventral blade of the dentate gyrus and in the hilus of the dentate gyrus. In the same areas, using Fluoro-Jade B dye, signs of neurodegeneration were classified, using Fluoro-Jade B dye. Nicotine administration increased the number of NADPH-diaphorase positive neurons in the CA3 area of the hippocampus and in the hilus of the dentate gyrus with no effect in the remaining areas studied. Fluoro-Jade staining did not reveal any degenerating neurons in the hippocampus as an effect of nicotine administration.

Animals↗
PubMed2005

Effect of the perinatal alcohol abuse on the development of neuronal population in the hippocampus.

The study deals with neurotoxic effects of alcohol on the CNS of laboratory rats in the prenatal period. The aim of the experiment is to analyse structure of the hippocampus after the prenatal exposure to alcohol and to identify the most vulnerable hippocampal regions. Pregnant Wistar rats of our own breed received alcohol (2 g per 100 g of body i.p.) each day since the first to the last day of pregnancy. Since the birth till the age of 34 days offsprings were kept together with their mother and were not exposed to alcohol. At the age of 35 days animals were perfused under the deep thiopental anaesthesia with buffered solution of paraformaldehyde. In the CA1 area of the hippocampus groups of degenerating cells were observed. In the CA3 area degenerating cells were also found. Some cells with fine granulated karyons were identified, which were accompanied with high number of glial cells. Our results demonstrate the neurotoxic effects of alcohol and the high vulnerability of the developing CNS. Remarkable is the observation of the high number of dying cells 35 days after the last exposition to alcohol. It suggests a long-term process of neuronal circuit remodelling in the juvenile tissue, probably triggered by apoptosis. The identification of cells with fine granulated karyons indicates the role of apoptotic mechanism in the cell death.

Animals↗
PubMed2005

Repeated kainic acid administration and hippocampal neuronal degeneration.

Many animal models have been established to study the mechanisms leading to excitotoxicity. One of the more commonly used models is kainic acid (KA) induced excitotoxicity. Upon administration of KA in rodents, KA produces acute status epilepticus and neuronal damage. The aim of the study was to examine the morphologic alteration in the hippocampus of mature rats, after repeated KA administration. The first group was given KA repeatedly in six doses (10 mg/1000 g), each second day. The second group was given KA i.p. repeatedly in six smaller doses (5 mg/1000 g), each second day. The third group (control animals) received corresponding volumes of the normal saline (5 or 10 mg/1000 g respectively). Animals were transcardially perfused; serial sections were stained with Fluoro-Jade B and DNA-specific dye bis-benzimide (Hoechst). In CA1 region of the first group many degenerating cells were observed. The CA2 region was not as much affected as CA1. In the CA3 region no degenerating cells were observed. In the second group the most prominent was the cell loss both in the CA3 region and in the hilus of the dentate gyrus.

Animals↗
PubMed2005

[Purkinje's concept of a neuron].

With his experiments and findings J. Ev. Purkyne influenced 34 scientific disciplines; in some of them he is assumed to be their founder (embryophysiology, histology, pharmacological physiology, biophysics, comparative physiology). He was the pioneer in the field of neuroscience not only due to his neuroanatomical descriptions but namely due to his neurophysiological experiments. Beside the description of "Purkyne cells" and cells of other regions of the brain, Purkyne studied also the structure of neuronal processes and it is possible to attribute him the first description of dendrites. Existing material shows that Purkyne studied also the structure of hippocampus. Those and other papers prove that Purkyne recognised possible functional differences between various types of neurons and he speculated about their mutual relations. Only contemporary particularly detailed knowledge on the structure of hippocampal neuronal circuits, description of the mediator interaction and modulation together with the identification of neuroplastic processes in the hippocampus enable to accomplish the Purkyne's attempt to correlate the structure and function.

Czechoslovakia↗
PubMed2004

Excitation of vibrations in microtubules in living cells.

Microtubules, which are thought to be the primary organizers of the cytoskeleton, are electrical polar structures with extraordinary elastic deformability at low stress and with energy supply from hydrolysis of guanosine triphosphate (GTP) to guanosine diphosphate (GDP). At least a part of the energy supplied from hydrolysis can excite vibrations. Energy is mainly lost by viscous damping of the surrounding cytosol. Viscous damping is diminished by a slip layer which is formed by an attracted ionic charge layer and by a thin surface layer of the microtubule. Relaxation time caused by viscous damping may be several orders of magnitude greater than period of vibrations at 10 MHz. Energy supplied to the microtubule is of the order of magnitude of 10(-14) W cm(-1) (per unit length of the microtubule).

Animals↗
PubMed2004

The relation between emergency and burn medicine.

Emergency Medicine (EM) has evolved since 1950s--in the Czech Republic as well as abroad--from Anaesthesiology and Resuscitation in parallel with the Burn Medicine which has separated from Plastic Surgery. EM creates a link between the laymen first aid and the specialized hospital care, which is realized by the Emergency Medical Service (EMS). The EMS interventions for serious burn patients comprise the early professional prehospital medical care: establishing free airway and breathing, establishing intravenous/intraosseous access into the blood circulation, early shock therapy, early pharmacotherapy and analgesia, aseptic covering of damaged body surface, releasing escharotomies of circumferential burns of the chest and neck and optimal transport of patients into burn centres.

Burns↗
PubMed2004

Effects of intracarotid injection of methylprednisolone on cellular oedema after osmotic opening of the blood-brain barrier in rats.

In our work we studied methylprednisolone (MP) for its effects on the permeability of cytoplasmatic membranes of neuronal populations in the rat. We used a standard model of cellular oedema induced by water intoxication, applying MP selectively into the internal carotid (ICA) after opening the blood-brain-barrier (BBB) with mannitol. The results were assessed under fluorescence microscopy in keeping with the Intracellular Distribution Index of Evans Blue (IDI) in the neocortical field (Cortex) and in hippocampal areas CA1, CA3 and GD. Evans blue (EB) was applied similarly as MP Three different experiments were carried out. In experiment 1--EB alone and no MP was applied. In experiment 2--5.4 mg/kg MP and EB were applied. In experiment 3--54 mg/kg MP and EB were applied. In experiment 1 the IDI values were high (>1), indicating the presence of large quantities of EB in the cells. In experiments 2 and 3 the IDI values were low (<1), indicating more EB outside than inside cells. IDI differences between experiments 2 and 1 and experiments 3 and 1 were statistically significant (p<0.05). This morphological evidence sufficiently proved the possibility to restore the cell membrane integrity by means of MP administration.

Animals↗
PubMed2004

Plasticity of the brain in neuroontogenesis.

Plasticity is a specific endowment of the nervous system to develop, to react or to adjust to the internal and external 'environmental changes, both in the physiological and pathological conditions. Cumulative evidence has revealed the dynamism of the nervous system, based on the balance between the rigidity and plasticity. Different aspects of neuroplasticity can employ common general cellular mechanism. Effects of plasticity can be either positive or negative changes during the development (evolutional plasticity), after the short-term exposition (reactive plasticity), after the long-term or permanent stimuli (adaptational plasticity), and during functional or structural recovery of the damaged neuronal circuits (reparation plasticity). Manifestations of plasticity have probably the same basis, irrespective of a cause, which triggered them, or the brain region where they were accomplished. Activity of neuroplastic processes appears to be especially high in the immature nervous tissue.

Animals↗
PubMed2003

Morphology and ultrastructure of rat hippocampal formation after i.c.v. administration of N-acetyl-L-aspartyl-L-glutamate.

N-Acetyl-L-aspartyl-L-glutamate (NAAG) is one of the most abundant neuroactive compounds in the mammalian CNS. Our recent observations have suggested that NAAG administered into rat cerebral ventricles can cause neuronal death by apparently excitotoxic mechanisms that can be antagonized by the N-methyl-D-aspartate-receptor blockers and by ligands of metabotropic glutamate receptor of Group II. Therefore, the principal aim of the present study has been to use quantitative morphology, electron microscopy and terminal deoxynucleotidyl transferase-mediated biotin dUTP nick-end labeling to study a dose- and time-dependence as well as regional distribution of neurodegeneration in hippocampi of rats after the intraventricular infusion of 0.25 micromol NAAG/ventricle and of equimolar doses of L-glutamate (L-GLU) and N-acetyl-L-aspartate (NAA), breakdown products of NAAG. The degenerative changes were observed after the infusion of 0.25 and 1.25 micromol of NAAG/ventricle, but not when a dose of 0.05 micromol of NAAG/ventricle was injected into each lateral cerebral ventricle. With a dose of 0.25 micromol of NAAG/ventricle the number of degenerated neurons reached a maximum on the fourth day after the infusion. The neuronal damage following bilateral administration of 0.25 micromol of NAAG/lateral cerebral ventricle exhibited features of a delayed neuronal degeneration, expressed mainly in the layer of dentate granule neurons. The degeneration was characterized on the basis of ultrastructural appearance and DNA-fragmentation. The morphological changes caused by L-glutamate and NAA were much smaller than those observed after the administration of NAAG and displayed a different pattern of regional distribution. The present findings suggest that NAAG can cause a loss of hippocampal neurons in vivo, apparently resulting from the neurotoxicity of NAAG itself.

Animals↗
PubMed2003

Influence of laminar flow on preorientation of coal tar pitch structural units: Raman microspectroscopic study.

In order to estimate the role of laminar flow of viscous, aromatic matter of carbonaceous precursor on microtextural preorientation in pregraphitization stage, we performed experiments with coal tar pitch (CTP). The principal hypothesis of preorientation of basic structural units (BSUs) in the case of laminar flow (pressure impregnation of CTP into porous matrix) and secondary release of volatiles during carbonization were studied. Glass microplates, planar porous medium with average distance between single microplates 5 microm were used as suitable porous matrix. Samples of CTP were carbonized up to 2500 degrees C. Optical microscopy reveals large flow domains in the sample of cokes carbonized between glass microplates. Raman microspectroscopy and high resolution transmission electron microscopy (HRTEM) show that at nanometric scale, the samples do not support the proposed hypotheses. With increasing temperature of pyrolysis, the graphitization of CTP impregnated into porous matrix proceeds to lower degree of structural ordering in comparison with single pyrolyzed CTP. This is explained by the release of volatile matter during carbonization in geometrically restricted spaces. More evident structural changes were discovered with the sample of single coke, where parts of fine grain mosaics, relicts of 'so called QI parts', reveal higher structural organization, in comparison with large and prolonged flow domains, similar to flow domains of cokes from microplates.

Coal Tar↗
PubMed2003

Expression of serotonin receptors in mouse oocytes and preimplantation embryos.

Serotonin receptors have been found in several reproductive organs as well as in the central nervous system. Serotonin-binding sites have been demonstrated in duck ovarian follicles and the testis, hamster ovaries, human granulosa cells and mouse placenta. Local production of serotonin by the rat ovary, oviduct, uterus and testis has also been reported. We analyzed the expression of three types of serotonin receptors: 5-HT1B, 5-HT2C and 5-HT1D by reverse transcription-polymerase chain reaction in mouse unfertilized oocytes and preimplantation embryos from zygotes to the blastocyst stage in vivo. Transcripts for 5-HT1B and 5-HT2C serotonin receptors were detected neither in unfertilized oocytes nor at any stages of in vivo developing preimplantation embryos. Serotonin 5-HT1D receptor mRNA was present in unfertilized oocytes, zygotes, 2-cell embryos, compacted morulae and in vivo produced expanded blatocysts. The expression of the mRNA 5-HT1D serotonin receptor was also detected in blastocysts cultured in vitro. When added to the culture medium, specific serotonin 5-HT1D agonist sumatriptan (1 microM) significantly inhibited the development of mouse embryos cultured in vitro. Demonstration of the expression of 5-HT1D serotonin receptor in mouse oocytes and preimplantation embryos supports the idea of a functional serotonin (5-HT1D) receptor in early mammalian development.

Animals↗
PubMed2003

Altered blood-brain barrier permeability and its effect on the distribution of Evans blue and sodium fluorescein in the rat brain applied by intracarotid injection.

The aim was to study the blood-brain permeability according to the distribution in the rat brain of Evans blue (EB) and sodium fluorescein (NaFl) administered by an intracarotid injection. Eighteen animals were divided into six groups according to the state of the blood-brain barrier (BBB) at the moment when the dyes were being applied. In the first two groups, the BBB was intact, in groups 3 and 4 the barrier had been opened osmotically prior to the application of the dyes, and in groups 5 and 6 a cellular edema was induced by hyperhydration before administration of the dyes. The intracellular and extracellular distribution of the dyes was studied by fluorescence microscopy. The histological picture thus represented the morphological correlate of the way BBB permeability had been changed before the application of the dyes.

Animals↗
PubMed2003

Evans blue distribution in the rate brain after intracarotid injection with the blood-brain barrier intact and open to osmosis.

Evans blue was applied to 12 rats by way of intracarotid injection into the common carotid artery or internal carotid artery both with the blood-brain barrier intact and after its mannitol-induced osmotic opening. For each type of application, a histological picture of Evans blue propagation through the brain was obtained by means of fluorescence microscopy. An assessment was made of the overall intensity of staining, and the ratio was established of the intra:extra-cellular Evans blue distribution in the cortex and hippocampus of both hemispheres. The histological picture obtained on injecting Evans blue into the internal carotic artery two minutes after the blood-brain barrier opening with mannitol can be seen as morphological evidence of the fact that the substance thus applied does have an effect on cell homeostasis since the intracellular share of Evans blue distribution is considerable.

Animals↗