Biomedical subjects

R Druga

Publications and source records attributed to R Druga.

At least 19 recordsLinked to original sources

PubMed2005

Densities of parvalbumin-immunoreactive neurons in non-malformed hippocampal sclerosis-temporal neocortex and in cortical dysplasias.

The changes in density of inhibitory parvalbumin-immunoreactive interneurons were quantitatively studied by immunohistochemistry in a series of human neocortical samples comprising the spectrum of malformations of cortical development (MCD) encountered in epilepsy surgery and the non-malformed hippocampal sclerosis-temporal neocortex in patients with refractory temporal lobe epilepsy. The highest relative density of parvalbumin-immunoreactive cells was obtained in the control samples (n = 21). The number of parvalbumin-immunoreactive neurons was significantly decreased in non-malformed hippocampal sclerosis-temporal neocortex (n = 73, 80.5% of control values). In a proportion of the latter samples as well as in two controls we observed patchy regions of absence of parvalbumin staining. The total counts of parvalbumin-immunoreactive cells in all the categories of MCD - "mild MCD" (n = 25), focal cortical dysplasia type I (n = 19) and type II (n = 15) - were decreased representing 72.4%, 55.0% and 12.2% of control values, respectively. Significantly different parvalbumin-immunoreactive cell densities were demonstrated between the focal cortical dysplasia types IIA and IIB. In "mild MCD", we observed a more pronounced decrease of parvalbumin-immunoreactive cells in the infragranular layers. No significant differences were revealed between the temporal and extratemporal examples of analogous MCD types. This study provides evidence for reduction of inhibitory parvalbumin-immunoreactive interneurons in the epileptic neocortex affected by MCD as well as in morphologically unaffected epileptic temporal neocortex, thus representing a possible mechanism for their epileptogenicity.

Adolescent↗

PubMed2005

Effects of a free radical scavenger N-tert-butyl-alpha-phenylnitrone (PBN) on short-term recovery of immature rats after status epilepticus.

The present study examined the effects of a free radical scavenger, N-tert-butyl-alfa-phenylnitrone (PBN) on lithium-pilocarpine-induced status epilepticus (SE) and its short-term consequences in rats 12 (P12) or 25 (P25) days old. PBN (2 x 100 mg/kg i.p.) was injected according to the following schedules: 1) PBN-pretreated animals received the first dose 30 min prior to pilocarpine, the second dose was given 1 min after SE onset, and 2) PBN-treated animals received the first dose of PBN 1 min after SE onset and the second one 60 min later. Paraldehyde was administered to decrease mortality. Effects of PBN were highly age-dependent. In P25 group, PBN-pretreatment increased latency to SE onset and significantly suppressed the severity of motor manifestation of SE. Both PBN pretreatment and treatment improved recovery after SE. In contrast, administration of PBN in P12 animals did not affect SE pattern or recovery after SE. Administration of PBN had no effects on the motor performance of animals 3 and 6 days after SE. Neuronal damage was examined 24 h and 7 days after SE using Fluoro-Jade B staining. Mild neuroprotective effects of PBN in hippocampal fields CA1 and CA3 occurred in P25 rats in both experimental schedules. In contrast, administration of PBN aggravated neuronal injury in the hippocampus in P12 rats. Administration of PBN to intact rats did not induce neurodegeneration in either age group.

Age Factors↗

PubMed2003

Long-term changes of activity of cortical neurons after status epilepticus induced at early developmental stages in rats.

Spontaneous activity of cortical neurons was studied under urethane anesthesia in adult rats 3 months after convulsive status epilepticus induced by lithium-pilocarpine administration at the age of 12 (SE12 group) or 25 (SE25 group) days. Whereas random firing neurons dominated in control animals (61 out of 98 cells), SE25 animals exhibited a significant increase in the incidence of bursting cells (38 out of 59 units). Similar change in SE12 animals did not reach the level of statistical significance. Status epilepticus at an early developmental stage may result in a long-lasting change in functions of surviving cortical neurons.

Animals↗

PubMed2003

NADPH-diaphorase-positive neurons in the auditory cortex of young and old rats.

Age-related changes in NADPH-diaphorase (NADPH-d)-positive neurons were examined in the auditory cortex of young (3 months old) and very old (36 months old) rats (strain Long Evans). In very old rats a significant reduction was found in the thickness of the auditory cortex, to 54% of that in young animals, as well as changes in the shape and configuration of nerve cell bodies and dendrites. Quantitative analysis demonstrated an age-related increase in the number of dendritic segments and dendritic branching points. The length of dendrites in NADPH-d-positive neurons and their density increased in very old rats. The total number of NADPH-d-positive neurons within the Te 1 and Te 3 fields was 13% lower in the old rats than in the young.

Aging↗

PubMed2003

Lithium/pilocarpine status epilepticus-induced neuropathology of piriform cortex and adjoining structures in rats is age-dependent.

Distribution of LiCl/pilocarpine status epilepticus-induced neuronal damage was studied in the piriform cortex and in adjoining structures in 12-day-old, 25-day-old and adult rats. No distinct structural and neuronal alterations were detected in the basal telencephalon in 12-day-old rats surviving status epilepticus (SE) for one week or two months. In 25-day-old rats a decrease in Nissl staining was evident. There was also cell loss and gliosis in the caudal 2/3 of the piriform cortex, in the superficial amygdaloid nuclei, in the dorsal and ventral endopiriform nucleus and in the rostrolateral part of the entorhinal cortical area. In adult animals, the topography of neuropathological changes in the basal telencephalon was comparable to those in 25-day-old rats. The damage in the caudal 2/3 or caudal half of the piriform cortex in adult rats with survival times one week or two months was characterized by a marked loss of neurons and striking glial infiltration. The thickness of the piriform cortex and superficial amygdaloid nuclei was significantly reduced. In 25-day-old and in adult animals the sublayer IIb and layer III of the piriform cortex was more affected, while sublayer IIa was less damaged. Parvalbumin (PV) immunocytochemistry revealed a significant decrease in the number of PV-immunoreactive neurons in the rostral piriform cortex and in the dorsal claustrum in animals surviving for two months.

Aging↗

PubMed2003

Olfactory activity in the human brain identified by fMRI.

BACKGROUND: Modern imaging methods such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET) enable us to map brain activities associated with stimulation of various functional systems in the human brain. Data concerning the localization and lateralization of secondary olfactory areas are not in agreement. SUBJECTIVE THE AIM OF THE STUDY: localization of secondary olfactory brain areas activated by a pleasant stimulus--vanillin. METHODS AND MATERIAL: Our fMRI method was based on the blood-oxygen-level dependent effect. All measurements were carried out on a 1.5 T scanner (Siemens-Vision), using gradient-echo EPI technic. The basic block-like scheme included no odour/and odour was repeated 8 times. In the definitive phase of the study, experiments were performed on 12 healthy volunteers aged from 20 to 68 (9 men and 3 women) stimulated birhinally by vanillin odour. RESULTS: Bilateral activations of the inferior frontal gyrus, anterior insular-periinsular area, hippocampus, amygdala, caudate nucleus and cerebellum were seen. A greater extent of activation was evident in the right hemisphere and in the right half of the cerebellum. CONCLUSIONS: The anterior insular-periinsular area and hippocampus can be considered as secondary olfactory areas in human brain. Strong activation of the right inferior frontal gyrus demonstrated in our study may be related to effort to name the presented odour. Activation of the cerebellum may be evaluated as a consequent phenomenon due to extensive activation of the frontal lobe.

Adult↗

PubMed2003

[Microscopic disorders of cortical development of the brain and its etiopathogenic importance for detection in patients with temporal epilepsy associated with hippocampal sclerosis].

Hippocampal sclerosis represents a common structural basis of temporal lobe epilepsy. However, the etiological factors and mechanisms leading to its development still remain unexplained. In our study, we present neuropathological findings in the resected hippocampus and the pole of the temporal lobe in 15 patients with hippocampal sclerosis. "Initial precipitating injuries" that are thought to cause the development of hippocampal sclerosis (febrile seizures in early childhood, head injury or meningoencephalitis) were present in the history of 12 patients. In the remaining 3 cases, no predisposing factors were found. Attention was paid to the histopathological identification of disturbed neuronal migration and differentiation in the temporal lobe. These defects were observed in 7 cases; in three of these, no predisposing factors were stated in the patients' histories. We suggest that in these cases, hippocampal sclerosis arises due to previously undetected disorders of cortical development. A latent neocortical malformation may also contribute to the development of hippocampal sclerosis in patients with an initial precipitating injury in anamnensis. Histopathological examination of resected epileptic brain tissue can provide insights into the individual pathogenesis of epileptic disorders, especially by the detection of microscopic disorders of cortical development.

Adolescent↗

PubMed2002

Gap detection threshold in the rat before and after auditory cortex ablation.

Gap detection threshold (GDT) was measured in adult female pigmented rats (strain Long-Evans) by an operant conditioning technique with food reinforcement, before and after bilateral ablation of the auditory cortex. GDT was dependent on the frequency spectrum and intensity of the continuously present noise in which the gaps were embedded. The mean values of GDT for gaps embedded in white noise or low-frequency noise (upper cutoff frequency 3 kHz) at 70 dB sound pressure level (SPL) were 1.57+/-0.07 ms and 2.9+/-0.34 ms, respectively. Decreasing noise intensity from 80 dB SPL to 20 dB SPL produced a significant increase in GDT. The increase in GDT was relatively small in the range of 80-50 dB SPL for white noise and in the range of 80-60 dB for low-frequency noise. The minimal intensity level of the noise that enabled GDT measurement was 20 dB SPL for white noise and 30 dB SPL for low-frequency noise. Mean GDT values at these intensities were 10.6+/-3.9 ms and 31.3+/-4.2 ms, respectively. Bilateral ablation of the primary auditory cortex (complete destruction of the Te1 and partial destruction of the Te2 and Te3 areas) resulted in an increase in GDT values. The fifth day after surgery, the rats were able to detect gaps in the noise. The values of GDT observed at this time were 4.2+/-1.1 ms for white noise and 7.4+/-3.1 ms for low-frequency noise at 70 dB SPL. During the first month after cortical ablation, recovery of GDT was observed. However, 1 month after cortical ablation GDT still remained slightly higher than in controls (1.8+/-0.18 for white noise, 3.22+/-0.15 for low-frequency noise, P<0.05). A decrease in GDT values during the subsequent months was not observed.

Acoustic Stimulation↗

PubMed2002

Dynamic changes of status epilepticus-induced neuronal degeneration in the mediodorsal nucleus of the thalamus during postnatal development of the rat.

PURPOSE: Status epilepticus (SE) was previously found to induce damage in the mediodorsal nucleus of the thalamus (MD) in both adult and immature rats. This study was designed to describe age-related changes of SE-induced neuronal degeneration in this part of the brain. METHODS: SE was induced by LiCl/pilocarpine in five age groups of rats (P12-P25). Distribution of degenerating neurons was studied at various time intervals from 4 h up to 1 week using Fluoro Jade B (FJB) staining. For P12 and P25 rats, an interval of 3 months was added. RESULTS: Damaged neurons were found in all age groups during a 1-week period after SE. Patterns of neuronal degeneration, however, changed in an age-related manner. In animals at P12 and P15, FJB-labeled neurons were located in the central and lateral segment of the MD. In the P18 group, degenerating neurons occurred in all three segments of the MD, with a prevalence in central and lateral subdivisions. In contrast, in P21 and P25 rats, FJB-labeled neurons were predominantly located in the central and medial segments. Degenerating neurons were still present 3 months after SE in the medial segment in P25 animals, whereas no labeled neurons were detected in the P12 group at this time. CONCLUSIONS: Our data demonstrate that the pattern of neuronal degeneration in MD is mainly related to age at SE onset. In addition to damage occurring during the acute phase of SE, a population of degenerating neurons was detected in P25 animals during the chronic period 3 months after SE.

Aging↗

PubMed2002

Are acute changes after status epilepticus in immature rats persistent?

Early consequences of lithium-pilocarpine convulsive status epilepticus (SE) were studied six days after this status had been induced in rat pups at the age of either 12 or 25 days. Studies of spontaneous EEG activity demonstrated the presence of epileptic phenomena (isolated spikes) in both hippocampus and cortex (cortical spikes were more expressed in the older group). There were no marked behavioral correlates of spikes and transition into the ictal phase was exceptional. The motor performance on a rotorod and a horizontal bar was the same in experimental and control rats of both ages. Behavior in the open field was changed in a reverse manner in the two age groups: the locomotor activity of rats with induced seizures at the age of 12 days was significantly lower than that of their control siblings, whereas animals undergoing status at the age of 25 days were hyperactive. In addition, they also exhibited increased exploratory activity (rearing) and their habituation to the open field was deranged. Nissl-stained brain sections demonstrated extensive brain damage in the older group in contrast to the negative findings in younger animals. EEG, behavioral and morphological changes induced by status epilepticus in developing rats persisted for 6 days after the status. They markedly differed according to the age of animals.

Acute Disease↗

PubMed2001

Effect of auditory cortex lesions on NADPH-diaphorase staining in the inferior colliculus of rat.

Projections from the auditory cortex (AC) in the rat terminate in the dorsal cortex (DC) and in the external cortex (EC) of the inferior colliculus (IC), areas which exhibit a moderate number of nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d) positive neurons. NADPH-d co-localizes with nitric oxide synthase, which is responsible for the production of the transcellular messenger, nitric oxide. Changes in NADPH-d staining in the IC were found after unilateral lesions of the AC. Lesions resulted in a reduction in NADPH-d staining in neurons and neuropil within the ipsilateral DC and EC with the maximum reduction occurring 3-4 days after lesion. The reduction in NADPH-d staining in the contralateral IC was less pronounced. Lesions affecting auditory areas Te 1 and Te 3 produced the largest decrease in NADPH-d staining in neurons and neuropil. This finding may be related to the abolition of the influence of glutamatergic corticocollicular and commissural pathways.

Animals↗

PubMed2001

Status epilepticus causes necrotic damage in the mediodorsal nucleus of the thalamus in immature rats.

Status epilepticus (StE) in immature rats causes long-term functional impairment. Whether this is associated with structural alterations remains controversial. The present study was designed to test the hypothesis that StE at an early age results in neuronal loss. StE was induced with lithium-pilocarpine in 12-d-old rats, and the presence of neuronal damage was investigated in the brain from 12 hr up to 1 week later using silver and Fluoro-Jade B staining techniques. Analysis of the sections indicated consistent neuronal damage in the central and lateral segments of the mediodorsal nucleus of the thalamus, which was confirmed using adjacent cresyl violet-stained preparations. The mechanism of thalamic damage (necrosis vs apoptosis) was investigated further using TUNEL, immunohistochemistry for caspase-3 and cytochrome c, and electron microscopy. Activated microglia were detected using OX-42 immunohistochemistry. The presence of silver and Fluoro-Jade B-positive degenerating neurons in the mediodorsal thalamic nucleus was associated with the appearance of OX-42-immunopositive activated microglia but not with the expression of markers of programmed cell death, caspase-3, or cytochrome c. Electron microscopy revealed necrosis of the ultrastructure of damaged neurons, providing further evidence that the mechanism of StE-induced damage in the mediodorsal thalamic nucleus at postnatal day 12 is necrosis rather than apoptosis. Finally, these data together with previously described functions of the medial and lateral segments of the mediodorsal thalamic nucleus suggest that some functions, such as adaptation to novelty, might become compromised after StE early in development.

Animals↗

PubMed2001

An animal model of nonconvulsive status epilepticus: a contribution to clinical controversies.

PURPOSE: To characterize electroencephalographic and behavioral effects as well as electrophysiologic and morphologic consequences of a subconvulsive dose of pilocarpine in lithium chloride-pretreated rats. METHODS: Pilocarpine (15 mg/kg) was administered intraperitoneally to adult rats pretreated with lithium chloride (3 mEq/kg, i.p.). Behavior was observed for 2 h and videotaped in three consecutive sessions. At the same time, EEG was recorded from the sensorimotor cortex and the dorsal hippocampus. Threshold intensities of currents necessary to elicit hippocampal afterdischarges were determined 24 h and 1 week after the pilocarpine administration. The brains were histologically examined 1 week after pilocarpine administration using Nissl stain. RESULTS: Pilocarpine induced time-limited nonconvulsive status epilepticus (NCSE). Epileptic EEG activity concurrent with prominent behavioral features was observed both in the neocortex and, predominantly, in the hippocampus. No changes in afterdischarge thresholds were observed in the dorsal hippocampus 24 h and 1 week after NCSE. One week after NCSE, seizure-related brain damage was found mainly in the motor neocortical fields. CONCLUSIONS: Pilocarpine-induced NCSE in rats strongly resembles a short-term human complex partial status epilepticus. Our animal model is suitable for studying the possible adverse effects of prolonged nonconvulsive seizures.

Animals↗

PubMed2000

Nonconvulsive status epilepticus in rats: impaired responsiveness to exteroceptive stimuli.

An animal model of human complex partial status epilepticus induced by lithium chloride and pilocarpine administration was developed in our laboratory. The objective of the study was to provide a detailed analysis of both ictal and postictal behavior and to quantify seizure-related morphological damage. In order to determine the animal's responsiveness to either visual or olfactory stimuli, adult male rats were submitted to the following behavioral paradigms: the object response test, the social interaction test, and the elevated plus-maze test. The rotorod test was used to evaluate motor performance. Two weeks after status epilepticus, brains were morphologically examined and quantification of the brain damage was performed. Profound impairment of behavior as well as responsiveness to exteroceptive stimuli correlated with the occurrence of epileptic EEG activity. When the epileptic EEG activity ceased, responsiveness of the pilocarpine-treated animals was renewed. However, remarkable morphological damage persisted in the cortical regions two weeks later. This experimental study provides support for the clinical evidence that even nonconvulsive epileptic activity may cause brain damage. We suggest that the model can be used for the study of both functional and morphological consequences of prolonged nonconvulsive seizures.

Animals↗

PubMed2000

Brain activation during volitional control of breathing.

Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during volitional control of breathing in nine healthy human subjects. This type of breathing was induced by acoustic stimuli dictating the respiratory frequency. During the period of dictated breathing not only the frontal and temporal lobes of the brain, but also the parietal lobes were bilaterally activated. The frontal lobe was activated bilaterally in all subjects, with frequent activation of Brodmann areas 4 and 6. In the parietal lobe, activation could mostly be demonstrated in gyrus postcentralis and the same was true for area 22 in the temporal lobe.

Acoustic Stimulation↗

PubMed1999

Changes in NADPH-diaphorase positivity induced by status epilepticus in allocortical structures of the immature rat brain.

The distribution and time course of changes of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) positivity were studied in immature rats (12 and 25 days old) surviving motor status epilepticus (SE) induced by a high dose of pilocarpine. Motor SE characterized by continuous convulsions was interrupted after 2 h by an injection of clonazepam (0.5 mg/kg or 1 mg/kg in 12- and 25-day-old rats, respectively) in order to reduce mortality. Correlation between electroencephalographic and behavioral seizure activity was confirmed using animals with electrodes implanted bilaterally in the hippocampus and sensorimotor cortex. Brains were examined 2, 6, 13, and 21 days after motor SE using NADPH-diaphorase histochemistry. Two types of changes were found in both age groups: (a) decrease of NADPH-d positivity occurred in both neuropil and cell bodies in piriform, periamygdalar, and entorhinal cortices; and (b) NADPH-d positivity was induced in the cell bodies in the hippocampal fields CA1/2, CA3, and dentate gyrus. These changes were more intense in animals surviving SE at postnatal day 25 than in younger age group, and they peaked 2 days after SE. The changes observed after SE disappeared quickly in 12-day-old rat pups, where only moderate changes could be observed in piriform, periamygdalar, and entorhinal cortices 6 days after SE, whereas the changes in the histochemical positivity persisted in older animals even 21 days after SE.

Aging↗

PubMed1999

Control of breathing and brain activation in human subjects seen by functional magnetic resonance imaging.

Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during transition from unconscious to conscious breathing in seven healthy human subjects. In right-handed volunteers, the activated areas were found in both hemispheres. The medial part of the precentral gyrus (area 4) was constantly activated in the left hemisphere. Additional activated areas were demonstrated in the premotor cortex and in the posterior parietal cortex. The activated cortical sites exhibited analogous distribution in the right hemisphere. In two out of the seven subjects. activated sites were also observed in the cerebellar hemispheres, and in the lentiform and caudate nuclei.

Adult↗

PubMed1997

[The role of the basal ganglia in control of motor activity].

Morphological, histochemical and functional analysis of the role of basal ganglia in the motor control is presented. The inhibiting effect of basal ganglia on the motor activity, their role in programming the slow and stereotyped movements, and the presentation of emotional and memory centres to the motor mechanisms of behaviour is emphasised.

Animals↗