S. aureus PFGE patterns of lesional or non lesional strains from patients with impetigo: association of individual bands with lesional or non lesional areas

PFGE has been extensively used to obtain a reliable intra-species differentiation, although this technique has not been completely standardized. In this study, PFGE was applied to analyze in detail the patterns of 19 lesional S. aureus strains isolated from patients with impetigo, compared with 15 non-lesional strains isolated from nasal or pharyngeal swabs of the same patients. The strain DNA was extracted and processed as previously reported, using the strictest protocol to limit the variations between different analytical sets. To obtain maximum sensitivity and comparability, the electrophoresis patterns were analyzed by an automated and computerized reader (GelDoc1000). The DNA fragments (range 12-15 bands) obtained for each individual strain were then divided into 39 zones including from 1 to 4 bands for a total of at least 91 possible different gel positions. The positivity for each zone (and/or the positivity for the individual bands contained) was associated with the lesional/non-lesional origin and with the face localization of the strains.     

Comparative study of Staphylococcus aureus isolated from lesional and non-lesional skin of atopic dermatitis patients

The skin of patients with atopic dermatitis (AD) is often colonized by Staphylococcus aureus, and superantigenic exotoxins produced by the organism are thought to be an important precipitating factor of AD. However, there are few reports comparing the characteristics of S. aureus isolated from the lesional and non-lesional skin of identical AD patients. In this study, therefore, we examined whether the presence of superantigen-producing S. aureus correlates with the formation of eczematous lesion of AD patients. The detection rate of S. aureus on the lesional skin of AD patients was higher than on the non-lesional skin of AD patients. Furthermore, the bacterial cell count of S. aureus on the lesional skin of AD patients was also significantly higher than that of the non-lesional skin of AD patients. However, there was no significant difference between the detection rate of superantigenic exotoxin-producing S. aureus on the lesional and nonlesional skin of AD patients. These results suggest that the number of S. aureus present is more important in the formation of eczematous lesion of AD patients than the presence of superantigenic exotoxin-producing S. aureus strains per se.     

Localizing confined epileptic foci in patients with an unclear focus or presumed multifocality using a component-based EEG-fMRI method

Precise localization of epileptic foci is an unavoidable prerequisite in epilepsy surgery. Simultaneous EEG-fMRI recording has recently created new horizons to locate foci in patients with epilepsy and, in comparison with single-modality methods, has yielded more promising results although it is still subject to limitations such as lack of access to information between interictal events. This study assesses its potential added value in the presurgical evaluation of patients with complex source localization. Adult candidates considered ineligible for surgery on account of an unclear focus and/or presumed multifocality on the basis of EEG underwent EEG-fMRI. Adopting a component-based approach, this study attempts to identify the neural behavior of the epileptic generators and detect the components-of-interest which will later be used as input in the GLM model, substituting the classical linear regressor. Twenty-eight sets interictal epileptiform discharges (IED) from nine patients were analyzed. In eight patients, at least one BOLD response was significant, positive and topographically related to the IEDs. These patients were rejected for surgery because of an unclear focus in four, presumed multifocality in three, and a combination of the two conditions in two. Component-based EEG-fMRI improved localization in five out of six patients with unclear foci. In patients with presumed multifocality, component-based EEG-fMRI advocated one of the foci in five patients and confirmed multifocality in one of the patients. In seven patients, component-based EEG-fMRI opened new prospects for surgery and in two of these patients, intracranial EEG supported the EEG-fMRI results. In these complex cases, component-based EEG-fMRI either improved source localization or corroborated a negative decision regarding surgical candidacy. As supported by the statistical findings, the developed EEG-fMRI method leads to a more realistic estimation of localization compared to the conventional EEG-fMRI approach, making it a tool of high value in pre-surgical evaluation of patients with refractory epilepsy. To ensure proper implementation, we have included guidelines for the application of component-based EEG-fMRI in clinical practice.     

Association between lesional or non lesional S. aureus strains from patients with impetigo and exfoliative toxin production. No association with SmaI PFGE patterns

Contrasting data are reported in the literature on the percent positivity rates (13.5%-100%) of exfoliative toxin (ET) production by S. aureus strains isolated from impetigo patients in Japan and in France. In the present study, by means of a recently available latex-test, toxin-A (ETA) or toxin-B (ETB) production was found in 67.6% of the 34 S. aureus strains isolated from 19 lesional (63.2%) and 15 non-lesional (nose or pharynx, 73.3%) areas of patients with impetigo (with no significant difference between the lesional and non-lesional isolates). ETA + ETB were produced by 44.1% of the strains, while 32.4% were non-producers. In contrast, the percent positivity rate observed in 40 [20 lesional and 20 non-lesional (nose or pharynx)] strains isolated in patients with atopic dermatitis was 15.0% (p < 0.001 both for the lesional and non-lesional strains versus impetigo, with no significant difference between lesional and non lesional strains). Finally, 26 strains from other types of specimens (abscesses, hemocultures, urine, central venous catheters, bronchoalveolar lavages) showed an 11.5% production rate of ETA or ETB (p < 0.001 versus impetigo strains, no significance versus atopic dermatitis). These data point to a significant association between exfoliative toxin production and S. aureus strains isolated in impetigo, both in lesional areas and in nasal/pharyngeal reservoirs. An attempt to correlate SmaI pulsed-field gel electrophoresis (PFGE) restriction patterns and exfoliative toxin production showed no significant association in either group.     

Phospholipid content in "late" posttraumatic epileptic focus in rabbits

The phospholipids content in the cortex, hippocamp and stem tissues in rabbits with "late" posttraumatic epileptic focus (1 year after the light brain injury) was estimated. There was established an increase of the content of phosphatidylethanolamine, sphingomyeline, phosphatidylinosite, phosphatidic acid, non-identified phospholipids, decrease of the content of phosphatidylcholine and cardiolipine and appearance of lysophosphatidylcholine in the cortical epileptic focus tissues. The conclusion is made that the changes within the phospholipids pool may cause the epileptogenic disturbance in the neurons, i.e. the changes of functional properties of the excitable membranes and the activity of the mytochondrial phospholipid-dependent enzyme complex.     

Visual field asymmetries in attention and learning

It has been suggested that attentional resolution is greater in the lower than in the upper visual field. As there is no corresponding asymmetry between the areas in the primary visual cortex where the input from upper and lower visual fields is processed, an 'attentional filter' has been proposed to act in one or more higher visual cortical areas in order to constrict the availability of visual information to the level of awareness. To investigate this, a visual search array was presented to the entire visual field and reaction times from upper and lower visual fields compared. In a second experiment, subjects were trained in detecting targets in different visual fields. There was no significant difference between reaction times for targets presented in either upper or lower visual fields when the array was presented to the entire visual field. However, when the array was restricted to either the upper or lower visual fields, reaction times were significantly slower for detection in the upper visual field.     

Unit activity in an epileptic focus formed in the cat motor cortex with tetanus toxin

Single unit activity was recorded intracellularly in the zone of an epileptic focus produced by injection of tetanus toxin into the cerebral cortex of cats. Epileptic activity of all neurons tested correlated with cortical discharges between fits. A group of neurons with continuous spontaneous activity, in which a steady fall of membrane potential and cyclic changes in the frequency of the spike discharges were observed was distinguished. In these neurons paroxysmal depolarization changes of membrane potential were found in the discharges between fits, without subsequent hyperpolarization of the membrane. Hyperpolarization potentials after paroxysmal depolarization shifts could be observed in neurons of other groups. The role of neurons of the different groups in the formation of an "epileptic aggregate," the main generator of pathologically enhanced excitation, is discussed.Institute of Normal and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Institute of Clinical and Experimental Neurology, Ministry of Health of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 10, No. 6, pp. 582–589, November–December, 1978.     

Chromosomal investigations in epileptic children during long-term therapy with phenytoin or primidone

Summary In epileptic children the long-term therapy with anticonvulsant drugs is absolutely necessary. However, anticonvulsant drugs have been suspected to be mutagenic and teratogenic. To investigate this problem metaphase chromosome observations were performed using short-time culture of peripheral blood lymphocytes from twenty children. Ten of the children had been treated with phenytoin and the other ten with primidone on monotherapy. The long-term administration of anticonvulsant drugs was monitored by measurement of the serum concentrations of phenytoin and primidone, by seizure anamnesis, and by repeated EEG investigations. Analyzing 100 mitoses from each proband, we found no increase of structural or numerical aberrations in our patients compared with six controls. In adults, however, anticonvulsant drugs have been found to cause structural aberrations and chromosomal damage. The absence of these lesions in children may reflect the higher efficiency of DNA-repair in local DNA-damage.Dedicated to Prof. Dr. H. Schoenenberg, Aachen, on his 65th birthdayThis work contains parts of the M.D. theses of U.M. and E.M.     

Effect of diazepam on cyclic change of excitability in a cortical epileptic focus

On application of penicillin solution to the motor cortex of rats and electrical stimulation of the ventroposterolateral thalamic nucleus (VPL) with a frequency of 1/sec and with a strength three times greater than the threshold for the primary evoked potential, alternation of "active" and "passive" neurons was observed in the zone of the epileptic focus. "Active" neurons were characterized by the regular appearance of epileptiform discharges in response to each stimulation of VPL. In the course of the "passive" periods stimulation of VPL led only to the appearance of primary evoked potentials. Diazepam in a dose of 2 mg/kg completely disturbed spike generation in the epleptic focus, but in a dose of 0.1 mg/kg it caused disturbance of the established cyclic change of excitability in the focus, which was restored after stimulation with a frequency of 2/sec.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 563–570, November–December, 1980.     

A study of caudate inhibition on an epileptic focus in the cat hippocampus

The mechanisms whereby the caudate nucleus modifies hippocampal spiking activity have been studied. Epileptiform activity was induced in the cat hippocampus by topical application of sodium penicillin in different concentrations. The frequency of induced spikes appeared to be directly correlated to the two doses of epileptogenic agent. The inhibitory effect of 10 Hz caudate stimulation on spike frequency was present even when stimulation lasted for 180 s. Likewise 25 Hz caudate stimulation brought about an inhibition which was maintained by stimulus trains lasting up to 90 s, while the degree of inhibition was reduced by trains of longer duration (120, 150 and 180 s); similar results were also noted in some atropine-treated cats. The time course of spikes in cats with electrolytic lesions of the caudate exhibited an increase in both frequency and duration. The results indicate that there is an optimal parameter for caudate stimulation causing inhibition of penicillin-induced hippocampal spiking activity, and suggest the possibility of tonic control of hippocampal excitability exerted by the caudate nucleus.     

Induction of astrocytic cyclooxygenase-2 in epileptic patients with hippocampal sclerosis

Induction of cyclooxygenase-2 (COX-2) has been described in a wide range of neurological diseases including animal models of epilepsy. The present study was undertaken to assess COX-2 expression in hippocampal biopsies from patients with therapy-refractive temporal lobe epilepsy (TLE). For this purpose, hippocampal CA1 subfield was dissected from epileptic patients with (n=5) or without (n=2) hippocampal sclerosis (HS). COX-2 expression was investigated using immunohistochemistry and semi-quantitative RT-PCR. COX-2 immunoreactivity in TLE patient material in the absence of HS was restricted to a few neurons of the hippocampus. In the presence of HS, on the other hand, a significant induction of astrocytic COX-2 immunoreactivity associated with a concomitant increase in the steady-state level of COX-2 mRNA was observed in the CA1 subfield. These findings suggest that induction of astrocytic COX-2 is implicated in the pathogenesis of HS in TLE and is consistent with the previous findings of increased concentrations of prostaglandins in the cerebrospinal fluid of these patients.     

Visual attention mediated by biased competition in extrastriate visual cortex.

According to conventional neurobiological accounts of visual attention, attention serves to enhance extrastriate neuronal responses to a stimulus at one spatial location in the visual field. However, recent results from recordings in extrastriate cortex of monkeys suggest that any enhancing effect of attention is best understood in the context of competitive interactions among neurons representing all of the stimuli present in the visual field. These interactions can be biased in favour of behaviourally relevant stimuli as a result of many different processes, both spatial and non-spatial, and both bottom-up and top-down. The resolution of this competition results in the suppression of the neuronal representations of behaviourally irrelevant stimuli in extrastriate cortex. A main source of top-down influence may derive from neuronal systems underlying working memory.     

Neuronal electrical activity in the epileptic focus produced by electrical stimulation in an isolated cortical slab

Characteristics of neuronal activity in an isolated cortical slab were investigated during the onset of seizure spikes induced by frequent and powerful stimulation of the slab during experiments on unanesthetized immobilized cats. A high degree of coordination between the activity of cellular elements was found in the focus of epileptiform activity studied: convulsive shifts in membrane potential exactly corresponding to electrocorticograms of convulsive activity waves were observed in all neurons studied using intracellular techniques. No action potentials occurred in the soma of any of these neurons, moreover. Bursting spike discharges were recorded from neurons of the isolated slab at the same time. Findings from extra- and intracellular recordings of activity in the same neurons showed that action potentials are generated during convulsive activity at certain trigger zones remote from the cell in question without involving the soma, from which convulsive shifts in membrane potentials were recorded simultaneously. Mechanisms possibly underlying the generation of spike activity in neurons of the isolated slab undergoing development of generalized convulsive state are discussed.I. I. Mechnikov State University, Odessa. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 357–365, May–June, 1988.