Hemolytic-uremic syndrome surveillance to monitor trends in infection with Escherichia coli O157 and non-O157 enterohemorrhagic E. coli in Austria

Austrian data underline that relying on the number of enterohemorrhagic Escherichia coli (EHEC) O157 strains isolated from clinical specimens does not allow assessment of the actual incidence of EHEC infections. A hospital-based system for identification of hemolytic-uremic syndrome cases based on voluntary cooperation was established in 1995 and provides information needed to monitor trends in the incidence of O157 and non-O157 EHEC infections.

Mechanisms to synchronize neuronal activity

Temporal aspects of neuronal activity have received increasing attention in recent years. Oscillatory dynamics and the synchronization of neuronal activity are hypothesized to be of functional relevance to information processing in the brain. Here we review theoretical studies of single neurons at different levels of abstraction, with an emphasis on the implications for properties of networks composed of such units. We then discuss the influence of different types of couplings and choices of parameters to the existence of a stable state of synchronous or oscillatory activity. Finally we relate these theoretical studies to the available experimental data, and suggest future lines of research.

Energy dependence of quasiparticle relaxation in a disordered fermi liquid

A spectroscopic method is applied to measure the inelastic quasiparticle relaxation rate in a disordered Fermi liquid. The quasiparticle relaxation rate gamma is deduced from the magnitude of fluctuations in the local density of states, which are probed using resonant tunneling through a localized impurity state. We study its dependence on the excitation energy E measured from the Fermi level. In a disordered metal (heavily doped GaAs) we find that gamma~E3/2 within the experimentally accessible energy interval, in agreement with the Altshuler-Aronov theory for electron-electron interactions in diffusive conductors.

Maintenance electroconvulsive therapy in affective and schizoaffective disorder

Twenty-one patients (13 depressives and 8 schizoaffectives) who underwent maintenance electroconvulsive therapy (M-ECT) were compared with controls who received maintenance pharmacotherapy alone. Measures of effectiveness and safety of maintenance treatment were prospectively obtained during a 1-year follow-up. Survival analysis demonstrated a significantly better outcome defined by time to rehospitalization for all patients of the M-ECT group. Regarding the subgroups, depressives of the M-ECT group had markedly decreased rehospitalization rates compared to depressive controls. Furthermore, M-ECT in depressives resulted in a significant reduction in hospitalization rates and duration during follow-up. In schizoaffective patients, a significant difference in survival time was found in favor of the M-ECT group. In both groups, schizoaffectives had a markedly poorer outcome compared to depressive subjects. Our results indicate that in selected patients M-ECT, at least in combination with supporting medication, may be an efficient and safe alternative to pharmacological continuation or maintenance therapy alone.

NOSIP, a novel modulator of endothelial nitric oxide synthase activity

Production of nitric oxide (NO) in endothelial cells is regulated by direct interactions of endothelial nitric oxide synthase (eNOS) with effector proteins such as Ca2+-calmodulin, by posttranslational modifications such as phosphorylation via protein kinase B, and by translocation of the enzyme from the plasma membrane caveolae to intracellular compartments. Reversible acylation of eNOS is thought to contribute to the intracellular trafficking of the enzyme; however, protein factor(s) that govern the translocation of the enzyme are still unknown. Here we have used the yeast two-hybrid system and identified a novel 34 kDa protein, termed NOSIP (eNOS interacting protein), which avidly binds to the carboxyl-terminal region of the eNOS oxygenase domain. Coimmunoprecipitation studies demonstrated the specific interaction of eNOS and NOSIP in vitro and in vivo, and complex formation was inhibited by a synthetic peptide of the caveolin-1 scaffolding domain. NO production was significantly reduced in eNOS-expressing CHO cells (CHO-eNOS) that transiently overexpressed NOSIP. Stimulation with the calcium ionophore A23187 induced the reversible translocation of eNOS from the detergent-insoluble to the detergent-soluble fractions of CHO-eNOS, and this translocation was completely prevented by transient coexpression of NOSIP in CHO-eNOS. Immunofluorescence studies revealed a prominent plasma membrane staining for eNOS in CHO-eNOS that was abolished in the presence of NOSIP. Subcellular fractionation studies identified eNOS in the caveolin-rich membrane fractions of CHO-eNOS, and coexpression of NOSIP caused a shift of eNOS to intracellular compartments. We conclude that NOSIP is a novel type of modulator that promotes translocation of eNOS from the plasma membrane to intracellular sites, thereby uncoupling eNOS from plasma membrane caveolae and inhibiting NO synthesis.

Top-down processing mediated by interareal synchronization

Perception and cortical responses are not only driven "bottom-up" by the external stimulus but are altered by internal constraints such as expectancy or the current behavioral goal. To investigate neurophysiological mechanisms of such top-down effects, we analyzed the temporal interactions of neurons on different levels of the cortical hierarchy during perception of stimuli with varying behavioral significance. We found that interareal interactions in a middle-frequency range (theta and alpha; 4-12 Hz) strongly depend on the associated behavior, with a phase relationship and a layer specificity indicating a top-down-directed interaction. For novel unexpected stimuli, presumably processed in a feed-forward fashion, no such interactions occurred but high-frequency interactions (gamma; 20-100 Hz) were observed. Thus corticocortical synchronization reflects the internal state of the animal and may mediate top-down processes.

A case of pharmacokinetic interference in comedication of clozapine and valproic acid

In 4-6% of treatment histories, clozapine induces generalized seizures by reducing the seizure threshold. Despite the knowledge of high risks combined therapy (such as bone marrow suppression, pathological EEG changes), some authors even suggest the prophylactic combination with anticonvulsants in high dose treatment of clozapine. We report a case of a 33-year-old female patient, a heavy smoker, suffering from mixed schizoaffective disorder from 1989 onwards. At her 8th admission in 1998, she was rehospitalized after experiencing her first generalized seizure under clozapine treatment, although no seizure phenomenon or other relevant side-effects under several previous clozapine therapies had been observed. Therefore, she received a valproic acid co-medication during her clozapine therapy. Based on therapeutic drug monitoring of clozapine (weekly) under compliance-controlled conditions, the serum levels of clozapine significantly decreased, probably induced by valproic acid. According to the literature, this case report might support the clinical relevance of therapeutic drug monitoring when clozapine therapy is combined with valproic acid as co-medication.

Apoptosis of tubular epithelial cells in familial juvenile gouty nephropathy

Two patients, a 47-year-old woman suffering from chronic renal failure, hyperuricemia and gout, and her 26-year-old son with hyperuricemia and chronic renal failure, are described. The father and two siblings of the woman had died of chronic renal failure. Both patients had a markedly reduced fractional excretion of urate, which was significantly increased by both benzbromarone and probenecid. A renal biopsy of the son revealed an unspecific chronic tubulointerstitial nephropathy. By light microscopy, many proximal tubular epithelial cells showed signs of apoptosis, which was confirmed with the specific TUNEL assay. We propose a hypothesis based on a gain-of-function mutation of the luminal anion exchanger of the proximal tubulus to explain reduced uric acid excretion, dominant inheritance and apoptosis of tubular epithelial cells in this rare disease. Treatment with a combination of allopurinol to reduce the renal urate load and benzbromarone to block the tubular anion exchanger and normalize fractional uric acid excretion is suggested.

Pyuria in patients treated with indinavir is associated with renal dysfunction

BACKGROUND

Indinavir therapy is associated with a continuum of crystal-related syndromes, including nephrolithiasis, renal colic, flank pain without recognizable stone formation, dysuria and asymptomatic crystalluria. A frank nephropathy has been recognized recently as part of the spectrum.

METHODS

A retrospective analysis of 72 HIV-infected individuals receiving indinavir was performed to identify the frequency and risk factors for indinavir-associated nephropathy and urinary complications. Individuals treated with nucleoside analogues alone served as controls.

RESULTS

Mean serum creatinine levels rose from 1.03 +/- 0.16 mg/dl to 1.11 +/- 0.22 mg/dl at week 12 and 1.15 +/- 0.27 mg/dl at week 24 (both, p < 0.01). Thirteen individuals developed serum creatinine levels > or =1.4 mg/dl. Increased serum creatinine levels were found more frequently in women (p < 0.01) and were associated with pyuria and microhematuria (p < 0.01). Frank renal colic and/or nephrolithiasis (seven patients) and urinary pH were not associated with serum creatinine levels > or =1.4 mg/dl. The mean duration of indinavir treatment, until sterile pyuria occurred, were 22 weeks and 32 weeks until the first rise of serum creatinine levels to > or =1.4 mg/dl. Ten patients showed both findings, pyuria preceded the first rise in serum creatinine levels to > or = 1.4 mg/dl (18 vs. 27 weeks, p = 0.02). Renal biopsy, done in three patients, revealed tubulointerstitial disease with crystals in collecting ducts. In 21 patients, among them 11 with pyuria, indinavir was replaced for various reasons and pyuria disappeared in nine. In these patients mean serum creatinine levels decreased from 1.43 mg/dl at withdrawal of indinavir to 1.04 mg/dl three months later (p < 0.01).

CONCLUSION

Indinavir therapy is associated with a decrease in renal function which is reversible after withdrawal. In addition, indinavir-associated tubulointerstitial disease does no in patients taking indinavir may help to identify patients being at risk for nephrotoxicity.

A spike based learning rule for generation of invariant representations

For biological realism, models of learning in neuronal networks often assume that synaptic plasticity solely depends on locally available signals, in particular only on the activity of the pre- and post-synaptic cells. As a consequence, synapses influence the plasticity of other synapses exclusively via the post-synaptic activity. Inspired by recent research on the properties of apical dendrites it has been suggested, that a second integration site in the apical dendrite may mediate specific global information. Here we explore this issue considering the example of learning invariant responses by examining a network of spiking neurones with two sites of synaptic integration. We demonstrate that results obtained in networks of units with continuous outputs transfer to the more realistic neuronal model. This allows a number of more specific experimental predictions, and is a necessary step to unified description of learning rules exploiting timing of action potentials.

Bi-directional interactions between visual areas in the awake behaving cat

The study of the cooperativity among cortical areas is essential to our understanding of brain functioning. Here we investigated the relative contributions of top-down and bottom-up directed interactions between area 17 and area 7 of the cat visual system. Bipolar local field potentials were recorded while the animals performed a go/no-go task or were in a quiet resting state. The data were analyzed by applying measures of interaction based on the Wiener-Granger causality concept. We found that during the visual task top-down directed interactions were of a similar magnitude as the bottom-up component. Second, interareal couplings tended to increase in conditions requiring a discriminative effort. Third, during behaviors not dominated by visual processing non-directed interactions increased.

Integrating top-down and bottom-up sensory processing by somato-dendritic interactions

The classical view of cortical information processing is that of a bottom-up process in a feedforward hierarchy. However, psychophysical, anatomical, and physiological evidence suggests that top-down effects play a crucial role in the processing of input stimuli. Not much is known about the neural mechanisms underlying these effects. Here we investigate a physiologically inspired model of two reciprocally connected cortical areas. Each area receives bottom-up as well as top-down information. This information is integrated by a mechanism that exploits recent findings on somato-dendritic interactions. (1) This results in a burst signal that is robust in the context of noise in bottom-up signals. (2) Investigating the influence of additional top-down information, priming-like effects on the processing of bottom-up input can be demonstrated. (3) In accordance with recent physiological findings, interareal coupling in low-frequency ranges is characteristically enhanced by top-down mechanisms. The proposed scheme combines a qualitative influence of top-down directed signals on the temporal dynamics of neuronal activity with a limited effect on the mean firing rate of the targeted neurons. As it gives an account of the system properties on the cellular level, it is possible to derive several experimentally testable predictions.

Local and global gating of synaptic plasticity

Mechanisms influencing learning in neural networks are usually investigated on either a local or a global scale. The former relates to synaptic processes, the latter to unspecific modulatory systems. Here we study the interaction of a local learning rule that evaluates coincidences of pre- and postsynaptic action potentials and a global modulatory mechanism, such as the action of the basal forebrain onto cortical neurons. The simulations demonstrate that the interaction of these mechanisms leads to a learning rule supporting fast learning rates, stability, and flexibility. Furthermore, the simulations generate two experimentally testable predictions on the dependence of backpropagating action potential on basal forebrain activity and the relative timing of the activity of inhibitory and excitatory neurons in the neocortex.

Transcranial magnetic stimulation induces 'pseudoabsence seizure'

OBJECTIVE

Several studies support the hypothesis of an antidepressive or mood-enhancing effect of repetitive transcranial magnetic stimulation (rTMS) on depressive patients. The most acute concern regarding rTMS is possible seizure induction; therefore, reports on seizure during rTMS are of special significance.

METHOD

We describe a case in which high frequency rTMS over the left dorsolatero-prefrontal cortex (DLPC) applied as an add-on antidepressive strategy may have induced a frontal lobe complex partial seizure in a female patient affected by drug-resistant depression.

RESULTS

The epileptic seizure was self-limited, and the patient did not report any physical sequelae. The psychopathological improvement, observed immediately after the incident in question, did not last.

CONCLUSION

In this case train duration in rTMS, combined with drugs modulating the norepinephrine turnover, may have contributed to the occurrence of this complex partial seizure, which neuroanatomically seems to be localized in the DLPC.

Preliminary findings of simultaneous 18F-FDG and 99mTc-HMPAO SPECT in patients with depressive disorders at rest: differential correlates with ratings of anxiety

The assumption of a dynamic coupling between regional cerebral blood flow (rCBF) and cerebral glucose metabolic rates (rCMRGlu) has been challenged by simultaneous measurements of both. Through the use of a dual-headed gamma camera with a 511-keV collimator applying the double isotope 18F-FDG and 99mTc-HMPAO SPECT technique, the uptake rates of these isotopes can be semi-quantitatively evaluated. Sixteen depressed patients, diagnosed by ICD-10 criteria and assessed with the 17-item Hamilton Rating Scale for Depression (HRSD), were studied. Based on the severity of HRSD-rated anxiety (item 10: low=1-21; high=3-4), two eight-patient subgroups were formed and compared with 12 age- and handedness-matched healthy control subjects. As regions of interest, we selected areas implicated in the neuroanatomy of anxiety and depression: hippocampus (hippo), basal ganglia (BG) and gyri temporales superiores (G.t.s.). In the control subjects, a significant statistical coupling between rCBF and rCMRGlu was revealed by the Spearman correlation coefficient only in left hippo and left BG. Patients in the low-anxiety subgroup demonstrated a marked dynamic coupling bilaterally for the G.t.s., while patients in the high-anxiety subgroup showed a significant statistical correlation of rCBF and rCMRGlu only in the left G.t.s. These findings indicate that a dynamic coupling between blood flow and glucose metabolism exists only in distinct brain regions, and that the depressive illness has an uncoupling effect on this correlation in the left BG. Furthermore, our results suggest that the HRSD anxiety score might interact with the underlying depressive illness to influence the relationship of rCBF and rCMRGlu.

The effects of cromolyn sodium and nedocromil sodium in early asthma prevention

The possibility of irreversible obstruction and therefore the need for early intervention is being much debated. Some investigators suggested that delay in starting inhaled corticosteroids will result in irreversible obstruction. Our own long-term study, specifically designed to detect irreversible obstruction showed that a step-wise approach (starting with cromolyn sodium and switching to inhaled corticosteroids if clinical control and pulmonary function tests are not satisfactorily controlled) resulted in an increase in pulmonary function and not a deterioration. There was no evidence that a delay in starting inhaled corticosteroids will result in irreversible obstruction or clinical worsening. However, delay in starting cromolyn sodium in patients treated with bronchodilators alone did result in worsening pulmonary function tests and worse clinical outcomes. One study from Finland and another study from Australia came to the same conclusion. Even though some studies with cromolyn sodium did not show benefit in the first year of life, other studies did show a good response. The choice between nonsteroidal drugs, such as cromolyn sodium and inhaled corticosteroids as first-line drugs, has to be made on the risk/benefit ratio of these drugs. Although in severe asthma inhaled corticosteroids have greater efficacy, in mild-to-moderate asthma there is comparable efficacy, and the nonsteroidal drugs have better safety. A step-wise approach is still a logical approach

Learning with two sites of synaptic integration

Since the classical work of D O Hebb 1949 The Organization of Behaviour (New York: Wiley) it is assumed that synaptic plasticity solely depends on the activity of the pre- and the postsynaptic cells. Synapses influence the plasticity of other synapses exclusively via the post-synaptic activity. This confounds effects on synaptic plasticity and neuronal activation and, thus, makes it difficult to implement networks which optimize global measures of performance. Exploring solutions to this problem, inspired by recent research on the properties of apical dendrites, we examine a network of neurons with two sites of synaptic integration. These communicate in such a way that one set of synapses mainly influences the neurons' activity; the other set gates synaptic plasticity. Analysing the system with a constant set of parameters reveals: (1) the afferents that gate plasticity act as supervisors, individual to every cell. (2) While the neurons acquire specific receptive fields the net activity remains constant for different stimuli. This ensures that all stimuli are represented and, thus, contributes to information maximization. (3) Mechanisms for maximization of coherent information can easily be implemented. Neurons with non-overlapping receptive fields learn to fire correlated and preferentially transmit information that is correlated over space. (4) We demonstrate how a new measure of performance can be implemented: cells learn to represent only the part of the input that is relevant to the processing at higher stages. This criterion is termed 'relevant infomax'.

A learning rule for dynamic recruitment and decorrelation

The interest in neuronal networks originates for a good part in the option not to construct, but to train them. The mechanisms governing synaptic modifications during such training are assumed to depend on signals locally available at the synapses. In contrast, the performance of a network is suitably measured on a global scale. Here we propose a learning rule that addresses this conflict. It is inspired by recent physiological experiments and exploits the interaction of inhibitory input and backpropagating action potentials in pyramidal neurons. This mechanism makes information on the global scale available as a local signal. As a result, several desirable features can be combined: the learning rule allows fast synaptic modifications approaching one-shot learning. Nevertheless, it leads to stable representations during ongoing learning. Furthermore, the response properties of the neurons are not globally correlated, but cover the whole stimulus space.

Hereditary internal anal sphincter myopathy causing proctalgia fugax and constipation: further clinical and histological characterization in a patient

Hereditary internal anal sphincter myopathy is a very rare condition, only three families have so far been described in the literature. In this case report further clinical and histological findings of one affected member of one of the above families are presented.