Neural bases of cognitive ERPs: more than phase reset

Up to now, two conflicting theories have tried to explain the genesis of averaged event-related potentials (ERPs): Whereas one hypothesis claims that ERPs originate from an event-related activation of neural assemblies distinct from background dynamics, the other hypothesis states that ERPs are produced by phase resetting of ongoing oscillatory activity. So far, this question has only been addressed for early ERP components. Late ERP components, however, are generally thought to represent superimposed activities of several anatomically distinct brain areas. Thus, the question of which mechanism underlies the genesis of late ERP components cannot be easily answered based on scalp recordings. In contrast, two well-investigated late ERP components recorded invasively from within the human medial temporal lobe (MTL) in epilepsy patients, the so-called MTL-P300 and the anterior MTL-N400 (AMTL-N400), are based on single source activity. Hence, we investigated whether the MTL-P300 and the AMTL-N400 are based on an event-related activity increase, a phase reset of ongoing oscillatory activity or both. ERPs were recorded from the hippocampus and rhinal cortex in subjects performing a visual oddball paradigm and a visual word recognition paradigm. With wavelet techniques, stimulus-related phase-locking and power changes were analyzed in a frequency range covering 2 to 48 Hz. We found that the MTL-P300 is accompanied by both phase reset and power increase and that both effects overlap partly in time. In contrast, the AMTL-N400 is initially associated with phase locking without power increase and only later during the course of the AMTL-N400 we observed an additional power increase. In conclusion, both aspects, event-related activation of neural assemblies and phase resetting of ongoing activity seem to be involved in the generation of late ERP components as recorded in cognitive tasks. Therefore, separate analysis of event-related power and phase-locking changes might reveal specific insights into the mechanisms underlying different cognitive functions.     

Reversible loss of vision in severe preeclampsia: case report and review of the literature

Visual disturbances occur in up to 25 % of the patients with preeclampsia. However, blindness remains a rare phenomenon. A 39 year old primigravida was admitted for observation at 30 weeks gestation with signs of preeclampsia. After 11 days she suffered a complete loss of vision. The blindness reversed completely after cesarean section and antihypertensive treatment. Blindness in preeclamptic patients is mostly caused by hypertensive encephalopathy. We discuss pathophysiological aspects as well as diagnostic approaches and therapeutic options with respect to the available literature.     

Impact of three-dimensionally measured endometrial volume on the pregnancy rate after intrauterine insemination

OBJECTIVE: The success of artificial reproductive techniques not only depends on the quality of oocytes and spermatozoa but also on the receptivity of the endometrium. The aim of this study was to assess the role of endometrial volume measurement by three-dimensional ultrasound in predicting the pregnancy rate (PR) in women receiving controlled ovarian hyperstimulation followed by intrauterine insemination. MATERIAL AND METHODS: 104 patients having intrauterine insemination (IUI) were included in this prospective trial. Ovarian hyperstimulation was performed with gonadotropins in 73 % of patients and with clomiphene citrate (CC) in 27 % of patients. Endometrial thickness, pattern and three-dimensional volume were measured immediately before insemination. RESULTS: In 104 IUI cycles a total of 14 clinical pregnancies were recorded (PR=13.5 %). The endometrial volume was 3.5 ml and was not significantly different in pregnant (4.0 +/- 1.5 ml) from non-pregnant women (3.4 +/- 1.9 ml). In the subgroup of women with an endometrial volume > or = 2 ml and trilaminar endometrium the pregnancy rate was 22 %, significantly higher than that in women without these two criteria (PR 6 %, p < 0.05). The negative predictive value of an endometrial volume < 2 ml for a clinical pregnancy after IUI was 96 %. Endometrial volume and thickness were significantly higher after ovarian hyperstimulation with gonadotropins (3.7 ml and 11.0 mm) than with CC (2.8 ml and 9.5 mm; p < 0.05). CONCLUSIONS: An endometrial volume < 2 ml at the day of insemination is associated with a poor likelihood of pregnancy. Endometrial volume measured by 3D ultrasound is a new objective parameter to predict endometrial receptivity.     

Trends in birth statistics in Europe

Obstetrics services in Europe are dominated by a persistently low birth rate, the average number of children born to a woman in her lifetime now being 1,45 for the European Community in general. This low rate has persisted for the last 20 years. During the past 10 years, childlessness has been steadily increasing. Maternal age at first delivery has also increased. Obstetric departments are increasingly subject to market principles and the trend towards centralization, which has been developing for some years, will continue.     

Influence of the intramural innervation on the morphogenesis of the enteroendocrine cells and the genetic construct involved (review)

The influence of intramural intestinal innervation on the morphogenesis of the mucosa and in particular of the enteroendocrine cells (EECs) has been studied on male Wistar rats with morphometric, autoradiographic and immuno-histochemical methods in the duodenum, proximal and distal jejunum and ilium before and after myenteric ablation with benzalkonium chloride (BAC). Twenty-one days after denervation alterations were observed in the mucosal structure with thickening of the mucosa, increase in the proliferation rate and with changes in numerical and spatial distribution of D-cells, I-cells, N-cells, glucagon and glicentin i.r. L-cells and 5-HT i.r. cells which myenteric ablation caused. Analysis of the genetic constructs involved in the alterations of EECs on the EECs provide evidence for the cAMP responsive elements as the main mediator.     

Hippocampal function and visual object processing in temporal lobe epilepsy

Limbic event-related potentials related to verbal but not to visual recognition memory have been found to be attenuated within the epileptic hippocampus of patients with temporal lobe epilepsy (TLE). To identify hippocampal contributions to visual processing and memory we recorded intracranial ERPs directly from within the epileptic and the non-epileptic hippocampus in 12 patients with unilateral TLE during a visual object decision and naming task. While the non-epileptic hippocampus differentiated reliably between real and nonsense objects, this effect was completely eliminated within the epileptic mesial temporal lobe. This finding suggests that the hippocampus proper contributes to the semantic processing of visual objects and may help to explain visual memory deficits in TLE.     

Inhibition of ATP-induced surfactant exocytosis by dihydropyridine (DHP) derivatives: a non-stereospecific, photoactivated effect and independent of L-type Ca2+ channels

Purinergic stimulation of surfactant secretion via exocytosis of lamellar bodies is mediated by an elevation of the intracellular Ca2+ concentration ([Ca2+](i)). We tested the dihydropyridine (DHP) analogues isradipine (+/-enantiomers), nifedipine and Bay K 8644 (racemic forms) on ATP-induced surfactant secretion and [Ca2+](i) in single type II cells, using FM1-43 and fura-2 fluorescence. None of the DHPs (2 microM) had an effect on ATP-induced surfactant secretion in the dark. They did, however, inhibit secretion in a concentration-dependent manner during illumination, particularly with UV light. This effect was not stereospecific, because it was mimicked by (-)-isradipine. In addition, (+)- or (-)-isradipine, but not nifedipine or Bay K 8644, elicited a slow increase of [Ca2+](i) during illumination with UV light, which was reversible by exposure to dark. None of the DHPs inhibited the ATP-induced Ca2+ signal. In perforated patch clamp experiments, depolarizing voltage steps did not induce L-type Ca2+ (Sr(2+)) currents, even in the presence of the agonist Bay K 8644 (1 microM). We conclude that impairment of ATP-induced surfactant secretion by all tested DHPs and alterations of Ca2+ homeostasis by isradipine are photoactivated effects, independent of L-type Ca2+ channels.     

Noncardiac surgery in patients with left ventricular assist devices

BACKGROUND. Noncardiac surgery, especially abdominal surgical procedures in patients with long-term mechanical circulatory support and strong anticoagulation, is difficult. METHODS. We report on 14 patients (aged 44 +/- 15 years) with a portable Novacor or HeartMate system, who underwent noncardiac surgical procedures while being supported by the device. RESULTS. The patients underwent 20 procedures for noncardiac reasons; most had an intestinal operation or cholecystectomy. Half of the procedures were performed within 30 days after placement of the device (mean interval, 53 +/- 57 days), only 6 interventions were necessary after 100 days of mechanical support. Complications occurred in 8 patients (57%), 5 of whom had undergone cholecystectomy and had unacceptably high sanguineous drainage losses. CONCLUSIONS. An elective surgical procedure can be performed with an acceptable risk if the operation is carefully managed. Postponing resumption of full anticoagulation is advisable as it may reduce bleeding complications without apparently increasing the risk for thromboembolism. Emergency interventions remain a difficult task.