CT findings in patients with chronic thrombembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is thought to be a rare complication of pulmonary embolism. However, it was recently demonstrated that CTEPH is more common than previously thought after pulmonary embolism. Without treatment, CTEPH is associated with a very high mortality rate. Making the correct diagnosis early is essential, because there is a potential curative treatment in the form of pulmonary thromboendarterectomy (PTE). Because of the unspecific clinical symptoms of CTEPH, the different imaging modalities play a crucial role in diagnosis making. Since the introduction of the multidetector CT technology, CT has become an important part in the diagnostic work up of pulmonary embolism and CTEPH and is often used as a first-line diagnostic tool. CT is not only a reliable tool for the diagnosis of CTEPH, but also is helpful in estimating the operability of these patients. PTE is still associated with a mortality rate of about 10%. Particularly an insufficient decrease of the pulmonary vascular resistance after PTE leads to a very high mortality rate. Therefore, it is crucial to correlate the degree of the surgical accessible obstruction of the pulmonary vasculature with the degree of pulmonary hypertension in deciding for or against PTE. The aim of this review is to describe the CT findings in patients with CTEPH and their use in differentiating CTEPH from other diseases like acute pulmonary embolism and primary pulmonary hypertension. Moreover, the correlation of different CT imaging features with surgical success after PTE will be discussed.     

Individual value of brain tissue oxygen pressure, microvascular oxygen saturation, cytochrome redox level, and energy metabolites in detecting critically reduced cerebral energy state during acute changes in global cerebral perfusion

The authors assessed the diagnostic value of brain tissue oxygen tension (PbrO2), microvascular oxygen saturation (SmvO2), cytochrome oxidase redox level (Cyt a+a3 oxidation), and cerebral energy metabolite concentrations in detecting acute critical impairment of cerebral energy homeostasis. Each single parameter as well as derived multimodal indices (arteriovenous difference in oxygen content [AVDO2], cerebral metabolic rate for oxygen [CMRO2], fractional microvascular oxygen extraction [OEF]) were investigated during controlled variation of global cerebral perfusion using a cisternal infusion technique in 16 rabbits. The objective of this study was to determine whether acute changes between normal, moderately, and critically reduced cerebral perfusion as well as frank ischemia defined by local cortical blood flow (lcoBF), brain electrical activity (BEA), and brain stem vasomotor control can be reliably identified by SmvO2, PbrO2, Cyt a+a3 oxidation, or energy metabolites (glutamate, lactate/pyruvate ratio). PbrO2, SmvO2, and Cyt a+a3 oxidation, but not cerebral perfusion pressure, were closely linked to lcoBF and BEA and allowed discrimination between normal, moderately reduced, and critically reduced cerebral perfusion (P < 0.01). Glutamate concentrations and the lactate/pyruvate ratio varied significantly only between moderately reduced cerebral perfusion and frank ischemia (complete loss of BEA and brain stem vasomotor control). Therefore, PbrO2, SmvO2, and Cyt a+a3 oxidation, but not glutamate and the lactate/pyruvate ratio, reliably predict the transition from moderately to critically reduced cerebral perfusion with impending energy failure.     

Transcriptional activators Cat8 and Sip4 discriminate between sequence variants of the carbon source-responsive promoter element in the yeast<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis>

The structural genes for gluconeogenesis in the yeast Saccharomyces cerevisiae are activated by the carbon source-responsive element (CSRE) found in the respective upstream regions. Regulatory genes CAT8 and SIP4 both encode zinc-cluster proteins which can bind to CSRE motifs and activate target genes under conditions of glucose deprivation. In this work, we describe a functional analysis of sequence variants containing single mutations within the strongly activating CSRE(ICL1) motif. While the sequence CCNNNNNNCCG was required as the minimal UAS for gene activation by both Cat8 and Sip4, the activators responded differently to sequence variations in the central part of the CSRE. Our results allowed us to derive a consensus sequence for efficient gene activation by Cat8 (YCCNYTNRKCCG), while a more specific motif is required for activation by Sip4 (TCCATTSRTCCGR). Although their zinc cluster domains are clearly related, Cat8 and Sip4 are not isofunctional. This conclusion is further supported by the finding that biosynthetic derepression of Cat8 in the presence of a nonfermentable carbon source precedes that of Sip4 by about 90 min.     

Detection of nitric oxide synthase (NOS) immunoreactive neurons in the human septal area: a matter of method?

There is a remarkable discrepancy between biochemical and cell morphological findings with regard to the presence of NADPH diaphorase/neuronal nitric oxide synthase (NOS) in the primate septal area. Whereas considerable concentrations of neuronal nitric oxide synthase and high enzyme activities have been measured in postmortem human septal nuclei, histochemical studies were either unable to detect any nitric oxide synthase immunoreactivity in primate septal neurons, or found only a very few nitrergic neurons in this region. This study aimed to investigate the possible presence of nitrergic neurons in human the septal region in greater detail. After having studied a total of 16 postmortem human brains we conclude that the immunohistochemical demonstration of nitric oxide synthase in human septal neurons is largely dependent on the mode of tissue handling: in brain specimens which were fixed en-bloc with paraffin and embedded in paraplast, nitric oxide synthase immunoreactivity is barely detectable, whereas a satisfying immunostaining is obtained on free-floating frozen sections after an immersion–fixation with 4% paraformaldehyde and 0.5% glutaraldehyde, followed by sucrose protection of the specimens. We show herein that there are indeed nitric oxide synthase-containing neurons in the human septum, thus supporting results from previous biochemical studies.     

Effects of hippocampal lesions on acquisition and retention of spatial learning in zebra finches

We tested the role of the hippocampus in spatial memory of zebra finches. The birds were trained to find the location of a food site among four identical feeders arranged on the aviary floor. Extra-maze cues were present. The birds had to perform the task from four different starting points. Successful visits and the time to find the food were recorded. Hippocampal lesions made before acquisition led to a decrease in correct choices. Hippocampal lesions following training disrupted the retention of the spatial memory. Surprisingly, birds with hippocampal damage reached the food as quickly as intact birds, but they needed more visits to find the correct feeder. Therefore, the birds with hippocampal damage used an alternative, nonspatial memory-based strategy to find the food.     

Long-term results of bilateral pallidal stimulation in Parkinson's disease

We followed up 11 patients for up to 5 years after bilateral pallidal deep brain stimulation for advanced Parkinson's disease. Dyskinesias remained significantly reduced until the last assessment. The initial improvement of off-period motor symptoms and fluctuations, however, was not sustained and gradually declined. Beneficial effects of pallidal deep brain stimulation on activities of daily living in the on- and off-period were lost after the first year. Replacement of pallidal electrodes into the subthalamic nucleus in four patients could restore the initial benefit of deep brain stimulation and allowed a significant reduction of dopaminergic drug therapy.     

c-fos is induced in the hippocampus during consolidation of sexual imprinting in the zebra finch (Taeniopygia guttata)

c-fos was used to mark regions of enhanced neuronal activity during sexual imprinting, an early learning process by which information about the prospective sexual partner is acquired and consolidated. In the present study, we demonstrate that the hippocampus, already known for its specialized spatial memory capacities in navigating pigeons and in food-storing birds, depicts a selective differential c-fos induction in a situation shown to lead to sexual imprinting, that is, exposing previously isolated male birds to a female for 1 h. c-fos induction is lateralized, the left hippocampus showing more c-fos activity than the right. Our results would indicate a role for the hippocampus in the consolidation process of imprinting, probably in the transfer of information to the other telencephalic areas that show alterations in synaptic connectivity as a result of consolidation of sexual imprinting.     

Effect of routine MR imaging of the brain at 1.5 T on subsequent magnetoencephalography: results in nine volunteers

PURPOSE: To investigate whether routine magnetic resonance (MR) imaging of the brain with a whole-body 1.5-T imager affects the results of subsequent magnetoencephalography (MEG). MATERIALS AND METHODS: Nine healthy volunteers (six women, mean age of 23 years, age range of 20-27 years; three men, mean age of 24 years, age range of 23-25 years) underwent one MEG session before and two MEG sessions after MR imaging of the brain. The first MEG session was completed about 20 minutes before brain MR imaging began, the second MEG session (MEG 2) was performed within 30 minutes after MR imaging, and the third MEG session was performed 2 hours after MEG 2. Each MEG session involved measurement of spontaneous brain activity and, in seven patients, of brain activity during stimulation of the median nerve. MR imaging included T1- and T2-weighted fast spin-echo and gradient-echo sequences applied with a 1.5-T clinical imager. Data were compared by using a repeated-measures analysis of variance (general linear model) both with and without Greenhouse-Geisser correction. RESULTS: MEG signals were detected and measured without difficulty in all volunteers. No statistically significant difference was seen between estimated noise at MEG before and after MR imaging (P =.588 with correction, P =.665 without correction). MEG records obtained in all volunteers enabled localization of evoked response to median nerve stimulation before and after MR imaging. No measurable differences were observed between relative power spectra of spontaneous brain activity before and after MR imaging (P >.290 with correction, P >or=.295 without correction). CONCLUSION: No measurable effect of 1.5-T brain MR imaging on subsequent MEG was detected.