The scrapie prion protein is present in flotillin-1-positive vesicles in central- but not peripheral-derived neuronal cell lines

Abstract Transmissible prion diseases are fatal neurodegenerative diseases associated with the conversion of the normal host prion protein (PrP c) into an abnormal isoform (PrP Sc) that accumulates in brain. This pathology affects neurons of the central nervous system whereas no clear toxic effect has been reported for peripheral neurons. We examined the subcellular distribution of PrP c and PrP Sc in the scrapie-infected mouse neuronal cell lines GT1-7 and N2a, derived, respectively, from the central and peripheral nervous system. We observed that in both cell types, PrP c is present in the endocytic compartment, mainly in LAMP-1-positive late endosomes, but excluded from LYAAT-1-lysosomes. In contrast, PrP Sc was distributed differently in the two cell lines. In infected N2a, PrP Sc and PrP c had comparable distribution patterns. In infected GT1-7, PrP Sc is present in an additional vesicular compartment which is flotillin-1-positive. The level of expression of flotillin-1 is higher in GT1-7 than in N2a cells, but no difference is observed between infected and noninfected cells. In Alzheimer's disease patients, it has been reported that flotillin-1 is abundant in brain areas containing the beta-amyloid protein, which accumulates in endosomal vesicles in primary neurons. We propose that the flotillin compartment could store aggregated proteins and play a role in these neurodegenerative pathologies.     

Offer and demand: proliferation and survival of neurons in the dentate gyrus

The proliferation and survival of new cells in the dentate gyrus of mammals is a complex process that is subject to numerous influences, presenting a confusing picture. We suggest regarding these processes on the level of small networks, which can be simulated in silico and which illustrate in a nutshell the influences that proliferating cells exert on plasticity and the conditions they require for survival. Beyond the insights gained by this consideration, we review the available literature on factors that regulate cell proliferation and neurogenesis in the dentate gyrus in vivo. It turns out that the rate of cell proliferation and excitatory afferents via the perforant path interactively determine cell survival, such that the best network stability is achieved when either of the two is increased whereas concurrent activation of the two factors lowers cell survival rates. Consequently, the mitotic activity is regulated by systemic parameters in compliance with the hippocampal network's requirements. The resulting neurogenesis, in contrast, depends on local factors, i.e. the activity flow within the network. In the process of cell differentiation and survival, each cell's spectrum of afferent and efferent connections decides whether it will integrate into the network or undergo apoptosis, and it is the current neuronal activity which determines the synaptic spectrum. We believe that this framework will help explain the biology of dentate cell proliferation and provide a basis for future research hypotheses.     

Chronic Abdominal Pain In Children: a Technical Report of the American Academy of Pediatrics and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

Chronic abdominal pain, defined as long-lasting intermittent or constant abdominal pain, is a common pediatric problem encountered by primary care physicians, medical subspecialists and surgical specialists. Chronic abdominal pain in children is usually functional-that is, without objective evidence of an underlying organic disorder. The Subcommittee on Chronic Abdominal Pain of the American Academy of Pediatrics and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition has prepared this report based on a comprehensive, systematic review and rating of the medical literature. This report accompanies a clinical report based on the literature review and expert opinion.The subcommittee examined the diagnostic and therapeutic value of a medical and psychologic history, diagnostic tests, and pharmacological and behavioral therapy. The presence of alarm symptoms or signs (such as weight loss, gastrointestinal bleeding, persistent fever, chronic severe diarrhea and significant vomiting) is associated with a higher prevalence of organic disease. There was insufficient evidence to state that the nature of the abdominal pain or the presence of associated symptoms (such as anorexia, nausea, headache and joint pain) can discriminate between functional and organic disorders. Although children with chronic abdominal pain and their parents are more often anxious or depressed, the presence of anxiety, depression, behavior problems or recent negative life events does not distinguish between functional and organic abdominal pain. Most children who are brought to the primary care physician's office for chronic abdominal pain are unlikely to require diagnostic testing. Pediatric studies of therapeutic interventions were examined and found to be limited or inconclusive.     

Short communication: HIV type 2 dynamics

To gain a better understanding of why HIV-2 is less virulent than HIV-1 the viral dynamics of HIV-2 were studied in two Swedish HIV-2-infected patients after starting antiretroviral therapy. Linear regression analysis of log virus levels in plasma showed that virus decline during the first 2 weeks of therapy followed an exponential decay with half-lives of 2.2 and 2.0 days, respectively. These half-life measurements reflect the decline in the number of cells actively producing the virus, but may represent an underestimation of the true turnover of HIV-2. In one patient, preliminary estimates of the first and second phase of virus decline (halflife 1.3 and 15 days, respectively) were made. The viral dynamics of HIV-2 infection are strikingly similar to those for HIV-1. Thus, HIV-1 and HIV-2 appear to have similar rates of production and clearance in vivo. Consequently, the large differences in plasma virus levels, virulence, and natural course of the disease between the two infections are due to other factors that are yet to be identified.     

Stroke etiology among Haitians living in Miami

The black Caribbean population continues to grow in the US and little is known about stroke etiologies in that community. We examined stroke subtypes in 175 consecutive Haitian-born patients living in Miami, admitted for acute stroke. Ischemic stroke was diagnosed in 72%. Small vessel occlusion was the most frequent stroke subtype. There was a high prevalence of hypertension, medication noncompliance and intracranial atherosclerosis. Hypertension was the only cardiovascular risk factor significantly associated with small vessel infarction when compared with non-small vessel infarcts.     

Inhibitors of cation-chloride-cotransporters affect hypoxic/hypoglycemic injury in hippocampal slices

Electroneutral cation-chloride cotransporters are abundantly expressed in the brain and are involved in the regulation of the intracellular Cl(-) concentration and thus gamma-aminobutyric acid-dependent inhibition of neuronal excitability. As yet there is little evidence whether or not Na(+)-K(+)-2Cl(-) or K(+)-Cl(-) cotransporters are involved in neuronal hyperexcitability and death in cerebral ischemia. In this study, by measuring propidium iodide staining in organotypic hippocampal slice cultures from young rats and population spike recovery in acutely isolated hippocampal slices from adult rats after a hypoxic/hypoglycemic insult, we were able to assess if cation-chloride cotransport inhibitors reduce neuronal injury. The Na(+)-K(+)-2Cl(-) cotransport inhibitor bumetanide in the range of 1-10 microM reduced neuronal damage in the slice cultures by 25%, but did not affect population spike recovery in acutely isolated slices. In contrast the K(+)-Cl(-) cotransport inhibitor [(dihydroindenyl)oxy] alkanoic acid (DIOA, 100 microM) significantly diminished the restitution of the population spikes from 33% before to 8% after hypoxia/hypoglycemia and increased the damage in the slice cultures by 60%. Consequently, our data suggest that the Na(+)-K(+)-2Cl(-) cotransporter may contribute to neuronal injury and that the activity of the K(+)-Cl(-) cotransporters is an intrinsic protective mechanism of neurons against ischemic damage.     

Computation of tactile object properties requires the integrity of praxic skills

We describe a series of experiments to examine the tactile identification of objects over the course of neurological recovery in a patient with an intracerebral haemorrhage involving the left inferior and superior parietal lobe. Tactile agnosia in this case involved the ipsilesional as well as the contralesional hand, allowing us to observe the effects of dominant parietal lobe damage without the confounding effects of hemiparesis. The findings demonstrate that both apraxia and tactile apperceptive agnosia may result from a unilateral lesion involving the left parietal lobe. The findings further suggest that the computation of macro-geometrical and micro-geometrical tactile object properties is dissociable. Macro-geometrical tactile analysis depends on intact programming of exploratory hand movements, while the role of such movements in micro-geometrical analysis is less clear.     

Homodimerization and internalization of galanin type 1 receptor in living CHO cells

Galanin is a 29- to 30-aa-long neuropeptide affecting feeding, cognitive, and sexual behavior. It exerts its effects through galanin receptors 1, 2 and 3, which are all seven transmembrane domain G-protein coupled receptors (GPCRs). The GPCRs have been shown to function as monomers, homodimers, heterodimers and oligomers. In this study, we examined the extent of galanin receptor 1 (GalR1) dimerization and internalization in living CHO cells using fluorescence resonance energy transfer (FRET) and time lapse confocal imaging. Ratio imaging analysis and emission spectral analysis revealed substantial homodimerization of GalR1. In addition, internalization of GalR1 after 1h of agonist stimulation with the GalR1 agonist galanin (1-29) was observed with time lapse fluorescence imaging, whereas stimulation with the GalR2 specific agonist galanin (2-11) did not lead to internalization. Treatment of GalR1 transfected cells with the non-selective adenylyl cyclase activator forskolin influenced the rate of internalization when administered together with galanin (1-29). These results indicate that GalR1 can act as a dimer on the cell surface and that receptor desensitization and internalization was observed after stimulation with the agonist galanin (1-29). Western blots further confirm the FRET data that GalR1-XFP dimerizes and can be detected in the cell as a monomer or dimer using antibodies to XFP. Internalization and dimerization of GalR1 is shown, contributing to the regulation of galanergic signaling.