Axonal ion homeostasis and glial differentiation.

The brain is the ultimate control unit of the body. It conducts accurate, fast and reproducible calculations to control motor actions affecting mating, foraging and flight or fight decisions. Therefore, during evolution, better and more efficient brains have emerged. However, even simple brains are complex organs. They are formed by glial cells and neurons that establish highly intricate networks to enable information collection, processing and eventually, a precise motor control. Here, we review and connect some well-established and some hidden pieces of information to set the focus on ion homeostasis as a driving force in glial differentiation promoting signalling speed and accuracy.

Glial-dependent clustering of voltage-gated ion channels in Drosophila precedes myelin formation.

Neuronal information conductance often involves the transmission of action potentials. The spreading of action potentials along the axonal process of a neuron is based on three physical parameters: the axial resistance of the axon, the axonal insulation by glial membranes, and the positioning of voltage-gated ion channels. In vertebrates, myelin and channel clustering allow fast saltatory conductance. Here, we show that in Drosophila melanogaster voltage-gated sodium and potassium channels, Para and Shal, co-localize and cluster in an area resembling the axon initial segment. The local enrichment of Para but not of Shal localization depends on the presence of peripheral wrapping glial cells. In larvae, relatively low levels of Para channels are needed to allow proper signal transduction and nerves are simply wrapped by glial cells. In adults, the concentration of Para increases and is prominently found at the axon initial segment of motor neurons. Concomitantly, these axon domains are covered by a mesh of glial processes forming a lacunar structure that possibly serves as an ion reservoir. Directly flanking this domain glial processes forming the lacunar area appear to collapse and closely apposed stacks of glial cell processes can be detected, resembling a myelin-like insulation. Thus, Drosophila development may reflect the evolution of myelin which forms in response to increased levels of clustered voltage-gated ion channels.

Evolution of glial wrapping: A new hypothesis.

Animals are able to move and react in numerous ways to external stimuli. Thus, environmental stimuli need to be detected, information must be processed and finally an output decision must be transmitted to the musculature to get the animal moving. All these processes depend on the nervous system which comprises an intricate neuronal network and many glial cells. In the last decades, a neurono-centric view on nervous system function channeled most of the scientific interest toward the analysis of neurons and neuronal functions. Neurons appeared early in animal evolution and the main principles of neuronal function from synaptic transmission to propagation of action potentials are conserved during evolution. In contrast, not much is known on the evolution of glial cells that were initially considered merely as static support cells. Although it is now accepted that glial cells have an equally important contribution as their neuronal counterpart to nervous system function, their evolutionary origin is unknown. Did glial cells appear several times during evolution? What were the first roles glial cells had to fulfil in the nervous system? What triggered the formation of the amazing diversity of glial morphologies and functions? Is there a possible mechanism that might explain the appearance of complex structures such as myelin in vertebrates? Here, we postulate a common evolutionary origin of glia and depict a number of selective forces that might have paved the way from a simple supporting cell to a wrapping and myelin forming glial cell.

Brain inflammation triggers macrophage invasion across the blood-brain barrier in Drosophila during pupal stages.

The nervous system is shielded from circulating immune cells by the blood-brain barrier (BBB). During infections and autoimmune diseases, macrophages can enter the brain where they participate in pathogen elimination but can also cause tissue damage. Here, we establish a Drosophila model to study macrophage invasion into the inflamed brain. We show that the immune deficiency (Imd) pathway, but not the Toll pathway, is responsible for attraction and invasion of hemolymph-borne macrophages across the BBB during pupal stages. Macrophage recruitment is mediated by glial, but not neuronal, induction of the Imd pathway through expression of Pvf2. Within the brain, macrophages can phagocytose synaptic material and reduce locomotor abilities and longevity. Similarly, we show that central nervous system infection by group B Streptococcus elicits macrophage recruitment in an Imd-dependent manner. This suggests that evolutionarily conserved inflammatory responses require a delicate balance between beneficial and detrimental activities.

Drosophila ßHeavy-Spectrin is required in polarized ensheathing glia that form a diffusion-barrier around the neuropil.

In the central nervous system (CNS), functional tasks are often allocated to distinct compartments. This is also evident in the Drosophila CNS where synapses and dendrites are clustered in distinct neuropil regions. The neuropil is separated from neuronal cell bodies by ensheathing glia, which as we show using dye injection experiments, contribute to the formation of an internal diffusion barrier. We find that ensheathing glia are polarized with a basolateral plasma membrane rich in phosphatidylinositol-(3,4,5)-triphosphate (PIP3) and the Na+/K+-ATPase Nervana2 (Nrv2) that abuts an extracellular matrix formed at neuropil-cortex interface. The apical plasma membrane is facing the neuropil and is rich in phosphatidylinositol-(4,5)-bisphosphate (PIP2) that is supported by a sub-membranous ßHeavy-Spectrin cytoskeleton. ßHeavy-spectrin mutant larvae affect ensheathing glial cell polarity with delocalized PIP2 and Nrv2 and exhibit an abnormal locomotion which is similarly shown by ensheathing glia ablated larvae. Thus, polarized glia compartmentalizes the brain and is essential for proper nervous system function.

Non-Cell-Autonomous Function of the GPI-Anchored Protein Undicht during Septate Junction Assembly.

Occluding cell-cell junctions are pivotal during the development of many organs. One example is septate junction (SJ) strands, which are found in vertebrates and invertebrates. Although several proteins have been identified that are responsible for septate junction formation in Drosophila, it is presently unclear how these structures are formed or how they are positioned in a coordinated manner between two neighboring cells and within the tissue. Here, we identified a GPI-anchored protein called Undicht required for septate junction formation. Clonal analysis and rescue experiments show that Undicht acts in a non-cell-autonomous manner. It can be released from the plasma membrane by the proteolytic activity of two related ADAM10-like proteases, Kuzbanian and Kuzbanian-like. We propose that juxtacrine function of Undicht coordinates the formation of septate junction strands on two directly neighboring cells, whereas paracrine activity of Undicht controls the formation of occluding junctions within a tissue.

Complaints of heroin-maintained patients: A survey of symptoms ascribed to diacetylmorphine.

Prescribing of injectable diacetylmorphine (DAM) for heroin dependence has raised concerns about its safety. In light of various reports by heroin-maintained patients of DAM-related adverse events, and previously established unwanted effects of opioids in pain management, we undertook a survey in February 2001 of a random sample of 132 (127 participated) of 1061 patients prescribed DAM in Switzerland at that time. The purpose was to document the prevalence rates of a list of unintended symptoms experienced and attributed to DAM by patients. To assess symptom complaints and other data, staff administered a six-page self-report questionnaire. The patients ascribed numerous symptoms to DAM, with the best-known being the most frequently reported (e.g. skin itching, sweating, constipation). Among potentially more problematic complaints ranged irregular menses, cognitive deficits, muscle twitches, labored breathing, pains in the cardiac region, and temporary paralysis of limbs. In the absence of a control group, however, these may also be due to other factors, such as expectation, co-medication, concomitant substance use or co-morbidity. This pilot study emphasizes the necessity of rigorous assessment of the true rates, types, severity and preventability of such complications, especially given the current efforts to establish heroin maintenance as an optional treatment for heroin dependence.

Darbepoetin alpha in lower-than-equimolar doses maintains haemoglobin levels in stable haemodialysis patients converting from epoetin alpha/beta.

BACKGROUND: The conversion of patients on stable epoetin therapy to darbepoetin alpha is usually carried out according to the '1 microg darbepoetin =200 U epoetin' rule, which is based on the protein content of the two compounds. Since several observations have suggested that this conversion factor leads to an overestimate of the required darbepoetin dose, the present multicentre study was designed to assess the true conversion ratio by prospectively evaluating the change in darbepoetin alpha dose after conversion from epoetin, which was required to keep haemoglobin (Hb) stable. METHODS: Haemodialysis patients with stable Hb and maintained on either s.c. or i.v. epoetin (alpha or beta) were switched to intravenously administered darbepoetin alpha according to the 1:200 rule. Subjects treated with epoetin two or three times per week received one weekly dose of darbepoetin alpha, subjects on weekly epoetin received darbepoetin alpha every 2 weeks. For 20 weeks, darbepoetin alpha was changed every 2 weeks according to a pre-specified algorithm, if this was needed to keep Hb within +/-1.0 g/dl of each subject's individual baseline. Thereafter, patients entered a 4-week evaluation period. RESULTS: One hundred ad thirty-two patients in 17 Swiss centres were enrolled and 100 completed the study throughout the evaluation period. While mean Hb was maintained stable between baseline and evaluation period (11.8+/-0.6 g/dl in both), the mean required darbepoetin alpha dose decreased from 34.7+/-2.1 to 26.0+/-1.8 microg (-25%, P<0.0001), yielding a mean final conversion ratio of 1:336. A dose decrease was observed in 56 patients, no dose change in 28 and an increase in 16 patients. Dose reduction strongly depended on baseline epoetin dose: no dose reduction was required for baseline epoetin doses <5000 U/week, whereas a 37% lower mean dose was necessary for baseline doses of 7000-10 000 U/week. The darbepoetin alpha dose reduction did not depend on the previous epoetin type (alpha or beta) or the previous epoetin administration route (i.v. vs s.c.). CONCLUSIONS: The mean darbepoetin alpha dose needed to keep Hb stable in patients previously treated with epoetin is significantly lower than the equimolar dose. Although the equimolar 1:200 conversion ratio is appropriate for lower epoetin doses (<5000 IU/week), the darbepoetin dose for patients converting from >or=5000 IU of epoetin per week is more likely to follow a 1:250 to 1:350 conversion rule. If pricing is based on the 1:200 rule such as in Switzerland, this may translate into cost savings.

Análise das complicaçöes pós-operatórias em decolostomias / Analysis of postoperative complications in colostomy closure

Este estudo teve como objetivo analisar a ocorrência de complicações em pacientes submetidos à colostomia e reconstrução do trânsito intestinal. Para isto, estudou-se 56 pacientes, com idade média de 39 anos, sendo 37 homens e 19 mulheres. As principais indicações para a colostomia foram ferimento por arma de fogo (35 por cento), doença diverticular perfurada (12,5 por cento) e câncer colo-retal (12 por cento). O tipo de colostomia mais realizado foi terminal (70 por cento), com utilização do sigmóide em 71,4 por cento dos casos. O tempo médio de permanência da colostomia foi de 5,5 meses. A reconstrução do trânsito foi realizada através de anastomose término-terminal em 85,7 por cento dos pacientes, através de síntese mecânica com stapler circular em 5 pacientes ou manual em 51 pacientes. Observou-se taxa de complicações de 25 por cento, sendo as mais frequentes a infecção de parede (35,7 por cento), as fístulas (28,6 por cento) e a hemorragia digestiva baixa (21,4 por cento). Conclui-se que a reconstrução do trânsito intestinal não está isenta de riscos cirúrgicos e apresenta taxas consideráveis de complicações pós-operatórias, sendo que a infecção continua a ser um dos maiores desafios existentes neste procedimento.

Análise das complicações pós-operatórias em decolostomias

The aim of the present study was to analyse the complications seen in patients who underwent colostomy and reconstruction of the intestinal tract Fifty six patients, with a mean age of 39 years) were studied _ 37were men and 19 women. The indications for colostomy were: gunshot wounds (35%), perforated diverticulitis (12.5%) and colorectal cancer (12%). Terminal colostomy on the sigmoid colon was the most frequent ostomy performed (71,4%). The mean time for colostomy closure was 5.5 months. In 85.7% of the patients transit reconstruction was performed through an end to end anastomosis, using mechanical suture (in 5 patients), hand sewing (in 51 patients). The rate of complications observed was 25%. The most frequent complications were abdominal wall wound infection (35,7%), fistulas (28.6%) and haemorrhage (21.4%). It was concluded that reconstruction of the intestinal tract carries a high risk of complication and infection continues to be a great challenge in these procedures.

Este estudo teve como objetivo analisar a ocorrência de complicações em pacientes submetidos à colostomia e reconstrução do trânsito intestinal. Para isto, estudou-se 56 pacientes, com idade média de 39 anos, sendo 37 homens e 19 mulheres. As principais indicações para a colostomia foram ferimento por arma de fogo (35%), doença diverticular perfurada (12,5%) e câncer colo-retal (12%). O tipo de colostomia mais realizado foi terminal (70%), com utilização do sigmóide em 71,4% dos casos. O tempo médio de permanência da colostomia foi de 5,5 meses. A reconstrução do trânsito foi realizada através de anastomose término-terminal em 85,7% dos pacientes, através de síntese mecânica com stapler circular em 5 pacientes ou manual em 51 pacientes. Observou-se taxa de complicações de 25%, sendo as mais frequentes a infecção de parede (35,7%), as fístulas (28,6%) e a hemorragia digestiva baixa (21,4%). Conclui-se que a reconstrução do trânsito intestinal não está isenta de riscos cirúrgicos e apresenta taxas consideráveis de complicações pós-operatórias, sendo que a infecção continua a ser um dos maiores desafios existentes neste procedimento.

Estudo da influência do dreno de Penrose na cicatrização de lesão contaminada no ceco de ratos / Study of the Penrose drain influence in rats cecum contaminated injuries

Racional - A utilização de drenos na cavidade abdominal define-sepor princípios específicos, aspectos da experiência pessoal e por vezes em indicações empíricas. A experimentação define critérios que auxiliam as decisões do cirurgião...