Establishing a new model system for phase state measurments: The "swimming neuron" Paramecium

The origin of cellular excitability has not yet been clearly elucidated. It has been proposed that the nonlinear stimulus-response curve of excitable cells, manifesting in all-or-none pulses (action potentials), is based on a phase transition in the cell membrane and is not a purely molecule-based phenomenon. Indeed, typical traces of transitions have already been found in a small number of studies with excitable cells. Further investigations are needed to show whether these findings are of a general nature. In this work, state diagrams of the cell membrane of intact, motile specimens of the ”swimming neuron” Paramecium are measured. Therefore, individual cells were trapped in a microfluidic channel and investigated by fluorescence spectroscopy. The thermo-optical state diagrams exhibited reversible sigmoidal and break-like regimes, which are clear indications for a transition in the cell cortical membranes. This transition had a width of ∼ 10 − 15°C and a midpoint that was located ∼ 4°C below the growth temperature. It can be shifted due to changes in growth temperature or by the addition of an anesthetic (hexanol). These results suggested that the cortical membrane(s) of Paramecia reside in a phase transition regime under physiological growth conditions.Der Ursprung zellulärer Erregbarkeit ist bis heute noch nicht eindeutig geklärt. Es wird vermutet, dass die nichtlineare Reiz-Antwort-Kurve erregbarer Zellen, die sich in Alles-oder-Nichts-Pulsen (Aktionspotentialen) manifestiert, auf einen Phasenübergang in der Zellmembran und nicht auf ein rein molekulares Phänomen zurückzuführen ist. Tatsächlich wurden bereits in wenigen Studien mit erregbaren Zellen typische Spuren von Übergängen gefunden. Ob diese Befunde allgemeiner Natur sind, müssen weitere Ergebnisse zeigen. In dieser Arbeit werden Zustandsdiagramme der Zellmembran intakter, beweglicher Exemplare des ”schwimmenden Neurons” Paramecium gemessen. Dazu wurden einzelne Zellen in einem mikrofluidischen Kanal eingefangen und fluoreszenzspektroskopisch untersucht. Die thermooptischen Zustandsdiagramme zeigten sigmoidale und bruchartige Regime, die klare Hinweise auf einen reversiblen Übergang in den kortikalen Zellmembranen sind. Dieser Übergang hatte eine Breite von ∼ 10 − 15°C und einen Mittelpunkt, der ∼ 4°C unterhalb der Wachstumstemperatur lag. Er kann aufgrund von Änderungen der Wachstumstemperatur oder durch Zugabe eines Anästhetikums (Hexanol) verschoben werden. Diese Ergebnisse legen nahe, dass sich die kortikale(n) Membran(en) von Paramecien unter physiologischen Wachstumsbedingungen im Bereich eines Phasenübergangs befinden

The Role of Noradrenaline in Energy Homeostasis

Obesity is a condition that is associated with excessive weight gain and fat mass storage whose prevalence is increasing within western populations. A variety of co-morbidities are linked to obesity such as type 2 diabetes mellitus, cardiovascular diseases and neurodegenerative disorders, including Alzheimer’s disease and Parkinson’s disease. Together, this contributes to substantial costs of healthcare programs. In non-obese indi- viduals, energy intake and energy expenditure is precisely matched over a long time period in order to maintain energy resources and fat mass. This mechanism, termed energy homeostasis is accomplished by regulatory neuronal networks in the central nervous system (CNS). To better understand and counteract obesity and its co-morbidities, increasing efforts are being made to define the control mechanisms in the CNS, that regulate body weight and energy homeostasis. The focus of this study is the noradrenergic (noradrenaline; NA) modulation of energy homeostasis. Anti-obesity drugs, for example amphetamines, can exert strong anorexigenic effects on eating behaviour in humans. However, these drugs generally affect multiple transmitter and neuromodulator pathways, such as the dopaminergic and serotonergic system, leading to undesired side effects. Pharmacological studies indicate that the anorexigenic effect of amphetamine and related drugs are caused in part by modulation of the NA system. In order to devise strategies and develop specific drugs with minimized side effects in support of weight loss programs, it is critical to understand in detail the mechanisms in the CNS by which NA contributes to energy homeostasis. Besides the well established role of the paraventricular nucleus of the hypothalamus in NA-mediated modulation of food intake, studies indicate that NA input on the homeostatic system in the arcuate nucleus of the hypothalamus (ARC) might also modulate eating behaviour. In the ARC, two key neuronal populations, pro-opiomelanocortin (POMC) and agouti-related peptide (AgRP) expressing neurons sense and integrate peripheral and nutritional signals. Once activated, POMC neurons promote satiety and xi activation of AgRP neurons leads to food intake and decreased energy expenditure. Mechanisms that mediate the possible NA action in the ARC are unknown. In this study, the effect of NA on POMC and AgRP expressing neurons has been investigated. Application of NA inhibits POMC neurons, while AgRP neurons are excited. Pharmacological experiments revealed that these effects are mediated by α2A- and α1A-adrenergic receptors (AR). This suggests a potent NA modulation of food intake. With respect to these effects, afferent projections from NA nuclei and the conditions under which NA is released into the ARC are of greatest interest. As a potential NA source, the locus coeruleus (LC) in the brainstem contains 50% of the NA neurons in CNS. Efferent projections from the LC to the ARC have been identified. Besides the contribution to autonomic functions in general, studies indicate that the LC is also involved in glucose metabolism and the control of brown adipose tissue (BAT). Moreover, BAT thermogenesis is dependent on NA and plasma glucose. Therefore, the effects of changes in extracellular glucose concentrations have been inves- tigated. Around 40% of neurons in the LC responded with increasing spike frequency due to elevated glucose levels, identifying these neurons as glucose-excited. A small subpopulation responded with a moderate inhibition and is considered as glucose- inhibited. Expression of a mutant variant of the ATP dependent potassium channel in mice silenced a large number of LC neurons and abolished responses to glucose. Moreover, sympathetic nerve activity was reduced and led to a white-adipose-tissue-like morphology of BAT, alongside with impairment of thermogenesis. As a consequence of decreased energy expenditure, these mice developed obesity. The modulation of POMC and AgRP neurons by NA indicates a critical role of the catecholamine in the control of energy homeostasis. Moreover, this study reveals that the LC contains glucose-sensing neurons and contributes to the control of glucose metabolism and the activity of BAT. Its projection patterns in the CNS identify the LC as a potential source for NA release into the ARC. These results lead to new insights and the expansion of the current role of NA in the control of energy homeostasis. Importantly, this may help to develop new strategies and drugs with minimized side effects in the treatment of obesity

Long-Term Pioglitazone Treatment Has No Significant Impact on Microglial Activation and Tau Pathology in P301S Mice

Neuroinflammation is one disease hallmark on the road to neurodegeneration in primary tauopathies. Thus, immunomodulation might be a suitable treatment strategy to delay or even prevent the occurrence of symptoms and thus relieve the burden for patients and caregivers. In recent years, the peroxisome proliferator-activated receptor & gamma;(PPAR & gamma;) has received increasing attention as it is immediately involved in the regulation of the immune system and can be targeted by the anti-diabetic drug pioglitazone. Previous studies have shown significant immunomodulation in amyloid-& beta;(A & beta;) mouse models by pioglitazone. In this study, we performed long-term treatment over six months in P301S mice as a tauopathy model with either pioglitazone or placebo. We performed serial 18 kDa translocator protein positron-emission-tomography (TSPO-PET) imaging and terminal immunohistochemistry to assess microglial activation during treatment. Tau pathology was quantified via immunohistochemistry at the end of the study. Long-term pioglitazone treatment had no significant effect on TSPO-PET, immunohistochemistry read-outs of microglial activation, or tau pathology levels in P301S mice. Thus, we conclude that pioglitazone modifies the time course of A & beta;-dependent microglial activation, but does not significantly modulate microglial activation in response to tau pathology

Costs of Measuring Outcomes of Acute Hospital Care in a Longitudinal Outcomes Measurement System

It is widely acknowledged that the measurement of outcomes of care and the comparison of outcomes over time within health care providers and risk-adjusted comparisons among providers are important parts of improving quality and cost-effectiveness of care. However, few studies have assessed the costs of measuring outcomes of care. We sought to evaluate the personnel and financial resources spent for a prospective assessment of outcomes of acute hospital care by health professionals in internal medicine. The study included 15 primary care hospitals participating in a longitudinal outcomes measurement program and 2005 patients over an assessment period with an average duration of 6 months. Each hospital project manager participated in a previously-tested structured 30-minute telephone interview. Outcome measures include time spent by the individual job titles in implementing and running the outcomes measurement program. Job-title-specific times were used to calculate costs from the hospitals' perspective. One-time costs (C2132 + 1352) and administrative costs (95 97 per week) varied substantially. Costs per patient were fairly stable at around 20. We estimated that the total cost for each hospital to assess outcomes of care for accreditation (10 tracer diagnoses over 6 months) would be 9700 and that continuous monitoring of outcomes (5 tracer diagnoses) would cost 12,400 per year. This study suggests that outcomes of acute hospital care can be assessed with limited resources and that standardized training programs would reduce variability in overall costs. This study should help hospital decision makers to estimate the necessary funding for outcomes measurement initiatives