Imaging African trypanosomes

Trypanosoma brucei are extracellular kinetoplastid parasites transmitted by the blood-sucking tsetse fly. They are responsible for the fatal disease human African trypanosomiasis (HAT), also known as sleeping sickness. In late-stage infection, trypanosomes cross the blood–brain barrier (BBB) and invade the central nervous system (CNS) invariably leading to coma and death if untreated. There is no available vaccine and current late-stage HAT chemotherapy consists of either melarsoprol, which is highly toxic causing up to 8% of deaths, or nifurtimox–eflornithine combination therapy (NECT), which is costly and difficult to administer. There is therefore an urgent need to identify new late-stage HAT drug candidates. Here, we review how current imaging tools, ranging from fluorescent confocal microscopy of live immobilized cells in culture to whole-animal imaging, are providing insight into T. brucei biology, parasite-host interplay, trypanosome CNS invasion and disease progression. We also consider how imaging tools can be used for candidate drug screening purposes that could lead to new chemotherapies

Simonide, Eumelos et la Korinthiaka (Simon. 545 PMG): un fragment irrecuperable?

In proof of the story about Medea's rule over Corinth, the scholiast quotes some verses coming apparently from Simonides, although previously he named Eumelos too. There is no doubt that this poet of the Corinthian school of epic would be a much better authority than Simonides is. A new examination of the quotations shows that originally there were two separate verses, one from Eumelos, the other from Simonides. Only the latter is well preserved.No dispoinible

The role of moral residue in determining the reality of genuine moral dilemmas.

Thesis (M.A.)-University of Natal, Pietermaritzburg, 2003.The debate surrounding whether genuine moral dilemmas exist or is a longstanding one. Proponents of the existence of genuine moral dilemmas like Ruth Barcan Marcus and Bernard Williams have appealed to the moral residue argument as a means of proving that moral dilemmas exist. Opponents like WaIter SinnottArmstrong, Patricia Greenspan, and Terence McConnell, however, have denied its efficacy on the basis that the moral residue argument begs the question on two counts: Firstly, by assuming that rationally irresolvable conflicts of commitments exist, and secondly, by assuming that agents who experience moral residue have necessarily done something wrong. I argue in this thesis that there is a way that the moral residue argument can be salvaged and provide a more precise account of appropriate moral residue - an account that simultaneously overcomes the objections. Specifically, I argue that the moral residue argument, when interpreted in terms ofthe independent standard of integrity, can provide an account of appropriate moral residue that can explain what the agent has done wrong, and that is neither too strict nor overlooks the fact ofthe agent's harsh self-assessment and moral residue. In so doing I show how the specific accounts of appropriate moral residue assumed in the objections are flawed and miss the force of the point about moral residue. By examining two case studies - Williams Styron's Sophie 's Choice, and Euripides' Jphigenia at Aulis - I show that it can be established independently that both Sophie and Agamemnon do something wrong and would do something wrong no matter how they acted in their respective situations. Through Lynn McFall's conception of integrity I show that Sophie and Agamemnon would undermine their integrity regardless ofwhich oftheir alternative they chose to act on. In so doing I establish that their moral residue is appropriate and would be appropriate had they acted on their other alternative. By this means I demonstrate how - when interpreted in terms of the independent standard of integrity - the moral residue argument can support the existence of genuine moral dilemmas

Untersuchung des Lipidgehalts und Beeinflussung der Lipidproduktion von Mikroalgen durch Nährstofflimitierung : Optimierung und Anwendung der Lipidmarkierung mit Nilrot

Mikroalgen sind in der Lage Lipide zu produzieren, welche für die Nahrungsmittel-, Biotreibstoff- und Tierfutterindustrie von grosser Bedeutung sind. Damit eine Produktion wirtschaftlich ist, muss der Lipidgehalt und die Biomassenproduktion der Mikroalgen maximiert werden. Der Lipidgehalt in Mikroalgen ist hauptsächlich von der Nährstoffverfügbarkeit, im speziellen Stickstoff, abhängig. Für die Bestimmung des Lipidgehalts wird eine rasche Messmethode benötigt. Dazu eignet sich die Markierung der Lipide mit Nilrot mit anschliessender Fluoreszenzmessung. Aus diesem Grund wurde die Nilrotmethode optimiert und in einem Ver-such zur Beeinflussung der Lipidproduktion durch Entzug von Nährstoffen angewendet. Die optimierte Methode der Nilrot-Fluoreszenz wurde mit der gravimetrischen Lipidbestimmung mittels Soxhlet-Extraktion verglichen. Für die Beeinflussung der Lipidproduktion wurden Chlamydomonas noctigama, Chlorella vulgaris und Tetradesmus obliquus bei einer Limitierung aller Nährstoffe, einer Limitierung von Stickstoff und einem nicht-nährstofflimitierten Medium über 24 Tagen inkubiert und überwacht. Die Proben für die Messung des Lipidgehalts wurden für 30 Minuten bei Raumtemperatur in DMSO inkubiert. Der Lipidgehalt wurde nach zehn Minuten Anfärbezeit in einer Mikrotiterplatte bei einer Anregung von 535 nm und einer Emission von 595 gemessen. Das optimierte Protokoll zeigte eine mässige Korrelation mit der Bestimmung des Lipidgehalts mittels Soxhlet-Extraktion. Die Beeinflussung der Lipidproduktion ergab, dass mit dem Entzug von Nährstoffen der Lipidgehalt in den Mikroalgen bis zu 4.5-fach erhöht werden konnte. Dabei ergab eine Limitierung aller Nährstoffe zwar höhere Lipidgehalte pro mg Trockenmasse, der Lipidgehalt in der Kultur lag bei der Stickstofflimitierung höher. Die Methode der Nilrot-Fluoreszenz eignet sich für eine halbquantitative Bestimmung von Lipiden in Mikroalgen. Wird eine quantitative Bestimmung verlang, muss die Nilrotfluoreszenz immer mit einer gravimetrischen Methode überprüft werden. Der Entzug von Nährstoffen führte eindeutig zur Erhöhung der Lipidproduktion, jedoch zu einer Abnahme des Wachstums. Für eine Optimierung dieses Verhältnisses sind noch weitere Untersuchungen nötig.Microalgae are able to produce lipids that are of great importance for the food, biofuel and animal feed industries. For production to be economical, the lipid content and biomass production of microalgae must be maximized. The lipid content in microalgae depends mainly on the availability of nutrients, in particular nitrogen. For the determination of the lipid content a rapid measuring method is required. The marking of lipids with Nile red with subsequent fluorescence measurement is suitable for this purpose. For this reason, the Nile red method was optimized and used in an experiment to influence lipid production by removing nutrients. The optimized method of Nile red fluorescence was compared with gravimetric lipid determination using Soxhlet extraction. To influence lipid production, Chlamydomonas noctigama, Chlorella vulgaris and Tetradesmus obliquus were incubated and monitored for 24 days with a limitation of all nutrients, a limitation of nitrogen and a medium not limited to nutrients. The samples for lipid measurement were incubated in DMSO for 30 minutes at room temperature. The lipid content was measured after ten minutes staining time in a microtiter plate at an excitation of 535 nm and an emission of 595. The optimized protocol showed a moderate correlation with the determination of the lipid content using Soxhlet extraction. The influence on lipid production showed that with the removal of nutrients the lipid content in the microalgae could be increased up to 4.5-fold. Although a limitation of all nutrients resulted in higher lipid contents per mg dry matter, the lipid content in the culture was higher with nitrogen limitation. The Nile red fluorescence method is suitable for the semi-quantitative determination of lipids in microalgae. If a quantitative determination is required, the Nile red fluorescence must always be checked by a gravimetric method. The removal of nutrients clearly led to an increase in lipid production, but a decrease in growth. Further investigations are necessary to optimize this ratio

Immunopathological aspects of trypanosomal meningoencephalitis in vervet monkeys after relapse following BerenilR treatment

Four quarantined vervet monkeys were treated with intramuscular BerenilR in patent CNS infection after experimental trypanosome inoculation with Trypanosoma brucei rhodesiense or T. brucei brucei. All four animals relapsed in the post-therapeutic survival time of 37 to 209 days when they had fully developed meningoencephalitis in histological sections with the presence of interstitial intracerebral trypanosomes, which were confirmed in two monkeys by electron microscopy. In both, sequential samples of the serum and cerebrospinal fluid were analysed for circulating immune complexes, immunoglobulins and albumin. From these results the intracerebral IgG synthesis and the impairment of the blood-brain-barrier were calculated, both being present in advanced infection. Circulating immune complexes were present in the serum, but could not be demonstrated in the cerebrospinal fluid. The monkey model therefore permits the study of various aspects of cerebral trypanosomiasis. BerenilR treatment is inefficient in patent CNS infection and leads to a protracted, less virulent disease course with terminal meningoencephalitis and intracerebral "persister” trypanosomes. This drug-induced trypanosome shift with meningoencephalitis could be used for chemotherapeutic purposes to test new compounds in late stage diseas

T. brucei cathepsin-L increases arrhythmogenic sarcoplasmic reticulum-mediated calcium release in rat cardiomyocytes

Aims: African trypanosomiasis, caused by Trypanosoma brucei species, leads to both neurological and cardiac dysfunction and can be fatal if untreated. While the neurological-related pathogenesis is well studied, the cardiac pathogenesis remains unknown. The current study exposed isolated ventricular cardiomyocytes and adult rat hearts to T. brucei to test whether trypanosomes can alter cardiac function independent of a systemic inflammatory/immune response. Methods and results: Using confocal imaging, T. brucei and T. brucei culture media (supernatant) caused an increased frequency of arrhythmogenic spontaneous diastolic sarcoplasmic reticulum (SR)-mediated Ca2+ release (Ca2+ waves) in isolated adult rat ventricular cardiomyocytes. Studies utilising inhibitors, recombinant protein and RNAi all demonstrated that this altered SR function was due to T. brucei cathepsin-L (TbCatL). Separate experiments revealed that TbCatL induced a 10–15% increase of SERCA activity but reduced SR Ca2+ content, suggesting a concomitant increased SR-mediated Ca2+ leak. This conclusion was supported by data demonstrating that TbCatL increased Ca2+ wave frequency. These effects were abolished by autocamtide-2-related inhibitory peptide, highlighting a role for CaMKII in the TbCatL action on SR function. Isolated Langendorff perfused whole heart experiments confirmed that supernatant caused an increased number of arrhythmic events. Conclusion: These data demonstrate for the first time that African trypanosomes alter cardiac function independent of a systemic immune response, via a mechanism involving extracellular cathepsin-L-mediated changes in SR function

Cardiac Alterations in Human African Trypanosomiasis (T.b. gambiense) with Respect to the Disease Stage and Antiparasitic Treatment

In Human African Trypanosomiasis (HAT), neurological symptoms dominate and cardiac involvement has been suggested. Because of increasing resistance to the available drugs for HAT, new compounds are desperately needed. Evaluation of cardiotoxicity is one parameter of drug safety, but without knowledge of the baseline heart involvement in HAT, cardiologic findings and drug-induced alterations will be difficult to interpret. The electrocardiogram (ECG) is a tool to evaluate cardiac involvement and the risk of arrythmias. We analysed the ECG of 465 HAT patients and compared them with the ECG of 61 healthy volunteers. In HAT patients the QTc interval was prolonged. This comprises a risk of fatal arrhythmias if new drugs with antiarrhythmic potential will be used. Further, repolarization changes and low voltage were more frequent than in healthy controls. This could be explained by an inflammation of the heart. Treatment of HAT was associated with appearance of repolarization changes but not with a QTc prolongation. These changes appear to be associated with the disease, but not with a specific drug. The main conclusion of this study is that heart involvement is frequent in HAT and mostly well tolerated. However, it can become relevant, if new compounds with antiarrhythmic potential will be used

Computation of Lipid Headgroup Interactions

The equilibrium structure of lipid aggregates is determined by the balance of numerous forces between hydrophobic acyl chains, hydrophilic lipid headgroups, and the lipid\u27s environment. Among these forces, lipid headgroup interactions are both important to the stability of lipid structures and responsible for many of the interactions between biological membranes and aqueous solutes including ions and soluble peptides. In order to model these headgroup interactions, we consider the electrical properties of the headgroup molecules via the multipole expansion. While common lipid headgroups such as phosphatidylcholine are electrically neutral, they are characterized by non-zero higher order terms in the multipole expansion. Making a dipole approximation, we employ a two dimensional lattice of classical dipoles to model the headgroup networks of lipid aggregates. Restrictions to each dipole\u27s position and orientation are imposed to account for the effect of hydrocarbon chains which are not included in the model. A Monte Carlo algorithm is used to calculate headgroup-headgroup interactions and network energies in both dipole and point-charge approximations