The electron transport chain in anaerobically functioning eukaryotes

AbstractMany lower eukaryotes can survive anaerobic conditions via a fermentation pathway that involves the use of the reduction of endogenously produced fumarate as electron sink. This fumarate reduction is linked to electron transport in an especially adapted, anaerobically functioning electron-transport chain.An aerobic energy metabolism with Krebs cycle activity is accompanied by electron transfer from succinate to ubiquinone via complex II of the respiratory chain. On the other hand, in an anaerobic metabolism, where fumarate functions as terminal electron acceptor, electrons are transferred from rhodoquinone to fumarate, which is the reversed direction. Ubiquinone cannot replace rhodoquinone in the process of fumarate reduction in vivo, as ubiquinone can only accept electrons from complex II and cannot donate them to fumarate. Rhodoquinone, with its lower redox potential than ubiquinone, is capable of donating electrons to fumarate. Eukaryotic fumarate reductases were shown to interact with rhodoquinone (a benzoquinone), whereas most prokaryotic fumarate reductases interact with the naphtoquinones menaquinone and demethylmenaquinone.Fumarate reductase, the enzyme essential for the anaerobic functioning of many eukaryotes, is structurally very similar to succinate dehydrogenase, the Krebs cycle enzyme catalysing the reverse reaction. In prokaryotes these enzymes are differentially expressed depending on the external conditions. Evidence is now emerging that also in eukaryotes two different enzymes exist for succinate oxidation and fumarate reduction that are differentially expressed

Is paromomycin the drug of choice for eradication of Dientamoeba fragilis in adults?

Dientamoeba fragilis is a debated protozoan parasite that is often detected in stools of patients with chronic gastro-intestinal complaints. A retrospective follow-up study of a large cohort of patients was performed to better understand the natural course of the infection and possible treatment options. D. fragilis was spontaneously cleared in 41% of untreated cases. With an eradication rate of 98%, treatment with paromomycin appeared more effective than treatment with clioquinol (83%) or metronidazole (57%)

Tailoring endocrine therapy in early breast cancer:prolonged duration and potential drawbacks

This dissertation focuses on the hormonal treatment of postmenopausal women with early-stage breast cancer, with the focus on the question what the optimal duration of this treatment is and what the potential side effects are. We have concluded that prolonging adjuvant hormonal therapy with an aromatase inhibitor from 3 to 6 years, after 2-3 years of tamoxifen treatment, should only be considered if there is a high risk of disease recurrence, for example in the presence of regional lymph node metastases. The second part of this thesis focuses on the treatment of a specific subgroup of women with breast cancer who have become postmenopausal as a result of chemotherapy. The third part focuses on the development of bone density during hormonal therapy

Recurrent amebic liver abscesses over a 16-year period: A case report

Background: Amebic liver abscess is a rare disease in high-income countries. Recurrence of amebic liver abscess is even rarer with only a few previous reports. Here we present a patient who developed three subsequent amebic liver abscesses over a sixteen-year period. Case presentation: A Caucasian male developed recurrent amebic liver abscesses, when aged 23, 27 and 39 years. Only on the first occasion did this coincide with a recent visit to the tropics. The patient received adequate treatment during each episode. Possible explanations are persistent asymptomatic carrier state, cysts passage in his family, re-infection or chance. Conclusion: We describe the unusual case of a healthy male who developed recurrent amebic liver abscesses over a long period despite adequate treatment. Possible pathophysiological explanations are explored