Several human fecal isolates of Bacteroides have been found to produce bacteriocins. The bacteriocin-producing strain Ti-i was studied in the most detail. Strain Tl-l belongs to the 0061-1 deoxyribonucleic acid (DNA) homology group of Bacteroides. This homology group phenotypically resembles Bacteroides thetaiotaomicron but has little DNA homology with it. The bacteriocinproducing strains Ti-12 and Ti-48 belong to the 3452-A DNA homology group. This group has DNA homology with B. thetaiotaomicron and Bacteroides ovatus. The bacteriocin-producing strain Ti-42 remains unidentified in that it does not belong to any recognized DNA homology group of the saccharolytic intestinal bacteroides. The extracellular bacteriocin produced by strain Ti-i was specifically bactericidal for other bacteria within the genus Bacteroides. The highest bacteriocin titers (32 to 64) were produced in complex media, with only trace amounts being produced in a defined medium. The bacteriocin appeared to have a high molecular weight (-300,000) and was unusual because it was stable from pH 1 to.,12 and only a 50% reduction in activity resulted after 15 min at 12i°C in an autoclave. It was inactivated by trypsin and Pronase. Strain Tl-l was isolated from all three fecal samples obtained over a 25-week period from an individual who was part of a National Aeronautics and Space Administration mock Skylab flight. Strains Ti-12, Ti-48, and Ti-42 were isolated only from the first fecal sample. Each of these strains was immune to the bacteriocins produced by the others. These strains were found to coexist in the colon with a larger population of non-bacteriocin-producing, bacteriocin-susceptible strains of Bacteroides.

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Background: The forefront treatment of Parkinson's disease (PD) is Levodopa. When patients are treated with Levodopa cerebral blood flow is increased while cerebral metabolic rate is decreased in key subcortical regions including the putamen. This phenomenon is especially pronounced in patients with Levodopa-induced dyskinesia (LID).Method: To study the effect of clinically-determined anti-parkinsonian medications, 10 PD patients (5 with LID and 5 without LID) have been scanned with FDG-PET (a probe for glucose metabolism) and perfusion MRI (a probe for cerebral blood flow) both when they are ON and OFF medications. Patients additionally underwent resting state fMRI to detect changes in dopamine-mediated cortico-striatal connectivity. The degree of blood flow-glucose metabolism dissociation was quantified by comparing the FDG-PET and perfusion MRI data.Results: A significant interaction effect (imaging modality × medication; blood flow-glucose metabolism dissociation) has been found in the putamen (p = 0.023). Post-hoc analysis revealed that anti-parkinsonian medication consistently normalized the pathologically hyper-metabolic state of the putamen while mixed effects were observed in cerebral blood flow changes. This dissociation was especially predominant in patients with LID compared to those without. Unlike the prior study, this differentiation was not observed when cortico-striatal functional connectivity was assessed.Conclusion: We confirmed striatal neurovascular dissociation between FDG-PET and perfusion MRI in response to clinically determined anti-parkinsonian medication. We further proposed a novel analytical method to quantify the degree of dissociation in the putamen using only the ON condition scans, Putamen-to-thalamus Hyper-perfusion/hypo-metabolism Index (PHI), which may have the potential to be used as a biomarker for LID (correctly classifying 8 out 10 patients). For wider use of PHI, a larger validation study is warranted.