Probing the Biology of Giardia intestinalis Mitosomes Using In Vivo Enzymatic Tagging

Giardia intestinalis parasites contain mitosomes, one of the simplest mitochondrion-related organelles. Strategies to identify the functions of mitosomes have been limited mainly to homology detection, which is not suitable for identifying species-specific proteins and their functions. An in vivo enzymatic tagging technique based on the Escherichia coli biotin ligase (BirA) has been introduced to G. intestinalis; this method allows for the compartment-specific biotinylation of a protein of interest. Known proteins involved in the mitosomal protein import were in vivo tagged, cross-linked, and used to copurify complexes from the outer and inner mitosomal membranes in a single step. New proteins were then identified by mass spectrometry. This approach enabled the identification of highly diverged mitosomal Tim44 (GiTim44), the first known component of the mitosomal inner membrane translocase (TIM). In addition, our subsequent bioinformatics searches returned novel diverged Tim44 paralogs, which mediate the translation and mitosomal insertion of mitochondrially encoded proteins in other eukaryotes. However, most of the identified proteins are specific to G. intestinalis and even absent from the related diplomonad parasite Spironucleus salmonicida, thus reflecting the unique character of the mitosomal metabolism. The in vivo enzymatic tagging also showed that proteins enter the mitosome posttranslationally in an unfolded state and without vesicular transport.     

Exploring the associations between microRNA expression profiles and environmental pollutants in human placenta from the National Children's Study (NCS)

The placenta is the principal regulator of the in utero environment, and disruptions to this environment can result in adverse offspring health outcomes. To better characterize the impact of in utero perturbations, we assessed the influence of known environmental pollutants on the expression of microRNA (miRNA) in placental samples collected from the National Children''s Study (NCS) Vanguard birth cohort. This study analyzed the expression of 654 miRNAs in 110 term placentas. Environmental pollutants measured in these placentas included dichlorodiphenyldichloroethylene (DDE), bisphenol A (BPA), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), arsenic (As), mercury (Hg), lead (Pb), and cadmium (Cd). A moderated t-test was used to identify a panel of differentially expressed miRNAs, which were further analyzed using generalized linear models. We observed 112 miRNAs consistently expressed in >70% of the samples. Consistent with the literature, miRNAs located within the imprinted placenta-specific C19MC cluster, specifically mir-517a, mir-517c, mir-522, and mir-23a, are among the top expressed miRNA in our study. We observed a positive association between PBDE 209 and miR-188–5p and an inverse association between PBDE 99 and let-7c. Both PCBs and Cd were positively associated with miR-1537 expression level. In addition, multiple let-7 family members were downregulated with increasing levels of Hg and Pb. We did not observe DDE or BPA levels to be associated with placental miRNA expression. This is the first birth cohort study linking environmental pollutants and placental expression of miRNAs. Our results suggest that placental miRNA profiles may signal in utero exposures to environmental chemicals.     

Morphological variability of achenes of some European populations of Lactuca serriola L.

This study focuses on the morphological variability of Lactuca serriola achenes in relation to eco-geographic features. Fifty L. serriola populations from four European countries, Czech Republic, Germany, the Netherlands and United Kingdom, were studied. Five morphological characters of the achenes - length and width of achene, length/width index, length of beak, and number of ribs - were evaluated. Significant differences exist in achene morphology of two leaf forms of L. serriola, forma serriola and forma integrifolia. Achenes of f. serriola are shorter, thinner, shorter beaked, lower length/width index, and higher number of ribs compared to f. integrifolia. There was significant variation in the measured characters. Statistical analysis indicated that achene length and width increased along an east-west transect from 2.95 to 3.35 mm and 0.93 to 1.00 mm, respectively. Mean beak length had a similar trend with the exception of German achenes. They had shorter beaks than achenes originating from the Czech Republic with 4.38 and Germany with 4.33 mm. The same trend was evident for L/W index from Czech with a ratio of 3.21 and Germany with 3.14. The number of ribs increased from east to the west in continental Europe, whereas the lowest number of ribs was recorded in achenes collected in Czech with 10.89 and the UK with 10.59. Achene morphology was significantly correlated with three eco-geographic features; longitude, latitude, soil texture of the habitats. The other eco-geographic factors, altitude and population size, did not significantly correlate with the studied characters of L. serriola achenes.     

Verhalten von Eu- und Heterochromatin und interphasisches Kernwachstum beiRhoeo discolor; Vergleich von Mitose und Endomitose

Ohne Zusammenfassung     

A GLASS ELECTRODE APPARATUS FOR MEASURING THE pH VALUES OF VERY SMALL VOLUMES OF SOLUTION

A glass electrode apparatus is described with which pH measurements can be made with as small volumes as 2 drops (about 0.14 cc.) of solution. Using this apparatus the change of pH of the vacuolar sap of Nitella, due to the penetration of brilliant cresyl blue, has been readily followed. The sap and the dye have been found to poison the usual type of hydrogen electrode.