Phosphate translocator and adenylate translocator in chromoplast membranes

It is shown by the criteria of saturation kinetics, specificity, and inhibition experiments that chromoplast membranes from the daffodil flower contain a phosphate translocator for the counter-exchange of phosphate, and 3-phosphoglycerate, as well as phosphoenolpyruvate; they also contain an adenylate translocator. This is the first report on the occurrence of these translocators in non-green plastids. Both translocators exhibit certain dissimilar properties when compared to the corresponding systems of chloroplasts. The transport rates of both translocators are sufficient to allow a prominent fatty acid synthesis in isolated chromoplasts when C₃ intermediates of the glycolytic pathway or adenine nucleotides are used as energy sources.     

A Structural Study of Isolated Mammalian Centrioles Using Negative Staining Electron Microscopy

We have used a combination of centrifugation onto electron microscope grids and negative staining to study the structure of isolated mammalian centrioles. The technique relies on visualisation of structural detail by use of a goldthioglucose negative stain. The approach provides an easy structural definition of the mature and immature centriole and has revealed some novel proximal projections on the mature centriole. The rapid technique should prove of use in future analyses of centriolar structure and biochemistry.     

Tricholongins BI and BII, 19-residue peptaibols from Trichoderma longibrachiatum. Solution structure from two-dimensional NMR spectroscopy

Two nonadecapeptides, tricholongins BI and BII, which display antifungal and antibacterial activities, have been isolated from in vitro cultures of the fungus Trichoderma longibrachiatum. The peptides were separated by reversed-phase HPLC; their amino acid compositions were determined by gas chromatography and their sequences by positive-ion fast-atom-bombardment mass spectrometry and high-field NMR. These linear peptides, containing mainly hydrophobic L-amino acids, 8-9 2-aminoisobutyric acid residues and exhibiting an acetylated N-terminal residue and an amino alcohol C-terminal leucinol belong to the peptaibol class. The methanol solution structure of tricholongins BI and BII has been investigated using both one- and two-dimensional NMR techniques. The total 1H-NMR and 13C-NMR assignments are given. By a combination of the 3JNH,C alpha H coupling constant values, temperature coefficients of the NH and CO groups, amide hydrogen/deuterium-exchange rate measurements and NOE data, a secondary structure for tricholongins in solution has been proposed. Both peptides adopt a similar alpha-helical conformation with a hinge around Pro13 resulting from two 3(10) bonds. The results suggest that the N-terminus contains mixed alpha/3(10) bonds. The membrane permeability modifications induced by tricholongins have been assayed by the use of liposomes composed of egg phosphatidylcholine with 20-30% cholesterol. The peptide-induced leakage of an entrapped fluorescent probe has been followed by fluorescence spectroscopy. In a concentration range of 0.13-0.31 microM, tricholongins induce the leakage of 50% of the entrapped material in 20 min.     

Microornamentation of leaf chameleons (Chamaeleonidae: Brookesia,Rhampholeon, and Rieppeleon)—with comments on the evolution of microstructures in the chamaeleonidae

Chameleons (Chamaeleonidae) feature many adaptations to their arboreal lifestyle, including zygodactylous feet, a prehensile tail, and epidermal microstructures. In arboreal tree chameleons, the substrate‐contacting site of the feet and tail is covered by microscopic hair‐like structures (setae) of 6–20 µm length. Their friction enhancing function has been shown in recent studies. Leaf chameleons and one representative of the tree chameleons (Chamaeleo namaquensis) secondarily have become ground‐dwelling. Because leaf chameleons are paraphyletic, one could expect that in the three leaf chameleon genera Brookesia, Rhampholeon, and Rieppeleon and the tree chameleon Ch. namaquensis, epidermis has adapted independently to terrestrial locomotion. Using scanning electron microscopy, we investigated the substrate‐contacting surfaces of the feet (subdigital) of 17 leaf chameleon species and five tree chameleon species that have not yet been examined. Additionally, surfaces not involved in locomotion, the flanks (dorsolateral), and scale interstices, were examined. Although the subdigital microstructures in leaf chameleons are more diverse than in tree chameleons, we found some features across the genera. The subdigital microornamentation of Rhampholeon spinosus consists of long thin setae and spines, comparable to those of tree chameleons. All other Rhampholeon species have spines or short but broad setae. Rh. spectrum had tooth‐like structures instead of setae. Subdigital scales of Brookesia have either thorns or conical scale‐tops in the center and feature honeycomb microstructures. In Rieppeleon, subdigital scales have a thorn. Scale surfaces are covered by honeycombs and short hair‐like structures (spines). As subdigital scales with a thorn in the center and honeycomb microstructures were also found in the terrestrial tree chameleon Ch. namaquensis, one can assume that this geometry is a convergent adaptation to terrestrial locomotion. Despite the great number of genus‐specific traits, the convergent evolution of honey‐comb structures in Brookesia, Rieppeleon, and Ch. namaquensis and the high variability of spines and setae in Rhampholeon suggests a rapid adaptation of subdigital microornamentation in Chamaeleonidae. J. Morphol. 276:167–184, 2015. © 2014 Wiley Periodicals, Inc.     

Body nitrosation potential measured by a novel N breath test

Oxygenated nitrogen species, for example, the protonated form of nitrous acid (H₂ONO⁺), dinitrogentrioxide (N₂O₃), dinitrogentetroxide (N_2O4), or peroxynitrite (ONOO⁻), can react with amines to form molecular nitrogen. These reactions can occur spontaneously with primary aliphatic amines or via cytochrome P450 catalysed reactions with secondary amines. In principle measurements of the excretion of the molecular nitrogen generated by these reactions could be used as an index of the levels of oxygenated nitrogen compounds acting as nitrosating agents. To test this idea, [¹⁵N₂]urea (3 mmol) was administered orally to five patients infected with Helicobacter pylori (as diagnosed by the [¹³C]urea breath test) and to four healthy volunteers. All participants ingested 3-mmol sodium nitrate as a precursor for NA 5 min before the ingestion of the nitrogen tracer. During the test the participants breathed 100% oxygen to increase the sensitivity of detection of endogenous molecular nitrogen. After the administration of [¹⁵N₂]urea, the patients with H. pylori showed significantly increased ¹⁵N enrichments of exhaled N₂, expressed as δ value (‰), compared with healthy volunteers (patients: 3.5 ± 0.9 vs. volunteers: 1.3 ± 0.4; p < .05). We speculate that the endogenous production of molecular nitrogen is a protective process controlling the body NO and nitrite levels. The ¹⁵N breath technique allows the noninvasive estimation of the body nitrosation and could indicate the health risk, possibly the oxidative stress status, caused by highly reactive oxygenated nitrogen species and carbenium ion intermediates.     

Abundance, encystment and sedimentation of acantharia during autumn 1990 in the East Greenland Sea

The abundance and sedimentation of acantharia and their cystswas recorded in the water column and sediment traps in the EastGreenland Sea in August-September 1990. Although acanthariaconstituted <1% of total suspended particulate organic carbon(POC) in the water column, up to 90% (average 55%) of the POCsedimenting in 100 m was present in the form of acanthariancysts during a 9 day drift experiment. Rapid dissolution ofstrontium sulphate, of which their shells and spines are constructed,was evidenced by their disappearance with depth in the watercolumn, maximum dissolution occurring between 500 and 1000 mwater depth. Mass encystment and sedimentation of this singlegroup of sarcodine protozoa can have dramatic effects on, themeasurement of particulate fluxes in the open ocean, and maybe a recurrent phenomenon in the eastern North Atlantic.     

A fossil <Emphasis Type="Italic">Potadoma</Emphasis> (Gastropoda: Pachychilidae) from Pleistocene central Kalahari fluvio-lacustrine sediments

A shell of the gastropod Potadoma was discovered in fluvio-lacustrine sediments of the Kalahari (Botswana). A late Pleistocene age of the sediments of ca. 46,000 cal. years BP was established by radiocarbon dating. It is the first record of the freshwater genus Potadoma from southern Africa. Modern counterparts as well as other Pleistocene species of Potadoma had been reported elsewhere from (palaeo-) habitats located at least 2,000 km further in the north, e.g., in the Congo Basin. So far it can be only speculated about possible causes for such a disjunct distribution. The discovery of Potadoma and five more fossil gastropods from the same sediments was used to outline palaeolimnological features. Considering the geomorphological setting, the assemblage of fossil gastropods indicates that the nowadays mainly dry Boteti River was permanently flowing through the western Makgadikgadi Pans ca. 46,000 cal. years BP. The existence of such a riverine palaeoenvironment in the pans demonstrates that the so-called Lake Palaeo-Makgadikgadi was comparatively small during that time, not spanning the area of investigation.