Trophic niche ontogeny and palaeoecology of early Toarcian Stenopterygius (Reptilia: Ichthyosauria)

Reconstructing ecological niche shifts during ontogeny in extinct animals with no living analogues is difficult without exceptional fossil collections. Here we demonstrate how a previously identified ontogenetic shift in the size and shape of the dentition in the early Toarcian ichthyosaur Stenopterygius quadriscissus accurately predicts a particular dietary shift. The smallest S. quadriscissus fed on small, burst‐swimming fishes, with a steady shift towards faster moving fish and cephalopods with increasing body size. Larger adult specimens appear to have been completely reliant on cephalopods, with fish completely absent from gut contents shortly after onset of sexual maturity. This is consistent with a previously proposed ontogenetic niche shift based on tooth shape and body size, corroborating the idea that dental ontogeny may be a useful predictor of dietary shifts in marine reptiles. Applying the theoretical framework used here to other extinct species will improve the resolution of palaeoecological reconstructions, where appropriate sample sizes exist.     

Trichinella spiralis: comparison of stages in host intestine with those of an Arctic Trichinella sp

The intestinal phase of Trichinella spiralis and of Trichinella sp. isolated in the Arctic were compared in experimental animals. Reproductive capacity, pathogenicity, distribution, and persistence of adults in the small intestine, morphological measurements, and release of newborn larvae in vitro were examined. Numerous passages of 40 days each for T. spiralis and the Trichinella sp. isolate in mice did not affect reproductive capacity, distribution of adults in the small intestine, and size of worms. Reproductive capacity index for T. spiralis, I = 151.27 ± 27.30 was significantly higher compared to the Trichinella sp. isolate index, I = 63.46 ± 19.34. The Trichinella sp. isolate was more pathogenic to mice and wild rodents compared to T. spiralis during the intestinal phase. Both parasites were located in the anterior part of the small intestine but the position of T. spiralis adults (P = 17.08) differed from position of the Trichinella sp. isolate adults (P = 23.46) in the small intestine. Intestinal phase of T. spiralis was longer (20 days) compared to the Trichinella sp. isolate (15 days) but sex ratios (:♂) were similar for both parasites. T. spiralis females released significantly higher numbers of larvae in vitro/24 hr compared to the Trichinella sp. isolate. Release of larvae was continuous during the intestinal phase and the average fecundity for T. spiralis was 335 larvae/female and for the Trichinella sp. isolate 114 larvae/female. Adults of T. spiralis and the Trichinella sp. isolate were morphologically indistinguishable and did not differ in size. A comparative index for the intestinal phase is proposed for comparison of any Trichinella spp. isolates and standard T. spiralis.     

Altered patterns and synthesis of extracellular matrix macromolecules in early osteoarthritis.

The synthesis and contents of extracellular non-collagenous matrix macromolecules was studied in early and late human osteoarthritic (OA) cartilage obtained at surgery for sarcomas in the lower extremities (normal and early OA) or for total knee replacement (late stage OA). The early OA samples were those that had some fibrillation in the joint by visual examination. One group had fibrillation in the area sampled and the other group had no fibrillation. Cartilage was taken from the same topographical area on the medial femoral condyle in all the samples, labeled with [3H]leucine and [35S]sulfate for 4 h at 37 degrees C and extracted with 4 M guanidine-HCl. Analysis of the extracts showed that the total amount of proteoglycans relative to hydroxyproline content was higher in the early and late OA than in the normal cartilage. These proteoglycans showed a relatively lower [35S]sulfate incorporation into GAG chains and a higher [3H]leucine incorporation. The pattern of newly synthesized proteins was altered similarly in early and late OA. Notably, synthesis of cartilage oligomeric matrix protein (COMP), fibronectin, and cartilage intermediate layer protein (CILP) was increased, also reflected in their abundance as determined by enzyme-linked immunosorbent assay (ELISA). Collagen synthesis appeared significantly increased only in the late stage OA. The observed altered composition and pattern of biosynthesis indicate that the joint undergoes metabolic alterations early in the disease process, even before there is overt fibrillation of the tissue. The early OA samples studied appear to represent two distinct groups of early lesions in different stages of the process of cartilage deterioration as shown by their differences in relative rates of synthesis and abundance of proteins.     

Spatial variation in population density across the geographical range in helminth parasites of yellow perch Perca flavescens

The abundance of a species is not constant across its geographical range; it has often been assumed to decrease from the centre of a species’ range toward its margins. The central assumption of this “favourable centre” model is tested for the first time with parasites, using different species of helminth parasites exploiting fish as definitive hosts. Data on prevalence (percentage of hosts that are infected) and abundance (mean no. parasites per host) were compiled for 8 helminth species occurring in 23 populations of yellow perch Perca flavescens, from continental North America. For each parasite species, correlations were computed between latitude and both local prevalence and abundance values. In addition, the relationships between the relative prevalence or abundance in one locality and the distance between that locality and the one where the maximum value was reported, were assessed separately for each species to determine whether abundance tends to decrease away from the presumed centre of the range, where it peaks. For both the cestode Proteocephalus pearsei and the acanthocephalan Leptorhynchoides thecatus, there was a positive relationship between prevalence or abundance and the latitude of the sampled population. There was also a significant negative relationship between relative prevalence and the distance from the locality showing the maximum value in P. pearsei, but no such pattern was observed for the other 7 parasite species. Since this single significant decrease in prevalence with increasing distance from the peak value may be confounded by a latitudinal gradient, it appears that the distribution of abundance in parasites of perch does not follow the favourable centre model. This means that the environmental variables affecting the density of parasites (host availability, abiotic conditions) do not show pronounced spatial autocorrelation, with nearby sites not necessarily providing more similar conditions for the growth of parasite populations than distant sites.     

Effects of the emerald ash borer invasion on the community composition of arthropods associated with ash tree boles in Maryland,U.S.A.

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Structure of Ddn, the deazaflavin-dependent nitroreductase from Mycobacterium tuberculosis involved in bioreductive activation of PA-824

Tuberculosis continues to be a global health threat, making bicyclic nitroimidazoles an important new class of therapeutics. A deazaflavin-dependent nitroreductase (Ddn) from Mycobacterium tuberculosis catalyzes the reduction of nitroimidazoles such as PA-824, resulting in intracellular release of lethal reactive nitrogen species. The N-terminal 30 residues of Ddn are functionally important but are flexible or access multiple conformations, preventing structural characterization of the full-length, enzymatically active enzyme. Several structures were determined of a truncated, inactive Ddn protein core with and without bound F(420) deazaflavin coenzyme as well as of a catalytically competent homolog from Nocardia farcinica. Mutagenesis studies based on these structures identified residues important for binding of F(420) and PA-824. The proposed orientation of the tail of PA-824 toward the N terminus of Ddn is consistent with current structure-activity relationship data.     

Regulation of cell proliferation by nucleocytoplasmic dynamics of postnatal and embryonic exon-II-containing MBP isoforms

The only known structural protein required for formation of myelin, produced by oligodendrocytes in the central nervous system, is myelin basic protein (MBP). This peripheral membrane protein has different developmentally-regulated isoforms, generated by alternative splicing. The isoforms are targeted to distinct subcellular locations, which is governed by the presence or absence of exon-II, although their functional expression is often less clear. Here, we investigated the role of exon-II-containing MBP isoforms and their link with cell proliferation. Live-cell imaging and FRAP analysis revealed a dynamic nucleocytoplasmic translocation of the exon-II-containing postnatal 21.5-kDa MBP isoform upon mitogenic modulation. Its nuclear export was blocked upon treatment with leptomycin B, an inhibitor of nuclear protein export. Next to the postnatal MBP isoforms, embryonic exon-II-containing MBP (e-MBP) is expressed in primary (immature) oligodendrocytes. The e-MBP isoform is exclusively present in OLN-93 cells, a rat-derived oligodendrocyte progenitor cell line, and interestingly, also in several non-CNS cell lines. As seen for postnatal MBPs, a similar nucleocytoplasmic translocation upon mitogenic modulation was observed for e-MBP. Thus, upon serum deprivation, e-MBP was excluded from the nucleus, whereas re-addition of serum re-established its nuclear localization, with a concomitant increase in proliferation. Knockdown of MBP by shRNA confirmed a role for e-MBP in OLN-93 proliferation, whereas the absence of e-MBP similarly reduced the proliferative capacity of non-CNS cell lines. Thus, exon-II-containing MBP isoforms may regulate cell proliferation via a mechanism that relies on their dynamic nuclear import and export, which is not restricted to the oligodendrocyte lineage.     

Synthesis, structural characterization and in vitro cytotoxicity and anti-bacterial activity of some copper(I) complexes with N,N′-disubstituted thioureas

A series of copper(I) complexes of N,N′-disubstituted thioureas, [C₆H₅CONHCSNHR]Cu(I)Cl where R = C₆H₅ (1a), 2-ClC₆H₄ (2a), 3-ClC₆H₄ (3a), 4-ClC₆H₄ (4a), 2,3-Cl₂C₆H₃ (5a), 2,4-Cl₂C₆H₃ (6a), 2,5-Cl₂C₆H₃ (7a), 2,6-Cl₂C₆H₃ (8a), 3,4-Cl₂C₆H₃ (9a) and 3,5-Cl₂C₆H₃ (10a) have been synthesized. These complexes (1a–10a) have been characterized by elemental analyses, IR, ¹H and ¹³C NMR spectroscopy, cyclic voltammetry and single crystal XRD for 1a and 8a, and for ligand 7. The X-ray crystal structures reveal that the complexes 1a and 8a are mononuclear in the solid state in which the copper atoms adopt a distorted tetrahedral geometry. In both the cases, the neutral N,N′-disubstituted thiourea ligands have been coordinated to the Cu(I) through the sulphur atom in a terminal mode. The complexes have been screened for their in vitro cytotoxic activity in human cell lines carcinomas A498 (Renal), EVSA-T (Breast), H226 (Lung), IGROV (Ovarian), M19 (Melanoma-Skin), MCF-7 (Breast) and WIDR (Colon). They show a moderate cytotoxicity against these seven human cancer cell lines comparable to that of the less active standard chemotherapeutic drugs used for comparison. They were also screened for their anti-bacterial activity and were found less active than the standard drug Imipenem.