Ultrastructure of the tegument of the cestode Paraechinophallus japonicus (Bothriocephalidea: Echinophallidae), a parasite of the bathypelagic fish Psenopsis anomala

Abstract. The ultrastructure of the tegument in Paraechinophallus japonicus (Bothriocephalidea: Echinophallidae), a cestode parasite of the bathypelagic fish Psenopsis anomala , was studied using scanning and transmission electron microscopy. Paraechinophallus japonicus lacks a true scolex. Four different types of microtriches have been observed on the tegumental surface of P. japonicus. Capilliform (∼2.3-μm long) and blade-like spiniform (∼1.4-μm long) microtriches are intermingled on the surface of the pseudoscolex. Capilliform microtriches are distinct in possessing a short base and a long electron-lucent cap. The strobila is covered with two types of microtriches, namely filiform (∼2.1-μm long) and tusk-shaped microtriches (≤4.5-μm long). Tusk-shaped microtriches are limited to the posterior border of each proglottid and are characterized by a short and narrow base, and a large and wide, sharply pointed, electron-dense cap. Similar tusk-shaped microtriches were previously found in members of the family Echinophallidae and may represent an autapomorphy of echinophallid cestodes, all of them being parasitic in centrolophid fish. A unified terminology of microthrix parts is proposed.     

Inorganic phosphate stimulates the toxic effects of Tl+ in rat liver mitochondria

We studied action of inorganic phosphate (P(i)) on toxic effects of Tl+ in isolated rat liver mitochondria. This is a convenient model to study the toxicity of heavy metals. P(i) markedly retarded contraction of energized mitochondria swollen in the TlNO3 medium and even stronger stimulated swelling and state 4 of succinate-energized mitochondria in the TlNO3 medium. A valinomycin-induced decrease of K+-diffusion potential was also accelerated by Tl+ in the presence of P(i). The mitochondrial permeability transition pore in the medium containing Ca2+, TlNO3, and nitrates of univalent cations was distinctly stimulated by P(i). However, P(i) did not affect both the Tl+-stimulated swelling of nonenergized mitochondria in the TlNO3 medium and swelling of energized mitochondria in the Tl acetate medium. Respiration stimulated by 2,4-dinitrophenol and monoamine oxidase activity of energized mitochondria were not affected by Tl+ regardless of the presence of P(i). We suggested that stimulation by P(i) of toxic action of Tl+ in mitochondria and cells could be due to even greater enhancement of uncoupling of mitochondria as shown by an additional increase of swelling and state 4, and in the greater probability of opening of MPTP in the presence of P(i) and Ca2+.     

A FAK/Src chimera with gain-of-function properties promotes formation of large peripheral adhesions associated with dynamic actin assembly

Formation of a complex between the tyrosine kinases FAK and Src is a key integrin-mediated signaling event implicated in cell motility, survival, and proliferation. Past studies indicate that FAK functions in the complex primarily as a "scaffold," acting to recruit and activate Src within cell/matrix adhesions. To study the cellular impact of FAK-associated Src signaling we developed a novel gain-of-function approach that involves expressing a chimeric protein with the FAK kinase domain replaced by the Src kinase domain. This FAK/Src chimera is subject to adhesion-dependent activation and promotes tyrosine phosphorylation of p130Cas and paxillin to higher steady-state levels than is achieved by wild-type FAK. When expressed in FAK -/- mouse embryo fibroblasts, the FAK/Src chimera resulted in a striking cellular phenotype characterized by unusual large peripheral adhesions, enhanced adhesive strength, and greatly reduced motility. Live cell imaging of the chimera-expressing FAK -/- cells provided evidence that the large peripheral adhesions are associated with a dynamic actin assembly process that is sensitive to a Src-selective inhibitor. These findings suggest that FAK-associated Src kinase activity has the capacity to promote adhesion integrity and actin assembly.     

Setting clock speed in mammals: the CK1 epsilon tau mutation in mice accelerates circadian pacemakers by selectively destabilizing PERIOD proteins

The intrinsic period of circadian clocks is their defining adaptive property. To identify the biochemical mechanisms whereby casein kinase1 (CK1) determines circadian period in mammals, we created mouse null and tau mutants of Ck1 epsilon. Circadian period lengthened in CK1epsilon-/-, whereas CK1epsilon(tau/tau) shortened circadian period of behavior in vivo and suprachiasmatic nucleus firing rates in vitro, by accelerating PERIOD-dependent molecular feedback loops. CK1epsilon(tau/tau) also accelerated molecular oscillations in peripheral tissues, revealing its global role in circadian pacemaking. CK1epsilon(tau) acted by promoting degradation of both nuclear and cytoplasmic PERIOD, but not CRYPTOCHROME, proteins. Together, these whole-animal and biochemical studies explain how tau, as a gain-of-function mutation, acts at a specific circadian phase to promote degradation of PERIOD proteins and thereby accelerate the mammalian clockwork in brain and periphery.     

Exogenous cadaverine induces oxidative burst and reduces cadaverine conjugate content in the common ice plant

The effect of free cadaverine (Cad) on its conjugates formation was analyzed in roots of the common ice plants (Mesembryanthemum crystallinum L.). It was found for the first time that Cad could induce oxidative burst in the roots of adult plants, as was evident from the sharp decrease in the content of Cad soluble or insoluble conjugates. This unusual effect was associated with the increased oxidative degradation of exogenous Cad (1mM, 1.5h) and intense H(2)O(2) production in the root cells of adult plants. Root treatment of both juvenile and adult plants with H(2)O(2) (1mM, 1.5h) reduced the content of soluble Cad conjugates and increased the content of their components, free Cad and phenols. We also found that one of the possible reasons of the negative effect of exogenous diamine on the formation of conjugated forms in adult roots was alkalization of the root apoplast at Cad addition to nutrient medium and the unusual O(2)(-) synthase function as a pH-dependent guaiacol peroxidase in the presence of a high content of H(2)O(2). This was confirmed by the data on the accumulation of O(2)(-) and enhanced superoxide dismutase activity in adult roots under treatment with Cad. It is possible that the accumulation of O(2)(-) together with H(2)O(2) was also responsible for oxidative burst, which induced a decrease in the content of Cad conjugates in adult roots of the common ice plants.     

Mustela or Vison? Evidence for the taxonomic status of the American mink and a distinct biogeographic radiation of American weasels

The American mink’s relationship to the weasels in Mustela has been uncertain. Karyological, morphological, and phylogenetic comparisons to Eurasian Mustela support placing the mink outside the genus as Neovison vison. However, genetic comparisons that incorporate other endemic American Mustela suggest the interpretation of N. vison’s position to Mustela has been handicapped by biased geographic sampling. Here, we analyzed mitochondrial cytochrome-b from all weasels endemic to the Americas, including two poorly known South American species (M. felipei, M. africana), weasels native to North America (M. vison, M. frenata, M. nigripes), Mustela migrant to North America (M. erminea, M. nivalis), palearctic Mustela, and other American members of Mustelidae. Bayesian and likelihood inference methods were used to construct a phylogeny of Mustela, and relaxed Bayesian phylogenetic techniques estimated ages of divergence within the genus using priors calibrated by fossil ages. Our analyses show that the American mink and the smaller Mustela endemic to the Americas represent a distinct phylogenetic heritage apart from their Eurasian cousins, and biogeographic barriers like the Bering and Panamanian land bridges have influenced the evolutionary history of Mustela in the Americas.     

Midzone organization restricts interpolar microtubule plus‐end dynamics during spindle elongation

To study the dynamics of interpolar microtubules (iMTs) in Saccharomyces cerevisiae cells, we photobleached a considerable portion of the middle region of anaphase spindles in cells expressing tubulin‐green fluorescent protein (GFP) and followed fluorescence recovery at the iMT plus‐ends. We found that during anaphase, iMTs show phases of fast growth and shrinkage that are restricted to the iMT plus‐ends. Our data indicate that iMT plus‐end dynamics are regulated during mitosis, as fluorescence recovery was faster in intermediate anaphase (30 s) compared with long (100 s) and pre‐anaphase (80 s) spindles. We also observed that deletion of Cin8, a microtubule‐crosslinking kinesin‐5 motor protein, reduced the recovery rate in anaphase spindles, indicating that Cin8 contributes to the destabilization of iMT plus‐ends. Finally, we show that in cells lacking the midzone organizing protein Ase1, iMTs are highly dynamic and are exchangeable throughout most of their length, indicating that midzone organization is essential for restricting iMT dynamics.     

Synthesis and ocular effects of imidazole nitrolic acid and amidoxime esters

Esters of 1-(H)-imidazole-5-nitrolic acid and 1-methyl-imidazole-5-carboxamide oxime were prepared to study the effect of esterification on the ocular effects of these compounds. Esterifications were performed with acid chloride. Acid chloride also reacts with the ring nitrogen of 1-(H)-imidazole-5-nitrolic acid, but the desired esters could be selectively prepared by adjustment of the reaction conditions. Esterification led to loss of the ocular effects exhibited by the parent compounds.     

Ribokinase from E. coli: expression, purification, and substrate specificity

Ribokinase (RK) was expressed in the Escherichia coli ER2566 cells harboring the constructed expression plasmid encompassing the rbsK gene, encoding ribokinase. The recombinant enzyme was purified from sonicated cells by double chromatography to afford a preparation that was ca. 90% pure and had specific activity of 75 micromol/min mg protein. Catalytic activity of RK: (i) is strongly dependent on the presence of monovalent cations (potassium>ammonium>cesium), and (ii) is cooperatively enhanced by divalent magnesium and manganese ions. Besides D-ribose and 2-deoxy-D-ribose, RK was found to catalyze the 5-O-phosphorylation of D-arabinose, D-xylose, and D-fructose in the presence of ATP, and potassium and magnesium ions; L-ribose and L-arabinose are not substrates for the recombinant enzyme. A new radiochemical method for monitoring the formation of D-pentofuranose-5-[32P]phosphates in the presence of [gamma-32P]ATP and RK is reported.     

Efficacy of a fipronil bait in reducing the number of fleas (Oropsylla spp.) infesting wild black‐tailed prairie dogs

Bubonic plague (Yersinia pestis) is a deadly zoonosis with black‐tailed prairie dogs (Cynomys ludovicianus) as a reservoir host in the United States. Systemic insecticides are a promising means of controlling the vectors, Oropsylla spp. fleas, infesting these prairie dogs, subsequently disrupting the Y. pestis cycle. The objective of this study was to conduct a field trial evaluating the efficacy of a grain rodent bait containing fipronil (0.005%) against fleas infesting prairie dogs. The study was performed in Larimer County, CO, where bait was applied to a treatment area containing a dense prairie dog population, three times over a three‐week period. Prairie dogs were captured and combed for fleas during four study periods (pre‐, mid‐, 1^st post‐, and 2^nd post‐treatment). Results indicated the use of bait containing fipronil significantly reduced flea burden. The bait containing fipronil was determined to reduce the mean number of fleas per prairie dog >95% for a minimum of 52 days post‐initial treatment application and 31 days post‐final treatment application. These results suggest the potential for this form of treatment to reduce flea population density on prairie dogs, and subsequently plague transmission, among mammalian hosts across the United States and beyond.