Ticks harbor and excrete chronic wasting disease prions

Chronic wasting disease (CWD) is a fatal neurodegenerative disease caused by infectious prions (PrP^CWD) affecting cervids. Circulating PrP^CWD in blood may pose a risk for indirect transmission by way of hematophagous ectoparasites acting as mechanical vectors. Cervids can carry high tick infestations and exhibit allogrooming, a common tick defense strategy between conspecifics. Ingestion of ticks during allogrooming may expose naïve animals to CWD, if ticks harbor PrP^CWD. This study investigates whether ticks can harbor transmission-relevant quantities of PrP^CWD by combining experimental tick feeding trials and evaluation of ticks from free-ranging white-tailed deer (Odocoileus virginianus). Using the real-time quaking-induced conversion (RT-QuIC) assay, we show that black-legged ticks (Ixodes scapularis) fed PrP^CWD-spiked blood using artificial membranes ingest and excrete PrP^CWD. Combining results of RT-QuIC and protein misfolding cyclic amplification, we detected seeding activity from 6 of 15 (40%) pooled tick samples collected from wild CWD-infected white-tailed deer. Seeding activities in ticks were analogous to 10-1000 ng of CWD-positive retropharyngeal lymph node collected from deer upon which they were feeding. Estimates revealed a median infectious dose range of 0.3-42.4 per tick, suggesting that ticks can take up transmission-relevant amounts of PrP^CWD and may pose a CWD risk to cervids.

Interfacial electrostatics of poly(vinylamine hydrochloride), poly(diallyldimethylammonium chloride), poly-l-lysine, and poly-l-arginine interacting with lipid bilayers

Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from SHG spectroscopy and QCM-D measurements.

A feasibility study comparing checklists and global rating forms to assess resident performance in clinical skills

This study evaluated the feasibility of two different scoring forms for assessing the clinical performance of residents in anaesthesiology. One of the forms had a checklist format including task-specific items and the other was a global rating form with general dimensions of competence including 'clinical skills', 'communication skills' and 'knowledge'. Thirty-two clinicians representing 25 (83%) of the 30 training hospitals in the country participated in the study. The clinicians were randomized into two groups, each of which used one of the scoring formats to assess a resident's performance in four simulated clinical scenarios on videotape. Clinicians' opinions about the appropriateness of the scoring forms were rated on a scale of 1-5. The checklist format was rated significantly higher compared with the global rating form (mean 4.6, 0.5 vs. mean 3.5, 1.4, p < 0.001). The inter-rater agreement regarding pass/fail decisions was poor irrespective of the scoring form used. This was explained by clinicians' leniency as assessors rather than by lack of vigilance in the observations or disagreements on standards for good performance.

Characterization and mass load estimates of organic compounds in agricultural irrigation runoff

Investigations of agricultural chemicals in surface runoff typically target nutrients or specific pesticides; however, numerous other organic compounds are regularly applied to agricultural fields in pesticide formulations, irrigation water, soil amendments and fertilizers. Many of these compounds have toxicological significance. We conducted a broad spectrum analysis of surface runoff from individual irrigated agricultural fields in coastal southern California to characterize organic compounds amenable to analysis by gas chromatography-mass spectrometry and to estimate the mass flux of selected chemicals. Aqueous phase extracts contained several pesticides, as well as personal care product ingredients and pharmaceutically active compounds apparently derived from treated wastewater used for irrigation. Several compounds potentially associated with pesticide adjuvants were also present in aqueous phase extracts. Dissolved NOM constituents in water phase extracts included n-fatty acids, aliphatic alcohols and plant terpenoids. Tentatively identified compounds sorbed to suspended particles included pesticides, a fecal sterol, aliphatic and alicyclic hydrocarbons, aliphatic alcohols, aldehydes, and C14 and C16 n-fatty acids and fatty acid esters. Bicyclic and polycyclic aromatic hydrocarbons were identified in both aqueous and suspended particle phases. Constituent concentrations, including total suspended solids (TSS), varied over the course of the sampled events by up to an order of magnitude, and typically were not correlated with flow. Variation in sorbed organic compound concentrations often did not parallel those for TSS concentration. Mass load estimates were strongly influenced by the choice of sampling interval.

Lactoperoxidase-induced protein oxidation in milk

The reaction between lactoperoxidase (LPO) and H(2)O(2) in the presence of bovine serum albumin (BSA), beta-lactoglobulin, or casein was investigated for the formation of protein radicals by freeze-quench electron spin resonance (ESR) and by the formation of the protein oxidation product, dityrosine. The presence of BSA resulted in a dramatic change after 1 min of reaction in the obtained ESR spectrum compared with the spectrum obtained for LPO and H(2)O(2) alone. Furthermore, experiments employing BSA or beta-lactoglobulin resulted in the formation of long-lived protein radicals detectable 10 min after initiation of the reaction. The presence of casein resulted in a minor change in the fine structure of the ESR spectrum after 1 min of reaction compared with LPO and H(2)O(2) alone, but no difference between the two reaction mixtures could be observed after 10 min of reaction. The formation of dityrosine could be detected in reaction mixtures containing LPO and H(2)O(2) after 1 and 10 min of incubation at 25 degrees C both in the absence and in the presence of BSA, beta-lactoglobulin, or casein. The presence of casein resulted in an increased dityrosine concentration compared with the reaction with LPO and H(2)O(2) alone. Endogenous LPO in unpasteurized milk was activated at 25 degrees C by adding 1 mM H(2)O(2). Radical species could be detected directly in the milk by freeze-quench ESR during the initial phase of the reaction, and dityrosine could be measured after 4 h of incubation. The role of LPO activity in the formation of ESR detectable radical species and dityrosine in milk was further verified in ultrahigh temperature (UHT) milk with no endogenous enzyme activity, as the formation of ESR detectable radical species and dityrosine took place in UHT milk only upon the addition of both H(2)O(2) and exogenous LPO.

Cytotoxicity and mode of action of aeroplysinin-1 and a related dienonefrom the sponge Aplysina aerophoba

Aeroplysinin-1 (1) and the structurally related dienone 2 were cytotoxic to Ehrlich ascites tumor (EAT) cells and HeLa tumor cells in the microculture tetrazolium (MTT) and clonogenic assays. Both compounds are bromotyrosine derivatives, isolated from the marine spong Aplysina aerophoba. As the effective concentrations in the MTT assay were lower than in the clonogenic assay, 1 and 2 are able to cause growth inhibition as well as actual cell death in these cell lines. With an IC50 value of 8.2 microM (MTT assay, 2-h incubation, EAT cells), 1 was the more toxic compound. When the cells were depleted of glutathione by pretreatment with buthionine sulfoximine, they were significantly more sensitive toward 1 and 2 in the MTT assay. A dose-enhancement factor as high as 11.8 was found in EAT cells after 2-h incubation with 2. Using electron paramagnetic resonance we were able to measure free radical formation of 1 and 2, yielding the semiquinone structures 3 and 4, respectively, in a culture medium with tumor cells. It is concluded that free radicals are, at least in part, responsible for the cytotoxicity of 1 and 2. This conclusion is in line with expectations derived from the chemical structures of both compounds.

Vinyl ketone reagents for covalent protein modification. Nitroxide derivatives suited to rotational diffusion studies by saturation transfer electron spin resonance, using membrane-bound Na,K-ATPase as an example

The reactivity of a series of substituted vinyl ketone nitroxides with an integral membrane protein, the Na,K-ATPase, is described. Increasing the electrophilicity of the conjugated double bond enhances reactivity markedly, with some spin labels showing higher reactivity than the conventionally used maleimide derivatives. The spectroscopic characteristics of the spin-labeled protein are also better suited for motional analysis by the saturation transfer electron spin resonance (STESR) method than with previous labeling procedures. The rotational correlation time, deduced from STESR experiments, is in the same range (100-300 microseconds) irrespective of the vinyl ketone derivative used, and the rotational mobility corresponds to an (alpha beta)2 or higher oligomer of the membrane-bound Na,K-ATPase.

Properies of tRNAPhe from yeast carrying a spin label on the 3'-terminal. Interaction with yeast phenylalanyl-tRNA Synthetase and elongation factor Tu from Escherichia coli

The 2-thioketo function of tRNAPhe-C-s2C-A in which the penultimate cytidine residue is replaced by 20thiocytidine can serve as a site of specific attachment of spin label. By alkylation of tRNAPhe-C-s2C-A with iodoacetamide or its spin label derivatives tRNAPhe-C-(acm)s2C-A or tRNAPheC-(SL)s2C-A are formed. The enzymatic phenylalanylation of these tRNAsPhe revealed that the 2-position of the penultimate cytidine can be modified without impairing this enzymatic reaction but there exists a sterical limitation for the subsituent on this position beyond which the tRNAPhe:phenylalanyl-tRNA synthetase recognition is not possible. Both Phe-tRNAPhe-C-(acm)s2C-A as well as Phe-tRNAPhe-C(SL)s2C-A form ternary complexes with EF-Tu.GTP. The part of the 3'-terminus of tRNAPhe where the additional substituents are attached is therefore not involved in the interaction with this elongation factor. This could be also demonstrated by ESR measurements of spin labelled tRNAsPhe. The correlation times, tauc, for tRNAPhe-C-(SL)s2C-A, Phe-tRNAPhe-C-(SL)s2C-A and Phe-tRNAPhe-C-(SL)s2C-A.EF-Tu:GTP are essentially identical indicating that the structure of the 3'-end of tRNAPhe is not influenced significantly by aminoacylation or ternary complex formation.