Identification of N5-methyl-N5-formyl-2,5,6-triamino-4-hydroxypyrimidine as a major adduct in rat liver DNA after treatment with the carcinogens, N,N-dimethylnitrosamine or 1,2-dimethylhydrazine

Human Tamm-Horsfall urinary glycoprotein from an individual of the blood group Sd(a+) phenotype was tritium-labelled by treatment with galactose oxidase and sodium boro[3H]hydride and was then digested with endo-beta-galactosidase. A series of dialysable, labelled fragments was released from which a pentasaccharide was isolated that strongly inhibited the agglutination of Sd(a+) red cells by human anti-Sda serum and hence contained the Sda determinant structure. Reduction, methylation analysis and sequential exo-glycosidase digestion established the structure of the pentasaccharide as: GalNAc beta(1 leads to 4)[NeuAc(2 leads to 3)]Gal beta(1 leads to 4)GlcNAc beta(1 leads to 3)Gal     

Inhibition of Neuronal Degenerin/Epithelial Na+ Channels by the Multiple Sclerosis Drug 4-Aminopyridine

The voltage-gated K⁺ (Kv) channel blocker 4-aminopyridine (4-AP) is used to target symptoms of the neuroinflammatory disease multiple sclerosis (MS). By blocking Kv channels, 4-AP facilitates action potential conduction and neurotransmitter release in presynaptic neurons, lessening the effects of demyelination. Because they conduct inward Na⁺ and Ca²⁺ currents that contribute to axonal degeneration in response to inflammatory conditions, acid-sensing ion channels (ASICs) contribute to the pathology of MS. Consequently, ASICs are emerging as disease-modifying targets in MS. Surprisingly, as first demonstrated here, 4-AP inhibits neuronal degenerin/epithelial Na⁺ (Deg/ENaC) channels, including ASIC and BLINaC. This effect is specific for 4-AP compared with its heterocyclic base, pyridine, and the related derivative, 4-methylpyridine; and akin to the actions of 4-AP on the structurally unrelated Kv channels, dose- and voltage-dependent. 4-AP has differential actions on distinct ASICs, strongly inhibiting ASIC1a channels expressed in central neurons but being without effect on ASIC3, which is enriched in peripheral sensory neurons. The voltage dependence of the 4-AP block and the single binding site for this inhibitor are consistent with 4-AP binding in the pore of Deg/ENaC channels as it does Kv channels, suggesting a similar mechanism of inhibition in these two classes of channels. These findings argue that effects on both Kv and Deg/ENaC channels should be considered when evaluating the actions of 4-AP. Importantly, the current results are consistent with 4-AP influencing the symptoms of MS as well as the course of the disease because of inhibitory actions on Kv and ASIC channels, respectively.     

Specific silver staining of experimentally undercondensed chromosome regions

Treatment of human and mouse cell cultures with DNA binding AT-specific compounds and with some base analogues induced distinct undercondensations in several heterochromatic chromosome regions. All those heterochromatic regions undercondensed by AT-specific DNA ligands (distamycin A, DAPI, Hoechst 33258) could be heavily labeled with the silver(Ag)-staining technique; but the heterochromatic regions undercondensed with the cytidine analogue 5-azacytidine were Ag-negative. In metaphase chromosomes from BrdU-treated human cell cultures, the bifilarly substituted chromatids, which show a slight undercondensation, were also Ag-negative. Cytochemical analyses of the Ag-stained undercondensed heterochromatic regions showed that the Ag-stainable material consisted of nonhistone proteins. The mechanism of Ag staining in the undercondensed heterochromatic regions was compared with Ag staining of the nucleolus organizer regions.     

A Systematic Approach towards Optimizing a Cohabitation Challenge Model for Infectious Pancreatic Necrosis Virus in Atlantic Salmon (Salmo salar L.)

A cohabitation challenge model was developed for use in evaluating the efficacy of vaccines developed against infectious pancreatic necrosis virus (IPNV) in Atlantic salmon (Salmo salar L) using a stepwise approach. The study involved identifying a set of input variables that were optimized before inclusion in the model. Input variables identified included the highly virulent Norwegian Sp strain NVI015-TA encoding the T₂₁₇A₂₂₁ motif having the ability to cause >90% mortality and a hazard risk ratio of 490.18 (p<0.000) for use as challenge virus. The challenge dose was estimated at 1x10⁷ TCID₅₀/mL per fish while the proportion of virus shedders was estimated at 12.5% of the total number of fish per tank. The model was designed based on a three parallel tank system in which the Cox hazard proportional regression model was used to estimate the minimum number of fish required to show significant differences between the vaccinated and control fish in each tank. All input variables were optimized to generate mortality >75% in the unvaccinated fish in order to attain a high discriminatory capacity (DC) between the vaccinated and control fish as a measure of vaccine efficacy. The model shows the importance of using highly susceptible fish to IPNV in the optimization of challenge models by showing that highly susceptible fish had a better DC of differentiating vaccine protected fish from the unvaccinated control fish than the less susceptible fish. Once all input variables were optimized, the model was tested for its reproducibility by generating similar results from three independent cohabitation challenge trials using the same input variables. Overall, data presented here show that the cohabitation challenge model developed in this study is reproducible and that it can reliably be used to evaluate the efficacy of vaccines developed against IPNV in Atlantic salmon. We envision that the approach used here will open new avenues for developing optimal challenge models for use in evaluating the efficacy of different vaccines used in aquaculture.     

Virulence-associated characteristics and phage lysogenicity of two morphologically distinct colonies of Vibrio cholerae O139 serogroup

Abstract The presence of a temperate phage was demonstrated in a strain of Vibrio cholerae O139 isolated from a patient. Spontaneous variants with translucent colonies had lost this phage. The loss of the phage was associated with increased hydrophobicity, indicating the loss of the capsule. These clones were sensitive to serum bactericidal activity, showed decreased expression of such presumed virulence factors as proteases, motility and mannose-sensitive pili. Furthermore, excision of the phage made the strain dependent on purines for growth.     

Assessing the promise of user involvement in health service development: ethnographic study

Objectives To understand how the policy of user involvement is interpreted in health service organisations and to identify factors that influence how user involvement is put into practice.Design Ethnographic study using participant observation, interviews, and collection of documentary evidence.Setting A multiagency modernisation programme to improve stroke services in two London boroughs.Participants Service users, National Health Service managers, and clinicians.Results User involvement in the programme was initiated and led by professionals. Professionals determined the areas of service improvement service users could participate in. A wide range of activities were considered “user involvement,” from patient satisfaction surveys to service users delivering peer support. Involvement tended to be most active in the least technical areas and areas with least input from clinicians. Factors that might explain this included organisational structure, the vagueness of the concept of user involvement, the value attributed to service users’ experiential knowledge, and variations in professional and service user understandings of and commitment to involvement. The gains of involvement were harder to identify in terms of impact on services. More evident were the personal gains for those involved: satisfaction of feeling listened to by professionals, social opportunities of meeting others in a similar situation, and increased knowledge about stroke and services available.Conclusions User involvement may not automatically lead to improved service quality. Healthcare professionals and service users understand and practise user involvement in different ways according to individual ideologies, circumstances, and needs. Given the resource implications of undertaking user involvement in service development there is a need for critical debate on the purpose of such involvement as well as better evidence of the benefits claimed for it.