Temporal Discrimination Thresholds and Proprioceptive Performance: Impact of Age and Nerve Conduction

Background

Increasing attention is payed to the contribution of somatosensory processing in motor control. In particular, temporal somatosensory discrimination has been found to be altered differentially in common movement disorders. To date, there have only been speculations as to how impaired temporal discrimination and clinical motor signs may relate to each other. Prior to disentangling this relationship, potential confounders of temporal discrimination, in particular age and peripheral nerve conduction, should be assessed, and a quantifiable measure of proprioceptive performance should be established.

Objective

To assess the influence of age and polyneuropathy (PNP) on somatosensory temporal discrimination threshold (STDT), temporal discrimination movement threshold (TDMT), and behavioral measures of proprioception of upper and lower limbs.

Methods

STDT and TDMT were assessed in 79 subjects (54 healthy, 25 with PNP; age 30–79 years). STDT was tested with surface electrodes over the thenar or dorsal foot region. TDMT was probed with needle electrodes in flexor carpi radialis (FCR) and tibialis anterior (TA) muscle. Goniometer-based devices were used to assess limb proprioception during (i) active pointing to LED markers, (ii) active movements in response to variable visual cues, and (iii) estimation of limb position following passive movements. Pointing (or estimation) error was taken as a measure of proprioceptive performance.

Results

In healthy subjects, higher age was associated with higher STDT and TDMT at upper and lower extremities, while age did not correlate with proprioceptive performance. Patients with PNP showed higher STDT and TDMT values and decreased proprioceptive performance in active pointing tasks compared to matched healthy subjects. As an additional finding, there was a significant correlation between performance in active pointing tasks and temporal discrimination thresholds.

Conclusion

Given their notable impact on measures of temporal discrimination, age and peripheral nerve conduction need to be accounted for if STDT and TDMT are applied in patients with movement disorders. As a side observation, the correlation between measures of proprioception and temporal discrimination may prompt further studies on the presumptive link between these two domains.

50 Years of Environmental Monitoring at Henkel

The gradually increasing detergents consumption in Germany since 1950 resulted in higher emissions of their ingredients to the environment. The first generation of mineral oil-based surfactants, tetrapropylene benzene sulfonate (TPS), exhibited poor biodegradability and caused public environmental concerns. These prompted Henkel in 1958 to start a systematic measurement of some main detergent constituents in the river Rhine in Germany. Since then, a number of monitoring activities regarding the determination of detergent ingredients concentrations and freights in rivers and waste water treatment plants (WWTP) followed. This paper summarizes 50 years experience at Henkel in monitoring of detergent ingredients in the aquatic environment. The long-term monitoring results on the river Rhine provides an impressive record of the development of the environmental burden by surfactant emissions and of the gradual improvement of river water quality over time. The reasons for the changes are discussed. Further monitoring activities on WWTPs have shown for the first time, that domestic wastewater treatment plants (DWTP) are similarly suitable for the removal of surfactants like municipal ones. The good removal of prominent organic detergent ingredients was shown by several time-proportional sampling campaigns in municipal WWTPs. Finally the positive impact of the modernisation of a municipal WWTP on the chemical and biological water quality on a small river creek is reported over the time period of 7 years. All of the reported studies indicate a low environmental burden due to the use of detergents ingredients today. The learnings from the different activities in environmental monitoring by Henkel have contributed to a solid understanding of the fate of detergent ingredients in the environment. This in turn was the prerequisite for development of reliable exposure prediction models. Today, Henkel employs both, environmental monitoring and modeling instruments, for assessing the environmental exposure of chemicals.

Detergent Phosphates and their Environmental Relevance in Future European Perspectives

This paper provides a generic overview of the relative contribution of different sources to the load of phosphorus (P) in surface waters in 18 European countries. Based on the current P-inputs into surface waters, future scenarios reflecting further reductions of P from municipal waste water are presented. A significant P-reduction can be achieved by improving the wastewater treatment situation and by introducing P-free product alternatives for laundry detergents. The remaining fraction of P in surface waters originating from automatic dishwashing detergents (ADD) only has a minor relevance for the aquatic ecosystem and may be reduced to a maximum of <1–4% when sewage treatment situation is improved. It can be concluded that ADD as P-source in the aquatic environment may not significantly contribute to the nutrient status, especially in eutrophication sensitive areas, where efficient P removal from sewages is regulated by the Urban Wastewater Directive (91/271/EEC). With respect to a requested evaluation of potential legislative steps by the EUDetergent Regulation (648/2004/EEC), a total ban of P in detergents seems not an appropriate measure to achieve significant reductions of P-concentrations in surface waters.

Anaerobic Biodegradation of Surfactants – Scientific Review

The anaerobic biodegradation of surfactants is used as an acceptability criterion in some environmental pieces of legislation (eco-label, risk assessment, etc.), without a proper evaluation of the relevance of such a characteristic. Available screening test methods to assess the anaerobic biodegradation do not simulate the real conditions prevailing in these anaerobic compartments but rather reflect more stringent conditions, due to the high test substance/biomass ratio, possibility of inhibitory effects and limited possibility for adaptation. Therefore positive results are indicative of a similar behaviour under environmental conditions, while a negative result cannot be necessarily interpreted as inherent anaerobic recalcitrance. The majority of surfactants entering the environment will be exposed to and degraded under aerobic conditions, and only less than 20 % will potentially reach temporarily anaerobic environmental compartments. In contrast to the well documented adverse effects observed in the absence of aerobic biodegradation, the lack of anaerobic biodegradation does not seem to be correlated with any apparent environmental problem for most compartments after more than 40 years of widely use of such products. The scientific review concluded that anaerobic biodegradability does not have the same environmental relevance as the aerobic one. Anaerobic biodegradability should not, therefore, be used as a pass/fail property for the environmental acceptability of surfactants which are readily biodegradable under aerobic conditions.

Parenting stress in mothers and fathers of a child with a hemiparesis: sources of stress, intervening factors and long-term expressions of stress

BACKGROUND

In a substantial minority of children with a hemiparesis, motor impairments are accompanied by behavioural problems. This combination confronts parents with several persistent, frequently intense, sources of stress. At the same time, it is likely to reduce the effectiveness of psychosocial resources, such as feelings of competence, which would normally buffer the impact of the stressors. Aim To investigate the association between motor and behavioural problems in children with a hemiparesis and symptoms of stress in their parents, with particular attention to psychosocial factors which may mediate between the child's problems and parents' symptoms of stress.

METHOD

Questionnaires assessing the medical, functional and behaviour problems of the child, and the parents' experience of stress were completed by the mothers and fathers of 108 children with a hemiparesis who were members of the Association for the Motor Handicapped in the Netherlands.

RESULTS

Both parents reported (extremely) high levels of long-term stress significantly more frequently than parents in a normative sample. Indices of long-term stress were associated with the child's behavioural problems and, less strongly, with dysfunctionality in daily life. However, behavioural problems and dysfunctionality also reduced parents' feelings of competence and social support. A mediation analysis showed that feelings of incompetence and social isolation mediated between the child's problems and the parents' symptoms of stress. Fathers and mothers did not differ in level of reported stress, or in the associations between the child's problems and degree of experienced stress.

CONCLUSION

Both parents of a child with a hemiparesis experience high levels of stress, which are strongly associated with feelings of incompetence and social isolation. This suggests that one focus of intervention should be the alleviation of parenting stress with particular attention to increasing perceived competence in the parenting role and reducing feelings of social isolation.

Determination of the fate of alcohol ethoxylate homologues in a laboratory continuous activated-sludge unit study

Environmental monitoring indicates that the distribution of alcohol ethoxylate (AE) homologues in wastewater treatment plant (WWTP) effluents differs from the distribution in commercial AE products, with a relative higher proportion of fatty alcohol (AOH, which is AE with zero ethoxylation). To determine the contribution of AE-derived AOH to the total concentration of AE and AOH in WWTP effluents, we conducted a laboratory continuous activated-sludge study (CAS). This consisted of a test unit fed with AE-amended synthetic sewage and a control unit fed with only synthetic sewage to avoid AE contamination from the feed. The removal efficiencies of some 114 AE homologues were determined by the application of a specific and sensitive analytical method. The extent of the removal of AE ranged from 99.70% for C18 compounds to > 99.98% for C12-16. Relatively high-AOH concentrations were observed in the effluents from blank and test units. By building the concentration difference from the test minus the control unit, the AE in the CAS effluent originating from AE in the influent was determined. Thus, it could be shown that AOH represented only 19% of the total AE (EO0-18) in the CAS, while monitoring in 29 WWTP effluents (European, Canadian, and US) revealed in total a mean AOH fraction of 55% (5-82%) of the total AE (EO0-18). This shows that only a small fraction of AOH in WWTP effluents originates from AE entering the WWTP.

Aquatic risk assessment of alcohol ethoxylates in North America and Europe

An environmental risk assessment for alcohol ethoxylates (AE) is presented that integrates wastewater treatment plant monitoring, fate, and ecotoxicity research with a new application of mixture toxicity theory based on simple similar concentration addition of AE homologs in a species-sensitivity distribution (SSD) context. AEs are nonionic surfactants composed of a homologous series of molecules that range in alkyl chain length from 12 to 18 carbons and ethoxylates from 0 to 18 units. Chronic ecotoxicity of AE is summarized for 17 species in 60 tests and then normalized to monitoring data for AE mixtures. To do so, chronic aquatic toxicity was first expressed as EC10 per species (the concentration predicted to cause a 10% reduction in an important ecological endpoint). Normalization integrated several new quantitative structure-activity relationships for algae, daphnids, fish, and mesocosms and provided an interpretation of toxicity test data as a function of individual homologs in an AE mixture. SSDs were constructed for each homolog and the HC5 (hazardous concentration protective of 95% of species based on a small biological effect [the chronic EC10]) was predicted. Total mass of AE in monitored effluents from 29 sites in Europe, Canada, and the United States averaged 6.8, 2.8, and 3.55 microg/L, respectively. For risk assessment purposes, correction of exposure to account for fatty alcohol derived from sources other than AE and for sorbed components based on experimental evidence was used to determine AE concentrations in undiluted (100%) effluents from North America and Europe. Exposure and effect findings were integrated in a toxic unit (TU)-based model that considers the measured distribution of individual AE homologs in effluent with their corresponding SSDs. Use of environmentally relevant exposure corrections (bioavailability and accounting for AE-derived alcohol) resulted in TUs ranging from 0.015 to 0.212. Low levels of risk are concluded for AE in the aquatic environments of Europe and North America.

Predicting the sorption of fatty alcohols and alcohol ethoxylates to effluent and receiving water solids

Alcohol ethoxylates (AEs) are an important group of nonionic surfactants. Commercial AEs consist of a mixture of several homologues of varying carbon chain length (Cx) and degree of ethoxylation (EOy). The major disposal route of AE is down the drain to municipal wastewater treatment plants that discharge into receiving surface waters. Sorption of AE homologues onto activated sludge and river water solids is an important factor in assessing exposure of AE in the environment. This study presents the experimental determination of sorption coefficients for a wide array of AE homologues including five alcohols under environmentally relevant conditions and combines these data with literature data to generate a predictive model for the sorption of AEs in the environment. These results demonstrate that sorption can be effectively modeled using a log Kd vs. Cx and EOy predictive equation having the form log Kd = 0.331C - 0.00897EO - 1.126(R2 = 0.64).

Ecotoxicity quantitative structure-activity relationships for alcohol ethoxylate mixtures based on substance-specific toxicity predictions

Traditionally, ecotoxicity quantitative structure-activity relationships (QSARs) for alcohol ethoxylate (AE) surfactants have been developed by assigning the measured ecotoxicity for commercial products to the average structures (alkyl chain length and ethoxylate chain length) of these materials. Acute Daphnia magna toxicity tests for binary mixtures indicate that mixtures are more toxic than the individual AE substances corresponding with their average structures (due to the nonlinear relation of toxicity with structure). Consequently, the ecotoxicity value (expressed as effects concentration) attributed to the average structures that are used to develop the existing QSARs is expected to be too low. A new QSAR technique for complex substances, which interprets the mixture toxicity with regard to the "ethoxymers" distribution (i.e., the individual AE components) rather than the average structure, was developed. This new technique was then applied to develop new AE ecotoxicity QSARs for invertebrates, fish, and mesocosms. Despite the higher complexity, the fit and accuracy of the new QSARs are at least as good as those for the existing QSARs based on the same data set. As expected from typical ethoxymer distributions of commercial AEs, the new QSAR generally predicts less toxicity than the QSARs based on average structure.

Environmental concentrations of boron, LAS, EDTA, NTA and Triclosan simulated with GREAT-ER in the river Itter

A computer simulation of the environmental concentrations of some typical consumer-product ingredients was performed using the geo-referenced exposure model GREAT-ER (Geo-referenced Regional Environmental Assessment Tool for European Rivers) in the river Itter. Boron and LAS were chosen as typical detergent ingredients along with EDTA, NTA and Triclosan as examples of household and cosmetic product ingredients. The simulations were based on consumption figures of the respective chemical in consumer products in the year 2000. For EDTA, the consumption figure used for the calculation had to be extended to commercial products since the EDTA-use in domestic products could not account for the measured concentrations alone. The resulting PEC (Predicted Environmental Concentration) for all investigated compounds showed very good accordance to the measured concentrations in the Itter which were monitored in the same year. The concentrations did not deviate more than by a factor of 3. GREAT-ER's calculated 90th-percentile was never exceeded by the monitoring result thus reflecting a reasonable accuracy.

Prognosis of environmental concentrations by geo-referenced and generic models: a comparison of GREAT-ER and EUSES exposure simulations for some consumer-product ingredients in the Itter

The aim of this study was the comparison between predicted environmental concentrations (PEC) derived using a generic aspacial model, European Union System for the Evaluation of Substances (EUSES), and a geo-referenced model, the Geo-referenced Regional Environmental Assessment Tool for European Rivers (GREAT-ER). The PECs of some consumer-product ingredients (boron, LAS) and professional uses (EDTA, NTA and Triclosan) were calculated for the river catchment of the Itter, a small tributary to the river Rhine. The PEClocal and PECregional for the water compartment generated by EUSES (default scenario) were subsequently refined with data that realistically reflects the region of North Rhine-Westphalia (NRW scenario) and the Itter catchment (Itter scenario). The results of the three scenarios were then compared with the PECinitial and PECcatchment calculated by GREAT-ER, that was designed as a higher-tiered exposure assessment tool, and with concrete concentrations in the Itter, measured as 24-h composite samples. While the PECregional of all scenarios was close to the lower end of the measured concentrations, the geo-referenced PECs described equally well the real spacial situation. The measured environmental concentrations confirmed the built-in conservatism of the PEClocal calculations by EUSES showing for all investigated chemicals an unrealistically high PEClocal (default). The refinement in the more realistic scenarios could not provide a straight forward general improvement of the PEClocal. In conclusion, when the EUSES prognosis is refined using more detailed substance and regional specific data, it may provide a fairly accurate modelling especially of substances that are not eliminated in the environment. However, in the case of eliminable substances, it does not match the accuracy of higher-tiered geo-referenced exposure models like GREAT-ER.

Generation and epitope mapping of high-affinity scFv to eukaryotic elongation factor 1A by dual application of phage display

To generate specific tools for, in particular, localization studies of the eukaryotic elongation factor 1A (eEF1A), we have applied phage display in various formats to affinity-improve and map epitopes of two previously isolated, low-affinity single-chain Fv (scFv) G3 and D1. The scFv differ in their reactivity toward the eEF1A isoforms, eEF1A-1 and eEF1A-2. By PCR-based randomization of six residues within the variable light chain CDR3 (LCDR3), and subsequent phage-based affinity-selection, two 'families' of affinity-improved scFv were obtained. The scFv of highest affinity, A8, has a Kd of 9 nM to eEF1A-1. Interestingly, two affinity-improved scFvs have abnormally short LCDR3 consisting of two and four residues compared to 11 in the parental scFv. Hence, the LCDR3 of the parental clones may play a modulating rather than a direct role in antigen-binding. Despite different preferences for the eEF1A isoforms, both families of scFv recognize antigenic determinant(s), which was mapped to residues 413-450 of eEF1A-1/2 by Western blot analysis of recombinant human eEF1A (hEF1A) fragments. Prior to the Western blotting analysis, the epitope location had been suggested using a novel approach where phage-antibody repertoire derived scFv were used to select phage-displayed peptides. Hereby, peptides containing a SFXD motif, matching the SFSD(414-418) sequence found in hEF1A-1 were isolated. The structure of eukaryotic EF1A from yeast indicates a discontinuous nature of the epitope with distal functional elements juxtaposed by the protein fold. Finally, the scFv A8 was applied for immunofluorescence studies of transformed human amnion cells and MCF-7 fibroblasts. In both cases a perinuclear localization of hEF1A was observed. No evidence for the reported nuclear localization of hEF1A was obtained.

Epitope mapping for four monoclonal antibodies against human plasminogen activator inhibitor type-1: implications for antibody-mediated PAI-1-neutralization and vitronectin-binding

The inhibitory mechanism of serine proteinase inhibitors of the serpin family is based on their unique conformational flexibility. The formation of a stable proteinase-serpin complex implies insertion of the reactive centre loop of the serpin into the large central beta-sheet A and a shift in the relative positions of two groups of secondary structure elements, the smaller one including alpha-helix F. In order to elucidate this mechanism, we have used phage-display and alanine scanning mutagenesis to map the epitopes for four monoclonal antibodies against alpha-helix F and its flanking region in the serpin plasminogen activator inhibitor-1 (PAI-1). One of these is known to inhibit the reaction between PAI-1 and its target proteinases, an effect that is potentiated by vitronectin, a physiological carrier protein for PAI-1. When combined with the effects these antibodies have on PAI-1 activity, our epitope mapping points to the mobility of amino-acid residues in alpha-helix F and the loop connecting alpha-helix F and beta-strand 3A as being important for the inhibitory function of PAI-1. Although all antibodies reduced the affinity of PAI-1 for vitronectin, the potentiating effect of vitronectin on antibody-induced PAI-1 neutralization is based on formation of a ternary complex between antibody, PAI-1 and vitronectin, in which PAI-1 is maintained in a state behaving as a substrate for plasminogen activators. These results thus provide new details about serpin conformational changes and the regulation of PAI-1 by vitronectin and contribute to the necessary basis for rational design of drugs neutralizing PAI-1 in cancer and cardiovascular diseases.

Identification of phage antibodies toward the Werner protein by selection on Western blots

A procedure was established for selecting phage antibodies (phage-abs) from phage-displayed antibody repertoires by panning against proteins, separated by sodium dodecyl phosphate-polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotted onto nitrocellulose membranes (Western blots). This immobilization strategy is applicable for secondary rounds of panning in selections against semipurified proteins, and directs the selection toward antibodies suitable as immunochemical reagents in Western blots. In model experiments, enrichment factors as high as 1.9x10(5) were obtained in a single round of panning. Furthermore, we demonstrate the application of this approach by selection of phage-abs recognizing the human Werner protein, which is defective in a premature aging syndrome.

Display of Ras on filamentous phage through cysteine replacement

Phage display technology has been used in a variety of contexts to understand and manipulate biomolecular interactions between proteins and other biomolecules. In this paper we describe the establishment of a phage display system for elucidation of the interactions between the GTPase Ras and its panel of effectors. It is shown how technical problems associated with phage display of a protein with unpaired cysteines, likely to be caused by the oxidizing environment of the bacterial periplasm into which the protein is directed, can be overcome by cysteine replacement based on functional and structural studies. First, the catalytic domain (residues 1-166) of mammalian H-Ras (Ras) was observed to be displayed on phage in an incorrect conformation not detectable by antibodies recognizing conformational epitopes on Ras. Although truncation of the phage coat protein used as fusion partner (g3p) resulted in minor improvements in the display, Ras was tailored for phage display by cysteine replacement. By replacing the three cysteines at positions 51, 80 and 118 of Ras with the corresponding residues in Saccharomyces cerevisiae RAS1, the resulting fusion-phage is recognized by the conformation-dependent anti-Ras antibodies. Furthermore, display of cysteine-free Ras is demonstrated by GTP-analogue dependent binding to the Ras-binding domain of the Ras-effector Raf1. These data pave the way for analysis of Ras-effector interactions using phage display technology yet demonstrate that phage display of proteins with normally reduced cysteines should be approached with caution.

Sulfate-reducing bacteria in rice field soil and on rice roots

Rice plants that were grown in flooded rice soil microcosms were examined for their ability to exhibit sulfate reducing activity. Washed excised rice roots showed sulfate reduction potential when incubated in anaerobic medium indicating the presence of sulfate-reducing bacteria. Rice plants, that were incubated in a double-chamber (phylloshpere and rhizosphere separated), showed potential sulfate reduction rates in the anoxic rhizosphere compartment. These rates decreased when oxygen was allowed to penetrate through the aerenchyma system of the plants into the anoxic root compartment, indicating that sulfate reducers on the roots were partially inhibited by oxygen or that sulfate was regenerated by oxidation of reduced S-compounds. The potential activity of sulfate reducers on rice roots was consistent with MPN enumerations showing that H2-utilizing sulfate-reducing bacteria were present in high numbers on the rhizoplane (4.1 x 10(7) g-1 root fresh weight) and in the adjacent rhizosperic soil (2.5 x 10(7) g-1 soil dry weight). Acetate-oxidizing sulfate reducers, on the other hand, showed highest numbers in the unplanted bulk soil (1.9 x 10(6) g-1 soil dry weight). Two sulfate reducing bacteria were isolated from the highest dilutions of the MPN series and were characterized physiologically and phylogenetically. Strain F1-7b which was isolated from the rhizoplane with H2 as electron donor was related to subgroup II of the family Desulfovibrionaceae. Strain EZ-2C2, isolated from the rhizoplane on acetate, grouped together with Desulforhabdus sp. and Syntrophobacter wolinii. Other strains of sulfate-reducing bacteria originated from bulk soil of rice soil microcosms and were isolated using different electron donors. From these isolates, strains R-AcA1, R-IbutA1, R-PimA1 and R-AcetonA170 were Gram-positive bacteria which were affiliated with the genus Desulfotomaculum. The other isolates were members of subgroup II of the Desulfovibrionaceae (R-SucA1 and R-LacA1), were related to Desulforhabdus sp. (strain BKA11), Desulfobulbus (R-PropA1), or culstered between Desulfobotulus sapovorans and Desulfosarcina variabilis (R-ButA1 and R-CaprA1).

Sulfur oxidation in rice field soil: activity, enumeration, isolation and characterization of thiosulfate-oxidizing bacteria

In rice paddy fields the bulk soil is anoxic, but oxygenated zones occur in the surrounding of the rice roots to where oxygen is transported via the aerenchyma system of the rice plants. In the anaerobic soil compartments sulfate is consumed by sulfate-reducing bacteria. In the rhizosphere the reduced sulfur compounds can be reoxidized by sulfur-oxidizing bacteria. Measurements of the potential activity of thiosulfate-oxidizing bacteria in soil slurries derived from planted rice soil microcosms showed turnover rates of 2-6 mumol d-1 g-dw-1. Thiosulfate was oxidized to sulfate with tetrathionate as intermediate. Most probable number (MPN) enumeration with three aerobic media and one anaerobic nitrate-amended medium showed that thiosulfate-oxidizing bacteria were abundant in paddy soil and in rhizosphere soil at numbers of 10(5) to 10(6) per gram dry weight soil. Nine isolates of S-oxidizing bacteria were obtained from enrichment cultures or from the highest dilutions of the MPN series and were affiliated to four different phylogenetic groups. These isolates were characterized by physiological properties and by comparative 16S rDNA sequence analysis. Three isolates (TA1-AE1, TA1-A1 and TA12-21) were shown to be facultatively chemolithoautotrophic strains of Ancylobacter aquaticus. Three further isolates (Tv6-2b, Z2A-6A and Z4A-2A) were also facultatively chemolithoautotrophic and were affiliated with the Xanthobacter sp. group, probably representing new strains of X. flavus or X. tagetidis. Strain SZ-2111 was phylogenetically related to Bosea thiooxidans. However, the genus Bosea is described as obligately heterotrophic, whereas strain 5Z-2111 was able to grow autotrophically. The isolates 5Z-C1 and TBW3 were obligate chemolithoautotrophs and were closely affiliated with Thiobacillus thioparus. Our results showed that S-oxidizing bacteria were abundant and active in rice paddy soil and consisted of physiologically and phylogenetically diverse populations.

Glycerol diversifies phage repertoire selections and lowers non-specific phage absorption

Using a semi-synthetic phage displayed antibody repertoire, isoform-specific and cross-reactive phage-antibodies to eukaryotic elongation factor 1A (eEF1A) have been selected. Enrichment of specific antibodies was found to depend on the presence of glycerol. Further selections against lactate dehydrogenase (LDH) revealed that the dominance of a phage-antibody clone to LDH was inhibited by glycerol, a notable feature for selection strategies where a broad variety of binding clones is desired. The impact of glycerol in distinct steps of the selection protocol was examined and glycerol found to affect certain antibody-antigen interactions. Furthermore, the nonspecific phage binding was lowered by three orders of magnitude at a 20% (v/v) glycerol concentration.

Retrieval of phage displayed scFv fragments using direct bacterial elution

Phage displayed repertoires of antibody fragments, either single chain Fv (scFv) or Fab, have become a real alternative to traditional hybridoma technology in the generation of monoclonal antibodies. The steps usually taken in the selection from such repertoires were analysed and the necessity of chemical elution of bound phage-Abs and precipitation of amplified phage particles questioned. By using a semi-synthetic scFv library as a source, phage antibodies recognising a panel of seven antigens were isolated utilising direct bacterial elution of bound phage. Selections against two antigens were subsequently performed with bacterial or chemical elution in parallel and the resulting pools of phage antibodies compared. It is demonstrated that direct bacterial elution can be used when selecting from phage displayed antibody repertoires but that the enrichment of high affinity binders might be jeopardised. In addition, a simplified and more rapid scheme for amplification and use of phage displayed repertoires is described.

Activation of ATP-sensitive potassium channels decreases neuronal injury caused by chemical hypoxia

Cerebral ischemia is known to induce endogenous adaptive mechanisms such as the activation of ATP-sensitive potassium channels that can prevent or delay neuronal injury. This process can be therapeutically mimicked by treatment with potassium channel openers. Primary neuronal cell cultures were derived from embryonic chick telencephalon and were exposed to chemical hypoxia (1 mM cyanide) or excitotoxic injury (1 mM L-glutamate). While treatments with the potassium channel openers bimakalim (1-10 microM) and EMD 57283 (0.1-10 microM) were clearly able to maintain neuronal viability after chemical hypoxia, similar concentrations of the drugs had negligible effects on glutamate-induced neurotoxicity. In contrast, both types of neuronal injury were sensitive to the protective action of the glutamate receptor antagonist dizocilpine (MK-801; 0.1-1 microM). The neuroprotective effect of bimakalim against chemically induced hypoxic injury was reversed by tolbutamide (1 microM), an ATP-sensitive potassium channel blocker. These experiments demonstrate neuroprotective effects of potassium channel openers that could be related to inhibition of neurotransmitter release.

A model phage display subtraction method with potential for analysis of differential gene expression

In order to establish a subtractive procedure that makes it possible to enrich selectively phage displayed antibodies directed against proteins constituting a difference between two populations of cells, a competitive selection strategy utilising two solid phases was developed and tested. Antibodies recognising a defined difference between two otherwise identical protein mixtures were isolated and their specificity confirmed. To test further the efficacy of selection inhibition during the competitive selections, selections towards a total cell extract were performed with and without competition from the same extract. An analysis of the resulting phage antibodies confirmed the subtractive nature of the system described.