Particle size of insoluble fibres and gelation of soluble fibres influence digesta passage rate throughout the gastrointestinal tract of finishing pigs

Fibres, as abundant in agricultural by-products, exhibit a large range of physicochemical properties that can influence digestive processes such as digesta mean retention time (MRT), thereby affecting nutrient digestion kinetics. In this study, we investigated the effects of particle size of insoluble fibres, and gelation of soluble fibres on MRT of liquids, fine solids, and fibrous particles in the different segments of the gastrointestinal tract (GIT) of pigs. Twenty-four boars (51.6 ± 4.90 kg) were allocated to four diets; two diets contained 15% wheat straw, either coarsely chopped or finely ground (1-mm screen), two diets contained 27% wheat bran without or with the addition of 10% low-methylated pectin. After 14 days of adaptation to the diet, a total collection of faeces was performed to determine the total tract digestibility of nutrients. Thereafter, pigs were fed diets supplemented with tracers for at least 5 days and dissected following a frequent feeding procedure to approach steady-state passage of digesta. The MRT of liquids (Co-EDTA), fine solids (TiO2), and fibrous particles (Chromium-mordanted fibres) in the different segments of the GIT were quantified. In the stomach, particle size reduction of straw decreased the MRT of fine solids by 02:39 h, and fibrous particles by 07:21 h (P < 0.10). Pectin addition to the wheat bran diet reduced the MRT of fine solids by 03:09 h, and fibrous particles by 07:10 h (P < 0.10), but not of liquids, resulting in less separation between digesta phases in the stomach compared with the bran diet (P < 0.05). In the mid-small intestine (SI), pectin addition reduced the MRT of fibrous particles and the separation between fibrous particles and fine solids. No further effects of particle size reduction of straw nor pectin addition on MRT and digestibility of starch, nitrogen, or fat were observed in the SI. In the large intestine (LI), particle size reduction of straw reduced separation between fibrous particles and fine solids (P < 0.10), while pectin addition had no effects. Total tract, non-starch polysaccharide degradation of straw was poor (∼31%), and unaffected by particle size reduction (P > 0.10). The complete fermentation of pectin did not influence the degradation of wheat bran fibres (∼51%). In conclusion, the effects of particle size of insoluble fibres and gelling properties of soluble fibres on the passage of digesta phases were most pronounced in the stomach, but less prominent in distal segments of the GIT.

SNAPIG: a model to study nutrient digestion and absorption kinetics in growing pigs based on diet and ingredient properties

Current feed formulation and evaluation practices rely on static values for the nutritional value of feed ingredients and assume additivity. Hereby, the complex interplay among nutrients in the diet and the highly dynamic digestive processes are ignored. Nutrient digestion kinetics and diet × animal interactions should be acknowledged to improve future predictions of the nutritional value of complex diets. Therefore, an in silico nutrient-based mechanistic digestion model for growing pigs was developed: "SNAPIG" (Simulating Nutrient digestion and Absorption kinetics in PIGs). Aiming to predict the rate and extent of nutrient absorption from diets varying in ingredient composition and physicochemical properties, the model represents digestion kinetics of ingested protein, starch, fat, and non-starch polysaccharides, through passage, hydrolysis, absorption, and endogenous secretions of nutrients along the stomach, proximal small intestine, distal small intestine, and caecum + colon. Input variables are nutrient intake and the physicochemical properties (i.e. solubility, and rate and extent of degradability). Data on the rate and extent of starch and protein hydrolysis of different ingredients per digestive segment were derived from in vitro assays. Passage of digesta from the stomach was modelled as a function of feed intake level, dietary nutrient solubility and diet viscosity. Model evaluation included testing against independent data from in vivo studies on nutrient appearance in (portal) blood of growing pigs. When simulating diets varying in physicochemical properties and nutrient source, SNAPIG can explain variation in glucose absorption kinetics (postprandial time of peak, TOP: 20-100 min observed vs 25-98 min predicted), and predict variation in the extent of ileal protein and fat digestion (root mean square prediction errors (RMSPE) = 12 and 16%, disturbance error = 12 and 86%, and concordance correlation coefficient = 0.34 and 0.27). For amino acid absorption, the observed variation in postprandial TOP (61 ± 11 min) was poorly predicted despite accurate mean predictions (58 ± 34 min). Recalibrating protein digestion and amino acid absorption kinetics require data on net-portal nutrient appearance, combined with observations on digestion kinetics, in pigs fed diets varying in ingredient composition. Currently, SNAPIG can be used to forecast the time and extent of nutrient digestion and absorption when simulating diets varying in ingredient and nutrient composition. It enhances our quantitative understanding of nutrient digestion kinetics and identifies knowledge gaps in this field of research. Already useful as research tool, SNAPIG can be coupled with a postabsorptive metabolism model to predict the effects of dietary and feeding-strategies on the pig's growth response.

Standardisation of the C:N ratio in ileal digesta changes relationships among fermentation end-products during in vitro hindgut fermentation in pigs

Undigested proteins that become available for the microbiota in the hindgut can be used as building blocks for bacterial cells, or can enter various catabolic pathways. Degradation via protein fermentation pathways is least preferred, as several fermentation end-products released can be toxic for the host. Directing microbial protein metabolism towards protein synthesis or degradative pathways that result in less toxic end-products, for example through nutritional interventions, is an interesting strategy for improving health. We studied variation in protein fermentation patterns, resulting from variation in substrate composition. Ileal digesta, obtained from cannulated pigs fed different protein sources, were subjected to fermentation in vitro under different conditions; (1) ileal digesta were fermented as-is, (2) ileal digesta were fermented after standardisation to a constant high C:N ratio, by addition of high fermentable carbohydrates and (3) ileal digesta samples were incubated under limiting N concentrations. Gas production was monitored as an indirect measure of microbial activity, and fermentation end-products at different points in time were analysed by gas chromatography and high resolution mass spectrometry. Using principal component analysis, we identified patterns in protein fermentation end-products and related them to the composition of ileal digesta. Protein-associated fermentation end-product concentrations of e.g. isovaleric-, isobutyric-, phenylacetic acid and p-cresol were negatively affected by the available amount of high fermentable carbohydrates combined with a high C:N ratio. The aforementioned fermentation end-products positively correlated with NH3 concentrations and negatively with short-chain fatty acid (SCFA) concentrations. Standardisation to a constant high C:N ratio changed their relationship; isovaleric-, isobutyric-, phenylacetic acid and p-cresol lost their correlation with NH3 concentrations, became positively correlated with SCFA concentrations, and now showed a positive correlation with available amounts of high fermentable carbohydrates. Our observations demonstrate an important role of the C:N ratio in the relationship between fermentation end-products. At constant C:N, protein fermentation end-products correlate with end-products of carbohydrate fermentation and NH3, often considered as a proxy for protein fermentation, loses its predictive power.

Short communication: Estimation of ileal digestibility in chickens using single- and dual-tracer methods

Fractionation of digesta, as occurs during gastrointestinal transit in chickens, complicates accurate measurements of ileal digestibility using tracers. Dual-tracer methods using separate tracers for solid and fluid digesta phases may improve the accuracy of digestibility measurements when assumptions of the single tracer method are violated. The aim of the present study was to compare the apparent ileal digestibility (AID) of nutrients calculated with single- and dual-tracer methods in chickens fed diets varying in particle size, anticipating digesta phase separation in the proximal gastrointestinal tract. A total of 112 Dekalb White (BW: 1.53 ± 0.107 kg) and 112 Bovans Black (BW: 1.79 ± 0.127 kg) 29-week-old laying hens were distributed over 32 pens (seven birds/pen). Within breed, pens were randomly assigned to one of two experimental diets (coarse vs fine oat hulls; n = 8 replicate pens per diet/breed combination). Diets were supplemented with TiO2 (3 g/kg) and Co-EDTA (2 g/kg). On days 34, 35, or 36, birds were euthanised and digesta from the ileum was collected for tracer and nutrient analyses. Apparent ileal digestibility was subsequently calculated by single- and dual-tracer methods. Although coarse oat hulls were hypothesised to increase the fractionation of solid and fluid digesta phases, no breed or diet × method interactions were found. Using a single tracer method based on TiO2, AID of nitrogen (N) was overestimated by 3%-units (P < 0.01) compared with the dual-tracer method, whereas AID estimates of DM, starch, fat, and non-starch polysaccharides did not differ (P > 0.09) and precision of all AID estimates was improved. In conclusion, these results show that although from a conceptual perspective, dual-tracer methods are presumed to better account for the variation in flow behaviour of different digesta phases, AID estimates obtained by the commonly used single tracer method using solid-phase tracer TiO2 were more precise and only marginally differed from estimates obtained by a dual-tracer method using distinct tracers for solid (TiO2) and liquid (Co-EDTA) digesta phases. Considering technical and economical constraints, the single tracer method may thus be the method of choice in many situations. Only when digestibility of proteins or amino acids is of specific interest, single tracer methods using a solid-phase tracer may not suffice. Nevertheless, for both single- and dual-tracer methods, tracer selection is critical, and the choice of tracers should depend on the nutrient(s) of interest.

A dynamic model to measure retention of solid and liquid digesta fractions in chickens fed diets with differing fibre sources

Dietary fibres impact multiple digestive processes, and insights into the effects of various types of fibre on digesta retention time are required to optimise current feed formulation systems. Therefore, the objective of this study was to apply a dynamic modelling approach to generate estimates for the retention time of solid and liquid digesta in broilers fed different fibre sources. A maize-wheat-soybean meal control diet was compared against three diets in which wheat was partially substituted with oat hulls, rice husks, or sugar beet pulp (3% w/w). Non-starch polysaccharide (NSP) digestibility was evaluated in broilers between 23 and 25 days of age (n = 60 birds/treatment) using titanium dioxide (TiO₂, 0.5 g/kg) as a marker, after feeding the experimental diets for 21 days. Digesta mean retention time (MRT) was measured in another 108 birds at 30 days of age by the administration of an oral pulse dose of chromium sesquioxide (Cr₂O₃) as solid marker and Cobalt-EDTA as liquid marker, and subsequent measurement of marker recovery in compartments of the digestive tract (n = 2 or 3 replicate birds/time point/treatment). Marker recovery models to estimate fractional passage rates for solid and liquid digesta in crop, gizzard, small intestine, and caeca compartments of the gastrointestinal tract were developed to predict MRT of solid and liquid digesta for each dietary treatment. The models were composed of a series of first-order differential equations, representing the variation of marker concentration in a compartment over time. Estimated MRT of solid and liquid digesta in the gizzard varied from 20 min for oat hulls and 34 min for rice husks diets to 14 min for sugar beet pulp and 12 min for control diets. In the caeca, liquid MRT was decreased compared to the control diet (989 min) for the sugar beet pulp diet (516 min), while it was increased for both the oat hulls and rice husks diets (≈1 500 min). Overall, these estimates are greater than those previously reported, suggesting that liquid digesta retention in the caeca previously has been underestimated. Digestibility of total NSP was increased by dietary fibre inclusion, regardless of the fibre type, although degradation of constituent sugars of NSP varied among diets. In conclusion, the inclusion of fibre sources at a low level (3% w/w) in the diet of broiler modulated retention time mainly in the gizzard and caeca, and increased digestibility of NSP.

Effects of early nutrition and sanitary conditions on antibody levels in early and later life of broiler chickens

Immune maturation of broiler chickens may be affected by management, such as early life feeding strategy (early versus delayed nutrition) or by low or high sanitary conditions (LSC versus HSC). We compared systemic maternal (MAb), natural (NAb), natural auto- (NAAb), and antigen specific antibody (SpAb) levels (IgM, IgY) between broilers (n = 48 per treatment) that received early (EN) or delayed nutrition for 72 h (DN) housed in either low (LSC) or high sanitary conditions (HSC) between 7 and 35 d of age. We found minimal interactions between feeding strategy and sanitary conditions. At 7 d of age, broilers receiving EN compared with DN, had elevated levels of IgM binding keyhole limpet hemocyanin (KLH), phosphoryl-conjugated ovalbumin (PC-OVA), and muramyl dipeptide (MDP), whereas effects of feeding strategy diminished at later ages. In LSC compared with HSC broilers, levels of NAb agglutinating RRBC and sheep red blood cells (SRBC) were already elevated from 14 d of age onwards. At 33 d of age, antibody levels (NAb, NAAb, anti-LPS, anti-MDP) were all elevated in LSC, compared with HSC broilers, for both IgM and IgY, but not IgM against KLH. Western blotting revealed different binding patterns of NAAb against chicken liver homogenate, which may indicate that the NAAb repertoire is affected by antigenic pressure. Our data suggest that antibody levels are affected for an important part by environmental conditions (feeding strategy and sanitary conditions), but minimally by their interaction. However, it remains to be further studied whether the enhanced levels of antibodies as initiated by EN and LSC contribute to enhanced resistance to infectious diseases.

Polysaccharide source altered ecological network, functional profile, and short-chain fatty acid production in a porcine gut microbiota

Several validated dynamic in vitro models of the colon have been developed for humans, but there is no dynamic in vitro fermentation model for pigs. This study was conducted to modify the human, dynamic, computer-controlled TNO in vitro model of the colon (TIM-2) for pigs and investigate effects of different starch sources and polysaccharides on swine microbiota structure, ecological network, predictive functional profile, and short-chain fatty acids production. Our study showed that three different types of starch or two polysaccharides greatly impacted microbiota composition. Co-occurrence network analysis indicated that microbiota fed with different sources of starch changed the network topological properties. Functional profiles were predicted to vary significantly among the three starch treatments, and the original pig faecal inoculum was more similar to maize starch treatment. On the other hand, compared with maize starch and arabinoxylans (AX), the microbial composition of the original inoculum was more similar when AX-XG (arabinoxylans and xyloglucan) were added, and the functional profile of the original inoculum also clustered with AX-XG. The cumulative production of acetic, propionic, and butyric acid on maize starch were significantly higher than those on potato starch and wheat starch, while only the amount of acetic acid was significant higher on AX-XG than that on AX. In conclusion, supplementation of maize starch as the starch source together with AX and XG, leads to the bacteria being more stable in the in vitro model and closer to the original inoculum and microbial function compared to potato starch, wheat starch and AX. A maize basal diet may improve energy absorption in the large intestine in growing pigs.

Intestinal epithelium integrity after delayed onset of nutrition in broiler chickens

Fasting older broiler chickens (>7 d of age) enlarges the intestinal tight junction (TJ) pore size, resulting in high paracellular intestinal permeability. Broiler chickens often do not receive feed and water (nutrition) directly after hatch, which may result in fasting up to 72 h of age. Whether perinatal fasting affects intestinal permeability is minimally studied. We therefore investigated whether delayed access to nutrition after hatch increases intestinal permeability, compared with broilers receiving early access to nutrition. Therefore, 432 hatched broilers received nutrition 72 h after hatch (delayed nutrition [DN]) or directly after hatch (early nutrition [EN]) and were reared under similar conditions until 14 d of age. Two hours after application of an oral pulse dose (3.85 mg) of fluorescein isothiocyanate-dextran (4000 Da) at 4, 10, and 14 d of age, blood plasma concentrations of the marker were measured in 24 to 36 broilers per treatment and time point. Marker concentration in plasma did not differ between DN and EN broilers at any age. The villus width measured in at least 8 broilers per treatment was smaller in DN than in EN broilers at 4 d for both the ileum (92 ± 3 μm vs. 121 ± 4; P < 0.001) and colon (100 ± 3 vs. 120 ± 4; P < 0.01). Real-time quantitative PCR revealed that the expression of TJ protein claudin 3 in the ceca was elevated in DN, compared with EN broilers at 4 d of age, whereas that of zonula occludens 1 in the ileum was reduced. Expression of host defense-related genes was reduced in DN, compared with EN broilers, in the ileum (cyclo-oxygenase 2, mucin 2) and ceca (interleukin 1β, cyclo-oxygenase 2). We conclude that 72-hour DN reduced the BW up to 14 d of age, coinciding with transient effects on the villus width in the ileum and colon, and divergent expression of genes involved in TJ formation and host defense. These effects likely reflect the delayed onset of intestinal and immune development in DN, compared with EN broilers, while DN does not fundamentally alter intestinal permeability.

Keeping your eye on the target: eye-hand coordination in a repetitive Fitts' task

In a cyclical Fitts' task, hand movements transition from continuous to discrete movements when the Index of Difficulty (ID) increases. Moreover, at high ID (small target), the eyes saccade to and subsequently fixate the targets at every movement, while at low ID (large target) intermittent monitoring is used. By hypothesis, the (periodic) gaze shifts are abandoned for movement times shorter than about 0.350 s due to systemic constraints (i.e., a refractory period and intrinsic latency). If so, the transition in eye and hand movements is independent. To investigate these issues, the present study examined the effects of changing ID via the targets' width or distance as well as hysteresis in eye-hand coordination. To this aim, 14 participants performed a cyclical Fitts' task while their hand and eye movements were recorded simultaneously. The results show that the transition in eye-hand synchronization (at 2.87 bit; 0.25 s) and in hand dynamics (at 4.85 bit; 0.81 s) neither co-occurred nor correlated. Some small width vs. distance dissociations and hysteresis effects were found, but they disappeared when eye-hand synchronization was viewed as a function of movement time rather than ID. This confirms that a minimal between-saccade time is the limiting factor in eye-hand synchronization. Additionally, the timing between the start of the hand movement and the saccade appeared to be relatively constant (at 0.15 s) and independent of movement time, implying a constant delay that should be implemented in a dynamical model of eye-hand coordination.

[Incidence of incontinence after radical prostatectomy using claims-based data]

OBJECTIVE

To determine the effect of radical prostatectomy (RP) hospital volume on the probability of post-RP incontinence.

DESIGN

Retrospective research based on claims-based data of health insurers.

METHOD

For every patient with RP the probability of incontinence was determined, based on the definition of claims of one or more incontinence pads per day. Casemix corrections were made based on indicators available in claims-data: age, lymph node dissection, and radiotherapy. No casemix corrections could be made for tumour stage and surgical technique.

RESULTS

A total of 1590 patients were included in this study; for 26.0% of these patients, an average of one or more incontinence pads per day were claimed for. A significant relation between the volume of RP per hospital and the claims of incontinence material was observed. The probability of incontinence was significantly lower in hospitals with a volume of more than 100 RP patients per year when compared to hospitals with less than 100 RP patients per year.

CONCLUSION

The probability of post-RP incontinence decreases as hospitals conduct more RP procedures. The casemix factors included in the analysis only had a limited impact on this observation.

Incomplete and incorrect epinephrine auto-injector training to food-allergic patients by pharmacists in the Netherlands

BACKGROUND

Successful treatment of anaphylaxis in the community relies on early and correct use of epinephrine auto-injectors (EAI). In the Netherlands, pharmacists supply EAIs to patients and have a crucial role in instructing patients in how and when to use EAI. However, there are currently no data in Europe on the quality of such instruction provided by pharmacists. Therefore, the aims of this study were to investigate the knowledge, attitudes, and beliefs regarding food allergy among pharmacists in the Netherlands and to investigate the quality of EAI instructions and demonstrations to patients by pharmacists.

METHODS

Pharmacists were asked to complete an online questionnaire. Quality of instructions and demonstration accuracy were assessed in mystery guest visits to randomly selected pharmacies. For the statistical analysis, descriptive methods were used.

RESULTS

In total, 25 of 115 questionnaires were completed. Only two (8%) respondents gave correct answers concerning the proper EAI demonstration. Twenty-one (84%) respondents thought that the provision of instructions was the responsibility of pharmacists. In total, ten pharmacies were included in simulated patient visits. Five of them (50%) demonstrated the EAI. None of them demonstrated the EAI use correctly.

CONCLUSION

Food-allergic patients at high risk for anaphylaxis who receive their EAI from a community pharmacy are often not instructed on how to use an EAI or receive incorrect instructions. Pharmacists show considerable gaps in knowledge about food allergy and its management. These data suggest that opportunities exist to improve the quality of care provided by pharmacies to high-risk food-allergic patients.

Potential application of notochordal cells for intervertebral disc regeneration: an in vitro assessment

Recent studies suggest that notochordal cells (NCs) might be involved in intervertebral disc homeostasis, a role exploitable to counteract matrix degradation as observed during degeneration. This study aimed to evaluate the potential of NCs to promote matrix production by nucleus pulposus cells (NPCs) and to compare it to the currently proposed addition of bone marrow stromal cells (BMSCs). Using alginate beads, bovine NPCs were exposed for 28 d to porcine NC conditioned medium (NCCM); direct co-culture with porcine NCs or bovine BMSCs; or the combination of BMSCs and NCCM. Effects on cell proliferation, disc matrix production (proteoglycans, collagens) and disc matrix protein expression (aggrecan, collagen 1 and 2, SOX9) were determined and compared to TGFβ stimulation. NCCM strongly promoted NPC proliferation (x 2.2) and matrix production (x 3.9) to levels similar to that with TGFβ, whereas the direct addition of NCs had no effect. Co-culture of NPCs and BMSCs led to proteoglycan synthesis similar to NPCs alone, which was slightly improved by NCCM (x 1.5). Histological analysis confirmed biochemical data. Gene expression of analysed proteins remained stable for all groups and unaffected by medium conditions. NCs could substantially stimulate NPCs through factors secreted into conditioned medium and in levels similar to the addition of BMSCs. This study showed that molecular agents secreted by NCs constitute a promising alternative to the proposed "standard" injection of BMSCs for disc repair: their effects are similar, do not require the injection of a large number of cells and can be further amplified when the factors are identified.

Effects of processing technologies combined with cell wall degrading enzymes on in vitro degradability of barley

Effects of processing technologies and cell wall degrading enzymes on in vitro degradation of barley were tested in a 5 × 2 factorial arrangement: 5 technologies (unprocessed, wet-milling, extrusion, autoclaving, and acid-autoclaving), with or without enzymes. Upper gastrointestinal tract digestion (Boisen incubation) and large intestinal fermentation (gas production technique) were simulated in duplicate. All technologies increased digestion of DM (13 to 43% units) and starch (22 to 51% units) during Boisen incubation, compared with the unprocessed control (P < 0.01). Wet-milling, extrusion, and acid-autoclaving increased CP digestion by 29 to 33% units (P < 0.01). Xylanase and β-glucanase addition increased digestion of DM (≈ 20% units), starch (≈ 20% units), and CP (≈ 10% units) in unprocessed and autoclaved barley (P < 0.01). Wet-milling, extrusion, and acid-autoclaving, reduced the extent (50%) and maximum rate (60 to 75%) of fermentation (P < 0.01), which appeared to reflect the reduced amount of starch present in the Boisen residues. In conclusion, wet-milling, extrusion, and acid-autoclaving improved in vitro starch and CP digestion in barley, which is related to the cell wall matrix disruption. Addition of xylanases and β-glucanases improved in vitro starch and CP digestion only in unprocessed barley or barley poorly affected by processing.

Morbidity is related to a green living environment

BACKGROUND

As a result of increasing urbanisation, people face the prospect of living in environments with few green spaces. There is increasing evidence for a positive relation between green space in people's living environment and self-reported indicators of physical and mental health. This study investigates whether physician-assessed morbidity is also related to green space in people's living environment.

METHODS

Morbidity data were derived from electronic medical records of 195 general practitioners in 96 Dutch practices, serving a population of 345,143 people. Morbidity was classified by the general practitioners according to the International Classification of Primary Care. The percentage of green space within a 1 km and 3 km radius around the postal code coordinates was derived from an existing database and was calculated for each household. Multilevel logistic regression analyses were performed, controlling for demographic and socioeconomic characteristics.

RESULTS

The annual prevalence rate of 15 of the 24 disease clusters was lower in living environments with more green space in a 1 km radius. The relation was strongest for anxiety disorder and depression. The relation was stronger for children and people with a lower socioeconomic status. Furthermore, the relation was strongest in slightly urban areas and not apparent in very strongly urban areas.

CONCLUSION

This study indicates that the previously established relation between green space and a number of self-reported general indicators of physical and mental health can also be found for clusters of specific physician-assessed morbidity. The study stresses the importance of green space close to home for children and lower socioeconomic groups.

[Characterization of membrane-bound Fe(III)-EDTA reductase activities of the thermophilic gram-positive dissimilatory iron-reducing bacterium Thermoterrabacterium ferrireducens]

Whole-cell suspensions of T. ferrireducens reduced Fe(III) citrate, Fe(III)-EDTA, and ferrihydrite with glycerol as an electron donor. After cell disruption, the highest activity was registered with Fe(III)-EDTA as the electron acceptor and NADH or NAD(P)H as electron donors. About 80% of the NAD(P)H-dependent Fe(III)-EDTA reductase activities were associated with the membrane fraction of the cells. Treatment of the membranes with lauryl maltoside led to complete solubilization of the NADH-dependent and 70% solubilization of the NADPH-dependent Fe(III)-EDTA reductase activities. After purification by ion-exchange chromatography, the NADH-dependent activity was concentrated 8-fold, and the NADPH-dependent activity was concentrated 11-fold, with a yield of about 10% for both activities. The Fe(III)-EDTA-reducing enzyme complex included c-type cytochromes and a protein with a molecular mass of ca. 115 k Da, consisting of two polypeptides. This is the first description of membrane-bound Fe(III)-reducing oxidoreductase activities from a gram-positive dissimilatory Fe(III)-reducing bacterium.

Effective oligonucleotide-mediated gene disruption in ES cells lacking the mismatch repair protein MSH3

We have previously demonstrated that site-specific insertion, deletion or substitution of one or two nucleotides in mouse embryonic stem cells (ES cells) by single-stranded deoxyribo-oligonucleotides is several hundred-fold suppressed by DNA mismatch repair (MMR) activity. Here, we have investigated whether compound mismatches and larger insertions escape detection by the MMR machinery and can be effectively introduced in MMR-proficient cells. We identified several compound mismatches that escaped detection by the MMR machinery to some extent, but could not define general rules predicting the efficacy of complex base-pair substitutions. In contrast, we found that four-nucleotide insertions were largely subject to suppression by the MSH2/MSH3 branch of MMR and could be effectively introduced in Msh3-deficient cells. As these cells have no overt mutator phenotype and Msh3-deficient mice do not develop cancer, Msh3-deficient ES cells can be used for oligonucleotide-mediated gene disruption. As an example, we present disruption of the Fanconi anemia gene Fancf.

Low-temperature kinetic measurements of microsecond freeze-hyperquench (MHQ) cytochrome oxidase monitored by UV-visible spectroscopy with a newly designed cuvette

A special cuvette was designed to measure optical changes of MHQ (microsecond freeze-hyperquench) powder samples at temperatures below approx. 250 K. Reduced cytochrome c oxidase from Paracoccus denitrificans was reacted with O(2) for 100 micros, frozen as a powder and transferred to the cuvette. Subsequently, cytochrome oxidase was allowed to react further following stepwise increments of the temperature from 100 K up to 250 K while recording spectra between 300 and 700 nm. The temperature was raised only when no further changes in the spectra could be detected. The experiment yielded spectra of the A, P(M), F and O intermediate states. This demonstrated that the catalytic cycle of cytochrome oxidase at low temperature is similar to that at room temperature and so verifies the suitability of this method for the study of enzymes with high catalytic-centre activity.

The Cape Triage Score -- a triage system for South Africa

The Cape Triage Score (CTS) has been derived by the Cape Triage Group (CTG) for use in emergency units throughout South Africa. It can also be used in the pre-hospital setting, although it is not designed for mass casualty situations. The CTS comprises a physiologically based scoring system and a list of discriminators, designed to triage patients into one of five priority groups for medical attention. Three versions have been developed, for adults, children and infants.

Membrane-bound denitrification in the Gram-positive bacterium Bacillus azotoformans

Gram+ bacteria are capable of complete denitrification just like Gram- (Gram-negative) bacteria. However, Gram+ (Gram-positive) bacteria have a very small periplasmic-like space. This leads to the question of whether those enzymes and electron carriers involved in denitrification, which are normally located in the periplasmic space in Gram- bacteria, are located in the periplasmic-like space in Gram+ bacteria or have been modified as membrane-bound proteins. Using Bacillus azotoformans as a Gram+ bacterial model, our study demonstrates that anaerobic denitrification is catalysed by four membrane-bound enzymes and that the electron carriers are membrane-bound c-type cytochromes and menaquinol. NADH dehydrogenase is coupled with the denitrification pathway providing menaquinol. In addition, the cytochrome b(6)f complex forms part of the denitrification pathway, oxidizing menaquinol and reducing at least three different membrane-bound c-type cytochromes. We determined that the NO reductase, qCu(A)NOR (where NOR stands for nitric oxide reductase), can accept electrons from two donors, a specific cytochrome c(551) and menaquinol. Similarly, nitrite reductase, a copper enzyme, and nitrous oxide reductase may be bifunctional enzymes. Regarding the bifunctionality of qCu(A)NOR, we propose that the menaquinol-linked pathway is involved in the detoxification of NO.

Electroconvulsive therapy for the treatment of clozapine nonresponders suffering from schizophrenia--an open label study

OBJECTIVE

This open label study describes the efficacy of electroconvulsive therapy (ECT) as adjunctive treatment in clozapine nonresponders suffering from schizophrenia.

METHOD

The results of clozapine and ECT treatment in 11 clozapine nonresponders suffering from schizophrenia are reported in terms of remission and relapse.

RESULTS

Eight patients had a remission with this combination treatment. After remission of symptoms five patients had a relapse. Three of the five patients who relapsed had a second successful ECT course and remained well with maintenance ECT and clozapine. No evidence for adverse effects was found.

CONCLUSION

Adjunctive ECT can be efficacious in clozapine nonresponders suffering from schizophrenia.

Choledochal cysts: age of presentation, symptoms, and late complications related to Todani's classification

PURPOSE

The aim of this study was to compare presentation, complications, diagnosis, and treatment of choledochal cysts in pediatric and adult patients.

METHODS

Forty-two patients were analyzed after subdivision into 3 groups: group A, less than 2 years (n = 10); group B, 2 to 16 years (n = 11); group C, greater than 16 years (n = 21).

RESULTS

The cysts were classified as extrahepatic (n = 33), intrahepatic (n = 5), and combined (n = 4). Seventy-six percent of patients presented with abdominal pain, (20 of 21 group C), and 57% with jaundice, (10 of 10 group A). Cholangiocarcinoma occurred in 6 patients, 4 of whom had previously undergone internal drainage procedures. Excision of the extrahepatic cyst was performed in 27 of 37 patients. Five patients, of whom, 4 had cholangiocarcinoma, were beyond curative treatment at the time of diagnosis. Six patients had died at the closure of this study, 5 of them had carcinoma.

CONCLUSIONS

Presenting symptoms are age dependent with jaundice prevailing in children and abdominal pain in adults. In view of the high risk of cholangiocarcinoma, early resection and not internal drainage is the appropriate treatment of extrahepatic cysts. Patients who had undergone internal drainage in the past still should undergo resection of the cyst.

Comparison between the nitric oxide reductase family and its aerobic relatives, the cytochrome oxidases

The denitrification pathway has been studied in the hyperthermophilic archaeon Pyrobaculum aerophilum. In contrast with Gram-negative bacteria, all four denitrification enzymes are membrane-bound. P. aerophilum is also the only denitrifyer identified so far in which menaquinol is the electron donor to all four denitrification reductases. The NO reductase (NOR) of P. aerophilum belongs to the superfamily of haem-copper oxidases and is of the qNOR (quinol-dependent) type. Three types of NOR have been purified so far: cNOR (cytochrome c/pseudoazurin-dependent), qNOR and qCu(A)NOR (qNOR that contains Cu(A) at the electron entry site). It is proposed that the NORs and the various cytochrome oxidases have evolved by modular evolution, in view of the structure of their electron donor sites. qNOR is further proposed to be the ancestor of all NORs and cytochrome oxidases belonging to the superfamily of haem-copper oxidases.

Virtual reality treatment versus exposure in vivo: a comparative evaluation in acrophobia

The aim of the present study was to evaluate the effectiveness of low-budget virtual reality (VR) exposure versus exposure in vivo in a between-group design in 33 patients suffering from acrophobia. The virtual environments used in treatment were exactly copied from the real environments used in the exposure in vivo program. VR exposure was found to be as effective as exposure in vivo on anxiety and avoidance as measured with the Acrophobia Questionnaire (AQ), the Attitude Towards Heights Questionnaire (ATHQ) and the Behavioral Avoidance Test (BAT). Results were maintained up to six months follow-up. The present study shows that VR exposure can be effective with relatively cheap hardware and software on stand-alone computers currently on the market. Further studies into the effectiveness of VR exposure are recommended in other clinical groups as agoraphobics and social phobics and studies in which VR exposure is compared with more emerging virtual worlds as presented in CAVE-type systems.

Binding of nucleotides by T4 DNA ligase and T4 RNA ligase: optical absorbance and fluorescence studies

The interaction of nucleotides with T4 DNA and RNA ligases has been characterized using ultraviolet visible (UV-VIS) absorbance and fluorescence spectroscopy. Both enzymes bind nucleotides with the K(d) between 0.1 and 20 microM. Nucleotide binding results in a decrease of absorbance at 260 nm due to pi-stacking with an aromatic residue, possibly phenylalanine, and causes red-shifting of the absorbance maximum due to hydrogen bonding with the exocyclic amino group. T4 DNA ligase is shown to have, besides the catalytic ATP binding site, another noncovalent nucleotide binding site. ATP bound there alters the pi-stacking of the nucleotide in the catalytic site, increasing its optical extinction. The K(d) for the noncovalent site is approximately 1000-fold higher than for the catalytic site. Nucleotides quench the protein fluorescence showing that a tryptophan residue is located in the active site of the ligase. The decrease of absorbance around 298 nm suggests that the hydrogen bonding interactions of this tryptophan residue are weakened in the ligase-nucleotide complex. The excitation/emission properties of T4 RNA ligase indicate that its ATP binding pocket is in contact with solvent, which is excluded upon binding of the nucleotide. Overall, the spectroscopic analysis reveals important similarities between T4 ligases and related nucleotidyltransferases, despite the low sequence similarity.

Properties of a thermostable nitrate reductase from the hyperthermophilic archaeon Pyrobaculum aerophilum

The nitrate reductase of the hyperthermophilic archaeon Pyrobaculum aerophilum was purified 137-fold from the cytoplasmic membrane. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, the enzyme complex consists of three subunits with apparent molecular weights of 130,000, 52,000, and 32,000. The enzyme contained molybdenum (0.8-mol/mol complex), iron (15.4-mol/mol complex) and cytochrome b (0.49-mol/mol complex) as cofactors. The P. aerophilum nitrate reductase distinguishes itself from nitrate reductases of mesophilic bacteria and archaea by its very high specific activity using reduced benzyl viologen as the electron donor (V(max) with nitrate, 1,162 s(-1) (326 U/mg); V(max) with chlorate, 1,348 s(-1) (378 U/mg) [assayed at 75 degrees C]). The K(m) values for nitrate and chlorate were 58 and 140 microM, respectively. Azide was a competitive inhibitor and cyanide was a noncompetitive inhibitor of the nitrate reductase activity. The temperature optimum for activity was > 95 degrees C. When incubated at 100 degrees C, the purified nitrate reductase had a half-life of 1.5 h. This study constitutes the first description of a nitrate reductase from a hyperthermophilic archaeon.

A novel copper A containing menaquinol NO reductase from Bacillus azotoformans

The molecular biology and biochemistry of denitrification in gram-negative bacteria has been studied extensively. However, little is known about this process in gram-positive bacteria. We have purified the NO reductase from the cytoplasmic membrane of the gram-positive bacterium Bacillus azotoformans. The purified enzyme consists of two subunits with apparent molecular masses of 16 and 40 kDa based on SDS-PAGE. Analytical and spectroscopic determinations revealed the presence of one non-heme iron, two copper atoms and of two b-type hemes per enzyme complex. Heme c was absent. Using EPR and UV-visible spectroscopy, it was determined that one of the hemes is a low-spin heme b, in which the two axial histidine imidazole planes are positioned at an angle of 60-70 degrees. The second heme b is high-spin binding CO in the reduced state. The high-spin heme center and the non-heme iron are EPR silent. They are proposed to form a binuclear center where reduction of NO occurs. There are two novel features of this enzyme that distinguish it from other NO reductases. First, the enzyme contains copper in form of copper A, an electron carrier up to now only detected in cytochrome oxidases and nitrous oxide reductases. Second, the enzyme uses menaquinol as electron donor, whereas cytochrome c, which is the substrate of other NO reductases, is not used. Copper A and both hemes are reducible by menaquinol. This new NO reductase is thus a menaquinol:NO oxidoreductase. With respect to its prosthetic groups the B. azotoformans NO reductase is a true hybrid between copper A containing cytochrome oxidases and NO reductases present in gram-negative bacteria. It may represent the most ancient "omnipotent" progenitor of the family of heme-copper oxidases.

High prevalence of parvovirus B19 IgG antibodies among Dutch hemophilia patients

BACKGROUND AND OBJECTIVES

Human parvovirus B19 is a potential risk to hemophiliac patients receiving blood products.

MATERIALS AND METHODS

To determine the prevalence of the corresponding antibody in patients with hemophilia A or B von Willebrand's disease, we tested 326 hemophilia patients for anti-B19 IgG. The results were compared with those of 203 age-matched controls (male blood donors and children).

RESULTS

The overall prevalence of B19 IgG in the hemophilia patients was 302/326, and in the controls 123/203. Below the age of 10, hemophilia patients had a higher prevalence of B19 IgG (76%, 42/55) than the controls (23%, 11/48; p < 0.00001). In those below the age of 5 who had been treated exclusively with monoclonally purified concentrate, it made no difference whether the product was pasteurized or solvent-detergent treated. There was significantly lower incidence in patients who were rarely treated.

CONCLUSION

Parvovirus B19 if frequently transmitted in blood products. Existing virus-inactivating methods do not prevent transmission.

The NosX and NirX proteins of Paracoccus denitrificans are functional homologues: their role in maturation of nitrous oxide reductase

The nos (nitrous oxide reductase) operon of Paracoccus denitrificans contains a nosX gene homologous to those found in the nos operons of other denitrifiers. NosX is also homologous to NirX, which is so far unique to P. denitrificans. Single mutations of these genes did not result in any apparent phenotype, but a double nosX nirX mutant was unable to reduce nitrous oxide. Promoter-lacZ assays and immunoblotting against nitrous oxide reductase showed that the defect was not due to failure of expression of nosZ, the structural gene for nitrous oxide reductase. Electron paramagnetic resonance spectroscopy showed that nitrous oxide reductase in cells of the double mutant lacked the Cu(A) center. A twin-arginine motif in both NosX and NirX suggests that the NosX proteins are exported to the periplasm via the TAT translocon.

The lactoperoxidase system: the influence of iodide and the chemical and antimicrobial stability over the period of about 18 months

The lactoperoxidase (LP) system is a natural antimicrobial system, the use of which has been suggested as a preservative in foods and pharmaceuticals. The effect of adding iodide to the LP system, the chemical stability and the change in antimicrobial effectiveness during storage was studied. Addition of iodide with thiocyanate increased the fungicidal and bactericidal effect against Candida albicans, Escherichia coli and Staphylococcus aureus. Pseudomonas aeruginosa showed the same inhibition in the LP system with iodide and without iodide. Storage of the LP system in completely filled airtight containers for 18 months caused a 35% loss of the initial thiocyanate concentration. The antimicrobial activity of this LP system was strong enough to kill inocula of 106 cfu ml-1 of the four test organisms within 2 h of contact time. During storage of the air-containing LP system, the concentration of thiocyanate was reduced below detection limit within 7 d, the concentrations of hypothiocyanite and hypoiodite within 350 d. After 516 d the antimicrobial activity of air-containing LP system was strong enough to kill inocula of 106 cfu ml-1 Ps. aeruginosa within 2 h, Staph. aureus within 4 h and Candida albicans and E. coli within 1 week of contact time.

Involvement of a novel hydroxylamine oxidoreductase in anaerobic ammonium oxidation

In this study a novel hydroxylamine oxidoreductase (HAO) was purified and characterized from an anaerobic ammonium-oxidizing (Anammox) enrichment culture. The enzyme, which constituted about 9% of the protein mass in the soluble fraction of the cell extract, was able to oxidize hydroxylamine and hydrazine. When phenazine methosulfate and methylthiazolyltetrazolium bromide were used as electron acceptors, a V(max) [21 and 1.1 micromol min(-)(1) (mg of protein)(-)(1)] and K(m) (26 and 18 microM) for hydroxylamine and hydrazine were determined, respectively. The hydroxylamine oxidoreductase is a trimer and contains about 26 hemes per 183 kDa. As deduced from UV/vis spectra, hydroxylamine reduced more and different cytochromes than hydrazine. The dithionite-reduced spectrum showed an unusual 468 nm peak. Inhibition experiments with H(2)O(2) showed that hydroxylamine bound to this P-468 cytochrome, which is assumed to be the putative substrate binding site. Cyanide and hydrazine inhibited the oxidation of hydroxylamine. The amino acid sequences of several peptide fragments of HAO from Anammox showed a clear difference with the deduced amino acid sequence of HAO from the aerobic ammonia-oxidizing bacterium Nitrosomonas europaea. In EPR spectra of the Anammox HAO, two g-values (g(z)() = 2.37 and 2.42) were observed, which were not present in HAO of N. europaea.

In vivo analysis of the mechanisms for oxidation of cytosolic NADH by Saccharomyces cerevisiae mitochondria

During respiratory glucose dissimilation, eukaryotes produce cytosolic NADH via glycolysis. This NADH has to be reoxidized outside the mitochondria, because the mitochondrial inner membrane is impermeable to NADH. In Saccharomyces cerevisiae, this may involve external NADH dehydrogenases (Nde1p or Nde2p) and/or a glycerol-3-phosphate shuttle consisting of soluble (Gpd1p or Gpd2p) and membrane-bound (Gut2p) glycerol-3-phosphate dehydrogenases. This study addresses the physiological relevance of these mechanisms and the possible involvement of alternative routes for mitochondrial oxidation of cytosolic NADH. Aerobic, glucose-limited chemostat cultures of a gut2Delta mutant exhibited fully respiratory growth at low specific growth rates. Alcoholic fermentation set in at the same specific growth rate as in wild-type cultures (0.3 h(-1)). Apparently, the glycerol-3-phosphate shuttle is not essential for respiratory glucose dissimilation. An nde1Delta nde2Delta mutant already produced glycerol at specific growth rates of 0.10 h(-1) and above, indicating a requirement for external NADH dehydrogenase to sustain fully respiratory growth. An nde1Delta nde2Delta gut2Delta mutant produced even larger amounts of glycerol at specific growth rates ranging from 0.05 to 0.15 h(-1). Apparently, even at a low glycolytic flux, alternative mechanisms could not fully replace the external NADH dehydrogenases and glycerol-3-phosphate shuttle. However, at low dilution rates, the nde1Delta nde2Delta gut2Delta mutant did not produce ethanol. Since glycerol production could not account for all glycolytic NADH, another NADH-oxidizing system has to be present. Two alternative mechanisms for reoxidizing cytosolic NADH are discussed: (i) cytosolic production of ethanol followed by its intramitochondrial oxidation and (ii) a redox shuttle linking cytosolic NADH oxidation to the internal NADH dehydrogenase.

Direct measurement of electrical transport through DNA molecules

Attempts to infer DNA electron transfer from fluorescence quenching measurements on DNA strands doped with donor and acceptor molecules have spurred intense debate over the question of whether or not this important biomolecule is able to conduct electrical charges. More recently, first electrical transport measurements on micrometre-long DNA 'ropes', and also on large numbers of DNA molecules in films, have indicated that DNA behaves as a good linear conductor. Here we present measurements of electrical transport through individual 10.4-nm-long, double-stranded poly(G)-poly(C) DNA molecules connected to two metal nanoelectrodes, that indicate, by contrast, large-bandgap semiconducting behaviour. We obtain nonlinear current-voltage curves that exhibit a voltage gap at low applied bias. This is observed in air as well as in vacuum down to cryogenic temperatures. The voltage dependence of the differential conductance exhibits a peak structure, which is suggestive of the charge carrier transport being mediated by the molecular energy bands of DNA.