Chemical method to enhance transungual transport and iontophoresis efficiency

Transungual transport is hindered by the inherent small effective pore size of the nail even when it is fully hydrated. The objectives of this study were to determine the effects of chemical enhancers thioglycolic acid (TGA), glycolic acid (GA), and urea (UR) on transungual transport and iontophoresis efficiency. In vitro passive and iontophoretic transport experiments of model permeants mannitol (MA), UR, and tetraethylammonium (TEA) ion across the fully hydrated, enhancer-treated and untreated human nail plates were performed in phosphate-buffered saline. The transport experiments consisted of several stages, alternating between passive and anodal iontophoretic transport at 0.1mA. Nail water uptake experiments were conducted to determine the water content of the enhancer-treated nails. The effects of the enhancers on transungual electroosmosis were also evaluated. Nails treated with GA and UR did not show any transport enhancement. Treatment with TGA at 0.5M enhanced passive and iontophoretic transungual transport of MA, UR, and TEA. Increasing the TGA concentration to 1.8M did not further increase TEA iontophoresis efficiency. The effect of TGA on the nail plates was irreversible. The present study shows the possibility of using a chemical enhancer to reduce transport hindrance in the nail plate and thus enhance passive and iontophoretic transungual transport.

Rotation and asymmetric development of the zebrafish heart requires directed migration of cardiac progenitor cells

We have used high-resolution 4D imaging of cardiac progenitor cells (CPCs) in zebrafish to investigate the earliest left-right asymmetric movements during cardiac morphogenesis. Differential migratory behavior within the heart field was observed, resulting in a rotation of the heart tube. The leftward displacement and rotation of the tube requires hyaluronan synthase 2 expression within the CPCs. Furthermore, by reducing or ectopically activating BMP signaling or by implantation of BMP beads we could demonstrate that BMP signaling, which is asymmetrically activated in the lateral plate mesoderm and regulated by early left-right signals, is required to direct CPC migration and cardiac rotation. Together, these results support a model in which CPCs migrate toward a BMP source during development of the linear heart tube, providing a mechanism by which the left-right axis drives asymmetric development of the vertebrate heart.

Production, secretion, and biological activity of the C-terminal flanking peptide of human progastrin

BACKGROUND & AIMS

Processing of progastrin, the 80-amino acid precursor of the hormone gastrin, generates a variety of peptides with distinct distributions and biological activities. However, little is known regarding the expression, secretion, and biological activity of the 6-amino acid C-terminal flanking peptide (CTFP) of progastrin. The objectives were to determine the concentration of CTFP in normal subjects and patients with gastrointestinal diseases and to investigate the biological activity of CTFP.

METHODS

CTFP, gastrin-amide (Gamide), glycine-extended gastrin (Ggly), and progastrin were measured using region-specific radioimmunoassay (RIA) in antral extracts and resected colorectal cancers (CRC) and in plasma from normal subjects (fasting and meal stimulated) and from patients with CRC, multiple endocrine neoplasia type 1 (MEN-1), or pernicious anemia. The effect of CTFP on proliferation, migration, and activation of the mitogen-activated protein kinase (MAPK) pathway in several types of gastrointestinal cell lines was determined.

RESULTS

CTFP is by far the predominant progastrin-derived peptide found in the antrum (4-fold higher than Gamide), resected CRC, and circulation (60-fold higher than Gamide) and is released after meal stimulation. The hypergastrinemic patients (MEN-1, pernicious anemia) had elevated plasma Gamide but unaltered CTFP demonstrating differential secretion of these 2 progastrin-derived peptides. Finally, CTFP stimulated proliferation and migration and activated MAPK of cells in culture.

CONCLUSIONS

The high and regulated expression of CTFP in healthy and diseased subjects combined with the evidence for biological activity of CTFP demonstrates that CTFP is not an inactive metabolite of progastrin processing but is a bioactive peptide with potential roles in the normal and diseased gastrointestinal tract.

Circulating gastrin is increased in hemochromatosis

Gastric acid production is important in intestinal iron absorption. The peptide hormone gastrin exists in both amidated and non-amidated forms, which stimulate and potentiate gastric acid secretion, respectively. Since non-amidated gastrins require ferric ions for biological activity in vitro, this study investigated the connection between iron status and gastrin by measurement of circulating gastrin concentrations in mice and humans with hemochromatosis. Gastrin concentrations are increased in the plasma and gastric mucosa of Hfe(-/-) mice, and in the sera of humans with HFE-related hemochromatosis. The discovery of a relationship between iron status and circulating gastrin concentrations opens a new perspective on the mechanisms of iron homeostasis.

Enhancing phosphorus removal in constructed wetlands with ochre from mine drainage treatment

No single end-use has yet been identified that is capable of consuming the projected production of ochre (mainly iron (III) oxides) from mine drainage treatment. However, the high sorption capacity of ochre for phosphorus (up to 26 mg kg(-1)) means that it could be used in constructed wetlands to enhance phosphorus removal. Laboratory batch experiments showed that coarse-grained ochre removes 90% of all phosphorus forms from sewage effluent after 15 minutes of shaking. From a larger-scale experiment, it is estimated that constructed wetlands with an ochre substrate should remove phosphorus from sewage effluent for up to 200-300 years. The suitability of ochre for phosphorus removal is being investigated at the field scale in a wastewater constructed wetland (175 m2 area) in Berwickshire, UK. The hydraulic and treatment performance of the wetland were monitored for 15 months prior to installation at the inlet in November 2003 of a tank containing approximately 1200 kg ochre. Results so far show that improved hydraulic design is required for ochre to increase the mean phosphorus removal efficiency of the system (27 +/- 28%), but potentially toxic metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, Zn) have not been released from the ochre into the wetland outflow.

Encapsulated drop breakup in shear flow

We investigate the deformation and breakup in shear flow of an encapsulated drop in which both the core and shell are Newtonian fluids. The equations of motion are solved numerically using a level set method to track interface motion. We consider the case of a drop stretched to a given length in constant shear and then allowed to relax. A range of morphologies is produced, and novel kinematics occur, due to the interaction of the core and outer interfaces. A phase diagram is presented to describe the morphologies produced over a range of capillary numbers and core interfacial tensions.

Demystified...recombinant antibodies

Recombinant antibodies are important tools for biomedical research and are increasingly being used as clinical diagnostic/therapeutic reagents. In this article, a background to humanized antibodies is given, together with details of the generation of antibody fragments--for example, single chain Fv fragments. Phage antibody fragments are fast becoming popular and can be generated by simple established methods of affinity enrichment from libraries derived from immune cells. Phage display methodology can also be used for the affinity enrichment of existing antibody fragments to provide a reagent with a higher affinity. Here, phage antibodies are demystified to provide a greater understanding of the potential of these reagents and to engage clinicians and biomedical scientists alike to think about potential applications in pathology and clinical settings.

Dynamics of a drop at a fluid interface under shear

We analyze the dynamics of a two-dimensional drop lying on a fluid interface, sometimes called a liquid lens, subjected to simple shear flow. The three fluids, the drop and the two external fluids, meet at a triple point (or a triple line in three dimensions). A requirement for steady drop shapes is that the triple points are stationary. This leads to a flow topology different than that of a freely suspended drop. Results are substantiated with numerical results using a level set method for interface evolution and treatment of triple points. Possible implications for new drop instabilities are also discussed.

Movement of entomopathogenic nematodes in soils of Fragaria spp

The mobility of three entomopathogenic nematodes (Steinernema carpocapsae UK and All Strain, and S. glaseri (Nematoda: Steinernematidae) was observed in strawberry fields in Vancouver, WA. Nematodes were sprinkled over the soil surface using a mason jar. Soil and soil-moisture content, soil composition, soil pH and conductivity was reported over the evaluation period. 12 cm deep soil samples were taken after surface application at 9 and 25 days, 7, 26 and 45 and 6, 22, 37 and 50 days at the three different test sites within the surface application site and at 5 cm distance. Soil samples taken were divided into three layers (0-4, 5-8 and 9-12 cm) and exposed once to five Galleria larvae in the laboratory to evaluate nematode presence and movement. Results after surface application demonstrated more vertical movement of S. glaseri into deeper soil layers in comparison to both S. carpocapsae strains.

Treatment of posterior third ventricular central neurocytoma with endoscopic biopsy, endoscopic third ventriculostomy and stereotactic radiosurgery

Central neurocytomas of the posterior third ventricle are rare. These typically benign lesions have recently been shown to respond well to Gamma knife stereotactic radiosurgery (SRS). We present the case of a posterior third ventricle central neurocytoma presenting with aqueduct obstruction. The patient was treated with endoscopic biopsy and endoscopic third ventriculostomy, followed by Gamma knife radiosurgery. At 2 years the tumor has diminished in size and the patient is neurologically intact. This treatment strategy may avoid the risk of open ventricular surgery and the need for shunts in patients with central neurocytomas of appropriate size and location.

Isolation and characterisation of vascular endothelial growth factor-165 specific scFv fragments by phage display

Vascular endothelial growth factor (VEGF) is a multifunctional cytokine which plays a major role in angiogenesis. Alternative splicing causes the production of several different isoforms (VEGF-A 121, 145, 165, 189, 206). VEGF is essential for tumor angiogenesis and several studies have correlated elevated VEGF levels with tumor stage, metastases and progression. Antibody phage display was employed to isolate two scFv antibody fragments, D8 and F10, with specificity for the VEGF165 isoform. It was shown by ELISA and competitive immunohistochemistry that each clone bound to VEGF165 but not VEGF121. Immunohistochemistry with D8 and F10 on colorectal carcinoma and adenoma sections revealed positive staining similar to that shown by a polyclonal VEGF antibody. The scFv antibody fragments, D8 and F10, will be useful in specifically detecting circulating VEGF165 in cancer patients as most studies to date have quantified the total level of circulating VEGF (121 and 165). These reagents will allow further elucidation of the role of VEGF in tumor angiogenesis.

Effects of 9,10 anthraquinone on ruminal fermentation, total-tract digestion, and blood metabolite concentrations in sheep

The objective of this study was to evaluate the effects of adding 9,10 anthraquinone, a known inhibitor of methanogenesis and sulfate reduction, on blood metabolites, digestibility, and distribution of gas in sheep. In all experiments, we fed a complete pelleted diet that contained 17.5% crude protein and 24.5% acid detergent fiber. In an 8-wk study, feeding up to 66 ppm (dry matter basis) of 9,10 anthraquinone had no adverse effects on blood metabolites including indicators of normal enzyme function, mineral concentrations, and hematological measurements. Feeding 9,10 anthraquinone had no effect on average daily gain, although sheep fed a diet containing 66 ppm of 9,10 anthraquinone numerically gained the least weight. The ruminal molar proportions of acetic acid were decreased (P < 0.05) and the molar proportions of propionic acid were increased (P < 0.05) in sheep fed 1.5 and 66 ppm 9,10 anthraquinone when compared to those fed an unsupplemented diet. In a digestion trial, 9,10 anthraquinone (33 and 66 ppm) had no effect on the apparent digestion of nutrients in the total gastrointestinal tract. In a metabolism study, ruminal gasses were collected by rumenocentesis and analyzed for methane and hydrogen concentrations. Feeding 500 ppm of 9,10 anthraquinone to sheep resulted in a decrease (P < 0.07) in the concentration of methane, but an increase (P < 0.05) in hydrogen concentration of ruminal gas throughout the 19 d of feeding. There was no indication of ruminal adaptation throughout this time. These results are the first to show that 9,10 anthraquinone can partially inhibit in vivo rumen methanogenesis, which supports previous in vitro findings. In addition, at the concentrations used in this study, 9,10 anthraquinone was not toxic to ruminants.

Cerebellar responses during anticipation of noxious stimuli in subjects recovered from depression. Functional magnetic resonance imaging study

BACKGROUND

Subjects recovered from depression have a substantial risk for recurrence of depression, suggesting persistent abnormalities in brain activity.

AIMS

To test whether women recovered from depression show abnormal brain activity in functional magnetic resonance imaging (fMRI) during a conditioning paradigm with a noxious pain stimulus.

METHOD

Ten unmedicated women who had recovered from major depression and eight healthy control women each received either noxious hot or non-noxious warm stimuli, the onset of which was signalled by a specific coloured light during 3-tesla echo planar imaging-based fMRI.

RESULTS

Similar patterns of brain activation were found during painful stimulation for both patients and healthy controls. However, relative to healthy controls, subjects recovered from depression showed a reduced response in the cerebellum during anticipation of the noxious stimulus compared with anticipation of the non-noxious stimulus.

CONCLUSIONS

Our data suggest that abnormal cerebellar function could be a marker of vulnerability to recurrent depression. This could provide a new target for therapeutic interventions.

The effects of tryptophan depletion on cognitive and affective processing in healthy volunteers

RATIONALE

Cognitive impairment is a common feature of depressive illness. While accumulating evidence suggests that brain serotonin (5-HT) pathways play an important role in the neurobiology of depression, the extent to which altered 5-HT function is responsible for the associated changes in cognition and emotion remains unclear.

OBJECTIVE

The present study examined the effects of acute dietary depletion of tryptophan (TRP) on cognitive and affective processing in healthy volunteers and explored the putative role of 5-HT in the neuropsychology of depression.

METHODS

We administered computerised cognitive tests to healthy control participants following ingestion of TRP-free and nutritionally balanced amino acid drinks in a double-blind, placebo-controlled, crossover design.

RESULTS

The TRP-free amino acid mixture significantly lowered plasma total and free TRP concentrations relative to baseline values and produced selective deficits similar to those observed previously in cases of clinical depression. In particular, TRP depletion increased response times for happy but not sad targets in an affective go/no-go task and slowed responding in a visual discrimination and reversal learning task. These deficits were not due to a global sedative effect, as planning ability was unimpaired.

CONCLUSIONS

The present data indicate that serotonergic factors may be more involved in the disrupted inhibitory and emotional processing characteristic of depression than in other aspects of executive function, such as planning ability. These findings support the recent proposal that serotonergic manipulation may have greater effects on tasks mediated by frontal circuitry that includes the orbitofrontal cortex than by dorsolateral prefrontal cortex circuitry.

To cure chronic HIV infection, a new therapeutic strategy is needed

With the advent of highly active anti-retroviral therapy (HAART) in 1997, most investigators felt that HIV infection would be cured with a few years of antiviral therapy. It is now clear that antiviral drugs alone cannot cure the infection, even when applied within a few weeks of initial symptoms. There are now several reports of the discontinuation of HAART after several years of effective suppression of detectable plasma virus. Relapse occurs universally within a few weeks. More promising results have been reported if HAART is initiated early after infection. However, even in this instance, most patients suffer a relapse within a few weeks. If diagnostic treatment interruptions are performed, some individuals appear to control plasma virus concentrations at low levels - <5000 HIV RNA molecules/ml. We have similar results from subjects who were infected chronically before HAART was initiated, so that it is clear that the previous dogma that HIV-specific immune reactivity is absent in individuals who are chronically infected is incorrect. Immune reactivity to HIV does exist, and is detectable in vivo, even when the infection becomes chronic before therapy is initiated. Consequently, we are now faced with a new therapeutic dilemma: how can a cure of this infection be achieved? This review is focused on the rationale and methods to design clinical trials directed towards achieving a cure of HIV infection.

Identification of antigenic domains on the human sodium-iodide symporter which are recognized by autoantibodies from patients with autoimmune thyroid disease

The sodium-iodide symporter (NIS) is a novel autoantigen in autoimmune thyroid disease. In the present study we have characterized the antigenic domains on the human symporter which are recognized by autoantibodies from patients with either Graves' disease (GD) or autoimmune hypothyroidism (AH). Deletion derivatives of complementary DNA (cDNA) encoding the Na(+)/I(-) symporter were constructed using polymerase chain reaction (PCR) amplification. These deletion constructs were translated in vitro with the concomitant incorporation of [(35)S]methionine into the protein products. The reactivity of seven GD and six AH sera, which were known to contain symporter-binding antibodies, to each of the radiolabelled modified symporters was then determined in immunoprecipitation experiments. Analyses of the results obtained in the radiobinding assays suggest the existence of multiple antibody binding sites on human NIS (hNIS), including regions between amino acids (aa) 1--134, 191--286, 290--411, 411--520 and 520--588. Computer prediction of the potential B cell epitopes on the symporter revealed that, apart from aa 134--191, all the epitope domains identified overlapped, at least in part, with areas predicted to be highly antigenic. Interestingly, the antigenic domains represented by aa 191--286, 290--411 and 411--520 include regions of the polypeptide which form putative extracellular domains in the secondary structure model of the rat symporter. No correlation between the recognition of specific epitopes on the human symporter and the type of autoimmune thyroid disease was demonstrated.

Effect of postoperative atrial fibrillation on length of stay after cardiac surgery (The Postoperative Atrial Fibrillation in Cardiac Surgery study [PACS(2)]

Atrial fibrillation (AF) after cardiac surgery is thought to increase length of stay (LOS). A clinical pathway focused on the management of postoperative AF, including prophylaxis with beta blockers, was implemented to assess the effect of AF on LOS after cardiac surgery. Data were obtained on consecutive cardiac surgery patients in preoperative normal sinus rhythm, no prior history of AF, and no chronic antiarrhythmic therapy from January to May 1995 (control) and November 1996 to June 1997 (pathway). Statistical analysis was performed to assess the effect of postoperative AF on the LOS, clinical outcomes, and cost after cardiac surgery. Despite the clinical pathway, the LOS (7 days for both periods; p = 0.12) and incidence of AF (28.9% vs 28.4%; p = 0.92) remained unchanged. Unadjusted direct costs were 15% higher in the pathway period (p <0.001). Increased rates of beta-blocker therapy had a marginal effect on the incidence of postoperative AF, except in the group who only underwent primary coronary artery bypass graft surgery (31.2% vs 25.3%; p = 0.31). Multivariate analysis revealed that AF contributed only 1 to 1.5 days to the LOS. Thus, this investigation represents the most recent analysis of the effects of postoperative AF on LOS, clinical outcomes, and cost after cardiac surgery. Unlike prior studies, the impact of postoperative AF is less prominent in the current era of cardiac surgical care regardless of the presence of a clinical pathway addressing AF.

Cytokine response gene 8 (CR8) regulates the cell cycle G1-S phase transition and promotes cellular survival

Cellular proliferation and survival are modulated by the expression of specific genes. Cytokine response gene 8 (CR8), which was originally cloned as an IL-2-induced gene in human T lymphocytes, encodes a basic helix--loop--helix (bHLH) transcription factor. The CR8 gene product is highly conserved among human, mouse and rat, and contains sequence motifs that distinguish it from other bHLH families. The CR8 gene is ubiquitously expressed, and CR8 gene expression is induced by both growth-promoting as well as growth-inhibitory stimuli. As bHLH proteins have been found to regulate both the G1-S phase cell cycle transition, as well as cellular survival, the effects of CR8 on these processes were investigated. Ectopic CR8 expression in asynchronous U2OS cell cultures reduces the percentage of cells in the cell cycle S phase, and also slows the entry of G1-synchronized cells into S phase. The prolonged G1 interval correlates with impaired elevation of cyclin E protein and prolonged p21 protein expression in G1. CR8 expression also protects U2OS cells from serum-withdrawal induced apoptosis. These results indicate that CR8 is an important modulator of both the G1-S phase cell cycle transition, and cellular survival.

PU.1 is a lineage-specific regulator of tyrosine phosphatase CD45

The hematopoietic cell-specific ets family transcription factor PU.1 regulates many lymphoid and myeloid genes. We have determined that PU.1 is critical for lineage-specific expression of the tyrosine phosphatase CD45. CD45 is expressed exclusively in hematopoietic cells at all stages of development, except for mature red cells and platelets. Although CD45 is normally expressed in all leukocyte lineages, it is critically regulated by PU.1 only in myeloid cells. Whereas myeloid cells from PU.1 null mice failed to express CD45, lymphoid cells were CD45(+) by flow cytometry. Additionally, mRNA for CD45 was absent from PU.1-deficient myeloid cells. To understand the molecular basis for these observations, we characterized a transcriptional regulatory region of the murine CD45 gene containing exons 1a, 1b, and 2. Distinct transcriptional initiation sites for CD45 were demonstrated in T and B cells versus myeloid cells. A transcriptional initiation site in exon 1b (P1b) was principally utilized by myeloid cells. A PU.1 binding site was identified upstream of exon 1b by sequence analysis and DNA binding assays. Using this region of the CD45 locus we demonstrated that PU.1 directly transactivated reporter gene expression. Finally, retrovirus-mediated restoration of PU.1 expression to PU.1-deficient myeloid cells resulted in expression of cell surface CD45 and restored phosphatase activity, confirming the role of PU.1 in the positive regulation of this well known signaling molecule. We conclude that CD45 is regulated differentially in myeloid and lymphoid cells and that sequences critical to direct myeloid expression include a PU.1 binding site upstream of the P1b transcriptional initiation site.

Low-dose daily interleukin-2 immunotherapy: accelerating immune restoration and expanding HIV-specific T-cell immunity without toxicity

There is now a great deal of interest in therapies focused on improving the function of the immune system in the treatment of individuals infected with the HIV. Although the antiviral drugs effectively suppress replication of the virus, they cannot cure the infection. Therefore, it now appears that both antivirals and immune system stimulants will be necessary to maximally suppress residual latent virus, thereby allowing the discontinuation of the antivirals without relapse of detectable plasma virus. Interleukin-2 (IL-2) the first cytokine to be discovered at the molecular level has been used as a therapeutic in HIV infection, because it is critical for a normal functioning immune response. IL-2 is essential for the survival and proliferative expansion of antigen-activated T cells and natural killer (NK) cells, and also for promoting their differentiated functions of cytokine secretion and cytolysis. However, as IL-2 stimulates both the innate and acquired immune responses, when used as a therapeutic it can lead to severe toxicity when given in high doses. This review focuses on low dose, daily IL-2 therapy, used to accelerate the recovery of the immune system when viral replication is suppressed maximally with antivirals. In addition, the principles of the use of IL-2 to activate HIV-specific immune reactivity are discussed. At least two signals are required to promote the proliferative expansion and function of antiviral effector lymphocytes, HIV antigens and IL-2.

Nutrient losses by surface run-off following the application of organic manures to arable land. 2. Phosphorus

Phosphorus (P) surface run-off losses were studied following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farm yard manure (FYM) and inorganic nitrogen (N) and P fertiliser were compared, over a 4-year period (1993-97). N losses from the same studies are reported in a separate paper. The application of cattle FYM and, especially slurry, to the silty clay loam soil increased both particulate and soluble P loss in surface water flow. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increased application of slurry solids increased all forms of P loss via surface run-off; the results suggested that a threshold for greatly increased risk of P losses via this route, as for N, occurred at ca. 2.5-3.0 t/ha solids loading. This approximates to the 50 m3/ha application rate limit suggested for slurry within UK 'good agricultural practice'. The studies also provided circumstantial evidence of the sealing of the soil surface by slurry solids as the major mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Losses of total and soluble P, recorded for each of the 4 years of experiments, reached a maximum of only up to 2 kg/ha total P (TP), even after slurry applications initiating run-off. Whilst these losses are insignificant in agronomic terms, peak concentrations of P (up to 30,000 micrograms/l TP) in surface water during a run-off event, could be of considerable concern in sensitive catchments. Losses of slurry P via surface run-off could make a significant contribution to accelerated eutrophication on entry to enclosed waters, particularly when combined with high concentrations of NO3(-)-N. Restricting slurry application rates to those consistent with good agronomic practice, and within the limits specified in existing guidelines on good agricultural practice, offers the simplest and most effective control measure against this potentially important source of diffuse pollution.

Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

Research was conducted on nitrogen (N) surface run-off losses following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farmyard manure and inorganic N and phosphorus (P) fertiliser were compared, over a 4-year period (1993-97). P losses from the same studies are reported in a separate paper. The application of cattle slurries to the silty clay loam soil increased the loss of solids and NH4(+)-N in surface water flow compared to control plots receiving inorganic fertiliser only, or no treatment, but had little effect on NO3(-)-N losses by this route. Results were consistent with other observations that rainfall events immediately after manure applications are particularly likely to be associated with nutrient run-off losses. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increasing slurry application rate and, in particular, slurry solids loading, increased solids and NH4(-)-N losses via surface run-off. The threshold, above which the risk of losses via surface run-off appeared to be greatly increased, was ca. 2.5-3.0 t/ha slurry solids, which approximates to the 50 m3/ha limit suggested for slurry within UK 'good agricultural practice'. Sealing of the soil surface by slurry solids appears to be a possible mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Total losses of NH4(+)-N and NO3(-)-N during the 4-year monitoring period were insignificant in agronomic terms, but average soluble N concentrations (NH4(+)-N + NO3(-)-N) in run-off, ranging from ca. 2.0 mg/l, up to 14.0 mg/l for the higher rate slurry treatments. Peak concentrations of NH4(+)-N > 30 mg/l, are such as to be of concern in sensitive catchments, in terms of the potential for contribution to accelerated eutrophication and adverse effects on freshwater biota.