The questionable value of some science-based 'welfare' assessments in intensive animal farming: sow stalls as an illustrative example.

A recent review of the code of practice for pigs brought attention to the question of how to assess the impact of housing conditions on pig welfare. The stance adopted by the law-makers, which mirrors that of industry, is that the status quo should be maintained until there is irrefutable scientific evidence in favour of change. Sows in intensive pig farms are often confined in cages (sow stalls) that are little bigger than their body. Many people find this repellent and the question of whether keeping sows in stalls is detrimental to their welfare has become a major focus of debate. All animal welfare groups in Australia, including the RSPCA, oppose the use of sow stalls. This brief essay critically examines the rationale for refusing to sanction change unless supported by scientific evidence. We conclude that the criteria for assessing welfare should not be restricted to consideration of scientific evidence alone, but should be widened to encompass moral and ethical considerations.

Comparison of different stomatal conductance algorithms for ozone flux modelling.

A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221-224.] algorithm for calculating stomatal conductance (g(s)) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of g(s), whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (A(n)).

Effects of anti-arthritic drugs on proteoglycan synthesis by equine cartilage.

The concentration-effect relationships of phenylbutazone, indomethacin, betamethasone, pentosan polysulphate (PPS) and polysulphated glycosaminoglycan (PSGAG), on proteoglycan synthesis by equine cultured chondrocytes grown in monolayers, and articular cartilage explants were measured. The effect of PSGAG on interleukin-1beta induced suppression of proteogycan synthesis was also investigated. Proteoglycan synthesis was measured by scintillation assay of radiolabelled sulphate (35SO4) incorporation. Polysulphated glycosaminoglycan and PPS stimulated proteoglycan synthesis in chondrocyte monolayers in a concentration-related manner with maximal effects being achieved at a concentration of 10 microg/mL. Polysulphated glycosaminoglycan reversed the concentration-related suppression of proteoglycan synthesis induced by interleukin-1beta. Neither PSGAG nor PPS exerted significant effects on radiolabel incorporation in cartilage explants. Betamethasone suppressed proteoglycan synthesis by both chondrocytes and explants at high concentrations (0.1-100 microg/mL), but the effect was not concentration-related. At low concentrations (0.001-0.05 microg/mL) betamethasone neither increased nor decreased proteoglycan synthesis. Phenylbutazone and indomethacin increased radiolabel incorporation in chondrocyte cultures but not in cartilage explants at low (0.1, 1 and 10 microg/mL), but not at high (20 and 100 microg/mL) concentrations. These findings may be relevant to the clinical use of these drugs in the treatment of equine disease.

Modelling stomatal ozone flux across Europe.

A model has been developed to estimate stomatal ozone flux across Europe for a number of important species. An initial application of this model is illustrated for two species, wheat and beech. The model calculates ozone flux using European Monitoring and Evaluation Programme (EMEP) model ozone concentrations in combination with estimates of the atmospheric, boundary layer and stomatal resistances to ozone transfer. The model simulates the effect of phenology, irradiance, temperature, vapour pressure deficit and soil moisture deficit on stomatal conductance. These species-specific microclimatic parameters are derived from meteorological data provided by the Norwegian Meteorological Institute (DNMI), together with detailed land-use and soil type maps assembled at the Stockholm Environment Institute (SEI). Modelled fluxes are presented as mean monthly flux maps and compared with maps describing equivalent values of AOT40 (accumulated exposure over threshold of 40 ppb or nl l(-1)), highlighting the spatial differences between these two indices. In many cases high ozone fluxes were modelled in association with only moderate AOT40 values. The factors most important in limiting ozone uptake under the model assumptions were vapour pressure deficit (VPD), soil moisture deficit (for Mediterranean regions in particular) and phenology. The limiting effect of VPD on ozone uptake was especially apparent, since high VPDs resulting in stomatal closure tended to co-occur with high ozone concentrations. Although further work is needed to link the ozone uptake and deposition model components, and to validate the model with field measurements, the present results give a clear indication of the possible implications of adopting a flux-based approach for future policy evaluation.

Kinin B2 and B1 receptor-mediated vasoactive effects in rabbit synovium.

Blood flow in response to bradykinin (BK, B2 receptor agonist) and desArg9 BK (B1 receptor agonist) was measured by laser Doppler flowmetry, as a reversal of noradrenaline (50 nmol)-induced decreased blood flow, in the synovium of the anaesthetised rabbit. Either a pretreatment (-6 h) of the cytokines IL-1beta (10 pmol) plus TNFalpha (10 pmol) or saline was injected intra-articularly. BK increased blood flow irrespective of pretreatment, whereas desArg9BK increased blood flow only in the cytokine-pretreated joints. The B2 antagonist HOE 140 reversed (p < 0.01) only the BK responses, and the B1 antagonist desArg9Leu8BK only reversed desArg9BK responses (p < 0.001). A nitric oxide synthase inhibitor, (L-NAME, 10 micromol kg(-1)), reversed the effects of the kinins (p < 0.05), but not sodium nitroprusside-stimulated responses. The results suggest that the B2 receptor is constitutively expressed and that the B1 receptor can mediate responses in inflamed tissues. The results, in addition, indicate that the responses, mediated via both receptors, are nitric oxide-dependent.

Calcitonin gene-related peptide: vasoactive effects and potential therapeutic role.

1. The cardiovascular biology of calcitonin gene-related peptide (CGRP) and the structurally related peptides amylin and adrenomedullin are briefly reviewed. 2. CGRP is a potent and long-lasting vasodilator; its possible role in disease, and the therapeutic potential of CGRP receptor agonists and antagonists is discussed.

Investigation of 6-hydroxydopamine-induced plasma extravasation in rat skin.

Perfusion of 6-hydroxydopamine into the rat knee and trachea induces plasma extravasation, possibly by tissue-specific mechanisms involving sympathetic and sensory nerves respectively, and we aimed to identify the mediators which contribute to this response in skin. 6-Hydroxydopamine (both hydrobromide and hydrochloride salts), dose dependently increased plasma extravasation into rat dorsal skin, however, when compared to bradykinin or the tachykinin NK1 receptor agonist GR73632, high concentrations of 6-hydroxydopamine (1-10 mumol/site) were required. The response to 6-hydroxydopamine was not inhibited in chemically sympathectomised rats (6-hydroxydopamine, 300 mg/kg i.p. over 7 days) but was significantly reduced by co-administration with the histamine (H1) and the 5-HT receptor antagonists mepyramine and methysergide and in skin sites pre-injected with compound 48/80 (4 micrograms, -18 h) to degranulate dermal mast cells. The response was not inhibited by co-injection of the tachykinin NK1 receptor antagonist SRI40333 or by the cyclo-oxygenase inhibitor indomethacin (5 mg kg-1 i.p., -30 min) except at the lowest dose of 6-hydroxydopamine (1 mumol/site). We conclude that 6-hydroxydopamine is not a potent or selective mediator of increased vascular permeability in rat skin but, at high concentrations, may induce oedema formation via release of vasoactive amines from mast cells, augmented by generation of prostaglandins.

The effect of intra-articular capsaicin on nerve fibres within the synovium of the rat knee joint.

The aim of this study was to establish the effects of intra-articular capsaicin (pelargonic acid vallinylamide) on synovial innervation of the rat knee. Rats were sacrificed 1, 2, 4 and 7 days after intra-articular injection of capsaicin and joint tissues stained with either conventional haematoxylin and eosin (H and E) or with specific antibodies to the calcitonin gene-related peptide (CGRP), substance P (both of which are markers for primary afferent fibres), the C-flanking peptide of neuropeptide Y (CPON) (localised in postganglionic sympathetic fibres), or protein gene product 9.5 (a pan-neuronal marker). At lower concentrations (0.1% and 0.25%), capsaicin produced no change in peptide staining pattern or histological appearance. At 0.5% capsaicin, there was complete loss of nerve fibres showing positive staining for CGRP and substance P at all time points. Staining for CPON and protein gene product 9.5 was still present, but decreased, 1 and 2 days after treatment and virtually absent at 4 and 7 days. These findings provide evidence for partially selective denervation induced by 0.5% capsaicin, in contrast to 1% capsaicin which abolished staining for all peptide markers, indicating a total ablation of nerve fibres. A consistent but unexpected finding was the presence of a severe inflammatory response in joints treated with 0.5% and 1% capsaicin. An influx of polymorphonuclear leucocytes was found to occur within 4 h of injection, with progressive appearance of mononuclear cells after this time. We conclude that it is difficult to specifically deplete sensory nerve fibres from the synovium by means of local capsaicin injection. Although selective loss of staining for sensory nerve fibres could be achieved by injection of 0.5% capsaicin, there was progressive non-specific loss of post-ganglionic autonomic fibres which may be related to the severe inflammatory response provoked by the higher doses of capsaicin.

Mechanism of bradykinin-induced plasma extravasation in the rat knee joint.

1. We have investigated the mechanism of bradykinin (BK)-induced plasma extravasation into the knee joint of the anaesthetized rat. Accumulation of [125I]-human serum albumin within the synovial cavity was used as a marker of increased vascular permeability. 2. Perfusion with BK (1 microM) produced significant plasma extravasation into the knee which was inhibited by co-perfusion of the selective bradykinin B2 receptor antagonist D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin (Hoe 140, 200 nM). 3. The bradykinin B1 receptor agonist, [des-Arg9]-BK (up to 100 mM), did not induce plasma extravasation into the knee joint, over this time period. 4. Chemical sympathectomy by chronically administered 6-hydroxydopamine (6-OHDA) did not inhibit bradykinin-induced plasma extravasation. Acute intra-articular perfusion with 6-OHDA (to stimulate transmitter release from sympathetic nerve terminals) at concentrations up to 50 mM did not induce significant plasma extravasation. Intra-articular perfusion of 100 mM 6-OHDA induced significant plasma extravasation but produced severe systemic toxicity. 5. The selective neurokinin1 (NK1) receptor antagonist, RP67580 (230 nmol kg-1), or receptor antagonists for the mast cell products histamine and 5-hydroxytryptamine did not significantly inhibit BK-induced plasma extravasation. 6. Co-perfusion of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) (1 mM) did not significantly inhibit the response to BK. 133Xe clearance from L-NAME (1 mM)-injected joints was significantly (P < 0.05) reduced compared to D-NAME injected joints, suggesting a reduction in blood flow as a result of decreased basal NO production. Systemic administration of L-NAME at doses sufficient to produce significant and sustained elevation of blood pressure (5 or 30 mg kg-1, i.v. 15 min prior to BK perfusion) also failed to significantly inhibit the BK-induced response.7 We conclude that, in normal joints, BK induces plasma extravasation by acting on bradykinin B2 receptors and that this response is not dependent on secondary release of mediators from sympathetic nerve terminals, sensory nerves, mast cells or on generation of NO.

The effect of intra-articular capsaicin on passive synovial anaphylaxis and blood flow in the rat knee joint.

Normal rat and human synovium is innervated by small diameter, unmyelinated, peptide-containing nerves. A close anatomical association between these nerves and mast cells has been postulated23, although functional interactions have not been described. Capsaicin is frequently used to activate sensory nerves and we have examined both acute and long-term effects of capsaicin on passive synovial anaphylaxis (PSA) and blood flow in the rat knee joint. The acute injection of capsaicin into the synovial space (330 nmol, 30 min prior to antigen) significantly inhibited plasma extravasation into the joint tissues (measured by accumulation of [125I]-human serum albumin) following PSA, and produced vasoconstriction in normal joints (measured by 133Xe clearance). There was no effect on plasma extravasation when capsaicin was injected 3 h prior to antigen. Inhibition of the PSA response following acute intra-articular capsaicin was not reversed by pretreatment with the cyclo-oxygenase inhibitor indomethacin (to inhibit thromboxane generation) or in rats chronically treated with guanethidine (to deplete noradrenaline from post-ganglionic sympathetic fibres). Further, a longer term pre-treatment of the joints with a single intra-articular injection of capsaicin (3.3 mumol) also attenuated plasma extravasation following induction of PSA 7 days later, and was accompanied by a non-significant decrease in joint blood flow. Plasma extravasation in response to compound 48/80, a non-immunological mediator of mast-cell degranulation, was not affected in joints treated with capsaicin 7 days previously.(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of calcitonin gene-related peptide (CGRP) to neurogenic vasodilator responses.

The neuropeptide calcitonin gene-related peptide (CGRP) is a potent vasodilator in the microcirculation of many tissues including the skin and joint. In order to elucidate the mechanism of endogenous CGRP release, we have used a multiple site 133Xe clearance technique to measure local blood flow changes in response to agents injected intradermally in the rabbit. Capsaicin (100 nmol/site) and human alpha CGRP (3 pmol/site) stimulated similar increases in blood flow and, in both cases, the effect was totally abolished by the CGRP antagonist, CGRP8-37 (1 nmol/site). By contrast, the nitric oxide synthase inhibitor L-nitro arginine methyl ester (L-NAME, 30 nmol/site) had little effect on human alpha CGRP-induced vasodilation, but caused significant inhibition of the response to capsaicin (p < 0.05). These results show that increased blood flow in rabbit skin caused by exogenous CGRP is independent of nitric oxide. In addition, however, they suggest that nitric oxide is required for either the release of endogenous CGRP from capsaicin-sensitive nerves or its subsequent activity.

Calcitonin gene-related peptide increases blood flow and potentiates plasma protein extravasation in the rat knee joint.

1. The effects of calcitonin gene-related peptide (CGRP) and other vasoactive mediators of inflammation on blood flow in the synovial vessels and plasma protein extravasation into the knee (femoro-tibial) joint of the pentobarbitone-anaesthetized rat were measured. 2. Changes in synovial blood flow were estimated by 133xenon clearance from the synovial cavity. CGRP (0.1 pmol and 10 pmol) and prostaglandin E1 (PGE1; 3 pmol and 300 pmol) significantly increased clearance from the knee joint measured 5 min after intra-articular injection. Substance P (10 pmol) had no effect on synovial blood flow. 3. Intra-articular perfusion of the rat knee with CGRP at concentrations up to 0.1 mM, or PGE1 at concentrations up to 10 microM, did not increase plasma extravasation into the synovial cavity measured by accumulation of intravenously injected 125I-albumin in the perfusate. 4. Plasma extravasation into the knee was significantly increased by infusion of bradykinin (0.1 microM), 5-hydroxytryptamine (1 microM) and histamine (0.1 mM), compared with the contralateral joints in the same animals which were perfused with Tyrode solution. 5. Perfusion of the knee joint with substance P did not specifically induce 125I-labelled albumin accumulation in the synovial cavity even at doses that had systemic effects as observed by marked plasma extravasation into other tissues. 6. The increase in plasma extravasation induced by histamine (0.1 mM) was potentiated by co-infusion with CGRP (0.1 microM) and PGE1 (3 microM). However the response to a submaximal dose (0.1 microM) of bradykinin, which induced similar plasma extravasation to histamine (0.1 mM), was not increased by co-infusion with CGRP or PGE1.7. These results show that CGRP is a potent vasodilator in the rat knee. CGRP released from sensory nerves may act synergistically with mediators of increased vascular permeability to modify the inflammatory response in this site.

Evidence that calcitonin gene-related peptide contributes to inflammation in the skin and joint.

Calcitonin gene-related peptide produces dose-related vasodilatation after intradermal injection in several species. In the present study, CGRP increased blood flow in rabbit skin but had no direct effect on edema formation in rat or rabbit skin or in the rat knee joint. However, CGRP produced significant potentiation of edema formation when co-injected with histamine, a potent mediator of increased vascular permeability. Therefore, release of CGRP from stimulated C-fiber nerves may contribute to the vascular changes that are an integral part of the inflammatory process. The activity of the putative CGRP antagonist CGRP8-37 (300 pmol) against CGRP was also investigated in rabbit and rat skin. Whereas it was found to selectively antagonize the effects of CGRP in rabbit skin, the antagonist produced edema in rat skin at the same dose. Thus, CGRP8-37 may be used in the rabbit to study the effects of endogenously released CGRP, but caution is required when this antagonist is used in the rat.

Influence of feeding schedule on the absorption of orally administered flunixin in the horse.

The effects of access to hay and of restricted feeding on the pharmacokinetics of flunixin administered orally to six healthy ponies were compared in a cross-over study. No access to feed for a few hours before and after flunixin administration resulted in rapid absorption with a mean peak plasma concentration of 2.84 +/- 0.28 micrograms/ml attained in an average time of 0.76 +/- 0.18 h, followed by an exponential decline in plasma concentration. A lower peak plasma concentration was obtained when ponies had free access to hay before and after drug dosing. The mean maximum concentration (Cmax) was 1.30 +/- 0.23 micrograms/ml and maximum time (tmax) was prolonged to a mean time of 7.66 +/- 1.74 h. Free access to hay reduced and delayed the peak plasma concentration resulting in two or three separate concentration peaks in some ponies. The mean area under the plasma concentration-time curve was not significantly different for the two feeding regimens.

Antithrombotic actions of aspirin in the horse.

The antithrombotic effects of aspirin at two dose rates (4 mg/kg and 11 mg/kg bodyweight [bwt] were evaluated in normal, healthy ponies by measuring template bleeding time. Inhibition of platelet aggregation in response to adenosine diphosphate (ADP) and collagen was evaluated and cyclo-oxygenase activity was monitored by radioimmunoassay of thromboxane B2 (TXB2), the stable metabolite of thromboxane A2 (TXA2). TXB2 was measured in serum and platelet rich plasma. Bleeding time was prolonged significantly until 48 h after treatment at 12 mg/kg bwt and until 4 h at the lower dose rate. Synthesis of TXB2 and collagen induced aggregation were diminished for much greater periods with similar results at each of the dose rates. The prolonged effects of aspirin on platelet function occurred in spite of a very short plasma half-life of aspirin, because of its irreversible action on platelet cyclo-oxygenase. The results show that low dose aspirin has a potential role in antithrombotic therapy in horses although the relationship between skin bleeding time in normal horses and improvement of clinical conditions requires further research and evaluation in clinical trials. TXB2 measurement appears to overestimate the duration of antithrombotic effects of aspirin in vivo.

Functional and morphological studies on blood platelets in a thrombasthenic horse.

A four-year-old Standardbred gelding presented with a 3.5 year history of intermittent epistaxis and spontaneous submucosal petechiae and ecchymoses in the nares and the mouth. Routine haematological and biochemical examinations were unremarkable. A thrombocytopathy was suspected when activated partial thromboplastin time, one stage prothrombin time, plasma fibrinogen and the platelet count were all normal. The patient's platelets failed to aggregate with serotonin, adenosine diphosphate, collagen (at 20 micrograms/ml) or the endoperoxide analogue U46619. Very high levels of collagen (100 micrograms/ml) did cause aggregation. The response to the calcium ionophore A23187 was reduced and although complete degranulation occurred the resulting aggregates were unstable. Thromboxane generation in response to collagen and ADP was inferred from the concentration of its stable metabolite thromboxane B2 and was reduced. A diagnosis of a thrombasthenia-like syndrome possibly equivalent to Type II Glanzmann's thrombasthenia in people was made.

Plasma thromboxane B2 levels in horses experimentally infected with Strongylus vulgaris.

Plasma thromboxane B2 (TXB2) the stable inactive metabolite of thromboxane A2 (TXA2), was measured daily by specific radioimmunoassay in three groups of animals before and after experimental infection with Strongylus vulgaris. Infection of four 'parasite naive' foals produced a typical acute syndrome with intermittent but statistically insignificant rises in TXB2 levels. Interpretation of results was complicated by the presence of a non-septic peritonitis associated with implantation of the foals with electrodes for recording myoelectrical activity. In two foals of similar age, with some natural exposure to S. vulgaris, there was little or no clinical response to infection and increases in TXB2 were absent. Baseline levels were also much lower, indicating that the peritonitis may have affected the results obtained in the first group of foals. Severe mesenteric arteritis was confirmed at necropsy in all six foals. A third group of yearling horses, all with natural exposure to the parasite, were generally resistant to infection. One animal developed arteritis with clinical signs of diarrhoea and mild colic, and also showed intermittent increases in TXB2. The mean plasma TXB2 level after infection was significantly higher than in the control period, although absolute levels were lower than those recorded in the 'parasite naive' foals. Other animals in this group had low TXB2 levels and minimal arteritis was found at necropsy. These results indicate that although infection appears to have an effect on plasma TXB2, the changes are inconsistent and not reliable indicators of the presence of verminous arteritis. The results also confirm the difficulty in establishing infection and the variability of the response in animals with previous exposure.

The effect of Strongylus vulgaris larvae on equine intestinal myoelectrical activity.

The myoelectrical activity of the ileum, caecum and large colon was monitored from Ag-AgCl bipolar recording electrodes in four conscious 'parasite-naive' weanling foals. All foals were inoculated with 1000 infective 3rd-stage Strongylus vulgaris larvae and alterations to the myoelectrical activity observed. The frequencies of caecal and colonic spike bursts increased significantly in all post infection periods coinciding with assumed larval penetration into the intestinal mucosa and migration through the vasculature. Peaks in caecal and colonic activity occurred at Days 1 to 5 post infection. In the caecum, peaks occurred again at Days 15 and 31 post infection, preceding similar rises in colonic spike burst frequency at Days 19 and 35. Longer term changes indicated a return towards pre-infection levels of activity suggesting smooth muscle adaptation to decreased blood flow. The analysis of caecal and colonic spike burst propagation indicated that the increases in burst frequency were not attributable to an increase in the propagation of spike bursts in any particular direction, but rather to proportional increases in all directions of activity. There was a slight decrease in the simple ileal spike burst frequency immediately post-infection. None of the experimental animals exhibited signs of abdominal pain during the trial, and there was no evidence of bowel infarction at post mortem examination despite the presence of severe parasite-induced arterial lesions. The results suggest that increased caecal and colonic motility is an important host response in susceptible foals exposed to S. vulgaris larvae.

Radioimmunoassay of thromboxane B2 in horse plasma.

A radioimmunoassay for thromboxane B2 (TXB2) in unextracted horse plasma was evaluated. Sensitivity of the assay was 14.0 (SD 5.6) pg ml-1 of plasma. Interassay and intra-assay variation were 21.3 per cent and 4.3 per cent, respectively. The percentage of tracer bound in unextracted plasma in the absence of TXB2 was often higher than that in buffer. Therefore standard curves were obtained using standards diluted in plasma from horses treated with aspirin or in charcoal treated TXB2-free plasma. Standard curves determined in plasma and buffer were parallel. This assay was used to determine the half-life of exogenous TXB2 in horses. The mean value of 20.7 minutes (n = 3) is similar to that determined in other species. Storage of plasma samples at -20 degrees C for four months was found to alter the TXB2 levels in an unpredictable manner. Mean recovery was 102.4 per cent (SD 44.1). Effect of variability in sample collection and handling was assessed, but no consistent source of artifactual generation of TXB2 was found.