Ethical challenges facing veterinary professionals in Ireland: results from Policy Delphi with vignette methodology

Ethics is key to the integrity of the veterinary profession. Despite its importance, there is a lack of applied research on the range of ethical challenges faced by veterinarians. A three round Policy Delphi with vignette methodology was used to record the diversity of views on ethical challenges faced by veterinary professionals in Ireland. Forty experts, comprising veterinary practitioners, inspectors and nurses, accepted to participate. In round 1, twenty vignettes describing a variety of ethically challenging veterinary scenarios were ranked in terms of ethical acceptability, reputational risk and perceived standards of practice. Round 2 aimed at characterising challenges where future policy development or professional guidance was deemed to be needed. In round 3, possible solutions to key challenges were explored. Results suggest that current rules and regulations are insufficient to ensure best veterinary practices and that a collective approach is needed to harness workable solutions for the identified ethical challenges. Challenges pertaining mostly to the food chain seem to require enforcement measures whereas softer measures that promote professional discretion were preferred to address challenges dealing with veterinary clinical services. These findings can support veterinary representative bodies, advisory committees and regulatory authorities in their decision making, policy and regulation.

What do European veterinary codes of conduct actually say and mean? A case study approach

Codes of Professional Conduct (CPCs) are pivotal instruments of self-regulation, providing the standards to which veterinarians should, and sometimes must, comply. Despite their importance to the training and guidance of veterinary professionals, research is lacking on the scope and emphasis of the requirements set out in veterinary CPCs. This paper provides the first systematic investigation of veterinary CPCs. It relies on a case study approach, combining content and thematic analyses of five purposively selected European CPCs: Federation of Veterinarians of Europe (FVE), Denmark, Ireland, Portugal and the UK. Eight overarching themes were identified, including 'definitions and framing concepts', 'duties to animals', 'duties to clients', 'duties to other professionals', 'duties to competent authorities', 'duties to society', 'professionalism' and 'practice-related issues'. Some differences were observed, which may be indicative of different approaches to the regulation of the veterinary profession in Europe (which is reflected in having a 'code of ethics' or a 'code of conduct'), cultural differences on the status of animals in society, and regulatory bodies' proactivity in adapting to professional needs and to societal changes regarding the status of animals. These findings will contribute to an improved understanding of the roles of CPCs in regulating the veterinary profession in Europe.

Physiological, physical and behavioural changes in dogs (Canis familiaris) when kennelled: testing the validity of stress parameters

Domestic dogs (Canis familiaris) housed in kennelling establishments are considered at risk of suffering poor welfare. Previous research supporting this hypothesis has typically used cortisol:creatinine ratios (C/Cr) to measure acute and chronic stress in kennelled dogs. However, the value of C/Cr as a welfare indicator has been questioned. This study aimed to test the validity of a range of physiological, physical and behavioural welfare indicators and to establish baseline values reflecting good dog welfare. Measurements were taken from 29 privately-owned dogs (14 males, 15 females), ranging in age and breed, in their own home and in a boarding kennel environment, following a within-subjects, counterbalanced design. Pairwise comparisons revealed that C/Cr and vanillylmandelic acid:creatinine ratios (VMA/Cr) were higher in the kennel than home environment (P=0.003; P=0.01, respectively) and were not associated with differences in movement/exercise between environments. Dogs' surface temperature was lower in kennels (P=0.001) and was not associated with ambient temperature. No association with age, or effects of kennel establishment, kennelling experience, sex or source were found. Dogs were generally more active in kennels, but showed considerable individual variability. C/Cr and 5-HIAA:creatinine ratios (5-HIAA/Cr) were negatively correlated with lip licking in kennels. Baseline values for each parameter are presented. The emotional valence of responses was ambiguous and no definitive evidence was found to suggest that dogs were negatively stressed by kennelling. It was concluded that C/Cr and, particularly, VMA/Cr and surface temperature provide robust indicators of psychological arousal in dogs, while spontaneous behaviour might be better used to facilitate interpretation of physiological and physical data on an individual level.

A guide to defining and implementing protocols for the welfare assessment of laboratory animals: eleventh report of the BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement

The refinement of husbandry and procedures to reduce animal suffering and improve welfare is an essential component of humane science. Successful refinement depends upon the ability to assess animal welfare effectively, and detect any signs of pain or distress as rapidly as possible, so that any suffering can be alleviated. This document provides practical guidance on setting up and operating effective protocols for the welfare assessment of animals used in research and testing. It sets out general principles for more objective observation of animals, recognizing and assessing indicators of pain or distress and tailoring these to individual projects. Systems for recording indicators, including score sheets, are reviewed and guidance is set out on determining practical monitoring regimes that are more likely to detect any signs of suffering. This guidance is intended for all staff required to assess or monitor animal welfare, including animal technologists and care staff, veterinarians and scientists. It will also be of use to members of ethics or animal care and use committees. A longer version of this document, with further background information and extra topics including training and information sharing, is available on the Laboratory Animals website.

DNA fingerprints of dogs and cats

Human minisatellite probes consisting of tandem repeats of the 'core' sequence, a putative recombination signal in human DNA, cross-hybridize to multiple polymorphic fragments in dog and cat DNA to produce individual-specific DNA 'fingerprints'. Pedigree analysis shows that most of the DNA fragments detected in an individual are heterozygous, and that these fragments are derived from multiple dispersed autosomal loci. DNA fingerprints of cats and dogs should prove suitable for individual identification and for establishing family relationships. They are also suitable for rapid marker generation in large pedigrees and could be applied to linkage analysis in these animals.

Vaccines and animal welfare

Vaccination promotes animal welfare by protecting animal health, but it also has other welfare benefits, e.g. recent investigations have looked at the potential of vaccines in immunoneutering such as immunocastration--a humane alternative to the painful traditional methods. Similarly, vaccination can be used during disease outbreaks as a viable alternative to stamping-out, thus avoiding the welfare problems that on-farm mass slaughter can cause. Protecting animal health through vaccination leads to improved animal welfare, and maintaining good welfare ensures that animals can respond successfully to vaccination (as poor welfare can lead to immunosuppression, which can affect the response to vaccination). It is clear that vaccination has tremendous advantages for animal welfare and although the possible side effects of vaccination can have a negative effect on the welfare of some individual animals, the harm caused by these unwanted effects must be weighed against the undoubted benefits for groups of animals.

Assessing the welfare of genetically altered mice

In 2003, under the auspices of the main UK funders of biological and biomedical research, a working group was established with a remit to review potential welfare issues for genetically altered (GA) mice, to summarize current practice, and to recommend contemporary best practice for welfare assessments. The working group has produced a report which makes practical recommendations for GA mouse welfare assessment and dissemination of welfare information between establishments using a 'mouse passport'. The report can be found at www.nc3rs.org.uk/GAmice and www.lal.org.uk/gaa and includes templates for the recommended welfare assessment scheme and the mouse passport. An overview is provided below.

Degrees of aversion shown by rats and mice to different concentrations of inhalational anaesthetics

The distress associated with the induction of anaesthesia with halothane, isoflurane, enflurane and carbon dioxide was investigated in rats and mice by measuring the level of aversion they displayed on exposure to low, medium and high concentrations of these agents. The animals were exposed to each agent in a test chamber containing air or gas mixtures, which they were able to enter and leave at will, and the level of aversion was assessed in terms of the initial withdrawal and total dwelling times in the chamber. Comparisons between the anaesthetic and air-control treatments indicated that concentrations of the agents recommended for the rapid and efficient induction of anaesthesia were associated with some degree of aversion. Carbon dioxide was by far the most aversive gas for both rats and mice, with the least aversive being halothane for rats, and halothane and enflurane for mice. With all the anaesthetics, the level of aversion increased as the concentration increased.

The novel guanylyl cyclase MsGC-I is strongly expressed in higher-order neuropils in the brain of Manduca sexta

Guanylyl cyclases are usually characterized as being either soluble (sGCs) or receptor (rGCs). We have recently cloned a novel guanylyl cyclase, MsGC-I, from the developing nervous system of the hawkmoth Manduca sexta that cannot be classified as either an sGC or an rGC. MsGC-I shows highest sequence identity with receptor guanylyl cyclases throughout its catalytic and dimerization domains, but does not contain the ligand-binding, transmembrane or kinase-like domains characteristic of receptor guanylyl cyclases. In addition, MsGC-I contains a C-terminal extension of 149 amino acid residues. In this paper, we report the expression of MsGC-I in the adult. Northern blots show that it is expressed preferentially in the nervous system, with high levels in the pharate adult brain and antennae. In the antennae, immunohistochemical analyses show that it is expressed in the cell bodies and dendrites, but not axons, of olfactory receptor neurons. In the brain, it is expressed in a variety of sensory neuropils including the antennal and optic lobes. It is also expressed in structures involved in higher-order processing including the mushroom bodies and central complex. This complicated expression pattern suggests that this novel guanylyl cyclase plays an important role in mediating cyclic GMP levels in the nervous system of Manduca sexta.

Identification of the cellular target for eclosion hormone in the abdominal transverse nerves of the tobacco hornworm, Manduca sexta

The isolated abdominal central nervous system of Manduca sexta undergoes an increase in cyclic GMP (cGMP) when exposed to the insect peptide eclosion hormone (EH) before pupal ecdysis. Previously, cGMP immunocytochemistry revealed that the EH-stimulated increase in cGMP was contained in numerous filamentous processes within the transverse nerve associated with each abdominal ganglion. These processes seemed to be the axons of neurosecretory cells projecting to this neurohemal organ. In the present paper, we now show that the EH-stimulated cGMP is not present in neurosecretory terminals. There is no colocalization of the EH-stimulated cGMP with immunoreactivity of two peptides, known to be present in axons in the transverse nerves. Furthermore, there is no colocalization of EH-stimulated cGMP with the synaptic vesicle protein, synaptotagmin. The neurosecretory axons are localized to a narrow band at the anterior margin of the transverse nerve, whereas the cellular elements showing an EH-stimulated cGMP increase are primarily present in the posterior region. There are two cell types in this region: a granular and a nongranular type. The cGMP immunoreactivity seems to be contained within the nongranular type. During adult development, the cells of the posterior compartment spread in a thin layer between the transverse and dorsal nerves, become positive for myosin immunoreactivity between pupal stages 5 and 8, and seem to form the adult ventral diaphragm muscles. We conclude that the EH-sensitive filaments in the transverse nerves of Manduca are most likely to be intrinsic cells that subsequently develop into the ventral diaphragm muscles of the adult.

Radiofrequency thermal balloon angioplasty in an experimental model of peripheral arterial stenosis

RATIONALE

To assess the effect of thermal balloon angioplasty on surgically created peripheral arterial stenoses.

METHODS

Unilateral femoral arterial stenoses were created in 17 neonatal lambs (Dorset X Suffolk/Mule), using absorbable sutures. Six to 8 weeks later, the stenoses were dilated using either a standard (N=5), or thermal balloon angioplasty (N=9). Immediate angiography, flow and pressure gradient measurements were made to assess the acute result following either procedure. The survivors were followed up for a further period of 4 to 6 weeks, and a terminal angiographic study performed. The thermally treated segments of vessels were removed for qualitative histologic analysis.

RESULTS

Thermal angioplasty appeared to be acutely successful in eight of nine animals, compared with one of five successful procedures following standard angioplasty. Higher therapeutic temperatures (> or = 80 degrees C) were associated with vascular complications. At the terminal study, stenoses had recurred in four of six survivors successfully treated with thermal angioplasty. Histologic studies demonstrated non-uniform effects of thermal dilation on the vessel wall, with variable changes ranging from partial or full-thickness tears, fibroblastic or myocyte proliferation, and disorganization of the vessel wall layers.

CONCLUSION

Thermal angioplasty appears to be acutely more beneficial compared with standard angioplasty. However there is a significant recurrence of stenoses, and non-uniform changes in the vessel wall.

Neurons involved in nitric oxide-mediated cGMP signaling in the tobacco hornworm, Manduca sexta

Recently, both nitric oxide synthase (NOS), and nitric oxide (NO)-sensitive guanylyl cyclase were cloned in Manduca sexta and implicated in several cellular, developmental, and behavioral processes (Nighorn et al. [1998] J Neurosci 18:7244-7255). However, NO is a highly diffusive gas, and little is known about the range and specificity of its actions on neurons. To begin examining the role of NO as a neurotransmitter in the central nervous system (CNS) of larval Manduca, we have mapped potential NO-producing neurons using fixation-resistant NADPH-diaphorase staining and antisera that recognize a NOS-specific epitope. In addition, to detect NO-responsive neurons, we treated the CNS with NO donors and used antibodies that recognize elevated levels of cyclic 3;,5;-guanosine monophosphate (cGMP). Many potential NO-producing neurons were mapped, including the ventral unpaired median cells and three pairs of lateral cells in each abdominal ganglion. Additional neurons in the dorsal midline of ganglia A5-7 (PM2) appear to express NOS in a segment-specific manner. At the larval-to-pupal transition, this staining pattern changes; the PM2 neurons stain weakly or are undetectable and there is novel expression of NOS in cell 27. In response to NO donors, a small number of neurons produce detectable cGMP accumulation in a segment-specific pattern. These include a pair of posteriodorsally positioned interneurons (IN505) in all the abdominal ganglia, PM2 neurons in A5, and PM1 and PM2 neurons in A7. Hence, PM2 neurons in A5 and A7 are potentially capable of producing and responding to NO. These identified NO-producing and responding neurons provide a tractable model system for studying the dynamics and specificity of NO signaling in the CNS.

Self-consciousness and animal suffering

Animals with relatively highly developed brains are likely to experience some degree of self-awareness and the ability to think. As well as being interesting in its own right, self-consciousness matters from an ethical point of view, since it can give rise to forms of suffering above and beyond the immediate physical sensations of pain or distress. This article surveys the evidence for animal self-consciousness and its implications for animal welfare.

Refinement of in vivo tests

It is important, both morally, scientifically and legally, that animal experimentation causes the minimum amount of suffering necessary to achieve the scientific objective. This paper describes an approach that facilitates the recognition and assessment of animal pain and distress through the use of clinical signs. The score sheet system can help to indicate new scientific responses, as well as to determine and to validate humane end points in the safety testing of biological products using animals. Some examples are given.

Identification of a novel guanylyl cyclase that is related to receptor guanylyl cyclases, but lacks extracellular and transmembrane domains

We have identified a novel guanylyl cyclase, named MsGC-I, that is expressed in the nervous system of Manduca sexta. MsGC-I shows highest sequence identity with receptor guanylyl cyclases throughout its catalytic and dimerization domains but does not contain the ligand-binding, transmembrane, or kinase-like domains characteristic of receptor guanylyl cyclases. In addition, MsGC-I contains a C-terminal extension of 149 amino acids that is not present in other receptor guanylyl cyclases. The sequence of MsGC-I contains no regions that show similarity to the regulatory domain of soluble guanylyl cyclases. Thus, MsGC-I appears to represent a member of a new class of guanylyl cyclases. We show that both a transcript and a protein of the sizes predicted from the MsGC-I cDNA are present in the nervous system of Manduca and that MsGC-I is expressed in a small population of neurons within the abdominal ganglia. When expressed in COS-7 cells, MsGC-I appears to exist as a soluble homodimer with high levels of basal guanylyl cyclase activity that is insensitive to stimulation by nitric oxide. Western blot analysis, however, shows that MsGC-I is localized to the particulate fraction of nervous system homogenates, suggesting that it may be membrane-associated in vivo.

Identification and characterization of a novel beta subunit of soluble guanylyl cyclase that is active in the absence of a second subunit and is relatively insensitive to nitric oxide

Previously characterized soluble guanylyl cyclases form alpha-beta heterodimers that can be activated by the gaseous messenger, nitric oxide. In mammals, four subunits have been cloned, named alpha1, alpha2, beta1, and beta2. We have identified a novel soluble guanylyl cyclase isoform from the nervous system of the insect Manduca sexta that we have named M. sexta guanylyl cyclase beta3 (MsGC-beta3). It is most closely related to the mammalian beta subunits but has several features that distinguish it from previously identified soluble cyclases. Most importantly, MsGC-beta3 does not need to form heterodimers to form an active enzyme because guanylyl cyclase activity can be measured when it is expressed alone in COS-7 cells. Moreover, this activity is only weakly enhanced in the presence of the nitric oxide donor, sodium nitroprusside. Several of the amino acids in rat beta1 subunits, previously identified as being important in heme binding or necessary for nitric oxide activation, are substituted with nonsimilar amino acids in MsGC-beta3. There are also an additional 315 amino acids C-terminal to the catalytic domain of MsGC-beta3 that have no sequence similarity to any known protein. Northern blot analysis shows that MsGC-beta3 is primarily expressed in the nervous system of Manduca.

The nitric oxide-cGMP pathway may mediate communication between sensory afferents and projection neurons in the antennal lobe of Manduca sexta

The nitric oxide (NO)-cGMP signaling system is thought to play important roles in the function of the olfactory system in both vertebrates and invertebrates. One way of studying the role of NO in the nervous system is to study the distribution and properties of NO synthase (NOS), as well as the soluble guanylyl cyclases (sGCs), which are the best characterized targets of NO. We study NOS and sGC in the relatively simple and well characterized insect olfactory system of the hawkmoth, Manduca sexta. We have cloned Manduca sexta nitric oxide synthase (MsNOS) and two sGCs (MsGCalpha1 and MsGCbeta1), characterized their basic biochemical properties, and studied their expression in the olfactory system. The sequences of the Manduca genes are highly similar to their mammalian homologs and show similar biochemical properties when expressed in COS-7 cells. In particular, we find that MsGC functions as an obligate heterodimer that is stimulated significantly by NO. We also find that MsNOS has a Ca2+-sensitive NO-producing activity similar to that of mammalian neuronal NOS. Northern and in situ hybridization analyses show that MsNOS and the MsGCs are expressed in a complementary pattern, with MsNOS expressed at high levels in the antennae and the MsGCs expressed at high levels in a subset of antennal lobe neurons. The expression patterns of these genes suggest that the NO-sGC signaling system may play a role in mediating communication between olfactory receptor neurons and projection neurons in the glomeruli of the antennal lobe.

Norepinephrine increases cyclic GMP levels in cerebellar cells from neuronal nitric oxide synthase knockout mice

Cyclic GMP is an important intracellular messenger in the nervous system that may mediate cellular forms of neuronal plasticity. Previous studies show that most neurotransmitters stimulate cyclic GMP levels by the activation of nitric oxide synthase (NOS). In this study, we report that in primary cell cultures from the cerebellum of neuronal NOS knockout mice, norepinephrine stimulates an increase in cyclic GMP content. This increase is seen in both granule cell and astrocyte cultures and is not blocked by inhibitors of NOS or by inhibition of soluble guanylyl cyclase. These results suggest a novel pathway by which norepinephrine enhances cyclic GMP levels in the nervous system.

Up- and downregulation of esr20, an ecdysteroid-regulated gene expressed in the tracheae of Manduca sexta

Investigations of ecdysteroid-regulated gene cascades in Drosophila have shown that characteristics of downstream genes in such cascades include their repression by high ecdysteroid levels, their expression at low hormone levels, and the dependence of their expression on protein synthesis. In an earlier study, we identified a gene, esr20, which is expressed in the tracheae of the tobacco hornworm, Manduca sexta, prior to larval and pupal ecdyses. Initial characterization of the expression of esr20 suggested that it had the above characteristics of a downstream gene in an ecdysteroid-regulated cascade. The present study shows that, unlike the downstream genes in Drosophila, the expression of esr20 in tracheae cannot be induced by changes in the ecdysteroid levels alone. We present evidence which suggests that a decline in ecdysteroid is necessary but not sufficient for expression. Soon after pupal ecdysis the level of the esr20 transcript drops fourfold, and by 24 h after ecdysis the transcript is undetectable. Evidence is presented which suggests that this decline in transcript levels requires protein synthesis and appears to result from a decline in the stability of the transcript.

Expression of a developmentally regulated gene, Mng10, in identified neurosecretory cells in the CNS of Manduca sexta

We are interested in the molecular events underlying the development of the nervous system of Manduca sexta during the final 24 h of the pupal molt. In this article we describe a gene, Mng10, that is expressed in the abdominal nervous system of M. sexta and is developmentally regulated over this 24-h period. In situ hybridization analysis shows that the transcript is localized predominantly to a single pair of uniquely identifiable neurosecretory neurons, the NS-L1 cells in the abdominal ganglia. Mng10 is a single copy gene encoding a 229 amino acid protein with a predicted molecular mass of 26 kDa. At the amino acid level the protein shows 34% identity to the yeast transcription unit, Yer082. Northern blot analysis shows that the transcript of Mng10 is very rare, comprising about 0.001% of the poly (A)+ RNA from the CNS and is detectable at 4 h but not 24 h prior to pupal ecdysis. One of the physiological events that develops over the final 24 h of the pupal molt is the ability of the nervous system to respond to the neuropeptide eclosion hormone. In this context, it is interesting to note that the NS-L1 cells are members of the group of 50 neurons that show increased cGMP immunoreactivity when the nervous system is exposed to the neuropeptide eclosion hormone.

Comparison of the expression patterns of five developmentally regulated genes in Manduca sexta and their regulation by 20-hydroxyecdysone in vitro

A previous study, using subtractive hybridization, identified five genes (esr16, esr20, Mng10, Mng14 and tps9) whose transcripts were up-regulated prior to metamorphosis in Manduca sexta nervous tissue. The developmental time points chosen for subtraction suggested that expression could be coordinately regulated and should be negatively regulated by the steroid hormones, the ecdysteroids. In the present paper, we present an analysis of the expression patterns of these five genes, using reverse transcription-polymerase chain reaction (RT-PCR), at various times during development and assess the effects of 20-hydroxyecdysone and cycloheximide on their expression in vitro. This analysis revealed that with the exception of esr20 all transcripts were detectable at all times and that all but one of the genes were up-regulated in vivo and in vitro in the absence or in the presence of low levels of the ecdysteroids. In the absence of ecdysteroids, cycloheximide blocked the accumulation of only two transcripts, esr16 and esr20. These results reveal a much more complex pattern of gene expression in the central nervous system prior to metamorphosis than previously imagined.

Insect physiology: the emerging story of ecdysis

The discovery of a new insect peptide hormone that triggers ecdysis - shedding of an old cuticle - has revealed hidden layers of intricacy about an insect behavior previously thought to be mediated by a single neuropeptide.

Subtractive hybridization strategy using paramagnetic oligo(dT) beads and PCR

Subtractive hybridization has been widely used for the identification of differentially expressed genes. Here we describe a simple, sensitive strategy of subtractive hybridization that involves binding the driver poly(A)+ RNA pool to paramagnetic Dynabeads Oligo (dT)25. After hybridization with target cDNA, the molecules common to both pools are removed. The subtracted cDNA is then amplified with PCR and used for library screening. Using this method, we have identified four cDNA clones that represent developmentally regulated transcripts in the central nervous system of the tobacco hornworm Manduca sexta. All four transcripts are of low abundance, comprising only 0.001%-0.5% of the poly(A)+ RNA pool.

Neuropeptide-stimulated cyclic guanosine monophosphate immunoreactivity in the neurosecretory terminals of a neurohemal organ

The neuropeptide eclosion hormone acts on the nervous system of the tobacco hornworm, Manduca sexta, to increase cyclic guanosine monophosphate (cGMP) levels. In this study I describe the localization of some of the sites where these increases occur. Prior to pupal ecdysis, eclosion hormone stimulates an increase in cGMP in a network of fibers in the transverse nerve of each abdominal ganglion. Double-label experiments with propidium iodide suggest that the cGMP immunoreactivity is primarily localized in neurosecretory nerve endings. The time course of the increase in cGMP immunoreactivity and its requirement for lipid metabolism is similar to that of the cGMP increase measured by radioimmunoassay. The cGMP response in the transverse nerve is stage-specific, occurring prior to pupal ecdysis and not prior to larval or adult ecdysis.

Identification of a developmentally regulated gene, esr16, in the tracheal epithelium of Manduca sexta, with homology to a protein from human epididymis

Events related to both ecdysis and metamorphosis require the expression of a new set of genes, the majority of which are regulated by the changes in ecdysteroid levels. We have initiated studies to identify genes whose expression is up-regulated between 24 and 4 h before pupal ecdysis in Manduca sexta. In this paper we report the partial characterization of one such gene, esr16. The transcript of esr16 is detected by Northern blot analysis in nervous tissue, muscle and trachea isolated from animals 4 h before, but not 24 h before pupal ecdysis. In situ hybridization showed that the transcript was expressed in epithelial cells of the large tracheae surrounding the nervous system and muscle. Sequence analysis suggested that the gene encoded a secreted protein with 35% identity to HE1, a human epididymal-specific gene.

Eclosion hormone-stimulated cGMP levels in the central nervous system of Manduca sexta: inhibition by lipid metabolism blockers, increase in inositol(1,4,5)trisphosphate and further evidence against the involvement of nitric oxide

Previous studies have shown that the neuropeptide, eclosion hormone, stimulates a nitric oxide-independent increase in the levels of cGMP in the nervous system of Manduca sexta. By contrast, recent results in Bombyx mori suggest that eclosion hormone increases cGMP via the production of nitric oxide. In view of these conflicting results we have carried out additional studies to test whether nitric oxide is involved in this process in Manduca. Evidence presented here supports our earlier observations that in Manduca the eclosion hormone-stimulated increase in cGMP is nitric oxide- and carbon monoxide-independent. In addition, we show that a wide variety of inhibitors of lipid metabolism block the eclosion hormone-stimulated cGMP increase. This supports the hypothesis that the activation of the guanylate cyclase is mediated by a lipid messenger. We also show that eclosion hormone stimulates an increase in the levels of inositol(1,4,5)trisphosphate. The time-course of this increase is consistent with the hypothesis that eclosion hormone stimulation of a phospholipase C is an early event in the cascade that results in an increase in cGMP. Receptor-mediated lipid hydrolysis is often mediated by G protein-coupled receptors. Experiments using pertussis toxin show that the eclosion hormone-stimulated increase in cGMP is not mediated by a pertussis toxin-sensitive G protein.

Effects of acute and chronic restraint on the adrenal gland weight and serum corticosterone concentration of mice and their faecal output of oocysts after infection with Eimeria apionodes

Experiments were designed to investigate the potential stress of procedures commonly used for restraining mice and to discover whether habituation of the adrenocortical response occurred when chronic restraint was used. The study also examined the effect of chronic restraint on the faecal output of oocysts by mice trickle infected with Eimeria apionodes. The results showed that restraining mice for one hour was stressful and that restraining them repeatedly for one hour daily for seven or 21 days did not lead to habituation of the adrenocortical response. Restraint for one hour daily for seven days did not cause the recurrence of a clinical infection in mice which were chronically infected with E apionodes. Restraining mice for one hour daily for seven days before and for 14 days during the infection also had no effect on the prepatency, patency or intensity of an E apionodes infection.

Effect of cycloheximide on eclosion hormone sensitivity and the developmental appearance of the eclosion hormone and cGMP regulated phosphoproteins in the CNS of the tobacco hornworm, Manduca sexta

The neuropeptide, eclosion hormone (EH), triggers ecdysis behavior at the end of each molt in Manduca sexta. Previous studies have shown that the action of EH is mediated by an increase in cGMP and is associated with the phosphorylation of two proteins, named the EGPs. The ability of insects to respond to EH is developmentally regulated with sensitivity being first seen at about 8 hr prior to the normal time of ecdysis. The EGPs are also first detectable in the CNS at 8 hr prior to ecdysis, suggesting that it is their synthesis which determines EH sensitivity. The protein synthesis inhibitor, cycloheximide was used to study the development of the events leading to pupal ecdysis in Manduca. The results of these experiments suggest that protein synthesis is necessary about 10 hr before ecdysis for both the development of EH sensitivity and for the appearance of the EGPs.

Stress measurements in mice after transportation

Experiments were performed using physiological measures and behavioural parameters to find the acclimatization period in mice to common scientific procedures. Corticosterone levels were significantly elevated in mice killed immediately after being moved to an experimental room (P < 0.05) but levels returned to the normal in less than 1 day, despite mice being exposed to additional stressors such as novel environment, new cages, new bedding material, separation from their cage mates, regrouping, isolation in individually housed mice and a new handler. Behaviours such as rearing, climbing, grooming, feeding and sexual, changed significantly immediately after transportation of mice but most of these behaviours stabilized relatively quickly. In spite of the corticosterone levels, our behavioural observations suggest that even 4 days were not enough to allow the mice to acclimatize fully.

Remodeling of the insect nervous system

Our nervous systems and behavior are shaped by hormonally driven developmental changes that continue beyond the embryonic period. Key insights into this process have emerged from studies of the insect nervous system. During insect metamorphosis, the nervous system is remodeled through postembryonic neurogenesis, programmed cell death and the modification of persistent neurons. These changes are regulated to a large degree by gene cascades that are triggered by steroid hormones, the ecdysteroids. Current studies are attempting to reveal the molecular mechanisms involved in regulating these dramatic examples of developmental plasticity.

Corticosterone, adrenal and spleen weight in mice after tail bleeding, and its effect on nearby animals

Experiments were performed in mice to study if stress was involved in tail bleeding and to investigate any transmittable signal at killing. A second study looked at the time taken to recover from stress elicited by these procedures. Corticosterone levels were significantly higher in mice immediately after the completion of tail bleeding than in control mice (P < 0.05) suggesting that tail bleeding in mice was stressful. This study did not show any evidence for an odour or sound being released during killing or tail bleeding as there was no significant effect on corticosterone levels in mice present in the same room at the time these procedures were carried out. Corticosterone levels in mice killed on days 1, 3, and 7 after tail bleeding were significantly lower (P < 0.05) than the average corticosterone level in tail blood on day 1, indicating that mice recovered within 24 h from the stress of tail bleeding.

Spatiotemporal pattern of expression of tenascin-like molecules in a developing insect olfactory system

During the development of the olfactory (antennal) lobe of the moth Manduca sexta, olfactory sensory axons induce glomerular branching patterns in their target neurons. Glial cells, by surrounding the developing glomerular template, are thought to mediate the developmental influence of olfactory axons on these branching patterns. Previous studies have demonstrated that, in the absence of glia, neurons in the antennal lobe branch in an aglomerular fashion, even in the presence of competent antennal axons (Oland and Tolbert, 1988, J. Comp. Neurol. 278:377-387; Oland et al., 1988, J. Neurosci. 8:353-367). We have begun to explore the molecular basis by which glial cells could influence patterns of neurite branching. For this work, we have utilized immunocytochemical techniques and a partial biochemical analysis to demonstrate that molecules antigenically similar and comparable in size to mammalian tenascin are localized on the neuropil-associated glial cells that form borders around glomeruli in the developing antennal lobe. These tenascin-like molecules associated with neuropilar glia are present at critical stages of glomerulus development; tenascin-like immunoreactivity declines after glomeruli form and become stabilized. Neither the arrival nor the absence of antennal axons in the lobe induces changes in either the molecular forms or the amounts of tenascin-like molecules. The spatiotemporal pattern of expression of tenascin-like molecules suggests that they are in a position to participate in the formation of a glomerular neuropil and could form a molecular barrier that constrains neurite outgrowth strictly to glomeruli.