Abstracts of the 24th international isotope society (UK group) symposium: synthesis and applications of labelled compounds 2015.

The 24th annual symposium of the International Isotope Society's United Kingdom Group took place at the Møller Centre, Churchill College, Cambridge, UK on Friday 6th November 2015. The meeting was attended by 77 delegates from academia and industry, the life sciences, chemical, radiochemical and scientific instrument suppliers. Delegates were welcomed by Dr Ken Lawrie (GlaxoSmithKline, UK, chair of the IIS UK group). The subsequent scientific programme consisted of oral presentations, short 'flash' presentations in association with particular posters and poster presentations. The scientific areas covered included isotopic synthesis, regulatory issues, applications of labelled compounds in imaging, isotopic separation and novel chemistry with potential implications for isotopic synthesis. Both short-lived and long-lived isotopes were represented, as were stable isotopes. The symposium was divided into a morning session chaired by Dr Rebekka Hueting (University of Oxford, UK) and afternoon sessions chaired by Dr Sofia Pascu (University of Bath, UK) and by Dr Alan Dowling (Syngenta, UK). The UK meeting concluded with remarks from Dr Ken Lawrie (GlaxoSmithKline, UK).

Think regionally, act locally: metals in honeybee workers in the Netherlands (surveillance study 2008).

In June 2008, a surveillance study for metals in honeybees was performed in the Netherlands. Randomly, 150 apiaries were selected. In each apiary, five colonies were sampled. Per apiary, the hive samples were pooled. The apiary sample was analysed for Al, As, Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Sb, Se, Sn, Sr, Ti, V and Zn. All metals could be detected in all apiaries. As, Li, Sb, Sn and V were detected in part of the apiaries. The overall picture showed a regional pattern. In apiaries in the east of the Netherlands, Al, Ba, Cr, Mn, Mo, Ni, Se and Ti are found in higher concentrations compared to the west. In-region variation was demonstrated, indicating local effects. The vicinity of the apiaries was mapped afterwards and characterised as land uses of >50 % agricultural area, >50 % wooded area, >50 % urban area and mixed land use within a circle of 28 km(2) around the apiary. The results indicated that in apiaries located in >50 % wooded areas, significantly higher concentrations of Al, Ba, Cd, Cr, Cu, Li, Mn, Mo, Ni, Sb, Sr, Ti and Zn were found compared to agricultural, urban and mixed land use areas. We conclude that (1) the ratio between metal concentrations varies per region, demonstrating spatial differences, and (2) there is in-region local variation per metal. The results indicate the impact of land use on metal concentrations in honeybees. For qualitative bioindication studies, regional, local and land use effects should be taken into account.

The Fusarium oxysporum effector Six6 contributes to virulence and suppresses I-2-mediated cell death.

Plant pathogens secrete effectors to manipulate their host and facilitate colonization. Fusarium oxysporum f. sp. lycopersici is the causal agent of Fusarium wilt disease in tomato. Upon infection, F. oxysporum f. sp. lycopersici secretes numerous small proteins into the xylem sap (Six proteins). Most Six proteins are unique to F. oxysporum, but Six6 is an exception; a homolog is also present in two Colletotrichum spp. SIX6 expression was found to require living host cells and a knockout of SIX6 in F. oxysporum f. sp. lycopersici compromised virulence, classifying it as a genuine effector. Heterologous expression of SIX6 did not affect growth of Agrobacterium tumefaciens in Nicotiana benthamiana leaves or susceptibility of Arabidopsis thaliana toward Verticillium dahliae, Pseudomonas syringae, or F. oxysporum, suggesting a specific function for F. oxysporum f. sp. lycopersici Six6 in the F. oxysporum f. sp. lycopersici- tomato pathosystem. Remarkably, Six6 was found to specifically suppress I-2-mediated cell death (I2CD) upon transient expression in N. benthamiana, whereas it did not compromise the activity of other cell-death-inducing genes. Still, this I2CD suppressing activity of Six6 does not allow the fungus to overcome I-2 resistance in tomato, suggesting that I-2-mediated resistance is independent from cell death.

Which anatomical region determines a positive flexion test of the distal aspect of a forelimb in a nonlame horse?

REASONS FOR PERFORMING STUDY: The flexion test is used routinely as part of lameness and prepurchase examinations. However, little is known about the mechanisms that cause a positive response to a flexion test. OBJECTIVE: To determine which anatomical regions play a role in a positive outcome of a flexion test of the distal aspect of a forelimb in a nonlame horse. METHODS: Eight clinically sound Dutch Warmblood horses were subjected to a standardised flexion test (force 250 N, time 60 s) inducing a consistent lameness. To discriminate between different areas of the distal aspect of a forelimb, effects of various nerve blocks on the outcome of the flexion test were investigated. Low palmar digital, palmar at the abaxial aspects of the base of the proximal sesamoids, high palmar, ulnar and low 4-point nerve blocks were performed. Flexion test induced lameness was scored before and after each nerve block in separate sessions. RESULTS: The low palmar digital nerve blocks and nerve blocks of the palmar nerves at the abaxial aspect of the base of the proximal sesamoid bones had no significant effect on the flexion test induced lameness score. The ulnar, high palmar and, most dramatically, the low 4-point nerve blocks all caused a significant (P<0.05) reduction in the flexion test induced lameness score. CONCLUSIONS: Anatomical structures (soft tissue nor synovial structures) located distal to the metacarpophalangeal joint appear to contribute only minimally to the outcome of a positive flexion test of the distal aspect of a forelimb in a clinically nonlame horse. The structures in the region of, and including, the metacarpophalangeal joint appear to contribute most to a positive flexion test of the distal aspect of a forelimb in a nonlame horse. POTENTIAL RELEVANCE: The flexion test of the distal aspect of a forelimb may be sensitive for investigating the metacarpophalangeal joint region in horses free from lameness, but may be less relevant for structures distal to this region.

Comparing Morphology and Hemodynamics of Stable-versus-Growing and Grown Intracranial Aneurysms.

BACKGROUND AND PURPOSE: Aneurysm growth has been related to higher rupture risk. A better understanding of the characteristics related to growth may assist in the treatment decisions of unruptured intracranial aneurysms. This study aimed to identify morphologic and hemodynamic characteristics associated with aneurysm growth and to determine whether these characteristics deviate further from those of stable aneurysms after growth. MATERIALS AND METHODS: We included 81 stable and 56 growing aneurysms. 3D vascular models were segmented on CTA, MRA, or 3D rotational angiographic images. With these models, we performed computational fluid dynamics simulations. Morphologic (size, size ratios, and shape) and hemodynamic (inflow, vorticity, shear stress, oscillatory shear index, flow instability) characteristics were automatically calculated. We compared the characteristics between aneurysms that were stable and those that had grown at baseline and final imaging. The significance level after Bonferroni correction was P < .002. RESULTS: At baseline, no significant differences between aneurysms that were stable and those that had grown were detected (P > .002). Significant differences between aneurysms that were stable and those that had grown were seen at the final imaging for shear rate, aneurysm velocity, vorticity, and mean wall shear stress (P < .002). The latter was 11.5 (interquartile range, 5.4-18.8 dyne/cm2) compared with 17.5 (interquartile range, 11.2-29.9 dyne/cm2) in stable aneurysms (P = .001). Additionally, a trend toward lower area weighted average Gaussian curvature in aneurysms that had grown was observed with a median of 6.0 (interquartile range, 3.2-10.7 cm-2) compared with 10.4 (interquartile range, 5.0-21.2 cm-2) in stable aneurysms (P = .004). CONCLUSIONS: Morphologic and hemodynamic characteristics at baseline were not associated with aneurysm growth in our population. After growth, almost all indices increase toward values associated with higher rupture risks. Therefore, we stress the importance of longitudinal imaging and repeat risk assessment in unruptured aneurysms.

Impact of Intracranial Aneurysm Morphology and Rupture Status on the Particle Residence Time.

BACKGROUND AND PURPOSE: Aneurysm hemodynamics play an important role in aneurysm growth and subsequent rupture. Within the available hemodynamic characteristics, particle residence time (PRT) is relatively unexplored. However, some studies have shown that PRT is related to thrombus formation and inflammation. The goal of this study is to evaluate the association between PRT and aneurysm rupture and morphology. METHODS: We determined the PRT for 113 aneurysms (61 unruptured, 53 ruptured) based on computational fluid dynamic models. Virtual particles were injected into the parent vessel and followed during multiple cardiac cycles. PRT was defined as the time needed for 99% of the particles that entered an aneurysm to leave the aneurysm. Subsequently, we evaluated the association between PRT, rupture, and morphology (aneurysm type, presence of blebs, or multiple lobulations). RESULTS: PRT showed no significant difference between unruptured (1.1 seconds interquartile range [IQR .39-2.0 seconds]) and ruptured aneurysms (1.2 seconds [IQR .47-2.3 seconds]). PRT was influenced by aneurysm morphology. Longer PRTs were seen in bifurcation aneurysms (1.3 seconds [IQR .54-2.4 seconds], P = .01) and aneurysms with blebs or multiple lobulations (1.92 seconds [IQR .94-2.8 seconds], P < .001). Four of five partially thrombosed aneurysms had a long residence time (>1.9 seconds). CONCLUSIONS: Our study shows an influence of aneurysm morphology on PRT. Nevertheless, it suggests that PRT cannot be used to differentiate unruptured and ruptured aneurysms.

Aneurysmal Parent Artery-Specific Inflow Conditions for Complete and Incomplete Circle of Willis Configurations.

BACKGROUND AND PURPOSE: Hemodynamics are thought to play a role in intracranial aneurysm growth and rupture. Computational fluid dynamics is frequently performed to assess intra-aneurysmal hemodynamics, using generalized flow waveforms of healthy volunteers as inflow boundary conditions. The purpose of this study was to assess differences in inflow conditions for different aneurysmal parent artery locations and variations of circle of Willis configurations. MATERIALS AND METHODS: In a series of 96 patients with 103 aneurysms, velocity measurements were acquired using 2D phase-contrast MR imaging perpendicular to the aneurysmal parent arteries in the circle of Willis. Circle of Willis configurations were inspected for variations using multiple overlapping thin-slab-acquisition MRAs. Flow rates, velocity magnitudes, and pulsatility indices were calculated for each parent artery location in subgroups of complete and incomplete circle of Willis configurations. RESULTS: Flow rates, velocity magnitudes, and pulsatility indices were significantly different among aneurysmal parent arteries. Incomplete circle of Willis configurations were observed in 24% of the cases. Significantly lower basilar artery flow rates were observed in configurations with hypoplastic P1 segments. Significantly higher A1 flow rates were observed in configurations with a hypoplastic contralateral A1 segment. CONCLUSIONS: Inflow conditions vary substantially between aneurysmal parent arteries and circle of Willis configurations. We have created a collection of parent artery-specific inflow conditions tailored to the patient-specific circle of Willis configuration that can be used in future computational fluid dynamics studies analyzing intra-aneurysmal hemodynamics.

Fusarium oxysporum evades I-3-mediated resistance without altering the matching avirulence gene.

I-3-Mediated resistance of tomato against Fusarium wilt disease caused by Fusarium oxysporum f. sp. lycopersici depends on Six1, a protein that is secreted by the fungus during colonization of the xylem. Among natural isolates of F. oxysporum f. sp. lycopersici are several that are virulent on a tomato line carrying only the I-3 resistance gene. However, evasion of I-3-mediated resistance by these isolates is not correlated with mutation of the SIX1 gene. Moreover, the SIX1 gene of an I-3-virulent isolate was shown to be fully functional in that i) the gene product is secreted in xylem sap, ii) deletion leads to a further increase in virulence on the I-3 line as well as reduced virulence on susceptible lines, and iii) the gene confers full avirulence on the I-3 line when transferred to another genetic background. Remarkably, all I-3-virulent isolates were of race 1, suggesting a link between the presence of AVR1 and evasion of I-3-mediated resistance.

Comparison between 1 T MRI and non-MRI based volumetry in inoculated tumours in mice.

Tumour volume is an important therapeutic endpoint for mouse tumour models in the evaluation of new chemotherapeutic drugs and in pre-clinical evaluation of new radioimmunotherapy pharmaceuticals. In this study, two 1 T MRI-based methods both using T1-T2 hybrid weighting, a manual method (determination of the area per slice) and a semi-automated method (using thresholding), are compared with two classical methods, the abovementioned calliper method and volumetry by water displacement after dissection of the tumour. Interoperator and intraoperator differences for both MRI-based methods were good (no differences p<0.05 using a repeated measures analysis of variance (ANOVA) test). Correlation between the different methods was excellent. No significant differences were obtained (p<0.05), except for the semi-automated method, because it automatically excludes necrotic regions from the tumour. Therefore, we conclude that both manual and semi-automated tumour volumetry in subcutaneous tumour bearing athymic mice by low-field MRI are accurate and reliable methods. The semi-automated method is especially useful for larger tumour volumes, since it accounts for necrotic areas within the tumour.

Development of an enzymatic pretargeting strategy for dual-modality imaging.

A pretargeted imaging strategy based on the HaloTag dehalogenase enzyme is described. Here, a HaloTag-Trastuzumab conjugate has been used as the primary agent targeting HER2 expression, and three new radiolabelled HaloTag ligands have been used as secondary agents, two of which offer dual-modality (SPECT/optical) imaging capability.

Hemodynamic Differences in Intracranial Aneurysms before and after Rupture.

BACKGROUND AND PURPOSE: Rupture risk of intracranial aneurysms may depend on hemodynamic characteristics. This has been assessed by comparing hemodynamic data of ruptured and unruptured aneurysms. However, aneurysm geometry may change before, during, or just after rupture; this difference causes potential changes in hemodynamics. We assessed changes in hemodynamics in a series of intracranial aneurysms, by using 3D imaging before and after rupture. MATERIALS AND METHODS: For 9 aneurysms in 9 patients, we used MRA, CTA, and 3D rotational angiography before and after rupture to generate geometric models of the aneurysm and perianeurysmal vasculature. Intra-aneurysmal hemodynamics were simulated by using computational fluid dynamics. Two neuroradiologists qualitatively assessed flow complexity, flow stability, inflow concentration, and flow impingement in consensus, by using flow-velocity streamlines and wall shear stress distributions. RESULTS: Hemodynamics changed in 6 of the 9 aneurysms. The median time between imaging before and after rupture was 678 days (range, 14-1461 days) in these 6 cases, compared with 151 days (range, 34-183 days) in the 3 cases with unaltered hemodynamics. Changes were observed for flow complexity (n = 3), flow stability (n = 3), inflow concentration (n = 2), and region of flow impingement (n = 3). These changes were in all instances associated with aneurysm displacement due to rupture-related hematomas, growth, or newly formed lobulations. CONCLUSIONS: Hemodynamic characteristics of intracranial aneurysms can be altered by geometric changes before, during, or just after rupture. Associations of hemodynamic characteristics with aneurysm rupture obtained from case-control studies comparing ruptured with unruptured aneurysms should therefore be interpreted with caution.

A virus-inducible tobacco gene encoding a glycine-rich protein shares putative regulatory elements with the ribulose bisphosphate carboxylase small subunit gene.

cDNA to an mRNA that is strongly induced in Samsun NN tobacco after tobacco mosaic virus (TMV) infection or salicylic acid treatment was used to probe a genomic blot and to screen a genomic library. The mRNA corresponds to a family of approximately eight genes, four of which were cloned. The sequence of the genes and flanking DNA in two clones was determined. One gene was found to contain an intron of 555 bp; S1-nuclease mapping studies indicated that this gene is expressed. The other gene is interrupted by an intron of 1,954 bp and is probably not expressed after TMV infection. The genes encode a protein of 109 amino acids with a putative N-terminal signal peptide of 26 amino acids. The protein contains a high proportion of glycine (25%) and charged amino acids (29%), suggesting that it may be a cell wall component. A comparison of the upstream sequences of the genes encoding the glycine-rich protein and the pathogenesis-related protein 1a showed only limited homology, although both genes are TMV- and salicylic acid-inducible. However, the upstream sequence of the glycine-rich protein gene contains a 64-bp inverted repeat that occurs in a similar position in the tobacco ribulose bisphosphate carboxylase small subunit gene.

Analysis of acidic and basic chitinases from tobacco and petunia and their constitutive expression in transgenic tobacco.

cDNA clones of messenger RNAs for acidic and basic chitinases were isolated from libraries of tobacco mosaic virus-infected Samsun NN tobacco and petunia. The tobacco cDNA clones for acidic chitinase fell into two different groups, whereas all petunia cDNA clones had the same sequence. Also, tobacco genomic clones were isolated and one was characterized. This genomic clone, corresponding to one of the cDNA clones, showed that this acidic chitinase gene contains two introns. The amino acid sequences of the acidic chitinases from tobacco, as deduced from the cDNA clones, fully agreed with partial sequences derived from peptides obtained from purified tobacco-derived pathogenesis-related proteins PR-P and PR-Q. The deduced amino acid sequences showed that PR-P and PR-Q are 93 and 78%, respectively, identical to the petunia enzyme. All deduced chitinase sequences indicated the presence of an NH2-terminal, highly hydrophobic signal peptide. In addition, the polysaccharide-binding domain present at the NH2-terminus of basic chitinases from mature tobacco is not present in these acidic chitinases. Furthermore, the complete coding sequence for the petunia chitinase, constructed downstream of the cauliflower mosaic virus 35S promoter, was used to transform tobacco. The resulting chimeric gene was constitutively expressed, and the petunia enzyme was targeted to the extracellular fluid. In contrast, a basic chitinase of tobacco, expressed from a chimeric gene, was found in total leaf extracts but not in preparations of extracellular fluid.

Nucleotide sequence and organization of potato leafroll virus genomic RNA.

The nucleotide sequence of the genomic RNA of potato leafroll virus was determined and its genetic organization deduced. The RNA is 5882 nucleotides long and contains 6 open reading frames (ORFs) encoding proteins of 70, 70, 56, 28, 23 and 17 kDa. The putative genes for the coat protein (23 kDa) and the RNA-dependent RNA polymerase (70 kDa) were identified by interviral amino acid sequence homologies. For expression of the different ORFs, translational frameshift and readthrough events are proposed.

Loss of Avirulence and Reduced Pathogenicity of a Gamma-Irradiated Mutant of Fusarium oxysporum f. sp. lycopersici.

ABSTRACT The tomato Fusarium resistance gene I-2 confers resistance to F. oxy-sporum f. sp. lycopersici race 2, which expresses the corresponding aviru-lence gene avrI-2. To elucidate the molecular basis of this gene-for-gene interaction, we initiated a search for the avrI-2 gene. Gamma irradiation mutagenesis, using (137)Cs, was performed to generate an avrI-2 mutant of F. oxysporum f. sp. lycopersici. To this end, a race 2 isolate was first transformed with a phleomycine resistance gene and a GUS marker gene in order to distinguish mutants from contaminating isolates. A total of 21,712 mutagenized colonies was tested for loss of avirulence on I-2-containing tomato seedlings. One mutant was selected that showed the expected loss of avirulence but, surprisingly, also showed reduced pathogenicity toward susceptible tomato plants. DNA analysis was subsequently used to visualize genomic changes in the mutant. Southern analysis on contour-clamped homogeneous electrophoretic field blots demonstrated a translocation of a 3.75-Mb chromosome in the mutant. Random amplified polymorphic DNA and amplified fragment length polymorphism analysis identified at least nine polymorphisms between the wild-type and mutant isolates. Most of these polymorphisms appeared as extra fragments in the mutant and contained repetitive DNA sequences.

Biological and Molecular Characterization of Fusarium oxysporum f. sp. lycopersici Divides Race 1 Isolates into Separate Virulence Groups.

ABSTRACT A collection of race 1 and race 2 isolates of Fusarium oxysporum f. sp. lycopersici was screened for vegetative compatibility and characterized by random amplified polymorphic DNA (RAPD) analysis to establish the identity and genetic diversity of the isolates. Comparison of RAPD profiles revealed two main groups that coincide with vegetative compatibility groups (VCGs). In addition, several single-member VCGs were identified that could not be grouped in one of the two main RAPD clusters. This suggests that F. oxysporum f. sp. lycopersici is a polyphyletic taxon. To assign avirulence genotypes to race 1 isolates, they were tested for their virulence on a small set of tomato lines (Lycopersicon esculentum), including line OT364. This line was selected because it shows resistance to race 2 isolates but, unlike most other race 2-resistant lines, susceptibility to race 1 isolates. To exclude the influence of other components than those related to the race-specific resistance response, we tested the virulence of race 1 isolates on a susceptible tomato that has become race 2 resistant by introduction of an I-2 transgene. The results show that both line OT364 and the transgenic line were significantly affected by four race 1 isolates, but not by seven other race 1 isolates nor by any race 2 isolates. This allowed a subdivision of race 1 isolates based on the presence or absence of an avirulence gene corresponding to the I-2 resistance gene. The data presented here support a gene-for-gene relationship for the interaction between F. oxysporum f. sp. lycopersici and its host tomato.

Innervation of the equine mature and immature proximal sesamoid bone by calcitonin gene-related peptide and substance P-containing nerves.

OBJECTIVE: To localize and determine relative frequency of occurrence of calcitonin gene-related peptide (CGRP) and substance P (SP) fibers in the proximal sesamoid bones (PSB) and adjacent structures in sound horses. SAMPLE POPULATION: 4 foals and 3 adult horses. PROCEDURE: Medial PSB and adjacent ligaments of both forelimbs were collected, flushed, and fixed in buffered 4% formalin. The left PSB were cut into 5 longitudinal, sagittally oriented slabs, and the right PSB were cut into 5 transverse slabs. After decalcification in EDTA, slices were transferred to a 30% sucrose solution, deep frozen, sectioned (80 microm), and stored in Tris-buffered saline solution for free-floating immunocytochemical processing, staining of which was performed by use of the peroxidase-antiperoxidase method with polyclonal rabbit antibodies against CGRP and SP. Sections were examined by light microscopy. RESULTS: Calcitonin gene-related peptide and SP fibers were present throughout the PSB; in ligaments, they were concentrated at the attachment sites. Presentation of the fibers, the innervation pattern, and intensity in the bones of horses differed from that in foals, in which the fibers were more delicate and frequency of occurrence was lower. In horses, innervation with CGRP and SP fibers was more dense in the periphery of the bone, whereas in foals, local difference in innervation of the bone was not evident. With the exception of the intersesamoidean ligament, ligaments were more richly innervated than was bone. CONCLUSION: Presence of the nociceptive peptides CGRP and SP indicated that the PSB and, more practically, the adjacent ligaments are sensitive structures.

Experimental model of synovitis/capsulitis in the equine metacarpophalangeal joint.

OBJECTIVE: To develop and define a model of acute synovitis/capsulitis in the equine metacarpophalangeal joint (fetlock) to study clinical effects of diagnostic or therapeutic procedures. ANIMALS: 5 adult Standardbreds. PROCEDURE: Polyvinyl alcohol foam particles were injected into the left front fetlock of horses; the right front fetlock was used as a control. Horses were examined clinically and for lameness on a regular basis. Blood samples were taken to measure routine variables. Synovial fluid samples were collected from both fetlocks, and macroscopic, microscopic, and biochemical variables were measured. The effects of local diagnostic nerve blocks and intra-articular anesthesia of the fetlock on ensuing lameness were determined on days 2 and 3. After macroscopic evaluation at necropsy, histologic examination was performed on the fetlock cartilage and capsule. RESULTS: Changes in synovial fluid variables included increased TNF-alpha and matrix metalloproteinases values and in other indicators of acute inflammation. With respect to application of local nerve blocks, lameness decreased most after a combination of metacarpal and palmar nerve blocks, whereas lameness could only partially be blocked by intra-articular anesthesia. At necropsy, mild chronic inflammation of the synovium and deeper layers of the joint capsule was found; polyvinyl alcohol particles had been incorporated into the joint capsule. There was no evidence of articular cartilage damage. CONCLUSIONS: Injection of polyvinyl alcohol foam particles induces transient synovitis/capsulitis in the fetlock, mimicking clinical joint disorders. The model does not seriously affect the horse's long-term wellbeing. Such model serves well for studying the effect of diagnostic or therapeutic procedures.

The diagnostic nerve block of the sesamoidean nerve: desensitized structures and possible clinical applications.

The sesamoidean nerve branches from the palmar nerve and runs towards the proximal sesamoid bone. To study the structures innervated by this nerve, a technique for blocking it was developed. The effect of this nerve block was determined in ponies with an induced lameness located in the lateral proximal sesamoid bone (5 ponies) or in the distal part of the lateral branch of the suspensory ligament (5 ponies), and in 10 horses with clinical sesamoidosis. A lameness provoked by the implantation of an expansion plug in the proximal sesamoid bone could, to a large extent, be anaesthetized by a sesamoidean nerve block. However, lameness due to a local tendonitis in the lateral branch of the suspensory ligament, was only partially eliminated by a sesamoidean nerve block. In horses with sesamoidosis the lameness improved, on average, by about 30%. It is concluded that the sesamoidean nerve contains sensory fibres that innervate the proximal sesamoid bone. The sesamoidean nerve block is highly specific for pain originating from the proximal sesamoid bone including the adjacent distal part of the extensor branch of the suspensory ligament. In horses suffering from sesamoidosis the main source of pain appears not to be located in the proximal sesamoid bone. The specificity of the sesamoidean nerve block makes it a useful technique for differentiating the site of a lameness located in the fetlock area.

The arterial shift features in the equine proximal sesamoid bone.

Sesamoidosis in horses is characterised by lameness and radiographic changes in the proximal sesamoid bones and the aetiology is attributed to either mechanical factors or circulatory disturbances. In this study arteriograms of proximal sesamoid bones were investigated in 17 lame patients suffering from sesamoidosis, 6 sound horses and 4 yearlings. The arterial patterns of the proximal sesamoid bones from the patients, showed a shift from an abaxial to a basal arterial blood supply. This shift was only found in radiographically changed bones. Histological evaluation showed a significantly higher percentage of arteries with a large diameter in sections from the base of proximal sesamoid bones that showed an arterial shift. The presence of the shift appeared to be related to a change in shape of the bone, in particular to new bone formation along the abaxial border. The results of this study suggest that in horses suffering from sesamoidosis changes in the arterial pattern arise which might be a compensatory mechanism in respons to a vascular iischaemic challenge. Further investigations are needed to characterise the initial stimulus that induces this compensation and to determine if the compensation is sufficient to maintain a continuous and adequate blood supply.