Muscle moment arms of pelvic limb muscles of the ostrich (Struthio camelus)

Muscle moment arms were measured for major muscles of the pelvic limb of the ostrich (Struthio camelus) in order to assess specific functional behaviour and to apply this to locomotor performance. Pelvic limbs of six juvenile ostriches were used for this study. The tendon travel technique was used to measure moment arms of 21 muscles at the hip, knee, ankle and metatarsophalangeal joints throughout the ranges of motion observed during level running. Six of the 21 muscles measured were found to have moment arms that did not change with joint angle, whilst the remainder all demonstrated angle-dependent changes for at least one of the joints crossed. Moment arm lengths tended to be longest for the large proximal muscles, whilst the largest relative changes were found for the moment arms of the distal muscles. For muscles where moment arm varied with joint angle: all hip muscles were found to have increasing moment arms with extension of the joint, knee flexors were found to have moment arms that increased with extension, knee extensor moment arms were found to increase with flexion and ankle extensor moment arms increased with extension. The greatest relative changes were observed in the flexors of the metatarsophalangeal joint, for which a three-fold increase in moment arm was observed from flexion to full extension. Changes in muscle moment arm through the range of motion studied appear to optimize muscle function during stance phase, increasing the effective mechanical advantage of these muscles.

Changes in plasma cortisol and ascorbic acid in horses with and without recurrent airway obstruction upon exercise and ascorbic acid supplementation

Diminished basal plasma cortisol concentrations and a blunted cortisol response to exercise have been observed in human asthmatics. In horses with recurrent airway obstruction (RAO), plasma concentrations of cortisol at rest are not significantly different from those of healthy horses, but the effect of exercise on endogenous cortisol concentrations has not been described. Ascorbic acid is a non-enzymatic antioxidant with proposed immune-modulating properties. In man, supplementation with ascorbic acid has been shown to attenuate the exercise-induced increase in plasma cortisol following prolonged, submaximal exercise. The relationship between cortisol and ascorbic acid has not previously been investigated in the horse. In a blinded cross-over design, five horses with RAO and six healthy non-RAO controls performed a standard exercise test following 4 weeks of supplementation with either an antioxidant (providing 10 mg ascorbic acid kg−1day−1) or a placebo (<1 mg ascorbic acid kg−1day−1). Venous blood samples were obtained 1 h prior to exercise and at 0, 15, 60 min and 24 h thereafter. Exercise resulted in a significant increase in plasma cortisol concentrations in both groups of horses (P<0.05). Basal and post-exercise concentrations of plasma cortisol in the RAO group (136±16 and 210±16 μmol l−1, respectively) were not significantly different from those in the non-RAO group (129±43 and 218±30 μmol l−1, respectively). Antioxidant supplementation increased basal and post-exercise concentrations of plasma ascorbic acid in RAO and non-RAO horses (P<0.05) but had no effect on plasma cortisol concentration in either group, before or after exercise (RAO: rest 157±27 μmol l−1, post-exercise 222±21 μmol l−1; non-RAO: rest 140±11 μmol l−1, post-exercise 227±35 μmol l−1). In conclusion, RAO-affected horses in remission demonstrate the same cortisol response to exercise as healthy controls. Antioxidant supplementation had no impact on post-exercise concentrations of plasma cortisol in either healthy or RAO-affected horses in remission.

Comparison of the antioxidant status in tracheal and bronchoalveolar epithelial lining fluids in recurrent airway obstruction

REASONS FOR PERFORMING STUDY

Following a period of airway inflammation the clearance of inflammatory cells along the mucociliary escalator may impose a considerable oxidant load on the trachea.

OBJECTIVES

To determine the degree of oxidative stress in tracheal epithelial lining fluid (ELF) in comparison to that present in peripheral airways after an acute exposure to organic dust.

METHODS

Tracheal wash fluid and bronchoalveolar lavage fluid (BALF) were collected for cytology and antioxidant analyses from 6 recurrent airway obstruction (RAO)-affected horses and 6 healthy control horses before and after stabling on straw bedding for 24 h.

RESULTS

In RAO-affected horses, organic dust exposure resulted in a significant decrease in ascorbic acid concentration in tracheal ELF (P<0.0001), which was greater than the decrease in bronchoalveolar ELF (P = 0.0003). The percentage decrease in tracheal ELF ascorbic acid correlated with the percentage decrease in bronchoalveolar ELF ascorbic acid (r = 0.76; P = 0.004) following exposure.

CONCLUSIONS

Acute organic dust exposure results in significant antioxidant depletion in the trachea, which may reflect inflammation and oxidative processes in peripheral airways.

POTENTIAL RELEVANCE

Further work is required to evaluate the role of ascorbic acid depletion in the pathogenesis of RAO.

The coccidian oocyst: a tough nut to crack!

Coccidian parasites are transmitted between hosts by the ingestion of food or water contaminated with oocysts, followed by the release of infectious sporozoites and invasion of the gastro-intestinal tract. In the external environment, sporozoites are protected from desiccation and chemical disinfection by the oocyst wall. This unique structure guarantees successful disease transmission and is as vital to the coccidian parasite as the exoskeleton is to insects--without it they would die. Here, we revisit the early work and combine it with newer molecular data to describe our present understanding of the coccidian oocyst wall.

An Australian network to support the understanding and control of parasites

The Australian Research Council (ARC) and the National Health and Medical Research Council (NHMRC) Research Network for Parasitology will focus and coordinate the fundamental, strategic and applied parasitology research in Australia. It will raise the standing of Australia in the field, assist in the community understanding of parasitology, and maintain and improve the capacity of Australia to keep its stock, crops, wildlife and people free from disease. On an international scale, the ARC/NHMRC Network will work with other countries to develop new technologies for the detection and control of parasites.

Functional specialisation of pelvic limb anatomy in horses (Equus caballus)

We provide quantitative anatomical data on the muscle-tendon units of the equine pelvic limb. Specifically, we recorded muscle mass, fascicle length, pennation angle, tendon mass and tendon rest length. Physiological cross sectional area was then determined and maximum isometric force estimated. There was proximal-to-distal reduction in muscle volume and fascicle length. Proximal limb tendons were few and, where present, were relatively short. By contrast, distal limb tendons were numerous and long in comparison to mean muscle fascicle length, increasing potential for elastic energy storage. When compared with published data on thoracic limb muscles, proximal pelvic limb muscles were larger in volume and had shorter fascicles. Distal limb muscle architecture was similar in thoracic and pelvic limbs with the exception of flexor digitorum lateralis (lateral head of the deep digital flexor), the architecture of which was similar to that of the pelvic and thoracic limb superficial digital flexors, suggesting a functional similarity.

Transient disturbance in physeal morphology is associated with long-term effects of nitrogen-containing bisphosphonates in growing rabbits

Bisphosphonates have clinical benefit in children with severe osteogenesis imperfecta or osteoporosis and potential benefit in children with Perthes disease or undergoing distraction osteogenesis. However, there is concern about the effects of bisphosphonates on the physis and bone length. In 44 growing rabbits, zoledronic acid caused a transient disruption of physeal morphology, retention of cartilaginous matrix in trabeculae and cortical bone of the metaphysis, and a minor decrement in tibial bone length at maturity.

INTRODUCTION

Data from growing animal models suggest that bisphosphonates cause retention of longitudinal cartilaginous septa at the chondro-osseous junction, extension of trabeculae to the metaphyseal-diaphyseal junction, and varying dose-dependent effects on longitudinal growth. However, there is a lack of data regarding effects of intermittent use of nitrogen-containing bisphosphonates on the physis and on tibial length in models reaching maturity.

MATERIALS AND METHODS

Contralateral tibias of juvenile rabbits were examined after right tibial distraction osteogenesis from two previous studies. Animals were randomized to receive 0.1 mg/kg zoledronic acid (ZA) IV at 8 weeks of age (ZA*1) or 8 and 10 weeks of age (ZA*2) or saline. Body mass was analyzed from 5 to 44 weeks of age; tibial length and proximal physeal-metaphyseal histology and histomorphometry were analyzed at 8-52 weeks of age.

RESULTS

Tibial length was 3% less at 14 weeks of age in the ZA*2-treated versus saline group (p<0.05) in both studies, and this difference persisted at maturity in the long-term study group (26 weeks of age, p<0.05). Total body mass gain from 5 to 26 weeks of age was 14% less in ZA*2-treated than saline animals (p<0.05). Rate of weight gain from 8 to 10 weeks of age was 76% less in ZA*2 compared with saline animals (p<0.05). Radiographs showed radiodense lines in the metaphyses of ZA-treated bones, corresponding to the number of doses. Histologically, lines resulting from the first dose of ZA contained longitudinal cartilaginous matrix cores surrounded by bone, whereas those from the second dose contained spherical cores of matrix caused by transient disruption of physeal morphology after the first dose of ZA. Resorption of these lines at later times was radiographically and histologically evident, but remnants of cartilaginous matrix remained in the cortical bone of ZA-treated animals.

CONCLUSIONS

ZA treatment within the final 13.5% of the rabbit tibial growth period caused a transient disruption in physeal morphology and resorption associated with retention of cartilaginous matrix and coinciding with a persistent 3% decrement in tibial length. Disruption of physeal morphology and potential loss of bone length should be considered when administering nitrogen-containing bisphosphonates to children before closure of the major physes.

Antioxidant and inflammatory responses of healthy horses and horses affected by recurrent airway obstruction to inhaled ozone

REASONS FOR PERFORMING STUDY

Inhaled ozone can induce oxidative injury and airway inflammation. Horses affected by recurrent airway obstruction (RAO) have a decreased pulmonary antioxidant capacity, which may render them more susceptible to oxidative challenge. It is currently unknown whether RAO-affected horses are more susceptible to oxidative stress than those unaffected by RAO.

OBJECTIVES

To determine whether ozone exposure induces greater oxidative stress and airway inflammation in RAO-affected horses in remission than in healthy horses.

METHODS

Seven healthy control horses and 7 RAO-affected horses were exposed to 0.8 ppm ozone for 2 h at rest.

RESULTS

At baseline, bronchoalveolar lavage fluid (BALF) ascorbic acid concentrations were lower in RAO-affected horses than healthy controls. Ozone appeared to preferentially oxidise glutathione rather than ascorbic acid 6 h after exposure. Individual healthy and RAO-affected horses demonstrated oxidation of BALF glutathione after ozone exposure. Overall, RAO-affected horses did not demonstrate increased oxidative stress following ozone exposure, compared with healthy horses. Ozone did not induce significant airway inflammation in either group.

CONCLUSIONS

RAO-affected horses in remission are not more sensitive to ozone despite a decreased pulmonary antioxidant capacity. Sensitivity to ozone appears to be independent of initial pulmonary antioxidant status.

POTENTIAL RELEVANCE

Horses with high susceptibility to oxidative stress may benefit from antioxidant supplementation.

Focal fibrocartilaginous dysplasia in the upper limb: seven additional cases

Focal fibrocartilaginous dysplasia is a benign bone lesion known to cause deformity around the knee in young children. Three cases affecting the long bones of the upper limb have been reported, and little is known of the natural history. This study reports seven more cases affecting the upper extremity. All patients presented with deformity in early childhood. The location was the radius in two, the ulna in three, the proximal phalanx in one, and the middle phalanx in one. The radiographic appearance of the condition is diagnostic, regardless of the bone it affects. Proportional shortening of the affected segment was present in all patients. The phalangeal cases had marked deformity and were osteotomized, with early recurrence of the deformity in one case. The forearm lesions did not all resolve spontaneously. In the two patients with 7-year follow-up, the length discrepancy increased from 0.5 cm to 2 cm and a degree of cosmetic deformity remained, without functional impairment. Ulna lesions place the radiocapitellar joint at risk for dislocation and should be observed for this complication.

Characterisation of the antigenic and immunogenic properties of bacterially expressed, sexual stage antigens of the coccidian parasite, Eimeria maxima

Coccidiosis in poultry is caused by the intestinal parasite Eimeria; it causes significant financial losses to the commercial poultry industry worldwide. CoxAbic is the first commercially available subunit vaccine against coccidiosis. The vaccine consists of affinity purified sexual stage (gametocyte) antigens (APGA) isolated from Eimeria maxima. Production of this vaccine is time-consuming and laborious and, therefore, a recombinant subunit vaccine substitute for CoxAbic is desirable. The genes encoding the two immunodominant components of CoxAbic, gam56 and gam82, were cloned into the bacterial expression vector, pTRCHisB, and the proteins expressed and purified. Both recombinant proteins were recognised by protective chicken antibodies that were raised to APGA, by immunoblotting. In a competitive ELISA, a combination of the recombinant proteins inhibited the binding of anti-APGA antibodies to APGA by 76%, which was comparable to the inhibition of 98% observed when APGA was used as the competing protein in the assay. In two breeds of chicken (Australorp and Cobb500), the recombinant proteins alone, or in combination, elicited a dose-dependent, antibody response that recognised APGA by ELISA, and gametocytes by immunoblotting. Together, the results suggested that the development of a recombinant subunit vaccine that maintains the antigenic and immunogenic properties of the native protein vaccine, CoxAbic, is feasible.

Neonatal brachial plexus palsy. Outcome of absent biceps function at three months of age

BACKGROUND

An important prognostic factor in neonatal brachial plexus palsy is the time interval to biceps muscle recovery. Although the natural history is not clear, biceps muscle recovery after more than three months of age has been used to predict poor long-term shoulder function. The absence of biceps muscle function at three months of age has been adopted as an indication for early brachial plexus microsurgery, in an attempt to improve recovery. To provide a benchmark for outcome comparison, the long-term outcome of patients with absent biceps muscle function at three months of age was studied.

METHODS

Between 1980 and 1992, 170 patients with neonatal brachial plexus palsy were entered into a prospective study in which details of the birth and serial clinical examinations were recorded. Patients were grouped according to the level of injury and the time interval to biceps muscle recovery. Twenty-nine patients were observed to have absent biceps muscle function at three months of age. Twenty-eight of those patients were available for long-term followup at a mean age of eleven years and one month. At the time of follow-up, patients answered a questionnaire and underwent manual muscle strength testing, sensory evaluation, and grading of their shoulder function according to Gilbert's modification of the Mallet score, in which the function was graded as II, III, or IV with class I (no function) and V (normal) eliminated. The level of injury and the time that biceps muscle function returned were compared with the final outcomes.

RESULTS

The level of injury was C5-C6 in thirteen (46%) of our twenty-eight patients with absent biceps muscle function at three months of age, C5-C7 in five (18%), and pan-plexus (C5-T1) in ten (36%). Biceps contraction was observed by six months of age in twenty patients (71%), including all thirteen patients with a C5-C6 level of injury. Twenty-two patients did not have surgery on the brachial plexus, but nine of those patients had subsequent orthopaedic procedures. At the time of follow-up, twenty-seven of the twenty-eight patients had at least antigravity biceps muscle function. Patients who regained biceps muscle function between three and six months of age had better scores for abduction (p = 0.04) and for hand-to-neck (p = 0.05) and hand-to-back (p < 0.001) function than did patients who regained biceps muscle function after six months of age. Patients with a C5-C6 lesion had better scores for external rotation (p = 0.04) and for hand-to-neck (p = 0.05), hand-to-mouth (p < 0.01), and hand-to-back (p < 0.001) function than did patients with a pan-plexus lesion. Twelve (55%) of the twenty-two patients who did not have brachial plexus surgery had a class-IV shoulder (good function) according to the modified Mallet score. Of the twelve patients with a C5-C6 level of injury who did not have brachial plexus surgery, eight had a class-IV shoulder.

CONCLUSIONS

This study indicated associations between prolonged neurological recovery and a more extensive level of injury and worse long-term shoulder function. Patients with a C5-C6 injury and absent biceps muscle function at three months of age often have good long-term shoulder function without brachial plexus surgery.

Ultrasonic measurement of biparietal diameter and femur in foetal age determination

Our objective was to verify ultrasonic measurement of biparietal diameter and femur in foetal age determination in the second and third trimester of pregnancy. The prospective cross sectional study was carried out at the ultrasound department of Aberdeen Maternity Hospital Scotland. The study population consisted of 716 pregnant Scottish (Caucasian) women who were certain of their gestational ages and had their gestational ages confirmed in the first trimester by ultrasound. The findings revealed: (1) Linearity through out pregnancy using the femur length measurements while that of the biparietal diameter demonstrated poor correlation after 32 weeks of gestation. (2) The standard deviation and the correlation coefficient of the femur length measurements were 0.0042 and 0.9920 respectively while the corresponding values for biparietal diameter were 0.0045 and 0.9850 respectively. (3) The standard error for femur length estimate was 0.2251 as against 0.3009 for biparietal diameter estimate. The results suggest that femur length measurement is a more reliable index of late third trimester gestational age prediction than biparietal diameter.

Eimeria maxima TRAP family protein EmTFP250: subcellular localisation and induction of immune responses by immunisation with a recombinant C-terminal derivative

EmTFP250 is a high molecular mass, asexual stage antigen from Eimeria maxima strongly associated with maternally derived immunity to this protozoan parasite in hatchling chickens. Cloning and sequence analysis has predicted the antigen to be a novel member of the thrombospondin-related anonymous protein (TRAP) family of apicomplexan parasites. Members of the TRAP family are microneme proteins and are associated with host cell invasion and apicomplexan gliding motility. In order to assess the immunogenicity of EmTFP250, a C-terminal derivative encoding a low complex, hydrophilic region and putative transmembrane domain/cytosolic tail was expressed in a bacterial host system. The recombinant protein was used to immunise mice and chickens and found to induce strong IgG responses in both animal models as determined by specific ELISAs. Using Western blotting, protective maternal IgG antibodies previously shown to recognise native EmTFP250 recognised the recombinant protein and, in addition, antibodies raised against the recombinant protein were shown to recognise native EmTFP250. Localisation studies employing immuno-light microscopy and immuno-electron microscopy showed that antibodies to the recombinant protein specifically labeled micronemes within merozoites of E. maxima. Furthermore, antibodies to the recombinant EmTFP250 derivative showed similar labeling of micronemes within merozoites of Eimeria tenella. This study is further suggestive of a functional importance for EmTFP250 and underscores its potential as a candidate for a recombinant vaccine targeting coccidiosis in chickens.

The development of the macrogamete and oocyst wall in Eimeria maxima: immuno-light and electron microscopy

We have identified, and followed the development of three macrogamete organelles involved in the formation of the oocyst wall of Eimeria maxima. The first were small lucent vacuoles that cross-reacted with antibodies to the apple domains of the Toxoplasma gondii microneme protein 4. They appeared early in development and were secreted during macrogamete maturation to form an outer veil and were termed veil forming bodies. The second were the wall forming bodies type 1, large, electron dense vacuoles that stained positively only with antibodies raised to an enriched preparation of the native forms of 56 (gam56), 82 (gam82) and 230 kDa (gam230) gametocyte antigens (termed anti-APGA). The third were the wall forming bodies type 2, which appeared before the wall forming bodies type 1 but remain enclosed within the rough endoplasmic reticulum and stained positively with antibodies raised to recombinant versions of gam56 (anti-gam56), gam82 (anti-gam82) and gam230 (anti-gam230) plus anti-APGA. At the initiation of oocyst wall formation, the anti-T. gondii microneme protein 4 positive outer veil detached from the surface. The outer layer of the oocyst wall was formed by the release of the contents of wall forming bodies type 1 at the surface to form an electron dense, anti-APGA positive layer. The wall forming bodies type 2 appeared, subsequently, to give rise to the electron lucent inner layer. Thus, oocyst wall formation in E. maxima represents a sequential release of the contents of the veil forming bodies, wall forming bodies types 1 and 2 and this may be controlled at the level of the rough endoplasmic reticulum/Golgi body.

Pseudorotation of the little finger metacarpal

Fractures of the little finger metacarpal are common, and are often associated with significant soft-tissue swelling and the appearance of rotational malalignment when the fingers are flexed. Our hypothesis is that soft-tissue swelling causes this apparent rotational deformity of the flexed little finger. The fourth intermetacarpal spaces of three of the authors' non-dominant hands were injected with saline. Following injection, all the hands exhibited the appearance of internal rotation of the little finger. The mean change in rotation was 16 degrees and the maximum was 25 degrees. There was no change in the plane of the nail plate in extension in any hand. We conclude that soft-tissue swelling can cause the appearance of internal rotation of the flexed little finger in the absence of fracture.

Zoledronic acid prevents osteopenia and increases bone strength in a rabbit model of distraction osteogenesis

Prolonged healing times and stress-shielding osteopenia remain problematic in distraction osteogenesis. In this study of 30 rabbits, zoledronic acid increased regenerate volume, mineralization, and tibial strength and prevented osteopenia over a 6-week period. Translation to the clinical setting, if safe, could improve outcomes in distraction osteogenesis in children.

INTRODUCTION

Because the external fixators for limb lengthening and reconstruction are designed to control the positions of bone fragments accurately, they also produce stress-shielding effects on the forming regenerate and surrounding bone. Osteopenia, leading to refracture and limitations on rehabilitation, are common consequences, potentially increasing morbidity and detracting from final clinical outcome.

MATERIALS AND METHODS

We examined the effect of zoledronic acid on distraction osteogenesis in 42 immature male NZW rabbits. The model chosen results in reliable regenerate formation and stress-shielding osteopenia. Fourteen animals received either Saline, zoledronic acid 0.1 mg/kg at surgery (ZOL), or another dose 2 weeks postoperatively (Redosed ZOL). Rabbits underwent DXA for bone mineral content and bone mineral density in regenerate and surrounding segments of operated and contralateral tibias. After death at 6 weeks, 30 pairs of tibias underwent quantitative computerized tomography (QCT) and four-point bend testing, and 12 were examined by histomorphometry. The study was powered at 0.8 to show differences of 1.3 SDs for mineral and mechanical parameters.

RESULTS

Osteopenia observed in tibias of the Saline group was absent in ZOL and Redosed ZOL tibias, the latter exhibiting higher bone mineral density and bone mineral content over contralateral regions (p < 0.01). Regenerate bone mineral content was higher in ZOL and Redosed ZOL versus Saline groups at 4 and 6 weeks (p < 0.01). Cross-sectional area was 49% and 59% greater at 6 weeks in ZOL and Redosed ZOL regenerates compared with the Saline group (p < 0.01). ZOL and Redosed ZOL tibias were 29% and 89% stronger by four-point bending than the Saline group (p < 0.01). Histomorphometry in the regenerate of ZOL and Redosed ZOL groups revealed higher trabecular bone volume and trabecular number compared with the Saline group (p < 0.001).

CONCLUSIONS

Zoledronic acid administration led to significantly greater bone area, mineral content, strength, and trabecular number with reduced stress-shielding osteopenia in this model of distraction osteogenesis. These data suggest that intraoperative and postoperative zoledronic acid administration could improve outcomes in children undergoing limb lengthening.

Molecular characterisation of EmTFP250: a novel member of the TRAP protein family in Eimeria maxima

We have previously described a high molecular mass, asexual stage antigen from Eimeria maxima (EmTFP250), implicated as a target of maternal antibodies produced by breeding hens infected with this protozoan parasite. Following partial purification of the protein by ion exchange chromatography, N-terminal and internal peptide sequences were generated and used in the design of degenerate PCR primers. Using a rapid amplification of cDNA ends PCR-based strategy, the cDNA encoding EmTFP250 has been cloned and sequenced. Translation predicts a mature polypeptide with a molecular mass of 246kDa and an isoelectric point of 4.2. Analysis of the amino acid sequence has revealed a novel member of the TRAP (thrombospondin-related anonymous protein) family, containing 16 thrombospondin type-1 repeats and 31 epidermal growth factor-like calcium binding domains. EmTFP250 also contains two low complex, hydrophilic regions rich in glutamic acid and glycine residues, and a transmembrane domain/cytosolic tail associated with parasite gliding motility that is highly conserved within apicomplexan microneme proteins. The protein has 61% identity (71% similarity) with EtMIC4, a 218kDa microneme protein of Eimeria tenella also rich in epidermal growth factor-like and thrombospondin type-1 domains. Using Southern blotting, the gene encoding EmTFP250 has been determined to be present as a single copy within the genome, and reverse transcriptase-PCR has shown that expression is confined to the asexual stages of development. By employing a PCR-based method, a region of the E. maxima Houghton strain EmTFP250 gene was found conserved in Australian isolates of several (at least four) Eimeria species that parasitise chickens. The characterisation of EmTFP250 adds to the expanding apicomplexan TRAP family and suggests a functional significance for the protein.

Roles of tyrosine-rich precursor glycoproteins and dityrosine- and 3,4-dihydroxyphenylalanine-mediated protein cross-linking in development of the oocyst wall in the coccidian parasite Eimeria maxima

The oocyst wall of apicomplexan parasites protects them from the harsh external environment, preserving their survival prior to transmission to the next host. If oocyst wall formation could be disrupted, then logically, the cycle of disease transmission could be stopped, and strategies to control infection by several organisms of medical and veterinary importance such as Eimeria, Plasmodium, Toxoplasma, Cyclospora, and Neospora could be developed. Here, we show that two tyrosine-rich precursor glycoproteins, gam56 and gam82, found in specialized organelles (wall-forming bodies) in the sexual stage (macrogamete) of Eimeria maxima are proteolytically processed into smaller glycoproteins, which are then incorporated into the developing oocyst wall. The identification of high concentrations of dityrosine and 3,4-dihydroxyphenylalanine (DOPA) in oocyst extracts by high-pressure liquid chromatography, together with the detection of a UV autofluorescence in intact oocysts, implicates dityrosine- and possibly DOPA-protein cross-links in oocyst wall hardening. In addition, the identification of peroxidase activity in the wall-forming bodies of macrogametes supports the hypothesis that dityrosine- and DOPA-mediated cross-linking might be an enzyme-catalyzed event. As such, the mechanism of oocyst wall formation in Eimeria, is analogous to the underlying mechanisms involved in the stabilization of extracellular matrices in a number of organisms, widely distributed in nature, including insect resilin, nematode cuticles, yeast cell walls, mussel byssal threads, and sea urchin fertilization membranes.

Cloning and characterization of the 82 kDa tyrosine-rich sexual stage glycoprotein, GAM82, and its role in oocyst wall formation in the apicomplexan parasite, Eimeria maxima

The sexual (macrogamete/macrogametocyte) stage antigen, GAM82, in the apicomplexan parasite Eimeria maxima, has an apparent molecular mass of 82 kDa, and has been implicated in protective immunity against coccidiosis in poultry. The gene encoding this protein, gam82, was cloned and sequenced. It is a single-copy, intronless gene, which localizes to a 2145 bp transcript, and is first detected at 130 h post-infection. The gene predicts two distinct domains rich in the residues tyrosine and serine, amino acids that have been implicated in oocyst wall formation in other Eimeria spp., and in the extraorganismic sclerotization of structural proteins throughout the animal kingdom. A high number of small amino acids, predominantly alanine and proline, were detected in the intervening sequence between these two domains. The inference that GAM82 is involved in oocyst wall formation in Eimeria was confirmed when it was shown that a specific antibody to a recombinant version of GAM82 recognized the wall forming bodies in macrogametes, and the walls of oocysts in E. maxima. A closer biochemical analysis of the role of GAM82 in oocyst wall formation by sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting showed that the antibodies to the recombinant version of GAM82 recognized an 82 kDa protein in macrogametocyte extracts, and a 30 kDa protein in unsporulated and sporulated oocyst extracts, as well as in purified oocyst wall fragments. Together, these findings indicate that the 82 kDa macrogametocyte antigen, GAM82, is a tyrosine and serine rich precursor protein that is proteolytically processed during development to give rise to a 30 kDa protein, that is incorporated into the oocyst wall. In addition, these findings provide evidence that the oocyst wall of Eimeria species is composed of a family of tyrosine rich proteins, that arise from precursor proteins found in the wall forming bodies of macrogametes.

Functional genomics of gam56: characterisation of the role of a 56 kilodalton sexual stage antigen in oocyst wall formation in Eimeria maxima

Gam56 (M(r) 56,000) is an antigen found in the sexual (macrogametocyte) stage of the intestinal parasite Eimeria maxima that is implicated in protective immunity. The gene (gam56) encoding this protein was cloned and sequenced. It is a single-copy, intronless gene, that localises to a 1,754 bp transcript, and is first detected at 120 h p.i. The gene predicts two distinct protein domains; a tyrosine-serine rich region, composed of amino acids implicated in oocyst wall formation in Eimeria spp., and a proline-methionine rich region often detected in extensins, protein components of plant cell walls. The tyrosine-serine rich region predicts a secondary structure commonly seen in the structural protein fibroin, a component of the cocoon of the caterpillar Bombyx mori. The inference that gam56 is a structural component of the oocyst wall was confirmed when a specific antibody to gam56 recognised the wall forming bodies in macrogametocytes, and the walls of oocysts and sporocysts. Together, these data identify a developmentally regulated, sexual stage gene in E. maxima that shares primary and secondary structure features in common with intrinsic structural proteins in other parasites such as Schistosoma mansoni and Fasciola hepatica, and other organisms across different phyla, including the caterpillar Bombyx mori. In addition, these findings provide evidence for the molecular mechanisms underlying oocyst wall formation in Eimeria and the role of gametocyte antigens in this process.

Zoledronic acid improves the mechanical properties of normal and healing bone

OBJECTIVE

To determine the effects of the bisphosphonate zoledronic acid on the mechanical properties of normal and regenerating bone in a rabbit model of distraction osteogenesis.

BACKGROUND

Bisphosphonate therapy is used for treating osteoporosis and, more recently, to enhance bone healing and reduce stress-shielding osteoporosis in distraction osteogenesis.

METHODS

Thirty eight rabbits underwent 14 days of distraction osteogenesis on the right rear limb. They received either zero, one or two doses of intravenous zoledronic acid. Four point bending tests were performed to collect mechanical data.

RESULTS

The peak load capacity of the regenerating bone was significantly increased by bisphosphonate therapy, but a similar trend in normal bone was not significant. The energy absorbed to failure did not vary significantly in either group.

CONCLUSIONS

These data suggest that bisphosphonate therapy has a beneficial effect on the load capacity of regenerating bone, without increasing the brittleness of either new or existing bone.

RELEVANCE

Zoledronic acid administration may be a potentially valuable adjunct to distraction osteogenesis treatment, to enhance bone strength, thus reducing refracture complications.

Neospora caninum: a cause of immune-mediated failure of pregnancy?

Resistance to many intracellular protozoan parasites is dependent on T helper cell 1 cytokine responses. This has important repercussions for pregnant females because strong T helper cell 1 cytokine responses are incompatible with successful pregnancy. Thus, there are two possible consequences of infection with protozoans such as Leishmania major, Plasmodium falciparum and Toxoplasma gondii during pregnancy: (1) pregnancy is compromised; or (2) resistance to the parasite is compromised. The apicomplexan Neospora caninum is a parasite renowned for its association with abortion in cattle. Furthermore, a major route of transmission for this parasite is congenital. The evidence for the hypothesis that T helper cell 1 cytokines play a role in these events is reviewed here.

Heat shock protein 70 is a potential virulence factor in murine toxoplasma infection via immunomodulation of host NF-kappa B and nitric oxide

We propose that the 70-kDa heat shock protein (HSP70) protects virulent Toxoplasma gondii from the effects of the host by immunomodulation. This hypothesis was tested using quercetin and antisense oligonucleotides targeting the start codon of the virulent T. gondii HSP70 gene. Oligonucleotides were transiently transfected into two virulent (RH, ENT) and two avirulent (ME49, C) strains of T. gondii, significantly reducing HSP70 expression in treated parasites. Virulent parasites with reduced HSP70 expression displayed reduced proliferation in vivo, as measured by the number of tachyzoites present in spleens of infected mice. They also exhibited an enhanced rate of conversion from tachyzoites to bradyzoites in vitro. Our results implicate HSP70 as a means by which virulent strains of T. gondii evade host proinflammatory responses: when RAW 264.7 cells were exposed to parasites with reduced HSP70 expression, differential expression of inducible NO synthase (iNOS) and cell NO production were observed between infections with normal and HSP70-deficient T. gondii. iNOS message levels were significantly increased when host cells were infected with HSP70 reduced virulent tachyzoites and HSP70-related inhibition of iNOS transcription resulted in altered host NO production by virulent T. gondii infection. Virulent parasites expressing reduced levels of HSP70 initiated significantly more NF-kappa B activation in host splenocytes than infections with untreated parasites. Neither proliferative ability nor conversion from tachyzoites to bradyzoites was affected by lack of HSP70 in avirulent strains of T. gondii. Furthermore, avirulent T. gondii strains induced high levels of host iNOS expression and NO production, regardless of HSP70 expression in these parasites, and inhibition of HSP70 had no significant effects on translocation of NF-kappa B to the nucleus. Therefore, the 70-kDa parasite stress protein may be part of an important survival strategy by which virulent strains down-regulate host parasiticidal mechanisms.