A comparison of the moment arms of pelvic limb muscles in horses bred for acceleration (Quarter Horse) and endurance (Arab)

Selective breeding for performance has resulted in distinct breeds of horse, such as the Quarter Horse (bred for acceleration) and the Arab (bred for endurance). Rapid acceleration, seen during Quarter Horse racing, requires fast powerful muscular contraction and the generation of large joint torques, particularly by the hind limb muscles. This study compared hind limb moment arm lengths in the Quarter Horse and Arab. We hypothesized that Quarter Horse hind limb extensor muscles would have longer moment arms when compared to the Arab, conferring a greater potential for torque generation at the hip, stifle and tarsus during limb extension. Six Quarter Horse and six Arab hind limbs were dissected to determine muscle moment arm lengths for the following muscles: gluteus medius, biceps femoris, semitendinosus, vastus lateralis, gastrocnemius (medialis and lateralis) and tibialis cranialis. The moment arms of biceps femoris (acting at the hip) and gastrocnemius lateralis (acting at the stifle) were significantly longer in the Quarter Horse, although the length of the remaining muscle moment arms were similar in both breeds of horse. All the Quarter Horse muscles were capable of generating greater muscle moments owing to their greater physiological cross-sectional area (PCSA) and therefore greater isometric force potential, which suggests that PCSA is a better determinant of muscle torque than moment arm length in these two breeds of horse. With the exception of gastrocnemius and tibialis cranialis, the observed muscle fascicle length to moment arm ratio (MFL : MA ratio) was greater for the Arab horse muscles. It appears that the Arab muscles have the potential to operate at slower velocities of contraction and hence generate greater force outputs when compared to the Quarter Horse muscles working over a similar range of joint motion; this would indicate that Arab hind limb muscles are optimized to function at maximum economy rather than maximum power output.

Functional anatomy and muscle moment arms of the thoracic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

We provide quantitative muscle-tendon architecture and geometry data for the racing greyhound thoracic limb. Muscle mass, belly length, fascicle lengths, pennation angles and moment arms were measured, as were tendon masses and lengths. Maximum isometric force and maximum power were estimated for muscles, and maximum stress and strain were estimated for tendons. Results are compared with other fast quadrupedal runners, and to previously published data in mixed-breed dogs. The implications of the functional adaptations of the greyhound thoracic limb for sprinting performance are discussed. The thoracic limb was found to benefit from a similar proportion of locomotor muscle mass to the pelvic limb, suggesting that it may be used to some extent in propulsion, or alternatively that stabilisation is very important in this animal. Extrinsic muscles, especially latissimus dorsi and pectoralis profundus, were predicted to be powerful and important for generating net positive work during accelerations. Proximal biarticular muscles show specialisation toward preventing collapse of the shoulder and elbow joints to enable strut-like limb function, or some form of dynamic control. Distal muscles did not appear specialised for elastic energy storage, a functional difference to pelvic limb muscles, and the equivalents in horse thoracic limbs. The greyhound thoracic limb appears to possess substantial differences from both that of more 'sub-maximal specialist' quadrupeds, and from the greyhound pelvic limb.

Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

We provide quantitative anatomical data on the muscle-tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance.

A comparative study of the physiological costs of walking in ten bilateral amputees

The physiological cost of walking is greater in bilateral amputees (BA) than in both unilateral amputee and non-pathological gait. The aim of this study was to describe the physiological costs and other standard gait characteristics in a sample population of BA, walking at self-selected (comfortable) speeds. Amputees had bilateral trans-tibial, bilateral trans-femoral or trans-tibial/trans-femoral amputations as a result of trauma or congenital defects. All amputees wore their own prosthetic limbs which were either full-length prostheses or short non-articulating pylon prostheses (SNAPPs). The results were compared with a base line data set collected from a non-pathological control group. It was anticipated that amputees with high-level amputations would walk at the slowest speeds, have the highest physiological costs and lowest perception of walking ability. However, varying walking speeds resulted in varying exercise intensities, exercise heart rates and perceptions of walking that could not be directly related to amputation levels. It is therefore concluded that bilateral amputee gait is complex, varied and not easily categorized.

Comparative anatomy and muscle architecture of selected hind limb muscles in the Quarter Horse and Arab

The Quarter Horse (bred for acceleration) and the Arab (bred for endurance) are situated at either end of the equine athletic spectrum. Studies into the form and function of the leg muscles in human sprint and endurance runners have demonstrated that differences exist in their muscle architecture. It is not known whether similar differences exist in the horse. Six Quarter Horse and six Arab fresh hind limb cadavers were dissected to gain information on the muscle mass and architecture of the following muscles: gluteus medius; biceps femoris; semitendinosus; vastus lateralis; gastrocnemius; tibialis cranialis and extensor digitorum longus. Specifically, muscle mass, fascicle length and pennation angle were quantified and physiological cross-sectional area (PCSA) and maximum isometric force were estimated. The hind limb muscles of the Quarter Horse were of a significantly greater mass, but had similar fascicle lengths and pennation angles when compared with those of the Arab; this resulted in the Quarter Horse hind limb muscles having greater PCSAs and hence greater isometric force potential. This study suggests that Quarter Horses as a breed inherently possess large strong hind limb muscles, with the potential to accelerate their body mass more rapidly than those of the Arab.

The energetic costs of load-carrying and the evolution of bipedalism

The evolution of habitual bipedalism is still a fundamental yet unsolved question for paleoanthropologists, and carrying is popular as an explanation for both the early adoption of upright walking and as a positive selection pressure once a terrestrial lifestyle had been adopted. However, to support or reject any hypothesis that suggests carrying efficiency was an important selective pressure, we need quantitative data on the costs of different forms of carrying behavior, especially infant-carrying since reduction in the grasping capabilities of the foot would have prevented infants from clinging on for long durations. In this study, we tested the hypothesis that the mode of load carriage influences the energetic cost of locomotion. Oxygen consumption was measured in seven female participants walking at a constant speed while carrying four different 10-kg loads (a weighted vest, 5-kg dumbbells carried in each hand, a mannequin infant carried on one hip, and a 10-kg dumbbell carried in a single hand). Oxygen consumption was also measured during unloaded standing and unloaded walking. The results show that the weighted vest requires the least amount of energy of the four types of carrying and that, for this condition, humans are as efficient as mammals in general. The balanced load was carried with approximately the predicted energy cost. However, the asymmetrical conditions were considerably less efficient, indicating that, unless infant-carrying was the adaptive response to a strong environmental selection pressure, this behavior is unlikely to have been the precursor to the evolution of bipedalism.

Functional specialisation of the thoracic limb of the hare (Lepus europeus)

We provide quantitative anatomical data on the muscle-tendon architecture of the hare thoracic limb (specifically muscle mass, fascicle length, pennation angle, tendon mass and length). In addition, moment arms of major thoracic limb muscles were measured. Maximum isometric force and power of muscles, the moment of force about a joint, and tendon stress and strain were estimated. Data are compared with those from other cursorial mammals. The thoracic limb of the hare consists predominantly of extrinsic musculature with long parallel fascicles, specialised for generating force over a large range. A large shoulder flexor/elbow extensor muscle mass is present, in particular Triceps brachii. The pennate nature of the long head of this muscle suggests it has an important role in stabilising the elbow joint during stance, whilst moment arm curves suggest that it may also play a role in initiating shoulder flexion. In addition, Supraspinatus and Infraspinatus are capable of generating high forces, potentially to stabilise the shoulder joint during the stance phase of locomotion. Supraspinatus may in addition play an important role in forelimb protraction. The Subscapularis muscle was capable of generating surprisingly high forces, suggesting that the hare must be able to withstand/produce high forces during activities that need medio-lateral stability, such as turning. Distally, tendons were relatively short, showing little potential for elastic energy storage when compared with both their pelvic limb counterparts and their equivalents in the horse thoracic limb. Thus, a 'stiffer' thoracic limb may be beneficial in terms of behaving like a strut, simply supporting and deflecting the body during high-speed running. This more distal/less proximal distribution of limb mass is also likely to be important in retaining the manipulative/adaptive/non-locomotor capabilities of the limb.

Muscle architecture and functional anatomy of the pelvic limb of the ostrich (Struthio camelus)

The functional anatomy of the pelvic limb of the ostrich (Struthio camelus) was investigated in order to assess musculoskeletal specialization related to locomotor performance. The pelvic limbs of ten ostriches were dissected and detailed measurements of all muscle tendon units of the pelvic limb were made, including muscle mass, muscle length, fascicle length, pennation angle, tendon mass and tendon length. From these measurements other muscle properties such as muscle volume, physiological cross-sectional area (PCSA), tendon cross-sectional area, maximum isometric muscle force and tendon stress were derived, using standard relationships and published muscle data. Larger muscles tended to be located more proximally and had longer fascicle lengths and lower pennation angles. This led to an expected proximal to distal reduction in total muscle mass. An exception to this trend was the gastrocnemius muscle, which was found to have the largest volume and PCSA and also had the highest capacity for both force and power production. Generally high-power muscles were located more proximally in the limb, while some small distal muscles (tibialis cranialis and flexor perforatus digiti III), with short fibres, were found to have very high force generation capacities. The greatest proportion of pelvic muscle volume was for the hip extensors, while the highest capacity for force generation was observed in the extensors of the ankle, many of which were also in series with long tendons and thus were functionally suited to elastic energy storage.

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.

Functional specialisation of the pelvic limb of the hare (Lepus europeus)

We provide quantitative anatomical data on the muscle-tendon architecture of the hare pelvic limb (specifically muscle mass, fascicle length, pennation angle, tendon mass and length). In addition, moment arms of major pelvic limb muscles were measured. Maximum isometric force and power of muscles, the moment of force about a joint, and tendon stress and strain were estimated. Data are compared with published data for other cursorial mammals such as the horse and dog, and a non-specialised Lagamorph, the rabbit. The pelvic limb of the hare was found to contain substantial amounts of hip extensor and adductor/abductor muscle volume, which is likely to be required for power production and stability during rapid turning. A proximal to distal reduction in muscle volume and fascicle length was also observed, as is the case in other cursorial quadrupeds, along with a reduction in distal limb mass via the replacement of muscle volume by long distal limb tendons, capable of storing large amounts of elastic energy. The majority of hare pelvic limb muscle moment arms varied with joint position, giving the hare the capacity to vary muscle function with limb posture and presumably different locomotor activities.

Morphological analysis of the hindlimb in apes and humans. II. Moment arms

Flexion/extension moment arms were obtained for the major muscles crossing the hip, knee and ankle joints in the orang-utan, gibbon, gorilla (Eastern and Western lowland) and bonobo. Moment arms varied with joint motion and were generally longer in proximal limb muscles than distal limb muscles. The shape of the moment arm curves (i.e. the plots of moment arm against joint angle) differed in different hindlimb muscles and in the same muscle in different subjects (both in the same and in different ape species). Most moment arms increased with increasing joint flexion, a finding which may be understood in the context of the employment of flexed postures by most non-human apes (except orang-utans) during both terrestrial and arboreal locomotion. When compared with humans, non-human great apes tended to have muscles better designed for moving the joints through large ranges. This was particularly true of the pedal digital flexors in orang-utans. In gibbons, the only lesser ape studied here, many of the moment arms measured were relatively short compared with those of great apes. This study was performed on a small sample of apes and thus differences noted here warrant further investigation in larger populations.

Morphological analysis of the hindlimb in apes and humans. I. Muscle architecture

We present quantitative data on the hindlimb musculature of Pan paniscus, Gorilla gorilla gorilla, Gorilla gorilla graueri, Pongo pygmaeus abelii and Hylobates lar and discuss the findings in relation to the locomotor habits of each. Muscle mass and fascicle length data were obtained for all major hindlimb muscles. Physiological cross-sectional area (PCSA) was estimated. Data were normalized assuming geometric similarity to allow for comparison of animals of different size/species. Muscle mass scaled closely to (body mass)(1.0) and fascicle length scaled closely to (body mass)(0.3) in most species. However, human hindlimb muscles were heavy and had short fascicles per unit body mass when compared with non-human apes. Gibbon hindlimb anatomy shared some features with human hindlimbs that were not observed in the non-human great apes: limb circumferences tapered from proximal-to-distal, fascicle lengths were short per unit body mass and tendons were relatively long. Non-human great ape hindlimb muscles were, by contrast, characterized by long fascicles arranged in parallel, with little/no tendon of insertion. Such an arrangement of muscle architecture would be useful for locomotion in a three dimensionally complex arboreal environment.

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.

The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.

The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 +/- 17 mm) fascicles, arranged at about 45 degrees to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb.

Automated assay for HER-2/neu in serum

BACKGROUND

The extracellular domain of the HER-2/neu oncogene product is increased in sera of some patients with epithelial cancers. Our aim was to develop an automated serum assay for the extracellular domain of the HER-2/neu protein.

METHODS

We used a monoclonal antibody labeled with fluorescein for capture and a monoclonal Fab' fragment labeled with alkaline phosphatase for detection. Separation of bound and free detection conjugate was performed with magnetizable particles coated with monoclonal antibody to fluorescein. Alkaline phosphatase activity was measured kinetically at 405 or 450 nm.

RESULTS

The assay was linear from 0.1 to 250 microg/L. No hook effect was evident up to 10 000 microg/L. Within-run imprecision (CV) was 0.8-1.2%, and total imprecision was 1.1-1.7%. Cross-reactivity with human epidermal growth factor receptor, which has extensive homology with HER-2/neu extracellular domain, was <0.6%. Human anti-mouse antibodies, heterophilic antibodies, and rheumatoid factor did not interfere, nor did the therapeutic monoclonal antibody Herceptin((R)). In 51 healthy females, the mean value was 9.3 microg/L with a range of 6.4-14.0 microg/L. No reagent lot-to-lot variability was detected over four lots of reagents tested.

CONCLUSION

The Bayer Immuno 1(TM) assay for HER-2/neu was precise and resistant to interferences, characteristics that are essential for longitudinal monitoring of cancer patients.

Efficacy of Cymelarsan in Friesian Holstein calves infected with Trypanosoma evansi

Two studies on the efficacy of mel Cy (Cymelarsan, Rhone Merieux, France) for the treatment of cattle infected with Trypanosoma evansi were carried out with groups of 5 Friesian Holstein calves infected with an Indonesian stock of T. evansi and treated 14 days after infection. In the first study 3 groups were injected subcutaneously with Cymelarsan at dose rates of 0.125, 0.25 and 0.50 mg/kg and in the second study 2 i/m at 0.50 and 0.75 mg/kg. The response to treatment was monitored parasitologically by daily microhaematocrit centrifugation technique and weekly mouse inoculation. Enzyme linked immunosorbent assays were used to monitor trypanosomal antibodies and trypanosomal antigens in serum samples collected weekly. Relapse infections occurred in all the groups given the drug s/c whilst all the animals treated i/m remained parasitologically negative up to 80 days after treatment. Results from serological assays, however, suggested the possible persistence of trypanosome infection in the animals treated at a dose rate of 0.50 mg/kg i/m although trypanosomes could not be demonstrated parasitologically. A dose rate of 0.75 mg/kg administered i/m is recommended, therefore, for the treatment of T. evansi infection in Friesian Holstein cattle.

The effect of Trypanosoma evansi infection on the oestrous cycle of Friesian Holstein heifers

The effect of Trypanosoma evansi infection on oestrous cycling was studied in 12 Friesian Holstein heifers. In the Phase 1 of the investigation, six heifers were infected with T. evansi, the remaining six acted as uninfected controls. Daily body temperature, packed red cell volume (PCV) and parasitaemia measurements were obtained from each animal for 90 days. The animals were examined for external signs of oestrous activity twice daily, blood samples were taken three times a week and subjected to an enzyme-linked immunosorbent assay to detect plasma progesterone. Body weights were measured weekly. Parasites were eliminated by trypanocidal drug treatment 90 days after infection. In Phase 2 of the trial, the uninfected heifers were injected with a different stock of parasites and monitoring was continued as before. Infection with T. evansi resulted in a marked reduction in the rate of weight gain, an increase in body temperatures and a fall in PCV values. Eleven of the heifers continued to cycle normally for the duration of the study, irrespective of their infective status. One animal which stopped cycling lost 16.2% of its pre-infection body weight as a result of the infection and cessation of oestrous activity was considered to have been due to weight loss.

Experimental infection of Friesian Holstein calves with an Indonesian isolate of Trypanosoma evansi

The effect of a single, primary, artificial infection with Trypanosoma evansi was studied in nine Friesian Holstein calves. Body temperature, packed cell volume (PCV) and parasitaemia measurements were obtained daily from each of the infected calves for up to 90 days after parasites were injected, body weights were monitored weekly. T. evansi infection had a marked depressive effect on PCV profiles and the rate of body weight gain.

Trypanosoma evansi infection in worked and unworked buffaloes (Bubalus bubalis) in Indonesia

The effect of controlled amounts of exercise on the outcome of Trypanosoma evansi infection was studied in groups of swamp buffaloes (Bubalus bubalis) experimentally infected with T. evansi. Daily body temperature, packed cell volume (PCV) and parasitaemia measurements were obtained from each animal for up to 110 days after infection. Exercise did not appear to exacerbate the effect of T. evansi infection in that similar temperature, PCV and parasitaemia profiles were obtained with both exercised and rested animals. Trypanosoma evansi infection, however, had a marked effect on temperature and PCV profiles, both of which could adversely affect an infected animal's work output and work tolerance.

Trypanosoma evansi infection in bovine and buffalo calves in Indonesia

Fifteen bovine and 11 buffalo calves born on different farms in a Trypanosoma evansi-endemic area of West Java were monitored for the presence of T. evansi and T. evansi antibody at monthly intervals until they were 12 months of age. Fifty percent of the bovine and 83% of the buffalo calves sampled in the first month of life were antibody positive. This antibody was considered to be of colostral origin. Antibody developing later in life persisted for up to 12 months and was considered to have arisen in response to T. evansi infection. No protective function could be ascribed to the colostral antibody.

Trypanosoma evansi infection in cattle, buffaloes and horses in Indonesia

Cattle, buffaloes and horses in several areas of Indonesia were examined for evidence of infection with Trypanosoma evansi by the microhaematocrit centrifugation technique (MHCT) and an enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to T. evansi. Evidence of infection was found in animals at each sampling site although differences were seen in prevalence rates between sites. Prevalence rates in buffalo were usually higher than in cattle in the same area while in horses they were much lower than in cattle or buffalo. An age-dependent prevalence rate was seen in buffalo and cattle with the highest rates seen in animals older than 2 years. These results concur with the view that T. evansi infection is widespread throughout most of the livestock-producing areas of Indonesia. The apparent lack of any obvious disease owing to T. evansi infection in the sampled animals suggests that a form of stability exists in most endemic areas which serves to ameliorate the effect of T. evansi infection and has an immunological basis linked to the parasite's limited antigenic diversity.

Metal ion and substrate structure dependence of the processing of tRNA precursors by RNase P and M1 RNA

A synthetic tRNA precursor analog containing the structural elements of Escherichia coli tRNA(Phe) was characterized as a substrate for E. coli ribonuclease P and for M1 RNA, the catalytic RNA subunit. Processing of the synthetic precursor exhibited a Mg2+ dependence quite similar to that of natural tRNA precursors such as E. coli tRNA(Tyr) precursor. It was found that Sr2+, Ca2+, and Ba2+ ions promoted processing of the dimeric precursor at Mg2+ concentrations otherwise insufficient to support processing; very similar behavior was noted for E. coli tRNA(Tyr). As noted previously for natural tRNA precursors, the absence of the 3'-terminal CA sequence in the synthetic precursor diminished the facility of processing of this substrate by RNase P and M1 RNA. A study of the Mg2+ dependence of processing of the synthetic tRNA dimeric substrate radiolabeled between C75 and A76 provided unequivocal evidence for an alteration in the actual site of processing by E. coli RNase P as a function of Mg2+ concentration. This property was subsequently demonstrated to obtain (Carter, B. J., Vold, B.S., and Hecht, S. M. (1990) J. Biol. Chem. 265, 7100-7103) for a mutant Bacillus subtilis tRNAHis precursor containing a potential A-C base pair at the end of the acceptor stem.

An outbreak of trypanosomiasis caused by Trypanosoma evansi on the island of Madura, Indonesia

During an outbreak of trypanosomiasis in cattle, buffalo and horses on the island of Madura, a survey was conducted to determine the prevalence of Trypanosoma evansi in the region. Blood samples were collected from 130 cattle and 147 buffalo in 5 villages, whole blood was examined for trypanosomes by the microhaematocrit (MHCT) method and serum samples were subjected to an enzyme linked immuno absorbent assay to detect T. evansi antibodies. T. evansi was detected by MHCT in 50% of the buffalo examined and 13% of the cattle, while antibodies were detected in 47% of the buffalo and 30% of the cattle. The outbreak was brought under control following the administration of Nagano (Suramin, Bayer) to infected animals and animals considered to be at risk of infection.

Tick-borne diseases of cattle in Paraguay. II. Immunisation against anaplasmosis and babesiosis

A total of 102 susceptible adult Holstein Friesian cattle imported into an area of Paraguay where anaplasmosis and babesiosis are endemic were immunised by infection with Anaplasma centrale and attenuated forms of Babesia bigemina and Babesia bovis obtained from Uruguay. The results indicated that the attenuated forms of both Babesia species protected cattle against heterologous field challenge whereas A. centrale did not invariably confer sufficient protection against a field challenge of A. marginale.

Tick-borne diseases of cattle in Paraguay. I. Seroepidemiological studies on anaplasmosis and babesiosis

A serological survey was carried out in Paraguay to determine the prevalence of antibodies to Anaplasma marginale, Babesia bigemina and Babesia bovis. The results suggest that the parasites are widely distributed throughout the country with prevalence rates of 92% for A. marginale, 79% for B. bigemina and 71% for B. bovis. Epidemiological studies on calves demonstrated that initial infection with the three blood parasites occurs in most animals within the first nine months of life. It is likely therefore that most of the country can be considered as being enzootically stable with respect to anaplasmosis and babesiosis.

Malic enzyme type VII isoenzyme as an indicator of suramin resistance in Trypanosoma evansi

This study analysed the suramin sensitivity of 29 stocks of Trypanosoma evansi isolated from Egypt, Sudan, and Indonesia and compared the results with the isoenzyme banding patterns of 20 soluble enzymes in these stocks of T. evansi. The results showed that the type VII banding pattern of malic enzyme was found only in T. evansi stocks which were highly resistant to suramin.

Preparation of misacylated aminoacyl-tRNA(Phe)'s useful as probes of the ribosomal acceptor site

Several pyroglutamylaminoacyl-tRNA's were prepared by T4 RNA ligase mediated condensation of synthetic pyroglutamylaminoacyl-pCpA's with tRNA's from which the last two nucleotides at the 3'-end had been removed. The derived pyroglutamylaminoacyl-tRNA's were incubated in the presence of calf liver pyroglutamate aminopeptidase, which effected their conversion to free aminoacyl-tRNA's. The lack of contaminating esterase activities in the pyroglutamate aminopeptidase was verified by direct assay for the presence of the aminoacyl moieties in the formed aminoacyl-tRNA's and by the use of the deblocked aminoacyl-tRNA's as acceptors in the peptidyltransferase reaction using an Escherichia coli ribosomal system. These findings provide the wherewithal for a detailed investigation of the substrate specificity of the peptidyltransferase center and for the elaboration of polypeptides containing modified amino acids at predetermined sites.

Escherichia coli tryptophan synthase: synthesis of catalytically competent alpha subunit in a cell-free system containing preacylated tRNAs

A cell-free protein biosynthesizing system prepared from Escherichia coli CF300 was found to synthesize E. coli tryptophan synthase alpha subunit in a time-dependent manner when programmed with pBN69 plasmid DNA. This plasmid contains the trp promoter from Serratia marcescens adjacent to the coding region of E. coli tryptophan synthase alpha protein [Nichols, B.P., & Yanofsky, C. (1983) Methods Enzymol. 101, 155-164]. The synthesized tryptophan synthase alpha subunit was found to be indistinguishable from authentic alpha subunit protein when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and to have the same specific activity for catalyzing the conversion of indole----L-tryptophan by tryptophan synthase beta 2 subunit, as well as the conversion of indole + glyceraldehyde 3-phosphate to indole-3-glycerol phosphate. In the absence of exogenously added phenylalanine, admixture of E. coli phenylalanyl-tRNAPhe to the protein biosynthesizing system stimulated the production of functional alpha protein; the analogous result was obtained when valine was replaced by E. coli valyl-tRNAVal. The ability of a misacylated tRNA to participate in alpha protein synthesis in this system was established by the use of E. coli phenylalanyl-tRNAVal in the absence of added valine. Protein biosynthesis proceeded normally and gave a product having the approximate molecular weight of tryptophan synthase alpha subunit; as expected, this polypeptide lacked catalytic activity.

Regulation of uridine kinase. Evidence for a regulatory site

Uridine kinase from mouse Ehrlich ascites tumor cells may exist at 4 degrees C in multiple aggregation states that only slowly equilibrate with one another. Increasing the temperature leads to dissociation, and the appearance of a single predominant species: at 22 degrees C the enzyme exists as a tetramer. There is also a break in the dependence of enzyme activity on temperature as measured in an Arrhenius plot. The feedback inhibitors CTP and UTP cause the enzyme to dissociate to the monomer, whereas the substrate ATP reverses this process. Kinetic studies show that the monomer has little or no activity. Studies of the reaction mechanism show that binding of substrates is ordered, leading to a ternary complex, and release of products is ordered: uridine is the first substrate bound, ADP the first product released. Except for the inhibitors UTP and CTP, all other nucleoside triphosphates, whether purine or pyrimidine, or containing ribose or deoxyribose, act as phosphate donor. Especially interesting are the opposite effects of CTP and dCTP on uridine kinase: unlike CTP, dCTP does not dissociate the enzyme and is competent as a phosphate donor. We propose that the various effects of different ligands are best explained by the existence of a regulatory site (with more stringent specificity than the catalytic site) that controls dissociation of uridine kinase to the inactive monomer.

Homogeneous uridine kinase from Ehrlich ascites tumor: substrate specificity and inhibition by bisubstrate analogs

Uridine kinase has been purified to homogeneity from Ehrlich ascites tumor cells. For the phosphate acceptor site, the enzyme shows substrate specificity only for ribopyrimidine nucleosides and is active with various analogs that have limited structural alterations; both endocyclic and exocyclic substituents can be acceptable. Of nucleosides that have been used in the chemotherapy of cancer, 5-fluorouridine, 6-azauridine, and 3-deazauridine are good substrates, whereas arabinosylcytosine is a poor substrate. No analogs are better substrates than the physiological substrates uridine and cytidine. 5', 5''' -P1, P4-Bisnucleoside oligophosphate bisubstrate analogs (e.g., Ap4U, Ap5U) were synthesized and tested as inhibitors. The most effective compound was Ap4U; with a Ki of 197 microM, it bound more tightly than ATP but no better than uridine. Ap3A, Ap4A, and Ap5A were also tested, with the result that both Ap4A and Ap4U were most effective, suggesting that this size of bisubstrate analog most closely approaches the spacing of the catalytic site.

Uridine kinase from Ehrlich ascites carcinoma. Purification and properties of homogeneous enzyme

Uridine kinase from Ehrlich ascites tumor cells has been purified about 60,000-fold to apparent homogeneity and with an overall recovery of about 40%. This purification was achieved using phosphocellulose and adenosine 5'-triphosphate-agarose affinity chromatography. The subunit molecular mass as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 31,000 daltons. With two-dimensional electrophoresis, only one spot was observed, indicating the absence of isoenzymes. Multiple peaks of activity are routinely observed on ion exchange chromatography or gel filtration, for both crude preparations or homogeneous uridine kinase, in agreement with our earlier results that this enzyme exists as multiple interconvertible oligomeric forms (Payne, R. C., and Traut, T. W. (1982) J. Biol. Chem. 257, 12485-12488). The purified enzyme has a specific activity of 283 mumol/min/mg of protein at 22 degrees C. Initial velocity studies using uridine and ATP are consistent with a sequential mechanism. Km values for uridine, cytidine, and ATP are 40, 57, and 450 microM, respectively. CTP and UTP are competitive inhibitors with respect to ATP, with Ki values for CTP and UTP of 10 and 61 microM, respectively. The enzyme was active with several nucleoside analogs, the Km values being 69 microM (5-fluorouridine), 200 microM (3-deazauridine), and 340 microM (6-azauridine). The pure enzyme is very sensitive to freezing, but can be maintained at O degrees C for 8 weeks with only 20% loss of activity. For long-term storage, enzyme in 50% glycerol can be maintained at -20 degrees C for many months with no detectable loss of activity.

The ultrastructure of dentinal tubules from erupted human premolar teeth

Different regions of crown dentin from erupted human premolars were examined ultrastructurally to determine the contents of the dentinal tubules. Odontoblast processes were limited to inner dentin, and nerve fibers were not observed in any tubules examined.

Regulation of uridine kinase quaternary structure. Dissociation by the inhibitor CTP

Uridine kinase from mouse Ehrlich ascites cells can exist in a variety of different aggregation states, from monomer up to aggregates that may contain 32 or more subunits. With very crude enzyme preparations, uridine kinase activity is always associated with several different coexisting molecular weight species. Changes in the aggregation state are produced in the presence of normal effectors (orthophosphate, ATP and CTP) at physiological concentrations. With uridine kinase that has been purified 9,000-fold, enzyme activity is associated with only a single molecular weight species, but is still responsive to the same physiological effectors. In the presence of orthophosphate, uridine kinase has a molecular weight of 380,000 (appropriate for a dodecamer). In the presence of CTP, the enzyme dissociates with concomitant loss of activity. The dissociated enzyme can be reassociated to the native size. These results imply that alteration of the enzyme's quaternary structure by normal effectors constitutes a mechanism for regulating uridine kinase activity in vivo.

Anaplasmosis and babesiosis in El Salvador

A serological survey was carried out in the Central American state of El Salvador to determine the distribution and prevalence of Anaplasma marginale, Babesia bigemina and Babesia bovis. the results suggest that the parasites are widely distributed throughout the country and prevalence rates of 78.5% for A. marginale, 70.5% for B. bigemina and 73.5% for B. bovis were obtained. Tick counts suggest that boophilus microplus is the main blood parasite vector. Epidemiological studies showed that initial infection with the 3 blood parasites occurs in most animals during the first 7 months of life. Notwithstanding these facts which indicate an area of enzootic stability outbreaks of clinical disease were frequently reported. Twenty-two such outbreaks were investigated and management factors predisposing to outbreaks of clinical disease are discussed.

Dependence of the aggregation and conformation states of uridine 5'-phosphate synthase on pyrimidine nucleotides. Evidence for a regulatory site

Uridine 5'-phosphate (UMP) synthase is multifunctional protein that contains the last two enzyme activities of the de novo pathway for UMP biosynthesis, orotate phosphoribosyltransferase (EC 2.4.2.10) and orotidine-5'-phosphate (OMP) decarboxylase (EC 4.1.1.23). We have previously reported that UMP synthase from mouse Ehrlich ascites cells can exist in at least three distinct aggregation and/or conformation states, as measured by changes in sedimentation through sucrose gradients [Traut, T. W., & Jones, M. E. (1979) J. Biol. Chem, 254, 1143-1150]. The major sedimenting species were a 3.6S monomer, a 5.1S dimer, and a 5.6S species. The formation of the 5.1S dimer from the 3.6S monomer occurs in the presence of ligands that are competitive inhibitors at the OMP decarboxylase catalytic site. This paper presents evidence for a regulatory site, distinct from either of the two catalytic sites, which appears to mediate the conversion of the 5.1S dimer to the 5.6S form upon binding certain pyrimidine nucleotides (OMP, UMP, and 6-azaUMP). Since UMP synthase sediments predominantly as a dimer in the presence of substrates, regulation of the aggregation/conformation state of this multifunctional protein may be physiologically significant.

Dependence of the catalytic activities on the aggregation and conformation states of uridine 5'-phosphate synthase

Uridine 5'-phosphate (UMP) synthase is a multifunctional protein that contains the last two enzyme activities for the de novo biosynthesis of UMP, orotate phosphoribosyltransferase (EC 2.4.2.10) and orotidine-5'-phosphate (OMP) decarboxylase (EC 4.1.1.23). The native enzyme from mouse Ehrlich ascites cells exists in at least three distinct aggregation/conformation states as measured by sedimentation in sucrose gradients: a 3.6S monomer, a 5.1S dimer, and a conformationally altered 5.6S dimer. It has previously been reported that a variety of ligands (of which the most effective is OMP) mediate the conversion of the 3.6S monomer to the two types of dimers. Initial velocity studies with the enzyme in the different native states show that all three forms of UMP synthase have phosphoribosyltransferase activity but that the OMP decarboxylase is either uniquely or at least predominantly associated with the 5.6S form. Activation of this enzyme activity by the substrate appears to be the result of both a dimerization and a conformation step.

Serological comparison of British Theileria mutans and Japanese T sergenti

A serological comparison between British Theileria mutans and Japanese T sergenti using the indirect fluorescent antibody test, showed that the two parasites were indistinguishable. On the basis of this and previous findings it is suggested that the British parasite is identical with the Japanese one and that its name should therefore be changed to T sergenti.

Comparisons of serological tests for Babesia in British cattle

A comparison was made between the microplate enzyme linked immunosorbent assay (ELISA) and the indirect fluorescent antibody (IFA) and complement fixation (CF) tests for the detection of antibodies in the serum of cattle experimentally infected with Babesia divergens and B major. Antibodies were detected using all three tests but they were detected earlier using the CF test. However CF titres were consistently lower than those obtained using the other tests. Although there was little to choose between the IFA and ELISA tests, it was suggested that the ELISA may be preferable since it is less subject to operator error and operator stress, and can be adapted readily to field use.

Cryopreservation of bovine blood infected with Babesia major for use in the indirect fluorescent antibody test

Washed erythrocytes infected with Babesia major were mixed with glycerol and snap frozen in liquid nitrogen. After thawing, these cells were used for the preparation of antigen slides for immunofluorescence studies.