Parameters and functional analysis of the deep epaxial muscles in the thoracic, lumbar and sacral regions of the equine spine.

The epaxial muscles produce intervertebral rotation in the transverse, vertical and axial axes. These muscles also counteract the movements induced by gravitational and inertial forces and movements produced by antagonistic muscles and the intrinsic muscles of the pelvic limb. Their fascicles are innervated by the dorsal branch of the spinal nerve, which corresponds to the metamere of its cranial insertion in the spinous process. The structure allows the function of the muscles to be predicted: those with long and parallel fibres have a shortening function, whereas the muscles with short and oblique fibres have an antigravity action. In the horse, the multifidus muscle of the thoracolumbar region extends in multiple segments of two to eight vertebral motion segments (VMS). Functionally, the multifidus muscle is considered a spine stabiliser, maintaining VMS neutrality during spine rotations. However, there is evidence of the structural and functional heterogeneity of the equine thoracolumbar multifidus muscle, depending on the VMS considered, related to the complex control of the required neuromuscular activity. Osteoarticular lesions of the spine have been directly related to asymmetries of the multifidus muscle. The lateral (LDSM) and medial (MDSM) dorsal sacrocaudal muscles may be included in the multifidus complex, the function of which is also unclear in the lumbosacral region. The functional parameters of maximum force (Fmax ), maximum velocity of contraction (Vmax ) and joint moment (M) of the multifidus muscles inserted in the 4th, 9th, 12th and 17th thoracic and 3rd and 4th lumbar vertebrae of six horses were studied postmortem (for example: 4MT4 indicates the multifidus muscle that crosses four metameres with cranial insertion in the T4 vertebra). Furthermore, the structural and functional characteristics of LDSM and MDSM were determined. Data were analysed by analysis of variance (anova) in a randomised complete block design (P ≤ 0.05). For some muscles, the ordering of Vmax values was almost opposite to that of Fmax values, generally indicating antigravity or dynamic functions, depending on the muscle and VMS. The muscles 3MT12, 3ML3 and 4ML4 exhibited high Fmax and low Vmax values, indicating a stabilising action. The very long 7MT4 and 8MT4 multifidus had low Fmax and high Vmax values, suggesting a shortening action. However, some functional characteristics of interest did not fall within these general observations, also indicating a dual action. In summary, the results of the analysis of various structural and functional parameters confirm the structural and functional heterogeneity of the equine thoracolumbar multifidus complex, depending on the VMS, regardless of the number of metameres crossing each fascicle. To clarify the functions of the equine multifidus muscle complex, this study aimed to assess its functional parameters in thoracolumbar VMSs with different movement characteristics and in the MDSM and LDSM muscles, hypothesising that the functional parameters vary significantly when the VMS is considered.

Structural and functional characteristics of the thoracolumbar multifidus muscle in horses.

The multifidus muscle fascicles of horses attach to vertebral spinous processes after crossing between one to six metameres. The fascicles within one or two metameres are difficult to distinguish in horses. A vertebral motion segment is anatomically formed by two adjacent vertebrae and the interposed soft tissue structures, and excessive mobility of a vertebral motion segment frequently causes osteoarthropathies in sport horses. The importance of the equine multifidus muscle as a vertebral motion segment stabilizer has been demonstrated; however, there is scant documentation of the structure and function of this muscle. By studying six sport horses postmortem, the normalized muscle fibre lengths of the the multifidus muscle attached to the thoracic (T)4, T9, T12, T17 and lumbar (L)3 vertebral motion segments were determined and the relative areas occupied by fibre types I, IIA and IIX were measured in the same muscles after immunohistochemical typying. The values for the normalized muscle fibre lengths and the relative areas were analysed as completely randomized blocks using an anova (P ≤ 0.05). The vertebral motion segments of the T4 vertebra include multifidus bundles extending between two and eight metameres; the vertebral motion segments of the T9, T12, T17 and L3 vertebrae contain fascicles extending between two and four metameres The muscle fibres with high normalized lengths that insert into the T4 (three and eight metameres) vertebral motion segment tend to have smaller physiological cross-sectional areas, indicating their diminished capacity to generate isometric force. In contrast, the significantly decreased normalized muscle fibre lengths and the increased physiological cross-sectional areas of the fascicles of three metameres with insertions on T9, T17, T12, L3 and the fascicles of four metameres with insertions on L3 increase their capacities to generate isometric muscle force and neutralize excessive movements of the vertebral segments with great mobility. There were no significant differences in the values of relative areas occupied by fibre types I, IIA and IIX. In considering the relative areas occupied by the fibre types in the multifidus muscle fascicles attached to each vertebral motion segment examined, the relative area occupied by the type I fibres was found to be significantly higher in the T4 vertebral motion segment than in the other segments. It can be concluded that the equine multifidus muscle in horses is an immunohistochemically homogeneous muscle with various architectural designs that have functional significance according to the vertebral motion segments considered. The results obtained in this study can serve as a basis for future research aimed at understanding the posture and dynamics of the equine spine.

Evidence for three fast myosin heavy chain isoforms in type II skeletal muscle fibers in the adult llama (Lama glama).

Skeletal muscle fiber types classified on the basis of their content of different myosin heavy chain (MHC) isoforms were analyzed in samples from hindlimb muscles of adult sedentary llamas (Lama glama) by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies, myofibrillar ATPase (mATPase) histochemistry, and quantitative histochemistry of fiber metabolic and size properties. The immunohistochemical technique allowed the separation of four pure (i.e., expressing a unique MHC isoform) muscle fiber types: one slow-twitch (Type I) and three fast-twitch (Type II) phenotypes. The same four major fiber types could be objectively discriminated with two serial sections stained for mATPase after acid (pH 4.5) and alkaline (pH 10.5) preincubations. The three fast-twitch fiber types were tentatively designated as IIA, IIX, and IIB on the basis of the homologies of their immunoreactivities, acid denaturation of their mATPase activity, size, and metabolic properties expressed at the cellular level with the corresponding isoforms of rat and horse muscles. Acid stability of their mATPase activity increased in the rank order IIA>IIX>IIB. The same was true for size and glycolytic capacity, whereas oxidative capacity decreased in the same rank order IIA>IIX>IIB. In addition to these four pure fibers (I, IIA, IIX, and IIB), four other fiber types with hybrid phenotypes containing two (I+IIA, IIAX, and IIXB) or three (IIAXB) MHCs were immunohistochemically delineated. These frequent phenotypes (40% of the semitendinosus muscle fiber composition) had overlapped mATPase staining intensities with their corresponding pure fiber types, so they could not be delineated by mATPase histochemistry. Expression of the three fast adult MHC isoforms was spatially regulated around islets of Type I fibers, with concentric circles of fibers expressing MHC-IIA, then MHC-IIX, and peripherally MHC-IIB. This study demonstrates that three adult fast Type II MHC isoproteins are expressed in skeletal muscle fibers of the llama. The general assumption that the very fast MHC-IIB isoform is expressed only in small mammals can be rejected.

Non satellite veins in the pelvic limb of the llama (Lama glama).

The objective of this study was to determine the major differences in the venous system of the pelvic limb of the llama (Lama glama) and that of other mammals, including humans. Eight adult llamas, preserved by means of 6% formalin solution at 0 degrees C, were dissected. The venous system was perfused with a solution of 17% coloured industrial gelatin. Two venous systems are recognised, superficial and deep. The veins of the deep system follow the same course as the arteries, except for two important veins located in the femoral, popliteal and crural regions. A more voluminous vein than the femoral originates in a venous tripod in the proximal part of the femoral canal and forms an anastomosis with the femoral vein distally. The popliteal vein gives off an expansion located along the popliteal region. In the leg, it continues with a vein that accompanies the tibial nerve and forms an anastomosis distally with the medial saphenous vein. The described venous distribution represents an interesting complement to the medial saphenous, popliteal and femoral veins, being more important than the last one for its volume. In the thigh it would correspond to the deep femoral vein as in humans and dogs; the homology in the popliteal and leg regions is too difficult because it probably corresponds to the caudal tibial vein of the human, the caudal branch of the medial saphenous vein, and the satellite vein of the tibial nerve in the horse.

The psychosocial and cognitive impact of Duchenne's muscular dystrophy.

Duchenne's muscular dystrophy (DMD) is the most prevalent and devastating of neuromuscular disorders. Children given this diagnosis not only face inevitable deterioration of physical functioning, but they also become susceptible to emotional/behavioral problems, as well as reduced cognitive functioning and learning problems. This article (1) reviews the emotional/behavioral issues that may impact the child with DMD and the affected child's family members and caregivers; (2) examines the research describing the cognitive and learning issues associated with DMD; (3) provides recommendations for physicians who work with these families; and (4) recommends directions for future research that will help to further elucidate emotional/behavioral issues and cognitive and learning correlates of DMD.

Irrigación de la rodilla y pierna de la llama (lama glama) / Knee and leg irrigation of the llama (lama glama)

Dado el escaso material bibliográfico existente y la poca profundidad en sus detalles, se estudiaron las regiones de la rodilla y pierna hasta el nivel de la articulación tarsocrural, describiéndose las relaciones y las estructuras irrigadas. Se utilizaron 7 cadáveres conservados de llamas, en solución de formol al 6 por ciento, a 0ºC y perfundidos por vía arterial con yeso al 14 por ciento y por vía venosa con gelatina industrial al 17 por ciento. Por la forma de la distribución arterial en esta especie, podemos clasificarla como de tipo safeno, suministrando la arteria safena la mayor parte de la irrigación en caudal de la pierna y casi la totalidad del pie. Presenta una rama dorsal distal proveniente de la arteria safena, no presente en los animales domésticos, y la arteria comitans del nervio tibial es semejante a la del equino. La irrigación de la articulación de la rodilla es completa; la arteria media de la rodilla cursa hacia la fosa intercondílea. La arteria tibial craneal es la continuación de la arteria poplítea, cursando en el tercio medio y proximal de la pierna, por la celda lateral, desde que alcanza el espacio interóseo; la arteria tibial caudal es de escaso desarrollo