Dependence of developing group Ia afferents on neurotrophin-3

At birth, group Ia proprioceptive afferents and muscle spindles, whose formation is Ia afferent-dependent, are absent in mice carrying a deletion in the gene for neurotrophin-3 (NT-3-/-). Whether Ia afferents contact myotubes, resulting in the formation of spindles which subsequently degenerate, or whether Ia afferents and spindles never form was examined in NT-3-/- mice at embryonic days (E) 10.5-18.5 by light and electron microscopy. Three sets of data indicate that Ia neurons do not develop and spindles do not form in NT-3-deficient mice. First, peripheral projections of Ia afferents did not innervate hindlimbs of NT-3-/- mice, as reflected by a deficiency of nerve fibers in limb peripheral nerves and an absence of afferent nerve-muscle contacts and spindles in the soleus muscle at E13.5-E18.5. Second, central projections of Ia afferents did not innervate the spinal cord in the absence of NT-3, as shown by an atrophy of the dorsal spinal roots and absence of afferent projections from limb musculature to spinal motor neurons at E13.5 or E15.5. Lastly, the lumbar dorsal root ganglia (DRGs) at E10.5-E14.5, the stages of development that precede or coincide with the innervation of the spinal cord and hindlimbs by Ia afferents, were 20-64% smaller in mutant than in wild-type mice, presumably because the cell bodies of Ia neurons were absent in embryos lacking NT-3. The failure of Ia neurons to differentiate and/or survive and Ia afferent projections to form in early fetal mice lacking NT-3 suggests that NT-3 may regulate neuronal numbers by mechanisms operating prior to neurite outgrowth to target innervation fields. Thus, developing Ia neurons may be dependent on NT-3 intrinsic to the DRGs before they reach a stage of potential dependence on NT-3 retrogradely derived from skeletal muscles or spinal motor neurons.     

Brachially innervated ectopic hindlimbs in the chick embryo. I. Limb motility and motor system anatomy during the development of embryonic behavior

The functional status of brachially innervated hindlimbs, produced by transplanting hindlimb buds of chick embryos in place of forelimb buds, was quantified by analyzing the number and temporal distribution of spontaneous limb movements. Brachially innervated hindlimbs exhibited normal motility until E10 but thereafter became significantly less active than normal limbs and the limb movements were more randomly distributed. Contrary to the findings with axolotls and frogs, functional interaction between brachial motoneurons and hindlimb muscles cannot be sustained in the chick embryo. Dysfunction is first detectable at E10 and progresses to near total immobility by E20 and is associated with joint ankylosis and muscular atrophy. Although brachially innervated hindlimbs were virtually immobile by the time of hatching (E21), they produced strong movements in response to electrical stimulation of their spinal nerves, suggesting a central rather than peripheral defect in the motor system. The extent of motoneuron death in the brachial spinal cord was not significantly altered by the substitution of the forelimb bud with the hindlimb bud, but the timing of motoneuron loss was appropriate for the lumbar rather than brachial spinal cord, indicating that the rate of motoneuron death was dictated by the limb. Measurements of nuclear area indicated that motoneuron size was normal during the motoneuron death period (E6-E10) but the nuclei of motoneurons innervating grafted hindlimbs subsequently became significantly larger than those of normal brachial motoneurons. Although the muscle mass of the grafted hindlimb at E18 was significantly less than that of the normal hindlimb (and similar to that of a normal forelimb), electronmicroscopic examination of the grafted hindlimbs and brachial spinal cords of E20 embryos revealed normal myofiber and neuromuscular junction ultrastructure and a small increase in the number of axosomatic synapses on cross-sections of motoneurons innervating grafted hindlimbs compared to motoneurons innervating normal forelimbs. The anatomical data indicate that, rather than being associated with degenerative changes, the motor system of the brachial hindlimb of late-stage embryos is intact, but inactive.     

Temperature dependence of metabolic processes in perfused rat liver (author''s transl)

The ruthenium red (RR) stained forelimb musculature of three species of urodeles Triturus (Notophthalmus) viridescens, Amblystoma maculatum, Amblystoma opacum in various stages of growth were examined with the electron microscope for the presence of satellite cells. It was found that RR staining facilitated greatly the identification of satellite cells. In young larvae of all three species satellite cells were detected with a frequency of 29% to 48% per total number of nuclei. In adult Triturus and Amblystoma maculatum satellite cells were no longer detected; instead "pericytes" as described by Hay ('74) were seen with a frequency of 12% and 3% respectively. During metamorphosis of Triturus satellite cells, with part of their myofiber-satellite cell intercellular space filled with basement membrane material, occurred at a peak frequency. The cells presumably are intermediate in the formation of "pericytes." At ten days after metamorphosis satellite cells and intermediate cells were no longer detected and the limb musculature contained only "pericytes" similar to the ones observed in adult newts. The significance of the presence of satellite cells in relation to limb regeneration and muscle regeneration is discussed.     

MyoD and Myf-5 differentially regulate the development of limb versus trunk skeletal muscle

The myogenic progenitors of epaxial (paraspinal and intercostal) and hypaxial (limb and abdominal wall) musculature are believed to originate in dorsal-medial and ventral-lateral domains, respectively, of the developing somite. To investigate the hypothesis that Myf-5 and MyoD have different roles in the development of epaxial and hypaxial musculature, we further characterized myogenesis in Myf-5- and MyoD-deficient embryos by several approaches. We examined expression of a MyoD-lacZ transgene in Myf-5 and MyoD mutant embryos to characterize the temporal-spatial patterns of myogenesis in mutant embryos. In addition, we performed immunohistochemistry on sectioned Myf-5 and MyoD mutant embryos with antibodies reactive with desmin, nestin, myosin heavy chain, sarcomeric actin, Myf-5, MyoD and myogenin. While MyoD(-/-) embryos displayed normal development of paraspinal and intercostal muscles in the body proper, muscle development in limb buds and brachial arches was delayed by about 2.5 days. By contrast, Myf-5(-/-) embryos displayed normal muscle development in limb buds and brachial arches, and markedly delayed development of paraspinal and intercostal muscles. Although MyoD mutant embryos exhibited delayed development of limb musculature, normal migration of Pax-3-expressing cells into the limb buds and normal subsequent induction of Myf-5 in myogenic precursors was observed. These results suggest that Myf-5 expression in the limb is insufficient for the normal progression of myogenic development. Taken together, these observations strongly support the hypothesis that Myf-5 and MyoD play unique roles in the development of epaxial and hypaxial muscle, respectively.     

Transfer of loads between lumbar tissues during the flexion-relaxation phenomenon

STUDY DESIGN AND METHODS: This study used an anatomically detailed model of the lumbar tissues, driven from biologic signals of vertebral displacement and myoelectric signals, to estimate individual muscle and passive tissue force-time histories during the performance of the "flexion-relaxation" maneuver. Eight male university students performed three trials each of the "flexion-relaxation" maneuver with six pairs of surface myoelectric electrodes monitoring the right side of the trunk musculature, an electromagnetic device to record lumbar flexion, and videotape to record body segment displacement. OBJECTIVES: To examine the loads on individual tissues during the transfer of moment support responsibility from predominantly active muscle to predominantly passive tissue. SUMMARY OF BACKGROUND DATA: No previous studies, to the authors' knowledge, have examined individual tissue loading during the flexion-relaxation maneuver. RESULTS: Although most subjects were able to "relax" their lumbar extensors in full flexion, activity remained in the thoracic extensors and abdominals. Tissue load predictions suggested that while the lumbar extensor muscles were neurally "relaxed" (i.e., myoelectric silence), substantial elastic forces would assist the passive tissues in extensor moment support. On average, subjects sustained almost 3 kN in compressive load on the lumbar spine and about 755 N of anterior shear during full flexion with only 8 kg held in the hands. CONCLUSIONS: The "relaxation" of lumbar extensor muscles appeared to occur only in an electrical sense because they generated substantial force elastically through stretching. Loading of the interspinous and supraspinous ligaments, in particular, was high relative to their failure tolerance.     

Biliary complications of liver transplant. Role of cholangiography with magnetic resonance

The association between physical training, low back extensor (erector spinae plus multifidus muscles) and psoas muscle cross-sectional areas (CSA) and strength characteristics of trunk extension and flexion were studied in adolescent girls. A group of athletes (n = 49) (age range 13.7-16.3 years) consisting of gymnasts, figure skaters and ballet dancers was age-matched with non-athletes (n = 17) who acted as a sedentary control group. The CSA of psoas muscles and multifidus plus erector spinae muscles were measured from lumbar axial images by magnetic resonance imaging. Maximal trunk extension and flexion forces were measured in a standing position using a dynamometer and trunk musculature endurance was evaluated using static holding tests. When CSA were adjusted with body mass, the athletes showed significantly greater CSA in both muscles studied (psoas P < 0.001; erector spinae plus multifidus P < 0.05) than the non-athletes. The athletes also had a greater absolute psoas muscle CSA (P < 0.01) and trunk flexion force (P < 0.01) compared to the controls. When the forces were expressed relative to body mass, the athletes were superior both in trunk flexion (P < 0.001) and extension (P < 0.001). There was a significant correlation between muscle CSA and strength parameters, but the force per muscle CSA did not differ significantly between the athletes and the non-athletes. In addition, the athletes showed a better body mass adjusted muscle endurance in trunk flexion (P < 0.05) than the non-athletes. Our study indicated that regular physical training enhances trunk musculature hypertrophy, force and endurance in adolescent girls, and that there is an association between muscle CSA and strength parameters.     

Aerobic workout and bone mass in females

This cross-sectional study aimed to investigate bone mass in females participating in aerobic workout. Twenty-three females (age 24.1 +/- 2.7 years), participating in aerobic workout for about 3 hours/week, were compared with 23 age-, weight- and height-matched non-active females. Areal bone mineral density (BMD) was measured in total body, head, whole dominant humerus, lumbar spine, right femoral neck, Ward's triangle, trochanter femoris, in specific sites in right femur diaphysis, distal femur, proximal tibia and tibial diaphysis, and bone mineral content (BMC) was measured in the whole dominant arm and right leg, using dual energy X-ray absorptiometry. The aerobic workout group had significantly (P < 0.05-0.01) higher BMD in total body (3.7%), lumbar spine (7.8%), femoral neck (11.6%), Ward's triangle (11.7%), trochanter femoris (9.6%), proximal tibia (6.8%) and tibia diaphysis (5.9%) compared to the non-active controls. There were no differences between the groups concerning BMD of the whole dominant humerus, femoral diaphysis, distal femur and BMC and lean mass of the whole dominant arm and right leg. Leaness of the whole dominant arm and leg was correlated to BMC of the whole dominant arm and right leg in both groups. In young females, aerobic workout containing alternating high and low impact movements for the lower body is associated with a higher bone mass in clinically important sites like the lumbar spine and hip, but muscle strengthening exercises like push-ups and soft-glove boxing are not associated with a higher bone mass in the dominant humerus. It appears that there is a skeletal adaptation to the loads of the activity.     

Determination of bone mineral density in the third lumbar vertebral body using photon absorptiometry techniques

Dual-photon absorptiometry and triple-energy X-ray absorptiometry were used to investigate the total bone mineral content and density as well as the trabecular bone mineral density in the third lumbar vertebral body. Both anteroposterior (AP) and lateral (LAT) measurements were performed. By combining the two projections it was found that the mean trabecular bone mineral density for all 202 subjects included in the study was 52% (SD +/- 20%) of the total bone mineral density in the third lumbar vertebral body. The mean trabecular bone mineral density as a fraction of the total vertebral body bone mineral density decreased as a function of age. The relative annual change in this fraction differed between males and females. It was also found that neither trabecular nor total bone mineral density differed significantly between male and female subjects aged 25-35 years, and bone mineral density (BMD), expressed in g/cm3, showed no correlation to subject height, body weight or body mass index (BMI). Male and female individuals showed different rates of change of trabecular bone mineral density with age.     

Thymulin stimulates prolactin and thyrotropin release in an age-related manner

Reduction in the biomechanical competence of the axial skeleton can result in challenging complications. Osteoporosis consists of a heterogeneous group of syndromes in which bone mass per unit volume is reduced in otherwise normal bone, which results in more fragile bone. The geriatric population has an increased risk for debilitating postural changes because of several factors. The two most apparent factors are involutional loss of functional muscle motor units and the greater prevalence of osteoporosis in this population. Obviously, the main objective of rehabilitation is to prevent fractures rather than to treat the complications. These complications can vary from "silent" compression fractures of vertebral bodies, to sacral insufficiency fractures, to "breath-taking" fractures of the spine or femoral neck. The exponential loss of bone at the postmenopausal stage is not accompanied by an incremental loss of muscle strength. The loss of muscle strength follows a more gradual course and is not affected significantly by a sudden hormonal decline, as is the case with bone loss. This muscle loss may contribute to osteoporosis-related skeletal disfigurations. In men and women, the combination of aging and reduction of physical activity can affect musculoskeletal health, and contribute to the development of bone fragility. The parallel decline in muscle mass and bone mass with age is more than a coincidence, and inactivity may explain some of the bone loss previously associated with aging per se. Kyphotic postural change is the most physically disfiguring and psychologically damaging effect of osteoporosis and can contribute to an increment in vertebral fractures and the risk of falling. Axial skeletal fractures, such as fracture of the sacral alae (sacral insufficiency fracture) and pubic rami, may not be found until radiographic changes are detected. Management of chronic pain should include not only improvement of muscle strength and posture but also, at times, reduction of weight bearing on the painful pelvis with insufficiency fractures. Axial skeletal health can be assisted with improvement of muscular supportive strength. Disproportionate weakness in the back extensor musculature relative to body weight or flexor strength considerably increases the risk of compressing porous vertebrae. A proper exercise program, especially osteogenic exercises, can improve musculoskeletal health in osteoporotic patients. Exercise not only improves musculoskeletal health but also can reduce the chronic pain syndrome and decrease depression. Application of a proper back support can decrease kyphotic posturing and can expedite the patient's return to ambulatory activities. Measures that can increase safety during ambulatory activities can reduce risk of falls and fractures. Managing the musculoskeletal challenges of osteoporosis goes hand in hand with managing the psychological aspects of the disease.     

Two cases of the retroaortic left renal vein and a morphogenetic consideration of the anomalous vein

The left renal vein rarely passing behind the abdominal aorta is called "the retroaortic left renal vein". We encountered two cases of the retroaortic left renal vein during the student course of dissection at Iwate Medical University School of Medicine in the years 1986-1997. The incidence of the retroaortic left renal vein was calculated at 2/266 or 0.75%. We observed and recorded the two cases of the retroaortic left renal vein by photographs and line drawings. Then, to consider the morphogenesis of the anomalous vein, we studied 16 cases of the renal collar (the circumaortic renal venous ring) from 149 bodies. Moreover, we observed and recorded the relations between the left renal vein and the lumbar veins in 19 bodies dissected in 1996. Results were compared with those of the reports by some different authors and conclusions were as follows. 1. The incidence of the retroaortic left renal vein is estimated approximately at 0.75%. 2. The retroaortic left renal vein is derived from the renal collar (circumaortic renal venous ring) at an embryonic stage and is completed by the regression and disappearance of the ventral (preaortic) limb and the persistence of the dorsal (postaortic) limb at a later stage. The ventral limb originates from the anastomosis between the subcardinal veins and the dorsal limb originates from the anastomosis between the supracardinal veins (external vertebral venous plexus). The left lumbar veins drain into the inferior vena cava by using the intersupracardinal anastomosis (external vertebral venous plexus). The dorsal limb and the left lumbar veins are considered to use a same venous route passing dorsal to the abdominal aorta. Indeed, in the 16 cases of the renal collar studied, the dorsal limb use the left second lumbar vein in 7 cases, the third lumbar vein in 6 cases, the fourth lumbar vein in 1 case, both the second and the third lumbar veins in 1 case and unknown lumbar vein in 1 case. Moreover, in the two cases of the retroaortic left renal vein the dorsal limb use the third lumbar vein. 3. The retroaortic left renal vein of our cases leaves the renal hilus behind the renal artery (usually in front of the artery) at the level of the intervertebral disc between the second and the third lumbar vertebrae (just one verteral body lower than usual) and flows into the inferior vena cava by using the left third lumbar vein. The reason why ventral (normal) route of the left renal vein disappear may be that the vein leaves the renal hilus at the lower level and the more dorsal position than usual.     

Heterogeneity among muscle precursor cells in adult skeletal muscles with differing regenerative capacities

Skeletal muscle has a remarkable capacity to regenerate after injury, although studies of muscle regeneration have heretofore been limited almost exclusively to limb musculature. Muscle precursor cells in skeletal muscle are responsible for the repair of damaged muscle. Heterogeneity exists in the growth and differentiation properties of muscle precursor cell (myoblast) populations throughout limb development but whether the muscle precursor cells differ among adult skeletal muscles is unknown. Such heterogeneity among myoblasts in the adult may give rise to skeletal muscles with different regenerative capacities. Here we compare the regenerative response of a masticatory muscle, the masseter, to that of limb muscles. After exogenous trauma (freeze or crush injuries), masseter muscle regenerated much less effectively than limb muscle. In limb muscle, normal architecture was restored 12 days after injury, whereas in masseter muscle, minimal regeneration occurred during the same time period. Indeed, at late time points, masseter muscles exhibited increased fibrous connective tissue in the region of damage, evidence of ineffective muscle regeneration. Similarly, in response to endogenous muscle injury due to a muscular dystrophy, widespread evidence of impaired regeneration was present in masseter muscle but not in limb muscle. To explore the cellular basis of these different regenerative capacities, we analyzed the myoblast populations of limb and masseter muscles both in vivo and in vitro. From in vivo analyses, the number of myoblasts in regenerating muscle was less in masseter compared with limb muscle. Assessment of population growth in vitro indicated that masseter myoblasts grow more slowly than limb myoblasts under identical conditions. We conclude that the impaired regeneration in masseter muscles is due to differences in the intrinsic myoblast populations compared to limb muscles.     

Maximal isometric force and muscle cross-sectional area of the forearm in fencers

The maximal isometric force (MIF) of a muscle is directly related to its cross-sectional area (CSA). Strength training produces an increase in muscular force while muscular hypertrophy becomes appreciable at a later time; in asymmetric sports, training causes significant increases in force and muscular mass of the dominant limb of the athlete. The aim of this study was to analyse the differences in muscular force and trophism between the dominant and non-dominant forearms in fencers and in controls. The data of 17 male distance runners (age 21.4 +/- 2.4 years, body mass 74.0 +/- 5.0 kg, height 180 +/- 6 cm) were compared with those of 58 male fencers (age 23.0 +/- 6.7 years, body mass 71.9 +/- 9.3 kg, height 178 +/- 7 cm) drawn from the ranking lists of the National Fencing Committee. They trained for a mean of 11.4 +/- 6.0 (range 2-36) years, commencing at 10.7 +/- 4.5 years of age. Cross-sectional area (muscle plus bone) was estimated in the dominant and non-dominant forearm using a simplified anthropometric method. Maximal isometric force was determined using a mechanical handgrip dynamometer. The differences in CSA and isometric force between the two limbs and between fencers and controls were tested using paired and unpaired Student's t-tests, respectively. Significant differences in CSA and maximal force were observed between the dominant and non-dominant forearm in fencers (both P < 0.001) and in controls (P < 0.005 and P < 0.001, respectively). The fencers showed a greater CSA (P < 0.001) and force (P < 0.001) in the dominant forearm compared with the control group. Furthermore, the differences between the dominant and non-dominant limb of the fencers were significantly greater than the differences between the dominant and non-dominant limb of the controls (P < 0.001 for CSA and P < 0.05 for force). No significant differences in stress ratio (force/CSA) were obtained in either group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between muscle fiber composition and functional capacity of back muscles in healthy subjects and patients with back pain

Back muscles are important to the stability of the lumbar spine. Muscle fiber composition may give some indication of the functional capacity of these muscles. This review explores the relationship between muscle fiber composition and functional capacity of back muscles. The reference values for the type and size of the muscle fibers found in the back musculature of healthy subjects and patients with back pain are also presented. A high percentage of type I fibers, which are larger in size than type II fibers, has been found in back muscles at the thoracic and lumbar levels. This is in accordance with the postural function of these muscles. The diameter of type II fibers is smaller in females than males, which may partly explain the lesser strength and greater endurance capacity of back muscles in females. Due to the limited amount of pertinent data, no conclusive evidence is available regarding age-related changes in muscle fiber composition in the musculature of the back. In patients with lumbar disorders, pathological changes and selective atrophy of type II fibers are seen, and these can be changed with adequate exercises. Further research is suggested to address issues related to gender, age, back pain, and exercise and their effects on the apparent back muscle fiber composition.     

Periosteal migration in the growing mandible: an animal model

Migration of mandibular periosteum and attached musculature was tracked along the inferior border of the ramus in growing and nongrowing guinea pigs (Cavia porcellus) over a 6-week period. Particulate metallic growth-tracing implants were placed through the bony mandible and adjacent musculature at two anteroposterior locations and two bony reference markers were placed anteriorly. Quantification from weekly radiographs of growing animals showed marked posterior migration of the periosteum, whereas in nongrowing animals there was negligible periosteum movement. Significantly greater migration occurred in posterior (6.37 +/- 0.76 mm) implants relative to the anterior implants (3.45 +/- 0.86 mm, p < 0.001). The neutral zone, where little periosteal migration occurs, was calculated to be approximately at the anteroposterior center of the molar tooth row. Analysis of the orientation of the medial pterygoid muscle relative to the mandible showed that muscle fibers on average become more horizontal. Thus, the study found differential anteroposterior migration of the mandibular periosteum in growing animals and correlative changes in orientation of the medial pterygoid muscle.     

Co-contraction of lumbar muscles during the development of time-varying triaxial moments

The recruitment and co-contraction of lumbar muscles were investigated during the voluntary development of slowly and rapidly varying trunk flexion and extension, lateral bending, and axial twisting moments. Myoelectric signals were recorded from 14 lumbar muscles in nine young men during maximum voluntary exertions and cyclic isometric exertions. System identification techniques were used to calibrate dynamic models of the relationship between myoelectric signals and force. To assess co-contraction, the predicted muscle forces were subdivided into a task-moment set of muscle forces that minimally satisfied moment equilibrium and a co-contraction set of muscle forces that produced zero net moment. The sum of co-contraction muscle forces was used to quantify the degree of co-contraction present. Co-contraction was largely dependent on the direction of exertion and relatively less dependent on the subject or the rate of exertion. Co-contractions were estimated to contribute approximately 16-19% to the sum of muscle forces at a lumbar cross section during attempted extension of the trunk. Estimated co-contractions during attempted lateral bending and axial twisting were two to three times greater, which demonstrates that co-contraction is a major determinant of spinal loading in these tasks. This analysis suggests that substantial contractions of lumbar muscles, especially during asymmetric exertions, are used for reasons other than equilibrating moments at the L3-L4 level.     

Can transplantation of neurons facilitate motor recovery in paraplegics? Study of an animal model

This review strives forward at least two goals. First, to take from the literature the arguments demonstrating that hindlimbs locomotion is controlled by a spinal network of neurons (the so-called Central Pattern Generator for locomotion--CPG) known to be able to generate locomotor activity independently of the control of supraspinal nervous structures, as it is after thoracic lesions of the spinal cord. The principles of work of the CPG and its intrinsic possibilities to adapt its working are reviewed. Special reference is made to the various ways used during experiments to activate the CPG in spinal animals or clinical practice in paraplegic men: training to walk, electrical stimulations, pharmacological stimulations. Second, to show, from our own results, obtained from the study of an animal model of paraplegia, the adult spinal rat, how it could be possible to take advantage of the autonomy of the CPG, with special reference to its sensibility to monoamines, to obtain locomotor recovery in hindlimbs after section of the thoracic spinal cord, by means of transplantation of noradrenergic and/or serotonergic embryonic neurons in the lumbo-sacral spinal cord. Section of the spinal cord at a thoracic level results in an important locomotor deficit in hindlimbs, likely linked to degeneration of monoaminergic terminals in the lumbar enlargement. In the adult spinal rat, sub-lesional injection of a suspension of embryonic nervous cells, taken from either locus coeruleus or raphe sites, leads to reinnervation of the lumbar enlargement with monoaminergic terminals. Despite the fact that connections with supraspinal structures are not reestablished, transplanted animals recover progressively a posture convenient for locomotion. The hindlimbs, which are in an extended position a few days after the lesion, become progressively flexed and able to support the body weight. This evolution does not appear in spinal but non transplanted animals. But, the main point is that transplanted animals develop, within the few weeks that follow transplantation, a good-quality locomotor activity in hindlimbs which had no equivalent in spinal but non transplanted animals. The reality of a lumbar CPG for locomotion and the efficacy of pharmacological treatments and training to walk, to elicit recovery of stepping, are discussed in man, in connection with the relevance to use transplantation of monoaminergic nervous cells in the spinal cord of paraplegics.     

Effect of starvation on gene expression of regulatory enzymes of glycolysis/gluconeogenesis in genetically obese (fa/fa) Zucker rats

The use of electromyographic measures, in concert with modeled or empirical representations of muscle physiology, is a common approach for estimation of muscle force. Existing models of the lumbar musculature have allowed model parameters to vary for an individual subject. While this approach improves apparent predictive ability, it loses some degree of construct validity since parameter variability may not be physiologically justifiable. An EMG-based five-parameter model, adapted and generalized from earlier reports, is presented here. Inherent in the model is the requirement of subject-invariant modeling parameters. As a practical analysis tool was desired, the model relies on relatively few calibration constants whose determination is described. Empirical evaluation was undertaken using a database of 398 experimental trials involving lifting and transferring objects of moderate mass. Model performance, evaluated by comparison of measured and predicted lumbar moments, was comparable to earlier models, with r2 mean (S.D.) values of 0.76(0.15) for sagittal plane moments, and rms mean (S.D.) errors of 14.1(7.4), 9.7(5.3), and 8.6(3.6) Nm in the sagittal, frontal, and horizontal planes, respectively. These empirical results and the argument of physiological veracity support the use of a subject-invariant model.     

Randomised controlled study of effect of parathyroid hormone on vertebral-bone mass and fracture incidence among postmenopausal women on oestrogen with osteoporosis

BACKGROUND: Small increases in bone mass are commonly seen with existing treatments for osteoporosis, which reduce bone remodelling and primarily prevent bone loss. Since these drugs reduce but do not eliminate risk of fractures, an anabolic agent that would increase bone mass and potentially cure the underlying skeletal problem is needed. METHODS: We did a 3-year randomised controlled trial to find out the effects of 1-34 human parathyroid hormone (hPTH [1-34], 400 U/25 micrograms daily subcutaneously) in postmenopausal women with osteoporosis taking hormone-replacement therapy (n = 17). The controls were women taking hormone-replacement therapy only (n = 17). The primary outcome was bone-mineral density of the lumbar vertebrae, with bone-mineral density at other sites and vertebral fractures as secondary endpoints. FINDINGS: Patients taking hormone-replacement therapy and PTH (1-34) had continuous increase in vertebral bone-mineral density during the 3 years, whereas there was no significant change in the control group. The total increase in vertebral bone-mineral density was 13.0% (p < 0.001); 2.7% at the hip (p = 0.05); and 8.0% in total-body bone mineral (p = 0.002). No loss of bone mass was found at any skeletal site. Increased bone mass was associated with a reduction in the rate of vertebral fractures, which was significant when fractures were taken as a 15% reduction in vertebral height (p = 0.04). During the first 6 months of treatment, serum osteocalcin concentration, which reflects bone formation, increased by more than 55%, whereas excretion of crosslinked n-telopeptide, which reflects bone resorption, increased by only 20%, which suggests some uncoupling of bone formation and resorption. By 6 months, there were similar increases in both markers, which gradually returned towards baseline as the study progressed. Vertebral bone-mineral density increased most during the first year of PTH treatment. INTERPRETATION: We found that PTH has a pronouned anabolic effect on the central skeleton in patients on hormone-replacement therapy. PTH also increases total-body bone mineral, with no detrimental effects at any skeletal site. The increased vertebral mass was associated with a reduced rate of vertebral fracture, despite increased bone turnover. Bone-mass changes may be consistent with a reduction in all osteoporotic fractures. If confirmed in larger studies, these data have important implications for the treatment of postmenopausal osteoporosis.     

Measurements of vertebral shape by radiographic morphometry: sex differences and relationships with vertebral level and lumbar lordosis

OBJECTIVE: To examine sex-related and vertebral-level-specific differences in vertebral shape and to investigate the relationships between the lumbar lordosis angle and vertebral morphology. DESIGN AND PATIENTS: Lateral thoracic and lumbar spine radiographs were obtained with a standardized protocol in 142 healthy men and 198 healthy women over 50 years old. Anterior (Ha), central (Hc) and posterior (Hp) heights of each vertebra from T4 to L4 were measured using a digitizing technique, and the Ha/Hp and Hc/Hp ratios were calculated. The lumbar lordosis angle was measured on the lateral lumbar spine radiographs. RESULTS: Ha/Hp and Hc/Hp ratios were smaller in men than women by 1.8% and 0.7%, respectively, and these ratios varied with vertebral level. Significant correlations were found between vertebral shape and the lumbar lordosis angle. CONCLUSIONS: These results demonstrate that vertebral shape varies significantly with sex, vertebral level and lumbar lordosis angle. Awareness of these relationships may help prevent misdiagnosis in clinical vertebral morphometry.