Mycobacterium kansasii septic arthritis: French retrospective study of 5 years and review.
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Septic arthritis due to Mycobacterium kansasii is rare; only 40 cases have been published. A French national inquiry revealed the occurrence of 10 new cases between 1992 and 1997 (8 men and 2 women: mean age, 37 years; range, 25-54 years). Seven had an underlying condition: AIDS (n=4), chronic skin psoriasis and AIDS (n=2), or a renal transplant (n=1). Trauma to the joint, use of intra-articular corticosteroid(s) 1 month to 2 years after the event, and chronic skin psoriasis were risk factors. The mean interval between appearance of the first symptoms of arthritis and the diagnosis was 5 months. Monarthritis was localized to the knee (n=4), wrist (n=3), finger (n=1), elbow (n=1), or ankle (n=1). The main diagnostic procedure was culture of a synovial biopsy specimen. In all cases, debridement was associated with antimycobacterial treatment. Three patients died of AIDS during treatment, and another is still undergoing treatment; the other 6 patients were cured. M. kansasii infection should be considered in all cases of indolent arthritis with any of the following risk factors: local trauma, local or systemic corticosteroid therapy, chronic skin psoriasis, and immunodepression, especially that due to human immunodeficiency virus infection. (+info)
Attributes of quiet stance in the chronic spinal cat.
(66/2057)
Standing is a dynamic task that requires antigravity support of the body mass and active regulation of the position of the body center of mass. This study examined the extent to which the chronic spinal cat can maintain postural orientation during stance and adapt to changes in stance distance (fore-hindpaw separation). Intact cats adapt to changes in stance distance by maintaining a constant horizontal orientation of the trunk and changing orientation of the limbs, while keeping intralimb geometry constant and aligning the ground reaction forces closely with the limb axes. Postural adaptation was compared in four cats before and after spinalization at the T(6) level, in terms of the forces exerted by each paw against the support, body geometry (kinematics) and electromyographic (EMG) activity recorded from chronic, indwelling electrodes, as well as the computed net torques in the fore and hindlimbs. Five fore-hindpaw distances spanning the preferred distance were tested before spinalization, with a total range of 20 cm from the shortest to the longest stance. After spinalization, the cats were trained on a daily basis to stand on the force platform, and all four cats were able to support their full body weight. Three of the four cats could adapt to changes in stance distance, but the range was smaller and biased toward the shorter distances. The fourth cat could stand only at one stance distance, which was 8 cm shorter than the preferred distance before spinalization. All cats shifted their center of pressure closer to the forelimbs after spinalization, but the amount of shift could largely be accounted for by the weight loss in the hindquarters. The three cats that could adapt to changes in stance distance used a similar strategy as the intact cat by constraining the trunk and changing orientation of the limb axes in close relation with the forces exerted by each limb. However, different postures in the fore- and hindlimbs were adopted, particularly at the scapula (more extended) and pelvis (tipped more anteriorly). Other changes from control included a redistribution of net extensor torque across the joints of the forelimb and of the hindlimb. We concluded that the general form of body axis orientation is relatively conserved in the spinal cat, suggesting that the lumbosacral spinal circuitry includes rudimentary set points for hindlimb geometry. Both mechanical and neural elements can contribute toward maintaining body geometry through stiffness regulation and spinal reflexes. (+info)
Weight support and balance during perturbed stance in the chronic spinal cat.
(67/2057)
The intact cat maintains balance during unexpected disturbances of stance through automatic postural responses that are stereotyped and rapid. The extent to which the chronic spinal cat can maintain balance during stance is unclear, and there have been no quantitative studies that examined this question directly. This study examined whether the isolated lumbosacral cord of the chronic spinal cat can generate automatic postural responses in the hindlimbs during translation of the support surface. Responses to 16 directions of linear translation in the horizontal plane were quantified before and after spinalization at the T(6) level in terms of forces exerted by each paw against the support, motion of the body segments (kinematics), and electromyographic (EMG) activity. After spinalization, the cats were trained on a daily basis to stand on the force platform, and all four cats were able to support their full body weight. The cats usually required assistance for balance or stability in the horizontal plane, which was provided by an experimenter exerting gentle lateral force at the level of the hips. Three of the four animals could maintain independent stance for a brief period (10 s) after the experimenter stabilized them. The fourth cat maintained weight support but always required assistance with balance. Perturbations were delivered during the periods of independent stance in three cats and during assisted stance in the fourth. A response to translation in the spinal cats was observed only in those muscles that were tonically active to maintain stance and never in the flexors. Moreover, latencies were increased and amplitudes of activation were diminished compared with control. Nevertheless, flexors and extensors were recruited easily during behaviors such as paw shake and stepping. It is concluded that centers above the lumbosacral cord are required for the full elaboration of automatic postural responses. Although the spinal cat can achieve good weight support, it cannot maintain balance during stance except for brief periods and within narrow limits. This limited stability is probably achieved through spinal reflex mechanisms and the stiffness characteristics of the tonically active extensors. (+info)
New vessels, new approaches: angiogenesis as a therapeutic target in musculoskeletal disorders.
(68/2057)
Musculoskeletal disorders such as rheumatoid arthritis (RA) and osteoarthritis are a common cause of pain and disability. The vasculature is an important component of the musculoskeletal system, and vascularization is a key event in the development of normal cartilage and bone. By promoting the delivery of nutrients, oxygen and cells, blood vessels help maintain the structural and functional integrity of joints and soft tissue and may facilitate tissue repair and healing. The identification of pro-angiogenic mediators such as vascular endothelial growth factor (VEGF) has led to the development of antiangiogenic therapies for the treatment of neoplastic diseases. The important role of angiogenesis, and especially VEGF, in the pathogenesis of joint disorders such as RA suggests that antiangiogenic therapy may be a useful adjunct to existing approaches in RA. (+info)
Heterogenous response of knee cartilage to pregnancy in the rabbit: assessment of specific mRNA levels.
(69/2057)
OBJECTIVE: The purpose of this study was to evaluate the effect of pregnancy on mRNA levels for several relevant molecules between five articular cartilage surfaces of the rabbit knee joint. DESIGN: Total RNA was extracted from the following five knee joint articular surfaces: the lateral and medial femoral condyles (LFC and MFC); the lateral and medial tibial plateau (LTP and MTP); and the femoral groove (G) from pregnant and age-matched non-pregnant skeletally immature New Zealand White rabbits. The RNA was analysed by the sensitive molecular technique of semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) using rabbit specific primer sets. Two types of comparisons were performed: (i) comparison of mRNA levels between cartilage surfaces and (ii) comparison of mRNA levels between pregnant and non-pregnant rabbits within the same articular surfaces. RESULTS: (i) Total RNA yield from the MFC and G represented 53 and 58% of the total RNA amount from the five cartilage surfaces in both non-pregnant and pregnant rabbits, respectively. Transcript levels for progesterone receptor (PR), aggrecan and biglycan were similar in all of the cartilage surfaces. In contrast, the cartilage surfaces exhibited significantly different transcript levels with a similar pattern for the estrogen receptor (ER), collagenase and urokinase (i.e., MTP+info)
The arthritogenic T cell receptor and its ligand in a model of spontaneous arthritis.
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OBJECTIVE: Spontaneous arthritis in the KRN transgenic mouse model is due to the autoreactivity of the transgenic T cell receptor (TCR) against Ag7 major histocompatibility complex (MHC) molecules, which leads to strong but incomplete clonal deletion. We sought to determine whether other stimuli triggering this receptor might provoke arthritis, whether the apparently systemic reactivity might have some joint-preferential component explaining the paradoxical arthritic phenotype, and whether the transgenic receptor was the only one required or whether other TCRs might be ferried along in a leaky tolerance process. METHODS: Crosses and radiation chimeras involving a panel of transgenic and knockout mouse lines were used. The reactivity of the KRN TCR was tested in carboxyfluorescein diacetate succinimidyl ester-transfer experiments and in crosses with transgenic or inbred mice expressing other molecules that stimulate the KRN receptor (the mls-1a superantigen, the Aalpha(k69)Abeta(k) mutant MHC molecule). The arthritogenic capacity of T cells expressing only the KRN TCR was tested by crossing to recombination-activating gene-knockout mice, and constructing bone marrow chimeras with precursors to these strictly monoclonal T cells. RESULTS: The data show that the KRN TCR itself is the only receptor needed. It needs to be triggered by the Ag7 molecule loaded with self-peptides in order to provoke arthritis, but there is no indication of preferential presentation of joint-derived peptides. CONCLUSION: Arthritis can be generated by systemic recognition of self-MHC-peptide complexes by autoreactive T cells. This triggers B lymphocytes to produce arthritogenic antibodies, without the involvement of joint-specific T cell targets. (+info)
Interneurones in pathways from group II muscle afferents in the lower-lumbar segments of the feline spinal cord.
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Interneurones receiving excitatory input from group II muscle afferents of hindlimb nerves and located in the lower-lumbar (L6-L7) segments of the cat spinal cord were investigated using both extracellular and intracellular recording. The interneurones were located mainly in the lateral parts of laminae IV-VII, dorsal and lateral to the main region in which interneurones with input from group I muscle afferents are located. Almost half the sample of interneurones (38 of 76) were characterized by an ipsilateral ascending projection within the lateral funiculus to the L4 level. The most powerful group II excitation was produced by afferents of the quadriceps and deep peroneal muscle nerves (which discharged 70-80% of extracellularly recorded neurones) while group II afferents of tibialis posterior, posterior biceps-semitendinosus and gastrocnemius soleus were also highly effective (discharging 45-55% of extracellularly recorded neurones). A proportion of intracellularly recorded group II EPSPs were monosynaptic. Seventy-five per cent of the extracellularly recorded interneurones were discharged by group II afferents of two or more muscle nerves and 43% by afferents of three or more nerves. Group I muscle afferents evoked small EPSPs in over one-quarter of the intracellularly recorded interneurones and virtually all were strongly excited by cutaneous afferents. Evidence of excitatory input from joint, interosseous and group III muscle afferents was also observed. The properties of the interneurones are compared with those of others in the lumbosacral segments and the possibility that they may function as last-order premotor interneurones is discussed. (+info)
Control strategies for the transition from multijoint to single-joint arm movements studied using a simple mechanical constraint.
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Changes were studied in neuromotor control that were evoked by constraining the motion of the elbow joint during planar, supported movements of the dominant arm in eight normal human subjects. Electromyograph (EMG) recordings from shoulder and arm muscles were used to determine whether the normal multijoint muscle activity patterns associated with reaching to a visual target were modified when the movement was reduced to a single-joint task, by pinning the elbow to a particular location in the planar work space. Three blocks of 150 movements each were used in the experiments. Subjects were presented with the unconstrained task in the first and third blocks with an intervening block of constrained trials. Kinematic, dynamic, and EMG measures of performance were compared across blocks. The imposition of the pin constraint caused predictable changes in kinematic performance, in that near-linear motions of the hand became curved. This was followed by changes in limb dynamic performance at the elbow. However, changes in EMG activity at the shoulder lagged the kinematic changes substantially (by about 15 trials). The gradual character of the changes in EMG timing does not support a primary role for segmental reflex action in mediating the transition between multijoint and single-joint control strategies. Furthermore, the scope and magnitude of these changes argues against the notion that human motor performance is driven by the optimization of muscle- or joint-related criteria alone. The findings are best described as reflecting the actions of a feedforward adaptive controller that has properties that are modified progressively according to the environmental state. (+info)