Force depression following muscle shortening of voluntarily activated and electrically stimulated human adductor pollicis. (65/402)

The purpose of this study was to investigate steady-state force depression following active muscle shortening in human adductor pollicis during voluntary and electrically induced contractions. Subjects (n = 12; age 28 +/- 5 years; 7 males and 5 females) performed isometric reference contractions and isometric-shortening-isometric contractions, using maximal voluntary effort and near-maximal electrical stimulation. Force depression was assessed by comparing the steady-state isometric forces produced following active muscle shortening with the purely isometric reference forces obtained at the corresponding muscle length. In order to test for effects of the shortening conditions on the steady-state force depression, the amplitude and speed of shortening were changed systematically in a random order but balanced design. Thumb adduction force and carpometacarpal joint angle were continuously measured using a custom-designed dynamometer. During voluntary contractions, muscle activation was recorded using electromyography and the superimposed twitch technique. During electrically induced contractions, muscle stiffness was assessed using a quick-stretch method. Force depression during voluntary contractions, with a constant level of muscle activation, was similar to that obtained during electrically induced contractions. Force depression increased with increasing amplitudes of shortening (9.9 +/- 1.6%, 15.6 +/- 2.4% and 22.4 +/- 2.4% for 10, 20 and 30 deg of shortening, respectively) and decreased with increasing speeds of shortening (27.1 +/- 2.5%, 19.3 +/- 1.6% and 15.6 +/- 1.8% for 20, 60 and 300 deg s(-1) of shortening, respectively), regardless of the activation method. Muscle stiffness was significantly lower in the force-depressed state (5.9 +/- 0.2 N deg(-1)) compared with that of the isometric reference contractions (7.2 +/- 0.3 N deg(-1)), and decreased with increasing force depression (6.6 +/- 0.5, 6.0 +/- 0.5 and 5.3 +/- 0.4 N deg(-1) for the 10, 20 and 30 deg of shortening test contractions, respectively). Force depression appeared to be fully established at the end of the shortening phase. The results of this study suggest that steady-state force depression for voluntary movements is similar to that observed using electrical stimulation. Furthermore, it appears that force depression is established at the end of the shortening phase and is associated with a reduction in muscle stiffness and thus, presumably, a decrease in the proportion of attached cross-bridges.  (+info)

Mutations at the SALL4 locus on chromosome 20 result in a range of clinically overlapping phenotypes, including Okihiro syndrome, Holt-Oram syndrome, acro-renal-ocular syndrome, and patients previously reported to represent thalidomide embryopathy. (66/402)

We have recently shown that Okihiro syndrome results from mutation in the putative zinc finger transcription factor gene SALL4 on chromosome 20q13.13-13.2. There is considerable overlap of clinical features of Okihiro syndrome with other conditions, most notably Holt-Oram syndrome, a condition in part resulting from mutation of the TBX5 locus, as well as acro-renal-ocular syndrome. We analysed further families/patients with the clinical diagnosis of Holt-Oram syndrome and acro-renal-ocular syndrome for SALL4 mutations. We identified a novel SALL4 mutation in one family where the father was originally thought to have thalidomide embryopathy and had a daughter with a similar phenotype. We also found two novel mutations in two German families originally diagnosed as Holt-Oram syndrome and a further mutation in one out of two families carrying the diagnosis acro-renal-ocular syndrome. Our results show that some cases of "thalidomide embryopathy" might be the result of SALL4 mutations, resulting in an increased risk for similarly affected offspring. Furthermore we confirm the overlap of acro-renal-ocular syndrome with Okihiro syndrome at the molecular level and expand the phenotype of SALL4 mutations.  (+info)

Significance of the innervation pattern of the human abductor pollicis longus muscle. (67/402)

The abductor pollicis longus muscle (APL) can be separated into 2 divisions, deep and superficial. The deep division has more bellies, each of which has its own site of insertion. The superficial division is situated on top of the deep tendon. Each division is innervated by a separate branch of the radial nerve. This pattern of innervation may indicate independent actions by individual muscle parts. The deep division, inserting around the carpometacarpal joint of the thumb, has a nerve supply that reaches each separate muscle belly. This division should have a stabilising action on the joint. The superficial division, together with the extensor pollicis brevis, is innervated from the ulnar side by a terminal branch of the radial nerve. This division should, in cooperation with the extensor pollicis brevis and longus muscles and the thenar muscles, act to move the thumb in various directions.  (+info)

Anatomical study of preaxial polydactyly in 158 hands. (68/402)

Preaxial polydactyly is a common congenital hand anomaly. Here in 138 patients with 158 duplicated thumbs, a new classification of this anomaly was done from analysis of radiographs and operation records. Initially all the duplicated thumbs were arranged into from Type I to VII on the basis of radiological extent of bifurcation. Appendage type was noted as a separate entity. Type IV was found the most common and had 53 thumbs (33.6%) involved. But findings on surgery indicated that the exact level of bifurcation varied in each type, and Type VII became three times as frequent as previously noted from x-ray examination at the time of surgery. Radiologically encountered duplications at IP (Type II), MP (Type IV) and CM (Type VI) joints were specifically classified into five groups from A to E on the basis of the structural changes detected on surgery. Details in each group were discussed.  (+info)

Detection of cytomegalovirus antigens in phagocytosed serum complexes from a patient with rheumatoid arthritis, vasculitis, peripheral neuropathy, cutaneous ulceration, and digital gangrene. (69/402)

A patient with rheumatoid arthritis, vasculitis, peripheral neuropathy, cutaneous ulceration, and digital gangrene was studied. Circulating immune complexes were detected by C1q binding although serum complement levels were within the normal range. Immunofluorescent staining of buffy coat cells with specific antisera showed the presence of IgG and IgM in phagocytosed inclusions but complement C3 was not detected. A monoclonal antibody specific for cytomegalovirus detected antigens in phagocytosed inclusions on one occasion. These results may suggest that cytomegalovirus antigens are a hitherto unidentified component of serum complexes in patients with rheumatoid arthritis and may contribute to the pathogenesis of the vasculitic complications of rheumatoid arthritis by participating in immune complex formation.  (+info)

Servo action in the human thumb. (70/402)

1. The servo-like properties of muscle in healthy human subjects have been studied by interfering unexpectedly with flexion movements of the top joint of the thumb. This movement is carried out by the flexor pollicis longus muscle only. 2. The movements were standardized in rate by giving the subject a tracking task. They started off against a constant torque load offered by an electric motor. 3. In some movements the load remained constant, but in others, in mid-course, perturbations were introduced at random. Either the movement was halted, or released and allowed to accelerate by reducing the load, or reversed by suddenly increasing the current in the motor, so stretching the muscle. 4. Usually eight or sixteen responses to each kind of perturbation and a similar number of controls against a constant load were averaged. 5. Muscle activity was recorded as the electromyogram from surface electrodes over the belly of the long flexor in the lower forearm. Action potentials were usually full-wave rectified and integrated. 6. About 50 msec after a perturbation the muscle's activity alters in such a sense as to tend to compensate for the perturbation, i.e. it increases after a halt or a stretch and decreases after a release. The latency is similar in each case. 7. These responses are interpreted as manifestations of automatic servo action based on the stretch reflex. They are considered to be too early to be voluntary. 8. This interpretation was supported by measuring voluntary reaction times to perturbations under tracking conditions. They were found to be 90 msec or longer. 9. When the initial load was increased by a factor of 10, the servo responses were all scaled up likewise. Thus to a first approximation the gain of the servo is proportional to initial load. 10. It follows that in relaxed muscle the gain should be zero. This was confirmed by showing that stretching a relaxed muscle gives no reflex, or only a small one. 11. Gain appears to be determined by the level of muscle activation as determined by the effort made by the subject, rather than by the actual pressure exerted by the thumb. 12. Thus in fatigued muscle gain is boosted as the muscle has to be activated more strongly to keep up the same force output. The net effect is to compensate for fatigue and maintain the performance of the servo. 13. The Discussion centres on the implications of gain control in the servo. For a start, if the gain of the stretch reflex arc is zero in relaxed muscle, contractions cannot be initiated via the stretch reflex by simply causing the spindles to contract, as proposed on the original 'follow-up' servo theory.  (+info)

DE QUERVAIN'S DISEASE: STENOSING TENOVAGINITIS AT THE RADIAL STYLOID PROCESS. (71/402)

Twelve cases of stenosing tenovaginitis at the radial styloid process (de Quervain's disease), including two bilateral cases, are reviewed. These patients presented the typical symptoms of pain just proximal to the radial styloid process accompanied by limitation of abduction of the thumb. Many previous reports have emphasized the frequency of aberrant tendons in this region and have implied that such anomalies may play a part in the etiology of this disorder. In our cases aberrant tendons were not found. Pronounced thickening of the tendon sheaths was present at operation and accumulations of fluid resembling ganglion formation were frequently noticed. All forms of therapy except surgical excision of the involved tendon sheaths were largely ineffective. This surgical procedure was so simple and satisfactory that it is recommended as the treatment of choice. The diagnosis of de Quervain's disease is easily missed unless the examining physician constantly keeps it in mind.  (+info)

Paronychia due to Prevotella bivia that resulted in amputation: fast and correct bacteriological diagnosis is crucial. (72/402)

Prevotella bivia is mainly associated with endometritis. The case of a patient with paronychia in a thumb due to P. bivia resulting in osteitis and amputation is reported. The species was not acknowledged in the first bacterial culture 2 weeks before surgery.  (+info)