Biomedical subjects

L Ambrose

Publications and source records attributed to L Ambrose.

12 recordsLinked to original sources

PubMed1997

Identification of a chromosomal Shigella flexneri multi-antibiotic resistance locus which shares sequence and organizational similarity with the resistance region of the plasmid NR1.

The ampicillin resistance gene from Shigella flexneri 2a strain YSH6000 was cloned and shown by Southern hybridization analysis to be closely linked to the previously cloned streptomycin, chloramphenicol, and tetracycline resistance determinants, which are borne on a chromosomally integrated 99-kb element. Analysis of this chromosomal multi-antibiotic resistance locus revealed that it had a high level of sequence and organizational similarity to an equivalent region of the Shigella R-plasmid, NR1. However, the chromosomal locus exhibited several differences, including the presence of two stretches of sequence derived from IS elements, the precise insertion of a beta-lactamase encoding oxal cassette into the Tn21-borne integron In2, a possible 17.5-kb deletion, and the loss or inactivation of the mercury resistance determinant. Based on these data, it is proposed that the chromosomal locus arose following integration of an NR1-like plasmid.

Ampicillin↗

PubMed1992

The effects of scaphoid intercarpal stabilizations on wrist mechanics: an experimental study.

A fresh cadaver study of the effects of a variety of scaphoid stabilizations on wrist motions is reported. Scaphoid-trapezium-trapezoid stabilizations with the scaphoid in its normal anatomic position and the same stabilizations with the scaphoid in malposition, either vertical or horizontal in relation to the radius, were compared. Scaphoid-capitate stabilizations with the scaphoid in its normal position were also studied. With the scaphoid vertical, a scaphoid-trapezium-trapezoid stabilization resulted in greater loss of wrist flexion and ulnar deviation whereas, with the scaphoid horizontal, wrist extension and radial deviation were more severely affected than when the scaphoid was stabilized in its normal position. With the scaphoid in its anatomic position, both scaphoid-trapezium-trapezoid and scaphoid-capitate stabilizations resulted in similar patterns of wrist motion.

Bone Nails↗

PubMed1992

Lunate-triquetral and midcarpal joint instability.

Instability of the ulnar side of carpus centers around the triquetrum, which is suspended by the ulnar triquetral ligaments and supported proximally by the TFCC. The triquetrum guides the lunate by an interosseous membrane and stout palmar ligaments that provide a relatively rigid connection between the two bones. Disruption of the LT ligament is frequently associated with pathology in the ulnar carpal area and may progress to triquetral instability, VISI, and finally, degenerative arthritic changes on the ulnar side of the carpus. The diagnosis of LT injuries is made by stress radiographs, arthrography, video-fluoroscopy, and arthroscopy. Treatment is initially nonoperative, but if symptoms persist, surgery is warranted. Arthroscopic debridement and pinning the LT joint, ligament repair or reconstruction, and intercarpal arthrodesis have all been reported as successful treatments. For the chronic problem confined to the LT joint, a limited intercarpal arthrodesis of the joint is the most predictable procedure for relieving pain without causing any significant restrictions in wrist motions. When there is a dissociation pattern in addition to LT instability, a more extensive intercarpal arthrodesis is required. Midcarpal instability occurs at the triquetral-hamate joint and is characterized by a dynamic subluxation of the joint. During ulnar deviation, the joint undergoes an exaggerated shift from volar flexion to dorsiflexion. Supportive care is generally successful; although in chronic cases, a midcarpal joint arthrodesis is often required.

Arthrodesis↗

PubMed1991

Malunited Colles' fractures: correction with a biplanar closing wedge osteotomy.

A malunited Colles' fracture causes distortion of three anatomic features of the distal radius: length of the bone and the angles of its articular surface in both frontal and sagittal planes. The relative importance of each of these factors was studied in a series of 14 patients with malunited Colles' fractures and severe disabilities. Reversal of the normal palmar tilt of the distal radius in the sagittal plane was the most consistent and serious deformity of the bone, and in five patients it was associated with dorsal subluxation of the entire carpus. Correction of the malunion was achieved with a biplanar closing wedge osteotomy without a bone graft. Resection of the ulna head and decompression of the median nerve within the carpal tunnel were done to reduce the likelihood that additional surgery would be required in the future.

Adolescent↗

PubMed1991

Excision of the distal ulna in rheumatoid arthritis.

Resection of the ulna is an effective operation in the treatment of rheumatoid disorders of the distal radioulnar joint. Tenosynovectomies of the overlying extensor tendons and synovectomy of the joint are integral parts of the procedure. Following resection, the ulna usually remains in alignment with the radius, although some dorsal displacement is common. Restoring stability to the ulna as well as reconstructing a new sheath for the extensor carpi ulnaris can be accomplished in most cases by using the extensor retinaculum. In those cases where the retinaculum has been destroyed by the disease process or when the distal ulna is severely displaced, stability can be restored using the extensor carpi ulnaris for a tenodesis.

Arthritis, Rheumatoid↗

PubMed1989

Boxer's knuckle--dorsal capsular rupture of the metacarpophalangeal joint of a finger.

An injury to the dorsal aspect of the metacarpophalangeal joint of a finger usually damages the sagittal fibers of the extensor tendon mechanism. Rupture of the underlying joint capsule, a far more serious injury, has received scant attention in the medical literature. The problem is often unrecognized because the extensor tendon may remain in its normal midline position. Eight dorsal capsular ruptures are described in six patients who had closed direct trauma to either the knuckle of their index or long fingers. Most of the injuries occurred in professional boxers.

Adult↗

PubMed1988

Intrinsic muscle advancement to treat chronic palmar instability of the metacarpophalangeal joint of the thumb.

Chronic palmar instability of the metacarpophalangeal joint of the thumb can result in a significant disability. Grasp, particularly pinch, is painful and weak because the thumb goes into hyperextension. Stabilization of the metacarpophalangeal joint can be achieved by distal advancement of the conjoined tendon of the abductor pollicis brevis and lateral fibers of the flexor pollicis brevis.

Adolescent↗

PubMed1978