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Biomedical subjects

J S Shah

Publications and source records attributed to J S Shah.

At least 37 records · Page 2Linked to original sources
PubMed1986

Characterization of a ribosomal DNA clone of Brugia malayi.

The structure of ribosomal DNA (rDNA) clone pBmr7 from microfilariae of the human parasite Brugia malayi has been examined in detail by Southern blot analysis and S-1 mapping techniques. The results demonstrate that this clone contains regions homologous to 28S, 18S and 5.8S rDNAs. A noncoding or 'spacer' region lies between the 3' end of 28S rDNA and the 5' end of 18S rDNA. An AccI-Sau3AI fragment of approximately 900 bp from this spacer region cross-hybridizes to genomic DNA fragments of different sizes from Brugia pahangi and Dirofilaria immitis. The differences observed in hybridization suggest that this rDNA fragment can be used to differentiate between various filariid species.

Animals↗
PubMed1985

The development of tissue around various prosthetic implants used as replacements for ligaments and tendons.

Currently, no ideal prosthesis is available for the repair or replacement of tendons and ligaments. Although filamentous carbon is a useful fibrogenic material, it does not fulfill the ideal requirements of a soft-tissue prosthesis. A number of other synthetic fibers were examined for biocompatibility and fibrogenic properties in both cell culture and in vivo implantation. It was found that the less extensible materials could adversely affect the normal morphology of the induced collagen. None of the materials examined exhibited mechanical properties similar to those of collagen; therefore, a composite prosthesis was designed to incorporate three criteria: mechanical characteristics similar to those of the normal tissue, fibrogenic capability to induce replacement collagen, and replacement collagen developing with normal morphologic characteristics. A prototype prosthesis for the Achilles tendon in rabbits, evaluated by mechanical and histologic methods, shows that these criteria can be fulfilled and thus form the basis for future prosthetic tendon and ligament research.

Animals↗
PubMed1984

Morphology of human palmaris longus tendon.

A systematic morphological investigation of human palmaris longus tendons by polarisation microscopy and low angle x-ray diffraction is reported. It is shown that contrary to some previously reported observations, and in common with other tension bearing soft collagenous tissues, the fibres in this tendon are crimped. A new method of preparation of the tissue enabling one to see directly the crimped organisation in scanning electron microscopy was used to reinforce the findings by other methods.

Adult↗
PubMed1983

Relationship between multiple copies of a T. brucei variable surface glycoprotein gene whose expression is not controlled by duplication.

Unlike many other T. brucei variable surface glycoprotein (VSG) genes, the IITat 1.3 gene is not duplicated when it is expressed. Analysis of the multiple copies of this gene present in all IITaR 1 trypanosome clones by restriction enzyme mapping and sequencing shows that the expressed copy may have arisen by duplication and transposition to a telomeric site, as is observed for those VSG genes whose expression is linked to duplication. The existence of a mechanism selecting between a number of complete telomeric VSG gene copies for expression is implied by these results. Comparisons of the nontelomeric copies of the IITat 1.3 gene are consistent with involvement of gene duplication and mutational drift in the evolution of new VSG genes.

Animals↗
PubMed1978

The distribution of surface strain in the cadaveric lumbar spine.

The fourth lumbar vertebrae and L4-5 discs from six cadaveric lumbar spines were subjected to detailed strain gauge analysis under conditions of controlled loading. With central compression loads, maximal compressive strain was found to occur near the bases of the pedicles and on both superficial and deep surfaces of the pars interarticularis, which emphasises the importance of the posterior elements of lumbar vertebrae in transmitting load. Radial bulge and tangential strain of the disc wall were maximal at the posterolateral surface, in agreement with the fact that disc degeneration and prolapse commonly occur there. Under posterior offset loads simulating extension, both compressive and tensile strains were found to be increased on both surfaces of the pars interarticularis, which suggests that hyperextension may lead to stress fractures and spondylolisthesis. Posterior offset loads also increased the radial bulge of the posterior disc wall and tangential strain at the anterior surface of the disc. Anterior offset loads simulating flexion increased the radial bulge of the anterior disc wall and tangential strain at the posterior surface of the disc. These findings are compatible with movement of the nucleus pulposus within the disc during flexion and extension. This hypothesis was supported by post-mortem discography.

Adolescent↗
PubMed1977

Low tension studies of collagen fibres from ligaments of the human spine.

On polarization microscopy collagen fibres from human cadaveric anterior longitudinal, posterior longitudinal, and interspinous ligaments show a series of transmission and extinction bands. By observing changes in this pattern on rotating the polarizing stage and on rotating the fibres a crimped structure of the fibres was deduced and its parameters were calculated. From these data the force/strain behaviour of the fibres under low tension was calculated. This corresponded closely with the results from mechanical measurement. At the same time we documented alterations in the transmission and extinction patterns while under tensile load. The results suggest that it is the crimped structure that is responsible for the high extensibility of the collagen fibres under low tension. The initial extension is by deformity of the crimp segment. This avoids risk of tearing the collagen fibres.

Adult↗
PubMed1976

Surface strain distribution in isolated single lumbar vertebrae.

The surface strains of isolated single lumbar vertebrae under compressive load were examined by the techniques of brittlecoat and photoelastic analysis. Directions of principal strain components have been determined. Areas of stress concentration were found around the vertebral rims, near the pedicles, and around the foramina of the basivertebral veins.

Adult↗
PubMed1975

Bone deformation recorded in vivo from strain gauges attached to the human tibial shaft.

A strain gauge rosette was attached to the midshaft of a man's tibia. This demonstrated that during every stride the bone surface was subjected to a number of discrete deformation cycles. During each cycle the bone was deformed from a particular direction, released at least partially and then deformed from another direction. This feature has been observed from a number of sites in experimental animals. The largest deformation occurred while the subject was running; the principal tension then reached 850 microstrain applied in line with the bone's long axis at 13 times 10-3 microstrain per second. When walking the largest deformation occurred prior to 'toe off'; compression was then the larger principal strain about minus 400 microstrain applied at 37 degrees to the bone's long axis at minus 4 times 10-3 microstrain per second. These strain values are the same order of size as those recorded from the long bones of sheep and pigs during their locomotion.

Adult↗