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Biomedical subjects

R Parsons

Publications and source records attributed to R Parsons.

133 records · Page 8Linked to original sources
PubMedDate not supplied

Transjugular intrahepatic portosystemic shunt: correlation of portal vein velocity measurements and portosystemic pressure gradients.

To assess the relationship between portal vein velocity measurements and portosystemic gradients, color Doppler sonography was performed on 12 patients before and after transjugular intrahepatic portosystemic shunt placement. An additional patient was examined before and after shunt modification. The average maximum portal vein velocity increased from 15.7 cm s-1 before shunt placement to 43.5 cm s-1 after shunt placement, while the average portosystemic gradient decreased from 22.0 mm Hg before shunt placement to 7.9 mm Hg after shunt placement. Flow was observed within the shunt in 11 of the 12 cases. Shunt velocity was measurable in nine patients, with an average value of 115.7 cm s-1. Reversal of intrahepatic portal vein flow was observed in 10 cases following shunt placement. Color Doppler sonography is a useful non-invasive tool in the evaluation of intrahepatic portosystemic shunts, and changes in portal vein velocity correlate well with changes in the portosystemic gradient.

Blood Flow Velocity↗
PubMedDate not supplied

Salmonella infections of the abdominal aorta.

Endovascular infection of the atherosclerotic aorta is a substantial risk in patients older than 50 years of age who have bacteremia due to Salmonella. Until recently, the resultant salmonella aortitis was uniformly fatal. Two patients who were cured are described, and the characteristics of 10 other reported long-term survivors are given. This recent improvement in prognosis may have been related to (1) earlier diagnosis, (2) improved surgical management (axillofemoral bypass graft), and/or (3) increased use of bactericidal antibiotics. A change in bacteriology (fewer infections due to Salmonella cholerae-suis) was also seen in the more recent cases.

Aorta, Abdominal↗
PubMedDate not supplied

An investigation of the influence of the extracellular environment on the regeneration of the normal and dystrophic mouse muscle in vitro.

The regenerative response of normal and dystrophic muscle cultured with fetal spinal cord has been investigated. Nearly all the normal muscle explants regenerated, but the dystrophic muscle gave a much more varied response as only 30% regenerated, and 38% showed total explant degradation with loss of all recognisable muscle elements. Forty-five % of the dystrophic explants, produced 'pseudostraps' in which there was an apparent block of myoblast fusion. Cultures in which cellular contact between spinal cord tissue and the normal or dystrophic muscle was prevented showed less regeneration than when it was allowed. However, the incidence of regeneration in these cultures was much higher than when the muscle was cultured in isolation. Direct cellular contact between the cord and the muscle is, therefore, not necessary to initiate regeneration which is presumably mediated in these cultures by changes in the chemical environment. This is substantiated by the almost complete absence of regeneration in cultures of muscle alone, where the fibres were shown to be devoid of nuclei within 5 days. The experiments have shown that under our conditions, a myogenic defect is apparent in the dystrophic muscle. This does not exclude a possible neuronal involvement in the aetiology of the disease, although we have no evidence to support it.

Animals↗
PubMedDate not supplied

An electron microscopic study of satellite-cells and regeneration in dystrophic mouse muscle.

Triceps and gastrocnemius muscles from dystrophic (129 Rej dy/dy) and normal mice were examined by electron microscopy at different stages in development for evidence of regeneration. Mitotic satellite cells were present only in dystrophic muscle. Myoblasts containing myofilaments, and multinucleate myotubes were observed within foci of regeneration. Approximately 50% of the myotubes showed features indicative of degeneration or abnormal development. These features included the presence of membrane whorls, and myofibrillar and sarcolemma breakdown. Quantitative studies suggest that the number of satellite cells is increased in dystrophic muscle. It is concluded that there are sufficient satellite cells in dystrophic mouse muscle to allow regeneration, and they are able to proliferate and form well differentiated myotubes. However, subsequent development of the myotubes can be ineffective, or 'abortive', reducing the regeneration capacity to the muscle.

Aging↗
PubMedDate not supplied

A quantitative assessment of dystrophic mouse (129 ReJ dy/dy) myogenesis in vitro.

A quantitative assessment was made of the myogenic capability in vitro of muscle cells from dystrophic (129 Rej dy/dy) and normal mice from birth to 5 months old. Seeding efficiency was increased in dystrophic cells from neonatal and 1-week-old mice compared to age-matched controls. The extent of myogenesis in cultures from neonatal and 1-week-old dystrophic mice did not differ from controls. Muscle colony formation in cultures established from 5-month-old dystrophic mice was reduced by 80% compared with normal cultures. Normal and dystrophic cultures established from 5-month-old mice contained equal numbers of fibroblast colonies. The results suggest that decreased myogenesis in cultures from 5-month-old dystrophic mice is due to a relative absence of myogenic cells rather than a numerical dilution of the cultures by fibroblasts. This may be due to population of nonviable satellite cells or to necrosis of dystrophic myotubes in vitro.

Aging↗
PubMedDate not supplied

Multiple genotypes of St. Louis encephalitis virus (Flaviviridae: Flavivirus) circulate in Harris County, Texas.

St. Louis encephalitis (SLE) is endemic in Harris County, Texas. The disease is a public health concern in Houston, the largest city in Harris County, and in the state. Consequently, intensive surveillance for SLE virus in local mosquito populations is carried out by the Harris County Mosquito Control Division each year. In this study, we examined genetic variation among SLE isolates obtained during routine virus surveillance over a 13-year time period (1986-1999). St. Louis encephalitis virus isolates were tested for genetic variation using reverse transcription-polymerase chain reaction followed by single-strand conformation polymorphism (SSCP). The results indicated that multiple genotypes of the virus circulate in Harris County. During several years, the genotypes were restricted in their location, i.e., each general area within the county had a specific genotype of the virus. In other years, the various genotypes were widely distributed throughout the county. The presence of multiple distinct genotypes suggests that viruses with different biological characteristics may be circulating in Harris County, and that discrete foci of SLE virus activity occur simultaneously.

Animals↗