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Biomedical subjects

P Summers

Publications and source records attributed to P Summers.

21 records · Page 2Linked to original sources

Early and late results of balloon valvuloplasty for severe aortic stenosis.

Balloon aortic valvuloplasty has been used as treatment for selected patients with severe aortic stenosis. We report our experience of 11 procedures, performed on ten patients between October 1987 and June 1988. The peak aortic systolic gradient was reduced by 53% from 77 +/- 22 to 37 +/- 14 mmHg (p less than 0.0001) whilst cardiac output did not change significantly (4.1 +/- 1.7 to 3.8 +/- 1.6 (p less than 0.0001) whilst cardiac output did not change significantly (4.1 +/- 1.7 to 3.8 +/- 1.6 L/min). Aortic valve area was increased by 50%, from 0.4 +/- 0.2 to 0.6 +/- 0.2 cm2 (p less than 0.0001). Initial symptomatic improvement was achieved in eight patients. Echocardiographically demonstrated aortic regurgitation did not increase after valvuloplasty. There were no deaths during the procedure, no embolic events and no femoral artery complications. The mean follow-up for survivors was 9 +/- 3 months. Five patients died and three had symptom recurrence at an average of 13 weeks (six-24 weeks). Only two patients reported a continued improvement in symptoms. Balloon aortic valvuloplasty produced a small increase in aortic valve area and a satisfactory initial clinical response, but there was a high incidence of symptom recurrence. The procedure may have a role in the short-term palliation of severely symptomatic patients who are unable to have aortic valve replacement.

Acute Disease↗

Expression of dengue virus structural proteins and nonstructural protein NS1 by a recombinant vaccinia virus.

A recombinant vaccinia virus containing cloned DNA sequences coding for the three structural proteins and nonstructural proteins NS1 and NS2a of dengue type 4 virus was constructed. Infection of CV-1 cells with this recombinant virus produced dengue virus structural proteins as well as the nonstructural protein NS1. These proteins were precipitated by specific antisera and exhibited the same molecular size and glycosylation patterns as authentic dengue virus proteins. Infection of cotton rats with the recombinant virus induced NS1 antibodies in 1 of 11 animals. However, an immune response to the PreM and E glycoproteins was not detected. A reduced level of gene expression was probably the reason for the limited serologic response to these dengue virus antigens.

Animals↗

Stretch-induced growth in chicken wing muscles: nerve-muscle interaction in muscular dystrophy.

Skeletal muscle growth following denervation and denervation plus passive stretch was characterized in the patagialis muscle of normal and dystrophic chicks until 8 wk of age. In both genotypes, muscles denervated at 1 wk of age grew at reduced rates compared with contralateral control muscles whether or not they were passively stretched. Histograms of fiber size distributions as well as morphological criteria showed that passive stretch of denervated dystropic muscles substantially delayed the development of pathology. Denervation alone provided less protection. There was no evidence of fiber necrosis in any denervated dystrophic muscle, although many fibers did exhibit extreme hypertrophy and abnormal morphology. When denervated dystrophic muscles were allowed to reinnervate, growth and development of pathology was rapid. Because denervation, denervation with passive stretch, or passive stretch alone retards, but does not prevent, the development of pathology, it is concluded that dystrophy in the chick is a myogenic defect that is exacerbated by neurally mediated contractile activity.

Animals↗