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Biomedical subjects

J Sorrell

Publications and source records attributed to J Sorrell.

13 recordsLinked to original sources
PubMed2001

A general method for estimating deformation and forces imposed in vivo on bioprosthetic heart valves with flexible annuli: in vitro and animal validation studies.

BACKGROUND AND AIM OF THE STUDY: The use of flexible structures within cardiovascular prostheses such as valves, stents and vascular grafts has been proposed as a means of more closely modeling native mechanics, and thereby reducing the biomechanical problems associated with rigid materials. However, the design of such materials has been hampered by the paucity of quantitative information on the in-vivo behavior of such structures. The aim of this study was to explore the use of 3D ultrasound imaging coupled with finite element analysis (FEA) as a tool to estimate deformation and forces imposed in vivo on a novel bioprosthetic valve design. METHODS: The method was first tested using in-vitro static loading conditions, where good agreement between displacements seen on video and those obtained from application of the identical force within the finite element program was seen. The method was then tested in a porcine model with valves implanted in the mitral position. Images of the deforming annular ring were obtained over the cardiac cycle using 3D intravascular ultrasound; these images were fed into the FEA program for calculation of reaction forces. RESULTS: Results in vitro showed that a force of 2.7-8.0 Newtons (N) was required to produce a deformation of between 1.0 and 3.0 mm in the radial direction. A time history of deformation and force around the ring of the valve stent could be obtained for the in-vivo conditions. These results revealed a maximum deformation of 0.5-1.7 mm along the short axis (anteroposterior) of the mitral valve. Coupled to this, a peak reaction force of 4.4-13.9 N was found at the points corresponding to maximal deflection. Both deformation and reaction force reached maximum during atrial contraction. CONCLUSION: This method provides an accurate means of estimating deformation and corresponding forces imposed in vivo on intracardiac prostheses. The results provide information on the dynamic behavior of the mitral valve annulus. Such information should be useful in the design of flexible cardiovascular prostheses.

Animals↗
PubMed2000

Effect of interleukin-1 gene polymorphisms on gingival inflammation assessed by bleeding on probing in a periodontal maintenance population.

Bleeding on probing (BOP) is the most significant clinical parameter for the assessment of periodontal inflammation. The aim of this prospective longitudinal trial was to study the association between allelic variants of the IL-1 gene complex and gingival inflammation. Three hundred and twenty-three randomly selected periodontal maintenance patients (64.4% females) received a periodontal examination that included probing depth measurements and BOP at each of 4 supportive periodontal therapy (SPT) appointments. A blood sample taken from each subject was analysed for the presence of specific allotypes of the IL-1 gene complex. Two polymorphisms located at +4845 bp in the IL-1 alpha region and at +3954 bp in the IL-1 beta region were evaluated by a polymerase chain reaction method; 35.3% of the examined subjects were positive for specific combinations of allotypes of the IL-1 gene complex previously associated with an increased risk for severe periodontitis. The population consisted of 90 current smokers and 94 former smokers. An analysis of the association between the IL-1 genotype and BOP in the whole population (including smokers) did not reach statistical significance because of the overriding effect of smoking. A subset analysis of the 139 never smokers indicated that genotype positive patients had a significantly elevated chance of presenting an increase in the BOP% over a 4-appointment recall period (p = 0.03) after correcting for oral hygiene. In fact, patients who were genotype-negative had a 50% smaller chance of showing increases in BOP% during SPT. A further analysis explored the relationship between the genotype and the level of BOP% at the most recent recall visit. A generalized linear model showed a statistically significant effect of the genotype status after correcting for plaque accumulation and prevalence of residual pockets (> or = 5 mm). Genotype-negative subjects had significantly lower BOP% (p = 0.0097). It is concluded that the increased BOP prevalence and incidence observed in IL-1 genotype-positive subjects indicates that some individuals have a genetically determined hyper-inflammatory response that is expressed in the clinical response of the periodontal tissues.

Adult↗
PubMed2000

Low prevalence of a periodontitis-associated interleukin-1 composite genotype in individuals of Chinese heritage.

BACKGROUND: Polymorphisms in the interleukin-1 (IL-1) gene cluster have been associated with an increased risk of developing certain diseases. A specific composite genotype of IL-1A and IL-1B polymorphisms, consisting of allele 2 of both IL-1A +4845 and IL-1B +3954 (formerly +3953) has been associated with an increased risk of severe adult periodontitis. Approximately 30% of the European population carry this genotype. The prevalence of the above IL-1A and IL-1B composite genotype in populations of different ethnic origins is unknown. Therefore, the primary aim of this study was to determine the prevalence of the IL-1 composite genotype in individuals of Chinese heritage, since epidemiologic studies indicate that periodontitis is widespread among ethnic Chinese. An additional aim was to evaluate if there was an association between the composite genotype and the severity of periodontal disease. METHODS: A convenience sample of 300 volunteers of Chinese heritage (ages 21 to 69 years) received a periodontal examination including full-mouth clinical attachment loss measurements, probing depths, plaque index scores, and bleeding on probing. Blood was collected from a fingerstick and placed on a blotting paper card. The blood samples were analyzed for IL-1A +4845 and IL-1B +3954 polymorphisms using polymerase chain reaction (PCR)-based methods. RESULTS: Only 7 of the 300 subjects (2.3%) carried the composite IL- 1 genotype consisting of allele 2 of both IL-1A +4845 and IL-1B +3954. Allele 2 of the IL-1A +4845 polymorphism was carried by 17.0% (51/300) of the subjects; of these, only 2 were homozygous. Allele 2 of the IL-1B +3954 polymorphism was much rarer with only 3.3% (10/300) of the study population carrying this marker. All of the people who carried the IL-1B polymorphism were heterozygous. Too few of the subjects were positive for the IL-1 composite genotype to establish any relationship with the susceptibility to periodontitis. CONCLUSIONS: It was concluded that the prevalences of both IL-1A and IL-1B polymorphisms are dramatically lower in Chinese than those reported for Europeans. Findings from this study bring into question the usefulness of the composite genotype of allele 2 of both IL-1A +4845 and IL-1B +3954 as a method for determining the susceptibility of Chinese patients to adult periodontitis.

Adult↗
PubMed1993

Strategies for teaching nursing research. Collaborative clinical research.

Formative evaluation of the CCRM model suggests that it is effective for students in fostering greater knowledge and skills in nursing research and an appreciation for the value of research in advanced nursing practice. The model has also generated enthusiasm in faculty and clinicians, as they work collaboratively with students to bridge the gap between theoretical and clinical aspects of nursing research.

Clinical Nursing Research↗
PubMed1986

The ethical dilemmas of a rural physician.

Physicians in rural settings confront many of the same ethical dilemmas as their urban counterparts: confidentiality, quality-of-life decisions, resource allocation, and their moral responsibility for bettering the life of the community. However, the courses of action they choose as morally justifiable are influenced by distance from other professional facilities, the interrelationship of private and professional roles in a small community, and the non-specialized orientation of their practices.

Confidentiality↗
PubMed1978

Is aplastic anaemia due to abnormality of D.N.A.?

Lymphocytes from eleven patients with aplastic anaemia were cultured with various agents which interact with D.N.A., and the proliferative responses to phytohaemagglutinin were measured. Lymphocytes from seven of the eleven patients were unduly sensitive to bleomycin, an agent causing strand breaks in D.N.A. The findings suggest that D.N.A. in these seven patients was abnormal, possibly as a result of an abnormality of D.N.A. repair. It is suggested that in aplastic anaemia D.N.A. damage in stem cells may lead to a failure of proliferation.

Adolescent↗