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Biomedical subjects

K Buchan

Publications and source records attributed to K Buchan.

13 recordsLinked to original sources
PubMed2006

Determination of the pressure required to cause mitral valve failure.

A method has been developed for applying water pressure to a closed mitral valve on the side corresponding to the heart's left ventricle. The pressure is increased until fluid flows through the valve, i.e. until it fails. A specific dissection technique has been developed to produce a specimen with two annular rings, mitral annulus and papillary muscle annulus. Since the valve is maintained intact, with its leaflets attached to papillary muscles by the chordae tendineae, this method allows the effects of ruptured chordae and their surgical repair or replacement to be assessed in vitro. The chamber that holds the valve supports both the mitral annulus and papillary muscle annulus of the specimen. The mitral annulus is sutured onto rubber sheeting held in the chamber. The papillary muscle annulus is held in place by a Perspex support. The main part of the apparatus consists of a water pump connected through flexible tubing to the chamber that holds the valve in place. The pressure at failure is measured using a pressure transducer. Preliminary experiments demonstrate that anterior leaflet marginal chordae, but not strut chordae, are vital to valve function. Posterior leaflet chordae have been found to be important for valve competence.

Aortic Valve↗
PubMed2001

Twenty years' experience with the Medtronic Hall valve.

OBJECTIVE: To assess the performance of the Medtronic Hall valve (Medtronic, Inc, Minneapolis, Minn) in one institution over a 20-year period. METHODS: Since 1979, Medtronic Hall valves have been used in 1766 procedures (736 aortic, 796 mitral, and 234 double). Patients were followed up prospectively at 6- to 12-month intervals for a total of 12,688 follow-up years. Anticoagulation data (international normalized ratio) were recorded for all patients (approximately 95,000 observations). RESULTS: Linearized rates of valve-related late death for aortic, mitral, and double valve replacement were 0.8%/y, 0.9%/y, and 1.1%/y, respectively. Risk factors for late mortality were (relative risk) diabetes (1.9), decade of age (1.6), concomitant coronary artery bypass grafting (1.4), hypertension (1.3), non-sinus rhythm (1.3), large valve size (1.1), valve regurgitation (1.3), and male sex (1.2). For aortic, mitral, and double valve replacement, linearized rates (percent per year) of adverse events were valve thrombosis 0.04, 0.03, and 0.0; all thromboembolism 2.3, 4.0, and 3.4; stroke 0.6, 0.8, and 0.6; major hemorrhage 1.2, 1.4, and 1.6; and prosthetic endocarditis 0.4, 0.4, and 0.7. Risk factors for thromboembolism were (relative risk) mitral valve replacement (1.9), diabetes (1.8), hypertension (1.5), and history of embolism (1.4). CONCLUSION: At 20 years the Medtronic Hall valve demonstrates excellent durability, good hemodynamic performance, and very low thrombogenicity, with a valve thrombosis rate lower than those reported for bileaflet designs. With this prosthesis, both survival and thromboembolic events are predominantly determined by patient risk factors.

Adult↗
PubMed1999

Thoracic organ transplantation at Papworth Hospital.

More than 1,200 patients have now undergone thoracic transplantation at Papworth Hospital and about 90 transplants are performed annually. Papworth remains one of the largest transplant units in the UK. Unique activities include a very large heart-lung transplant program: 247 patients have now undergone heart-lung transplants and 73 domino heart transplants have been performed. The 5-year survival rates are 71% for heart transplants, 48% for heart-lung and 41% for lung transplants, respectively. Chronic obliterative bronchiolitis remains an important limitation for heart-lung and lung transplant survival.

Adolescent↗
PubMed1997

pPV: a novel IRES-containing vector to facilitate plasmid immunization and antibody response characterization.

BACKGROUND: The ability to derive immunological reagents for basic and applied research in a timely fashion is a basic requirement of many research projects and is becoming increasingly important as the number of novel gene products of potential interest continues to evolve rapidly. DNA immunization provides a means of facilitating the production of antibody reagents by circumventing the need to derive either purified protein or define peptides before initiating an in vivo immunization protocol. OBJECTIVES: The DNA construct pPV, for plasmid vaccination, has been designed to facilitate the generation and characterization of antibody reagents against either random or defined molecular targets. STUDY DESIGN: pPV incorporates mammalian regulatory and structural features that promote expression of a bifunctional messenger RNA (mRNA) from a single promoter within mammalian cells both in vitro and in vivo. The bifunctional mRNA encodes a control epitope (human IL5), and the 'test' epitope expressed as a tagged recombinant polypeptide in either a random 'shot-gun' mode or a predetermined fashion. In addition, to aid subsequent characterization of antibody responses elicited in vivo, a T7 promoter is included to enable in vitro expression of tagged recombinant polypeptides. RESULTS: The utility and functionality of pPV for the in vitro expression of recombinant protein and the in vivo elicitation of antibody responses is illustrated using a defined 'test' epitope, human proIL1 beta. CONCLUSION: It is anticipated pPV will find particular utility in the future rapid generation and characterization of antibody reagents against the plethora of novel genes emerging from ongoing genomics activity in a directed or genome wide fashion.

Amino Acid Sequence↗
PubMed1995

Surgical management of penetrating mediastinal arterial trauma.

Fifty-two patients with penetrating injury to the arteries caudal to the thoracic inlet and cephalad to the heart came under the care of the Durban Metropolitan Vascular Service, South Africa, over a 13-year period. The innominate artery was the commonest vessel injured (n = 23). Five patients (11%) had multiple vessel injuries, four of which involved the aortic arch, and 18 (34%) had arteriovenous fistulae. Mortality was greatest with injuries involving the aortic arch (n = 17) and ascending aorta (n = 4) in which intra-operative exsanguination was the leading cause of death (five patients). Injuries involving the inferior and posterior walls of the aortic arch and those located between the innominate and left common carotid origins were the most difficult to control. Seven patients with aortic injuries presented with cardiac tamponade, three of whom had associated injuries involving the atria. Seven of 21 (33%) patients with aortic injuries died compared to 2 of 31 (6%) with aortic arch branch injury (p < 0.05, chi-square) for an overall mortality of 17%.

Adolescent↗
PubMed1989

The epidemiology of mumps in southern Alberta 1980-1982.

The full spectrum of mumps in Southern Alberta was studied over the years 1980-1982. In the community, a random sample of 3,497 children was tested for prevalence of immunity to mumps. The 1,816 who were not immune were retested after one year. The incidence of new immunity was 16.5%. Most seroconverters had no illness suggestive of mumps. History of previous mumps or immunization were found to be unreliable predictors of serologic immune status. In the family study, information was obtained on 342 cases diagnosed as mumps by family physician recorders. The overall complication rate was 10.8% and the secondary attack rate within families was 11.7%. Hospital records of all 25 patients admitted in Calgary with mumps during the same period were analyzed. Estimated costs of unopposed mumps over 20 years compared with the estimated costs of vaccination showed that a vaccination program could give a benefit-cost ratio between 6.4 and 247. These studies show that mumps is a mild disease with relatively few serious complications or sequelae. Even so, there would be definite medical and economic benefit with immunization. A low-cost addition of mumps vaccine to the immunization program would be justified.

Adolescent↗
PubMed1988

Herpes simplex virus infection of the hand. A profile of 79 cases.

Seventy-nine cases of herpes simplex (HSV) infection of the hand were documented by viral culture over a 40-month period. A marked bimodal age distribution was found with 32 cases occurring in adults aged 21 to 30 years and 16 occurring in children less than 10 years old. The infection most commonly occurred on the fingers (69 percent) and thumb (21 percent). All 20 herpes simplex type 2 (HSV-2) isolates came from patients over 20 years old. All of the 13 specimens that were typed after isolation from patients under 20 years old were herpes simplex type 1 (HSV-1). Only seven of the 49 adult cases were identified in health care professionals. In this series, HSV infection of the hand occurred in 2.4 cases per 100,000 population per year. In adults, women with recurrent infections from HSV-2 and a history compatible with genital herpes predominated. In children, a primary HSV-1 infection associated with gingivostomatitis was common.

Adult↗
PubMed1987

Reovirus type 3 infection in patients with primary biliary cirrhosis and primary sclerosing cholangitis.

Reovirus type 3 (Reo-3) infection has recently been implicated in the pathogenesis of certain idiopathic, cholestatic liver diseases of newborns. In the present study, antibody titres to Reo-3 virus (anti-Reo-3) were determined in sera from 43 adults with idiopathic cholestatic liver disease, including 34 patients with primary biliary cirrhosis (PBC) and 9 patients with primary sclerosing cholangitis (PSC). Seventy-four adults with various other causes of chronic liver disease and 16 healthy volunteers served as controls. Geometric mean titres of anti-Reo-3 were significantly higher in PBC and PSC sera than chronic liver disease and healthy controls (P less than 0.005). Mean antibody titres for all patient groups, however, were within the 95% confidence limits for normals. Seven of 34 (21%) PBC patients and 3/9 (33%) PSC patients had elevated titres of anti-Reo-3, as compared to only 4/74 (5%) chronic liver disease (P less than 0.05) and 0/16 (0%) healthy control subjects (P less than 0.05) (Fisher's Exact Test). Antibody titres to five other common viruses were normal in patients with high anti-Reo-3 titres when compared to age- and sex-matched controls with liver disease. Immunoperoxidase staining for Reo-3 viral markers and cultures of liver biopsy material for Reo-3 virus were negative in both patients and controls. The results of this study indicate that, although patients with PBC and PSC have higher anti-Reo-3 antibody titres than patients with other forms of chronic liver disease or healthy volunteers, only a minority of these patients have titres that exceed the 95% confidence limits for normals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Elevated serum gamma-aminobutyric acid levels in children with Reye's syndrome.

Elevated serum levels of gamma-aminobutyric acid (GABA), a potent inhibitory neurotransmitter, have recently been implicated in the pathogenesis of hepatic encephalopathy. In this study, serum GABA levels were measured in five children with severe Reye's syndrome, 10 children with acute viral hepatitis, and seven healthy volunteers. Serum GABA levels were highest in the five Reye's syndrome patients. The mean serum GABA level for the Reye's syndrome group (3.0 +/- 1.3 microM, mean +/- SEM) was significantly elevated as compared to the mean of the viral hepatitis group (0.72 +/- 0.07 microM, p less than 0.05) and the healthy volunteers (0.38 +/- 0.04 microM, p less than 0.05). These results provide preliminary evidence to suggest that elevated serum GABA levels may in part be responsible for the encephalopathic state observed in children with Reye's syndrome.

Child↗