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Biomedical subjects

N Wilson

Publications and source records attributed to N Wilson.

At least 37 records · Page 2Linked to original sources
PubMed2002

Community-based stream conservation initiatives in British Columbia, Canada.

British Columbia is a diverse province, with ecosystems ranging from semi-arid deserts to valley glaciers and vast ice fields. By world standards, BC has an abundance of fresh water in its lakes and rivers. However, rivers have been exploited for social and industrial purposes, often to the detriment of the natural values. Community groups and non-government organizations have been active in rehabilitating and restoring waterways. The Outdoor Recreation Council of BC is a provincial non-government organization that has been instrumental in river conservation issues in BC. Three key initiatives have been established by the Council since its formation in 1975. BC Rivers Day has grown into the largest river celebration of its kind in North America, and there is a move to establish a national Rivers Day in Canada based on the model established in BC. Second is the annual Endangered Rivers List compiled by the Council and released each spring. The third initiative is the River Recovery Project in which dams and impoundment structures were evaluated against a set of criteria. A short list of candidates was generated by the project that will be further studied to determine what actions should be taken to alter the management of the structures to restore ecological values of the rivers and streams on which they are built. The three initiatives described rely on local community support. The Outdoor Recreation Council of BC provides coordination, promotion, and publicity as well as some resource materials while local groups and communities take on stewardship roles for their local streams. This model may be useful for other jurisdictions.

British Columbia↗
PubMed2001

Smoke gets in your eyes: smoking and visual impairment in New Zealand.

AIM: To estimate the burden of visual impairment attributable to smoking in New Zealand. METHODS: Review of Medline-indexed literature on the relationship between smoking and eye disease and use of relevant New Zealand morbidity and smoking prevalence data. RESULTS: The international literature indicates there is strong evidence that smoking is a major cause of eye disease and blindness--particularly for cataracts and age-related macular degeneration (AMD). Using the most relevant international risk estimates, we estimated that 1335 people who are registered blind in New Zealand have AMD attributable to current and past smoking (26.8% of all AMD cases in the 55 years plus age-group). It was also estimated that 31 of the registered cases of visual impairment due to cataract and 396 hospitalisations for cataract surgery per year, are attributable to smoking. While subject to various methodological limitations, these estimates are probably under-estimates of the true burden of eye disease attributable to smoking. CONCLUSIONS: Smoking is a major cause of untreatable visual impairment and also a significant reason for cataract surgery in New Zealand. There is a need for more intensive tobacco control activities in New Zealand.

Cataract↗
PubMed2001

Development and testing of the Helex septal occluder, a new expanded polytetrafluoroethylene atrial septal defect occlusion system.

BACKGROUND: A variety of transcatheter atrial septal defect (ASD) occluders are currently in use around the world. Although for the most part effective, all of these devices lack features that would be desirable in a "perfect" device. The Helex septal occluder is a new type of device designed to improve the results of transcatheter ASD closure. This study was designed to examine the effectiveness and safety of this occluder in an animal model. METHODS AND RESULTS: The Helex was implanted into 24 dogs with surgically created ASDs. Procedural details focusing on deployment, removal, and early closure rates were examined. Follow-up consisted of sequential transesophageal echocardiography and fluoroscopy as well as epicardial contrast echocardiography and angiography at the time of death. Specimens were examined grossly and histologically, and devices were tested for metal fatigue. All animals had successful ASD closure. Implantation was uncomplicated (mean fluoroscopy time 11.7 minutes), and removal or repositioning was always possible. Closure rate as judged by transesophageal echocardiography was 88% initially and 100% at 2-week follow-up. Devices rapidly became infiltrated with connective tissue without inflammation and were endothelialized over time. There were no instances of thromboembolism. A single wire-frame fracture occurred secondary to a prototype delivery system malfunction. CONCLUSIONS: The Helex septal occluder proved safe and effective for ASD closure. Several advantages over currently available devices were evident in this model. Controlled prospective clinical trials are needed.

Animals↗
PubMed2001

Diagnosis of anthracycline-induced late cardiomyopathy by exercise-spiroergometry and stress-echocardiography.

UNLABELLED: Anthracyclines are used in the therapy of several of the most common paediatric oncological disorders. The usefulness of these agents is limited by cardiotoxicity, with congestive heart failure developing in up to 20% of patients. To stratify possible risk factors, we investigated 38 children with acute lymphoblastic leukaemia for signs of late cardiomyopathy. Exercise-spiroergometry and stress-echocardiography with measurement of fractional shortening (FS) and ejection fraction (EF) as indicators of left ventricular function were performed. ECG, 24 h Holter monitoring, chest X-ray, virus serology and carnitine were analysed. Control subjects were 38 healthy children matched for age and body surface area. All 38 patients had normal echocardiographic findings at rest (EF: 0.73 +/- 0.06; FS: 0.35 +/- 0.05). ten patients had a significant attenuation of left ventricular function after exercise assessed by stress-echocardiography compared to the remaining 28 patients and 38 healthy control subjects (EF: 0.52 +/- 0.08 versus 0.77 +/- 0.06 and 0.80 +/- 0.08; FS: 0.29 +/- 0.06 versus 0.39 +/- 0.05 and 0.41 +/- 0.02); patients with reduced ventricular function after exercise had significant low anaerobic threshold, subnormal maximal oxygen uptake and decreased carnitine levels. The findings were not related to the dosage of administered doxorubicin. There exists no correlation between ECG, 24 h ECG, chest X-ray, virology and left ventricular dysfunction. The benefit of angiotensin converting enzyme inhibitors and the administration of carnitine remains speculative. CONCLUSION: exercise-spiroergometry and stress-echocardiography are sensitive investigations for diagnosing subclinical cardiomyopathy late after completion of chemotherapy. Investigative findings of cardiomyopathy are not dose related and may provide information for therapeutic prevention before clinical symptoms of cardiomyopathy appear.

Antibiotics, Antineoplastic↗
PubMed2001

Mutations changing the kinetics of class II MHC peptide exchange.

IE/DR MHC class II molecules have an extensive H-bonding network under the bound peptide. In IE(k), two alpha chain acidic amino acids in the core of this network were mutated to amides. At low pH, the mutant molecule exchanged peptide much more rapidly than the wild-type. The crystal structure of the mutant IE(k) revealed the loss of a single buried water molecule and a reorganization of the predicted H-bonding network. We suggest that these mutations enhance the transition of MHC class II to an open conformation at low pH allowing the bound peptide to escape. In wild-type IE(k), the need to protonate these amino acids also may be a bottleneck in the return to a closed conformation after peptide binding.

Amino Acid Sequence↗
PubMed2001

Stage one Norwood procedure results: the green lane experience.

AIMS: This study examined the presentation outcome, morbidity and mortality of infants who have undergone the stage one Norwood procedure for single ventricle reconstruction. METHODS: A retrospective review was done on the first 20 patients to undergo this procedure at Green Lane Hospital, Auckland, New Zealand. Seven patients were diagnosed antenatally. Fetal cardiology records in the same time period were reviewed. RESULTS: Twelve of the 20 patients (60%) have survived, and all of these patients have undergone their bi-directional Glenn procedure with no mortality. Eight patients died, with five of the deaths occurring in the perioperative period. Initial surgical mortality was 75%, decreasing to 25% since 1998. Antenatal diagnosis has not improved surgical outcome to date. CONCLUSION: With advances in surgical technique and pre- and postoperative care, neonates born with single ventricle anatomy have an acceptable surgical option. Babies who survive the Norwood operation have a good chance of surviving the later stages of the cardiac reconstruction process, and they have a reasonable outlook in the intermediate term.

Journal Article↗
PubMed2001

Health status assessments using the Veterans SF-12 and SF-36: methods for evaluating otucomes in the Veterans Health Administration.

This article describes a study in which the administration of two health surveys, the Veterans SF-36 and SF-12, by telephone and mail-out was used to assess the differences in the health surveys' costs and scores by mode of administration and determine which mode was cost-efficient. The study employed a crossover design: after 12 unsuccessful attempts to contact patients by telephone, the patients were administered the survey by mail, and after 2 unsuccessful mail-outs, up to three attempts were made to interview the patients by telephone. The analysis of the data showed that mail administration, with or without crossover to telephone, was more cost-efficient than telephone administration, having both lower average total and variable costs per completed questionnaire. Overall, telephone administration was about 30% more expensive that mail administration, primarily due to the cost of labor. The marginal cost of an additional completed Veterans SF-12 or Veterans SF-36 was also substantially lower for mail administration. Mail administration without crossover to telephone administration was the most cost-efficient strategy for administering both the Veterans SF-12 and SF-36. The results of this study strongly suggest the need to consider the mode of administration if questionnaires like the Veterans SF-12 or SF-36 are to be used to assess health outcomes within and across large health care systems.

Costs and Cost Analysis↗
PubMed2000

Tat-specific cytotoxic T lymphocytes select for SIV escape variants during resolution of primary viraemia.

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by early peaks of viraemia that decline as strong cellular immune responses develop. Although it has been shown that virus-specific CD8-positive cytotoxic T lymphocytes (CTLs) exert selective pressure during HIV and SIV infection, the data have been controversial. Here we show that Tat-specific CD8-positive T-lymphocyte responses select for new viral escape variants during the acute phase of infection. We sequenced the entire virus immediately after the acute phase, and found that amino-acid replacements accumulated primarily in Tat CTL epitopes. This implies that Tat-specific CTLs may be significantly involved in controlling wild-type virus replication, and suggests that responses against viral proteins that are expressed early during the viral life cycle might be attractive targets for HIV vaccine development.

AIDS Vaccines↗
PubMed2000

The effectiveness of the infant hepatitis B immunisation program in Fiji, Kiribati, Tonga and Vanuatu.

The aims of this project were: (1) to determine the extent to which infant hepatitis B immunisation is preventing chronic hepatitis B infection in children living in a sample of Pacific Island countries; and (2) to identify factors associated with the successful prevention of hepatitis B infection in these populations. A regional hepatitis B immunisation project which supplied hepatitis B vaccine to 10 Pacific Island countries began in 1995. Seroepidemiological surveys were conducted in Fiji, Kiribati, Tonga and Vanuatu in early 1998. These included immunised pre-school children and their biological mothers, and a historical control group of unimmunised students. Prevalence rates for hepatitis B surface antigen (HBsAg) in the populations of students, mothers and their pre-school children were respectively: Fiji: 6.9, 6.6, 0.7%; Kiribati: 27.4, 15.1, 3.8%; Tonga: 11.1, 18.6, 3.8%; Vanuatu: 16.3, 12.3, 3.0%; and for all four countries: 13.2, 12.5, 2.6%. Compared to the historical control group of students, the pre-school population had a much lower probability of HBsAg positivity (relative risk [RR]=0.19 [95%CI: 0.12-0.31]). Statistically significant differences in risk were apparent for all the countries: Fiji: RR=0.10; Kiribati: RR=0.14; Tonga: RR=0.34; Vanuatu: RR=0.19. This is equivalent to an overall program effectiveness of 81% (95%CI: 69-88%) in reducing chronic carriage. Also, the overall protective effectiveness against vertical hepatitis B transmission resulting in HBsAg positivity among children exposed to HBeAg positive and negative carrier mothers, was estimated to be 70%. By age 6 months, when all children should have had three vaccine doses, completed immunisation rates ranged from 22 (Fiji) to 84% (Vanuatu). Coverage of the first dose being given within 2 days of birth varied from 43% in Kiribati to 92% in Tonga. In conclusion hepatitis B immunisation of infants in these four countries is having a substantial beneficial effect in preventing chronic hepatitis B infection. Nevertheless, there is significant scope for further improving the timeliness of immunisation.

Adolescent↗