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Biomedical subjects

M Nelson

Publications and source records attributed to M Nelson.

At least 55 records · Page 3Linked to original sources
PubMed2004

Impact of tea drinking on iron status in the UK: a review.

BACKGROUND: The aims of this review are (1) to evaluate the literature on the likely impact of tea drinking on the iron status of different groups within the UK population and (2) to formulate targeted and evidence based advice on tea drinking in the context of iron nutrition in different groups of people. METHOD: A literature search identified 35 references specific to the effects of black tea on iron absorption and iron nutrition plus one recent review article. Each study was assessed in terms of methodogical quality and relevance to the tea drinking patterns of the UK population. RESULTS: There is clear evidence to show that tea drinking limits the absorption of nonhaem iron. However, there are few studies which have assessed the influence of tea drinking on indicators of iron status. There are no intervention studies and the conclusions reported in this review are based on 12 observational studies mostly from other countries. These studies have reported either significant negative correlations between tea drinking and blood indicators of iron status or more cases of anemia in tea drinkers compared with nontea drinkers. Many of the studies reviewed report additional relationships between iron status indices and other factors (both dietary and nondietary), highlighting the complexity of influences on iron absorption and iron status. CONCLUSION: From the available evidence there is no need to advise any restriction on tea drinking in healthy people with no risk of iron deficiency. In groups at risk of iron deficiency the advice should be to drink tea between meals and to wait at least 1 h after eating before drinking tea.

Anemia, Iron-Deficiency↗
PubMed2004

Differentiation between African populations is evidenced by the diversity of alleles and haplotypes of HLA class I loci.

The allelic and haplotypic diversity of the HLA-A, HLA-B, and HLA-C loci was investigated in 852 subjects from five sub-Saharan populations from Kenya (Nandi and Luo), Mali (Dogon), Uganda, and Zambia. Distributions of genotypes at all loci and in all populations fit Hardy-Weinberg equilibrium expectations. There was not a single allele predominant at any of the loci in these populations, with the exception of A*3002 [allele frequency (AF) = 0.233] in Zambians and Cw*1601 (AF = 0.283) in Malians. This distribution was consistent with balancing selection for all class I loci in all populations, which was evidenced by the homozygosity F statistic that was less than that expected under neutrality. Only in the A locus in Zambians and the C locus in Malians, the AF distribution was very close to neutrality expectations. There were six instances in which there were significant deviations of allele distributions from neutrality in the direction of balancing selection. All allelic lineages from each of the class I loci were found in all the African populations. Several alleles of these loci have intermediate frequencies (AF = 0.020-0.150) and seem to appear only in the African populations. Most of these alleles are widely distributed in the African continent and their origin may predate the separation of linguistic groups. In contrast to native American and other populations, the African populations do not seem to show extensive allelic diversification within lineages, with the exception of the groups of alleles A*02, A*30, B*57, and B*58. The alleles of human leukocyte antigen (HLA)-B are in strong linkage disequilibrium (LD) with alleles of the C locus, and the sets of B/C haplotypes are found in several populations. The associations between A alleles with C-blocks are weaker, and only a few A/B/C haplotypes (A*0201-B*4501-Cw*1601; A*2301-B*1503-Cw*0202; A*7401-B* 1503-Cw*0202; A*2902-B*4201-Cw*1701; A*3001-B*4201-Cw*1701; and A*3601-B*5301-Cw*0401) are found in multiple populations with intermediate frequencies [haplotype frequency (HF) = 0.010-0.100]. The strength of the LD associations between alleles of HLA-A and HLA-B loci and those of HLA-B and HLA-C loci was on average of the same or higher magnitude as those observed in other non-African populations for the same pairs of loci. Comparison of the genetic distances measured by the distribution of alleles at the HLA class I loci in the sub-Saharan populations included in this and other studies indicate that the Luo population from western Kenya has the closest distance with virtually all sub-Saharan population so far studied for HLA-A, a finding consistent with the putative origin of modern humans in East Africa. In all African populations, the genetic distances between each other are greater than those observed between European populations. The remarkable current allelic and haplotypic diversity in the HLA system as well as their variable distribution in different sub-Saharan populations is probably the result of evolutionary forces and environments that have acted on each individual population or in their ancestors. In this regard, the genetic diversity of the HLA system in African populations poses practical challenges for the design of T-cell vaccines and for the transplantation medical community to find HLA-matched unrelated donors for patients in need of an allogeneic transplant.

Africa South of the Sahara↗
PubMed2004

Emtricitabine (FTC) for the treatment of HIV infection.

Emtricitabine (FTC) is a synthetic nucleoside analogue of cytosine, which is intracellularly phosforylated to form the active form emtricitabine 5'triphosphate (E5TP). E5TP inhibits both HIV and Hepatitis B reverse transcriptase. Clinical trials have shown FTC to be active as part of highly active anti-retroviral therapy in naïve HIV-positive patients. FTC may be dosed once daily and in vitro is less associated with the M184V mutation, which is classically associated with failure of treatment with lamivudine. In clinical practice, toxicity with FTC is unusual. The most common treatment-related adverse events are diarrhoea, headache, nausea, dizziness, abdominal pain, aesthenia and rash. Skin discolouration, which is typically reported as hyperpigmentation and usually affecting either the palms of the hands or the soles of the feet, is reported on under 2% of individuals and is almost exclusive to patients of African origin.

Animals↗
PubMed2004

Treatment of primary HIV-1 infection with nonnucleoside reverse transcriptase inhibitor-based therapy is effective and well tolerated.

OBJECTIVES: Highly active antiretroviral therapy (HAART) has been advocated for the management of primary HIV-1 infection. We investigated the use of a nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimen in this setting. METHODS: Twenty-one antiretroviral-naïve individuals with early HIV-1 disease were treated with a combination of efavirenz and Combivir (GlaxoSmithKline, Uxbridge, Middlesex, UK). They were evaluated for immune and lymphocyte function by standard immunological assays. RESULTS: The median time to an undetectable HIV-1 viral load was 12 weeks (range 4-36 weeks). CD4 and CD16/56 counts increased during treatment and CD8 counts decreased minimally. The main side-effects observed were transient sleep disturbances (five patients). In addition, we observed a decrease in lymphocyte activation as assessed by CD38 surface expression. CONCLUSIONS: This study demonstrates that primary HIV-1 infection can be treated with NNRTI-based HAART.

Adult↗
PubMed2004

Sexual trauma associated with fisting and recreational drugs.

There is a rising trend in high risk sexual behaviour among men who have sex with men (MSM), with concomitant use of recreational drugs. Activities include fisting and unprotected anal intercourse with a partner who is HIV serodiscordant or of unknown status. We describe three cases of HIV positive MSM who have recently attended our unit as a result of complications secondary to fisting.

Adult↗
PubMed2004

Head and neck cancer in patients with human immunodeficiency virus-1 infection: incidence, outcome and association with Epstein-Barr virus.

Head and neck cancers have been described in patients with human immunodeficiency virus-1 (HIV-1) infection. However the incidence, aetiology and clinical features of the disease remain unclear. Patients with head and neck cancer and HIV were identified from a large HIV centre. The incidence and clinical features were recorded, and the tumours were stained for Epstein-Barr virus (EBV). Head and neck cancer occurred more frequently than in an age-matched control group (1.66 vs 0.55/10,000 patient years respectively p < 0.05). Highly active anti-retroviral therapy has not significantly altered the incidence of the disease. All of the tumours tested were positive for EBV. Patients were moderately immunosuppressed at diagnosis and had aggressive tumours. All but one of the patients died of cancer with a median survival of 28 months. Head and neck cancer occurs more frequently in HIV. It is an aggressive disease and EBV may play a role in its pathogenesis.

Adult↗
PubMed2004

The emergence of Stenotrophomonas maltophilia as a significant nosocomial pathogen at the University Hospital of the West Indies.

Stenotrophomonas maltophilia is emerging worldwide as a nosocomial pathogen. It is associated with certain risk factors and a wide range of infections. This study was done to document its emergence at the University Hospital of the West Indies and to determine the incidence, distribution and risk factors associated with it. A retrospective study was conducted over the period April 1997 to December 2000. Clinical records were available for 46 of the 66 patients identified over the study period. Fifty-five per cent of the cases came from the Intensive Care Unit (ICU) and the rest from other wards. There was a slight increase in the prevalence of infection with increasing age. The surgical service accounted for the largest number of isolates. Of the cases presented, 95.7% were exposed to a wide range of antibiotics and had some form of instrumentation. Underlying disease was found in 71.7% of the patients. S maltophilia was found most often in the sputum of ICU patients whereas it was most often isolated from wound swabs in the ward patients. The organism was isolated from blood more often in ICU patients (23.3%) than in ward patients (9.5%) and there was a 44% mortality rate among the cases in ICU compared with those on the wards (4.8%). Stenotrophomonas maltophilia is an important nosocomial pathogen and occurs in a wide cross-section of patients. The risk factors must be addressed and infection control measures implemented to restrict the spread of this organism.

Adolescent↗
PubMed2004

A national survey on preoperative fasting policies and practices in Jamaican hospitals.

Controversy has arisen regarding the length and nature of the preoperative fast that should be required of patients with normal gastric emptying time undergoing elective surgery. Various studies and editorials have indicated that the traditional preoperative fasting policy of "NPO after midnight" may be illogical as it makes no distinction between solid foods and clear fluids. Successive National Surveys conducted in the United States of America (USA) have shown an increasing number of Ambulatory Surgery Hospitals adopting more liberal preoperative fasting guidelines. Jamaican practitioners have also begun implementing some of these new liberal practices, even in institutions where "NPO after midnight" remain the official policy of the institution in which they practice. This has created a discordance between individual practice and institutional policy. In view of the fact that the extent of this discrepancy has not yet been studied and documented in Jamaica, and in an effort to better characterize the nature of the changes taking place in preoperative fasting practices in Jamaican hospitals, including those related to knowledge and attitude of practitioners, we embarked on this National Survey. The survey consisted of a questionnaire comprised of 13 questions which were to be completed by all surgeons and anaesthetists practising in a wide cross-section of public hospitals throughout Jamaica, providing an initial sample size of 201 subjects. We had a response rate of 74%, or 148 responses. At all the hospitals surveyed, the traditional NPO policy continued to be the official institutional policy. However, at the individual level, 37% of respondents had already revised their policy, and were allowing their patients to have clear fluids up to three hours before the induction of anaesthesia. Also, 66%, 68%, and 73% of respondents stated that, in the future, they were prepared to allow their patients a solid meal up to eight hours, light breakfast up to six hours, and clear fluids up to three hours, respectively. We concluded that, whilst the traditional NPO policy remained firmly entrenched at the institutional level, many anaesthetists and surgeons show a positive inclination towards more liberal fasting practices. We recommend the formation of a local task force to determine what aspects of the new liberal guidelines may be safely and effectively adopted, taking account of local circumstances.

Data Collection↗
PubMed2003

Does HIV adversely influence the outcome in advanced non-small-cell lung cancer in the era of HAART?

The objectives of the study are to assess the impact of HIV status on the outcome of patients with non-small-cell lung cancer (NSCLC) in the era of highly active antiretroviral therapy (HAART). Patients diagnosed with HIV-related NSCLC in the HAART era (since January 1996) were identified from a prospective single-centre lung cancer database. The clinicopathological characteristics and outcome of each HIV-positive patient were compared to three age- and stage-matched HIV-negative controls with NSCLC who were diagnosed over the same time period and treated in an identical manner. The results showed that the two groups had similar disease characteristics and received a similar amount of chemotherapy. The median overall survival of the two groups was the same (4 months, log rank P=0.55). None of the HIV-positive patients developed an AIDS defining illness or died of HIV during treatment or follow-up. In conclusion, in this cohort, HIV status does not influence the prognosis of advanced NSCLC. This suggests that the survival of patients with HIV-related NSCLC may have improved since the introduction of HAART, and this may be due to a decrease in HIV-related deaths.

Adult↗
PubMed2003

Multicenter study of human immunodeficiency virus-related germ cell tumors.

PURPOSE: Testicular germ cell tumors (GCT) occur at increased frequency in men with human immunodeficiency virus (HIV). This multicenter study addresses the characteristics of these tumors. PATIENTS AND METHODS: Patients with HIV-related GCT were identified from six HIV treatment centers. The incidence was calculated from the center with the most complete linked oncology and HIV databases. RESULTS: Thirty-five patients with HIV-related GCT were identified. The median age at GCT diagnosis was 34 years (range, 27 to 64 years). The median CD4 cell count was 315/mm3 (range, 90 to 960/mm3) at this time. The histologic classification was seminoma in 26 patients (74%) and nonseminomatous GCT in nine patients (26%). Twenty-one patients (60%) had stage I disease and 14 patients had metastatic disease. Overall six patients relapsed, three died from GCT, and seven died from HIV disease, resulting in a 2-year overall survival rate of 81%. HIV-related seminoma occurred more frequently than in the age- and sex-matched HIV-negative population, with a relative risk of 5.4 (95% confidence interval, 3.35 to 8.10); however, nonseminomatous GCT did not occur more frequently, and there was no change in the incidence of GCT since the introduction of highly active antiretroviral therapy. CONCLUSION: Testicular seminoma occurs significantly more frequently in HIV-positive men than in the matched control population. Patients with HIV-related GCTs present and should be treated in a similar manner to those in the HIV-negative population. After a median follow-up of 4.6 years, 9% of the patients died from GCT. Most of the mortality relates to HIV infection.

Adolescent↗
PubMed2003

An open-label study of tenofovir in HIV-1 and Hepatitis B virus co-infected individuals.

BACKGROUND: Tenofovir is a novel nucleotide analogue recommended for use in HIV-1 infected treatment-experienced patients. Recent data suggest an effect on Hepatitis B virus (HBV) replication. We therefore investigated the use of tenofovir in HIV-1 and HBV co-infected individuals. METHODS: Twenty HIV-1/HBV co-infected patients with a median of 108 weeks lamivudine experience (range, 0-270 weeks) received tenofovir 245 mg daily in addition to or as part of their combination antiretroviral therapy. Their immunologic parameters and HIV-1 RNA and HBV DNA viral loads were followed over a period of 52 weeks. In addition, their HBV DNA polymerase was sequenced at baseline to measure the frequency of YMDD mutations that are associated with lamivudine resistance. FINDINGS: A significant decrease in HBV DNA viral load (4 x log ) and alanine aminotransferase levels was observed. There were no significant overall differences between the lamivudine-experienced (n = 15) and -naive (n = 5) individuals and tenofovir was well tolerated. Five patients (25%) underwent HBe antigen seroconversion during the study period. Out of the 15 lamivudine-experienced individuals, 10 had YMDD mutations and one had YIDD mutations in HBV DNA. INTERPRETATION: These results indicate that 52 weeks of tenofovir in addition to antiretroviral therapy is active against HBV, and it appears to overcome lamivudine resistance.

Adenine↗
PubMed2003

Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base.

For humans to survive during long-term missions on the Martian surface, bioregenerative life support systems including food production will decrease requirements for launch of Earth supplies, and increase mission safety. It is proposed that the development of "modular biospheres"--closed system units that can be air-locked together and which contain soil-based bioregenerative agriculture, horticulture, with a wetland wastewater treatment system is an approach for Mars habitation scenarios. Based on previous work done in long-term life support at Biosphere 2 and other closed ecological systems, this consortium proposes a research and development program called Mars On Earth(TM) which will simulate a life support system designed for a four person crew. The structure will consist of 6 x 110 square meter modular agricultural units designed to produce a nutritionally adequate diet for 4 people, recycling all air, water and waste, while utilizing a soil created by the organic enrichment and modification of Mars simulant soils. Further research needs are discussed, such as determining optimal light levels for growth of the necessary range of crops, energy trade-offs for agriculture (e.g. light intensity vs. required area), capabilities of Martian soils and their need for enrichment and elimination of oxides, strategies for use of human waste products, and maintaining atmospheric balance between people, plants and soils.

Air Conditioning↗
PubMed2003

Advantages of using subsurface flow constructed wetlands for wastewater treatment in space applications: ground-based Mars Base prototype.

Research and design of subsurface flow wetland wastewater treatment systems for a ground-based experimental prototype Mars Base facility has been carried out, using a subsurface flow approach. These systems have distinct advantages in planetary exploration scenarios: they are odorless, relatively low-labor and low-energy, assist in purification of water and recycling of atmospheric CO2, and will support some food crops. An area of 6-8 m2 may be sufficient for integration of wetland wastewater treatment with a prototype Mars Base supporting 4-5 people. Discharge water from the wetland system will be used as irrigation water for the agricultural crop area, thus ensuring complete recycling and utilization of nutrients. Since the primary requirements for wetland treatment systems are warm temperatures and lighting, such bioregenerative systems may be integrated into early Mars base habitats, since waste heat from the lights may be used for temperature maintenance in the human living environment. "Wastewater gardens (TM)" can be modified for space habitats to lower space and mass requirements. Many of its construction requirements can eventually be met with use of in-situ materials, such as gravel from the Mars surface. Because the technology requires little machinery and no chemicals, and relies more on natural ecological mechanisms (microbial and plant metabolism), maintenance requirements are minimized, and systems can be expected to have long operating lifetimes. Research needs include suitability of Martian soil and gravel for wetland systems, system sealing and liner options in a Mars Base, and wetland water quality efficiency under varying temperature and light regimes.

Ecological Systems, Closed↗
PubMed2003

The legacy of Biosphere 2 for the study of biospherics and closed ecological systems.

The unprecedented challenges of creating Biosphere 2, the world's first laboratory for biospherics, the study of global ecology and long-term closed ecological system dynamics, led to breakthrough developments in many fields, and a deeper understanding of the opportunities and difficulties of material closure. This paper will review accomplishments and challenges, citing some of the key research findings and publications that have resulted from the experiments in Biosphere 2. Engineering accomplishments included development of a technique for variable volume to deal with pressure differences between the facility and outside environment, developing methods of atmospheric leak detection and sealing, while achieving new standards of closure, with an annual atmospheric leakrate of less than 10%, or less than 300 ppm per day. This degree of closure permitted detailed tracking of carbon dioxide, oxygen, and trace gases such as nitrous oxide and ethylene over the seasonal variability of two years. Full closure also necessitated developing new approaches and technologies for complete air, water, and wastewater recycle and reuse within the facility. The development of a soil-based highly productive agricultural system was a first in closed ecological systems, and much was learned about managing a wide variety of crops using non-chemical means of pest and disease control. Closed ecological systems have different temporal biogeochemical cycling and ranges of atmospheric components because of their smaller reservoirs of air, water and soil, and higher concentration of biomass, and Biosphere 2 provided detailed examination and modeling of these accelerated cycles over a period of closure which measured in years. Medical research inside Biosphere 2 included the effects on humans of lowered oxygen: the discovery that human productivity can be maintained with good health with lowered atmospheric oxygen levels could lead to major economies on the design of space stations and planetary/lunar settlements. The improved health resulting from the calorie-restricted but nutrient dense Biosphere 2 diet was the first such scientifically controlled experiment with humans. The success of Biosphere 2 in creating a diversity of terrestrial and marine environments, from rainforest to coral reef, allowed detailed studies with comprehensive measurements such that the dynamics of these complex biomic systems are now better understood. The coral reef ecosystem, the largest artificial reef ever built, catalyzed methods of study now being applied to planetary coral reef systems. Restoration ecology advanced through the creation and study of the dynamics of adaptation and self-organization of the biomes in Biosphere 2. The international interest that Biosphere 2 generated has given new impetus to the public recognition of the sciences of biospheres (biospherics), biomes and closed ecological life systems. The facility, although no longer a materially-closed ecological system, is being used as an educational facility by Columbia University as an introduction to the study of the biosphere and complex system ecology and for carbon dioxide impacts utilizing the complex ecosystems created in Biosphere '. The many lessons learned from Biosphere 2 are being used by its key team of creators in their design and operation of a laboratory-sized closed ecological system, the Laboratory Biosphere, in operation as of March 2002, and for the design of a Mars on Earth(TM) prototype life support system for manned missions to Mars and Mars surface habitats. Biosphere 2 is an important foundation for future advances in biospherics and closed ecological system research.

Agriculture↗
PubMed2003

Earth applications of closed ecological systems: relevance to the development of sustainability in our global biosphere.

The parallels between the challenges facing bioregenerative life support in artificial closed ecological systems and those in our global biosphere are striking. At the scale of the current global technosphere and expanding human population, it is increasingly obvious that the biosphere can no longer safely buffer and absorb technogenic and anthropogenic pollutants. The loss of biodiversity, reliance on non-renewable natural resources, and conversion of once wild ecosystems for human use with attendant desertification/soil erosion, has led to a shift of consciousness and the widespread call for sustainability of human activities. For researchers working on bioregenerative life support in closed systems, the small volumes and faster cycling times than in the Earth's biosphere make it starkly clear that systems must be designed to ensure renewal of water and atmosphere, nutrient recycling, production of healthy food, and safe environmental methods of maintaining technical systems. The development of technical systems that can be fully integrated and supportive of living systems is a harbinger of new perspectives as well as technologies in the global environment. In addition, closed system bioregenerative life support offers opportunities for public education and consciousness changing of how to live with our global biosphere.

Biodiversity↗
PubMed2003

Initial experimental results from the Laboratory Biosphere closed ecological system facility.

An initial experiment in the Laboratory Biosphere facility, Santa Fe, New Mexico, was conducted May-August 2002 using a soil-based system with light levels (at 12 h per day) of 58-mol m-2 d-1. The crop tested was soybean, cultivar Hoyt, which produced an aboveground biomass of 2510 grams. Dynamics of a number of trace gases showed that methane, nitrous oxide, carbon monoxide, and hydrogen gas had initial increases that were substantially reduced in concentration by the end of the experiment. Methane was reduced from 209 ppm to 11 ppm, and nitrous oxide from 5 ppm to 1.4 ppm in the last 40 days of the closure experiment. Ethylene was at elevated levels compared to ambient during the flowering/fruiting phase of the crop. Soil respiration from the 5.37 m2 (1.46 m3) soil component was estimated at 23.4 ppm h-1 or 1.28 g CO2 h-1 or 5.7 g CO2 m-2 d-1. Phytorespiration peaked near the time of fruiting at about 160 ppm h-1. At the height of plant growth, photosynthesis CO2 draw down was as high as 3950 ppm d-1, and averaged 265 ppm h-1 (whole day averages) during lighted hours with a range of 156-390 ppm h-1. During this period, the chamber required injections of CO2 to continue plant growth. Oxygen levels rose along with the injections of carbon dioxide. Upon several occasions, CO2 was allowed to be drawn down to severely limiting levels, bottoming at around 150 ppm. A strong positive correlation (about 0.05 ppm h-1 ppm-1 with r2 about 0.9 for the range 1000-5000 ppm) was observed between atmospheric CO2 concentration and the rate of fixation up to concentrations of around 8800 ppm CO2.

Biomass↗