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Biomedical subjects

R Nathan

Publications and source records attributed to R Nathan.

At least 19 recordsLinked to original sources
PubMed2006

Analysis of spatial genetic structure in an expanding Pinus halepensis population reveals development of fine-scale genetic clustering over time.

We analysed the change of spatial genetic structure (SGS) of reproductive individuals over time in an expanding Pinus halepensis population. To our knowledge, this is the first empirical study to analyse the temporal component of SGS by following the dynamics of successive cohorts of the same population over time, rather than analysing different age cohorts at a single time. SGS is influenced by various factors including restricted gene dispersal, microenvironmental selection, mating patterns and the spatial pattern of reproductive individuals. Several factors that affect SGS are expected to vary over time and as adult density increases. Using air photo analysis, tree-ring dating and molecular marker analysis we reconstructed the spread of reproductive individuals over 30 years beginning from five initial individuals. In the early stages, genotypes were distributed randomly in space. Over time and with increasing density, fine-scale (< 20 m) SGS developed and the magnitude of genetic clustering increased. The SGS was strongly affected by the initial spatial distribution and genetic variation of the founding individuals. The development of SGS may be explained by fine-scale environmental heterogeneity and possibly microenvironmental selection. Inbreeding and variation in reproductive success may have enhanced SGS magnitude over time.

Biomarkers↗
PubMed2005

Mechanistic analytical models for long-distance seed dispersal by wind.

We introduce an analytical model, the Wald analytical long-distance dispersal (WALD) model, for estimating dispersal kernels of wind-dispersed seeds and their escape probability from the canopy. The model is based on simplifications to well-established three-dimensional Lagrangian stochastic approaches for turbulent scalar transport resulting in a two-parameter Wald (or inverse Gaussian) distribution. Unlike commonly used phenomenological models, WALD's parameters can be estimated from the key factors affecting wind dispersal--wind statistics, seed release height, and seed terminal velocity--determined independently of dispersal data. WALD's asymptotic power-law tail has an exponent of -3/2, a limiting value verified by a meta-analysis for a wide variety of measured dispersal kernels and larger than the exponent of the bivariate Student t-test (2Dt). We tested WALD using three dispersal data sets on forest trees, heathland shrubs, and grassland forbs and compared WALD's performance with that of other analytical mechanistic models (revised versions of the tilted Gaussian Plume model and the advection-diffusion equation), revealing fairest agreement between WALD predictions and measurements. Analytical mechanistic models, such as WALD, combine the advantages of simplicity and mechanistic understanding and are valuable tools for modeling large-scale, long-term plant population dynamics.

Models, Theoretical↗
PubMed2004

Planning a family: priorities and concerns in rural Tanzania.

A fertility survey using qualitative and quantitative techniques described a high fertility setting (TFR 5.8) in southern Tanzania where family planning use was 16%. Current use was influenced by rising parity, educational level, age of last born child, breastfeeding status, a preference for longer than the mean birth interval (32 months), not being related to the household head, and living in a house with a tin roof. Three principal concerns amongst women were outlined from the findings. First, that there is a large unmet need for family planning services in the area particularly among teenagers for whom it is associated with induced abortion. Second, that family planning is being used predominantly for spacing but fears associated with it often curtail effective use. Third, that service provision is perceived to be lacking in two main areas--regularity of supply, and addressing rumours and fears associated with family planning. Reproductive health interventions in the area should ultimately be more widespread and, in particular, abortion is highlighted as an urgent issue for further research. The potential for a fast and positive impact is high, given the simplicity of the perceived needs of women from this study.

Abortion, Legal↗
PubMed2002

Anaemia during pregnancy in southern Tanzania.

Anaemia in pregnancy is associated with maternal morbidity and mortality and is a risk factor for low birth-weight. Of 507 pregnant women recruited in a community, cross-sectional study in southern Tanzania, 11% were severely anaemic (<8 g haemoglobin/dl). High malarial parasitaemia [odds ratio (OR)=2.3] and iron deficiency (OR=2.4) were independent determinants of anaemia. Never having been married (OR=2.9) was the most important socio-economic predictor of severe anaemia. A subject recruited in the late dry season was six times more likely to be severely anaemic than a subject recruited in the early dry season. Compared with the women who were not identified as severely anaemic, the women with severe anaemia were more likely to present at mother-and-child-health (MCH) clinics early in the pregnancy, to seek medical attention beyond the MCH clinics, and to report concerns about their own health. Pregnancy-related food taboos in the study area principally restrict the consumption of fish and meat. Effective anti-malaria and iron-supplementation interventions are available but are not currently in place; improvements in the mechanisms for the delivery of such interventions are urgently required. Additionally, opportunities for contacting the target groups beyond the clinic environment need to be developed.

Adolescent↗
PubMed2001

Effect of large-scale social marketing of insecticide-treated nets on child survival in rural Tanzania.

BACKGROUND: Insecticide-treated nets have proven efficacy as a malaria-control tool in Africa. However, the transition from efficacy to effectiveness cannot be taken for granted. We assessed coverage and the effect on child survival of a large-scale social marketing programme for insecticide-treated nets in two rural districts of southern Tanzania with high perennial malaria transmission. METHODS: Socially marketed insecticide-treated nets were introduced step-wise over a 2-year period from May, 1997, in a population of 480000 people. Cross-sectional coverage surveys were done at baseline and after 1, 2, and 3 years. A demographic surveillance system (DSS) was set up in an area of 60000 people to record population, births, and deaths. Within the DSS area, the effect of insecticide-treated nets on child survival was assessed by a case-control approach. Cases were deaths in children aged between 1 month and 4 years. Four controls for each case were chosen from the DSS database. Use of insecticide-treated nets and potential confounding factors were assessed by questionnaire. Individual effectiveness estimates from the case-control study were combined with coverage to estimate community effectiveness. FINDINGS: Insecticide-treated net coverage of infants in the DSS area rose from less than 10% at baseline to more than 50% 3 years later. Insecticide-treated nets were associated with a 27% increase in survival in children aged 1 month to 4 years (95% CI 3-45). Coverage in such children was higher in areas with longer access to the programme. The modest average coverage achieved by 1999 in the two districts (18% in children younger than 5 years) suggests that insecticide-treated nets prevented 1 in 20 child deaths at that time. INTERPRETATION: Social marketing of insecticide-treated nets has great potential for effective malaria control in rural African settings.

Bedding and Linens↗
PubMed2001

Impact on malaria morbidity of a programme supplying insecticide treated nets in children aged under 2 years in Tanzania: community cross sectional study.

OBJECTIVE: To assess the impact of a social marketing programme for distributing nets treated with insecticide on malarial parasitaemia and anaemia in very young children in an area of high malaria transmission. DESIGN: Community cross sectional study. Annual, cross sectional data were collected at the beginning of the social marketing campaign (1997) and the subsequent two years. Net ownership and other risk and confounding factors were assessed with a questionnaire. Blood samples were taken from the children to assess prevalence of parasitaemia and haemoglobin levels. SETTING: 18 villages in the Kilombero and Ulanga districts of southwestern Tanzania. PARTICIPANTS: A random sample of children aged under 2 years. MAIN OUTCOME MEASURES: The presence of any parasitaemia in the peripheral blood sample and the presence of anaemia (classified as a haemoglobin level of <80 g/l). RESULTS: Ownership of nets increased rapidly (treated or not treated nets: from 58% to 83%; treated nets: from 10% to 61%). The mean haemoglobin level rose from 80 g/l to 89 g/l in the study children in the successive surveys. Overall, the prevalence of anaemia in the study population decreased from 49% to 26% in the two years studied. Treated nets had a protective efficacy of 62% (95% confidence interval 38% to 77%) on the prevalence of parasitaemia and of 63% (27% to 82%) on anaemia. CONCLUSIONS: These results show that nets treated with insecticide have a substantial impact on morbidity when distributed in a public health setting.

Bedding and Linens↗
PubMed2001

Patients receiving immunotherapy report it is effective as assessed by the rhinitis outcomes questionnaire (ROQ) in a private practice setting.

BACKGROUND: Outcomes measurement is a proficient method in determining the effectiveness of medical therapy. Currently, there are no easy-to-use and inexpensive questionnaires available to evaluate the effectiveness of immunotherapy by allergists in private practice. OBJECTIVE: To evaluate the effectiveness of immunotherapy in the treatment of patients with allergic rhinitis in a private practice setting using the rhinitis outcomes questionnaire (ROQ). METHODS: One hundred seventy-five patients were randomly chosen from three private practices nationwide. They were surveyed regarding global systemic problems and nasal, eye, and chest symptoms, as well as their medical treatment history. This questionnaire was administered twice in one sitting, with the first a recall of symptoms before immunotherapy treatment, and the second an evaluation of current symptoms. RESULTS: The data revealed that 81% of the patients believed immunotherapy worked, with 19% unsure. Patients experienced a 67% decrease in antibiotic use, a 68% decrease in emergency room visits, a 75% decrease in days lost from work or school, and a 79% decrease in hospital admissions. The average symptom score reduction with immunotherapy was 52%. CONCLUSIONS: This study demonstrates that the user-friendly ROQ can be effectively and inexpensively used in a private practice setting and that immunotherapy is effective in the treatment of allergic rhinitis.

Female↗
PubMed2001

Validation of the rhinitis outcomes questionnaire (ROQ).

BACKGROUND: Currently, there is no easy-to-use and comprehensive questionnaire that measures the effectiveness of treatment of rhinitis-related symptoms in a private practice setting. OBJECTIVE: To validate a brief, effective, self-administered rhinitis symptoms questionnaire that can easily be used in a private practice setting for tracking treatment outcomes. METHODS: One hundred seventy-five patients were randomly chosen from three private practices nationwide and were surveyed regarding systemic problems, nasal, eye, and chest symptoms, as well as medical treatment obtained. This survey was administered twice in one sitting with the first administration a recall of symptoms before immunotherapy, and the second administration an evaluation of current symptoms. Appropriate statistical methods were used to evaluate the validity, reliability, and responsiveness of the questionnaire presented. The validation of this instrument included content, statistical, construct, and predictive validity. RESULTS: Both the content and statistical validity were very good in that the questionnaire was easily understood and covered required domains. Construct validity revealed that the items were sensibly related to the domains that contained them and had less association with items from different domains. The reliability of the scales was very good (Cronbach's alpha = 0.80) to outstanding (Cronbach's alpha = 0.92). CONCLUSIONS: Functionality was established for the rhinitis outcomes questionnaire (ROQ) for use in a private practice setting. This allows private practice allergists to collect reliable data with the ROQ.

Adult↗
PubMed2001

Diagnostic accuracy and case management of clinical malaria in the primary health services of a rural area in south-eastern Tanzania.

Malaria control continues to rely on the diagnosis and prompt treatment of both suspected and confirmed cases through the health care structures. In south-eastern Tanzania malaria is one of the leading causes of morbidity and mortality. The absence of microscopic examination in most of the health facilities implies that health workers must rely on clinical suspicion to identify the need of treatment for malaria. Of 1558 randomly selected paediatric consultations at peripheral health facilities throughout Kilombero District, 41.1% were diagnosed by the attending health worker as clinical malaria cases and 42.5% prescribed an antimalarial. According to our malaria case definition of fever or history of fever with asexual falciparum parasitaemia of any density, 25.5% of all children attending the health services had malaria. This yielded a sensitivity of 70.4% (IC95% = 65.9-74.8%) and a specificity of 68.9% (IC95% = 66.2-71.5%). Accordingly, 30.4% of confirmed cases left with no antimalarial treatment. Among malaria-diagnosed patients, 10% were underdosed and 10.5% were overdosed. In this area, as in many African rural areas, the low diagnostic accuracy may imply that the burden of malaria cases may be overestimated. Greater emphasis on the functioning and quality of basic health services in rural endemic areas is required if improved case management of malaria is to help roll back this scourge.

Antimalarials↗
PubMed2001

Introducing insecticide-treated nets in the Kilombero Valley, Tanzania: the relevance of local knowledge and practice for an information, education and communication (IEC) campaign.

Since 1997 the WHO has been recommending an integrative strategy to combat malaria including new medicines, vaccines, improvements of health care systems and insecticide-treated nets (ITNs). After successful controlled trials with ITNs in the past decade, large-scale interventions and research now focus on operational issues of distribution and financing. In developing a social marketing approach in the Kilombero Valley in south-east Tanzania in 1996, a combination of qualitative and quantitative methods was employed to investigate local knowledge and practice relating to malaria. The findings show that the biomedical concept of malaria overlaps with several local illness concepts, one of which is called malaria and refers to mild malaria. Most respondents linked malaria to mosquitoes (76%) and already used mosquito nets (52%). But local understandings of severe malaria differed from the biomedical concept and were not linked to mosquitoes or malaria. A social marketing strategy to promote ITNs was developed on the basis of these findings, which reinforced public health messages and linked them with nets and insecticide. Although we did not directly evaluate the impact of promotional activities, the sharp rise in ownership and use of ITNs by the population (from 10 to > 50%) suggests that they contributed significantly to the success of the programme. Local knowledge and practice is highly relevant for social marketing strategies of ITNs.

Adolescent↗
PubMed2000

Spatial patterns of seed dispersal, their determinants and consequences for recruitment.

Growing interest in spatial ecology is promoting new approaches to the study of seed dispersal, one of the key processes determining the spatial structure of plant populations. Seed-dispersion patterns vary among plant species, populations and individuals, at different distances from parents, different microsites and different times. Recent field studies have made progress in elucidating the mechanisms behind these patterns and the implications of these patterns for recruitment success. Together with the development and refinement of mathematical models, this promises a deeper, more mechanistic understanding of dispersal processes and their consequences.

Journal Article↗
PubMed2000

Inhaled mometasone furoate reduces oral prednisone requirements while improving respiratory function and health-related quality of life in patients with severe persistent asthma.

BACKGROUND: Inhaled corticosteroid therapy in severe persistent asthma has been shown to reduce or eliminate oral corticosteroid (OCS) use while retaining effective asthma control. OBJECTIVE: We sought to evaluate the ability of mometasone furoate (MF) delivered by means of dry powder inhaler to reduce daily oral prednisone requirements in OCS-dependent patients with severe persistent asthma. METHODS: We performed a 12-week, double-blind, placebocontrolled trial (21 centers, 132 patients) comparing 2 doses of MF (400 and 800 microg administered twice daily) with placebo, followed by a 9-month open-label phase in which 128 patients received treatment with MF. RESULTS: At the endpoint of the double-blind trial, MF 400 and 800 mg twice daily reduced daily OCS requirements by 46.0% and 23.9%, respectively, whereas placebo increased OCS requirements by 164.4% (P <.01). Oral steroids were eliminated in 40%, 37%, and 0% of patients in the MF 400 and 800 mg twice daily and placebo groups, respectively. Pulmonary function and quality of life significantly increased for MF-treated patients. Further reductions in OCS requirements were achieved with long-term MF treatment in the open-label phase. CONCLUSION: MF inhaled orally as a dry powder is an effective alternative to systemic corticosteroids in patients with severe persistent asthma.

Administration, Inhalation↗
PubMed2000

Maternal mortality in a rural district of southeastern Tanzania: an application of the sisterhood method.

BACKGROUND: Deaths from maternal causes represent the leading cause of death among women of reproductive age in most developing countries. It is estimated that the highest risk occurs in Africa, with 20% of world births but 40% of the world maternal deaths. The level of maternal mortality is difficult to assess especially in countries without an adequate vital registration system. Indirect techniques are an attractive cost-effective tool to provide estimates of orders of magnitude for maternal mortality. METHOD: The level of maternal mortality estimated by the sisterhood method is presented for a rural district in the Morogoro Region of Southeastern Tanzania and the main causes of maternal death are studied. Information from region-specific data using the sisterhood method is compared to data from other sources. RESULTS: The maternal mortality ratio (MMR) was 448 maternal deaths per 100,000 live births (95%CI : 363-534 deaths per 100,000 live births). Maternal causes accounted for 19% of total mortality in this age group. One in 39 women who survive until reproductive age will die before age 50 due to maternal causes. The main cause of death provided by hospital data was puerperal sepsis (35%) and postpartum haemorrhage (17%); this is compatible with the main causes reported for maternal death in settings with high levels of maternal mortality, and similar to data for other regions in Tanzania. The sisterhood method provides data comparable with others, together with a cost-effective and reliable estimate for the determination of the magnitude of maternal mortality in the rural Kilombero District.

Adolescent↗
PubMed2000

Rotary subluxation of the scaphoid. Revisited.

The SL ligament complex and volar radiocarpal ligaments provide scaphoid stability both at the SL joint and, more importantly, at its distal radius articulation. With disruption or attenuation of these ligaments, rotational displacement of the scaphoid occurs about its longitudinal axis. This results in distal scaphoid flexion and proximal pole subluxation dorsally, toward the distal radius rim. Rotary subluxation of the scaphoid accurately describes this condition, and represents a spectrum of radioscaphoid instability based upon the severity and chronicity of ligamentous disruption. Diagnosis is based upon identification of specific clinical and radiographic features. Recognition of this entity provides for a more rational basis for treatment of ligamentous injuries of the wrist.

Athletic Injuries↗
PubMed1999

The management of penetrating trauma to the hand.

Penetrating gunshot wounds to the hand are becoming more common with the increase of gang violence and the availability of firearms. Hand surgeons treating victims of gunshot wounds must be familiar with the peculiarities of the penetrating missile, the special structural considerations of the hand, and the unique demands and rehabilitation needs of this difficult patient population. This article discusses penetrating trauma to the hand and includes a review of ballistics.

Amputation, Surgical↗