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At least 1,207 records · Page 67Linked to original sources
PubMed2006

The role of climate in human mitochondrial DNA evolution: a reappraisal.

Previous studies have proposed that selection has been involved in the differentiation of human mitochondrial DNA (mtDNA) and climate was the main driving force. This viewpoint, however, gets no support from the subsequent studies and remains controversial thus far. To clarify this issue, a total of 237 complete mtDNA sequences belonging to autochthonous lineages from South Asia, Oceania, and East Asia were collected to seek for the imprint of selection. Based on nonsynonymous (N) and synonymous (S) substitutions analysis, our results confirmed that purifying selection was the predominant force during the evolution of human mtDNA. However, no significant and extensive difference was detected among these three regions, which did not support the climate adaptation hypothesis but preferred random genetic drift to be the main factor in shaping the current landscape of human mtDNA, at least those from Asian and Oceanian regions.

Amino Acid Substitution↗
PubMed1997

Availability of Haemonchus contortus L3 larvae on pasture at Kiboko: a semi-arid warm agro-climatic zone in Kenya.

A study was carried out to determine the availability of Haemonchus contortus L3 larvae on pasture in a semi-arid warm agro-climatic zone of Kenya. By means of tracer sheep, it was shown that no H. contortus L3 larvae were available on pasture during the dry periods of the year (July-October and February). They were only available on pasture during the rainy season (November-January and March-June). Sheep permanently grazed on the same pasture however, harboured adult H. contortus in their abomasa throughout the year indicating that the perpetuation of haemonchosis in livestock in this agro-climatic zone was greatly dependent on the ability of the parasite to survive in the host throughout all seasons.

Animals↗
PubMed2002

Integrated summary of Ortho Evra/Evra contraceptive patch adhesion in varied climates and conditions.

OBJECTIVE: To assess the adhesive reliability of the contraceptive patch (Ortho Evra/Evra). DESIGN: Pooled data of 3,319 women from three contraceptive studies of up to 13 treatment cycles; a subset of 325 women of the pooled data from warm and humid climates; and 30 women from a three-period, crossover exercise study. SETTING: 184 centers. PATIENT(S): 3,349 healthy women. INTERVENTION(S): In the contraceptive studies, each treatment cycle consisted of three consecutive 7-day patches (21 days) followed by one patch-free week. During each treatment period in the exercise study, women wore the patch for 7 days and participated in one of six activities (normal activity, excluding bathing; sauna; whirlpool; treadmill; cool-water immersion; or a combination of activities) each day at a supervised health center. MAIN OUTCOME MEASURE(S): Patch adhesion. RESULT(S): In the contraceptive studies, 4.7% of patches were replaced because they fell off (1.8% [1,297 of 70,552 patches]) or became partly detached (2.9% [2,050 of 70,552 patches]); patch replacement rates in centers from a warm, humid climate were 1.7% (85 of 4,877 patches) and 2.6% (128 of 4,877 patches), respectively. Only one of 87 patches (1.1%) completely detached in the exercise study. CONCLUSION(S): The reliability of adhesion of the contraceptive patch is excellent and consistent across all studies; only 1.8% and 2.9% of patches required replacement due to complete or partial detachment, respectively. Heat, humidity, and exercise do not affect adhesion.

Adhesives↗
PubMed2003

Lutzomyia vectors for cutaneous leishmaniasis in Southern Brazil: ecological niche models, predicted geographic distributions, and climate change effects.

Geographic and ecological distributions of three Lutzomyia sand flies that are cutaneous leishmaniasis vectors in South America were analysed using ecological niche modelling. This new tool provides a large-scale perspective on species' geographic distributions, ecological and historical factors determining them, and their potential for change with expected environmental changes. As a first step, the ability of this technique to predict geographic distributions of the three species was tested statistically using two subsampling techniques: a random-selection technique that simulates 50% data density, and a quadrant-based technique that challenges the method to predict into broad unsampled regions. Predictivity under both test schemes was highly statistically significant. Visualisation of ecological niches provided insights into the ecological basis for distributional differences among species. Projections of potential geographic distributions across scenarios of global climate change suggested that only Lutzomyia whitmani is likely to be experiencing dramatic improvements in conditions in south-eastern Brazil, where cutaneous leishmaniasis appears to be re-emerging; Lutzomyia intermedia and Lutzomyia migonei may be seeing more subtle improvements in climatic conditions, but the implications are not straightforward. More generally, this technique offers the possibility of new views into the distributional ecology of disease, vector, and reservoir species.

Algorithms↗
PubMedDate not supplied

Impact of climate on thermal rhythm in pastoral sheep.

The effects of environmental conditions on temperature rhythms were investigated in ewe lambs at pasture. Two groups of 20 lambs had heart rate (HR), vaginal temperature (T(v)), ear-canal temperature (T(c)) and ear-pinna temperature (T(p)) monitored continuously for 3 days. Climatic conditions were recorded at the same time and Temperature Humidity Index (THI) calculated. One group experienced fine clear weather for the 3 days, the other group experienced 2 days of heavy rain. During periods of fine weather, the daily rhythm for T(v) and T(c) was monophasic. However, heavy rain and a constant THI reduced the amplitude of the recorded temperature rhythms. Daily T(v) and T(c) patterns correlated strongly with THI, with a phase lag of 2 h. Peak T(v) and T(c) were at approximately 17:00 h each day. Mean maximum daily amplitudes were approximately 1.3 degrees C for T(v) and T(c). Mean T(v) was 39.3+/-0.1 and 39.6+/-0.1 for weeks 1 and 2, respectively, while mean T(c) was 38.9+/-0.1 and 39.2+/-0.1. Changes in T(v) and T(c) were closely correlated. We conclude that climate has a major effect on body temperature rhythms.

Acclimatization↗
PubMedDate not supplied

Microbial keratitis in Hong Kong: relationship to climate, environment and contact-lens disinfection.

Microbial keratitis has been studied in Hong Kong as a representative sub-tropical climate of south China. An 18-month investigation in 1997/98 of 223 cases of ulcerative keratitis (presumed microbial) was conducted in the 2 million population of Shatin and Kowloon at the Prince of Wales and Hong Kong Eye Hospitals respectively with comprehensive microbiology. A case-control study was pursued at the same time between 45 contact-lens wearers (CLW) developing microbial keratitis and 135 lens-wearing volunteers matched for age, sex, educational status and visual acuity. Home water supplies were sampled for Acanthamoeba. Previous ocular surface disease and trauma (preventable by wearing goggles for grinding) were common predisposing causes while cosmetic wear of contact lenses was responsible for 26% of cases overall. Pseudomonas aeruginosa was the commonest bacterium isolated, from both CLW and non-CLW, with infection being acquired within the community. These 28 pseudomonads remained fully sensitive to the third-generation cephalosporins, aminoglycosides and quinolone antibiotics, which is very encouraging. Fungi were isolated, predominantly Fusarium sp., but less commonly than expected. A fungal/bacterial ratio was obtained of 1/17, while in comparison, the expected ratio for a tropical climate ranges from 1/5 (Singapore) to 1/2 (South India). Acanthamoeba was the second commonest microbe isolated from keratitis of CLW. The domestic water environment of 8% of homes of both patients and controls wearing contact lenses was colonized with Acanthamoeba. Lack of hygiene, use of tap water for storing lenses, failure to air-dry lens-storage cases or use of one-step hydrogen peroxide disinfectant were identified as risk factors for keratitis in CLW. The study results commend use of multipurpose solutions by CLW in Hong Kong to achieve the lowest expected rates of infection.

Acanthamoeba Keratitis↗
PubMed2003

Sludge accumulation pattern in an anaerobic pond under Mediterranean climatic conditions.

The main objective of this study was to observe the sludge accumulation pattern of an experimental, covered, anaerobic pond treating municipal wastewater under Mediterranean climatic conditions throughout a 2-year operational period (1999-2000) in order to form a seasonal sludge accumulation model which may be used to predict the required desludging time, not only of the particular anaerobic pond used in the study, but also for other types of anaerobic ponds and operational situations. The 4-m deep pond was supplied with pre-screened, untreated wastewater from the nearby treatment plant of Thessaloniki, Greece, initially at a flow rate of 120m3/day and later at a flow rate of 150m3/day. The influent characteristics were BOD5 441 mg O2/L, COD 942 mg O2/L and suspended solids (SS) 574 mg/L. BOD5, COD, and SS concentrations of the pond effluent were reduced by 50%, 53%, and 64%, respectively, in comparison with those of the influent. During the operational period, three distinctly different zones were seen to form within the anaerobic pond: The first zone, which formed at the bottom of the pond, consisted of inert, high-density sludge. The second zone, which formed above this, contained a high concentration of volatile (easily biodegradable) sludge. The third upper zone (supernatant), was a liquid layer low in suspended solids. The accumulation of sludge in the pond followed an annual sinusoidal pattern with high values during winter and low ones during summer due to the increased digestion rate. The maximum high-density sludge height observed was 0.7m, or 2% (14 m3) of the total pond volume. The maximum volatile sludge accumulation reached 3.1 m, or 53% (300 m3) of the pond volume. A seasonal sludge accumulation model, based on the sludge inflow and seasonal digestion rates, was used to simulate the annual fluctuation in accumulation rate for the local (Mediterranean type) climatic conditions. Monthly values of accumulation (or digestion) rate of sludge (K(AS)) were experimentally estimated at specific mean monthly air temperatures and approximated by a regression second degree polynomial equation to be used with the model. The predicted desludging interval for our experimental pond was 3 years.

Bacteria, Anaerobic↗
PubMed2003

The effects of variation in climatic temperature (1980-2001) on breeding activity and tadpole stage duration in the common toad, Bufo bufo.

The effects of variation in climatic temperature on breeding behaviour and tadpole growth were investigated using data collected during a 22-year study of a single population of common toads, Bufo bufo, in southern England. Although the start of the breeding season each year, taken as the day when adult toads first arrived at their breeding pond in large numbers, showed no trend over time (1980-2001) it was highly correlated with climatic temperature. Thus, toads started breeding approximately 50 days earlier in the year following very mild winters (1993: February 2nd) compared with very cold ones (1986: March 23rd). Regression analysis of the relationship between the mean temperature of the 40 days immediately preceding the main arrival of toads at the breeding pond revealed that for every 1 degrees increase (or decrease) the toads arrived 12 days earlier (or later). Although the duration of the tadpole stage was longer when spawning was early, toadlets still emerged from the pond earlier than when spawning was late. The increased length of the tadpole stage, in years when spawning was early, was due to an increase in the proportion of cold days when the minimum ground temperature was at or below 0 degrees C. Thus, the tadpole stage was approximately 6 days longer (or shorter) for every 5% increase (or decrease) in the proportion of cold days the tadpoles were exposed to.

Animals↗
PubMed2003

Modelling intertidal sediment transport for nutrient change and climate change scenarios.

A model of intertidal sediment transport, including effects of bioturbation and biostabilisation, was applied to two transects on the east coast of England: Leverton (within the Wash) and Skeffling (in the Humber Estuary). The physical and biological parameters were chosen to represent four 1-year scenarios: a baseline year (1995), the same year but with estuarine nitrate inputs reduced by 50% and by 16%, and a year with climate change effects estimated for 2050. The changes in nitrate supply can potentially change microphytobenthos numbers within the surface sediment, which will then affect erodibility. The model results show a range of behaviour determined by bathymetry, external forcing and biotic state. When intertidal sediment transport is dominated by external sediment supply, the model produces highest deposition at the most offshore point, and there is greatest deposition in the winter and spring, when offshore sediment concentrations are highest. When intertidal processes dominate intertidal sediment transport, there is a peak of deposition at the high-shore level and erosion at mid-tide levels. The greatest deposition now occurs in winter and summer, when low chlorophyll levels mean that the sediment is most erodible. The Skeffling transect was dominated by intertidal processes for the baseline scenario and with a 16% reduction in nitrate. Under the climate change (warm winter) scenario, the Skeffling transect was dominated by external sediment supply. The scenario with 50% reduction in nitrate gave intermediate behaviour at Skeffling (intertidally driven during the winter and summer, and governed by offshore sediment supply during spring and autumn). The Leverton transect was dominated by offshore sediment supply for all the scenarios.

Chlorophyll↗
PubMed1991

Climatic droplet keratopathy with corneal amyloidosis.

Climatic droplet keratopathy (CDK) is a degenerative disease of the cornea, highly prevalent in Saudi Arabia. It is characterized by aggregates of small, golden-yellow globules that accumulate in the subepithelial layers, Bowman's layer, and the superficial stroma of the cornea. The authors report on 22 patients (40 eyes) with CDK and lattice lines in the cornea. The condition occurred late in life (mean age, 67 years). It was bilateral in 82% of patients, with no family history of lattice dystrophy or systemic amyloidosis. These lines were found in all layers of the stroma. Results of histopathologic and electron microscopic examination of the lattice lines confirmed the presence of amyloid. Results of immunohistochemical examination showed evidence of deposition of AP protein. The cause of these deposits in the cornea is not known, but the authors speculate that environmental factors causing CDK also may play a role in the deposition of protein AP in the cornea. The contribution of trachoma to the degenerative changes in the cornea and secondary amyloidosis could not be ruled out, as all patients had inactive trachoma. Climatic droplet keratopathy with corneal amyloidosis, therefore, represents a form of "lattice degeneration" of the cornea.

Adult↗
PubMed2004

An examination of seasonality experienced by Australians living in a continental temperate climate zone.

BACKGROUND: To date, there has been only limited information on factors associated with seasonal changes in mood and behaviour experienced by a random sample of Australians living in a continental temperate climate region. This paper identifies socio-demographic, psychological and personality factors associated with reporting higher levels of seasonality. METHOD: Information on seasonal change using the Seasonal Pattern Assessment Questionnaire (SPAQ) was obtained from 7485 persons in three age groups. Age and sex differences in seasonality scores were examined. Those meeting probable caseness for seasonal affective disorder were identified and compared with less-seasonal participants on a range of state and trait measures. RESULTS: Levels of seasonality reported by survey participants were comparable to those reported in northern hemisphere studies of randomly selected community samples. However, these levels were significantly lower than other key studies outside Australia and previous Australian findings. Compared with less-seasonal participants, those reporting seasonal change had more current depressive and anxiety symptoms and higher levels of negative affect, regardless of season of interview. LIMITATIONS: This study is likely to over-estimate the number of participants who meet requirements for caseness for seasonal affective disorder. CONCLUSION: Levels of seasonality experienced by a random sample of Australians living in a temperate climate are comparable to those reported by similar groups in the northern hemisphere. Importantly, this study found that those experiencing higher levels of seasonality had significantly more current depressive symptoms than less-seasonal participants across all seasons. These results raise questions about the usefulness of the SPAQ as a measure of seasonal variation in mood and behaviour.

Adult↗
PubMed1999

A climate-based distribution model of malaria transmission in sub-Saharan Africa.

Malaria remains the single largest threat to child survival in sub-Saharan Africa and warrants long-term investment for control. Previous malaria distribution maps have been vague and arbitrary. Marlies Craig, Bob Snow and David le Sueur here describe a simple numerical approach to defining distribution of malaria transmission, based upon biological constraints of climate on parasite and vector development. The model compared well with contemporary field data and historical 'expert opinion' maps, excepting small-scale ecological anomalies. The model provides a numerical basis for further refinement and prediction of the impact of climate change on transmission. Together with population, morbidity and mortality data, the model provides a fundamental tool for strategic control of malaria.

Africa South of the Sahara↗
PubMed2002

Characterization of flow and transport processes within the unsaturated zone of Yucca Mountain, Nevada, under current and future climates.

This paper presents a large-scale modeling study characterizing fluid flow and tracer transport in the unsaturated zone of Yucca Mountain, Nevada, a potential repository site for storing high-level radioactive waste. The study has been conducted using a three-dimensional numerical model, which incorporates a wide variety of field data and takes into account the coupled processes of flow and transport in the highly heterogeneous, unsaturated fractured porous rock. The modeling approach is based on a dual-continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. Various scenarios of current and future climate conditions and their effects on the unsaturated zone are evaluated to aid in the assessment of the proposed repository's system performance using different conceptual models. These models are calibrated against field-measured data. Model-predicted flow and transport processes under current and future climates are discussed.

Climate↗
PubMed2002

Gaseous carbon dioxide and methane, as well as dissolved organic carbon losses from a small temperate wetland under a changing climate.

Temperate forests can contain large numbers of wetlands located in areas of low relief and poor drainage. These wetlands can make a large contribution to the dissolved organic carbon (DOC) load of streams and rivers draining the forests, as well as the exchange of methane (CH4) and carbon dioxide (CO2) with the atmosphere. We studied the carbon budget of a small wetland, located in Kejimkujik National Park, Nova Scotia, Canada. The study wetland was the Pine Marten Brook site, a poor fen draining a mixed hardwood-softwood forest. We studied the loss of DOC from the wetland via the outlet stream from 1990 to 1999 and related this to climatic and hydrologic variables. We added the DOC export information to information from a previously published model describing CH4 and CO2 fluxes from the wetland as a function of precipitation and temperature, and generated a new synthesis of the major C losses from the wetland. We show that current annual C losses from this wetland amount to 0.6% of its total C mass. We then predicted that under climate changes caused by a doubling of atmospheric CO2 expected between 2040 and 2050, total C loss from the wetland will almost double to 1.1% of total biomass. This may convert this wetland from what we assume is currently a passive C storage area to an active source of greenhouse gases.

Carbon↗
PubMed1999

Current concerns about control programs in temperate climates.

Efforts to control cyathostome nematodes in temperate climates have not been uniformly successful, as evidenced by contemporary reports of clinical disease and widespread anthelmintic failure. Indeed, effective control is confounded by numerous factors, including ignorance of local transmission patterns, confusing or conflicting control recommendations, and use of ineffective anthelmintics or regimens. Most of these problems are universal rather than being climatically unique, and it is important to recognize that they are mere symptoms of larger and more comprehensive problems. The most basic problem in managing cyathostomes is inadequate knowledge of biological factors that influence control recommendations. These include population dynamics, arrested development, host resistance, and regional bionomics. Another hindrance is the absence of objective criteria to define effective control. Target fecal egg counts are arbitrary and subjective, and parameters to measure the subclinical impact of cyathostome infection in well-managed horses have not been identified. The final general challenge to effective parasite control is motivation and education of equine practitioners and horse owners, who currently receive much of their parasite control information in the form of biased advertising. Ultimately, more effective equine parasite control will result from collaborative efforts of basic research, clinical application, and improved information transfer.

Animals↗
PubMed1999

Seasonal transmission of equine cyathostomes in warm climates.

Few studies investigating the seasonal transmission of equine cyathostomes have been done in warm climates. Two Australian studies used experimentally-infected plots to determine hatching, development and survival of free living stages of equine cyathostomes. Four studies in the southern United States used pasture larval counts, and in some instances tracer animals, to determine seasonal availability of infective cyathostome larvae on naturally-infected pastures. With the exception of the dry Australian tropics, a general pattern of peak transmission of cyathostomes during the cooler seasons of the year and minimal transmission during the warmest seasons was observed. Infective larvae and developing stages survived poorly in hot weather, although the rate of development was most rapid during that time. In contrast, infective larvae and developing stages survived well in cool weather, although the rate of development was slower. Adequate moisture was crucial to cyathostome transmission in warm climates, thus hot, dry weather effectively sterilized a pasture, whereas cool, moist weather was optimum for transmission. These data suggest that suppression of cyathostome egg output in feces of horses beginning shortly before the onset of cooler and/or more moist weather, and continued through the favorable period for development and survival of larvae on pasture - usually the autumn and winter should provide adequate control of these parasites. However, the efficacy of such seasonal control programs has yet to be adequately tested against that of traditional year round treatments.

Animals↗
PubMed2003

Climatic and diurnal variation in suicide attempts in the ED.

The aim of this study was to determine whether there is a relationship between climatic factors and suicidal behavior. A total of 1,119 suicide attempts were collected from hospital records between 1996 and 2001. A clear seasonal variation was seen in suicide attempts in the 15-24, 25-34, and over 65 age groups in men and in the 15-24, 25-34, and 35-44 age groups in women with peaks in the spring and summer. Suicide attempts were more frequent between the hours of 6:00-9:00 pm in males and 3:00-6:00 pm in females. People attempting suicide who have depression, anxiety, or a psychotic disorder usually attempt suicide in the summer. Whereas the monthly averages of humidity, ambient temperature, duration and intensity of sunlight were positively correlated with the number of monthly suicide attempts, cloudiness and atmospheric pressure were negatively correlated. In conclusion, we must keep in mind that suicides and suicide attempts are not only the effect of climatic changes and that the most important component is the individual's ability to deal with conflicts.

Adolescent↗
PubMed1986

Epidemiology and control of parasites in warm climates.

The kind of parasites a horse acquires depends upon its environment. Because patterns of transmission vary greatly with climate and management, no one worming program has universal applications. This article discusses epidemiology and control of equine parasites in the southern United States, where climates vary from warm temperate to subtropical and from humid in the southeast to arid in the southwest.

Animals↗