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At least 217 records · Page 12Linked to original sources

PubMed2001

Chill-coma tolerance, a major climatic adaptation among Drosophila species.

Most drosophilid species can be classified either as temperate or tropical. Adults of species were submitted to a cold treatment (0 degrees C) and then brought back to ambient temperature. They generally exhibited a chill coma and the time needed to recover was measured. We found in a set of 26 temperate species that recovery was rapid (average 1.8 min, range 0.15-4.9). In contrast, a long recovery time (average 56 min, range 24-120) was observed for 48 tropical species. A few species, like Drosophila melanogaster, are cosmopolitan and can proliferate under temperate and tropical climates. In 9 of 10 such species, slight genetic differences were found: a shorter recovery in temperate than in tropical populations. Comparing physiological data to phylogeny suggests that chill-coma tolerance has been a recurrent adaptation that is selected for in cold climates but tends to disappear under a permanently warm environment. This major climatic adaptation, evidenced in drosophilids, seems to occur in other insect groups also.

Acclimatization↗

PubMed2005

Seasonality in vestibular disorders.

Our objective in this study was to evaluate a causal relationship between vestibular pathological findings and climatic variations during the year (summer, autumn, winter, and spring). The study was conducted in a Brazilian clinic located in a tropical climate and having well-defined warm and cold weather. For this retrospective study, our outpatients were the subjects, and the diagnosis was made on the basis of clinical (ear, nose, and throat) and electronystagmographic evaluation. Data were collected, matched with the year's seasons, and analyzed for significance statistics. We found no significant differences among the illnesses in relation to the climatic seasons. We concluded that a correlation did not exist between annual seasons and vestibular disorders in our environment.

Adolescent↗

PubMed2003

[Prevalence of varicella-zoster virus antibodies in young adults from different Brazilian climatic regions].

To evaluate the prevalence of varicella-zoster virus infection in young adults from different Brazilian urban regions, 975 serum samples from blood donors aged 20 to 29 years, from tropical climate cities (Salvador and Fortaleza) and from temperate climate cities (S o Paulo, Curitiba and Porto Alegre) were tested by an in-house ELISA for detection of anti-varicella-zoster virus IgG antibodies. The overall prevalence was 94.2%. The lowest rate was observed in Fortaleza (88.7%) and the highest in Curitiba (99.5%). Seroprevalence in tropical regions of Brazil (89.4%) was significantly higher than in temperate regions (97.3%), a similar pattern to that observed in other tropical countries.

Adult↗

PubMed1979

Biochemical changes of normal pregnancy and puerperium in Lagos, Nigeria.

A cross-sectional study is presented of biochemical changes in the third trimester of normal pregnancy and puerperium during the wet season in the tropical climate of Lagos, Nigeria. These changes are less marked in first than in subsequent pregnancies, and although qualitatively similar, in some respects they differ from those observed in the temperate climatic zone. The indications are that quantitative differences may exist which could be relevant to the management of pregnancy in the tropics.

Adult↗

PubMed1988

Incidence of enteric adenoviruses among children in Thailand and the significance of these viruses in gastroenteritis.

In countries with temperate climates, enteric adenoviruses have been shown to be a substantial cause of pediatric gastroenteritis. To determine the incidence of adenovirus infection in a tropical climate, stools were collected from children under age 7 during a 1-year period at an outpatient clinic in Bangkok, Thailand. Stools from 1,114 children with gastroenteritis and from 947 children without gastroenteritis were tested. Each stool was tested for adenovirus group antigen and for specific enteric adenovirus types (Ad40 and Ad41) by monoclonal antibody enzyme immunoassays. We found that 4.4% (49 of 1,114) of children with gastroenteritis and 1.8% (17 of 947) of children without gastroenteritis were positive for adenovirus group antigen. In tests for specific enteric adenovirus types, 2.0% (22 of 1,114) of the tests were positive in children with gastroenteritis and 0.6% (6 of 947) were positive in children without gastroenteritis. There was a significant correlation (P less than 0.02) of gastroenteritis with nonenteric adenovirus types (27 of 1,114) as well as with specific enteric adenovirus types (P less than 0.01). By comparison, 19.7% of children with gastroenteritis and 0.7% of those without gastroenteritis were positive for rotavirus infection. In the adenovirus-infected children with gastroenteritis, there were coinfections with rotavirus only in those with nonenteric adenovirus infection (7 of 27 children). There were no significant differences in the association of bacterial or parasitic infections with either enteric or nonenteric adenovirus infections in either group of children studied. These data demonstrate that Ad40 and Ad41 are causes of gastroenteritis in this population, but among the spectrum of diarrheal etiologies, they may be proportionately less important than they are in countries with temperate climates.

Adenoviridae Infections↗

PubMed2005

Diversity of flowering and fruiting phenology of trees in a tropical deciduous forest in India.

BACKGROUND AND AIMS: In the dry tropics, vegetative phenology varies widely with tree characteristics and soil conditions. The present work aims to document the phenological diversity of flowering and fruiting with reference to leafing events in Indian dry-tropical tree species. METHODS: Nine tree species, including one leaf-exchanging and eight deciduous showing varying leafless periods, were studied. Monthly counts of leaves, flowers and fruits were made on 160 tagged twigs on ten individuals of each species for initiation, completion and duration of different phenological events through two annual cycles. KEY RESULTS: Variation in flowering relative to leaf flushing (which occurred just prior to or during a hot, dry summer) revealed five flowering types: summer flowering (on foliated shoots), rainy-season flowering (on foliated shoots following significant rains), autumn flowering (on shoots with mature leaves), winter flowering (on shoots undergoing leaf fall) and dry-season flowering (on leafless shoots). Duration of the fruiting phenophase was shortest (3-4 months) in dry-season and winter-flowering species, 6-9 months in rainy-and autumn-flowering species, and maximum (11 months) in summer-flowering species. A wide range of time lag (<1 to >8 months) between the start of vegetative (first-leaf flush) and reproductive (first-visible flower) phases was recorded in deciduous species; this time lag was correlated with the extent of the leafless period. A synthesis of available phenological information on 119 Indian tropical trees showed that summer-flowering species were most abundant (56 % of total species) amongst the five types recognized. CONCLUSIONS: The wide diversity of seasonal flowering and fruiting with linkages to leaf flush time and leafless period reflect the fact that variable reproductive and survival strategies evolved in tree species under a monsoonic bioclimate. Flowering periodicity has evolved as an adaptation to an annual leafless period and the time required for the fruit to develop. The direct relationship between leafless period (inverse of growing period) and time lag between onset of vegetative and reproductive phases reflects the partitioning of resource use for supporting these phases. Predominance of summer flowering coupled with summer leaf flushing seems to be a unique adaptation in trees to survive under a strongly seasonal tropical climate.

Biodiversity↗

PubMed1976

Forest to pasture: development or destruction?

The expansion of artifical or planted pastures (repasto) at the expense of both natural forest and cropland has brought major changes to the landscape and economy of Central America in recent years. On the pioneer fronts at the forest margin agriculture is commonly a transitory stage between forest felling and the establishment of permanent pasture. In the past 15 years the area in planted pasture and the total numbers of beef cattle have nearly doubled in several Central American countries while the per capita consumption of beef has actually declined. The "grassland revolution" that is occuring in Central America and Panama has been based almost exclusively on grass species of African origin which have in most cases been introduced into Central America only in this century. Of these jaragua, guinea, pangola, and kikuyu are the most important. The ecologic consequences of the conversion of forest to pasture are little understood. Intensive management practices, including the application of high-cost and scarce fertilizers and carefully-manged rotational grazing, will probably be necessary to sustain the productivity of these lands under conditions of tropical climate.

Agriculture↗

PubMed2004

High-latitude influence on the eastern equatorial Pacific climate in the early Pleistocene epoch.

Many records of tropical sea surface temperature and marine productivity exhibit cycles of 23 kyr (orbital precession) and 100 kyr during the past 0.5 Myr (refs 1-5), whereas high-latitude sea surface temperature records display much more pronounced obliquity cycles at a period of about 41 kyr (ref. 6). Little is known, however, about tropical climate variability before the mid-Pleistocene transition about 900 kyr ago, which marks the change from a climate dominated by 41-kyr cycles (when ice-age cycles and high-latitude sea surface temperature variations were dictated by changes in the Earth's obliquity) to the more recent 100-kyr cycles of ice ages. Here we analyse alkenones from marine sediments in the eastern equatorial Pacific Ocean to reconstruct sea surface temperatures and marine productivity over the past 1.8 Myr. We find that both records are dominated by the 41-kyr obliquity cycles between 1.8 and 1.2 Myr ago, with a relatively small contribution from orbital precession, and that early Pleistocene sea surface temperatures varied in the opposite sense to local annual insolation in the eastern equatorial Pacific Ocean. We conclude that during the early Pleistocene epoch, climate variability at our study site must have been determined by high-latitude processes that were driven by orbital obliquity forcing.

Alkenes↗

PubMed2006

Foliar temperature tolerance of temperate and tropical evergreen rain forest trees of Australia.

Australian rain forests extend from tropical climates in the north to temperate climates in the south, providing an opportunity to investigate physiological responses to temperature of both temperate and tropical species within the same forest type. Eight, rain forest canopy tree species were selected to cover the 33 degrees latitudinal range of rain forests in eastern Australia. Temperature tolerance was measured in 6-year-old plants grown in a common environment, by exposing leaves to a series of high temperatures during late summer and a series of freezing temperatures during midwinter. Damage was evaluated based on chlorophyll fluorescence measurements made 2 h after exposure and by visual assessment of leaf damage made a week after exposure. Leaves of the tropical species were more heat tolerant and less frost tolerant than leaves of the temperate species, which is consistent with their climate distributions. In contrast, the temperature tolerance of the photosynthetic apparatus was unrelated to climate in a species' native habitat. However, the tropical species underwent significant photoinhibition during winter. All species maintained the integrity of the photosynthetic apparatus and avoided tissue damage over a similar span of temperatures (about 60 degrees C), reflecting the similar annual temperature ranges in Australia's temperate and tropical rain forests. Chlorophyll fluorescence measurements and visual assessment of leaf damage provided different estimates of the absolute and relative temperature tolerances of the species, thus emphasizing the importance of a direct assessment of tissue damage for determining a species' temperature tolerance.

Australia↗

PubMed1994

Psoriasis in the tropics. Epidemiologic, genetic, clinical, and therapeutic aspects.

There is a dearth of information on psoriasis in the tropics. Psoriasis occurs more frequently in northern geographic regions than in tropical climates. Its prevalence varies not only within the ethnic groups of a country but from country to country. A review of published studies on the natural history of psoriasis in the tropics is presented in this article.

Africa↗

PubMed2001

Exercise-induced bronchoconstriction among Malay schoolchildren.

OBJECTIVE: Exercise-induced bronchoconstriction (EIB) may be demonstrated in 60-70% of asthmatic children in temperate climates. In areas of high humidity it is postulated to be low. The aim of the study was to determine the prevalence of EIB in a population of schoolchildren with wheezing, living in the humid tropical climate of Kuala Lumpur, Malaysia. METHOD: We performed a cross-sectional study using the International Study of Asthma and Allergies in Childhood questionnaire to identify 7-12-year-old Malay children with asthma symptoms from a primary school in central Kuala Lumpur. Sixty-five of 76 children with 'ever wheeze' performed an exercise challenge test successfully in an uncontrolled environment. A random sample of 80 schoolchildren with no history of wheeze were similarly tested as controls. The relative humidity and temperature were recorded. A fall of > 15% was considered as clinically important. RESULTS: The prevalence of EIB in schoolchildren with 'ever wheeze' was 47.7%. The prevalence of EIB in children with 'current wheeze' was 51.6%. The prevalence of EIB in controls was 7.5%. The relative humidity during the study ranged from 41 to 90%. There was no significant relationship between different humidity levels and EIB (P = 0.58, regression analysis). CONCLUSION: This study demonstrates that EIB is present in asthmatic children despite the highly humid tropical environment.

Asthma, Exercise-Induced↗

PubMed1998

Effect of dietary calcium and phosphorus concentrations on retention of these nutrients by caged layers.

1. A 5 x 3 factorial experiment was carried out with caged White Leghorn hens with 5 concentrations of calcium (26.0, 29.0, 32.5, 36.0, 39.0 g/kg) and 3 concentrations of phosphorus (4.3, 5.0 and 6.0 g/kg) for 120 d. Variables observed were hen day egg production, food consumption, shell weight, shell weight per unit surface area (SWUSA) and egg content. 2. 36.0 g calcium (Ca) and 4.3 g phosphorus (P) kg were found to be the dietary concentrations that resulted in optimal hen day egg production, shell weight, SWUSA and egg content. 3. Lack of a significant interaction between the effects of calcium and phosphorus on production parameters showed that the dietary Ca:P ratio is not of great importance for the laying hen. 4. Absolute retentions of Ca and P were inversely related to percentage retentions. 5. A balance study of calcium and phosphorus also showed optima at 36.0 g Ca and 4.3 g P per kg. 6. It was inferred that 36.0 g Ca and 5.0 g total P per kg are the optimal concentrations in diets for caged layers in a tropical climate.

Animal Feed↗

PubMed2006

Heart rate, thermoregulatory and humoral responses during a 9-day cycle race in a hot and humid climate.

Seven acclimated elite road cyclists were recruited from among the participants in the Tour de Guadeloupe, a 9-day cycle race (D1-D9) held in hot/humid climate (approximately 31 degrees C dry temperature and 76 % relative humidity). Each day of the competition, heart rate (HR) was recorded every 15 s, tympanic temperature (Ttym) was recorded before exercise and immediately at the end of each stage, and body mass loss (BML) was measured by changes in nude body mass at rest and after each stage. Blood lactate concentration [La] was measured at rest and 5 min after each stage. Venous blood samples were collected before the competition and on the 4 th and 8 th days (D4, D8) for hematological and serum determinations and biochemical analyses. No significant differences were found in cardiac, thermoregulatory, or [La] parameters at rest over the 9 days. The subjects spent 31 +/- 6 % of their time below the lactate threshold (LT), 52 +/- 8 % between LT and the onset of blood lactate accumulation (OBLA), and 18 +/- 6 % above OBLA. The increase in Ttym at D3 (0.48 +/- 0.3 degrees C) was significantly lower (p < 0.05) than at D1, D4, D5, and D6. No difference was found for BML between the different stages. Significant increases (p < 0.05) were observed in monocytes at D8 vs. D4 and pre-race values (D0) and in serum Cl-concentration at D4 vs. D0 and D8 (p < 0.05). A significant reduction was observed in mean corpuscular hemoglobin concentration (MCHC) at D8 and D4 vs. D0 (p < 0.01). No difference was found in other blood parameters at D0, D4, or D8. Taken together, these results suggest that a consecutive 9-day cycle competition in hot/humid climate did not alter homeostasis at rest in acclimated well-trained cyclists. No major effect of repeated cycling stages on thermoregulatory and blood parameters was observed during the Tour de Guadeloupe. Further research is needed to compare the cardiac adaptations of natives to tropical climate and un-acclimated subjects during long-duration exercise.

Adult↗

PubMed2006

A simple fluorogenic method to detect Vibrio cholerae and Aeromonas hydrophila in well water for areas impacted by catastrophic disasters.

The colony overlay procedure for peptidases (COPP) is a simple, fluorogenic assay that can rapidly detect and quantify Vibrio cholerae and Aeromonas hydrophila in well water. Cleavage of the substrate L-lysyl-7-amino-4-trifluoromethylcoumarin by enzymes present in Vibrio and Aeromonas species produces fluorescent foci on cellulose acetate membranes exposed to long-wave ultraviolet light. Vibrio cholerae O1, O139, O155, and A. hydrophila were readily detected using this procedure, whereas Enterobacteriaceae and other non-Vibrionaceae pathogens did not produce fluorescence. The assay is practical for assessing the relative safety of well water in areas that have experienced catastrophic devastation from natural disasters, acts of war, or civil strife and may help curb outbreaks of cholera and other enteric illnesses in affected areas. In tropical climates, the procedure may be adapted for use in areas without electricity.

Aeromonas hydrophila↗

PubMed1980

Racial differences in subcutaneous fat patterns in children aged 7--15 years.

In a stratified random sample of 278 children aged 7--15 years of an entire biracial community, skinfold measurements were taken on six standard body sites. We found that white children had generally thicker skinfolds than blacks for the same body weight, with a consistent exception: the subscapular skinfold was relatively thicker in blacks. It is suggested that this racial difference in distribution of fat may manifest a genetic adaptive trait developed under circumstances demanding both a caloric reserve and facilitation of convective heat loss in tropical climates.

Adaptation, Physiological↗

PubMed2004

Progesterone profiles and oestrous cycle changes following superovulatory treatment of Holstein-Friesian dairy cows in a tropical environment.

Changes of progesterone (P4) profiles and oestrous cycle were investigated up to 70 days in 20 superovulated Holstein-Friesian cows in a dry tropical environment (Brazil). Superovulated cows showed no significant differences in relation to P4 level at the time of embryo recovery (39.0 +/- 27.1 nmol/L, P = 0.536), first and second (12.0 +/- 6.0 and 10.7 +/- 2.2 nmol/L, P = 0.543) cycle. There was a close correlation between serum P4 concentration and the number of corpora lutea (CL; 13.3 +/- 9.5) at the recovery (P < 0.0001). After the embryo collection, cows returned to cycle in different ways: (i) group of donors returning to cycle after 2.2 +/- 0.8 days, (ii) group with a delay of 11.0 +/- 1.9 days; and (iii) animals having a long (28.8 +/- 2.2 days) acyclic period, which is significant (P < 0.001). The remaining animals (30%) showed cystic ovarian malformations. P4 level at the time of embryo recovery does not influence the oestrous cycle changes. The results suggest that Holstein-Friesian donor cows may suffer from cystic ovarian degeneration and may have a long acyclic period after superovulatory treatment in a tropical climate.

Adaptation, Physiological↗

PubMed1983

The concept of "productive adaptability" of domestic animals in tropical and subtropical regions.

The complex trait "productive adaptability" is shown to be a useful parameter for selection work in tropical climates. Characters such as rectal temperature in poultry and hair colour and structure in cattle used as indicators of heat tolerance prove to be of little value. "Productive adaptability" is also genetically more suited for selection procedures. Our results confirm that body size is a significant indicator of an animal's productive adaptability and that it is a suitable criterion for use in improving the genetic potential of livestock in warm climates. The special use of major genes in breeding programmes to improve productive adaptability is demonstrated.

Acclimatization↗

PubMed2003

Seasonal changes of CO(2), CH(4) and N(2)O fluxes in relation to land-use change in tropical peatlands located in coastal area of South Kalimantan.

Tropical peatland could be a source of greenhouse gases emission because it contains large amounts of soil carbon and nitrogen. However these emissions are strongly influenced by soil moisture conditions. Tropical climate is characterized typically by wet and dry seasons. Seasonal changes in the emission of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O) were investigated over a year at three sites (secondary forest, paddy field and upland field) in the tropical peatland in South Kalimantan, Indonesia. The amount of these gases emitted from the fields varied widely according to the seasonal pattern of precipitation, especially methane emission rates were positively correlated with precipitation. Converting from secondary forest peatland to paddy field tended to increase annual emissions of CO(2) and CH(4) to the atmosphere (from 1.2 to 1.5 kg CO(2)-C m(-2)y(-1) and from 1.2 to 1.9 g CH(4)-C m(-2)y(-1)), while changing land-use from secondary forest to upland tended to decrease these gases emissions (from 1.2 to 1.0 kg CO(2)-C m(-2)y(-1) and from 1.2 to 0.6 g CH(4)-C m(-2)y(-1)), but no clear trend was observed for N(2)O which kept negative value as annual rates at three sites.

Carbon Dioxide↗