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PubMed2006

Wet-season dormancy release in seed banks of a tropical leguminous shrub is determined by wet heat.

BACKGROUND AND AIMS: Hard-seeded (physical) dormancy is common among plants, yet mechanisms for dormancy release are poorly understood, especially in the tropics. The following questions are asked: (a) whether dormancy release in seed banks of the tropical shrub Parkinsonia aculeata (Caesalpiniaceae) is determined by wet heat (incubation under wet, warm to hot, conditions); and (b) whether its effect is modified by microclimate. METHODS: A seed burial trial was conducted in the wet-dry tropics (northern Australia) to compare dormancy release across different habitats (open, artificial cover, ground cover and canopy cover), burial depths (0, 3 and 20 cm) and burial durations (2, 6 and 14 weeks). Results were compared with predictions using a laboratory-derived relationship between wet heat and dormancy release, and microclimate data collected during the trial. KEY RESULTS: Wet heat (defined as the soil temperature above which seeds were exposed to field capacity or higher for a cumulative total of 24 h) was 43.6 degrees C in the 0 cm open treatment, and decreased with increasing shade and depth to 29.5 degrees C at 20 cm under canopy cover. The dormancy release model showed that wet heat was a good predictor of the proportion of seeds remaining dormant. Furthermore, dormancy release was particularly sensitive to wet heat across the temperature range encountered across treatments. This resulted in a 16-fold difference in dormancy levels between open (<5 % of seeds still dormant) and covered (82 %) microhabitats. CONCLUSIONS: These results demonstrate that wet heat is the principal dormancy release mechanism for P. aculeata when conditions are hot and wet. They also highlight the potential importance of microclimate in driving the population dynamics of such species.

Fabaceae↗

PubMed1991

The effect of E. coli STa enterotoxin on the absorption of weakly dissociable anti-malarial drugs from rat intestine in vivo.

1. The effect of E. coli heat stable (STa) enterotoxin on the absorption of radiolabelled anti-malarial weak bases and their appearance in peripheral blood was assessed in vivo by a recirculation procedure in rat intestinal loops. 2. Enterotoxin increased the jejunal disappearance of quinine (P less than 0.05), trimethoprim (P less than 0.05), proguanil (P less than 0.05) and chloroquine (P less than 0.001) and left pyrimethamine disappearance unaltered. Peripheral blood levels of trimethoprim (P less than 0.02) and proguanil (P less than 0.05) were higher after STa exposure. 3. In the ileum, enterotoxin increased the luminal disappearance (P less than 0.05) and peripheral blood appearance (P less than 0.001) of chloroquine. The luminal disappearance rate of trimethoprim was reduced (P less than 0.05) and that of pyrimethamine unchanged. 4. The increased jejunal absorption of the anti-malarial drugs occurred despite STa causing a reduction in the amount of net fluid absorption. It seems likely that the enhanced absorption with STa exposure is related to the effect of STa on the microclimate pH. An elevation in the microclimate pH would increase the amount of undissociated weak base available for non-ionic diffusion. 5. The favourable elevation of microclimate pH by STa seemed to be outweighted by the reduced fluid absorption in the ileum. Only chloroquine still showed enhanced absorption in the ileum and this may have been because unlike the other antimalarial drugs, chloroquine has two dissociable groups likely to be affected by the mucosal surface pH changes.

Acid-Base Equilibrium↗

PubMed1992

Effect of theophylline on the intestinal clearance of drugs in rats.

Intestinal exsorption of salicylic acid, urea and quinidine was measured during the perfusion of the rat intestinal lumen with Tyrode solution. The intestinal clearance (CLi) of the three compounds was measured by dividing the rate of appearance in the intestinal luminal perfusate by the plasma concentration of the compound. Co-administration of theophylline (0.2 mg h-1) with the test agents increased the CLi of salicylic acid, did not alter the CLi of urea, but decreased the CLi of quinidine. The effect of theophylline on the CLi of quinidine was enhanced with increasing dose. Theophylline was found to increase microclimate-pH at the intestinal surface, but the magnitude of delta pH alone could not explain the effect of theophylline on the CLi of quinidine. The data, together with previous observations, suggest that the intestinal exsorption of drugs was affected by the microclimate pH and by the unstirred water layer. Theophylline affects CLi of salicylic acid and quinidine partly by increasing the microclimate pH of the intestine. Theophylline may also affect quinidine CLi by inhibiting the carrier-mediated pathway.

Algorithms↗

PubMed1992

Concentration-dependent exsorption of quinidine in the rat intestine.

During intravenous infusion, the luminal concentration of quinidine was higher than the plasma concentration. The intestinal clearance (CLi) of the drug was measured by dividing the rate of appearance of the drug in the intestinal luminal perfusate by the plasma concentration. The CLi of quinidine was therefore much higher than the rate of luminal perfusion. Over the infusion dose range of 0.1-2 mg h-1, the CLi of quinidine decreased with increasing plasma concentration of quinidine. Adding quinidine into the luminal perfusate had little effect on the CLi of quinidine. Co-administration of quinidine with other agents intravenously did not alter the CLi of salicylic acid and urea, while the same treatment decreased the CLi of theophylline and S-disopyramide. In-vitro experiments on brush-border membrane vesicles showed that quinidine decreased the rate of Na+ uptake and H+ efflux. The inhibition was significant at quinidine concentrations above 20 microM. Quinidine was a more potent inhibitor than amiloride. At quinidine infusion rates less than 2 mg h-1, quinidine concentration in plasma or in the luminal perfusate was at the lower limit of the inhibitory concentration. Microclimate pH at the intestinal surface was also measured. At mid-jejunum, the microclimate pH increased 0.3 pH units by infusing 2 mg h-1 of quinidine, while the microclimate pH at most other measuring sites was not significantly altered by quinidine infusion. It was concluded that quinidine is exsorbed from blood into the intestinal lumen by a carrier-mediated pathway in addition to the passive diffusion. At high plasma concentration, quinidine exsorption becomes saturated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Annual fluctuations in rheumatoid arthritis.

A literature survey revealed many reports implicating the microclimate and seasonal changes in arthritic diseases. Therefore, a retrospective study of the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) concentration of 2,802 rheumatoid arthritis (RA) was performed. No statistically significant fluctuation was found when analyzed according to the month of the year in which blood was taken. The significance of this is discussed in relation to other RA symptoms, meteorologic phenomena, microclimate, and the joint circulatory responses in RA. The observations reported are consistent with the concept that seasons and microclimate may affect some of the symptoms of RA, but not the inflammatory processes represented by the ESR and CRP.

Arthritis, Rheumatoid↗

PubMed1995

Metabolic rates and thermal conductance in four species of neotropical bats roosting in hot caves.

Data are presented on metabolic rates and thermal conductance for four species of neotropical bats, Pteronotus quadridens, Mormoops blainvillii (Mormoopidae), Monophyllus redmani and Erophylla bombifrons (Phyllostomidae). Each of these bats predominantly or exclusively roosts in hot caves (28-40 degrees C) in Puerto Rico. Basal metabolic rates (BMR) for these four species were 55%, 48%, 66%, and 66% of values expected from the Kleiber curve, respectively. Thermal conductance was 93%, 55%, 175%, and 158% of values expected from the Aschoff curve, respectively. These data indicate that, in addition to food habits, variation in BMR is highly correlated to roost microclimate. Pteronotus and Mormoops, like other insectivorous species, have low BMRs. The low BMR of the nectar/fruit eating Monophyllus and Erophylla, as well as the low termal conductance in Mormoops, is consistent with their habit of roosting in hot caves, suggesting that roost microclimate is an important selective force in the physiological adaptation of these bats.

Adaptation, Physiological↗

PubMed2005

Environmental physiology of three species of Collembola at Cape Hallett, North Victoria Land, Antarctica.

The environmental physiology of three speciesof Collembola: Cryptopygus cisantarcticus, Isotoma klovstadi (Isotomidae) and Friesea grisea (Neanuridae) was investigated from November 2002 to February 2003 at Cape Hallett, North Victoria Land, Antarctica. All three species were freeze avoiding, and while supercooling points were variable on seasonal and daily scales in I. klovstadi and C. cisantarcticus, they remained largely static in F. grisea. LT50 (temperature where 50% of animals are killed by cold) was -13.6, -19.1 and -19.8 degrees C for C. cisantarcticus, I. klovstadi and F. grisea, respectively. Upper lethal temperature was 34, 34 and 38 degrees C for C. cisantarcticus, I. klovstadi and F. grisea. Critical thermal minimum onset (the temperature where individuals entered chill coma) was ca. -7, -12 and -8 degrees C for C. cisantarcticus, I. klovstadi and F. grisea, and 25% of I. klovstadi individuals froze without entering chill coma. Critical thermal maximum (the onset of spasms at high temperature) was 30, 33 and 34 degrees C for C. cisantarcticus, I. klovstadi and F. grisea. Haemolymph osmolality was approximately 720 mOsm for C. cisantarcticus and 680 mOsm for I. klovstadi, and both species showed a moderate degree of thermal hysteresis, which persisted through the season. Desiccation resistance was measured as survival above silica gel, and the species survived in the rank order of C. cisantarcticus<< I. klovstadi = F. grisea. Desiccation resulted in an increase in haemolymph osmolality in I. klovstadi, and water was quickly regained by desiccation-stressed individuals that had access to liquid water, but not by individuals placed in high humidity, indicating that this species is unable to absorb atmospheric water vapour. SDS-PAGE did not suggest any strong patterns in protein synthesis either seasonally or in response to temperature or desiccation stress. Microclimate temperatures were measured at sites representative of collection sites for the three species. Microclimate temperatures were highly variable on a diurnal and weekly scale (the latter relating to weather patterns), but showed little overall variation across the summer season. Potentially lethal high and low temperatures were recorded at several sites, and it is suggested that these temperature extremes account for the observed restriction of the less-tolerant C. cisantarcticus at Cape Hallett. Together, these data significantly increase the current knowledge of the environmental physiology of Antarctic Collembola.

Animals↗

PubMed2004

Analysis and design of micro-climate around the human body with respiration by CFD.

UNLABELLED: This paper reviewed the CFD (Computational Fluid Dynamics) study conducted by our group on analyzing and designing the microclimate surrounding the human body. First, it describes the analysis results of flow and temperature fields around the human body. Next, it refers to the analysis and design of the quality of air inhaled and exhaled by the human body. Lastly, it describes the CFD and experimental study on the microclimate around the eyes, focusing on dry eye syndrome. PRACTICAL IMPLICATIONS: The CFD method presented will be a valuable and powerful tool for analysis and design of healthy indoor environments.

Air Movements↗

PubMed2006

[Temperature modifications in shantytown environments and thermal discomfort].

OBJECTIVE: To study aspects of the microclimate in a shantytown (favela), in order to understand the influence of the land occupation pattern on its climatic parameters. METHODS: The study was carried out in a shantytown located in the southwestern region of the city of São Paulo, Brazil, between February 19 and July 31, 2003, i.e. covering the whole autumn and parts of the summer and winter. The air temperatures were measured every hour on a microclimate scale, at four points within this densely populated shantytown and, as a control, on a tree-lined street nearby. RESULTS: In the summer, the average hourly temperatures in the shantytown were between 18.5 degrees C and 29.5 degrees C but, away from it, they were 2 degrees C to 3 degrees C lower at the hottest times of the day. In the autumn, the temperatures ranged from 15.5 degrees C to 25.5 degrees C and in the winter, 13.5 degrees C to 25.5 degrees C. The chilliest time in the shantytown was before dawn in the autumn and at 7 a.m. in the winter. The temperature variation was greater inside the shantytown than outside of it. The temperatures were within the comfort range for around 50% of the time. Temperatures below the lower limit (18 degrees C) were more frequent than those above the upper limit (24 degrees C). Temperatures above the upper limit were more frequent in the shantytown than outside of it. CONCLUSIONS: The land occupation is a temperature differentiation factor. In the shantytown, the temperatures were higher during the daytime (by up to 3 degrees C) and lower at nighttime (by 1 degrees C on average). The shantytown environment accentuated the temperature extremes, while the temperatures in the control street were milder.

Brazil↗

PubMed1975

Population structure and dynamics of the house dust mite Dermatophagoides farinae (Acarina: Pyroglyphidae) in Czechoslovakia.

The relationship between the room microclimate and population dynamics of the house dust mite Dermatophagoides farinae Hughes, 1961 was studied. A distinct increase of the mite population density in mattresses was observed only in the period, when the monthly means of relative air humidity in rooms were higher than 47-50%, denominated by the author as critical air humidity. This is a considerably lower value than that relevant to Dermatophagoides pteronyssinus (Trouessart, 1897) from the paper by Bronswijk et al. (1971) (critical air humidity 60-65%). The climatic humidity affecting the room microclimate is consequently the main reason why one species or another is predominant under different geographical conditions. From October till May the D. farinae population is primarily composed of protonymphs, in the period of maximum population density (May-October) the presence of adults is predominant. Protonymphs are considered to be least resistant to the humidity decrease in their environment.

Animals↗

PubMed2002

[Effects of free-air CO2 enrichment on rice canopy microlimate].

In this study, the free-air CO2 enrichment (FACE) system (setup at at Anzhen, Wuxi, Jiangsu Province in 2001) was used to investigate the effects of FACE on rice canopy microclimate. The rice canopy microclimate observations were carried out from August 26 to October 13, 2001, when the rice crops were at the heading to maturing development stage. The results showed that FACE reduced the rice leaf stomatal conductance. The rice leaf stomatal conductance difference between FACE and ambient was larger among upper layer leaves than among lower layer leaves and at heading and milk filling stages than at maturing stage. FACE increased daytime rice canopy temperature but had little effect on nighttime rice canopy temperature. The daytime rice canopy temperature difference between FACE and ambient was larger at heading and milk filling stages than at maturing stage. From heading to flowering, the daily maximum rice canopy temperature difference between FACE and ambient reached 1.2 degrees C under fine weather condition. The average daytime rice canopy temperature from flowering to maturing stage was about 0.43 degree C. Daytime air temperature inside rice canopy was also affected by FACE. Daytime air temperature inside rice canopy was higher in FACE plot than in ambient plot. The value of daytime air temperature difference between FACE and ambient increased with the increase of solar radiation and varied with height. The maximum daytime air temperature difference between FACE and ambient varied between 0.47-1.2 degrees C and 0.37-0.8 degree C at middle of canopy and canopy height, respectively. Air humidity and nighttime air temperature inside rice canopy were not significantly affected by FACE. These results indicate that FACE reducing rice leaf stomatal conductance was the major cause of the increase of canopy temperature and inside canopy air temperature in FACE plot. The higher canopy temperature and inside canopy air temperature in FACE plot resulted in the earlier maturity of rice crop in FACE plot than that in the ambient plot.

Air↗

PubMed1991

[Physiological and hygienic characteristics of working conditions of bus drivers in the Tadzhik SSR].

In warm seasons of the year, the major unfavourable factors in the labour conditions of bus-drivers engaged in local and transrepublican bus routes were heating microclimate, neuropsychic and physical overload, excessive noise levels. The unsatisfactory labour conditions resulted into strain and overstrain of the thermoregulatory function and cardio-vascular system, decreased working capacity and increased fatiguability, as well as in development of nonspecific pathology in the drivers. Improving of the labour conditions should include measures towards optimization of the microclimate and modernization of the cabin's design, rationalization of the labour regimen and improvement of services on the roads.

Automobile Driving↗

PubMed1991

[Thermal body condition of workers in the Dushanbe house-building complex].

Performed was a hygienic assessment of the occupational microclimate conditions in constructional industry site in Tajikistan. The article provides data on the work load and heat-related state of workers in major professions. It was established that, in the hot and dry climate conditions, the major factor is infavourable microclimate: heat in summer and cold in winter, which resulted in heat disbalances in workers.

Adult↗

PubMed1991

[Morbidity with temporary disability of the workers of coal-processing factories].

A profound analysis of morbidity with temporary disability (MTD) revealed low health states of the women engaged in coal preparation plants in both Northern and Southern regions of the country. The results obtained proved the major role of labour conditions in the structure of the MTD levels, particularly in such diseases as acute respiratory (dust, hazardous microclimate), hypertension (noise), vascular dystonia (noise and vibration), radiculitis and myositis (poor microclimate). The data proposed a basis for planning health improvement measures.

Adult↗

PubMedDate not supplied

[Ergonomic evaluation of working conditions and the possibilities of their optimal improvement in small slaughterhouses].

Assessment of working conditions in small slaughter-butcher workshops was based on the measurements of microclimate, illumination intensity, noise level, physical work, load, health risk factors and of other parameters which increased the work strenuousness. The analysis showed that the working conditions were harmful, mainly due to unfavourable microclimate, too poor illumination and the magnitude of physical load which reached mid-heavy and heavy levels. Based on performed analysis of occupational hazards a list of simple technical procedures which could improve working conditions was established by the authors.

Abattoirs↗

PubMed1990

[The cardiopulmonary age of workers in hot jobs in glass manufacture].

Data are reported on the effect of heating microclimate on the enhancement of functional aging of the cardiovascular system in workers of the glass industry. It is shown that enhancement of the aging tempo was noted during the first 5 years of work in condition of hot microclimate and following 15 years of work in these conditions. The enhancement of biological aging of the individual is also influenced by the age of the worker beginning to work in conditions of hot climate.

Adult↗

PubMed1989

[Use of preventive reflexotherapy in workers at an electrode-manufacturing plant].

Reflexoprevention was carried out in 5 workers engaged in electrode production and exposed to such occupational factors as high gas and dust loading, heating microclimate, significant physical stress at workplace. Electropuncture was carried out by means of an electrostimulator EPB-50-01. The workers were exposed only to heating microclimate and physical load. Positive effect of reflexoprevention was confirmed.

Acupuncture Therapy↗

PubMed1989

[Hygienic characteristics of working conditions and their effect on the functional state of workers engaged in the manufacture of reinforced concrete products].

The study of the impact of working conditions on body functioning state of those engaged in the production of reinforced concrete products showed that these working conditions were characterized by a number of unfavourable factors, complex occupational aerosol and industrial microclimate being the leading ones. It was pointed out that working conditions affected the degree and the character of shifts in workers' body functioning state. Climatic and geographical characteristics also had some influence on the parameters of occupational microclimate and workers' body functioning state.

Adult↗