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PubMed2006

Dynamics of spatial heterogeneity of stomatal closure in Tradescantia virginiana altered by growth at high relative air humidity.

The spatial heterogeneity of stomatal closure in response to rapid desiccation of excised well-watered Tradescantia virginiana leaves grown at moderate (55%) or high (90%) relative air humidity (RH) was studied using a chlorophyll fluorescence imaging system under non-photorespiratory conditions. Following rapid desiccation, excised leaves grown at high RH had both a greater heterogeneity and a higher average value of PSII efficiency (Phi(PSII)) compared with leaves grown at moderate RH. Larger decreases in relative water content resulted in smaller decreases in water potential and Phi(PSII) of high RH-grown leaves compared with moderate RH-grown leaves. Moreover, the Phi(PSII) of excised high RH-grown leaves decreased less with decreasing water potential, implying that the stomata of high RH-grown leaves are less sensitive to decreases in leaf water potential compared with moderate RH-grown leaves. After desiccation, some non-closing stomata were distributed around the main vein in high RH-grown leaves. Direct measurements of stomatal aperture showed 77% stomatal closure in the margins after 2 h desiccation compared with 40% closure of stomata in the main-vein areas in high RH-grown leaves. Faster closure of stomata in leaf margins compared with main-vein areas of leaves grown at high RH was related to substantially lower relative water content in these areas of the leaves.

Desiccation↗

PubMed2006

The role of abscisic acid in disturbed stomatal response characteristics of Tradescantia virginiana during growth at high relative air humidity.

In this study, the role of abscisic acid (ABA) in altered stomatal responses of Tradescantia virginiana leaves grown at high relative air humidity (RH) was investigated. A lower ABA concentration was found in leaves grown at high RH compared with leaves grown at moderate RH. As a result of a daily application of 20 microM ABA to leaves for 3 weeks during growth at high RH, the stomata of ABA-treated leaves grown at high RH showed the same behaviour as did the stomata of leaves grown at moderate RH. For example, they closed rapidly when exposed to desiccation. Providing a high RH around a single leaf of a plant during growth at moderate RH changed the stomatal responses of this leaf. The stomata in this leaf grown at high RH did not close completely in response to desiccation in contrast to the stomata of the other leaves from the same plant. The ABA concentration on a fresh weight basis, though not on a dry weight basis, of this leaf was significantly lower than that of the others. Moreover, less closure of stomata was found in the older leaves of plants grown at high RH in response to desiccation compared with younger leaves. This was correlated with a lower ABA concentration in these leaves on a fresh weight basis, though not on a dry weight basis. Stomata of leaves grown at moderate RH closed in response to short-term application of ABA or sodium nitroprusside (SNP), while for leaves grown at high RH there was a clear difference in stomatal responses between the leaf margins and main-vein areas. The stomatal aperture in response to short-term application of ABA or SNP at the leaf margins of leaves grown at high RH remained significantly wider than in the main-vein areas. It was concluded that: (i) a long-term low ABA concentration in well-watered plants during growth at high RH could be a reason for less or no stomatal closure under conditions of drought stress; and (ii) the long-term ABA concentration on a fresh weight basis rather than on a dry weight basis is likely to be responsible for structural or physiological changes in stomata during leaf growth.

Abscisic Acid↗

PubMed2000

Effects of relative humidity during the last five days of incubation and brooding temperature on performance of broiler chicks from young broiler breeders.

Broiler hatching eggs were subjected to one RH condition (53% RH) from 0 to 16 d and switched to one of three different RH conditions (43, 53, or 63%) from transfer at 16 d to pull time at 21.67 d of incubation. The broiler breeder ages were 27, 29, and 31 wk for Trial 1, and 26, 28, and 30 wk for Trial 2 in Experiment 1. For both trials, BW at hatch, BW at pull, hatch time, and chick weight loss between hatching and pull were measured. All unhatched eggs were opened and examined macroscopically. Experiment 2 was conducted using the chicks produced in Experiment 1. The chicks were immediately placed after pull and randomly distributed by sex into brooding pens by RH treatment in Trial 1, and by sex, RH, and brooding temperature in Trial 2. Two brooding conditions, warm and cool, were used in Trial 2. Body weight at placement, BW gain to 12 d, feed conversion, and mortality were recorded. There was no effect of RH treatment on fertile hatchability. Body weight at hatch, pull, and placement increased with hen age. Mortality was higher for the late-hatching chicks in the warm brooding conditions in Trials 1 and 2 of Experiment 2, whereas mortality was significantly greater for the early-hatching chicks and those chicks hatched at 43% RH under the cool-brooding temperature conditions. Relative humidity treatment had no effect on chick performance in the presence of warm brooding conditions. Warm brooding conditions improved BW gain to 12 d compared with cold brooding conditions. Overall, optimal chick performance was achieved at 53% RH. Chick quality problems that may be due to high or low RH during incubation can be ameliorated by proper brooding conditions.

Animals↗

PubMed2000

Effects of relative humidity during incubation on hatchability and body weight of broiler chicks from young breeder flocks.

We conducted an experiment to determine the effect of relative humidity (RH) during incubation on characteristics of hatched chicks from eggs produced by young broiler breeders. Eggs were collected for 6 consecutive d, every other week, in each of two trials from broiler breeder flocks at 26, 28, and 30 wk of age. The eggs were randomly distributed in machines according to RH treatments that were 43, 53, and 63% RH from set to pulling time at 21.75 and 22 d of incubation for Trials 1 and 2, respectively. The same dry bulb temperature (37.5 C) was used throughout incubation for both trials. Body weight at hatch, but not BW at pull (removal from machine), increased significantly with increasing RH treatment. The BW at hatch and BW at pull increased with increasing hen age. Percentages of late dead and fertile hatchability were the highest for the 63% and 53% RH treatments, respectively. These data demonstrated that, although a high RH during incubation produced chicks with increased BW at hatch, this extra weight was greatly reduced by time of pull, which suggests a significant rate of evaporation even in the presence of high RH. Further, the high RH appears to have a detrimental effect on embryonic development, as evidenced by the increased percentage of late dead.

Animals↗

PubMed2001

Effects of incubator humidity and hen age on yolk composition in broiler hatching eggs from young breeders.

The effects of broiler breeder age (26, 28, and 30 wk) and incubator relative humidity (43, 53, and 63% RH) on yolk sac weight and composition in broiler hatching eggs between 16 and 19 d of incubation were evaluated. Percentage yolk sac weight was reduced in eggs from the youngest (26 wk) breeder hens and in eggs incubated at 53% RH. Percentage yolk moisture, in eggs from the youngest hens, was lowest at 16 d and was highest at 19 d, and percentage yolk lipid was highest at 16 and 17 d of incubation in eggs from 30-wk-old hens. Percentage yolk lipid content was higher at 63% RH compared with 53% RH in eggs from 26-wk-old breeders but was lower in eggs incubated at a 43% RH compared with 53 and 63% RH from 30-wk-old breeders. Yolk stearic and arachidonic acid concentrations were higher and myristic acid concentration was lower in eggs from the 26-wk-old hens. Conversely, the highest yolk concentrations of linolenic and palmitoleic acids occurred in eggs from 30- and 28-wk-old breeders, respectively. At 16, 17, 18, and 19 d of incubation, yolk oleic acid concentrations were significantly, but variably, affected by breeder age, whereas linoleic acid concentration was highest in 26-wk-old breeders only at 19 d. Palmitic acid concentration at 17 d was lower in eggs incubated at 53% RH compared with 43 and 63% RH. Rate of yolk uptake from the yolk sac by embryos may be increased by incubating eggs at 53% RH, and the effects of changes in RH between 43 and 63% on yolk lipid content are influenced by breeder age.

Age Factors↗

PubMed1978

A high-humidity circle system for infants and children.

A scaled-down version of a modified adult circle system capable of increasing normal humidity output 300% was constructed for pediatric use. The moisture content of the gases leaving the system was tested and found to be superior to that of any pediatric circle system commercially available that does not incorporate an electrically heated water vaporizer.

Anesthesia↗

PubMed1990

Performance of a diffusion barrier charcoal adsorption 222Rn monitor under conditions of varying humidity and temperature.

An investigation of the performance of a diffusion barrier, charcoal-based 222Rn monitor under several artificial environmental conditions showed that both temperature and relative humidity levels affect 222Rn uptake. A physical model was developed adequately describing the temperature effects, while an empirical model was used to summarize the combined effects of temperature and atmospheric water concentration.

Charcoal↗

PubMed1995

A theoretical model for 222Rn adsorption on activated charcoal canisters in humid air based on Polanyi's potential theory.

Water vapor interferes with the adsorption of 222Rn gas by passive activated charcoal devices used to estimate indoor air concentrations. The 222Rn adsorption coefficient is the fundamental parameter characterizing charcoal's ability to adsorb 222Rn. The Dubinin-Radushkevich equation, based on Polanyi's potential theory, was modified to include two terms quantifying the effect of both water vapor and sampling time on the 222Rn adsorption coefficient of passive charcoal devices. A single equation was derived that quantifies the 222Rn adsorption coefficients at any temperature, humidity and exposure time using six experimentally determined physical constants that are unique for a particular passive charcoal device. The theoretical model was verified with published experimental data, and it showed a good correlation between theory and experiment. The model proved to be consistent with experimental data, provided that the amount of water vapor adsorbed by the charcoal device during sampling remains below a critical level, termed the breakpoint.

Adsorption↗

PubMed1991

The contribution of environmental temperature and humidity to geographic variations in blood pressure.

The pattern of geographic blood pressure variations in Britain has raised the possibility that temperature or other climatic factors may be of importance. Data from two population studies have been examined: the British Regional Heart Study (BRHS), which involved 7735 mean aged 40-59 years, and the Nine Towns Study (NTS), concerning blood pressure among 2596 men and women aged 25-59 years. In the BRHS, significant negative associations were found between daily maximum outdoor temperature and systolic blood pressure (-0.38 mmHg/degrees C; P less than 0.001) and diastolic blood pressure (-0.18 mmHg/degrees C; P less than 0.001). There were similar, although non-significant, associations in the NTS. No significant associations were found between blood pressure and room temperature in either study after taking account of town blood pressure differences, nor between blood pressure and outdoor humidity in the NTS. In the NTS, skin temperature was negatively associated with blood pressure after the adjustment for body mass index, significantly so for male diastolic (-0.62 mmHg/degrees C; P less than 0.05). The BRHS estimates suggest that, in Britain, geographic differences in outdoor temperature may contribute no more than 2 mmHg systolic and 1 mmHg diastolic to regional blood pressure variations. This represents a relatively small proportion of the town differences in blood pressure observed in both the BRHS and NTS. Furthermore, international comparisons suggest that environmental temperature is not an important determinant of population blood pressure levels.

Adult↗

PubMed2006

Short-term effects of atmospheric temperature and humidity on morbidity from acute coronary syndromes in free of air pollution rural Greece.

STUDY OBJECTIVE: An evaluation of the effect of ambient temperature on morbidity from acute coronary syndromes (ACS) while avoiding confounding by air pollution. DESIGN: An ecological study in rural Greece. METHODS: Daily admissions to hospital because of ACS were recorded for 1 year and analysed versus daily temperature and humidity. RESULTS: For a 1 degrees C decrease in temperature there was a 1.6% (95% confidence interval 0.9-2.2%) increase in admissions. This effect was more prominent in the elderly. No difference was detected according to sex or type of ACS. CONCLUSION: It is important to implement measures against cold in coronary heart disease prevention, irrespective of air pollution.

Air Pollution↗

PubMed1980

Effect of temperature, humidity and exposure to oxygen on the survival of anaerobic bacteria.

The relative effect of humidity, temperature and exposure to oxygen on the survival of 11 strains of Bacteriodes spp., Fusobacterium necrophorum, Eubacterium lentum, Clostridium ramosum, Peptococcus asaccharolyticus and Peptostreptococcus anaerobius was evaluated. Suspensions of the test strains were applied to membrane filters either in empty sterile petri dishes or on plates of non-nutrient agar to provide dry or moist conditions. The filters were stored aerobically or anaerobically in an atmosphere containing 10% CO2 at either 4 degrees C or 35 degrees C. After holding periods of 0.375-384 h, the filters were transferred to nutrient plates inside an anaerobic glove box. After incubation the growth on the filters was compared with that on control filters that had not been stored. Survival was better at 4 degrees C than at 35 degrees C. For the gram-negative organisms, survival was better under moist than under dry conditions, whereas for gram-positive organisms this finding was sometimes reversed. The results indicate that, generally, anaerobic bacteria kept under aerobic conditions survive best under moist conditions at 4 degrees C.

Anaerobiosis↗

PubMed2001

Dynamic response of tetragonal lysozyme crystals to changes in relative humidity: implications for post-growth crystal treatments.

The dynamic response of tetragonal lysozyme crystals to dehydration has been characterized in situ using a combination of X-ray topography, high-resolution diffraction line-shape measurements and conventional crystallographic diffraction. For dehydration from 98% relative humidity (r.h.) to above 89%, mosaicity and diffraction resolution show little change and X-ray topographs remain featureless. Lattice constants decrease rapidly but the lattice-constant distribution within the crystal remains very narrow, indicating that water concentration gradients remain very small. Near 88% r.h., the c-axis lattice parameter decreases abruptly, the steady-state mosaicity and diffraction resolution degrade sharply and topographs develop extensive contrast. This transformation exhibits metastability and hysteresis. At fixed r.h. < 88% it is irreversible, but the original order can be almost completely restored by rehydration. These results suggest that this transformation is a first-order structural transition involving an abrupt loss of crystal water. The front between transformed and untransformed regions may propagate inward from the crystal surface and the resulting stresses along the front may degrade mosaicity. Differences in crystal size, shape and initial perfection may produce the observed variations in degradation timescale. Consequently, the success of more general post-growth treatments may often involve identifying procedures that either avoid lattice transitions, minimize disorder created during such transitions or maintain the lattice in an ordered metastable state.

Crystallography, X-Ray↗

PubMed1998

Plasticity, hydration and accessibility in ribonuclease A. The structure of a new crystal form and its low-humidity variant.

The structures of a new crystal form of ribonuclease A and its low-humidity variant, each containing two crystallographically independent molecules, have been determined and refined. A detailed comparison of these structures with those of the other known crystal forms of the enzyme, which have different packing arrangements and solvent composition, leads to a meaningful delineation of the rigid and flexible regions of the protein molecule and the nature of its plasticity. Many of the water molecules which are common to all the structures are involved in bridging different regions of the protein molecule, thus emphasizing the role of water in stabilizing the tertiary structure. The analysis of the structures shows that for a given N or O atom, the level of hydration increases with accessible surface area, but levels off at an area of about 10 A2. Generally, the hydration level tends to drop when the area increases beyond about 20 A2. This drop correlates with an increase in the displacement parameter. The analysis also suggests that the van der Waals radii and probe radius normally used in accessible surface area calculations are not appropriate for dealing with all situations.

Animals↗

PubMed1999

Crystallization and preliminary analysis of a DNA dodecamer of d(CGCGmo6AATCCGCG) containing 2'-deoxy-N6-methoxyadenosine: change in crystal packing with different humidity.

The DNA dodecamer of (CGCGmo6AATCCGCG) containing 2'-deoxy-N6-methoxyadenosine has been crystallized for X-ray analysis in order to investigate the effects of the modified adenosine on base pairing. It has been found that the crystal changes from one form to another during data collection in a manner similar to a phase transition. The two crystal structures show that this phenomenon, ascribed to differences in humidity, is correlated with a change in the contact angle between the two duplexes.

Crystallization↗

PubMed2004

Effects of relative humidity and ambient temperature on the ballistic delivery of micro-particles to excised porcine skin.

The effectiveness of ballistic particle delivery to the skin is often dependent upon breaching the stratum corneum (SC) and targeting cells within defined layers of the viable epidermis. This paper experimentally determines the influence of relative humidity (RH) and temperature on the ballistic delivery of particles to the skin. Gold particles of radius 0.9+/-0.6 microm were accelerated by a hand-held supersonic device to impact freshly excised porcine skin at 410-665 m per s. Increasing the RH from 15% to 95% (temperature at 25 degrees C) led to a particle penetration increase by a factor of 1.8. Temperature increases from 20 degrees C to 40 degrees C (RH at 15%) enhanced particle penetration 2-fold. In both cases, these increases were sufficient to move the target layer from the SC to the viable epidermis. Relative trends in particle penetration compared well with predictions from a theoretical model well. Calculated absolute penetration depths are 6-fold greater than the measurements. The inversely calculated dynamic yield stress of the SC is up to a factor of 10 higher than reported quasi-static measurements, due to changes in tissue failure modes over a strain-rate range spanning 10 orders of magnitude. If targeted particle delivery is required, it is recommended that the environmental RH and temperature be monitored.

Animals↗

PubMed2003

The association between ambient air conditions (temperature and absolute humidity), irritant sodium lauryl sulfate patch test reactions and patch test reactivity to standard allergens.

To support the decision as to whether erythematous patch test reactions to allergens are irritant or allergic, sodium lauryl sulfate (SLS, 0.5% in water) has been added to the standard patch tests since July 1996 in the Dortmund Department of Dermatology. Data on 1600 patients patch tested up until June 2001, as well as standardized data on ambient temperature and humidity obtained by the German Meteorological Service, were included in a logistic regression analysis taking age, sex and atopy as potential confounders into account. The pattern of association was heterogeneous: while doubtful reactions to nickel sulfate were significantly associated with dry/cold weather conditions, but not with SLS reactivity, the opposite was observed for lanolin alcohol, benzocaine and Myroxylon pereirae resin (balsam of Peru). Doubtful reactions to other allergens, namely formaldehyde, fragrance mix or p-phenylenediamine, were associated with both factors. For several other allergens of the standard series, no distinct, significant pattern could be discerned. In conclusion, meteorological conditions and SLS reactivity independently contribute information on individual irritability at the time of patch testing, and both should be considered.

Allergens↗

PubMed1995

Resistance, humidity and temperature of the tracheal airway.

Patients after laryngectomy are subject to a high incidence of chest complaints. In attempting to reduce these a number of 'new nose' stoma filters have recently been introduced which claim to humidify and warm air, filter particulate matter and, by increasing tracheal airway resistance, to improve lung function. Our study defines the normal tracheal temperature, humidity and resistance values which were obtained from 16 patients with a normal upper respiratory tract. These parameters will allow the available filters to be evaluated objectively and may lead to the development of a more physiological 'new nose'.

Airway Resistance↗

PubMed1995

Effect of ambient temperature and humidity on performance of blood glucose meters.

The accuracy of four blood glucose meters (Accutrend, ExacTech Companion, Medisense Companion 2, and Glucometer III) was tested at temperatures ranging from 4 to 44 degrees C (control solutions) and 8 degrees C, 24 degrees C, and 36 degrees C (venous blood) and at humidities of 60% and 80%. Low and high temperatures resulted in a number of statistically significant changes in glucose readings with all meters. However, Accutrend, Medisense Companion 2, and Glucometer III were 100% clinically accurate at all temperatures. With the ExacTech Companion, only 70.8% of control solution and 55.6% of venous blood results were clinically accurate. The main errors were: (1) cold temperatures lowered the result so that euglycaemic levels erroneously read in the hypoglycaemic range and hyperglycaemic levels gave a better than actual result and (2) hot temperatures increased the result whereby hypoglycaemic levels falsely gave a euglycaemic result. Weather conditions at which blood glucose meters may be operated can affect results and potentially lead to errors in clinical decisions.

Blood Glucose↗