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PubMed1978

Effect of serum albumin on dynamic force-area curve of dipalmitoyl lecithin.

In line with previous findings at 25 degrees C, solutions of serum albumin in the subphase stabilized the surface activity of DPL spread films at 25 degrees C as well as 37 degrees C. In contrast, films adsorbed from mixtures of DPL and albumin exhibitied a marked inhibitory action of the albumin on DPL activity. The inhibitory effect increased with the relative protein concentration but, with albumin/DPL ratios smaller than 2, the DPL activity was regained gradually with cycling. With larger albumin/DPE negative effect of albumin was counteracted by higher temperatures (37 degrees C vs 25 degress C) and modest cholesterol concentrations; with greater cholesterol concentrations the known inhibitory effect of cholesterol prevailed. The inhibitory effect of albumin was potentiated by humidity; saturation of the atmosphere with water vapor at 37 degrees C abolished the DPL character of DPL-RSA mixtures and prevented its return (zero surface tension) upon reversal of the atmosphere from saturated water vapor to dry air. The data are important in the interpretation of the surface activity of pulmonary washings and other pulmonary extracts.

Adsorption↗
PubMed1993

Coated surface acoustic wave sensor employing a reversible mass-amplifying ligand substitution reaction for real-time measurement of 1,3-butadiene at low- and sub-ppm concentrations.

Real-time measurement of 1,3-butadiene gas using a surface acoustic wave (SAW) sensor coated with the square-planar Pt(II)-olefin pi-complex PtCl2-(1-hexene) (pyridine) and related complexes is described. Amplification of the sensor response results from displacement of two 1-hexene molecules by each butadiene molecule and formation of the bridged complex [PtCl2(pyridine)]2(1,3-butadiene). Using a 30-MHz SAW oscillator, the rate of frequency change is linearly related to the butadiene air concentration from 150 ppb to > or = 13 ppm and a calculated detection limit of 101 ppb is obtained. Using a 60-MHz oscillator, the detection limit is reduced to 24 ppb. No effect on the sensor response is observed with changes in relative humidity from 5 to 80% or changes in temperature from 25 to 35 degrees C. No interference is observed from several industrially relevant non-olefin organic gases and vapors. Responses are obtained for several olefins, but they interfere with the response to butadiene only at higher relative concentrations. The reagent can be regenerated repeatedly by brief exposure to 1-hexene vapor with retention of the original response characteristics upon subsequent exposure. The potential for using this sensor to monitor occupational 1,3-butadiene exposures is discussed in light of the recently proposed occupational exposure limit of 2 ppm.

Air Pollutants, Occupational↗
PubMed1983

Deposition of sulfuric acid mists in the respiratory tract of beagle dogs.

Beagle dogs were exposed to 35S-labeled sulfuric acid mists. The size range of the mist droplets was 0.4-1.1 micrometer mass median aerodynamic diameter (MMAD), and the external relative humidity was 20 or 80%. Immediate isolation of the respiratory tract and measurement of radioactivity in specified portions allowed determination of regional deposition. It was found that inhaled sulfuric acid mists in the size ranges studied had deposition patterns similar to those for dry aerosols. The effect of hygroscopicity for these aerosols was not dominant in determining the site of deposition.

Aerosols↗
PubMed1995

Associations between criteria air pollutants and asthma.

The evidence that asthma is increasing in prevalence is becoming increasingly compelling. This trend has been demonstrated not only in the United States, but also in the United Kingdom, New Zealand, Australia, and several other Western countries. In the United States, the increase is largest in the group under 18 years of age. There is mounting evidence that certain environmental air pollutants are involved in exacerbating asthma. This is based primarily on epidemiologic studies and more recent clinical studies. The U.S. Clean Air Act of 1970 provides special consideration to the class of outdoor air pollutants referred to as criteria pollutants, including O3, sulfur dioxide (SO2), particulate matter (PM), NOx, CO, and Pb. Standards for these pollutants are set by the U.S. Environmental Protection Agency with particular concern for populations at risk. Current evidence suggests that asthmatics are more sensitive to the effects of O3, SO2, PM, and NO2, and are therefore at risk. High SO2 and particulate concentrations have been associated with short-term increases in morbidity and mortality in the general population during dramatic air pollution episodes in the past. Controlled exposure studies have clearly shown that asthmatics are sensitive to low levels of SO2. Exercising asthmatics exposed to SO2 develop bronchoconstriction within minutes, even at levels of 0.25 ppm. Responses are modified by air temperature, humidity, and exercise level. Recent epidemiologic studies have suggested that exposure to PM is strongly associated with morbidity and mortality in the general population and that hospital admissions for bronchitis and asthma were associated with PM10 levels. In controlled clinical studies, asthmatics appear to be no more reactive to aerosols than healthy subjects. Consequently, it is difficult to attribute the increased mortality observed in epidemiologic studies to specific effects demonstrated in controlled human studies. Epidemiologic studies of hospital admissions for asthma have implicated O3 as contributing to the exacerbation of asthma; however, most study designs could not separate the O3 effects from the concomitant effects of acid aerosols and SO2. Controlled human clinical studies have suggested that asthmatics have similar changes in spirometry and airway reactivity in response to O3 exposure compared to healthy adults. However, a possible role of O3 in worsening atopic asthma has recently been suggested in studies combining allergen challenge following exposure to O3. Attempts at identification of factors that predispose asthmatics to responsiveness to NO2 has produced inconsistent results and requires further investigation. In summary, asthmatics have been shown to be a sensitive subpopulation relative to several of the criteria pollutants. Further research linking epidemiologic, clinical, and toxicologic approaches is required to better understand and characterize the risk of exposing asthmatics to these pollutants.

Adolescent↗
PubMed2026

Self-healing materials for food packaging: Design principles, activation mechanisms and implications for food safety.

Self-healing materials (SHMs), originally developed to restore mechanical integrity, have recently attracted growing interest in food packaging. By autonomously repairing physical damage, SHMs help preserve packaging integrity, barrier performance, food safety, and shelf-life during storage and transportation. This review summarizes recent advances in the design principles, activation mechanisms, material systems and food packaging applications of SHMs. Key healing strategies, including microencapsulation, dynamic covalent bond exchange, reversible non-covalent interactions and responsiveness to external stimuli such as temperature, pH, and humidity, are discussed. Representative material systems, including biopolymer-based films, hydrogels, nanocomposites, and stimuli-responsive polymers are evaluated with respect to their relevance to packaging animal-derived foods, fruits, and vegetables. Performance evaluation methods, sustainability implications, and food-contact safety concerns are addressed. Despite promising healing efficiency and mechanical resilience, challenges remain regarding production cost, food-grade safety, migration risks, trigger compatibility and stability under fluctuating environmental conditions. Future research should focus on scalable manufacturing, standardized evaluation protocols, repeated damage-healing safety assessment, regulatory compliance, and integration with intelligent packaging technologies.

Food Packaging↗
PubMed1982

Responses of the pituitary-adrenal system of mice to an environment of high temperature and humidity.

1. Changes in plasma glucose and corticosterone levels under an environment of high temperature and humidity similar to summers in Japan were investigated. 2. When mice were exposed to high temperature (30-40 degrees C) and humidity (70%), the plasma glucose levels increased with a short-term exposure and decreased with a long-term exposure compared to that of the control mice housed at room temperature (23 degrees C) and humidity (55%). 3. The magnitude of increase of plasma corticosterone levels depended on the degree of ambient temperature and the duration of exposure to the stressful conditions. The plasma corticosterone concentration was highest at 2 hr after initiation of the temperature stress and was reduced at 4 and 6 hr after the treatment: The plasma corticosterone had returned to the control level at 8 hr after the exposure. 4. The dexamethasone treatment inhibited the increase of plasma corticosterone in stress-mice. 5. These results suggest that the response of the plasma corticosterone is a better index than that of glucose for estimation of stress-degree.

Animals↗
PubMed1983

Modifications of sweating responses to thermal transients following heat acclimation.

The sweating response was studied before and after passive humid heat acclimation in four resting male subjects who were exposed to slow thermal transients increasing air and wall temperatures from 28 degrees C to 45 degrees C. The slopes of the ambient temperature increases were +0.19 degrees C . min-1; +0.16 degrees C . min-1 or +0.14 degrees C . min-1. Dew-point temperature and air velocity were kept constant (17.5 degrees C; 0.3 m . s-1). Continuous measurements were made of oesophageal temperature, mean skin temperature, whole-body sweat loss and of right upper limb sweating responses. The local sweating response was measured from an arm chamber under a local thermal clamp (Tsk,1 = 38 degrees C). The results confirmed the fact that heat acclimation to humid heat induces a shortening in the time lag of sweat onset and increases the local sweating rates while internal temperature changes are reduced. These modifications are interpreted as a non-linearity in the response of the central controller, involving both a change in the central gain and an upward resetting of the "local sweating rate-body temperature" curves, without any shifting of the hypothalamic set-point temperature as it is currently described. However, a modification of local sweat gland activity occurring with heat acclimation cannot be ruled out.

Acclimatization↗
PubMed2000

Influence of relative humidity on particle size and UV sensitivity of Serratia marcescens and Mycobacterium bovis BCG aerosols.

SETTING: A study of Serratia marcescens and BCG aerosols. OBJECTIVE: To evaluate the effect of relative humidity (RH) on (1) the particle size and (2) sensitivity of 254nm germicidal ultraviolet (UV) irradiation. METHODS: We built a RH controlled experimental chamber into which bacteria were aerosolized, exposed to varying amounts of UV irradiance over measured time periods, and quantitatively evaluated for viability. Aerosolized Serratia marcescens and bacille Calmette-Guérin (BCG) were subject to UV doses ranging from 57-829 microW. sec/cm(2), and sampled with a six-stage Andersen culture plate impactor at RHs ranging from 25-95%. RESULTS: Percent survival for both organisms was inversely related to UV dose. Serratia marcescens was more susceptible to UV than BCG under all conditions. More than 95% of the bacterial aerosol particles were 1.1-4.7 microm in aerodynamic diameter, and particles sizes increased from low (25-36%) to high (85-95%) RH. The count median diameter ranged from 1.9-2.6 microm for Serratia marcescens and from 2.2-2.7 microm for BCG as RH increased. For both Serratia marcescens and BCG, resistance to UV increased as RH increased. The UV resistance of both Serratia marcescens and BCG aerosols dramatically increased at RH higher than 85%. CONCLUSIONS: Our results indicate that differences in UV dose, kinds of microorganisms, airborne particle size and RH affect UV susceptibility.

Aerosols↗
PubMed1988

An assessment of nasal functions in control of breathing.

Breathing pattern and steady-state CO2 ventilatory response during mouth breathing were compared with those during nose breathing in nine healthy adults. In addition, the effect of warming and humidification of the inspired air on the ventilatory response was observed during breathing through a mouthpiece. We found the following. 1) Dead space and airway resistance were significantly greater during nose than during mouth breathing. 2) The slope of CO2 ventilatory responses did not differ appreciably during the two types of breathing, but CO2 occlusion pressure response was significantly enhanced during nose breathing. 3) Inhalation of warm and humid air through a mouthpiece significantly depressed CO2 ventilation and occlusion pressure responses. These results fit our observation that end-tidal PCO2 was significantly higher during nose than during mouth breathing. It is suggested that a loss of nasal functions, such as during nasal obstruction, may result in lowering of CO2, fostering apneic spells during sleep.

Adult↗
PubMed2026

Balancing growth and immunity of potato by humidity-dependent expression of a late blight resistance gene.

Inducible expression of resistance genes is an effective approach to balance plant growth and immunity, thus facilitating the development of disease-resistant crop cultivars. While pathogen-responsive and immunity-related promoters have been adopted for this purpose, alternative design strategies remain to be explored. High relative humidity (RH) has been recognized as a crucial permissive environmental condition for the occurrence of devastating plant diseases including tomato and potato late blight. Here, we identified humidity-activated cis-regulatory elements (HAEs) in Solanum lycopersicum through an integrative analysis of transcriptomics and chromatin accessibility data. Sequence homology-inferred HAEs in S. tuberosum can predict humidity-elicited changes in downstream gene expression. Transgenic S. tuberosum lines expressing a late blight resistance gene driven by an artificial humidity-inducible promoter containing a natural S. tuberosum HAE were generated. These transgenic lines exhibited comparable late blight resistance levels to the lines overexpressing the same resistance gene in controlled zoospore inoculation bioassays, while avoiding growth suppression and tuber yield penalties in common garden experiments. Our findings highlight the importance of plant cis-regulatory elements in the transcriptional responses to high RH and provide a proof-of-concept for a humidity-inducible environment-responsive resistance gene deployment strategy to engineer disease-resistant crop cultivars without compromising growth and yield.

Phytophthora infestans↗
PubMed1999

Do changing patterns of heat and humidity influence thermoregulation and endurance performance?

The purpose of this project was to determine whether changing patterns of temperature and humidity, as expected in the morning versus afternoon, had a differential effect on thermoregulation and endurance performance. Eight male distance runners each participated in two heat pattern tests consisting of two hours treadmill running at 70%-maximum oxygen consumption. The mean heat load for each test was identical (22.2 degrees C wet bulb temperature) but either dry bulb temperature increased (24 to 27.5 degrees C) or decreased (27.5 to 24 degrees C) over the course of the two hour heat stress test. Whole body sweat rate was 10.7% higher (p<0.05) and there was greater plasma volume loss (2.7 versus 1.6%, p<0.05) in the cooling versus warming pattern test. Mean skin and body temperature changed in a significantly different (p<0.05) manner between the two patterns and closely followed ambient dry bulb temperature change. The thermoregulatory variables of heart rate and rectal temperature were not affected and performance did not differ between pattern tests. Ratings of perceived exertion (RPE) and oxygen consumption were also not significantly different between cooling and warming test. In summary, although some minor differences were noted, thermal homeostasis was maintained equally well during either warming or cooling for wet bulb temperatures between 24 and 27 degrees C. The mean heat load is therefore more important than changing patterns of temperature and humidity in determining an individual's physiological response to exercise in a warm environment.

Adult↗
PubMed1985

Laboratory evaluation of stain-length passive dosimeters for monitoring of vinyl chloride and ethylene oxide.

The effects of vapor concentration in the range of 1.2 to 5.1 ppm (vinyl chloride) and 8.3 to 29.1 ppm (ethylene oxide) on the response of new stain-length passive dosimeters were evaluated separately in a dynamic exposure chamber. The vinyl chloride dosimeter was prepared with a permanganate impregnated blend of Chromosorb W and silica gel, while a silica gel-coated plastic strip (TLC plate) impregnated with dichromate was used to detect ethylene oxide. The use of a TLC plate as the inert support allowed us to reduce the amount of reagent loaded per length of tube, thus significantly enhancing in the sensitivity of the unit, which was necessary for accurately detecting ethylene oxide at these low concentrations. At the vinyl chloride exposure of 8 ppm-hrs the length of stain was 0.76 cm and the 95% confidence interval about this point was +/- 1.4 ppm-hrs (18%). For the ethylene oxide dosimeter the length of stain at the exposure of 80 ppm-hrs was 0.90 cm and the 95% confidence interval about this point was +/- 16 ppm-hrs (20%). Although some shortening of the stain was noted at low relative humidity (26%) in the vinyl chloride device, no effect on the dosimeter response was observed over the range of relative humidity of 35 to 96%. The ethylene oxide dosimeter response was not affected by relative humidity in the range of 28 to 90%. The use of a TLC plate as the inert support of the colorimetric reagent has proven to be an excellent means of improving the sensitivity of these stain-length passive dosimeters.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗
PubMed1992

Effect of breeding state, moulting, dehydration, exposure to saturated atmosphere, and arginine vasotocin on cutaneous water permeability in the toad Bufo bufo.

Cutaneous water permeability was assessed in hydrated male toads under a variety of conditions, including dehydration and rehydration, and the effects of exogenous arginine vasotocin (AVT) were determined. Cutaneous water permeability (the rate of water uptake by toads in water) was high in toads collected in the breeding pond and declined steeply during the first week, coincident with reduced activity of the cutaneous mucus glands. The slopes of the dose-response curves relating AVT to cutaneous water influx were about the same at the transition from the breeding to the nonbreeding state, but the level of influx was higher in the breeding state. The dose-response relationship in long-term terrestrial-acclimated toads was similar to that in water-acclimated toads. The threshold dose for effect on the cutaneous water permeability was about 1 ng AVT. Dehydration had a substantially greater effect on the cutaneous water permeability than AVT. The ratio between dehydration and AVT responses tended to increase with increasing water transport capacity of the skin. Moulting and acclimation to a saturated atmosphere in fully hydrated toads more than doubled the water permeability and abolished the response to AVT. It is suggested that AVT and other factors increase the cutaneous water permeability by similar mechanisms, such as insertion of water channels in the apical membrane of the epidermal cells. The effect of AVT on the toad skin is interpreted as reflecting the general high potency of neurohypophysial hormones in stimulating the water permeability of membranes of variable permeability.

Acclimatization↗
PubMed2004

Aroma sensing and indoor air monitoring by quartz crystal resonators with sensory films prepared by sputtering of biomaterials and sintered polymers.

Thickness shear mode quartz-crystal resonator coated with plasma polymer films (PPFs) produced by radio-frequency sputtering of biomaterials and synthetic polymers were examined with respect to their abilities to continuously monitor indoor air. We confirmed the sensory capabilities of an array of PPF sensors to aromas emitted from essential oils at concentrations as low as the detection threshold of human olfaction. Changes in humidity induced a drift in the response curves of PPF sensors. On the contrary, volatile compounds exhibited pulse signals. The pulse signals of a D-phenylalanine sensor and a polyethylene sensor were synchronous, but the direction of the peaks was inverted in most cases. Compared with a photo-ionization detector sensor, the PPF sensors were able to detect subtle changes in the concentrations of volatile compounds in indoor air.

Air Pollution, Indoor↗
PubMed2000

Amperometric sensing of ethylene oxide in the gas phase.

The sensing device used is based on a porous Pt electrode, which is supported on an ion-exchange membrane and directly exposed to the gas phase. Under acid conditions, ethylene oxide was found to be oxidized on the platinum oxide surface at +550 mV vs MSE, thus enabling its monitoring via the measurement of the associated current. A detection limit of 15 ppb was obtained, based on a signal-to-noise ratio of three, and a linear dynamic range was found up to 100 ppm. The effects of mass transport, humidity, and oxygen on the cell response, as well as the cross sensitivity to other organic vapors and inorganic gases are discussed.

Carcinogens↗
PubMed2003

Influence of hydration on dihydroxyacetone-induced pigmentation of stratum corneum.

Dihydroxyacetone, the browning ingredient in sunless tanning formulations, reacts with amino acids in the outer stratum corneum to form a mixture of high molecular weight pigments. Our initial observations indicated that high hydration of dihydroxyacetone-treated skin completely inhibited development of pigmentation. To investigate the mechanism underlying this effect, studies were carried out in isolated murine epidermis, polyvinyl alcohol/lysine films, and lysine in glycerol/water solvent. Murine epidermis treated with dihydroxyacetone showed a biphasic dependence on relative humidity: maximum pigmentation developed at 84% relative humidity and minimum pigmentation at 0% and 100% relative humidity. Filaggrin proteolysis, which shows a similar dependence on relative humidity and provides free amino acids in the outer stratum corneum, did not account for the relative humidity dependence of dihydroxyacetone pigmentation. A similar biphasic pigmentation response was obtained when polyvinyl alcohol film containing lysine was treated with dihydroxyacetone and incubated at various relative humidities, indicating that the structure of the stratum corneum was not a major factor. To remove the influence of the matrix, the reaction of dihydroxyacetone with lysine was followed at varying concentrations of water in mixed glycerol/buffer solvent. Again, greater pigment formation was found at an intermediate level of water (6% vol/vol) and little pigmentation at 0% and 100% water content. These results are consistent with a requirement for water at low relative humidity, which facilitates formation of free amine groups needed for the initial reaction with dihydroxyacetone, and with inhibition of the dehydration reactions by water through the law of mass action at high relative humidity.

Amino Acids↗
PubMed2005

Effects of microbial cocultivation on inflammatory and cytotoxic potential of spores.

Microbial growth on moisture-damaged building materials is commonly associated with adverse health effects in the occupants. In moisture damage situations, the environmental conditions as well as the dominant microbial species will vary, leading to a diversity of microbes and continual changes in the different microbial populations. Currently, very little is known about the effects of microbial cocultures on the potential harmfulness of the microbial population. In this study we have investigated the effects of cocultivation of certain indoor air microbes on the inflammatory and cytotoxic potential of their spores. We grew various microbial combinations made from strains of Streptomyces californicus, Stachybotrys chartarum, Aspergillus versicolor, and Penicillium spinulosum on wetted plasterboard. After 5 or 10 wk of growth, the spores were collected from the plasterboards, mouse RAW264.7 macrophages were exposed to the spores, and after 24 h the induced inflammatory and cytotoxic responses were analyzed. Among all the tested microbes and their combinations, the spores of Str. californicus proved to be the most potent inducer of cytotoxicity and inflammatory responses. These results indicate also that microbial coculture may support the growth of certain microbes with high immunotoxic potency such as Str.californicus. Furthermore, coculture containing S. chartarum and A. versicolor caused a synergistic increase in cytotoxicity compared to the sum response induced by the pure cultures, but no effect on inflammatory responses was detected. Generally, spore-induced cytotoxicity and production of inflammatory markers increased during the growth period from 5 to 10 wk, suggesting that the immunotoxic potency of spores increases with time.

Air Pollution, Indoor↗
PubMedDate not supplied

Ecotypic differentiation of gas exchange responses and leaf anatomy in a tropical forest understory shrub from areas of contrasting rainfall regimes.

Many studies have documented genetic differentiation of physiological ecotypes along environmental gradients in the temperate zone, but this topic has received little attention in tropical plants. We collected cuttings of Psychotria horizontalis (Rubiaceae) from Atlantic and Pacific coastal areas in central Panama, which differed twofold in annual rainfall, and grew them under common conditions in a screened, open-air growing house for 14 months. Plants from the wetter (Atlantic) region showed significantly higher stomatal conductance, but photosynthetic rates were similar in both groups, leading to higher water use efficiency in plants from the drier (Pacific) region. Responses of stomatal conductance to atmospheric humidity were similar in both groups. Anatomical studies show that plants from the wetter region had a higher mesophyll surface area per unit leaf area (A(mes)/A(leaf)) than plants from the drier region (17.2 versus 13.9), and also had a higher stomatal density (161.5 versus 98.0 mm(-2)) and fewer trichomes (2.0 versus 18.7 mm(-2)). The proportion of palisade cell surface area that was exposed to intercellular airspaces is higher in plants from the Pacific coast than from the Atlantic coast, such that the total palisade cell surface area exposed to the intercellular airspaces is similar in plants from the two regions (A(mes)/A(leaf) = 1.7). Paired plants transplanted into natural forest understory conditions showed considerable variability among sites, but plants from the drier region consistently had lower stomatal conductance than plants from the wetter region. After 20 months in the field, plant growth was similar regardless of plant origin, but plants of Pacific coast origin had longer roots and more (but smaller) leaves than plants of Atlantic coast origin. Stomatal density in field-grown plants was higher in plants of Atlantic (135.9 mm(-2)) than Pacific (90.1 mm(-2)) origin. An understanding of genetically based adaptations to local environmental conditions is important for predicting the consequences of climatic change and forest fragmentation.

Journal Article↗