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At least 793 records · Page 44Linked to original sources

PubMed2004

Continuous recording of excretory water loss from Musca domestica using a flow-through humidity meter: hormonal control of diuresis.

Water loss from adult male houseflies was continuously recorded using a flow-through humidity meter, which enabled losses to be apportioned between the sum of cuticular and respiratory transpiration, salivation and excretion. Transpiration accounted for >95% of water lost from sham-injected flies, compared with excretion (3.0%) and salivation (2.4%). In contrast, excretion accounted for 40% of water lost from flies injected with > or =3 microl of saline, whereas salivary losses were unchanged. Saline injections (1-5 microl) expanded the abdomen in the dorsal-ventral plane, and this expansion was positively correlated with the magnitude of the ensuing diuresis, suggesting the signal for diuretic hormone release originates from stretch receptors in abdominal tergal-sternal muscles. The effects of decapitation, severing the ventral nerve cord within the neck or ligaturing the neck, showed the head was needed to initiate and maintain diuresis, but was neither the source of diuretic hormone nor did it control the discharge of urine from the anus. These findings indicate the head is part of the neural-endocrine pathway between abdominal stretch receptors and sites for diuretic hormone release from the thoracic-abdominal ganglion mass. Evidence is presented for Musdo-K having a hormonal role in the control of diuresis, although other neuropeptides may also be implicated.

Animals↗

PubMed2006

Ambient humidity influences the rate of skin barrier maturation in extremely preterm infants.

OBJECTIVES: To test the hypothesis that the level of relative humidity (RH) in which preterm infants are nursed might influence their postnatal skin maturation. STUDY DESIGN: In 22 preterm infants (GA 23-27 weeks), transepidermal water loss (TEWL) was determined at postnatal ages (PNA) of 0, 3, 7, 14, and 28 days. At a PNA of 7 days, the infants were randomized to care at either 50% or 75% RH. RESULTS: TEWL decreased at a slower rate in infants nursed at the higher RH. At a PNA of 28 days, TEWL was about twice as high in infants nursed at 75% RH (22 +/- 2 g/m2 h) than in those nursed at 50% RH (13 +/- 1 g/m2 h; P < .001). CONCLUSIONS: The results indicate that the level of RH influences skin barrier development, with more rapid barrier formation in infants nursed at a lower RH. The findings have an impact on strategies for promoting skin barrier integrity in extremely preterm infants.

Female↗

PubMed2006

The effects of culture media, solid substrates, and relative humidity on growth, sporulation and conidial discharge of Valdensinia heterodoxa.

Valdensinia heterodoxa (Sclerotiniacae) is a potential fungal bioherbicide for control of salal (Gaultheria shallon). The effect of culture media, substrates and relative humidity (RH) on growth, sporulation and conidial discharge of V. heterodoxa was determined for two isolates PFC2761 and PFC3027 in vitro. Culture media significantly affected the growth, sporulation, and conidial discharge of V. heterodoxa. Of eight agar media used, colony radial growth was optimal on salal oatmeal agar and salal potato dextrose agar for isolates PFC2761 and PFC3027, respectively; whereas sporulation was at an optimum on salal oatmeal agar for both isolates. Of the eight liquid media tested, mycelial production was highest on wheat bran-salal-potato dextrose broth. Growth on solid substrates greatly stimulated sporulation and conidial discharge of V. heterodoxa. Of the 12 solid substrates used, the greatest numbers of discharged conidia were observed from wheat bran and wheat bran-salal within 14d of sporulation. Sporulation on solid substrates continued for 42d. RH significantly affected the sporulation and conidial discharge for both isolates across all solid substrates tested. No conidia were produced or discharged below 93 % RH on wheat bran-salal and millet. With an increase of the RH from 93 to 97 %, sporulation and the number of discharged conidia increased significantly for both isolates on wheat bran-salal, but not on millet.

Agar↗

PubMed2003

Use of ISO-NOP200 for measurement of NO in the gas phase under controlled humidity conditions.

A technique has been developed to measure nitric oxide (NO) in the gas phase using the ISO-NOP200 NO-specific probe, which was designed to only measure NO in solution. It was found that probe output was responsive to the relative humidity (RH) of the atmosphere. Increasing sensitivity of probe output to NO was observed with increasing RH but the time to achieve a stable output was also increased. The recommended method to give high sensitivity but an acceptable time between analyses was to hold the probe at a constant temperature (20 degrees C) in a sealed 20 ml glass vial containing 4 ml of a saturated solution of NaCl, which provides a constant RH of 75%. NO standards and samples were injected directly into the vial and provided good baseline stability and a limit of detection of 0.18 microl/L in the vial. The limit of detection of the analytical sample will depend on the volume of gas injected into the vial. Up to 4 ml could be injected without disturbing probe stability and this equates to a detection limit of 0.75 microl/L NO. However, analysis of the internal atmosphere of banana fruit could only consistently extract 1 ml of gas, which gave a detection limit of 3 microl/L NO.

Electrochemistry↗

PubMed1999

Temperature and relative humidity affect the selection of shelters by Triatoma infestans, vector of Chagas disease.

The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects preferred refuges at a temperature of 34 degrees C rather than 26 degrees C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperature and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an inner climate favourable to T. infestans. Typical refuges in adobe walls showed strongly damped fluctuations in minimum and maximum temperatures, and delayed changes in these parameters when compared with an external reference. Similarly, the jarilla (Larrea sp.), a plant used for constructing roofing, damps fluctuations in minimum and maximum RH and delays these RH fluctuations when compared to an external reference. We discuss possible effects of environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones.

Animals↗

PubMedDate not supplied

The effects of age, environmental temperature and relative humidity on the bacterial flora of the upper respiratory tract in calves.

The effects of age, environmental temperature and relative humidity on the bacterial flora of the nose and trachea of calves were investigated by sequential sampling of three groups each of eight Friesian-Holstein male calves kept in three different environmental conditions. All calves were vaccinated with a live attenuated vaccine against infectious bovine rhinotracheitis (IBR) when they were 12 weeks old. Nasal and tracheal swabs were collected at 14-day intervals for bacteriological examinations. The upper respiratory tract of calves started to be colonized by various species of bacteria within the first day of life. Although they were born at different periods of the year, the calves in all three groups had similar bacterial loads in their noses and tracheas when they were 1 day old (P greater than 0.05). The total bacterial colony forming units (BCFU) were highly variable from calf to calf and from one time of sampling to another. Despite these variations, there were age-related increases in the total BCFU in nasal and tracheal swabs in all experiments. These increases were influenced by environmental temperature. Vaccination of the calves with a live IBR vaccine appeared to enhance the bacterial colonization of the upper respiratory tract.

Age Factors↗

PubMed1997

Treatment with hot, humid air reduces the nasal response to allergen challenge.

Ten subjects with asymptomatic seasonal allergy, outside of their allergy season, underwent allergen provocation following 1 hour of exposure to air at either 20 degrees C and 30% relative humidity (RH) or air at 37 degrees C and 90% RH. The ipsilateral changes following antigen challenge were compared under the two conditions. Conditioning of the nose to 37 degrees C, 90% RH reduced total histamine release (7.9 +/- 1.8 ng vs 4.2 +/- 1.3 ng; p < or = 0.05), sneezes (6 +/- 2 vs 3 +/- 1; p < or = 0.05), pruritus (score of 17.4 +/- 6.0 vs score of 2.0 +/- 1.8 out of a total score of 100, p < or = 0.01), nasal airway resistance (1.4 +/- 0.8 kPa/L/sec vs 0.2 +/- 0.1 kPa/L/sec; p < or = 0.05), human serum albumin levels (389.6 +/- 53.4 micrograms vs 242.2 +/- 37.9 micrograms; p < or = 0.05), and congestion (score of 23.8 +/- 4.8 vs score of 10.6 +/- 5.4 out of a total score of 100, p < or = 0.01). It had no effect on the volume of secretions (p = 0.8), lactoferrin levels (p = 0.3), or rhinorrhea (p = 1.0). Thus air at 37 degrees C and 90% RH partially reduces the early response to antigen. Its effects are greatest on histamine release, the vascular response, and neural responses, with no effect on the glandular response. The mechanisms underlying these effects are unknown.

Adult↗

PubMed1999

Reducing relative humidity to control the house dust mite Dermatophagoides farinae.

BACKGROUND: Indoor relative humidity (RH) is the key factor that determines the survival and population development of the house dust mite Dermatophagoides farinae. Maintaining RH below 50% is one recommendation in a comprehensive plan to reduce house dust mites and mite allergen levels in homes. Even when mean daily RH is reduced below 50%, RH may rise above 50% intermittently for brief periods because of activities in the home (eg, cooking, bathing, and ventilation). OBJECTIVE: The purpose of this study was to determine how brief daily periods of moist air alternating with long spells of low ambient RH (0% or 35%) influence population survival and growth of D farinae. METHODS: Population growth was determined for D farinae at daily RH regimens of 2, 4, 6, and 8 hours at 75% or 85% RH alternating with 22, 20, 18, and 16 hours at 0% or 35% RH. RESULTS: D farinae populations declined at daily regimens of 2 hours at 75% or 85% RH alternating with 22 hours at 0% or 35% RH. Daily regimens of 4, 6, and 8 hours at 75% RH alternating with 20, 18, and 16 hours, respectively, at 35% RH provided sufficient moisture for small growths in population size. These growths after 10 weeks were reduced by 98.2%, 98.0%, and 97.3% for daily regimens of 4, 6, and 8 hours, respectively, at 75% RH (with the remainder of the day at 35% RH) compared with the growth of populations continuously exposed to 75% RH. Continuous exposure to 85% RH inhibited population growth, but alternating daily regimens of 16, 18, and 20 hours at 35% RH allowed small populations to develop, although they were reduced by 99.4%, 98.8%, and 99.1% compared with population growth at a continuous 75% RH. CONCLUSION: This study indicates that maintaining mean daily RH below 50%, even when RH rises above 50% for 2 to 8 hours daily, effectively restricts population growth of these mites and thus the production of allergen. To completely prevent population growth of D farinae, RH must be maintained below 35% for at least 22 hours per day when the daily RH is 75% or 85% for the remainder of the day.

Allergens↗

PubMed2002

Modeling the effects of concentration history on the slow desorption of trichloroethene from a soil at 100% relative humidity.

To determine the effects of concentration history on slow sorption processes, desorption kinetic profiles for trichloroethene (TCE) were measured for a soil at 100% relative humidity subject to different exposure concentrations and exposure times. Exposure concentrations ranged from 1% to 80% of the saturation vapor pressure (Ps) for TCE, and exposure times (i.e., time allowed for sorption before desorption begins) ranged from 1 to 96 days. A spherical diffusion model based on a gamma distribution of sorption rates and a gamma distribution of desorption rates was developed and applied to the data. At 80% P/Ps, the entire gamma distributions of sorption and desorption rates were available for TCE. In accordance with a micropore filling mechanism, the fraction of these distributions available for TCE sorption decreased with decreasing P/Ps. Experimental results are consistent with a micropore-filling mechanism, where the amount of slow desorbing mass decreased with decreasing exposure time, and the fraction of slow desorbing sites filled decreased with decreasing exposure concentration. Simulation results suggest that diffusion limits the rates that micropores fill, and that rates of sorption and desorption for soil contaminated at smaller values of P/Ps are, on average, less than those at larger values of P/Ps (i.e., slow desorption rates are a function of exposure concentration). Simulation results also suggest that the model adequately describes the effects of exposure concentration and exposure time on the rates of sorption and desorption, but not on the capacity of the slow sites for TCE. This work is important because contaminant concentrations in the subsurface vary in space and time, and the proposed model represents a new and mechanistically based approach to capture the effects of this heterogeneity on slow desorption.

Adsorption↗

PubMedDate not supplied

[Do the incontinent patients improve their equality of life using a humidity detector device?].

BACKGROUND: To evaluate the effect of a humidity detector device on the quality of life of patients with urinary incontinence IU. METHOD: Quasi-experimental study: a series of ten cases followed for a month. The devices were placed and the questionnaires filled in before and after using it for at least ten hours a day during a month. Health related quality of life was assessed through the questionnaires for IU convalidated and adapted to our specific environment: Urogenital Inventory Distress (UDI) and Incontinence Impact Questionary (IIQ). An improvement of 58 points by a four option Likert scale was considered a positive impact in the quality of life (IIQ). The scores obtained in UDI and IIQ are described before and after use the device and paried T test and Wilcoxon sign test were carried out to compare the scores obtained in each instance. The capacity to detect a difference of 58 points on the UDI scale was calculated (minimum relevant difference). A binomial test was undertaken to ascertain a probability of achieving an increase in the above mentioned index which would exceed the clinical relevance threshold. RESULTS: Average increase in IIQ improvement: x = 5.48 (Std Error = 20.43) 95% CI = -34.56 to 45.56. Average increase in UDI improvement: x = -11.87 (Std Error = 20.70) 95% IC = -52.45 to 28.70. The power of the analysis to detect as relevant a difference of a 588 point increase in IIQ 71.1% and probability of obtaining a relevant improvement in the questionnaire IIQ 10% (IC 95%) 0% to 39.4%. CONCLUSIONS: A negative impact in the Quality of Life due to frequent changes of incontinence pads.

Humans↗

PubMed2000

Sexual behaviour of Zebu bulls in the humid tropics of Costa Rica: single versus multiple-sire groups.

This study compares the courtship and mounting behaviour of Bos indicus bulls in single- and multiple-sire groups in Costa Rica (latitude 10 degrees 25'N, longitude 84 degrees 32'W, annual precipitation of 3096mm, temperature of 24 degrees C and humidity of 85.3%). Four, 3-4 year-old Brahman bulls with previous sexual experience were used to sire a group of 120 multiparous cows (average of 128 days post-partum and a body condition score of 2.5) allocated to two groups of 60 each: (1) single-sire mating group (SSM) and (2) multiple-sire mating group of three bulls (MSM). Bulls were rotated among groups every 7 days for 28 days. The frequency, type and duration of sexual activities (mounting and mounting attempts) and courtship activities (smelling and licking genital area, butting, supporting the head over a female and the sign of Flehmen) were calculated for each mating group. Descriptive and non-parametric statistics (Wilcoxon, Mann-Withney tests) were used to calculate differences between mating programmes. Sexual activities tended to be more frequent in the SSM group than the MSM group (267 versus 124, P>0.05). Differences in the ratios of sexual to courtship activities between both groups were significant (1:3 in SSM and 1:6 in MSM, P>0.05). Pregnancy rate averages were 28 and 37%, respectively, (P>0.05). It is concluded that under these conditions multiple-sire mating and single-sire mating achieved similar pregnancy rates.

Animals↗

PubMed2002

Dry powder inhaler: influence of humidity on topology and adhesion studied by AFM.

In the dry powder inhalers (DPIs), the adhesion results of the interactions between the active substance and the excipient. The carrier and the micronized drug particle morphologies are believed to affect the delivery of the drug. In this work, the couple studied was the lactose monohydrate and micronized zanamivir, used for the treatment of influenza. In a first approach, observations by scanning electron microscopy (SEM) have shown that the relative humidity (RH) greatly influenced the zanamivir amount fixed on the lactose monohydrate surface. This paper deals with the direct measurement in controlled atmosphere by atomic force microscopy (AFM) of the forces and the interaction ranges between a zanamivir probe and a lactose substrate. Selected zanamivir crystals were attached to the standard AFM probe. Different RH have been used in order to determine influent parameters permitting to identify the nature of adhesion forces between them. This study demonstrated that the increase of RH modified progressively the surface topology of the two components and increased the adhesion force.

Aerosols↗

PubMed1997

The effect of relative humidity of inhaled air on acoustic parameters of voice in normal subjects.

The hypothesis that relative humidity (RH) of air exerts an effect on voice has been widely accepted. The aim of this study has been to assess whether this can be demonstrated. Eight healthy subjects inhaled during ten minutes three different air conditions: dry, standard room, and humidified air. After inhalation, the subjects produced repeatedly a sustained /a/ of controlled pitch and loudness, which was analyzed for perturbation and noise-to-harmonic parameters. Perturbation measures increased after inhalation of dry air. No significant differences existed between standard and humidified air. No significant difference in the noise-to-harmonic ratio was found among the three conditions. We conclude that the human voice is very sensitive to decreases in RH of inhaled air, because even after a short provocation with dry air, a significant increase in perturbation measures was found.

Adult↗

PubMed2000

Female Pied Flycatchers fail to respond to variations in nest humidity.

We examined the possibility that a cavity-nesting passerine, the Pied Flycatcher (Ficedula hypoleuca), can modify the permeability of its eggs to water vapor facultatively in response to variations in nest humidity (P(N)). We found no significant relationship between the water-vapor conductance (G(E)) of flycatcher eggs and P(N). In addition, incubating female flycatchers failed to change their patterns of incubation when we modified P(N) experimentally. These data, coupled with large variations that occur in the G(E) of the eggs within individual clutches, suggest that Pied Flycatchers do not alter the structure of their eggs as they lay them and may not be aware of differences in P(N). It is more likely that G(E) is determined genetically and has been established by natural selection for eggs with high degrees of hatchability.

Adaptation, Physiological↗

PubMed1979

The effect of relative humidity on swine vesicular disease virus in dried films before and during formaldehyde fumigation.

Swine Vesicular Disease virus (SVDV) did not survive drying at high relative humidities (r.h.) but there was little virus loss at low r.h. Purified virus dried in films was inactivated by formaldehyde fumigation only at high r.h. Inactivation was also influenced by the suspending medium from which the virus was dried. Purified virus resuspended in distilled water and then dried, was rapidly killed, but that in tissue culture fluid survived.

Animals↗

PubMed2004

Durable microfabricated high-speed humidity sensors.

We describe a durable microfabricated humidity sensor made of interdigitated rhodium electrodes on a silicon substrate covered with a sensing film of Nafion perfluorosulfonate ionomer. Rhodium electrodes are much less prone to oxidative degradation compared to previously described gold electrode-based sensors. Even with dc excitation, Rh electrode sensors exhibit excellent long-term response stability. It has been found that low-amplitude (+/-1 V) square wave excitation can prolong the usability of gold electrode-based sensors to at least several months; however, this mode of interrogation cannot provide subsecond response times. Rhodium deposition on the microsensors is much more difficult than that of gold. We were able to attain crack-free Rh deposits by adaptation of pulsed electroplating techniques. At excitation voltages of >2 V dc, the Rh sensors respond to moisture with 10 <--> 90% rise and fall times of 30-50 ms. These are the fastest microfabricated water vapor sensors reported to date. We demonstrate applications as a breath monitor. Such sensors should also be of utility in atmospheric eddy measurements. Short-term repeatability is better than 0.6% RSD (n = 7).

Biosensing Techniques↗

PubMedDate not supplied

Plasticized waxy maize starch: effect of polyols and relative humidity on material properties.

The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on waxy maize starch was investigated. The concentration of plasticizer was fixed at 33 wt % (dry basis of starch). The structure and mechanical performance of resulting films conditioned at different relative humidity levels were studied in detail. The effect of the plasticizer on the glass-rubber transition temperature (T(g)) and crystallinity was characterized using differential scanning calorimetry. It was found that T(g) decreases with increasing moisture content and decreasing molecular weight of the plasticizer. The water resistance of starch increased steadily with the molecular weight of the plasticizer and was directly proportional to the ratio of the end to total hydroxyl groups. As the molecular weight of the plasticizer increased, the brittleness of the dry system increased. However, the use of high molecular plasticizer allowed good mechanical properties of the moist material to be obtained in terms of both stiffness and elongation at break.

Humidity↗

PubMed2001

Effects of surface type and relative humidity on the production and concentration of nitrous acid in a model indoor environment.

A nested chamber design was constructed for the purpose of studying parameters that affect indoor air chemistry. Experiments were conducted in this system to investigate the effects of three surface types (Teflon, wallpaper, and carpet) and two levels of relative humidity (50% and 70% RH) on the formation of gas-phase nitrous acid (HONO) through the heterogeneous reaction of nitrogen dioxide (NO2) with sorbed water vapor. The results of this investigation show that, compared with Teflon surfaces, carpet made of synthetic fibers increased the NO2 surface removal rate by nearly an order of magnitude and resulted in higher peak HONO concentrations. The results also suggest that the capacity of a surface to sorb water will determine if HONO is released from that surface after the NO2 source has been turned off and the heterogeneous reaction between NO2 and sorbed water is no longer significant. Vinyl-coated wallpaper was found to release HONO for prolonged periods of time after the NO2 source was turned off at both 50% and 70% RH whereas Teflon was found to do so only at 70% RH. The results of this investigation also demonstrate the utility of the nested chamber design in investigating indoor air chemistry.

Air Pollution, Indoor↗