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Results for “Environment, Controlled”

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PubMed1990

Is increased metabolism in rats in the cold mediated by the thyroid?

1. In the rat variation of metabolic heat production is the principal effector of thermoregulation. There is a continuous relationship between ambient temperature and metabolic rat over the whole range of tolerable environmental temperature. The mechanism that controls metabolic rate is unknown; this paper reports an attempt to test whether thyroid hormones provide the controlling pathway. 2. First, the changes in metabolic rate and in the plasma concentrations of thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) were measured in rats living in a controlled environment, first at 23 degrees C and then at 6 degrees C. Metabolic rate increased from approximately 290 to 470 kJ day-1 when the temperature was lowered, a factor of ca 1.6, and the diurnal rhythm disappeared. The concentration of TSH increased from approximately 320 to 450 ng ml-1 (with loss of diurnal rhythm) and of T3 from ca 0.7 to 1.0 nmol l-1, a factor of ca 1.4 in each case. T4 concentration did not change. 3. Next, a dose schedule of T3 was found that, when injected I.V. via indwelling jugular cannulae in the same rats in an environment at 23 degrees C, maintained an increase in T3 concentration rather greater than had been found at 6 degrees C. 4. This dose of T3, given to the same rats at 23 degrees C, did not affect metabolic rate (or its diurnal pattern). 5. It is therefore unlikely that the increase in T3 concentration evoked the increase in metabolic rate when ambient temperature was changed from 23 to 6 degrees C; and therefore that the thyroid controls variation of metabolic rate in 'everyday' thermoregulation in the rat.

Animals↗

PubMed1998

A clinical study of bacterial contamination of chlorhexidine-coated filaments of an interdental brush.

The purpose of this study was to assess the effectiveness of a chlorhexidine coating on the nylon filaments of an interdental brush in reducing bacterial contamination from actual clinical usage. In addition, the residual antimicrobial capacity of the coating over time from clinical exposure was studied. The same type of interdental brush, one with chlorhexidine-coated nylon filaments (antibacterial) and one with uncoated (control) nylon filaments was used with 20 subjects who were participating in a periodontal maintenance program. All subjects had more than four interproximal spaces large enough to accommodate the interdental brush at the start of the study. The subjects served as their own controls in this cross-over design. They used their brushes daily for one and two weeks, respectively. After the last use, each brush was kept in a controlled environment (20-22 degrees C, 65% relative humidity) for 24 hours for air drying. It was found that antimicrobial activity was detected on the chlorhexidine-coated filaments, even after one or two weeks of storage. The mean residual antimicrobial activity of the test filaments at one week was significantly higher than that found on the filaments after two weeks. The mean number of bacteria attached to the antimicrobial filaments were significantly fewer than those on uncoated, control filaments at both one week and two weeks of usage. These results suggest that chlorhexidine-coated filaments on an interdental brush can significantly reduce bacterial contamination and retain this antimicrobial activity for up to two weeks of use.

Adult↗

PubMed2005

Assessing performance in complex team environments.

This paper provides a brief introduction to team performance assessment. It highlights some critical aspects leading to the successful measurement of team performance in realistic console operations; discusses the idea of process and outcome measures; presents two types of team data collection systems; and provides an example of team performance assessment. Team performance assessment is a complicated endeavor relative to assessing individual performance. Assessing team performance necessitates a clear understanding of each operator's task, both at the individual and team level, and requires planning for efficient data capture and analysis. Though team performance assessment requires considerable effort, the results can be very worthwhile. Most tasks performed in Command and Control environments are team tasks, and understanding this type of performance is becoming increasingly important to the evaluation of mission success and for overall system optimization.

Humans↗

PubMed2006

Paradoxical sleep deprivation and sleep recovery: effects on the hypothalamic-pituitary-adrenal axis activity, energy balance and body composition of rats.

Numerous studies indicate that sleep deprivation alters energy expenditure. However, this conclusion is drawn from indirect measurements. In the present study, we investigated alterations of energy expenditure, body composition, blood glucose levels, plasma insulin, adrenocorticotropic hormone (ACTH) and corticosterone levels immediately after 4 days of sleep deprivation or after 4 days of sleep recovery. Rats were sleep deprived or maintained in a control environment (groups sleep-deprived/deprivation and control/deprivation). One half of these animals were sacrificed at the end of the deprivation period and the other half was transported to metabolic cages, where they were allowed to sleep freely (groups sleep-deprived/recovery and control/recovery). At the end of the sleep recovery period, these rats were sacrificed. After sleep deprivation, sleep-deprived rats exhibited loss of body weight, augmented energy expenditure and reduced metabolic efficiency compared to control rats. These alterations were normalised during the sleep recovery period. The body composition of sleep-deprived rats was altered insofar as there was a loss of fat content and gain of protein content in the carcass compared to control rats. However, these alterations were not reversed by sleep recovery. Finally, plasma levels of insulin were reduced during the sleep deprivation period in both control and sleep deprived groups compared to the recovery period. After the deprivation period, plasma ACTH and corticosterone levels were increased in sleep-deprived rats compared to control rats, and although ACTH levels were similar between the groups after the sleep recovery period, corticosterone levels remained elevated in sleep-deprived rats after this period. By means of direct measurements of metabolism, our results showed that sleep deprivation produces increased energy expenditure and loss of fat content. Most of the alterations were reversed by sleep recovery, except for corticosterone levels and body composition.

Adipose Tissue↗

PubMed1975

Shigellosis in day-care centres.

Increasing numbers of outbreaks of shigellosis in day-care centres have been reported to the Center for Disease Control since 1972. Investigations reveal certain unique epidemiological features of shigellosis in this setting. Attack-rates tend to be higher than in outbreaks in primary schools, and epidemiologically these outbreaks resemble those in custodial institutions. Person-to-person transmission is the usual mode of spread; secondary spread within households is common, and there may also be significant spread to the community at large. Preventive measures should be directed at children, staff, and the day-care centre environment. Control of outbreaks may require closing the centre and must include separation of infected and uninfected persons, judicious use of antibiotics, and correction of deficiencies in hygiene and health education. Improved surveillance of shigellosis in day-care centres will be an aid in efforts toward controlling this increasingly important public-health problem.

Adult↗

PubMed1996

GTP synthases. Proton pumping and phosphorylation in ligand-receptor-G alpha-protein complexes.

A structural model for a ligand-receptor-Gs alpha-protein complex to function as a GTP synthase is presented. The mechanism which is dependent on the movement and rotation of the G alpha-protein alpha 2-helix is seen to involve the delivery of, at least, one proton to the phosphorylation site in the rotation of this helix. The cycle is driven by a ligand-mediated proton pump through the alpha-helices of the receptor, attachment of the conserved Tyr-Arg-Tyr receptor proton shuttle being made to an aspartate group on the Gs alpha-protein terminal sidechain, which is itself linked to the Asn-Gln interaction known to control movement and rotation of the alpha 2-helix between .GDP and .GTP structures. The energetics of proton transfer through the shuttle mechanism and delivery of a proton to the aspartate group are shown to be sufficient to rupture this controlling interaction and its associated backbone bond. The complex leads to full spatial and energetic definition of the receptor proton shuttle mechanism, while there is a striking association of further Tyrosine and Arginine residues in the vicinity of the Gs alpha-protein Asn-Gln interaction. Calculations at the HF 6-31G** level confirm that a critical balance between ion pair and neutral forms of Tyr-Arg interactions under multiply hydrogen bonded conditions in a hydrophobic environment controls proton transfer and recovery mechanisms. The intrinsic preference of the neutral Tyr-Arg form over the ion-pair is 14.0 kcal/mol. Activation of the Tyrosine oxygen atom in the neutral form by single-NH or -OH groups reduces this difference by some 6.4-8.6 kcal/mol but the dominance of the neutral form is maintained. The expected slight overestimates are consistent with the maximum activation enthalpy of 11.0-12.0 kcal/ mol required to initiate proton transfer through the shuttle. The extended form of the shuttle with the Arginine acting competitively between the two Tyrosine residues allows interpretation of observed enthalpic differences in ligand binding with and without the presence of GTP. The uniqueness of Gs proteins among the G alpha-proteins is seen as their inability to transfer a proton directly through the alpha 2-helix switch Asn-Gln residues. A possible proton pathway to the mid-point of the Gs alpha-protein alpha 2 helix is outlined.

Amino Acid Sequence↗

PubMed1981

Portal blood concentrations of conjugated cholic and chenodeoxycholic acids. Relationships to bile salt synthesis in liver cells.

1. Rats were maintained in a strictly controlled environment of 12 h illumination and 12 h darkness. At regular intervals during the light/dark cycle the portal blood conjugated cholic acid and conjugated chenodeoxycholic acid concentrations were measured. The bile salt concentrations exhibited similar diurnal rhythms, the highest concentrations occurring in the middle of the dark phase. 2. The concentrations of conjugated cholic and chenodeoxycholic acids in the portal blood of rats fed a diet containing the bile salt sequestrant, cholestyramine, were significantly lower than those found in rats given a control diet. 3. During total biliary drainage the portal blood concentrations of conjugated cholic and chenodeoxycholic acids fell to a minimum 6--8 h after the start of the experiment, whereas bile salt synthesis in hepatocytes isolated from the rats was not increased until the least 13 h after the commencement of total biliary drainage. 4. These results suggest that the concentrations of bile salts in the portal blood do not affect directly the diurnal fluctuation in rates of bile salt synthesis, as the response of synthesis to a change in portal blood bile salt concentrations is too slow. 5. When the rats were given a small supplement of cholesterol in the diet to suppress hepatic cholesterologenesis prior to being subjected to total biliary drainage, the changes in the portal blood concentrations of conjugated cholic and chenodeoxycholic acids and the synthesis of the two bile salts by isolated hepatocytes were similar to those found in rats given the control diet. 6. The rise in bile salt production seen during biliary drainage may not be dependent exclusively on a preceding increase in cholesterol synthesis.

Animals↗

PubMed1995

Physiological and nutritional responses of steers infested with varying densities of Amblyomma americanum (Acari: Ixodidae).

The effects of varying densities of lone star tick, Amblyomma americanum (L.), on measured physiological parameters of beef cattle in a controlled environment was determined. Steers were infested with either 0, 20, 60, or 120 pairs of adult ticks. Heart rate, respiration, rectal temperature, fecal and urine excretions, and water and feed consumption were monitored daily. Blood samples were taken every 3rd d to measure cortisol, total proteins, urea nitrogen, and glucose levels. Hematocrits were also taken at each blood sampling. Results showed that A. americanum evoked elevated heart rates. The other measured physiological and nutritional responses of parasitized steers were similar to the control steers. These results suggest that tick densities were too low to cause physiological stress under the conditions used in this study. The methodology precluded detection of the parameters measured. A. americanum does not affect the parameters measured, or that fluctuating environmental parameters and varying host nutritional states may play major roles in modulating the effect of A. americanum infestations on cattle in nature.

Animal Nutritional Physiological Phenomena↗

PubMed1997

In vivo and vitro in diagnosis of latex allergy at Groote Schuur Hospital.

OBJECTIVE: The aim of this study was to evaluate the diagnostic utility of skin-prick tests, radio-allergosorbent tests (CAP RASTs), basophil histamine release, sulphidoleukotriene release and Western blotting in the diagnosis of latex allergy at Groote Schuur Hospital. DESIGN: Patients with a history suggesting latex hypersensitivity were recruited via staff health and allergy clinics at Groote Schuur Hospital. A clinical assessment was followed by laboratory investigation and skin-prick testing. A control group consisted of laboratory and hospital staff who had regular latex exposure but were asymptomatic. SETTING: Hospital-based cohort at Groote Schuur Hospital. PARTICIPANTS: Twenty-three patients with suspected latex allergy; 10 control subjects exposed to, but not clinically sensitive to, latex. MAIN OUTCOME: Skin-prick testing was more sensitive than in vitro diagnostic tests for the diagnosis of latex allergy. RESULTS: Eighteen of 21 (85.7%) of the patients tested had a positive skin-prick test with a commercial latex solution (Allerbioprick) and 17/21 (80%) tested skin-prick-positive with an in-house glove extract. CAP RASTs were positive in 13/23 patients (56.5%), sulphidoleukotriene release was positive in 10/23 (43%), histamine release assay was positive in 10/23 (45%) and Western blots were positive in 8/23 (34.7%). All patients with only urticaria were Western blot-negative and CAP RAST-negative, suggesting that they have very little circulating latex-specific IgE. Although patients who were Western blot-positive tended to have multi-organ involvement, both patients with anaphylaxis were Western blot-negative. CONCLUSION: Latex allergy is a significant clinical problem at Groote Schuur Hospital. Titrated skin-prick testing performed in a controlled environment can safely and reliably confirm the diagnosis in patients who do not give a history of anaphylaxis. The CAP RAST was the most sensitive in vitro test for latex allergy locally available, but lacks sensitivity in patients presenting with urticaria only.

Adult↗

PubMed1977

Acquisition and extinction of an operant response in differentially reared rats.

Rats reared in either socially isolated or control environments were trained to bar press for food on a variable interval schedule of reinforcement, beginning at 125 days of age for 37 consecutive days. Following this phase the subjects were tested for response persistence during an extinction test. Next, the subjects were compared on measures of spontaneous recovery and the rate of response reacquisition when the reinforcement contingencies were once again reinstated. Though no differences were discerned between the groups on measures of acquisition, maintenance, and reacquisition, isolated rats emitted many more responses than the controls during extinction testing.

Animals↗

PubMed2002

Hydroponically cultivated radish fed L-galactono-1,4-lactone exhibit increased tolerance to ozone.

Leaf L-ascorbate content of an ozone (O3)-sensitive radish genotype (Raphanus sativus L. cv. Cherry Belle) was increased 2-fold by feeding hydroponically cultivated plants L-galactono- 1,4-lactone (GalL). Plants were grown in controlled-environment chambers ventilated with charcoal/Purafil-filtered air, and administered one of two O3 fumigation regimes: chronic exposure (75 nmol O3 mol(-1) for 7 h day(-1) for 21 days) and acute exposure (180 nmol O3 mol(-1) for 9 h). Chronic O3 exposure decreased root growth by 11% in plants maintained in pure nutrient solution (-GalL), but resulted in no change in root growth in GalL-fed plants (+GalL). Similarly, GalL-feeding counteracted the negative effects of O3 on CO2 assimilation rate observed in control plants (-GalL). Under acute O3 exposure, GalL-fed plants showed none of the visible symptoms of injury, which were extensive in plants not fed GalL. Leaf CO2 assimilation rate was decreased by acute 03 exposure in both GalL treatments, but the extent of the decline was less marked in GalL-fed plants. No significant changes in stomatal conductance resulted from GalL treatment, so O3 Uptake into leaves was equivalent in + GalL and -GalL plants. Feeding GalL, on the other hand, enhanced the level of ascorbate, and resulted in the maintenance of the redox state of ascorbate under acute O3 fumigation, in both the leaf apoplast and symplast. The effect of GalL treatment on ascorbate pools was consistent with the reduction in O3 damage observed in GalL-fed plants. Attempts to model O3 interception by the ascorbate pool in the leaf apoplast suggested a greater capacity for O3 detoxification in GalL-fed plants, which corresponded with the increase in O3 tolerance observed. However, modelled data for GalL-fed plants suggested that additional constituents of the leaf apoplast may play an important role in the attenuation of environmentally-relevant O3 fluxes.

Air Pollutants↗

PubMed1981

Complement receptor positive spleen cells in microwave (2450-MHz)-irradiated mice.

Male CBA/J mice were exposed under far-field conditions in a temperature and humidity controlled environment to 2450-MHz (CW) microwaves. Mice were exposed once for 30 minutes at a power density of 15, 20, 30, or 40 mW/cm2. The whole-body-averaged dose rate was approximately 0.7 mW/g per mW/cm2. Six days after irradiation, the percentage of complement-receptor-positive (CR+) spleen cells was determined. No difference was observed in the percentage of CR+ spleen cells of young adult (10-12-week-old) mice exposed at any of the power densities as compared with sham-irradiated controls. However, a significant (P less than .05) increase was observed in the percentage of CR+ cells from 16-week old mice exposed at 40 mW/cm2. This increase in CR+ cells was accompanied by a significant (P less than .05) decrease in the number of nucleated cells in the spleens of these mice. This change in CR+ and nucleated spleen cells was not consistently produced. The available data indicate that the age and strain of the mouse, the microwave exposure characteristics, and the environmental conditions may all be sources of variation that affect the CR+ end point.

Animals↗

PubMed1995

Effects of reactive hydrocarbons and hydrogen peroxide on antioxidant activity in cherry leaves.

One-year-old cherry trees were fumigated with propene and gas-phase hydrogen peroxide, singly and in combination, in controlled-environment chambers for an 8-week period during the summer season. A UV light source was included with the combined propene and hydrogen peroxide regime to provide a source of hydroxyl radicals and ozone, and thus all the constituents of a photochemical smog. Measurements were made of soluble protein concentration and of glutathione reductase activity in leaf extracts from two or three leaf classes in plants from each treatment regime at the end of each fumigation period. Significant increases in soluble protein concentration with respect to the controls were found in plants fumigated with propene and hydrogen peroxide. The occurrence and extent of these differences depended on the leaf class and on the timing of the fumigation period over the summer with respect to bud break. The activity of glutathione reductase was found to be significantly increased in mature lower leaves of plants which had been fumigated with hydrogen peroxide. This effect was independent of the timing of fumigation with respect to bud break. Enzyme activity was also increased in propene and in propene plus hydrogen peroxide treatments, but only when plants were fumigated early in the growth season.

Journal Article↗

PubMed1998

Contingent negative variation in patients with chronic daily headache.

The aim of this study was the investigation of amplitude and habituation of contingent negative variation (CNV) in migraine and chronic daily headache (CDH) patients in order to describe possible neurophysiological features responsible for the clinical transformation and worsening of the headache. Fifteen females suffering from migraine without aura and 15 females diagnosed with CDH evolved from migraine without aura with interparoxysmal chronic tension-type headache (transformed migraine), underwent CNV recording. Fifteen healthy females matched for age served as controls. CNV was obtained from C3 and C4 using the standard reaction time paradigm and 3 sec ISI. The amplitudes and habituation of total CNV, early and late components, and of post-imperative negative variation (PINV) were calculated. The migraine patients were characterized by significantly more pronounced negativity of the early component and total CNV, compared to CDH sufferers and controls. CDH patients demonstrated significantly reduced negativity of the late component and pronounced PINV compared to the other groups. The early component of CNV did not habituate in migraine or CDH patients. However, the impaired habituation in CDH was related to significantly lower amplitudes. These results support the diagnostic and scientific value of habituation in migraine research and therapy. Late components of CNV and PINV can be considered as predictive variables for transformation of migraine. The results are discussed in terms of the relationship between late CNV, PINV, environment control abilities and susceptibility for development of depression.

Adaptation, Psychological↗

PubMed1989

Health care delivery systems in review.

As physicians grapple with restrictive utilization review procedures, evidence indicates that these measures are not as cost effective as originally believed. Cost containment pressures from employers, limitations on price fixing and incentive arrangements all contribute to a further controlled environment for physicians practicing within HMOs. An SMG census reveals that HMO enrollment grew significantly in 1988, while the number of plans declined. The financial condition of the industry is improving, despite the demise of one of the largest plans. Successful plans are analyzing their market share and developing niche products to improve their position.

Cost Control↗

PubMedDate not supplied

Controlled exposure of volunteers with chronic obstructive pulmonary disease to nitrogen dioxide.

Twenty-two volunteers with chronic obstructive pulmonary disease were exposed to nitrogen dioxide at 0.0, 0.5, 1.0, and 2.0 ppm in a controlled environment chamber. Exposure lasted 1 hr and included two 15-min exercise periods, during which the mean ventilation rate was roughly 16 L/min. Pulmonary mechanical function was evaluated pre-exposure, after initial exercise, and at the end of exposure. Blood oxygenation was measured by ear oximetry pre-exposure and during the second exposure period. Symptoms were recorded during exposures and for 1-wk periods afterward. No statistically significant changes in symptom reporting could be attributed to nitrogen dioxide exposure at any concentration, compared to the 0.0 ppm control condition. Measures of pulmonary mechanics showed either no significant changes, or small and equivocal changes. Arterial oxygen saturation showed marginal improvement with exercise, regardless of nitrogen dioxide concentration.

Aged↗

PubMed1992

Familial influence on plaque formation in the beagle brain.

Aged canines exhibit central neuropathological changes strikingly similar to those seen in patients with Alzheimer's disease. In this study, brain tissue from pure bred beagles raised in a controlled environment were examined for Alzheimer-like pathology. The mean age of the animals was 15.6 years. The incidence of plaques among these 29 dogs was 65.5%. Of the 19 samples that demonstrated Alzheimer-like pathology, 18 were characterized as diffuse and one as neuritic. Plaque density was found to be independent of age. Plaque numbers were highest in the perirhinal cortex and the adjacent temporal cortex. Familial influence on plaque development is supported by congruence within 15 of the 16 litters examined (p < 0.001). In this environmentally controlled group the diffuse plaques were rarely converted to the dense neuritic plaques found in Alzheimer's disease.

Aging↗

PubMed2004

Experimental infection of house finches with Mycoplasma gallisepticum.

Mycoplasma gallisepticum (MG) has caused an endemic upper respiratory and ocular infection in the eastern house finch (Carpodacus mexicanus) after the epidemic first described in 1994. The disease has been studied by a number of investigators at a population level and reports describe experimental infection in group-housed MG-free house finches. Because detailed observation and evaluation of individual birds in group-housed passerines is problematic, we studied individually housed house finches that were experimentally inoculated with the finch strain of MG in a controlled environment. To accomplish this, a study was conducted spanning the period of November 2001-April 2002 with 20 MG-free (confirmed by the rapid plate agglutination assay and polymerase chain reaction [PCR] assay) eastern house finches captured in the Cayuga Basin area of central New York (USA) in the summer of 2001. After a period of acclimatization and observation (12 wk), 20 finches were inoculated with a 0.05-ml aliquot of MG (3.24 x 10(5) colony-forming units/ml) via bilateral conjunctival sac instillations. Two additional finches acted as controls and were inoculated in the same manner with preservative-free sterile saline solution. After inoculation, all finches except the controls exhibited clinical signs of conjunctivitis within 2-6 days. The progression of the disease was evaluated by several methods, including PCR, behavioral observations, and physical examination including eye scoring, body weight, and body condition index. Over a period of 21 wk, MG-infected finches developed signs of disease and recovered (80%), developed signs of disease and progressed to become chronically infected (15%), or died (5%). We hypothesize that the high survival rate and recovery of these finches after infection was associated with the use of controlled environmental conditions, acclimatization, a high plane of nutrition, and low stocking (housing) density, all of which are factors documented to be important in the outcome of MG infections in domestic poultry and other species.

Animals↗