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Results for “Environment, Controlled”

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At least 235 records · Page 13Linked to original sources

PubMed1979

Toxoplasma gondii-vertebrate cell interactions. II. The intracellular reproductive phase.

The reproduction of Toxoplasma gondii RH-strain in vertebrate cells was studied in a controlled-environment culture system. The lag period before reproduction and the doubling time of individual parasites were determined using a least-squares linear regression method of analysis which does not artificially constrain the data. In the majority of cases, the time intercept of the linear regression line was either zero, implying the lack of a lag phase before reproduction, or negative, implying the parasite had completed part of its reproductive cycle before entering the host cell. The mean doubling time of T. gondii is 10.9 h in bovine embryo skeletal muscle cells and 8.3 h in HeLa cells. This difference is not significant at the 5% level. The population doubling times of mouse-derived parasites is best described by a gamma distribution.

Animals↗

PubMed1984

Effects of environmental control on pulmonary function of horses affected with chronic obstructive pulmonary disease.

The effects of environmental control on horses affected with chronic obstructive pulmonary disease was assessed by clinical examination and pulmonary function tests, ie, maximum change in intrathoracic pressure, tidal volume, minute volume, non-elastic work of breathing, dynamic compliance, inspiratory and expiratory flow rates and arterial blood gas analysis. A controlled environment (ie, bedding horses on shredded paper and feeding a complete cubed diet) caused symptomatic COPD affected horses to become asymptomatic within four to 24 days (mean +/- sd 8.4 +/- 4.8 days). When asymptomatic, their pulmonary function values did not differ significantly from those of normal horses, which indicates that the pathophysiological changes occurring in equine COPD are reversible. The time taken for horses to become asymptomatic correlated significantly with age, duration of illness and severity of disease as adjudged by the non-elastic work of breathing.

Animals↗

PubMed1997

Evidence that elevated CO2 levels can indirectly increase rhizosphere denitrifier activity.

We examined the influence of elevated CO2 concentration on denitrifier enzyme activity in wheat rhizoplanes by using controlled environments and solution culture techniques. Potential denitrification activity was from 3 to 24 times higher on roots that were grown under an elevated CO2 concentration of 1,000 micromoles of CO2 mol-1 than on roots grown under ambient levels of CO2. Nitrogen loss, as determined by a nitrogen mass balance, increased with elevated CO2 levels in the shoot environment and with a high NO3- concentration in the rooting zone. These results indicated that aerial CO2 concentration can play a role in rhizosphere denitrifier activity.

Ammonia↗

PubMed1979

Renal and hindlimb vascular control during acute emotion in the baboon.

Blood pressure, heart rate, oxygen consumption, and blood flow to the renal and hind-limb vasculatures were measured in healthy, unanesthetized baboons (Papio cynocephalus) in a controlled environment. Appropriate behavioral techniques were applied to allow the reproducible elicitation of a conditional emotional response (CER). Section of renal nerves and autonomic pharmacologic interventions were used to determine the mechanisms for the cardiovascular responses accompanying the CER. The resistance changes in the renal and hind-limb vascular beds were generated by rapid, neurally mediated vasoconstriction of the renal vasculature and by a slower acting, circulating vasoactive agent, most probably epinephrine, which causes a delayed second constriction in the renal bed and a net dilation in the hind limbs.

Animals↗

PubMed1977

24-hour rhythms in uterine and umbilical blood flows of conscious pregnant sheep.

The possibility that 24-hour rhythms exist in uterine blood flow (UtBF) and umbilical blood (UmBF) was investigated in 5 days postoperative chronically instrumented near-term pregnant sheep acclimated to a controlled environment. UtBF, UmBF and pressure measurements were made at 15-min intervals over 24 h beginning at 0800 h. Each data series was examined for the presence of significant rhythms of a 24-hour period using a method of Fourier analysis. UtBF 24-hour rhythms were found in all ewes; UmBF 24-hour rhythms were found in 4 of 5 lambs. A consistent reciprocal phase relationship between UtBF and UmBF was evident within animals. There were no associated rhythms in maternal arterial, fetal arterial, or amniotic fluid pressures. These results indicate that the presence of circadian rhythms must be considered as a possible variable when long-term uteroplacental hemodynamic studies are planned.

Amniotic Fluid↗

PubMed1978

Establishment of small breeding colony of rhesus monkeys.

A breeding colony of 22 female and 4 male rhesus monkeys (Macaca mulatta) was established in a controlled-environment building with an outdoor run. The animals were quarantined for 2 years prior to their release into the unit. The housing, release and management of the colony are described. During the first year 19 young were born of which 17 have survived to 6 months of age. The cost of production and maintenance of the colony when compared with the cost of importing rhesus monkeys would appear to be acceptable.

Animal Feed↗

PubMed2000

[Stress management in the workplace in the era of industrial and economic change].

The globalization of the economy and the recent economic recession in Japan has accelerated down-sizing or restructuring of corporations and has resulted in the induction of a wage system according to achievement instead of the traditional seniority wage system, break-down of the life-long employment system, excess labor and increased unemployment. These rapid changes in the labor situation have increased job stress. It was reported in the survey conducted by the Ministry of Labor in 1997 that 62.8 percent of 16,000 workers had anxiety, worry and stress regarding their working life. The need for effective stress management at work has been increasing in this situation, but in the survey mentioned above only 26.5 percent of 12,000 companies replied that they had incorporated mental health measures. The characteristic features of the approaches for stress management in Japan are summarized as follows: 1) The most popular approaches are education and consultation for individual workers. 2) Systematic preventive approaches such as work control, working environment control, organizational change in the health management system, and systematic and continuous educational programs for managers are inadequate. 3) Systems to evaluation the effectiveness of these interventional approaches are also inadequate. Considering the current situation in which there is increasing job stress and a need for the occupational mental health promotion, we propose a series of mini-reviews regarding stress management at work and mention the composition of this series.

Health Promotion↗

PubMedDate not supplied

Photoperiod regulation of floral initiation for soybean plants at different ages.

Soybean plants [Glycine max (L.) Merr.] of the determinate cultivar Ransom growing in controlled environments under 16-h photoperiods were exposed to 10, 12, 14, 15, and 16-h photoperiods upon expansion of either the two primaries or fifth trifoliolate leaf (V1 and V6 developmental stages, respectively) to determine the influence of plant size on sensitivity to photoperiod. Plants were sampled at 2 to 3-day intervals over a 21-day treatment period and examined microscopically for evidence of floral development. Time of floral initiation for plants exposed to photoperiod treatments at either V1 or V6 stage varied only by a few days among photoperiods, but the subsequent differentiation of floral primordia was much more rapid at shorter than at longer photoperiods. These results confirm previous observations for plants transferred upon expansion of the first trifoliolate leaf (V2 stage) and indicate that sensitivity of floral responsiveness to photoperiod changed little with plant size.

Environment, Controlled↗

PubMedDate not supplied

Modeling the effects of light, carbon dioxide, and temperature on the growth of potato.

This study examined the effects of light, temperature and carbon dioxide on the growth of potato (Solanum tuberosum L.) in a controlled environment in order to ascertain the best growing conditions for potato in life support systems in space. 'Norland' and 'Russet Burbank' were grown in 6-L pots of peat-vermiculite for 56 d in growth chambers at the University of Wisconsin Biotron. Environmental factor levels included continuous light (24-h photoperiod) at 250, 400, and 550 micromoles m-2 s-1 PPF; constant temperature at 16, 20, and 24 degrees C; and CO2 at approximately 400, 1000, and 1600 microliters L-1. Separate effects analysis and ridge analysis provided a means to examine the effects of individual environmental factors and to determine combinations of factors that are expected to give the best increases in yields over the central design point. The response surface of Norland indicated that tuber yields were highest with moderately low temperature (18.7 degrees C), low CO2 (400 microliters L-1) and high light (550 micromoles m-2 s-1 PPF). These conditions also favored shorter stem growth. Russet Burbank tuber yields were highest at moderately low temperature (17.5 degrees C), high CO2 (1600 microliters L-1) and medium analyses will be used to project the most efficient conditions for growth of potatoes in closed ecological life support systems (CELSS) in space colonies.

Carbon Dioxide↗

PubMed1975

Response of mice to repeated photoperiod shifts: susceptibility to stress and barbiturates.

Three inbred strains of mice selected for their spontaneous aggressive behavior and differential susceptibility to stress were exposed to a controlled environment where on an average of once every 4 days for 76 days and subsequently on an average of once every 2 days for an additional 55 days a 12L:12D photoperiod was reversed by 180 degrees. This procedure did not affect the growth of the mice and appeared to reduce fighting. However, plasma corticosterone concentrations in all three strains of mice were high, and their response to a 24-hr cold stress was no longer evident. The most pronounced effect of the altered photoperiod was on the barbiturate-induced sleeping time which showed a 40% reduction in all strains in spite of differential suceptibility to the drug among strains. It is concluded that repeated random phase shifting by varying the photoperiod is a stressful experience to which animals do not adapt and that the ability to respond to an additional stimulus or drugs may be greatly altered.

Aggression↗

PubMed1977

Acute and repetitive human exposure to isobutane.

Eight adult volunteers of both sexes were exposed to isobutane in a controlled-environment chamber for the purpose of monitoring their physiological responses to a series of gas concentrations ranging from 250 to 1,000 ppm. First, the response to exposure periods of 1 min, 2 min, 1 h, 2 h, and 8 h were studied. There being no untoward responses to these acute exposures, the eight volunteers were exposed repetitively to isobutane at concentrations of 500 ppm, 1, 2 or 8 h per day, five days per week for two weeks. Then exposures to two mixtures of isobutane and propane for 1, 2 or 8 h per day for two days were studied. During the investigation all subjects were kept under comprehensive medical surveillance. No untoward subjective responses or abnormal physiological responses occurred during or following these exposures. Special emphasis was placed on evaluating the cardiac and pulmonary response to these exposures through the use of continuous ECG telemetry and serial computerized spirometric measurements. The following serial laboratory studies were unaltered by the exposures: complete blood count, urinalysis, serum alkaline phosphatase, SGOT, LDH, serum bilirubin, blood sugar, serum calcium, serum phosphorus, BUN, spontaneous electroencephalogram, visual evoked response, a battery of cognitive tests, and an ACTH stimulation test.

Adrenal Cortex↗

PubMed1996

The NASA OCEAN project--an ocean-space analog

An advanced life support system (ALS) with bioregenerative components may one day be required for long-term, deep space exploration, in extended missions to Mars or in establishing long-term bases on the moon. Intensive research programs on such ALS systems have been ongoing throughout the National Aeronautics and Space Administration (NASA) since 1988. Notably, projects have been initiated at the John F. Kennedy Space Center (KSC), Ames Research Center (ARC), and the Lyndon B. Johnson Space Center (JSC). The KSC ALS work has been named the "Breadboard Project" because of its approach developing the components and combining them into a breadboard to understanding the bioregenerative ALS picture [also called a Controlled Ecological Life Support System (CELSS)] in smaller pieces, similar to an electronic "breadboard." The Breadboard Project has been involved for 7 years in the study of higher crops grown in a 113 m3 chamber--the longest operating and largest such closed, controlled growth chamber in the world. This chamber has proven itself to be very successful in growing a wide variety of crops from seedlings to harvest and in helping researchers understand the complex biological cycle of such edible plants in closed, environmentally controlled environments. Because the system's ultimate use will be a more challenging environment, moving a specially designed piece of the system into extreme conditions was an important test. Engineers at KSC developed a compact, portable, functional plant module for testing in the world's only fixed seafloor laboratory at Key Largo, FL. The laboratory, called MarineLab, is operated out of the facilities of the Marine Resources Development Foundation in a lagoon of some 10 m depth. The project was called the OCEAN project (Ocean CELSS Experimental Analog NASA).

Ecological Systems, Closed↗

PubMed1989

Potato growth in response to relative humidity.

Potato plants (Solanum tuberosum L. cvs. Russet Burbank, Norland, and Denali) were grown for 56 days in controlled-environment rooms under continuous light at 20C and 50% or 85% RH. No significant differences in total plant dry weight were measured between the humidity treatments, but plants grown under 85% RH produced higher tuber yields. Leaf areas were greater under 50% RH and leaves tended to be larger and darker green than at 85% RH.

Biomass↗

PubMed1998

Microwave lamp characterization.

The operating properties of the SAA microwave lamp developed by Fusion Lighting, Inc. were determined with reference to its usefulness in Bioregenerative Life Support Systems (BLSS). Lamp flux density in several wavelength ranges, spectral output, and temperature response (-10 to +40 degrees C) were determined by mounting the lamp and sensors in a controlled environment chamber. Lamp intensity distribution also was measured using a swing arm apparatus with a 1-m radius. A model was developed to characterize the intensity distribution of the lamp as a function of lamp geometry and output properties. The lamp was found to produce a spectral output similar to that of earlier lamp models, but with a higher photosynthetic output per lumen and per input watt. Radiant energy output was measured to be 0.399 radiant watts per micromole s-1 PAR compared with 0.56 radiant watts per micromoles s-1 PAR for high-pressure sodium lamps. Total lamp output dropped approximately 0.4% for every degree Celsius rise in ambient temperature, with little change in light quality. The intensity distribution of the lamp was found to produce a fairly uniform flux density (+/- 22%) in a 40 degrees cone from lamp nadir.

Ecological Systems, Closed↗

PubMed1983

Enhancement of lettuce yield by manipulation of light and nitrogen nutrition.

Several levels of photosynthetic photon flux density (PPFD) were tested for effects on growth of 4 cultivars of lettuce (Lactuca sativa L.) under controlled-environment conditions. Growth of 'Salad Bowl', 'Bibb', and 'Ruby' was greater at 932 micromoles s-1 m-2 than at < or = 644 micromoles s-1 m-2 under a 16-hour photoperiod. Thirty mM NO3- or 5 mM NH4+ + 25 mM NO3- increased leaf dry weight while reducing leaf chlorosis in 'Salad Bowl' and 'Grand Rapids' relative to that with 15 mM NO3-, and reduced leaf purpling in 'Bibb' and 'Ruby' with little or no effect on yield. Continuous illumination with 455 or 918 micromoles s-1 m-2 stimulated yield of 'Salad Bowl' and 'Bibb' when 30 mM N as NH4+ + NO3- was used relative to that with 15 mM NO3-.

Culture Media↗

PubMed1999

Coupling machine vision and crop models for closed-loop plant production in advanced life support systems.

We present a conceptual framework for coupling nondestructive sensing to crop models for closed-loop plant production for NASA's program in advanced life support. Coupling is achieved by comparing nondestructive observations with model predictions of plant growth and development. The information thus provided may be useful in diagnosing problems with the plant growth system, or as a feedback to the model for evaluation of plant scheduling and potential yield. We illustrate this concept using canopy height and machine vision measured top projected canopy area (TPCA), and the CROPGRO crop growth model. Model simulations of soybean TPCA and canopy height were evaluated against data for hydroponic soybean grown under two separate light/dark cycle temperature regimes (23/19 degrees C and 26/22 degrees C). Our results suggest that TPCA and canopy height are potentially useful variables for closed-loop plant production in controlled environments during the first few weeks of growth, before canopy closure.

Biomass↗

PubMed2005

Packing room cleanliness studied.

Comparing the performance of eight sterile service department packing rooms with regard to their environmental cleanliness has shown: All those tested have airborne particle levels at an acceptable level but some were significantly better than others. Microbial sampling of the packing room air using active sampling techniques has clearly shown that in some departments the levels are unacceptable. This is in contrast to passive air sampling (settle plates), which does not clearly reveal this difference. Examination of the microbial levels on surfaces has shown that a) the bacterial levels on work stations surfaces is variable and this probably reflects different working practices and cleaning regimes and b) the bacterial level on floors is variable and could be improved on. A better awareness of what controls are necessary in the controlled environment of a packing room is clearly required by all. This would include designers as well as those involved in daily operations.

Air Pollution, Indoor↗

PubMed2004

Space Station Biological Research Project (SSBRP) Cell Culture Unit (CCU) and incubator for International Space Station (ISS) cell culture experiments.

The CCU and Incubator are habitats under development by SSBRP for gravitational biology research on ISS. They will accommodate multiple specimen types and reside in either Habitat Holding Racks, or the Centrifuge Rotor, which provides selectable gravity levels of up to 2 g. The CCU can support multiple Cell Specimen Chambers, CSCs (18, 9 or 6 CSCs; 3, 10 or 30 mL in volume, respectively). CSCs are temperature controlled from 4-39 degrees C, with heat shock to 45 degrees C. CCU provides automated nutrient supply, magnetic stirring, pH/O2 monitoring, gas supply, specimen lighting, and video microscopy. Sixty sample containers holding up to 2 mL each, stored at 4-39 degrees C, are available for automated cell sampling, subculture, and injection of additives and fixatives. CSCs, sample containers, and fresh/spent media bags are crew-replaceable for long-term experiments. The Incubator provides a 4-45 degrees C controlled environment for life science experiments or storage of experimental reagents. Specimen containers and experiment unique equipment are experimenter-provided. The Specimen Chamber exchanges air with ISS cabin and has 18.8 liters of usable volume that can accommodate six trays and the following instrumentation: five relocatable thermometers, two 60 W power outlets, four analog ports, and one each relative humidity sensor, video port, ethernet port and digital input/output port.

Automation↗