PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Environment, Controlled”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed1980

A monogamous system of breeding chimpanzees in a controlled environment.

The management and reproductive performance of a chimpanzee colony is discussed. Short-term monogamous breedings, arranged at the estimated time of ovulation, as determined by the cyclical changes in sex skin tumescence and by a new immunological test for the preovulatory peak in urinary LH excretion, are planned according to blood group and social compatibility. Progress of gestation is monitored weekly by the "NICHD subhuman primate pregnancy test" and by prenatal clinical examinations in the last trimester. Fertility of individual animals, and of the colony as a whole, is reflected in the number of cycles of breeding required for conception. The indoor system of single caging of adults and the special system of animal waste collection offers the ability to completely control and manipulate the animals for efficient breeding, for clinical health care, and for implementation of scientific protocols.

Animals↗
PubMed1996

Biomass accumulation in hydroponically grown sweetpotato in a controlled environment: a preliminary study.

In the development of a plant growth model, the assumptions made and the general equations representing an understanding of plant growth are gradually refined as more information is acquired through experimentation. One such experiment that contributed to sweetpotato model development consisted of measuring biomass accumulation of sweetpotato grown in hydroponic culture in a plant growth chamber. Plants were started from fifteen centimeter long 'TU-82-155' sweetpotato vine cuttings spaced 25 cm apart in each of 18 rectangular growing channels (0.15 by 0.15 by 1.2m) in a system designed to use the nutrient film technique (NFT). Each channel contained four plants. The 3.5m by 5.2m plant growth chamber environmental parameters included an 18h photoperiod, 500 micromoles m-2 s-1 of photosynthetic photon flux (PPF), and a diurnal light/dark temperature of 28 degrees C/22 degrees C. The relative humidity was 80 +/- 5% and the CO2 partial pressure was ambient (350 ppm). The nutrient solution contained in 30L reservoirs was a modified half Hoagland's solution with a 1:2.4 N:K ratio and a pH of 6.2. Solution replenishment occurred when the electrical conductivity (EC) level dropped below 1050. Plants were harvested at 15 days after planting (DAP) and weekly thereafter until day 134. By 57 DAP, stems and fibrous roots had acquired 90% of their total dry biomass, while leaves had reached 84% of their maximum dry biomass. Beginning at 64 DAP dry biomass accumulation in the storage roots dominated the increase in dry biomass for the plants. Dry weight of storage roots at 120 DAP was 165 g/plant or 1.1 kg/m2. Resulting growth curves were consistent with the physiological processes occurring in the plant. Results from this study will be incorporated in a plant growth model for use in conjunction with controlled life support systems for long-term manned space missions.

Biomass↗
PubMed2006

Temporal and spatial dispersal of cladobotryum conidia in the controlled environment of a mushroom growing room.

Cladobotryum spp. are responsible for cobweb disease of mushrooms. In two commercial and one experimental mushroom-growing room, Cladobotryum conidia were released into the air in direct response to physical disturbance of disease colonies during either crop watering or treatment by covering with salt to 10 mm. Conidia were detected using a Burkard spore trap or agar-based trap plates. A maximum concentration of approximately 25,000 conidia m(-3) was recorded in a small (75-m(3)) experimental growing room in the hour following the salting of 16 cobweb patches (0.55 m(2)). Concentrations of 100 and 40 conidia m(-3) were recorded in the two larger commercial growing rooms in the hour following the salting of 18 and 11 patches of cobweb (diameter, approximately 50 to 200 mm), respectively. In controlled experiments, disturbed conidia were dispersed rapidly throughout a small growing room, with 91 to 97% of conidia settling out within 15 min. Eighty-five percent of conidia settled out within a 0.5-m radius when air-conditioning fans were switched off, consistent with airborne spore dispersal. Alternative methods for treating diseased areas to minimize conidial release and distribution were investigated and included covering disease colonies with damp paper tissue prior to salt application (tissue salting) and holding a dust extractor above disease colonies during salt application. Both methods resulted in no detectable airborne conidia, but the tissue paper salting technique was more convenient. Prevention of airborne conidial release and distribution is essential to avoid mushroom spotting symptoms, secondary colonies, and early crop termination.

Agaricus↗
PubMed1999

Fine root respiration in mature eastern white pine (Pinus strobus) in situ: the importance of CO(2) in controlled environments.

We measured seasonal fine root respiration rate in situ while controlling chamber temperature and [CO(2)]. Atmospheric [CO(2)] ([CO(2)](a)) and measured soil [CO(2)] ([CO(2)](s)) were alternately delivered to a cuvette containing intact fine roots of eastern white pine (Pinus strobus L.). Respiration rates were consistently higher in [CO(2)](a) than in [CO(2)](s) and were almost three times higher during midsummer. Respiration rates were immediately reversed after returning to the alternate [CO(2)] (i.e., [CO(2)](a) --> [CO(2)](s) --> [CO(2)](a), and vice versa) suggesting a direct effect of elevated [CO(2)] on apparent respiration. Soil-[CO(2)]-based respiration rates decreased with increasing [CO(2)] on a dry mass and tissue [N] basis. We conclude that estimates of soil CO(2) flux and soil carbon budgets may be improved by more completely accounting for the rhizosphere microclimate (i.e., soil temperature and [CO(2)](s)) during measurement of fine root respiration.

Journal Article↗
PubMed1990

Hippocampal Complex Spike Cells do not Change Their Place Fields if the Goal is Moved Within a Cue Controlled Environment.

It has been shown that most hippocampal complex-spike cells fire at specific locations in relation to a set of controlled spatial cues and that they continue to fire in the appropriate places when the cues are removed (O'Keefe and Conway, 1978; O'Keefe and Speakman, 1987). However, the goal remained in a constant position relative to the controlled cues throughout these experiments. It is therefore possible that the unit firing was related to the goal location and not to the controlled cues as was suggested. For example, firing in a particular location might signal the rat's intention to make a particular turn towards the goal from that location and not the location itself. There are many reasons for believing that this is an unlikely class of explanations; nevertheless a test of this hypothesis was undertaken in the present experiment. Nineteen place units were recorded from three rats as they performed the task of finding the goal location. After obtaining an accurate picture of the place fields in relation to the controlled cues and the goal, the location of the goal relative to the cues was moved and the animal retrained to the new goal. After the new goal was being consistently chosen, a second picture of the place fields of the same units was obtained. If the fields were related to the environment created by the cues then they would remain the same during the two stages of the experiment. If they were related to the goal, or to the intended movements towards the goal, then they would rotate relative to the cues. As expected, the majority of place fields remained in the same place in relation to the cues during the two stages of the experiment and were not influenced by the goal relocation. In only two cases was there any suggestion that the place fields changed their location after the goal was moved. It was concluded that the activity of place cells is related to an animal's location in an environment and that the results accord with cognitive map theory of hippocampal function (O'Keefe and Nadel, 1978).

Journal Article↗
PubMed1992

Effects of transcutaneous monitor electrode heat on skin servo-controlled environments.

This study tested the hypotheses that (1) the heat generated by a transcutaneous monitor electrode is sufficient to decrease skin servo-controlled radiant warmer heat output when it is positioned next to the operating skin servo-thermistor, and (2) the decrease in radiant warmer heat output is enough to lower body temperatures or cause a heat-conserving response in a baby. Seventeen newborns less than or equal to 5 days old, gestational age 29 to 40 weeks, cared for under radiant warmers were studied before and for 30 minutes after juxtaposition of the transcutaneous monitor electrode and the skin servo-controlled thermistor. Mean radiant warmer heat output, measured as watt-hours/5 minute periods, decreased for the first 15 minutes after movement, mainly in the infants cared for under an older model radiant warmer. Mean skin temperature and foot temperature decreased, and esophageal-foot temperature gradient increased for those under the older model radiant warmer. Despite differences in the gestational age of the infants under the older compared with the newer model radiant warmer, multiple regression analysis indicated a significant effect of the model of radiant warmer on the results. Many factors can influence the proper functioning of servo-controlled heating systems, including the type of electronic logic and extraneous sources of heat. These factors require more study, and should be considered in the evaluation of thermal control problems.

Body Temperature↗
PubMed2004

Capillary electrophoresis of proteins in a quality control environment.

A method for determining the purity of recombinant carboxypeptidase B utilizing CE-SDS has been developed and validated for use in a manufacturing quality control laboratory. The method was optimized, prior to validation, to allow for the lowest limit of quantitation. The method was validated with the typical ICHQ2A parameters, including accuracy, linearity, LOQ, precision, robustness/ruggedness, and specificity. All validation parameters met the acceptance criteria defined in the validation protocol.

Carboxypeptidase B↗
PubMed1971

Growth and metabolism of L cells in a chemically defined medium in a controlled environment culture system. I. Effects of O2 tension on L-cell cultures.

Six water-jacketed 500-ml Bellco spinner flasks were equipped to monitor and control environmental variables to study their effects on the growth and metabolism of mammalian cells. Studies with automated control of pO(2) levels of l-cell cultures, grown at pH 6.9 +/- 0.1, showed that dissolved O(2) tensions of ca. 9% were optimal for cell growth. At pO(2) values of 5 and 20%, maximum cell yields as well as growth rates were reduced by approximately 20%. Peak yields of L-cell cultures exceeded 5 x 10(6) cells/ml when grown for 4 days without medium renewal from inocula of ca. 10(6) cells/ml in a defined medium sparged with 5% CO(2) and maintained at 9% dissolved O(2) tension. The redox potentials of L-cell cultures reflected the pO(2) levels in the medium and ranged from -45 to +160 mv (versus calomel reference) for O(2) values ranging from 2 to 20% dissolved oxygen tension. Increased utilization of glucose per cell occurred in the presence of increased pO(2), whereas minimal accumulation of ammonia occurred with a pO(2) value maintained at 9%.

Ammonia↗
PubMed1978

Separation testing of hemodialysis shunts using dynamic and static forces in a controlled environment.

Analytical methods are presented for determining the longitudinal dynamic and static forces needed to overcome the transverse frictional forces and effect the separation of hemodialysis shunt connections under controlled environmental conditions. Results for different types of shunts and their associated connectors are reported along with the factors that affect the separation force and separation times.

Biomedical Engineering↗
PubMed1975

[Induction of sexual maturation and egg-laying in the prawn Penaeus japonicus Bate in a controlled environment].

Studies on the endocrine mechanisms which regulate the reproduction processes in the prawn Penaeus japonicus Bate led us to investigate the role of temperature and light; these parameters probably affect the "biological clock" controlling these phenomena. Complete sexual maturation was achieved within a three month period. During the next three months, 72 spawnings from a population of 60 one and two year old females were observed corresponding to 960,000 nauplii.

Animals↗
PubMed2004

Scanning tunneling spectroscopy investigation of self-assembled plastocyanin mutants onto gold substrates under controlled environment.

The study of the electronic conduction through plastocyanin (PC) mutants assembled on a gold surface has been addressed by scanning tunneling spectroscopy. The two mutants exploit a single thiol group (PCSH) or a disulfide bridge (PCSS) to covalently bind at gold surface. The I-V measurements were performed by positioning the STM tip on top of a single molecule and sweeping the bias potential between +/-1 V, under both ambient and controlled atmosphere. For PCSS, under ambient conditions, asymmetric I-V characteristics were obtained, which disappear under nitrogen atmosphere. PCSH, instead shows a symmetric I-V relation in air and under nitrogen environment. Here, as factors underlying this distinct electron conductive behaviour, a potential role for hydration water molecules and for copper redox levels are discussed.

Air↗
PubMed2000

A new method for on-line measurement of diurnal change in potato tuber growth under controlled environments.

An on-line laser micrometer system was applied to measurement of diurnal change in potato (Solanum tuberosum L.) tuber growth. Diameters of the potato tuber were scanned by moving a laser micrometer along the longitudinal axis of the tuber at constant speed, and tuber volume was evaluated as an aggregate of thin discs. A single potato tuber, without competitive sink tubers in the plant, was grown in controlled air at 20 degrees C and 80% RH, and tuber volume was measured at 30 min intervals. During the growth experiment, the potato tuber increased in size without any inhibitory effect of periodical laser beam irradiation. Greatest expansion generally occurred during the early night, and transient contraction of the tuber occurred at the beginning of the light period.

Circadian Rhythm↗
PubMed1991

The cellular environment controls the expression of engrailed-like protein in the cranial neuroepithelium of quail-chick chimeric embryos.

We have previously shown that one of two chicken engrailed-like genes, chick En-2, is expressed in a restricted region of the early chick embryo brain: the mes/metencephalon (Gardner et al. 1988). In this study, we examine the role of the cellular environment in regulation of engrailed-like (En) protein expression in quail-chick chimeric embryos. Two types of transplant surgery were performed at the 9-15 somite stage to produce chimeric embryos. In the first, the mid-mesencephalic vesicle or caudal mesencephalic vesicle alar plate (which is En protein-positive) was transplanted from a quail embryo into an En protein-negative region of chick neuroepithelium, the prosencephalon (mMP and cMP grafts, respectively). In the second reciprocal surgery, prosencephalic alar plate which is En protein-negative, was transplanted into the En protein-positive mesencephalic vesicle (PM grafts). A polyclonal antiserum, alpha Enhb-1, which recognizes chick En proteins (Davis et al. 1991) was used to identify En-positive cells 48 h after surgery. In mMP embryos, 71% of integrated grafts had lost En expression (n = 17). In contrast, in cMP grafts, 93% of integrated grafts continued to stain with the antiserum (n = 14). In addition, in 86% of these embryos, the graft induced adjacent chick host diencephalic cells to become En protein-positive as well. All PM grafts contained aEnhb-1-positive cells; such cells never expressed this protein in their normal environment. These early changes in En protein expression correlate well with the morphological changes observed in similar graft surgeries assayed later in development. Thus, our results are consistent with the hypothesis that En genes play a role in the regionalization of the early cranial neuroepithelium.

Animals↗
PubMed1987

Avoidance of Phycomyces in a controlled environment.

The sporangiophore of the fungus Phycomyces bends away from nearby objects without ever touching them. It has been thought that these objects act as aerodynamic obstacles that damp random winds, thereby generating asymmetric distributions of a growth-promoting gas emitted by the growth zone. In the interest of testing this hypothesis, we studied avoidance in an environmental chamber in which convection was suppressed by a shallow thermal gradient. We also controlled pressure, temperature, and relative humidity of the air, electrostatic charge, and ambient light. A protocol was established that yielded avoidance rates constant from sporangiophore to sporangiophore to within +/- 10%. We found that avoidance occurred at normal rates in the complete absence of random winds. The rates were smaller at 100% than at lower values of relative humidity, but not by much. Remarkably, at a distance as great as 0.5 mm, avoidance from a 30-micron diam glass fiber (aligned parallel to the sporangiophore) was about the same as that from a planar glass sheet. However, the rate for the fiber fell more rapidly with distance. The rate for the sheet remained nearly constant out to approximately 4 mm. We conclude that avoidance depends either on adsorption by the barrier of a growth-inhibiting substance or emission by the barrier of a growth-promoting substance; it cannot occur by passive reflection. Models that can explain these effects are analyzed in the Appendix.

Mathematics↗
PubMed1997

Distribution of elements along the length of Scots pine needles in a heavily polluted and a control environment.

Pollution often causes visible symptoms of foliar injury. The injury is sometimes associated with an increase in the accessibility of toxic elements to plants as a result of acidification of the soil. We investigated the distribution of elements (N, P, K, Ca, Mg, Mn, S, Fe, B, Cu, Zn, Al, F, Pb, Cd, Cr, Ni and Co) in healthy current-year needles of Scots pine (Pinus sylvestris L.) growing at an unpolluted control site and at a site polluted mainly by SO(2), HF and Al(3+) from a fertilizer factory established in 1917. Needles from both sites were sampled before the appearance of visible injury and cut into five sections of equal length (tip, base and three middle parts). The mean concentrations of major nutrients were 20-30% lower in needles at the polluted site than in needles at the control site, whereas the concentrations of aluminum and fluorine were higher in needles at the polluted site. An increase in concentration from needle base to tip was detected for N, Fe, B, and Al at both sites and for Mn only at the polluted site. Fluoride accumulated in the tips of needles only at the polluted site, which could explain the necroses of needle tips at this site. The distribution of elements along the length of the needles was influenced by pollution, element mobility and the distal accumulation of toxic elements.

Journal Article↗