Effects Of Various Intensities Research Articles

Assessing the Mutagenicity Potential of Multiphoton Excitation during Imaging of Intrinsic Fluorescence from Cells and Tissues

Multiphoton-excited intrinsic fluorescence emission signals from cells and tissues can be used for metabolic imaging and studies of disease morphology in chronic animal imaging experiments, and has diagnostic potential as a future in vivo clinical imaging tool. However, the signals are generally weak and require high laser intensities for imaging. Consequently, not only are viability studies important, but an investigation into the extent that multiphoton excitation is a mutagenic agent is critical. Information on the magnitude of permissible intensity levels of femtosecond pulsed near-IR light is vital to human clinical applications, yet there are currently no regulations that specifically indicate such parameters. This study is directed towards determining whether multiphoton imaging of cellular autofluorescence using 700 - 800 nm wavelength excitations causes mutations in mammalian cells. The induction of mutation by pulsed laser radiation employed for multiphoton imaging entails a risk of carcinogenicity in living tissue. The assessment of potential laser illumination toxicity was carried out by the hypoxanthine-guanine phosphoribosyl (HPRT) mammalian cell gene mutation assay, which measures mutation at the HPRT gene locus in cells, and is one of a handful of reporter loci that have been used as molecular biomarkers for both human and rodent exposure to mutagens and UV light. Experiments were performed to assess possible mutagenic effects of various intensities of 755 nm, 100 fs laser irradiation. Laser powers ranging from 20 to as high as 100 mW delivered as raster scanned excitation through a 0.7 NA objective for 20 seconds was found to be nonmutagenic to the HPRT gene locus test system, while higher laser powers initiated mutagenic responses.

The damaging effect of various intensities of light on retinal function in pigmented rats.

Abstract Purpose To investigate the functional retinal damage following the short term (6h) light exposure in pigmented rats. Methods One group of dark adapted Brown‐Norway rats was exposed for 6 h to 10 klux without mydriasis. Five groups of rats were exposed to different intensities of light (10, 5, 3.4, 2.7 and 1.7 klux) for 6 h with pupil dilatation. Electroretinography (ERG) was recorded prior to, and at 1st and 7th day after light damage (LD). ERG protocol enabled quantification of scotopic sensitivity parameters (Vmax‐saturated b‐wave amplitude and k‐ luminance to reach Vmax/2),photopic cone response and oscillatory potentials(OPs). Results The exposure to 10 klux without mydriasis did not result in significant retinal injury. In groups subjected to mydriasis, the light of 1.7 klux resulted in nonsignificant (ns) decrease of ERG response. However, the severe loss of retinal function was reported after exposure to higher intensities. The value of Vmax at 1st day after LD was reduced respectively to 90±25%(ns), 19±5%, 7±4%, 4±1% and 3±0.3% of baseline value (p<0.05).No significant improvement was recorded during the following 7 days. The parallel decrease was observed in scotopic mixed (rod+cone) a‐ and b‐wave amplitude,in photopic response and in OPs. The scotopic threshold luminance increased gradually together with the damaging light intensity, while the value of parameter k was only narrowly altered (p>0.05) after LD in all animal groups. Conclusion Our results show, that a few hours' illumination with the light of even moderate intensity may result in severe functional retinal impairment in pigmented rats. Presented model may be useful to study the cell degenerations in pigmented retinas.

Relationship between blue light-induced apoptosis and mitochondrial membrane potential and cytochrome C in cultured human retinal pigment epithelium cells

To investigate the effect of blue light on apoptosis and mitochondrial permeability transition (MPT) of cultured human retinal pigment epithelium (RPE) cells in vitro. Human RPE cells were exposed to blue light (wave length 470 -490 nm). The present study consisted of three parts. Part one studied the effect of various intensities of blue light on the RPE cells. Cells were irradiated with (500+/-100) lx (group 1) , (2000+/-500) lx (group 2) and (3000+/-500)lx ( group 3) blue light, and followed by 24 hours observation. Part two studied the effect of various duration of blue light at identical intensity on the RPE cells. For the study on various subtypes of RPE cells, cells were irradiated by blue light at (2000+/-500) x for 6, 12, and 24 hours. For the study of mitochondrial membrane potential, cells were irradiated for 3, 6, and 12 hours. Part three studied cells irradiated with blue light at identical intensity and duration, but with various prolongation of post-exposure culture. The prolongation of post-exposure culture was 6, 12, 24, and 36 hours. Phototoxicity was quantified at various periods after exposure by staining of the nuclei of membrane-compromised cells, by TdT-dUTP terminal nick-end labeling (TUNEL) of apoptotic cells and by Annexin V labeling for phosphatidylserine exposure. Transmission electronmicroscopy was used to determine the ultrastructure changes of RPE cells. Mitochondrial membrane potential ( deltaPsim ) was measured by rhodamine 123 staining and subsequent flow cytometry. Cytochrome C activity was assayed by ELISA. Caspase-3 was detected by colorimetric assay. TUNEL-positive labeling cells in first group of part two study showed cell shrinkage, membrane blebbing, apoptotic body, condensation and fragmentation of chromatin. Mitochondrial swelling, extinction of inner mitochondrial membrane ridge, dilation of rough endoplasmic reticulum and increase of the lysosome were also observed in transmission electronmicroscopy. Blue light at (500 +/- 100) x intensity did not induce damage to RPE cells, but decrease of delta Psim was observed. A significant increase of apoptotic, apoptotic necrotic and necrotic percentages, as well as significant decrease of deltaPsim were observed at higher light intensity in part one study. Increase of apoptotic percentage was the main response to shorter exposure of blue light. Increase of apoptotic necrotic and necrotic percentage and pronounced decrease of deltaPsim occurred in cells irradiated by longer exposure in part two study. In part 3 study, apoptotic response was increased gradually during 6 and 12 hours prolongation of post-exposure culture, more apoptotic necrosis or necrosis were found after post-exposure 24 hours. Decrease of deltaPsim was observed in 6 hours prolongation of post-exposure culture and lasting for 48 hours. The concentration of cytochrome C was significantly increased in post-exposure 24 and 36 hours, without any changes of Caspase-3 activity. Blue light exposure can induce damages to human RPE cells in vitro, which include apoptosis, apoptotic necrosis and necrosis. These changes are caused by triggering the mitochondrial permeability transition, which results in decrease of deltaPsim and release of cytochrome C. deltaPsim can be used as a earlier parameter of blue light-induced apoptosis.

Effects of mahogany ( Swietenia macrophylla) logging on small mammal communities, habitat structure, and seed predation in the southeastern Amazon Basin

Vast areas of the Amazon have been subjected to low-intensity selective logging for high value timber species such as mahogany ( Swietenia macrophylla). Although the ecological consequences of such logging are often assumed to be minimal, few studies have directly tested this assumption. In this paper we examine the effects of various intensities of mahogany logging on small mammal communities, habitat structure, and seed predation in the southeastern Amazon Basin. We sampled small mammal communities using live traps at two logged and two unlogged sites. Within each site, we established five 1 ha sampling grids that sampled the range of logging damage (in the case of logged sites) or mahogany densities (in the case of unlogged sites). Grids were sampled with 10 trap stations on the ground, 10 in the understory (at 1–3 m in height), and five in the canopy (at approximately 10 m in height) during three, 10-night trapping sessions over the course of the 10-month study. We measured a suite of forest structure and small mammal food resource (insect and fruit abundances) variables at each station and mahogany and peanut seed predation rates were measured at five locations per grid. We captured a total of 817 individuals of eight marsupial and 17 rodent species in 29,500 trap nights. Neither mahogany density across unlogged grids nor logging damage across logged grids were significantly correlated with variation in any of the measured habitat variables, seed predation rates, or measures of small mammal resource abundance. However, site-specific means for several variables (volume of downed wood, number of vines per tree, number of vines, number of herbaceous stems, and understory density) were higher in logged than unlogged sites, but significantly so in only two cases (number of vines per tree, volume of downed wood). When pooled, the logged grids had higher small mammal abundances and species richness than unlogged grids; however, predation of mahogany seeds and peanuts did not differ significantly between the two site types. When the two logged sites were analyzed separately, the effects of logging were found to be very different at the two sites. One of the logged sites showed few effects of logging and had similar forest structure and small mammal communities to the unlogged sites, whereas the other logged site demonstrated effects consistent with previous reports on logging, including increased small mammal abundances, increased seed predation, and decreases in seedling and sapling densities as a function of increasing levels of logging damage. This study provides evidence that the ecological consequences of mahogany logging are strongly dependent on local site features; however, the overall effects of the logging appeared to be small, suggesting that areas that have been subjected to only low-levels of logging can still make valuable contributions to conservation.

Moderate-Intensity Exercise Effective for Weight Loss

How much exercise should clinicians prescribe to help patients improve their cardiovascular health and control their body weight? These researchers examined the effects of varying intensities and durations of exercise in 201 overweight, sedentary women (mean age, 37; mean BMI, 32.6). The women were enrolled in a university-based weight-control program, in which they attended behavioral group meetings and were instructed to reduce their energy intake to 1200-1500 …

The effect of electric and magnetic fields on the operation of a photovoltaic cell

In this work, we have investigated the effects of electric and magnetic fields on the operation of a CdS/CuInSe 2 photovoltaic cell. Various electric field intensities changing from 0 to 35000 V dc/m, were applied to the sample while it was irradiated by a He–Ne laser with a wavelength λ=670 nm. As a result, the typical values for the open circuit voltage of the photovoltaic cell significantly changed with various intensities of the electric field E dc. We also applied magnetic fields varying from 0.003 to 0.079 T using a solenoid with an inductance of 10.55 mH and the response of the sample was observed. In the third step of the experiment, instead of the laser beam, various intensities of white light of 50, 100,150 and also 250 lux were utilised. 250 lux was measured to be equivalent to the radiation power of He–Ne laser beam on the surface of the photovoltaic cell. The effect of electric fields from 0 up to 3×10 5 V dc was applied and some significant experimental results were obtained. As a result of the illumination of the photovoltaic cell by the stimulated and spontaneous light emission sources under the effect of various intensities of electric field E dc, different electrical behaviours were observed.

Relaxation of the magnetostatic wave absorption in the ferrite-semiconductor structure

In this paper, the results of the theoretical studies of magnetostatic surface wave (MSSW) propagation in layer-photosensitive semiconductor-ferrite waveguides when the external electromagnetic wave affects the semiconductor surface are reported. Dispersion relation of MSSW has been found and the effects of various intensities of electromagnetic wave on the propagation characteristics have been examined. It has been shown that MSSW propagation loss can decrease and there is a frequency band in which MSSW has amplification with increasing intensity of the external light.

Magnetostatic wave characteristics control by light at the ferrite-semiconductor layer structure

This paper reports results of theoretical studies of magnetostatic surface wave (MSSW) propagation in a photosensitive semiconductor-ferrite layer structure while the external electromagnetic wave acts on the semiconductor surface. The photoelectromagnetic effect is included in the theory. The dispersion relation of MSSW has been found and the effects of various intensities of the electromagnetic wave on the propagation characteristics have been examined. Values for CdSe and yttrium iron garnet parameters were used for computer simulation. It has been shown that the MSSW propagation loss increases, the frequency range in which the MSSW exist narrows and the group time delay decreases by a factor of 3–4 with increasing the intensity of the external wave.

Surface disturbance of cryptobiotic soil crusts: Nitrogenase activity, chlorophyll content, and chlorophyll degradation

Cryptobiotic soil crusts are an important component of semiarid and arid ecosystems. An important role of these crusts is the contribution of fixed nitrogen to cold‐desert ecosystems. This study examines the residual effects of various intensities and combinations of different surface disturbances (raking, scalping, and tracked vehicles) on nitrogenase activity, chlorophyll content, and chlorophyll degradation in these soil crusts. Nine months after disturbance chlorophyll content of disturbed soils was not statistically different from undisturbed controls, except in the scalped treatments, indicating recovery of this characteristic is fairly quick unless surface material is removed. Differences in chlorophyll degradation among treatments were not statistically significant. However, nitrogenase activity in all treatments showed tremendous reductions, ranging from 77–97%, when compared to the control, indicating this characteristic is slow to recover. Consequently, assessment of crustal recovery from disturbance must include not only visual and biomass characteristics but other physiological measurements as well. Areas dominated by these crusts should be managed conservatively until the implications of crustal disturbance is better understood.

Structure and conductivity of CoMnNiO multi-composition amorphous thin film

In this paper, the results of the theoretical studies of magnetostatic surface wave (MSSW) propagation in layer-photosensitive semiconductor-ferrite waveguides when the external electromagnetic wave affects the semiconductor surface are reported. Dispersion relation of MSSW has been found and the effects of various intensities of electromagnetic wave on the propagation characteristics have been examined. It has been shown that MSSW propagation loss can decrease and there is a frequency band in which MSSW has amplification with increasing intensity of the external light.

11. The effects of peripheral nerve conditioning stimuli on responses of lumbar spinal cord neurons to noxious thermal stimulation of the skin in the cat

Consideration of the stimulus intensities and evoked sensations produced by pain relieving transcutaneous nerve stimulation (TENS) and acupuncture suggests that a wide range of primary afferents may be involved. High frequency (over 50 Hz), low intensity TENS probably only activates large mechanoreceptive primary afferents innervating skin, whereas low frequency, higher intensity TENS (Eriksson et al. 1979) and acupuncture will also activate other types of primary afferent from skin and deeper tissues. Studies in spinal cats have shown that conditioning stimuli applied to muscle nerve at intensities that would evoke group III (Sjölund et al. 1979) and C fibre (Chung et al. 1983) afferents, will inhibit reflex responses to cutaneous nerve stimulation at intensities which would evoke C fibre activity. These preliminary experiments have been carried out to examine the effects of various intensities and frequencies of peripheral nerve, particularly muscle nerve, stimulation, on responses of lumbar spinal cord neurons to noxious thermal stimulation of the skin.

Light Intensity Required for Maximum Egg Production in Hens ,

Two experiments were conducted with a medium weight, brown egg hen to investigate the effects of various intensities of illumination upon egg production, feed consumption and mortality over a 50-week production period. Intensities of 5.38, 21.53 and 53.82 lux and a treatment consisting of a three month progressive increase on each intensity with the final period utilizing 107.64 lux were tested. In each of two trials, the birds exposed to 5.38 lux had the highest egg production; but the differences in egg production between the various treatments were not statistically significant. Feed consumption per hen and laying house mortality were not significantly influenced by light intensity.

Experimental Observations on the Effects of Predation by Goldfish (Carassius auratus) on the Zooplankton of a Small Saline Lake

The short-term effects of various intensities offish predation on zooplankton communities were examined. Field studies indicated that fish predation was, as expected, size-selective: in the presence of fish, size distributions of the principal prey, Daphnia pulex, were skewed toward the smaller size-classes and the minimum size of egg-bearing D. pulex was also smaller. Fecundity of Diaptomus ashlandi, and probably also of Daphnia pulex, was greater with fish present. This caused the abundance of these two dominant species to increase initially with increasing predation. Subsequently, the species declined at higher predation levels in order of their interest to fish, with large D. pulex[Formula: see text] declining before small D. pulex (< 1.35 mm) and both groups doing so at lower predation levels than Diaptomus ashlandi.

Root Development of Native Plants Under Three Grazing Intensities

The purpose of this study was to determine the effects of various intensities of grazing upon roots and root systems of plants native to the ponderosa pine zone of the Colorado Front Range. It was designed to ascertain the root characteristics of certain species of the plant community and any changes in root distribution induced by 17 years of moderate and heavy grazing by cattle. The cumulative effects of such grazing are also illustrated. Most studies concerning the effects of plant defoliation show that any cropping (clipping or grazing) reduces plant growth, especially root growth. The initial root and rhizome response to defoliation is the cessation of elongation (Parker and Sampson 1931, Crider 1955). Subsequent reactions to continued defoliation are reduction in root numbers and branching (Jacques 1937, Albertson, Riegel, and Launchbaugh 1953), root diameter (Biswell and Weaver 1933), and depth of soil penetration (Ruby and Young 1953, Cook, Stoddart, and Kinsinger 1958). The amount of reduction is directly related to the severity and frequency of defoliation (Graber 1931, Albertson et al. 1953, Thaine 1954). In general the degree of defoliation is more detrimental to root growth than frequency of defoliation. Crider (1955) showed that apical growth of grass roots stopped within 24 hr after the removal of 40% or more of the foliage in one operation. The time required for roots to resume growth varied directly with the degree of foliage removal. The consequences of overgrazing are apparently carried over from season to season. WVeaver

A study of the effects of various intensities of cultivation on yields of chou moellier and on soil nitrate levels

Abstract Orthodox cultivation by ploughing, rolling, discing, levelling, and harrowing, with and without subsoiling, was compared with subsurface loosening to plough depth without soil inversion, with shallow surface cultivation, and with no cultivation, on 2 successive crops of chou moellier. The first crop was out of medium to good quality grass-clover pasture. The soil was a heavy silt loam on clay loam. Herbicides were used on all treatments except on those receiving orthodox cultivation. Results were as follows: 1. Crop yields were not significantly affected by sub-surface loosening or by subsoiling. 2. A very marked decline in nitrogen fertility was observed in the second year. 3. Herbicides without cultivation produced as good a crop as orthodox cultivation in the first year in the presence of large amounts of decomposing plant residue derived from grass-clover pasture, but produced an inferior crop in the second year when much less plant residue was present. 4. The cultivation treatments significa...

Effect of Burning and Clipping on Growth of Native Prairie in Iowa

In range or native pasture management it is important to know how burning, mowing, grazing, complete protection or combinations thereof, will affect individual plants and communities of plants. The effects of fire on vegetation, especially natural grassland, is indeed a controversial subject. This is not surprising when one considers the complexity of prairie communities and the versatility of the component plants. Advantages or disadvantages of burning apparently depend on a myriad of factors peculiar to a given location, time, and desired objective. The additional effects of various intensities of clipping with burning further complicate interpretation of plant responses. This paper is based on results of a study conducted during 1954, 1955, and 1956 to determine the effects of both burning and clipping on growth habits of component plants as well as plant communities of mesic upland prairie in Iowa.

Effects of Various Intensities of X Radiation on Chromosomal Aberrations

American Journal of BotanyVolume 43, Issue 5 p. 328-332 Article EFFECTS OF VARIOUS INTENSITIES OF X RADIATION ON CHROMOSOMAL ABERRATIONS Alvin V. Beatty, Alvin V. Beatty Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this authorJeanne W. Beatty, Jeanne W. Beatty Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this authorCynthia Collins, Cynthia Collins Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this author Alvin V. Beatty, Alvin V. Beatty Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this authorJeanne W. Beatty, Jeanne W. Beatty Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this authorCynthia Collins, Cynthia Collins Department of Biology, Emory University, Emory University, GeorgiaSearch for more papers by this author First published: 01 May 1956 https://doi.org/10.1002/j.1537-2197.1956.tb10498.xCitations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume43, Issue5May 1956Pages 328-332 RelatedInformation

Range Conservation and Season-Long Grazing

Conservation of range land is basically EL matter of grazing management but the rancher is also concerned with other practices such as fencing, water development, salting, and weed eradication. Though many factors arr involved, the most important are correct numbers of livratoek, including good distribution, and grazing during the proper season. These are two of the most difficult and important problems clue to the fact that (a) various range units involve many forage species, many having different values and different growth habits, (b) quantitative analysis of the forage cover on various range units is difficult, (c) the effect of various intensities and ~ensons of use upon the physiological well-being of forage plants is little understood, and (d) fluctuations in weather, especially precipitation, 0 c c u r from season to season and from year to year, accompanied by a confusing complexity of variations in forage yields and developmental behavior. Despite those difficulties, accurate drtwminations of the grazing capacity must be made if the range is to be handled properly. Continued failure to evaluate correctly the capacity of range land is certain to result in failure of the livestock enterpriseand in impaired land vnlues. Grazing land vnlues generally are proportionate to the expected annual returns in the form of livestock products. When continuous overutilization is allowed to take place, the forage cover is reduwd and livestock production declines, thus reducing the capital value of the land. Roth quantity and quality of range vegetation are reduced as range condition (or state of health) goes from excellent to poor. This is indicated in Table I from the work of Allred (1950) in Texas.

Effects of Different Intensities of Clipping on Short Grasses in West‐Central Kansas

Since appearance of the buffalo (Bison bison bison (L) ), vegetation of the Great Plains has been subjected to various degrees of utilization. It is probably safe to assume that at least moderate use was common, and that grazing was most intense during dry cycles or when population of the buffalo was greatest. As the pioneer white man occupied the plains region, the number of livestock gradually increased. Also, during this period vast amounts of prairie sod were plowed up for growing wheat and other crops, thereby reducing the area left in native vegetation. Little attention was given to intensity of grazing until the great drought of the 1930's when production of native vegetation suffered an alarming reduction. During this disastrous period, the most mesophytic plants survived only in favored locations, and even the most xerophytic species were greatly reduced in both abundance and frequency under heavy use by livestock. Also, the yield of native vegetation which at one time probably averaged from 2,000 to 3,000 pounds per acre, was suddenly reduced to little more than 100 pounds (Weaver and Albertson 1944). This tragic experience caused federal and state agencies, as well as individuals, to give serious thought to the ecology and economics of overuse on grasslands. The college pasture, an area of 830 acres of mixed prairie (Albertson 1937), was selected for study to determine effects of various intensities of clipping upon the most important grasses. The investigation was conducted on a portion of the pasture dominated by short grasses since this is the most common type of prairie vegetation of the Great Plains.

The relative effects of various intensities of punishment on learning and efficiency.

The relative effects of various intensities of punishment on learning and efficiency.