The Experts below are selected from a list of 2808 Experts worldwide ranked by ideXlab platform
Robert E Reed - One of the best experts on this subject based on the ideXlab platform.
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Geotaxis phototaxis and biochemical patterns in heterocapsa cachonina illdefina dinophyceae during diel vertical migrations
Journal of Phycology, 1999Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E Reed, Wenchen LiuAbstract:Two separate experiments with Heterocapsa (=Cachonina) illdefina Herman et Sweeney, one with and the other without water volume replacement, were performed in a 250-L laboratory mesocosm (45-cm diameter × 150-cm height) to examine how diel vertical migration (DVM) relates to taxis sign and strength and to cellular biochemical state. Although only the cell population grown with water volume replacement maintained a division per day over the course of the experiment, periodic measurements during both experiments demonstrated that cells aggregating at the surface during the light period generally were deficient in all measured biochemical constituents compared to cells obtained from a midcolumn depth. More specifically, H. illdefina cells that aggregated at the surface during the light period in both experiments exhibited weakened positive Geotaxis but strengthened positive phototaxis and were very deficient in lipid and free amino acid compared to midcolumn cells. Cells sampled at midcolumn during the light period exhibited similar but weaker taxes changes compared to surface samples, and Geotaxis strength was inversely correlated with cell diameter, cellular DNA and protein content, and RNA/DNA ratio. In comparison, published data on Gymnodinium breve Davis, a harmful algal bloom species, showed that cells aggregating at the surface during the light period generally exhibited weakened negative Geotaxis and strengthened positive phototaxis and were very deficient in lipid and chl a compared to midcolumn cells. Although the persistent tendency toward negative Geotaxis was weaker in midcolumn subpopulations throughout the day, its strength was inversely correlated with cell diameter and cellular lipid content. The combined results for both species support a revised conceptual model of optimized DVM in autotrophic marine dinoflagellates incorporating generalized expressions of taxis and biochemical state of individual cells.
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Geotaxis/PHOTOTAXIS AND BIOCHEMICAL PATTERNS IN HETEROCAPSA (=CACHONINA) ILLDEFINA (DINOPHYCEAE) DURING DIEL VERTICAL MIGRATIONS
Journal of Phycology, 1999Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E Reed, Wenchen LiuAbstract:Two separate experiments with Heterocapsa (=Cachonina) illdefina Herman et Sweeney, one with and the other without water volume replacement, were performed in a 250-L laboratory mesocosm (45-cm diameter × 150-cm height) to examine how diel vertical migration (DVM) relates to taxis sign and strength and to cellular biochemical state. Although only the cell population grown with water volume replacement maintained a division per day over the course of the experiment, periodic measurements during both experiments demonstrated that cells aggregating at the surface during the light period generally were deficient in all measured biochemical constituents compared to cells obtained from a midcolumn depth. More specifically, H. illdefina cells that aggregated at the surface during the light period in both experiments exhibited weakened positive Geotaxis but strengthened positive phototaxis and were very deficient in lipid and free amino acid compared to midcolumn cells. Cells sampled at midcolumn during the light period exhibited similar but weaker taxes changes compared to surface samples, and Geotaxis strength was inversely correlated with cell diameter, cellular DNA and protein content, and RNA/DNA ratio. In comparison, published data on Gymnodinium breve Davis, a harmful algal bloom species, showed that cells aggregating at the surface during the light period generally exhibited weakened negative Geotaxis and strengthened positive phototaxis and were very deficient in lipid and chl a compared to midcolumn cells. Although the persistent tendency toward negative Geotaxis was weaker in midcolumn subpopulations throughout the day, its strength was inversely correlated with cell diameter and cellular lipid content. The combined results for both species support a revised conceptual model of optimized DVM in autotrophic marine dinoflagellates incorporating generalized expressions of taxis and biochemical state of individual cells.
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relationships between Geotaxis phototaxis and diel vertical migration in autotrophic dinoflagellates
Journal of Plankton Research, 1998Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E ReedAbstract:Marine dinoflagellate diel vertical migrations are often conceptually explained by a species' geotactic and phototactic preferences, but actual simultaneous measurements are rare. Newly collected simultaneous measurements on Heterocapsa (Cachonina) illdefina (Herman and Sweeney) and Gymnodinium breve (Davis) are combined with similar literature information on Amphidinium carterae (Hulbert), Peridinium faeroense (Paulsen) and Prorocentrum micans (Ehrenberg) to explore several examples of the actual relationships between diel vertical migration and Geotaxis/phototaxis. Amphidinium carterae does not migrate, but it exhibits a negative Geotaxis that may counter a small sinking velocity. The four other species all exhibit diel vertical migrations that yield surface aggrega- tions during daylight, but the associated combinations of Geotaxis and phototaxis precision (which is strongest when every cell in a population exhibits the same response to a stimulus and weakest when the response is random) and sign (which is positive (negative) when motion is toward (away from) the stimulus) are different in each case. These different taxis combinations may be related to species- specific sensor structure and/or placement. Furthermore, variations in the different biochemical pools over a species* cell cycle may contribute to structural/mechanical changes that influence how a given sensory array functions at a given time. If so, this coupling may be an important link in the growth optimization mechanisms and occasional bloom successes of different autotrophic dinoflagellate species under varying environmental conditions.
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Relationships between Geotaxis/phototaxis and diel vertical migration in autotrophic dinoflagellates
Journal of Plankton Research, 1998Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E ReedAbstract:Marine dinoflagellate diel vertical migrations are often conceptually explained by a species' geotactic and phototactic preferences, but actual simultaneous measurements are rare. Newly collected simultaneous measurements on Heterocapsa (Cachonina) illdefina (Herman and Sweeney) and Gymnodinium breve (Davis) are combined with similar literature information on Amphidinium carterae (Hulbert), Peridinium faeroense (Paulsen) and Prorocentrum micans (Ehrenberg) to explore several examples of the actual relationships between diel vertical migration and Geotaxis/phototaxis. Amphidinium carterae does not migrate, but it exhibits a negative Geotaxis that may counter a small sinking velocity. The four other species all exhibit diel vertical migrations that yield surface aggrega- tions during daylight, but the associated combinations of Geotaxis and phototaxis precision (which is strongest when every cell in a population exhibits the same response to a stimulus and weakest when the response is random) and sign (which is positive (negative) when motion is toward (away from) the stimulus) are different in each case. These different taxis combinations may be related to species- specific sensor structure and/or placement. Furthermore, variations in the different biochemical pools over a species* cell cycle may contribute to structural/mechanical changes that influence how a given sensory array functions at a given time. If so, this coupling may be an important link in the growth optimization mechanisms and occasional bloom successes of different autotrophic dinoflagellate species under varying environmental conditions.
Mike Grotewiel - One of the best experts on this subject based on the ideXlab platform.
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Genetic and environmental factors impact age-related impairment of negative Geotaxis in Drosophila by altering age-dependent climbing speed.
Experimental gerontology, 2008Co-Authors: Devin Rhodenizer, Ian Martin, Poonam Bhandari, Scott D. Pletcher, Mike GrotewielAbstract:Age-related locomotor impairment in humans is important clinically because it is associated with several co-morbidities and increased risk of death. One of the hallmarks of age-related locomotor impairment in humans is a decrease in walking speed with age. Genetically tractable model organisms such as Drosophila are essential for delineating mechanisms underlying age-related locomotor impairment and age-related decreases in locomotor speed. Negative Geotaxis, the ability of flies to move vertically when startled, is a common measure of locomotor behavior that declines with age in Drosophila. Toward further developing Drosophila as a model for age-related locomotor impairment, we investigated whether negative Geotaxis reflects climbing or a combination of climbing and other behaviors such as flying and jumping. Additionally, we investigated whether locomotor speed in negative Geotaxis assays declines with age in flies as found for walking speed in humans. We find that the vast majority of flies climb during negative Geotaxis assays and that removal of hind legs, but not wings, impairs the behavior. We also find that climbing speed decreases with age in four wild type genetic backgrounds, in flies housed at different temperatures, and in control and long-lived flies harboring a mutation in OR83b. The decreases in climbing speed correlate with the age-related impairments in the distance climbed. These studies establish negative Geotaxis in Drosophila as a climbing behavior that declines with age due to a decrease in climbing speed. Age-related decreases in locomotor speed are common attributes of locomotor senescence in flies and humans.
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Rapid iterative negative Geotaxis (RING): a new method for assessing age-related locomotor decline in Drosophila.
Experimental gerontology, 2005Co-Authors: Julia Warner Gargano, Ian Martin, Poonam Bhandari, Mike GrotewielAbstract:Age-related behavioral declines are common manifestations of aging in animals. Negative Geotaxis, an innate escape response during which flies ascend the wall of a cylinder after being tapped to its bottom, is one of the behaviors that senesces in Drosophila. Many laboratories, including ours, have used a variety of negative Geotaxis assays based on the performance of single flies. To circumvent limitations of single-fly assays, we developed a new method for assessing negative Geotaxis called rapid iterative negative Geotaxis (RING). In RING assays, digital photography is used to document negative Geotaxis in multiple groups of animals simultaneously. We show that performance in RING assays is not influenced by the density of flies being tested, the time of day, or repeated testing. We used the RING assay to demonstrate that negative Geotaxis declines with the age of animals as previously shown in single fly studies and that senescence of negative Geotaxis is sensitive to genetic background. Finally, we used RING assays to show that long-lived Indy and chico mutants exhibit delayed senescence of negative Geotaxis. Our results demonstrate that RING is a powerful method for assessing negative Geotaxis that should facilitate the search for manipulations that influence behavioral aging in Drosophila.
Daniel Kamykowski - One of the best experts on this subject based on the ideXlab platform.
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Geotaxis phototaxis and biochemical patterns in heterocapsa cachonina illdefina dinophyceae during diel vertical migrations
Journal of Phycology, 1999Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E Reed, Wenchen LiuAbstract:Two separate experiments with Heterocapsa (=Cachonina) illdefina Herman et Sweeney, one with and the other without water volume replacement, were performed in a 250-L laboratory mesocosm (45-cm diameter × 150-cm height) to examine how diel vertical migration (DVM) relates to taxis sign and strength and to cellular biochemical state. Although only the cell population grown with water volume replacement maintained a division per day over the course of the experiment, periodic measurements during both experiments demonstrated that cells aggregating at the surface during the light period generally were deficient in all measured biochemical constituents compared to cells obtained from a midcolumn depth. More specifically, H. illdefina cells that aggregated at the surface during the light period in both experiments exhibited weakened positive Geotaxis but strengthened positive phototaxis and were very deficient in lipid and free amino acid compared to midcolumn cells. Cells sampled at midcolumn during the light period exhibited similar but weaker taxes changes compared to surface samples, and Geotaxis strength was inversely correlated with cell diameter, cellular DNA and protein content, and RNA/DNA ratio. In comparison, published data on Gymnodinium breve Davis, a harmful algal bloom species, showed that cells aggregating at the surface during the light period generally exhibited weakened negative Geotaxis and strengthened positive phototaxis and were very deficient in lipid and chl a compared to midcolumn cells. Although the persistent tendency toward negative Geotaxis was weaker in midcolumn subpopulations throughout the day, its strength was inversely correlated with cell diameter and cellular lipid content. The combined results for both species support a revised conceptual model of optimized DVM in autotrophic marine dinoflagellates incorporating generalized expressions of taxis and biochemical state of individual cells.
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Geotaxis/PHOTOTAXIS AND BIOCHEMICAL PATTERNS IN HETEROCAPSA (=CACHONINA) ILLDEFINA (DINOPHYCEAE) DURING DIEL VERTICAL MIGRATIONS
Journal of Phycology, 1999Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E Reed, Wenchen LiuAbstract:Two separate experiments with Heterocapsa (=Cachonina) illdefina Herman et Sweeney, one with and the other without water volume replacement, were performed in a 250-L laboratory mesocosm (45-cm diameter × 150-cm height) to examine how diel vertical migration (DVM) relates to taxis sign and strength and to cellular biochemical state. Although only the cell population grown with water volume replacement maintained a division per day over the course of the experiment, periodic measurements during both experiments demonstrated that cells aggregating at the surface during the light period generally were deficient in all measured biochemical constituents compared to cells obtained from a midcolumn depth. More specifically, H. illdefina cells that aggregated at the surface during the light period in both experiments exhibited weakened positive Geotaxis but strengthened positive phototaxis and were very deficient in lipid and free amino acid compared to midcolumn cells. Cells sampled at midcolumn during the light period exhibited similar but weaker taxes changes compared to surface samples, and Geotaxis strength was inversely correlated with cell diameter, cellular DNA and protein content, and RNA/DNA ratio. In comparison, published data on Gymnodinium breve Davis, a harmful algal bloom species, showed that cells aggregating at the surface during the light period generally exhibited weakened negative Geotaxis and strengthened positive phototaxis and were very deficient in lipid and chl a compared to midcolumn cells. Although the persistent tendency toward negative Geotaxis was weaker in midcolumn subpopulations throughout the day, its strength was inversely correlated with cell diameter and cellular lipid content. The combined results for both species support a revised conceptual model of optimized DVM in autotrophic marine dinoflagellates incorporating generalized expressions of taxis and biochemical state of individual cells.
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relationships between Geotaxis phototaxis and diel vertical migration in autotrophic dinoflagellates
Journal of Plankton Research, 1998Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E ReedAbstract:Marine dinoflagellate diel vertical migrations are often conceptually explained by a species' geotactic and phototactic preferences, but actual simultaneous measurements are rare. Newly collected simultaneous measurements on Heterocapsa (Cachonina) illdefina (Herman and Sweeney) and Gymnodinium breve (Davis) are combined with similar literature information on Amphidinium carterae (Hulbert), Peridinium faeroense (Paulsen) and Prorocentrum micans (Ehrenberg) to explore several examples of the actual relationships between diel vertical migration and Geotaxis/phototaxis. Amphidinium carterae does not migrate, but it exhibits a negative Geotaxis that may counter a small sinking velocity. The four other species all exhibit diel vertical migrations that yield surface aggrega- tions during daylight, but the associated combinations of Geotaxis and phototaxis precision (which is strongest when every cell in a population exhibits the same response to a stimulus and weakest when the response is random) and sign (which is positive (negative) when motion is toward (away from) the stimulus) are different in each case. These different taxis combinations may be related to species- specific sensor structure and/or placement. Furthermore, variations in the different biochemical pools over a species* cell cycle may contribute to structural/mechanical changes that influence how a given sensory array functions at a given time. If so, this coupling may be an important link in the growth optimization mechanisms and occasional bloom successes of different autotrophic dinoflagellate species under varying environmental conditions.
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Relationships between Geotaxis/phototaxis and diel vertical migration in autotrophic dinoflagellates
Journal of Plankton Research, 1998Co-Authors: Daniel Kamykowski, Edward J Milligan, Robert E ReedAbstract:Marine dinoflagellate diel vertical migrations are often conceptually explained by a species' geotactic and phototactic preferences, but actual simultaneous measurements are rare. Newly collected simultaneous measurements on Heterocapsa (Cachonina) illdefina (Herman and Sweeney) and Gymnodinium breve (Davis) are combined with similar literature information on Amphidinium carterae (Hulbert), Peridinium faeroense (Paulsen) and Prorocentrum micans (Ehrenberg) to explore several examples of the actual relationships between diel vertical migration and Geotaxis/phototaxis. Amphidinium carterae does not migrate, but it exhibits a negative Geotaxis that may counter a small sinking velocity. The four other species all exhibit diel vertical migrations that yield surface aggrega- tions during daylight, but the associated combinations of Geotaxis and phototaxis precision (which is strongest when every cell in a population exhibits the same response to a stimulus and weakest when the response is random) and sign (which is positive (negative) when motion is toward (away from) the stimulus) are different in each case. These different taxis combinations may be related to species- specific sensor structure and/or placement. Furthermore, variations in the different biochemical pools over a species* cell cycle may contribute to structural/mechanical changes that influence how a given sensory array functions at a given time. If so, this coupling may be an important link in the growth optimization mechanisms and occasional bloom successes of different autotrophic dinoflagellate species under varying environmental conditions.
Konstantin G. Iliadi - One of the best experts on this subject based on the ideXlab platform.
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Increased recombination frequencies resulting from directional selection for Geotaxis in Drosophila
Heredity, 1994Co-Authors: Abraham B. Korol, Konstantin G. IliadiAbstract:Increased recombination frequencies resulting from directional selection for Geotaxis in Drosophila
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Increased recombination frequencies resulting from directional selection for Geotaxis in Drosophila.
Heredity, 1994Co-Authors: Abraham B. Korol, Konstantin G. IliadiAbstract:Several classes of models have been suggested to explain how natural selection can favour non-zero recombination. Directional and fluctuating selection, abiotic and biotic, and selection against harmful mutations seem to be the most plausible factors, but little has been done to test the problem experimentally. Here we show that long-term selection for positive or negative Geotaxis in Drosophila melanogaster results in a dramatic increase in recombination rates in different genomic regions. The total increment in recombination for the genome portion considered is 78 cM for geo+ and 66 cM for geo-. Selection for negative Geotaxis did not result in recombination changes in chromosome 2 whereas selection in the opposite direction caused nearly a four-fold increase in the b-cn segment and a significant, albeit not as high, increase in the adjacent regions, al-b and cn-vg. In chromosomes X and 3, a significant increase in recombination was found in both selected lines. In total, the increment in exchange frequency in chromosome X (y-cv-ct-v-car) was from 72.6 per cent (the control level) to 124.7 and 110.3 per cent geo- and geo+, respectively, whereas for the studied portion of chromosome 3 (ru-h-cu-sr-e) we obtained, correspondingly, 60.8, 76.4 and 73.8 per cent. Thus, in general, selection for Geotaxis resulted in increased recombination frequencies regardless of the direction of selection.(ABSTRACT TRUNCATED AT 250 WORDS)
Jeffrey R. Alberts - One of the best experts on this subject based on the ideXlab platform.
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The validity and utility of Geotaxis in young rodents.
Neurotoxicology and teratology, 2005Co-Authors: Benjamin A. Motz, Jeffrey R. AlbertsAbstract:Negative Geotaxis, an automatic, reliable, stimulus-bound, orientation and movement directionally against gravitational cues, is often used for behavioral assessments of infant rodents. We summarize historical and contemporary analyses and conclude that negative Geotaxis does not exist in infant rats. Infant rodents placed on inclined surfaces (ranging from 15° to 70° in most tests) are posturally unstable and their compensatory responses have been misinterpreted as negative Geotaxis. In fact, recent findings suggest that if infant rats display a Geotaxis, they show positive Geotaxis on shallow angles of inclination (e.g., 4° and 8°). There may be utility in assessing postures and motoric responses of infant rats on relatively robust angles of inclination, but these are not tests of negative Geotaxis.
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What's a word worth?
Neurotoxicology and Teratology, 2005Co-Authors: Benjamin A. Motz, Jeffrey R. AlbertsAbstract:Geotaxis denotes automatic, reliable orientation and movement in relation to a gravitational stimulus. It is, by definition, dependent on perception of gravitational cues or of stimuli that arise from gravitational forces, such as proprioceptive cues. Recent empirical re-examinations of negative Geotaxis in infant rats, briefly reviewed in our commentary, indicate that the behavior of rats on an inclined plane is not Geotaxis. Depending on factors such as the angle of incline or the substrate material, a rat pup may be observed to orient up, down, or in no particular direction. Absent is a robust, reliable and valid gravity-oriented response by infant rodents on inclined surfaces. There was no substantive disagreement expressed by the commentators on these points. The discrepancy between the specificity of the term, Geotaxis, and the general absence of an oriented response to gravitational cues bothers each of the commentators and us in different ways and to varying degrees. Despite these differences, it was gratifying that a common theme in each of the Open Peer Commentaries is a basic concern with the conduct of science. Krieder and Blumberg drew a parallel between lack of terminological rigor and the absence of methodological standardization in testing infant rodents’ performance on an inclined surface. They see dual benefits to the use of standardized methods. First would be consistency, so that results from different laboratories could be compared legitimately. This is essentially impossible today, due to the wide variation of what is performed under the label of tests of negative Geotaxis (see Kreider and Blumberg’s Peer Commentary).
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Positive Geotaxis in infant rats (Rattus norvegicus): a natural behavior and a historical correction.
Journal of comparative psychology (Washington D.C. : 1983), 2004Co-Authors: Jeffrey R. Alberts, Benjamin A. Motz, Jeffrey C. SchankAbstract:Infant rats (Rattus norvegicus) placed on a shallow incline (2 degrees, 4 degrees, or 8 degrees) oriented and moved downhill within 1 min; that is, they displayed positive Geotaxis. Their downhill translocation increased with angle of inclination. A variety of possible behavioral elements (e.g., initial orientation, rotational movements, ambulatory velocities) were eliminated as explanations of the Geotaxis. Wall contact was recognized as a determinative event: Pups on the inclines showed no orientation with respect to the geogravitational stimulus before contacting a wall. The event of wall contact, however, evoked reliable downhill orientation and more linear movements. Positive Geotaxis was created by pups' orientation against walls and an associated increase in movement velocity. This is a distinct perspective on a behavioral response that replaces a traditionally misinterpreted phenomenon. The authors discuss the ecological validity and historical context of these findings.