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D B Dusenbery

Publications and source records attributed to D B Dusenbery.

15 recordsLinked to original sources
PubMed1989

Efficiency and the role of adaptation in klinokinesis.

Klinokinesis is a behavioral mechanism in which an organism moves toward or away from a stimulus source by altering its frequency of change of direction without biasing its turns with respect to the stimulus field. Computer simulation was used to study the efficiency of, and the effect of sensory adaptation on, this behavioral strategy. In modeling an organism with perfect performance (no error in determining the intensity of the stimulus and ability to move in perfectly straight lines) efficiency was about 70% without adaptation, and declined as the rate of adaptation increased. In contrast, models with non-perfect (noisy) performance were frequently able to double or triple their reduced efficiency by adapting to the stimulus intensity. Three types of noise that degraded performance were simulated: (1) intensity noise described random fluctuations in the intensity of the stimulus that were not associated with movement of the organism in the stimulus field; (2) motor noise described random fluctuations in the direction of locomotion as the organism moved along; (3) developmental noise described random differences between individuals in a constant tendency to turn to a certain degree as they moved forward. Adaptation had similar effects with any of the three types of noise. If a particular type of noise was strong enough to degrade performance significantly, then optimal performance occurred with an adaptation rate of about 0.2 per step.

Adaptation, Physiological↗
PubMed1989

The value of asymmetric signal processing in klinokinesis.

Klinokinesis is a behavioral mechanism in which an organism moves toward or away from a stimulus source by altering its frequency of change of direction without biasing its turns with respect to the stimulus field. Previous studies of a variety of organisms have demonstrated that rates of adaptation (or other information processing features) for increases and decreases in stimulus intensity are often very different from one another. In order to determine if such asymmetric signal processing could improve the efficiency of klinokinesis, computer modeling studies were performed. The model involved a simple generic version of klinokinesis in 2 dimensions with the rate of adaptation for increasing intensity varied independently of the rate for decreasing intensity. The effects of three types of noise that limit the performance of the model were tested - intensity noise, motor noise, and developmental noise. The results demonstrated that, with all three types of noise, the two adaptation rates had quite different effects on efficiency. The overall pattern of effects was different for each type of noise. In the cases of intensity noise and motor noise, the optimum combination of adaptation rates had a 3- to 5-fold higher rate for decreases in attractant than for increases, which is similar to what has previously been found with bacteria and nematodes.

Adaptation, Physiological↗
PubMed1988

Limits of thermal sensation.

The sensitivity of thermal receptors and responses is compared with thermal noise in receptor cells and with thermal signals in the environment. It is demonstrated that the most sensitive responses known are far less sensitive than is physically possible but sufficiently sensitive to detect the smallest signals likely to be present in the environment. Expressions for the minimal thermal gradients detectable by organisms moving through them are derived. Thermal fluctuations in a receptor over physiologically relevant times and distances are almost certainly less than 10(-6) degrees C. The most sensitive responses reported in any organism are about a thousand times larger. The thermal gradient present in soil is nearly always greater than 10(-3) degrees C/cm and it is probably higher in other environments. The suggestion that nematodes locate plant roots based on heat production is shown to be unlikely because the gradients produced are smaller than those from other causes. Bacteria, a slime mold, rattlesnakes, and mammals are discussed in addition to nematodes.

Animals↗
PubMed1988

Using the nematode Caenorhabditis elegans to predict mammalian acute lethality to metallic salts.

The acute lethality of the salts of eight metals--HgCl2, BeSO4.4H2O, Al(NO3)3.9H2O, CuCl2.2H2O, ZnCl2, Pb(NO3)2, CdCl2, and Sr(NO3)2--was determined using a type of free-living nematode, Caenorhabditis elegans. The LC50 values were compared to the published mammalian oral LD50 values for salts of the same metals. Within this set of chemicals, C. elegans was found to be a predictor of mammalian acute lethality, generating LC50 values parallel to the rat and mouse LD50 values. The total expenses for this testing are about 10% of the cost for mammalian acute lethality testing. The method is considered to have great promise, but further study is needed.

Animals↗
PubMed1985

Using a microcomputer and video camera to simultaneously track 25 animals.

A system that can simultaneously track about 25 animals with the position of each determined once a second is described. The system includes a 6809 microprocessor, OS-9 operating system and application programs written in assembly and BASICO9. The movements and changes in direction of the subjects can be determined and displayed in real time. The system has proven to be valuable in studying the chemotaxis of nematodes and should be applicable to the study of other animals that can be viewed with high contrast.

Animals↗
PubMed1975

The avoidance of D-tryptophan by the nematode Caenorhabditis elegans.

In chemotactic studies employing countercurrent separation the nematode aenorhabditis elegans was found to avoid D-tryptophan with a threshold in the range 10(-4) to 10(-3) M. There was no response to L-tryptophan up to 10(-2) M although it appeared to partially inhibit the response to D-tryptophan.

Animals↗
PubMed1975

Chemotaxis-defective mutants of the nematode Caenorhabditis elegans.

The technique of countercurrent separation has been used to isolate 17 independent chemotaxis-defective mutants of the nematode Caenorhabditis elegans. The mutants, selected to be relatively insensitive to the normally attractive salt NaCl, show varying degrees of residual sensitivity; some are actually weakly repelled by NaCl. The mutants are due to single gene defects, are autosomal and recessive, and identify at least five complementation groups.

Animals↗
PubMed1973

Countercurrent separation: a new method for studying behavior of small aquatic organisms.

A new method for the analysis of behavior in small free-swimming aquatic organisms is described. In this procedure, called countercurrent separation, a dense solution flows down along the bottom of an inclined chamber while a light solution flows in the opposite direction, upward along the top of the chamber. The attraction of animals (injected into the center of the chamber) to one solution or the other is then determined by observing the proportion of animals that emerges from the chamber in that solution. When used with the nematode Caenorhabditis elegans, it is estimated that the apparatus is equivalent to at least nine theoretical plates.

Animals↗
PubMed1972

The interaction of acridine dyes with the densely packed DNA of bacteriophage.

The interactions of acridine dyes with intact phage DNA differ from those with extracted DNA in the following respects. Strong binding (intercalation) is greatly reduced in intact phage but probably not eliminated. The cooperative, weak binding is stronger and the stacking tendency is increased. In gels of DNA the stacking tendency is seen to increase with decreasing hydration. These influences of the dense packing of DNA must be taken into account when using basic dyes to study chromosome structure.

Acridines↗
PubMed1972

The inhibition of bacteriophage DNA injection by dyes bound to the DNA.

A delay ( approximately 10 min) in the appearance of intracellular phage is caused by preincubating the infecting phage T4o(1) in proflavine, acridine orange, or ethidium, but not polyamines. No significant delay in attachment is observed. Apparently the presence of the dye is required inside the permeability barrier of the phage at the time of infection. The effect of proflavine is reduced in the presence of polyamines, suggesting that the active site is on DNA. The phage-host complex is sensitive to shear if the infecting phage have been incubated in proflavine or ethidium, indicating that the completion of DNA injection is delayed. Finally no partially injected complexes could be detected after shearing, which suggests that most of the delay occurs near the beginning of the injection process.

Acridines↗
PubMed1972

The orientation of DNA within 80-Angstrom chromatin fibers.

Squashing salivary glands of Chironomus thummi larvae, Amblystoma tigrinum erythrocytes, or Spirostromum frequently results in stretched chromatin having highly oriented DNA as determined by polarized fluorescence microscopy of acridine orange-stained preparations. The examination of such material from C. thummi in the electron microscope indicates that the individual chromatin fibers have an average thickness of 80 A as is usually found in embedded and sectioned material. It is thus concluded that the DNA lies nearly parallel to the axis of these chromatin fibers. Detailed calculations of the polarization expected from various models of DNA packing are contained in an appendix.

Ambystoma↗
PubMedDate not supplied

A promising indicator of neurobehavioral toxicity using the nematode Caenorhabditis elegans and computer tracking.

A promising screening test for neurotoxicity has been developed using a computer tracking system and a species of nematode, Caenorhabditis elegans. The animals are viewed in dark-field illumination by a video camera interfaced directly to a microcomputer. Several hundred nematodes are tracked simultaneously and rates of locomotion and frequency of change of direction are reported in real time. This system can rapidly obtain reliable data on a variety of behavioral parameters relating to locomotion and response to sensory stimulation. Initial testing has examined the effects of six chemicals on locomotion. Four metals (copper, beryllium, mercury, and lead) and two organophosphate pesticides (malathion and vapona) have been studied. Copper and beryllium were chosen as chemicals that have not been shown to be neurotoxins and the other four chemicals were chosen as substances known to be neurotoxins. Our findings indicate that the rate of movement of exposed nematodes compared to the rate of movement of vehicle controls may prove to be useful as an indicator of neurotoxicity.

Animals↗