Biomedical subjects

D B Dusenbery

Publications and source records attributed to D B Dusenbery.

23 records · Page 2Linked to original sources

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↗