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Biomedical subjects

K V Anderson

Publications and source records attributed to K V Anderson.

At least 55 records · Page 3Linked to original sources
PubMed1984

Simultaneous demonstration of neuronal somata that innervate the tooth pulp and adjacent periodontal tissues, using two retrogradely transported anatomic markers.

Two axonally transported substances were used to demonstrate the spatial relationships between trigeminal ganglion cells innervating the tooth pulp and adjacent periodontal tissues of the mandibular canine teeth in cats. 4',6-Diamidino-2-phenylindole (DAPI) and horseradish peroxidase (HRP) were applied in the periodontal tissues and in the tooth pulp, respectively. The trigeminal ganglion and brain stem were then examined for the presence of fluorescent DAPI-labeled cells, HRP-labeled cells, and cells containing both labels. Cells containing either DAPI or HRP were observed in the mandibular portion of the ganglion; DAPI-labeled cells were observed in the pontine portion of the mesencephalic nucleus of the trigeminal nerve. Examples of double labeling, indicative of collateralization of single neurons to innervate both the tooth pulp and adjacent tissues, were not commonly observed. Finally, there was no indication of a mesencephalic nucleus contribution to the tooth pulp innervation.

Animals↗
PubMed1980

Changing rates of histone mRNA synthesis and turnover in Drosophila embryos.

The rates of synthesis and turnover of histone mRNA in Drosophila embryos were determined by hybridization of in vivo and in vitro labeled embryonic RNA to Drosophila histone DNA of the recombinant plasmid cDm500. There is a large store of maternal histone mRNA, equivalent to at least 7 X 10(7) copies of each of the five classes of histone mRNA per embryo. Embryonic synthesis of histone mRNA begins at 90 min after oviposition, making the histone genes among the first to be transcribed by embryonic nuclei. Embryonic histone mRNA accumulates rapidly during the blastoderm and gastrula stages. The peak in the rate of histone mRNA synthesis per embryo coincides with the peak in the rate of DNA synthesis per embryo, which occurs at 6 hr after oviposition. After 6 hr, as the rate of DNA synthesis per embryo decreases, the rate of histone mRNA synthesis and the total mass of histone mRNA per embryo both drop sharply. The rate of histone mRNA synthesis per gene falls more than 60 fold in the first 13 hr after oviposition, from 1.3 -2.5 copies per gene-min at 2 hr to 0.02-0.03 copies per gene-min at 13 hr. From measurements of the mass of histone mRNA per embryo and of the rate of accumulation of newly synthesized histone mRNA at a number of stages of early embryogenesis we determined that the cytoplasmic half-life of histone mRNA decreases approximately 7 fold during early Drosophila development, from 2.3 hr at blastoderm to 20 min by the end of gastrulation. Thus the level of expression of histone genes in Drosophila development is controlled not only by the size of the maternal mRNA pool and changes in the rate of histone mRNA synthesis, but also by changes in the rate of histone mRNA turnover.

Animals↗
PubMed1978

Comparison of light-microscopic methods for visualizing horseradish peroxidase granules in stained and unstained tissue.

This study was directed toward a comparison of the effectiveness of three different light-microscopical methods for identifying and studying the features of cells that contain horseradish peroxidase (HRP) granules. The cells studied were located in the trigeminal ganglia and were labeled after the injection of HRP solutions into single, maxillary, canine teeth. The tissue was examined with light field, dark field, and differential interference optical systems. The results indicated that differential interference optics were especially useful in revealing the presence of intracellular HRP granules in both unstained and stained tissue, particularly when cells only contained small amounts of HRP. It was also noted that a wide variety of quantitative analyses could be performed with differential interference optics, even when using unstained tissue.

Afferent Pathways↗
PubMed1977

Response properties of cells in the dorsal lateral geniculate nucleus of the albino rat.

The response patterns of cells in the dorsal lateral geniculate nucleus of the albino rat were studied in order to examine the functional organization of the lateral geniculate nucleus. Both photic stimulation and electrical stimulation of the optic tract were used to activate single units in the lateral geniculate nuclei. Three different types of response patterns were found for principal cells, while interneurons all had similar response patterns. The first class of principal cells, E-S cells, responded to stimulation with a period of excitation, followed by a period when activity was suppressed. A second class of cells, S cells, responded to photic stimulation with an initial period when activity was suppressed. The final class of cells, E cells, responded with a period of excitation followed by a return to spontaneous rates of firing. The response patterns of E cells suggest that this type of principal neuron does not receive feedback inhibition of the type proposed in previous models of the lateral geniculate nuclei. Based on these and other observations, a new model of the functional organization of the lateral geniculate nuclei is proposed.

Animals↗
PubMed1976

Behavioral evidence showing the predominance of diffuse pain stimuli over discrete stimuli in influencing perception.

This experiment was directed toward determining the relative effectiveness of discrete and diffuse pain stimuli in influencing perception and behavior. Shocks to the footpads were used to activate the discrete pain pathways and shocks to the upper canine teeth to activate the diffuse pain pathways. In the first phase of this experiment, cats were trained to escape from foot shock in a shuttle box. Current applied to the feet was varied in ascending and descending sequences for each animal according to the psychophysical method of limits and each animal was trained until stable thresholds for escape responding were achieved. In the second phase of the experiment, the effect on behavior of simultaneous activation of both the discrete and diffuse pain systems was assessed. The principal finding is this experiment was that excape responding that was well established when foot shock was presented alone was routinely abolished on trials when tooth shock and foot shock were presented together. These results were interpreted as indicating that the diffuse pain system was prepotent in influencing behavior when both the discrete and diffuse pain systems were activated simultaneously.

Animals↗
PubMed1975

Single-cell responses associated with rhythmic slow-wave potentials in rat superior colliculi.

The present study was designed to investigate the features of rhythmic slow-wave potentials in the superior colliculi of rats and to study the relationship between these potentials and the activity of single colliculi neurons. In contrast to studies in other portions of the visual system, rhythmic slow-wave potentials in the colliculi fell within a single limited range of frequencies from 9 to 26 cycl/sec. Single-cell recordings revealed that numerous collicular neurons were also responding rhythmically, with discharge frequencies generally coinciding with those established for collicular slow-wave potentials. In some animals slow-wave and single-cell potentials were recorded simultaneously through adjacent electrodes, and in all instances the frequency of discharge of single neurons coincided with the frequency of oscillation of the slow-wave potentials. These data suggest that rhythmic postsynaptic potentials in individual collicular neurons may be the mechanism by which rhythmic slow-wave potentials are generated.

Animals↗
PubMed1975

Extraocular muscle degeneration and regeneration after exposure of rats to incandescent radiant energy.

Exposure of albino rats to incandescent radiant energy for a short period of time in an elevated environmental temperature (39 degrees C) causes degenerative changes in the extraocular muscles. The muscle fibres regenerate and the muscles reorganize if the animals are returned to room lighting and temperature. Extraocular muscles (EOMs) were damaged first near their insertion on the eyeball. All EOMs of both eyes were affected, but the degeneration did not extend the entire length of the muscle. The peripheral fibres of each muscle were damaged before the more central fibres. Mitochondria were swollen and often contained dense bodies. Numerous vesicular profiles, possibly from the sarcotubular system, were present. Myofibrils of the more severely damaged fibres lacked typical Z-disk structures, and I-bands had disappeared by 24 h after the exposure period, a degenerative pattern which seems to be unique for this method of EOM damage. EOM degeneration appeared to be dependent on the interaction between thermal and radiant energy on the orbital contents. However, EOMs were only rarely and very slightly affected when rats were exposed to elevated temperature in the absence of incandescent radiant energy. When an opaque, black, ocular occluder was placed over one eye and the contralateral eye was left unoccluded, EOMs and retinas of occluded eyes were undamaged, while those tissues were severely damaged in unoccluded eyes. Therefore, the most critical single variable in inducing EOM degeneration appears to be exposure to radiant energy.

Animals↗