Catecholamine varicosities in cat dorsal root ganglion and spinal ventral roots.
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Adrenergic Fibers↗
Biomedical subjects
R T Stevens
Publications and source records attributed to R T Stevens.
Dorsolateral pontine inhibition of dorsal horn cell responses to cutaneous stimulation: lack of dependence on catecholaminergic systems in cat.
The effect of stimulating the dorsolateral pons (DLP) in the region of locus ceruleus (LC) on lumbar dorsal horn cell responses to innocuous and noxious cutaneous stimuli was assessed and the dependence of these effects on intact pontospinal catecholaminergic systems was tested in chloralose-anesthetized cats. DLP stimulation inhibited the responses of dorsal horn cells to both noxious and innocuous skin stimuli. The inhibitory effect was most prominent when the responses to noxious stimuli were tested. The thresholds for eliciting DLP-spinal inhibition were lowest (less than 30 microA) in the region of LC. The inhibitory effect was found in both ipsilateral and contralateral dorsal horns. The DLP-spinal inhibition was unaltered by depletion of spinal catecholamines brought about by repeated lumbar intrathecal administration of 6-hydroxydopamine or systemic administration of reserpine. We conclude that the DLP-dorsal horn inhibition is not related to a catecholaminergic ceruleospinal system in the cat and that the dependence of pain modulation by catecholamine systems is a reflection of other descending pathways.
Animals↗
Kölliker-Fuse nucleus: the principal source of pontine catecholaminergic cells projecting to the lumbar spinal cord of cat.
Using retrograde transport of the fluorescent dye Evans Blue (EB), in combination with glyoxylic acid histofluorescence, the ponto-spinal catecholaminergic pathways were investigated. The cells which contain catecholamine and project to the lumbar spinal cord of the cat are most densely concentrated in the Kölliker-Fuse nucleus. Locus coeruleus, the subcoeruleus area, and the parabrachial nuclei were found to have relatively few cells that both contain catecholamine and project to the lumbar spinal cord.
Animals↗
Fine structure of sporogenesis and septum formation in Micromonospora globosa Kriss and M. fusca Jensen.
Sporogenesis in two species of Micromonospora M. globosa and M. fusca (Actinomycetes) was quite similar. As in fungi, spore formation began as a blowing-out of a hyphal tip with the subsequent centripetal invagination of the plasma membrane. Septal wall material was deposited in a typical three-layered pattern, i.e., two electron-opaque layers separated by an electron-transparent layer. A second electron-opaque wall layer was later formed within the spore and finally a third, less electron-opaque wall was produced. Spore dihiscence was facilitated by the fragmentation of the first-formed wall surrounding the spore. Sporogenesis in Micromonospora is blastic in nature producing terminal, thick-walled spores. In M. fusca, a sporulation process was observed which closely resembled sporangial formation. The process appeared similar to that described for the genus Actinoplanes. Swollen, multiseptate structures were also present. Also in M. fusca, perforate septa with flared pore margins were observed. These septa were similar in appearance to the dolipore septa of Basidiomycetes although they lack a parenthesome and pore plug. Although an extensive membrane system (mesosome) was associated with the finishing septum, its function in the process of septum formation was not determined.
Cell Membrane↗
Use-dependent plasticity in barrel cortex: intrinsic signal imaging reveals functional expansion of spared whisker representation into adjacent deprived columns.
We used optical imaging of intrinsic cortical signals, elicited by whisker stimulation, to define areas of activation in primary sensory cortex of normal hamsters and hamsters subjected to neonatal follicle ablation at postnatal day seven (P7). Follicle ablations were unilateral, and spared either C-row whiskers or the second whisker arc. This study was done to determine if the intrinsic cortical connectivity pattern of the barrel cortex, established during the critical period, affects the process of representational plasticity that follows whisker follicle ablation. Additionally, we tested the ability to monitor such changes in individual cortical whisker representations using intrinsic signal imaging. Stimulation of a single whisker yielded peak activation of a barrel-sized patch in the somatotopically appropriate location in normal cortex. In both row and arc-spared animals, functional representations corresponding to spared follicles were significantly stronger and more oblong than normal. The pattern of activation differed in the row-sparing and arc-sparing groups, in that the expansion was preferentially into deprived, not spared areas. Single whisker stimulation in row-spared cases preferentially activated the corresponding barrel arc, while stimulation of one whisker in arc-spared cases produced elongated activation down the barrel row. Since whisker deflection normally has a net inhibitory effect on neighboring barrels, our data suggest that intracortical inhibition fails to develop normally in deprived cortical columns. Because thalamocortical projections are not affected by follicle ablation after P7, we suggest that the effects we observed are largely cortical, not thalamocortical.
Animals↗