Biomedical subjects

D Onstott

Publications and source records attributed to D Onstott.

6 recordsLinked to original sources

PubMed1993

Nitric oxide synthase immunoreactive neurons anatomically define a longitudinal dorsolateral column within the midbrain periaqueductal gray of the rat: analysis using laser confocal microscopy.

Nitric oxide has recently been proposed as a neuronal messenger in both the central and peripheral nervous system. Antibodies against nitric oxide synthase (NOS), the synthesizing enzyme for nitric oxide, were used in combination with immunocytochemistry and confocal laser microscopy to analyze the distribution of this enzyme in the midbrain periaqueductal gray (PAG) of the rat. NOS immunoreactive neurons were localized predominantly in a longitudinally oriented column in the dorsolateral PAG. NOS immunoreactive fibers and processes were scattered throughout the PAG but were most prevalent in the dorsolateral column and in the juxta-aqueductal column. This study provides neurochemical support for the existence of longitudinal columns in the PAG which are postulated to underlie the functional organization of this complex brainstem region.

Amino Acid Oxidoreductases↗

PubMed1993

Distance- and error-related discharge of cells in premotor cortex of rhesus monkeys.

Previous work on the premotor cortex has emphasized its role in preparation for movement. In this study, we concentrated on the activity that occurs during a movement, particularly when the required movement amplitude is unexpectedly changed by introduction of a visuo-spatial error. In two rhesus monkeys, discharge of premotor neurons was recorded during a multi-joint reaching movement. Units could be divided into two categories: (1) those whose discharge monotonically increased or decreased with movement amplitude; and (2) those whose discharge was modulated with the unexpected change in amplitude but not monotonically. We suggest that the latter class of cells may be detecting or responding to a visuo-motor error. Thus, the premotor cortex is not only involved in preparation but plays a role in the ongoing control of movement execution.

Animals↗

PubMed1986

Immunohistochemical localization of urotensin I/corticotropin-releasing factor, urotensin II, and serotonin immunoreactivities in the caudal spinal cord of nonteleost fishes.

Neurosecretory cells in the caudal spinal cord of fishes were first discovered in elasmobranches. However, most of the subsequent work on the caudal neurosecretory system has emphasized its morphology and function in teleosts. Two major peptides, urotensins I and II (UI and UII), have been isolated from this system in teleosts and their amino acid sequences have been determined. We have used immunohistochemical techniques to confirm and expand previous morphological and pharmacological findings regarding the phylogenetic occurrence and the anatomical organization of the caudal neurosecretory system and to localize putative neurohormonal products within its structural elements. UII-immunoreactive neuronal structures were found in the holocephalan, Hydrolagus collei; the elasmobranches, Squalus acanthias, Dasyatis sabina, and Raja binoculata; the dipnoan, Protopterus annectens; the brachiopterygian, Erpetoichthys calabaricus; the chondrostean, Polyodon spathula; and the holosteans Lepisosteus platyrhinchus and Amia calva. UI/corticotropin-releasing-factor immunoreactive elements were detected in the caudal spinal cords of Petromyzon marinus, Raja binoculata, Polydon spathula, Lepisosteus platyrhinchus, L. osseus, L. platostomus, and Amia calva. In addition, in several of these species, immunohistochemical techniques have provided evidence for serotoninergic input to the caudal neurosecretory system.

Animals↗

PubMed1986

Coexistence of urotensin I/corticotropin-releasing factor and urotensin II immunoreactivities in cells of the caudal neurosecretory system of a teleost and an elasmobranch fish.

By use of the indirect immunofluorescence method in conjunction with an elution-restaining technique, cells in the caudal neurosecretory system of the big skate (Raja binoculata) and the plainfin midshipman (Porichthys notatus) were shown to contain both urotensin I (UI)/corticotropin-releasing factor (CRF) and urotensin II (UII) immunoreactivities. In the skate coexistence was complete, while in the midshipman some cells demonstrated immunoreactivity for only one or the other neuropeptide. The present results do not support previous suggestions that, like vasopressin and oxytocin in the hypothalamic magnocellular system, UI and UII exist in separate cellular populations in the caudal neurosecretory system. Results of these and other experiments indicate that there exists a wide range of species variation in the degree of coexistence of UI/CRF and UII immunoreactivities within caudal neurosecretory cells.

Animals↗

PubMed1984

Peptidergic regulation in neuroendocrine and autonomic systems.

Neuropeptides are found in dense networks of neuronal perikarya, fibers and terminals within numerous brain regions. Among the more striking of these collections are sites within the central nervous system that are presumed to regulate either endocrine or autonomic function. A recent example of a neuropeptide which is likely to play a significant role in endocrine regulation is cortocotropin releasing factor (CRF). Immunohistochemical studies revealed that CRF immunoreactivity was found in many brain regions, including the paraventriculo-infundibular pathway. CRF released from nerve terminals belonging to this pathway presumably regulates ACTH release. Treatment of rats with reserpine depletes CRF as well as vasopressin from the external layer of the median eminence, suggesting tonic, monoaminergic inhibition of CRF and vasopressin containing neurons. CRF antisera were found which stain urotensin I immunoreactivity within the caudal neurosecretory system of fish. Numerous putative neurotransmitters impinge upon preganglionic sympathetic neurons within the intermediolateral cell column of the spinal cord. Preganglionic sympathetic neurons which innervate the adrenal medulla appear to have a specific input from somatostatin immunoreactive fibers. In addition, binding sites for serotonin and alpha-2 adrenergic ligands are more highly concentrated over sympathoadrenal neurons. Finally, the pancreatic islet contains peptide producing endocrine cells which possess several neuron-like properties. Some of these properties are reviewed, especially the finding that the insulin producing cells contain glutamate decarboxylase immunoreactivity, the biosynthetic enzyme for GABA. Further studies revealed that GABA agonists inhibit somatostatin release from islet cells.

Adrenal Medulla↗

PubMed1984

Immunohistochemical localization of urotensin I/corticotropin-releasing factor immunoreactivity in neurosecretory neurons in the caudal spinal cord of fish.

Urotensin I (UI), one of the biologically active peptides isolated from the caudal spinal cord and urophysis of fish, exhibits a strong sequence homology with mammalian corticotropin-releasing factor (CRF). We have applied an antiserum to ovine CRF that cross-reacts completely with UI to sections taken from the caudal spinal cord and urophysis of the channel catfish (Ictalurus punctatus). Using the indirect immunofluorescence technique, the presence of striking UI-like immunoreactivity was observed within discrete neuronal structures. UI immunoreactivity was found within large-diameter neuronal perikarya in spinal cord segments immediately rostral to the urophysis, in fascicles of nerve fibers as the urophysis emerges, and in a dense plexus of nerve fibers and terminals which abut capillary loops within the urophysis. The localization of UI immunoreactivity within discrete neurosecretory neurons of this system will make it possible to more fully determine the nature of the regulatory mechanisms controlling its secretion.

Animals↗