Biomedical subjects

O Shupliakov

Publications and source records attributed to O Shupliakov.

40 records · Page 3Linked to original sources

PubMed1992

Thyrotropin-releasing hormone (TRH)-like immunoreactivity in the grey monkey (Macaca fascicularis) spinal cord and medulla oblongata with special emphasis on the bulbospinal tract.

The distribution of thyrotropin-releasing hormone (TRH)-like immunoreactivity (LI) has been studied in the grey monkey (Macaca fascicularis) spinal cord and medulla oblongata by the use of indirect immunofluorescence and the peroxidase-antiperoxidase (PAP) technique. Furthermore, double-labeling experiments were performed in order to study colocalization of 5-hydroxytryptamine (5-HT)- and substance P-LI. A dense innervation of TRH-immunoreactive (IR) varicose fibers was found in the ventral horn motor nuclei, in the region surrounding the central canal, in the intermediolateral cell column, and in the dorsal horn laminae II and III. In addition, cell bodies harboring TRH-LI were found in the dorsal horn laminae II-IV. In the ventral horn, many of the large cell bodies and their proximal dendrites were totally encapsulated by TRH-IR fibers. From double-labeled sections a high degree of coexistence could be established between TRH-/5-HT-LI, TRH-/substance P-LI, and 5-HT-/substance P-LI in fibers in the motor nuclei; as a consequence, a large proportion of these fibers should harbor TRH-/5-HT-/substance P-LI. A coexistence between TRH-/5-HT-LI could also be demonstrated in the intermediolateral cell column. However, no unequivocal coexistence could be found between TRH-/substance P-LI and 5-HT-/substance P-LI in this region. In the dorsal horn, no clear coexistence could be encountered for any of the above indicated combinations. Electron microscopic analysis of material from the lumbar lateral motor nucleus demonstrated TRH-IR terminals making synapses with large cell bodies and dendrites. In addition, contacts lacking synaptic specializations could also be verified. In the medulla oblongata, with the use of the PAP technique, a large number of cell bodies containing TRH-LI were encountered in the midline raphe nuclei and in nucleus reticularis lateralis. A similar distribution pattern could be found for 5-HT-LI, but no cell bodies containing substance P-LI could be seen in these regions. Chemical analysis of specimens from cervical, thoracic, and lumbar spinal cord revealed higher concentrations of TRH- and 5-HT-LI in the ventral quadrants, whereas substance P-LI dominated in the dorsal quadrants. Thus, the concentrations of TRH-, 5-HT-, and substance P-LI was in accordance with the observed regional variation in density of IR-fibers and varicosities found in the spinal cord. We have shown that TRH-LI has a distribution in the monkey spinal cord and medulla oblongata similar to that previously demonstrated in other species.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Two types of motoneurons supplying dorsal fin muscles in lamprey and their activity during fictive locomotion.

The location and dendritic morphology of motoneurons supplying the dorsal fin muscles were studied in the lamprey spinal cord (Ichthyomyzon unicuspis). Motoneurons were retrogradely labelled after injection of HRP into the fin muscles or after its application on the cut ends of the ventral roots. HRP-labelled cells were subsequently reconstructed, in the horizontal and/or transverse planes. Fin motoneurons were also injected intracellularly with Lucifer Yellow and their detailed three-dimensional structure was analysed by confocal laser-scanning microscopy. Unlike myotomal motoneurons, which are closely spaced in the lateral cell column, fin motoneurons were distributed along the spinal cord separately or in pairs. They could be distinguished from motoneurons supplying trunk muscles by having a limited number of dendrites in the lateral part of the spinal cord. In addition, some fin motoneurons extend their dendrites into the dorsal column. The motor cells innervating fin muscles were divided into two types based on their dendritic morphology. Type I have a widespread dendritic tree in the rostrocaudal direction and, with few exceptions, completely restricted to the ipsilateral side. A proportion (25%) of these cells have dendrites extending into the dorsal column. Type II fin motoneurons extended their dendrites both ipsi- and contra-laterally. The contra-lateral dendrites pass below and above the central canal. The dendrites send off branches into the dorsal columns on both the ipsi- and the contra-lateral sides. Electron microscopic analysis showed that both type I and type II fin motoneurons receive numerous synaptic contacts from dorsal column axons. During fictive locomotion both types of motoneurons are active in antiphase in relation to myotomal motoneurons and to the main locomotor burst.

Animals↗

PubMed1992

Immunogold quantification of glutamate in two types of excitatory synapse with different firing patterns.

A quantitative immunocytochemical method was used to study the regional levels of glutamate in two types of lamprey (Ichtyomyzon unicuspis) axon, which both activate excitatory amino acid receptors, but which when active exhibit different firing patterns. Giant reticulospinal axons fire in brief bursts, while dorsal column axons, mainly belonging to cutaneous afferents, show a sustained firing at high frequency. In both types of axon, clusters of synaptic vesicles showed a strong accumulation of glutamate immunogold labeling, and the density of gold particles correlated strictly with the packing density of synaptic vesicles. The most densely packed vesicle areas had a particle density corresponding to a concentration of fixed glutamate of about 30 mM in coprocessed glutamate conjugates, suggesting an intravesicular glutamate concentration of at least 60 mM. The level of labeling in axoplasmic matrix was considerably lower, but differed significantly between the two types of axon. Dorsal column axons showed a particle density in axoplasmic matrix that was approximately four times higher than that in giant reticulospinal axons. The mitochondrial glutamate labeling was also significantly stronger in the dorsal column axons. In addition, the number of mitochondrial profiles surrounding vesicle clusters was about four times higher in dorsal column synapses than in reticulospinal synapses. Antisera to aspartate, GABA, glutamine, and homocysteate failed to produce a specific labeling of synaptic vesicle clusters in reticulospinal or dorsal column axons. In conjunction with previous demonstrations of a stimulus-induced vesicle depletion in giant reticulospinal synapses (Wickelgren et al., 1985), these results imply that glutamate is released from synaptic vesicles. The different extravesicular glutamate levels in reticulospinal axons and dorsal column axons may relate to different requirements for the refilling of synaptic vesicles in these functionally divergent neurons.

Animals↗

PubMed1992

Distribution of calbindin D28k-like immunoreactivity (LI) in the monkey ventral horn: do Renshaw cells contain calbindin D28k-LI?

By use of indirect immunofluorescence and peroxidase-antiperoxidase immunohistochemistry, we show that the monkey (Macaca fascicularis) ventral horn harbors small- to medium-sized neurons in lamina VII as well as a dense network of fibers in laminae IX and VII that contain calbindin D28k (calbindin)-like immunoreactivity. The highest frequency of immunoreactive (IR) cell bodies was found at the levels of the cervical and lumbar intumescences. Furthermore, rostrocaudally oriented calbindin-IR fibers were encountered in the ventral and ventrolateral funiculi throughout the whole length of the cord, with the highest density at cervical and lumbar intumescences. Analysis at the EM level revealed calbindin-IR terminals in contact preferentially with dendrites of variable size and occasionally also large cell bodies, presumably belonging to motoneurons, in the lateral motor nucleus. The location of calbindin-IR neurons, as well as the distribution and ultrastructural characteristics of the calbindin-IR axonal system, makes it highly likely that these neurons are Renshaw cells that mediate recurrent inhibition to motoneurons.

Animals↗