136 results on '"Fyffe R"'
Search Results
2. Signal transduction mechanisms of K+-Cl− cotransport regulation and relationship to disease
- Author
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Adragna, N. C., Ferrell, C. M., Zhang, J., Di Fulvio, M., Temprana, C. F., Sharma, A., Fyffe, R. E. W., Cool, D. R., and Lauf, P. K.
- Published
- 2006
3. Focal aggregation of voltage-gated, Kv2.1 subunit-containing, potassium channels at synaptic sites in rat spinal motoneurones
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Muennich, Elizabeth A. L. and Fyffe, R. E. W.
- Published
- 2004
4. EXPLOITATION OF FORESTS IN UGANDA
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Fyffe, R.
- Published
- 1926
5. Ultrastructure of hair follicle afferent fibre terminations in the spinal cord of the cat
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Maxwell, D. J., Bannatyne, B. A., Fyffe, R. E. W., and Brown, A. G.
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- 1982
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6. Focal aggregation of voltage-gated, Kv2.1 subunit-containing, potassium channels at synaptic sites in rat spinal motoneurones
- Author
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Muennich, Elizabeth A L and Fyffe, R E W
- Subjects
Male ,Motor Neurons ,Afferent Pathways ,Potassium Channels ,Research Papers ,Immunohistochemistry ,Rats ,Rats, Sprague-Dawley ,Shab Potassium Channels ,nervous system ,Spinal Cord ,Interneurons ,Potassium Channels, Voltage-Gated ,Synapses ,Animals ,Microscopy, Immunoelectron ,Delayed Rectifier Potassium Channels - Abstract
Delayed rectifier K+ currents are involved in the control of alpha-motoneurone excitability, but the precise spatial distribution and organization of the membrane ion channels that contribute to these currents have not been defined. Voltage-activated Kv2.1 channels have properties commensurate with a contribution to delayed rectifier currents and are expressed in neurones throughout the mammalian central nervous system. A specific antibody against Kv2.1 channel subunits was used to determine the surface distribution and clustering of Kv2.1 subunit-containing channels in the cell membrane of alpha-motoneurones and other spinal cord neurones. In alpha-motoneurones, Kv2.1 immunoreactivity (-IR) was abundant in the surface membrane of the soma and large proximal dendrites, and was present also in smaller diameter distal dendrites. Plasma membrane-associated Kv2.1-IR in alpha-motoneurones was distributed in a mosaic of small irregularly shaped, and large disc-like, clusters. However, only small to medium clusters of Kv2.1-IR were observed in spinal interneurones and projection neurones, and some interneurones, including Renshaw cells, lacked demonstrable Kv2.1-IR. In alpha-motoneurones, dual immunostaining procedures revealed that the prominent disc-like domains of Kv2.1-IR are invariably apposed to presynaptic cholinergic C-terminals. Further, Kv2.1-IR colocalizes with immunoreactivity against postsynaptic muscarinic (m2) receptors at these locations. Ultrastructural examination confirmed the postsynaptic localization of Kv2.1-IR at C-terminal synapses, and revealed clusters of Kv2.1-IR at a majority of S-type, presumed excitatory, synapses. Kv2.1-IR in alpha-motoneurones is not directly associated with presumed inhibitory (F-type) synapses, nor is it present in presynaptic structures apposed to the motoneurone. Occasionally, small patches of extrasynaptic Kv2.1-IR labelling were observed in surface membrane apposed by glial processes. Voltage-gated potassium channels responsible for the delayed rectifier current, including Kv2.1, are usually assigned roles in the repolarization of the action potential. However, the strategic localization of Kv2.1 subunit-containing channels at specific postsynaptic sites suggests that this family of voltage-activated K+ channels may have additional roles and/or regulatory components.
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- 2003
7. The Atlantis OBS Project: Node Handling and Deployment
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Thompson, J., primary, Fraser, D., additional, and Fyffe, R., additional
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- 2006
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8. Comparison of the Morphological and Electrotonic Properties of Renshaw Cells, Ia Inhibitory Interneurons, and Motoneurons in the Cat
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Bui, T. V., primary, Cushing, S., additional, Dewey, D., additional, Fyffe, R. E., additional, and Rose, P. K., additional
- Published
- 2003
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9. Light microscopic observations on the relationships between 5-hydroxytryptamine-immunoreactive axons and dorsal spinocerebellar tract cells in Clarke's column in the cat
- Author
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Pearson, J. C., primary, Sedivec, M. J., additional, Dewey, D. E., additional, and Fyffe, R. E. W., additional
- Published
- 1999
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10. Distribution of cholinergic contacts on Renshaw cells in the rat spinal cord: a light microscopic study
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Alvarez, F. J., primary, Dewey, D. E., additional, McMillin, P., additional, and Fyffe, R. E. W., additional
- Published
- 1999
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11. Electrotonic architecture of cat gamma motoneurons
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Burke, R. E., primary, Fyffe, R. E., additional, and Moschovakis, A. K., additional
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- 1994
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12. Involvement of GABA and glycine in recurrent inhibition of spinal motoneurons
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Schneider, S. P., primary and Fyffe, R. E., additional
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- 1992
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13. The size and dendritic structure of HRP‐labeled gamma motoneurons in the cat spinal cord
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Moschovakis, A. K., primary, Burke, R. E., additional, and Fyffe, R. E. W., additional
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- 1991
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14. Spatial distribution of recurrent inhibitory synapses on spinal motoneurons in the cat
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Fyffe, R. E., primary
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- 1991
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15. Signal transduction mechanisms of K+-Cl− cotransport regulation and relationship to disease.
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Adragna, N. C., Ferrell, C. M., Zhang, J., Di Fulvio, M., Temprana, C. F., Sharma, A., Fyffe, R. E. W., Cool, D. R., and Lauf, P. K.
- Subjects
CELLULAR signal transduction ,PLATELET-derived growth factor ,MESSENGER RNA ,CELLULAR mechanics ,CONFOCAL microscopy ,IMMUNOFLUORESCENCE - Abstract
The K
+ -Cl− cotransport (COT) regulatory pathways recently uncovered in our laboratory and their implication in disease state are reviewed. Three mechanisms of K+ -Cl− COT regulation can be identified in vascular cells: (1) the Li+ -sensitive pathway, (2) the platelet-derived growth factor (PDGF)-sensitive pathway and (3) the nitric oxide (NO)-dependent pathway. Ion fluxes, Western blotting, semi-quantitative RT-PCR, immunofluorescence and confocal microscopy were used. Li+ , used in the treatment of manic depression, stimulates volume-sensitive K+ -Cl− COT of low K+ sheep red blood cells at cellular concentrations <1 mm and inhibits at >3 mm, causes cell swelling, and appears to regulate K+ -Cl− COT through a protein kinase C-dependent pathway. PDGF, a potent serum mitogen for vascular smooth muscle cells (VSMCs), regulates membrane transport and is involved in atherosclerosis. PDGF stimulates VSM K+ -Cl− COT in a time- and concentration-dependent manner, both acutely and chronically, through the PDGF receptor. The acute effect occurs at the post-translational level whereas the chronic effect may involve regulation through gene expression. Regulation by PDGF involves the signalling molecules phosphoinositides 3-kinase and protein phosphatase-1. Finally, the NO/cGMP/protein kinase G pathway, involved in vasodilation and hence cardiovascular disease, regulates K+ -Cl− COT in VSMCs at the mRNA expression and transport levels. A complex and diverse array of mechanisms and effectors regulate K+ -Cl− COT and thus cell volume homeostasis, setting the stage for abnormalities at the genetic and/or regulatory level thus effecting or being affected by various pathological conditions. [ABSTRACT FROM AUTHOR]- Published
- 2006
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16. Intracellular staining study of the feline cuneate nucleus. II. Thalamic projecting neurons.
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Fyffe, R. E., Cheema, S. S., Light, A. R., and Rustioni, A.
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- 1986
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17. Intracellular staining study of the feline cuneate nucleus. I. Terminal patterns of primary afferent fibers.
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Fyffe, R. E., Cheema, S. S., and Rustioni, A.
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- 1986
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18. Morphology of neurons in area 4γ of the cat's cortex studied with intracellular injection of HRP.
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Ghosh, S., Fyffe, R. E. W., and Porter, R.
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- 1988
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19. KCl co-transport: immunocytochemical and functional evidence for more than one KCC isoform in high K and low K sheep erythrocytes
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Lauf, P. K., Zhang, J., Delpire, E., Fyffe, R. E., Mount, D. B., and Adragna, N. C.
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- 2001
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20. Distribution of 5-hydroxytryptamine-immunoreactive boutons on immunohistochemically-identified Renshaw cells in cat and rat lumbar spinal cord
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Cart, P. A., Pearson, J. C., and Fyffe, R. E. W.
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- 1999
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21. The morphology of group Ia afferent fibre collaterals in the spinal cord of the cat.
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Brown, A G and Fyffe, R E
- Abstract
1. The enzyme horseradish peroxidase (HRP) was injected into single Ia muscle afferent fibres in anaesthetized cats. Subsequent histochemistry allowed the morphology of the axons and their collaterals in the lumbosacral spinal cord to be determined. 2. Fifteen Ia axons were stained, four from medial gastrocnemius, four from lateral gastrocnemius‐soleus and seven from muscles innervated by the posterior tibial nerve. All thirteen axons that could be traced into the dorsal roots bifurcated upon entering the cord. Between 4 and 11 mm of axons were stained and they gave off eighty seven collaterals over distances between 3 and 9 mm. Collaterals were given off at intervals of 100‐2600 micron at an average spacing of about 1000 micron. 3. All Ia collaterals had a characteristic morphology. After leaving the parent axon they ran ventrally to lamina VI and then ventrolaterally to the motor nuclei. The collaterals coursed cranially from their point of origin to the motor nuclei so that their lamina VI terminations were about 100‐300 micro caudal to their terminations in motor nuclei. Terminal arborizations were limited to three sites; lamina VI (the intermediate region), lamina VII (the Ia inhibitory interneurone region) and lamina IX (the motor nuclei). The three sets of terminals had characteristic arborizations and bouton arrangements. 4. The results are discussed in relation to previous anatomical studies. In particular the present results suggest that a single Ia collateral makes contact with many more motoneurones than has previously been suggested in fact with fifty to sixty rather than with about ten.
- Published
- 1978
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22. Projections from Pacinian corpuscles and rapidly adapting mechanoreceptors of glabrous skin to the cat's spinal cord.
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Brown, A G, Fyffe, R E, and Noble, R
- Abstract
1. Single axons innervating Pacinian corpuscles and rapidly adapting mechanoreceptors of the foot and toe pads were injected with horseradish peroxidase near their entrance to the lumbosacral spinal cord in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. Subsequent histochemistry revealed the morphology of the intra‐spinal parts of the axons. 2. All Pacinian corpuscle axons that could be traced into the dorsal root bifurcated upon entering the cord into ascending and descending branches. All Pacinian corpuscle axons gave rise to collaterals that entered the dorsal horn. 3. The collaterals of Pacinian corpuscle afferent fibres had a distinctive morphology. They provided two regions of termination, a larger dorsal region in laminae III and IV and a smaller ventral region in laminae V and VI. Within the dorsal region the terminal axons ran mainly in the longitudinal axis of the cord and carried many boutons en passant. Within the ventral region the axons ran dorso‐ventrally in the transverse plane of the cord and although carrying some boutons en passant also gave rise to clusters of boutons. 4. The collaterals of rapidly adapting afferent fibres had a distinctive morphology different from that of the Pacinian corpuscle afferent fibre collaterals. The termination region of rapidly adapting afferents was limited almost exclusively to lamina III, with only slight extension into lamina IV. Boutons were mainly of the en passant type and terminal axons were generally orientated within the longitudinal axis of the cord. 5. The morphology of the afferent fibre collaterals is discussed in relation to the physiology of the dorsal horn.
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- 1980
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23. Direct observations on the contacts made between Ia afferent fibres and alpha‐motoneurones in the cat's lumbosacral spinal cord.
- Author
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Brown, A G and Fyffe, R E
- Abstract
1. The enzyme horseradish peroxidase was injected into identified lumbosacral alpha‐motoneurones and Group Ia afferent fibres in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. Subsequent histological examination allowed the determination of (a) the extent of the motoneuronal dendritic trees, (b) the number and location of Ia synapses upon the motoneurones. 2. alpha‐motoneurones had seven to eighteen primary dendrites and each produced daughter branches up to the fourth to the sixth order. At dendritic bifurcations Rall's 3/2 Power Law was obeyed. There was little or no dendritic tapering up to about 800 micrometers from the soma. Beyond this distance, however, there was considerable tapering. 3. Horseradish peroxidase injections revealed that motoneuronal dendrites are much longer than previously thought. Individual dendrites could be traced for up to 1600 micrometers from the soma and dendritic trees were usually 2‐3 mm from tip to tip. Nearly all the motoneurones had dendrites that entered the white matter of the cord. Dendrites could also reach as far dorsally as laminae V and VI. 4. Ia synapses upon motoneuronal somata were examined in cords counterstained with cresyl violet or methylene green. About 10% of Ia boutons in lamina IX were on somata and each Ia collateral terminated on 3.66 motoneuronal somata or the most proximal (30 micrometer) dendrites, with on average about two contacts per motoneurone. 5. Ten Ia afferent fibre‐motoneurone pairs were injected with horseradish peroxidase. The following conclusions were drawn: (i) only one collateral of any given Ia axon makes contact with a motoneurone even though other collaterals from the same axon might pass through the dendritic tree, (ii) usually all contacts made between a Ia fibre and a motoneurone are at about the same geometrical distance from the soma, even when on different dendrites, (iii) between two and five contacts are made upon the dendritic tree (average 3.4) at distances of between 20 and 820 micrometers from the soma. 6. The results are discussed in relation to previous anatomical and electrophysiological work.
- Published
- 1981
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24. Spinal cord collaterals from axons of type II slowly adapting units in the cat.
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Brown, A G, Fyffe, R E, Rose, P K, and Snow, P J
- Abstract
1. The morphology of single axons, and their collaterals, of Type II slowly adapting mechanoreceptors situated at the claw bases was studied. Intra‐axonal injections of horseradish peroxidase were made into the axons near their entrance to the lumbosacral spinal cord of anaesthetized cats. The morphology was revealed by subsequent histochemistry. 2. Nine Type II axons were stained. All but one bifurcated into ascending and descending branches upon entering the cord. Eighty‐nine collaterals arose from the axons at a mean spacing of about 570 micrometers. 3. The collaterals formed plate‐like arborizations usually about 500‐600 micrometers wide in the transverse plane but only 100‐300 micrometers thick in the longitudinal axis of the cord. The terminal arborizations were in laminae III‐VI. 4. Synaptic boutons in laminae III and IV were more numerous than in laminae V and VI. Boutons en passant were common in laminae III and IV and arranged in series of three to six, whereas in deeper laminae only two or three boutons formed a series de passage. 5. The morphology of the slowly adapting Type II collateral is discussed. 6. Some general principles of the organization of cutaneous afferent fibres in the lumbosacral cord are presented.
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- 1981
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25. Receptive field organization and response properties of spinal neurones with axons ascending the dorsal columns in the cat.
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Brown, A G, Brown, P B, Fyffe, R E, and Pubols, L M
- Abstract
Micro‐electrode recordings were made from single post‐synaptic axons in the dorsal columns of cats anaesthetized with chloralose and paralysed with gallamine triethiodide. The recordings were made from the L5 segment and the axons were shown to project to the upper cervical level. Forty‐eight units were recorded and the axons had conduction velocities of 22‐61 ms‐1, averaging 38.3 ms‐1. Excitatory receptive fields were complex in many units, being made up of clearly defined, separate, low and high threshold areas. The receptive fields were often discontinuous. Only a few units behaved as if they received excitatory input from a single class of mechanoreceptors. A minority (13%) of units had labile, excitatory receptive fields that expanded in size during the recording period. About 40% of the units had inhibitory receptive fields. These were of two main types: either small and within or adjacent to the excitatory field, or large and separated from or adjacent to the excitatory field. The great majority of units had resting discharges upon isolation and these consisted of single impulses or bursts of impulses at short intervals separated by longer, irregular periods. The time course of inhibition produced by electrical stimulation of cutaneous nerves suggested presynaptic inhibitory components to the inhibition. Some inhibitory curves were very prolonged with maxima at about 100 ms and total durations of up to 400 ms. The complexity of the receptive field organization in these dorsal horn neurones is discussed, as is their possible significance as input neurones to the dorsal column nuclei.
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- 1983
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26. Effects of dorsal root section on spinocervical tract neurones in the cat
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Brown, A. G., Brown, P. B., Fyffe, R. E. W., and Pubols, Lillian M.
- Abstract
1. In nine cats, dorsal roots L6and L7were sectioned under pentobarbitone anaesthesia using strict aseptic precautions. In two cats all lumbosacral roots except L6were sectioned under similar conditions. 27‐75 days after the dorsal rhizotomies, under chloralose anaesthesia, neurones of the spinocervical tract (s.c.t.) were recorded electrophysiologically both extracellularly and intracellularly, their response properties and receptive fields were analysed, and they were injected with horseradish peroxidase (HRP). Twenty‐five cells were recorded extracellularly and twenty were recorded intracellularly and stained with the enzyme.
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- 1983
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27. The density, distribution and topographical organization of spinocervical tract neurones in the cat
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Brown, A. G., Fyffe, R. E. W., Noble, R., Rose, P. K., and Snow, P. J.
- Abstract
1. In acute experiments, detailed grids of micro‐electrode recordings were made from spinocervical tract (s.c.t.) cells in the lumbosacral cord of anaesthetized cats. These grids provided electrophysiological data on the location, distribution, density and somatotopic organization of s.c.t. neurones.
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- 1980
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28. Form and function of dorsal horn neurones with axons ascending the dorsal columns in cat.
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Brown, A G and Fyffe, R E
- Abstract
1. Extracellular and intracellular recordings were made from dorsal horn neurones sending their axons through the dorsal columns in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. 2. Seventeen neurones were injected with horseradish peroxidase through the intracellular micro‐electrode, recovered from the histological material and shown to send their axons into the dorsal columns. 3. The cells had axonal conduction velocities of 30‐‐47 ms‐1; excitatory receptive fields that usually showed multireceptive characteristics, often including input from sensitive mechanoreceptors in glabrous skin; a third of the sample had a marked subliminal fringe to the excitatory field; inhibitory fields were usually situated proximal to the excitatory field and contiguous with it. 4. The cells were located in laminae III, IV and medial V. Dorsal cells had restricted dendritic trees that ascended in an essentially cylindrical volume of tissue through lamina II and often into I; cells intermediate in depth had more primary dendrites than the others, usually dorsally directed into lamina II, and a more extensive rostro‐caudal development; deep, medial cells had dendritic trees that radiated extensively from the cell body but were restricted to the transverse plane. Two cells had axons that ascended the dorsolateral funiculus for a few mm before re‐entering the dorsal horn, crossing it and reaching the dorsal columns. Collaterals were given off the axons in the grey matter, in the dorsolateral funiculus and the dorsal columns. 5. The form and function of the neurones are discussed.
- Published
- 1981
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29. Effects of hind limb nerve section on lumbosacral dorsal horn neurones in the cat.
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Brown, A G, Fyffe, R E, Noble, R, and Rowe, M J
- Abstract
The sciatic and saphenous nerves of one hind limb were sectioned in young adult cats anaesthetized with halothane. Between 19 and 55 days later, under chloralose anaesthesia, dorsal horn neurones in the L6 and L7 segments were recorded and their receptive field properties examined. In seven animals recordings were made from identified spinocervical tract, post‐synaptic dorsal column and dorsolateral funicular neurones as well as from neurones that did not project through these pathways. Thirty‐one neurones were intracellularly stained with horseradish peroxidase, and fifty‐three were recorded extracellularly and located by reference to stained cells. In two animals (both 31 days after nerve section) no attempt was made to identify axonal projections of the dorsal horn neurones in order to avoid any effects of cervical cord search stimuli on the cells' properties, but all isolated extracellularly recorded units were examined. On the side ipsilateral to the nerve sections 143 units were recorded. In all experiments, neurones in the medial three‐quarters of the dorsal horn had no discernible cutaneous, mechanosensitive receptive fields between 19 and 55 days after nerve section. There were only two exceptions to this generalization, one neurone being one of the most rostral cells in the sample (in caudal L5) and the other being one of the most caudal cells (in caudal L7). We present evidence to show that neither of these two neurones had inappropriate receptive fields in terms of the somatotopic organization of the dorsal horn. All other neurones with receptive fields on the skin were appropriately located in the somatotopic map laid out in the dorsal horn. There was no evidence for gross anatomical changes in the dendritic trees of dorsal horn neurones following sciatic and saphenous nerve sections. We have been unable to confirm that, following loss of cutaneous receptive fields by peripheral nerve section, dorsal horn neurones in adult cats acquire 'inappropriate' receptive fields. Possible reasons for this are discussed.
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- 1984
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30. The morphology of group Ib afferent fibre collaterals in the spinal cord of the cat.
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Brown, A G and Fyffe, R E
- Abstract
1. The enzyme horseradish peroxidase (HRP) was injected into single Ib muscle afferent fibres in anaesthetized cats. Subsequently, histochemistry allowed the morphology of the axons and their collaterals in the lumbosacral spinal cord to be determined. 2. Eleven Ib axons were stained, seven from lateral gastrocneminus‐soleus, one from medial gastrocnemius and three from muscles innervated by the posterior tibial nerve. Ten of the axons were traced into the dorsal roots and all but one (from the posterior tibial nerve) bifurcated upon entering the cord. Between 5.1 and 9.9 mm of each axon was stained and the fibres gave off eighty‐four collaterals at intervals of 100‐2300 micron, at an average spacing of about 900 micron. The spacing between collaterals on the (finer) descending axon branches was generally less than the intervals between collaterals on ascending branches. 3. All Ib collaterals had a characteristic morphology. The collaterals coursed cranially on a direct path through the dorsal horn to lamina IV or V before branching. They arborized widely in the intermediate region, mainly in lamina VI and in the dorsal part of lamina VII. Occasionally, less extensive arborizations were seen more dorsally in lamina IV and V. The rostro‐caudal extent of individual collateral arborizations was limited to 200‐400 micron and there was no overlap between adjacent collaterals. Each terminal arborization gave rise to 56‐384 boutons, mainly of them ‘en passant’ type. 4. The results are discussed in relation to previous anatomical and electrophysiological studies.
- Published
- 1979
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31. Is ATP a central synaptic mediator for certain primary afferent fibers from mammalian skin?
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Fyffe, R E and Perl, E R
- Abstract
The possibility that ATP acts as a synaptic mediator at the central terminals of primary afferent fibers was examined by applying it iontophoretically to neurons of the outer layers of the cat spinal cord in vivo. ATP proved to be selectively excitatory for a limited subset of spinal neurons. Those units consistently excited by ATP iontophoresis with very small currents (2-15 nA) responded to gentle mechanical stimulation of the skin and usually evidenced excitatory input from unmyelinated primary afferent fibers. Most units excited by ATP were specifically mechanoreceptive; a few neurons receiving excitatory input from both low-threshold mechanoreceptors and nociceptors also responded to ATP. Selectively nocireceptive neurons were unresponsive. Generally, the mechanoreceptive neurons excited by ATP were located in the deeper substantia gelatinosa or in the immediately adjacent nucleus proprius of the dorsal horn. The results suggest the presence of a purinergic excitatory receptor on central neurons receiving excitatory projection from tactile mechanoreceptors with fine-diameter afferent fibers and are consistent with the possibility that an ATP-like agent may mediate central synaptic excitation for this set of sense organs.
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- 1984
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32. Is ATP a central synaptic mediator for certain primary afferent fibers from mammalian skin?
- Author
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Fyffe, R. E. and Perl, E. R.
- Subjects
nervous system - Abstract
The possibility that ATP acts as a synaptic mediator at the central terminals of primary afferent fibers was examined by applying it iontophoretically to neurons of the outer layers of the cat spinal cord in vivo. ATP proved to be selectively excitatory for a limited subset of spinal neurons. Those units consistently excited by ATP iontophoresis with very small currents (2-15 nA) responded to gentle mechanical stimulation of the skin and usually evidenced excitatory input from unmyelinated primary afferent fibers. Most units excited by ATP were specifically mechanoreceptive; a few neurons receiving excitatory input from both low-threshold mechanoreceptors and nociceptors also responded to ATP. Selectively nocireceptive neurons were unresponsive. Generally, the mechanoreceptive neurons excited by ATP were located in the deeper substantia gelatinosa or in the immediately adjacent nucleus proprius of the dorsal horn. The results suggest the presence of a purinergic excitatory receptor on central neurons receiving excitatory projection from tactile mechanoreceptors with fine-diameter afferent fibers and are consistent with the possibility that an ATP-like agent may mediate central synaptic excitation for this set of sense organs.
- Published
- 1984
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33. Neurophysiology
- Author
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Brown, A. G. and Fyffe, R. E. W.
- Published
- 1980
34. Neurophysiology: Sensory Mechanisms of the Spinal Cord . W. D. Willis and R. E. Coggeshall. Plenum, New York, 1978, x, 486 pp., illus. $35.
- Author
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Brown, A. G., primary and Fyffe, R. E. W., additional
- Published
- 1980
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35. LIGHT AND ELECTRON MICROSCOPY OF DORSAL SPINOCEREBELLAR TRACT NEURONES IN THE CAT: AN INTRACELLULAR HORSERADISH PEROXIDASE STUDY
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Houchin, Jane, primary, Maxwell, D. J., additional, Brown, A. G., additional, and Fyffe, R. E. W., additional
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- 1983
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36. FINE STRUCTURE OF PRIMARY AFFERENT AXON TERMINALS PROJECTING FROM RAPIDLY ADAPTING MECHANORECEPTORS OF THE TOE AND FOOT PADS OF THE CAT
- Author
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Maxwell, D. J., primary, Bannatyne, B. A., additional, Brown, A. G., additional, and Fyffe, R. E. W., additional
- Published
- 1984
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37. FINE STRUCTURE OF PRIMARY AFFERENT AXON TERMINALS OF SLOWLY ADAPTING CUTANEOUS RECEPTORS IN THE CAT
- Author
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Bannatyne, B. A., primary, Maxwell, D. J., additional, Fyffe, R. E. W., additional, and Brown, A. G., additional
- Published
- 1984
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38. Widespread exposure to anticoagulant rodenticides among common urban mesopredators in Chicago.
- Author
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Buckley JY, Murray MH, de la Sancha NU, Fidino M, Byers KA, Fyffe R, and Magle S
- Abstract
Anticoagulant rodenticides (ARs) are currently the most common method to control rats in cities, but these compounds also cause morbidity and mortality in non-target wildlife. Little attention has been focused on AR exposure among mesopredators despite their ecological role as scavengers and prey for larger carnivores, thus serving as an important bridge in the biomagnification of rodenticides in food webs. In this study, we sampled liver tissue from raccoons (Procyon lotor; n = 37), skunks (Mephitis mephitis; n = 15), and Virginia opossums (Didelphis virginiana; n = 45) euthanized by pest professionals and brown rats (Rattus norvegicus; n = 101) trapped in alleys in Chicago, USA to evaluate how often these species are exposed to ARs. We tested whether mesopredators had a higher prevalence of ARs and to more AR compounds compared to rats and calculated biomagnification factors (mean concentration in mesopredators/rats) as indicators of biomagnification. Of 93 sampled mesopredators, 100 % were exposed to at least one AR compound, mainly brodifacoum (≥80 %), and 79 % were exposed to multiple AR compounds. We also documented teal stomach contents consistent with the consumption of rat bait and altricial young tested positive to the same AR as their mother, suggesting mammary transfer. Of the 101 rats, 74 % tested positive to at least one AR compound and 32 % were exposed to multiple AR compounds. All mesopredator species had biomagnification factors exceeding 1.00 for brodifacoum (6.57-29.07) and bromadiolone (1.08-4.31). Our results suggest widespread exposure to ARs among urban mesopredators and biomagnification of ARs in mesopredators compared to rats. Policies that limit AR availability to non-target species, such as restricting the sale and use of ARs to licensed professionals in indoor settings, education on alternatives, and more emphasis on waste management may reduce health risks for urban wildlife and people in cities around the world., (Copyright © 2024. Published by Elsevier B.V.)
- Published
- 2024
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39. Population genomic structure of a widespread, urban-dwelling mammal: The eastern grey squirrel (Sciurus carolinensis).
- Author
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Fusco NA, Cosentino BJ, Gibbs JP, Allen ML, Blumenfeld AJ, Boettner GH, Carlen EJ, Collins M, Dennison C, DiGiacopo D, Drapeau Picard AP, Edmonson J, Fisher-Reid MC, Fyffe R, Gallo T, Grant A, Harbold W, Heard SB, Lafferty DJR, Lehtinen RM, Marino S, McDonald JE, Mortelliti A, Murray M, Newman A, Oswald KN, Ott-Conn C, Richardson JL, Rimbach R, Salaman P, Steele M, Stothart MR, Urban MC, Vandegrift K, Vanek JP, Vanderluit SN, Vezina L, and Caccone A
- Subjects
- Animals, Humans, Urban Population, Ecosystem, Sciuridae genetics, Metagenomics, Animals, Wild
- Abstract
Urbanization is a persistent and widespread driver of global environmental change, potentially shaping evolutionary processes due to genetic drift and reduced gene flow in cities induced by habitat fragmentation and small population sizes. We tested this prediction for the eastern grey squirrel (Sciurus carolinensis), a common and conspicuous forest-dwelling rodent, by obtaining 44K SNPs using reduced representation sequencing (ddRAD) for 403 individuals sampled across the species' native range in eastern North America. We observed moderate levels of genetic diversity, low levels of inbreeding, and only a modest signal of isolation-by-distance. Clustering and migration analyses show that estimated levels of migration and genetic connectivity were higher than expected across cities and forested areas, specifically within the eastern portion of the species' range dominated by urbanization, and genetic connectivity was less than expected within the western range where the landscape is fragmented by agriculture. Landscape genetic methods revealed greater gene flow among individual squirrels in forested regions, which likely provide abundant food and shelter for squirrels. Although gene flow appears to be higher in areas with more tree cover, only slight discontinuities in gene flow suggest eastern grey squirrels have maintained connected populations across urban areas in all but the most heavily fragmented agricultural landscapes. Our results suggest urbanization shapes biological evolution in wildlife species depending strongly on the composition and habitability of the landscape matrix surrounding urban areas., (© 2023 John Wiley & Sons Ltd.)
- Published
- 2024
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40. City sanitation and socioeconomics predict rat zoonotic infection across diverse neighbourhoods.
- Author
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Murray MH, Fidino M, Fyffe R, Byers KA, Pettengill JB, Sondgeroth KS, Killion H, Magle SB, Rios MJ, Ortinau N, and Santymire RM
- Subjects
- Animals, Bacterial Infections epidemiology, Bacterial Infections microbiology, Chicago epidemiology, Female, Humans, Male, Odds Ratio, Rats, Risk Factors, Sanitation, Socioeconomic Factors, Bacterial Infections veterinary, Rodent Diseases microbiology, Zoonoses
- Abstract
Rat-associated zoonoses transmitted through faeces or urine are of particular concern for public health because environmental exposure in homes and businesses may be frequent and undetected. To identify times and locations with greater public health risks from rats, we investigated whether rat characteristics, environmental features, socioeconomic factors, or season could predict rat infection risk across diverse urban neighbourhoods. In partnership with a pest management company, we sampled rats in 13 community areas along an income gradient in Chicago, a large city where concern about rats has increased in recent years. We collected kidneys for Leptospira spp. testing and colon contents for aerobic bacteria such as Salmonella spp. and Escherichia coli. Of 202 sampled rats, 5% carried Leptospira spp. and 22% carried E. coli. Rats were significantly more likely to carry Leptospira spp. on blocks with more standing water complaints in higher-income neighbourhoods (OR = 6.74, 95% CI: 1.54-29.39). Rats were significantly more likely to carry E. coli on blocks with more food vendors (OR = 9.94, 2.27-43.50) particularly in low-income neighbourhoods (OR = 0.26, 0.09-0.82) and in the spring (OR = 15.96, 2.90-88.62). We detected a high diversity of E. coli serovars but none contained major virulence factors. These associations between environmental features related to sanitation and infection risk in rats support transmission through water for Leptospira spp. and faecal-oral transmission for E. coli. We also found opposing relationships between zoonotic infection risk and income for these two pathogens. Thus, our results highlight the importance of sanitation for predicting zoonotic disease risks and including diverse urban areas in pathogen surveillance to mitigate public health risks from rats., (© 2020 Blackwell Verlag GmbH.)
- Published
- 2020
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41. Lateral superior olive function in congenital deafness.
- Author
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Couchman K, Garrett A, Deardorff AS, Rattay F, Resatz S, Fyffe R, Walmsley B, and Leão RN
- Subjects
- Animals, Auditory Pathways metabolism, Carrier Proteins metabolism, Cochlear Nerve physiopathology, Deafness congenital, Deafness metabolism, Deafness psychology, Disease Models, Animal, Electric Stimulation, Evoked Potentials, Auditory, Brain Stem, Excitatory Postsynaptic Potentials, Glutamine metabolism, Glycine metabolism, Immunohistochemistry, Membrane Proteins genetics, Membrane Proteins metabolism, Mice, Mice, Mutant Strains, Models, Neurological, Mutation, Neural Inhibition, Olivary Nucleus metabolism, Patch-Clamp Techniques, Time Factors, Auditory Pathways physiopathology, Auditory Perception, Deafness physiopathology, Olivary Nucleus physiopathology
- Abstract
The development of cochlear implants for the treatment of patients with profound hearing loss has advanced considerably in the last few decades, particularly in the field of speech comprehension. However, attempts to provide not only sound decoding but also spatial hearing are limited by our understanding of circuit adaptations in the absence of auditory input. Here we investigate the lateral superior olive (LSO), a nucleus involved in interaural level difference (ILD) processing in the auditory brainstem using a mouse model of congenital deafness (the dn/dn mouse). An electrophysiological investigation of principal neurons of the LSO from the dn/dn mouse reveals a higher than normal proportion of single spiking (SS) neurons, and an increase in the hyperpolarisation-activated I(h) current. However, inhibitory glycinergic input to the LSO appears to develop normally both pre and postsynaptically in dn/dn mice despite the absence of auditory nerve activity. In combination with previous electrophysiological findings from the dn/dn mouse, we also compile a simple Hodgkin and Huxley circuit model in order to investigate possible computational deficits in ILD processing resulting from congenital hearing loss. We find that the predominance of SS neurons in the dn/dn LSO may compensate for upstream modifications and help to maintain a functioning ILD circuit in the dn/dn mouse. This could have clinical repercussions on the development of stimulation paradigms for spatial hearing with cochlear implants., (Copyright © 2011 Elsevier B.V. All rights reserved.)
- Published
- 2011
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42. Sound stimulation modulates high-threshold K(+) currents in mouse auditory brainstem neurons.
- Author
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Leão KE, Leão RN, Deardorff AS, Garrett A, Fyffe R, and Walmsley B
- Subjects
- Animals, Cell Membrane metabolism, Female, Male, Mice, Neurons, Afferent cytology, Patch-Clamp Techniques, Potassium metabolism, Potassium Channel Blockers metabolism, Proto-Oncogene Proteins c-fos metabolism, Tetraethylammonium metabolism, Acoustic Stimulation methods, Action Potentials physiology, Auditory Pathways physiology, Brain Stem cytology, Neurons, Afferent metabolism, Shaw Potassium Channels metabolism
- Abstract
The auditory system provides a valuable experimental model to investigate the role of sensory activity in regulating neuronal membrane properties. In this study, we have investigated the role of activity directly by measuring changes in medial nucleus of the trapezoid body (MNTB) neurons in normal hearing mice subjected to 1-h sound stimulation. Broadband (4-12 kHz) chirps were used to activate MNTB neurons tonotopically restricted to the lateral MNTB, as confirmed by c-Fos-immunoreactivity. Following 1-h sound stimulation a substantial increase in Kv3.1b-immunoreactivity was measured in the lateral region of the MNTB, which lasted for 2 h before returning to control levels. Electrophysiological patch-clamp recordings in brainstem slices revealed an increase in high-threshold potassium currents in the lateral MNTB of sound-stimulated mice. Current-clamp and dynamic-clamp experiments showed that MNTB cells from the sound-stimulated mice were able to maintain briefer action potentials during high-frequency firing than cells from control mice. These results provide evidence that acoustically driven auditory activity can selectively regulate high-threshold potassium currents in the MNTB of normal hearing mice, likely due to an increased membrane expression of Kv3.1b channels., (© 2010 The Authors. European Journal of Neuroscience © 2010 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.)
- Published
- 2010
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43. MicroRNAs and regeneration: Let-7 members as potential regulators of dedifferentiation in lens and inner ear hair cell regeneration of the adult newt.
- Author
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Tsonis PA, Call MK, Grogg MW, Sartor MA, Taylor RR, Forge A, Fyffe R, Goldenberg R, Cowper-Sal-lari R, and Tomlinson CR
- Subjects
- Animals, Cell Differentiation physiology, Gene Expression Regulation physiology, Lens, Crystalline growth & development, MicroRNAs genetics, Morphogenesis physiology, Salamandridae anatomy & histology, Salamandridae growth & development, Hair Cells, Auditory, Inner cytology, Hair Cells, Auditory, Inner metabolism, Lens, Crystalline cytology, Lens, Crystalline metabolism, Proteome metabolism, Regeneration physiology, Salamandridae metabolism
- Abstract
MicroRNAs are known to regulate the expression of many mRNAs by binding to complementary target sequences at the 3'UTRs. Because of such properties, miRNAs may regulate tissue-specific mRNAs as a cell undergoes transdifferentiation during regeneration. We have tested this hypothesis during lens and hair cell regeneration in newts using microarray analysis. We found that distinct sets of miRNAs are associated with lens and hair cell regeneration. Members of the let-7 family are expressed in both events and they are regulated in a similar fashion. All the let-7 members are down regulated during the initiation of regeneration, which is characterized by dedifferentiation of terminally differentiated cells. This is the first report to correlate expression of miRNAs as novel regulators of vertebrate regeneration, alluding to a novel mechanism whereby transdifferentiation occurs.
- Published
- 2007
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44. K-Cl co-transport: immunocytochemical and functional evidence for more than one KCC isoform in high K and low K sheep erythrocytes.
- Author
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Lauf PK, Zhang J, Delpire E, Fyffe RE, Mount DB, and Adragna NC
- Subjects
- Animals, Microscopy, Fluorescence, Sheep, K Cl- Cotransporters, Erythrocytes metabolism, Potassium blood, Protein Isoforms blood, Symporters blood
- Abstract
K-Cl co-transport (COT) is significantly higher in low K (LK), L-antigen (L) positive, than in high K (HK), M-antigen (M) positive, sheep red blood cells (SRBCs) and is inhibited by sheep allo-anti-L1 antibody. To answer the question of whether this difference in K-Cl co-transport activity resides at the level of the transporter or its regulation, a combined immunocytochemical and functional approach was taken. At least four isoforms of K-Cl COT encoded by different KCC genes are known, with 12 transmembrane domains and cytoplasmic C- and N-terminal domains (Ctd and Ntd, respectively). Polyclonal anti-rat (rt)KCC1 antibodies against a fusion peptide with 77 amino acids from the Ctd of rtKCC1 and anti-human (h)KCC3 against an 18-aa peptide from the Ntd of hKCC3, were prepared in rabbits (rb). Two distinctly separate protein bands of 180 and 145 kDa molecular mass were detected in hemoglobin-free ghosts from RBCs of two LK (one homozygous LL and one heterozygous LM) and one HK (homozygous MM) sheep by Western blots with rb anti-rtKCC1 and rb anti-hKCC3. Confocal microscopy showed specific immunostaining of KCC1 with rb anti-rtKCC1, and of KCC3 with rb anti-hKCC3, in white ghosts from both LK and HK SRBCs. To test the functional heterogeneity of K-Cl COT, the effect of the anti-L1 antibody was assessed on K-Cl COT activated by the kinase inhibitor staurosporine. Incubation of LK SRBCs with anti-L1 serum inhibited by 30% staurosporine-stimulated K-Cl COT suggesting that approximately two-thirds of the transport activity is independent of the L1 antigen. That staurosporine altered the L1 antigen/antibody reaction is unlikely since the action of another antibody, anti-Lp, stimulating the Na/K pump flux, was not modified. The present results, in conjunction with earlier work, lead to the hypothesis that the partial anti-L1 inhibition of K-Cl COT may be related to the molecular KCC dimorphism, seen in these cells with anti-KCC1 and anti-KCC3 antibodies.
- Published
- 2001
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45. The Cav2.1/alpha1A (P/Q-type) voltage-dependent calcium channel mediates inhibitory neurotransmission onto mouse cerebellar Purkinje cells.
- Author
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Stephens GJ, Morris NP, Fyffe RE, and Robertson B
- Subjects
- Action Potentials physiology, Animals, Calcium Channels physiology, Calcium Channels, N-Type physiology, Electrophysiology, In Vitro Techniques, Male, Mice, Presynaptic Terminals physiology, Synapses physiology, Tissue Distribution, Calcium Channels, P-Type physiology, Calcium Channels, Q-Type physiology, Neural Inhibition physiology, Purkinje Cells physiology, Synaptic Transmission physiology
- Abstract
The effects of voltage-dependent calcium channel (VDCC) antagonists on spontaneous inhibitory postsynaptic currents (sIPSCs) in mouse Purkinje cells were examined using in vitro cerebellar slices. The inorganic ion Cd2+ reduced sIPSC amplitude and frequency. No additional block was seen with the Na+ channel antagonist tetrodotoxin (TTX) suggesting that all action potential-evoked inhibitory GABA release was mediated by high-voltage-activated VDCCs. No evidence was found for involvement of Cav1/alpha1C and alpha1D (L-type), Cav2.2/alpha1B (N-type) or Cav2.3/alpha1E (R-type) high-voltage-activated VDCCs or low-voltage-activated Cav3/alpha1G, alpha1H and alpha1I (T-type) VDCCs in mediating presynaptic GABA release. Blockade of sIPSCs by 200 nM omega-agatoxin IVA implicated the Cav2.1/alpha1A (P/Q-type) subtype of high-voltage-activated VDCCs in mediating inhibitory transmission. Inhibition by omega-agatoxin IVA was similar to that seen with Cd2+ and TTX. Selective antibodies directed against the Cav2.1 subunit revealed staining in regions closely opposed to Purkinje cell somata. Cav2.1 staining was colocalized with staining for antibodies against glutamic acid decarboxylase and corresponded well with the pericellular network formed by GABAergic basket cell interneurons. Antibody labelling of Cav2.3 revealed a region-specific expression. In the cerebellar cortex anterior lobe, Cav2.3 staining was predominantly somatodendritic; whilst in the posterior lobe, perisomatic staining was seen primarily. However, electrophysiological data was not consistent with a role for the Cav2.3 subunit in mediating presynaptic GABA release. No consistent staining was seen for other Cav (alpha1) subunits. Electrophysiological and immunostaining data support a predominant role for Cav2.1 subunits in mediating action potential-evoked inhibitory GABA release onto mouse Purkinje cells.
- Published
- 2001
- Full Text
- View/download PDF
46. K-Cl cotransport: immunohistochemical and ion flux studies in human embryonic kidney (HEK293) cells transfected with full-length and C-terminal-domain-truncated KCC1 cDNAs.
- Author
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Lauf PK, Zhang J, Gagnon KB, Delpire E, Fyffe RE, and Adragna NC
- Subjects
- Carrier Proteins antagonists & inhibitors, Carrier Proteins genetics, DNA, Complementary, Ethylmaleimide pharmacology, Furosemide pharmacology, Genistein pharmacology, Humans, Hydrogen-Ion Concentration, Immunohistochemistry, Ion Transport, Kidney cytology, Kidney drug effects, Kidney embryology, Microscopy, Confocal, Microscopy, Fluorescence, Osmolar Concentration, Oxazoles pharmacology, Rubidium metabolism, Transfection, K Cl- Cotransporters, Carrier Proteins metabolism, Chlorides metabolism, Kidney metabolism, Potassium metabolism, Symporters
- Abstract
Coupled K and Cl movements are mediated by several isoforms of the K-Cl cotransporter (COT) encoded by the KCC genes. The ubiquitous KCC1 isoform, important for cell volume and ion homeostasis, has 12 transmembrane domains (Tmds), and cytoplasmic N- and C-terminal domains (Ntd and Ctd). This study investigates the cellular localization of KCC1 by confocal microscopy, activation of K-Cl COT by various non-osmotic and osmotic interventions with net unidirectional K and Rb fluxes at 37( degrees )C, and the effect of Ctd deletion on K-Cl COT regulation. Human embryonic kidney (HEK293) cells were transfected with full-length (fl) rabbit (rb)KCC1 and - CtdKCC1 cDNAs obtained after truncation at nucleotide 2011. Normal cells exposed to polyclonal anti-Ctd antibodies against Ctd epitopes within a 77 amino acid sequence (a.a.943-1020) revealed granular membrane and cytoplasmic immunostaining, presumably endogenous KCC1. Additional diffuse membrane and cytoplasmic immunofluorescence in flKCC1-transfected cells was absent in -CtdKCC1-transfected cells. Monoclonal antibodies against a c-myc epitope at the protein Ntd showed both membrane and cytosolic fluorescence. Basal and N-ethylmaleimide (NEM)-stimulated Rb influxes through K-Cl COT, calculated as Cl-dependent Rb fluxes, were 2-3-fold higher in flKCC1-transfected than in normal cells. NEM stimulation of K-Cl COT was highest in flKCC1-transfected cells, significantly lower in stably and abrogated in transiently -CtdKCC1-transfected cells. Furosemide, calyculin and genistein inhibited basal and NEM-stimulated K-Cl COT in normal and transfected cells. Staurosporine and hydroxylamine were ineffective stimulators. No effect of pH(0) changes (6.3-8.4) was observed in basal or NEM-stimulated K-Cl COT, in both normal and transfected cells. However, inhibition by NEM occurred at pH(0) 8.4. Furthermore, in a Cl-independent manner, NEM lowered cell K content by >30% and hypotonicity (210-70mOsM) stimulated furosemide-sensitive Rb influx and K loss. Thus, in cultured normal and KCC1-transfected cells, K-Cl COT shows significant differences from erythrocytes, and NEM and cell swelling open furosemide-sensitive and Cl-independent K/Rb channels. Failure of K-Cl COT in cells transfected with Ctd-truncated KCC1 to respond to NEM suggests a role of the Ctd for signal transduction., (Copyright 2001 S. Karger AG, Basel)
- Published
- 2001
- Full Text
- View/download PDF
47. Factors regulating AMPA-type glutamate receptor subunit changes induced by sciatic nerve injury in rats.
- Author
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Alvarez FJ, Fyffe RE, Dewey DE, Haftel VK, and Cope TC
- Subjects
- Animals, Axotomy, Calcitonin Gene-Related Peptide metabolism, Cell Size, Male, Motor Neurons drug effects, Motor Neurons metabolism, Motor Neurons physiology, Nerve Block, Neuronal Plasticity physiology, Protein Isoforms metabolism, Receptors, Metabotropic Glutamate metabolism, Reference Values, Sciatic Nerve pathology, Synapses physiology, Synaptophysin metabolism, Tetrodotoxin pharmacology, Wounds and Injuries pathology, Rats physiology, Receptors, AMPA metabolism, Sciatic Nerve injuries, Sciatic Nerve metabolism, Wounds and Injuries metabolism
- Abstract
Excitatory glutamatergic neurotransmission at Ia afferent-motoneuron synapses is enhanced shortly after physically severing or blocking impulse propagation of the afferent and/or motoneuron axons. We considered the possibility that these synaptic changes occur because of alterations in the number or properties of motoneuron alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. Therefore, we quantitatively analyzed glutamate receptor (GluR)1, GluR2/3, and GluR4 AMPA subunit immunoreactivity (ir) in motoneurons 3, 7, or 14 days after axotomy or continuous tetrodotoxin (TTX) block of the sciatic nerve. GluR1-ir remained low in experimental and control motoneurons with either treatment and at any date. However, there was a large reduction of GluR2/3-ir (peak at 7 days >60% reduced) and a smaller, but statistically significant, reduction of GluR4-ir (around 10% reduction at days 3, 7, and 14) in axotomized motoneurons. TTX sciatic blockade did not affect AMPA subunit immunostainings. Axonal injury or interruption of the trophic interaction between muscle and spinal cord, but not activity disruption, appears therefore more likely responsible for altering AMPA subunit immunoreactivity in motoneurons. These findings also suggest that synaptic plasticity induced by axotomy or TTX block, although similar in the first week, could be related to different mechanisms. The effects of axotomy or TTX block on motoneuron expression of the metabotropic glutamate receptor mGluR1a were also studied. mGluR1a-ir was also strongly decreased after axotomy but not after TTX treatment. The time course of the known stripping of synapses from the cell somas of axotomized motoneurons was studied by using synaptophysin antibodies and compared with AMPA and mGluR1a receptor changes. Coverage by synaptophysin-ir boutons was only clearly decreased 14 days post axotomy and not at shorter intervals or after TTX block., (Copyright 2000 Wiley-Liss, Inc.)
- Published
- 2000
- Full Text
- View/download PDF
48. A functional role for the two-pore domain potassium channel TASK-1 in cerebellar granule neurons.
- Author
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Millar JA, Barratt L, Southan AP, Page KM, Fyffe RE, Robertson B, and Mathie A
- Subjects
- Animals, Base Sequence, Cells, Cultured, Cerebellum cytology, Cerebellum metabolism, Cytoplasmic Granules metabolism, DNA Primers, Membrane Potentials physiology, Nerve Tissue Proteins, Neurons metabolism, Potassium Channels genetics, RNA, Messenger genetics, Rats, Rats, Sprague-Dawley, Reverse Transcriptase Polymerase Chain Reaction, Cerebellum physiology, Cytoplasmic Granules physiology, Neurons physiology, Potassium Channels physiology, Potassium Channels, Tandem Pore Domain
- Abstract
Cerebellar granule neurons (CGNs) are one of the most populous cells in the mammalian brain. They express an outwardly rectifying potassium current, termed a "standing-outward" K(+) current, or IK(SO), which does not inactivate. It is active at the resting potential of CGNs, and blocking IK(SO) leads to cell depolarization. IK(SO) is blocked by Ba(2+) ions and is regulated by activation of muscarinic M(3) receptors, but it is insensitive to the classical broad-spectrum potassium channel blocking drugs 4-aminopyridine and tetraethylammonium ions. The molecular nature of this important current has yet to be established, but in this study, we provide strong evidence to suggest that IK(SO) is the functional correlate of the recently identified two-pore domain potassium channel TASK-1. We show that IK(SO) has no threshold for activation by voltage and that it is blocked by small extracellular acidifications. Both of these are properties that are diagnostic of TASK-1 channels. In addition, we show that TASK-1 currents expressed in Xenopus oocytes are inhibited after activation of endogenous M(3) muscarinic receptors. Finally, we demonstrate that mRNA for TASK-1 is found in CGNs and that TASK-1 protein is expressed in CGN membranes. This description of a functional two-pore domain potassium channel in the mammalian central nervous system indicates its physiological importance in controlling cell excitability and how agents that modify its activity, such as agonists at G protein-coupled receptors and hydrogen ions, can profoundly alter both the neuron's resting potential and its excitability.
- Published
- 2000
- Full Text
- View/download PDF
49. Nociceptors for the 21st century.
- Author
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Alvarez FJ and Fyffe RE
- Subjects
- Animals, Humans, Mechanoreceptors metabolism, Nerve Fibers metabolism, Nerve Fibers, Myelinated metabolism, Nerve Growth Factors metabolism, Receptors, Drug metabolism, Receptors, Purinergic metabolism, Signal Transduction physiology, Thermosensing physiology, Neurons, Afferent metabolism, Neuropeptides metabolism, Nociceptors metabolism, Pain physiopathology
- Abstract
This review summarizes recent developments in the context of the neurochemical classification of nociceptors and explores the relationships between functionally and neurochemically defined subgroups. Although the complete picture is not yet available, several lines of intriguing evidence suggest that despite the complexity and diversity of nociceptor properties, a relatively "simple" neurochemical classification fits well with several recently identified molecular characteristics.
- Published
- 2000
- Full Text
- View/download PDF
50. Distribution of 5-hydroxytryptamine-immunoreactive boutons on immunohistochemically-identified Renshaw cells in cat and rat lumbar spinal cord.
- Author
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Carr PA, Pearson JC, and Fyffe RE
- Subjects
- Animals, Calbindin 1, Calbindins, Carrier Proteins metabolism, Cats, Immunohistochemistry, Lumbosacral Region, Male, Membrane Proteins metabolism, Rats, Rats, Sprague-Dawley, S100 Calcium Binding Protein G metabolism, Spinal Cord cytology, Tissue Distribution, Neurons metabolism, Presynaptic Terminals metabolism, Serotonin metabolism, Spinal Cord metabolism
- Abstract
A combination of anti-gephyrin- and anti-calbindin D28k-immunoreactivity was used to identify 129 and 171 Renshaw cells and their dendrites in cat and rat lumbar spinal cord, respectively. Using anti-5-hydroxytryptamine-immunoreactivity to label serotoninergic fibers and boutons, 1048 serotoninergic boutons were observed in close contact with the immunolabeled Renshaw cells, with an average of 4.4 and 2.8 close contacts on cat and rat Renshaw cells, respectively. Two-thirds of the observed appositions were formed on the somatic membrane., (Copyright 1999 Elsevier Science B.V.)
- Published
- 1999
- Full Text
- View/download PDF
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