Although the Centers for Disease Control and Prevention (CDC) reports that brain abnormalities in... more Although the Centers for Disease Control and Prevention (CDC) reports that brain abnormalities in infants with laboratory-confirmed Zika infection include microcephaly, disrupted brain growth, intracranial calcifications, and abnormal eye findings—it is not known presently if the Zika virus itself causes any of these. In a recent 2016 review of Zika dealing with possible brain abnormalities appearing with Zika, Melo et al. mention that among the Flaviviruses, which Zika is, such brain insults and pathologic findings are practically unheard of. Melo et al. conclude that until more cases are diagnosed and more histopathological proofs are obtained, the possibility of other causes besides Zika cannot be ruled out. This paper considers just such other possible causes that have, to this point, escaped general notice. The Aedes aegypti and other Aedes species can transmit tiny viral-like, cell-wall-deficient mycobacterial forms, independent of viruses, yet prevalent in the very same Rhesus Monkey used in the original 1952 Zika communication—which spoke of " A filterable transmissible agent ". In addition, the universal fetal prenatal vaccination of Brazilian neonates is considered, strongly discouraged by The Royal Children's Hospital in Melbourne, which forbids BCG vaccination of pregnant women and those immunosuppressed or already having tuberculosis (TB) or AIDS. And finally thought is focused on the prime candidate itself, towards explaining what an alternative cause for " Zika " might look like—an infectious agent with transmissible , filterable, viral-like forms. One which can be transmitted by the very same Aedes mosquitoes that carry Zika—one that is neurotrophic, and extremely prevalent in Brazil —and that can disrupt brain growth, cause microcephalus, cause a fever, is sexually transmissible, instigates Guillain-Barré syndrome and causes cranial calcifications —the Mycobacterium tuberculosis complex , which includes the Mycobacterium africanum prevalent, yet completely ignored, in the Rhesus monkeys used in the original Zika study.
Hypoglossal motor neurons (XII MNs) innervate tongue muscles important in breathing, suckling and... more Hypoglossal motor neurons (XII MNs) innervate tongue muscles important in breathing, suckling and vocalization. Morphological properties of 103 XII MNs were studied using NeurobiotinTM filling in transverse brainstem slices from C57/Bl6 mice (n=34) from embryonic day (E) 17 to postnatal day (P) 28. XII MNs from areas thought to innervate different tongue muscles showed similar morphology in most, but not all, features. Morphological properties of XII MNs were established prior to birth, not differing between E17–18 and P0. MN somatic volume gradually increased for the first 2 weeks post-birth. The complexity of dendritic branching and dendrite length of XII MNs increased throughout develop- ment (E17–P28). MNs in the ventromedial XII motor nucleus, likely to innervate the genioglossus, frequently (42 %) had dendrites crossing to the contralateral side at all ages, but their number declined with postnatal develop- ment. Unexpectedly, putative dendritic spines were found in all XII MNs at all ages, and were primarily localized to XII MN somata and primary dendrites at E18–P4, increased in distal dendrites by P5–P8, and were later predominantly found in distal dendrites. Dye-coupling between XII MNs was common from E18 to P7, but declined strongly with maturation after P7. Axon collaterals were found in 20 % (6 of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor nucleus. These results reveal new morphological features of mouse XII MNs, and suggest that dendritic projection pat- terns, spine density and distribution, and dye-coupling patterns show specific developmental changes in mice.
Motoneurons develop extensive dendritic trees for receiving excitatory and inhibitory synaptic in... more Motoneurons develop extensive dendritic trees for receiving excitatory and inhibitory synaptic inputs to perform a variety of complex motor tasks. At birth, the somatodendritic domains of mouse hypoglossal and lumbar motoneurons have dense filopodia and spines. Consistent with Vaughn’s synaptotropic hypothesis, we propose a developmental unified-hybrid model implicating filopodia in motoneuron spinogenesis/synaptogenesis and dendritic growth and branching critical for circuit formation and synaptic plasticity at embryonic/prenatal/neonatal period. Filopodia density decreases and spine density initially increases until postnatal day 15 (P15) and then decreases by P30. Spine distribution shifts towards the distal dendrites, and spines become shorter (stubby), coinciding with decreases in frequency and increases in amplitude of excitatory postsynaptic currents with maturation. In transgenic mice, either overexpressing the mutated human Cu/Zn-superoxide dismutase (hSOD1G93A) gene or deficient in GABAergic/glycinergic synaptic transmission (gephyrin, GAD-67, or VGAT gene knockout), hypoglossal motoneurons develop excitatory glutamatergic synaptic hyperactivity. Functional synaptic hyperactivity is associated with increased dendritic growth, branching, and increased spine and filopodia density, involving actin-based cytoskeletal and structural remodelling. Energy-dependent ionic pumps that maintain intracellular sodium/calcium homeostasis are chronically challenged by activity and selectively overwhelmed by hyperactivity which eventually causes sustained membrane depolarization leading to excitotoxicity, activating microglia to phagocytose degenerating neurons under neuropathological conditions.
ABSTRACT Neural development is characterized by the formation of complex neural networks such as ... more ABSTRACT Neural development is characterized by the formation of complex neural networks such as the neuromotor system. During embryonic development approximately half the number of motoneurons generated undergo cell death. This is at a time when motoneurons are making contact with skeletal muscle, and when contacts onto motoneurons by other neurons are being established. This suggests that both central and peripheral synaptic contacts act to regulate the number of motoneurons during this embryonic period. Recent studies have suggested that glycinergic and GABAergic synaptic activity may be essential for the maturation and refinement of developing neural networks. These transmitters switch from producing excitation to inhibition during late embryonic and early postnatal stages. We and others have shown that functional neuromuscular synaptic outputs regulate motoneuron death. This leaves open the question as to whether central synaptic inputs to the motoneuron might also influence survival or death of the motoneuron during this period of neuron cell death. Morphological and functional evidence indicates that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during the period of developmental motoneuron death. This evidence is from the physiological and morphological analyses of mice that lack GABA (GAD67 - deficient mice) and from mice lacking post-synaptic Glycine receptors (Gephyrin - deficient mice).
GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinem... more GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinement of the developing CNS. Here we provide morphological and functional evidence that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during programmed cell death. In gephyrin-deficient mice that lack all postsynaptic glycine receptor and some GABA(A) receptor clusters, there was increased spontaneous respiratory motor activity, reduced respiratory motoneuron survival, and decreased innervation of the diaphragm. In contrast, limb-innervating motoneurons showed decreased spontaneous activity, increased survival, and increased innervation of their target muscles. Both GABA and glycine increased limb-innervating motoneuron activity and decreased respiratory motoneuron activity in wild-type mice, but only glycine responses were abolished in gephyrin-deficient mice. Our results provide genetic evidence that the development of glycinergic and GABAergic synaptic inputs onto motoneurons plays an important role in the survival, axonal branching, and spontaneous activity of motoneurons in developing mammalian embryos.
Pflügers Archiv - European Journal of Physiology, 2008
Intracellular sharp-electrode, whole-cell patch clamp and juxtacellular labeling methods have pre... more Intracellular sharp-electrode, whole-cell patch clamp and juxtacellular labeling methods have previously been developed for combined analysis of neuronal structure and function. We describe a novel electroporation technique for labeling neurons with Neurobiotin, using patch electrodes in a semi-loose seal configuration (R = 100-300 MOmega) with very small amplitude pulses (50 mV). The addition of 2% Neurobiotin to the intracellular solution in the patch electrode reduces the dielectric membrane breakdown voltage threshold by about threefold. The resulting pore formation allows for (1) the stable recording of spontaneous and light-evoked postsynaptic potentials without significant cytoplasmic washout and (2) the passage of dye without spillover. The efficiency and reliability of the method makes it particularly suitable for the serial recording and labeling of multiple neurons in a small area of tissue.
The distribution of the P2X2 receptor subunit of the adenosine 5'-triphosphate (ATP)-gate... more The distribution of the P2X2 receptor subunit of the adenosine 5'-triphosphate (ATP)-gated ion channels was examined in the adult rat central nervous system (CNS) by using P2X2 receptor-specific antisera and riboprobe-based in situ hybridisation. P2X2 receptor mRNA expression matched the P2X2 receptor protein localisation. An extensive expression pattern was observed, including: olfactory bulb, cerebral cortex, hippocampus, habenula, thalamic and subthalamic nuclei, caudate putamen, posteromedial amygdalo-hippocampal and amygdalo-cortical nuclei, substantia nigra pars compacta, ventromedial and arcuate hypothalamic nuclei, supraoptic nucleus, tuberomammillary nucleus, mesencephalic trigeminal nucleus, dorsal raphe, locus coeruleus, medial parabrachial nucleus, tegmental areas, pontine nuclei, red nucleus, lateral superior olive, cochlear nuclei, spinal trigeminal nuclei, cranial motor nuclei, ventrolateral medulla, area postrema, nucleus of solitary tract, and cerebellar cortex. In the spinal cord, P2X2 receptor expression was highest in the dorsal horn, with significant neuronal labeling in the ventral horn and intermediolateral cell column. The identification of extensive P2X2 receptor immunoreactivity and mRNA distribution within the CNS demonstrated here provides a basis for the P2X receptor antagonist pharmacology reported in electrophysiological studies. These data support the role for extracellular ATP acting as a fast neurotransmitter at pre- and postsynaptic sites in processes such as sensory transmission, sensory-motor integration, motor and autonomic control, and in neuronal phenomena such as long-term potentiation (LTP) and depression (LTD). Additionally, labelling of neuroglia and fibre tracts supports a diverse role for extracellular ATP in CNS homeostasis.
In the cochlea, extracellular ATP influences the endocochlear potential, micromechanics, and neur... more In the cochlea, extracellular ATP influences the endocochlear potential, micromechanics, and neurotransmission via P2 receptors. Evidence for this arises from studies demonstrating widespread expression of ATP-gated ion channels (assembled from P2X receptor subunits) and G protein-coupled receptors (P2Y receptors). P2X2 receptor subunits are localized to the luminal membranes of epithelial cells and hair cells lining scala media. These ion channels provide a shunt pathway for K+ ion egress. Thus, when noise exposure elevates ATP levels in this cochlear compartment, the K+ conductance through P2X receptors reduces the endocochlear potential. ATP-mediated K+ efflux from scala media is complemented by a P2Y receptor G protein-coupled pathway that provides coincident reduction of K+ transport into scala media from the stria vascularis when autocrine or paracrine ATP signalling is invoked. This purinergic signalling likely provides a basis for a reactive homoeostatic regulatory mechanism limiting cochlear sensitivity under stressor conditions. Elevation of ATP in the perilymphatic compartment under such conditions is also likely to invoke purinergic receptor-mediated changes in supporting cell micromechanics, mediated by Ca2+ influx and gating of Ca2+ stores. Independent of these humoral actions, ATP can be classified as a putative auditory neurotransmitter based on the localization of P2X receptors at the spiral ganglion neuron-hair cell synapse, and functional verification of ATP-gated currents in spiral ganglion neurons in situ. Expression of P2X receptors by type II spiral ganglion neurons supports a role for ATP as a transmitter encoding the dynamic state of the cochlear amplifier.
Abstract Hypoglossal motor neurons (XII MNs) inner- vate tongue muscles important in breathing, s... more Abstract Hypoglossal motor neurons (XII MNs) inner- vate tongue muscles important in breathing, suckling and vocalization. Morphological properties of 103 XII MNs were studied using NeurobiotinTM filling in transverse brainstem slices from C57/Bl6 mice (n = 34) from embryonic day (E) 17 to postnatal day (P) 28. XII MNs from areas thought to innervate different tongue muscles showed similar morphology in most, but not all, features. Morphological properties of XII MNs were established prior to birth, not differing between E17–18 and P0. MN somatic volume gradually increased for the first 2 weeks post-birth. The complexity of dendritic branching and dendrite length of XII MNs increased throughout develop- ment (E17–P28). MNs in the ventromedial XII motor nucleus, likely to innervate the genioglossus, frequently (42 %) had dendrites crossing to the contralateral side at all ages, but their number declined with postnatal develop- ment. Unexpectedly, putative dendritic spines were found in all XII MNs at all ages, and were primarily localized to XII MN somata and primary dendrites at E18–P4, increased in distal dendrites by P5–P8, and were later predominantly found in distal dendrites. Dye-coupling between XII MNs was common from E18 to P7, but declined strongly with maturation after P7. Axon collaterals were found in 20 % (6 of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor nucleus. These results reveal new morphological features of mouse XII MNs, and suggest that dendritic projection pat- terns, spine density and distribution, and dye-coupling patterns show specific developmental changes in mice.
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 1997
The role of P2 receptors in controlling hypoglossal motoneuron (XII MN) output was examined (1) e... more The role of P2 receptors in controlling hypoglossal motoneuron (XII MN) output was examined (1) electrophysiologically, via application of ATP to the hypoglossal nucleus of rhythmically active mouse medullary slices and anesthetized adult rats; (2) immunohistochemically, using an antiserum against the P2X2 receptor subunit; and (3) using PCR to identify expression of P2X2 receptor subunits in micropunches of tissue taken from the XII motor nucleus. Application of ATP to the hypoglossal nucleus of mouse medullary slices and anesthetized rats produced a suramin-sensitive excitation of hypoglossal nerve activity. Additional in vitro effects included potentiation of inspiratory hypoglossal nerve output via a suramin- and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS)-sensitive mechanism, XII MN depolarization via activation of a suramin-sensitive inward current, decreased neuronal input resistance, and a slow-onset theophylline-sensitive reduction of inspiratory ...
The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosens... more The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosensitive neurons in the rostral ventrolateral medulla and their immunoreactivity for a catecholamine synthesizing enzyme, tyrosine hydroxylase. Thirty neurons displaying inhibitory postsynaptic potentials following stimulation of the aortic depressor nerve were intracellularly labelled with Lucifer Yellow or Neurobiotin. Some of these neurons could be excited antidromically from the second thoracic segment of the spinal cord, with conduction velocities of spinal axons ranging from 1.9 to 7.2 m/s. The filled somas were found immediately caudal to the facial nucleus and ventral or ventromedial to compact formation of the nucleus ambiguus. Some dendrites reached the ventral medullary surface. Axons usually projected dorsomedially and then made a sharp rostral and/or caudal turn. The caudally projecting axon could, in some cases, be followed to the first cervical segment of the spinal cord. Sev...
Although the Centers for Disease Control and Prevention (CDC) reports that brain abnormalities in... more Although the Centers for Disease Control and Prevention (CDC) reports that brain abnormalities in infants with laboratory-confirmed Zika infection include microcephaly, disrupted brain growth, intracranial calcifications, and abnormal eye findings—it is not known presently if the Zika virus itself causes any of these. In a recent 2016 review of Zika dealing with possible brain abnormalities appearing with Zika, Melo et al. mention that among the Flaviviruses, which Zika is, such brain insults and pathologic findings are practically unheard of. Melo et al. conclude that until more cases are diagnosed and more histopathological proofs are obtained, the possibility of other causes besides Zika cannot be ruled out. This paper considers just such other possible causes that have, to this point, escaped general notice. The Aedes aegypti and other Aedes species can transmit tiny viral-like, cell-wall-deficient mycobacterial forms, independent of viruses, yet prevalent in the very same Rhesus Monkey used in the original 1952 Zika communication—which spoke of " A filterable transmissible agent ". In addition, the universal fetal prenatal vaccination of Brazilian neonates is considered, strongly discouraged by The Royal Children's Hospital in Melbourne, which forbids BCG vaccination of pregnant women and those immunosuppressed or already having tuberculosis (TB) or AIDS. And finally thought is focused on the prime candidate itself, towards explaining what an alternative cause for " Zika " might look like—an infectious agent with transmissible , filterable, viral-like forms. One which can be transmitted by the very same Aedes mosquitoes that carry Zika—one that is neurotrophic, and extremely prevalent in Brazil —and that can disrupt brain growth, cause microcephalus, cause a fever, is sexually transmissible, instigates Guillain-Barré syndrome and causes cranial calcifications —the Mycobacterium tuberculosis complex , which includes the Mycobacterium africanum prevalent, yet completely ignored, in the Rhesus monkeys used in the original Zika study.
Hypoglossal motor neurons (XII MNs) innervate tongue muscles important in breathing, suckling and... more Hypoglossal motor neurons (XII MNs) innervate tongue muscles important in breathing, suckling and vocalization. Morphological properties of 103 XII MNs were studied using NeurobiotinTM filling in transverse brainstem slices from C57/Bl6 mice (n=34) from embryonic day (E) 17 to postnatal day (P) 28. XII MNs from areas thought to innervate different tongue muscles showed similar morphology in most, but not all, features. Morphological properties of XII MNs were established prior to birth, not differing between E17–18 and P0. MN somatic volume gradually increased for the first 2 weeks post-birth. The complexity of dendritic branching and dendrite length of XII MNs increased throughout develop- ment (E17–P28). MNs in the ventromedial XII motor nucleus, likely to innervate the genioglossus, frequently (42 %) had dendrites crossing to the contralateral side at all ages, but their number declined with postnatal develop- ment. Unexpectedly, putative dendritic spines were found in all XII MNs at all ages, and were primarily localized to XII MN somata and primary dendrites at E18–P4, increased in distal dendrites by P5–P8, and were later predominantly found in distal dendrites. Dye-coupling between XII MNs was common from E18 to P7, but declined strongly with maturation after P7. Axon collaterals were found in 20 % (6 of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor nucleus. These results reveal new morphological features of mouse XII MNs, and suggest that dendritic projection pat- terns, spine density and distribution, and dye-coupling patterns show specific developmental changes in mice.
Motoneurons develop extensive dendritic trees for receiving excitatory and inhibitory synaptic in... more Motoneurons develop extensive dendritic trees for receiving excitatory and inhibitory synaptic inputs to perform a variety of complex motor tasks. At birth, the somatodendritic domains of mouse hypoglossal and lumbar motoneurons have dense filopodia and spines. Consistent with Vaughn’s synaptotropic hypothesis, we propose a developmental unified-hybrid model implicating filopodia in motoneuron spinogenesis/synaptogenesis and dendritic growth and branching critical for circuit formation and synaptic plasticity at embryonic/prenatal/neonatal period. Filopodia density decreases and spine density initially increases until postnatal day 15 (P15) and then decreases by P30. Spine distribution shifts towards the distal dendrites, and spines become shorter (stubby), coinciding with decreases in frequency and increases in amplitude of excitatory postsynaptic currents with maturation. In transgenic mice, either overexpressing the mutated human Cu/Zn-superoxide dismutase (hSOD1G93A) gene or deficient in GABAergic/glycinergic synaptic transmission (gephyrin, GAD-67, or VGAT gene knockout), hypoglossal motoneurons develop excitatory glutamatergic synaptic hyperactivity. Functional synaptic hyperactivity is associated with increased dendritic growth, branching, and increased spine and filopodia density, involving actin-based cytoskeletal and structural remodelling. Energy-dependent ionic pumps that maintain intracellular sodium/calcium homeostasis are chronically challenged by activity and selectively overwhelmed by hyperactivity which eventually causes sustained membrane depolarization leading to excitotoxicity, activating microglia to phagocytose degenerating neurons under neuropathological conditions.
ABSTRACT Neural development is characterized by the formation of complex neural networks such as ... more ABSTRACT Neural development is characterized by the formation of complex neural networks such as the neuromotor system. During embryonic development approximately half the number of motoneurons generated undergo cell death. This is at a time when motoneurons are making contact with skeletal muscle, and when contacts onto motoneurons by other neurons are being established. This suggests that both central and peripheral synaptic contacts act to regulate the number of motoneurons during this embryonic period. Recent studies have suggested that glycinergic and GABAergic synaptic activity may be essential for the maturation and refinement of developing neural networks. These transmitters switch from producing excitation to inhibition during late embryonic and early postnatal stages. We and others have shown that functional neuromuscular synaptic outputs regulate motoneuron death. This leaves open the question as to whether central synaptic inputs to the motoneuron might also influence survival or death of the motoneuron during this period of neuron cell death. Morphological and functional evidence indicates that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during the period of developmental motoneuron death. This evidence is from the physiological and morphological analyses of mice that lack GABA (GAD67 - deficient mice) and from mice lacking post-synaptic Glycine receptors (Gephyrin - deficient mice).
GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinem... more GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinement of the developing CNS. Here we provide morphological and functional evidence that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during programmed cell death. In gephyrin-deficient mice that lack all postsynaptic glycine receptor and some GABA(A) receptor clusters, there was increased spontaneous respiratory motor activity, reduced respiratory motoneuron survival, and decreased innervation of the diaphragm. In contrast, limb-innervating motoneurons showed decreased spontaneous activity, increased survival, and increased innervation of their target muscles. Both GABA and glycine increased limb-innervating motoneuron activity and decreased respiratory motoneuron activity in wild-type mice, but only glycine responses were abolished in gephyrin-deficient mice. Our results provide genetic evidence that the development of glycinergic and GABAergic synaptic inputs onto motoneurons plays an important role in the survival, axonal branching, and spontaneous activity of motoneurons in developing mammalian embryos.
Pflügers Archiv - European Journal of Physiology, 2008
Intracellular sharp-electrode, whole-cell patch clamp and juxtacellular labeling methods have pre... more Intracellular sharp-electrode, whole-cell patch clamp and juxtacellular labeling methods have previously been developed for combined analysis of neuronal structure and function. We describe a novel electroporation technique for labeling neurons with Neurobiotin, using patch electrodes in a semi-loose seal configuration (R = 100-300 MOmega) with very small amplitude pulses (50 mV). The addition of 2% Neurobiotin to the intracellular solution in the patch electrode reduces the dielectric membrane breakdown voltage threshold by about threefold. The resulting pore formation allows for (1) the stable recording of spontaneous and light-evoked postsynaptic potentials without significant cytoplasmic washout and (2) the passage of dye without spillover. The efficiency and reliability of the method makes it particularly suitable for the serial recording and labeling of multiple neurons in a small area of tissue.
The distribution of the P2X2 receptor subunit of the adenosine 5'-triphosphate (ATP)-gate... more The distribution of the P2X2 receptor subunit of the adenosine 5'-triphosphate (ATP)-gated ion channels was examined in the adult rat central nervous system (CNS) by using P2X2 receptor-specific antisera and riboprobe-based in situ hybridisation. P2X2 receptor mRNA expression matched the P2X2 receptor protein localisation. An extensive expression pattern was observed, including: olfactory bulb, cerebral cortex, hippocampus, habenula, thalamic and subthalamic nuclei, caudate putamen, posteromedial amygdalo-hippocampal and amygdalo-cortical nuclei, substantia nigra pars compacta, ventromedial and arcuate hypothalamic nuclei, supraoptic nucleus, tuberomammillary nucleus, mesencephalic trigeminal nucleus, dorsal raphe, locus coeruleus, medial parabrachial nucleus, tegmental areas, pontine nuclei, red nucleus, lateral superior olive, cochlear nuclei, spinal trigeminal nuclei, cranial motor nuclei, ventrolateral medulla, area postrema, nucleus of solitary tract, and cerebellar cortex. In the spinal cord, P2X2 receptor expression was highest in the dorsal horn, with significant neuronal labeling in the ventral horn and intermediolateral cell column. The identification of extensive P2X2 receptor immunoreactivity and mRNA distribution within the CNS demonstrated here provides a basis for the P2X receptor antagonist pharmacology reported in electrophysiological studies. These data support the role for extracellular ATP acting as a fast neurotransmitter at pre- and postsynaptic sites in processes such as sensory transmission, sensory-motor integration, motor and autonomic control, and in neuronal phenomena such as long-term potentiation (LTP) and depression (LTD). Additionally, labelling of neuroglia and fibre tracts supports a diverse role for extracellular ATP in CNS homeostasis.
In the cochlea, extracellular ATP influences the endocochlear potential, micromechanics, and neur... more In the cochlea, extracellular ATP influences the endocochlear potential, micromechanics, and neurotransmission via P2 receptors. Evidence for this arises from studies demonstrating widespread expression of ATP-gated ion channels (assembled from P2X receptor subunits) and G protein-coupled receptors (P2Y receptors). P2X2 receptor subunits are localized to the luminal membranes of epithelial cells and hair cells lining scala media. These ion channels provide a shunt pathway for K+ ion egress. Thus, when noise exposure elevates ATP levels in this cochlear compartment, the K+ conductance through P2X receptors reduces the endocochlear potential. ATP-mediated K+ efflux from scala media is complemented by a P2Y receptor G protein-coupled pathway that provides coincident reduction of K+ transport into scala media from the stria vascularis when autocrine or paracrine ATP signalling is invoked. This purinergic signalling likely provides a basis for a reactive homoeostatic regulatory mechanism limiting cochlear sensitivity under stressor conditions. Elevation of ATP in the perilymphatic compartment under such conditions is also likely to invoke purinergic receptor-mediated changes in supporting cell micromechanics, mediated by Ca2+ influx and gating of Ca2+ stores. Independent of these humoral actions, ATP can be classified as a putative auditory neurotransmitter based on the localization of P2X receptors at the spiral ganglion neuron-hair cell synapse, and functional verification of ATP-gated currents in spiral ganglion neurons in situ. Expression of P2X receptors by type II spiral ganglion neurons supports a role for ATP as a transmitter encoding the dynamic state of the cochlear amplifier.
Abstract Hypoglossal motor neurons (XII MNs) inner- vate tongue muscles important in breathing, s... more Abstract Hypoglossal motor neurons (XII MNs) inner- vate tongue muscles important in breathing, suckling and vocalization. Morphological properties of 103 XII MNs were studied using NeurobiotinTM filling in transverse brainstem slices from C57/Bl6 mice (n = 34) from embryonic day (E) 17 to postnatal day (P) 28. XII MNs from areas thought to innervate different tongue muscles showed similar morphology in most, but not all, features. Morphological properties of XII MNs were established prior to birth, not differing between E17–18 and P0. MN somatic volume gradually increased for the first 2 weeks post-birth. The complexity of dendritic branching and dendrite length of XII MNs increased throughout develop- ment (E17–P28). MNs in the ventromedial XII motor nucleus, likely to innervate the genioglossus, frequently (42 %) had dendrites crossing to the contralateral side at all ages, but their number declined with postnatal develop- ment. Unexpectedly, putative dendritic spines were found in all XII MNs at all ages, and were primarily localized to XII MN somata and primary dendrites at E18–P4, increased in distal dendrites by P5–P8, and were later predominantly found in distal dendrites. Dye-coupling between XII MNs was common from E18 to P7, but declined strongly with maturation after P7. Axon collaterals were found in 20 % (6 of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor nucleus. These results reveal new morphological features of mouse XII MNs, and suggest that dendritic projection pat- terns, spine density and distribution, and dye-coupling patterns show specific developmental changes in mice.
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 1997
The role of P2 receptors in controlling hypoglossal motoneuron (XII MN) output was examined (1) e... more The role of P2 receptors in controlling hypoglossal motoneuron (XII MN) output was examined (1) electrophysiologically, via application of ATP to the hypoglossal nucleus of rhythmically active mouse medullary slices and anesthetized adult rats; (2) immunohistochemically, using an antiserum against the P2X2 receptor subunit; and (3) using PCR to identify expression of P2X2 receptor subunits in micropunches of tissue taken from the XII motor nucleus. Application of ATP to the hypoglossal nucleus of mouse medullary slices and anesthetized rats produced a suramin-sensitive excitation of hypoglossal nerve activity. Additional in vitro effects included potentiation of inspiratory hypoglossal nerve output via a suramin- and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS)-sensitive mechanism, XII MN depolarization via activation of a suramin-sensitive inward current, decreased neuronal input resistance, and a slow-onset theophylline-sensitive reduction of inspiratory ...
The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosens... more The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosensitive neurons in the rostral ventrolateral medulla and their immunoreactivity for a catecholamine synthesizing enzyme, tyrosine hydroxylase. Thirty neurons displaying inhibitory postsynaptic potentials following stimulation of the aortic depressor nerve were intracellularly labelled with Lucifer Yellow or Neurobiotin. Some of these neurons could be excited antidromically from the second thoracic segment of the spinal cord, with conduction velocities of spinal axons ranging from 1.9 to 7.2 m/s. The filled somas were found immediately caudal to the facial nucleus and ventral or ventromedial to compact formation of the nucleus ambiguus. Some dendrites reached the ventral medullary surface. Axons usually projected dorsomedially and then made a sharp rostral and/or caudal turn. The caudally projecting axon could, in some cases, be followed to the first cervical segment of the spinal cord. Sev...
Although the Centers for Disease Control and Prevention (CDC) reports brain abnormalities in infa... more Although the Centers for Disease Control and Prevention (CDC) reports brain abnormalities in infants with laboratory-confirmed Zika infection include microcephaly, disrupted brain growth, intracranial calcifications, and abnormal eye findings ― it is not known presently if the Zika virus itself causes any of these. In a recent 2016 review of Zika dealing with possible brain abnormalities appearing with Zika, Melo et al. mentions that among the Flaviviruses, which Zika is, such brain insults and pathologic findings are practically unheard of. Melo et al. concludes that until more cases are diagnosed and more histopathological proof obtained, the possibility of other causes besides Zika cannot be ruled out. This paper considers just such other possible causes that have, to this point, escaped general notice. The Aedes egypti and other Aedes species can transmit tiny viral-like, cell-wall-deficient mycobacterial forms, independent of viruses, yet prevalent in the very same Rhesus Monkey’s used in the original 1952 Zika communication ― which spoke of “A filterable transmissible agent.” In addition, considered is the universal fetal prenatal vaccination of Brazilian neonates, strongly discouraged by The Royal Children’s Hospital in Melbourne, which forbids BCG vaccination of pregnant women and those immunosuppressed or that already have tuberculosis (TB) or AIDS. And finally thought is focused on the prime candidate itself, towards explaining what an alternative cause for “Zika” might look like ― an infectious agent with transmissible, filterable, viral-like forms. One which can be transmitted by the very same Aedes mosquitoes that carry Zika ― one that is neurotrophic, that is extremely prevalent in Brazil ― and that can disrupt brain growth, cause microcephalus, cause a fever, is sexually transmissible, instigates Guillain-Barré syndrome and causes cranial calcifications ― the Mycobacterium tuberculosis complex, which includes the Mycobacterium africanum so prevalent in the Rhesus monkies used in the original Zika study.
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from areas thought to innervate different tongue muscles
showed similar morphology in most, but not all, features.
Morphological properties of XII MNs were established
prior to birth, not differing between E17–18 and P0. MN
somatic volume gradually increased for the first 2 weeks
post-birth. The complexity of dendritic branching and
dendrite length of XII MNs increased throughout develop-
ment (E17–P28). MNs in the ventromedial XII motor
nucleus, likely to innervate the genioglossus, frequently
(42 %) had dendrites crossing to the contralateral side at all
ages, but their number declined with postnatal develop-
ment. Unexpectedly, putative dendritic spines were found
in all XII MNs at all ages, and were primarily localized to
XII MN somata and primary dendrites at E18–P4, increased
in distal dendrites by P5–P8, and were later predominantly
found in distal dendrites. Dye-coupling between XII MNs
was common from E18 to P7, but declined strongly with
maturation after P7. Axon collaterals were found in 20 % (6
of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor
nucleus. These results reveal new morphological features of
mouse XII MNs, and suggest that dendritic projection pat-
terns, spine density and distribution, and dye-coupling
patterns show specific developmental changes in mice.
from areas thought to innervate different tongue muscles
showed similar morphology in most, but not all, features.
Morphological properties of XII MNs were established
prior to birth, not differing between E17–18 and P0. MN
somatic volume gradually increased for the first 2 weeks
post-birth. The complexity of dendritic branching and
dendrite length of XII MNs increased throughout develop-
ment (E17–P28). MNs in the ventromedial XII motor
nucleus, likely to innervate the genioglossus, frequently
(42 %) had dendrites crossing to the contralateral side at all
ages, but their number declined with postnatal develop-
ment. Unexpectedly, putative dendritic spines were found
in all XII MNs at all ages, and were primarily localized to
XII MN somata and primary dendrites at E18–P4, increased
in distal dendrites by P5–P8, and were later predominantly
found in distal dendrites. Dye-coupling between XII MNs
was common from E18 to P7, but declined strongly with
maturation after P7. Axon collaterals were found in 20 % (6
of 28) of XII MNs with filled axons; collaterals terminated widely outside and, in one case, within the XII motor
nucleus. These results reveal new morphological features of
mouse XII MNs, and suggest that dendritic projection pat-
terns, spine density and distribution, and dye-coupling
patterns show specific developmental changes in mice.
This paper considers just such other possible causes that have, to this point, escaped general notice. The Aedes egypti and other Aedes species can transmit tiny viral-like, cell-wall-deficient mycobacterial forms, independent of viruses, yet prevalent in the very same Rhesus Monkey’s used in the original 1952 Zika communication ― which spoke of “A filterable transmissible agent.” In addition, considered is the universal fetal prenatal vaccination of Brazilian neonates, strongly discouraged by The Royal Children’s Hospital in Melbourne, which forbids BCG vaccination of pregnant women and those immunosuppressed or that already have tuberculosis (TB) or AIDS. And finally thought is focused on the prime candidate itself, towards explaining what an alternative cause for “Zika” might look like ― an infectious agent with transmissible, filterable, viral-like forms. One which can be transmitted by the very same Aedes mosquitoes that carry Zika ― one that is neurotrophic, that is extremely prevalent in Brazil ― and that can disrupt brain growth, cause microcephalus, cause a fever, is sexually transmissible, instigates Guillain-Barré syndrome and causes cranial calcifications ― the Mycobacterium tuberculosis complex, which includes the Mycobacterium africanum so prevalent in the Rhesus monkies used in the original Zika study.