Dog behaviour as related to spinal cord temperature

Summary 3 dogs could behaviourally modify their own spinal cord temperature (T_{spin. cord}). In a hot environment, 2 dogs did not cool their spinal cord, 1 dog warmed it. The higher the environmental temperature, the higher the chosen T_{spin. cord}. These results seem to imply that this latter dog tended, in warm environment, to behaviourally reduce: T_s>T_{spin. cord} (T_s mean skin temperature). Data obtained previously support this explanation.This experiment has been supported by the Centre National de la Recherche Scientifique (L.A. No. 181 C.N.R.S.) and by the Institut National de la Santé et de la Recherche Médicale I.N.S.E.R.M./A.T.P. No. 4-74-25).     

Production of temperature signals in the peripherally denervated spinal cord of the dog

Summary Selective warming of the spinal cord with ventral and dorsal roots cut can generate panting in the conscious dog.     

Tolerance to cold and glucose homeostasis in adrenal demedullated dogs

Summary The rise in O₂ consumption and in glucose turnover, induced by acute cold exposure is not suppressed by adrenal demedullation in dogs. However, both at neutral and cold ambient temperature, the mean plasma glucose concentrations are higher in normal (N) than in adrenal-demedullated dogs (ADMX). In the cold, the fall in rectal temperature is larger in ADMX than in N dogs.This work was supported by a grant from Université Claude Bernard (U.E.R. Lyon Nord and U.E.R. Biologie Humaine).The authors thank D. Rougier and G. Dallevet for their excellent technical assistance and A. Brillant for secreterial assistance.     

Konstante Stromwirkung und « funktionelle Polarität »

Summary Scheminzky found that the effect produced by passing a constant current through a frog depended on the direction of the current. While a descending current (directed from heat to foot) produced paralysis, an ascending current produced convulsions.Scheminzky believed that it was impossible to explain this phenomenon in any other way than by a functional polarity, involving a special microstructure in the cells of the spinal cord.—We found that the observed effect is in no way connected with the direction of the current, and that, on the contrary, it depends exclusively upon the electrical charge applied to the upper centres. The cathode on the spinal cord produces convulsions while the anode does not. The effects remain unchanged if the second electrode is removed from the spinal cord and applied to some spot outside the central nervous system. If, following extirpation of a small segment of the spinal cord, one electrode is placed on the head and the second electrode is applied to the cut surface of the lower part of the spinal cord, a perfect reversal of theScheminzky phenomenon can be obtained.TheScheminzky phenomenon is thus reduced to the well-known stimulating effect of the cathode and the paralysing effect of the anode. The question why a current passing in one direction (descending) should produce the anodic effect, while a current passing in the opposite direction (ascending) should produce the cathodic effect, can easily be explained by another well-known fact, i.e. the dependance of the lower spinal centres upon the higher ones. If the brain and upper centres are nearer to the anode (descending current), their anelectrotonic elimination has a paralysing effect, while their catelectrotonic excitation with an ascending current produces convulsions.     

Stem cells from human apical papilla decrease neuro-inflammation and stimulate oligodendrocyte progenitor differentiation via activin-A secretion

Secondary damage following spinal cord injury leads to non-reversible lesions and hampering of the reparative process. The local production of pro-inflammatory cytokines such as TNF-α can exacerbate these events. Oligodendrocyte death also occurs, followed by progressive demyelination leading to significant tissue degeneration. Dental stem cells from human apical papilla (SCAP) can be easily obtained at the removal of an adult immature tooth. This offers a minimally invasive approach to re-use this tissue as a source of stem cells, as compared to biopsying neural tissue from a patient with a spinal cord injury. We assessed the potential of SCAP to exert neuroprotective effects by investigating two possible modes of action: modulation of neuro-inflammation and oligodendrocyte progenitor cell (OPC) differentiation. SCAP were co-cultured with LPS-activated microglia, LPS-activated rat spinal cord organotypic sections (SCOS), and LPS-activated co-cultures of SCOS and spinal cord adult OPC. We showed for the first time that SCAP can induce a reduction of TNF-α expression and secretion in inflamed spinal cord tissues and can stimulate OPC differentiation via activin-A secretion. This work underlines the potential therapeutic benefits of SCAP for spinal cord injury repair.     

Chemokines in neuron–glial cell interaction and pathogenesis of neuropathic pain

Neuropathic pain resulting from damage or dysfunction of the nervous system is a highly debilitating chronic pain state and is often resistant to currently available treatments. It has become clear that neuroinflammation, mainly mediated by proinflammatory cytokines and chemokines, plays an important role in the establishment and maintenance of neuropathic pain. Chemokines were originally identified as regulators of peripheral immune cell trafficking and were also expressed in neurons and glial cells in the central nervous system. In recent years, accumulating studies have revealed the expression, distribution and function of chemokines in the spinal cord under chronic pain conditions. In this review, we provide evidence showing that several chemokines are upregulated after peripheral nerve injury and contribute to the pathogenesis of neuropathic pain via different forms of neuron–glia interaction in the spinal cord. First, chemokine CX3CL1 is expressed in primary afferents and spinal neurons and induces microglial activation via its microglial receptor CX3CR1 (neuron-to-microglia signaling). Second, CCL2 and CXCL1 are expressed in spinal astrocytes and act on CCR2 and CXCR2 in spinal neurons to increase excitatory synaptic transmission (astrocyte-to-neuron signaling). Third, we recently identified that CXCL13 is highly upregulated in spinal neurons after spinal nerve ligation and induces spinal astrocyte activation via receptor CXCR5 (neuron-to-astrocyte signaling). Strategies that target chemokine-mediated neuron-glia interactions may lead to novel therapies for the treatment of neuropathic pain.     

Localization of substance P in the nervous system of the human fetus : preliminary results

Substance P (SP) immunoreactive structures were localized by immunofluorescence technique within the central nervous system of human fetuses (12, 15, 19 and 24 weeks old). Specificity of the anti-SP serum was established by immunocytology and radio-immunology. A wide distribution of SP positive structures (pericaryons and/or fibres) was found in brain, spinal cord and dorsal root ganglia. Mesencephalon, pons and dorsal horns of the spinal cord showed very intense fluorescence. The preliminary observations are the first report concerning SP ontogeny in the Human central nervous system. However, it was difficult to ascribe a significance to this neuropeptide during fetal life.     

Evidence for the existence of an agent in the serum of the cyclic hematopoietic dog which influences hemoglobin synthesis

Summary Serum samples collected through the cycle of a cyclic hematopoietic (CH) dog under reduced atmospheric conditions, were assayed for their ability to affect hemoglobin synthesis by normal canine bone marrow. Varying levels of hemoglobin synthesis in the presence of different serum samples suggest an agent cycles in the serum of CH dogs which influences hemoglobin synthesis.     

Spontaneous morphine withdrawal from the rat spinal cord

A characteristic and reproducible sign of narcotic withdrawal is the naloxone induced increase in arterial pressure. In morphine-dependent rats allowed to undergo spontaneous withdrawal (6-24 h) and then transected at the spinal C-1 level, arterial pressure was maintained at a significantly higher level than either spinal-transected nondependent controls or morphine-dependent, spinal-transected rats pithed from C-1 to L-4. These findings indicate that the morphine-dependent spinal cord, independent of supraspinal influences, is able to exhibit an autonomic component of spontaneous withdrawal.     

Post-tetanic changes of bilateral dorsal root potentials evoked by stimulation of the cutaneous afferents.

In spinal cats following tetanic stimulation of the cutaneous nerve bilateral dorsal root potentials in the lumbar spinal cord are depressed. Because of differences between ipsi- and contralateral potentials, this depression can usually be evoked only on one side of the cord.     

Response of respiration to selective heating of the spinal cord below partial transection

Conclusions The experiments indicate that the signals arising from thermal stimulation of the spinal cord are conducted to higher spinal and to supraspinal thermoregulatory effector systems by afferent fibers which run in the ventrolateral, but not in the dorsal portions of the spinal ascending tracts. This corresponds to the observation ofWünnenberg andBrück that shivering induced by external cooling is not inhibited by heating the lower cervical and upper thoracic spinal cord, if the ventral funiculi are transected at a higher cervical level. -These findings are parallel to the observation that the inhibitory effect on shivering of skin pressure is no longer present after contralateral transection of the ventrolateral funiculus at a higher level, i. e. after transection of the so-called ventral spinothalamic tract. Likewise, it has been observed that modifications of electrocortical activity following thermal stimulation of the skin or following changes of environmental temperature are abolished, if the ventrolateral funiculi are transected at the cervical level. -It may be suggested, therefore, that the afferent signals arising from spinal thermosensitive structures might follow the same ascending pathway as do the discharges of peripheral thermodetectors.

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Zusammenfassung Der Einfluss thermischer Reizung des Rückenmarks unterhalb einer Teildurchschneidung in Höhe von Th 4–Th 11 auf Atmung, Hautdurchblutung und motorische Aktivität wurde an leicht narkotisierten Kaninchen untersucht. Mittels Marchi-Färbung einige Tage nach Durchschneidung wurden die ausgeschalteten afferenten Bahnen ermittelt. Nach Durchschneidung der Hinterstränge und anschliessender Abschnitte der Seitenstränge konnte durch Rückenmarkwärmung unterhalb der Durchschneidung eine thermische Tachypnoe und eine Hautvasodilatation oberhalb der Durchschneidung ausgelöst werden. Diese Reaktion war nach Durchschneidung der Vorderseitenstränge erloschen.

     

Fever and survival in the rat. The effect of enhancing the cold defence response

Summary Continuous cooling of the spinal cord for 6 and 28 days had a probably beneficial effect on the outcome of salmonellosis in the rat, suggesting that the apparently harmful effect of high fevers is not due to the cold defence response but may rather be caused by the high body temperature.I thank Dr W. Mannheim from the Institute of Hygiene for kindly furnishing the cultures ofS. enteritidis. This work was supported by the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 122 and Schwerpunktprogramm Temperature-regulation und-adaptation).     

Post-tetanic changes of bilateral dorsal root potentials evoked by stimulation of the cutaneous afferents

Summary In spinal cats following tetanic stimulation of the cutaneous nerve bilateral dorsal root potentials in the lumbar spinal cord are depressed. Because of differences between ipsi- and contralateral potentials, this depression can usually be evoked only on one side of the cord.     

Electrophysiologic and anatomic demonstration of inhibitory commisural vestibular neurons in the tench (Tinca tinca)]

Horseradish peroxydase was injected intracellularly in some of the medullary neurons which, in Fish, exhibit a passive hyperpolarizing potential after spinal cord stimulation (this indicates that such neurons both electrical and chemical inhibitions of the Mauthner cells). With positive staining, commissural vestibular neurons were identified; their axons cross the midline and they establish connexions with the Mauthner cell and with vestibular neurons of both sides. Thus the existence of a crossed vestibular inhibitory pathway, previously suggested by electrophysiological studies in lower Vertebrates as well as in Mammals, is now correlated with histological evidence.     

Transplantation into the mammalian adult spinal cord

Summary Embryonic cerebral cortical tissue obtained from rat embryos of 15-day gestation was transplanted into the cervical spinal cord of adult rats. The cortical transplants survived, grew, and established connections with the host animal's spinal cord. In other animals, knife lesions were first made in the host's spinal cord, and then embryonic cortical tissue was transplanted into the site of the lesion. The cortical transplants in these animals were observed to become an integral part of the host animal's spinal cord.     

Increased migration of olfactory ensheathing cells secreting the Nogo receptor ectodomain over inhibitory substrates and lesioned spinal cord

Olfactory ensheathing cell (OEC) transplantation emerged some years ago as a promising therapeutic strategy to repair injured spinal cord. However, inhibitory molecules are present for long periods of time in lesioned spinal cord, inhibiting both OEC migration and axonal regrowth. Two families of these molecules, chondroitin sulphate proteoglycans (CSPG) and myelin-derived inhibitors (MAIs), are able to trigger inhibitory responses in lesioned axons. Mounting evidence suggests that OEC migration is inhibited by myelin. Here we demonstrate that OEC migration is largely inhibited by CSPGs and that inhibition can be overcome by the bacterial enzyme Chondroitinase ABC. In parallel, we have generated a stable OEC cell line overexpressing the Nogo receptor (NgR) ectodomain to reduce MAI-associated inhibition in vitro and in vivo. Results indicate that engineered cells migrate longer distances than unmodified OECs over myelin or oligodendrocyte-myelin glycoprotein (OMgp)-coated substrates. In addition, they also show improved migration in lesioned spinal cord. Our results provide new insights toward the improvement of the mechanisms of action and optimization of OEC-based cell therapy for spinal cord lesion.     

The change of vagal activity evoked by spinal cord thermal stimulation in anesthetized rabbits

Summary Vagal activity decreased significantly during spinal cord warming and increased significantly during spinal cord cooling in anesthetized, immobilized rabbits. The result provide the first direct proof of changes in parasympathetic activity during spinal thermal stimulation.     

Spontaneous morphine withdrawal from the rat spinal cord

Summary A characteristic and reproducible sign of narcotic withdrawal is the naloxone induced increase in arterial pressure. In morphine-dependent rats allowed to undergo spontaneous withdrawal (6–24 h) and then transected at the spinal C-1 level, arterial pressure was maintained at a significantly higher level than either spinal-transected nondependent controls or morphine-dependent, spinal-transected rats pithed from C-1 to L-4. These findings indicate that the morphine-dependent spinal cord, independent of supraspinal influences, is able to exhibit an autonomic component of spontaneous withdrawal.This study was supported by the Medical Research Service of the Veterans Administration. A preliminary report of aspects of this work appeared in Soc. Neurosci. Abs.10 (1984) 1113.     

Viscero-somatic reflexes following distension of urinary bladder in cats: role of supraspinal neuraxis

Viscero-somatic reflexes have been studied by recording monosynaptic reflexes following distension of the urinary bladder in intact, decerebrate and spinal animals. It was observed that the viscero-somatic responses following bladder distension are inhibitory in nature and this inhibition was highest in decerebrates and least in spinal animals. The site of viscero-somatic interaction probably lies in the bulbar area (supraspinal) and spinal cord.