Photon spectra in NPL standard monoenergetic neutron fields.

A High Purity Germanium (HPGe) detector has been used to measure the photon spectra in the majority of monoenergetic neutron fields produced at NPL (0.144, 0.250, 0.565, 2.0, 5.0 and 16.5 MeV). The HPGe was characterised and then modelled to produce a response matrix. The measured pulse height spectra were then unfolded to produce photon fluence spectra. The new spectra were used to improve the photon to neutron dose equivalent ratios from some earlier work at NPL with Geiger-Muller tubes and electronic personal dosemeters.

Light and electron microscopic evidence for a direct corticospinal projection to superficial laminae of the dorsal horn in cats and monkeys.

The anterograde transport of horseradish peroxidase (HRP) and wheat germ agglutin conjugated to horseradish peroxidase (WGA-HRP) was employed in cats and monkeys to investigate, at both the light and electron microscopical levels, the contribution of the corticospinal tract (CST) to the superficial laminae of the dorsal horn. At the light microscopic level, this approach not only confirmed the previously documented pattern of CST termination, but also revealed a sparse projection to laminae VIII and IX of the cat and a prominent projection to the most superficial parts of the brachial dorsal horn, i.e., laminae I and II. Discrete injections involving particular cytoarchitectonic areas (4, 3a, 3b, and 1-2) of monkeys showed that the superficial laminae receive their corticofugal inputs primarily from areas 3b, 1, and 2. Electron microscopic observations were made on CST fibers and boutons which were labelled, after histochemical processing, with the reaction product of anterogradely transported WGA-HRP. The labelled fibers in the superficial laminae were small (+/- 0.5 micron), and boutons established mainly axodendritic contacts, contained mostly clear, spherical, or pleomorphic vesicles, but sometimes also displayed dense core vesicles. These boutons were primarily in lamina I and outer lamina II, but not in inner lamina II. The possible role of a direct monosynaptic pathway from the cerebral cortex to the superficial laminae of the dorsal horn is discussed in relation to the previous reports that laminae I and II play a significant role in nociception.

Thalamic projections to sensorimotor cortex in the macaque monkey: use of multiple retrograde fluorescent tracers.

We used several fluorescent dyes (Fast Blue, Diamidino Yellow, Rhodamine Latex Microspheres, Evans Blue, and Fluoro-Gold) in each of eight macaques, to examine the patterns of thalamic input to the sensorimotor cortex of macaques 12 months or older. Inputs to different zones of motor, premotor, and postarcuate cortex, supplementary motor area, and areas 3b/1 and 2/5 in the postcentral cortex, were examined. Coincident labeling of thalamocortical neuron populations with different dyes (1) increased the precision with which their soma distributions could be related within thalamic space, and (2) enabled the detection by double labeling, of individual thalamic neurons that were common to the thalamic soma distributions projecting to separate, dye-injected cortical zones. Double-labeled thalamic neurons projecting to sensorimotor cortex were rarely seen in mature macaques, even when the injection sites were only 1-1.5 mm apart, implying that their terminal arborizations were quite restricted horizontally. By contrast, separate neuron populations in each thalamic nucleus with input to sensorimotor cortex projected to more than one cytoarchitecturally distinct cortical area. In ventral posterior lateral (oral) (VPLo), for example, separate populations of cells sent axons to precentral medial, and lateral area 4, medial premotor, and postarcuate cortex, as well as to supplementary motor area. Extensive convergence of thalamic input even to the smallest zones of dye uptake in the cortex (approximately 0.5 mm3) characterized the sensorimotor cortex. The complex forms of these projection territories were explored using 3-dimensional reconstructions from coronal maps. These projection territories, while highly ordered, were not contained by the cytoarchitectonic boundaries of individual thalamic nuclei. Their organization suggests that the integration of the diverse information from spinal cord, cerebellum, and basal ganglia that is needed in the execution of complex sensorimotor tasks begins in the thalamus.

Thalamic projections to sensorimotor cortex in the newborn macaque.

In the present experiments thalamocortical projections to different functional areas of the newborn (or prematurely delivered) macaque's sensorimotor cortex were labeled using retrogradely transported fluorescent dyes. Several dyes were used in each animal to (1) enable the direct comparison of the soma distributions of different thalamocortical projections within thalamic space, and (2) identify by double labeling neurons shared between these distributions. The projection patterns in the newborn macaque were compared with those of the mature animal reported by Darian-Smith et al. (J. Comp. Neurol. 1990;298:000-000). The main observations were (1) all thalamocortical projections to the sensorimotor cortex of the mature macaque are well established by embryonic days 146-150, as was shown by labeling these pathways in infants delivered by cesarean section, (2) a significant number of thalamocortical neurons in the newborn were double-labeled following dye injections into different pre- or postcentral areas, and where the margins of the dye uptake zones were separated by 3-8 mm, and (3) extensive projections from the anterior pulvinar nucleus to the motor and premotor cortex, and to the supplementary motor cortex were labeled in the newborn macaque. Both the exuberant terminal arborizations, and the precentral pulvinar projections were diminished by the 6th postnatal month, and absent in the mature macaque. The role of epigenetic determinants of these postnatal events is briefly considered.

Up-regulation of leukaemia inhibitory factor and interleukin-6 in transected sciatic nerve and muscle following denervation.

Leukaemia inhibitory factor (LIF) and Interleukin-6 (IL-6) are multifunctional cytokines that are related on the basis of their predicted structural similarities and shared signal transducing receptor components. Both these factors stimulate myoblast proliferation, and whereas LIF is neurotrophic for sensory neurons, and for the motor neurons which innervate muscle, IL-6 has only been reported to act on a population of septal neurons in the brain. We have looked at the effect of peripheral nerve trauma on the expression of these factors. We show here that whereas LIF and IL-6 mRNAs are expressed in low levels in normal sciatic nerve and skeletal muscle, there is significant up-regulation in the nerve segments after injury, with proximally and distally. There is also an increase in LIF and IL-6 expression in the denervated muscle located largely in the muscle cells. In addition, while there is retrograde axonal transport of LIF by the sciatic nerve, IL-6 is not retrogradely transported, and as a result, IL-6 does not stimulate the survival of sensory neurons in vitro. Both growth factors are produced by Schwann cells. These results show a rapid response in the expression of these genes after injury and suggest that LIF and IL-6 act as trauma factors but with different roles in injured peripheral nerve.

Leukaemia inhibitory factor rescues motoneurones from axotomy-induced cell death.

The death of spinal motoneurones after axotomy provides a useful model for studying novel factors which prevent motoneurone loss in vivo. Peripheral nerves of newborn rats were unilaterally transected and treated with either a vehicle solution or leukaemia inhibitory factor (LIF). Compared with the vehicle controls, treatment with a gelfoam containing LIF significantly reduced motoneurone loss: from 38% to 22% after 3 days and from 55% to 38% after 7 days. The loss of motoneurones was further reduced by placing the LIF-containing gelfoam inside a silicone chamber: from 39% to 15% after 7 days, which represented a 62% rescue. Thus, LIF is a potential therapeutic agent for preventing the loss of injured or diseased motoneurones.

Leukemia inhibitory factor maintains choline acetyltransferase expression in vivo.

Following axotomy most medial septal neurons in the adult rat brain have dramatically reduced numbers of choline acetyltransferase (ChAT) positive neurons. Since leukemia inhibitory factor (LIF) promotes cholinergic expression in several neuronal populations, the aim of this study was to determine if LIF would continue to support cholinergic expression in axotomized medial septal neurons. Mini-osmotic pumps were used to infuse saline or LIF into the lateral cerebral ventricle. Counts of ChAT and low-affinity nerve growth factor (p75NGFR) immunostained neurons indicated that LIF-treated animals retained ChAT expression in > 90% of axotomized neurons whereas in saline-infused animals this was < 30%. Also, LIF was equally effective in maintaining p75NGFR expression levels in axotomized medial septal neurons.

Neurotrophin receptor expression and responsiveness by postnatal cerebral oligodendroglia.

The low affinity neurotrophin receptor (p75(NTR)) is implicated in promoting oligodendrocytic death after nerve growth factor (NGF) stimulation but NGF and neurotrophin-3 (NT-3) can also potentiate oligodendrocytic survival. We show regional variability in p75(NTR) expression within the central nervous system of the postnatal rat; expression is readily detectable by immunohistochemistry upon a subset of CNPase-positive oligodendroglia in optic nerve but not within the cerebrum. Nevertheless, oligodendroglia isolated from the cerebrum and cultured for 16 hours express p75(NTR) as well as the trkC but not the TrkA gene. Viability was not, however, influenced by exposure to either NGF or NT-3. Cells overexpressing p75(NTR) remained unresponsive to NGF but exhibited potentiated survival with NT-3, correlating with the differential expression profile of their high affinity receptors.

Infrapyramidal mossy fibers in the hippocampus of methylazoxymethanol acetate-induced microcephalic rats.

Treatment of pregnant rats with methylazoxymethanol acetate results in the invasion of mossy fibers into the infrapyramidal region of the hippocampus in the offspring. Since such an invasion of mossy fibers has also been reported in neonatal hyperthyroidism, prenatal ethanol exposure and neonatal lesion of CA3, a common etiology for this phenomenon is proposed.

Leukaemia inhibitory factor abrogates Paclitaxel-induced axonal atrophy in the Wistar rat.

A prominent side effect of Paclitaxel chemotherapy is sensorimotor peripheral neuropathy. Leukaemia inhibitory factor (LIF) supports the survival and regrowth of axotomised sensory and motor neurons and we therefore investigated if systemically administered LIF abrogated Paclitaxel-induced neuropathy. We found that whereas animals administered Paclitaxel alone exhibited a significant decrease in the percentage of large myelinated axons, this reduction was prevented by the co-administration of LIF.

Leukemia inhibitory factor by systemic administration rescues spinal motor neurons in the SOD1 G93A murine model of familial amyotrophic lateral sclerosis.

Leukemia inhibitory factor (LIF) is a survival factor for motoneurons. In this study we investigated whether intense systemic LIF therapy prevents the loss of lumbar motoneurons in the transgenic SOD1 G93A mouse model of familial amyotrophic lateral sclerosis. Treatment involved daily 25 microg/kg intraperitoneal injection for a period of 6 weeks starting at 70 days of age. Using the unbiased optical dissector technique, significant rescue of motoneurons in the LIF-treated group (3809+/-455) was found compared to the vehicle group (1085+/-140).

Degeneration of corticospinal and bulbospinal systems in the superoxide dismutase 1(G93A G1H) transgenic mouse model of familial amyotrophic lateral sclerosis.

In the superoxide dismutase 1 (SOD1)(G93A G1H) transgenic mouse, the primary pathology and disease signs are associated with the degeneration of motor neurons in the lumbar spinal cord. It is unclear if the descending motor pathways from the cortex and brainstem are also compromised. The retrograde tracer Fluorogold was inserted into the T(12) segment of the spinal cord and the number of labelled neurons counted in the sensorimotor cortex and brainstem of 60, 90 and 110 day-old mice. A small loss of corticospinal and bulbospinal projections was detected at 60 days. By 110 days, 53% of corticospinal, 41% of bulbospinal and 43% of rubrospinal neurons were lost. The progressive loss of corticospinal axons was confirmed using the stereological fractionator method. These findings suggest that the expression of the SOD1(G93A G1H) mutant protein results in a disease that resembles the late stages of human motor neuron disease. This involves not only the destruction of lower motor neurons in the spinal cord, but also additional loss of descending cortical and bulbar neurons.

Differential loss of spinal sensory but not motor neurons in the p75NTR knockout mouse.

Sensory neurons in the dorsal root ganglia (DRG) and motor neurons in the spinal cord express the 75 kDa low-affinity neurotrophin receptor (p75NTR) during prenatal development. The p75NTR gene knockout mouse provides a unique opportunity to assess the role of p75NTR during this period. Quantitative analysis of the p75NTR knockout mouse revealed a significant developmental loss of sensory neurons. In the cervico-thoracic ganglia approximately 75% of the neurons are lost, while in the lumbar ganglia the loss is approximately 50%. In contrast, motor neurons were not lost in either the cervical or lumbar spinal cord. These data suggest that p75NTR is essential for the prenatal survival of a significant number of sensory, but not motor neurons.

The engraftment of transplanted primary neuroepithelial cells within the postnatal mouse brain.

Primary neuroepithelial precursor cells carrying the reporter gene lacZ were transplanted into postnatal murine brain and assessed for their engraftment capacity. Freshly dissected precursors, derived from lacZ transgenic embryonic day 10 mouse brain, predominantly engrafted as discrete clusters, whereas the same precursors cultured in vitro with fibroblast growth factor-2, engrafted as single cells within the parenchyma of the hippocampus. Approximately 0.5% of the transplanted cells survived in the host brain for up to 3 months. Many of these cells displayed neuronal and astrocyte morphologies. These observations suggest that transplanted primary precursors derived from the embryonic brain can engraft and commit in situ to a variety of developmental fates.

Expression of leukemia inhibitory factor receptor mRNA in sensory dorsal root ganglion and spinal motor neurons of the neonatal rat.

Previous studies have shown that the application of leukemia inhibitory factor to the proximal nerve stump prevents the degeneration of axotomized sensory neurons in the dorsal root ganglion and motor neurons in the spinal cord of newborn rats. This study investigated the expression of leukemia inhibitory factor receptor mRNA in these neurons using in situ hybridization. Leukemia inhibitory factor receptor mRNA was detected both in sensory neurons within the dorsal root ganglion and motor neurons of the cervical spinal cord. Twenty-four hours after axotomy these neurons continue to express leukemia inhibitory factor receptor mRNA. This pattern of leukemia inhibitory factor receptor expression provides a mechanism by which endogenous and exogenous leukemia inhibitory factor could act on injured sensory and motor neurons.

IgA-dominant glomerulonephritis associated with hepatitis A.

Unlike hepatitis B and C, renal involvement has been extremely uncommon in patients with hepatitis Avirus (HAV) infection. Nephrotic syndrome has been documented as a rare complication in association with HAV infection. In this report, we describe a patient with serologically documented HAV infection, who presented with nephrotic syndrome. The renal biopsy showed an immunoglobulin A- (IgA) dominant glomerulonephritis (GN) with subendothelial immune deposits. This is the second biopsy-proven case report of a patient with acute HAV associated with IgA-dominant immune complex glomerulonephritis and nephrotic syndrome. This is perhaps the first case in which a patient experienced both IgA-dominant glomerulonephritis and cutaneous cryoglobulinemic vasculitis.

A comparison between antisense p75NTR oligonucleotides and neurotrophic factors in promoting the survival of postnatal sensory neurons in vitro.

The 75-kDa low-affinity neurotrophin receptor (p75NTR) has been shown in previous reports to mediate neuronal cell death in vitro and in vivo under certain circumstances. Antisense oligonucleotides directed against p75NTR promote the survival of nerve growth factor-deprived dorsal root ganglia sensory neurons in vitro (Barrett, G.; Bartlett, P., Proc. Natl. Acad. Sci. USA 91:6501-6505; 1994) and axotomized dorsal root ganglia sensory neurons in vivo (Cheema, S. S.; Barrett, G. L.; Bartlett, P. F., J. Neurosci. Res. 46:239-245; 1996). In this study we compared the neuroprotective effects of antisense p75NRT oligonucleotides with two neurotrophic factors, namely nerve growth factor (NGF) and leukemia inhibitory factor, on cultured sensory neurons derived from postnatal day 7 and 14 rat dorsal root ganglia. After 3 d in culture, treatment with the neurotrophic factors had significant survival effects on sensory neuron cultures compared to treatment with basal medium (control). However, after 6 and 9 d in culture these rescue effects were not apparent. In contrast, antisense p75NTR oligonucleotides rescued significantly higher numbers of dorsal root ganglia sensory neurons after 6 and 9 d in culture than treatment with neurotrophic factors, sense oligonucleotides, and basal medium. Furthermore, antisense p75NTR oligonucleotides rescued trkA-, B-, and C-expressing neurons, while NGF and leukemia inhibitory factor targeted primarily the trkA-positive neurons. These findings suggest that antisense-based strategies that inhibit gene expression of cytotoxic molecules are more efficient at preventing postnatal sensory neuronal death in vitro than treatment with individual neurotrophic factors.

Induction of endogenous neural precursors in mouse models of spinal cord injury and disease.

Adult neural precursor cells (NPCs) in the mammalian central nervous system (CNS) have been demonstrated to be responsive to conditions of injury and disease. Here we investigated the response of NPCs in mouse models of spinal cord disease [motor neuron disease (MND)] with and without sciatic nerve axotomy, and spinal cord injury (SCI). We found that neither axotomy, nor MND alone brought about a response by Nestin-positive NPCs. However, the combination of the two resulted in mobilization of NPCs in the spinal cord. We also found that there was an increase in the number of NPCs following SCI which was further enhanced by systemic administration of the neuregulatory cytokine, leukaemia inhibitory factor (LIF). NPCs were demonstrated to differentiate into astrocytes in axotomized MND mice. However, significant differentiation into the various neural cell phenotypes was not demonstrated at 1 or 2 weeks following SCI. These data suggest that factors inherent to injury mechanisms are required for induction of an NPC response in the mammalian spinal cord.

Effects of intraperitoneal injection of Rofecoxib in a mouse model of ALS.

There is increasing evidence that inflammatory mechanisms are involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). Inhibition of a key mediator of inflammation, cyclooxygenase 2 (COX-2), represents a promising therapeutic approach in ALS. Here we tested the in vivo effects of a specific COX-2 inhibitor, Rofecoxib, administered by intraperitoneal injection, in the SOD1(G93A G1H) mouse model of the familial form of ALS (fALS). Rofecoxib administration commenced at postnatal day 60 (P60), since the hallmarks of inflammation in the spinal cord were found to occur beyond this time-point in this mouse model of fALS. We found a significant but small delay in the onset of locomotor impairment in mice treated with Rofecoxib at the dose of 10 mg/kg of weight. However, survival was not effected by treatment. As prostaglandin E2 levels in spinal cord or in plasma were not reduced by Rofecoxib treatment, these results may suggest lack of sufficient bioavailability as the reason for the modest clinical changes observed.

Incomplete Freund's adjuvant enhances locomotor performance following spinal cord injury.

Following spinal cord injury (SCI), the pathological sequelae which ensue through the secondary mechanisms of degeneration produce myelin deposits which are potent inhibitors of endogenous neuroregeneration. We have enhanced the immune-mediated response following a hemisection lesion by immunizing adult C57Bl/6 female mice against the inhibitor of neurite outgrowth Nogo-A(623-640) peptide. Moderate anti-Nogo-A(623-640) antibody titre levels were obtained by using Montanide as the adjuvant. However, this antibody response was not obtained using incomplete Freund's adjuvant (IFA). Significant benefit in locomotor performance was demonstrated only in animals which were vaccinated with IFA and not with Montanide. No further benefit could be demonstrated with the Nogo-A(623-640) peptide beyond that seen for adjuvant alone. These data imply that generating antibodies against Nogo-A(623-640) in vivo alone is not sufficient to enhance locomotor recovery and that subcutaneous injection of IFA prior to SCI can enhance locomotor performance.