Rodent Nervous System Research Articles

Transganglionic Neuropeptide Y Response to Sciatic Nerve Injury in Young and Aged Rats

Gracile neuroaxonal dystrophy (NAD) is a hallmark of the aging human and rodent sensory nervous systems which may represent an abnormal transganglionic response to peripheral axonal injury. To examine the structural plasticity of central dorsal root ganglia (DRG)-derived axons in the gracile nucleus, we evaluated the response of the lumbar DRG and their central projections to sciatic nerve injury in young and old rats. In uninjured rats neither the DRG nor its central projections contained histochemical immunoreactivity for neuropeptide Y (NPY). However, within 1 week of sciatic nerve crush or transection injury, NPY immunoreactivity appeared in the lumbar DRG and its central projections, reaching an apparent maximum in number and intensity of processes at 28 days. Neuropeptide Y immunoreactivity was more intense and sustained in response to transection compared to crush injury, results supported by NPY radioimmunoassay. Neuropeptide Y-immunoreactive processes in the gracile nuclei of axotomized young animals consisted of delicate axons or slightly enlarged profiles that may represent regenerative elements. Lumbar dorsal rhizotomy performed simultaneously with sciatic nerve transection prevented the transganglionic NPY response. Dystrophic axons in the gracile nucleus of non-lesioned aged animals were not NPY-immunoreactive; however, after sciatic nerve transection, NPY immunoreactivity developed in both delicate axons and markedly swollen dystrophic elements, a finding confirmed by ultrastructural immunolocalization. These results establish that despite the presence of NAD in DRG projections to aged gracile nuclei these elements remain capable of a plastic NPY response to peripheral nerve injury.

Resistance to nitroprusside neurotoxicity in perinatal rat brain

Nitric oxide (NO) may mediate some of the toxic effects of the excitatory amino acid (EAA) glutamate when there is overactivation of the N- methyl- d-aspartate (NMDA) receptor. In the developing rodent nervous system, NMDA neurotoxicity peaks at postnatal day 7. To assess whether NO toxicity exhibits a similar developmental profile, we injected the NO generator sodium nitroprusside into the immature and adult rodent hippocampal formation and striatum, using a dose known to damage the adult nervous system. Contrary to our expectations, we found the immature brain highly resistant to the toxic effects of sodium nitroprusside.

Localization of CNTF immunoreactivity to neurons and astroglia in the CNS

Species specific antibodies were raised to a peptide of rat ciliary neurotrophic factor (CNTF — amino acids number 131–147). Following affinity purification, these antibodies were used to determine the pattern of CNTF immunoreactivity in adult rat and mouse brain, spinal cord, and sciatic nerve. Alternate sections stained using neurofilament and the affinity purified anti-CNTF antibody (HARC-1) demonstrate that CNTF immunoreactive neurons are present within the facial nucleus, dentate gyrus, olfactory bulb, basal forebrain, locus coeruleus, cortex and substantia nigra. In addition, neurons throughout the hippocampus, and Purkinje cells within the cerebellum also exhibit CNTF immunoreactivity. CNTF immunopositive neurons demonstrate a preponderance of nuclear staining, with some staining present in the cytoplasm. Alternate sections incubated with glial fibrillary acidic protein (GFAP) antibody also demonstrate glia which are positive for CNTF. In the peripheral nervous system, Schwann cells of the sciatic nerve exhibit strong immunoreactivity for CNTF, however staining is confined to the cytoplasm and is absent from the cell nucleus. These data demonstrate that CNTF immunoreactivity is broadly distributed throughout neurons and glia of the adult rodent nervous system.

Neu and its ligands: from an oncogene to neural factors.

Transmembrane receptor tyrosine kinases that bind to peptide factors transmit essential growth and differentiation signals. A growing list of orphan receptors, of which some are oncogenic, holds the promise that many unknown ligands may be discovered by tracking the corresponding surface molecules. The neu gene (also called erbB-2 and HER-2) encodes such a receptor tyrosine kinase whose oncogenic potential is released in the developing rodent nervous system through a point mutation. Amplification and overexpression of neu are thought to contribute to malignancy of certain human adenocarcinomas. The search for soluble factors that interact with the Neu receptor led to the discovery of a 44 kDa glycoprotein that induces phenotypic differentiation of cultured mammary tumor cells to growth-arrested and milk-producing cells. The Neu differentiation factor (NDF or heregulin), however, also acts as a mitogen for epithelial, Schwann and glial cells. Multiple forms of the factor are produced by alternative splicing and their expression is confined predominantly to the central and to the peripheral nervous systems. One identified neuronal function of this family of polypeptides is to control the formation of neuromuscular junctions, but their physiological role in secretory epithelia is still unknown. Other open questions relate to the transmembrane topology of various precursors, the identity of a putative coreceptor, the possible existence of additional ligands of Neu and the functional significance of the interaction between Neu and at least three highly related receptor tyrosine kinases.

Distribution and expression of SNAP-25 immunoreactivity in rat brain, rat PC-12 cells and human SMS-KCNR neuroblastoma cells

Immunocytochemical, immunoblotting and in situ hybridization studies were used to map the distribution of SNAP-25 protein and mRNA in the rodent nervous system. These experiments demonstrated that subsets of neurons expressed SNAP-25, and that several patterns of expression emerged: SNAP-25 expression in caudate nucleus was initially concentrated in axons, which subsequently was localized in presynaptic regions of these axons. Other regions, typified by neocortex, showed developmental increases and persistent adult neuronal immunoreactivity for SNAP-25. Finally, olfactory bulb contained neurons which initially expressed SNAP-25, but lost expression during maturation. Additional studies in cultured human and rat cell lines derived from neural crest suggested that SNAP-25 is expressed in such lines, but not in glial or fibroblast lines. Differentiation of rat PC-12 cells with nerve growth factor failed to alter steady-state levels of SNAP-25 protein; similar responses were seen in human SMS-KCNR neuroblastoma cells differentiated using retinoic acid. The presence of SNAP-25 in presynaptic regions of numerous neuronal subsets and in neural crest cell lines suggests that this protein subserves an important function in neuronal tissues.

Localization of the aplysia epitope A1–186 in rodent nervous system

Localization of the aplysia epitope A1–186 in rodent nervous system

An Analysis of Mast Cell Frequency in the Rodent Nervous System: Numbers Vary between Different Strains and Can Be Reconstituted in Mast Cell-Deficient Mice

There is evidence that nervous system mast cells may play a role in the pathogenesis of the experimental autoimmune demyelinating diseases, experimental allergic neuritis (EAN), and experimental allergic encephalomyelitis (EAE). We compared mast cell numbers in the peripheral nervous system (PNS) and central nervous system (CNS) of rodent strains that differed in their susceptibility to experimental demyelination. Mast cells were counted by toluidine blue staining of formalin-fixed tissue. Normal Lewis rats (susceptible to both EAN and EAE) had significantly greater numbers of mast cells in the dura mater (about 6x) of the meninges and the sciatic nerve (3x) than Brown Norway rats (resistant to EAE and EAN induction under normal circumstances). Similarly SJL/J mice (susceptible to EAE and EAN) had significantly greater numbers of CNS (3x) and PNS (8x) mast cells than C3H mice (more resistant to disease induction). Other mouse strains were also examined, and PNS mutant Trembler mice had high numbers of PNS mast cells, while the mast cell deficient W/Wv mice contained no detectable mast cells in either the CNS or PNS. Reconstitution of W/Wv mast cells was accomplished by intravenous injection of bone marrow cells from congenic littermates. After seven months, mast cells could be seen in both the CNS and PNS of reconstituted animals. The possibility that mast cells and mast cell precursors can migrate into the nervous system of animals, in the absence of inflammatory disease, may have implications for their role in the pathogenesis of experimental demyelinating diseases.

Pharmacokinetics of 2-nitroimidazole Hypoxic Cell Radiosensitizers in Rodent Peripheral Nervous Tissue

The concentrations of seven 2-nitroimidazoles--including misonidazole, etanidazole (SR-2508), pimonidazole (Ro 03-8799), desmethylmisonidazole (Ro 05-9963), RK28, RP170, and KU2285--were measured in the sciatic nerves of C3H/He mice using reverse-phase high-performance liquid chromatography. Drug exposure to the peripheral nervous system was highest for misonidazole, followed by desmethylmisonidazole, etanidazole, pimonidazole and RK28. The lower drug exposure of pimonidazole and RK28 seemed to be related to their lower hydrophilicity. The apparent biological half-lives of the compounds in the peripheral nerves were correlated to their hydrophilicity: the more hydrophilic the compound, the longer the apparent biological half-life in the peripheral nervous tissue of the mice. Measurement of drug exposure in the rodent peripheral nervous system, rather than in the brain, was a better indicator for estimating the occurrence of clinical peripheral neuropathy by 2-nitroimidazoles.

Carbonic anhydrase activity in the trigeminal primary afferent neuronal cell bodies with peripheral axons innervating tha mandibular molar tooth pulps of the rat

Trigeminal primary afferent neuronal cell bodies were labeled with FITC-WGA retrogradely transported from the mandibular molar tooth pulp (tooth pulp) and the cutaneous branch of the mylohyoid nerve (cutaneous nerve) in the rat. Tissue sections were then incubated in Hansson's medium for histological demonstration of carbonic anhydrase (CA) activity. About 85% of primary neurons innervating the tooth pulp had medium to large cell bodies (⩾ 300 μm 2 in cross-sectional area), while 77% of those innervating the cutaneous nerve were small (< 300 μm 2). A total of 32% of the tooth pulp cells exhibited CA activity. CA-containing cells constituted only about 4% of the cutaneous nerve cells. In view of the known distribution of CA within the rodent nervous system, the CA-containing cells are considered to represent the tooth pulp primaries conducting in A-beta velocity range and projecting to rostral subdivisions of the brainstem sensory trigeminal nuclear complex.

Molecular cloning of a neuron-specific transcript and its regulation during normal and aberrant cerebellar development.

PEP-19 is a brain-specific polypeptide whose levels increase dramatically during the late maturation of the rodent nervous system. By using immunocytochemistry, PEP-19 is shown to be localized to several regions of the central nervous system, notably cerebellum, thalamus caudate putamen, and olfactory bulb. We have isolated a 0.5-kilobase cDNA clone that encodes the entire PEP-19 protein sequence, making this one of the smallest primary transcripts and translation products ever identified in eukaryotes. The cDNA was used to investigate the developmental expression of PEP-19 in rodent brain. PEP-19 mRNA rises from low levels at embryonic day 17 of gestation in the rat to a plateau value by day 18 postpartum. This mirrored the levels of the protein determined by radioimmunoassay. Since the rise coincided with the formation of synaptic contacts onto Purkinje cells (a major site of PEP-19 expression), the hypothesis was tested that the activity and/or presence of afferent input modulated PEP-19 expression. Parallel fiber innervation was disrupted either by killing granule cells with the cytostatic agent methylazoxymethanol or by examining PEP-19 levels in cerebellar granuloprival mutant mice (reeler and weaver). The influence of climbing fiber input was assessed by either eliminating them with 3-acetylpyridine or stimulating them with harmaline in both neonatal and mature rats. None of the above altered PEP-19 gene expression in cerebellum, leading us to propose that the signals triggering the PEP-19 gene do not emanate from granule cells or neurons in the olivary nucleus. However, preliminary evidence suggests that PEP-19 is under posttranscriptional regulation.

Transplacental initiation of liver, lung, neurogenic, and connective tissue tumors by N-nitroso compounds in mice

Epidemiological studies have implicated nitroso compounds as possible causative agents for human childhood cancers, including those of neurogenic orgin. Published evidence from animal models, which is reviewed in this report, indicates that capacity for metabolic activation of nitrosamines is limited in rodent fetuses and that nitrosamines are correspondingly weak transplacental carcinogens. The C3H mouse fetus, however, has both moderate capability for activation of N-nitrosodimethylamine (NDMA) and proven susceptibility to transplacental causation of neurogenic tumors by a nitrosourea. We tested whether NDMA could act as a transplacental carcinogen in the C3H mouse, and whether it or N-nitrosodiethylamine (NDEA) would initiate neurogenic tumors. N-Nitrosoethylurea (NEU) served as positive control. C3H HeNCr MTV − pregnant mice were treated ip on Gestation Day 16 or 19 with NDMA (0.1 mmol, 7.4 mg/kg, maximum nonfetotoxic dose), NDEA (0.5 mmol, 51 mg/kg), or NEU (0.4 mmol, 47 mg/kg). NDMA had significant transplacental carcinogenic effects, resulting in an increase in percentage female offspring with hepatocellular carcinomas and in average number of liver tumors after treatment on either gestational day, compared with controls. In the males there was a significant increase in numbers of liver tumors and carcinomas following Day 19 exposure. An increase in incidence of histiocytic and undifferentiated sarcomas was also of statistical significance. There was no change in number of pulmonary tumors. One intracranial schwannoma resulted. NDEA had no effect when given on Gestation Day 16, but caused a significant increase in liver and lung tumor numbers in both sexes when treatment was on Day 19. NEU induced the expected high incidence of lung tumors, significantly increased liver tumor incidence in females (Day 19 exposure), and produced schwannomas in 14 and 35% of the offspring after Days 16 or 19 treatment, respectively. The results show that NDMA at even a low dose had significant transplacental carcinogenic effects, including one schwannoma, which was most unlikely to have occurred spontaneously. However, this single neurogenic tumor contrasts with the absence of similar neoplasms in mice exposed transplacentally to NDEA, in view of the generally greater efficiency of ethylating agents as carcinogens for the nervous system in rodents. These data thus neither conclusively support nor refute the hypothesis that nitrosamines may initiate neurogenic tumors in fetuses.

Transplacental Initiation of Liver, Lung, Neurogenic, and Connective Tissue Tumors by N-Nitroso Compounds in Mice

Transplacental Initiation of Liver, Lung, Neurogenic, and Connective Tissue Tumors by N-Nitroso Compounds in Mice. ANDERSON, L. M., HAGIWARA, A., KOVATCH, R. M., REHM, S., AND RICE, J. M. (1989). Fundam. Appl Toxicol. 12, 604–620. Epidemiological studies have implicated nitroso compounds as possible causative agents for human childhood cancers, including those of neurogenic origin. Published evidence from animal models, which is reviewed in this report, indicates that capacity for metabolic activation of nitrosamines is limited in rodent fetuses and that nitrosamines are correspondingly weak transplacental carcinogens. The C3H mouse fetus, however, has both moderate capability for activation of N-nitrosodimethylamine (NDMA) and proven susceptibility to transplacental causation of neurogenic tumors by a nitrosourea. We tested whether NDMA could act as a transplacental carcinogen in the C3H mouse, and whether it or N-nitrosodiethylamine (NDEA) would initiate neurogenic tumors. N-Nitrosoethylurea (NEU) served as positive control. C3H/HeNCr MTV− pregnant mice were treated ip on Gestation Day 16 or 19 with NDMA (0.1 mmol, 7.4 mg/kg, maximum nonfetotoxic dose), NDEA (0.5 mmol, 51 mg/kg), or NEU (0.4 mmol, 47 mg/kg). NDMA had significant transplacental carcinogenic effects, resulting in an increase in percentage female offspring with hepatocellular carcinomas and in average number of liver tumors after treatment on either gestational day, compared with controls. In the males there was a significant increase in numbers of liver tumors and carcinomas following Day 19 exposure. An increase in incidence of histiocytic and undifferentiated sarcomas was also of statistical significance. There was no change in num ber of pulmonary tumors. One intracranial schwannoma resulted. NDEA had no effect when given on Gestation Day 16, but caused a significant increase in liver and lung tumor numbers in both sexes when treatment was on Day 19. NELl induced the expected high incidence of lung tumors, significantly increased liver tumor incidence in females (Day 19 exposure), and produced schwannomas in 14 and 35% of the offspring after Days 16 or 19 treatment, respectively. The results show that NDMA at even a low dose had significant transplacental carcino genic effects, including one schwannoma, which was most unlikely to have occurred spontaneously. However, this single neurogenic tumor contrasts with the absence of similar neoplasms in mice exposed transplacentally to NDEA, in view of the generally greater efficiency of ethylat ing agents as carcinogens for the nervous system in rodents. These data thus neither conclusively support nor refute the hypothesis that nitrosamines may initiate neurogenic tumors in fetuses.

Immunocytochemical localization of carbonic anhydrase in myelinated fibers in peripheral nerves of rat and mouse.

Rat sciatic nerve, spinal root, and cranial nerve were immunostained with an antibody against rat brain carbonic anhydrase II (ca), to determine the localization of ca in the rat peripheral nervous system (PNS). Similar methods were applied to mouse nerves to see if that antigen could be detected in the PNS of this species. In rat nerves, intense immunostaining was observed in the axoplasm of many of the myelinated fibers, whereas others were stained less intensely or were negative. A heterogeneous pattern of immunostaining was also found in neuronal perikarya within the ganglia, and in some regions of the ganglia ca immunostaining was found in putative satellite cells and their processes. Ca in rat PNS therefore appears to occur at both neuronal and glial sites, whereas it is exclusively glial in the CNS. In longitudinal sections of some fibers within rat nerves, ca immunostaining could be detected at the inner boundaries of the myelin sheaths. In mouse nerves, axoplasmic staining was observed but it was fainter than in rat nerves. Interspecies differences were most obvious in the dorsal columns of the spinal cord. In rat, intensely stained axons proceeded through the roots into the gracilis or cuneate and often into the gray matter. In mouse, there was much less immunostaining of axons but more intense ca immunostaining in CNS myelin than in the CNS myelin in the rat cord. The implications concerning putative functions of ca in the rodent nervous system are discussed.

Immunocytochemical localization of coated vesicle protein in rodent nervous system.

Immunocytochemistry has been used to study the distribution of the major 180,000-mol wt protein of coated vesicles in rodent cerebellum. An antibody to the coat protein was prepared in rabbits and characterized by immunodiffusion and immunofixation of polyacrylamide gels. At the light microscope level the protein was primarily localized in punctate profiles surrounding Purkinje cells and within the cerebellar glomeruli. At the electron microscope level the punctate distribution was confined to presynaptic terminals of basket and Golgi II neurons as well as mossy fiber terminals of the glomeruli. This label was heaviest on the lattice coat of coated vesicles but, in addition, label was found within the presynaptic axoplasm and along the cytoplasmic surface of the plasmalemma. Coated vesicles in cell somata were labeled as well as the cytosol around groupings of these vesicles. These data suggest that there may be two forms (or more) of coated vesicle protein in neurons, a lattice form associated with coated vesicles and a soluble form associated with the cytoplasmic matrix.

Effects of nerve growth factor administration on N-ethyl-N-nitrosourea carcinogenesis

We attempted to determine whether the sympathetic nervous system in rodents is susceptible to co-carcinogenesis, employing murine salivary nerve growth factor (NGF) as a co-carcinogenic agent. NGF had no co-carcinogenic effect with either methylcholanthrene or ethylnitrosuorea (ENU) on the sympathetic nervous system of the mouse, whether administered transplacentally, postnatally, or both transplacentally and postnatally. At a dose of ENU of 30 μg/g body weight, NGF did not shorten the latent period for tumor induction of BD-IX rats. In contrast, a 25% reduction in latent period was brought about by NGF for tumor appearance in BD-IX rats receiving 90 μg/g ENU. In both cases the frequency of urogenital tumors in rats was increased as a result of NGF administration, at the apparent expense of neural tumors.

Influence of ionizing radiations on the development of the nervous system

SUMMARYThe first cellular differentiation in the process of segmentation leads to the embryonic period, the major organogenetic period for the nervous system. In man, it appears between the second and the eighth week after conception.During the foetal and perinatal periods, the nervous organization mainly develops at the cerebellum and cerebral cortex levels. The cerebrum functional maturation continues well beyond birth.Neuroblasts are the most widespread mother-cells in the developing nervous system during the embryonic period, but some are still to be found after birth.Animal experiment has demonstrated that ionizing radiations were able to disorganize neurogenesis in any of its maturation stages, even at very low doses. It is possible to establish a chronological table showing the anatomical or functional deformities in relation with the embryonic age at which rays have been given.It appears that in man the most dangerous period is between the beginning of the second and the end of the eighth week after conception. At that moment, pregnancy is often ignored and a dose of 20 to 40 r is sufficient to entail serious damages, such as microcephaly, protrusions of the brain or mental retardation. On drawing near to birth the foetal or neonatal nervous system of rodents or primates is still radiosensitive, especially at the cerebral cortex level and the consequences will be of a neurophysiologic or psychosensorial nature. Certain embryopathies or neurologic alterations would only be apparent in subsequent generations, following mutations induced into the mother-cells of the nervous system. Genetic deformities of the nervous system can also result from moderate irradiations of the gonads.Further to the precise experimental research work on the radiovulnerability of the embryonic or foetal nervous system of the animal, certain clinical observations are presented, which lead to similar conclusions.The atomic bombardments have caused numerous neurological trouble among the children who had been irradiated in utero. And the genetic effects are not yet perfectly known to-date.This set of experimental and clinical data must prompt us to be very careful when using ionizing radiations, even at low doses, in pregnant women and newborn.