Degeneration Of Sciatic Nerve Research Articles

Assessment of 3-nitropropionic acid-evoked peripheral neuropathy in rats: Neuroprotective effects of acetyl- l-carnitine and resveratrol

Oxidative stress and secondary excitotoxicity, due to cellular energy deficit, are major factors playing roles in 3-nitropropionic acid (3-NPA) induced mitochondrial dysfunction. Acute or chronic exposure to 3-NPA also leads to neuronal degeneration in different brain regions. The present study quantitatively assessed peripheral neuropathy induced by chronic exposure to 3-NPA in rats. The neuroprotective abilities of two antioxidants, acetyl- l-carnitine and resveratrol, were investigated as well. Rats were exposed for up to four weeks to 3-NPA alone or 3-NPA combined with acetyl- l-carnitine or resveratrol, administered peripherally. The experimental outcome was evaluated by neurophysiological, histological, and morphometric analyses. Rats exposed to 3-NPA developed hind limb paresis. Furthermore, a significant decrease in motor nerve conduction velocity (MCV) was detected in tail nerves and axonal degeneration in sciatic nerves ( p < 0.05). Treatment with resveratrol prevented the functional effects of 3-NPA exposure, whereas treatment with acetyl- l-carnitine, preventing paresis, was not effective to MCV and morphological changes. These data suggest that resveratrol is a good candidate for treatment of metabolic neuropathy. The experimental outcome of this study shows that chronic treatment with 3-NPA in rats is relevant in development of an experimental model of toxic neuropathy.

2,4-Dinitrophenol Blocks Neurodegeneration and Preserves Sciatic Nerve Function after Trauma

Preventing the harm caused by nerve degeneration is a major challenge in neurodegenerative diseases and in various forms of trauma to the nervous system. The aim of the current work was to investigate the effects of systemic administration of 2,4-dinitrophenol (DNP), a compound with newly recognized neuroprotective properties, on sciatic-nerve degeneration following a crush injury. Sciatic-nerve injury was induced by unilateral application of an aneurysm clip. Four groups of mice were used: uninjured, injured treated with vehicle (PBS), injured treated with two intraperitoneal doses of DNP (0.06 mg DNP/kg every 24 h), and injured treated with four doses of DNP (every 12 h). Animals were sacrificed 48 h post injury and both injured and uninjured (contralateral) sciatic nerves were processed for light and electron microscopy. Morphometric, ultrastructural, and immunohistochemical analysis of injured nerves established that DNP prevented axonal degeneration, blocked cytoskeletal disintegration, and preserved the immunoreactivity of amyloid precursor protein (APP) and Neuregulin 1 (Nrg1), proteins implicated in neuronal survival and myelination. Functional tests revealed preservation of limb function following injury in DNP-treated animals. Results indicate that DNP prevents nerve degeneration and suggest that it may be a useful small-molecule adjuvant in the development of novel therapeutic approaches in nerve injury.

Ameliorative effects of amiloride and pralidoxime in chronic constriction injury and vincristine induced painful neuropathy in rats

The present study was designed to investigate the ameliorative effects of clinically available drugs, with Na +/Ca 2+ and Na +/H + exchange inhibitory actions, in chronic constriction injury and vincristine induced painful neuropathy in rats. Sciatic nerve ligation and vincristine treatment (50 µg/kg for 10 days) was employed to induce neuropathy in rats. Paw pressure, von Frey hair, acetone drop, and tail heat immersion tests were performed to assess degree of mechano-hyperalgesia, mechano-allodynia, cold chemical allodynia and spinal thermal sensation respectively. Axonal degeneration of sciatic nerve was assessed histopathologically. The levels of thio-barbituric acid reactive species, reduced glutathione, and total calcium were determined to assess biochemical alterations. Amiloride (15 mg/kg i.p.), Na +/Ca 2+ and Na +/H + exchange inhibitor, and pralidoxime (20 mg/kg i.p.), Na +/Ca 2+ exchange inhibitor, were administered for 10 consecutive days starting from the day of surgery or vincristine administration. Sciatic nerve ligation and vincristine treatment resulted in significant axonal degeneration, development of mechano-hyperalgesia, mechano-allodynia, cold chemical allodynia and spinal heat hyperalgesia and also resulted in rise in thio-barbituric acid reactive species, total calcium and decrease in reduced glutathione levels. Administration of amiloride and pralidoxime attenuated chronic constriction injury and vincristine induced axonal degeneration and reduction of nociceptive threshold along with reduction in calcium levels and oxidative stress. The observed anti-nociceptive effects of amiloride and pralidoxime may possibly be attributed to inhibition of Na +/Ca 2+ and Na +/H + exchangers with subsequent decrease in Ca 2+ ions and oxidative stress.

Antibody-Drug Conjugates with Uncleavable Linkers for the Treatment of Non-Hodgkin Lymphoma.

Antibody-drug conjugates (ADCs), potent cytotoxic drugs linked to antibodies via specialized chemical linkers, provide a means to increase the effectiveness of chemotherapy by targeting the drug to neoplastic cells while reducing side effects. Our research has focused on ADCs that contain the maytansinoid DM1, monomethylauristatin E (MMAE), or monomethylauristatin F (MMAF), all of which are potent inhibitors of microtubule polymerization. These drugs are attached to the antibody via several different linker formats (Table 1).Table 1Linker-drugLinker MechanismLinked viaDrug Cell PermeablePAB-vc-MC-MMAECleavage of peptide bondCysteineYesMC-MMAFUncleavableCysteineNoSPP-DM1Reduction of disulfide bondLysineYesMCC-DM1UncleavableLysineYesWe identified seven cell surface proteins expressed in non-Hodgkin lymphoma (NHL) with limited expression patterns in normal tissue (CD19, CD20, CD21, CD22, CD72, CD79, and CD180), as potential therapeutic targets for ADCs. ADCs directed to any of these seven targets are effective in xenograft models when containing linkers that can be cleaved in the tumor microenvironment or when internalized by tumor cells. However, ADCs with uncleavable linkers, i.e., linkers that are active when antibody is internalized and degraded within cells, are effective only when targeted to CD22 or CD79b. This suggests that these antigens provide the desired intracellular targeting of the cytotoxic drug. Further, we demonstrated that the uncleavable-linker anti-CD22 and anti-CD79b ADCs result in complete tumor regression with no recurrence in some xenograft models of NHL. In vitro experiments revealed that sensitivity of a given cell line to the ADCs anti-CD22-MCC-DM1 and anti-CD79b-MCC-DM1, correlated more with sensitivity of the cell line to the corresponding free drug, than to the amount of surface expression of the target or the amount of internalized ADC. We conducted pilot safety studies in rats (non-binding species) and cynomolgus monkeys (binding species). In rats, ADCs with uncleavable linkers caused less target-independent hepatic and hematologic toxicity than their counter parts with cleavable linkers, likely due to their decreased systemic release of free drug. Because of these results, we evaluated three ADCs with uncleavable linkers (anti-CD22-MCC-DM1, anti-cynomolgus monkey CD79b-MCC-DM1, and anti-CD22-MC-MMAF) at ∼30 mg/kg q3 weeks for 2 doses in cynomolgus monkeys. Normal B-cells were depleted in circulation and in tissue, particularly in germinal centers of lymphoid tissues; an expected pharmacological effect. Other findings included clinically tolerated and reversible elevations in liver enzymes (MCC-DM1 and MC-MMAF conjugates) and decreases in platelet counts (MCC-DM1 conjugates); and minimal to mild sciatic nerve degeneration (MCC-DM1 conjugates). The data demonstrate that anti-CD22 and anti-CD79b ADCs with uncleavable linkers have potent efficacy in xenograft models of NHL, favorable safety profiles in pilot animal studies, and suggest that for specific targets, uncleavable linkers provide a promising mechanism to improve margins of safety in humans.

Axonal Degeneration Induced by Intraneural Injection of Campylobacter jejuni Antiserum Containing High Titer Anti-GM1 Antibody

Ganglioside-like structures in CAMPYLOBACTER JEJUNI ( C. JEJUNI) lipooligosaccharide (LOS) can induce antiganglioside antibodies, which might cause nerve damage. In this study, we injected the following three antisera directly into the sciatic nerve of guinea pigs, to investigate the role of anti-glycolipids antibody in inducing neural injury: (i) the wild strain antiserum, a mixture of the sera obtained from the guinea pigs immunized with C. JEJUNI wild-type strain (HS:19) that had a high titer anti-GM1 IgG antibody (range: 800-6,400; median: 2,400) and a high titer anti-LOS IgG antibody; (ii) the GALE mutant antiserum, a mixture of the sera obtained from the guinea pigs immunized with the GALE mutant strain that had only a high titer anti-LOS IgG antibody but no anti-GM1 antibody; and (iii) the control antiserum, a mixture of the sera obtained from the guinea pigs immunized with Freund's complete adjuvant alone which had no anti-GM1 or anti-LOS IgG antibody. Pathological examinations showed that the wild strain C. JEJUNI antiserum produced axonal degeneration in sciatic nerves. Demyelination was rare, and no inflammatory cells were present. The pathological features are consistent with those seen in human patients with axonal GBS. No such changes were observed in nerves injected with the GALE mutant antiserum. The experiment showed that passive transfer of serum containing high titer GM1 antibody caused axonal degeneration of peripheral nerves. The result, which reproduced our previous findings in an active immunization study, therefore further confirmed the critical role of the anti-glycolipid antibody in the induction of neuropathy.

Atrophy and degeneration in sciatic nerve of presymptomatic mice carrying the Huntington's disease mutation

Huntington's disease (HD) is a progressive neurological disorder characterised by motor impairments caused by degeneration in the striatum. The mechanism by which the HD mutation leads to the neurodegenerative pathology of HD is still unknown. Recently it was shown that, in HD patients, early pathological changes in white matter precede selective cell death in the striatum. We wondered whether axonal pathology is also an early pathological feature in a transgenic mouse model carrying the HD mutation (R/2 line). R6/2 mice show brain atrophy, a progressive neurological deterioration and skeletal muscle atrophy that resemble those seen in HD patients. However, there is very little neuronal cell loss seen in these animals, even when they show severe symptoms. Here we used sciatic nerve to look for evidence of early neurodegenerative changes in axons of the R6/2 mouse at an ultrastructural level. We observed ultrastructural changes that preferentially affected large myelinated fibres of the sciatic nerve in 10-week-old asymptomatic R6/2 mice. The changes included a significant decrease in the axoplasm diameter of myelinated neurons and an increase in the number of degenerating myelinated fibres compared to age-matched wild type littermates. Myelin thickness and unmyelinated fibre diameter were not affected. The abnormalities described here precede the appearance of overt motor symptoms in the R6/2 mouse and occur in parallel with pathophysiological changes at the neuromuscular junction. We suggest that degenerative changes in axons are likely to contribute to the early pathological phenotype in HD, even in the absence of frank neuronal cell loss.

Experimental axonopathy induced by immunization with Campylobacter jejuni lipopolysaccharide from a patient with Guillain-Barré syndrome

New Zealand white rabbits were immunized with a lipopolysaccharide (LPS) extracted from a Campylobacter jejuni HS:19 strain isolated from a GBS patient expressing GM1 and GD1a-like epitopes, Freund's adjuvant (group I) and Freund's adjuvant plus keyhole lympet hemocyanin (KLH) (group II). Both groups showed high titers of anti-LPS and anti-GM1 and lower titers of anti-GD1b and anti-GD1a antibodies. Weakness and axonal degeneration in sciatic nerves was detected in 1/11 of group I and 6/7 of group II. This model replicates, at least in part, the pathogenetic process hypothesized in the human axonal GBS with antiganglioside antibodies post C. jejuni infection and indicates that KLH plays an additional role in neuropathy induction.

Experimental axonopathy induced by immunization with campylobacter jejuni lipopolysaccharide from a patient with guillain‐barré syndrome

Campylobacter jejuni (C. jejunj) infection is the most common antecedent in the axonal variant of Guillain‐Barré syndrome (GBS). Antibodies against nerve gangliosides found in GBS patients recognize cross‐reactive epitopes in the lipopolysaccharide (LPS) of C. jejuni. This led to the molecular mimicry hypothesis of GBS. We immunized eleven rabbits with a LPS extracted from HS:19 C. jejuni strain isolated from a patient with GBS and complete Freund's adjuvant (CFA)(group I). In a second experiment we immunized seven rabbits with LPS, CFA and keyhole limpet hemocyanin (KLH)(group II). All group I rabbits developed high titers of anti‐LPS, anti‐GM1, anti‐GD1b antibodies and lower titers of anti‐GD1a. One rabbit, 50 days after initial inoculation, showed tremor and weakness. All rabbits of group II developed high titres of antiganglioside antibodies and six animals showed weakness 59–113 days after initial inoculation. Two rabbits died. Pathology showed mild to moderate, tendentially grouped, axonal degeneration in sciatic nerves of four out of five animals. Control rabbits of group I (immunized with CFA only) did not develop antibodies, controls of group II (immunized with CFA + KLH) developed low titers of IgG anti‐GM1. None developed neurological signs or showed axonal degeneration. C. jejuni LPS is a potent B‐cell stimulator capable to induce a strong antiganglioside response in rabbits. However, to induce the neuropathy is crucial to employ KLH, a glycoprotein known to stimulate both humoral and cellular responses. This animal model reproduces the pathogenetic process hypothesized in axonal GBS with antiganglioside antibodies post C. jejuni infection.

Effects of the New Herbicide Fentrazamide on the Glucose Utilization in Neurons and Erythrocytes In Vitro

Treatment of rats with fentrazamide for 2 years at 3000 ppm (males) and 4000 ppm (females) led to an increased incidence and degree of axonal degeneration in sciatic nerve as well as to effects on red blood cells. The mechanism underlying these effects was investigated in vitro using various cell cultures (permanent rodent cell lines from the nervous system, liver, kidney, skeletal and heart muscle and fibroblasts, primary cortical neurons and erythrocytes from the rat). Added to cultured rat cortical neurons for 1 week, fentrazamide considerably decreased glucose consumption, ATP levels and mitochondrial membrane potential and lowered the GSH level, however, it had little impact on viability and neurofilaments and did not induce oxidative stress (ROS) over the first 2 h. After recovery for 1 week, in addition some destruction of neurofilaments had occurred probably secondary to the disturbance of energy production. These effects were prevented by pyruvate. Further studies indicated that fentrazamide primarily inhibited glucose utilization, most likely by interfering with glycolysis. Similar effects were found in erythrocytes treated with fentrazamide over a period of 7 days. Primarily, the glucose consumption was reduced after 1-day treatment, followed by a marked reduction of the energy supply at days 3 and 7. Comparable to the neurons, the GSH level was significantly reduced. A marked hemolysis of the red blood cells was then observed after prolonged treatment. The extensive energy demand and exclusive dependency on glucose utilization of neurons and erythrocytes may explain the specific vulnerability of motor neurons and erythrocytes. When comparing the concentrations necessary for inducing effects in vitro on neuronal cells and erythrocytes to the very low plasma concentrations of fentrazamide in treated rats it is suggested that only a small impact of fentrazamide on the energy status at high doses will occur in vivo. Therefore, aging of the rat as another factor compromising mitochondrial energy production in motor neurons must be considered as additional contribution for the induction of axonal degeneration. It is concluded that this effect of fentrazamide in rats poses no specific risk under the exposure conditions relevant to humans.

Regulation of the expression of peripheral benzodiazepine receptors and their endogenous ligands during rat sciatic nerve degeneration and regeneration: a role for PBR in neurosteroidogenesis

Peripheral benzodiazepine receptors (PBR) and their endogenous ligands, the diazepam-binding inhibitor derived-peptides, are present in Schwann cells in the peripheral nervous system. The aim of this study was to determine the influence of reversible (freeze-injury) and permanent (transection and ligature) nerve lesion on PBR density and on the levels of their endogenous ligands, by autoradiography (using [ 3 H ]PK11195) and radioimmunoassay (using antisera directed against the octadecaneuropeptide (ODN), a diazepam-binding inhibitor fragment). The potential role of PBR on peripheral nerve steroidogenesis, was studied by investigating the effect of specific PBR agonists and antagonists on pregnenolone levels in the sciatic nerve. Sixteen to 30 days after nerve lesion, PBR density and ODN–LI level were highly increased. Their expression returned to normal level when regeneration was completed 60 days after freeze-injury, but remained elevated when regeneration did not occur in transected distal stumps. Reverse-phase HPLC analysis of ODN–LI showed that in control nerve extracts, the major immunoreactive peak co-elutes with triakontatetraneuropeptide (TTN). After freeze-injury, intermediate molecular forms eluting between ODN and TTN were predominant and remained elevated at day 60. The greater accumulation of intermediate forms when regeneration is allowed to occur may indicate a particular role of these forms in axonal elongation and myelination. Ro5–4864, a high affinity PBR agonist increased pregnenolone concentration in the sciatic nerve. This effect was antagonised by PK11195, a high affinity PBR antagonist, which had no effect on pregnenolone basal level, indicating a specific action of PBR in neurosteroid production. These results suggest a role for PBR and their endogenous ligands in peripheral nerve regeneration. A trophic effect could be exerted via stimulation of steroid synthesis.

Activation of ErbB2 during Wallerian Degeneration of Sciatic Nerve

We used anti-phosphopeptide-immunodetecting antibodies as immunohistochemical reagents to define the location and activity state of p185(erbB2) during Wallerian degeneration. Nerve damage induces a phosphorylation event at Y1248, a site that couples p185(erbB2) to the Ras-Raf-MAP kinase signal transduction pathway. Phosphorylation of p185(erbB2) occurs within Schwann cells and coincides in time and space with Schwann cell mitotic activity, as measured by bromodeoxyuridine uptake. These visual images of receptor autophosphorylation link activation of p185(erbB2) to the Schwann cell proliferation that accompanies nerve regeneration.

Impaired myelinated fiber regeneration following freeze-injury in rats with streptozotocin-induced diabetes: involvement of the polyol pathway

This study examined the effects of streptozotocin-induced diabetes mellitus and aldose reductase inhibitor (ZD5522) treatment on myelinated fiber regeneration in rats. After 2 months of diabetes, with or without ZD5522 treatment (10 mg · kg −1 · day −1) from induction, sciatic nerve degeneration was initiated by a punctate lesion using a liquid NZ 2 cooled probe. Regeneration was studied over a subsequent 14-day period using in vitro electrophysiological techniques. There was a 21.4% ( P < 0.001) deficit in the maximum fiber regeneration distance in diabetic rats, 14 days postlesion. This was partially (64.9%, P < 0.01) prevented by aldose reductase inhibitor treatment, the resultant regeneration distance being not significantly different from that of age-matched nondiabetic control rats. The regeneration rate, assessed from data collected 4, 9 and 14 days postlesion, was 23.7% ( P < 0.001) reduced by diabetes and ZD5522 treatment provided 73.1% protection ( P < 0.01). We conclude that polyol pathway activity is involved in impaired regeneration in experimental diabetes, potential pathophysiological mechanisms involving a reduction in neurotrophic support and impaired endoneurial blood supply.

A Lifetime Oncogenicity Study in Rats with Acrylamide

A Lifetime Oncogenicity Study in Rats with Acrylamide. Friedman, M. A., Dulak, L. H., and Stedham, M. A. (1995). Fundam. Appl. Toxicol. 27, 95-105. A lifetime oncogenicity study in Fischer 344 rats was conducted to accurately characterize the carcinogenic potency of acrylamide. Acrylamide was administered in drinking water throughout the 106-week study at concentrations required to provide a dose of 0, 0.1, 0.5, or 2.0 mg/kg/day to males or 0, 1.0, or 3.0 mg/kg/day to females. Complete necropsy and gross pathology examinations were performed on all study animals. Histopathology examinations were conducted on selected tissues of all high-dose and control animals. Selected tissues from intermediate and low-dose groups were subjected to histopathological examinations as required to clarify high- and control-dose group observations. There was no visual observation of neurotoxicity in any study animal but sciatic nerve degeneration was observed in the male and female high-dose groups. Increased mortality related to acrylamide was observed in the high-dose male group from Month 17 to the end of the study and in the high-dose females during Month 24. Mesotheliomas of the testicular tunic were significantly increased in the high-dose male group. The combined incidence of mammary gland adenocarcinomas and fibroadenomas was significantly increased in both acrylamide-dosed female groups. Males and females in the high-dose groups as well as females of the low-dose group had significantly ( p < 0.001) increased thyroid follicular cell adenomas and adenocarcinomas. A variety of other tumor types observed with increased incidence in a previous acrylamide oncogenicity study (i.e., combined CNS glial neoplasms, papillomas of the oral cavity, adenomas of the clitoral gland, and uterine adenocarcinomas) were not observed to be present at increased incidence in this study. This study confirms previously described acrylamide induction of benign tumors of the thyroid and mammary glands as well as mesotheliomas of the testis. By using a larger number of animals with an unbalanced study design, this study showed that acrylamide did not induce glial tumors and demonstrated that the no-observable-effect level for scrotal mesotheliomas is 0.5 mg/kg. It also demonstrated that the increased incidence of mammary tumors was again within historical control ranges.

Elements in the 5' flanking sequences of the mouse low-affinity NGF receptor gene direct appropriate CNS, but not PNS, expression in transgenic mice

We have initiated a characterization of the cis-acting regulatory elements of the murine low-affinity NGF receptor (p75NGFR) gene. Despite studies in cultured cells that suggest the p75NGFR promoter is constitutive, a detailed analysis of this promoter in five lines of transgenic mice demonstrated a high degree of cell-type specificity: 8.4 kb of 5' flanking sequence directs expression of a lacZ reporter to retinal and CNS neurons normally expressing p75NGFR. A transgene with 470 bp of 5' flanking sequence is also expressed in the CNS, but its regulation is aberrant, with a loss of basal forebrain expression. In non-neural tissues, both transgenes were expressed only in the testis, kidney, anterior pituitary, and pancreatic islets; with the exception of the renal pattern of expression, transgene activity was confined to appropriate cells within these tissues. In contrast, although expression of both transgenes was prominent in adrenal medulla and gastrointestinal myenteric neurons, neither construct was active in several sensory or sympathetic ganglia that strongly express the endogenous p75NGFR gene, indicating that genetic elements necessary for expression in these neurons are not present in these promoter sequences. In addition, neither transgene was activated in Schwann cells during Wallerian degeneration of sciatic nerve. We conclude that regulation of the p75NGFR gene is complex, with the first 470 bp of 5' flanking sequence sufficient for expression in enteric and CNS neurons and additional elements within the first 8.4 kb of 5' flanking sequence required for restriction to appropriate CNS neurons. Further regulatory elements are possibly required for expression in at least some sensory and sympathetic neurons in the PNS and in Schwann cells. To identify potential regulatory elements in the 470 bp of 5' flanking sequence from the smaller transgene, we compared the sequences of equivalent regions from the mouse, rat, and human p75NGFR genes. This "phylogenetic footprint" identified conserved motifs potentially important for the regulation of this gene in the CNS.

A Lifetime Oncogenicity Study in Rats with Acrylamide

A lifetime oncogenicity study in Fischer 344 rats was conducted to accurately characterize the carcinogenic potency of acrylamide. Acrylamide was administered in drinking water throughout the 106-week study at concentrations required to provide a dose of 0, 0.1, 0.5, or 2.0 mg/kg/day to males or 0, 1.0, or 3.0 mg/kg/day to females. Complete necropsy and gross pathology examinations were performed on all study animals. Histopathology examinations were conducted on selected tissues of all high-dose and control animals. Selected tissues from intermediate and low-dose groups were subjected to histopathological examinations as required to clarify high- and controldose group observations. There was no visual observation of neurotoxicity in any study animal but sciatic nerve degeneration was observed in the male and female high-dose groups. Increased mortality related to acrylamide was observed in the high- dose male group from Month 17 to the end of the study and in the high-dose females during Month 24. Mesotheliomas of the testicular tunic were significantly increased in the high-dose male group. The combined incidence of mammary gland adenocarcinomas and fibroadenomas was significantly increased in both acrylamide-dosed female groups. Males and females in the high-dose groups as well as females of the low-dose group had significantly (p<0.001) increased thyroid follicular cell adenomas and adenocarcinomas. A variety of other tumor types observed with increased incidence in a previous acrylamide onco genicity study (i.e., combined CNS glial neoplasms, papillomas of the oral cavity, adenomas of the clitoral gland, and uterine adenocarcinomas) were not observed to be present at increased incidence in this study. This study confirms previously described acrylamide induction of benign tumors of the thyroid and mammary glands as well as mesotheliomas of the testis. By using a larger number of animals with an unbalanced study design, this study showed that acrylamide did not induce glial tumors and demonstrated that the no-observable-effect level for scrotal mesotheliomas is 0.5 mg/kg. It also demonstrated that the in creased incidence of mammary tumors was again within historical control ranges.

Differential regulation of S100β and mRNAS coding for S100‐like proteins (42A and 42C) during development and after lesion of rat sciatic nerve

The changes in the levels of S100 beta (a protein that stimulates neurite extension and neuronal survival) and 42A and 42C (S100-like proteins whose mRNAs are induced in PC12 cells by nerve growth factor) during development and after rat sciatic nerve lesions were analyzed. S100 beta, 42A, and 42C mRNAs showed differential regulation during development. S100 beta mRNA was present both in sciatic nerve and brain, and increased more than 11-fold during the first 3 wk of nerve postnatal development. 42A and 42C mRNAs were essentially restricted to sciatic nerve, with little found in either embryonic or adult brain. The levels of 42C and 42A mRNAs in sciatic nerve increased 4- and 14-fold, respectively, by postnatal day 23 compared to postnatal day 2. 42A, 42C, and S100 beta mRNAs also showed a differential regulation during sciatic nerve degeneration and regeneration. Axotomized and control sciatic nerves were examined by Northern blots at various times after a crush or cut injury. 42A and 42C mRNA levels increased rapidly in the distal segment of axotomized nerve, remained two- to five-fold higher than controls at day 14 after injury but returned to control levels by 40 days. In contrast, S100 beta mRNA showed a three-fold decrease in the axotomized nerve between days 1 and 3 after injury, and slowly returned towards control levels over the next few weeks. The decrease in S100 beta mRNA was reflected by a corresponding decrease in S100 beta protein levels. The induction of 42A and 42C mRNAs and repression of S100 beta mRNA remained if nerve regeneration was prevented.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed Wallerian degeneration in sciatic nerves of C57BL/Ola mice is associated with impaired regeneration of sensory axons

Wallerian degeneration is delayed following sciatic nerve crush in C57BL/Ola mice. Compared to C57BL/6J mice, regeneration of sensory axons is significantly slowed in the Ola mice, but reinnervation does eventually occur. We conclude that Wallerian degeneration is a prerequisite for normal sensory axon regeneration following a crush injury to peripheral nerve.

Chronic toxicity and oncogenicity studies of Macrodantin in Sprague-Dawley rats

Chronic toxicity and oncogenicity studies of nitrofurantoin formulated as Macrodantin have been undertaken. The doses ranged from 12 to 116 mg/kg body weight/day. At 116 mg/kg/day, female rats showed a decreased weight gain. In the high-dose groups in the chronic toxicity study (males, 81 mg/kg/day; females, 116 mg/kg/day) there was an increase in testicular degeneration, sciatic nerve degeneration and fibrosis in both males and females, and an increase in focal biliary proliferation in females. There was no evidence of renal toxicity. There was no compound-related effect upon neoplasms at any site. In the oncogenicity study, an increase in focal biliary proliferation was observed in females given 31 or 56 mg/kg/day. There was no treatment-related increase in the incidence of neoplasms at any site. In particular there was no increase in the incidence of mammary or renal tumours. The observations in these studies indicate that therapeutic uses of Macrodantin would not present a carcinogenic hazard to man.

Myelin phagocytosis in Wallerian degeneration. Properties of millipore diffusion chambers and immunohistochemical identification of cell populations.

Myelin phagocytosis in Wallerian degeneration was studied using a model of murine sciatic nerve degeneration in millipore diffusion chambers in the peritoneal cavity of host mice. Immunocytological investigations showed the dependence of myelin digestion on the invasion of Fc-positive, Mac-1-positive and partly Ia-positive monocytes. Lymphocytes did not play a prominent role. Compared to Wallerian degeneration in situ, phagocytosis was decreased in nerves enclosed by millipore membranes on both sides of the chamber. The membrane acted as a trap for invading monocytes/macrophages. Neither tissue integrity nor genetic strain influenced the degree of phagocytosis. A modification of the experimental technique is introduced which permits myelin phagocytosis in the peritoneal cavity in a degree comparable to that in Wallerian degeneration in situ.

Delayed neurotoxicity of O-ethyl O-2,4-dichlorophenyl phenylphosphonothioate: Effects of a single oral dose on hens

Delayed neurotoxicity was produced in hens after the administration of a single oral dose of technical (96.43%) O-ethyl O-2,4-dichlorophenyl phenylphosphonothioate (S-Seven) in a gelatin capsule. Doses ranged from 800 to 5000 mg/kg. Hens given 5000 mg/kg also received atropine sulfate to protect them against acute toxicity. S-Seven caused loss of appetite and weight and resulted in ataxia which progressed in some hens to paralysis and death. Controls consisted of four groups of hens given a single oral dose of 500 mg/kg tri- o-cresyl phosphate (TOCP), 10 mg/kg parathion, 30 mg/kg atropine sulfate, or an empty gelatin capsule. TOCP-Treated hens developed delayed neurotoxicity while those given parathion showed weakness but subsequently recovered. Atropine sulfate and gelatin capsule controls remained normal. Degeneration of axons and myelin in the spinal cord was the most consistent histologic change and was identical to that found in TOCP control hens. Only one hen showed sciatic nerve degeneration. Three groups of hens which were given single oral doses of 100, 200, or 400 mg/kg S-Seven showed no neurologic signs of delayed neurotoxicity and their nerve tissues were not damaged. These results add strong confirmative evidence to the hypothesis that delayed neurotoxicity is a general feature of phenylphosphonothioate insecticides.