Terminal Swelling Research Articles

Inhibiting the activation of enteric glial cells alleviates intestinal inflammation and comorbid anxiety- and depressive-like behaviors in the ulcerative colitis mice

Ulcerative colitis (UC) is a common inflammatory bowel disease with a complex origin in clinical settings. It is frequently accompanied by negative emotional responses, including anxiety and depression. Enteric glial cells (EGCs) are important components of the gut-brain axis and are involved in the development of the enteric nervous system (ENS), intestinal neuroimmune, and regulation of intestinal motor functions. Since there is limited research encompassing the regulatory function of EGCs in anxiety- and depression-like behaviors induced by UC, this study aims to reveal their regulatory role in such behaviors and associated intestinal inflammation. This study applied morphological, molecular biological, and behavioral methods to observe the morphological and functional changes of EGCs in UC mice. The results indicated a significant activation of EGCs in the ENS of dextran sodium sulfate -induced UC mice. This activation was evidenced by morphological alterations, such as elongation or terminal swelling of processes. Besides EGCs activation, UC mice exhibited significantly elevated expression levels of pro-inflammatory cytokines in the peripheral blood, accompanied by anxiety- and depression-like behaviors. The inhibition of EGCs activity within the ENS can ameliorate the anxiety- and depression-like behaviors caused by UC. Our data suggest that UC and its resulting behaviors may be related to the activation of EGCs within the ENS. Moreover, the modulation of intestinal inflammation through inhibition of EGCs activation emerges as a promising clinical approach for alleviating UC-induced anxiety- and depression-like behaviors.

A New Species of Photonectes from the Pacific Ocean off Oahu, Hawaii with a Revised Identification Key for the Genus (Teleostei: Stomiidae: Melanostomiinae)

A new species of scaleless black dragonfish, Photonectes klepadloae, new species, is described on the basis of a single specimen collected in the central north Pacific Ocean off the Hawaiian Islands. The new species is readily distinguished from all congeners by the postorbital organ shifted forward to below eye, by the presence of the blue luminous tissue on the body arranged in two widely spaced interrupted lines between IV photophores and a streak-like patch on each side above 10th to 12th PV photophores, and by the structure of the mental barbel lacking a bulb, but having the long unpigmented distal appendage without a terminal swelling, and a pair of enlarged stalked photophore-like structures on the distal extremity of the stem. A revised key of the known species of Photonectes is presented.

Influence of injected interstitials on the void swelling in two structural variants of 304L stainless steel induced by self-ion irradiation at 500 °C

Two variants of AISI 304L stainless steel (SS) with different grain size distributions were ion irradiated at 500°C to a peak dose of ∼60dpa. In the coarse-grained annealed variant, a peak swelling of ∼12% was observed closer to the specimen surface rather than at the depth of peak displacement damage. The forward shift in depth between peak swelling and peak dose is proposed to be a consequence of suppression of void nucleation by injected interstitials. The swelling behavior in the front portion of the ion range mirrors that of neutron-induced swelling in this steel, exhibiting significant curvature with increasing dose as the swelling rate approaches the terminal swelling rate of 1%/dpa. An ultrafine grain variant of this steel produced by severely plastic deformation exhibits a similar suppression of void nucleation in the injected interstitial region, but also shows a significantly extended transient regime, not reaching the terminal swelling rate by 60dpa.

FIRST REPORT OF CLADOSPORIUM OXYSPORUM CAUSING LEAF SPOT OF ROSA INDICA IN PAKISTAN

In December 2014, necrotic leaf spots were observed on more than fifty rose ( Rosa indica ) plants in a private garden at Lahore, Pakistan, all showing the same symptoms The infected plants were 1-2 year old and on an average 90% of the leaves were covered with 2-5 mm circular black spots, with irregu- lar margins without chlorosis around the margins. Initially, infected leaves remained attached to the plants but dropped when the spots coalesced and covered more than 80% leaf area. No symptoms were observed on flowers. For pathogen isolation, one spot per leaf from six symptomatic leaves of dif- ferent plants were cut into pieces, surface sterilized, inoculated on 2% malt extract agar (MEA) and incubated at 25 ± 2oC. Morphological observations were made on 7-day-old pure cul- tures. Colonies were greenish black and attained the diameter of 4 mm. Conidiophores were macronematous, smooth walled, up to 500μm long and 4-5μm wide, with intercalary and termi- nal swellings. Conidia were pale brown arising from terminal swelling of conidiophores, in the form of simple or branched chains. Conidia were spherical, subspherical or limoniform, 3-6 μm in diameter; ramoconidia were 2-4×7-3 μm in size. A representative pure culture of the fungus was deposited to First Fungal Culture Bank of Pakistan under the accession No.FCBP1517. Based on morphology, the fungus was identi- fied as Cladosporium oxysporum (Bensch et al ., 2010). For se- quencing of ITS region, a DNA fragment of ca . 600 bp was amplified using universal primer pair ITS1/ITS4 and total ge- nomic DNA as template. BLASTn results indicated that ITS nucleotide sequence of this strain (KT283681) had 99% simi- larity with many other isolates of C . oxysporum in GenBank, including KT936546, LC040920, KJ475816 and JQ775499. Pathogenicity test was performed three times on young pot- ted rose plants using two different isolates. Since the inoculum of this fungus persists in soil, conidia from pure cultures were suspended in sterilized water (10 7 spores/ml) and sprayed in the soil of three healthy plants; three control plants were treated similarly with sterilized water. All plants, covered with poly- thene bags, were kept in a growth chamber at 23 ± 2oC. Ne- crotic spots similar to those described above started appearing on leaves only on inoculated plants after 21 days of incubation. Re-isolation of same fungus fulfilled Koch’s postulates. To our knowledge, this is the first report of R . indica leaf spot caused by C . oxysporum in Pakistan.

Efficacy of a type of endotracheal tube of extended with terminal swelling and resistance bending pressure for airway management during mechanical ventilation in children in prone position

Objective To evaluate the efficacy of a type of endotracheal tube of extended with terminal swelling and resistance bending pressure for airway management during mechanical ventilation in children in prone position. Methods Sixty pediatric patients with cerebral palsy of both sexes, aged 3-7 yr, weighing 11-23 kg, of American Society of Anesthesiologists physical statusⅠor Ⅱ, scheduled for elective selective functional posterior rhizotomy, were randomly allocated into 2 groups (n=30 each) using a random number table: endotracheal tube of extended with terminal swelling and resistance bending pressure group (group E) and reinforced tracheal tube group (group C). After induction of anesthesia, the type of endotracheal tube of extended with terminal swelling and resistance bending pressure was inserted in group E, and the reinforced endotracheal tube was inserted in group C. The tidal volume, minute ventilation, dynamic lung compliance, arterial oxygen saturation and end-tidal pressure of carbon dioxide in pressure-controlled ventilation mode were recorded in the two groups.Tube shedding caused by using of the extended tube was recorded during operation.Blood samples were collected from the femoral artery for blood gas analysis. Results Compared with group C, the tidal volume and minute ventilation were significantly increased (P 0.05). Compared with the value before anesthesia, no significant change was found in pH value, arterial oxygen partial pressure and partial pressure of arterial carbon dioxide at the end of operation in the two groups (P>0.05). In group C, the extended tube was used in 3 patients, and among the 3 cases, one patient developed tube shedding which was treated immediately. Conclusion The type of endotracheal tube of extended with terminal swelling and resistance bending pressure provides better efficacy than the reinforced endotracheal tube when used for airway management during mechanical ventilation in children in prone position. Key words: Intubation, intratracheal; Respiration, artificial; Prone position; Child

Altered active zones, vesicle pools, nerve terminal conductivity, and morphology during experimental MuSK myasthenia gravis.

Recent studies demonstrate reduced motor-nerve function during autoimmune muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG). To further understand the basis of motor-nerve dysfunction during MuSK-MG, we immunized female C57/B6 mice with purified rat MuSK ectodomain. Nerve-muscle preparations were dissected and neuromuscular junctions (NMJs) studied electrophysiologically, morphologically, and biochemically. While all mice produced antibodies to MuSK, only 40% developed respiratory muscle weakness. In vitro study of respiratory nerve-muscle preparations isolated from these affected mice revealed that 78% of NMJs produced endplate currents (EPCs) with significantly reduced quantal content, although potentiation and depression at 50 Hz remained qualitatively normal. EPC and mEPC amplitude variability indicated significantly reduced number of vesicle-release sites (active zones) and reduced probability of vesicle release. The readily releasable vesicle pool size and the frequency of large amplitude mEPCs also declined. The remaining NMJs had intermittent (4%) or complete (18%) failure of neurotransmitter release in response to 50 Hz nerve stimulation, presumably due to blocked action potential entry into the nerve terminal, which may arise from nerve terminal swelling and thinning. Since MuSK-MG-affected muscles do not express the AChR γ subunit, the observed prolongation of EPC decay time was not due to inactivity-induced expression of embryonic acetylcholine receptor, but rather to reduced catalytic activity of acetylcholinesterase. Muscle protein levels of MuSK did not change. These findings provide novel insight into the pathophysiology of autoimmune MuSK-MG.

Effects of calcium on rhizotoxicity and the accumulation and translocation of copper by grapevines

We assessed the effects of background concentrations of calcium (Ca) in solution on rhizotoxicity of copper (Cu) in and the accumulation and translocation of Cu by the grapevine, Vitis vinifera L. var. Kyoho. Grapevine cuttings in a hydroponic system were exposed to Cu-spiked solutions (0, 1, 2.5, 5, 10, and 25 μM) with two Ca backgrounds (0.5 and 5 mM) for 15 days. We found that when Cu exposure exceeded 5 μM, no new white roots were generated from the cuttings. When exposed to a Cu concentration of 25 μM, the lateral roots were sparse, appeared dark and exhibited malformed terminal swellings. The morphological phenomena of root response to an increase in Cu levels were relatively pronounced at a background concentration of 5 mM Ca; epidermal cell walls thickened, cortical cells remained intact and root terminal swelling was enhanced with Cu exposure. A 5 mM Ca background concentration enhanced the reduction in relative root elongation, but alleviated the reduction in relative root dry weight with increased Cu exposure. Moreover, there was a prominent increase in root Cu concentrations with increased Cu exposure, but the increases in leaf Cu concentrations were much less. The Cu profile of Cu exposure in a 5 mM Ca background concentration appeared higher in root, but lower in leaf than the Cu profile in a 0.5 mM Ca background; therefore, increase of Ca background concentrations would enhance Cu to be accumulated by root, but not translocated into the leaf.

Swelling and creep observed in AISI 304 fuel pin cladding from three MOX fuel assemblies irradiated in EBR-II

Three 37-pin MOX-fueled experimental subassemblies were irradiated in EBR-II with fuel pin cladding constructed from annealed AISI 304 stainless steel. Analysis of the swelling and irradiation creep of the cladding showed that the terminal swelling rate of AISI 304 stainless steel appears to be ∼1%/dpa and that swelling is very reproducible for identical irradiation conditions. The swelling at a given neutron fluence is rather sensitive to both irradiation temperature and especially to the neutron flux, however, with the primary influence residing in the transient regime. As the neutron flux increases the duration of the transient regime is increased in agreement with other recent studies. The duration of the transient regime is also decreased by increasing irradiation temperature. In these assemblies swelling reached high levels rather quickly, reducing the opportunity for fuel pin cladding interaction and thereby reducing the contribution of irradiation creep to the total deformation. It also appears that in this swelling-before-creep scenario that the well-known “creep disappearance” phenomenon was operating strongly.

Observations at the CNS–PNS Border of Ventral Roots Connected to a Neuroma

Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. However, no study with a focus on how such sprouts behave when they reach the border between the central and peripheral nervous system (CNS–PNS border) has been published. In this study we have in detail examined the CNS–PNS border of ventral roots in kittens with light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS–PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury. Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS–PNS border.

The pertinence between the concentrations of seminal leptin and genital endocrine hormones and the effect of leptin on spermatic function

Objective To explore the pertinence between the concentrations of seminal leptin (lep) and genital endocrine hormones, such as testosterone(T), follicle stimulating hormone( FSH), luteotropic hormone(LH) and insulin growth factor-1 (IGF-1), as well as the effect of Lep on sperm concentration,motility and genital function indexes.Methods 126 cases of infertility and 30 cases of normal fertility were randomly chosen.The contents of Lep, T, FSH and LH were detected by radioimmunoassay (RIA) and the IGF-1 content were detected by immunoradiometric assay (IRMA).The infertility group was divided into group A (sperm count ≥ 20×109 /L), group B (sperm count ＜ 20×109 /L) and group C of azoospermia.According to the number of white blood cell ( WBC ) in 10 high power fields (HPF), the infertility group was further divided into group WBC (WBC count ≥ 1×109 /L) and group Non-WBC(WBC count ＜ 1×109 /L).According to the sperm vitality and the rate of motility, group A was subdivided into the group of normal spermatic vitality (a + b≥50% ), the group of abnormal vitality( a + b ＜ 50% ) (a refers to the number of sperms with fast forward movement, and b refers to the number of sperms with slow or sluggish forward movement), the group of normal rate of spermatic motility( the rate ≥60% ) and the group of decreased rate of motility( the rate ＜60% ).According to the examination results of the normal contrast group, group A and group B were respectively divided into the following groups: the group of normal sperm penetrating power(≥40 mm), the group of decreased penetrating power( ＜ 40 mm), the group of normal intact acrosome rate(≥80% ), the group of decreased intact acrosome rate( ＜ 80% ), the group of normal terminal swelling rate( ≥60% ) and the group of decreased terminal swelling rate( ＜60% ).Results The concentration of Lep in the infertility group was (2.77±0.80) μg/L, significantly higher than the level of Lep [ (1.14 ± 0.31 ) μg/L ] in the contrast group ( t = 10.943,P ＜ 0.05 ).The contents of IGF-1 and T were ( 17.67±8.09) μg/L and (4.84±2.15) nmol/L respectively, significantly lower than the levels of IGF-1 [(24.79±9.32) μg/L] and T [(6.30±2.53) nmol/L] in the contrast group (t =4.205,3.228,P＜0.01).There existed no significant differences of the concentrations of FSH and LH between the two groups ( t = 1.655,1.378 ,P ＞ 0.05 ).The concentrations of FSH and LH were (32.61±9.14) U/L and (40.57 ± 12.40) U/L respectively in the infertility group and(29.63±7.56) U/L and (37.25±9.19) U/L respectively in the contrast group.The concentrations of Lep and IGF-1 and T showed negative correlation in the infertility group (r = -0.237, -0.316,P ＜ 0.01 ).The concentration of Lep had no correlation to the FSH and LH concentration (r = 0.104, 0.112, P ＞ 0.05 ).The concentration of Lep showed a gradual increase within group A, group B and group C (F = 115.93, P ＜ 0.01 ).The leptin contents in the above mentioned normal subgroups were found to be lower than the abnormal groups.Conclusions There exists pertinence between the Lep concentration and the concentrations of TGF-1, T, FSH and LH.Lep may decrease the sperm density and inhibit sperm vitality and the motility rate through inhibiting androgen secretion and sperm capacitation. Key words: Infertility, male; Sperm motility; Semen; Leptin; Testosterone; Follicle stimulating hormone

Very high swelling and embrittlement observed in a Fe–18Cr–10Ni–Ti hexagonal fuel wrapper irradiated in the BOR-60 fast reactor

The highest void swelling level ever observed in an operating fast reactor component has been found after irradiation in BOR-60 with swelling in Kh18H10T (Fe–18Cr–10Ni–Ti) austenitic steel exceeding 50%. At such high swelling levels the steel has reached a terminal swelling rate of ∼1%/dpa after a transient that depends on both dpa rate and irradiation temperature. The transient duration at the higher irradiation temperatures is as small as 10–13 dpa depending on which face was examined. When irradiated in a fast reactor such as BOR-60 with a rather low inlet temperature, most of the swelling occurs above the core center-plane and produces a highly asymmetric swelling loop when plotted vs. dpa. Voids initially harden the alloy but as the swelling level becomes significant the elastic moduli of the alloy decreases strongly with swelling, leading to the consequence that the steel actually softens with increasing swelling. This softening occurs even as the elongation decreases as a result of void linkage during deformation. Finally, the elongation decreases to zero with further increases of swelling. This very brittle failure is known to arise from segregation of nickel to void surfaces which induces a martensitic instability leading to a zero tearing modulus and zero deformation.

Void nucleation, growth, and coalescence in irradiated metals

A novel computational treatment of dense, stiff, coupled reaction rate equations is introduced to study the nucleation, growth, and possible coalescence of cavities during neutron irradiation of metals. Radiation damage is modeled by the creation of Frenkel pair defects and helium impurity atoms. A multi-dimensional cluster size distribution function allows independent evolution of the vacancy and helium content of cavities, distinguishing voids and bubbles. A model with sessile cavities and no cluster–cluster coalescence can result in a bimodal final cavity size distribution with coexistence of small, high-pressure bubbles and large, low-pressure voids. A model that includes unhindered cavity diffusion and coalescence ultimately removes the small helium bubbles from the system, leaving only large voids. The terminal void density is also reduced and the incubation period and terminal swelling rate can be greatly altered by cavity coalescence. Temperature-dependent trapping of voids/bubbles by precipitates and alterations in void surface diffusion from adsorbed impurities and internal gas pressure may give rise to intermediate swelling behavior through their effects on cavity mobility and coalescence.

Sutterella parvirubra sp. nov. and Megamonas funiformis sp. nov., isolated from human faeces

Three strains of anaerobic, non-spore-forming, Gram-negative coccobacilli (YIT 11816T, YIT 11817 and YIT 11818) were isolated from human faeces. On the basis of 16S rRNA gene sequence similarity, these strains were shown to belong to the family Alcaligenaceae and to be related to the type strain of Sutterella stercoricanis (94.9 %) and to Sutterella wadsworthensis WAL 7877 (94.3 %); the similarity to strains of any other species with a validly published name within the family Alcaligenaceae was less than 92 %. Biochemical data supported the affiliation of these strains to the genus Sutterella. These strains therefore represent a novel species, for which the name Sutterella parvirubra sp. nov. is proposed; the type strain is YIT 11816T (=DSM 19354T =JCM 14724T). The cells of another isolate, strain YIT 11815T, were non-spore-forming, Gram-negative, very large rods, 1x5-200 microm in size, with or without a central, subterminal or terminal swelling of 2-4 microm diameter when grown in a broth medium supplemented with glucose. Based on comparative 16S rRNA gene sequencing, this bacterium is a member of the family Acidaminococcaceae, and most closely related to Megamonas hypermegale (95.3 % similarity to the type strain). Interestingly, the 16S rRNA gene sequence of strain YIT 11815T showed 99 % similarity to sequences of uncultured colonic bacteria. A 16S rRNA gene sequence divergence value of >3 % from known cultured species suggested that isolate YIT 11815T represents a novel species, for which the name Megamonas funiformis sp. nov. is proposed; the type strain is YIT 11815T (=DSM 19343T =JCM 14723T).

A role for caveolin‐1 in post‐injury reactive neuronal plasticity

Remodeling and plasticity in the adult brain require cholesterol redistribution and synthesis for the formation of new membrane components. Caveolin-1 is a cholesterol-binding membrane protein involved in cellular cholesterol transport and homeostasis. Evidence presented here demonstrates an up-regulation of caveolin-1 in the hippocampus, which was temporally correlated with an increase in synaptophysin during the reinnervation phase in a mouse model of hippocampal deafferentation. Using an in vitro model of neuronal reactive plasticity, we examined the effect of virally mediated overexpression of caveolin-1 on injured differentiated PC12 cells undergoing terminal remodeling. Three days post lesion, caveolin-1-overexpressing cells revealed increases in synaptophysin and GAP-43, two markers of neurite sprouting and synaptogenesis. Morphologically, caveolin-1-overexpressing cells showed a decrease in primary neurite outgrowth and branching as well as an increase in neurite density. Caveolin-1-overexpressing cells also revealed the presence of terminal swelling and beading along processes, consistent with a possible alteration of microtubules stability. Moreover, a focal enrichment of caveolin-1 immunofluorescence was observed at the bases of axonal and dendritic terminals of mouse primary hippocampal neurons. Altogether, these results indicate that caveolin-1 plays an active role in the regulation of injury-induced synaptic and terminal remodeling in the adult CNS.

Morphometric characterization of the neuromuscular junction of rodents intoxicated with 2,4-dithiobiuret: evidence that nerve terminal recycling processes contribute to muscle weakness

2,4-Dithiobiuret (DTB) causes ascending motor weakness when given chronically to rodents. In muscles of animals with DTB-induced weakness, quantal release of acetylcholine (ACh) is impaired. We examined in detail the structural changes that occurred at neuromuscular junctions and their associated Schwann cells of extensor digitorum longus (EDL) muscles of male rats treated with DTB to the onset of muscle weakness, 5–8 days. Our objective was to assess the involvement of the Schwann cells and to determine the most likely primary targets of DTB. At the onset of muscle weakness, nerve terminals exhibited some enlarged regions, but did not sprout. Terminal Schwann cells became flatter and expanded to cover most of the endplate. The extent of invasion of the synaptic cleft by Schwann cell processes was not significantly different from controls; extension of Schwann cell sprouts away from the junction was not seen. Thus, the morphology of the Schwann cells, although clearly affected by DTB, does not suggest that they contribute directly to the physiological defects of DTB-treated terminals. Abnormal tubulovesicular structures or tangles of neurofilaments were clustered in the centers of about 25% of treated terminals. Fewer synaptic vesicles occupied the region opposite the postsynaptic folds. Vesicle volumes were variable and included some very large vesicles, corresponding with the variable MEPP amplitudes reported previously for terminals of DTB-treated rodents. The postsynaptic area stained by rhodamine-labeled α-bungarotoxin expanded with terminal swelling, apparently by unpleating of the postsynaptic folds. No loss of ACh receptors or spread of ACh receptors beyond terminal boundaries was detected. Morphometric data are consistent with the conclusion that DTB affects, either directly or indirectly, vesicular release of ACh and the subsequent vesicular recycling process.

Primary cilia in vertebrate corneal endothelial cells.

The presence of primary cilia in corneal endothelial cells of a range of species from six non-mammalian vertebrate classes (Agnatha, Elasmobranchii, Amphibia, Teleostei, Reptilia and Aves) is examined by scanning and transmission electron microscopy. Our aim is to assess whether these non-motile cilia protruding into the anterior chamber of the eye are a consistent phylogenetic feature of the corneal endothelium and if a quantitative comparison of their morphology is able to shed any new light on their function. The length (0.42-3.80 microm) and width (0.12-0.44 microm) of the primary cilia varied but were closely allied with previous studies in mammals. However, interspecific differences such as the presence of a terminal swelling in the Teleostei and Amphibia suggest there are functional differences. Approximately one-third of the endothelial cells possess cilia but the extent of protrusion above the cell surface varies greatly, supporting a dynamic process of retraction and elongation. The absence of primary cilia in primitive vertebrates (Agnatha and Elasmobranchii) that possess other mechanisms to control corneal hydration suggests an osmoregulatory and/or chemosensory function.

Neuropathology of Skin Denervation in Acrylamide-Induced Neuropathy

Previous studies have established the neurotoxicity and pathology of acrylamide to large-diameter nerves. It remains unclear (1) whether small-diameter sensory nerves are vulnerable to acrylamide and (2) if so, how the pathology evolves during intoxication. We investigated the influence of acrylamide on small-diameter sensory nerves by studying the pathology of sensory nerve terminals in the skin. The neurotoxic effects of acrylamide (400 ppm in drinking water) on mice were assessed by immunostaining the skin with protein gene product 9.5, a ubiquitin C-terminal hydrolase, particularly useful for demonstrating cutaneous nerve terminals. Within 5 days of acrylamide administration (the initial stage), epidermal nerves showed two major changes: (1) terminal swelling and (2) increased branching. There was a progressive reduction in epidermal nerve density (END) thereafter. Fifteen days after acrylamide intoxication (the late stage), reduction in END became evident (25.22 ± 2.19 fibers/mm vs 41.74 ± 2.60 fibers/mm in control mice, P < 0.003). At this stage, there was significant dermal nerve degeneration with ultrastructural demonstrations of vacuolar changes. These findings establish the pathological consequences of acrylamide neurotoxicity in cutaneous sensory nerves with far-reaching implications: (1) providing an animal system to study “dying-back” pathology of nociceptive nerves and (2) forming the ultrastructural foundation for interpreting the pathology of cutaneous nerve degeneration in skin biopsies.

Nerve Terminals as the Primary Site of Acrylamide Action: A Hypothesis

Acrylamide (ACR) is considered to be prototypical among chemicals that cause a central–peripheral distal axonopathy. Multifocal neurofilamentous swellings and eventual degeneration of distal axon regions in the CNS and PNS have been traditionally considered the hallmark morphological features of this axonopathy. However, ACR has also been shown to produce early nerve terminal degeneration of somatosensory, somatomotor and autonomic nerve fibers under a variety of dosing conditions. Recent research from our laboratory has demonstrated that terminal degeneration precedes axonopathy during low-dose subchronic induction of neurotoxicity and occurs in the absence of axonopathy during higher-dose subacute intoxication. This relationship suggests that nerve terminal degeneration, and not axonopathy, is the primary or most important pathophysiologic lesion produced by ACR. In this hypothesis paper, we review evidence suggesting that nerve terminal degeneration is the hallmark lesion of ACR neurotoxicity, and we propose that this effect is mediated by the direct actions of ACR at nerve terminal sites. ACR is an electrophile and, therefore, sulfhydryl groups on presynaptic proteins represent rational molecular targets. Several presynaptic thiol-containing proteins (e.g. SNAP-25, NSF) are critically involved in formation of SNARE (soluble N-ethylmaleimide (NEM)-sensitive fusion protein receptor) complexes that mediate membrane fusion processes such as exocytosis and turnover of plasmalemmal proteins and other constituents. We hypothesize that ACR adduction of SNARE proteins disrupts assembly of fusion core complexes and thereby interferes with neurotransmission and presynaptic membrane turnover. General retardation of membrane turnover and accumulation of unincorporated materials could result in nerve terminal swelling and degeneration. A similar mechanism involving the long-term consequences of defective SNARE-based turnover of Na +/K +-ATPase and other axolemmal constituents might explain subchronic induction of axon degeneration. The ACR literature occupies a prominent position in neurotoxicology and has significantly influenced development of mechanistic hypotheses and classification schemes for neurotoxicants. Our proposal suggests a reevaluation of current classification schemes and mechanistic hypotheses that regard ACR axonopathy as a primary lesion.

Cutaneous nerve degeneration induced by acrylamide in mice

Acrylamide is a neurotoxin producing distal axonopathy. Previous studies mainly focused on large-diameter motor and sensory nerves, and the influences of acrylamide neurotoxicity on small-diameter sensory nerves in the skin remained elusive. We investigated skin innervation in mice intoxicated by acrylamide. Small-diameter sensory nerves in the skin degenerated after acrylamide intoxication. Epidermal nerve swelling was the earliest sign of acrylamide intoxication, with 29.5±2.4% of swollen epidermal nerves in the initial stage ( P<0.001). There was a trend of progressive loss of epidermal nerves with a significantly reduced epidermal nerve density in the late stage ( P<0.003). In the mean time, degenerating dermal nerves exhibited a beaded appearance. These results suggest the scenario of small-diameter cutaneous nerve degeneration in acrylamide neurotoxicity: beginning with epidermal nerve terminal swelling in the initial stage and resultant epidermal nerve depletion in the late phase.

Mechanism responsible for the formation of focal swellings on injured neuronal processes using a novel in vitro model of axonal injury

A novel in vitro model of axonal injury using PC12 cells was designed to introduce traumatic alterations on neuronal processes and to identify mechanisms responsible for the formation of focal swellings by observation with phase-contrast and transmission electron microscopes. The injury on the processes was developed by one-dimensional, horizontal oscillation. Phase-contrast microscopic observation on the injured processes showed their terminal increase in diameter. Long term observation of cellular responses to the mechanical insult disclosed that the terminal swelling coincided with the detachment of growth cones from the culture plate. The finding suggests that the detachment of the growth cone would destroy a cytoskeletal network, which determines and maintains the cell shapes, and then cause the spherical deformation of the processes. Ultramicroscopically, the processes with terminal swellings regenerated the growth cones by the cytoskeletal reconstruction.