Inhibition of rat testicular nuclear kinesins (krp2; KIFC5A) by acrylamide as a basis for establishing a genotoxicity threshold.

Acrylamide is a toxic substance that induces a variety of cellular responses including neurotoxicity, male reproductive toxicity, tumorigenicity, clastogenicity, and DNA alkylation. Evidence is provided that inhibition of the microtubule motor protein kinesin is responsible for acrylamide-induced clastogenicity and aneuploidy. Two kinesin motors, KIFC5A and KRP2, which are responsible for spindle assembly and disassembly of kinetochore MT, respectively, are inhibited by acrylamide.

Chronic, intermittent exposure to chlorpyrifos in rats: protracted effects on axonal transport, neurotrophin receptors, cholinergic markers, and information processing.

Persistent behavioral abnormalities have been commonly associated with acute organophosphate (OP) pesticide poisoning; however, relatively little is known about the consequences of chronic OP exposures that are not associated with acute cholinergic symptoms. In this study, the behavioral and neurochemical effects of chronic, intermittent, and subthreshold exposures to the OP pesticide, chlorpyrifos (CPF), were investigated. Rats were injected with CPF s.

Acrylamide effects on kinesin-related proteins of the mitotic/meiotic spindle.

The microtubule (MT) motor protein kinesin is a vital component of cells and organs expressing acrylamide (ACR) toxicity. As a mechanism of its potential carcinogenicity, we determined whether kinesins involved in cell division are inhibited by ACR similar to neuronal kinesin [Sickles, D.W.

Chlorpyrifos, chlorpyrifos-oxon, and diisopropylfluorophosphate inhibit kinesin-dependent microtubule motility.

Diisopropylfluorophosphate, originally developed as a chemical warfare agent, is structurally similar to nerve agents, and chlorpyrifos has extensive worldwide use as an agricultural pesticide. While inhibition of cholinesterases underlies the acute toxicity of these organophosphates, we previously reported impaired axonal transport in the sciatic nerves from rats treated chronically with subthreshold doses of chlorpyrifos. Those data indicate that chlorpyrifos (and/or its active metabolite, chlorpyrifos-oxon) might directly affect the function of kinesin and/or microtubules--the principal proteins that mediate anterograde axonal transport.

Repeated exposures to subthreshold doses of chlorpyrifos in rats: hippocampal damage, impaired axonal transport, and deficits in spatial learning.

Organophosphorus (OP) compounds are detectable in the environment for years after use and endanger many populations. Although the effects of acutely toxic doses of many OP compounds are well described, much less is known about repeated low-level exposures. The purpose of these studies was to further evaluate potential toxicological effects of the extensively used OP pesticide chlorpyrifos (CPF) in rats.

Fast axonal transport: a site of acrylamide neurotoxicity?

The cellular and molecular site and mode of action of acrylamide (ACR) leading to neurotoxicity has been investigated for four decades, without resolution. Although fast axonal transport compromise has been the central theme for several hypotheses, the results of many studies appear contradictory. Our analysis of the literature suggests that differing experimental designs and parameters of measurement are responsible for these discrepancies.

Neurofilaments are nonessential to the pathogenesis of toxicant-induced axonal degeneration.

Axonal neurofilament (NF) accumulations occur before development of symptoms and before other pathological changes among idiopathic neurodegenerative diseases and toxic neuropathies, suggesting a cause-effect relationship. The dependence of symptoms and axonal degeneration on neurofilament accumulation has been tested here in a transgenic mouse model (Eyer and Peterson, 1994) lacking axonal NFs and using two prototypic toxicant models. Chronic acrylamide (ACR) or 2,5-hexanedione exposure resulted in progressive and cumulative increases in sensorimotor deficits.

Neurofilaments are non-essential elements of toxicant-induced reductions in fast axonal transport: pulse labeling in CNS neurons.

Acrylamide (ACR) and g-diketones (g-DK) produce distal sensory-motor neuropathy in a variety of species, including humans. The specific molecular site and mechanism of toxicant action leading to specific morphological and behavioral abnormalities requires definition. The relative roles of fast anterograde axonal transport and neurofilaments (NF) are investigated using optic nerves of mice, with and without axonal neurofilaments.

Axonal neurofilaments are nonessential elements of toxicant-induced reductions in fast axonal transport: video-enhanced differential interference microscopy in peripheral nervous system axons.

Neurofilament modification and accumulation, occurring in toxicant-induced neuropathies, has been proposed to compromise fast axonal transport and contribute to neurological symptoms or pathology. The current study compares the effects of the neurotoxicants acrylamide (ACR) and 2,5-hexanedione (2,5-HD) on the quantity of fast, bidirectional vesicular traffic within isolated mouse sciatic nerve axons from transgenic mice lacking axonal neurofilaments (Eyer and Peterson, Neuron 12, 1-20, 1994) and nontransgenic littermates possessing neurofilaments. Fast anterograde and retrograde membrane bound organelle (MBO) traffic was quantitated within axons, before and after toxicant exposure, using video-enhanced differential interference contrast (AVEC-DIC) microscopy.

Vascular recruitment increases evidence of lung injury.

Objective: Changes in pulmonary blood flow rate can alter the size of the perfused pulmonary capillary surface area. We tested the hypothesis that full recruitment of the pulmonary vascular bed may decrease evidence of lung injury by recruiting less injured capillaries. We also tested the hypothesis that endothelial ectoenzyme activity is an earlier indicator of lung injury than are permeability measures.

Direct effect of the neurotoxicant acrylamide on kinesin-based microtubule motility.

Acrylamide (ACR) is an environmental toxicant and prototypic tool for studying mechanisms of peripheral neuropathies. Reductions in fast anterograde axonal transport (faAXT) are thought to be a critical step leading to axonal degeneration. Kinesin and microtubules (MT) were evaluated as molecular sites of action using an in vitro MT motility assay.

Decreased GAP-43 accumulation in neurite tips of cultured hippocampal neurons by acrylamide.

The critical axonopathy- producing effect of acrylamide (ACR) is hypothesized to be an interruption of fast vesicular transport resulting in a deficiency of distal axonal proteins. This study used the accumulation of growth associated protein- 43 (GAP-43) in neurite tips of cultured hippocampal neurons as a model to examine the effect of an ACR block of fast transport on the eventual protein concentration within the distal axon. Twenty-four hour incubation with ACR produced a dose-dependent reduction with 0.

Acrylamide arrests mitosis and prevents chromosome migration in the absence of changes in spindle microtubules.

Cultured HT 1080 fibrosarcoma cells were exposed to acrylamide (ACR), an industrial neurotoxicant that disrupts neuronal intracellular transport, to determine if mitosis (another microtubule-based intracellular transport system) was adversely affected. The number of cells arrested in mitosis increased, in a concentration-dependent manner, from 1 to 10 mM acrylamide. A 4-h exposure to 10 mM acrylamide increased the mitotic index by 4.

Toxic axonal degeneration occurs independent of neurofilament accumulation.

Alteration of neurofilament (NF) proteins is considered a critical component and a causative factor for a number of neuropathologies, especially certain neurotoxicities. Correlative observations have supported this hypothesis; the current study tests this relationship by exposure of neurotoxicants to crayfish, a species lacking NFs. Morphological and immunological tests verified the absence of NFs in crayfish peripheral nerve axons.

Toxic neurofilamentous axonopathies and fast axonal transport. V. Reduced bidirectional vesicle transport in cultured neurons by acrylamide and glycidamide.

Fast axonal transport deficiencies as mechanisms of action of acrylamide in producing axonal degeneration are under evaluation. The current study determines the effects of acrylamide and several analogues on the number of vesicles moving within the neurite processes of cultured rat embryonic neurons. Acrylamide produced severe, concentration-dependent (0.

Toxic neurofilamentous axonopathies and fast anterograde axonal transport. IV. In vitro analysis of transport following acrylamide and 2,5-hexanedione.

Recent investigations into the mechanisms of neurotoxicity of acrylamide and gamma-diketones have demonstrated reductions in the delivery of radiolabelled proteins to the distal axon. To differentiate a toxicant-induced compromise in the capacity of the fast anterograde axonal transport system from a neuron cell body processing effect, selective exposure of either the L5 dorsal root ganglion or sciatic nerve to 0.7 mM acrylamide (ACR) or 4 mM 2,5-hexanedione (2,5-HD) was performed during in vitro transport.

Toxic neurofilamentous axonopathies and fast anterograde axonal transport. III. Recovery from single injections and multiple dosing effects of acrylamide and 2,5-hexanedione.

Fast anterograde axonal transport has been advanced as a potential site of action of acrylamide (ACR) and the neurotoxic gamma-diketones in producing nerve degeneration. The segmental analysis method of axonal transport was used to measure the rate and quantity of protein transport in the rat sciatic nerve from 1 to 24 hr after a single injection of 50 mg/kg (0.7 mmol/kg) ACR or 4 mmol/kg 2,5-hexanedione (2,5-HD).

Effects of neurofilamentous axonopathy-producing neurotoxicants on in vitro production of ATP by brain mitochondria.

The site and mode of action of acrylamide (ACR), gamma-diketone hexacarbons and 3',3'-iminodipropionitrile (IDPN) in producing a neurofilamentous axonopathy are unknown. Whether the neuropathy is caused by reduction in axonal transport produced by energy depletion is under investigation. Reductions in the quantity of proteins fast transported following a single dose of ACR or neurotoxic gamma-diketones have been reported.

Toxic neurofilamentous axonopathies and fast anterograde axonal transport. I. The effects of single doses of acrylamide on the rate and capacity of transport.

Acrylamide (ACR) produces a neuropathy in the central and peripheral nervous systems characterized by neurofilament-containing swellings in the distal nerve and eventual dying-back degeneration of axons. The effects of a single exposure to ACR on the rate and quantity of protein transported in the rat sciatic nerve has been measured to determine whether fast axonal transport is compromised by this toxicant. Using the segmental analysis of radioactive label of proteins following 3H-leucine injections into the DRG, ACR (50-100 mg/kg) significantly reduced the rate of fast anterograde transport by 9.

Toxic neurofilamentous axonopathies and fast anterograde axonal transport. II. The effects of single doses of neurotoxic and non-neurotoxic diketones and beta, beta'-iminodipropionitrile (IDPN) on the rate and capacity of transport.

The site and mode of action of neurotoxic chemicals producing neurofilamentous axonopathies has been speculated to be the axonal transport system. The current study determined the effects of neurotoxic and non-neurotoxic gamma-diketones as well as beta, beta'-iminodipropionitrile (IDPN) upon both the rate and quantity of protein transported in the fast anterograde component of the rat sciatic nerve. 2,5-Hexanedione (2,5-HD), given as 4, 6 and 8 mmoles/kg single ip injections reduced the rate of transport by 18.

Enzyme activity changes in rat soleus motoneurons and muscle after synergist ablation.

Quantitative enzyme histochemical methods have been used to determine the effect of ablation of synergists on the oxidative metabolism of the alpha-motoneurons and muscle fibers of the rat soleus. Sixty days postablation, the NADH-tetrazolium reductase (NADH-TR) activity of soleus motoneurons decreased 12.5% from 0.

Hyperthyroidism selectively increases oxidative metabolism of slow-oxidative motor units.

The effects of thyroid hormone on the NADH-tetrazolium reductase activity (oxidative metabolism marker) of soleus (slow-oxidative) and tensor fascia lata (fast-glycolytic) motoneurons were determined and compared with changes in a variety of enzyme activities in the corresponding muscle fibers. Histochemical assays have demonstrated a selective and qualitative conversion in muscle fiber ATPase and quantitative increases of NADH-tetrazolium reductase (oxidative) and mitochondrial alpha-glycerophosphate dehydrogenase (glycolytic) activities in the soleus muscle. Paralleling the selective action upon the soleus slow muscle fibers was a selective central nervous system effect of thyroid hormone on oxidative enzymes of soleus slow-oxidative motoneurons.

Carbohydrate, lipid and oxidative metabolism in the sympathetically aneural chick heart.

Ablation of premigratory trunk neural crest over somites 10 through 20 gives rise to chick hearts which lack sympathetic innervation. Norepinephrine, the neurotransmitter of the postganglionic sympathetic nerves, increases the rate of formation of cyclic AMP (cAMP) in cells. Cyclic AMP the modulator of certain key enzymes of metabolism, was decreased in sympathetically-aneural hearts.

Neural specificity of acrylamide action upon enzymes associated with oxidative energy-producing pathways. I. Histochemical analysis of NADH-tetrazolium reductase activity.

The mechanism by which acrylamide (ACR) produces a distal neurofilamentous axonopathy has not been determined. Our investigations are focused upon the effects of this toxicant on energy transformations; more specifically, on enzymes of oxidative metabolism. The current study determines the effects of ACR on NADH-tetrazolium reductase (TR) activity (composite of primarily lipoamide and NADH dehydrogenases) in a variety of neural and non-neural tissues in order to test for a correlation between the neural specificity of enzyme inhibition with specific neurotoxicity.