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D C Anthony

Publications and source records attributed to D C Anthony.

At least 91 records · Page 5Linked to original sources
PubMed1987

Occlusion of the basilar artery within a fracture of the clivus. Case report.

Following a 15-foot fall from a roof, a 70-year-old man became comatose and developed signs of pontine dysfunction. There was a severely comminuted fracture of the distal left femur suggesting that he had landed in an upright position. It was clinically unclear whether the fall was secondary to a pontine infarct; however, an autopsy revealed a fracture of the clivus which had entrapped and occluded the basilar artery, causing death. These findings, and those in similar cases, suggest that this entity results from a force transmitted in an axial direction.

Aged↗
PubMed1985

Covalent crosslinking of neurofilaments in the pathogenesis of n-hexane neuropathy.

These studies test the hypothesis that in n-hexane neuropathy the gamma-diketone metabolite 2,5-hexanedione (2,5-HD) results in covalent crosslinking of neurofilaments via nucleophilic attack on oxidized pyrrole rings formed from the reaction of 2,5-HD with epsilon-amino groups of lysyl residues. The 2,5-HD analogue and gamma-diketone,3,4-dimethyl-2,5-hexanedione (DMHD), was found to result in more rapid pyrrole formation, pyrrole autoxidation, and protein crosslinking when compared with 2,5-HD. DMHD was 20-30 times more potent than 2,5-HD in producing hindlimb paralysis. Following 2,5-HD intoxication the neurofilament filled axonal swellings were found in the distal, subterminal axon. After treatment with DMHD, swellings were present in the proximal axon, similar to those seen after intoxication with beta,beta'-iminodipropionitrile (IDPN). DMHD was proposed as a connecting link between the proximal neurofilamentous axonopathy caused by IDPN and the distal neurofilamentous axonopathies from n-hexane, acrylamide, and carbon disulfide intoxication. [14C]DMHD was found to alkylate nerve protein and to result in polymers of radiolabeled protein too large to pass through nitrocellulose filters with pore sizes as large as 12 nm. An even greater proportion of radiolabeled protein was retained by nitrocellulose filters when DMHD was reacted with nerve in which SCa (slow component a of axonal transport) had been pulse-labeled with [35S] methionine. Radiolabeled nerve proteins acylated with [125I]Bolton-Hunter reagent were minimally retained by nitrocellulose filters, suggesting that filter retention reflects polymerization rather than non-specific adsorption.

Acrylamide↗
PubMed1984

In vitro evidence that covalent crosslinking of neurofilaments occurs in gamma-diketone neuropathy.

We have postulated that the toxic neuropathies associated with neurofilament-filled axonal swellings have a common pathogenesis, the covalent crosslinking of neurofilaments during anterograde transport. The newly described gamma-diketone, 3,4-dimethyl-2,5-hexanedione (DMHD), is a more potent analogue of the toxic metabolite of n-hexane, 2,5-hexanedione. The axonal swellings observed in DMHD toxicity are in the proximal axon, as seen in intoxication with beta, beta'-iminodipropionitrile, rather than in the distal axon, where neurofilamentous swellings are observed in n-hexane, carbon disulfide, and acrylamide neurotoxicity. In these studies, 14C-labeled DMHD and 2-butanone were synthesized and allowed to react with peripheral nerve. Only 14C-labeled DMHD resulted in stable radiolabeled protein polymers, which were retained by nitrocellulose filters with pore sizes as large as 12 microns. More specific evidence for covalent crosslinking of neurofilaments was obtained when DMHD was allowed to react with peripheral nerve in which the neurofilaments had been pulse-labeled with L-[35S]methionine.

Animals↗
PubMed1984

3,4-Dimethyl-2,5-hexanedione impairs the axonal transport of neurofilament proteins.

Accumulations of neurofilaments are observed in a variety of neurological disorders, and their pathogenesis is a fundamental problem of neuropathology. 2,5-Hexanedione (HD) neurotoxicity provides an extensively studied model of axonal neurofibrillary changes in which the pathogenetic mechanisms have been conjectural. Chronic exposure to HD results in neurofilament-filled swellings in the distal regions of large axons of exposed humans and experimental animals. In this report we describe the changes produced by a potent analogue of HD, 3,4-dimethyl-2,5-hexanedione ( DMHD ), in slow axonal transport in the rat sciatic motor axons. Young rats received 0.6 mmol/kg of DMHD for 5 days before [35S]methionine was injected into the lumbar ventral horns. Slow axonal transport of the neurofilament proteins, tubulin, and selected slow component b (SCb) proteins in DMHD -treated animals was compared to the profiles found in age-matched control animals. DMHD administration reduced the rate of transport of the neurofilament proteins 75 to 90%, while tubulin and the SCb proteins were only modestly retarded. No alterations in electrophoretic mobilities of slowly transported proteins were found, nor were any proteins accelerated in transport. These findings were systematically compared to the changes produced by administration of beta,beta'- immino - dipropionitrile (IDPN) (2.0 gm/kg, i.p.), an agent known to impair neurofilament transport. Although slightly less severe, the changes produced by DMHD were nearly identical to those of IDPN. In correlative morphological studies, the neurofilamentous changes were also comparable. The results indicate that DMHD and IDPN share the capacity to interfere selectively with neurofilament transport and thereby share pathogenetic mechanisms. DMHD provides a new agent for exploration of the organization and transport of the neuronal cytoskeleton.

Animals↗
PubMed1983

The effect of 3,4-dimethyl substitution on the neurotoxicity of 2,5-hexanedione. I. Accelerated clinical neuropathy is accompanied by more proximal axonal swellings.

The neurotoxicity of the gamma-diketone, 3,4-dimethyl-2,5-hexanedione, was studied in rats and compared to the known neurotoxicity of the parent compound, 2,5-hexanedione. The test compound was found to be 20 to 30 times more potent on a molar basis than hexanedione. In addition, unlike the distal axonal changes associated with hexanedione, the neurofilamentous swellings following exposure to the dimethyl analog occurred more proximally in the axon, with a preponderance in the anterior horn and lateral tracts of the spinal cord, and in the anterior roots. Since alkyl substitution causes branched-chain compounds to cyclize more rapidly than unbranched analogs, the greater neurotoxicity of the dimethyl compound implicates pyrrole formation in the pathogenesis of n-hexane neuropathy. Furthermore, the location of the axonal swellings induced with 3,4-dimethyl 2,5-hexanedione suggests that there is a common mechanism of injury for the entire class of neurofilament neuropathies, providing a continuum between the intraspinal swellings of beta, beta'-iminodipropionitrile (IDPN) and the distal axonopathies of 2,5-hexanedione, carbon disulfide, and acrylamide. In addition, lower doses of 3,4-dimethyl-2,5-hexanedione for longer periods of time led to a shift in the location of the axonal swellings to include more distal sites. These observations support the hypothesis that covalent crosslinking of the stable neurofilament is the primary event in the molecular pathogenesis of these toxic neuropathies, and that the rate of crosslinking of neurofilaments determines the proximodistal location of the axonal swelling.

Animals↗
PubMed1983

The effect of 3,4-dimethyl substitution on the neurotoxicity of 2,5-hexanedione. II. Dimethyl substitution accelerates pyrrole formation and protein crosslinking.

3,4-Dimethyl-2,5-hexanedione and 2,5-hexanedione were reacted with model amines to yield N-substituted 2,3,4,5-tetramethylpyrroles and 2,5-dimethylpyrroles, respectively. When compared to the unsubstituted parent compound 2,5-hexanedione, 3,4-dimethyl-2,5-hexanedione was found to cyclize approximately eight times as rapidly on a molar basis at 37 degrees C, with an activation energy of 3290 cal/mole less than 2,5-hexanedione. In addition, 1-benzyl-2,3,4,5-tetramethylpyrrole oxidized more readily than 1-benzyl-2,5-dimethylpyrrole with a difference in the half-wave potentials of 0.29 V. Both gamma-diketones led to progressive crosslinking of proteins in vitro, with the dimethyl substitution accelerating this process by a factor of 40. The formation of pyrrolyl derivatives in vivo was demonstrated by the characteristic absorption spectra obtained following reaction of erythrocyte proteins from intoxicated rats with Ehrlich's reagent. There was progressive formation of protein-bound dimethylpyrroles following exposure to 2,5-hexanedione and formation of tetramethylpyrroles following exposure to 3,4-dimethyl-2,5-hexanedione in vivo. Preparations of axonal pads also demonstrated pyrrole derivatization in vivo. In addition, spectrin preparations of erythrocytes from intoxicated rats showed a large amount of high molecular weight protein (400,000 Da), corresponding to dimerized spectrin. Thus, 3,4-dimethyl-2,5-hexanedione, which is 20 to 30 times more potent on a molar basis than 2,5-hexanedione in leading to a neurofilamentous neuropathy, is associated with more rapid pyrrole formation and protein crosslinking in vitro, and it has been demonstrated that these processes occur in vivo. These observations support the hypothesis that pyrrole formation and autoxidation occur following exposure to gamma-diketones, leading to covalent crosslinking of proteins in vivo, a process which may explain the pathogenesis of neurofilament accumulation in these neuropathies.

Animals↗
PubMed1983

The spatio-temporal pattern of the axonopathy associated with the neurotoxicity of 3,4-dimethyl-2,5-hexanedione in the rat.

The neurotoxicity of the gamma-diketone 3,4-dimethyl-2,5-hexanedione(DMHD) was studied to determine the distribution of the neuropathologic changes and the temporal sequence during the intoxication period and following five and 15 weeks of recovery. Intoxication with 3,4-dimethyl-2,5-hexanedione at a daily dose of 0.25 mmoles/kg led to a profound clinical neuropathy, resulting in paralysis of all four limbs after 12-15 days. The cumulative toxic dose for this gamma-diketone was 3-4 mmoles/kg, indicating that dimethyl substitution increased the neurotoxicity of gamma-diketones by a factor of 20-30. The neuropathy was characterized histologically by giant axonal swellings in the proximal axon of the lower motor neuron in a distribution similar to IDPN (beta,beta'-iminodipropionitrile)-neuropathy, with swellings in the anterior horn, intraspinal anterior root, and the proximal anterior root. These swellings developed from six to 12 days of intoxication and were still evident after 15 weeks of recovery. The fact that dimethyl substitution of 2,5-hexanedione accelerated the neuropathy and was characterized by proximal axonal swellings has two important implications: 1) that formation of pyrrole derivatives may be an important step in the pathogenesis of gamma-diketone neuropathies, and 2) that the neurofilament neuropathies may represent a continuum of toxic neuropathies in which the rate of action of the neurotoxin ultimately determines the proximo-distal location of the axonal swellings.

Animals↗
PubMedDate not supplied

Pyrrole oxidation and protein cross-linking as necessary steps in the development of gamma-diketone neuropathy.

It has been well documented that the gamma-diketone HD1 is the ultimate toxic metabolite of n-hexane. Furthermore, it has been shown that the pathogenetic mechanism by which HD exerts its neurotoxic effects is through binding to protein lysly residues and cyclization to pyrroles. The present study sought to determine whether the presence of pyrrole residues on NF1 proteins is sufficient to cause the NF-filled axonal swellings associated with n-hexane and other gamma-diketone neuropathies or whether pyrrole oxidation and protein cross-linking also have to occur in order for neurotoxicity to develop. We synthesized the HD analogue AcHD1 and assessed its rate of pyrrole formation in vitro, the ease of oxidation of its resulting pyrroles, and its ability to cross-link proteins in vitro. The in vivo effects of AcHD on rats were examined following daily ip1 injections. AcHD was found to have a rate of pyrrole formation comparable to that of the potent HD analogue DMHD1 at 35 degrees C. The pyrrole derived from AcHD was more resistant to oxidation than that derived from the neurotoxic compound HD. AcHD did not cross-link proteins in vitro. Pyrrole derivatives were demonstrated on hemoglobin isolated from animals treated with HD, DMHD, and AcHD. Cross-linked spectrin was detected in animals treated with HD and DMHD but not with AcHD. Rats receiving 0.1 or 0.25 mmol of AcHD/kg/day did not reach the end point of hindlimb paralysis observed in the gamma-diketone neuropathies, and the NF-filled axonal swellings seen following exposure to the neurotoxic gamma-diketones were not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Covalent cross-linking of proteins by carbon disulfide.

Carbon disulfide is known to react with amino groups of proteins to generate dithiocarbamates (2). We observed covalent cross-linking of dithiocarbamate-derivatized proteins under physiological conditions which may occur through several mechanisms. Evidence for the structure of these covalent bridges and the reactive intermediate was obtained using 13C NMR spectroscopy in conjunction with specific isotopic labeling. On incubation at 37 degrees C oxidative coupling of dithiocarbamates generated bis(thiocarbamoyl) disulfides (3) which were reduced by cysteine. In addition, an electrophilic isothiocyanate (4) was generated from decomposition of the dithiocarbamate. Nucleophilic addition of sulfhydryl and amine moieties to the isothiocyanate produced dithiocarbamate ester (5) and thiourea linkages (6), respectively. Evidence for the presence of inter- and intramolecular cross-links was obtained using denaturing polyacrylamide gel electrophoresis under reducing conditions. The formation of isothiocyanate in neutral solution, through elimination of sulfhydryl ion, was correlated with increased pKa values of the parent amine of amino acids. Dithiocarbamates derived from terminal amino groups of proteins did not appear to generate isothiocyanate or form thiourea or dithiocarbamate ester. Both the thiourea and the dithiocarbamate ester were stable at reduced pH, whereas in alkaline media the thiourea was stable but dithiocarbamate ester was hydrolyzed. Although the disulfide and ester linkages were formed more rapidly than the thiourea, generation of the latter appeared to be irreversible, leading to its gradual accumulation over a longer period of time. Generation of isothiocyanate by CS2-derived dithiocarbamates and subsequent covalent cross-linking of proteins may provide a molecular mechanism for CS2-induced axonopathy.

Amino Acids↗
PubMedDate not supplied

Bilateral infantile cataractogenesis in a patient with deficiency of complex I, a mitochondrial electron transport chain enzyme.

Progressive bilateral cataracts developed in infancy in a 5-month-old girl with deficiency of complex I, a mitochondrial electron transport chain enzyme. In the newborn period, she had severe lactic acidosis and the diagnosis of complex I deficiency was confirmed by mitochondrial respiratory chain assay on muscle biopsy. By 5 months, she had completely opaque nuclear sclerotic cataracts, with loss of fixation and the red reflex. She underwent bilateral, sequential cataract extraction. The lens aspirate was submitted for cytologic analysis and electron microscopy, which revealed increased intracellular glycogen and swollen mitochondria. To our knowledge the association of complex I deficiency with cataracts in infancy has not been reported previously. The diagnosis of a respiratory chain enzyme defect in infancy is an indication for early ophthalmic evaluation to identify cataracts that may result in visual loss. Conversely, the recognition of cataracts in infants with unexplained neurologic disease or metabolic acidosis may necessitate further evaluation for metabolic etiologies, including mitochondrial disorders.

Acidosis, Lactic↗
PubMedDate not supplied

[The evidence for primary axonal loss in multiple sclerosis].

INTRODUCTION: At what stage in the pathogenesis of multiple sclerosis (MS) does the damage to axons occur, and why should there be any axon loss at all in what is thought to be principally an axon sparing demyelinating disease? A recently described new technique for investigating axon damage depends for its ability on the immunoreactivity of amiloid precursor protein (APP), which has been shown to be more sensitive than silver stains for detecting damaged axons. DEVELOPMENT: We used APP immunoreactivity as a method to investigate whether axon damage occurs in acute MS lesions. The results of our APP staining showed that the expression of APP in MS lesions is associated with acute MS lesions and the active border of less acute lesions. There was little, if any, APP expression in the chronic lesions. If we accept that the APP staining represents irreversible damage to some axons, the next question is what factors are responsible for mediating damage to axons in MS? Matrix metalloproteinases (MMP) are expressed by macrophages in acute MS lesions and in the active borders of active chronic lesions. The injection of highly-purified MMP into the brain results in demyelination, blood-brain barrier breakdown, and axonal loss. Moreover, the inhibition of the MMP activity reduces the severity of MS-like lesions in experimental models. Thus the properties and distribution of these enzymes make them rational targets for therapeutic intervention. CONCLUSION: Whatever mechanism proves to be responsible for axonal damage in MS, it is clear that this disease should, perhaps, be more appropriately recognized as a primary demyelinating entity with associated primary axonal loss.

Acute Disease↗
PubMedDate not supplied

Adult onset Niemann-Pick disease type C presenting with dementia and absent organomegaly.

A 39-year-old female presented to the Bryan Memory Disorders Clinic at Duke University with a 7-year history of an atypical progressive dementia, mildly impaired vertical gaze, dysarthria and mild ataxia. There was no evidence of organomegaly by clinical examination or by radionuclide liver/spleen scan. Brain biopsy disclosed a neuronal storage disorder characterized by ballooned neurons filled with oligo-lamellar cytosomes and lipid droplets. Cultured skin fibroblasts had diminished sphingomyelinase activity and impaired cholesterol esterification, although peripheral leukocyte sphingomyelinase activity was normal. Two years after biopsy, follow-up examination revealed marked progression of vertical gaze paralysis and ataxia. This case expands the clinical spectrum of Niemann-Pick disease type C by presenting in adulthood with subtle neurologic abnormalities; no visceromegaly and profound dementia.

Adult↗
PubMedDate not supplied

Arterial border zone necrosis of the spinal cord.

A 74-year-old man developed necrosis of the spinal cord following an episode of severe hypotension associated with dissection of the aorta. The area of necrosis was confined to the arterial border zone between the anterior and posterior spinal arteries, and involved both gray and white matter symmetrically. The periphery of the cord was spared. Only the lower thoracic cord, which represents a border zone between segmental radicular arteries, was involved. Extensive arterial border zone necrosis was also present in the cerebral cortex and cerebellum. The fact that arterial border zone necrosis is much less common in the spinal cord than in the brain suggests that its development requires a local compromise of the spinal cord circulation in addition to systemic arterial hypotension.

Aged↗
PubMedDate not supplied

In vitro and in vivo studies of the molecular pathogenesis of n-Hexane neuropathy.

In vivo intoxication of rats with 2,5-hexanedione and 3,4-dimethyl-2,5-hexanedione, which results in axonal swellings filled with neurofilaments, has been combined with in vitro exposure of proteins and model amines to the gamma-diketones in attempts to explain the molecular pathogenesis of n-hexane neuropathy and related neurofilament neuropathies. The heretofore untested gamma-diketone, 3,4-dimethyl-2,5-hexanedione is proposed as a "missing link" between beta, beta'-iminodipropionitrile, which produces proximal aggregates of neurofilaments, and 2,5-hexanedione, acrylamide, and carbon disulfide, which result in neurofilament-filled swellings in the distal axon.

Animals↗