Thomas W. Bouldin

Immunocytochemical and ultrastructural studies of Werdnig-Hoffmann disease

SummaryNeuronal alterations in two cases of Werdnig-Hoffmann disease (WH) were investigated immunocytochemically and ultrastructurally. Ballooned neurons (BNs) were found in anterior horn, Clarkes column, dorsal root ganglion and thalamus. Anti-phosphorylated neurofilament antibodies preferentially stained the peripheral perikarya and proximal neuronal processes of BNs, whereas anti-ubiquitin antibodies preferentially stained the central perikarya of BNs. Ultrastructurally, BNs showed degenerative changes ranging from a diffuse increase of neurofilaments to a centrally accentuated accumulation of mitochondria and vesicular or membranous profiles. Our studies suggest that ubiquitinated degradation products accumulate in the center of the BNs perikaryon and displace aberrantly phosphorylated neurofilaments to the periphery. BNs in WH probably reflect an intrinsic alteration in the metabolism of neurofilaments that is associated with regressive changes in the neuron and eventually neuronal death.

Nerve Regeneration Occurs in the Absence of Apolipoprotein E in Mice

Abstract: The concentration of apolipoprotein E (apoE), a high‐affinity ligand for the low‐density lipoprotein receptor, increases dramatically in peripheral nerve following injury. This endoneurial apoE is thought to play an important role in the redistribution of lipids from the degenerating axonal and myelin membranes to the regenerating axons and myelin sheaths. The importance of apoE in nerve repair was examined using mutant mice that lack apoE. We show that at 2 and 4 weeks following sciatic nerve crush, regenerating nerves in apoE‐deficient mice were morphologically similar to regenerating nerves in control animals, indicating that apoE is not essential for peripheral nerve repair. Moreover, cholesterol synthesis was reduced in regenerating nerves of apoE‐deficient mice as much as in regenerating nerves of control animals. These results suggest that the intraneural conservation and reutilization of cholesterol following nerve injury do not require apoE.

Ocular and associated neuropathologic observations in suspected whiplash shaken infant syndrome. A retrospective study of 12 cases

We examined the eyes of 12 infants who died with the clinical and pathologic diagnosis of the shaken baby syndrome. The ocular histopathologic findings and the neuropathologic findings were compared. Preretinal, intraretinal, and subretinal hemorrhages were observed; hemorrhages of the superficial retinal layers and subsensory retinal space predominated. Retinal hemorrhages were found in 12 cases, intracranial hemorrhage was found in 11 cases, and cerebral edema was found in 10 cases. The intraretinal and periretinal hemorrhages were most prevalent at the posterior pole. Five cases had retinal folds. There was a low incidence of optic disc edema and choroidal hemorrhage.

A unique pattern of astrocytosis in the primary motor area in amyotrophic lateral sclerosis

SummaryWe examined the primary motor area (PMA, Brodmann area 4) from 23 cases of adult-onset sporadic amyotrophic lateral sclerosis (ALS) with immunocytochemistry using anti-glial fibrillary acidic protein antibody. There was astrocytosis in the middle of the pyramidal cell layer in all cases except for one that did not present any upper motor neuron signs clinically. The astrocytosis was characterized by multiple clusters of astrocytes, some of which showed a close association with macrophages. In about a half of the cases, these multiple clusters of astrocytes became confluent and presented as a laminar astrocytosis in the middle of the pyramidal cell layer. Our studies demonstrate a unique pattern of astrocytosis in the PMA in ALS. This pattern of astrocytosis may be useful not only for diagnostic purposes, but also for a better understanding of the pathological process involving the PMA in ALS.

A case of progressive multifocal leukoencephalopathy in a patient treated with infliximab

We describe a 72-year-old white man with erosive rheumatoid arthritis in whom subacute neurologic and psychiatric symptoms developed after 3 years of treatment with infliximab, prednisone, and methotrexate. White matter demyelination was seen on magnetic resonance imaging of the brain, and progressive multifocal leukoencephalopathy (PML) was ultimately confirmed by brain biopsy. The patient was treated with supportive therapy and discontinuation of disease-modifying antirheumatic drugs, resulting in stabilization of the disease process. The patient survived, but neurologic and cognitive deficits persisted. The distribution and pathology of this patients disease are unique from almost all reported incidents of oral methotrexate-associated leukoencephalopathy. The pathogenesis of disease may be linked to a T cell-mediated process that is potentially impacted by infliximab. This case provides the first reported evidence that PML can be seen in association with infliximab therapy.

Clinical applications of proton MR spectroscopy in oncology.

Proton magnetic resonance spectroscopy (H1-MRS) has been increasingly receiving more attention from radiologists, neurosurgeons, radiation and medical oncologists in the “in situ” clinical evaluation of human tumors. The utilization of H1-MRS, especially in human brain tumors, coupled to both routine magnetic resonance imaging (MRI) and functional MRI techniques provides greater information concerning tumor grading and extension and characterization of the normal surrounding tissue than what is possible with any other imaging technique alone. In this paper, we will review the current status of proton MR spectroscopy with emphasis on its clinical utility to diagnose tumors, its utility in planning surgical and radiation therapy interventions, and in its use in monitoring tumor treatment.

Tellurium-induced neuropathy: metabolic alterations associated with demyelination and remyelination in rat sciatic nerve.

Abstract: Rats fed a diet containing 1.25% elemental tellurium initiated on postnatal day 20 undergo a transient neuropathy characterized by synchronous demyelination of peripheral nerves. In sciatic nerve, the extent of demyelination was maximal after 5 days of tellurium exposure; there was a loss of 25% of the myelin, as assayed by concentration of myelin‐specific P0 protein. Tellurium‐induced alterations in the metabolic capacity of Schwann cells were examined by measuring the synthesis of myelin lipids in vitro in isolated sciatic nerve segments. Exposure to tellurium resulted in an early marked decrease of ∼50% in overall incorporation of [14C]acetate into lipids, with a preferential depression in synthesis of cerebrosides, cholesterol, and ethanolamine plasmalogens (components enriched in myelin). Most dramatically, within 1 day of initiation of tellurium exposure, there was a profound increase in [14C]acetate‐derived radioactivity in squalene; 23% of incorporated label was in this intermediate of cholesterol biosynthesis, compared to < 0.5% in controls. In association with the remyelinating phase seen after 5 days of tellurium exposure, synthesis of myelin components gradually returned to normal levels. After 30 days, metabolic and morphologic alterations were no longer apparent. We suggest that the sequence of metabolic events in sciatic nerve following tellurium treatment initially involves inhibition of the conversion of squalene to 2,3‐epoxysqualene, and that this block in the cholesterol biosynthesis pathway results, either directly or indirectly, in the inhibition of the synthesis of myelin components and breakdown of myelin.

Nerve Regeneration and Cholesterol Reutilization Occur in the Absence of Apolipoproteins E and A-I in Mice

Abstract: Apolipoproteins have been implicated in the salvage and reutilization of myelin cholesterol during Wallerian degeneration and the subsequent nerve regeneration. Current evidence suggests that myelin cholesterol complexes with apolipoproteins E and A‐I to form lipoproteins that are taken up via low‐density lipoprotein receptors on myelinating Schwann cells. We recently reported, however, that apolipoprotein E is not required for nerve regeneration or reutilization of myelin cholesterol. We have now investigated nerve regeneration and the reutilization of cholesterol in mutant mice deficient in both apolipoproteins E and A‐I. Morphologic examination of nerves 4 and 12 weeks after crush injury revealed that regeneration proceeded at a normal rate in the absence of these apolipoproteins. Autoradiography of regenerating nerves indicated that prelabeled myelin lipid was reutilized in the regenerating myelin. 3‐Hydroxy‐3‐methylglutaryl‐CoA reductase, the rate‐limiting enzyme in cholesterol synthesis, was down‐regulated in the regenerating nerves, indicative of cholesterol uptake via lipoproteins. Prelabeled myelin cholesterol was present in lipoprotein fractions isolated from crushed nerves of mutant mice. These data suggest that there is considerable redundancy in the process of cholesterol reutilization within nerve, and that apolipoproteins other than apolipoproteins E and A‐I may be involved in the recycling of myelin cholesterol.

Lipid Metabolism During Early Stages of Wallerian Degeneration in the Rat Sciatic Nerve

Abstract We examined changes in biosynthetic capacity of sciatic nerve during the early stages of Wallerian degeneration, utilizing a model that permits exclusion of nonresident cells from degenerating nerve. Sciatic nerve segments were placed in either 5‐μm pore (allowing infiltration of nonresident cells) or 0.22‐μm pore (excluding nonresident cells) Millipore diffusion chambers and then implanted in the peritoneal cavity of the same 32‐34‐day‐old rat. At times up to 7 days post‐surgery, nerve segments from the chambers, as well as control segments from the contralateral sciatic nerve, were removed and their capacity to incorporate radioactive precursors into lipids and proteins assayed in vitro. In nerve segments from both the 0.22‐ and 5‐μm pore chambers, incorporation of [14C]acetate into total lipids was decreased relative to control by 50% at 12 h postsurgery and by 85% at day 3. This decreased incorporation of [14C]acetate reflects primarily decreased de novo synthesis of cholesterol and of fatty acyl residues incorporated into glycerolipids and sphingolipids. There was a preferentially decreased synthesis of cerebrosides and cholesterol (components enriched in myelin) relative to other lipids, while cholesterol esters and free fatty acids (products of membrane degradation) accounted for a greater proportion of the greatly reduced levels of total lipid label. In contrast to [14C]acetate, incorporation of [3H]glycerol into lipids was increased up to fourfold, relative to control, 1 day after nerve transection. This increased incorporation of [3H]glycerol does not reflect de novo synthesis of lipids (which is decreased), but rather removal of toxic fatty acyl residues derived from degradation of myelin lipids; these toxic compounds must be removed by resynthesis into nonmyelin glycerolipids and cholesterol esters. The inhibition of de novo synthesis of myelin lipids in Schwann cells during the early stages of Wallerian degeneration occurs independently of hematogenously‐derived cells. We suggest that Wallerian degeneration rapidly results in some breakdown of myelin, and that the increased free fatty acid levels resulting from degradation of myelin lipids inhibit the de novo synthesis of new myelin lipid.

Immunocytochemical and ultrastructural studies of upper motor neurons in amyotrophic lateral sclerosis

SummaryThe pathological alterations in upper motor neurons were investigated in 27 cases of adult-onset sporadic amyotrophic lateral sclerosis (ALS). No signficant cytoskeletal alterations were found in the Betz cells of any of the cases except one, although cytoskeletal pathology was consistently present in lower motor neurons. The one case had severe circumscribed atrophy of the precentral gyrus and, microscopically, had argentophilic intracytoplasmic inclusions in Betz cells and other pyramidal neurons in the primary motor area as eell as in the lower motor neurons. Immunocytochemically these inclusions contained the epitope of phosphorylated neurofilament and ubiquitin and ultrastructurally consisted of granule-associated filaments with neurofilaments. This is the first demonstration of alterations of cytoskeleton and ubiquitination in the giant cells of Betz, an established subset of upper motor neurons in ALS. Thus, although uncommon, cytoskeletal changes can be found in upper motor neurons in some ALS cases.