Altered protein composition of isolated human cortical neurons in Alzheimer disease

To characterize the protein composition of degenerating neurons in Alzheimer disease, enriched fractions of isolated cortical neurons from postmortem Alzheimer brain were compared by ultrastructural and biochemical techniques to neuronal isolates from aged normal controls and from patients with the nonfibrillary degenerative dementia, Huntington disease. Electron microscopy of isolated neurons showed well-preserved organelles, including nuclear membranes, mitochondria, endoplasmic reticulum, ribosomes, and lipofuscin. Abundant paired helical filaments (PHF) were preserved in affected Alzheimer perikarya. In both sporadic and familial Alzheimer disease, sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed marked augmentation of a 20,000 mw protein (P20) in neuronal fractions from affected cortex compared to Huntington disease patients and controls. P20 was commonly increased in hippocampal, temporal, and frontal neurons but not in cortex free of PHF. The augmentation of P20 in Alzheimer disease samples appeared to correlate with the presence of PHF-bearing neurons in the fractions. The increase in P20 in Alzheimer disease was observed in the presence of proteolysis inhibitors, in reverse-sieved samples, and in whole cortical homogenates. Neurofilament proteins, tubulins, and a 50,000 mw protein showed no changes. In Huntington disease, marked augmentation of a 49,000 mw protein was found in striatal but not cortical homogenates. The relationship of these findings to the biochemistry of brain fibrous proteins and to the molecular pathology of Alzheimer disease is discussed.

Biochemical and immunological characterization of neurofilaments in experimental neurofibrillary degeneration induced by aluminum

In order to identify the protein composition of 10 nm neuronal filaments, we prepared enriched fractions of rabbit spinal neurons undergoing experimental neurofilamentous degeneration induced by aluminum. Electron microscopy of the isolated perikarya showed well-preserved, large perinuclear masses of neurofilaments, which were not found in similarly isolated control perikarya. Comparison of these glial-free fractions by SDS-polyacrylamide gel electrophoresis revealed several-fold augmentation in the filament-enriched neurons of proteins migrating at 68,000 and 160,000 daltons, with an additional component at 200,000 daltons. Otherwise, the protein patterns were identical; no band was found at 51,000 daltons, the molecular weight assigned to the major proteins both of glial filaments and of a previously reported bovine brain filament preparation. An antiserum raised against the 160,000 dalton component of a modified bovine brain filament fraction produced specific and intense fluorescent staining of the aluminum-induced neurofilament bundles. Antibodies to the 51,000 dalton protein of brain filaments and to tubulin failed to stain the induced filaments. The results strongly support the hypothesis that both normal and aluminum-induced neuronal filaments are composed of 68,000, 160,000 and 200,000 dalton polypeptides and do not contain significant amounts of the 51,000 dalton filament protein. The likelihood of biochemical heterogeneity among organelles with similar morphology, namely the glial and neuronal filaments, is raised.

Neurologic and cardiovascular effects of hypotension in the monkey

Thirty monkeys were exposed to controlled systemic hypotension of different magnitudes and duration to determine factors leading to brain injury or cardiovascular failure. Fourteen monkeys developed brain injury. Of these, 6 survived indifinitely and 8 were sacrificed or died within 12-62 hours due to neurologic deterioration accompanied by respiratory failure. Sixteen animals did not develop brain injury, but 9 of these died within 24 hours from documented cardiovascular failure with the remaining 7 survived indefinitely. A highly reproducible threshold for the development of brain injury was found at a mean arterial blood pressure (MABP) of 25 mm Hg. Maintenance MABP was less than or equal to 25 mm Hg in 13 of 14 lesioned monkeys and greater than 25 mm Hg in 15 of 16 non-lesioned monkeys. Maintenance MABP averaged 20.1 +/- 1.1 mm /g in lesioned and 32.1 +/- 1.7 mm Hg in non-lesioned animals (p less than 0.001). Among the non-lesioned animals, death from delayed cardiovascular failure ensued when MABP was maintained between 27 and 35 mm Hg for 90 min or longer. Animals exposed to this range of hypotension for less than 90 min or to MABP exceeding 35 mm Hg for as long as 3 h survived intact. EEG changes occurring during hypotension most accurately predicted neurologic outcome. The threshold MABP required to produce cerebral electric silence was 21-22 mm Hg. Monkeys developing marked brain injury had greater than 25 minutes of EEG flattening, while slightly injured animals had it for 5-15 minutes and those without injury for less than 5 min. Changes in acid-base state, common carotid artery blood flow, and cerebral uptake of glucose and oxygen during hypotension also correlated with neurologic and cardiovascular outcome. Hypoxemia and hypercarbia were not contributory factors in the production of brain injury in this study.

Effects of neurotoxic industrial solvents on cultured neuroblastoma cells: methyl n-butyl ketone, n-hexane and derivatives

The neurotoxic effects of the commercial organic solvents n-hexane and methyl n-butyl ketone (MBK), recently discovered to cause profound peripheral neuropathy in man, were studied in neuronal-like cells in tissue culture. These agents are known to induce marked proliferation of 10nm neurofilaments in peripheral and central axons of both humans and rats. In a murine neuroblastoma cell line, previously reported to show filamentous hyperplasia when exposed to aluminum ions, both MBK and n-hexane induced a highly reproducible series of cytotoxic effects at the light and electron microscopic levels and caused dose-dependent inhibition of cellular proliferation. In contrast, two closely related but clinically non-toxic solvents, methyl isobutyl ketone and methyl ethyl ketone, caused little or no cytopathological or growth inhibiting effects. MBK and its major water soluble derivative, 2,5-hexane dione (HD), produced identical cytotoxic changes in vitro, supporting the postulate that HD is the toxically active agent in victims exposed to MBK. Although MBKlthought MBK and n-hexand adversely affected the extension of maintenance of neuritic processes, electron microscopy and immunofluorescent reaction failed to reveal any proliferation of 10 nm cytoplasmic filaments in the intoxicated cells. Also, these agents had no deleterious effect on in vitro brain microtubule polymerization. In contrast, aluminum ions produced a doserelated inhibition of neurotubule assembly, similar to that seen with the filament-inducing agents colchicine and vinblastine. The results suggest that the fibrous cytoskeleton may not be the primary or essential target of MBK n-hexane and related human neurotoxins.

Pure motor hemiplegia secondary to brain-stem tumour

'Pure motor hemiplegia' is a common stroke syndrome defined by Fisher as paralysis of face, arm, and leg on one side, unaccompanied by sensory signs, visual field defect, aphasia, or apractognosia. It occurs almost exclusively in hypertensive patients and carried a good prognosis. We report a case of a normotensive patient in whom pure motor hemiplegia was the presenting feature, not of a cerebrovascular syndrome, but of a pontine glioblastoma. We note that brain-stem tumours may masquerade as brain-stem strokes.