Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methyl n-butyl ketone (MBK) is known to produce a giant axonal neuropathy in man and experimental animals characterized pathologically by a gradual increase in the number of neurofilaments which become associated with focal areas of axonal swelling and thinning of the myelin sheath. Fast axoplasmic transport was studied in rats exposed to MBK. In 10 severely paralyzed rats exposed to MBK there was a significant impediment of fast axoplasmic transport following dorsal root ganglion injections (x +/- S.D. = 283.2 +/- 20.34 mm/day) compared to normal controls (417.6 +/- 23.78 mm/day). In rats undergoing injections into the ventral horn of the spinal cord there was a gradual impairment of the mean down flow rate for transport of [3H]leucine which correlated with the severity of the MBK induced neuropathy. Quantitative morphological determinations showed that the total number of neurotubules per unit cross-sectional myelin area and the number of neurotubules associated with mitochondria in swollen axons was unchanged from normal. The total number of mitochondria in randomly sampled axons varied significantly from controls but the absolute number of mitochondria associated with neurotubules was unchanged from normal. The results of these studies suggest that the impediment of fast axoplasmic transport may be related to the increased neurofilaments producing focal areas of axonal blockage.
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PMID:Alterations of fast axoplasmic transport in experimental methyl n-butyl ketone neuropathy. 7 Nov 85

Following contusion (500 g-cm) at upper thoracic levels, sections from the spinal cords of 13 rhesus monkeys were examined with the electron microscope. Survival times ranged from 4 hr to 10 weeks. Samples were taken from the lesion site, from areas 3 and 10 mm rostral and caudal to the lesion center, and from the lumbosacral cord. Four hours postoperatively, several small axons located close to the grey matter at the lesion site exhibit abnormal accumulations of organelles including mitochondria, dense bodies, vesicular structures, and multivesicular bodies. By 12 hr postoperatively many axons at the lesion site appear to be swollen with organelles and exhibit thinning of their myelin sheath. Some organelle-rich profiles lack a myelin sheath altogether. At this time dark axons are present, and myelin sheaths which appear to be empty or to contain small amounts of flocculent material. By 18 hr the first signs of axonal changes appear in the tissue taken 3 mm from the center of the lesion, both swollen and pyknotic axons being present. The axonal pathology spreads from the central part of the cord to the periphery at the impact site, and from the impact site rostrally and caudally, beginning at 18 hr and continuing for the duration of the study. Small fibers degenerate first and large fibers later. The axonal changes observed appear to be comparable to those reported for the central and peripheral nervous systems in other species.
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PMID:An electron-microscopic analysis of axonal alterations following blunt contusion of the spinal cord of the rhesus monkey (Macaca mulatta). 9 94

A study of the sequential morphological changes in the peripheral nerve induced by experimental inhalation exposure of methyl n-butyl ketone (MBK) revealed that the earliest change was an increase in the number of neurofilaments in the large myelinated nerve fibers. This change occurred prior to axonal swelling or myelin thinning. As the duration of exposure lengthened the number of neurofilaments gradually increased and ultimately produced axonal swelling with secondary thinning of the myelin sheath. This appears to be the pathogenesis of the "giant axonal" neuropathy. Another change observed early in this neuropathy was the presence of inpouchings of the myelin sheath, which also increased in number in parallel to the duration of exposure. A careful study of the sequential changes in the entire motor unit did not show a predilection for early morphological changes at the axon terminal. Abnormalities at the neuromuscular junction occurred only after a full spectrum of changes were seen in the main nerve trunk, nerve roots and intramuscular nerves. An important observation was the marked potentiation of peripheral neurotoxicity observed when animals were exposed to MBK in combination with methyl ethyl ketone (MEK) at a ratio of 1:5, MBK:MEK. The latter solvent showed no neurotoxic effect alone. This might help explain a recent outbreak of a polyneuropathy affecting many workers. One further observation was that the sural nerve of a patient with prolonged exposure to MBK showed changes similar to those induced experimentally.
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PMID:Peripheral nerve changes induced by methyl n-butyl ketone and potentiation by methyl ethyl ketone. 17 32

Seven men aged 17 to 22 years developed severe distal symmetrical predominately motor polyneuropathy after repeated inhalation of a commercially available brand of lacquer thinner. Motor nerve conduction velocities were markedly slowed. Fascicular biopsy specimens of sural nerve showed a striking loss of myelinated nerve fibers. Prominent neurofilamentous masses resulted insegmental paranodal distention of axons with secondary thinning and retraction of myelin from the node of Ranvier. Autopsy material from one case revealed central chromatolysis of anterior horn cells in the lumbosacral enlargement and axonal swellings in the fasciculus gracilis. One or more volatile hydrocarbons contained in the lacquer thinner involved may be neurotoxic if inhaled to excess any many cause a neuropathy with characteristic pathological features.
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PMID:Pathology of lacquer thinner induced neuropathy. 18 61

We have correlated the clinical and histopathologic features of the eyes and central nervous system in a patient with Hallervorden-Spatz syndrome who died at age 11 years. The main ocular findings included degeneration of photoreceptors, marked thinning of the outer nuclear and outer plexiform layers, retinal gliosis, narrowing and obliteration of blood vessels with a perivascular cuffing of pigment cells, and degenerative changes in the retinal pigment epithelial cells with accumulation of melanolipofuscin. The positive findings in the brain included a symmetrical, partially destructive lesion of the globus pallidus, especially in its internal fibers and neurons; in addition, we noted gliosis, widely disseminated axonal spheroidal bodies, which were most numerous in the globus pallidus and pars reticulata, as well as deposits of iron. Our histopathologic findings implicate three possible mechanisms, namely, lipid peroxidation, a deficiency of fatty acid membrane components, and increased cGMP which, either singly or in combination, are responsible for a pathogenesis that is common to the eye and brain in Hallervorden-Spatz syndrome.
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PMID:Clinicopathologic correlation and pathogenesis of ocular and central nervous system manifestations in Hallervorden-Spatz syndrome. 155 43

The morphological mechanism of the reconstitution of shunted mantle was studied histopathologically in 22 kaolin-treated hydrocephalic puppies. A remarkable attenuation of cerebral mantle to less than 1 cm in thickness was seen on computerized tomography (CT) scans of four animals sacrificed 1 to 2 months after kaolin treatment (preshunt group). Ventricular shunting resulted in successful recovery of the mantle on repeated CT scans obtained 1 to 2 months after shunting in seven animals (postshunt group). In the remaining 11 animals the cerebral mantle, which had been reduced to 4 mm in thickness prior to shunting, failed to recover even 2 months after the procedure (shunt-refractory group). On gross inspection, the preshunt specimens showed marked thinning of the white matter, with the cortical ribbon well preserved, while the postshunt specimens consisted predominantly of thickened white matter. Histopathological examination of the attenuated white matter of the preshunt specimens showed decreased nerve-fiber density, myelin destruction with myelin regeneration and/or repair of myelin sheaths, and reactive astrocytosis, which were prominent especially in the periventricular white matter. The main findings in the reconstituted white matter of the postshunt specimens were extensive myelin regeneration of residual axons and remarkable astroglial proliferation with mesenchymal reaction, particularly at capillaries. No clear evidence of increased numbers of nerve fibers or axonal regeneration was observed. The shunt-refractory specimens showed remarkable attenuation of cortex, in which reduced numbers of neurons and loss of cortical lamination were noted, with vestigial white matter. The results indicate that astroglial proliferation with mesenchymal reaction and myelin regeneration contribute to the reconstitution of the cerebral mantle volume following ventricular shunting in this model. It is suggested that the critical factor for mantle reconstitution in chronic hydrocephalus is whether cortex is preserved.
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PMID:Reconstitution of shunted mantle in experimental hydrocephalus. 156 46

1. We applied morphological, pharmacological, electrophysiological, and computer simulation techniques to analyze the origin of impulse initiation in amphibian retinal ganglion cells. 2. Morphological studies of retinal ganglion cells in the mudpuppy (Necturus maculosus) and larval tiger salamander (Ambystoma tigrinum) were carried out with the use of either retrograde or intracellular labeling with horseradish peroxidase. These studies identified a characteristic thinning of the axon that begins after the initial segment of axon emerges from the ganglion cell soma or primary dendrite. Morphometric analysis of the thin segment revealed an average length of 74 microns with a standard deviation of 22 microns. For 20 conventionally placed ganglion cells, the length of the thin segment could not be correlated with soma size, initial segment diameter, or distance from the optic disk. There was also little or no correlation for seven displaced ganglion cells. The diameter of the thin segment was below reliable estimation by light microscopy. 3. We studied the possible significance of the thin axonal segment for ganglion cell impulse generation through a combination of electrophysiological recordings (intracellular and whole-cell recordings) together with computer modeling experiments. 4. Electrophysiological experiments are consistent with the idea that the thin segment and cell soma are less excitable than the initial segment region, which appears to be the principal site of initiation of the nerve impulse. The initial segment is that portion of the axon that is bounded by the soma (or proximal dendrite) at its origin and the thin segment at its distal end. 5. Computer simulations of impulse activation were carried out with the use of two different anatomic constraints: one class of simulations did not take into account the thin segment and assumed uniform cylinder conditions, whereas the other class of simulations included a model of the thin axonal segment. These comparative simulations indicate that the thin segment must contain a relatively high density of voltage-gated Na+ channels and support impulse traffic to account for physiological observations on orthodromic and antidromic impulse propagation. In addition, to match the physiological recordings, it is necessary for both the initial segment and the soma compartments to contain moderately high levels of Na+ channels. 6. Our physiological and simulation studies are consistent with the idea that the nerve impulse is normally initiated in the initial segment of axon and then spreads to activate a somatic impulse in the retrograde direction and the axonal impulse in the anterograde direction.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Site of action potential initiation in amphibian retinal ganglion cells. 156 62

Localized hypertrophic mononeuropathy (LHM) is a rare foccal neuropathy associated with perineurial cell proliferation due to an undefined stimulus. We report a case of LHM involving the proximal ulnar nerve in a 13-year-old boy. Serial clinical and electrophysiological observations were done, including intraoperative recordings directly from the nerve on two occasions. The evolution of abnormalities, as documented by electrophysiological and immunohistochemical studies, is compatible with a process of progressive thinning of myelin sheaths, culminating in axonal degeneration in later stages. Intraoperative recording of nerve action potentials was used to guide surgical management of the lesion. Ultimately, there was a good clinical and electrophysiological response to resection of the lesion and sural nerve fascicular grafting.
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PMID:Electrophysiological findings in localized hypertrophic mononeuropathy. 185 Dec 47

The clinical features of patients with hydrocephalus include generalized reductions in coordinated motor and cognitive functions. Although some group similarities have been noted, the outward manifestations of this dysfunction vary in degree and character, with some subjects revealing no overt signs of the underlying hydrocephalus. A retrospective review of subjects with MR criteria of hydrocephalus was undertaken to reevaluate the specific imaging correlates of the signs and symptoms associated with this pathologic process. Forty adults with hydrocephalus on MR evaluation were carefully scrutinized in an effort to elucidate specific clinicoradiologic patterns of abnormality. Spin-echo MR techniques were used with T1 and/or T2 weighting in three orthogonal planes. MR criteria of hydrocephalus encompassed dilated lateral ventricles to include the temporal horns, a pronounced upward elevation of the corpus callosum, and an outward expansion of the cerebral hemispheres at the expense of the subarachnoid space overlying the convexities. The significant related morphologic change on MR that has not been previously described in hydrocephalus was a localized dorsal flattening and thinning of the posterior body of the corpus callosum. Importantly, all but three of the 24 patients with this phenomenon manifested varying combinations of imbalance, gait disturbance, incontinence, short-term memory deficits, and global dementia. In the presence of hydrocephalus, but in the absence of this specific callosal configuration, only one of the remaining 16 subjects revealed symptoms that might suggest the presence of hydrocephalus (i.e., profound dementia). The structure responsible for this focal callosal flattening and thinning in hydrocephalus is the rigid free surface of the falx cerebri as it impinges on the caudal extent of the upwardly expanding corpus callosum and supracallosal hippocampal formation. This mechanical insult hypothetically causes variable axonal dysfunction, ranging from decreased to increased neurophysiologic activity. In summary, it is postulated that callosal impingement represents a dynamic partial hemispheric disconnection and accounts, in part, for the complex clinical state associated with hydrocephalus.
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PMID:Clinical manifestations of hydrocephalus caused by impingement of the corpus callosum on the falx: an MR study in 40 patients. 190 38

The sexual dimorphism of the human corpus callosum (CC) is currently controversial, possibly because of difficulties in morphometric analysis. We have reinvestigated the issue by using morphometric techniques specially designed to yield objective measurements of CC size and shape. The development of the CC was studied with similar techniques in order to investigate whether its final shape and size might be influenced by axonal elimination, as could be expected from previous animal studies. We have measured the CCs of 32 men and 26 women; 27 male and 19 female CCs were from brain tissue, the others were from magnetic resonance imaging graphs. Women tended to have 1) a smaller cross-sectional callosal area (CCA); 2) a larger fraction of CCA in the posterior fifth of the CC; 3) more slender CCs; and 4) more bulbous splenia. These differences could not be detected by simple inspection but were demonstrated by measurement and statistical analysis. However, CCA was correlated with the other sexually dimorphic parameters, and the sex-related differences in the latter became nonsignificant when variations in CCA were factored out or when male and female populations with similar CCA were compared. In addition, we analyzed CCs of 16 male and 16 female fetuses and of 13 male and 15 female infants and children. This sample ranged in age between 20 weeks of gestation and 14 years but covered in detail the period up to 14 months after birth. CCA increased throughout the latter period but decreased slightly between about 33 weeks of gestation and the beginning of the second postnatal mouth. This decrease coincided with thinning of the CC and a marked increase in bulbosity of the splenium. No sexual dimorphism could be demonstrated until the beginning of the postnatal period. In the age group between birth (at term) and the 14th month, CCA was, as in the adult, larger in males. Unlike in the adults, the CC was longer in males and the bulbosity index was the same in the two sexes. Axonal elimination may play a role in the perinatal pause in CCA growth and in the concomitant changes in callosal shape.
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PMID:Forms and measures of adult and developing human corpus callosum: is there sexual dimorphism? 292 93


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